Expression of CXC chemokine receptors 1-5 and their ligands in human glioma tissues: role of CXCR4 and SDF1 in glioma cell proliferation and migration. Neurochem Int. 2006;49:423-432. [PMID: 16621164 DOI: 10.1016/j.neuint.2006.03.003]

Patient-based multilevel transcriptome exploration highlights relevant chemokines and chemokine receptor axes in glioblastoma

Chemokines and their receptors form a complex interaction network, crucial for precise leukocyte positioning and trafficking. In cancer, they promote malignant cell proliferation and survival but are also critical for immune cell infiltration in the tumor microenvironment. Glioblastoma (GBM) is the most common and lethal brain tumor, characterized by an immunosuppressive TME, with restricted immune cell infiltration. A better understanding of chemokine-receptor interactions is therefore essential for improving tumor immunogenicity. In this study, we assessed the expression of all human chemokines in adult-type diffuse gliomas, with particular focus on GBM, based on patient-derived samples. Publicly available bulk RNA sequencing datasets allowed us to identify the chemokines most abundantly expressed in GBM, with regard to disease severity and across different tumor subregions. To gain insight into the chemokines-receptor network at the single cell resolution, we explored GBmap, a curated resource integrating multiple scRNAseq datasets from different published studies. Our study constitutes the first patient-based handbook highlighting the relevant chemokine-receptor crosstalks, which are of significant interest in the perspective of a therapeutic modulation of the TME in GBM.

Relationship between chemokine/chemokine receptor and glioma prognosis and outcomes: Systematic review and meta-analysis

BACKGROUND

Glioma is a primary tumor originating from the central nervous system, and despite ongoing efforts to improve treatment, its overall survival rate remains low. There are a limited number of reports regarding the clinical grading, prognostic impact, and utility of chemokines. Therefore, conducting a meta-analysis is necessary to obtain convincing and conclusive results.

METHODS

A comprehensive literature search was conducted using various databases, including PubMed, Web of Science, The Cochrane Library, Embase, Ovid Medline, CNKI, Wanfang Database, VIP, and CBM. The search encompassed articles published from the inception of the databases until March 2024. The estimated odds ratio (ORs), standard mean difference (SMDs), and hazard ratio (HR) with their corresponding 95% confidence intervals (95% CI) were calculated to assess the predictive value of chemokine and receptor levels in glioma risk. Additionally, heterogeneity tests and bias tests were performed to evaluate the reliability of the findings.

RESULTS

This meta-analysis included a total of 36 studies, involving 2,480 patients diagnosed with glioma. The results revealed a significant association between the expression levels of CXCR4 (n = 8; OR = 22.28; 95 % CI = 11.47-43.30; p = 0.000), CXCL12 (n = 4; OR = 10.69; 95 % CI = 7.03-16.24; p = 0.000), CCL2 (n = 6; SMD = -0.83; 95 % CI = -0.98--0.67; p = 0.000), CXCL8 (n = 3; SMD = 0.75; 95 % CI = 0.47-1.04; p = 0.000), CXCR7 (n = 3; OR = 20.66; 95 % CI = 10.20-41.82; p = 0.000), CXCL10 (n = 2; SMD = 3.27; 95 % CI = 2.91-3.62; p = 0.000) and the risk of glioma. Additionally, a significant correlation was observed between CXCR4 (n = 8; OR = 4.39; 95 % CI = 3.04-6.32; p = 0.000), (n = 6; SMD = 1.37; 95 % CI = 1.09-1.65; p = 0.000), CXCL12 (n = 6; OR = 6.30; 95 % CI = 3.87-10.25; p = 0.000), (n = 5; ES = 2.25; 95 % CI = 1.15-3.34; p = 0.041), CCL2 (n = 3; OR = 9.65; 95 % CI = 4.55-20.45; p = 0.000), (n = 4; SMD = -1.47; 95 % CI = -1.68--1.26; p = 0.000), and CCL18 (n = 3; SMD = 1.62; 95 % CI = 1.30-1.93; p = 0.000) expression levels and high-grade glioma (grades 3-4). Furthermore, CXCR4 (HR = 2.38, 95 % CI = 1.66-3.40; p = 0.000) exhibited a strong correlation with poor overall survival (OS) rates in glioma patients.

CONCLUSION

The findings of this study showed a robust association between elevated levels of CXCR4, CXCL12, CCL2, CXCL8, CXCL10 and CXCR7 with a higher risk of glioma. Furthermore, the WHO grading system was validated by the strong correlation shown between higher expression of CXCR4, CXCL12, CCL2, and CCL18 and WHO high-grade gliomas (grades 3-4). Furthermore, the results of the meta-analysis suggested that CXCR4 might be a helpful biomarker for predicting the worse prognosis of glioma patients.

Exploring the gut microbiota and its potential as a biomarker in gliomas

Gut microbiome alterations are associated with various cancers including brain tumours such as glioma and glioblastoma. The gut communicates with the brain via a bidirectional pathway known as the gut-brain axis (GBA) which is essential for maintaining homeostasis. The gut microbiota produces many metabolites including short chain fatty acids (SCFAs) and essential amino acids such as glutamate, glutamine, arginine and tryptophan. Through the modulation of these metabolites the gut microbiome is able to regulate several functions of brain cells, immune cells and tumour cells including DNA methylation, mitochondrial function, the aryl hydrocarbon receptor (AhR), T-cell proliferation, autophagy and even apoptosis. Here, we summarise current findings on gut microbiome with respect to brain cancers, an area of research that is widely overlooked. Several studies investigated the relationship between gut microbiota and brain tumours. However, it remains unclear whether the gut microbiome variation is a cause or product of cancer. Subsequently, a biomarker panel was constructed for use as a predictive, prognostic and diagnostic tool with respect to multiple cancers including glioma and glioblastoma multiforme (GBM). This review further presents the intratumoural microbiome, a fascinating microenvironment within the tumour as a possible treatment target that can be manipulated to maximise effectiveness of treatment via personalised therapy. Studies utilising the microbiome as a biomarker and therapeutic strategy are necessary to accurately assess the effectiveness of the gut microbiome as a clinical tool with respect to brain cancers.

The role of angiogenic growth factors in the immune microenvironment of glioma

Angiogenic growth factors (AGFs) are a class of secreted cytokines related to angiogenesis that mainly include vascular endothelial growth factors (VEGFs), stromal-derived factor-1 (SDF-1), platelet-derived growth factors (PDGFs), fibroblast growth factors (FGFs), transforming growth factor-beta (TGF-β) and angiopoietins (ANGs). Accumulating evidence indicates that the role of AGFs is not only limited to tumor angiogenesis but also participating in tumor progression by other mechanisms that go beyond their angiogenic role. AGFs were shown to be upregulated in the glioma microenvironment characterized by extensive angiogenesis and high immunosuppression. AGFs produced by tumor and stromal cells can exert an immunomodulatory role in the glioma microenvironment by interacting with immune cells. This review aims to sum up the interactions among AGFs, immune cells and cancer cells with a particular emphasis on glioma and tries to provide new perspectives for understanding the glioma immune microenvironment and in-depth explorations for anti-glioma therapy.

Development of a Synthetic, Injectable Hydrogel to Capture Residual Glioblastoma and Glioblastoma Stem-Like Cells with CXCL12-Mediated Chemotaxis

Glioblastoma (GBM), characterized by high infiltrative capacity, is the most common and deadly type of primary brain tumor in adults. GBM cells, including therapy-resistant glioblastoma stem-like cells (GSCs), invade the healthy brain parenchyma to form secondary tumors even after patients undergo surgical resection and chemoradiotherapy. New techniques are therefore urgently needed to eradicate these residual tumor cells. A thiol-Michael addition injectable hydrogel for compatibility with GBM therapy is previously characterized and optimized. This study aims to develop the hydrogel further to capture GBM/GSCs through CXCL12-mediated chemotaxis. The release kinetics of hydrogel payloads are investigated, migration and invasion assays in response to chemoattractants are performed, and the GBM-hydrogel interactions in vitro are studied. With a novel dual-layer hydrogel platform, it is demonstrated that CXCL12 released from the synthetic hydrogel can induce the migration of U251 GBM cells and GSCs from the extracellular matrix microenvironment and promote invasion into the synthetic hydrogel via amoeboid migration. The survival of GBM cells entrapped deep into the synthetic hydrogel is limited, while live cells near the surface reinforce the hydrogel through fibronectin deposition. This synthetic hydrogel, therefore, demonstrates a promising method to attract and capture migratory GBM cells and GSCs responsive to CXCL12 chemotaxis.

Exploring the Vital Link Between Glioma, Neuron, and Neural Activity in the Context of Invasion

Because of their ability to infiltrate normal brain tissue, gliomas frequently evade microscopic surgical excision. The histologic infiltrative property of human glioma has been previously characterized as Scherer secondary structures, of which the perivascular satellitosis is a prospective target for anti-angiogenic treatment in high-grade gliomas. However, the mechanisms underlying perineuronal satellitosis remain unclear, and therapy remains lacking. Our knowledge of the mechanism underlying Scherer secondary structures has improved over time. New techniques, such as laser capture microdissection and optogenetic stimulation, have advanced our understanding of glioma invasion mechanisms. Although laser capture microdissection is a useful tool for studying gliomas that infiltrate the normal brain microenvironment, optogenetics and mouse xenograft glioma models have been extensively used in studies demonstrating the unique role of synaptogenesis in glioma proliferation and identification of potential therapeutic targets. Moreover, a rare glioma cell line is established that, when transplanted in the mouse brain, can replicate and recapitulate the human diffuse invasion phenotype. This review discusses the primary molecular causes of glioma, its histopathology-based invasive mechanisms, and the importance of neuronal activity and interactions between glioma cells and neurons in the brain microenvironment. It also explores current methods and models of gliomas.

Is 3D Printing Promising for Osteochondral Tissue Regeneration?

Osteochondral tissue regeneration is quite difficult to achieve due to the complexity of its organization. In the design of these complex multilayer structures, a fabrication method, 3D printing, started to be employed, especially by using extrusion, stereolithography and inkjet printing approaches. In this paper, the designs are discussed including biphasic, triphasic, and gradient structures which aim to mimic the cartilage and the calcified cartilage and the whole osteochondral tissue closely. In the first section of the review paper, 3D printing of hydrogels including gelatin methacryloyl (GelMa), alginate, and polyethylene glycol diacrylate (PEGDA) are discussed. However, their physical and biological properties need to be augmented, and this generally is achieved by blending the hydrogel with other, more durable, less hydrophilic, polymers. These scaffolds are very suitable to carry growth factors, such as TGF-β1, to further stimulate chondrogenesis. The bone layer is mimicked by printing calcium phosphates (CaPs) or bioactive glasses together with the hydrogels or as a component of another polymer layer. The current research findings indicate that polyester (i.e. polycaprolactone (PCL), polylactic acid (PLA) and poly(lactide-co-glycolide) (PLGA)) reinforced hydrogels may more successfully mimic the complex structure of osteochondral tissue. Moreover, more recent printing methods such as melt electrowriting (MEW), are being used to integrate polyester fibers to enhance the mechanical properties of hydrogels. Additionally, polyester scaffolds that are 3D printed without hydrogels are discussed after the hydrogel-based scaffolds. In this review paper, the relevant studies are analyzed and discussed, and future work is recommended with support of tables of designed scaffolds. The outcome of the survey of the field is that 3D printing has significant potential to contribute to osteochondral tissue repair.

Nanomedicines Targeting Glioma Stem Cells

Glioblastoma (GBM), classified as a grade IV glioma, is a rapidly growing, aggressive, and most commonly occurring tumor of the central nervous system. Despite the therapeutic advances, it carries an ominous prognosis, with a median survival of 14.6 months after diagnosis. Accumulating evidence suggests that cancer stem cells in GBM, termed glioma stem cells (GSCs), play a crucial role in tumor propagation, treatment resistance, and tumor recurrence. GSCs, possessing the capacity for self-renewal and multilineage differentiation, are responsible for tumor growth and heterogeneity, leading to primary obstacles to current cancer therapy. In this respect, increasing efforts have been devoted to the development of anti-GSC strategies based on targeting GSC surface markers, blockage of essential signaling pathways of GSCs, and manipulating the tumor microenvironment (GSC niches). In this review, we will discuss the research knowledge regarding GSC-based therapy and the underlying mechanisms for the treatment of GBM. Given the rapid progression in nanotechnology, innovative nanomedicines developed for GSC targeting will also be highlighted from the perspective of rationale, advantages, and limitations. The goal of this review is to provide broader understanding and key considerations toward the future direction of GSC-based nanotheranostics to fight against GBM.

Hypoxia-Induced Autophagy Is Involved in Radioresistance via HIF1A-Associated Beclin-1 in Glioblastoma Multiforme

Radioresistance is the major factor of glioblastoma multiforme (GBM) treatment failure and relapse. Hypoxia and autophagy are linked to radioresistance and poor prognosis in solid tumors, but mechanisms remain unknown. Thus, we hypothesize that hypoxia may activate autophagy through two critical factors, HIF1A and Beclin-1, resulting in radioresistance of GBM in vitro and in vivo. In this study, we first demonstrated that HIF1A was overexpressed in GBM tissues and predicted a poor prognosis via bioinformatics. Secondly, we determined that hypoxia induced high expression of HIF1A and upregulated levels of Beclin-1 and autophagy, while HIF1A knockdown by shRNA reduced the expression of Beclin-1. Then we revealed the crosstalk and mechanisms of HIF1A-associated-Beclin-1 in three aspects: (a) transcriptional regulation, (b) protein interaction, and (c) HIF1A/BNIP3/Beclin-1 signaling pathway. Furthermore, we confirmed that silencing HIF1A enhanced the radiosensitivity of GBM in vitro and in vivo. Additionally, Beclin-1 suppression by 3-MA could reverse radioresistance induced by HIF1A under hypoxia. In conclusion, we demonstrated that hypoxia triggered autophagy via HIF1A-associated Beclin-1, resulting in radioresistance in GBM. HIF1A knockdown improved GBM radiosensitivity, and silencing Beclin-1 could reverse HIF1A-induced radioresistance under hypoxic conditions. These findings may help us comprehend the molecular underpinnings of hypoxia-induced autophagy and provide a novel perspective and prospective treatment for GBM radiosensitization.

Modulation of the Immune System Promotes Tissue Regeneration

The immune system plays an essential role in the angiogenesis, repair, and regeneration of damaged tissues. Therefore, the design of scaffolds that manipulate immune cells and factors in such a way that could accelerate the repair of damaged tissues, following implantation, is one of the main goals of regenerative medicine. However, before manipulating the immune system, the function of the various components of the immune system during the repair process should be well understood and the fabrication conditions of the manipulated scaffolds should be brought closer to the physiological state of the body. In this article, we first review the studies aimed at the role of distinct immune cell populations in angiogenesis and support of damaged tissue repair. In the second part, we discuss the use of strategies that promote tissue regeneration by modulating the immune system. Given that various studies have shown an increase in tissue repair rate with the addition of stem cells and growth factors to the scaffolds, and regarding the limited resources of stem cells, we suggest the design of scaffolds that are capable to develop repair of damaged tissue by manipulating the immune system and create an alternative for repair strategies that use stem cells or growth factors.

Single-cell RNA sequencing reveals evolution of immune landscape during glioblastoma progression

Glioblastoma (GBM) is an incurable primary malignant brain cancer hallmarked with a substantial protumorigenic immune component. Knowledge of the GBM immune microenvironment during tumor evolution and standard of care treatments is limited. Using single-cell transcriptomics and flow cytometry, we unveiled large-scale comprehensive longitudinal changes in immune cell composition throughout tumor progression in an epidermal growth factor receptor-driven genetic mouse GBM model. We identified subsets of proinflammatory microglia in developing GBMs and anti-inflammatory macrophages and protumorigenic myeloid-derived suppressors cells in end-stage tumors, an evolution that parallels breakdown of the blood-brain barrier and extensive growth of epidermal growth factor receptor⁺ GBM cells. A similar relationship was found between microglia and macrophages in patient biopsies of low-grade glioma and GBM. Temozolomide decreased the accumulation of myeloid-derived suppressor cells, whereas concomitant temozolomide irradiation increased intratumoral GranzymeB⁺ CD8⁺T cells but also increased CD4⁺ regulatory T cells. These results provide a comprehensive and unbiased immune cellular landscape and its evolutionary changes during GBM progression.

Hyaluronic acid-based hydrogels loaded with chemoattractant and anticancer drug - new formulation for attracting and tackling glioma cells

Over the last few years, significant interest has emerged in the development of localised therapeutic strategies for the treatment of glioblastoma (GBM). The concept of attracting and trapping residual tumour cells within a confined area to facilitate their eradication has developed progressively. Herein, we propose a new design of hyaluronic acid-based hydrogel which can be utilized as a matrix containing a soluble chemoattractant to attract residual glioma cells and chemotherapeutic agents to eradicate them in a less invasive and more efficient way compared to the currently available methods. Hydrogels were prepared at different crosslinking densities, e.g. low and high density, by crosslinking hyaluronic acid with various concentrations of adipic acid dihydrazide and U87MG GBM cell morphology, survival and CD44 expression were evaluated. As a proof-of-concept, hydrogels were loaded with a small peptide chemokine, human urotensin II (hUII), and the migration and survival of U87MG GBM cells were studied. Chemoattractant-containing hydrogels were also loaded with chemotherapeutic drugs to promote cell death in culture. The results showed that U87MG cells were able to invade the hydrogel network and to migrate in response to the chemoattractant hUII. In addition, in static condition, hydrogels loaded with doxorubicin demonstrated significant cytotoxicity leading to less than 80% U87MG cell viability after 48 hours when compared to the control sample. In addition, in in vitro invasive assays, it was originally shown that the chemoattractant effect of hUII can be effective before the cytotoxic action of doxorubicin on the U87MG cells trapped in the hydrogel. Our results provide new insights into a promising approach which can be readily translated in vivo for the treatment of one of the most devastating brain tumours.

The Embryonic Key Pluripotent Factor NANOG Mediates Glioblastoma Cell Migration via the SDF1/CXCR4 Pathway

NANOG is a key transcription factor required for maintaining pluripotency of embryonic stem cells. Elevated NANOG expression levels have been reported in many types of human cancers, including lung, oral, prostate, stomach, breast, and brain. Several studies reported the correlation between NANOG expression and tumor metastasis, revealing itself as a powerful biomarker of poor prognosis. However, how NANOG regulates tumor progression is still not known. We previously showed in medaka fish that Nanog regulates primordial germ cell migration through Cxcr4b, a chemokine receptor known for its ability to promote migration and metastasis in human cancers. Therefore, we investigated the role of human NANOG in CXCR4-mediated cancer cell migration. Of note, we found that NANOG regulatory elements in the CXCR4 promoter are functionally conserved in medaka fish and humans, suggesting an evolutionary conserved regulatory axis. Moreover, CXCR4 expression requires NANOG in human glioblastoma cells. In addition, transwell assays demonstrated that NANOG regulates cancer cell migration through the SDF1/CXCR4 pathway. Altogether, our results uncover NANOG-CXCR4 as a novel pathway controlling cellular migration and support Nanog as a potential therapeutic target in the treatment of Nanog-dependent tumor progression.

Natural Killer Cell-Derived Extracellular Vesicles: Novel Players in Cancer Immunotherapy

Natural killer (NK) cells are critical components of host innate immunity and function as the first line of defense against tumors and viral infection. There is increasing evidence that extracellular vesicles (EVs) are involved in the antitumor activity of NK cells. NK cell-derived EVs (NKEVs) carrying cargo such as cytotoxic proteins, microRNAs, and cytokines employ multiple mechanisms to kill tumor cells, but also exhibit immunomodulatory activity by stimulating other immune cells. Several studies have reported that NKEVs can reverse immune suppression under tolerogenic conditions and contribute to NK-mediated immune surveillance against tumors. Thus, NKEVs are a promising tool for cancer immunotherapy. In this review, we describe the biological effects and potential applications of NKEVs in antitumor immunity.

CXCR4 expression in glioblastoma tissue and the potential for PET imaging and treatment with [68Ga]Ga-Pentixafor /[177Lu]Lu-Pentixather

Purpose

CXCR4 (over)expression is found in multiple human cancer types, while expression is low or absent in healthy tissue. In glioblastoma it is associated with a poor prognosis and more extensive infiltrative phenotype. CXCR4 can be targeted by the diagnostic PET agent [⁶⁸Ga]Ga-Pentixafor and its therapeutic counterpart [¹⁷⁷Lu]Lu-Pentixather. We aimed to investigate the expression of CXCR4 in glioblastoma tissue to further examine the potential of these PET agents.

Methods

CXCR4 mRNA expression was examined using the R2 genomics platform. Glioblastoma tissue cores were stained for CXCR4. CXCR4 staining in tumor cells was scored. Stained tissue components (cytoplasm and/or nuclei of the tumor cells and blood vessels) were documented. Clinical characteristics and information on IDH and MGMT promoter methylation status were collected. Seven pilot patients with recurrent glioblastoma underwent [⁶⁸Ga]Ga-Pentixafor PET; residual resected tissue was stained for CXCR4.

Results

Two large mRNA datasets (N = 284; N = 540) were assesed. Of the 191 glioblastomas, 426 cores were analyzed using immunohistochemistry. Seventy-eight cores (23 tumors) were CXCR4 negative, while 18 cores (5 tumors) had both strong and extensive staining. The remaining 330 cores (163 tumors) showed a large inter- and intra-tumor variation for CXCR4 expression; also seen in the resected tissue of the seven pilot patients—not directly translatable to [⁶⁸Ga]Ga-Pentixafor PET results. Both mRNA and immunohistochemical analysis showed CXCR4 negative normal brain tissue and no significant correlation between CXCR4 expression and IDH or MGMT status or survival.

Conclusion

Using immunohistochemistry, high CXCR4 expression was found in a subset of glioblastomas as well as a large inter- and intra-tumor variation. Caution should be exercised in directly translating ex vivo CXCR4 expression to PET agent uptake. However, when high CXCR4 expression can be identified with [⁶⁸Ga]Ga-Pentixafor, these patients might be good candidates for targeted radionuclide therapy with [¹⁷⁷Lu]Lu-Pentixather in the future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05196-4.

Cross talk between mesenchymal and glioblastoma stem cells: Communication beyond controversies

Mesenchymal stem cells (MSCs) can be isolated from bone marrow or other adult tissues (adipose tissue, dental pulp, amniotic fluid, and umbilical cord). In vitro, MSCs grow as adherent cells, display fibroblast-like morphology, and self-renew, undergoing specific mesodermal differentiation. High heterogeneity of MSCs from different origin, and differences in preparation techniques, make difficult to uniform their functional properties for therapeutic purposes. Immunomodulatory, migratory, and differentiation ability, fueled clinical MSC application in regenerative medicine, whereas beneficial effects are currently mainly ascribed to their secretome and extracellular vesicles. MSC translational potential in cancer therapy exploits putative anti-tumor activity and inherent tropism toward tumor sites to deliver cytotoxic drugs. However, controversial results emerged evaluating either the therapeutic potential or homing efficiency of MSCs, as both antitumor and protumor effects were reported. Glioblastoma (GBM) is the most malignant brain tumor and its development and aggressive nature is sustained by cancer stem cells (CSCs) and the identification of effective therapeutic is required. MSC dualistic action, tumor-promoting or tumor-targeting, is dependent on secreted factors and extracellular vesicles driving a complex cross talk between MSCs and GBM CSCs. Tumor-tropic ability of MSCs, besides providing an alternative therapeutic approach, could represent a tool to understand the biology of GBM CSCs and related paracrine mechanisms, underpinning MSC-GBM interactions. In this review, recent findings on the complex nature of MSCs will be highlighted, focusing on their elusive impact on GBM progression and aggressiveness by direct cell-cell interaction and via secretome, also facing the perspectives and challenges in treatment strategies.

Double-Targeted Knockdown of miR-21 and CXCR4 Inhibits Malignant Glioma Progression by Suppression of the PI3K/AKT and Raf/MEK/ERK Pathways

Currently, miR-21 and CXCR4 are being extensively investigated as two key regulators in glioma malignancy. In this study, we investigated the combined effects of these two factors on glioma progression. Herein, the expression of miR-21 and CXCR4 was increased in tumor tissues and cell lines. Inhibition of miR-21, CXCR4, and miR-21 and CXCR4 together all reduced the migration, invasiveness, proliferation, and enhanced apoptosis in glioma cells, as well as reduced tumor volume and mass in xenograft model. The inhibition effect was strongest in double-targeted knockdown of miR-21 and CXCR4 group, whose downstream pathways involved in AKT axis and ERK axis activation. In conclusion, our findings reported that double-targeted knockdown of miR-21 and CXCR4 could more effectively inhibit the proliferation, migration, invasion, and growth of transplanted tumor and promote cell apoptosis, which were involved in the PI3K/AKT and Raf/MEK/ERK signaling pathways.

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.

Characterization and Mathematical Modeling of Alginate/Chitosan-Based Nanoparticles Releasing the Chemokine CXCL12 to Attract Glioblastoma Cells

Chitosan (Chit) currently used to prepare nanoparticles (NPs) for brain application can be complexed with negatively charged polymers such as alginate (Alg) to better entrap positively charged molecules such as CXCL12. A sustained CXCL12 gradient created by a delivery system can be used, as a therapeutic approach, to control the migration of cancerous cells infiltrated in peri-tumoral tissues similar to those of glioblastoma multiforme (GBM). For this purpose, we prepared Alg/Chit NPs entrapping CXCL12 and characterized them. We demonstrated that Alg/Chit NPs, with an average size of ~250 nm, entrapped CXCL12 with ~98% efficiency for initial mass loadings varying from 0.372 to 1.490 µg/mg NPs. The release kinetic profiles of CXCL12 were dependent on the initial mass loading, and the released chemokine from NPs after seven days reached 12.6%, 32.3%, and 59.9% of cumulative release for initial contents of 0.372, 0.744, and 1.490 µg CXCL12/mg NPs, respectively. Mathematical modeling of released kinetics showed a predominant diffusive process with strong interactions between Alg and CXCL12. The CXCL12-NPs were not toxic and did not promote F98 GBM cell proliferation, while the released CXCL12 kept its chemotaxis effect. Thus, we developed an efficient and tunable CXCL12 delivery system as a promising therapeutic strategy that aims to be injected into a hydrogel used to fill the cavity after surgical tumor resection. This system will be used to attract infiltrated GBM cells prior to their elimination by conventional treatment without affecting a large zone of healthy brain tissue.

Signaling Determinants of Glioma Cell Invasion

Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. In addition, there is accumulating evidence that current therapeutic modalities, including anti-angiogenic therapy and radiotherapy, can enhance glioma invasiveness. Glioma cell invasion is stimulated by both autocrine and paracrine factors that act on a large array of cell surface-bound receptors. Key signaling elements that mediate receptor-initiated signaling in the regulation of glioblastoma invasion are Rho family GTPases, including Rac, RhoA and Cdc42. These GTPases regulate cell morphology and actin dynamics and stimulate cell squeezing through the narrow extracellular spaces that are typical of the brain parenchyma. Transient attachment of cells to the extracellular matrix is also necessary for glioblastoma cell invasion. Interactions with extracellular matrix components are mediated by integrins that initiate diverse intracellular signalling pathways. Key signaling elements stimulated by integrins include PI3K, Akt, mTOR and MAP kinases. In order to detach from the tumor mass, glioma cells secrete proteolytic enzymes that cleave cell surface adhesion molecules, including CD44 and L1. Key proteases produced by glioma cells include uPA, ADAMs and MMPs. Increased understanding of the molecular mechanisms that control glioma cell invasion has led to the identification of molecular targets for therapeutic intervention in this devastating disease.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

Cocktail Strategy Based on NK Cell-Derived Exosomes and Their Biomimetic Nanoparticles for Dual Tumor Therapy

Successful cancer therapy requires drugs being precisely delivered to tumors. Nanosized drugs have attracted considerable recent attention, but their toxicity and high immunogenicity are important obstacles hampering their clinical translation. Here we report a novel “cocktail therapy” strategy based on excess natural killer cell-derived exosomes (NKEXOs) in combination with their biomimetic core–shell nanoparticles (NNs) for tumor-targeted therapy. The NNs were self- assembled with a dendrimer core loading therapeutic miRNA and a hydrophilic NKEXOs shell. Their successful fabrication was confirmed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The resulting NN/NKEXO cocktail showed highly efficient targeting and therapeutic miRNA delivery to neuroblastoma cells in vivo, as demonstrated by two-photon excited scanning fluorescence imaging (TPEFI) and with an IVIS Spectrum in vivo imaging system (IVIS), leading to dual inhibition of tumor growth. With unique biocompatibility, we propose this NN/NKEXO cocktail as a new avenue for tumor therapy, with potential prospects for clinical applications.

Sustained Release SDF-1α/TGF-β1-Loaded Silk Fibroin-Porous Gelatin Scaffold Promotes Cartilage Repair

Continuous delivery of growth factors to the injury site is crucial to creating a favorable microenvironment for cartilage injury repair. In the present study, we fabricated a novel sustained-release scaffold, stromal-derived factor-1α (SDF-1α)/transforming growth factor-β1 (TGF-β1)-loaded silk fibroin-porous gelatin scaffold (GSTS). GSTS persistently releases SDF-1α and TGF-β1, which enhance cartilage repair by facilitating cell homing and chondrogenic differentiation. Scanning electron microscopy showed that GSTS is a porous microstructure and the protein release assay demonstrated the sustainable release of SDF-1α and TGF-β1 from GSTS. Bone marrow-derived mesenchymal stem cells (MSCs) maintain high in vitro cell activity and excellent cell distribution and phenotype after seeding into GSTS. Furthermore, MSCs acquired enhanced chondrogenic differentiation capability in the TGF-β1-loaded scaffolds (GSTS or GST: loading TGF-β1 only) and the conditioned medium from SDF-1α-loaded scaffolds (GSTS or GSS: loading SDF-1α only) effectively promoted MSCs migration. GSTS was transplanted into the osteochondral defects in the knee joint of rats, and it could promote cartilage regeneration and repair the cartilage defects at 12 weeks after transplantation. Our study shows that GSTS can facilitate in vitro MSCs homing, migration, chondrogenic differentiation and SDF-1α and TGF-β1 have a synergistic effect on the promotion of in vivo cartilage forming. This SDF-1α and TGF-β1 releasing GSTS have promising therapeutic potential in cartilage repair.

Biodegradable water-based polyurethane scaffolds with a sequential release function for cell-free cartilage tissue engineering

Three-dimensional (3D) printing technology has rapidly developed as a promising technology for manufacturing tissue engineering scaffolds. Cells used in tissue engineering are subjected to the quality management and risk of contamination, while cell-free scaffolds may not have sufficient therapeutic efficacy. In this study, water-based 3D printing ink containing biodegradable polyurethane (PU), chemokine SDF-1, and Y27632 drug-embedding PU microspheres was printed at low temperature (-40 °C) to fabricate tissue engineering scaffolds with sequential drug release function. The scaffolds containing 200 ng/ml SDF-1 and 22 wt% Y27632-encapsulated microspheres (55 µg/ml Y27632 in microspheres) (abbreviated PU/SDF-1/MS_Y scaffolds) had the optimal performance. The structural design of the scaffolds allowed each of SDF-1 and Y27632 to be released sequentially in vitro and reach the effective concentration (∼100 ng/ml and 3.38 µg/ml, respectively) after the appropriate time (24 h and 62 h, respectively). Human mesenchymal stem cells (hMSCs) seeded in the scaffolds showed significant GAG deposition in 7 days. Besides, the gradual release of SDF-1 from the PU/SDF-1/MS_Y scaffolds could induce the migration of hMSCs. Implantation of the cell-free PU/SDF-1/MS_Y scaffolds in rabbit articular cartilage defects supported the potential of the scaffolds to promote cartilage regeneration. The 3D printed scaffolds with sequential releases of SDF-1 and Y27632 may have potential in cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: The clinical success of tissue engineering depends highly on the quality of externally supplied cells, while cell-free scaffolds may not have sufficient therapeutic efficacy. In this manuscript, water-based 3D printing ink containing biodegradable polyurethane (PU), chemokine SDF-1, and Y27632 drug-embedding PU microspheres was printed at low temperature to fabricate tissue engineering scaffolds with sequential drug release function. The structural design of the scaffolds allowed each of SDF-1 and Y27632 to be released sequentially in vitro. SDF-1 was released earlier from the scaffolds to promote cell migration. The drug Y27632 was released later from the microspheres into the matrix of the scaffolds to induce the chondrogenic differentiation of the attracted cells. Implantation of the cell-free PU/SDF-1/MS_Y scaffolds in rabbit articular cartilage defects supported the potential of the scaffolds to promote cartilage regeneration. We hypothesized that the cell-free scaffolds may improve the clinical applicability and convenience without the use of exogenous cells or growth factor.

Gliotransmitters and cytokines in the control of blood-brain barrier permeability

The contribution of astrocytes and microglia to the regulation of neuroplasticity or neurovascular unit (NVU) is based on the coordinated secretion of gliotransmitters and cytokines and the release and uptake of metabolites. Blood-brain barrier (BBB) integrity and angiogenesis are influenced by perivascular cells contacting with the abluminal side of brain microvessel endothelial cells (pericytes, astrocytes) or by immune cells existing (microglia) or invading the NVU (macrophages) under pathologic conditions. The release of gliotransmitters or cytokines by activated astroglial and microglial cells is provided by distinct mechanisms, affects intercellular communication, and results in the establishment of microenvironment controlling BBB permeability and neuroinflammation. Glial glutamate transporters and connexin and pannexin hemichannels working in the tight functional coupling with the purinergic system serve as promising molecular targets for manipulating the intercellular communications that control BBB permeability in brain pathologies associated with excessive angiogenesis, cerebrovascular remodeling, and BBB-mediated neuroinflammation. Substantial progress in deciphering the molecular mechanisms underlying the (patho)physiology of perivascular glia provides promising approaches to novel clinically relevant therapies for brain disorders. The present review summarizes the current understandings on the secretory machinery expressed in glial cells (glutamate transporters, connexin and pannexin hemichannels, exocytosis mechanisms, membrane-derived microvesicles, and inflammasomes) and the role of secreted gliotransmitters and cytokines in the regulation of NVU and BBB permeability in (patho)physiologic conditions.

High co-expression of the SDF1/CXCR4 axis in hepatocarcinoma cells is regulated by AnnexinA7 in vitro and in vivo

BACKGROUND

SDF1/CXCR4 and AnnexinA7 play important roles in many physiological and pathological conditions, but the molecular association between them in cancer cells has not been studied thus far.

METHODS

The expression changes of SDF1/CXCR4 were detected by gene transcriptome sequencing, qRT-PCR, Western blotting, cytoimmunofluorescence and immunohistochemistry in mouse hepatocarcinoma F/P cells, AnnexinA7 downregulated expression F (FA7DOWN) cells, AnnexinA7 overexpression P (PA7UP) cells, AnnexinA7 unrelated sequence F (FSHUS) cells, empty vector P (PNCEV) cells and normal liver cells in vitro and in vivo.

RESULTS

SDF1 and CXCR4 were co-expressed in hepatocarcinoma cells. SDF1 was localized mainly in the cytoplasm of cells, while CXCR4 was mainly localized in the cell membrane. Both in vitro and in vivo, expression levels of SDF1/CXCR4 in F and P cells were higher than in normal liver cells, and expression levels of SDF1/CXCR4 in F cells with high lymphatic metastatic potential were higher than those in P cells with low lymphatic metastatic potential. Expression of SDF1 was higher than that of CXCR4 in P cells and normal liver cells, while expression of CXCR4 was higher than that of SDF1 in F cells. Expression levels of SDF1/CXCR4 were completely consistent with AnnexinA7 regulation. After the AnnexinA7 gene was downregulated or upregulated, expression levels of SDF1/CXCR4 in FA7DOWN/PA7UP cells were lower or higher than those in FSHUS/PNCEV cells. Furthermore, CXCR4 was more sensitively modulated by AnnexinA7 regulation than SDF1.

CONCLUSIONS

High co-expression of SDF1/CXCR4 is a molecular characteristic of hepatocarcinoma cells, especially those with high lymphatic metastatic potential. AnnexinA7 positively regulates expression levels of SDF1/CXCR4, in particular CXCR4, and AnnexinA7 is a functional regulator of SDF1/CXCR4.

Glioblastoma niches: from the concept to the phenotypical reality

Recently, the concept of niches as sites of tumor progression, invasion, and angiogenesis in glioblastoma (GB) has been extensively debated. Niches, considered the sites in which glioblastoma stem cells (GSCs) reside, have been classified as perivascular, perinecrotic, and invasive. However, from a neuropathological point of view, it is not easy to establish when a tumor structure can be considered a niche. The relevant literature has been reviewed in the light of our recent experience on the subject. As for perinecrotic niches, the occurrence of GSCs around necrosis is interpreted as triggered by hypoxia through HIF-1α. Our alternative hypothesis is that, together with progenitors, they are the cell constituents of hyper-proliferative areas of GB, where perinecrotic niches have developed, and they would, therefore, represent the remnants of GSCs/progenitors spared by the developing necrosis. Perivascular structures originate from both transport vessels and exchange vessels, i.e., venules, arterioles, or the undefinable neo-formed small vessels, but only those in which a direct contact between GSCs/progenitors and endothelial cells occurs can be called niches. Both pericytes and microglia/macrophages play a role in niche function: Macrophages of blood origin invade GB only after the appearance of "mother vessels" with consequent blood-brain barrier disruption. Not all vessel/tumor cell structures can be considered niches, that is, crucial sites of tumor progression, invasion, and angiogenesis.

Cytoplasmic expression of Twist1, an EMT-related transcription factor, is associated with higher grades renal cell carcinomas and worse progression-free survival in clear cell renal cell carcinoma

Twist1 is a key transcription factor, which confers tumor cells with cancer stem cell (CSC)-like characteristics and enhances epithelial-mesenchymal transition in pathological conditions including tumor malignancy and metastasis. This study aimed to evaluate the expression patterns and clinical significance of Twist1 in renal cell carcinoma (RCC). The cytoplasmic and nuclear expression of Twist1 were examined in 252 well-defined renal tumor tissues, including 173 (68.7%) clear cell renal cell carcinomas (ccRCC), 45 (17.9%) papillary renal cell carcinomas (pRCC) and 34 (13.5%) chromophobe renal cell carcinoma, by immunohistochemistry on a tissue microarray. The association between expression of this marker and clinicopathologic parameters and survival outcomes were then analyzed. Twist1 was mainly localized to the cytoplasm of tumor cells (98.8%). Increased cytoplasmic expression of Twist1 was associated with higher grade tumors (P = 0.045), renal vein invasion (P = 0.031) and microvascular invasion (P = 0.044) in RCC. It was positively correlated with higher grade tumors (P = 0.026), shorter progression-free survival time (P = 0.027) in patients with ccRCC, and also with higher stage in pRCC patients (P = 0.036). Significantly higher cytoplasmic expression levels of Twist1 were found in ccRCC and pRCC subtypes, due to their more aggressive tumor behavior. Increased cytoplasmic expression of Twist1 had a critical role in worse prognosis in ccRCC. These findings suggest that cytoplasmic, rather than nuclear expression of Twist1 can be considered as a prognostic and therapeutic marker for targeted therapy of RCC, especially for ccRCC patients.

Different Effects of Human Umbilical Cord Mesenchymal Stem Cells on Glioblastoma Stem Cells by Direct Cell Interaction or Via Released Soluble Factors

Glioblastoma (GBM), the most common primary brain tumor in adults, is an aggressive, fast-growing and highly vascularized tumor, characterized by extensive invasiveness and local recurrence. In GBM and other malignancies, cancer stem cells (CSCs) are believed to drive invasive tumor growth and recurrence, being responsible for radio- and chemo-therapy resistance. Mesenchymal stem cells (MSCs) are multipotent progenitors that exhibit tropism for tumor microenvironment mediated by cytokines, chemokines and growth factors. Initial studies proposed that MSCs might exert inhibitory effects on tumor development, although, to date, contrasting evidence has been provided. Different studies reported either MSC anti-tumor activity or their support to tumor growth. Here, we examined the effects of umbilical cord (UC)-MSCs on in vitro GBM-derived CSC growth, by direct cell-to-cell interaction or indirect modulation, via the release of soluble factors. We demonstrate that UC-MSCs and CSCs exhibit reciprocal tropism when co-cultured as 3D spheroids and their direct cell interaction reduces the proliferation of both cell types. Contrasting effects were obtained by UC-MSC released factors: CSCs, cultured in the presence of conditioned medium (CM) collected from UC-MSCs, increased proliferation rate through transient ERK1/2 and Akt phosphorylation/activation. Analysis of the profile of the cytokines released by UC-MSCs in the CM revealed a strong production of molecules involved in inflammation, angiogenesis, cell migration and proliferation, such as IL-8, GRO, ENA-78 and IL-6. Since CXC chemokine receptor 2 (CXCR2), a receptor shared by several of these ligands, is expressed in GBM CSCs, we evaluated its involvement in CSC proliferation induced by UC-MSC-CM. Using the CXCR2 antagonist SB225002, we observed a partial but statistically significant inhibition of CSC proliferation and migration induced by the UC-MSC-released cytokines. Conversely, CXCR2 blockade did not reduce the reciprocal tropism between CSCs and UC-MSCs grown as spheroids. In conclusion, we show that direct (cell-to-cell contact) or indirect (via the release of soluble factors) interactions between GBM CSCs and UC-MSCs in co-culture produce divergent effects on cell growth, invasion and migration, with the former mainly causing an inhibitory response and the latter a stimulatory one, involving a paracrine activation of CXCR2.

Multifaceted C-X-C Chemokine Receptor 4 (CXCR4) Inhibition Interferes with Anti-Vascular Endothelial Growth Factor Therapy-Induced Glioma Dissemination

Resistance to antiangiogenic therapy in glioblastoma (GBM) patients may involve hypoxia-induced expression of C-X-C motif chemokine receptor 4 (CXCR4) on invading tumor cells, macrophage/microglial cells (MGCs), and glioma stem cells (GSCs). We determined whether antagonizing CXCR4 with POL5551 disrupts anti-vascular endothelial growth factor (VEGF) therapy-induced glioma growth and dissemination. Mice bearing orthotopic CT-2A or GL261 gliomas received POL5551 and/or anti-VEGF antibody B20-4.1.1. Brain tissue was analyzed for tumor volume, invasiveness, hypoxia, vascular density, proliferation, apoptosis, GSCs, and MGCs. Glioma cells were evaluated for CXCR4 expression and polymorphism and POL5551's effects on CXCR4 ligand binding, cell viability, and migration. No CXCR4 mutations were identified. POL5551 inhibited CXCR4 binding to its ligand, stromal cell-derived factor-1α, and reduced hypoxia- and stromal cell-derived factor-1α-mediated migration dose-dependently but minimally affected cell viability. In vivo, B20-4.1.1 increased hypoxic foci and invasiveness, as seen in GBM patients receiving anti-VEGF therapy. Combination of POL5551 and B20-4.1.1 reduced both glioma invasiveness by 16% to 39% and vascular density compared to B20-4.1.1 alone in both glioma models. Reduced populations of GSCs and MGCs were also seen in CT-2A tumors. POL5551 concentrations, evaluated by mass spectrometry, were higher in tumors than in neighboring brain tissues, likely accounting for the results. Inhibition of CXCR4-regulated tumoral, stem cell, and immune mechanisms by adjunctive CXCR4 antagonists may help overcome antiangiogenic therapy resistance, benefiting GBM patients.

CCL2/CCR2 signaling pathway in glioblastoma multiforme

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

Engineering NK Cells Modified With an EGFRvIII-specific Chimeric Antigen Receptor to Overexpress CXCR4 Improves Immunotherapy of CXCL12/SDF-1α-secreting Glioblastoma

Natural killer (NK) cells are promising effector cells for adjuvant immunotherapy of cancer. So far, several preclinical studies have shown the feasibility of gene-engineered NK cells, which upon expression of chimeric antigen receptors (CARs) are redirected to otherwise NK cell-resistant tumors. Yet, we reasoned that the efficiency of an immunotherapy using CAR-modified NK cells critically relies on efficient migration to the tumor site and might be improved by the engraftment of a receptor specific for a chemokine released by the tumor. On the basis of the DNAX-activation protein 12 (DAP12), a signaling adapter molecule involved in signal transduction of activating NK cell receptors, we constructed an epidermal growth factor variant III (EGFRvIII)-CAR, designated MR1.1-DAP12 which confers specific cytotoxicity of NK cell towards EGFRvIII glioblastoma cells in vitro and to established subcutaneous U87-MG tumor xenografts. So far, infusion of NK cells with expression of MR1.1-DAP12 caused a moderate but significantly delayed tumor growth and increased median survival time when compared with NK cells transduced with an ITAM-defective CAR. Notably, the further genetic engineering of these EGFRvIII-specific NK cells with the chemokine receptor CXCR4 conferred a specific chemotaxis to CXCL12/SDF-1α secreting U87-MG glioblastoma cells. Moreover, the administration of such NK cells resulted in complete tumor remission in a number of mice and a significantly increased survival when compared with the treatment of xenografts with NK cells expressing only the EGFRvIII-specific CAR or mock control. We conclude that chemokine receptor-engineered NK cells with concomitant expression of a tumor-specific CAR are a promising tool to improve adoptive tumor immunotherapy.

Intranasal Oncolytic Virotherapy with CXCR4-Enhanced Stem Cells Extends Survival in Mouse Model of Glioma

The challenges to effective drug delivery to brain tumors are twofold: (1) there is a lack of non-invasive methods of local delivery and (2) the blood-brain barrier limits systemic delivery. Intranasal delivery of therapeutics to the brain overcomes both challenges. In mouse model of malignant glioma, we observed that a small fraction of intranasally delivered neural stem cells (NSCs) can migrate to the brain tumor site. Here, we demonstrate that hypoxic preconditioning or overexpression of CXCR4 significantly enhances the tumor-targeting ability of NSCs, but without altering their phenotype only in genetically modified NSCs. Modified NSCs deliver oncolytic virus to glioma more efficiently and extend survival of experimental animals in the context of radiotherapy. Our findings indicate that intranasal delivery of stem cell-based therapeutics could be optimized for future clinical applications, and allow for safe and repeated administration of biological therapies to brain tumors and other CNS disorders.

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Intranasal delivery of NSCs is a promising platform for glioma therapy

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Hypoxia or CXCR4 overexpression enhances NSC migration to glioma

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Oncolytic viruses loaded in CXCR4-enhanced NSCs improve animal survival

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Non-invasive intranasal NSC-based therapies warrant clinical translation

Study of angiogenic signaling pathways in hemangioblastoma

Hemangioblastoma (HB) is mainly located in the brain and the spinal cord. The tumor is composed of two major components, namely neoplastic stromal cells and abundant microvessels. Thus, hyper-vascularization is the hallmark of this tumor. Despite the identification of germline and/or epigenetic mutations of Von Hippel Lindau (VHL) gene as an important pathogenic mechanism of HB, little is known about the molecular signaling involved in this highly vascularized tumor. The present study investigated the key players of multiple angiogenic signaling pathways including VEGF/VEGFR2, EphB4/EphrinB2, SDF1α/CXCR4 and Notch/Dll4 pathways in surgical specimens of 22 HB. The expression of key angiogenic factors was detected by RT² -PCR and Western blot. Immunofluorescent staining revealed the cellular localization of these proteins. We demonstrated a massive upregulation of mRNA levels of VEGF and VEGFR2, CXCR4 and SDF1α, EphB4 and EphrinB2, as well as the main components of Dll4-Notch signaling in HB. An increase in the protein expression of VEGF, CXCR4 and the core-components of Dll4-Notch signaling was associated with an activation of Akt and Erk1/2 and accompanied by an elevated expression of PCNA. Immuofluorescent staining revealed the expression of VEGF and CXCR4 in endothelial cells as well as in tumor cells. Dll4 protein was predominantly found in tumor cells, whereas EphB4 immunoreactivity was exclusively detected in endothelial cells. We conclude that multiple key angiogenic pathways were activated in HB, which may synergistically contribute to the abundant vascularization in this tumor. Identification of these aberrant pathways provides potential targets for a possible future application of anti-angiogenic therapy for this tumor, particularly when a total surgical resection becomes difficult due to the localization or multiplicity of the tumor.

Chemokines accentuating protumoral activities in oral cancer microenvironment possess an imperious stratagem for therapeutic resolutions

Chemokines, the chemotactic cytokines have established their role in tumorigenesis and tumor progression. Studies, which explored their role in oral cancer for protumoral activity, point towards targeting chemokines for oral squamous cell carcinoma therapy. The need of the hour is to emphasize/divulge in the activities of chemokine ligands and their receptors in the tumor microenvironment for augmentation of such stratagems. This progressing sentience of chemokines and their receptors has inspired this review which is an endeavour to comprehend their role as an aid in accentuating hallmarks of cancer and targeted therapy.

Compound K attenuates stromal cell-derived growth factor 1 (SDF-1)-induced migration of C6 glioma cells

BACKGROUND/OBJECTIVES

Stromal cell-derived growth factor 1 (SDF-1), also known as chemokine ligand 12, and chemokine receptor type 4 are involved in cancer cell migration. Compound K (CK), a metabolite of protopanaxadiol-type ginsenoside by gut microbiota, is reported to have therapeutic potential in cancer therapy. However, the inhibitory effect of CK on SDF-1 pathway-induced migration of glioma has not yet been established.

MATERIALS/METHODS

Cytotoxicity of CK in C6 glioma cells was determined using an EZ-Cytox cell viability assay kit. Cell migration was tested using the wound healing and Boyden chamber assay. Phosphorylation levels of protein kinase C (PKC)α and extracellular signal-regulated kinase (ERK) were measured by western blot assay, and matrix metallopeptidases (MMP) were measured by gelatin-zymography analysis.

RESULTS

CK significantly reduced the phosphorylation of PKCα and ERK1/2, expression of MMP9 and MMP2, and inhibited the migration of C6 glioma cells under SDF-1-stimulated conditions.

CONCLUSIONS

CK is a cell migration inhibitor that inhibits C6 glioma cell migration by regulating its downstream signaling molecules including PKCα, ERK1/2, and MMPs.

Glioblastoma Stem Cells Microenvironment: The Paracrine Roles of the Niche in Drug and Radioresistance

Among all solid tumors, the high-grade glioma appears to be the most vascularized one. In fact, "microvascular hyperplasia" is a hallmark of GBM. An altered vascular network determines irregular blood flow, so that tumor cells spread rapidly beyond the diffusion distance of oxygen in the tissue, with the consequent formation of hypoxic or anoxic areas, where the bulk of glioblastoma stem cells (GSCs) reside. The response to this event is the induction of angiogenesis, a process mediated by hypoxia inducible factors. However, this new capillary network is not efficient in maintaining a proper oxygen supply to the tumor mass, thereby causing an oxygen gradient within the neoplastic zone. This microenvironment helps GSCs to remain in a "quiescent" state preserving their potential to proliferate and differentiate, thus protecting them by the effects of chemo- and radiotherapy. Recent evidences suggest that responses of glioblastoma to standard therapies are determined by the microenvironment of the niche, where the GSCs reside, allowing a variety of mechanisms that contribute to the chemo- and radioresistance, by preserving GSCs. It is, therefore, crucial to investigate the components/factors of the niche in order to formulate new adjuvant therapies rendering more efficiently the gold standard therapies for this neoplasm.

Critical roles of chemokine receptor CCR5 in regulating glioblastoma proliferation and invasion

Glioblastoma (GBM) is the most prevalent malignant primary brain tumor in adults and exhibits a spectrum of aberrantly aggressive phenotype. Tumor cell proliferation and invasion are critically regulated by chemokines and their receptors. Recent studies have shown that the chemokine CCL5 and its receptor CCR5 play important roles in tumor invasion and metastasis. Nonetheless, the roles of the CCR5 in GBM still remain unclear. The present study provides the evidence that the chemokine receptor CCR5 is highly expressed and associated with poor prognosis in human GBM. Mechanistically, CCL5-CCR5 mediates activation of Akt, and subsequently induces proliferation and invasive responses in U87 and U251 cells. Moreover, down-regulation of CCR5 significantly inhibited the growth of glioma in U87 tumor xenograft mouse model. Finally, high CCR5 expression in GBM is correlated with increased p-Akt expression in patient samples. Together, these findings suggest that the CCR5 is a critical molecular event associated with gliomagenesis.

Radiation-induced pulmonary injury accelerated pulmonary metastasis in a mouse model of breast cancer

The aim of the present study was to investigate the acceleration of pulmonary metastasis due to pulmonary injury caused by radiation treatment in a mouse model of breast cancer, in addition to determining the associated mechanism. The passive metastatic breast cancer model was used in radiation-treated BALB/c mice. In total, 24 mice were randomly separated into two groups, with 12 mice per group, and the groups were treated with or without pulmonary radiation. The survival time and variation of the weights of the lungs, spleen and liver were recorded. Lung metastasis was also evaluated, and chemokine (C-X-C motif) ligand 12 (CXCL12)/chemokine (C-X-C motif) receptor 4 (CXCR4) expression was determined. The results revealed that the group with radiation-induced pulmonary injury exhibited an increased incidence of pulmonary metastasis and shorter survival time compared with the mice without pulmonary radiation. The radiation-treated group possessed an increased number of metastatic nodules in the lungs, but metastasis was not evident in the liver and spleen. The CXCL12/CXCR4 axis was markedly expressed and the expression was significantly increased subsequent to radiation compared with the expression in normal lung tissues. The present study demonstrated that radiation-induced pulmonary injury may accelerate metastatic tumor growth and decrease the overall survival rate of the mice following in situ injection of tumor cells. Tumor localization and growth may have been favored by metastatic conditioning in the lung subsequent to radiotherapy. The CXCL12/CXCR4 axis may affect key elements in the multistep process of metastasis induced by radiation injury.

Directional migration of adult hematopoeitic progenitors to C6 glioma in vitro

Multiform glioblastoma is the most common primary, highly invasive, malignant tumor of the central nervous system, with an extremely poor prognosis. The median survival of patients following surgical resection, radiation therapy and chemotherapy does not exceed 12–15 months and thus, novel approaches for the treatment of the disease are required. The phenomenon of the directed migration of stem cells in tumor tissue presents a novel approach for the development of technologies that facilitate the targeted delivery of drugs and other therapeutic agents to the tumor foci. Hematopoietic cluster of differentiation (CD)34⁺/CD133⁺ stem cells possess significant reparative potential and are inert with respect to normal neural tissue. The aim of the present study was to investigate the substantiation ability of adult hematopoietic progenitors to the directed migration of glioma cells. A C6 glioma cell line, a culture of hematopoietic CD34⁺/CD133⁺ stem cells and primary cultures of rat astrocytes and fibroblasts were used. The cells were co-cultured for five days. The results revealed the formation of cell shaft hematopoietic stem cells on the perimeter of the culture inserts containing the glioma culture. However, this was not observed in the wells with fibroblast and astrocyte cultures. The results indicated that hematopoietic stem cells exhibit a high potential for the directional migration of C6 glioma cells, which allows them to be considered as a promising cell line for the development of novel anticancer biomedical technologies and increases our understanding with regard to previously unclear aspects of glial tumor carcinogenesis.

Relationship between expression of stromal cell-derived factor-1α and lymph node metastasis in early gastric cancer

AIM: To investigate the relationship between the expression of stromal cell-derived factor-1α (SDF-1α) and the risk of lymph node metastasis in early gastric cancer (EGC).

METHODS: We examined the expression of SDF-1α in 168 archival tissue specimens of EGC by immunohistochemical method.

RESULTS: Of the included specimens, 72 (42.9%) and 96 (57.1%) were grouped into SDF-1α-positive and SDF-1α-negative groups, respectively. No significant differences existed with respect to age, gender, proportion of tumors > 20 mm in size, macroscopic type, depth of invasion or histology between the SDF-1α-positive and SDF-1α-negative groups. However, the SDF-1α-positive group was significantly correlated with lymphovascular invasion and lymph node metastasis. Univariate analysis indicated that lymphovascular invasion, undifferentiated histology and SDF-1α positivity were risk factors significantly affecting lymph node metastasis in patients with EGC. Multivariate analysis showed that lymphovascular invasion [hazard ratio (HR) = 3.753, 95% confidence interval (CI): 1.674-8.415; P = 0.001], undifferentiated histology (HR = 2.038, 95%CI: 1.100-3.775; P = 0.024) and SDF-1α positivity (HR = 3.631, 95%CI: 1.101-11.977; P = 0.034) were independent risk factors for lymph node metastasis in EGC.

CONCLUSION: Our findings suggest that SDF-1α expression is closely related to the risk of lymph node metastasis in EGC, and SDF-1α expression in tumor cells is a predictive marker of lymph node metastasis in EGC.

Understanding cell homing-based tissue regeneration from the perspective of materials

The triad of cell homing-based tissue engineering.

High expression of CXCR3 is an independent prognostic factor in glioblastoma patients that promotes an invasive phenotype

Chemokines are a superfamily of small heparin-binding cytokines that induce leukocytes to migrate to sites of inflammation or injury through interacting with specific transmembrane G protein-coupled receptors. Currently, attention is focused on chemokine/chemokine receptor pairs and their ability to promote tumor cell migration and angiogenesis. The chemokine receptor CXCR3 is involved in tumor metastasis and is used as a prognostic biomarker. However, its relationship with the clinicopathological features of primary glioblastoma multiforme (pGBM) and its potential prognostic value have yet to be investigated. Here, we report that high CXCR3 expression conferred poor survival in pGBM patients. Further analysis showed that CXCR3 served as an independent prognostic biomarker for pGBM patients. In addition, functional assays indicated that CXCR3 induced glioma cell invasion. Therefore, this evidence indicates CXCR3 is an independent prognostic factor for pGBM patients and promotes an invasive phenotype, which suggests a new potential biotarget for glioblastoma multiforme therapy.

The Clinical Implications of Chemokine Receptor CXCR4 in Grade and Prognosis of Glioma Patients: A Meta-Analysis

Chemokine receptor CXCR4 has been identified to affect glioma progression by dominating cancer cell survival, proliferation, and migration in vitro recently. However, the implications and utilities of CXCR4 in clinical grade and prognosis were rarely reported. Thus, it is essential to carry out a meta-analysis to draw a convincing conclusion. The relevant articles were included through careful assessment, and then, odds ratios (ORs), standard mean differences (SMDs), and hazard ratios (HRs) with 95% confidence intervals (95% CIs) were estimated. Heterogeneity and funnel plots evaluation were conducted. In this meta-analysis, all 13 eligible studies involving 785 patients were included and conducted in China. Ten studies revealed altered CXCR4 expression in glioma tissues was closely associated with high WHO grade (III + IV) (n = 10, OR 5.46, 95% CI 3.81-7.84; p = 0.000); besides, six studies also demonstrated CXCR4 expression intensity extremely correlated to high grade (n = 6, SMD -2.45, 95% CI -2.78, -2.12; p = 0.000). Most importantly, three articles identified that CXCR4 expression significantly correlated to 3-year overall survival (OS) (HR 7.32, 95 % CI 4.16-12.90; p = 0.000) in glioma patients. No heterogeneity and publication bias were observed across all studies. Taken together, this meta-analysis suggests CXCR4 expression in gliomas can be recommended as evidence of WHO grade and indeed predict 3-year overall survival. We also provided a scientific rationale for clinically pathological detection of CXCR4 that is required for treatment of glioma patients.

Adiponectin as novel regulator of cell proliferation in human glioblastoma

Adiponectin (Acrp30) is an adipocyte-secreted hormone with pleiotropic metabolic effects, whose reduced levels were related to development and progression of several malignancies. We looked at the presence of Acrp30 receptors in human glioblastomas (GBM), hypothesizing a role for Acrp30 also in this untreatable cancer. Here we demonstrate that human GBM express Acrp30 receptors (AdipoR1 and AdipoR2), which are often co-expressed in GBM samples (70% of the analyzed tumors). To investigate the effects of Acrp30 on GBM growth, we used human GBM cell lines U87-MG and U251, expressing both AdipoR1 and AdipoR2 receptors. In these cells, Acrp30 treatment inhibits DNA synthesis and cell proliferation rate, inducing arrest in G1 phase of the cell cycle. These effects were correlated to a sustained activation of ERK1/2 and Akt kinases, upon Acrp30 treatment. Our results suggest that Acrp30 may represent a novel endogenous negative regulator of GBM cell proliferation, to be evaluated for the possible development of novel pharmacological approaches.

G protein-coupled receptors as oncogenic signals in glioma: emerging therapeutic avenues

Gliomas are the most common malignant intracranial tumors. Newly developed targeted therapies for these cancers aim to inhibit oncogenic signals, many of which emanate from receptor tyrosine kinases, including the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR). Unfortunately, the first-generation treatments targeting these oncogenic signals provide little survival benefit in both mouse xenograft models and human patients. The search for new treatment options has uncovered several G protein-coupled receptor (GPCR) candidates and generated a growing interest in this class of proteins as alternative therapeutic targets for the treatment of various cancers, including glioblastoma multiforme (GBM). GPCRs constitute a large family of membrane receptors that influence oncogenic pathways through canonical and non-canonical signaling. Accordingly, evidence indicates that GPCRs display a unique ability to crosstalk with receptor tyrosine kinases, making them important molecular components controlling tumorigenesis. This review summarizes the current research on GPCR functionality in gliomas and explores the potential of modulating these receptors to treat this devastating disease.

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.