Up-regulation Of GRP78 And GRP94 And Their Correlation With Chemotherapy Resistance To VP-16 In Human Lung Cancer Cell Line SK-MES-1

Objective: The glucose-regulated protein (GRP78) and GRP94 have been implicated in the development of tumorigenicity, the proliferation of tumor, suvival, metastasis and drug resistance. In the study, we investigated the expression of GRP78 and GRP94 under the induction of A23187 and their association with drug resistance to VP-16 in human lung cancer cell line SK-MES-1.Methods: The expression of GRP78 and GRP94 at mRNA and protein level induced by A23187 at different concentrations (0,0.5,1,1.5,2,4,6μM) in SK-MES-1 cell line was quantitive analized by RT-PCR and Western blotting respectively. Cell survival to VP-16 was determined using a colony-formation assay with the account of IC50.Results: The mRNA expression of GRP78 and GRP94 in the cells was corresponded well with their survival to VP-16. The resistance index (RI) was caculated by the IC50 of the controled curve divided by the IC50 of the treated curve. To a certain extent, the expression of GRP78 and GPR94 induced by A23187 both at mRNA level and protien level was significantly increased in SK-MES-1 cells, exhibiting a dose-dependent manner to A23187. The mRNA expression of GRP78 and GPR94 was elevated up to 1.4-3.9 folds and 1.1-2.4 folds respectively compared to the control. Similarly, the expression of them at protein level was increased up to 2.1-5.3 folds and 1.9-3.1 folds. The IC50s to VP-16 also showed a substantial elevation for the cells induced by A23187 at different concentrations (0,0.5,1,1.5,2,4,6μM), which were 5.72±0.32,5.57±0.49,7.42±0.53,7.27±0.81,10.73±0.40,15.5±70.7,23.2±0.56 respectively. Survival curves analysis demostrated that A23187 induction caused a significant prolonged survival for the cells subjected to VP-16. (P<0.05)Conclusions: Our findings indicated that A23187 treatment was fairly effective for the induction of GRP78 and GRP94, which subsequently resulted in development of the resistance to VP-16 in the human lung cancer cell line SK-MES-1. Correlation analysis suggested that there was a positive correlation between GRP94 and GRP78 at both mRNA level and protein level. Based on the pattern of the changes of IC50 and the relative expression of the two molecular chaperons and the survival of the cells,we concluded that up-regulated GRP78 and GRP94 are associated with the chemoresistance to VP-16 in human lung cancer cell line SK-MES-1.