Temporal and regional expression changes and co-staining patterns of metabolic and stemness-related markers during glioblastoma progression

Glioblastomas (GBMs) are characterized by high heterogeneity, involving diverse cell types, including those with stem-like features contributing to GBM's malignancy. Moreover, metabolic alterations promote growth and therapeutic resistance of GBM. Depending on the metabolic state, antimetabolic treatments could be an effective strategy. Against this background, we investigated temporal and regional expression changes and co-staining patterns of selected metabolic markers [pyruvate kinase muscle isozyme 1/2 (PKM1/2), glucose transporter 1 (GLUT1), monocarboxylate transporter 1/4 (MCT1/4)] in a rodent model and patient-derived samples of GBM. To understand the cellular sources of marker expression, we also examined the connection of metabolic markers to markers related to stemness [Nestin, Krüppel-like factor 4 (KLF4)] in a regional and temporal context. Rat tumour biopsies revealed a temporally increasing expression of GLUT1, higher expression of MCT1/4, Nestin and KLF4, and lower expression of PKM1 compared to the contralateral hemisphere. Patient-derived tumours showed a higher expression of PKM2 and Nestin in the tumour centre vs. edge. Whereas rare co-staining of GLUT1/Nestin was found in tumour biopsies, PKM1/2 and MCT1/4 showed a more distinct co-staining with Nestin in rats and humans. KLF4 was mainly co-stained with GLUT1, MCT1 and PKM1/2 in rat and human tumours. All metabolic markers yielded individual co-staining patterns among themselves. Co-staining mainly occurred later in tumour progression and was more pronounced in tumour centres. Also, positive correlations were found amongst markers that showed co-staining. Our results highlight a link between metabolic alterations and stemness in GBM progression, with complex distinctions depending on studied markers, time points and regions.

Nitrogen-15 dynamic nuclear polarization of nicotinamide derivatives in biocompatible solutions

Dissolution dynamic nuclear polarization (dDNP) increases the sensitivity of magnetic resonance imaging by more than 10,000 times, enabling in vivo metabolic imaging to be performed noninvasively in real time. Here, we are developing a group of dDNP polarized tracers based on nicotinamide (NAM). We synthesized 1-15N-NAM and 1-15N nicotinic acid and hyperpolarized them with dDNP, reaching (13.0 ± 1.9)% 15N polarization. We found that the lifetime of hyperpolarized 1-15N-NAM is strongly field- and pH-dependent, with T1 being as long as 41 s at a pH of 12 and 1 T while as short as a few seconds at neutral pH and fields below 1 T. The remarkably short 1-15N lifetime at low magnetic fields and neutral pH drove us to establish a unique pH neutralization procedure. Using 15N dDNP and an inexpensive rodent imaging probe designed in-house, we acquired a 15N MRI of 1-15N-NAM (previously hyperpolarized for more than an hour) in less than 1 s.

Insights into Gene Regulation under Temozolomide-Promoted Cellular Dormancy and Its Connection to Stemness in Human Glioblastoma

The aggressive features of glioblastoma (GBM) are associated with dormancy. Our previous transcriptome analysis revealed that several genes were regulated during temozolomide (TMZ)-promoted dormancy in GBM. Focusing on genes involved in cancer progression, Chemokine (C-C motif) Receptor-Like (CCRL)1, Schlafen (SLFN)13, Sloan-Kettering Institute (SKI), Cdk5 and Abl Enzyme Substrate (Cables)1, and Dachsous Cadherin-Related (DCHS)1 were selected for further validation. All showed clear expression and individual regulatory patterns under TMZ-promoted dormancy in human GBM cell lines, patient-derived primary cultures, glioma stem-like cells (GSCs), and human GBM ex vivo samples. All genes exhibited complex co-staining patterns with different stemness markers and with each other, as examined by immunofluorescence staining and underscored by correlation analyses. Neurosphere formation assays revealed higher numbers of spheres during TMZ treatment, and gene set enrichment analysis of transcriptome data revealed significant regulation of several GO terms, including stemness-associated ones, indicating an association between stemness and dormancy with the involvement of SKI. Consistently, inhibition of SKI during TMZ treatment resulted in higher cytotoxicity, proliferation inhibition, and lower neurosphere formation capacity compared to TMZ alone. Overall, our study suggests the involvement of CCRL1, SLFN13, SKI, Cables1, and DCHS1 in TMZ-promoted dormancy and demonstrates their link to stemness, with SKI being particularly important.

Establishment of a Rodent Glioblastoma Partial Resection Model for Chemotherapy by Local Drug Carriers-Sharing Experience

Local drug delivery systems (LDDS) represent a promising therapy strategy concerning the most common and malignant primary brain tumor glioblastoma (GBM). Nevertheless, to date, only a few systems have been clinically applied, and their success is very limited. Still, numerous new LDDS approaches are currently being developed. Here, (partial resection) GBM animal models play a key role, as such models are needed to evaluate the therapy prior to any human application. However, such models are complex to establish, and only a few reports detail the process. Here, we report our results of establishing a partial resection glioma model in rats suitable for evaluating LDDS. C6-bearing Wistar rats and U87MG-spheroids- and patient-derived glioma stem-like cells-bearing athymic rats underwent tumor resection followed by the implantation of an exemplary LDDS. Inoculation, tumor growth, residual tumor tissue, and GBM recurrence were reliably imaged using high-resolution Magnetic Resonance Imaging. The release from an exemplary LDDS was verified in vitro and in vivo using Fluorescence Molecular Tomography. The presented GBM partial resection model appears to be well suited to determine the efficiency of LDDS. By sharing our expertise, we intend to provide a powerful tool for the future testing of these very promising systems, paving their way into clinical application.

Sequential Treatment with Temozolomide Plus Naturally Derived AT101 as an Alternative Therapeutic Strategy: Insights into Chemoresistance Mechanisms of Surviving Glioblastoma Cells

Glioblastoma (GBM) is a poorly treatable disease due to the fast development of tumor recurrences and high resistance to chemo- and radiotherapy. To overcome the highly adaptive behavior of GBMs, especially multimodal therapeutic approaches also including natural adjuvants have been investigated. However, despite increased efficiency, some GBM cells are still able to survive these advanced treatment regimens. Given this, the present study evaluates representative chemoresistance mechanisms of surviving human GBM primary cells in a complex in vitro co-culture model upon sequential application of temozolomide (TMZ) combined with AT101, the R(-) enantiomer of the naturally occurring cottonseed-derived gossypol. Treatment with TMZ+AT101/AT101, although highly efficient, yielded a predominance of phosphatidylserine-positive GBM cells over time. Analysis of the intracellular effects revealed phosphorylation of AKT, mTOR, and GSK3ß, resulting in the induction of various pro-tumorigenic genes in surviving GBM cells. A Torin2-mediated mTOR inhibition combined with TMZ+AT101/AT101 partly counteracted the observed TMZ+AT101/AT101-associated effects. Interestingly, treatment with TMZ+AT101/AT101 concomitantly changed the amount and composition of extracellular vesicles released from surviving GBM cells. Taken together, our analyses revealed that even when chemotherapeutic agents with different effector mechanisms are combined, a variety of chemoresistance mechanisms of surviving GBM cells must be taken into account.

A biopolymeric mesh enriched with PLGA microparticles loaded with AT101 for localized Glioblastoma treatment

Current treatment strategies for glioblastoma (GBM) including surgical resection and adjuvant radio/chemotherapy result in a limited progression-free survival time of patients due to rapidly occurring tumor recurrences. The urgent need for more effective treatments has led to the development of different approaches for localized drug delivery systems (DDS) offering the advantages of reduced systemic side effects. A promising candidate for the treatment of GBMs is AT101, the R-(-)-enantiomer of gossypol due to its ability to induce apoptosis or trigger autophagic cells death in tumor cells. Here, we present an alginate-based drug-releasing mesh ladened with AT101-loaded PLGA microspheres (AT101-GlioMesh). The AT101-loaded PLGA microspheres were fabricated using an oil-in-water emulsion solvent evaporation method obtaining a high encapsulation efficiency. The drug-loaded microspheres enabled the release of AT101 over several days at the tumor site. The cytotoxic effect of the AT101-loaded mesh was evaluated using two different GBM cell lines. Strikingly, encapsulation of AT101 in PLGA-microparticles and subsequent embedding in GlioMesh resulted in a sustained delivery and more efficient cytotoxic effect of AT101 on both GBM cell lines. Thus, such a DDS holds promise for GBM therapy likely by preventing the development of tumor recurrences.

Fetal and perinatal expression profiles of proinflammatory cytokines in the neuroplacodes of rats with myelomeningoceles: A contribution to the understanding of secondary spinal cord injury in open spinal dysraphism

The cellular and molecular mechanisms that presumably underlie the progressive functional decline of the myelomeningocele (MMC) placode are not well understood. We previously identified key players in posttraumatic spinal cord injury cascades in human MMC tissues obtained during postnatal repair. In this study we conducted experiments to further investigate these mediators in the prenatal time course under standardized conditions in a retinoic-acid-induced MMC rat model. A retinoic acid MMC model was established using time-dated Sprague-Dawley rats, which were gavage-fed with all-trans retinoic acid (RA; 60 mg/kg) dissolved in olive oil at E10. Control animals received olive oil only. Fetuses from both groups were obtained at E16, E18, E22. The spinal cords (SCs) of both groups were formalin-fixed or snap-frozen. Tissues were screened by real-time RT-PCR for the expression of cytokines and chemokines known to play a role in the lesion cascades of the central nervous system after trauma. MMC placodes exhibited inflammatory cells and glial activation in the later gestational stages. At the mRNA level, IL-1b, TNFa, and TNF-R1 exhibited significant induction at E22. IL1-R1 mRNA was induced significantly at E16 and E22. Double labeling experiments confirmed the costaining of these cytokines and their receptors with Iba1 (i.e., inflammatory cells), Vimentin, and Nestin in different anatomical SC areas and NeuN in ventral horn neurons. CXCL12 mRNA was elevated in control and MMC animals at E16 compared to E18 and E22. CX3CL1 mRNA was lower in MMC tissues than in control tissues on E16. The presented findings contribute to the concept that pathophysiological mechanisms, such as cytokine induction in the neuroplacode, in addition to the "first hit", promote secondary spinal cord injury with functional loss in the late fetal time course. Furthermore, these mediators should be taken into consideration in the development of new therapeutic approaches for open spinal dysraphism.

Influence of Simulated Deep Brain Stimulation on the Expression of Inflammatory Mediators by Human Central Nervous System Cells In Vitro

Deep brain stimulation (DBS) seems to modulate inflammatory processes. Whether this modulation leads to an induction or suppression of inflammatory mediators is still controversially discussed. Most studies of the influence of electrical stimulation on inflammation were conducted in rodent models with direct current stimulation and/or long impulses, both of which differ from the pattern in DBS. This makes comparisons with the clinical condition difficult. We established an in-vitro model that simulated clinical stimulation patterns to investigate the influence of electrical stimulation on proliferation and survival of human astroglial cells, microglia, and differentiated neurons. We also examined its influence on the expression of the inflammatory mediators C-X-C motif chemokine (CXCL)12, CXCL16, CC-chemokin-ligand-2 (CCL)2, CCL20, and interleukin (IL)-1β and IL-6 by these cells using quantitative polymerase chain reaction. In addition, protein expression was assessed by immunofluorescence double staining. In our model, electrical stimulation did not affect proliferation or survival of the examined cell lines. There was a significant upregulation of CXCL12 in the astrocyte cell line SVGA, and of IL-1β in differentiated SH-SY5Y neuronal cells at both messenger RNA and protein levels. Our model allowed a valid examination of chemokines and cytokines associated with inflammation in human brain cells. With it, we detected the induction of inflammatory mediators by electrical stimulation in astrocytes and neurons.

Cannabidiol converts NFκB into a tumor suppressor in glioblastoma with defined antioxidative properties

Background

The transcription factor NF-κB drives neoplastic progression of many cancers including primary brain tumors (glioblastoma [GBM]). Precise therapeutic modulation of NF-κB activity can suppress central oncogenic signaling pathways in GBM, but clinically applicable compounds to achieve this goal have remained elusive.

Methods

In a pharmacogenomics study with a panel of transgenic glioma cells, we observed that NF-κB can be converted into a tumor suppressor by the non-psychotropic cannabinoid cannabidiol (CBD). Subsequently, we investigated the anti-tumor effects of CBD, which is used as an anticonvulsive drug (Epidiolex) in pediatric neurology, in a larger set of human primary GBM stem-like cells (hGSC). For this study, we performed pharmacological assays, gene expression profiling, biochemical, and cell-biological experiments. We validated our findings using orthotopic in vivo models and bioinformatics analysis of human GBM datasets.

Results

We found that CBD promotes DNA binding of the NF-κB subunit RELA and simultaneously prevents RELA phosphorylation on serine-311, a key residue that permits genetic transactivation. Strikingly, sustained DNA binding by RELA-lacking phospho-serine 311 was found to mediate hGSC cytotoxicity. Widespread sensitivity to CBD was observed in a cohort of hGSC defined by low levels of reactive oxygen species (ROS), while high ROS content in other tumors blocked CBD-induced hGSC death. Consequently, ROS levels served as a predictive biomarker for CBD-sensitive tumors.

Conclusions

This evidence demonstrates how a clinically approved drug can convert NF-κB into a tumor suppressor and suggests a promising repurposing option for GBM therapy.

Effects of the Anti-Tumorigenic Agent AT101 on Human Glioblastoma Cells in the Microenvironmental Glioma Stem Cell Niche

Glioblastoma (GBM) is a barely treatable disease due to its profound chemoresistance. A distinct inter- and intratumoral heterogeneity reflected by specialized microenvironmental niches and different tumor cell subpopulations allows GBMs to evade therapy regimens. Thus, there is an urgent need to develop alternative treatment strategies. A promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of gossypol. The present study evaluates the effects of AT101, alone or in combination with temozolomide (TMZ), in a microenvironmental glioma stem cell niche model of two GBM cell lines (U251MG and U87MG). AT101 was found to induce strong cytotoxic effects on U251MG and U87MG stem-like cells in comparison to the respective native cells. Moreover, a higher sensitivity against treatment with AT101 was observed upon incubation of native cells with a stem-like cell-conditioned medium. This higher sensitivity was reflected by a specific inhibitory influence on the p-p42/44 signaling pathway. Further, the expression of CXCR7 and the interleukin-6 receptor was significantly regulated upon these stimulatory conditions. Since tumor stem-like cells are known to mediate the development of tumor recurrences and were observed to strongly respond to the AT101 treatment, this might represent a promising approach to prevent the development of GBM recurrences.

Erroneous expression of NKG2D on granulocytes detected by phycoerythrin-conjugated clone 149810 antibody

BACKGROUND

The activating Natural killer group 2 member D (NKG2D) receptor is typically expressed on NK cells, CD8 T lymphocytes, γδ T cells and small subsets of CD4 T lymphocytes. During the course of an extensive flow cytometry phenotyping of immune cells in the peripheral blood of patients with glioblastoma multiforme (GBM) we noticed an unexpected expression of NKG2D receptor on granulocytes using the phycoerythrin (PE)-conjugated clone 149810 antibody.

METHODS

Peripheral blood samples from 35 patients with GBM and 22 age-matched healthy control (HC) donors were analyzed using flow cytometry, imaging cytometry and real-time quantitative reverse transcription PCR to validate the observed expression of NKG2D receptor on myeloid cells.

RESULTS

Reactivity with PE-149810 was mostly observed on granulocytes from GBM patients on dexamethasone treatment where it correlated with inferior survival rates. Surprisingly, such NKG2D expression on granulocytes was not observed using the allophycocyanin (APC)-conjugate of the same clone 149810 antibody or an indirect staining procedure with unconjugated clone 149810 antibody. Moreover, the PE-conjugate of a different anti-NKG2D clone (1D11) also did not stain granulocytes. Imaging cytometry indicated cell surface and intracellular localization of PE-149810 but not of PE-1D11 in granulocytes.

CONCLUSION

Our results uncover an erroneous and false positive reactivity of PE-labeled (but not of APC-labeled or unconjugated) anti-NKG2D antibody 149810 on granulocytes from dexamethasone-treated GBM patients and raise a note of caution for studies of NKG2D expression on non-lymphoid cells.

Evaluation of a Brown Seaweed Extract from Dictyosiphon foeniculaceus as a Potential Therapeutic Agent for the Treatment of Glioblastoma and Uveal Melanoma

Ingredients of brown seaweed like fucoidans are often described for their beneficial biological effects, that might be interesting for a medical application. In this study, we tested an extract from Dictyosiphon foeniculaceus (DF) to evaluate the effects in glioblastoma and uveal melanoma, looking for a possible anti-cancer treatment. We investigated toxicity, VEGF (vascular endothelial growth factor) secretion and gene expression of tumor and non-tumor cells. SVGA (human fetal astrocytes), the human RPE (retinal pigment epithelium) cell line ARPE-19, the tumor cell line OMM-1 (human uveal melanoma), and two different human primary glioblastoma cultures (116-14 and 118-14) were used. Tests for cell viability were conducted with MTS-Assay (3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium), and the proliferation rate was determined with cell counting. VEGF secretion was assessed with ELISA (enzyme-linked immunosorbent assay). The gene expression of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2) and VEGF-A was determined with real-time qPCR (quantitative polymerase chain reaction). DF lowered the cell viability of OMM-1. Proliferation rates of ARPE-19 and OMM-1 were decreased. The VEGF secretion was inhibited in ARPE-19 and OMM-1, whereas it was increased in SVGA and 116-14. The expression of VEGFR1 was absent and not influenced in OMM-1 and ARPE-19. VEGFR2 expression was lowered in 116-14 after 24 h, whereas VEGF-A was increased in 118-14 after 72 h. The extract lowered cell viability slightly and was anti-proliferative depending on the cell type investigated. VEGF was heterogeneously affected. The results in glioblastoma were not promising, but the anti-tumor properties in OMM-1 could make them interesting for further research concerning cancer diseases in the human eye.

AT101-Loaded Cubosomes as an Alternative for Improved Glioblastoma Therapy

Introduction

AT101, the R-(-)-enantiomer of the cottonseed-derived polyphenol gossypol, is a promising drug in glioblastoma multiforme (GBM) therapy due to its ability to trigger autophagic cell death but also to facilitate apoptosis in tumor cells. It does have some limitations such as poor solubility in water-based media and consequent low bioavailability, which affect its response rate during treatment. To overcome this drawback and to improve the anti-cancer potential of AT101, the use of cubosome-based formulation for AT101 drug delivery has been proposed. This is the first report on the use of cubosomes as AT101 drug carriers in GBM cells.

Materials and Methods

Cubosomes loaded with AT101 were prepared from glyceryl monooleate (GMO) and the surfactant Pluronic F-127 using the top-down approach. The drug was introduced into the lipid prior to dispersion. Prepared formulations were then subjected to complex physicochemical and biological characterization.

Results

Formulations of AT101-loaded cubosomes were highly stable colloids with a high drug entrapment efficiency (97.7%) and a continuous, sustained drug release approaching 35% over 72 h. Using selective and sensitive NMR diffusometry, the drug was shown to be efficiently bound to the lipid-based cubosomes. In vitro imaging studies showed the high efficiency of cubosomal nanoparticles uptake into GBM cells, as well as their marked ability to penetrate into tumor spheroids. Treatment of GBM cells with the AT101-loaded cubosomes, but not with the free drug, induced cytoskeletal rearrangement and shortening of actin fibers. The prepared nanoparticles revealed stronger in vitro cytotoxic effects against GBM cells (A172 and LN229 cell lines), than against normal brain cells (SVGA and HMC3 cell lines).

Conclusion

The results indicate that GMO-AT101 cubosome formulations are a promising basic tool for alternative approaches to GBM treatment.

Liposomal Encapsulated Curcumin Effectively Attenuates Neuroinflammatory and Reactive Astrogliosis Reactions in Glia Cells and Organotypic Brain Slices

Introduction

The polyphenolic spice and food coloring ingredient curcumin has beneficial effects in a broad variety of inflammatory diseases. Amongst them, curcumin has been shown to attenuate microglia reaction and prevent from glial scar formation in spinal cord and brain injuries.

Methods

We developed a protocol for the efficient encapsulation of curcumin as a model for anti-inflammatory drugs yielding long-term stable, non-toxic liposomes with favorable physicochemical properties. Subsequently, we evaluate the effects of liposomal curcumin in experimental models for neuroinflammation and reactive astrogliosis.

Results

We could show that liposomal curcumin can efficiently reduce the reactivity of human microglia and astrocytes and preserve tissue integrity of murine organotypic cortex slices.

Discussion and Perspective

In perspective, we want to administer this curcumin formulation in brain implant coatings to prevent neuroinflammation and glial scar formation as foreign body responses of the brain towards implanted materials.

Dormancy and NKG2D system in brain metastases: Analysis of immunogenicity

Patients with breast cancer (BC) and lung cancer (LC) are prone to developing brain metastases, which are associated with devastating prognoses. Dormant tumor cells, a population of non-apoptotic quiescent cells and immunological escape mechanisms, including the Natural Killer Group 2 member D (NKG2D) receptor-ligand system, represent potential mechanisms of tumor recurrence. To date, the immunological characteristics of dormant tumor cells concerning the NKG2D system in cerebral malignancies are mostly unknown. In the present study, an extensive characterization of dormant and NKG2D ligand (NKG2DL)⁺ cells in cerebral metastases was performed. The expression profiles and localization patterns of various NKG2DL and several dormancy markers were analyzed in solid human brain metastases from patients with BC and LC using immunostaining and reverse transcription-quantitative polymerase chain reaction analyses. Statistical analysis was performed using Student's t-test and Bravais-Pearson correlation analysis. Not only 'peripheral', but also 'central' dormancy markers, which had been previously described in primary brain tumors, were identified in all cerebral metastases at detectable levels at protein and mRNA levels. Notably, the majority of NKG2DL⁺ cells were also positive for 'central' dormancy markers, but not 'peripheral' dormancy markers in both patient groups. This cell population may represent a promising future therapeutic target.

Combined treatment of AT101 and demethoxycurcumin yields an enhanced anti-proliferative effect in human primary glioblastoma cells

PURPOSE

Glioblastoma multiforme (GBM) is a poorly curable disease due to its profound chemoresistance. Despite recent advances in surgery, radiotherapy and chemotherapy, the efficient treatment of GBMs is still a clinical challenge. Beside others, AT101, the R-(-) enantiomer of gossypol, and demethoxycurcumin (DMC), a curcumin-related demethoxy compound derived from Curcuma longa, were considered as possible alternative drugs for GBM therapy.

METHODS

Using different human primary GBM cell cultures in a long-term stimulation in vitro model, the cytotoxic and anti-proliferative effects of single and combined treatment with 5 µM AT101 and 5 µM or 10 µM DMC were investigated. Furthermore, western blots on pAkt and pp44/42 as well as JC-1 staining and real-time RT-PCR were performed to understand the influence of the treatment at the molecular and gene level.

RESULTS

Due to enhanced anti-proliferative effects, we showed that combined therapy with both drugs was superior to a single treatment with AT101 or DMC. Here, by determination of the combination index, a synergism of the combined drugs was detectable. Phosphorylation and thereby activation of the kinases p44/42 and Akt, which are involved in proliferation and survival processes, were inhibited, the mitochondrial membrane potential of the GBM cells was altered, and genes involved in dormancy-associated processes were regulated by the combined treatment strategy.

CONCLUSION

Combined treatment with different drugs might be an option to efficiently overcome chemoresistance of GBM cells in a long-term treatment strategy.

P10.05 NKG2DL expression and dormancy in cerebral metastases: impact of chemotherapeutic treatment

Background: Cerebral metastases are common intracranial lesions and have enormous prognostic impact. In many cases, brain metastases seem to be insensitive to chemotherapeutic treatment and are often source of recurrence. To date, the reasons for this are not entirely known. Dormant tumor cells are a population of non-apoptotic, low proliferating cells, which have the ability to be reactivated and can be the source of recurrence. Another mechanism of tumor cell survival are immunological escape mechanisms, involving the Natural Killer Group 2, member D (nkg2d) receptor-ligand system. In a previous study we were able to show that human brain metastases of pulmonary and breast cancer harbor a significant amount of dormant tumor cells, which often coexpress NKG2D ligands. We now wanted to investigate, whether chemotherapeutic treatment has an effect on expression of dormancy markers and nkg2d ligands.

Materials and Methods: The murine breast cancer cell line E0771 and the murine pulmonary cancer cell line LLC were treated with ascending doses of cisplatin and cyclophosphamid, two chemotherapeutics which are also used in humans, for 2 to 10 days in comparison to negative controls. We performed a cytotoxicity assay. Expression of the dormancy-associated markers pdgf, fgf2, hif1alpha, epha5, h2bk and igfbp5 and the nkg2d ligands mult1, h60a, h60b, h60c and raet1b were analyzed by qrtPCR and immunocytochemistry (IHC).

Results: Cytotoxicity assay revealed, that cells from both lines died significantly after treatment with Cisplatin in comparison to control conditions. Whereas cyclophosphamide had no effect on dormancy marker and nkg2dl expression, treatment with cisplatin led to a significant upregulation of many nkg2dl and dormancy marker expression in LLC and E0771 in a dose and time dependent manner. Results were confirmed via IHC.Conclusions: Although chemotherapy with cisplatin leads to death of many cells in culture, the surviving cells show a high expression of dormancy markers and of certain nkg2d ligands. Not only acquisition of dormancy but also nkg2d ligand expression might play an important role in chemoresistance of brain metastases. Markers from both groups could therefore be effective therapeutic targets.

Linking pre-existing biorepositories for medical research: the PopGen 2.0 Network

The significance of human biorepositories for modern medical research, particularly for comprehensive population-based genetic analyses, is constantly growing. While large and centralized institutions are usually considered best suited to meet the increasing demand for high-quality “biobanks,” most medical research institutions still host rather heterogeneous and fragmented biobanking activities, undertaken by clinical departments with oftentimes rather different scientific scope. Undoubtedly, most clinicians and medical researchers would appreciate infrastructural support in terms of the storage and handling of their biosamples, but they are also likely to expect access to their samples avoiding extensive formal requirements. We report on the establishment of the PopGen 2.0 Network (P2N), an overarching alliance of initially seven biobanks from Northern Germany which adopted a joint but lean governance structure and use-and-access policy for their samples and data. In addition, the members of P2N have pursued an intense collaboration on ethical, legal and social issues and maintain a common IT infrastructure. The implementation of P2N has substantially improved the prospects of biobank-based research at the participating institutions. The network may thus serve as a role model for similar initiatives geared at linking pre-existing biorepositories for the benefit of research quality, efficiency, and transparency.

Expression profiles of pro-inflammatory and pro-apoptotic mediators in secondary tethered cord syndrome after myelomeningocele repair surgery

PURPOSE

The literature on histopathological and molecular changes that might underlie secondary tethered cord syndrome (TCS) after myelomeningocele (MMC) repair surgeries remains sparse. To address this problem, we analyzed specimens, which were obtained during untethering surgeries of patients who had a history of MMC repair surgery after birth.

METHODS

Specimens of 12 patients were analyzed in this study. Clinical characteristics were obtained retrospectively including pre-operative neurological and bowel/bladder-function, contractures and spasticity of lower extremities, leg and back pain, syringomyelia, and conus position on spinal MRI. Cellular marker expression profiles were established. Further, immunoreactivities (IR) of IL-1ß/IL-1R1, TNF-α/TNF-R1, and HIF-1α/-2α were analyzed qualitatively and semi-quantitatively by densitometry. Co-labeling with cellular markers was determined by multi-fluorescence-labeling. Cytokines were further analyzed on mRNA level. Immunostaining for cleaved PARP and TUNEL was performed to detect apoptotic cells.

RESULTS

Astrocytosis, appearance of monocytes, activated microglia, and apoptotic cells in TCS specimens were one substantial finding of these studies. Besides neurons, these cells co-stained with IL-1ß and TNF-α and their receptors, which were found on significantly elevated IR-level and partially mRNA-level in TCS specimens. Staining for HIF-1α/-2α confirmed induction of hypoxia-related factors in TCS specimens that were co-labeled with IL-1ß. Further, hints for apoptotic cell death became evident by TUNEL and PARP-positive cells in TCS neuroepithelia.

CONCLUSIONS

Our studies identified pro-inflammatory and pro-apoptotic mediators that, besides mechanical damaging and along with hypoxia, might promote TCS development. Besides optimizing surgical techniques, these factors should also be taken into account when searching for further options to improve TCS treatment.

APOBEC3B is expressed in human glioma, and influences cell proliferation and temozolomide resistance

Highly malignant gliomas are characterized by pronounced intra‑ and intertumoral heterogeneity. On the genetic level, this heterogeneity may be caused by spontaneous mutation events, but recent studies have reported distinct mutational signatures that may be caused by an enzyme family with cytidine desaminase activity, the apolipoprotein B mRNA editing enzyme catalytic polypeptide‑like (APOBEC) proteins. Among these, APOBEC3B contributes to tumor progression in a variety of types of tumor, including breast cancer. In the present study, the expression of APOBEC3B was detected at the mRNA and protein levels in solid human glioma tissue and human glioma cell lines. In vitro, treatment with temozolomide, the most commonly used chemotherapeutic in glioma therapy, induced APOBEC3B expression. Furthermore, the knockdown of APOBEC3B by clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 resulted in reduced proliferation and enhanced chemosensitivity of glioma cells. Thus, APOBEC3B contributes to glioma progression and may be a future target for therapeutic intervention.

Effects of sequentially applied single and combined temozolomide, hydroxychloroquine and AT101 treatment in a long-term stimulation glioblastoma in vitro model

PURPOSE

Glioblastoma multiforme (GBM) is a poorly curable disease due to its heterogeneity that enables single cells to survive treatment regimen and initiate tumor regrowth. Although some progress in therapy has been achieved in the last years, the efficient treatment of GBMs is still a clinical challenge. Besides the standard therapeutic drug temozolomide (TMZ), quinoline-based antimalarial drugs such as hydroxychloroquine (HCQ) and BH3 mimetics such as AT101 were considered as possible drugs for GBM therapy.

METHODS

We investigated the effects of sequentially applied single and combined TMZ, HCQ and AT101 treatments in a long-term stimulation GBM in vitro model. We performed all investigations in parallel in human astrocytes and two differentially TMZ-responsive human GBM cell lines and adjusted used drug concentrations to known liquor/plasma concentrations in patients. We determined amounts of dead cells and still remaining growth rates and depicted our results in a heatmap-like summary to visualize which sequential long-term treatment schedule seemed to be most promising.

RESULTS

We showed that sequential stimulations yielded higher cytotoxicity and better tumor growth control in comparison to single TMZ treatment. This was especially the case for the sequences TMZ/HCQ and TMZ + AT101/AT101 which was as effective as the non-sequential combination TMZ + AT101. Importantly, those affected both less and more TMZ-responsive glioma cell lines, whilst being less harmful for astrocytes in comparison to single TMZ treatment.

CONCLUSIONS

Sequential treatment with mechanistically different acting drugs might be an option to reduce side effects in long-term treatment, for example in local administration approaches.

Modeling treatment-dependent glioma growth including a dormant tumor cell subpopulation

Background

Tumors comprise a variety of specialized cell phenotypes adapted to different ecological niches that massively influence the tumor growth and its response to treatment.

Methods

In the background of glioblastoma multiforme, a highly malignant brain tumor, we consider a rapid proliferating phenotype that appears susceptible to treatment, and a dormant phenotype which lacks this pronounced proliferative ability and is not affected by standard therapeutic strategies. To gain insight in the dynamically changing proportions of different tumor cell phenotypes under different treatment conditions, we develop a mathematical model and underline our assumptions with experimental data.

Results

We show that both cell phenotypes contribute to the distinct composition of the tumor, especially in cycling low and high dose treatment, and therefore may influence the tumor growth in a phenotype specific way.

Conclusion

Our model of the dynamic proportions of dormant and rapidly growing glioblastoma cells in different therapy settings suggests that phenotypically different cells should be considered to plan dose and duration of treatment schedules.

Spatial and Cellular Expression Patterns of Erythropoietin-Receptor and Erythropoietin during a 42-Day Post-Lesional Time Course after Graded Thoracic Spinal Cord Impact Lesions in the Rat

Erythropoietin (Epo) exhibits promising neuroregenerative potential for spinal cord injury (SCI), and might be involved in other long-term sequelae, such as neuropathic pain development. The current studies investigated the time courses and spatial and cellular patterns of Epo and erythropoietin receptor (EpoR) expression along the spinal axis after graded SCI. Male Long Evans rats received 100 kdyn, 150 kdyn, and 200 kdyn thoracic (T9) contusions from an Infinite Horizon impactor. Sham controls received laminectomies. Anatomical and quantitative immunohistochemical analyses of the EpoR/Epo expression along the whole spinal axis were performed 7, 15, and 42 postoperative days (DPO) after the lesioning. Cellular expression was investigated by double- and triple-labeling for EpoR/Epo with cellular markers and proliferating cells in subgroups of 5-bromo-2-deoxyuridine pre-treated animals. Prolonged EpoR/Epo-expression was confirmed by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Quantified EpoR/Epo immunoreactivities in pain-related spinal cord regions and ventrolateral white matter (VLWM) were correlated with the mechanical sensitivity thresholds and locomotor function of the respective animals. EpoR and Epo were constitutively expressed in the ventral horn neurons and vascular and glial cells in the dorsal columns (DC) and the VLWM. After SCI, in addition to expression in the lesion core, EpoR/Epo immunoreactivities exhibited significant time- and lesion grade-dependent induction in the DC and VLWM along the spinal axis. EpoR and Epo immunoreactive cells were co-stained with markers for astroglial, neural precursor cell and vascular markers. In the VLWM, EpoR- and Epo-positive proliferating cells were co-stained with glial fibrillary acidic protein (GFAP) and nestin. The DC EpoR/Epo immunoreactivities exhibited linear relationships with the behavioral correlates of post-lesional chronic pain development at DPO 42. SCI leads to long-lasting multicellular EpoR/Epo induction beyond the lesion core in the spinal cord regions that are involved in central pain development and regenerative processes. Our studies provide a time frame to investigate the effects of Epo application on motor function or pain development, especially in the later time course after lesioning.

Dormant glioblastoma cells acquire stem cell characteristics and are differentially affected by Temozolomide and AT101 treatment

Cellular dormancy is defined as a state in which cells enter quiescence driven by intrinsic or extrinsic factors, and striking parallels exist between the concept of cellular dormancy in malignancies and the cancer stem cell theory. We showed now that the proven dormancy markers insulin-like growth factor-binding protein 5, ephrin receptor A5 and histone cluster 1 H2B family member K were expressed in human glioblastomas in situ, were located in single tumor cells, and could be co-stained with each other and with the stem cell markers krüppel-like factor 4, octamer binding transcription factor 4 and sex determining region Y-box 2. Human non-stem glioblastoma cell lines and primary cultures were characterized by expression of individual, cell-type specific dormancy- and stemness-associated markers, which were (up)regulated and could be co-stained in a cell-type specific manner upon Temozolomide-induced dormancy in vitro. The induction patterns of dormancy- and stemness-associated markers were reflected by cell-type specific responses to Temozolomide-induced and combined Temozolomide/AT101-mediated cytotoxicity in different glioblastoma cell lines and primary cultures in vitro, and accompanied by higher self-renewal capacity and lower TMZ-sensitivity of Temozolomide-pretreated cells. We postulate that a better understanding of the dormant state of tumor cells is essential to further improve efficiency of treatment.

In-depth immunophenotyping of patients with glioblastoma multiforme: Impact of steroid treatment

Despite aggressive treatment regimens based on surgery and radiochemotherapy, the prognosis of patients with grade IV glioblastoma multiforme (GBM) remains extremely poor, calling for alternative options such as immunotherapy. Immunological mechanisms including the Natural Killer Group 2 member D (NKG2D) receptor-ligand system play an important role in tumor immune surveillance and targeting the NKG2D system might be beneficial. However, before considering any kind of immunotherapy, a precise characterization of the immune system is important, particularly in GBM patients where conventional therapies with impact on the immune system are frequently co-administered. Here we performed an in-depth immunophenotyping of GBM patients and age-matched healthy controls and analyzed NKG2D ligand expression on primary GBM cells ex vivo. We report that GBM patients have a compromised innate immune system irrespective of steroid (dexamethasone) medication. However, dexamethasone drastically reduced the number of immune cells in the blood of GBM patients. Moreover, higher counts of immune cells influenced by dexamethasone like CD45⁺ lymphocytes and non-Vδ2 γδ T cells were associated with better overall survival. Higher levels of NKG2D ligands on primary GBM tumor cells were observed in patients who received radiochemotherapy, pointing towards increased immunogenic potential of GBM cells following standard radiochemotherapy. This study sheds light on how steroids and radiochemotherapy affect immune cell parameters of GBM patients, a pre-requisite for the development of new therapeutic strategies targeting the immune system in these patients.

"Inverse signaling" of the transmembrane chemokine CXCL16 contributes to proliferative and anti-apoptotic effects in cultured human meningioma cells

Background

Chemokines and their receptors play a decisive role in tumor progression and metastasis. We recently found a new signaling mechanism in malignant glioma cells mediated by transmembrane chemokines that we termed “inverse signaling”. According to this hypothesis, soluble (s)-CXCL16 binds to the surface-expressed transmembrane (tm) -CXCL16, and induces signaling and different biological effects in the stimulated cells, so that the transmembrane ligand itself acts as a receptor for its soluble counterpart. Now, we hypothesized that “inverse signaling” via tm-CXCL16 might also take place in meningiomas, a completely different, benign tumor entity.

Methods

We used quantitative reverse-transcription polymerase chain reaction, immunocytochemistry and western blot to detect CXCL16 and CXCR6 in human meningioma cells isolated from 28 human meningiomas. Subsequently, we stimulated cultured human tm-CXCL16-positive, CXCR6-negative meningioma cells with recombinant s-CXCL16 and analyzed binding, signaling and biological effects using RNAi silencing to verify specificity.

Results

In fact, cultured human meningioma cells considerably express CXCL16, but substantially lack CXCR6, the only known CXCL16 receptor. These receptor-negative cells could bind s-CXCL16, and responded to s-CXCL16 application with activation of the intracellular kinases ERK1/2 und Akt. As a consequence, we observed increased proliferation and rescue of apoptosis of cultured meningioma cells. Since binding and signaling were abolished by siRNA silencing, we concluded that tm-CXCL16 specifically acts as a receptor for s-CXCL16 also in human meningioma cells.

Conclusion

These findings underline our recent report on the mechanism of inverse signaling as a broad biological process also observable in more benign tumor cells and contributing to tumor progression.

Isolation and Characterization of Fast-Migrating Human Glioma Cells in the Progression of Malignant Gliomas

Gliomas are the most common primary brain tumors. The most malignant form, the glioblastoma multiforme (GBM; WHO IV), is characterized by an invasive phenotype, which enables the tumor cells to infiltrate into adjacent brain tissue. When investigating GBM migration and invasion properties in vitro, in most cases GBM cell lines were analyzed. Comprehensive investigations focusing on progression-dependent characteristics of migration processes using fresh human glioma samples of different malignancy grades do not exist. Thus, we isolated fast-migrating tumor cells from fresh human glioma samples of different malignancy grades (astrocytomas WHO grade II, grade III, GBM, and GBM recurrences) and characterized them with regard to the transcription of genes involved in the migration and invasion, tumor progression, epithelial-to-mesenchymal transition, and stemness. In addition, we transferred our results to GBM cell lines and glioma stem-like cells and examined the influence of temozolomide on the expression of the above-mentioned genes in relation to migratory potential. Our results indicate that "evolutionary-like" expression alterations occur during glioma progression when comparing slow- and fast-migrating cells of fresh human gliomas. Furthermore, a close relation between migratory and stemness properties seems to be most likely. Variations in gene expression were also identified in GBM cell lines, not only when comparing fast- and slow-migrating cells but also regarding temozolomide-treated and untreated cells. Moreover, these differences coincided with the expression of stem cell markers and their migratory potential. Expression of migration-related genes in fast-migrating glioma cells is not only regulated in a progression-dependent manner, but these cells are also characterized by specific stem cell-like features.

Stem cell markers in glioma progression and recurrence

Aggressive cancer cells show histological similarities to embryonic stem cells. As differentiated cells can re-acquire pluripotency and self-renewal by transfection with the transcription factors OCT4, SOX2, KLF4 and MYC, with Nanog as readout for success, we comprehensively investigated their occurrence and frequency in human astrocytomas of different malignancy grades, primary and matched recurrent glioblastomas, short- and long-term glioblastoma cultures and glioma cell lines. Among astrocytomas, mRNA expression of OCT4, MYC and (less robust) KLF4 increased with malignancy, while in recurrent glioblastomas MYC expression slightly decreased. Correlation analysis revealed distinct positive correlation between distinct stem cell markers, and this effect was most prominent in the recurrent glioblastoma cohort. In situ, embryonic stem cell factors were found also in more differentiated tumor regions. Respective cells were rarely actively proliferating and showed single or combined expression signatures, which, at least in parts, corresponded to observed positive correlations of mRNA expression. However, a 'master-marker' defining the complete glioma stem cell subset could not be confirmed. In glioma cell lines, long- and short-term cultures, embryonic markers were detected at comparable levels. Upon exposure to temozolomide, increased expression of KLF4 (and lesser Nanog and OCT4) was observed. Experimental intrinsic overexpression of SOX2, KLF4 or OCT4 did not affect the other stem cell factors. The embryonic stem cell factors comprehensively investigated in this project can control self-renewal and pluripotency, and therefore tumorigenicity. They should be considered for the development of future diagnostic and therapeutic strategies.

Cellular Profiles and Molecular Mediators of Lesion Cascades in the Placode in Human Open Spinal Neural Tube Defects

Myelomeningoceles (mmc) are clinically challenging CNS malformations. Although improvement in their management has been achieved with respect to antenatal diagnosis, prevention, and fetal surgery, the cellular mechanisms of damage in the neural placode are poorly understood. We aimed to identify cellular and molecular factors in lesion amplifying cascades in mmc placodes. Seventeen mmc specimens obtained during reconstructive surgery that harbored sufficient neuroepithelial tissue were investigated. Normal adult and stillborn spinal cord tissue served as controls. Placodes exhibited similar cellular profiles with consistent neuronal marker expression, elevated GFAP-/vimentin immunoreactivity in all, and CD3/CD11b/CD68-immunolabeling in some cases. Increased expression of pro-inflammatory (tumor necrosis factor, interleukin-1β [Il-1β]/IL-1 receptor type 1 [IL-R1]) and neuroprotective erythropoietin/erythropoietin receptor (Epo/EpoR) cytokines was detected by immunohistochemistry, double-fluorescence labeling, and real-time RT-PCR. In all cases, there was a multi-cellular induction of IL-1β and IL1-R1. EpoR and Epo immunoreactivity was elevated in some cases with neuronal expression patterns. Epo was further co-expressed with HIF-1/-2α, which paralleled Epo induction in the corresponding placodes. These observations confirm the induction of cellular and molecular alterations in human mmc placodes that resemble the secondary lesion cascades induced by spinal cord injury. The pro-inflammatory and neuroprotective cytokine expression in mmc placodes may represent new targets for the treatment of open neural tube defects.

Down regulation of Akirin-2 increases chemosensitivity in human glioblastomas more efficiently than Twist-1

The Twist-1 transcription factor and its interacting protein Akirin-2 regulate apoptosis. We found that in glioblastomas, highly malignant brain tumors, Akirin-2 and Twist-1 were expressed in glial fibrillary acidic protein positive tumor regions as well as in tumor endothelial cells and infiltrating macrophages / microglia. Temozolomide (TMZ) induced the expression of both molecules, partly shifting their nuclear to cytosolic localization. The knock-down (kd) of Akirin-2 increased the activity of cleaved (c)Caspase-3/-7, the amounts of cCaspases-3, -7 and cPARP-1 and resulted in an increased number of apoptotic cells after TMZ exposure. Glioblastoma cells containing decreased amounts of Akirin-2 after kd contained increased amounts of cCaspase-3 as determined by the ImageStream^x Mark II technology. For Twist-1, similar results were obtained with the exception that the combination of TMZ treatment and Twist-1 kd failed to significantly reduce chemoresistance compared with controls. This could be attributed to a cell population containing only slightly increased cCaspase-3 together with decreased Twist-1 levels, which was clearly larger than the respective population observed under Akirin-2 kd. Our results showed that, compared with Twist-1, Akirin-2 is the more promising target for RNAi strategies antagonizing Twist-1/Akirin-2 facilitated glioblastoma cell survival.

Differential expression of CXCR4 and CXCR7 with various stem cell markers in paired human primary and recurrent glioblastomas

The chemokine CXCL12 (also termed SDF-1, stromal cell-derived factor-1) and its receptors CXCR4 and CXCR7 are known to play a pivotal role in tumor progression including glioblastomas (GBM). Previous investigations focused on the expression and functional roles of CXCR4 and CXCR7 in different GBM cell subpopulations, but comparative analysis in matched primary versus recurrent GBM samples are still lacking. Thus, here we investigated the expression of CXCR4 and CXCR7 on mRNA and protein level using matched primary and recurrent GBM pairs. Additionally, as GBM CXCR4-positive stem-like cells are supposed to give rise to recurrence, we compared the expression of both receptors in primary and recurrent GBM cells expressing either neural (MUSASHI-1) or embryonic stem cell markers (KLF-4, OCT-4, SOX-2, NANOG). We were able to show that both CXCR4 and CXCR7 were expressed at considerable mRNA and protein levels. CXCR7 was downregulated in relapse cases, and different groups regarding CXCR4/CXCR7 expression differences between primary and recurrent samples could be distinguished. A co-expression of both receptors was rare. In line with this, CXCR4 was co-expressed with all investigated neural and embryonic stem cell markers in both primary and recurrent tissues, whereas CXCR7 was mostly found on stem cell marker-negative cells, but was co-expressed with KLF-4 on a distinct GBM cell subpopulation. These results point to an individual role of CXCR4 and CXCR7 in stem cell marker-positive GBM cells in glioma progression and underline the opportunity to develop new therapeutic tools for GBM intervention.

Transmembrane chemokines act as receptors in a novel mechanism termed inverse signaling

The transmembrane chemokines CX3CL1/fractalkine and CXCL16 are widely expressed in different types of tumors, often without an appropriate expression of their classical receptors. We observed that receptor-negative cancer cells could be stimulated by the soluble chemokines. Searching for alternative receptors we detected that all cells expressing or transfected with transmembrane chemokine ligands bound the soluble chemokines with high affinity and responded by phosphorylation of intracellular kinases, enhanced proliferation and anti-apoptosis. This activity requires the intracellular domain and apparently the dimerization of the transmembrane chemokine ligand. Thus, shed soluble chemokines can generate auto- or paracrine signals by binding and activating their transmembrane forms. We term this novel mechanism “inverse signaling”. We suppose that inverse signaling is an autocrine feedback and fine-tuning system in the communication between cells that in tumors supports stabilization and proliferation.

DOI:http://dx.doi.org/10.7554/eLife.10820.001

The cells that make up an animal need to communicate with each other for a variety of purposes, including controlling the growth and repair of tissues. Commonly, such signaling involves ‘ligand’ molecules binding to specific ‘receptor’ proteins embedded in the cell membrane. When a ligand docks to the right receptor protein, the parts of the receptor inside the cell change shape. This activates signaling pathways within that cell.

Types of ligands called transmembrane ligands are found embedded in cell membranes. Some cancer cells have high levels of transmembrane ligands called CXCL16 and CX3CL1 but do not produce the corresponding receptors for these molecules. The part of these ligands that sits outside of the cells can also be separated from the rest of the molecule to produce a soluble ligand that can move around outside the cell.

By studying cancer cells using microscopy and biochemical approaches, Hattermann, Gebhardt et al. now show that the soluble forms of CXCL16 and CX3CL1 bind to their transmembrane equivalents. This activates signaling pathways that promote cell growth and make the cancer cells more resistant to cell death. However, this signaling did not occur if the transmembrane ligands were altered to lack the part normally found inside the cell, which suggests that transmembrane CXCL16 and CX3CL1 act as receptors.

It was not previously known that a soluble ligand could activate its transmembrane equivalent. Hattermann, Gebhardt et al. have named this process “inverse signaling”, and suggest that it helps to fine-tune the communication between cells. Future experiments will need to study the importance of inverse signaling in living animals and investigate how it works alongside other signaling methods.

DOI:http://dx.doi.org/10.7554/eLife.10820.002

NKG2D- and T-cell receptor-dependent lysis of malignant glioma cell lines by human γδ T cells: Modulation by temozolomide and A disintegrin and metalloproteases 10 and 17 inhibitors

The interaction of the MHC class I-related chain molecules A and B (MICA and MICB) and UL-16 binding protein (ULBP) family members expressed on tumor cells with the corresponding NKG2D receptor triggers cytotoxic effector functions in NK cells and γδ T cells. However, as a mechanism of tumor immune escape, NKG2D ligands (NKG2DLs) can be released from the cell surface. In this study, we investigated the NKG2DL system in different human glioblastoma (GBM) cell lines, the most lethal brain tumor in adults. Flow cytometric analysis and ELISA revealed that despite the expression of various NKG2DLs only ULBP2 is released as a soluble protein via the proteolytic activity of "a disintegrin and metalloproteases" (ADAM) 10 and 17. Moreover, we report that temozolomide (TMZ), a chemotherapeutic agent in clinical use for the treatment of GBM, increases the cell surface expression of NKG2DLs and sensitizes GBM cells to γδ T cell-mediated lysis. Both NKG2D and the T-cell receptor (TCR) are involved. The cytotoxic activity of γδ T cells toward GBM cells is strongly enhanced in a TCR-dependent manner by stimulation with pyrophosphate antigens. These data clearly demonstrate the complexity of mechanisms regulating NKG2DL expression in GBM cells and further show that treatment with TMZ can increase the immunogenicity of GBM. Thus, TMZ might enhance the potential of the adoptive transfer of ex vivo expanded γδ T cells for the treatment of malignant glioblastoma.

Epithelial-to-mesenchymal transition in paired human primary and recurrent glioblastomas

Patients with highly malignant glioblastomas have a short median survival time mainly due to aggressive relapses after therapeutic treatment. Beside others, they achieve their progressive character via epithelial-to-mesenchymal transition (EMT). However, comprehensive investigations on EMT in paired primary-recurrent glioblastoma pairs are presently not available. Thus, in our present study we examined the expression profile of different EMT-markers in 17 matched primary and recurrent glioblastomas by qPCR and double-immunofluorescence stainings to identify EMT marker expressing cell types. Additionally, we analyzed the influence of temozolomide on EMT marker expression in vitro. In comparison to primary tumors, expression of β-catenin (p<0.05), Snail1 (p<0.05), Snail2/Slug (p<0.05), biglycan (p<0.05) and Twist1 (p<0.01) was downregulated in recurrence whereas L1CAM showed upregulation (p<0.05; qPCR). Expression of desmoplakin, vimentin, fibronectin and TGF-β1 with its receptors TGF-βR1 and TGF-βR2 was almost unchanged. Comparing each individual pair, five different 'EMT groups' within our glioblastoma collective were identified according to the regulation of mRNA expression of GFAP, desmoplakin, Snail1, Snail2, Twist1 and vimentin. Additionally, double-stainings of EMT markers in combination with cell specific markers (glial fibrillary acidic protein, CD11b, von Willebrand factor) revealed that EMT markers were expressed in a complex pattern with all three cellular types as possible sources. Temozolomide treatment significantly induced mRNA expression of nearly all investigated EMT markers in T98G glioma cells. Thus, EMT seems to be involved in glioma progression in a complex way requiring an individualized analysis, and is influenced by commonly used therapeutic options in glioma therapy.

Impact of chemokines on the properties of spinal cord-derived neural progenitor cells in a rat spinal cord lesion model

The existence of endogenous neural progenitor cells (NPCs) in the adult spinal cord (sc) provides the potential for tailored repair therapies after spinal cord injury (SCI). This study investigates the impact of inflammatory mediators on properties of NPC cultures derived from adult rats after SCI. The Infinite Horizon impactor was used to apply 200-kdyn thoracic sc lesions in adult rats. Control groups received laminectomies to equivalent sc regions. Thoracic sc segments were taken for neurosphere cell cultures. Cell proliferation was found to be significantly higher in lesion groups. Neurosphere-derived cells differentiated into neurons, oligodendroglia, and astroglia. Lesion cultures exhibited significantly higher amounts of glial fibrillary acidic protein (GFAP) mRNA (P < 0.0005) and β-III-tubulin mRNA (P < 0.05) compared with sham animals. Neurospheres from different treatment groups exhibited the same amounts of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 mRNA. C-C chemokine receptor (CCR) expression on neurospheres was examined by real-time RT-PCR. CCR1 was expressed most consistently in mRNA levels in neurospheres from both treatment groups. After cell differentiation, CCR1 mRNA amounts decreased. CCR1 was detectable by immunohistochemistry in neurospheres and differentiated cells of both groups. Application of CCL3 during differentiation cycles led to significantly higher GFAP mRNA amounts in sham animals compared with CCL3-free cultures; in contrast, CCL3 had no impact on cell differentiation in the lesion group. In conclusion, impact SCI alters differentiation tendencies and proliferation rates of adult-derived sc NPCs. Thereby, CCR1/CCL3 promotes specifically astroglial differentiation of NPCs, which provides a potential target for future neurorestorative approaches.

Expression of DNA mismatch repair proteins MLH1, MSH2, and MSH6 in recurrent glioblastoma

OBJECTIVES

Methylated O6-methylguanin-DNA-methytransferase (MGMT) promoter methylation is associated with survival in patients with glioblastoma. Current evidence suggests that further mismatch repair genes play a pivotal role in the tumor response to treatment. Candidate genes are MLH1, MSH2, and MSH6. Formerly, we found evidence of prognostic impact of MLH1 and MSH6 immunohistochemical expression in a small series of patients with initial glioblastoma.

METHODS

Two hundred and eleven patients were included who underwent macroscopically total removal of primary glioblastoma and at least one re-craniotomy for recurrence. Immunohistochemical staining was performed on paraffin-embedded specimens of initial tumors with specific antibodies against MLH1, MSH2, and MSH6. RESULTS were compared to the Ki67 proliferation index and patient survival. Additionally, fresh frozen samples from 16 paired initial and recurrent specimens were examined using real-time reverse transcription polymerase chain reaction (RT-PCR) with specific primers against MLH1, MSH2, and MSH6. RESULTS were compared to MGMT status and survival.

RESULTS

(1) Immunohistochemical expression of MSH6 was significantly associated with the Ki67 proliferation index (P<0.001) but not with survival. (2) PCR revealed two patients with increasing expression of MLH1, MLH2, and MSH6 over treatment combined with lacking MGMT methylation. In another two patients, decreased MLH1, MSH2, and MSH6 expression was observed in combination with MGMT promoter methylation.

DISCUSSION

Our data indicate that there may be glioblastoma patient subgroups characterized by MMR-expression changes beyond MGMT promoter methylation. The immunohistochemical expression of MLH1, MSH2, and MSH6 in initial glioblastoma is not associated with patient survival.

M1 and M2: there is no "good" and "bad"-How macrophages promote malignancy-associated features in tumorigenesis

We recently identified tumor-associated macrophages from pancreatic ductal adenocarcinoma sharing pro- and anti-inflammatory characteristics. Already in residence in the setting of chronic pancreatitis, local macrophages confer malignancy-associated features to premalignant pancreatic ductal epithelial cells by both promoting and inhibiting inflammation, either of which can foster malignant conversion. Our findings support the concept that contrasting modes of inflammation can promote tumorigenesis.

Chemokine expression profile of freshly isolated human glioblastoma-associated macrophages/microglia

Several studies have substantiated the hypothesis that tumor progression is not only driven by the tumor cells themselves but also by their interaction with intrinsic and surrounding stromal cells. Tumor-associated macrophages and microglial cells (TAMs) represent one major stromal cell component of glioblastomas. Additionally, in many gliomas, chemokines are highly expressed and some chemokines were already linked to settlement of TAMs in tumors. However, although chemoattraction mechanisms mediated by chemokines and their receptors are well documented, information on their expression and role in TAMs, particularly in patients, is limited. Therefore, we investigated the transcription of the chemokine-receptor combinations CXCL12-CXCR4-CXCR7, CXCL16-CXCR6 and CX3CL1-CX3CR1 in freshly isolated TAMs from 20 human glioblastomas in relation to in vitro polarized M1- and M2-macrophages. We demonstrated that TAMs express both M1- and M2-markers. Compared to in vitro polarized macrophages, the M1-marker interleukin (IL)-6 was similarly expressed, whereas IL-1β and tumor necrosis factor (TNF)-α were found at lower levels. The M2-marker IL-10 was comparably expressed, while CD163 and transforming growth factor (TGF)-β were detected with one tenth lower intensities in TAMs. All investigated chemokines/receptors were transcribed at moderate to high levels in TAMs as well as in vitro polarized macrophages. However, CX3CR1 was markedly higher and CXCR7 was somewhat higher expressed in TAMs, whereas M2-macrophages were characterized by the highest CXCL12 and a moderate CX3CL1 expression. Collectively, TAMs share properties of M1- and M2-macrophages and show a considerably higher expression of the chemokine receptors CXCR7 and CX3CR1.

Effects of the chemokine CXCL12 and combined internalization of its receptors CXCR4 and CXCR7 in human MCF-7 breast cancer cells

The chemokine CXCL12 (stromal cell-derived factor-1, SDF-1) and its receptor CXCR4 play a major role in tumor initiation, promotion, progression and metastasis, especially for breast cancer cells. Recently, CXCR7 has been identified as a second receptor for CXCL12; nevertheless, it also binds CXCL11 (interferon-inducible T cell α chemoattractant, I-TAC). However, little is known about the co-expression of the two receptors and their interactions. Quantitative reverse transcription plus the polymerase chain reaction has demonstrated that both receptors are frequently co-expressed in breast cancer cell lines, whereas other tumor cell lines often express only one of them. For interaction studies, we chose MCF-7 breast cancer cells, since they highly express CXCR4 and CXCR7 at the protein level but not CXCR3 (another target for CXCL11). Immunofluorescence and gold–labeling by light and electron microscopy, respectively, revealed that both receptors were localized at the cell surface in non-stimulated cells. After exposure to CXCL12 or CXCL11, the receptors were rapidly internalized alone or in close proximity. Stimulation with the CXCR4- or CXCR7-selective non-peptide antagonists AMD3100 and CCX733 resulted not only in single internalization but partly also in co-internalization of the two receptors. Furthermore, both chemokine ligands reduced staurosporine-induced apoptosis and caspase-3/7 activation; however, the selective inhibitors merely had partial inhibitory effects on these biological responses. Our findings suggest that CXCR4 and CXCR7 closely interact in breast cancer cells. Both are co-internalized, transduce signals and induce further biological effects partly independently of a selective stimulus or antagonist.

Tumor-associated macrophages exhibit pro- and anti-inflammatory properties by which they impact on pancreatic tumorigenesis

Pancreatic ductal adenocarcinoma (PDAC) still ranking 4th in the order of fatal tumor diseases is characterized by a profound tumor stroma with high numbers of tumor-associated macrophages (TAMs). Driven by environmental factors, monocytes differentiate into M1- or M2-macrophages, the latter commonly regarded as being protumorigenic. Because a detailed analysis of TAMs in human PDAC development is still lacking, freshly isolated PDAC-derived TAMs were analyzed for their phenotype and impact on epithelial-mesenchymal-transition (EMT) of benign (H6c7) and malignant (Colo357) pancreatic ductal epithelial cells. TAMs exhibited characteristics of M1-macrophages (expression of HLA-DR, IL-1β, or TNF-α) and M2-macrophages (expression of CD163 and IL-10). In the presence of TAMs, H6c7, and Colo357 cells showed an elongated cell shape along with an increased expression of mesenchymal markers such as vimentin and reduced expression of epithelial E-cadherin. Similar to TAMs, in vitro generated M1- and M2-macrophages both mediated EMT in H6c7 and Colo357 cells. M1-macrophages acquired M2-characteristics during coculture that could be prevented by GM-CSF treatment. However, M1-macrophages still potently induced EMT in H6c7 and Colo357 cells although lacking M2-characteristics. Overall, these data demonstrate that TAMs exhibit anti- as well as proinflammatory properties that equally contribute to EMT induction in PDAC initiation and development.

Topical application of phosphatidyl-inositol-3,5-bisphosphate for acute lung injury in neonatal swine

Hypoxemic respiratory failure of the neonatal organism involves increased acid sphingomyelinase (aSMase) activity and production of ceramide, a second messenger of a pro-inflammatory pathway that promotes increased vascular permeability, surfactant alterations and alveolar epithelial apoptosis. We comparatively assessed the benefits of topical aSMase inhibition by either imipramine (Imi) or phosphatidylinositol-3,5-bisphosphate (PIP2) when administered into the airways together with surfactant (S) for fortification. In this translational study, a triple-hit acute lung injury model was used that entails repeated airway lavage, injurious ventilation and tracheal lipopolysaccharide instillation in newborn piglets subject to mechanical ventilation for 72 hrs. After randomization, we administered an air bolus (control), S, S+Imi, or S+PIP2. Only in the latter two groups we observed significantly improved oxygenation and ventilation, dynamic compliance and pulmonary oedema. S+Imi caused systemic aSMase suppression and ceramide reduction, whereas the S+PIP2 effect remained compartmentalized in the airways because of the molecule's bulky structure. The surfactant surface tensions improved by S+Imi and S+PIP2 interventions, but only to a minor extent by S alone. S+PIP2 inhibited the migration of monocyte-derived macrophages and granulocytes into airways by the reduction of CD14/CD18 expression on cell membranes and the expression of epidermal growth factors (amphiregulin and TGF-β1) and interleukin-6 as pro-fibrotic factors. Finally we observed reduced alveolar epithelial apoptosis, which was most apparent in S+PIP2 lungs. Exogenous surfactant “fortified” by PIP2, a naturally occurring surfactant component, improves lung function by topical suppression of aSMase, providing a potential treatment concept for neonates with hypoxemic respiratory failure.

Expression of the chemokines CXCL12 and CX3CL1 and their receptors in human nerve sheath tumors

Peripheral nerve sheath tumors are in most cases slowly growing neoplasms that can be adequately cured by surgical resection. However, facing the risk of a neurosurgical intervention and the trend of multiple relapses of nerve sheath tumors the development of additional therapy strategies seems to be favourable, and therefore substantiated knowledge of molecular and cellular mechanisms in nerve sheath tumors should be achieved. Here, we firstly describe the expression of the chemokines CXCL12 (SDF-1) and CX3CL1 (fractalkine) and their respective receptors CXCR4, CXCR7 and CX3CR1 in different entities of human nerve sheath tumors and normal control tissues. Both ligands and their receptors are expressed in high to moderate levels on mRNA and protein level in benign and malignant nerve sheath tumors. While CXCL12 was mainly found in schwannoma cells (S100⁺) in situ, its receptor CXCR4 is also partly found on CD11b-positive macrophages / microglia and its alternative receptor CXCR7 is also expressed by endothelial cells and macrophages. CX3CL1 is expressed by parts of the schwannoma and endothelial cells, whereas its receptor CX3CR1 is expressed by nearly all tumor cells and macrophages, but not by endothelial cells. Taken together, we could show the presence of CXCL12 and CX3CL1 and their respective receptors in benign and malignant human nerve sheath tumors. Further investigations may show their functional role in health and disease.

The CXCL16-CXCR6 chemokine axis in glial tumors

Since chemokines and their receptors play a pivotal role in tumors, we investigated the CXCL16-CXCR6-axis in human astroglial tumors. The transmembrane chemokine CXCL16 is heavily expressed by tumor, microglial and endothelial cells in situ and in vitro. In contrast, the receptor CXCR6 is restricted in glioblastomas to a small subset of proliferating cells positive for the stem-cell markers Musashi, Nanog, Sox2 and Oct4. In particular, the vast majority (about 90%) of Musashi-positive cells stained also for CXCR6. Thus, CXCL16 is highly expressed by glial tumor and stroma cells whereas CXCR6 defines a subset of cells with stem cell character.