Replication of Prostate Cancer Risk Variants in a Danish Case-Control Association Study

Background: Prostate cancer is one of the main causes for cancer morbidity and mortality in Western countries. Recently, several single nucleotide polymorphisms (SNPs) associated with prostate cancer have been identified in genome-wide association studies and multiple variant models have been developed to predict prostate cancer risk. The association between genetic markers and clinico-pathological tumor variables has, however, been inconsistent. Methods and Materials: A total of 32 previously identified prostate cancer-associated risk SNPs were genotyped in 648 prostate cancer cases and 526 age-matched controls. Family history was obtained by questionnaire. Age at diagnosis, clinical tumor variables including pre- and postoperative PSA, Gleason score, and T stage were obtained from prospectively collected clinical data (Aarhus Prostate Cancer Study). The SNPs were genotyped using Sequenom and Taqman assays and associations between SNPs, prostate cancer risk, and clinico-pathological variables were assessed. Results: Seventeen SNPs were successfully replicated in our case-control study and the association estimates were consistent with previous reports. Four markers were excluded from further analysis due to linkage disequilibrium. The cumulative effect of having the disease-associated genotype at five SNPs (rs4430796, rs6983267, rs1859962, rs1447295 and rs16901979) increased the prostate cancer risk with odds ratio 6.02 (95% CI: 2.21 - 16.38;P = 1.0 × 10–4) in patients with any combination of ≥4 markers compared with patients without any of the five SNPs (P for trend = 1.0 × 10–4). Six markers were significantly associated with clinico-pathological variables: SNP rs2735839 (GG) at locus 19q13, which is in the KLK3 gene encoding PSA, was associated with high preoperative PSA (P = 0.04), low Gleason score (P = 0.01) and low T stage (P = 0.02). Variants rs5759167 (GG/GT) (22q13) and rs7679673 (CC/CA) (4q24) were correlated with low risk for biochemical relapse (P = 0.015 and P = 0.009, respectively), whereas rs6983267 (GG) (8q24) was significantly associated with biochemical recurrence (P = 0.045). In addition, variants rs6983267 (GG) and rs5759167 (GG/GT) were significantly associated with negative family history (P = 0.04 and P = 0.02, respectively). Conclusion: We replicated 17 previously identified prostate cancer-associated risk SNPs in a Danish case-control study and found a cumulative and significant association between five SNPs and prostate cancer. Overall, we noted significant associations between several prostate cancer-associated risk genotypes and less aggressive tumor variables, high level of PSA, and low risk for biochemical reccurrence.

Clinico-Pathological Characterization of Hereditary, Familial and Sporadic Prostate Cancer

Aim: To characterize familial prostate cancer including hereditary prostate cancer and assess the disease-free survival following radical prostatectomy. Methods: A self-administered written questionnaire was forwarded to 709 prostatectomized patients from the Aarhus Prostate Cancer Study containing questions about cases of prostate cancer (PC), age at diagnosis, vital status, and age at death for all first-degree relatives. Patients were then divided into groups according to their family history: hereditary prostate cancer (HPC), familial prostate cancer (FPC), and sporadic prostate cancer (SPC) groups. The information from a subset of both FPC (n = 17) and SPC (n = 17) groups were validated in the Danish Cancer Register and the Civil Registration System. Between groups, we described the association of age, prostatespecific antigen (PSA), postoperative Gleason score and T Stage. A Kaplan-Meier curve demonstrated postoperative disease-free survival in each group. Results: The response rate was 81% (574/709). About 21% of the patients were categorized in the FPC group, of which 7% were identified as having HPC. The median follow-up time was 63 months for HPC, 65 months for FPC and 88 months for SPC. Overall, there was no significant difference between groups in clinical features and disease-free survival except that patients with HPC were significantly associated with younger age than sporadic cases (p = 0.02). The proportion of self-reported PC diagnoses confirmed in the cancer register was 27.8%. The index persons with SPC reported no PC in first-degree relatives and none was found the cancer register. Conclusion: Overall, we found no difference in clinical characteristics and survival, following radical prostatectomy except that patients with HPC were younger at diagnosis. These results are in line with previously reported data.

Expression Profiling of Hereditary versus Sporadic Prostate Cancer Suggests CYR61, EGR3, KLF6 and SNF1LK as Differentially Expressed Genes

Background: Distinguishing between sub-clinical and aggressive forms of prostate cancer is difficult due to the heterogeneity of the disease. It is, however, important to identify aggressive forms to guide proper treatment. This study compared gene expression profiles in cancer cells from hereditary and sporadic prostate cancer cases and attempted to correlate differentially regulated genes with clinico-pathological characteristics and prognosis. Materials and methods: The study population comprised patients diagnosed with clinically localized prostate cancer undergoing prostatectomy. Patients were divided into hereditary and sporadic cancer cases based on their family history. Fresh frozen biopsies from prostatectomy specimens were laser-dissected for RNA-extraction. Affymetrix HG-U133 Plus GeneChips were used to measure gene expression loaded onto Cluster 3.0 and Ingenuity Pathway Analysis softwares to examine the relationship among genes between groups. Differentially expressed genes were selected for protein expression analysis using immunohistochemistry on histological sections and tissue microarrays. Results: No single genes were signifycantly differentially expressed between hereditary and sporadic cases after adjustment for multiple testing. Using cluster analysis, four transcripts were found to be upregulated in hereditary prostate cancer tissue: CYR61, EGR3, KLF6 and SNF1LK. The intensity of CYR61, EGR2, KLF6 and SNF1LK immunostainings, however, were not significantly different in a separate sample of hereditary and sporadic prostate cancers. Furthermore, no correlations between CYR61, EGR2, KLF6, and SNF1LK staining intensities and the clinico-pathological variables or disease-free survival were detected, except for EGR3 that was significantly associated with T stage (p = 0.04). Conclusion: Overall, no single transcript level was significantly associated with hereditary prostate cancer. Cluster analysis suggested that the expression of CYR61, EGR3, KLF6 and SNF1LK were upregulated in cancer tissue from hereditary cases, but we were not able to confirm this on the protein level, and levels of these proteins were not found to correlate with clinico-pathological characteristics or biochemical recurrence.