Novel oncogenic function of ATDC in bladder cancer.

Abstract

4591 Background: Bladder cancer is a common and deadly disease, but the molecular events leading to its initiation and progression are incompletely understood. We recently identified Ataxia-Telangiectasia Group D Associated (ATDC) as a novel oncogene which drives tumor proliferation and invasion in pancreatic carcinoma (Cancer Cell, 2009). In this study, we describe the role of ATDC as an oncogene in bladder cancer. Methods: To further determine the oncogenic role of ATDC, we generated ATDC transgenic (tg) mice in which ATDC expression was driven by a CMV promoter and characterized the resulting tumors. Results: Interestingly, the dominant phenotype in these mice was the development of both non-invasive and invasive urothelial carcinomas (9% and 20% respectively, average age of onset 10-12 months of age). Histologically, these tumors were indistinguishable from human urothelial carcinomas. Gene expression profiling of invasive tumors derived from ATDC tg mice demonstrated a marked overlap with gene signatures of human invasive bladder cancers. ATDC was the 11th most highly up-regulated gene in bladder cancers represented in the Oncomine gene expression database. Analysis of a human bladder cancer tissue microarray (311 samples) by IHC showed elevated expression in 70% (173/252) of muscle-invasive carcinomas, 22% (5/23) of papillary tumors and little or no expression in normal bladder urothelium. ATDC tg mouse bladder tumors demonstrated loss of p53 signaling and down-regulation of PTEN expression, which correlated with ATDC induced methylation of the PTEN promoter by DNMT3A. Furthermore, ATDC knock-down in invasive cancer cell lines resulted in decreased proliferation, invasion and reactivation of p53-mediated signaling and PTEN expression. Conclusions: ATDC is a novel oncogene that is highly expressed in human bladder cancers and is sufficient to drive the development of invasive bladder tumors in tg mice. The mechanism by which ATDC drives bladder cancer formation involves alterations in p53 and PTEN pathways known to be important in bladder tumorigenesis.