Abstract A67: IL-16 variants associated with prostate cancer risk in African Americans

Abstract

Abstract Background: Prostate cancer (Pca) is the most common type of cancer among men in the United States, and its disproportionate incidence and mortality rates among ethnic groups are likely due to a combination of genes and environmental factors. While genome-wide association studies (GWASs) of European descents have identified candidate loci associated with Pca risk, including rs4072111 located in IL-16, the replication studies in African Americans (AAs) have been inconsistent, and GWASs have not yet produced many findings to resolve Pca health disparities. IL-16 is over-expressed in tumor cells possibly mediating expression of other cytokines that promote tumor growth. Here we explore SNP variation in IL-16 in AAs and test for association with Pca in AAs. Method: Two hundred and seventy-seven (277) tagging SNPs spanning IL-16 (79.20Mb to 79.45Mb on chromosome 15) were genotyped in 496 AA Pca cases and 501 controls from Washington, DC. In order to replicate our findings, 11 of the SNPs were also typed in additional 400 AA Pca cases and controls from Chicago, IL. One hundred (100) unlinked ancestry informative markers were also typed for each sample. West African genetic ancestry estimates were obtained using STRUCTURE. We tested for allelic association and calculated odds ratios using logistic regression, adjusting for West African ancestry and age. Empiric p-values were obtained by adaptive permutation. Results: Our first stage analyses revealed that a cluster of 20 IL-16 SNPs were significantly associated with Pca risk. The strongest association was found at rs7175701 (P=1.2 × 10−8), which lies within intron 26 of IL-16. In the replication population, two SNPs, slightly linked to rs7175701, but within the 3′UTR region were also strongly associated with Pca risk (P<0.005). Our study provides evidence that IL-16 polymorphisms likely play a role to Pca susceptibility in AAs. Many of the significantly associated SNPs are linked to rs11325 which is a candidate SNP for a miRNA target region in IL-16. Although the exact mechanism is unclear, additional functional studies are warranted. Impact: Our findings are significant given that there has been limited focus on the role of IL-16 genetic polymorphisms on Pca risk in AAs. Understanding the role of cytokines such as IL-16 in tumor growth in diverse populations is important, and could likely lead to the development of useful biomarkers for cancer screening and/or potential therapeutics. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A67.