The Expression Of Glucose-regulated Protein 78/94 Induced By A23187 And Drug Resistance In Lung Cancer

Objective:To investigate the expression of GRP78 and GRP94 under the induction of A23187 and its significance in the resistance to anti-tumor drugs VP-16 in a human small cell lung cancer NCI-H446 cell line.Methods:RT-PCR and Western Blotting were used in analyzing the expression of GRP78/GRP94 at mRNA and protein levels in NCI-H446 cell line induced by A23187 at different concentrations (0, 0.5, 1, 1.5, 2, 4, 6μM). Cell survival to VP-16 was determined by a colony- formation assay.Results:The expression of GRP78/GRP94 at both mRNA and protein levels were increased obviously in NCI-H446 cell line induced by A23187. This induction caused a dose-dependent increase in GRP78/GRP94 expression to a great degree. However, the elevation of GRP78/GRP94 at protein level did not always correspond with that at mRNA level. Firstly, the starting induced concentration for GRP78 at mRNA level and protein level is 1μM and 1.5μM respectively. Second, 4μM of A23187 is the most concentration for the induction of GRP78 at mRNA level, which means an around 4 folds elevation compared to the control, whereas, for GRP78 at protein level, 6μM is the most, which means a 3 folds elevation compared to the control. Similar, the starting induced concentrations for GRP94 at mRNA level and protein level are both 1μM. Meanwhile, 2μM of A23187 is the most for the induction of GRP94 at mRNA level, which means an around 2 folds elevation compared to the control, whereas, for GRP94 at protein level, 6μM is the most, which means a 4 folds elevation compared to the control. Commonly, the induction of GRP78/GRP94 at mRNA level is easier than that at protein level. The IC50 to VP-16 for the cells under the induction of A23187 (from 2μM to 6μM) are higher than the control.Furthermore, it showed a dose-responsive trait. Based on the trend of the changes of IC50 and the expression of GRP78/94 in different disposed cells, we conclude GRP78/GRP94 is associate with resistance to VP-16.and this resistance is dependent on the level of GRP78/GRP94 in NCI-H446 cell line to a great degree.Conclusions:A23187 treatment is highly effective in the induction of GRP78/GRP94 and subsequent development of resistance to VP-16 in human lung cancer NCI-H446 cell line. Based on the trend of the changes of IC50 and the level of GRP78/GRP94 in different disposed cells, we conclude that there is correlation between the expression of GRP78/GRP94 and resistance to VP-16. This suggest that down-regulation of GRP78/GRP94 or inhibition of GRP78/GRP94 activity by small molecular may offer a new therapeutic approach to lung cancer.