Smac playing vital role in enhancing the sensitivity of cyclophosphamide and doxorubicin in breast cancer MCF-7 cell line / 国际肿瘤学杂志

ABSTRACT

Objective To investigate the influence of Smac to the chemosensitivity of cyclophosphamide (CTX) and doxorubicin (DOX) in MCF-7 cells.Methods MCF-7 cells were exposed to CTX,DOX and the combination of both.3-(4,5-dimethyl-2-thiazoly)-2,5-diphenyl-2 H-tetrazolium bromide (MTT) assay was used to estimate the cell viability.Apoptosis was measured by acridine orange staining and Ho.33342/PI dou-ble staining.The mRNA and protein expressions of Smac were determined by RT-PCR and Western blotting.The study also analyzed the changes of pro-apoptotic proteins active caspase-3 and active caspase-9.Results CTX,DOX and the combination of both drugs reduced the cell survival rates in a concentration-dependent manner.The cell viability after being treated with 4.0 μg/ml CTX or 0.2 μg/ml DOX or 2.0 μg/ml CTX and 0.1 μg/ml DOX for 48 hours was (52.90 ± 8.78) ％,(53.35 ± 6.29) ％ and (34.19 ± 5.43) ％,respectively.The drug combination developed a stronger inhibitory effect compared to the single drugs (t =9.051,P=0.014;t =9.074,P =0.014).The Smac mRNA and protein levels in 2.0 μg/ml CTX and 0.1 μg/ml DOX group were 7.47 ± 0.82 and 4.13 ± 0.36,which were higher than those in 4.0 μg/ml CTX group (3.27 ± 0.40 and 2.28 ± 0.27;t =-50.120,P =0.000;t =-42.588,P =0.000) and 0.2 μg/ml DOXgroup (3.34±0.62and2.45±0.40;t=-46.233,P=0.000;t=-39.541,P=0.000).Furthermore,pro-apoptotic proteins active caspase-3 and active caspase-9 increased activity was confirmed by Western blotting.Conclusion Smac plays a vital role in enhancing the sensitivity of chemotherapeutic drugs CTX and DOX in MCF-7 cell line.