Akira Makino

Polymeric nanoparticles are known for their ability to encapsulate and release various compounds. We hypothesized that encapsulating anti-cancer drugs alongside therapeutic radionuclides could enable combination therapy using brachytherapy and localized chemotherapy. This study was aimed at developing biodegradable polymer-based nanocarriers that can serve as a radiation source for brachytherapy and determining whether this combination of brachytherapy and chemotherapy could offer a higher therapeutic response than conventional brachytherapy. A block polymer consisting of poly(l-lactic acid) and poly(N-n-propylglycine) units was chemically synthesized. Additionally, a poly(l-lactic acid) homopolymer was labeled with the β-ray-emitting radionuclide 64Cu via a chelating moiety. Using a mixture of the block polymer, 64Cu labeled poly(l-lactic acid), and the anti-cancer drug docetaxel, we prepared a core–shell-type polymer micelle in an ice-cooled aqueous solution. This micelle solution was locally injected into the tumor region of mice, and radioactivity distribution was evaluated using an animal positron emission tomography system. Therapeutic efficacy was assessed by monitoring changes in tumor volume over time. The block polymer exhibited thermodynamic behavior, forming micelles in ice-cold conditions. When the temperature of the micelle solution was raised, µm-sized aggregates formed rapidly at 25–30 °C due to the hydrophobization of poly(N-n-propylglycine) units on the micelle surface. Importantly, 64Cu remained stable within the aggregates, while docetaxel was gradually released. After the local injection of the micelle solution into subcutaneously implanted tumors, radioactivity was stably detected at the injection site. The combination of 64Cu brachytherapy and localized docetaxel chemotherapy significantly suppressed cancer progression compared to either 64Cu brachytherapy or docetaxel chemotherapy alone. The thermosensitive micelles developed in this study can be used as a radiation source for brachytherapy, eliminating the need for permanent metal seed insertion. Moreover, combining local anti-cancer therapy with brachytherapy offers higher therapeutic efficacy than conventional brachytherapy alone.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder shaped by genetic factors such as copy number variations (CNVs) and immunological factors such as maternal infection. However, most studies on the development of genetic ASD have focused on neurological aspects, and the role of immunity in genetic ASD remains unclear. Here, we demonstrate increased γδ T cells in the brains of 15q11-13 duplication ( 15q dup ) mice, which model a common CNV associated with ASD. Elevated CXCL16 in the brains of 15q dup mice promoted γδ T cell infiltration, specifically of Vγ6 ⁺ γδ T cells that produce IL-17A. Deletion of Vγ6 ⁺ γδ T cells throughout development or treatment with neutralizing antibodies against Vγ6 or IL-17A increased social behavior in 15q dup mice. These findings suggest that immune dysregulation contributes to social behavior deficits in 15q dup mice, consistent with observations in maternal immune activation models, and may represent a potential target for interventions for ASD-associated differences in social behavior.

Lactosome is a polymeric micelle composed of an amphiphilic polydepsipeptide, a hydrophilic block poly(sarcosine)70, and a hydrophobic block poly(L-lactic acid)30(PSar70-block-PLLA30), which accumulates in solid tumors through the enhanced permeability and retention effect. However, following administration its pharmacokinetics shift from tumor accumulation to liver sequestration due to anti-lactosome IgM production triggered by the initial administration. This phenomenon is called Accelerated Blood Clearance. To enhance tumor accumulation after multiple doses, a novel nanoparticle composed of lactosome modified with linear-poly(glycerol)10 (lin-PG10) (lin-PG10 lactosome) was prepared. Amphiphilic polymer with lin-PG10 and PLLA30 were synthesized and modified into lactosome by the Film method. IgM production of lin-PG10 lactosome was evaluated by ELISA using mice plasma collected 7 days after dosing. 125I-labeled 10%lin-PG10 lactosome was prepared by incorporating N-[125I]iodobenzoyl poly(L-lactic acid)30(125I-BzPLLA30). Biodistribution was compared 1st and 2nd doses using Colon-26 bearing mice. 10%lin-PG10 lactosome was reduced anti-lactosome IgM production compared with lactosome. Evaluation of biodistribution in Colon-26 bearing mice showed that the 1st dose showed accumulation in tumors, but the 2nd dose showed a reduction in the amount of accumulation in tumors, which was not sufficient improvement. This suggests that antibody production may be inhibited by introducing functional groups into lactosomes, although there is room for improvement.

Objective: Compared with radiation therapy using photon beams, particle therapies, especially those using carbons, show a high relative biological effectiveness and low oxygen enhancement ratio. Using cells cultured under normoxic conditions, our group reported a greater suppressive effect on cell growth by carbon beams than X-rays, and the subsequent therapeutic effect can be predicted by the cell uptake amount of 3'-deoxy-3'-[¹⁸F]fluorothymidine (¹⁸F-FLT) the day after treatment. On the other hand, a hypoxic environment forms locally around solid tumors, influencing the therapeutic effect of radiotherapy. In this study, the influence of tumor hypoxia on particle therapies and the ability to predict the therapeutic effect using ¹⁸F-FLT were evaluated. Methods: Using a murine colon carcinoma cell line (colon 26) cultured under hypoxic conditions (1.0% O₂ and 5.0% CO₂), the suppressive effect on cell growth by X-ray, proton, and carbon irradiation was evaluated. In addition, the correlation between decreased ¹⁸F-FLT uptake after irradiation and subsequent suppression of cell proliferation was investigated. Results: Tumor cell growth was suppressed most efficiently by carbon-beam irradiation. ¹⁸F-FLT uptake temporarily increased the day after irradiation, especially in the low-dose irradiation groups, but then decreased from 50 h after irradiation, which is well correlated with the subsequent suppression on tumor cell growth. Conclusions: Carbon beam treatment shows a strong therapeutic effect against cells under hypoxia. Unlike normoxic tumors, it is desirable to perform ¹⁸F-FLT positron emission tomography 2–3 days after irradiation for early prediction of the treatment effect. Graphical

Coronavirus disease (COVID-19) vaccination is known to cause a diagnostic dilemma due to false-positive findings on [¹⁸F]FDG PET in vaccine-associated hypermetabolic lymphadenopathy. We present two case reports of women with estrogen-receptor (ER)-positive cancer of the breast who were vaccinated for COVID-19 in the deltoid muscle. [¹⁸F]FDG positron emission tomography (PET) demonstrated primary breast cancer and multiple axillary lymph nodes with increased [¹⁸F]FDG uptake, diagnosed as vaccine-associated [¹⁸F]FDG-avid lymph nodes. Subsequent [¹⁸F]FES PET revealed single axillary lymph node metastasis in the vaccine-associated [¹⁸F]FDG-avid lymph nodes. To the best of our knowledge, this is the first study showing the usefulness of [¹⁸F]FES PET in diagnosing axillary lymph node metastasis in COVID-19-vaccinated patients harboring ER-positive breast cancer. Thus, [¹⁸F]FES PET has potential applications in the detection of true-positive metastatic lymph nodes in patients with ER-positive breast cancer regardless of the ipsilateral or contralateral side, who have received COVID-19 vaccination.

Oxidative stress imaging using diacetyl-bis (N⁴-methylthiosemicarbazone) (Cu-ATSM) was applied to the evaluation of patients with early Alzheimer’s disease (eAD). Ten eAD patients (72 ± 9 years) and 10 age-matched healthy controls (HCs) (73 ± 9 years) participated in this study. They underwent dynamic PET/MRI using ¹¹C-PiB and ⁶⁴Cu-ATSM with multiple MRI sequences. To evaluate cerebral oxidative stress, three parameters of ⁶⁴Cu-ATSM PET were compared: standardized uptake value (SUV), tracer influx rate (K_in), and a rate constant k₃. The input functions were estimated by the image-derived input function method. The relative differences were analyzed by statistical parametric mapping (SPM) using SUV and K_in images. All eAD patients had positive and HC subjects had negative PiB accumulation, and MMSE scores were significantly different between them. The ⁶⁴Cu-ATSM accumulation tended to be higher in eAD than in HCs for both SUV and K_in. When comparing absolute values, eAD patients had a greater K_in in the posterior cingulate cortex and a greater k₃ in the hippocampus compared with lobar cortical values of HCs. In SPM analysis, eAD had an increased left operculum and decreased bilateral hippocampus and anterior cingulate cortex compared to HCs. ⁶⁴Cu-ATSM PET/MRI and tracer kinetic analysis elucidated cerebral oxidative stress in the eAD patients, particularly in the cingulate cortex and hippocampus.

We designed and synthesized non-peptide organic molecular ligands for integrin α_vβ₃. Candidate ligands featured amidino analog and carboxy groups as binding sites on either side of a spacer, which consisted of benzophenone or an analog, such as diphenyl sulfide, diphenyl sulfoxide, diphenyl sulfone, or diphenyl ether. Competitive binding assays to integrin α_vβ₃ with respect to [¹²⁵I]echistatin were used to determine inhibitory activity of the synthetic ligands. Ligands bearing 2-aminobenzimidazoyl and glycyl groups separated by a benzophenone spacer demonstrated more potent binding than did a linear Arg-Gly-Asp (RGD) tripeptide that represents the native integrin α_vβ₃ binding motif. Ligands possessing 2-aminobenzimidazoyl and carboxy groups and diphenyl sulfoxide or diphenyl ether spacers inhibited binding of [¹²⁵I]echistatin with IC₅₀ values similar to that of the linear RGD tripeptide.

Osimertinib is an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor approved for treating non-small-cell lung cancer (NSCLC) with EGFR mutations. Genetic testing is required to detect the mutation for selecting patients who can use osimertinib. Here, we report an attempt to develop nuclear imaging probes that detect the EGFR mutations. We designed and synthesized I-osimertinib and Br-osimertinib with a radioactive or nonradioactive halogen atom at an indole ring in osimertinib and evaluated them. In vitro assays suggested that both I-osimertinib and Br-osimertinib exhibit a specifically high activity toward NSCLC with EGFR L858R/T790M mutations. In biodistribution experiments, the accumulation of both [¹²⁵I]I-osimertinib and [⁷⁷Br]Br-osimertinib in tumors with mutations was significantly higher than that in blood and muscle. However, these osimertinib derivatives showed a significantly higher accumulation in lungs than in tumors. Therefore, for detecting the mutations in lung cancer, further structural modifications of the probes are required.

Activating double mutations L858R/T790M in the epidermal growth factor receptor (EGFR) region are often observed as the cause of resistance to tyrosine kinase inhibitors (TKIs). Third-generation EGFR-TKIs, such as osimertinib and rociletinib (CO-1686), was developed to target such resistance mutations. The detection of activating L858R/T790M mutations is necessary to select sensitive patients for therapy. Hence, we aimed to develop novel radiobromine-labeled CO-1686 as a positron emission tomography (PET) imaging probe for detecting EGFR L858R/T790M mutations. Nonradioactive brominated-CO1686 (BrCO1686) was synthesized by the condensation of N-(3-[{2-chloro-5-(trifluoromethyl)pyrimidin-4-yl}amino]-5-bromophenyl) acrylamide with the corresponding substituted 1-(4-[4-amino-3-methoxyphenyl]piperazine-1-yl)ethan-1-one. The radiobrominated [⁷⁷Br]BrCO1686 was prepared through bromodestannylation of the corresponding tributylstannylated precursor with [⁷⁷Br]bromide and N-chlorosuccinimide. Although we aimed to provide a novel PET imaging probe, ⁷⁷Br was used as an alternative radionuclide for ⁷⁶Br. We fundamentally evaluated the potency of [⁷⁷Br]BrCO1686 as a molecular probe for detecting EGFR L858R/T790M using human non-small-cell lung cancer (NSCLC) cell lines: H1975 (EGFR L858R/T790M), H3255 (EGFR L858R), and H441 (wild-type EGFR). The BrCO1686 showed high cytotoxicity toward H1975 (IC₅₀ 0.18 ± 0.06 µM) comparable to that of CO-1686 (IC₅₀ 0.14 ± 0.05 µM). In cell uptake experiments, the level of accumulation of [⁷⁷Br]BrCO1686 in H1975 was significantly higher than those in H3255 and H441 upon 4 h of incubation. The radioactivity of [⁷⁷Br]BrCO1686 (136.3% dose/mg protein) was significantly reduced to 56.9% dose/mg protein by the pretreatment with an excess CO-1686. These results indicate that the binding site of the radiotracers should be identical to that of CO-1686. The in vivo accumulation of radioactivity of [⁷⁷Br]BrCO1686 in H1975 tumor (4.51 ± 0.17) was higher than that in H441 tumor (3.71 ± 0.13) 1 h postinjection. Our results suggested that [⁷⁷Br]BrCO1686 has specificity toward NSCLC cells with double mutations EGFR L858R/T790M compared to those in EGFR L858R and wild-type EGFR. However, the in vivo accumulation of radioactivity in the targeted tumor needs to be optimized by structural modification.