The occurrence of liver metastasis is the major cause of death in colorectal cancer patients. The treatment consists of surgery and chemotherapy. However, the patient outcome is very unfavorable. Thus, the development of new therapeutic regimens to treat this condition is urgent and demand the establishment of good animal models. Among the models that have being used, the patient-derived xenografts (PDX) have emerged as one of the most promising. PDXs are preclinical models that faithfully represent the individuality of human cancer, by grafting fresh human tumor in severely immunodeficient mice which allows for higher tumor implantation rates and growth. Metastatic disease could be also modeled using orthotopic implantation into the affected organ. The patient-derived orthotopic xenografts (PDOX) can be interrogated for different treatment strategies based on the individualized gene signature of the human tumor, and the results can inform clinically relevant treatment strategies for the patient. With the objective to establish a PDOX from metastatic colorectal tumors in athymic nude mice, we implanted fresh tumor fragments into mouse liver parenchyma and propagated tumors from three patients which could be serially implanted in second and third mice generations. The morphological and immunohistochemical characterization indicate that xenografts recapitulate the tumor architecture and the expression of mismatch repair genes (MLH1, MSH2, MSH1, PMS2). After tumor implantation in first passage, the time of tumor growth decrease from 150-250 days to 30-100 days without loss of tumor identity. The growth of a post-transplantation lymphoproliferative disease (PTLD) was observed in one case. This pilot study was successful to establish the institutional PDX preclinical platform to study new therapeutic strategies, biomarkers of disease progression and treatment responsiveness.

Citation Format: Tiago Goss dos Santos, Bruno Roque, Caroline Roque, Maria Dirlei Begnani, Eduardo Lima, Felipe Coimbra, Rubens Chojniak. Development of patient derived orthotopic xenografts from metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1045.