Abstract: AIM: To investigate the inhibitory effect of fraction C Ⅱ from Naja naja Actra Venom (FC Ⅱ NNAV) on multidrug-resistant human leukemia cell line K562/A02 and its mechanisms.METHODS: The cytotoxicity of FC ⅡNNAV on K562/A02 and k562 cells was measured by MTT assay.The protein expression of P-gp and Bcl-2 of K562/A02 was observed by flow cytometry. The activation of Caspase-3 was detected by colorimetric assay.RESULTS: FC ⅡNNAV had the inhibitory effect on K562/A02 and K562.The values of IC50 were 0.75±0.01 and 0.67±0.11 μg·ml^-1, respectively.The expression of P-gp and Bcl-2 decreased after application of FC Ⅱ NNAV and Caspase-3 was activated by FC Ⅱ NNAV.CONCLUSION: FC ⅡNNAV has the inhibitory effect on K562/A02 and K562.FC ⅡNNAV can induce K562/A02 cell apoptosis through down-regulation expression of P-gp and Bcl-2 and activating Caspase-3.

Key words: snake venom, neoplasm, multidrug resistance, apoptosis, P-glycoprotein