Cancer therapy monitoring in xenografts by quantitative analysis of circulating tumor DNA.

Context: Circulating tumor DNA (ctDNA) is a promising biomarker in cancer. Materials and methods: We generated xenograft models of cancer and detected ctDNA in plasma by qRCR targeting human AluJ sequences. Results: Our assay reached single cell sensitivity in vitro and a correlation between ctDNA amount and tumor size was observed in vivo. Treatment with a mitogen activated protein kinase kinase (MEK)-inhibitor (BAY 869766) reduced ctDNA levels. Using this assay, we also confirmed that high levels of cell-free DNA are found in cancer patients compared to healthy individuals. Discussion and conclusion: We show that ctDNA may be useful biomarker for monitoring tumor growth and treatment response. [ABSTRACT FROM AUTHOR]