Down-regulation of GRP78 is associated with the sensitivity of chemotherapy to VP-16 in small cell lung cancer NCI-H446 cells

The SCLC NCI-H446 cells were divided into three groups: BAPTA-AM→A23187-treated group, A23187-treated group and control-group. Immunofluorescence, western blot and RT-PCR were used to assess the expression of GRP78 at both protein and mRNA levels. Cell apoptosis and the cell cycle distributions of the cells were analyzed by flow cytometry in order to evaluate the therapeutic sensitivity to VP-16.The expression of GRP78 at both protein and mRNA levels in the BAPTA-AM→A23187-treated cells dramatically decreased as compared to that in both A23187-treated and control groups. After treatment by VP-16, the percentage of apoptotic cells in BAPTA-AM→A23187-treated cells were: 33.4 ± 1.01%, 48.2 ± 1.77%, 53.0 ± 1.43%, 56.5 ± 2.13%, respectively, corresponding to the concentrations of BAPTA-AM 10, 15, 25, 40 μM, which was statistically significant high in comparison with the A23187-treated group and untreated-group (7.18 ± 1.03% and 27.8 ± 1.45%, respectively, p < 0.05). The results from analysis of cell cycle distribution showed that there was a significantly decreased in G1 phase and a dramatically increased in S phase for the BAPTA-AM→A23187-treated cells as compared with the untreated cells.BAPTA-AM is a strong inhibitor of GRP78 in the NCI-H446 cell line, the down-regulation of GRP78 can significantly increase the sensitivity to VP-16. The suppression of GRP78 may offer a new surrogated therapeutic approach to the clinical management of lung cancer.Lung cancer is currently the leading cause of cancer deaths worldwide no matter in men or women [1]. Small cell lung cancer (SCLC) accounts for 13%–15% of all lung cancer worldwide [2]. Chemotherapy is an important means of the treatment for patients with SCLC. However, the drug resistance as developed during the treatment really limits the efficacy of chemotheraspy. Multiple pathways are suggested to be involved in the complexity of chemotherapy resistance in SCLC. A favorable mechanism for explaining the chemotherapy resista