Detection of circulating tumor DNA for early diagnosis of human cancers

Human cancers have stereotype of being “incurable diseases”, as they are usually diagnosed at terminal stages when most therapies are inefficient. The biomarkers to identify cancers at early stages, particularly during ordinary blood examination, are of great demand. Certain promises have been previously installed on protein biomarkers (such as alpha-fetoprotein, carcinoembryonic antigen, carbohydrate antigen 15-3 and prostate-specific antigen) in biological fluids; however, their use is limited due to lack of sufficient sensitivity, specificity, and stability. Recently, a number of studies have showed that tumour DNA can be efficiently detected in the blood plasma during various stages of cancer, what claims an amazing diagnostic potential of extracellular tumor DNA for the early diagnosis of oncological disorders. Various approaches to detect cancer-derived DNA in blood circulation have been investigated in the past. Those predominantly included either PCR amplification of DNA carrying hotspot mutations or customized tumour-specific qPCR assays (including break-point specific PCR). The targeted exome sequencing of cell-free DNA has been also shown to be a powerful tool for diagnosis and monitoring of metastatic cancers.

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