Re-adapting T cells for cancer therapy: from mouse models to clinical trials

Anti-Tumor Effects after Adoptive Transfer of IL-12 Transposon-Modified Murine Splenocytes in the OT-I-Melanoma Mouse Model

Adoptive transfer of gene modified T cells provides possible immunotherapy for patients with cancers refractory to other treatments. We have previously used the non-viral piggyBac transposon system to gene modify human T cells for potential immunotherapy. However, these previous studies utilized adoptive transfer of modified human T cells to target cancer xenografts in highly immunodeficient (NOD-SCID) mice that do not recapitulate an intact immune system. Currently, only viral vectors have shown efficacy in permanently gene-modifying mouse T cells for immunotherapy applications. Therefore, we sought to determine if piggyBac could effectively gene modify mouse T cells to target cancer cells in a mouse cancer model. We first demonstrated that we could gene modify cells to express murine interleukin-12 (p35/p40 mIL-12), a transgene with proven efficacy in melanoma immunotherapy. The OT-I melanoma mouse model provides a well-established T cell mediated immune response to ovalbumin (OVA) positive B16 melanoma cells. B16/OVA melanoma cells were implanted in wild type C57Bl6 mice. Mouse splenocytes were isolated from C57Bl6 OT-I mice and were gene modified using piggyBac to express luciferase. Adoptive transfer of luciferase-modified OT-I splenocytes demonstrated homing to B16/OVA melanoma tumors in vivo. We next gene-modified OT-I cells to express mIL-12. Adoptive transfer of mIL-12-modified mouse OT-I splenocytes delayed B16/OVA melanoma tumor growth in vivo compared to control OT-I splenocytes and improved mouse survival. Our results demonstrate that the piggyBac transposon system can be used to gene modify splenocytes and mouse T cells for evaluating adoptive immunotherapy strategies in immunocompetent mouse tumor models that may more directly mimic immunotherapy applications in humans.

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.

Adoptive T-cell therapy for cancer: The era of engineered T cells

Tumors originate from a number of genetic events that deregulate homeostatic mechanisms controlling normal cell behavior. The immune system, devoted to patrol the organism against pathogenic events, can identify transformed cells, and in several cases cause their elimination. It is however clear that several mechanisms encompassing both central and peripheral tolerance limit antitumor immunity, often resulting into progressive diseases. Adoptive T-cell therapy with either allogeneic or autologous T cells can transfer therapeutic immunity. To date, genetic engineering of T cells appears to be a powerful tool for shaping tumor immunity. In this review, we discuss the most recent achievements in the areas of suicide gene therapy, and TCR-modified T cells and chimeric antigen receptor gene-modified T cells. We provide an overview of current strategies aimed at improving the safety and efficacy of these approaches, with an outlook on prospective developments.

Pancreatic cancer: optimizing treatment options, new, and emerging targeted therapies

Pancreatic cancer is the fourth leading cause of cancer death in the US and is expected to become the second leading cause of cancer-related deaths in the next decade. Despite 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel significantly improving outcomes for metastatic cancer, refractory disease still poses significant challenges. Difficulties with early detection and the inherent chemo- and radio-resistant nature of this malignancy led to attempts to define the sequential biology of pancreatic cancer in order to improve survival outcomes. Pancreatic adenocarcinoma is characterized by several germline or acquired genetic mutations, the most common being KRAS (90%), CDK2NA (90%), TP53 (75%-90%), DPC4/SMAD4 (50%). In addition, the tumor microenvironment, chemoresistant cancer stem cells, and the desmoplastic stroma have been the target of some promising clinical investigations. Among the core pathways reproducibly shown to lead the development and progression of this disease, DNA repair, apoptosis, G1/S cell cycle transition, KRAS, Wnt, Notch, Hedgehog, TGF-beta, and other cell invasion pathways, have been the target of "precision therapeutics". No single molecularly targeted therapeutic though has been uniformly successful, probably due to the tumor heterogeneity, but biomarker research is evolving and it hopes to select more patients likely to benefit. Recent reports note activity with immunotherapies such as CD40 agonists, CCR2 inhibitors, cancer vaccines, and novel combinations against the immunosuppressive tumor milieu are ongoing. While many obstacles still exist, clearly we are making progress in deciphering the heterogeneity within pancreatic cancers. Integrating conventional and immunological targeting will be the key to effective treatment of this deadly disease.

Targeting CD8+ T-cell tolerance for cancer immunotherapy

In the final issue of Science in 2013, the American Association of Science recognized progress in the field of cancer immunotherapy as the 'Breakthrough of the Year.' The achievements were actually twofold, owing to the early success of genetically engineered chimeric antigen receptors (CAR) and to the mounting clinical triumphs achieved with checkpoint blockade antibodies. While fundamentally very different, the common thread of these independent strategies is the ability to prevent or overcome mechanisms of CD8(+) T-cell tolerance for improved tumor immunity. Here we discuss how circumventing T-cell tolerance has provided experimental insights that have guided the field of clinical cancer immunotherapy to a place where real breakthroughs can finally be claimed.

[Pluripotent stem cells as a source for T cell research and clinical application]

Recently, promising clinical outcomes of cancer immunotherapy including administration of an anti PD-1 antibody targeting for T cell reactivation has gained particular attention worldwide. Adoptive cell therapy with tumor infiltrating lymphocytes and TCR/CAR (Chimeric Antigen Receptor) transgenic T cells are also under development. Although it has become clearer that the efficacy of adoptive cell therapy correlate with the quality of infusing T cells, antigen specific T cells in patients with chronic infection and cancer have been exhausted. We have succeeded to generate rejuvenated antigen specific T cells by reprogramming to pluripotency and differentiation. In this article, we introduce fundamentals of this technology and describe its potential for adoptive cell therapy in the future.

New approaches for the immunotherapy of acute myeloid leukemia

Acute myeloid leukemia (AML) is a set of related diseases characterized by the immortalization and uncontrolled expansion of myeloid precursor cells. Core therapy for AML has remained unchanged for nearly 30 years, and survival rates remain unsatisfactory. However, advances in the immunotherapy of AML have created opportunities for improved outcomes. Enforcing a tumor-specific immune response through the re-direction of the adaptive immune system, which links remarkable specificity with potent cytotoxic effector functions, has proven particularly compelling. This may be coupled with immune checkpoint blockade and conventional therapies for optimal effect. Engineered antibodies are currently in use in AML and the repertoire of available therapeutics will expand. NK cells have shown effectiveness in this disease. New methods to optimize their activation and the targeting of AML show potential. Most significantly, adoptive immunotherapy with tumor-specific T cells, and particularly T cells re-directed using genetically introduced TCR or chimeric antigen receptors, have demonstrated promise. Each of these approaches has unique benefits and challenges that we explore in this review.

SUMO2 overexpression enhances the generation and function of interleukin-17-producing CD8⁺ T cells in mice

Small ubiquitin-like modifier (SUMO) 2 is a small protein that controls the activity and stability of other proteins by SUMOylation. In this study, T cell-specific SUMO2 overexpressing transgenic mice were generated to study the effect of SUMO2 on T lymphocytes. SUMO2 overexpression promoted differentiation of interleukin (IL)-17-producing CD8(+) T cells, and significantly suppressed the growth of EL4 tumor cells in vivo. Moreover, the tumor tissue from SUMO2-overexpressing mice had higher interferon (IFN)-γ and granzyme B mRNA levels. Although SUMO2 overexpression did not increase IFN-γ or granzyme B production in cytotoxic T lymphocytes, IL-12 treatment restored and increased IFN-γ secretion in IL-17-producing CD8(+) T cells. SUMO2 overexpression also increased gene expression of chemokines, CCL4, and CXCL10, which attract cytotoxic T lymphocytes to tumor tissues. Additionally, SUMO2-overexpressing T cells exhibited increased STAT3 phosphorylation, implying a SUMO2 target which up-regulates STAT3 activity governing IL-17A-producing CD8(+) T cell differentiation and antitumor immune responses.

Biomarkers in preclinical cancer imaging

In view of the trend towards personalized treatment strategies for (cancer) patients, there is an increasing need to noninvasively determine individual patient characteristics. Such information enables physicians to administer to patients accurate therapy with appropriate timing. For the noninvasive visualization of disease-related features, imaging biomarkers are expected to play a crucial role. Next to the chemical development of imaging probes, this requires preclinical studies in animal tumour models. These studies provide proof-of-concept of imaging biomarkers and help determine the pharmacokinetics and target specificity of relevant imaging probes, features that provide the fundamentals for translation to the clinic. In this review we describe biological processes derived from the “hallmarks of cancer” that may serve as imaging biomarkers for diagnostic, prognostic and treatment response monitoring that are currently being studied in the preclinical setting. A number of these biomarkers are also being used for the initial preclinical assessment of new intervention strategies. Uniquely, noninvasive imaging approaches allow longitudinal assessment of changes in biological processes, providing information on the safety, pharmacokinetic profiles and target specificity of new drugs, and on the antitumour effectiveness of therapeutic interventions. Preclinical biomarker imaging can help guide translation to optimize clinical biomarker imaging and personalize (combination) therapies.

Inducible T-cell receptor expression in precursor T cells for leukemia control

Co-transplantation of hematopoietic stem cells with those engineered to express leukemia-reactive T-cell receptors (TCRs) and differentiated ex vivo into precursor T cells (preTs) may reduce the risk of leukemia relapse. As expression of potentially self-(leukemia-) reactive TCRs will lead to negative selection or provoke autoimmunity upon thymic maturation, we investigated a novel concept whereby TCR expression set under the control of an inducible promoter would allow timely controlled TCR expression. After in vivo maturation and gene induction, preTs developed potent anti-leukemia effects. Engineered preTs provided protection even after repeated leukemia challenges by giving rise to effector and central memory cells. Importantly, adoptive transfer of TCR-transduced allogeneic preTs mediated anti-leukemia effect without evoking graft-versus-host disease (GVHD). Earlier transgene induction forced CD8(+) T-cell development was required to obtain a mature T-cell subset of targeted specificity, allowed engineered T cells to efficiently pass positive selection and abrogated the endogenous T-cell repertoire. Later induction favored CD4 differentiation and failed to produce a leukemia-reactive population emphasizing the dominant role of positive selection. Taken together, we provide new functional insights for the employment of TCR-engineered precursor cells as a controllable immunotherapeutic modality with significant anti-leukemia activity.

T-cell immune suppression in patients with hematologic malignancies: clinical implications

SUMMARY 

The reversion of immune suppression and restoration of T-cell function against leukemia remains a significant clinical challenge. However, the advent of improved antileukemia-specific T-cell induction and the generation of gene-modified T cells has extended cellular immunotherapy to hematological malignancies. Numerous immunotherapeutic protocols have been developed aiming to enhance antileukemia T-cell immune function, eliminate leukemic cells and prevent relapse. By contrast, abnormal expression of CTLA-4 and PD1/PD-L1 plays a critical role in effector T-cell responses and increases Treg suppressive activity in patients with tumors; therefore, blocking CTLA-4, PD1 and PD-L1 is a novel approach for immunotherapy.

Molecular pathways: myeloid complicity in cancer

Cancer-induced inflammation results in accumulation of myeloid cells. These myeloid cells include progenitors and progeny of monocytes, granulocytes, macrophages, and dendritic cells. It has become increasingly evident that tumor-dependent factors can condition myeloid cells toward an immunosuppressive and protumorigenic phenotype. Thus, myeloid cells are not simply bystanders in malignancy or barometers of disease burden. Reflecting their dynamic and plastic nature, myeloid cells manifest a continuum of cellular differentiation and are intimately involved at all stages of neoplastic progression. They can promote tumorigenesis through both immune-dependent and -independent mechanisms and can dictate response to therapies. A greater understanding of the inherent plasticity and relationships among myeloid subsets is needed to inform therapeutic targeting. New clinical trials are being designed to modulate the activities of myeloid cells in cancer, which may be essential to maximize the efficacy of both conventional cytotoxic and immune-based therapies for solid tumors. Clin Cancer Res; 20(20); 5157-70. ©2014 AACR.

Stromal reengineering to treat pancreas cancer

Pancreatic ductal adenocarcinoma co-opts multiple cellular and extracellular mechanisms to create a complex cancer organ with an unusual proclivity for metastasis and resistance to therapy. Cell-autonomous events are essential for the initiation and maintenance of pancreatic ductal adenocarcinoma, but recent studies have implicated critical non-cell autonomous processes within the robust desmoplastic stroma that promote disease pathogenesis and resistance. Thus, non-malignant cells and associated factors are culprits in tumor growth, immunosuppression and invasion. However, even this increasing awareness of non-cell autonomous contributions to disease progression is tempered by the conflicting roles stromal elements can play. A greater understanding of stromal complexity and complicity has been aided in part by studies in highly faithful genetically engineered mouse models of pancreatic ductal adenocarcinoma. Insights gleaned from such studies are spurring the development of therapies designed to reengineer the pancreas cancer stroma and render it permissive to agents targeting cell-autonomous events or to reinstate immunosurveillance. Integrating conventional and immunological treatments in the context of stromal targeting may provide the key to a durable clinical impact on this formidable disease.