Preliminary Study of Apoptotic Inhibition and Its Molecular Mechanism of Dexamethasone on Cisplatin-induced

Objective To study the apoptotic inhibition and its molecular mechanism of dexamethasone (Dex) on cisplatin (CDDP)-induced human lung adenocarcinoma cells. Methods The human lung adenocarcinoma cell line, SPCA/Ⅰ, was pre-cultured in vitro for 24 hours with Dex in different concentration and then different concentration of CDDP was added. The cells were cultured for another 48 hours. The survival rate of the cells was determined by MTT colorimetry. The appototic rate of SPCA/Ⅰ cells measured by flow cytometer. Using 1 μmol/L Dex to stimulate the SPCA/Ⅰ cells RNAs of the cells at different time points (1 h, 2 h, 4 h, 6 h, 12 h) were extractedrespectively. Semi-quantitative RT-PCR technology was used to detect the expression of the serum and glucocorticoid-induced kinase (SGK-1) and mitogen-activated protein kinase phosphatase-1(MKP-1) in SPCA/Ⅰ cells. Simultaneously the glucocorticoid receptor (GR) of the SPCA/Ⅰ cell line cells were measured by using biotin-labeled anti-glucocorticoid receptor antibody with immunohistochemistry assay. Results SPCA/Ⅰ cells showed resistance to CDDP-induced apoptosis while pre-cultured with Dex and the resistance intensity was Dex concentration-dependent. After Dex stimulating the SPCA/Ⅰ cells, SGK-1 expressed increased and reached the peak at 12 h. But the expression of MKP-1 was not detected. Immunohistochemistry results showed that up-regulated GR in SPCA/Ⅰ cells after stimulation with Dex. The number of intracellular GR was significantly higher than that of control group. Conclusion The experimental results in vitro demonstrated that Dex inhibits apoptosis on CDDP-induced human lung adenocarcinoma cell line, SPCA/Ⅰ. This anti-apoptosis effect might due to Dex increasing the expression of SGK-1, an anti-apoptotic protein, in its downstream signal pathway through the increasement of intracellular GR of SPCA/Ⅰ cells.