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Purpose: Metabolism within the tumor microenvironment (TME) represents an increasing area of interest to understand glioma initiation and progression. Stable isotope tracing is a technique critical to the study of tumor metabolism. Cell culture models of this disease are not routinely cultured under physiologically relevant nutrient conditions and do not retain cellular heterogeneity present in the parental TME. Moreover, in vivo, stable isotope tracing in intracranial glioma xenografts, the gold standard for metabolic investigation, is time consuming and technically challenging. To provide insights into glioma metabolism in the presence of an intact TME, we performed stable isotope tracing analysis of patient-derived, heterocellular Surgically eXplanted Organoid (SXO) glioma models in human plasma-like medium (HPLM). Methods: Glioma SXOs were established and cultured in conventional media or transitioned to HPLM. We evaluated SXO cytoarchitecture and histology, then performed spatial transcriptomic profiling to identify cellular populations and differential gene expression patterns. We performed stable isotope tracing with 15N2-glutamine to evaluate intracellular metabolite labeling patterns. Results: Glioma SXOs cultured in HPLM retain cytoarchitecture and cellular constituents. Immune cells in HPLM-cultured SXOs demonstrated increased transcription of immune-related signatures, including innate immune, adaptive immune, and cytokine signaling programs. 15N isotope enrichment from glutamine was observed in metabolites from diverse pathways, and labeling patterns were stable over time. Conclusion: To enable ex vivo, tractable investigations of whole tumor metabolism, we developed an approach to conduct stable isotope tracing in glioma SXOs cultured under physiologically relevant nutrient conditions. Under these conditions, SXOs maintained viability, composition, and metabolic activity while exhibiting increased immune-related transcriptional programs.
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The creation of patient-derived cancer organoids represents a key advance in preclinical modeling and has recently been applied to a variety of human solid tumor types. However, conventional methods used to assess in vivo tumor tissue treatment response are poorly suited for the evaluation of cancer organoids because they are time-intensive and involve tissue destruction. To address this issue, we established a suite of 3-dimensional patient-derived glioma organoids, treated them with chemoradiotherapy, stained organoids with non-toxic cell dyes, and imaged them using a rapid laser scanning confocal microscopy method termed "Apex Imaging." We then developed and tested a fragmentation algorithm to quantify heterogeneity in the topography of the organoids as a potential surrogate marker of viability. This algorithm, SSDquant, provides a 3-dimensional visual representation of the organoid surface and a numerical measurement of the sum-squared distance (SSD) from the derived mass center of the organoid. We tested whether SSD scores correlate with traditional immunohistochemistry-derived cell viability markers (cellularity and cleaved caspase 3 expression) and observed statistically significant associations between them using linear regression analysis. Our work describes a quantitative, non-invasive approach for the serial measurement of patient-derived cancer organoid viability, thus opening new avenues for the application of these models to studies of cancer biology and therapy.
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OBJECTIVE: Cortical mapping has been used as a tool to ensure maximal safe resection of intracranial tumors for several decades. Post-surgical motor and language deficits, including seizures, weakness, aphasia, and dysarthria have been well-documented in patients undergoing these operations, particularly on eloquent cortical regions. However, it is not known whether awake versus asleep cortical mapping contributes to differences in postoperative neurological deficits. METHODS: A comprehensive review of the literature utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was completed for articles describing cortical mapping for tumor resection. We critically assessed all articles published in the last 20 years describing complications of patients who had undergone either awake or asleep motor mapping for eloquent brain tumor resection. Studies were analyzed for number of patients, follow-up duration, rates of transient and permanent motor and sensory deficits in the perioperative period, and outcomes at one-month follow-up. RESULTS: Thirty-one studies met inclusion criteria, 24 of which reported long-term post-operative follow-up data. Follow-up among selected studies ranged from one month to four years. Nine of the 31 studies directly compared the postoperative outcomes of awake versus asleep mapping. The rate of transient deficits among patients who underwent awake and asleep mapping was 31.6% and 32.7%, respectively. The rate of permanent deficits was 10.8% in awake mapping patients and 12.7% in asleep mapping patients. Qualitative analysis showed that motor and sensory complications occurred at similar rates. CONCLUSIONS: Review of the current evidence suggests that the rates of transient and permanent postoperative neurologic deficits among awake versus asleep cortical mapping groups are similar. Thus, use of both techniques is reasonable to minimize perioperative morbidity.
