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.
Methods: 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.