CX3CR1/CX3CL1 axis negatively controls glioma cell invasion and is modulated by transforming growth factor-β1

Bulk and single-cell transcriptome revealed the metabolic heterogeneity in human glioma

Background

Emerging perspectives on tumor metabolism reveal its heterogeneity, a characteristic yet to be fully explored in gliomas. To advance therapies targeting metabolic processes, it is crucial to uncover metabolic differences and identify distinct metabolic subtypes. Therefore, we aimed to develop a classification system for gliomas based on the enrichment levels of four key metabolic pathways: glutaminolysis, glycolysis, the pentose phosphate pathway, and fatty acid oxidation.

Methods

Energy-related features of glioma were characterized through integrative analyses of multiple datasets, including bulk, single-cell, and spatial transcriptome profiling. The glioma energy metabolic subtypes were constructed using the R package ConsensusClusterPlus. Kaplan-Meier analysis was conducted to compare clinical outcomes between different metabolic groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were employed to elucidate the biological functions of genes of interest. Cell-cell communication analysis was performed at single-cell resolution using the R package CellChat and at spatial resolution using the standard stLearn pipeline.

Results

Glioma samples were stratified into two prognostic subtypes. Group 1, enriched in the glutaminolysis pathway, had better clinical outcomes. In contrast, Group 2 exhibited high activities in glycolysis, the pentose phosphate pathway, and fatty acid oxidation, correlating with decreased survival time. Group 1 samples were predominantly located in the peripheral region and had a high composition of neuron cells. Group 2, however, had increased infiltration of tumor-promoting immune cells, such as M2 macrophages, and was characterized by traits of invasion, hypoxia, and immunity. Lastly, cell-cell communications were compared across different tumor regions, and the CX3CL1/CX3CR1 ligand-receptor pair was validated using spatial transcriptomic data.

Conclusions

Our work revealed the metabolic heterogeneity in glioma by developing a new classification system with significant prognostic and therapeutic value. Single-cell transcriptional profiles offer novel insights into tumor metabolic reprogramming, which could enhance therapies tailored to cell- or patient-specific metabolic patterns.

The Role of Fractalkine in Diabetic Retinopathy: Pathophysiology and Clinical Implications

Diabetic retinopathy (DR) is a complication of diabetes, characterized by progressive microvascular dysfunction that can result in vision loss. Chronic hyperglycemia drives oxidative stress, endothelial dysfunction, and inflammation, leading to retinal damage and complications such as neovascularization. Current treatments, including anti-VEGF agents, have limitations, necessitating the exploration of alternative therapeutic strategies. Fractalkine (CX3CL1), a chemokine with dual roles as a membrane-bound adhesion molecule and a soluble chemoattractant, has emerged as a potential therapeutic target. Its receptor, CX3CR1, is expressed on immune cells and mediates processes such as immune cell recruitment and microglial activation through intracellular signaling pathways. In DR, soluble fractalkine plays critical roles in retinal inflammation, angiogenesis, and neuroprotection, balancing tissue damage and repair. In DR, elevated fractalkine levels are associated with retinal inflammation and endothelial dysfunction. Experimental studies suggest that fractalkine deficiency exacerbates the severity of diabetic retinopathy (DR), whereas exogenous fractalkine appears to reduce inflammation, oxidative stress, and neuronal damage. However, its role in pathological angiogenesis within DR remains unclear and warrants further investigation. Preclinical evidence indicates that fractalkine may hold therapeutic potential, particularly in mitigating tissue injury and inflammation associated with early-stage DR.

Suppressive immune microenvironment and CART therapy for glioblastoma: Future prospects and challenges

Glioblastoma, a highly malignant intracranial tumor, has acquired slow progress in treatment. Previous clinical trials involving targeted therapy and immune checkpoint inhibitors have shown no significant benefits in treating glioblastoma. This ineffectiveness is largely due to the complex immunosuppressive environment of glioblastoma. Glioblastoma cells exhibit low immunogenicity and strong heterogeneity and the immune microenvironment is replete with inhibitory cytokines, numerous immunosuppressive cells, and insufficient effective T cells. Fortunately, recent Phase I clinical trials of CART therapy for glioblastoma have confirmed its safety, with a small subset of patients achieving survival benefits. However, CART therapy continues to face challenges, including blood-brain barrier obstruction, antigen loss, and an immunosuppressive tumor microenvironment (TME). This article provides a detailed examination of glioblastoma's immune microenvironment, both from intrinsic and extrinsic tumor cell factors, reviews current clinical and basic research on multi-targets CART treatment, and concludes by outlining the key challenges in using CART cells for glioblastoma therapy.

3D-Bioprinted Co-Cultures of Glioblastoma Multiforme and Mesenchymal Stromal Cells Indicate a Role for Perivascular Niche Cells in Shaping Glioma Chemokine Microenvironment

3D bioprinting has become a valuable tool for studying the biology of solid tumors, including glioblastoma multiforme (GBM). Our analysis of publicly available bulk RNA and single-cell sequencing data has allowed us to define the chemotactic profile of GBM tumors and identify the cell types that secrete particular chemokines in the GBM tumor microenvironment (TME). Our findings indicate that primary GBM tissues express multiple chemokines, whereas spherical monocultures of GBM cells significantly lose this diversity. Subsequently, the comparative analysis of GBM spherical monocultures vs. 3D-bioprinted multicultures of cells showed a restoration of chemokine profile diversity in 3D-bioprinted cultures. Furthermore, single-cell RNA-Seq analysis showed that cells of the perivascular niche (pericytes and endocytes) express multiple chemokines in the GBM TME. Next, we 3D-bioprinted cells from two glioblastoma cell lines, U-251 and DK-MG, alone and as co-cultures with mesenchymal stromal cells (representing cells of the perivascular niche) and assessed the chemokine secretome. The results clearly demonstrated that the interaction of tumors and mesenchymal cells leads to in a significant increase in the repertoire and levels of secreted chemokines under culture in 21% O2 and 1% O2. Our study indicates that cells of the perivascular niche may perform a substantial role in shaping the chemokine microenvironment in GBM tumors.

Distinct tumor-TAM interactions in IDH-stratified glioma microenvironments unveiled by single-cell and spatial transcriptomics

Tumor-associated macrophages (TAMs) residing in the tumor microenvironment (TME) are characterized by their pivotal roles in tumor progression, antitumor immunity, and TME remodeling. However, a thorough comparative characterization of tumor-TAM crosstalk across IDH-defined categories of glioma remains elusive, likely contributing to mixed outcomes in clinical trials. We delineated the phenotypic heterogeneity of TAMs across IDH-stratified gliomas. Notably, two TAM subsets with a mesenchymal phenotype were enriched in IDH-WT glioblastoma (GBM) and correlated with poorer patient survival and reduced response to anti-PD-1 immune checkpoint inhibitor (ICI). We proposed SLAMF9 receptor as a potential therapeutic target. Inference of gene regulatory networks identified PPARG, ELK1, and MXI1 as master transcription factors of mesenchymal BMD-TAMs. Our analyses of reciprocal tumor-TAM interactions revealed distinct crosstalk in IDH-WT tumors, including ANXA1-FPR1/3, FN1-ITGAVB1, VEGFA-NRP1, and TNFSF12-TNFRSF12A with known contribution to immunosuppression, tumor proliferation, invasion and TAM recruitment. Spatially resolved transcriptomics further elucidated the architectural organization of highlighted communications. Furthermore, we demonstrated significant upregulation of ANXA1, FN1, NRP1, and TNFRSF12A genes in IDH-WT tumors using bulk RNA-seq and RT-qPCR. Longitudinal expression analysis of candidate genes revealed no difference between primary and recurrent tumors indicating that the interactive network of malignant states with TAMs does not drastically change upon recurrence. Collectively, our study offers insights into the unique cellular composition and communication of TAMs in glioma TME, revealing novel vulnerabilities for therapeutic interventions in IDH-WT GBM.

"Find Me" and "Eat Me" signals: tools to drive phagocytic processes for modulating antitumor immunity

Phagocytosis, a vital defense mechanism, involves the recognition and elimination of foreign substances by cells. Phagocytes, such as neutrophils and macrophages, rapidly respond to invaders; macrophages are especially important in later stages of the immune response. They detect "find me" signals to locate apoptotic cells and migrate toward them. Apoptotic cells then send "eat me" signals that are recognized by phagocytes via specific receptors. "Find me" and "eat me" signals can be strategically harnessed to modulate antitumor immunity in support of cancer therapy. These signals, such as calreticulin and phosphatidylserine, mediate potent pro-phagocytic effects, thereby promoting the engulfment of dying cells or their remnants by macrophages, neutrophils, and dendritic cells and inducing tumor cell death. This review summarizes the phagocytic "find me" and "eat me" signals, including their concepts, signaling mechanisms, involved ligands, and functions. Furthermore, we delineate the relationships between "find me" and "eat me" signaling molecules and tumors, especially the roles of these molecules in tumor initiation, progression, diagnosis, and patient prognosis. The interplay of these signals with tumor biology is elucidated, and specific approaches to modulate "find me" and "eat me" signals and enhance antitumor immunity are explored. Additionally, novel therapeutic strategies that combine "find me" and "eat me" signals to better bridge innate and adaptive immunity in the treatment of cancer patients are discussed.

Unveiling cytokine charge disparity as a potential mechanism for immune regulation

Cytokines are small signaling proteins that regulate the immune responses to infection and tissue damage. Surface charges of cytokines determine their in vivo fate in immune regulation, e.g., half-life and distribution. The overall negative charges in the extracellular microenvironment and the acidosis during inflammation and infection may differentially impact cytokines with different surface charges for fine-tuned immune regulation via controlling tissue residential properties. However, the trend and role of cytokine surface charges has yet to be elucidated in the literature. Interestingly, we have observed that most pro-inflammatory cytokines have a negative charge, while most anti-inflammatory cytokines and chemokines have a positive charge. In this review, we extensively examined the surface charges of all cytokines and chemokines, summarized the pharmacokinetics and tissue adhesion of major cytokines, and analyzed the link of surface charge with cytokine biodistribution, activation, and function in immune regulation. Additionally, we identified that the general trend of charge disparity between pro- and anti-inflammatory cytokines represents a unique opportunity to develop precise immune modulation approaches, which can be applied to many inflammation-associated diseases including solid tumors, chronic wounds, infection, and sepsis.

Microglia in Glioblastomas: Molecular Insight and Immunotherapeutic Potential

Glioblastoma (GBM) is one of the most aggressive and devastating primary brain tumors, with a median survival of 15 months following diagnosis. Despite the intense treatment regimen which routinely includes maximal safe neurosurgical resection followed by adjuvant radio- and chemotherapy, the disease remains uniformly fatal. The poor prognosis associated with GBM is multifactorial owing to factors such as increased proliferation, angiogenesis, and metabolic switching to glycolytic pathways. Critically, GBM-mediated local and systemic immunosuppression result in inadequate immune surveillance and ultimately, tumor-immune escape. Microglia-the resident macrophages of the central nervous system (CNS)-play crucial roles in mediating the local immune response in the brain. Depending on the specific pathological cues, microglia are activated into either a pro-inflammatory, neurotoxic phenotype, known as M1, or an anti-inflammatory, regenerative phenotype, known as M2. In either case, microglia secrete corresponding pro- or anti-inflammatory cytokines and chemokines that either promote or hinder tumor growth. Herein, we review the interplay between GBM cells and resident microglia with a focus on contemporary studies highlighting the effect of GBM on the subtypes of microglia expressed, the associated cytokines/chemokines secreted, and ultimately, their impact on tumor pathogenesis. Finally, we explore how understanding the intricacies of the tumor-immune landscape can inform novel immunotherapeutic strategies against this devastating disease.

Integrated bioinformatics analysis and experimental validation identified CDCA families as prognostic biomarkers and sensitive indicators for rapamycin treatment of glioma

The cell division cycle associated (CDCA) genes regulate the cell cycle; however, their relationship with prognosis in glioma has been poorly reported in the literature. The Cancer Genome Atlas (TCGA) was utilized to probe the CDCA family in relation to the adverse clinical features of glioma. Glioma single-cell atlas reveals specific expression of CDCA3, 4, 5, 8 in malignant cells and CDCA7 in neural progenitor cells (NPC)-like malignant cells. Glioma data from TCGA, the China Glioma Genome Atlas Project (CGGA) and the gene expression omnibus (GEO) database all demonstrated that CDCA2, 3, 4, 5, 7 and 8 are prognostic markers for glioma. Further analysis identified CDCA2, 5 and 8 as independent prognostic factors for glioma. Lasso regression-based risk models for CDCA families demonstrated that high-risk patients were characterized by high tumor mutational burden (TMB), low levels of microsatellite instability (MSI), and low tumor immune dysfunction and rejection (TIDE) scores. These pointed to immunotherapy for glioma as a potentially viable treatment option Further CDCA clustering suggested that the high CDCA subtype exhibited a high macrophage phenotype and was associated with a higher antigen presentation capacity and high levels of immune escape. In addition, hsa-mir-15b-5p was predicted to be common regulator of CDCA3 and CDCA4, which was validated in U87 and U251 cells. Importantly, we found that CDCAs may indicate response to drug treatment, especially rapamycin, in glioma. In summary, our results suggest that CDCAs have potential applications in clinical diagnosis and as drug sensitivity markers in glioma.

The CX3CL1-CX3CR1 chemokine axis can contribute to tumor immune evasion and blockade with a novel CX3CR1 monoclonal antibody enhances response to anti-PD-1 immunotherapy

CX3CL1 secreted in the tumor microenvironment serves as a chemoattractant playing a critical role in metastasis of CX3CR1 expressing cancer cells. CX3CR1 can be expressed in both cancer and immune-inhibitory myeloid cells to facilitate their migration. We generated a novel monoclonal antibody against mouse CX3CR1 that binds to CX3CR1 and blocks the CX3CL1-CX3CR1 interaction. We next explored the immune evasion strategies implemented by the CX3CL1-CX3CR1 axis and find that it initiates a resistance program in cancer cells that results in 1) facilitation of tumor cell migration, 2) secretion of soluble mediators to generate a pro-metastatic niche, 3) secretion of soluble mediators to attract myeloid populations, and 4) generation of tumor-inflammasome. The CX3CR1 monoclonal antibody reduces migration of tumor cells and decreases secretion of immune suppressive soluble mediators by tumor cells. In combination with anti-PD-1 immunotherapy, this CX3CR1 monoclonal antibody enhances survival in an immunocompetent mouse colon carcinoma model through a decrease in tumor-promoting myeloid populations. Thus, this axis is involved in the mechanisms of resistance to anti-PD-1 immunotherapy and the combination therapy can overcome a portion of the resistance mechanisms to anti-PD-1.

Recent Emerging Immunological Treatments for Primary Brain Tumors: Focus on Chemokine-Targeting Immunotherapies

Primary brain tumors are a leading cause of death worldwide and are characterized by extraordinary heterogeneity and high invasiveness. Current drug and radiotherapy therapies combined with surgical approaches tend to increase the five-year survival of affected patients, however, the overall mortality rate remains high, thus constituting a clinical challenge for which the discovery of new therapeutic strategies is needed. In this field, novel immunotherapy approaches, aimed at overcoming the complex immunosuppressive microenvironment, could represent a new method of treatment for central nervous system (CNS) tumors. Chemokines especially are a well-defined group of proteins that were so named due to their chemotactic properties of binding their receptors. Chemokines regulate the recruitment and/or tissue retention of immune cells as well as the mobilization of tumor cells that have undergone epithelial–mesenchymal transition, promoting tumor growth. On this basis, this review focuses on the function and involvement of chemokines and their receptors in primary brain tumors, specifically examining chemokine-targeting immunotherapies as one of the most promising strategies in neuro-oncology.

Pan-Cancer Landscape of NEIL3 in Tumor Microenvironment: A Promising Predictor for Chemotherapy and Immunotherapy

With the aim of enhancing the understanding of NEIL3 in prognosis prediction and therapy administration, we conducted a pan-cancer landscape analysis on NEIL3. The mutation characteristics, survival patterns, and immune features of NEIL3 across cancers were analyzed. Western blotting, qPCR, and immunohistochemistry were conducted to validate the bioinformatics results. The correlation between NEIL3 and chemotherapeutic drugs, as well as immunotherapies, was estimated. NEIL3 was identified as an oncogene with prognostic value in predicting clinical outcomes in multiple cancers. Combined with the neoantigen, tumor mutational burden (TMB), and microsatellite instability (MSI) results, a strong relationship between NEIL3 and the TME was observed. NEIL3 was demonstrated to be closely associated with multiple immune parameters, including infiltrating immunocytes and pro-inflammatory chemokines, which was verified by experiments. More importantly, patients with a higher expression of NEIL3 were revealed to be more sensitive to chemotherapeutic regimens and immune checkpoint inhibitors in selected cancers, implying that NEIL3 may be an indicator for therapeutic administration. Our study indicated NEIL3 has a strong association with the immune microenvironment and phenotypic changes in certain types of cancers, which facilitated the improved understanding of NEIL3 across cancers and highlighted the potential for clinical application of NEIL3 in precision medical stratification.

Diet-Induced Obesity Promotes Liver Metastasis of Pancreatic Ductal Adenocarcinoma via CX3CL1/CX3CR1 Axis

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers, and the patients are generally diagnosed with distant metastasis. Liver is one of the preferred organs of distant metastasis, and liver metastasis is the leading cause of death in PDAC. Diet-induced obesity (DIO) is a risk factor for PDAC, and it remains unclear whether and how DIO contributes to liver metastasis of PDAC. In our study, we found that DIO significantly promoted PDAC liver metastasis compared with normal diet (ND) in intrasplenic injection mouse model. RNA-seq analysis for liver metastasis nodules showed that the various chemokines and several chemokine receptors were altered between ND and DIO samples. The expression levels of CX3CL1 and CX3CR1 were significantly upregulated in DIO-induced liver metastasis of PDAC compared to ND. Increased CX3CL1 promoted the recruitment of CX3CR1-expressing pancreatic tumor cells. Taken together, our data demonstrated that DIO promoted PDAC liver metastasis via CX3CL1/CX3CR1 axis.

Friends with Benefits: Chemokines, Glioblastoma-Associated Microglia/Macrophages, and Tumor Microenvironment

Glioma is the most common primary intracranial tumor and has the greatest prevalence of all brain tumors. Treatment resistance and tumor recurrence in GBM are mostly explained by considerable alterations within the tumor microenvironment, as well as extraordinary cellular and molecular heterogeneity. Soluble factors, extracellular matrix components, tissue-resident cell types, resident or newly recruited immune cells together make up the GBM microenvironment. Regardless of many immune cells, a profound state of tumor immunosuppression is supported and developed, posing a considerable hurdle to cancer cells' immune-mediated destruction. Several studies have suggested that various GBM subtypes present different modifications in their microenvironment, although the importance of the microenvironment in treatment response has yet to be determined. Understanding the microenvironment and how it changes after therapies is critical because it can influence the remaining invasive GSCs and lead to recurrence. This review article sheds light on the various components of the GBM microenvironment and their roles in tumoral development, as well as immune-related biological processes that support the interconnection/interrelationship between different cell types. Also, we summarize the current understanding of the modulation of soluble factors and highlight the dysregulated inflammatory chemokine/specific receptors cascades/networks and their significance in tumorigenesis, cancer-related inflammation, and metastasis.

Physical exercise is associated with a reduction in plasma levels of fractalkine, TGF-β1, eotaxin-1 and IL-6 in younger adults with mobility disability

Mobility disability (MD) refers to substantial limitations in life activities that arise because of movement impairments. Although MD is most prevalent in older individuals, it can also affect younger adults. Increasing evidence suggests that inflammation can drive the development of MD and may need to be targeted for MD prevention. Physical exercise has anti-inflammatory properties and has been associated with MD prevention. However, no studies to date have examined whether exercise interventions affect the peripheral inflammatory status in younger adults with MD. To this end, we used blood samples from young and middle-aged adults with MD (N = 38; median age = 34 years) who participated in a 12-week intervention that included aerobic and resistance exercise training. A pre-post assessment of inflammatory biomarkers was conducted in plasma from two timepoints, i.e., before the exercise trial and at follow-up (3–7 days after the last exercise session). We successfully measured 15 inflammatory biomarkers and found that exercise was associated with a significant reduction in levels of soluble fractalkine, transforming growth factor beta 1 (TGF-β1), eotaxin-1 and interleukin (IL) 6 (corrected α = 0.004). We also found significant male-specific effects of exercise on (i) increasing IL-16 and (ii) decreasing vascular endothelial growth factor-A (VEGF-A). In line with our results, previous studies have also found that exercise can reduce levels of TGF-β1, eotaxin-1 and IL-6. However, our finding that exercise reduces plasma levels of fractalkine in younger adults with MD, as well as the sex-dependent findings, have not been previously reported and warrant replication in larger cohorts. Given the suggested role of inflammation in promoting MD development, our study provides additional support for the use of physical exercise as a treatment modality for MD.

Transcriptomic Analysis Identified Two Subtypes of Brain Tumor Characterized by Distinct Immune Infiltration and Prognosis

Background

Brain tumor ranks as the most devastating cancer type. The complex tumor immune microenvironment prevents brain tumor from receiving therapeutic benefits. The purpose of this study was to stratify brain tumors based on their distinct immune infiltration signatures to facilitate better clinical decision making and prognosis prediction.

Methods

We developed a deep learning model to characterize immune infiltration from transcriptome. The developed model was applied to distill expression signatures of transcriptome of brain tumor samples. We performed molecular subtyping with the extracted expression signatures to unveil brain tumor subtypes. Computational methods, including gene set enrichment analysis, Kaplan-Meier survival and multivariate Cox regression analyses, were employed.

Results

We identified two distinctive subtypes (i.e. C1/2) of brain tumor featured by distinct immune infiltration signatures. The C1 subtype is characterized by protective immune infiltration signatures, including high infiltration of CD8+ T cells and activation of CX3CL1. The C2 subtype has an extensive infiltration of tumor-associated macrophages and microglia, and was enriched with immune suppressive, wound-healing, and angiogenic signatures. The C1 subtype had significantly better prognosis as compared with C2 (Log-rank test, HR: 2.5, 95% CI: 2.2 – 2.7; P = 8.2e-78). This difference remained statistically significant (multivariate Cox model, HR: 2.2, 95% CI: 1.7 – 2.9; P = 3.7e-10) by taking into account age, gender, recurrent/secondary status at sampling time, tumor grade, histology, radio-chemotherapy, IDH mutation, MGMT methylation, and co-deletion of 1p and 19q. This finding was validated in six datasets. The C2 subtype of glioblastoma patients with IDH mutation has poor survival analogous to those without IDH mutation (Log-rank test, adjusted P = 0.8), while C1 has favorable prognosis as compared with glioblastoma of C2 subtype with IDH mutation (Log-rank test, adjusted P = 1.2e-3) or without IDH mutation (Log-rank test, adjusted P = 1.3e-6).

Conclusions

We identified two distinctive subtypes of brain tumor with different immune infiltration signatures, which might be helpful as an independent prognosticator for brain tumor.

Advances in Chemokine Signaling Pathways as Therapeutic Targets in Glioblastoma

With a median patient survival of 15 months, glioblastoma (GBM) is still one of the deadliest malign tumors. Despite immense efforts, therapeutic regimens fail to prolong GBM patient overall survival due to various resistance mechanisms. Chemokine signaling as part of the tumor microenvironment plays a key role in gliomagenesis, proliferation, neovascularization, metastasis and tumor progression. In this review, we aimed to investigate novel therapeutic approaches targeting various chemokine axes, including CXCR2/CXCL2/IL-8, CXCR3/CXCL4/CXCL9/CXCL10, CXCR4/CXCR7/CXCL12, CXCR6/CXCL16, CCR2/CCL2, CCR5/CCL5 and CX3CR1/CX3CL1 in preclinical and clinical studies of GBM. We reviewed targeted therapies as single therapies, in combination with the standard of care, with antiangiogenic treatment as well as immunotherapy. We found that there are many antagonist-, antibody-, cell- and vaccine-based therapeutic approaches in preclinical and clinical studies. Furthermore, targeted therapies exerted their highest efficacy in combination with other established therapeutic applications. The novel chemokine-targeting therapies have mainly been examined in preclinical models. However, clinical applications are auspicious. Thus, it is crucial to broadly investigate the recently developed preclinical approaches. Promising preclinical applications should then be investigated in clinical studies to create new therapeutic regimens and to overcome therapy resistance to GBM treatment.

Vertebral-specific activation of the CX3CL1/ICAM-1 signaling network mediates non-small-cell lung cancer spinal metastasis by engaging tumor cell-vertebral bone marrow endothelial cell interactions

Rationale: The spine is one of the most common metastatic sites of non-small cell lung cancer (NSCLC), and NSCLC spinal metastasis results in serious consequences. Metastatic extravasation of disseminated cancer cells including increased invasiveness, adhesion and transendothelial migration is crucial for tumor metastasis. This study aimed to investigate the mechanisms underlying NSCLC spinal metastasis based on the C-X3-C motif chemokine ligand 1- (CX3CL1) and intercellular adhesion molecule-1- (ICAM-1) mediated signaling network. Methods: Immunohistochemistry, western blotting, and reverse transcription-quantitative PCR were conducted to detect the distribution of CX3CL1/ICAM-1 in different organs. Transwell, adhesion, and transendothelial migration assays were performed to evaluate the regulatory effects of CX3CL1/ICAM-1 on NSCLC cell invasion, adhesion, and transendothelial migration in vitro. A spontaneous spinal metastasis mouse model was established via injection of NSCLC cells into the left cardiac ventricle of NOD/SCID mice. The effects of CX3CL1/ICAM-1 on NSCLC spinal metastasis in vivo were validated using bioluminescent, micro-computerized tomography, immunohistochemistry and histological analyses. Results: CX3CL1 expression was specifically higher in vertebral bone compared with limb bones and lung tissue, and was associated with NSCLC spinal metastasis. Mechanically, vertebral bone marrow endothelial cells (VBMECs) enhanced NSCLC cell invasion via CX3CL1 signaling-mediated activation of the PI3K/AKT pathway. Furthermore, we found that VBMECs effectively induced ICAM-1-dependent NSCLC cell adhesion in coordination with platelets through the CX3CL1/ICAM-1/LFA-1 pathway. Meanwhile, CX3CL1 enhanced NSCLC cell transendothelial migration by increasing permeability of VBMECs via ICAM-1-dependent activation of the Src/GEF-H1 pathway. Interestingly, NSCLC cells were indicated to promote CX3CL1 secretion of VBMECs through MAPK14/ADMA17-dependent CX3CL1 release and NF-κB-dependent CX3CL1 synthesis. Based on these findings, we revealed a novel feedback cycle between circulating NSCLC cells and VBMECs mediated by CX3CL1/ICAM-1 signaling. Further disengagement of the CX3CL1/ICAM-1-mediated feedback cycle in vivo significantly restricted metastasis and prolonged mouse survival. Conclusions: Our results indicated a unique feedback cycle between circulating NSCLC cells and VBMECs mediated by CX3CL1/ICAM-1 signaling, which is necessary for NSCLC spinal metastasis. This work provides a new perspective for underlying the mechanisms of NSCLC spinal metastasis and indicates potential novel targets for the prevention of NSCLC spinal metastasis.

Transforming growth factor-β-regulated fractalkine as a marker of erosive bone invasion in oral squamous cell carcinoma

Patients with oral squamous cell carcinoma (OSCC) bone invasion are surgically treated with bone resection, which results in severe physical and psychological damage. Here, we investigated the potential of fractalkine (CX3CL1), which is regulated by transforming growth factor (TGF-β), as a novel biomarker for correct prediction and early detection of OSCC-associated bone invasion. TGF-β knockdown and treatment with a TGF-β-neutralizing antibody decreased the level of fractalkine in the culture media of HSC-2 and YD10B OSCC cells. Treatment with a fractalkine-neutralizing antibody reduced TGF-β-stimulated invasion by HSC-2 and YD10B cells. Fractalkine treatment increased the viability, invasion, and uPA secretion of both OSCC cell lines. Furthermore, OSCC cell bone invasion was assessed following subcutaneous inoculation of wild-type or TGF-β knockdown OSCC cells in mouse calvaria. TGF-β knockdown prevented erosive bone invasion, reduced the number of osteoclasts at the tumor-bone interface, and downregulated fractalkine expression in mouse tumor tissues. Our results indicate that the production of fractalkine is stimulated by TGF-β and mediates TGF-β-induced cell invasion in several OSCC cell lines showing an erosive pattern of bone invasion. Fractalkine may be a useful predictive marker and therapeutic target for OSCC-induced bone destruction.

Malignancy and IFITM3: Friend or Foe?

The prevalence and incidence of cancers has risen over the last decade. Available treatments have improved outcomes, yet mortality and morbidity remain high, creating an urgent demand for personalized and new therapy targets. Interferon induced transmembrane protein (IFITM3) is highly expressed in cancers and is a marker of poor prognosis. In this review, we discuss recent advances in IFITM3 biology, the regulatory pathways, and its function within cancer as part of immunity and maintaining stemness. Overexpression of IFITM3 is likely an indirect effect of ongoing inflammation, immune and cancer epithelial-to-mesenchymal (EMT) related pathways i.e., interferons, TGF-β, WNT/β-catenin, etc. However, IFITM3 also influences tumorigenic phenotypes, such as cell proliferation, migration and invasion. Furthermore, IFITM3 plays a key role in cancer growth and maintenance. Silencing of IFITM3 reduces these phenotypes. Therefore, targeting of IFITM3 will likely have implications for potential cancer therapies.

Role of CX3CR1 signaling in malignant transformation of gliomas

BACKGROUND

Chemokine signaling may contribute to progression of low-grade gliomas (LGGs) by altering tumor behavior or impacting the tumor microenvironment. In this study, we investigated the role of CX3C chemokine receptor 1 (CX3CR1) signaling in malignant transformation of LGGs.

METHODS

Ninety patients with LGGs were genotyped for the presence of common CX3CR1 V249I polymorphism and examined for genotype-dependent alterations in survival, gene expression, and tumor microenvironment. A genetically engineered mouse model was leveraged to model endogenous intracranial gliomas with targeted expression of CX3C ligand 1 (CX3CL1) and CX3CR1, individually or in combination.

RESULTS

LGG patients who were heterozygous (V/I; n = 43) or homozygous (I/I; n = 2) for the CX3CR1 V249I polymorphism had significantly improved median overall (14.8 vs 9.8 y, P < 0.05) and progression-free survival (8.6 vs 6.5 y, P < 0.05) compared with those with the wild type genotype (V/V; n = 45). Tumors from the V/I + I/I group exhibited significantly decreased levels of CCL2 and MMP9 transcripts, correlating with reduced intratumoral M2 macrophage infiltration and microvessel density. In an immunocompetent mouse model of LGGs, coexpression of CX3CL1 and CX3CR1 promoted a more malignant tumor phenotype characterized by increased microglia/macrophage infiltration and microvessel density, resulting in shorter survival.

CONCLUSIONS

CX3CR1 V249I polymorphism is associated with improved overall and progression-free survival in LGGs. CX3CR1 signaling enhances accumulation of tumor associated microglia/macrophages and angiogenesis during malignant transformation.

Pivotal Involvement of the CX3CL1-CX3CR1 Axis for the Recruitment of M2 Tumor-Associated Macrophages in Skin Carcinogenesis

We previously revealed the crucial roles of a chemokine, CX3CL1, and its receptor, CX3CR1, in skin wound healing. Although repeated wounds frequently develop into skin cancer, the roles of CX3CL1 in skin carcinogenesis remain elusive. Here, we proved that CX3CL1 protein expression and CX3CR1+ macrophages were observed in human skin cancer tissues. Similarly, we observed the enhancement of CX3CL1 expression and the abundant accumulation of CX3CR1+ tumor-associated macrophages with M2-like phenotypes in the skin carcinogenesis process induced by the combined treatment with 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate. In this mouse skin carcinogenesis process, CX3CR1+ tumor-associated macrophages exhibited M2-like phenotypes with the expression of Wnt3a and angiogenic molecules including VEGF and matrix metalloproteinase 9. Compared with wild-type mice, CX3CR1-deficient mice showed fewer numbers of skin tumors with a lower incidence. Concomitantly, M2-macrophage numbers and neovascularization were reduced with the depressed expression of angiogenic factors and Wnt3a. Thus, the CX3CL1-CX3CR1 axis can crucially contribute to skin carcinogenesis by regulating the accumulation and functions of tumor-associated macrophages. Thus, this axis can be a good target for preventing and/or treating skin cancers.

Fractalkine/CX3CL1 in Neoplastic Processes

Fractalkine/CX3C chemokine ligand 1 (CX3CL1) is a chemokine involved in the anticancer function of lymphocytes-mainly NK cells, T cells and dendritic cells. Its increased levels in tumors improve the prognosis for cancer patients, although it is also associated with a poorer prognosis in some types of cancers, such as pancreatic ductal adenocarcinoma. This work focuses on the 'hallmarks of cancer' involving CX3CL1 and its receptor CX3CR1. First, we describe signal transduction from CX3CR1 and the role of epidermal growth factor receptor (EGFR) in this process. Next, we present the role of CX3CL1 in the context of cancer, with the focus on angiogenesis, apoptosis resistance and migration and invasion of cancer cells. In particular, we discuss perineural invasion, spinal metastasis and bone metastasis of cancers such as breast cancer, pancreatic cancer and prostate cancer. We extensively discuss the importance of CX3CL1 in the interaction with different cells in the tumor niche: tumor-associated macrophages (TAM), myeloid-derived suppressor cells (MDSC) and microglia. We present the role of CX3CL1 in the development of active human cytomegalovirus (HCMV) infection in glioblastoma multiforme (GBM) brain tumors. Finally, we discuss the possible use of CX3CL1 in immunotherapy.

The Role of Selected Chemokines and Their Receptors in the Development of Gliomas

Among heterogeneous primary tumors of the central nervous system (CNS), gliomas are the most frequent type, with glioblastoma multiforme (GBM) characterized with the worst prognosis. In their development, certain chemokine/receptor axes play important roles and promote proliferation, survival, metastasis, and neoangiogenesis. However, little is known about the significance of atypical receptors for chemokines (ACKRs) in these tumors. The objective of the study was to present the role of chemokines and their conventional and atypical receptors in CNS tumors. Therefore, we performed a thorough search for literature concerning our investigation via the PubMed database. We describe biological functions of chemokines/chemokine receptors from various groups and their significance in carcinogenesis, cancer-related inflammation, neo-angiogenesis, tumor growth, and metastasis. Furthermore, we discuss the role of chemokines in glioma development, with particular regard to their function in the transition from low-grade to high-grade tumors and angiogenic switch. We also depict various chemokine/receptor axes, such as CXCL8-CXCR1/2, CXCL12-CXCR4, CXCL16-CXCR6, CX3CL1-CX3CR1, CCL2-CCR2, and CCL5-CCR5 of special importance in gliomas, as well as atypical chemokine receptors ACKR1-4, CCRL2, and PITPMN3. Additionally, the diagnostic significance and usefulness of the measurement of some chemokines and their receptors in the blood and cerebrospinal fluid (CSF) of glioma patients is also presented.

TRAF6 Activates Fibroblasts to Cancer-Associated Fibroblasts through FGF19 in Tumor Microenvironment to Benefit the Malignant Phenotype of Melanoma Cells

Cancer-associated fibroblasts (CAFs) are an important component of the tumor microenvironment and mediate tumor progression in various cancers. A previous study demonstrated that TRAF6 promotes the malignant phenotype of melanoma cells. However, the role of TRAF6 in melanoma CAFs remains unclear. In this study, we found that TRAF6 was significantly upregulated in CAFs adjacent to melanoma cells. Functional assays showed that TRAF6 promoted fibroblast proliferation and migration as well as MMP and α-SMA expression. Moreover, the expression of TRAF6 in fibroblasts promoted the malignant phenotype of melanoma cells in vitro and in vivo. Meanwhile, the intervention of TRAF6 expression in melanoma cells affected the activation of CAFs. We found that FGF19 was a key cytokine regulated by TRAF6 through NF-κB1 using luciferase assay and chromatin immunoprecipitation in melanoma cells. Because plasma FGF19 levels are elevated in patients with melanoma, it may significantly induce fibroblast activation in vitro and in vivo. Taken together, our results support that TRAF6 is a key molecule that mediates the interaction between melanoma cells and stromal fibroblasts, suggesting that TRAF6 is a potentially promising target in melanoma therapy.

The flavonoid rutin and its aglycone quercetin modulate the microglia inflammatory profile improving antiglioma activity

Microglia cells are the immune effector in the Central Nervous System (CNS). However, studies have showed that they contribute more to glioma progression than to its elimination. Rutin and its aglycone quercetin are flavonoids present in many fruits as well as plants and have been demonstrated to bear anti-inflammatory, antioxidant and antitumor properties also to human glioblastoma cell lines. Previous studies also demonstrated that rutin, isolated from the Brazilian plant Dimorphandra mollis Bent., presents immunomodulatory effect on astrocytes and microglia. In this study, we investigate the antitumor and immunomodulatory properties of rutin and its aglycone quercetin on the viability of glioma cells alone and under direct and indirect interaction with microglia. Flavonoid treatment of rat C6 glioma cells induced inhibition of proliferation and migration, and also induced microglia chemotaxis that was associated to the up regulation of tumor necrosis factor (TNF) and the down regulation of Interleukin 10 (IL-10) at protein and mRNA expression levels, regulation of mRNA expression for chemokines CCL2, CCL5 and CX3CL1, and Heparin Binding Growth Factor (HDGF), Insulin-like growth factor (IGF) and Glial cell-derived neurotrophic factor (GDNF) growth factors. Treatment of human U251 and TG1 glioblastoma cells with both flavonoids also modulated negatively the expression of mRNA for IL-6 and IL-10 and positively the expression of mRNA for TNF characterizing changes to the immune regulatory profile. Treatment of microglia and C6 cells either in co-cultures or during indirect interaction, via conditioned media from glioma cells treated with flavonoids or via conditioned media from microglia treated with flavonoids reduced proliferation and migration of glioma cells. It also directed microglia towards an inflammatory profile with increased expression of mRNA for IL-1β, IL-6, IL-18 and decreased expression of mRNA for nitric oxide synthase 2 (NOS2) and prostaglandin-endoperoxide synthase 2 (PTGS2), arginase and transforming growth factor beta (TGF-β), as well as Insulin-like growth factor (IGF). Treatment of U251 cells with flavonoids also reduced tumorigenesis when the cells were xenotransplanted in rat brains, and directed microglia and also astrocytes in the microenvironment of tumor cell implantation as well as in the brain parenchyma to a not favorable molecular inflammatory profile to the glioma growth, as observed in cultures. Together these results demonstrate that the flavonoid rutin and its aglycone quercetin present antiglioma effects related to the property of modulating the microglial inflammatory profile and may be considered for molecular and preclinical studies as adjuvant molecules for treatment of gliomas.

Role of Infiltrating Microglia/Macrophages in Glioma

In this chapter we describe the state of the art knowledge of the role played by myeloid cells in promoting and supporting the growth and the invasive properties of a deadly brain tumor, glioblastoma. We provide a review of the works describing the intercellular communication among glioma and associated microglia/macrophage cells (GAMs) using in vitro cellular models derived from mice, rats and human patients and in vivo animal models using syngeneic or xenogeneic experimental systems. Special emphasis will be given to 1) the timing alteration of brain microenvironment under the influence of glioma, 2) the bidirectional communication among tumor and GAMs, 3) possible approaches to interfere with or to guide these interactions, with the aim to identify molecular and cellular targets which could revert or delay the vicious cycle that favors tumor biology.

Role of CX3CL1/CX3CR1 Signaling Axis Activity in Osteoporosis

Osteoporosis is a civilization disease which is still challenging for contemporary medicine in terms of treatment and prophylaxis. It results from excessive activation of the osteoclastic cell line and immune cells like macrophages and lymphocytes. Cell-to-cell inflammatory information transfer occurs via factors including cytokines which form a complex network of cell humoral correlation, called cytokine network. Recently conducted studies revealed the participation of CX3CL1 chemokine in the pathogenesis of osteoporosis. CX3CL1 and its receptor CX3CR1 present unique properties among over 50 described chemokines. Apart from its chemotactic activity, CX3CL1 is the only chemokine which may function as an adhesion molecule which facilitates easier penetration of immune system cells through the vascular endothelium to the area of inflammation. The present study, based on world literature review, sums and describes convincing evidences of a significant role of the CX3CL1/CX3CR1 axis in processes leading to bone mineral density (BMD) reduction. The CX3CL1/CX3CR1 axis plays a principal role in osteoclast maturation and binding them with immune cells to the surface of the bone tissue. It promotes the development of inflammation and production of many inflammatory cytokines near the bone surface (i.e., TNF-α, IL-1β, and IL-6). High concentrations of CX3CL1 in serum are directly proportional to increased concentrations of bone turnover and inflammatory factors in human blood serum (TRACP-5b, NTx, IL-1β, and IL-6). Regarding the fact that acting against the CX3CL1/CX3CR1 axis is a potential target of immune treatment in osteoporosis, the number of available papers tackling the topic is certainly insufficient. Therefore, it seems justified to continue research which would precisely determine its role in the metabolism of the bone tissue as one of the most promising targets in osteoporosis therapy.

Overexpression of CD44 is associated with a poor prognosis in grade II/III gliomas

PURPOSE

Overexpression of CD44 has been detected in many types of tumor tissues. Moreover, CD44 is recognized as a cancer stem cell marker for many cancers. However, the prognostic value of CD44 for glioma patients has not yet been clarified. The authors tried to explore the impact of CD44 expression on grade II/III glioma patients.

METHODS

To assess the RNA expression levels of CD44 in glioma tissues and normal brain tissues, meta-analyses were conducted in the online Oncomine database. The mRNA expression levels of CD44, CD44s, and CD44v2-v10 in 112 grade II/III glioma patients in Hokkaido University Hospital (HUH) were detected by qPCR. The RNA-seq data and clinical data of grade II/III glioma patients were obtained from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) databases.

RESULTS

Based on the Oncomine database, CD44 has significantly high expression in glioma tissues as compared with normal tissues. We explored the clinical relevance of CD44 mRNA expression based on the HUH cohorts, the TCGA cohorts, and the CGGA cohorts. In survival analysis, high mRNA expression of CD44 was correlated with poor overall survival and poor progression-free survival in grade II/III glioma patients. Multivariate Cox regression analyses confirmed CD44 as an independent prognostic factor for grade II/III glioma patients.

CONCLUSIONS

The present study suggests that overexpression of CD44 is associated with a poor prognosis for grade II/III glioma patients. Moreover, our findings suggest that CD44 could serve as a prognostic biomarker in grade II/III glioma patients.

IFITM3/STAT3 axis promotes glioma cells invasion and is modulated by TGF-β

Glioma is the most aggressive primary brain tumor. We have previously provided evidence that IFITM3 promoted glioma cells migration. However, the mechanism of how IFITM3 regulates glioma cells invasion and whether IFITM3 participates in TGF-β-mediated glioma invasion are still unknown. In this paper, we proved that IFITM3 was notably up-regulated in glioma tissues. Knockdown of IFITM3 suppressed STAT3 phosphorylation in vitro, and a specific STAT3 inhibitor AG490 reversed IFITM3-induced invasion of glioma cells. Furthermore, IFITM3 expression was induced by TGF-β in glioma and IFITM3 knockdown abolished TGF-β-mediated glioma cells invasion. Collectively, the results indicate that IFITM3/STAT3 axis may promote TGF-β-induced glioma cells invasion. This study provided some suggestions for the clinical treatment of the brain tumor.

NFATc3 controls tumour growth by regulating proliferation and migration of human astroglioma cells

Calcium/Calcineurin/Nuclear Factor of Activated T cells (Ca/CN/NFAT) signalling pathway is the main calcium (Ca²⁺) dependent signalling pathway involved in the homeostasis of brain tissue. Here, we study the presence of NFATc members in human glioma by using U251 cells and a collection of primary human glioblastoma (hGB) cell lines. We show that NFATc3 member is the predominant member. Furthermore, by using constitutive active NFATc3 mutant and shRNA lentiviral vectors to achieve specific silencing of this NFATc member, we describe cytokines and molecules regulated by this pathway which are required for the normal biology of cancer cells. Implanting U251 in an orthotopic intracranial assay, we show that specific NFATc3 silencing has a role in tumour growth. In addition NFATc3 knock-down affects both the proliferation and migration capacities of glioma cells in vitro. Our data open the possibility of NFATc3 as a target for the treatment of glioma.

LncRNA-ATB promotes TGF-β-induced glioma cells invasion through NF-κB and P38/MAPK pathway

Glioma constitutes the most aggressive primary intracranial malignancy in adults. We previously showed that long noncoding RNA activated by TGF-β (lncRNA-ATB) promoted the glioma cells invasion. However, whether lncRNA-ATB is involved in TGF-β-mediated invasion of glioma cells remains unknown. In this study, quantitative real-time polymerase chain reaction and western blot analysis were used for detecting the mRNA and protein expression of related genes, respectively. Transwell assay was performed to assess the impact of lncRNA-ATB on TGF-β-induced glioma cells migration and invasion. Immunofluorescence staining was utilized to characterize related protein distribution. Results showed that TGF-β upregulated lncRNA-ATB expression in glioma LN-18 and U251 cells. Overexpression of lncRNA-ATB activated nuclear factor-κB (NF-κB) pathway and promoted P65 translocation into the nucleus, thus facilitated glioma cells invasion stimulated by TGF-β. Similarly, lncRNA-ATB markedly enhanced TGF-β-mediated invasion of glioma cells through activation P38 mitogen-activated protein kinase (P38/MAPK) pathway. Moreover, both the NF-κB selected inhibitor pyrrolidinedithiocarbamate ammonium and P38/MAPK specific inhibitor SB203580 partly reversed lncRNA-ATB induced glioma cells invasion mediated by TGF-β. Collectively, this study revealed that lncRNA-ATB promotes TGF-β-induced glioma cell invasion through NF-κB and P38/MAPK pathway and established a detailed framework for understanding the way how lncRNA-ATB performs its function in TGF-β-mediated glioma invasion.

Overexpression of CX3CR1 in Adipose-Derived Stem Cells Promotes Cell Migration and Functional Recovery After Experimental Intracerebral Hemorrhage

Stem cell therapy has emerged as a new promising therapeutic strategy for intracerebral hemorrhage (ICH). However, the efficiency of stem cell therapy is partially limited by low retention and engraftment of the delivered cells. Therefore, it’s necessary to improve the migration ability of stem cells to the injured area in order to save the costs and duration of cell preparation. This study aimed to investigate whether overexpression of CX3CR1, the specific receptor of chemokine fractalkine (FKN), in adipose-derived stem cells (ADSCs) can stimulate the cell migration to the injured area in the brain, improve functional recovery and protect against cell death following experimental ICH. ADSCs were isolated from subcutaneous adipose tissues of rats. ICH was induced by means of an injection of collagenase type VII. ELISA showed that the expression levels of fractalkine/FKN were increased at early time points, with a peak at day 3 after ICH. And it was found that different passages of ADSCs could express the chemokine receptor CX3CR1. Besides, the chemotactic movements of ADSCs toward fractalkine have been verified by transwell migration assay. ADSCs overexpressing CX3CR1 were established through lentivirus transfection. We found that after overexpression of CX3CR1 receptor, the migration ability of ADSCs was increased both in vitro and in vivo. In addition, reduced cell death and improved sensory and motor functions were seen in the mice ICH model. Thus, ADSCs overexpression CX3CR1 might be taken as a promising therapeutic strategy for the treatment of ICH.

The R132H mutation in IDH1 promotes the recruitment of NK cells through CX3CL1/CX3CR1 chemotaxis and is correlated with a better prognosis in gliomas

Mutations in the isocitrate dehydrogenase (IDH) 1 gene, especially the R132H mutation, have been reported to be associated with a better prognosis in glioma patients. However, the underlying molecular mechanisms are not yet well understood. Many factors may contribute to differences in the survival of IDH1 wild-type and IDH1 mutant glioma patients, in which immune components play a potentially important role. In this study, we analyzed The Cancer Genome Atlas (TCGA), and the Chinese Glioma Genome Atlas (CGGA) databases, as well as glioma patient-derived tumor samples. We found that there was a higher infiltration of natural killer (NK) cells in IDH1 mutant glioma patients, and this was correlated with a better prognosis. We also showed that IDH1-R132 tumor cells had higher expression levels of the chemokine CX3CL1. This arises as a result of the conversion of α-ketoglutarate to R(-)-2-hydroxyglutarate by the IDH1 mutant and the resultant phosphorylation of nuclear factor kappa B. Knockdown of CX3CL1 decreased the migration of NK cells. In addition, the high levels of expression of CX3CL1 were positively correlated with glioma patient survival in the TCGA and CGGA databases, and in the clinical samples. Overall, our data have identified a novel mechanism in which R132H mutation of the IDH1 gene serves as a tumor suppressor by promoting the recruitment of NK cells through CX3CL1/CX3CR1 chemotaxis.

Increased CX3CL1 mRNA expression level is a positive prognostic factor in patients with lung adenocarcinoma

Chemokines are a family of small cytokines, which are signalling proteins secreted by cells. The principal role of chemokines is to serve as chemoattractants to guide the migration of their target cells. Chemokine C-X3-C motif ligand 1 (CX3CL1) is a protein-coding gene of fractalkine, which serves as a ligand for chemokine C-X3-C motif receptor 1 (CX3CR1) and integrins. However, the roles of CX3CL1 in different pathological types of lung cancer remain poorly understood. The present study aimed to investigate the potential clinical and biological function of CX3CL1 mRNA expression in patients with lung cancer. In the present study, lung cancer data obtained from the Gene Expression Omnibus database and The Cancer Genome Atlas were downloaded and analysed, and the results demonstrated that an increased CX3CL1 mRNA expression in tumour tissues from lung adenocarcinoma (LUAD) was associated with improved overall survival. However, no significant association was identified between CX3CL1 expression and the prognosis of lung squamous cell carcinoma (LUSC). Furthermore, the genes whose expression levels were correlated with CX3CL1 expression were subjected to enrichment analysis, and the results for the LUAD data demonstrated that the most significant biological processes included ‘positive regulation of cell adhesion’, ‘leukocyte cell-cell adhesion’, ‘leukocyte migration’ and ‘T cell activation’, whereas, the important highly ranked pathways included ‘cell adhesion molecules (CAMs)’, ‘leukocyte transendothelial migration’ and ‘natural killer cell-mediated cytotoxicity’. However, in the patients with LUSC, the genes that were highly correlated with CX3CL1 were not enriched for any biological processes or signalling pathways. Based on the data of the present study, it was hypothesised that CX3CL1 may serve as a prognostic marker for LUAD.

Ccl5 establishes an autocrine high-grade glioma growth regulatory circuit critical for mesenchymal glioblastoma survival

Glioblastoma (GBM) is the most common malignant brain tumor in adults, with a median survival of 15 months. These poor clinical outcomes have prompted the development of drugs that block neoplastic cancer cell growth; however, non-neoplastic cell-derived signals (chemokines and cytokines) in the tumor microenvironment may also represent viable treatment targets. One such chemokine, Ccl5, produced by low-grade tumor-associated microglia, is responsible for maintaining neurofibromatosis type 1 (NF1) mouse optic glioma growth in vivo. Since malignant gliomas may achieve partial independence from growth regulatory factors produced by non-neoplastic cells in the tumor microenvironment by producing the same cytokines secreted by the stromal cells in their low-grade counterparts, we tested the hypothesis that CCL5/CCL5-receptor signaling in glioblastoma creates an autocrine circuit important for high-grade glioma growth. Herein, we demonstrate that increased CCL5 expression was restricted to both human and mouse mesenchymal GBM (M-GBM), a molecular subtype characterized by NF1 loss. We further show that the NF1 protein, neurofibromin, negatively regulates Ccl5 expression through suppression of AKT/mTOR signaling. Consistent with its role as a glioblastoma growth regulator, Ccl5 knockdown in M-GBM cells reduces M-GBM cell survival in vitro, and increases mouse glioblastoma survival in vivo. Finally, we demonstrate that Ccl5 operates through an unconventional CCL5 receptor, CD44, to inhibit M-GBM apoptosis. Collectively, these findings reveal an NF1-dependent CCL5-mediated pathway that regulates M-GBM cell survival, and support the concept that paracrine factors important for low-grade glioma growth can be usurped by high-grade tumors to create autocrine regulatory circuits that maintain malignant glioma survival.

Migrating Interneurons Secrete Fractalkine to Promote Oligodendrocyte Formation in the Developing Mammalian Brain

During development, newborn interneurons migrate throughout the embryonic brain. Here, we provide evidence that these interneurons act in a paracrine fashion to regulate developmental oligodendrocyte formation. Specifically, we show that medial ganglionic eminence (MGE) interneurons secrete factors that promote genesis of oligodendrocytes from glially biased cortical precursors in culture. Moreover, when MGE interneurons are genetically ablated in vivo prior to their migration, this causes a deficit in cortical oligodendrogenesis. Modeling of the interneuron-precursor paracrine interaction using transcriptome data identifies the cytokine fractalkine as responsible for the pro-oligodendrocyte effect in culture. This paracrine interaction is important in vivo, since knockdown of the fractalkine receptor CX3CR1 in embryonic cortical precursors, or constitutive knockout of CX3CR1, causes decreased numbers of oligodendrocyte progenitor cells (OPCs) and oligodendrocytes in the postnatal cortex. Thus, in addition to their role in regulating neuronal excitability, interneurons act in a paracrine fashion to promote the developmental genesis of oligodendrocytes.

TGF-β1 Downregulates the Expression of CX3CR1 by Inducing miR-27a-5p in Primary Human NK Cells

Activity of human natural killer (NK) cells against cancer cells is deeply suppressed by TGF-β1, an immunomodulatory cytokine that is released and activated in the tumor microenvironment. Moreover, our previous data showed that TGF-β1 modifies the chemokine receptor repertoire of NK cells. In particular, it decreases the expression of CX₃CR1 that drives these effectors toward peripheral tissues, including tumor sites. To identify possible mechanisms mediating chemokine receptors modulation, we analyzed the microRNA profile of TGF-β1-treated primary NK cells. The analysis pointed out miR-27a-5p as a possible modulator of CX₃CR1. We demonstrated the functional interaction of miR-27a-5p with the 3′ untranslated region (3′UTR) of CX₃CR1 mRNA by two different experimental approaches: by the use of a luciferase assay based on a reporter construct containing the CX₃CR1 3′UTR and by transfection of primary NK cells with a miR-27a-5p inhibitor. We also showed that the TGF-β1-mediated increase of miR-27a-5p expression is a consequence of miR-23a-27a-24-2 cluster induction. Moreover, we demonstrated that miR-27a-5p downregulates the surface expression of CX₃CR1. Finally, we showed that neuroblastoma cells induced in resting NK cells a downregulation of the CX₃CR1 expression that was paralleled by a significant increase of miR-27a-5p expression. Therefore, the present study highlights miR-27a-5p as a pivotal TGF-β1-induced regulator of CX₃CR1 expression.

Fractalkine/CX3CL1 induced intercellular adhesion molecule-1-dependent tumor metastasis through the CX3CR1/PI3K/Akt/NF-κB pathway in human osteosarcoma

Osteosarcoma is the most common primary bone tumor in children and teens. The exact molecular mechanism underlying osteosarcoma progression still remains unclear. The CX3CL1/fractalkine has been implicated in various tumors but not in osteosarcoma. This study is the first to show that fractalkine promotes osteosarcoma metastasis by promoting cell migration. Fractalkine expression was higher in osteosarcoma cell lines than in normal osteoblasts. Fractalkine induced cell migration by upregulating intercellular adhesion molecule-1 (ICAM-1) expression via CX3CR1/PI3K/Akt/NF-κB pathway in human osteosarcoma cells. Knockdown of fractalkine expression markedly inhibited cell migration and lung metastasis in osteosarcoma. Finally, we showed a clinical correlation between CX3CL1 expression and ICAM-1 expression as well as tumor stage in human osteosarcoma tissues. In conclusion, our results indicate that fractalkine promotes cell migration and metastasis of osteosarcoma by upregulating ICAM-1 expression. Thus, fractalkine could serve a novel therapeutic target for preventing osteosarcoma metastasis.

Role of CX3CL1 in Diseases

Chemokines are a family of small 8-10 kDa inducible cytokines. Initially characterized as chemotactic factors, they are now considered to affect not just cellular recruitment. CX3CL1 is a unique chemokine that can exist in a soluble form, as a chemotactic cytokine, or in a membrane-attached form that acts as a binding molecule. Recently, the effects of CX3CL1 on diseases, such as inflammation and cancer, have been supported and confirmed by numerous publications. However, due to its dual effects, CX3CL1 exerts numerous effects on pathophysiological conditions that have both negative and positive consequences on pathogenesis and outcome. This review article summarizes the important scientific and clinical data that now point to a critical role for CX3CL1 in diseases.

The Fractalkine-Receptor Axis Improves Human Colorectal Cancer Prognosis by Limiting Tumor Metastatic Dissemination

Human colorectal cancer (CRC) is a frequent neoplasia in Western countries, and its metastatic progression is a major cause of cancer-related death. In search of specific molecules upregulated in CRC, with possible clinical relevance, we performed a differential gene-profiling analysis in surgery-derived CRC samples and adjacent uninvolved intestinal mucosa. The chemokine CX3CL1 and its specific receptor CX3CR1 were significantly upregulated in tumors. Higher expression of CX3CL1 and CX3CR1 was confirmed by immunohistochemistry in 100 CRC tumor samples (stages I-III). Unexpectedly, high immune scores of CX3CL1 did not correlate with the density of tumor-infiltrating CD3(+) T cells or CD68(+) macrophages. Coexpression of ligand and receptor by tumor cells (axis-positive tumors) significantly associated with longer disease-free (p = 0.01) and disease-specific survival (p = 0.001). Conversely, axis-negative tumors (with low expression of both ligand and receptor) had increased risk of tumor relapse (p = 0.02), and increased likelihood of metachronous metastasis (p = 0.001), including after stage adjustment (p = 0.006). Transduction of CX3CL1 and CX3CR1 in CRC tumor cell lines induced cell aggregation that strongly inhibited in vitro migration in chemotaxis assays. In a mouse model of spleen-liver metastases, cancer dissemination to liver was dramatically reduced in CX3CL1-CX3CR1-expressing tumors, and ligand-receptor interaction was confirmed in cancer cells in vivo by fluorescence resonance energy transfer analysis. In conclusion, tumoral expression of the CX3CL1-CX3CR1 chemokine axis functions as a retention factor, increasing homotypic cell adhesion and limiting tumor spreading to metastatic sites. Lack or low levels of expression of CX3CL1-CX3CR1 by tumor cells identifies a group of CRC patients at increased risk of metastatic progression.

Comparative transcriptomics reveals similarities and differences between astrocytoma grades

Background

Astrocytomas are the most common primary brain tumors distinguished into four histological grades. Molecular analyses of individual astrocytoma grades have revealed detailed insights into genetic, transcriptomic and epigenetic alterations. This provides an excellent basis to identify similarities and differences between astrocytoma grades.

Methods

We utilized public omics data of all four astrocytoma grades focusing on pilocytic astrocytomas (PA I), diffuse astrocytomas (AS II), anaplastic astrocytomas (AS III) and glioblastomas (GBM IV) to identify similarities and differences using well-established bioinformatics and systems biology approaches. We further validated the expression and localization of Ang2 involved in angiogenesis using immunohistochemistry.

Results

Our analyses show similarities and differences between astrocytoma grades at the level of individual genes, signaling pathways and regulatory networks. We identified many differentially expressed genes that were either exclusively observed in a specific astrocytoma grade or commonly affected in specific subsets of astrocytoma grades in comparison to normal brain. Further, the number of differentially expressed genes generally increased with the astrocytoma grade with one major exception. The cytokine receptor pathway showed nearly the same number of differentially expressed genes in PA I and GBM IV and was further characterized by a significant overlap of commonly altered genes and an exclusive enrichment of overexpressed cancer genes in GBM IV. Additional analyses revealed a strong exclusive overexpression of CX3CL1 (fractalkine) and its receptor CX3CR1 in PA I possibly contributing to the absence of invasive growth. We further found that PA I was significantly associated with the mesenchymal subtype typically observed for very aggressive GBM IV. Expression of endothelial and mesenchymal markers (ANGPT2, CHI3L1) indicated a stronger contribution of the micro-environment to the manifestation of the mesenchymal subtype than the tumor biology itself. We further inferred a transcriptional regulatory network associated with specific expression differences distinguishing PA I from AS II, AS III and GBM IV. Major central transcriptional regulators were involved in brain development, cell cycle control, proliferation, apoptosis, chromatin remodeling or DNA methylation. Many of these regulators showed directly underlying DNA methylation changes in PA I or gene copy number mutations in AS II, AS III and GBM IV.

Conclusions

This computational study characterizes similarities and differences between all four astrocytoma grades confirming known and revealing novel insights into astrocytoma biology. Our findings represent a valuable resource for future computational and experimental studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1939-9) contains supplementary material, which is available to authorized users.

Macrophage and cancer cell cross-talk via CCR2 and CX3CR1 is a fundamental mechanism driving lung cancer

RATIONALE

Recent studies indicate that tumor-associated macrophages (MΦ) with an M2 phenotype can influence cancer progression and metastasis, but the regulatory pathways remain poorly characterized.

OBJECTIVES

This study investigated the role of tumor-associated MΦ in lung cancer.

METHODS

Coculturing of MΦ with mouse Lewis lung carcinoma (LLC1) and 10 different human lung cancer cell lines (adenocarcinoma, squamous cell carcinoma, and large cell carcinoma) caused up-regulation of CCR2/CCL2 and CX3CR1/CX3CL1 in both the cancer cells and the MΦ.

MEASUREMENTS AND MAIN RESULTS

In the MΦ-tumor cell system, IL-10 drove CCR2 and CX3CR1 up-regulation, whereas CCL1, granulocyte colony-stimulating factor, and MIP1α were required for the up-regulation of CCL2 and CX3CL1. Downstream phenotypic effects included enhanced LLC1 proliferation and migration and MΦ M2 polarization. In vivo, MΦ depletion (clodronate, MΦ Fas-induced apoptosis mice) and genetic ablation of CCR2 and CX3CR1 all inhibited LLC1 tumor growth and metastasis, shifted tumor-associated MΦ toward M1 polarization, suppressed tumor vessel growth, and enhanced survival (metastasis model). Furthermore, mice treated with CCR2 antagonist mimicked genetic ablation of CCR2, showing reduced tumor growth and metastasis. In human lung cancer samples, tumor MΦ infiltration and CCR2 expression correlated with tumor stage and metastasis.

CONCLUSIONS

Tumor-associated MΦ play a central role in lung cancer growth and metastasis, with bidirectional cross-talk between MΦ and cancer cells via CCR2 and CX3CR1 signaling as a central underlying mechanism. These findings suggest that the therapeutic strategy of blocking CCR2 and CX3CR1 may prove beneficial for halting lung cancer progression.

MicroRNA-29b regulates migration in oral squamous cell carcinoma and its clinical significance

OBJECTIVES

MicroRNA (miRNA) machinery regulates cancer cell behavior, and has been implicated in patients' clinical status and prognosis. We found that microRNA-29b (miR-29b) increased significantly in advanced migratory cells. However, miR-29b controls the migration ability, and its regulatory mechanism in oral squamous cell carcinoma (OSCC) remains unknown.

MATERIALS AND METHODS

We triggered miR-29b expression in OSCC patients and cell lines by conducting real-time quantitative PCR. We determined the functions of miR-29b in the migration of OSCC cells by using gain- and loss-of-function approaches. We elevated the target genes of miR29b through software predictions and a luciferase report assay. We used an orthotopic OSCC animal model to investigate the effects of miR29b on OSCC cell metastasis in vivo.

RESULTS

The clinical data revealed that miR-29b expression was correlated with lymph node metastasis and an advanced tumor stage in 98 OSCC patients. Furthermore, multivariate analysis revealed that miR-29b expression was significantly correlated with recurrence, and indicated poor survival. MiR-29b promoted OSCC cell migration and downregulated CX3CL1, a cell-cell adhesion regulator, which plays an essential role in miR-29b-regulated OSCC cell migration machinery. Furthermore, we found that CX3CL1 expression was correlated with lymph node metastasis and an early tumor stage in OSCC patients, and negatively correlated with miR-29b expression.

CONCLUSION

MiR-29b acts as an oncomir, promoting cell migration through CX3CL1 suppression, and could be a potential therapeutic target for preventing OSCC progression.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Role of fractalkine/CX3CL1 and its receptor in the pathogenesis of inflammatory and malignant diseases with emphasis on B cell malignancies

Fractalkine/CX3CL1, the only member of the CX3C chemokine family, exists as a membrane-anchored molecule as well as in soluble form, each mediating different biological activities. It is constitutively expressed in many hematopoietic and nonhematopoietic tissues such as endothelial and epithelial cells, lymphocytes, neurons, microglial osteoblasts. The biological activities of CX3CL1 are mediated by CX3CR1, that is expressed on different cell types such as NK cells, CD14⁺ monocytes, cytotoxic effector T cells, B cells, neurons, microglia, smooth muscle cells, and tumor cells. The CX3CL1/CX3CR1 axis is involved in the pathogenesis of several inflammatory cancer including various B cell malignancies. In tumors the interaction between cancer cells and cellular microenvironment creates a context that may promote tumor growth, increase tumor survival, and facilitate metastasis. Therefore the role of the CX3CL1/CX3CR1 has attracted interest as to the development of potential therapeutic approaches. Here we review the different effects of the CX3CL1/CX3CR1 axis in several inflammatory and neurodegenerative diseases and in cancer, with emphasis on human B cell lymphomas.