Effects of G207, a conditionally replication-competent oncolytic herpes simplex virus, on the developing mammalian brain

Viral oncolytic therapy for malignant brain tumors involves local intratumoral delivery of a genetically engineered virus with tumor cell-specific lytic activity. Promising preliminary results have been achieved in preclinical models with G207, a replication-competent herpes simplex virus type 1 constructed with multiple directed mutations. Although the safety of G207 has been demonstrated in adults, application of viral oncolytic therapy to children with brain tumors has been delayed because of previous lack of data concerning the impact of a replication-competent oncolytic virus on the developing mammalian brain. In this study there was no significant difference in long-term physical development, cognitive performance, or exploratory behaviors between mice that received intracerebral inoculation of G207 or control saline at 4 days of age. However, histological examination and magnetic resonance imaging revealed frequent unilateral ventriculomegaly ipsilateral to the site of injection in only the G207 group. These results suggest that although it is unlikely that G207 will have significant adverse effects on neurodevelopmental outcomes of pediatric patients with brain tumors, an initial study of G207 in children should exclude those patients with tumors in or near the ventricular system as well as patients less than 2 years of age. Furthermore, patients in such a study will need to be closely monitored for the development of hydrocephalus.

Gene delivery into malignant glioma by infectivity-enhanced adenovirus: in vivo versus in vitro models

Adenoviral (Ad) vectors demonstrate several attributes of potential utility for glioma gene therapy. Although Ad infection is limited in vitro by low expression levels of the coxsackie-adenoviral receptor (CAR), in vivo studies have shown the efficacy of Ad vectors as gene delivery vectors. To evaluate the in vivo utility of CAR-independent, infectivity-enhanced Ad vectors, we employed genetically modified Ad vectors in several experimental models of human gliomas. We used three capsid-modified Ad vectors: (1) a chimeric Ad vector with a human Ad backbone and a fiber knob of a canine Ad, (2) an Ad vector with a polylysine motif incorporated into the fiber gene, and (3) a double-modified Ad vector incorporating both an RGD4C peptide and the polylysine motif. These three modified Ad vectors target, respectively, the putative membrane receptor(s) of the canine Ad vector, heparan sulfate proteoglycans (HSPGs), and both integrins and HSPGs. Our in vitro studies indicated that these retargeting strategies all enhanced CAR-independent infectivity in both established and primary low-passage glioma cells. Enhancement of in vitro gene delivery by the capsid-modified vectors correlated inversely with the levels of cellular CAR expression. However, in vivo in orthotopic human glioma xenografts, the unmodified Ad vector was not inferior relative to the capsid-modified Ad vector. Although genetic strategies to circumvent CAR deficiency in glioma cells could reproducibly expand the cellular entry mechanisms of Ad vectors in cultured and primary glioma cells, these approaches were insufficient to confer in vivo significant infectivity enhancement over unmodified Ad vectors. Other factors, probably the extracellular matrix, stromal cells, and the three-dimensional tumor architecture, clearly play important roles in vivo and interfere with Ad-based gene delivery into glioma tumors.

Mutation of Escherichia coli cytosine deaminase significantly enhances molecular chemotherapy of human glioma

Combined treatment using adenoviral (Ad)-directed enzyme/prodrug therapy and radiation therapy has the potential to become a powerful method of cancer therapy. We have developed an Ad vector encoding a mutant bacterial cytosine deaminase (bCD) gene (AdbCD-D314A), which has a higher affinity for cytosine than wild-type bCD (bCDwt). The purpose of this study was to evaluate cytotoxicity in vitro and therapeutic efficacy in vivo of the combination of AdbCD-D314A with the prodrug 5-fluorocytosine (5-FC) and ionizing radiation against human glioma. The present study demonstrates that AdbCD-D314A infection resulted in increased 5-FC-mediated cell killing, compared with AdbCDwt. Furthermore, a significant increase in cytotoxicity following AdbCD-D314A and radiation treatment of glioma cells in vitro was demonstrated as compared to AdbCDwt. Animal studies showed significant inhibition of subcutaneous or intracranial tumor growth of D54MG glioma xenografts by the combination of AdbCD-D314A/5-FC with ionizing radiation as compared with either agent alone, and with AdbCDwt/5-FC plus radiation. The results suggest that the combination of AdbCD-D314A/5-FC with radiation produces markedly increased cytotoxic effects in cancer cells in vitro and in vivo. These data indicate that combined treatment with this novel mutant enzyme/prodrug therapy and radiotherapy provides a promising approach for cancer therapy.

Enhanced antiglioma activity of chimeric HCMV/HSV-1 oncolytic viruses

Oncolytic herpes simplex virus (HSV)-1 gamma(1)34.5-deletion mutants (Deltagamma(1)34.5 HSV) are promising agents for tumor therapy. The attenuating mutation renders the virus aneurovirulent but also limits late viral protein synthesis and efficient replication in many tumors. We tested whether one function of gamma(1)34.5 gene, which mediates late viral protein synthesis through host protein kinase R (PKR) antiviral response evasion, could be restored, without restoring the neurovirulence. We have previously reported the construction of two chimeric Deltagamma(1)34.5 HSV vectors (chimeric HSV), C130 and C134, which express the human cytomegalovirus (HCMV) PKR-evasion genes TRS1 and IRS1, respectively. We now demonstrate the following. The HCMV/HSV-1 chimeric viruses (i) maintain late viral protein synthesis in the human malignant glioma cells tested (D54-MG, U87-MG and U251-MG); (ii) replicate to higher titers than Deltagamma(1)34.5 HSV in malignant glioma cells in vitro and in vivo; (iii) are aneurovirulent; and (iv) are superior to other Deltagamma(1)34.5 HSV with both improved reduction of tumor volumes in vivo, and improved survival in two experimental murine brain tumor models. These findings demonstrate that transfer of HCMV IRS1 or TRS1 gene into Deltagamma(1)34.5 HSV significantly improves replication in malignant gliomas without restoring wild-type neurovirulence, resulting in enhanced tumor reduction and prolonged survival.

Directing adenovirus across the blood–brain barrier via melanotransferrin (P97) transcytosis pathway in an in vitro model

Adenovirus serotype 5 (Ad5) is widely used in the development of gene therapy protocols. However, current gene therapy strategies involving brain are mostly based on intra-cranial injection. A major obstacle for systemically administered vectors to infect brain tissue is the blood-brain barrier (BBB). One strategy to cross the BBB is transcytosis, a transcellular transport process that shuttles a molecule from one side of the cell to the other side. Recently, melanotransferrin (MTf)/P97 was found to be able to cross the BBB and accumulate in brain. We thus hypothesize that re-directing Ad5 vectors to the MTf transcytosis pathway may facilitate Ad5 vectors to cross the BBB. To test this hypothesis, we constructed a bi-specific adaptor protein containing the extracellular domain of the coxsackie-adenovirus receptor (CAR) and the full-length melanotransferrin (sCAR-MTf), and investigated its ability to re-direct Ad5 vectors to the MTf transcytosis pathway. We found this adaptor protein could re-direct Ad5 to the MTf transcytosis pathway in an in vitro BBB model, and the transcytosed Ad5 viral particles retained their native infectivity. The sCAR-MTf-mediated Ad5 transcytosis was temperature- and dose dependent. In addition, we examined the directionality of sCAR-MTf-mediated Ad5 transcytosis, and found the efficiency of apical-to-basal transcytosis was much higher than that of basal-to-apical direction, supporting a role of this strategy in transporting Ad5 vectors towards the brain. Taken together, our study demonstrated that re-directing Ad5 to the MTf transcytosis pathway could facilitate gene delivery across the BBB.

Oncolytic HSV-1 for the treatment of brain tumours

The prognosis for patients diagnosed with malignant glioma, the most common primary tumour of the central nervous system, remains poor despite decades of research and advances in surgery, radiation and chemotherapy. The development of new approaches for the treatment of these tumours has led to the emergence of oncolytic viral therapy, with the use of conditionally replicating viruses, as a potential new intervention. Herpes simplex virus type 1 has emerged as the leading candidate oncolytic virus, with six different trials either completed or underway for patients with malignant glioma. In this review, the background of this approach will be discussed, followed by a discussion of the clinical trials, as well as potential directions for future trials.

Engineered herpes simplex virus expressing bacterial cytosine deaminase for experimental therapy of brain tumors

Lack of effective therapy of primary brain tumors has promoted the development of novel experimental approaches utilizing oncolytic viruses combined with gene therapy. Towards this end, we have assessed a conditionally replication-competent, gamma(1)34.5-deleted herpes simplex virus type 1 (HSV-1) expressing cytosine deaminase (CD) for treatment of malignant brain tumors. Our results are summarized as follows: (i) a recombinant HSV (M012) was constructed in which both copies of the gamma(1)34.5 gene were replaced with the bacterial CD gene, under the control of the cellular promoter Egr-1; (ii) M012-infected cells in vitro efficiently convert 5-fluorocytosine (5-FC) to 5-fluorouracil, thereby enhancing cytotoxicity of neighboring, uninfected cells; (iii) both direct and bystander cytotoxicity of murine neuroblastoma and human glioma cell lines after infection with M012 were demonstrated; (iv) direct intracerebral inoculation of A/J mice demonstrated lack of neurotoxicity at doses similar to G207, a gamma(1)34.5-deleted HSV with demonstrated safety in human patient trials and (v) intratumoral injection of M012 into Neuro-2a flank tumors in combination with 5-FC administration significantly reduced tumor growth versus tumors treated with R3659 combined with 5-FC, or treated with M012 alone. Thus, M012 is a promising new oncolytic HSV vector with an enhanced prodrug-mediated, antineoplastic effect that is safe for intracranial administration.

Serial passage through human glioma xenografts selects for a Deltagamma134.5 herpes simplex virus type 1 mutant that exhibits decreased neurotoxicity and prolongs survival of mice with experimental brain tumors

Previous studies have described in vitro serial passage of a Deltagamma(1)34.5 herpes simplex virus type 1 (HSV-1) strain in SK-N-SH neuroblastoma cells and selection of mutants that have acquired the ability to infect and replicate in this previously nonpermissive cell line. Here we describe the selection of a mutant HSV-1 strain by in vivo serial passage, which prolongs survival in two separate experimental murine brain tumor models. Two conditionally replication-competent Deltagamma(1)34.5 viruses, M002, which expresses murine interleukin-12, and its parent virus, R3659, were serially passaged within human malignant glioma D54-MG cell lines in vitro or flank tumor xenografts in vivo. The major findings are (i) viruses passaged in vivo demonstrate decreased neurovirulence, whereas those passaged in vitro demonstrate a partial recovery of the neurovirulence associated with HSV-1; and (ii) vvD54-M002, the virus selected after in vivo serial passage of M002 in D54-MG tumors, improves survival in two independent murine brain tumor models compared to the parent (unpassaged) M002. Additionally, in vitro-passaged, but not in vivo-passaged, M002 displayed changes in the protein synthesis profile in previously nonpermissive cell lines, as well as early U(S)11 transcription. Thus, a mutant HSV-1 strain expressing a foreign gene can be selected for enhanced antitumor efficacy via in vivo serial passage within flank D54-MG tumor xenografts. The enhanced antitumor efficacy of vvD54-M002 is not due to restoration of protein synthesis or early U(S)11 expression. This finding emphasizes the contribution of the in vivo tumor environment for selecting novel oncolytic HSV specifically adapted for tumor cell destruction in vivo.

Pharmacologic manipulations of mitochondrial membrane potential (DeltaPsim) selectively in glioma cells

Metabolic control theory applies principles of bioenergetics for the control or management of complex diseases. Since metabolism is a general process underlying all biologic phenotypes, changes in metabolism can potentially modify phenotype. Therefore, it is reasonable to assume that experimental modulation of the availability of cellular energy can potentially alter cell phenotypes and cell functions critical to tumor progression including cell division. The purpose of this study was to determine if OMX-2, a methylquinone system designed to shuttle electrons from mitochondrial complexes, was able to target mitochondria in cancer cells and trigger cell death. Using flow cytometry, cell viability assays, and ATP measurements, we found that OMX-2 differentially decreased DeltaPsim without triggering cell death. In contrast, known blockers of the Electron Transport Chain (ETC) decreased DeltaPsim and triggered cell death. When normal cells were treated with OMX-2, neither DeltaPsim or cell death was triggered. Furthermore, OMX-2 modulated intracellular ATP and decreased cell numbers of glioma cells. Cell cycle analysis indicated that OMX-2 induced a reversible cell cycle arrest in G1/S. Finally, impairment of glycolysis by 2-Deoxyglucose (2-DOG) acted synergistically with OMX-2 to trigger cell death. Overall, these results indicate that it is possible to selectively target cancer cells by decreasing DeltaPsim and induced cell cycle arrest without triggering cell death. Moreover, pharmacological approaches designed to act on both glycolysis and oxidative phosphorylation can be considered as a new approach to selectively kill cancer cells.

Increased Expression of Thymidylate Synthetase (TS), Ubiquitin Specific Protease 10 (USP10) and Survivin is Associated with Poor Survival in Glioblastoma Multiforme (GBM)

BACKGROUND

The limited success of empirically designed treatment paradigms for patients diagnosed with glioblastoma multiforme (GBM) emphasizes the need for rationally designed treatment strategies based on the molecular profile of tumor samples and their correlation to clinical parameters.

METHODS

In the current study, we utilize a novel real-time quantitative low density array (RTQ-LDA) to identify differentially expressed genes in de novo GBM tissues obtained from patients with distinctly different clinical outcomes. Total RNA was isolated from a cohort of 21 GBM specimens obtained from patients with either good (long-term survival (LTS) >36 months post surgery, n = 8) or poor (died of the disease (DOD) <24 months post surgery, n = 13) prognosis. Non-neoplastic brain tissue (n = 5) was obtained from patients who underwent surgery for refractory epilepsy. Demographic data was assessed for correlation with survival using Cox proportional hazards models. Sufficient RNA was available to use RTQ-LDA to quantify the expression of 93 independent genes in 5 LTS, 4 DOD, and 5 non-neoplastic brain samples. The eight differentially expressed genes identified by RTQ-LDA in LTS versus DOD (P <or= 0.050) were subsequently quantified in all 21 GBM samples by real-time quantitative PCR (RTQ).

RESULTS

A correlation between younger patients and good prognosis was demonstrated (P <or= 0.05). The combination of RTQ-LDA and RTQ identified thymidylate synthetase (TS), ubiquitin specific protease 10 (USP10), and survivin as significantly over-expressed (P <or= 0.050) in DOD compared to LTS patients. Ribonucleotide reductase subunit M2 (RRM2) was identified as tumor-specific, but not associated with survival.

CONCLUSIONS

Taken collectively, TS, USP10, survivin and RRM2 may be useful as prognostic indicators and/or in the development of rationally designed treatment protocols.

Surface expression of ASIC2 inhibits the amiloride-sensitive current and migration of glioma cells

Gliomas are primary brain tumors with a complex biology characterized by antigenic and genomic heterogeneity and a propensity for invasion into normal brain tissue. High grade glioma cells possess a voltage-independent, amiloride-inhibitable, inward Na+ current. This current does not exist in normal astrocytes or low grade tumor cells. Inhibition of this conductance decreases glioma growth and cell migration making it a potential therapeutic target. Our previous results have shown that the acid-sensing ion channels (ASICs), members of the epithelial Na+ channel (ENaC)/degenerin (DEG) family of ion channels are part of this current pathway. We hypothesized that one member of the ENaC/DEG family, ASIC2, is retained intracellularly and that it is the lack of functional expression of ASIC2 at the cell surface that results in hyperactivity of this conductance in high grade gliomas. In this study we show that the chemical chaperone, glycerol, and the transcriptional regulator, sodium 4-phenylbutyrate, inhibit the constitutively activated inward current and reduce cell growth and migration in glioblastoma multiforme. The results suggest that these compounds induce the movement of ASIC2 to the plasma membrane, and once there, the basally active inward current characteristic of glioma cells is abolished by inherent negative regulatory mechanisms. This in turn compromises the ability of the glioma cell to migrate and proliferate. These results support the hypothesis that the conductance pathway in high grade glioma cells is comprised of ENaC/DEG subunits and that abolishing this channel activity promotes a reversion of a high grade glioma cell to a phenotype resembling that of normal astrocytes.

Systemic anti-hepatocyte growth factor monoclonal antibody therapy induces the regression of intracranial glioma xenografts

PURPOSE

Hepatocyte growth factor (HGF) and its receptor Met are involved in the initiation, progression, and metastasis of numerous systemic and central nervous system tumors. Thus, an anti-HGF monoclonal antibody (mAb) capable of blocking the HGF-Met interaction could have broad applicability in cancer therapy.

EXPERIMENTAL DESIGN

An anti-HGF mAb L2G7 that blocks binding of HGF to Met was generated by hybridoma technology, and its ability to inhibit the various biological activities of HGF was measured by in vitro assays. The ability of L2G7 to inhibit the growth of tumors was determined by establishing s.c. and intracranial xenografts of human U87 and U118 glioma cell lines in nude mice, and treatment with 100 microg of L2G7 or control given i.p. twice per week.

RESULTS

MAb L2G7 strongly inhibited all biological activities of HGF measured in vitro, including cell proliferation, cell scattering, and endothelial tubule formation. Treatment with L2G7 completely inhibited the growth of established s.c. xenografts in nude mice. Moreover, systemic administration of L2G7 from day 5 induced the regression of intracranial U87 xenografts and dramatically prolonged the survival of tumor-bearing mice from a median of 39 to >90 days. L2G7 treatment of large intracranial tumors (average tumor size, 26.7 mm(3)) from day 18 induced substantial tumor regression (control group, 134.3 mm(3); L2G7 treated group, 11.7 mm(3)) by day 29 and again prolonged animal survival.

CONCLUSIONS

These findings show that blocking the HGF-Met interaction with systemically given anti-HGF mAb can have profound antitumor effects even within the central nervous system, a site previously believed to be resistant to systemic antibody-based therapeutics.

Xanthine oxidase-dependent regulation of hypoxia-inducible factor in cancer cells

During chemical hypoxia induced by cobalt chloride (CoCl2), hypoxia-inducible factor 1alpha (HIF1-alpha) mediates the induction of a variety of genes including erythropoietin and vascular endothelial growth factor. We used glioma cells with oxidative phosphorylation-dependent (D54-MG) and glycolytic-dependent (U251-MG) phenotypes to monitor HIF1-alpha regulation in association with redox responsiveness to CoCl2 treatment. We showed that CoCl2 increased xanthine oxidase (XO)-derived reactive oxygen species (ROS), which causes accumulation of HIF1-alpha protein in U251-MG cells. Under these conditions, blockade of XO activity by pharmacologic (N-acetyl-L-cysteine or allopurinol) or molecular (by small interfering RNA) approaches significantly attenuated HIF1-alpha expression. Exogenous H2O2 stabilizes HIF1-alpha protein. XO was present in these cells and was the primary source of free radicals. We also showed higher XO activity in cells exposed to CoCl2 compared with cells grown in normoxia. From the experiments shown here, we concluded that ROS were indeed generated in D54-MG cells exposed to CoCl2 but it was unlikely that ROS participated in the hypoxic signal transduction pathways in this cell type. Possibly, cell type-dependent and stimulus-dependent factors may control ROS dependency or redox sensitivity of HIF1-alpha and thus HIF1-alpha activation either directly or by induction of specific signaling cascades. Our findings reveal that XO-derived ROS is a novel and critical component of HIF1-alpha regulation in U251-MG cells, pointing toward a more general role of this transcription factor in tumor progression.

Genetically engineered herpes simplex viruses that express IL-12 or GM-CSF as vaccine candidates

We are using genetically modified, conditionally replicating herpes simplex virus (HSV) that express either interleukin (IL)-12 or granulocyte macrophage-colony stimulating factor (GM-CSF) as live, attenuated vaccine candidates for protection against HSV infection and/or disease. We report the following: (1) animals previously vaccinated with these candidate vaccines exhibited dose-dependent protection after intranasal, intraperitoneal or intracranial challenge with the highly virulent E377-MB wild-type HSV-1; (2) the IL-12 expressing virus (M002) consistently conferred protection at lower immunization doses than GM-CSF expressing virus (M004); (3) between 80 and 100% protection from E377-MB challenge was conferred after intramuscular immunization of mice with any of the three Deltagamma1 34.5 HSV, as opposed to 50% protection elicited after immunization with wild-type HSV-1 (F); and (4) latent virus was not detected at a higher rate in animals immunized and subsequently challenged with E377-MB than in immunized animals alone. These data suggest that conditionally replicating, cytokine-expressing HSV are able to elicit protective immune responses while retaining safety in an experimental murine model.

Inhibition of cystine uptake disrupts the growth of primary brain tumors

Glial cells play an important role in sequestering neuronally released glutamate via Na+-dependent transporters. Surprisingly, these transporters are not operational in glial-derived tumors (gliomas). Instead, gliomas release glutamate, causing excitotoxic death of neurons in the vicinity of the tumor. We now show that glutamate release from glioma cells is an obligatory by-product of cellular cystine uptake via system xc-, an electroneutral cystine-glutamate exchanger. Cystine is an essential precursor for the biosynthesis of glutathione, a major redox regulatory molecule that protects cells from endogenously produced reactive oxygen species (ROS). Glioma cells, but not neurons or astrocytes, rely primarily on cystine uptake via system xc- for their glutathione synthesis. Inhibition of system xc- causes a rapid depletion of glutathione, and the resulting loss of ROS defense causes caspase-mediated apoptosis. Glioma cells can be rescued if glutathione status is experimentally restored or if glutathione is substituted by alternate cellular antioxidants, confirming that ROS are indeed mediators of cell death. We describe two potent drugs that permit pharmacological inhibition of system xc-. One of these drugs, sulfasalazine, is clinically used to treat inflammatory bowel disease and rheumatoid arthritis. Sulfasalazine was able to reduce glutathione levels in tumor tissue and slow tumor growth in vivo in a commonly used intracranial xenograft animal model for human gliomas when administered by intraperitoneal injection. These data suggest that inhibition of cystine uptake into glioma cells through the pharmacological inhibition of system xc- may be a viable therapeutic strategy with a Food and Drug Administration-approved drug already in hand.

Divergent effects of oncostatin M on astroglioma cells: influence on cell proliferation, invasion, and expression of matrix metalloproteinases

Oncostatin M (OSM), a cytokine of the interleukin-6 (IL-6) family, can either promote or inhibit cell growth in various normal and tumor cells. We addressed the effects of exogenous OSM on the proliferation and invasion of human astroglioma cells. In addition, we investigated one of the possible mechanisms involved: modulation of matrix metalloproteinase (MMP) expression and enzymatic activity. We found that OSM inhibited the proliferation of two human astroglioma cell lines (CH235-MG and U87-MG), and that this effect was not due to apoptosis. The inhibitory effect of OSM on proliferation was mediated through the gp130/OSMRbeta receptor complex. To extend these findings, we analyzed the effects of OSM on primary tumor cells from glioblastoma patients. OSM suppressed the proliferation of primary glioblastoma cells, but not that of normal astrocytes. Interestingly, OSM did not suppress astroglioma cell invasion. This may be due to the differential regulation of MMPs by OSM. We found that OSM inhibited the constitutive expression of MMP-2, while MMP-9 expression was enhanced in astroglioma cell lines. We conclude that OSM inhibits proliferation of human astroglioma cells and primary glioblastoma cells via the gp130/OSMRbeta receptor complex. However, OSM does not affect the invasive capacity of the astroglioma cells, which may be due to the divergent effects of OSM on MMP-2 and MMP-9 expression. Collectively, these findings suggest a complex role for OSM in astroglioma biology.

A novel technique to quantify glioma tumor invasion using serial microscopy sections

Here we present a new technique to quantitatively characterize malignant glioma invasion in a syngeneic mouse model. The GL261 mouse malignant glioma cell line was injected intracerebrally into the C57B1/6 black mouse and allowed to propagate for 10 or 17 days, followed by euthanasia of the animal, harvesting of the brain, fixation, and serial sectioning. Histologic examination was performed and the primary tumor mass and discontinuous sites of tumor invasion were traced on digital images of serial microscopy sections, followed by analysis of the invasion characteristics using a custom-written MATLAB program. We found a significant increase in the number of discontinuous tumor invasion sites and in the distance of these sites from the tumor centroid in mice that were euthanized at 17 days post-tumor cell injection, as compared to mice euthanized at 10 days. Furthermore, a scatter plot analyses indicated that the invasion site data could be grouped based on the characteristics of area and distance from the tumor centroid to reveal significant differences between the two experimental groups of mice. This quantitative method will allow a future in vivo analysis of invasion characteristics in glioma cells expressing altered levels or function of invasion genes, and of new therapy targeting invading glioma cells.

Polymerase Chain Reaction for the Rapid Detection of Cerebrospinal Fluid Shunt or Ventriculostomy Infections

OBJECTIVE:

Infection after cerebrospinal fluid (CSF) shunts or ventriculostomies is a common complication associated with significant morbidity and mortality. Polymerase chain reaction (PCR) is a powerful molecular technique that allows rapid and precise amplification of bacterial deoxyribonucleic acid (DNA) and has proven a powerful tool in the detection of a wide variety of clinically important infectious diseases. We analyzed specimens of CSF derived from ventriculoperitoneal shunts or external ventricular drains by using both conventional cultures and PCR and report herein our preliminary results.

METHODS:

We selected 86 CSF samples from adult patients who underwent either shunt tap or routine surveillance cultures of their ventriculostomy. These specimens were chosen from a larger group of 300 specimens that were routinely collected (many serially) in our clinical practice. They were chosen because clinical suspicion of infection was increased because of either patient signs and symptoms (fever, stiff neck, lethargy, worsening neurological examination) or preliminary laboratory analysis of CSF data (increased white blood cell count, increased protein level, decreased glucose). We considered this subgroup optimal to efficiently initiate our investigation of the correlation of PCR and culture results. CSF was increased by using standard culture techniques and by using PCR. Samples of CSF that were to undergo PCR had DNA extracted, purified, and amplified for 16S rRNA using primers 16S-Forward and 16S-Reverse of conserved sequence regions of all bacteria. DNA was PCR-amplified for 30 cycles. One microliter of the first PCR product was subjected to nested PCR using primers specific for gram-positive and gram-negative bacteria. Samples were also subjected to PCR amplification for specific detection of Propionibacterium acnes, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus using specific primers for 16S rRNA Propionibacterium, nuclease gene of Staphylococcus, and Mec gene of methicillin-resistant Staphylococcus aureus.

RESULTS:

For 18 of 86 specimens (21%), both the culture and PCR were positive. For 30 of 86 specimens (35%), both the PCR and culture results were negative. For 42 of 86 specimens (49%), cultures were negative and PCR was positive. There were no positive culture results with negative PCR results. Most negative culture/positive PCR cases occurred after prolonged intravenous antibiotics. Of the 56 PCR-positive specimens, 30 were positive for Propionibacterium acnes, whereas 40 were positive for Staphylococcus aureus. Of the Staphylococcus aureus-positive specimens, two were positive for methicillin resistant-Staphylococcus aureus. Among the 56 PCR-positive specimens, 30 were positive for both Propionibacterium acnes and Staphylococcus aureus; gram-negative organisms were not detected by any method in these specimens.

CONCLUSION:

These preliminary data suggest that PCR is a highly sensitive, rapid, and potentially promising modality for the detection and treatment of CSF shunt ventriculostomy infection.

Lyn kinase activity is the predominant cellular SRC kinase activity in glioblastoma tumor cells

Cellular Src activity modulates cell migration, proliferation, and differentiation, and recent reports suggest that individual members of the Src family may play specific roles in these processes. As we have found that Lyn, but not Fyn, activity promotes migration of glioblastoma cells in response to the cooperative signal generated by platelet-derived growth factor receptor beta and integrin alpha(v)beta3, we compared the activity and expression of Lyn and Fyn in glioblastoma (grade IV) tumor biopsy samples with that in anaplastic astrocytoma (grade III) tumors, nonneoplastic brain, and normal autopsy brain samples. Lyn kinase activity was significantly elevated in glioblastoma tumor samples. Notably, the Lyn kinase activity accounted for >90% of pan-Src kinase activity in glioblastoma samples but only approximately 30% of pan-Src kinase activity in the other groups. The levels of phosphorylation of the autophosphorylation site were consistent with significantly higher Lyn activity in glioblastoma tumor tissue than nonneoplastic brain. Although the normalized levels of Lyn protein and the relative levels of Lyn message were significantly higher in glioblastoma samples than nonneoplastic brain, the normalized levels of Lyn protein did not correlate with Lyn activity in the glioblastoma samples. There was no significant difference in the normalized levels of c-Src and Fyn protein and message in the glioblastoma and nonneoplastic brain. Immunostaining revealed that Lyn is located primarily in the glioblastoma cells in the tumor biopsies. These data indicate that Lyn kinase activity is significantly elevated in glioblastoma tumors and suggest that it is the Lyn activity that promotes the malignant phenotype in these tumors.

Increased efficacy of an interleukin-12-secreting herpes simplex virus in a syngeneic intracranial murine glioma model

Long-term survivors of glioblastoma multiforme, the most common form of primary intracranial malignancy in adults, are extremely rare. Experimental animal models that more closely resemble human disease are essential for the identification of effective novel therapies. We report here an extensive analysis of the 4C8 glioma model to assess its suitability for evaluating novel type 1 herpes simplex virus (HSV-1) therapies of malignant glioma. We first determined that expression of major histocompatibility complex I and II and of alphavbeta3 in the 4C8 model was comparable to that seen in human glioma cells. Next, using a panel of Delta(gamma1)34.5 HSVs, we demonstrated that, in vitro, 4C8 cells were as sensitive as human glioma cells to both infection and lysis and that the 4C8 cells supported the production of foreign gene products. Replication competence of HSV was demonstrated in vitro. Finally, 4C8 intracranial gliomas were established in immunologically competent syngeneic B6D2F1 mice, treated by intratumoral injection of selected engineered HSVs, including the interleukin-12-expressing virus, M002. Survival data from these studies demonstrated that 4C8 cells in vivo are sensitive to both direct oncolysis and HSV-mediated interleukin-12 expression. Fluorescence-activated cell sorting analyses of immune-related infiltrating cells supported the concept that survival was prolonged in part because of antitumor actions of these cells. We conclude that the 4C8/B6D2F1 syngeneic glioma model is suitable for preclinical evaluation of HSV-based therapies and that M002 is a superior virus for the treatment of murine glioma in this model.

Glucose Metabolism Heterogeneity in Human and Mouse Malignant Glioma Cell Lines

The current study examined specific bioenergetic markers associated with the metabolic phenotype of several human and mouse glioma cell lines. Based on preliminary studies, we hypothesized that glioma cells would express one of at least two different metabolic phenotypes, possibly acquired through progression. The D-54MG and GL261 glioma cell lines displayed an oxidative phosphorylation (OXPHOS)-dependent phenotype, characterized by extremely long survival under glucose starvation, and low tolerance to poisoning of the electron transport chain (ETC). Alternatively, U-251MG and U-87MG glioma cells exhibited a glycolytic-dependent phenotype with functional OXPHOS. These cells displayed low tolerance to glucose starvation and were resistant to a ETC blocker. Moreover, these cells could be rescued in low glucose conditions by oxidative substrates (e.g., lactate, pyruvate). Finally, these two phenotypes could be distinguished by the differential expression of LDH isoforms. OXPHOS-dependent cells expressed both LDH-A and -B isoforms whereas glycolytic-dependent glioma cells expressed only LDH-B. In the latter case, LDH-B would be expected to be essential for the use of extracellular lactate to fuel cell activities. These observations raise the possibility that the heterogeneity in glucose metabolism and, in particular, the sole expression of LDH-B, might identify an important biological marker of glioma cells that is critical for their progression and that might afford a new target for anticancer drugs.

Changes in intracellular Ca2+and pH in response to thapsigargin in human glioblastoma cells and normal astrocytes

Despite extensive work in the field of glioblastoma research no significant increase in survival rates for this devastating disease has been achieved. It is known that disturbance of intracellular Ca2+([Ca2+]i) and intracellular pH (pHi) regulation could be involved in tumor formation. The sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) is a major regulator of [Ca2+]i. We have investigated the effect of inhibition of SERCA by thapsigargin (TG) on [Ca2+]iand pHiin human primary glioblastoma multiforme (GBM) cells and GBM cell lines, compared with normal human astrocytes, using the fluorescent indicators fura-2 and BCECF, respectively. Basal [Ca2+]iwas higher in SK-MG-1 and U87 MG but not in human primary GBM cells compared with normal astrocytes. However, in tumor cells, TG evoked a much larger and faster [Ca2+]iincrease than in normal astrocytes. This increase was prevented in nominally Ca2+-free buffer and by 2-APB, an inhibitor of store-operated Ca2+channels. In addition, TG-activated Ca2+influx, which was sensitive to 2-APB, was higher in all tumor cell lines and primary GBM cells compared with normal astrocytes. The pHiwas also elevated in tumor cells compared with normal astrocytes. TG caused acidification of both normal and all GBM cells, but in the tumor cells, this acidification was followed by an amiloride- and 5-( N, N-hexamethylene)-amiloride-sensitive recovery, indicating involvement of a Na+/H+exchanger. In summary, inhibition of SERCA function revealed a significant divergence in intracellular Ca2+homeostasis and pH regulation in tumor cells compared with normal human astrocytes.

Antibiotic-mediated chemoprotection enhances adaptation of E. coli PNP for herpes simplex virus-based glioma therapy

The E. coli PNP suicide gene sensitizes solid tumors to nucleoside prodrugs, such as 6-methylpurine-2'-deoxyriboside (MeP-dR). In this study using lentiviral, MuLv, and HSV-based gene transfer, we quantified thresholds for inhibition of tumor growth and bystander killing by E. coli PNP and tested the role of intestinal flora in this process. Regressions of human glioma tumors following retroviral transduction exhibited dose dependence on both the level of PNP expression and the dose of MeP-dR administered, including strong tumor inhibition when 90-99% bystander cells comprised the tumor mass. A replication competent, non-neurovirulent herpes simplex virus (HSV) deficient in both copies of the gamma-1 34.5 gene was next engineered to express E. coli PNP under the egr-1 promoter (HSV-PNP). HSV-PNP injected intratumorally (17 million pfu/0.05 ml) in nude mice bearing 300 mg human glioma flank tumors produced a delay in tumor growth (approximately 24 days delay to one doubling). MeP-dR treatment after antibiotic therapy (to eliminate enteric flora encoding PNP enzymes) resulted in antitumor enhancement, with arrest of tumor growth (delay to doubling >50 days). Bystander killing of the magnitude described here has been difficult to accomplish with other suicide genes, such as HSV-tk or cytosine deaminase. The results establish a model for applying E. coli PNP to HSV treatment of glioma.

Enhanced inhibition of syngeneic murine tumors by combinatorial therapy with genetically engineered HSV-1 expressing CCL2 and IL-12

Herpes simplex viruses type 1 (HSV-1) that lack the gamma(1)34.5 gene are unable to replicate in the central nervous system (CNS), but maintain replication competence in actively dividing tumors. To determine if antitumor therapy by M002, a gamma(1)34.5(-) HSV that expresses interleukin-12 (IL-12), could be augmented by combinatorial therapy with another gamma(1)34.5-deleted HSV-1 engineered to express the chemokine CCL2, Neuro-2a tumors were established subcutaneously in the syngeneic A/J mouse strain. Tumors received multiple injections intratumorally either of saline, the parent, non-cytokine-expressing virus R3659, M002, M010 (gamma(1)34.5(-) HSV expressing CCL2), or a combination of M002 and M010. Efficacies were evaluated by monitoring inhibition of tumor growth over time. Results demonstrated the following: (1) inhibition of tumor growth was most pronounced in tumors treated with a combination of M002 and M010; (2) enhanced tumor growth inhibition for the combinatorial treatment group was statistically significant compared to either M002 or M010 alone; and (3) the variability between slopes of the tumor growth rates within an individual treatment group appeared to be virus-dependent, and was reproducible between experiments. Our results demonstrate that combinatorial cytokine/chemokine gamma(1)34.5(-) HSV therapies can provide superior antitumor effects in experimental tumors as a model for malignancies arising in the brain.

Radiation dosimetry of 131I-chlorotoxin for targeted radiotherapy in glioma-bearing mice

Chlorotoxin, or TM-601, is a peptide derived from the venom of the scorpionLeiurus Quinquestriatus that specifically binds to malignant brain tumors, but not to normal tissues. Targeted radiotherapy using 131I-Chlorotoxin is promising for post-surgery treatment of brain tumors. This study reports dosimetry results of 131I-Chlorotoxin in athymic nude mice with intracranially implanted human glioma xenografts and projected radiation doses in patients receiving 370 MBq of 131I-Chlorotoxin. 125I/131I-Chlorotoxin were injected into the right brain where D54 MG xenografts were implanted. Mice were sacrificed 24-96 h later. The blood, normal organs, and tumors were weighed and counted to determine 131I-Chlorotoxin concentration. The radiation dose from 131I was calculated based on non-penetrating radiation in the mouse model. Assuming similar tissue uptake in mice and patients, radiation doses for patients were extrapolated. Distributions of 125I/131I-Chlorotoxin were only significant in tumor, stomach, kidneys, and brain (injection site), reflecting non-specific uptake of Chlorotoxin in normal tissues. Mean radiation dose (cGy/37 kBq) was 58.2 for tumor, 17.9 for brains, 1.8 for marrow, 27.1 for stomach, 16.0 for kidneys in mice. For intracranial injection of 370 MBq 131I-Chlorotoxin in patients, extrapolated patient dose (cGy) was 70 for brains, 6 for marrow, 35 for stomach, 60 to kidneys, 227 to tumor, suggesting that 3.7 GBq of 131I-Chlorotoxin can be safely administrated to patients. These promising results demonstrated potential in improving patient survival using this novel targeting agent.

Transcriptional Targeting of Adenovirally Delivered Tumor Necrosis Factor α by Temozolomide in Experimental Glioblastoma

Temozolomide is an oral alkylating agent shown to have modest efficacy in the treatment of glioblastoma multiforme. Tumor necrosis factor alpha (TNF-alpha) is a polypeptide cytokine with synergistic antitumor activity in combination therapy with alkylating agents. We investigated the combined use of Ad.Egr-TNF, a replication-defective adenoviral vector encoding the cDNA for TNF-alpha under the control of chemo-inducible elements of the egr1 gene promoter, and intraperitoneal temozolomide in an intracranial human malignant glioma model. In hind limb U87MG xenografts, temozolomide produced a 6.4-fold greater induction of TNF-alpha after infection with Ad.Egr-TNF compared with Ad.Egr-TNF alone at 96 hours (P < 0.02). TNF-alpha and temozolomide combination leads to a synergistic decrease in U87 cell viability at 72 hours compared with either treatment alone (P < 0.001). Median survival for animals treated with Ad.Egr-TNF alone, temozolomide alone, and Ad.Egr-TNF/temozolomide was 21, 28, and 74 days, respectively (P < 0.001 by log-rank). Flow cytometric assessment of apoptosis revealed a synergistic increase in U87 cell apoptosis in vitro at 72 hours (P < 0.05), and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) evaluation of tumor sections revealed significantly increased TUNEL-positive cells after combination treatment compared with either treatment alone (P < 0.05). In conclusion, combination treatment with transcriptionally activated intratumoral TNF-alpha and systemic temozolomide significantly prolongs survival in an experimental glioblastoma multiforme model.

Cation selectivity and inhibition of malignant glioma Na+ channels by Psalmotoxin 1

Psalmotoxin 1 (a component of the venom of a West Indies tarantula) is a 40-amino acid peptide that inhibits cation currents mediated by acid-sensing ion channels (ASIC). In this study we performed electrophysiological experiments to test the hypothesis that Psalmotoxin 1 (PcTX1) inhibits Na+ currents in high-grade human astrocytoma cells (glioblastoma multiforme, or GBM). In whole cell patch-clamped cultured GBM cells, the peptide toxin quickly and reversibly inhibited both inward and outward current with an IC50 of 36 +/- 2 pM. The same inhibition was observed in freshly resected GBM cells. However, when the same experiment was performed on normal human astrocytes, the toxin failed to inhibit the whole cell current. We also determined a cationic selectivity sequence for inward currents in three cultured GBM cell lines (SK-MG-1, U87-MG, and U251-MG). The selectivity sequence yielded a unique biophysical fingerprint with inward K+ conductance approximately fourfold greater than that of Na+, Li+, and Ca2+. These observations suggest that PcTX1 may prove useful in determining whether GBM cells express a specific ASIC-containing ion channel type that can serve as a target for both diagnostic and therapeutic treatments of aggressive malignant gliomas.

Protein kinase C mediates induced secretion of vascular endothelial growth factor by human glioma cells

To understand how vascular endothelial growth factor (VEGF) production is activated in malignant glioma cells, we employed protein tyrosine kinase (PTK) and protein kinase C (PKC) inhibitors to evaluate the extent to which these protein kinases were involved in signal transduction leading to VEGF production. PTK inhibitors blocked glioma proliferation and epidermal growth factor (EGF)-induced VEGF secretion, while H-7, a PKC inhibitor, inhibited both EGF-induced and baseline VEGF secretion. Phorbol 12-myristate 13-acetate (PMA), a non-specific activator of PKC, induced VEGF secretion by glioma cells, which was enhanced by calcium ionophore A23187, but completely blocked after prolonged treatment of cells with 1 microM PMA, by presumably depleting PKC. All inhibitors (genistein, AG18, AG213, H-7, prolonged PMA treatment) which inhibited EGF-induced VEGF secretion in glioma cells also inhibited cell proliferation at similar concentrations. However, PKC inhibition only blocked 50% of the VEGF secretion induced by growth factors (EGF, platelet-derived growth factor-BB, or basic fibroblast growth factor). This reserve capacity could be ascribed to a PKC-independent effect, or to PKC isoenzymes not down-regulated by PMA. These findings extend our previous assertion that VEGF secretion is tightly coupled with proliferation by suggesting that activation of convergent growth factor signaling pathways will lead to increased glioma VEGF secretion. Understanding of signal transduction of growth factor-induced VEGF secretion should provide a rational basis for the development of novel strategies for therapy.

Oncolytic Viruses: Clinical Applications as Vectors for the Treatment of Malignant Gliomas

Gene therapy using viral vectors for the treatment of primary brain tumors has proven to be a promising novel treatment modality. Much effort in the past has been placed in utilizing replication-defective viruses to this end but they have shown many disadvantages. Much recent attention has been focused on the potential of replication-competent viruses to discriminatingly target, replicate within, and destroy tumor cells via oncolysis, leaving adjacent post-mitotic neurons unharmed. The engineered tumor-selective herpes simplex-1 virus (HSV-1) mutants G207 and HSV1716 have completed Phase I investigations in the treatment of recurrent high-grade glioma. The results of these clinical trials are reviewed here. This review also aims to examine the manipulation and development of other viruses for the treatment of malignant glioma, including Newcastle disease virus, reovirus, poliovirus, vaccinia virus, and adenoviruses, in particular the adenovirus mutant ONYX-015.

Molecular cloning and characterization of human acid sensing ion channel (ASIC)2 gene promoter

Acid sensing ion channel (ASIC)2 belongs to the amiloride-sensitive Na(+)-channel/ degenerin family. Our previous studies suggested that differential regulation of ASIC2 expression occurs between high-grade glial-derived tumor cells and normal astrocytes. To investigate the mechanisms involved in the regulation of ASIC2 gene expression, the human ASIC2 promoter region (-1551 to +117) was cloned and characterized. The ASIC2 promoter lacked a canonical TATA box, but contained one putative CCAAT box. Nucleotide sequencing of the promoter revealed the presence of a number of transcription factor-binding sites and a 404 bp CpG island upstream the transcription start site. Nested deletion mutants and transfection results showed that the construct between -133 and +117 base pairs conferred basal transcription specific activity. Mutation of Sp1 and CP2 sites in this region resulted in a 70 and 95% decrease in promoter activity, respectively. Gel shift assays demonstrated the existence of specific protein binding to the SP1 and CP2 elements. There was no mutation in the CpG island in six glioma cell lines, but methylation-specific PCR showed methylation in some of glioma cell lines and tumor tissues, and treatment with the methylation inhibitor 5-Aza-2'-deoxycytidine could partially restore ASIC2 expression in cell lines, suggesting that epigenetic mechanisms may contribute to dysregulated ASIC2 expression.

Acid-sensing ion channels in malignant gliomas

High grade glioma cells derived from patient biopsies express an amiloride-sensitive sodium conductance that has properties attributed to the human brain sodium channel family, also known as acid-sensing ion channels (ASICs). This amiloride-sensitive conductance was not detected in cells obtained from normal brain tissue or low grade or benign tumors. Differential gene profiling data showed that ASIC1 and ASIC2 mRNA were present in normal and low grade tumor cells. Although ASIC1 was present in all of the high grade glial cells examined, ASIC2 mRNA was detected in less than half. The main purpose of our work was to examine the molecular mechanisms that may underlie the constitutively activated sodium currents present in high grade glioma cells. Our results show that 1) gain-of-function mutations of ASIC1 were not present in a number of freshly resected and cultured high grade gliomas, 2) syntaxin 1A inhibited ASIC currents only when ASIC1 and ASIC2 were co-expressed, and 3) the inhibition of ASIC currents by syntaxin 1A had an absolute requirement for either gamma- or delta-hENaC. Transfection of cultured cells originally derived from high grade gliomas (U87-MG and SK-MG1) with ASIC2 abolished basal amiloride-sensitive sodium conductance; this inhibition was reversed by dialysis of the cell interior with Munc-18, a syntaxin-binding protein that typically blocks the interaction of syntaxin with other proteins. Thus, syntaxin 1A cannot inhibit Na(+) permeability in the absence of adequate plasma membrane ASIC2 expression, accounting for the observed functional expression of amiloride-sensitive currents in high grade glioma cells.

Synthesis and biological evaluation of paclitaxel-C225 conjugate as a model for targeted drug delivery

Tumor-targeted drug delivery is an attractive strategy in cancer treatment. We have previously reported a paclitaxel model conjugate using a bombesin receptor-recognizing peptide in which the drug cytotoxicity against H1299 human nonsmall cell lung cancer was enhanced compared to unconjugated taxol. In an effort to expand the development of tumor-recognizing taxanes, paclitaxel (PTX, taxol) was conjugated to the anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody (MAb) Erbitux (C225) to serve as a model MAb-mediated drug delivery compound. Thus, paclitaxel was derivatized at its 2'-hydroxy function by introduction of a succinate linker, and the carboxyl group of the latter was covalently attached to C225 through amide bond formation. The final product conjugate (PTXC225) was analyzed mass spectrometrically for assessment of the drug-to-antibody ratios. Cytotoxicity screening of the drug-antibody conjugate against A431, UM-SCC-1, and UM-SCC-6 cells indicated an enhancement in cytocidal effect of paclitaxel as compared to those of the free drug, the intact antibody, and a physical mixture of the two (the controls). In A431 cells, the conjugate showed 25.2% +/- 2.2% of apoptosis induction as compared to little or no apoptosis caused by the controls. Biodistribution analysis of the PTXC225 in tumor-implanted nude mice and a tyrosine-kinase assay showed that conjugation of the drug did not interfere with the immunoreactivity of the antibody. The 24-h tumor uptake of C225 and PTXC225 were 11.7% +/- 6.0% and 7.1% +/- 3.6% of the injected dose per gram of tissue (%ID/g), respectively, which were not significantly different. Also, in A431-implanted nude mice, the conjugate and C225 showed tumor growth inhibition effects of 57.2% and 41.2%, respectively, against a saline-treated control, which were not significantly different from each other. This lack of difference in the in vivo antitumor activity of the MAb-delivered drug and free PTX may be due to either a relatively low dose of the antibody-delivered drug (346 microg/kg), or an untimely release of it, or both. The tumor growth inhibition pattern of the conjugate, however, was identical to that of C225, indicating that the attachment of PTX did not affect the antigen-binding and growth inhibitory features of the MAb. These preliminary results demonstrate the potential of tumor-targeted delivery of taxol as a promising strategy in cancer treatment and warrant further work to develop more suitable drug-MAb linkers as well as improved dosage and treatment protocols.

Induction of thymidine phosphorylase in both irradiated and shielded, contralateral human U87MG glioma xenografts: implications for a dual modality treatment using capecitabine and irradiation

In the United States, tumors of the central nervous system remain the third leading cancer-related cause of death in young adults with a median survival time of < 1 year. A recent case study suggested that Capecitabine (a novel, fluoropyrimidine prodrug) may be effective in the treatment of brain metastases. Pharmacogenomic studies have correlated the antitumor response to Capecitabine with the expression of the drug metabolizing enzymes thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD). In the current study, we examined TP and DPD expression in normal human brain tissues and in glioblastoma multiforme, the most common and malignant type of brain tumor. Because previous reports suggest a tumor necrosis factor (TNF)-alpha-mediated increase in TP expression after irradiation (a current standard of care for glioblastoma multiforme), we also examined the effect of irradiation on the expression of TP, DPD, and TNF-alpha in both irradiated and lead-shielded contralateral U87MG glioma xenografts within the same animal. Expression levels were determined using real-time quantitative PCR as described previously. Results demonstrate an approximately 70-fold increase in TP mRNA levels 4 days after irradiation, relative to initial control levels. Interestingly, TP mRNA in the lead-shielded tumors (contralateral to irradiated tumors) increased approximately 60-fold by day 10 relative to initial control levels. Elevated TP levels were sustained for 20 days in irradiated xenografts but began to decrease after 15 days in the shielded/contralateral tumors, returning to baseline by 20 days. TP mRNA levels in normal mouse liver were unaltered, suggesting a tumor-associated effect. TNF-alpha mRNA levels did not increase after irradiation; therefore, mRNA expression of 11 additional cytokines [interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, and IFN-gamma] in both the irradiated and shielded xenografts was quantitated. Results demonstrated increased levels of IFN-gamma, IL-10, and IL-1 alpha by 6.3-, 3.7-, and 1.6-fold, respectively, in irradiated tumors only. DPD mRNA levels did not change after irradiation. The tumor-associated induction of TP in irradiated and lead-shielded tumors within the same animal may have significant implications for the combined modality treatment of cancer patients with Capecitabine in conjunction with radiotherapy and may apply to the treatment of distant tumors and or metastatic disease.

Protein kinase C isoform antagonism controls BNaC2 (ASIC1) function

We explored the involvement of protein kinase C (PKC) and its isoforms in the regulation of BNaC2. Reverse transcriptase PCR evaluation of PKC isoform expression at the level of mRNA revealed the presence of alpha and epsilon/epsilon' in all glioma cell lines analyzed; most, but not all cell lines expressed delta and zeta. No messages were found for the betaI and betaII isotypes of PKC in the tumor cells. Normal astrocytes expressed beta but not gamma. The essential features of these results were confirmed at the protein level by Western analysis. This disproportionate pattern of PKC isoform expression in glioma cell lines was further echoed in the functional effects of these PKC isoforms on BNaC2 activity in bilayers. PKC holoenzyme or the combination of PKCbetaI and PKCbetaII isoforms inhibited BNaC2. Neither PKCepsilon nor PKCzeta or their combination had any effect on BNaC2 activity in bilayers. The inhibitory effect of the PKCbetaI and PKCbetaII mixture on BNaC2 activity was abolished by a 5-fold excess of a PKCepsilon and PKCzeta combination. PKC holoenzymes, PKCbetaI, PKCbetaII, PKCdelta, PKCepsilon, and PKCzeta phosphorylated BNaC2 in vitro. In patch clamp experiments, the combination of PKCbetaI and PKCbetaII inhibited the basally activated inward Na(+) conductance. The variable expression of the PKC isotypes and their functional antagonism in regulating BNaC2 activity support the idea that the participation of multiple PKC isotypes contributes to the overall activity of BNaC2.

Adenovirus-mediated transfer of BAX driven by the vascular endothelial growth factor promoter induces apoptosis in lung cancer cells

Apoptosis induction is a promising approach for cancer gene therapy. Bax is a death-promoting member of the Bcl2 family of genes that are intimately involved in apoptosis. Overexpression of BAX protein can accelerate cell death by homodimers that promote apoptosis in a variety of cancer cell lines. The cytotoxic effect of BAX was evaluated in vitro by a recombinant adenovirus system expressing the human BAX gene under control of human vascular endothelial growth factor (VEGF) promoter element (AdVEGFBAX). Overexpression of BAX in human lung carcinoma cells resulted in apoptosis induction, caspase activation, and cell growth suppression, none of which were observed in BEAS-2B normal human bronchial epithelial cells that do not overexpress VEGF under normoxic conditions. To examine the hypoxia responsiveness of the VEGF promoter, lung cancer cells were transiently exposed to hypoxia; this treatment increased enhanced green fluorescent protein (EGFP) expression after AdVEGFEGFP infection in both normal and cancer cell lines, and enhanced apoptosis and decreased the number of surviving cancer cells compared with the Ad/BAX plus Ad/Cre binary adenoviral system. These results suggest a possible therapeutic application of cancer-specific expression of the pro-apoptotic Bax gene driven by the VEGF promoter.

Human cytomegalovirus infection and expression in human malignant glioma

Malignant gliomas are the most common primary brain tumors in adults, have no known etiology, and are generally rapidly fatal despite current therapies. Human cytomegalovirus (HCMV) is beta-herpesvirus trophic for glial cells that persistently infects 50-90% of the adult human population. HCMV can be reactivated under conditions of inflammation and immunosuppression, and HCMV gene products can dysregulate multiple cellular pathways involved in oncogenesis. Here we show that a high percentage of malignant gliomas are infected by HCMV and multiple HCMV gene products are expressed in these tumors. These data are the first to show an association between HCMV and malignant gliomas and suggest that HCMV may play an active role in glioma pathogenesis.

Focal adhesion kinase enhances signaling through the Shc/extracellular signal-regulated kinase pathway in anaplastic astrocytoma tumor biopsy samples

Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase that on activation generates signals that can modulate crucial cell functions, including cell proliferation, migration, and survival. In vitro, overexpression of FAK has been shown to promote cell proliferation by signaling through the Ras/mitogen-activated protein kinase cascade in several cell types. We have shown previously that overexpression of exogenous FAK lacking alternative splicing in malignant astrocytoma clones injected intracerebrally into SCID mouse brains promotes tumor cell proliferation. Here, we show that in anaplastic astrocytoma biopsy samples, FAK is expressed as an unspliced variant and migrates with a faster mobility similar to that observed in embryonic brain. Compared with nonneoplastic adult brain biopsies, the levels of FAK protein are elevated as are its levels of activation as assessed by autophosphorylation and overall tyrosine phosphorylation. The activity of Src kinase in these tumors is also elevated, as well as the activity of Src kinase associated with FAK; the latter may result in enhanced Src kinase phosphorylation of FAK. Phosphorylated Shc is associated with FAK in the anaplastic astrocytoma biopsy samples and in astrocytoma cells overexpressing FAK in vitro but not in nonneoplastic brain biopsy samples. Elevated extracellular signal-regulated kinase-2 activation and elevated expression of cyclins D and E are also found in anaplastic astrocytoma biopsy samples. These data provide evidence that the increased FAK activity in these tumors contributes to phosphorylation of Shc and likely to the promotion of Ras activity, extracellular signal-regulated kinase-2 activation, and cell proliferation in vivo.

Intratumoral 5-fluorouracil produced by cytosine deaminase/5-fluorocytosine gene therapy is effective for experimental human glioblastomas

5-Fluorouracil (5-FU) is a potent antimetabolite used for chemotherapy of gastrointestinal (GI), breast, and head and neck malignancies. Although clinical trials have been conducted, the poor therapeutic index of 5-FU has precluded its clinical use for a number of other tumor types. It is unclear whether this lack of utility is due to problems with drug delivery or inherent insensitivity. Adenovirus (Ad) vector-mediated cytosine deaminase (CD)/5-fluorocytosine (5-FC) gene therapy has the potential to overcome pharmacokinetic issues associated with systemic 5-FU and is particularly well suited to use with tumors in which local control is paramount, such as recurrent, localized prostate cancer and malignant gliomas. In this study, the in vitro response by a panel of human tumor cell lines derived from both GI (colon, pancreas) and non-GI (prostate, glioma) tumors to 5-FU and to AdCMVCD (an Ad encoding Escherichia coli CD)/5-FC was examined. Whereas the sensitivity (IC(50)) of individual cell lines to these agents varied, no significant difference in median IC(50) for either 5-FU or AdCMVCD/5-FC was evident for the four tumor types tested (P > 0.1). The relevant contributions of Ad gene transfer efficiency and inherent 5-FU sensitivity in determining response to AdCMVCD/5-FC were then assessed. Multiple linear regression analysis revealed that whereas both factors significantly contribute to the response, inherent 5-FU sensitivity was substantially more important (beta= 0.78 versus 0.48; P < 0.001). Finally, the therapeutic efficacy of a single intratumoral injection of AdCMVCD followed by systemic 5-FC was assessed in three intracranial C.B17 severe combined immunodeficient mouse models of human glioma. AdCMVCD/5-FC efficacy was specific, virus dose-dependent, and closely paralleled in vitro 5-FU and CD/5-FC sensitivity in two of three models tested. These results reveal that glioma cells are as sensitive as GI tumor cells to the antineoplastic effects of 5-FU, identify inherent 5-FU sensitivity as an important factor in determining CD/5-FC efficacy, and confirm previous findings in rat models that demonstrate the potential clinical utility of AdCMVCD/5-FC gene therapy for gliomas.

Second-site mutation outside of the U(S)10-12 domain of Deltagamma(1)34.5 herpes simplex virus 1 recombinant blocks the shutoff of protein synthesis induced by activated protein kinase R and partially restores neurovirulence

Earlier studies have shown that herpes simplex virus type 1 (HSV-1) activated protein kinase R (PKR) but that the product of the product of the gamma(1)34.5 gene binds and redirects the host phosphatase 1 to dephosphorylate the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2alpha). In consequence, the gamma(1)34.5 gene product averts the threatened shutoff of protein synthesis caused by activated PKR. Serial passages of Deltagamma(1)34.5 mutants in human cells led to isolation of two classes of second-site, compensatory mutants. The first, reported earlier, resulted from the juxtaposition of the alpha promoter of the U(S)12 gene to the coding sequence of the U(S)11 gene. The mutant blocks the phosphorylation of eIF-2alpha but does not restore the virulence phenotype of the wild-type virus. We report another class of second-site, compensatory mutants that do not map to the U(S)10-12 domain of the HSV-1 genome. All mutants in this series exhibit sustained late protein synthesis, higher yields in human cells, and reduced phosphorylation of PKR that appears to be phosphatase dependent. Specific dephosphorylation of eIF-2alpha was not demonstrable. At least one mutant in this series exhibited a partial restoration of the virulence phenotype characteristic of the wild-type virus phenotype. The results suggest that the second-site mutations reflect activation of fossilized functions designed to block the interferon response pathways in cells infected with the progenitor of present HSV.

Fas engagement increases expression of interleukin-6 in human glioma cells

Although Fas (APO-1/CD95) is expressed ubiquitously and induces cell death, it is also known to mediate other responses such as inflammation and angiogenesis in vivo. Previously, we have reported that Fas ligation induces selective expression of chemokines (IL-8 and MCP-1) in human astroglioma cells in vitro. In this study, we investigated whether Fas ligation can induce expression of other cytokines. Expression of IL-1alpha, IL-1beta, IL-6, IL-10, IL-12, IFN-beta, IFN-gamma, LT-beta, TGF-beta, TNF-a and TNF-beta mRNA levels in CRT-MG human astroglioma cells upon Fas ligation was investigated using RNase protection assay (RPA). We found that IL-6 mRNA is selectively induced upon Fas ligation, and IL-6 mRNA and protein expression was further investigated using single probe RPA and ELISA. To investigate the in vivo expression of IL-6, human brain specimens were homogenized and ELISA was performed for IL-6 expression. Herein, we demonstrate that: (1) Among these cytokines, only IL-6 was induced upon Fas ligation in a dose- and time-dependent manner; (2) A selective p38 MAP kinase inhibitor, SB202190, and a MEK inhibitor, U0126, suppressed induction of IL-6 mRNA and protein expression by Fas ligation; and (3) Glioblastoma multiforme samples (n = 11) contain significantly higher levels of IL-6 compared to those of control brains (n = 5), which correlate with increased levels of Fas. These results suggest that the Fas-FasL system may play a role in the regulation of tumor growth and survival by inducing the pleiotropic cytokine IL-6.

The use of a genetically engineered herpes simplex virus (R7020) with ionizing radiation for experimental hepatoma

The herpes simplex virus (HSV) recombinant virus R7020 is an attenuated virus designed as a candidate for immunization against both HSV-1 and HSV-2 infections. It was extensively tested in an experimental animal system and in a healthy human adult population without significant untoward effects. We report on the use of R7020 with ionizing radiation as an oncolytic agent for hepatomas. Two hepatoma cell lines were studied, Hep3B and Huh7. R7020 replicated to higher titers in Hep3B cells than in Huh7 cells. Tissue culture studies correlated with hepatoma xenograft responses to R7020. R7020 was more effective in mediating Hep3B tumor xenograft regression compared with Huh7. Ionizing radiation combined with R7020 also showed differential results in antitumor efficacy between the two cell lines in tumor xenografts. Ionizing radiation enhanced the replication of R7020 in Hep3B xenografts. Moreover, the combination of ionizing radiation and virus caused a greater regression of xenograft volume than either R7020 or radiation alone. Ionizing radiation had no effect on the replication of R7020 virus in Huh7 xenografts. These results indicate that a regimen involving infection with an appropriate herpesvirus such as R7020 in combination with ionizing radiation can be highly effective in eradicating certain tumor xenografts.

RNA replicons derived from poliovirus are directly oncolytic for human tumor cells of diverse origins

The failure and/or toxicity of conventional therapies for many types of human cancers underscore the need for development of safe and effective alternative treatments. Toward this goal, we describe the direct oncolytic activity of RNA-based vectors derived from poliovirus, termed replicons, which are genetically incapable of producing infectious virus. These replicons are cytopathic in vitro for human tumor cells originating from brain, breast, lung, ovary, and skin (melanoma). The cytopathic effects in a malignant glioma cell line were associated with nuclear DNA condensation, indicative of cells undergoing apoptosis. Injection of replicons into established xenograft flank tumors in scid mice resulted in oncolytic activity and extended survival. Inoculation of replicons into established intracranial xenograft tumors in scid mice resulted in tumor infection within 8 h and extended survival. Histological analysis revealed that replicons had infected tumor cells at the site of inoculation and, most importantly, diffused to infect tumor cells that had metastasized from the initial site of implantation. The wide spectrum of cytopathic activity for human tumors combined with effective distribution after in vivo inoculation establishes the therapeutic potential of poliovirus replicons for a variety of cancers.

pH alterations "reset" Ca2+ sensitivity of brain Na+ channel 2, a degenerin/epithelial Na+ ion channel, in planar lipid bilayers

Members of the degenerin/epithelial Na(+) channel superfamily of ion channels subserve many functions, ranging from whole body sodium handling to mechanoelectrical transduction. We studied brain Na(+) channel 2 (BNaC-2) in planar lipid bilayers to examine its single channel properties and regulation by Ca(2+). Upon incorporation of vesicles made from membranes of oocytes expressing either wild-type (WT) BNaC-2 or BNaC-2 with a gain-of-function (GF) point mutation (G433F), functional channels with different properties were obtained. WT BNaC-2 resided in a closed state with short openings, whereas GF BNaC-2 was constitutively activated; a decrease in the pH in the trans compartment of the bilayer activated WT BNaC-2 and decreased its permeability for Na(+) over K(+). Moreover, these maneuvers made the WT channel more resistant to amiloride. In contrast, GF BNaC-2 did not respond to a decrease in pH, and its amiloride sensitivity and selectivity for Na(+) over K(+) were unaffected by this pH change. Buffering the bathing solutions with EGTA to reduce the free [Ca(2+)] to <10 nm increased WT single channel open probability 10-fold, but not that of GF BNaC-2. Ca(2+) blocked both WT and GF BNaC-2 in a dose- and voltage-dependent fashion; single channel conductances were unchanged. A drop in pH reduced the ability of Ca(2+) to inhibit these channels. These results show that BNaC-2 is an amiloride-sensitive sodium channel and suggest that pH activation of these channels could be, in part, a consequence of H(+) "interference" with channel regulation by Ca(2+).

Evidence for peroxynitrite-mediated modifications to p53 in human gliomas: possible functional consequences

Based on previous findings of increased nitric oxide synthase (NOS) expression in human gliomas (4), we hypothesized that peroxynitrite, a highly reactive metabolite of nitric oxide (NO) and superoxide (O(*-)(2)), might be increased in these tumors in vivo. Here we demonstrate that nitrotyrosine (a footprint of peroxynitrite protein modification) is present in human malignant gliomas. Furthermore, we show that p53, a key tumor suppressor protein, has evidence of peroxynitrite-mediated modifications in gliomas in vivo. Experiments in vitro demonstrate that peroxynitrite treatment of recombinant wild-type p53 at physiological concentrations results in formation of higher molecular weight aggregates, tyrosine nitration, and loss of specific DNA binding. Peroxynitrite treatment of human glioma cell lysates similarly resulted in selective tyrosine nitration of p53 and was also associated with loss of p53 DNA binding ability. These data indicate that tyrosine nitration of proteins occurs in human gliomas in vivo, that p53 may be a target of peroxynitrite in these tumors, and that physiological concentrations of peroxynitrite can result in a loss of p53 DNA binding ability in vitro. These findings raise the possibility that peroxynitrite may contribute to loss of wild-type p53 functional activity in gliomas by posttranslational protein modifications.

VEGF-D is an X-linked/AP-1 regulated putative onco-angiogen in human glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM) is a hypervascularized and locally infiltrating brain tumor of astroglial origin with a very poor prognosis. An X-linked c-fos oncogene-inducible mitogenic, morphogenic, and angiogenic factor, endothelial growth factor-D (VEGF-D), is the newest mammalian member of VEGF family. We analyzed VEGF-D in GBM because of its high angiogenic potential and its linkage to the X chromosome.

MATERIALS AND METHODS

Nonmalignant brain and GBM tissue sections as well as GBM cell lines were analyzed by immunofluorescence for the expression of VEGF-D, factor VIII (endothelial cell marker), glial-fibrillary acidic protein (GFAP) (astrocytic cell lineage cytoplasmic marker), and several Fos family transcription factors, including c-Fos and Fra-1. The proteins were also detected by Western blots. The differences between genotypes of normal brain and GBM cells were examined by cDNA microarrays.

RESULTS AND CONCLUSIONS

GBM expressed ubiquitously VEGF-D, which colocalized with GFAP. Contrary to our expectations, low levels of c-Fos were detected in GBM cells. However, we identified another Fos family member, Fra-1, together with its transcriptional activation partner, c-Jun, as being stably up-regulated in GBM cells. Furthermore, we demonstrated that a fra-1 transgene induced VEGF-D expression in cultured cells and GBM cell stimulation evoked a sustained increase in both Fra-1 and VEGF-D levels. This study reveals that an up-regulation of AP-1 factors may be a hallmark of GBM. Because VEGF-D activates VEGF receptor 2 and 3, receptors important for tumor angiogenesis, it may represent an X-linked/AP-1-regulated onco-angiogen in human GBM. The VEGF-D system and AP-1 activity appear to be very attractive targets for new molecular diagnostics and rational molecular anti-cancer therapies.

Fas-induced expression of chemokines in human glioma cells: involvement of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase

Fas transduces not only apoptotic signals through various pathways but also angiogenic and proinflammatory responses in vivo. Human glioma cells express Fas although sensitivity to Fas-mediated cell death is variable, suggesting that Fas may have functions other than apoptosis in these cells. In this study, we addressed alternative functions of Fas expressed on human gliomas by Fas ligation in three human glioma cell lines, CRT-MG, U373-MG, and U87-MG, and the in vivo expression of Fas and chemokines in human glioblastoma multiforme (GBM). Herein, we demonstrate that: (a) stimulation with agonistic anti-Fas monoclonal antibody CH-11 and human recombinant soluble Fas ligand induces expression of the CC chemokine MCP-1 and the CXC chemokine interleukin-8 by human glioma cell lines at the mRNA and protein levels in a dose- and time-dependent manner; (b) selective pharmacological inhibitors of MEK1 (U0126 and PD98059) and p38 mitogen-activated protein kinase (MAPK) (SB202190) suppress Fas-mediated chemokine expression in a dose-dependent manner; (c) Fas ligation on human glioma cells leads to activation of both extracellular signal-regulated kinases ERK1/ERK2 and p38 MAPK; and (d) GBM samples express higher levels of Fas compared with normal control brain, which correlates with increased interleukin 8 expression. These findings indicate that Fas ligation on human glioma cells leads to the selective induction of chemokine expression, which involves the ERK1/ERK2 and p38 MAPK signaling pathways. Therefore, the Fas-Fas ligand system in human brain tumors may be involved not only in apoptotic processes but also in the provocation of angiogenic and proinflammatory responses.

Genetically engineered human herpes simplex virus in the treatment of brain tumours

Central nervous system malignancies--particularly glioblastoma multiforme--pose significant problems for the development of novel therapeutics. In the absence of advances with standard surgical and chemotherapeutic approaches, the utilization of genetically engineered viruses--both as direct oncolytic agents (virus therapy) and for the delivery of foreign proteins (gene therapy)--represents a significant advance in the experimental approach to the management of patients with incurable tumours. Among other viruses, herpes simplex virus (HSV) offers an opportunity to influence the replication of tumour cells directly within the central nervous system. The propensity for HSV to replicate in tumour cells, and its large coding capacity, provide an experimental model for the development of novel therapeutics. The status of these experimental approaches and Phase I studies are summarized.

HuR, a RNA stability factor, is expressed in malignant brain tumors and binds to adenine- and uridine-rich elements within the 3' untranslated regions of cytokine and angiogenic factor mRNAs

Tumors of the central nervous system (CNS) often have sustained expression of labile genes, including angiogenic growth factors and immunosuppressive cytokines, which promote tumor progression. Stabilization of the RNA transcripts for these genes, such as vascular endothelial growth factor (VEGF), is an important molecular pathway for this up-regulation. HuR, a member of the Elav family of RNA-binding proteins, has been implicated in this pathway through its binding to adenine and uridine (AU)-rich stability elements (ARE) located in the 3' untranslated regions (3'-UTRs) of the mRNA. Whereas three of the Elav family members (Hel-N1, HuC, and HuD) are restricted to young and mature neurons, HuR is more broadly expressed, including proliferating cells of the developing CNS. Because RNA stabilization of labile genes may promote tumor growth, we analyzed and compared the expression pattern of HuR in 35 freshly resected and cultured CNS tumors to determine whether there was any correlation with tumor grade or histological type. We found that HuR mRNA was consistently expressed in all of the tumors, regardless of cell origin or degree of malignancy. Using a novel HuR-specific polyclonal antibody, we found that strong HuR protein expression was limited to high-grade malignancies (glioblastoma multiforme and medulloblastoma). Within the glioblastoma multiforme, prominent HuR expression was also detected in perinecrotic areas in which angiogenic growth factors are up-regulated. To further define its role as a potential RNA stabilizer, we analyzed whether HuR could bind to the stability motifs within the 3'-UTRs of cytokines and growth factors linked to brain tumor progression. We used a novel ELISA-based RNA binding assay and focused on the 3'-UTRs of angiogenic factors VEGF, COX-2, and (interleukin) IL-8 as well as the immunomodulating factors IL-6, transforming growth factor (TGF)-beta and tumor necrosis factor (TNF)-alpha as potential RNA ligands. Our results indicated overall a very high binding affinity to these RNA targets. A comparison of these ligands revealed a hierarchy of binding affinities with the angiogenic factors, and TGF-beta showing the highest (Kd of 1.8-3.4 nM), and TNF-alpha the lowest (Kd of 18.3 nM). The expression pattern of HuR, coupled with the RNA binding data, strongly suggests a role for this protein in the posttranscriptional regulation of these genes in CNS tumors.