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Proc Natl Acad Sci U S A. 2017 Apr 11;114(15):E3101-E3109. doi: 10.1073/pnas.1700759114. Epub 2017 Mar 28.

Mutational spectra of aflatoxin B1 in vivo establish biomarkers of exposure for human hepatocellular carcinoma.

Author information

1
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139.
2
Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.
3
Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139.
4
Department of Pathology, University of Washington, Seattle, WA 98195.
5
Department of Biochemistry, University of Washington, Seattle, WA 98195.
6
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139; jessig@mit.edu wogan@mit.edu.

Abstract

Aflatoxin B1 (AFB1) and/or hepatitis B and C viruses are risk factors for human hepatocellular carcinoma (HCC). Available evidence supports the interpretation that formation of AFB1-DNA adducts in hepatocytes seeds a population of mutations, mainly G:C→T:A, and viral processes synergize to accelerate tumorigenesis, perhaps via inflammation. Responding to a need for early-onset evidence predicting disease development, highly accurate duplex sequencing was used to monitor acquisition of high-resolution mutational spectra (HRMS) during the process of hepatocarcinogenesis. Four-day-old male mice were treated with AFB1 using a regimen that induced HCC within 72 wk. For analysis, livers were separated into tumor and adjacent cellular fractions. HRMS of cells surrounding the tumors revealed predominantly G:C→T:A mutations characteristic of AFB1 exposure. Importantly, 25% of all mutations were G→T in one trinucleotide context (CGC; the underlined G is the position of the mutation), which is also a hotspot mutation in human liver tumors whose incidence correlates with AFB1 exposure. The technology proved sufficiently sensitive that the same distinctive spectrum was detected as early as 10 wk after dosing, well before evidence of neoplasia. Additionally, analysis of tumor tissue revealed a more complex pattern than observed in surrounding hepatocytes; tumor HRMS were a composite of the 10-wk spectrum and a more heterogeneous set of mutations that emerged during tumor outgrowth. We propose that the 10-wk HRMS reflects a short-term mutational response to AFB1, and, as such, is an early detection metric for AFB1-induced liver cancer in this mouse model that will be a useful tool to reconstruct the molecular etiology of human hepatocarcinogenesis.

KEYWORDS:

cancer; duplex sequencing; mouse model; mutagenesis; mycotoxins

PMID:
28351974
PMCID:
PMC5393230
DOI:
10.1073/pnas.1700759114
[Indexed for MEDLINE]
Free PMC Article

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