Endoscopy-guided orthotopic implantation of colorectal cancer cells results in metastatic colorectal cancer in mice.

Advanced stage colorectal cancer (CRC) is still associated with limited prognosis. For preclinical evaluation of novel therapeutic approaches, murine models with orthotopic tumor growth and distant metastases are required. However, these models usually require surgical procedures possibly influencing tumor immunogenicity and development. The aim of this study was to establish a minimal-invasive endoscopy-based murine orthotopic model of metastatic CRC. During colonoscopy of CD-1 nude and non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, implantation of Caco-2 and HT-29 CRC cells was performed subcutaneously (s.c.) or orthotopic into the colonic submucosa. White light endoscopy (WLE) and fluorescence endoscopy (FE) were applied for tumor detection in vivo. Ex vivo, resected tumors were examined by fluorescence reflectance imaging (FRI), histology, gelatin zymography and immunohistochemistry. In CD-1 nude mice, marked tumor growth was observed within 14 days after subcutaneous implantation while submucosal implantation failed to induce CRC after 17 weeks. In contrast, in NOD/SCID mice submucosal injection of HT-29 cells resulted in pronounced tumor growth 12 days post injectionem. Subsequently, rapid tumor expansion occurred, occupying the entire colonic circumference. Importantly, post mortem histological analyses confirmed liver metastases in 28.6 % and peritoneal metastases in 14.3 % of all mice. FRI and gelatin zymography did not detect a significantly increased matrix metalloproteinases (MMPs) expression in s.c. implanted tumors while MMP-tracer uptake was significantly enhanced in orthotopic implanted tumors. Neither s.c. nor orthotopic Caco-2 cell implantation resulted in tumor development. We successfully established an endoscopy-based model of metastatic CRC in immunodeficient mice.