Effects Of GRP78 On The Reactivity Of NSCLC Cells Harboring EGFR L858R Mutation To Erlotinib

ObjectiveTo investigate the effect of GRP78 on the sensitivity to erlotinib in NSCLC cells harboring L858 R mutation,offer new theoretical basis for NSCLC patients who eventually develop erlotinib resistance.MethodsImmunohistochemistry was used to detect the expression of GRP78 in lung cancer tissues with L858 R mutation.The gene transfection was used to upregulate the expression of wild-type GRP78 and its ATPase and PBD domain deleted mutants in EGFR L858 R mutant cell line H3255.MTT assay was used to examine the inhibitory effect of erlotinib on H3255 cells overexpressing GRP78 or its domain deleted mutants.Flow cytometry and FITC-tunnel were used to observe the status of cell apoptosis.Immunoblotting was performed to detect the expression and phosphorylation of EGFR and ERK.ResultsThe results of immunohistochemistry showed that the expression level of GRP78 in lung cancer tissues with EGFR L858 R mutation was significantly higher than that of wild type EGFR lung cancer tissues.The results of MTT showed that overexpression of GRP78 and its PBD domain deleted mutant could significantly reduce the reactivity of H3255 cells to erlotinib,whereas overexpression of ATPase domain deleted mutant raised the reactivity of H3255 cells to erlotinib.Flow cytometry analysis and FITC-tunel results showed that overexpression of GRP78 and its PBD domain deleted mutant could significantly inhibit erlotinib-induced apoptosis,and overexpression of ATPase domain deleted mutant promoted apoptosis.Western blot results showed that overexpression of GRP78 and its PBD domain deleted mutant could significantly promote the phosphorylation of EGFR and ERK.overexpression of ATPase domain deleted mutant inhibited EGFR and ERK phosphorylation.ConclusionsOverexpression of GRP78 confers the acquired resistance to erlotinib in NSCLC cells harboring EGFR L858 R mutation,and its ATPase domain played an important role in this process.