Immunotherapy of Cancer: Regression of Established Intradermal Tumors After Intralesional Injection of Mycobacterial Cell Walls Attached to Oil Droplets
Intralesional injection of Mycobacterium bovis (strain BCG) cell walls attached to mineral oil droplets caused regression of established tumors and prevented the growth of lymph node metastases in 55% of treated animals. The minimal effective dose of mycobacterial cell walls was 30 µg when injected in admixture with 1.4 µl of mineral oil and 0.8 µl Tween. Cells walls from M. bovis, M. tuberculosis, and M. kansasii possessed tumor-suppressive properties. Cell walls from M. smegmatis, Nocardia asteroides, and Corynebacterium parvum lacked these properties. Treatment of BCG cell walls with proteolytic enzymes, organic solvents, acid, or alkali decreased tumor-suppressive properties.