Prevention of colonic preneoplastic lesions by the probiotic Lactobacillusacidophilus NCFMTM in F344 rats

The experiments described here were aimed at developing novel probiotic str ains that may aid in the reduction of colon cancer risk. We assessed the po tential anticancer properties of Lactobacillus acidophilus NCFMTM in male F 344 rats using inhibition of the formation of azoxymethane (AOM)-induced ab errant crypt foci (ACF) in the colon as the measure of preventive efficacy. At 6 weeks of age, groups of rats were fed the experimental diets containi ng 0, 2% or 4% lyophilized cultures of L. acidophilus NCFMTM. At 7 weeks of age, all animals in each dietary group, except the vehicle-treated rats, w ere s.c. injected with AOM (15 mg/kg body weight) once weekly for two weeks . The vehicle-treated groups were given s.c. injections of normal saline. A ll rats were necropsied 10 weeks after the last AOM injection and ACF in fo rmalin-fixed, methylene blue-stained colonic tissues were counted under the light microscope. The contents of the cecum were analyzed for bacterial R- glucuronidase activity. Diet supplementation with the probiotic strain NCFM TM significantly suppressed AOM-induction of colonic ACF, in terms of total number, as well as crypt multiplicity and number of ACF/cm(2) colon (P<0.0 1 - 0.001). NCFMTM inhibited AOM-induced colonic ACF formation in a dose-de pendent manner (P<0.01). A significant dose-dependent reduction of cecal be ta-glucuronidase activities was observed in the rats fed 2% (P<0.04) and 4% (P<0.0001) NCFMTM. These results suggest that Lactobacillus acidophilus NC FMTM may potentially prevent colon cancer development. Further studies are warranted to determine the full potential of this probiotic strain in precl inical efficacy studies.