Oncogenic role of miRNA 221 222 in breast cancer

Breast cancer stills remains as one of the major health problems in the world which ranks as the top cause of death of women with a percentage of 21.4%. There is connection of microRNAs (miRNA) with carcinogenesis process. miRNAs are small non coding RNAs (18 to 24 nucleotides) and formed as single-stranded RNAs (ssRNAs). The action of miRNAs is depended from their expression levels and function which can either promote oncogenesis (oncomiRs) or act as tumor suppressor pathways. One of the oncomiRs is miR-221 and miR-222, both are expressed by single transcription that are found on the X chromosome. The regulation transcription of miR-221/222 gene is control by positive and negative feedback. miR-221/222 directly targets PTEN, pro-apoptotic protein and tumor suppression gene, SOCS1 and CDKN1B in order to promote the proliferation of the cells. miR-221/222 enhances the aggressiveness of tumor through regulates the epithelial to mesenchymal transition (EMT) by targeting Tricho-rhino phalangeal syndrome type 1 (TRPS1) gene. miR-221/222 induces resistance of endocrine therapy in breast cancer especially tamoxifen and fulvestrant. The role of miR-221/222 in carcinogenesis is very complex that can upregulate or downregulate a protein. In addition, overexpression of miR-221/222 also enhances aggressiveness characteristics of breast cancer.