Garcia, David M.

Abstract The mutation status of isocitrate dehydrogenase (IDH) in glioma patients has diagnostic and prognostic significance but is available only after surgery. Rapid and sensitive intraoperative molecular diagnosis is essential for distinguishing tumor from infiltrative and from normal brain tissue to maximize safe resection. IDH-mutant (mut)tumors produce high concentrations of 2-hydroxyglutarate (2HG), which serves as a surrogate marker of IDH mutation. Here, we use desorption electrospray ionization-multiple reaction monitoring (DESI-MRM), a form of mass spectrometry (MS), for rapid prediction of IDH mutation status. A set of 30 human brain smears was analyzed using DESI-MRM experiments to predict the mutation status of IDH and quantify 2HG in glioma samples within 2 min (endogenous reference molecule) or 7 min (external standard). Nanoelectrospray ionization (nESI) was employed as a validation method. An isotopically labeled surrogate internal standard allowed quantitative measurement of 2HG and clear separation between IDH-mut and IDH-wildtype (wt) samples, showing 100% agreement with clinical diagnosis. 2HG concentrations in IDH-mut samples ranged from 88 to 1445 ng mg–1, while IDH-wt samples exhibited 2HG concentrations of 9–15 ng mg–1. Calibration curves showed method accuracy within ≤15%. The quantitative results obtained using isotopically labeled standards showed a strong correlation between IDH mutation score and 2HG concentrations, as did an earlier semiquantitative (ratiometric, endogenous standard) method. These findings highlight the standalone capability of DESI-MRM for making measurements to justify assessments for intraoperative diagnosis and to support surgical decision-making to improve patient outcomes.

Abstract Background Glioblastoma (GBM) remains a devastating cancer with limited treatment options, largely due to its heterogeneity. While supramaximal resection has recently provided survival benefits, therapeutic profiling of different tumor compartments, particularly its infiltrative edge remains largely unexplored. Methods Here, we leveraged magnetic resonance imaging (MRI)-guided multi-sampling, collecting 2 cores and 2 margins per case, to query GBM heterogeneity. Whole-exome and RNA-seq with drug testing in two patient-derived 3D models were used to reveal similarities and differences in genomic and transcriptomic makeups, cellular compositions, and drug responses across cores and margins. Bioinformatics interrogations further identified response biomarkers. Results Mutation analysis showed that oncogenes exhibited a higher degree of spatial heterogeneity than tumor suppressor genes, regardless of MRI status. While the mesenchymal transcriptional subtype with extracellular matrix remodeling, stress response, and immune programs were preferentially enriched in enhancing cores, proneural tumors with neurological processes favored non-enhancing margins. Using a 15-drug GBM-targeted panel, ERK (ulixertinib) and PI3K pathway (paxalisib, CC-115) inhibitors showed preferential efficacy in enhancing cores and non-enhancing margins, respectively. The anti-apoptosis, pan-Bcl2 agent navitoclax and the epigenetic drug trotabresib represented the most effective, tumor-wide monotherapies. Importantly, drug combinations generally outperformed single agents across all regions. Conclusions This work demonstrates the regional heterogeneity of therapeutic vulnerabilities in GBM ex vivo, showing various drugs with tumor-wide or MRI-enhancement informed activity. These findings offer preclinical bases of numerous monotherapies and drug combinations for future clinical trial design.