Therapeutic targeting of tumor-associated macrophages and microglia in glioblastoma

PTP4A2 Promotes Glioblastoma Progression and Macrophage Polarization under Microenvironmental Pressure

Phosphatase of regenerating liver 2 (also known as PTP4A2) has been linked to cancer progression. Still, its exact role in glioblastoma (GBM), the most aggressive type of primary brain tumor, remains elusive. In this study, we report that pharmacologic treatment using JMS-053, a pan-phosphatase of regenerating liver inhibitor, inhibits GBM cell viability and spheroid growth. We also show that PTP4A2 is associated with a poor prognosis in gliomas, and its expression correlates with GBM aggressiveness. Using a GBM orthotopic xenograft model, we show that PTP4A2 overexpression promotes tumor growth and reduces mouse survival. Furthermore, PTP4A2 deletion leads to increased apoptosis and proinflammatory signals. Using a syngeneic GBM model, we show that depletion of PTP4A2 reduces tumor growth and induces a shift in the tumor microenvironment (TME) toward an immunosuppressive state. In vitro assays show that cell proliferation is not affected in PTP4A2-deficient or -overexpressing cells, highlighting the importance of the microenvironment in PTP4A2 functions. Collectively, our results indicate that PTP4A2 promotes GBM growth in response to microenvironmental pressure and support the rationale for targeting PTP4A2 as a therapeutic strategy against GBM.

SIGNIFICANCE

High levels of PTP4A2 are associated with poor outcomes in patients with glioma and in mouse models. PTP4A2 depletion increases apoptosis and proinflammatory signals in GBM xenograft models, significantly impacts tumor growth, and rewires the TME in an immunocompetent host. PTP4A2 effects in GBM are dependent on the presence of the TME.

Overcoming Resistance to Temozolomide in Glioblastoma: A Scoping Review of Preclinical and Clinical Data

Glioblastoma (GB) is the most common and most aggressive primary brain tumor in adults, with an overall survival almost 14.6 months. Optimal resection followed by combined temozolomide chemotherapy and radiotherapy, also known as Stupp protocol, remains the standard of treatment; nevertheless, resistance to temozolomide, which can be obtained throughout many molecular pathways, is still an unsurpassed obstacle. Several factors influence the efficacy of temozolomide, including the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. The blood-brain barrier, which serves as both a physical and biochemical obstacle, the tumor microenvironment's pro-cancerogenic and immunosuppressive nature, and tumor-specific characteristics such as volume and antigen expression, are the subject of ongoing investigation. In this review, preclinical and clinical data about temozolomide resistance acquisition and possible ways to overcome chemoresistance, or to treat gliomas without restoration of chemosensitinity, are evaluated and presented. The objective is to offer a thorough examination of the clinically significant molecular mechanisms and their intricate interrelationships, with the aim of enhancing understanding to combat resistance to TMZ more effectively.

Drug Delivery of Solid Lipid Nanoparticles (SLNs) and Nanostructured Lipid Carriers (NLCs) to Target Brain Tumors

Brain, predisposed to local and metastasized tumors, has always been the focus of oncological studies. Glioblastoma multiforme (GBM), the most common invasive primary tumor of the brain, is responsible for 4% of all cancer-related deaths worldwide. Despite novel technologies, the average survival rate is 2 years. Physiological barriers such as blood-brain barrier (BBB) prevent drug molecules penetration into brain. Most of the pharmaceuticals present in the market cannot infiltrate BBB to have their maximum efficacy and this in turn imposes a major challenge. This mini review discusses GBM and physiological and biological barriers for anticancer drug delivery, challenges for drug delivery across BBB, drug delivery strategies focusing on SLNs and NLCs and their medical applications in on-going clinical trials. Numerous nanomedicines with various characteristics have been introduced in the last decades to overcome the delivery challenge. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) were introduced as oral drug delivery nanomedicines which can be encapsulated by both hydrophilic and lipophilic pharmaceutical compounds. Their biocompatibility, biodegradability, lower toxicity and side effects, enhanced bioavailability, solubility and permeability, prolonged half-life and stability and finally tissue-targeted drug delivery makes them unique among all.

Interdependencies of the Neuronal, Immune and Tumor Microenvironment in Gliomas

Gliomas are the most common primary brain malignancy and are universally fatal. Despite significant breakthrough in understanding tumor biology, treatment breakthroughs have been limited. There is a growing appreciation that major limitations on effective treatment are related to the unique and highly complex glioma tumor microenvironment (TME). The TME consists of multiple different cell types, broadly categorized into tumoral, immune and non-tumoral, non-immune cells. Each group provides significant influence on the others, generating a pro-tumor dynamic with significant immunosuppression. In addition, glioma cells are highly heterogenous with various molecular distinctions on the cellular level. These variations, in turn, lead to their own unique influence on the TME. To develop future treatments, an understanding of this complex TME interplay is needed. To this end, we describe the TME in adult gliomas through interactions between its various components and through various glioma molecular phenotypes.

Advanced immunotherapies for glioblastoma: tumor neoantigen vaccines in combination with immunomodulators

Glial-origin brain tumors, including glioblastomas (GBM), have one of the worst prognoses due to their rapid and fatal progression. From an oncological point of view, advances in complete surgical resection fail to eliminate the entire tumor and the remaining cells allow a rapid recurrence, which does not respond to traditional therapeutic treatments. Here, we have reviewed new immunotherapy strategies in association with the knowledge of the immune micro-environment. To understand the best lines for the future, we address the advances in the design of neoantigen vaccines and possible new immune modulators. Recently, the efficacy and availability of vaccine development with different formulations, especially liposome plus mRNA vaccines, has been observed. We believe that the application of new strategies used with mRNA vaccines in combination with personalized medicine (guided by different omic's strategies) could give good results in glioma therapy. In addition, a large part of the possible advances in new immunotherapy strategies focused on GBM may be key improving current therapies of immune checkpoint inhibitors (ICI), given the fact that this type of tumor has been highly refractory to ICI.

Nanoparticle designs for delivery of nucleic acid therapeutics as brain cancer therapies

Glioblastoma (GBM) is an aggressive central nervous system cancer with a dismal prognosis. The standard of care involves surgical resection followed by radiotherapy and chemotherapy, but five-year survival is only 5.6% despite these measures. Novel therapeutic approaches, such as immunotherapies, targeted therapies, and gene therapies, have been explored to attempt to extend survival for patients. Nanoparticles have been receiving increasing attention as promising vehicles for non-viral nucleic acid delivery in the context of GBM, though delivery is often limited by low blood-brain barrier permeability, particle instability, and low trafficking to target brain structures and cells. In this review, nanoparticle design considerations and new advances to overcome nucleic acid delivery challenges to treat brain cancer are summarized and discussed.

P2Y12 Purinergic Receptor and Brain Tumors: Implications on Glioma Microenvironment

Gliomas are the most common malignant brain tumors in adults, characterized by a high proliferation and invasion. The tumor microenvironment is rich in growth-promoting signals and immunomodulatory pathways, which increase the tumor's aggressiveness. In response to hypoxia and glioma therapy, the amounts of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) strongly increase in the extracellular space, and the purinergic signaling is triggered by nucleotides' interaction in P2 receptors. Several cell types are present in the tumor microenvironment and can facilitate tumor growth. In fact, tumor cells can activate platelets by the ADP-P2Y₁₂ engagement, which plays an essential role in the cancer context, protecting tumors from the immune attack and providing molecules that contribute to the growth and maintenance of a rich environment to sustain the protumor cycle. Besides platelets, the P2Y₁₂ receptor is expressed by some tumors, such as renal carcinoma, colon carcinoma, and gliomas, being related to tumor progression. In this context, this review aims to depict the glioma microenvironment, focusing on the relationship between platelets and tumor malignancy.

PI3Kγ inhibition suppresses microglia/TAM accumulation in glioblastoma microenvironment to promote exceptional temozolomide response

Precision medicine in oncology leverages clinical observations of exceptional response. Toward an understanding of the molecular features that define this response, we applied an integrated, multiplatform analysis of RNA profiles derived from clinically annotated glioblastoma samples. This analysis suggested that specimens from exceptional responders are characterized by decreased accumulation of microglia/macrophages in the glioblastoma microenvironment. Glioblastoma-associated microglia/macrophages secreted interleukin 11 (IL11) to activate STAT3-MYC signaling in glioblastoma cells. This signaling induced stem cell states that confer enhanced tumorigenicity and resistance to the standard-of-care chemotherapy, temozolomide (TMZ). Targeting a myeloid cell restricted an isoform of phosphoinositide-3-kinase, phosphoinositide-3-kinase gamma isoform (PI3Kγ), by pharmacologic inhibition or genetic inactivation disrupted this signaling axis by reducing microglia/macrophage-associated IL11 secretion in the tumor microenvironment. Mirroring the clinical outcomes of exceptional responders, PI3Kγ inhibition synergistically enhanced the anti-neoplastic effects of TMZ in orthotopic murine glioblastoma models. Moreover, inhibition or genetic inactivation of PI3Kγ in murine glioblastoma models recapitulated expression profiles observed in clinical specimens isolated from exceptional responders. Our results suggest key contributions from tumor-associated microglia/macrophages in exceptional responses and highlight the translational potential for PI3Kγ inhibition as a glioblastoma therapy.

miR-106b-5p Inhibits IRF1/IFN-β Signaling to Promote M2 Macrophage Polarization of Glioblastoma

Purpose

The microRNA (miRNA) profile changes in the tumor-associated macrophages. However, the role of miR-106b-5p in the glioblastoma-associated macrophages is poorly understood.

Materials and Methods

In our study, miR-106b-5p and M2 macrophage markers were detected by qRT-PCR and Western blotting in THP1 cells, with the conditioned medium from U251 cells or M2 macrophages in response to IL-4 stimulation and M1 macrophages stimulated by LPS and IFN-γ. IFN regulatory factor (IRF1) was identified as a target of miR-106b-5p in the glioma infiltrating macrophages by luciferase reporter assay. The molecular mechanisms involved in the miR-106b-5p-mediated regulation of M2 polarization were clarified by shRNA knockdown assay.

Results

Our results showed miR-106b-5p expression was upregulated in glioma-infiltrating macrophages. miR-106b-5p regulated M2 polarization of glioma infiltrating macrophages and enhanced the growth of glioma-infiltrating macrophages. IRF1 was identified as a target of miR-106b-5p. Furthermore, miR-106b-5p inhibited IRF1 expression by targeting IRF1/IFN-β pathway to promote M2 polarization of macrophages.

Conclusion

miR-106b-5p may inhibit IRF1/IFN-β signaling to promote M2 macrophage polarization of glioblastoma, and it may become a novel target for the treatment of glioblastoma.

Molecular Heterogeneity and Immunosuppressive Microenvironment in Glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a poor prognosis, despite surgical resection combined with radio- and chemotherapy. The major clinical obstacles contributing to poor GBM prognosis are late diagnosis, diffuse infiltration, pseudo-palisading necrosis, microvascular proliferation, and resistance to conventional therapy. These challenges are further compounded by extensive inter- and intra-tumor heterogeneity and the dynamic plasticity of GBM cells. The complex heterogeneous nature of GBM cells is facilitated by the local inflammatory tumor microenvironment, which mostly induces tumor aggressiveness and drug resistance. An immunosuppressive tumor microenvironment of GBM provides multiple pathways for tumor immune evasion. Infiltrating immune cells, mostly tumor-associated macrophages, comprise much of the non-neoplastic population in GBM. Further understanding of the immune microenvironment of GBM is essential to make advances in the development of immunotherapeutics. Recently, whole-genome sequencing, epigenomics and transcriptional profiling have significantly helped improve the prognostic and therapeutic outcomes of GBM patients. Here, we discuss recent genomic advances, the role of innate and adaptive immune mechanisms, and the presence of an established immunosuppressive GBM microenvironment that suppresses and/or prevents the anti-tumor host response.

Entry and exit of chemotherapeutically-promoted cellular dormancy in glioblastoma cells is differentially affected by the chemokines CXCL12, CXCL16, and CX3CL1

Glioblastoma multiforme (GBM) is a malignant brain tumor that evades therapy regimens. Since cellular dormancy is one strategy for surviving, and since chemokines determine the environmental conditions in which dormancy occurs, we investigated how chemokines affect temozolomide (TMZ)-promoted cellular dormancy entry and exit in GBM cells. TMZ administration over ten days promoted cellular dormancy entry, whereas discontinuing TMZ for a further 15 days resulted in resumption of proliferation. Co-administration of a chemokine cocktail containing CXCL12, CXCL16, and CX3CL1 resulted in both delayed entry and exit from cellular dormancy. A microarray-based transcriptome analysis in LN229 GBM cells revealed that cellular dormancy entry was characterized by an increased expression of CCL2 and SAA2, while THSD4, FSTL3, and VEGFC were upregulated during dormancy exit. Co-stimulation with the chemokine cocktail reduced upregulation of identified genes. After verifying the appearance of identified genes in human GBM primary cultures and ex vivo samples, we clarified whether each chemokine alone impacts cellular dormancy mechanisms using specific antagonists and selective CRISPR/Cas9 clones. While expression of CCL2 and SAA2 in LN229 cells was altered by the CXCL12-CXCR4-CXCR7 axis, CXCL16 and CX3CL1 contributed to reduced upregulation of THSD4 and, to a weaker extent, of VEGFC. The influence on FSTL3 expression depended on the entire chemokine cocktail. Effects of chemokines on dormancy entry and exit-associated genes were detectable in human GBM primary cells, too, even if in a more complex, cell-specific manner. Thus, chemokines play a significant role in the regulation of TMZ-promoted cellular dormancy in GBMs.

Prognostic value of a nine-gene signature in glioma patients based on tumor-associated macrophages expression profiling

Tumor-associated macrophages (TAMs) are regarded as the most abundantly infiltrating immune cells around the tumor microenvironment in gliomas, which plays an important role in tumorgenesis and immunosuppression. A total of 216 patients diagnosed with primary glioma were obtained from the Chinese Glioma Genome Atlas of which the RNA sequencing data was used as training set. RNA sequencing from the Cancer Genome Atlas was applicated for validation. We found that mesenchymal subtype showed strong positive correlation with macrophage-related genes (MRGs) expression. Survival analysis showed that high expression level of MRG predicted poor prognosis. A TAM-based nine-gene signature was constructed, which divided the samples into high- and low-risk of unfavorable outcome. The result of Cox regression analysis showed that the risk score was an independent prognostic factor in gliomas. Hence, the expression of TAMs was correlated with patient survival. The nine-TAM-related gene signature can predict patient survival efficiently.

Repolarization of glioblastoma macrophage cells using non-agonistic Dectin-1 ligand encapsulating TLR-9 agonist: plausible role in regenerative medicine against brain tumor

AIM OF THE STUDY

Glioblastoma multiforme (GBM) is the most severe forms of brain cancer, eventually becoming the leading cause of brain cancer-related death worldwide. Owing to the bleak surgical interventions and resistance to the different treatment regime, GBM is a parlous disease demanding newer therapeutical perspective for its treatment. Toll-like receptors (TLRs) are well-known members of pathogen recognition receptors (PRRs) and have been extensively explored for their therapeutic and prophylactic potential in an array of disease including cancer. Recent trends in drug delivery research has shown shift towards delivering short DNA sequences (CpG DNA) to endosomal TLR9 within immune cells (macrophages, dendritic cells, etc.) for the activation of desired inflammatory response using non-agonistic β-glucan particles; a well-known ligand for Dectin-1 receptors. Our study is therefore focused to explore the role of nano-encapsulated CpG ODN as critical players in polarizing M2 scavenging to much desired pro-inflammatory type.

MATERIALS AND METHODS

The nanoparticles entrapping CpG ODN 1826 were prepared by using a fungal polymer Schizophyllan (SPG). The constructed nanoparticles were characterized and assessed for their efficacy on rat glioblastoma cells (C6).

RESULTS

The constructed Schizophyllan (SPG) nanoparticles entrapping CpG ODN 1826 (95.3%) were of 25.49 nm in diameter and thus capable of crossing blood-brain barrier. The rat glioblastoma (C6) cells evaluated for intracellular oxidative burst and cytokine levels pre- and post-incubation with nanoparticles exhibited marked elevation in the expression of intracellular ROS and IFN-γ as well as IL-1β post treatment.

CONCLUSION

The findings indicate towards potentiality of repolarizing the M2 macrophages to much desired M1 phase by inducing higgh levels of oxidative burst and inflammatory cytokines. Consequently, the apoptosis was induced in glioblastoma cells establishing the suitablity of CpG ODN carrying nanoformulations as emerging therapeutic intervention for GBM.

Re-education of macrophages as a therapeutic strategy in cancer

Tumor-associated macrophages (TAMs) can be educated within the tumor microenvironment to promote cancer development and progression. While TAM-targeted agents have largely focused on macrophage depletion as an anticancer strategy, it is becoming increasingly evident that TAM re-education may represent a more effective approach. In this perspective, we discuss different means to achieve TAM re-education, and review the beneficial effects of these strategies, particularly when combined with immune checkpoint inhibitors.

Current state and future of co-inhibitory immune checkpoints for the treatment of glioblastoma

In the interaction between a tumor and the immune system, immune checkpoints play an important role, and in tumor immune escape, co-inhibitory immune checkpoints are important. Immune checkpoint inhibitors (ICIs) can enhance the immune system’s killing effect on tumors. To date, impressive progress has been made in a variety of tumor treatments; PD1/PDL1 and CTLA4 inhibitors have been approved for clinical use in some tumors. However, glioblastoma (GBM) still lacks an effective treatment. Recently, a phase III clinical trial using nivolumab to treat recurrent GBM showed no significant improvement in overall survival compared to bevacizumab. Therefore, the use of immune checkpoints in the treatment of GBM still faces many challenges. First, to clarify the mechanism of action, how different immune checkpoints play roles in tumor escape needs to be determined; which biomarkers predict a benefit from ICIs treatment and the therapeutic implications for GBM based on experiences in other tumors also need to be determined. Second, to optimize combination therapies, how different types of immune checkpoints are selected for combined application and whether combinations with targeted agents or other immunotherapies exhibit increased efficacy need to be addressed. All of these concerns require extensive basic research and clinical trials. In this study, we reviewed existing knowledge with respect to the issues mentioned above and the progress made in treatments, summarized the state of ICIs in preclinical studies and clinical trials involving GBM, and speculated on the therapeutic prospects of ICIs in the treatment of GBM.

[Assessment of the cytokine-producing resource of tumor biopsy samples from patients with invasive carcinoma of no special type and with non-malignant breast diseases]

Breast cancer, in most cases, is a malignant neoplasm associated with infiltration of a tumor with the cells that form its microenvironment and produce various cytokines. The aim of the study was to evaluate the cytokine-producing function of tumor cells and their microenvironment in biopsy specimen of patients with invasive carcinoma of no special type and in patients with benign breast diseases. To assess the cytokine-producing activity of the tumor and its microenvironment, the index of polyclonal activators influence on cytokine production by biopsy specimens of patients with invasive carcinoma of no special type (group I) and in patients with benign breast tumors (group II) was calculated. Group II was further subdivided into group IIa, which included only patients with fibroadenoma, and group IIb, which included the patients with leaf-shaped fibroadenoma, fibroadenomatosis, fibrocystic mastopathy, intraductal papillomatosis, sclerosing adenosis and fibrocystic mastopathy with microcalcifications. The concentrations of IL-2, IL-6, IL-8, IL-10, IL-17, IL-18, IL-1β, IL-1Ra, TNF-α, IFN-γ, G-CSF, GM-CSF, VEGF, and MCP-1 were measured in tumor biopsy supernatants. When comparing groups I and II, higher indices of the polyclonal activators influence on the production of IL-17, IL-18 and TNF-α were observed in patients with benign diseases. Higher indices of the polyclonal activators influence on the production of IL-18, TNF-α, and IL-1β and the ratio of IL1β/IL1Ra were observed in patients with fibroadenoma as compared to those with invasive carcinoma of no special type. There were no significant differences in the indices of the polyclonal activators influence between groups I and IIb. This suggests the existence of changes in the mammary gland in patients of group IIb similar to those present in patients with invasive carcinoma of no special type. Higher indices of polyclonal activators influence on the production of IL-1β, as well as the ratio of IL1β/IL1Ra were observed in the patients of group IIa compared to the patients of group IIb. The results of the study identify the features of the cytokine-producing resource of tumor biopsy specimens in patients with invasive carcinoma of no special type and with benign breast tumors.

Challenges to curing primary brain tumours

Despite decades of research, brain tumours remain among the deadliest of all forms of cancer. The ability of these tumours to resist almost all conventional and novel treatments relates, in part, to the unique cell-intrinsic and microenvironmental properties of neural tissues. In an attempt to encourage progress in our understanding and ability to successfully treat patients with brain tumours, Cancer Research UK convened an international panel of clinicians and laboratory-based scientists to identify challenges that must be overcome if we are to cure all patients with a brain tumour. The seven key challenges summarized in this Position Paper are intended to serve as foci for future research and investment.

Increased Antiangiogenic Effect by Blocking CCL2-dependent Macrophages in a Rodent Glioblastoma Model: Correlation Study with Dynamic Susceptibility Contrast Perfusion MRI

When glioblastoma multiforme (GBM) is treated with anti-vascular endothelial growth factor (VEGF) agents, it commonly exhibits tumor progression due to the development of resistance, which results in a dismal survival rate. GBM tumors contain a large number of monocytes/macrophages, which have been shown to be resistant to the effects of bevacizumab. It has been reported that tumor-associated macrophages (TAMs) promote resistance to bevacizumab treatment. Therefore, it is important to target TAMs in the GBM microenvironment. TAMs, which depend on chemokine ligand 2 (CCL2) for differentiation and survival, induce the expression of proangiogenic factors such as VEGF. Dynamic susceptibility contrast (DSC)-MR imaging is an advanced technique that provides information on tumor blood volume and can potentially predict the response to several treatments, including anti-angiogenic agents such as bevacizumab, in human GBM. In this study, we used a CCL2 inhibitor, mNOX-E36, to suppress the recruitment of TAMs in a CCL2-expressing rat GBM model and investigated the effect of combination therapy with bevacizumab using DSC-MR imaging. We demonstrated that the inhibition of CCL2 blocked macrophage recruitment and angiogenesis, which resulted in decreased tumor volume and blood volume in CCL2-expressing GBM in a rat model. Our results provide direct evidence that CCL2 expression can increase the resistance to bevacizumab, which can be assessed noninvasively with the DSC-MR imaging technique. This study shows that the suppression of CCL2 can play an important role in increasing the efficacy of anti-angiogenic treatment in GBM by inhibiting the recruitment of CCL2-dependent macrophages.

Preclinical Evidence of STAT3 Inhibitor Pacritinib Overcoming Temozolomide Resistance via Downregulating miR-21-Enriched Exosomes from M2 Glioblastoma-Associated Macrophages

Background: The tumor microenvironment (TME) plays a crucial role in virtually every aspect of tumorigenesis of glioblastoma multiforme (GBM). A dysfunctional TME promotes drug resistance, disease recurrence, and distant metastasis. Recent evidence indicates that exosomes released by stromal cells within the TME may promote oncogenic phenotypes via transferring signaling molecules such as cytokines, proteins, and microRNAs. Results: In this study, clinical GBM samples were collected and analyzed. We found that GBM-associated macrophages (GAMs) secreted exosomes which were enriched with oncomiR-21. Coculture of GAMs (and GAM-derived exosomes) and GBM cell lines increased GBM cells’ resistance against temozolomide (TMZ) by upregulating the prosurvival gene programmed cell death protein 4 (PDCD4) and stemness markers SRY (sex determining region y)-box 2 (Sox2), signal transducer and activator of transcription 3 (STAT3), Nestin, and miR-21-5p and increasing the M2 cytokines interleukin 6 (IL-6) and transforming growth factor beta 1(TGF-β1) secreted by GBM cells, promoting the M2 polarization of GAMs. Subsequently, pacritinib treatment suppressed GBM tumorigenesis and stemness; more importantly, pacritinib-treated GBM cells showed a markedly reduced ability to secret M2 cytokines and reduced miR-21-enriched exosomes secreted by GAMs. Pacritinib-mediated effects were accompanied by a reduction of oncomiR miR-21-5p, by which the tumor suppressor PDCD4 was targeted. We subsequently established patient-derived xenograft (PDX) models where mice bore patient GBM and GAMs. Treatment with pacritinib and the combination of pacritinib and TMZ appeared to significantly reduce the tumorigenesis of GBM/GAM PDX mice as well as overcome TMZ resistance and M2 polarization of GAMs. Conclusion: In summation, we showed the potential of pacritinib alone or in combination with TMZ to suppress GBM tumorigenesis via modulating STAT3/miR-21/PDCD4 signaling. Further investigations are warranted for adopting pacritinib for the treatment of TMZ-resistant GBM in clinical settings.

The Role of Platelets in Cancer Pathophysiology: Focus on Malignant Glioma

The link between thrombocytosis and malignancy has been well known for many years and its associations with worse outcomes have been reported mainly for solid tumors. Besides measuring platelet count, it has become popular to assess platelet function in the context of malignant diseases during the last decade. Malignant gliomas differ tremendously from malignancies outside the central nervous system because they virtually never form distant metastases. This review summarizes the current understanding of the platelet-immune cell communication and its potential role in glioma resistance and progression. Particularly, we focus on platelet-derived proinflammatory modulators, such as sphingosine-1-phosphate (S1P). The multifaceted interaction with immune cells puts the platelet into an interesting perspective regarding the recent advances in immunotherapeutic approaches in malignant glioma.

Brain Tumor Microenvironment and Host State: Implications for Immunotherapy

Glioblastoma (GBM) is a highly lethal brain tumor with poor responses to immunotherapies that have been successful in more immunogenic cancers with less immunosuppressive tumor microenvironments (TME). The GBM TME is uniquely challenging to treat due to tumor cell-extrinsic components that are native to the brain, as well as tumor-intrinsic mechanisms that aid in immune evasion. Lowering the barrier of immunosuppression by targeting the genetically stable tumor stroma presents opportunities to treat the tumor in a way that circumvents the complications of targeting a constantly mutating tumor with tumor antigen-directed therapies. Tumor-associated monocytes, macrophages, and microglia are a stromal element of particular interest. Macrophages and monocytes compose the bulk of infiltrating immune cells and are considered to have protumor and immunosuppressive effects. Targeting these cells or other stromal elements is expected to convert what is considered the "cold" TME of GBM to a more "hot" TME phenotype. This conversion could increase the effectiveness of what have become conventional frontline immunotherapies in GBM-creating opportunities for better treatment through combination therapy.

Harnessing the immune system in glioblastoma

Glioblastoma is the most common primary malignant brain tumour. Survival is poor and improved treatment options are urgently needed. Although immunotherapies have emerged as effective treatments for a number of cancers, translation of these through to brain tumours is a distinct challenge, particularly due to the blood-brain barrier and the unique immune tumour microenvironment afforded by CNS-specific cells. This review discusses the immune system within the CNS, mechanisms of immune escape employed by glioblastoma, and the immunological effects of conventional glioblastoma treatments. Novel therapies for glioblastoma that harness the immune system and their current clinical progress are outlined, including cancer vaccines, T-cell therapies and immune checkpoint modulators.

Targeted Theranostic Nanoparticles for Brain Tumor Treatment

The poor prognosis and rapid recurrence of glioblastoma (GB) are associated to its fast-growing process and invasive nature, which make difficult the complete removal of the cancer infiltrated tissues. Additionally, GB heterogeneity within and between patients demands a patient-focused method of treatment. Thus, the implementation of nanotechnology is an attractive approach considering all anatomic issues of GB, since it will potentially improve brain drug distribution, due to the interaction between the blood⁻brain barrier and nanoparticles (NPs). In recent years, theranostic techniques have also been proposed and regarded as promising. NPs are advantageous for this application, due to their respective size, easy surface modification and versatility to integrate multiple functional components in one system. The design of nanoparticles focused on therapeutic and diagnostic applications has increased exponentially for the treatment of cancer. This dual approach helps to understand the location of the tumor tissue, the biodistribution of nanoparticles, the progress and efficacy of the treatment, and is highly useful for personalized medicine-based therapeutic interventions. To improve theranostic approaches, different active strategies can be used to modulate the surface of the nanotheranostic particle, including surface markers, proteins, drugs or genes, and take advantage of the characteristics of the microenvironment using stimuli responsive triggers. This review focuses on the different strategies to improve the GB treatment, describing some cell surface markers and their ligands, and reports some strategies, and their efficacy, used in the current research.

A nonmyeloablative chimeric mouse model accurately defines microglia and macrophage contribution in glioma

Aims

Resident and peripherally derived glioma associated microglia/macrophages (GAMM) play a key role in driving tumour progression, angiogenesis, invasion and attenuating host immune responses. Differentiating these cells’ origins is challenging and current preclinical models such as irradiation‐based adoptive transfer, parabiosis and transgenic mice have limitations. We aimed to develop a novel nonmyeloablative transplantation (NMT) mouse model that permits high levels of peripheral chimerism without blood‐brain barrier (BBB) damage or brain infiltration prior to tumour implantation.

Methods

NMT dosing was determined in C57BL/6J or Pep3/CD45.1 mice conditioned with concentrations of busulfan ranging from 25 mg/kg to 125 mg/kg. Donor haematopoietic cells labelled with eGFP or CD45.2 were injected via tail vein. Donor chimerism was measured in peripheral blood, bone marrow and spleen using flow cytometry. BBB integrity was assessed with anti‐IgG and anti‐fibrinogen antibodies. Immunocompetent chimerised animals were orthotopically implanted with murine glioma GL‐261 cells. Central and peripheral cell contributions were assessed using immunohistochemistry and flow cytometry. GAMM subpopulation analysis of peripheral cells was performed using Ly6C/MHCII/MerTK/CD64.

Results

NMT achieves >80% haematopoietic chimerism by 12 weeks without BBB damage and normal life span. Bone marrow derived cells (BMDC) and peripheral macrophages accounted for approximately 45% of the GAMM population in GL‐261 implanted tumours. Existing markers such as CD45 high/low proved inaccurate to determine central and peripheral populations while Ly6C/MHCII/MerTK/CD64 reliably differentiated GAMM subpopulations in chimerised and unchimerised mice.

Conclusion

NMT is a powerful method for dissecting tumour microglia and macrophage subpopulations and can guide further investigation of BMDC subsets in glioma and neuro‐inflammatory diseases.

IL-10 secreted by M2 macrophage promoted tumorigenesis through interaction with JAK2 in glioma

M2 tumor-associated macrophage has been found to play a supportive role in the progression of glioma. The underlying mechanism, nevertheless, has been largely unknown. In our study, to investigate how M2 macrophage played role in glioma, firstly we've analyzed the clinicopathological significance of M2 macrophage existence on clinical tissues of glioma using detection of CD163 expression with immunohistochemistry. Then, we've artificially induced M2 macrophage from human monocyte cell line THP-1, followed by co-culture with glioma cell lines in vitro. It was found that M2 macrophage was shown to be markedly distributed in glioma relative to paired normal control; and high prevalence of M2 macrophage was significantly associated with poorer overall survival and tumor progression. Moreover, M2 macrophage was found to be able to promote the growth in vitro and tumorigenesis in vivo in xenografted mice model. Mechanistically, it is IL-10 from M2 macrophage that was shown to promote proliferation, dependent on activation of JAK2/STAT3 pathway. Further, IL-10 was found to be able to interact with JAK2 in glioma cells. Taking together, we for the first time found that IL-10 from M2 macrophage promoted proliferation of glioma through interaction with JAK2; thereby activating the JAK2/STAT3 pathway, indicative of IL-10 could be used as a therapeutic target in the curing of glioma.

Novel TREM-1 Inhibitors Attenuate Tumor Growth and Prolong Survival in Experimental Pancreatic Cancer

Pancreatic cancer (PC) is a highly lethal cancer with an urgent need to expand the limited treatment options for patients. Tumor-associated macrophages (TAMs) promote tumor aggressiveness and metastasis. High expression of triggering receptor expressed on myeloid cells 1 (TREM-1) on TAMs directly correlates with poor survival in patients with non-small cell lung cancer (NSCLC). We have previously hypothesized that blockade of TREM-1 could be a promising therapeutic strategy to treat cancer and shown that the novel, ligand-independent TREM-1 inhibitory peptides rationally designed using the signaling chain homooligomerization (SCHOOL) strategy suppress NSCLC growth in vivo. Here, we evaluated the therapeutic potential of these inhibitors in three human PC xenograft mouse models. Administration of SCHOOL peptides resulted in a strong antitumor effect achieving an optimal treatment/control (T/C) value of 19% depending on the xenograft and formulation used and persisting even after treatment was halted. The effect correlated significantly with increased survival and suppressed TAM infiltration. The peptides were well-tolerated when deployed either in free form or formulated into lipopeptide complexes for peptide half-life extension and targeted delivery. Finally, blockade of TREM-1 significantly reduced serum levels of interleukin (IL)-1α, IL-6, and macrophage colony-stimulating factor (M-CSF), but not vascular endothelial growth factor, suggesting M-CSF-dependent antitumor mechanisms. Collectively, these promising data suggest that SCHOOL TREM-1-specific peptide inhibitors have a cancer type independent, therapeutically beneficial antitumor activity and can be potentially used as a stand-alone therapy or as a component of combinational therapy for PC, NSCLC, and other solid tumors.

Integration of RNA-Seq and RPPA data for survival time prediction in cancer patients

Integration of several types of patient data in a computational framework can accelerate the identification of more reliable biomarkers, especially for prognostic purposes. This study aims to identify biomarkers that can successfully predict the potential survival time of a cancer patient by integrating the transcriptomic (RNA-Seq), proteomic (RPPA), and protein-protein interaction (PPI) data. The proposed method -RPBioNet- employs a random walk-based algorithm that works on a PPI network to identify a limited number of protein biomarkers. Later, the method uses gene expression measurements of the selected biomarkers to train a classifier for the survival time prediction of patients. RPBioNet was applied to classify kidney renal clear cell carcinoma (KIRC), glioblastoma multiforme (GBM), and lung squamous cell carcinoma (LUSC) patients based on their survival time classes (long- or short-term). The RPBioNet method correctly identified the survival time classes of patients with between 66% and 78% average accuracy for three data sets. RPBioNet operates with only 20 to 50 biomarkers and can achieve on average 6% higher accuracy compared to the closest alternative method, which uses only RNA-Seq data in the biomarker selection. Further analysis of the most predictive biomarkers highlighted genes that are common for both cancer types, as they may be driver proteins responsible for cancer progression. The novelty of this study is the integration of a PPI network with mRNA and protein expression data to identify more accurate prognostic biomarkers that can be used for clinical purposes in the future.

Spatial Targeting of Tumor-Associated Macrophages and Tumor Cells with a pH-Sensitive Cluster Nanocarrier for Cancer Chemoimmunotherapy

Chemoimmunotherapy, which combines chemotherapeutics with immune-modulating agents, represents an appealing approach for improving cancer therapy. To optimize its therapeutic efficacy, differentially delivering multiple therapeutic drugs to target cells is desirable. Here we developed an immunostimulatory nanocarrier (denoted as ^BLZ-945SCNs/Pt) that could spatially target tumor-associated macrophages (TAMs) and tumor cells for cancer chemoimmunotherapy. ^BLZ-945SCNs/Pt undergo supersensitive structure collapse in the prevascular regions of tumor tissues and enable the simultaneous release of platinum (Pt)-prodrug conjugated small particles and BLZ-945, a small molecule inhibitor of colony stimulating factor 1 receptor (CSF-1R) of TAMs. The released BLZ-945 can be preferentially taken up by TAMs to cause TAMs depletion from tumor tissues, while the small particles carrying Pt-prodrug enable deep tumor penetration as well as intracellularly specific drug release to kill more cancer cells. Our studies demonstrate that ^BLZ-945SCNs/Pt outperform their monotherapy counterparts in multiple tumor models. The underlying mechanism studies suggest that the designer pH-sensitive codelivery nanocarrier not only induces apoptosis of tumor cells but also modulates the tumor immune environment to eventually augment the antitumor effect of CD8⁺ cytotoxic T cells through TAMs depletion.

The Microenvironmental Landscape of Brain Tumors

The brain tumor microenvironment (TME) is emerging as a critical regulator of cancer progression in primary and metastatic brain malignancies. The unique properties of this organ require a specific framework for designing TME-targeted interventions. Here, we discuss a number of these distinct features, including brain-resident cell types, the blood-brain barrier, and various aspects of the immune-suppressive environment. We also highlight recent advances in therapeutically targeting the brain TME in cancer. By developing a comprehensive understanding of the complex and interconnected microenvironmental landscape of brain malignancies we will greatly expand the range of therapeutic strategies available to target these deadly diseases.

CCL2/CCR2 signaling pathway in glioblastoma multiforme

Glioblastoma multiform (GBM) is described as one of the most frequent primary brain tumors. These types of malignancies constitute only 15% of all primary brain tumors. Despite, extensive developments on effective therapeutic methods during the 20th century as well as the first decade of the present century (21st), the median survival rate for patients suffering from GBM is only approximately 15 months, even in response to multi-modal therapy. numerous types of reticuloendothelial system cells such as macrophages and microglial cells occupied within both GBM and also normal surrounding tissues. These immune cells acquire an otherwise activated phenotype with potent tumor-tropic functions that contribute to the glioma growth and invasion. The CC chemokine, CCL2 (previously named MCP-1) is of the most important CC chemokines family member involving in regulation of oriented migration and penetrative infiltration of mainly reticuloendothelial system cells specifically monocyte/macrophage phenotypes. Fundamental parts are played by CCL2 and its related receptor (the CCR2) in brain tumors and obviously in migration of monocytes from the bloodstream through the vascular endothelium. Therefore, CCL2/CCR2 axis is required for the routine immunological surveillance of tissues, in accordance with response to inflammation. Briefly, in this review, we have tried our best to collect the latest, straightened and summarize literature reports exist within data base regarding the interaction between microglia/macrophages and CCL2/CCR2 axis in GBM. We aimed to discuss potential application of this chemokine/receptor interaction axis for the expansion of future anti-glioma therapies as well.

Macrophage Ontogeny Underlies Differences in Tumor-Specific Education in Brain Malignancies

Extensive transcriptional and ontogenetic diversity exists among normal tissue-resident macrophages, with unique transcriptional profiles endowing the cells with tissue-specific functions. However, it is unknown whether the origins of different macrophage populations affect their roles in malignancy. Given potential artifacts associated with irradiation-based lineage tracing, it remains unclear if bone-marrow-derived macrophages (BMDMs) are present in tumors of the brain, a tissue with no homeostatic involvement of BMDMs. Here, we employed multiple models of murine brain malignancy and genetic lineage tracing to demonstrate that BMDMs are abundant in primary and metastatic brain tumors. Our data indicate that distinct transcriptional networks in brain-resident microglia and recruited BMDMs are associated with tumor-mediated education yet are also influenced by chromatin landscapes established before tumor initiation. Furthermore, we demonstrate that microglia specifically repress Itga4 (CD49D), enabling its utility as a discriminatory marker between microglia and BMDMs in primary and metastatic disease in mouse and human.

Targeting the Tumor Microenvironment: The Protumor Effects of IL-17 Related to Cancer Type

The inflammatory process contributes to immune tolerance as well as to tumor progression and metastasis. By releasing extracellular signals, cancerous cells constantly shape their surrounding microenvironment through their interactions with infiltrating immune cells, stromal cells and components of extracellular matrix. Recently, the pro-inflammatory interleukin 17 (IL-17)-producing T helper lymphocytes, the Th17 cells, and the IL-17/IL-17 receptor (IL-17R) axis gained special attention. The IL-17 family comprises at least six members, IL-17A, IL-17B, IL-17C, IL-17D, IL-17E (also called IL-25), and IL-17F. Secreted as disulfide-linked homo- or heterodimers, the IL-17 bind to the IL-17R, a type I cell surface receptor, of which there are five variants, IL-17RA to IL-17RE. This review focuses on the current advances identifying the promoting role of IL-17 in carcinogenesis, tumor metastasis and resistance to chemotherapy of diverse solid cancers. While underscoring the IL-17/IL-17R axis as promising immunotherapeutic target in the context of cancer managing, this knowledge calls upon further in vitro and in vivo studies that would allow the development and implementation of novel strategies to combat tumors.

Trial Watch: Immunotherapy plus radiation therapy for oncological indications

Malignant cells succumbing to some forms of radiation therapy are particularly immunogenic and hence can initiate a therapeutically relevant adaptive immune response. This reflects the intrinsic antigenicity of malignant cells (which often synthesize a high number of potentially reactive neo-antigens) coupled with the ability of radiation therapy to boost the adjuvanticity of cell death as it stimulates the release of endogenous adjuvants from dying cells. Thus, radiation therapy has been intensively investigated for its capacity to improve the therapeutic profile of several anticancer immunotherapies, including (but not limited to) checkpoint blockers, anticancer vaccines, oncolytic viruses, Toll-like receptor (TLR) agonists, cytokines, and several small molecules with immunostimulatory effects. Here, we summarize recent preclinical and clinical advances in this field of investigation.

The tumor microenvironment underlies acquired resistance to CSF-1R inhibition in gliomas

Macrophages accumulate with glioblastoma multiforme (GBM) progression and can be targeted via inhibition of colony-stimulating factor-1 receptor (CSF-1R) to regress high-grade tumors in animal models of this cancer. However, whether and how resistance emerges in response to sustained CSF-1R blockade is unknown. We show that although overall survival is significantly prolonged, tumors recur in >50% of mice. Gliomas reestablish sensitivity to CSF-1R inhibition upon transplantation, indicating that resistance is tumor microenvironment-driven. Phosphatidylinositol 3-kinase (PI3K) pathway activity was elevated in recurrent GBM, driven by macrophage-derived insulin-like growth factor-1 (IGF-1) and tumor cell IGF-1 receptor (IGF-1R). Combining IGF-1R or PI3K blockade with CSF-1R inhibition in recurrent tumors significantly prolonged overall survival. Our findings thus reveal a potential therapeutic approach for treating resistance to CSF-1R inhibitors.

Intratumoral heterogeneity in glioblastoma: don't forget the peritumoral brain zone

Glioblastoma (GB) is the most frequent and aggressive primary tumor of the central nervous system. Prognosis remains poor despite ongoing progress. In cases where the gadolinium-enhanced portion of the GB is completely resected, 90% of recurrences occur at the margin of surgical resection in the macroscopically normal peritumoral brain zone (PBZ). Intratumoral heterogeneity in GB is currently a hot topic in neuro-oncology, and the GB PBZ may be involved in this phenomenon. Indeed, this region, which possesses specific properties, has been less studied than the core of the GB tumor. The high rate of local recurrence in the PBZ and the limited success of targeted therapies against GB demonstrate the need for a better understanding of the PBZ. We present here a review of the literature on the GB PBZ, focusing on its radiological, cellular, and molecular characteristics. We discuss how intraoperative analysis of the PBZ is important for the optimization of surgical resection and the development of targeted therapies against GB.

Microenvironmental regulation of therapeutic response in cancer

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis but also has profound effects on therapeutic efficacy. In the case of microenvironment-mediated resistance this can involve an intrinsic response, including the co-option of pre-existing structural elements and signaling networks, or an acquired response of the tumor stroma following the therapeutic insult. Alternatively, in other contexts, the TME has a multifaceted ability to enhance therapeutic efficacy. This review examines recent advances in our understanding of the contribution of the TME during cancer therapy and discusses key concepts that may be amenable to therapeutic intervention.