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The demand for natural alternatives to prevent enteric cancers especially colonic cancers are increasing. The use of probiotics has attracted much interest due to their long history of safe use and numerous positive clinical evidences. Probiotics are viable microorganisms that confer health benefits to the host once consumed in adequate amounts, primarily by promoting the proliferation of beneficial gastrointestinal indigenous microflora. Various mechanisms have been evaluated on the roles of probiotics in preventing enteric tumour and cancer. Enteric cancers are often induced by carcinogens and mutagens upon prolong or excessive exposures. Probiotics have been found to alleviate the detrimental effects of mutagens and carcinogens leading to reduced colon adenocarcinomas and colon tumour multiplicity. Some mechanisms include the ability of probiotics to reduce the production of b-glucuronidase by pathogenic microflora, absorption of harmful carcinogens, and deactivation of mutagens leading to reduced damage of colonic mucosal cells. Probiotics have also been found to possess systemic anti-neoplastic activities, and thus play a crucial role in the prevention of colorectal cancer. Clinical studies have shown that probiotics could decrease neoplastic transformation via controlling proto-oncogenes and tumour suppressor genes, and via inhibition of pathogens that produce carcinogenic enzymes that form detrimental secondary bile salts, deoxycholic and lithocholic acids. Probiotics have also been associated with reduced mutations of enteric cells caused by DNA damages. One of the largest roles of probiotics lies on their ability to inhibit pathogenic bacteria residing in the colons that release by-products such as superoxide and hydrogen peroxide that could damage the DNA of colonic epithelial cells. Other roles include mucin secretion, bioproduction of conjugated linoleic acid, and the production of short chain fatty acids that modulate the induction of DNA damages. Lesions in the enteric regions of mammals have been reported to progress to tumours and probiotics have been found to decrease the generation of these lesions. Lactobacilli- and bifidobacteria-type probiotics have been found to inhibit the development of aberrant crypt foci, increased plasma total antioxidant potentials, decreased plasma lipid peroxidation, and the inhibition of attaching-effacing lesion formation, that lead to decreased and/or improved incidences of gut lesions. [ABSTRACT FROM AUTHOR]

The zebrafish (Danio rerio) has been increasingly recognized as a promising animal model for cancer research. Zebrafish tumors can be generated by treatment with chemical carcinogens or by genetic approaches. The liver has been a main target organ for tumorigenesis after carcinogen treatment while many other tissue-specific tumors have been generated by tissue-specific expression of proven oncogenes. We have used both the chemical and transgenic approaches to generate liver tumors. By comparative analyses of transcriptome profiles between human liver tumors and carcinogen-induced zebrafish liver tumors, we have demonstrated a remarkable similarity in the molecular hallmarks during liver tumorigenesis between humans and zebrafish, thus validating the zebrafish model for human cancer studies. Recently, we have also generated stable transgenic zebrafish lines overexpressing the c-Myc and krasV12 in the liver using two different inducible gene expression systems. In both cases, we found that tumors can be reproducibly induced in the liver, and histopathological examination confirmed the production of liver neoplasia including heptocellular carcinoma. Thus, we have successfully established transgenic zebrafish models for liver cancers and these models will be further characterized in order to understand the molecular and genetic mechanisms of liver carcinogenesis as well as for anti-cancer drug discovery. [ABSTRACT FROM AUTHOR]