TP53 and lung cancer: One of the most well-established p53-target genes in regulating senescence is p21, which is an inhibitor of cell cycle progression.1 However, the molecular mechanisms of p53-mediated senescence remain elusive.1 In addition to p21 induction, we found that p53 acted as an upstream negative regulator of hTERT activity and expression in H460 (p53 wild type) but not H1299 (p53 null) lung cancer cells (Figure 4).