RESUMEN
PURPOSE: Boron neutron capture therapy (BNCT) has been used clinically as a single modality treatment for high-grade gliomas and melanomas metastatic to the brain. The purpose of the present study was to determine whether its efficacy could be enhanced by an X-ray boost administered after BNCT. Two brain tumor models were used, the F98 glioma as a model for primary brain tumors and the MRA 27 human melanoma as a model for metastatic brain tumors. METHODS AND MATERIALS: For biodistribution studies, either 10(5) F98 glioma cells were implanted stereotactically into the brains of syngeneic Fischer rats or 10(6) MRA 27 melanoma cells were implanted intracerebrally into National Institutes of Health (NIH)-rnu nude rats. Biodistribution studies were performed 11-13 days after implantation of the F98 glioma and 20-24 days after implantation of the MRA 27 melanoma. Animals bearing the F98 glioma received a combination of two boron-containing drugs, sodium borocaptate at a dose of 30 mg/kg and boron phenylalanine (BPA) at a dose of 250 mg/kg. MRA 27 melanoma-bearing rats received BPA (500 mg/kg) containing an equivalent amount of 10B (27 mg B/kg). The drugs were administered by either intracarotid or i.v. injection. RESULTS: The tumor boron concentration after intracarotid injection was approximately 50% greater in the F98 glioma and MRA 27 melanoma after intracarotid injection (20.8 and 36.8 microg/g, respectively) compared with i.v. injection (11.2 and 19.5 microg/g, respectively). BNCT was carried out at the Brookhaven National Laboratory Medical Research Reactor approximately 14 days after tumor implantation of either the F98 glioma or the MRA 27 melanoma. Approximately 7-10 days after BNCT, subsets of animals were irradiated with 6-MV photons, produced by a linear accelerator at a total dose of 15 Gy, delivered in 5-Gy daily fractions. F98 glioma-bearing rats that received intracarotid or i.v. sodium borocaptate plus BPA, followed 2.5 h later by BNCT and 7-10 days later by X-rays, had similar mean survival times (61 days and 53 days, respectively, p = 0.25), and the non X-irradiated, BNCT-treated animals had a mean survival time of 52 and 40 days, respectively, for intracarotid vs. i.v. injection; the latter was equivalent to that of the irradiated animals. The corresponding survival time for MRA 27 melanoma-bearing rats that received intracarotid or i.v. BPA, followed by BNCT and then X-irradiation, was 75 and 82 days, respectively (p = 0.5), 54 days without X-irradiation (p = 0.0002), 37 days for X-irradiation alone, and 24 days for untreated controls. In contrast to the data obtained with the F98 glioma, MRA 27 melanoma-bearing rats that received i.v. BPA, followed by BNCT, had a highly significant difference in mean survival time compared with the irradiated controls (54 vs. 37 days, p = 0.008). CONCLUSION: Our data are the first to suggest that a significant therapeutic gain may be obtained when BNCT is combined with an X-ray boost. Additional experimental studies are required to determine the optimal combination of X-radiation and neutron doses and whether it is more advantageous to administer the photon boost before or after BNCT.
Asunto(s)
Compuestos de Boro/uso terapéutico , Terapia por Captura de Neutrón de Boro , Neoplasias Encefálicas/radioterapia , Glioma/radioterapia , Melanoma/radioterapia , Animales , Borohidruros/uso terapéutico , Neoplasias Encefálicas/secundario , Línea Celular Tumoral , Humanos , Melanoma/secundario , Dosificación Radioterapéutica , Ratas , Ratas Endogámicas F344 , Ratas Desnudas , Compuestos de Sulfhidrilo/uso terapéuticoRESUMEN
PURPOSE: This study was aimed at the in vitro evaluations of folate receptor (FR)-targeted liposomes as carriers for a lipophilic boron agent, K[nido-7-CH3(CH2)15-7,8-C2B9H11, in FR-overexpressing tumor cells for neutron capture therapy. METHODS: Large unilamellar vesicles (-200 nm in diameter) were prepared with the composition of egg PC/chol/K[nido-7-CH3(CH2)15-7,8-C2B9H11] (2:2:1, mol/mol), with an additional 0.5 mol % of folate-PEG-DSPE or PEG-DSPE added for the FR-targeted or nontargeted liposomal formulations, respectively. RESULTS: Boron-containing, FR-targeted liposomes readily bound to KB cells, an FR-overexpressing cell line, and were internalized via FR-mediated endocytosis. The boron uptake in cells treated with these liposomes was approximately 10 times greater compared with those treated with control liposomes. In contrast, FR-targeted and nontargeted liposomes showed no difference in boron delivery efficiency in F98 cells, which do not express the FR. The subcellular distribution of the boron compound in KB cells treated with the FR-targeted liposomes was investigated by cellular fractionation experiments, which showed that most of the boron compound was found in either the cytosol/endosomal or cell membrane fractions, indicating efficient internalization of the liposomal boron. CONCLUSION: FR-targeted liposomes incorporating the lipophilic boron agent, K[nido-7-CH3(CH2)15-7,8-C2B9H11], into its bilayer were capable of specific receptor binding and receptor-mediated endocytosis in cultured KB cells. Such liposomes warrant further investigations for use in neutron capture therapy.
Asunto(s)
Compuestos de Boro/administración & dosificación , Proteínas Portadoras/metabolismo , Sistemas de Liberación de Medicamentos/métodos , Terapia por Captura de Neutrón/métodos , Receptores de Superficie Celular , Compuestos de Boro/farmacocinética , Receptores de Folato Anclados a GPI , Humanos , Células KB , LiposomasRESUMEN
Success of boron neutron capture therapy (BNCT) is dependent on cellular and molecular targeting of sufficient amounts of boron-10 to sustain a lethal (10)B (n, alpha) (7)Li capture reaction. The purpose of the present study was to determine the efficacy of boronated epidermal growth factor (EGF) either alone or in combination with boronophenylalanine (BPA) as delivery agents for an epidermal growth factor receptor (EGFR) -positive glioma, designated F98(EGFR). A heavily boronated precision macromolecule [boronated starburst dendrimer (BSD)] was chemically linked to EGF by heterobifunctional reagents. Either F98 wild-type (F98(WT)) receptor (-) or EGFR gene-transfected F98(EGFR) cells, which expressed 5 x 10(5) receptor sites/cell, were stereotactically implanted into the brains of Fischer rats, and 2 weeks later biodistribution studies were initiated. For biodistribution studies rats received an intratumoral (i.t.) injection of (125)I-labeled BSD-EGF and were euthanized either 6 or 24 h later. At 6 h, equivalent amounts of BSD-EGF were detected in F98(EGFR) and F98(WT) tumors. Persistence of the bioconjugate in F98(EGFR) tumors was specifically determined by EGFR expression. By 24 h 33.2% of injected dose/g of EGF-BSD was retained by F98(EGFR) gliomas compared with 9.4% % of injected dose/g in F98(WT) gliomas, and the corresponding boron concentrations were 21.1 microg/g and 9.2 microg/g, respectively. Boron concentrations in normal brain, blood, liver, kidneys, and spleen all were at nondetectable levels (<0.5 microg/g). On the basis of these results, BNCT was initiated at the Brookhaven National Laboratory Medical Research Reactor. Two weeks after implantation of 10(3) F98(EGFR) or F98(WT) tumor cells, rats received an i.t. injection of BSD-EGF (approximately 60 microg (10)B/approximately 15 microg EGF) either alone or in combination with i.v. BPA (500 mg/kg). Rats were irradiated at the Brookhaven Medical Research Reactor 24 h after i.t. injection, which was timed to coincide with 2.5 h after i.v. injection of BPA for those animals that received both capture agents. Untreated control rats had a mean survival time (MST) +/- SE of 27 +/- 1 day, and irradiated controls had a MST of 31 +/- 1 day. Animals bearing F98(EGFR) gliomas, which had received i.t. BSD-EGF and BNCT, had a MST of 45 +/- 5 days compared with 33 +/- 2 days for animals bearing F98(WT) tumors (P = 0.0032), and rats that received i.t. BSD-EGF in combination with i.v. BPA had a MST of 57 +/- 8 days compared with 39 +/- 2 days for i.v. BPA alone (P = 0.016). Our data are the first to show in vivo efficacy of BNCT using a high molecular weight boronated bioconjugate to target amplified EGFR expressed on gliomas, and they provide a platform for the future development of combinations of high and low molecular weight agents for BNCT.
Asunto(s)
Compuestos de Boro/farmacocinética , Terapia por Captura de Neutrón de Boro/métodos , Neoplasias Encefálicas/radioterapia , Factor de Crecimiento Epidérmico/metabolismo , Receptores ErbB/metabolismo , Glioma/radioterapia , Animales , Compuestos de Boro/administración & dosificación , Compuestos de Boro/uso terapéutico , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patología , Factor de Crecimiento Epidérmico/administración & dosificación , Receptores ErbB/genética , Glioma/genética , Glioma/metabolismo , Glioma/patología , Humanos , Ratas , Ratas Endogámicas F344 , Distribución Tisular , TransfecciónRESUMEN
PURPOSE: Multicentric cerebral metastases of melanoma represent an important clinical problem for which there currently is no satisfactory treatment. We previously developed a model for melanoma metastatic to the brain employing nude rats bearing intracerebral implants of the human MRA27 melanoma. The purpose of the present study was to determine if the efficacy of boron neutron capture therapy (BNCT) could be improved by either Cereport (RMP-7) mediated modulation of blood-brain barrier (BBB) permeability or hyperosmotic mannitol-induced BBB disruption using boronophenylalanine (BPA) as the capture agent. METHODS AND MATERIALS: Biodistribution studies were carried out at 0.5, 2.5, and 4 h after intracarotid administration of Cereport (1.5 microg/kg) and intracarotid or i.v. administration of BPA (500 mg/kg). Peak tumor boron concentrations (65.4 microg/g) and the best composite tumor:brain (6.1:1) and tumor:blood (6.3:1) ratios were observed at 2.5 h after intracarotid administration. BNCT was initiated at the Brookhaven Medical Research Reactor 13-14 days after intracerebral implantation of 10(6) MRA27 cells. RESULTS: Untreated control rats had a median survival time (MeST) of 22 days and for irradiated controls, it was 30 days. Rats that received i.v. or intracarotid BPA without Cereport followed by BNCT 2.5 h later had MeSTs of 41 days and 57 days, respectively, with 20% long-term survivors (>180 days) in the latter group. Rats that received intracarotid BPA with Cereport had an MeST of 86 days with 36% long-term survivors, which was very close to that of rats that had hyperosmotic mannitol-induced disruption of the BBB (85 days with 25% long-term survivors). When these two groups were combined, and survival times were compared, using the Wilcoxon rank sum test, to those of rats that received intracarotid BPA without blood-brain barrier disruption, these differences were significant at the level p = 0.01. CONCLUSIONS: Our data show that optimizing the delivery of BPA by means of intracarotid injection combined with opening the BBB by infusing Cereport or a hyperosmotic solution of mannitol significantly enhanced survival times and produced long-term cures of MRA27 melanoma-bearing rats. These observations are relevant to future clinical studies using BNCT for the treatment of intracerebral melanoma.