Identification of miRNAs that target an epigenetic supressor RNF2 gene and its effect on metastasis and invasion

Breast cancer is the most common type of cancer among women and has a high mortality rate. In addition to its histopathological diversity, new molecular and molecular investigations are needed in the treatment of breast cancer due to its complex molecular background. RNF2 is a protein that is repressed by ubiquitin binding of the protein bound in the polycomb repressor complex. RNF2, which plays an important role in a number of biological processes in embryonic development and adult stage, has acquired an oncogenic role due to overexpression in several types of metastatic cancers, as well as silencing tumor suppressor genes. In this study, changes in the level of RNF2 gene expression in breast cancer cell lines were analyzed and whether this gene was suppressed by miR-17-5p, miR-20a-5p and miR-106b-5p. Furthermore, the effect of transfection of these miRNAs on metastasis and invasion has been investigated. For this reason, RNF2 gene expression levels before and after miRNA transfection in MCF-7, MDA-MB-231, SK-BR-3 and ZR-75-1 breast cancer cell lines were analyzed by qRT-PCR and western blot analysis of protein expression levels. The effect on metastasis and invasion was observed using wound healing and dyed chamber methods. RNF2 was overexpressed 4.1 and 7.1fold in the MDA-MB-231 and SK-BR-3 cell lines, respectively (p=0,048 ve 0,045 respectively). A significant decrease in gene expression after miRNA transfection was observed in miR-17-5p and miR-20a-5p (3.5 and 7.3 fold, respectively) (p= 0,045 ve 0,039 respectively) at MDA-MB-231 cell line. At the protein level, it was observed that all three miRNAs decreased RNF2 protein at MDA-MB-231 cell line. It was also observed that miR-17-5p and miR-20a-5p suppressed metastasis and invasion and miR-106b-5p could not suppress it. As a result, RNF2 is overexpressed in breast cancer cells with more metastatic ability. miR-17-5p and miR-20a-5p suppress RNF2 targeting and suppress metastasis and invasion in this direction. RNF2 may be considered as a candidate gene to be a prognostic marker for breast cancer. Key Words: Breast cancer, metastasis, miRNA, polycomb, RNF2.