A comprehensive overview of exosome lncRNAs: Emerging biomarkers and potential therapeutics in gynecological cancers.

An exosome is a cell-secreted nanoscale vesicle containing DNA, proteins, lipids, RNA, metabolites, cytokines, transcription factor receptors, and other biologically active substances ( 1 ). Its composition is similar to that of parental cells and can be used as a “fingerprint” to identify relevant cells and provide specific signals that can be traced in circulating blood ( 2 ). The composition is similar to that of parental cells and can be used to identify relevant cells by providing specific signals that can be traced in circulating blood. Long noncoding RNAs (lncRNAs) are noncoding RNAs that are abundant in the cytoplasm and nucleus ( 3 ). They do not have protein-coding functions, but they can influence cancer development in a variety of ways and can be specifically sorted into the exosome ( 4 ). Despite the presence of RNA enzymes in the blood, lncRNAs can persist due to exosome protection ( 5 , 6 ). Tumor-derived exosomes (TDE) lncRNAs can contribute to cancer progression in a variety of ways by altering the tumor microenvironment, the epithelial-mesenchymal transition (EMT), and angiogenesis, as well as playing a role in cancer growth maintenance and stabilization. Because cancer invasion, metastasis, treatment, and drug resistance are all intertwined, it is of great scientific importance to mine and explores the exosome lncRNAs that affect malignant biological behavior, as this can help to further investigate the mechanism of cancer development and provide new ideas and strategies for cancer treatment ( 7 , 8 ).

Ovarian cancer (OC) is the most difficult to diagnose and has the worst prognosis of all malignant cancers of the female reproductive system, causing serious health problems in women ( 68 ). The pathogenesis of OC is complex, the early clinical symptoms are subtle, and the metastatic potential is high. When most patients are diagnosed, they are already in an advanced stage of the disease ( 69 ), so radical surgery cannot be used, the treatment effect is inadequate, and more than 70% of OC patients have a recurrence. The Food and Drug Administration (FDA) has approved only two biomarkers, CA125 and HE4, as diagnostic biomarkers for OC ( 70 ). CA125 is widely used in clinical settings, but it has some limitations ( 71 ). CA125, for example, is less sensitive in early-stage OC and can be elevated in pregnancy, pelvic inflammatory disease, endometriosis, and other conditions. In the presence of conditions such as acute and chronic renal insufficiency, HE4 can also indicate gynecological diseases and abnormal changes ( 72 ). As a result, a new reliable marker is required for the early detection of OC ( 73 ). Exosome lncRNA can be used as a non-invasive diagnostic and screening tool, requiring only a small amount of fresh or frozen blood from OC patients and simultaneously analyzing for DNA, RNA, and protein. Exosomes can be extracted from the urine and blood of OC patients using a human recombinant S100A8 protein aptamer bound to cell membrane HSP70 ( 74 ). CD24 was found in exosomes from malignant ascites and in vitro cancer cells. This marker has been used to predict the prognosis of OC, demonstrating the exosome’s utility as a minimally invasive biopsy ( 75 ). Experiments with magnetic nanobeads revealed that many HER2-positive exosomes were found in the serum of OC patients ( 76 ). Chen et al. ( 77 ) discovered that CA125 levels were higher in exosomes than in serum, that serum exosome-derived CA125 improved the sensitivity of OC diagnosis, and that serum HE4 combined with exosome CA125 improved the diagnostic efficiency of OC. Zhang et al. ( 78 ) examined the circulating exosomes in the plasma of OC patients and identified seven biomarkers with diagnostic ability, including HER2, EGFR, Folate Receptor (FR), CA-125, Epithelial Cell Adhesion Molecule (EpCAM), CD24, and (CD9+CD63), and demonstrated that these exosome biomarkers not only distinguished OC patients from benign subjects but also differentiated early and advanced OC, indicating the MALAT1 is a long noncoding RNA that is involved in the angiogenesis and metastasis of OC. Sun et al. ( 79 ) discovered that the lncRNA MALAT1 plays an important role in the development of OC by mediating the Janus kinase 2 (JAK2)/STAT3 signaling pathway, promoting OC cell proliferation, and inhibiting cancer cell apoptosis. Jin et al. ( 80 ) discovered that the lncRNA MALAT1 could increase OC cell proliferation while inhibiting cancer cell apoptosis via the PI3K-protein kinase B (PKB, AKT) signaling pathway, enhancing OC cell invasion, migration, and EMT function. Some researchers discovered that the expression level of serum exosomes ( 81 ) was higher when testing the expression of serum exosome MALAT1. MALAT1 expression was significantly higher in epithelial OC patients than in controls, and it was associated with an advanced International Federation of Gynecology and Obstetrics (FIGO) stage, a high histological grade, and lymph node metastasis. Increased serum exosomeMALAT1 expression was associated with a progressive metastatic epithelial OC phenotype and a poor prognosis, suggesting that it could be used as a prognostic or predictive biomarker for epithelial OC. The HOXA transcript at the distal tip (HOTTIP), a homeobox lncRNA, is critical in the progression of OC. HOTTIP overexpression was found to increase IL-6 expression and secretion in OC cells. IL-6 activated the STAT3 pathway by binding to IL-6 receptors on the surface of neutrophils surrounding cancer cells, increasing the expression of PD-L1 on the surface of neutrophils, inhibiting T cell activity further, accelerating OC immune escape, and ultimately promoting cancer cell growth and metastasis ( 82 ). The lncRNA NEAT1 was found to be significantly overexpressed in ovarian cancer cells compared to normal human ovarian epithelial cells. Through sponge adsorption of miR-36, lncRNA NEAT1 may promote ovarian cancer cell proliferation by upregulating fibroblast growth factor (FGF) 9. The use of exosomes for vaccine preparation is a novel approach in cancer immunotherapy. TDE has low immunogenicity, a low drug attrition rate, and easy tissue diffusion, making it suitable for use as a drug or gene carrier for targeting OC and as a cancer vaccine to inhibit cancer growth. The cytotoxicity of paclitaxel-loaded macrophage exosomes against drug-resistant P-gp transfected Manin-Darby canine kidney epithelial cells (MDCKMDR1) cell line was increased more than 50-fold, and the anti-cancer effect of the drug-loaded exosomes was demonstrated ( 83 ). Farrukh et al. ( 84 ) discovered that exosome delivery of anthocyanin had a strong therapeutic effect on both drug-sensitive and drug-resistant human ovarian cancer cells and that its therapeutic activity was synergistically enhanced when combined with cisplatin. The co-culture of the hypoxic OC cell line exosome (HEX) with cancer cells during cisplatin treatment improved cell survival, according to Kalpana et al. ( 85 ). Simultaneously, a known inhibitor, STAT3, inhibited exosome release. Exosome release and cisplatin treatment increased apoptosis, indicating that HEX can promote OC metastasis and increase chemoresistance, and could be a new mechanism for cancer metastasis and chemoresistance, as well as a therapeutic intervention to improve clinical outcomes. Endometrial carcinoma (EC) is one of the most common malignant cancers of the female reproductive system ( 86 ), accounting for 20%–30% of all malignancies of the female genital tract. In recent years, the incidence of EC has been increasing year after year, and the age of onset has gotten younger. EC can be diagnosed clinically based on symptoms such as vaginal bleeding or increased fluid discharge, but a definitive diagnosis requires further examination improvement. Fear of diagnostic scraping and hysteroscopy causes some patients to postpone their investigation, delaying the best time for diagnosis and treatment. Those who do not receive timely treatment at an early stage frequently have poor prognoses and survival rates. When the presence of lesions in the endometrium is determined through diagnostic scraping, the distribution of lesions cannot be accurately grasped, and small local lesions may be missed, increasing the rate of EC misdiagnosis. The clinical treatment of EC is primarily surgical, with the decision to combine radiotherapy based on high-risk factors. There are few adjuvant treatment options for advanced and recurrent cancers. As a result, identifying practical early diagnostic markers and precise therapeutic targets is critical. Exosome lncRNA regulates EC proliferation and invasion primarily through angiogenesis, EMT, and immune regulation, among other things. Exosome lncRNA promotes the formation of a tumor microenvironment by transforming related cells, which not only speeds up normal cell proliferation but also changes the biological characteristics of nearby and distant non-cancer cells, allowing cancer cells to spread. Through related signaling pathways, some lncRNAs can effectively promote EC cell proliferation and enhance EC cell invasion, migration, and EMT function, thereby promoting cancer growth ( 87 ). Some lncRNAs, on the other hand, can effectively inhibit cancer cell proliferation, block the cell cycle process, and promote cancer cell apoptosis via related signaling pathways, which may be related to the composition of the tumor microenvironment, particularly CAFs ( 88 ). MEG3 is a long noncoding RNA with anti-cancer properties ( 89 ). Reduced expression of MEG3, which inhibits cancer cell proliferation, migration, and invasion and promotes apoptosis, has been linked to cancer development and progression ( 90 , 91 ). MEG3 activity is controlled by both TP53-dependent and TP53-independent mechanisms. The TP53 gene is mutated in the majority of human cancers, and it functions as a transcription factor, controlling the expression of many target genes and thus inhibiting cancer development and growth. The differential expression of TP53 in normal and cancerous tissues suggests that MEG3 could be used to assess cancer staging and prognosis ( 92 ). Guo et al. examined the expression of MEG3 and Notch signaling molecules in EC tissues and cell lines using real-time quantitative PCR and Western blotting. MEG3 expression was found to be significantly downregulated in EC tissues, whereas Notch protein expression was found to be upregulated in both. MEG3 downregulation inhibits EC proliferation by inhibiting the Notch signaling pathway ( 93 ). In EC patients, low expression of exosome lncRNA MEG3 in plasma predicts more high-risk factors, a higher recurrence rate, and a worse prognosis. By comparing the serum expression levels of lncRNA ROR and miR-29 in EC patients and healthy women and using ROC curves to assess the diagnostic value of both in EC, Serum lncRNA ROR and miR-29 levels were found to be significantly higher in EC patients than in healthy women. The expression levels in patients with TNM stages I–II increased dramatically, indicating the combined serum level ( 94 ). MALAT1 overexpression is associated with a poor prognosis for EC, implying that MALAT1 could be used as a novel biomarker and diagnostic target for EC ( 95 ). The primary issue with cancer drug therapy is cancer drug resistance, particularly in recurrent cancers where acquired drug resistance renders the therapeutic effect ineffective. Exosome-mediated lncRNA communication in the tumor microenvironment has been shown in studies to be one of the reasons for increased drug resistance. It is possible to inhibit the production or uptake of an exosome-carrying “oncogene” and promote the production or uptake of an exosome-carrying “oncogene” based on the fact that exosomes can transport proteins and nucleic acids related to cancer invasion, metastasis, angiogenesis, and drug resistance. This opens up a new avenue for the future use of exosomes in the treatment of EC. The engineered exosome is more effective in targeting therapy than the original exosome, and it also reduces cytotoxicity and significantly inhibits tumor growth ( 96 ). Exosome lncRNAs play an important role in the development of EC, opening up new avenues for the early diagnosis and treatment of EC patients. They may also become an important tool in monitoring the progression and prognosis of EC in the future. Cervical cancer (CC) is one of the most common cancers in women. According to data, more than 500,000 people are diagnosed with CC each year, with the majority of deaths occurring in developing countries ( 97 , 98 ). As a result, CC is a global public health issue that should not be underestimated ( 99 ). Despite the fact that chemotherapy combined with targeted therapy can improve overall survival (OS), progression-free survival (PFS), and cancer mortality in CC patients, cancer incidence continues to rise. The prognosis of advanced CC, which has a low local control rate and is prone to distant metastasis, is influenced by high-risk factors. The treatment effect is frequently poor, with only a 60% 5-year survival rate ( 100 ). As a result, improving early diagnosis of CC, identifying therapeutic targets, and investigating biomarkers that can indicate prognosis have emerged as top priorities in CC basic and clinical research ( 101 ). Because of the impact of exosome LncRNA on the tumor microenvironment and its biological properties, it has the potential to become a cancer biomarker for CC patients, which has important clinical implications in cancer screening, treatment detection, and prognosis evaluation ( 102 ). Exosomes from HeLa cells in CC have been shown to promote distant metastasis by inducing endothelial cell endoplasmic reticulum stress and disrupting vascular endothelial cell integrity, thereby disrupting tight endothelial junctions ( 103 ). When CC HeLa cell exosomes were injected into mice, they found increased vascular permeability and cancer metastasis. The primary mechanism involved the CC HeLa cell exosome regulating the expression of closed junction proteins. Immunity against CC was improved in a mouse model of CC by increasing the cytotoxic activity of DEX-induced CD8+ T cells against cancer cells, prompting CD8+ T cell proliferation, and increasing IFN secretion ( 104 ). HOXA11 is a recently discovered and researched lncRNA ( 105 ). HOXA11-AS has been shown in studies to promote cancer cell proliferation by regulating the expression of miR-124, miR-140-5p, LATS1, PADI2, and other genes ( 106 – 108 ). Exosome lncRNA HOXA11-AS may increase the expression of SRY-related high-mobility group box 4 (SOX4) in endothelial cells, increasing the proliferative capacity of endothelial cells involved in cervical cancer. According to the ROC curve, the specificity of lncRNA gradually increased during hepatocarcinogenesis (GIHCG), and the sensitivity was 88.75% in distinguishing between healthy people and CC patients. In the future, lncRNA GIHCG could be used to predict CC ( 109 ). HOTAIR and MALAT1 lncRNAs were found to be significantly overexpressed in exosomes isolated from the lavage fluid of CC patients (111.112). The lncRNA MEG3 was found to be significantly reduced and correlated with cancer stage, metastasis, and other factors. Chen et al. demonstrated that MEG3 can inhibit cervical cancer cell proliferation, invasion, and migration by regulating the Rac1 and PI3K/AKT/MMP-2/9 signaling pathways ( 110 ). When compared to non-neoplastic cervical tissues, the expression of lncRNA MEG3 was significantly downregulated in the histopathological grading of cervical intraepithelial neoplasia (CIN) in CIN 2 and CIN3. According to one study, MEG3 expression was reduced in cervical tissues, and it was associated with cancer size, lymph node metastasis, high-risk HPV infection, and the FIGO stage. In vitro , ectopic expression of MEG3 may inhibit the proliferation of human CC cells HeLa and C-33A. The researchers discovered that NF-kappaB interacting lncRNA (NKILA) inhibits proliferation and promotes apoptosis in cervical squamous cells by down-regulating miRNA-21 expression. LncRNA ArfGAP with the RhoGAP domain, ankyrin repeat, and PH domain 1 antisense RNA (ARAP1-AS1) can promote proto-oncogene c-Myc translation in cervical cancer by separating dimers and promoting tumorigenesis ( 59 ). Furthermore, through interactions with recombinant Polypyrimidine Tract Binding Protein 1 (PTBP1), LncRNA surfactant associated 1 (SFTA1P) promoted the degradation of tropomyosin 4 (TPM4) mRNA and the progression of cervical cancer ( 52 ). These findings support MEG3’s critical role in the molecular etiology of CC and point to MEG3’s potential use in the treatment of CC ( 111 ) ( Table 1 ). The expression and functions of exosomal lncRNAs in gynecological cancers.

The noncoding region of the human genome contains approximately 88% of single nucleotide polymorphisms. Non-coding RNA is classified into two types based on its length: LncRNA and short-stranded noncoding RNA. LncRNA is a class of single-stranded RNA molecules with sizes less than 200 nt, the majority of which are found in the nucleus and some in the cytoplasm, and are classified as sense lncRNA, antisense lncRNA (AS lncRNA), bidirectional lncRNA, intronic lncRNA, and intergenic lncRNA ( 23 ). When compared to most protein-coding genes, lncRNAs have better cell specificity and relatively stable local secondary and tertiary structures, making them easier to detect in body fluids and capable of interacting with DNA, RNA, or proteins. They play an essential role in the physiological and pathological processes of the body ( 24 ). LncRNAs participate in a variety of biological pathways, including cell growth, by regulating gene transcription and post-translational expression. By regulating innate and adaptive immunity, lncRNAs can participate in a variety of immune pathways, and dysregulation of their expression levels can disrupt immune homeostasis. It is anticipated that it will be one of the most promising biomarkers for disease diagnosis and prognosis ( 25 ) ( Figure 2 ). The role of lncRNAs in regulating cellular processes. LncRNAs play a critical role in the regulation of cell proliferation, cell apoptotic death, cell cycle, cell migration and invasion, epithelial-mesenchymal transition (EMT), cancer stem cells, DNA damage and drug resistance in cancer ( 25 ). LncRNAs are important regulators at the epigenetic, transcriptional, and post-transcriptional levels ( 26 ). Epigenetic silencing or activation of target genes: lncRNAs can regulate gene expression at the epigenetic level via DNA methylation, demethylation, histone modification, and chromosome remodeling ( 27 ). MEG3 expression was found to be significantly reduced in glioblastoma due to DNA methyltransferase I-mediated hypermethylation of the MEG3 promoter, which downregulated MEG3 expression in glioblastoma and inhibited p53 protein activation. Transcriptional level: Long noncoding RNAs (lncRNAs) can interact with transcription factors, enhancers, and promoters to regulate RNA transcription, localization, and stability ( 28 ). The lncRNA Gas5 can compete with the glucocorticoid response element (GRE) for binding to the glucocorticoid receptor (GR), preventing GR transcriptional activation and resulting in an autoimmune response. In breast cancer, low Gas5 expression increased cancer cells’ survival during starvation. P21-associated noncoding RNA with DNA damage activation (lncRNA PANDA) was found to promote osteosarcoma cell proliferation. Further research revealed that the lncRNA PANDA inhibited apoptosis in normal human fibroblasts by binding to transcription factors that prevented it from binding to apoptosis-related gene promoters. Long noncoding RNA homeobox (HOX) A11 antisense lncRNA (HOXA11-AS) was discovered to bind to transcription factor WD repeat domain 5 (WDR5) in the promoter region, promote -catenin transcription, and activate the Wingless-Type MMTV Integration Site Family (WNT) signaling pathway, accelerating cancer metastasis in vivo . Post-transcriptionally, lncRNAs can form RNA dimers with target mRNAs via complementary base pairing, obstruct transcription factor binding, or directly recruit specific translation repressor proteins to regulate mRNA shearing, translation, and degradation ( 29 ). KLF4 is a transcriptional activator of vascular endothelial growth factor (VEGF). The lncRNA H19 can bind to miR-7, allowing miR-competitive endogenous RNA (ceRNA-7) to release translational repression of KLF4 and activate the KLF4/VEGF signaling pathway. Stable knockdown of exosome lncRNA H19 can significantly affect KLF4 and VEGF mRNA and protein expression levels, which affect the formation of the pre-metastatic microenvironment, inhibit cancer cell migration and invasion, and regulate the tumor microenvironment and vascular normalization. During the progression of hepatocellular carcinoma, the expression level of long noncoding RNA-activated by transforming growth factor beta (lncRNA-ATB) was increased and directly linked to IL-11, which altered IL-11 tertiary structure, increased the stability of IL-11 mRNA, induced IL-11 autocrine, triggered the signal transducer and activator of transcription 3 (STAT3) pathway, and promoted cancer metastasis and organ colonization. The first lncRNA with trans-activation, HOX transcript antisense RNA (HOTAIR), acts as a pro-oncogene in a variety of cancer cells, including breast cancer and hepatocellular carcinoma ( 30 ). HOTAIR, a lncRNA with sponge adsorption for miR-122, can regulate cancer cell epithelial-mesenchymal transition ( 31 ).

Exosomal lncRNA has a wide range of research applications ( 114 ). Exosome lncRNAs regulate a variety of pathophysiological processes, including cancer cell genesis, invasion, metastasis, and vascular neogenesis, as well as mediate cancer drug resistance and play an important role in cancer development. Exosome lncRNA is thought to be a novel marker for gynecologic cancer diagnosis, efficacy evaluation, and prognosis prediction. Exosome lncRNA research is still in its early stages, and its functions are not fully understood. There are the following flaws: The specificity of exosome lncRNA as a molecular marker for gynecological tumor diagnosis has yet to be determined; The technology of exosome in vitro synthesis as a carrier of targeted therapeutic drugs has yet to be improved; Exosome lncRNAs play a role in a variety of cancers, and multiple exosome lncRNAs have the same cancer action target, but their interaction is still unknown, making it difficult to fully resolve their regulatory network. The above problems can be solved one by one with the rapid development of proteomics, high-throughput sequencing, transcriptomics, and bioinformatics analysis, and researchers will have a better understanding of the mechanisms of exosome-derived lncRNAs in the development of gynecological malignancies and their clinical applications.

MW, LF, YX, SM, XZ, and LZ performed literature searches and selected the studies and reviews discussed in the manuscript. The first draft of the manuscript was prepared by MW, LF, YX, SM, and XZ and made subsequent amendments. LZ revised the manuscript. All authors contributed to the article and approved the submitted version.