Evaluation of miR-34a Effect on CCND1 mRNA Level and Sensitization of Breast Cancer Cell Lines to Paclitaxel

Background: A growing body of literature has revealed the effective role of miR-34a, as a tumor suppressor and regulator of expression of multiple targets in tumorigenesis and cancer progression. This study aimed at evaluating the potential effects of miR-34a alone or in combination with paclitaxel on breast cancer cells. Methods: After miR-34a transduction by lentiviral vectors in two MCF-7 and MDA-MB-231 cell lines of breast cancer, effects of the elevated expression of miR-34a in the cell viability and the cell proliferation were determined using MTT assay  in treated and untreated cells with paclitaxel. The mRNA level of the CCND1 (Cyclin D1)gene was then measured in the two cell lines using the qRT-PCR assay. Finally, the influence of miR-34a and paclitaxel on apoptosis and cell cycle progression were examined by flow cytometry. Results: The CCND1 mRNA expression levels were significantly down-regulated by overexpressed lentiviral miR-34a in MCF-7 and MDA-MB-231 cells. Combined treatment by miR-34a and paclitaxel reduced the cell viability and proliferation compared to single-drug treatment. In addition, the cell cycle arrest appeared at two phases by the combination of miR-34a and paclitaxel in MDA-MB-231 cells. Conclusion: Our results suggest that miR34a, in combination with paclitaxel, has a potential for decreasing the cell viability and proliferation. Moreover, it can reduce the expression of CCND1 mRNA independent of the paclitaxel effect.