Micro-RNAs and Their Roles in Breast Cancer Pathogenesis; An Updated Review Article

Abstract

Introduction: Micro-RNAs (miRNAs) were discovered in 1993 by Rosalind Lee and Rhonda Feinbaum while working on the lin-14 gene in the C. Elegans. In fact, one of the most important recent advances in biochemical research was the discovery of noncoding long 22 nucleotide RNAs called miRNAs that are involved in regulating genes' expressions via mRNA degradation or preventing its translation and modulating a variety of basic cellular processes. Today a few number of miRNAs have been studied and the performance of this number included cell differentiation, proliferation, apoptosis, and anti-viral and anti-cancer defenses. About 50% of miRNAs are placed within genes and it is expected that approximately 50% of them be placed in introns. More than half of miRNA genes are located on chromosome's fragile sites that allow duplication, deletion, and cell movement during the cancer development process. These areas can affect the expression of miRNAs. Recent research has shown that these molecules can act as either oncogenes or tumor suppressors. Given the importance of etiology and treatment of tumors and due to many unknown causes of cancers, extensive studies have discussed around the role of these micro molecules in the pathogenesis of cancers. Many studies have examined the possible molecules involved in cancer. Today, several review articles have been published regarding several aspects of miRNAs in breast cancer. In this review article, we attempted to collate recent articles regarding miRNAs in breast cancer to update our knowledge and discuses about the production and performance of miRNAs and their involvement in the pathogenesis of breast cancer. Materials and Methods: In order to find recent investigations regarding the roles of miRNAs in breast cancer, three main databases including PubMed, Scopus, and Google Scholar were searched using “miRNA, micro-RNA, and breast cancer” keywords. Results: According to the results achieved in the presented studies, it seems that miRNAs b27, 31, 125, 141, 145, a2196, 200 family, 205, 206, 210, 429, and 499 along with let-7 are the molecules that have preapoptotic function and reduce the expression of oncogenic proteins and increase the expression of antiapoptotic molecules. Accordingly, it may be concluded that the prevention of cancers such as breast cancer is plausible by increasing their expression. Conclusion: Given the role of miRNAs in cancer induction or prevention as well as invasiveness or non-invasiveness, it seems that these micro molecules can be used as biomarkers for early detection of breast cancer and progression. Release of miRNAs from the tumor to the blood circulation is performed through the exosome vesicles and apoptotic bodies, hence, miRNAs present in blood circulation can be used as diagnostic indicators. Therefore, the levels of miRNAs' expression can be considered in the monitoring of tumor status. It is worth to note that the removal of primary tumor reduces the rotational miRNAs. Hence, this investigation showed that we can consider these micro molecules in the identification of patients' status and treatment pathways.