The detection of early stage colorectal cancer (CRC) significantly improves chances of a cure and is a key factor in reducing CRC mortality rates. Colonoscopy is currently the gold standard for CRC diagnosis, but a somewhat troublesome and invasive procedure makes its acceptance not high in the general public as a screening tool. Epigenetic silencing of tumor-related genes by promoter methylation is common in CRC, but no biomarker has been proven to be individually of sufficient sensitivity or specificity in routine clinical practice. Objective: To identify tumor-derived methylated genes in the serum of stage IIA CRC and assessed their diagnostic potentials for early stage of colorectal cancer.
In this prospective study, DNA methylation levels were measured by quantitative methylation-specific PCR. Seven genes were screened in an exploratory set of case-control serum samples. Promising methylation markers were selected and verified in the serum of a test set compromising 60 stage IIA CRC and 60 age-gender-matched healthy controls. Receiver operating characteristic curve (ROC) was constructed for assessment of assay performance.
Serum methylation levels of TAC1, EYA4 and SST were significantly higher in stage IIA patients as compared to healthy controls (all P < 0.001, Mann-Whitney U test). Area under the receiver operating curve (AUC) using serum methylation of TAC1 and EYA4 was 0.76 [95% confidence interval (CI), 0.68-0.85] and 0.73 (95% CI, 0.64-0.82), respectively. At a specificity of 85%, the assay sensitivity of TAC1 and EYA4 was 58.3% and 43.3%, respectively. Combination of serum methylation levels of EYA4 and SST improved the assay sensitivity to 52.5%. With TAC1 and SST being investigated in tumor DNA as well, we noticed that methylation of both genes in the serum DNA always mirrored that of tumor DNA, exhibiting 100% concordance.
Serum methylation levels of TAC1, EYA4 and SST might be useful for minimally invasive detection of early stage of colorectal cancer. Validation study in larger and independent cohorts is necessary.
Clinical trial identification
Legal entity responsible for the study
Singapore General Hospital.
National Medical Research Council, Singapore.
All authors have declared no conflicts of interest.