CBIO-06. POTENTIAL ROLE OF RNU6 ISOLATED FROM CIRCULATING EXOSOMES AS A DIAGNOSTIC BIOMARKER FOR GLIOBLASTOMA

Abstract

Glioblastomas (GBM) are highly malignant brain tumors with a poor prognosis despite intensive research and clinical effort. Circulating biomarkers for the disease would be desirable in order to allow for non-invasive tumor detection and follow-up. Recent findings show that GBM cells release microvesicles that contain a select subset of cellular proteins and RNA. Previously, we observed that exosomes isolated from serum of GBM patients had an increased expression of RNU6 (a small non-coding RNA) compared to control samples, and hence could serve as a non-invasive diagnostic biomarker for GBM. In this study, we set to investigate whether this small non-coding RNA could serve as a differential diagnostic biomarker to distinguish GBM from other brain lesions resembling GBM in neuroimaging. We analyzed the expression of RNU6 in circulating exosomes of patients with six types of brain lesions that can mimic GBM on magnetic resonance imaging (i.e. subacute stroke, acute-subacute haemorrhage, acute demyelinating lesions, abscesses, brain metastases and primary CNS lymphomas). First, we isolated the exosomes from the serum of a subset of patients (20–30 patients) with these pathological conditions using an adsorption method (Exoquick). The same was done in a similar group of healthy controls and GBM patients. Then RNU6 levels were analyzed by digital droplet PCR (ddPCR). Corroborating our previous results, we found that the expression of RNU6 was significantly higher in GBM patients than in healthy controls. In addition, RNU6 levels were significantly higher in exosomes from GBM patients than in exosomes from patients with stroke, haemorrhage or acute multiple sclerosis lesions. We are currently analyzing the data regarding the expression of RNU6 in CNS metastasis and lymphomas. Our preliminary data suggest that RNU6 could serve as a differential diagnostic biomarker for GBM patients.