Effect of BCG on dimethylhydrazine induction of colon tumors in rats

The effect of BCG injection into the colon wall on the induction of colon tumors by 1,2-dimethylhydrazine dihydrochloride (DMH) was assessed in male rats. Persistent, generalized BCG infection followed the intracolonic injection of 6.7 times 10(6) organisms in otherwise untreated rats. In rats given DMH (30 mg/kg/wk) intragastrically for 5 weeks and then infected with BCG, colon tumors developed at the same rate and in the same incidence as in uninfected rats, but more tumors were mucinous adenocarcinomas and metastasized to the abdominal lymph nodes. In a few rats with large, established colon tumors, the injection of BCG into tumors induced no apparent change in them when examined at autopsy 1-22 weeks later.