384 Background: Identification of blood-based biomarkers for cancer screening is essential in order to develop novel and minimally invasive methods for colorectal cancer screening. Our lab has successfully applied a novel nanotechnology that allows us to detect and amplify a single tumor DNA fragment in a plasma sample. This DNA is tested for methylation of several genes including TFPI2 which has shown to be highly sensitive and specific for the detection colorectal cancer in stool. Methods: Whole blood was obtained from 18 colorectal cancer patients and plasma was isolated. Plasma was processed using Methylation On Beads nanotechnology (MOB) and bisulfate treated. Methylation status was determined via quantitative PCR method. Results: Two genes, TFPI2 and IGFBP3, were detected with a high sensitivity. TFPI2, demonstrated a methylation frequency of 94.4%, which is concordant with the TFPI2 methylation frequency of 99% in primary colorectal cancer tissues. IGFBP3 showed the methylation frequency of 61.1%, which corresponds with the methylation frequency of 52% in retrospective colorectal cancer tissues in previous studies. Quantification using standard curves indicated a single copy level of DNA found in plasma. Conclusions: Blood-based screening is challenging due to extremely low quantities of circulating DNA in blood. Utilizing a novel nanotechnology that detects DNA at a single copy level, the methylation changes in colorectal cancer were successfully detected in plasmas at similar frequencies as in tissue samples. This study has demonstrated the feasablility and applicability to blood-based screening. Future studies will focus on improving the sensitivity and determining the specificity of this method.
MLH1 Promoter Methylation Frequency in Colorectal Cancer Patients and Related Clinicopathological and Molecular Features
