Can DNA sampling from the rectal mucosa be a novel tool for the detection of colorectal cancer?

DNA quantification of exfoliated colonocytes as a novel screening tool for colorectal cancer

AIMS

Colorectal cancer (CRC) sheds viable cells in the mucocelluar layer overlaying the colonic mucosa which travels distally alongside the faecal stream. These cells can be retrieved from the surface of the rectal mucosa. DNA quantification of these cells may be a marker of CRC, assessment of which was aim of this study.

METHODS

A prospective double-blinded study of 467 consecutive patients referred with symptoms suggestive of CRC. Cells were collected from the surface of the rectal mucosa and total DNA quantified. DNA scores were compared with outcome after subjects had completed bowel investigations. Analysis of receiver operating characteristic (ROC) curves was performed to determine the optimum cut-off point for a positive result.

RESULTS

107 of the 467 patients were excluded due to; excessive faecal contamination of samples (n = 84); declined investigations (n = 17); inappropriate referral (n = 5); unfit (n = 1). 263 patients had lower GI endoscopy; 89 CT colonography and 8 barium enema. The diagnosis were; CRC (n = 23), inflammatory bowel disease (IBD) (n = 7), adenomatous polyps (AP) (n = 20) and no significant abnormality detected (n = 310). ROC analysis revealed that sensitivities at a specificity of 60% for detecting CRC were 91.3%; for CRC and IBD 86.7%; and for CRC, IBD and AP 72.0%.

CONCLUSION

In symptomatic patients DNA quantification of cells retrieved from the surface of the rectal mucosa is sensitive for the detection of CRC. Although faecal contamination is a limitation of this technique, refinement and application of other molecular tests hold promise for a better non invasive method for the detection of CRC.

Protein biomarkers in exfoliated cells collected from the human rectal mucosa: implications for colorectal disease detection and monitoring

PURPOSE

Colorectal disease biomarkers in stool are actively explored, but instability of biomolecules in faeces constitutes a problem. Collection of exfoliated cells from the surface of the rectal mucosa provides an alternative to stool-based methods. We aimed to develop an original approach allowing preservation and quantification of protein biomarkers in exfoliated material and tested it in a pilot clinical study.

METHODS

A novel method of cell and protein preservation in ammonium sulphate-rich buffers was developed using cultured human cells and applied to exfoliated cell samples collected from 139 faecal occult blood test (FOBT)-positive patients prior to colonoscopies. Protein biomarkers comprising calprotectin, eosinophil-derived neurotoxin (EDN), dimeric pyruvate kinase type M2 (M2PK), soluble cytokeratin-18, d-dimer and glyceraldehyde 3-phosphate dehydrogenase were quantified using enzyme-linked immunosorbent assays with parallel cytological and immunocytochemical analysis.

RESULTS

Long-term preservation of cells and their protein constituents at ambient temperature was achieved using buffers containing saturated ammonium sulphate. Application of this approach to exfoliated cell samples allowed consistent protein quantification. Calprotectin, EDN, M2PK, soluble cytokeratin 18 and d-dimer showed dramatic increase in a few cases of inflammatory bowel disease (IBD) detected among trial participants. Cytological signs of inflammation were also present in these samples.

CONCLUSIONS

Application of exfoliated cells collected from the surface of the rectal mucosa provides a reliable method for quantifying protein biomarkers of gastrointestinal diseases. Our preliminary results obtained in a limited number of cases indicate that the approach might be especially useful for IBD diagnosis and monitoring, but further studies are needed to assess its diagnostic value.