J. W. Harris1, P. Rychahou1, M. Evers1 1University Of Kentucky,Department Of General Surgery,Lexington, KY, USA
Introduction: Colorectal cancer (CRC) is the second leading cause of cancer death in the US. The K-ras gene is mutated in 30-50% of patients with CRC; mutations in the gene encoding p53 acquire oncogenic properties that enable them to promote invasion, metastasis, proliferation and cell survival and are present in up to 50% of CRCs. The purpose of this study was to develop a novel model of de novo CRC through activation of oncogenic K-ras and the loss of function of p53 in combination with the intracolonic delivery of adenovirus.
Methods: K-ras/p53 mutant mice (3 male, 3 female) received an intracolonic submucosal injection of 30 µL (3×107) Ad-CMV-Cre adenovirus under endoscopic guidance using a high resolution mouse video endoscopic system. The mice underwent surveillance endoscopy and were sacrificed 8 wks after initial adenovirus injection. Endoscopy video and images were recorded for technical evaluation and confirmation of tumor formation. Colonic tissues were sectioned and stained with H&E to confirm histologic presence of tumor.
Results: K-ras/p53 mutant mice do not spontaneously develop de novo CRCs without exposure to an oncogenic vector, nor do wild type mice typically develop CRCs when exposed to adenovirus. De novo CRC was noted in all male mice (n=3); one mouse developed a colo-cutaneous fistula, one developed an obstructing tumor, and the last mouse had a nearly obstructing tumor. H&E staining confirmed the presence of CRC in the male mice. In contrast, none of the female mice developed tumors.
Conclusion: Our technique using adenovirus to establish a primary intracolonic mucosal CRC is novel and reproducible. This conditional orthotopic model is important to better investigate genetically induced tumors and targeted therapeutics in their natural environment. Further research is required to better address the impact of genetic mutations and gender differences of CRC development in animal and human studies.