Chemotherapeutic sensitivity of human colorectal tumor xenografts

Studies were made of the therapeutic response of six human colorectal tumor lines serially transplanted in immunosuppressed mice. The tumors with adenomatous structure showed greater sensitivity against different cytotoxic agents than the gelatinous ones. Among the drugs, 5-FU, BCNU and MeCCNU proved to be the most effective, producing not only temporary but long-term regressions. BCNU had its maximal effect at a single, oral administration. 5-FU sensitive and insensitive lines showed an equal uptake and incorporation of radiolabeled 5-FU. Both the take rate and the growth of nontreated and treated tumors in the same host revealed the influence of host-defence mechanisms on tumor progression.