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PLoS Genet. 2016 Jul 18;12(7):e1006162. doi: 10.1371/journal.pgen.1006162. eCollection 2016 Jul.

Fragment Length of Circulating Tumor DNA.

Author information

1
Department of Pediatrics, Division of Medical Genetics, University of Utah, Salt Lake City, Utah, United States of America.
2
Department of Radiology, University of Utah, Salt Lake City, Utah, United States of America.
3
Department of Neurological Surgery, University of Washington, Seattle, Washington, United States of America.
4
Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America.
5
Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America.
6
ARUP Laboratories, Salt Lake City, Utah, United States of America.
7
Department of Pathology, University of Utah, Salt Lake City, Utah, United States of America.

Abstract

Malignant tumors shed DNA into the circulation. The transient half-life of circulating tumor DNA (ctDNA) may afford the opportunity to diagnose, monitor recurrence, and evaluate response to therapy solely through a non-invasive blood draw. However, detecting ctDNA against the normally occurring background of cell-free DNA derived from healthy cells has proven challenging, particularly in non-metastatic solid tumors. In this study, distinct differences in fragment length size between ctDNAs and normal cell-free DNA are defined. Human ctDNA in rat plasma derived from human glioblastoma multiforme stem-like cells in the rat brain and human hepatocellular carcinoma in the rat flank were found to have a shorter principal fragment length than the background rat cell-free DNA (134-144 bp vs. 167 bp, respectively). Subsequently, a similar shift in the fragment length of ctDNA in humans with melanoma and lung cancer was identified compared to healthy controls. Comparison of fragment lengths from cell-free DNA between a melanoma patient and healthy controls found that the BRAF V600E mutant allele occurred more commonly at a shorter fragment length than the fragment length of the wild-type allele (132-145 bp vs. 165 bp, respectively). Moreover, size-selecting for shorter cell-free DNA fragment lengths substantially increased the EGFR T790M mutant allele frequency in human lung cancer. These findings provide compelling evidence that experimental or bioinformatic isolation of a specific subset of fragment lengths from cell-free DNA may improve detection of ctDNA.

PMID:
27428049
PMCID:
PMC4948782
DOI:
10.1371/journal.pgen.1006162
[Indexed for MEDLINE]
Free PMC Article

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