Suppression and regression of a transplanted tumor in the guinea pig colon mediated by Mycobacterium bovis, strain BCG.

The growth in the colon wall of a diethylnitrosamine-induced hepatocarcinoma was suppressed by BCG. Injection of BCG into established colon-wall tumors caused tumor regression. Successful therapy required a limited tumor burden. Guinea pigs in which growth of the neoplasm was suppressed at the site of BCG infection developed systemic tumor transplantation immunity.