Chemotherapy of cell-line-derived human colon carcinomas in mice immunosuppressed with antithymocyte serum

An in vivo model is described for assessing the antitumor activity of chemotherapeutic agents. Tumors derived from human colon carcinoma cell lines injected into antithymocyte serum (ATS) immunosuppressed mice were used. In this system, both antitumor effects and host toxicity can be quantitated, permitting calculation of a Therapeutic Index. Compared with other xenograft models, the present system is simple, experiments are completed in less than 2 weeks, and the use of cultured cell lines allows in vitro studies to be performed. The in vitro sensitivities of one colon cell line to 22 chemotherapeutic agents and of four cell lines to three agents is reported. Four drugs used in treating colon cancer (Mitomycin C, 5-FU, BCNU, and methyl-CCNU) show antitumor activity in vivo in this system. Each has a low therapeutic index. Further work with this model is indicated, with the goal of finding new drugs with high Therapeutic Indices.