Transforming growth factor-beta receptor blockade augments the effectiveness of adoptive T-cell therapy of established solid cancers

Cancer-associated fibroblasts barrier breaking via TGF-β blockade paved way for docetaxel micelles delivery to treat pancreatic cancer

TGF-β is a crucial regulator in tumor microenvironment (TME), especially for myofibroblastic cancer-associated fibroblasts (myCAFs). The myCAFs can be motivated by TGF-β signaling to erect pro-tumor TME, meanwhile, myCAFs overexpress TGF-β to mediate the crosstalk between tumor and stromal cells. The blockade of TGF-β can break cancer-associated fibroblasts barrier, consequently opening the access for drugs into tumor. The TGF-β is a promising target in anti-tumor therapy. Herein, we introduced a two-stage combination therapy (TC-Therapy), including TGF-β receptor I inhibitor SB525334 (SB) and cytotoxicity agent docetaxel micelle (DTX-M). We found that SB and DTX-M synergistically inhibited myCAFs proliferation and elevated p53 protein expression in BxPC-3/3T3 mixed cells. Gene and protein tests demonstrated that SB cut off TGF-β signaling via receptor blockade and it did not arouse TGF-β legend compensated internal autocrine. On the contrary, two agents combined decreased TGF-β secretion and inhibited myCAFs viability marked by α-SMA and FAPα. TC-Therapy was applied in BxPc-3/3T3 mixed tumor-bearing mice model. After TC-Therapy, the α-SMA+/ FAPα+ myCAFs faded increasingly and collagenous fibers mainly secreted by myCAFs decreased dramatically as well. More than that, the myCAFs barrier breaking helped to normalize micro-vessels and paved way for micelle penetration. The TGF-β protein level of TC-Therapy in TME was much lower than that of simplex DTX-M, which might account for TME restoration. In conclusion, TGF-β inhibitor acted as the pioneer before nano chemotherapeutic agents. The TC-Therapy of TGF-β signaling inhibition and anti-tumor agent DTX-M is a promising regimen without arising metastasis risk to treat pancreatic cancer. The therapeutic regimen focused on TGF-β related myCAFs reminds clinicians to have a comprehensive understanding of pancreatic cancer.

Molecular understanding and clinical outcomes of CAR T cell therapy in the treatment of urological tumors

Chimeric antigen receptor engineered T (CAR T) cell therapy has developed rapidly in recent years, leading to profound developments in oncology, especially for hematologic malignancies. However, given the pressure of immunosuppressive tumor microenvironments, antigen escape, and diverse other factors, its application in solid tumors is less developed. Urinary system tumors are relatively common, accounting for approximately 24% of all new cancers in the United States. CAR T cells have great potential for urinary system tumors. This review summarizes the latest developments of CAR T cell therapy in urinary system tumors, including kidney cancer, bladder cancer, and prostate cancer, and also outlines the various CAR T cell generations and their pathways and targets that have been developed thus far. Finally, the current advantages, problems, and side effects of CAR T cell therapy are discussed in depth, and potential future developments are proposed in view of current shortcomings.

Chimeric antigen receptor T cells in the treatment of osteosarcoma (Review)

Osteosarcoma (OS) is a frequently occurring primary bone tumor, mostly affecting children, adolescents and young adults. Before 1970, surgical resection was the main treatment method for OS, but the clinical results were not promising. Subsequently, the advent of chemotherapy has improved the prognosis of patients with OS. However, there is still a high incidence of metastasis or recurrence, and chemotherapy has several side effects, thus making the 5‑year survival rate markedly low. Recently, chimeric antigen receptor T (CAR‑T) cell therapy represents an alternative immunotherapy approach with significant potential for hematologic malignancies. Nevertheless, the application of CAR‑T cells in the treatment of OS faces numerous challenges. The present review focused on the advances in the development of CAR‑T cells to improve their clinical efficacy, and discussed ways to overcome the difficulties faced by CAR T‑cell therapy for OS.

Recent advances of bioresponsive polymeric nanomedicine for cancer therapy

A bioresponsive polymeric nanocarrier for drug delivery is able to alter its physical and physicochemical properties in response to a variety of biological signals and pathological changes, and can exert its therapeutic efficacy within a confined space. These nanosystems can optimize the biodistribution and subcellular location of therapeutics by exploiting the differences in biochemical properties between tumors and normal tissues. Moreover, bioresponsive polymer-based nanosystems could be rationally designed as precision therapeutic platforms by optimizing the combination of responsive elements and therapeutic components according to the patient-specific disease type and stage. In this review, recent advances in smart bioresponsive polymeric nanosystems for cancer chemotherapy and immunotherapy will be summarized. We mainly discuss three categories, including acidity-sensitive, redox-responsive, and enzyme-triggered polymeric nanosystems. The important issues regarding clinical translation such as reproducibility, manufacture, and probable toxicity, are also commented.

Advances and Hurdles in CAR T Cell Immune Therapy for Solid Tumors

Chimeric antigen receptor (CAR) T cells in solid tumors have so far yielded limited results, in terms of therapeutic effects, as compared to the dramatic results observed for hematological malignancies. Many factors involve both the tumor cells and the microenvironment. The lack of specific target antigens and severe, potentially fatal, toxicities caused by on-target off-tumor toxicities constitute major hurdles. Furthermore, the tumor microenvironment is usually characterized by chronic inflammation, the presence of immunosuppressive molecules, and immune cells that can reduce CAR T cell efficacy and facilitate antigen escape. Nonetheless, solid tumors are under investigation as possible targets despite their complexity, which represents a significant challenge. In preclinical mouse models, CAR T cells are able to efficiently recognize and kill several tumor xenografts. Overall, in the next few years, there will be intensive research into optimizing novel cell therapies to improve their effector functions and keep untoward effects in check. In this review, we provide an update on the state-of-the-art CAR T cell therapies in solid tumors, focusing on the preclinical studies and preliminary clinical findings aimed at developing optimal strategies to reduce toxicity and improve efficacy.

Impact of tumor microenvironment on adoptive T cell transfer activity

Recent advances in immunotherapy have revolutionized the treatment of cancer. The use of adoptive cell therapies (ACT) such as those based on tumor infiltrating lymphocytes (TILs) or genetically modified cells (transgenic TCR lymphocytes or CAR-T cells), has shown impressive results in the treatment of several types of cancers. However, cancer cells can exploit mechanisms to escape from immunosurveillance resulting in many patients not responding to these therapies or respond only transiently. The failure of immunotherapy to achieve long-term tumor control is multifactorial. On the one hand, only a limited percentage of the transferred lymphocytes is capable of circulating through the bloodstream, interacting and crossing the tumor endothelium to infiltrate the tumor. Metabolic competition, excessive glucose consumption, the high level of lactic acid secretion and the extracellular pH acidification, the shortage of essential amino acids, the hypoxic conditions or the accumulation of fatty acids in the tumor microenvironment (TME), greatly hinder the anti-tumor activity of the immune cells in ACT therapy strategies. Therefore, there is a new trend in immunotherapy research that seeks to unravel the fundamental biology that underpins the response to therapy and identifies new approaches to better amplify the efficacy of immunotherapies. In this review we address important aspects that may significantly affect the efficacy of ACT, indicating also the therapeutic alternatives that are currently being implemented to overcome these drawbacks.

Tracing New Landscapes in the Arena of Nanoparticle-Based Cancer Immunotherapy

Over the past two decades, unique and comprehensive cancer treatment has ushered new hope in the holistic management of the disease. Cancer immunotherapy, which harnesses the immune system of the patient to attack the cancer cells in a targeted manner, scores over others by being less debilitating compared to the existing treatment strategies. Significant advancements in the knowledge of immune surveillance in the last few decades have led to the development of several types of immune therapy like monoclonal antibodies, cancer vaccines, immune checkpoint inhibitors, T-cell transfer therapy or adoptive cell therapy (ACT) and immune system modulators. Intensive research has established cancer immunotherapy to be a safe and effective method for improving survival and the quality of a patient’s life. However, numerous issues with respect to site-specific delivery, resistance to immunotherapy, and escape of cancer cells from immune responses, need to be addressed for expanding and utilizing this therapy as a regular mode in the clinical treatment. Development in the field of nanotechnology has augmented the therapeutic efficiency of treatment modalities of immunotherapy. Nanocarriers could be used as vehicles because of their advantages such as increased surface areas, targeted delivery, controlled surface and release chemistry, enhanced permeation and retention effect, etc. They could enhance the function of immune cells by incorporating immunomodulatory agents that influence the tumor microenvironment, thus enabling antitumor immunity. Robust validation of the combined effect of nanotechnology and immunotherapy techniques in the clinics has paved the way for a better treatment option for cancer than the already existing procedures such as chemotherapy and radiotherapy. In this review, we discuss the current applications of nanoparticles in the development of ‘smart’ cancer immunotherapeutic agents like ACT, cancer vaccines, monoclonal antibodies, their site-specific delivery, and modulation of other endogenous immune cells. We also highlight the immense possibilities of using nanotechnology to accomplish leveraging the coordinated and adaptive immune system of a patient to tackle the complexity of treating unique disease conditions and provide future prospects in the field of cancer immunotherapy.

Biomimetic and Materials-Potentiated Cell Engineering for Cancer Immunotherapy

In cancer immunotherapy, immune cells are the main force for tumor eradication. However, they appear to be dysfunctional due to the taming of the tumor immunosuppressive microenvironment. Recently, many materials-engineered strategies are proposed to enhance the anti-tumor effect of immune cells. These strategies either utilize biomimetic materials, as building blocks to construct inanimate entities whose functions are similar to natural living cells, or engineer immune cells with functional materials, to potentiate their anti-tumor effects. In this review, we will summarize these advanced strategies in different cell types, as well as discussing the prospects of this field.

CAR-NK cells for cancer immunotherapy: from bench to bedside

Natural killer (NK) cells are unique innate immune cells and manifest rapid and potent cytotoxicity for cancer immunotherapy and pathogen removal without the requirement of prior sensitization or recognition of peptide antigens. Distinguish from the T lymphocyte-based cythotherapy with toxic side effects, chimeric antigen receptor-transduced NK (CAR-NK) cells are adequate to simultaneously improve efficacy and control adverse effects including acute cytokine release syndrome (CRS), neurotoxicity and graft-versus-host disease (GVHD). Moreover, considering the inherent properties of NK cells, the CAR-NK cells are “off-the-shelf” product satisfying the clinical demand for large-scale manufacture for cancer immunotherapy attribute to the cytotoxic effect via both NK cell receptor-dependent and CAR-dependent signaling cascades. In this review, we mainly focus on the latest updates of CAR-NK cell-based tactics, together with the opportunities and challenges for cancer immunotherapies, which represent the paradigm for boosting the immune system to enhance antitumor responses and ultimately eliminate malignancies. Collectively, we summarize and highlight the auspicious improvement in CAR-NK cells and will benefit the large-scale preclinical and clinical investigations in adoptive immunotherapy.

Emerging Novel Combined CAR-T Cell Therapies

Simple Summary

As a result of FDA approval of CAR-T cell treatments in the last few years, this immunotherapy has provided further direction to precision medicine through its combination with other therapeutic approaches. In the past year, several review articles have been published focusing on advances in this fast-developing field, especially with respect to efforts to overcome hurdles associated with applying CAR-T cells in solid tumors. This review paper focuses on combining CAR-T cell therapy with small molecule drugs, up-to-date progress in CAR-T cell therapy research, and advances in combined CAR-T immunotherapy with other treatments targeting solid tumors.

Abstract

Chimeric antigen receptors (CAR) T cells are T cells engineered to express membrane receptors with high specificity to recognize specific target antigens presented by cancer cells and are co-stimulated with intracellular signals to increase the T cell response. CAR-T cell therapy is emerging as a novel therapeutic approach to improve T cell specificity that will lead to advances in precision medicine. CAR-T cells have had impressive outcomes in hematological malignancies. However, there continue to be significant limitations of these therapeutic responses in targeting solid malignancies such as heterogeneous antigens in solid tumors, tumor immunosuppressive microenvironment, risk of on-target/off-tumor, infiltrating CAR-T cells, immunosuppressive checkpoint molecules, and cytokines. This review paper summarizes recent approaches and innovations through combination therapies of CAR-T cells and other immunotherapy or small molecule drugs to counter the above disadvantages to potentiate the activity of CAR-T cells.

Engineering Nano-Therapeutics to Boost Adoptive Cell Therapy for Cancer Treatment

Although adoptive transfer of therapeutic cells to cancer patients is demonstrated with great success and fortunately approved for the treatment of leukemia and B-cell lymphoma, potential issues, including the unclear mechanism, complicated procedures, unfavorable therapeutic efficacy for solid tumors, and side effects, still hinder its extensive applications. The explosion of nanotechnology recently has led to advanced development of novel strategies to address these challenges, facilitating the design of nano-therapeutics to improve adoptive cell therapy (ACT) for cancer treatment. In this review, the emerging nano-enabled approaches, that design multiscale artificial antigen-presenting cells for cell proliferation and stimulation in vitro, promote the transducing efficiency of tumor-targeting domains, engineer therapeutic cells for in vivo imaging, tumor infiltration, and in vivo functional sustainability, as well as generate tumoricidal T cells in vivo, are summarized. Meanwhile, the current challenges and future perspectives of the nanostrategy-based ACT for cancer treatment are also discussed in the end.

Reprogramming Immune Cells for Enhanced Cancer Immunotherapy: Targets and Strategies

Cancer is one of the leading causes of death and a major public health problem all over the world. Immunotherapy is becoming a revolutionary clinical management for various cancer types. Restoration of aberrant immune surveillance on cancers has achieved markable progress in the past years by either in vivo or ex vivo engineering of the immune cells. Here, we summarized the central roles of immune cells in tumor progression and regression, and the existing and emerging strategies for different immune cell-based immunotherapies. In addition, the current challenges and the potential solutions in translating the immunotherapies into the clinic are also discussed.

DNA scaffolds enable efficient and tunable functionalization of biomaterials for immune cell modulation

Biomaterials can improve the safety and presentation of therapeutic agents for effective immunotherapy, and a high level of control over surface functionalization is essential for immune cell modulation. Here, we developed biocompatible immune cell-engaging particles (ICEp) that use synthetic short DNA as scaffolds for efficient and tunable protein loading. To improve the safety of chimeric antigen receptor (CAR) T cell therapies, micrometre-sized ICEp were injected intratumorally to present a priming signal for systemically administered AND-gate CAR-T cells. Locally retained ICEp presenting a high density of priming antigens activated CAR T cells, driving local tumour clearance while sparing uninjected tumours in immunodeficient mice. The ratiometric control of costimulatory ligands (anti-CD3 and anti-CD28 antibodies) and the surface presentation of a cytokine (IL-2) on ICEp were shown to substantially impact human primary T cell activation phenotypes. This modular and versatile biomaterial functionalization platform can provide new opportunities for immunotherapies.

Non-invasive monitoring of the kinetic infiltration and therapeutic efficacy of nanoparticle-labeled chimeric antigen receptor T cells in glioblastoma via 7.0-Tesla magnetic resonance imaging

BACKGROUND AIMS

Chimeric antigen receptor (CAR) T-cell therapy is a promising treatment strategy in solid tumors. In vivo cell tracking techniques can help us better understand the infiltration, persistence and therapeutic efficacy of CAR T cells. In this field, magnetic resonance imaging (MRI) can achieve high-resolution images of cells by using cellular imaging probes. MRI can also provide various biological information on solid tumors.

METHODS

The authors adopted the amino alcohol derivatives of glucose-coated nanoparticles, ultra-small superparamagnetic particles of iron oxide (USPIOs), to label CAR T cells for non-invasive monitoring of kinetic infiltration and persistence in glioblastoma (GBM). The specific targeting CARs included anti-human epidermal growth factor receptor variant III and IL13 receptor subunit alpha 2 CARs.

RESULTS

When using an appropriate concentration, USPIO labeling exerted no negative effects on the biological characteristics and killing efficiency of CAR T cells. Increasing hypointensity signals could be detected in GBM models by susceptibility-weighted imaging MRI ranging from 3 days to 14 days following the injection of USPIO-labeled CAR T cells. In addition, nanoparticles and CAR T cells were found on consecutive histopathological sections. Moreover, diffusion and perfusion MRI revealed significantly increased water diffusion and decreased vascular permeability on day 3 after treatment, which was simultaneously accompanied by a significant decrease in tumor cell proliferation and increase in intercellular tight junction on immunostaining sections.

CONCLUSION

These results establish an effective imaging technique that can track CAR T cells in GBM models and validate their early therapeutic effects, which may guide the evaluation of CAR T-cell therapies in solid tumors.

Immune cell engineering: opportunities in lung cancer therapeutics

Engineered immune cells offer a prime therapeutic alternate for some aggressive and frequently occurring malignancies like lung cancer. These therapies were reported to result in tumor regression and overall improvement in patient survival. However, studies also suggest that the presence of cancer cell-induced immune-suppressive microenvironment, off-target toxicity, and difficulty in concurrent imaging are some prime impendent in the success of these approaches. The present article reviews the need and significance of the currently available immune cell-based strategies for lung cancer therapeutics. It also showcases the utility of incorporating nanoengineered strategies and details the available formulations of nanocarriers. In last, it briefly discussed the existing methods for nanoparticle fuctionalization and challenges in translating basic research to the clinics. Graphical Abstract.

Blockade of Platelets Using Tumor-Specific NO-Releasing Nanoparticles Prevents Tumor Metastasis and Reverses Tumor Immunosuppression

The tumor microenvironment maintains a sufficient immunosuppressive state owing to the existence of the immunosuppressive factors. The most prominent such factor is transforming growth factor β (TGF-β), which is mainly provided by platelets. Moreover, platelets have been shown to be the main accomplice in assisting tumor metastasis. Therefore, blocking tumor-associated platelets is endowed with functions of enhancing immunity and reducing metastasis. Herein, we designed a tumor microenvironment-responsive nitric oxide (NO) release nanoparticle, Ptx@AlbSNO, which was able to specifically and safely co-deliver the antiplatelet agent NO and the chemotherapeutic agent paclitaxel (Ptx) into tumor tissues and inhibit platelet-tumor cell interactions. We discovered that Ptx@AlbSNO could successfully block tumor-specific platelet functions, thereby suppressing the process of tumor epithelial-mesenchymal transition (EMT), preventing platelet adhesion around circulating tumor cells (CTCs) and reducing distant metastasis. In vivo studies demonstrate that the co-delivery of NO and Ptx can suppress primary tumor growth. With the ability to effectively inhibit activated platelets and TGF-β secretion in tumors, Ptx@AlbSNO can enhance intratumoral immune cell infiltration to reverse the immunosuppressive tumor microenvironment.

Innovative CAR-T Cell Therapy for Solid Tumor; Current Duel between CAR-T Spear and Tumor Shield

Novel engineered T cells containing chimeric antigen receptors (CAR-T cells) that combine the benefits of antigen recognition and T cell response have been developed, and their effect in the anti-tumor immunotherapy of patients with relapsed/refractory leukemia has been dramatic. Thus, CAR-T cell immunotherapy is rapidly emerging as a new therapy. However, it has limitations that prevent consistency in therapeutic effects in solid tumors, which accounts for over 90% of all cancer patients. Here, we review the literature regarding various obstacles to CAR-T cell immunotherapy for solid tumors, including those that cause CAR-T cell dysfunction in the immunosuppressive tumor microenvironment, such as reactive oxygen species, pH, O₂, immunosuppressive cells, cytokines, and metabolites, as well as those that impair cell trafficking into the tumor microenvironment. Next-generation CAR-T cell therapy is currently undergoing clinical trials to overcome these challenges. Therefore, novel approaches to address the challenges faced by CAR-T cell immunotherapy in solid tumors are also discussed here.

The application of nanotechnology in enhancing immunotherapy for cancer treatment: current effects and perspective

Cancer immunotherapy is emerging as a promising treatment modality that suppresses and eliminates tumors by re-activating and maintaining the tumor-immune cycle, and further enhancing the body's anti-tumor immune response. Despite the impressive therapeutic potential of immunotherapy approaches such as immune checkpoint inhibitors and tumor vaccines in pre-clinical and clinical applications, the effective response is limited by insufficient accumulation in tumor tissues and severe side-effects. Recent years have witnessed the rise of nanotechnology as a solution to improve these technical weaknesses due to its inherent biophysical properties and multifunctional modifying potential. In this review, we summarized and discussed the current status of nanoparticle-enhanced cancer immunotherapy strategies, including intensified delivery of tumor vaccines and immune adjuvants, immune checkpoint inhibitor vehicles, targeting capacity to tumor-draining lymph nodes and immune cells, triggered releasing and regulating specific tumor microenvironments, and adoptive cell therapy enhancement effects.

Current Progress in CAR-T Cell Therapy for Solid Tumors

Cancer immunotherapy by chimeric antigen receptor-modified T (CAR-T) cells has shown exhilarative clinical efficacy for hematological malignancies. Recently two CAR-T cell based therapeutics, Kymriah (Tisagenlecleucel) and Yescarta (Axicabtagene ciloleucel) approved by US FDA (US Food and Drug Administration) are now used for treatment of B cell acute lymphoblastic leukemia (B-ALL) and diffuse large B-cell lymphoma (DLBCL) respectively in the US. Despite the progresses made in treating hematological malignancies, challenges still remain for use of CAR-T cell therapy to treat solid tumors. In this landscape, most studies have primarily focused on improving CAR-T cells and overcoming the unfavorable effects of tumor microenvironment on solid tumors. To further understand the current status and trend for developing CAR-T cell based therapies for various solid tumors, this review emphasizes on CAR-T techniques, current obstacles, and strategies for application, as well as necessary companion diagnostics for treatment of solid tumors with CAR-T cells.

Application of CAR T cells for the treatment of solid tumors

CAR T cell therapy of cancers promises to revolutionize oncology by harnessing the powers of synthetic biology and immunotherapy in a single agent. CARs are synthetic receptors composed of an extracellular antigen binding domain and one or more intracellular signaling domains which act in concert to activate the T cell upon antigen recognition. CARs targeting B cell associated CD19 demonstrated robust in vivo cytolytic activity, expansion, and persistence upon antigen exposure paving the way for clinical application of this technology and ultimately FDA approval for pediatric and young adult acute lymphoblastic leukemia as well as patients with relapsed or refractory diffuse large B cell lymphoma. However, these successes have not yet been replicated in the arena of solid tumors. Unlike hematologic malignancies, solid tumors present numerous challenges in the form of an immunosuppressive tumor microenvironment. In this chapter, we will highlight clinical application of CAR T cells in solid tumors, discuss hurdles that have impeded CAR T cell function in these malignancies, and propose methods to overcome these limitations.

Blockade of TGF-β signaling to enhance the antitumor response is accompanied by dysregulation of the functional activity of CD4+CD25+Foxp3+ and CD4+CD25-Foxp3+ T cells

Background

The pleiotropic cytokine, transforming growth factor (TGF)-β, and CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) play a critical role in actively suppressing antitumor immune responses. Evidence shows that TGF-β produced by tumor cells promotes tolerance via expansion of Tregs. Our group previously demonstrated that blockade of TGF-β signaling with a small molecule TGF-β receptor I antagonist (SM16) inhibited primary and metastatic tumor growth in a T cell dependent fashion. In the current study, we evaluated the effect of SM16 on Treg generation and function.

Methods

Using BALB/c, FoxP3eGFP and Rag^−/− mice, we performed FACS analysis to determine if SM16 blocked de novo TGF-β-induced Treg generation in vitro and in vivo. CD4⁺ T cells from lymph node and spleen were isolated from control mice or mice maintained on SM16 diet, and flow cytometry analysis was used to detect the frequency of CD4⁺CD25⁻FoxP3⁺ and CD4⁺CD25⁺FoxP3⁺ T cells. In vitro suppression assays were used to determine the ability to suppress naive T cell proliferation in vitro of both CD4⁺CD25⁺FoxP3⁺ and CD4⁺CD25⁻FoxP3⁺ T cell sub-populations. We then examined whether SM16 diet exerted an inhibitory effect on primary tumor growth and correlated with changes in FoxP3⁺expression. ELISA analysis was used to measure IFN-γ levels after 72 h co-culture of CD4⁺CD25⁺ T cells from tumor-bearing mice on control or SM16 diet with CD4⁺CD25⁻ T cells from naive donors.

Results

SM16 abrogates TGF-β-induced Treg generation in vitro but does not prevent global homeostatic expansion of CD4⁺ T cell sub-populations in vivo. Instead, SM16 treatment causes expansion of a population of CD4⁺CD25⁻Foxp3⁺ Treg-like cells without significantly altering the overall frequency of Treg in lymphoreplete naive and tumor-bearing mice. Importantly, both the CD4⁺CD25⁻Foxp3⁺ T cells and the CD4⁺CD25⁺Foxp3⁺ Tregs in mice receiving SM16 diet exhibited diminished ability to suppress naive T cell proliferation in vitro compared to Treg from mice on control diet.

Conclusions

These findings suggest that blockade of TGF-β signaling is a potentially useful strategy for blunting Treg function to enhance the anti-tumor response. Our data further suggest that the overall dampening of Treg function may involve the expansion of a quiescent Treg precursor population, which is CD4⁺CD25⁻Foxp3⁺.

Delivery technologies for cancer immunotherapy

Immunotherapy has become a powerful clinical strategy for treating cancer. The number of immunotherapy drug approvals has been increasing, with numerous treatments in clinical and preclinical development. However, a key challenge in the broad implementation of immunotherapies for cancer remains the controlled modulation of the immune system, as these therapeutics have serious adverse effects including autoimmunity and nonspecific inflammation. Understanding how to increase the response rates to various classes of immunotherapy is key to improving efficacy and controlling these adverse effects. Advanced biomaterials and drug delivery systems, such as nanoparticles and the use of T cells to deliver therapies, could effectively harness immunotherapies and improve their potency while reducing toxic side effects. Here, we discuss these research advances, as well as the opportunities and challenges for integrating delivery technologies into cancer immunotherapy, and we critically analyse the outlook for these emerging areas.

CAR T Cell Therapy for Neuroblastoma

Patients with high risk neuroblastoma have a poor prognosis and survivors are often left with debilitating long term sequelae from treatment. Even after integration of anti-GD2 monoclonal antibody therapy into standard, upftont protocols, 5-year overall survival rates are only about 50%. The success of anti-GD2 therapy has proven that immunotherapy can be effective in neuroblastoma. Adoptive transfer of chimeric antigen receptor (CAR) T cells has the potential to build on this success. In early phase clinical trials, CAR T cell therapy for neuroblastoma has proven safe and feasible, but significant barriers to efficacy remain. These include lack of T cell persistence and potency, difficulty in target identification, and an immunosuppressive tumor microenvironment. With recent advances in CAR T cell engineering, many of these issues are being addressed in the laboratory. In this review, we summarize the clinical trials that have been completed or are underway for CAR T cell therapy in neuroblastoma, discuss the conclusions and open questions derived from these trials, and consider potential strategies to improve CAR T cell therapy for patients with neuroblastoma.

Chimeric antigen receptor-engineered T-cell therapy for liver cancer

BACKGROUND

Chimeric antigen receptor-engineered T-cell (CAR-T) therapy is a newly developed immunotherapy used in the treatment of cancers. Because CAR-T therapy has shown great success in treating CD19-positive hematological malignancies, its application has been explored in the treatment of solid tumors, such as liver cancer. In this review, we discuss the immune characteristics of liver cancer, the obstacles encountered during the application of CAR-T therapy, and preclinical and clinical progress in the use of CAR-T therapy in patients with liver cancer.

DATA SOURCES

The data on CAR-T therapy related to liver cancers were collected by searching PubMed and the Web of Science databases prior to December 2017 with the keywords "chimeric antigen receptor", "CAR-T", "liver cancer", "hepatocellular carcinoma", and "solid tumor". Additional articles were identified by manual search of references found in the primary articles. The data for clinical trials were collected by searching ClinicalTrials.gov.

RESULTS

The liver has a tolerogenic nature in the intrahepatic milieu and its tumor microenvironment significantly affects tumor progression. The obstacles that reduce the efficacy of CAR-T therapy in solid tumors include a lack of specific tumor antigens, limited trafficking and penetration of CAR-T cells to tumor sites, and an immunosuppressive tumor microenvironment. To overcome these obstacles, several strategies have emerged. In addition, several strategies have been developed to manage the side effects of CAR-T, including enhancing the selectivity of CARs and controlling CAR-T activity. To date, no clinical trials of CAR-T therapy against HCC have been completed. However, preclinical studies in vitro and in vivo have shown potent antitumor efficacy. Glypican-3, mucin-1, epithelial cell adhesion molecule, carcinoembryonic antigen, and other targets are currently being studied.

CONCLUSIONS

The application of CAR-T therapy for liver cancer is just beginning to be explored and more research is needed. However, we are optimistic that CAR-T therapy will offer a new approach for the treatment of liver cancers in the future.

Enhancing T cell therapy through TCR-signaling-responsive nanoparticle drug delivery

Adoptive cell therapy (ACT) with antigen-specific T cells has shown remarkable clinical success, but approaches to safely and effectively augment T cell function, especially in solid tumors, remain of great interest. Here we describe a strategy to “backpack” large quantities of supporting protein drugs on T cells using protein nanogels (NGs) that selectively release these cargos in response to T cell receptor (TCR) activation. We design cell surface-conjugated NGs that respond to an increase in T cell surface reduction potential upon antigen recognition, limiting drug release to sites of antigen encounter such as the tumor microenvironment. Using NGs carrying an IL-15 superagonist complex, we demonstrate that relative to systemic administration of free cytokines, NG delivery selectively expands T cells 16-fold in tumors, and allows at least 8-fold higher doses of cytokine to be administered without toxicity. The improved therapeutic window enables substantially increased tumor clearance by murine T cell and human CAR-T cell therapy in vivo.

Experimental Inhibition of Periostin Attenuates Kidney Fibrosis

BACKGROUND

Periostin is responsible for tissue regeneration, fibrosis, and wound healing via its interaction with integrin. Recently, the role of periostin has been shown to contribute to fibrosis in chronic kidney disease. We investigated the role of periostin and the effect of periostin blockade in renal fibrogenesis.

METHODS

We investigated the function of periostin in vivo in wild-type and periostin-null mice (Postn-KO) in a unilateral ureteral obstruction (UUO) model. For the in vitro experiments, primary cultured inner medullary collecting duct cells from the wild-type and Postn-KO mice were used.

RESULTS

Periostin expression was strongly induced by UUO in the wild-type mice. UUO induced renal fibrosis and morphological changes in the obstructed kidney of wild-type mice, whereas global knockout of periostin reduced fibrosis induced by UUO and improved kidney structure. Fibrosis- and inflammation-related mRNA were significantly induced in the wild-type mice and were decreased in the Postn-KO mice. Additionally, α-smooth muscle actin expression was increased following the administration of recombinant periostin in vitro. The effect of periostin blockade was examined using 2 methods. The integrin blockade peptide decreased fibrosis-related gene expression in in vitro experiments. Anti-periostin polyclonal antibody attenuated renal fibrosis induced by UUO through changes in transforming growth factor-β signaling and the inflammatory and apoptotic pathways.

CONCLUSION

Periostin is a marker of renal fibrosis and may augment the progression of fibrogenesis as an extracellular matrix protein. Periostin blockade effectively attenuated renal fibrogenesis. Thus, periostin inhibition may be a therapeutic strategy for the amelioration of renal disease progression.

Naive CD4+ T Cells Carrying a TLR2 Agonist Overcome TGF-β-Mediated Tumor Immune Evasion

TLR agonists are effective at treating superficial cancerous lesions, but their use internally for other types of tumors remains challenging because of toxicity. In this article, we report that murine and human naive CD4⁺ T cells that sequester Pam₃Cys₄ (CD4⁺ T^Pam3) become primed for T_h1 differentiation. CD4⁺ T^Pam3 cells encoding the OVA-specific TCR OT2, when transferred into mice bearing established TGF-β-OVA-expressing thymomas, produce high amounts of IFN-γ and sensitize tumors to PD-1/programmed cell death ligand 1 blockade-induced rejection. In contrast, naive OT2 cells without Pam₃Cys₄ cargo are prone to TGF-β-dependent inducible regulatory Foxp3⁺ CD4⁺ T cell conversion and accelerate tumor growth that is largely unaffected by PD-1/programmed cell death ligand 1 blockade. Ex vivo analysis reveals that CD4⁺ T^Pam3 cells are resistant to TGF-β-mediated gene expression through Akt activation controlled by inputs from the TCR and a TLR2-MyD88-dependent PI3K signaling pathway. These data show that CD4⁺ T^Pam3 cells are capable of T_h1 differentiation in the presence of TGF-β, suggesting a novel approach to adoptive cell therapy.

Targeting TGF-β Signaling for Therapeutic Gain

Transforming growth factor βs (TGF-βs) are closely related ligands that have pleiotropic activity on most cell types of the body. They act through common heterotetrameric TGF-β type II and type I transmembrane dual specificity kinase receptor complexes, and the outcome of signaling is context-dependent. In normal tissue, they serve a role in maintaining homeostasis. In many diseased states, particularly fibrosis and cancer, TGF-β ligands are overexpressed and the outcome of signaling is diverted toward disease progression. There has therefore been a concerted effort to develop drugs that block TGF-β signaling for therapeutic benefit. This review will cover the basics of TGF-β signaling and its biological activities relevant to oncology, present a summary of pharmacological TGF-β blockade strategies, and give an update on preclinical and clinical trials for TGF-β blockade in a variety of solid tumor types.

Targeting TGF-β Signaling for Therapeutic Gain

Transforming growth factor βs (TGF-βs) are closely related ligands that have pleiotropic activity on most cell types of the body. They act through common heterotetrameric TGF-β type II and type I transmembrane dual specificity kinase receptor complexes, and the outcome of signaling is context-dependent. In normal tissue, they serve a role in maintaining homeostasis. In many diseased states, particularly fibrosis and cancer, TGF-β ligands are overexpressed and the outcome of signaling is diverted toward disease progression. There has therefore been a concerted effort to develop drugs that block TGF-β signaling for therapeutic benefit. This review will cover the basics of TGF-β signaling and its biological activities relevant to oncology, present a summary of pharmacological TGF-β blockade strategies, and give an update on preclinical and clinical trials for TGF-β blockade in a variety of solid tumor types.

CAR T-cell therapy for lung cancer and malignant pleural mesothelioma

Immunotherapy is a promising field that harnesses the power of the immune system as a therapeutic agent for cancer treatment. Beneficial outcomes shown in patients with non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM) with relatively higher tumor-infiltrating T cells, combined with impressive responses obtained in a cohort of patients with NSCLC following checkpoint blockade therapy, lays a strong foundation to promote effector immune responses in these patients. One such approach being investigated is administration of tumor antigen-targeted T cells with transduction of a chimeric antigen receptor (CAR). CARs are synthetic receptors that enhance T-cell antitumor effector function and have gained momentum to investigate in solid tumors based on recent successes of clinical trials treating patients with B-cell hematologic malignancies. This review summarizes target antigens for CAR T-cell therapy that are being investigated in preclinical studies and clinical trials for both NSCLC and MPM patients. We discuss the rationale for combination immunotherapies for NSCLC and MPM patients. Additionally, we have highlighted the challenges and strategies for overcoming the obstacles facing translation of CAR T-cell therapy to solid tumors.

Chimeric-antigen receptor T (CAR-T) cell therapy for solid tumors: challenges and opportunities

Chimeric antigen receptor (CAR)-engineered T cells (CAR-T cells) have been shown to have unprecedented efficacy in B cell malignancies, most notably in B cell acute lymphoblastic leukemia (B-ALL) with up to a 90% complete remission rate using anti-CD19 CAR-T cells. However, CAR T-cell therapy for solid tumors currently is faced with numerous challenges such as physical barriers, the immunosuppressive tumor microenvironment and the specificity and safety. The clinical results in solid tumors have been much less encouraging, with multiple cases of toxicity and a lack of therapeutic response. In this review, we will discuss the current stats and challenges of CAR-T cell therapy for solid tumors, and propose possibl e solutions and future perspectives.

[Adoptive transfer of T lymphocytes]

Within a few years, the success of treatments based on the use of T-cells armed with a chimeric T-receptor for the CD19 molecule (CAR-T CD19) has revolutionized the perception of adoptive transfer approaches. The levels of responses observed in acute leukemias, of the order of 70-90 % are indeed unprecedented. The medical and financial enthusiasm aroused by these results has led to the current situation where more than 300 clinical trials are under way, against some thirty different antigens. This enthusiasm, well justified by the first successes, must however be tempered by the difficulties associated with the use of these cells. Indeed, the management of patients is made very complex both for medical reasons, because the toxicities associated with these treatments are important, and for technical reasons, because the preparation of T lymphocytes for therapeutic use requires dedicated structures. During this same period, knowledge of the mechanisms of regulation of T lymphocytes and the possibilities offered by synthetic biology and techniques of genome engineering have progressed considerably. Combined, they allow envisaging a true "programming" of the T lymphocytes, intended to improve the efficiency of the treatments and the safety of the patients. Medical and industrial perspectives and the role of these approaches in the arsenal of cancer therapies will depend largely on two conditions: the emergence of a robust demonstration of their effectiveness in solid tumors, and the establishment of an acceptable production and distribution model 1.

Platelets subvert T cell immunity against cancer via GARP-TGFβ axis

Cancer-associated thrombocytosis has long been linked to poor clinical outcome, but the underlying mechanism is enigmatic. We hypothesized that platelets promote malignancy and resistance to therapy by dampening host immunity. We show that genetic targeting of platelets enhances adoptive T cell therapy of cancer. An unbiased biochemical and structural biology approach established transforming growth factor β (TGFβ) and lactate as major platelet-derived soluble factors to obliterate CD4⁺ and CD8⁺ T cell functions. Moreover, we found that platelets are the dominant source of functional TGFβ systemically as well as in the tumor microenvironment through constitutive expression of the TGFβ-docking receptor glycoprotein A repetitions predominant (GARP) rather than secretion of TGFβ per se. Platelet-specific deletion of the GARP-encoding gene Lrrc32 blunted TGFβ activity at the tumor site and potentiated protective immunity against both melanoma and colon cancer. Last, this study shows that T cell therapy of cancer can be substantially improved by concurrent treatment with readily available antiplatelet agents. We conclude that platelets constrain T cell immunity through a GARP-TGFβ axis and suggest a combination of immunotherapy and platelet inhibitors as a therapeutic strategy against cancer.

CAR T Cell Therapy for Solid Tumors

The field of cancer immunotherapy has been re-energized by the application of chimeric antigen receptor (CAR) T cell therapy in cancers. These CAR T cells are engineered to express synthetic receptors that redirect polyclonal T cells to surface antigens for subsequent tumor elimination. Many CARs are designed with elements that augment T cell persistence and activity. To date, CAR T cells have demonstrated tremendous success in eradicating hematologic malignancies (e.g., CD19 CARs in leukemias). However, this success has yet to be extrapolated to solid tumors, and the reasons for this are being actively investigated. We characterize some of the challenges that CAR T cells have to surmount in the solid tumor microenvironment and new approaches that are being considered to overcome these hurdles.

Chimeric antigen receptor T-cell therapy for solid tumors

Chimeric antigen receptor (CAR) T cells are engineered constructs composed of synthetic receptors that direct T cells to surface antigens for subsequent elimination. Many CAR constructs are also manufactured with elements that augment T-cell persistence and activity. To date, CAR T cells have demonstrated tremendous success in eradicating hematological malignancies (e.g., CD19 CARs in leukemias). This success is not yet extrapolated to solid tumors, and the reasons for this are being actively investigated. Here in this mini-review, we discuss some of the key hurdles encountered by CAR T cells in the solid tumor microenvironment.

Enhanced NK cell adoptive antitumor effects against breast cancer in vitro via blockade of the transforming growth factor-β signaling pathway

Natural killer (NK) cells have great potential for improving cancer immunotherapy. Adoptive NK cell transfer, an adoptive immunotherapy, represents a promising nontoxic anticancer therapy. However, existing data indicate that tumor cells can effectively escape NK cell-mediated apoptosis through immunosuppressive effects in the tumor microenvironment, and the therapeutic activity of adoptive NK cell transfer is not as efficient as anticipated. Transforming growth factor-beta (TGF-β) is a potent immunosuppressant. Genetic and epigenetic events that occur during mammary tumorigenesis circumvent the tumor-suppressing activity of TGF-β, thereby permitting late-stage breast cancer cells to acquire an invasive and metastatic phenotype in response to TGF-β. To block the TGF-β signaling pathway, NK cells were genetically modified with a dominant-negative TGF-β type II receptor by optimizing electroporation using the Amaxa Nucleofector system. These genetically modified NK cells were insensitive to TGF-β and resisted the suppressive effect of TGF-β on MCF-7 breast cancer cells in vitro. Our results demonstrate that blocking the TGF-β signaling pathway to modulate the tumor microenvironment can improve the antitumor activity of adoptive NK cells in vitro, thereby providing a new rationale for the treatment of breast cancer.

Enhancing the efficacy of adoptive cellular therapy by targeting tumor-induced immunosuppression

Strategies aimed at stimulating the immune system against cancer have signaled a new era for designing new effective therapies for patients. Recent breakthroughs in adoptive cellular therapy and in using checkpoint inhibitors for some patients have renewed much enthusiasm in this field. However, it has become apparent that tumors can use a multitude of inhibitory networks to effectively reduce antitumor immunity. This review discusses our current knowledge of these immune suppressive mechanisms used by tumors and describes potential new strategies that may counteract this problem resulting in significantly increasing therapeutic outcomes of adoptive immunotherapy in a higher proportion of patients.

The role of the immune system in non-small cell lung carcinoma and potential for therapeutic intervention

Over a hundred years after the first description of this disease, lung cancer represents one of the major challenges in oncology. Radical treatment cannot be introduced in more than 70% of cases and overall survival rate does not exceed 15%. The immunosurveillance of lung cancer may be effective in early oncogenesis but is inhibited in the course of developing a clinically detectable tumor. Very low and heterogonous antigenicity of lung cancer cells leads to passive escape from anti-cancer immune defense. The cytotoxic lymphocytes (CTLs) that play a main role in the anticancer response are actively suppressed in the tumor environment and following regulatory mechanisms inhibit the recognition of tumor antigens by antigen presenting cells. The population of regulatory T cells (Tregs) is augmented and the expression of transcription factor-Foxp3 is markedly increased on tumor cells and tumor infiltrating lymphocytes (TIL). It is accomplished by M2 macrophage polarization, the activity of myeloid derived suppressor cells (MDSCs) and a significantly elevated concentration of cytokines: transforming growth factor beta (TGFβ) and IL-10 in the tumor microenvironment. Very active suppression of immune protection is the predominant role of the programmed death 1 (PD-1)-PD-L1 pathway. The blockage of this pathway was found to be an effective treatment approach; therefore the monoclonal antibodies are being intensively investigated in lung cancer patients. Cytotoxic T lymphocyte antigen-4 (CTLA-4) is the molecule capable of inhibiting the activation signal. The antibody anti-CTLA-4 improves CTLs function in solid tumors and lung cancer patients may benefit from use of this agent. The second way in lung cancer immunotherapy is production of anti-cancer vaccines using recognized cancer antigens: MAGE-A3, membrane associated glycoprotein (MUC-1), and EGF. It was recently shown in ongoing clinical trials that combined therapies: immune- and chemotherapy, radiotherapy or targeted therapy seem to be effective. Immunotherapy in lung cancer has an individual character-there is a need to assess the patient's immune status prior to implementation of immunomodulating therapy.

STAT3 Signaling Is Required for Optimal Regression of Large Established Tumors in Mice Treated with Anti-OX40 and TGFβ Receptor Blockade

In preclinical tumor models, αOX40 therapy is often successful at treating small tumors, but is less effective once the tumors become large. For a tumor immunotherapy to be successful to cure large tumors, it will most likely require not only an agonist to boost effector T-cell function but also inhibitors of T-cell suppression. In this study, we show that combining αOX40 antibodies with an inhibitor of the TGFβ receptor (SM16) synergizes to elicit complete regression of large established MCA205 and CT26 tumors. Evaluation of tumor-infiltrating T cells showed that SM16/αOX40 dual therapy resulted in an increase in proliferating granzyme B(+) CD8 T cells, which produced higher levels of IFNγ, compared with treatment with either agent alone. We also found that the dual treatment increased pSTAT3 expression in both CD4 and CD8 T cells isolated from tumors. Because others have published that STAT3 signaling is detrimental to T-cell function within the tumor microenvironment, we explored whether deletion of STAT3 in OX40-expressing cells would affect this potent combination therapy. Surprisingly, we found that deletion of STAT3 in OX40-expressing cells decreased the efficacy of this combination therapy, showing that the full therapeutic potential of this treatment depends on STAT3 signaling, most likely in the T cells of tumor-bearing mice.

TGFβ and IL10 have an impact on risk group and prognosis in childhood ALL

BACKGROUND

Cytokines and their genes have been described to have an influence on incidence and prognosis in malignant, infectious and autoimmune disease. We previously described the impact of cytokine production on prognosis in paediatric standard-risk acute lymphoblastic leukaemia (ALL).

PROCEDURE

In this study, we investigated the influence of cytokine gene polymorphisms (TNFα, TGFβ, IL10 and IFNγ) on frequency, risk group and prognosis in 95 paediatric ALL-patients. We further report on intracellular production of these cytokines in T-cells.

RESULTS

IL10 high-producer-haplotypes were reduced in ALL-patients compared with healthy controls and resulted in a reduced relapse rate compared with low-producer haplotypes. TGFβ high-producer-haplotypes were correlated with a high initial blast-count (codon 25: G/G) and were elevated in high-risk ALL-patients (codon 10: T/T). IL10 was positively and IFNγ-production was negatively correlated with initial blast-count. At diagnosis the expression of TNFα and IFNγ was reduced in patients compared with healthy controls. This was more pronounced in high-risk and in T-ALL-patients.

CONCLUSION

We conclude that gene-polymorphisms of the regulatory/anti-inflammatory cytokines, TGFβ and IL10, but not of the pro-inflammatory cytokines, IFNγ and TNFα, have an impact on prognosis and risk-group of ALL. However, the reduced capacity to produce pro-inflammatory cytokines at diagnosis may serve as another important, functional risk factor. These data may help in further risk stratification and adaptation of therapy-intensity in paediatric patients with ALL.

A new hope in immunotherapy for malignant gliomas: adoptive T cell transfer therapy

Immunotherapy emerged as a promising therapeutic approach to highly incurable malignant gliomas due to tumor-specific cytotoxicity, minimal side effect, and a durable antitumor effect by memory T cells. But, antitumor activities of endogenously activated T cells induced by immunotherapy such as vaccination are not sufficient to control tumors because tumor-specific antigens may be self-antigens and tumors have immune evasion mechanisms to avoid immune surveillance system of host. Although recent clinical results from vaccine strategy for malignant gliomas are encouraging, these trials have some limitations, particularly their failure to expand tumor antigen-specific T cells reproducibly and effectively. An alternative strategy to overcome these limitations is adoptive T cell transfer therapy, in which tumor-specific T cells are expanded ex vivo rapidly and then transferred to patients. Moreover, enhanced biologic functions of T cells generated by genetic engineering and modified immunosuppressive microenvironment of host by homeostatic T cell expansion and/or elimination of immunosuppressive cells and molecules can induce more potent antitumor T cell responses and make this strategy hold promise in promoting a patient response for malignant glioma treatment. Here we will review the past and current progresses and discuss a new hope in adoptive T cell therapy for malignant gliomas.

Immunological effects of the TGFβ-blocking antibody GC1008 in malignant pleural mesothelioma patients

We evaluated a neutralizing anti-TGFβ antibody (GC1008) in cancer patients with malignant pleura mesothelioma (MPM). The goal of this study was to assess immunoregulatory effects in relation to clinical safety and clinical response. Patients with progressive MPM and 1-2 prior systemic therapies received GC1008 at 3mg/kg IV over 90 min every 21 d as part of an open-label, two-center Phase II trial. Following TGFβ blockade therapy, clinical safety and patient survival were monitored along with the effects of anti-TGFβ antibodies on serum biomarkers and peripheral blood mononuclear cells (PBMC). Although designed as a larger trial, only 13 patients were enrolled when the manufacturer discontinued further development of the antibody for oncology indications. All participants tolerated therapy. Although partial or complete radiographic responses were not observed, three patients showed stable disease at 3 mo. GC1008 had no effect in the expression of NK, CD4+, or CD8+ T cell activating and inhibitory markers, other than a decrease in the expression of 2B4 and DNAM-1 on NK cells. However, serum from 5 patients showed new or enhanced levels of antibodies against MPM tumor lysates as measured by immunoblotting. Patients who produced anti-tumor antibodies had increased median overall survival (OS) (15 vs 7.5 mo, p < 0.03) compared with those who did not. To our knowledge, these data represent the first immune analysis of TGFβ- blockade in human cancer patients.

Blocking transforming growth factor-β signaling pathway augments antitumor effect of adoptive NK-92 cell therapy

Natural killer (NK) cells hold great potential for improving the immunotherapy of cancer. However, existing data indicate that tumor cells can effectively escape NK cell-mediated apoptosis through immunosuppressive effect in the tumor microenvironment. Transforming growth factor-β (TGF-β) is a potent immunosuppressant. The present study was intended to develop a treatment strategy through adoptive transfer of TGF-β insensitive NK-92 cells. To block TGF-β signaling pathway, NK-92 cells were genetically modified with dominant negative TGF-β type II receptor (DNTβRII) by optimizing electroporation using the Amaxa Nucleofector system. These genetically modified NK-92 cells were insensitive to TGF-β and able to resist the suppressive effect of TGF-β on Calu-6 lung cancer cells in vitro. To determine the antitumor activity in vivo, recipient mice were challenged with a single subcutaneous injection of Calu-6 cells. Adoptive transfer of TGF-β insensitive NK-92 cells decreased tumor proliferation, reduced lung metastasis, produced more IFN-γ, and increased the survival rate of nude mice bearing established Calu-6 cells. Hence, we have demonstrated that blocking transforming growth factor-β signaling pathway in NK cells provides a novel therapeutic strategy and warrants further investigation.

TGF-β signalling and its role in cancer progression and metastasis

The transforming growth factor-β (TGF-β) system signals via protein kinase receptors and SMAD mediators to regulate a large number of biological processes. Alterations of the TGF-β signalling pathway are implicated in human cancer. Prior to tumour initiation and early during progression, TGF-β acts as a tumour suppressor; however, at later stages, it is often a tumour promoter. Knowledge about the mechanisms involved in TGF-β signal transduction has allowed a better understanding of cancer progression, invasion, metastasis and epithelial-to-mesenchymal transition. Furthermore, several molecular targets with great potential in therapeutic interventions have been identified. This review discusses the TGF-β signalling pathway, its involvement in cancer and current therapeutic approaches.

Using macrophage activation to augment immunotherapy of established tumours

Background:

Successful immunotherapy will require alteration of the tumour microenvironment and/or decreased immune suppression. Tumour-associated macrophages (TAMs) are one major factor affecting tumour microenvironment. We hypothesised that altering TAM phenotype would augment the efficacy of immunotherapy.

Methods:

We and others have reported that 5,6-Dimethylxanthenone-4-acetic-acid (DMXAA, Vadimezan) has the ability to change TAM phenotypes, inducing a tumour microenvironment conducive to antitumour immune responses. We therefore combined DMXAA with active immunotherapies, and evaluated anti-tumour efficacy, immune cell phenotypes (flow cytometry), and tumour microenvironment (RT–PCR).

Results:

In several different murine models of immunotherapy for lung cancer, DMXAA-induced macrophage activation significantly augmented the therapeutic effects of immunotherapy. By increasing influx of neutrophils and anti-tumour (M1) macrophages to the tumour, DMXAA altered myeloid cell phenotypes, thus changing the intratumoural M2/non-M2 TAM immunoinhibitory ratio. It also altered the tumour microenvironment to be more pro-inflammatory. Modulating macrophages during immunotherapy resulted in increased numbers, activity, and antigen-specificity of intratumoural CD8⁺ T cells. Macrophage depletion reduced the effect of combining immunotherapy with macrophage activation, supporting the importance of TAMs in the combined effect.

Conclusion:

Modulating intratumoural macrophages dramatically augmented the effect of immunotherapy. Our observations suggest that addition of agents that activate TAMs to immunotherapy should be considered in future trials.

Induction of apoptosis-resistant and TGF-β-insensitive murine CD8(+) cytotoxic T lymphocytes specific for HIV-1 gp160

Although TGF-β and IL-6 would turn CD8(+) T cells to differentiate into non-cytotoxic state, these treated cells were converted to cytolytic phenotypes after re-exposure to their antigenic epitope in vitro. Here, using spleen cells from TCR transgenic mice expressing TCRαβ genes of clone RT1 recognizing an epitope peptide (P18-I10: RGPGRAFVTI) of HIV-1 gp160, we generated CD8(+) cytotoxic T lymphocytes (CTLs) activated by re-exposure to P18-I10 after primarily cultured with TGF-β and IL-6 in vitro to examine their effector function. The CTLs, having strong cytotoxic activity in vitro, were not only resistant to Fas-FasL mediated apoptosis, but also insensitive to the suppression of their cytotoxicity by re-exposure to TGF-β in vitro. Moreover, adoptive transfer experiments indicated that the CTLs are capable of eliminating recombinant vaccinia virus expressing HIV-1 gp160 in vivo. Taken together, our data suggest that TGF-β and IL-6 may play pivotal roles in inducing apoptosis-resistant and TGF-β-insensitive CTLs in vitro.