CDKN1A and cancer: Other components of the DNA damage response are also targeted by miRNAs; the TP53 gene itself which encodes p53 is targeted by miR-504 and miR-125b in several cell lines [25,26] whereas the CDKN1A/p21 gene was demonstrated to be directly regulated by miR-106b in samples from five different solid tumours (breast, colon, kidney, gastric, and lung) when compared with non-cancer control tissue [27].