Recent studies have indicated that a significant survival advantage is conferred to patients with gliomas whose lesions harbor mutations in the genes isocitrate dehydrogenase 1 and 2 (IDH1/2). IDH1/2 mutations result in aberrant enzymatic production of the potential oncometabolite D-2-hydroxyglutarate (2HG). Here, we report on the ex vivo detection of 2HG in IDH1-mutated tissue samples from patients with recurrent low-grade gliomas using the nuclear magnetic resonance technique of proton high-resolution magic angle spinning spectroscopy. Relative 2HG levels from pathologically confirmed mutant IDH1 tissues correlated with levels of other ex vivo metabolites and histopathology parameters associated with increases in mitotic activity, relative tumor content, and cellularity. Ex vivo spectroscopic measurements of choline-containing species and in vivo magnetic resonance measurements of diffusion parameters were also correlated with 2HG levels. These data provide extensive characterization of mutant IDH1 lesions while confirming the potential diagnostic value of 2HG as a surrogate marker of patient survival. Such information may augment the ability of clinicians to monitor therapeutic response and provide criteria for stratifying patients to specific treatment regimens.

Two double-cysteine mutants of a small protein judiciously modified so that the cysteines appear at axially opposite sides of the native fold were prepared such that different axes were defined in the two mutants. Upon reduction, the disulfide bonds are broken, and the proteins act as bifunctional ligands toward Ag nanoparticles, encouraging their assembly into nanoparticle dimers and small aggregates such that, when excited with laser light, the proteins are automatically located at electromagnetic hot spots within the aggregates. Because the protein molecules are small (~2.3 nm) and because the electromagnetic energy at a hot spot tends to increase as the size of the interparticle gap decreases, this nanoparticle-protein-nanoparticle geometry significantly enhances the Raman emission at the metallic surface. Exploiting this effect, we have recorded surface-enhanced Raman spectra (SERS) of the proteins at near-single-molecule level. The observed SERS spectra were dominated by the vibrations of molecular groups near the anchor points of the proteins.

Infiltrating low grade gliomas (LGGs) are heterogeneous in their behavior and the strategies used for clinical management are highly variable. A key factor in clinical decision-making is that patients with mutations in the isocitrate dehydrogenase 1 and 2 (IDH1/2) oncogenes are more likely to have a favorable outcome and be sensitive to treatment. Because of their relatively long overall median survival, more aggressive treatments are typically reserved for patients that have undergone malignant progression (MP) to an anaplastic glioma or secondary glioblastoma (GBM). In the current study, ex vivo metabolic profiles of image-guided tissue samples obtained from patients with newly diagnosed and recurrent LGG were investigated using proton high-resolution magic angle spinning spectroscopy (1H HR-MAS). Distinct spectral profiles were observed for lesions with IDH-mutated genotypes, between astrocytoma and oligodendroglioma histologies, as well as for tumors that had undergone MP. Levels of 2-hydroxyglutarate (2HG) were correlated with increased mitotic activity, axonal disruption, vascular neoplasia, and with several brain metabolites including the choline species, glutamate, glutathione, and GABA. The information obtained in this study may be used to develop strategies for in vivo characterization of infiltrative glioma, in order to improve disease stratification and to assist in monitoring response to therapy.

Gliomas are routinely graded according to histopathologic criteria established by the World Health Organization (WHO). Although this classification can be used to understand some of the variance in the clinical outcome of patients, there is still substantial heterogeneity within and between lesions of the same grade. This study evaluated image-guided tissue samples acquired from a large cohort of patients presenting with either new or recurrent gliomas of grades II-IV using ex vivo proton high-resolution magic-angle spinning (1H HR-MAS) spectroscopy. Quantification of metabolite levels revealed several discrete profiles associated with primary glioma subtypes, as well as secondary subtypes that had undergone transformation to a higher grade at the time of recurrence. Statistical modeling further demonstrated that these metabolomic profiles could be differentially classified with respect to pathologic grading and inter-grade conversions. Importantly, the myo-inositol-to-total-choline index (MCI) allowed for a separation of recurrent low-grade gliomas on different pathologic trajectories; the heightened ratio of PC/GPC uniformly characterized several forms of glioblastoma multiforme (GBM); and onco-metabolite D-2-hydroxyglutarate (2HG) was shown to help distinguish secondary from primary grade IV glioma, as well as grade II and III from grade IV glioma. These data provide evidence that metabolite levels are of interest for assessing both intra-grade and intra-lesional malignancy. Such information could be used to enhance the diagnostic specificity of in vivo spectroscopy and to aid in selecting the most appropriate therapy for individual patients.