Immunotherapy of a carcinogen-induced murine sarcoma with soluble tumor-specific transplantation antigens.

Tumor-specific transplantation antigens (TSTA), extracted from the 3-methylcholanthrene-induced sarcoma MCA-F and partially purified by flat-bed isoelectric focusing, were used to treat syngeneic inbred C3H/HeJ mice bearing supralethal neoplastic challenges. Three weekly injections of 25 micrograms TSTA increased the survival times of hosts inoculated 1 day earlier with ten times the lethal dose of MCA-F cells. In another protocol TSTA injections decreased the incidence and outgrowth of a local metastasis in mice given sc supralethal inoculations and completely resected of established 1-cm tumors. In addition, weekly injections of 25 micrograms MCA-F TSTA decreased the tumor recurrence rate and increased the survival times of hosts with recurrent neoplastic disease by virtue of residual tumor cells following resection of 2-cm masses. The therapeutic effect of TSTA was immunologically specific: Animals cured of local MCA-F recurrences promptly died from primary challenge with the non-cross-reacting sarcoma MCA-D. The results suggest that active specific immunotherapy may represent a useful adjunct to treatment of hosts bearing modest tumor burdens.