Gut microbes define liver cancer risk in mice exposed to chemical and viral transgenic hepatocarcinogens
- James G Fox1,
- Yan Feng1,
- Elizabeth J Theve1,
- Rebecca C Fry2,
- Jeannette L A Fiala1,
- Amy L Doernte1,
- Michelle Williams1,
- Arkadiusz R Raczynski1,
- Jose L McFaline1,
- John M Essigmann1,
- David B Schauer1,
- Steven R Tannenbaum1,
- Peter C Dedon1,
- Steven A Weinman3,
- Stanley M Lemon3,
- Arlin B Rogers2,*
- 1 Massachusetts Institute of Technology, United States;
- 2 University of North Carolina at Chapel Hill, United States;
- 3 University of Texas Medical Branch, Galveston, United States
- Correspondence to: Arlin B Rogers, Lineberger Comprehensive Cancer Center, University of North Carolina, Campus Box 7431, Chapel Hill, NC, 27599-7431, United States;
- Received 23 March 2009
- Accepted 22 August 2009
- Published Online First 22 October 2009
Background & Aims: Hepatocellular carcinoma (HCC) frequently results from synergism between chemical and infectious liver carcinogens. Worldwide, the highest incidence of HCC is in regions endemic for the food-borne contaminant aflatoxin B1 (AFB1) and hepatitis B virus (HBV) infection. Recently, gut microbes have been implicated in multisystemic diseases including obesity and diabetes. Here, we tested in chemical and viral-transgenic mouse models the hypothesis that specific intestinal bacteria promote liver cancer.
Methods: Helicobacter-free C3H/HeN mice were inoculated with AFB1 and/or Helicobacter hepaticus. Incidence, multiplicity and surface area of liver tumors were quantitated at 40 weeks. Molecular pathways involved in tumorigenesis were analyzed by microarray, qRT-PCR, LC/MS, ELISA, Western blot and immunohistochemistry. In a separate experiment, C57BL/6 FL-N/35 mice harboring a full-length hepatitis C virus (HCV) transgene were crossed with C3H/HeN mice and cancer rates compared between offspring with and without H. hepaticus.
Results: Intestinal colonization by H. hepaticus was sufficient to promote aflatoxin- and HCV transgene-induced HCC. Neither bacterial translocation to the liver nor induction of hepatitis was necessary. From its preferred niche in the intestinal mucus layer, H. hepaticus activated nuclear factor-κB (NF-κB)-regulated networks associated with innate and Th1-type adaptive immunity both in the lower bowel and liver. Biomarkers indicative of tumor progression included hepatocyte turnover, Wnt/β-catenin activation, and oxidative injury with decreased phagocytic clearance of damaged cells.
Conclusions: Enteric microbiota define HCC risk in mice exposed to carcinogenic chemicals or hepatitis virus transgenes. These results have implications for human liver cancer risk assessment and prevention.