Suppression and immunotherapy of the guinea pig line-10 hepatocarcinoma mediated by nonviable Staphylococcus aureus.

Suppression of growth of the line-10 guinea pig hepatocarcinoma was achieved after the simultaneous injection of line-10 cells and heat-killed Staphylococcus aureus. Growth of tumor was also suppressed when line-10 cells were injected alone, contralaterally, at the same time as the vaccine mixture. Immunity developed to subsequent line-10 cell challenges but not to other syngeneic tumors. Similar results were obtained with the use of protein A-rich or -deficient strains of S. aureus. Multiple intratumor injections of heat-killed S. aureus were therapeutically effective against 6-day tumors. The antitumor effects of nonviable S. aureus were similar in many ways to those of living BCG or bacterial products suspended in oil droplets.