Previous studies in rats have provided evidence that brief, early-life exposures to bisphenol A (BPA) at environmentally relevant doses results in developmental reprogramming of the prostate gland via epigenetic modifications that enhance carcinogenic susceptibility later in life. While dose-response profiles, BPA pharmacokinetics and route of exposure studies in rodent models are underway to validate these findings, there is a current and compelling need for research on BPA effects in the developing human prostate gland. The National Toxicology Program 2008 report summarily stated that """"""""studies in laboratory animals provide only limited evidence for adverse effects on development and more research is needed to better understand their implications for human health"""""""". In response to this need, novel models have been developed with human prostate progenitor cells that permit a direct examination of the impact of low-dose BPA exposures as they form prostate-like structures in vitro and in vivo. The goals of the proposed studies are to determine if exposure to environmentally relevant levels of BPA during the early stages of human prostate development increases susceptibility to prostate carcinogenesis later in life and to identify the underlying mechanism of this reprogramming event. It is hypothesized that prostate epithelial progenitor cells are the direct targets of BPA action during early gland formation. Further, it is predicted that BPA-induced reprogramming is mediated through a combination of altered DNA methylation and histone modifications that are heritable as progenitor cells self renew, transmitting altered epigenomic information throughout the lifespan of the individual. The proposed research thus represents a new paradigm that human prostate carcinogenesis may begin early in life in response to adverse environmental influences that epigenetically alter progenitor cells. An innovative approach will be exploited to test this hypothesis and directly examine BPA effects on human prostate progenitor cells using two model systems: 1) a 3-D co-culture system with human primary prostate epithelial/stromal cells to form prostaspheres in vitro, and 2) as recombinants with rat urogenital sinus mesenchyme grafted to murine kidney capsules for 1-3 months to form chimeric prostate-like tissues in vivo. These novel approaches will permit an examination of differentiation defects (Aim 1) and carcinogenesis (Aim 2) in the human prostate epithelial cells as a function of developmental BPA exposures. These studies will be informed by genome-wide studies of DNA methylation patterns and heritable chromatin modifications using human gene promoter arrays and Solexa ChIP-seq analysis (Aim 3). Using integrative bioinformatics, it is expected to identify BPA reprogrammed gene candidates that may serve as biomarkers for early-life BPA exposures in human epidemiology studies. To determine the potential relevance of BPA-reprogrammed candidate genes to human prostate cancer, tissue microarrays (TMAs) of human prostate cancer will be utilized to screen for misexpression of gene candidates as a function of disease stage, progression and ethnicity. The information gained from the proposed studies will be of high impact on the scientific, medical and regulatory communities in terms of 1) providing strong and compelling evidence for negative effects of BPA in humans, 2) establishing a mechanistic framework for developmental reprogramming, 3) identifying BPA-reprogrammed candidate genes for use as biomarkers, 4) ascertaining relevance of BPA-genes to human prostate cancer, 5) validating a useful model system for screening other endocrine disrupting chemicals, and 6) establishing a basis for studies on BPA in other organ systems and diseases.
There is increasing evidence in rodent models that brief, early-life exposures to bisphenol A (BPA) at dose levels typically found in humans results in developmental reprogramming of the prostate gland and increases susceptibility to prostate cancer later in life. The present proposal will test for this possibility in human prostate tissue using newly developed model systems with human prostate progenitor cells. Identification of epigenetic marks and BPA-reprogrammed genes may serve as biomarkers for developmental BPA exposures and provide molecular insight into the epigenomic plasticity that predisposes to prostate cancer with aging. The findings will be of high value to the medical and regulatory communities and serve as a model for human exposures to prevalent environmental endocrine disruptors with suspected carcinogenic potential.
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