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.

Boron neutron capture therapy of brain tumors: functional and neuropathologic effects of blood-brain barrier disruption and intracarotid injection of sodium borocaptate and boronophenylalanine.

Sodium borocaptate (BSH) and boronophenylalanine (BPA) are two drugs that have been used clinically for boron neutron capture therapy (BNCT) of brain tumors. We previously have reported that hyperosmotic mannitol-induced disruption of the blood-brain barrier (BBB-D), followed by intracarotid (i.c.) administration of BPA or BSH, either individually or in combination, significantly enhanced tumor boron delivery and the efficacy of BNCT in F98 glioma bearing rats. The purpose of the present study was to determine the short-term neuropathologic consequences of this treatment and the long-term effects on motor and cognitive function, as well as the neuropathologic sequelae 1 year following neutron capture irradiation. BBB-D was carried out in non-tumor bearing Fischer rats by infusing a 25% solution of mannitol i.c. followed by i.c. injection of BPA or BSH, either individually or in combination, immediately thereafter. Animals were euthanized 2 days after compound administration, and their brains were processed for neuropathologic examination, which revealed sporadic, mild, focal neuronal degeneration, hemorrhage, and necrosis. To assess the long-term effects of such treatment followed by neutron capture irradiation, non-tumor bearing rats were subjected to BBB-D after which they were injected i.c. with BPA (25 mg B/kg body weight (b.w)) or BSH (30 mg B/kg b.w.) either individually or in combination (BPA 12.5 mg and BSH 14 mg B/kg b.w.). Two and a half hours later they were irradiated at the Medical Research Reactor, Brookhaven National Laboratory, Upton, NY, with the same physical radiation doses (5.79, 8.10 or 10.06 Gy), delivered to the brain, as those that previously had been used for our therapy experiments. The animals tolerated this procedure well, after which they were returned to Columbus, Ohio where their clinical status was monitored weekly. After 1 year, motor function was assessed using a sensitive and reliable locomotor rating scale for open field testing in rats and cognitive function was evaluated by their performance in the Morris water maze, the results of which were similar to those obtained with age matched controls. After functional evaluation, the rats were euthanized, their brains were removed, and then processed for neuropathologic examination. Subtle histopathologic changes were seen in the choroid plexuses of irradiated animals that had received BPA, BSH or saline. Radiation related ocular changes consisting of keratitis, blepharitis, conjunctivitis and cataract formation were seen with similar frequency in most rats in each treatment group. Based on these observations, and the previously reported significant therapeutic gain associated with BBB-D and i.c. injection of BSH and BPA, the present observations establish its safety in rats and suggest that further studies in large animals and humans are warranted.

Improved survival after boron neutron capture therapy of brain tumors by Cereport-mediated blood-brain barrier modulation to enhance delivery of boronophenylalanine.

OBJECTIVE: Cereport (Alkermes, Inc., Cambridge, MA), or, as it has been previously called, RMP-7 (receptor-mediated permeabilizer-7), is a bradykinin analog that has been shown to produce a transient, pharmacologically mediated opening of the blood-brain barrier. The purpose of the present study was to determine whether the efficacy of boron neutron capture therapy (BNCT) could be enhanced by means of intracarotid (i.c.) infusion of Cereport, in combination with intravenous (i.v.) injection or i.c. infusion of boronophenylalanine (BPA) in the F98 rat glioma model. METHODS: For biodistribution studies, Fischer rats bearing intracerebral implants of the F98 glioma received i.v. or i.c. injections of 300 or 500 mg/kg body weight (b.w.) of BPA with or without i.c. infusion of 1.5 microg/kg b.w. of Cereport. For therapy studies, BNCT was initiated 14 days after intracerebral implantation of 10(3) F98 cells. The i.v. or i.c. injection of BPA (500 mg/kg b.w.) was given with or without Cereport, and the animals were irradiated 2.5 hours later at the Brookhaven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head. RESULTS: At a BPA dose of 500 mg/kg b.w., tumor boron concentrations (mean +/- standard deviation) were 55.7 +/- 9.6 microg/g with Cereport versus 33.6 +/- 3.9 microg/g without Cereport at 2.5 hours after i.c. infusion of BPA, and concentrations were 29.4 +/- 9.9 microg/g with Cereport versus 15.4 +/- 3.5 microg/g without Cereport (P < 0.05) after i.v. injection of BPA. After i.c. administration of BPA and Cereport, the tumor-to-blood ratio was 5.4 +/- 0.6, and the tumor-to-brain ratio was 5.2 +/- 2.4. After BNCT with BPA at a dose of 500 mg/kg, the survival time was 50 +/- 16 days for i.c. administration of BPA with Cereport versus 40 +/- 6 days without Cereport (P = 0.05), 38 +/- 4 days for i.v. administration of BPA with Cereport versus 34 +/- 3 days without Cereport (P = 0.02), 28 +/- 5 days for irradiated controls, and 23 +/- 3 days for untreated controls. Compared with untreated controls, there was a 117% increase in lifespan in rats that received an i.c. infusion of Cereport and then BPA, and an 86% increase in lifespan in rats that received i.c. administration of BPA without Cereport. CONCLUSION: These studies have established that i.c. administration of Cereport can not only increase tumor uptake of BPA, but also enhance the efficacy of BNCT.

Boron neutron capture therapy of brain tumors: enhanced survival and cure following blood-brain barrier disruption and intracarotid injection of sodium borocaptate and boronophenylalanine.

PURPOSE: Boronophenylalanine (BPA) and sodium borocaptate (Na(2)B(12)H(11)SH or BSH) have been used clinically for boron neutron capture therapy (BNCT) of high-grade gliomas. These drugs appear to concentrate in tumors by different mechanisms and may target different subpopulations of glioma cells. The purpose of the present study was to determine if the efficacy of BNCT could be further improved in F98-glioma-bearing rats by administering both boron compounds together and by improving their delivery by means of intracarotid (i.c.) injection with or without blood-brain barrier disruption (BBB-D). METHODS AND MATERIALS: For biodistribution studies, 10(5) F98 glioma cells were implanted stereotactically into the brains of syngeneic Fischer rats. Eleven to 13 days later animals were injected intravenously (i.v.) with BPA at doses of either 250 or 500 mg/kg body weight (b.w.) in combination with BSH at doses of either 30 or 60 mg/kg b.w. or i.c. with or without BBB-D, which was accomplished by i.c. infusion of a hyperosmotic (25%) solution of mannitol. For BNCT studies, 10(3) F98 glioma cells were implanted intracerebrally, and 14 days later animals were transported to the Brookhaven National Laboratory (BNL). They received BPA (250 mg/kg b.w.) in combination with BSH (30 mg/kg b.w. ) by i.v. or i.c. injection with or without BBB-D, and 2.5 hours later they were irradiated with a collimated beam of thermal neutrons at the BNL Medical Research Reactor. RESULTS: The mean tumor boron concentration +/- standard deviation (SD) at 2.5 hours after i. c. injection of BPA (250 mg/kg b.w.) and BSH (30 mg/kg b.w.) was 56. 3 +/- 37.8 microgram/g with BBB-D compared to 20.8 +/- 3.9 microgram/g without BBB-D and 11.2 +/- 1.8 microgram/g after i.v. injection. Doubling the dose of BPA and BSH produced a twofold increase in tumor boron concentrations, but also concomitant increases in normal brain and blood levels, which could have adverse effects. For this reason, the lower boron dose was selected for BNCT studies. The median survival time was 25 days for untreated control rats, 29 days for irradiated controls, 42 days for rats that received BPA and BSH i.v., 53 days following i.c. injection, and 72 days following i.c. injection + BBB-D with subsets of long-term survivors and/or cured animals in the latter two groups. No histopathologic evidence of residual tumor was seen in the brains of cured animals. CONCLUSIONS: The combination of BPA and BSH, administered i.c. with BBB-D, yielded a 25% cure rate for the heretofore incurable F98 rat glioma with minimal late radiation-induced brain damage. These results demonstrate that using a combination of boron agents and optimizing their delivery can dramatically improve the efficacy of BNCT in glioma-bearing rats.

Enhanced survival of glioma bearing rats following boron neutron capture therapy with blood-brain barrier disruption and intracarotid injection of boronophenylalanine.

Boronophenylalanine (BPA) has been used for boron neutron capture therapy (BNCT) of brain tumors in both experimental animals and humans. The purpose of the present study was to determine if the efficacy of BNCT could be enhanced by means of intracarotid (i.c.) injection of BPA with or without blood-brain barrier disruption (BBB-D) and neutron irradiation using a rat brain tumor model. For biodistribution studies, F98 glioma cells were implanted stereotactically into the brains of Fischer rats, and 12 days later BBB-D was carried out by i.c. infusion of 25% mannitol (1.373 mOsmol/ml), followed immediately by i.c. administration of 300, 500 or 800 mg of BPA/kg body weight (b.w.). At the 500 mg dose a fourfold increase in tumor boron concentration (94.5 micrograms/g) was seen at 2.5 hours after BBB-D. compared to 20.8 micrograms/g in i.v. injected animals. The best composite tumor to normal tissue ratios were observed at 2.5 hours after BBB-D, at which time the tumor: blood (T: Bl) ratio was 10.9, and the tumor: brain (T:Br) ratio was 7.5, compared to 3.2 and 5.0 respectively for i.v. injected rats. In contrast, animals that had received i.c. BPA without BBB-D had T : Bl and T:Br ratios of 8.5 and 5.9, respectively, and the tumor boron concentration was 42.7 micrograms/g. For therapy experiments, initiated 14 days after intracerebral implantation of F98 glioma cells, 500 mg/kg b.w. of BPA were administered i.v. or i.c. with or without BBB-D, and the animals were irradiated 2.5 hours later at the Brook-haven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head. The mean survival time for untreated control rats was 24 +/- 3 days, 30 +/- 2 days for irradiate controls, 37 +/- 3 days for those receiving i.v. BPA, 52 +/- 15 days for rats receiving i.c. BPA without BBB-D, and 95 +/- 95 days for BBB-D followed by i.c. BPA and BNCT. The latter group had a 246% increase in life span (ILS) compared to untreated controls and a 124% ILS compared to that of i.v. injected animals. These survival data are the best ever obtained with the F98 glioma model and suggest that i.c. administration of BPA with or without BBB-D may be useful as a means to increase the efficacy of BNCT.

Boron neutron capture therapy of brain tumors: enhanced survival following intracarotid injection of either sodium borocaptate or boronophenylalanine with or without blood-brain barrier disruption.

The purpose of the present study was to determine whether the efficacy of boron neutron capture therapy could be enhanced by means of intracarotid (i.c.) injection of sodium borocaptate (BSH) or boronophenylalanine (BPA) with or without blood-brain barrier disruption (BBB-D). For biodistribution studies, F98 glioma-bearing rats were injected i.v. or i.c. with either BSH (30 mg of boron/kg of body weight) or BPA (24 mg of boron/kg of body weight) with or without mannitol-induced, hyperosmotic BBB-D and killed 2.5 h later. The highest tumor boron concentrations for BSH and BPA were attained following i.c. injection with BBB-D (48.6 and 94.0 microg/g, respectively) compared to i.c. (30.8 and 42.7 microg/g) and i.v. injection (12.9 and 20.8 microg). Using the same doses of BSH and BPA, therapy experiments were initiated 14 days after intracerebral implantation of F98 glioma cells. Animals were irradiated 2.5 h after i.v. or i.c. administration of the capture agent with or without BBB-D using a collimated beam of thermal neutrons at the Brookhaven Medical Research Reactor. The median survival times of rats given BSH or BPA i.c. were 52 and 69 days, respectively, for rats with BBB-D; 39 and 48 days for rats without BBB-D; 33 and 37 days for i.v. injected rats; 29 days for irradiated controls; and 24 days for untreated controls. i.c. injection of either BSH or BPA resulted in highly significant enhancement (P = 0.01 and P = 0.0002, respectively) of survival times compared to i.v. injection, and this was further augmented by BBB-D (P = 0.02 and P = 0.04, respectively) compared to i.c. injection. Normal brain tissue tolerance studies were carried out with non-tumor-bearing rats, which were treated in the same way as tumor-bearing animals. One year after irradiation, the brains of these animals showed only minimal radiation-induced changes in the choroid plexus, but no differences were discernible between irradiated controls and those that had BBB-D followed by i.c. injection of either BSH or BPA. Our data clearly show that the route of administration, as well as BBB-D, can enhance the uptake of BSH and BPA, and, subsequently, the efficacy of boron neutron capture therapy.

Boron neutron capture therapy of brain tumors: enhanced survival following intracarotid injection of sodium borocaptate with or without blood-brain barrier disruption.

PURPOSE: Sodium borocaptate (Na2B12H11SH or BSH) has been used clinically for boron neutron capture therapy (BNCT) of patients with primary brain tumors. The purpose of the present study was to determine if tumor uptake of BSH and efficacy of BNCT could be enhanced in F98 glioma-bearing rats by intracarotid (i.c.) injection of the compound with or without blood-brain barrier disruption (BBB-D). METHODS AND MATERIALS: For biodistribution studies 100,000 F98 glioma cells were implanted stereotactically into the brains of Fischer rats, and 12 days later BBB-D was carried out by i.c. infusion of 25% mannitol, followed immediately thereafter by i.c. injection of BSH (30 mg B/kg body weight). Animals were killed 1, 2.5, and 5 h later, and their brains were removed for boron determination. For BNCT experiments, which were initiated 14 days after intracerebral implantation of 1000 F98 cells, BSH (30 mg B/kg b.wt. was administered intravenously (i.v.) without BBB-D, or i.c. with or without BBB-D. The animals were irradiated 2.5 h later with a collimated beam of thermal neutrons at the Brookhaven National Laboratory Medical Research Reactor. RESULTS: The mean tumor boron concentration after i.c. injection with BBB-D was 48.6 +/- 17.2 microg/g at 2.5 h compared with 30.8 +/- 12.2 microg/g after i.c. injection without BBB-D and 12.9 +/- 4.2 microg/g after i.v. injection. The best composite tumor to normal tissue ratios were observed at 2.5 h after BBB-D, at which time the tumor:blood (T:B1) ratio was 5.0, and the tumor: brain (T:Br) ratio was 12.3, compared to 1.1 and 4.6, respectively, in i.v. injected rats. The mean survival time for untreated control rats was 24 +/- 3 days, 29 +/- 4 days for irradiated controls, 33 +/- 6 days for those receiving i.v. injection of BSH, 40 +/- 8 days for rats receiving i.c. BSH without BBB-D, and 52 +/- 13 days for BBB-D followed by BNCT (p = 0.003 vs. i.v. injected BSH). CONCLUSIONS: Intracarotid administration of BSH with or without BBB-D significantly increased tumor uptake of BSH and enhanced survival of F98 glioma-bearing rats following BNCT. BBB-D may be a useful way to enhance the delivery of both low and high molecular weight boron compounds to brain tumors. Further studies are in progress to assess this approach with other boron delivery agents.

Evaluation of in vitro cytotoxicity of carboranyl amino acids, their chemical precursors and nido carboranyl amino acids for boron neutron capture therapy.

The purpose of the present study was to define the in vitro cellular toxicity of three carborane-containing amino acids: p-(o-carboran-yl)-phenylalanine (CBPA), O-(o-carboran-1-ylmethyl)-tyrosine (CBT), and o-carboranylalanine (CBA), which are analogues of phenylalanine, tyrosine, and alanine respectively. In addition, two of their chemical precursors: CBACN (B10H11C2-CH2CHNH2CN) and CBTCN (B10H11C2-CH2OC6H4CH2CHNH2CN) and nido CBA were evaluated for their toxicity on human MRA 27 melanoma cells. Hydroxypropyl-beta-cyclodextrin (beta-CD) initially was used to solubilize all the compounds except nido CBA in the toxicity assays Cells were incubated with the test compounds at varying concentrations for 24 hrs, following which the proliferative activity of surviving cells was determined by pulsing with tritiated thymidine ([3H]-TdR) for an additional 18 hrs. CBT at a concentration of 280 micrograms/ml was non-toxic when solubilized with beta-CD. CBA at a concentration of 350 micrograms/ml was non-toxic when solubilized with beta-CD, but when solubilized with DMSO produced a 50% reduction in uptake of [3H]-TdR at a concentration of 75 micrograms/ml. CBPA, solubilized with beta-CD, was nontoxic at a concentration of 400 micrograms/ml, while CBTCN and CBACN at concentrations of 50 micrograms/ml and 40 micrograms/ml, respectively, were both toxic, even when solubilized with beta-CD. Nido CBA at a concentration of 400 micrograms/ml in medium was non-toxic. Although the toxicity of these boron compounds precludes their use as capture agents for Neutron Capture Therapy, they may have some potential for cytoreductive chemotherapy of cancer, and further evaluation may be warranted.

In vitro and in vivo evaluation of o-carboranylalanine as a potential boron delivery agent for neutron capture therapy.

o-Carboranylalanine (B10H10C2CH2CHNH2COOH) is a carborane-containing amino acid, which has been synthesized as a potential capture agent for boron neutron capture therapy (BNCT) of cancer. The purpose of the present study was to develop a rational approach for the in vitro and in vivo evaluation of boron containing compounds that possibly might be used for BNCT. The in vitro uptake of carboranylalanine (CBA) was evaluated using two cell lines, the human melanoma MRA 27, and the murine Harding-Passey melanoma. Uptake of CBA by MRA 27 cells ranged from 135-551 micrograms B/10(9) cells following 3 hrs incubation with medium containing 100-113 micrograms B/ml and was not reduced by exposing the tumor cells to either rotenone, an inhibitor of electron transport, or by culturing them at ambient temperature (approximately 22 degrees C). Cellular uptake and elution of CBA occurred rapidly under in vitro conditions. Uptake of CBA was slightly greater than that of boronophenylalanine (BPA). Following a 3 hr incubation with CBA at a concentration of 106 micrograms B/ml, cell boron content was 255 micrograms B/10(9) MRA 27 cells, compared to 192 micrograms B/10(9) cells when cells were incubated with BPA at a concentration of 95 micrograms B/ml. In vivo studies initially were carried out using the Harding-Passey melanoma, which had been implanted intramuscularly (i.m.) into the right flank of BALB/c mice. Tumors were allowed to grow for 14 days at which time mice were injected intraperitoneally (i.p.) with either CBA or BPA (1.25 mgB/mouse), and were killed 3, 6 and 8 hrs later. CBA attained a low tumor to blood ratio(1.0-1.4), and the tumor boron levels ranged from 15.7-26.2 micrograms B/g at 3 hrs and 3.3-19.9 micrograms B/g at 6 hrs. Higher blood and lower tumor boron levels were observed at all time points with CBA compared to BPA, suggesting that CBA was not taken up selectively by the melanoma. Similar studies, carried out in rats bearing intra-cerebral gliomas, failed to reveal detectable amounts of boron in the tumor. From the present study, it can be concluded that CBA does not appear to possess the requisite properties to be useful as a boron delivery agent for BNCT.

Lack of effect of recombinant human interferon-alpha 2b on expression of 17-1A antigen on human colon cancer cells.

The effects of recombinant human interferon alpha (rHuIFN-alpha 2b) on cell growth, expression of antigenic receptor sites (r) and the affinity constant (Ka) of monoclonal antibody CO 17-1A IgG were studied on two human colorectal cancer cell lines, CX-1 and SW 1116. Cells were incubated with varying concentrations of rHuIFN-alpha 2b prior to exposure to 125I-labeled 17-1A IgG at 37 degrees C following which r and Ka were determined by means of Scatchard plots. Varying concentrations of rHuIFN-alpha 2b had significant growth inhibitory effects on CX-1 and SW 1116 cells, which were time and concentration dependent, but no effects on expression of r and Ka compared to controls. Our data indicate that rHuIFN-alpha 2b does not invariably increase the expression of tumor-associated antigens and that this effect may be independent of its antiproliferative activity. The in vitro response or lack thereof of neoplastic cells to rHuIFN-alpha 2b may be useful to identify those patients who potentially might gain from a clinical course of rHuIFN-alpha 2b for either therapeutic or diagnostic purposes.

Alterations in monoclonal antibody affinity and antigenic receptor site expression on mycoplasma-infected human colorectal cancer cells.

The affinity of MoAb CO 17-1A and expression of its antigenic target were studied on uninfected and mycoplasma-infected colorectal cancer cell lines SW 1116 and SW 948. Binding of 125I-labeled CO 17-1A to SW 1116 cells was quantified at 37 degrees C by determination of the affinity constant (Ka) and the number of antigenic receptor sites (r) per cell using Scatchard plots. When mycoplasma-free SW 1116 cells were used as targets, Ka was 0.92 +/- 0.06 x 10(8) M-1 and r = 1.32 +/- 0.14 x 10(6) at 37 degrees C. One batch of unspeciated, mycoplasma-infected SW 116 cells had reduced affinity and a decreased number of antigenic receptor sites per cell for 125I-labeled 17-1A, while another batch of infected SW 1116 cells had a 4- to 5-fold increase in r and diminished Ka for the antibody compared with uninfected cells. When unspeciated, mycoplasma-infected SW 948 cells were exposed to 125I-labeled 17-1A and the data subjected to Scatchard analysis, the affinity of the antibody deviated markedly from linearity and rendered analysis for Ka and r meaningless. These data indicate that mycoplasma infection can produce variable effects on the cellular expression of antigenic receptor sites and the affinity of antibody for its target, and emphasize the importance of using mycoplasma-free cell lines in studies of these parameters.