Tissue 2-Hydroxyglutarate as a Biomarker for <i>Isocitrate Dehydrogenase</i> Mutations in Gliomas.

Abstract

<i>Isocitrate dehydrogenase (IDH)</i> mutations are common in low-grade gliomas and the IDH mutation status is now integrated into the WHO classification of gliomas. IDH mutations lead to preferential accumulation of the R- relative to the S-enantiomer of 2-hydroxyglutarate (2-HG). We investigated the utility of tissue total 2-HG, R-2-HG, and the R-2-HG/S-2-HG ratio (rRS) as diagnostic and prognostic biomarkers for <i>IDH</i> mutations in gliomas.<b>Experimental Design:</b> Glioma tissue and blood samples from 87 patients were analyzed with HPLC-MS/MS coupled with a CHIROBIOTIC column to quantify both enantiomers of 2-HG. ROC analysis was conducted to evaluate the sensitivity and specificity of 2-HG, R-2-HG, and rRS. The feasibility of real-time determination of IDH status was evaluated in 11 patients intraoperatively. The prognostic value of rRS was evaluated using the Kaplan-Meier method. The rRS in glioma tissues clearly distinguished patients with <i>IDH</i>-mutant versus wild-type tumors (<i>P</i> < 0.001). Sensitivity and specificity using an rRS cut-off value of 32.26 were 97% and 100%, respectively. None of total 2-HG, R-2-HG, or rRS was elevated in serum samples. Among patients with <i>IDH</i>-mutant tumors, tissue rRS stratifies overall survival. The duration of tissue analysis is approximately 60 minutes. Our study demonstrates that rRS is a reliable biomarker of <i>IDH</i> mutation status. This technique can be used to determine <i>IDH</i> mutation status intraoperatively, and to guide treatment decisions based on <i>IDH</i> mutation status in real time. Finally, rRS values may provide additional prognostic information and further validation is required.