Common variants inABCG8andTRAF3genes confer risk for gallstone disease and gallbladder cancer in admixed Latinos with Mapuche Native American ancestry

BackgroundLatin Americans and Chilean Amerindians have the highest prevalence of cholesterol gallstone disease (GSD) and gallbladder cancer (GBC) in the world. A handful of loci have been associated with GSD in populations of predominantly European ancestry, however they only explain a small portion of the population-attributable risk of the disease.MethodsWe performed a genome-wide association study (GWAS) for GSD in 1,095 admixed Latinos with Mapuche Native American Ancestry, followed by a replication analysis of 10 candidate single nucleotide polymorphisms (SNPs) with suggestive genome-wide significance (P<1×10−5) in 1,643 individuals. Disease status was assessed by cholecystectomy or abdominal ultrasonography. Logistic regression analyses were adjusted for age, sex, BMI, Type 2 Diabetes and Amerindian ancestry. Associated variants were further examined in two large GSD European populations and in a Chilean gallbladder cancer (GBC) cohort. We determined the expression levels of a novel GSD-candidate gene in normal and GSD-tissue samples.ResultsWe consistently replicated theABCG8gene (rs11887534; P=3.24×10−8, OR=1.74) associated with GSD in admixed Latinos and identified a novel candidate signal within theTRAF3gene on chromosome 14 (rs12882491; P=1.11×10−7, OR=1.40).ABCG8andTRAF3variants also conferred risk to GBC. Gene expression analyses indicated thatTRAF3levels were significantly decreased in the gallbladder (P=0.015) and the duodenal mucosa (P=0.001) of affected GSD individuals compared to healthy controls.ConclusionsWe confirmedABCG8and identifiedTRAF3both associated with GSD and GBC in admixed Latinos. Decreased TRAF3 expression levels could enhance gallbladder inflammation as is observed in GSD and GSD-associated GBC.