TP53 and neoplasm: In contrast, after the same treatment, MRC-5 human lung fibroblasts (tNOX−) experienced an opposite effect on the intracellular NAD+/NADH ratio, the elevation of which resulted in a substantial enhancement of SIRT1 activity and the subsequent decline in p53 acetylation levels, followed by the induction of cellular autophagy without affectation on the viability of non-tumor cells [40].