Abstract:

Aim: It was aimed to investigate the effect of miR-34a-5p and miR-145-5p on breast cancer cell line MDA-MB-231 and to determine the expression of target genes of these microRNAs (miRNAs). Materials and Methods: Firstly, literature search and in silico analysis were performed to detect possible target genes of miR-34a-5p and miR-145-5p, which are known to be tumor suppressors. Mimic miR-34a-5p and miR-145-5p were transfected to the breast cancer cell line MDA-MB-231. Deregulated genes were investigated by the quantitative real-time polymerase chain reaction compared to control cells. Also, the effect of these miRNAs on proliferation was determined using the Water Soluble Tetrazolium Salt-8 method. Finally, the expressions of epithelial mesenchymal transition (EMT) markers, which are known to be important in the metastatic process, are examined. Results: The proliferation of the miR-34a-5p or miR-145-5p transfected cells decreased compared to the control groups. The expression of E2F transcription factor 1 (E2F1) (p=0.009), mitogen activated protein kinase 1 (MEK1) (p=0.001) and cyclin dependent kinase 4 (CDK4) (p=0.005) genes, which were among the genes targeted by miR-34a-5p, were significantly reduced. EMT markers were significantly changed in miR-34a-5p transfected cells (E-Cad increase p=0.01; Vimentin decrease p=0.008). Kruppel-like factor 4 (KLF4) (p=0.007) targeted miR-145-5p were significantly reduced and EMT markers were significantly changed in miR-145-5p transfected cells (E-Cad increase p=0.0005; Vimentin decrease p=0.006). Conclusion: miR-34a-5p and miR-145-5p may have an impact on the breast cancer cell line MDA-MB-231 proliferation and EMT mechanism. At the same time, according to our study results, it was revealed that E2F1, MEK1 and CDK4 genes, whose expression level decreased after transfection of mimic miR-34a-5p, could be targeted by miR-34a-5p in breast cancer, and that the expression level of KLF4, which decreased as a result of mimic miR-145-5p transfection, could be the target.

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