Safety and efficacy of Tet-regulated IL-12 expression in cancer-specific T cells

Multi-armored allogeneic MUC1 CAR T cells enhance efficacy and safety in triple-negative breast cancer

Solid tumors, such as triple-negative breast cancer (TNBC), are biologically complex due to cellular heterogeneity, lack of tumor-specific antigens, and an immunosuppressive tumor microenvironment (TME). These challenges restrain chimeric antigen receptor (CAR) T cell efficacy, underlining the importance of armoring. In solid cancers, a localized tumor mass allows alternative administration routes, such as intratumoral delivery with the potential to improve efficacy and safety but may compromise metastatic-site treatment. Using a multi-layered CAR T cell engineering strategy that allowed a synergy between attributes, we show enhanced cytotoxic activity of MUC1 CAR T cells armored with PD1KO, tumor-specific interleukin-12 release, and TGFBR2KO attributes catered towards the TNBC TME. Intratumoral treatment effectively reduced distant tumors, suggesting retention of antigen-recognition benefits at metastatic sites. Overall, we provide preclinical evidence of armored non-alloreactive MUC1 CAR T cells greatly reducing high TNBC tumor burden in a TGFB1- and PD-L1-rich TME both at local and distant sites while preserving safety.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

Engineered Treg cells as putative therapeutics against inflammatory diseases and beyond

Regulatory T (Treg) cells ensure tolerance against self-antigens, limit excessive inflammation, and support tissue repair processes. Therefore, Treg cells are currently attractive candidates for the treatment of certain inflammatory diseases, autoimmune disorders, or transplant rejection. Early clinical trials have proved the safety and efficacy of certain Treg cell therapies in inflammatory diseases. We summarize recent advances in engineering Treg cells, including the concept of biosensors for inflammation. We assess Treg cell engineering possibilities for novel functional units, including Treg cell modifications influencing stability, migration, and tissue adaptation. Finally, we outline perspectives of engineered Treg cells going beyond inflammatory diseases by using custom-designed receptors and read-out systems, aiming to use Treg cells as in vivo diagnostic tools and drug delivery vehicles.

CAR immune cells: design principles, resistance and the next generation

The remarkable clinical activity of chimeric antigen receptor (CAR) therapies in B cell and plasma cell malignancies has validated the use of this therapeutic class for liquid cancers, but resistance and limited access remain as barriers to broader application. Here we review the immunobiology and design principles of current prototype CARs and present emerging platforms that are anticipated to drive future clinical advances. The field is witnessing a rapid expansion of next-generation CAR immune cell technologies designed to enhance efficacy, safety and access. Substantial progress has been made in augmenting immune cell fitness, activating endogenous immunity, arming cells to resist suppression via the tumour microenvironment and developing approaches to modulate antigen density thresholds. Increasingly sophisticated multispecific, logic-gated and regulatable CARs display the potential to overcome resistance and increase safety. Early signs of progress with stealth, virus-free and in vivo gene delivery platforms provide potential paths for reduced costs and increased access of cell therapies in the future. The continuing clinical success of CAR T cells in liquid cancers is driving the development of increasingly sophisticated immune cell therapies that are poised to translate to treatments for solid cancers and non-malignant diseases in the coming years.

Reprogramming of IL-12 secretion in the PDCD1 locus improves the anti-tumor activity of NY-ESO-1 TCR-T cells

Introduction

Although the engineering of T cells to co-express immunostimulatory cytokines has been shown to enhance the therapeutic efficacy of adoptive T cell therapy, the uncontrolled systemic release of potent cytokines can lead to severe adverse effects. To address this, we site-specifically inserted the interleukin-12 (IL-12) gene into the PDCD1 locus in T cells using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-based genome editing to achieve T-cell activation-dependent expression of IL-12 while ablating the expression of inhibitory PD-1.

Methods

New York esophageal squamous cell carcinoma 1(NY-ESO-1)-specific TCR-T cells was investigated as a model system. We generated ΔPD-1-IL-12 -edited NY-ESO-1 TCR-T cells by sequential lentiviral transduction and CRISPR knock-in into activated human primary T cells.

Results

We showed that the endogenous PDCD1 regulatory elements can tightly control the secretion of recombinant IL-12 in a target cell-dependent manner, at an expression level that is more moderate than that obtained using a synthetic NFAT-responsive promoter. The inducible expression of IL-12 from the PDCD1 locus was sufficient to enhance the effector function of NY-ESO-1 TCR-T cells, as determined by upregulation of effector molecules, increased cytotoxic activity, and enhanced expansion upon repeated antigen stimulation in vitro. Mouse xenograft studies also revealed that PD-1-edited IL-12-secreting NY-ESO-1 TCR-T cells could eliminate established tumors and showed significantly greater in vivo expansion capacity than control TCR-T cells.

Discussion

Our approach may provide a way to safely harness the therapeutic potential of potent immunostimulatory cytokines for the development of effective adoptive T cell therapies against solid tumors.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

A compact and simple method of achieving differential transgene expression by exploiting translational readthrough

The development of multicistronic vectors enabling differential transgene expression is a goal of gene therapy and poses a significant engineering challenge. Current approaches rely on the insertion of long regulatory sequences that occupy valuable space in vectors, which have a finite and limited packaging capacity. Here we describe a simple method of achieving differential transgene expression by inserting stop codons and translational readthrough motifs (TRMs) to suppress stop codon termination. TRMs reduced downstream transgene expression ∼sixfold to ∼140-fold, depending on the combination of stop codon and TRM used. We show that a TRM can facilitate the controlled secretion of the highly potent cytokine IL-12 at therapeutically beneficial levels in an aggressive immunocompetent mouse melanoma model to prevent tumor growth. Given their compact size (6 bp) and ease of introduction, we envisage that TRMs will be widely adopted in recombinant DNA engineering to facilitate differential transgene expression.

IL-12 nanochaperone-engineered CAR T cell for robust tumor-immunotherapy

Although chimeric antigen receptor T (CAR T) cell immunotherapy has demonstrated remarkable success in clinical, therapeutic effects are still limited in solid tumor due to lack of activated T cell infiltration in immunosuppression of tumor microenvironment. Herein, we develop IL-12 nanostimulant-engineered CAR T cell (INS-CAR T) biohybrids for boosting antitumor immunity of CAR T cells via immunofeedback. As stimulating nanochaperone, IL-12-loaded human serum albumin (HSA) nanoparticles are effectively conjugated onto CAR T cells via bioorthogonal chemistry without influencing their antitumor capabilities. IL-12 is responsively released from INS-CAR T biohybrids in presence of the increased thiol groups on cell-surface triggered by tumor antigens. In return, released IL-12 obviously promotes the secretion of CCL5, CCL2 and CXCL10, which further selectively recruits and expands CD8⁺ CAR T cells in tumors. Ultimately, the immune-enhancing effects of IL-12 nanochaperone significantly boost CAR T cell antitumor capabilities, dramatically eliminated solid tumor and minimized unwanted side effects. Hence, immunofeedback INS-CAR T biohybrids, which include INS that serves as an intelligent 'nanochaperone', could provide a powerful tool for efficient and safe antitumor immunotherapy.

Adoptive T cell therapy of solid tumors: time to team up with immunogenic chemo/radiotherapy

Adoptive T cell therapy (ACT) with tumor-reactive lymphocytes can overcome the immune desert of poorly immunogenic tumors and instruct tumor eradication. Several hurdles limit the efficacy of this strategy against solid tumor including, but not limited to, sub optimal T cell engraftment, tumor infiltration, poor tumor antigenicity/immunogenicity, and immunosuppressive or resistance mechanisms. Recent advances indicate that concomitant treatments can be set in place to offset such barriers. In this review, we highlight the beneficial effects of combining ACT with conventional chemo and/or radiotherapy. While originally classified as immunosuppressive, these methodologies can also promote the engraftment of ACT products, immunogenic cell death, and the reprogramming of more favorable microenvironments. Data indicates that systemic and local chemo/radiotherapy regimens promote intratumoral cytokine and chemokine upregulation, tumor antigen presentation and cross presentation, infiltration and in situ T cells reactivation. Here we review the most recent contributions supporting these notions and discuss further developments.

Brief in vitro IL-12 conditioning of CD8 + T Cells for anticancer adoptive T cell therapy

Cancer immunotherapy represents a potential treatment approach through non-specific and specific enhancement of the immune responses. Adoptive cell therapy (ACT) is a potential modality of immunotherapy that depends on harvesting T cells from the tumor-bearing host, activating them in vitro and infusing them back to the same host. Several cytokines, in particular IL-2, IL-7 and IL-15, have been used to enhance survival T cells in vitro. Although effective, conditioning of T cells in vitro with these cytokines requires long-term culture which results in the loss of expression of their trafficking receptors mainly CD62L. It also results in exhaustion of the activated T cells and reduction in their functions upon adoptive transfer in vivo. Our recent studies and those of other groups showed that brief (3 days) conditioning of CD8⁺ T cells by IL-12 in vitro can result in enhancing function of tumor-reactive CD8⁺ T cells. Adoptive transfer of these IL-12-conditioned CD8⁺ T cells into tumor-bearing mice, preconditioned with cyclophosphamide, 1 day before ACT, induced tumor eradication that was associated with generation of tumor-specific memory response. In this review, we summarize studies that indicated to the superiority of IL-12 as a potential cytokine for conditioning T cells for ACT. In addition, we discuss some of the cellular and molecular mechanisms that govern how IL-12 programs CD8⁺ T cells to enhance their functionality especially in vitro and its implication in combination with other ACT modalities, opening a avenue for the clinical application of this cytokine.

Transdermal delivery of interleukin-12 gene targeting dendritic cells enhances the anti-tumour effect of programmed cell death protein 1 monoclonal antibody

Recent studies have suggested that the anti-tumour effect of the programmed cell death protein 1 monoclonal antibody (aPD-1) depends on the expression of interleukin-12 (IL-12) by dendritic cells (DCs). Since DCs are abundant in skin tissues, transdermal delivery of IL-12 targeting DCs may significantly improve the anti-tumour effect of aPD-1. In this study, a novel mannosylated chitosan (MC)-modified ethosome (Eth^-MC) was obtained through electrostatic adsorption. The Eth^-MC loaded with plasmid containing the IL-12 gene (p^IL-12@Eth^-MC) stimulated DCs to express mature-related molecular markers such as CD86, CD80, and major histocompatibility complex-II in a targeted manner. The p^IL-12@Eth^-MC was then mixed with polyvinyl pyrrolidone solution to make microspheres using the electrospray technique, and sprayed onto the surface of electrospun silk fibroin-polyvinyl alcohol nanofibres to obtain a PVP-p^IL-12@Eth^-MC/silk fibroin-polyvinyl alcohol composite nanofibrous patch (termed a transcutaneous immunization (TCI) patch). The TCI patch showed a good performance on transdermal drug release. Animal experiments on melanoma-bearing mice showed that topical application of the TCI patches promoted the expression of IL-12 and inhibited the growth of tumour. Furthermore, combined application of the TCI patch and aPD-1 showed a stronger anti-tumour effect than aPD-1 monotherapy. The combination therapy significantly promoted the expression of IL-12, interferon-γ and tumour necrosis factor-α, the infiltration of CD4⁺ and CD8⁺ T cells into tumour tissues, and thus promoted the apoptosis of tumour cells. The present study provides a convenient and non-invasive strategy for improving the efficacy of immune checkpoint inhibitor therapy. This study was approved by the Institutional Animal Care and Use Committee at Donghua University (approval No. DHUEC-NSFC-2020-11) on March 31, 2020.

Engineered Cytokine Signaling to Improve CAR T Cell Effector Function

Adoptive immunotherapy with T cells genetically modified to express chimeric antigen receptors (CARs) is a promising approach to improve outcomes for cancer patients. While CAR T cell therapy is effective for hematological malignancies, there is a need to improve the efficacy of this therapeutic approach for patients with solid tumors and brain tumors. At present, several approaches are being pursued to improve the antitumor activity of CAR T cells including i) targeting multiple antigens, ii) improving T cell expansion/persistence, iii) enhancing homing to tumor sites, and iv) rendering CAR T cells resistant to the immunosuppressive tumor microenvironment (TME). Augmenting signal 3 of T cell activation by transgenic expression of cytokines or engineered cytokine receptors has emerged as a promising strategy since it not only improves CAR T cell expansion/persistence but also their ability to function in the immunosuppressive TME. In this review, we will provide an overview of cytokine biology and highlight genetic approaches that are actively being pursued to augment cytokine signaling in CAR T cells.

Gene Augmentation and Editing to Improve TCR Engineered T Cell Therapy against Solid Tumors

Recent developments in gene engineering technologies have drastically improved the therapeutic treatment options for cancer patients. The use of effective chimeric antigen receptor T (CAR-T) cells and recombinant T cell receptor engineered T (rTCR-T) cells has entered the clinic for treatment of hematological malignancies with promising results. However, further fine-tuning, to improve functionality and safety, is necessary to apply these strategies for the treatment of solid tumors. The immunosuppressive microenvironment, the surrounding stroma, and the tumor heterogeneity often results in poor T cell reactivity, functionality, and a diminished infiltration rates, hampering the efficacy of the treatment. The focus of this review is on recent advances in rTCR-T cell therapy, to improve both functionality and safety, for potential treatment of solid tumors and provides an overview of ongoing clinical trials. Besides selection of the appropriate tumor associated antigen, efficient delivery of an optimized recombinant TCR transgene into the T cells, in combination with gene editing techniques eliminating the endogenous TCR expression and disrupting specific inhibitory pathways could improve adoptively transferred T cells. Armoring the rTCR-T cells with specific cytokines and/or chemokines and their receptors, or targeting the tumor stroma, can increase the infiltration rate of the immune cells within the solid tumors. On the other hand, clinical “off-tumor/on-target” toxicities are still a major potential risk and can lead to severe adverse events. Incorporation of safety switches in rTCR-T cells can guarantee additional safety. Recent clinical trials provide encouraging data and emphasize the relevance of gene therapy and gene editing tools for potential treatment of solid tumors.

Breaking Bottlenecks for the TCR Therapy of Cancer

Immune checkpoint inhibitors have redefined the treatment of cancer, but their efficacy depends critically on the presence of sufficient tumor-specific lymphocytes, and cellular immunotherapies develop rapidly to fill this gap. The paucity of suitable extracellular and tumor-associated antigens in solid cancers necessitates the use of neoantigen-directed T-cell-receptor (TCR)-engineered cells, while prevention of tumor evasion requires combined targeting of multiple neoepitopes. These can be currently identified within 2 weeks by combining cutting-edge next-generation sequencing with bioinformatic pipelines and used to select tumor-reactive TCRs in a high-throughput manner for expeditious scalable non-viral gene editing of autologous or allogeneic lymphocytes. "Young" cells with a naive, memory stem or central memory phenotype can be additionally armored with "next-generation" features against exhaustion and the immunosuppressive tumor microenvironment, where they wander after reinfusion to attack heavily pretreated and hitherto hopeless neoplasms. Facilitated by major technological breakthroughs in critical manufacturing steps, based on a solid preclinical rationale, and backed by rapidly accumulating evidence, TCR therapies break one bottleneck after the other and hold the promise to become the next immuno-oncological revolution.

Adoptive T Cell Therapy with IL-12-Preconditioned Low-Avidity T Cells Prevents Exhaustion and Results in Enhanced T Cell Activation, Enhanced Tumor Clearance, and Decreased Risk for Autoimmunity

Optimal ex vivo expansion protocols of tumor-specific T cells followed by adoptive cell therapy must yield T cells able to home to tumors and effectively kill them. Our previous study demonstrated ex vivo activation in the presence of IL-12-induced optimal CD8⁺ T cell expansion and melanoma regression; however, adverse side effects, including autoimmunity, can occur. This may be due to transfer of high-avidity self-specific T cells. In this study, we compared mouse low- and high-avidity T cells targeting the tumor Ag tyrosinase-related protein 2 (TRP2). Not surprisingly, high-avidity T cells provide superior tumor control, yet low-avidity T cells can promote tumor regression. The addition of IL-12 during in vitro expansion boosts low-avidity T cell responsiveness, tumor regression, and prevents T cell exhaustion. In this study, we demonstrate that IL-12-primed T cells are resistant to PD-1/PD-L1-mediated suppression and retain effector function. Importantly, IL-12 preconditioning prevented exhaustion as LAG-3, PD-1, and TOX were decreased while simultaneously increasing KLRG1. Using intravital imaging, we also determined that high-avidity T cells have sustained contacts with intratumoral dendritic cells and tumor targets compared with low-avidity T cells. However, with Ag overexpression, this defect is overcome, and low-avidity T cells control tumor growth. Taken together, these data illustrate that low-avidity T cells can be therapeutically beneficial if cocultured with IL-12 cytokine during in vitro expansion and highly effective in vivo if Ag is not limiting. Clinically, low-avidity T cells provide a safer alternative to high-avidity, TCR-engineered T cells, as IL-12-primed, low-avidity T cells cause less autoimmune vitiligo.

Engineering CD4+ T Cells to Enhance Cancer Immunity

This review presents key advances in combining T cell receptor (TCR) gene transfer to redirect T-cell specificity with gene engineering in order to enhance cancer-protective immune function. We discuss how emerging insights might be applied to CD4+ T cells. Although much attention has been paid to the role of CD8+ cytotoxic T cells in tumour protection, we provide convincing evidence that CD4+ helper T cells play a critical role in cancer immune responses in animal models and also in patients. We demonstrate that genetic engineering technologies provide exciting opportunities to extend the specificity range of CD4+ T cells from MHC class-II-presented epitopes to include peptides presented by MHC class I molecules. Functional enhancement of tumour immunity can improve the sensitivity of T cells to cancer antigens, promote survival in a hostile tumour microenvironment, boost cancer-protective effector mechanisms and enable the formation of T-cell memory. Engineered cancer-specific CD4+ T cells may contribute to protective immunity by a direct pathway involving cancer cell killing, and by an indirect pathway that boosts the function, persistence and memory formation of CD8+ T cells.

T-Cell Receptor-Based Immunotherapy for Hematologic Malignancies

Adoptive immunotherapy with engineered T cells is at the forefront of cancer treatment. T cells can be engineered to express T-cell receptors (TCRs) specific for tumor-associated antigens (TAAs) derived from intracellular or cell surface proteins. T cells engineered with TCRs (TCR-T) allow for targeting diverse types of TAAs, including proteins overexpressed in malignant cells, those with lineage-restricted expression, cancer-testis antigens, and neoantigens created from abnormal, malignancy-restricted proteins. Minor histocompatibility antigens can also serve as TAAs for TCR-T to treat relapsed hematologic malignancies after allogeneic hematopoietic cell transplantation. Moreover, TCR constructs can be modified to improve safety and enhance function and persistence of TCR-T. Transgenic T-cell receptor therapies targeting 3 different TAAs are in early-phase clinical trials for treatment of hematologic malignancies. Preclinical studies of TCR-T specific for many other TAAs are underway and offer great promise as safe and effective therapies for a wide range of cancers.

Engineering Strategies to Enhance TCR-Based Adoptive T Cell Therapy

T cell receptor (TCR)-based adoptive T cell therapies (ACT) hold great promise for the treatment of cancer, as TCRs can cover a broad range of target antigens. Here we summarize basic, translational and clinical results that provide insight into the challenges and opportunities of TCR-based ACT. We review the characteristics of target antigens and conventional αβ-TCRs, and provide a summary of published clinical trials with TCR-transgenic T cell therapies. We discuss how synthetic biology and innovative engineering strategies are poised to provide solutions for overcoming current limitations, that include functional avidity, MHC restriction, and most importantly, the tumor microenvironment. We also highlight the impact of precision genome editing on the next iteration of TCR-transgenic T cell therapies, and the discovery of novel immune engineering targets. We are convinced that some of these innovations will enable the field to move TCR gene therapy to the next level.

T-cell receptor and chimeric antigen receptor in solid cancers: current landscape, preclinical data and insight into future developments

PURPOSE OF REVIEW

The remarkable and durable clinical responses seen in certain solid tumours using checkpoint inhibitors and in haematological malignancies using chimeric antigen receptor (CAR) T therapy have led to great interest in the possibility of using engineered T-cell receptor (TCR) and CAR T therapies to treat solid tumours.

RECENT FINDINGS

In this article, we focus on the published clinical data for engineered TCR and CAR T therapy in solid tumours and recent preclinical work to explore how these therapies may develop and improve. We discuss recent approaches in target selection, encouraging epitope spreading and replicative capacity, CAR activation, T-cell trafficking, survival in the immunosuppressive microenvironment, universal T-cell therapies, manufacturing processes and managing toxicity.

SUMMARY

In haematological malignancies, CAR T treatments have shown remarkable clinical responses. Engineered TCR and CAR therapies demonstrate responses in numerous preclinical models of solid tumours and have shown objective clinical responses in select solid tumour types. It is anticipated that the integration of efficacious changes to the T-cell products from disparate preclinical experiments will increase the ability of T-cell therapies to overcome the challenges of treating solid tumours and note that healthcare facilities will need to adapt to deliver these treatments.

Synthetic immunity by remote control

Cell-based immunotherapies, such as T cells engineered with chimeric antigen receptors (CARs), have the potential to cure patients of disease otherwise refractory to conventional treatments. Early-on-treatment and long-term durability of patient responses depend critically on the ability to control the potency of adoptively transferred T cells, as overactivation can lead to complications like cytokine release syndrome, and immunosuppression can result in ineffective responses to therapy. Drugs or biologics (e.g., cytokines) that modulate immune activity are limited by mass transport barriers that reduce the local effective drug concentration, and lack site or target cell specificity that results in toxicity. Emerging technologies that enable site-targeted, remote control of key T cell functions - including proliferation, antigen-sensing, and target-cell killing - have the potential to increase treatment precision and safety profile. These technologies are broadly applicable to other immune cells to expand immune cell therapies across many cancers and diseases. In this review, we highlight the opportunities, challenges and the current state-of-the-art for remote control of synthetic immunity.

Boosting Interleukin-12 Antitumor Activity and Synergism with Immunotherapy by Targeted Delivery with isoDGR-Tagged Nanogold

The clinical use of interleukin-12 (IL12), a cytokine endowed with potent immunotherapeutic anticancer activity, is limited by systemic toxicity. The hypothesis is addressed that gold nanoparticles tagged with a tumor-homing peptide containing isoDGR, an αvβ3-integrin binding motif, can be exploited for delivering IL12 to tumors and improving its therapeutic index. To this aim, gold nanospheres are functionalized with the head-to-tail cyclized-peptide CGisoDGRG (Iso1) and murine IL12. The resulting nanodrug (Iso1/Au/IL12) is monodispersed, stable, and bifunctional in terms of αvβ3 and IL12-receptor recognition. Low-dose Iso1/Au/IL12, equivalent to 18-75 pg of IL12, induces antitumor effects in murine models of fibrosarcomas and mammary adenocarcinomas, with no evidence of toxicity. Equivalent doses of Au/IL12 (a nanodrug lacking Iso1) fail to delay tumor growth, whereas 15 000 pg of free IL12 is necessary to achieve similar effects. Iso1/Au/IL12 significantly increases tumor infiltration by innate immune cells, such as NK and iNKT cells, monocytes, and neutrophils. NK cell depletion completely inhibits its antitumor effects. Low-dose Iso1/Au/IL12 can also increase the therapeutic efficacy of adoptive T-cell therapy in mice with autochthonous prostate cancer. These findings indicate that coupling IL12 to isoDGR-tagged nanogold is a valid strategy for enhancing its therapeutic index and sustaining adoptive T-cell therapy.

CAR T-cell therapy of solid tumors: promising approaches to modulating antitumor activity of CAR T cells

Adoptive immunotherapy that makes use of genetically modified autologous T cells carrying a chimeric antigen receptor (CAR) with desired specificity is a promising approach to the treatment of advanced or relapsed solid tumors. However, there are a number of challenges facing the CAR T-cell therapy, including the ability of the tumor to silence the expression of target antigens in response to the selective pressure exerted by therapy and the dampening of the functional activity of CAR T cells by the immunosuppressive tumor microenvironment. This review discusses the existing gene-engineering approaches to the modification of CAR T-cell design for 1) creating universal “switchable” synthetic receptors capable of attacking a variety of target antigens; 2) enhancing the functional activity of CAR T cells in the immunosuppressive microenvironment of the tumor by silencing the expression of inhibiting receptors or by stimulating production of cytokines.

IFN-γ: A cytokine at the right time, is in the right place

Interferon gamma has long been studied as a critical mediator of tumor immunity. In recent years, the complexity of cellular interactions that take place in the tumor microenvironment has become better appreciated in the context of immunotherapy. While checkpoint inhibitors have dramatically improved remission rates in cancer treatment, IFN-γ and related effectors continue to be identified as strong predictors of treatment success. In this review, we provide an overview of the multiple immunosuppressive barriers that IFN-γ has to overcome to eliminate tumors, and potential avenues for modulating the immune response in favor of tumor rejection.