CDKN1A and neoplasm: The transcription factor p53/TP53, which is a tumor suppressor that turns aggressively oncogenic when mutated, is dysfunctional in more than half of all cancers studied.30 This is considered a cancer hallmark, including in NSCLC.31,32 p53 is a master transcription factor and functions by directing cell cycle arrest or inducing apoptosis in response to cellular stress, including DNA damage and oncogenic stimulation.33 p53 directly regulates cell cycle and apoptosis genes, such as cyclin G, bax, and CDKN1A/p21WAF1/CIP1.