Role of FOXM1 expression inbibition regulated by thiostrepton in the proliferation and apoptosis of lung cancer cells

Abstract

Objective To investigate the effect of thiostrepton (TST) on cell proliferation,apoptosis and the chemosensitivity of non-small cell cancer (NSCLC) cell lines A549 to AG1478 (EGFR-TKI).Methods NSCLC cell A549 was treated with TST,AG1478 or the combination of the two drugs.CCK-8 cell viability assay was performed to determine the relative growth suppression rate of A549 cell.The expression level of forkhead transcription factors M1 (FOXM1) was studied by western blot.Caspase-3 colorimetric assay was employed to evaluate the effect of TST on Caspase-3 activity.A siRNA targeting FOXM1 was designed and transfected into A549 cells.RT-PCR and western blot were used to examine the expressions of FOXM1 and proliferation and apoptosis related molecules.Results TST increased the chemosensitivity of A59 cells to AG1478,a kind of molecular-targeted agent to advanced lung cancer,which made the IC50 value reduce from (4.35 ±0.45) μmol/L to (0.73 ± 0.05) μmol/L (t =11.02,P ＜ 0.05).Besides,TST inhibited the expressions of FOXM1 and its effectors including c-Myc,Cyclin B1 and Bcl-2,while up-regulated P21,Cleaved Caspase-3 and Cleaved PARP.Meanwhile,TST improved the activity of Caspase-3,which showed time-and dose-dependent effects.FOXM1 siRNA changes the expression of the downstream effectors such as c-Myc,Cyclin B1,Bcl-2,P21 and Cleaved PARP,which was similar to the effect of TST.Also,the fluorescent expression of Cleaved Caspase-3 significantly increased in A549 cells.Conclusion TST can significantly inhibit proliferation and induce apoptosis by downregulating the expression of FOXM1,and then increase chemosensitivity of A549 cell to AG1478. Key words: Lung neoplasms; RNA interference ; Forkhead transcription factors M1 ; Thiostrepton; Drug sensitivity