Abstract
Colonic adenomatous polyps are common tumors occurring in 50% of Western populations with 10% risk of malignant progression. To date, the environmental exposures proposed to promote the development of colorectal cancer (CRC) have been primarily dietary agents. However, the local environment to which the colonic mucosa is exposed is created by the bacterial microbiota of the colon and their metabolic products that include toxins. African Americans are known to have a higher incidence of colon cancer than other groups.
We analyzed the gut flora from African Americans patients by both 16S rDNA sequencing and HIT (Human Intestinal Tract) Chip. Our findings reflected a high prevalence of Bacteroidetes and Clostridia groups with the Bacteroidetes slightly more represented in patients with colon polyps than healthy ones. While Bifidobacteria were not detected at all in all samples, Lactobacilliwere present at a very low frequency. Both bacteria are referred to as “good bacteria” and are generally associated with healthy colon. Helicobacter bacteria, associated with gastric cancer, were also detected in all analysed samples. Bacteroides fragilis and relatives were present in all samples at a high frequency. It is noteworthy that an enterotoxigenic Bacteroides fragilis have been found to trigger colon polyps formation in Min mice through a pSTAT3 pathway. A tissue microarray immunohistochemistry experiment on colon adenoma and matched normals revealed a strong expression of pSTAT3 both in colonic epithelial cells and in colonic immune cells in adenoma samples but not as much in normal ones. These findings highlight the presence of a possible ETBF-like induction mechanism in the analysed samples.
Enzyme immunoassay for the detection of antibodies against ETBF toxin would confirm such findings and a metagenomic analysis of the analysed samples would shed light on predominant bacterial functions in adenoma patients that might play a role in colon oncogenic transformation in this population.
Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B48.