Prostate cancer is a common complex disease that disproportionately affects men of African descent. Recently, several different common variants on chromosome 8q24 have been shown to be associated with prostate cancer in multiple studies and ethnic groups. The objective of this study was to confirm the association of 8q24 markers with prostate cancer in African Americans. We genotyped 24 markers along 8q24 and 80 unlinked ancestry informative markers in a hospital-based case-control sample of 1057 African American men (490 prostate cancer cases and 567 controls). Association analyses of 8q24 markers with prostate cancer risk were adjusted for both global and local 8q24 admixture stratification using estimates from ancestry informative markers. We report that rs7008482, which maps to the 8q24.13 region, is an additional independent prostate cancer risk variant (P = 5 × 10 −4 ), and we also replicate the association of rs16901979 with prostate cancer (P = 0.002). Other published risk variants in the region such as rs1447295 and rs6983267 showed a similar direction and magnitude of effect, but were not significant in our population. Both rs7008482 and rs16901979 independently predicted risk and remained significant (P < 0.001) after controlling for each other. Our data combined with additional replications of 8q24 markers provide compelling support for multiple regions of risk for prostate cancer on 8q24.

It was evident that study design exclusion and inclusion criteria rendered the majority of the study population ineligible. Among African Americans, comorbidity is a major issue that warrants considerable attention.

CYP3A4-V, an A to G promoter variant associated with prostate cancer in African Americans, exhibits large differences in allele frequency between populations. Given that the African American population is genetically heterogeneous because of its African ancestry and subsequent admixture with European Americans, case-control studies with African Americans are highly susceptible to spurious associations. To test for association with prostate cancer, we genotyped CYP3A4-V in 1376 (2 N) chromosomes from prostate cancer patients and age- and ethnicity-matched controls representing African Americans, Nigerians, and European Americans. To detect population stratification among the African American samples, 10 unlinked genetic markers were genotyped. To correct for the stratification, the uncorrected association statistic was divided by the average of association statistics across the 10 unlinked markers. Sharp differences in CYP3A4-V frequencies were observed between Nigerian and European American controls (0.87 and 0.10, respectively; P<0.0001). African Americans were intermediate (0.66). An association uncorrected for stratification was observed between CYP3A4-V and prostate cancer in African Americans (P=0.007). A nominal association was also observed among European Americans (P=0.02) but not Nigerians. In addition, the unlinked genetic marker test provided strong evidence of population stratification among African Americans. Because of the high level of stratification, the corrected P-value was not significant (P=0.25). Follow-up studies on a larger dataset will be needed to confirm whether the association is indeed spurious; however, these results reveal the potential for confounding of association studies by using African Americans and the need for study designs that take into account substructure caused by differences in ancestral proportions between cases and controls.

Purpose African Americans experience greater prostate cancer risk and mortality than do Caucasians. An analysis of pooled phase III data suggested differences in overall survival (OS) between African American and Caucasian men receiving sipuleucel-T. We explored this in PROCEED (NCT01306890), an FDA-requested registry in over 1900 patients with metastatic castration-resistant prostate cancer (mCRPC) treated with sipuleucel-T. Patients and methods OS for patients who received ≥1 sipuleucel-T infusion was compared between African American and Caucasian men using an all patient set and a baseline prostate-specific antigen (PSA)-matched set (two Caucasians to every one African American with baseline PSAs within 10% of each other). Univariable and multivariable analyses were conducted. Survival data were examined using Kaplan-Meier and Cox proportional hazard methodologies. Results Median follow-up was 46.6 months. Overall survival differed between African American and Caucasian men with hazard ratios (HR) of 0.81 (95% confidence interval [CI]: 0.68-0.97, P = 0.03) in the all patient set and 0.70 (95% CI: 0.57-0.86, P < 0.001) in the PSA-matched set. Median OS was longer in African Americans than in Caucasian men for both analysis sets, e.g., 35.3 and 25.8 months, respectively, in the PSA-matched set. Similar results were observed in the all patient set. Differences were larger when treatment began at lower baseline PSA; curves were more similar among patients with higher baseline PSA. In patients with baseline PSA below the median, the HR was 0.52 (95% CI: 0.37-0.72, P < 0.001), with median OS of 54.3 versus 33.4 months. Known prognostic factors and African American race (multivariable analyses; HR: 0.60, 95% CI: 0.48-0.74, P < 0.001) were independently associated with OS. Use of post-sipuleucel-T anticancer interventions was balanced between races. Conclusion In this exploratory analysis of a registry including nearly 12% African American men with mCRPC, OS was significantly different between African Americans and Caucasians, indicating further research is warranted.

Cyclooxygenase-2 (COX-2) is a key rate-limiting enzyme that converts arachidonic acid into pro-inflammatory prostaglandins. COX-2 expression is strongly correlated with increased tumor microvasculature density and plays an important role in inhibiting apoptosis, stimulating angiogenesis and promoting tumor cell metastasis and invasion. However, little is known about the role that sequence variation of the COX-2 gene contributes to prostate cancer. Thus, we searched for polymorphisms in the promoter region of the COX-2 gene using denaturing high-performance liquid chromatography. Four single nucleotide polymorphisms (SNPs), -1285A/G, -1265G/A, -899G/C and -297C/G, were detected and confirmed by direct sequencing. Three of the SNPs in the promoter region of COX-2 gene create at least three putative transcription factor binding sites and eliminate CCAAT/enhancer binding protein alpha (C/EBP alpha) and NF-kappa B binding sites. A case-control study of the four SNPs in African American (n = 288), Bini Nigerian (n = 264) and European American (n = 184) prostate cancer cases and age-matched controls revealed that SNP -297G was associated with a decreased risk for prostate cancer [odds ratio (OR) = 0.49; CI = 0.2-0.9; P = 0.01]. The effect on risk was observed in both African Americans (OR = 0.51; CI = 0.2-0.9; P = 0.01) and European Americans (OR = 0.33; CI = 0.1-0.9; P = 0.02). In addition, SNPs -1265A and -899C were associated with increased prostate cancer risk in African Americans (OR = 2.72; CI = 1.3-5.8; P = 0.007 and OR = 3.67; CI = 1.4-9.9; P = 0.007, respectively). Haplotype analyses revealed modest effects on susceptibility to prostate cancer across populations. Haplotype GGCC conferred increased risk in the African American and Nigerian populations. Conversely, haplotype AGGG exhibited a negative association with prostate cancer risk in African Americans (OR = 0.4; CI = 0.1-0.9; P = 0.02) and European Americans (OR = 0.2; CI = 0.1-0.9; P = 0.03). These data suggest that variation of the COX-2 promoter may influence the risk and development of prostate cancer.