ABSTRACT
Objective To study the effect and mechanism of the thapsigargin combined with gefitinib on the proliferation of human lung adenocarcinoma gefitinib resistance cell line PC9/GR. Methods The cell viability of PC9/GR treated with gefitinib alone or gefitinib combined with thapsigargin was evaluated by CCK8 assay. The flow cytometry was used to analyze the PC9/GR cell apoptosis indued by the two group drugs. The ATF-6 and IRE1α protein expression of PC9/GR cells treated with the two group drugs were detected by Western blotting. Results The group of drug combination exhibited enhanced ability to inhibit cell proliferation, promote cell apoptosis and upregulate the ATF-6 and IRE1α protein expression of the PC9/GR compared with the group gefitinib used alone. Conclusion The sensitivity of PC9/GR to gefitinib was increased when the cells were treated by thapsigargin, which may be related with the state of endoplasmic reticulum stress（ERS） induced by thapsigargin.