Detection of PIK3CA Mutations in Plasma Tumor DNA Circulating in Peripheral Blood of Breast Cancer Patients

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Date
2014-04-10
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Johns Hopkins University
Abstract
Tumor-specific mutations are used as genetic biomarkers for breast cancer diagnosis and prognosis. The detection and quantification of mutations in tumor DNA circulating in peripheral blood offers a non-invasive approach for measuring the presence of cancer in patients and for evaluating individual responses to targeted therapies. We studied the feasibility of detecting two common mutations in the phosphatidylinositol- 4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) gene, in circulating plasma tumor DNA (ptDNA) of early stage breast cancer patients. We used two Polymerase Chain Reaction platforms, BEAMing and droplet digital PCR (ddPCR), and showed that both platforms detect PIK3CA mutations in ptDNA with high specificity and differential sensitivity (30% for BEAMing, and 93.3% for ddPCR). Additionally, we showed that the sensitivity of ddPCR for ptDNA detection decreased in blood stored at room temperature for one week in tubes that do not prevent blood lysis. Our results provide a novel and non-invasive alternative for clinically detecting and quantifying breast cancer biomarkers in blood, and suggest the use of blood collection tubes that prevent lymphocyte lysis for blood storage and transportation. The method presented herein, can allow physicians to measure tumor burden in breast cancer patients in response to targeted therapies, and to make more informed decisions regarding the administration of toxic systemic therapies.
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Keywords
breast cancer, early stage breast cancer, PIK3CA mutations, cell-free DNA, plasma tumor DNA, cancer biomarkers, cancer therapies, cancer genetics, droplet digital PCR
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