Abstract: Objective: To investigate the influence of arsenic troxide(As₂O₃) and γ-secretase inhibitor MW167 used alone or in combination in the drug resistance of HepG/ADM cells,and to clarify its mechanisms. Methods: The HepG₂/ADM cells were treated with different concentrations of As₂O₃(0.25,0.50,1.00,2.00,4.00,8.00 mg·L^-1) and MW167(10,20,40 μmol·L^-1) for 24,48 and 72 h,and MTT method was used to detect the optical density (A) values,then the inhibitory rates of proliferation were calculated and the drug concentration and treatment time were confirmed.The HepG₂/ADM cells were divided into blank group,As₂O₃ group, MW167 group and combination group; the non-cytotoxic doses of As₂O₃ and MW167 according to the results of MTT were chosen and the HepG₂/ADM cells were intervened for 48 h; the apoptotic rates were detected by FCM; RT-PCR and Western blotting methods were employed to detect the mRNA and protein expression levels of Notch-1,Hes-1,MDR-1 (P-gp),Bcl-2 and Bax in the cells in various groups. Results: At the same concentration,the inhibitory rates of proliferation of HepG₂/ADM cells were enhanced with the prolongation of the treatment time of As₂O₃ and MW167(P<0.05 or P<0.01); at the same time point,the inhibitory rates of proliferation of As₂O₃ and MW167 in the HepG₂/ADM cells were increased with the increasing of drug concentration (P<0.05); the non-toxic doses of As₂O₃ and MW167 were 0.25 mg·L^-1 and 10 μmol·L^-1 and the intervention time was 48 h.After treatment for 48 h,compared with blank group,the apoptotic rates in various intervention groups were increased (P<0.05),especially in combination group (P<0.01); the expression levels of Notch-1,Hes-1,MDR-1 (P-gp),Bcl-2 mRNA and protein in various intervention groups were lower than those in blank group (P<0.05),especially in combination group (P<0.01);compared with blank group,the expression levels of Bax mRNA and protein in various intervention groups were increased (P<0.05),especially in combination group (P<0.01). Conclusion: As₂O₃ can reverse the drug resistance of HepG₂/ADM cells,its mechanism may be related to inhibition of cell proliferation,promotion of apoptosis,down-regulation of the expression levels of Notch-1,Hes-1,MDR (P-gp),Bcl-2 and up-regulation of the expression levels of Bax mRNA and protein.

Key words: multidrug resistance, apoptosis, liver neoplasms, Notch signaling pathway, cell proliferation, arsenic trioxide