CDKN1A and squamous cell carcinoma: In the FAK knockout cell line of squamous cell carcinoma of theskin, radiation suppresses transcription of the p21 gene andother p53 target genes mediating cell cycle arrest and DNA damage repair.Suppression of p53 and p21 activationpromotes radiosensitization of tumor cells; this was not observed for intactFAK [65].