Role of GSK-3β Activation in Responses of Colorectal Cancer Cells to EGFR and IGFR-1 Inhibitor

Objective To investigate the role of glycogen syntheses kinase 3β(GSK-3β) activation in response of colorectal cancer cells to epidermal growth factor receptor(EGFR)inhibitor gefitinib and insulin-like growth factor receptor-1(IGFR-1)inhibitor AG1024.Methods Western blot analysis was used to detect the expression levels of activated GSK-3β.Cell proliferation rate of colorectal cancer cells treated with GSK-3β inhibitor lithium chloride(LiCl)was determined by MTT assay.Laserscaning microscopy based on immunofluorescence staining for activated GSK-3β performed to observe its cellular expression and intranuclear accumulation.Results The expression level of activated GSK-3β significately increased in Lovo cells after treated with gefitinib,in contrast,no obvious changes in the other cell lines.HT29 cells showed a marked increase in GSK-3β activation after treated with the combination of gefitinib and AG1024,and so did HCT116 cells after the AG1024 treatment(P0.05).Cell growth suppression of gefitinib-treated Lovo cells was rescued by the addition of LiCl,and the similar effect that resulted from LiCl action was also conducted with combination-treated HT29 cells,as well as AG1024-treated HCT116 cells(P0.05).As confocal analysis shown,the significantly increased activated GSK-3β expression was found in the Lovo cells treated with the gefitinib,HT29 treated with the combination,and HCT116 treated with the AG1024,compared with their untreated-treated control groups respectively.More noticeable,subcellular localization of the activated GSK-3β displayed intranuclear accumulation when the cells were treated with the corresponding agents.Conclusion Gefitinib and/or AG1024-induced cell growth suppression was mediated by GSK-3β activation,suggesting that the responses of colorectal cancer cells to EGFR/IGFR-1β blockade could be predicted early in the course of treatment by measuring the activation of GSK-3β.