Biomedical subjects

C M Kramm

Publications and source records attributed to C M Kramm.

At least 19 recordsLinked to original sources

PubMed2006

Serum cystatin C is a suitable marker for routine monitoring of renal function in pediatric cancer patients, especially of very young age.

BACKGROUND: Monitoring renal function is crucial in children undergoing chemotherapy. To date, a combination of routine serum creatinine (SCR) monitoring with occasional determination of creatinine clearance ratio (CCR) is widely used as clinical standard for this purpose. Both methods have their limitations regarding diagnostic value (SCR) or practicability (CCR), especially in young children. Diagnostic alternatives, such as glomerular filtration rate (GFR) estimation formulas have not been proved to be superior. The aim of the study was to evaluate whether serum cystatin C (CysC) may have a diagnostic impact on pediatric patients. PROCEDURE: CysC, SCR, several GFR estimation formulas (Counahan-Barratt, Ghazali-Barratt, Schwartz, Shull, Traub), and CCR were studied in 80 pediatric cancer patients (age range: 0.17-17.9 years) during their chemotherapy. Special attention was given to children under the age of 3 in whom accurate urine collection for CCR is difficult. RESULTS: All parameters correlated similarly well with CCR. Total accuracy was 66% and 67% for CysC and SCR, respectively. In very young children (<3 years), correlation with CCR was for CysC r = -0.74 with an area under the curve (AUC) of 0.646, and for SCR r = -0.27 with AUC = 0.594. Total accuracy was 60% for CysC, 50% for SCR. CONCLUSIONS: CysC represents a suitable marker for monitoring renal function in pediatric cancer patients. In young children (<3 years), CysC may have a better diagnostic value than SCR. Future studies should show if CysC can improve renal monitoring by replacing SCR, especially in very young children.

Adolescent↗

PubMed2004

Oncological management of pediatric cancer patients belonging to Jehovah's Witnesses: a two-institutional experience report.

OBJECTIVES: Aim of this study was to analyze the feasibility of oncological treatment in pediatric patients belonging to Jehovah's Witnesses and to describe the changing policy in performing transfusions and supportive care measures at two German pediatric cancer institutions. PATIENTS AND METHODS: Over a period of 16 years 21 treatments according to the current cooperative protocols were performed in 14 children of Jehovah's Witnesses. Various hematological supportive care measures such as supplementation with iron, human erythropoietin, interleukin 11, granulocyte colony-stimulating factor and autologous or allogeneic stem cell rescue had been applied. For comparison matched pairs treated in our hospitals not belonging to Jehovah's Witnesses and 50 pediatric and adult oncological patients belonging to Jehovah's Witnesses reviewed from the international literature were analyzed with respect to transfusions and outcome. RESULTS: So far, 9 of 14 children are surviving 16-195 months (median 26 months). During the primary therapy they received markedly less transfusions than the control cohort (-39,1% red blood cell transfusions and -37,5% platelet transfusions). The review of 50 reported cases showed that oncological therapy can also be successfully performed with a restricted transfusion regimen in children and particularly in adults. CONCLUSION: Pediatric cancer patients belonging to Jehovah's Witnesses can be treated similarly to other patients. A restrictive transfusion policy and the broad application of hematopoietic supportive care measures may reduce transfusions. This treatment policy and a continuous collaboration with the Hospital Liaison Committee for Jehovah's Witnesses appears to create an oncological treatment situation with a high compliance of patients and parents where court orders may not be necessary.

Blood Loss, Surgical↗

PubMed2002

Systemic activation of the immune system during ganciclovir treatment following intratumoral herpes simplex virus type 1 thymidine kinase gene transfer in an adolescent ependymoma patient.

During ganciclovir treatment of an adolescent ependymoma patient two weeks after intracranial implantation of HSVtk retroviral vector producer cells, increasing numbers of peripheral T- and B-cells were found as well as enhanced T-cell activation and elevated serum levels of interleukin 12 and soluble Fas ligand. These findings suggest the systemic activation of the immune system during ganciclovir treatment in our patient. The induction of an immune response by HSVtk/ganciclovir supports the concept of an anti-tumor vaccination effect by prodrug activating gene therapy systems and may open new promising perspectives for enhancing therapeutic efficiency by combined prodrug activating and immunological gene therapy strategies.

Adolescent↗

PubMed2001

Infectious complications in children with acute lymphoblastic leukemia and T-cell lymphoma--a rationale for tailored supportive care.

Infections still remain a major cause of therapy-associated morbidity and death in patients with malignant diseases. To further lower the risk of serious and long-lasting infections by additional supportive measures, detailed information on the frequency and characteristic features of infections is needed. Therefore, patient data from 112 children with acute lymphoblastic leukemia and T-cell lymphoma who were treated according to the COALL-05-92 protocol in our department were analyzed for differences in the frequency and origin of febrile episodes in relation to age, immunological type of leukemia, treatment in group assessed as being at high or low risk of relapse, actual occurrence of relapse, and course of chemotherapy. At the time of diagnosis, low-risk patients more commonly presented with febrile episodes than high-risk patients. In total, patients developed a fever in 313 (24%) of 1,307 evaluated chemotherapy cycles. Febrile episodes were associated with microbiologically or clinically documented infections in 60% of all cases, while in 40% the fever was of unknown origin. Gram-positive pathogens had a markedly higher incidence than gram-negative or fungal ones. The incidence of febrile episodes during therapy appeared to be correlated with certain chemotherapeutic drug combinations. The highest rate was found after high-dose cytarabine and asparaginase causing a long period of leukopenia. However, after other chemotherapy courses with a similar duration of leukopenia the incidence of febrile episodes was significantly lower, suggesting that specific interactions of different chemotherapeutic agents with the immune response might be an important factor in development of infections. Individual factors might also account for an increased incidence of infections, since the number of high-risk patients with recurrent infections was significantly higher than expected on the basis of statistical evaluation. In conclusion, our findings suggest that the risk of infections during chemotherapy may not only be influenced by leukopenia, but that drug-specific effects of the various chemotherapeutic agents and individual factors may also be important contributory factors. These observations must be further expanded in prospective studies so that new tailored supportive care protocols can be elaborated.

Adolescent↗

PubMed2001

Temozolomide enhances herpes simplex virus thymidine kinase/ganciclovir therapy of malignant glioma.

Gene therapy for malignant glioma with the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system is already in the stage of clinical trials, but still needs major improvement to achieve greater clinical efficacy. The aim of this study was to determine whether combining HSV-tk/GCV gene therapy with temozolomide (TMZ), an alkylating drug clinically proven to be efficient in recurrent high-grade gliomas, would result in enhanced antitumor effect in malignant glioma in culture and in vivo. Human U87MG glioblastoma (GBM) cells with or without expression of HSV-tk were treated with different concentrations of GCV, TMZ, or both drugs. Cell viability was accessed by an automated microplate assay (MTT). The isobologram method and the combination index (CI) method of Chou-Talalay were used to measure the interactions between the two drugs when applied simultaneously. U87-tk and control U87 cells (5x10(6) each) were implanted in the flanks of nude mice, and animals were treated with GCV or TMZ or with both drugs. All tumors were measured and weighed at specified time points. IC(50) for GCV was 511 microM in control U87 cells and 14.3 microM in U87-tk cells, resulting in 35.7-fold increase of toxicity in the HSV-tk-expressing cells. TMZ had an IC(50) of 20.2 mM in control cells and 2.35 mM in U87-tk cells, resulting in 8.6-fold increase in sensitivity of the HSV-tk-expressing cells. TMZ and HSV-tk/GCV actions were synergistic (CI<1) in both control and U87-tk cells with higher synergism in U87-tk cells at high effect levels. Tumors expressing HSV-tk and treated with TMZ and GCV were significantly smaller than those treated by TMZ, but not by GCV. There was also a significant difference between the weight of HSV-tk expressing versus control tumors treated with TMZ, with GCV, or with both drugs. These data demonstrate synergism between HSV-tk/GCV and TMZ and higher sensitivity against TMZ in HSV-tk-expressing GBM cells. The potential importance for clinical studies combining both local tumor gene therapy and systemic chemotherapy should be explored further.

Animals↗

PubMed2001

Vector delivery methods and targeting strategies for gene therapy of brain tumors.

Efficient virus and non-virus vector systems for gene transfer to tumor cells have been developed and tested in cell culture and in animal experiments. With some of the earliest and most comprehensively evaluated vectors, such as retroviruses, advanced clinical trials were performed in tumor patients. Malignant primary brain tumors (gliomas) have been chosen for the first clinical studies on novel gene therapy approaches because these tumors are non-metastatic and develop on the largely postmitotic background of normal glial and neuronal tissue. However, the human cancer gene therapy studies performed so far were not as successful as preclinical animal experiments. Furthermore, the clinical studies did not address major limiting factors for in vivo gene therapy, such as insufficient gene transfer rates to the tumor with the used local delivery modalities, and the resulting inability of a particular transgene-prodrug system to confer permanently eradicating cytotoxicity to the whole neoplasm. Critical evaluation of gene transfer and therapy studies has led to the conclusion that, even using identical vectors, the anatomical route of vector administration can dramatically affect both the efficiency of tumor transduction and its spatial distribution, as well as the extent of intratumoral and intracerebral transgene expression. This review concentrates on different physical methods for vector delivery to malignant primary brain tumors in experimental or clinical settings: stereotactic or direct intratumoral injection or convection-enhanced bulk-flow interstitial delivery; intrathecal and intraventricular injection; and intravascular infusion with or without modification of the blood-tumor-barrier. The advantages and drawbacks of the different modes and delivery routes of in vivo vector application, and the possibilities for tumor targeting by modifications of the native tropism of virus vectors or by using tissue-specific or inducible transgene expression are summarized.

Animals↗

PubMed2000

Bcl-2 expression in higher-grade human glioma: a clinical and experimental study.

Bcl-2 protein plays an important role in inhibiting apoptosis and protecting normal and neoplastic cells from toxicity. Bcl-2 overexpression in malignant tumors, on the other hand, may cause resistance against adjuvant treatment. Since there are subpopulations of patients with glioma that differ considerably in their treatment benefit, it is important to identify prognostic factors for outcome and to tailor adjuvant protocols in accordance with specific biological features of the respective tumor. The present study aimed at investigating the role of bcl-2 expression in higher-grade glioma (WHO grade III and IV). Bcl-2 expression was correlated with clinical and paraclinical parameters, and evaluated in univariate and multivariate statistical models. In addition, bcl-2-overexpressing human glioma cells in culture were used for modeling the in vivo findings and for investigating the importance of bcl-2 for tumor resistance against cytotoxic treatment. A group of 86 patients with higher-grade glioma were investigated. Anaplastic astrocytoma (AA; WHO G III, n = 29) showed bcl-2 expression in 48% of the cases, and immunohistochemical positivity was associated with a significantly shorter survival time (p = 0.0068). In glioblastoma patients (GBM; WHO G IV, n = 57), 51% of tumors were bcl-2 positive, but bcl-2 expression did not correlate significantly with survival (p = 0.39). In a Cox proportional hazards regression model, bcl-2 positivity was confirmed as a negative prognostic parameter in AA, but not in GBM. Bcl-2 overexpressing and control human glioma cell clones (T98MG line) were treated in culture with the cytotoxic drugs carmustine (BCNU), paclitaxel, vincristine, and doxorubicin. In addition, bcl-2-overexpressing and control cells were infected with a retrovirus carrying the herpes-simplex-virus thymidine kinase gene (HSV-tk), and then treated with ganciclovir (GCV). Bcl-2 overexpression significantly increased tumor cell resistance against all of the above cytotoxic drugs, and also against HSV-TK/GCV mediated gene therapy.

Astrocytoma↗

PubMed2000

Enhanced green fluorescent protein fusion proteins of herpes simplex virus type 1 thymidine kinase and cytochrome P450 4B1: applications for prodrug-activating gene therapy.

To monitor therapeutic transgene expression, we developed fusion genes of enhanced green fluorescent protein (EGFP) with two different prodrug-activating enzyme genes: herpes simplex virus type 1 thymidine kinase (HSV-tk) and rabbit cytochrome P450 4B1 (cyp4b1). Expression of the resulting fusion proteins, TK-EGFP and 4B1-EGFP, rendered transduced human and rodent glioma cells sensitive to cytotoxic treatment with the corresponding prodrugs ganciclovir and 4-ipomeanol. Ganciclovir and 4-ipomeanol sensitivity was comparable with that achieved with the native HSV-TK and CYP4B1 proteins. As shown by fluorescence microscopy, TK-EGFP was expressed predominantly intranuclearly, whereas 4B1-EGFP was detectable in the cytoplasm, thereby displaying the orthotopic subcellular distribution of the corresponding native enzymes. The fluorescence intensity correlated well with the corresponding prodrug sensitivity, as shown by fluorescence-activated cell sorter analysis. EGFP expression was also used for the selection of stably HSV-tk-transduced cells by flow cytometric cell sorting. Resulting cell populations showed a homogeneity of fluorescence intensity similar to single-cell clones after antibiotic selection. In conclusion, tk-egfp and 4b1-egfp fusion genes are valuable tools for monitoring prodrug-activating gene therapy in living cells. EGFP fusion genes/proteins provide a simple and reproducible means for the detection, selection, and characterization of cells expressing enzyme genes for prodrug activation.

Animals↗

PubMed2000

Immune response induced by retrovirus-mediated HSV-tk/GCV pharmacogene therapy in patients with glioblastoma multiforme.

This study was conducted to investigate immunological components of somatic gene therapy for primary glioblastoma multiforme (GBM) in adults. It involved 13 patients treated by surgical resection of tumor with subsequent radiation therapy. Seven of them received additional herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) gene therapy by direct intracerebral injection of retrovirus (RV) vector producing cells (VPC) during tumor surgery and subsequent systemic administration of GCV. Peripheral blood for FACS immunophenotyping, isolation of peripheral mononuclear cells (PMNC), and serum ELISA assays for IL-12 and soluble Fas ligand (sFasL) was collected daily during the first 4 post-operative weeks. Tumor specimens were obtained at primary or recurrent surgery and at autopsy. Tumors from gene therapy patients showed varying degrees of peritumoral necrosis around the former tumor resection cavity. Numbers of tumor-infiltrating lymphocytes found weeks after gene therapy were not significantly increased compared with primary tumors. Mitotic tumor cells were sparse close to the VPC injection sites, but abundant in brain areas somewhat distant from these sites. Serum ELISA revealed significantly increased sFasL and IL-12 levels in the gene therapy group compared with controls. Immunophenotyping of PMNC did not show a significant activation of T cells or NK cells during gene therapy. Interferon gamma secretion was evaluated by ELISPOT assays employing PMNC cocultivated with autologous tumor cells. It demonstrated an antitumor immune response in the gene therapy group, but not in the control group. These findings support the concept of in vivo induction of a systemic immune response by local intracerebral HSV-tk/GCV pharmacogene therapy for primary human GBM.

Aged↗

PubMed1999

Folylpolyglutamyl synthetase gene transfer and glioma antifolate sensitivity in culture and in vivo.

BACKGROUND: Although antifolates are popular agents for use in chemotherapy, they display minimal toxicity against slow-growing tumors and are toxic to actively replicating cells in normal tissues. These drugs are converted intracellularly into polyglutamate derivatives by the enzyme folylpolyglutamyl synthetase (FPGS). Because tumors with high expression of FPGS often respond to nontoxic antifolate doses, we investigated whether augmenting tumoral FPGS activity by gene delivery would enhance tumoral antifolate sensitivity. METHODS: 9L rat gliosarcoma cells were stably transfected with a human FPGS complementary DNA (cDNA), producing 9L/FPGS cells. The sensitivity of these cells to the antifolates methotrexate and edatrexate was measured in culture and in subcutaneous tumors, as was their ability to increase the chemosensitivity of nearby nontransfected cells, i.e., a bystander effect. The antifolate sensitivity of nonselected cells transduced with a hybrid amplicon vector that expressed FPGS was also ascertained. RESULTS: In comparison with 9L cells, 9L/FPGS cells displayed enhanced sensitivity to 4-hour pulses of antifolate. Subcutaneous 9L/FPGS tumors responded as well to methotrexate given every third day as 9L tumors did to daily treatment. A modest bystander effect was observed with edatrexate treatment in culture and in vivo. The observed bystander effect appeared to result from the release of antifolates by transfected cells after the removal of extracellular drug. In culture, enhanced antifolate sensitivity was also seen in other stably transfected rodent and human glioma cell lines, including one with high pre-existing FPGS activity, and in canine and human glioblastoma cell lines transduced with a vector bearing FPGS cDNA. CONCLUSIONS: FPGS gene delivery enhances the antifolate sensitivity of several glioma cell lines and merits further evaluation as a therapeutic strategy.

Aminopterin↗

PubMed1998

New prodrug activation gene therapy for cancer using cytochrome P450 4B1 and 2-aminoanthracene/4-ipomeanol.

Vector-mediated transfer of prodrug-activating genes provides a promising means of cancer gene therapy. In a search for more selective and more potent bioactivating enzymes for gene therapy of malignant brain tumors, the toxicity-generating capacity of the rabbit cytochrome P450 isozyme CYP4B1 was investigated. Rabbit CYP4B1, but not rat or human isozymes, efficiently converts the inert prodrugs, 2-aminoanthracene (2-AA) and 4-ipomeanol (4-IM), into highly toxic alkylating metabolites. Toxicity of these two prodrugs was evaluated in culture in parental and genetically modified rodent (9L) and human (U87) glioma cell lines stably expressing CYP4B1, and in vivo in a subcutaneous 9L tumor model in nude mice. The most sensitive CYP4B1-expressing glioma clone, 9L4B1-60, displayed an LD50 of 2.5 microM for 2-AA and 4-IM after 48 h of prodrug incubation, whereas 20 times higher prodrug concentrations did not cause any significant toxicity to control cells. Substantial killing of control tumor cells by 2-AA was achieved by co-culturing these cells with CYP4B1-expressing cells at a ratio of 100:1, and toxic metabolites could be transferred through medium. In both CYP4B1-expressing cells and co-cultured control cells, prodrug bioactivation was associated with DNA fragmentation, as assayed by fluorescent TUNEL assays and by annexin V staining. Alkaline elution of cellular DNA after exposure to 4-IM revealed extensive protein-DNA crosslinking with single-strand breakage. Growth of 9L-4B1 tumors in nude mice was inhibited by intraperitoneal injection of 4-IM with minimal side effects. Potential advantages of the CYP4B1 gene therapy paradigm include: the low concentrations of prodrug needed to kill sensitized tumor cells; low prodrug conversion by human isozymes, thus reducing toxicity to normal cells; a tumor-killing bystander effect that can occur even without cell-to-cell contact; and the utilization of lipophilic prodrugs that can penetrate the blood-brain barrier.

Animals↗

PubMed1998

Synergistic anticancer effects of ganciclovir/thymidine kinase and 5-fluorocytosine/cytosine deaminase gene therapies.

BACKGROUND: A bacterial enzyme, Escherichia coli cytosine deaminase, which converts the prodrug 5-fluorocytosine into the toxic drug 5-fluorouracil, and a viral enzyme, herpes simplex virus thymidine kinase, which converts ganciclovir from an inactive prodrug to a cytotoxic agent by phosphorylation, are being actively investigated for use in gene therapy for cancer. The purpose of this study was to determine whether combining these prodrug-activating gene therapies might result in enhanced anticancer effects. METHODS: Rat 9L gliosarcoma cells were transfected with plasmids containing the E. coli cytosine deaminase gene (9L/CD cells), with plasmids containing the herpes simplex virus thymidine kinase gene (9L/TK cells), or with both expression plasmids (9L/CD-TK cells). The drug sensitivities of the cell lines were evaluated; in addition, the sensitivities of 9L and 9L/CD-TK cells mixed in varied proportions were measured. The effects of prodrug treatment on 9L/CD-TK tumor growth (i.e., size and volume) in nude mice were monitored. The isobologram method of Loewe and the multiple drug-effect analysis method of Chou-Talalay were used to measure the interaction between the two prodrug-activating gene therapies. To elucidate the mechanism of interaction, the phosphorylation of ganciclovir in 9L/CD-TK cells after varying prodrug treatments was studied. RESULTS AND CONCLUSIONS: The presence of transfected cytosine deaminase and thymidine kinase genes in 9L gliosarcoma cells reduced cell survival, both in vitro and in vivo, following treatment with the relevant prodrugs; the effects of the two components appeared to be synergistic and related mechanistically to the enhancement of ganciclovir phosphorylation by thymidine kinase following 5-fluorouracil treatment.

Animals↗

PubMed1998

Pre-existing herpes simplex virus 1 (HSV-1) immunity decreases, but does not abolish, gene transfer to experimental brain tumors by a HSV-1 vector.

The influence of pre-existing anti-herpes simplex type 1 (HSV-1) immunity on HSV-1 vector-mediated gene transfer to glioma cells was analyzed in this gene marking study using intracranial D74 gliomas in syngeneic Fischer rats. The HSV-1 mutant virus used, hrR3, is defective in ribonucleotide reductase and bears the marker genes E. coli lacZ and HSV-1 thymidine kinase (HSVtk). Initial marker gene expression in tumors 12 h after direct virus injection was reduced in immunized animals to about 15% of that in nonimmunized animals. Marker gene expression in both sets stayed at initial levels for 2 days after intratumoral injection and declined markedly on day 5. Inflammatory infiltrates in the tumor were more prominent in HSV-1-immunized, as compared with nonimmunized animals, at 12 and 24 h, but appeared similar at 2-5 days after injection. By day 10, the immune reaction had subsided in immunized animals and macrophages remained only in nonimmunized animals. In conclusion, gene transfer to brain tumors using a HSV-1 vector was greatly reduced, but not completely abolished, under pre-immunization conditions. Pre-existing antibodies to HSV-1 may also serve a positive role in providing an increased margin of safety in intracranial application of HSV-1 vectors by limiting spread of the virus within the brain and to other tissues.

Animals↗

PubMed1997

Therapeutic efficiency and safety of a second-generation replication-conditional HSV1 vector for brain tumor gene therapy.

A second-generation replication-conditional herpes simplex virus type 1 (HSV) vector defective for both ribonucleotide reductase (RR) and the neurovirulence factor gamma34.5 was generated and tested for therapeutic safety and efficiency in two different experimental brain tumor models. In culture, cytotoxic activity of this double mutant HSV vector, MGH-1, for 9L gliosarcoma cells was similar to that of the HSV mutant, R3616, which is defective only for gamma34.5, but was significantly weaker than that of the HSV mutant hrR3, which is defective only for RR. The diminished tumoricidal effect of the gamma34.5 mutants could be accounted for by their reduced ability to replicate in 9L cells. The MGH-1 vector did not achieve significant prolongation of survival in vivo in the syngeneic 9L rat gliosarcoma model for either single brain tumor focus or multiple intracerebral and leptomeningeal tumors, when the vector was applied intratumorally or intrathecally, respectively, and with or without subsequent ganciclovir (GCV) treatment. In identical 9L brain tumor models with single and multiple foci, application of hrR3 with or without GCV was previously shown to result in marked long-term survival. Contrary to the findings with intrathecal injection of hrR3, no vector-related mortality was observed in any animals treated with MGH-1. Thus, in these rat brain tumor models, the double mutant, replication-conditional HSV vector MGH-1 showed a higher therapeutic safety than the RR-minus vector, hrR3, but had clearly decreased therapeutic efficiency compared to hrR3. The development of new HSV vectors for brain tumor gene therapy will require a balance between maximizing therapeutic efficacy and minimizing toxicity to the brain. Standardized application in brain tumor models as presented here will help to screen new HSV vectors for these requirements.

Animals↗

PubMed1996

Long-term survival in a rodent model of disseminated brain tumors by combined intrathecal delivery of herpes vectors and ganciclovir treatment.

Brain tumors that have disseminated into cerebrospinal fluid (CSF) pathways are an unresolved therapeutic problem, especially in pediatric neurooncology. Here a gene therapy approach using the herpes simplex virus type 1 thymidine kinase (HSV-TK)/ganciclovir (GCV) paradigm was tested using an HSV vector in a rodent model of disseminated central nervous system tumors. 9L-gliosarcoma cells were implanted simultaneously into the brain and the CSF of syngeneic rats. Five days later, resulting intracerebral and leptomeningeal tumors were treated by intrathecal injection of a replication-conditional HSV vector. This vector was defective for the ribonucleotide reductase gene, but contained an intact HSV-tk gene. Systemic GCV treatment was started 2 days after vector application and continued for 14 days. Tumor-free, long-term survival (LTS) was achieved in 90% of the animals treated with this combined therapeutic approach, whereas only 30% LTS was found in animals that had received the vector alone and 10% LTS in untreated animals. This therapeutic response probably involves oncolytic, on-site replication of the vector, activation of GCV by a HSV-TK, and a strong immune response both to the vector and to 9L cells. Apparent vector-related mortality was observed in 20% of animals without subsequent GCV therapy, but no vector-related mortality was found when the animals were treated with GCV after vector application. Given the successful outcome of this experimental treatment and the apparent potential of GCV to control HSV-related toxicity, intrathecal application of HSV vectors combined with GCV treatment may be a promising approach for treatment of disseminated brain tumors.

Animals↗

PubMed1996

Herpes vector-mediated delivery of marker genes to disseminated central nervous system tumors.

The present study investigated the ability of a recombinant herpes simplex virus type 1 (HSV) vector to deliver genes into disseminated brain tumor foci through intrathecal injection of the vector. The animal model was designed to simulate brain tumors with cerebrospinal fluid (CSF) metastases, which are found especially in the pediatric population. 9L gliosarcoma cells were injected both into the right frontal lobe and in through the cisterna magna of adult rats. The HSV vector, hrR3, was inoculated intrathecally 5 days later. This vector is defective in the gene for ribonucleotide reductase, and, therefore, replicates preferentially in dividing cells; it retains an intact HSV-thymidine kinase gene (HSV-tk). Two days after injection of the vector, immunohistochemical staining for HSV thymidine kinase (HSV-TK) revealed expression in frontal tumors, as well as in leptomeningeal tumor foci along the entire neuroaxis. HSV-TK-immunopositive cells were most frequent in small tumors contacting the CSF pathways. Frontal lobe tumors showed the highest density of HSV-TK-immunopositive cells around their periphery with little expression in central parts. Some paraventricular neurons temporarily showed HSV-TK-immunolabeling at this early time point. The number of HSV-TK-immunopositive tumor cells markedly decreased 5 days after injection of the HSV vector. In all animals, some toxicity was observed in the first 2-4 days after virus injection with extensive leptomeningeal inflammation. In conclusion, intrathecal application of HSV vectors can mediate widespread transfer of the therapeutic HSV-tk gene into disseminated tumors throughout the brain and CSF pathways. Although there was marked toxicity associated with intrathecal injection of this vector, this mode of gene delivery offers a promising approach for treatment of CSF-metastases in conjunction with development of less toxic vectors.

Animals↗

PubMed1995

Selective uptake of viral and monocrystalline particles delivered intra-arterially to experimental brain neoplasms.

In this study we investigated the intra-arterial delivery of viral and nonviral particles to experimental brain tumors. A herpes simplex virus (HSV) vector and monocrystalline iron oxide nanoparticles (MION) were injected into the internal carotid artery of Fisher 344 rats harboring intracerebral 9L gliosarcomas, using bradykinin to disrupt the blood-tumor barrier. Brain and internal organs were stained both for virus-mediated gene expression and for iron. Quantitative comparisons of gene expression and MION uptake with and without blood-tumor barrier disruption were performed in the center and at the periphery of the tumor mass, as well as in normal brain. In addition, MION distribution was traced in vivo by MR imaging. Delivery of HSV into 9L gliosarcoma cells was greatly enhanced by intra-carotid bradykinin infusion. Virus-mediated expression of the HSV-thymidine kinase (TK) and beta-galactosidase gene products was highest at the tumor periphery as compared to the tumor center. Selective HSV infection of multiple tumor foci was achieved in both hemispheres without affecting normal brain. MION uptake was high at the tumor periphery even without blood-tumor barrier disruption. Bradykinin increased MION uptake predominantly in the center of the tumor with virtually no effect at the periphery. These findings show that selective blood-tumor barrier disruption by bradykinin can be used to enhance HSV-mediated gene delivery to tumor cells in the periphery of brain tumors. A crucial aspect in the treatment of malignant brain tumors is the eradication of tumor cells infiltrating the brain; bradykinin may facilitate access of vectors to these areas by selective disruption of their neovasculature.

Animals↗

PubMed1995

Gene therapy for brain tumors.

Gene therapy has opened new doors for treatment of neoplastic diseases. This new approach seems very attractive, especially for glioblastomas, since treatment of these brain tumors has failed using conventional therapy regimens. Many different modes of gene therapy for brain tumors have been tested in culture and in vivo. Many of these approaches are based on previously established anti-neoplastic principles, like prodrug activating enzymes, inhibition of tumor neovascularization, and enhancement of the normally weak anti-tumor immune response. Delivery of genes to tumor cells has been mediated by a number of viral and synthetic vectors. The most widely used paradigm is based on the activation of ganciclovir to a cytotoxic compound by a viral enzyme, thymidine kinase, which is expressed by tumor cells, after the gene has been introduced by a retroviral vector. This paradigm has proven to be a potent therapy with minimal side effects in several rodent brain tumor models, and has proceeded to phase 1 clinical trials. In this review, current gene therapy strategies and vector systems for treatment of brain tumors will be described and discussed in light of further developments needed to make this new treatment modality clinically efficacious.

Antibody Formation↗