miR-202 acts as a potential tumor suppressor in breast cancer.

Breast cancer affects ~10% of women worldwide and is responsible for ~12% of all cancer-associated mortalities. Breast cancer is more prone to metastasis compared with other types of cancer. Up to 5% of patients with breast cancer present with incurable metastasis and an additional 10-15% of patients develop metastases within 3 years of their initial diagnosis. MicroRNAs (miRNAs) are short RNAs, 21-25 nucleotides in length, that have been shown to significantly affect gene expression. In total >2,000 miRNAs have been identified and specific miRNAs have been revealed to be associated with cancer. In the present study, we observed that the majority of breast cancer specimens collected expressed low levels of miR-202 compared with adjacent tissues and normal cell lines. Mechanistic investigations identified KRAS as a potential target gene of miR-202 and it was demonstrated that miR-202 exerted its tumor-suppressive effects by regulating the expression of KRAS in breast cancer cells. Functional assays revealed that miR-202 significantly reduced cell proliferation, migration and invasion in vitro. In summary, these results indicate the function of miR-202 in breast cancer progression and suggest that its use within breast cancer therapy is promising.