APC mutational patterns in gastric adenocarcinoma are enriched for missense variants with associated decreased survival.

Abstract

Adenomatous polyposis coli (APC) mutations are causally associated with familial adenomatous polyposis (FAP) and are recurrent somatic events across numerous tumor types, including gastric adenocarcinoma. Severity of disease in FAP correlates with specific APC mutations, but the impact of given mutations on phenotype in gastric cancer is not well studied. Sequencing data from the Genomic Data Commons (GDC) demonstrate an APC mutational pattern in gastric cancer that differs dramatically from that seen in colon cancer. Exome sequencing data from APC-mutant colon and gastric adenocarcinomas in GDC was filtered for single nucleotide variants (SNVs) using MuTect2 Variant Aggregation and Masking pipeline, Somatic Aggregation Workflow. APC mutations were found in 57/441 gastric (12.9%) and 309/433 colon adenocarcinomas (71.4%). There was a significant difference in the proportion of stopgain, frameshift, and missense mutations between tumor types(P < .00001). Colon tumors were predominated by frameshift and stopgains, comprising 47.7% and 35.7%, respectively. In contrast, 47.1% of gastric mutations were missense. Gastric tumors harboring missense mutations showed decreased overall survival relative to other mutational subtypes(P = .008). In the gastric samples, 25.9% of frameshift and stopgain mutations are in the 3' portion of the gene, compared to 1.4% of colon samples. APC mutations demonstrate different distributions in gastric and colon adenocarcinoma, with a shift toward missense variants in gastric tumors and worse survival in gastric tumors harboring them. As different mutations confer variable degrees of protein dysfunction and resultant clinical manifestation, expanded investigation of specific mutational patterns will prove integral to future-risk stratification strategies.