MODULATION OF IGF-II IMPRINTING IN THE AGING PROSTATE

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Three important features of prostate cancer will be addressed in the present proposal that will improve our understanding of risk factors for the development of prostate cancer. These features include: i) the multifocality of prostate cancer which implicates a generalized or field change in cancer susceptibility, ii) the age-dependence of prostate cancer development, and iii) the important role of the Insulin-like Growth Factor Axis in both aging-related and genetic-related cancers. IGF-II is an auto-paracrine growth stimulator that is an important positive modulator of cancer development. We provide preliminary evidence that a loss of imprinting (LOI), or biallelic expression, is an age-related specific epigenetic alteration that occurs in the peripheral prostate of the human. The imprinting of IGF-II in adult tissues is typically maintained and LOI is a common attribute of prostate cancers. Since DNA methylation is a major determinant of IGF-II imprinting we would anticipate that changes in methylation would be associated with altered imprinting status. It is our hypothesis to be tested that a loss of genomic imprinting in IGF-II is an age-related event in prostate epithelial cells and may be modulated by changes in DNA methylation. In Specific Aim 1, we will determine if a LOI of IGF-II occurs in the aging mouse prostate. In Specific Aim 2, the impact of accelerating DNA methylation loss on imprinting in mouse and an in vitro human model will be assessed. Specific Aim 3 will determine whether these mechanisms, and/or others, engender the increase in IGF-II expression seen in aging. This proposal is significant and novel in that it has the ability to provide a critical epigenetic link between the aging process, diet and prostate carcinogenesis in vivo. We expect to determine whether IGF-II imprinting is altered with aging and whether altered DNA methylation is an underlying mechanism for this. Even in the unlikely event the IGF-II plays only a minor role in prostate carcinogenesis, this proposal represents a novel and important methodological approach to evaluating epigenetic field changes that may explain the age-, organ- and diet-related specificity of prostate cancer.