Furthermore, miR-21 has been identified as a key regulator of several target genes, including PTEN (Phosphatase and tensin homolog) a tumor suppressor gene that regulates cell growth and apoptosis, through an antagonistic relationship, where miR-21 downregulates PTEN expression, thereby promoting cell proliferation and survival of CRC cells [17,20,21]. The gene discussed is PTEN; the disease is colorectal carcinoma.