In Vitro and In Vivo Evaluation of Fluorescently Labeled Borocaptate-Containing Liposomes.

Boron neutron capture therapy (BNCT), a binary cancer therapeutic modality, has moved to a new phase since development of accelerator-based neutron sources and establishment of BNCT centers in Finland and Japan. That stimulated efforts for better boron delivery agent development. As liposomes have shown effective boron delivery properties and sufficient tumor retention, fluorescent liposome labelling may serve as a rapid method to study initial ability of newly synthesized liposomes to be captured by tumor cells prior to experiments on boron accumulation and neutron irradiation. In this work, we studied the accumulation and biodistribution of pegylated liposomes with encapsulated borocaptate (BSH) and a fluorescent label (Nile Red) in U87 (human glioblastoma), SW-620 (human colon carcinoma), SK-MEL-28 (human melanoma), FetMSC (mesenchymal human embryo stem cells), and EMBR (primary embryocytes) cell lines as well as an orthotopic xenograft model of U87 glioma in SCID mice. Results indicate that fluorescent microscopy is effective at determining the intracellular localization of the liposomes using a fluorescent label. The synthesized, pegylated liposomes showed higher accumulation in tumors compared to normal cells, with characteristic concentration peaks in SW-620 and U87 cell lines, and provided in vivo tumor selectivity with several-fold higher tumor tissue fluorescence at the 6-h timepoint. Graphical abstract Fluorescent images of U-87 glioma cells after 24 hours of incubation with BSH-containing liposomes labeled with lipophilic Nile Red (red color)and water-soluble FITC-Dextran (green color); cell nuclei in blue color (DAPI-staining) (×400). Scale bar is 50 µm. Fluorescent labelling serves as anexpress method to study liposome delivery efficiency prior to boron accumulation evaluation and BNCT irradiation experiments.

Accelerator-based boron neutron capture therapy for malignant glioma: a pilot neutron irradiation study using boron phenylalanine, sodium borocaptate and liposomal borocaptate with a heterotopic U87 glioblastoma model in SCID mice.

Purpose: To evaluate the efficacy of boron neutron capture therapy (BNCT) for a heterotopic U87 glioblastoma model in SCID mice using boron phenylalanine (BPA), sodium borocaptate (BSH) and liposomal BSH as boron compounds at a unique, accelerator-based neutron source.Materials and methods: Glioblastoma models were obtained by subcutaneous implantation of U87 cells in the right thighs of SCID mice before administration of 350 mg/kg of BPA (BPA-group), 100 mg/kg of BSH (BSH-group) or 100 mg/kg of BSH in PEGylated liposomes (liposomal BSH-group) into the retroorbital sinus. Liposomes were prepared by reverse-phase evaporation. Neutron irradiation was carried out at a proton accelerator with a lithium target developed for BNCT at the Budker Institute of Nuclear Physics, Novosibirsk, Russian Federation. A proton beam current integral of 3 mA/h and energy of 2.05 MeV were used for neutron generation.Results: Boron compound accumulation in tumor tissues at the beginning of irradiation was higher in the BPA group, followed by the Liposomal BSH and BSH groups. Tumor growth was significantly slower in all irradiated mice from the 7th day after BNCT compared to untreated controls (p < .05). Tumor growth in all treated groups showed no large variation, apart from the Irradiation only group and the BPA group on the 7th day after BNCT. The overall trend of tumor growth was clear and the differences between treatment groups became significant from the 50th day after BNCT. Tumor growth was significantly slower in the Liposomal BSH group compared to the Irradiation only group on the 50th (p = .012), 53rd (p = .005), and the 57th (p = .021) days after treatment. Tumor growth in the Liposomal BSH group was significantly different from that in the BPA group on the 53rd day after BNCT (p = .021) and in the BSH group on the 50th (p = .024), 53rd (p = .015), and 57th (p = .038) days after BNCT. Skin reactions in the form of erosions and ulcers in the tumor area developed in treated as well as untreated animals with further formation of fistulas and necrotic decay cavities in most irradiated mice.Conclusions: We observed a tendency of BNCT at the accelerator-based neutron source to reduce or suspend the growth of human glioblastoma in immunodeficient animals. Liposomal BSH showed better long-term results compared to BPA and non-liposomal BSH. Further modifications in liposomal boron delivery are being studied to improve treatment outcomes.

A realistic appraisal of boron neutron capture therapy as a cancer treatment modality.

Boron neutron capture therapy (BNCT) is a binary therapeutic modality based on the nuclear capture and fission reactions that occur when the stable isotope boron-10 is irradiated with neutrons to produce high-energy alpha particles and recoiling lithium-7 nuclei. In this Commentary we will focus on a number of papers that were presented at a Symposium entitled "Current Clinical Status of Boron Neutron Capture Therapy and Paths to the Future", which was held in September 2017 at the China National Convention Center in Beijing. Results were presented by clinicians from Japan, Finland, the United States, the China mainland and Taiwan, China who have been working in the multiple disciplines that are required for carrying out clinical BNCT. The main focus was on the treatment of patients with malignant brain tumors, recurrent tumors of the head and neck region, and cutaneous melanomas. The results obtained in treating these patients were reported in detail and, although most of the patients with brain tumors and head and neck cancer were not cured, there was evidence of some clinical efficacy. Although there are a number of problems that must be addressed, further clinical studies to evaluate the efficacy of BNCT are warranted. First, despite considerable effort by numerous investigators over the past 40 years, there still are only two boron-containing drugs in clinical use, L-boronophenylalanine (BPA) and sodium borocaptate (BSH). Therefore, until new and more effective boron delivery agents are developed, efforts should be directed to improving the dosing and delivery of BPA and BSH. Second, due to a variety of reasons, nuclear reactor-based BNCT has ended except for its use in the China mainland and Taiwan. Therefore, the future of BNCT depends upon the results of the ongoing Phase II clinical trials that are being carried out in Japan and the soon to be initiated trials that will be carried out in Finland. If the results obtained from these clinical trials are sufficiently promising, then BNCT will have a clear path to the future, especially for patients with the therapeutically challenging malignancies that in the past have been treated with reactor-based BNCT.

Correlation between radiation dose and histopathological findings in patients with gliblastoma treated with boron neutron capture therapy (BNCT).

The purpose of this study was to clarify the correlation between the radiation dose and histopathological findings in patients with glioblastoma multiforme (GBM) treated with boron neutron capture therapy (BNCT). Histopathological studies were performed on specimens from 8 patients, 3 had undergone salvage surgery and 5 were autopsied. For histopathological cure of GBM at the primary site, the optimal minimal dose to the gross tumor volume (GTV) and the clinical target volume (CTV) were 68Gy(w) and 44Gy(w), respectively.

The acceleration of boron neutron capture therapy using multi-linked mercaptoundecahydrododecaborate (BSH) fused cell-penetrating peptide.

New anti-cancer therapy with boron neutron capture therapy (BNCT) is based on the nuclear reaction of boron-10 with neutron irradiation. The median survival of BNCT patients with glioblastoma was almost twice as long as those receiving standard therapy in a Japanese BNCT clinical trial. In this clinical trial, two boron compounds, BPA (boronophenylalanine) and BSH (sodium borocaptate), were used for BNCT. BPA is taken up into cells through amino acid transporters that are expressed highly in almost all malignant cells, but BSH cannot pass through the cell membrane and remains outside the cell. We simulated the energy transfer against the nucleus at different locations of boron from outside the cell to the nuclear region with neutron irradiation and concluded that there was a marked difference between inside and outside the cell in boron localization. To overcome this disadvantage of BSH in BNCT, we used a cell-penetrating peptide system for transduction of BSH. CPP (cell-membrane penetrating peptide) is very common peptide domains that transduce many physiologically active substances into cells in vitro and in vivo. BSH-fused CPPs can penetrate the cell membrane and localize inside a cell. To increase the boron ratio in one BSH-peptide molecule, 8BSH fused to 11R with a dendritic lysine structure was synthesized and administrated to malignant glioma cells and a brain tumor mouse model. 8BSH-11R localized at the cell nucleus and showed a very high boron value in ICP results. With neutron irradiation, the 8BSH-11R administrated group showed a significant cancer killing effect compared to the 100 times higher concentration of BSH-administrated group. We concluded that BSH-fused CPPs were one of the most improved and potential boron compounds in the next-stage BNCT trial and 8BSH-11R may be applied in the clinical setting.

Case numbers for a randomized clinical trial of boron neutron capture therapy for Glioblastoma multiforme.

Boron neutron capture therapy (BNCT) with Na2B12H11SH (BSH) or p-dihydroxyborylphenylalanine (BPA), and with a combination of both, was compared to radiotherapy with temozolomide, and the number of patients required to show statistically significant differences between the treatments was calculated. Whereas arms using BPA require excessive number of patients in each arm, a two-armed clinical trial with BSH and radiotherapy plus temozolomide is feasible.

Biodistribution of (10)B for Boron Neutron Capture Therapy (BNCT) in a mouse model after injection of sodium mercaptoundecahydro-closo-dodecaborate and l-para-boronophenylalanine.

In boron neutron capture therapy, the absorbed dose from the (10)B(n,alpha)(7)Li reaction depends on the (10)B concentration and (10)B distribution in the irradiated volume. Thus compounds used in BNCT should have tumor-specific uptake and low accumulation in normal tissues. This study compares in a mouse model the (10)B uptake in different organs as delivered by l-para-boronophenylalanine (BPA, 700 mg/kg body weight, i.p.) and/or sodium mercaptoundecahydro-closo-dodecaborate (BSH, 200 mg/kg body weight, i.p). After BSH injection, the (10)B concentration was high in kidneys (20 +/- 12 microg/g) and liver (20 +/- 12 microg/g) but was low in brain (1.0 +/- 0.8 microg/g) and muscle (1.9 +/- 1.2 microg/g). After BPA injection, the (10)B concentration was high in kidneys (38 +/- 25 microg/g) and spleen (17 +/- 8 microg/g) but low in brain (5 +/- 3 microg/g). After combined BPA and BSH injection, the effect on the absolute (10)B concentration was additive in all organs. The ratio of the (10)B concentrations in tissues and blood differed significantly for the two compounds depending on the compound combination, which implies a different uptake profile for normal organs.

EORTC trial 11001: distribution of two 10B-compounds in patients with squamous cell carcinoma of head and neck, a translational research/phase 1 trial.

Boron neutron capture therapy (BNCT) provides highly targeted delivery of radiation through the limited spatial distribution of its effects. This translational research/phase I clinical trial investigates whether BNCT might be developed as a treatment option for squamous cell carcinoma of head and neck (SCCHN) relying upon preferential uptake of the two compounds, sodium mercaptoundecahydro-closo-dodecaborate (BSH) or L-para-boronophenylalanine (BPA) in the tumour. Before planned tumour resection, three patients received BSH and three patients received BPA. The (10)B-concentration in tissues and blood was measured with prompt gamma ray spectroscopy. Adverse effects from compounds did not occur. After BPA infusion the (10)B-concentration ratio of tumour/blood was 4.0 +/- 1.7. (10)B-concentration ratios of tumour/normal tissue were 1.3 +/- 0.5 for skin, 2.1 +/- 1.2 for muscle and 1.4 +/- 0.01 for mucosa. After BSH infusion the (10)B-concentration ratio of tumour/blood was 1.2 +/- 0.4. (10)B-concentration ratios of tumour/normal tissue were 3.6 +/- 0.6 for muscle, 2.5 +/- 1.0 for lymph nodes, 1.4 +/- 0.5 for skin and 1.0 +/- 0.3 for mucosa. BPA and BSH deliver (10)B to SCCHN to an extent that might allow effective BNCT treatment. Mucosa and skin are the most relevant organs at risk.

Boron neutron capture therapy at the crossroads: challenges and opportunities.

Over the past 25 years research on boron neutron capture therapy (BNCT) has progressed relatively slowly but steadily with the greatest progress in the field of clinical studies. These specifically have included the use of BNCT to treat a variety of malignancies other than high grade gliomas and melanomas. However, there are a number of key areas where little, if any, significant progress has been made. First and foremost among these has been the lack of new boron delivery agents. Improvement in drug delivery and the development of the best dosing paradigms for both boronophenylalanine (BPA) and sodium borocaptate (BSH) are of major importance and these still have not been optimized. Dosimetry for BNCT is still imprecise and is based on treating to normal tissue tolerance, based on blood boron values, rather than any real-time information on the boron content of the residual tumor that is to be irradiated. Another major problem has been the total dependence on nuclear reactors as neutron sources for BNCT. However, this will change in the near future when a clinically useful accelerator comes into use in 2009. Like it or not, in order to gain the credibility of a broad community of physicians who treat brain tumor patients, there will have to be a randomized clinical trial. Finally, BNCT will have to compete with new therapeutic approaches that are less costly and more effective for the treatment of brain tumors. These challenges notwithstanding, BNCT can fill an important niche for those malignancies, whether primary or recurrent, for which there is currently no effective therapy.

Towards improved boron neutron capture therapy agents: evaluation of in vitro cellular uptake of a glutamine-functionalized carborane.

Sodium borocaptate (BSH) is widely used for boron neutron capture therapy (BNCT) of brain tumors. One drawback is the large uptake by the liver causing a decrease of its availability at the tumor region as well as bringing about toxicity problems. A novel carborane-based compound containing a boron payload very similar to that of BSH has been synthesized and tested on rat glioma (C6) cells, hepatoma tissue culture (HTC) cells, and hepatocytes. The newly synthesized system consists of an o-carborane unit (C(2)B(10)H(11), o-CB) conjugated to a glutamine residue through a proper spacer, namely, o-CB-Gln. As compared with BSH, it showed the same uptake by C6 cells, but a 50% decrease in uptake by HTC cells and an 80% decrease in uptake by healthy hepatocytes. On this basis o-CB-Gln appears an interesting candidate for BNCT of brain tumors as it is expected to have a therapeutic index analogous to that of BSH accompanied by a much lower liver toxicity.

Boron neutron capture therapy (BNCT) inhibits tumor development from precancerous tissue: an experimental study that supports a potential new application of BNCT.

We previously demonstrated the efficacy of boron neutron capture therapy (BNCT) mediated by boronophenylalanine (BPA), GB-10 (Na(2)(10)B(10)H(10)) and (GB-10+BPA) to control tumors, with no normal tissue radiotoxicity, in the hamster cheek pouch oral cancer model. Herein we developed a novel experimental model of field-cancerization and precancerous lesions (globally termed herein precancerous tissue) in the hamster cheek pouch to explore the long-term potential inhibitory effect of the same BNCT protocols on the development of second primary tumors from precancerous tissue. Clinically, second primary tumor recurrences occur in field-cancerized tissue, causing therapeutic failure. We performed boron biodistribution studies followed by in vivo BNCT studies, with 8 months follow-up. All 3 BNCT protocols induced a statistically significant reduction in tumor development from precancerous tissue, reaching a maximum inhibition of 77-100%. The inhibitory effect of BPA-BNCT and (GB-10+BPA)-BNCT persisted at 51% at the end of follow-up (8 months), whereas for GB-10-BNCT it faded after 2 months. Likewise, beam-only elicited a significant but transient reduction in tumor development. No normal tissue radiotoxicity was observed. At 8 months post-treatment with BPA-BNCT or (GB-10+BPA)-BNCT, the precancerous pouches that did not develop tumors had regained the macroscopic and histological appearance of normal (non-cancerized) pouches. A potential new clinical application of BNCT would lie in its capacity to inhibit local regional recurrences.

Biodistribution of BPA and BSH after single, repeated and simultaneous administrations for neutron-capture therapy of cancer.

The effect of administration mode of L-BPA and BSH on the biodistribution in the melanoma-bearing hamsters was investigated. In single intravenous (i.v.) administration, BSH (100 mg BSH/kg) showed no significant retention of (10)B in all the tissues, including tumors, while long-term retention of (10)B in the tumor, muscle and brain was observed with L-BPA (500 mg BPA/kg). The dose escalation of L-BPA and the simultaneous single administration of L-BPA and BSH were not so effective at increasing boron accumulation in tumor after bolus i.v. injection. The boron concentration in tumor was 41 microg B/g after single bolus i.v. injection even at the dose of 1000 mg BPA/kg. In contrast, two sequential bolus i.v. injections of l-BPA with the dose of 500 mg BPA/kg each was found to be effective at increasing (10)B accumulation in the tumor; the maximum (10)B concentration in the tumor reached 52 microg B/g at 3 h after the second i.v. injection.

Disposition of TF-PEG-Liposome-BSH in tumor-bearing mice.

BNCT requires high concentration and selective delivery of (10)B to the tumor cell. To improve the drug delivery in BNCT, we conducted a study by devising TPLB. We administrated three types of boron delivery systems: BSH, PLB and TPLB, to Oral SCC bearing mice. Results confirmed that (10)B concentration is higher in the TPLB group than in the BSH group and that TPLB is significantly effective as boron delivery system.

Survival benefit from boron neutron capture therapy for the newly diagnosed glioblastoma patients.

OBJECTIVE: Since 2002-2007, we applied boron neutron capture therapy (BNCT) to >50 cases of malignant gliomas (MGs) with epithermal neutron irradiations. Recently, we showed the early radiographical improvement of malignant glioma patients by our modified BNCT, with simultaneous use of BPA (borono-phenylalanine) and BSH (sodium borocaptate). In this time, we focused on the survival benefit from BNCT for the newly diagnosed glioblastoma patients. METHODS: BNCT group including 21 newly histological confirmed glioblastoma patients treated with surgical removal followed by BNCT in Osaka Medical College during 2002-2006 period. Ten patients were treated with BNCT only, and in the other 11 patients, 20-30 Gy fractionated external beam X-ray irradiation therapy (XRT) was performed after BNCT. No chemotherapy was administered until tumor progression was observed. RESULTS: Treatments were well tolerated. Any kind of acute systemic or local severe toxicity were not demonstrated. Mean over all survival of the patients treated by BNCT was 20.7 and the median was 15.6 months with 2-years survival of 25%. Stratification by RPA criteria showed 6, 6, 8 and 1 patients, respectively, in classes III-VI. Three patients out of six in class III and one out of eight in class V are alive at the end point of this study. All the patients in classes IV and VI died. Median survival time for the BNCT group compared to the RTOG database was as follows: 20.6 months vs. 17.9 months for class III; 16.9 months vs. 11.1 months for class IV; 13.2 months vs. 8.9 months for class V. CONCLUSION: The RTOG RPA prognostic criteria were helpful in establishing which class of glioma patients could potentially benefit from BNCT. BNCT showed a survival benefit in all of the RPA classes of the RTOG database not only for the good prognosis group.

Suitability of boron carriers for BNCT: accumulation of boron in malignant and normal liver cells after treatment with BPA, BSH and BA.

Hepatocellular carcinoma remains widely prevalent in tropical Africa and south-east Asia. At present, there are no effective treatments for hepatoma and its prognosis is extremely poor unless the tumor was diagnosed in an early stage and resected before metastasis. Therefore, boron neutron capture therapy (BNCT) may provide an alternative therapy for treatment of hepatocellular carcinoma. In this study, the intracellular concentrations of L-boronophenylalanine (BPA), sodium borocaptate (BSH) and boric acid (BA) were examined in human hepatoma HepG2 and liver Clone 9 cell cultures. With the use of 25 microgB/mL media of BPA, BSH and BA, the intracellular uptake of boron in HepG2 and Clone 9 cells was compared. The suitability of BPA, BSH and BA were further evaluated on the basis of organ-specific boron distribution in normal rat tissues. BPA, BSH and BA were administered via intraperitoneal injection into rats with corresponding boron concentrations of 7, 25, and 25mg/kg body weight, respectively. The accumulation rates of BPA, BSH and BA in HepG2 cells were higher than that of Clone 9 cells. Boron concentration in BPA, BSH and BA treated HepG2 cells were 1.8, 1.5, and 1.6-fold of Clone 9 cells at 4h, respectively. In both HepG2 and Clone 9 cells, although the concentration of boron in BPA-treated cells exceeded that in BA-treated ones, however, cells treated with BPA had similar surviving fraction as those treated with BA after neutron irradiation. The accumulation ratios of boron in liver, pancreas and kidney to boron in blood were 0.83, 4.16 and 2.47, respectively, in BPA treated rats, and 0.75, 0.35 and 2.89, respectively, in BSH treated rats at 3h after treatment. However, boron does not appear to accumulate specifically in soft tissues in BA treated rats. For in situ BNCT of hepatoma, normal organs with high boron concentration and adjacent to liver may be damaged in neutron irradiation. BPA showed high retention in pancreas and may not be a good drug for BNCT of hepatoma. BSH had higher retention in liver but low level in pancreas and spleen appears to be a better candidate BNCT drug for hepatoma. These preliminary results provide useful information on future application of BNCT for hepatoma.

Dose distribution and clinical response of glioblastoma treated with boron neutron capture therapy.

The dose distribution and failure pattern after treatment with the external beam boron neutron capture therapy (BNCT) protocol were retrospectively analyzed. BSH (5 g/body) and BPA (250 mg/kg) based BNCT was performed in eight patients with newly diagnosed glioblastoma. The gross tumor volume (GTV) and clinical target volume (CTV)-1 were defined as the residual gadolinium-enhancing volume. CTV-2 and CTV-3 were defined as GTV plus a margin of 2 and 3 cm, respectively. As additional photon irradiation, a total X-ray dose of 30 Gy was given to the T2 high intensity area on MRI. Five of the eight patients were alive at analysis for a mean follow-up time of 20.3 months. The post-operative median survival time of the eight patients was 27.9 months (95% CI=21.0-34.8). The minimum tumor dose of GTV, CTV-2, and CTV-3 averaged 29.8+/-9.9, 15.1+/-5.4, and 12.4+/-2.9 Gy, respectively. The minimum tumor non-boron dose of GTV, CTV-2, and CTV-3 averaged 2.0+/-0.5, 1.3+/-0.3, and 1.1+/-0.2 Gy, respectively. The maximum normal brain dose, skin dose, and average brain dose were 11.4+/-1.5, 9.6+/-1.4, and 3.1+/-0.4 Gy, respectively. The mean minimum dose at the failure site in cases of in-field recurrence (IR) and out-field recurrence (OR) was 26.3+/-16.7 and 14.9 GyEq, respectively. The calculated doses at the failure site were at least equal to the tumor control doses which were previously reported. We speculate that the failure pattern was related to an inadequate distribution of boron-10. Further improvement of the microdistribution of boron compounds is expected, and may improve the tumor control by BNCT.

Early clinical trial concept for boron neutron capture therapy: a critical assessment of the EORTC trial 11001.

BNCT causes selective damage to tumor cells by neutron capture reactions releasing high LET-particles where (10)B-atoms are present. Neither the (10)B-compound nor thermal neutrons alone have any therapeutic effect. Therefore, the development of BNCT to a treatment modality needs strategies, which differ from the standard phase I-III clinical trials. An innovative trial design was developed including translational research and a phase I aspect. The trial investigates as surrogate endpoint BSH and BPA uptake in different tumor entities.

Delivery of sodium borocaptate to glioma cells using immunoliposome conjugated with anti-EGFR antibodies by ZZ-His.

Nanoparticles are effective of delivering cargo into cells. Here, sodium borocaptate (BSH) was encapsulated in liposomes composed of nickel lipid, and anti-epidermal growth factor receptor (EGFR) antibodies were conjugated to the liposomes using the antibody affinity motif of protein A (ZZ) as an adaptor (immunoliposomes). The immunoliposomes were used to deliver BSH into EGFR-overexpressing glioma cells. Immunohistochemical analysis using an anti-BSH monoclonal antibody revealed that BSH was delivered effectively into the cells but not into EGFR-deficient glioma or primary astrocytes. In an animal model of brain tumors, both the liposomes and the BSH were only observed in the tumor. Moreover, the efficiency of (10)B's delivery into glioma cells was confirmed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) both in vitro and in vivo. The results suggest that this system utilizing immunoliposomes provides an effective means of delivering (10)B into glioma cells in boron neutron capture therapy (BNCT).

Chemically modified beta-glucuronidase crosses blood-brain barrier and clears neuronal storage in murine mucopolysaccharidosis VII.

Enzyme replacement therapy has been used successfully in many lysosomal storage diseases. However, correction of brain storage has been limited by the inability of infused enzyme to cross the blood-brain barrier. The newborn mouse is an exception because recombinant enzyme is delivered to neonatal brain after mannose 6-phosphate receptor-mediated transcytosis. Access to this route is very limited after 2 weeks of age. Recently, several studies showed that multiple infusions of high doses of enzyme partially cleared storage in adult brain. These results raised the question of whether correction of brain storage by repeated high doses of enzyme depends on mannose 6-phosphate receptor-mediated uptake or whether enzyme gains access to brain storage by another route when brain capillaries are exposed to prolonged, high levels of circulating enzyme. To address this question, we used an enzyme whose carbohydrate-dependent receptor-mediated uptake was inactivated by chemical modification. Treatment of human beta-glucuronidase (GUS) with sodium metaperiodate followed by sodium borohydride reduction (PerT-GUS) eliminated uptake by mannose 6-phosphate and mannose receptors in cultured cells and dramatically slowed its plasma clearance from a t(1/2) of <10 min to 18 h. Surprisingly, PerT-GUS infused weekly for 12 weeks was more effective in clearing central nervous system storage than native GUS at the same dose. In fact, PerT-GUS resulted in almost complete reversal of storage in neocortical and hippocampal neurons. This enhanced correction of neuronal storage by long-circulating enzyme, which targets no known receptor, suggests a delivery system across the blood-brain barrier that might be exploited therapeutically.

Boron neutron capture therapy using mixed epithermal and thermal neutron beams in patients with malignant glioma-correlation between radiation dose and radiation injury and clinical outcome.

PURPOSE: To clarify the correlation between the radiation dose and clinical outcome of sodium borocaptate-based intraoperative boron neutron capture therapy in patients with malignant glioma. METHODS AND MATERIALS: The first protocol (P1998, n = 8) prescribed a maximal gross tumor volume (GTV) dose of 15 Gy. In 2001, a dose-escalated protocol was introduced (P2001, n = 11), which prescribed a maximal vascular volume dose of 15 Gy or, alternatively, a clinical target volume (CTV) dose of 18 Gy. RESULTS: The GTV and CTV doses in P2001 were 1.1-1.3 times greater than those in P1998. The maximal vascular volume dose of those with acute radiation injury was 15.8 Gy. The mean GTV and CTV dose in long-term survivors with glioblastoma was 26.4 and 16.5 Gy, respectively. A statistically significant correlation between the GTV dose and median survival time was found. In the 11 glioblastoma patients in P2001, the median survival time was 19.5 months and 1- and 2-year survival rate was 60.6% and 37.9%, respectively. CONCLUSION: Dose escalation contributed to the improvement in clinical outcome. To avoid radiation injury, the maximal vascular volume dose should be <12 Gy. For long-term survival in patients with glioblastoma after boron neutron capture therapy, the optimal mean dose of the GTV and CTV was 26 and 16 Gy, respectively.