Background: Increased DNA methylation is an epigenetic alteration that is common in human cancers and is often associated with transcriptional silencing. Aberrantly methylated DNA has also been proposed as a potential tumor marker. However, genes such as vimentin, which are transcriptionally silent in normal epithelium, have not until now been considered as targets for cancer-associated aberrant methylation and for use as cancer markers.
Methods: We applied methylation-specific polymerase chain reaction to the vimentin gene, which is transcriptionally silent in normal colonocytes, and compared methylation of vimentin exon 1 in cancer tissues and in fecal DNA from colon cancer patients versus control samples from healthy subjects.
Results: Vimentin exon-1 sequences were unmethylated in 45 of 46 normal colon tissues. In contrast, vimentin exon-1 sequences were methylated in 83% (38 of 46) and 53% (57 of 107) of tumors from two independently collected groups of colon cancer patients. When evaluated as a marker for colon cancer detection in fecal DNA from another set of colon cancer patients, aberrant vimentin methylation was detected in fecal DNA from 43 of 94 patients, for a sensitivity of 46% (95% confidence interval [CI] = 35% to 56%). The sensitivity for detecting stage I and II cancers was 43% (26 of 60 case patients) (95% CI = 31% to 57%). Only 10% (20 of 198 case patients) of control fecal DNA samples from cancer-free individuals tested positive for vimentin methylation, for a specificity of 90% (95% CI = 85% to 94%).
Conclusions: Aberrant methylation of exon-1 sequences within the nontranscribed vimentin gene is a novel molecular biomarker of colon cancer and can be successfully detected in fecal DNA to identify nearly half of individuals with colon cancer.