SFRP2 methylation in fecal DNA--a marker for colorectal polyps.

Introduction: DNA methylation of secreted frizzled-related proteins (SFRPs) can be detected in colorectal cancer (CRC) tissue, in tissue of adenomas, and in aberrant crypt foci, whereas in normal colorectal mucosa tissue, SFRP genes are unmethylated. Recently, our study group was able to demonstrate SFRP2 methylation as the most sensitive single DNA-based marker in stool for identification of CRC. The purpose of this study was to clarify whether SFRP2 methylation in fecal DNA can be found in stool of individuals with hyperplastic and adenomatous colorectal polyps.

Materials And Methods: Patients who were diagnosed with colorectal polyps or showed negative colonoscopy were included in this study. DNA from stool samples was isolated. SFRP2 methylation was assessed by means of MethyLight.

Results: Stool samples from 68 individuals were checked for DNA content; 23% of the samples (6 of 26) from healthy controls, 46% of the samples (6 of 13) from patients with hyperplastic polyps, and 45% of the samples (13 of 29) from patients with adenomas were positive for human DNA. SFRP2 methylation in stool samples was found in none of the healthy controls, in 33% (2 of 6) patients with hyperplastic polyps, and in 46% (6 of 13) patients with adenomas. Statistical analysis revealed that the frequency of SFRP2 methylation increased significantly (P=0.028) from healthy controls to patients with hyperplastic polyps and to patients with adenomas.

Conclusions: In the current study, we report for the first time that SFRP2 methylation in fecal DNA increases significantly from healthy controls to patients with hyperplastic polyps and to patients with adenomas. SFRP2 methylation may serve as a marker for molecular stool-based adenoma and CRC screening.