Myosin 10 Regulates Invasion, Mitosis, and Metabolic Signaling in Glioblastoma

Invasion and proliferation are defining phenotypes of cancer, and in glioblastoma blocking one stimulates the other, implying that effective therapy must inhibit both, ideally through a single target that is also dispensable for normal tissue function. The molecular motor myosin 10 meets these criteria. Myosin 10 knockout mice can survive to adulthood, implying that normal cells can compensate for its loss; its deletion impairs invasion, slows proliferation, and prolongs survival in murine models of glioblastoma. Myosin 10 deletion also enhances tumor dependency on the DNA damage and the metabolic stress responses and induces synthetic lethality when combined with inhibitors of these processes. Our results thus demonstrate that targeting myosin 10 is active against glioblastoma by itself, synergizes with other clinically available therapeutics, may have acceptable side effects in normal tissues, and has potential as a heretofore unexplored therapeutic approach for this disease.

DDEL-07. A PHASE I STUDY EXAMINING THE FEASIBILITY OF INTERMITTENT CONVECTION-ENHANCED DELIVERY (CED) OF MTX110 FOR THE TREATMENT OF CHILDREN WITH NEWLY DIAGNOSED DIFFUSE MIDLINE GLIOMAS

Convection-enhanced delivery (CED, the infusion of drugs under controlled pressure to the brain parenchyma via targeted micro-catheters, allows accurate anatomical targeting and delivery of higher (therapeutic) drug concentrations through clinically relevant volumes of brain tissue or tumor. Histone deacetylase inhibitors have been found in vitro to be the most active agents against Diffuse Midline Gliomas (DMGs) Using a novel device (implantable subcutaneous pump connected with catheter directly implanted into the pons/thalamus) we are performing a Phase I safety study of repeated infusions of MTX110 (MTX110, Midatech) in a dose escalation manner. Eligible patients include 3–18 years of age with newly diagnosed DMGs following radiation therapy without evidence of hemorrhage or cysts with intact organ function. Patients undergo a tumor biopsy and a single catheter (Spetzler lumbar shunt catheter, Integra, Plainsboro, NJ) is placed stereotactically into the geometric center of the tumor. A second catheter is inserted subcutaneously with the distal tubing connected to the infusion pump, (SynchroMed II (Medtronic)), also inserted subcutaneously. The infusion pump is prefilled with MTX110 and administered using wireless N’Vison Clinical programmer into two 24-hour infusions, consisting of 20 hours of drug infusions at 0.2mL/hr. The pulse is completed 7 days later. This is a dose escalation study with the infusate consisting of gadolinium and MTX110 (30, 60, or 90 microM). The study describing the first use in children of this device for direct-to-tumor drug delivery is open to recruitment (January 2020) and the preliminary data will be available for presentation by June 2020.

MODL-09. FEASIBILITY OF ACUTE SLICE CULTURE-SINGLE CELL SEQUENCING DRUG SCREENING AS A TOOL TO SELECT THERAPY FOR CHILDREN WITH RELAPSED BRAIN TUMORS

Children with relapsed brain tumors are less responsive to treatment. These children often receive therapies without having any robust predictive method of potential benefit. Acute slice culturing(ASC) is a methodology permitting freshly operated tumor to undergo a culturing process preserving the tumor’s micro-environment. With the current study, we investigated the feasibility of obtaining therapeutically meaningful data in a timely manner (3–5 days), performing direct drug testing and single cell sequencing using ASC. Previously, we have combined ex vivo slices of intact, patient-derived Glioblastoma tissue with single-cell RNA-seq for small-scale drug screening and assessment of patient and cell type-specific drug responses. We generated slices from preclinical mouse glioma models and surgical specimens from adult Glioblastoma patients, as well as from children with relapsed Ependymomas, Medulloblastomas, and Gliomas. We demonstrated that these acute slices preserved both the tumor heterogeneity and tumor microenvironment observed in single-cell RNA-seq of cells directly isolated from tumor tissue. Testing drug responses, we then treated tissue slices from the Glioblastoma mouse models and different patients with multiple drugs and combinations. This technique allowed us to identify drug-induced transcriptional responses in specific subpopulations of tumor cells, patient-specific drug sensitivities, and drug effects conserved in both mouse and human tumors. Preliminary data suggests that we can apply this procedure within 5–7 days and provide real-time drug screening/single cell sequencing ASC results to Recurrent/ Progressive pediatric Low-Grade Gliomas, High Grade Gliomas, Ependymomas and Medulloblastomas.

DDEL-13. FOCUSED ULTRASOUND MEDIATED BLOOD BRAIN BARRIER DISRUPTION IN A MURINE MODEL OF PONTINE GLIOMA: A SAFETY AND FEASIBILITY STUDY

BACKGROUND

Drug delivery remains a major obstacle in DIPG, as the blood brain barrier (BBB) limits the penetration of systemic therapies to the brainstem. Focused ultrasound (FUS) is an exciting new technology that, when combined with microbubbles, can open the BBB permitting the entry of drugs across the cerebrovasculature. Given that the utility of FUS in brainstem tumors remains unknown, the purpose of our study was to determine the safety and feasibility of this technique in a murine pontine glioma model.

METHODS

A syngeneic orthotopic model was established by stereotactic injection of PDGF-B+PTEN-/-p53-/- murine glioma cells (10,000/1ul) into the pons of B6 albino mice. A single-element, spherical-segment FUS transducer (center frequency=1.5MHz) driven by a function generator through a power amplifier (acoustic pressure=0.7MPa) was used with concurrent intravenous microbubble injection (FUS+MB) to sonicate the tumor on post-injection day 14. BBB opening was confirmed with gadolinium-enhanced MRI and Evans blue. Kondziela inverted screen (KIS) testing was completed to measure motor function. Mice were either immediately sacrificed for histopathological assessment or serially monitored for survival.

RESULTS

In mice treated with FUS (n=11), there was no measured deficit in KIS testing. Additionally, the degree of intra-tumoral hemorrhage and inflammation on H&E in control (n=5) and treated mice (n=5) was similar. Lastly, there was no difference in survival between the groups (control, n=6, median=26 days; FUS, n=6, median=25 days, p>0.05).

CONCLUSION

FUS+MB is a safe and feasible technique to open the BBB in a preclinical pontine glioma model.

Assessment of Prognostic Value of Cystic Features in Glioblastoma Relative to Sex and Treatment With Standard-of-Care

Glioblastoma (GBM) is the most aggressive primary brain tumor and can have cystic components, identifiable through magnetic resonance imaging (MRI). Previous studies suggest that cysts occur in 7–23% of GBMs and report mixed results regarding their prognostic impact. Using our retrospective cohort of 493 patients with first-diagnosis GBM, we carried out an exploratory analysis on this potential link between cystic GBM and survival. Using pretreatment MRIs, we manually identified 88 patients with GBM that had a significant cystic component at presentation and 405 patients that did not. Patients with cystic GBM had significantly longer overall survival and were significantly younger at presentation. Within patients who received the current standard of care (SOC) (N = 184, 40 cystic), we did not observe a survival benefit of cystic GBM. Unexpectedly, we did not observe a significant survival benefit between this SOC cystic cohort and patients with cystic GBM diagnosed before the standard was established (N = 40 with SOC, N = 19 without SOC); this significant SOC benefit was clearly observed in patients with noncystic GBM (N = 144 with SOC, N = 111 without SOC). When stratified by sex, the survival benefit of cystic GBM was only preserved in male patients (N = 303, 47 cystic). We report differences in the absolute and relative sizes of imaging abnormalities on MRI and the prognostic implication of cysts based on sex. We discuss hypotheses for these differences, including the possibility that the presence of a cyst could indicate a less aggressive tumor.

Integrating single-cell RNA-seq and imaging with SCOPE-seq2

Live cell imaging allows direct observation and monitoring of phenotypes that are difficult to infer from transcriptomics. However, existing methods for linking microscopy and single-cell RNA-seq (scRNA-seq) have limited scalability. Here, we describe an upgraded version of Single Cell Optical Phenotyping and Expression (SCOPE-seq2) for combining single-cell imaging and expression profiling, with substantial improvements in throughput, molecular capture efficiency, linking accuracy, and compatibility with standard microscopy instrumentation. We introduce improved optically decodable mRNA capture beads and implement a more scalable and simplified optical decoding process. We demonstrate the utility of SCOPE-seq2 for fluorescence, morphological, and expression profiling of individual primary cells from a human glioblastoma (GBM) surgical sample, revealing relationships between simple imaging features and cellular identity, particularly among malignantly transformed tumor cells.

EPCO-16. LACTIC ACID IS AN EPIGENETIC METABOLITE THAT DRIVES GLIOBLASTOMA SURVIVAL AND GROWTH

Glioblastoma (GBM) is the most common primary malignant brain tumor with an unfavorable prognosis and a reprogrammed metabolism. While tumors utilize glucose, there are other carbon sources at their disposal. Originally considered as a waste product of glucose catabolism, lactate accumulates to a significant amount in tumor tissue. We launched our studies with the central hypothesis that lactate is metabolized by GBM cells to promote their survival via modulation of the epigenome. We showed that lactate rescued patient-derived xenograft (PDX) GBM cells from nutrient deprivation mediated cell death and inhibition of growth. Transcriptome analysis, Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq), and CHIP-seq. showed that lactic acid exposure entertained a signature of cell cycle progression, oxidative phosphorylation (OXPHOS) and MYC target expression. LC/MS analysis demonstrated that U-13C-Lactate elicited substantial labeling of TCA-cycle metabolites, acetyl-CoA and histone protein acetyl-residues in PDX derived GBM cells. Given that acetyl-CoA is pivotal for histone acetylation we observed a dose-dependent elevation of histone marks (e.g. H3K27ac), which was rescued by genetic and pharmacological inhibition of lactic acid-uptake, ATP-citrate lyase, p300 histone-acetyl-transferase and OXPHOS, resulting in reversal of lactate mediated protection from cell death or facilitation of GBM growth. CHIP-seq. analysis demonstrated that lactic acid facilitated enhanced binding of H3K27ac to gene promoters and cis-regulatory elements (e.g. super-enhancers). Consistently, ATAC-seq. analysis highlighted enhanced accessibility of the chromatin by lactic acid. Finally, we assessed whether lactic acid is actively metabolized in vivo, utilizing an orthotopic PDX model of GBM. In a combined tracer experiment (U-13C-glucose and 3-C13-lactate), we made the fundamental observation that lactic acid carbons were predominantly labeling the TCA cycle metabolites over glucose, implying a critical role of lactic acid in GBMs and establishing lactic acid metabolism as a novel drug target for GBM that may be targeted with epigenetic drugs.

NIMG-67. DISAPPEARING DOTS – TRANSIENT LATE ENHANCING LESIONS YEARS AFTER BRAIN RADIOTHERAPY

BACKGROUND

Late-delayed radiation effects appear 6 months to years following radiotherapy. We characterize a species of small enhancing lesions in the late-delayed phase of post-radiotherapy that are distinct from the classic descriptions of radiation necrosis or pseudoprogression associated with mass effect and edema. These “disappearing dots” are small, do not exert mass effect nor edema, and spontaneously resolve.

METHOD

We retrospectively describe a series of cases with “disappearing dots” following brain radiotherapy.

RESULTS

There were 10 cases (4 men), median age 42 years (range 29-63). Diagnoses were glioblastoma (3); low grade astrocytoma, anaplastic astrocytoma, and anaplastic oligodendroglioma (2 each); and solitary fibrous tumor (1). All patients received 54-60 Gy (Gray) of external beam radiotherapy, except one (proton beam therapy to 60 cobalt Gray equivalent). Disappearing dots appeared at a median of 27 months (range 5-197) post-radiotherapy. Lesions were relatively small (~< 1 cm3), peri-ventricular, and within the radiotherapy field. Most enlarged before resolving. Advanced MR imaging and fluorodeoxyglucose (FGD)-PET results were inconsistent. Lesions persisted a median of 8.5 months (range 1-49) before spontaneous resolution. All were asymptomatic. Biopsy in one case revealed treatment effects rather than recurrent tumor.

CONCLUSIONS

Asymptomatic small periventricular enhancing lesions can develop and remit spontaneously, years following brain radiotherapy. Such disappearing dots should be part of the differential diagnosis along with tumor recurrence. of new enhancing lesions in the late-delayed phase post-radiotherapy.

CTNI-25. PHASE IB CLINICAL TRIAL OF CHRONIC CONVECTION-ENHANCED DELIVERY OF TOPOTECAN FOR RECURRENT GLIOBLASTOMA

OBJECTIVES

Convection-enhanced delivery (CED) provides pharmacokinetic advantages over systemic delivery for achieving cytotoxic drug levels into targeted regions of the brain. A major shortcoming of CED has been the need to limit treatment duration because of infection risks associated with external pumps. We engineered a subcutaneously implanted catheter-pump construct for prolonged CED which was successfully tested in a large animal model and then approved by the FDA for a Phase Ib clinical trial with topotecan in patients with refractory glioblastoma (IND 131889).

METHODS

Five patients with recurrent glioblastoma underwent surgical implantation of a subcutaneous pump and catheter that infused intracerebral topotecan over 30 days. Gadolinium was co-infused as a surrogate tracer and advanced non-invasive radiographic imaging was used to monitor drug distribution and pharmacological effects. Tissue from multiple radiographically-localized regions of each tumor and surrounding brain was procured pre-treatment at the time of catheter implantation and then post-treatment when tumors were surgically resected. Tissue was used for drug level measurements and advanced molecular, genomic and cellular analysis of treatment effects.

RESULTS

Treatments were successfully completed in all five patients without significant complications. The safety and tolerability of treatment was validated by quality-of-life measures and neurological assessments. Noninvasive imaging demonstrated large and stable drug distribution volumes. Comprehensive tissue analysis demonstrated effective targeting of mitotically active tumor cells while sparing neurons.

CONCLUSIONS

We engineered a subcutaneously implanted catheter-pump construct for chronic CED that was successfully tested in a Phase Ib clinical trial with topotecan in recurrent glioblastoma patients. Analysis of pre- and post-treatment tissue showed significant anti-tumor activity from topotecan that was not harmful to normal brain. Chronic CED combined with non-invasive real time drug distribution monitoring provides a safe and effective glioma strategy suitable for clinical use.

EPCO-07. LEVERAGING TRANSCRIPTOME SEQUENCING AND MATHEMATICAL MODELING TO INVESTIGATE GLIOBLASTOMA-MACROPHAGE INTERACTIONS

Glioblastoma (GBM) is the one of the most aggressive and common primary brain malignancies, with a poor median overall survival of less than 15 months. While the immune system is activated and brain-resident microglia and blood-derived macrophages combat the tumor, the tumor can convert some microglia and macrophages to instead exhibit an immune-suppressive phenotype. These co-opted immune cells are thereby termed ‘glioma-associated microglia and macrophages’ (GAMMs), as they allow for continued tumor growth. However, limited clinical data has been collected to understand this phenomenon. As a result, we have collected spatially-distributed image-localized biopsies from a cohort of patients and performed RNA sequencing on each sample. Correlations between normalized RNA counts of genetic markers for macrophages (i.e., CD68, CD163), tumor populations (i.e., SOX2, OLIG2), and key cell functions (i.e., KI67, CASP3) were analyzed. To further investigate the temporal effects that GAMMs have on GBM growth, we proposed the Proliferation-Invasion-Macrophage (PIM) model. This system of partial differential equations incorporates the proliferative and invasive behavior of GBM, as well as populations for both ‘healthy’ and ‘glioma-associated’ macrophages. By exploring the parameter space, we classified the various dynamics of tumor progression and how they relate to the immune response. With further insights of the interactions between GBM and macrophage populations, we can begin to parameterize the model on a patient-specific basis and provide insights to personalized immunotherapies and other novel immune-targeted treatments.

TAMI-33. AURKA INHIBITION REPROGRAMS METABOLISM AND IS SYNTHETICALLY LETHAL WITH FATTY ACID OXIDATION INHIBITION IN GLIOBLASTOMA

Aurora kinase A (AURKA) has emerged as a viable drug target for glioblastoma (GBM), the most common malignant primary brain tumor in adults with a life expectancy of 12-15 months. However, resistance to therapy remains a critical issue, which partially may be driven by reprogramming of metabolism. By integration of transcriptome, chromatin immunoprecipitation with sequencing (CHIP-seq.), assay for transposase-accessible chromatin with sequencing (ATAC-seq.), proteomic and metabolite screening followed by carbon tracing (U-13C-Glucose, U-13C-Glutamine and U-13C-Palmitic acid) and extracellular flux analysis we provided evidence that genetic (shRNA and CRISPR/Cas9) and pharmacological (Alisertib) AURKA inhibition elicited substantial metabolic reprogramming mediated in part by inhibition of MYC targets and concomitant activation of PPARA (e.g. PGC1A) signaling. While glycolysis was suppressed by AURKA inhibition, we noted a compensatory increase in oxygen consumption rate (OCR) fueled by fatty acid oxidation (FAO). Whereas interference with AURKA elicited a suppression of c-Myc, we detected an upregulation of PGC1A, a master regulator of oxidative metabolism, upon AURKA inhibition. Silencing of PGC1A reversed the increase in OCR and sensitized GBM cells to AURKA inhibition mediated reduction in cellular viability. CHIP experiments confirmed binding of c-Myc to the promoter region of PGC1A, which is abrogated by AURKA inhibition and in turn unleashed PGC1A expression. ATAC-seq. confirmed higher accessibility of the MYC binding region within the PGC1A promoter. Forced expression of c-Myc blocked AURKA inhibition mediated increase of PGC1A, suggesting that c-Myc acted as a repressor. To interfere with this oxidative metabolic reprogramming, we combined AURKA inhibitors with blockers of FAO (etomoxir), which elicited substantial synergistic growth inhibition and extension of overall survival in orthotopic patient derived xenografts of GBM in mice without induction of toxicity in normal tissue. Taken together, these data support that simultaneous targeting of oxidative metabolism and AURKA inhibition might be a potential novel therapy against GBM.

Neuronophagia and microglial nodules in a SARS-CoV-2 patient with cerebellar hemorrhage

We document the neuropathologic findings of a 73-year old man who died from acute cerebellar hemorrhage in the context of relatively mild SARS-CoV2 infection. The patient developed sudden onset of headache, nausea, and vomiting, immediately followed by loss of consciousness on the day of admission. Emergency medical services found him severely hypoxemic at home, and the patient suffered a cardiac arrest during transport to the emergency department. The emergency team achieved return of spontaneous circulation after over 17 min of resuscitation. A chest radiograph revealed hazy bilateral opacities; and real-time-PCR for SARS-CoV-2 on the nasopharyngeal swab was positive. Computed tomography of the head showed a large right cerebellar hemorrhage, with tonsillar herniation and intraventricular hemorrhage. One day after presentation, he was transitioned to comfort care and died shortly after palliative extubation. Autopsy performed 3 h after death showed cerebellar hemorrhage and acute infarcts in the dorsal pons and medulla. Remarkably, there were microglial nodules and neuronophagia bilaterally in the inferior olives and multifocally in the cerebellar dentate nuclei. This constellation of findings has not been reported thus far in the context of SARS-CoV-2 infection.

Rapid, label-free detection of diffuse glioma recurrence using intraoperative stimulated Raman histology and deep neural networks

BACKGROUND

Detection of glioma recurrence remains a challenge in modern neuro-oncology. Noninvasive radiographic imaging is unable to definitively differentiate true recurrence versus pseudoprogression. Even in biopsied tissue, it can be challenging to differentiate recurrent tumor and treatment effect. We hypothesized that intraoperative stimulated Raman histology (SRH) and deep neural networks can be used to improve the intraoperative detection of glioma recurrence.

METHODS

We used fiber-laser-based SRH, a label-free, non-consumptive, high-resolution microscopy method (<60 secs per 1 x 1 mm2) to image a cohort of patients (n = 35) with suspected recurrent gliomas who underwent biopsy or resection. The SRH images were then used to train a convolutional neural network (CNN) and develop an inference algorithm to detect viable recurrent glioma. Following network training, the performance of the CNN was tested for diagnostic accuracy in a retrospective cohort (n = 48).

RESULTS

Using patch-level CNN predictions, the inference algorithm returned a single Bernoulli distribution for the probability of tumor recurrence for each surgical specimen or patient. The external SRH validation dataset consisted of 48 patients (recurrent, 30; pseudoprogression, 18), and we achieved a diagnostic accuracy of 95.8%.

CONCLUSION

SRH with CNN-based diagnosis can be used to improve the intraoperative detection of glioma recurrence in near-real time. Our results provide insight into how optical imaging and computer vision can be combined to augment conventional diagnostic methods and improve the quality of specimen sampling at glioma recurrence.

Fluorescein-guided resection of gliomas

Standard of care in the management of high-grade gliomas includes gross total resection (GTR) followed by treatment with radiation and temozolomide. GTR remains one of the few independent prognostic factors for improved survival in this disease. Sodium fluorescein is an organic fluorophore that has been studied as a surgical adjunct to improve the likelihood of achieving GTR in gliomas. Though sodium fluorescein does not selectively accumulate in glioma cells, it allows for real-time identification of regions of blood brain barrier breakdown, corresponding to the contrast-enhancing cores of high-grade gliomas. In addition to its high predictive value for identifying pathologic tissue, use of fluorescein has been shown to improve rates of GTR. In stereotactic needle biopsies, it helps reduce procedure time by rapidly confirming the presence of diagnostic tissue. Furthermore, in non-enhancing, low-grade gliomas, it labels focal regions of vascular dysregulation that have been correlated with high-grade features. Fluorescein has also been shown to be significantly less expensive than other contemporary surgical adjuncts such as intraoperative ultrasound, intraoperative MRI, and the recently FDA approved fluorophore, 5-aminolevulinic acid (5-ALA). Here, we review the current literature on the effectiveness of fluorescein as a surgical tool in the resection of gliomas.

HDAC inhibitors elicit metabolic reprogramming by targeting super-enhancers in glioblastoma models

The Warburg effect is a tumor-related phenomenon that could potentially be targeted therapeutically. Here, we showed that glioblastoma (GBM) cultures and patients' tumors harbored super-enhancers in several genes related to the Warburg effect. By conducting a transcriptome analysis followed by ChIP-Seq coupled with a comprehensive metabolite analysis in GBM models, we found that FDA-approved global (panobinostat, vorinostat) and selective (romidepsin) histone deacetylase (HDAC) inhibitors elicited metabolic reprogramming in concert with disruption of several Warburg effect-related super-enhancers. Extracellular flux and carbon-tracing analyses revealed that HDAC inhibitors blunted glycolysis in a c-Myc-dependent manner and lowered ATP levels. This resulted in the engagement of oxidative phosphorylation (OXPHOS) driven by elevated fatty acid oxidation (FAO), rendering GBM cells dependent on these pathways. Mechanistically, interference with HDAC1/-2 elicited a suppression of c-Myc protein levels and a concomitant increase in 2 transcriptional drivers of oxidative metabolism, PGC1α and PPARD, suggesting an inverse relationship. Rescue and ChIP experiments indicated that c-Myc bound to the promoter regions of PGC1α and PPARD to counteract their upregulation driven by HDAC1/-2 inhibition. Finally, we demonstrated that combination treatment with HDAC and FAO inhibitors extended animal survival in patient-derived xenograft model systems in vivo more potently than single treatments in the absence of toxicity.

Sex-specific impact of patterns of imageable tumor growth on survival of primary glioblastoma patients

Background

Sex is recognized as a significant determinant of outcome among glioblastoma patients, but the relative prognostic importance of glioblastoma features has not been thoroughly explored for sex differences.

Methods

Combining multi-modal MR images, biomathematical models, and patient clinical information, this investigation assesses which pretreatment variables have a sex-specific impact on the survival of glioblastoma patients (299 males and 195 females).

Results

Among males, tumor (T1Gd) radius was a predictor of overall survival (HR = 1.027, p = 0.044). Among females, higher tumor cell net invasion rate was a significant detriment to overall survival (HR = 1.011, p < 0.001). Female extreme survivors had significantly smaller tumors (T1Gd) (p = 0.010 t-test), but tumor size was not correlated with female overall survival (p = 0.955 CPH). Both male and female extreme survivors had significantly lower tumor cell net proliferation rates than other patients (M p = 0.004, F p = 0.001, t-test).

Conclusion

Despite similar distributions of the MR imaging parameters between males and females, there was a sex-specific difference in how these parameters related to outcomes.

CD8+ T-cell-Mediated Immunoediting Influences Genomic Evolution and Immune Evasion in Murine Gliomas

PURPOSE

Cancer immunoediting shapes tumor progression by the selection of tumor cell variants that can evade immune recognition. Given the immune evasion and intratumor heterogeneity characteristic of gliomas, we hypothesized that CD8⁺ T cells mediate immunoediting in these tumors.

EXPERIMENTAL DESIGN

We developed retrovirus-induced PDGF⁺ Pten ^-/- murine gliomas and evaluated glioma progression and tumor immunogenicity in the absence of CD8⁺ T cells by depleting this immune cell population. Furthermore, we characterized the genomic alterations present in gliomas that developed in the presence and absence of CD8⁺ T cells.

RESULTS

Upon transplantation, gliomas that developed in the absence of CD8⁺ T cells engrafted poorly in recipients with intact immunity but engrafted well in those with CD8⁺ T-cell depletion. In contrast, gliomas that developed under pressure from CD8⁺ T cells were able to fully engraft in both CD8⁺ T-cell-depleted mice and immunocompetent mice. Remarkably, gliomas developed in the absence of CD8⁺ T cells exhibited increased aneuploidy, MAPK pathway signaling, gene fusions, and macrophage/microglial infiltration, and showed a proinflammatory phenotype. MAPK activation correlated with macrophage/microglia recruitment in this model and in the human disease.

CONCLUSIONS

Our studies indicate that, in these tumor models, CD8⁺ T cells influence glioma oncogenic pathways, tumor genotype, and immunogenicity. This suggests immunoediting of immunogenic tumor clones through their negative selection by CD8⁺ T cells during glioma formation.

Extent of resection, molecular signature, and survival in 1p19q-codeleted gliomas

OBJECTIVE

Genomic analysis in neurooncology has underscored the importance of understanding the patterns of survival in different molecular subtypes within gliomas and their responses to treatment. In particular, diffuse gliomas are now principally characterized by their mutation status (IDH1 and 1p/19q codeletion), yet there remains a paucity of information regarding the prognostic value of molecular markers and extent of resection (EOR) on survival. Furthermore, given the modern emphasis on molecular rather than histological diagnosis, it is important to examine the effect of maximal resection on survival in all gliomas with 1p/q19 codeletions, as these will now be classified as oligodendrogliomas under the new WHO guidelines. The objectives of the present study were twofold: 1) to assess the association between EOR and survival for patients with oligodendrogliomas in the National Cancer Database (NCDB), which includes information on mutation status, and 2) to demonstrate the same effect for all patients with 1p/19q codeleted gliomas in the NCDB.

METHODS

The NCDB was queried for all cases of oligodendroglioma between 2004 and 2014, with follow-up dates through 2016. The authors found 2514 cases of histologically confirmed oligodendrogliomas for the final analysis of the effect of EOR on survival. Upon further query, 1067 1p/19q-codeleted tumors were identified in the NCDB. Patients who received subtotal resection (STR) or gross-total resection (GTR) were compared to those who received no tumor debulking surgery. Univariable and multivariable analyses of both overall survival and cause-specific survival were performed.

RESULTS

EOR was associated with increased overall survival for both histologically confirmed oligodendrogliomas and all 1p/19q-codeleted-defined tumors (p < 0.001 and p = 0.002, respectively). Tumor grade, location, and size covaried predictably with EOR. When evaluating tumors by each classification system for predictors of overall survival, facility setting, age, comorbidity index, grade, location, chemotherapy, and radiation therapy were all shown to be significantly associated with overall survival. STR and GTR were independent predictors of improved survival in historically classified oligodendrogliomas (HR 0.83, p = 0.18; HR 0.69, p = 0.01, respectively) and in 1p/19q-codeleted tumors (HR 0.49, p < 0.01; HR 0.43, p < 0.01, respectively).

CONCLUSIONS

By using the NCDB, the authors have demonstrated a side-by-side comparison of the survival benefits of greater EOR in 1p/19q-codeleted gliomas.

Glioma-Induced Alterations in Neuronal Activity and Neurovascular Coupling during Disease Progression

Diffusely infiltrating gliomas are known to cause alterations in cortical function, vascular disruption, and seizures. These neurological complications present major clinical challenges, yet their underlying mechanisms and causal relationships to disease progression are poorly characterized. Here, we follow glioma progression in awake Thy1-GCaMP6f mice using in vivo wide-field optical mapping to monitor alterations in both neuronal activity and functional hemodynamics. The bilateral synchrony of spontaneous neuronal activity gradually decreases in glioma-infiltrated cortical regions, while neurovascular coupling becomes progressively disrupted compared to uninvolved cortex. Over time, mice develop diverse patterns of high amplitude discharges and eventually generalized seizures that appear to originate at the tumors' infiltrative margins. Interictal and seizure events exhibit positive neurovascular coupling in uninfiltrated cortex; however, glioma-infiltrated regions exhibit disrupted hemodynamic responses driving seizure-evoked hypoxia. These results reveal a landscape of complex physiological interactions occurring during glioma progression and present new opportunities for exploring novel biomarkers and therapeutic targets.

Abstract A61: Human leukocyte antigen G as a novel target for switch-based chimeric antigen receptor natural killer cell therapy of solid cancers

Human leukocyte antigen G (HLA-G) is a molecule within the tumor microenvironment (TME) that modulates the innate and adaptive immune systems by interacting with inhibitory receptors on the surface of immune cells and thus functions as an immune checkpoint. It could be potentially expressed by all tumor types but is not expressed by either healthy tissues surrounding the tumor cells or vital normal tissues. Chimeric antigen receptors (CARs) for adoptive cell therapy (ACT) have been successful in clinical trials against hematologic cancers; however, challenges have been encountered when applying this approach to the treatment of solid tumors. These obstacles are mainly due to the lack of a ubiquitous tumor-associated antigen (TAA) across different tumor types without “on-target/off-tumor” reactivity and the immunosuppressive nonphysical TME. To address these issues, we developed a novel switch HLA-G CAR carrying an inducible Caspase9 (iC9) suicide gene system that binds to HLA-G1~G7 isoforms and expressed this CAR in natural killer (NK) cells. We tested these HLA-G CAR-NK cells in a variety of adult cancer models and discovered that they mediate significant tumor cytolysis in triple-negative breast cancer (TNBC), glioblastoma (GBM), pancreatic (PA) cancer, and ovarian (OV) cancer in vitro and in TNBC and GBM xenograft models in vivo. Coculturing HLA-G CAR-NK cells with vital normal cell lines did not cause cell damage. We further discovered that surface-exposed HLA-G is chemoinducible, which in turn increases tumor sensitivity to both HLA-G CAR effector-mediated antitumor responses and tumor-infiltrative NK cells. The underlying mechanism of tumor and HLA-G CAR NK cell interaction may be through upregulation of membranous HLA-G via demethylation of the TAP-1 promoter or enhanced activity of the TAP1/signal peptide peptidase (SPP) pathways. In conclusion, HLA-G CAR-NK cells could be an option for treating solid tumors of different cell types, and a regimen comprising chemotherapy followed by HLA-G CAR immunotherapy may improve responses compared to those achieved with CAR-T cell immunotherapy alone.

Citation Format: Chia-Ing Jan, Shi-Wei Huang, Peter Canoll, Yu-Chuan Lin, Hsin-Man Lu, Shao-Chih Chio, Der-Yang Cho. Human leukocyte antigen G as a novel target for switch-based chimeric antigen receptor natural killer cell therapy of solid cancers [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A61.

From cells to tissue: How cell scale heterogeneity impacts glioblastoma growth and treatment response

Glioblastomas are aggressive primary brain tumors known for their inter- and intratumor heterogeneity. This disease is uniformly fatal, with intratumor heterogeneity the major reason for treatment failure and recurrence. Just like the nature vs nurture debate, heterogeneity can arise from intrinsic or environmental influences. Whilst it is impossible to clinically separate observed behavior of cells from their environmental context, using a mathematical framework combined with multiscale data gives us insight into the relative roles of variation from different sources. To better understand the implications of intratumor heterogeneity on therapeutic outcomes, we created a hybrid agent-based mathematical model that captures both the overall tumor kinetics and the individual cellular behavior. We track single cells as agents, cell density on a coarser scale, and growth factor diffusion and dynamics on a finer scale over time and space. Our model parameters were fit utilizing serial MRI imaging and cell tracking data from ex vivo tissue slices acquired from a growth-factor driven glioblastoma murine model. When fitting our model to serial imaging only, there was a spectrum of equally-good parameter fits corresponding to a wide range of phenotypic behaviors. When fitting our model using imaging and cell scale data, we determined that environmental heterogeneity alone is insufficient to match the single cell data, and intrinsic heterogeneity is required to fully capture the migration behavior. The wide spectrum of in silico tumors also had a wide variety of responses to an application of an anti-proliferative treatment. Recurrent tumors were generally less proliferative than pre-treatment tumors as measured via the model simulations and validated from human GBM patient histology. Further, we found that all tumors continued to grow with an anti-migratory treatment alone, but the anti-proliferative/anti-migratory combination generally showed improvement over an anti-proliferative treatment alone. Together our results emphasize the need to better understand the underlying phenotypes and tumor heterogeneity present in a tumor when designing therapeutic regimens.

Near real-time intraoperative brain tumor diagnosis using stimulated Raman histology and deep neural networks

Intraoperative diagnosis is essential for providing safe and effective care during cancer surgery1. The existing workflow for intraoperative diagnosis based on hematoxylin and eosin staining of processed tissue is time, resource and labor intensive2,3. Moreover, interpretation of intraoperative histologic images is dependent on a contracting, unevenly distributed, pathology workforce4. In the present study, we report a parallel workflow that combines stimulated Raman histology (SRH)5-7, a label-free optical imaging method and deep convolutional neural networks (CNNs) to predict diagnosis at the bedside in near real-time in an automated fashion. Specifically, our CNNs, trained on over 2.5 million SRH images, predict brain tumor diagnosis in the operating room in under 150 s, an order of magnitude faster than conventional techniques (for example, 20-30 min)2. In a multicenter, prospective clinical trial (n = 278), we demonstrated that CNN-based diagnosis of SRH images was noninferior to pathologist-based interpretation of conventional histologic images (overall accuracy, 94.6% versus 93.9%). Our CNNs learned a hierarchy of recognizable histologic feature representations to classify the major histopathologic classes of brain tumors. In addition, we implemented a semantic segmentation method to identify tumor-infiltrated diagnostic regions within SRH images. These results demonstrate how intraoperative cancer diagnosis can be streamlined, creating a complementary pathway for tissue diagnosis that is independent of a traditional pathology laboratory.

Ex vivo multi-electrode analysis reveals spatiotemporal dynamics of ictal behavior at the infiltrated margin of glioma

The purpose of this study is to develop a platform in which the cellular and molecular underpinnings of chronic focal neocortical lesional epilepsy can be explored and use it to characterize seizure-like events (SLEs) in an ex vivo model of infiltrating high-grade glioma. Microelectrode arrays were used to study electrophysiologic changes in ex vivo acute brain slices from a PTEN/p53 deleted, PDGF-B driven mouse model of high-grade glioma. Electrode locations were co-registered to the underlying histology to ascertain the influence of the varying histologic landscape on the observed electrophysiologic changes. Peritumoral, infiltrated, and tumor sites were sampled in tumor-bearing slices. Following the addition of zero Mg²⁺ solution, all three histologic regions in tumor-bearing slices showed significantly greater increases in firing rates when compared to the control sites. Tumor-bearing slices demonstrated increased proclivity for SLEs, with 40 events in tumor-bearing slices and 5 events in control slices (p-value = .0105). Observed SLEs were characterized by either low voltage fast (LVF) onset patterns or short bursts of repetitive widespread, high amplitude low frequency discharges. Seizure foci comprised areas from all three histologic regions. The onset electrode was found to be at the infiltrated margin in 50% of cases and in the peritumoral region in 36.9% of cases. These findings reveal a landscape of histopathologic and electrophysiologic alterations associated with ictogenesis and spread of tumor-associated seizures.