Control of large, established tumor xenografts with genetically retargeted human T cells containing CD28 and CD137 domains. Proc Natl Acad Sci U S A. 2009;106:3360-3365. [PMID: 19211796 DOI: 10.1073/pnas.0813101106]

Anti-GD3 chimeric sFv-CD28/T-cell receptor zeta designer T cells for treatment of metastatic melanoma and other neuroectodermal tumors

PURPOSE

The aims of this study are to compare antitumor activities of two generations of GD3-specific chimeric antigen receptors (CAR) in human primary T lymphocytes in vitro and to evaluate the antitumor efficacy of using a combination of systemic infusion of interleukin-2 (IL2) and designer T cells to eradicate subcutaneous established GD3+ melanoma in nude mice.

EXPERIMENTAL DESIGN

Antitumor activities were compared for two generations of designer T cells, the progenitor first-generation with immunoglobulin T-cell receptor (TCR) with Signal 1 and the second-generation designer T cells with Signal 1+2. Osmotic IL2 pumps were used to deliver the maximum tolerated dose of IL2 to enhance the antitumor effects of designer T cells on subcutaneous established melanoma in nude mice.

RESULTS

Melanoma is associated with high expression of ganglioside GD3, which has been targeted with modest effect in antibody therapies. We previously showed that an anti-GD3 CAR (sFv-TCRzeta) will recruit T cells to target this non-T-dependent antigen, with potent killing of melanoma cells. Here, we report the addition of a CD28 costimulation domain to create a second-generation CAR, called Tandem for two signals. We show that this Tandem sFv-CD28/TCRzeta receptor on T cells confers advantages of improved cytokine secretion, cytotoxicity, proliferation, and clonal expansion on tumor contact versus the same CAR without costimulation. In an adoptive transfer model using established melanoma tumors, designer T cells with CD28 showed a 50% rate of complete remissions but only where IL2 was supplemented.

CONCLUSIONS

As a reagent for clinical development, the second-generation product is shown to have superior properties to warrant its preference for clinical designer T-cell immunotherapy for melanoma and other tumors. Systemic IL2 was required for optimal activity in an established tumor model.

Chimeric antigen receptor-engineered T cells for immunotherapy of cancer

CD4⁺ and CD8⁺ T lymphocytes are powerful components of adaptive immunity, which essentially contribute to the elimination of tumors. Due to their cytotoxic capacity, T cells emerged as attractive candidates for specific immunotherapy of cancer. A promising approach is the genetic modification of T cells with chimeric antigen receptors (CARs). First generation CARs consist of a binding moiety specifically recognizing a tumor cell surface antigen and a lymphocyte activating signaling chain. The CAR-mediated recognition induces cytokine production and tumor-directed cytotoxicity of T cells. Second and third generation CARs include signal sequences from various costimulatory molecules resulting in enhanced T-cell persistence and sustained antitumor reaction. Clinical trials revealed that the adoptive transfer of T cells engineered with first generation CARs represents a feasible concept for the induction of clinical responses in some tumor patients. However, further improvement is required, which may be achieved by second or third generation CAR-engrafted T cells.

Ex vivo culture of chimeric antigen receptor T cells generates functional CD8+ T cells with effector and central memory-like phenotype

The anti-tumor efficacy of adoptively transferred T cells requires their in vivo persistence and memory polarization. It is unknown if human chimeric antigen receptor (CAR)-expressing T cells can also undergo memory polarization. We examined the functional status of CAR CD8(+) T cells, re-directed to Lewis Y antigen (LeY-T), throughout a period of ex vivo expansion. Immediately before culture CD8(+) T cells comprised a mixture of phenotypes including naive (CD45RA(+)/CCR7(+)/CD27(+)/CD28(+)/perforin-), central memory (CM, CD45RA(-)/CCR7(lo)/CD27(+)/CD28(+)/perforin(lo)), effector memory (EM, CD45RA(-)/CCR7(-)/CD27(+)/CD28(+)/perforin(mod)) and effector (Eff, CD45RA(+)/CCR7(-)/CD27(-)/CD28(-)/perforin(hi)) cells. After transduction and expansion culture of peripheral blood mononuclear cells from normal donors or multiple myeloma patients, CD8(+) LeY-T cells polarized to EM- and CM-like phenotype. CD8(+) LeY-T cells differed from starting CD8(+) CM and EM T cells in that CD27, but not CD28, was downregulated. In addition, CD8(+) LeY-T cells expressed high levels of perforin, similar to starting CD8(+) Eff. CD8(+) LeY-T cells also showed hallmarks of both memory and Eff function, underwent homeostatic proliferation in response to interleukin (IL)-15, and showed interferon (IFN)-γ production and cytotoxicity in response to Le-Y antigen on OVCAR-3 (human ovarian adenocarcinoma) cells. This study confirms CD8(+) LeY-T cells have a CM- and EM-like phenotype and heterogeneous function consistent with potential to persist in vivo after adoptive transfer.

Engineering CD19-specific T lymphocytes with interleukin-15 and a suicide gene to enhance their anti-lymphoma/leukemia effects and safety

T lymphocytes expressing a chimeric antigen receptor (CAR) targeting the CD19 antigen (CAR.19) may be of value for the therapy of B-cell malignancies. Because the in vivo survival, expansion and anti-lymphoma activity of CAR.19⁺ T cells remain suboptimal even when the CAR contains a CD28 costimulatory endodomain, we generated a novel construct that also incorporates the interleukin-15 (IL15) gene and an inducible caspase-9-based suicide gene (iC9/CAR.19/IL15). We found that compared to CAR.19⁺ T cells, iC9/CAR.19/IL15⁺ T cells had: (i) greater numeric expansion upon antigen stimulation (10-fold greater expansion in vitro, and 3 to 15 fold greater expansion in vivo) and reduced cell death rate (Annexin-V⁺/7-AAD⁺ cells 10% ± 6% for iC9/CAR.19/IL15⁺ T cells and 32% ± 19% CAR.19⁺ T cells); (ii) reduced expression of the programmed death 1 (PD-1) receptor upon antigen stimulation (PD-1⁺ cells <15% for iC9/CAR.19/IL15⁺ T cells versus >40% for CAR.19⁺ T cells); (iii) improved anti-tumor effects in vivo (from 4.7 to 5.4-fold reduced tumor growth). In addition, iC9/CAR.19/IL15⁺ T cells were efficiently eliminated upon pharmacologic activation of the suicide gene. In summary, this strategy safely increases the anti-lymphoma/leukemia effects of CAR.19-redirected T lymphocytes and may be a useful approach for treatment of patients with B-cell malignancies.

Adoptive immunotherapy for B-cell malignancies with autologous chimeric antigen receptor modified tumor targeted T cells

Chemotherapy-resistant B-cell hematologic malignancies may be cured with allogeneic hematopoietic stem cell transplantation (HSCT), demonstrating the potential susceptibility of these tumors to donor T-cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. For this reason, there is an urgent need for less-toxic forms of immune-based cellular therapy to treat these malignancies. Adoptive transfer of autologous T cells genetically modified to express chimeric antigen receptors (CARs) targeted to specific tumor-associated antigens represents an attractive means of overcoming the limitations of conventional HSCT. To this end, investigators have generated CARs targeted to various antigens expressed by B-cell malignancies, optimized the design of these CARs to enhance receptor mediated T cell signaling, and demonstrated significant anti-tumor efficacy of the resulting CAR modified T cells both in vitro and in vivo mouse tumor models. These encouraging preclinical data have justified the translation of this approach to the clinical setting with currently 12 open clinical trials and one completed clinical trial treating various B-cell malignancies utilizing CAR modified T cells targeted to either the CD19 or CD20 B-cell specific antigens.

T cells and stromal fibroblasts in human tumor microenvironments represent potential therapeutic targets

The immune system of cancer patients recognizes tumor-associated antigens expressed on solid tumors and these antigens are able to induce tumor-specific humoral and cellular immune responses. Diverse immunotherapeutic strategies have been used in an attempt to enhance both antibody and T cell responses to tumors. While several tumor vaccination strategies significantly increase the number of tumor-specific lymphocytes in the blood of cancer patients, most vaccinated patients ultimately experience tumor progression. CD4+ and CD8+ T cells with an effector memory phenotype infiltrate human tumor microenvironments, but most are hyporesponsive to stimulation via the T cell receptor (TCR) and CD28 under conditions that activate memory T cells derived from the peripheral blood of the cancer patients or normal donors. Attempts to identify cells and molecules responsible for the TCR signaling arrest of tumor-infiltrating T cells have focused largely upon the immunosuppressive effects of tumor cells, tolerogenic dendritic cells and regulatory T cells. Here we review potential mechanisms by which human T cell function is arrested in the tumor microenvironment with a focus on the immunomodulatory effects of stromal fibroblasts. Determining in vivo which cells and molecules are responsible for the TCR arrest in human tumor-infiltrating T cells will be necessary to formulate and test strategies to prevent or reverse the signaling arrest of the human T cells in situ for a more effective design of tumor vaccines. These questions are now addressable using novel human xenograft models of tumor microenvironments.

4-1BB and CD28 signaling plays a synergistic role in redirecting umbilical cord blood T cells against B-cell malignancies

Umbilical cord blood (UCB) T cells can be redirected to kill leukemia and lymphoma cells by engineering with a single-chain chimeric antigen receptor (CAR) and thus may have general applications in adoptive cell therapy. However, the role of costimulatory molecules in UCB T-cell activation and effector functions in context with CAR remains elusive. To investigate the effect of costimulatory molecules (4-1BB and CD28) on UCB T cells, we transduced UCB T cells with lentiviral vectors expressing Green Fluorescent Protein (GFP) and CAR for CD19 containing an intracellular domain of the CD3zeta chain and either a 4-1BB (UCB-19BBzeta) or a CD28 intracellular domain (UCB-1928zeta), both (UCB-1928BBzeta), or neither (UCB-19zeta). We found that UCB-19BBzeta and UCB-28BBzeta T cells exhibited more cytotoxicity to CD19(+) leukemia and lymphoma cell lines than UCB-19zeta and UCB-1928zeta, although differences in secretion of interleukin-2 and interferon-gamma by these T cells were not evident. In vivo adoptive transfer of these T cells into intraperitoneal tumor-bearing mice demonstrated that UCB-19BBzeta and UCB-1928BBzeta T cells mounted the most potent antitumor response. The mice adoptively transferred with UCB-1928BBzeta cells survived longer than the mice with UCB-19BBzeta. Moreover, UCB-1928BBzeta T cells mounted a more robust antitumor response than UCB-19BBzeta in a systemic tumor model. Our data suggest a synergistic role of 4-1BB and CD28 costimulation in engineering antileukemia UCB effector cells and implicate a design for redirected UCB T-cell therapy for refractory leukemia.

Mathematical modeling of chimeric TCR triggering predicts the magnitude of target lysis and its impairment by TCR downmodulation

We investigated relationships among chimeric TCR (cTCR) expression density, target Ag density, and cTCR triggering to predict lysis of target cells by cTCR(+) CD8(+) T human cells as a function of Ag density. Triggering of cTCR and canonical TCR by Ag could be quantified by the same mathematical equation, but cTCR represented a special case in which serial triggering was abrogated. The magnitude of target lysis could be predicted as a function of cTCR triggering, and the predicted minimum cTCR density required for maximal target lysis by CD20-specific cTCR was experimentally tested. cTCR density below approximately 20,000 cTCR/cell impaired target lysis, but increasing cTCR expression above this density did not improve target lysis or Ag sensitivity. cTCR downmodulation to densities below this critical minimum by interaction with Ag-expressing targets limited the sequential lysis of targets in a manner that could be predicted based on the number of cTCRs remaining. In contrast, acute inhibition of lysis of primary, intended targets (e.g., leukemic B cells) due to the presence of an excess of secondary targets (e.g., normal B cells) was dependent on the Ag density of the secondary target but occurred at Ag densities insufficient to promote significant cTCR downmodulation, suggesting a role for functional exhaustion rather than insufficient cTCR density. This suggests increasing cTCR density above a critical threshold may enhance sequential lysis of intended targets in isolation, but will not overcome the functional exhaustion of cTCR(+) T cells encountered in the presence of secondary targets with high Ag density.

Genetic redirection of T cells for cancer therapy

Adoptive immunotherapy can induce dramatic tumor regressions in patients with melanoma or viral-induced malignancies, but extending this approach to many common cancers has been hampered by a lack of naturally occurring tumor-specific T cells. In this review, we describe recent advances in the genetic modification of T cells using genes encoding cell-surface receptors specific for tumor-associated antigen. Using genetic modification, the many functional properties of T cells, including cytokine secretion and cytolytic capacity, are redirected from their endogenous specificity toward the elimination of tumor cells. Advances in gene design, vectors, and cell production are discussed, and details of the progress in clinical application of this approach are provided.

Case report of a serious adverse event following the administration of T cells transduced with a chimeric antigen receptor recognizing ERBB2

In an attempt to treat cancer patients with ERBB2 overexpressing tumors, we developed a chimeric antigen receptor (CAR) based on the widely used humanized monoclonal antibody (mAb) Trastuzumab (Herceptin). An optimized CAR vector containing CD28, 4-1BB, and CD3zeta signaling moieties was assembled in a gamma-retroviral vector and used to transduce autologous peripheral blood lymphocytes (PBLs) from a patient with colon cancer metastatic to the lungs and liver, refractory to multiple standard treatments. The gene transfer efficiency into autologous T cells was 79% CAR(+) in CD3(+) cells and these cells demonstrated high-specific reactivity in in vitro coculture assays. Following completion of nonmyeloablative conditioning, the patient received 10(10) cells intravenously. Within 15 minutes after cell infusion the patient experienced respiratory distress, and displayed a dramatic pulmonary infiltrate on chest X-ray. She was intubated and despite intensive medical intervention the patient died 5 days after treatment. Serum samples after cell infusion showed marked increases in interferon-gamma (IFN-gamma), granulocyte macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10, consistent with a cytokine storm. We speculate that the large number of administered cells localized to the lung immediately following infusion and were triggered to release cytokine by the recognition of low levels of ERBB2 on lung epithelial cells.

Gene therapy for mesothelioma and lung cancer

Both malignant pleural mesothelioma and advanced stage lung cancer are associated with a poor prognosis. Unfortunately, current treatment regimens have had only a modest effect on their progressive course. Gene therapy for thoracic malignancies represents a novel therapeutic approach and has been evaluated in a number of clinical trials over the last two decades. Using viral vectors or anti-sense RNA, strategies have included induction of apoptosis, tumor suppressor gene replacement, suicide gene expression, cytokine-based therapy, various vaccination approaches, and adoptive transfer of modified immune cells. This review will consider the clinical results, limitations, and future directions of gene therapy trials for thoracic malignancies.

Natural expression of the CD19 antigen impacts the long-term engraftment but not antitumor activity of CD19-specific engineered T cells

T cells gene-modified to express chimeric Ag receptors (CARs) have shown potent antitumor activity in vivo and are in clinical trials at locations worldwide. However, CAR activity has been investigated in mouse models in which Ag expression is restricted to the tumor. To explore the impact of normal tissue expression of the target Ag, we developed a mouse CD19-specific CAR to investigate antitumor efficacy against a syngeneic B cell lymphoma cell line within a background of normal CD19(+) host B cells. Mouse T cells engrafted with the amCD19CD3zeta CAR specifically lysed A20 lymphoma targets and B cells in vitro. These T cells also eradicated a 12-d established disseminated A20 lymphoma in mice preconditioned with 6 Gy total body irradiation. In the short-term (7 d after adoptive transfer), amCD19z T cells underwent Ag-dependent proliferation in vivo with a concomitant depletion in host B cell levels. However, the levels of amCD19z CAR(+) T cells decreased significantly at later time points, at which point host B cells returned, eventually reaching normal levels. In contrast, CAR(+) T cells lacking a signaling domain or specificity for mCD19 persisted over extended periods in blood and spleen. Importantly, no overt clinical signs of autotoxicity were observed in tumor-free or tumor-bearing mice treated with amCD19z T cells over an extended period of time. These observations highlight the importance of studying the activity of CAR(+) T cells in autologous models that have the normal range of tissue expression of Ag.

HER2-specific T cells target primary glioblastoma stem cells and induce regression of autologous experimental tumors

PURPOSE

Glioblastoma multiforme (GBM) is the most aggressive human primary brain tumor and is currently incurable. Immunotherapies have the potential to target GBM stem cells, which are resistant to conventional therapies. Human epidermal growth factor receptor 2 (HER2) is a validated immunotherapy target, and we determined if HER2-specific T cells can be generated from GBM patients that will target autologous HER2-positive GBMs and their CD133-positive stem cell compartment.

EXPERIMENTAL DESIGN

HER2-specific T cells from 10 consecutive GBM patients were generated by transduction with a retroviral vector encoding a HER2-specific chimeric antigen receptor. The effector function of HER2-specific T cells against autologous GBM cells, including CD133-positive stem cells, was evaluated in vitro and in an orthotopic murine xenograft model.

RESULTS

Stimulation of HER2-specific T cells with HER2-positive autologous GBM cells resulted in T-cell proliferation and secretion of IFN-gamma and interleukin-2 in a HER2-dependent manner. Patients' HER2-specific T cells killed CD133-positive and CD133-negative cells derived from primary HER2-positive GBMs, whereas HER2-negative tumor cells were not killed. Injection of HER2-specific T cells induced sustained regression of autologous GBM xenografts established in the brain of severe combined immunodeficient mice.

CONCLUSIONS

Gene transfer allows the reliable generation of HER2-specific T cells from GBM patients, which have potent antitumor activity against autologous HER2-positive tumors including their putative stem cells. Hence, the adoptive transfer of HER2-redirected T cells may be a promising immunotherapeutic approach for GBM.

Non-MHC-dependent redirected T cells against tumor cells

Adoptive transfer of T cells with restricted tumor specificity provides a promising approach to immunotherapy of cancers. However, the isolation of autologous cytotoxic T cells that recognize tumor-associated antigens is time consuming and fails in many instances. Alternatively, gene modification with tumor antigen-specific T-cell receptors (TCR) or chimeric antigen receptors (CARs) can be used to redirect the specificity of large numbers of immune cells toward the malignant cells. Chimeric antigen receptors are composed of the single-chain variable fragment (scFv) of a tumor-recognizing antibody cloned in frame with human T-cell signaling domains (e.g., CD3zeta, CD28, OX40, 4-1BB), thus combining the specificity of antibodies with the effector functions of cytotoxic T cells. Upon antigen binding, the intracellular signaling domains of the CAR initiate cellular activation mechanisms including cytokine secretion and cytolysis of the antigen-positive target cell.In this chapter, we provide detailed protocols for large-scale ex vivo expansion of T cells and manufacturing of medium-scale batches of CAR-expressing T cells for translational research by mRNA electroporation. An anti-CD19 chimeric receptor for the targeting of leukemias and lymphomas was used as a model system. We are currently scaling up the protocols to adapt them to cGMP production of a large number of redirected T cells for clinical applications.

Adoptive cellular therapy

Cell-based therapies with various lymphocytes and antigen-presenting cells are promising approaches for cancer immunotherapy. The transfusion of T lymphocytes, also called adoptive cell therapy (ACT), is an effective treatment for viral infections, has induced regression of cancer in early stage clinical trials, and may be a particularly important and efficacious modality in the period following hematopoietic stem cell transplantation (HSCT). Immune reconstitution post-SCT is often slow and incomplete, which in turn leads to an increased risk of infection and may impact relapse risk in patients with malignant disease. Immunization post-HSCT is frequently unsuccessful, due to the prolonged lymphopenia, especially of CD4 T cells, seen following transplant. ACT has the potential to enhance antitumor and overall immunity, and augment vaccine efficacy in the post-transplant setting. The ability to genetically engineer lymphocyte subsets has the further potential to improve the natural immune response, correct impaired immunity, and redirect T cells to an antitumor effector response. This chapter focuses on various applications of ACT for cancer immunotherapy, and we discuss some of the latest progress and hurdles in translating these technologies to the clinic.

Treatment of lymphoma with adoptively transferred T cells

BACKGROUND

Chemotherapy-resistant lymphomas can be cured with allogeneic hematopoietic cell transplantation, demonstrating the susceptibility of these tumors to T cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. Efforts have, therefore, been made to develop alternative T cell based therapies, and there is growing evidence that adoptive therapy with T cells targeted to lymphoma-associated antigens may be a safe and effective new method for treating this group of diseases.

OBJECTIVE/METHODS

We review publications on adoptive therapy with ex vivo expanded T cells targeting viral antigens, as well as genetically modified autologous T cells, as strategies for the treatment of lymphoma, with the goal of providing an overview of these approaches.

RESULTS/CONCLUSIONS

Epstein-Barr virus specific T cell therapy is an effective and safe method of treating Epstein-Barr virus associated lymphomas; however, most lymphoma subtypes do not express EBV antigens. For these diseases, adoptive immunotherapy with genetically modified T cells expressing chimeric T cell receptors targeting lymphoma-associated antigens such as CD19 and CD20 appears to be a promising alternative. Recent innovations including enhanced co-stimulation, exogenous cytokine administration and use of memory T cells promise to overcome many of the limitations and pitfalls initially encountered with this approach.

Adoptive immunotherapy for cancer: the next generation of gene-engineered immune cells

Adoptive cellular immunotherapy involving transfer of tumor-reactive T cells has shown some notable antitumor responses in a minority of cancer patients. In particular, transfer of tumor-infiltrating lymphocytes has resulted in long-term objective responses in patients with advanced melanoma. However, the inability to isolate sufficient numbers of tumor-specific T cells from most malignancies has restricted the broad utility of this approach. An emerging approach to circumvent this limitation involves the genetic modification of effector cells with T cell receptor (TCR) transgenes or chimeric single-chain variable fragment (scFv) receptors that can specifically redirect T cells to tumor. There has been much progress in the design of TCR and scFv receptors to enhance the antigen-specific activation of effector cells and their trafficking and persistence in vivo. Considerable effort has been directed toward improving the safety of this approach and reducing the immunogenicity of the receptor. This review discusses the latest developments in the field of adoptive immunotherapy using genetically modified immune cells that have been transduced with either TCR or scFv receptor transgenes and used in preclinical and clinical settings as anticancer agents.

Engineering lymphocyte subsets: tools, trials and tribulations

Cell-based therapies with various lymphocyte subsets hold promise for the treatment of several diseases, including cancer and disease resulting from inflammation and infection. The ability to genetically engineer lymphocyte subsets has the potential to improve the natural immune response and correct impaired immunity. In this Review we focus on the lymphocyte subsets that have been modified genetically or by other means for therapeutic benefit, on the technologies used to engineer lymphocytes and on the latest progress and hurdles in translating these technologies to the clinic.

Antibody-mediated B-cell depletion before adoptive immunotherapy with T cells expressing CD20-specific chimeric T-cell receptors facilitates eradication of leukemia in immunocompetent mice

We have established a model of leukemia immunotherapy using T cells expressing chimeric T-cell receptors (cTCRs) targeting the CD20 molecule expressed on normal and neoplastic B cells. After transfer into human CD20 (hCD20) transgenic mice, cTCR(+) T cells showed antigen-specific delayed egress from the lungs, concomitant with T-cell deletion. Few cTCR(+) T cells reached the bone marrow (BM) in hCD20 transgenic mice, precluding effectiveness against leukemia. Anti-hCD20 antibody-mediated B-cell depletion before adoptive T-cell therapy permitted egress of mouse CD20-specific cTCR(+) T cells from the lungs, enhanced T-cell survival, and promoted cTCR(+) T cell-dependent elimination of established mouse CD20(+) leukemia. Furthermore, CD20-specific cTCR(+) T cells eliminated residual B cells refractory to depletion with monoclonal antibodies. These findings suggest that combination of antibody therapy that depletes antigen-expressing normal tissues with adoptive T-cell immunotherapy enhances the ability of cTCR(+) T cells to survive and control tumors.

Immunotherapy of human cancers using gene modified T lymphocytes

Adoptive T cell therapies can produce objective clinical responses in patients with hematologic and solid malignancies. Genetic manipulation of T lymphocytes has been proposed as a means of increasing the potency and range of this anti-tumor activity. We now review how coupling expression of transgenic receptors with countermeasures against potent tumor immune evasion strategies is proving highly effective in pre-clinical models and describe how these approaches are being evaluated in human subjects.

Genetic modification of T cells with IL-21 enhances antigen presentation and generation of central memory tumor-specific cytotoxic T-lymphocytes

An optimized antigen-presenting cell for tumor immunotherapy should produce a robust antigen specific cytotoxic T lymphocytes (CTL) response to tumor-associated antigens, which can persist in vivo and expand on antigen reencounter. Interleukin (IL)-21 synergizes with other gamma-chain cytokines to enhance the frequency and cytotoxicity of antigen-specific CTL. As T cells themselves may serve as effective antigen-presenting cells (T antigen-presenting cells; TAPC) and may be useful in vivo as cellular vaccines, we examined whether CD8(+) T cells genetically modified to produce IL-21 could induce immune responses to tumor associated antigen peptides in healthy human leukocyte antigen-A2(+) donors. We found that IL-21 modified TAPC enhanced both the proliferation and survival of MART-1 specific CD8(+) T cells, which were enriched by >8-fold over cultures with control nontransgenic TAPC. MART-1-specific CTL produced interferon-gamma in response to cognate peptide antigen and killed primary tumor cells expressing MART-1 in a major histocompatibility complex restricted manner. IL-21 modified TAPC similarly enhanced generation of functional CTL against melanoma antigen gp100 and the B-cell chronic lymphocytic leukemia associated RHAMM antigen. Antigen-specific CTL generated using IL-21 gene-modified TAPC had a central memory phenotype characterized by CD45RA(-), CD44(high), CD27(high), CD28(high), CD62L(high), and IL-7 receptor-alpha(high), contrasting with the terminal effector phenotype of CTL generated in the absence of IL-21. Thus, TAPC stimulation in the presences of IL-21 enhances proliferation of tumor antigen-specific T cells and favors induction of a central memory phenotype, which may improve proliferation, survival, and efficacy of T-cell based therapies for the treatment of cancer.

Chimeric antigen receptors combining 4-1BB and CD28 signaling domains augment PI3kinase/AKT/Bcl-XL activation and CD8+ T cell-mediated tumor eradication

To enhance the strength of activation afforded by tumor antigen-specific receptors, we investigated the effect of adding combined CD28 and 4-1BB costimulatory signaling domains to a chimeric antigen receptor (CAR) specific for prostate-specific membrane antigen (PSMA). Having transferred receptors encompassing the CD28, 4-1BB, and/or CD3zeta cytoplasmic domains in primary human CD8(+) T cells, we find that the P28BBz receptor, which includes all three signaling domains, is superior to receptors that only include one or two of these domains in promoting cytokine release, in vivo T-cell survival and tumor elimination following intravenous T-cell administration to tumor-bearing severe combined immunodeficient (SCID)/beige mice. Upon in vitro exposure to PSMA, the P28BBZ receptor-induced the strongest PI(3)Kinase/Akt activation and Bcl-X(L) expression, and the least apoptosis in transduced peripheral blood CD8(+) T cells. These findings further support the concept of integrating optimized costimulatory properties into recombinant antigen receptors to augment the survival and function of genetically targeted T cells within the tumor microenvironment.

Cellular immunotherapy for ovarian cancer

BACKGROUND

Ovarian cancer is frequently diagnosed at an advanced stage, and although initially responsive to surgery and chemotherapy, has a high rate of recurrence and mortality. Cellular immunotherapy may offer the prospect of treatment to prevent or delay recurrent metastatic disease.

OBJECTIVE

To provide an overview of current innovations in cellular immunotherapy for ovarian cancer, with an emphasis on dendritic cell vaccination and adoptive T-cell immunotherapy.

METHODS

Three key areas are explored in this review: first, an appraisal of the current state of the art of cellular immunotherapy for treatment of ovarian cancer; second, a discussion of the immunological defenses erected by ovarian cancer to prevent immunological attack, with an emphasis on the role of tumor-associated regulatory T cells; and third, an exploration of innovative techniques that may enhance the ability of cellular immunotherapy to overcome ovarian tumor-associated immune suppression.

RESULTS/CONCLUSION

Ovarian cancer is recognized as a paradigm for tumor-associated immune suppression. Innovative approaches for antagonism of tumor-associated regulatory T-cell infiltration and redirection of self antigen-driven regulatory T-cell activation may provide the key to development of future strategies for cellular immunotherapy against ovarian cancer.

Chimeric receptors containing CD137 signal transduction domains mediate enhanced survival of T cells and increased antileukemic efficacy in vivo

Persistence of T cells engineered with chimeric antigen receptors (CARs) has been a major barrier to use of these cells for molecularly targeted adoptive immunotherapy. To address this issue, we created a series of CARs that contain the T cell receptor-zeta (TCR-zeta) signal transduction domain with the CD28 and/or CD137 (4-1BB) intracellular domains in tandem. After short-term expansion, primary human T cells were subjected to lentiviral gene transfer, resulting in large numbers of cells with >85% CAR expression. In an immunodeficient mouse xenograft model of primary human pre-B-cell acute lymphoblastic leukemia, human T cells expressing anti-CD19 CARs containing CD137 exhibited the greatest antileukemic efficacy and prolonged (>6 months) survival in vivo, and were significantly more effective than cells expressing CARs containing TCR-zeta alone or CD28-zeta signaling receptors. We uncovered a previously unrecognized, antigen-independent effect of CARs expressing the CD137 cytoplasmic domain that likely contributes to the enhanced antileukemic efficacy and survival in tumor bearing mice. Furthermore, our studies revealed significant discrepancies between in vitro and in vivo surrogate measures of CAR efficacy. Together these results suggest that incorporation of the CD137 signaling domain in CARs should improve the persistence of CARs in the hematologic malignancies and hence maximize their antitumor activity.

Preclinical rationale for combining radiation therapy and immunotherapy beyond checkpoint inhibitors (i.e., CART)

An increasing appreciation for the role of the immune system in targeting cancer cells over the last decade has led to the development of several immunomodulatory agents aimed at enhancing the systemic antitumor immune response. One such method is the use of T cells that are genetically engineered to express chimeric antigen receptors (CARs). The remarkable success of this approach in advanced hematologic malignancies has garnered much enthusiasm for using this novel tool in treating other cancers. However, multiple challenges have hampered the application of this therapy to a broader set of solid tumors, most notably lung cancer. Immunotherapy has already shown great success in lung cancer, and is now the first-line treatment in PD-L1 expressing metastatic disease. Given the mounting evidence that radiation therapy plays a crucial role in amplifying the immune response elicited by immunomodulatory agents, there is potential for radiation to help in overcoming some of these challenges. In this review, we describe the basic principles of CAR T cell therapy and examine its successes and challenges to date. We then discuss the preclinical and clinical data supporting the use of radiation with immunomodulatory agents with a focus on preclinical rationale for combining CAR T cells and radiation therapy in future experiments with a focus on lung cancer.