Scorpion venom induces glioma cell apoptosis <Emphasis Type="Italic">in vivo</Emphasis> and inhibits glioma tumor growth <Emphasis Type="Italic">in vitro</Emphasis>

Summary Malignant gliomas are the main brain tumors notoriously resistant to currently available therapies, since they fail to undergo apoptosis upon anticancer treatment. Recent progress on enhanced studies of ion channels involved in glioma cells shed new light on the investigation of glioma cell growth and proliferation. Here we report BmK scorpion venom, a rich resource of various ion channels blockers/modulators, induces cell death of cultured malignant glioma U251-MG cells in vitro specifically at a dose of 10 mg/ml while shows no effect on human hepatocellular carcinoma cells and Chinese hamster ovary cells. The glioma cell death was then determined as apoptosis using 4,6-diamidino-2-phenylindole staining and fluorescence-activated cell sorting analysis. After incubation with BmK venom for 32 and 40 h, 36.20% and 63.08% of U251-MG cells showed apoptosis. Furthermore, BmK venom could significantly inhibit the tumor growth in vitro, which was assessed using U251-MG tumor xenografts on severe combined immunodeficiency mice. The tumor volume of the BmK venom treated mice is nearly 1/8 of that of control after 21 days, and the tumor weight is less than half of that of control. That BmK venom induces apoptosis and inhibits growth of glioma may result from the inhibition and/or modulation of various ion channels in glioma cells.     

The Bleb Formation of the Extracellular Pseudopodia; Early Evidence Of Microtubule Depolymerization by Estramustine Phosphate in Glioma Cell; In Vitro Study

Estramustine phosphate (EMP) is an anti-microtubule agent that depolymerizes microtubules and also causes apoptosis of glioma cells. Both of these pharmacological actions have been previously studied within the same cytotoxic range of EMP concentrations. The purpose of this study was to investigate which of these two phenomena occurred before the other. A preliminary MTT assay was done to distinguish non-cytotoxic (0.005–0.1M) and cytotoxic (0.5–10M) of EMP for BT4C cells. To investigate apoptotic changes, transmission electron microscopy (TEM), DNA laddering, and in situ endo-labeling (TUNEL) method were employed. A chemotaxis assay was used to assess cell motility. Scanning electron microscopy and TEM immunocytochemistry with an anti- tubulin antibody were applied to detect morphological changes of the microtubules. Suppression of cell motility by cytotoxic doses of EMP (0.5–10M) group was attributed by the cyto-reductive effect, relating to apoptosis. At 0.01–0.1M (non-cytotoxic doses), EMP did not indue apoptosis. At these concentrations, TEM and immunohistochemistry revealed the formation of blebs on the tip of the pseudopodia that contained abnormally depolymerized microtubules, a finding that was not observed at a low temperature or during cell migration. Cell chemotaxis was significantly inhibited by cytostatic EMP doses (0.05 and 0.1M). Bleb formation of the pseudopodia might be evidence of the abnormal disassembly of microtubules by cytostatic EMP concentrations, prior to the induction of apoptosis. In glioma cells EMP probably initiates apoptosis by causing the depolymerization of microtubules. Inhibition of cell motility by cytostatic doses of EMP could be beneficial to support other therapies.     

Cytotoxic effect and uptake of estramustine in a rat glioma model

The cytotoxic effect of estramustine-phosphate (EMP) and the uptake in tumor tissue were investigated in a rat glioma model in vitro and in vivo. EMP, a combination of nornitrogen mustard and 17beta-estradiol, is a cytotoxic drug which main target is assumed to be the microtubule system. EMP and its metabolite estramustine (EaM) have a demonstrated anti-tumorous effect on human glioma cells in vitro. The drug uptake in tumor tissue and subsequently also the cytotoxic effect, is believed to depend, at least partially, on a specific estramustine-binding protein (EMBP) which is present in human glioma tissue. In this study we have examined the effects and pharmacokinetics of EaM in the nitrosourea induced BT4C rat glioma model. The tumor was characterized by infiltrative growth with a histopathological picture resembling gliosarcoma. The presence of EMBP was demonstrated by immunohistology. In vitro EMP caused a dose-related inhibition of BT4C-cell growth. In vivo, in the rat model, a significant inhibition of tumor growth was obtained after administration of EaM 20 mg/kg/d i.p. The pharmacokinetics of EaM resembled that found in the human clinical situation with EaM as the main metabolite accumulating in tumor tissue. The mean concentration ratio of EaM was 15.6 in tumor versus serum, and 1.8 in tumor versus normal brain of 1.8. The cytotoxic effect demonstrated in the rat glioma model justifies further evaluation of EMP/EaM in the treatment of malignant gliomas.     

Phase II Study of Combination Taxol and Estramustine Phosphate in the Treatment of Recurrent Glioblastoma Multiforme

Taxol has activity in the treatment of high grade gliomas but estramustine phosphate (EMP) has not been used in this setting. In vitro data demonstrates that EMP is cytotoxic to glioma cell lines and estramustine binding proteins are expressed by glioma cells. The combination of Taxol and EMP is reported to be active in the treatment of hormone-refractory prostate cancer and in taxane-resistant breast and ovarian cancer. We therefore performed a phase II study to assess the activity and toxicity of this combination in high grade gliomas. Taxol was given at a dose of 225mg/m² intravenously over three hours on day 1 and EMP was given at a dose of 900mg/m² orally on days 1 through 3. Cycles were repeated every three weeks. Twenty patients with recurrent glioblastoma multiforme (GBM) were enrolled: 11 male, median age 45 years. All patients received anti-epileptic medications and 17 (80%) had received prior chemotherapy. Of 18 evaluable patients, two had partial responses (11%) and six had stable disease (33%) for a minimum of eight weeks. Treatment was well tolerated with grade 3 neutropenia occurring in only three patients. There were no other grade 3 or 4 toxicities. The median time to progression for the cohort was only six weeks (range 3–60+ weeks). The median overall survival was 12 weeks (range 3–60+ weeks). In conclusion, the combination of Taxol and EMP is well tolerated and has modest activity in the treatment of recurrent GBM.     

Drug-induced Apoptosis by Anti-microtubule Agent,Estramustine Phosphate on Human Malignant Glioma Cell Line,U87MG; in vitro Study

The drug effect of estramustine phosphate (EMP), an anti-microtubule agent on human glioma cells has been studied with the focus being mainly its cytotoxity or its targeting of organelles. However, the pharmacological knowledge of estramustine with respect to its cytotoxity and mechanism is limited. To acquire such knowledge, the present study investigates the ability of EMP to induce apoptosis in a human malignant glioma cell line. Transmission electron microscope (TEM) images were examined to monitor periodic changes. Agarose gel electrophoresis was also examined. Cellular DNA fragmentation ELISA was performed to investigate the DNA fragmentation rates and an MTT assay was studied to evaluate the ID₅₀. A TEM study revealed condensing and fragmentation of the chromatin. Laddering of the bands was observed in all EMP exposure groups in agarose gel electrophoresis. DNA fragmentation in all EMP groups began at 0.5h following an exposure with EMP and increased in a dose- and time-dependent manner as revealed by DNA ELISA fragmentation. ID₅₀ at 24h was 5.0µM according to the MTT assay, a value close to 4.8µM of ID₅₀ was revealed by the DNA fragmentation assay. None of the above mentioned changes was observed in the control group. These results indicated that EMP caused a drug-induced apoptosis in the human malignant glioma cell line, U87MG.     

The Antimicrotubule Drug Estramustine but not Irradiation Induces Apoptosis in Malignant Glioma Involving AKT and Caspase Pathways

Irradiation is one of the cornerstones used in the treatment of malignant glioma. However, the effect is modest and glioma cells generally display a pronounced radio-resistance. In this study, the effect of irradiation, alone and in combination with the antimicrotubule drug estramustine (EaM), was investigated in vitro using the BT4C rat glioma cell line, and in vivo the BT4C rat intracerebral glioma model was used. Apoptosis was detected by analysing DNA laddering, in situ end labelling (ISEL) and Annexin V reactivity. In addition, phosphorylation status of MAPK, JNK, p38, and AKT, proteins involved in pro- and anti-apoptotic signalling pathways was analysed by Western blotting. Irradiation did not induce apoptosis, neither in vitro nor in vivo. EaM, however, induced apoptosis in vivo and in vitro, regardless of whether EaM was given alone, before or after irradiation. When BT4C cells were treated with the caspase-3 inhibitor Ac-DEVD-CHO prior to EaM, the number of apoptotic cells was decreased, indicating an involvement of caspase-3. The signalling pathways regulating apoptosis are complex and involve kinases such as MAPK, JNK, p38 and AKT. Irradiation did not induce any changes in the expression levels or phosphorylation status of these proteins. On the other hand, the phosphorylation level of AKT was reduced after EaM treatment, which might, in part, propose how EaM induces apoptosis in glioma cells.     

Autologous Adjuvant Linked Fibroblasta Induce Anti-Glioma Immunity: Implications for Development of a Glima Vaccine

Objectives: Adjuvant-linked vaccines have been shown to induce anti-tumor immunity in patients with a variety of solid tumors. In this study we describe an in vitro model of active immunotherapy using autologous fibroblasts as immunogen. Correlative results from glioma patients immunized with autologous fibroblasts are also described. Methods: Peripheral blood lymphocytes (PBLs) from normal subjects were immunized in vitro against autologous skin fibroblasts coupled to the adjuvant muramyl dipeptide. The lymphocytes developed cell-mediated cytotoxicity that was measured with a short-term chromium release assay. Results of in vitro experiments were compared to data derived from glioma patients immunized with subcutaneous injection of an autologous adjuvant-linked fibroblast vaccine. Glioma target cells and fibroblast immunogens were derived from early passage primary tissue culture. Results: A comparison of autologous vs. homologous immunogen indicated that major histocompatibility complex matching was required at the sensitization stage of immunity (17.2 ± 3.4% specific lysis vs. 0.4 ± 3.1%, P < 0.01). Pre-treatment of fibroblast immunogen cells with interferon gamma (IFN-) was found to significantly increase immunity (42.2 ± 10.0%, P < 0.01), as did IFN- pre-treatment of tumor target cells (35.8 ± 9.0%, P < 0.01). The positive effect of IFN- was diminished by treatment of cells with IFN-. These in vitro results correlated well with in vivo data derived from glioma patients immunized with an autologous adjuvant-linked fibroblast vaccine. PBLs from patients developed direct cell-mediated cytotoxicity against autologous tumor cells. Lysis of tumor targets after in vivo immunization increased over a three-week interval (from 1.2 ± 3.0% to 21.0 ± 3.4%, P < 0.01) while lysis of a non-MHC matched control cell line remained essentially unchanged. Conclusions: Specific lysis of glioma targets in vitro was achieved after in vivo sensitization with autologous adjuvant-linked fibroblasts. Collectively, the data indicate that biochemically modified autologous cells can stimulate anti-glioma immunity in humans. The degree of specific immunity seen in our patients compares favorably with other published series using glioma cells as an antigenic source. Accordingly, fibroblasts may represent a practical alternative to glioma cells for vaccine construction.     

Human Malignant Glioma Therapy Using Anti-αVβ3 Integrin Agents

Glioblastoma multiforme (GBM) is the most frequent malignant brain tumor in adults and is invariably fatal. We have investigated the effect of cyclo-(Arg-Gly-Asp-D-Phe-Val) (cRGDfV) peptide on survival of human malignant glioma cells in vitro and in vivo. Immunofluorescent analyses revealed the presence of _V3 integrin on U-87MG and U-373MG cells, but minimal expression on U-251MG cells. Treatment of U-87MG and U-373MG cells in vitro with cRGDfV (20µg/ml), but not the linear peptide, resulted in the appearance of rounded and loosely attached cells with subsequent cell death. By comparison, neither this cyclic peptide nor its linear homolog had any significant effect on growth and morphology of U-251MG cells. The death of cRGDfV-treated (20µg/ml) glioma cells was blocked by pretreatment (10µM) of cells with DEVD-FMK and LEHD-FMK, inhibitors of caspase-3 and caspase-9, respectively. Moreover, when glioma cells grown as spheroids were treated with cRGDfV (50µg/ml), spheroid formation was markedly reduced. Further, treatment of intracranial U-87MG tumors in scid mice with cyclic peptide significantly (p<0.001) prolonged their survival. These results indicated (i) that cRGDfV induced apoptosis of human glioma cells by binding _V3 integrin expressed on their cell surfaces and (ii) that cRGDfV may be an effective and non-toxic direct anti-tumor therapy for _V3-expressing GBMs.     

Assessment of laminin-mediated glioma invasion in vitro and by glioma tumors engrafted within rat spinal cord

Summary Cell motility within central nervous system (CNS) neuropil may be largely restricted yet infiltration by glioma cells is commonly observed. Glioma cells remodel nervous tissue and may assemble extracellular matrix in order to migrate. We examined the rat C6 glioma cell line for laminin expression and response in vitro and following engraftment into rat spinal cord. C6 cell cultures expressed laminin-2. C6 cells attached equally well to substrates of purified laminin-1 and laminin-2 and laminin-2-enriched C6 conditioned medium. In contrast, C6 cell migration was substantially greater on laminin-2 and C6-derived substrata than on laminin-1. Glioma cell attachment to laminin-1 and -2 was largely inhibited by antibody to the laminin receptor LBP110 and by an IKVAV peptide but not by YIGSR or control peptides. IKVAV peptide and anti-LBP110 antibodies also inhibited glioma cell invasion through synthetic basement membrane. Anti-₁ integrin antibody selectively inhibited cell migration and invasion on laminin-2 substrata without affecting percent cell attachment. These findings suggest C6 cell migration and invasion are promoted by autocrine release of laminin-2 and involve LPB110 and ₁ integrin laminin receptors.A possible role for laminin-2 in CNS infiltration in vivo was examined following glioma engraftment into rat spinal cord. Engrafted C6 tumors share many histologic features of invasive human glioma. Engrafted glioma cells expressed laminin, LBP110 and ₁ integrin antigens, indicating the molecular mechanisms of C6 motility observed in culture may contribute to glioma invasion in vivo. NMR and corroborative immunocytochemistry provided precise means to monitor tumor progression following glioma engraftment into rat spinal cord. Advantages of this glioma model are discussed regarding the assessment of anti-adhesive therapies in vivo.     

Effect of pharmacologic doses of zinc on the therapeutic index of brain tumor chemotherapy with carmustine

To evaluate the potential differential effect of pretreatment with pharmacologic doses of the trace element zinc on the chemosensitivity of glioma cells and bone marrow cells for carmustine (BCNU), we performed in vitro and in vivo studies of zinc toxicity as well as of the combined treatment with zinc and the anticancer drug. We studied the in vitro effects on established human and rat glioma cell lines using a microcolorimetric growth assay and on murine bone marrow using a clonogenic assay for committed progenitor cells of the granulocyte-monocyte lineage. Zinc exposures of up to 100 M for 120 h did not influence the growth of six of seven human glioma cell lines. Only U87MG demonstrated statistically significant toxicity during high zinc exposure (100 M over 120 h). Dose-response growth curves generated for BCNU did not show protection against the anticancer agents by a 48-h pretreatment with different zinc concentrations. The clonogenic capacity of bone marrow cells was slightly reduced by in vitro culture for 24 and 48 h. Although this effect appeared to be more prominent in the presence of zinc supplementation, overall a statistically significant inhibition was seen only after exposure to a concentration of 100 M zinc over 48 h. As compared with chemotherapy alone, in vitro pretreatment with 50 M zinc over 48 h followed by chemotherapy resulted in an increased number of colony-forming unit-granulocyte monocyte (CFU-GM): CFU-GM increased by a factor of 2 for BCNU (60 M×2 h). This statistically significant in vitro chemoprotection would translate into a dose-protection factor of 1.5, i.e., for the same level of myelosuppression, zinc pretreatment would allow administration of a 50% increased dose of BCNU. The in vivo studies were performed in an s.c. xenograft model of the human glioma cell line U87MG in athymic mice. The maximal tolerable pretreatment with zinc was determined to be a 10-day course of daily i.p. injections of 10 mg/kg ZnCl₂. The subsequent i.p. administration of the dose lethal to 10% of the mice (LD₁₀) and of a 1.5×LD₁₀ dose of BCNU resulted in less bone marrow toxicity in pretreated animals than in non-zinc-pretreated mice as determined in a CFU-GM assay. Glioma colony-forming efficiency (CFE) assays, on the other hand, did not show any zinc-related difference in the BCNU sensitivity of U87MG. Our in vitro and in vivo results suggest the potential usefulness of high-zinc pretreatment for improving the therapeutic index of BCNU chemotherapy for gliomas.     

Tissue microarray analysis for epithelial membrane protein-2 as a novel biomarker for gliomas

Epithelial membrane protein-2 (EMP2) expression is noted in many human cancers. We evaluated EMP2 as a biomarker in gliomas. A large tissue microarray of lower grade glioma (WHO grades II–III, n = 19 patients) and glioblastoma (GBM) (WHO grade IV, n = 50 patients) was stained for EMP2. EMP2 expression was dichotomized to low or high expression scores and correlated with clinical data. The mean EMP2 expression was 1.68 in lower grade gliomas versus 2.20 in GBMs (P = 0.01). The percentage of samples with high EMP2 expression was greater in GBMs than lower grade gliomas (90.0 vs. 52.6%, P = 0.001). No significant difference was found between median survival among patients with GBM tumors exhibiting high EMP2 expression and survival of those with low EMP2 expression (8.38 vs. 10.98 months, P = 0.39). However, EMP2 expression ≥2 correlated with decreased survival (r = ?0.39, P = 0.001). The EMP2 expression level also correlated with Ki-67 positivity (r = 0.34, P = 0.008). The mortality hazard ratio for GBM patients with EMP2 score of 3 or higher was 1.92 (CI 0.69–5.30). Our findings suggest that elevated EMP2 expression is associated with GBM. With other biomarkers, EMP2 may have use as a molecular target for the diagnosis and treatment of gliomas.     

External irradiation models for intracranial 9L glioma studies

Purpose

Radiotherapy has been shown to be an effective for the treatment human glioma and consists of 30 fractions of 2 Gy each for 6-7 weeks in the tumor volume with margins. However. in preclinical studies, many different radiation schedules are used. The main purpose of this work was to review the relevant literature and to propose an external whole-brain irradiation (WBI) protocol for a rat 9L glioma model.

Materials and methods

9L cells were implanted in the striatum of twenty 344-Fisher rats to induce a brain tumor. On day 8, animals were randomized in two groups: an untreated group and an irradiated group with three fractions of 6 Gy at day 8, 11 and 14. Survival and toxicity were assessed.

Results

Irradiated rats had significantly a longer survival (p = 0.01). No deaths occurred due to the treatment. Toxicities of reduced weight and alopecia were increased during the radiation period but no serious morbidity or mortality was observed. Moreover, abnormalities disappeared the week following the end of the therapeutic schedule.

Conclusions

Delivering 18 Gy in 3 fractions of 6 Gy every 3 days, with mild anaesthesia, is safe, easy to reproduce and allows for standardisation in preclinical studies of different treatment regimens glioma rat model.     

Daily Low-dose Carboplatin as a Radiation Sensitizer for Newly Diagnosed Malignant Glioma

Surgical resection followed by local field radiotherapy is currently our most effective approach to treatment for most patients with malignant glioma. Carboplatin chemotherapy has direct cytotoxic effects on glioma cells and acts as a radiation sensitizer to enhance cell killing. Its demonstrated efficacy as a sensitizer in other solid tumors led to this clinical trial of carboplatin as a radiation sensitizer in the treatment of newly diagnosed glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA). Fourteen patients (nine GBM and five AA) were treated with daily low-dose carboplatin 25mg/m² intravenously within 2h of their fractionated radiotherapy to a total dose of 600mg/m². No significant toxicities attributable to this combined therapy were observed. All patients have progressed, with median time to progression of 16 weeks. Eleven patients have died, with median survival of 38 weeks for the entire cohort. Although this regimen appeared safe, there was no benefit in survival time compared to historical patients treated with radiotherapy. The limitations and future potential for the strategy of radiation sensitization are discussed.     

Implantable biodegradable polymers for IUdR radiosensitization of experimental human malignant glioma

Purpose: The potential of halogenated pyrimidines for the radiosensitization of human malignant gliomas remains unrealized. To assess the role of local delivery for radiosensitization, we tested a synthetic, implantablebiodegradable polymer for the controlled release of 5-iodo-2-deoxyuridine (IUdR) both in vitro and in vivo and the resultant radiosensitizationof human malignant glioma xenografts in vivo.Materials and methods: In vitro: To measure release, increasing (10%, 30%, 50%) proportions (weight/weight) of IUdR in the polyanhydride [(poly(bis(p-carboxyphenoxy)-propane) (PCPP) :sebacic acid (SA) (PCPP : SA ratio 20 : 80)] polymer discs were incubated (1 ml phosphate-buffered saline, 37° C). The supernatant fractions were serially assayed using high performance liquid chromatography. To measure modulation of release,polymer discs were co-loaded with 20 Ci 5-125-iodo-2-deoxyuridine (125-IUdR) and increasing (10%, 30%, or 50%) proportions of D-glucose. To test radiosensitization, cells (U251 human malignant glioma) were sequentially exposed to increasing (0 or 10 M) concentrations of IUdR and increasing (0, 2.5, 5.0, or 10 Gy) doses of acute radiation. In vivo: To measure release, PCPP : SA polymerdiscs having 200 Ci 125-IUdR were surgically placed in U251 xenografts (0.1—0.2 cc) growing in the flanksof nude mice. The flanks were reproducibly positioned over a collimated scintillation detector and counted. To measure radiosensitization, PCPP : SApolymer discs having 0% (empty) or 50% IUdR wereplaced in the tumor or contralateral flank. After five days, the tumors were acutely irradiated (500 cGy × 2 daily fractions).Results: In vitro: Intact IUdR was released from the PCPP : SA polymer discs in proportion to the percentage loading. After 4 days the cumulative percentages of loaded IUdR that were released were 43.7 $plusmn; 0.1, 70.0 ± 0.2, and 90.2 ± 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings. With 0, 10, 30,or 50% D-glucose co-loading, the cumulative release of 125-IUdR from PCPP : SA polymers was 21, 70, 92, or 97%(p < 0.001), respectively, measured 26 days after incubation.IUdR radiosensitized U251 cells in vitro. Cell survival (log₁₀) was – 2.02 ± 0.02 and – 3.68± 0.11 (p < 0.001) after the 10 Gy treatment and no (control) or 10 M IUdR exposures, respectively. In vivo: 125-IUdR Release: The average counts (log₁₀ cpm ± SEM) (hours after implant) were 5.2 ± 0.05 (0.5), 4.3 ± 0.07 (17), 3.9 ± 0.08 (64), and 2.8 ± 0.06 (284). Radiosensitization: Afterintratumoral implantation of empty polymer or intratumoral 50%IUdR polymer, or implantation of 50% IUdR polymers contralateral to tumors, the average growth delays of tumors to4 times the initial volumes were 15.4 ± 1.8, 20.1 + 0.1,and 20.3 + 3.6 (mean + SEM) days, respectively (p = 0.488one-way ANOVA). After empty polymer and radiation treatments,no tumors regressed and the growth delay was 31.1 + 2.1 (p = 0.046 vs. empty polymer alone) days. After implantation of50% IUdR polymers either contralateral to the tumors orinside the tumors, followed by radiation, tumors regressed; growth delays to return to the initial average volumes of 14.0+ 3.6 or 24.2 + 0.2 (p < 0.01) days, respectively.Conclusions: Synthetic, implantable biodegradable polymers hold promise for the controlled release and local delivery ofIUdR for radiosensitization of gliomas.     

Accelerated Radiotherapy with Concomitant ACNU/Ara-C for the Treatment of Malignant Glioma

Purpose To evaluate activity and toxicity of simultaneous ACNU and Ara-C with concurrent accelerated hyperfractionated radiotherapy in the treatment of high-grade glioma. Patients and Methods Thirty patients aged 23–71 years (median 47.5), 16 patients with glioblastoma multiforme (GBM) and 14 patients with grade-III glioma, received 93 courses of ACNU/Ara-C (median 4 courses) at following dose levels (ACNU/Ara-C in mg/m²/day): 70/90 (11 courses), 75/100 (36 courses) and 90/120 (46 courses). ACNU was administered IV on day 1 of each cycle, Ara-C as a 2h-intravenous infusion on days 1–3. Patients received concomitant radiation therapy with 2 daily fractions of 1.75Gy up to 57Gy (median). Results Median survival of all patients was 13 months, 11 months for GBM and >28 months for grade-III glioma; 31% (9 patients) survived longer than 24 months. The percentage of grade IV hematological toxicity was dose-dependent: 33% at the 70/90 dose level, 40% at 75/100 and 58% at 90/120. Six patients required platelet transfusion, 1 patient red blood cells; no febrile neutropenia occurred. Among 18 patients evaluable for response, 3 (17%) showed PR, 8 (44%) NC and 7 (39%) PD at completion of chemoradiation. No acute or late neurological toxicity occurred in this study. Younger age (p = 0.0001) and grade-III histology (p = 0.0009) were important prognostic factors for prolonged survival. Conclusion This chemoradiation regimen is active in malignant gliomas and can be safely recommended at a dose level using 70mg/m² ACNU together with 90mg/m² Ara-C.     

A modelled comparison of prostate cancer control rates after high-dose-rate brachytherapy (3145 multicentre patients) combined with,or in contrast to,external-beam radiotherapy

Background and purpose

To analyse biochemical relapse-free-survival results for prostate cancer patients receiving combined external beam and high-dose-rate brachytherapy, in comparison with expected results using projections based on dose/fractionation/response parameter values deduced from a previous external-beam-alone 5969-patient multicentre dataset.

Material and methods

Results on a total of 3145 prostate cancer patients receiving brachytherapy (BT) as part or all of their treatment were collected from 10 institutions, and subjected to linear-quadratic (LQ) modelling of dose response and fractionation parameters.

Results

Treatments with BT components of less than 25 Gy, 3–4 BT fractions, doses per BT fraction up to 6 Gy, and treatment times of 3–7 weeks, all gave outcomes expected from LQ projections of the external-beam-alone data (α/β = 1.42 Gy). However, BT doses higher than 30 Gy, 1–2 fractions, 9 fractions (BT alone), doses per fraction of 9–15 Gy, and treatment in only 1 week (one example), gave local control levels lower than the expected levels by up to ∼35%.

Conclusions

There are various potential causes of the lower-than-projected control levels for some schedules of brachytherapy: it seems plausible that cold spots in the brachytherapy dose distribution may be contributory, and the applicability of the LQ model at high doses per fraction remains somewhat uncertain. The results of further trials may help elucidate the true benefit of hypofractionated high-dose-rate brachytherapy.     

A phase I trial of arsenic trioxide chemoradiotherapy for infiltrating astrocytomas of childhood

Background

Arsenic trioxide (ATO) has demonstrated preclinical evidence of activity in the treatment of infiltrating astrocytomas.

Methods

We conducted a phase I trial of ATO given concomitantly with radiation therapy in children with newly diagnosed anaplastic astrocytoma, glioblastoma, or diffuse intrinsic pontine glioma. Eligible patients received a fixed daily dose of 0.15 mg/kg of ATO once a week, with each subsequent cohort of patients receiving an additional dose per week up to a planned frequency of ATO administration 5 days per week as tolerated. Twenty-four children were enrolled and 21 children were evaluable.

Results

ATO was well tolerated throughout the entire dose escalation, resulting in confirmation of safety when administered 5 days per week during irradiation.

Conclusions

The recommended dose of ATO during conventional irradiation is 0.15 mg/kg given on a daily basis with each fraction of radiation therapy administered.     

Radiation sensitization of glioblastoma by cilengitide has unanticipated schedule‐dependency

We investigated whether cilengitide could amplify the antitumor effects of radiotherapy in an orthotopic rat glioma xenograft model. Cilengitide is a specific inhibitor of αv series integrins, and acts as an antiangiogenic. U251 human glioma cells express αvβ3 and αvβ5 integrins. We used in vitro assays of adhesion and growth of tumor and endothelial cells to evaluate cytotoxicity and the potential for cilengitide to enhance radiation toxicity. Treatment was then evaluated in an orthotopic model to evaluate synergy with therapeutic radiation in vivo. In vitro, cilengitide blocked cell adhesion, but did not influence the effects of radiation on U251 cells; cilengitide strongly amplified radiation effects on endothelial cell survival. In vivo, radiotherapy prolonged the survival of U251 tumor‐bearing rats from 50 to over 110 days. Cotreatment with cilengitide and radiation dramatically amplified the effects of radiation, producing survival over 200 days and triggering an enhanced apoptotic response and suppression of tumor growth by histology at necropsy. Signaling pathways activated in the tumor included NFκb, a documented mediator of cellular response to radiation. Because cilengitide has a short plasma half‐life (t_½ ～ 20 min), antiangiogenic scheduling typically uses daily injections. We found that a single dose of cilengitide (4 mg/kg) given between 4 and 12 hr prior to radiation was sufficient to produce the same effect. Our results demonstrate that blockade of αv integrins mediates an unanticipated rapid potentiation of radiation, and suggests possible clinical translation for glioma therapy. © 2008 Wiley‐Liss, Inc.