Genetic diagnosis of gastrointestinal cancer using peripheral blood DNA or ascitis DNA

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Evidences of circulating soluble DNA in bloodstream of cancer patients has emerged. Because the plasma DNA is largely derived from cancer cells, genetic analysis of plasma DNA is important to understand the molecular events occurred in cancer patient. Seven microsatellite markers in the soluble plasma DNA from patients with pancreatic adenocarcinoma and other paucreato-biliary malignant tumors were examined for microsatellite instability (MSI) and allelic imbalance (AI). As the result, a variety of genetic alterations including MSI and AI were detected in the plasma DNA. Some alterations were detected before recurrence of the tumor was verified. Analysis of five primary pancreatic adenocarcinomas by microdissection revealed that the heterogenous nature of pancreatic tumors is associated with both MSI and AI in the same tumor. The presence of altered plasma DNA including MSI and/or AI from the same pancreatic cancer patient may be important evidence for the presence of theses alterations in heterogenous primary tumor. Analysis of plasma DNA could hopefully become one of the diagnostic or therapeutic measure for this formidable pancreatic adenocarcinoma.