Delayed tumor growth caused by a combined treatment with BCG and Pseudomonas aeruginosa

Summary Sera from mice treated i.v. with 1 mg BCG, followed 14 days later by 0.1 ml (10⁸ killed organisms) of Pseudomonas aeruginosa have shown the capacity to induce tumor necrosis when injected into mice bearing subcutaneous transplants either of a methyl-cholanthrene-induced sarcoma or of the P815 mastocytoma. Furthermore, immunotherapeutic trials were performed in mice bearing a subcutaneous transplanted sarcoma by combining BCG and low doses (0.01 to 0.05 ml) of Pseudomonas. Tumor necrosis was detectable 24 hours later only in the group treated by both BCG and Pseudomonas. In this group, we have also observed a significant decrease of tumor size in comparison with the groups of mice receiving BCG or Pseudomonas alone or no treatment.