Developmental exposure to natural or environmental estrogens predisposes to prostate carcinogenesis with aging;however, the molecular underpinnings of this phenomenon are unclear. We present evidence that developmental reprogramming of the prostate by estrogens may be mediated, in part, through epigenetic alterations. Using methylation-sensitive fingerprinting (MSRP) as an initial screen for genome-wide methylation changes, we identified multiple prostatic genes whose methylation status was permanently altered in rats as a result of neonatal estradiol and bisphenol A (BPA) exposures at environmentally relevant doses. Detailed characterization of phosphodiesterase 4D4 (PDE4D4) and HPCAL, enzymes involved in cAMP breakdown and formation, respectively, revealed aberrant promoter CpG island methylation patterns with resultant changes in gene transcription as the animals aged. Importantly, these epigenetic alterations were associated with increased susceptibility to hormonal carcinogenesis of the rat prostate gland. Thus we hypothesize that early estrogenic imprinting of the prostate gland with resultant predisposition to carcinogenesis with aging is mediated through epigenetic modifications which permanently affect gene expression in the gland. The objectives of the present proposal are to further characterize our model of developmental reprogramming by low dose estradiol or BPA, to characterize in detail the prostatic gene methylation and transcriptional alterations which result from early life estrogenic exposures and to identify the methylation candidate genes contribute to increased carcinogenic potential in the developmentally estrogenized prostate glands.
In Aim 1, we will determine the dose-response relationship for prostatic- BPA effects and establish the developmental windows of susceptibility. We will also use a novel tissue recombination model to test whether BPA modifies carcinogenic susceptibility and methylation patterns in human prostate-like structures.
In Aim 2, we will characterize in detail the altered rat prostate methylome with resultant alterations in gene expression as a result of developmental exposures to environmentally relevant doses of BPA or estradiol. MSRP and methylation arrays will be used to expand our prostatic screen to identify a full panel of candidate genes and a stringent algorithm will be followed to identify candidates with regulatory CpG islands. Site-specific methylation and resultant transcriptional regulation will be confirmed.
In Aim 3, we will directly test whether the genes epigenetically modified by estrogenic exposures play an active role in prostate gland carcinogenesis using a variety of in vitro and in vivo studies.
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