Abstract 2713: The Pten and p53 tumor suppressors cooperate to constrain the PI3K/mTOR pathway activation.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Loss of Pten expression and mutational inactivation of p53 are frequent molecular events in liver cancer associated with advanced disease stage and poor prognosis. The tumor suppressor PTEN is a phosphoinositide phosphatase that antagonizes the class IA PI3K-engaged oncogenic signaling by dephosphorylating PtdIns(3,4,5)P(3); however, the specific roles of class IA PI3K isoforms, p110a and p110b, have not been assessed in genetically engineered mouse models of liver cancer with Pten inactivation. Furthermore, effective treatment strategies for Pten and p53 deficient liver malignancy remain to be defined. In this study, we showed that combined deletion of Pten and p53 in liver led to rapid development of hepatocellular carcinoma and cholangiocellular carcinoma, the two most common types of liver cancer, with complete penetrance. While a single ablation of p110a or p110b markedly reduced the tumor burden, inactivation of both p110a and p110b completely blocked the liver tumorigenesis. Although liver tumors driven by inactivation of Pten and p53 showed a good response to GDC-0941, a pan-PI3K inhibitor, the combined treatment with both GDC-0941 and Rad001, an mTOR inhibitor or single-agent BEZ235, a dual pan-PI3K and mTOR inhibitor, led to marked tumor regression. These studies suggest that Pten and p53 cooperate to constrain the PI3K/mTOR pathway activation and inhibitors targeting both PI3K and mTOR may effectively treat Pten and p53 deficient liver cancers. Citation Format: Pixu Liu, Hailing Cheng, Lynn Symonds, Erbo Xu, Sauveur-Michel Maira, Emmanuelle di Tomaso, Thomas Roberts, Jean Zhao. The Pten and p53 tumor suppressors cooperate to constrain the PI3K/mTOR pathway activation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2713. doi:10.1158/1538-7445.AM2013-2713