PGP and neoplasm: Hyperglycemia increases the expression of Nampt and Sirt1 in gastric cancer tissues and the expression of mutant p53 (compared with wild-type p53, the overexpression of mutant p53 in tumor cells is positively correlated with the high level expression of P-gp), resulting in the up-regulation of P-glycoprotein (P-gp) and down-regulation of Topoisomerase IIα (Topo-IIα).