Sensitization of human cervical cancer HeLa cells to TRAIL-induced apoptosis by apigenin via constitutively activating JNK

【Objective】 To investigate whether apigenin(API) enhance apoptosis induced by recombinant human soluble TNF-related apoptosis-inducing ligand(TRAIL) through constitutively activating JNK in human cervical cancer HeLa cell line.【Methods】 Human cervical cancer HeLa cells were treated with API and /or TRAIL in vitro.The characteristic features of cell apoptosis were examined by PI fluorescence staining combined with flow cytometry,assay of caspase-3 activity using colorimetric method,and DNA agarose gel electrophoresis.The expressions of protein were analyzed by Western blot.【Results】 Flow cytometry(FCM) analysis with PI staining indicated that the percentage of sub-G1 cells in human cervical cancer HeLa cells treated with API(20 μmol/L) or TRAIL(20 ng/mL) alone,and with combination for 48h were(3.5±0.20)%,(6.69±0.40)%,and(59.87±4.20)% respectively.Caspase-3 activity in HeLa cells was 1.4,1.5,39 fold in comparison with medium group.Co-treatment with API[0] and TRAIL increased the apoptosis of Hela cells as shown in apoptotic DNA ladder experience,which was ameliorated by zDEVD-fmk,the inhibitor of caspase-3.Western blot analysis indicated that API elevated the phosphorylation level of JNK in a time-dependent manner,which was blocked by the specific inhibitor of JNK,SP600125.Furthermore,SP600125 resulted in decrease the percentage of sub-G1 cells from(58.50±6.10)% to(15.70±2.46)%(P 0.01) in combination of TRAIL(20 ng/mL) and API(20 μmol/L).【Conclusion】 The sensitization of HeLa cells to TRAIL induced apoptosis by API is associated with constitutively activating JNK.