Tumorigenesis in transgenic mice in which the SV40 T antigen is driven by the brain-specific FGF1 promoter

Effects of hydrophilic fullerene nanoarchitectured structures on the behaviour of neural stem cells

The interaction between nanoarchitectonic fullerenes and cells is essential for their applications in the biological field. Herein we reported the preparation and investigation of the function of different types of water-dispersible self-assembled fullerenes. The hydrophobic self-assembled fullerenes were either surface-modified or chemically etched to become water dispersible. Different types of fullerenes were then examined for their effects on the behavior of neural stem cells (NSCs). Our results indicated that only the hydrophilic fullerene nanotubes (FNTs, diameter ∼480 nm) created by chemically etching were endocytosed by NSCs, which showed a spindle-like morphology after the uptake. Meanwhile, the FNTs did not increase the reactive oxygen species (ROS) production of the cells. The expression levels of neural-related genes (CNPase and β-tubulin) were upregulated 1.5-fold in the presence of FNTs. The differentiation of NSCs depended on the size, shape, and surface functional group of various fullerenes. Besides, the addition of FNTs in a chitosan self-healing hydrogel did not influence the integrity, injectability, and self-healing properties of the composite hydrogel. These results revealed that FNTs induced the neural differentiation of NSCs in the composite hydrogel. The addition of FNTs at a low concentration (50 μg mL^-1) was enough to create such effects in the composite hydrogel. The expression levels of the oligodendrocytic marker gene CNPase and the neuronal marker gene β-tubulin were increased remarkably by ∼14.5- and ∼8.4-fold, respectively, by the composite self-healing hydrogel containing 50 μg mL^-1 FNTs. The fullerene nanoarchitectured structures may have potential for use as nanovehicles and in neural tissue engineering in the future.

Gene expression profiling of 19q-loss astrocytomas suggest a specific pattern associated with the better prognosis

PURPOSE

We previously reported that there was a subgroup of IDH-mutated astrocytomas harboring only 19q-loss showing oligodendroglioma-like morphology and significantly longer overall survival (OS) compared with 19q-intact astrocytomas. The aim of this study was to further explore the biological characteristics of this possible subgroup and obtain insight into the mechanism of their relatively benign clinical behavior.

METHODS

We compared gene expression pattern between five 19q-loss and five 19q-intact IDH-mutated astrocytomas by microarray analysis.

RESULTS

By comparing expression levels of genes of 19q-loss astrocytomas to those of 19q-intact astrocytomas, 102 up-regulated genes and 162 down-regulated genes were extracted. The down-regulated genes clustered heavily to 19q and 4p while the up-regulated genes clustered to 4q. It was noteworthy that fibroblast growth factor 1 associated with stem cell maintenance and multiple genes associated with glioma progression were down-regulated in 19q-loss astrocytomas, and these results were validated with the independent TCGA data set. On t-SNE analysis of the 19q-loss astrocytomas with other IDH-mutant glioma subgroups from the TCGA datasets, the expression pattern of the 19q-loss astrocytomas showed no shift toward oligodendrogliomas with 1p/19q codeletion but rather constituted a subgroup of astrocytoma.

CONCLUSIONS

These findings suggested that 19q-loss in astrocytomas is more likely acquired event rather than an early event in oncogenesis like the 1p/19q-codeletion in oligodendrogliomas, and that the biological features of 19q-loss astrocytomas are possibly related to differentially expressed genes associated with stem cell maintenance and glioma progression.

Host immune response to anti-cancer camptothecin conjugated cyclodextrin-based polymers

Introduction

Efficacy and safety are critical concerns when designing drug carriers. Nanoparticles are a particular type of carrier that has gained recent attention in cancer therapeutics.

Methods

In this study, we assess the safety profile of IT-101, a nanoparticle formed by self-assembly of camptothecin (CPT) conjugated cyclodextrin-based polymers. IT-101 delivers CPT to target cancer cells in animal models of numerous human cancers and in humans. Previous data from preclinical and clinical trials indicate that IT-101 has no notable immunological side effects. However, there have been no published studies focused on evaluating the effects of IT-101 on host immune systems.

Results

In this work, we demonstrate that IT-101 diminished initial host immune response following first injection of the nanopharmaceutical and induced NK cell activation and T cell proliferation upon further IT-101 exposure. Additionally, IT-101 could attenuate tumor growth more efficiently than CPT treatment only.

Conclusions

Drugs administration in whole-body circulation may lead to poorly bioavailable in central nervous system and often has toxic effects on peripheral tissues. Conjugated with cyclodextrin-based polymers not only reduce adverse effects but also modulate the immune responses to elevate drug efficacy. These immune responses may potentially facilitate actions of immune blockage, such as PD1/PDL1 in cancer treatment.

A Tri-fusion Reporter Mouse Reveals Tissue-Specific FGF1B Promoter Activity in vivo

Transgenic mice harboring imaging reporters take full advantage of imaging technologies in studies using living mice. Here, we established a tri-fusion multimodal reporter gene containing fragments from firefly luciferase, enhanced green fluorescent protein, and herpes simplex virus type 1 thymidine kinase and generated tri-fusion reporter Tg mice. Fibroblast growth factor type 1 (FGF1), a multifunctional mitogen to a wide range of tissues, regulates proliferation of neural stem cells of the brain, where FGF1 expression is initiated through activation of the FGF1B (F1B) promoter. The reporter mouse under the control of the human F1B promoter enables visualization in vivo where F1B activity is elevated, including tissues not only in the brain but also in the nasopharynx, skull, spine, and testes, particularly in Leydig cells. Treating Tg mice with the alkylating agent busulfan, which is known to eradicate Leydig cells and disrupt spermatogenesis in mice, eliminated the reporter signals. Restoring Leydig cells recovered reporter expression, indicating that the reporter can be used as a surrogate marker for Leydig cells. The F1B tri-fusion reporter mouse model can be utilized in longitudinal monitoring of the health status of the male reproductive system, such as in studies exploring the toxicity of chemicals to spermatogenesis.

Neural Stem Cells, Neural Progenitors, and Neurotrophic Factors

Neural stem cells (NSCs) have been proposed as a promising cellular source for the treatment of diseases in nervous systems. NSCs can self-renew and generate major cell types of the mammalian central nervous system throughout adulthood. NSCs exist not only in the embryo, but also in the adult brain neurogenic region: the subventricular zone (SVZ) of the lateral ventricle. Embryonic stem (ES) cells acquire NSC identity with a default mechanism. Under the regulations of leukemia inhibitory factor (LIF) and fibroblast growth factors, the NSCs then become neural progenitors. Neurotrophic and differentiation factors that regulate gene expression for controlling neural cell fate and function determine the differentiation of neural progenitors in the developing mammalian brain. For clinical application of NSCs in neurodegenerative disorders and damaged neurons, there are several critical problems that remain to be resolved: 1) how to obtain enough NSCs from reliable sources for autologous transplantation; 2) how to regulate neural plasticity of different adult stem cells; 3) how to control differentiation of NSCs in the adult nervous system. In order to understand the mechanisms that control NSC differentiation and behavior, we review the ontogeny of NSCs and other stem cell plasticity of neuronal differentiation. The role of NSCs and their regulation by neurotrophic factors in CNS development are also reviewed.

Water-Soluble Fullerene Derivatives as Brain Medicine: Surface Chemistry Determines If They Are Neuroprotective and Antitumor

Delivering drugs to the central nervous system (CNS) is a major challenge in treating CNS-related diseases. Nanoparticles that can cross blood-brain barrier (BBB) are potential tools. In this study, water-soluble C₆₀ fullerene derivatives with different types of linkages between the fullerene cage and the solubilizing addend were synthesized (compounds 1-3: C-C bonds, compounds 4-5: C-S bonds, compound 6: C-P bonds, and compounds 7-9: C-N bonds). Fullerene derivatives 1-6 were observed to induce neural stem cell (NSC) proliferation in vitro and rescue the function of injured CNS in zebrafish. Fullerene derivatives 7-9 were found to inhibit glioblastoma cell proliferation in vitro and reduce glioblastoma formation in zebrafish. These effects were correlated with the cell metabolic changes. Particularly, compound 3 bearing residues of phenylbutiryc acids significantly promoted NSC proliferation and neural repair without causing tumor growth. Meanwhile, compound 7 with phenylalanine appendages significantly inhibited glioblastoma growth without retarding the neural repair. We conclude that the surface functional group determines the properties as well as the interactions of C₆₀ with NSCs and glioma cells, producing either a neuroprotective or antitumor effect for possible treatment of CNS-related diseases.

Activation of Aurora A kinase through the FGF1/FGFR signaling axis sustains the stem cell characteristics of glioblastoma cells

Fibroblast growth factor 1 (FGF1) binds and activates FGF receptors, thereby regulating cell proliferation and neurogenesis. Human FGF1 gene 1B promoter (-540 to +31)-driven SV40 T antigen has been shown to result in tumorigenesis in the brains of transgenic mice. FGF1B promoter (-540 to +31)-driven green fluorescent protein (F1BGFP) has also been used in isolating neural stem cells (NSCs) with self-renewal and multipotency from developing and adult mouse brains. In this study, we provide six lines of evidence to demonstrate that FGF1/FGFR signaling is implicated in the expression of Aurora A (AurA) and the activation of its kinase domain (Thr288 phosphorylation) in the maintenance of glioblastoma (GBM) cells and NSCs. First, treatment of FGF1 increases AurA expression in human GBM cell lines. Second, using fluorescence-activated cell sorting, we observed that F1BGFP reporter facilitates the isolation of F1BGFP(+) GBM cells with higher expression levels of FGFR and AurA. Third, both FGFR inhibitor (SU5402) and AurA inhibitor (VX680) could down-regulate F1BGFP-dependent AurA activity. Fourth, inhibition of AurA activity by two different AurA inhibitors (VX680 and valproic acid) not only reduced neurosphere formation but also induced neuronal differentiation of F1BGFP(+) GBM cells. Fifth, flow cytometric analyses demonstrated that F1BGFP(+) GBM cells possessed different NSC cell surface markers. Finally, inhibition of AurA by VX680 reduced the neurosphere formation of different types of NSCs. Our results show that activation of AurA kinase through FGF1/FGFR signaling axis sustains the stem cell characteristics of GBM cells.

IMPLICATIONS

This study identified a novel mechanism for the malignancy of GBM, which could be a potential therapeutic target for GBM.

Inhibition of Neurosphere Formation in Neural Stem/Progenitor Cells by Acrylamide

Previous studies showed that transplantation of cultured neural stem/progenitor cells (NSPCs) could improve functional recovery for various neurological diseases. This study aims to develop a stem cell-based model for predictive toxicology of development in the neurological system after acrylamide exposure. Treatment of mouse (KT98/F1B-GFP) and human (U-1240 MG/F1B-GFP) NSPCs with 0.5 mM acrylamide resulted in the inhibition of neurosphere formation (definition of self-renewal ability in NSPCs), but not inhibition of cell proliferation. Apoptosis and differentiation of KT98 (a precursor of KT98/F1B-GFP) and KT98/F1B-GFP are not observed in acrylamide-treated neurospheres. Analysis of secondary neurosphere formation and differentiation of neurons and glia illustrated that acrylamide-treated KT98 and KT98/F1B-GFP neurospheres retain the NSPC properties, such as self-renewal and differentiation capacity. Correlation of acrylamide-inhibited neurosphere formation with cell-cell adhesion was observed in mouse NSPCs by live cell image analysis and the presence of acrylamide. Protein expression levels of cell adhesion molecules [neural cell adhesion molecule (NCAM) and N-cadherin] and extracellular signal-regulated kinases (ERK) in acrylamide-treated KT98/F1B-GFP and U-1240 MG/F1B-GFP neurospheres demonstrated that NCAM decreased and phospho-ERK (pERK) increased, whereas expression of N-cadherin remained unchanged. Analysis of AKT (protein kinase B, PKB)/β-catenin pathway showed decrease in phospho-AKT (p-AKT) and cyclin D1 expression in acrylamide-treated neurospheres of KT98/F1B-GFP. Furthermore, PD98059, an ERK phosphorylation inhibitor, attenuated acrylamide-induced ERK phosphorylation, indicating that pERK contributed to the cell proliferation, but not in neurosphere formation in mouse NSPCs. Coimmunoprecipitation results of KT98/F1B-GFP cell lysates showed that the complex of NCAM and fibroblast growth factor receptor 1 (FGFR1) is present in the neurosphere, and the amount of this complex decreases after acrylamide treatment. Our results reveal that acrylamide inhibits neurosphere formation through the disruption of the neurosphere architecture in NSPCs. The downregulation of cell-cell adhesion resulted from decreasing the levels of NCAM as well as the formation of NCAM/ FGFR complex.

Human FGF1 promoter is active in ependymal cells and dopaminergic neurons in the brains of F1B-GFP transgenic mice

FGF1 is involved in multiple biological functions and exhibits the importance in neuroprotective effects. Our previous studies indicated that, in human brain and retina, the FGF1B promoter controlled the expression of FGF1. However, the exact function and regulation of FGF1 in brain is still unclear. Here, we generated F1B-GFP transgenic mice that expressed the GFP reporter gene under the control of human FGF1B promoter (-540 to +31). Using the fresh brain sections of F1B-GFP transgenic mice, we found that the F1B-GFP cells expressed strong fluorescent signals in the ventricular system throughout the brain. The results of immunohistochemistry further showed that two distinct populations of F1B-GFP(+) cells existed in the brains of F1B-GFP transgenic mice. We demonstrated that one population of F1B-GFP(+) cells was ependymal cells, which distributed along the entire ventricles, and the second population of F1B-GFP(+) cells was neuronal cells that projected their long processes into multiple directions in specific areas of the brain. The double labeling of F1B-GFP(+) cells and tyrosine hydroxylase indicated that a subpopulation of F1B-GFP(+) -neuronal cells was dopaminergic neurons. Importantly, these F1B-GFP(+) /TH(+) cells were distributed in the main dopaminergic neuronal groups including hypothalamus, ventral tegmental area, and raphe nuclei. These results suggested that human FGF1B promoter was active in ependymal cells, neurons, and a portion of dopaminergic neurons. Thus, the F1B-GFP transgenic mice provide an animal model not only for studying FGF1 gene expression in vivo but also for understanding the role of FGF1 contribution in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease.

Single-cell enzyme-free dissociation of neurospheres using a microfluidic chip

Obtaining single dissociated cells from neurospheres is difficult using nonenzymatic methods. In this paper we report the development of a microfluidic-chip-based approach that utilizes flow and microstructures to dissociate neurospheres. We show that this microfluidic-chip-based neurosphere-dissociation method can generate high yields of single cells from dissociated neurospheres of mouse KT98 and DC115 cell models (passage number, 3-8; diameter range, 40-250 μm): 90% and 95%, respectively. The microfluidic-chip-dissociated cells had high viabilities (80-85%) and the ability to regrow into neurospheres, demonstrating the applicability of this device to neurosphere assay applications. In addition, the dissociated cells retained their normal differentiation potentials, as shown by their capabilities to differentiate into three neural lineages (neurons, astroglia, and oligodendrocytes) when cultured in differentiation culture conditions. Since this microfluidic-chip-based method does not require the use of enzymatic reagents, the risk of contamination from exogenous substances could be reduced, making it an attractive tool for a wide range of applications where neurosphere dissociation is needed.

Radial coherence of diffusion tractography in the cerebral white matter of the human fetus: neuroanatomic insights

High angular resolution diffusion imaging (HARDI) demonstrates transient radial coherence of telencephalic white matter in the human fetus. Our objective was to define the neuroanatomic basis of this radial coherence through correlative HARDI- and postmortem tissue analyses. Applying immunomarkers to radial glial fibers (RGFs), axons, and blood vessels in 18 cases (19 gestational weeks to 3 postnatal years), we compared their developmental profiles to HARDI tractography in brains of comparable ages (n = 11). At midgestation, radial coherence corresponded with the presence of RGFs. At 30-31 weeks, the transition from HARDI-defined radial coherence to corticocortical coherence began simultaneously with the transformation of RGFs to astrocytes. By term, both radial coherence and RGFs had disappeared. White matter axons were radial, tangential, and oblique over the second half of gestation, whereas penetrating blood vessels were consistently radial. Thus, radial coherence in the fetal white matter likely reflects a composite of RGFs, penetrating blood vessels, and radial axons of which its transient expression most closely matches that of RGFs. This study provides baseline information for interpreting radial coherence in tractography studies of the preterm brain in the assessment of the encephalopathy of prematurity.

Ciliogenic RFX transcription factors regulate FGF1 gene promoter

Fibroblast growth factor 1 (FGF1) has been shown to regulate cell proliferation, cell division, and neurogenesis. Human FGF1 gene 1B promoter (-540 to +31)-driven green fluorescence (F1BGFP) was shown to recapitulate endogenous FGF1 gene expression. It can also be used to isolate neural stem/progenitor cells (NSPCs) and glioblastoma stem cells (GBM-SCs) from developing mouse brains and human glioblastoma tissues, respectively. However, the regulatory mechanisms of FGF-1B promoter and F1BGFP(+) cells are not clear. In this study, we present several lines of evidence to show the roles of ciliogenic RFX transcription factors in the regulation of FGF-1B gene promoter and F1BGFP(+) cells: (i) RFX1, RFX2, and RFX3 transcription factors could directly bind the 18-bp cis-element (-484 to -467), and contribute to the regulation of FGF1 promoter and neurosphere formation. (ii) We demonstrated RFX2/RFX3 complex could only be detected in the nuclear extract of FGF-1B positive cells, but not in FGF-1B negative cells. (iii) Protein kinase C inhibitors, staurosporine and rottlerin, could decrease the percentage of F1BGFP(+) cells and their neurosphere formation efficiency through reducing the RFX2/3 complex. (iv) RNA interference knockdown of RFX2 could significantly reduce the percentage of F1BGFP(+) cells and their neurosphere formation efficiency whereas overexpression of RFX2 resulted in the opposite effects. Taken together, this study suggests ciliogenic RFX transcription factors regulate FGF-1B promoter activity and the maintenance of F1BGFP(+) NSPCs and GBM-SCs.

Local interstitial delivery of z-butylidenephthalide by polymer wafers against malignant human gliomas

We have shown that the natural compound z-butylidenephthalide (Bdph), isolated from the chloroform extract of Angelica sinensis, has antitumor effects. Because of the limitation of the blood-brain barrier, the Bdph dosage required for treatment of glioma is relatively high. To solve this problem, we developed a local-release system with Bdph incorporated into a biodegradable polyanhydride material, p(CPP-SA; Bdph-Wafer), and investigated its antitumor effects. On the basis of in vitro release kinetics, we demonstrated that the Bdph-Wafer released 50% of the available Bdph by the sixth day, and the release reached a plateau phase (90% of Bdph) by the 30th day. To investigate the in situ antitumor effects of the Bdph-Wafer on glioblastoma multiforme (GBM), we used 2 xenograft animal models-F344 rats (for rat GBM) and nude mice (for human GBM)-which were injected with RG2 and DBTRG-05MG cells, respectively, for tumor formation and subsequently treated subcutaneously with Bdph-Wafers. We observed a significant inhibitory effect on tumor growth, with no significant adverse effects on the rodents. Moreover, we demonstrated that the antitumor effect of Bdph on RG2 cells was via the PKC pathway, which upregulated Nurr77 and promoted its translocation from the nucleus to the cytoplasm. Finally, to study the effect of the interstitial administration of Bdph in cranial brain tumor, Bdph-Wafers were surgically placed in FGF-SV40 transgenic mice. Our Bdph-Wafer significantly reduced tumor size in a dose-dependent manner. In summary, our study showed that p(CPP-SA) containing Bdph delivered a sufficient concentration of Bdph to the tumor site and effectively inhibited the tumor growth in the glioma.

Regulation of FGF1 gene promoter through transcription factor RFX1

Fibroblast growth factor 1 (FGF1) has been suggested to have an important role in cell growth, proliferation, and neurogenesis. Human FGF1 gene 1B promoter (-540 to +31)-driven green fluorescence (F1BGFP) has been shown to monitor endogenous FGF1 expression. F1BGFP could also be used to isolate neural stem/progenitor cells from embryonic, neonatal, and adult mouse brains or to isolate glioblastoma stem cells (GBM-SCs) from human glioblastoma tissues. Here, we present evidence that transcription factor RFX1 could bind the 18-bp cis-elements (-484 to -467) of the F1B promoter, modulate F1BGFP expression and endogenous FGF1 expression, and further regulate the maintenance of GBM-SCs. These observations were substantiated by using yeast one-hybrid assay, electrophoretic mobility shift assay, chromatin immunoprecipitation assay, gain- and loss-of-function assays, and neurosphere assays. Overexpression of RFX1 was shown to down-regulate FGF-1B mRNA expression and neurosphere formation in human glioblastoma cells, whereas RNA interference knockdown of RFX1 demonstrated the opposite effects. Our findings provide insight into FGF1 gene regulation and suggest that the roles of FGF1 and RFX1 in the maintenance of GBM-SCs. RFX1 may negatively regulate the self-renewal of GBM-SCs through modulating FGF-1B and FGF1 expression levels by binding the 18-bp cis-elements of the F1B promoter.

Immunological considerations of modern animal models of malignant primary brain tumors

Recent advances in animal models of glioma have facilitated a better understanding of biological mechanisms underlying gliomagenesis and glioma progression. The limitations of existing therapy, including surgery, chemotherapy, and radiotherapy, have prompted numerous investigators to search for new therapeutic approaches to improve quantity and quality of survival from these aggressive lesions. One of these approaches involves triggering a tumor specific immune response. However, a difficulty in this approach is the the scarcity of animal models of primary CNS neoplasms which faithfully recapitulate these tumors and their interaction with the host's immune system. In this article, we review the existing methods utilized to date for modeling gliomas in rodents, with a focus on the known as well as potential immunological aspects of these models. As this review demonstrates, many of these models have inherent immune system limitations, and the impact of these limitations on studies on the influence of pre-clinical therapeutics testing warrants further attention.

Brain-specific 1B promoter of FGF1 gene facilitates the isolation of neural stem/progenitor cells with self-renewal and multipotent capacities

Fibroblast growth factor 1 (FGF1) has been shown to maintain proliferation and self-renewal capacities of neural stem/progenitor cells (NSPCs) in vitro. We have previously identified FGF1B as the major transcript of FGF1 gene expressed exclusively in brain areas that are known to be abundant for NSPCs in vivo. The 540-bp (-540 to +31) sequence upstream of the 1B transcription start site (F1B) is sufficient to drive the expression of a heterologous luciferase reporter in cultured cells. In this study, we report a direct genetic and functional approach to isolate F1B(+) NSPCs using green fluorescent protein (GFP) reporter gene under the control of human F1B promoter. The F1B-GFP reporter could facilitate the isolation of NSPCs with self-renewal and multipotent capacities from human glioblastoma tissues, developing or adult mouse brains by fluorescence-activated cell sorting. Future work elucidating the mechanisms that control FGF1B expression will help to identify new NSPC-related genes.

SV40 T antigen disrupted the cell metabolism and the balance between proliferation and apoptosis in lens tumors of transgenic mice

PURPOSE

Simian Vacuolating Virus 40 (SV40) T antigen perturbed p53 and RB to cause cell malignant transformation. The purpose of this study was to identify the molecular changes during lens carcinogenesis and cancer progression induced by SV40 T antigen.

METHODS

The different lens lesions of alpha A-crystallin/SV40 T antigen transgenic mice were examined using cDNA microarray, immunohistochemistry and TUNEL to scan the influenced molecules and signal pathways.

RESULTS

There appeared dysplasia, carcinoma in situ, followed by invasion inside or outside eyeball, and final metastasis into lymph node or lung. Cell functions largely changed from such many aspects as cell cycle, cell morphology, cell development, cell-to-cell signaling and so forth since lens carcinogenesis. The significant differences were observed in such signaling pathways as metabolism about carbohydrate, amino acid, nucleotides, Xenobiotics and nitrogen (P < 0.05).The remarkable distinction of cell proliferation and cell death was found after carcinoma began to invade. There was significant alteration in cell growth, cell cycle, cell-to-cell signaling and metabolism since carcinoma invasion outside the eyeball happened. Parafibromin, Stat 1alpha, Mek kinase-1, CK2alpha, GRP78, Arp2 and Apr3 were not expressed in wild-type mice lens, but in others. The proliferative levels of dysplasia, carcinoma in situ and invasive carcinoma inside eyeballs were statistically higher than other groups (P < 0.05). The apoptotic levels of dysplasia were significantly higher than wild-type control (P < 0.05), but lower than the others (P < 0.05).

CONCLUSION

SV40 T antigen remarkably targeted the cell metabolism and disrupted the balance between proliferation and apoptosis during the lens carcinogenesis and following progression.

Characterization and application of polyclonal antibodies that specifically recognize JC virus large T antigen

Polyomavirus JC virus (JCV) is the causative agent of progressive multifocal leukoencephalopathy, a fatal demyelinating disease of the central nervous system. Similar to other polyomaviruses, such as simian vacuolating virus 40 (SV40) and BK virus (BKV), JCV is also associated with human tumours. The Polyomavirus early protein large T antigen (TAg) plays a crucial role in tumour pathogenesis. An antibody to SV40 TAg (PAb416), which cross-reacts with TAgs of both JCV and BKV, has been used widely for the detection of JCV and BKV TAgs. As a consequence, it is difficult to discriminate between the TAgs of SV40, BKV and JCV by immunohistochemical analyses. In the present study, we generated JCV TAg-specific polyclonal antibodies (JCT629 and JCT652) by immunization of New Zealand white rabbits with synthetic peptides reproducing the JCV TAg carboxyl-terminal region as immunogens. Immunoblotting analyses indicated that the new antibodies bind specifically to JCV TAg, and not to those of SV40 or BKV. We also demonstrated that these antibodies can be used for immunoprecipitation, immunocytochemical analyses and immunohistochemical staining of routinely processed specimens. In conclusion, the newly generated JCV-specific TAg antibodies may be useful both in the investigation of the pathophysiological function of JCV TAg and in discriminating between Polyomavirus-related clinical samples.

Novel integrase-defective lentiviral episomal vectors for gene transfer

High levels of circular viral extrachromosomal DNA (E-DNA) are normally produced after infection with integration-competent and -incompetent lentiviruses. Although E-DNA has been shown to be transcriptionally active, it lasts for only a short time in replicating cells. Here, we report an integrase (IN)-defective lentiviral episomal vector in which insertion of the simian virus 40 (SV40) promoter, containing the origin of replication (ori), is associated with long-term expression and persistence of E-DNA in the presence of SV40 large T antigen (TAg) from 293T cells. 293 and 293T cell lines transduced with IN-competent lentiviral vectors expressing green fluorescent protein (GFP) or luciferase from the cytomegalovirus (CMV) or SV40 promoter gave similar levels of transduction and expression. In contrast, only transient reporter expression occurred when using the CMV IN-defective control vector in both 293 and 293T cells. However, reporter gene expression was maintained for more than 8 weeks in 293T, but not 293, cells transduced with the IN-defective lentiviral vector containing the SV40-ori promoter. Polymerase chain reaction for two-long terminal repeat (2LTR) extrachromosomal circular forms, a marker of lentiviral E-DNA, and fluorescence in situ hybridization analysis confirmed the persistence and episomal nature of circular E-DNA up to 60 days after transduction. Taken together, these results indicate that insertion of the SV40-ori promoter in a lentiviral vector contributes to long-term expression by promoting episomal replication when TAg is provided in trans. Lentiviral episomal vectors may serve as specific tools for therapeutic approaches to diseases, particularly those associated with episomal replication of DNA viruses including papillomaviruses, polyomaviruses, and herpesviruses.

Neuropathology of genetically engineered mice: consensus report and recommendations from an international forum

The Mouse Models of Cancer Consortium of the NCI sponsored a meeting of neuropathologists and veterinary pathologists in New York City in November of 2000. A rapidly growing number of genetically engineered mice (GEM) predisposed to tumors of the nervous system have led to a concomitant need for neuropathological evaluation and validation of these models. A panel of 13 pathologists reviewed material representing most of the available published and unpublished GEM models of medulloblastoma, primitive neuroectodermal tumor, astrocytoma, oligodendroglioma, mixed glioma, and tumors of the peripheral nerve. The GEM tumors were found to have many similarities and some distinct differences with respect to human disease. After review of the biology and pathology for all models presented, participants were split into groups reflective of clinical expertise in human pathology, tumor biology, neuroimaging, or treatment/intervention. Recommendations were made detailing an extensive and complete neuropathological characterization of animals. Importance was placed on including information on strains, tumor clonality, and examination for genetic mutation or altered gene expression characteristics of the corresponding human malignancy. Specific proposals were made to incorporate GEM models in emerging neuroradiological modalities. Recommendations were also made for preclinical validation of these models in cancer therapeutics, and for incorporation of surrogate markers of tumor burden to facilitate preclinical evaluation of new therapies.