Strikingly, accumulating evidence shows that the gut microbiota can influence diseases found in organs or tissues distant from the gut, such as obesity, diabetes, autism, rheumatoid arthritis, allergies, and chronic liver disease. Recent studies have presented strong evidences howing that intestinal microbiota Nicaraven modulates the efficacy of chemotherapy. For example, it was found that beta-glucuronidase in intestinal microbiota contributes to the delayed diarrhea caused by the antitumor Voglibose camptothecin derivative irinote can hydrochloride. Later study showed that mice tolerated higher dosages of CPT-11 when the drug was administered together with a beta-glucuronidase inhibitor. Commensal intestinal microbiota might also play a prominent role in the development and severity of chemotherapy-induced mucositis in cancer patients. Animal studies have demonstrated that intestinal microbiota modulates the antitumor efficacy of cyclophosphamide, in part, through the induction of ��pathogenic�� Th17cells. Along this line, a recent report has shown that disruption of commensal microbiota impairs the response of subcutaneous tumors to CpG-oligonucleotide immunotherapy and platinum chemotherapy. In addition to their impact on chemotherapy, the gut microbiota has been suggested to mediate the effect of diet or dietary compounds in cancer prevention and cancer risk. For instance, a resveratrol-supplemented diet significantly reduced the colonic tumors in rats through the reduction of bacterial glucuronidase. A combination of beneficial microbes and specific dietary compounds has been found to prevent the development of colonic polyps in both animals and humans. Overall, the dynamic interplay between the gut microbiota and ingested drugs or dietary compounds impacts on cancer risks and their treatment. Athymic nude mice have been a major animal model for cancer research. Their impaired immune system facilitates tumor grafting avoiding the risk of graft rejection by the animal��s immune system. Early study of mouse gastro intestinal microecology showed that the loss of T cell function does not drastically alter the cultivable gut microbiota in Bal b/c athymic mice as compared to heterozygous or thymus-implanted nude mice.