Induction of apoptosis on human small cell lung cancer NCI-H446 cell line via increasing the ratio of Noxa to Mcl-1 by 8-bromo-7-methoxychrysin

OBJECTIVE:To investigate the apoptotic inducing effect of 8-bromo-7-methoxychrysin(BrMChR)in human small cell lung cancer(NCI-H446)cell line in vitro,and its mechanism that is whether or not involved in increasing the ratio of Noxa to Mcl-1 protein.METHODS:Human small cell lung cancer(NCI-H446)cell line and Chinese Hamsters pulmonary epithelial(CHL)cell line were cultured in vitro.The cell viability inhibitory effect and the selection index of BrMChR on NCI-H446 cells and CHL cells were measured by MTT colometric assay.BrMChR-induced apoptosis rates of NCI-H446 cells were observed by Flow cytomtry(FCM)with PI staining.The influences of BrMChR on protein expression level and activity of Noxa,Mcl-1and Caspase-3 were analyzed by indirect immunofluorescence technique using flow cytometry.RESULTS:The MTT assay showed that BrMChR had a significantly inhibiting effect on the cell viability in NCI-H446 cells in a concentration-dependent manner,but there was little effect on CHL cells.The selective index to NCI-H446 cells was 46.The flow cytometry with PI staining indicated that the apoptosis rates of NCI-H446 cells treated with 0.3,3.0 and 30.0 μmol/L BrMChR for 48 h were 8.83%,23.7% and 34.9% respectively and significantly higher when treated with 3.0 and 30.0 μmol/L BrMChR than those with 30.0 μmol/L ChR(19.7%).The results of indirect immunofluorescence technique demonstrated that the expressions of Noxa and Caspase-3 increased,and Caspase-3 activated,while Mcl-1 down-regulated.CONCLUSION:BrMChR possesses a significant function for inducing apoptosis of NCI-H446 cells,which seems to be due to associated with increasing the ratio of Noxa/Mcl-1 protein and activating Caspase-3.