This PhD aimed to elucidate the mechanisms by which polymorphisms may alter androgen-induced transactivation of androgen receptor (AR) target genes which may be important in prostate cancer aetiology. The second aspect of this PhD focused on identifying and characterising functional polymorphisms that may have utility as predictive risk indicators for prostate cancer and which may aid in earlier therapeutic intervention and better disease management. Analyses were carried out on the kallikrein-related peptidase 3 (KLK3), also known as the prostate specific antigen (PSA), gene and the kallikrein-related peptidase 4 (KLK4) gene. The PSA and KLK4 genes are part of the serine protease family that have trypsin or chymotrypsin like activity and are thought to play a role in the development of hormone-dependent cancers in tissues such as those in the prostate, breast, endometrium and ovaries. In the prostate, PSA is regulated by androgens and three androgen response elements (AREs) have been described in the promoter and upstream enhancer region. The PSA ARE I harbours a polymorphism at -158 bp from the transcription initiation site (TIS) that results in a G to A transition (G-158A). This PhD investigated the functional significance of the PSA G-158A polymorphism which has been reported to be associated with prostate cancer risk. Electromobility shift assays (EMSAs) investigating the interaction of ARE I variants with the AR DNA binding domain (AR-DBD) demonstrated that the A allele had a two-fold increased binding affinity for the AR-DBD when compared with the G allele. This was confirmed with endogenous AR in limited proteolysis-EMSA experiments. The limited proteolysis-EMSA experiments also demonstrated differential sensitivities of PSA ARE I alleles to trypsin digestion, which suggests that the G-158A polymorphism has an allosteric effect on the AR that alters AR/ARE I complex stability. Furthermore, Chromatin Immunoprecipitation (ChIP) assays suggest that the A allele more readily recruited the AR in vivo when compared with the G allele and is consistent with the in vitro binding data. Luciferase reporter assays carried out in both LNCaP and 22Rv1 prostate cancer cells, and using the natural (dihydrotestosterone; DHT) ligand demonstrated that the A allele was more responsive to androgens in LNCaP cells. Hence, this study has elucidated the potential mechanisms by which the G-158A polymorphism may differentially regulate PSA expression (of which up-regulation of PSA is thought to be important in prostate cancer development and progression). KLK4 has similar tissue-restricted expression as PSA and is up-regulated by steroid hormones in many endocrine cells including those in the prostate. A putative ARE (KLK4-pARE) located at -1,005 to -1019 relative to the more predominantly used transcription initiation site, TIS3, was initially found in supershift assays using AR antibodies to interact with endogenous AR. However, subsequent EMSA analysis using purified AR-DBD suggest that KLK4-pARE may be interacting with the AR indirectly. To investigate this hypothesis, a tandem construct of KLK4-pARE was cloned into the pGL3-Promoter vector for hormone-induced reporter assays. However, reporter assays did not demonstrate any responsiveness of KLK4-pARE to androgens, estradiol or progestins. Consequently, Real-Time PCR was carried out to reassess the hormonal regulation of KLK4 at the mRNA level. Consistent with the literature, data from this study suggests that KLK4 may be up-regulated by androgens, progestins and estradiol in a cyclical manner. Hormone-induced luciferase reporter assays were then carried out on seven promoter constructs that span 2.8 kb of the KLK4 promoter from TIS3. However, none of the seven promoter constructs demonstrated any significant responsiveness to androgens, estradiol or progestins. This study suggests that hormone response elements (HREs) that may drive the hormonal regulation of KLK4 in prostate cancer may be located further upstream from the promoter region investigated in this PhD, or alternatively, may lie 3' of TIS3. The characterisation of KLK4 promoter polymorphisms and their flanking sequences were also carried out in parallel to the functional work with the intent to assess the functional significance of any polymorphisms that may be located within HREs. In total 19 polymorphisms were identified from the public databases and from direct sequencing within 2.8 kb of the KLK4 promoter from TIS3. However, the functional and clinical significance of these 19 polymorphisms were not further pursued given the negative findings from the functional work. The PSA AR enhancer region was also assessed for potential polymorphisms that may be associated with prostate cancer risk. A total of 12 polymorphisms were identified in the PSA enhancer of which two (A-4643G and T-5412C) have been reported to alter functionality of the enhancer region and thus, prioritised for further analysis. Association analysis for prostate cancer risk was then carried out on these PSA enhancer polymorphisms as none of the KLK4 promoter polymorphisms were found in functional HREs. No significant association for either the A-4643G or T-5412C polymorphism with prostate cancer risk was found at the P = 0.05 level. However, under an age-adjusted dominant model a 1.22- (95% CI = 1.16-1.26) and 1.23-fold (95% CI = 1.17-1.29) increased risk for prostate cancer was found for the A-4643G or T-5412C polymorphisms, respectively. Both polymorphisms were also assessed for association with tumour grade and stage and PSA levels. Genotypes were significantly different for the A-4643G and T-5412C polymorphisms with tumour stage and PSA levels, respectively. However, these results are likely to be biased by the case population which consist primarily of men who presented with incidental (pT1) and organ-confined (pT2) tumours. To summarise, the A-4643G and T-5412C polymorphisms are unlikely to be associated with prostate cancer risk, PSA levels or stage/grade of disease. However, further analyses in a larger cohort is warranted given that these polymorphisms alter androgen responsiveness of the PSA enhancer and that elevated PSA levels are indicative of men with prostate cancer. To summarise, this PhD has elucidated the functional significance of the PSA G-158A polymorphism in prostate cancer and which may be important in prostate cancer patho-physiology. This PhD has also furthered the understanding of the hormonal regulation of KLK4 in prostate cancer cells. Finally, this PhD has carried out a pilot study on two functional PSA enhancer polymorphisms (A-4643G and T-5412C) with prostate cancer risk.

Hormone-dependent cancers (HDCs), such as those of the prostate, ovary, breast and endometrium, share characteristics that indicate similar underlying mechanisms of carcinogenesis. Through steroid hormone signalling on "down-stream" target genes, the growth, development and progression of HDCs are regulated. One such family of target genes, highly expressed in HDCs and regulated by steroid hormones, are the tissue kallikreins (KLKs). The KLKs are a multigene family of serine proteases involved in physiological processes such as blood pressure regulation, inflammation, and tumour development and progression via the hydrolysis of specific substrates. Although the KLK gene family is clearly implicated in tumourigenesis, the precise roles played by these genes are largely unknown. Additionally, except for the androgen-responsive genes, KLK2 and KLK3, the mechanisms underlying their hormonal regulation in HDCs are yet to be identified. The initial focus of this thesis was to examine the regulation of the kallikreins, KLK1 and KLK4, by estradiol and progesterone in endometrial and breast cancer cell lines. From these studies, progesterone clearly regulated KLK4 expression in T47D cells and therefore, the focus of the remaining studies was to further examine this regulation at the transcriptional level. An overview of the results obtained is detailed below. Human K1 and hK4 protein levels were increased by 10 nmol/L estradiol benzoate, progesterone, or a combination of the two, over 48 hours in the endometrial cancer cell line, KLE. However, these same treatments resulted in no change in KLK1 gene or hK1 protein levels in the endometrial cancer cell lines, HEC1A or HEC1B (only hK1 analysed). Progesterone treatment (0-100 nmol/L) over 24 hours resulted in a clear increase in KLK4 mRNA at the 10 nmol/L dose in the breast cancer cell line, T47D. Additionally, treatment of T47D cells with 10 nmol/L progesterone over 0-48 hr, resulted in the rapid expression of the hK4 protein at 2 hr which was sustained for 24 hr. Further analysis of this latter progesterone regulation with the antiprogesterone, RU486, over 24 hours, resulted in an observable decrease in hK4 levels at 1 µmol/L RU486. Although the estrogen and progesterone regulation of the hK1 protein was not further analysed, the data obtained for hK4 regulation in T47D cell lines, supported the premise that this gene was progesterone-responsive. The rapid expression of hK4 protein by progesterone at two hours suggests that KLK4 transcription is directly coupled to progesterone regulation, perhaps through progesterone receptor (PR) binding to progesterone-responsive regions within the KLK4 promoter or far "up-stream" regions. Thus, the following further studies were performed. To test this hypothesis, the transcription initiation site (TIS) and 5' flanking regions of the KLK4 gene in T47D cells were interrogated. Primer extension and 5' RACE identified the TIS 78 bp 5' of the putative ATG site for translation as identified by Korkmaz et al. (2001). This KLK4 gene transcript consists of only four exons, and thus excludes the pre/pro signal peptide. Although a TATA-box is not present within -25 to -30 bp 5' of the identified TIS, a number of consensus binding motifs for Sp1 and estrogen receptor half-sites were identified. It is possible that the Sp1 sites are involved in the basal levels of transcription for this gene. Additionally, a putative progesterone response element (PRE) was identified in the far "up-stream" regions of the KLK4 gene. Basal levels of transcription were observed within the KLK4 proximal promoter region when coupled to a luciferase reporter gene and transfected into T47D cell lines. Additionally, the KLK4 proximal promoter region did not induce the luciferase reporter gene expression when progesterone was added to the system, however, estradiol was inhibitory for luciferase gene expression. This suggests that the proximal promoter region of the KLK4 gene could contain functional EREs but not PREs. In keeping with this hypothesis, some ER half-sites were identified, but PR sites were not obvious within this region. The identified PRE in the far "up-stream" region of the KLK4 gene assembled the progesterone receptor in vitro, and in vivo, as assessed by electromobility shift assays and chromatin immunoprecipitation assays (EMSAs and ChIPs), respectively. The binding of the PR to the KLK4 PRE was successfully competed out by a PR antibody and not by an androgen receptor antibody, and thus confirms the specificity of the KLK4 PRE-PR complex. Additionally, the PR was recruited and assembled onto and off the progesterone-responsive KLK4 region in a cyclic fashion. Thus, these data strongly suggest that the PR represents one of the core components of a transcription complex for the KLK4 gene, and presumably also contributes to the expression of this gene. Moreover, these data suggest a functional coordination between the PR and the KLK4 progesterone-responsive region in T47D cells, and thus, provide a model system to further study these events in vivo.