Dual Role of WISP1 in maintaining glioma stem cells and tumor-supportive macrophages in glioblastoma

IFI35 regulates non-canonical NF-κB signaling to maintain glioblastoma stem cells and recruit tumor-associated macrophages

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor characterized by a highly heterogeneous and immunosuppressive tumor microenvironment (TME). The symbiotic interactions between glioblastoma stem cells (GSCs) and tumor-associated macrophages (TAM) in the TME are critical for tumor progression. Here, we identified that IFI35, a transcriptional regulatory factor, plays both cell-intrinsic and cell-extrinsic roles in maintaining GSCs and the immunosuppressive TME. IFI35 induced non-canonical NF-kB signaling through proteasomal processing of p105 to the DNA-binding transcription factor p50, which heterodimerizes with RELB (RELB/p50), and activated cell chemotaxis in a cell-autonomous manner. Further, IFI35 induced recruitment and maintenance of M2-like TAMs in TME in a paracrine manner. Targeting IFI35 effectively suppressed in vivo tumor growth and prolonged survival of orthotopic xenograft-bearing mice. Collectively, these findings reveal the tumor-promoting functions of IFI35 and suggest that targeting IFI35 or its downstream effectors may provide effective approaches to improve GBM treatment.

Wnt signaling: Modulating tumor-associated macrophages and related immunotherapeutic insights

Wnt signaling pathways are highly conserved cascades that mediate multiple biological processes through canonical or noncanonical pathways, from embryonic development to tissue maintenance, but they also contribute to the pathogenesis of numerous cancers. Recent studies have revealed that Wnt signaling pathways critically control the interplay between cancer cells and tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) and potentially impact the efficacy of cancer immunotherapy. In this review, we summarize the evidence that Wnt signaling pathways boost the maturation and infiltration of macrophages for immune surveillance in the steady state but also polarize TAMs toward immunosuppressive M2-like phenotypes for immune escape in the TME. Both cancer cells and TAMs utilize Wnt signaling to transmit signals, and this interaction is crucial for the carcinogenesis and progression of common solid cancers, such as colorectal, gastric, hepatocellular, breast, thyroid, prostate, kidney, and lung cancers; osteosarcoma; and glioma. Specifically, compared with those in solid cancers, Wnt signaling pathways play a distinct role in the pathogenesis of leukemia. Efforts to develop Wnt-based drugs for cancer treatment are still ongoing, and some indeed enhance the anticancer immune response. We believe that the combination of Wnt signaling-based therapy with conventional or immune therapies is a promising therapeutic approach and can facilitate personalized treatment for most cancers.

Tumor microenvironment of cancer stem cells: Perspectives on cancer stem cell targeting

There are few tumor cell subpopulations with stem cell characteristics in tumor tissue, defined as cancer stem cells (CSCs) or cancer stem-like cells (CSLCs), which can reconstruct neoplasms with malignant biological behaviors such as invasiveness via self-renewal and unlimited generation. The microenvironment that CSCs depend on consists of various cellular components and corresponding medium components. Among these factors existing at a variety of levels and forms, cytokine networks and numerous signal pathways play an important role in signaling transduction. These factors promote or maintain cancer cell stemness, and participate in cancer recurrence, metastasis, and resistance. This review aims to summarize the recent molecular data concerning the multilayered relationship between CSCs and CSC-favorable microenvironments. We also discuss the therapeutic implications of targeting this synergistic interplay, hoping to give an insight into targeting cancer cell stemness for tumor therapy and prognosis.

Immune Response and Metastasis-Links between the Metastasis Driver MACC1 and Cancer Immune Escape Strategies

Metastasis remains the most critical factor limiting patient survival and the most challenging part of cancer-targeted therapy. Identifying the causal drivers of metastasis and characterizing their properties in various key aspects of cancer biology is essential for the development of novel metastasis-targeting approaches. Metastasis-associated in colon cancer 1 (MACC1) is a prognostic and predictive biomarker that is now recognized in more than 20 cancer entities. Although MACC1 can already be linked with many hallmarks of cancer, one key process-the facilitation of immune evasion-remains poorly understood. In this review, we explore the direct and indirect links between MACC1 and the mechanisms of immune escape. Therein, we highlight the signaling pathways and secreted factors influenced by MACC1 as well as their effects on the infiltration and anti-tumor function of immune cells.

Chronic hypoxia remodels the tumor microenvironment to support glioma stem cell growth

Cerebral organoids co-cultured with patient derived glioma stem cells (GLICOs) are an experimentally tractable research tool useful for investigating the role of the human brain tumor microenvironment in glioblastoma. Here we describe long-term GLICOs, a novel model in which COs are grown from embryonic stem cell cultures containing low levels of GSCs and tumor development is monitored over extended durations (ltGLICOs). Single-cell profiling of ltGLICOs revealed an unexpectedly long latency period prior to GSC expansion, and that normal organoid development was unimpaired by the presence of low numbers of GSCs. However, as organoids age they experience chronic hypoxia and oxidative stress which remodels the tumor microenvironment to promote GSC expansion. Receptor-ligand modelling identified astrocytes, which secreted various pro-tumorigenic ligands including FGF1, as the primary cell type for GSC crosstalk and single-cell multi-omic analysis revealed these astrocytes were under the control of ischemic regulatory networks. Functional validation confirmed hypoxia as a driver of pro-tumorigenic astrocytic ligand secretion and that GSC expansion was accelerated by pharmacological induction of oxidative stress. When controlled for genotype, the close association between glioma aggressiveness and patient age has very few proposed biological explanations. Our findings indicate that age-associated increases in cerebral vascular insufficiency and associated regional chronic cerebral hypoxia may contribute to this phenomenon.

UBDP1 pseudogene and UBD network competitively bind miR‑6072 to promote glioma progression

Increasing evidence suggests that pseudogenes play crucial roles in various cancers, yet their functions and regulatory mechanisms in glioma pathogenesis remain enigmatic. In the present study, a novel pseudogene was identified, UBDP1, which is significantly upregulated in glioblastoma and positively correlated with the expression of its parent gene, UBD. Additionally, high levels of these paired genes are linked with a poor prognosis for patients. In the present study, clinical samples were collected followed by various analyses including microarray for long non‑coding RNAs, reverse transcription‑quantitative PCR, fluorescence in situ hybridization and western blotting. Cell lines were authenticated and cultured then subjected to various assays for proliferation, migration, and invasion to investigate the molecular mechanisms. Bioinformatic tools identified miRNA targets, and luciferase reporter assays validated these interactions. A tumor xenograft model in mice was used for in vivo studies. In vitro and in vivo studies have demonstrated that UBDP1, localized in the cytoplasm, functions as a tumor‑promoting factor influencing cell proliferation, migration, invasion and tumor growth. Mechanistic investigations have indicated that UBDP1 exerts its oncogenic effects by decoying miR‑6072 from UBD mRNA, thus forming a competitive endogenous RNA network, which results in the enhanced oncogenic activity of UBD. The present findings offered new insights into the role of pseudogenes in glioma progression, suggesting that targeting the UBDP1/miR‑6072/UBD network may serve as a potential therapeutic strategy for glioma patients.

Crosstalk between glioblastoma and tumor microenvironment drives proneural-mesenchymal transition through ligand-receptor interactions

Glioblastoma (GBM) is the most common intrinsic and aggressive primary brain tumor in adults, with a median survival of approximately 15 months. GBM heterogeneity is considered responsible for the treatment resistance and unfavorable prognosis. Proneural-mesenchymal transition (PMT) represents GBM malignant progression and recurrence, which might be a breakthrough to understand GBM heterogeneity and overcome treatment resistance. PMT is a complicated process influenced by crosstalk between GBM and tumor microenvironment, depending on intricate ligand-receptor interactions. In this review, we summarize the autocrine and paracrine pathways in the GBM microenvironment and related ligand-receptor interactions inducing PMT. We also discuss the current therapies targeting the PMT-related autocrine and paracrine pathways. Together, this review offers a comprehensive understanding of the failure of GBM-targeted therapy and ideas for future tendencies of GBM treatment.

Targeting Wnt signaling for improved glioma immunotherapy

Introduction

Despite aggressive standard-of-care therapy, including surgery, radiation, and chemotherapy, glioblastoma recurrence is almost inevitable and uniformly lethal. Activation of glioma-intrinsic Wnt/β-catenin signaling is associated with a poor prognosis and the proliferation of glioma stem-like cells, leading to malignant transformation and tumor progression. Impressive results in a subset of cancers have been obtained using immunotherapies including anti-CTLA4, anti-PD-1, and anti-PD-L1 or chimeric antigen receptor (CAR) T cell therapies. However, the heterogeneity of tumors, low mutational burden, single antigen targeting, and associated antigen escape contribute to non-responsiveness and potential tumor recurrence despite these therapeutic efforts. In the current study, we determined the effects of the small molecule, highly specific Wnt/CBP (CREB Binding Protein)/β-catenin antagonist ICG-001, on glioma tumor cells and the tumor microenvironment (TME)-including its effect on immune cell infiltration, blood vessel decompression, and metabolic changes.

Methods

Using multiple glioma patient-derived xenografts cell lines and murine tumors (GL261, K-Luc), we demonstrated in vitro cytostatic effects and a switch from proliferation to differentiation after treatment with ICG-001.

Results

In these glioma cell lines, we further demonstrated that ICG-001 downregulated the CBP/β-catenin target gene Survivin/BIRC5-a hallmark of Wnt/CBP/β-catenin inhibition. We found that in a syngeneic mouse model of glioma (K-luc), ICG-001 treatment enhanced tumor infiltration by CD3+ and CD8+ cells with increased expression of the vascular endothelial marker CD31 (PECAM-1). We also observed differential gene expression and induced immune cell infiltration in tumors pretreated with ICG-001 and then treated with CAR T cells as compared with single treatment groups or when ICG-001 treatment was administered after CAR T cell therapy.

Discussion

We conclude that specific Wnt/CBP/β-catenin antagonism results in pleotropic changes in the glioma TME, including glioma stem cell differentiation, modulation of the stroma, and immune cell activation and recruitment, thereby suggesting a possible role for enhancing immunotherapy in glioma patients.

Regulation of cancer stem cells and immunotherapy of glioblastoma (Review)

Glioblastoma (GB) is one of the most adverse diagnoses in oncology. Complex current treatment results in a median survival of 15 months. Resistance to treatment is associated with the presence of cancer stem cells (CSCs). The present review aimed to analyze the mechanisms of CSC plasticity, showing the particular role of β-catenin in regulating vital functions of CSCs, and to describe the molecular mechanisms of Wnt-independent increase of β-catenin levels, which is influenced by the local microenvironment of CSCs. The present review also analyzed the reasons for the low effectiveness of using medication in the regulation of CSCs, and proposed the development of immunotherapy scenarios with tumor cell vaccines, containing heterogenous cancer cells able of producing a multidirectional antineoplastic immune response. Additionally, the possibility of managing lymphopenia by transplanting hematopoietic stem cells from a healthy sibling and using clofazimine or other repurposed drugs that reduce β-catenin concentration in CSCs was discussed in the present study.

Silencing of METTL3 prevents the proliferation, migration, epithelial-mesenchymal transition, and renal fibrosis of high glucose-induced HK2 cells by mediating WISP1 in m6A-dependent manner

Diabetic nephropathy (DN) is one of the most serious complications in diabetic patients. And m6A modifications mediated by METTL3 are involved multiple biological processes. However, the specific function and mechanism of METTL3 in DN remains unclear. DN model mice were first established with streptozotocin, and WISP1 expression was confirmed by qRT-PCR. Then the influences of WISP1 or/and METTL3 on the proliferation, migration, and epithelial-mesenchymal transition (EMT) and fibrosis-related proteins of high glucose (HG)-induced HK2 cells or HK2 cells were tested through CCK-8, wound healing, and western blot. We first revealed that WISP1 was highly expressed in renal tissues of DN model mice and HG-induced HK2 cells. Functionally, WISP1 or METTL3 silencing could weaken the proliferation, migration, EMT, and fibrosis of HG-treated HK2 cells, and WISP1 or METTL3 overexpression could induce the proliferation, migration, EMT, and fibrosis of HK2 cells. Additionally, METTL3 silencing could decrease WISP1 m6A modification, and silencing of METTL3 also could notably suppress the biological functions of HG-induced HK2 cells by downregulating WISP1. Silencing of METTL3 prevents DN development process by decreasing WISP1 with m6A modification pattern. Therefore, we suggest that METTL3/WISP1 axis might be a novel therapeutic target for DN.

Head-to-Head Comparison of CCN4, DNMT3A, PTPN11, and SPARC as Suppressors of Anti-tumor Immunity

Purpose

Emergent cancer cells likely secrete factors that inhibit anti-tumor immunity. To identify such factors, we applied a functional assay with proteomics to an immunotherapy resistant syngeneic mouse melanoma model. Four secreted factors were identified that potentially mediate immunosuppression and could become targets for novel immunotherapies. We tested for consistent clinical correlates in existing human data and verified in vivo whether knocking out tumor cell production of these factors improved immune-mediated control of tumor growth.

Methods

Existing human data was analyzed for clinical correlates. A CRISPR/Cas9 approach to generate knockout cell lines and a kinetic analysis leveraging a Markov Chain Monte Carlo (MCMC) approach quantified the various knockouts' effect on cells' intrinsic growth rate. Flow cytometry was used to characterize differences in immune infiltration.

Results

While all four gene products were produced by malignant melanocytes, only increased CCN4 expression was associated with reduced survival in primary melanoma patients. In immunocompetent C57BL/6 mice the CCN4 knockout increased survival while the other knockouts had no effect. This survival advantage was lost when the CCN4 knockout cells were injected into immunocompromised hosts, indicating that the effect of CCN4 may be immune mediated. Parameter estimation from the MCMC analysis shows that CCN4 was the only knockout tested that decreased the net tumor growth rate in immunocompetent mice. Flow cytometry showed an increase in NK cell infiltration in CCN4 knockout tumors.

Conclusions

The results suggest that CCN4 is a mediator of immunosuppression in the melanoma tumor microenvironment and a potential collateral immunotherapy target.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00787-7.

Immunobiology of cancer stem cells and their immunoevasion mechanisms

Cancer stem cells (CSCs) defined as a small fraction of cells within malignancies have been isolated from tumors with different histological origins with stem related characteristics such as self-replicating potential, tumorigenesis, and therapy resistance. The dynamic communication between CSCs and tumor microenvironment particularly immune cells orchestrates their fate and plasticity as well as the patient outcome. According to recent evidence, it has been reported that they harness different immunological pathways to escape immunosurveillance and express aberrantly immunomodulatory agents or decreased levels of factors forming antigen presenting machinery (APM), subsequently followed by impaired antigen presentation and suppressed immune detection. As effective therapies are expected to be able to eradicate CSCs, mechanistic understanding of such interactions can provide insights into causes of therapy failure particularly in immunotherapy. Also, it can contribute to enhance the practical interventions against CSCs and their immunomodulatory features resulting in CSCs eradication and improving patient clinical outcome. The aim of this review is to explain the present knowledge regarding the immunobiology of CSCs and the immunoevasion mechanisms they use.

scRNA-seq and proteomics reveal the distinction of M2-like macrophages between primary and recurrent malignant glioma and its critical role in the recurrence

AIMS

Tumor-associated macrophages (TAMs) in the immune microenvironment play an important role in the increased drug resistance and recurrence of malignant glioma, but the mechanism remains incompletely inventoried. The focus of this study was to investigate the distinctions of M2-like TAMs in the immune microenvironment between primary and recurrent malignant glioma and its influence in the recurrence.

METHODS

We employed single-cell RNA sequencing to construct a single-cell atlas for a total of 23,010 individual cells from 6 patients with primary or recurrent malignant glioma and identified 5 cell types, including TAMs and malignant cells. Immunohistochemical techniques and proteomics analysis were performed to investigate the role of intercellular interaction between malignant cells and TAMs in the recurrence of malignant glioma.

RESULTS

Six subgroups of TAMs were annotated and M2-like TAMs were found to increase in recurrent malignant glioma significantly. A pseudotime trajectory and a dynamic gene expression profiling during the recurrence of malignant glioma were reconstructed. Up-regulation of several cancer pathways and intercellular interaction-related genes are associated with the recurrence of malignant glioma. Moreover, the M2-like TAMs can activate the PI3K/Akt/HIF-1α/CA9 pathway in the malignant glioma cells via SPP1-CD44-mediated intercellular interaction. Interestingly, high expression of CA9 can trigger the immunosuppressive response in the malignant glioma, thus promoting the degree of malignancy and drug resistance.

CONCLUSION

Our study uncovers the distinction of M2-like TAMs between primary and recurrent glioma, which offers unparalleled insights into the immune microenvironment of primary and recurrent malignant glioma.

Repurposing Clemastine to Target Glioblastoma Cell Stemness

Brain tumor-initiating cells (BTICs) and tumor cell plasticity promote glioblastoma (GBM) progression. Here, we demonstrate that clemastine, an over-the-counter drug for treating hay fever and allergy symptoms, effectively attenuated the stemness and suppressed the propagation of primary BTIC cultures bearing PDGFRA amplification. These effects on BTICs were accompanied by altered gene expression profiling indicative of their more differentiated states, resonating with the activity of clemastine in promoting the differentiation of normal oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes. Functional assays for pharmacological targets of clemastine revealed that the Emopamil Binding Protein (EBP), an enzyme in the cholesterol biosynthesis pathway, is essential for BTIC propagation and a target that mediates the suppressive effects of clemastine. Finally, we showed that a neural stem cell-derived mouse glioma model displaying predominantly proneural features was similarly susceptible to clemastine treatment. Collectively, these results identify pathways essential for maintaining the stemness and progenitor features of GBMs, uncover BTIC dependency on EBP, and suggest that non-oncology, low-toxicity drugs with OPC differentiation-promoting activity can be repurposed to target GBM stemness and aid in their treatment.

Dual Role of CXCL8 in Maintaining the Mesenchymal State of Glioblastoma Stem Cells and M2-Like Tumor-Associated Macrophages

PURPOSE

The dynamic interplay between glioblastoma stem cells (GSC) and tumor-associated macrophages (TAM) sculpts the tumor immune microenvironment (TIME) and promotes malignant progression of glioblastoma (GBM). However, the mechanisms underlying this interaction are still incompletely understood. Here, we investigate the role of CXCL8 in the maintenance of the mesenchymal state of GSC populations and reprogramming the TIME to an immunosuppressive state.

EXPERIMENTAL DESIGN

We performed an integrative multi-omics analyses of RNA sequencing, GBM mRNA expression datasets, immune signatures, and epigenetic profiling to define the specific genes expressed in the mesenchymal GSC subsets. We then used patient-derived GSCs and a xenograft murine model to investigate the mechanisms of tumor-intrinsic and extrinsic factor to maintain the mesenchymal state of GSCs and induce TAM polarization.

RESULTS

We identified that CXCL8 was preferentially expressed and secreted by mesenchymal GSCs and activated PI3K/AKT and NF-κB signaling to maintain GSC proliferation, survival, and self-renewal through a cell-intrinsic mechanism. CXCL8 induced signaling through a CXCR2-JAK2/STAT3 axis in TAMs, which supported an M2-like TAM phenotype through a paracrine, cell-extrinsic pathway. Genetic- and small molecule-based inhibition of these dual complementary signaling cascades in GSCs and TAMs suppressed GBM tumor growth and prolonged survival of orthotopic xenograft-bearing mice.

CONCLUSIONS

CXCL8 plays critical roles in maintaining the mesenchymal state of GSCs and M2-like TAM polarization in GBM, highlighting an interplay between cell-autonomous and cell-extrinsic mechanisms. Targeting CXCL8 and its downstream effectors may effectively improve GBM treatment.

Stromal heterogeneity may explain increased incidence of metaplastic breast cancer in women of African descent

The biologic basis of genetic ancestry-dependent variability in disease incidence and outcome is just beginning to be explored. We recently reported enrichment of a population of ZEB1-expressing cells located adjacent to ductal epithelial cells in normal breasts of women of African ancestry compared to those of European ancestry. In this study, we demonstrate that these cells have properties of fibroadipogenic/mesenchymal stromal cells that express PROCR and PDGFRα and transdifferentiate into adipogenic and osteogenic lineages. PROCR + /ZEB1 + /PDGFRα+ (PZP) cells are enriched in normal breast tissues of women of African compared to European ancestry. PZP: epithelial cell communication results in luminal epithelial cells acquiring basal cell characteristics and IL-6-dependent increase in STAT3 phosphorylation. Furthermore, level of phospho-STAT3 is higher in normal and cancerous breast tissues of women of African ancestry. PZP cells transformed with HRasG12V ± SV40-T/t antigens generate metaplastic carcinoma suggesting that these cells are one of the cells-of-origin of metaplastic breast cancers.

CD44+ lung cancer stem cell-derived pericyte-like cells cause brain metastases through GPR124-enhanced trans-endothelial migration

Brain metastasis of lung cancer causes high mortality, but the exact mechanisms underlying the metastasis remain unclear. Here we report that vascular pericytes derived from CD44+ lung cancer stem cells (CSCs) in lung adenocarcinoma (ADC) potently cause brain metastases through the G-protein-coupled receptor 124 (GPR124)-enhanced trans-endothelial migration (TEM). CD44+ CSCs in perivascular niches generate the majority of vascular pericytes in lung ADC. CSC-derived pericyte-like cells (Cd-pericytes) exhibit remarkable TEM capacity to effectively intravasate into the vessel lumina, survive in the circulation, extravasate into the brain parenchyma, and then de-differentiate into tumorigenic CSCs to form metastases. Cd-pericytes uniquely express GPR124 that activates Wnt7-β-catenin signaling to enhance TEM capacity of Cd-pericytes for intravasation and extravasation, two critical steps during tumor metastasis. Furthermore, selective disruption of Cd-pericytes, GPR124, or the Wnt7-β-catenin signaling markedly reduces brain and liver metastases of lung ADC. Our findings uncover an unappreciated cellular and molecular paradigm driving tumor metastasis.

The Importance of M1-and M2-Polarized Macrophages in Glioma and as Potential Treatment Targets

Glioma is the most common and malignant tumor of the central nervous system. Glioblastoma (GBM) is the most aggressive glioma, with a poor prognosis and no effective treatment because of its high invasiveness, metabolic rate, and heterogeneity. The tumor microenvironment (TME) contains many tumor-associated macrophages (TAMs), which play a critical role in tumor proliferation, invasion, metastasis, and angiogenesis and indirectly promote an immunosuppressive microenvironment. TAM is divided into tumor-suppressive M1-like (classic activation of macrophages) and tumor-supportive M2-like (alternatively activated macrophages) polarized cells. TAMs exhibit an M1-like phenotype in the initial stages of tumor progression, and along with the promotion of lysing tumors and the functions of T cells and NK cells, tumor growth is suppressed, and they rapidly transform into M2-like polarized macrophages, which promote tumor progression. In this review, we discuss the mechanism by which M1- and M2-polarized macrophages promote or inhibit the growth of glioblastoma and indicate the future directions for treatment.

Interactions between microglia and glioma in tumor microenvironment

Gliomas, the most prevalent primary tumors in the central nervous system, are marked by their immunosuppressive properties and consequent poor patient prognosis. Current evidence emphasizes the pivotal role of the tumor microenvironment in the progression of gliomas, largely attributed to tumor-associated macrophages (brain-resident microglia and bone marrow-derived macrophages) that create a tumor microenvironment conducive to the growth and invasion of tumor cells. Yet, distinguishing between these two cell subgroups remains a challenge. Thus, our review starts by analyzing the heterogeneity between these two cell subsets, then places emphasis on elucidating the complex interactions between microglia and glioma cells. Finally, we conclude with a summary of current attempts at immunotherapy that target microglia. However, given that independent research on microglia is still in its initial stages and has many shortcomings at the present time, we express our related concerns and hope that further research will be carried out to address these issues in the future.

Novel INHAT repressor drives glioblastoma growth by promoting ribosomal DNA transcription in glioma stem cells

BACKGROUND

Cancer cells including cancer stem cells exhibit a higher rate of ribosome biogenesis than normal cells to support rapid cell proliferation in tumors. However, the molecular mechanisms governing the preferential ribosome biogenesis in glioma stem cells (GSCs) remain unclear. In this work, we show that the novel INHAT repressor (NIR) promotes ribosomal DNA (rDNA) transcription to support GSC proliferation and glioblastoma (GBM) growth, suggesting that NIR is a potential therapeutic target for GBM.

METHODS

Immunoblotting, immunohistochemical and immunofluorescent analysis were used to determine NIR expression in GSCs and human GBMs. Using shRNA-mediated knockdown, we assessed the role and functional significance of NIR in GSCs and GSC-derived orthotopic GBM xenografts. We further performed mass spectrometry analysis, chromatin immunoprecipitation, and other biochemical assays to define the molecular mechanisms by which NIR promotes GBM progression.

RESULTS

Our results show that high expression of NIR predicts poor survival in GBM patients. NIR is enriched in the nucleoli of GSCs in human GBMs. Disrupting NIR markedly suppresses GSC proliferation and tumor growth by inhibiting rDNA transcription and pre-ribosomal RNA synthesis. In mechanistic studies, we find that NIR activates rDNA transcription to promote GSC proliferation by cooperating with Nucleolin (NCL) and Nucleophosmin 1 (NPM1), 2 important nucleolar transcription factors.

CONCLUSIONS

Our study uncovers a critical role of NIR-mediated rDNA transcription in the malignant progression of GBM, indicating that targeting this axis may provide a novel therapeutic strategy for GBM.

Cancer stem cells in brain tumors: From origin to clinical implications

Malignant brain tumors are highly heterogeneous tumors with a poor prognosis and a high morbidity and mortality rate in both children and adults. The cancer stem cell (CSC, also named tumor-initiating cell) model states that tumor growth is driven by a subset of CSCs. This model explains some of the clinical observations of brain tumors, including the almost unavoidable tumor recurrence after initial successful chemotherapy and/or radiotherapy and treatment resistance. Over the past two decades, strategies for the identification and characterization of brain CSCs have improved significantly, supporting the design of new diagnostic and therapeutic strategies for brain tumors. Relevant studies have unveiled novel characteristics of CSCs in the brain, including their heterogeneity and distinctive immunobiology, which have provided opportunities for new research directions and potential therapeutic approaches. In this review, we summarize the current knowledge of CSCs markers and stemness regulators in brain tumors. We also comprehensively describe the influence of the CSCs niche and tumor microenvironment on brain tumor stemness, including interactions between CSCs and the immune system, and discuss the potential application of CSCs in brain-based therapies for the treatment of brain tumors.

Single-cell transcriptomics reveals cellular heterogeneity and macrophage-to-mesenchymal transition in bicuspid calcific aortic valve disease

BACKGROUND

Bicuspid aortic valve (BAV) is the most prevalent congenital valvular heart defect, and around 50% of severe isolated calcific aortic valve disease (CAVD) cases are associated with BAV. Although previous studies have demonstrated the cellular heterogeneity of aortic valves, the cellular composition of specific BAV at the single-cell level remains unclear.

METHODS

Four BAV specimens from aortic valve stenosis patients were collected to conduct single-cell RNA sequencing (scRNA-seq). In vitro experiments were performed to further validate some phenotypes.

RESULTS

The heterogeneity of stromal cells and immune cells were revealed based on comprehensive analysis. We identified twelve subclusters of VICs, four subclusters of ECs, six subclusters of lymphocytes, six subclusters of monocytic cells and one cluster of mast cells. Based on the detailed cell atlas, we constructed a cellular interaction network. Several novel cell types were identified, and we provided evidence for established mechanisms on valvular calcification. Furthermore, when exploring the monocytic lineage, a special population, macrophage derived stromal cells (MDSC), was revealed to be originated from MRC1+ (CD206) macrophages (Macrophage-to-Mesenchymal transition, MMT). FOXC1 and PI3K-AKT pathway were identified as potential regulators of MMT through scRNA analysis and in vitro experiments.

CONCLUSIONS

With an unbiased scRNA-seq approach, we identified a full spectrum of cell populations and a cellular interaction network in stenotic BAVs, which may provide insights for further research on CAVD. Notably, the exploration on mechanism of MMT might provide potential therapeutic targets for bicuspid CAVD.

The role of lysosomal peptidases in glioma immune escape: underlying mechanisms and therapeutic strategies

Glioblastoma is the most common primary malignant tumor of the central nervous system, which has the characteristics of strong invasion, frequent recurrence, and rapid progression. These characteristics are inseparable from the evasion of glioma cells from immune killing, which makes immune escape a great obstacle to the treatment of glioma, and studies have confirmed that glioma patients with immune escape tend to have poor prognosis. The lysosomal peptidase lysosome family plays an important role in the immune escape process of glioma, which mainly includes aspartic acid cathepsin, serine cathepsin, asparagine endopeptidases, and cysteine cathepsins. Among them, the cysteine cathepsin family plays a prominent role in the immune escape of glioma. Numerous studies have confirmed that glioma immune escape mediated by lysosomal peptidases has something to do with autophagy, cell signaling pathways, immune cells, cytokines, and other mechanisms, especially lysosome organization. The relationship between protease and autophagy is more complicated, and the current research is neither complete nor in-depth. Therefore, this article reviews how lysosomal peptidases mediate the immune escape of glioma through the above mechanisms and explores the possibility of lysosomal peptidases as a target of glioma immunotherapy.

Wnt Signaling in Brain Tumors: A Challenging Therapeutic Target

The involvement of Wnt signaling in normal tissue homeostasis and disease has been widely demonstrated over the last 20 years. In particular, dysregulation of Wnt pathway components has been suggested as a relevant hallmark of several neoplastic malignancies, playing a role in cancer onset, progression, and response to treatments. In this review, we summarize the current knowledge on the instructions provided by Wnt signaling during organogenesis and, particularly, brain development. Moreover, we recapitulate the most relevant mechanisms through which aberrant Wnt pathway activation may impact on brain tumorigenesis and brain tumor aggressiveness, with a particular focus on the mutual interdependency existing between Wnt signaling components and the brain tumor microenvironment. Finally, the latest anti-cancer therapeutic approaches employing the specific targeting of Wnt signaling are extensively reviewed and discussed. In conclusion, here we provide evidence that Wnt signaling, due to its pleiotropic involvement in several brain tumor features, may represent a relevant target in this context, although additional efforts will be needed to: (i) demonstrate the real clinical impact of Wnt inhibition in these tumors; (ii) overcome some still unsolved concerns about the potential systemic effects of such approaches; (iii) achieve efficient brain penetration.

Exosome-based nanoimmunotherapy targeting TAMs, a promising strategy for glioma

Exosomes, the cell-derived small extracellular vehicles, play a vital role in intracellular communication by reciprocally transporting DNA, RNA, bioactive protein, chains of glucose, and metabolites. With great potential to be developed as targeted drug carriers, cancer vaccines and noninvasive biomarkers for diagnosis, treatment response evaluation, prognosis prediction, exosomes show extensive advantages of relatively high drug loading capacity, adjustable therapeutic agents release, enhanced permeation and retention effect, striking biodegradability, excellent biocompatibility, low toxicity, etc. With the rapid progression of basic exosome research, exosome-based therapeutics are gaining increasing attention in recent years. Glioma, the standard primary central nervous system (CNS) tumor, is still up against significant challenges as current traditional therapies of surgery resection combined with radiotherapy and chemotherapy and numerous efforts into new drugs showed little clinical curative effect. The emerging immunotherapy strategy presents convincing results in many tumors and is driving researchers to exert its potential in glioma. As the crucial component of the glioma microenvironment, tumor-associated macrophages (TAMs) significantly contribute to the immunosuppressive microenvironment and strongly influence glioma progression via various signaling molecules, simultaneously providing new insight into therapeutic strategies. Exosomes would substantially assist the TAMs-centered treatment as drug delivery vehicles and liquid biopsy biomarkers. Here we review the current potential exosome-mediated immunotherapeutics targeting TAMs in glioma and conclude the recent investigation on the fundamental mechanisms of diversiform molecular signaling events by TAMs that promote glioma progression.

Interaction of tumor-associated microglia/macrophages and cancer stem cells in glioma

Glioma is the most common tumor of the primary central nervous system, and its malignant phenotype has been shown to be closely related to glioma stem cells (GSCs). Although temozolomide has significantly improved the therapeutic outcome of glioma with a high penetration rate of the blood-brain barrier, resistance is often present in patients. Moreover, evidence has shown that the crosstalk between GSCs and tumor-associated microglia/macrophages (TAMs) affect the clinical occurrence, growth, and multi-tolerance of chemoradiotherapy in gliomas. Here, we highlight its vital roles in the maintenance of the stemness of GSCs and the ability of GSCs to recruit TAMs to the tumor microenvironment and promote their polarization into tumor-promoting macrophages, hence providing groundwork for future research into new treatment strategies of cancer.

Cancer stem cells: Recent insights and therapies

Tumors are intricate ecosystems containing malignant components that generate adaptive and evolutionarily driven abnormal tissues. Through self-renewal and differentiation, cancers are reconstructed by a dynamic subset of stem-like cells that enforce tumor heterogeneity and remodel the tumor microenvironment (TME). Through recent technology advances, we are now better equipped to investigate the fundamental role of cancer stem cells (CSCs) in cancer biology. In this review, we discuss the latest insights into characteristics, markers and mechanism of CSCs and describe the crosstalk between CSCs and other cells in TME. Additionally, we explore the performance of single-cell sequencing and spatial transcriptome analysis in CSCs studies and summarize the therapeutic strategies to eliminate CSCs, which could broaden the understanding of CSCs and exploit for therapeutic benefit.

ZBTB7A suppresses glioblastoma tumorigenesis through the transcriptional repression of EPB41L5

Glioblastoma multiforme (GBM), the most aggressive and malignant glioma, has a poor prognosis. Although patients with GBM are treated with surgery, chemotherapy, and radiation therapy, GBM is highly resistant to treatment, making it difficult and expensive to treat. In this study, we analyzed the Gene Expression Profiling Interactive Analysis dataset, the Cancer Genome Atlas dataset, and Gene Expression Omnibus array data. ZBTB7A (also called FBI1/POKEMON/LRF) was found to be highly expressed in low-grade glioma but significantly downregulated in patients with GBM. ZBTB7A is a transcription factor that plays an important role in many developmental stages, including cell proliferation. The activation of epithelial-mesenchymal transition (EMT) is a key process in cancer progression and metastasis. Erythrocyte membrane protein band 4.1 like 5 (EPB41L5) is an essential protein for EMT progression and metastasis in various types of cancer. We found that ZBTB7A depletion in U87 cells induced GBM progression and metastasis. Based on RNA sequencing data, ZBTB7A directly binds to the promoter of the EPB41L5 gene, reducing its expression and inhibiting GBM progression. We demonstrated that ZBTB7A dramatically inhibits GBM tumor growth through transcriptional repression of EPB41L5. Thus, both ZBTB7A and EPB41L5 may be potential biomarkers and novel therapeutic targets for GBM treatment. Overall, we discovered the role of a novel tumor suppressor that directly inhibits GBM progression (ZBTB7A) and identified EPB41L5 as a therapeutic target protein for patients with GBM.

Repairing a critical cranial defect using WISP1-pretreated chondrocyte scaffolds

In cranial flat bone fractures, spontaneous bone repair will occur only when the fracture ends are in close contact. However, in cases wherein bone discontinuity is extensive, surgical interventions are often required. To this end, autologous bone is harvested and surgically integrated into the site of fracture. Here we propose to use cartilage, as an alternative autologous source, to promote cranial fracture repair. The advantage of this approach is the potential reduction in donor site morbidity, likely due to the avascular and aneural nature of cartilage. As a first step we attempted to induce cartilage mineralization in vitro, using micromass primary chondrocyte cultures, incubated with BMP2 and/or WISP1, which were examined histologically following a 3-week culture period. Next, chondrocyte seeded collagen scaffolds were evaluated in vitro for expression profiles and ALP activity. Finally, chondrocyte-seeded collagen scaffolds were implanted in a Lewis rats 8 mm critical calvaria defect model, which was imaged via live CT for 12 weeks until sacrifice. End points were analyzed for microCT, histology, and serum levels of bone related markers. Micromass cultures exhibited an osseous inducing trend following WISP1 administration, which was maintained in chondrocyte seeded scaffolds. Accordingly, in vivo analysis was carried out to assess the impact of WISP1-pretreated chondrocytes (WCS) versus untreated chondrocytes (UCS) in calvaria defect model and compared to untreated control comprised of a defect-associated blood clot (BC) or empty collagen scaffold (CS) implant. Live CT and microCT exhibited higher mineralization volumes in critical defect implanted with UCS, with some structural improvements in WCS. Histological analysis exhibited higher anabolic bone formation in WCS and trabecular bone was detected in WCS and UCS groups. Chondrocytes implanted into critical cranial defect expedite the formation of native-like osseous tissue, especially after WISP1 priming in culture. Ultimately, these data support the use of autologous chondrocytes to repair critical maxillofacial defects.

Stromal protein CCN family contributes to the poor prognosis in lower-grade gioma by modulating immunity, matrix, stemness, and metabolism

Background: The CCN family of stromal proteins is involved in the regulation of many important biological functions. However, the role of dysregulated CCN proteins in lower-grade glioma (LGG) remain less understand. Methods: The clinical significance of the CCN proteins was explored based on RNA-seq profiles from multiple cohorts. A CCNScore was constructed using LASSO regression analysis. The PanCanAtlas data and MEXPRESS database were employed to elucidate molecular underpinnings. Results: The expression of CCN4 was associated with poor prognosis in LGG. The CCNScore (CCN1 = 0.06, CCN4 = 0.86) showed implication in prognosis prediction, subtype assessment and therapy selection. The gene mutation pattern of the high-CCNScore group was similar with glioblastoma, including EGFR, PTEN, and NF1 mutation frequently. Besides, the high-CCNScore group was comprised of samples mainly classic-like and mesenchymal-like, had lower methylation levels, higher stemness, higher inflammation, higher levels of extracellular matrix remodel and dysfunction of metabolic pathways. On the other hand, the low-CCNScore group consisted mainly of IDH-mutation LGG, and was characterized by TP53, CIC, and ATRX gene mutations, hyper-methylation status, lower stemness, lower proliferation, immune quietness and low extracellular matrix stiffness. Conclusion: In summary, these results outlined the role of CCN family in LGG and provided a potential and promising therapeutic target.

Microglia and Brain Macrophages as Drivers of Glioma Progression

Evidence is accumulating that the tumour microenvironment (TME) has a key role in the progression of gliomas. Non-neoplastic cells in addition to the tumour cells are therefore finding increasing attention. Microglia and other glioma-associated macrophages are at the centre of this interest especially in the context of therapeutic considerations. New ideas have emerged regarding the role of microglia and, more recently, blood-derived brain macrophages in glioblastoma (GBM) progression. We are now beginning to understand the mechanisms that allow malignant glioma cells to weaken microglia and brain macrophage defence mechanisms. Surface molecules and cytokines have a prominent role in microglia/macrophage-glioma cell interactions, and we discuss them in detail. The involvement of exosomes and microRNAs forms another focus of this review. In addition, certain microglia and glioma cell pathways deserve special attention. These "synergistic" (we suggest calling them "Janus") pathways are active in both glioma cells and microglia/macrophages where they act in concert supporting malignant glioma progression. Examples include CCN4 (WISP1)/Integrin α6β1/Akt and CHI3L1/PI3K/Akt/mTOR. They represent attractive therapeutic targets.

Worldwide productivity and research trend of publications concerning glioma-associated macrophage/microglia: A bibliometric study

Glioma-associated macrophage/microglia (GAM) represents a key player in shaping a unique glioma ecosystem to facilitate tumor progression and therapeutic resistance. Numerous studies have been published concerning GAM, but no relevant bibliometric study has been performed yet. Our bibliometric study aimed to comprehensively summarize and analyze the global scientific output, research hotspots, and trendy topics of publications on GAM over time. Data on publications on GAM were collected using the Web of Science (WoS). The search date was 16 January 2022, and the publications were collected from 2002 to 2021. Totally, 1,224 articles and reviews were incorporated and analyzed in the current study. It showed that the annual publications concerning GAM kept increasing over the past 20 years. The United States had the largest number of publications and total citations. Holland, Kettenmann, and Gutmann were the top three authors in terms of citation frequency. Neuro-oncology represented the most influential journal in GAM studies, with the highest H-index, total citations, and publication numbers. The paper published by Hambardzumyan in 2016 had the highest local citations. Additionally, the analysis of keywords implied that "prognosis," "tumor microenvironment," and "immunotherapy" might become research hotspots. Furthermore, trendy topics in GAM studies suggested that "immune infiltration," "immune microenvironment," "bioinformatics," "prognosis," and "immunotherapy" deserved additional attention. In conclusion, this bibliometric study comprehensively analyzed the publication trend of GAM studies for the past 20 years, in which the research hotspots and trendy topics were also uncovered. This information offered scholars critical references for conducting in-depth studies on GAM in the future.

Ruxolitinib enhances cytotoxic and apoptotic effects of temozolomide on glioblastoma cells by regulating WNT signaling pathway-related genes

Although temozolomide is the primary chemotherapeutic agent in glioblastoma, current studies have focused on its combinational applications to overcome resistance by targeting multiple pathways. JAK/STAT and WNT are among the essential cancer-related signaling pathways. Ruxolitinib, the first approved JAK1/2 inhibitor, has promise in glioblastoma with its blood-brain barrier (BBB) crossing ability. The mentioned study aims to evaluate the anti-cancer potential of ruxolitinib individually and in combination with temozolomide on glioblastoma cells, brain cancer stem cells (BCSCs), and BBB-forming healthy cells. It also intends to determine the effects of JAK inhibitor treatment in combination with temozolomide on WNT signaling, which is known to cross-talk with the JAK/STAT pathway. The U87MG, BCSC, and HBMEC cell lines were the in vitro models. The cytotoxic and apoptotic effects of ruxolitinib and the combination were determined by the WST-1 test and Annexin V assay, respectively. The expression level changes of WNT signaling pathway genes caused by ruxolitinib and the combination treatments were defined by the qRT-PCR method. Network analysis of significantly upregulated and downregulated genes was performed via the GO KEGG pathway enrichment module of the String V11.5 database. The IC₅₀ value of the ruxolitinib on U87MG glioblastoma cells was determined as 94.07 µM at 24th h. The combination of temozolomide and ruxolitinib had a synergistic effect on U87MG cells at 24th h. The combination index (CI) was determined as 0.796, and ED₆₀ values of ruxolitinib and temozolomide were determined as 89.75 and 391.48 µM, respectively. Ruxolitinib improves the apoptotic effect of temozolomide on glioblastoma cells and brain cancer stem cells. Ruxolitinib regulates the WNT signaling pathway both individually and in combination with temozolomide. Our study indicates the potential of ruxolitinib to increase the cytotoxic and apoptotic activity of temozolomide in glioblastoma cells, also considering CSCs and healthy BBB-forming cells. As supported by gene expression and network analyses, the BBB-crossing agent ruxolitinib promises the potential to increase the efficacy of temozolomide in glioblastoma by affecting multiple signaling pathways in both cancer cells and CSCs.

Reflected stemness as a potential driver of the tumour microenvironment

A fundamental requirement for cancer initiation is the activation of developmental programmes by mutant cells. Oncogenic signals often confer an undifferentiated, stem cell-like phenotype that supports the long-term proliferative potential of cancer cells. Although cancer is a genetically driven disease, mutations in cancer-driver genes alone are insufficient for tumour formation, and the proliferation of cells harbouring oncogenic mutations depends on their microenvironment. In this Opinion article we discuss how the reprogrammed status of cancer cells not only represents the essence of their tumorigenicity but triggers 'reflected stemness' in their surrounding normal counterparts. We propose that this reciprocal interaction underpins the establishment of the tumour microenvironment (TME).

Therapy-induced shaping of the glioblastoma microenvironment: Macrophages at play

The intricate cross-talks between tumor cells and their microenvironment play a key role in cancer progression and resistance to treatment. In recent years, targeting pro-tumorigenic components of the tumor microenvironment (TME) has emerged as a tantalizing strategy to improve the efficacy of standard-of-care (SOC) treatments, particularly for hard-to-treat cancers such as glioblastoma. In this review, we explore how the distinct microenvironmental niches characteristic of the glioblastoma TME shape response to therapy. In particular, we delve into the interplay between tumor-associated macrophages (TAM) and glioblastoma cells within angiogenic and hypoxic niches, and interrogate their dynamic co-evolution upon SOC therapies that fuels malignancy. Resolving the complexity of therapy-induced alterations in the glioblastoma TME and their impact on disease relapse is a stepping stone to identify targetable pro-tumorigenic pathways and TAM subsets, and may open the way to efficient combination therapies that will improve clinical outcomes.

Heterogeneity of glioblastoma stem cells in the context of the immune microenvironment and geospatial organization

Glioblastoma (GBM) is an extremely aggressive and incurable primary brain tumor with a 10-year survival of just 0.71%. Cancer stem cells (CSCs) are thought to seed GBM's inevitable recurrence by evading standard of care treatment, which combines surgical resection, radiotherapy, and chemotherapy, contributing to this grim prognosis. Effective targeting of CSCs could result in insights into GBM treatment resistance and development of novel treatment paradigms. There is a major ongoing effort to characterize CSCs, understand their interactions with the tumor microenvironment, and identify ways to eliminate them. This review discusses the diversity of CSC lineages present in GBM and how this glioma stem cell (GSC) mosaicism drives global intratumoral heterogeneity constituted by complex and spatially distinct local microenvironments. We review how a tumor's diverse CSC populations orchestrate and interact with the environment, especially the immune landscape. We also discuss how to map this intricate GBM ecosystem through the lens of metabolism and immunology to find vulnerabilities and new ways to disrupt the equilibrium of the system to achieve improved disease outcome.

Origin, activation, and targeted therapy of glioma-associated macrophages

The glioma tumor microenvironment plays a crucial role in the development, occurrence, and treatment of gliomas. Glioma-associated macrophages (GAMs) are the most widely infiltrated immune cells in the tumor microenvironment (TME) and one of the major cell populations that exert immune functions. GAMs typically originate from two cell types-brain-resident microglia (BRM) and bone marrow-derived monocytes (BMDM), depending on a variety of cytokines for recruitment and activation. GAMs mainly contain two functionally and morphologically distinct activation types- classically activated M1 macrophages (antitumor/immunostimulatory) and alternatively activated M2 macrophages (protumor/immunosuppressive). GAMs have been shown to affect multiple biological functions of gliomas, including promoting tumor growth and invasion, angiogenesis, energy metabolism, and treatment resistance. Both M1 and M2 macrophages are highly plastic and can polarize or interconvert under various malignant conditions. As the relationship between GAMs and gliomas has become more apparent, GAMs have long been one of the promising targets for glioma therapy, and many studies have demonstrated the therapeutic potential of this target. Here, we review the origin and activation of GAMs in gliomas, how they regulate tumor development and response to therapies, and current glioma therapeutic strategies targeting GAMs.

Signaling pathways in the regulation of cancer stem cells and associated targeted therapy

Cancer stem cells (CSCs) are defined as a subpopulation of malignant tumor cells with selective capacities for tumor initiation, self-renewal, metastasis, and unlimited growth into bulks, which are believed as a major cause of progressive tumor phenotypes, including recurrence, metastasis, and treatment failure. A number of signaling pathways are involved in the maintenance of stem cell properties and survival of CSCs, including well-established intrinsic pathways, such as the Notch, Wnt, and Hedgehog signaling, and extrinsic pathways, such as the vascular microenvironment and tumor-associated immune cells. There is also intricate crosstalk between these signal cascades and other oncogenic pathways. Thus, targeting pathway molecules that regulate CSCs provides a new option for the treatment of therapy-resistant or -refractory tumors. These treatments include small molecule inhibitors, monoclonal antibodies that target key signaling in CSCs, as well as CSC-directed immunotherapies that harness the immune systems to target CSCs. This review aims to provide an overview of the regulating networks and their immune interactions involved in CSC development. We also address the update on the development of CSC-directed therapeutics, with a special focus on those with application approval or under clinical evaluation.

Chitinase-3 like-protein-1 promotes glioma progression via the NF-κB signaling pathway and tumor microenvironment reprogramming

Background: Chitinase-3-like protein 1 (CHI3L1) is overexpressed in various types of tumors, especially in glioma, and contributes to tumor progression. However, the definite role of CHI3L1 and involved pathway in glioma progression are not completely understood.

Methods: CHI3L1 expression in human gliomas and its association with patient survival was determined using enzyme-linked immunosorbent assay, western blot, immunohistochemistry, and public databases. Single-cell RNA-seq was used to characterize the landscape of tumor and myeloid cells. Human proteome microarray assay was applied to identify the binding partners of CHI3L1. Protein-protein interactions were analyzed by co-immunoprecipitation and cellular co-localization. The roles of CHI3L1 in glioma proliferation and invasion were investigated in tumor cell lines by gain- and loss- of function, as well as in vivo animal experiments.

Results: CHI3L1 was up-regulated in all disease stages of glioma, which was closely related with tumor survival, growth, and invasion. CHI3L1 was primarily expressed in glioma cells, followed by neutrophils. Moreover, glioma cells with high expression of CHI3L1 were significantly enriched in NF-κB pathway. Pseudo-time trajectory analysis revealed a gradual transition from CHI3L1^low to CHI3L1^high glioma cells, along with the NF-κB pathway gradually reversed from inhibition to activation. Intriguingly, CHI3L1 binds to actinin alpha 4 (ACTN4) and NFKB1, and enhances the NF-κB signaling pathway by promoting the NF-κB subunit nuclear translocation in glioma cells. Further, CHI3L1 were released into the tumor microenvironment (TME) and interacted with CD44 expressed on tumor-associated macrophages to activate AKT pathway, thereby contributing to M2 macrophage polarization. In addition, CHI3L1 positively correlated to the expression of immune checkpoints, such as CD274 (PD-L1) and HAVCR2 (LAG3), which then remodeled the TME to an immunosuppressive phenotype.

Conclusion: Our research revealed that CHI3L1 facilitated NF-κB pathway activation within glioma cells and reprogramed the TME, thereby serving as a promising therapeutic target for glioma.

Pathophysiological roles of integrins in gliomas from the perspective of glioma stem cells

Glioblastoma is the most common primary intracranial tumor and is also one of the most malignant central nervous system tumors. Its characteristics, such as high malignancy, abundant tumor vasculature, drug resistance, and recurrence-prone nature, cause great suffering to glioma patients. Furthermore, glioma stem cells are the primordial cells of the glioma and play a central role in the development of glioma. Integrins—heterodimers composed of noncovalently bound a and ß subunits—are highly expressed in glioma stem cells and play an essential role in the self-renewal, differentiation, high drug resistance, and chemo-radiotherapy resistance of glioma stem cells through cell adhesion and signaling. However, there are various types of integrins, and their mechanisms of function on glioma stem cells are complex. Therefore, this article reviews the feasibility of treating gliomas by targeting integrins on glioma stem cells.

Microglia-T cell conversations in brain cancer progression

The highly immunosuppressive and heterogeneous milieu of brain malignancies contributes to their dismal prognosis. Regardless of their cellular origin, brain tumors grow in an environment with various specialized organ-resident cells. Although homeostatic microglia contribute to a healthy brain, conversations between disease-associated microglia and T cells compromise their individual and collective capacity to curb malignant growth. We review the mechanisms of T cell-microglia interactions and discuss how their collaboration fosters heterogeneity and immunosuppression in brain cancers. Because of the importance of microglia and T cells in the brain tumor microenvironment, it is crucial to understand their interactions to derive innovative therapeutics.

Hypoxia-Driven M2-Polarized Macrophages Facilitate Cancer Aggressiveness and Temozolomide Resistance in Glioblastoma

Hypoxia-induced M2 phenotypes of tumor associated macrophages (TAMs) promote the development and chemoresistance of multiple types of cancers, including glioblastoma (GBM). However, the detailed molecular mechanisms have not been fully understood. In this study, we firstly reported that hypoxic pressure promoted M2 macrophage generation, which further promoted cancer progression and temozolomide (TMZ) resistance in GBM through secreting vascular endothelial growth factor (VEGF). Specifically, the clinical data suggested that M2 macrophages were significantly enriched in GBM tissues compared with the adjacent normal tissues, and the following in vitro experiments validated that hypoxic pressure promoted M2-polarized macrophages through upregulating hypoxia-inducible factor-1α (HIF-1α). In addition, hypoxic M2 macrophages VEGF-dependently promoted cell proliferation, epithelial-mesenchymal transition (EMT), glioblastoma stem cell (GSC) properties, and TMZ resistance in GBM cells through activating the PI3K/Akt/Nrf2 pathway. Also, M2 macrophages secreted VEGF to accelerate angiogenesis in human umbilical vein endothelial cells (HUVECs) through interacting with its receptor VEGFR. In general, we concluded that hypoxic M2 macrophages contributed to cancer progression, stemness, drug resistance, and angiogenesis in GBM through secreting VEGF, and our data supported the notion that targeting hypoxia-associated M2 macrophages might be an effective treatment strategy for GBM in clinical practices.

Molecular subtypes of osteosarcoma classified by cancer stem cell related genes define immunological cell infiltration and patient survival

Recent studies have shown that tumor stemness has biological significance in tumorigenicity and tumor progression. However, the characteristics of TME immune infiltration in osteosarcoma mediated by the combined effects of multiple cancer stem cell-related genes remain unknown.

Methods

In this study, we identified different cancer stem cell-associated subtypes in osteosarcoma based on 25 cancer stem cell-associated genes by consensus clustering analysis, and we comprehensively evaluated the association between these subtypes and immunocytes infiltration in the TME. The cancer stem cell (CSC) score was constructed to quantify the stemness of individual tumors.

Results

We performed a comprehensive evaluation of 218 osteosarcoma patients based on 25 cancer stem cell-related genes. Three different cancer stem cells related subtypes were identified, which were related to different biological processes and clinical outcomes. The three subtypes have different TME cells infiltrating characteristics, and CSC Cluster A had a higher level of immunocyte infiltration compared to CSC Cluster B and C. We constructed a scoring system, called the CSC score, to assess the stemness of individual patients. Then we found that the prognosis of patients was predicted by CSC score, and patients with low CSC score had prolonged survival. Further analyses showed that low CSC score was correlated with enhanced immune infiltration. CSC score may predict the effect of immunotherapy, and patients with low CSC score may have better immune response and clinical prognosis.

Conclusions

This study demonstrates that there could be three cancer stem cell-associated subtypes in osteosarcoma and that they were associated with different patient prognosis and TME immune infiltration characteristics. CSC score could be used to assess the stemness of individual patients, improve our comprehension of TME characteristics, and direct more effective immune therapy.

Current Opportunities for Targeting Dysregulated Neurodevelopmental Signaling Pathways in Glioblastoma

Glioblastoma (GBM) is the most common and highly lethal type of brain tumor, with poor survival despite advances in understanding its complexity. After current standard therapeutic treatment, including tumor resection, radiotherapy and concomitant chemotherapy with temozolomide, the median overall survival of patients with this type of tumor is less than 15 months. Thus, there is an urgent need for new insights into GBM molecular characteristics and progress in targeted therapy in order to improve clinical outcomes. The literature data revealed that a number of different signaling pathways are dysregulated in GBM. In this review, we intended to summarize and discuss current literature data and therapeutic modalities focused on targeting dysregulated signaling pathways in GBM. A better understanding of opportunities for targeting signaling pathways that influences malignant behavior of GBM cells might open the way for the development of novel GBM-targeted therapies.

Phenotypic, functional, and metabolic heterogeneity of immune cells infiltrating non–small cell lung cancer

Lung cancer is the leading cancer in the world, accounting for 1.2 million of new cases annually, being responsible for 17.8% of all cancer deaths. In particular, non–small cell lung cancer (NSCLC) is involved in approximately 85% of all lung cancers with a high lethality probably due to the asymptomatic evolution, leading patients to be diagnosed when the tumor has already spread to other organs. Despite the introduction of new therapies, which have improved the long-term survival of these patients, this disease is still not well cured and under controlled. Over the past two decades, single-cell technologies allowed to deeply profile both the phenotypic and metabolic aspects of the immune cells infiltrating the TME, thus fostering the identification of predictive biomarkers of prognosis and supporting the development of new therapeutic strategies. In this review, we discuss phenotypic and functional characteristics of the main subsets of tumor-infiltrating lymphocytes (TILs) and tumor-infiltrating myeloid cells (TIMs) that contribute to promote or suppress NSCLC development and progression. We also address two emerging aspects of TIL and TIM biology, i.e., their metabolism, which affects their effector functions, proliferation, and differentiation, and their capacity to interact with cancer stem cells.

WNT signaling and cancer stemness

Cancer stemness, defined as the self-renewal and tumor-initiation potential of cancer stem cells (CSCs), is a cancer biology property featuring activation of CSC signaling networks. Canonical WNT signaling through Frizzled and LRP5/6 receptors is transmitted to the β-catenin-TCF/LEF-dependent transcription machinery to up-regulate MYC, CCND1, LGR5, SNAI1, IFNG, CCL28, CD274 (PD-L1) and other target genes. Canonical WNT signaling causes expansion of rapidly cycling CSCs and modulates both immune surveillance and immune tolerance. In contrast, noncanonical WNT signaling through Frizzled or the ROR1/2 receptors is transmitted to phospholipase C, Rac1 and RhoA to control transcriptional outputs mediated by NFAT, AP-1 and YAP-TEAD, respectively. Noncanonical WNT signaling supports maintenance of slowly cycling, quiescent or dormant CSCs and promotes epithelial–mesenchymal transition via crosstalk with TGFβ (transforming growth factor-β) signaling cascades, while the TGFβ signaling network induces immune evasion. The WNT signaling network orchestrates the functions of cancer-associated fibroblasts, endothelial cells and immune cells in the tumor microenvironment and fine-tunes stemness in human cancers, such as breast, colorectal, gastric and lung cancers. Here, WNT-related cancer stemness features, including proliferation/dormancy plasticity, epithelial–mesenchymal plasticity and immune-landscape plasticity, will be discussed. Porcupine inhibitors, β-catenin protein–protein interaction inhibitors, β-catenin proteolysis targeting chimeras, ROR1 inhibitors and ROR1-targeted biologics are investigational drugs targeting WNT signaling cascades. Mechanisms of cancer plasticity regulated by the WNT signaling network are promising targets for therapeutic intervention; however, further understanding of context-dependent reprogramming trajectories might be necessary to optimize the clinical benefits of WNT-targeted monotherapy and applied combination therapy for patients with cancer.

Hypoxia-induced polypoid giant cancer cells in glioma promote the transformation of tumor-associated macrophages to a tumor-supportive phenotype

Aims

Polypoid giant cancer cells (PGCCs) represent a unique subgroup of stem‐like cells, acting as a critical factor in promoting the recurrence of various solid tumors. The effect of PGCCs on the tumor malignancy of glioma and its immune microenvironment remains unclear.

Methods

Bioinformatic analysis was performed to investigate the relationship between M2 tumor‐associated macrophages (TAMs) infiltration and survival of glioblastoma (GBM) patients. The spatial location of M2 TAMs in GBM was also investigated using the Ivy Glioblastoma Atlas Project (Ivy GAP) database. PGCCs were quantified in glioma of different grades. CoCl₂ was used to induce PGCCs in cultures of A172 cells. PGCCs, and their progeny cells in cultures were further evaluated for morphological features, tumorsphere formation, and TAMs activation.

Results

The magnitude of M2 TAMs infiltration is significantly correlated with poor survival in GBM patients. M2 TAMs were enriched in the perinecrotic zone (PNZ) of GBM and positively correlated with hypoxic levels. Increased PGCCs were detected in glioma specimens of higher grades. CoCl₂ induced hypoxia and the transformation of A172 cultures into PGCCs, producing the progeny cells, PGCCs‐Dau, through asymmetric division. PGCCs and PGCCs‐Dau possessed tumor stem cell‐like features, while PGCCs‐Dau enhanced the polarization of TAMs into an M2 phenotype with relevance to immunosuppression and malignancy in GBM.

Conclusions

PGCCs promote malignancy and immune‐suppressive microenvironment in GBM. PGCCs or their progeny cells may be a potential therapeutic target for GBM.

Macrophages Are a Double-Edged Sword: Molecular Crosstalk between Tumor-Associated Macrophages and Cancer Stem Cells

Cancer stem cells (CSCs) are a subset of highly tumorigenic cells in tumors. They have enhanced self-renewal properties, are usually chemo-radioresistant, and can promote tumor recurrence and metastasis. They can recruit macrophages into the tumor microenvironment and differentiate them into tumor-associated macrophages (TAMs). TAMs maintain CSC stemness and construct niches that are favorable for CSC survival. However, how CSCs and TAMs interact is not completely understood. An understanding on these mechanisms can provide additional targeting strategies for eliminating CSCs. In this review, we comprehensively summarize the reported mechanisms of crosstalk between CSCs and TAMs and update the related signaling pathways involved in tumor progression. In addition, we discuss potential therapies targeting CSC–TAM interaction, including targeting macrophage recruitment and polarization by CSCs and inhibiting the TAM-induced promotion of CSC stemness. This review also provides the perspective on the major challenge for developing potential therapeutic strategies to overcome CSC-TAM crosstalk.

The complex relationship between integrins and oncolytic herpes Simplex Virus 1 in high-grade glioma therapeutics

High-grade gliomas (HGGs) are lethal central nervous system tumors that spread quickly through the brain, making treatment challenging. Integrins are transmembrane receptors that mediate cell-extracellular matrix (ECM) interactions, cellular adhesion, migration, growth, and survival. Their upregulation and inverse correlation in HGG malignancy make targeting integrins a viable therapeutic option. Integrins also play a role in herpes simplex virus 1 (HSV-1) entry. Oncolytic HSV-1 (oHSV) is the most clinically advanced oncolytic virotherapy, showing a superior safety and efficacy profile over standard cancer treatment of solid cancers, including HGG. With the FDA-approval of oHSV for melanoma and the recent conditional approval of oHSV for malignant glioma in Japan, usage of oHSV for HGG has become of great interest. In this review, we provide a systematic overview of the role of integrins in relation to oHSV, with a special focus on its therapeutic potential against HGG. We discuss the pros and cons of targeting integrins during oHSV therapy: while integrins play a pro-therapeutic role by acting as a gateway for oHSV entry, they also mediate the innate antiviral immune responses that hinder oHSV therapeutic efficacy. We further discuss alternative strategies to regulate the dual functionality of integrins in the context of oHSV therapy.

Signal Pathways Involved in the Interaction Between Tumor-Associated Macrophages/TAMs and Glioblastoma Cells

It is commonly recognized, that glioblastoma is a large complex composed of neoplastic and non-neoplastic cells. Tumor-associated macrophages account for the majority of tumor bulk and play pivotal roles in tumor proliferation, migration, invasion, and survival. There are sophisticated interactions between malignant cells and tumor associated-macrophages. Tumor cells release a variety of chemokines, cytokines, and growth factors that subsequently lead to the recruitment of TAMs, which in return released a plethora of factors to construct an immunosuppressive and tumor-supportive microenvironment. In this article, we have reviewed the biological characteristics of glioblastoma-associated macrophages and microglia, highlighting the emerging molecular targets and related signal pathways involved in the interaction between TAMs and glioblastoma cells, as well as the potential TAMs-associated therapeutic targets for glioblastoma.