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H Brem

Publications and source records attributed to H Brem.

At least 91 records · Page 5Linked to original sources
PubMed1994

AGM-1470 inhibits the growth of human glioblastoma cells in vitro and in vivo.

Glioblastoma is the most malignant primary brain tumor. Inhibition of angiogenesis is one potential strategy for treating this fatal hypervascular tumor. AGM-1470 (also called TNP-470), a novel, potent, fungus-derived inhibitor of angiogenesis, was tested on the growth of human glioblastoma cells in culture and on the growth of the tumor in nude mice. In nude mice with subrenally implanted U-87 MG glioblastomas, AGM-1470 significantly inhibited tumor growth (P < 0.01), and in nude mice with intracranial U-87 MG glioblastomas, AGM-1470 prolonged survival. In addition to its expected action as an angiogenesis inhibitor, AGM-1470 also directly inhibited U-87 MG cells in culture at concentrations similar to those that inhibited endothelial cells. The combined inhibition of glioblastoma cell mitosis and of glioblastoma-induced neovascularization suggests that AGM-1470 should be considered for further investigation in the treatment of this fatal tumor.

Animals↗
PubMed1994

Biodegradable polymers for controlled delivery of chemotherapy with and without radiation therapy in the monkey brain.

Sustained drug delivery by biodegradable polymer devices can increase the therapeutic efficacy of drugs by producing high local tissue concentrations over extended periods of time. It has been shown previously that implantation of controlled-release polymers impregnated with the nitrosourea carmustine (BCNU) extended the period of survival in rats bearing the 9L glioma compared with similar rats treated with systemically administered BCNU. This study evaluated the effect on the monkey brain of interstitial delivery of BCNU by the biodegradable polyanhydride copolymer poly[bis(p-carboxyphenoxy)propane]anhydride (PCPP) and sebacic acid (SA) in a 20:80 formulation (PCPP:SA). The effect of combining interstitial BCNU with radiation therapy was also evaluated. Eighteen male cynomolgus monkeys were randomly assigned to one of four groups: a control group; a group with implantation of empty polymer; a group with implantation of BCNU-loaded polymer; and a group with implantation of empty polymer in the right hemisphere and BCNU-loaded polymer in the left hemisphere, followed by irradiation. The effects were evaluated radiologically and histologically at specified times. A local reaction by the brain to the polymer was found, which was greater when the polymer contained BCNU. Local cerebral edema was observed radiographically on postoperative Day 14 and had resolved by Day 72. Histologically, a subacute cellular inflammatory response was seen on postoperative Day 16, which had changed to a chronic inflammatory response by Day 72. In the group with radiation therapy administered to the hemisphere bearing BCNU-loaded polymer, only localized pathological changes were detected. In all animals, brain distant from the polymer implantation site was normal. No neurological or general deleterious effects were seen in any of the animals. It is concluded that the interstitial delivery of BCNU by the polyanhydride polymer PCPP:SA is safe in the primate brain and that concomitant radiation therapy did not lead to any adverse effects. These experimental findings are important to an understanding of the clinical effects of PCPP:SA implants in treating brain diseases.

Animals↗
PubMed1993

The influence of angiogenesis inhibitor AGM-1470 on immune system status and tumor growth in vitro.

The synthetic angiogenesis modulator-1470 O-(chloroacetyl-carbamoyl, AGM-1470) is a potent inhibitor of neovascularization. We have investigated the potential influence of this inhibitor in tumor immunobiology using both in vivo and in vitro models. Mice given a single tail-vein injection of tumor cells were later treated wtih AGM-1470 by s.c. injection. After tumor injection, the lungs were evaluated for macroscopic tumor nodules. AGM-1470 significantly reduced the development of macroscopic pulmonary disease but did not eliminate disease. However, tumor-bearing mice treated with AGM-1470 had significantly reduced spleen weight compared to controls. To determine if the observed decrease in spleen weight in the treated animals was associated with immunosuppression, we studied the possible immunomodulatory effects of AGM-1470. AGM-1470 induced no changes in spleen-cell viability compared to controls. However, addition of angioinhibin at the beginning of IL-2-induced spleen-cell activation significantly inhibited the development of NK-mediated tumor-cell killing. Similarly, splenic T-cell proliferation induced by a mitogenic monoclonal antibody to murine T cells was significantly inhibited when activated in the presence of AGM-1470. The in vitro studies were extended by evaluation of immune system status in tumor-bearing mice treated with AGM-1470. In vivo therapy with AGM-1470 did not significantly change the mean splenic lymphocyte counts and CD4/CD8 ratios from control values. In addition, the induction of splenic NK-mediated tumor killing with IL-2 as well as mitogen-induced T-cell activation was not significantly different from control values. These results suggest that AGM-1470 inhibits tumor growth by blocking neovascularization and may, under certain conditions of drug administration, inhibit immune system function.

Animals↗
PubMed1993

Dexamethasone reduces vascular density and plasminogen activator activity in 9L rat brain tumors.

Angiogenesis, a process dependent upon perivascular proteolysis, is required for solid tumor growth and is inhibited by certain steroids including glucocorticoids. We examined the relationship between tumor growth and vessel density in experimental rat brain 9L glial tumors following chronic treatment with the glucocorticoid dexamethasone. Tumor growth was inhibited by intraperitoneal administration of 3 mg/kg/day dexamethasone. Maximal cross-sectional areas of post-implantation day 9 tumors were 4.6 +/- 1.0 mm2 in dexamethasone-treated animals and 17.0 +/- 3.4 mm2 in controls (P < 0.01). Microvessel density assessed by laminin immunohistochemistry was 59% lower in dexamethasone-treated tumors (P < 0.01). Plasminogen activator (PA) activity, a proteolytic enzyme related to endothelial migration and vessel growth, was 4.2 +/- 0.9 IU/micrograms protein in dexamethasone-treated tumors and 9.0 +/- 1.0 IU/micrograms protein in control tumors (P < 0.01). Exposure of cultured 9L and central nervous system microvessel endothelial cells to dexamethasone concentrations comparable to those achieved in vivo had no effect on cell growth, but reduced the PA activity of culture supernatant fractions by 78% and 99%, respectively. These findings suggest that inhibition of proteolytic steps involved in vessel growth may underlie, in part, the mechanism by which glucocorticoids decrease brain tumor growth.

Animals↗
PubMed1993

Interstitial chemotherapy of the 9L gliosarcoma: controlled release polymers for drug delivery in the brain.

The administration of drugs directly into the central nervous system using polymers as drug carriers may improve the treatment of malignant brain tumors. In this study, the effect of the interstitial, localized delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) incorporated into controlled release polymers implanted adjacent to the 9L gliosarcoma was assessed in s.c. and intracranial (i.c.) models. In the s.c. experiment, the 9L gliosarcoma was implanted in the flank of rats and subsequently treated with BCNU either (a) delivered in controlled release polymers inserted adjacent to the tumor or (b) administered systemically by i.p. injections or by controlled release polymers inserted at a site distant from the tumor. The interstitial release of BCNU adjacent to the tumor in the flank resulted in a significant tumor growth delay of 16.3 days, as compared to a growth delay of 9.3 and 11.2 days obtained with the systemic administration of BCNU. In the i.c. experiment, the 9L gliosarcoma was implanted in the brain of Fischer 344 rats and treated either (a) with controlled release polymers containing BCNU inserted into the brain or (b) with the systemic i.p. administration of BCNU. The interstitial release of BCNU in the brain resulted in a significant 5.4- to 7.3-fold increased survival, compared with a 2.4-fold increased survival after the systemic administration of the same dose of BCNU. The two groups with i.c. tumors treated interstitially had 17 and 42% cures, but no long-term cures were obtained in the group treated with systemic therapy. The localized, controlled delivery of chemotherapeutic agents in the s.c. tissues and in the brain via polymeric carriers may be more effective than standard systemic chemotherapy. This approach could be used to deliver a wide variety of agents into the central nervous system to treat diverse neuropathological conditions which remain refractory to systemic therapy.

Animals↗
PubMed1993

Direct delivery of platinum-based antineoplastics to the central nervous system: a toxicity and ultrastructural study.

Platinum drugs are playing an increasingly major role in cancer treatment, but systemic administration of these agents has resulted in significant toxicity. To examine the effects of cisplatin and two newer agents, iproplatin and carboplatin, we injected the agents directly into the cerebrospinal fluid of rats and found that neurotoxic reactions resulted from doses of cisplatin (10 nmol) much lower than those of iproplatin (40 nmol) or carboplatin (80 nmol). Moreover, central nervous system tissue appeared to be less adversely affected by direct exposure to carboplatin since chronic toxicity was not observed in any of the animals receiving carboplatin until a lethal dose was reached. Furthermore, only the animals receiving cisplatin showed histologic damage in their spinal cords, and ultrastructural studies confirmed that while significant abnormalities were observed in the spinal cords of rats receiving 40 nmol cisplatin, no architectural changes were detected in the spinal cords of animals receiving 240 nmol carboplatin. We conclude that platinum drugs can be delivered intrathecally to achieve a much greater concentration of active drug than can be achieved by intravenous administration and that carboplatin appears to be the most suitable platinum-based drug for use in systems delivering drugs directly to the brain and spinal cord.

Animals↗
PubMed1993

Analysis of experimental antiangiogenic therapy.

Angiogenesis is a fundamental process by which new blood vessels are formed. Progressive tumor growth necessitates the continuous induction of new capillary blood vessels which converge upon the tumor. Suppression of tumor growth can be accomplished with the use of antiangiogenesis agents. AGM-1470 is a potent angiogenesis inhibitor in vitro and in vivo. In mouse studies, AGM-1470 has suppressed the growth and neovascularization induced by four murine tumors resulting in a 55% to 77% decrease in tumor growth. In these mice significant toxicity did not result from AGM-1470 therapy. AGM-1470 administered systemically to C57BI/6 male mice for 20 to 28 days inhibited the growth of: (1) Lewis lung carcinoma resulting in a T/C (treatment/control = mean tumor volume of treated/mean tumor volume of control) of 0.38 +/- 0.03 (P < .001); (2) colon adenocarcinoma 38 resulting in a T/C of 0.23 +/- 0.02 (P < .001); and (3) fibrosarcoma 105 resulting in a T/C of 0.31 +/- 0.05 (P < .001). To determine if antiangiogenic therapy was equally effective in mice of both sexes and in immunodeficient animals, we tested AGM-1470 in the treatment of fibrosarcoma 105 in both female mice and nude mice. For female mice T/C was 0.24 +/- 0.06 (P < .001). For nude mice T/C was 0.27 +/- 0.06 (P < .001). These results demonstrate that AGM-1470 suppresses the growth of a variety of different tumors. Furthermore, the antitumor effect of AGM-1470 therapy is independent of the immune system and sex.

Adenocarcinoma↗
PubMed1993

The combination of antiangiogenic agents to inhibit primary tumor growth and metastasis.

Neovascularization is a critical component for the growth of tumors and is a dominant feature in diseases such as diabetic retinopathy and hemangiomas in infancy. Angiogenesis inhibition is a potentially important therapeutic modality. We have previously reported that AGM-1470 is a fungal-derived angiogenesis inhibitor that suppresses primary tumor growth and metastases and is also nontoxic. alpha-Interferon, an angiogenesis inhibitor, is effective in the treatment of life-threatening hemangiomas. We therefore attempted to treat murine primary tumors and metastases with a combination of AGM-1470 and alpha/beta-interferon. Treatment began after solid tumors formed. Six-week-old syngeneic C57BI/6 mice were treated for 21 days with either AGM-1470, or alpha/beta-interferon or AGM-1470 + alpha/beta-interferon. The combination of the angiogenesis inhibitors AGM-1470 and alpha/beta-interferon suppressed tumor growth by 80% compared with controls (P < or = .001). AGM-1470 and alpha/beta-interferon inhibited pulmonary metastatic tumor growth greater than sevenfold (P < or = .001) compared with controls. These effects were better than either inhibitor alone, and the combined effect was additive. Combination of angiogenesis inhibitors may be useful in the treatment of tumors and other angiogenesis-dependent diseases.

Animals↗
PubMed1993

Frameless stereotaxic integration of CT imaging data: accuracy and initial applications.

To evaluate the spatial accuracy of a rapid interactive method of transferring computed tomographic (CT) information between its display on a computer screen to its source (test object, operating field), a multidimensional computer combined with a six-jointed position-sensing mechanical arm was tested with a Plexiglas model consisting of 50 rods of varied height and known location, a plastic replica of the skull, and, subsequently, three patients. The median error value between image and real location was 1-2 mm (P > .95), regardless of the registration target sites. The accuracy, however, increased with the selection of widespread registration points, and 95% of all errors were below 3.70 mm (P > .95). The results compare favorably with the four most commonly used stereotaxic framed units. A misregistration error of 0.3-2.2 mm was found during intraoperative correlation between anatomy on the CT display and actual anatomic location in the operative field.

Child↗
PubMed1993

Inhibition of angiogenesis and growth of human nerve-sheath tumors by AGM-1470.

The effectiveness of AGM-1470, a potent, fungal-derived inhibitor of angiogenesis, in suppressing the neovascularization and growth of human Schwann cell tumors was tested in six schwannomas, seven neurofibromas, and one neurofibrosarcoma. Tumor fragments from surgical specimens were implanted into the subrenal capsule of 348 nude mice (nu/nu). Seven days after implantation, the tumors were measured and vascularity was graded. The animals were then randomly assigned to one of two groups, to receive either saline (control group) or systemic AGM-1470 treatment. After 2 to 6 weeks of treatment, tumor size and degree of vascularity were recorded. In the six different schwannomas implanted into 138 mice, the average vascular grade in the control group after 2 weeks of treatment increased from 2.2 to 3.2 (+1.0), while in the AGM-1470-treated group it decreased from 2.2 to 1.7 (-0.5) (p < 0.01). In the seven different neurofibromas implanted into 158 mice, the change in the average vascular grade in control and AGM-1470-treated animals was +0.5 and -1.0, respectively (p < 0.01). In the one neurofibrosarcoma implanted into 52 mice, the change in average vascular grade in each group during the 6-week treatment period was +1.9 and -1.0, respectively (p < 0.01). Neurofibrosarcoma growth after 6 weeks of AGM-1470 treatment was only 8.5% of the growth found in the control animals (p < 0.01). This study determined that AGM-1470 is effective in inhibiting angiogenesis and the growth of human nerve-sheath tumors.

Animals↗
PubMed1992

Selective endothelial growth inhibition by tetracyclines that inhibit collagenase.

The potential of angiogenesis inhibitors as therapy for human diseases is limited by a lack of clinically available agents. We investigated the mechanism of the anti-angiogenesis effects of minocycline, a commonly used drug, and several derivatives. Endothelial cell proliferation was inhibited by several of these compounds. We found that inhibition was associated with inhibition of collagenase, did not require antibiotic activity, and was not related to cytotoxicity. Other microvessel-associated cells were unaffected. This endothelial antiproliferative effect is a potential mechanism of the anti-angiogenic activity of minocycline.

Animals↗
PubMed1992

Ameloblastoma of the mandible with intracranial metastasis. A case study.

Ameloblastoma is an aggressive locally recurring neoplasm of odontogenic epithelium. We describe a case of a mandibular ameloblastoma with a 17-year history of local recurrences followed by two metachronous intracranial metastases. Central nervous system metastasis without pulmonary involvement is previously unreported in a living patient with ameloblastoma. The behavior of this tumor qualifies it as a malignant ameloblastoma.

Aged↗
PubMed1992

Vascular differentiation and glucose transporter expression in rat gliomas: effects of steroids.

The GLUT1 isoform of the glucose transporter is normally expressed at high levels in differentiated brain vessels that also express a permeability barrier. In contrast, malignant brain neoplasms have relatively undifferentiated vessels that are highly permeable, proliferate to high vascular densities, and often lose GLUT1 expression. Using the rat intracerebral 9L glioma model, we investigated whether dexamethasone-induced changes in permeability are associated with the appearance of other differentiated vascular properties. The percentage of vessels expressing immunohistochemically detectable GLUT1 (74.2 +/- 6.1%) and the tumor vessel density as assessed by laminin immunostaining (282 +/- 37 vessels/mm2) did not vary with control tumor size. Dexamethasone treatment resulted in an 83% reduction of vascular permeability to intravenous Evans blue, an increased percentage of vessels expressing GLUT1 (106.4 +/- 10.5%), lower vascular density (102 +/- 64 vessels/mm2), and smaller tumor size (control cross-sectional area, 17.0 +/- 3.4 mm2; treated, 4.6 +/- 1.0 mm2). Essentially all vessels became GLUT1-positive after dexamethasone treatment. Increased GLUT1 expression by glioma vessels in association with the appearance of other signs of differentiation (low vascular density, slow tumor growth) suggests that immunostaining for GLUT1 may identify neoplasms that are biologically less aggressive.

Animals↗
PubMed1992

Chromosome abnormalities in low-grade central nervous system tumors.

Ependymomas, oligodendrogliomas, and low-grade astrocytomas are slow-growing central nervous system (CNS) tumors that occur in both adults and children, whereas craniopharyngiomas and choroid plexus papillomas occur predominantly in children. We examined karyotypes of 32 of these low-grade tumors, including ten oligodendrogliomas, six ependymomas, 11 low-grade astrocytomas, four craniopharyngiomas, and one choroid plexus papilloma. Only normal karyotypes were obtained from 6 oligodendrogliomas. The rest had normal stemlines; three tumors had 45,X,-Y sidelines and one tumor had a sideline of monosomy 22. The most frequent abnormalities in the ependymomas were +7 (three tumors), -21 (two tumors), -22 (two tumors), and del(9)(p22) (two tumors). Gains of chromosome 7 and deletions of 9p were found more often in high-grade gliomas. Seven low-grade astrocytomas had normal stemlines, two had chromosome 7 abnormalities, a pilocystic astrocytoma had +der(15), and one tumor had a -Y sideline. The four craniopharyngiomas and one choroid plexus tumor were all apparently normal. The cytogenetics of low-grade CNS tumors differ from higher grade gliomas in that most low-grade tumors show little deviation from the normal karyotype.

Adolescent↗
PubMed1992

The intracerebral distribution of BCNU delivered by surgically implanted biodegradable polymers.

The local concentration and distribution of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) within normal brain tissue were studied following surgical implantation of biodegradable polymer containing BCNU in New Zealand White rabbits. Cylindrical discs of poly(bis(p-carboxyphenoxy)-propane:sebacic acid) copolymer in a 20:80 formulation were made containing [3H]-inulin or [3H]-BCNU labeled in the methylene hydrogens of the chloroethyl groups. These were implanted in the brains of 56 New Zealand White rabbits. The animals were sacrificed 3, 7, 14, or 21 days later and the brains were rapidly removed, frozen, and prepared for quantitative autoradiography. Autoradiographs from coronal sections bisecting the polymer were analyzed to determine both the proportion of the brain section exposed to the tracer and the local drug concentrations as a function of distance from the polymer. Tritiated BCNU was also injected directly into the brains of eight additional rabbits, and local brain concentrations were studied over time. The results of this study demonstrate that approximately 50% of the area of the brain sections was exposed to radiolabeled compound 3 days after BCNU-polymer implantation, 15% at 7 days, and less than 10% at 14 and 21 days. Polymer discs containing 600 micrograms BCNU generated 6 mM concentrations of BCNU in brain tissue 10 mm from the polymer at 3 and 7 days. Pharmacological studies demonstrated that approximately 25% of the tritium label was associated with intact BCNU 3 days following polymer implantation. Radiolabeled inulin delivered by polymer remained dispersed throughout the ipsilateral hemisphere for 14 days. Direct injection of [3H]-BCNU into brain parenchyma resulted in widely distributed tracer at 1 and 3 hours with rapid disappearance thereafter. It is concluded that local delivery of BCNU to brain tissue with this polymeric drug delivery system results in sustained high local concentrations of BCNU which may be of value in the treatment of patients with brain tumors.

Animals↗
PubMed1992

Biology and therapy of glial tumors.

Glial tumors remain challenging problems for the clinician and researcher. Despite more aggressive therapy, the majority of these tumors recur locally. This review will provide an update on the new strategies being developed to treat gliomas. Advances in our understanding of the biology of glial tumors will provide new targets at which to direct therapy.

Antineoplastic Agents↗