[Application of a novel method to collect large amount of fecal mucosa in screening colorectal cancer].

OBJECTIVE: To explore the application of a novel device of collecting large amount of fecal mucosa for detecting the DNA methylation and screening colorectal cancer.

METHODS: Preoperative complete fecal sample and surgical specimen of 10 patients with colorectal cancer, and complete fecal sample and normal bowel mucosal samples confirmed by colonoscopy of 6 hospitalization cases at The Third Affiliated Hospital, Nanjing University of TCM from March to April 2014 were collected. A self-made bowel mucosa collector (consisting of upper, middle, lower three containers of 1 000 ml volume, with filter screen in each bottom whose pore diameter is 100, 200 and 300 mesh.) was used to collect mucosal exfoliation cells. Fecal DNA kit was applied to extract DNA of exfoliation cells and the concentration and purity of DNA were measured by UV spectrophotometer (A260/A280), meanwhile DNA methylation of fecal fluid and mucosal tissues was detected by bisulfite sequencing pCR(BSP).

RESULTS: DNA methylation sequencing showed that FBN1, SPG20, and SNCA genes presented methylation in CpG island in fecal fluid and cancer tissues from 10 colorectal cancer patients, but did not presented methylation in fecal fluid and mucosa from 6 control cases. When fecal amount was below 100 g, collection rate of fecal fluid was 60% to 80%; when fecal amount was over 100 g, collection rate of fecal fluid was unstable. When fecal amount was 50 to 100 g, DNA A260/A280 value was 1.6 to 1.8, and DNA concentration was 5.0 to 56.1 ng/L.

CONCLUSION: Collection rate of fecal fluid with this self-made fecal mucosa collector is quite stable when managing fecal amount of 50 to 100 g once, and can obtain higher purity and concentration of DNA, meeting the demand of methylation detection for screening colorectal cancer.