Shirin Eyvazi - Department of Biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Vahideh Tarhriz - Molecular Medicine Research Center, Tabriz University of Medical Sciences, Tabriz, Iran

Introduction & Aim: MicroRNAs have emerged as key regulators of cancer cell biology. MiRNAs play roles in almost all aspects of cancer biology, such as proliferation, apoptosis, invasion/metastasis, and angiogenesis. MiRNAs may function as either oncogenes or tumor suppressors under certain conditions. The aim of this study is determination of the role of miR-191 as an oncomir on p53 as a tumor suppressor gene in breast cancer cell line. Methods MiR-191 was cloned in pCMV-MIR vector. The vector was transfected into MCF7 cell line using lipofectamine 2000. After 48 h, the expression of miR-191 was verified by qRT-PCR. The level of p53 in transfected and untransfected cells was determined by western blot analysis. Results: PCR and restriction analyses confirmed the cloning of the mir-191 in the vector. The transfection was confirmed by PCR analysis. qRT-PCR result showed that miR-191 was overexpressed in MCF7 cell line. Western blot analysis showed that protein level of p53 has been reduced in mir-191 transfected MCF7 breast cancer cell line. Conclusion: In the study, we showed that overexpression of miR-191 reduced protein level of p53 in MCF7 breast cancer cell line. P53 is a nuclear transcription factor with a pro-apoptotic function. Therefore, miR-191 inhibits apoptosis by downregulating of p53.