Abstract 5344: Rapid induction and progression of PhIP+DSS-induced colon carcinogenesis in CYP1A-humanized mice

Abstract

Abstract 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most abundant heterocyclic amine generated from high temperature cooking of meat and fish, is metabolically activated by human cytochrome P450 (CYP)1A2 to a proximate carcinogen. Using CYP1A-humanized (hCYP1A) mice, previous study in our lab demonstrated that a single i.g. administration of PhIP (200mg/kg b.w.), followed by 1.5% Dextran Sodium Sulfate (DSS) in drinking water for 7 days, can rapidly induce tumors in the colon with 100% incidence. Multiple adenocarcinomas were observed with elevation of β-catenin, a key protein in the Wnt signaling pathway, as well as iNOS, COX-2, cyclin D1 and c-Myc. In the present study, we investigated the early stage colon carcinogenesis in the hCYP1A mice treated with PhIP (2x 100mg/kg b.w.) and DSS (4 days). After 4 days of DSS treatment, clinical manifestation such as weight loss, diarrhea, and bloody stools were observed. At day 1 after DSS cessation, we found severe damages to the colon epithelium with expansive crypt degeneration, ulcerations and inflammation. At days 3 and 7, we detected epithelial hyperplasia and dysplasia in addition to extensive ulcerations and inflammation. At days 11 and 17, we identified early adenoma and adenocarcinoma, respectively. Similar adenomatous lesions were not observed in hCYP1A mice treated with only DSS. Using immunohistochemistry, we detected strong nuclear staining of β-catenin, specifically within the early adenomas and adenocarcinomas. Further examination using Ki67 marker revealed strong nuclear staining in the adenomas and adenocarcinomas as well as areas of hyperplasia and dysplasia, indicating their high level of proliferation and generation. DNA sequencing revealed 96% of the PhIP+DSS induced colon tumors at week 10 carried a β-catenin mutation, particularly in the codon 32, 33, and 34. Altogether, we demonstrate the rapid induction and progression of colon tumorigenesis in hCYP1A mice, initiated by PhIP-induced Wnt dysregulation and promoted by DSS-induced colitis. (Supported by NIH grants F31CA168333, RO1CA120915 and RO1CA133021 as well as shared facilities funded by CA72720 and ES05022) Citation Format: Jayson X. Chen, Hong Wang, Guangxun Li, Anna Liu, Chung S. Yang. Rapid induction and progression of PhIP+DSS-induced colon carcinogenesis in CYP1A-humanized mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5344. doi:10.1158/1538-7445.AM2014-5344