Biomedical subjects

S D Rabkin

Publications and source records attributed to S D Rabkin.

At least 37 records · Page 2Linked to original sources

PubMed1999

Herpes simplex virus as an in situ cancer vaccine for the induction of specific anti-tumor immunity.

The success of cancer gene therapy is likely to require the targeting of multiple antitumor mechanisms. One strategy involves the use of attenuated, replication-competent virus vectors, such as herpes simplex virus type 1 (HSV-1) mutant G207, which is able to replicate in human tumor cells with resultant cell death and tumor growth inhibition, yet is nonpathogenic in normal tissue. In this study, we demonstrate that infection of established tumors with G207 also induces a highly specific systemic anti-tumor immune response. In a syngeneic, bilateral established subcutaneous tumor model, with mouse CT26 colorectal carcinoma cells in BALB/c mice or M3 melanoma cells in DBA/2 mice, unilateral intratumoral inoculation with G207 caused a significant reduction in the growth of both the inoculated and contralateral noninoculated tumors. This elicited anti-tumor response is dependent on viral infection of the tumor, as intradermal inoculation of G207 in BALB/c mice had no effect on CT26 tumor growth. Treatment of subcutaneous CT26 tumors by intratumoral inoculation of G207 induced a tumor-specific T cell response. CD8+ cytotoxic T lymphocyte (CTL) activity was generated that recognized a dominant "tumor-specific" major histocompatibility complex (MHC) class I-restricted epitope (AH1) from CT26 cells. In immune-competent animals, G207 is acting as an in situ tumor vaccine. Therefore, intratumoral G207 inoculation is able to inhibit tumor growth both by local cytotoxic viral replication in tumor cells and induction of a systemic anti-tumor immune response.

Animals↗

PubMed1999

Hepatoma-specific antitumor activity of an albumin enhancer/promoter regulated herpes simplex virus in vivo.

Targeting viral vectors to appropriate cell types so that normal cells are not adversely affected is an important goal for gene therapy. Previously, we described a novel approach to viral gene therapy using a conditional, replication-competent herpes simplex virus (HSV), where replication and associated cytotoxicity are limited to a specific cell-type by the regulated expression of an essential immediate-early viral gene product. In this report we analyze the hepatoma-specific replication, cytotoxicity and anti-tumor effect of recombinant HSV G92A, regulated by the albumin enhancer/promoter. G92A efficiently replicated in vitro in two human hepatoma cell lines expressing albumin, but not in four human non-hepatoma, albumin-non-expressing tumor cell lines, while all cell lines were equally susceptible to a tissue nonspecific HSV recombinant, hrR3. In vivo, G92A replicated well in subcutaneous xenografts of human hepatoma cells (Hep3B) in athymic mice, but not in non-hepatoma subcutaneous tumors (PC3 and HeLa), whereas, hrR3 replicated well in both tumor types. Intratumoral inoculation of G92A inhibited the growth of established subcutaneous hepatoma tumors in nude mice, but not prostate tumors. Replication-competent viral vectors controlled by cell-specific transcriptional regulatory sequences provide a new therapeutic strategy for tumor therapy.

Albumins↗

PubMed1999

Replication-competent herpes simplex virus vector G207 and cisplatin combination therapy for head and neck squamous cell carcinoma.

Replication-competent virus vectors are attractive therapeutic agents for cancer. G207, a second-generation, multimutated herpes simplex virus type 1 (HSV-1), is one such vector that is safe in primates and efficacious against human tumors in athymic mice. Squamous cell carcinoma is the most frequently encountered malignancy of the head and neck, and the chemotherapeutic agent cisplatin is a standard treatment for recurrent head and neck cancer. In this study we examine the therapeutic potential of G207, alone and in combination with cisplatin, against squamous cell carcinoma. Human squamous cell carcinoma cell lines are sensitive to G207 replication and cytotoxicity in vitro at a multiplicity of infection of 0.01, including cisplatin sensitive (UMSCC-22A), moderately sensitive (UMSCC-38), and weakly sensitive (SQ20B) cell lines. Cisplatin did not inhibit the cytopathic effect of G207. G207 inhibited the growth of established subcutaneous head and neck tumors in athymic mice. The therapeutic effects of cisplatin and G207 in vivo were independent. However, in cisplatin-sensitive tumors (UMSCC-38), combination therapy resulted in 100% cures in contrast to 42% with G207 or 14% with cisplatin alone. We conclude that G207 should be considered for the treatment of head and neck cancer and that combination with chemotherapeutic agents may improve efficacy.

Animals↗

PubMed1999

Attenuated, replication-competent herpes simplex virus type 1 mutant G207: safety evaluation of intracerebral injection in nonhuman primates.

This study examined the safety of intracerebral inoculation of G207, an attenuated, replication-competent herpes simplex virus type 1 (HSV-1) recombinant, in nonhuman primates. Sixteen New World owl monkeys (Aotus nancymae [karyotype 1, formerly believed to be A. trivirgatus]), known for their exquisite susceptibility to HSV-1 infection, were evaluated. Thirteen underwent intracerebral inoculation with G207 at doses of 10(7) or 10(9) PFU, two were vehicle inoculated, and one served as an infected wild-type control and received 10(3) PFU of HSV-1 strain F. HSV-1 strain F caused rapid mortality and symptoms consistent with HSV encephalitis, including fever, hemiparesis, meningitis, and hemorrhage in the basal ganglia. One year after G207 inoculation, seven of the animals were alive and exhibited no evidence of clinical complications. Three deaths resulted from nonneurologic causes unrelated to HSV infection, and three animals were sacrificed for histopathologic examination. Two animals were reinoculated with G207 (10(7) PFU) at the same stereotactic coordinates 1 year after the initial G207 inoculation. These animals were alive and healthy 2 years after the second inoculation. Cerebral magnetic resonance imaging studies performed both before and after G207 inoculation failed to reveal radiographic evidence of HSV-related sequelae. Despite the lack of outwardly observable HSV pathology, measurable increases in serum anti-HSV titers were detected. Histopathological examination of multiple organ tissues found no evidence of HSV-induced histopathology or dissemination. We conclude that intracerebral inoculation of up to 10(9) PFU of G207, well above the efficacious dose in mouse tumor studies, is safe and therefore appropriate for human clinical trials.

Animals↗

PubMed1998

Activation of CNS circuits producing a neurogenic cystitis: evidence for centrally induced peripheral inflammation.

We present a model of neurogenic cystitis induced by viral infection of specific neuronal circuits of the rat CNS. Retrograde infection by pseudorabies virus (PRV) of neuronal populations neighboring those that innervate the bladder consistently led to a localized immune response in the CNS and bladder inflammation. Infection of bladder circuits themselves or of circuits distant from these rarely produced cystitis. Absence of virus in bladder and urine ruled out an infectious cystitis. Total denervation of the bladder, selective C-fiber deafferentation, or bladder sympathectomy prevented cystitis without affecting the CNS disease, indicating a neurogenic component to the inflammation. The integrity of central bladder-related circuits is necessary for the appearance of bladder inflammation, because only CNS lesions affecting bladder circuits, i.e., bilateral dorsolateral or ventrolateral funiculectomy, as well as bilateral lesions of Barrington's nucleus/locus coeruleus area, prevented bladder inflammation. The close proximity in the CNS of noninfected visceral circuits to infected somatic neurons would thus permit a bystander effect, leading to activation of the sensory and autonomic circuits innervating the bladder and resulting in a neurogenic inflammation localized to the bladder. The present study indicates that CNS dysfunction can bring about a peripheral inflammation.

Animals↗

PubMed1998

Novel synthesis and release of GABA in cerebellar granule cell cultures after infection with defective herpes simplex virus vectors expressing glutamic acid decarboxylase.

The inhibitory amino acid neurotransmitter gamma-aminobutyric acid (GABA) is synthesized from glutamate in a single step by the enzyme glutamatic acid decarboxylase (GAD). We sought to determine whether viral vectors containing GAD cDNA could be used to enhance synthesis and stimulation-evoked release of GABA in cultures of CNS neurons. For this purpose, we generated double-cassette defective herpes simplex virus (HSV) vectors that expressed one of the two GAD isoforms (GAD65 or GAD67), and Escherichia coli LacZ. Infection of cerebellar granule cell (CGC) cultures with vectors containing GAD cDNA resulted in a significant increase in isoform-specific expression of GAD, synthesis of GABA, and stimulation-evoked GABA release. GAD65 and GAD67 vector-infected neurons exhibited a comparable profile of GABA levels, synthesis and release, as well as GAD protein distribution. In CGCs cultured for 6 days in vitro (DIV), GABA synthesized after vector-derived GAD expression was released by treatment with glutamate or veratridine, but only in a Ca2+-independent fashion. In more mature (10 DIV) cultures, both Ca2+-dependent, K+ depolarization-induced, as well as Ca2+-independent, veratridine-induced, GABA release was significantly enhanced by GAD vector infection. Treatment of CGCs with kainic acid, which destroys most of the GABAergic neurons (<1% remaining), did not prevent vector-derived expression of GAD nor synthesis of GABA. This suggests that defective HSV vector-derived GAD expression can be used to increase GABA synthesis and release in CNS tissue, even in the relative absence of GABAergic neurons. The use of such GAD vectors in the CNS has potential therapeutic value in neurologic disorders such as epilepsy, chronic pain, Parkinson's and Huntington's disease.

Animals↗

PubMed1998

Treatment of human breast cancer in a brain metastatic model by G207, a replication-competent multimutated herpes simplex virus 1.

We investigated the therapeutic efficacy of G207, a replication-competent multimutated herpes simplex virus type 1, for the treatment of human malignant mammary tumors metastatic to the brain. In vitro studies demonstrated that G207 efficiently destroyed three of four human malignant breast cancer cell lines. MDA-MB-435 was most susceptible and MDA-MB-231 was least susceptible to G207. In athymic mice harboring subcutaneous or intracerebral MDA-MB-435 cells, intraneoplastic inoculation of G207 caused growth inhibition and/or prolonged survival. In contrast, G207 had minimal effects on MDA-MB-231 subcutaneous tumor growth or survival in the intracerebral tumor model. The efficacy of G207 therapy in vivo correlated well with the susceptibility of the human cancer cells to G207 in vitro. Histological studies indicate that G207 replication is restricted to tumor cells in vivo and does not occur in the surrounding brain tissue. These results suggest that G207 shows particular promise for use as a novel antineoplastic agent for metastatic brain tumors and that in vitro testing may predict which tumors will be most responsive in vivo.

Adenocarcinoma↗

PubMed1998

In situ cancer vaccination: an IL-12 defective vector/replication-competent herpes simplex virus combination induces local and systemic antitumor activity.

Intratumoral inoculation of replication-competent, attenuated herpes simplex virus (HSV) mutants inhibits tumor growth by direct cytotoxic viral replication and induction of a tumor-specific immune response. To boost the antitumor response, we describe a defective HSV vector encoding IL-12 as an adjuvant to in situ vaccination by the replication-competent HSV helper virus. The defective HSV vector system consists of defective particles containing tandem repeats of the cytokine genes (p40 and p35) in combination with a HSV helper virus. Heterodimeric IL-12 was expressed and secreted after IL-12 defective vector infection of tumor cells. In a syngeneic, bilateral established tumor model with CT26 murine colon carcinoma, unilateral intratumoral inoculation with an IL-12 defective/replication-competent HSV vector combination significantly reduced tumor growth of the inoculated and noninoculated contralateral tumors. This antitumor effect was significantly greater than with a lacZ-defective/replication-competent HSV vector combination, which itself was significantly greater than the mock inoculation. Efficacy is associated with enhancement of tumor-specific CTL activity, including specificity against the CT26 immunodominant MHC class I restricted Ag AH1, and IFN-gamma production. There was no significant tumor growth inhibition after intratumoral inoculation of s.c. CT26 tumors in athymic mice. We conclude that this defective HSV vector system is an effective method for cytokine gene delivery to tumors in situ and IL-12 expression in tumors synergizes the antitumor activity mediated by the replication-competent HSV helper virus.

Animals↗

PubMed1998

GABA synthesis in astrocytes after infection with defective herpes simplex virus vectors expressing glutamic acid decarboxylase 65 or 67.

Defective herpes simplex virus (HSV) vectors containing glutamic acid decarboxylase (GAD) cDNAs, either GAD65 or GAD67, were used to examine GAD function and GABA synthesis in rat cortical astrocytes, CNS cells that do not endogenously synthesize GABA. GAD vector infection resulted in isoform-specific expression of GAD as determined by western blotting and immunohistochemistry. Astrocytes infected with a beta-galactosidase vector or uninfected expressed no GAD and contained no detectable GABA. GABA was detected in glial fibrillary acid protein-expressing cells after GAD65 vector infection. Significant amounts of GABA, as determined by HPLC, were synthesized in cultures infected with either GAD vector. The levels of GABA in GAD67 vector-infected cells were almost twofold higher than in GAD65 vector-infected cells. Vector infection did not alter levels of other intracellular amino acids. GABA was tonically released from astrocytes infected with the GAD67 vector, but no increase in release could be detected after treatment of the cells with K+, veratridine, glutamate, or bradykinin. The ability to transduce astrocytes so that they express GAD and thereby increase GABA levels provides a potential strategy for the treatment of neurologic disorders associated with hyperexcitable or diminished inhibitory activity.

Animals↗

PubMed1997

Transcriptional targeting of herpes simplex virus for cell-specific replication.

Tissue- or cell-specific targeting of vectors is critical to the success of gene therapy. We describe a novel approach to virus-mediated gene therapy, where viral replication and associated cytotoxicity are limited to a specific cell type by the regulated expression of an essential immediate-early viral gene product. This is illustrated with a herpes simplex virus type 1 (HSV-1) vector (G92A) whose growth is restricted to albumin-expressing cells. G92A was constructed by inserting an albumin enhancer/promoter-ICP4 transgene into the thymidine kinase gene of mutant HSV-1 d120, deleted for both copies of the ICP4 gene. This vector also contains the Escherichia coli lacZ gene under control of the thymidine kinase promoter, a viral early promoter, to permit easy detection of infected cells containing replicating vector. In the adult, albumin is expressed uniquely in the liver and in hepatocellular carcinoma and is transcriptionally regulated. The plaquing efficiency of G92A is > 10(3) times higher on human hepatoma cells than on non-albumin-expressing human cells. The growth kinetics of G92A in albumin-expressing cells is delayed compared with that of wild-type HSV-1, likely due to aberrant expression of ICP4 protein. Cells undergoing a productive infection expressed detectable levels of ICP4 protein, as well as the reporter gene product beta-galactosidase. Confining a productive, cytotoxic viral infection to a specific cell type should be useful for tumor therapy and the ablation of specific cell types for the generation of animal models of disease.

Albumins↗

PubMed1996

Expression of L1 in primary astrocytes via a defective herpes simplex virus vector promotes neurite outgrowth and neural cell migration.

The neural cell adhesion molecule L1 is a transmembrane glycoprotein of approximately 200 kDa molecular weight that is a member of the immunoglobulin super family. Multiple functions of L1 have been reported, including cell-cell interactions, neurite elongation, axonal fasciculation, cell migration, and myelination. L1 plays important roles in neural development and axonal regeneration in the peripheral nervous system (PNS), however, in the adult it is only present on neurons in the central nervous system (CNS). In the present study we have used defective herpes simplex virus (HSV) vectors to express full-length human or rat L1 in cultured primary rat cortical astrocytes. Rat cerebellar granule cells, a rather homogeneous population of neurons, co-cultured on a substrate layer of L1-expressing astrocytes demonstrated increased migration and neurite extension compared with neurons co-cultured on lacZ-expressing astrocytes of uninfected astrocytes. There was no detectable difference between human and rat L1. Because this vector system can be used to confer phenotypic changes in primary nervous system cells it will be useful for in vitro and in vivo studies of neural regenerative sprouting and plasticity in the CNS.

Animals↗

PubMed1996

Co-expression of two gene products in the CNS using double-cassette defective herpes simplex virus vectors.

Defective herpes simplex virus (HSV) vectors are an efficient means to deliver genes to cells of the central nervous system (CNS). Such vectors containing two independent transcription units would be extremely valuable for many studies, including the comparative analysis of promoter function and expression of multiple gene products in the CNS. We have constructed a 'double-cassette' vector expressing two easily detectable marker enzymes, beta-galactosidase (beta-gal) and human placental alkaline phosphatase (AP). Cells infected in vitro, including neurons and glia, and in vivo expressed both gene products.

Animals↗

PubMed1996

Treatment of glioblastoma U-87 by systemic administration of an antisense protein kinase C-alpha phosphorothioate oligodeoxynucleotide.

Glioblastoma multiforme is the most common form of malignant brain cancer in adults and, unfortunately, is not amenable to treatment with current therapeutic modalities. Human glioblastoma U-87 has many of the distinguishing phenotypic features of primary glioblastoma, including an autocrine form of proliferation, high levels of protein kinase C alpha (PKC alpha), and infiltration via white matter tracts. We show that treatment of mice bearing U-87 xenografts with an antisense phosphorothioate oligodeoxynucleotide (S-oligodeoxynucleotide) against the 3'-untranslated region of PKC alpha mRNA results in suppression of tumor growth. Growth was inhibited in both subcutaneous and intracranial tumors, and in the latter instance, treatment with the antisense PKC alpha S-oligodeoxynucleotide resulted in a doubling in median survival time ( > 80 days), with 40% long term survivors. The antisense S-oligodeoxynucleotide did not produce systemic toxicity in mice with subcutaneous or intracranial tumors after daily intraperitoneal injection for 21 or 80 days, respectively, and a scrambled S-oligodeoxynucleotide with the same nucleotide composition as the antisense S-oligodeoxynucleotide did not produce an antitumor effect. The intratumoral levels of both antisense and scrambled S-oligodeoxynucleotide in subcutaneous tumors were 2 microM after 21 daily doses of 20 mg/kg S-oligodeoxynucleotide. The antisense S-oligodeoxynucleotide selectively reduced the levels of PKC alpha in subcutaneous tumors but not those of protein kinase C epsilon or protein kinase C zeta. This is the first demonstration that the growth of glioblastoma multiforme can be suppressed by an antisense PKC alpha S-oligodeoxynucleotide and suggests that this may represent an effective therapy for this type of malignancy.

Animals↗

PubMed1996

Gene therapy: targeting tumor cells for destruction.

Human gene therapy involves the transfer of genetic material into cells of a patient, either in vitro or in situ, for the therapeutic purpose of correcting or ameliorating genetic defects, alleviating disease, inhibiting infectious agents or destroying cancer cells. After identification of an appropriate disease target (inherited or acquired) for treatment, a number of basic technical issues underlie any gene therapy strategy. These include the choice of genetic material to be transferred, target cell or organ for gene modification, delivery systems and representative animal models of the targeted human disease. Tumor gene therapy represents a somewhat special category for gene therapy because its intended goal is the destruction of tissue rather than its correction or preservation. For an experimental therapeutic, cancer represents a useful target due to the paucity of effective treatments and the terminal nature of the disease. Viral vectors, currently the most widely used agents for gene delivery, generally fall into two classes; defective, which are unable to replicate; and replication-competent, which are able to replicate and spread within defined cell types. The strategies employed for cancer gene therapy range from cytotoxicity, either direct or through a 'suicide' gene-producing, to induction of a host antitumor immune response. Gene therapy is rapidly moving into the clinic, yet its efficacy remains to be demonstrated. Research into the underlying fundamentals of gene therapy discussed in this review will be critical to the ultimate success of this therapeutic modality.

Animals↗

PubMed1995

Treatment of human malignant meningiomas by G207, a replication-competent multimutated herpes simplex virus 1.

We have demonstrated that replication-competent attenuated mutants of herpes simplex virus type 1 (HSV-1) have therapeutic potential for malignant gliomas. Moreover, a recently described multiple mutant HSV (termed G207) has properties which may allow human clinical trials. G207 is able to replicate within and kill cells from three human malignant meningiomas in cell culture. In nude mice harboring s.c. human malignant meningioma (F5), G207 can inhibit growth in a dose-dependent fashion. In nude mice harboring intracranial subdural human malignant meningioma (F5), one injection of G207 caused significantly decreased tumor growth and one apparent cure with neither neurological dysfunction nor pathological changes in the surrounding brain. These results suggest that G207 should be considered for therapeutic trials in the treatment of malignant meningioma refractory to currently available therapies.

Animals↗

PubMed1995

Inhibition of angiogenesis and growth of human non-malignant and malignant meningiomas by TNP-470.

Meningiomas are relatively common (22%) vascular brain tumors. 3-11% of meningiomas are malignant, and defy currently available therapy. Inhibition of neovascularization is one potential strategy for treating these hypervascular tumors. Inhibition of tumor-induced angiogenesis by TNP-470 (previously termed AGM-1470), a synthetic analogue of fumagillin, was tested on the growth of human non-malignant and malignant meningiomas in nude mice. TNP-470 significantly inhibited tumor neovascularization and tumor growth of both non-malignant and malignant meningiomas. TNP-470 is now in human trial and should be tested for efficacy in treating malignant or recurrent aggressive meningiomas.

Animals↗

PubMed1995

Attenuated multi-mutated herpes simplex virus-1 for the treatment of malignant gliomas.

We have created a double mutant of the herpes simplex virus (HSV) type 1 (termed G207) with favourable properties for treating human malignant brain tumours: replication-competence in glioblastoma cells (and other dividing cells), attenuated neurovirulence, temperature sensitivity, ganciclovir hypersensitivity, and the presence of an easily detectable histochemical marker. G207 has deletions at both gamma 34.5 (RL1) loci and a lacZ gene insertion inactivating the ICP6 gene (UL39). G207 kills human glioma cells in monolayer cultures. In nude mice harbouring subcutaneous or intracerebral U-87MG gliomas, intraneoplastic inoculation with G207 causes decreased tumour growth and/or prolonged survival. G207 is avirulent upon intracerebral inoculation of mice and HSV-sensitive non-human primates. These results suggest that G207 should be considered for clinical evaluation in the treatment of glioblastomas.

Animals↗

PubMed1994

Preproenkephalin promoter yields region-specific and long-term expression in adult brain after direct in vivo gene transfer via a defective herpes simplex viral vector.

We have previously used a defective herpes simplex virus vector to express a foreign gene in the adult rat brain. One application of this technology would be the in vivo analysis of promoter function in brain after de novo transfer, which would allow the rapid generation of vectors with localized application in a broad range of mammalian species while avoiding influences of other nearby promoters. A 2.7-kb fragment of the rat preproenkephalin promoter was placed upstream of the bacterial lacZ gene in our herpes simplex virus amplicon. A restricted pattern of lacZ expression was observed in vivo, which follows previously observed patterns of endogenous preproenkephalin expression. These results, from the direct gene transfer into an adult animal brain for in vivo promoter analysis, demonstrate that sequence information that influences restricted expression of preproenkephalin is located within 2.7 kb upstream of transcriptional initiation. lacZ expression was also observed in rat brain for 2 months after direct transfer, and PCR analysis confirmed the continued presence of amplicon DNA in lacZ-positive sections. Restricted and long-term expression observed with an endogenous promoter has important implications for gene therapy using viral vectors.

Animals↗