Tumorigenic, invasive, karyotypic, and immunocytochemical characteristics of clonal cell lines derived from a spontaneous canine anaplastic astrocytoma

Potential therapeutic efficiency of pan-ERBB inhibitors for canine glioma

Canine glioma is one of the most common brain tumors with poor prognosis, making effective chemotherapy highly desirable. Previous studies have suggested that ERBB4, a signaling molecule involving one of the epidermal growth factor receptors (EGFR), may be a promising therapeutic target. In this study, the anti-tumor effects of pan-ERBB inhibitors, which can inhibit the phosphorylation of ERBB4, were evaluated both in vitro and in vivo using a canine glioblastoma cell line. The results demonstrated that both afatinib and dacomitinib effectively reduced the expression of phosphorylated ERBB4, and significantly decreased the number of viable cells, ultimately prolonging the survival time of orthotopically xenografted mice. Further downstream of ERBB4, afatinib was found to suppress the expression of phosphorylated Akt and phosphorylated Extracellular signal-related kinases1 and 2 (ERK1/2) and induced apoptotic cell death. Thus, pan-ERBB inhibition is a promising therapeutic strategy for the treatment of canine gliomas.

Evaluation of in vitro intrinsic radiosensitivity and characterization of five canine high-grade glioma cell lines

Glioma is the most common primary brain tumor in dogs and predominantly affects brachycephalic breeds. Diagnosis relies on CT or MRI imaging, and the proposed treatments include surgical resection, chemotherapy, and radiotherapy depending on the tumor's location. Canine glioma from domestic dogs could be used as a more powerful model to study radiotherapy for human glioma than the murine model. Indeed, (i) contrary to mice, immunocompetent dogs develop spontaneous glioma, (ii) the canine brain structure is closer to human than mice, and (iii) domestic dogs are exposed to the same environmental factors than humans. Moreover, imaging techniques and radiation therapy used in human medicine can be applied to dogs, facilitating the direct transposition of results. The objective of this study is to fully characterize 5 canine glioma cell lines and to evaluate their intrinsic radiosensitivity. Canine cell lines present numerous analogies between the data obtained during this study on different glioma cell lines in dogs. Cell morphology is identical, such as doubling time, clonality test and karyotype. Immunohistochemical study of surface proteins, directly on cell lines and after stereotaxic injection in mice also reveals close similarity. Radiosensitivity profile of canine glial cells present high profile of radioresistance.

Establishment and characterization of two novel patient-derived lines from canine high-grade glioma

High-grade glioma is an aggressive cancer that occurs naturally in pet dogs. Canine high-grade glioma (cHGG) is treated with radiation, chemotherapy or surgery, but has no curative treatment. Within the past eight years, there have been advances in our imaging and histopathology standards as well as genetic charactereization of cHGG. However, there are only three cHGG cell lines publicly available, all of which were derived from astrocytoma and established using methods involving expansion of tumour cells in vitro on plastic dishes. In order to provide more clinically relevant cell lines for studying cHGG in vitro, the goal of this study was to establish cHGG patient-derived lines, whereby cancer cells are expanded in vivo by injecting cells into immunocompromized laboratory mice. The cells are then harvested from mice and used for in vitro studies. This method is the standard in the human field and has been shown to minimize the acquisition of genetic alterations and gene expression changes from the original tumour. Through a multi-institutional collaboration, we describe our methods for establishing two novel cHGG patient-derived lines, Boo-HA and Mo-HO, from a high-grade astrocytoma and a high-grade oligodendroglioma, respectively. We compare our novel lines to G06-A, J3T-Bg, and SDT-3G (traditional cHGG cell lines) in terms of proliferation and sensitivity to radiation. We also perform whole genome sequencing and identify an NF1 truncating mutation in Mo-HO. We report the characterization and availability of these novel patient-derived lines for use by the veterinary community.

Expression and therapeutic targeting of BMI1 in canine gliomas

The BMI1 proto-oncogene, polycomb ring finger protein (BMI1) is a key component of the epigenetic polycomb repressor complex 1, and has been associated with aggressive behavior and chemotherapeutic resistance in various malignances including human gliomas. Similar to humans, spontaneous canine gliomas carry a poor prognosis with limited therapeutic options. BMI1 expression and the effects of BMI1 inhibition have not been evaluated in canine gliomas. Here, we demonstrate that BMI1 is highly expressed in canine gliomas. Although increased BMI1 protein expression correlated with higher glioma grade in western blot assays, this correlation was not observed in a larger sample set using immunohistochemical analysis. The BMI1 inhibitor, PTC-209, suppressed BMI1 expression in established canine glioma cell lines and resulted in antiproliferative activity when used alone and in combination with chemotherapeutic agents. PTC-209 targeting of BMI1 activated the RB pathway through downregulation of total and phosphorylated RB, independent of INK4A/ARF signaling, likely through BMI1-inhibition mediated upregulation of p21. These data support the rationale for targeting of BMI1 signaling and the use of canine glioma as a translational therapeutic model for human disease. This article is protected by copyright. All rights reserved.

Rat and Mouse Brain Tumor Models for Experimental Neuro-Oncology Research

Rodent brain tumor models have been useful for developing effective therapies for glioblastomas (GBMs). In this review, we first discuss the 3 most commonly used rat brain tumor models, the C6, 9L, and F98 gliomas, which are all induced by repeated injections of nitrosourea to adult rats. The C6 glioma arose in an outbred Wistar rat and its potential to evoke an alloimmune response is a serious limitation. The 9L gliosarcoma arose in a Fischer rat and is strongly immunogenic, which must be taken into consideration when using it for therapy studies. The F98 glioma may be the best of the 3 but it does not fully recapitulate human GBMs because it is weakly immunogenic. Next, we discuss a number of mouse models. The first are human patient-derived xenograft gliomas in immunodeficient mice. These have failed to reproduce the tumor-host interactions and microenvironment of human GBMs. Genetically engineered mouse models recapitulate the molecular alterations of GBMs in an immunocompetent environment and “humanized” mouse models repopulate with human immune cells. While the latter are rarely isogenic, expensive to produce, and challenging to use, they represent an important advance. The advantages and limitations of each of these brain tumor models are discussed. This information will assist investigators in selecting the most appropriate model for the specific focus of their research.

Effect of the NFL-TBS.40-63 peptide on canine glioblastoma cells

Glioblastomas are the most frequent and aggressive cancer of the nervous system. The standard treatment is composed of neurosurgery followed by radiotherapy and chemotherapy, but the median survival remains very low. The NFL-TBS.40-63 peptide, also known as NFL-peptide, is capable to specifically penetrating all glioblastoma cell lines tested so far (rat, mouse and human), where it alters their microtubule network. Consequently, the peptide inhibits selectively the in vitro cell division of glioblastoma cells and their tumor development in vivo. When lipid nanocapsules are functionalized with the NFL-peptide, their uptake is targeted into glioblastoma cells both in vitro and in vivo. Here, we evaluated the impact of the NFL-peptide on J3T cells derived from a canine spontaneous glioblastoma, and its activity when functionalized to nanocapsules. Both flow cytometry and confocal microscopy experiments indicate that the NFL-peptide interacts with these cells and affects their biology, but it cannot enter in cells. By functionalizing lipid nanoparticles with the NFL-peptide, their uptake is also increased, while the peptide stays outside. This investigation reveals similarities and major differences between these canine cells and other glioblastoma cells, which are important aspects to consider when using this type of drug delivery system or performing pre-clinical studies with this animal model.

Annexin A2-STAT3-Oncostatin M receptor axis drives phenotypic and mesenchymal changes in glioblastoma

Glioblastoma (GBM) is characterized by extensive tumor cell invasion, angiogenesis, and proliferation. We previously established subclones of GBM cells with distinct invasive phenotypes and identified annexin A2 (ANXA2) as an activator of angiogenesis and perivascular invasion. Here, we further explored the role of ANXA2 in regulating phenotypic transition in GBM. We identified oncostatin M receptor (OSMR) as a key ANXA2 target gene in GBM utilizing microarray analysis and hierarchical clustering analysis of the Ivy Glioblastoma Atlas Project and The Cancer Genome Atlas datasets. Overexpression of ANXA2 in GBM cells increased the expression of OSMR and phosphorylated signal transducer and activator of transcription 3 (STAT3) and enhanced cell invasion, angiogenesis, proliferation, and mesenchymal transition. Silencing of OSMR reversed the ANXA2-induced phenotype, and STAT3 knockdown reduced OSMR protein expression. Exposure of GBM cells to hypoxic conditions activated the ANXA2–STAT3–OSMR signaling axis. Mice bearing ANXA2-overexpressing GBM exhibited shorter survival times compared with control tumor-bearing mice, whereas OSMR knockdown increased the survival time and diminished ANXA2-mediated tumor invasion, angiogenesis, and growth. Further, we uncovered a significant relationship between ANXA2 and OSMR expression in clinical GBM specimens, and demonstrated their correlation with tumor histopathology and patient prognosis. Our results indicate that the ANXA2–STAT3–OSMR axis regulates malignant phenotypic changes and mesenchymal transition in GBM, suggesting that this axis is a promising therapeutic target to treat GBM aggressiveness.

Differential Expression of miRNAs in Hypoxia ("HypoxamiRs") in Three Canine High-Grade Glioma Cell Lines

Dogs with spontaneous high-grade gliomas increasingly are being proposed as useful large animal pre-clinical models for the human disease. Hypoxia is a critical microenvironmental condition that is common in both canine and human high-grade gliomas and drives increased angiogenesis, chemo- and radioresistance, and acquisition of a stem-like phenotype. Some of this effect is mediated by the hypoxia-induced expression of microRNAs, small (~22 nucleotides long), non-coding RNAs that can modulate gene expression through interference with mRNA translation. Using an in vitro model with three canine high-grade glioma cell lines (J3T, SDT3G, and G06A) exposed to 72 h of 1.5% oxygen vs. standard 20% oxygen, we examined the global “hypoxamiR” profile using small RNA-Seq and performed pathway analysis for targeted genes using both Panther and NetworkAnalyst. Important pathways include many that are well-established as being important in glioma biology, general cancer biology, hypoxia, angiogenesis, immunology, and stem-ness, among others. This work provides the first examination of the effect of hypoxia on miRNA expression in the context of canine glioma, and highlights important similarities with the human disease.

Fibroblast growth factor 13 regulates glioma cell invasion and is important for bevacizumab-induced glioma invasion

Glioblastoma has the poorest prognosis, and is characterized by excessive invasion and angiogenesis. To determine the invasive mechanisms, we previously used two glioma cell lines (J3T-1 and J3T-2) with different invasive phenotypes. The J3T-1 showed abundant angiogenesis and tumor cell invasion around neovasculature, while J3T-2 showed diffuse cell infiltration into surrounding healthy parenchyma. Microarray analyses were used to identify invasion-related genes in J3T-2 cells, and the expressed genes and their intracellular and intratumoral distribution patterns were evaluated in J3T-2 cell lines, human glioma cell lines, human glioblastoma stem cells and human glioblastoma specimens. To determine the role of the invasion-related genes, invasive activities were evaluated in vitro and in vivo. Fibroblast growth factor 13 (FGF13) was overexpressed in J3T-2 cells compared to J3T-1 cells, and in human glioma cell lines, human glioblastoma stem cells and human glioblastoma specimens, when compared to that of normal human astrocytes. Immunohistochemical staining and the RNA-seq (sequencing) data from the IVY Glioblastoma Atlas Project showed FGF13 expression in glioma cells in the invasive edges of tumor specimens. Also, the intracellular distribution was mainly in the cytoplasm of tumor cells and colocalized with tubulin. Overexpression of FGF13 stabilized tubulin dynamics in vitro and knockdown of FGF13 decreased glioma invasion both in vitro and in vivo and prolonged overall survival of several xenograft models. FGF13 was negatively regulated by hypoxic condition. Silencing of FGF13 also decreased in vivo bevacizumab-induced glioma invasion. In conclusion, FGF13 regulated glioma cell invasion and bevacizumab-induced glioma invasion, and could be a novel target for glioma treatment.

Expression and targeting of transcription factor ATF5 in dog gliomas

BACKGROUND

Activating transcription factor 5 (ATF5) is a transcription factor that is highly expressed in undifferentiated neural progenitor/stem cells as well as a variety of human cancers including gliomas.

AIMS

In this study, we examined the expression and localization of ATF5 protein in canine gliomas, and targeting of ATF5 function in canine glioma cell lines.

MATERIALS AND METHODS

Paraffin-embedded canine brain glioma tissue sections and western blots of tumours and glioma cells were immunoassayed with anti-ATF5 antibody. Viability of glioma cells was tested with a synthetic cell-penetrating ATF5 peptide (CP-d/n ATF5) ATF5 antagonist.

RESULTS

ATF5 protein expression was in the nucleus and cytoplasm and was present in normal adult brain and tumour samples, with significantly higher expression in tumours as shown by western immunoblotting. CP-d/n ATF5 was found to decrease cell viability in canine glioma cell lines in vitro in a dose-dependent manner.

CONCLUSION

Similarities in expression of ATF5 in rodent, dog and human tumours, and cross species efficacy of the CP-d/n ATF5 peptide support the development of this ATF5-targeting approach as a novel and translational therapy in dog gliomas.

Canine brain tumours: a model for the human disease?

Canine brain tumours are becoming established as naturally occurring models of disease to advance diagnostic and therapeutic understanding successfully. The size and structure of the dog's brain, histopathology and molecular characteristics of canine brain tumours, as well as the presence of an intact immune system, all support the potential success of this model. The limited success of current therapeutic regimens such as surgery and radiation for dogs with intracranial tumours means that there can be tremendous mutual benefit from collaboration with our human counterparts resulting in the development of new treatments. The similarities and differences between the canine and human diseases are described in this article, emphasizing both the importance and limitations of canines in brain tumour research. Recent clinical veterinary therapeutic trials are also described to demonstrate the areas of research in which canines have already been utilized and to highlight the important potential benefits of translational research to companion dogs.

Molecular signalling pathways in canine gliomas

In this study, we determined the expression of key signalling pathway proteins TP53, MDM2, P21, AKT, PTEN, RB1, P16, MTOR and MAPK in canine gliomas using western blotting. Protein expression was defined in three canine astrocytic glioma cell lines treated with CCNU, temozolamide or CPT-11 and was further evaluated in 22 spontaneous gliomas including high and low grade astrocytomas, high grade oligodendrogliomas and mixed oligoastrocytomas. Response to chemotherapeutic agents and cell survival were similar to that reported in human glioma cell lines. Alterations in expression of key human gliomagenesis pathway proteins were common in canine glioma tumour samples and segregated between oligodendroglial and astrocytic tumour types for some pathways. Both similarities and differences in protein expression were defined for canine gliomas compared to those reported in human tumour counterparts. The findings may inform more defined assessment of specific signalling pathways for targeted therapy of canine gliomas.

Proteomics-based analysis of invasion-related proteins in malignant gliomas

One of the insidious biological features of gliomas is their potential to extensively invade normal brain tissue, yet molecular mechanisms that dictate this locally invasive behavior remain poorly understood. To investigate the molecular basis of invasion by malignant gliomas, proteomic analysis was performed using a pair of canine glioma subclones - J3T-1 and J3T-2 - that show different invasion phenotypes in rat brains but have similar genetic backgrounds. Two-dimensional protein electrophoresis of whole-cell lysates of J3T-1 (angiogenesis-dependent invasion phenotype) and J3T-2 (angiogenesis-independent invasion phenotype) was performed. Twenty-two distinct spots were recognized when significant alteration was defined as more than 1.5-fold change in spot intensity between J3T-1 and J3T-2. Four proteins that demonstrated increased expression in J3T-1, and 14 proteins that demonstrated increased expression in J3T-2 were identified using liquid chromatography-mass spectrometry analysis. One of the proteins identified was annexin A2, which was expressed at higher levels in J3T-1 than in J3T-2. The higher expression of annexin A2 in J3T-1 was corroborated by quantitative RT-PCR of the cultured cells and immunohistochemical staining of the rat brain tumors. Moreover, immunohistochemical analysis of human glioblastoma specimens showed that annexin A2 was expressed at high levels in the tumor cells that formed clusters around dilated vessels. These results reveal differences in the proteomic profiles between these two cell lines that might correlate with their different invasion profiles. Thus, annexin A2 may be related to angiogenesis-dependent invasion.

Novel animal glioma models that separately exhibit two different invasive and angiogenic phenotypes of human glioblastomas

OBJECTIVE

Invasive behaviors of malignant gliomas are fundamental traits and major reasons for treatment failure. Delineation of invasive growth is important in establishing treatment for gliomas and experimental neuro-oncology could benefit from an invasive glioma model. In this study, we established two new cell line-based animal models of invasive glioma.

METHODS

Two cell lines, J3T-1 and J3T-2, were derived from the same parental canine glioma cell line, J3T. These cells were inoculated to establish brain tumors in athymic mice and rats. Pathologic samples of these animal gliomas were examined to analyze invasive patterns in relation to angiogenesis, and were compared with human glioblastoma samples. The molecular profiles of these cell lines were also shown.

RESULTS

Histologically, J3T-1 and J3T-2 tumors exhibited different invasive patterns. J3T-1 cells clustered around newly developed vessels at tumor borders, whereas J3T-2 cells showed diffuse single cell infiltration into surrounding healthy parenchyma. In human malignant glioma samples, both types of invasion were observed concomitantly. Molecular profiles of these cell lines were analyzed by immunocytochemistry and with quantitative reverse transcription polymerase chain reaction. Vascular endothelial growth factor, matrix metalloproteinase-9, hypoxia-inducible factor-1, and platelet-derived growth factor were overexpressed in J3T-1 cells rather than in J3T-2 cells, whereas integrin αvβ3, matrix metalloproteinase-2, nestin, and secreted protein acidic and rich in cysteine were overexpressed in J3T-2 cells rather than in J3T-1 cells.

CONCLUSIONS

These animal models histologically recapitulated two invasive and angiogenic phenotypes, namely angiogenesis-dependent and angiogenesis-independent invasion, also observed in human glioblastoma. These cell lines provided a reproducible in vitro and in vivo system to analyze the mechanisms of invasion and angiogenesis in glioma progression.

TP53 mutations in canine brain tumors

The p53 tumor suppressor gene (TP53) is the most frequently altered gene in human cancer. Mutation of the gene has been shown to be an important mechanism of p53 pathway inactivation in a variety of human brain tumors, particularly those of astrocytic origin. Genomic DNA from a series of 37 glial and 51 nonglial canine brain tumors was sequenced to determine the frequency of TP53 gene mutations involving exons 3-9. Exonic mutations were found in 3 of 88 tumors (3.4%) and specifically in 1 of 18 astrocytic tumors (5.5%). This is markedly lower than that reported in comparable human tumors, suggesting that alternative mechanisms of p53 inactivation are likely to be present if p53 function contributes significantly to oncogenesis in canine brain tumors.

Expression of receptor tyrosine kinases VEGFR-1 (FLT-1), VEGFR-2 (KDR), EGFR-1, PDGFRalpha and c-Met in canine primary brain tumours

Inhibition of tumour growth and angiogenesis by targeting key growth factor receptors is a promising therapeutic strategy for central nervous system tumours. Characterization of these growth factor receptors in canine primary brain tumours has not been done. Using quantitative real-time TaqMan polymerase chain reaction (PCR), we evaluated the expression of messenger RNA (mRNA) for five tyrosine kinase growth factor receptors (vascular endothelial growth factor receptor [VEGFR]-1, VEGFR-2, endothelial growth factor receptor [EGFR]-1, platelet-derived growth factor receptor a [PDGFRa], and c-Met) relative to normal cerebral cortex in 66 spontaneous canine primary brain tumours. Increased expression of VEGFR-1 and VEGFR-2 mRNA was greatest in grade IV astrocytomas (glioblastoma multiforme) and grade III (anaplastic) oligodendrogliomas. EGFR-1 mRNA expression was more consistently increased than the other receptors in all tumour types, while increased PDGFRa mRNA expression was mostly restricted to oligodendrogliomas. The similarities in increased expression of these tyrosine kinase growth factor receptors in these canine tumours, as compared to data from their human counterparts, suggest that common molecular mechanisms may be present.

Adenoviral-mediated gene transfer into the canine brain in vivo

OBJECTIVE

Glioblastoma multiforme (GBM) is a devastating brain tumor for which there is no cure. Adenoviral-mediated transfer of conditional cytotoxic (herpes simplex virus [HSV] 1-derived thymidine kinase [TK]) and immunostimulatory (Fms-like tyrosine kinase 3 ligand [Flt3L]) transgenes elicited immune-mediated long-term survival in a syngeneic intracranial GBM model in rodents. However, the lack of a large GBM animal model makes it difficult to predict the outcome of therapies in humans. Dogs develop spontaneous GBM that closely resemble the human disease; therefore, they constitute an excellent large animal model. We assayed the transduction efficiency of adenoviral vectors (Ads) encoding beta-galactosidase (betaGal), TK, and Flt3L in J3T dog GBM cells in vitro and in the dog brain in vivo.

METHODS

J3T cells were infected with Ads (30 plaque-forming units/cell; 72 h) encoding betaGal (Ad-betaGal), TK (Ad-TK), or Flt3L (Ad-Flt3L). We determined transgene expression by immunocytochemistry, betaGal activity, Flt3L enzyme-linked immunosorbent assay, and TK-induced cell death. Ads were also injected intracranially into the parietal cortex of healthy dogs. We determined cell-type specific transgene expression and immune cell infiltration.

RESULTS

Adenoviral-mediated gene transfer of HSV1-TK, Flt3L, and betaGal was detected in dog glioma cells in vitro (45% transduction efficiency) and in the dog brain in vivo (10-mm area transduced surrounding each injection site). T cells and macrophages/activated microglia infiltrated the injection sites. Importantly, no adverse clinical or neuropathological side effects were observed.

CONCLUSION

We demonstrate effective adenoviral-mediated gene transfer into the brain of dogs in vivo and support the use of these vectors to develop an efficacy trial for canine GBM as a prelude to human trials.

Potentiated gene delivery to tumors using herpes simplex virus/Epstein-Barr virus/RV tribrid amplicon vectors

The development and use of gene transfer techniques creates an opportunity to achieve better treatment modalities for numerous disease entities. Promising results for treatment in tumor cells in culture and in small animal models have been reported. Nevertheless, the lack of widespread vector distribution throughout tumor tissue is one of the current limitations for successful clinical application of gene therapy paradigms. The use of migratory tumor cells themselves as vector delivery vehicles may allow wider vector distribution in tumors. In addition, continuous release of retrovirus vectors on-site could generate a high local virion concentration over an extended time period with consequent increases in transduction efficiency. In this paper, we present in culture and in vivo data of a herpes simplex virus-Epstein-Barr virus hybrid amplicon vector containing retrovirus vector components (tribrid vector) that allows conversion of tumor cells into retroviral producer cells. With this method, we were able to achieve a local fourfold amplification of stable transgene expression in tumors. The application of this system, which can integrate a transgene cassette into tumors with therapeutic bystander effects, could increase the local amplification effect to a level of clinical relevance.

Generation of stable retrovirus packaging cell lines after transduction with herpes simplex virus hybrid amplicon vectors

BACKGROUND

A number of properties have relegated the use of Moloney murine leukemia virus (Mo-MLV)-based retrovirus vectors primarily to ex vivo protocols. Direct implantation of retrovirus producer cells can bypass some of the limitations, and in situ vector production may result in a large number of gene transfer events. However, the fibroblast nature of most retrovirus packaging cells does not provide for an effective distribution of vector producing foci in vivo, especially in the brain. Effective development of new retrovirus producer cells with enhanced biologic properties may require the testing of a large number of different cell types, and a quick and efficient method to generate them is needed.

METHODS

Moloney murine leukemia virus (Mo-MLV) gag-pol and env genes and retrovirus vector sequences carrying lacZ were cloned into different minimal HSV/AAV hybrid amplicons. Helper virus-free amplicon vectors were used to co-infect glioma cells in culture. Titers and stability of retrovirus vector production were assessed.

RESULTS

Simultaneous infection of two glioma lines, Gli-36 (human) and J3T (dog), with both types of amplicon vectors, generated stable packaging populations that produced retrovirus titers of 0.5-1.2 x 10(5) and 3.1-7.1 x 10(3) tu/ml, respectively. Alternatively, when cells were first infected with retrovirus vectors followed by infection with HyRMOVAmpho amplicon vector, stable retrovirus packaging populations were obtained from Gli-36 and J3T cells producing retrovirus titers comparable to those obtained with a traditional retrovirus packaging cell line, Psi CRIPlacZ.

CONCLUSIONS

This amplicon vector system should facilitate generation of new types of retrovirus producer cells. Conversion of cells with migratory or tumor/tissue homing properties could result in expansion of the spatial distribution or targeting capacity, respectively, of gene delivery by retrovirus vectors in vivo.

Single-step conversion of cells to retrovirus vector producers with herpes simplex virus-Epstein-Barr virus hybrid amplicons

We report here on the development and characterization of a novel herpes simplex virus type 1 (HSV-1) amplicon-based vector system which takes advantage of the host range and retention properties of HSV-Epstein-Barr virus (EBV) hybrid amplicons to efficiently convert cells to retrovirus vector producer cells after single-step transduction. The retrovirus genes gag-pol and env (GPE) and retroviral vector sequences were modified to minimize sequence overlap and cloned into an HSV-EBV hybrid amplicon. Retrovirus expression cassettes were used to generate the HSV-EBV-retrovirus hybrid vectors, HERE and HERA, which code for the ecotropic and the amphotropic envelopes, respectively. Retrovirus vector sequences encoding lacZ were cloned downstream from the GPE expression unit. Transfection of 293T/17 cells with amplicon plasmids yielded retrovirus titers between 10(6) and 10(7) transducing units/ml, while infection of the same cells with amplicon vectors generated maximum titers 1 order of magnitude lower. Retrovirus titers were dependent on the extent of transduction by amplicon vectors for the same cell line, but different cell lines displayed varying capacities to produce retrovirus vectors even at the same transduction efficiencies. Infection of human and dog primary gliomas with this system resulted in the production of retrovirus vectors for more than 1 week and the long-term retention and increase in transgene activity over time in these cell populations. Although the efficiency of this system still has to be determined in vivo, many applications are foreseeable for this approach to gene delivery.

Gap junction intercellular communication in gliomas is inversely related to cell motility

Gliomas are lethal because of local invasion into brain parenchyma. Glioma cells were isolated from different regions (white matter, gray matter and tumor core) of a glioma-bearing dog brain. Individual clonal cell lines were established from each area, and characterized for growth, migration and gap junctions. The regional clonal cell lines differed in rates and preferred substrate for migration. Cell lines generated from invaded white matter showed stimulated migration on collagen and variable migration on merosin, whereas migration of cell lines derived from invaded gray matter showed the reciprocal responses: stimulation on merosin and inhibition on collagen. Gap junctional communication showed significant degrees of variation between the different clones. A direct inverse relationship between the number of cells demonstrating gap junctional communication and migration rate of cells away from multicellular spheroids was evident. Glioma cells which have a reduced capacity to connect to each other have an accelerated migration rate onto autologous, glioma-derived matrix. These results suggest that invasive glioma cells suppress autologous cell-to-cell cohesion, partly evident as reduced formation of gap junctions. In addition, glioma cells were stimulated to migrate in a dose-dependant manner in response to epidermal growth factor (EGF) coincident with the reduction of Cx43 levels and increased serine phosphorylation. We speculate that in order for glioma cells to invade locally into brain parenchyma they must first detach from neighboring cells ("let go...let's go" paradigm of invasion).

Allogeneic astrocytoma in immune competent dogs

We have induced in canines long-term immune tolerance to an allogeneic cell line derived from a spontaneous canine astrocytoma. Allogeneic astrocytoma cells were implanted endoscopically into the subcutaneous space of fetal dogs before the onset of immune competency (< 40th gestational day). At adulthood, dogs rendered tolerant successfully serve as recipients of intracranial transplants of their growing allogeneic, subcutaneous tumor. Transplanted dogs subsequently develop a solid brain tumor with histological features similar to the original astrocytoma. This model may allow rapid development and evaluation of new therapies for brain tumors, as well as afford tumor biology studies that are untenable in smaller, immune incompetent, or inbred animals harboring less representative tumors.

Comparative aspects of neoplastic invasion of the brain

This review of the invasion of the human brain by tumors is based upon a comparative approach. The taxonomic distribution of a structure of the CNS to be considered a brain is present in the following taxonomic groups: Mollusca (Cephalopoda, Pulmonata) Sipunculida, Echiurida, Annelida, Arthropoda and Vertebrata (fishes, amphibians, reptiles, birds and mammals). The comparative approach (inter-, and intraspecies specific) provides a more informative, indicative, understanding of invasion of the human brain; especially in view of the morphological and functional heterogeneity of structures playing a role in the neoplastic invasion to and from the brain. It can be distinguished among primary invasiveness (as cancer in situ) and local recurrence on the one hand and remote spreading, such as metastasis, on the other. A review of the recent literature arranged according to tumor types is provided and comparative conclusions elucidated, especially to underline the tumor specificity of the invasion of brain tumors, especially the second or intra-species specific approach is therapeutically important. This is set forth against a background of epidemiology and species specificity. Due to the lack of bony skull capsule an extensive knowledge of the brain of cephalopod molluscs with its functional and morphological similarity to the human eye, and also that of the pulmonate Helix pomatia, the vineyard snail, could well serve as excellent oncologic models. Some conclusions can be drawn dealing with the theoretical possibility of first appearance of the different and heterogeneous components of the complicated structure known as brain including its supporting accessory organs during phylogeny.