Application of Mixture Design Response Surface Methodology for Combination Chemotherapy in PC-3 Human Prostate Cancer Cells

Combining chemotherapeutics to treat malignant tumors has been shown to be effective in preventing drug resistance, tumor recurrence, and reducing tumor size. We modeled combination drug therapy in PC-3 human prostate cancer cells using mixture design response surface methodology (MDRSM), a statistical technique designed to optimize compositions that we applied in a novel manner to design combinations of chemotherapeutics. Conventional chemotherapeutics (mitoxantrone, cabazitaxel, and docetaxel) and natural bioactive compounds (resveratrol, piperlongumine, and flavopiridol) were used in 12 different combinations containing three drugs at varying concentrations. Cell viability and cell cycle data were collected and used to plot response surfaces in MDRSM that identified the most effective concentrations of each drug in combination. MDRSM allows for extrapolation of data from three or more compounds in variable ratio combinations, unlike the Chou-Talalay method. MDRSM combinations were compared with combination index data from the Chou-Talalay method and were found to coincide. We propose MDRSM as an effective tool in devising combination treatments that can improve treatment effectiveness and increase treatment personalization, because MDRSM measures effectiveness rather than synergism, potentiation, or antagonism.

CAR T-cell immunotherapy: The path from the by-road to the freeway?

Chimeric antigen receptors are genetically encoded artificial fusion molecules that can re-program the specificity of peripheral blood polyclonal T-cells against a selected cell surface target. Unparallelled clinical efficacy has recently been demonstrated using this approach to treat patients with refractory B-cell malignancy. However, the approach is technically challenging and can elicit severe toxicity in patients. Moreover, solid tumours have largely proven refractory to this approach. In this review, we describe the important structural features of CARs and how this may influence function. Emerging clinical experience is summarized in both solid tumours and haematological malignancies. Finally, we consider the particular challenges imposed by solid tumours to the successful development of CAR T-cell immunotherapy, together with a number of innovative strategies that have been developed in an effort to reverse the balance in favour of therapeutic benefit.

Chimeric antigen receptor-engineered T cells for the treatment of metastatic prostate cancer

Cancer immunotherapy was selected as the Breakthrough of the Year 2013 by the editors of Science, in part because of the successful treatment of refractory hematological malignancies with adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells. Effective treatment of B cell leukemia may pave the road to future treatment of solid tumors, using similar approaches. The prostate expresses many unique proteins and, since the prostate gland is a dispensable organ, CAR T cells can potentially be used to target these tissue-specific antigens. However, the location and composition of prostate cancer metastases complicate the task of treating these tumors. It is therefore likely that more sophisticated CAR T cell approaches are going to be required for prostate metastasis than for B cell malignancies. Two main challenges that need to be resolved are how to increase the migration and infiltration of CAR T cells into prostate cancer bone metastases and how to counteract the immunosuppressive microenvironment found in bone lesions. Inclusion of homing (chemokine) receptors in CAR T cells may improve their recruitment to bone metastases, as may antibody-based combination therapies to normalize the tumor vasculature. Optimal activation of CAR T cells through the introduction of multiple costimulatory domains would help to overcome inhibitory signals from the tumor microenvironment. Likewise, combination therapy with checkpoint inhibitors that can reduce tumor immunosuppression may help improve efficacy. Other elegant approaches such as induced expression of immune stimulatory cytokines upon target recognition may also help to recruit other effector immune cells to metastatic sites. Although toxicities are difficult to predict in prostate cancer, severe on-target/off-tumor toxicities have been observed in clinical trials with use of CAR T cells against hematological malignancies; therefore, the choice of the target antigen is going to be crucial. This review focuses on different means of accomplishing maximal effectiveness of CAR T cell therapy for prostate cancer bone metastases while minimizing side effects and CAR T cell-associated toxicities. CAR T cell-based therapies for prostate cancer have the potential to be a therapy model for other solid tumors.

Chimeric Antigen Receptor- and TCR-Modified T Cells Enter Main Street and Wall Street

The field of adoptive cell transfer (ACT) is currently comprised of chimeric Ag receptor (CAR)- and TCR-engineered T cells and has emerged from principles of basic immunology to paradigm-shifting clinical immunotherapy. ACT of T cells engineered to express artificial receptors that target cells of choice is an exciting new approach for cancer, and it holds equal promise for chronic infection and autoimmunity. Using principles of synthetic biology, advances in immunology, and genetic engineering have made it possible to generate human T cells that display desired specificities and enhanced functionalities. Clinical trials in patients with advanced B cell leukemias and lymphomas treated with CD19-specific CAR T cells have induced durable remissions in adults and children. The prospects for the widespread availability of engineered T cells have changed dramatically given the recent entry of the pharmaceutical industry to this arena. In this overview, we discuss some of the challenges and opportunities that face the field of ACT.

Development of T cells redirected to glypican-3 for the treatment of hepatocellular carcinoma

PURPOSE

The aim of our study is to elucidate whether T cells expressing GPC3-targeted chimeric antigen receptor (CAR) can efficiently eliminate GPC3-positive HCC cells and their potential in the treatment of HCC.

EXPERIMENTAL DESIGN

T cells expressing a first-generation and third-generation GPC3-targeted CAR were prepared using lentiviral vector transduction. The in vitro and in vivo cytotoxic activities of the genetically engineered CAR T cells were evaluated against various HCC cell lines.

RESULTS

GPC3-targeted CAR T cells could efficiently kill GPC3-positive HCC cells but not GPC3-negative cells in vitro. These cytotoxic activities seemed to be positively correlated with GPC3 expression levels in the target cells. In addition, T cells expressing the third-generation GPC3-targeted CAR could eradicate HCC xenografts with high level of GPC3 expression and efficiently suppress the growth of HCC xenografts with low GPC3 expression level in vivo. The survival of the mice bearing established orthotopic Huh-7 xenografts was significantly prolonged by the treatment with the third-generation GPC3-targeted CAR T cells.

CONCLUSIONS

GPC3-targeted CAR T cells could potently eliminate GPC3-positive HCC cells, thereby providing a promising therapeutic intervention for GPC3-positive HCC.

Efficacy of CAR T-cell therapy in large tumors relies upon stromal targeting by IFNγ

Adoptive T-cell therapy using chimeric antigen receptor-modified T cells (CAR-T therapy) has shown dramatic efficacy in patients with circulating lymphoma. However, eradication of solid tumors with CAR-T therapy has not been reported yet to be efficacious. In solid tumors, stroma destruction, due to MHC-restricted cross-presentation of tumor antigens to T cells, may be essential. However, CAR-Ts recognize antigens in an MHC-independent manner on cancer cells but not stroma cells. In this report, we show how CAR-Ts can be engineered to eradicate large established tumors with provision of a suitable CD28 costimulatory signal. In an HER2-dependent tumor model, tumor rejection by HER2-specific CAR-Ts was associated with sustained influx and proliferation of the adoptively transferred T cells. Interestingly, tumor rejection did not involve natural killer cells but was associated instead with a marked increase in the level of M1 macrophages and a requirement for IFNγ receptor expression on tumor stroma cells. Our results argue that CAR-T therapy is capable of eradicating solid tumors through a combination of antigen-independent stroma destruction and antigen-specific tumor cell targeting.

Design and development of therapies using chimeric antigen receptor-expressing T cells

Investigators developed chimeric antigen receptors (CARs) for expression on T cells more than 25 years ago. When the CAR is derived from an antibody, the resultant cell should combine the desirable targeting features of an antibody (e.g. lack of requirement for major histocompatibility complex recognition, ability to recognize non-protein antigens) with the persistence, trafficking, and effector functions of a T cell. This article describes how the past two decades have seen a crescendo of research which has now begun to translate these potential benefits into effective treatments for patients with cancer. We describe the basic design of CARs, describe how antigenic targets are selected, and the initial clinical experience with CAR-T cells. Our review then describes our own and other investigators' work aimed at improving the function of CARs and reviews the clinical studies in hematological and solid malignancies that are beginning to exploit these approaches. Finally, we show the value of adding additional engineering features to CAR-T cells, irrespective of their target, to render them better suited to function in the tumor environment, and discuss how the safety of these heavily modified cells may be maintained.

Elimination of progressive mammary cancer by repeated administrations of chimeric antigen receptor-modified T cells

Continuous oncogenic processes that generate cancer require an on-going treatment approach to eliminate the transformed cells, and prevent their further development. Here, we studied the ability of T cells expressing a chimeric antibody-based receptor (CAR) to offer a therapeutic benefit for breast cancer induced by erbB-2. We tested CAR-modified T cells (T-bodies) specific to erbB-2 for their antitumor potential in a mouse model overexpressing a human erbB-2 transgene that develops mammary tumors. Comparing the antitumor reactivity of CAR-modified T cells under various therapeutic settings, either prophylactic, prior to tumor development, or therapeutically. We found that repeated administration of CAR-modified T cells is required to eliminate spontaneously developing mammary cancer. Systemic, as well as intratumoral administered CAR-modified T cells accumulated at tumor sites and eventually eliminated the malignant cells. Interestingly, within a few weeks after a single CAR T cells' administration, and rejection of primary lesion, tumors usually relapsed both in treated mammary gland and at remote sites; however, repeated injections of CAR-modified T cells were able to control the secondary tumors. Since spontaneous tumors can arise repeatedly, especially in the case of syndromes characterized by specific susceptibility to cancer, multiple administrations of CAR-modified T cells can serve to control relapsing disease.

Engineered T cells for cancer treatment

Adoptively transferred T cells have the capacity to traffic to distant tumor sites, infiltrate fibrotic tissue and kill antigen-expressing tumor cells. Various groups have investigated different genetic engineering strategies designed to enhance tumor specificity, increase T cell potency, improve proliferation, persistence or migratory capacity and increase safety. This review focuses on recent developments in T cell engineering, discusses the clinical application of these engineered cell products and outlines future prospects for this therapeutic modality.

T cells expressing chimeric antigen receptors can cause anaphylaxis in humans

T cells can be redirected to overcome tolerance to cancer by engineering with integrating vectors to express a chimeric antigen receptor (CAR). In preclinical models, we have previously shown that transfection of T cells with mRNA coding for a CAR is an alternative strategy that has antitumor efficacy and the potential to evaluate the on-target off-tumor toxicity of new CAR targets safely due to transient mRNA CAR expression. Here, we report the safety observed in four patients treated with autologous T cells that had been electroporated with mRNA coding for a CAR derived from a murine antibody to human mesothelin. Because of the transient nature of CAR expression on the T cells, subjects in the clinical study were given repeated infusions of the CAR-T cells to assess their safety. One subject developed anaphylaxis and cardiac arrest within minutes of completing the third infusion. Although human anti-mouse immunoglobulin (Ig)G antibodies have been known to develop with CAR-transduced T cells, they have been thought to have no adverse clinical consequences. This is the first description of clinical anaphylaxis resulting from CAR-modified T cells, most likely through IgE antibodies specific to the CAR. These results indicate that the potential immunogenicity of CARs derived from murine antibodies may be a safety issue for mRNA CARs, especially when administered using an intermittent dosing schedule.

Natural killer cells generated from cord blood hematopoietic progenitor cells efficiently target bone marrow-residing human leukemia cells in NOD/SCID/IL2Rg(null) mice

Natural killer (NK) cell-based adoptive immunotherapy is an attractive adjuvant treatment option for patients with acute myeloid leukemia. Recently, we reported a clinical-grade, cytokine-based culture method for the generation of NK cells from umbilical cord blood (UCB) CD34⁺ hematopoietic progenitor cells with high yield, purity and in vitro functionality. The present study was designed to evaluate the in vivo anti-leukemic potential of UCB-NK cells generated with our GMP-compliant culture system in terms of biodistribution, survival and cytolytic activity following adoptive transfer in immunodeficient NOD/SCID/IL2Rg^null mice. Using single photon emission computed tomography, we first demonstrated active migration of UCB-NK cells to bone marrow, spleen and liver within 24 h after infusion. Analysis of the chemokine receptor expression profile of UCB-NK cells matched in vivo findings. Particularly, a firm proportion of UCB-NK cells functionally expressed CXCR4, what could trigger BM homing in response to its ligand CXCL12. In addition, high expression of CXCR3 and CCR6 supported the capacity of UCB-NK cells to migrate to inflamed tissues via the CXCR3/CXCL10-11 and CCR6/CCL20 axis. Thereafter, we showed that low dose IL-15 mediates efficient survival, expansion and maturation of UCB-NK cells in vivo. Most importantly, we demonstrate that a single UCB-NK cell infusion combined with supportive IL-15 administration efficiently inhibited growth of human leukemia cells implanted in the femur of mice, resulting in significant prolongation of mice survival. These preclinical studies strongly support the therapeutic potential of ex vivo-generated UCB-NK cells in the treatment of myeloid leukemia after immunosuppressive chemotherapy.

Re-directed T cells for the treatment of fibroblast activation protein (FAP)-positive malignant pleural mesothelioma (FAPME-1)

Background

Asbestos is the main cause of MPM in industrialized countries. Even since asbestos is banned in most developed countries, the peak wave of MPM incidence is anticipated for the next years due to the long latency of asbestos induced MPM. MPM patients not eligible for surgical procedures like decortication or pleuro-pneumectomie have a median survival of 12 months with palliative chemotherapy. Therefore, new therapeutic approaches are of crucial need in this clinical situation.

Methods/design

This is a phase I trial for patients with malignant pleural mesothelioma with pleural effusion testing the safety of a fixed single dose of 1x10⁶ adoptively transferred FAP-specific re-directed T cells given directly in the pleural effusion. Lymphocytes will be taken 21 days before transfer from peripheral blood. CD8 positive T cells will be isolated and re-programmed by retroviral transfer of a chimeric antigen receptor recognizing FAP which serves as target structure in MPM. At day 0 of the protocol, re-directed T cells will be injected in the pleural effusion and patients will be monitored for 48h under intermediate care conditions. AE, SAE, SADR and SUSAR will be monitored for 35 days and evaluated by an independent safety board to define any dose limiting toxicity (DLT). No further patient can be treated before the previous patient passed day 14 after T cell transfer. The protocol will be judged as save when no DLT occurred in the first 3 patients, or 1 DLT in 6 patients. Secondary objectives are feasibility and immune monitoring.

Discussion

Adoptive T cell transfer is a new and rapidly expanding branch of immunotherapies focusing on cancer treatment. Recently, objective responses could be observed in patients with chronic lymphatic leukemia treated with adoptively transferred CD19-specific re-directed T cells. The choice of the target antigen determines the possible on-target off-tissue toxicity of such approaches. There are reports of severe toxicity in patients who received T cells intravenously due to unexpected expression of the target antigen (on-target) in other tissues than the tumor (off-tissue). To minimize the risk of on-target off-tissue toxicity and to maximize the on-target anti-tumor effect we propose a clinical protocol with loco-regional administration of re-directed T cells. FAP-specific T cells will be directly injected in the pleural effusion of patients with MPM.

Trial registration

ClinicalTrials.gov (NCT01722149)

Immunotherapy of malignant disease using chimeric antigen receptor engrafted T cells

Chimeric antigen receptor- (CAR-) based immunotherapy has been under development for almost 25 years, over which period it has progressed from a new but cumbersome technology to an emerging therapeutic modality for malignant disease. The approach involves the genetic engineering of fusion receptors (CARs) that couple the HLA-independent binding of cell surface target molecules to the delivery of a tailored activating signal to host immune cells. Engineered CARs are delivered most commonly to peripheral blood T cells using a range of vector systems, most commonly integrating viral vectors. Preclinical refinement of this approach has proceeded over several years to the point that clinical testing is now being undertaken at several centres, using increasingly sophisticated and therapeutically successful genetic payloads. This paper considers several aspects of the pre-clinical and clinical development of CAR-based immunotherapy and how this technology is acquiring an increasing niche in the treatment of both solid and haematological malignancies.

Redirected T cells that target pancreatic adenocarcinoma antigens eliminate tumors and metastases in mice

BACKGROUND & AIMS

Pancreatic adenocarcinoma (PAC) is often diagnosed at an advanced and inoperable stage, and standard systemic treatments are generally ineffective. We investigated the effects of adoptive transfer of tumor-specific T cells that express chimeric antibody-based receptors (CAR) to mice with primary and metastatic PAC xenografts.

METHODS

Human effector T cells were genetically modified to express CAR against Her2/neu or CD24, a putative PAC stem cell antigen. The antitumor reactivity of the engineered T cells (T-bodies) was evaluated in SCID mice with different PAC xenografts. A total of 1 × 10(7) T-bodies were injected via the tail vein or directly administered to the subcutaneous tumor on 3 or 4 alternating days. Mice were then given twice-daily intraperitoneal injections of interleukin-2 for 10 days.

RESULTS

Intratumor injection of human CD24 and Her2/neu-specific T-bodies completely eliminated the tumors from most animals. Intravenous injection of T-bodies reduced tumor size and prolonged survival of mice with orthotopically transplanted tumors; more than 50% of animals appeared to be disease-free more than 2 months later. Additional systemic administration of T-bodies 8 weeks after the initial injection eliminated primary tumors, along with liver and draining lymph node metastases. A single administration of the Her2/neu-specific T-bodies prolonged the survival of mice with tumors in which most of the cells expressed the target antigen. In contrast, the CD24-specific T-bodies prolonged survival of mice in which only a subpopulation of the tumor cells expressed the antigen.

CONCLUSIONS

CAR-redirected T cells stop growth and metastasis of PAC xenografts in mice. T-bodies specific to CD24, a putative cancer stem cell antigen, were effective against PAC xenografts that had only a subset of antigen-expressing cells.

Tumor-associated antigens for specific immunotherapy of prostate cancer

Prostate cancer (PCa) is the most common noncutaneous cancer diagnosis and the second leading cause of cancer-related deaths among men in the United States. Effective treatment modalities for advanced metastatic PCa are limited. Immunotherapeutic strategies based on T cells and antibodies represent interesting approaches to prevent progression from localized to advanced PCa and to improve survival outcomes for patients with advanced disease. CD8⁺ cytotoxic T lymphocytes (CTLs) efficiently recognize and destroy tumor cells. CD4⁺ T cells augment the antigen-presenting capacity of dendritic cells and promote the expansion of tumor-reactive CTLs. Antibodies mediate their antitumor effects via antibody-dependent cellular cytotoxicity, activation of the complement system, improving the uptake of coated tumor cells by phagocytes, and the functional interference of biological pathways essential for tumor growth. Consequently, several tumor-associated antigens (TAAs) have been identified that represent promising targets for T cell- or antibody-based immunotherapy. These TAAs comprise proteins preferentially expressed in normal and malignant prostate tissues and molecules which are not predominantly restricted to the prostate, but are overexpressed in various tumor entities including PCa. Clinical trials provide evidence that specific immunotherapeutic strategies using such TAAs represent safe and feasible concepts for the induction of immunological and clinical responses in PCa patients. However, further improvement of the current approaches is required which may be achieved by combining T cell- and/or antibody-based strategies with radio-, hormone-, chemo- or antiangiogenic therapy.

From whole monoclonal antibodies to single domain antibodies: think small

The development of therapeutic monoclonal antibodies over the last 35 years has led to the emergence of a new class of useful therapeutic molecules. These "first generation" antibodies have been obtained thanks to the conjugated and huge efforts of both academic and biotech researchers. About 30 monoclonal antibodies are currently approved for therapeutic use in Europe, USA, and China. Strikingly, only a restricted number of these antibodies are immunoglobulin fragments, single variable domains, or multiunit formats based on the engineering of immunoglobulin variable domains. In the present chapter, we will review the major steps of the therapeutic antibodies history and we will highlight the enormous potential of antibody fragments, either used as multiunits such as bispecific antibodies, single units, or as cell modifiers such as intrabodies or cell surface-expressed molecules.

Engineered T cells for the adoptive therapy of B-cell chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (B-CLL) remains an incurable disease due to the high risk of relapse, even after complete remission, raising the need to control and eliminate residual tumor cells in long term. Adoptive T cell therapy with genetically engineered specificity is thought to fulfil expectations, and clinical trials for the treatment of CLL are initiated. Cytolytic T cells from patients are redirected towards CLL cells by ex vivo engineering with a chimeric antigen receptor (CAR) which binds to CD19 on CLL cells through an antibody-derived domain and triggers T cell activation through CD3ζ upon tumor cell engagement. Redirected T cells thereby target CLL cells in an MHC-unrestricted fashion, secret proinflammatory cytokines, and eliminate CD19(+) leukaemia cells with high efficiency. Cytolysis of autologous CLL cells by patient's engineered T cells is effective, however, accompanied by lasting elimination of healthy CD19(+) B-cells. In this paper we discuss the potential of the strategy in the treatment of CLL, the currently ongoing trials, and the future challenges in the adoptive therapy with CAR-engineered T cells.

Redirected tumor-specific allogeneic T cells for universal treatment of cancer

Adoptive cell transfer of allogeneic tumor-specific T cells could potentially be used as a universal treatment for cancer. We present a novel approach for adoptive immunotherapy using fully MHC-mismatched allogeneic T cells redirected with tumor-specific, non-MHC-restricted antibody-based chimeric antigen receptor (T-bodies) in the absence of GVHD. Mice bearing systemic metastatic disease were lymphodepleted by irradiation and treated with Her2/neu re-directed T cells. Lymphodepletion created a 'therapeutic window', which allowed the allo-T-bodies to attack the tumor before their rejection. A single split dose administration of allogeneic T-bodies extended the survival of tumor-bearing mice similarly to syngeneic T-bodies, and to a significantly greater extent than nonspecific allogeneic T cells. Blocking egress of lymphocytes from lymphoid organs using the sphingosine-1-phosphate agonist, FTY720, extended the persistence of allogeneic T cells such that allogeneic T-bodies provided superior therapeutic benefit relative to syngeneic ones, and dramatically extended the median survival time of the treated mice for more than a year. Therefore, we suggest that ex-vivo generated MHC-mismatched T-bodies can be used universally for off-the-shelf cancer immunotherapy and that their graft-versus-host reactivity can be safely harnessed to potentiate adoptive cell therapy.

Chimeric antigen receptor (CAR)-engineered lymphocytes for cancer therapy

INTRODUCTION

Chimeric antigen receptors (CARs) usually combine the antigen binding site of a monoclonal antibody with the signal activating machinery of a T cell, freeing antigen recognition from MHC restriction and thus breaking one of the barriers to more widespread application of cellular therapy. Similar to treatment strategies employing monoclonal antibodies, T cells expressing CARs are highly targeted, but additionally offer the potential benefits of active trafficking to tumor sites, in vivo expansion and long-term persistence. Furthermore, gene transfer allows the introduction of countermeasures to tumor immune evasion and of safety mechanisms.

AREAS COVERED

The basic structure of so-called first and later generation CARs and their potential advantages over other immune therapy systems. How these molecules can be grafted into immune cells (including retroviral and non-retroviral transduction methods) and strategies to improve the in vivo persistence and function of immune cells expressing CARs. Examples of tumor-associated antigens that have been targeted in preclinical models and clinical experience with these modified cells. Safety issues surrounding CAR gene transfer into T cells and potential solutions to them.

EXPERT OPINION

Because of recent advances in immunology, genetics and cell processing, CAR-modified T cells will likely play an increasing role in the cellular therapy of cancer, chronic infections and autoimmune disorders.

Adoptive transfer of syngeneic T cells transduced with a chimeric antigen receptor that recognizes murine CD19 can eradicate lymphoma and normal B cells

Adoptive T-cell therapy with anti-CD19 chimeric antigen receptor (CAR)-expressing T cells is a new approach for treating advanced B-cell malignancies. To evaluate anti-CD19-CAR-transduced T cells in a murine model of adoptive T-cell therapy, we developed a CAR that specifically recognized murine CD19. We used T cells that were retrovirally transduced with this CAR to treat mice bearing a syngeneic lymphoma that naturally expressed the self-antigen murine CD19. One infusion of anti-CD19-CAR-transduced T cells completely eliminated normal B cells from mice for at least 143 days. Anti-CD19-CAR-transduced T cells eradicated intraperitoneally injected lymphoma cells and large subcutaneous lymphoma masses. The antilymphoma efficacy of anti-CD19-CAR-transduced T cells was critically dependent on irradiation of mice before anti-CD19-CAR-transduced T-cell infusion. Anti-CD19-CAR-transduced T cells had superior antilymphoma efficacy compared with the anti-CD19 monoclonal antibody from which the anti-CD19 CAR was derived. Our results demonstrated impressive antilymphoma activity and profound destruction of normal B cells caused by anti-CD19-CAR-transduced T cells in a clinically relevant murine model.

When gene therapy meets adoptive cell therapy: better days ahead for cancer immunotherapy?

Evaluation of: Johnson LA, Morgan RA, Dudley ME et al. Gene therapy with human and mouse T-cell receptors mediates cancer regression and targets normal tissues expressing cognate antigen. Blood 114(3), 535-546 (2009). Effective cancer immunotherapy requires large numbers of antitumor lymphocytes with effective homing and effector functions over a prolonged time. Adoptive cell therapy (ACT) has proven a promising immunotherapy approach by achieving clinical responses in patients bearing metastatic melanoma. ACT expands a cancer patient's own cytotoxic lymphocytes in vitro and reinfuses them in vivo. Identifying cytotoxic T lymphocytes directed against cancer cells can, however, be a tedious endeavor. The paper under evaluation overcomes this hurdle and proposes a highly effective gene therapy approach to transduce a patient's lymphocytes with a high-avidity T-cell receptor, thus turning reinfused lymphocytes into strong effector cells directed against cancer. Furthermore, transgenic mice were used to broaden the repertoire of human transduced T-cell receptor to evasive tumor-associated antigens. Patients bearing metastatic melanoma were successfully treated with ACT using peripheral blood lymphocytes transduced with Mart-1 and gp100 tumor-associated epitopes. Objective clinical response rates of 30 and 19% were obtained in patients treated with the human and mouse T-cell receptors, respectively. Gene-engineered cells persisted in all patients at high level for 1 month after treatment. These findings have two major implications: first, transgenic mice can be used to obtain high-avidity T-cell receptors specific for elusive tumor-associated antigens, bypassing the need for frustrating immunizations attempts. Second, a gene therapy approach to ACT allows for an efficient transduction of patient's lymphocytes into highly avid tumor-specific cytotoxic cells, eliminating the requirement for identification and selection of tumor-specific lymphocytes in individual patients. Taken together, these results mark a step towards standardized immunotherapy protocols open to all patients and that will be able to deliver consistent clinical results.

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.

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.

Re-targeting T-cells against cancer by gene-transfer of tumor-reactive receptors

BACKGROUND

Adoptive transfer of T-lymphocytes is a promising treatment for a variety of malignancies, but is often not feasible due to difficulties in generating T-cells reactive with the targeted antigen from patients. To facilitate rapid generation of cells for therapy, T-cells can be programmed with genes encoding for an antigen-specific T-cell receptor (TCR) or chimeric receptors.

OBJECTIVE

To discuss the molecular design and selected pitfalls of TCR gene modified T-cells and T-cells expressing chimeric receptors, so called T-bodies.

METHODS

A selected review of the recent literature.

CONCLUSION

Clinical trials report so far only limited efficacy of adoptively transferred genetically modified T-cells. However, the recent progress in engineering tumor-reactive T cells is providing a promising basis to further explore this treatment modality.

Reprogramming T lymphocytes for melanoma adoptive immunotherapy by T-cell receptor gene transfer with lentiviral vectors

T-cell receptor (TCR) gene transfer for cancer immunotherapy is limited by the availability of large numbers of tumor-specific T cells. TCR alpha and beta chains were isolated from a highly lytic HLA-A2-restricted cytotoxic T lymphocyte (CTL) clone recognizing the melanoma-associated Melan-A/MART-1 antigen and inserted into a lentiviral vector carrying a bidirectional promoter capable of robust and coordinated expression of the two transgenes. Lentiviral vector-based gene delivery systems have shown increased transfer efficiency and transgene expression compared with the widely used gamma-retroviral vectors. This vector performed more efficiently than a gamma-retrovirus-based vector containing the same expression cassette, resulting in a T-cell population with 60% to 80% of transgenic TCR expression with mainly CD8(+) intermediate effector phenotype. Transgenic T cells specifically produced cytokine in response to and killed antigen-expressing melanoma cells, retained an overlapping functional avidity in comparison with the TCR donor CTL clone, and exerted significant therapeutic effects in vivo upon adoptive transfer in melanoma-bearing severe combined immunodeficient mice. Optical imaging showed their accumulation in the tumor site. Overall, our results indicate that lentiviral vectors represent a valid tool for stable and high-intensity expression of transgenic TCR and support clinical exploitation of this approach for therapeutic application.

Cancer immunotherapy

Recent scientific advances have expanded our understanding of the immune system and its response to malignant cells. The clinical goal of tumour immunotherapy is to provide either passive or active immunity against malignancies by harnessing the immune system to target tumours. Monoclonal antibodies, cytokines, cellular immunotherapy, and vaccines have increasingly become successful therapeutic agents for the treatment of solid and haematological cancers in preclinical models, clinical trials, and practice. In this article, we review recent advances in the immunotherapy of cancer, focusing on new strategies and future perspectives as well as on clinical trials attempting to enhance the efficacy of immunotherapeutic modalities and translate this knowledge into effective cancer therapies.

Small interfering RNA-directed targeting of Toll-like receptor 4 inhibits human prostate cancer cell invasion, survival, and tumorigenicity

A major cause of tumor treatment failure is cancer cell metastasis. Toll-like receptor 4 (TLR4)-mediated signaling has been implicated in tumor cell invasion, survival, and metastasis in a variety of cancers. In this study, we investigated the biological roles of TLR4 in prostate metastatic cell invasion and survival, and the potential of gene silencing of TLR4 using small interfering RNA (siRNA) for treatment of cancer. In cultured human prostate cancer cell lines, TLR4 were higher PC3 and DU145 as compared with the poorly metastatic LNCaP indicating that up-regulation of TLR4 was positively correlated with metastasis of tumor cell. In the highly metastatic cancer cell PC3, gene silencing of TLR4 using siRNA significantly inhibited TLR4 mRNA expression and protein level. Knockdown of TLR4 in PC3 cells resulted in a dramatic reduction of tumor cell migration and invasion as indicated by a Matrigel invasion assay. Furthermore, TLR4 siRNA suppressed cell viability and ultimately caused the induction of apoptotic cell death. The effects were associated with abrogating TLR4-mediated signaling to downstream target molecules such as myeloid differentiation factor 88 (MyD88), adaptor-inducing IFN-beta (TRIF), and interferon regulatory factor-1 (IRF-1). In a mouse prostate cancer model, administration with the plasmid construct expressing siRNA for TLR4 obviously inhibited established tumor growth and survival. These studies revealed evidence of a multifaceted signaling network operating downstream of TLR4-mediated tumor cell invasion, proliferation, and survival. Thus, RNA interference-directed targeting of TLR4 may raise the potential of its application for cancer therapy.

Androgens induce oxidative stress and radiation resistance in prostate cancer cells though NADPH oxidase

Androgen deprivation therapy (ADT) facilitates the response of prostate cancer (PC) to radiation. Androgens have been shown to induce elevated basal levels of reactive oxygen species (ROS) in PC, leading to adaptation to radiation-induced cytotoxic oxidative stress. Here, we show that androgens increase the expression of p22^phox and gp91^phox subunits of NADPH oxidase (NOX) and ROS production by NOX2 and NOX4 in PC. Pre-radiation treatment of 22Rv1 human PC cells with NOX inhibitors sensitize the cells to radiation similarly to ADT, suggesting that their future usage may spare the need for adjuvant ADT in PC patients undergoing radiation.

The Lewis-Y carbohydrate antigen is expressed by many human tumors and can serve as a target for genetically redirected T cells despite the presence of soluble antigen in serum

In this study we aimed to determine the suitability of the Lewis-Y carbohydrate antigen as a target for immunotherapy using genetically redirected T cells. Using the 3S193 monoclonal antibody and immunohistochemistry, Lewis-Y was found to be expressed on a range of tumors including 42% squamous cell lung carcinoma, 80% lung adenocarcinoma, 25% ovarian carcinoma, and 25% colorectal adenocarcinoma. Expression levels varied from low to intense on between 1% and 90% of tumor cells. Lewis- was also found in soluble form in sera from both normal donors and cancer patients using a newly developed enzyme-linked immunosorbent assay. Serum levels in patients was often less than 1 ng/mL, similar to normal donors, but approximately 30% of patients had soluble Lewis-Y levels exceeding 1 ng/mL and up to 9 ng/mL. Lewis-Y-specific human T cells were generated by genetic modification with a chimeric receptor encoding a single-chain humanized antibody linked to the T-cell signaling molecules, T-cell receptor-zeta, and CD28. T cells responded against the Lewis-Y antigen by cytokine secretion and cytolysis in response to tumor cells. Importantly, the T-cell response was not inhibited by patient serum containing soluble Lewis-Y. This study demonstrates that Lewis-Y is expressed on a large number of tumors and Lewis-Y-specific T cells can retain antitumor function in the presence of patient serum, indicating that this antigen is a suitable target for this form of therapy.

Gene therapy with human and mouse T-cell receptors mediates cancer regression and targets normal tissues expressing cognate antigen

Gene therapy of human cancer using genetically engineered lymphocytes is dependent on the identification of highly reactive T-cell receptors (TCRs) with antitumor activity. We immunized transgenic mice and also conducted high-throughput screening of human lymphocytes to generate TCRs highly reactive to melanoma/melanocyte antigens. Genes encoding these TCRs were engineered into retroviral vectors and used to transduce autologous peripheral lymphocytes administered to 36 patients with metastatic melanoma. Transduced patient lymphocytes were CD45RA(-) and CD45RO(+) after ex vivo expansion. After infusion, the persisting cells displayed a CD45RA(+) and CD45RO(-) phenotype. Gene-engineered cells persisted at high levels in the blood of all patients 1 month after treatment, responding patients with higher ex vivo antitumor reactivity than nonresponders. Objective cancer regressions were seen in 30% and 19% of patients who received the human or mouse TCR, respectively. However, patients exhibited destruction of normal melanocytes in the skin, eye, and ear, and sometimes required local steroid administration to treat uveitis and hearing loss. Thus, T cells expressing highly reactive TCRs mediate cancer regression in humans and target rare cognate-antigen-containing cells throughout the body, a finding with important implications for the gene therapy of cancer. This trial was registered at www.ClinicalTrials.gov as NCI-07-C-0174 and NCI-07-C-0175.

Amelioration of colitis by genetically engineered murine regulatory T cells redirected by antigen-specific chimeric receptor

BACKGROUND & AIMS

The therapeutic application of regulatory T cells (Tregs) for the treatment of inflammatory diseases is limited by the scarcity of antigen-specific Tregs. A preferred approach to endow effector T cells (Teff) with a desired specificity uses chimeric immune receptors with antibody-type specificity. Accordingly, employing such chimeric immune receptors to redirect Tregs to sites of inflammation may be a useful therapeutic approach to alleviate a broad scope of diseases in which an uncontrolled inflammatory response plays a major role.

METHODS

To enable application of the approach in clinical setting, which requires the genetic modification of the patient's own Tregs, we describe here a novel protocol that allows the efficient retroviral transduction and 2,4,6-trinitrophenol-specific expansion of murine naturally occurring regulatory T cells (nTregs), with a 2,4,6-trinitrophenol-specific tripartite chimeric receptor.

RESULTS

Transduced Tregs maintained their Foxp3 level, could undergo repeated expansion upon ex vivo encounter with their cognate antigen in a major histocompatibility complex-independent, costimulation-independent, and contact-dependent manner and specifically suppressed Teff cells. Adoptive transfer of small numbers of the transduced nTregs was associated with antigen-specific, dose-dependent amelioration of trinitrobenzenesulphonic acid colitis.

CONCLUSIONS

This study demonstrates that nTregs can be efficiently transduced to express functional, antigen-specific chimeric receptors that enable the specific suppression of effector T cells both in vitro and in vivo. This approach may enable future cell-based therapeutic application in inflammatory bowel disease, as well as other inflammatory disorders.

Adoptive transfer of gene-modified primary NK cells can specifically inhibit tumor progression in vivo

NK cells hold great potential for improving the immunotherapy of cancer. Nevertheless, tumor cells can effectively escape NK cell-mediated apoptosis through interaction of MHC molecules with NK cell inhibitory receptors. Thus, to harness NK cell effector function against tumors, we used Amaxa gene transfer technology to gene-modify primary mouse NK cells with a chimeric single-chain variable fragment (scFv) receptor specific for the human erbB2 tumor-associated Ag. The chimeric receptor was composed of the extracellular scFv anti-erbB2 Ab linked to the transmembrane and cytoplasmic CD28 and TCR-zeta signaling domains (scFv-CD28-zeta). In this study we demonstrated that mouse NK cells gene-modified with this chimera could specifically mediate enhanced killing of an erbB2(+) MHC class I(+) lymphoma in a perforin-dependent manner. Expression of the chimera did not interfere with NK cell-mediated cytotoxicity mediated by endogenous NK receptors. Furthermore, adoptive transfer of gene-modified NK cells significantly enhanced the survival of RAG mice bearing established i.p. RMA-erbB2(+) lymphoma. In summary, these data suggest that use of genetically modified NK cells could broaden the scope of cancer immunotherapy for patients.

The combination of cyclophosphamide and human T cells genetically engineered to target CD19 can eradicate established B-cell lymphoma

T cells genetically engineered to express tumour-targeting receptors are attractive anti-cancer therapeutic agents. Human T cells engrafted with a chimeric receptor specific for the B-cell lymphoma antigen CD19 fused to the CD3zeta receptor (aCD19z) are functional in vitro. Current successful clinical protocols targeting melanoma use pre-conditioning chemotherapy in combination with T cells. This study demonstrated that interleukin-2 expanded aCD19z T cells combined with cyclophosphamide effectively treated five-day established Raji B-cell lymphoma in an immunocompromised model system with 50% of mice surviving >100 days. This observation strongly supports the combination of antibody targeted T cells with chemotherapy as a novel approach for the therapy of CD19(+) B-cell malignancies.

The T-body approach: redirecting T cells with antibody specificity

"T-bodies" are genetically engineered T cells armed with chimeric receptors whose extracellular recognition unit is comprised of an antibody-derived recognition domain and whose intracellular region is derived from lymphocyte stimulating moiety(ies). The structure of the prototypic chimeric receptor, also known as a chimeric immune receptor, is modular, designed to accomodate various functional domains and thereby to enable choice of specificity and controlled activation of T cells. The preferred antibody-derived recognition unit is a single chain variable fragment (scFv) that combines the specificity and binding residues of both the heavy and light chain variable regions of a monoclonal antibody. The most common lymphocyte activation moieties include a T-cell costimulatory (e.g. CD28) domain in tandem with a T-cell triggering (e.g. CD3zeta) moiety. By arming effector lymphocytes (such as T cells and natural killer cells) with such chimeric receptors, the engineered cell is redirected with a predefined specificity to any desired target antigen, in a non-HLA restricted manner. Chimeric receptor (CR) constructs are introduced ex vivo into T cells from peripheral lymphocytes of a given patient using retroviral vectors. Following infusion of the resulting T-bodies back into the patient, they traffic, reach their target site, and upon interaction with their target cell or tissue, they undergo activation and perform their predefined effector function. Therapeutic targets for the T-body approach include cancer and HIV-infected cells, or autoimmune effector cells. To date, the most investigated area is cancer therapy. Here, the T-bodies are advantageous because their tumor recognition is not HLA-specific and, therefore, the same constructs can be used for a wide spectrum of patients and cancers.

Genetically targeted T cells eradicate systemic acute lymphoblastic leukemia xenografts

PURPOSE

Human T cells targeted to the B cell-specific CD19 antigen through retroviral-mediated transfer of a chimeric antigen receptor (CAR), termed 19z1, have shown significant but partial in vivo antitumor efficacy in a severe combined immunodeficient (SCID)-Beige systemic human acute lymphoblastic leukemia (NALM-6) tumor model. Here, we investigate the etiologies of treatment failure in this model and design approaches to enhance the efficacy of this adoptive strategy.

EXPERIMENTAL DESIGN

A panel of modified CD19-targeted CARs designed to deliver combined activating and costimulatory signals to the T cell was generated and tested in vitro to identify an optimal second-generation CAR. Antitumor efficacy of T cells expressing this optimal costimulatory CAR, 19-28z, was analyzed in mice bearing systemic costimulatory ligand-deficient NALM-6 tumors.

RESULTS

Expression of the 19-28z CAR, containing the signaling domain of the CD28 receptor, enhanced systemic T-cell antitumor activity when compared with 19z1 in treated mice. A treatment schedule of 4 weekly T-cell injections, designed to prolong in vivo T-cell function, further improved long-term survival. Bioluminescent imaging of tumor in treated mice failed to identify a conserved site of tumor relapse, consistent with successful homing by tumor-specific T cells to systemic sites of tumor involvement.

CONCLUSIONS

Both in vivo costimulation and repeated administration enhance eradication of systemic tumor by genetically targeted T cells. The finding that modifications in CAR design as well as T-cell dosing allowed for the complete eradication of systemic disease affects the design of clinical trials using this treatment strategy.

Androgen induces adaptation to oxidative stress in prostate cancer: implications for treatment with radiation therapy

Radiation therapy is a standard treatment for prostate cancer (PC). The postulated mechanism of action for radiation therapy is the generation of reactive oxygen species (ROS). Adjuvant androgen deprivation (AD) therapy has been shown to confer a survival advantage over radiation alone in high-risk localized PC. However, the mechanism of this interaction is unclear. We hypothesize that androgens modify the radioresponsiveness of PC through the regulation of cellular oxidative homeostasis. Using androgen receptor (AR)(+) 22rv1 and AR(-) PC3 human PC cell lines, we demonstrated that testosterone increased basal reactive oxygen species (bROS) levels, resulting in dose-dependent activation of phospho-p38 and pAKT, and increased expression of clusterin, catalase, and manganese superoxide dismutase. Similar data were obtained in three human PC xenografts; WISH-PC14, WISH-PC23, and CWR22, growing in testosterone-supplemented or castrated SCID mice. These effects were reversible through AD or through incubation with a reducing agent. Moreover, testosterone increased the activity of catalase, superoxide dismutases, and glutathione reductase. Consequently, AD significantly facilitated the response of AR(+) cells to oxidative stress challenge. Thus, testosterone induces a preset cellular adaptation to radiation through the generation of elevated bROS, which is modified by AD. These findings provide a rational for combined hormonal and radiation therapy for localized PC.

Antitumor activity of dual-specific T cells and influenza virus

Activation and expansion of T cells are important in disease resolution, but tumors do not usually satisfy these immune requirements. Therefore, we employed a novel strategy whereby dual-specific T cells were generated that could respond to both tumor and influenza virus, reasoning that immunization with influenza virus would activate and expand tumor-specific cells, and inhibit tumor growth. Dual-specific T cells were generated by gene modification of influenza virus-specific mouse T cells with a chimeric gene-encoding reactivity against the erbB2 tumor-associated antigen. Dual-specific T cells were demonstrated to respond against both tumor and influenza in vitro, and expanded in vitro in response to influenza to a much greater degree than in response to tumor cells. Following adoptive transfer and immunization of tumor-bearing mice with influenza virus, dual-specific T cells expanded greatly in numbers in the peritoneal cavity and spleen. This resulted in a significant increase in time of survival of mice. However, tumors were not eradicated, which may have been due to the observed poor penetration of tumor by T cells. This is the first demonstration that the potent immunogenic nature of an infectious agent can be utilized to directly impact on T-cell expansion and activity against tumor in vivo.

Use of a lentivirus/VSV pseudotype virus for highly efficient genetic redirection of human peripheral blood lymphocytes

Genetic redirection of lymphocytes that have been engineered to recognize antigens other than those originally programmed by their rearranged germlines is a potentially powerful immunotherapeutic tool. The rationale for the protocol described here is that many cancers and persistent or latent viruses have developed strikingly similar mechanisms of evading attack by host immunity that can often be overcome by redirection of host lymphocytes using chimeric T-cell receptor (chTCR) genes. However, for human peripheral blood lymphocytes (PBLs), this is generally regarded as a technically demanding procedure with unacceptably low efficiency using either contemporary transfection methods or retroviral transduction. One of the main difficulties with retroviruses is their reliance on rapidly dividing cells for integration of their genomes carrying the desired chTCR. Here we describe a highly efficient protocol that uses a lentivirus/vesicular stomatitis virus pseudotyped virus to engineer CD3/CD28-stimulated human peripheral blood cells (i.e., primarily T cells), with near 100% efficiency.

TCR Activation Eliminates Glutamate Receptor GluR3 from the Cell Surface of Normal Human T Cells, via an Autocrine/Paracrine Granzyme B-Mediated Proteolytic Cleavage

The majority of resting normal human T cells, like neuronal cells, express functional receptors for glutamate (the major excitatory neurotransmitter in the CNS) of the ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-receptor subtype 3 (GluR3). Glutamate by itself ( approximately 10 nM) activates key T cell functions, including adhesion to fibronectin and laminin and chemotactic migration toward CXCL12/stromal cell-derived factor 1. In this study, we found by GluR3-specific immunostaining, flow cytometry, and Western blots that GluR3 cell surface expression decreases dramatically following TCR activation of human T cells. CXCR4, VLA-4, and VLA-6 also decrease substantially, whereas CD147 increases as expected, after TCR activation. Media of TCR-activated cells "eliminates" intact GluR3 (but not CXCR4 and VLA-6) from the cell surface of resting T cells, suggesting GluR3 cleavage by a soluble factor. We found that this factor is granzyme B (GB), a serine protease released by TCR-activated cells, because the extent of GluR3 elimination correlated with the active GB levels, and because three highly specific GB inhibitors blocked GluR3 down-regulation. Media of TCR-activated cells, presumably containing cleaved GluR3B peptide (GluR3 aa 372-388), inhibited the specific binding of anti-GluR3B mAb to synthetic GluR3B peptide. In parallel to losing intact GluR3, TCR-activated cells lost glutamate-induced adhesion to laminin. Taken together, our study shows that "classical immunological" TCR activation, via autocrine/paracrine GB, down-regulates substantially the expression of specific neurotransmitter receptors. Accordingly, glutamate T cell neuroimmune interactions are influenced by the T cell activation state, and glutamate, via AMPA-GluR3, may activate only resting, but not TCR-activated, T cells. Finally, the cleavage and release to the extracellular milieu of the GluR3B peptide may in principle increase its antigenicity, and thus the production, of anti-self GluR3B autoantibodies, which activate and kill neurons, found in patients with various types of epilepsy.

A phase I study on adoptive immunotherapy using gene-modified T cells for ovarian cancer

PURPOSE

A phase I study was conducted to assess the safety of adoptive immunotherapy using gene-modified autologous T cells for the treatment of metastatic ovarian cancer.

EXPERIMENTAL DESIGN

T cells with reactivity against the ovarian cancer-associated antigen alpha-folate receptor (FR) were generated by genetic modification of autologous T cells with a chimeric gene incorporating an anti-FR single-chain antibody linked to the signaling domain of the Fc receptor gamma chain. Patients were assigned to one of two cohorts in the study. Eight patients in cohort 1 received a dose escalation of T cells in combination with high-dose interleukin-2, and six patients in cohort 2 received dual-specific T cells (reactive with both FR and allogeneic cells) followed by immunization with allogeneic peripheral blood mononuclear cells.

RESULTS

Five patients in cohort 1 experienced some grade 3 to 4 treatment-related toxicity that was probably due to interleukin-2 administration, which could be managed using standard measures. Patients in cohort 2 experienced relatively mild side effects with grade 1 to 2 symptoms. No reduction in tumor burden was seen in any patient. Tracking 111In-labeled adoptively transferred T cells in cohort 1 revealed a lack of specific localization of T cells to tumor except in one patient where some signal was detected in a peritoneal deposit. PCR analysis showed that gene-modified T cells were present in the circulation in large numbers for the first 2 days after transfer, but these quickly declined to be barely detectable 1 month later in most patients. An inhibitory factor developed in the serum of three of six patients tested over the period of treatment, which significantly reduced the ability of gene-modified T cells to respond against FR+ tumor cells.

CONCLUSIONS

Large numbers of gene-modified tumor-reactive T cells can be safely given to patients, but these cells do not persist in large numbers long term. Future studies need to employ strategies to extend T cell persistence. This report is the first to document the use of genetically redirected T cells for the treatment of ovarian cancer.

Adoptive immunotherapy for cancer: building on success

Adoptive cell transfer after host preconditioning by lymphodepletion represents an important advance in cancer immunotherapy. Here, we describe how a lymphopaenic environment enables tumour-reactive T cells to destroy large burdens of metastatic tumour and how the state of differentiation of the adoptively transferred T cells can affect the outcome of treatment. We also discuss how the translation of these new findings might further improve the efficacy of adoptive cell transfer through the use of vaccines, haematopoietic-stem-cell transplantation, modified preconditioning regimens, and alternative methods for the generation and selection of the T cells to be transferred.

Supernatural T cells: genetic modification of T cells for cancer therapy

Immunotherapy is receiving much attention as a means of treating cancer, but complete, durable responses remain rare for most malignancies. The natural immune system seems to have limitations and deficiencies that might affect its ability to control malignant disease. An alternative to relying on endogenous components in the immune repertoire is to generate lymphocytes with abilities that are greater than those of natural T cells, through genetic modification to produce 'supernatural' T cells. This Review describes how such T cells can circumvent many of the barriers that are inherent in the tumour microenvironment while optimizing T-cell specificity, activation, homing and antitumour function.

Targeted elimination of prostate cancer by genetically directed human T lymphocytes

The genetic transfer of antigen receptors is a powerful approach to rapidly generate tumor-specific T lymphocytes. Unlike the physiologic T-cell receptor, chimeric antigen receptors (CARs) encompass immunoglobulin variable regions or receptor ligands as their antigen recognition moiety, thus permitting T cells to recognize tumor antigens in the absence of human leukocyte antigen expression. CARs encompassing the CD3zeta chain as their activating domain induce T-cell proliferation in vitro, but limited survival. The requirements for genetically targeted T cells to function in vivo are less well understood. We have, therefore, established animal models to assess the therapeutic efficacy of human peripheral blood T lymphocytes targeted to prostate-specific membrane antigen (PSMA), an antigen expressed in prostate cancer cells and the neovasculature of various solid tumors. In vivo specificity and antitumor activity were assessed in mice bearing established prostate adenocarcinomas, using serum prostate-secreted antigen, magnetic resonance, computed tomography, and bioluminescence imaging to investigate the response to therapy. In three tumor models, orthotopic, s.c., and pulmonary, we show that PSMA-targeted T cells effectively eliminate prostate cancer. Tumor eradication was directly proportional to the in vivo effector-to-tumor cell ratio. Serial imaging further reveals that the T cells must survive for at least 1 week to induce durable remissions. The eradication of xenogeneic tumors in a murine environment shows that the adoptively transferred T cells do not absolutely require in vivo costimulation to function. These results thus provide a strong rationale for undertaking phase I clinical studies to assess PSMA-targeted T cells in patients with metastatic prostate cancer.

T cell-mediated immunotherapy of metastases: state of the art in 2005

Advances in cellular and molecular immunology have led to the development of strategies for effective augmentation of antitumour immune responses in cancer patients. This review focuses on the manipulation of T cell immunity either by active specific immunotherapy (ASI) using tumour vaccines, or by adoptive immunotherapy (ADI) with immune T cells. Such therapies offer exquisite specificity of tumour recognition based on the ability of the T cell to distinguish single amino acid differences in any protein from any compartment of the tumour cell. Examples are presented of clinical survival benefits for cancer patients by postoperative ASI with a modified autologous tumour vaccine of high quality. Furthermore, clinical studies employing ADI with T cells activated and expanded ex vivo have demonstrated 'proof of principle' that tumour-specific T cells are capable of mediating anticancer activity in vivo, as measured by regression of metastatic tumours. Translation of these findings into a standardised immunotherapy is, however, not easy and will require coordination and cooperation among academic, private and federal sectors.