Abstract: Objective To investigate the effect of cobalt chloride on tumor cells proliferation and apoptosis in vitro, to explore the reasonable strategy of chemical hypoxia induced by CoCl2. Methods Two tumor cell lines (A549 and HeLa) were respectively exposed to CoCl2 (0.05~2mmol/L) for different time period (4~48h), cells viability、proliferation and apoptosis were maesured by MTT and FCM methods. HIF-1α and related apoptosis proteins expression were detected by Western blot. Results Cells viability were weakly changed in low concentration（≤200?mol/L）of CoCl2 within 24h. However, higher dose or prolonged challenge of CoCl2 significantly decreased cell survival rate (p<0.05). Most of the damaged cells were early apoptosis population after CoCl2 (200?mol/L) incubation within 24h, major of the damaged cells were late apoptosis and necrosis part after CoCl2(800?mol/L) treatment. CoCl2 (200?mol/L) exposure implicated in up-regulating the expression of HIF-1α, Bax, P53 and down-regulating the expression of Bcl-2 in A549 cell within 24h. However, higher concentration (~400?mol/L) or prolonged CoCl2 challenge lead to HIF-1α expression decreasing. Similar results were observed in HeLa cell, except P53. Conclusions Effect of CoCl2 on the tumor cells proliferation and apoptosis is dose and time-dependent. But prolonged or higher dose of cobalt exposure was not positive to expected chemical hypoxia effect (HIF-1α expression). The concentration and duration of CoCl2 administration should be taken into consideration in chemical hypoxia.

Key words: Cobalt chloride, A549 cell, HeLa cell, Apoptosis, HIF-1α