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PubMedDate not supplied

Sensitizing effect of the phosphatidylinositol 3-kinase inhibitor wortmannin on thermal neutron irradiation with or without boron compound.

Wortmannin, a phosphatidylinositol 3-kinase inhibitor, has been found to be an efficient radiosensitizer. We have investigated the radiosensitizing effect of wortmannin on cell killing against thermal neutrons produced by the Kyoto University Research (KUR) reactor. Wortmannin was added to cells 2 hours before irradiation and removed 16 hours after irradiation. Cells were irradiated by thermal neutrons with or without boron at 0, 10, and 20 ppm. The biological end point of cell survival was measured by colony formation assay. The D0 values of thermal neutrons in different boron concentrations, 0, 10, and 20 ppm were 1.2, 1.1, and 1.0 Gy, respectively. When cells were treated with wortmannin, the D0 values decreased to 0.5, 0.6, and 0.8 Gy at boron concentrations of 0, 10, and 20 ppm, respectively. Wortmannin enhanced cell death against thermal neutron irradiation especially in the absence of boron. Thus, our results suggest that wortmannin may be useful to combine with boron neutron capture therapy (BNCT) treatment when boron uptake by cells is limited.

Androstadienes↗
PubMed1997

Mutagenic effects at HPRT locus induced in Chinese hamster ovary cells by thermal neutrons with or without boron compound.

CHO cells were exposed to thermal neutrons and their mutation frequency was determined. The Kyoto University Research Reactor (KUR), which has a very low level of contamination by gamma-rays and fast neutrons was used as a thermal neutron source. Cells were irradiated in the presence or absence of boric acid to determine mutation frequency and cell survival. Thermal neutron irradiation was 2.5 times as mutagenic as gamma-irradiation without boron. In the presence of boron, however, thermal neutron irradiation was from 4.2 to 4.5 times as mutagenic as gamma-irradiation. When the mutation frequency was plotted against the survival fraction, a higher degree of mutagenicity was observed in the presence than in the absence of boron. These results suggest that the enhancement of thermal neutron-induced mutation with boron is strongly associated with alpha-particles released by 10B(n, alpha)7 Li reaction.

Animals↗
PubMed2006

Three-in-one: the novel packing and structures of three independent molecules of a tricyclic boron compound.

The three independent molecules in a single crystal of the tricyclic compound 15-[3-(dimethylamino)propoxy]-5,5,13,13-tetramethyl-1,7,9,14,16-pentaoxa-5,13-diazonia-15-bora-6,8-diboratadispiro[5.1.5.3]hexadecane, C15H36B3N3O6, are bound in dense layers by C-H...O(B) intermolecular interactions. The 3-(dimethylamino)propoxy arms adopt three different conformations with only van der Waals contact distances between the layers. The replicated differences in the B-N bond lengths [mean 1.723 (7) and 1.678 (5) A] for equivalent geometries are addressed using density functional theory (DFT) calculations.

Journal Article↗
PubMed1994

Pharmacokinetics in melanoma-bearing mice of 5-dihydroxyboryl-6-propyl-2-thiouracil (BPTU), a candidate compound for boron neutron capture therapy.

Blood pharmacokinetics and tissue distribution of 5-dihydroxyboryl-6-propyl-2-thiouracil (BPTU), a boron carrier with postulated melanin-seeking properties for boron neutron capture therapy, were determined in C57/BL mice with subcutaneous pigmented or non-pigmented B16 melanomas. Borocaptate sodium (BSH) was used as a boron compound without melanin-seeking properties in a comparative biodistribution study in the same animal tumour models. Administration of single doses showed that BPTU was retained better in the pigmented B16 tumour than in the non-pigmented variant. BPTU was found in large concentrations in kidney and liver. Brain boron was approximately 10-fold lower than tumour boron. On a molar basis, BPTU demonstrated higher affinity for B16 tumours than BSH. Owing to solubility limits, tumour boron concentrations in this mouse study were too low for effective application of BNCT. However, the high tumour-to-blood and tumour-to-normal tissues ratios indicate that, with appropriate formulation, BPTU could be a promising candidate for clinical BNCT.

Animals↗
PubMed2004

Biodistribution of GB-10 (Na(2)(10)B10H10 compound for boron neutron capture therapy (BNCT) in an experimental model of oral cancer in the hamster cheek pouch.

OBJECTIVE: We previously proposed the hamster cheek pouch model of oral cancer for BNCT studies. We herein present the biodistribution of a non-toxic boron compound, GB-10 (Na(2)(10)B10H10), in this model to assess its potential for BNCT or BNCT enhanced Fast Neutron Therapy. MATERIALS AND METHODS: We evaluated the uptake and retention of GB-10 in tumour and precancerous tissue and in potentially dose-limiting, clinically relevant normal tissues. RESULTS: Mean tumour boron concentration delivered by GB-10 (50mgB/kg) peaked to 77.7+/-28.0 ppm at 20min post-administration and remained at therapeutically useful values of 31.9+/-21.4 ppm at 3h. The clearance rate for normal tissues was faster than for tumour tissue. The consistently low brain and spinal cord values would preclude normal tissue toxicity. The uptake of GB-10 by precancerous tissue may be of potential use in the treatment of field cancerized areas. GB-10 was deposited homogeneously in different tumour areas, an asset when treating heterogenous tumours. The data suggests that the joint administration of BPA and GB-10 may improve the therapeutic efficacy of BNCT. CONCLUSIONS: GB-10 is a potential boron carrier for BNCT of head and neck tumours and for BNCT-FNT.

Animals↗
PubMed2003

Boron concentrations in brain during boron neutron capture therapy: in vivo measurements from the phase I trial EORTC 11961 using a gamma-ray telescope.

PURPOSE: Gamma-ray spectroscopic scans to measure boron concentrations in the irradiated volume were performed during treatment of 5 patients suffering from brain tumors with boron neutron capture therapy (BNCT). In BNCT, the dose that is meant to be targeted primarily to the tumor is the dose coming from the reaction 10B(n,alpha)7Li, which is determined by the boron concentration in tissue and the thermal neutron fluence rate. The boron distribution throughout the head of the patient during the treatment is therefore of major interest. The detection of the boron distribution during the irradiation was until now not possible. METHODS AND MATERIALS: Five patients suffering from glioblastoma multiforme and treated with BNCT in a dose escalation study were administered the boron compound, boron sulfhydryl (BSH; Na(2)B(12)H(11)SH). Boron concentrations were reconstructed from measurements performed with the gamma-ray telescope which detects locally the specific gamma rays produced by neutron capture in 10B and 1H. RESULTS: For all patients, at a 10B concentration in blood of 30 ppm, the boron concentration in nonoperated areas of the brain was very low, between 1 and 2.5 ppm. In the target volume, which included the area where the tumor had been removed and where remaining tumor cells have to be assumed, much higher boron concentrations were measured with large variations from one patient to another. Superficial tissue contained a higher concentration of 10B than the nonoperated areas of the brain, ranging between 8 and 15 ppm. CONCLUSIONS: The measured results correspond with previous tissue uptake studies, confirming that normal brain tissue hardly absorbs the boron compound BSH. Gamma-ray telescope measurements seem to be a promising method to provide information on the biodistribution of boron during therapy. Furthermore, it also opens the possibility of in vivo dosimetry.

Boron↗
PubMed1995

A stochastic model for subcellular dosimetry in boron neutron capture therapy.

The therapeutic effectiveness of boron neutron capture therapy is highly dependent on the microscopic distribution of the administered boron compound. Two boron compounds with different uptake mechanisms in the tumour cells may thus cause effects of different degrees even if the macroscopic boron concentrations in the tumour tissue are the same. This difference is normally expressed quantitatively by the so-called relative local efficiency (RLE). In this work, a stochastic model for the subcellular dosimetry has been developed. This model can be used to calculate the probability for an energy deposition above a certain threshold level in the cell nucleus due to a single neutron capture reaction. If a threshold cell-kill function is assumed, and if the dose is low enough that multiple energy depositions are rare, the model can also be applied to calculations of the survival probability for a cell population. Subcellular boron distributions in rats carrying RG 2 rat gliomas were measured by subcellular fractionation after administration of two different boron compounds: a sulphydryl boron hydride (BSH) and a boronated porphyrin (BOPP). Based on these data, the RLE factors were then calculated for these compounds using the stochastic model.

Animals↗
PubMed1993

Radiobiological considerations concerning the development of compounds for boron neutron capture therapy.

An analysis is carried out to evaluate the suitability of compounds for boron neutron capture therapy (BNCT). Suitable boron compounds are not necessarily those that show a high uptake ratio between tumor and healthy tissue. Compounds with lower uptake ratios, but higher concentrations in both healthy tissue and tumor, can be as effective in increasing the dose to the tumor over that of healthy tissue. In compound synthesis and evaluation, the parameters for optimization should therefore not be limited to the uptake ratio. A final assessment of the question whether and how well a given compound is suitable for BNCT can only be made after a study of its radiobiological effects on tissue. The analysis also illustrates the importance of beam quality in thermal and epithermal BNCT. An increase of adventitious radiation must be compensated by higher absolute tissue levels of a given boron compound and/or a higher uptake ratio, in order to arrive at the same dose differential between tumor and healthy tissue.

Boron Compounds↗
PubMed2002

Determination of boron-containing compounds in urine and blood plasma from boron neutron capture therapy patients. The importance of using coupled techniques.

The necessity of using coupled techniques to analyze samples from boron neutron capture therapy (BNCT) patients prior to element-specific detection has been demonstrated. BNCT patients were infused with p-boronophenylalanine (BPA)-fructose complex before the therapy started. Urine and blood plasma samples were collected at different times after the start of the BPA administration and were run on a porous graphitic carbon column coupled on-line to an inductively coupled plasma-atomic emission spectrometer (ICP-AES) and an ICP time-of-flight mass spectrometer (TOF-MS). In addition to BPA, a possible metabolite to BPA and some minor boron-containing compounds, eluting close to the front, were also found in the urine and plasma samples. Because only the total concentration of boron has been measured so far in earlier studies, the suspected metabolite could not be detected, and this is the first report indicating its presence in urine and plasma of BNCT patients. The abundance of 10B in urine was about the same for BPA and its possible metabolite (98-99%). The ratio between the possible metabolite and BPA was found to differ in the urine from different patients. Most of the patients had a metabolite concentration of approximately 10 mol % of the BPA content in their urine 5-11 h after the start of the BPA administration. This ratio increased to between 30 and 80% when 24 h had passed. The ratio of metabolite to BPA was found to be lower in the plasma than in the urine samples at comparable time after the start of BPA infusion. Preliminary results from micro-LC-electrospray ionization (ESI)-MS/MS measurements on four urine samples indicate that the metabolite has a higher mass than BPA.

Boron Compounds↗
PubMed2003

Boronic acid compounds as potential pharmaceutical agents.

Boronic acid compounds have been used, because of their unique structural features, for the development of potent enzyme inhibitors, boron neutron capture agents for cancer therapy, and as antibody mimics that recognize biologically important saccharides. Consequently, there has been a surge of interests in boronic acid compounds. This study reviews the recent development in this area during the last six years.

Acids↗
PubMed1997

In vitro effects of boron-containing compounds upon glioblastoma cells.

Boron-neutron capture therapy (BNCT) is currently under investigation as a novel therapeutic modality for glioblastoma. This study was undertaken to determine whether boron-containing compounds 4-borono-2-fluoro-D,L-phenylalanine (FBPA) and FBPA-fructose have direct effects upon kinetics of A172, a glioblastoma cell line. Flow cytometry analyzed cell-cycle distribution and S-phase kinetics (bromo deoxyuridine [BUdR] incorporation). BUdR incorporation was increased during a 1-hr pulse after 24-hr or 72-hr exposure of cells to varying concentrations of FBPA or FBPA-fructose. Results suggest that boron-containing compounds may effect cell kinetics apart from neutron activation, and this effect should be further evaluated for potential impact upon tumor responsiveness to BNCT.

Boron Compounds↗