Abstract: Objective: To observe the effect of CoCl₂ on the cisplatin sensitivity of human ovarian cancer SKOV3 cells, and to clarify the possible mechanism.Methods: The SKOV3 cells were cultured in vitro and randomly divided into control group, CoCl₂ group, cisplatin (DDP) group and CoCl₂ combined with DDP(combination) group. The cells in CoCl₂ group were cultured in normal cell medium for 20 h after cultured in 200 μmol·L^-1 CoCl₂ for 4 h, the cells in DDP group were cultured in normal cell medium containing 10 mg·L^-1 DDP for 24 h, and the cells in combination group were cultured in 10 mg·L^-1 DDP for 20 h after cultured in 200 μmol·L^-1 CoCl₂ for 4 h. The survival rates of SKOV3 cells in various groups were detected by MTT method, and the positive expression intensities of hypoxia-inducible factor-1 α (HIF-1α) and inducible nitric oxide synthase (iNOS) in the cells in various groups were detected by immunofluorescence method. Rhod 2-AM fluorescence probe was used to observe the levels of Ca²⁺ in mitochondria in the cells in various groups. Western blotting method was used to observe the expression levels of cytochrome C (cyto C), cysteinyl aspartase 3 (caspase 3) and cleaved cysteinyl aspartase 3 (cleaved caspase 3). Muse^® apoptosis assay kit was used to detect the apoptotic rates of cells in various groups.Results: Compared with control group, the survival rate of the cells in CoCl₂ group had no significant change (P>0.05), and the survival rates of the cells in DDP and combination groups were decreased (P<0.05); the survival rate in combination group was higher than that in DDP group (P<0.05). Compared with control group, the positive expression intensities of HIF-1α in CoCl₂ and combination groups were increased (P<0.05). Compared with control group, the positive expressions of iNOS in DDP and combination groups were increased (P<0.05). The Ca²⁺ levels in the cells in DDP group and combination groups were higher than that in control group (P<0.05) and the Ca²⁺ level in DDP group was higher than that in combination group (P<0.05). Compared with control group, the expression levels of cyto C,caspase 3 and cleaved caspase 3 proteins in the SKOV3 cells in CoCl₂ group had no significant changes (P>0.05), and the expression levels of cyto C,caspase 3 and cleaved caspase 3 in DDP group were increased significantly(P<0.05); compared with DDP group, they were lower than those in combination group (P<0.05). Compared with control group, the apoptotic rate of SKOV3 cells in DDP group was increased significantly(P<0.05); the apoptotic rate of SKOV3 cells in combination group was lower than that in DDP group (P<0.05).Conclusion: CoCl₂ can redece the mitochondrial apoptosis of human ovarian cancer SKOV3 cells by inhibiting the DDP-induced enhancement of iNOS expression and decrease the sensitivity of SKOV3 cells to cisplatin.

Key words: hypoxia-inducible factor-1 α, cobalt chloride, inducible nitric oxide synthase, ealciumion, cisplatin sensitivity, SKOV3 cells