TP53 and neoplasm: In addition, cell cycle checkpoint genes (PCNA, BRAC1, CD6, MCM3, MCM6 and BIRC5) and genes of the p53 signalling pathway (CDK2NA, CHEK2, CDK4, CCNE1, CCNB3, TP53AIP1, IGFBP3, SERPINB5, GTSE1 and TP73) were strongly activated in LUSC but not in LUAD tumours.