| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 93 === Probiotics are thought to be protective against colon cancer. Strain differences might contribute to inconsistency of data concerning the anti-carcinogenic activities of some probiotics. Therefore, we study whether Bifidobacterium longum (B.longum) or Lactobacillus gasseri (L.gasseri) protect mouse against 1,2-dimethylhydrazine (DMH)-induced colon tumor. Aberrant crypt foci (ACF) and tumor in colon were induced by i.m. injecting in 6-week-old, ICR male mouse with 20 mg/kg DMH once per week for 10 weeks. Short period (15 weeks) and long period (24 weeks) animal models were designed to evaluate the anti-tumor ability and related pathways of probiotics. The results suggest that mice treated with B. or L. had significantly lower numbers of ACFs and tumors in colon than mice treated with DMH alone. Mitotic index was decreased in mice treated with high or low dose B.longum compared to DMH alone. Apoptosis was slightly increased in mice treated with probiotics. Proliferation rate was decreased in mice treated with high dose B.longum or/and L.gasseri compared to DMH alone. In addition, L.gasseri was found to increase cell viability of RAW 264.7 macrophage by using MTT assay, implicating an enhancement of immunity. Moreover, BrdU incorporation assay revealed an increased DNA synthesis rate in L.-treated RAW 264.7 cells. Cell cycle-related gene expression were analyzed by western blot and the results indicated that Cyclin A and PCNA were up-regulated. Our results indicate a potential anti-tumor activity of B.longum or L.gasseri in colon cancer prevention.
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