[Show abstract][Hide abstract] ABSTRACT: The Sonic Hedgehog (SHH) pathway plays a central role in the developing mammalian CNS. In our study, we aimed to investigate the spatiotemporal SHH pathway expression pattern in human fetal brains. We analyzed 22 normal fetal brains for Shh, Patched, Smoothened, and Gli1-3 expression by immunohistochemistry. In the telencephalon, strongest expression of Shh, Smoothened, and Gli2 was found in the cortical plate (CP) and ventricular zone. Patched was strongly upregulated in the ventricular zone and Gli1 in the CP. In the cerebellum, SHH pathway members were strongly expressed in the external granular layer (EGL). SHH pathway members significantly decreased over time in the ventricular and subventricular zone and in the cerebellar EGL, while increasing levels were found in more superficial telencephalic layers. Our findings show that SHH pathway members are strongly expressed in areas important for proliferation and differentiation and indicate a temporal expression gradient in telencephalic and cerebellar layers probably due to decreased proliferation of progenitor cells and increased differentiation. Our data about the spatiotemporal expression of SHH pathway members in the developing human brain serves as a base for the understanding of both normal and pathological CNS development.
[Show abstract][Hide abstract] ABSTRACT: Current pathological diagnostics include the analysis of (epi-)genetic alterations as well as oncogenic pathways. Deregulated mammalian target of rapamycin complex 1 (mTORC1) signaling has been implicated in a variety of cancers including malignant gliomas and is considered a promising target in cancer treatment. Monitoring of mTORC1 activity before and during inhibitor therapy is essential. The aim of our study is to provide a recommendation and report on pitfalls in the use of phospho-specific antibodies against mTORC1-targets phospho-RPS6 (Ser235/236; Ser240/244) and phospho-4EBP1 (Thr37/46) in formalin fixed, paraffin embedded material.
Primary, established cell lines and brain tumor tissue from routine diagnostics were assessed by immunocyto-, immunohistochemistry, immunofluorescent stainings and immunoblotting. For validation of results, immunoblotting experiments were performed. mTORC-pathway activation was pharmacologically inhibited by torin2 and rapamycin. Torin2 treatment led to a strong reduction of signal intensity and frequency of all tested antibodies. In contrast phospho-4EBP1 did not show considerable reduction in staining intensity after rapamycin treatment, while immunocytochemistry with both phospho-RPS6-specific antibodies showed a reduced signal compared to controls. Staining intensity of both phospho-RPS6-specific antibodies did not show considerable decrease in stability in a timeline from 0-230 minutes without tissue fixation, however we observed a strong decrease of staining intensity in phospho-4EBP1 after 30 minutes. Detection of phospho-signals was strongly dependent on tissue size and fixation gradient. mTORC1-signaling was significantly induced in glioblastomas although not restricted to cancer cells but also detectable in non-neoplastic cells.
Here we provide a recommendation for phospho-specific immunohistochemistry for patient-orientated therapy decisions and monitoring treatment response.
PLoS ONE 05/2015; 10(5):e0127123. DOI:10.1371/journal.pone.0127123 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hypoxia is a key driver for infiltrative growth in experimental gliomas. It has remained elusive whether tumor hypoxia in glioblastoma patients contributes to distant or diffuse recurrences. We therefore investigated the influence of perioperative cerebral ischemia on patterns of progression in glioblastoma patients.
We retrospectively screened MRI scans of 245 patients with newly diagnosed glioblastoma undergoing resection for perioperative ischemia near the resection cavity. 46 showed relevant ischemia nearby the resection cavity. A control cohort without perioperative ischemia was generated by a 1:1 matching using an algorithm based on gender, age and adjuvant treatment. Both cohorts were analyzed for patterns of progression by a blinded neuroradiologist.
The percentage of diffuse or distant recurrences at first relapse was significantly higher in the cohort with perioperative ischemia (61.1%) compared to the control cohort (19.4%). The results of the control cohort matched well with historical data. The change in patterns of progression was not associated with a difference in survival.
This study reveals an unrecognized association of perioperative cerebral ischemia with distant or diffuse recurrence in glioblastoma. It is the first clinical study supporting the concept that hypoxia is a key driver of infiltrative tumor growth in glioblastoma patients.
[Show abstract][Hide abstract] ABSTRACT: Flubendazole was shown to exert anti-leukaemia and anti-myeloma activity through inhibition of microtubule function. Here, flubendazole was tested for its effects on the viability of in total 461 cancer cell lines. Neuroblastoma was identified as highly flubendazole-sensitive cancer entity in a screen of 321 cell lines from 26 cancer entities. Flubendazole also reduced the viability of five primary neuroblastoma samples in nanomolar concentrations thought to be achievable in humans and inhibited vessel formation and neuroblastoma tumour growth in the chick chorioallantoic membrane assay. Resistance acquisition is a major problem in high-risk neuroblastoma. 119 cell lines from a panel of 140 neuroblastoma cell lines with acquired resistance to various anti-cancer drugs were sensitive to flubendazole in nanomolar concentrations. Tubulin-binding agent-resistant cell lines displayed the highest flubendazole IC50 and IC90 values but differences between drug classes did not reach statistical significance. Flubendazole induced p53-mediated apoptosis. The siRNA-mediated depletion of the p53 targets p21, BAX, or PUMA reduced the neuroblastoma cell sensitivity to flubendazole with PUMA depletion resulting in the most pronounced effects. The MDM2 inhibitor and p53 activator nutlin-3 increased flubendazole efficacy while RNAi-mediated p53-depletion reduced its activity. In conclusion, flubendazole represents a potential treatment option for neuroblastoma including therapy-refractory cells.
[Show abstract][Hide abstract] ABSTRACT: Background
The Wnt/beta-catenin and the Hedgehog (Hh) pathway interact in various cell types while eliciting opposing or synergistic cellular effects. Both pathways are known as exclusive drivers of two distinct molecular subtypes of medulloblastoma (MB).In sonic hedgehog (Shh)-driven MB, activation of Wnt signaling has been shown to suppress tumor growth by either beta-catenin-dependent or -independent inhibition of Shh signaling. However, mechanistic insight in how beta-catenin inhibits the Hh pathway is not known.FindingsHere we show that beta-catenin stabilization by the glycogen synthase kinase 3 inhibitor lithium chloride (LiCl) reduced growth of primary hedgehog-driven MB tumor spheres from patched heterozygous mice (Ptch+/-) in vitro. LiCl treatment of MB spheres down-regulated the Hh target Gli1, whereas the repressive Gli3 protein (Gli3R) was increased. Mechanistically, we show by co-immunoprecipitation and proximity ligation assay that stabilized beta-catenin physically interacts with Gli1, leading to Gli1 sequestration and inhibition of its transcriptional activity. Reduction of Hh signaling upon LiCl stimulation resulted in reduced proliferation, sphere self renewal, a G2/M arrest and induction of a senescent-like state, indicated by p21 upregulation and by increased staining of senescence-associated beta-galactosidase (SA-betaGal). Moreover, LiCl treatment of subcutaneously transplanted MB cells significantly reduced tumor initiation defined as ¿tumor take¿. Although tumor progression was similar, LiCl-treated tumors showed decreased mitotic figures and phospho-histone H3 staining.Conclusion
We propose that beta-catenin stabilization increases its physical interaction with Gli1, leading to Gli1 degradation and inhibition of Hh signaling, thereby promoting tumor cell senescence and suppression of ¿tumor take¿ in mice.
Molecular Cancer 02/2015; 14(1):17. DOI:10.1186/s12943-015-0294-4 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anti-angiogenic therapy in glioblastoma (GBM) has unfortunately not led to the anticipated improvement in patient prognosis. We here describe how human GBM adapts to bevacizumab treatment at the metabolic level. By performing 13C6-glucose metabolic flux analysis, we show for the first time that the tumors undergo metabolic re-programming toward anaerobic metabolism, thereby uncoupling glycolysis from oxidative phosphorylation. Following treatment, an increased influx of 13C6-glucose was observed into the tumors, concomitant to increased lactate levels and a reduction of metabolites associated with the tricarboxylic acid cycle. This was confirmed by increased expression of glycolytic enzymes including pyruvate dehydrogenase kinase in the treated tumors. Interestingly, l-glutamine levels were also reduced. These results were further confirmed by the assessment of in vivo metabolic data obtained by magnetic resonance spectroscopy and positron emission tomography. Moreover, bevacizumab led to a depletion in glutathione levels indicating that the treatment caused oxidative stress in the tumors. Confirming the metabolic flux results, immunohistochemical analysis showed an up-regulation of lactate dehydrogenase in the bevacizumab-treated tumor core as well as in single tumor cells infiltrating the brain, which may explain the increased invasion observed after bevacizumab treatment. These observations were further validated in a panel of eight human GBM patients in which paired biopsy samples were obtained before and after bevacizumab treatment. Importantly, we show that the GBM adaptation to bevacizumab therapy is not mediated by clonal selection mechanisms, but represents an adaptive response to therapy.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-014-1352-5) contains supplementary material, which is available to authorized users.
[Show abstract][Hide abstract] ABSTRACT: AimsThe paired box gene 8 (PAX8) plays crucial roles in organ patterning and cellular differentiation during development and tumorigenesis. While its function is partly understood in vertebrate development, there is poor data concerning human CNS development and brain tumors.Methods
We investigated developing human (n=19) and mouse (n=3) brains as well as medulloblastomas (n=113) for PAX8 expression by immunohistochemistry. Human medulloblastoma cell lines were assessed for PAX8 expression using PCR and immunoblotting and analysed for growth and migration following PAX8 knockdown by siRNA.ResultsPAX8 protein expression was associated with germinal layers in human and murine forebrain and hindbrain development. PAX8 expression significantly decreased over time in the external granule cell layer, but increased in the internal granule cell layer. In medulloblastoma (MB) subtypes we observed an association of PAX8 expression with SHH (sonic hedgehog) and WNT subtypes but not with group 3 and 4 MBs. Beyond that, we detected high PAX8 levels in desmoplastic MB subtypes. Univariate analyses revealed high PAX8 levels as a prognostic factor associated with a significantly better patient prognosis in human MB (overall survival: Log-Rank p=0.0404, Wilcoxon p=0.0280; progression-free survival: Log-Rank p=0.0225; Wilcoxon p=0.0136). In vitro assays revealed increased proliferation and migration of medulloblastoma cell lines after PAX8 siRNA knockdown.Conclusion
In summary, high PAX8 expression is linked to better prognosis in medulloblastomas potentially by suppressing both proliferative and migratory properties of MB cells. The distinct spatio-temporal expression pattern of PAX8 during brain development might contribute to the understanding of distinct MB subtype histogenesis.
[Show abstract][Hide abstract] ABSTRACT: Pre-B-cell leukemia homeobox (Pbx)-regulating protein-1 (Prep1) is a ubiquitous homeoprotein involved in early development, genomic stability, insulin sensitivity, and hematopoiesis. Previously we have shown that Prep1 is a haploinsufficient tumor suppressor that inhibits neoplastic transformation by competing with myeloid ecotropic integration site 1 for binding to the common heterodimeric partner Pbx1. Epithelial-mesenchymal transition (EMT) is controlled by complex networks of proinvasive transcription factors responsive to paracrine factors such as TGF-β. Here we show that, in addition to inhibiting primary tumor growth, PREP1 is a novel EMT inducer and prometastatic transcription factor. In human non-small cell lung cancer (NSCLC) cells, PREP1 overexpression is sufficient to trigger EMT, whereas PREP1 down-regulation inhibits the induction of EMT in response to TGF-β. PREP1 modulates the cellular sensitivity to TGF-β by inducing the small mothers against decapentaplegic homolog 3 (SMAD3) nuclear translocation through mechanisms dependent, at least in part, on PREP1-mediated transactivation of a regulatory element in the SMAD3 first intron. Along with the stabilization and accumulation of PBX1, PREP1 induces the expression of multiple activator protein 1 components including the proinvasive Fos-related antigen 1 (FRA-1) oncoprotein. Both FRA-1 and PBX1 are required for the mesenchymal changes triggered by PREP1 in lung tumor cells. Finally, we show that the PREP1-induced mesenchymal transformation correlates with significantly increased lung colonization by cells overexpressing PREP1. Accordingly, we have detected PREP1 accumulation in a large number of human brain metastases of various solid tumors, including NSCLC. These findings point to a novel role of the PREP1 homeoprotein in the control of the TGF-β pathway, EMT, and metastasis in NSCLC.
Proceedings of the National Academy of Sciences 08/2014; 111(36). DOI:10.1073/pnas.1407074111 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
We investigated the prognostic role of tumour-associated macrophages (TAMs) in patients with head and neck squamous cell carcinoma (HNSCC) treated with definitive chemoradiotherapy (CRT).
The expression of CD68+, CD163+ and CD11b+ cells was assessed using immunohistochemistry in n=106 pre-treatment tumour biopsy samples and was correlated with clinicopathological characteristics, including T-stage, N-stage, grading, tumour localisation, age and sex as well as local failure-free survival (LFFS), distant metastases-free survival (DMFS), progression-free (PFS), and overall survival (OS). Finally, TAMs expression and vessel density (CD31) were examined in n=12 available early local recurrence samples and compared with their matched primary tumours . The diagnostic images and radiotherapy plans of these 12 patients were also analysed. All local recurrences occurred in the high radiation dose region (⩾70 Gy).
With a median follow-up of 40 months, OS at 2 years was 60.5%. High CD163 expression in primary tumours was associated with decreased OS (P=0.010), PFS (P=0.033), LFFS (P=0.036) and DMFS (P=0.038) in multivariate analysis. CD163 demonstrated a strong prognostic value only in human papillomavirus (p16(INK4))-negative patients. Early local recurrence specimens demonstrated a significantly increased infiltration of CD11b+ myeloid cells (P=0.0097) but decreased CD31-positive vessel density (P=0.0004) compared with their matched primary samples.
Altogether, baseline CD163 expression predicts for an unfavourable clinical outcome in HNSCC after definitive CRT. Early local recurrences showed increased infiltration by CD11b+ cells. These data provide important insight on the role of TAMs in mediating response to CRT in patients with HNSCC.
British Journal of Cancer 08/2014; 111(8). DOI:10.1038/bjc.2014.446 · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The macrophage migration inhibitory factor (MIF) receptor CD74 is overexpressed in various neoplasms, mainly in hematological tumors, and currently investigated in clinical studies. CD74 is quickly internalized and recycles after antibody binding therefore it constitutes an attractive target for antibody-based treatment strategies. CD74 has been further described as one of the most upregulated molecules in human glioblastomas. To assess the potential relevance for anti-CD74 treatment we determined the cellular source and clinico-pathological relevance of CD74 expression in human gliomas by immunohistochemistry, immunofluorescence, immunoblotting, cell sorting analysis and qPCR. Furthermore, we fractionated glioblastoma cells and glioma-associated microglia/macrophages (GAMs) from primary tumors and compared CD74 expression in cellular fractions with whole tumor lysates. Our results show that CD74 is restricted to GAMs in vivo, while being absent on tumor cells, the latter strongly expressing its ligand MIF. Most interestingly, a higher amount of CD74-positive GAMs was associated with beneficial patient survival constituting an independent prognostic parameter and with an anti-tumoral M1-polarization. In summary, CD74 expression in human gliomas is restricted to GAMs and positively associated with patient survival. In conclusion, CD74 represents a positive prognostic marker most probably due to its association with a M1-polarized immune milieu in high-grade gliomas.
[Show abstract][Hide abstract] ABSTRACT: Angiogenesis inhibitors have evolved in the past decade as one of the most promising biology based therapeutic strategies. Promising pre-clinical studies (published in 1993 and 1994) provided proof of principle that blocking of VEGF dramatically inhibits tumor growth. These observations led to the successful development of inhibitors for VEGF and VEGF receptors by various pharmaceutical companies. Bevacizumab, a monoclonal antibody neutralizing VEGF, was the first-in class drug to achieve FDA approval for the treatment of colorectal carcinoma in 2004 and later on in other cancer types, including glioblastoma. Anti-VEGF therapy led to an increase in progression free survival in recurrent and primary GBM, but its role in first-line treatment is less clear. Importantly, several preclinical studies suggested that resistance to anti-angiogenic therapy might evolve in the course of the treatment due to an infiltration of specially polarized myeloid cells.
[Show abstract][Hide abstract] ABSTRACT: Objectives:
To investigate the relevance of bevacizumab (BEV)-induced diffusion-restricted lesions and T1-hyperintense lesions in patients with recurrent glioblastoma.
We prospectively screened 74 BEV-treated patients with recurrent glioblastoma for (1) diffusion-restricted lesions and/or, (2) lesions with a hyperintense signal on precontrast T1-weighted images. We further evaluated overall survival (OS), histopathology of the lesions, and patterns of progression.
Twenty-five of 74 patients (34%) developed T1-hyperintense lesions, whereas diffusion-restricted lesions could be detected in 35 of 74 patients (47%). In 21 of 74 patients (28%), the lesions displayed both features ("double-positive"). OS for patients with double-positive lesions was 13.0 months; patients with neither of these lesions had an OS of 6.6 months (p < 0.005). Histologic evaluation of double-positive lesions revealed extensive calcified necrosis in 4 of 4 patients. Notably, these double-positive lesions were rarely involved in further tumor progression. However, they were associated with an increase in distant recurrences at BEV failure.
BEV-induced double-positive MRI lesions are a predictive imaging marker associated with a substantial survival benefit and with improved local control in patients with recurrent glioblastoma. Our data suggest that these lesions are the result of a sustained focal antitumor activity of BEV.
[Show abstract][Hide abstract] ABSTRACT: B10 is a glycosylated derivative of betulinic acid with promising activity against glioma cells. Lysosomal cell death pathways appear to be essential for its cytotoxicity. We investigated the influence of hypoxia, nutrient deprivation and current standard therapies on B10 cytotoxicity. The human glioma cell lines LN-308 and LNT-229 were exposed to B10 alone or together with irradiation, temozolomide, nutrient deprivation or hypoxia. Cell growth and viability were evaluated by crystal violet staining, clonogenicity assays, propidium iodide uptake and LDH release assays. Cell death was examined using an inhibitor of lysosomal acidification (bafilomycin A1), a cathepsin inhibitor (CA074-Me) and a short-hairpin RNA targeting cathepsin B. Hypoxia substantially enhanced B10-induced cell death. This effect was sensitive to bafilomycin A1 and thus dependent on hypoxia-induced lysosomal acidification. Cathepsin B appeared to mediate cell death because either the inhibitor CA074-Me or cathepsin B gene silencing rescued glioma cells from B10 toxicity under hypoxia. B10 is a novel antitumor agent with substantially enhanced cytotoxicity under hypoxia conferred by increased lysosomal cell death pathway activation. Given the importance of hypoxia for therapy resistance, malignant progression, and as a result of antiangiogenic therapies, B10 might be a promising strategy for hypoxic tumors like malignant glioma.
PLoS ONE 04/2014; 9(4):e94921. DOI:10.1371/journal.pone.0094921 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The multifunctional molecule netrin-1 is upregulated in various malignancies and has recently been presented as a major general player in tumorigenesis leading to tumor progression and maintenance in various animal models. However, there is still a lack of clinico-epidemiological data related to netrin-1 expression. Therefore, the aim of our study was to elucidate the association of netrin-1 expression and patient survival in brain metastases since those constitute one of the most limiting factors for patient prognosis. We investigated 104 brain metastases cases for netrin-1 expression using in-situ hybridization and immunohistochemistry with regard to clinical parameters such as patient survival and MRI data. Our data show that netrin-1 is strongly upregulated in most cancer subtypes. Univariate analyses revealed netrin-1 expression as a significant factor associated with poor patient survival in the total cohort of brain metastasis patients and in sub-entities such as non-small cell lung carcinomas. Interestingly, many cancer samples showed a strong nuclear netrin-1 signal which was recently linked to a truncated netrin-1 variant that enhances tumor growth. Nuclear netrin-1 expression was associated with poor patient survival in univariate as well as in multivariate analyses. Our data indicate both total and nuclear netrin-1 expression as prognostic factors in brain metastases patients in contrast to other prognostic markers in oncology such as patient age, number of brain metastases or Ki67 proliferation index. Therefore, nuclear netrin-1 expression constitutes one of the first reported molecular biomarkers for patient survival in brain metastases. Furthermore, netrin-1 may constitute a promising target for future anti-cancer treatment approaches in brain metastases.
PLoS ONE 03/2014; 9(3):e92311. DOI:10.1371/journal.pone.0092311 · 3.23 Impact Factor