CTLA-4 blockade induces a microglia-Th1 cell partnership that stimulates microglia phagocytosis and anti-tumor function in glioblastoma

Biological effects of rapid short pulses of focused ultrasound for drug delivery to the brain

Focused ultrasound in combination with intravenously injected microbubbles offers a non-invasive and localised method to deliver drugs across the blood-brain barrier, enabling targeted treatment of brain disorders. Recently, we have shown that applying sequences of Rapid Short-Pulses (RaSP; 5 μs pulses emitted at 1.25 kHz grouped into 10 ms bursts) of ultrasound can deliver drugs with an improved efficacy and safety profile compared with traditionally-used longer pulses (> 10 ms). In this study, we examined the extent to which RaSP sequences allowed the extravasation of endogenous blood proteins, including albumin and immunoglobulin, as well as T cells, into the brain parenchyma. We also investigated the effect of RaSP ultrasound treatments on synaptic connectivity, and the distribution and excretion of fluorescently-labelled 3 kDa dextran delivered to the brain with RaSP. The left hippocampus of mice was sonicated with either a RaSP sequence (5 μs at 1.25 kHz in groups of 10 ms at 0.5 Hz) or a long pulse sequence (10 ms at 0.5 Hz), at 0.35, 0.53 and 0.71 MPa with a 1-MHz center frequency. Significantly less albumin was detected in RaSP-treated brains immediately after treatment and was cleared within 10 min compared to those treated with long pulses, while immunoglobulin was hardly detected in RaSP-treated brains at 0, 10 or 20 min after treatment. No T cells were detected in RaSP-treated brains at 0.35, 0.53 or 0.71 MPa after 0 or 2 h. In long pulse samples, however, T cells did extravasate when using the two higher acoustic pressures, 0.53 and 0.71 MPa, immediately after treatment. Quantification of dendritic spine area revealed no differences between RaSP-treated hippocampi compared to untreated contralateral hippocampi and control mice following three weekly ultrasound treatments. Finally, fluorescently-labelled dextran increasingly moved towards blood vessels and away from the parenchyma once delivered to the brain with both RaSP and long pulse sequences. Uptake of dextran within cells decreased over time with both sequences, and long pulses lead to a larger number of vessels with dextran uptake. This study highlights that RaSP ultrasound sequences can deliver molecules across the blood-brain barrier with minimal extravasation of endogenous proteins and no T cell infiltration, while preserving dendritic spine integrity, thus offering an improved safety profile.

Glioblastoma-instructed astrocytes suppress tumour-specific T cell immunity

Glioblastoma is the most common and aggressive primary brain cancer and shows minimal response to therapies. The immunosuppressive tumour microenvironment in glioblastoma contributes to the limited therapeutic response. Astrocytes are abundant in the central nervous system and have important immunoregulatory roles. However, little is known about their role in the immune response to glioblastoma1. Here we used single-cell and bulk RNA sequencing of clinical glioblastoma samples and samples from preclinical models, multiplexed immunofluorescence, in vivo CRISPR-based cell-specific genetic perturbations and in vitro mouse and human experimental systems to address this gap in knowledge. We identified an astrocyte subset that limits tumour immunity by inducing T cell apoptosis through the death receptor ligand TRAIL. Moreover, we identified that IL-11 produced by tumour cells is a driver of STAT3-dependent TRAIL expression in astrocytes. Astrocyte signalling through STAT3 and TRAIL expression were associated with a shorter time to recurrence and overall decreased survival in patients with glioblastoma. Genetic inactivation of the IL-11 receptor or TRAIL in astrocytes extended survival in mouse models of glioblastoma and enhanced T cell and macrophage responses. Finally, treatment with an oncolytic HSV-1 virus engineered to express a TRAIL-blocking single-chain antibody in the tumour microenvironment extended survival and enhanced tumour-specific immunity in preclinical models of glioblastoma. In summary, we establish that IL-11-STAT3-driven astrocytes suppress glioblastoma-specific protective immunity by inducing TRAIL-dependent T cell apoptosis, and engineered therapeutic viruses can be used to target this mechanism of astrocyte-driven tumour immunoevasion.

Irreversible electroporation combined with PD-L1/IL-6 dual blockade promotes anti-tumor immunity via cDC2/CD4+T cell axis in MHC-I deficient pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a "cold" solid tumor with frequent Major Histocompatibility Complex I (MHC-I) deficiency, thereby making it resistant to type-1-conventional dendritic cell (cDC1)-CD8+T cell mediated anti-tumor immunity. Current studies have demonstrated the emerging compensatory role of MHC-II-mediated antigen presentation and CD4+T cell activation in anti-tumor immunity against MHC-I-deficient tumors. However, the underlying mechanism of the compensatory immune response by CD4+T cells in cancer ablation therapy remains to be elucidate. In clinical samples and murine models, we observed that irreversible electroporation (IRE) ablation therapy promoted immune infiltration and the conversion of CD4+T cells into anti-tumor IFN-γ+Th1 cells and Th17 cells in MHC-I low-expressed PDAC using scRNA-seq and flow-cytometry analyses. Furthermore, we found that PD-L1 blockade predominantly enhanced the activation of CD11b+CD103-type-2 conventional dendritic cells (cDC2s) and their antigen presentation to CD4+T cells after ablation, stimulating the anti-tumor immune response through the tumor antigen-specific IFN-γ+Th1-NK cell axis. Elevated plasma levels of IL-6 in pancreatic cancer patients receiving ablation therapy are significant indicators for impaired prognosis. IL-6 and PD-L1 dual blockade could significantly augment the ratio of IFN-γ+Th1 in CD4+T cells to boost the anti-tumor immunity of NK cells, leading to prolonged survival of mouse bearing pancreatic cancer. Collectively, we have elucidated that PD-L1 blockade activates the cDC2-CD4+T cell axis after IRE therapy, thereby playing a pivotal compensatory anti-tumor role in MHC-I low-expressed pancreatic cancer. Moreover, a combination strategy involving dual-target blockade of PD-L1/IL-6 along with ablation therapy could emerge as a novel therapeutic approach for MHC-I deficient tumors.

Advancing Cancer Treatment: A Review of Immune Checkpoint Inhibitors and Combination Strategies

A groundbreaking milestone in oncology has been the recognition and targeted elimination of malignant cells through cancer immunotherapy, which harnesses the body's immune system to attack cancer [...].

Targeting DKK3 to remodel tumor immune microenvironment and enhance cancer immunotherapy

Cancer immunotherapy such as immune checkpoint blockade (ICB) therapy has made important breakthroughs in cancer treatment, however, currently only parts of cancer patients benefit from ICB therapy. The suppressive tumor immune microenvironment (TIME) impedes the treatment response of immunotherapy, indicating the necessity to explore new treatment targets. Here, we reported a new potential immunotherapeutic target, Dickkopf-3 (DKK3), for cancer treatment. DKK3 expression is up-regulated in the tumors from multiple cancer types, and high DKK3 expression is associated with worse survival outcome across different cancers. We observed that DKK3 directly inhibits the activation of CD8+ T cells and the Th1 differentiation of CD4+ T cells ex vivo. Also, by establishing four different mouse cancer models, we found that DKK3 blockade triggers effective anti-tumor effects and improve the survival of tumor-bearing mice in vivo. DKK3 blockade also remodels the suppressive TIME of different cancer types, including the increased infiltration of CD8+ T cells, IFN-γ+CD8+ T cells, Th1 cells, and decreased infiltration of M2 macrophages and MDSCs in the TIME. Moreover, we found that combined blockade of DKK3 and PD-1 induces synergistic tumor-control effect in our mouse cancer model. Therefore, our study reveals the impact of DKK3 in the TIME and cancer progression, which suggests that DKK3 is a novel and promising immunotherapeutic target for enhanced cancer immunotherapy.

CD86 immunohistochemical staining for the detection of Talaromyces marneffei in lesions

Talaromycosis is an invasive fungal disease caused by the pathogenic thermodimorphic fungus Talaromyces marneffei (TM), which is often overlooked in tropical and subtropical regions of Asia. In view of the diversity of clinical manifestations in patients with TM infection, early diagnosis remains challenging. We assessed the sensitivity and specificity of a novel immunohistochemical staining by performing CD86 immunohistochemical staining on 56 tissue sections from patients with talaromycosis who had fungal culture or metagenomic next-generation sequencing confirmed to exist in clinical specimens, as well as 26 patients with other fungi that had been culture-proven. Hematoxylin and eosin and periodic acid Schiff (PAS) stains were also applied to each specimen. We found that anti-CD86 antibody can label TM pathogens in 38 HIV-negative specimens (38/42) and 14 HIV-positive specimens (14/14); conversely, PAS staining yielded positive results in seven cases of HIV-negative specimens (7/42) and 13 cases of HIV-positive specimens (13/14). Additionally, CD86 immunohistochemical staining was negative in other fungi. Importantly, CD86 immunohistochemical staining significantly outperformed PAS staining in terms of localizing and highlighting TM yeasts, as well as demonstrating the specificity of 100% and a significantly higher sensitivity compared to PAS staining at 92.9% versus 35.7% (P < 0.05, McNemar test). Our findings suggest that CD86 immunohistochemical staining has the potential for the rapid diagnosis of talaromycosis.IMPORTANCETalaromycosis is an opportunistic endemic disease without typical clinical manifestations that has emerged as a fungal disease impacting the survival and mortality of immunocompromised individuals and HIV-positive individuals in endemic regions. Nonetheless, talaromycosis is completely curable if it is accurately diagnosed and treated effectively at an early stage. Rapid pathological diagnosis relies on the unique morphological features of Talaromyces marneffei observed under the microscope. This study introduces a novel pathological diagnostic approach, CD86 immunohistochemical staining, to enhance the early detection of TM-infected lesions.

Opportunities to Modulate Tumor Ecosystem Toward Successful Glioblastoma Immunotherapy

Over the past decade, the failure of multiple clinical trials has confirmed the need for a systematic and comprehensive understanding of glioblastoma (GBM). Current immunotherapies aiming to harness the immune system to achieve anti-tumor effects remain largely ineffective, highlighting the complexities of the GBM microenvironment. However, our recent understanding of immune niches within the central nervous system provides both opportunities and challenges in translating these insights into successful immunotherapy implementation. We discuss these strategies, including targeting multiple antigens within the heterogeneous GBM microenvironment, identifying new druggable targets to abrogate immunosuppression, and understanding niche-specific immune cell functionality to modulate tumor-immune-stroma interactions.

Identification and Validation of Prognostic Genes Related to Histone Lactylation Modification in Glioblastoma: An Integrated Analysis of Transcriptome and Single-cell RNA Sequencing

Background: The impact of histone lactylation modification (HLM) on glioblastoma (GBM) progression is not well understood. This study aimed to identify HLM-associated prognostic genes in GBM and explore their mechanisms of action. Methods: The presence and role of lactylation in glioma clinical tissue samples and its correlation with GBM progression were analysed through immunohistochemical staining and Western blotting. Sequencing data for GBM were obtained from publicly available databases. An initial correlation analysis was performed between global HLM levels and GBM. Differentially expressed HLM-related genes (HLMRGs) in GBM were identified by intersecting differentially expressed genes (DEGs) from the TCGA-GBM dataset, key module genes derived from weighted gene coexpression network analysis (WGCNA), and previously reported HLMRGs. Prognostic genes were subsequently identified through univariate Cox regression and least absolute shrinkage and selection operator (LASSO) regression analyses, which formed the basis for constructing a risk prediction model. Associations between HLMRGs and GBM were further evaluated via single-cell RNA sequencing (scRNA-seq) datasets. Complementary analyses, including functional enrichment, immune infiltration, somatic mutation, and nomogram-based survival prediction, were conducted alongside in vitro experiments. Additionally, drug sensitivity and Chinese medicine prediction analyses were performed to identify potential therapeutic agents for GBM. Results: We detected a significant increase in global lactylation levels in GBM, which correlated with patient survival. We identified 227 differentially expressed HLMRGs from the intersection of 3,343 differentially expressed genes and 948 key module genes, indicating strong prognostic potential. Notably, genes such as SNCAIP, TMEM100, NLRP11, HOXC11, and HOXD10 were highly expressed in GBM. Functional analysis suggested that HLMRGs are involved primarily in pathways related to cytokine‒cytokine receptor interactions, cell cycle regulation, and cellular interactions, including microglial differentiation states. Further connections were established between HLMRGs and infiltrating immune cells, particularly type 1 T helper (Th1) cells, as well as mutations in genes such as PTEN. The potential therapeutic agents identified included ATRA and Can Sha. Conclusion: The HLM-related gene risk prediction model shows substantial promise for improving patient management in GBM, providing crucial insights for clinical prognostic evaluations and immunotherapeutic approaches in GBM.

Targeting HIF-2α in glioblastoma reshapes the immune infiltrate and enhances response to immune checkpoint blockade

Glioblastoma (GBM) is an aggressive primary brain tumor with dismal clinical prognosis and resistance to current therapies. GBM progression is facilitated by the tumor microenvironment (TME), with an immune infiltrate dominated by tumor-associated microglia/macrophages (TAMs) and regulatory T cells (Tregs). The TME is also characterized by hypoxia and the expression of hypoxia-inducible factors (HIFs), with HIF-2α emerging as a potential regulator of tumor progression. However, its role in GBM immunosuppression remains unknown. Here, we investigate HIF-2α and the use of the HIF-2α inhibitor PT2385 to modulate the TME in the immunocompetent GL261 mouse GBM model. PT2385 administration in vivo decreased tumor volume and prolonged survival of tumor-bearing mice, without affecting GL261 viability in vitro. Notably, HIF-2α inhibition alleviated the immunosuppressive TME and synergized with immune checkpoint blockade (ICB) using αPD-1 and αTIM-3 antibodies to promote long-term survival. Comprehensive analysis of the immune infiltrate through single-cell RNA sequencing and flow cytometry revealed that combining PT2385 with ICB reduced numbers of pro-tumoral macrophages and Tregs while increasing numbers of microglia, with a corresponding transcriptional modulation towards an anti-tumoral profile of these TAMs. In vitro, deletion of HIF-2α in microglia impeded their polarization towards a pro-tumoral M2-like profile, and its inhibition impaired Treg migration. Our results show that targeting HIF-2α can switch an immunosuppressive TME towards one that favors a robust and sustained response to ICB based immunotherapy. These findings establish that clinically relevant HIF-2α inhibitors should be explored not only in malignancies with defects in the HIF-2α axis, but also in those exhibiting an immunosuppressive TME that limits immunotherapy responsiveness.

Microglial reprogramming enhances antitumor immunity and immunotherapy response in melanoma brain metastases

Melanoma is one of the tumor types with the highest risk of brain metastasis. However, the biology of melanoma brain metastasis and the role of the brain immune microenvironment in treatment responses are not yet fully understood. Using preclinical models and single-cell transcriptomics, we have identified a mechanism that enhances antitumor immunity in melanoma brain metastasis. We show that activation of the Rela/Nuclear Factor κB (NF-κB) pathway in microglia promotes melanoma brain metastasis. Targeting this pathway elicits microglia reprogramming toward a proinflammatory phenotype, which enhances antitumor immunity and reduces brain metastatic burden. Furthermore, we found that proinflammatory microglial markers in melanoma brain metastasis are associated with improved responses to immune checkpoint inhibitors in patients and targeting Rela/NF-κB pathway in mice improves responses to these therapies in the brain, suggesting a strategy to enhance antitumor immunity and responses to immune checkpoint inhibitors in patients with melanoma brain metastasis.

Intratumoral gene delivery of 4-1BBL boosts IL-12-triggered anti-glioblastoma immunity

The standard of care in high-grade gliomas has remained unchanged in the past 20 years. Efforts to replicate effective immunotherapies in non-cranial tumors have led to only modest therapeutical improvements in glioblastoma (GB). Here, we demonstrate that intratumoral administration of recombinant interleukin-12 (rIL-12) promotes local cytotoxic CD8 POS T cell accumulation and conversion into an effector-like state, resulting in a dose-dependent survival benefit in preclinical GB mouse models. This tumor-reactive CD8 T cell response is further supported by intratumoral rIL-12-sensing dendritic cells (DCs) and is accompanied by the co-stimulatory receptor 4-1BB expression on both cell types. Given that DCs and CD8 POS T cells are functionally suppressed in the tumor microenvironments of de novo and recurrent glioma patients, we tested whether anti-tumor response at the rIL-12-inflamed tumor site could be enhanced with 4-1BBL, the ligand of 4-1BB. 4-1BBL was delivered using an adeno-associated virus (AAV) vector targeting GFAP-expressing cells and resulted in prolonged survival of rIL-12 treated GB-bearing mice. This study establishes that tumor antigen-specific CD8 T cell activity can be directed using an AAV-vector-mediated gene therapy approach, effectively enhancing anti-GB immunity.

Revitalizing systemic immune responses in advanced NSCLC using FLT3L and SBRT

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide. For patients who develop progressive disease after treatment with chemotherapy and immunotherapy, treatment options are limited. Here, we report the results of a Phase II clinical trial where twenty-nine patients with advanced, previously treated NSCLC were treated with stereotactic body radiotherapy (SBRT) targeting a single site of disease along with CDX-301, a recombinant human Fms-like tyrosine kinase 3 ligand (FLT3L). The primary study endpoint was progression-free survival four months after study entry (PFS4), which was achieved for 14 patients (48%). Abscopal responses were observed on fludeoxyglucose-18 positron emission tomography (FDG-PET) in nine patients (31%). The median overall survival for all participants was 18 months, with a median overall survival for participants with abscopal response of 31 months. To identify underlying immune signatures of response, we developed a high dimensional flow cytometric approach that quantified 31 distinct cell subsets from peripheral blood, and performed multiplex proteomic analysis of 92 proteins from plasma. SBRT combined with CDX-301 significantly increased circulating myeloid cells, including monocytes, myeloid derived suppressor cells (MDSCs) and dendritic cells (DCs). Among DCs, FceR1-expressing DC2 and DC3 subsets changed most robustly upon treatment. These dynamic changes in DCs and MDSCs following initiation of SBRT and CDX-301 returned to baseline by 8 weeks. However, these changes were also associated with treatment-induced T cell activation with quantitatively robust activation of CD4 T cells. Abscopal responses were associated with a prolonged increase in DC1 cells, Th1-like CD4 T cells, circulating IL-12 and FLT3L. Integrated analysis of multiple types of immune parameters revealed a strong association between coordinated DC induction, CD4 T cell and CD8 T cell activation, and inflammatory cytokine activity in patients with abscopal responses, compared to a stark lack of immune coordination in patients without abscopal responses. These coordinated immune responses were sustained for over 4 weeks in responders, highlighting a potential therapeutic axis engaged in a systemic immune response against multiple lesions in NSCLC. Overall, these findings underscore the potential of combining in situ vaccination, using SBRT, with strategies to enhance the activation of innate immune cells, such as DCs through FLT3L, to potentiate robust anti-tumor T cell responses.

Oncolytic reprogramming of tumor microenvironment shapes CD4 T-cell memory via the IL6ra-Bcl6 axis for targeted control of glioblastoma

Oncolytic viruses (OVs) emerge as a promising cancer immunotherapy. However, the temporal impact on tumor cells and the tumor microenvironment, and the nature of anti-tumor immunity post-therapy remain largely unclear. Here we report that CD4+ T cells are required for durable tumor control in syngeneic murine models of glioblastoma multiforme after treatment with an oncolytic herpes simplex virus (oHSV) engineered to express IL-12. The upregulated MHCII on residual tumor cells facilitates programmed polyfunctional CD4+ T cells for tumor control and for recall responses. Mechanistically, the proper ratio of Bcl-6 to T-bet in CD4+ T cells navigates their enhanced anti-tumor capacity, and a reciprocal IL6ra-Bcl-6 regulatory axis in a memory CD4+ T-cell subset, which requires MHCII signals from reprogrammed tumor cells, tumor-infiltrating and resident myeloid cells, is necessary for the prolonged response. These findings uncover an OV-induced tumor/myeloid-CD4+ T-cell partnership, leading to long-term anti-tumor immune memory, and improved OV therapeutic efficacy.

Overcoming immune evasion with innovative multi-target approaches for glioblastoma

Glioblastoma (GBM) cells leverage complex endogenous and environmental regulatory mechanisms to drive proliferation, invasion, and metastasis. Tumor immune evasion, facilitated by a multifactorial network, poses a significant challenge to effective therapy, as evidenced by the limited clinical benefits of monotherapies, highlighting the adaptive nature of immune evasion. This review explores glioblastoma's immune evasion mechanisms, the role of ICIs in the tumor microenvironment, and recent clinical advancements, offering theoretical insights and directions for monotherapy and combination therapy in glioblastoma management.

CD97 maintains tumorigenicity of glioblastoma stem cells via mTORC2 signaling and is targeted by CAR Th9 cells

Glioblastoma (GBM) stem cells (GSCs) contribute to poor prognosis in patients with GBM. Identifying molecular markers is crucial for developing targeted therapies. Here, we identify cluster of differentiation 97 (CD97) as an optimal GSC surface antigen for potential targeting by chimeric antigen receptor (CAR) T cell therapy through in vitro antibody screening. CD97 is consistently expressed in all validated patient-derived GSCs and positively correlated with known intracellular GSC markers. Silencing CD97 reduces GSC tumorigenicity-related activities, including self-renewal, proliferation, and tumor progression. Transcriptome analysis reveals that CD97 activates mTORC2, leading to AKT S473 phosphorylation and enhanced expression of the downstream genes ARHGAP1, BZW1, and BZW2. Inhibiting mTORC2 with JR-AB2-011 suppresses GSC tumorigenicity and downstream gene expression. We develop CD97-CAR T helper (Th) 9 cells, which exhibit potent cytotoxic effects in vitro and extend survival in mice. These findings suggest that CD97 is a promising GSC-enriched antigen and that targeting it with CAR Th9 cells offers a potential therapeutic strategy for GBM.

Intracranial administration of anti-PD-1 and anti-CTLA-4 immune checkpoint-blocking monoclonal antibodies in patients with recurrent high-grade glioma

BACKGROUND

Recurrent high-grade glioma (rHGG) lacks effective life-prolonging treatments and the efficacy of systemic PD-1 and CTLA-4 immune checkpoint inhibitors is limited. The multi-cohort Glitipni phase I trial investigates the safety and feasibility of intraoperative intracerebral (iCer) and postoperative intracavitary (iCav) nivolumab (NIVO) ± ipilimumab (IPI) treatment following maximal safe resection (MSR) in rHGG.

MATERIALS AND METHODS

Patients received 10 mg IV NIVO within 24 h before surgery, followed by MSR, iCer 5 mg IPI and 10 mg NIVO, and Ommaya catheter placement in the resection cavity. Biweekly postoperative iCav administrations of 1-5-10 mg NIVO (cohort 4) or 10 mg NIVO plus 1-5-10 mg IPI (cohort 7) were combined with 10 mg IV NIVO for 11 cycles.

RESULTS

42 rHGG patients underwent MSR with iCer NIVO + IPI. 16 pts were treated in cohort 4 (postoperative iCav NIVO at escalating doses) while 28 patients were treated in cohort 7 (intra and postoperative iCav NIVO and escalating doses of IPI). The most common TRAE was fatigue; no grade 5 AE occurred. Dose-limiting toxicity was grade 3 neutrophilic pleocytosis (4 pts) receiving iCav NIVO plus 5 or 10 mg IPI. PFS and OS did not significantly differ between cohorts (median OS: 42 [95% CI 26-57] vs. 35 [29-40] weeks; 1-year OS rate: 37% vs. 29%). Baseline B7-H3 expression significantly correlated with worse survival. OS compared favorably to a historical pooled cohort (n = 469) of Belgian rHGG pts treated with anti-VEGF therapies (log-rank P = .015).

CONCLUSION

Intraoperative iCer IPI + NIVO with postoperative iCav NIVO ± IPI up to biweekly doses of 1 mg IPI + 10 mg NIVO is feasible and safe, showing encouraging OS in rHGG patients. ClinicalTrials.gov registration: NCT03233152.

Expression and Clinical Significance of Lymphocyte Subpopulations and Peripheral Inflammatory Markers in Glioma

Purpose

Patients with glioma often fail to achieve satisfactory outcomes despite receiving surgery, radiotherapy, and chemotherapy. Photodynamic therapy (PDT) shows promise in addressing the limitations of traditional treatments. However, the immunological effects of PDT in glioma patients remain underexplored. This study aims to fill this gap by analyzing lymphocyte subpopulations and inflammatory markers in glioma patients undergoing PDT-assisted surgery.

Patients and Methods

To enhance our comprehension of the immunobiology of glioma within a clinical framework, we conducted a retrospective analysis of glioma patients from September 2019 to December 2023. Peripheral blood lymphocyte subpopulations (CD3+, CD19+, CD4+, CD8+, CD4+/CD8+) and hematological inflammatory factors were compared among 18 patients who underwent surgery with PDT, 10 patients treated with surgery alone, and healthy controls. Additionally, lymphocyte subpopulations from 48 healthy individuals and hematology inflammatory factors from 38 healthy controls were regarded as controls.

Results

PDT-assisted surgery resulted in significant alterations in lymphocyte subpopulations and inflammatory markers before and after treatment, particularly in CD4+ and CD8+ T cells. PDT-treated patients demonstrated a superior therapeutic response compared to surgery alone (P=0.035). Notably, primary glioma patients had more prolonged overall survival than recurrent glioma patients (P=0.039).

Conclusion

PDT-assisted surgery significantly affects lymphocyte subpopulations and inflammatory markers, enhancing immune response in glioma patients. These findings support the use of PDT as an effective adjuvant therapy. Monitoring lymphocyte subpopulations and inflammatory markers may be valuable for glioma prognosis and treatment optimization.

TKI resistance in brain metastasis: A CTLA4 state of mind

Resistance to tyrosine kinase inhibitors (TKIs) in lung cancer brain metastasis (LCBM) remains a clinical challenge. Recently in Cancer Cell, Fu et al. reveal how TKIs reshape the immune microenvironment of LCBM and propose CTLA4 blockade as a promising strategy to overcome resistance.

Microglia and monocyte-derived macrophages drive progression of pediatric high-grade gliomas and are transcriptionally shaped by histone mutations

Pediatric high-grade gliomas (pHGGs), including hemispheric pHGGs and diffuse midline gliomas (DMGs), harbor mutually exclusive tumor location-specific histone mutations. Using immunocompetent de novo mouse models of pHGGs, we demonstrated that myeloid cells were the predominant infiltrating non-neoplastic cell population. Single-cell RNA sequencing (scRNA-seq), flow cytometry, and immunohistochemistry illustrated the presence of heterogeneous myeloid cell populations shaped by histone mutations and tumor location. Disease-associated myeloid (DAM) cell phenotypes demonstrating immune permissive characteristics were identified in murine and human pHGG samples. H3.3K27M DMGs, the most aggressive DMG, demonstrated enrichment of DAMs. Genetic ablation of chemokines Ccl8 and Ccl12 resulted in a reduction of DAMs and an increase in lymphocyte infiltration, leading to increased survival of tumor-bearing mice. Pharmacologic inhibition of chemokine receptors CCR1 and CCR5 resulted in extended survival and decreased myeloid cell infiltration. This work establishes the tumor-promoting role of myeloid cells in DMG and the potential therapeutic opportunities for targeting them.

In vivo mouse models for adult brain tumors: Exploring tumorigenesis and advancing immunotherapy development

Brain tumors, particularly glioblastoma (GBM), are devastating and challenging to treat, with a low 5-year survival rate of only 6.6%. Mouse models are established to understand tumorigenesis and develop new therapeutic strategies. Large-scale genomic studies have facilitated the identification of genetic alterations driving human brain tumor development and progression. Genetically engineered mouse models (GEMMs) with clinically relevant genetic alterations are widely used to investigate tumor origin. Additionally, syngeneic implantation models, utilizing cell lines derived from GEMMs or other sources, are popular for their consistent and relatively short latency period, addressing various brain cancer research questions. In recent years, the success of immunotherapy in specific cancer types has led to a surge in cancer immunology-related research which specifically necessitates the utilization of immunocompetent mouse models. In this review, we provide a comprehensive summary of GEMMs and syngeneic mouse models for adult brain tumors, emphasizing key features such as model origin, genetic alteration background, oncogenic mechanisms, and immune-related characteristics. Our review serves as a valuable resource for the brain tumor research community, aiding in the selection of appropriate models to study cancer immunology.

Fc-enhanced anti-CTLA-4, anti-PD-1, doxorubicin, and ultrasound-mediated blood-brain barrier opening: A novel combinatorial immunotherapy regimen for gliomas

BACKGROUND

Glioblastoma is a highly aggressive brain cancer that is resistant to conventional immunotherapy strategies. Botensilimab, an Fc-enhanced anti-CTLA-4 antibody (FcE-aCTLA-4), has shown durable activity in "cold" and immunotherapy-refractory cancers.

METHODS

We evaluated the efficacy and immune microenvironment phenotype of a mouse analogue of FcE-aCTLA-4 in treatment-refractory preclinical models of glioblastoma, both as a monotherapy and in combination with doxorubicin delivered via low-intensity pulsed ultrasound and microbubbles (LIPU/MB). Additionally, we studied 4 glioblastoma patients treated with doxorubicin, anti-PD-1 with concomitant LIPU/MB to investigate the novel effect of doxorubicin modulating FcγR expressions in tumor-associated macrophages/microglia (TAMs).

RESULTS

FcE-aCTLA-4 demonstrated high-affinity binding to FcγRIV, the mouse ortholog of human FcγRIIIA, which was highly expressed in TAMs in human glioblastoma, most robustly at diagnosis. Notably, FcE-aCTLA-4-mediated selective depletion of intratumoral regulatory T cells (Tregs) via TAM-mediated phagocytosis, while sparing peripheral Tregs. Doxorubicin, a chemotherapeutic drug with immunomodulatory functions, was found to upregulate FcγRIIIA on TAMs in glioblastoma patients who received doxorubicin and anti-PD-1 with concomitant LIPU/MB. In murine models of immunotherapy-resistant gliomas, a combinatorial regimen of FcE-aCTLA-4, anti-PD-1, and doxorubicin with LIPU/MB, achieved a 90% cure rate, that was associated robust infiltration of activated CD8+ T cells and establishment of immunological memory as evidenced by rejection upon tumor rechallenge.

CONCLUSIONS

Our findings demonstrate that FcE-aCTLA-4 promotes robust immunomodulatory and anti-tumor effects in murine gliomas and is significantly enhanced when combined with anti-PD-1, doxorubicin, and LIPU/MB. We are currently investigating this combinatory strategy in a clinical trial (clinicaltrials.gov NCT05864534).

Tumor perfusion enhancement by focus ultrasound-induced blood-brain barrier opening to potentiate anti-PD-1 immunotherapy of glioma

OBJECTIVE

To demonstrate the feasibility of using focused ultrasound to enhance delivery of PD-1 inhibitors in glioma rats and determine if such an approach increases treatment efficacy.

METHODS

C6 glioma in situ rat model was used in this study. Transcranial irradiation with FUS combined with microbubbles was administered to open the blood-brain barrier (BBB). The efficacy of BBB opening was evaluated in normal rats. The rats with glioma were grouped to evaluate the role of PD-1 inhibitors combined with FUS-induced immune responses in suppressing glioma when the BBB opens. Flow cytometry was used to examine the changes of immune cell populations of lymphocytes in peripheral blood, tumor tissue and spleen tissue of the rats. A section of rat brain tissue was also used for histological and immunohistochemical analysis. The survival of the rats was then monitored; the tumor progression and changes in blood perfusion of tumor were dynamically observed in vivo using multimodal MRI.

RESULTS

FUS combined with microbubbles could enhance the blood perfusion of tumors by increasing the permeability of BBB (p < 0.0001), thus promoting the infiltration of CD4+ T lymphocytes (p < 0.01). Compared with the control group, the combination treatment group had increased in the infiltration number of CD4+(p < 0.05) and CD8+ T (p < 0.05); the tumor volume of the combined treatment group was smaller than that of the control group (p < 0.01) and the survival rate of the rats was prolonged (p < 0.05).

CONCLUSIONS

In this study, we demonstrated that the transient opening of the BBB induced by FUS enhanced tumor vascular perfusion and facilitated the delivery of PD-1 inhibitors, ultimately improving the therapeutic efficacy for glioblastoma.

Immunotherapy in the Fight Against Bone Metastases: A Review of Recent Developments and Challenges

OPINION STATEMENT

Bone metastasis, a frequent and detrimental complication of advanced cancers, often triggers bone deterioration events that severely compromise patient quality of life and prognosis. The past few years have witnessed the emergence and continuous advancements in immunotherapy, ushering in innovative therapeutic prospects for bone metastasis. These advancements include not only the use of immune checkpoint inhibitors (ICIs), both as standalone and combined treatments, but also the investigation of novel targets within immune cells residing in bone metastases. These breakthroughs have instilled fresh optimism for effectively managing patients with bone metastasis. This article endeavors to present an exhaustive review of the recent progress made across a spectrum of immunotherapeutic strategies and targeted therapies specifically designed for individuals battling bone metastasis from malignant tumors. By doing so, it seeks to offer insights that can inform clinical practices and guide further medical research in this domain.

Architecture sets the path: Breast cancer subtypes differently shape the early brain metastatic niche

The ability of disseminated cancer cells to colonize the brain is highly dependent on initial survival cues, often evoking early microenvironmental adaptations. In this issue of Cancer Cell, Gan et al. unveil disparate tumor architectures in early stage HER2+ breast cancer and triple-negative breast cancer brain metastases that shape stromal interactions, providing a rationale for subtype-dependent patient stratification.

Distinct tumor architectures and microenvironments for the initiation of breast cancer metastasis in the brain

Brain metastasis, a serious complication of cancer, hinges on the initial survival, microenvironment adaptation, and outgrowth of disseminated cancer cells. To understand the early stages of brain colonization, we investigated two prevalent sources of cerebral relapse, triple-negative (TNBC) and HER2+ (HER2BC) breast cancers. Using mouse models and human tissue samples, we found that these tumor types colonize the brain, with a preference for distinctive tumor architectures, stromal interfaces, and autocrine programs. TNBC models tend to form perivascular sheaths with diffusive contact with astrocytes and microglia. In contrast, HER2BC models tend to form compact spheroids driven by autonomous tenascin C production, segregating stromal cells to the periphery. Single-cell transcriptomics of the tumor microenvironment revealed that these architectures evoke differential Alzheimer's disease-associated microglia (DAM) responses and engagement of the GAS6 receptor AXL. The spatial features of the two modes of brain colonization have relevance for leveraging the stroma to treat brain metastasis.

IMMUNE AND MOLECULAR CORRELATES OF RESPONSE TO IMMUNOTHERAPY REVEALED BY BRAIN-METASTATIC MELANOMA MODELS

Despite the promising results of immune checkpoint blockade (ICB) therapy, outcomes for patients with brain metastasis (BrM) remain poor. Identifying resistance mechanisms has been hindered by limited access to patient samples and relevant preclinical models. Here, we developed two mouse melanoma BrM models that recapitulate the disparate responses to ICB seen in patients. We demonstrate that these models capture the cellular and molecular complexity of human disease and reveal key factors shaping the tumor microenvironment and influencing ICB response. BR1-responsive tumor cells express inflammatory programs that polarize microglia into reactive states, eliciting robust T cell recruitment. In contrast, BR3-resistant melanoma cells are enriched in neurological programs and exploit tolerance mechanisms to maintain microglia homeostasis and limit T cell infiltration. In humans, BR1 and BR3 expression signatures correlate positively or negatively with T cell infiltration and BrM patient outcomes, respectively. Our study provides clinically relevant models and uncovers mechanistic insights into BrM ICB responses, offering potential biomarkers and therapeutic targets to improve therapy efficacy.

Barriers to T Cell Functionality in the Glioblastoma Microenvironment

Glioblastoma (GBM) is an aggressive primary brain tumor depicted by a cold tumor microenvironment, low immunogenicity, and limited effective therapeutic interventions. Its location in the brain, a highly immune-selective organ, acts as a barrier, limiting immune access and promoting GBM dissemination, despite therapeutic interventions. Currently, chemotherapy and radiation combined with surgical resection are the standard of care for GBM treatment. Although immune checkpoint blockade has revolutionized the treatment of solid tumors, its observed success in extracranial tumors has not translated into a significant survival benefit for GBM patients. To develop effective immunotherapies for GBM, it is vital to tailor treatments to overcome the numerous immunosuppressive barriers that inhibit T cell responses to these tumors. In this review, we address the unique physical and immunological barriers that make GBM challenging to treat. Additionally, we explore potential therapeutic mechanisms, studied in central nervous system (CNS) and non-CNS cancers, that may overcome these barriers. Furthermore, we examine current and promising immunotherapy clinical trials and immunotherapeutic interventions for GBM. By highlighting the array of challenges T cell-based therapies face in GBM, we hope this review can guide investigators as they develop future immunotherapies for this highly aggressive malignancy.

MAPK/ERK signaling in gliomas modulates interferon responses, T cell recruitment, microglia phenotype, and immune checkpoint blockade efficacy

Background

Glioblastoma (GB) remains a formidable challenge in neuro-oncology, with immune checkpoint blockade (ICB) showing limited efficacy in unselected patients. We previously recently established that MAPK/ERK signaling is associated with overall survival following anti-PD-1 and anti-CTLA-4 treatment in recurrent GB. However, the causal relationship between MAPK/ERK signaling and susceptibility to ICB, as well as the mechanisms underlying this association, remain poorly understood.

Method

We conducted in vivo kinome-wide CRISPR/Cas9 screenings in murine gliomas to identify key regulators of susceptibility to anti-PD-1 and CD8+ T cell responses and performed survival studies to validate the most relevant genes. Additionally, paired single cell RNA-sequencing (scRNA-seq) with p-ERK staining, spatial transcriptomics on GB samples, and ex-vivo slice culture of a BRAFV600E mutant GB tumor treated with BRAFi/MEKi were used to determine the causal relationship between MAPK signaling, tumor cell immunogenicity, and modulation of microglia phenotype.

Results

CRISPR/Cas9 screens identified the MAPK pathway, particularly the RAF-MEK-ERK pathway, as the most critical modulator of glioma susceptibility to CD8+ T cells, and anti-PD-1 across all kinases. Experimentally-induced ERK phosphorylation in gliomas enhanced survival with ICB treatment, led to durable anti-tumoral immunity upon re-challenge and memory T cell infiltration in long-term survivors. Elevated p-ERK in glioma cells correlated with increased interferon responses, antigen presentation and T cell infiltration in GB. Moreover, spatial transcriptomics and scRNA-seq analysis revealed the modulation of interferon responses by the MAPK/ERK pathway in BRAFV600E human GB cells with ERK1/2 knockout and in slice cultures of human BRAFV600E GB tissue. Notably, BRAFi/MEKi treatment disrupted the interaction between tumor cells and tumor-associated macrophages/microglia in slice cultures from BRAFV600E mutant GB.

Conclusion

Our data indicate that the MAPK/ERK pathway is a critical regulator of GB cell susceptibility to anti-tumoral immunity, modulating interferon responses, and antigen-presentation in glioma cells, as well as tumor cell interaction with microglia. These findings not only elucidate the mechanistic underpinnings of immunotherapy resistance in GB but also highlight the MAPK/ERK pathway as a promising target for enhancing immunotherapeutic efficacy in this challenging malignancy.

Enhancing cancer immunotherapy: Nanotechnology-mediated immunotherapy overcoming immunosuppression

Immunotherapy is an important cancer treatment method that offers hope for curing cancer patients. While immunotherapy has achieved initial success, a major obstacle to its widespread adoption is the inability to benefit the majority of patients. The success or failure of immunotherapy is closely linked to the tumor's immune microenvironment. Recently, there has been significant attention on strategies to regulate the tumor immune microenvironment in order to stimulate anti-tumor immune responses in cancer immunotherapy. The distinctive physical properties and design flexibility of nanomedicines have been extensively utilized to target immune cells (including tumor-associated macrophages (TAMs), T cells, myeloid-derived suppressor cells (MDSCs), and tumor-associated fibroblasts (TAFs)), offering promising advancements in cancer immunotherapy. In this article, we have reviewed treatment strategies aimed at targeting various immune cells to regulate the tumor immune microenvironment. The focus is on cancer immunotherapy models that are based on nanomedicines, with the goal of inducing or enhancing anti-tumor immune responses to improve immunotherapy. It is worth noting that combining cancer immunotherapy with other treatments, such as chemotherapy, radiotherapy, and photodynamic therapy, can maximize the therapeutic effects. Finally, we have identified the challenges that nanotechnology-mediated immunotherapy needs to overcome in order to design more effective nanosystems.

Glioblastoma stem cell metabolism and immunity

Despite enormous efforts being invested in the development of novel therapies for brain malignancies, there remains a dire need for effective treatments, particularly for pediatric glioblastomas. Their poor prognosis has been attributed to the fact that conventional therapies target tumoral cells, but not glioblastoma stem cells (GSCs). GSCs are characterized by self-renewal, tumorigenicity, poor differentiation, and resistance to therapy. These characteristics represent the fundamental tools needed to recapitulate the tumor and result in a relapse. The mechanisms by which GSCs alter metabolic cues and escape elimination by immune cells are discussed in this article, along with potential strategies to harness effector immune cells against GSCs. As cellular immunotherapy is making significant advances in a variety of cancers, leveraging this underexplored reservoir may result in significant improvements in the treatment options for brain malignancies.

Classical Monocytes Shuttling for Precise Delivery of Nanotherapeutics to Glioblastoma

Glioblastoma (GBM) is the most aggressive brain tumor for which current therapies have limited efficacy. Immunosuppression and difficulties in accessing tumors with therapeutic agents are major obstacles for GBM treatments. Classical monocytes (CMs) possess the strongest infiltration among myeloid cells recruited into tumors during tumorigenesis. In this study, CMs are utilized to deliver the small-molecule CUDC-907 encapsulated in nanoparticles (907-NPs@CMs) for GBM therapy. Hitchhiking on CMs enables more 907-NPs to successfully penetrate the blood-brain barrier (BBB) and reach the interior of tumors. Results demonstrate that 907-NPs@CMs significantly improve the survival rates by suppressing tumor growth and reversing the immunosuppression of tumor microenvironment (TME). Furthermore, the high delivery efficiency of CMs reduces the amount of CUDC-907 required for treatments, reducing the physiological toxicity and off-target effects caused by high doses. 907-NPs@CMs is a safe and versatile therapeutic system that provides a platform for targeted drug delivery to tumors and the ability to treat GBM through a combination of chemotherapy and immunotherapy.

Deciphering Regulatory T-Cell Dynamics in Cancer Immunotherapy: Mechanisms, Implications, and Therapeutic Innovations

This Review explores how tumor-associated regulatory cells (Tregs) affect cancer immunotherapy. It shows how Tregs play a role in keeping the immune system in check, how cancers grow, and how well immunotherapy work. Tregs use many ways to suppress the immune system, and these ways are affected by the tumor microenvironment (TME). New approaches to cancer therapy are showing promise, such as targeting Treg checkpoint receptors precisely and using Fc-engineered antibodies. It is important to tailor treatments to each patient's TME in order to provide personalized care. Understanding Treg biology is essential for creating effective cancer treatments and improving the long-term outcomes of immunotherapy.

Deacetylase SIRT2 Inhibition Promotes Microglial M2 Polarization Through Axl/PI3K/AKT to Alleviate White Matter Injury After Subarachnoid Hemorrhage

White matter injury (WMI) subsequent to subarachnoid hemorrhage (SAH) frequently leads to an unfavorable patient prognosis. Previous studies have indicated that microglial M1 polarization following SAH results in the accumulation of amyloid precursor protein (APP) and degradation of myelin basic protein (MBP), thereby catalyzing the exacerbation of WMI. Consequently, transitioning microglial polarization towards the M2 phenotype (neuroprotective state) represents a potential therapeutic approach for reversing WMI. The SIRT2 gene is pivotal in neurological disorders such as neurodegeneration and ischemic stroke. However, its function and underlying mechanisms in SAH, particularly how it influences microglial function to ameliorate WMI, remain unclear. Our investigations revealed that in post-SAH, there was a temporal increase in SIRT2 expression, predominantly in the cerebral corpus callosum area, with notable colocalization with microglia. However, following the administration of the SIRT2 inhibitor AK-7, a shift in microglial polarization towards the M2 phenotype and an improvement in both short-term and long-term neuronal functions in rats were observed. Mechanistically, CO-IP experiments confirmed that SIRT2 can interact with the receptor tyrosine kinase Axl within the TAM receptor family and act as a deacetylase to regulate the deacetylation of Axl. Concurrently, the inhibition of SIRT2 by AK-7 can lead to increased expression of Axl and activation of the anti-inflammatory pathway PI3K/Akt signaling pathway, which regulates microglial M2 polarization and consequently reduces WMI. However, when Axl expression was inhibited by the injection of the shAxl virus into the lateral ventricles, the downstream signaling pathways were significantly suppressed. Rescue experiments also confirmed that the neuroprotective effects of AK-7 can be reversed by PI3K inhibitors. These data suggest that SIRT2 influences WMI by affecting microglial polarization through the Axl/PI3K/AKT pathway, and that AK-7 could serve as an effective therapeutic drug for improving neurological functions in SAH patients.

Advancing precision medicine in gliomas through single-cell sequencing: unveiling the complex tumor microenvironment

Glioblastoma (GBM) displays an infiltrative growth characteristic that recruits neighboring normal cells to facilitate tumor growth, maintenance, and invasion into the brain. While the blood-brain barrier serves as a critical natural defense mechanism for the central nervous system, GBM disrupts this barrier, resulting in the infiltration of macrophages from the peripheral bone marrow and the activation of resident microglia. Recent advancements in single-cell transcriptomics and spatial transcriptomics have refined the categorization of cells within the tumor microenvironment for precise identification. The intricate interactions and influences on cell growth within the tumor microenvironment under multi-omics conditions are succinctly outlined. The factors and mechanisms involving microglia, macrophages, endothelial cells, and T cells that impact the growth of GBM are individually examined. The collaborative mechanisms of tumor cell-immune cell interactions within the tumor microenvironment synergistically promote the growth, infiltration, and metastasis of gliomas, while also influencing the immune status and therapeutic response of the tumor microenvironment. As immunotherapy continues to progress, targeting the cells within the inter-tumor microenvironment emerges as a promising novel therapeutic approach for GBM. By comprehensively understanding and intervening in the intricate cellular interactions within the tumor microenvironment, novel therapeutic modalities may be developed to enhance treatment outcomes for patients with GBM.

Phagocytosis Checkpoints in Glioblastoma: CD47 and Beyond

Glioblastoma multiforme (GBM) is one of the deadliest human cancers with very limited treatment options available. The malignant behavior of GBM is manifested in a tumor which is highly invasive, resistant to standard cytotoxic chemotherapy, and strongly immunosuppressive. Immune checkpoint inhibitors have recently been introduced in the clinic and have yielded promising results in certain cancers. GBM, however, is largely refractory to these treatments. The immune checkpoint CD47 has recently gained attention as a potential target for intervention as it conveys a "don't eat me" signal to tumor-associated macrophages (TAMs) via the inhibitory SIRP alpha protein. In preclinical models, the administration of anti-CD47 monoclonal antibodies has shown impressive results with GBM and other tumor models. Several well-characterized oncogenic pathways have recently been shown to regulate CD47 expression in GBM cells and glioma stem cells (GSCs) including Epidermal Growth Factor Receptor (EGFR) beta catenin. Other macrophage pathways involved in regulating phagocytosis including TREM2 and glycan binding proteins are discussed as well. Finally, chimeric antigen receptor macrophages (CAR-Ms) could be leveraged for greatly enhancing the phagocytosis of GBM and repolarization of the microenvironment in general. Here, we comprehensively review the mechanisms that regulate the macrophage phagocytosis of GBM cells.

Role of gut microbiota in regulating immune checkpoint inhibitor therapy for glioblastoma

Glioblastoma (GBM) is a highly malignant, invasive, and poorly prognosed brain tumor. Unfortunately, active comprehensive treatment does not significantly prolong patient survival. With the deepening of research, it has been found that gut microbiota plays a certain role in GBM, and can directly or indirectly affect the efficacy of immune checkpoint inhibitors (ICIs) in various ways. (1) The metabolites produced by gut microbiota directly affect the host's immune homeostasis, and these metabolites can affect the function and distribution of immune cells, promote or inhibit inflammatory responses, affect the phenotype, angiogenesis, inflammatory response, and immune cell infiltration of GBM cells, thereby affecting the effectiveness of ICIs. (2) Some members of the gut microbiota may reverse T cell function inhibition, increase T cell anti-tumor activity, and ultimately improve the efficacy of ICIs by targeting specific immunosuppressive metabolites and cytokines. (3) Some members of the gut microbiota directly participate in the metabolic process of drugs, which can degrade, transform, or produce metabolites, affecting the effective concentration and bioavailability of drugs. Optimizing the structure of the gut microbiota may help improve the efficacy of ICIs. (4) The gut microbiota can also regulate immune cell function and inflammatory status in the brain through gut brain axis communication, indirectly affecting the progression of GBM and the therapeutic response to ICIs. (5) Given the importance of gut microbiota for ICI therapy, researchers have begun exploring the use of fecal microbiota transplantation (FMT) to transplant healthy or optimized gut microbiota to GBM patients, in order to improve their immune status and enhance their response to ICI therapy. Preliminary studies suggest that FMT may enhance the efficacy of ICI therapy in some patients. In summary, gut microbiota plays a crucial role in regulating ICIs in GBM, and with a deeper understanding of the relationship between gut microbiota and tumor immunity, it is expected to develop more precise and effective personalized ICI therapy strategies for GBM, in order to improve patient prognosis.

Non-targeted effects of radiation therapy for glioblastoma

Radiotherapy is recommended for the treatment of brain tumors such as glioblastoma (GBM) and brain metastases. Various curative and palliative scenarios suggest improved local-regional control. Although the underlying mechanisms are not yet clear, additional therapeutic effects have been described, including proximity and abscopal reactions at the treatment site. Clinical and preclinical data suggest that the immune system plays an essential role in regulating the non-targeted effects of radiotherapy for GBM. This article reviews current biological mechanisms for regulating the non-targeted effects caused by external and internal radiotherapy, and how they might be applied in a clinical context. Optimization of therapeutic regimens requires assessment of the complexity of the host immune system on the activity of immunosuppressive or immunostimulatory cells, such as glioma-associated macrophages and microglia. This article also discusses recent preclinical models adapted to post-radiotherapy responses. This narrative review explores and discusses the current status of immune responses both locally via the "bystander effect" and remotely via the "abscopal effect". Preclinical and clinical observations demonstrate that unirradiated cells, near or far from the irradiation site, can control the tumor response. Nevertheless, previous studies do not address the problem in its global context, and present gaps regarding the link between the role of the immune system in the control of non-targeted effects for different types of radiotherapy and different fractionation schemes applied to GBM. This narrative synthesis of the scientific literature should help to update and critique available preclinical and medical knowledge. Indirectly, it will help formulate new research projects based on the synthesis and interpretation of results from a non-systematic selection of published studies.

GAS-Luc2 Reporter Cell Lines for Immune Checkpoint Drug Screening in Solid Tumors

Recent studies highlight the integral role of the interferon gamma receptor (IFNγR) pathway in T cell-mediated cytotoxicity against solid but not liquid tumors. IFNγ not only directly facilitates tumor cell death by T cells but also indirectly promotes cytotoxicity via myeloid phagocytosis in the tumor microenvironment. Meanwhile, full human ex vivo immune checkpoint drug screening remains challenging. We hypothesized that an engineered gamma interferon activation site response element luciferase reporter (GAS-Luc2) can be utilized for immune checkpoint drug screening in diverse ex vivo T cell-solid tumor cell co-culture systems. We comprehensively profiled cell surface proteins in ATCC's extensive collection of human tumor and immune cell lines, identifying those with endogenously high expression of established and novel immune checkpoint molecules and binding ligands. We then engineered three GAS-Luc2 reporter tumor cell lines expressing immune checkpoints PD-L1, CD155, or B7-H3/CD276. Luciferase expression was suppressed upon relevant immune checkpoint-ligand engagement. In the presence of an immune checkpoint inhibitor, T cells released IFNγ, activating the JAK-STAT pathway in GAS-Luc2 cells, and generating a quantifiable bioluminescent signal for inhibitor evaluation. These reporter lines also detected paracrine IFNγ signaling for immune checkpoint-targeted ADCC drug screening. Further development into an artificial antigen-presenting cell line (aAPC) significantly enhanced T cell signaling for superior performance in these ex vivo immune checkpoint drug screening platforms.

Glucose-driven histone lactylation promotes the immunosuppressive activity of monocyte-derived macrophages in glioblastoma

Immunosuppressive macrophages restrict anti-cancer immunity in glioblastoma (GBM). Here, we studied the contribution of microglia (MGs) and monocyte-derived macrophages (MDMs) to immunosuppression and mechanisms underlying their regulatory function. MDMs outnumbered MGs at late tumor stages and suppressed T cell activity. Molecular and functional analysis identified a population of glycolytic MDM expressing GLUT1 with potent immunosuppressive activity. GBM-derived factors promoted high glycolysis, lactate, and interleukin-10 (IL-10) production in MDMs. Inhibition of glycolysis or lactate production in MDMs impaired IL-10 expression and T cell suppression. Mechanistically, intracellular lactate-driven histone lactylation promoted IL-10 expression, which was required to suppress T cell activity. GLUT1 expression on MDMs was induced downstream of tumor-derived factors that activated the PERK-ATF4 axis. PERK deletion in MDM abrogated histone lactylation, led to the accumulation of intratumoral T cells and tumor growth delay, and, in combination with immunotherapy, blocked GBM progression. Thus, PERK-driven glucose metabolism promotes MDM immunosuppressive activity via histone lactylation.

TREM2 mediates MHCII-associated CD4+ T-cell response against gliomas

BACKGROUND

Myeloid cells comprise up to 50% of the total tumor mass in glioblastoma (GBM) and have been implicated in promoting tumor progression and immunosuppression. Modulating the response of myeloid cells to the tumor has emerged as a promising new approach for cancer treatment. In this regard, we focus on the Triggering Receptor Expressed on Myeloid Cells 2 (TREM2), which has recently emerged as a novel immune modulator in peripheral tumors.

METHODS

We studied the TREM2 expression profile in various patient tumor samples and conducted single-cell transcriptomic analysis in both GBM patients and the GL261 mouse glioma model. We utilized multiple mouse glioma models and employed state-of-the-art techniques such as invivo 2-photon imaging, spectrum flow cytometry, and in vitro co-culture assays to study TREM2 function in myeloid cell-mediated phagocytosis of tumor cells, antigen presentation, and response of CD4+ T cells within the tumor hemispheres.

RESULTS

Our research revealed significantly elevated levels of TREM2 expression in brain tumors compared to other types of tumors in patients. TREM2 was predominantly localized in tumor-associated myeloid cells and was highly expressed in nearly all microglia, as well as various subtypes of macrophages. Surprisingly, in preclinical glioma models, TREM2 deficiency did not confer a beneficial effect; instead, it accelerated glioma progression. Through detailed investigations, we determined that TREM2 deficiency impaired the ability of tumor-myeloid cells to phagocytose tumor cells and led to reduced expression of MHCII. This deficiency further significantly decreased the presence of CD4+ T cells within the tumor hemispheres.

CONCLUSIONS

Our study unveiled a previously unrecognized protective role of tumor-myeloid TREM2. Specifically, we found that TREM2 enhances the phagocytosis of tumor cells and promotes an immune response by facilitating MHCII-associated CD4+ T-cell responses against gliomas.

Machine Learning Links T-cell Function and Spatial Localization to Neoadjuvant Immunotherapy and Clinical Outcome in Pancreatic Cancer

Tumor molecular data sets are becoming increasingly complex, making it nearly impossible for humans alone to effectively analyze them. Here, we demonstrate the power of using machine learning (ML) to analyze a single-cell, spatial, and highly multiplexed proteomic data set from human pancreatic cancer and reveal underlying biological mechanisms that may contribute to clinical outcomes. We designed a multiplex immunohistochemistry antibody panel to compare T-cell functionality and spatial localization in resected tumors from treatment-naïve patients with localized pancreatic ductal adenocarcinoma (PDAC) with resected tumors from a second cohort of patients treated with neoadjuvant agonistic CD40 (anti-CD40) monoclonal antibody therapy. In total, nearly 2.5 million cells from 306 tissue regions collected from 29 patients across both cohorts were assayed, and over 1,000 tumor microenvironment (TME) features were quantified. We then trained ML models to accurately predict anti-CD40 treatment status and disease-free survival (DFS) following anti-CD40 therapy based on TME features. Through downstream interpretation of the ML models' predictions, we found anti-CD40 therapy reduced canonical aspects of T-cell exhaustion within the TME, as compared with treatment-naïve TMEs. Using automated clustering approaches, we found improved DFS following anti-CD40 therapy correlated with an increased presence of CD44+CD4+ Th1 cells located specifically within cellular neighborhoods characterized by increased T-cell proliferation, antigen experience, and cytotoxicity in immune aggregates. Overall, our results demonstrate the utility of ML in molecular cancer immunology applications, highlight the impact of anti-CD40 therapy on T cells within the TME, and identify potential candidate biomarkers of DFS for anti-CD40-treated patients with PDAC.

Glioblastoma-instructed microglia transition to heterogeneous phenotypic states with phagocytic and dendritic cell-like features in patient tumors and patient-derived orthotopic xenografts

BACKGROUND

A major contributing factor to glioblastoma (GBM) development and progression is its ability to evade the immune system by creating an immune-suppressive environment, where GBM-associated myeloid cells, including resident microglia and peripheral monocyte-derived macrophages, play critical pro-tumoral roles. However, it is unclear whether recruited myeloid cells are phenotypically and functionally identical in GBM patients and whether this heterogeneity is recapitulated in patient-derived orthotopic xenografts (PDOXs). A thorough understanding of the GBM ecosystem and its recapitulation in preclinical models is currently missing, leading to inaccurate results and failures of clinical trials.

METHODS

Here, we report systematic characterization of the tumor microenvironment (TME) in GBM PDOXs and patient tumors at the single-cell and spatial levels. We applied single-cell RNA sequencing, spatial transcriptomics, multicolor flow cytometry, immunohistochemistry, and functional studies to examine the heterogeneous TME instructed by GBM cells. GBM PDOXs representing different tumor phenotypes were compared to glioma mouse GL261 syngeneic model and patient tumors.

RESULTS

We show that GBM tumor cells reciprocally interact with host cells to create a GBM patient-specific TME in PDOXs. We detected the most prominent transcriptomic adaptations in myeloid cells, with brain-resident microglia representing the main population in the cellular tumor, while peripheral-derived myeloid cells infiltrated the brain at sites of blood-brain barrier disruption. More specifically, we show that GBM-educated microglia undergo transition to diverse phenotypic states across distinct GBM landscapes and tumor niches. GBM-educated microglia subsets display phagocytic and dendritic cell-like gene expression programs. Additionally, we found novel microglial states expressing cell cycle programs, astrocytic or endothelial markers. Lastly, we show that temozolomide treatment leads to transcriptomic plasticity and altered crosstalk between GBM tumor cells and adjacent TME components.

CONCLUSIONS

Our data provide novel insights into the phenotypic adaptation of the heterogeneous TME instructed by GBM tumors. We show the key role of microglial phenotypic states in supporting GBM tumor growth and response to treatment. Our data place PDOXs as relevant models to assess the functionality of the TME and changes in the GBM ecosystem upon treatment.

Regulation and impact of tumor-specific CD4+ T cells in cancer and immunotherapy

CD4+ T cells are crucial in generating and sustaining immune responses. They orchestrate and fine-tune mammalian innate and adaptive immunity through cell-based interactions and the release of cytokines. The role of these cells in contributing to the efficacy of antitumor immunity and immunotherapy has just started to be uncovered. Yet, many aspects of the CD4+ T cell response are still unclear, including the differentiation pathways controlling such cells during cancer progression, the external signals that program them, and how the combination of these factors direct ensuing immune responses or immune-restorative therapies. In this review, we focus on recent advances in understanding CD4+ T cell regulation during cancer progression and the importance of CD4+ T cells in immunotherapies.

Epigenetic remodeling to improve the efficacy of immunotherapy in human glioblastoma: pre-clinical evidence for development of new immunotherapy approaches

BACKGROUND

Glioblastoma multiforme (GBM) is a highly aggressive primary brain tumor, that is refractory to standard treatment and to immunotherapy with immune-checkpoint inhibitors (ICI). Noteworthy, melanoma brain metastases (MM-BM), that share the same niche as GBM, frequently respond to current ICI therapies. Epigenetic modifications regulate GBM cellular proliferation, invasion, and prognosis and may negatively regulate the cross-talk between malignant cells and immune cells in the tumor milieu, likely contributing to limit the efficacy of ICI therapy of GBM. Thus, manipulating the tumor epigenome can be considered a therapeutic opportunity in GBM.

METHODS

Microarray transcriptional and methylation profiles, followed by gene set enrichment and IPA analyses, were performed to study the differences in the constitutive expression profiles of GBM vs MM-BM cells, compared to the extracranial MM cells and to investigate the modulatory effects of the DNA hypomethylating agent (DHA) guadecitabine among the different tumor cells. The prognostic relevance of DHA-modulated genes was tested by Cox analysis in a TCGA GBM patients' cohort.

RESULTS

The most striking differences between GBM and MM-BM cells were found to be the enrichment of biological processes associated with tumor growth, invasion, and extravasation with the inhibition of MHC class II antigen processing/presentation in GBM cells. Treatment with guadecitabine reduced these biological differences, shaping GBM cells towards a more immunogenic phenotype. Indeed, in GBM cells, promoter hypomethylation by guadecitabine led to the up-regulation of genes mainly associated with activation, proliferation, and migration of T and B cells and with MHC class II antigen processing/presentation. Among DHA-modulated genes in GBM, 7.6% showed a significant prognostic relevance. Moreover, a large set of immune-related upstream-regulators (URs) were commonly modulated by DHA in GBM, MM-BM, and MM cells: DHA-activated URs enriched for biological processes mainly involved in the regulation of cytokines and chemokines production, inflammatory response, and in Type I/II/III IFN-mediated signaling; conversely, DHA-inhibited URs were involved in metabolic and proliferative pathways.

CONCLUSIONS

Epigenetic remodeling by guadecitabine represents a promising strategy to increase the efficacy of cancer immunotherapy of GBM, supporting the rationale to develop new epigenetic-based immunotherapeutic approaches for the treatment of this still highly deadly disease.

Signaling Pathways of AXL Receptor Tyrosine Kinase Contribute to the Pathogenetic Mechanisms of Glioblastoma

Brain tumors are a diverse collection of neoplasms affecting the brain with a high prevalence rate in people of all ages around the globe. In this pathological context, glioblastoma, a form of glioma that belongs to the IV-grade astrocytoma group, is the most common and most aggressive form of the primary brain tumors. Indeed, despite the best treatments available including surgery, radiotherapy or a pharmacological approach with Temozolomide, glioblastoma patients' mortality is still high, within a few months of diagnosis. Therefore, to increase the chances of these patients surviving, it is critical to keep finding novel treatment opportunities. In the past, efforts to treat glioblastoma have mostly concentrated on customized treatment plans that target specific mutations such as epidermal growth factor receptor (EGFR) mutations, Neurotrophic Tyrosine Receptor Kinase (NTRK) fusions, or multiple receptors using multi-kinase inhibitors like Sunitinib and Regorafenib, with varying degrees of success. Here, we focused on the receptor tyrosine kinase AXL that has been identified as a mediator for tumor progression and therapy resistance in various cancer types, including squamous cell tumors, small cell lung cancer, and breast cancer. Activated AXL leads to a significant increase in tumor proliferation, tumor cell migration, and angiogenesis in different in vitro and in vivo models of cancer since this receptor regulates interplay with apoptotic, angiogenic and inflammatory pathways. Based on these premises, in this review we mainly focused on the role of AXL in the course of glioblastoma, considering its primary biological mechanisms and as a possible target for the application of the most recent treatments.

Understanding current experimental models of glioblastoma-brain microenvironment interactions

Glioblastoma (GBM) is a common and devastating primary brain tumor, with median survival of 16-18 months after diagnosis in the setting of substantial resistance to standard-of-care and inevitable tumor recurrence. Recent work has implicated the brain microenvironment as being critical for GBM proliferation, invasion, and resistance to treatment. GBM does not operate in isolation, with neurons, astrocytes, and multiple immune populations being implicated in GBM tumor progression and invasiveness. The goal of this review article is to provide an overview of the available in vitro, ex vivo, and in vivo experimental models for assessing GBM-brain interactions, as well as discuss each model's relative strengths and limitations. Current in vitro models discussed will include 2D and 3D co-culture platforms with various cells of the brain microenvironment, as well as spheroids, whole organoids, and models of fluid dynamics, such as interstitial flow. An overview of in vitro and ex vivo organotypic GBM brain slices is also provided. Finally, we conclude with a discussion of the various in vivo rodent models of GBM, including xenografts, syngeneic grafts, and genetically-engineered models of GBM.

Uniting innate and adaptive immunity in glioblastoma; an α-CTLA-4 quest

Immunotherapies have thus far led to disappointing outcomes in patients suffering from glioblastoma. Published in Immunity, Chen et al.'s recent study shows the therapeutic potential of an αCTLA-4 antibody (Ab), specifically in murine mesenchymal-like glioblastoma. αCTLA-4 Ab efficacy relied on the distinctive cooperation between CD4+ Th1 T cells and microglia, unleashing a potent antitumor response.

Expansion of CD4+ cytotoxic T lymphocytes with specific gene expression patterns may contribute to suppression of tumor immunity in oral squamous cell carcinoma: single-cell analysis and in vitro experiments

Background

Cancer immunotherapy targeting CD8+ T cells has made remarkable progress, even for oral squamous cell carcinoma (OSCC), a heterogeneous epithelial tumor without a substantial increase in the overall survival rate over the past decade. However, the therapeutic effects remain limited due to therapy resistance. Thus, a more comprehensive understanding of the roles of CD4+ T cells and B cells is crucial for more robust development of cancer immunotherapy.

Methods

In this study, we examined immune responses and effector functions of CD4+ T cells, CD8+ T cells and B cells infiltrating in OSCC lesions using single-cell RNA sequencing analysis, T cell receptor (TCR) and B cell receptor (BCR) repertoire sequencing analysis, and multi-color immunofluorescence staining. Finally, two Kaplan-Meier curves and several Cox proportional hazards models were constructed for the survival analysis.

Results

We observed expansion of CD4+ cytotoxic T lymphocytes (CTLs) expressing granzymes, which are reported to induce cell apoptosis, with a unique gene expression patterns. CD4+ CTLs also expressed CXCL13, which is a B cell chemoattractant. Cell-cell communication analysis and multi-color immunofluorescence staining demonstrated potential interactions between CD4+ CTLs and B cells, particularly IgD- CD27- double negative (DN) B cells. Expansion of CD4+ CTLs, DN B cells, and their contacts has been reported in T and B cell-activated diseases, including IgG4-related disease and COVID-19. Notably, we observed upregulation of several inhibitory receptor genes including CTLA-4 in CD4+ CTLs, which possibly dampened T and B cell activity. We next demonstrated comprehensive delineation of the potential for CD8+ T cell differentiation towards dysfunctional states. Furthermore, prognostic analysis revealed unfavorable outcomes of patients with a high proportion of CD4+ CTLs in OSCC lesions.

Conclusion

Our study provides a dynamic landscape of lymphocytes and demonstrates a systemic investigation of CD4+ CTL effects infiltrating into OSCC lesions, which may share some pathogenesis reported in severe T and B cell-activated diseases such as autoimmune and infectious diseases.

Machine learning links T cell function and spatial localization to neoadjuvant immunotherapy and clinical outcome in pancreatic cancer

Tumor molecular datasets are becoming increasingly complex, making it nearly impossible for humans alone to effectively analyze them. Here, we demonstrate the power of using machine learning to analyze a single-cell, spatial, and highly multiplexed proteomic dataset from human pancreatic cancer and reveal underlying biological mechanisms that may contribute to clinical outcome. A novel multiplex immunohistochemistry antibody panel was used to audit T cell functionality and spatial localization in resected tumors from treatment-naive patients with localized pancreatic ductal adenocarcinoma (PDAC) compared to a second cohort of patients treated with neoadjuvant agonistic CD40 (αCD40) monoclonal antibody therapy. In total, nearly 2.5 million cells from 306 tissue regions collected from 29 patients across both treatment cohorts were assayed, and more than 1,000 tumor microenvironment (TME) features were quantified. We then trained machine learning models to accurately predict αCD40 treatment status and disease-free survival (DFS) following αCD40 therapy based upon TME features. Through downstream interpretation of the machine learning models' predictions, we found αCD40 therapy to reduce canonical aspects of T cell exhaustion within the TME, as compared to treatment-naive TMEs. Using automated clustering approaches, we found improved DFS following αCD40 therapy to correlate with the increased presence of CD44+ CD4+ Th1 cells located specifically within cellular spatial neighborhoods characterized by increased T cell proliferation, antigen-experience, and cytotoxicity in immune aggregates. Overall, our results demonstrate the utility of machine learning in molecular cancer immunology applications, highlight the impact of αCD40 therapy on T cells within the TME, and identify potential candidate biomarkers of DFS for αCD40-treated patients with PDAC.