The Expanding Role of Epigenetics in the Development, Diagnosis and Treatment of Prostate Cancer and Benign Prostatic Hyperplasia

Abstract

Prostate cancer research has focused significant attention on the mutation, deletion or amplification of the DNA base sequence that encodes critical growth or suppressor genes. However, these changes have left significant gaps in our understanding of the development and progression of disease. It has become clear that epigenetic changes or modifications that influence phenotype without altering the genotype present a new and entirely different mechanism for gene regulation. Several interrelated epigenetic modifications that are altered in abnormal growth states are DNA methylation changes, histone modifications and genomic imprinting. We discuss the status of epigenetic alterations in prostate cancer and benign prostatic hyperplasia progression. In addition, the rationale and status of ongoing clinical trials altering epigenetic processes in urological diseases are reviewed. An online search of current and past peer reviewed literature on DNA methylation, histone acetylation and methylation, imprinting and epigenetics in prostate cancer and benign prostatic hyperplasia was performed. Relevant articles and reviews were examined and a synopsis of reproducible data was generated with the goal of informing the practicing urologist of these advances and their implications. Only 20 years ago the first study was published demonstrating global changes in DNA methylation patterns in tumors. Accumulating data have now identified specific genes that are commonly hypermethylated and inactivated during prostate cancer progression, including GSTpi, APC, MDR1, GPX3 and 14-3-3sigma. Altered histone modifications, including acetylation and methylation, were also recently described that may modify gene function, including androgen receptor function. These epigenetic changes are now being used to assist in prostate cancer diagnosis and cancer outcome prediction. Epigenetic changes appear to have a role in benign prostatic hyperplasia development as well as in the susceptibility of the prostate to developing cancer. Treatments involving 5-aza-deoxycytosine and other, more selective DNA methyltransferase inhibitors remove methyl residues from silenced genes, generating re-expression, and are currently being used in therapeutic trials. Histone deacetylase inhibitors have shown promise, not only by directly reactivating silenced genes, but also as regulators of apoptosis and sensitizers to radiation therapy. Evolving data support a significant role for epigenetic processes in the development of prostate cancer and benign prostatic hyperplasia. Epigenetic changes can predict tumor behavior and often distinguish between genetically identical tumors. Targeted drugs that alter epigenetic modifications hold promise as a tool for curing and preventing these diseases.