Enhanced success rate of transplantation with human tumors in cyclophosphamide-treated nude mice.

Immunosuppression was investigated to enhance the take rate of various human tumor types in nude BALB/c or B10.LP/Cpb mice. Cyclophosphamide (CY), known as an immunosuppressive agent, was injected ip at a dose of 100 mg/kg 24 hours prior to subcutaneous implantation of tumor fragments obtained from established xenograft lines or from patients. In 3 out of 8 ovarian adenocarcinoma tumor lines, with a take of 50% or less in untreated control animals, tumor take was significantly increased by CY treatment to values between 75 and 100%. No effect of CY treatment on tumor take was seen with squamous cell carcinomas of the head and neck region and with lung and prostatic carcinomas. The growth rate of these xenografts was not affected by CY pretreatment. These results indicate that immunologic mechanisms indeed can play a role in the inhibition of tumor growth in nude mice. CY pretreatment may enhance the success rate of transplantation, but this effect appears to be limited to certain tumors.