Comprehensive patterns in microRNA regulation of transcription factors during tumor metastasis

MiR-337-3p improves metabolic-associated fatty liver disease through regulation of glycolipid metabolism

Epigenetic regulations play crucial roles in the pathogenesis of metabolic-associated fatty liver disease; therefore, elucidating the biological functions of differential miRNAs helps us to understand the pathogenesis. Herein, we discovered miR-337-3p was decreased in patients with NAFLD from Gene Expression Omnibus dataset, which was replicated in various cell and mouse models with lipid disorders. Subsequently, overexpression of miR-337-3p in vivo could ameliorate hepatic lipid accumulation, reduce fasting blood glucose, and improve insulin resistance. Meanwhile, we determined miR-337-3p might influence multiple genes involved in glycolipid metabolism through mass spectrometry detection, bioinformatics analysis, and experimental verification. Finally, we selected HMGCR as a representative example to investigate the molecular mechanism of miR-337-3p regulating these genes, where the seed region of miR-337-3p bound to 3'UTR of HMGCR to inhibit HMGCR translation. In conclusion, we discovered a new function of miR-337-3p in glycolipid metabolism and that might be a new therapeutic target of MAFLD.

Slug contributes to gemcitabine resistance through epithelial-mesenchymal transition in CD133(+) pancreatic cancer cells

CD133-positive pancreatic cancer is correlated with unfavorable survival despite current development of therapy. Slug acts as a master regulator of epithelial-mesenchymal transition (EMT) which is the essential process in cancer progression. The aim of this study was to investigate the role of Slug in gemcitabine treatment for CD133-positive pancreatic cancer cells. We used a previously established pancreatic cancer cell line expressing high level of CD133 (Capan-1M9), which also expresses high level of Slug. We generated Slug knock-down subclone (shSlug M9) from this cell line, and compared expression of EMT-related genes, migration, invasion and gemcitabine resistance between two cell lines. Slug knock-down in CD133-positive pancreatic cancer cell line led to the reduction of migration and invasion ability. Furthermore, Slug knock-down sensitized CD133-positive pancreatic cancer cell line to gemcitabine. These results suggest that Slug plays an important role in not only invasion ability through EMT but also gemcitabine resistance of CD133-positive pancreatic cancer cells.

miRNA-transcription factor interactions: a combinatorial regulation of gene expression

Developmental processes require a precise spatio-temporal regulation of gene expression wherein a diverse set of transcription factors control the signalling pathways. MicroRNAs (miRNAs), a class of small non-coding RNA molecules have recently drawn attention for their prominent role in development and disease. These tiny sequences are essential for regulation of processes, including cell signalling, cell development, cell death, cell proliferation, patterning and differentiation. The consequence of gene regulation by miRNAs is similar to that by transcription factors (TFs). A regulatory cascade essential for appropriate execution of several biological events is triggered through a combinatorial action of miRNAs and TFs. These two important regulators share similar regulatory logics and bring about a cooperative action in the gene regulatory network, dependent on the binding sites present on the target gene. The review addresses the biogenesis and nomenclature of miRNAs, outlines the mechanism of action and regulation of their expression, and focuses on the combinatorial action of miRNAs and TFs for the expression of genes in various regulatory cascades.

Loss of Git2 induces epithelial-mesenchymal transition by miR146a-Cnot6L controlled expression of Zeb1

Epithelial-mesenchymal transition (EMT) can be induced by several pleiotropically activated transcription factors, including the zinc-finger, E-box-binding protein, Zeb1. Mechanisms regulating Zeb1 expression have been partly uncovered, showing a critical role for the miR-200 family members. Here, we show that Zeb1 is regulated by the Arf GTPase-activating protein (GAP), Git2. Following the loss of Git2, we found that miR-146a maturation is enhanced, which in turn promotes the expression of Zeb1 and induction of EMT. Furthermore, we found that Cnot6L, a validated target of miR-146a, affects the stability of Zeb1 mRNA through its deadenylase activity. Our results present evidence for a new role for loss of Git2 in promoting EMT through a novel regulatory pathway.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

Correlation between Slug transcription factor and miR-221 in MDA-MB-231 breast cancer cells

BACKGROUND

Breast cancer and its metastatic progression is mainly directed by epithelial to mesenchymal transition (EMT), a phenomenon supported by specific transcription factors and miRNAs.

METHODS

In order to investigate a possible correlation between Slug transcription factor and miR-221, we performed Slug gene silencing in MDA-MB-231 breast cancer cells and evaluated the expression of genes involved in supporting the breast cancer phenotype, using qRT-PCR and Western blot analysis. Chromatin immunoprecipitation and wound healing assays were employed to determine a functional link between these two molecules.

RESULTS

We showed that Slug silencing significantly decreased the level of miR-221 and vimentin, reactivated Estrogen Receptor α and increased E-cadherin and TRPS1 expression. We demonstrated that miR-221 is a Slug target gene, and identified a specific region of miR-221 promoter that is transcriptionally active and binds the transcription factor Slug "in vivo". In addition, we showed that in Slug-silenced cells, wich retained residual miR-221 (about 38%), cell migration was strongly inhibited. Cell migration was inhibited, but to a less degree, following complete knockdown of miR-221 expression by transfection with antagomiR-221.

CONCLUSIONS

We report for the first time evidence of a correlation between Slug transcription factor and miR-221 in breast cancer cells. These studies suggest that miR-221 expression is, in part, dependent on Slug in breast cancer cells, and that Slug plays a more important role than miR-221 in cell migration and invasion.