scholarly journals The landscape of bispecific T cell engager in cancer treatment

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Shujie Zhou ◽  
Mingguo Liu ◽  
Fei Ren ◽  
Xiangjiao Meng ◽  
Jinming Yu
Keyword(s):  
T Cells ◽  
T Cell ◽  
Immune Cell ◽  
Immune Checkpoints ◽  
T Cell Infiltration ◽  
Combination Strategies ◽  
Response Predictors ◽  
Current Therapies ◽  
Antigen Loss ◽  
Bispecific T Cell Engager

AbstractT cell-based immunotherapies have revolutionized treatment paradigms in various cancers, however, limited response rates secondary to lack of significant T-cell infiltration in the tumor site remain a major problem. To address this limitation, strategies for redirecting T cells to treat cancer are being intensively investigated, while the bispecific T cell engager (BiTE) therapy constitutes one of the most promising therapeutic approaches. BiTE is a bispecific antibody construct with a unique function, simultaneously binding an antigen on tumor cells and a surface molecule on T cells to induce tumor lysis. BiTE therapy represented by blinatumomab has achieved impressive efficacy in the treatment of B cell malignancies. However, major mechanisms of resistance to BiTE therapy are associated with antigen loss and immunosuppressive factors such as the upregulation of immune checkpoints. Thus, modification of antibody constructs and searching for combination strategies designed to further enhance treatment efficacy as well as reduce toxicity has become an urgent issue, especially for solid tumors in which response to BiTE therapy is always poor. In particular, immunotherapies focusing on innate immunity have attracted increasing interest and have shown promising anti-tumor activity by engaging innate cells or innate-like cells, which can be used alone or complement current therapies. In this review, we depict the landscape of BiTE therapy, including clinical advances with potential response predictors, challenges of treatment toxicity and resistance, and developments of novel immune cell-based engager therapy.

scholarly journals DNA Methylation based glioblastoma subclassification is related to tumoral T cell infiltration and patient survival

2020 ◽  
Author(s):  
Joost Dejaegher ◽  
Lien Solie ◽  
Zoé Hunin ◽  
Raf Sciot ◽  
David Capper ◽  
...  
Keyword(s):  
Dna Methylation ◽  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Immune Cell ◽  
Methylation Pattern ◽  
Response To Therapy ◽  
Cell Infiltration ◽  
Mesenchymal Tumors ◽  
T Cell Infiltration

Abstract Background Histologically classified Glioblastomas (GBM) can have different clinical behavior and response to therapy, for which molecular subclassifications have been proposed. We evaluated the relationship of epigenetic GBM subgroups with immune cell infiltrations, systemic immune changes during radiochemotherapy and clinical outcome. Methods 450K genome-wide DNA methylation was assessed on tumor tissue from 93 patients with newly diagnosed GBM, treated with standard radiochemotherapy and experimental immunotherapy. Tumor infiltration of T cells, myeloid cells and PD-1 expression were evaluated. Circulating immune cell populations and selected cytokines were assessed on blood samples taken before and after radiochemotherapy. Results Forty-two tumors had a mesenchymal, 27 a RTK II, 17 a RTK I and 7 an IDH DNA methylation pattern Mesenchymal tumors had the highest amount of tumor-infiltrating CD3+ and CD8+ T cells and IDH tumors the lowest. There were no significant differences for CD68+ cells, FoxP3+ cells and PD-1 expression between groups. Systemically, there was a relative increase of CD8+ T cells and CD8+ PD-1 expression and a relative decrease of CD4+ T cells after radiochemotherapy in all subgroups except IDH tumors. Overall survival was the longest in the IDH group (median 36 months), intermediate in RTK II tumors (27 months) and significantly lower in mesenchymal and RTK I groups (15.5 and 16 months respectively). Conclusions Methylation based stratification of GBM is related to T cell infiltration and survival, with IDH and mesenchymal tumors representing both ends of a spectrum. DNA methylation profiles could be useful in stratifying patients for immunotherapy trials.

Tumor-derived GDF-15 to suppress t-lymphocyte recruitment to the tumor microenvironment resulting in resistance to ANTI-PD-1 treatment.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e14532-e14532
Author(s):  
Joerg Wischhusen ◽  
Markus Haake ◽  
Neha Vashist ◽  
Sabrina Genßler ◽  
Kilian Wistuba-Hamprecht ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Immune Cell ◽  
Serum Levels ◽  
Cell Infiltration ◽  
Immune Cell Infiltration ◽  
T Cell Infiltration ◽  
Melanoma Patients

e14532 Background: Growth and differentiation factor 15 (GDF-15) is a divergent member of the TGF-β superfamily with low to absent expression in healthy tissue. GDF-15 has been linked to feto-maternal immune tolerance, to prevention of excessive immune cell infiltration during tissue damage, and to anorexia. Various major tumor types secrete high levels of GDF-15. In cancer patients, elevated GDF-15 serum levels correlate with poor prognosis and reduced overall survival (OS). Methods: Impact of a proprietary GDF-15 neutralizing antibody (CTL-002) regarding T cell trafficking was analyzed by whole blood adhesion assays, a HV18-MK melanoma-bearing humanized mouse model and a GDF-15-transgenic MC38 model. Additionally, patient GDF-15 serum levels were correlated with clinical response and overall survival in oropharyngeal squamous cell carcinoma (OPSCC) and melanoma brain metastases. Results: In whole blood cell adhesion assays GDF-15 impairs adhesion of T and NK cells to activated endothelial cells. Neutralization of GDF-15 by CTL-002 rescued T cell adhesion. In HV18-MK-bearing humanized mice CTL-002 induced a strong increase in TIL numbers. Subset analysis revealed an overproportional enrichment of T cells, in particular CD8+ T cells. As immune cell exclusion is detrimental for checkpoint inhibitor (CPI) therapy, a GDF-15-transgenic MC38 model was tested for anti-PD-1 therapy efficacy. In GDF-15 overexpressing MC38 tumors response to anti PD-1 therapy was reduced by 90% compared to wtMC38 tumors. Combining aPD-1 with CTL-002 resulted in 50% of the mice rejecting their GDF-15 overexpressing tumors. Clinically, inverse correlations of GDF-15 levels with CD8+ T cell infiltration were shown for HPV+ OPSCC and for melanoma brain metastases. GDF-15 serum levels were significantly higher in HPV- than in HPV+ OPSCC patient (p < 0.0001). Low GDF-15 levels corresponded to longer OS in both HPV- and HPV+ OPSCC. In two independent melanoma patient cohorts treated with nivolumab or pembrolizumab low baseline serum GDF-15 levels were predictive for clinical response to anti-PD1 treatment and superior OS. Bivariate analysis including LDH indicates that GDF-15 independently predicts poor survival in aPD-1 treated melanoma patients. Conclusions: Taken together our in vitro and in vivo data show that elevated GDF-15 levels block T-cell infiltration into tumor tissues. Neutralizing GDF-15 with CTL-002 restores the ability of T cells to extravasate blood vessels and enter tumor tissue both in vitro and in vivo. In melanoma, patients with higher GDF-15 levels have significantly shorter survival and are less likely to respond to anti-PD1 therapy. GDF-15 may thus serve as a new predictive biomarker for anti-PD1 response, but most importantly also represents a novel target for cancer immunotherapy to improve tumor immune cell infiltration and response to anti-PD1 therapy.

Immunotherapy combinations overcome resistance to bispecific T cell engager treatment in T cell–cold solid tumors

2021 ◽  
Vol 13 (608) ◽  
pp. eabd1524
Author(s):  
Brian Belmontes ◽  
Deepali V. Sawant ◽  
Wendy Zhong ◽  
Hong Tan ◽  
Anupurna Kaul ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Solid Tumors ◽  
Immune Checkpoint Blockade ◽  
Clinical Activity ◽  
Cell Trafficking ◽  
Critical Determinant ◽  
Immune Correlates ◽  
Combination Strategies ◽  
Bispecific T Cell Engager

Therapeutic approaches are needed to promote T cell–mediated destruction of poorly immunogenic, “cold” tumors typically associated with minimal response to immune checkpoint blockade (ICB) therapy. Bispecific T cell engager (BiTE) molecules induce redirected lysis of cancer cells by polyclonal T cells and have demonstrated promising clinical activity against solid tumors in some patients. However, little is understood about the key factors that govern clinical responses to these therapies. Using an immunocompetent mouse model expressing a humanized CD3ε chain (huCD3e mice) and BiTE molecules directed against mouse CD19, mouse CLDN18.2, or human EPCAM antigens, we investigated the pharmacokinetic and pharmacodynamic parameters and immune correlates associated with BiTE efficacy across multiple syngeneic solid-tumor models. These studies demonstrated that pretreatment tumor-associated T cell density is a critical determinant of response to BiTE therapy, identified CD8+ T cells as important targets and mediators of BiTE activity, and revealed an antagonistic role for CD4+ T cells in BiTE efficacy. We also identified therapeutic combinations, including ICB and 4-1BB agonism, that synergized with BiTE treatment in poorly T cell–infiltrated, immunotherapy-refractory tumors. In these models, BiTE efficacy was dependent on local expansion of tumor-associated CD8+ T cells, rather than their recruitment from circulation. Our findings highlight the relative contributions of baseline T cell infiltration, local T cell proliferation, and peripheral T cell trafficking for BiTE molecule–mediated efficacy, identify combination strategies capable of overcoming resistance to BiTE therapy, and have clinical relevance for the development of BiTE and other T cell engager therapies.

Abstract 350: Immune Profiling and Causal Antigen Discovery in Mouse and Human Models of Immune Checkpoint Inhibitor-induced Myocarditis

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Han Zhu ◽  
Daniel Lee ◽  
Waliany Sarah ◽  
Francisco X Galdos ◽  
Jessica D’Addabbo ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Immune Checkpoint ◽  
Checkpoint Inhibitors ◽  
Myocardial Damage ◽  
T Cell Subsets ◽  
Immune Checkpoints ◽  
Fulminant Myocarditis ◽  
T Cell Infiltration ◽  
Life Threatening

Introduction: Immune checkpoint inhibitors (ICIs) are novel drugs that activate T cell-mediated anti-tumor response by blocking immune checkpoints such as PD-1 or CTLA-4, leading to improved cancer patient survival. Despite these benefits, ICIs can result in autoimmune side effects including fulminant myocarditis and heart failure. While ICI-induced myocarditis is characterized by myocardial T cell infiltration, the causal mechanisms remain unknown. We hypothesize that ICI-induced myocarditis is caused by cardiac-specific auto-antigens triggering clonal expansion of myocardial CD8+ T-cells, leading to T-cell mediated myocardial damage. Methods/Results: We have explored the ICI-induced inflammatory response in a mouse model of myocarditis induced by PD-1 knockout and in patients with ICI-induced myocarditis. PD-1 deficient-mice on a lupus-like autoimmune background (i.e. MRL/Pcd1-/- mice) develop spontaneous fatal myocarditis in 70% of animals by 5 weeks of age, with massive cardiac infiltration of CD8>CD4+ T-cells. Likewise, patients with ICI-induced myocarditis have CD8>CD4+ T-cell infiltrate in the heart. We have performed time-of-flight mass cytometry (CyTOF) to immunophenotype the T-cell subsets in the blood/myocardium of MRL/Pcd1-/- mice and in ICI-myocarditis patients. We have also conducted single cell sequencing of T-cell receptors (TCRs) from the blood +/- myocardial-derived T-cell samples of the mice and patients. Our preliminary results in ICI-myocarditis patients confirmed the previously reported CD8+ T-cell expansion in the blood and myocardium of myocarditis patients compared with healthy control. We are currently identifying candidate cardiac auto-antigen(s) responsible for this disease by performing Grouping Lymphocyte Interactions by Paratope Hotspots (GLIPH). Conclusion: Myocarditis is a serious and life-threatening complication of ICI treatment. By understanding the unique immune response present during ICI-induced myocarditis and the responsible cardiac auto-antigen(s) involved, we will pave the way for the development of adjuvant therapies that target these antigens and mitigate their deleterious effects.

scholarly journals The anti-tumor effects of cetuximab in combination with VTX-2337 are T cell dependent

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yinwen Cheng ◽  
Nicholas Borcherding ◽  
Ayomide Ogunsakin ◽  
Caitlin D. Lemke-Miltner ◽  
Katherine N. Gibson-Corley ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tumor Growth ◽  
Mouse Models ◽  
Cd8 T Cells ◽  
Immune Cell ◽  
Syngeneic Mouse ◽  
T Cell Infiltration ◽  
Cancer Immunotherapeutic

AbstractThe Toll-like receptor 8 (TLR8) agonist VTX-2337 (motolimod) is an anti-cancer immunotherapeutic agent that is believed to augment natural killer (NK) and dendritic cell (DC) activity. The goal of this work is to examine the role of TLR8 expression/activity in head and neck squamous cell carcinoma (HNSCC) to facilitate the prediction of responders to VTX-2337-based therapy. The prognostic role of TLR8 expression in HNSCC patients was assessed by TCGA and tissue microarray analyses. The anti-tumor effect of VTX-2337 was determined in SCCVII/C3H, mEERL/C57Bl/6 and TUBO-human EGFR/BALB/c syngeneic mouse models. The effect of combined VTX-2337 and cetuximab treatment on tumor growth, survival and immune cell recruitment was assessed. TLR8 expression was associated with CD8+ T cell infiltration and favorable survival outcomes. VTX-2337 delayed tumor growth in all 3 syngeneic mouse models and significantly increased the survival of cetuximab-treated mice. The anti-tumor effects of VTX-2337+ cetuximab were accompanied by increased splenic lymphoid DCs and IFNγ+ CD4+ and tumor-specific CD8+ T cells. Depletion of CD4+ T cells, CD8+ T cells and NK cells were all able to abolish the anti-tumor effect of VTX-2337+ cetuximab. Altogether, VTX-2337 remains promising as an adjuvant for cetuximab-based therapy however patients with high TLR8 expression may be more likely to derive benefit from this drug combination compared to patients with low TLR8 expression.

scholarly journals Tumoral HLA Class I and APM Expression and Its Effect on Intratumoral T-cell Reaction and Outcome in HPV-Negative Oral Squamous Cell Carcinoma

2020 ◽  
Author(s):  
Claudia Wickenhauser ◽  
Daniel Bethmann ◽  
Matthias Kappler ◽  
Alexander Walter Eckert ◽  
André Steven ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
T Cells ◽  
T Cell ◽  
Oral Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Cd8 T Cells ◽  
Immune Cell ◽  
Hla Class I ◽  
T Cell Infiltration

Progression of oral squamous cell carcinoma (OSCC) has been associated with an escape of tumor cells from the host immune surveillance with growing evidence of its underlying molecular mechanisms and its interaction with the immune cell control. In this study the expression of HLA class I (HLA-I) antigens and of components of the antigen processing machinery (APM) was analyzed in 160 consecutive human papilloma virus (HPV)-negative OSCC lesions and correlated to tumor specific parameters, the intratumoral immune cell response and to the patients outcome. A heterogeneous, but predominantly lower constitutive protein expression of HLA-I APM components was seen in OSCC sections when compared to non-neoplastic cells. Based on the expression levels of HLA-I APM components three main OSCC subgroups were detected and categorized into HLA-Ihigh/APMhigh, HLA-Ilow/APMlow and HLA-Idiscordant high/low/APMhigh phenotypes. In the HLA-Ihigh/APMhigh group, the highest frequency of intratumoral CD8+ T cells and lowest number of CD8+ T cells close to FoxP3 cells was found. Despite being associated with the highest T cell infiltration, patients within this group presented the most unfavorable survival, which was most evident in stage T2 tumors. Thus, the presented findings strongly indicate the presence of additional factors involved in the immunomodulatory process of HPV-negative OSCC with a possible tumor-burden-dependent complex network of immune escape mechanisms beyond HLA-I/APM components and T cell infiltration in this tumor entity.

scholarly journals Neoadjuvant PD-1 blockade induces T cell and cDC1 activation but fails to overcome the immunosuppressive tumor associated macrophages in recurrent glioblastoma

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alexander H. Lee ◽  
Lu Sun ◽  
Aaron Y. Mochizuki ◽  
Jeremy G. Reynoso ◽  
Joey Orpilla ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Immune Cell ◽  
Neoadjuvant Treatment ◽  
Recurrent Glioblastoma ◽  
T Cell Infiltration ◽  
Treatment Paradigm ◽  
Clinical Models ◽  
Chemotactic Factors

AbstractPrimary brain tumors, such as glioblastoma (GBM), are remarkably resistant to immunotherapy, even though pre-clinical models suggest effectiveness. To understand this better in patients, here we take advantage of our recent neoadjuvant treatment paradigm to map the infiltrating immune cell landscape of GBM and how this is altered following PD-1 checkpoint blockade using high dimensional proteomics, single cell transcriptomics, and quantitative multiplex immunofluorescence. Neoadjuvant PD-1 blockade increases T cell infiltration and the proportion of a progenitor exhausted population of T cells found within the tumor. We identify an early activated and clonally expanded CD8+ T cell cluster whose TCR overlaps with a CD8+ PBMC population. Distinct changes are also observed in conventional type 1 dendritic cells that may facilitate T cell recruitment. Macrophages and monocytes still constitute the majority of infiltrating immune cells, even after anti-PD-1 therapy. Interferon-mediated changes in the myeloid population are consistently observed following PD-1 blockade; these also mediate an increase in chemotactic factors that recruit T cells. However, sustained high expression of T-cell-suppressive checkpoints in these myeloid cells continue to prevent the optimal activation of the tumor infiltrating T cells. Therefore, future immunotherapeutic strategies may need to incorporate the targeting of these cells for clinical benefit.

scholarly journals Reversing Epigenetic Gene Silencing to Overcome Immune Evasion in CNS Malignancies

2021 ◽  
Vol 11 ◽  
Author(s):  
Nivedita M. Ratnam ◽  
Heather M. Sonnemann ◽  
Stephen C. Frederico ◽  
Huanwen Chen ◽  
Marsha-Kay N. D. Hutchinson ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tumor Growth ◽  
Immune Evasion ◽  
Immune Cell ◽  
Single Agent ◽  
Cell Infiltration ◽  
Cell Trafficking ◽  
T Cell Infiltration ◽  
Dismal Prognosis

Glioblastoma (GBM) is an aggressive brain malignancy with a dismal prognosis. With emerging evidence to disprove brain-immune privilege, there has been much interest in examining immunotherapy strategies to treat central nervous system (CNS) cancers. Unfortunately, the limited success of clinical studies investigating immunotherapy regimens, has led to questions about the suitability of immunotherapy for these cancers. Inadequate inherent populations of tumor infiltrating lymphocytes (TILs) and limited trafficking of systemic, circulating T cells into the CNS likely contribute to the poor response to immunotherapy. This paucity of TILs is in concert with the finding of epigenetic silencing of genes that promote immune cell movement (chemotaxis) to the tumor. In this study we evaluated the ability of GSK126, a blood-brain barrier (BBB) permeable small molecule inhibitor of EZH2, to reverse GBM immune evasion by epigenetic suppression of T cell chemotaxis. We also evaluated the in vivo efficacy of this drug in combination with anti-PD-1 treatment on tumor growth, survival and T cell infiltration in syngeneic mouse models. GSK126 reversed H3K27me3 in murine and human GBM cell lines. When combined with anti-PD-1 treatment, a significant increase in activated T cell infiltration into the tumor was observed. This resulted in decreased tumor growth and enhanced survival both in sub-cutaneous and intracranial tumors of immunocompetent, syngeneic murine models of GBM. Additionally, a significant increase in CXCR3+ T cells was also seen in the draining lymph nodes, suggesting their readiness to migrate to the tumor. Closer examination of the mechanism of action of GSK126 revealed its ability to promote the expression of IFN-γ driven chemokines CXCL9 and CXCL10 from the tumor cells, that work to traffic T cells without directly affecting T maturation and/or proliferation. The loss of survival benefit either with single agent or combination in immunocompromised SCID mice, suggest that the therapeutic efficacy of GSK126 in GBM is primarily driven by lymphocytes. Taken together, our data suggests that in glioblastoma, epigenetic modulation using GSK126 could improve current immunotherapy strategies by reversing the epigenetic changes that enable immune cell evasion leading to enhanced immune cell trafficking to the tumor.

Role of CD8+ T-cell infiltration in breast tumors of Black women compared to White women.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. e13608-e13608
Author(s):  
Yara Abdou ◽  
Kristopher Attwood ◽  
Song Yao ◽  
Ting-Yuan David Cheng ◽  
Elisa Bandera ◽  
...  
Keyword(s):  
Breast Cancer ◽  
T Cells ◽  
Black Women ◽  
T Cell ◽  
Cell Density ◽  
Immune Cell ◽  
Beta Blockers ◽  
Breast Cancer Patients ◽  
T Cell Infiltration ◽  
Black Patients

e13608 Background: Literature regarding racial differences in tumor immune responses in breast cancer remains sparse. To address this research gap, we assessed CD8+ T-cells in breast tumor samples from the Women’s Circle of Health Study (WCHS) population of predominantly Black breast cancer patients. We characterized and compared the density of CD8+ T cells, their prognostic value and their association with pharmacologic beta-blockers. Prior studies suggest that reducing adrenergic signaling through beta blockers can stimulate CD8+ T-cells. Methods: Tumor-infiltrating CD8+ T-cells were assessed by IHC staining of tissue microarray cores from 688 breast cancer patients, including 550 Blacks and 138 Whites. CD8+ T cells were scored with digital image analysis. Comparisons of demographic and clinical variables (including CD8+ T cell density) were made using the Mann-Whitney U or Kruskal-Wallis and Fisher’s exact tests. Associations with overall survival (OS) and disease-specific (DSS) survival were evaluated using the log-rank test of Cox regression. Analyses were performed in the overall sample and by disease sub-type. Results: Higher CD8+ T cell density was seen in Black women compared to White, with mean values of 756.2/mm2 and 292.4/mm2 respectively (p < 0.001). Within the overall population and in black women, CD8+ T cell density was significantly higher in younger patients, patients with high grade, and ER negative tumors. No significant associations were observed between CD8+ T cell density and OS or DSS. However, when stratified by subtype, Black patients with triple negative breast cancer and high CD8+ T cell density showed a trend towards improved OS in comparison to patients with low CD8+ T cell density (p = 0.065). 170 patients with information on beta blocker usage were analyzed. No significant associations were noted between CD8+ T cell density and beta blocker use. Conclusions: We observe a significantly higher CD8+ T cell density in Blacks compared to Whites, but this does not confer a survival advantage. Additionally, beta-blockers did not seem to enhance CD8+ T cell infiltration in tumors from Black patients. Our data raise the possibility that distinct mechanisms of immune cell action may occur in different racial groups. Future studies are needed to determine the functional properties of CD8+ T cells in Black women and to characterize additional immune cell subtypes that may also play a role.

scholarly journals Neoadjuvant PD-1 blockade induces T cell and cDC1 activation but fails to overcome the immunosuppressive tumor associated macrophages in recurrent glioblastoma

2021 ◽  
Author(s):  
Alexander Lee ◽  
Lu Sun ◽  
Aaron Mochizuki ◽  
Jeremy Reynoso ◽  
Joey Orpilla ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Immune Cell ◽  
Neoadjuvant Treatment ◽  
Recurrent Glioblastoma ◽  
T Cell Infiltration ◽  
Treatment Paradigm ◽  
Clinical Models ◽  
Chemotactic Factors

Abstract Primary brain tumors, such as glioblastoma (GBM), have been remarkably resistant to immunotherapy, even though pre-clinical models suggest effectiveness. To understand this better in patients, we took advantage of our recent neoadjuvant treatment paradigm to map the infiltrating immune cell landscape of GBM and how this is altered following PD-1 checkpoint blockade using high dimensional proteomics, single cell transcriptomics, and quantitative multiplex immunofluorescence. Neoadjuvant PD-1 blockade increased T cell infiltration and proportion of a progenitor exhausted population of T cells found within the tumor. We identified an early activated and clonally expanded CD8+ T cell cluster whose TCR overlapped with a CD8+ PBMC population. Distinct changes were also observed in conventional type 1 dendritic cells that may facilitate T cell recruitment. Macrophages and monocytes still constituted the majority of infiltrating immune cells, even after anti-PD-1 therapy. Interferon-mediated changes in the myeloid population were consistently observed following PD-1 blockade; these also mediated an increase in chemotactic factors that recruit T cells. However, sustained high expression of T-cell-suppressive checkpoints in these myeloid cells continued to prevent the optimal activation of the tumor infiltrating T cells. Therefore, future immunotherapeutic strategies may need to incorporate the targeting of these cells for clinical benefit.

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