The MUTYH hotspot mutations p.G396D and p.Y179C do not cause substantial genetic susceptibility to biliary cancer

Inflammation-associated oxidative stress and DNA damage are involved in malignant transformation of cholangiocytes. Defective DNA repair mechanisms may predispose to cholangiocarcinoma (CCA) formation, and an elevated CCA risk for MutY human homologue (MUTYH) germline mutation carriers has been proposed previously. The aim of this study was to re-evaluate the MUTYH hotspot mutations p.Y179C (rs34612342) and p.G396D (rs36053993) as genetic susceptibility factors in a large CCA cohort. The study population consisted of 219 Caucasian CCA patients (66.2 ± 11.9 years, 130 males, 89 females; 43 intrahepatic and 176 extrahepatic tumours; tissue diagnosis in 77.6 %) and 355 healthy controls (61.0 ± 11.0 years; 158 males, 197 females). MUTYH hotspot variants were genotyped using TaqMan assays. Four CCA patients were monoallelic mutation carriers (3 p.G396D; 1 p.Y179C) whereas 6 control subjects were heterozygotes (5 p.G396D; 1 p.Y179C). None of the patients carried a biallelic hotspot mutation. The observed allele frequencies did not differ significantly between cases and controls (p > 0.05) and association tests did not provide evidence for an involvement of p.Y179C (OR 1.6 [95 % CI 0.1-26.0]) or p.G396D (OR 1.0 [95 % CI 0.2-4.1]) in the susceptibility to CCA. Power analysis identified a sufficient power only for large effect sizes (>90 % for OR > 5.8 for p.G396D and OR > 18.5 for p.Y179C). Monoallelic MUTYH hotspot mutations do not act as major genetic susceptibility factors causing a substantial CCA risk in the Caucasian population. Due to the low statistical power for the identification of small effect sizes, much larger studies will be needed to detect such effects of minor clinical significance.