Background:One of the most prevalent cancers befell to women is considered to be breast cancer (BC). It is also the deadliest among the female population after lung cancer. Additionally, several studies have demonstrated that there is an association between microRNA34-a and breast cancer.Method:We searched PubMed, Web of Science, and Google Scholar up to December 2018. Those studies which have been studied miR-34a and its tumor-suppressing capabilities were considered as the most important topics. Moreover, we extracted articles which were solely focused on microRNA-34a in breast cancer therapy. Finally, 80 articles were included.Results:In comparison with the normal tissues, down-regulation of miR-34a expression is shown considerably in tumor cells. Overexpression of miR-34a acts as a tumor suppressor by transcriptional regulating one of the signaling pathways (TP53), NOTCH, and transforming growth factor beta (TGF-β), Bcl- 2 and SIRT1genes, HDAC1 and HDAC7, Fra-1, TPD52, TLR Via CXCL10. Moreover, drug resistance declines which lead to the apoptosis, cell cycle arrest and senescence. As a result, the proliferation, invasion and metastasis of the tumor are suppressed. The Mrx34 drug contains miR-34a mimic and a lipid vector. MiR-34a as the active ingredient portrays the role of a tumor suppressor. This drug has recently entered the clinical trials studies.Conclusion:These findings suggest a robust cause for developing miR-34a as a therapeutic agent to target BC. In that scenario, miR-34a is strongly useful to introduce new therapeutic goals for BC. Moreover, this review aims to confirm the signal pathways, therapeutic and diagnostic values of miR- 34a in BC and beyond.
