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]. The gene discussed is CDKN1B; the disease is breast carcinoma.