Role of aberrant PI3K pathway activation in gallbladder tumorigenesis.

// Andrea Lunardi 1 , Kaitlyn A. Webster 1 , Antonella Papa 1 , Bhavik Padmani 2 , John G. Clohessy 2 , Roderick T. Bronson 3 and Pier Paolo Pandolfi 1 1 Cancer Research Institute, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA 2 Preclinical Murine Pharmacogenetics Facility, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. 3 The Dana Farber/Harvard Comprehensive Cancer Center, Boston MA, USA. Correspondence: Pier Paolo Pandolfi, email: // Keywords : PI3K, PTEN, gallbladder tumorigenesis, mouse model. Received : February 8, 2014 Accepted : March 8, 2014 Published : March 10, 2014 Abstract The PI3K/AKT pathway governs a plethora of cellular processes, including cell growth, proliferation, and metabolism, in response to growth factors and cytokines. By acting as a unique lipid phosphatase converting phosphatidylinositol-3,4,5,-trisphosphate (PIP3) to phosphatidylinositol-4,5,-bisphosphate (PIP2), phosphatase and tensin homolog (PTEN) acts as the major cellular suppressor of PI3K signaling and AKT activation. Recently, PI3K mutations and loss/mutation of PTEN have been characterized in human gallbladder tumors; whether aberrant PTEN/PI3K pathway plays a causal role in gallbladder carcinogenesis, however, remains unknown. Herein we show that in mice, deregulation of PI3K/AKT signaling is sufficient to transform gallbladder epithelial cells and trigger fully penetrant, highly proliferative gallbladder tumors characterized by high levels of phospho-AKT. Histopathologically, these mouse tumors faithfully resemble human adenomatous gallbladder lesions. The identification of PI3K pathway deregulation as both an early event in the neoplastic transformation of the gallbladder epithelium and a main mechanism of tumor growth in Pten heterozygous and Pten mutant mouse models provides a new framework for studying in vivo the efficacy of target therapies directed against the PI3K pathway, as advanced metastatic tumors are often addicted to “trunkular” mutations.