Genetic Features of Aflatoxin-Associated Hepatocellular Carcinoma.
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.
['Zhang|Weilong|W|', 'He|Huan|H|', 'Zang|Mengya|M|', 'Wu|Qifeng|Q|', 'Zhao|Hong|H|', 'Lu|Ling-Ling|LL|', 'Ma|Peiqing|P|', 'Zheng|Hongwei|H|', 'Wang|Nengjin|N|', 'Zhang|Ying|Y|', 'He|Siyuan|S|', 'Chen|Xiaoyan|X|', 'Wu|Zhiyuan|Z|', 'Wang|Xiaoyue|X|', 'Cai|Jianqiang|J|', 'Liu|Zhihua|Z|', 'Sun|Zongtang|Z|', 'Zeng|Yi-Xin|YX|', 'Qu|Chunfeng|C|', 'Jiao|Yuchen|Y|']
D000348:Aflatoxins D042501:Angiogenic Proteins D018952:Antigens, CD34 D060890:B7-H1 Antigen D002273:Carcinogens D006528:Carcinoma, Hepatocellular D004252:DNA Mutational Analysis D059472:Exome D006801:Humans D008113:Liver Neoplasms D016246:Lymphocytes, Tumor-Infiltrating D055806:Microvessels D009154:Mutation D043562:Receptors, G-Protein-Coupled D016159:Tumor Suppressor Protein p53
Risk Factor Liver Cancer Aspergillus Pathogenesis