Role of homeobox pathway in prostate carcinogenesis.

Abstract

126 Background: Identifying aberrant activity of developmental pathways in prostate cancer provides therapeutic opportunities. To this end, despite a shared embryonic origin and similarities to prostate cancer in histology and androgen dependence, seminal vesicle cancer is exceptionally rare. Genomic pathway analyses of their critical developmental differences may reveal uncharacterized oncogenic pathways. Previous attempts to do so have used whole tissue preparations. We hypothesized that careful gene profiling of pure primary epithelial cultures from normal prostate and seminal vesicles would reduce confounding noise during analysis and provide more robust pathway prioritization. Methods: Paired normal prostate and seminal vesicle epithelium cultures were created from three de-identified patients. Derived gene expression profiles were grouped into cancer biomodules using a protein-protein network algorithm to analyze their relationship to known oncogenes. Each resultant biomodule was assayed for its prognostic ability in independent Kaplan-Meier analyses of prostate cancer patients for time to recurrence and overall survival. Protein products from prioritized biomodule genes were then evaluated in vitro. Results: Gene expression profiling and protein network prioritization resulted in three cancer biomodules. Survival analysis revealed that the embryonic developmental biomodule centered on homeobox genes Meis1, Meis2 and Pbx1 to have clinical import. This homeobox biomodule detected a survival difference in a set of active surveillance patients (n=172, p=0.05) and identified men who were more likely to recur biochemically post-prostatectomy (n=78, p=0.02). We analyzed in vitro protein expression of Meis1, Meis2, Pbx1 and confirmed decreased gene expression in independent datasets of prostate cancer versus normal tissue. Conclusions: The Meis1/Meis2/Pbx1 biomodule may explain key differences in seminal vesicle and normal prostate epithelium development. In contrast to other cancers, Meis1, Meis2, and Pbx1 may play a tumor suppressor role in prostate cancer. Thus deregulation of this biomodule may be critical in prostate cancer oncogenesis.