Cell-free circulating ALU repeats in serum have a prognostic value for colorectal cancer patients

Abstract

BACKGROUND: Carcinoembryonic antigen (CEA) is the only established serum biomarker for colorectal cancer (CRC). To facilitate therapy decisions and improve the overall survival of CRC patients, prognostic biomarkers are required. OBJECTIVE: We studied the prognostic value of five different cell free circulating DNA (fcDNA) fragments. The potential markers were ALU115, ALU247, LINE1-79, LINE1-300 and ND1-mt. METHODS: The copy numbers of the DNA fragments were measured in the peripheral blood serum of 268 CRC patients using qPCR, the results were compared to common and previously described markers. RESULTS: We found that ALU115 and ALU247 fcDNA levels correlate significantly with several clinicopathological parameters. An increased amount of ALU115 and ALU247 fcDNA fragments coincides with methylation of HPP1 (P< 0.001; P< 0.01), which proved to be a prognostic marker itself in former studies and also with increased CEA level (both P< 0.001). ALU115 and ALU247 can define patients with poor survival in UICC stage IV (ALU115: HR = 2.9; 95% Cl 1.8–4.8, P< 0.001; ALU247: HR = 2.2; 95% Cl 1.3–3.6; P= 0.001). Combining ALU115 and HPP1, the prognostic value in UICC stage IV is highly significant (P< 0.001). CONCLUSIONS: This study shows that an increased level of ALU fcDNA is an independent prognostic biomarker for advanced colorectal cancer disease.