SIRT1 and neoplasm: When affected by external oxidative stress, ionizing radiation, telomere shortening, and loss of tumor inhibition, SIRT1 gene is indirectly inhibited, and FOXO3 gene is directly inhibited, p21 gene is directly promoted through ionization, CDK2 gene and CycE gene are directly inhibited, RB gene is directly inhibited by phosphorylation, and finally E2F gene is directly inhibited.