Abstract: AIM:To investigate the inhibition of frac-tion C Ⅱ from naja naja actra venom(FC ⅡNNAV)on multidrug-resistant tumor cell lines KBv200 and K562 A02.METHODS: Cytotoxicities of FC ⅡNNAV on KB、 KBv200、K562 and K562/A02 cells were measured by MTT assay.And the apoptosis induced by FC ⅡNNAV on K562/A02 cells were observed by DNA Ladder and flow cytometry (FCM).RESULTS: FC ⅡNNAV had the in-hibitory effects on KB 、KBv200、K562 and K562/A02 cells.The IC₅₀ were 0.87 ±0.15、1.07 ±0.08、0.67 ± 0.11 and 0.75±0.01 μg·ml^-1, respectively.It was obvi-ous that FC ⅡNNAV could induce cell apoptosis of K562 A02.CONCLUSION: FCⅡNNAV has the inhibitory ef-fect on KB、KBv200、K562 and K562/A02 cells.FC Ⅱ NNAV can induce apoptosis on multidrug-resistant tumor cell, which may be one of mechanisms for circumventing tumor multidrug-resistant.

Key words: snake venom, neoplasm, multidrug re-sistance, apoptosis