Genetic Features Of Aflatoxin-Associated Hepatocellular Carcinomas

BACKGROUND&AIMS:Dietary exposure to aflatoxin is an important risk factor for hepatocellular carcinoma(HCC).However,little is known about the genomic features and mutations of aflatoxin-associated HCCs compared with HCCs not associated with aflatoxin exposure.We investigated the genetic features of aflatoxin-associated HCC that can be used to differentiate them from HCCs not associated with this carcinogen.METHODS:We obtained HCC tumor tissues and matched non-tumor liver tissues from 49 patients,collected from 1990 through 2016,at the Qidong Liver Cancer Hospital Institute in China—a high-risk region for aflatoxin exposure(38.2%of food samples test positive for aflatoxin contamination).Somatic variants were identified using GATK Best Practices Pipeline.We validated part of the mutations from whole-genome sequencing and whole-exome sequencing by Sanger sequencing.We also analyzed genomes of 1072 HCCs,obtained from 5 datasets from China,the United States,France,and Japan.Mutations in 49 aflatoxin-associated HCCs and 1072 HCCs from other regions were analyzed using the Wellcome Trust Sanger Institute mutational signatures framework with non-negative matrix factorization.The mutation landscape and mutational signatures from the aflatoxin-associated HCC and HCC samples from general population were compared.We identified genetic features of aflatoxin-associated HCC,and used these to identify aflatoxin-associated HCCs in datasets from other regions.Tumor samples were analyzed by immunohistochemistry to determine microvessel density and levels of CD34 and CD274(PD-L1).RESULTS:Aflatoxin-associated HCCs frequently contained C>A transversions,the sequence motif GCN,and strand bias.In addition to previously reported mutations in TP53,we found frequent mutations in the adhesion G protein-coupled receptor B1 gene(ADGRB1),which were associated with increased capillary density of tumor tissue.Aflatoxin-associated HCC tissues contained high-level potential mutation-associated neoantigens,and many infiltrating lymphocytes and tumors cells that expressed PD-L1,compared to HCCs not associated with aflatoxin.Of the HCCs from China,9.8%contained the aflatoxin-associated genetic features,whereas 0.4%-3.5%of HCCs from other regions contained these genetic features.Conclusions:We identified specific genetic and mutation features of HCCs associated with aflatoxin exposure,including mutations in ADGRB1,compared to HCCs from general populations.We associated these mutations with increased vascularization and expression of PD-L1 in HCC tissues.These findings might be used to identify patients with HCC due to aflatoxin exposure,and select therapies.