IGF1 (CA)19 Repeat and IGFBP3 -202 A/C Genotypes and the Risk of Prostate Cancer in Black and White Men

Abstract

We investigated the relationship between the insulin-like growth factor-1 (IGF1) cytosine-adenine repeat (CA)₁₉ polymorphism located upstream of the gene's transcription start site, the insulin-like growth factor binding protein-3 (IGFBP3) −202 A/C promoter region polymorphism, and prostate cancer risk in Black and White men. Study subjects were U.S. veterans ages 41 to 75 years identified at the Durham Veterans Administration Medical Center over a 2.5-year period. Controls (n = 93) were frequency matched to cases (n = 100) based on race (Black or White) and age. Multivariable unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for the associations between the polymorphisms and prostate cancer risk. For Blacks and Whites combined, an inverse association between prostate cancer and being homozygous for the most common IGF1 repeat allele, (CA)₁₉, (adjusted OR, 0.3; 95% CI, 0.1-0.7) was observed. Similar associations were noted for both Blacks (OR, 0.2; 95% CI, 0.0-0.8) and Whites (OR, 0.4; 95% CI, 0.1-1.6) separately. No statistically significant associations between the IGFBP3 C allele and prostate cancer were noted for Blacks (adjusted OR, 2.3; 95% CI, 0.8-6.2) or Whites (OR, 1.0; 95% CI, 0.3-3.1). The prevalence of the homozygous IGF1 (CA)₁₉ genotype was much lower in Black controls (21%) than White controls (46%), which may, in part, explain the increased prostate cancer incidence in Black versus White men. Further research is needed to confirm these findings.