The genetics of neuroendocrine prostate cancers: a review of current and emerging candidates

Abstract

Prostate cancer (PC) displays a strong familial link and genetic factors; genes regulating inflammation may have a pivotal role in the disease. Epigenetic changes control chromosomal integrity, gene functions, and, ultimately, carcinogenesis. The most widely studied epigenetic event in PC is aberrant DNA methylation (hypo- and hypermethylation); besides this, chromatin remodeling and micro RNA (miRNA) are other studied alterations in PC. These all lead to genomic instability and inappropriate gene expression. Causative dysfunction of histone modifying enzymes results in generic and locus-specific changes in chromatin remodeling. miRNA deregulation also contributes to prostate carcinogenesis, including interference with androgen-receptor signaling and apoptosis. These epigenetic alterations have the potential to act as biomarkers for PC for screening and diagnosis as well as prognosis and follow-up. The variable biological potential for a newly diagnosed PC is one of the biggest challenges. The other major clinical problem is in the management of castration-resistant PC. Neuroendocrine (NE) differentiation is one of the putative explanations for the development of castration-resistant disease. Most advanced and poorly differentiated cancer does not produce prostate-specific antigen (PSA) in response to disease progression. Circulating and tissue biomarkers like chromogranin A (CgA) thus become important tools. There is the potential to use various genetic and epigenetic alterations and NE differentiation as therapeutic targets in the management of PC. However, we are still some distance from developing clinically effective tools. Valuable insights into the nature of NE differentiation in PC have been gained in the last decades, but additional understanding of its pathogenetic mechanisms is needed. This will help in devising novel therapeutic strategies to develop targeted therapies. CgA has the potential to become an important marker of advanced castration-resistant PC in cases where prostate-specific antigen can no longer be relied upon. Aberrant androgen-receptor signaling at various levels provides evidence of the importance of this pathway for the development of castration-resistant PC. Many epigenetic influences – in particular, the role of changing miRNA expression – provide valuable insights. Currently, massive sequencing efforts are underway to define important somatic genetic alterations (amplifications, deletions, point mutations, translocations) in PC, and these alterations hold great promise as prognostic markers and for predicting response to therapy.