Bifidobacterium longum, a lactic acid-producing intestinal bacterium inhibits colon cancer and modulates the intermediate biomarkers of colon carcinogenesis |
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Authors: | Singh J; Rivenson A; Tomita M; Shimamura S; Ishibashi N; Reddy BS |
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Institution: | Division of Nutritional Carcinogenesis, American Health Foundation, Valhalla, NY 10595, USA. |
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Abstract: | The human colon can be described as a complex microbial ecosystem,
comprising several hundred bacterial species. Some of these enteric
bacteria are beneficial to the host and have been shown to exert
antimutagenic and anticarcinogenic properties. We have investigated the
colon tumor inhibitory activity of Bifidobacterium longum, a lactic
acid-producing enterobacterium. The modifying effects of this lactic
culture on colonic mucosal and/or tumor cell proliferation, ODC activity
and ras-p21 oncoprotein expression in colon carcinogenesis were also
analyzed. Male F344 rats were fed a modified AIN-76A diet containing 0 or
2% lyophilized cultures of B. longum and s.c. administered azoxymethane
(AOM) dissolved in normal saline at a dose of 15 mg/kg body wt, once weekly
for 2 weeks. Vehicle controls received an equal volume of normal saline
s.c. Animals were maintained on control or experimental diets until
termination of the study. Animals intended for analysis of cell
proliferation were killed 20 weeks after the second AOM injection, whereas
animals intended for colon tumor analysis and measurement of ODC activity
and ras-p21 expression were killed 40 weeks after the last AOM injection.
The data demonstrate that dietary administration of lyophilized cultures of
B. longum resulted in significant suppression of colon tumor incidence and
tumor multiplicity and also reduced tumor volume. Results also revealed
that ingestion of B. longum significantly inhibited AOM-induced cell
proliferation, ODC activity and expression of ras-p21 oncoprotein. Data
suggest that oral administration of probiotic B. longum exerts strong
antitumor activity, as indicated by modulation of the intermediate
biomarkers of colon cancer, and consequently reduced tumor outcome.
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