A Two-Gene Blood Test for Methylated DNA Sensitive for Colorectal Cancer

<div><p>Background</p><p>Specific genes are methylated with high frequency in colorectal neoplasia, and may leak into blood. Detection of multiple methylated DNA biomarkers in blood may improve assay sensitivity for colorectal cancer (CRC) relative to a single marker. We undertook a case-control study evaluating the presence of two methylation DNA markers, <i>BCAT1</i> and <i>IKZF1</i>, in circulation to determine if they were complementary for detection of CRC.</p><p>Methods</p><p>Methylation-specific PCR assays were developed to measure the level of methylated <i>BCAT1</i> and <i>IKZF1</i> in DNA extracted from plasma obtained from colonoscopy-confirmed 144 healthy controls and 74 CRC cases.</p><p>Results</p><p>DNA yields ranged from 2 to 730 ng/mL plasma (mean 18.6ng/mL; 95% CI 11-26 ng/mL) and did not correlate with gender, age or CRC status. Methylated <i>BCAT1</i> and <i>IKZF1</i> DNA were detected in respectively 48 (65%) and 50 (68%) of the 74 cancers. In contrast, only 5 (4%) and 7 (5%) controls were positive for <i>BCAT1</i> and <i>IKZF1</i> DNA methylation, respectively. A two-gene classifier model (“either or” rule) improved segregation of CRC from controls, with 57 of 74 cancers (77%) compared to only 11 of 144 (7.6%) controls being positive for <i>BCAT1</i> and/or <i>IKZF1</i> DNA methylation. Increasing levels of methylated DNA were observed as CRC stage progressed.</p><p>Conclusions</p><p>Detection of methylated <i>BCAT1</i> and/or <i>IKZF1</i> DNA in plasma may have clinical application as a novel blood test for CRC. Combining the results from the two methylation-specific PCR assays improved CRC detection with minimal change in specificity. Further validation of this two-gene blood test with a view to application in screening is now indicated.</p>