New method for colorectal cancer diagnosis based on SSCP analysis of DNA from exfoliated colonocytes in naturally evacuated feces

Background: Establishment of a sensitive, reliable and non-invasive method for the diagnosis of early-stage colorectal cancer is necessary, because colorectal cancer can be cured surgically if diagnosed early. The aim of the present study was to evaluate the feasibility of using PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism) analysis of the DNA extracted from the colonocytes isolated from naturally evacuated feces, in order to detect colorectal cancer. Materials and Methods: Colonocytes exfoliated into feces, retrieved from 33 patients with colorectal cancer and 63 healthy volunteers, were analyzed for the presence of mutations in their DNA. The DNA extracted from the colonocytes was examined for mutations of the APC, K-ras and p53 genes using direct sequence analysis, and also subjected to PCR-SSCP analysis. Results: Genetic alterations were detected in the colonocytes isolated from the feces of 12 out of 33 patients with colorectal cancer (36.4%) by direct sequence analysis. PCR-SSCP analysis using the same DNA samples revealed abnormal signals in 18 of the 33 patients (54.5%). However, 3 and 7 among the 63 healthy volunteers were also found to have abnormal genetic alterations by direct sequence and PCR-SSCP analysis, respectively. Conclusion: The present study indicated the feasibility of using PCR-SSCP analysis for the detection of mutations in the DNA extracted from colonocytes isolated from naturally evacuated fecal samples.