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Background: Human leukocyte antigen (HLA)-E is overexpressed by a large proportion of solid tumors, including malignant glioblastoma, and acts as a major checkpoint for NKG2A + CD8 + T cells and natural killer (NK) cells in the tumor microenvironment and circulation. This axis operates alongside PD-L1 to inhibit effector responses by T and NK cells., Methods: We engineered a chimeric A/C switch receptor, combining the high HLA-E binding affinity of the NKG2A receptor ectodomain with the activating signaling of the NKG2C receptor endodomain. The cytotoxic function of A/C switch-transduced NK and T cells was evaluated against tumor cells with varying levels of HLA-E expression. In vivo efficacy was assessed using a xenograft model of glioblastoma., Findings: A/C switch-transduced NK and T cells exhibited superior and specific cytotoxicity against tumor cells with medium to high HLA-E expression. A/C switch-expressing human T cells demonstrated enhanced anti-tumor function in a glioblastoma xenograft model. The activity of the modified T cells was governed by an equilibrium between A/C switch levels and HLA-E expression, creating a therapeutic window to minimize on-target, off-tumor toxicities. Normal cells remained insensitive to A/C switch T cells, even after interferon (IFN)-γ pretreatment to induce HLA-E expression., Conclusions: The A/C switch receptor effectively targets tumor cells expressing high levels of HLA-E, either alone or in combination with other engineered specificities, to overcome the suppressive NKG2A/HLA-E checkpoint. This approach offers a promising therapeutic strategy with a favorable safety profile for targeting HLA-E-overexpressing tumors., Funding: This work was funded by The Research Council of Norway, the Norwegian Cancer Society, and the National Cancer Institute., Competing Interests: Declaration of interests K.-J.M. is a consultant and has research support from Fate Therapeutics. K.-J.M. has research support from Oncopeptides. K.-J.M. and Q.H. are consultants at Vycellix. All relationships have been approved by Oslo University Hospital, University of Oslo and Karolinska Institute. M. Sadelain reports research funding from Takeda Pharmaceuticals, Atara Biotherapeutics, Fate Therapeutics, and Mnemo Therapeutics, all of which are unrelated to the present research. M. Sadelain is a scientific cofounder of Mnemo Therapeutics., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

We designed a CD19-targeted CAR comprising a calibrated signaling module, termed 1XX, that differs from that of conventional CD28/CD3z and 4-1BB/CD3z CARs. Here we report the first-in-human, phase 1 clinical trial of 19(T2)28z-1XX CAR T cells in relapsed/refractory large B-cell lymphoma. We hypothesized that 1XX CAR T cells may be effective at low doses and investigated 4 doubling dose levels starting from 25×10 6 CAR T cells. The overall response rate (ORR) was 82% and complete response (CR) rate 71% in the entire cohort (n=28) and 88% ORR and 75% CR in 16 patients treated at 25×10 6 . With the median follow-up of 24 months, the 1-year EFS was 61% (95% CI: 45-82%). Overall, grade ≥3 CRS and ICANS rates were low at 4% and 7%. The calibrated potency of the 1XX CAR affords excellent efficacy at low cell doses and may benefit the treatment of other hematological malignancies, solid tumors and autoimmunity., Competing Interests: Competing Interests J.H.P. received consulting fees from Affyimmune Therapeutics, Amgen, Autolus, Be Biopharma, Beigene, Bright Pharmaceutical Services, Inc., Caribou Biosciences, Curocell, Galapagos, In8Bio, Kite, Medpace, Minerva Biotechnologies, Pfizer, Servier, Sobi, and Takeda; received honoraria from OncLive, Physician Education Resource, and MJH Life Sciences; serves on scientific advisory board of Allogene Therapeutics, Artiva Biotherapeutics and Green Cross Biopharma; and received institutional research funding from Autolus, Genentech, Fate Therapeutics, InCyte, Servier, and Takeda. M.L.P. received consulting fees from BMS, Cellectis, Kite, Mustang Bio and Synthekine. G.Sh. received research funding to the institution from Amgen, BMS, Beyond Spring, Janssen, and GPCR, and serves on DSMB for Arcellx. P.D. received consulting fees from Kite. M.Sc. served as a paid consultant for McKinsey & Company, Angiocrine Bioscience, Inc., Kite, and Omeros Corporation; received research funding from Angiocrine Bioscience, Inc., Omeros Corporation, and Amgen, Inc.; served on ad hoc advisory boards for Kite-A Gilead company; and received honoraria from i3Health, Medscape and CancerNetwork for CME-related activity. G.Sa. has received financial compensations for participating in advisory boards or consulting for Abbvie, Atbtherapeutics, Beigene, BMS, Debiopharm Genentech/Roche, Genmab, Incyte, Ipsen, Janssen, Kite/Gilead, Loxo/Lilly, Merck, Molecular Partners, Nordic Nanovector, Novartis, Nurix and Orna. He is also a shareholder of: Owkin; he received Research Support managed by his institution from Genentech, Janssen, Ipsen, Nurix. Y.K.V. received one time consulting fee from EastRx. J.M.S. is an inventor on 1XX related IP. I.R. reports grants from Takeda Pharmaceuticals and Atara, personal fees from Mnemo Therapeutics, Akron, the Centre for Commercialization of Cancer, and Oribiotech, and other support from Bristol Myers Squibb outside the submitted work. M. S. reports grants from Atara Biotherapeutics outside the submitted work, as well as patent 8389282 issued and licensed to Juno Therapeutics, patent 11242375 issued and licensed to Atara Biotherapeutics, patent 10370452 issued, licensed, and with royalties paid from Fate Therapeutics, patent 11377637 issued and licensed to Takeda Pharmaceuticals, patent 11377637 issued and licensed to Mnemo Therapeutics, and patent 11377637 issued and licensed to Minerva Biotechnologies. MSK has licensed 1XX technology to Atara Biotherapy, Fate Therapeutics, Minerva Therapeutics, and Takeda Pharmaceuticals.

Acute myeloid leukemia (AML) poses a singular challenge for chimeric antigen receptor (CAR) therapy owing to its phenotypic heterogeneity and similarity to normal hematopoietic stem/progenitor cells (HSPCs). Here we expound a CAR strategy intended to efficiently target AML while minimizing HSPC toxicity. Quantification of target expression in relapsed/refractory patient samples and normal HSPCs reveals a therapeutic window for gated co-targeting of ADGRE2 and CLEC12A: We combine an attenuated ADGRE2-CAR with a CLEC12A-chimeric costimulatory receptor (ADCLEC.syn1) to preferentially engage ADGRE2 pos CLEC12A pos leukemic stem cells over ADGRE2 low CLEC12A neg normal HSPCs. ADCLEC.syn1 prevents antigen escape in AML xenograft models, outperforms the ADGRE2-CAR alone and eradicates AML despite proximate myelopoiesis in humanized mice. Off-target HSPC toxicity is similar to that of a CD19-CAR and can be mitigated by reducing CAR T cell-derived interferon-γ. Overall, we demonstrate the ability of target density-adapted cooperative CAR targeting to selectively eliminate AML and potentially obviate the need for hematopoietic rescue., Competing Interests: Declaration of interests Memorial Sloan Kettering has submitted a patent application (WO2022232016A2) based in part on results presented in this manuscript (M.Sa., S.H., and J.M.-S. are listed among the inventors). M.Sa. and S.H. report research support and research funding from Takeda Pharmaceuticals related to the present research. M.Sa. reports research funding from Atara Biotherapeutics, Fate Therapeutics, and Mnemo Therapeutics unrelated to the present research. M.Sa. and I.R. are scientific cofounders of Mnemo Therapeutics. I.R. reports research funding from Atara Biotherapeutics, Takeda Pharmaceuticals; ownership/equity interests at Fate Therapeutics and Mnemo Therapeutics; intellectual property rights at Juno Therapeutics. K.F., M.R.N., and I.R. report employment at Takeda Pharmaceuticals. M.Su. declares the following competing interests: Novartis: Consultancy, Research Funding; Janssen: Consultancy; Seattle Genetics: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Kite/Gilead: Consultancy, Honoraria, Research Funding; Roche AG: Consultancy, Research Funding. J.H.P. declares the following competing interest: research funding support from Takeda Pharmaceuticals, Fate Therapeutics, Genentech, InCyte and Servier; Consultancy from Amgen, Autolus, BMS, Curocel, Kite, Legend Biotech, Minerva, Pfizer, Servier, Sobi, and Takeda Pharmaceuticals; and serves on Scientific Advisory Board of Allogene, Artiva Biotherapeutics, and GC Cell Corporation., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Cell therapies that rely on engineered immune cells can be enhanced by achieving uniform and controlled transgene expression in order to maximize T-cell function and achieve predictable patient responses. Although they are effective, current genetic engineering strategies that use γ-retroviral, lentiviral, and transposon-based vectors to integrate transgenes, unavoidably produce variegated transgene expression in addition to posing a risk of insertional mutagenesis. In the setting of chimeric antigen receptor (CAR) therapy, inconsistent and random CAR expression may result in tonic signaling, T-cell exhaustion, and variable T-cell persistence. Here, we report and validate an algorithm for the identification of extragenic genomic safe harbors (GSH) that can be efficiently targeted for DNA integration and can support sustained and predictable CAR expression in human peripheral blood T cells. The algorithm is based on 7 criteria established to minimize genotoxicity by directing transgene integration away from functionally important genomic elements, maximize efficient CRISPR/Cas9-mediated targeting, and avert transgene silencing over time. T cells engineered to express a CD19 CAR at GSH6, which meets all 7 criteria, are curative at low cell dose in a mouse model of acute lymphoblastic leukemia, matching the potency of CAR T cells engineered at the TRAC locus and effectively resisting tumor rechallenge 100 days after their infusion. The identification of functional extragenic GSHs thus expands the human genome available for therapeutic precision engineering., (© 2023 by The American Society of Hematology.)

The success of chimeric antigen receptor (CAR) T cells targeting B-cell malignancies propelled the field of synthetic immunology and raised hopes to treat solid tumors in a similar fashion. Antigen escape and the paucity of tumor-restricted CAR targets are recognized challenges to fulfilling this prospect. Recent advances in CAR T cell engineering extend the toolbox of chimeric receptors available to calibrate antigen sensitivity and combine receptors to create adapted tumor-sensing T cells. Emerging engineering strategies to lower the threshold for effective antigen recognition, when needed, and enable composite antigen recognition hold great promise for overcoming tumor heterogeneity and curbing off-tumor toxicities., Significance: Improving the clinical efficacy of CAR T cell therapies will require engineering T cells that overcome heterogeneous and low-abundance target expression while minimizing reactivity to normal tissues. Recent advances in CAR design and logic gating are poised to extend the success of CAR T cell therapies beyond B-cell malignancies., (©2023 The Authors; Published by the American Association for Cancer Research.)

Chimeric antigen receptor (CAR) T cell therapy relies on T cells that are guided by synthetic receptors to target and lyse cancer cells. CARs bind to cell surface antigens through an scFv (binder), the affinity of which is central to determining CAR T cell function and therapeutic success. CAR T cells targeting CD19 were the first to achieve marked clinical responses in patients with relapsed/refractory B cell malignancies and to be approved by the U.S. Food and Drug Administration (FDA). We report cryo-EM structures of CD19 antigen with the binder FMC63, which is used in four FDA-approved CAR T cell therapies (Kymriah, Yescarta, Tecartus, and Breyanzi), and the binder SJ25C1, which has also been used extensively in multiple clinical trials. We used these structures for molecular dynamics simulations, which guided creation of lower- or higher-affinity binders, and ultimately produced CAR T cells endowed with distinct tumor recognition sensitivities. The CAR T cells exhibited different antigen density requirements to trigger cytolysis and differed in their propensity to prompt trogocytosis upon contacting tumor cells. Our work shows how structural information can be applied to tune CAR T cell performance to specific target antigen densities.

Further advances in cell engineering are needed to increase the efficacy of chimeric antigen receptor (CAR) and other T cell-based therapies 1-5 . As T cell differentiation and functional states are associated with distinct epigenetic profiles 6,7 , we hypothesized that epigenetic programming may provide a means to improve CAR T cell performance. Targeting the gene that encodes the epigenetic regulator ten-eleven translocation 2 (TET2) 8 presents an interesting opportunity as its loss may enhance T cell memory 9,10 , albeit not cause malignancy 9,11,12 . Here we show that disruption of TET2 enhances T cell-mediated tumour rejection in leukaemia and prostate cancer models. However, loss of TET2 also enables antigen-independent CAR T cell clonal expansions that may eventually result in prominent systemic tissue infiltration. These clonal proliferations require biallelic TET2 disruption and sustained expression of the AP-1 factor BATF3 to drive a MYC-dependent proliferative program. This proliferative state is associated with reduced effector function that differs from both canonical T cell memory 13,14 and exhaustion 15,16 states, and is prone to the acquisition of secondary somatic mutations, establishing TET2 as a guardian against BATF3-induced CAR T cell proliferation and ensuing genomic instability. Our findings illustrate the potential of epigenetic programming to enhance T cell immunity but highlight the risk of unleashing unchecked proliferative responses., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Improved identification of anti-tumor T cells is needed to advance cancer immunotherapies. CD39 expression is a promising surrogate of tumor-reactive CD8 + T cells. Here, we comprehensively profiled CD39 expression in human lung cancer. CD39 expression enriched for CD8 + T cells with features of exhaustion, tumor reactivity, and clonal expansion. Flow cytometry of 440 lung cancer biospecimens revealed weak association between CD39 + CD8 + T cells and tumoral features, such as programmed death-ligand 1 (PD-L1), tumor mutation burden, and driver mutations. Immune checkpoint blockade (ICB), but not cytotoxic chemotherapy, increased intratumoral CD39 + CD8 + T cells. Higher baseline frequency of CD39 + CD8 + T cells conferred improved clinical outcomes from ICB therapy. Furthermore, a gene signature of CD39 + CD8 + T cells predicted benefit from ICB, but not chemotherapy, in a phase III clinical trial of non-small cell lung cancer. These findings highlight CD39 as a proxy of tumor-reactive CD8 + T cells in human lung cancer., Competing Interests: Declaration of interests C.A.K. received research funding support from Kite/Gilead and Intima Bioscience; is on the Scientific and/or Clinical Advisory Boards of Achilles Therapeutics, Aleta BioTherapeutics, Bellicum Pharmaceuticals, Catamaran Bio, Obsidian Therapeutics, and T-knife; and has performed consulting services for Bristol Myers Squibb, PACT Pharma, and Roche/Genentech. C.A.K. is a co-inventor on patent applications related to TCRs targeting public neoantigens unrelated to the current work. M.D.H. received a research grant from BMS; personal fees from Achilles, Arcus, AstraZeneca, Blueprint, BMS, Genentech/Roche, Genzyme, Immunai, Instil Bio, Janssen, Merck, Mirati, Natera, Nektar, Pact Pharma, Regeneron, Shattuck Labs, and Syndax; and equity options from Arcus, Factorial, Immunai, and Shattuck Labs. A patent filed by MSKCC related to the use of tumor mutational burden to predict response to immunotherapy (PCT/US2015/062208) is pending and licensed by PGDx. J.D.W. is a consultant for Amgen, Apricity, Ascentage Pharma, Astellas, AstraZeneca, Bicara Therapeutics, Boehringer Ingelheim, Bristol Myers Squibb, CellCarta, Chugai, Daiichi Sankyo, Dragonfly, Georgiamune, Idera, Imvaq, Larkspur, Maverick Therapeutics, Merck, Psioxus, Recepta, Tizona, Trishula, Sellas, Surface Oncology, and Werewolf Therapeutics. J.D.W. receives grant/research support from Bristol Myers Squibb and Sephora. J.D.W. has equity in Apricity, Arsenal IO, Ascentage, Beigene, Imvaq, Linneaus, Georgiamune, Maverick, Tizona Pharmaceuticals, and Trieza. J.D.W. is a co-inventor on the following patent application: xenogeneic (canine) DNA vaccines, myeloid-derived suppressor cell (MDSC) assay, anti-PD1 antibody, anti-CTLA4 antibodies, anti-GITR antibodies and methods of use thereof, Newcastle disease viruses for cancer therapy, and prediction of responsiveness to treatment with immunomodulatory therapeutics and method of monitoring abscopal effects during such treatment. J.D.W. and T.M. are co-inventors on patent applications related to CD40 and in situ vaccination (PCT/US2016/045970). T.M. is a consultant for Immunos Therapeutics and Pfizer. T.M. is a cofounder of and equity holder in IMVAQ Therapeutics. T.M. receives research funding from Bristol Myers Squibb, Surface Oncology, Kyn Therapeutics, Infinity Pharmaceuticals, Peregrine Pharmaceuticals, Adaptive Biotechnologies, Leap Therapeutics, and Aprea Therapeutics. T.M. is an inventor on patent applications related to work on oncolytic viral therapy, alpha virus-based vaccine, neoantigen modeling, CD40, GITR, OX40, PD-1, and CTLA-4. C.M.R. has consulted regarding oncology drug development with AbbVie, Amgen, Ascentage, AstraZeneca, BMS, Celgene, Daiichi Sankyo, Genentech/Roche, Ipsen, Loxo, and PharmaMar and is on the scientific advisory boards of Elucida, Bridge, and Harpoon. B.Y.N. and X.G. are employees and stockholders of Genentech/Roche., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The production of autologous T cells expressing a chimaeric antigen receptor (CAR) is time-consuming, costly and occasionally unsuccessful. T-cell-derived induced pluripotent stem cells (TiPS) are a promising source for the generation of 'off-the-shelf' CAR T cells, but the in vitro differentiation of TiPS often yields T cells with suboptimal features. Here we show that the premature expression of the T-cell receptor (TCR) or a constitutively expressed CAR in TiPS promotes the acquisition of an innate phenotype, which can be averted by disabling the TCR and relying on the CAR to drive differentiation. Delaying CAR expression and calibrating its signalling strength in TiPS enabled the generation of human TCR - CD8αβ + CAR T cells that perform similarly to CD8αβ + CAR T cells from peripheral blood, achieving effective tumour control on systemic administration in a mouse model of leukaemia and without causing graft-versus-host disease. Driving T-cell maturation in TiPS in the absence of a TCR by taking advantage of a CAR may facilitate the large-scale development of potent allogeneic CD8αβ + T cells for a broad range of immunotherapies., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Chimeric antigen receptors (CARs) are receptors for antigen that direct potent immune responses. Tumor escape associated with low target antigen expression is emerging as one potential limitation of their efficacy. Here we edit the TRAC locus in human peripheral blood T cells to engage cell-surface targets through their T cell receptor-CD3 complex reconfigured to utilize the same immunoglobulin heavy and light chains as a matched CAR. We demonstrate that these HLA-independent T cell receptors (HIT receptors) consistently afford high antigen sensitivity and mediate tumor recognition beyond what CD28-based CARs, the most sensitive design to date, can provide. We demonstrate that the functional persistence of HIT T cells can be augmented by constitutive coexpression of CD80 and 4-1BBL. Finally, we validate the increased antigen sensitivity afforded by HIT receptors in xenograft mouse models of B cell leukemia and acute myeloid leukemia, targeting CD19 and CD70, respectively. Overall, HIT receptors are well suited for targeting cell surface antigens of low abundance., (© 2022. The Author(s), under exclusive licence to Springer Nature America, Inc.)

β-Thalassemias are inherited anemias that are caused by the absent or insufficient production of the β chain of hemoglobin. Here we report 6-8-year follow-up of four adult patients with transfusion-dependent β-thalassemia who were infused with autologous CD34 + cells transduced with the TNS9.3.55 lentiviral globin vector after reduced-intensity conditioning (RIC) in a phase 1 clinical trial ( NCT01639690) . Patients were monitored for insertional mutagenesis and the generation of a replication-competent lentivirus (safety and tolerability of the infusion product after RIC-primary endpoint) and engraftment of genetically modified autologous CD34 + cells, expression of the transduced β-globin gene and post-transplant transfusion requirements (efficacy-secondary endpoint). No unexpected safety issues occurred during conditioning and cell product infusion. Hematopoietic gene marking was very stable but low, reducing transfusion requirements in two patients, albeit not achieving transfusion independence. Our findings suggest that non-myeloablative conditioning can achieve durable stem cell engraftment but underscore a minimum CD34 + cell transduction requirement for effective therapy. Moderate clonal expansions were associated with integrations near cancer-related genes, suggestive of non-erythroid activity of globin vectors in stem/progenitor cells. These correlative findings highlight the necessity of cautiously monitoring patients harboring globin vectors., (© 2022. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Despite the high remission rates achieved using T cells bearing a chimeric antigen receptor (CAR) against hematogical malignancies, there is still a considerable proportion of patients who eventually experience tumor relapse. Clinical studies have established that mechanisms of treatment failure include the down-regulation of target antigen expression and the limited persistence of effective CAR T cells. We hypothesized that dual targeting mediated by a CAR and a chimeric costimulatory receptor (CCR) could simultaneously enhance T cell cytotoxicity and improve durability. Concomitant high-affinity engagement of a CD38-binding CCR enhanced the cytotoxicity of BCMA-CAR and CD19-CAR T cells by increasing their functional binding avidity. In comparison to second-generation BCMA-CAR or CD19-CAR T cells, double-targeted CAR + CD38-CCR T cells exhibited increased sensitivity to recognize and lyse tumor variants of multiple myeloma and acute lymphoblastic leukemia with low antigen density in vitro. In addition, complimentary costimulation by 4-1BB and CD28 endodomains provided by the CAR and CCR combination conferred increased cytokine secretion and expansion and improved persistence in vivo. The cumulatively improved properties of CAR + CCR T cells enabled the in vivo eradication of antigen-low tumor clones, which were otherwise resistant to treatment with conventional CAR T cells. Therefore, multiplexing targeting and costimulation through the combination of a CAR and a CCR is a powerful strategy to improve the clinical outcomes of CAR T cells by enhancing cytotoxic efficacy and persistence, thus preventing relapses of tumor clones with low target antigen density.

Cellular senescence is characterized by stable cell-cycle arrest and a secretory program that modulates the tissue microenvironment 1,2 . Physiologically, senescence serves as a tumour-suppressive mechanism that prevents the expansion of premalignant cells 3,4 and has a beneficial role in wound-healing responses 5,6 . Pathologically, the aberrant accumulation of senescent cells generates an inflammatory milieu that leads to chronic tissue damage and contributes to diseases such as liver and lung fibrosis, atherosclerosis, diabetes and osteoarthritis 1,7 . Accordingly, eliminating senescent cells from damaged tissues in mice ameliorates the symptoms of these pathologies and even promotes longevity 1,2,8-10 . Here we test the therapeutic concept that chimeric antigen receptor (CAR) T cells that target senescent cells can be effective senolytic agents. We identify the urokinase-type plasminogen activator receptor (uPAR) 11 as a cell-surface protein that is broadly induced during senescence and show that uPAR-specific CAR T cells efficiently ablate senescent cells in vitro and in vivo. CAR T cells that target uPAR extend the survival of mice with lung adenocarcinoma that are treated with a senescence-inducing combination of drugs, and restore tissue homeostasis in mice in which liver fibrosis is induced chemically or by diet. These results establish the therapeutic potential of senolytic CAR T cells for senescence-associated diseases.

Chimeric antigen receptors (CARs) are synthetic antigen receptors that reprogram T cell specificity, function and persistence 1 . Patient-derived CAR T cells have demonstrated remarkable efficacy against a range of B-cell malignancies 1-3 , and the results of early clinical trials suggest activity in multiple myeloma 4 . Despite high complete response rates, relapses occur in a large fraction of patients; some of these are antigen-negative and others are antigen-low 1,2,4-9 . Unlike the mechanisms that result in complete and permanent antigen loss 6,8,9 , those that lead to escape of antigen-low tumours remain unclear. Here, using mouse models of leukaemia, we show that CARs provoke reversible antigen loss through trogocytosis, an active process in which the target antigen is transferred to T cells, thereby decreasing target density on tumour cells and abating T cell activity by promoting fratricide T cell killing and T cell exhaustion. These mechanisms affect both CD28- and 4-1BB-based CARs, albeit differentially, depending on antigen density. These dynamic features can be offset by cooperative killing and combinatorial targeting to augment tumour responses to immunotherapy.

The β-thalassemias are inherited blood disorders that result from insufficient production of the β-chain of hemoglobin. More than 200 different mutations have been identified. β-Thalassemia major requires life-long transfusions. The only cure for severe β-thalassemia is to provide patients with hematopoietic stem cells. Globin gene therapy promises a curative autologous stem cell transplantation without the immunologic complications of allogeneic transplantation. The future directions of gene therapy include enhancement of lentiviral vector-based approaches, fine tuning of the conditioning regimen, and the design of safer vectors. Progress in genetic engineering bodes well for finding a cure for severe globin disorders., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Chimeric antigen receptor (CAR) therapy targeting CD19 has yielded remarkable outcomes in patients with acute lymphoblastic leukemia. To identify potential CAR targets in acute myeloid leukemia (AML), we probed the AML surfaceome for overexpressed molecules with tolerable systemic expression. We integrated large transcriptomics and proteomics datasets from malignant and normal tissues, and developed an algorithm to identify potential targets expressed in leukemia stem cells, but not in normal CD34 + CD38 - hematopoietic cells, T cells, or vital tissues. As these investigations did not uncover candidate targets with a profile as favorable as CD19, we developed a generalizable combinatorial targeting strategy fulfilling stringent efficacy and safety criteria. Our findings indicate that several target pairings hold great promise for CAR therapy of AML., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Chimeric antigen receptors (CARs) are synthetic receptors that redirect and reprogram T cells to mediate tumour rejection. The most successful CARs used to date are those targeting CD19 (ref. 2), which offer the prospect of complete remission in patients with chemorefractory or relapsed B-cell malignancies. CARs are typically transduced into the T cells of a patient using γ-retroviral vectors or other randomly integrating vectors, which may result in clonal expansion, oncogenic transformation, variegated transgene expression and transcriptional silencing. Recent advances in genome editing enable efficient sequence-specific interventions in human cells, including targeted gene delivery to the CCR5 and AAVS1 loci. Here we show that directing a CD19-specific CAR to the T-cell receptor α constant (TRAC) locus not only results in uniform CAR expression in human peripheral blood T cells, but also enhances T-cell potency, with edited cells vastly outperforming conventionally generated CAR T cells in a mouse model of acute lymphoblastic leukaemia. We further demonstrate that targeting the CAR to the TRAC locus averts tonic CAR signalling and establishes effective internalization and re-expression of the CAR following single or repeated exposure to antigen, delaying effector T-cell differentiation and exhaustion. These findings uncover facets of CAR immunobiology and underscore the potential of CRISPR/Cas9 genome editing to advance immunotherapies.

As their names imply, parvoviruses of the genus Dependovirus rely for their efficient replication on the concurrent presence of a helpervirus, such as herpesvirus, adenovirus, or papilloma virus. Adeno-associated virus 2 (AAV2) is such an example, which in turn can efficiently inhibit the replication of each helpervirus by distinct mechanisms. In a previous study we have shown that expression of the AAV2 rep gene is not compatible with efficient replication of herpes simplex virus 1 (HSV-1). In particular, the combined DNA-binding and ATPase/helicase activities of the Rep68/78 proteins have been shown to exert opposite effects on the replication of AAV2 and HSV-1. While essential for AAV2 DNA replication these protein activities account for the Rep-mediated inhibition of HSV-1 replication. Here, we describe a novel Rep mutant (Rep-D371Y), which displayed an unexpected phenotype. Rep-D371Y did not block HSV-1 replication, but still supported efficient AAV2 replication, at least when a double-stranded AAV2 genome template was used. We also found that the capacity of Rep-D371Y to induce apoptosis and a Rep-specific DNA damage response was significantly reduced compared to wild-type Rep. These findings suggest that AAV2 Rep-helicase subdomains exert diverging activities, which contribute to distinct steps of the AAV2 life cycle. More important, the novel AAV2 mutant Rep-D371Y may allow deciphering yet unsolved activities of the AAV2 Rep proteins such as DNA second-strand synthesis, genomic integration or packaging, which all involve the Rep-helicase activity., Competing Interests: The authors have declared that no competing interests exist.

The beta-thalassemias are inherited anemias caused by mutations that severely reduce or abolish expression of the beta-globin gene. Like sickle cell disease, a related beta-globin gene disorder, they are ideal candidates for performing a genetic correction in patient hematopoietic stem cells (HSCs). The most advanced approach utilizes complex lentiviral vectors encoding the human β-globin gene, as first reported by May et al. in 2000. Considerable progress toward the clinical implementation of this approach has been made in the past five years, based on effective CD34+ cell mobilization and improved lentiviral vector manufacturing. Four trials have been initiated in the United States and Europe. Of 16 evaluable subjects, 6 have achieved transfusion independence. One of them developed a durable clonal expansion, which regressed after several years without transformation. Although globin lentiviral vectors have so far proven to be safe, this occurrence suggests that powerful insulators with robust enhancer-blocking activity will further enhance this approach. The combined discovery of Bcl11a-mediated γ-globin gene silencing and advances in gene editing are the foundations for another gene therapy approach, which aims to reactivate fetal hemoglobin (HbF) production. Its clinical translation will hinge on the safety and efficiency of gene targeting in true HSCs and the induction of sufficient levels of HbF to achieve transfusion independence. Altogether, the progress achieved over the past 15 years bodes well for finding a genetic cure for severe globin disorders in the next decade.

Epigenetic regulation of key transcriptional programs is a critical mechanism that controls hematopoietic development, and, thus, aberrant expression patterns or mutations in epigenetic regulators occur frequently in hematologic malignancies. We demonstrate that the Polycomb protein L3MBTL1, which is monoallelically deleted in 20q- myeloid malignancies, represses the ability of stem cells to drive hematopoietic-specific transcriptional programs by regulating the expression of SMAD5 and impairing its recruitment to target regulatory regions. Indeed, knockdown of L3MBTL1 promotes the development of hematopoiesis and impairs neural cell fate in human pluripotent stem cells. We also found a role for L3MBTL1 in regulating SMAD5 target gene expression in mature hematopoietic cell populations, thereby affecting erythroid differentiation. Taken together, we have identified epigenetic priming of hematopoietic-specific transcriptional networks, which may assist in the development of therapeutic approaches for patients with anemia., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

The adeno-associated virus (AAV) encodes four regulatory proteins called Rep. The large AAV Rep proteins Rep68 and Rep78 are essential factors required in almost every step of the viral life cycle. Structurally, they share two domains: a modified version of the AAA(+) domain that characterizes the SF3 family of helicases and an N-terminal domain that binds DNA specifically. The combination of these two domains imparts extraordinary multifunctionality to work as initiators of DNA replication and regulators of transcription, in addition to their essential role during site-specific integration. Although most members of the SF3 family form hexameric rings in vitro, the oligomeric nature of Rep68 is unclear due to its propensity to aggregate in solution. We report here a comprehensive study to determine the oligomeric character of Rep68 using a combination of methods that includes sedimentation velocity ultracentrifugation, electron microscopy, and hydrodynamic modeling. We have determined that residue Cys151 induces Rep68 to aggregate in vitro. We show that Rep68 displays a concentration-dependent dynamic oligomeric behavior characterized by the presence of two populations: one with monomers and dimers in slow equilibrium and a second one consisting of a mixture of multiple-ring structures of seven and eight members. The presence of either ATP or ADP induces formation of larger complexes formed by the stacking of multiple rings. Taken together, our results support the idea of a Rep68 molecule that exhibits the flexible oligomeric behavior needed to perform the wide range of functions occurring during the AAV life cycle.

The four Rep proteins of adeno-associated virus (AAV) orchestrate all aspects of its viral life cycle, including transcription regulation, DNA replication, virus assembly, and site-specific integration of the viral genome into the human chromosome 19. All Rep proteins share a central SF3 superfamily helicase domain. In other SF3 members this domain is sufficient to induce oligomerization. However, the helicase domain in AAV Rep proteins (i.e. Rep40/Rep52) as shown by its monomeric characteristic, is not able to mediate stable oligomerization. This observation led us to hypothesize the existence of an as yet undefined structural determinant that regulates Rep oligomerization. In this document, we described a detailed structural comparison between the helicase domains of AAV-2 Rep proteins and those of the other SF3 members. This analysis shows a major structural difference residing in the small oligomerization sub-domain (OD) of Rep helicase domain. In addition, secondary structure prediction of the linker connecting the helicase domain to the origin-binding domain (OBD) indicates the potential to form α-helices. We demonstrate that mutant Rep40 constructs containing different lengths of the linker are able to form dimers, and in the presence of ATP/ADP, larger oligomers. We further identified an aromatic linker residue (Y224) that is critical for oligomerization, establishing it as a conserved signature motif in SF3 helicases. Mutation of this residue critically affects oligomerization as well as completely abolishes the ability to produce infectious virus. Taken together, our data support a model where the linker residues preceding the helicase domain fold into an α-helix that becomes an integral part of the helicase domain and is critical for the oligomerization and function of Rep68/78 proteins through cooperative interaction with the OBD and helicase domains.

Sickle cell anaemia is a severe inherited blood disorder for which there is presently no curative therapy other than allogeneic haematopoietic stem cell (HSC) transplantation. This therapeutic option, however, is not available to most patients because of the lack of a matched related donor. Different genetic strategies aiming to treat the anaemia and prevent sickling are under investigation. They include strategies to transfer a regulated globin gene in autologous HSCs-the most developed approach, which is about to undergo clinical evaluation-, and strategies to either restore endogenous HBG expression, repair or eliminate HBB(S) mutant transcripts, or correct the sickle mutation in HSCs or induced pluripotent stem cells. Their common ultimate goals are to afford therapeutic levels of HbA or HbF in the erythroid progeny of autologous HSCs (sufficient to prevent pathological sickling) and engraft the genetically modified HSCs with minimal short-term toxicity (primarily caused by the conditioning regimen) and long-term toxicity (primarily caused by genotoxicity). We discuss here the status of application of these technologies, outlining recent advances and the hurdles that lay ahead., (© 2011 Blackwell Publishing Ltd.)

Rep68 is a multifunctional protein of the adeno-associated virus (AAV), a parvovirus that is mostly known for its promise as a gene therapy vector. In addition to its role as initiator in viral DNA replication, Rep68 is essential for site-specific integration of the AAV genome into human chromosome 19. Rep68 is a member of the superfamily 3 (SF3) helicases, along with the well-studied initiator proteins simian virus 40 large T antigen (SV40-LTag) and bovine papillomavirus (BPV) E1. Structurally, SF3 helicases share two domains, a DNA origin interaction domain (OID) and an AAA(+) motor domain. The AAA(+) motor domain is also a structural feature of cellular initiators and it functions as a platform for initiator oligomerization. Here, we studied Rep68 oligomerization in vitro in the presence of different DNA substrates using a variety of biophysical techniques and cryo-EM. We found that a dsDNA region of the AAV origin promotes the formation of a complex containing five Rep68 subunits. Interestingly, non-specific ssDNA promotes the formation of a double-ring Rep68, a known structure formed by the LTag and E1 initiator proteins. The Rep68 ring symmetry is 8-fold, thus differing from the hexameric rings formed by the other SF3 helicases. However, similiar to LTag and E1, Rep68 rings are oriented head-to-head, suggesting that DNA unwinding by the complex proceeds bidirectionally. This novel Rep68 quaternary structure requires both the DNA binding and AAA(+) domains, indicating cooperativity between these regions during oligomerization in vitro. Our study clearly demonstrates that Rep68 can oligomerize through two distinct oligomerization pathways, which depend on both the DNA structure and cooperativity of Rep68 domains. These findings provide insight into the dynamics and oligomeric adaptability of Rep68 and serve as a step towards understanding the role of this multifunctional protein during AAV DNA replication and site-specific integration.

The 12/23 rule is a critical step for regulation of V(D)J recombination. To date, only the RAG proteins and high mobility group protein 1 or 2 have been implicated in 12/23 regulation. Through protein fractionation and biochemical experiments, we find that Ku70/Ku80 and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) modulate RAG-mediated cleavage. Modulation of cleavage by Ku70/80 and DNA-PKcs results in preferential inhibition of 12/12 and 23/23 DNA cleavage, thus increasing 12/23 rule specificity. This observation indicates that DNA repair factors, Ku70/80 and DNA-PKcs, might be present upstream of the DNA cleavage events and not recruited downstream as is currently thought, assigning new nonrepair functions to the DNA-dependent protein kinase.

Numerous studies have demonstrated the persistent localization of matrix metalloproteinase (MMP) expression to the interface between invading human colorectal cancer (CRC) cells and surrounding stroma supporting a role for MMPs in CRC invasion and metastasis. The present study sought to determine whether CRC cells of varying metastatic potential would have differential effects on host MMP release. Subcutaneous CRC tumors were generated in BALB/c nude mice using three CRC cell lines: SW480, SW620, and the highly metastatic SW620S5 clone. Representative samples from the subcutaneous CRC were then orthotopically implanted on the cecum of recipient nude mice. Subcutaneous and cecal tumors were analyzed for MMP expression via zymography, western blot, and RT-PCR. In vitro, none of the three cell lines expressed MMP-2 nor MMP-9. In contradistinction, the subcutaneous tumors expressed limited amounts of MMP-2 and MMP-9 while the cecal tumors expressed significant amounts of MMP-2 and MMP-9 as well as other smaller members of the MMP family. MMP-9 mRNA and protein was confirmed as host in origin by RT-PCR with mouse specific primers and a mouse MMP-9 molecular weight of 105 kDa as determined by zymography and western blot analysis. In situ hybridization also localized the mRNA for MMP-9 to the host stromal cells. In conclusion, CRC cells appear incapable of producing MMP-2 and MMP-9 in vitro but are capable of up-regulating host MMP production in vivo. Enhanced host MMP-9 production in metastatic CRC cell-derived subcutaneous and cecal tumors suggests that metastatic colon cells may acquire the expression of important MMP regulating factor(s) in vivo.

Despite the importance of hairpin opening in antigen receptor gene assembly, the molecular machinery that mediates this reaction has not been defined. Here, we show that RAG1 plus RAG2 can open DNA hairpins. Hairpin opening by RAGs is not sequence specific, but in Mg2+, hairpin opening occurs only in the context of a regulated cleavage complex. The chemical mechanism of hairpin opening by RAGs resembles RSS cleavage and 3' end processing by HIV integrase and Mu transposase in that these reactions can proceed through alcoholysis. Mutations in either RAG1 or RAG2 that interfere with RSS cleavage also interfere with hairpin opening, suggesting that RAGs have a single active site that catalyzes several distinct DNA cleavage reactions.