ZFIN ID: ZDB-PUB-130402-16
H. pylori Virulence Factor CagA Increases Intestinal Cell Proliferation by Wnt Pathway Activation in a Transgenic Zebrafish Model
Neal, J.T., Peterson, T.S., Kent, M.L., and Guillemin, K.
Infection with Helicobacter pylori is a major risk factor for the development of gastric cancer, and infection with strains carrying the virulence factor CagA
significantly increases this risk. To investigate the mechanisms by which CagA promotes carcinogenesis, we generated transgenic
zebrafish expressing CagA ubiquitously or in the anterior intestine. Transgenic zebrafish expressing either wild type or a
phosphorylation-resistant form of CagA exhibited significantly increased rates of intestinal epithelial cell proliferation
and showed significant upregulation of the Wnt target genes cyclinD1, axin2, and the zebrafish c-myc ortholog myca. Co-expression of CagA with a loss-of-function allele encoding the β-catenin destruction complex protein Axin1 resulted in
a further increase in intestinal proliferation, while co-expression of CagA with a null allele of the key β-catenin transcriptional
cofactor Tcf4 restored intestinal proliferation to wild-type levels. These results provide in vivo evidence of Wnt pathway
activation by CagA downstream of or in parallel to the β-catenin destruction complex and upstream of Tcf4. Long-term transgenic
expression of wild type CagA, but not the phosphorylation-resistant form, resulted in significant hyperplasia of the adult
intestinal epithelium. We further utilized this model to demonstrate that oncogenic cooperation between CagA and a loss-of-function
allele of p53 is sufficient to induce high rates of intestinal small cell carcinoma and adenocarcinoma, establishing the utility of our
transgenic zebrafish model in the study of CagA-associated gastrointestinal cancers.