Makoto Shirakawa

Synthesis and evaluation of a novel liposome containing BPA-peptide conjugate for BNCT.

We aimed at securing sufficient concentrations of (10)B in boron neutron capture therapy (BNCT) by developing a new drug delivery system. We have designed and developed a novel lipid analog and succeeded in using it to develop the new boron component liposome. It consisted of three different kinds of amino acid derivatives and two fatty acids, and could react directly with the peptide synthesized first on resin by Fmoc solid-phase synthesis. In this study, lipid analog conjugated with HIV-TAT peptide (domain of human immunodeficiency virus TAT protein) and boronophenylalanine (BPA) was synthesized and successfully incorporated into liposomes.

The optimization of fluorescence imaging of brain tumor tissue differentiated from brain edema—-In vivo kinetic study of 5-aminolevulinic acid and talaporfin sodium

OBJECTIVE We aimed to clarify the optimal timing for the fluorescence imaging of brain tumor tissue differentiated from brain edema after the administration of photosensitizers. METHODS We have performed an in vivo study of the kinetics of 5-aminolevulinic acid (5-ALA) in comparison with talaporfin sodium using the rat brain tumor model and rat vasogenic edema model produced by cold injury. The in vivo kinetics of 5-ALA and talaporfin sodium in brain tumor model and the vasogenic edema model was determined by a fluorescence macroscope and a microplate reader. RESULTS The in vivo kinetic study of 5-ALA showed mild fluorescence intensity of protoporphyrin IX (PpIX) in brain tumor differentiated from vasogenic edema. The mean lesion-to-normal-brain ratio (L/N ratio) in the group of brain tumor model 2h after the administration of 5-ALA was 7.78+/-4.61, which was significantly higher (P<0.01) than that of the vasogenic edema 2h after the administration of 5-ALA (2.75+/-1.12). In vivo kinetic study of talaporfin sodium showed high fluorescence intensity and retention in brain tumor differentiated from vasogenic edema. The mean L/N ratio of the fluorescence intensity in the group of brain tumor model 12h after the administration of talaporfin sodium was 23.1+/-11.9, which was significantly higher (P<0.01) than that of the vasogenic edema 12h after the administration (8.93+/-8.03). CONCLUSIONS The optimization of fluorescence imaging of brain tumors differentiated from brain edema is possible in the case of 5-ALA within 6h, and also possible in the case of talaporfin sodium beyond 12h.

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.

Current practices and future directions of therapeutic strategy in glioblastoma: Survival benefit and indication of BNCT

Since 1998, we are performing clinical studies on treatment of GBM using conventional fractionated photon radiation therapy (CRT), proton beam therapy (PBT) or boron neutron capture therapy (BNCT). We investigated whether these radiation modalities improves the survival of patients with GBM. Sixty-eight cases of newly diagnosed GBM have been treated in our institution. After surgery, radiation therapy was performed using CRT with a dose of 60.0-61.2 Gy (n=36), hyperfractionated PBT concomitant with fractionated photon irradiation with a total dose of 96.6 Gy (n=17), or a single fraction of BNCT (n=15). In PBT, the surrounding volume of 2 cm from main tumor mass and the volume of perifocal edema were irradiated at dose of 75.6 and 60 Gy, respectively. The median OS time of the case series of BNCT for GBM has been reported as 13-20.7 M. In this study, the median OS and median time to MR change (TTM) for all patients were 25.7 and 11.9 M, respectively. The 1- and 2-year survival rates were 85.7% and 45.5%, respectively. On the other hand, in the patients who underwent CRT and ACNU-based chemotherapy, OS and 2-year survival rate were 14.2M and 17.9%, respectively. In the patients who underwent high-dose PBT, OS and 2-year survival rate were 21.3M and 38.5%, respectively. The present small case series of selected patients showed survival benefit after BNCT. The comparison using previously reported prognostic factor-based classifications suggest that outcome of BNCT in terms of survival appeared to have non-inferiority compared to the standard therapy. With respect to the case series as a high-dose radiation trial, the outcome (OS: 9.5-25 M) of previously reported may still be comparable to that of BNCT. Randomized trials of comparably selected patients are required to demonstrate conclusively that prolonged survival is a result of this tumor-selective radiotherapy.

Boron neutron capture therapy for newly diagnosed glioblastoma: A pilot study in Tsukuba

Neutron capture therapy (NCT) theoretically allows an unique tumor-cell-selective high-LET particle radiotherapy. The survival benefits and safety of NCT were evaluated in 15 patients with newly diagnosed glioblastoma multiforme (GBM). Seven patients received intra-operative (IO-) NCT and eight patients received external beam (EB-) NCT. Sulfhydryl borane (BSH, 5 g/body) was administered intravenously 12 h before neutron irradiation. Additionally, p-dihydroxyboryl-phenylalanine (BPA, 250 mg/kg) was given 1 h before irradiation to the eight patients who underwent EB-NCT. EB-NCT was combined with fractionated photon irradiation. Five of 15 patients were alive at analysis for a mean follow-up time of 20.3 M. In 11 of 15 patients followed up for more than 1-year, eight (72.7%) maintained their Karnofsky performance status (KPS; 90 in 6 and 100 in 2). The median overall survival (OS) and time to magnetic resonance (MR) change (TTM) for all patients were 25.7 and 11.9 M, respectively. There was no difference in TTM between the IO-NCT (12.0 M) and EB-NCT (11.9 M) groups. The 1- and 2-year survival rates were 85.7% and 45.5%, respectively. This NCT pilot study in 15 patients with newly diagnosed GBM showed survival benefits, suggesting that the neutron capture reaction may function sufficiently to control tumors locally, and that further optimized studies in large series of patients are warranted.

Intra-tumor distribution of metallofullerene using micro-particle induced X-ray emission (PIXE).

To clarify the intra tumor distribution of gadlinium containing fullerene (Gd@C82), micro particle induced X-ray emission (Micro-PIXE) analysis were performed. The tumor bearing BALB/c mice were injected Gd@C82 and subcutaneous tumors were taken from 48h after the intravenous injection. Using the Micro-PIXE method, we could visualize Gd intra tumor distribution. Therefore our results indicate the possibility that Micro-PIXE is useful technique for imaging the bioditribution of Gd, and Gd@C82 is potentially useful Gd carrier for NCT.

T2 corrected quantification method of l-p-boronophenylalanine using proton magnetic resonance spectroscopy for boron neutron capture therapy

In the present study, we aimed to evaluate a T2 corrected quantification method of l-p-boronophenylalanine (BPA) concentration using proton magnetic resonance spectroscopy (MRS). We used five phantoms containing BPA (1.5, 3.0, 5.0, 7.5, and 10 mmol/kg=15, 30, 50, 75, and 100 microg(10)B/g), N-acetyl-aspartic acid (NAA: 3.0 mmol/kg), creatine (Cr: 5.0 mmol/kg), and choline (Cho: 3.0 mmol/kg). The signal intensities of BPA and internal water were corrected by T2 relaxation time. The absolute concentrations of BPA were calculated by proton MRS using an internal water signal as a standard. The major BPA peaks were detected between 7.1 and 7.6 ppm. Mean T2 relaxation time was 314.3+/-10.8 ms in BPA, 885.1+/-39.7 ms in internal water. The calculated BPA concentrations were almost same as the actual concentration of BPA and the correlation coefficient was 0.99. Our BPA quantification method was very simple and non-invasive, also it had high accuracy. Therefore, our results indicate that proton MRS can be potentially useful technique for in vivo BPA quantification in boron neutron capture therapy (BNCT).

Pretreatment with buthionine sulfoximine enhanced uptake and retention of BSH in brain tumor.

To determine the influence of buthionine sulfoximine (BSO) on boron biodistribution after sulfhydryl borane (BSH) administration for boron neutron capture therapy, the effectiveness of the combination of BSO with sulfhydril- (BSH) and non-sulfhydril (B12H12 and BNH3) boron compounds, and the interval between BSO and BSH administration, the retention of boron in tissues have been evaluated using a 9L rat tumor model. Simultaneous administration of BSH and BSO showed significantly higher boron accumulation compared to that without BSO, however there was no difference in tissue boron level between B12H12 and BNH3 administration with BSO or without BSO. The longer interval (6h) between BSH and BSO administration related to the highest boron concentration in the brain and subcutaneous tumors compared to shorter intervals (0.5, 3h). Boron concentration in subcutaneous and brain tumors was maintained for 6 and 12h after the administration of BSH following BSO pretreatment.

Intracellular uptake of a new boronated porphyrin EC032

We measured the toxicity and intracellular uptake of a newly developed boronated porphyrin EC032, and verified the fluorescence-based boron concentration measuring methods. Toxicity study showed that concentration required to produce a 50% reduction in viability (IC(50)) of EC032 was more than 0.25 mM. Fluorescence study showed the intracellular uptake of EC032 increased up until 24 h after its exposure to C6, 9L, U87, and U251 cells. There was also a linear correlation between ICP-AES and fluorescence intensity as an arbitrary unit about measurement of boron concentration. Fluorescence-based boron concentration measuring methods are very simple and useful methods, especially for screening of slight test dose of porphyrin compounds.

Corrigendum to “The optimization of fluorescence imaging of brain tumor tissue differentiated from brain edema-in vivo kinetic study of 5-aminolevulinic acid and talaporfin sodium” [Photodiagn. Photodyn. Ther. 6 (2009), 19–27]

Please cite this article in press as: T. Tsurubuchi, et al., Corrigendum to “The optimization of fluorescence imaging of brain tumor tissue differentiated from brain edema-in vivo kinetic study of 5-aminolevulinic acid and talaporfin sodium” [Photodiagn. Photodyn. Ther. 6 (2009), 19–27], Photodiagnosis and Photodynamic Therapy (2017), http://dx.doi.org/10.1016/j.pdpdt.2016.12.008 The authors regret that the surname of the second author has a misprint in it. The correct surname is Zaboronok. There is only one ffiliation for all the authors and the upper register letters a and b is a single institution, as b is indicating the address of the affiliation. The authors would like to apologise for any inconvenience caused.