It has been shown that miR-221 and miR-222 functionally target and inhibit the expression of tumor suppressor genes (such as CDKN1B/p27 and CDKN1C/p57) and oncogenes (such as BCL2L1 and ER) in various cancers, including glioblastoma, hepatocellular carcinoma, breast cancer, and PCa [167,168]. This evidence concerns the gene CDKN1C and breast cancer.