FZD10-targeted α-radioimmunotherapy with 225Ac-labeled OTSA101 achieves complete remission in a synovial sarcoma model

Synovial sarcomas are rare tumors arising in adolescents and young adults. The prognosis for advanced disease is poor, with an overall survival of 12-18 months. Frizzled homolog 10 (FZD10) is overexpressed in most synovial sarcomas, making it a promising therapeutic target. The results of a phase 1 trial of β-radioimmunotherapy (RIT) with the 90Y-labeled anti-FZD10 antibody OTSA101 revealed a need for improved efficacy. The present study evaluated the potential of α-RIT with OTSA101 labeled with the α-emitter 225Ac. Competitive inhibition and cell binding assays showed that specific binding of 225Ac-labeled OTSA101 to SYO-1 synovial sarcoma cells was comparable to that of the imaging agent 111In-labeled OTSA101. Biodistribution studies showed high uptake in SYO-1 tumors and low uptake in normal organs, except for blood. Dosimetric studies showed that the biologically effective dose (BED) of 225Ac-labeled OTSA101 for tumors was 7.8 Bd higher than that of 90Y-labeled OTSA101. 90Y- and 225Ac-labeled OTSA101 decreased tumor volume and prolonged survival. 225Ac-labeled OTSA101 achieved a complete response in 60% of mice, and no recurrence was observed. 225Ac-labeled OTSA101 induced a larger amount of necrosis and apoptosis than 90Y-labeled OTSA101, although the cell proliferation decrease was comparable. The BED for normal organs and tissues was tolerable; no treatment-related mortality or obvious toxicity, except for temporary body weight loss, was observed. 225Ac-labeled OTSA101 provided a high BED for tumors and achieved a 60% complete response in the synovial sarcoma mouse model SYO-1. RIT with 225Ac-labeled OTSA101 is a promising therapeutic option for synovial sarcoma

Knockdown of COPA, Identified by Loss-of-Function Screen, Induces Apoptosis and Suppresses Tumor Growth in Mesothelioma Mouse Model

AbstractMalignant mesothelioma is a highly aggressive tumor arising from serosal surfaces of the pleura and is triggered by past exposure to asbestos. Currently, there is no widely accepted treatment for mesothelioma. Development of effective drug treatments for human cancers requires identification of therapeutic molecular targets. We therefore conducted a large-scale functional screening of mesothelioma cells using a genome-wide small interfering RNA library. We determined that knockdown of 39 genes suppressed mesothelioma cell proliferation. At least seven of the 39 genes—COPA, COPB2, EIF3D, POLR2A, PSMA6, RBM8A, and RPL18A—would be involved in anti-apoptotic function. In particular, the COPA protein was highly expressed in some mesothelioma cell lines but not in a pleural mesothelial cell line. COPA knockdown induced apoptosis and suppressed tumor growth in a mesothelioma mouse model. Therefore, COPA may have the potential of a therapeutic target and a new diagnostic marker of mesothelioma

Defective repair of radiation-induced DNA damage is complemented by a CHORI-230-65K18 BAC clone on rat chromosome 4

AbstractThe Long Evans cinnamon (LEC) rat is highly susceptible to X-irradiation due to defective DNA repair and is thus a model for hepatocellular carcinogenesis. We constructed a bacterial artificial chromosome (BAC) contig of rat chromosome 4 completely covering the region associated with radiation susceptibility. We used transient and stable transfections to demonstrate that defective DNA repair in LEC cells is fully complemented by a 200-kb BAC, CHORI-230-65K18. Further analysis showed that the region associated with radiation susceptibility is located in a 128,543-bp region of 65K18 that includes the known gene Rpn1. However, neither knockdown nor overexpression of Rpn1 indicated that this gene is associated with radiation susceptibility. We also mapped three ESTs (TC523872, TC533727, and CB607546) in the 128,543-bp region, suggesting that 65K18 contains an unknown gene associated with X-ray susceptibility in the LEC rat

Translocator protein imaging with 18F-FEDAC-positron emission tomography in rabbit atherosclerosis and its presence in human coronary vulnerable plaques

Background and aims: This study aimed to investigate whether N-benzyl-N-methyl-2-[7,8-dihydro-7-(2-[18F]fluoroethyl)-8-oxo-2-phenyl-9H-purin-9-yl]acetamide (18F-FEDAC), a probe for translocator protein (TSPO), can visualize atherosclerotic lesions in rabbits and whether TSPO is localized in human coronary plaques.Methods: 18F-FEDAC-PET of a rabbit model of atherosclerosis induced by a 0.5% cholesterol diet and ballooninjury of the left carotid artery (n = 7) was performed eight weeks after the injury. The autoradiography intensity of 18F-FEDAC in carotid artery tissue sections was measured, and TSPO expression was evaluated immunohistochemically.TSPO expression was examined in human coronary arteries obtained from autopsy cases (n = 16), and in human coronary plaques (n = 12) aspirated from patients with acute myocardial infarction (AMI).Results: 18F-FEDAC-PET visualized the atherosclerotic lesions in rabbits as high-uptake areas, and the standard uptake value was higher in injured arteries (0.574 ± 0.24) than in uninjured arteries (0.277 ± 0.13, p < 0.05) or myocardium (0.189 ± 0.07, p < 0.05). Immunostaining showed more macrophages and more TSPO expression in atherosclerotic lesions than in uninjured arteries. TSPO was localized in macrophages, and arterial autoradiography intensity was positively correlated with macrophage concentration (r = 0.64) and TSPO (r = 0.67). TSPO expression in human coronary arteries was higher in AMI cases than in non-cardiac death, or in the vulnerable plaques than in early or stable lesions, respectively. TSPO was localized in macrophages in all aspirated coronary plaques with thrombi.Conclusions: 18F-FEDAC-PET can visualize atherosclerotic lesions, and TSPO-expression may be a marker of highrisk coronary plaques

A tyrosine-kinase inhibitor enhanced antitumor effects of ROBO1-targeted radioimmunotherapy in an SCLC mouse model

ROBO1 is a membrane protein that is frequently expressed in small cell lung cancer (SCLC). We previously reported our radioimmunotherapy (RIT) agent 90Y-labeled anti-ROBO1 IgG showed significant anti-tumor effects such as tumor shrinkage, but the tumors showed regrowth, suggesting the necessity for more effective therapy. Here, we evaluated the efficacy of a combination therapy of the RIT agent and a tyrosine-kinase inhibitor nintedanib in SCLC xenograft mice. Four groups of SCLC xenograft mice were treated with saline (control), nintedanib alone, RIT alone, and a combination of RIT and nintedanib, respectively. In the nintedanib alone group, no anti-tumor effects such as tumor growth suppression were observed. The RIT alone group and the combination group showed remarkable tumor shrinkage and prolonged survival compared with the control group. Tumor regrowth was observed in all 6 cases in the RIT alone group and 1 of 6 cases in the combination group by 100 days post-treatment. These results suggest that the tyrosine-kinase inhibitor nintedanib enhances anti-tumor effects of RIT with 90Y-labeled anti-ROBO1 IgG. The combination has the potential as an option for SCLC treatment.第79回日本癌学会学術総

Proof of Concept Study for Increasing Tenascin-C-Targeted Drug Delivery to Tumors Previously Subjected to Therapy: X-Irradiation Increases Tumor Uptake.

In treatment-refractory cancers, tumor tissues damaged by therapy initiate the repair response; therefore, tumor tissues must be exposed to an additional burden before successful repair. We hypothesized that an agent recognizing a molecule that responds to anticancer treatment-induced tissue injury could deliver an additional antitumor agent including a radionuclide to damaged cancer tissues during repair. We selected the extracellular matrix glycoprotein tenascin-C (TNC) as such a molecule, and three antibodies recognizing human and murine TNC were employed to evaluate X-irradiation-induced changes in TNC uptake by subcutaneous tumors. TNC expression was assessed by immunohistochemical staining of BxPC-3 tumors treated with or without X-irradiation (30 Gy) for 7 days. Antibodies against TNC (3-6, 12-2-7, TDEAR) and a control antibody were radiolabeled with In and injected into nude mice having BxPC-3 tumors 7 days after X-irradiation, and temporal uptake was monitored for an additional 4 days by biodistribution and single-photon emission computed tomography with computed tomography (SPECT/CT) studies. Intratumoral distribution was analyzed by autoradiography. The immunohistochemical signal for TNC expression was faint in nontreated tumors but increased and expanded with time until day 7 after X-irradiation. Biodistribution studies revealed increased tumor uptake of all three In-labeled antibodies and the control antibody. However, a statistically significant increase in uptake was evident only for In-labeled 3-6 (35% injected dose (ID)/g for 30 Gy vs. 15% ID/g for 0 Gy at day 1, < 0.01), whereas limited changes in In-labeled TDEAR2, 12-2-27, and control antibody were observed (several % ID/g for 0 and 30 Gy). Serial SPECT/CT imaging with In-labeled 3-6 or control antibody provided consistent results. Autoradiography revealed noticeably stronger signals in irradiated tumors injected with In-labeled 3-6 compared with each of the nonirradiated tumors and the control antibody. The signals were observed in TNC-expressing stroma. Markedly increased uptake of In-labeled 3-6 in irradiated tumors supports our concept that an agent, such as an antibody, that recognizes a molecule involved in tissue injury repair, such as TNC, could enhance drug delivery to tumor tissues that have undergone therapy. The combination of antibody 3-6 coupled to a tumoricidal drug and conventional therapy has the potential to achieve better outcomes for patients with refractory cancer

Quantitative radionuclide imaging study for enhanced drug delivery induced by near-infrared photoimmunotherapy

Objective: Photoimmunotherapy (PIT) is an upcoming potential cancer treatment modality. Meanwhile, due to the limited therapeutic effect of PIT alone, the combination of anticancer agents with PIT is an option to improve the therapeutic outcome. PIT causes a super-enhanced permeability and retention (SUPR) effect. The selection of drug molecule sizes that are suitable for enhanced permeability is also important for optimizing therapeutic efficacy. Thus, a method that supports to investigate the drug delivery of varying molecular weights coupled with PIT is desirable. Here, we evaluated the SUPR effect using radiolabeled drugs of varying molecular weights ( 18F-5FU, 111In-DTPA, 99mTc-HSA-D, and 111In-IgG) to determine the appropriate drug size. Methods: PIT was conducted with an indocyanine green-labeled anti-HER2 antibody and an 808-nm laser irradiation. Mice were subcutaneously inoculated with HER2-positive cells in both legs. The tumor on one side was treated with PIT, and the contralateral side was not treated. The differences between tumor accumulations were quantitatively evaluated using positron emission tomography (PET) or single-photon emission computed tomography (SPECT). In this study, we used the four radionuclide imaging probes: 18F-5FU, a low-molecular-weight (148 Da) PET probe; 111In-DTPA, a low-molecular-weight (504 Da) SPECT probe, 99mT- HSA-D, a medium-molecular-weight (66492 Da) SPECT probe, and 111In-IgG, a high-molecular-weight (147111 Da) SPECT probe to quantify the SUPR effect induced by PIT. high-molecular-weight (147111 Da) SPECT probe to quantify the SUPR effect induced by PIT. Results: PIT-treated tumors showed significantly increased uptake of 18F-5FU (P < 0.001), 111In-DTPA (P < 0.05), and 99mTc-HSA-D (P < 0.02). A tendency toward increased accumulation of 111In-IgG was observed. These findings suggest that low- and medium-molecular-weight agents are promising candidates for combined PIT, and so are macromolecules; hence, administration after PIT could enhance their efficacy. Conclusion: The radionuclide imaging approach is elucidated for the PIT-mediated SUPR effect and can help in optimizing therapeutic measures by means of the feasibility of selecting a drug size and monitoring its distribution. Our findings encourage further preclinical and clinical studies to develop a combination therapy of PIT with conventional anticancer drugs.World Molecular Imaging Congres