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The application of chimeric antigen receptor (CAR) T cell therapy in solid tumors is hindered by life-threatening toxicities resulting from on-target, off-tumor killing of nonmalignant cells that express low levels of the target antigen. Mesothelin (MSLN) has been identified as a target antigen for CAR T cell treatment of mesothelioma, lung, ovarian, and other cancers because of its high expression on tumor cells and limited expression on mesothelial cells. However, fatal off-tumor toxicity of high-affinity MSLN-targeting CAR T cells has been reported in multiple clinical trials. In this study, we constructed CARs using mutant variants of a single-domain nanobody that bind both human and mouse MSLN with a wide range of affinities and examined tumor responses and their toxicities from on-target, off-tumor interactions in mouse models. CAR T cells with low nanomolar affinity (equilibrium dissociation constant, KD) exhibited profound systemic expansion with no apparent infiltration into the tumor. With a gradual reduction of CAR affinity toward the micromolar KD, the expansion of CAR T cells became more restricted to tumors. Our preclinical studies demonstrated that high-affinity MSLN CARs were associated with fatal on-target, off-tumor toxicity and that affinity-tuned CARs rendered T cells more selective for MSLN-high tumors.

Ionizing radiation has garnered considerable attention as a combination partner for immunotherapy due to its potential immunostimulatory effects. In contrast to the more commonly used external beam radiation, we explored the feasibility of combining chimeric antigen receptor (CAR) T cell therapy with targeted radionuclide therapy (TRT), which is achieved by delivering β -emitting 177 Lu-DOTATATE to tumor via tumor-infiltrating CAR T cells that express somatostatin receptor 2 (SSTR2). We hypothesized that the delivery of radiation to tumors could synergize with CAR T therapy, resulting in enhanced antitumor immunity and tumor response. To determine the optimal dosage and timing of 177 Lu-DOTATATE treatment, we measured CAR T cell infiltration and expansion in tumors longitudinally through positron emission tomography (PET) using a SSTR2-specific positron-emitting radiotracer, 18 F-NOTA-Octreotide. In animals receiving CAR T cells and a low-dose (2.5 Gy) of TRT following the administration of 177 Lu-DOTATATE, we observed a rapid regression of large subcutaneous tumors, which coincided with a dramatic increase in serum proinflammatory cytokines. Tumor burden was also reduced when a higher radiation dose (6 Gy) was delivered to the tumor. However, this higher dose led to cell death in both the tumor and CAR T cells. Our study suggests that there may exist an optimum range of TRT dosage that can enhance T cell activity and sensitize tumor cells to T cell killing, which may result in more durable tumor control compared to a higher radiation dose., Competing Interests: MJ is a founder and equity stakeholder of Affyimmune Therapeutics, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Vedvyas, Alcaina, Son, Min and Jin.)

Epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen that is frequently overexpressed in various carcinomas. We have developed chimeric antigen receptor (CAR) T cells specifically targeting EpCAM for the treatment of gastric cancer. This study sought to unravel the precise mechanisms by which tumors evade immune surveillance and develop resistance to CAR T cell therapy. Through a combination of whole-body CAR T cell imaging and single-cell multiomic analyses, we uncovered intricate interactions between tumors and tumor-infiltrating lymphocytes (TILs). In a gastric cancer model, tumor-infiltrating CD8 T cells exhibited both cytotoxic and exhausted phenotypes, while CD4 T cells were mainly regulatory T cells. A T cell receptor (TCR) clonal analysis provided evidence of CAR T cell proliferation and clonal expansion within resistant tumors, which was substantiated by whole-body CAR T cell imaging. Furthermore, single-cell transcriptomics showed that tumor cells in mice with refractory or relapsing outcomes were enriched for genes involved in major histocompatibility complex (MHC) and antigen presentation pathways, interferon- γ and interferon- α responses, mitochondrial activities, and a set of genes (e.g., CD74 , IDO1 , IFI27 ) linked to tumor progression and unfavorable disease prognoses. This research highlights an approach that combines imaging and multiomic methodologies to concurrently characterize the evolution of tumors and the differentiation of CAR T cells.

Background: Iodine is required for the synthesis of thyroid hormone (TH), but its natural availability is limited. Dehalogenase1 (Dehal1) recycles iodine from mono- and diiodotyrosines (MIT, DIT) to sustain TH synthesis when iodine supplies are scarce, but its role in the dynamics of storage and conservation of iodine is unknown. Methods: Dehal1 -knockout ( Dehal1 KO) mice were generated by gene trapping. The timing of expression and distribution was investigated by X-Gal staining and immunofluorescence using recombinant Dehal1-beta-galactosidase protein produced in fetuses and adult mice. Adult Dehal1 KO and wild-type ( Wt ) animals were fed normal and iodine-deficient diets for 1 month, and plasma, urine, and tissues were isolated for analyses. TH status was monitored, including thyroxine, triiodothyronine, MIT, DIT, and urinary iodine concentration (UIC) using a novel liquid chromatography with tandem mass spectrometry method and the Sandell-Kolthoff (S-K) technique throughout the experimental period. Results: Dehal1 is highly expressed in the thyroid and is also present in the kidneys, liver, and, unexpectedly, the choroid plexus. In vivo transcription of Dehal1 was induced by iodine deficiency only in the thyroid tissue. Under normal iodine intake, Dehal1 KO mice were euthyroid, but they showed negative iodine balance due to a continuous loss of iodotyrosines in the urine. Counterintuitively, the UIC of Dehal1 KO mice is twofold higher than that of Wt mice, indicating that S-K measures both inorganic and organic iodine. Under iodine restriction, Dehal1 KO mice rapidly develop profound hypothyroidism, while Wt mice remain euthyroid, suggesting reduced retention of iodine in the thyroids of Dehal1 KO mice. Urinary and plasma iodotyrosines were continually elevated throughout the life cycles of Dehal1 KO mice, including the neonatal period, when pups were still euthyroid. Conclusions: Plasma and urine iodotyrosine elevation occurs in Dehal1-deficient mice throughout life. Therefore, measurement of iodotyrosines predicts an eventual iodine shortage and development of hypothyroidism in the preclinical phase. The prompt establishment of hypothyroidism upon the start of iodine restriction suggests that Dehal1 KO mice have low iodine reserves in their thyroid glands, pointing to defective capacity for iodine storage.

The limited number of targetable tumor-specific antigens and the immunosuppressive nature of the microenvironment within solid malignancies represent major barriers to the success of chimeric antigen receptor (CAR)-T cell therapies. Here, using epithelial cell adhesion molecule (EpCAM) as a model antigen, we used alanine scanning of the complementarity-determining region to fine-tune CAR affinity. This allowed us to identify CARs that could spare primary epithelial cells while still effectively targeting EpCAM high tumors. Although affinity-tuned CARs showed suboptimal antitumor activity in vivo, we found that inducible secretion of interleukin-12 (IL-12), under the control of the NFAT promoter, can restore CAR activity to levels close to that of the parental CAR. This strategy was further validated with another affinity-tuned CAR specific for intercellular adhesion molecule-1 (ICAM-1). Only in affinity-tuned CAR-T cells was NFAT activity stringently controlled and restricted to tumors expressing the antigen of interest at high levels. Our study demonstrates the feasibility of specifically gearing CAR-T cells towards recognition of solid tumors by combining inducible IL-12 expression and affinity-tuned CAR., (© 2023. The Author(s).)

The ability to image adoptively transferred T cells in the body and to eliminate them to avoid toxicity will be vital for chimeric antigen receptor (CAR) T cell therapy, particularly against solid tumors with higher risk of off-tumor toxicity. Previously, we have demonstrated the utility of somatostatin receptor 2 (SSTR2) for CAR T cell imaging, illustrating the expansion and contraction of CAR T cells in tumor as well as off-tumor expansion. Using intercellular adhesion molecule 1 (ICAM-1)-specific CAR T cells that secrete interleukin (IL)-12 as a model, herein we examined the potential of SSTR2 as a safety switch when combined with the SSTR2-specific maytansine-octreotate conjugate PEN-221. Constitutive secretion of IL-12 led to continuous expansion of CAR T cells after rapid elimination of tumors, causing systemic toxicity in mice with intact MHC expression. Treatment with PEN-221 rapidly reduced the abundance of CAR T cells, decreasing the severity of xenogeneic graft-versus-host disease (GvHD), and prolonged survival. Our study supports the development of SSTR2 as a single genetic marker for CAR T cells that is readily applicable to humans both for anatomical detection of T cell distribution and an image-guided safety switch for rapid elimination of CAR T cells., (© 2022. The Author(s).)

Adoptive transfer of chimeric antigen receptor (CAR) T cells has demonstrated unparalleled responses in hematologic cancers, yet antigen escape and tumor relapse occur frequently. CAR T-cell therapy for patients with solid tumors faces even greater challenges due to the immunosuppressive tumor environment and antigen heterogeneity. Here, we developed a bispecific CAR to simultaneously target epithelial cell adhesion molecule (EpCAM) and intercellular adhesion molecule 1 (ICAM-1) to overcome antigen escape and to improve the durability of tumor responses. ICAM-1 is an adhesion molecule inducible by inflammatory cytokines and elevated in many types of tumors. Our study demonstrates superior efficacy of bispecific CAR T cells compared with CAR T cells targeting a single primary antigen. Bispecific CAR T achieved more durable antitumor responses in tumor models with either homogenous or heterogenous expression of EpCAM. We also showed that the activation of CAR T cells against EpCAM in tumors led to upregulation of ICAM-1, which rendered tumors more susceptible to ICAM-1 targeting by bispecific CAR T cells. Our strategy of additional targeting of ICAM-1 may have broad applications in augmenting the activity of CAR T cells against primary tumor antigens that are prone to antigen loss or downregulation., (©2021 American Association for Cancer Research.)

Background: Diffuse intrinsic pontine glioma (DIPG) is a highly lethal malignancy that occurs predominantly in children. DIPG is inoperable and post-diagnosis survival is less than 1 year, as conventional chemotherapy is ineffective. The intact blood-brain barrier (BBB) blocks drugs from entering the brain. Convection-enhanced delivery (CED) is a direct infusion technique delivering drugs to the brain, but it suffers from rapid drug clearance. Our goal is to overcome the delivery barrier via CED and maintain a therapeutic concentration at the glioma site with a payload-adjustable peptide nanofiber precursor (NFP) that displays a prolonged retention property as a drug carrier., Methods: The post-CED retention of 89Zr-NFP was determined in real time using PET/CT imaging. Emtansine (DM1), a microtubule inhibitor, was conjugated to NFP. The cytotoxicity of the resulting DM1-NFP was tested against patient-derived DIPG cell lines. The therapeutic efficacy was evaluated in animals bearing orthotopic DIPG, according to glioma growth (measured using bioluminescence imaging) and the long-term survival., Results: DM1-NFP demonstrated potency against multiple glioma cell lines. The half-maximal inhibitory concentration values were in the nanomolar range. NFP remained at the infusion site (pons) for weeks, with a clearance half-life of 60 days. DM1-NFP inhibited glioma progression in animals, and offered a survival benefit (median survival of 62 days) compared with the untreated controls (28 days) and DM1-treated animal group (26 days)., Conclusions: CED, in combination with DM1-NFP, complementarily functions to bypass the BBB, prolong drug retention at the fusion site, and maintain an effective therapeutic effect against DIPG to improve treatment outcome., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Aims: To study the mechanisms of pluripotency induction, we compared gene expression in pluripotent embryonic germ cells (EGCs) and unipotent primordial germ cells (PGCs)., Results: We found 11 genes ≥1.5-fold overexpressed in EGCs. None of the genes identified was the Yamanaka genes but instead related to glycolytic metabolism. The prospect of pluripotency induction by cell metabolism manipulation was investigated by hypoxic culturing. Hypoxia induced a glycolytic program in PGCs in detriment of mitochondrial oxidative phosphorylation. We demonstrate that hypoxia alone induces reprogramming in PGCs, giving rise to hypoxia-induced EGC-like cells (hiEGLs), which differentiate into cells of the three germ layers in vitro and contribute to the internal cell mass of the blastocyst in vivo, demonstrating pluripotency. The mechanism of hypoxia induction involves HIF1α stabilization and Oct4 deregulation. However, hiEGL cannot be passaged long term. Self-renewal capacity is not achieved by hypoxia likely due to the lack of upregulation of c-Myc and Klf4. Gene expression analysis of hypoxia signaling suggests that hiEGLs have not reached the stabilization phase of cell reprogramming., Innovation and Conclusion: Our data suggest that the two main properties of stemness, pluripotency and self-renewal, are differentially regulated in PGC reprogramming induced by hypoxia.

Pluripotency is defined as the potential of a cell to differentiate into cells of the three germ layers: endoderm, mesoderm and ectoderm. In vivo, the presence of pluripotent stem cells is transient during the very early embryo. However, immortal cell lines with the same properties can be obtained in vitro and grown indefinitely in laboratories under specific conditions. These cells can be induced to differentiate into all the cell types of the organism through different assays, thereby proving their functional pluripotency. This review focuses on the pluripotent stem cells of mammals, giving special attention to the comparison between mouse and human. In particular, embryonic stem cells, epiblast-derived stem cells, primordial germ cells, embryonic germ cells, very small embryonic-like cells and induced pluripotent stem cells will be compared in terms of the following: in vivo specification and location; surface and intracellular markers; in vitro dependence on growth factors; signal transduction pathways; epigenetic characteristics; and pluripotency genes and functional assays.