Immunotherapy of cancer using systemically delivered gene-modified human T lymphocytes

Evolving CAR-T-Cell Therapy for Cancer Treatment: From Scientific Discovery to Cures

In recent years, chimeric antigen receptor (CAR)-T-cell therapy has emerged as the most promising immunotherapy for cancer that typically uses patients' T cells and genetically engineered them to target cancer cells. Although recent improvements in CAR-T-cell therapy have shown remarkable success for treating hematological malignancies, the heterogeneity in tumor antigens and the immunosuppressive nature of the tumor microenvironment (TME) limits its efficacy in solid tumors. Despite the enormous efforts that have been made to make CAR-T-cell therapy more effective and have minimal side effects for treating hematological malignancies, more research needs to be conducted regarding its use in the clinic for treating various other types of cancer. The main concern for CAR-T-cell therapy is severe toxicities due to the cytokine release syndrome, whereas the other challenges are associated with complexity and immune-suppressing TME, tumor antigen heterogeneity, the difficulty of cell trafficking, CAR-T-cell exhaustion, and reduced cytotoxicity in the tumor site. This review discussed the latest discoveries in CAR-T-cell therapy strategies and combination therapies, as well as their effectiveness in different cancers. It also encompasses ongoing clinical trials; current challenges regarding the therapeutic use of CAR-T-cell therapy, especially for solid tumors; and evolving treatment strategies to improve the therapeutic application of CAR-T-cell therapy.

Revolutionizing cancer treatment: a comprehensive review of CAR-T cell therapy

Chimeric antigen receptor (CAR)-T cell therapy is a promising new treatment for cancer that involves genetically modifying a patient's T-cells to recognize and attack cancer cells. This review provides an overview of the latest discoveries and clinical trials related to CAR-T cell therapy, as well as the concept and applications of the therapy. The review also discusses the limitations and potential side effects of CAR-T cell therapy, including the high cost and the risk of cytokine release syndrome and neurotoxicity. While CAR-T cell therapy has shown promising results in the treatment of hematologic malignancies, ongoing research is needed to improve the efficacy and safety of the therapy and expand its use to solid tumors. With continued research and development, CAR-T cell therapy has the potential to revolutionize cancer treatment and improve outcomes for patients with cancer.

Virulent Bacteria as Inflammatory and Immune Co-Factor in Colon Carcinogenesis: Evidence From Two Monozygotic Patients and Validation in CRC Patient and Healthy Cohorts

Colorectal carcinoma (CRC) is a common disease, the incidence of which is increasing according to Western lifestyle; it remains to have a poor prognosis. Western nutriments are presumed to induce mild inflammation within the colonic mucosa, resulting in the accumulation of DNA alterations in colonocytes through a multistage carcinogenesis process. This suggests that most CRCs are related to the environment. Of interest, fecal microbiota composition has been shown yielding a novel approach regarding how environment changes may impact health and disease. Here, we compare whole shotgun metagenomic gut microbiota of two monozygotic twin sisters, one of whom is suffering from an advance colorectal tumor with a profound disequilibrium of the composition of the gut microbiota due to the overexpression of virulent bacteria such as E. coli, Shigella, and Clostridium species in the colon cancer patient’s feces contrasting with low levels of bacterial species such as Faecalibacterium and Akkermansia usually enriched in the healthy adults’ microbial flora. The disequilibrium in microbiota of the CRC patient’s feces as compared to her monozygotic twin sister is linked to inflammatory and immune cell infiltrates in the patient’s colonic tissue. We speculate on the role of microbiota disequilibrium on the immune-tolerant cell infiltrate within CRCs.

Chimeric antigen receptor T-cell therapy for breast cancer

One of the main reasons that researchers pay enormous attention to immunotherapy is that, despite significant advances in conventional therapy approaches, breast cancer remains the leading cause of death from malignant tumors among women. Genetically modifying T cells with chimeric antigen receptors (CAR) is one of the novel methods that has exhibited encouraging activity with relative safety, further urging investigators to develop several CAR T cells to target overexpressed antigens in breast tumors. This article is aimed not only to present such CAR T cells and discuss their remarkable results but also indicates their shortcomings with the hope of achieving possible strategies for improving therapeutic response.

Genetically engineered CAR T-immune cells for cancer therapy: recent clinical developments, challenges, and future directions

Cancer immunotherapy offers tremendous clinical outcomes in cancer management with the potential to induce sustained remission in patients with refractory disease. One of these immunotherapy modalities is the adoptive transfer of autologous T-cells that are genetically engineered ex vivo to express chimeric antigen receptors (CARs). These receptors can direct T-cells to the surface antigens of tumor cells to initiate an efficient and specific cytotoxic response against tumor cells. This review elucidates the structural features of CAR T-cells and their different generations reaching the recent 4th generation (TRUCK). The step-wise treatment process using CAR T-cell therapy and some of the updated prominent clinical applications of this treatment modality in both hematologic and solid malignancies are also covered in the present review. The success of CAR T-cell therapy is still encountered by several limitations for a widespread clinical application of this treatment modality, these challenges along with the recent innovative strategies that have been developed to overcome such drawbacks, as well as, the approaches and future directions aiming for a commercial low cost CAR T-cell immunotherapy modality, are all covered in the present review.

New Approaches in CAR-T Cell Immunotherapy for Breast Cancer

Despite significant advances in surgery, chemotherapy, radiotherapy, endocrine therapy, and molecular-targeted therapy, breast cancer remains the leading cause of death from malignant tumors among women. Immunotherapy has recently become a critical component of breast cancer treatment with encouraging activity and mild safety profiles. CAR-T therapy using genetically modifying T cells with chimeric antigen receptors (CAR) is the most commonly used approach to generate tumor-specific T cells. It has shown good curative effect for a variety of malignant diseases, especially for hematological malignancies. In this review, we briefly introduce the history and the present state of CAR research. Then we discuss the barriers of solid tumors for CARs application and possible strategies to improve therapeutic response with a focus on breast cancer. At last, we outlook the future directions of CAR-T therapy including managing toxicities and developing universal CAR-T cells.

Adoptive transfer of T cells transduced with a chimeric antigen receptor to treat relapsed or refractory acute leukemia: efficacy and feasibility of immunotherapy approaches

Treatment outcomes of acute leukemia (AL) have not improved over the past several decades and relapse rates remain high despite the availability of aggressive therapies. Conventional relapsed leukemia treatment includes second allogeneic hematopoietic stem cell transplantation (allo-HSCT) and donor lymphocyte infusion (DLI), which in most cases mediate, at best, a modest graft-versus-leukemia effect, although their clinical efficacy is still limited. Although allo-HSCT following myeloablative conditioning is a curative treatment option for younger patients with acute myeloid leukemia (AML) in a first complete remission (CR), allo-HSCT as a clinical treatment is usually limited because of treatment-related toxicity. The overall DLI remission rate is only 15%-42% and 2-year overall survival (OS) is approximately 15%-20%, with a high (40%-60%) incidence of DLI-related graft-versus-host disease (GVHD). Therefore, development of new, targeted treatment strategies for relapsed and refractory AL patients is ongoing. Adoptive transfer of T cells with genetically engineered chimeric antigen receptors (CARs) is an encouraging approach for treating hematological malignancies. These T cells are capable of selectively recognizing tumor-associated antigens and may overcome many limitations of conventional therapies, inducing remission in patients with chemotherapy-refractory or relapsed AL. In this review, we aimed to highlight the current understanding of this promising treatment modality, discussing its adverse effects and efficacy.

Insight to drug delivery aspects for colorectal cancer

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide in human beings. Surgery, chemotherapy, radiotherapy and targeted therapies are the conventional four approaches which are currently used for the treatment of CRC. The site specific delivery of chemotherapeutics to their site of action would increase effectiveness with reducing side effects. Targeted oral drug delivery systems based on polysaccharides are being investigated to target and deliver chemotherapeutic and chemopreventive agents directly to colon and rectum. Site-specific drug delivery to colon increases its concentration at the target site, and thus requires a lower dose and hence abridged side effects. Some novel therapies are also briefly discussed in article such as receptor (epidermal growth factor receptor, folate receptor, wheat germ agglutinin, VEGF receptor, hyaluronic acid receptor) based targeting therapy; colon targeted proapoptotic anticancer drug delivery system, gene therapy. Even though good treatment options are available for CRC, the ultimate therapeutic approach is to avert the incidence of CRC. It was also found that CRCs could be prevented by diet and nutrition such as calcium, vitamin D, curcumin, quercetin and fish oil supplements. Immunotherapy and vaccination are used nowadays which are showing better results against CRC.

CAR-modified T-cell therapy for cancer: an updated review

The use of chimeric antigen receptor (CAR)-modified T cells is a promising approach for cancer immunotherapy. These genetically modified receptors contain an antigen-binding moiety, a hinge region, a transmembrane domain, and an intracellular costimulatory domain resulting in T-cell activation subsequent to antigen binding. Optimal tumor removal through CAR-modified T cells requires suitable target antigen selection, co-stimulatory signaling domain, and the ability of CAR T cells to traffic, persist, and retain antitumor function after adoptive transfer. There are several elements which can improve antitumor function of CAR T cells, including signaling, conditioning chemotherapy and irradiation, tumor burden of the disease, T-cell phenotype, and supplementary cytokine usage. This review outlines four generations of CAR. The pre-clinical and clinical studies showed that this technique has a great potential for treatment of solid and hematological malignancies. The main purpose of the current review is to focus on the pre-clinical and clinical developments of CAR-based immunotherapy.

Identification of chimeric antigen receptors that mediate constitutive or inducible proliferation of T cells

This study compared second-generation chimeric antigen receptors (CAR) encoding signaling domains composed of CD28, ICOS, and 4-1BB (TNFRSF9). Here, we report that certain CARs endow T cells with the ability to undergo long-term autonomous proliferation. Transduction of primary human T cells with lentiviral vectors encoding some of the CARs resulted in sustained proliferation for up to 3 months following a single stimulation through the T-cell receptor (TCR). Sustained numeric expansion was independent of cognate antigen and did not require the addition of exogenous cytokines or feeder cells after a single stimulation of the TCR and CD28. Results from gene array and functional assays linked sustained cytokine secretion and expression of T-bet (TBX21), EOMES, and GATA-3 to the effect. Sustained expression of the endogenous IL2 locus has not been reported in primary T cells. Sustained proliferation was dependent on CAR structure and high expression, the latter of which was necessary but not sufficient. The mechanism involves constitutive signaling through NF-κB, AKT, ERK, and NFAT. The propagated CAR T cells retained a diverse TCR repertoire, and cellular transformation was not observed. The CARs with a constitutive growth phenotype displayed inferior antitumor effects and engraftment in vivo. Therefore, the design of CARs that have a nonconstitutive growth phenotype may be a strategy to improve efficacy and engraftment of CAR T cells. The identification of CARs that confer constitutive or nonconstitutive growth patterns may explain observations that CAR T cells have differential survival patterns in clinical trials.

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.

Gene-engineered T cells for cancer therapy

T cells have the capacity to eradicate diseased cells, but tumours present considerable challenges that render T cells ineffectual. Cancer cells often make themselves almost 'invisible' to the immune system, and they sculpt a microenvironment that suppresses T cell activity, survival and migration. Genetic engineering of T cells can be used therapeutically to overcome these challenges. T cells can be taken from the blood of cancer patients and then modified with genes encoding receptors that recognize cancer-specific antigens. Additional genes can be used to enable resistance to immunosuppression, to extend survival and to facilitate the penetration of engineered T cells into tumours. Using genetic modification, highly active, self-propagating 'slayers' of cancer cells can be generated.

Novel cellular therapies for leukemia: CAR-modified T cells targeted to the CD19 antigen

The ability of immune-competent donor T cells to mediate a beneficial graft-versus-leukemia (GVL) effect was first identified in the setting of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematologic malignancies. Unfortunately, with the exception of chronic myelogenous leukemia and EBV-induced lymphoproliferative disease, allo-HSCT GVL lacks the potency to significantly affect disease progression or recurrence in most other hematologic malignancies. The inadequacy of a GVL effect using past approaches is particularly evident in patients with lymphoid malignancies. However, with the advent of improved gene transfer technology, genetically modified tumor-specific immune effectors have extended cellular immunotherapy to lymphoid malignancies. One promising strategy entails the introduction of genes encoding artificial receptors called chimeric antigen receptors (CARs), which redirect the specificity and function of immune effectors. CAR-modified T cells targeted to the B cell-specific CD19 antigen have demonstrated promising results in multiple early clinical trials, supporting further investigation in patients with B-cell cancers. However, disparities in clinical trial design and CAR structure have complicated the discovery of the optimal application of this technology. Recent preclinical studies support additional genetic modifications of CAR-modified T cells to achieve optimal clinical efficacy using this novel adoptive cellular therapy.

Chimeric antigen receptor-redirected T cells display multifunctional capacity and enhanced tumor-specific cytokine secretion upon secondary ligation of chimeric receptor

Aim: The aim of the current study was to fully elucidate the functions of T cells genetically modified with an erbB2-specific chimeric antigen receptor (CAR). Material & methods: In this study, key functional parameters of CAR T cells were examined following antigen-specific stimulation of the chimeric anti-erbB2 receptor. Results: Gene-modified T cells produced the cytokines IFN-γ, IL-2, IL-4, IL-10, TNF-α and IL-17, and the chemokine RANTES upon CAR ligation. A multifunctional capacity of these CAR T cells was also demonstrated, where 13.7% of cells were found to simultaneously express IFN-γ and CD107a, indicative of cytolytic granule release. In addition, the CAR T cells were able to respond to a greater degree on the second ligation of CAR, which has not been previously shown. IFN-γ secretion levels were significantly higher on second ligation than those secreted following initial ligation. CAR-expressing T cells were also demonstrated to lyze erbB2-expressing tumor cells in the absence of activity against bystander cells not expressing the erbB2 antigen, thereby demonstrating exquisite specificity. Conclusion: This study demonstrates the specificity of CAR gene-engineered T cells and their capacity to deliver a wide range of functions against tumor cells with an enhanced response capability after initial receptor engagement.

A mutant Tat protein provides strong protection from HIV-1 infection in human CD4+ T cells

Here we show potent inhibition of HIV-1 replication in a human T cell line and primary human CD4(+) cells by expressing a single antiviral protein. Nullbasic is a mutant form of the HIV-1 Tat protein that was previously shown to strongly inhibit HIV-1 replication in nonhematopoietic cell lines by targeting three steps of HIV-1 replication: reverse transcription, transport of viral mRNA, and trans-activation of HIV-1 gene expression. Here we investigated gene delivery of Nullbasic, using lentiviral and retroviral vectors. Although Nullbasic could be delivered by lentiviral vectors to target cells, transduction efficiencies were sharply reduced primarily because of negative effects on reverse transcription mediated by Nullbasic. However, Nullbasic did not inhibit transduction of HEK293T cells by a murine leukemia virus (MLV)-based retroviral vector. Therefore, MLV-based virus-like particles were used to transduce and express Nullbasic-EGFP or EGFP in Jurkat cells, a human leukemia T cell line, and Nullbasic-ZsGreen1 or ZsGreen1 in primary human CD4(+) cells. HIV-1 replication kinetics were similar in parental Jurkat and Jurkat-EGFP cells, but were strongly attenuated in Jurkat-Nullbasic-EGFP cells. Similarly, virus replication in primary CD4(+) cells expressing a Nullbasic-ZsGreen1 fusion protein was inhibited by approximately 8- to 10-fold. These experiments demonstrate the potential of Nullbasic, which has unique inhibitory activity, as an antiviral agent against HIV-1 infection.

Chimeric antigen receptors for T cell immunotherapy: current understanding and future directions

BACKGROUND

The genetic engineering of T cells through the introduction of a chimeric antigen receptor (CAR) allows for generation of tumor-targeted T cells. Once expressed by T cells, CARs combine antigen-specificity with T cell activation in a single fusion molecule. Most CARs are comprised of an antigen-binding domain, an extracellular spacer/hinge region, a trans-membrane domain and an intracellular signaling domain resulting in T cell activation after antigen binding.

METHODS

We performed a search of the literature regarding tumor immunotherapy using CAR-modified T cells to provide a concise review of this topic.

RESULTS

This review aims to focus on the elements of CAR design required for successful application of this technology in cancer immunotherapy. Most notably, proper target antigen selection, co-stimulatory signaling, and the ability of CAR-modified T cells to traffic, persist and retain function after adoptive transfer are required for optimal tumor eradication. Furthermore, recent clinical trials have demonstrated tumor burden and chemotherapy conditioning before adoptive transfer as being critically important for this therapy. Future research into counteracting the suppressive tumor microenvironment and the ability to activate an endogenous anti-tumor response by CAR-modified T cells may enhance the therapeutic potential of this treatment.

CONCLUSIONS

In conclusion, CAR-modified T cell therapy is a highly promising treatment for cancer, having already demonstrated both promising preclinical and clinical results. However, further modification and additional clinical trials will need to be conducted to ultimately optimize the anti-tumor efficacy of this approach.

Novel cellular therapies for leukemia: CAR-modified T cells targeted to the CD19 antigen

The ability of immune-competent donor T cells to mediate a beneficial graft-versus-leukemia (GVL) effect was first identified in the setting of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematologic malignancies. Unfortunately, with the exception of chronic myelogenous leukemia and EBV-induced lymphoproliferative disease, allo-HSCT GVL lacks the potency to significantly affect disease progression or recurrence in most other hematologic malignancies. The inadequacy of a GVL effect using past approaches is particularly evident in patients with lymphoid malignancies. However, with the advent of improved gene transfer technology, genetically modified tumor-specific immune effectors have extended cellular immunotherapy to lymphoid malignancies. One promising strategy entails the introduction of genes encoding artificial receptors called chimeric antigen receptors (CARs), which redirect the specificity and function of immune effectors. CAR-modified T cells targeted to the B cell–specific CD19 antigen have demonstrated promising results in multiple early clinical trials, supporting further investigation in patients with B-cell cancers. However, disparities in clinical trial design and CAR structure have complicated the discovery of the optimal application of this technology. Recent preclinical studies support additional genetic modifications of CAR-modified T cells to achieve optimal clinical efficacy using this novel adoptive cellular therapy.

Targeted immunotherapy of cancer with CAR T cells: achievements and challenges

The adoptive transfer of chimeric antigen receptor (CAR)-expressing T cells is a relatively new but promising approach in the field of cancer immunotherapy. This therapeutic strategy is based on the genetic reprogramming of T cells with an artificial immune receptor that redirects them against targets on malignant cells and enables their destruction by exerting T cell effector functions. There has been an explosion of interest in the use of CAR T cells as an immunotherapy for cancer. In the pre-clinical setting, there has been a considerable focus upon optimizing the structural and signaling potency of the CAR while advances in bio-processing technology now mean that the clinical testing of these gene-modified T cells has become a reality. This review will summarize the concept of CAR-based immunotherapy and recent clinical trial activity and will further discuss some of the likely future challenges facing CAR-modified T cell therapies.

Inhibition of p38 MAPK activity in B-NHL Raji cells by treatment with engineered CD20-specific T cells

Adoptive immunotherapy with T cells expressing CD20-specific chimeric T-cell receptors is a promising approach to lymphoma therapy. However, modification of the cellular signaling pathways in target tumor cells by treatment with engineered CD20-specific T cells has yet to be fully elucidated. In this study, the non-Hodgkin's lymphoma Raji cell line was co-cultured with T cells that were genetically modified with anti-CD20scFvFc/CD28/CD3ζ or anti-CD20scFvFc gene. The cytolytic activity of engineered CD20-specific T cells and IL-10 secretion was quantitated by Cytotoxicity and ELISA assays, respectively. The engineered CD20-specific T cells and Raji cells were sorted using flow cytomety for the Western blot analysis. Treatment of Raji cells with T cells genetically modified with anti-CD20scFvFc/CD28/CD3ζ chimera (compared to anti-CD20scFvFc) yielded a higher cytotoxicity against Raji cells in vitro. Additionally, we found that engineered CD20-specific T cells caused a decrease in IL-10 secretion and inhibition of phosphor-STAT3 and Bcl-2 expression in Raji cells, possibly through the down-regulation of p38 MAPK and NF-κB activity. These results indicate that the treatment of Raji cells with engineered CD20-specific T cells inhibited the cellular p38 MAPK signaling pathways, which enhanced its antitumor activities against CD20-positive tumor cells.

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.

Direct and indirect antitumor effects by human peripheral blood lymphocytes expressing both chimeric immune receptor and interleukin-2 in ovarian cancer xenograft model

Human peripheral blood lymphocytes (PBLs) electroporated with RNA encoding anti-Her-2/neu-specific chimeric immune receptor (CIR) have been reported to elicit potent immune responses against SKOV3 tumors in a nude mouse model. However, CIR-electroporated PBL (CIR-PBL) did not proliferate, and the cell number rapidly decreased in the absence of exogenous interleukin-2 (IL-2). In this study, PBLs electroporated with both CIR and IL-2 RNA (CIR/IL-2-PBL) were studied to determine whether antitumor effects could be improved by adoptive immunotherapy. CIR and IL-2 were expressed in CIR/IL-2-PBL at levels similar to PBLs electroporated, with IL-2 RNA (IL-2-PBL) or CIR-PBL. Transfer of IL-2 RNA induced proliferation and prolonged survival of PBLs in vitro. In a xenograft model, both IL-2-PBL and CIR/IL-2-PBL showed significantly higher antitumor effects than CIR-PBL. The number of tumor-infiltrating natural killer (NK) cells was significantly increased in IL-2-PBL and CIR/IL-2-PBL. After NK cell depletion, IL-2-PBL showed significantly lower antitumor effects than CIR/IL-2-PBL. These results suggest that transfer of IL-2 RNA to CIR-PBL can promote NK cell infiltration of tumors and prolong survival of infused PBLs in vivo. RNA electroporated PBLs may represent efficient tools for delivery of functional molecules to tumors by multiple gene transfer.

Adoptive T-cell immunotherapy of cancer using chimeric antigen receptor-grafted T cells

Harnessing the power of the immune system to target cancer has long been a goal of tumor immunologists. One avenue under investigation is the modification of T cells to express a chimeric antigen receptor (CAR). Expression of such a receptor enables T-cell specificity to be redirected against a chosen tumor antigen. Substantial research in this field has been carried out, incorporating a wide variety of malignancies and tumor-associated antigens. Ongoing investigations will ensure this area continues to expand at a rapid pace. This review will explain the evolution of CAR technology over the last two decades in addition to detailing the associated benefits and disadvantages. The outcome of recent phase I clinical trials and the impact that these have had upon the direction of future research in this field will also be addressed.

Gene-modified T cells as immunotherapy for multiple myeloma and acute myeloid leukemia expressing the Lewis Y antigen

We have evaluated the carbohydrate antigen Lewis(Y) (Le(Y)) as a potential target for T-cell immunotherapy of hematological neoplasias. Analysis of 81 primary bone marrow samples revealed moderate Le(Y) expression on plasma cells of myeloma patients and myeloblasts of patients with acute myeloid leukemia (AML) (52 and 46% of cases, respectively). We developed a retroviral vector construct encoding a chimeric T-cell receptor that recognizes the Le(Y) antigen in a major histocompatibility complex-independent manner and delivers co-stimulatory signals to achieve T-cell activation. We have shown efficient transduction of peripheral blood-derived T cells with this construct, resulting in antigen-restricted interferon-gamma secretion and cell lysis of Le(Y)-expressing tumor cells. In vivo activity of gene-modified T cells was demonstrated in the delayed growth of myeloma xenografts in NOD/SCID mice, which prolonged survival. Therefore, targeting Le(Y)-positive malignant cells with T cells expressing a chimeric receptor recognizing Le(Y) was effective both in vitro and in a myeloma mouse model. Consequently, we plan to use T cells manufactured under Good Manufacturing Practice conditions in a phase I immunotherapy study for patients with Le(Y)-positive myeloma or AML.

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.

Genetically targeted T cells eradicate established breast cancer in syngeneic mice

PURPOSE

The purpose of the present study was to evaluate the capacity and mechanisms of genetically modified erbB2-specific T cells to eradicate erbB2+ tumors in syngeneic mice.

EXPERIMENTAL DESIGN

Primary mouse T cells were modified to target the breast tumor-associated antigen erbB2 through retroviral-mediated transfer of a chimeric antigen receptor, termed single-chain antibody (scFv)-CD28-zeta. Antitumor efficacy of scFv-CD28-zeta-modified T cells was analyzed in mice bearing D2F2/E2 breast tumors.

RESULTS

The scFv-CD28-zeta-modified T cells were shown to specifically secrete T cytotoxic-1 cytokines and lyse erbB2+ breast tumor cells following receptor stimulation in vitro. Treatment with scFv-CD28-zeta-modified T cells was able to lead to long-term, tumor-free survival in mice bearing erbB2+ D2F2/E2 breast tumors. Importantly, the surviving mice developed a host memory response to D2F2/E2 tumor cells, and this host response was able to protect against a rechallenge with erbB2+ D2F2/E2 tumor cells and parental erbB2(-) D2F2 tumor cells. In addition, scFv-CD28-zeta T-cell expression of perforin and interferon-gamma were essential for complete antitumor efficacy.

CONCLUSIONS

Treatment with scFv-CD28-zeta-modified T cells was able to induce a host antitumor immunity in syngeneic mice. Complete tumor elimination by scFv-CD28-zeta-modified T cells required T cell-derived interferon-gamma and perforin, indicating that cytotoxicity and cytokine secretion play a role in the in vivo response.

Review article: future therapies for management of metastatic gastroenteropancreatic neuroendocrine tumours

BACKGROUND

Gastroenteropancreatic neuroendocrine tumours (GEP NETs) are relatively uncommon tumours that occur anywhere within the gastrointestinal tract. The prevalence of GEP NETs is estimated to be 35 per 100 000 population. Patients often present with metastatic disease and consequently, palliative treatments form the mainstay of therapy.

AIM

To review the current and novel therapeutic options for management of GEP NETs.

METHODS

Searches for all studies related to GEP NETs, NETs and carcinoid tumours in Medline and abstracts from international meetings.

RESULTS

Somatostatin analogues remain the first line therapy for management of symptoms of GEP NETs and may have anti-proliferative action. New somatostatin analogues with different somatostatin receptor affinity have been developed. Radionuclide peptide receptor therapy is established in patients with positive somatostatin scintigraphy. A number of new agents and targeted therapies are currently being evaluated in a phase I and II studies and these include angiogenic inhibitors, mammalian target of rapamycin inhibitors and immune therapies.

CONCLUSIONS

A number of nonsurgical therapies are available for management of gastroenteropancreatic neuroendocrine tumours. It is hoped, the development of some of these promising novel therapies will expand the therapeutic armamentarium.

The promise and potential pitfalls of chimeric antigen receptors

One important purpose of T cell engineering is to generate tumor-targeted T cells through the genetic transfer of antigen-specific receptors, which consist of either physiological, MHC-restricted T cell receptors (TCRs) or non MHC-restricted chimeric antigen receptors (CARs). CARs combine antigen-specificity and T cell activating properties in a single fusion molecule. First generation CARs, which included as their signaling domain the cytoplasmic region of the CD3zeta or Fc receptor gamma chain, effectively redirected T cell cytotoxicity but failed to enable T cell proliferation and survival upon repeated antigen exposure. Receptors encompassing both CD28 and CD3zeta are the prototypes for second generation CARs, which are now rapidly expanding to a diverse array of receptors with different functional properties. First generation CARs have been tested in phase I clinical studies in patients with ovarian cancer, renal cancer, lymphoma, and neuroblastoma, where they have induced modest responses. Second generation CARs, which are just now entering the clinical arena in the B cell malignancies and other cancers, will provide a more significant test for this approach. If the immunogenicity of CARs can be averted, the versatility of their design and HLA-independent antigen recognition will make CARs tools of choice for T cell engineering for the development of targeted cancer immunotherapies.

Adoptive immunotherapy using human peripheral blood lymphocytes transferred with RNA encoding Her-2/neu-specific chimeric immune receptor in ovarian cancer xenograft model

The current gene transfer technology for single chain (scFv)-based chimeric immune receptor (CIR) has relied on retrovirus and lentivirus vectors which require a long time to obtain sufficient number of transduced cells and stably incorporate into genome. To ameliorate these limitations, we applied RNA electroporation to human peripheral blood lymphocytes (PBLs) activated with anti-CD3 antibody and interleukin-2 (IL-2) for 3 days and assessed that PBL transiently expressing anti-Her-2/neu CIR (CIR-PBL) containing signaling portion of CD28 and CD3zeta could elicit strong cytotoxicity in vitro and antitumor responses in vivo. The CIR-PBL expressed high level of CIR in CD4+, CD8+ and CD56+ cells. Her-2/neu-specific stimulation induced secretion of type-I cytokines including interferon-gamma (IFN-gamma), IL-8 and granulocyte-macrophage colony-stimulating factor, and IFN-gamma secretion was mainly mediated by CD8+ T cells. CIR-PBL specifically killed SKOV3 cell line expressing Her-2/neu. Adoptive transfer of CIR-PBL in SKOV3 xenograft model led to significant inhibition of tumor growth compared with transfer of mock-transduced PBL and showed higher inhibition than those with Herceptin, humanized monoclonal antibody specific for Her-2/neu. These results provided evidence that electroporation of CIR RNA to human PBLs could be used for rapid generation and high number of therapeutic antigen-specific T cells for adoptive immunotherapy.

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.

Adoptive transfer of chimeric FcepsilonRI gene-modified human T cells for cancer immunotherapy

Immunotherapeutic approaches involving genetic modification of T cells show promise in generating highly specific tumor-reactive effector cells for cancer treatment. Given the high affinity of FcRI (the subtype I Fc receptor for IgE) for IgE monoclonal antibody (mAb), modification of T cells with chimeric FcRI in combination with tumor-specific IgE mAbs is potentially a powerful and effective strategy to specifically target T cells to tumor cells. In this study, we retrovirally transduce human primary T cells with a cDNA encoding the extracellular domain of FcRI linked to the hinge and transmembrane domains of FcRI and the cytoplasmic domains of CD28 and T cell receptor zeta chain (FcRI-CD28-zeta). We demonstrate that human T cells expressing FcRI-CD28-zeta, in the presence of tumor-specific IgE mAb recognizing mouse CD8 antigen (Ly- 2.1+), can specifically secrete cytokine, proliferate, and mediate cytotoxic function after antigen ligation. Furthermore, adoptive transfer of FcRI-CD28-zeta cells incubated with anti-Ly-2.1 IgE mAb significantly enhances the survival of irradiated nonobese diabetic-severe combined immunodeficiency mice bearing Ly-2.1+ tumor compared with control mice. Thus, this set of experiments demonstrates that Fc gene-engineered human T cells mediate effector function in vitro and in vivo in an IgE-dependent manner and thus a novel and valid approach for cancer therapy can now be further developed.

Cell and gene therapy in Australia

The expansion of human cells to produce cell therapeutic products for the treatment of disease is, with few exceptions, an experimental therapy. Because cell therapies involve a biological product, often with some genetic or other modification, they require extensive pre-clinical research and development. Cell therapy production processes and premises require licensing by the Therapeutic Goods Administration. In this review, timed to coincide with the international meetings of the ISCT and ISSCR in Australia, we describe some promising cell therapies currently under development.

Addition of the CD28 signaling domain to chimeric T-cell receptors enhances chimeric T-cell resistance to T regulatory cells

T cells can be engineered to target tumor cells by transduction of tumor-specific chimeric receptors, consisting of an extracellular antigen-binding domain and an intracellular signaling domain. However, the peripheral blood of cancer patients frequently contains an increased number of T regulatory cells, which appear to inhibit immune reactivity. We have investigated the effects of T regulatory cells on chimeric T cells specific for the B-cell antigen CD19, as B-cell malignancies are attractive targets for chimeric T-cell therapy. When a CD19 single-chain Fv antibody was coupled to the CD3 zeta (zeta) chain, there was sharply reduced activity on exposure to T regulatory cells, measured by CD19+ target-induced proliferation and cytotoxicity. By contrast, expression in T cells of a chimeric receptor consisting of the intracellular portion of the CD28 molecule fused to the zeta-chain and CD19 single-chain Fv not only produced a higher proliferative response and an increased nuclear factor kappaB activation but also sustained these activities in the presence of T regulatory cells. These effects are seen whether the chimeric T cells are derived from normal donors or from patients with B-cell chronic lymphocytic leukemia, indicating the potential for clinical application in B cell malignancies.

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.

Adoptive transfer of T cells modified with a humanized chimeric receptor gene inhibits growth of Lewis-Y-expressing tumors in mice

In this study, human T cells were provided with a reactivity against the Lewis-Y (Le(Y)) carbohydrate antigen, which is overexpressed on 70% of epithelial-derived tumors, but not normally recognized by T cells. Antitumor reactivity was achieved by transduction of T cells with a gene encoding a cell-surface chimeric receptor composed of single-chain anti-Le(Y) antibody linked to an enhanced cytoplasmic signaling domain made up of CD28 and CD3-zeta. Importantly, the single-chain antibody was humanized to try to reduce potential problems of human anti-mouse antibody responses in patients receiving chimeric receptor-modified T cells in future clinical trials. T cells expressing the chimeric receptor were demonstrated to secrete cytokines and proliferate in response to receptor ligation and lysed Le(Y+) tumors in vitro. Another aspect of this study was the finding that no activity was observed against normal tissue, as represented by autologous neutrophils that express low levels of Le(Y). Significantly, systemic delivery of anti-Le(Y) T cells dramatically inhibited established s.c. human ovarian OVCAR-3 tumors (a recognized difficult model to treat) in mice. Finally, we demonstrated that anti-Le(Y) T cells preferentially expanded or accumulated in the tumor compared with control empty vector T cells, thereby providing mechanistic insight into the specific antitumor response. This study supports the use of humanized gene-modified T cells as a potential therapy for Le(Y+) malignancies.

Adoptive transfer of gene-engineered CD4+ helper T cells induces potent primary and secondary tumor rejection

Because CD4+ T cells play a key role in aiding cellular immune responses, we wanted to assess whether increasing numbers of gene-engineered antigen-restricted CD4+ T cells could enhance an antitumor response mediated by similarly gene-engineered CD8+ T cells. In this study, we have used retroviral transduction to generate erbB2-reactive mouse T-cell populations composed of various proportions of CD4+ and CD8+ cells and then determined the antitumor reactivity of these mixtures. Gene-modified CD4+ and CD8+ T cells were shown to specifically secrete Tc1 (T cytotoxic-1) or Tc2 cytokines, proliferate, and lyse erbB2+ tumor targets following antigen ligation in vitro. In adoptive transfer experiments using severe combined immunodeficient (scid) mice, we demonstrated that injection of equivalent numbers of antigen-specific engineered CD8+ and CD4+ T cells led to significant improvement in survival of mice bearing established lung metastases compared with transfer of unfractionated (largely CD8+) engineered T cells. Transferred CD4+ T cells had to be antigen-specific (not just activated) and secrete interferon gamma (IFN-gamma) to potentiate the antitumor effect. Importantly, antitumor responses in these mice correlated with localization and persistence of gene-engineered T cells at the tumor site. Strikingly, mice that survived primary tumor challenge could reject a subsequent rechallenge. Overall, this study has highlighted the therapeutic potential of using combined transfer of antigen-specific gene-modified CD8+ and CD4+ T cells to significantly enhance T-cell adoptive transfer strategies for cancer therapy.