Quantification of LINE1 in circulating DNA as a molecular biomarker of breast cancer

Developing a noninvasive test for detecting and monitoring breast cancer progression would help in providing better procedures for the treatment of breast cancer. Increases in the absolute quantity of circulating DNA and DNA integrity have been previously reported in breast cancer patients. LINE1 is one of the most abundant sequences in the human genome, with about 520,000 copies per genome. To assess the combination of circulating DNA quantity and DNA integrity, we developed a long LINE1 (about 300-bp amplicon size) quantitative method. A quantitative real-time PCR (qPCR) technique was used to detect long LINE1. Breast cancer patients' sera was assessed preoperatively before primary tumor surgery. LINE1 could be detected in high levels of breast cancer patients' sera and in limited levels in normal females. We demonstrated that long LINE1 quantification of circulating DNA was useful for detecting early-stage breast cancer, and that copy number correlated with tumor size. This preliminary study demonstrates the potential clinical utility of LINE1 copy numbers in breast cancer patients.