CAR models: next-generation CAR modifications for enhanced T-cell function
2016; Elsevier BV; Volume: 3; Linguagem: Inglês
10.1038/mto.2016.14
ISSN2372-7705
AutoresDaniel Abate‐Daga, Marco L. Davila,
Tópico(s)Advancements in Semiconductor Devices and Circuit Design
ResumoT cells genetically targeted with a chimeric antigen receptor (CAR) to B-cell malignancies have demonstrated tremendous clinical outcomes. With the proof in principle for CAR T cells as a therapy for B-cell malignancies being established, current and future research is being focused on adapting CAR technology to other cancers, as well as enhancing its efficacy and/or safety. The modular nature of the CAR, extracellular antigen-binding domain fused to a transmembrane domain and intracellular T-cell signaling domains, allows for optimization by replacement of the various components. These modifications are creating a whole new class of therapeutic CARs. In this review, we discuss the recent major advances in CAR design and how these modifications will impact its clinical application. T cells genetically targeted with a chimeric antigen receptor (CAR) to B-cell malignancies have demonstrated tremendous clinical outcomes. With the proof in principle for CAR T cells as a therapy for B-cell malignancies being established, current and future research is being focused on adapting CAR technology to other cancers, as well as enhancing its efficacy and/or safety. The modular nature of the CAR, extracellular antigen-binding domain fused to a transmembrane domain and intracellular T-cell signaling domains, allows for optimization by replacement of the various components. These modifications are creating a whole new class of therapeutic CARs. In this review, we discuss the recent major advances in CAR design and how these modifications will impact its clinical application. T-cell-based immunotherapies have come of age as a feasible, safe, and efficacious approach to treating cancer. At the same time, the use of highly personalized, living therapeutics poses multiple challenges. Moreover, immunotherapies involving the genetic modification of T cells, such as those involving expression of chimeric antigen receptors (CAR) to modify T-cell specificity, require an additional level of optimization. In this article, we summarize our current understanding of the key aspects of CAR-T-cell design. This is not meant to be an extensive compilation of the full body of knowledge in the field, but rather an overview of the most relevant finding that have driven the field to its current stage, and those that will likely define its forthcoming directions. Antigen-specificity for a T cell is encoded by the T-cell receptor (TCR).1Sadelain M Rivière I Brentjens R Targeting tumours with genetically enhanced T lymphocytes.Nat Rev Cancer. 2003; 3: 35-45Crossref PubMed Scopus (401) Google Scholar T cells recognize and eradicate infected cells by TCR-mediated detection of microbial antigens, in the form of short amino acids presented by major histocompatibility complex proteins. TCR binding of a specific major histocompatibility complex and peptide combination initiates an intracellular signaling cascade that begins with phosphorylation of immunoreceptor tyrosine-based activation motif (ITAM) domains within TCR accessory proteins CD3ζ, CD3σ, CD3/, and CD3ɛ.2Abraham RT Weiss A Jurkat T cells and development of the T-cell receptor signalling paradigm.Nat Rev Immunol. 2004; 4: 301-308Crossref PubMed Scopus (382) Google Scholar,3Irving BA Weiss A The cytoplasmic domain of the T cell receptor zeta chain is sufficient to couple to receptor-associated signal transduction pathways.Cell. 1991; 64: 891-901Abstract Full Text PDF PubMed Scopus (626) Google Scholar This signaling cascade terminates in T-cell activation and killing of the target cell. T cells can also target cancerous cells by detection of tumor antigens, which can be novel, or normally expressed only in germ cells, or mutated self-antigens (neo-epitopes).4Restifo NP Dudley ME Rosenberg SA Adoptive immunotherapy for cancer: harnessing the T cell response.Nat Rev Immunol. 2012; 12: 269-281Crossref PubMed Scopus (1213) Google Scholar Investigators have confirmed the power of tumor-reactive T cells by isolating tumor-infiltrating lymphocytes (TILs) from patients with metastatic cancer, expanding them ex vivo, and infusing the TILs back into patients.4Restifo NP Dudley ME Rosenberg SA Adoptive immunotherapy for cancer: harnessing the T cell response.Nat Rev Immunol. 2012; 12: 269-281Crossref PubMed Scopus (1213) Google Scholar,5Stevanović S Draper LM Langhan MM Campbell TE Kwong ML Wunderlich JR et al.Complete regression of metastatic cervical cancer after treatment with human papillomavirus-targeted tumor-infiltrating T cells.J Clin Oncol. 2015; 33: 1543-1550Crossref PubMed Scopus (385) Google Scholar Some of these patients have achieved durable complete remission (CRs), which is unheard of with standard cytotoxic chemotherapies.6Dudley ME Yang JC Sherry R Hughes MS Royal R Kammula U et al.Adoptive cell therapy for patients with metastatic melanoma: evaluation of intensive myeloablative chemoradiation preparative regimens.J Clin Oncol. 2008; 26: 5233-5239Crossref PubMed Scopus (1084) Google Scholar However, a major impediment to the adaption of TIL therapy to many cancer patients is the laborious and time-consuming (>2–3 months) process required to achieve a sufficient number of tumor-reactive T cells.7Klapper JA Thomasian AA Smith DM Gorgas GC Wunderlich JR Smith FO et al.Single-pass, closed-system rapid expansion of lymphocyte cultures for adoptive cell therapy.J Immunol Methods. 2009; 345: 90-99Crossref PubMed Scopus (39) Google Scholar CARs provided the requisite technological advance and allowed the creation of a large, bulk population of tumor-reactive T cells within as short as 1 week and mediated positive clinical outcomes in many patients with acute or chronic leukemia.8Hollyman D Stefanski J Przybylowski M Bartido S Borquez-Ojeda O Taylor C et al.Manufacturing validation of biologically functional T cells targeted to CD19 antigen for autologous adoptive cell therapy.J Immunother. 2009; 32: 169-180Crossref PubMed Scopus (232) Google Scholar,9Kochenderfer JN Feldman SA Zhao Y Xu H Black MA Morgan RA et al.Construction and preclinical evaluation of an anti-CD19 chimeric antigen receptor.J Immunother. 2009; 32: 689-702Crossref PubMed Scopus (280) Google Scholar The CAR is a hybrid antigen receptor, part antibody and part TCR, and is composed of an extracellular antigen-binding domain and intracellular signaling domain(s) (Figure 1a).10Davila ML Sauter C Brentjens R CD19-targeted T cells for hematologic malignancies: clinical experience to date.Cancer J. 2015; 21: 470-474Crossref PubMed Scopus (24) Google Scholar Genetic retargeting of a T cell with a CAR endows a new antigen-specificity through the single-chain variable fragment (scFv), which is derived from a tumor-specific antibody.1Sadelain M Rivière I Brentjens R Targeting tumours with genetically enhanced T lymphocytes.Nat Rev Cancer. 2003; 3: 35-45Crossref PubMed Scopus (401) Google Scholar The scFv allows the T cell to bind a tumor antigen and T-cell activation is initiated through the intracellular domains, which are derived from CD3ζ ITAM domains.1Sadelain M Rivière I Brentjens R Targeting tumours with genetically enhanced T lymphocytes.Nat Rev Cancer. 2003; 3: 35-45Crossref PubMed Scopus (401) Google Scholar,3Irving BA Weiss A The cytoplasmic domain of the T cell receptor zeta chain is sufficient to couple to receptor-associated signal transduction pathways.Cell. 1991; 64: 891-901Abstract Full Text PDF PubMed Scopus (626) Google Scholar To complete the genetic construct for the CAR, a hinge and a transmembrane domain (TM), commonly from CD8α or immunoglobulin, bridges the extracellular scFv and intracellular CD3ζ ITAM domains. Early in vitro studies demonstrated that T cells gene-targeted with CARs that have an intracellular signaling domain composed of only CD3ζ, supported T-cell activation and target killing, however, these first-generation CAR T cells had very limited persistence and antitumor efficacy in vivo.11Brocker T Karjalainen K Signals through T cell receptor-zeta chain alone are insufficient to prime resting T lymphocytes.J Exp Med. 1995; 181: 1653-1659Crossref PubMed Scopus (197) Google Scholar Since one of the main advantages to the CAR technology is its modular nature it allows continual refinement and modification to optimize T-cell function, which is how first-generation CARs were replaced with second-generation CARs. The specificity of a TCR is for only a short peptide (8–12 amino acids) from a foreign (or nonself) antigen; so, there is potential for cross-reactivity to similar sequences of amino acids.12Rossjohn J Gras S Miles JJ Turner SJ Godfrey DI McCluskey J T cell antigen receptor recognition of antigen-presenting molecules.Annu Rev Immunol. 2015; 33: 169-200Crossref PubMed Scopus (442) Google Scholar TCR ligation of host antigen could lead to T-cell activation, autoimmunity, and even death. To minimize this potential, T cells require at least two signals to fully activate.13Sharpe AH Freeman GJ The B7-CD28 superfamily.Nat Rev Immunol. 2002; 2: 116-126Crossref PubMed Scopus (1387) Google Scholar The first signal is through the TCR, but the second signal, or costimulation, is mediated through ligation of CD28 by CD80 or CD86, which are normally expressed on antigen-presenting cells (APC).12Rossjohn J Gras S Miles JJ Turner SJ Godfrey DI McCluskey J T cell antigen receptor recognition of antigen-presenting molecules.Annu Rev Immunol. 2015; 33: 169-200Crossref PubMed Scopus (442) Google Scholar,13Sharpe AH Freeman GJ The B7-CD28 superfamily.Nat Rev Immunol. 2002; 2: 116-126Crossref PubMed Scopus (1387) Google Scholar Therefore, when a T cell encounters a cross-reactive peptide expressed on a normal (non-APC) cell, it is unable to provide costimulation and T-cell activation is unsuccessful. However, when APCs are activated, as during inflammation or infection, they upregulate CD80 and CD86 and can induce both signals 1 and 2, thereby supporting full T-cell activation, target killing, and long-term persistence.12Rossjohn J Gras S Miles JJ Turner SJ Godfrey DI McCluskey J T cell antigen receptor recognition of antigen-presenting molecules.Annu Rev Immunol. 2015; 33: 169-200Crossref PubMed Scopus (442) Google Scholar,13Sharpe AH Freeman GJ The B7-CD28 superfamily.Nat Rev Immunol. 2002; 2: 116-126Crossref PubMed Scopus (1387) Google Scholar CAR investigators therefore incorporated the two-signal model of T-cell activation by modifying CARs to include a CD28 costimulatory domain in tandem with CD3ζ ITAM domains (Figure 1a).14Maher J Brentjens RJ Gunset G Rivière I Sadelain M Human T-lymphocyte cytotoxicity and proliferation directed by a single chimeric TCRzeta /CD28 receptor.Nat Biotechnol. 2002; 20: 70-75Crossref PubMed Scopus (688) Google Scholar, 15Hombach A Wieczarkowiecz A Marquardt T Heuser C Usai L Pohl C et al.Tumor-specific T cell activation by recombinant immunoreceptors: CD3 zeta signaling and CD28 costimulation are simultaneously required for efficient IL-2 secretion and can be integrated into one combined CD28/CD3 zeta signaling receptor molecule.J Immunol. 2001; 167: 6123-6131Crossref PubMed Scopus (244) Google Scholar, 16Finney HM Lawson AD Bebbington CR Weir AN Chimeric receptors providing both primary and costimulatory signaling in T cells from a single gene product.J Immunol. 1998; 161: 2791-2797Crossref PubMed Google Scholar These second-generation CARs support in vitro T-cell activation and killing, but more importantly also support efficacious in vivo tumor killing and T-cell persistence. It has also been demonstrated that costimulatory domains other than CD28, such as CD27, 4-1BB, and OX40, provide similar in vivo enhancements to CAR T-cell function and persistence.17Imai C Mihara K Andreansky M Nicholson IC Pui CH Geiger TL et al.Chimeric receptors with 4-1BB signaling capacity provoke potent cytotoxicity against acute lymphoblastic leukemia.Leukemia. 2004; 18: 676-684Crossref PubMed Scopus (540) Google Scholar, 18Song DG Ye Q Poussin M Harms GM Figini M Powell Jr, DJ CD27 costimulation augments the survival and antitumor activity of redirected human T cells in vivo.Blood. 2012; 119: 696-706Crossref PubMed Scopus (252) Google Scholar, 19Hombach AA Abken H Of chimeric antigen receptors and antibodies: OX40 and 41BB costimulation sharpen up T cell-based immunotherapy of cancer.Immunotherapy. 2013; 5: 677-681Crossref PubMed Scopus (15) Google Scholar Second-generation CAR T cells have been confirmed to mediate potent antileukemia responses in phase 1 clinical trials. CR rates up to 90% have been obtained when patients with relapsed and/or refractory B-cell acute lymphoblastic leukemia (B-ALL) were infused with second-generation CD19-targeted T cells that included a CAR with a 4-1BB or CD28 costimulatory domain.20Davila ML Riviere I Wang X Bartido S Park J Curran K et al.Efficacy and toxicity management of 19-28z CAR T cell therapy in B cell acute lymphoblastic leukemia.Sci Transl Med. 2014; 6: 224ra25Crossref PubMed Scopus (1758) Google Scholar, 21Maude SL Frey N Shaw PA Aplenc R Barrett DM Bunin NJ et al.Chimeric antigen receptor T cells for sustained remissions in leukemia.N Engl J Med. 2014; 371: 1507-1517Crossref PubMed Scopus (3552) Google Scholar, 22Lee DW Kochenderfer JN Stetler-Stevenson M Cui YK Delbrook C Feldman SA et al.T cells expressing CD19 chimeric antigen receptors for acute lymphoblastic leukaemia in children and young adults: a phase 1 dose-escalation trial.Lancet. 2015; 385: 517-528Abstract Full Text Full Text PDF PubMed Scopus (2054) Google Scholar While great success has been noted with targeting CD19, there are significant safety and efficacy concerns with adapting this technology to other cancers. Anticipating these concerns, researchers have again looked to the modular nature of the CAR to further refine and optimize this novel antigen-receptor. For the remainder of this review, we will discuss how modifications to the scFv, hinge/spacer, and intracellular domains may render this engineered cell therapy safer and/or more efficacious. The scFv retargets a bulk population of autologous T cells with a new tumor-reactivity. However, recent studies have demonstrated that the scFv can impact CAR function beyond just tumor-specificity. In fact, investigators have demonstrated aspects of scFv design can modulate the safety and/or efficacy of CAR T cells. For example, the nonhuman origin of the antibodies used to create the scFv has resulted in anti-CAR immune responses, which may limit the persistence of the adoptively transferred CAR T cells.23Jensen MC Popplewell L Cooper LJ DiGiusto D Kalos M Ostberg JR et al.Antitransgene rejection responses contribute to attenuated persistence of adoptively transferred CD20/CD19-specific chimeric antigen receptor redirected T cells in humans.Biol Blood Marrow Transplant. 2010; 16: 1245-1256Abstract Full Text Full Text PDF PubMed Scopus (409) Google Scholar Furthermore, this anti-CAR immune response may have more profound implications considering that investigators postulate it resulted in fatal anaphylaxis in patients infused with multiple doses of CAR T cells.24Maus MV Haas AR Beatty GL Albelda SM Levine BL Liu X et al.T cells expressing chimeric antigen receptors can cause anaphylaxis in humans.Cancer Immunol Res. 2013; 1: 26-31Crossref Scopus (414) Google Scholar Therefore, while current lead CARs targeting B-cell malignancies include scFv with mouse origins, CARs targeting other cancers in the developmental pipeline will likely be "humanized" to minimize these immune responses. The affinity of scFv for its target is another CAR feature being modified to optimize gene-targeted T-cell function. CD19 has been an optimal target to establish the proof-of-principle of adoptive CAR T-cell therapy. It has also demonstrated that on-target/off-tumor toxicity is a concern since patients have been induced into long-term periods of B-cell aplasia.21Maude SL Frey N Shaw PA Aplenc R Barrett DM Bunin NJ et al.Chimeric antigen receptor T cells for sustained remissions in leukemia.N Engl J Med. 2014; 371: 1507-1517Crossref PubMed Scopus (3552) Google Scholar,25Kalos M Levine BL Porter DL Katz S Grupp SA Bagg A et al.T cells with chimeric antigen receptors have potent antitumor effects and can establish memory in patients with advanced leukemia.Sci Transl Med. 2011; 3: 95ra73Crossref PubMed Scopus (1796) Google Scholar,26Kochenderfer JN Dudley ME Feldman SA Wilson WH Spaner DE Maric I et al.B-cell depletion and remissions of malignancy along with cytokine-associated toxicity in a clinical trial of anti-CD19 chimeric-antigen-receptor-transduced T cells.Blood. 2012; 119: 2709-2720Crossref PubMed Scopus (1142) Google Scholar No major complications have been described secondary to B-cell aplasia, presumably due to intervention with gamma globulin and/or antibiotics. However, expression of the target on critical tissues, such as ERBB2 on respiratory epithelium, has resulted in death in at least one patient.27Morgan RA Yang JC Kitano M Dudley ME Laurencot CM Rosenberg SA Case report of a serious adverse event following the administration of T cells transduced with a chimeric antigen receptor recognizing ERBB2.Mol Ther. 2010; 18: 843-851Abstract Full Text Full Text PDF PubMed Scopus (1746) Google Scholar As CARs are developed against solid tumor malignancies the tumor targets will likely be shared on normal epithelial tissue, thereby increasing the possibility of dangerous complications. However, investigators have recently demonstrated that differential levels of antigen expression and scFv affinity can be used to differentiate between tumor targets and normal tissue. Investigators have demonstrated that low-affinity scFv's support CAR T-cell-mediated killing of tumor cells that express high level of antigen, but does not support killing of normal cells that express low or normal levels of the same antigen.28Liu X Jiang S Fang C Yang S Olalere D Pequignot EC et al.Affinity-tuned ErbB2 or EGFR chimeric antigen receptor T cells exhibit an increased therapeutic index against tumors in mice.Cancer Res. 2015; 75: 3596-3607Crossref PubMed Scopus (318) Google Scholar,29Caruso HG Hurton LV Najjar A Rushworth D Ang S Olivares S et al.Tuning sensitivity of CAR to EGFR density limits recognition of normal tissue while maintaining potent antitumor activity.Cancer Res. 2015; 75: 3505-3518Crossref PubMed Scopus (259) Google Scholar This discrimination between levels of antigen expression has been demonstrated both in vitro and in vivo and suggests that scFv affinity can be optimized to increase safety when a target is expressed on normal, healthy tissue.28Liu X Jiang S Fang C Yang S Olalere D Pequignot EC et al.Affinity-tuned ErbB2 or EGFR chimeric antigen receptor T cells exhibit an increased therapeutic index against tumors in mice.Cancer Res. 2015; 75: 3596-3607Crossref PubMed Scopus (318) Google Scholar,29Caruso HG Hurton LV Najjar A Rushworth D Ang S Olivares S et al.Tuning sensitivity of CAR to EGFR density limits recognition of normal tissue while maintaining potent antitumor activity.Cancer Res. 2015; 75: 3505-3518Crossref PubMed Scopus (259) Google Scholar A breakthrough in CAR design occurred when it was determined that inclusion of CD3ζ (signal 1) in tandem with CD28 costimulation (signal 2) on a single CAR genetic construct could replicate normal TCR activation and costimulation.14Maher J Brentjens RJ Gunset G Rivière I Sadelain M Human T-lymphocyte cytotoxicity and proliferation directed by a single chimeric TCRzeta /CD28 receptor.Nat Biotechnol. 2002; 20: 70-75Crossref PubMed Scopus (688) Google Scholar, 15Hombach A Wieczarkowiecz A Marquardt T Heuser C Usai L Pohl C et al.Tumor-specific T cell activation by recombinant immunoreceptors: CD3 zeta signaling and CD28 costimulation are simultaneously required for efficient IL-2 secretion and can be integrated into one combined CD28/CD3 zeta signaling receptor molecule.J Immunol. 2001; 167: 6123-6131Crossref PubMed Scopus (244) Google Scholar, 16Finney HM Lawson AD Bebbington CR Weir AN Chimeric receptors providing both primary and costimulatory signaling in T cells from a single gene product.J Immunol. 1998; 161: 2791-2797Crossref PubMed Google Scholar However, research has demonstrated that requiring combinatorial ligation of separate, distinct tumor antigens by bispecific CARs can increase safety, while also supporting efficacious cancer killing.30Kloss CC Condomines M Cartellieri M Bachmann M Sadelain M Combinatorial antigen recognition with balanced signaling promotes selective tumor eradication by engineered T cells.Nat Biotechnol. 2013; 31: 71-75Crossref PubMed Scopus (624) Google Scholar, 31Grada Z Hegde M Byrd T Shaffer DR Ghazi A Brawley VS et al.TanCAR: a novel bispecific chimeric antigen receptor for cancer immunotherapy.Mol Ther Nucleic Acids. 2013; 2: e105Abstract Full Text Full Text PDF PubMed Scopus (332) Google Scholar, 32Lanitis E Poussin M Klattenhoff AW Song D Sandaltzopoulos R June CH et al.Chimeric antigen receptor T cells with dissociated signaling domains exhibit focused antitumor activity with reduced potential for toxicity in vivo.Cancer Immunol Res. 2013; 1: 43-53Crossref PubMed Scopus (246) Google Scholar The underlying technology to this CAR advance relies on disassociating the activation and costimulatory domains onto separate complementary CARs. Therefore, CAR1 has only the CD3ζ activation domain, while CAR 2 has only costimulatory domains. Ligation of CAR1 by its antigenic target or ligation of CAR2 by its antigenic target is insufficient by itself to mediate full T-cell activation since they deliver only 1 signal. However, when both CAR1 and CAR2 bind their respective antigens, CD3ζ (signal 1) and costimulation (signal 2) occur in tandem and support T-cell activation and long-term in vivo function. In addition to this novel CAR design, other groups have created similar dual CAR systems and demonstrated the potential for enhancing safety and/or efficacy of tumor targeting.30Kloss CC Condomines M Cartellieri M Bachmann M Sadelain M Combinatorial antigen recognition with balanced signaling promotes selective tumor eradication by engineered T cells.Nat Biotechnol. 2013; 31: 71-75Crossref PubMed Scopus (624) Google Scholar, 31Grada Z Hegde M Byrd T Shaffer DR Ghazi A Brawley VS et al.TanCAR: a novel bispecific chimeric antigen receptor for cancer immunotherapy.Mol Ther Nucleic Acids. 2013; 2: e105Abstract Full Text Full Text PDF PubMed Scopus (332) Google Scholar, 32Lanitis E Poussin M Klattenhoff AW Song D Sandaltzopoulos R June CH et al.Chimeric antigen receptor T cells with dissociated signaling domains exhibit focused antitumor activity with reduced potential for toxicity in vivo.Cancer Immunol Res. 2013; 1: 43-53Crossref PubMed Scopus (246) Google Scholar For example, a second CAR that is specific for a normal tissue antigen can be conjugated to a suppression domain to prevent killing of normal tissue.33Fedorov VD Themeli M Sadelain M PD-1- and CTLA-4-based inhibitory chimeric antigen receptors (iCARs) divert off-target immunotherapy responses.Sci Transl Med. 2013; 5: 215ra172Crossref PubMed Scopus (484) Google Scholar Investigators propose to use this inhibitory bispecific CAR design to prevent normal tissue destruction.33Fedorov VD Themeli M Sadelain M PD-1- and CTLA-4-based inhibitory chimeric antigen receptors (iCARs) divert off-target immunotherapy responses.Sci Transl Med. 2013; 5: 215ra172Crossref PubMed Scopus (484) Google Scholar,34Fedorov VD Sadelain M Kloss CC Novel approaches to enhance the specificity and safety of engineered T cells.Cancer J. 2014; 20: 160-165Crossref PubMed Scopus (28) Google Scholar The demonstration that combinatorial antigen ligation and/or signal domain dissociation can be used to regulate T-cell activation and function suggest a robust platform for future CAR design manipulations to further enhance safety and/or function. While the scFv can be optimized to increase safety, others have replaced the scFv to create a ligand-based CAR or universal CAR. The ligand-based CAR replaces the scFv with a ligand for a tumor marker, for example, a CAR that expresses a ligand for the IL13 receptor (IL13R) allows redirection of T cells to IL13R expressed on glioblastoma.35Brown CE Badie B Barish ME Weng L Ostberg JR Chang WC et al.Bioactivity and safety of IL13Rα2-redirected chimeric antigen receptor CD8+ T cells in patients with recurrent glioblastoma.Clin Cancer Res. 2015; 21: 4062-4072Crossref PubMed Scopus (426) Google Scholar While ligands sometimes may have multiple binding partners, this IL13-zetakine is mutated to be highly-specific for the IL13R for glioblastoma. Universal CAR systems have also been developed to broaden the clinical applicability of CAR T-cell therapy (Figure 1b). These universal CARs retarget patients' T cells and mediate an antitumor response, regardless of cancer diagnosis. This technology relies on replacing the scFv with a binding domain that is specific for a tagged protein or molecule, such as biotin or fluorescein isothiocyanate.36Urbanska K Lanitis E Poussin M Lynn RC Gavin BP Kelderman S et al.A universal strategy for adoptive immunotherapy of cancer through use of a novel T-cell antigen receptor.Cancer Res. 2012; 72: 1844-1852Crossref PubMed Scopus (211) Google Scholar,37Tamada K Geng D Sakoda Y Bansal N Srivastava R Li Z et al.Redirecting gene-modified T cells toward various cancer types using tagged antibodies.Clin Cancer Res. 2012; 18: 6436-6445Crossref PubMed Scopus (168) Google Scholar The extracellular portion of the universal CAR is juxtaposed to a transmembrane domain, which is followed by intracellular sequences comprised of T-cell costimulatory and activation domains (Figure 1b). Therefore, after a tumor-specific antibody, labeled with fluorescein isothiocyanate or biotin, binds its target on a tumor cell it can then be bound by the universal CAR, which will support ligation, activation of the T cell, and killing of the tumor cell.36Urbanska K Lanitis E Poussin M Lynn RC Gavin BP Kelderman S et al.A universal strategy for adoptive immunotherapy of cancer through use of a novel T-cell antigen receptor.Cancer Res. 2012; 72: 1844-1852Crossref PubMed Scopus (211) Google Scholar,37Tamada K Geng D Sakoda Y Bansal N Srivastava R Li Z et al.Redirecting gene-modified T cells toward various cancer types using tagged antibodies.Clin Cancer Res. 2012; 18: 6436-6445Crossref PubMed Scopus (168) Google Scholar Research has validated the function of both universal CAR T-cell systems in animal models.36Urbanska K Lanitis E Poussin M Lynn RC Gavin BP Kelderman S et al.A universal strategy for adoptive immunotherapy of cancer through use of a novel T-cell antigen receptor.Cancer Res. 2012; 72: 1844-1852Crossref PubMed Scopus (211) Google Scholar,37Tamada K Geng D Sakoda Y Bansal N Srivastava R Li Z et al.Redirecting gene-modified T cells toward various cancer types using tagged antibodies.Clin Cancer Res. 2012; 18: 6436-6445Crossref PubMed Scopus (168) Google Scholar While the universal CAR T-cell technology has not been evaluated in patients as of yet, it has the major advantage that it can be applied to the many tumor-specific antibodies that have already been approved for clinical use or are currently in development. The hinge, spacer, and transmembrane domains connect the scFv to the activation domains and anchor the CAR in the T-cell membrane.1Sadelain M Rivière I Brentjens R Targeting tumours with genetically enhanced T lymphocytes.Nat Rev Cancer. 2003; 3: 35-45Crossref PubMed Scopus (401) Google Scholar Recent studies have demonstrated that these domains can have significant impact on CAR T-cell function and can be optimized to enhance antigen binding and T-cell signaling. This was revealed by demonstrating spacers are required to bind membrane-proximal epitopes and support efficacious target killing.38James SE Greenberg PD Jensen MC Lin Y Wang J Till BG et al.Antigen sensitivity of CD22-specific chimeric TCR is modulated by target epitope distance from the cell membrane.J Immunol. 2008; 180: 7028-7038Crossref PubMed Scopus (172) Google Scholar, 39Haso W Lee DW Shah NN Stetler-Stevenson M Yuan CM Pastan IH et al.Anti-CD22-chimeric antigen receptors targeting B-cell precursor acute lymphoblastic leukemia.Blood. 2013; 121: 1165-1174Crossref PubMed Scopus (413) Google Scholar, 40Guest RD Hawkins RE Kirillova N Cheadle EJ Arnold J O'Neill A et al.The role of extracellular spacer regions in the optimal design of chimeric immune receptors: evaluation of four different scFvs and antigens.J Immunother. 2005; 28: 203-211Crossref PubMed Scopus (225) Google Scholar In contrast, spacers reduce function when the epitope is expressed near the amino terminal portion of the cell surface protein.40Guest RD Hawkins RE Kirillova N Cheadle EJ Arnold J O'Neill A et al.The role of extracellular spacer regions in the optimal design of chimeric immune receptors: evaluation of four different scFvs and antigens.J Immunother. 2005; 28: 203-211Crossref PubMed Scopus (225) Google Scholar However, spacer length is not the only important consideration. Investigators have also determined that inclusion of Fc domains can support binding of antibodies that activate immune cells.41Hudecek M Sommermeyer D Kosasih PL Silva-Benedict A Liu L Rader C et al.The nonsignaling extracellular spacer domain of chimeric antigen receptors is decisive for in vivo antitumor activity.Cancer Immunol Res. 2015; 3: 125-135Crossref PubMed Scopus (312) Google Scholar, 42Hombach A Hombach AA Abken H Adoptive immunotherapy with genetically engineered T cells: modification of the IgG1 Fc 'spacer' domain in the extracellular moiety of chimeric antigen receptors avoids 'off-target' activation and unintended initiation of an innate immune response.Gene Ther. 2010; 17: 1206-1213Crossref PubMed Scopus (158) Google Scholar, 43Jonnalagadda M Mardiros A Urak R Wang X Hoffman LJ Bernanke
Referência(s)