The Methanol Extraction Residue of Bacillus Calmette-Guerin Protects against 7,12-Dimethylbenz(α)anthracene-Induced Rat Mammary Carcinoma 1

Summary Sprague-Dawley female rats were placed on a low-fat diet, a high saturated fat diet, or a high polyunsaturated fat diet at time of weaning (21 days of age). Half of the rats in each dietary group were given an intraperitoneal injection of MER (0.5 mg) on Day 28 and again on Day 35. On Day 50, all rats were given 10 mg of DMBA in 1 ml of stripped corn oil via stomach tube. Tumor incidence was determined weekly by palpation and confirmed by histological analysis upon completion of the experiment. In each dietary group, rats immunized with MER had a lower tumor incidence, a longer latent period, and smaller tumors compared to non-immunized rats. In other experiments, rats were placed on the high polyunsaturated fat diet at time of weaning, exposed to DMBA on Day 50, and maintained on this diet for either 3 or 4 weeks after DMBA. At those times, some rats were placed on the low-fat diet while other rats were maintained on the high polyunsaturated fat diet. Half of the rats from each group were treated with MER. Results indicate that the low-fat diet provided significant therapeutic benefit. Further benefit was observed if these rats had been treated with MER. However, MER was not beneficial if given to rats maintained on the high polyunsaturated fat diet.