VP-16 Resistance in the NCI-H460 Human Lung Cancer Cell Line is Significantly Associated with Glucose-regulated Protein78 (GRP78) Induction

Abstract

Aim: To investigate the relationship between the expression of glucose-regulated protein (GRP78) and resistance to VP-16 in the NCI-H460 cell line. Methods: RT-PCR, real-time RT-PCR and Western blotting were used in analyzing the expression of GRP78 at mRNA and protein levels in the NCI-H460 cell line induced by A23187 at different concentrations. Cell survival with VP-16 was determined using a colony-formation assay with the account of IC₅₀. Results: The expression of GRP78 at both the mRNA and protein levels was higher in the NCI-H460 cell line induced by A23187. A23187 treatment resulted in up to 4.8-fold elevation of GRP78 mRNA and up to 3.2-fold elevation of GRP78 protein in the experimental cells compared to the controls, all in a dose-dependent manner. The IC₅₀s for VP-16 in the cells pretreated with different concentrations of A23187 (0, 1, 2, 4 and 6 μM) were: 12.11±0.83, 12.68±1.04, 25.82±1.83, 37.46±1.89 and 45.19±2.34 μM, respectively. Compared to the control, there was a significant elevation of IC₅₀ for VP-16 in the cells pretreated with A23187. Survival curve analysis also showed that the induction of A23187 caused a significantly longer survival for the cells subjected to VP-16 treatment (p<0.05). Conclusion: A23187 treatment is highly effective for the induction of GRP78 and subsequent development of resistance to VP-16 in the human lung cancer NCI-H460 cell line. Based on the trend of the change in IC₅₀ and the expression of GRP78 in differently exposed cells, we conclude that the induction of GRP78 by A23187 is significantly associated with the resistance to VP-16.