Features of Circulating DNA Fragmentation in Blood of Healthy Females and Breast Cancer Patients

Abstract

Size and termini of cell-free DNA molecules circulating in blood plasma and being bound with blood cell surface of healthy females and untreated breast cancer patients were investigated. The size and concentration of circulating blood DNA were analyzed by Agilent 2100 Bioanalyser ^TM and TaqMan PCR. The termini of circulating DNA were examined by ligation using biotinylated double-stranded oligonucleotide adapters with random 1–3 b overhangs of both chains and subsequent quantification by PCR. Short (180 bp) and longer (>8 kbp) DNA fragments were found in cell free DNA from both groups, but short were less represented in primary breast cancer patient plasma. Predominantly high molecular weight DNA was found in cell surface bound DNA both in healthy females and breast cancer patients with a minor fraction of short fragments. Heterogeneous DNA molecules with diverse 5′- and 3′- protruding as well as blunt ends were found both in plasma DNA and cell bound DNA from healthy individuals. Cell surface bound DNA from breast cancer patients mainly contains 5′-protruding ends, whereas 5′- and 3′-protruding ends are equally presented in cell free DNA from these patients. The data obtained obviously reflect over-representation of specific nucleases in breast cancer.