The differences in colonic mucosal microbiota between normal individual and colon cancer patients by polymerase chain reaction-denaturing gradient gel electrophoresis.

OBJECTIVE: The aim of this study was to analyze the differences in the intestinal composition between normal individuals and colon cancer patients.
METHODS: To establish the criteria for screening a normal individual for colon cancer, human colonic biopsies were obtained at routine colonoscopy. For patients with colon cancer, samples were obtained from cancerous regions. For normal individuals, colonic biopsies were taken from 3 sites of large intestine (descending, transverse, and ascending colon). Thereafter, a comparison of the microbiota structure by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was carried out. At last, bacterial species were identified by sequencing special bands from DGGE gels and comparing data with sequence databases. RESULT: With PCR-DGGE, we have discovered that the diversity and richness of the bacterial community from colon cancer patient's colonic mucosa were lower than that of the normal individual's sample. Then, a special DGGE band was found in the colon cancer patients. After sequencing, we confirmed that it had a high level of similarity with bacteroides.
CONCLUSIONS: Colon cancers are closely related with the alteration of intestinal flora such as the reduction of biodiversity and richness of the bacterial community. Furthermore, the increase in proportion of bacteroides may be directly associated with colon cancer.