Diverse activity of miR-150 in Tumor development: shedding light on the potential mechanisms.

Angiogenesis is critical for tumor development and metastasis and is activated by chemical signals from cancer cells and the tumor microenvironment [ 104 ]. When tumor cells are actively starved for nutrition and oxygen, angiogenesis is triggered. Inhibitory and activating molecules affect angiogenesis. While increased angiogenic factor activity is necessary for tumor angiogenesis, negative regulators must also be suppressed [ 105 ]. More than a hundred proteins such as VEGF (vascular endothelial growth factor), bFGF (basic fibroblast growth factor), and angiogenin have been discovered as angiogenic inducers. By controlling the expression of many different related genes, miRNAs play an essential role in tumor angiogenesis [ 106 ]. As mentioned above, the tumor microenvironment has a profound effect on tumor angiogenesis. Following the research of Zhang et al. in tumor-associated macrophages (TAM), miR-150 has been shown to increase VEGF secretion from TAM and promote angiogenesis in mouse cancer models [ 107 ]. While VEGF is not a direct target of miR-150, this miRNA may regulate VEGF by focusing on upstream proteins. Based on molecular analysis, it has been shown that ING4 (inhibitor of growth family member 4) is a potential target of miR-150 in TAM. ING4 is an inhibitor for the function of HIF (hypoxia-inducible factor), which plays a crucial role in angiogenesis via inducing VEGF [ 108 ]. The pro-angiogenic activity of miR-150 has been confirmed in the tumor-associated monocyte [ 109 ]. The release of miR-150 from monocytes induces endothelial cell tube creation in vitro and in vivo assessments, while downregulation of miR-150 in monocytes prevents angiogenesis in breast cancer, non-small cell lung cancer, hepatocellular carcinoma, and colon cancer. However, the underlying mechanism and potential targets of monocyte-derived miR-150 in endothelial cells remain unclear. Direct targeting of VEGF and its receptor (VEGFR) by miR-150 is found in colorectal cancer [ 76 ]. Accordingly, the down-regulation of miR-150 in colorectal cancer has a negative correlation with angiogenesis induction.

MiR-150 has an ectopic expression during solid tumor metastasis and it is involved in EMT, migration, invasion, and angiogenesis. Reviewing the various studies on the role of miR-150 in EMT, cell proliferation, apoptosis, and angiogenesis processes revealed that miR-150 is up or down-regulated during tumor progression and targets a wide range of oncogene or tumor suppressor genes. Transcription factors such as ZEB1, HMGA2, FOXO4 and c-Myb, and key signaling pathways including Wnt/β-catenin and TGFβ are determined as miR-150 targets in the EMT process. Furthermore, miR-150 regulates cancer cell migration by affecting multiple effectors including matrix metalloproteinases (MMP14 and MMP13), cell adhesion molecules (ITGA3, ITGA6), transcription factors (MYB), and epigenetics factors (HMGA2 and EZH2). By interacting with cell surface receptors and lncRNAs, miR-150 exerts its regulatory role on cancer cell proliferation and apoptosis. The expression of miR-150 is frequently reduced in tumor cell migration and serves as a tumor suppressor. However, the level of miR-150 in the migration process of non-cancerous cells can increase or decrease. Concerning these findings, miR-150 levels are modulated by upstream signaling pathways, tumor-associated cells, and lncRNAs, which can vary based on cancer cell type, gene expression profile, tumor microenvironment, and pathological circumstances. Furthermore, the target genes of miR-150 determine its function as a tumor suppressor miRNA or oncomiR, and EMT, migration, cell proliferation, apoptosis, and angiogenesis are inhibited or induced. To completely understand the processes by which miR-150 influences metastasis in various cancer types and to investigate its potential as a therapeutic target for cancer therapy, further study is required.

Metastasis is known as the spread of malignant cells from the main tumor to some other area of the body through blood and lymph vessels, as well as their colonization and proliferation in the new region. This process is generally considered inefficient and only those survivors may spread to target organs under ideal circumstances [ 1 ]. Primary tumor cells are normally exposed to a wide range of environmental pressures, such as low pH, deficiency in oxygen, increased reactive oxygen species, and lack of nutrients [ 2 ]. These stressors may induce cancer cells to adopt an aggressive nature and phenotype. According to cellular and molecular insight, a primary tumor is composed of various cell clones with different properties, and rare clones acquire the ability to metastasize. Genomic and chromosomal instability increases certain mutations and alterations that cause tumor heterogeneity and the development of cancer cells with migration and invasion capacity [ 3 ]. Besides, abnormal cell cycle, impairment of DNA repair mechanism, telomere crisis, and epigenetic changes may affect DNA integrity and tumor heterogeneity [ 4 ]. Furthermore, various signaling pathways, a broad spectrum of subcellular functions, and regulatory apparatuses, such as microRNAs (miRNAs), are involved during tumor metastasis to facilitate cancer cell invasion. MiRNAs are defined as evolutionarily conserved non-coding RNA (18–22 nucleotide) that mainly interact with 3′ UTR of mRNA. This class of short non-coding RNAs post-transcriptionally modulates mRNA, which inhibits the translation of target mRNA or causes mRNA degradation. In 1993, LIN-4 was the first miRNA reported to inhibit LIN-14 in C. elegans [ 5 ]. Nowadays, over 2,600 mature miRNAs have since been discovered, and it is believed that they are responsible for controlling more than half of the protein-coding genes in humans [ 6 ]. The genes of miRNA are found as individual genes or within introns of protein-coding genes. RNA polymerase II mainly transcribes related genes as primary miRNA that consists of a 5′ cap, 3′ poly(A) tail, and hairpin structure [ 7 ]. The primary miRNAs are processed into functional or mature miRNAs during the biogenesis process. The levels of miRNAs are strictly controlled in many biological pathways and are essential for typical mammalian development. Therefore, many human disorders such as cancer can be linked to abnormal miRNA expression. The miR-150 has been extensively explored in both normal physiology and various kinds of cancer. MiRNA expression analysis revealed that miR-150 is among the most down-regulated miRNAs in different malignancies including liver, ovarian, pancreatic, colorectal, and neck squamous cell carcinoma [ 8 – 11 ]. It is speculated that miR-150 acts as a tumor suppressor gene in these mentioned cancers. On the other hand, overexpression of miR-150 in breast cancer has been documented. Due to stimulating tumor development and suppressing cell death, miR-150 is an oncogene in this type of cancer [ 12 ]. Interestingly, the evaluation of 165 triple-negative breast cancer and 59 control specimens has indicated that miR-150 is down-regulated in tumor specimens and has tumor suppressor activity [ 13 ]. As a consequence, the inconsistent effect of miR-150 is found not only in different cancers but also in tumors of the same cancer type. In this comprehensive review, we focused on miR-150 levels and potential targets in non-cancerous cells during migration to provide wide insight into the biological function of miR-150. The regulation of the EMT process via miR-150 by emphasizing EMT-related transcription factors (TFs) and signaling pathways was reviewed. MiR-150 can regulate the migration of cancer cells by affecting migration-associated matrix metalloproteinases (MMPs), cell adhesion molecules, epigenetics modulators, and TFs. Tumor microenvironment factors and tumor-associated cells such as macrophages modulate angiogenesis through miR-150.

Through a process known as epithelial-mesenchymal transition (EMT), epithelial cells lose their epithelial characteristics and obtain mesenchymal cells phenotype [ 14 ]. A wide range of factors such as microenvironmental stimuli causes tumor cells to initiate the EMT process. In the epithelial state, tumor cells are defined by apical–basal polarity, cell–cell junctions, and cell integration to the basement membrane. Due to changes in the post-translational regulatory process and gene expression, these epithelial features are suppressed and tumor cells acquire a fibroblast-like morphology [ 14 ]. In addition, cellular composition changes EMT and mesenchymal-like tumor cells have vimentin-based intermediate filaments and bind to the extracellular matrix through focal adhesions expressing integrin. MiR-150 is involved in EMT by regulating related TFs and signaling pathways (Table  2 ). Table 2 miR-150 is known as a modulator of epithelial-mesenchymal transition in various cancer Type of cancer Expression Non-coding RNA Target gene Description of target gene Signaling pathway Ref Ovarian and esophageal squamous cell carcinoma Decreased ZEB1 EMT-associated transcription factor [ 18 , 19 ] Non-small cell lung cancer Decreased Linc00673 [ 21 ] Osteosarcoma Decreased MIAT [ 22 ] Oral squamous cell carcinoma Decreased HMGA2 This transcription factor modulates several genes involved in EMT [ 24 ] Non-small cell lung cancer Increased FOXO4 FOXO4 is known as NF-κB/Snail axis inhibitor NF-κB [ 26 ] Ovarian Increased c-Myb Inhibiting c-Myb leads to the induction of Slug levels, an EMT-associated transcription factor [ 29 ] Colorectal cancer Increased EP300 and CREB1 Transcription factors related to CREB signaling pathway Wnt/β-catenin and CREB [ 33 ] Prostate cancer Decreased TRPM4 This non-specific ion channel promotes the activation of the Wnt/β-catenin signaling pathway Wnt/β-catenin [ 37 ] Cervical carcinoma Increased SRCIN1 A tumor suppressor SRC tyrosine kinase [ 40 ] Lung cancer Increased [ 42 ] Breast cancer Increased [ 43 ] Gastric cancer Increased [ 44 ] Hepatocellular carcinoma Decreased GAB1 a scaffolding linker that regulates signal transmission between receptors and subsequent signaling pathways ERK [ 9 ] Melanoma Decreased circVANGL1 TGFβ [ 50 ] miR-150 is known as a modulator of epithelial-mesenchymal transition in various cancer EMT is controlled by a limited set of transcription factor families, including the Zinc finger (such as Snail and ZEB), and basic helix-loop-helix (such as Twist) [ 15 ]. MiRNAs and EMT- related TFs form a complex interactome that is capable of sensing various signals from the microenvironment and relaying them to gene expression. Although research has been conducted on the interaction between miR-150 and EMT-related zinc finger transcription factors, there is no single study investigating miR-150 and basic helix-loop-helix TFs interaction in EMT. From yeast to humans, zinc finger TFs are evolutionarily conserved and have a zinc finger binding domain to interact with DNA and other targets [ 16 ]. Zinc finger domains rely on the presence of a zinc ion coupled with two cysteine and two histidine residues for their function and structure [ 17 ]. Slug, Snail, and ZEB are members of zinc finger TFs that regulate EMT-related biological markers. The transcription of miR-150 in esophageal squamous cell carcinoma and ovarian cancer is lower than in healthy specimens, according to a microarray database and experimental methods [ 18 , 19 ]. A novel miR-150 target, ZEB1, is determined. ZEB1 has been historically linked to the development of cancer and is required for EMT [ 20 ]. Targeting ZEB1 with miR-150 can increase E-cadherin expression (an epithelial cell marker) and inhibits esophageal squamous cell carcinoma and ovarian cancer development [ 18 , 19 ]. One of the reasons for the reduction of miR-150 expression can be long non-coding RNA (lncRNAs), which has been proven in non-small cell lung cancer and osteosarcoma [ 21 , 22 ]. It is recognized that the interaction between miRNA and lncRNAs is essential for gene regulation. LncRNAs perform as sponges that competitively bind to desired miRNAs and decrease their effects on associated mRNA [ 23 ]. Linc00673 and MIAT have a complementary binding site for miR-150 and reduce its function by sponging in non-small cell lung cancer and osteosarcoma, respectively. Therefore, ZEB1 levels are indirectly affected and EMT is promoted in both types of cancer [ 21 , 22 ]. The regulation of EMT at the molecular level through miR-150 and other less relevant TFs has been reported. It seems that miR-150 acts as a tumor suppressor in oral squamous cell carcinoma and its down-regulation is associated with poor prognosis and metastasis [ 24 ]. In light of further analysis, HMGA2 (the high mobility group A2) transcription factor is determined as a miR-150 direct target. This transcription factor modulates several genes involved in EMT including E-cadherin, N-cadherin, and snail [ 25 ]. Overexpression of miR-150 reduces EMT in oral squamous cell carcinoma by inhibiting HMGA2. In contrast, miR-150 acts as an oncogene and promotes EMT in human non-small cell lung cancer [ 26 ]. In metastatic non-small cell lung cancer specimens and cell lines, miR-150 levels are significantly increased and target FOXO4 (Forkhead box protein O4). Based on the promoter’s region and extracellular circumstances, this transcription factor either represses or activates gene expression [ 27 ]. FOXO4 low-level expression is found in non-small cell lung cancer and may contribute to EMT [ 28 ]. It has been shown that FOXO4 is known as NF-κB/Snail axis inhibitor and its downregulation provides the high activity of the NF-κB/Snail axis [ 26 ]. Eventually, EMT-inducing Snail leads to E-cadherin inhibition, vimentin induction, and N-cadherin up-regulation. Slug, a member of the Snail transcription factor family, is indirectly regulated via miR-150. Compared to primary tumors, miR-150 is elevated in recurrent tumors and enhances cell migration and EMT in ovarian cancer cells [ 29 ]. Indeed, miR-150 causes EMT via upregulating Slug by inhibiting c-Myb. The results of this investigation were somewhat unexpected. Slug expression is generally activated by c-Myb [ 30 , 31 ]; however, in this investigation, c-Myb suppresses Slug in ovarian cancer tissue. It seems that the c-Myb function may be associated with cell type. To induce EMT, various signaling pathways and molecules trigger corresponding receptors on the cell surface, which in turn activates a downstream signaling cascade that ultimately activates EMT TFs and their related co-regulators and epigenetic moderators [ 32 ]. Interestingly, similar to transcription factors, a particular miRNA may directly regulate the expression of dozens of genes by influencing cell signaling pathways. The question that arises is how miR-150 exerts its effects on EMT via associated signaling pathways. Guo et al. have described a molecular mechanism in which the Wnt/β-catenin and CREB signaling pathways are up and downstream of miR-150 in colorectal cancer, respectively [ 33 ]. Indeed, miR-150 has a central role in the interaction of two different types of signaling pathways. Upregulation of Wnt/β-catenin triggers miR-150 expression by binding the β-catenin/LEF1 component in the promotor region. As a result, overexpressed miR-150 significantly inhibited the CREB signaling pathway via binding to EP300 and CREB1 transcription factors (Fig.  1 ). Down-regulation of the CREB signaling pathway leads to EMT in colon cancer. However, CREB is mentioned as an oncogenic transcription factor in some cancer [ 34 ], the results of the investigation indicated that this transcription factor plays a tumor suppressor role in several cancers and its low-level expression promote metastasis [ 35 ]. EP300 is also typically low expressed in various forms of cancer, such as colon cancer and breast cancer [ 36 ]. Interestingly, Yu et al. have indicated that miR-150 can indirectly down-regulate the Wnt/β-catenin signaling pathway and suppresses EMT in prostate cancer [ 37 ]. According to microarray-based analysis, miR-150 and TRPM4 (transient receptor potential melastatin 4) have been down and up-regulated in prostate cancer tissue. TRPM4 is a non-specific ion channel accessible to K + and Na + that is stimulated via Ca2+ [ 38 ]. Current research indicates that TRPM4 promotes the activation of the Wnt/β-catenin and prostate cancer malignancy [ 39 ]. MiR-150 binds to TRPM4 mRNA and represses its biological function. Consequently, the down-regulation of TRPM4 results in reducing the Wnt/β-catenin signaling pathway and EMT [ 37 ]. Fig. 1 The miR-150/CREB axis in cancer. The miR-150 inhibits the CREB signaling. MiR-150 inhibits the CREB signaling pathway and thus affects EMT process The miR-150/CREB axis in cancer. The miR-150 inhibits the CREB signaling. MiR-150 inhibits the CREB signaling pathway and thus affects EMT process In cervical carcinoma cells, miR-150 serves as an oncogene in a different manner [ 40 ]. miR-150 has been found high-level expression in C-33 A and HeLa cervical carcinoma cell lines and promotes EMT features [ 40 ]. The analysis confirmed that miR-150 facilitates tumor malignancy by targeting a tumor suppressor, SRCIN1 (SRC kinase signaling inhibitor 1). Src signaling pathways, which are cellular tyrosine kinases, are typically overexpressed or abnormally activated in cancer cells [ 41 ]. As an effective tumor suppressor, SRCIN1 can suppress Src signaling pathways and downstream epidermal growth factor receptors, and focal adhesion kinases. Moreover, SRCIN1 was explored in lung, breast, and gastric cancer cells and its relation with miR-150 has been shown [ 42 – 44 ]. Overexpressed miR-150 causes A540 lung cancer cells, breast cancer cell lines, and BGC-823 gastric cancer cells to acquire malignancy behavior through suppressing SRCIN1. The miR-150 has tumor suppressor activity in hepatocellular carcinoma. According to hepatocellular carcinoma tissue evaluation, miR-150 is down-regulated upon metastasis [ 9 ]. On the other hand, GAB1 (Grb2-associated binding protein 1) has high-level expression in hepatocellular carcinoma tissue and is determined as a miR-150 target. The role of GAB1 in promoting EMT is not a surprise [ 45 ]. In fact, GAB1 is a scaffolding linker that regulates signal transmission between receptors and subsequent signaling pathways [ 46 ]. GAB1 triggers ERK signaling pathway activation, which is a key coordinator of EMT [ 47 ]. Transforming growth factor-β (TGFβ) is a cytokine binding to its specific cell surface receptor and triggers a signal from the cell membrane to the nucleus through canonical or non-canonical pathways [ 48 ]. Therefore, a wide range of genes undergoes regulation by TGFβ signal transduction, and consequently, various cellular functions such as proliferation, migration, apoptosis, cell polarity, and cytoskeleton restructuring are adjusted. This is perfectly sensible that aberrant activation of the TGFβ signaling pathway is related to human cancers. In the case of the TGFβ signaling pathway, it is accepted that TGFβ has tumor-suppressing actions in the beginning stages of cancer by preventing cell proliferation and promoting programmed cell death; however, TGFβ stimulates tumor metastasis in the advanced stage of the tumor [ 49 ]. The involvement of the TGFβ signaling pathway with the miRNA regulatory network might give further explanation for the inconsistent effect of TGFβ in cancer. In melanoma cells, circVANGL1(circular RNA VANGL1) is increased in melanoma cell lines and tissues by TGFβ [ 50 ]. Circular RNAs are a significant class of lncRNAs that have a single-stranded ring structure without a 3’ Poly A tail and a 5’ cap [ 51 ]. The sponging role of circVANGL1 has been observed in melanoma cells. During the EMT process, TGFβ singling pathway induces circVANGL1 levels and down-regulates miR-150 by sponging (Fig.  2 ) [ 50 ]. Down-regulation of miR-150 is related to an advanced stage of melanoma tumors. Fig. 2 TGFβ/circVANGL1/miR-150 pathway in cancer. TGFβ singling pathway induces circVANGL1 levels and down-regulates miR-150 by sponging TGFβ/circVANGL1/miR-150 pathway in cancer. TGFβ singling pathway induces circVANGL1 levels and down-regulates miR-150 by sponging