Metformin May Block the Way Breast Cancer Metastasis: A Meta-analysis and Mechanism Review

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Recently, its anti-tumor effect has been revealed. Here we performed a meta-analysis to summarize previous studies and a narrative review to gather the mechanisms involved in the potential relationship. Methods We searched related articles in database of Pubmed, EMbase, Web of science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), the Wanfang and Sinomed and obtained 8 clinic trials that investigated the connection between metformin and breast cancer metastasis, containing 2 randomized controlled trials (RCTs) and 6 retrospective cohort studies. We evaluated each retrospective cohort study by Newcastle-Ottawa Scale (NOS), while RCT by Chcorane Risk of Bias tool. Pooled hazard ratios (HRs), risk ratios (RRs) and we calculated associated 95% confidence intervals (CIs) with a random-effect, generic inverse variance method. We also collected the possible mechanisms of cancer metastasis inhibition from metformin. Results A total of 8 studies containing 13919 breast cancer patients without distant metastasis before they got anticancer treatment. The result showed that adjuvant metformin in treatment of local breast cancer facilitated to suppress metastasis (HR = 0.69, 95% CI = 0.57–0.82, p < 0.0001, I 2 = 0%), and the result was consistent with the subgroup of breast cancer patients with type 2 diabetes mellitus (T2DM) (HR = 0.68, 95% CI = 0.57–0.82, p < 0.0001, I 2 = 0%). Conclusion The meta-analysis suggested metformin might repress the metastasis and be benefit to distant metastasis-free survival (DMFS) when added to systemic breast cancer therapy, supporting anti-tumor effects of metformin on breast cancer. Cancer Biology Oncology metformin breast cancer distant metastasis AMPK AMPK inhibitor Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Background Breast cancer has a high incidence in female tumors, which affects the health of women around the world. In a sample survey conducted in mainland China in 2019, women with T2DM had an increased risk of breast cancer [ 1 ]. A lot of clinical and epidemiological evidences have linked hyperinsulinemia, insulin resistance, and diabetes to poor breast cancer outcomes [ 2 ]. In addition, early breast cancer patients with T2DM had an increased likelihood of recurrence and metastasis [ 3 , 4 ], implicating that T2DM might be a dependent risk factor of breast cancer prognosis. There are various treatments for early breast cancer, but for breast cancer with distant metastasis, the effective method is still a difficulty. Therefore, prevention breast cancer patients from metastasis is economical and available. Metformin, extracted from Galega officinalis (the French lilac) [ 5 ], is an anti-hyperglycemia drug and insulin sensitizer used in the therapy of T2DM, a chronic disease characterized by insulin resistance [ 6 ]. In recent years, metformin has also been reported to reduce cancer risk and improve clinical outcomes [ 7 , 8 ]. This drug inhibits tumor growth and cell proliferation in most breast cancer subtypes in vitro at different degrees [ 9 – 12 ]. Furthermore, the metformin targets to breast cancer stem cells (BCSCs), reduces tumor mass and prolongs remission with doxorubicin [ 13 ]. Based on these basic studies, various of clinic studies were conducted to explore whether adjuvant metformin may contribute to the prognosis of breast cancer patients [ 14 , 15 ]. We here provided a meta-analysis to explore whether metformin adjuvant therapy could reduce breast cancer metastasis and prolonged the distant metastasis-free survival (DMFS). We also collected the probable mechanisms about metformin. We hoped this study might help to deep comprehension of the role of metformin in cancer treatment. Methods Study selection We searched all published articles up to May 2020 in database of Pubmed, EMbase, Web of science, Cochrane Library and Chinese database of CNKI, WanFang and Sinomed for relevant studies. The keywords for searching included “metformin”, “breast neoplasms”, “therapies, drug” and “neoplasm metastasis”. Contralateral axillary lymph node metastasis is controversial in the clinical stage of breast cancer [ 16 ]. We here included “lymphatic metastasis” in our search terms as well. After that, the selected studies were manually screened and only human subjects and original articles were considered eligible. Selected publications were all in English or Chinese. Inclusion and exclusion criteria Since aiming to investigate whether metformin could suppress breast cancer metastasis, we set inclusion and exclusion criteria for the meta-analysis: All patients were diagnosed as primary breast cancer without metastatic disease before they got anticancer treatment; The breast cancer patients received not only antihyperglycemic therapy; The patients we included were divided into two group. The “metformin group” was defined as the breast cancer patients who received metformin including combination with other antihyperglycemic drugs during breast cancer therapy, while the “non-metformin group” was defined as patients who did not use metformin but chose other hypoglycemic drugs or they did not received any antihyperglycemic therapy during anti-tumor treatment; There were various methods to treat breast cancer systematically, thus, we set no limit on the consistency of other treatments except antihyperglycemic therapy; The number of patients who ended with distant metastasis and the number of patients who participated in the studies, or relevant Kaplan-Meier curves, or HRs, RRs with associated 95% CIs between study groups and control groups were provided; RCT, cross-sectional studies or cohort studies published as original manuscript. The TNM stage of breast cancer was based on the criteria of American joint committee on cancer (AJCC) 8th edition cancer staging manual and M-phase was considered as “distant metastasis” [ 17 ]. Data extraction and quality assessment Two authors reviewed each selected article independently and extracted relevant data with a structured table. We extracted data containing: authors, year of publication, country which the study was conducted in, study type, sample size, follow-up time, the average or median age of study population, the number of breast cancer patients with T2DM, other treatment than antihyperglycemic therapy, metformin dose, the distant metastasis number and total number of study group and control group/HR/RR. If there was any disagreement, the final decision would be made by the group discussion. Our work was performed according to the Preferred Reporting Items for Systematic Review ang Meta-Analysis Protocols (PRISMA-P) 2015 statement. The quality of retrospective cohort studies we intended to include was assessed with reference to the NOS, which was composed of three parts: selection, comparability and exposure, and only the study score was not less than 6 stars (up to 9 stars) could be accepted [ 18 , 19 ]. The rest of studies were RCTs, thus we chose Chcorane Risk of Bias tool to assess their quality. Statistical analyses If relative RRs and HRs with associated 95% CIs were not available, we would extract the metastasis numbers and total numbers in study group and control group, then used STATA14.0 (Stata, College Station) to calculated RRs and associated 95% CI. As the articles published before, the distinction between relative RR and HR was ignored [ 20 , 21 ]. HR/RR 1. Mantel-Haenszel random-effects model was chosen because of the assumption that studies might be different for random errors and between study variability and the pooled HRs/RRs with associated 95% CI were obtained upon generic inverse variance approach, which allowed the weight of each study based on variance and adjusted point estimates and standard errs from individual study to be extracted and combined [ 22 ], by Revman 5.3 software (RevMan, The Cochrane Collaboration). The Cochcrane Q test and I 2 statistic were used to assess and quantify heterogeneity, when I 2 75%, high heterogeneity [ 23 ]. Due to the limitation of the quantity of studies, the egger’s test was appropriate and we meant to use Funnel plot to show the publication bias of the included studies. A two-tailed p < 0.05 was thought statistically significant. Results Studies included in the meta-analysis From the 7 databases, we achieved 1121 literatures with search terms. 773 articles were left after deleting the duplication, while 46 articles were eligible for further full text assessment. After carefully reading full text, 8 studies met the inclusion criteria. The details of these studies were shown in Fig. 1 . The characteristics of studies and patients The 8 studies published before May 2020, included 13919 breast cancer patients, with a maximum sample size of 6769 and a minimum sample size of 61 participants. 4 in China[ 24 – 27 ], 1 in South Korea[ 28 ], 1 in America[ 29 ], 1 in Germany[ 30 ], 1 in Egypt[ 31 ]. Moreover, 2 were RCTs while 6 were retrospective cohort studies. Among these studies, 3598(25.73%) patients received metformin adjuvant therapy and 5784(41.56%) patients combined with T2DM. For other features of included studies, check Table 1 . Table 1 Characteristics of included studies Authors Year of publication Country Study type NOS score Sample size The numder of breast cancer patients with T2DM Follow-up time(average or median, month) Age (average or median, range, year) metformin dose other treatment than antihyperglycemic therapy Soley Bayraktar 2012 Amercia retrospective cohort studies 8 1448 130 62 41(21–87) not mentioned All received surgery and adjuvant chemotherapy(if necessary) Tangyan He 2017 China retrospective cohort studies 7 61 34 44 61.25(42–82) not mentioned All received surgery, chemotherapy and hormonal therapy(if necessary) Louis Jacob 2016 Germany retrospective cohort studies 7 4953 4953 55.2 71.4(40–90) not mentioned not mentioned Hee Jeong Kim 2015 South Korea retrospective cohort studies 7 6967 386 100.3 55 not mentioned Chemotherapy and Hormonal therapy(if necessary) Weili Min 2020 China retrospective cohort studies 7 89 89 55.1 64.4(55–73) not mentioned surgery Sahar Mohammed EL-Haggar 2016 Egypt RCT not applicable 102 0 22.8 48.8(40–65) 850 mg All recevievd Chemotherapy and 83.3% Hormonal therapy(if necessary) Haiyan Wang 2017 China RCT not applicable 128 128 55 57.2(45–76) 850 mg surgery Wenjie Zhu 2013 China retrospective cohort studies 6 171 64 45 52.4(24–79) not mentioned All received surgery, chemotherapy and hormonal therapy(if necessary) Metastasis A total of 8 studies investigated the relationship between adjuvant metformin and distant metastasis of breast cancer but only 3 of them reported that added metformin into general anti-tumor therapy prolonged DMFS with statistically significant. The analysis showed that metformin addition is related with inhibition of metastasis of breast cancer (HR = 0.69, 95% CI = 0.57–0.82, p < 0.0001, I 2 = 0%) (Fig. 2 A). Because different types of studies were included, we conducted subgroup analysis for RCTs (HR = 0.35, 95% CI = 0.16–0.78, p = 0.01, I 2 = 0%) (Fig. 2 B) and retrospective cohort studies (HR = 0.71, 95% CI = 0.59–0.86, p = 0.0003, I 2 = 0%) (Fig. 2 C) respectively. Considering that breast cancer patients using metformin were likely to be T2DM, we selected patients with breast cancer and T2DM from the included studies for subgroup analysis. Ultimately, 7 studies were eligible while the study population of Sahar’s research were all nondiabetic breast cancer women. It turned out that metformin protected T2DM breast cancer patients from metastasis (HR = 0.68, 95% CI = 0.57–0.82, p < 0.0001, I 2 = 0%) (Fig. 3 A). We performed subgroup analysis for 6 retrospective cohort studies only (HR = 0.69, 95% CI = 0.57–0.83, p < 0.0001, I 2 = 0%) (Fig. 3 B), for just 1 RCT included patients with T2DM. Publication bias The publication bias was evaluated by Egger’s test and displayed by Funnel plot. As shown in Fig. 4 , since associated-clinic trials was still low in quantity, the publication bias was difficult to avoid completely. The result of Egger’s test of this meta-analysis indicated there was no significant publication bias between the 8 literatures ( p = 0.15), meaning the result was acceptable and believable. Discussion Discussion on the meta-analysis Discovery anti-tumor drugs is a luxurious and time-consuming process, also the percentage of drugs meets the clinic is quite a little. Thus, the development of new functions of existing drugs has become a hot study topic. It is known to all that obesity and T2DM relate with poor prognosis of breast cancer closely. Metformin, the most widely used antihyperglycemic drug to treat T2DM, could maintain weight loss as well [ 5 ]. It has been verified that most tumors are sensitive to metformin [ 6 , 8 ]. Consistently, metformin synergizes with conventional anticancer therapy to kill tumors and repress migration [ 32 ]. But the outcomes of clinical studies of metformin in the treatment of breast cancer were not entirely positive [ 15 , 29 , 33 ], the metformin effect in breast cancer treatment was still under discussion. In this study, we intended to estimate the connection between metformin and distant breast cancer distant metastasis. With the forest plot (Figs. 2 and 3 ), we demonstrated that adjuvant metformin might contribute to suppress breast cancer metastasis. The adverse effects brought by metformin should not be neglected, while gastrointestinal distress, including transient mild nausea and moderate diarrhea, was the toxicity that people usually met during metformin treatment [ 31 , 34 ]. There was no grade 3 and 4 treatment-related adverse event (TRAE) reported in the included publications. This meta-analysis had several limitations. First, the small sample size limited to obtain firm conclusions. Second, the dose of metformin could not adjust to consistent because most of the trails were retrospective and the individual distinctions among the patients were unavoidable. It has been proved that adjuvant metformin therapy repressed HER 2 + breast cancer cells [ 35 , 36 ] while ER- breast cancer cells resisted to this drug [ 37 ]. Thus, the effects of metformin might depend on the molecular types of breast cancer. Here we recommended that subgroups for different hormone receptors status should be designed in the future clinical trials. The mechanisms of metformin to suppress tumor metastasis Inhibiting tumor metastasis by metformin was a complex process of multiple pathways, including: AMPK activation, epithelial mesenchymal transition (EMT) inversion, DNA methylation modulation, interfering with TGF-β pathway and tumor microenvironment. Moreover, N-cadherin, vimentin, β-catenin, snail, Rac1 and MMP-2/9 were downregulated while E-cadherin and phosphorylated AMPK increased, which resulted in tighter intercellular connections, weaker migration and movement of tumor cells. Metformin affected insulin-like growth factor (IGF) pathway by repressing IGF-1 receptor and IGF-2 molecule [ 38 ]. As shown in Fig. 5 , metformin mediated different pathways to prevent metastasis. Intercellular reaction AMPK, a widely known metformin effector, was activated in two pathways. One way was that metformin activated liver kinase B1 (LKB1), the upstream of AMPK, and the other pathway was mitochondrial complex I activation decreased ATP/AMP ratio under metformin stimulation, which triggered AMPK activation indirectly [ 39 , 40 ]. Phosphorylated AMPK functioned as an inhibitor to repress a series of moleculars activation, containing: STAT3, smad-2/3, Akt, ERK, mTOR, PKCγ and Twist. Snail, which was the downstream of ERK and Y-box binding protein-1 (YB-1) [ 41 , 42 ], a oncogenic transcription/translation factor, and also the direct target gene of metastasis-related gene YAP [ 43 ]. This protein regulated E-cad expression with Twist. Additionally, it participated in E-cad promoter hypomethylation modulation with Slug [ 41 ]. Metformin induced Snail ubiquitination after LKB1 phosphorylation, which helped Snail’s interaction with E3 ligase FBXL14 [ 44 ]. Furthermore, metformin decreased Twist with obliterating interaction between GSK-3β and Twist via reducing Akt/GSK-3β pathway [ 45 ]. mTOR, of which inhibition under metformin therapy mediated suppression of HIF-1α/VEGF-A and p70s6k [ 46 , 47 ], was another downstream molecule of Akt. In addition, metformin augmented Foxo3a nuclear localization and protein stabilization to active Foxo3a with IKKβ repression and MDM2 phosphorylation involvement, leading to the level of E-cad increase [ 42 ]. For protein kinase Cγ (PKCγ), which was attenuated after AMPK-α1 phosphorylation, it modulated Hs90α activation [ 48 ]. The Rac1 and RhoA GTP downstream migratory protein took charge of the migration of cell, thus they were required in cancer migration and metastasis. Metformin downregulates Rac1 in different pathways. Firstly, metformin suppressed FAK/Akt signaling pathway [ 49 ] or CXCL12/CXCR4 [ 50 ] to decrease downstream factors Rac1 and RhoA GTP expression. Secondly, metformin elevated the level of phosphatase and tensin (PTEN), a protein controls tumor metastasis, to inhibit Akt/Rac1 axis [ 51 ]. Thirdly, Rac1 GTP was reduced by metformin-mediated cAMP increase [ 50 ]. Moreover, CD24, a mucin-like adhesion molecule, enhanced the metastasis potential of malignant cells. Distant metastasis in patients with refractory breast cancer was mainly composed of CD24 positive cells, which was thought as a marker indicating poor prognosis of breast cancer. Recently, CD24 has been confirmed to significantly be downregulated by metformin [ 52 ]. Micro-RNA, modulators of many cellular signaling pathways, have been verified to take parts in metformin treatment. MiR-26a was enhanced under metformin stimulation to inhibit Akt phosphorylation [ 53 ]. Similarly, miR-381, upregulated by metformin, significantly interfered with YAP transcription to affect Snail [ 43 ]. MiR-30a, another member upregulated by metformin, attenuated SOX4, which was a oncogenic transcription factor and epithelial mesenchymal transformation (EMT) regulator, reversing the process of EMT [ 54 ]. Because of the DNA methylation, metformin therapy increased the level of mir-570-3p, while decreased lncRNA H19 by metformin-induced DNA methylation. The former was shown to reduce the invasion of tumor cells through inhibiting LCMR1 and ATG12 [ 55 ], while the latter was also been implicated to control tumor metastasis by not only reducing MMP-9, but also elevating AMPK phosphorylation and let-7, a potent tumor suppressor microRNA [ 56 , 57 ]. Effects on tumor microenvironment cells The word “tumor microenvironment” was created in 2011, and defined to include endothelial cells, pericytes and immune inflammatory cells [ 58 ]. Endothelial cells were shown to benefit to developmental and tumor-associated angiogenesis, while pericytes wrapped around the endothelial tubing of blood vessels and prevented the tumors from entering the circulatory system, making it possible to reduce subsequent hematogenous dissemination [ 59 , 60 ]. Metformin downregulated micro-vessel density (MVD) by inhibiting platelet-derived growth factor B (PDGF-B), ending with reducing the ratio of endothelial cells/ pericytes, leakage and hypoxia, namely “vessel normalization” [ 61 , 62 ]. Moreover, Angiopoietin-like protein 4 (ANGPIL4) was decreased during metformin treatment after HIF-1α suppression [ 63 ]. Another modulation of metformin to block tumor metastasis was the attenuation of M2-like polarization of tumor associated macrophages (TAM) with phosphorylated AMPK α1 [ 64 ]. Conclusion To the best of our knowledge, this was the first meta-analysis focused on the relationship between metformin and distant metastasis of breast cancer. The study showed that metastasis repression could be achieved by receiving metformin and general breast cancer treatment combination, and the association was supported by a wide range of basic studies, implicating the possibility for metformin becoming a new anticancer drug. However, this report was lack of prospective research, therefore, the veracity of conclusion remained to be verified. Further studies investigating connection metastasis of breast cancer and metformin were expected. Abbreviations CNKI China National Knowledge Infrastructure; RCT:randomized controlled trial; NOS:Newcastle-Ottawa Scale; HR:hazard ratio; RR:risk ratio; CI:confidence interval; DMFS:distant metastasis-free survival; T2DM:type 2 diabetes mellitus; BCSC:breast cancer stem cell; AJCC:American joint committee on cancer; ER:estrogen receptor; TRAE:treatment-related adverse event; IGF:insulin-like growth factor; AMPK:adenosine 5’-monophosphate-ativatied protein kinase; LKB1:liver kinase B1; YB-1:Y-box binding protein-1; PKCγ:protein kinase Cγ; PTEN:phosphatase and tensin; EMT:epithelial mesenchymal transformation; TGF-β:transforming growth factor; ERK:extracellular signal regulated kinase; STAT:Signal Transducer and Activator of Transcription; Akt:protein kinase B; IKKβ:inhibitor kappa B kinase β; CXCL:C-X-C motif ligand; CXCR:C-X-C motif receptor; cAMP:cyclic adenosine moriophosphate; PDGF-B:platelet-derived growth factor B; MVD:micro-vessel density; ANGPIL4:Angiopoietin-like protein 4; VEGF:vascular epidermal growth factor; TAM:tumor associated macrophages. Declarations Competing interests The authors declare that there are no conflicts of interest. Availability of data and materials The datasets supporting the conclusions of this study are included within the article and its additional files. Authors’ contributions YYW and ZHZ screened the reference. YYW drafted the manuscript and analyzed most of the data. YYW,JYP,XX and XW discussed and revised themanuscript. All authors read and approved final manuscript. Thanks to all authors for their time and effort and department of breast surgery from the first hospital of Jilin University for technical support. All authors have read and approved the manuscript. Consent for publication All coauthors were offered the opportunity to read the final manuscript and agreed to publish. Ethics approval and consent to participate Not applicable. Funding Not applicable. Acknowledgement This work was supported by the First Hospital of Jilin University and Jilin University. References Qi J, He P, Yao H, Song R, Ma C, Cao M, Cui B, Ning G. Cancer risk among patients with type 2 diabetes: A real-world study in Shanghai, China. Journal of diabetes. 2019;11:878–83. Goodwin PJ. Insulin in the adjuvant breast cancer setting: a novel therapeutic target for lifestyle and pharmacologic interventions? Journal of clinical oncology: official journal of the American Society of Clinical Oncology. 2008;26:833–4. Ma FJ, Liu ZB, Qu L, Hao S, Liu GY, Wu J, Shao ZM. Impact of type 2 diabetes mellitus on the prognosis of early stage triple-negative breast cancer in People's Republic of China. Onco Targets Ther. 2014;7:2147–54. Schrauder MG, Fasching PA, Häberle L, Lux MP, Rauh C, et al. Diabetes and prognosis in a breast cancer cohort. J Cancer Res Clin Oncol. 2011;137:975–83. Adak T, Samadi A, Ünal AZ, Sabuncuoğlu S. A reappraisal on metformin. Regulatory toxicology pharmacology: RTP. 2018;92:324–32. He H, Ke R, Lin H, Ying Y, Liu D, Luo Z. Metformin, an old drug, brings a new era to cancer therapy. Cancer journal (Sudbury Mass). 2015;21:70–4. Henderson D, Frieson D, Zuber J, Solomon SS. Metformin Has Positive Therapeutic Effects in Colon Cancer and Lung Cancer. Am J Med Sci. 2017;354:246–51. Coyle C, Cafferty FH, Vale C, Langley RE. Metformin as an adjuvant treatment for cancer: a systematic review and meta-analysis. Annals of oncology: official journal of the European Society for Medical Oncology. 2016;27:2184–95. Ben Sahra I, Laurent K, Loubat A, Giorgetti-Peraldi S, Colosetti P, Auberger P, Tanti JF, Le Marchand-Brustel Y, Bost F. The antidiabetic drug metformin exerts an antitumoral effect in vitro and in vivo through a decrease of cyclin D1 level. Oncogene. 2008;27:3576–86. Zakikhani M, Dowling R, Fantus IG, Sonenberg N, Pollak M. Metformin is an AMP kinase-dependent growth inhibitor for breast cancer cells. Cancer research. 2006;66:10269–73. Dowling RJ, Zakikhani M, Fantus IG, Pollak M, Sonenberg N. Metformin inhibits mammalian target of rapamycin-dependent translation initiation in breast cancer cells. Cancer research. 2007;67:10804–12. Liu B, Fan Z, Edgerton SM, Deng XS, Alimova IN, Lind SE, Thor AD. Metformin induces unique biological and molecular responses in triple negative breast cancer cells. Cell cycle (Georgetown Tex). 2009;8:2031–40. Hirsch HA, Iliopoulos D, Tsichlis PN, Struhl K. Metformin selectively targets cancer stem cells, and acts together with chemotherapy to block tumor growth and prolong remission. Cancer research. 2009;69:7507–11. Jiralerspong S, Palla SL, Giordano SH, Meric-Bernstam F, Liedtke C, et al. Metformin and pathologic complete responses to neoadjuvant chemotherapy in diabetic patients with breast cancer. Journal of clinical oncology: official journal of the American Society of Clinical Oncology. 2009;27:3297–302. Zhao Y, Gong C, Wang Z, Zhang J, Wang L, et al. A randomized phase II study of aromatase inhibitors plus metformin in pre-treated postmenopausal patients with hormone receptor positive metastatic breast cancer. Oncotarget. 2017;8:84224–36. Magnoni F, Colleoni M, Mattar D, Corso G, Bagnardi V, et al: Contralateral Axillary Lymph Node Metastases from Breast Carcinoma: Is it Time to Review TNM Cancer Staging? Annals of surgical oncology 2020. Giuliano AE, Connolly JL, Edge SB, Mittendorf EA, Rugo HS, Solin LJ, Weaver DL, Winchester DJ, Hortobagyi GN. Breast Cancer-Major changes in the American Joint Committee on Cancer eighth edition cancer staging manual. Cancer J Clin. 2017;67:290–303. Fu Y, Lee CH, Chi CC. Association of Psoriasis With Inflammatory Bowel Disease: A Systematic Review and Meta-analysis. JAMA dermatology. 2018;154:1417–23. Soneji S, Barrington-Trimis JL, Wills TA, Leventhal AM, Unger JB, et al. Association Between Initial Use of e-Cigarettes and Subsequent Cigarette Smoking Among Adolescents and Young Adults: A Systematic Review and Meta-analysis. JAMA pediatrics. 2017;171:788–97. Siristatidis C, Sergentanis TN, Kanavidis P, Trivella M, Sotiraki M, Mavromatis I, Psaltopoulou T, Skalkidou A, Petridou ET. Controlled ovarian hyperstimulation for IVF: impact on ovarian, endometrial and cervical cancer–a systematic review and meta-analysis. Hum Reprod Update. 2013;19:105–23. Biswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, Alter DA. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med. 2015;162:123–32. DerSimonian R, Laird N. Meta-analysis in clinical trials. Controlled clinical trials. 1986;7:177–88. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ. 2003;327:557–60. Min W, Wang B, Guo A, Mao G, Zhao Y, Zhang S, He R, Min Y, Huang Y. The effect of metformin on the clinicopathological features of breast cancer with type 2 diabetes. World Journal of Oncology. 2020;11:23–32. Wang H. Effect of metformin on prognosis of breast cancer patients complicated with type 2 diabetes mellitus[in Chinese]. Heilongjiang Medicine. 2017;30:109–11. He T: Clinical characteristics and prognosis of hormone-dependent breast cancer patients with type 2 diabetes mellitus[in Chinese]. Guangxi Medical University; 2017. Zhu W: Effect of metformin on prognosis of breast cancer patients complicated with type 2 diabetes mellitus[in Chinese]. Shandong University; 2013. Kim HJ, Kwon HW, Lee JW, Lee SB, Park HS, Ahn SH, Shin HN. Metformin increases survival in hormone receptor-positive, Her2-positive breast cancer patients with diabetes. Cancer research 2015, 75. Bayraktar S, Hernadez-Aya LF, Lei X, Meric-Bernstam F, Litton JK, Hsu L, Hortobagyi GN, Gonzalez-Angulo AM. Effect of metformin on survival outcomes in diabetic patients with triple receptor-negative breast cancer. Cancer. 2012;118:1202–11. Jacob L, Kostev K, Rathmann W, Kalder M. Impact of metformin on metastases in patients with breast cancer and type 2 diabetes. J Diabetes Complications. 2016;30:1056–9. EL-H SM, El-Shitany NA, Mostafa MF, El-Bassiouny NA. Metformin may protect nondiabetic breast cancer women from metastasis. Clin Exp Metas. 2016;33:339–57. Zheng Y, Zhu J, Zhang H, Liu Y, Sun H. Metformin inhibits ovarian cancer growth and migration in vitro and in vivo by enhancing cisplatin cytotoxicity. American journal of translational research. 2018;10:3086–98. Nanni O, Amadori D, De Censi A, Rocca A, Freschi A, et al. Metformin plus chemotherapy versus chemotherapy alone in the first-line treatment of HER2-negative metastatic breast cancer. The MYME randomized, phase 2 clinical trial. Breast cancer research treatment. 2019;174:433–42. Gonzalez-Angulo AM, Meric-Bernstam F. Metformin: a therapeutic opportunity in breast cancer. Clinical cancer research: an official journal of the American Association for Cancer Research. 2010;16:1695–700. Sonnenblick A, Agbor-Tarh D, Bradbury I, Di Cosimo S, Azim HA, Jr. et al: Impact of Diabetes, Insulin, and Metformin Use on the Outcome of Patients With Human Epidermal Growth Factor Receptor 2-Positive Primary Breast Cancer: Analysis From the ALTTO Phase III Randomized Trial. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 2017, 35:1421–1429. Kim HJ, Kwon H, Lee JW, Kim HJ, Lee SB, et al. Metformin increases survival in hormone receptor-positive, HER2-positive breast cancer patients with diabetes. Breast cancer research: BCR. 2015;17:64. Phoenix KN, Vumbaca F, Claffey KP. Therapeutic metformin/AMPK activation promotes the angiogenic phenotype in the ERalpha negative MDA-MB-435 breast cancer model. Breast cancer research treatment. 2009;113:101–11. Vacante F, Senesi P, Montesano A, Paini S, Luzi L, Terruzzi I: Metformin Counteracts HCC Progression and Metastasis Enhancing KLF6/p21 Expression and Downregulating the IGF Axis. International journal of endocrinology 2019, 2019:7570146. Lin H, Li N, He H, Ying Y, Sunkara S, Luo L, Lv N, Huang D, Luo Z. AMPK Inhibits the Stimulatory Effects of TGF-β on Smad2/3 Activity, Cell Migration, and Epithelial-to-Mesenchymal Transition. Mol Pharmacol. 2015;88:1062–71. Saini N, Yang X. Metformin as an anti-cancer agent: actions and mechanisms targeting cancer stem cells. Acta Biochim Biophys Sin (Shanghai). 2018;50:133–43. Banerjee P, Surendran H, Chowdhury DR, Prabhakar K, Pal R. Metformin mediated reversal of epithelial to mesenchymal transition is triggered by epigenetic changes in E-cadherin promoter. J Mol Med. 2016;94:1397–409. Chou CC, Lee KH, Lai IL, Wang D, Mo X, Kulp SK, Shapiro CL, Chen CS. AMPK reverses the mesenchymal phenotype of cancer cells by targeting the Akt-MDM2-Foxo3a signaling axis. Cancer research. 2014;74:4783–95. Jin D, Guo J, Wu Y, Chen W, Du J, et al. Metformin-repressed miR-381-YAP-snail axis activity disrupts NSCLC growth and metastasis. Journal of experimental clinical cancer research: CR. 2020;39:6. Song L, Guo J, Chang R, Peng X, Li J, Xu X, Zhan X, Zhan L. LKB1 obliterates Snail stability and inhibits pancreatic cancer metastasis in response to metformin treatment. Cancer Sci. 2018;109:1382–92. Chengye W, Yu T, Ping S, Deguang S, Keyun W, et al. Metformin reverses bFGF-induced epithelial-mesenchymal transition in HCC cells. Oncotarget. 2017;8:104247–57. Sun C, Li X, Guo E, Li N, Zhou B, et al. MCP-1/CCR-2 axis in adipocytes and cancer cell respectively facilitates ovarian cancer peritoneal metastasis. Oncogene. 2020;39:1681–95. Liu Z, Ren L, Liu C, Xia T, Zha X, Wang S. Phenformin Induces Cell Cycle Change, Apoptosis, and Mesenchymal-Epithelial Transition and Regulates the AMPK/mTOR/p70s6k and MAPK/ERK Pathways in Breast Cancer Cells. PloS one. 2015;10:e0131207. Gong Y, Wang C, Jiang Y, Zhang S, Feng S, Fu Y, Luo Y: Metformin Inhibits Tumor Metastasis through Suppressing Hsp90α Secretion in an AMPKα1-PKCγ Dependent Manner. Cells 2020, 9. Hakimee H, Hutamekalin P, Tanasawet S, Chonpathompikunlert P, Tipmanee V, Sukketsiri W. Metformin Inhibit Cervical Cancer Migration by Suppressing the FAK/Akt Signaling Pathway. Asian Pacific journal of cancer prevention: APJCP. 2019;20:3539–45. Dirat B, Ader I, Golzio M, Massa F, Mettouchi A, et al. Inhibition of the GTPase Rac1 mediates the antimigratory effects of metformin in prostate cancer cells. Mol Cancer Ther. 2015;14:586–96. Li Z, Wang L, Luo N, Zhao Y, Li J, Chen Q, Tian Y. Metformin inhibits the proliferation and metastasis of osteosarcoma cells by suppressing the phosphorylation of Akt. Oncol Lett. 2018;15:7948–54. Vazquez-Martin A, Oliveras-Ferraros C, Cufí S, Del Barco S, Martin-Castillo B, Lopez-Bonet E, Menendez JA. The anti-diabetic drug metformin suppresses the metastasis-associated protein CD24 in MDA-MB-468 triple-negative breast cancer cells. Oncol Rep. 2011;25:135–40. Cabello P, Pineda B, Tormo E, Lluch A, Eroles P. The Antitumor Effect of Metformin Is Mediated by miR-26a in Breast Cancer. International journal of molecular sciences 2016, 17. Zhang J, Shen C, Wang L, Ma Q, Xia P, Qi M, Yang M, Han B. Metformin inhibits epithelial-mesenchymal transition in prostate cancer cells: involvement of the tumor suppressor miR30a and its target gene SOX4. Biochem Biophys Res Commun. 2014;452:746–52. Bao X, Zhao L, Guan H, Li F. Inhibition of LCMR1 and ATG12 by demethylation-activated miR-570-3p is involved in the anti-metastasis effects of metformin on human osteosarcoma. Cell death disease. 2018;9:611. Yan L, Zhou J, Gao Y, Ghazal S, Lu L, et al. Regulation of tumor cell migration and invasion by the H19/let-7 axis is antagonized by metformin-induced DNA methylation. Oncogene. 2015;34:3076–84. Li P, Tong L, Song Y, Sun J, Shi J, Wu Z, Diao Y, Li Y, Wang Z. Long noncoding RNA H19 participates in metformin-mediated inhibition of gastric cancer cell invasion. Journal of cellular physiology. 2019;234:4515–27. Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011;144:646–74. Gerhardt H, Semb H. Pericytes: gatekeepers in tumour cell metastasis? J Mol Med. 2008;86:135–44. Raza A, Franklin MJ, Dudek AZ. Pericytes and vessel maturation during tumor angiogenesis and metastasis. Am J Hematol. 2010;85:593–8. Orecchioni S, Reggiani F, Talarico G, Mancuso P, Calleri A, et al. The biguanides metformin and phenformin inhibit angiogenesis, local and metastatic growth of breast cancer by targeting both neoplastic and microenvironment cells. Int J Cancer. 2015;136:E534–44. Wang JC, Li GY, Wang B, Han SX, Sun X, et al. Metformin inhibits metastatic breast cancer progression and improves chemosensitivity by inducing vessel normalization via PDGF-B downregulation. Journal of experimental clinical cancer research: CR. 2019;38:235. Kang YT, Hsu WC, Ou CC, Tai HC, Hsu HT, Yeh KT, Ko JL. Metformin Mitigates Nickel-Elicited Angiopoietin-Like Protein 4 Expression via HIF-1α for Lung Tumorigenesis. International journal of molecular sciences 2020, 21. Ding L, Liang G, Yao Z, Zhang J, Liu R, et al. Metformin prevents cancer metastasis by inhibiting M2-like polarization of tumor associated macrophages. Oncotarget. 2015;6:36441–55. Supplementary Files metforminNOS.xlsx Riskofbiasgraph.pdf MetforminPRISMA2009checklist.doc Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-56326","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research article","associatedPublications":[],"authors":[{"id":1466616,"identity":"d1cd5eb3-0e60-48dc-9a3c-a2e7d6f948c0","order_by":0,"name":"Ming Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIie3OsQrCMBCA4SsFXYpd20H0EQKBIhTsq7QIdgni6OBwIHR19T0E54SALi1dO7gJDuIguIqY4B7rJph/uRvugwOw2X42AuCDRLW5X5AQxVdEK+60JORQyUszP463QhQBLOIMuxU3k3I2jRk5T3ZckzLP0JulH/5hEWVETiJNnEJmGHjETOrrm1DU5NmGNIyeFBkT0ARbkLC5Rq4iacDFapTuc1p4zEx6NaN39pCJv5GiuS3j/rpbmsmQQydQU/3DAVK1dYz3qgGCe1MzAR8/3dpsNtu/9gLos033s9PiygAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-4901-840X","institution":"Department of Breast Surgery, The First Hospital of Jilin University, Changchun 130021, People’s Republic of China","correspondingAuthor":true,"prefix":"","firstName":"Ming","middleName":"","lastName":"Yang","suffix":""},{"id":1466617,"identity":"bf9fcef7-7820-49c5-8607-5f658aba81ce","order_by":1,"name":"Yueyuan Wang","email":"","orcid":"","institution":"Jilin University First Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yueyuan","middleName":"","lastName":"Wang","suffix":""},{"id":1466618,"identity":"d4bacbd5-2b78-46d9-b749-35ce706c9866","order_by":2,"name":"Zhihao Zhang","email":"","orcid":"","institution":"Jilin University First Hospital","correspondingAuthor":false,"prefix":"","firstName":"Zhihao","middleName":"","lastName":"Zhang","suffix":""},{"id":1466619,"identity":"1a08ba40-4ae9-4b85-b038-e5599978d631","order_by":3,"name":"Jingyu Peng","email":"","orcid":"","institution":"Jilin University First Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jingyu","middleName":"","lastName":"Peng","suffix":""},{"id":1466620,"identity":"7243a193-2f6a-4a0e-93d1-b78625e032fa","order_by":4,"name":"Xiao Xie","email":"","orcid":"","institution":"Jilin University First Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xiao","middleName":"","lastName":"Xie","suffix":""},{"id":1466621,"identity":"d898d64e-eb07-48ae-8f07-af3bd0db10f1","order_by":5,"name":"Xue Wei","email":"","orcid":"","institution":"Jilin University First Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xue","middleName":"","lastName":"Wei","suffix":""}],"badges":[],"createdAt":"2020-08-09 11:19:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-56326/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-56326/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":1976144,"identity":"15cfdc35-9aba-4906-b6b3-871bef345ebb","added_by":"auto","created_at":"2020-08-18 17:24:51","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":639630,"visible":true,"origin":"","legend":"Study selection. Note. n: number","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Fig1.jpg"},{"id":1976145,"identity":"b2da0474-9d6f-4f3f-826c-ab292e0b2848","added_by":"auto","created_at":"2020-08-18 17:24:52","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":576462,"visible":true,"origin":"","legend":"Summary of pooled risk estimates of all breast cancer patients. The association between metformin and general anti-tumor therapy combination used in women with breast cancer and (A) All-type of studies, (B) subgroup of RCTs and (C) subgroup of retrospective cohort studies. Note. HR: hazard ratio, CI: confidence intervals, SE: standard error","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Fig2.jpg"},{"id":1976146,"identity":"7d08e97b-3497-4201-86de-e5eaa765b142","added_by":"auto","created_at":"2020-08-18 17:24:52","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":458481,"visible":true,"origin":"","legend":"Summary of pooled risk estimates of breast cancer patients with T2DM. The association between metformin and general anti-tumor therapy combination used in women with breast cancer and T2DM. (A) All-type of studies, (B) subgroup of retrospective cohort studies. Note. HR: hazard ratio, CI: confidence intervals, SE: standard error","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Fig3.jpg"},{"id":1976147,"identity":"43f9251e-804f-421a-b6d5-7d3a2d3e805d","added_by":"auto","created_at":"2020-08-18 17:24:52","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":215816,"visible":true,"origin":"","legend":"Funnel plot about publication of included studies. ","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Fig4.jpg"},{"id":1976148,"identity":"7cbac229-bd5b-482b-9338-9811d47e7f42","added_by":"auto","created_at":"2020-08-18 17:24:53","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":700040,"visible":true,"origin":"","legend":"The possible mechanisms for metformin to suppressed tumor metastasis.","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Fig5.jpg"},{"id":13578719,"identity":"bf0482d7-58d9-45b5-adcd-cc0b8a779578","added_by":"auto","created_at":"2021-09-17 04:16:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":790136,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/8ed710ac-efc8-4a22-980f-ea59d35dda14.pdf"},{"id":1976150,"identity":"c9c9f3a1-ec47-46ec-9f48-8979d8eed18b","added_by":"auto","created_at":"2020-08-18 17:24:53","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":11779,"visible":true,"origin":"","legend":"","description":"","filename":"metforminNOS.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/metforminNOS.xlsx"},{"id":1976151,"identity":"c02f4287-e298-4509-a666-38f23ca9c82d","added_by":"auto","created_at":"2020-08-18 17:24:53","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":243768,"visible":true,"origin":"","legend":"","description":"","filename":"Riskofbiasgraph.pdf","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/Riskofbiasgraph.pdf"},{"id":1976152,"identity":"792a04e0-63ef-49e4-881f-4e15d8c9e98c","added_by":"auto","created_at":"2020-08-18 17:24:54","extension":"doc","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":74240,"visible":true,"origin":"","legend":"","description":"","filename":"MetforminPRISMA2009checklist.doc","url":"https://assets-eu.researchsquare.com/files/rs-56326/v1/MetforminPRISMA2009checklist.doc"}],"financialInterests":"","formattedTitle":"\u003cp\u003eMetformin May Block the Way Breast Cancer Metastasis: A Meta-analysis and Mechanism Review\u003c/p\u003e","fulltext":[{"header":"Background","content":" \u003cp\u003eBreast cancer has a high incidence in female tumors, which affects the health of women around the world. In a sample survey conducted in mainland China in 2019, women with T2DM had an increased risk of breast cancer [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. A lot of clinical and epidemiological evidences have linked hyperinsulinemia, insulin resistance, and diabetes to poor breast cancer outcomes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In addition, early breast cancer patients with T2DM had an increased likelihood of recurrence and metastasis [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], implicating that T2DM might be a dependent risk factor of breast cancer prognosis. There are various treatments for early breast cancer, but for breast cancer with distant metastasis, the effective method is still a difficulty. Therefore, prevention breast cancer patients from metastasis is economical and available.\u003c/p\u003e \u003cp\u003eMetformin, extracted from \u003cem\u003eGalega\u003c/em\u003e officinalis (the French lilac) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], is an anti-hyperglycemia drug and insulin sensitizer used in the therapy of T2DM, a chronic disease characterized by insulin resistance [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In recent years, metformin has also been reported to reduce cancer risk and improve clinical outcomes [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. This drug inhibits tumor growth and cell proliferation in most breast cancer subtypes in vitro at different degrees [\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Furthermore, the metformin targets to breast cancer stem cells (BCSCs), reduces tumor mass and prolongs remission with doxorubicin [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Based on these basic studies, various of clinic studies were conducted to explore whether adjuvant metformin may contribute to the prognosis of breast cancer patients [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe here provided a meta-analysis to explore whether metformin adjuvant therapy could reduce breast cancer metastasis and prolonged the distant metastasis-free survival (DMFS). We also collected the probable mechanisms about metformin. We hoped this study might help to deep comprehension of the role of metformin in cancer treatment.\u003c/p\u003e "},{"header":"Methods","content":" \u003cp\u003eStudy selection\u003c/p\u003e \u003cp\u003eWe searched all published articles up to May 2020 in database of Pubmed, EMbase, Web of science, Cochrane Library and Chinese database of CNKI, WanFang and Sinomed for relevant studies. The keywords for searching included \u0026ldquo;metformin\u0026rdquo;, \u0026ldquo;breast neoplasms\u0026rdquo;, \u0026ldquo;therapies, drug\u0026rdquo; and \u0026ldquo;neoplasm metastasis\u0026rdquo;. Contralateral axillary lymph node metastasis is controversial in the clinical stage of breast cancer [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. We here included \u0026ldquo;lymphatic metastasis\u0026rdquo; in our search terms as well. After that, the selected studies were manually screened and only human subjects and original articles were considered eligible. Selected publications were all in English or Chinese.\u003c/p\u003e \u003cp\u003eInclusion and exclusion criteria\u003c/p\u003e \u003cp\u003eSince aiming to investigate whether metformin could suppress breast cancer metastasis, we set inclusion and exclusion criteria for the meta-analysis:\u003c/p\u003e \u003cp\u003e \u003col style=\"list-style-type: lower-roman;\"\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAll patients were diagnosed as primary breast cancer without metastatic disease before they got anticancer treatment;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe breast cancer patients received not only antihyperglycemic therapy;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe patients we included were divided into two group. The \u0026ldquo;metformin group\u0026rdquo; was defined as the breast cancer patients who received metformin including combination with other antihyperglycemic drugs during breast cancer therapy, while the \u0026ldquo;non-metformin group\u0026rdquo; was defined as patients who did not use metformin but chose other hypoglycemic drugs or they did not received any antihyperglycemic therapy during anti-tumor treatment;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThere were various methods to treat breast cancer systematically, thus, we set no limit on the consistency of other treatments except antihyperglycemic therapy;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe number of patients who ended with distant metastasis and the number of patients who participated in the studies, or relevant Kaplan-Meier curves, or HRs, RRs with associated 95% CIs between study groups and control groups were provided;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eRCT, cross-sectional studies or cohort studies published as original manuscript.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eThe TNM stage of breast cancer was based on the criteria of American joint committee on cancer (AJCC) 8th edition cancer staging manual and M-phase was considered as \u0026ldquo;distant metastasis\u0026rdquo; [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eData extraction and quality assessment\u003c/p\u003e \u003cp\u003eTwo authors reviewed each selected article independently and extracted relevant data with a structured table. We extracted data containing: authors, year of publication, country which the study was conducted in, study type, sample size, follow-up time, the average or median age of study population, the number of breast cancer patients with T2DM, other treatment than antihyperglycemic therapy, metformin dose, the distant metastasis number and total number of study group and control group/HR/RR. If there was any disagreement, the final decision would be made by the group discussion. Our work was performed according to the Preferred Reporting Items for Systematic Review ang Meta-Analysis Protocols (PRISMA-P) 2015 statement. The quality of retrospective cohort studies we intended to include was assessed with reference to the NOS, which was composed of three parts: selection, comparability and exposure, and only the study score was not less than 6 stars (up to 9 stars) could be accepted [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The rest of studies were RCTs, thus we chose Chcorane Risk of Bias tool to assess their quality.\u003c/p\u003e \u003cp\u003eStatistical analyses\u003c/p\u003e \u003cp\u003eIf relative RRs and HRs with associated 95% CIs were not available, we would extract the metastasis numbers and total numbers in study group and control group, then used STATA14.0 (Stata, College Station) to calculated RRs and associated 95% CI. As the articles published before, the distinction between relative RR and HR was ignored [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. HR/RR\u0026thinsp;\u0026lt;\u0026thinsp;1 meant that metformin protected the breast cancer patients from metastasis, which is inversed when HR/RR\u0026thinsp;\u0026gt;\u0026thinsp;1. Mantel-Haenszel random-effects model was chosen because of the assumption that studies might be different for random errors and between study variability and the pooled HRs/RRs with associated 95% CI were obtained upon generic inverse variance approach, which allowed the weight of each study based on variance and adjusted point estimates and standard errs from individual study to be extracted and combined [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], by Revman 5.3 software (RevMan, The Cochrane Collaboration). The Cochcrane Q test and \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e statistic were used to assess and quantify heterogeneity, when \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;\u0026lt;\u0026thinsp;25%, no significant heterogeneity; 25% \u0026minus;\u0026thinsp;50%, low heterogeneity; 50% \u0026minus;\u0026thinsp;75%, medium heterogeneity; \u0026gt; 75%, high heterogeneity [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Due to the limitation of the quantity of studies, the egger\u0026rsquo;s test was appropriate and we meant to use Funnel plot to show the publication bias of the included studies. A two-tailed \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was thought statistically significant.\u003c/p\u003e "},{"header":"Results","content":" \u003cp\u003eStudies included in the meta-analysis\u003c/p\u003e \u003cp\u003eFrom the 7 databases, we achieved 1121 literatures with search terms. 773 articles were left after deleting the duplication, while 46 articles were eligible for further full text assessment. After carefully reading full text, 8 studies met the inclusion criteria. The details of these studies were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe characteristics of studies and patients\u003c/p\u003e \u003cp\u003eThe 8 studies published before May 2020, included 13919 breast cancer patients, with a maximum sample size of 6769 and a minimum sample size of 61 participants. 4 in China[\u003cspan additionalcitationids=\"CR25 CR26\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], 1 in South Korea[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], 1 in America[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], 1 in Germany[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], 1 in Egypt[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Moreover, 2 were RCTs while 6 were retrospective cohort studies. Among these studies, 3598(25.73%) patients received metformin adjuvant therapy and 5784(41.56%) patients combined with T2DM. For other features of included studies, check Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of included studies\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAuthors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYear of publication\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCountry\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStudy type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNOS score\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSample size\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eThe numder of breast cancer patients with T2DM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eFollow-up time(average or median, month)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eAge (average or median, range, year)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003emetformin dose\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eother treatment than antihyperglycemic therapy\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoley Bayraktar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAmercia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e130\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e41(21\u0026ndash;87)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAll received surgery and adjuvant chemotherapy(if necessary)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTangyan He\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e61.25(42\u0026ndash;82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAll received surgery, chemotherapy and hormonal therapy(if necessary)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLouis Jacob\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGermany\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e55.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e71.4(40\u0026ndash;90)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHee Jeong Kim\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e6967\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e386\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eChemotherapy and Hormonal therapy(if necessary)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeili Min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e55.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e64.4(55\u0026ndash;73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003esurgery\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSahar Mohammed EL-Haggar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEgypt\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003enot applicable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e48.8(40\u0026ndash;65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e850\u0026nbsp;mg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAll recevievd Chemotherapy and 83.3% Hormonal therapy(if necessary)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHaiyan Wang\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003enot applicable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e57.2(45\u0026ndash;76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e850\u0026nbsp;mg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003esurgery\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWenjie Zhu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eretrospective cohort studies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e171\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e52.4(24\u0026ndash;79)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003enot mentioned\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAll received surgery, chemotherapy and hormonal therapy(if necessary)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eMetastasis\u003c/p\u003e \u003cp\u003eA total of 8 studies investigated the relationship between adjuvant metformin and distant metastasis of breast cancer but only 3 of them reported that added metformin into general anti-tumor therapy prolonged DMFS with statistically significant. The analysis showed that metformin addition is related with inhibition of metastasis of breast cancer (HR\u0026thinsp;=\u0026thinsp;0.69, 95% CI\u0026thinsp;=\u0026thinsp;0.57\u0026ndash;0.82, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Because different types of studies were included, we conducted subgroup analysis for RCTs (HR\u0026thinsp;=\u0026thinsp;0.35, 95% CI\u0026thinsp;=\u0026thinsp;0.16\u0026ndash;0.78, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) and retrospective cohort studies (HR\u0026thinsp;=\u0026thinsp;0.71, 95% CI\u0026thinsp;=\u0026thinsp;0.59\u0026ndash;0.86, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0003, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC) respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eConsidering that breast cancer patients using metformin were likely to be T2DM, we selected patients with breast cancer and T2DM from the included studies for subgroup analysis. Ultimately, 7 studies were eligible while the study population of Sahar\u0026rsquo;s research were all nondiabetic breast cancer women. It turned out that metformin protected T2DM breast cancer patients from metastasis (HR\u0026thinsp;=\u0026thinsp;0.68, 95% CI\u0026thinsp;=\u0026thinsp;0.57\u0026ndash;0.82, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). We performed subgroup analysis for 6 retrospective cohort studies only (HR\u0026thinsp;=\u0026thinsp;0.69, 95% CI\u0026thinsp;=\u0026thinsp;0.57\u0026ndash;0.83, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), for just 1 RCT included patients with T2DM.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePublication bias\u003c/p\u003e \u003cp\u003eThe publication bias was evaluated by Egger\u0026rsquo;s test and displayed by Funnel plot. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, since associated-clinic trials was still low in quantity, the publication bias was difficult to avoid completely. The result of Egger\u0026rsquo;s test of this meta-analysis indicated there was no significant publication bias between the 8 literatures (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.15), meaning the result was acceptable and believable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e "},{"header":"Discussion","content":" \u003cp\u003eDiscussion on the meta-analysis\u003c/p\u003e \u003cp\u003eDiscovery anti-tumor drugs is a luxurious and time-consuming process, also the percentage of drugs meets the clinic is quite a little. Thus, the development of new functions of existing drugs has become a hot study topic. It is known to all that obesity and T2DM relate with poor prognosis of breast cancer closely. Metformin, the most widely used antihyperglycemic drug to treat T2DM, could maintain weight loss as well [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. It has been verified that most tumors are sensitive to metformin [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Consistently, metformin synergizes with conventional anticancer therapy to kill tumors and repress migration [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. But the outcomes of clinical studies of metformin in the treatment of breast cancer were not entirely positive [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], the metformin effect in breast cancer treatment was still under discussion. In this study, we intended to estimate the connection between metformin and distant breast cancer distant metastasis. With the forest plot (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), we demonstrated that adjuvant metformin might contribute to suppress breast cancer metastasis.\u003c/p\u003e \u003cp\u003eThe adverse effects brought by metformin should not be neglected, while gastrointestinal distress, including transient mild nausea and moderate diarrhea, was the toxicity that people usually met during metformin treatment [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. There was no grade 3 and 4 treatment-related adverse event (TRAE) reported in the included publications.\u003c/p\u003e \u003cp\u003eThis meta-analysis had several limitations. First, the small sample size limited to obtain firm conclusions. Second, the dose of metformin could not adjust to consistent because most of the trails were retrospective and the individual distinctions among the patients were unavoidable. It has been proved that adjuvant metformin therapy repressed HER 2\u0026thinsp;+\u0026thinsp;breast cancer cells [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] while ER- breast cancer cells resisted to this drug [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Thus, the effects of metformin might depend on the molecular types of breast cancer. Here we recommended that subgroups for different hormone receptors status should be designed in the future clinical trials.\u003c/p\u003e \u003cp\u003eThe mechanisms of metformin to suppress tumor metastasis\u003c/p\u003e \u003cp\u003eInhibiting tumor metastasis by metformin was a complex process of multiple pathways, including: AMPK activation, epithelial mesenchymal transition (EMT) inversion, DNA methylation modulation, interfering with TGF-β pathway and tumor microenvironment. Moreover, N-cadherin, vimentin, β-catenin, snail, Rac1 and MMP-2/9 were downregulated while E-cadherin and phosphorylated AMPK increased, which resulted in tighter intercellular connections, weaker migration and movement of tumor cells. Metformin affected insulin-like growth factor (IGF) pathway by repressing IGF-1 receptor and IGF-2 molecule [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, metformin mediated different pathways to prevent metastasis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eIntercellular reaction\u003c/h2\u003e \u003cp\u003eAMPK, a widely known metformin effector, was activated in two pathways. One way was that metformin activated liver kinase B1 (LKB1), the upstream of AMPK, and the other pathway was mitochondrial complex I activation decreased ATP/AMP ratio under metformin stimulation, which triggered AMPK activation indirectly [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Phosphorylated AMPK functioned as an inhibitor to repress a series of moleculars activation, containing: STAT3, smad-2/3, Akt, ERK, mTOR, PKCγ and Twist. Snail, which was the downstream of ERK and Y-box binding protein-1 (YB-1) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e], a oncogenic transcription/translation factor, and also the direct target gene of metastasis-related gene YAP [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. This protein regulated E-cad expression with Twist. Additionally, it participated in E-cad promoter hypomethylation modulation with Slug [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Metformin induced Snail ubiquitination after LKB1 phosphorylation, which helped Snail\u0026rsquo;s interaction with E3 ligase FBXL14 [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Furthermore, metformin decreased Twist with obliterating interaction between GSK-3β and Twist via reducing Akt/GSK-3β pathway [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. mTOR, of which inhibition under metformin therapy mediated suppression of HIF-1α/VEGF-A and p70s6k [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e], was another downstream molecule of Akt. In addition, metformin augmented Foxo3a nuclear localization and protein stabilization to active Foxo3a with IKKβ repression and MDM2 phosphorylation involvement, leading to the level of E-cad increase [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. For protein kinase Cγ (PKCγ), which was attenuated after AMPK-α1 phosphorylation, it modulated Hs90α activation [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe Rac1 and RhoA GTP downstream migratory protein took charge of the migration of cell, thus they were required in cancer migration and metastasis. Metformin downregulates Rac1 in different pathways. Firstly, metformin suppressed FAK/Akt signaling pathway [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e] or CXCL12/CXCR4 [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] to decrease downstream factors Rac1 and RhoA GTP expression. Secondly, metformin elevated the level of phosphatase and tensin (PTEN), a protein controls tumor metastasis, to inhibit Akt/Rac1 axis [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. Thirdly, Rac1 GTP was reduced by metformin-mediated cAMP increase [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Moreover, CD24, a mucin-like adhesion molecule, enhanced the metastasis potential of malignant cells. Distant metastasis in patients with refractory breast cancer was mainly composed of CD24 positive cells, which was thought as a marker indicating poor prognosis of breast cancer. Recently, CD24 has been confirmed to significantly be downregulated by metformin [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMicro-RNA, modulators of many cellular signaling pathways, have been verified to take parts in metformin treatment. MiR-26a was enhanced under metformin stimulation to inhibit Akt phosphorylation [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. Similarly, miR-381, upregulated by metformin, significantly interfered with YAP transcription to affect Snail [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. MiR-30a, another member upregulated by metformin, attenuated SOX4, which was a oncogenic transcription factor and epithelial mesenchymal transformation (EMT) regulator, reversing the process of EMT [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. Because of the DNA methylation, metformin therapy increased the level of mir-570-3p, while decreased lncRNA H19 by metformin-induced DNA methylation. The former was shown to reduce the invasion of tumor cells through inhibiting LCMR1 and ATG12 [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e], while the latter was also been implicated to control tumor metastasis by not only reducing MMP-9, but also elevating AMPK phosphorylation and let-7, a potent tumor suppressor microRNA [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eEffects on tumor microenvironment cells\u003c/h2\u003e \u003cp\u003eThe word \u0026ldquo;tumor microenvironment\u0026rdquo; was created in 2011, and defined to include endothelial cells, pericytes and immune inflammatory cells [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. Endothelial cells were shown to benefit to developmental and tumor-associated angiogenesis, while pericytes wrapped around the endothelial tubing of blood vessels and prevented the tumors from entering the circulatory system, making it possible to reduce subsequent hematogenous dissemination [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Metformin downregulated micro-vessel density (MVD) by inhibiting platelet-derived growth factor B (PDGF-B), ending with reducing the ratio of endothelial cells/ pericytes, leakage and hypoxia, namely \u0026ldquo;vessel normalization\u0026rdquo; [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. Moreover, Angiopoietin-like protein 4 (ANGPIL4) was decreased during metformin treatment after HIF-1α suppression [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e]. Another modulation of metformin to block tumor metastasis was the attenuation of M2-like polarization of tumor associated macrophages (TAM) with phosphorylated AMPK α1 [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e "},{"header":"Conclusion","content":" \u003cp\u003eTo the best of our knowledge, this was the first meta-analysis focused on the relationship between metformin and distant metastasis of breast cancer. The study showed that metastasis repression could be achieved by receiving metformin and general breast cancer treatment combination, and the association was supported by a wide range of basic studies, implicating the possibility for metformin becoming a new anticancer drug. However, this report was lack of prospective research, therefore, the veracity of conclusion remained to be verified. Further studies investigating connection metastasis of breast cancer and metformin were expected.\u003c/p\u003e "},{"header":"Abbreviations","content":" \u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCNKI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eChina National Knowledge Infrastructure; RCT:randomized controlled trial; NOS:Newcastle-Ottawa Scale; HR:hazard ratio; RR:risk ratio; CI:confidence interval; DMFS:distant metastasis-free survival; T2DM:type 2 diabetes mellitus; BCSC:breast cancer stem cell; AJCC:American joint committee on cancer; ER:estrogen receptor; TRAE:treatment-related adverse event; IGF:insulin-like growth factor; AMPK:adenosine 5\u0026rsquo;-monophosphate-ativatied protein kinase; LKB1:liver kinase B1; YB-1:Y-box binding protein-1; PKCγ:protein kinase Cγ; PTEN:phosphatase and tensin; EMT:epithelial mesenchymal transformation; TGF-β:transforming growth factor; ERK:extracellular signal regulated kinase; STAT:Signal Transducer and Activator of Transcription; Akt:protein kinase B; IKKβ:inhibitor kappa B kinase β; CXCL:C-X-C motif ligand; CXCR:C-X-C motif receptor; cAMP:cyclic adenosine moriophosphate; PDGF-B:platelet-derived growth factor B; MVD:micro-vessel density; ANGPIL4:Angiopoietin-like protein 4; VEGF:vascular epidermal growth factor; TAM:tumor associated macrophages.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets supporting the conclusions of this study are included within the article and its additional files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYYW and ZHZ screened the reference. YYW drafted the manuscript and analyzed most of the data. YYW,JYP,XX and XW discussed and revised themanuscript. All authors read and approved final manuscript. Thanks to all authors for their time and effort and department of breast surgery from the first hospital of Jilin University for technical support. All authors have read and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll coauthors were offered the opportunity to read the final manuscript and agreed to publish.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the First Hospital of Jilin University and Jilin University.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e \u003cspan\u003eQi J, He P, Yao H, Song R, Ma C, Cao M, Cui B, Ning G. Cancer risk among patients with type 2 diabetes: A real-world study in Shanghai, China. Journal of diabetes. 2019;11:878\u0026ndash;83.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eGoodwin PJ. Insulin in the adjuvant breast cancer setting: a novel therapeutic target for lifestyle and pharmacologic interventions? Journal of clinical oncology: official journal of the American Society of Clinical Oncology. 2008;26:833\u0026ndash;4.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eMa FJ, Liu ZB, Qu L, Hao S, Liu GY, Wu J, Shao ZM. Impact of type 2 diabetes mellitus on the prognosis of early stage triple-negative breast cancer in People's Republic of China. Onco Targets Ther. 2014;7:2147\u0026ndash;54.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSchrauder MG, Fasching PA, H\u0026auml;berle L, Lux MP, Rauh C, et al. Diabetes and prognosis in a breast cancer cohort. J Cancer Res Clin Oncol. 2011;137:975\u0026ndash;83.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eAdak T, Samadi A, \u0026Uuml;nal AZ, Sabuncuoğlu S. A reappraisal on metformin. Regulatory toxicology pharmacology: RTP. 2018;92:324\u0026ndash;32.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHe H, Ke R, Lin H, Ying Y, Liu D, Luo Z. Metformin, an old drug, brings a new era to cancer therapy. Cancer journal (Sudbury Mass). 2015;21:70\u0026ndash;4.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHenderson D, Frieson D, Zuber J, Solomon SS. Metformin Has Positive Therapeutic Effects in Colon Cancer and Lung Cancer. Am J Med Sci. 2017;354:246\u0026ndash;51.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eCoyle C, Cafferty FH, Vale C, Langley RE. Metformin as an adjuvant treatment for cancer: a systematic review and meta-analysis. Annals of oncology: official journal of the European Society for Medical Oncology. 2016;27:2184\u0026ndash;95.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBen Sahra I, Laurent K, Loubat A, Giorgetti-Peraldi S, Colosetti P, Auberger P, Tanti JF, Le Marchand-Brustel Y, Bost F. The antidiabetic drug metformin exerts an antitumoral effect in vitro and in vivo through a decrease of cyclin D1 level. Oncogene. 2008;27:3576\u0026ndash;86.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eZakikhani M, Dowling R, Fantus IG, Sonenberg N, Pollak M. Metformin is an AMP kinase-dependent growth inhibitor for breast cancer cells. Cancer research. 2006;66:10269\u0026ndash;73.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eDowling RJ, Zakikhani M, Fantus IG, Pollak M, Sonenberg N. Metformin inhibits mammalian target of rapamycin-dependent translation initiation in breast cancer cells. Cancer research. 2007;67:10804\u0026ndash;12.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eLiu B, Fan Z, Edgerton SM, Deng XS, Alimova IN, Lind SE, Thor AD. Metformin induces unique biological and molecular responses in triple negative breast cancer cells. Cell cycle (Georgetown Tex). 2009;8:2031\u0026ndash;40.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHirsch HA, Iliopoulos D, Tsichlis PN, Struhl K. Metformin selectively targets cancer stem cells, and acts together with chemotherapy to block tumor growth and prolong remission. Cancer research. 2009;69:7507\u0026ndash;11.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eJiralerspong S, Palla SL, Giordano SH, Meric-Bernstam F, Liedtke C, et al. Metformin and pathologic complete responses to neoadjuvant chemotherapy in diabetic patients with breast cancer. Journal of clinical oncology: official journal of the American Society of Clinical Oncology. 2009;27:3297\u0026ndash;302.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eZhao Y, Gong C, Wang Z, Zhang J, Wang L, et al. A randomized phase II study of aromatase inhibitors plus metformin in pre-treated postmenopausal patients with hormone receptor positive metastatic breast cancer. Oncotarget. 2017;8:84224\u0026ndash;36.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eMagnoni F, Colleoni M, Mattar D, Corso G, Bagnardi V, et al: Contralateral Axillary Lymph Node Metastases from Breast Carcinoma: Is it Time to Review TNM Cancer Staging? Annals of surgical oncology 2020.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eGiuliano AE, Connolly JL, Edge SB, Mittendorf EA, Rugo HS, Solin LJ, Weaver DL, Winchester DJ, Hortobagyi GN. Breast Cancer-Major changes in the American Joint Committee on Cancer eighth edition cancer staging manual. Cancer J Clin. 2017;67:290\u0026ndash;303.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eFu Y, Lee CH, Chi CC. Association of Psoriasis With Inflammatory Bowel Disease: A Systematic Review and Meta-analysis. JAMA dermatology. 2018;154:1417\u0026ndash;23.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSoneji S, Barrington-Trimis JL, Wills TA, Leventhal AM, Unger JB, et al. Association Between Initial Use of e-Cigarettes and Subsequent Cigarette Smoking Among Adolescents and Young Adults: A Systematic Review and Meta-analysis. JAMA pediatrics. 2017;171:788\u0026ndash;97.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSiristatidis C, Sergentanis TN, Kanavidis P, Trivella M, Sotiraki M, Mavromatis I, Psaltopoulou T, Skalkidou A, Petridou ET. Controlled ovarian hyperstimulation for IVF: impact on ovarian, endometrial and cervical cancer\u0026ndash;a systematic review and meta-analysis. Hum Reprod Update. 2013;19:105\u0026ndash;23.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBiswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, Alter DA. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med. 2015;162:123\u0026ndash;32.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eDerSimonian R, Laird N. Meta-analysis in clinical trials. Controlled clinical trials. 1986;7:177\u0026ndash;88.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHiggins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ. 2003;327:557\u0026ndash;60.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eMin W, Wang B, Guo A, Mao G, Zhao Y, Zhang S, He R, Min Y, Huang Y. The effect of metformin on the clinicopathological features of breast cancer with type 2 diabetes. World Journal of Oncology. 2020;11:23\u0026ndash;32.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eWang H. Effect of metformin on prognosis of breast cancer patients complicated with type 2 diabetes mellitus[in Chinese]. Heilongjiang Medicine. 2017;30:109\u0026ndash;11.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHe T: Clinical characteristics and prognosis of hormone-dependent breast cancer patients with type 2 diabetes mellitus[in Chinese]. Guangxi Medical University; 2017.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eZhu W: Effect of metformin on prognosis of breast cancer patients complicated with type 2 diabetes mellitus[in Chinese]. Shandong University; 2013.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eKim HJ, Kwon HW, Lee JW, Lee SB, Park HS, Ahn SH, Shin HN. Metformin increases survival in hormone receptor-positive, Her2-positive breast cancer patients with diabetes. Cancer research 2015, 75.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBayraktar S, Hernadez-Aya LF, Lei X, Meric-Bernstam F, Litton JK, Hsu L, Hortobagyi GN, Gonzalez-Angulo AM. Effect of metformin on survival outcomes in diabetic patients with triple receptor-negative breast cancer. Cancer. 2012;118:1202\u0026ndash;11.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eJacob L, Kostev K, Rathmann W, Kalder M. Impact of metformin on metastases in patients with breast cancer and type 2 diabetes. J Diabetes Complications. 2016;30:1056\u0026ndash;9.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eEL-H SM, El-Shitany NA, Mostafa MF, El-Bassiouny NA. Metformin may protect nondiabetic breast cancer women from metastasis. Clin Exp Metas. 2016;33:339\u0026ndash;57.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eZheng Y, Zhu J, Zhang H, Liu Y, Sun H. Metformin inhibits ovarian cancer growth and migration in vitro and in vivo by enhancing cisplatin cytotoxicity. American journal of translational research. 2018;10:3086\u0026ndash;98.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eNanni O, Amadori D, De Censi A, Rocca A, Freschi A, et al. Metformin plus chemotherapy versus chemotherapy alone in the first-line treatment of HER2-negative metastatic breast cancer. The MYME randomized, phase 2 clinical trial. Breast cancer research treatment. 2019;174:433\u0026ndash;42.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eGonzalez-Angulo AM, Meric-Bernstam F. Metformin: a therapeutic opportunity in breast cancer. Clinical cancer research: an official journal of the American Association for Cancer Research. 2010;16:1695\u0026ndash;700.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSonnenblick A, Agbor-Tarh D, Bradbury I, Di Cosimo S, Azim HA, Jr. et al: Impact of Diabetes, Insulin, and Metformin Use on the Outcome of Patients With Human Epidermal Growth Factor Receptor 2-Positive Primary Breast Cancer: Analysis From the ALTTO Phase III Randomized Trial. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 2017, 35:1421\u0026ndash;1429.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eKim HJ, Kwon H, Lee JW, Kim HJ, Lee SB, et al. Metformin increases survival in hormone receptor-positive, HER2-positive breast cancer patients with diabetes. Breast cancer research: BCR. 2015;17:64.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003ePhoenix KN, Vumbaca F, Claffey KP. Therapeutic metformin/AMPK activation promotes the angiogenic phenotype in the ERalpha negative MDA-MB-435 breast cancer model. Breast cancer research treatment. 2009;113:101\u0026ndash;11.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eVacante F, Senesi P, Montesano A, Paini S, Luzi L, Terruzzi I: Metformin Counteracts HCC Progression and Metastasis Enhancing KLF6/p21 Expression and Downregulating the IGF Axis. International journal of endocrinology 2019, 2019:7570146.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eLin H, Li N, He H, Ying Y, Sunkara S, Luo L, Lv N, Huang D, Luo Z. AMPK Inhibits the Stimulatory Effects of TGF-β on Smad2/3 Activity, Cell Migration, and Epithelial-to-Mesenchymal Transition. Mol Pharmacol. 2015;88:1062\u0026ndash;71.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSaini N, Yang X. Metformin as an anti-cancer agent: actions and mechanisms targeting cancer stem cells. Acta Biochim Biophys Sin (Shanghai). 2018;50:133\u0026ndash;43.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBanerjee P, Surendran H, Chowdhury DR, Prabhakar K, Pal R. Metformin mediated reversal of epithelial to mesenchymal transition is triggered by epigenetic changes in E-cadherin promoter. J Mol Med. 2016;94:1397\u0026ndash;409.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eChou CC, Lee KH, Lai IL, Wang D, Mo X, Kulp SK, Shapiro CL, Chen CS. AMPK reverses the mesenchymal phenotype of cancer cells by targeting the Akt-MDM2-Foxo3a signaling axis. Cancer research. 2014;74:4783\u0026ndash;95.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eJin D, Guo J, Wu Y, Chen W, Du J, et al. Metformin-repressed miR-381-YAP-snail axis activity disrupts NSCLC growth and metastasis. Journal of experimental clinical cancer research: CR. 2020;39:6.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSong L, Guo J, Chang R, Peng X, Li J, Xu X, Zhan X, Zhan L. LKB1 obliterates Snail stability and inhibits pancreatic cancer metastasis in response to metformin treatment. Cancer Sci. 2018;109:1382\u0026ndash;92.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eChengye W, Yu T, Ping S, Deguang S, Keyun W, et al. Metformin reverses bFGF-induced epithelial-mesenchymal transition in HCC cells. Oncotarget. 2017;8:104247\u0026ndash;57.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eSun C, Li X, Guo E, Li N, Zhou B, et al. MCP-1/CCR-2 axis in adipocytes and cancer cell respectively facilitates ovarian cancer peritoneal metastasis. Oncogene. 2020;39:1681\u0026ndash;95.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eLiu Z, Ren L, Liu C, Xia T, Zha X, Wang S. Phenformin Induces Cell Cycle Change, Apoptosis, and Mesenchymal-Epithelial Transition and Regulates the AMPK/mTOR/p70s6k and MAPK/ERK Pathways in Breast Cancer Cells. PloS one. 2015;10:e0131207.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eGong Y, Wang C, Jiang Y, Zhang S, Feng S, Fu Y, Luo Y: Metformin Inhibits Tumor Metastasis through Suppressing Hsp90α Secretion in an AMPKα1-PKCγ Dependent Manner. Cells 2020, 9.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHakimee H, Hutamekalin P, Tanasawet S, Chonpathompikunlert P, Tipmanee V, Sukketsiri W. Metformin Inhibit Cervical Cancer Migration by Suppressing the FAK/Akt Signaling Pathway. Asian Pacific journal of cancer prevention: APJCP. 2019;20:3539\u0026ndash;45.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eDirat B, Ader I, Golzio M, Massa F, Mettouchi A, et al. Inhibition of the GTPase Rac1 mediates the antimigratory effects of metformin in prostate cancer cells. Mol Cancer Ther. 2015;14:586\u0026ndash;96.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eLi Z, Wang L, Luo N, Zhao Y, Li J, Chen Q, Tian Y. Metformin inhibits the proliferation and metastasis of osteosarcoma cells by suppressing the phosphorylation of Akt. Oncol Lett. 2018;15:7948\u0026ndash;54.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eVazquez-Martin A, Oliveras-Ferraros C, Cuf\u0026iacute; S, Del Barco S, Martin-Castillo B, Lopez-Bonet E, Menendez JA. The anti-diabetic drug metformin suppresses the metastasis-associated protein CD24 in MDA-MB-468 triple-negative breast cancer cells. Oncol Rep. 2011;25:135\u0026ndash;40.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eCabello P, Pineda B, Tormo E, Lluch A, Eroles P. The Antitumor Effect of Metformin Is Mediated by miR-26a in Breast Cancer. International journal of molecular sciences 2016, 17.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eZhang J, Shen C, Wang L, Ma Q, Xia P, Qi M, Yang M, Han B. Metformin inhibits epithelial-mesenchymal transition in prostate cancer cells: involvement of the tumor suppressor miR30a and its target gene SOX4. Biochem Biophys Res Commun. 2014;452:746\u0026ndash;52.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eBao X, Zhao L, Guan H, Li F. Inhibition of LCMR1 and ATG12 by demethylation-activated miR-570-3p is involved in the anti-metastasis effects of metformin on human osteosarcoma. Cell death disease. 2018;9:611.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eYan L, Zhou J, Gao Y, Ghazal S, Lu L, et al. Regulation of tumor cell migration and invasion by the H19/let-7 axis is antagonized by metformin-induced DNA methylation. Oncogene. 2015;34:3076\u0026ndash;84.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eLi P, Tong L, Song Y, Sun J, Shi J, Wu Z, Diao Y, Li Y, Wang Z. Long noncoding RNA H19 participates in metformin-mediated inhibition of gastric cancer cell invasion. Journal of cellular physiology. 2019;234:4515\u0026ndash;27.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eHanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011;144:646\u0026ndash;74.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eGerhardt H, Semb H. Pericytes: gatekeepers in tumour cell metastasis? J Mol Med. 2008;86:135\u0026ndash;44.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eRaza A, Franklin MJ, Dudek AZ. Pericytes and vessel maturation during tumor angiogenesis and metastasis. Am J Hematol. 2010;85:593\u0026ndash;8.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eOrecchioni S, Reggiani F, Talarico G, Mancuso P, Calleri A, et al. The biguanides metformin and phenformin inhibit angiogenesis, local and metastatic growth of breast cancer by targeting both neoplastic and microenvironment cells. Int J Cancer. 2015;136:E534\u0026ndash;44.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eWang JC, Li GY, Wang B, Han SX, Sun X, et al. Metformin inhibits metastatic breast cancer progression and improves chemosensitivity by inducing vessel normalization via PDGF-B downregulation. Journal of experimental clinical cancer research: CR. 2019;38:235.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eKang YT, Hsu WC, Ou CC, Tai HC, Hsu HT, Yeh KT, Ko JL. Metformin Mitigates Nickel-Elicited Angiopoietin-Like Protein 4 Expression via HIF-1α for Lung Tumorigenesis. International journal of molecular sciences 2020, 21.\u003c/span\u003e \u003c/li\u003e \u003cli\u003e \u003cspan\u003eDing L, Liang G, Yao Z, Zhang J, Liu R, et al. Metformin prevents cancer metastasis by inhibiting M2-like polarization of tumor associated macrophages. Oncotarget. 2015;6:36441\u0026ndash;55.\u003c/span\u003e \u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"metformin, breast cancer, distant metastasis, AMPK, AMPK inhibitor","lastPublishedDoi":"10.21203/rs.3.rs-56326/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-56326/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMetformin, which is cheap and easy to get, is a first-line anti-hyperglycemia drug. Recently, its anti-tumor effect has been revealed. Here we performed a meta-analysis to summarize previous studies and a narrative review to gather the mechanisms involved in the potential relationship.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eWe searched related articles in database of Pubmed, EMbase, Web of science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), the Wanfang and Sinomed and obtained 8 clinic trials that investigated the connection between metformin and breast cancer metastasis, containing 2 randomized controlled trials (RCTs) and 6 retrospective cohort studies. We evaluated each retrospective cohort study by Newcastle-Ottawa Scale (NOS), while RCT by Chcorane Risk of Bias tool. Pooled hazard ratios (HRs), risk ratios (RRs) and we calculated associated 95% confidence intervals (CIs) with a random-effect, generic inverse variance method. We also collected the possible mechanisms of cancer metastasis inhibition from metformin.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eA total of 8 studies containing 13919 breast cancer patients without distant metastasis before they got anticancer treatment. The result showed that adjuvant metformin in treatment of local breast cancer facilitated to suppress metastasis (HR\u0026thinsp;=\u0026thinsp;0.69, 95% CI\u0026thinsp;=\u0026thinsp;0.57\u0026ndash;0.82, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%), and the result was consistent with the subgroup of breast cancer patients with type 2 diabetes mellitus (T2DM) (HR\u0026thinsp;=\u0026thinsp;0.68, 95% CI\u0026thinsp;=\u0026thinsp;0.57\u0026ndash;0.82, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, \u003cem\u003eI\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThe meta-analysis suggested metformin might repress the metastasis and be benefit to distant metastasis-free survival (DMFS) when added to systemic breast cancer therapy, supporting anti-tumor effects of metformin on breast cancer.\u003c/p\u003e","manuscriptTitle":"Metformin May Block the Way Breast Cancer Metastasis: A Meta-analysis and Mechanism Review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-08-18 17:24:13","doi":"10.21203/rs.3.rs-56326/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"86f97f87-5bd5-420c-a034-69801e0bee9a","owner":[],"postedDate":"August 18th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":313982,"name":"Cancer Biology"},{"id":313983,"name":"Oncology"}],"tags":[],"updatedAt":"2020-08-25T13:26:57+00:00","versionOfRecord":[],"versionCreatedAt":"2020-08-18 17:24:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-56326","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-56326","identity":"rs-56326","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}