Consistent high concentration of the viral microRNA BART17 in plasma samples from nasopharyngeal carcinoma patients - evidence of non-exosomal transport
1 Université Paris-Sud 11, CNRS-UMR 8126 and Institut de Cancérologie Gustave Roussy, 39 rue Camille Desmoulins, Villejuif 94805, France
2 Ecole du Val de Grâce, 1 place Alphonse Laveran, Paris 75005, France
3 Virology Department, Hôpital Tenon, 4 rue de la Chine, Paris 75020, France
4 Head and Neck Department, Hôpital Lariboisière, 2 rue Ambroise Paré, Paris 75010, France
5 INSERM UMRS 939 - Université Pierre et Marie Curie - Paris6, Hôpital de la Pitié, 83 boulevard de l’Hôpital, Paris 75013, France
6 Clinical Biology Department, Institut Salah Azaiz, Tunis, Tunisia
7 Head and Neck Tumors Department, Institut de Cancérologie Gustave Roussy, 39 rue Camille Desmoulins, Villejuif 94805, France
8 Radiotherapy Department, Hôpital Pitié-Salpétrière, 47 Boulevard de l’hôpital, Paris 75013, France
Virology Journal 2013, 10:119 doi:10.1186/1743-422X-10-119Published: 16 April 2013
Because latent Epstein Barr (EBV)-infection is a specific characteristic of malignant nasopharyngeal carcinoma (NPC), various molecules of viral origin are obvious candidate biomarkers in this disease. In a previous study, we could show in a few clinical samples that it was possible to detect a category of EBV microRNAs called miR-BARTs in the plasma of at least a fraction of NPC patients. The first aim of the present study was to investigate the status of circulating miR-BART17-5p (one of the miR-BARTs hereafter called miR-BART17) and EBV DNA in a larger series of NPC plasma samples. The second aim was to determine whether or not circulating miR-BART17 was carried by plasma exosomes.
Patients and methods
Plasma samples were collected from 26 NPC patients and 10 control donors, including 9 patients with non-NPC Head and Neck squamous cell carcinoma and one healthy EBV carrier. Concentrations of miR-BART17 and two cellular microRNAs (hsa-miR-16 and -146a) were assessed by real-time quantitative PCR with spike-in normalization and absolute quantification. In addition, for 2 patients, exosome distributions of miR-BART17 and miR-16 were investigated following plasma lipoprotein fractionation by isopycnic density gradient ultrcentrifugation.
The miR-BART17 was significantly more abundant in plasma samples from NPC patients compared to non-NPC donors. Above a threshold of 506 copies/mL, detection of miR-BART17 was highly specific for NPC patients (ROC curve analysis: AUC=0.87 with true positive rate = 0.77, false positive rate = 0.10). In this relatively small series, the concentration of plasma miR-BART17 and the plasma EBV DNA load were not correlated. When plasma samples were fractionated, miR-BART17 co-purified with a protein-rich fraction but not with exosomes.
Detection of high concentrations of plasma miR-BART17 is consistent in NPC patients. This parameter is, at least in part, independent of the viral DNA load. Circulating miR-BART17 does not co-purify with exosomes.