Objective The aberrantly activated anti-apoptotic PI3K/Akt signaling induced by cisplatin restrains the effectiveness of chemotherapy.Inhibition of this pathway may augment the sensitivity of cytotoxicity of tumor cells induced by cisplatin and promote apoptosis, CRM197, the non-toxic mutant of diphtheria toxin, could deliver the macromolecular substance across the blood-brain barrier.CRM197 also acts as an HB-EGF inhibitor and has some anti-cancer effects.This study aimed to investigate whether CRM197 could inhibit growth and induce apoptosis of human glioma cell line U251 and whether CRM197 could enhance the anti-cancer effects of cisplatin.Methods MTT and flow cytometric assays were used to detect the growth inhibition and apoptosis effects of U251 cells, and western blot analysis was used to detect the levels of phosphorylated Akt in U251 cells induced by CRM 197 combined with cisplatin.After pretreatment with the PI3K/Akt inhibitor LY294002 or wortmannin, the growth inhibition and apoptosis of U251 cells induced by CRM197 combined with cisplatin were detected.Results CRM197 inhibited cell growth and induced apoptosis of U251 cells.The growth inhibition rate reached a peak at 24 h, which was 47.36% of cisplatin at the same time.Compared with cisplatin alone, CRM197 combined with cisplatin significantly increased the inhibition rate and apoptosis rate of U251 cells.CRM 197 inhibited the Akt phosphorylation in a time-dependent manner.CRM197 markedly suppressed the Akt phosphorylation induced by cisplatin.Compared with LY294002, wortmannin significantly enhanced the inhibition rate and apoptosis rate of U251 ceils induced by CRM 197 combined with cisplatin.Conclusion CRM197 may inhibit the PI3K/Akt pathway induced by cisplatin to promote growth inhibition and apoptosis of glioma cells.