Proteomic analyses of Sirt1-mediated cisplatin resistance in OSCC cell line.

Oral squamous cell carcinoma (OSCC) accounts for about 90% of malignant oral lesions, and is recognized as the third most common cancer in developing nations and the sixth most common cancer worldwide. While chemotherapy remains the primary treatment for both resectable and advanced OSCC, most OSCC are naturally resistant to anticancer drugs, rendering new therapeutic avenues in dire need. Sirt1, a class III histone deacetylase, was linked to cisplatin resistance in several cancer types; however, the underlying mechanism is still unclear. Here, we demonstrated that overexpression of Sirt1 survived OSCC cell line Tca8113 under cisplatin treatment. Notably, BML-210, a chemical inhibitor of class III histone deacetylase, significantly abolished Sirt1-mediated cisplatin resistance in Tca8113 cells. Further, inactivation of endogenic Sirt1 by nicotinamide markedly increased chemo-sensitivity in cisplatin resistant sub-cell line Tca8113/CDDP. Proteomic strategy was applied to profile the differentially expressed proteins between pcDNA3.1-Sirt1- and mock vector-treated Tca8113 cells. Among 54 spots identified, 31 proteins were up-regulated and 23 proteins were down-regulated upon Sirt1 expression. Expression of four proteins with most significant alteration, including Annexin A4, Stathmin, SOD2 and thioredoxin, were validated by both RT-PCR and Western blot. Finally, we showed that Sirt1 could prevent cisplatin-induced ROS accumulation in Tca8113 cells. Our findings are considered as a significant step toward a better understanding of Sirt1-mediated cisplatin resistance.