Eradication of disseminated murine leukemia by chemoimmunotherapy with cyclophosphamide and adoptively transferred immune syngeneic Lyt-1+2- lymphocytes

Intratumoral immune triads are required for immunotherapy-mediated elimination of solid tumors

Tumor-specific CD8+ T cells are frequently dysfunctional and unable to halt tumor growth. We investigated whether tumor-specific CD4+ T cells can be enlisted to overcome CD8+ T cell dysfunction within tumors. We find that the spatial positioning and interactions of CD8+ and CD4+ T cells, but not their numbers, dictate anti-tumor responses in the context of adoptive T cell therapy as well as immune checkpoint blockade (ICB): CD4+ T cells must engage with CD8+ T cells on the same dendritic cell during the effector phase, forming a three-cell-type cluster (triad) to license CD8+ T cell cytotoxicity and cancer cell elimination. When intratumoral triad formation is disrupted, tumors progress despite equal numbers of tumor-specific CD8+ and CD4+ T cells. In patients with pleural mesothelioma treated with ICB, triads are associated with clinical responses. Thus, CD4+ T cells and triads are required for CD8+ T cell cytotoxicity during the effector phase and tumor elimination.

Role of antioxidants in modulating anti-tumor T cell immune resposne

It has been well established that in addition to oxygen's vital in cellular respiration, a disruption of oxygen balance can lead to increased stress and oxidative injury. Similarly, reduced oxygen during tumor proliferation and invasion generates a hypoxic tumor microenvironment, resulting in dysfunction of immune cells and providing a conducive milieu for tumors to adapt and grow. Strategies to improve the persistence tumor reactive T cells in the highly oxidative tumor environment are being pursued for enhancing immunotherapy outcomes. To this end, we have focused on various strategies that can help increase or maintain the antioxidant capacity of T cells, thus reducing their susceptibility to oxidative stress/damage. Herein we lay out an overview on the role of oxygen in T cell signaling and how pathways regulating oxidative stress or antioxidant signaling can be targeted to enhance immunotherapeutic approaches for cancer treatment.

Adoptive immunotherapy with cells from tumor-draining lymph nodes activated and expanded in vitro

Tumor-draining lymph nodes (tumor-DLNs) provide a rich source of tumor-reactive lymphocytes which can be used in adoptive immunotherapy (AIT) and that circumvent the need to resect autologous tumor, without the challenges and shortcomings associated with using autologous tumor or anti-CD3 monoclonal antibody. Bryostatin/Ionomycin (Bryo/Io) provide a useful method of activating tumor-DLNs such that they can readily be expanded to sufficient numbers to be used in AIT, and growing the tumor-DLN lymphocytes in the gamma chain cytokines IL-7 plus IL-15 is superior to IL-2 in terms of T cell numbers and phenotype. AIT with these cells induces tumor regression and provides protection against metastases and future tumor challenge. Here, we provide a stepwise protocol to sensitize tumor-DLN cells in donor mice, activate tumor-DLN T cells ex vivo using Bryo/Io, expansion of these cells in gamma chain cytokines and adoptive transfer of the expanded cells back into tumor-bearing hosts. Methods relevant to these experiments, such as injecting tumor cells intravenously and monitoring for pulmonary metastases, tumor volume measurement and resection, and use of luciferase-expressing tumor cells to monitor for metastases following resection, are described in detail. The methods outlined herein can be easily adapted to suit similar experiments across multiple tumor cell lines and syngeneic mouse models.

Intratumoral immune triads are required for adoptive T cell therapy-mediated elimination of solid tumors

Tumor-reactive CD8 T cells found in cancer patients are frequently dysfunctional, unable to halt tumor growth. Adoptive T cell transfer (ACT), the administration of large numbers of in vitro-generated cytolytic tumor-reactive CD8 T cells, is an important cancer immune therapy being pursued. However, a limitation of ACT is that transferred CD8 T cells often rapidly lose effector function, and despite exciting results in certain malignancies, few ACT clinical trials have shown responses in solid tumors. Here, we developed preclinical cancer mouse models to investigate if and how tumor-specific CD4 T cells can be enlisted to overcome CD8 T cell dysfunction in the setting of ACT. In situ confocal microscopy of color-coded cancer cells, tumor-specific CD8 and CD4 T cells, and antigen presenting cells (APC), combined with functional studies, revealed that the spatial positioning and interactions of CD8 and CD4 T cells, but not their numbers, dictates ACT efficacy and anti-tumor responses. We uncover a new role of antigen-specific CD4 T cells in addition to the known requirement for CD4 T cells during priming/activation of naïve CD8 T cells. CD4 T cells must co-engage with CD8 T cells and APC cross-presenting CD8- and CD4-tumor antigens during the effector phase, forming a three-cell-cluster (triad), to license CD8 T cell cytotoxicity and mediate cancer cell elimination. Triad formation transcriptionally and epigenetically reprogram CD8 T cells, prevent T cell dysfunction/exhaustion, and ultimately lead to the elimination of large established tumors and confer long-term protection from recurrence. When intratumoral triad formation was disrupted, adoptively transferred CD8 T cells could not be reprogrammed, and tumors progressed despite equal numbers of tumor-infiltrating CD8 and CD4 T cells. Strikingly, the formation of CD4 T cell::CD8 T cell::APC triads in tumors of patients with lung cancers treated with immune checkpoint blockade was associated with clinical responses, but not CD4::APC dyads or overall numbers of CD8 or CD4 T cells, demonstrating the importance of triads in non-ACT settings in humans. Our work uncovers intratumoral triads as a key requirement for anti-tumor immunity and a new role for CD4 T cells in CD8 T cell cytotoxicity and cancer cell eradication.

CD4+ T cells in cancer

Cancer immunology and immunotherapy are driving forces of research and development in oncology, mostly focusing on CD8⁺ T cells and the tumor microenvironment. Recent progress highlights the importance of CD4⁺ T cells, corresponding to the long-known fact that CD4⁺ T cells are central players and coordinators of innate and antigen-specific immune responses. Moreover, they have now been recognized as anti-tumor effector cells in their own right. Here we review the current status of CD4⁺ T cells in cancer, which hold great promise for improving knowledge and therapies in cancer.

Generation of TGFβR2(-1) neoantigen-specific HLA-DR4-restricted T cell receptors for cancer therapy

BACKGROUND

Adoptive transfer of patient's T cells, engineered to express a T cell receptor (TCR) with defined novel antigen specificity, is a convenient form of cancer therapy. In most cases, major histocompatibility complex (MHC) I-restricted TCRs are expressed in CD8⁺ T cells and the development of CD4⁺ T cells engineered to express an MHC II-restricted TCR lacks behind. Critical is the choice of the target antigen, whether the epitope is efficiently processed and binds with high affinity to MHC molecules. A mutation in the transforming growth factor β receptor 2 (TGFβR2(-1)) gene creates a frameshift peptide caused by the deletion of one adenine (-1) within a microsatellite sequence. This somatic mutation is recurrent in microsatellite instable colorectal and gastric cancers and, therefore, is a truly tumor-specific antigen detected in many patients.

METHODS

ABabDR4 mice, which express a diverse human TCR repertoire restricted to human MHC II molecule HLA-DRA/DRB1*0401 (HLA-DR4), were immunized with the TGFβR2(-1) peptide and TGFβR2(-1)-specific TCRs were isolated from responding CD4⁺ T cells. The TGFβR2(-1)-specific TCRs were expressed in human CD4⁺ T cells and their potency and safety profile were assessed by co-cultures and other functional assays.

RESULTS

We demonstrated that TGFβR2(-1) neoantigen is immunogenic and elicited CD4⁺ T cell responses in ABabDR4 mice. When expressed in human CD4⁺ T cells, the HLA-DR4 restricted TGFβR2(-1)-specific TCRs induced IFNy expression at low TGFβR2(-1) peptide amounts. The TGFβR2(-1)-specific TCRs recognized HLA-DR4⁺ lymphoblastoid cells, which endogenously processed and presented the neoantigen, and colorectal cancer cell lines SW48 and HCT116 naturally expressing the TGFβR2(-1) mutation. No MHC II alloreactivity or cross-reactivity to peptides with a similar TCR-recognition motif were observed, indicating the safety of the TCRs.

CONCLUSIONS

The data suggest that HLA-DR4-restricted TCRs specific for the TGFβR2(-1) recurrent neoantigen can be valuable candidates for adoptive T cell therapy of a sizeable number of patients with cancer.

Targeting Driver Oncogenes and Other Public Neoantigens Using T Cell Receptor-Based Cellular Therapy

T cell reactivity to tumor-specific neoantigens can drive endogenous and therapeutically induced antitumor immunity. However, most tumor-specific neoantigens are unique to each patient (private) and targeting them requires personalized therapy. A smaller subset of neoantigens includes epitopes that span recurrent mutation hotspots, translocations, or gene fusions in oncogenic drivers and tumor suppressors, as well as epitopes that arise from viral oncogenic proteins. Such antigens are likely to be shared across patients (public), uniformly expressed within a tumor, and required for cancer cell survival and fitness. Although a limited number of these public neoantigens are naturally immunogenic, recent studies affirm their clinical utility. In this review, we highlight efforts to target mutant KRAS, mutant p53, and epitopes derived from oncogenic viruses using T cells engineered with off-the-shelf T cell receptors. We also discuss the challenges and strategies to achieving more effective T cell therapies, particularly in the context of solid tumors.

New Developments in T Cell Immunometabolism and Implications for Cancer Immunotherapy

Despite rapid advances in the field of immunotherapy, the elimination of established tumors has not been achieved. Many promising new treatments such as adoptive cell therapy (ACT) fall short, primarily due to the loss of T cell effector function or the failure of long-term T cell persistence. With the availability of new tools and advancements in technology, our understanding of metabolic processes has increased enormously in the last decade. Redundancy in metabolic pathways and overlapping targets that could address the plasticity and heterogenous phenotypes of various T cell subsets have illuminated the need for understanding immunometabolism in the context of multiple disease states, including cancer immunology. Herein, we discuss the developing field of T cell immunometabolism and its crucial relevance to improving immunotherapeutic approaches. This in-depth review details the metabolic pathways and preferences of the antitumor immune system and the state of various metabolism-targeting therapeutic approaches.

TCR-T Immunotherapy: The Challenges and Solutions

T cell receptor-engineered T cell (TCR-T) therapy is free from the limit of surface antigen expression of the target cells, which is a potential cellular immunotherapy for cancer treatment. Significant advances in the treatment of hematologic malignancies with cellular immunotherapy have aroused the interest of researchers in the treatment of solid tumors. Nevertheless, the overall efficacy of TCR-T cell immunotherapy in solid tumors was not significantly high when compared with hematological malignancies. In this article, we pay attention to the barriers of TCR-T cell immunotherapy for solid tumors, as well as the strategies affecting the efficacy of TCR-T cell immunotherapy. To provide some reference for researchers to better overcome the impact of TCR-T cell efficiency in solid tumors.

Immersion in the search for effective cancer immunotherapies

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the Cerami Award Monograph is by Steven A. Rosenberg, Chief of Surgery at the National Cancer Institute in Bethesda, Maryland, USA. A pioneer in the development of immunotherapies and gene therapies for advanced cancers, this is the story of Dr. Rosenberg’s scientific journey.

HER2/neu DNA vaccination by intradermal gene delivery in a mouse tumor model: Gene gun is superior to jet injector in inducing CTL responses and protective immunity

DNA vaccines are potential tools for the induction of immune responses against both infectious disease and cancer. The dermal application of DNA vaccines is of particular interest since the epidermal and dermal layers of the skin are characterized by an abundance of antigen-presenting cells (APCs). The aim of our study was to compare tumor protection as obtained by two different methods of intradermal DNA delivery (gene gun and jet injector) in a well-established HER2/neu mouse tumor model. BALB/c mice were immunized twice with a HER2/neu-coding plasmid by gene gun or jet injector. Mice were then subcutaneously challenged with HER2/neu⁺ syngeneic D2F2/E2 tumor cells. Protection against subsequent challenges with tumor cells as well as humoral and T-cell immune responses induced by the vaccine were monitored. Gene gun immunization was far superior to jet injector both in terms of tumor protection and induction of HER2/neu-specific immune responses. After gene gun immunization, 60% of the mice remained tumor-free until day 140 as compared with 25% after jet injector immunization. Furthermore, gene gun vaccination was able to induce both a strong T_H1-polarized T-cell response with detectable cytotoxic T-lymphocyte (CTL) activity and a humoral immune response against HER2/neu, whereas the jet injector was not. Although the disadvantages that were associated with the use of the jet injector in our model may be overcome with methodological modifications and/or in larger animals, which exhibit a thicker skin and/or subcutaneous muscle tissue, we conclude that gene gun delivery constitutes the method of choice for intradermal DNA delivery in preclinical mouse models and possibly also for the clinical development of DNA-based vaccines.

The Anticancer Potential of T Cell Receptor-Engineered T Cells

Adoptively transferred T cell receptor (TCR)-transgenic T cells (TCR-T cells) are not restricted by cell surface expression of their targets and are therefore poised to become a main pillar of cellular cancer immunotherapies. Addressing clinical and laboratory data, we discuss emerging features for the efficient deployment of novel TCR-T therapies, such as selection of ideal TCRs targeting validated epitopes with well-characterized cancer cell expression and processing, enhancing TCR-T effector function, trafficking, expansion, persistence, and memory formation by strategic selection of substrate cells, and gene-engineering with synthetic co-stimulatory circuits. Overall, a better understanding of the relevant mechanisms of action and resistance will help prioritize the vast array of potential TCR-T optimizations for future clinical products.

Telomerase and CD4 T Cell Immunity in Cancer

Telomerase reverse transcriptase (TERT) is a conserved self-tumor antigen which is overexpressed in most tumors and plays a critical role in tumor formation and progression. As such, TERT is an antigen of great relevance to develop widely applicable immunotherapies. CD4 T cells play a major role in the anti-cancer response alone or with other effector cells such as CD8 T cells and NK cells. To date, efforts have been made to identify TERT peptides capable of stimulating CD4 T cells that are also able to bind diverse MHC-II alleles to ease immune status monitoring and immunotherapies. Here, we review the current status of TERT biology, TERT/MHC-II immunobiology, and past and current vaccine clinical trials. We propose that monitoring CD4 T cell immunity against TERT is a simple and direct way to assess immune surveillance in cancer patients and a new way to predict the response to immune checkpoint inhibitors (ICPi). Finally, we present the initial results of a systematic discovery of TERT peptides able to bind the most common HLA Class II alleles worldwide and show that the repertoire of MHC-II TERT peptides is wider than currently appreciated.

Current state of nonengrafting donor leukocyte infusion (focus on microtransplantation for acute myeloid leukemia)

PURPOSE OF REVIEW

Microtransplantation (or micro-stem cell transplantation, MST) is one permutation of alloreactive immunotherapy increasingly studied in clinical trials. It is most commonly applied to patients with myeloid malignancies who are not suitable candidates for allogeneic hematopoietic cell transplantation. This review highlights the past 2 years of work on stem/progenitor cell products in the field of nonengrafting donor leukocyte infusion (NE-DLI), with a focus on applications of MST in acute myeloid leukemia (AML).

RECENT FINDINGS

Assessing the utility of MST is hampered by lack of randomized controlled trials and by variability in donor selection algorithms, treatment timing, and unknown factors. The inherent complexity of the bidirectional alloreactive reactions, implicating many cell types, makes it challenging to move beyond correlative, population-level biology toward mechanistic explanations for MST's actions in any given patient-donor pair. Yet there are indicators that by stimulating a recipient-vs.-tumor effect, MST might substantially improve complete remission rates in AML and that it might find a role in postremission therapy.

SUMMARY

The mechanistic underpinnings of MST are gradually being disentangled and its clinical development remains in early stages.

Friend retrovirus studies reveal complex interactions between intrinsic, innate and adaptive immunity

Approximately 4.4% of the human genome is comprised of endogenous retroviral sequences, a record of an evolutionary battle between man and retroviruses. Much of what we know about viral immunity comes from studies using mouse models. Experiments using the Friend virus (FV) model have been particularly informative in defining highly complex anti-retroviral mechanisms of the intrinsic, innate and adaptive arms of immunity. FV studies have unraveled fundamental principles about how the immune system controls both acute and chronic viral infections. They led to a more complete understanding of retroviral immunity that begins with cellular sensing, production of type I interferons, and the induction of intrinsic restriction factors. Novel mechanisms have been revealed, which demonstrate that these earliest responses affect not only virus replication, but also subsequent innate and adaptive immunity. This review on FV immunity not only surveys the complex host responses to a retroviral infection from acute infection to chronicity, but also highlights the many feedback mechanisms that regulate and counter-regulate the various arms of the immune system. In addition, the discovery of molecular mechanisms of immunity in this model have led to therapeutic interventions with implications for HIV cure and vaccine development.

Immunotherapy for skin cancer

Among all tumor types, skin cancers are profoundly sensitive to immunotherapy. Indeed, the recently reported response rates for anti-PD-1 (anti-programmed-death 1) therapy for cutaneous malignant melanomas (MM), Merkel cell carcinomas, basal cell carcinomas, cutaneous squamous cell carcinomas and Kaposi sarcomas are all above 40%. This unique immunogenicity renders skin cancers as a paradigm for tumor-immune interactions and is driven by high mutational burdens, over-expressed tumor antigens and/or viral antigens. However, despite the clear demonstration of immunologic cure of skin cancer in some patients, most tumors develop either early (primary) or late (adaptive) resistance to immunotherapy. Resistance mechanisms are complex, and include contributions of tumor cell-intrinsic, T cell and microenvironment factors that have been recently further elucidated with the advent of single-cell technologies. This review will focus on the exciting progress with immunotherapy for skin cancers to date, and also our current understanding of the mechanisms of resistance to immunotherapy.

Effective NY-ESO-1-specific MHC II-restricted T cell receptors from antigen-negative hosts enhance tumor regression

Adoptive transfer of T cell receptor-engineered (TCR-engineered) T cells is a promising approach in cancer therapy but needs improvement for more effective treatment of solid tumors. While most clinical approaches have focused on CD8+ T cells, the importance of CD4+ T cells in mediating tumor regression has become apparent. Regarding shared (self) tumor antigens, it is unclear whether the human CD4+ T cell repertoire has been shaped by tolerance mechanisms and lacks highly functional TCRs suitable for therapy. Here, TCRs against the tumor-associated antigen NY-ESO-1 were isolated either from human CD4+ T cells or from mice that express a diverse human TCR repertoire with HLA-DRA/DRB1*0401 restriction and are NY-ESO-1 negative. NY-ESO-1-reactive TCRs from the mice showed superior recognition of tumor cells and higher functional activity compared with TCRs from humans. We identified a candidate TCR, TCR-3598_2, which was expressed in CD4+ T cells and caused tumor regression in combination with NY-ESO-1-redirected CD8+ T cells in a mouse model of adoptive T cell therapy. These data suggest that MHC II-restricted TCRs against NY-ESO-1 from a nontolerant nonhuman host are of optimal affinity and that the combined use of MHC I- and II-restricted TCRs against NY-ESO-1 can make adoptive T cell therapy more effective.

Merkel cell carcinoma: Current US incidence and projected increases based on changing demographics

BACKGROUND

Merkel cell carcinoma (MCC) incidence rates are rising and strongly age-associated, relevant for an aging population.

OBJECTIVE

Determine MCC incidence in the United States and project incident cases through the year 2025.

METHODS

Registry data were obtained from the SEER-18 Database, containing 6600 MCC cases. Age- and sex-adjusted projections were generated using US census data.

RESULTS

During 2000-2013, the number of reported solid cancer cases increased 15%, melanoma cases increased 57%, and MCC cases increased 95%. In 2013, the MCC incidence rate was 0.7 cases/100,000 person-years in the United States, corresponding to 2488 cases/year. MCC incidence increased exponentially with age, from 0.1 to 1.0 to 9.8 (per 100,000 person-years) among age groups 40-44 years, 60-64 years, and ≥85 years, respectively. Due to aging of the Baby Boomer generation, US MCC incident cases are predicted to climb to 2835 cases/year in 2020 and 3284 cases/year in 2025.

LIMITATIONS

We assumed that the age-adjusted incidence rate would stabilize, and thus, the number of incident cases we projected might be an underestimate.

CONCLUSION

An aging population is driving brisk increases in the number of new MCC cases in the United States. This growing impact combined with the rapidly evolving therapeutic landscape warrants expanded awareness of MCC diagnosis and management.

CD4 and CD8 T lymphocyte interplay in controlling tumor growth

The outstanding clinical success of immune checkpoint blockade has revived the interest in underlying mechanisms of the immune system that are capable of eliminating tumors even in advanced stages. In this scenario, CD4 and CD8 T cell responses are part of the cancer immune cycle and both populations significantly influence the clinical outcome. In general, the immune system has evolved several mechanisms to protect the host against cancer. Each of them has to be undermined or evaded during cancer development to enable tumor outgrowth. In this review, we give an overview of T lymphocyte-driven control of tumor growth and discuss the involved tumor-suppressive mechanisms of the immune system, such as senescence surveillance, cancer immunosurveillance, and cancer immunoediting with respect to recent clinical developments of immunotherapies. The main focus is on the currently existing knowledge about the CD4 and CD8 T lymphocyte interplay that mediates the control of tumor growth.

Transfer of Allogeneic CD4+ T Cells Rescues CD8+ T Cells in Anti-PD-L1-Resistant Tumors Leading to Tumor Eradication

Adoptively transferred CD8⁺ T cells can stabilize the size of solid tumors over long periods of time by exclusively recognizing antigen cross-presented on tumor stroma. However, these tumors eventually escape T-cell-mediated growth control. The aim of this study was to eradicate such persistent cancers. In our model, the SIYRYYGL antigen is expressed by cancer cells that lack the MHC-I molecule K^b needed for direct presentation, but the antigen is picked up and cross-presented by tumor stroma. A single injection of antigen-specific 2C CD8⁺ T cells caused long-term inhibition of tumor growth, but without further intervention, tumors started to progress after approximately 3 months. Escape was associated with reduced numbers of circulating 2C cells. Tumor-infiltrating 2C cells produced significantly less TNFα and expressed more of the "exhaustion" markers PD-1 and Tim-3 than T cells from lymphoid organs. High-dose local ionizing radiation, depletion of myeloid-derived suppressor cells, infusions of additional 2C cells, and antibodies blocking PD-L1 did not prevent tumor escape. In contrast, adoptive transfer of allogeneic CD4⁺ T cells restored the numbers of circulating Ag-specific CD8⁺ T cells and their intratumoral function, resulting in tumor eradication. These CD4⁺ T cells had no antitumor effects in the absence of CD8⁺ T cells and recognized the alloantigen cross-presented on tumor stroma. CD4⁺ T cells might also be effective in cancer patients when PD-1/PD-L1 blockade does not rescue intratumoral CD8⁺ T-cell function and tumors persist. Cancer Immunol Res; 5(2); 127-36. ©2017 AACR.

Chemo-immunotherapy induces tumor regression in a mouse model of spontaneous mammary carcinogenesis

Tumor-specific immune tolerance represents an obstacle for the development of effective anti-tumor immune responses through cancer vaccines. We here evaluated the efficacy of chemo-immunotherapy in breaking tumor-specific immune tolerance in an almost incurable mouse model of spontaneous carcinogenesis.Transgenic HER-2/neu mice bearing large mammary tumors received the adoptive transfer of splenocytes and serum isolated from immune donors, with or without pre-conditioning with cyclophosphamide. Treatment efficacy was assessed by monitoring tumor growth by manual inspection and by magnetic resonance imaging. The same chemo-immunotherapy protocol was tested on tumor-free HER-2/neu mice, to evaluate the effects on tumor emergence.Our data show that chemo-immunotherapy hampered carcinogenesis and caused the regression of large mammary tumor lesions in tumor-bearing HER-2/neu mice. The complete eradication of a significant number of tumor lesions occurred only in mice receiving cyclophosphamide shortly before immunotherapy, and was associated with increased serum anti HER-2/p185 antibodies and tumor leukocyte infiltration. The same protocol significantly delayed the appearance of mammary tumors when administered to tumor-free HER-2/neu mice, indicating that this chemo-immunotherapy approach acted through the elicitation of an effective anti-tumor immune response. Overall, our data support the immune-modulatory role of chemotherapy in overcoming cancer immune tolerance when administered at lymphodepleting non-myeloablative doses shortly before transfer of antigen-specific immune cells and immunoglobulins. These findings open new perspectives on combining immune-modulatory chemotherapy and immunotherapy to overcome immune tolerance in cancer patients.

Adoptive Transfer of Tumor-Specific Th2 Cells Eradicates Tumors by Triggering an In Situ Inflammatory Immune Response

Adoptive cell therapy (ACT) trials to date have focused on transfer of autologous tumor-specific cytotoxic CD8⁺ T cells; however, the potential of CD4⁺ T helper (Th) cells for ACT is gaining interest. While encouraging results have been reported with IFNγ-producing Th1 cells, tumor-specific Th2 cells have been largely neglected for ACT due to their reported tumor-promoting properties. In this study, we tested the efficacy of idiotype-specific Th2 cells for the treatment of mice with MHC class II-negative myeloma. Th2 ACT efficiently eradicated subcutaneous myeloma in an antigen-specific fashion. Transferred Th2 cells persisted in vivo and conferred long-lasting immunity. Cancer eradication mediated by tumor-specific Th2 cells did not require B cells, natural killer T cells, CD8⁺ T cells, or IFNγ. Th2 ACT was also curative against B-cell lymphoma. Upon transfer, Th2 cells induced a type II inflammation at the tumor site with massive infiltration of M2-type macrophages producing arginase. In vivo blockade of arginase strongly inhibited Th2 ACT, consistent with a key role of arginase and M2 macrophages in myeloma elimination by Th2 cells. These results illustrate that cancer eradication may be achieved by induction of a tumor-specific Th2 inflammatory immune response at the tumor site. Thus, ACT with tumor-specific Th2 cells may represent a highly efficient immunotherapy protocol against cancer. Cancer Res; 76(23); 6864-76. ©2016 AACR.

Potential Cancer Prevention and Treatment by Silencing the Killer Cell Immunoglobulin-like Receptor Gene in Natural Killer Cells Derived from Induced Pluripotent Stem Cells

Cancer immunosurveillance is an important host protection process, monitoring the presence of irregular cells that could potentially transform into tumor cells, effectively clearing the body of transformed tumor cells at their earliest stages, and thus maintaining regular cellular homeostasis. Natural killer (NK) cells are effector lymphocytes of the innate immune system, playing a critical role in surveillance for tumor cells, while also eliminating virally infected cells. The significance of the anti-tumor role of NK cells was recently further verified by findings that immunosuppression in most cancer patients is not perceptible until late stages. NK cells express the low-affinity Fc-activating receptor, CD16, and the inhibitory receptor, killer cell immunoglobulin-like receptor (KIR). Consequently, activation of NK cells is determined by the balance of inhibitory and activating receptor stimulation. Here, we propose establishing an induced pluripotent stem cell (iPSC)-derived NK cell line with KIR gene knockout or knockdown as a possible regimen to treat and prevent cancer. We further postulate that an optimal mixture of NK iPSCs with and without KIR gene knockout, would reach a maximum antitumor activity, with minimal side effects. We also discuss the possible advantages of KIR-knockout NK iPSCs for adoptive immunotherapy in patients with cancer.

New Strategies in Engineering T-cell Receptor Gene-Modified T cells to More Effectively Target Malignancies

The immune system, T cells in particular, have the ability to target and destroy malignant cells. However, antitumor immune responses induced from the endogenous T-cell repertoire are often insufficient for the eradication of established tumors, as illustrated by the failure of cancer vaccination strategies or checkpoint blockade for most tumors. Genetic modification of T cells to express a defined T-cell receptor (TCR) can provide the means to rapidly generate large numbers of tumor-reactive T cells capable of targeting tumor cells in vivo. However, cell-intrinsic factors as well as immunosuppressive factors in the tumor microenvironment can limit the function of such gene-modified T cells. New strategies currently being developed are refining and enhancing this approach, resulting in cellular therapies that more effectively target tumors and that are less susceptible to tumor immune evasion.

IL-2: the first effective immunotherapy for human cancer

The ability of IL-2 to expand T cells with maintenance of functional activity has been translated into the first reproducible effective human cancer immunotherapies. The administration of IL-2 can lead to durable, complete, and apparently curative regressions in patients with metastatic melanoma and renal cancer. The growth of large numbers of tumor-infiltrating lymphocytes with in vitro anti-cancer activity in IL-2 has led to the development of cell transfer therapies that are highly effective in patients with melanoma. The genetic modification of T cells with genes encoding αβ TCRs or chimeric Ag receptors and the administration of these cells after expansion in IL-2 have extended effective cell transfer therapy to other cancer types.

How Do CD4(+) T Cells Detect and Eliminate Tumor Cells That Either Lack or Express MHC Class II Molecules?

CD4⁺ T cells contribute to tumor eradication, even in the absence of CD8⁺ T cells. Cytotoxic CD4⁺ T cells can directly kill MHC class II positive tumor cells. More surprisingly, CD4⁺ T cells can indirectly eliminate tumor cells that lack MHC class II expression. Here, we review the mechanisms of direct and indirect CD4⁺ T cell-mediated elimination of tumor cells. An emphasis is put on T cell receptor (TCR) transgenic models, where anti-tumor responses of naïve CD4⁺ T cells of defined specificity can be tracked. Some generalizations can tentatively be made. For both MHCII^POS and MHCII^NEG tumors, presentation of tumor-specific antigen by host antigen-presenting cells (APCs) appears to be required for CD4⁺ T cell priming. This has been extensively studied in a myeloma model (MOPC315), where host APCs in tumor-draining lymph nodes are primed with secreted tumor antigen. Upon antigen recognition, naïve CD4⁺ T cells differentiate into Th1 cells and migrate to the tumor. At the tumor site, the mechanisms for elimination of MHCII^POS and MHCII^NEG tumor cells differ. In a TCR-transgenic B16 melanoma model, MHCII^POS melanoma cells are directly killed by cytotoxic CD4⁺ T cells in a perforin/granzyme B-dependent manner. By contrast, MHCII^NEG myeloma cells are killed by IFN-γ stimulated M1-like macrophages. In summary, while the priming phase of CD4⁺ T cells appears similar for MHCII^POS and MHCII^NEG tumors, the killing mechanisms are different. Unresolved issues and directions for future research are addressed.

CD4 T-cell immunotherapy for chronic viral infections and cancer

During chronic infections and cancer, T cells progressively lose function and become exhausted. However, effective T-cell responses are necessary to ultimately control viral infections and tumors. Hence, strategies that either restore endogenous immune responses or provide functional T cells by adoptive immunotherapy need to be explored. CD8 T cells play a prominent role in viral infections, as well as cancer, but CD4 T cells are necessary to support CD8 T-cell function. In addition, CD4 T cells exert direct effector functions, induce optimal B-cell responses and orchestrate innate immunity. Therefore, we propose that adoptive transfer strategies should exploit CD4 T cells alone or in combination with CD8 T cells, for the treatment of chronic infections and cancer. Furthermore, since adoptively transferred cells are subject to exhaustion, combining adoptive transfer therapy with immunotherapies that inhibit T-cell exhaustion should maximize the longevity and success rate of responses.

T cell immunotherapy for melanoma from bedside to bench to barn and back: how conceptual advances in experimental mouse models can be translated into clinical benefit for patients

A solid scientific basis now supports the concept that cytotoxic T lymphocytes can specifically recognize and destroy melanoma cells. Over the last decades, clinicians and basic scientists have joined forces to advance our concepts of melanoma immunobiology. This has catalyzed the rational development of therapeutic approaches to enforce melanoma-specific T cell responses. Preclinical studies in experimental mouse models paved the way for their successful translation into clinical benefit for patients with metastatic melanoma. A more thorough understanding of how melanomas develop resistance to T cell immunotherapy is necessary to extend this success. This requires a continued interdisciplinary effort of melanoma biologists and immunologists that closely connects clinical observations with in vitro investigations and appropriate in vivo mouse models: From bedside to bench to barn and back.

Molecular pathways: comparing the effects of drugs and T cells to effectively target oncogenes

Mutant cancer-driving oncogenes are the best therapeutic targets, both with drugs like small-molecule inhibitors (SMI) and adoptive T-cell therapy (ATT), the most effective form of immunotherapy. Cancer cell survival often depends on oncogenes, which implies that they are homogeneously expressed by all cancer cells and are difficult to select against. Mutant oncogene-directed therapy is relatively selective, as it targets preferentially the oncogene-expressing cancer cells. Both SMI and ATT can be highly effective in relevant preclinical models as well as selected clinical situations, and both share the risk of therapy resistance, facilitated by the frequent genetic instability of cancer cells. Recently, both therapies were compared in the same experimental model targeting the same oncogene. It showed that the oncogene-inactivating drug selected resistant clones, leading eventually to tumor relapse, whereas ATT eradicated large established tumors completely. The mode of tumor destruction likely explained the different outcome with only ATT destroying the tumor vasculature. Elucidating the cellular and molecular mechanisms responsible for tumor regression and relapse will define optimal conditions for the clinic. We argue that the ideal conditions of ATT in the experimental cancer model can be translated to individuals with cancer.

Polyfunctional CD4⁺ T cells are essential for eradicating advanced B-cell lymphoma after chemotherapy

The finding that many chemotherapeutic agents have immunostimulatory effects has provided the impetus to combine chemotherapy and immunotherapy for synergistic antitumor effects. However, the critical determinants of effective antitumor immunity after chemotherapy have not been defined. Here we report that adoptive transfer of tumor-specific CD4⁺ T cells after chemotherapy with cyclophosphamide gave rise to polyfunctional CD4⁺ effector cells, which in turn intensified the inflammatory milieu and enhanced the activation of CD8⁺ T cells in the tumor microenvironment. Although this combined chemoimmunotherapy initially resulted in progressive regression of advanced B-cell lymphoma, its therapeutic efficacy was not durable and most mice succumbed to late relapse. Notably, relapse was associated with acquisition of a tolerized phenotype in tumor-specific CD4⁺ T cells, characterized by overexpression of program death-1 (PD-1). Remarkably, effective antitumor immunity was maintained and cure became prevalent when polyfunctional CD4⁺ effector cells were prevented from undergoing PD-1-mediated tolerization, either by antibody blockade of the PD-1-PD-L1 pathway, or targeted ablation of PD-1 in tumor-specific CD4⁺ T cells. Our study suggests that tumor-reactive CD4⁺ T cells act as the "gatekeepers" of the host antitumor immunity in the postchemotherapy setting, thereby their functional status governs the choice between eradication versus regrowth of residual tumors.

A coreceptor-independent transgenic human TCR mediates anti-tumor and anti-self immunity in mice

Recent advancements in T cell immunotherapy suggest that T cells engineered with high-affinity TCR can offer better tumor regression. However, whether a high-affinity TCR alone is sufficient to control tumor growth, or the T cell subset bearing the TCR is also important remains unclear. Using the human tyrosinase epitope-reactive, CD8-independent, high-affinity TCR isolated from MHC class I-restricted CD4(+) T cells obtained from tumor-infiltrating lymphocytes (TIL) of a metastatic melanoma patient, we developed a novel TCR transgenic mouse with a C57BL/6 background. This HLA-A2-restricted TCR was positively selected on both CD4(+) and CD8(+) single-positive cells. However, when the TCR transgenic mouse was developed with a HLA-A2 background, the transgenic TCR was primarily expressed by CD3(+)CD4(-)CD8(-) double-negative T cells. TIL 1383I TCR transgenic CD4(+), CD8(+), and CD4(-)CD8(-) T cells were functional and retained the ability to control tumor growth without the need for vaccination or cytokine support in vivo. Furthermore, the HLA-A2(+)/human tyrosinase TCR double-transgenic mice developed spontaneous hair depigmentation and had visual defects that progressed with age. Our data show that the expression of the high-affinity TIL 1383I TCR alone in CD3(+) T cells is sufficient to control the growth of murine and human melanoma, and the presence or absence of CD4 and CD8 coreceptors had little effect on its functional capacity.

Novel strategies for immunotherapy in multiple myeloma: previous experience and future directions

Multiple myeloma (MM) is a life-threatening haematological malignancy for which standard therapy is inadequate. Autologous stem cell transplantation is a relatively effective treatment, but residual malignant sites may cause relapse. Allogeneic transplantation may result in durable responses due to antitumour immunity mediated by donor lymphocytes. However, morbidity and mortality related to graft-versus-host disease remain a challenge. Recent advances in understanding the interaction between the immune system of the patient and the malignant cells are influencing the design of clinically more efficient study protocols for MM. Cellular immunotherapy using specific antigen-presenting cells (APCs), to overcome aspects of immune incompetence in MM patients, has received great attention, and numerous clinical trials have evaluated the potential for dendritic cell (DC) vaccines as a novel immunotherapeutic approach. This paper will summarize the data investigating aspects of immunity concerning MM, immunotherapy for patients with MM, and strategies, on the way, to target the plasma cell more selectively. We also include the MM antigens and their specific antibodies that are of potential use for MM humoral immunotherapy, because they have demonstrated the most promising preclinical results.

Dysregulated recruitment of the histone methyltransferase EZH2 to the class II transactivator (CIITA) promoter IV in breast cancer cells

One mechanism frequently utilized by tumor cells to escape immune system recognition and elimination is suppression of cell surface expression of Major Histocompatibility Class II (MHC II) molecules. Expression of MHC II is regulated primarily at the level of transcription by the Class II Transactivator, CIITA, and decreased CIITA expression is observed in multiple tumor types. We investigate here contributions of epigenetic modifications to transcriptional silencing of CIITA in variants of the human breast cancer cell line MDA MB 435. Significant increases in histone H3 lysine 27 trimethylation upon IFN-γ stimulation correlate with reductions in transcription factor recruitment to the interferon-γ inducible CIITA promoter, CIITApIV, and with significantly increased CIITApIV occupancy by the histone methyltransferase enhancer of zeste homolog 2 (EZH2). Most compelling is evidence that decreased expression of EZH2 in MDA MB 435 variants results in significant increases in CIITA and HLA-DRA mRNA expression, even in the absence of interferon-γ stimulation, as well as increased cell surface expression of MHC II. Together, these data add mechanistic insight to prior observations of increased EZH2 expression and decreased CIITA expression in multiple tumor types.

Adoptive immunotherapy for cancer: harnessing the T cell response

Immunotherapy based on the adoptive transfer of naturally occurring or gene-engineered T cells can mediate tumour regression in patients with metastatic cancer. Here, we discuss progress in the use of adoptively transferred T cells, focusing on how they can mediate tumour cell eradication. Recent advances include more accurate targeting of antigens expressed by tumours and the associated vasculature, and the successful use of gene engineering to re-target T cells before their transfer into the patient. We also describe how new research has helped to identify the particular T cell subsets that can most effectively promote tumour eradication.

Cytotoxic chemotherapy and CD4+ effector T cells: an emerging alliance for durable antitumor effects

Standard cytotoxic chemotherapy can initially achieve high response rates, but relapses often occur in patients and represent a severe clinical problem. As increasing numbers of chemotherapeutic agents are found to have immunostimulatory effects, there is a growing interest to combine chemotherapy and immunotherapy for synergistic antitumor effects and improved clinical benefits. Findings from recent studies suggest that highly activated, polyfunctional CD4+ effector T cells have tremendous potential in strengthening and sustaining the overall host antitumor immunity in the postchemotherapy window. This review focuses on the latest progresses regarding the impact of chemotherapy on CD4+ T-cell phenotype and function and discusses the prospect of exploiting CD4+ T cells to control tumor progression and prevent relapse after chemotherapy.

Graft-versus-leukemia (GVL) against mouse blast-crisis chronic myelogenous leukemia (BC-CML) and chronic-phase chronic myelogenous leukemia (CP-CML): shared mechanisms of T cell killing, but programmed death ligands render CP-CML and not BC-CML GVL resistant

Graft-versus-leukemia (GVL) against chronic-phase chronic myelogenous leukemia (CP-CML) is potent, but it is less efficacious against acute leukemias and blast-crisis chronic myelogenous leukemia (BC-CML). The mechanisms underlying GVL resistance are unknown. Previously, we found that alloreactive T cell targeting of GVL-sensitive bcr-abl-induced mouse CP-CML (mCP-CML) required TCR-MHC interactions and that multiple and redundant killing mechanisms were in play. To better understand why BC-CML is resistant to GVL, we performed a comprehensive analysis of GVL against mouse BC-CML (mBC-CML) induced by the retroviral transfer of the bcr-abl and NUP98/HOXA9 fusion cDNAs. Like human BC-CML, mBC-CML was GVL resistant, and this was not due to accelerated kinetics or a greater leukemia burden. To study T cell recognition and killing mechanisms, we generated a panel of gene-deficient leukemias by transducing bone marrow from gene-deficient mice. T cell target recognition absolutely required that mBC-CML cells express MHC molecules. GVL against both mCP-CML and mBC-CML required leukemia expression of ICAM-1. We hypothesized that mBC-CML would be resistant to some of the killing mechanisms sufficient to eliminate mCP-CML, but we found instead that the same mechanisms were effective against both types of leukemia, because GVL was similar against wild-type or mBC-CML genetically lacking Fas, TRAIL-R, Fas/TRAIL-R, or TNFR1/R2 or when donor T cells were perforin(-/-). However, mCP-CML, but not mBC-CML, relied on expression of programmed death-1 ligands 1 and 2 (PD-L1/L2) to resist T cell killing, because only GVL against mCP-CML was augmented when leukemias lacked PD-L1/L2. Thus, mBC-CML cells have cell-intrinsic mechanisms, distinct from mCP-CML cells, which protect them from T cell killing.

Is secretion of tumour-specific antigen important for cancer eradication by CD4(+) T cells?--Implications for cancer immunotherapy by adoptive T cell transfer

The potential for cancer immunotherapy by adoptive transfer of CD4(+) T cells is gaining increased attention. Most cancer cells lack major histocompatibility complex (MHC) class II molecules and cannot present tumour-specific antigens (TSA) directly to CD4(+) T cells. We have reported that tumour-specific CD4(+) T cells collaborate with macrophages and dendritic cells. These professional antigen-presenting cells endocytose and process TSA to display antigenic peptides on their MHC class II molecules for indirect cancer cell recognition by CD4(+) T cells. We hypothesized that this critical step may depend on secretion of TSA by cancer cells. This was investigated in a mouse model for myeloma immunosurveillance mediated by CD4(+) T cells. From this study, several conclusions could be drawn. First, TSA secretion facilitates cancer immunosurveillance. Second, TSA secretion results in stronger activation of naïve tumour-specific CD4(+) T cells in lymph nodes. Third, TSA concentration within the tumour extracellular matrix must reach a certain threshold to allow successful cancer immunosurveillance. Fourth, treatment by local injection of purified TSA enhances immunity against cancer cells that do not secrete TSA. Fifth, secretion of TSA by at least some cancer cells within a tumour favours antitumour immunity. Therefore, we propose that CD4(+) T cells that recognize secreted TSA may be superior for immunotherapy by T cell transfer, because the local extracellular antigen concentration will be higher for secreted TSA. Thus, it is anticipated that secreted TSA will be more readily detected in vivo by transferred CD4(+) T cells, resulting in more efficient tumour eradication.

Bystander killing of cancer requires the cooperation of CD4(+) and CD8(+) T cells during the effector phase

Killing of nonmalignant stroma requires cooperation between CD4⁺ and CD8⁺ T cells during the effector phase in the tumor microenvironment.

Cancers frequently evade cytotoxic T lymphocyte–mediated destruction through loss or down-regulation of tumor antigens and antigen-presenting major histocompatibility complex molecules. Therefore, we have concentrated our efforts on immunological strategies that destroy nonmalignant stromal cells essential for the survival and growth of cancer cells. In this study, we developed a non–T cell receptor transgenic, immunocompetent tumor model to determine whether tumor-bearing hosts’ own immune systems could eliminate cancer cells through stromal targeting and what role CD4⁺ T cells play alongside CD8⁺ T cells in this process. We found that aggressive cancers could be eradicated by T cell targeting of tumor stroma. However, successful elimination required the cooperation of CD4⁺ and CD8⁺ T cells not only during the induction phase but also during the effector phase in the tumor microenvironment, implying a new role for CD4⁺ T cells that has not been previously described. Our study demonstrates the potential of stromal targeting as a cancer immunotherapy and suggests that successful anticancer strategies must facilitate cooperation between CD4⁺ and CD8⁺ T cells at the right times and the right places.

Chemotherapy rescues tumor-driven aberrant CD4+ T-cell differentiation and restores an activated polyfunctional helper phenotype

The functional development of tumor-specific CD4(+) T cells has a critical impact on the outcome of antitumor immune responses. Adoptive immunotherapy involving tumor-specific CD4(+) T cells has shown encouraging clinical benefits in some cancer patients. To mount an effective antitumor immunity, it is desirable to elicit activated type 1 T helper cells. Here, we report that type 1 T helper cell-like effector cells that arose in tumor-bearing hosts progressively expressed programmed death 1 during tumor growth. The programmed death 1(hi) effector cells displayed a dysfunctional phenotype, characterized by selective down-regulation of interleukin-7 receptor, heightened apoptosis, and poor antitumor efficacy. This tumor-driven aberrant T-cell response could be prevented by a single dose of the widely used chemotherapy agent cyclophosphamide. We show that chemotherapy conditioned the host environment, creating a transient window for optimal effector differentiation for adoptively transferred CD4(+) T cells. This robust effector differentiation, which was antigen-driven and mechanistically dependent on an intact host response to type I interferon, gave rise to activated polyfunctional T helper cells with high interleukin-7 receptor, rapid clonal expansion, and potent antitumor activity against established B-cell lymphomas. We hypothesize that prevention of tumor-induced effector cell dysfunction is a major mechanism contributing to the efficacy of combined chemoimmunotherapy.

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

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

Race between retroviral spread and CD4+ T-cell response determines the outcome of acute Friend virus infection

Retroviruses can establish persistent infection despite induction of a multipartite antiviral immune response. Whether collective failure of all parts of the immune response or selective deficiency in one crucial part underlies the inability of the host to clear retroviral infections is currently uncertain. We examine here the contribution of virus-specific CD4(+) T cells in resistance against Friend virus (FV) infection in the murine host. We show that the magnitude and duration of the FV-specific CD4(+) T-cell response is directly proportional to resistance against acute FV infection and subsequent disease. Notably, significant protection against FV-induced disease is afforded by FV-specific CD4(+) T cells in the absence of a virus-specific CD8(+) T-cell or B-cell response. Enhanced spread of FV infection in hosts with increased genetic susceptibility or coinfection with Lactate dehydrogenase-elevating virus (LDV) causes a proportional increase in the number of FV-specific CD4(+) T cells required to control FV-induced disease. Furthermore, ultimate failure of FV/LDV coinfected hosts to control FV-induced disease is accompanied by accelerated contraction of the FV-specific CD4(+) T-cell response. Conversely, an increased frequency or continuous supply of FV-specific CD4(+) T cells is both necessary and sufficient to effectively contain acute infection and prevent disease, even in the presence of coinfection. Thus, these results suggest that FV-specific CD4(+) T cells provide significant direct protection against acute FV infection, the extent of which critically depends on the ratio of FV-infected cells to FV-specific CD4(+) T cells.

Combining conventional therapies with intratumoral injection of autologous dendritic cells and activated T cells to treat patients with advanced cancers

Dendritic cells (DCs) are potent antigen-presenting cells that have been used in cancer immunotherapy. To take advantage of the ability of DCs to acquire antigenic materials from their environment and generate primary as well as recall immune responses, 37 patients with advanced cancers were enrolled in a series of protocols based on direct intratumoral injection of immature DCs. To augment antigen uptake and antitumor immune response, DC injection was combined with radiotherapy or chemotherapy and/or injection of activated T cells. Treatments were well tolerated with no adverse reactions. Clinical responses were based on Response Evaluation Criteria in Solid Tumors, with the majority of patients showing stable disease. One of two patients who also received local radiation achieved a sustained complete response at injected and metastatic sites. The clinical responses observed in cancer patients with advanced disease suggest potential effectiveness of combination strategies and establish the basis for the current treatment protocol that is underway.

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.

Developing dendritic cell-based therapies to condition immune responses to novel oncogenic proteins and stem cells

Cancer vaccines have been disappointing when utilized as stand-alone therapy, especially in late disease settings. However, recent clinical studies in prostate cancer have suggested that dendritic cellular (DC) vaccines may impact patient survival, reviving the notion that cancer vaccines can impact established cancer. In this review we will highlight the advances that have been made in the development of DC-based therapies activated by Toll-like receptor agonists with the capacity to condition toward strong Th1 cellular responses, through the production of cytokines and chemokines, and a capacity to induce apoptosis of tumor cells. Used in early cancer settings, these DCs induce clinically effective immune responses, thus shifting the emphasis toward using these cells earlier in the disease process. We will also discuss targeting novel molecules and cancer stem cells that can eliminate cells with high metastatic potential, moving DC-based therapies into mainstream cancer therapy.

Complete regression of advanced primary and metastatic mouse melanomas following combination chemoimmunotherapy

The development of therapeutic strategies which induce effective cellular antitumor immunity represents an important goal in cancer immunology. Here, we used the unique features of the genetically engineered Hgf-Cdk4(R24C) mouse model to identify a combination chemoimmunotherapy for melanoma. These mice develop primary cutaneous melanomas which grow progressively and metastasize in the absence of immunogenic foreign proteins such as oncogenes or antigens. Primary and metastatic tumors evade innate and adaptive immune defenses, although they naturally express melanocytic antigens which can be recognized by antigen-specific T cells. We found that primary melanomas continued to grow despite infiltration with adoptively transferred, in vivo-activated, tumor-specific CD8(+) T cells. To promote tumor immune defense, we developed a treatment protocol consisting of four complementary components: (a) chemotherapeutic preconditioning prior to (b) adoptive lymphocyte transfer and (c) viral vaccination followed by (d) adjuvant peritumoral injections of immunostimulatory nucleic acids. Lymphocyte ablation and innate antiviral immune stimulation cooperatively enhanced the expansion and the effector cell differentiation of adoptively transferred lymphocytes. The efficacy of the different treatment approaches converged in the tumor microenvironment and induced a strong cytotoxic inflammatory response enabling preferential recognition and destruction of melanoma cells. This combination chemoimmunotherapy caused complete regression of advanced primary melanomas in the skin and metastases in the lung with minimal autoimmune side effects. Our results in a clinically highly relevant experimental model provide a scientific rationale to evaluate similar strategies which unleash the power of innate and adaptive immune defense in future clinical trials.

Eradication of established B-cell lymphoma by CD19-specific murine T cells is dependent on host lymphopenic environment and can be mediated by CD4+ and CD8+ T cells

B-cell malignancies seem to be particularly amenable to immunotherapy and as such make particularly attractive targets for adoptive T-cell therapy. Murine T cells gene-modified to express a chimeric immune receptor specific for CD19+ (aCD19z) efficiently kill CD19 B-cell lymphoma cells in vitro. aCD19z T cells also secrete high levels of interleukin-2 during culture with target cells in a CD86 independent manner. aCD19z T cells proved effective at eradicating established B-cell lymphoma in a syngeneic model system when combined with a lymphodepleting preconditioning regimen. In mice deficient of T, B, and natural killer cells (severe combined immunodeficient/Beige), aCD19z T cells efficiently eradicated long-term (13 d) established tumors with 100% of treated animals remaining tumor free for greater than 77 days. Although gene-modified CD4+ and CD8+ were both active in this setting, poor engraftment by CD8+ T cells coupled with the rigorous expansion of CD4+ cells in the Balb/c background suggests that CD4+ T cells may be playing a predominant role in lymphoma rejection in this model. Taken together, the therapeutic effectiveness of aCD19z T cells in this model supports a recently opened phase 1 trial of this receptor in non-Hodgkin lymphoma.

Potent tumor-specific protection ignited by adoptively transferred CD4+ T cells

Administration of anti-CD25 mAb before an aggressive murine breast tumor inoculation provoked effective antitumor immunity. Compared with CD4(+) T cells purified from anti-CD25 mAb-pretreated mice that did not reject tumor, CD4(+) T cells purified from anti-CD25 mAb-pretreated mice that rejected tumor stimulated by dendritic cells (DCs) produced more IFN-gamma and IL-2, and less IL-17 in vitro, and ignited protective antitumor immunity in vivo in an adoptive transfer model. Tumor Ag-loaded DCs activated naive CD8(+) T cells in the presence of these CD4(+) T cells in vitro. Tumor Ag and adoptively transferred CD4(+) T cells were both required for inducing a long-term tumor-specific IFN-gamma-producing cellular response and potent protective antitumor activity. Although adoptively transferred CD4(+) T cells ignited effective tumor-specific antitumor immunity in wild-type mice, they failed to do so in endogenous NK cell-depleted, Gr-1(+) cell-depleted, CD40(-/-), CD11c(+) DC-depleted, B cell(-/-), CD8(+) T cell-depleted, or IFN-gamma(-/-) mice. Collectively, the data suggest that adoptively transferred CD4(+) T cells orchestrate both endogenous innate and adaptive immunity to generate effective tumor-specific long-term protective antitumor immunity. The data also demonstrate the pivotal role of endogenous DCs in the tumor-specific protection ignited by adoptively transferred CD4(+) T cells. Thus, these findings highlight the importance of adoptively transferred CD4(+) T cells, as well as host immune components, in generating effective tumor-specific long-term antitumor activity.