Influence of oil concentration on the efficacy of tumor regression by emulsified components of mycobacteria.

The influence of mineral oil content on the antitumor activity of emulsified Bacillus Calmette-Guérin cell walls (CW) was studied in mice each with an established transplant of a syngeneic fibrosarcoma. Animals received intratumoral injections of CW (0.02 to 0.6 mg/mouse) emulsified in 1 to 9% oil. The number of animals in which tumor regressed completely depended on the concentration of oil in the emulsion. The methanol extraction residue (MER) of Bacillus Calmette-Guérin administered intratumorally in oil in water emulsion was also immunotherapeutically active. Neither CW nor MER was active when given as aqueous suspensions without oil. Guinea pigs with transplanted hepatomas growing in their skin and with tumor cells in the draining lymph node could be cured of malignant disease by a single intralesional injection of CW or MER (1 mg per guinea pig) if these agents were emulsified in oil (3.3%) and water. Aqueous suspensions of CW and MER were not therapeutically active in the guinea pig.