Abstract:

Objective To examine the anti-tumor efficacy and induction of apoptosis in combination therapy with low dose Rapamycin(RAPA)and Oxaliplatin(L-OHP)in HCT116 colon cancer cell line in vitro.Methods The growth inhibitory effect was evaluated by MTT assay in single agent or combination therapy.IC₅₀ values were determined by using CalcuSyn 2.0 software.To determine interaction of the drugs,combination index(CI)were calculated by the method of Chou and Talalay.Apoptosis was investigated by flow cytometry and western blotting.Results Both RAPA and L-OHP inhibited cell proliferation in a does-dependent manner and the IC₅₀ values were (8.35±0.78)μM (r=0.99)and (223.44±38.10)nM(r=0.94),respectively.The CI values were 0.52 and 0.72 when a combination of 10nM RAPA(IC₂₀)with 1μM(IC₂₀)or 2.5μM(IC₃₀)L-OHP were used.The cytotoxicity of 10nM RAPA and 1μM L-OHP combination reached to 31%,which were nearly 2 folds of using L-OHP alone.The apoptotic rate of combination therapy after 24 hours treatment was higher than that of L-OHP alone,although RAPA at a subtoxic concentration of 10nm did not induce apoptosis.The cleaved-PARP protein expression level was the highest after 48 hours combination treatment.Conclusion RAPA at a subtoxic concentration in combination with low dose L-OHP synergistically inhibited HCT116 cancer cell growth in vitro.The mechanism was in relation to enhanced apoptosis.