5‐Methylcytosine—The Fifth Base of DNA: The Fifth Wheel on a Car or a Highly Promising Diagnostic and Therapeutic Target in Cancer?

The concept of early detection of tumours before they spread and become incurable, represents one of the most important challenges in reducing the impact of the growing burden of cancer worldwide. Whilst improvements in the methods of treating cancer have had some success, it is clear that tumour stage at diagnosis has a major effect on survival for all types of cancer. A non-invasive marker for cancer that will achieve early diagnosis as well as predicting prognosis and response to treatment and providing insight into aetiology, would be a powerful clinical tool. Recently, this search has intensified due to the introduction of novel molecular technologies with the potential to identify cellular changes at the epigenome level. In the late 1970s, Peter A. Jones and coworkers were the first to discover the role of DNA methylation in cellular differentiation. Over the last 25 years, epigenetics, a term covering hypomethylation, hypermethylation, loss of imprinting and chromatin modification, has been recognised to be as important as genetics in human cancer. This Special Issue of Disease Markers, appears at a critical time in the development of the field of cancer