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At least 415 records · Page 23Linked to original sources
PubMed1998

Positron emission tomography-based boron neutron capture therapy using boronophenylalanine for high-grade gliomas: part II.

Based on pharmacokinetic findings of fluorine-18-labeled L-fluoroboronophenylalanine by positron emission tomography (PET), methods for estimating tumor 10B concentration were devised. In clinical practice of boron neutron capture therapy (BNCT) for high-grade gliomas, a large amount of L-boronophenylalanine (L-10B-BPA)-fructose solution is used. Under these conditions, a slow i.v. infusion of L-10B-BPA-fructose solution should be performed for BNCT; therefore, the changes over time in 10B concentration in the target tissue were estimated by convoluting the actual time course of changes in plasma 10B concentration with a PET-based weight function including the proper rate constants [K1 (ml/g/min), k2 (min(-1)), k3 (min(-1)), and k4 (min(-1))]. With this method, the estimated values of 10B concentration in gliomas were very close to the 10B levels in surgical specimens. This demonstrated the similarity in pharmacokinetics between fluorine-18-labeled L-fluoroboronophenylalanine and L-10B-BPA. This method, using the appropriate rate constant, permits the determination of tumor 10B concentration and is widely suitable for clinical BNCT, because the averaged PET data are enough to use in future patients without individual PET study.

Boron↗
PubMed2000

The influence of lipophilicity on binding of boronated DNA-intercalating compounds in human glioma spheroids.

Five boronated DNA-intercalating compounds [5-ortho-carboranyl phenanthridinium (5-o-CP), 5-para-carboranyl phenanthridinium (5-p-CP), 6-para-carboranyl phenanthridinium, water-soluble boronated phenanthridinium and water-soluble boronated acridine (WSA1)], primarily developed for boron neutron capture therapy (BNCT), were analysed regarding their binding in cultured human malignant glioma spheroids. Comparisons were made with the corresponding DNA intercalators ethidium bromide and acridine orange. Octanol/phosphate buffered saline-water coefficients were determined for all compounds, and it was found that the most lipophilic (5-o-CP and 5-p-CP) were most toxic and accumulated high amounts of boron in monolayer cells. These compounds bound primarily in the outermost part of spheroids with poor penetration into the inner region, even after 2 days of continuous exposure. On the other hand, the most hydrophilic compound (WSA1) showed lower toxicity and lower boron accumulation in monolayer cells, and rapid binding in the inner region of spheroids. A reasonable explanation for this observation is that the lipophilic compounds interact mainly with lipophilic parts of the cells, like cellular membranes, and therefore rapidly binds to cells, preventing penetration and binding to cells in the deeper region of the spheroids. The possibility of using these compounds for BNCT are discussed.

Acridines↗
PubMed2005

Noninvasive quantitative in vivo mapping and metabolism of boronophenylalanine (BPA) by nuclear magnetic resonance (NMR) spectroscopy and imaging.

10B-enriched L-p-boronophenylalanine (BPA) is one of the compounds used in boron neutron capture therapy (BNCT). In this study, several variations of nuclear magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) were applied to investigate the uptake, clearance and metabolism of the BPA-fructose complex (BPA-F) in normal mouse kidneys, rat oligodendroglioma xenografts, and rat blood. Localized 1H MRS was capable of following the uptake and clearance of BPA-F in mouse kidneys with temporal resolution of a few minutes, while 1H MRSI was used to image the BPA distribution in the kidney with a spatial resolution of 9 mm3. The results also revealed significant dissociation of the BPA-F complex to free BPA. This finding was corroborated by 1H and 11B NMR spectroscopy of rat blood samples as well as of tumor samples excised from mice after i.v. injection of BPA-F. This investigation demonstrates the feasibility of using 1H MRS and MRSI to follow the distribution of BPA in vivo, using NMR techniques specifically designed to optimize BPA detection. The implementation of such procedures could significantly improve the clinical efficacy of BNCT.

Animals↗
PubMed1994

Cellular binding of carboranylalanine and some effects of boron neutron capture. Analysis of cultured melanoma B16 cells.

The boron containing substances L- and D-carboranylalanine might be of interest for boron neutron capture therapy, BNCT. Cultured mouse melanoma B16 cells were analyzed regarding binding of these substances and some introductory studies on effects of thermal neutron irradiation were also carried out. Comparisons were made with two boron containing compounds, p-boronophenylalanine (BPA) and boronated thiouracil (BTU-1), previously proposed for BNCT of melanomas. The results showed that both L- and D-carboranylalanine bound well in the B16 cells whereas BTU-1 gave no, and BPA only a low, binding. Thus, both forms of carboranes bound better than the two previously proposed substances. The carboranes also bound rather well in two tested human melanoma cell lines, IGR1 and RPMI-7951. Both L- and D-carboranylalanine showed a certain binding to isolated melanin but were not incorporated during melanin synthesis. Cultured glioma cells, used for comparison, bound BPA and to some extent the carboranes. This indicates that the substances are not melanoma specific. The carboranes caused some acute detachment of monolayer growing cells but were not strongly toxic since they did not reduce the growth rate. The cells treated with L-carboranylalanine or BPA showed, after neutron irradiation, a clear decrease in survival compared to the controls whereas no or only small effects were seen for cells treated with D-carboranylalanine or BTU-1. These results were conflicting since BPA gave therapeutical effects although only small amounts were bound while D-carboranylalanine gave no significant therapeutical effect in spite of better binding. One explanation might be different intracellular localizations. This has to be studied in more detail.

Animals↗
PubMed1994

The pharmacokinetics of p-Boronophenylalanine.fructose in human patients with glioma and metastatic melanoma.

PURPOSE: To study the biodistribution of p-Boronophenylalanine in patients undergoing surgery for intracranial tumors or metastatic melanoma. METHODS AND MATERIALS: D,L-p-Boronophenylalanine was administered as boronophenylalanine.fructose in an intravenous bolus 1-4 h before the operation. Blood samples were collected for 24 h from the time of administration of the compound, and the blood boron elimination parameters were determined. For the glioma patients tumor samples were obtained and skin, dura, periosteum, and surrounding brain samples were collected whenever possible. For the metastatic melanoma patients tumor, fat, skin, and muscle were collected. Determination of the boron content was performed using inductively coupled plasma-atomic emission spectrometry. Twelve melanoma patients and six glioma patients participated in the study. The melanoma patients included four cases of cutaneous metastatic melanoma, six cases of metastatic melanoma to the lymph nodes and two cases of cerebral metastasis. RESULTS: The results for the metastatic melanoma patients are encouraging with an average tumor:blood boron concentration ratio and standard deviation of about 4.4 +/- 3.2 and a maximum value of 10 for the cerebral metastasis. The glioma patients involved high grade glioma for which the tumor:blood ratio was 2.2 +/- 1.2. CONCLUSION: The tumor:blood ratios for melanoma fulfil requirements for epithermal boron neutron capture therapy for cerebral melanoma metastases, whereas those for high grade glioma do not.

Boron↗
PubMed2002

Synthesis of a novel potential tridentate anthracene ligand, 1,8-bis(dimethylamino)-9-bromoanthracene, and its application as chelate ligand for synthesis of the corresponding boron and palladium compounds.

A novel potential tridentate ligand, 1,8-bis(dimethylamino)-9-bromoanthracene, was synthesized. The key steps are as follows: 1) dimethylamination of 1,8-dibromo-9-methoxyanthracene by a modified Buchwald's method to afford 1,8-bis(dimethylamino)-9-methoxyanthracene, and 2) reduction of the methoxy group by LDBB (lithium di-tert-butylbiphenylide) followed by treatment with BrCF2CF2Br. The corresponding 1,8-bis(dimethylamino)-9-lithioanthracene, which should be a useful versatile tridentate ligand, could be generated by treatment of the bromide with one equivalent of nBuLi. The lithioanthracene reacted with B-chloroborane derivatives to give three 9-boryl derivatives. Although we recently reported that the crystal structure of 1,8-dimethoxy-9-B-catecholateborylanthracene was a symmetrical compound with the almost identical two O-B distances (2.379(2) and 2.441(2) A), the newly prepared 1,8-bis(dimethylamino)-9-borylanthracene derivatives clearly have unsymmetrical structures with coordination of only one NMe2 group toward the central boron atom. However, the energy difference between the unsymmetrical and symmeterical structures was found to be very small based on 1H NMR measurements, in which symmetrical anthracene patterns in the aromatic region (two kinds of doublets and a triplet) and a sharp singlet signal of the two NMe2 groups were observed even at -80 degrees C. 1,8-Bis(dimethylamino)-9-bromoanthracene itself can be a versatile ligand for transition metal compounds. In fact, direct palladation of the bromide took place by the reaction with [Pd2(dba)3].CHCl3 in THF to give the 9-palladated product. X-ray crystallographic analysis of the Pd compound showed that the square planar palladium atom was coordinated in a symmetrical fashion by both NMe2 groups (Pd-N bonds are 2.138(5) and 2.146(5) A).

Journal Article↗