Abstract 1642: TIP-1 regulates sensitivity of glioma cells to radio- and chemotherapeutic agents through modulating p53 stability and activation

Abstract

Abstract Malignant gliomas represent one group of tumors that poorly respond to chemo- and radio-therapies because of the intrinsic or acquired resistance. Identification of novel molecules that are involved in the therapeutics resistance is critical to develop new therapeutic modalities. Our previous studies show that TIP-1 involves in tumor cells response to ionizing radiation (IR). In this study, we found that TIP-1 expression level correlates to the clinical staging and overall patient survival time after diagnosis of malignant gliomas. We hypothesized that TIP-1 is one novel predictive biomarker of glioma cell response to treatment, and targeting TIP-1 represents one novel strategy to combat the disease of high mortality. Studies on cell-based models indicated that TIP-1 deficiency resulted in the enhanced sensitivity of D54 and GL261 glioma cell lines to IR and chemotherapeutic agents, whereas ectopic expression of TIP-1 conferred resistance to the therapeutics in the cells. The data also showed that sensitivity of the glioma cell lines to IR correlates to stability and activation of p53 protein after IR treatment. Yeast two-hybrid screening identified C53/LZAP as one TIP-1 interacting protein within glioma cells. PDZ domain within TIP-1 binds to one classic type I PDZ-binding motif at the carboxyl terminus of C53/LZAP protein. C53/LZAP has been studied as one tumor suppressor and modulator of the cancer cell susceptibility to genotoxic stress including IR and several chemotherapeutic agents. C53/LZAP interacts with ARF and protects p53 from Mdm2-mediated protein degradation. Our data demonstrated that, after irradiation, presence of TIP-1 enhanced C53/LZAP interaction with ARF, thus promoted Mdm2-mediated p53 ubiquitination and resulted in less stable p53 protein. On the other hand, with absence of TIP-1 protein, IR treatment resulted in more stabilized and activated p53 protein that drives IR-induced apoptosis of the glioma cells. Taken together, our data suggests that TIP-1 is one novel modulator of p53 tumor suppressor and contributes to chemo- and radio-resistance of glioma cells. Therefore, targeting TIP-1 represents one novel approach for the improved therapy of malignant glioma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1642. doi:10.1158/1538-7445.AM2011-1642