Date: 20 Jan 2011

Probiotics and Enteric Cancers

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Abstract

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.