Inducible Intestine-Specific Expression of kras(V12) Triggers Intestinal Tumorigenesis In Transgenic Zebrafish()

KRAS mutations are a major risk factor in colorectal cancers. In particular, a point mutation of KRAS of amino acid 12, such as KRAS(V12), renders it stable activity in oncogenesis. We found that kras(V12) promotes intestinal carcinogenesis by generating a transgenic zebrafish line with inducible kras(V12) expression in the intestine, Tg(ifabp:EGFP-kras(V12)). The transgenic fish generated exhibited significant increases in the rates of intestinal epithelial outgrowth, proliferation, and cross talk in the active Ras signaling pathway involving in epithelial-mesenchymal transition (EMT). These results provide in vivo evidence of Ras pathway activation via kras(V12) overexpression. Long-term transgenic expression of kras(V12) resulted in enteritis, epithelial hyperplasia, and tubular adenoma in adult fish. This was accompanied by increased levels of the signaling proteins p-Erk and p-Akt and by downregulation of the EMT marker E-cadherin. Furthermore, we also observed a synergistic effect of kras(V12) expression and dextran sodium sulfate treatment to enhance intestinal tumor in zebrafish. Our results demonstrate that kras(V12) overexpression induces intestinal tumorigenesis in zebrafish, which mimics intestinal tumor formation in humans. Thus, our transgenic zebrafish may provide a valuable in vivo platform that can be used to investigate tumor initiation and anticancer drugs for gastrointestinal cancers.