A functional genomics approach to study prostate disorders

Abstract

Benign prostate hyperplasia (BPH) and prostate cancer (PCa) are the two most common prostatic disorders in elderly man. Currently, the causes of both diseases are still not clear. However, androgen is a well recognized risk factor for both diseases. Androgen is a surviving factor to the prostate gland as androgen-ablation will cause the regression of the gland via an active apoptosis process. In the clinic, androgen-ablation is the most common treatment for advanced PCa. Nevertheless, most of these patients will eventually die of androgen-resistant prostate cancer (ARPC) progression.

High-throughput research techniques such as DNA microarray allows the study of thousands of genes in a single experiment and provides a revolutionary way to understand biology. The over all aim of this thesis was to apply a genomics approach to understand androgen actions in the prostate gland and delineate putative molecular mechanisms involved in the development of prostate hyperplasia and ARPC progression.

Gene expression profiling in rat ventral prostate identified many novel androgenregulated genes (ARG), which provided a base for a further understanding of androgen actions in prostate. Among them, several oxidative-stress related genes were modulated during prostate apoptosis induced by androgen deficiency indicating a contributing role of oxidative stress in this process. The role of a newly identified ARG, ezrin, in prostate disorders was further investigated using clinical PCa samples. Ezrin, a cytosekeleton linker which is related to tumor metastasis capacity, was overexpressed in high grade prostate intraepithelial neoplasia (HGPIN) and PCa.

Prolactin (PRL) transgenic mice develop a dramatic enlargement of the prostate gland. cDNA representational difference analysis (cDNA-RDA) coupled with microarray analysis were used to identify differentially expressed genes in the enlarged transgenic prostates compared with controls. Ten differentially expressed genes were found, some of them have been described to be involved in proliferation and apoptosis.

Finally, gene expression profiling combined with genomic analysis was applied to investigate the underlying mechanisms involved in ARPC development using an in vitro model. Unique chromosomal alterations as well as potential candidate genes associated with ARPC development were identified. The dysregulated genes in an androgen resistant cell line- LNCaP-r compared to the parental androgen sensitive cell line include genes involved in DNA methylation, apoptosis and androgen-signaling pathway.

In conclusion, we have shown that cDNA microarray can be used to further understand hormone actions in the prostate gland and the hormone resistant state of PCa. Importantly, findings in this thesis have generated new hypothesis regarding the molecular mechanisms involved in the development of BPH, PCa and ARPC.