Regression by active specific immunotherapy of established dermal tumor transplants and lymph node metastases in guinea pigs.

Guinea pigs, each with an established, syngeneic dermal tumor (line-10) and microscopic lymph node metastasis, were treated by intradermal inoculation of living line-10 tumor cells admixed with emulsified heat-killed Mycobacterium bovis BCG cells. This treatment caused complete regression of established dermal tumors (about 10 mm in diameter) and prevented the growth of microscopic lymph node metastases in 25 of 39 treated animals (64%). All control animals treated by intradermal inoculation with heat-killed M. bovis BCG cells attached to oil droplets died with progressive dermal and lymphatic tumor growth.