Circulating cell-free DNA in plasma of colorectal cancer patients - A potential biomarker for tumor burden

Abstract

Background: Measurement of cell-free DNA (cfDNA) in plasma - the so called liquid biopsy - is a novel method for early detection of cancer. Necrotic cancer cells release various DNA fragments that can be detected in plasma or serum. The aim of our study was to investigate the concentration of circulating ALU115, LINE79 and LINE297 fragments in plasma from venous and arterial blood of colorectal cancer (CRC) patients before, during and 5 days after surgical intervention.

Patients and methods: Thirty patients (16 female, 14 male, median age 56 years), undergoing surgery for colorectal and appendix cancer, and 17 healthy volunteers were included in this study. Plasma samples were collected from patients and healthy individuals. Qualitative polymerase chain reaction (PCR) and quantitative real-time PCR analyses were conducted using specific primers for ALU115, LINE79 and LINE297.

Results: The concentration of ALU115 was significantly increased in plasma of CRC patients compared to the control group (p = 0.002). Interestingly, the concentration of LINE297 was significantly higher in healthy individuals than patients (p = 0.031). We did not find any difference regarding LINE79 between the two groups (p = 0.893). The total cfDNA concentration was slightly increased in plasma after the surgery (p < 0.056), however, the difference was not significant. Interestingly, no correlation was detected between the peritoneal carcinosis index (PCI) and conventional tumor markers.

Conclusion: According to our results, the concentration of ALU115 in cfDNA could be a potential biomarker for diagnosis of CRC. LINE79 or the conventional tumor markers CEA or CA19-9 do not seem useful for the detection of malignant tumors. Whether the amount of LINE297 in cfDNA represents a reliable biomarker for early diagnosis has yet to be confirmed.

Keywords: CEA/CA 19-9; Cell-free DNA; Colorectal cancer; Liquid biopsy; Peritoneal carcinosis index.