CDKN1A and cancer: Additionally, we propose that miR-21 protects BMICs from apoptosis, regulates invasion by controlling matrix metalloproteinase inhibition and promotes cell proliferation by regulating genes such as SPRY2, TIMP3, CDKN1A, SERPINB5 and PTEN. These, together with other analyzed genes, were previously identified as targets of miR-21 in a variety of cancers [43–45, 61–63].