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Chimeric antigen receptor (CAR) tonic signaling, defined as spontaneous activation and release of proinflammatory cytokines by CAR-T cells, is considered a negative attribute because it leads to impaired antitumor effects. Here, we report that CAR tonic signaling is caused by the intrinsic instability of the mAb single-chain variable fragment (scFv) to promote self-aggregation and signaling via the CD3ζ chain incorporated into the CAR construct. This phenomenon was detected in a CAR encoding either CD28 or 4-1BB costimulatory endodomains. Instability of the scFv was caused by specific amino acids within the framework regions (FWR) that can be identified by computational modeling. Substitutions of the amino acids causing instability, or humanization of the FWRs, corrected tonic signaling of the CAR, without modifying antigen specificity, and enhanced the antitumor effects of CAR-T cells. Overall, we demonstrated that tonic signaling of CAR-T cells is determined by the molecular instability of the scFv and that computational analyses of the scFv can be implemented to correct the scFv instability in CAR-T cells with either CD28 or 4-1BB costimulation.

XLS file - 12K, Mutations of PTEN, TP53, and NF1 genes in glioblastoma neurospheres

PDF file - 41K, Table S2: EGFR gene copy number in neurospheres and the corresponding original glioblastomas. Table S3: Immunophenotype of neurospheres. Table S4: EGFR gene amplification, Met expression, and MET gene alterations in glioblastomas and corresponding neurospheres. Table S5: Multiple transcriptional signatures in Met-neg and Met-pos neurospheres. Table S6: Immunohistochemistry on tumors derived from neurospheres. Table S8: Antibodies used in flow-cytometric analysis

Cancer stem–like cells (CSC) could be a novel target for cancer therapy, including dendritic cell (DC) immunotherapy. To address this, we developed experiments aimed at DC targeting of neurospheres (NS) from GL261 glioma cells because neurospheres can be enriched in CSC. We obtained murine neurospheres by growing GL261 cells in epidermal growth factor/basic fibroblast growth factor without serum. GL261-NS recapitulated important features of glioblastoma CSC and expressed higher levels of radial glia stem cell markers than GL261 cells growing under standard conditions (GL261 adherent cells, GL261-AC), as assessed by DNA microarray and real-time PCR. GL261-NS brain gliomas were highly infiltrating and more rapidly lethal than GL261-AC, as evidenced by survival analysis (P < 0.0001), magnetic resonance imaging and histology. DC from the bone marrow of syngeneic mice were then used for immunotherapy of GL261-NS and GL261-AC tumors. Strikingly, DC loaded with GL261-NS (DC-NS) cured 80% and 60% of GL261-AC and GL261-NS tumors, respectively (P < 0.0001), whereas DC-AC cured only 50% of GL261-AC tumors (P = 0.0022) and none of the GL261-NS tumors. GL261-NS expressed higher levels of MHC and costimulatory molecules (CD80 and CD86) than GL261-AC; the JAM assay indicated that DC-NS splenocytes had higher lytic activity than DC-AC splenocytes on both GL261-NS and GL261-AC, and immunohistochemistry showed that DC-NS vaccination was associated with robust tumor infiltration by CD8+ and CD4+ T lymphocytes. These findings suggest that DC targeting of CSC provides a higher level of protection against GL261 gliomas, a finding with potential implications for the design of clinical trials based on DC vaccination. (Cancer Res 2006; 66(21): 10247-52)

PDF file - 454KB, Supplementary Figure 1: Sox2 expression in tumors analyzed by qRT-PCR. Supplementary Figure 2: SOX2 peptides are able to induce a specific anti-tumor immune response in the peripheral and local immune effector cells. Supplementary Figure 3: Sox2-deleted cells expressing differentiation markers in transplantated brain.

PDF file - 2.3MB, Figure S1: Histopathology of primary glioblastomas and genetic lesions of neurospheres. Figure S2: Genome-wide expression profiling and unsupervised hierarchical clustering of neurospheres (classical, mesenchymal and proneural centroids). Figure S3: Expression of MET, EGFR, and a panel of self-renewal markers in neurospheres. Figure S4: Genome-wide expression profiling and unsupervised hierarchical clustering of neurospheres (multiple signatures). Figure S5: Proliferative response, activation of tyrosine kinase receptors, and differentiation pattern in Met-neg-NS and Met-pos-NS. Figure S6: Methigh and Metneg sorting parameters. Figure S7: The Methigh subpopulation of Met-pos-NS retains clonogenic and tumorigenic cells. Figure S8: H&E and Met immunohistochemical staining of histological sections from tumors formed by BT302 neurosphere and its sorted subpopulations. Figure S9: HGF sustains the stem-like and invasive phenotype of Met-pos-NS.

Supplementary Methods and Figures 1-8 from Neurospheres Enriched in Cancer Stem–Like Cells Are Highly Effective in Eliciting a Dendritic Cell–Mediated Immune Response against Malignant Gliomas

XLS file - 44K, List of primer pairs used for gene sequencing

Supplementary Table S2 from Neurospheres Enriched in Cancer Stem–Like Cells Are Highly Effective in Eliciting a Dendritic Cell–Mediated Immune Response against Malignant Gliomas

PDF file - 125K

XLS file - 231KB, Excel file with the DEG genes from microarrays analysis.

Glioblastoma’s (GBM) origin, recurrence and resistance to treatment are driven by GBM cancer stem cells (GSCs). Existing transcriptomic characterisations of GBM classify the tumours to three subtypes: classical, proneural, and mesenchymal. The comprehension of how expression patterns of the GBM subtypes are reflected at global proteome level in GSCs is limited.To characterise protein expression in GSCs, we performed in-depth proteogenomic analysis of patient-derived GSCs by RNA-sequencing and mass-spectrometry proteomics. We identified and quantified over 10,000 proteins in two independent GSCs panels, and propose a GSC-associated proteomic signature (GSAPS) that defines two distinct morphological conditions; one defined by a set of proteins expressed in non-mesenchymal - proneural and classical - GSCs (GPC-like), and another expressed in mesenchymal GSCs (GM-like). The expression of GM-like protein set in GBM tissue was associated with hypoxia, necrosis, recurrence, and worse overall survival in GBM patients.In a proof-of-concept proteogenomic approach, we discovered 252 non-canonical peptides expressed in GSCs, i.e., protein sequences that are variant or derive from genome regions previously considered protein-non-coding. We report new variants of the heterogeneous ribonucleoproteins (HNRNPs), which are implicated in mRNA splicing. Furthermore, we show that per-gene mRNA-protein correlations in GSCs are moderate and vary compared to GBM tissue.

Despite the first classification of glioblastoma (GBM) as an immunologically “cold” tumor, evidence suggests that this cancer type is susceptible to T-cell infiltration, providing a glimmer of hope for developing effective immunotherapy approaches. However, whether the “exhausted” phenotype of tumor-infiltrating lymphocytes (TILs) and the immunosuppressive signaling in the GBM microenvironment (ME) can be therapeutically reprogrammed to unlock the anticancer potential of the immune system remains to be elucidated. We performed a histological analysis of GBM specimens collected pre-therapy from 24 newly-diagnosed GBM patients treated with dendritic cell (DC)-immunotherapy as part of the DENDR1 clinical trial (NCT04801147). Our preliminary results suggest an association between the distribution and density of CD8+ TIL subsets and patients’ responses to immunotherapy. TIL spatial patterns revealed either an immune-excluded or an immune-infiltrated scenario with either scattered or widespread TILs. A widespread CD8+ TIL pattern was significantly correlated with a better response to immunotherapy. It was also observed that the frequency of CD8+ TILs was significantly increased at recurrence compared to their primary tumors, suggesting that these patients are more likely to benefit from CD8+ T cell antitumor immunity. In light of these observations, we have hypothesized that tumor-reactive (TR) TILs isolated from GBM can be used as direct personalized treatment mediators exerting an effective antitumor activity with low side effects per se. TR-TILs were isolated from GBM surgical material using CD137 as a key marker, and successfully expanded from 50% of patients’ GBM showing specific reactivity against autologous tumor cells. For the remaining cases, TR-TILs failed to expand, suggesting terminal dysfunction. Single-cell sequencing of the transcriptome was performed on the immune contexture after CD137+ TILs enrichment revealing the presence of a specific signature related to exhausted, cytotoxic, and memory state. A gene signature highly upregulated in regulatory T cells (Treg) was related to a more immune-suppressive ME. Flow cytometry analysis on immune contexture confirmed the presence of FoxP3+ CD4+ T cells, expressing CD137 can be enriched and persist, dysregulating the expansion of TR-TILs during the early stage in culture. Our preliminary findings indicate that a high frequency of Treg can be investigated as a negative predictive indicator of ex-vivo expansion of TR-TILs, which should be taken into consideration when planning a personalized TIL therapy. Citation Format: Irene Sambruni, Silvia Musio, Natalia Di Ianni, Martina Maffezzini, Monica Patanè, Marica Eoli, Antonio Silvani, Bianca Pollo, Francesco DiMeco, Serena Pellegatta. Single-cell analysis of glioblastoma immune contexture identifies a subset of activated and memory tumor-reactive CD8+ TILs and a Treg signature contributing to TIL irreversible dysfunction. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4694.

Chimeric antigen receptor (CAR) tonic signaling, defined as spontaneous activation and release of proinflammatory cytokines by CAR-T cells, is considered a negative attribute because it leads to impaired antitumor effects. Here, we report that CAR tonic signaling is caused by the intrinsic instability of the mAb single-chain variable fragment (scFv) to promote self-aggregation and signaling via the CD3ζ chain incorporated into the CAR construct. This phenomenon was detected in a CAR encoding either CD28 or 4-1BB costimulatory endodomains. Instability of the scFv was caused by specific amino acids within the framework regions (FWR) that can be identified by computational modeling. Substitutions of the amino acids causing instability, or humanization of the FWRs, corrected tonic signaling of the CAR, without modifying antigen specificity, and enhanced the antitumor effects of CAR-T cells. Overall, we demonstrated that tonic signaling of CAR-T cells is determined by the molecular instability of the scFv and that computational analyses of the scFv can be implemented to correct the scFv instability in CAR-T cells with either CD28 or 4-1BB costimulation.

Glioblastomas (GBMs) in patients harboring somatic or germinal mutations of mismatch-repair (MMR) genes exhibit a hypermutable phenotype. Here, we describe a GBM patient with increased tumor mutational burden and germline MMR mutations, treated using anti-PD1 therapy. A woman with newly diagnosed GBM (nGBM) was treated by surgery, radiotherapy, and temozolomide. The tumor recurred after 13 months leading to a second surgery and treatment with nivolumab. Whole-exome sequencing was performed on the nGBM, recurrent GBM (rGBM), and blood. Immune infiltration was investigated by immunohistochemistry and the immune response in the blood during treatment was analyzed by flow cytometry. High density of infiltrating CD163 + cells was found in both GBM specimens. Large numbers of CD3 + and CD8 + T cells were homogeneously distributed in the nGBM. The infiltration of CD4 + T cells and a different CD8 + T cell density were observed in the rGBM. Both GBM shared 12,431 somatic mutations, with 113 substitutions specific to the nGBM and 1,683 specific to the rGBM. Germline variants included pathogenic mutation in the MSH2 (R359S) gene, suggesting the diagnosis of Lynch syndrome. Systemic immunophenotyping revealed the generation of CD8 + T memory cells and persistent activation of CD4 + T cells. The patient is still receiving nivolumab 68 months after the second surgery. Our observations indicate that the hypermutator phenotype associated with germinal mutations of MMR genes and abundant T-cell infiltration contributes to a durable clinical benefit sustained by a persistent and robust immune response during anti-PD1 therapy.

Glioblastoma multiforme (GBM) is considered the most malignant form of primary brain tumor. Despite multimodal treatment, prognosis remains poor. Ketogenic diet (KD) has been suggested for the treatment of GBM. In this study, the syngenic, orthotopic GL261 mouse glioma model was used to evaluate the effects of KD on the metabolic responses of the tumor using 7T magnetic resonance imaging/spectroscopy. GL261 cells were injected into the caudate nucleus of mice. Following implantation, animals were fed with standard chow or underwent a KD. 18 days after initiating the diet, mice fed with KD displayed significantly higher plasmatic levels of ketone bodies and survived longer than those fed with the standard diet. Decreased concentrations of gamma-aminobutyric acid, N-Acetyl-Aspartate and N-acetylaspartylglutamate were found in tumor tissue after 9 days into the KD, while a huge increase in beta-hydroxybutyrate (bHB) was detected in tumor tissue as compared to normal brain. The accumulation of bHB in the tumor tissue in mice undergoing the KD, may suggest either elevated uptake/release of bHB by tumor cells, or the inability of tumor cells in this context to use it for mitochondrial metabolism.

Background The dismal survival of glioblastoma (GBM) patients urgently calls for the development of new treatments. Chimeric antigen receptor T (CAR-T) cells are an attractive strategy, but preclinical and clinical studies in GBM have shown that heterogeneous expression of the antigens targeted so far causes tumor escape, highlighting the need for the identification of new targets. We explored if B7-H3 is a valuable target for CAR-T cells in GBM. Methods We compared mRNA expression of antigens in GBM using TCGA data, and validated B7-H3 expression by immunohistochemistry. We then tested the antitumor activity of B7-H3-redirected CAR-T cells against GBM cell lines and patient-derived GBM neurospheres in vitro and in xenograft murine models. Findings B7-H3 mRNA and protein are overexpressed in GBM relative to normal brain in all GBM subtypes. Of the 46 specimens analyzed by immunohistochemistry, 76% showed high B7-H3 expression, 22% had detectable, but low B7-H3 expression and 2% were negative, as was normal brain. All 20 patient-derived neurospheres showed ubiquitous B7-H3 expression. B7-H3-redirected CAR-T cells effectively targeted GBM cell lines and neurospheres in vitro and in vivo. No significant differences were found between CD28 and 4-1BB co-stimulation, although CD28-co-stimulated CAR-T cells released more inflammatory cytokines. Interpretation We demonstrated that B7-H3 is highly expressed in GBM specimens and neurospheres that contain putative cancer stem cells, and that B7-H3-redirected CAR-T cells can effectively control tumor growth. Therefore, B7-H3 represents a promising target in GBM. Fund Alex's Lemonade Stand Foundation; Il Fondo di Gio Onlus; National Cancer Institute; Burroughs Wellcome Fund.

The metabolism of glioblastoma (GBM), the most aggressive and lethal primary brain tumor, is flexible and adaptable to different adverse conditions, such as nutrient deprivation. Beyond glycolysis, altered lipid metabolism is implicated in GBM progression. Indeed, metabolic subtypes were recently identified based on divergent glucose and lipid metabolism. GBM is also characterized by an immunosuppressive microenvironment in which myeloid-derived suppressor cells (MDSCs) are a powerful ally of tumor cells. Increasing evidence supports the interconnection between GBM and MDSC metabolic pathways. GBM cells exert a crucial contribution to MDSC recruitment and maturation within the tumor microenvironment, where the needs of tumor-infiltrating lymphocytes (TILs) with antitumor function are completely neglected. In this review, we will discuss the unique or alternative source of energy exploited by GBM and MDSCs, exploring how deprivation of specific nutrients and accumulation of toxic byproducts can induce T-cell dysfunction. Understanding the metabolic programs of these cell components and how they impact fitness or dysfunction will be useful to improve treatment modalities, including immunotherapeutic strategies.

High-grade gliomas are the most common and aggressive malignant primary brain tumors. Current therapeutic schemes include a combination of surgical resection, radiotherapy and chemotherapy; even if major advances have been achieved in Progression Free Survival and Overall Survival for patients harboring high-grade gliomas, prognosis still remains poor; hence, new therapeutic options for malignant gliomas are currently researched. Sonodynamic Therapy (SDT) has proven to be a promising treatment combining the effects of low-intensity ultrasound waves with various sound-sensitive compounds, whose activation leads to increased immunogenicity of tumor cells, increased apoptotic rates and decreased angiogenetic potential. In addition, this therapeutic technique only exerts its cytotoxic effects on tumor cells, while both ultrasound waves and sensitizing compound are non-toxic per se. This review summarizes the present knowledge regarding mechanisms of action of SDT and currently available sonosensitizers and focuses on the preclinical and clinical studies that have investigated its efficacy on malignant gliomas. To date, preclinical studies implying various sonosensitizers and different treatment protocols all seem to confirm the anti-tumoral properties of SDT, while first clinical trials will soon start recruiting patients. Accordingly, it is crucial to conduct further investigations regarding the clinical applications of SDT as a therapeutic option in the management of intracranial gliomas.

Summary In glioblastoma (GBM), the most frequent and lethal brain tumor, therapies suppressing recurrently altered signaling pathways failed to extend survival. However, in patient subsets, specific genetic lesions can confer sensitivity to targeted agents. By exploiting an integrated model based on patient-derived stem-like cells, faithfully recapitulating the original GBMs in vitro and in vivo, here, we identify a human GBM subset (∼9% of all GBMs) characterized by ERBB3 overexpression and nuclear accumulation. ERBB3 overexpression is driven by inheritable promoter methylation or post-transcriptional silencing of the oncosuppressor miR-205 and sustains the malignant phenotype. Overexpressed ERBB3 behaves as a specific signaling platform for fibroblast growth factor receptor (FGFR), driving PI3K/AKT/mTOR pathway hyperactivation, and overall metabolic upregulation. As a result, ERBB3 inhibition by specific antibodies is lethal for GBM stem-like cells and xenotransplants. These findings highlight a subset of patients eligible for ERBB3-targeted therapy.

Background The efficacy of dendritic cell (DC) immunotherapy as a single therapeutic modality for the treatment of glioblastoma (GBM) patients remains limited. In this study, we evaluated in patients with GBM recurrence the immune-mediated effects of DC loaded with autologous tumor lysate combined with temozolomide (TMZ) or tetanus toxoid (TT). Methods In the phase I-II clinical study DENDR2, 12 patients were treated with 5 DC vaccinations combined with dose-dense TMZ. Subsequently, in eight patients, here defined as Variant (V)-DENDR2, the vaccine site was preconditioned with TT 24 hours before DC vaccination and TMZ was avoided. As a survival endpoint for these studies, we considered overall survival 9 months (OS9) after second surgery. Patients were analyzed for the generation of effector, memory, and T helper immune response. Results Four of 12 DENDR2 patients reached OS9, but all failed to show an immunological response. Five of eight V-DENDR2 patients (62%) reached OS9, and one patient is still alive (OS >30 months). A robust CD8+ T-cell activation and memory T-cell formation were observed in V-DENDR2 OS>9. Only in these patients, the vaccine-specific CD4+ T-cell activation (CD38+/HLA-DR+) was paralleled by an increase in TT-induced CD4+/CD38low/CD127high memory T cells. Only V-DENDR2 patients showed the formation of a nodule at the DC injection site infiltrated by CCL3-expressing CD4+ T cells. Conclusions TT preconditioning of the vaccine site and lack of TMZ could contribute to the efficacy of DC immunotherapy by inducing an effector response, memory, and helper T-cell generation.

Dendritic cells (DC) are the most potent antigen-presenting cells, strongly inducers of T cell-mediated immune responses and, as such, broadly used as vaccine adjuvant in experimental clinical settings. DC are widely generated from human monocytes following in vitro protocols which require 5&ndash, 7 days of differentiation with GM-CSF and IL-4 followed by 2&ndash, 3 days of activation/maturation. In attempts to shorten the vaccine&rsquo, s production, Fast-DC protocols have been developed. Here we reported a Fast-DC method in compliance with good manufacturing practices for the production of autologous mature dendritic cells loaded with antigens derived from whole tumor lysate, suitable for the immunotherapy in glioblastoma patients. The feasibility of generating Fast-DC pulsed with whole tumor lysate was assessed using a series of small-scale cultures performed in parallel with clinical grade large scale standard method preparations. Our results demonstrate that this Fast protocol is effective only in the presence of PGE2 in the maturation cocktail to guarantee that Fast-DC cells exhibit a mature phenotype and fulfill all requirements for in vivo use in immunotherapy approaches. Fast-DC generated following this protocol were equally potent to standard DC in inducing Ag-specific T cell proliferation in vitro. Generation of Fast-DC not only reduces labor, cost, and time required for in vitro clinical grade DC development, but can also minimizes inter-preparations variability and the risk of contamination.

Dendritic cells (DC) are the most potent antigen-presenting cells, strongly inducers of T cell-mediated immune responses and, as such, broadly used as vaccine adjuvant in experimental clinical settings. DC are widely generated from human monocytes following in vitro protocols which require 5–7 days of differentiation with GM-CSF and IL-4 followed by 2–3 days of activation/maturation. In attempts to shorten the vaccine’s production, Fast-DC protocols have been developed. Here we reported a Fast-DC method in compliance with good manufacturing practices for the production of autologous mature dendritic cells loaded with antigens derived from whole tumor lysate, suitable for the immunotherapy in glioblastoma patients. The feasibility of generating Fast-DC pulsed with whole tumor lysate was assessed using a series of small-scale cultures performed in parallel with clinical grade large scale standard method preparations. Our results demonstrate that this Fast protocol is effective only in the presence of PGE2 in the maturation cocktail to guarantee that Fast-DC cells exhibit a mature phenotype and fulfill all requirements for in vivo use in immunotherapy approaches. Fast-DC generated following this protocol were equally potent to standard DC in inducing Ag-specific T cell proliferation in vitro. Generation of Fast-DC not only reduces labor, cost, and time required for in vitro clinical grade DC development, but can also minimizes inter-preparations variability and the risk of contamination.

Simple Summary Active communication between GBM cells and tumor-infiltrating immune components contributes to establishing an immunosuppressive environment where T cells are scarce and exhausted. This condition is particularly exacerbated upon recurrence, which is almost inevitable for GBM patients. Immunotherapeutic approaches, including checkpoint inhibitors, have demonstrated limited efficacy and failed to prolong survival or recurrent GBM patients. Nevertheless, many studies have shown that T cell priming is possible in the GBM microenvironment, and that T cell exhaustion or dysfunction can be reprogrammed. We will revisit data from the literature and report original results obtained from recurrent GBM patients treated with dendritic cells to demonstrate the role of the microenvironment in predicting immunotherapy response and influencing decisions for personalized therapies. Abstract The interpretation of the presence and function of immune infiltration in glioblastoma (GBM) is still debated. Over the years, GBM has been considered a cold tumor that is less infiltrated by effector cells and characterized by a high proportion of immunosuppressive innate immune cells, including GBM-associated microglia/macrophages (GAMs). In this context, the failure of checkpoint inhibitors, particularly in recurrent GBM (rGBM), caused us to look beyond the clinical results and consider the point of view of immune cells. The tumor microenvironment in rGBM can be particularly hostile, even when exposed to standard immunomodulatory therapies, and tumor-infiltrating lymphocytes (TILs), when present, are either dysfunctional or terminally exhausted. However, after checkpoint blockade therapy, it was possible to observe specific recruitment of adaptive immune cells and an efficient systemic immune response. In this review article, we attempt to address current knowledge regarding the tumor and immune microenvironment in rGBM. Furthermore, immunosuppression induced by GAMs and TIL dysfunction was revisited to account for genetic defects that can determine resistance to therapies and manipulate the immune microenvironment upon recurrence. Accordingly, we reevaluated the microenvironment of some of our rGBM patients treated with dendritic cell immunotherapy, with the goal of identifying predictive immune indicators of better treatment response.

Evaluating changes induced by immunotherapies (IT) on conventional magnetic resonance imaging (MRI) is difficult because those treatments may produce inflammatory responses. To explore the potential contribution of advanced MRI to distinguish pseudoprogression (PsP) and true tumor progression (TTP), and to identify patients obtaining therapeutic benefit from IT, we examined aMRI findings in newly diagnosed glioblastoma treated with dendritic cell IT added to standard treatment. We analyzed longitudinal MRIs obtained in 22 patients enrolled in the EUDRACT N&deg, 2008-005035-15 trial. According to RANO criteria, we observed 18 TTP and 8 PsP. Comparing MRI performed at the time of TTP/PsP with the previous exam performed two months before, a difference in cerebral blood volume &Delta, rCBVmax &ge, 0.47 distinguished TTP from PsP with a sensitivity of 67% and specificity of 75% (p = 0.004). A decrease in minimal apparent diffusion coefficient rADCmin (1.15 vs. 1.01, p = 0.003) was observed after four vaccinations only in patients with a persistent increase of natural killer cells (response effectors during IT) in peripheral blood. Basal rADCmin &gt, 1 was independent predictor of longer progression free (16.1 vs. 9 months, p = 0.0001) and overall survival (32.8 vs. 17.5 months, p = 0.0005). In conclusion, rADC predicted response to immunotherapy and survival, Apparent Diffusion Coefficient (ADC) and Cerebral Blood Volume (CBV) modifications over time help differentiating PsP from TTP at onset.

Glioblastoma multiforme is the most malignant subtype of brain tumor. Despite multimodal treatment (surgical resection and chemo/radiotherapy) the prognosis remains unsatisfactory. Based on the Warburg hypothesis, ketogenic diet (KD) has been suggested in the treatment of GBM. The syngenic, orthotopic GL261 mouse glioma model was used to evaluate the effects of KD on 7T magnetic resonance imaging/spectroscopy and metabolic response of the tumor to diet. Mice were injected with 10^5 GL261 cells into the caudate nucleus. Following implantation, animals were fed standard chow for five days then were randomly assigned to standard diet or ketogenic diet. 18 days after diet start, mice fed at KD displayed significantly higher plasmatic levels of ketone bodies. Mice fed with KD survived longer than those fed with standard diet (p< 0.05). Decreased concentrations of gamma-aminobutyric acid, N Acetyl Aspartate and N-acetylaspartylglutamate were found in tumor tissue after 9 days from the beginning of the KD diet while a huge increase in beta-hydroxybutyrate (bHB) was detected in tumor tissue as compared to normal brain. The addition of bHB at various concentrations to low-glucose culture medium did not significantly improve GL261 in vitro growth suggesting that this cell line has a limited ability to use bHB as a carbon source. The accumulation of bHB in the tumor tissue in KD fed mice, may suggest either elevated uptake of/release of bHB by tumor cells or inability of tumor cells in this context to use it in mitochondrial metabolism; the latter hypothesis is supported by the observation that GL261 cells did not display an increase in in vitro proliferation when exposed to bHB. The far less evident peak of bHB at MRI spectroscopy in the healthy brain tissue of KD fed mice, on the other hand suggests that normal brain is able to use bHB as energy source.

Recently, we found that temozolomide (TMZ) can upregulate the expression of the multidrug-resistance protein ABCC3 in NK cells from both glioma-bearing mice and glioblastoma patients treated with dendritic cell immunotherapy combined with TMZ, allowing NK cells to escape apoptosis and favoring their role as antitumor effector cells. Here, we demonstrate that CD56dim NK cells expressing CD16+ are predominant in patients surviving more than 12 months after surgery without disease progression. CD56dim CD16+ NK cells co-expressed high levels of ABCC3 and IFN-γ. Notably, not only basal but also TMZ-induced ABCC3 expression was related to a strong, long-term NK cell response and a better prognosis of patients. The identification of the single nucleotide polymorphism (SNP) rs35467079 with the deletion of a cytosine (−897DelC) in the promoter region of the ABCC3 gene resulted associated with a better patient outcome. ABCC3 expression in patients carrying DelC compared to patients with reference haplotype was higher and modulated by TMZ. The transcription factor NRF2, involved in ABCC3 induction, was phosphorylated in CD56dim CD16+ NK cells expressing ABCC3 under TMZ treatment. Thus, ABCC3 protein and the SNP −897DelC can play a predictive role in patients affected by GBM, and possibly other cancers, treated with dendritic cell immunotherapy combined with chemotherapy.

Expression of neuron-glial antigen 2 (NG2) identifies an aggressive malignant phenotype in glioblastoma (GBM). Mouse models have implicated NG2 in the genesis, evolution, and maintenance of glial cancers and have highlighted potential interactions between NG2 and epidermal growth factor receptor (EGFR). However, it is unknown whether the lineage relationship of NG2+ and NG2- cells follows a hierarchical or stochastic mode of growth. Furthermore, the interaction between NG2 and EGFR signaling in human GBM is also unclear.Single GBM NG2+ and NG2- cells were studied longitudinally to assess lineage relationships. Short hairpin RNA knockdown of NG2 was used to assess the mechanistic role of NG2 in human GBM cells. NG2+ and NG2- cells and NG2 knockdown (NG2-KD) and wild type (NG2-WT) cells were analyzed for differential effects on EGFR signaling.Expression of NG2 endows an aggressive phenotype both at single cell and population levels. Progeny derived from single GBM NG2- or GBM NG2+ cells consistently establish phenotypic equilibrium, indicating the absence of a cellular hierarchy. NG2 knockdown reduces proliferation, and mice grafted with NG2-KD survive longer than controls. Finally, NG2 promotes EGFR signaling and is associated with EGFR expression.These data support a dynamic evolution in which a bidirectional relationship exists between GBM NG2+ and GBM NG2- cells. Such findings have implications for understanding phenotypic heterogeneity, the emergence of resistant disease, and developing novel therapeutics.

In glioma patients, high levels of glutamate can cause brain edema and seizures. GLAST, a glutamate-aspartate transporter expressed by astrocytes with a role in glutamate uptake, is highly expressed on the plasma membrane of glioblastoma (GBM) cells, and its expression significantly correlates with shortened patient survival. Here, it was demonstrated that inhibition of GLAST expression limited the progression and invasion of GBM xenografts. Magnetic resonance spectroscopy was used to measure glutamate in GLAST-expressing gliomas showing that these tumors exhibit increased glutamate concentration compared to GLAST-depleted glioma. Despite their GLAST expression, GBM stem-like cells (GSCs) released rather than taking up glutamate due to their lack of Na+/K+-ATPase. Overexpression of Na+/K+-ATPase in these cells restored glutamate uptake and induced apoptosis. The therapeutic relevance of targeting GLAST in gliomas was assessed using the inhibitor UCPH-101. In glioma-bearing mice, a single intratumoral injection of UCPH-101 significantly increased survival by decreasing GLAST expression and inducing apoptosis. Thus, GLAST has a novel role in GBM that appears to have crucial relevance in glutamate trafficking and may thus be a new therapeutic target.

Although some progress has been made in understanding GBM biology, treatment remains a challenge. There is increasing evidence that radiotherapy (RT) not only provides immunomodulatory effects on tumor microenvironment but also influences systemic immune response, supporting the advantage of combinatorial strategies with immunotherapy (IT). Using immune-competent mice in which syngeneic glioma cells are grown intracranially and treated with local fractionated radiation, we assessed the effects of RT on both local innate and adaptive immune cells. GL261-glioma bearing mice were locally irradiated with a total dose of 15 Gy in three consecutive fractions of 5 Gy on day 7, 8, and 9 after the tumor implantation. Irradiation was delivered both as exclusive (RT) and concomitant treatment in combination with dendritic cell (DC) immunotherapy (RT-IT). DCs were injected subcutaneously on day 16, 23, and 30 after tumor implantation. The potential role of RT in reprogramming the glioma-associated microglia is still poorly characterized. Microglia were isolated and enriched using CD11b microbeads from both the brain tumor hemisphere and contralateral hemisphere of RT, RT-IT, and control mice. A gene expression signature was analyzed on isolated microglia. Expression of mmp14 and trem2, involved in enhancing glioma proliferation, decreased in microglia isolated from RT mice (2.3 and 2.0-fold lower than in controls, day 16 P=0.01). The frequency of CD45dim/CD11b+/CD172A+ microglia showed an early increase at day 16 in the tumor mass and contralateral hemisphere in RT mice, but not in controls (p Citation Format: Serena Pellegatta, Natalia Di Ianni, Martina Maffezzini, Maria Luisa Fumagalli, Valentina Pinzi, Silvia Musio, Laura Fariselli, Gaetano Finocchiaro. Radiotherapy treatment in combination with Dendritic Cell Immunotherapy promotes a microglia activation and a disruption of the SIRPα-CD47 signaling axis in the GL261 glioma model [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO087.

In a two-stage phase II study, 24 patients with first diagnosis of glioblastoma (GBM) were treated with dendritic cell (DC) immunotherapy associated to standard radiochemotherapy with temozolomide (TMZ) followed by adjuvant TMZ. Three intradermal injections of mature DC loaded with autologous GBM lysate were administered before adjuvant TMZ, while 4 injections were performed during adjuvant TMZ. According to a two-stage Simon design, to proceed to the second stage progression-free survival (PFS) 12 months after surgery was expected in at least 8 cases enrolled in the first stage. Evidence of immune response and interaction with chemotherapy were investigated. After a median follow up of 17.4 months, 9 patients reached PFS12. In these patients (responders, 37.5%), DC vaccination induced a significant, persistent activation of NK cells, whose increased response was significantly associated with prolonged survival. CD8+ T cells underwent rapid expansion and priming but, after the first administration of adjuvant TMZ, failed to generate a memory status. Resistance to TMZ was associated with robust expression of the multidrug resistance protein ABCC3 in NK but not CD8+ T cells. The negative effect of TMZ on the formation of T cell-associated antitumor memory deserves consideration in future clinical trials including immunotherapy.

Different approaches have been explored to raise effective antitumor responses against glioblastoma (GBM), the deadliest of primary brain tumors. In many clinical studies, cancer vaccines have been based on dendritic cells (DCs) loaded with peptides, representing one or more specific tumor antigens or whole lysates as a source of multiple antigens. Randomized clinical trials using DCs are ongoing, and results of efficacy are not yet available. Such strategies are feasible and safe; however, immune-suppressive microenvironment, absence of appropriate specific epitopes to target, and cancer immunoediting can limit their efficacy. The aim of this review is to describe how the definition of novel and more specific targets may increase considerably the possibility of successful DC immunotherapy. By proposing to target glioblastoma stem-like cells (GSCs), the immune response will be pointed to eradicating factors and pathways highly relevant to GBM biology. Preclinical observations on efficacy, and preliminary results of immunotherapy trials, encourage exploring the clinical efficacy of DC immunotherapy in GBM patients using high-purity, GSC-loaded DC vaccines.

In a two-stage phase II study, 24 patients with first diagnosis of glioblastoma (GBM) were treated with dendritic cell (DC) immunotherapy associated to standard radiochemotherapy with temozolomide (TMZ) followed by adjuvant TMZ. Three intradermal injections of mature DC loaded with autologous GBM lysate were administered before adjuvant TMZ, while 4 injections were performed during adjuvant TMZ. According to a two-stage Simon design, to proceed to the second stage progression-free survival (PFS) 12 months after surgery was expected in at least 8 cases enrolled in the first stage. Evidence of immune response and interaction with chemotherapy were investigated. After a median follow up of 17.4 months, 9 patients reached PFS12. In these patients (responders, 37.5%), DC vaccination induced a significant, persistent activation of NK cells, whose increased response was significantly associated with prolonged survival. CD8+ T cells underwent rapid expansion and priming but, after the first administration of adjuvant TMZ, failed to generate a memory status. Resistance to TMZ was associated with robust expression of the multidrug resistance protein ABCC3 in NK but not CD8+ T cells. The negative effect of TMZ on the formation of T cell-associated antitumor memory deserves consideration in future clinical trials including immunotherapy.

Checkpoint inhibitors, like ipilimumab, nivolumab, and pembrolizumab, have provided a breakthrough in cancer immunotherapy, such as in the treatment of melanoma and colorectal and lung cancer. The close relationship between the number of mutations (mutational load) and the response to checkpoint immunotherapy has been convincingly demonstrated in these cancers. Hypermutations in tumors are caused by environmental factors, like UV radiations or cigarette smoking, or by germinal mutations affecting genes of the Mismatch Repair (MMR) machinery, as in the Lynch syndrome. In the context of a high mutational load, a number of neoantigens become visible to the immune system, creating the basis for effective T cell responses. In low- and high-grade gliomas, the most frequent brain tumors, germinal MMR defects are rare; however, hypermutations associated with mutations or decreased expression of MMR genes are rather frequent, occurring in 20-60% of the tumors at recurrence after alkylating chemotherapy with temozolomide. Ongoing clinical trials and genomic investigations will clarify if temozolomide-induced hypermutations, which usually occur in the presence of methylation of the methylguanine methyltransferase gene (MGMT), will be effectively targeted by immunotherapy with checkpoint inhibitors or dendritic cell immunotherapy, thus improving the survival expectations for patients affected by these tumors.