Vitamin D receptor polymorphisms and prostate cancer

Abstract

Prostate cancer is a common disease, yet determinants of prostate cancer risk remain largely unidentified. Low circulating levels of 1, 25-dihydroxy vitamin D (1,25-D) have been implicated as a risk factor for prostate cancer. In addition, 1,25-D exhibits significant antineoplastic properties both in vitro and in vivo, and these antiproliferative effects appear to be mediated through the vitamin D receptor (VDR). The VDR has a number of common polymorphisms, including a TaqI restriction fragment length polymorphism in exon 9 and a poly(A) length polymorphism in the 3'-untranslated region. Previous studies have found an association between the TaqI T allele or poly(A) L allele and prostate cancer. To further investigate the putative link between VDR polymorphisms and prostate cancer, we conducted a case-control study of prostate cancer patients from the Piedmont region of North Carolina. Using polymerase chain reaction-based techniques on DNA extracted from peripheral blood, we genotyped 77 cases (70 white, seven black) and 183 controls (169 white, 14 black) for the TaqI and poly(A) alleles. We report here an overall lack of association between either the TaqI or poly(A) genotype and prostate cancer odds ratio (OR)=1.4, 95% confidence interval (CI)=0.7-2.8; and OR=1.2, 95% CI=0.6-2.5, respectively). Using a case-case analysis, we tested whether these polymorphisms might be associated with more advanced disease but found no statistically significant association for the TaqI T or poly(A) L allele (OR=2.5, 95% CI=0.3-21.7; OR=2.8, 95% CI=0.3-23.8, respectively). We report strong evidence of linkage disequilibrium between the TaqI and poly(A) polymorphisms (P < 0.0001), with whites demonstrating stronger linkage disequilibrium than blacks (D=0.24 vs. D=0.18).