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PubMed1987

Quantitative neutron capture radiography for studying the biodistribution of tumor-seeking boron-containing compounds.

Biodistribution of two compounds presently considered for use in neutron capture therapy has been studied in mice carrying a transplantable Harding-Passey melanoma. A method is described by which quantitative assessment can be made of the boron distribution in whole-body sections of such animals. An alpha-particle-sensitive film is placed in close contact with a freeze-dried section of an animal and exposed to neutrons. The tracks visible after etching are analyzed optoelectronically in fields of 0.6 X 0.6 mm2 and compared to standards of boron homogeneously distributed in liver homogenates. The dynamic range of this method is about two orders of magnitude in concentration, with a lower detection limit of 0.1 to 0.01 ppm 10B, depending on the rate of induction of spurious tracks by fast neutrons present in the neutron beam chosen. In a transplantable Harding-Passey melanoma in mice, it was found that the sulfhydryl boron hydride Na2B12H11SH presently used for therapy of glioblastoma clears blood, muscle, and brain very rapidly. Its accumulation in tumors was persistent for more than three days. A higher tumor accumulation was observed with its disulfide, which has been suggested for neutron capture therapy. For both compounds, a marked heterogeneity of boron distribution within one tumor was found.

Animals↗

PubMed2002

Selective uptake of p-borophenylalanine by undifferentiated thyroid carcinoma for boron neutron capture therapy.

Undifferentiated thyroid carcinoma (UTC) lacks an effective treatment. Boron neutron capture therapy (BNCT) is based on the selective uptake of 10B-boronated compounds by some tumors, followed by irradiation with an appropriate neutron beam. The radioactive boron originated (11B) decays releasing 7Li, gamma rays and alpha particles, and these latter will destroy the tumor. In order to explore the possibility of applying BNCT to UTC we have studied the biodistribution of BPA. In in vitro studies, the uptake of p-10borophenylalanine (BPA) by the UTC cell line ARO, primary cultures of normal bovine thyroid cells (BT), and human follicular adenoma (FA) thyroid was studied. No difference in BPA uptake was observed between proliferating and quiescent ARO cells. The uptake by quiescent ARO, BT, and FA showed that the ARO/BT and ARO/FA ratios were 4 and 5, respectively (p < 0.001). In in vivo studies, ARO cells were transplanted into the scapular region of NIH nude mice, and after 2 weeks BPA (350 or 600 mg/kg body weight) was injected intraperitoneally. The animals were sacrificed between 30 and 150 minutes after the injection. With 350 mg, tumor uptake was highest after 60 minutes and the tumor/normal thyroid and tumor/blood ratios were 3 and 5, respectively. When 600 mg/kg body weight BPA were administered, after 90 minutes the tumor/blood, tumor/normal thyroid, and tumor/distal skin ratios for 10B concentrations per gram of tissue were approximately 3, showing a selective uptake by the tumor. The present experimental results open the possibility of applying BNCT for the treatment of UTC.

Adenoma↗

PubMedDate not supplied

In vivo evaluation of phosphorous-containing derivatives of dodecahydro-closo-dodecaborate for boron neutron capture therapy of gliomas and sarcomas.

The in vivo uptake of dodecahydro-closo-dodecaborate derivatives substituted with phosphate- and bisphosphonate groups was evaluated in two different experimental tumor model systems and compared to other boronated and non-boronated compounds. These phosphorous-containing boron clusters may have potential for use in boron neutron capture therapy, a chemoradiotherapeutic form of cancer treatment. Using the F98 rat glioma as a brain tumor model in syngeneic Fischer rats, there was selective tumor uptake of the phosphate derivative with 21.5 micrograms boron/g tumor versus 5.2 micrograms/g normal brain and a tumor:blood ratio of 2.7. However, this compound was toxic to test animals and lethal at relatively low doses. The uptake of the bisphosphonate by the murine K8 osteosarcoma was approximately 18 micrograms boron/g tumor with a T:Bl ratio of 7.6 and a tumor:bone ratio of 1.5. This compound was non toxic to the test animals. The results indicate that phosphate- and bisphosphonate derivatives of dodecahydro-closo-dodecaborate may have potential for BNCT of gliomas and osteosarcomas, respectively.

Animals↗

PubMed1992

Present status of boron neutron capture therapy.

The neutron capture reaction 10B(1n,4He)7Li produces two energetic particles, 4He2+ and 7Li3+ that are strongly cell toxic. Due to the short range of these nuclear fragments (5-9 microns) mainly those cells that have bound or internalized a 10B-containing substance are growth-inactivated. The most critical and difficult step in an efficient boron neutron capture therapy (BNCT) is the tumour targeting. It is today possible to synthesize a large number of boron compounds and conjugate them to tumour-seeking macromolecules, such as monoclonal antibodies or different polypeptides. The boron-containing substances presently considered for therapy are sulfhydryl boron hydride (BSH) and boron-phenylalanine, (BPA) for the treatment of gliomas and malignant melanomas respectively. Other boronated compounds considered are ligands for receptor-amplified tumour cells, antibodies for tumour cells with specific antigens and thioureas for treatment of melanotic melanomas. The required boron concentration is given by the relative dose due to neutron capture in 10B and that of the competing capture reactions in nitrogen and hydrogen. Capture in nitrogen produces protons with a range of about 10-11 microns and this gives a radiation dose to all cells in the neutron activated area. Calculations show that the local concentration of 10B near the critical radiation target, DNA, must be higher than 10 ppm (10 micrograms/g). Increased emphasis will be put on the development of combinations of treatments that fulfil the requirements for attacking the microscopic spread of the tumour.

Boron↗

PubMed2002

Improved treatment planning for boron neutron capture therapy for glioblastoma multiforme using fluorine-18 labeled boronophenylalanine and positron emission tomography.

Boron neutron capture therapy (BNCT) is a cancer brachytherapy based upon the thermal neutron reaction: 10B(n,alpha)7Li. The efficacy of the treatment depends primarily upon two conditions being met: (a) the preferential concentration of a boronated compound in the neoplasm and (b) an adequate fluence of thermal neutrons delivered to the neoplasm. The boronated amino acid, para-boronophenylalanine (BPA), is the agent widely used in clinical trials to deliver 10B to the malignancy. Positron emission tomography (PET) can be used to generate in vivo boron distribution maps by labeling BPA with the positron emitting nuclide fluorine-18. The incorporation of the PET-derived boron distribution maps into current treatment planning protocols is shown to provide improved treatment plans. Using previously established protocols, six patients with glioblastoma had 18BPA PET scans. The PET distribution maps obtained were used in the conventional BNCT treatment codes. The isodose curves derived from the PET data are shown to differ both qualitatively and quantitatively from the conventional isodose curves that were derived from calculations based upon the assumption of uniform uptake of the pharmaceutical in tumor and normal brain regions. The clinical course of each of the patients who eventually received BNCT (five of the six patients) was compared using both sets of isodose calculations. The isodose contours based upon PET derived distribution data appear to be more consistent with the patients' clinical course.

Boron Compounds↗

PubMedDate not supplied

Receptor-targeted liposomal delivery of boron-containing cholesterol mimics for boron neutron capture therapy (BNCT).

Liposomes have been a main focus of tumor-selective boron delivery strategies in boron neutron capture therapy (BNCT), a binary method for the treatment of cancer that is based on the nuclear reaction between boron atoms and low-energy thermal neutrons. Three novel carboranyl cholesterol derivatives were prepared as lipid bilayer components for the construction of nontargeted and receptor-targeted boronated liposomes for BNCT. A major structural feature of these novel boronated cholesterol mimics is the replacement of the B and the C ring of cholesterol with a carborane cluster. Computational analyses indicated that all three boronated compounds have structural features and physicochemical properties that are very similar to those of cholesterol. One of the synthesized boronated cholesterol mimics was stably incorporated into non-, folate receptor (FR)-, and vascular endothelial growth factor receptor-2 (VEGFR-2)-targeted liposomes. No major differences were found in appearance, size distribution, and lamellarity between conventional dipalmitoylphosphatidylcholine (DPPC)/cholesterol liposomes, nontargeted, and FR-targeted liposomal formulations of this carboranyl cholesterol derivative. FR-targeted boronated liposomes were taken up extensively in FR overexpressing KB cells in vitro, and the uptake was effectively blocked in the presence of free folate. In contrast, a boronated cholesterol mimic incorporated into nontargeted liposomes showed significantly lower cellular uptake. There was no apparent in vitro cytotoxicity in FR overexpressing KB cells and VEGFR-2 overexpressing 293/KDR cells when these were incubated with boronated FR- and (VEGFR-2)-targeted liposomes, respectively, although the former accumulated extensively in KB cells and the latter effectively interacted with VEGFR-2 by causing autophosphorylation and protecting 293/KDR cells from SLT (Shiga-like toxin)-VEGF cytotoxicity.

Boron Compounds↗

PubMed2003

Biodistribution of a carborane-containing porphyrin as a targeting agent for Boron Neutron Capture Therapy of oral cancer in the hamster cheek pouch.

Boron Neutron Capture Therapy (BNCT) is a bimodal cancer treatment based on the selective accumulation of 10B in tumors and concurrent irradiation with thermalized neutrons. The short-range, high-LET radiation produced by the capture of neutrons by 10B could potentially control tumor while sparing normal tissue if the boron compound targets tumor selectively within the treatment volume. In previous studies, we proposed and validated the hamster cheek pouch model of oral cancer for BNCT studies, proved that absolute and relative uptake of the clinically employed boron compound boronophenylalanine (BPA) would be potentially therapeutic in this model and provided evidence of the efficacy of in vivo BPA-mediated BNCT to control hamster oral mucosa tumors with virtually no damage to normal tissue. We herein present the biodistribution and pharmacokinetics of a lipophilic, carborane-containing tetraphenylporphyrin (CuTCPH) in the hamster oral cancer model. CuTCPH is a novel, non-toxic compound that may be advantageous in terms of selective and absolute delivery of boron to tumor tissues. For potentially effective BNCT, tumor boron concentrations from a new agent should be greater than 30 ppm and tumor/blood and tumor/normal tissue boron concentration ratios should be greater than 5/1 without causing significant toxicity. We administered CuTCPH intraperitoneally (i.p.) as a single dose of 32 microg/g body weight (b.w.) (10 microg B/g b.w.) or as four doses of 32 microg/g b.w. over 2 days. Blood (Bl) and tissues were sampled at 3, 6, 12, 24, 48, and 72 h in the single-dose protocol and at 1-4 days after the last injection in the multidose protocol. The tissues sampled were tumor (T), precancerous tissue surrounding tumor, normal pouch (N), skin, tongue, cheek and palate mucosa, liver, spleen, parotid gland and brain. The maximum mean B ratios for the single-dose protocol were T/N: 9.2/1 (12h) and T/Bl: 18.1/1 (72 h). The B value peaked to 20.7+/-18.5 ppm in tumor at 24h. The multidose protocol maximum mean ratios were T/N: 11.9/1 (3 days) and T/Bl: 235/1 (4 days). Absolute boron concentration in tumor reached a maximum value of 116 ppm and a mean value of 71.5+/-48.3 ppm at 3 days. The fact that absolute and relative B values markedly exceeded the BNCT therapeutic threshold with no apparent toxicity may confer on this compound a therapeutic advantage. CuTCPH-mediated BNCT would be potentially useful for the treatment of oral cancer in an experimental model.

Animals↗

PubMed1999

Boron neutron capture therapy of brain tumors: an emerging therapeutic modality.

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10, a stable isotope, is irradiated with low-energy thermal neutrons to yield alpha particles and recoiling lithium-7 nuclei. For BNCT to be successful, a large number of 10B atoms must be localized on or preferably within neoplastic cells, and a sufficient number of thermal neutrons must be absorbed by the 10B atoms to sustain a lethal 10B (n, alpha) lithium-7 reaction. There is a growing interest in using BNCT in combination with surgery to treat patients with high-grade gliomas and possibly metastatic brain tumors. The present review covers the biological and radiobiological considerations on which BNCT is based, boron-containing low- and high-molecular weight delivery agents, neutron sources, clinical studies, and future areas of research. Two boron compounds currently are being used clinically, sodium borocaptate and boronophenylalanine, and a number of new delivery agents are under investigation, including boronated porphyrins, nucleosides, amino acids, polyamines, monoclonal and bispecific antibodies, liposomes, and epidermal growth factor. These are discussed, as is optimization of their delivery. Nuclear reactors currently are the only source of neutrons for BNCT, and the fission reaction within the core produces a mixture of lower energy thermal and epithermal neutrons, fast or high-energy neutrons, and gamma-rays. Although thermal neutron beams have been used clinically in Japan to treat patients with brain tumors and cutaneous melanomas, epithermal neutron beams now are being used in the United States and Europe because of their superior tissue-penetrating properties. Currently, there are clinical trials in progress in the United States, Europe, and Japan using a combination of debulking surgery and then BNCT to treat patients with glioblastomas. The American and European studies are Phase I trials using boronophenylalanine and sodium borocaptate, respectively, as capture agents, and the Japanese trial is a Phase II study. Boron compound and neutron dose escalation studies are planned, and these could lead to Phase II and possibly to randomized Phase III clinical trials that should provide data regarding therapeutic efficacy.

Boron Neutron Capture Therapy↗

PubMed2002

Quantitative subcellular secondary ion mass spectrometry (SIMS) imaging of boron-10 and boron-11 isotopes in the same cell delivered by two combined BNCT drugs: in vitro studies on human glioblastoma T98G cells.

Ion microscopy was used for subcellular quantitative imaging of the isotopes 10B and 11B in the same cell to evaluate boron delivery using a mixture of two neutron capture therapy drugs, p-boronophenylalanine-fructose (BPA-F) and sodium borocaptate (BSH). The application of 10B-labeled BPA-F and 11B-labeled BSH allowed independent imaging of both 10B and 11B in the same cell using a CAMECA IMS-3f ion microscope. Mixed-drug treatments were compared to single-drug exposures given under identical conditions. 10BPA-F delivered 10B heterogeneously to T98G human glioblastoma cells, with a significantly reduced concentration in an organelle-rich perinuclear region. The intracellular distribution of 11B from 11BSH contrasted with that of the 10B from 10BPA-F, with 11B distributed nearly homogeneously throughout cells. The subcellular distributions of 10B and 11B were sustained in mixed-drug treatments and resembled their localizations after the single-drug treatments. In both single- and mixed-drug treatments, cellular levels of 10B from 10BPA-F nearly doubled between 1 h and 6 h, with a 3:1 intracellular to nutrient medium partitioning, while cellular levels of 11BSH remained essentially unchanged. The net effect of the combined treatment with 10BPA-F and 11BSH was an additive delivery of boron to cells. This study introduces a novel approach for checking potential synergistic, antagonistic or simple additive delivery of two mixed boronated compounds in cellular/subcellular compartments.

Borohydrides↗

PubMed2006

Boron impregnation treatment of Eucalyptus grandis wood.

Eucalyptus grandis is suitable for small timber purposes, but its wood is reported to be non-durable and difficult to treat. Boron compounds being diffusible, and the vacuum-pressure impregnation (VPI) method being more suitable for industrial-scale treatment, the possibility of boron impregnation of partially dry to green timber was investigated using a 6% boric acid equivalent (BAE) solution of boric acid and borax in the ratio 1:1.5 under different treatment schedules. It was found that E. grandis wood, even in green condition, could be pressure treated to desired chemical dry salt retention (DSR) and penetration levels using 6% BAE solution. Up to a thickness of 50mm, in order to achieve a DSR of 5 kg/m(3) boron compounds, the desired DSR level as per the Indian Standard for perishable timbers for indoor use, it was found that neither the moisture content of wood nor the treatment schedule posed any problem as far as the treatability of E. grandis wood was concerned.

Boron↗

PubMed1998

Antitumor properties of boron complexes with hydroxy biguanide and salicyl hydroxamic acid against Ehrlich ascites carcinoma.

A new derivative of hydroxamic acid, hydroxy biguanido hydrochloride monohydrate and its boron derivative, dihydroxy-oxybiguanido boron (III) hydrochloride monohydrate were synthesized. Another boron compound, hydroxo-salicyl-hydroxamato boron (III) was synthesized from known salicyl hydroxamic acid. Antitumor properties of all the compounds evaluated against Ehrlich ascites carcinoma in mice show enhanced survival time when boron is incorporated in the compounds. Hematological parameters, alkaline phosphatase in serum of the treated animals show minimum toxic effects after boron is coupled with their respective hydroxamic acids.

Animals↗

PubMed2006

Late effects of radiation on the central nervous system: role of vascular endothelial damage and glial stem cell survival.

Selective irradiation of the vasculature of the rat spinal cord was used in this study, which was designed specifically to address the question as to whether it is the endothelial cell or the glial progenitor cell that is the target responsible for late white matter necrosis in the CNS. Selective irradiation of the vascular endothelium was achieved by the intraperitoneal (ip) administration of a boron compound known as BSH (Na(2)B(12)H(11)SH), followed by local irradiation with thermal neutrons. The blood-brain barrier is known to exclude BSH from the CNS parenchyma. Thirty minutes after the ip injection of BSH, the boron concentration in blood was 100 microg (10)B/ g, while that in the CNS parenchyma was below the detection limit of the boron analysis system, <1 microg (10)B/g. An ex vivo clonogenic assay of the O2A (oligodendrocyte-type 2 astrocyte) glial progenitor cell survival was performed 1 week after irradiation and at various times during the latent period before white matter necrosis in the spinal cord resulted in myelopathy. One week after 4.5 Gy of thermal neutron irradiation alone (approximately one-third of the dose required to produce a 50% incidence of radiation myelopathy), the average glial progenitor cell surviving fraction was 0.03. The surviving fraction of glial progenitor cells after a thermal neutron irradiation with BSH for a comparable effect was 0.46. The high level of glial progenitor cell survival after irradiation in the presence of BSH clearly reflects the lower dose delivered to the parenchyma due to the complete exclusion of BSH by the blood-brain barrier. The intermediate response of glial progenitor cells after irradiation with thermal neutrons in the presence of a boron compound known as BPA (p-dihydroxyboryl-phenylalanine), again for a dose that represents one-third the ED(50) for radiation-induced myelopathy, reflects the differential partition of boron-10 between blood and CNS parenchyma for this compound, which crosses the blood-brain barrier, at the time of irradiation. The large differences in glial progenitor survival seen 1 week after irradiation were also maintained during the 4-5-month latent period before the development of radiation myelopathy, due to selective white matter necrosis, after irradiation with doses that would produce a high incidence of radiation myelopathy. Glial progenitor survival was similar to control values at 100 days after irradiation with a dose of thermal neutrons in the presence of BSH, significantly greater than the ED(100), shortly before the normal time of onset of myelopathy. In contrast, glial progenitor survival was less than 1% of control levels after irradiation with 15 Gy of thermal neutrons alone. This dose of thermal neutrons represents the approximate ED(90-100) for myelopathy. The response to irradiation with an equivalent dose of X rays (ED(90): 23 Gy) was intermediate between these extremes as it was to thermal neutrons in the presence of BPA at a slightly lower dose equivalent to the approximate ED(60) for radiation myelopathy. The conclusions from these studies, performed at dose levels approximately iso-effective for radiation-induced myelopathy as a consequence of white matter necrosis, were that the large differences observed in glial progenitor survival were directly related to the dose distribution in the parenchyma. These observations clearly indicate the relative importance of the dose to the vascular endothelium as the primary event leading to white matter necrosis.

Animals↗

PubMed1996

Boron neutron capture therapy of brain tumors: past history, current status, and future potential.

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10 is irradiated with low-energy thermal neutrons to yield alpha particles and recoiling lithium-7 nuclei. High-grade astrocytomas, glioblastoma multiforme, and metastatic brain tumors constitute a major group of neoplasms for which there is no effective treatment. There is growing interest in using BNCT in combination with surgery to treat patients with primary, and possibly metastatic brain tumors. For BNCT to be successful, a large number of 10B atoms must be localized on or preferably within neoplastic cells, and a sufficient number of thermal neutrons must reach and be absorbed by the 10B atoms to sustain a lethal 10B(n, alpha)7 Li reaction. Two major questions will be addressed in this review. First, how can a large number of 10B atoms be delivered selectively to cancer cells? Second, how can a high fluence of neutrons be delivered to the tumor? Two boron compounds currently are being used clinically, sodium borocaptate (BSH) and boronophenylalanine (BPA), and a number of new delivery agents are under investigation, including boronated porphyrins, nucleosides, amino acids, polyamines, monoclonal and bispecific antibodies, liposomes, and epidermal growth factor. These will be discussed, and potential problems associated with their use as boron delivery agents will be considered. Nuclear reactors, currently, are the only source of neutrons for BNCT, and the fission process within the core produces a mixture of lower-energy thermal and epithermal neutrons, fast or high (> 10,000 eV) energy neutrons, and gamma rays. Although thermal neutron beams have been used clinically in Japan to treat patients with brain tumors and cutaneous melanomas, epithermal neutron beams should be more useful because of their superior tissue-penetrating properties. Beam sources and characteristics will be discussed in the context of current and future BNCT trials. Finally, the past and present clinical trials on BNCT for brain tumors will be reviewed and the future potential of BNCT will be assessed.

Boron Compounds↗

PubMed2001

Dynamic secondary ion mass spectrometry analysis of boron from boron neutron capture therapy drugs in co-cultures: single-cell imaging of two different cell types within the same ion microscopy field of imaging.

A co-culture, cryogenic SIMS methodology is presented for the quantitative analysis of cell type-dependent accumulation of boron delivered by BPA-F and BSH, two clinically approved drugs used in boron neutron capture therapy of cancer. T98G human glioblastoma cells were co-cultured with morphologically different normal LLC-PK1 epithelial cells or GM3348 human skin fibroblasts. Our freeze-fracture method of cryogenic sample preparation successfully fractured the different cell types grown together in co-cultures. Quantitative observations revealed an active uptake of boron from BPA-F in both T98G and LLC-PK1 cells but did not show cell type-dependent differences. Accumulation of BSH in all three cell types examined also did not reveal any cell type-dependent differences in co-cultures. As this method relies on the analysis, within the same field of SIMS imaging, of two different cell types that have been maintained under identical conditions of growth, drug exposure, sample preparation, and instrumental analysis, it provides the most effective approach for comparing cell type-specific differences in boron concentrations. The most effective applications of this method will be realized in testing the selectivity of experimental boronated compounds designed to specifically target tumor cells.

Animals↗

PubMed2004

T cell uptake for the use of boron neutron capture as an immunologic research tool.

An immunologic tool based on manipulation of the boron neutron capture reaction was previously proposed in the context of heart transplantation research to examine the temporal relationship between parenchymal rejection (representing immune cell infiltration) and transplantation-associated arteriosclerosis (characterized by progressive vascular occlusion). Critical to the development of this method is the uptake of boron by specific cells of the immune system, namely T cells, without adverse effects on cell function, which may be assessed by the ability of boron-loaded cells to produce IFNgamma, a protein with substantial impact on rejection. This work presents the evaluation of two carboranyl thymidine analogs. Advantages of this type of boron compound are reduced risk of leakage and effective dose delivery based on their incorporation into cellular nuclear material. Results indicate that uptake of these boronated nucleosides is high with no adverse effects on cell function, thereby warranting the continued development of this technique that has potentially wide applicability in immunological models.

Animals↗

PubMed1994

Boron neutron capture therapy (BNCT): a radiation oncology perspective.

Boron neutron capture therapy (BNCT) offers considerable promise in the search for the ideal cancer therapy, a therapy which selectively and maximally damages malignant cells while sparing normal tissue. This bimodal treatment modality selectively concentrates a boron compound in malignant cells, and then "activates" this compound with slow neutrons resulting in a highly lethal event within the cancer cell. This article will review this treatment modality from a radiation oncology, biology, and physics perspective. The remainder of the articles in this special issue of the Journal will provide a survey of the current "state-of-the-art" in this rapidly expanding field, including information with regard to boron compounds and their localization.

Boron Neutron Capture Therapy↗

PubMed2005

Evaluation of pharmacokinetics of 4-borono-2-(18)F-fluoro-L-phenylalanine for boron neutron capture therapy in a glioma-bearing rat model with hyperosmolar blood-brain barrier disruption.

UNLABELLED: This study evaluated the pharmacokinetics and biodistribution of 4-borono-2-(18)F-fluoro-l-phenylalanine ((18)F-FBPA) after intracarotid injection and with blood-brain barrier disruption (BBB-D) in F98 glioma-bearing F344 rats. The pharmacokinetics of l-p-boronophenylalanine (BPA) and (18)F-FBPA following different administration routes were compared to demonstrate the optimal delivery route and the time period for thermal neutron irradiation. METHODS: F98 glioma-bearing rats were injected intravenously or intracarotidly with (18)F-FBPA and BPA and with or without mannitol-induced hyperosmotic BBB-D. The boron concentration and (18)F radioactivity in tissues were determined by invasive (inductively coupled plasma mass spectroscopy, gamma-counting) and noninvasive PET methods. RESULTS: The biodistributions of (18)F-FBPA and BPA in F98 glioma-bearing rats were similar after intracarotid administration with BBB-D. The accumulation of BPA and (18)F-FBPA in brain tumor and the tumor-to-ipsilateral brain ratios were the highest after intracarotid injection with BBB-D, whereas the retention of boron drugs in contralateral brains exhibited only nonsignificant differences compared with those after intracarotid injection without BBB-D and intravenous injection. The high boron concentration in brain tumor (76.6 mug/g) and the high tumor-to-ipsilateral brain ratio (6.3) may afford enough radiation doses to destroy the tumor cells while sparing the normal tissues in boron neutron capture therapy. The pharmacokinetic parameters of k(el), k(12), k(21), and V(1) for intracarotid injection of (18)F-FBPA with BBB-D derived from the open 2-compartment model are 0.0206 +/- 0.0018 min(-1), 0.0260 +/- 0.0016 min(-1), 0.0039 +/- 0.0003 min(-1), and 3.1 +/- 0.1 mL, respectively. The effect of BBB-D varied depending on the anesthetic agents used and the anesthetic conditions. A smaller degree of BBB-D and, thus, lower boron concentrations in tumor and ipsilateral brain were observed under isoflurane anesthesia than under ketamine anesthesia. The k(12)/k(21) ratio may serve as a good indication for evaluating the extent of BBB-D, tumor uptake, and tumor-to-brain ratio after intracarotid injection of boron compounds. CONCLUSION: Our findings provide important information for establishing an optimal treatment protocol when intracarotid injection with BPA after BBB-D is applied in clinical boron neutron capture therapy.

Animals↗

PubMed2001

Carboranyl bisglycosides for the treatment of cancer by boron neutron capture therapy.

Boron neutron capture therapy is a special type of radiotherapy for the treatment of cancer by using boron compounds. Problems often arise from the low water solubility of these compounds, their unselective uptake into the cancer cells, and their toxicity. Here we describe the novel water-soluble ortho-carboranyl bisglycosides 7 and 10 containing either lactose or glucose and the mixed bisglycosides 1 and 28 containing glucose, mannose, and galactose. The carboranyl bisglycosides show almost no toxicity toward bronchial carcinoma cells of line A549 up to a concentration of 0.50 mM. As anticipated, these compounds exhibit nearly no uptake into C6 glioma cells; they can therefore be used for a selective delivery into malignant cells by using conjugates of glycohydrolases and monoclonal antibodies which bind to tumor-associated antigens, since by enzymatic hydrolysis the bisglycosides are transformed into lipophilic compounds.

Antineoplastic Agents↗