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Biomedical subjects

J H Sampson

Publications and source records attributed to J H Sampson.

At least 19 recordsLinked to original sources

High-risk gestational trophoblastic neoplasia with brain metastases: individualized multidisciplinary therapy in the management of four patients.

PURPOSE: To report our recent experience managing four patients with brain metastases of gestational trophoblastic neoplasia (GTN), coordinating systemic chemotherapy with early neurosurgical intervention or stereotactic radiosurgery and intensive supportive care during initial therapy to prevent early mortality. MATERIALS AND METHODS: A series of four consecutive patients with brain metastases from high-risk Stage IV GTN managed at our institution in 2003 and 2005. Patients were assigned FIGO stage and risk score prospectively. Because of concern for chronic toxicity resulting from concurrent moderate dose methotrexate and whole brain radiation, an individualized multidisciplinary approach was used to manage patients. RESULTS: All four women presented with brain and pulmonary metastases; one had multiple liver metastases. Neurological symptoms at presentation included grand mal seizures in 2 patients, left upper extremity hemiparesis and headache each in 1 patient, while 1 patient was asymptomatic. Index pregnancies were term pregnancies in all patients with interval from prior delivery ranging from 2 weeks to 4 years. Two had received prior chemotherapy for postmolar GTN prior to the index pregnancy with incomplete follow-up. Initial hCG values ranged from 26,400 to 137,751 mIU/ml; FIGO risk scores were > or =16 for all patients. Systemic combination chemotherapy was initiated with etoposide and cisplatin followed by moderate/high-dose (500-1000 mg/m(2)) methotrexate combinations. Craniotomy was used before or during the first chemotherapy cycle to extirpate solitary lesions in 3 patients, while stereotactic radiosurgery was administered after the first cycle to treat two brain lesions in the remaining patient. None received whole brain radiation or intrathecal methotrexate. In one patient, selective angiographic embolization was used to control hemorrhage from multiple liver metastases. Two patients required ventilator support early in treatment to allow stabilization from intrathoracic hemorrhage and neutropenic sepsis with respiratory distress syndrome, respectively. Hysterectomy was performed in one patient after completion of salvage chemotherapy. All have completed maintenance chemotherapy and are in prolonged remission (12-24 months). Neurologic sequelae include persistent left upper extremity dyskinesia and weakness in one patient, and episodic grand mal seizures and pseudoseizures in a second patient with a pre-existing seizure disorder. CONCLUSION: This case series documents the utility for a multidisciplinary approach to the treatment of brain metastases from GTN. Using early craniotomy or stereotactic radiosurgery combined with etoposide-cisplatin and moderate/high-dose methotrexate combination chemotherapy, we were able to stabilize patients early in their treatment and avoid whole brain radiation therapy or intrathecal chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗

In vitro keratinocyte antiproliferant effect of Centella asiatica extract and triterpenoid saponins.

Psoriasis is a hyperproliferative skin disorder estimated to be present in 1-3% of most populations. Conventional therapy using corticosteroids, Vitamin D analogs and cytotoxic agents eg psoralens is associated with low success rate and many side effects. Traditional plant remedies may provide leads for new treatments. A rapid-throughput, in vitro bioassay has been utilised to examine plants for inhibitory effects on the growth of SVK-14 keratinocytes. Centella asiatica, a reputed anti-psoriatic herb, has been compared against the psoralen-containing seeds of Psoralea corylifolia and the synthetic anti-psoriatic agent dithranol (anthralin). Aqueous extracts of Psoralea corylifolia and Centella asiatica inhibited keratinocyte replication with IC50 values of 18.4 +/- 0.6 microg/ml and 209.9 +/- 9.8 mg/ml respectively prior to treatment with polyvinylpolypyrrolidone (PVPP) and 36.3 +/- 3.3 mg/ml and 238.0 +/- 2.5 mg/ml respectively after PVPP treatment of the extracts. The effect produced by C. asiatica is thus unlikely to be due to phenolic compounds. It may, however, be due to its two constituent triterpenoid glycosides madecassoside and asiaticoside which had IC50 values of 8.6 +/- 0.6 microM respectively. These values were comparable to their concentrations in the crude extract and to the IC50 of dithranol (5.1 +/- 0.4 microM). These results suggest that the potential use of C. asiatica extracts as a topical anti-psoriatic agent is worthy of further investigation.

Anti-Infective Agents↗

Phase I study of Gliadel wafers plus temozolomide in adults with recurrent supratentorial high-grade gliomas.

Both Gliadel wafers [1,3-bis(2-chloroethyl)-1-nitrosourea] and temozolomide (TEMO) have been shown in independent studies to prolong survival of patients with recurrent malignant glioma following surgery and radiotherapy. On the basis of preclinical evidence of synergism between Gliadel wafers and TEMO, a phase I study was designed to evaluate the toxicity of combining these 2 agents in the treatment of patients with recurrent supratentorial malignant glioma. All patients had surgical resection of the tumor at relapse, and up to 8 Gliadel (3.85%) wafers were placed in the surgical cavity following resection. Two weeks after surgery, TEMO was given orally daily for 5 days. Cohorts of 3 patients received TEMO at daily doses of 100 mg/m2, 150 mg/m2, and 200 mg/m2, respectively. Patients were assessed for toxicity 4 weeks after start of the first course of TEMO. Contrast-enhanced MRI of the brain was used to assesstumor response after the first cycle of TEMO. Patients with stable disease or response after the first cycle of TEMO were allowed to continue treatment at the same dose every 4 weeks for 12 cycles or until disease progression or unacceptable toxicity. Ten patients with a median age of 47 years (range, 22-66 years) were enrolled in this study. There were 7 patients with glioblastoma multiforme and 3 patients with anaplastic astrocytoma. Three patients were treated with TEMO at the first dose level of 100 mg/m2, 4 at the second dose level of 150 mg/m2, and 3 at the third dose level of 200 mg/m2. The 10 patients received a median of 3 cycles (range, 1-12 cycles) of TEMO following placement of Gliadel wafers. The treatment was well tolerated, with only 1 patient suffering grade III thrombocytopenia at the highest dose level. Two patients at each dose level had no evidence of disease progression after treatment. Four patients suffered progressive disease on therapy. Our study demonstrates that TEMO can be given safely after placement of Gliadel (3.85%) wafers. The recommended dosage for TEMO for a phase II study of this combination is 200 mg/m2 per day for 5 days.

Adult↗

Unarmed, tumor-specific monoclonal antibody effectively treats brain tumors.

The epidermal growth factor receptor (EGFR) is often amplified and rearranged structurally in tumors of the brain, breast, lung, and ovary. The most common mutation, EGFRvIII, is characterized by an in-frame deletion of 801 base pairs, resulting in the generation of a novel tumor-specific epitope at the fusion junction. A murine homologue of the human EGFRvIII mutation was created, and an IgG2a murine mAb, Y10, was generated that recognizes the human and murine equivalents of this tumor-specific antigen. In vitro, Y10 was found to inhibit DNA synthesis and cellular proliferation and to induce autonomous, complement-mediated, and antibody-dependent cell-mediated cytotoxicity. Systemic treatment with i.p. Y10 of s.c. B16 melanomas transfected to express stably the murine EGFRvIII led to long-term survival in all mice treated (n = 20; P < 0.001). Similar therapy with i.p. Y10 failed to increase median survival of mice with EGFRvIII-expressing B16 melanomas in the brain; however, treatment with a single intratumoral injection of Y10 increased median survival by an average 286%, with 26% long-term survivors (n = 117; P < 0.001). The mechanism of action of Y10 in vivo was shown to be independent of complement, granulocytes, natural killer cells, and T lymphocytes through in vivo complement and cell subset depletions. Treatment with Y10 in Fc receptor knockout mice demonstrated the mechanism of Y10 to be Fc receptor-dependent. These data indicate that an unarmed, tumor-specific mAb may be an effective immunotherapy against human tumors and potentially other pathologic processes in the "immunologically privileged" central nervous system.

Animals↗

Bone marrow-derived dendritic cells pulsed with tumor homogenate induce immunity against syngeneic intracerebral glioma.

To evaluate the efficacy and toxicity of dendritic cell (DC) based therapy for intracerebral gliomas, we utilized a cell line derived from an astrocytoma that arose spontaneously in a VM/Dk mouse. This astrocytoma mirrors human gliomas phenotypically, morphologically and secretes transforming growth factor (TGF)-betas, immunosuppressive cytokines secreted by human gliomas. Systemic vaccination of mice with DCs pulsed with tumor homogenate followed by intracranial tumor challenge produced a > 160% increase in median survival (p = 0.016) compared with mice vaccinated with PBS or unpulsed DCs (p = 0.083). Fifty percent of mice treated with pulsed DCs survived long-term. Immunologic memory was demonstrated by survival of mice rechallenged with tumor. Both cell-mediated and humoral immunity was induced. On histological examination only focal areas of demyelination at the tumor implantation site were present. There was no evidence that autoimmune encephalomyelitis was induced by DC vaccination. Therefore, in a murine model, vaccination with DCs pulsed with glioma tumor homogenate is a safe and effective therapy against a syngeneic glioma located in the immunologically privileged central nervous system (CNS).

Animals↗

Ethnomedicinally selected plants as sources of potential analgesic compounds: indication of in vitro biological activity in receptor binding assays.

A number of plant species used in traditional medicine for the relief of pain have been selected from the medicinal and scientific literature of China, South America, Asia and West Africa. Extracts were prepared and tested in three in vitro receptor radioligand binding assays to determine whether there was an indication of biological activity, in particular their selectivity to a single receptor implicated in the mediation of pain. The three neuropeptide receptors chosen were Bradykinin (BK II), expressed in Chinese hamster ovary cells (CHO), neurokinin 1 (NK 1) expressed in astrocytoma cells, and calcitonin gene related peptide (CGRP) which were all implicated in the mediation of acute pain in the mammaliancentral nervous system. The plant species chosen to investigate were Ageratum conyzoides, Barringtonia edulis, Croton tiglium, Ipomea pes-caprae, Panax ginseng, Physostigma venenosum, Sinomenium acutum, Solidago virgaurea, Symplocos leptophylla and Typhonium giganteum. The results showed that there was a strong indication of biological activity for some of the plants which are used ethnomedicinally to treat pain, in the three in vitro receptor binding assays used, and particular plant extracts exhibited selective action to a single receptor.

Analgesics, Non-Narcotic↗

Temozolomide delivered by intracerebral microinfusion is safe and efficacious against malignant gliomas in rats.

Intracerebral microinfusion (ICM) is an innovative technique of delivering therapeutic agents throughout large portions of the brain that circumvents the blood-brain barrier, minimizes systemic toxicity, and provides a homogeneous distribution of the infused agent. Temozolomide is a novel methylating agent with proven efficacy against malignant gliomas (MGs) after systemic administration but with dose-limiting myelotoxicity. Because MGs rarely metastasize, systemic drug delivery is unnecessary. Therefore, we evaluated the efficacy and toxicity of ICM with temozolomide in an athymic rat model of human MGs. Treatment of rats by ICM with temozolomide 3 days after intracerebral challenge with D54 human MG xenograft increased median survival by 128% compared with rats treated by ICM with saline, by 113% compared with rats treated with i.p. saline, and by 100% compared with rats treated with i.p. temozolomide (P < 0.001). Delay of treatment until 9 days after tumor challenge still resulted in a 23% increase in median survival in rats treated by ICM of temozolomide compared with rats treated with i.p. temozolomide. In addition, overall, 21.7% of rats treated by ICM with temozolomide survived for > 100 days without clinical or histological evidence of tumor. The dose of temozolomide delivered by ICM in this study was limited only by drug solubility, and no neurological or systemic toxicity could be attributed to ICM with temozolomide. Therefore, ICM of temozolomide may offer significant advantages in the treatment of MGs.

Animals↗

Intrathecal busulfan treatment of human neoplastic meningitis in athymic nude rats.

The current study was designed to evaluate the toxicity and activity of Spartaject Busulfan, a microcrystalline preparation of busulfan, following its intrathecal administration into a nude rat model of human neoplastic meningitis. Animals were treated through permanent indwelling subarachnoid catheters. Human glioma D-456 MG growing in the subarachnoid space was treated with 8.1 micromol of intrathecal Spartaject Busulfan. Single-dose therapy was also subsequently compared with 4 doses of 8.1 and 2.0 micromol busulfan, respectively, against D-456 MG neoplastic meningitis. Additional experiments evaluated a saline control versus 8.1 micromol x 1, 6.2 micromol x 4 and 4.1 micromol x 4, respectively, against D-456 MG. A single dose of 8.1 micromol of intrathecal Spartaject Busulfan resulted in an increase in median survival of 61.7% compared with the saline control. In experiment 2, all busulfan treatments showed increases in median survival of 142.8% (8.1 micromol x 1), 52.3% (2.0 micromol x 4), and 23% (8.1 micromol x 4) (p < 0.001 for all groups) compared with the saline control. These results suggest that a narrow therapeutic dose range for both toxicity and activity has been defined for intrathecal busulfan in the treatment of human neoplastic meningitis in athymic nude rats. Although busulfan has only limited activity against solid tumors, the high doses achievable in the CSF following intrathecal administration coupled with the steep dose-response relationships of alkylating agents, provide rationale for further evaluation of this agent.

Animals↗

Monoclonal antibody therapy of human gliomas: current status and future approaches.

The development of immunotherapeutic protocols for the treatment of human CNS neoplasia over the past two decades has been impressive. Several crucial aspects have been defined, characterized, and in many cases, optimized (Wikstrand CJ, Zalutsky MR, Bigner DD: In: Liau LM, Bigner DD (eds) Brain Tumor Immunotherapy. Humana Press (in press), 2000). Specific Mabs or constructs reacting with targetable antigens are currently available and in clinical trial. In addition, additional antigens currently under study (angiogenesis-related markers, developmentally associated antigens for medulloblastoma such as L1, and the identification of new targets by SAGE, just in its infancy, will provide a veritable library of available targets for therapy. The molecular engineering and affinity maturation techniques being applied to Mab fragment optimization have already been rapidly effective in generating a variety of Mab constructs of appropriate affinity for clinical trial; as new targets are defined, and experience is accrued with the various constructs currently and prospectively available, the optimal targeting of a multitude of antigens will be possible.

Animals↗

Treatment of neoplastic meningitis with intrathecal temozolomide.

Neoplastic meningitis (NM) results from leptomeningeal dissemination of cancers arising within the central nervous system or metastasizing to the leptomeninges from systemic neoplasms. The inability to produce therapeutic drug levels intrathecally (i.t.) with systemic administration and the minimal efficacy of chemotherapeutic agents currently available for direct i.t. use limit therapy. Temozolomide [8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4([3H])-one] is a novel methylating agent with proven activity against intraparenchymal malignant gliomas (MGs). Insolubility of the standard formulation prevents its efficacious use as an i.t. agent, however. To overcome this obstacle, we have developed a unique microcrystalline formulation of temozolomide with greatly enhanced solubility. Treatment of athymic rats bearing subarachnoid MER- human MG xenografts with four doses of i.t. microcrystalline temozolomide over a 2-week period produced a 142% increase in median survival at individual doses of 2.2 micromol (P = 0.0073) and a >367% increase in median survival at individual doses of 6.8 micromol (P = 0.0015). At the higher dose tested, three of eight rats treated developed no neurological symptoms and had no evidence of residual tumor on histological examination after treatment. Use of this microcrystalline formulation in athymic rats bearing subarachnoid MER+ human MG xenografts increased median survival >132% (P < 0.0058) at both dose levels tested. Toxicity directly attributable to the i.t. administration of microcrystalline temozolomide was exhibited in the highest dose groups only and was limited to small patchy areas of focal demyelination involving <5% of spinal cord long tracks.

Animals↗

Regional treatment of epidermal growth factor receptor vIII-expressing neoplastic meningitis with a single-chain immunotoxin, MR-1.

The incidence of neoplastic meningitis is on the rise. Neoplastic meningitis can result from a direct seeding of the neuraxis by primary brain tumors or by hematogeneous spread of systemic solid tumors. A frequent genetic alteration in primary brain tumors such as gliomas is an in-frame deletion in the epidermal growth factor receptor (EGFR) gene EGFRvIII, which brings together what were normally distant polypeptide sequences in the intact receptor. A novel glycine is formed at the fusion junction, resulting in a unique and tumor-specific target. By using phage display, we have isolated a single-chain antibody specific for the EGFRvIII mutation and expressed it with a modified form of the Pseudomonas exotoxin to form the immunotoxin MR1scFvPE38KDEL (MR-1). The multiple dose toxicity and therapeutic efficacy of MR-1 immunotoxin were tested in an athymic rat model of neoplastic meningitis. The maximally tolerated doses in non-tumor-bearing rats were three doses of 3 microg each. For therapeutic studies, the target was a neoplastic meningitis induced by intrathecal inoculation of the EGFRvIII-expressing human glioma U87MG.deltaEGFR. A dose escalation study compared the survival of three equal doses of 1, 2, and 3 microg of MR-1 immunotoxin with saline or 3 microg of the control immunotoxin specific for the interleukin 2 receptor, anti-Tac. All animals treated with three doses of saline or 3 microg of anti-Tac died, with median survival of 7 and 10 days, respectively. There were 75% (six of eight) long-term survivors in the group treated with three doses of 1 microg and 57% (four of seven) long-term survivors in the groups treated with three doses of either 2 or 3 microg of MR-1 immunotoxin. None of the MR-1 immunotoxin-treated groups reached median survival by the termination of the study at 53 days. Therefore, median survival was estimated to be >53 days, resulting in an estimated increase in median survival of >657% compared with saline and 430% versus anti-Tac. Compartmental therapy with three doses of 2 microg of MR-1 immunotoxin is effective in the treatment of EGFRvIII-expressing neoplastic meningitis. This dose was found to have no clinical or histopathological effects on non-tumor-bearing animals. MR-1 immunotoxin is, therefore, considered specific and safe within its therapeutic window. Phase I clinical trials for tumors invading the intrathecal space that express the EGFRvIII target should be initiated.

ADP Ribose Transferases↗

Experience with a cross-study endpoint review committee for AIDS clinical trials. Terry Beirn Community Programs for Clinical Research on AIDS.

OBJECTIVES: To describe the methods and results of a standardized system for clinical endpoint determination for defining and reviewing endpoints in clinical trials for HIV-infected individuals. DESIGN: A system was developed utilizing standard definitions for the 24 diagnoses or clinical events that serve as trial endpoints and together define the combined endpoint 'progression of HIV disease. A common set of case report forms were used for all trials. Thus, an event of Pneumocystis carinii pneumonia (PCP), for example, for a subject co-enrolled in an antiretroviral trial and a PCP prophylaxis trial was only reported once. METHODS: A central committee was established to define clinical events and review endpoints across all studies. Events were classified according to established criteria for confirmed, probable and possible levels of certainty. RESULTS: This report describes the methods used to ascertain and review endpoints, and summarized 2299 clinical events for 8097 subjects enrolled in one or more of nine clinical trials. Data on the diagnostic certainty of events and agreement between site clinicians and the endpoint committee are presented. CONCLUSIONS: Uniform classification of endpoints across AIDS clinical trials can be accomplished by multicenter, multitrial organizations with standardized definitions and review of endpoint documentation. Our experience suggests that nurse coordinators reviewing all submitted endpoints for every trial are warranted and the need for external review by a clinical events committee may depend on the type of trial conducted.

AIDS-Related Opportunistic Infections↗

Local production of TGF beta1 inhibits cerebral edema, enhances TNF-alpha induced apoptosis and improves survival in a murine glioma model.

We have previously reported that local secretion of either TNF-alpha or TGF beta1 by intracerebral SMA-560 malignant glioma tumor cells can reduce or eliminate tumor growth in mice. However, the use of TNF-alpha, while improving the overall survival of tumor bearing animals, was associated with early toxic deaths due to cerebral edema. In the present study, we demonstrate that TNF-alpha induces apoptosis of the SMA 560 cell line, as does TGF beta1, and that these two cytokines act in an additive fashion to enhance apoptosis and thus, to inhibit SMA 560 cell growth in vitro. Next, we show that the production of TGF beta1 when added to TNF-alpha production by central nervous system tumors in vivo abrogates any early deaths seen due to TNF-alpha toxicity and leads to a larger percentage of animals surviving CNS tumor challenge. Finally, we demonstrate that the production of TGF beta1 by tumor cells is associated with the abolition of tumor-associated cerebral edema in both TNF-alpha and in non-TNF-alpha producing tumors. These results are important for the development of effective and less toxic therapies for brain tumors, as well as for examining the pathogenesis of tumor-related cerebral edema.

Animals↗

A randomized, placebo-controlled trial of the safety and efficacy of oral ganciclovir for prophylaxis of cytomegalovirus disease in HIV-infected individuals. Terry Beirn Community Programs for Clinical Research on AIDS.

OBJECTIVE: Evaluate safety and efficacy of oral ganciclovir (GCV) for preventing cytomegalovirus (CMV) disease in HIV-infected persons at high risk for CMV disease. DESIGN: Double-blind, placebo-controlled, randomized clinical trial in primary care clinics and private practice offices specializing in the care of people with HIV. Interventions were oral GCV (1000 mg three times/day) or placebo. Protocol amendment allowed switch to open-label oral GCV. Main outcome measures were confirmed CMV retinal or gastrointestinal mucosal disease, and death. The study enrolled 994 people co-infected with CMV and HIV, with at least one CD4 count recorded < 100 x 10(6) cells/l. RESULTS: At study completion (15 months median follow-up), CMV event rates in the oral GCV and control groups were 13.1 and 14.6 per 100 person years, respectively, a hazard ratio (HR) of 0.92 [95% confidence interval (CI), 0.65-1.27; P = 0.6]. At protocol amendment event rates were 12.7 and 15.0, respectively (HR, 0.85; 95% CI, 0.56-1.30; P = 0.45). At study completion, event rates for death were 26.6 and 32.0 (HR, 0.84; P = 0.09), and at protocol amendment were 18.9 and 19.6 (HR, 0.95; P = 0.78), respectively. At protocol amendment for the CMV endpoint, the oral GCV treatment effect was associated with baseline use of didanosine (ddI). For patients taking ddI at randomization, HR was 7.48 (P = 0.02). For patients not taking ddI, HR was 0.62 (P = 0.04). These HR were statistically different (P = 0.0006). CONCLUSIONS: In our study, 3 g/day oral GCV did not significantly reduce CMV disease incidence, but there was a suggestion of a death-rate reduction. Furthermore, results suggest that oral GVC decreased risk of CMV disease in patients not prescribed ddI, and increased risk in those prescribed ddI. For the CMV endpoint, our study differs markedly from the only similar study, although for the death endpoint, a combined analysis of studies indicated significant reduction in death rate.

AIDS-Related Opportunistic Infections↗

Demographics, prognosis, and therapy in 702 patients with brain metastases from malignant melanoma.

UNLABELLED: Brain metastases are a common and devastating complication in patients with malignant melanoma. Therapeutic options for these patients are limited, and the prognosis is usually poor. OBJECT: A retrospective review of 6953 patients with melanoma treated at a single institution was undertaken to identify demographic factors associated with the development of clinically significant brain metastases in 702 of these patients and to determine the factors influencing the prognosis of this population to permit more informed recommendations regarding surgical therapy. METHODS: Factors found to be associated with the development of brain metastases included male gender, primary lesions located on mucosal surfaces or on the skin of the trunk or head and neck, thick or ulcerated primary lesions, and histological findings of acral lentiginous or nodular lesions. The overall median survival time of all patients with brain metastases was 113.2 days, and these metastases contributed to the death of 94.5% of the patients in this group. Patients with primary lesions located in the head or neck region had a significantly shorter survival time relative to other patients with brain metastases, whereas patients with a single brain metastasis, patients without lung or multiple other visceral metastases, and patients whose initial presentation with melanoma included a brain metastasis had a significantly better prognosis. The small group of patients who survived for more than 3 years was characterized by the presence of a surgically treated, single brain metastasis in the absence of other visceral metastatic disease. CONCLUSIONS: Although most patients with brain metastases resulting from melanoma have a dismal prognosis, some who are likely to survive for longer periods can be identified. In these patients surgical resection can significantly prolong meaningful survival. The decision to recommend surgery should be based primarily on the resectability of the brain metastases and on the status and number of other organs with metastatic lesions.

Adult↗

A genetically modified allogeneic cellular vaccine generates MHC class I-restricted cytotoxic responses against tumor-associated antigens and protects against CNS tumors in vivo.

An active immunotherapeutic strategy using transfected allogeneic cells for targeting the mutant epidermal growth factor receptor (EGFRvIII) on intracranial tumors was examined. Immunization with allogeneic 300.19/EGFRvIII cells induced CD8+ cytotoxic T-lymphocytes against EGFRvIII bearing syngeneic B16-F10 melanoma or 560 astrocytoma cells (H-2b), but not against allogeneic NR6 cells (H-2q) also bearing EGFRvIII significant NK cell activity was also noted in vitro. Vaccination protected against intracranial challenge with EGFRvIII-positive tumor, with 50% long term survival. In vivo depletions of effector cell subsets demonstrated the requirements for both CD8+ and CD4+ T-cells but not NK cells in producing this protective effect. These data demonstrate the generation of significant, antigen-specific and MHC class I-restricted cytotoxic immune responses which are effective against tumors present in the CNS.

Animals↗

Characterization of a spontaneous murine astrocytoma and abrogation of its tumorigenicity by cytokine secretion.

OBJECTIVE: The promise of immunotherapies developed against brain tumors in animal models has not been realized in human clinical trials. This may be because of the routine use of rodent tumors artificially induced by chemicals or viruses that do not accurately portray the intrinsic qualities of spontaneously arising human tumors and that often fail to incorporate the role of immunosuppressants, such as transforming growth factor-beta, that are secreted by human gliomas. From an astrocytoma that arose spontaneously in inbred VM/Dk mice, we have characterized a highly tumorigenic spontaneous murine astrocytoma cell line (SMA-560) that retains features of glial differentiation and naturally produces high levels of biologically active transforming growth factor-beta. We have used this model to determine whether cytokine production by tumor cells will inhibit intracerebral astrocytoma growth. METHODS: Packaging cell lines producing replication-incompetent retroviral vectors were used to transfect the SMA-560 cell line in vitro with the genes encoding the murine cytokines interleukin (IL)-2, IL-3, IL-4, IL-6, tumor necrosis factor-alpha, gamma-interferon, or granulocyte-macrophage colony-stimulating factor or the costimulatory molecule B7.1 (CD80). RESULTS: Mice challenged intracerebrally with 5000 untransfected SMA-560 cells all succumbed to tumor within 30 days, with a median survival of 25 days. In contrast, mice challenged with SMA-560 cells producing IL-2, IL-4, or tumor necrosis factor-alpha each had a more than 400% increase in median survival (P < 0.0001). In these groups, 78.3% (18 of 23 mice), 66.7% (10 of 15 mice), and 60% (6 of 10 mice) of the mice, respectively, remained alive without evidence of tumor for longer than 100 days after the initial tumor challenge. All other cytokines tested and the expression of B7.1 failed to result in an increase in median survival. CONCLUSION: Using a spontaneous astrocytoma model in an inbred mouse strain, we have shown that cytokine production by glial tumors can abrogate their tumorigenicity in vivo despite production of transforming growth factor-beta. These results predict that approaches directed at cytokine production within intracerebral astrocytomas may be efficacious in human trials and that the "immunological privilege" of the brain may not be absolute under such conditions.

Animals↗