Diagnostic Potential of Hypermethylated DNA in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common forms of cancer and the second leading cause of cancer-related deaths in the western world. CRC mortality is related to stage of disease with a five year survival for early-stage disease of 77.0% and 50.8% for late stage disease. Methods for early detection of primary as well as recurrent CRC are therefore important to increase patient survival. Tumour biomarkers from blood, stool, or urine could aid the early diagnostics of CRC, but despite extensive research such markers have only provided limited clinical value. Sporadic CRC develops as a result of the accumulation of genetic and epigenetic alterations. Epigenetic alterations include DNA hypermethylation, which through transcriptional silencing of tumour suppressor genes is associated with cancer development and cancer progression. The search for gene promoter regions hypermethylated in cancer has been ongoing for nearly two decades, and a number of genes have been shown to be preferentially hypermethylated in CRC. Therefore, hypermethylated DNA in plasma has been suggested as a marker for tumour-stage and survival in CRC patients. The only approved biomarker for the detection of CRC recurrence is the protein carcinoembryonic antigen (CEA). CEA is limited by its low sensitivity and therefore not recommended as a diagnostic biomarker. Hypermethylation of CRC specific genes as part of a molecular biomarker panel measured in blood could prove to be a recurrence marker in CRC patients, with elevated sensitivity and specificity. The aims of this project are to examine if hypermethylation of specific genes measured from cell-free DNA in plasma of CRC patients can be used to detect primary CRC, to detect CRC recurrence and to be a biomarker for CRC prognosis. Development of a reliable sensitive and specific biomarker for CRC will immensely improve the diagnostics and handling of CRC patients.