THE EFFECT OF LACTOBACILLUS GG ON THE INITIATION AND PROMOTION OF DMH-INDUCED INTESTINAL TUMORS IN THE RAT

Male Fischer 344 rats were fed a 20% or a 5% corn oil diet and were in jected subcutaneously with dimethylhydrazine (DMH) weekly for 16 weeks . In addition, an approximately equal number of animals challenged wit h DMH were fed daily, until the end of the study, 2 x 10(10) Lactobaci llus casei subsp. rhamnosus strain GG starting three weeks before DMH administration or after the ninth weekly injection. The feeding of the Lactobacillus GG before and during carcinogen treatment resulted in a significant decrease in the incidence of colon tumors and the number of small intestinal and colon tumors pet turner-bearing animal for rat s fed a 20% corn oil diet. This decrease in tumor incidence or number of tumors was not seen when animals were fed the Lactobacillus after t he ninth week of carcinogen treatment. Animals fed a 5% corn oil diet had a lower tumor incidence and number of tumors resulting from the de crease in dietary fat, in addition the feeding of Lactobacillus GG bef ore the carcinogen challenge resulted in a lower incidence of colon tu mors. These studies show that a specific strain oft. casei subsp. rham nosus designated GG can interfere with the initiation or early promoti onal stages of DMH-induced intestinal tumorigenesis, and this effect i s most pronounced for animals fed a high-fat diet.