الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Background: Baker’s yeast (S. cerevisiae) exerts anticancer activity against different kinds of cancer. However, its effects on skin cancer haven’t until now been examined. The present study investigated the apoptotic effect of intratumoral (IT) injection of heat-killed yeast on skin cancer in mice. Materials and Methods: Tumors were elicited in male Swiss albino mice by painting 7,12-dimethylbenz[α] anthracene (DMBA) followed one week afterward by 12-O-tetradecanoylphorbol 13-aceteate (TPA). Mice were divided into four groups: animal bearing tumor untreated with yeast and animal received IT injection of yeast (100µL) for 16 weeks at concentrations of 107, 108 and 109 cells/ml. The skin tumors were handled for histopathological analysis. The tumor homogenates in addition to normal control skin homogenate were used to analyze the levels of calcium ions and the apoptotic pathways, involving the manifestation of apoptotic regulators FasL, Bcl-2, Bax, cytochrome c and caspases 8, 9 and 3. Toxicity for baker’s yeast was examined chemically and histopathologically. Results: Mice treated by means of yeast showed significant histopathological changes. Results demonstrated that treatment with yeast caused a rise in calcium ions in the skin homogenate of mice bearing tumor as compared to mice with tumor alone. Yeast, in a dosage dependent manner, effectively modulates the intrinsic pathway by down-regulating Bcl-2 and up-regulating Bax and additionally increases the manifestation of both cytochrome c and caspases 9 and 3 relative to animals with tumor alone. Additionally, yeast induces cell death by extrinsic pathway as indicated by considerably decreasing the manifestation of FasL and increasing the levels of caspase 8. Further studies showed yeast treatment caused the recovery of the reduction in body weight owing to cancer. Conclusion: These results showed that IT treatment with baker’s yeast exerts anti-skin cancer activity in vivo via intrinsic and extrinsic apoptosis pathways with no toxicity and may suggest its use as a cure for the human skin cancer.