Immunotherapeutic effects of partially purified tumor-specific transplantation antigens on pulmonary metastases of a 3-methylcholanthrene-induced sarcoma in mice: a preliminary report.

Tumor-specific transplantation antigens (TSTA), which were partially purified by preparative isoelectric focusing of 3-M KCl extracts of a fibrosarcoma MCA-F induced in inbred female C3H/HeJ mice with 3-methylcholanthrene and previously shown to display immunotherapeutic activity against subcutaneous neoplasms, were effective against pulmonary metastases. Weekly sc injections of 25 micrograms fraction 15 decreased the number of pulmonary colonies after iv injection of tumor cells into syngeneic, virgin C3H/HeJ mice. The effect was immunologically specific; the immunoprotective fraction from the heterotypic, antigenically distinct MCA-D tumor did not affect the number of pulmonary MCA-F tumor colonies. Because fraction 15 treatment did not alter the number of extrapulmonary tumor colonies, the survival rates of hosts challenged iv with MCA-F cells were unaffected. The variant cell line MCA-F-4 was selected to detect prolonged host survival as a result of a therapeutic effect against pulmonary metastases. This line was selected for its proclivity for lung colonization and low propensity for growth in extrapulmonary sites. Cross-immunoprotection tests demonstrated that MCA-F-4 shares a TSTA with the parent tumor. Therapeutic administration of fraction 15 prolonged the survival of hosts in two settings: 1) after artificial iv injection of MCA-F-4 cells and 2) as treatment for hosts resected of 1-cm subcutaneous MCA-F-4 primary tumors and at high risk for spontaneous pulmonary metastases. Therefore, fraction 15 displayed therapeutic effects on both artificially induced and spontaneous pulmonary metastases.