Absence of host NF-κB p50 induces murine glioblastoma tumor regression, increases survival, and decreases T-cell induction of tumor-associated macrophage M2 polarization

TBK1 is involved in M-CSF-induced macrophage polarization through mediating the IRF5/IRF4 axis

TANK binding kinase 1 (TBK1) is an important kinase that is involved in innate immunity and tumor development. Macrophage colony-stimulating factor (M-CSF) regulates the differentiation and function of macrophages towards the immunosuppressive M2 phenotype in the glioblastoma multiforme microenvironment. The role of TBK1 in macrophages, especially in regulating macrophage polarization in response to M-CSF stimulation, remains unclear. Here, we found high TBK1 expression in human glioma-infiltrating myeloid cells and that phosphorylated TBK1 was highly expressed in M-CSF-stimulated macrophages but not in granulocyte-macrophage CSF-induced macrophages (granulocyte-macrophage-CSF is involved in the polarization of M1 macrophages). Conditional deletion of TBK1 in myeloid cells induced M-CSF-stimulated bone marrow-derived macrophages to exhibit a proinflammatory M1-like phenotype with increased protein expression of CD86, interleukin-1β and tumor necrosis factor-α, as well as decreased expression of arginase 1. Mechanistically, TBK1 deletion or inhibition by amlexanox or GSK8612 reduced the expression of the transcription factor interferon-regulatory factor (IRF)4 and increased the level of IRF5 activation in macrophages stimulated with M-CSF, leading to an M1-like profile with highly proinflammatory factors. IRF5 deletion reversed the effect of TBK1 inhibition on M-CSF-mediated macrophage polarization. Our findings suggest that TBK1 contributes to the regulation of macrophage polarization in response to M-CSF stimulation partly through the IRF5/IRF4 axis.

VISTA Emerges as a Promising Target against Immune Evasion Mechanisms in Medulloblastoma

BACKGROUND

Relapsed medulloblastoma (MB) poses a significant therapeutic challenge due to its highly immunosuppressive tumor microenvironment. Immune checkpoint inhibitors (ICIs) have struggled to mitigate this challenge, largely due to low T-cell infiltration and minimal PD-L1 expression. Identifying the mechanisms driving low T-cell infiltration is crucial for developing more effective immunotherapies.

METHODS

We utilize a syngeneic mouse model to investigate the tumor immune microenvironment of MB and compare our findings to transcriptomic and proteomic data from human MB.

RESULTS

Flow cytometry reveals a notable presence of CD45hi/CD11bhi macrophage-like and CD45int/CD11bint microglia-like tumor-associated macrophages (TAMs), alongside regulatory T-cells (Tregs), expressing high levels of the inhibitory checkpoint molecule VISTA. Compared to sham control mice, the CD45hi/CD11bhi compartment significantly expands in tumor-bearing mice and exhibits a myeloid-specific signature composed of VISTA, CD80, PD-L1, CTLA-4, MHCII, CD40, and CD68. These findings are corroborated by proteomic and transcriptomic analyses of human MB samples. Immunohistochemistry highlights an abundance of VISTA-expressing myeloid cells clustering at the tumor-cerebellar border, while T-cells are scarce and express FOXP3. Additionally, tumor cells exhibit immunosuppressive properties, inhibiting CD4 T-cell proliferation in vitro. Identification of VISTA's binding partner, VSIG8, on tumor cells, and its correlation with increased VISTA expression in human transcriptomic analyses suggests a potential therapeutic target.

CONCLUSIONS

This study underscores the multifaceted mechanisms of immune evasion in MB and highlights the therapeutic potential of targeting the VISTA-VSIG axis to enhance anti-tumor responses.

CCR7 affects the tumor microenvironment by regulating the activation of naïve CD8+ T cells to promote the proliferation of oral squamous cell carcinoma

BACKGROUND

Head and neck cancer is the sixth most common malignancy worldwide, and oral squamous cell carcinoma (OSCC) is the most common head and neck cancer, being one of the leading causes of cancer morbidity and mortality worldwide. CC Chemokine receptor 7(CCR7) is a multifunctional G protein-coupled trans-membrane chemokine that affects immune cell chemotaxis, migration, and cancer progression through its interaction with its ligands C-C motif chemokine ligand 19(CCL19) and C-C motif chemokine ligand 21(CCL21). Numerous studies have demonstrated the involvement of CCR7 in the malignant progression of a variety of cancers, reflecting the pro-cancer properties of CCR7. The Cancer Genome Atlas data suggests CCR7 has elevated expression in oral cancer. Specifically, CCR7 expression in tumor microenvironment (TME) may regulate the ability of some immune cells to engage in anti-tumor immune responses. Since CD8+ T cells have become a key immunotherapeutic target, the role of CCR7 in antitumor immune response of naïve CD8+ T cells in TME has not been thoroughly investigated.

METHODS

A CCR7 knockout mouse model was constructed, and the mechanism of ccr7 on the regulation of tumor microenvironment by naïve CD8+ T cells was verified under the guidance of single-cell RNA sequencing combined with in vivo animal experiments and in vitro cell experiments.

RESULTS

CCR7 is knocked out with impaired tumor growth and altered CD8+ T cell profiles, revealing the importance of this protein in OSCC.

CONCLUSIONS

Inhibition of CCR7 enhances CD8+ T cell activation, proliferation, and anti-tumor function, suggesting its potential as a therapeutic target.

Peritumoral brain zone in glioblastoma: biological, clinical and mechanical features

Glioblastoma is a highly aggressive and invasive tumor that affects the central nervous system (CNS). With a five-year survival rate of only 6.9% and a median survival time of eight months, it has the lowest survival rate among CNS tumors. Its treatment consists of surgical resection, subsequent fractionated radiotherapy and concomitant and adjuvant chemotherapy with temozolomide. Despite the implementation of clinical interventions, recurrence is a common occurrence, with over 80% of cases arising at the edge of the resection cavity a few months after treatment. The high recurrence rate and location of glioblastoma indicate the need for a better understanding of the peritumor brain zone (PBZ). In this review, we first describe the main radiological, cellular, molecular and biomechanical tissue features of PBZ; and subsequently, we discuss its current clinical management, potential local therapeutic approaches and future prospects.

Revealing the clinical effect and biological mechanism of acupuncture in COPD: A review

BACKGROUND

To provide new ideas for the clinical and mechanism research of acupuncture in the treatment of chronic obstructive pulmonary disease (COPD), this study systematically reviews clinical research and the progress of basic research of acupuncture in the treatment of COPD.

METHODS

PubMed and Web of Science databases were searched using acupuncture and COPD as keywords in the last 10 years, and the included literature was determined according to exclusion criteria.

FINDINGS

Acupuncture can relieve clinical symptoms, improve exercise tolerance, anxiety, and nutritional status, as well as hemorheological changes (blood viscosity), reduce the inflammatory response, and reduce the duration and frequency of COPD in patients with COPD. Mechanistically, acupuncture inhibits M1 macrophage activity, reduces neutrophil infiltration, reduces inflammatory factor production in alveolar type II epithelial cells, inhibits mucus hypersecretion of airway epithelial cells, inhibits the development of chronic inflammation in COPD, and slows tissue structure destruction. Acupuncture may control pulmonary COPD inflammation through the vagal-cholinergic anti-inflammatory, vagal-adrenomedullary-dopamine, vagal-dual-sensory nerve fiber-pulmonary, and CNS-hypothalamus-orexin pathways. Furthermore, acupuncture can increase endogenous cortisol levels by inhibiting the HPA axis, thus improving airway antioxidant capacity and reducing airway inflammation in COPD. In conclusion, the inhibition of the chronic inflammatory response is the key mechanism of acupuncture treatment for COPD.

Comparative Insight into Microglia/Macrophages-Associated Pathways in Glioblastoma and Alzheimer's Disease

Microglia and macrophages are pivotal to the brain's innate immune response and have garnered considerable attention in the context of glioblastoma (GBM) and Alzheimer's disease (AD) research. This review delineates the complex roles of these cells within the neuropathological landscape, focusing on a range of signaling pathways-namely, NF-κB, microRNAs (miRNAs), and TREM2-that regulate the behavior of tumor-associated macrophages (TAMs) in GBM and disease-associated microglia (DAMs) in AD. These pathways are critical to the processes of neuroinflammation, angiogenesis, and apoptosis, which are hallmarks of GBM and AD. We concentrate on the multifaceted regulation of TAMs by NF-κB signaling in GBM, the influence of TREM2 on DAMs' responses to amyloid-beta deposition, and the modulation of both TAMs and DAMs by GBM- and AD-related miRNAs. Incorporating recent advancements in molecular biology, immunology, and AI techniques, through a detailed exploration of these molecular mechanisms, we aim to shed light on their distinct and overlapping regulatory functions in GBM and AD. The review culminates with a discussion on how insights into NF-κB, miRNAs, and TREM2 signaling may inform novel therapeutic approaches targeting microglia and macrophages in these neurodegenerative and neoplastic conditions. This comparative analysis underscores the potential for new, targeted treatments, offering a roadmap for future research aimed at mitigating the progression of these complex diseases.

Anti-inflammatory effects of acupuncture in the treatment of chronic obstructive pulmonary disease

Numerous randomised controlled trials have suggested the positive effects of acupuncture on chronic obstructive pulmonary disease (COPD). However, the underlying therapeutic mechanisms of acupuncture for COPD have not been clearly summarized yet. Inflammation is central to the development of COPD. In this review, we elucidate the effects and underlying mechanisms of acupuncture from an anti-inflammatory perspective based on animal studies. Cigarette smoke combined with lipopolysaccharide is often used to establish animal models of COPD. Electroacupuncture can be an effective intervention to improve inflammation in COPD, and Feishu (BL13) and Zusanli (ST36) can be used as basic acupoints in COPD animal models. Different acupuncture types can regulate different types of inflammatory cytokines; meanwhile, different acupuncture types and acupoint options have similar effects on modulating the level of inflammatory cytokines. In particular, acupuncture exerts anti-inflammatory effects by inhibiting the release of inflammatory cells, inflammasomes and inflammatory cytokines. The main underlying mechanism through which acupuncture improves inflammation in COPD is the modulation of relevant signalling pathways: nuclear factor-κB (NF-κB) (e.g., myeloid differentiation primary response 88/NF-κB, toll-like receptor-4/NF-κB, silent information regulator transcript-1/NF-κB), mitogen-activated protein kinase signalling pathways (extracellular signal-regulated kinase 1/2, p38 and c-Jun NH2-terminal kinase), cholinergic anti-inflammatory pathway, and dopamine D2 receptor pathway. The current synthesis will be beneficial for further research on the effect of acupuncture on COPD inflammation. Please cite this article as: Jiang LH, Li PJ, Wang YQ, Jiang ML, Han XY, Bao YD, Deng XL, Wu WB, Liu XD. Anti-inflammatory effects of acupuncture in the treatment of chronic obstructive pulmonary disease. J Integr Med. 2023; 21(6): 518-527.

The diversity and dynamics of tumor-associated macrophages in recurrent glioblastoma

Despite tremendous efforts to exploit effective therapeutic strategies, most glioblastoma (GBM) inevitably relapse and become resistant to therapies, including radiotherapy and immunotherapy. The tumor microenvironment (TME) of recurrent GBM (rGBM) is highly immunosuppressive, dominated by tumor-associated macrophages (TAMs). TAMs consist of tissue-resident microglia and monocyte-derived macrophages (MDMs), which are essential for favoring tumor growth, invasion, angiogenesis, immune suppression, and therapeutic resistance; however, restricted by the absence of potent methods, the heterogeneity and plasticity of TAMs in rGBM remain incompletely investigated. Recent application of single-cell technologies, such as single-cell RNA-sequencing has enabled us to decipher the unforeseen diversity and dynamics of TAMs and to identify new subsets of TAMs which regulate anti-tumor immunity. Here, we first review hallmarks of the TME, progress and challenges of immunotherapy, and the biology of TAMs in the context of rGBM, including their origins, categories, and functions. Next, from a single-cell perspective, we highlight recent findings regarding the distinctions between tissue-resident microglia and MDMs, the identification and characterization of specific TAM subsets, and the dynamic alterations of TAMs during tumor progression and treatment. Last, we briefly discuss the potential of TAM-targeted strategies for combination immunotherapy in rGBM. We anticipate the comprehensive understanding of the diversity and dynamics of TAMs in rGBM will shed light on further improvement of immunotherapeutic efficacy in rGBM.

Infiltration of Apoptotic M2 Macrophage Subpopulation Is Negatively Correlated with the Immunotherapy Response in Colorectal Cancer

The polarization of tumor-associated macrophages (TAMs) plays a key role in tumor development and immunotherapy in colorectal cancer (CRC) patients. However, the impact of apoptosis on TAM polarization and immunotherapy efficacy in patients with different mismatch repair statuses (MMR) remains unclear. Here, we constructed an atlas of macrophage and found a higher rate of infiltration of M2-like TAM subpopulation in pMMR CRC tumor tissues compared with that in dMMR CRC tumor tissues. Importantly, a lower infiltration rate of M2c-like TAMs was associated with immunotherapy response. The M2 polarization trajectory revealed the apoptosis of M2c-like TAMs in dMMR while the differentiation of M2c-like TAMs in pMMR, implying a higher polarization level of M2 in pMMR. Furthermore, we found that a high expression of S100A6 induces the apoptosis of M2c-like TAMs in dMMR. In conclusion, we identified apoptotic TAM subpopulations in the M2 polarization trajectory and found that apoptosis caused by the high expression of S100A6 reduces their infiltration in tumors as well as the level of M2 polarization and contributes to a favorable immunotherapy response. These findings provide new insights into the potential role of apoptosis in suppressing tumors and enhancing immunotherapeutic efficacy.

The In Vitro Antimicrobial and Antibiofilm Activities of Lysozyme against Gram-Positive Bacteria

Objective

To analyze the in vitro antibacterial and antibiofilm activities of lysozyme (LYS) and its combination with various drugs against Gram-positive bacteria (GPB, n = 9), thus to provide an exploration direction for drug development.

Methods

The minimum inhibitory concentrations (MICs) of linezolid (LZD), amikacin (AMK), ceftriaxone/sulbactam (CRO/SBT), cefotaxime/sulbactam (CTX/SBT), piperacillin/sulbactam (PIP/SBT), doxycycline (DOX), levofloxacin (LVX), amoxicillin/clavulanate potassium (7 : 1, AK71), imipenem (IPM), azithromycin (AZM), and their combinations with LYS were determined with tuber twice dilution. The antimicrobial and antibiofilm activities of LYS, AZM, LVX, and their combinations with others were evaluated through MTT and crystal violet assay.

Results

High-dose LYS (30 μg/mL) combined with PIP/SBT and AK71, respectively, showed synergistic antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA), while it showed no synergistic activities when combined with other drugs. LYS and AZM inhibited the biofilm formation of one MRSA strain, but they and LVX had no similar activities against methicillin-resistant Staphylococcus epidermidis (MRSE) or vancomycin-resistant Enterococcus faecium (VREF). Particularly, LYS increased the permeability of biofilms of MRSA 33 and exhibited antibiofilm activities against MRSA 31 (inhibition rate = 38.1%) and MRSE 61 (inhibition rate = 46.6%). The combinations of PIP/SBT+LYS, AMK+LYS, and LZD+LYS showed stronger antibiofilm activities against MRSA 62, MRSE 62, MRSE 63, and VREF 11.

Conclusion

The antimicrobial and antibiofilm activities of LYS against MRSA were better than AZM, while that of LYS against MRSE and VREF, respectively, was similar with AZM and LVX.

A Quantitative Digital Analysis of Tissue Immune Components Reveals an Immunosuppressive and Anergic Immune Response with Relevant Prognostic Significance in Glioblastoma

Objectives: Immunostimulatory therapies using immune checkpoint blockers show clinical activity in a subset of glioblastoma (GBM) patients. Several inhibitory mechanisms play a relevant role in the immune response to GBM. With the objective of analyzing the tumor immune microenvironment and its clinical significance, we quantified several relevant immune biomarkers. Design: We studied 76 primary (non-recurrent) GBMs with sufficient clinical follow-up, including a subgroup of patients treated with a dendritic cell vaccine. The IDH-mutation, EGFR-amplification, and MGMT methylation statuses were determined. Several relevant immune biomarkers, including CD163, CD8, PD1, and PDL1, were quantified in representative selected areas by digital image analysis and semiquantitative evaluation. The percentage of each immune expression was calculated with respect to the total number of tumor cells. Results: All GBMs were wild-type IDH, with a subgroup of classical GBMs according to the EGFR amplification (44%). Morphologically, CD163 immunostained microglia and intratumor clusters of macrophages were observed. A significant direct correlation was found between the expression of CD8 and the mechanisms of lymphocyte immunosuppression, in such a way that higher values of CD8 were directly associated with higher values of CD163 (p < 0.001), PDL1 (0.026), and PD1 (0.007). In a multivariate analysis, high expressions of CD8+ (HR = 2.05, 95%CI (1.02−4.13), p = 0.034) and CD163+ cells (HR 2.50, 95%CI (1.29−4.85), p = 0.007), were associated with shorter survival durations. The expression of immune biomarkers was higher in the non-classical (non-EGFR amplified tumors) GBMs. Other relevant prognostic factors were age, receipt of the dendritic cell vaccine, and MGMT methylation status. Conclusions: In accordance with the inverse correlation between CD8 and survival and the direct correlation between effector cells and CD163 macrophages and immune-checkpoint expression, we postulate that CD8 infiltration could be placed in a state of anergy or lymphocytic inefficient activity. Furthermore, the significant inverse correlation between CD163 tissue concentration and survival explains the relevance of this type of immune cell when creating a strong immunosuppressive environment. This information may potentially be used to support the selection of patients for immunotherapy.

Chemerin enhances mesenchymal features of glioblastoma by establishing autocrine and paracrine networks in a CMKLR1-dependent manner

Glioblastoma multiforme (GBM) with mesenchymal features exhibits enhanced chemotherapeutic resistance and results in reduced overall survival. Recent studies have suggested that there is a positive correlation between the GBM mesenchymal status and immune cell infiltration. However, the mechanisms by which GBM acquires its mesenchymal features in a tumor immune microenvironment-dependent manner remains unknown. Here, we uncovered a chemerin-mediated autocrine and paracrine network by which the mesenchymal phenotype of GBM cells is strengthened. We identified chemerin as a prognostic secretory protein mediating the mesenchymal phenotype-promoting network between tumor-associated macrophages (TAMs) and tumor cells in GBM. Mechanistically, chemerin promoted the mesenchymal features of GBM by suppressing the ubiquitin-proteasomal degradation of CMKLR1, a chemerin receptor predominantly expressed on TAMs and partially expressed on GBM cells, thereby enhancing NF-κB pathway activation. Moreover, chemerin was found to be involved in the recruitment of TAMs in the GBM tumor microenvironment. We revealed that chemerin also enhances the mesenchymal phenotype-promoting ability of TAMs and promotes their M2 polarization via a CMKLR1/NF-κB axis, which further exacerbates the mesenchymal features of GBM. Blocking the chemerin/CMKLR1 axis with 2-(α-naphthoyl) ethyltrimethylammonium iodide disrupted the mesenchymal network and suppressed tumor growth in GBM. These results suggest the therapeutic potential of targeting the chemerin/CMKLR1 axis to block the mesenchymal network in GBM.

Transcription factors in glioblastoma - Molecular pathogenesis and clinical implications

Glioblastoma, also known as glioblastoma multiforme (GBM), is one of the most lethal human cancers, however, the molecular mechanisms driving GBM remain largely elusive. Recent studies have revealed that transcription factors are significantly involved in GBM biology. Transcription factors (TFs), which are proteins that bind DNA to regulate gene expression, have critical roles at focal points in signaling pathways, orchestrating many cellular processes, such as cell growth and proliferation, differentiation, apoptosis, immune responses, and metabolism. Dysregulated or mutated TFs are common in GBM, resulting in aberrant gene expression that promotes tumor initiation, progression, and resistance to conventional therapies. In the present Review, we focus on TFs that are implicated in GBM pathogenesis, highlighting their oncogenic or tumor suppressive functions and describing the molecular mechanisms underlying their effect on GBM cells. We also discuss their use as biomarkers for GBM prognosis and therapeutic response, as well as their targeting with drugs for GBM treatment. Deciphering the role of TFs in the biology of GBM will provide new insights into the pathological mechanisms and reveal novel biomarkers and therapeutic targets.

Polarized Macrophages in Periodontitis: Characteristics, Function, and Molecular Signaling

Periodontitis (PD) is a common chronic infectious disease. The local inflammatory response in the host may cause the destruction of supporting periodontal tissue. Macrophages play a variety of roles in PD, including regulatory and phagocytosis. Moreover, under the induction of different factors, macrophages polarize and form different functional phenotypes. Among them, M1-type macrophages with proinflammatory functions and M2-type macrophages with anti-inflammatory functions are the most representative, and both of them can regulate the tendency of the immune system to exert proinflammatory or anti-inflammatory functions. M1 and M2 macrophages are involved in the destructive and reparative stages of PD. Due to the complex microenvironment of PD, the dynamic development of PD, and various local mediators, increasing attention has been given to the study of macrophage polarization in PD. This review summarizes the role of macrophage polarization in the development of PD and its research progress.

p50 suppresses cytotoxic T lymphocyte effector function to regulate tumor immune escape and response to immunotherapy

Background

NF-κB is a key link between inflammation and cancer. Previous studies of NF-κB have largely focused on tumor cells, and the intrinsic function of NF-κB in T cells in tumor development and response to immunotherapy is largely unknown. We aimed at testing the hypothesis that NF-κB1 (p50) activation in T cells underlies human colon cancer immune escape and human cancer non-response to anti-PD-1 immunotherapy.

Methods

We screened NF-κB activation in human colon carcinoma and used mouse models to determine p50 function in tumor cells and immune cells. RNA-Seq was used to identify p50 target genes. p50 binding to target gene promoters were determined by electrophoresis mobility shift assay and chromatin immunoprecipitation. A p50 activation score was generated from gene expression profiling and used to link p50 activation to T-cell activation and function pre-nivolumab and post-nivolumab immunotherapy in human patients with cancer.

Results

p50 is the dominant form of NF-κB that is highly activated in immune cells in the human colorectal carcinoma microenvironment and neighboring non-neoplastic colon epithelial cells. Tumor cell intrinsic p50 signaling and T-cell intrinsic p50 signaling exert opposing functions in tumor growth control in vivo. Deleting Nfkb1 in tumor cells increased whereas in T cells decreased tumor growth in preclinical mouse models. Gene expression profiling identified Gzmb as a p50 target in T cells. p50 binds directly to a previously uncharacterized κB sequence at the Gzmb promoter in T cells, resulting in repression of Gzmb expression in tumor-infiltrating cytotoxic T lymphocytes (CTLs) to induce a dysfunctional CTL phenotype to promote tumor immune escape. p50 activation is inversely correlated with both GZMB expression and T-cell tumor infiltration in human colorectal carcinoma. Furthermore, nivolumab immunotherapy decreased p50 activation and increased GZMB expression in human patients with melanoma.

Conclusions

Inflammation activates p50 that binds to the Gzmb promoter to repress granzyme B expression in T cells, resulting in CTL dysfunction to confer tumor immune escape and decreased response to anti-PD-1 immunotherapy.

Regulation of Microglia for the Treatment of Glioma

Microglia are the resident macrophages of the central nervous system (CNS). They are derived from the erythromyeloid progenitors in the embryonic yolk sac, and they are maintained postnatally by limited self-renewal and longevity. As the most abundant immune cells in the CNS, they play critical roles in homeostasis and various CNS pathologies, including tumor, stroke, and neurodegenerative disease. For instance, in gliomas, up to more than 30% of cells in the tumor microenvironment can be microglia and tumor-associated macrophages. These cells are typically coopted by tumor cells to create a pro-tumorigenic microenvironment. The transcriptional regulation of the development and function of microglia in health and disease is not well understood. Transcription factors are master regulators of cell fates and functions and activate target genes that execute a genetic program typically initiated by external stimuli. Several transcription factors, not necessarily specific to microglia, have been shown to play roles in the development, function, and activation state of microglia. In this review, we summarize our current understanding of the roles of transcription factors in the functions of microglia in normal CNS homeostasis and in gliomas. A thorough understanding of the transcription factors and their target genes that mediate and regulate the functions of microglia in gliomas may help identify new targets for immune therapies. These stroma-directed therapies may be combined with tumor cell-directed therapies for more effective treatment of these diseases.

Tumor-Associated Microglia and Macrophages in the Glioblastoma Microenvironment and Their Implications for Therapy

Glioblastoma is the most frequent and malignant primary brain tumor. Standard of care includes surgery followed by radiation and temozolomide chemotherapy. Despite treatment, patients have a poor prognosis with a median survival of less than 15 months. The poor prognosis is associated with an increased abundance of tumor-associated microglia and macrophages (TAMs), which are known to play a role in creating a pro-tumorigenic environment and aiding tumor progression. Most treatment strategies are directed against glioblastoma cells; however, accumulating evidence suggests targeting of TAMs as a promising therapeutic strategy. While TAMs are typically dichotomously classified as M1 and M2 phenotypes, recent studies utilizing single cell technologies have identified expression pattern differences, which is beginning to give a deeper understanding of the heterogeneous subpopulations of TAMs in glioblastomas. In this review, we evaluate the role of TAMs in the glioblastoma microenvironment and discuss how their interactions with cancer cells have an extensive impact on glioblastoma progression and treatment resistance. Finally, we summarize the effects and challenges of therapeutic strategies, which specifically aim to target TAMs.

Role of Inflammatory Mediators, Macrophages, and Neutrophils in Glioma Maintenance and Progression: Mechanistic Understanding and Potential Therapeutic Applications

Gliomas are the most common, highly malignant, and deadliest forms of brain tumors. These intra-cranial solid tumors are comprised of both cancerous and non-cancerous cells, which contribute to tumor development, progression, and resistance to the therapeutic regimen. A variety of soluble inflammatory mediators (e.g., cytokines, chemokines, and chemotactic factors) are secreted by these cells, which help in creating an inflammatory microenvironment and contribute to the various stages of cancer development, maintenance, and progression. The major tumor infiltrating immune cells of the tumor microenvironment include TAMs and TANs, which are either recruited peripherally or present as brain-resident macrophages (microglia) and support stroma for cancer cell expansion and invasion. These cells are highly plastic in nature and can be polarized into different phenotypes depending upon different types of stimuli. During neuroinflammation, glioma cells interact with TAMs and TANs, facilitating tumor cell proliferation, survival, and migration. Targeting inflammatory mediators along with the reprogramming of TAMs and TANs could be of great importance in glioma treatment and may delay disease progression. In addition, an inhibition of the key signaling pathways such as NF-κB, JAK/STAT, MAPK, PI3K/Akt/mTOR, and TLRs, which are activated during neuroinflammation and have an oncogenic role in glioblastoma (GBM), can exert more pronounced anti-glioma effects.

NF-κB p50-deficient immature myeloid cell (p50-IMC) adoptive transfer slows the growth of murine prostate and pancreatic ductal carcinoma

Background

Macrophages and dendritic cells lacking the transcription factor nuclear factor kappa B p50 are skewed toward a proinflammatory phenotype, with increased cytokine expression and enhanced T cell activation; additionally, murine melanoma, fibrosarcoma, colon carcinoma, and glioblastoma grow slower in p50^−/− mice. We therefore evaluated the efficacy of p50-negative immature myeloid cells (p50-IMCs) adoptively transferred into tumor-bearing hosts. Immature cells were used to maximize tumor localization, and pretreatment with 5-fluorouracil (5FU) was examined due to its potential to impair marrow production of myeloid cells, to target tumor myeloid cells and to release tumor neoantigens.

Methods

Wild-type (WT)-IMC or p50-IMC were generated by culturing lineage-negative marrow cells from WT or p50^−/− mice in media containing thrombopoietin, stem cell factor and Flt3 ligand for 6 days followed by monocyte colony-stimulating factor for 1 day on ultralow attachment plates. Mice inoculated with Hi-Myc prostate cancer (PCa) cells or K-Ras^G12D pancreatic ductal carcinoma (PDC)-luciferase cells received 5FU followed 5 days later by three doses of 10⁷ immature myeloid cells (IMC) every 3–4 days.

Results

PCa cells grew slower in p50^−/− mice, and absence of host p50 prolonged the survival of mice inoculated orthotopically with PDC cells. IMC from Cytomegalovirus (CMV)-luciferase mice localized to tumor, nodes, spleen, marrow, and lung. 5FU followed by p50-IMC slowed PCa and PDC tumor growth, ~3-fold on average, in contrast to 5FU followed by WT-IMC, 5FU alone or p50-IMC alone. Slowed tumor growth was evident for 93% of PCa but only 53% of PDC tumors; we therefore focused on PCa for additional IMC analyses. In PCa, p50-IMC matured into F4/80⁺ macrophages, as well as CD11b⁺F4/80⁻CD11c⁺ conventional dendritic cells (cDCs). In both tumor and draining lymph nodes, p50-IMC generated more macrophages and cDCs than WT-IMC. Activated tumor CD8⁺ T cells were increased fivefold by p50-IMC compared with WT-IMC, and antibody-mediated CD8⁺ T cell depletion obviated slower tumor growth induced by 5FU followed by p50-IMC.

Conclusions

5FU followed by p50-IMC slows the growth of murine prostate and pancreatic carcinoma and depends on CD8⁺ T cell activation. Deletion of p50 in patient-derived marrow CD34⁺ cells and subsequent production of IMC for adoptive transfer may contribute to the therapy of these and additional cancers.

Reprogramming the immunosuppressive microenvironment of IDH1 wild-type glioblastoma by blocking Wnt signaling between microglia and cancer cells

The vast majority (>90%) of glioblastoma (GBM) patients belong to the isocitrate dehydrogenase 1 wild type (IDH1^WT) group which exhibits a poor prognosis with a median survival of less than 15 months. This study demonstrated numerous immunosuppressive genes as well as β-catenin gene, pivotal for Wnt/β-catenin signaling, were upregulated in 206 IDH1^WT glioma patients using the Chinese Glioma Genome Atlas (CGGA) database. The increase in microglia with an immunosuppressive phenotype and the overexpression of β-catenin protein were further verified in IDH1^WT GBM patients and IDH1^WT GL261 glioma allografts. Subsequently, we found that IDH1^WT GL261 cell-derived conditioned medium activated Wnt/β-catenin signaling in primary microglia and triggered their transition to an immunosuppressive phenotype. Blocking Wnt/β-catenin signaling not only attenuated microglial polarization to the immunosuppressive subtype but also reactivated immune responses in IDH1^WT GBM allografts by simultaneously enhancing cytotoxic CD8⁺ T cell infiltration and downregulating regulatory T cells. Positron emission tomography imaging demonstrated enhanced proinflammatory activities in IDH1^WT GBM allografts after the blockade of Wnt signaling. Finally, gavage administration of a Wnt signaling inhibitor significantly restrained tumor proliferation and improved the survival of model mice bearing IDH1^WT GBM allografts. Depletion of CD8⁺ T cells remarkably abrogated the therapeutic efficacy induced by the Wnt signaling inhibitor. Overall, the present work indicates that the crosstalk between IDH1^WT glioma cells and immunosuppressive microglia is important in maintaining the immunosuppressive glioma microenvironment. Blocking Wnt/β-catenin signaling is a promising complement for IDH1^WT GBM treatment by improving the hostile immunosuppressive microenvironment.

Adoptive transfer of immature myeloid cells lacking NF-κB p50 (p50-IMC) impedes the growth of MHC-matched high-risk neuroblastoma

High‐risk neuroblastomas harbor abundant myeloid cells that suppress antitumor immunity and support tumor growth. Macrophages lacking the inhibitory NF‐κB p50 subunit adopt a pro‐inflammatory phenotype. We now report that murine 9464D neuroblastoma cells, which express high levels of exogenous MYCN, grow slower in syngeneic p50(f/f);Lys‐Cre mice that lack p50 in macrophages and neutrophils, compared with p50(f/f) littermates. Tumors in p50(f/f);Lys‐Cre mice possess increased numbers of total and activated CD4⁺ and CD8⁺ T cells, and depletion of both of these T‐cell populations accelerates tumor growth. Anti‐PD‐1 T‐cell checkpoint blockade, or DNA methyltransferase and histone deacetylase inhibition, further slows tumor growth. In addition, adoptive transfer of immature myeloid cells lacking NF‐κB p50 (p50‐IMC), generated either from the bone marrow of p50^−/− mice or via nucleofection of a p50 sgRNA:Cas9 complex into wild‐type hematopoietic progenitors, also slowed growth of MHC‐matched 9464D tumors but not of MHC‐mismatched Neuro2A tumors. These findings further validate the utility of targeting myeloid NF‐κB p50 as a strategy for cancer therapy and demonstrate activity of p50‐IMC generated by gene editing of syngeneic marrow cells, a cell product relevant to clinical translation.

Tumor‐associated macrophages as treatment targets in glioma

Gliomas, the most common primary tumors in the central nervous system (CNS), can be categorized into 4 grades according to the World Health Organization. The most malignant glioma type is grade Ⅳ, also named glioblastoma multiforme (GBM). However, the standard treatment of concurrent temozolomide (TMZ) chemotherapy and radiotherapy after maximum resection does not improve overall survival in patients with GBM. Targeting components of the CNS microenvironment represents a new strategy for improving the efficacy of glioma treatment. Most recent studies focused on T cells. However, there is a growing body of evidence that tumor‐associated macrophages (TAMs) play an important role in tumor progression and can be regulated by a wide array of cytokines or chemokines. New TAM‐associated immunotherapies may improve clinical outcomes by blocking tumor progression and prolonging survival. However, understanding the exact roles and possible mechanisms of TAMs in the tumor environment is necessary for developing this promising therapeutic target and identifying potential diagnostic markers for improved prognosis. This review summarizes the possible interactions between TAMs and glioma progression and discusses the potential therapeutic directions for TAM‐associated immunotherapies.

USP14 negatively regulates RIG-I-mediated IL-6 and TNF-α production by inhibiting NF-κB activation

Ubiquitin specific protease 14 (USP14) is a regulator of protein deubiquitination and proteasome activation, and has been implicated in negative regulation of type I IFN signaling pathway. However, the effect of USP14 on RNA virus-related inflammatory response has not been studied. Retinoic acid-inducible gene I (RIG-I) is the important pattern recognition receptor of the innate immunity to detect RNA viruses or intracellular Poly(I:C)-LMW. Here, we reported that USP14 knockdown increased pro-inflammatory cytokines production in macrophages upon VSV infection or intracellular Poly(I:C)-LMW stimulation. USP14-overexpressed HeLa cells exhibited a decrease in RIG-I-mediated IL-6 and TNF-α expression. IU1, USP14 inhibitor, significantly promotes pro-inflammatory cytokines production in VSV-infected mice in vivo. Furthermore, USP14 was also found to inhibit the RIG-I-triggered NF-κB activation by deubiquitinating K63-linked RIG-I. Thus, our results demonstrate that USP14 is a negative regulator of RIG-I-mediated inflammatory response.

Targeting Tumor Associated Macrophages to Overcome Conventional Treatment Resistance in Glioblastoma

Glioblastoma (GB) is the most common and devastating form of brain cancer. Despite conventional treatments, progression or recurrences are systematic. In recent years, immunotherapies have emerged as an effective treatment in a number of cancers, leaving the question of their usefulness also faced with the particular case of brain tumors. The challenge here is major not only because the brain is the seat of our consciousness but also because of its isolation by the blood-brain barrier and the presence of a unique microenvironment that constitutes the central nervous system (CNS) with very specific constituent or patrolling cells. Much of the microenvironment is made up of immune cells or inflammation. Among these, tumor-associated macrophages (TAMs) are of significant interest as they are often involved in facilitating tumor progression as well as the development of resistance to standard therapies. In this review, the ubiquity of TAMs in GB will be discussed while the specific case of microglia resident in the brain will be also emphasized. In addition, the roles of TAMs as accomplices in the progression of GB and resistance to treatment will be presented. Finally, clinical trials targeting TAMs as a means of treating cancer will be discussed.

The dual roles of autophagy in gliomagenesis and clinical therapy strategies based on autophagic regulation mechanisms

Autophagy, a self-digestion intracellular catabolic process, plays a crucial role in cellular homeostasis under conditions of starvation, oxidative stress and genotoxic stress. The capability of maintaining homeostasis contributes to preventing malignant behavior in normal cells. Many studies have provided compelling evidence that autophagy is involved in brain tumor recurrence and chemotherapy and radiotherapy resistance. Gliomas, as the primary central nervous system (CNS) tumors, are characterized by rapid, aggressive growth and recurrence and have a poor prognosis and bleak outlook even with modern multimodality strategies involving maximal surgical resection, radiotherapy and alkylating agent-based chemotherapy. Autophagy-associated signaling pathways, such as the extracellular signal-regulated kinase1/2 (ERK1/2) pathway, class I phosphatidylinositol 3-phosphate kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway and nuclear factor kappa-B (NF-κB) pathway, act as tumor suppressors or protect tumor cells against chemotherapy/radiotherapy-induced cytotoxicity in gliomagenesis. Through these pathways, both lethal autophagy and protective autophagy play crucial roles in tumor initiation, chemoresistance and glioma stem cell differentiation. Moreover, lethal autophagy and protective autophagy have been identified as novel therapeutic targets in glioma according to the mechanisms described above. Here, we discuss the multiple impacts of the autophagic response on distinct phases of gliomagenesis and the advanced progress of therapies based on this concept.

Oligonucleotide Therapeutics as a New Class of Drugs for Malignant Brain Tumors: Targeting mRNAs, Regulatory RNAs, Mutations, Combinations, and Beyond

Malignant brain tumors are rapidly progressive and often fatal owing to resistance to therapies and based on their complex biology, heterogeneity, and isolation from systemic circulation. Glioblastoma is the most common and most aggressive primary brain tumor, has high mortality, and affects both children and adults. Despite significant advances in understanding the pathology, multiple clinical trials employing various treatment strategies have failed. With much expanded knowledge of the GBM genome, epigenome, and transcriptome, the field of neuro-oncology is getting closer to achieve breakthrough-targeted molecular therapies. Current developments of oligonucleotide chemistries for CNS applications make this new class of drugs very attractive for targeting molecular pathways dysregulated in brain tumors and are anticipated to vastly expand the spectrum of currently targetable molecules. In this chapter, we will overview the molecular landscape of malignant gliomas and explore the most prominent molecular targets (mRNAs, miRNAs, lncRNAs, and genomic mutations) that provide opportunities for the development of oligonucleotide therapeutics for this class of neurologic diseases. Because malignant brain tumors focally disrupt the blood-brain barrier, this class of diseases might be also more susceptible to systemic treatments with oligonucleotides than other neurologic disorders and, thus, present an entry point for the oligonucleotide therapeutics to the CNS. Nevertheless, delivery of oligonucleotides remains a crucial part of the treatment strategy. Finally, synthetic gRNAs guiding CRISPR-Cas9 editing technologies have a tremendous potential to further expand the applications of oligonucleotide therapeutics and take them beyond RNA targeting.