Disease progression in recurrent glioblastoma patients treated with the VEGFR inhibitor axitinib is associated with increased regulatory T cell numbers and T cell exhaustion

Unlocking Hope: Anti-VEGFR inhibitors and their potential in glioblastoma treatment

PURPOSE

This systematic review summarizes evidence of VEGFR gene mutations and VEGF/VEGFR protein expression in glioblastoma multiforme (GBM) patients, alongside the efficacy and safety of anti-VEGFR tyrosine kinase inhibitors (TKIs) for GBM treatment.

METHODS

A comprehensive literature review was conducted using PubMed up to August 2023. Boolean operators and MeSH term "glioma," along with specific VEGFR-related keywords, were utilized following thorough examination of existing literature.

RESULTS

VEGFR correlates with glioma grade and GBM progression, presenting a viable therapeutic target. Regorafenib and axitinib show promise among studied TKIs. Other multi-targeted TKIs (MTKI) and combination therapies exhibit potential, albeit limited by blood-brain barrier penetration and toxicity. Combining treatments like radiotherapy and enhancing BBB penetration may benefit patients. Further research is warranted in patient quality of life and biomarker-guided selection.

CONCLUSION

While certain therapies hold promise for GBM, future research should prioritize personalized medicine and innovative strategies for improved treatment outcomes.

Role of Molecular Targeted Therapeutic Drugs in Treatment of Glioblastoma: A Review Article

Glioblastoma is remarkably periodic primary brain tumor, characterizing an eminently heterogeneous pattern of neoplasms that are utmost destructive and threatening cancers. An enhanced and upgraded knowledge of the various molecular pathways that cause malignant changes in glioblastoma has resulted in advancement of numerous biomarkers and the interpretation of various agents that pointedly target tumor cells and microenvironment. In this review, literature or information on various targeted therapy for glioblastoma is discussed. English language articles were scrutinized in plentiful directory or databases like PubMed, ScienceDirect, Web of Sciences, Google Scholar, and Scopus. The important keywords used for searching databases are "Glioblastoma," "Targeted therapy in glioblastoma," "Therapeutic drugs in glioblastoma," and "Molecular targets in glioblastoma."

Protein Kinase Inhibitors as a New Target for Immune System Modulation and Brain Cancer Management

High-grade brain tumors are malignant tumors with poor survival and remain the most difficult tumors to treat. An important contributing factor to the development and progression of brain tumors is their ability to evade the immune system. Several immunotherapeutic strategies including vaccines and checkpoint inhibitors have been studied to improve the effectiveness of the immune system in destroying cancer cells. Recent studies have shown that kinase inhibitors, capable of inhibiting signal transduction cascades that affect cell proliferation, migration, and angiogenesis, have additional immunological effects. In this review, we explain the beneficial therapeutic effects of novel small-molecule kinase inhibitors and explore how, through different mechanisms, they increase the protective antitumor immune response in high-grade brain tumors.

T cell exhaustion assessment algorism in tumor microenvironment predicted clinical outcomes and immunotherapy effects in glioma

Despite the recent increase in the use of immune checkpoint blockade (ICB), no ICB medications have been approved or are undergoing large-scale clinical trials for glioma. T cells, the main mediators of adaptive immunity, are important components of the tumor immune microenvironment. Depletion of T cells in tumors plays a key role in assessing the sensitivity of patients to immunotherapy. In this study, the bioinformatics approach was applied to construct T cell depletion-related risk assessment to investigate the impact of T cell depletion on prognosis and ICB response in glioma patients. The Cancer Genome Atlas (TCGA) and GSE108474 glioma cohorts and IMvigor210 immunotherapy datasets were collected, including complete mRNA expression profiles and clinical information. We used cell lines to verify the gene expression and the R 3.6.3 tool and GraphPad for bioinformatics analysis and mapping. T cell depletion in glioma patients displayed significant heterogeneity. The T cell depletion-related prognostic model was developed based on seven prognostic genes (HSPB1, HOXD10, HOXA5, SEC61G, H19, ANXA2P2, HOXC10) in glioma. The overall survival of patients with a high TEXScore was significantly lower than that of patients with a low TEXScore. In addition, high TEXScore scores were followed by intense immune responses and a more complex tumor immune microenvironment. The “hot tumors” were predominantly enriched in the high-risk group, which patients expressed high levels of suppressive immune checkpoints, such as PD1, PD-L1, and TIM3. However, patients with a low TEXScore had a more significant clinical response to immunotherapy. In addition, HSPB1 expression was higher in the U251 cells than in the normal HEB cells. In conclusion, the TEXScore related to T cell exhaustion combined with other pathological profiles can effectively assess the clinical status of glioma patients. The TEXScore constructed in this study enables the effective assessment of the immunotherapy response of glioma patients and provides therapeutic possibilities.

Immunoregulatory signal networks and tumor immune evasion mechanisms: insights into therapeutic targets and agents in clinical development

Through activation of immune cells, the immune system is responsible for identifying and destroying infected or otherwise damaged cells including tumorigenic cells that can be recognized as foreign, thus maintaining homeostasis. However, tumor cells have evolved several mechanisms to avoid immune cell detection and killing, resulting in tumor growth and progression. In the tumor microenvironment, tumor infiltrating immune cells are inactivated by soluble factors or tumor promoting conditions and lose their effects on tumor cells. Analysis of signaling and crosstalk between immune cells and tumor cells have helped us to understand in more detail the mechanisms of tumor immune evasion and this forms basis for drug development strategies in the area of cancer immunotherapy. In this review, we will summarize the dominant signaling networks involved in immune escape and describe the status of development of therapeutic strategies to target tumor immune evasion mechanisms with focus on how the tumor microenvironment interacts with T cells.

Emerging immune-based technologies for high-grade gliomas

INTRODUCTION

The selection of a tailored and successful strategy for high-grade gliomas (HGGs) treatment is still a concern. The abundance of aberrant mutations within the heterogenic genetic landscape of glioblastoma strongly influences cell expansion, proliferation, and therapeutic resistance. Identification of immune evasion pathways opens the way to novel immune-based strategies. This review intends to explore the emerging immunotherapies for HGGs. The immunosuppressive mechanisms related to the tumor microenvironment and future perspectives to overcome glioma immunity barriers are also debated.

AREAS COVERED

An extensive literature review was performed on the PubMed/Medline and ClinicalTrials.gov databases. Only highly relevant articles in English and published in the last 20 years were selected. Data about immunotherapies coming from preclinical and clinical trials were summarized.

EXPERT OPINION

The overall level of evidence about the efficacy and safety of immunotherapies for HGGs is noteworthy. Monoclonal antibodies have been approved as second-line treatment, while peptide vaccines, viral gene strategies, and adoptive technologies proved to boost a vivid antitumor immunization. Malignant brain tumor-treating fields are ever-changing in the upcoming years. Constant refinements and development of new routes of drug administration will permit to design of novel immune-based treatment algorithms thus improving the overall survival.

Comprehensive Analyses of Ferroptosis-Related Alterations and Their Prognostic Significance in Glioblastoma

Background: This study was designed to explore the implications of ferroptosis-related alterations in glioblastoma patients.

Method: After obtaining the data sets CGGA325, CGGA623, TCGA-GBM, and GSE83300 online, extensive analysis and mutual verification were performed using R language-based analytic technology, followed by further immunohistochemistry staining verification utilizing clinical pathological tissues.

Results: The analysis revealed a substantial difference in the expression of ferroptosis-related genes between malignant and paracancerous samples, which was compatible with immunohistochemistry staining results from clinicopathological samples. Three distinct clustering studies were run sequentially on these data. All of the findings were consistent and had a high prediction value for glioblastoma. Then, the risk score predicting model containing 23 genes (CP, EMP1, AKR1C1, FMOD, MYBPH, IFI30, SRPX2, PDLIM1, MMP19, SPOCD1, FCGBP, NAMPT, SLC11A1, S100A10, TNC, CSMD3, ATP1A2, CUX2, GALNT9, TNFAIP6, C15orf48, WSCD2, and CBLN1) on the basis of “Ferroptosis.gene.cluster” was constructed. In the subsequent correlation analysis of clinical characteristics, tumor mutation burden, HRD, neoantigen burden and chromosomal instability, mRNAsi, TIDE, and GDSC, all the results indicated that the risk score model might have a better predictive efficiency.

Conclusion: In glioblastoma, there were a large number of abnormal ferroptosis-related alterations, which were significant for the prognosis of patients. The risk score-predicting model integrating 23 genes would have a higher predictive value.

Tumor-Mediated Neutrophil Polarization and Therapeutic Implications

Neutrophils are immune cells with reported phenotypic and functional plasticity. Tumor-associated neutrophils display many roles during cancer progression. Several tumor microenvironment (TME)-derived factors orchestrate neutrophil release from the bone marrow, recruitment and functional polarization, while simultaneously neutrophils are active stimulators of the TME by secreting factors that affect immune interactions and subsequently tumor progression. Successful immunotherapies for many cancer types and stages depend on the targeting of tumor-infiltrating lymphocytes. Neutrophils impact the success of immunotherapies, such as immune checkpoint blockade therapies, by displaying lymphocyte suppressive properties. The identification and characterization of distinct neutrophil subpopulations or polarization states with pro- and antitumor phenotypes and the identification of the major TME-derived factors of neutrophil polarization would allow us to harness the full potential of neutrophils as complementary targets in anticancer precision therapies.

Glioma targeted therapy: insight into future of molecular approaches

Gliomas are the common type of brain tumors originating from glial cells. Epidemiologically, gliomas occur among all ages, more often seen in adults, which males are more susceptible than females. According to the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5), standard of care and prognosis of gliomas can be dramatically different. Generally, circumscribed gliomas are usually benign and recommended to early complete resection, with chemotherapy if necessary. Diffuse gliomas and other high-grade gliomas according to their molecule subtype are slightly intractable, with necessity of chemotherapy. However, for glioblastoma, feasible resection followed by radiotherapy plus temozolomide chemotherapy define the current standard of care. Here, we discuss novel feasible or potential targets for treatment of gliomas, especially IDH-wild type glioblastoma. Classic targets such as the p53 and retinoblastoma (RB) pathway and epidermal growth factor receptor (EGFR) gene alteration have met failure due to complex regulatory network. There is ever-increasing interest in immunotherapy (immune checkpoint molecule, tumor associated macrophage, dendritic cell vaccine, CAR-T), tumor microenvironment, and combination of several efficacious methods. With many targeted therapy options emerging, biomarkers guiding the prescription of a particular targeted therapy are also attractive. More pre-clinical and clinical trials are urgently needed to explore and evaluate the feasibility of targeted therapy with the corresponding biomarkers for effective personalized treatment options.

Evaluation of β-Catenin Inhibition of Axitinib and Nitazoxanide in Human Monocyte-Derived Dendritic Cells

Modulation of β-catenin signaling has attractive therapeutic potential in cancer immunotherapy. Several studies have found that β-catenin can mediate immune evasion in cancer and promote anti-inflammatory features of antigen-presenting dendritic cells. Many small molecular compounds that inhibit Wnt/β-catenin signaling are currently in clinical development, but none have entered routine clinical use. New inhibitors of β-catenin signaling are consequently desirable. Here, we have tested, in monocyte-derived dendritic cells, the effects of two small molecular compounds, axitinib and nitazoxanide, that previously have been discovered to inhibit β-catenin signaling in colon cancer cells. Immature and lipopolysaccharide-matured dendritic cells prepared from healthy blood donor buffy coats were stimulated with 6-bromoindirubin-3′-oxime (6-BIO) to boost basal β-catenin activity, and the effects of axitinib and nitazoxanide were compared with the commercial β-catenin inhibitor ICG-001. Assays, including genome-wide RNA-sequencing, indicated that neither axitinib nor nitazoxanide demonstrated considerable β-catenin inhibition. Both compounds were found to be less toxic to monocyte-derived dendritic cells than either 6-BIO or ICG-001. Axitinib stimulated several aspects of dendritic cell function, such as IL12-p70 secretion, and counteracted IL-10 secretion, according to the present study. However, neither axitinib nor nitazoxanide were found to be efficient β-catenin inhibitors in monocyte-derived dendritic cells.

Metabolic Remodeling in Glioma Immune Microenvironment: Intercellular Interactions Distinct From Peripheral Tumors

During metabolic reprogramming, glioma cells and their initiating cells efficiently utilized carbohydrates, lipids and amino acids in the hypoxic lesions, which not only ensured sufficient energy for rapid growth and improved the migration to normal brain tissues, but also altered the role of immune cells in tumor microenvironment. Glioma cells secreted interferential metabolites or depriving nutrients to injure the tumor recognition, phagocytosis and lysis of glioma-associated microglia/macrophages (GAMs), cytotoxic T lymphocytes, natural killer cells and dendritic cells, promoted the expansion and infiltration of immunosuppressive regulatory T cells and myeloid-derived suppressor cells, and conferred immune silencing phenotypes on GAMs and dendritic cells. The overexpressed metabolic enzymes also increased the secretion of chemokines to attract neutrophils, regulatory T cells, GAMs, and dendritic cells, while weakening the recruitment of cytotoxic T lymphocytes and natural killer cells, which activated anti-inflammatory and tolerant mechanisms and hindered anti-tumor responses. Therefore, brain-targeted metabolic therapy may improve glioma immunity. This review will clarify the metabolic properties of glioma cells and their interactions with tumor microenvironment immunity, and discuss the application strategies of metabolic therapy in glioma immune silence and escape.

Circulating Biomarkers for Glioma: A Review

Accurate circulating biomarkers have potential clinical applications in population screening, tumor subclassification, monitoring tumor status, and the delivery of individualized treatments resulting from tumor genotyping. Recently, significant progress has been made within this field in several cancer types, but despite the many potential benefits, currently there is no validated circulating biomarker test for patients with glioma. A number of circulating factors have been examined, including circulating tumor cells, cell-free DNA, microRNA, exosomes, and proteins from both peripheral blood and cerebrospinal fluid with variable results. In the following article, we provide a narrative review of the current evidence pertaining to circulating biomarkers in patients with glioma, including discussion of the advantages and challenges encountered with the current methods used for discovery. Additionally, the potential clinical applications are described with reference to the literature.

Engineering a photosensitizer nanoplatform for amplified photodynamic immunotherapy via tumor microenvironment modulation

Photosensitizer-based photodynamic therapy (PDT) can not only kill tumor cells by the generated cytotoxic reactive oxygen species (ROS), but also trigger immunogenic cell death (ICD) and activate an immune response for immunotherapy. However, such photodynamic immunotherapy suffers from major obstacles in the tumor microenvironment. The hypoxic microenvironment greatly weakens PDT, while the immunosuppressive tumor microenvironment caused by aberrant tumor blood vessels and indoleamine 2,3-dioxygenase (IDO) leads to a significant reduction in immunotherapy. To overcome these obstacles, herein, an engineered photosensitizer nanoplatform is designed for amplified photodynamic immunotherapy by integrating chlorin e6 (Ce6, a photosensitizer), axitinib (AXT, a tyrosine kinase inhibitor) and dextro-1-methyl tryptophan (1MT, an IDO inhibitor). In our nanoplatform, AXT improves the tumor microenvironment by normalizing tumor blood vessels, which not only promotes PDT by reducing the level of hypoxia of the tumor microenvironment, but also promotes immunotherapy through facilitating infiltration of immune effector cells into the tumor and reversing the immunosuppressive effect of vascular endothelial growth factor (VEGF). Moreover, 1MT effectively inhibits the activity of IDO, further reducing the immunosuppressive nature of the tumor microenvironment. Therefore, this nanoplatform demonstrates an amplified photodynamic immunotherapy via tumor microenvironment modulation, exhibiting outstanding therapeutic efficacy against tumor growth and metastasis with negligible side toxicity. The current concept of engineering photosensitizer nanoplatforms for overcoming photodynamic immunotherapy obstacles provides a promising strategy against tumors.

Recent Advances in Immune Cell Therapy for Glioblastoma

Glioblastoma (GBM) is the most malignant form of astrocytoma with short survival and a high recurrence rate and remains a global problem. Currently, surgery, chemotherapy, radiotherapy, and other comprehensive treatments are the main treatment modalities, but patients still have a poor prognosis mainly due to the infiltrative growth of GBM and the protective effect of the blood–brain barrier on tumor cells. Therefore, immunotherapy is expected to be a good option for GBM. In the immune system, different cells play varying roles in the treatment of GBM, so understanding the roles played by various immune cells in treating GBM and considering how to combine these effects to maximize the efficacy of these cells is important for the selection of comprehensive and optimal treatment plans and improving GBM prognosis. Therefore, this study reviews the latest research progress on the role of various types of immune cells in the treatment of GBM.

Axitinib plus avelumab in the treatment of recurrent glioblastoma: a stratified, open-label, single-center phase 2 clinical trial (GliAvAx)

BACKGROUND

No treatment demonstrated to improve survival in patients with recurrent glioblastoma (rGB) in a randomized trial. Combining axitinib with the programmed cell death ligand 1 blocking monoclonal antibody avelumab may result in synergistic activity against rGB.

METHODS

Adult patients with rGB following prior surgery, radiation therapy and temozolomide chemotherapy were stratified according to their baseline use of corticosteroids. Patients with a daily dose of ≤8 mg of methylprednisolone (or equivalent) initiated treatment with axitinib (5 mg oral two times per day) plus avelumab (10 mg/kg intravenous every 2 weeks) (Cohort-1). Patients with a higher baseline corticosteroid dose initiated axitinib monotherapy; avelumab was added after 6 weeks of therapy if the corticosteroid dose could be tapered to ≤8 mg of methylprednisolone (Cohort-2). Progression-free survival at 6 months (6-m-PFS%), per immunotherapy response assessment for neuro-oncology criteria, served as the primary endpoint.

RESULTS

Between June 2017 and August 2018, 54 patients (27 per cohort) were enrolled and initiated study treatment (median age: 55 years; 63% male; 91% Eastern Cooperative Oncology Group Performance Status 0-1). Seventeen (63%) patients treated in Cohort-2 received at least one dose of avelumab. The 6-m-PFS% was 22.2% (95% CI 6.5% to 37.9%) and 18.5% (95% CI 3.8% to 33.2%) in Cohort-1 and Cohort-2, respectively; median overall survival was 26.6 weeks (95% CI 20.8 to 32.4) in Cohort-1 and 18.0 weeks (95% CI 12.5 to 23.5) in Cohort-2. The best objective response rate was 33.3% and 22.2% in Cohort-1 and Cohort-2, respectively, with a median duration of response of 17.9 and 19.0 weeks. The most frequent treatment-related adverse events were dysphonia (67%), lymphopenia (50%), arterial hypertension and diarrhea (both 48%). There were no grade 5 adverse events.

CONCLUSION

The combination of avelumab plus axitinib has an acceptable toxicity profile but did not meet the prespecified threshold for activity justifying further investigation of this treatment in an unselected population of patients with rGB.

A Multicenter Phase II Study of Second-Line Axitinib for Patients with Advanced Hepatocellular Carcinoma Failing First-Line Sorafenib Monotherapy

LESSONS LEARNED

For patients with advanced hepatocellular carcinoma after failure of first-line sorafenib monotherapy, second-line axitinib provides modest efficacy with tolerable toxicity. The discrepant tumor responses and survival outcomes in trials using axitinib as salvage therapy highlight the importance of optimal patient selection with the aid of clinical biomarkers.

BACKGROUND

Multikinase inhibitors have been effective treatment for hepatocellular carcinoma (HCC). This multicenter phase II study explored the efficacy and safety of second-line axitinib for advanced HCC.

METHODS

Patients with advanced HCC and Child-Pugh A liver function, experiencing progression on first-line sorafenib monotherapy, were eligible. Axitinib 5 mg twice daily was given continuously with allowed dose escalation. Tumor assessment was performed according to RECIST version 1.1. The primary endpoint was rate of disease control.

RESULTS

From April 2011 to March 2016, 45 patients were enrolled. Thirty-seven patients (82%) tested positive for hepatitis B surface antigen. The disease control rate was 62.2%, and the response rate was 6.7%, according to RECIST criteria. Median progression-free survival (PFS) and overall survival (OS) were 2.2 months and 10.1 months, respectively. Treatment-related adverse events were compatible with previous reports of axitinib.

CONCLUSION

Second-line axitinib has moderate activity and acceptable toxicity for patients with advanced HCC after failing the first-line sorafenib monotherapy.

Alterations of the tumor microenvironment in glioblastoma following radiation and temozolomide with or without bevacizumab

Background

The immunosuppressive tumor microenvironment (TME) contributes to the tumor progression and treatment failure. Our previous study demonstrated alterations in the TME during bevacizumab (Bev) therapy in human glioblastoma (GB) specimens obtained from patients who underwent surgical resection. Continuous Bev administration downregulates the expression of programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), suppresses the infiltration of tumor associated macrophages (TAMs) and regulatory T cells (Tregs), and increases cytotoxic T lymphocytes (CTLs) infiltration. However, one may argue that these immunosupportive effects might also be induced by radiation therapy (RT) or temozolomide (TMZ), and they cannot necessarily be attributed to Bev alone.

Methods

In the present study, changes in the molecules relevant to the TME were analyzed by immunohistochemistry using paired pre- and post-treatment samples of malignant glioma specimens from 15 patients who received RT and TMZ therapy without Bev.

Results

The expression levels of CD34, vascular endothelial growth factor (VEGF)-A, VEGF receptor 2 (VEGFR2), HIF-1α, CA9, nestin, CD4, CD8, CD163, PD-1, and PD-L1 were not significantly changed after the treatment with RT and TMZ. However, VEGFR1 expression and the number of Foxp3-positive cells tended to be upregulated and increased after the treatment (P=0.058, P=0.082, respectively).

Conclusions

This was the first study to show the alterations of TME following RT and TMZ therapy using paired pre- and post-treatment malignant glioma samples. Long-term treatment of RT and TMZ might worsen immunosuppressive TME in malignant gliomas.

Oncolytic Virus Encoding a Master Pro-Inflammatory Cytokine Interleukin 12 in Cancer Immunotherapy

Oncolytic viruses (OVs) are genetically modified or naturally occurring viruses, which preferentially replicate in and kill cancer cells while sparing healthy cells, and induce anti-tumor immunity. OV-induced tumor immunity can be enhanced through viral expression of anti-tumor cytokines such as interleukin 12 (IL-12). IL-12 is a potent anti-cancer agent that promotes T-helper 1 (Th1) differentiation, facilitates T-cell-mediated killing of cancer cells, and inhibits tumor angiogenesis. Despite success in preclinical models, systemic IL-12 therapy is associated with significant toxicity in humans. Therefore, to utilize the therapeutic potential of IL-12 in OV-based cancer therapy, 25 different IL-12 expressing OVs (OV-IL12s) have been genetically engineered for local IL-12 production and tested preclinically in various cancer models. Among OV-IL12s, oncolytic herpes simplex virus encoding IL-12 (OHSV-IL12) is the furthest along in the clinic. IL-12 expression locally in the tumors avoids systemic toxicity while inducing an efficient anti-tumor immunity and synergizes with anti-angiogenic drugs or immunomodulators without compromising safety. Despite the rapidly rising interest, there are no current reviews on OV-IL12s that exploit their potential efficacy and safety to translate into human subjects. In this article, we will discuss safety, tumor-specificity, and anti-tumor immune/anti-angiogenic effects of OHSV-IL12 as mono- and combination-therapies. In addition to OHSV-IL12 viruses, we will also review other IL-12-expressing OVs and their application in cancer therapy.

Effect of Apatinib on Serum CD4+CD25+ T cells, NK Cells, and T Cells Subgroup in Malignant Tumor

Objective:

The immune makers including CD4+CD25+ T cells, natural killer cells, and T cells subgroup were retrospectively analyzed to find the relationship between apatinib and the immune system in the patients treated with apatinib.

Method:

Forty-two patients with advanced malignant tumors orally took apatinib as treatment and 16 patients with the same situation did not take apatinib as a control group. These patients were all included in the study, and they orally received apatinib 500 mg daily as monotherapy or combination. The treatment was continued until disease progression or intolerable toxicity. CD4+CD25+ T cells, natural killer cells, and T cells subgroup were detected before and 1 month after therapy for all the patients. The relationship between the changing number of immune cells and progression-free survival was analyzed in this study.

Result:

For the apatinib group, the rate of CD4+CD25+ T cells significantly increased (P = .048). The median progression-free survival was 3.25 months for the 42 patients. The median progression-free survival in the patients with the rate of CD4+CD25+ T cells increased and decreased was 5.8 months and 2.9 months, respectively (P = .012). Multivariate analysis found the increased rate of CD4+CD25+ T cells was an independent prognostic factor for a longer progression-free survival. The rate of natural killer cells and T cells subgroup did not change much after apatinib therapy, and they were not independent prognostic factors for progression-free survival.

Conclusion:

The rate of CD4+CD25+ T cells is very important in patients with apatinib treatment. The changing number of CD4+CD25+ T cells may be a good indicator for apatinib prognosis. Natural killer cells and T cells subgroup did not change much after apatinib, and they were not independent prognostic factors for progression-free survival.

The role of vascular endothelial growth factor in the hypoxic and immunosuppressive tumor microenvironment: perspectives for therapeutic implications

The microvasculature and immune cells are major components of the tumor microenvironment (TME). Hypoxia plays a pivotal role in the TME through hypoxia-inducible factor 1-alpha (HIF-1α) which upregulates vascular endothelial growth factor (VEGF). VEGF, an angiogenesis stimulator, suppresses tumor immunity by inhibiting the maturation of dendritic cells, and induces immunosuppressive cells such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells. HIF-1α directly induces immune checkpoint molecules. VEGF/VEGF receptor (VEGFR)-targeted therapy as a cancer treatment has not only anti-angiogenic effects, but also immune-supportive effects. Anti-angiogenic therapy has the potential to change the immunological "cold tumors" into the "hot tumors". Glioblastoma (GB) is a hypervascular tumor with high VEGF expression which leads to development of an immuno suppressive TME. Therefore, in the last decade, several combination immunotherapies with anti-angiogenic agents have been developed for numerous tumors including GBs. In particular, combination therapy with an immune checkpoint inhibitor and VEGF/VEGFR-targeted therapy has been suggested as a synergic treatment strategy that may show favorable changes in the TME. In this article, we discuss the cross talk among immunosuppressive cells exposed to VEGF in the hypoxic TME of GBs. Current efficient combination strategies using VEGF/VEGFR-targeted therapy are reviewed and proposed as novel cancer treatments.

Glioblastoma heterogeneity and the tumour microenvironment: implications for preclinical research and development of new treatments

Glioblastoma is the deadliest form of brain cancer. Aside from inadequate treatment options, one of the main reasons glioblastoma is so lethal is the rapid growth of tumour cells coupled with continuous cell invasion into surrounding healthy brain tissue. Significant intra- and inter-tumour heterogeneity associated with differences in the corresponding tumour microenvironments contributes greatly to glioblastoma progression. Within this tumour microenvironment, the extracellular matrix profoundly influences the way cancer cells become invasive, and changes to extracellular (pH and oxygen levels) and metabolic (glucose and lactate) components support glioblastoma growth. Furthermore, studies on clinical samples have revealed that the tumour microenvironment is highly immunosuppressive which contributes to failure in immunotherapy treatments. Although technically possible, many components of the tumour microenvironment have not yet been the focus of glioblastoma therapies, despite growing evidence of its importance to glioblastoma malignancy. Here, we review recent progress in the characterisation of the glioblastoma tumour microenvironment and the sources of tumour heterogeneity in human clinical material. We also discuss the latest advances in technologies for personalised and in vitro preclinical studies using brain organoid models to better model glioblastoma and its interactions with the surrounding healthy brain tissue, which may play an essential role in developing new and more personalised treatments for this aggressive type of cancer.

Absolute numbers of regulatory T cells and neutrophils in corticosteroid-free patients are predictive for response to bevacizumab in recurrent glioblastoma patients

Bevacizumab (Bv) remains frequently prescribed in glioblastoma (GBM) patients, especially at recurrence. We conducted a prospective clinical trial with 29 recurrent GBM patients treated with Bv alone with a longitudinal follow-up of different circulating immune cells [complete blood count, myeloid-derived suppressor cells (MDSCs), classical, intermediate, non-classical and Tie2 monocytes, VEGFR1+ and regulatory T cells (Treg)]. We observed a significant increase for leucocytes, neutrophils, eosinophils and classical monocytes and a decrease for the fraction of Treg during the treatment. The best prognostic values for survival under Bv were obtained for basal neutrophils and Treg. Counts below 3.9 G/L for neutrophils and above 0.011 G/L for Treg were associated with an overall survival of 17.5 and 19.9 months, respectively, as compared with 5.4 and 5.6 months, respectively, for counts above and below these cutoffs (p = 0.004 and p < 0.001). No prognostic impact was observed for neutrophils in a retrospective cohort of 26 patients treated with nitrosoureas alone. In another retrospective validation cohort of 61 GBM patients treated at recurrence with a Bv-containing regimen, an interaction was observed between neutrophils and corticosteroid intake. The predictive value of neutrophils on survival under Bv was lost in patients treated with corticosteroids, when steroid-free patients with a low neutrophil count had a particularly long median survival of 3.4 years. These two simply accessible criteria (basal neutrophils and steroid intake) could be used to reserve this relatively costly treatment for patients likely to be the most responsive to Bv and prevent unnecessary side effects in others.

A Pilot Study of Vaccine Therapy with Multiple Glioma Oncoantigen/Glioma Angiogenesis-Associated Antigen Peptides for Patients with Recurrent/Progressive High-Grade Glioma

High-grade gliomas (HGGs) carry a dismal prognosis despite current treatments. We previously confirmed the safety and immunogenicity of a vaccine treatment targeting tumor angiogenesis with synthetic peptides, for vascular endothelial growth factor receptor (VEGFR) epitopes in recurrent HGG patients. In this study, we evaluated a novel vaccine therapy targeting not only tumor vasculature but also tumor cells, using multiple glioma oncoantigen (GOA)/glioma angiogenesis-associated antigen (GAAA) peptides in HLA-A2402+ recurrent/progressive HGG patients. The vaccine included peptide epitopes from four GOAs (LY6K, DEPDC1, KIF20A, and FOXM1) and two GAAAs (VEGFR1 and VEGFR2). Ten patients received subcutaneous vaccinations. The primary endpoint was the safety of the treatment. T-lymphocyte responses against GOA/GAAA epitopes and treatment response were evaluated secondarily. The treatment was well tolerated without any severe systemic adverse events. The vaccinations induced immunoreactivity to at least three vaccine-targeted GOA/GAAA in all six evaluable patients. The median overall survival time in all patients was 9.2 months. Five achieved progression-free status lasting at least six months. Two recurrent glioblastoma patients demonstrated stable disease. One patient with anaplastic oligoastrocytoma achieved complete response nine months after the vaccination. Taken together, this regimen was well tolerated and induced robust GOA/GAAA-specific T-lymphocyte responses in recurrent/progressive HGG patients.

Persistent restoration to the immunosupportive tumor microenvironment in glioblastoma by bevacizumab

Although vascular endothelial growth factor (VEGF) promotes the immunosuppressive microenvironment, the efficacy of bevacizumab (Bev) on tumor immunity has not been fully investigated. The present study used 47 glioblastoma tissues obtained at 3 different settings: tumors of initial resection (naïve Bev group), tumors resected following Bev therapy (effective Bev group), and recurrent tumors after Bev therapy (refractory Bev group). The paired samples of the initial and post-Bev recurrent tumors from 9 patients were included. The expression of programmed cell death-1 (PD-1)/PD ligand-1 (PD-L1), CD3, CD8, Foxp3, and CD163 was analyzed by immunohistochemistry. The PD-L1+ tumor cells significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (P < .01 for each). The PD-1+ cells significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (P < .01 for each). The amount of CD3+ and CD8+ T cell infiltration increased in the refractory Bev group compared with the naïve Bev group (CD3, P < .01; CD8, P = .06). Both Foxp3+ regulatory T cells and CD163+ tumor-associated macrophages significantly decreased in the effective or refractory Bev group compared with the naïve Bev group (Foxp3, P < .01 for each; CD163, P < .01 for each). These findings were largely confirmed by comparing paired initial and post-Bev recurrent tumors. Bevacizumab restores the immunosupportive tumor microenvironment in glioblastomas, and this effect persists during long-term Bev therapy.

Turn Back the TIMe: Targeting Tumor Infiltrating Myeloid Cells to Revert Cancer Progression

Tumor cells frequently produce soluble factors that favor myelopoiesis and recruitment of myeloid cells to the tumor microenvironment (TME). Consequently, the TME of many cancer types is characterized by high infiltration of monocytes, macrophages, dendritic cells and granulocytes. Experimental and clinical studies show that most myeloid cells are kept in an immature state in the TME. These studies further show that tumor-derived factors mold these myeloid cells into cells that support cancer initiation and progression, amongst others by enabling immune evasion, tumor cell survival, proliferation, migration and metastasis. The key role of myeloid cells in cancer is further evidenced by the fact that they negatively impact on virtually all types of cancer therapy. Therefore, tumor-associated myeloid cells have been designated as the culprits in cancer. We review myeloid cells in the TME with a focus on the mechanisms they exploit to support cancer cells. In addition, we provide an overview of approaches that are under investigation to deplete myeloid cells or redirect their function, as these hold promise to overcome resistance to current cancer therapies.

Identification of FDA-Approved Oncology Drugs with Selective Potency in High-Risk Childhood Ependymoma

Children with ependymoma (EPN) are cured in less than 50% of cases, with little improvement in outcome over the last several decades. Chemotherapy has not affected survival in EPN, due in part to a lack of preclinical models that has precluded comprehensive drug testing. We recently developed two human EPN cell lines harboring high-risk phenotypes which provided us with an opportunity to execute translational studies. EPN and other pediatric brain tumor cell lines were subject to a large-scale comparative drug screen of FDA-approved oncology drugs for rapid clinical application. The results of this in vitro study were combined with in silico prediction of drug sensitivity to identify EPN-selective compounds, which were validated by dose curve and time course modeling. Mechanisms of EPN-selective antitumor effect were further investigated using transcriptome and proteome analyses. We identified three classes of oncology drugs that showed EPN-selective antitumor effect, namely, (i) fluorinated pyrimidines (5-fluorouracil, carmofur, and floxuridine), (ii) retinoids (bexarotene, tretinoin and isotretinoin), and (iii) a subset of small-molecule multireceptor tyrosine kinase inhibitors (axitinib, imatinib, and pazopanib). Axitinib's antitumor mechanism in EPN cell lines involved inhibition of PDGFRα and PDGFRβ and was associated with reduced mitosis-related gene expression and cellular senescence. The clinically available, EPN-selective oncology drugs identified by our study have the potential to critically inform design of upcoming clinical studies in EPN, in particular for those children with recurrent EPN who are in the greatest need of novel therapeutic approaches. Mol Cancer Ther; 17(9); 1984-94. ©2018 AACR.

The multi-receptor inhibitor axitinib reverses tumor-induced immunosuppression and potentiates treatment with immune-modulatory antibodies in preclinical murine models

Cancer immunotherapies have significantly improved the prognosis of cancer patients. Despite the clinical success of targeting inhibitory checkpoint receptors, including PD-1 and/or CTLA-4 on T cells, only a minority of patients derive benefit from these therapies. New strategies to improve cancer immunotherapy are therefore needed. Combination therapy of checkpoint inhibitors with targeted agents has promisingly shown to increase the efficacy of immunotherapy. Here, we analyzed the immunomodulatory effects of the multi-receptor tyrosine kinase inhibitor axitinib and its efficacy in combination with immunotherapies. In different syngeneic murine tumor models, axitinib showed therapeutic efficacy that was not only mediated by VEGF-VEGFR inhibition, but also through the induction of anti-cancer immunity. Mechanistically, a significant reduction of immune-suppressive cells, including a decrease of tumor-promoting mast cells and tumor-associated macrophages was observed upon axitinib treatment. Inhibition of mast cells by axitinib as well as their experimental depletion led to reduced tumor growth. Of note, treatment with axitinib led to an improved T cell response, while the latter was pivotal for the therapeutic efficacy. Combination with immune checkpoint inhibitors anti-PD-1 and anti-TIM-3 and/or agonistic engagement of the activating receptor CD137 resulted in a synergistic therapeutic efficacy. This demonstrates non-redundant immune activation induced by axitinib via modulation of myeloid and mast cells. These findings provide important mechanistic insights into axitinib-mediated anti-cancer immunity and provide rationale for clinical combinations of axitinib with different immunotherapeutic modalities.

Combinatorial Effects of VEGFR Kinase Inhibitor Axitinib and Oncolytic Virotherapy in Mouse and Human Glioblastoma Stem-Like Cell Models

Purpose: Glioblastoma (GBM), a fatal brain cancer, contains a subpopulation of GBM stem-like cells (GSCs) that contribute to resistance to current therapy. Angiogenesis also plays a key role in GBM progression. Therefore, we developed a strategy to target the complex GBM microenvironment, including GSCs and tumor vasculature.Experimental Design: We evaluated the cytotoxic effects of VEFGR tyrosine kinase inhibitor (TKI) axitinib in vitro and then tested antitumor efficacy of axitinib in combination with oncolytic herpes simplex virus (oHSV) expressing antiangiogenic cytokine murine IL12 (G47Δ-mIL12) in two orthotopic GSC-derived GBM models: patient-derived recurrent MGG123 GSCs, forming vascular xenografts in immunodeficient mice; and mouse 005 GSCs, forming syngeneic tumors in immunocompetent mice.Results: GSCs form endothelial-like tubes and were sensitive to axitinib. G47Δ-mIL12 significantly improved survival, as did axitinib, while dual combinations further extended survival significantly compared with single therapies alone in both models. In MGG123 tumors, axitinib was effective only at high doses (50 mg/kg), alone and in combination with G47Δ-mIL12, and this was associated with greatly decreased vascularity, increased macrophage infiltration, extensive tumor necrosis, and PDGFR/ERK pathway inhibition. In the mouse 005 model, antiglioma activity, after single and combination therapy, was only observed in immunocompetent mice and not the T-cell-deficient athymic mice. Interestingly, immune checkpoint inhibition did not improve efficacy.Conclusions: Systemic TKI (axitinib) beneficially combines with G47Δ-mIL12 to enhance antitumor efficacy in both immunodeficient and immunocompetent orthotopic GBM models. Our results support further investigation of TKIs in combination with oHSV for GBM treatment. Clin Cancer Res; 24(14); 3409-22. ©2018 AACR.

Targeting tumour microenvironment by tyrosine kinase inhibitor

Tumour microenvironment (TME) is a key determinant of tumour growth and metastasis. TME could be very different for each type and location of tumour and TME may change constantly during tumour growth. Multiple counterparts in surrounding microenvironment including mesenchymal-, hematopoietic-originated cells as well as non-cellular components affect TME. Thus, therapeutics that can disrupt the tumour-favouring microenvironment should be further explored for cancer therapy. Previous efforts in unravelling the dysregulated mechanisms of TME components has identified numerous protein tyrosine kinases, while its corresponding inhibitors have demonstrated potent modulatory effect on TME. Recent works have demonstrated that beyond the direct action on cancer cells, tyrosine kinase inhibitors (TKIs) have been implicated in inactivation or normalization of dysregulated TME components leading to cancer regression. Either through re-sensitizing the tumour cells or reversing the immunological tolerance microenvironment, the emergence of these TME modulatory mechanism of TKIs supports the combinatory use of TKIs with current chemotherapy or immunotherapy for cancer therapy. Therefore, an appropriate understanding on TME modulation by TKIs may offer another mode of action of TKIs for cancer treatment. This review highlights mode of kinase activation or paracrine ligand production from TME components and summarises the findings on the potential use of various TKIs on regulating TME components. At last, the combination use of current TKIs with immunotherapy in the perspectives of efficacy and safety are discussed.