A new noninvasive blood-test for the early detection of colorectal cancer.

Abstract

348 Background: Colorectal cancer (CRC) remains a major medical problem in the world. Its early detection impacts the prognosis and the cost of treatment. Fecal occult blood test is a current noninvasive screening method for CRC detection in asymptomatic average risk individuals. It detects less than 50% of cancers and yields a high number of “normal” colonoscopies. The dysregulation of DNA methylation has been recognized as playing a crucial role during CRC development. The aim of the study was to develop a CRC-specific methylated DNA test in serum. Methods: First, the GoldenGate Methylation microarray containing 1,505 CpG loci within 807 cancer-related genes was used to study methylation patterns in CRC patients. We performed such assays on 9 tissues (4 CRC, 4 normal autologous tissues, 1 polyp), 17 blood and urine pooled samples (7 CRC, 6 polyps, 4 normal) and 20 stool samples (7 CRC, 3 polyps, 10 normal). The clinical status of each sample was assessed by colonoscopy and/or pathology findings. Among methylated genes detected in tumour tissue, stools, and blood, NPY, PENK and WIF1 genes were selected taking into account their high degree of methylation. We then carried out a clinical validation by quantitative multiplex methylation-specific PCR (QM-MSP) in two phases: firstly on 30 tissues (15 CRC, 15 homologous normal tissues) and secondly on 193 serum samples (32 CRC, 161 normal). Results: For to obtain the best accuracy of QM-MSP test, we defined for both biological sources a cumulative methylation index (CMI) by adding of the methylation percentage of each gene. At the CMI of 20.0% on tissues, our QM-MSP test allows to diagnose the CRC with the highest accuracy (100% of specificity and 100% of sensitivity). From sera, the CMI has been standardized at 2.0% giving a sensitivity and specificity for detecting CRC of 94.4% and 59.4% respectively (NPV of 92.1% and PPV of 67.8%). Conclusions: We developed a QM-MSP-based analysis of NPY, PENK, and WIF1 methylated genes in serum. This test classified correctly and with a high accuracy the healthy individuals and colon cancer patients. We propose here new sensitive serum-based epigenetic biomarkers as an effective and simple new noninvasive test for CRC screening in the average and high risk populations.