CD44 expression and hyaluronic acid binding of malignant glioma cells

Hyaluronic Acid-Coated Silica Nanoparticles for Targeted Delivery of Nitric Oxide to Cancer Cells

Drug resistance and off-target toxicity are two of the greatest challenges to chemotherapeutic melanoma treatments. Nitric oxide (NO) represents an attractive alternative to conventional therapeutics due to its numerous anticancer properties and low probability of engendering resistance. As NO is highly reactive, macromolecular NO donors are needed for the controlled and targeted delivery of NO for therapeutic applications. Herein, mesoporous silica nanoparticles (MSNs) coated with hyaluronic acid (HA) were developed as a NO delivery system to facilitate controlled delivery to cancer cells through both passive and active targeting via the enhanced permeation and retention effect and directed binding of HA with CD44 receptors, respectively. The aminosilane modification, HA concentration, and HA molecular weight were systematically evaluated to facilitate the MSN coating and NO loading. The hydrodynamic diameter and dispersity of the nanoparticles increased after HA coating due to the hydrophilic nature of HA, with greater increases observed at higher HA molecular weight. Lower starting concentrations of HA and aminosilanes with longer alkyl chains favored more efficient HA coating. Faster NO-release kinetics and lower NO payloads were observed for the HA-coated MSNs relative to uncoated MSNs. However, the localized delivery of NO to cancer cells through the active targeting conferred by HA increased levels of oxidative stress and induced mitochondria-mediated apoptosis in melanoma cells. Cytotoxicity was also evaluated against human dermal fibroblasts, with the use of 6 kDa HA-coated MSNs resulting in the greatest therapeutic indices. Enhanced internalization of HA-coated nanoparticles into melanoma cells versus uncoated nanoparticles was visualized with confocal microscopy and quantified by fluorescence spectroscopy. In total, HA-coated MSNs represent a promising NO delivery system for potential use as a chemotherapeutic for skin melanomas.

Recent advances in label-free optical, electrochemical, and electronic biosensors for glioma biomarkers

Gliomas are the most commonly occurring primary brain tumor with poor prognosis and high mortality rate. Currently, the diagnostic and monitoring options for glioma mainly revolve around imaging techniques, which often provide limited information and require supervisory expertise. Liquid biopsy is a great alternative or complementary monitoring protocol that can be implemented along with other standard diagnosis protocols. However, standard detection schemes for sampling and monitoring biomarkers in different biological fluids lack the necessary sensitivity and ability for real-time analysis. Lately, biosensor-based diagnostic and monitoring technology has attracted significant attention due to several advantageous features, including high sensitivity and specificity, high-throughput analysis, minimally invasive, and multiplexing ability. In this review article, we have focused our attention on glioma and presented a literature survey summarizing the diagnostic, prognostic, and predictive biomarkers associated with glioma. Further, we discussed different biosensory approaches reported to date for the detection of specific glioma biomarkers. Current biosensors demonstrate high sensitivity and specificity, which can be used for point-of-care devices or liquid biopsies. However, for real clinical applications, these biosensors lack high-throughput and multiplexed analysis, which can be achieved via integration with microfluidic systems. We shared our perspective on the current state-of-the-art different biosensor-based diagnostic and monitoring technologies reported and the future research scopes. To the best of our knowledge, this is the first review focusing on biosensors for glioma detection, and it is anticipated that the review will offer a new pathway for the development of such biosensors and related diagnostic platforms.

Interplay between mucus mobility and alveolar macrophage targeting of surface-modified liposomes

Alveolar macrophages play a crucial role in the initiation and resolution of the immune response in the lungs. Pro-inflammatory M1 alveolar macrophages are an interesting target for treating inflammatory and infectious pulmonary diseases. One commune targeting strategy is to use nanoparticles conjugated with hyaluronic acid, which interact with CD44 overexpressed on the membrane of those cells. Unfortunately, this coating strategy may be countered by the presence on the surface of the nanoparticles of a poly(ethylene glycol) corona employed to improve nanoparticles' diffusion in the lung mucus. This study aims to measure this phenomenon by comparing the behavior in a murine lung inflammation model of three liposomal platforms designed to represent different poly(ethylene glycol) and hyaluronic acid densities (Liposome-PEG, Liposome-PEG-HA and Liposome-HA). In this work, the liposomes were obtained by a one-step ethanol injection method. Their interaction with mucin and targeting ability toward pro-inflammatory macrophages were then investigated in vitro and in vivo in a LPS model of lung inflammation. In vitro, poly(ethylene glycol) free HA-liposomes display a superior targeting efficiency toward M1 macrophages, while the addition of poly(ethylene glycol) induces better mucus mobility. Interestingly in vivo studies revealed that the three liposomes showed distinct cell specificity with alveolar macrophages demonstrating an avidity for poly(ethylene glycol) free HA-liposomes, while neutrophils favored PEGylated liposomes exempt of HA. Those results could be explained by the presence of two forces exercising a balance between mucus penetration and receptor targeting. This study corroborates the importance of considering the site of action and the targeted cells when designing nanoparticles to treat lung diseases.

In vivo liquid biopsy for glioblastoma malignancy by the AFM and LSPR based sensing of exosomal CD44 and CD133 in a mouse model

Glioblastoma (GBM) is the fatal brain tumor in which secreted lactate enhances the expression of cluster of differentiation 44 (CD44) and the release of exosomes, cell-derived nanovesicles (30-200 nm), and therefore promotes tumor malignant progression. This study found that lactate-driven upregulated CD44 in malignant Glioblastoma cells (GMs) enhanced the release of CD44-enriched exosomes which increased GMs' migration and endothelial cells' tube formation, and CD44 in the secreted exosomes was sensitively detected by "capture and sensing" Titanium Nitride (TiN) - Nanoholes (NH) - discs immunocapture (TIC) - atomic force microscopy (AFM) and ultrasensitive TiN-NH-localized surface plasmon resonance (LSPR) biosensors. The limit of detection for exosomal CD44 with TIC-AFM- and TiN-NH-LSPR-biosensors was 5.29 × 10^-1 μg/ml and 3.46 × 10^-3 μg/ml in exosome concentration, respectively. Importantly, this work first found that label-free sensitive TiN-NH-LSPR biosensor could detect and quantify enhanced CD44 and CD133 levels in immunocaptured GMs-derived exosomes in the blood and the cerebrospinal fluid of a mouse model of GBM, supporting its potential application in a minimally invasive molecular diagnostic for GBM progression as liquid biopsy.

The scrambled story between hyaluronan and glioblastoma

Advances in cancer biology are revealing the importance of the cancer cell microenvironment on tumorigenesis and cancer progression. Hyaluronan (HA), the main glycosaminoglycan in the extracellular matrix, has been associated with the progression of glioblastoma (GBM), the most frequent and lethal primary tumor in the central nervous system, for several decades. However, the mechanisms by which HA impacts GBM properties and processes have been difficult to elucidate. In this review, we provide a comprehensive assessment of the current knowledge on HA's effects on GBM biology, introducing its primary receptors CD44 and RHAMM and the plethora of relevant downstream signaling pathways that can scramble efforts to directly link HA activity to biological outcomes. We consider the complexities of studying an extracellular polymer and the different strategies used to try to capture its function, including 2D and 3D in vitro studies, patient samples, and in vivo models. Given that HA affects not only migration and invasion, but also cell proliferation, adherence, and chemoresistance, we highlight the potential role of HA as a therapeutic target. Finally, we review the different existing approaches to diminish its protumor effects, such as the use of 4-methylumbelliferone, HA oligomers, and hyaluronidases and encourage further research along these lines in order to improve the survival and quality of life of GBM patients.

A Novel Four-Gene Signature Associated With Immune Checkpoint for Predicting Prognosis in Lower-Grade Glioma

The overall survival of patients with lower grade glioma (LGG) varies greatly, but the current histopathological classification has limitations in predicting patients’ prognosis. Therefore, this study aims to find potential therapeutic target genes and establish a gene signature for predicting the prognosis of LGG. CD44 is a marker of tumor stem cells and has prognostic value in various tumors, but its role in LGG is unclear. By analyzing three glioma datasets from Gene Expression Omnibus (GEO) database, CD44 was upregulated in LGG. We screened 10 CD44-related genes via protein–protein interaction (PPI) network; function enrichment analysis demonstrated that these genes were associated with biological processes and signaling pathways of the tumor; survival analysis showed that four genes (CD44, HYAL2, SPP1, MMP2) were associated with the overall survival (OS) and disease-free survival (DFS)of LGG; a novel four-gene signature was constructed. The prediction model showed good predictive value over 2-, 5-, 8-, and 10-year survival probability in both the development and validation sets. The risk score effectively divided patients into high- and low- risk groups with a distinct outcome. Multivariate analysis confirmed that the risk score and status of IDH were independent prognostic predictors of LGG. Among three LGG subgroups based on the presence of molecular parameters, IDH-mutant gliomas have a favorable OS, especially if combined with 1p/19q codeletion, which further confirmed the distinct biological pattern between three LGG subgroups, and the gene signature is able to divide LGG patients with the same IDH status into high- and low- risk groups. The high-risk group possessed a higher expression of immune checkpoints and was related to the activation of immunosuppressive pathways. Finally, this study provided a convenient tool for predicting patient survival. In summary, the four prognostic genes may be therapeutic targets and prognostic predictors for LGG; this four-gene signature has good prognostic prediction ability and can effectively distinguish high- and low-risk patients. High-risk patients are associated with higher immune checkpoint expression and activation of the immunosuppressive pathway, providing help for screening immunotherapy-sensitive patients.

Impact of breast cancer cells´ secretome on the brain metastatic niche remodeling

Brain metastases occur in approximately 10-20% of patients with metastatic breast cancer showing a very poor overall survival. Curiously, different molecular subtypes (that show specific gene expression signatures and differential prognostic significance) are associated with different risks for brain metastases development, suggesting that cancer cells harbor specific molecular programs that award them intrinsic advantages to survive in this specific foreign tissue. Emerging data has been revealing that biophysical and/or mechanical properties of the brain extracellular matrix (ECM), along with those of the brain resident cells, play a crucial role in creating the best conditions for survival, colonization and outgrowth of breast cancer cells in this distinct microenvironment. Although several reports show that cancer cells modulate metastatic niches way before they reach the target organ, few data exist for the brain metastatic niche. Indeed, little is known concerning how factors secreted by cancer cells activate brain resident cells and/or modify brain ECM biomechanical properties and how these modifications impact cells´ ability to metastasize the brain. The brain is a particular organ, protected by the blood brain barrier (BBB), and containing exclusive functional units and very special cell types. Additionally, it is the organ with the most singular ECM and biomechanical properties. Thus, this cancer cell-brain metastatic niche interaction must present distinct properties. Consequently, the search for putative molecular markers that modulate the brain pre-metastatic niche, thus promoting the successful metastatic homing of cancer cells, is urgently needed. In this review, we will discuss key aspects regarding breast cancer cells and the brain pre-metastatic niche paracrine communication that is crucial to initiate the metastatic cascade. We will focus on cancer cell`s secretome influence into the brain microenvironment, specifically on its impact on tissue mechanics and on brain resident cells as regulators of the pre-metastatic niche formation, ultimately promoting metastatic colonization.

A C-Terminal Fragment of Chlorotoxin Retains Bioactivity and Inhibits Cell Migration

Chlorotoxin was originally isolated from the venom of the Israeli scorpion Leiurus quinquestriatus, and has potential as a tumor imaging agent based on its selective binding to tumor cells. Several targets have been suggested for chlorotoxin including voltage-gated chloride channels, and it has been shown to have anti-angiogenic activity and inhibit cell migration. The structure of chlorotoxin is stabilized by four disulfide bonds and contains β-sheet and helical structure. Interestingly, the reduced form has previously been shown to inhibit cell migration to the same extent as the wild type, but structural analysis indicates that the reduced form of the peptide does not maintain the native secondary structure and appears unstructured in solution. This lack of structure suggests that a short stretch of amino acids might be responsible for the bioactivity. To explore this hypothesis, we have synthesized fragments of chlorotoxin without disulfide bonds. As expected for such small peptides, NMR analysis indicated that the peptides were unstructured in solution. However, the peptide corresponding to the eight C-terminal residues inhibited cell migration, in contrast to the other fragments. Our results suggest that the C-terminal region plays a critical role in the bioactivity of chlorotoxin.

Design of Tumor Microenvironment-Responsive Drug-Drug Micelle for Cancer Radiochemotherapy

Concomitant radiochemotherapy is a major therapeutic strategy for treating malignant tumors. However, the greatest challenge is how to improve the therapeutic effect of radiochemotherapy to achieve the proper synergetic chemo-/radiotherapy for the tumor. In this study, ferrocenium (antitumor effect) and nitroimidazole (hypoxic cell radiosensitization) conjugates were synthesized to form amphiphilic ferrocenium-hexane-nitroimidazole (Fe-NI), which can self-assemble in aqueous solution. The Fe-NI micelles successfully encapsulate the hydrophobic chemotherapy drug doxorubicin (DOX) and are modified with hyaluronic acid (HA) by electrostatic interactions to form HA-Fe-NIs-DOX micelles. HA-Fe-NIs-DOX micelles rapidly release DOX under tumor hypoxia and a high glutathione (GSH) environment and achieve a synergetic chemo-/radiotherapy for the tumor based on the properties of nitroimidazoles and ferrocenes. The biodistribution results obtained in vivo reveal an effective accumulation in the tumor. The HA-Fe-NIs-DOX micelles show a significant radiosensitizing effect on the tumors, and the combination of chemotherapy and radiotherapy is realized for the treatment of tumor in vitro and in vivo. These findings illustrate that HA-Fe-NIs micelles are a promising candidate, which enhances the antitumor effects as a DOX delivery system, owing to the synergistic mechanisms of antitumor agents and chemo-/radiotherapy.

Expression patterns of CD168 correlate with the stage and grade of squamous cell carcinoma of head and neck

The receptor for hyaluronan-mediated motility CD168 is associated with the processes of oncogenesis and metastasis. The objective of the present study was to determine the possible association between the expression and distribution of CD168 and the tumor stage of head-and-neck squamous cell carcinoma (SCC). Formalin-fixed and paraffin-embedded tumor samples obtained from 100 patients during primary resection of SCC from the oral cavity, oropharynx, hypopharynx or larynx were included in the present study. The patients were divided into two risk groups: Low risk, representing the early stage of completely resected SCCs with good-to-moderate differentiation, and the high-risk group, representing the advanced stage SCCs with positive resection margins, vascular invasion or locoregional metastasis. All specimens were stained with a monoclonal antibody against CD168. Percentage and staining intensity of CD168-positive cells were scored, and their spatial distribution within the tumor nests was noted. The results obtained were correlated with the tumor stage. The quantification of CD168 expression revealed significant differences between the two risk groups (t-test, P=0.002), with higher scores in tumors resected from the high-risk SSC group compared with those from the low-risk group. In addition, in the high-risk group, the CD168-positive cells were present predominantly in the periphery (70.4%) of tumor nests, whereas in the low-risk group, only 56.6% were located there; however, this trend did not reach the level of statistical significance. Taken together, the results from the present study suggested that CD168 expression patterns could potentially be used as a predictor of tumor aggressiveness, and therefore they may be a prognostic factor in head-and-neck SCC.

Tissue mechanics regulate brain development, homeostasis and disease

All cells sense and integrate mechanical and biochemical cues from their environment to orchestrate organismal development and maintain tissue homeostasis. Mechanotransduction is the evolutionarily conserved process whereby mechanical force is translated into biochemical signals that can influence cell differentiation, survival, proliferation and migration to change tissue behavior. Not surprisingly, disease develops if these mechanical cues are abnormal or are misinterpreted by the cells - for example, when interstitial pressure or compression force aberrantly increases, or the extracellular matrix (ECM) abnormally stiffens. Disease might also develop if the ability of cells to regulate their contractility becomes corrupted. Consistently, disease states, such as cardiovascular disease, fibrosis and cancer, are characterized by dramatic changes in cell and tissue mechanics, and dysregulation of forces at the cell and tissue level can activate mechanosignaling to compromise tissue integrity and function, and promote disease progression. In this Commentary, we discuss the impact of cell and tissue mechanics on tissue homeostasis and disease, focusing on their role in brain development, homeostasis and neural degeneration, as well as in brain cancer.

Peptides as a therapeutic avenue for nanocarrier-aided targeting of glioma

INTRODUCTION

Very few successful interventions have been possible in glioma therapy owing to its aggressive nature as well as its hindrance of targeted therapy together with the limited access afforded by the blood-brain barrier (BBB). With the advent of nanotechnology based delivery vehicles such as micelles, dendrimers, polymer-based nanoparticles and nanogels, the breach of the BBB has been facilitated. However, there remains the issue of targeted therapy for glioma cells. Peptide-mediated surface modification of nanocarriers serves this purpose, extending the ability to target glioma further than the enhanced permeability and retention effect. Areas covered: Here we have tried to re-establish the significance of peptides that could be used in various ways for treating glioma. Peptide-embellished nanocarriers used to deliver anticancer drugs; nucleic acids (siRNA, miRNA); micelles or dendrimers grafted with immunogenic glioma-derived peptides used for stimulating active immunity in vaccine therapy, glioma targets for cell penetrating peptides and homing to specific receptors are reviewed. Expert opinion: Peptides have multifunctional potential in targeting, BBB and cell penetration, and can serve as antagonists of various ligands and agonists of particular over-expressed receptors as discussed in this review. Using peptides in targeted personalized therapy would be one step forward and may offer new avenues for glioma therapeutics.

Hyaluronic acid as a potential boron carrier for BNCT: Preliminary evaluation

Hyaluronic acid (HA), a nonimmunogenic, biocompatible polymer found in different biological tissues, has the potential to attach to CD44 receptors on the surface of certain cancer cells, where the receptor is overexpressed compared with normal cells. Boron-hyaluronic acid (BHA) was tested for its feasibility as a potential agent for BNCT. BHA with low-viscosity 30 kDa HA could be administered by intravenous injection. The compound showed a certain degree of cytotoxicity and accumulation in C6 rat glioma cells in vitro. Instability of the chelate bonds between boron and HA and/or insufficient specificity of CD44 receptors on C6 cells to BHA could account for the insufficient in vitro accumulation. To ensure the future eligibility of BHA for BNCT experiments, using alternative tumor cell lines and chemically securing the chelate bonds or synthesizing BHA with boron covalently attached to HA might be required.

K604, a specific acyl‑CoA:cholesterol acyltransferase 1 inhibitor, suppresses proliferation of U251‑MG glioblastoma cells

Glioblastoma is the most aggressive type of brain tumor and has a poor prognosis. Increased levels of cholesteryl ester and simultaneous expression of acyl‑CoA:cholesterol acyltransferase 1 (ACAT1) in tumor cells indicated that cholesterol esterification is critical to tumor growth. The present study confirmed that human glioblastoma tissues as well as the glioblastoma cell line U251‑MG showed significant expression of ACAT1. ACAT1 expression in U251‑MG cells increased in a cell proliferation‑dependent manner. K604, a selective ACAT1 inhibitor, suppressed the proliferation of U251‑MG cells and downregulated the activation of Akt and extracellular signal‑regulated kinase in proliferating glioblastoma cells. These results suggested that ACAT1 may be a therapeutic target for the treatment of glioblastoma, with K604 as an effective therapeutic agent.

Extracellular vesicles and their synthetic analogues in aging and age-associated brain diseases

Multicellular organisms rely upon diverse and complex intercellular communications networks for a myriad of physiological processes. Disruption of these processes is implicated in the onset and propagation of disease and disorder, including the mechanisms of senescence at both cellular and organismal levels. In recent years, secreted extracellular vesicles (EVs) have been identified as a particularly novel vector by which cell-to-cell communications are enacted. EVs actively and specifically traffic bioactive proteins, nucleic acids, and metabolites between cells at local and systemic levels, modulating cellular responses in a bidirectional manner under both homeostatic and pathological conditions. EVs are being implicated not only in the generic aging process, but also as vehicles of pathology in a number of age-related diseases, including cancer and neurodegenerative and disease. Thus, circulating EVs-or specific EV cargoes-are being utilised as putative biomarkers of disease. On the other hand, EVs, as targeted intercellular shuttles of multipotent bioactive payloads, have demonstrated promising therapeutic properties, which can potentially be modulated and enhanced through cellular engineering. Furthermore, there is considerable interest in employing nanomedicinal approaches to mimic the putative therapeutic properties of EVs by employing synthetic analogues for targeted drug delivery. Herein we describe what is known about the origin and nature of EVs and subsequently review their putative roles in biology and medicine (including the use of synthetic EV analogues), with a particular focus on their role in aging and age-related brain diseases.

PTK7 regulates Id1 expression in CD44-high glioma cells

BACKGROUND

CD44 is a molecular marker associated with molecular subtype and treatment resistance in glioma. More effective therapies will result from approaches aimed at targeting the CD44-high gliomas.

METHODS

Protein tyrosine kinase 7 (PTK7) mRNA expression was analyzed based on The Cancer Genome Atlas glioblastoma dataset. PTK7 expression was depleted through lentivirus-mediated short hairpin RNA knockdown. Terminal deoxynucleotidyl transferase dUTP nick-end labeling was used to evaluate cell apoptosis following PTK7 knockdown. Gene expression analysis was performed on Affymetrix microarray. A nude mice orthotopic tumor model was used to evaluate the in vivo effect of PTK7 depletion.

RESULTS

PTK7 is highly expressed in CD44-high glioblastoma and predicts unfavorable prognosis. PTK7 knockdown attenuated cell proliferation, impaired tumorigenic potential, and induced apoptosis in CD44-high glioma cell lines. Gene expression analysis identified inhibitor of DNA Binding 1 (Id1) gene as a potential downstream effector for PTK7. Overexpression of Id1 mostly restored the cell proliferation and colony formation attenuated by PTK7 depletion. PTK7 enhanced anchorage-independent growth in normal human astrocytes, which was attenuated by Id1 knockdown. Furthermore, PTK7 regulated Id1 expression through modulating TGF-β/Smad signaling, while pharmacological inhibition on TGF-β/Smad signaling or PTK7/Id1 depletion attenuated TGF-β-stimulated cell proliferation. PTK7 depletion consistently reduced Id1 expression, suppressed tumor growth, and induced apoptosis in a murine orthotopic tumor model, which could be translated into prolonged survival in tumor-bearing mice.

CONCLUSIONS

PTK7 regulates Id1 expression in CD44-high glioma cell lines. Targeting PTK7 could be an effective strategy for treating glioma with high CD44 expression.

TGM2 inhibition attenuates ID1 expression in CD44-high glioma-initiating cells

BACKGROUND

CD44 is a molecular marker associated with cancer stem cell populations and treatment resistance in glioma. More effective therapies will result from approaches aimed at targeting glioma cells high in CD44.

METHODS

Glioma-initiating cell lines were derived from fresh surgical glioblastoma samples. Expression of tissue transglutaminase 2 (TGM2) was attenuated through lentivirus-mediated short hairpin RNA knockdown. MTT assay [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] was used to evaluate the growth inhibition induced by TGM2 inhibitor. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling was used to evaluate cell apoptosis following TGM2 inhibition. CD44(+) glioma stem cells were sorted by flow cytometry. A nude mice orthotopic xenograft model was used to evaluate the in vivo effect of TGM2 inhibitor.

RESULTS

TGM2 was highly expressed in CD44-high glioblastoma tissues and tumor-derived glioma-initiating cell lines. TGM2 knockdown impaired cell proliferation and induced apoptosis in CD44-high glioma-initiating cell lines. Further studies indicated that expression of inhibitor of DNA binding 1 protein (ID1) is regulated by TGM2 and might be an important mediator for TGM2-regulated cell proliferation in CD44-high glioma-initiating cell lines. TGM2 inhibitor reduces ID1 expression, suppresses cell proliferation, and induces apoptosis in CD44-high glioma-initiating cell lines. Furthermore, TGM2 is highly expressed in CD44(+) glioma stem cells, while pharmacological inhibition of TGM2 activity preferentially eliminates CD44(+) glioma stem cells. Consistently, TGM2 inhibitor treatment reduced ID1 expression and induced apoptosis in our orthotopic mice xenograft model, which can be translated into prolonged median survival in tumor-bearing mice.

CONCLUSIONS

TGM2 regulates ID1 expression in glioma-initiating cell lines high in CD44. Targeting TGM2 could be an effective strategy to treat gliomas with high CD44 expression.

Elucidating the mechanobiology of malignant brain tumors using a brain matrix-mimetic hyaluronic acid hydrogel platform

Glioblastoma multiforme (GBM) is a malignant brain tumor characterized by diffuse infiltration of single cells into the brain parenchyma, which is a process that relies in part on aberrant biochemical and biophysical interactions between tumor cells and the brain extracellular matrix (ECM). A major obstacle to understanding ECM regulation of GBM invasion is the absence of model matrix systems that recapitulate the distinct composition and physical structure of brain ECM while allowing independent control of adhesive ligand density, mechanics, and microstructure. To address this need, we synthesized brain-mimetic ECMs based on hyaluronic acid (HA) with a range of stiffnesses that encompasses normal and tumorigenic brain tissue and functionalized these materials with short Arg-Gly-Asp (RGD) peptides to facilitate cell adhesion. Scanning electron micrographs of the hydrogels revealed a dense, sheet-like microstructure with apparent nanoscale porosity similar to brain extracellular space. On flat hydrogel substrates, glioma cell spreading area and actin stress fiber assembly increased strongly with increasing density of RGD peptide. Increasing HA stiffness under constant RGD density produced similar trends and increased the speed of random motility. In a three-dimensional (3D) spheroid paradigm, glioma cells invaded HA hydrogels with morphological patterns distinct from those observed on flat surfaces or in 3D collagen-based ECMs but highly reminiscent of those seen in brain slices. This material system represents a brain-mimetic model ECM with tunable ligand density and stiffness amenable to investigations of the mechanobiological regulation of brain tumor progression.

Prognostic impact of CD168 expression in gastric cancer

BACKGROUND

Interactions of stromal hyaluronic acid (HA) with its binding protein RHAMM (receptor for HA-mediated motility) (CD168) have been reported to affect tumor extension and the migration of crucial molecules to promote tumor progression and metastases. Cancerous CD168 expression is correlated with aggressive biological features in several cancers. However, the clinical implications of CD168 positivity in gastric cancer have remained unclear.

METHODS

We examined the CD168 expression of 196 consecutive gastric cancer patients by immunohistochemistry. According to CD168 positivity, the 196 gastric cancer patients were divided into two groups (57 CD168-positive and 139 CD168-negative patients). The correlation between CD168 expression and clinicopathological factors (age, sex, histology, tumor depth, lymph node status, and vessel invasion) was evaluated according to the Japanese Classification of Gastric Carcinoma.

RESULTS

Cancerous CD168 expression was detectable in 57 of the 196 tumors (29%). CD168 positivity was significantly correlated with the depth of invasion, nodal involvement, and vessel invasion (p < 0.01). Survival analysis of the 196 gastric cancer patients showed that the CD168-positive group had a significantly higher mortality than the CD168-negative group (p < 0.01). In terms of a correlation with CD168 positivity at separate clinical stages, a significance difference was only found in stages II and III. Multivariate analysis revealed that CD168 expression was a significant independent prognostic marker (p = 0.013) after depth of invasion (p < 0.005) and nodal involvement (p < 0.01).

CONCLUSION

Our results suggest that cancerous CD168 positivity is strongly related to the invasion and metastasis of gastric cancer tumors. These results suggest that cancerous CD168 expression can be used as a prognostic marker of gastric cancer owing to its interactions with stromal hyaluronic acid.

The intracellular drug delivery and anti tumor activity of doxorubicin loaded poly(gamma-benzyl L-glutamate)-b-hyaluronan polymersomes

We have investigated the intracellular delivery of doxorubicin (DOX) loaded poly(gamma-benzyl L-glutamate)-block-hyaluronan (PBLG-b-HYA) based polymersomes (PolyDOX) in high (MCF-7) and low (U87) CD44 expressing cancer cell models. DOX was successfully loaded into polymersomes using nanoprecipitation method and in vitro drug release pattern were achieved at pH 5.5 and 7.4 up to 10 days. Block copolymer vesicles without loaded DOX were non cytotoxic in both cells at concentration 150-650 microg/mL. Flow cytometry data suggested successful uptake of PolyDOX in cells and high accumulation was found in MCF-7 than U87 cells. Microscopy imagings revealed that in MCF-7 cells PolyDOX was more in cytoplasm and free DOX in nuclei, whereas in U87 cells free DOX was also found in the cytoplasm. Cytotoxicity of the drug was concentration and exposure time dependent. In addition, PolyDOX significantly enhanced reactive oxygen species (ROS) level in both cells. PolyDOX also suppressed growth of breast tumor on female Sprague-Dawley (SD) rats as compared to phosphate buffer saline pH 7.4 (PBS) control group. In addition reduced level of serum enzymes (LDH and CPK) by PolyDOX formulation indicated less cardiotoxicity of DOX after loading in polymersomes. Results suggest that intracellular delivery of PolyDOX was depended on the CD44 expression level in cells due to presence of hyaluronic acid on the surface of polymersomes, and could be used as a self-targeting drug delivery cargo in over-expressed CD44 glycoprotein cells of breast cancer.

PKC-induced stiffening of hyaluronan/CD44 linkage; local force measurements on glioma cells

Interaction of cells with hyaluronan (HA) rich extracellular matrix involves the membrane receptor CD44. HA-CD44 interactions are particularly important in the development of glioma pathogenesis for its implication in tumor cells spreading. Highly motile states rely on the spaciotemporal regulation of HA-CD44 interactions occurring in specific cytoskeletal-supported membrane organization such as microvilli or the leading edge observed in migrating cell. We used AFM-based force measurement to probe the HA-CD44 interaction at localized regions at the surface of living glioma cells expressing high level of the CD44 standard isoform. We show that unstimulated cells interact with HA over their entire surfaces and are highly deformable when force is exerted on individual HA molecules bound to membrane CD44 receptors. Conversely, in PKC-activated cells the probed interactions are concentrated at the leading edge of the cells with reduced membrane deformability. Taken together, our results show that PKC-enhanced motility in glioma cells is associated with a redistribution of CD44 receptors at the leading edges concomitant with a stiffer anchoring of CD44 to the cell surface involving the actin cytoskeleton.

Direct binding of neutral endopeptidase 24.11 to ezrin/radixin/moesin (ERM) proteins competes with the interaction of CD44 with ERM proteins

Neutral endopeptidase 24.11 (NEP) is a cell surface peptidase expressed by numerous tissues including prostatic epithelial cells. We reported that NEP inhibits prostate cancer cell proliferation and cell migration by enzymatic inactivation of neuropeptide substrates and through protein-protein interaction independent of catalytic function. The cytoplasmic domain of NEP contains a positively charged amino acid cluster, previously identified as a binding site for ezrin/radixin/moesin (ERM) proteins. We report here that NEP co-immunoprecipitates with ERM proteins in NEP-expressing LNCaP prostate cancer cells and MeWo melanoma cells. Co-immunoprecipitation showed that ERM proteins associate with wild-type NEP protein but not NEP protein containing a truncated cytoplasmic domain or point mutations replacing the positively charged amino acid cluster. In vitro binding assays showed that NEP binds directly to recombinant N terminus fragments of ERM proteins at the positively charged amino acid cluster within the NEP cytoplasmic domain. Binding of ERM proteins to NEP results in decreased binding of ERM proteins to the hyaluronan receptor CD44, a main binding partner of ERM proteins. Moreover, cells expressing wild-type NEP demonstrate decreased adhesion to hyaluronic acid and cell migration. These data suggest that NEP can affect cell adhesion and migration through direct binding to ERM proteins.

Hyaluronidase gene profiling and role of hyal-1 overexpression in an orthotopic model of prostate cancer

The mRNA levels of hyal-1, hyal-2, LUCA3 and PH20, the 4 hyaluronidases with demonstrated endoglucosaminidase activity, were extensively profiled in normal and tumor tissues and cell lines, using dot blot analysis and quantitative PCR. In normal tissues, hyal-1, hyal-2 and LUCA3 all showed unique patterns of mRNA expression, but were generally of widespread distribution, whereas PH20 mRNA was restricted to testes. In a small set of breast tumor samples, no elevations in hyal-1, hyal-2 or LUCA3 mRNA were seen. Hyaluronidase activity measured by a novel assay or zymography was also not elevated in sera from a number of breast cancer patients, compared to sera from normal volunteers. In ex vivo xenograft tumor cell lines, however, hyal-1 or hyal-2 mRNA levels were frequently elevated, whereas LUCA3 was only infrequently elevated and PH20 not at all. Two cell lines were engineered to overexpress hyal-1: a breast cancer line (CAL51) and a prostate cancer line (PC3M). Although the in vitro properties of the hyal-1 overexpressing cell lines were indistinguishable from the parental cells, the orthotopic growth of hyal-1 expressing PC3M cells in nu/nu mice resulted in significantly increased numbers of metastases, supportive of a role for hyal-1 in extravasation and metastatic tumor formation in this model of prostate cancer.

Hyaluronate receptors mediating glioma cell migration and proliferation

The extracellular matrix (ECM) of the central nervous system (CNS) is enriched in hyaluronate (HA). Ubiquitous receptors for HA are CD44 and the Receptor for HA-Mediated Motility known as RHAMM. In the present study, we have investigated the potential role of CD44 and RHAMM in the migration and proliferation of human astrocytoma cells. HA-receptor expression in brain tumor cell lines and surgical specimens was determined by immunocytochemistry and western blot analyses. The ability of RHAMM to bind ligand was determined through cetylpyridinium chloride (CPC) precipitations of brain tumor lysates in HA-binding assays. The effects of HA, CD44 blocking antibodies, and RHAMM soluble peptide on astrocytoma cell growth and migration was determined using MTT and migration assays. Our results show that the expression of the HA-receptors, CD44, and RHAMM, is virtually ubiquitous amongst glioma cell lines, and glioma tumor specimens. There was a gradient of expression amongst gliomas with high grade gliomas expressing more RHAMM and CD44 than did lower grade lesions or did normal human astrocytes or non-neoplastic specimens of human brain. Specific RHAMM variants of 85- and 58-kDa size were shown to bind avidly to HA following CPC precipitations. RHAMM soluble peptide inhibited glioma cell line proliferation in a dose-dependent fashion. Finally, while anti-CD44 antibodies did not inhibit the migration of human glioma cells, soluble peptides directed at the HA-binding domain of RHAMM inhibited glioma migration both on and off an HA-based ECM. These data support the notion that HA-receptors contribute to brain tumor adhesion, proliferation, and migration, biological features which must be better understood before more effective treatment strategies for these tumors can be found.

Interferon gamma inhibits proliferation and hyaluronic acid adhesion of human malignant glioma cells in vitro

Malignant gliomas are frequent and the prognosis is poor. The cytokine interferon gamma (IFN-gamma) enhances several immune phenomena and may be used in immunotherapy of tumours. Therefore we investigated the influence of IFN-gamma on human cell lines T98G, U87MG, 86HG39 and 85HG66, measuring cell viability (MTT-test) and proliferation (3H-thymidine uptake). IFN-gamma markedly decreased viability and proliferation of all investigated cell lines. Expression of CD44 and adhesion to hyaluronic acid (HA) are involved in glioma invasion. Influence of IFN-gamma on these two features has also been investigated. IFN-gamma markedly decreased HA-adhesion in all three investigated cell lines, whereas CD44 expression remained uninfluenced. To summarise, IFN-gamma strongly decreased cell growth and HA-adhesion of malignant glioma cell lines in vitro. We suggest further investigations to characterise better the role of IFN-gamma as a treatment opportunity for malignant gliomas.