Effects of Antitumor Agents on Subcutaneous Implants and Hepatic Metastases of Colon Carcinoma 26 in Mice

We investigated the responses of experimentally produced hepatic metastases of colon carcinoma 26 tumor and subcutaneously (SC) implanted colon carcinoma 26 tumor in mice to 17 clinically used and one under‐development antitumor agents using same dose regimen. In intravenous administrations on days 7 and 14, there were no significant differences in their responses to most of the tested agents. However, there were big differences in the responses to some of the agents. Nimustine more effectively prolonged the lifespan of SC implanted tumor‐bearing mice than of mice bearing hepatic metastases. Mitomycin C was, however, considerably more effective on hepatic metastases than on SC implanted tumor. ME2303, a new fluorinated anthracycline derivative, showed a similar effect to doxorubicin on both tumors. However, administrations of ME2303 on days 7,11 and 15 showed more marked antitumor effect only on hepatic metastases than administrations on days 7 and 14. Doxorubicin was less active against both tumors for administrations on days 7, 11 and 15 than for those on days 7 and 14. These results suggest the importance of the site of tumor growth for the action of some drugs. ME2303 may be active against hepatic metastases if it is administered by multiple injections.