Anticancer drug response and expression of molecular markers in early-passage xenotransplanted colon carcinomas

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Despite some success in the treatment of colorectal carcinomas, novel rational therapies targeting specific cancer-related molecules are under development and urgently needed. These approaches need careful preclinical evaluation in models that closely mirror the clinical situation. Therefore, we established a panel of 15 xenotransplantable tumours directly from fresh surgical material. We showed that both the histology and expression of tumour-associated markers (Epithelial Cell Adhesion molecule (EpCAM), E-cadherin, carcinoembryonic antigen (CEA)) could be maintained during passaging in nude mice. Xenotransplanted tumours were characterised for chemosensitivity and revealed a response rate of 5/15 (33%) for 5-fluorouracil (5-FU), 15/15 (100%) for irinotecan and 8/14 (57%) for oxaliplatin. 5 patients out of 15 were treated with cytostatics because of synchronous metastases. The response to chemotherapy in these patients coincided very closely with the response of the individual xenografts. All of the xenografts expressed the proliferation marker Ki67 and the nuclear enzyme, Topoisomerase IIα (Topo IIα) at the protein level. Most of the xenografts also expressed the tumour suppressor, p53 (9/14) and the nuclear enzyme Topoisomerase Iα (Topo Iα) (13/14) at the protein level. Interestingly, the presence of a K-ras mutation in codon 12 (5/15 xenografts) coincided with a low response rate towards oxaliplatin. This observation needs further confirmation using a larger number of tumours. In conclusion, we were able to establish transplantable xenografts suitable to mimic the clinical situation. These well characterised models are useful tools for the preclinical development of novel therapeutic approaches and for investigating translational research aspects.