Plasma fetuin-A concentration, genetic variation in the AHSG gene and risk of colorectal cancer

Fetuin-A, also referred to as alpha 2-Heremans-Schmid glycoprotein (AHSG), is a liver protein known to inhibit insulin actions. Hyperinsulinemia is a possible risk factor for colorectal cancer; however, the role of fetuin-A in the development of colorectal cancer is unclear. We investigated the association between circulating fetuin-A and colorectal cancer risk in a nested case-control study within the European Prospective Investigation into Cancer and Nutrition. Fetuin-A concentrations were measured in prediagnostic plasma samples from 1,367 colorectal cancer cases and 1,367 matched controls. In conditional logistic regression models adjusted for potential confounders, the estimated relative risk (95% confidence interval) of colorectal cancer per 40 mg/mL higher fetuin-A concentrations (approximately one standard deviation) was 1.13 (1.02-1.24) overall, 1.21 (1.05-1.39) in men, 1.06 (0.93-1.22) in women, 1.13 (1.00-1.27) for colon cancer and 1.12 (0.94-1.32) for rectal cancer. To improve causal inference in a Mendelian Randomization approach, five tagging single nucleotide polymorphisms of the AHSG gene were genotyped in a subset of 456 case-control pairs. The AHSG allele-score explained 21% of the interindividual variation in plasma fetuin-A concentrations. In instrumental variable analysis, genetically raised fetuin-A was not associated with colorectal cancer risk (relative risk per 40 mg/mL genetically determined higher fetuin-A was 0.98, 95% confidence interval: 0.73-1.33). The findings of our study indicate a modest linear association between fetuin-A concentrations and risk of colorectal cancer but suggest that fetuin-A may not be causally related to colorectal cancer development.