Chemoimmunotherapy of syngeneic mouse mammary carcinomas employing methanol extraction residue

Isografts of two mammary carcinomas, one spontaneously arising in a BALB/cfC3H female infected with MTV and one free of MTV (tumor D7T4S), were removed surgically from Balb/c (MTV free) female hosts, and fragments of each tumor were immediately reimplanted in situ (simulated local recurrence challenge). The animals were then subjected to treatment with the MER fraction of tubercle bacilli, with one of three chemotherapeutic drugs (5-FU, cyclophosphamide, and methotrexate), or with both MER and one of the chemotherapeutic agents (chemoimmunotherapy). The incidence of progressively developing recurrence tumors and the longevity of the animals were determined. The therapeutic effects of treatment with MER alone were ascertained by comparing groups of mice that received the fraction by various schedules with saline-injected control groups; the efficacy of chemoimmunotherapy was assassed by comparing groups that received MER plus one of the drugs with groups subjected to drug intervention by itself. MER administered alone did not reduce the incidence of recurrent tumors but was consistently efficacious in prolonging the lives of animals challenged with the MTV (+) carcinoma, although considerably less so in animals tested with the weakly immunogenic tumor D7T4S. A negative effect by MER on tumor frequency did not occur and was seen only once with regard to host life duration. Combined intervention with MER and 5-FU proved to be significantly and consistently superior to similar treatment with only 5-FU in animals challenged with the MTV(+) carcinoma. No such additive action by MER plus 5-FU was seen in mice challenged with D7T4S, however, nor did the other two chemoimmunotherapeutic regimens differ significantly in therapeutic efficacy from the corresponding chemotherapy alone in most of the trials with both tumors.