Gene silencing of TGF-β1 enhances antitumor immunity induced with a dendritic cell vaccine by reducing tumor-associated regulatory T cells

Impaired function of dendritic cells within the tumor microenvironment

Dendritic cells (DCs), a class of professional antigen-presenting cells, are considered key factors in the initiation and maintenance of anti-tumor immunity due to their powerful ability to present antigen and stimulate T-cell responses. The important role of DCs in controlling tumor growth and mediating potent anti-tumor immunity has been demonstrated in various cancer models. Accordingly, the infiltration of stimulatory DCs positively correlates with the prognosis and response to immunotherapy in a variety of solid tumors. However, accumulating evidence indicates that DCs exhibit a significantly dysfunctional state, ultimately leading to an impaired anti-tumor immune response due to the effects of the immunosuppressive tumor microenvironment (TME). Currently, numerous preclinical and clinical studies are exploring immunotherapeutic strategies to better control tumors by restoring or enhancing the activity of DCs in tumors, such as the popular DC-based vaccines. In this review, an overview of the role of DCs in controlling tumor progression is provided, followed by a summary of the current advances in understanding the mechanisms by which the TME affects the normal function of DCs, and concluding with a brief discussion of current strategies for DC-based tumor immunotherapy.

Application of lipid-based nanoparticles in cancer immunotherapy

Immunotherapy is revolutionizing the clinical management of patients with different cancer types by sensitizing autologous or allogenic immune cells to the tumor microenvironment which eventually leads to tumor cell lysis without rapidly killing normal cells. Although immunotherapy has been widely demonstrated to be superior to chemotherapies, only a few populations of patients with specific cancer types respond to such treatment due to the failure of systemic immune activation. In addition, severe immune-related adverse events are rapidly observed when patients with very few responses are given higher doses of such therapies. Recent advances of lipid-based nanoparticles (NPs) development have made it possible to deliver not only small molecules but also mRNAs to achieve systemic anticancer immunity through cytotoxic immune cell activation, checkpoint blockade, and chimeric antigen receptor cell therapies, etc. This review summarized recent development and applications of LNPs in anticancer immunotherapy. The diversity of lipid-based NPs would encapsulate payloads with different structures and molecular weights to achieve optimal antitumor immunity through multiple mechanisms of action. The discussion about the components of lipid-based NPs and their immunologic payloads in this review hopefully shed more light on the future direction of anticancer immunotherapy.

Sp1 induced gene TIMP1 is related to immune cell infiltration in glioblastoma

Tumor immune microenvironment exerts a profound effect on the population of infiltrating immune cells. Tissue inhibitor of matrix metalloproteinase 1 (TIMP1) is frequently overexpressed in a variety of cells, particularly during inflammation and tissue injury. However, its function in cancer and immunity remains enigmatic. In this study, we find that TIMP1 is substantially up-regulated during tumorigenesis through analyzing cancer bioinformatics databases, which is further confirmed by IHC tissue microarrays of clinical samples. The TIMP1 level is significantly increased in lymphocytes infiltrating the tumors and correlated with cancer progression, particularly in GBM. Notably, we find that the transcriptional factor Sp1 binds to the promoter of TIMP1 and triggers its expression in GBM. Together, our findings suggest that the Sp1-TIMP1 axis can be a potent biomarker for evaluating immune cell infiltration at the tumor sites and therefore, the malignant progression of GBM.

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.

RNA-mediated immunotherapy regulating tumor immune microenvironment: next wave of cancer therapeutics

Accumulating research suggests that the tumor immune microenvironment (TIME) plays an essential role in regulation of tumor growth and metastasis. The cellular and molecular nature of the TIME influences cancer progression and metastasis by altering the ratio of immune- suppressive versus cytotoxic responses in the vicinity of the tumor. Targeting or activating the TIME components show a promising therapeutic avenue to combat cancer. The success of immunotherapy is both astounding and unsatisfactory in the clinic. Advancements in RNA-based technology have improved understanding of the complexity and diversity of the TIME and its effects on therapy. TIME-related RNA or RNA regulators could be promising targets for anticancer immunotherapy. In this review, we discuss the available RNA-based cancer immunotherapies targeting the TIME. More importantly, we summarize the potential of various RNA-based therapeutics clinically available for cancer treatment. RNA-dependent targeting of the TIME, as monotherapy or combined with other evolving therapeutics, might be beneficial for cancer patients’ treatment in the near future.

Overcoming TGFβ-mediated immune evasion in cancer

Transforming growth factor-β (TGFβ) signalling controls multiple cell fate decisions during development and tissue homeostasis; hence, dysregulation of this pathway can drive several diseases, including cancer. Here we discuss the influence that TGFβ exerts on the composition and behaviour of different cell populations present in the tumour immune microenvironment, and the context-dependent functions of this cytokine in suppressing or promoting cancer. During homeostasis, TGFβ controls inflammatory responses triggered by exposure to the outside milieu in barrier tissues. Lack of TGFβ exacerbates inflammation, leading to tissue damage and cellular transformation. In contrast, as tumours progress, they leverage TGFβ to drive an unrestrained wound-healing programme in cancer-associated fibroblasts, as well as to suppress the adaptive immune system and the innate immune system. In consonance with this key role in reprogramming the tumour microenvironment, emerging data demonstrate that TGFβ-inhibitory therapies can restore cancer immunity. Indeed, this approach can synergize with other immunotherapies - including immune checkpoint blockade - to unleash robust antitumour immune responses in preclinical cancer models. Despite initial challenges in clinical translation, these findings have sparked the development of multiple therapeutic strategies that inhibit the TGFβ pathway, many of which are currently in clinical evaluation.

Advances in siRNA delivery strategies for the treatment of MDR cancer

RNA interference (RNAi) represents a promising therapeutic method that uses siRNA for cancer treatment. Although the RNAi technique has been increasingly used for clinical trials, systemic siRNA delivery into targeted cells is still challenging. The barriers impeding siRNA therapeutics delivery and impacting the treatment outcome must overcome with negligible systemic toxicity for a desirable and successful delivery of siRNA to MDR cancer cells. Nano delivery strategies have been investigated for nanocarrier functionalization, cancer immunotherapy and cancer targeting. Lipid nanoparticles (LNPs), dynamic polyconjugates (DPC™), GalNAc-siRNA conjugates, exosome and RBC systems have shown potential for efficient delivery of siRNA to cancer cells. Delivery of siRNA to tumor cells, immune cells to regulate T cell functions for immunotherapy are promising approaches.

TGFβ1 neutralization displays therapeutic efficacy through both an immunomodulatory and a non-immune tumor-intrinsic mechanism

BACKGROUND

Transforming growth factor-β (TGFβ) is emerging as a promising target for cancer therapy, given its ability to promote progression of advanced tumors and to suppress anti-tumor immune responses. However, TGFβ also plays multiple roles in normal tissues, particularly during organogenesis, raising toxicity concerns about TGFβ blockade. Dose-limiting cardiovascular toxicity was observed, possibly due to the blockade of all three TGFβ isoforms. The dominant isoform in tumors is TGFβ1, while TGFβ2 and TGFβ3 seem to be more involved in cardiovascular development. Recent data indicated that selective targeting of TGFβ1 promoted the efficacy of checkpoint inhibitor anti-PD1 in transplanted preclinical tumor models, without cardiovascular toxicity.

METHODS

To further explore the therapeutic potential of isoform-specific TGFβ blockade, we developed neutralizing mAbs targeting mature TGFβ1 or TGFβ3, and tested them, in parallel with anti-panTGFβ mAb 1D11, in two preclinical models: the transplanted colon cancer model CT26, and the autochthonous melanoma model TiRP.

RESULTS

We observed that the blockade of TGFβ1, but not that of TGFβ3, increased the efficacy of a prophylactic cellular vaccine against colon cancer CT26. This effect was similar to pan-TGFβ blockade, and was associated with increased infiltration of activated CD8 T cells in the tumor, and reduced levels of regulatory T cells and myeloid-derived suppressor cells. In contrast, in the autochthonous TiRP melanoma model, we observed therapeutic efficacy of the TGFβ1-specific mAb as a single agent, while the TGFβ3 mAb was inactive. In this model, the anti-tumor effect of TGFβ1 blockade was tumor intrinsic rather than immune mediated, as it was also observed in T-cell depleted mice. Mechanistically, TGFβ1 blockade increased mouse survival by delaying the phenotype switch, akin to epithelial-to-mesenchymal transition (EMT), which transforms initially pigmented tumors into highly aggressive unpigmented tumors.

CONCLUSIONS

Our results confirm TGFβ1 as the relevant isoform to target for cancer therapy, not only in combination with checkpoint inhibitors, but also with other immunotherapies such as cancer vaccines. Moreover, TGFβ1 blockade can also act as a monotherapy, through a tumor-intrinsic effect blocking the EMT-like transition. Because human melanomas that resist therapy often express a gene signature that links TGFβ1 with EMT-related genes, these results support the clinical development of TGFβ1-specific mAbs in melanoma.

Cyano Enone-Bearing Triterpenoid Soloxolone Methyl Inhibits Epithelial-Mesenchymal Transition of Human Lung Adenocarcinoma Cells In Vitro and Metastasis of Murine Melanoma In Vivo

Introduction of α-cyano α,β-unsaturated carbonyl moiety into natural cyclic compounds markedly improves their bioactivities, including inhibitory potential against tumor growth and metastasis. Previously, we showed that cyano enone-bearing derivatives of 18βH-glycyrrhetinic (GA) and deoxycholic acids displayed marked cytotoxicity in different tumor cell lines. Moreover, GA derivative soloxolone methyl (SM) was found to induce ER stress and apoptosis in tumor cells in vitro and inhibit growth of carcinoma Krebs-2 in vivo. In this work, we studied the effects of these compounds used in non-toxic dosage on the processes associated with metastatic potential of tumor cells. Performed screening revealed SM as a hit compound, which inhibits motility of murine melanoma B16 and human lung adenocarcinoma A549 cells and significantly suppresses colony formation of A549 cells. Further study showed that SM effectively blocked transforming growth factor β (TGF-β)-induced epithelial-mesenchymal transition (EMT) of A549 cells: namely, inhibited TGF-β-stimulated motility and invasion of tumor cells as well as loss of their epithelial characteristics, such as, an acquisition of spindle-like phenotype, up- and down-regulation of mesenchymal (vimentin, fibronectin) and epithelial (E-cadherin, zona occludens-1 (ZO-1)) markers, respectively. Network pharmacology analysis with subsequent verification by molecular modeling revealed that matrix metalloproteinases MMP-2/-9 and c-Jun N-terminal protein kinase 1 (JNK1) can be considered as hypothetical primary targets of SM, mediating its marked anti-EMT activity. The inhibitory effect of SM on EMT revealed in vitro was further confirmed in a metastatic model of murine B16 melanoma: SM was found to effectively block metastatic dissemination of melanoma B16 cells in vivo, increase expression of E-cadherin and suppress expression of MMP-9 in lung metastatic foci. Altogether, our data provided valuable information for a better understanding of the antitumor activity of cyano enone-bearing semisynthetic compounds and revealed SM as a promising anti-metastatic drug candidate.

Nucleic Acid-Based Approaches for Tumor Therapy

Within the last decade, the introduction of checkpoint inhibitors proposed to boost the patients' anti-tumor immune response has proven the efficacy of immunotherapeutic approaches for tumor therapy. Furthermore, especially in the context of the development of biocompatible, cell type targeting nano-carriers, nucleic acid-based drugs aimed to initiate and to enhance anti-tumor responses have come of age. This review intends to provide a comprehensive overview of the current state of the therapeutic use of nucleic acids for cancer treatment on various levels, comprising (i) mRNA and DNA-based vaccines to be expressed by antigen presenting cells evoking sustained anti-tumor T cell responses, (ii) molecular adjuvants, (iii) strategies to inhibit/reprogram tumor-induced regulatory immune cells e.g., by RNA interference (RNAi), (iv) genetically tailored T cells and natural killer cells to directly recognize tumor antigens, and (v) killing of tumor cells, and reprograming of constituents of the tumor microenvironment by gene transfer and RNAi. Aside from further improvements of individual nucleic acid-based drugs, the major perspective for successful cancer therapy will be combination treatments employing conventional regimens as well as immunotherapeutics like checkpoint inhibitors and nucleic acid-based drugs, each acting on several levels to adequately counter-act tumor immune evasion.

The influences of TGF-β1 upon the human adenocarcinoma cell of lung A549 and cellular immunity

Background

The cellular immunity of lung cancer patients is mainly the immune response of T cells, which plays an important role in tumour cell killing and immune surveillance. Transforming growth factor 1 (TGF-β1) is secreted by tumour cells that can suppress the immune response and is an important group of immune down-regulation factors. Our study aims to investigate the effect of TGF-β1 on the morphology and cellular immune function of A549 and peripheral blood mononuclear cells (PBMCs).

Methods

A549 cell line was cultured, PBMCs were cultured with different concentrations of TGF-β1, and the morphology of A549 cells and PBMCs were seen. The levels of interleukin (IL)-2, IL-4, IL-6, IL-10, IFN-γ, and TNF and the numbers of CD3, CD4, CD8, CD4/CD8, and CD3 CD25 and CD4 CD25 in PBMCs were detected.

Results

During co-culture of A549 with PBMCs, TGF-β1 can induced A549 showing epithelial-to-mesenchymal transition, enhanced its ability of migration and infiltration. Simultaneously, TGF-β1 can depressing the growth and proliferation of PBMCs, inhibiting T-cell activation, and accelerating the PBMCs apoptosis. TGF-β1 can inhibits A549 Th1 related-cytokines, enhance Th2 related-cytokines, cause the disorder of Th1/Th2, resulting in the Th1 cellular dominate immunity decline.

Conclusions

TGF-β1 may affect the secretion of related cytokines, hinder the activation of T lymphocytes, destroy the immune surveillance and killing effect of the body, and thus inhibit the cellular immunity.

Upregulation of OSBPL3 by HIF1A promotes colorectal cancer progression through activation of RAS signaling pathway

Oxysterol-binding protein like protein 3 (OSBPL3) has been shown involving in the development of several human cancers. However, the relationship between OSBPL3 and colorectal cancer (CRC), particularly the role of OSBPL3 in the proliferation, invasion and metastasis of CRC remains unclear. In this study, we investigated the role of OSBPL3 in CRC and found that its expression was significantly higher in CRC tissues than that in normal tissues. In addition, high expression of OSBPL3 was closely related to poor differentiation, advanced TNM stage and poor prognosis of CRC. Further experiments showed that over-expression of OSBPL3 promoted the proliferation, invasion and metastasis of CRC in vitro and in vivo models. Moreover, we revealed that OSBPL3 promoted CRC progression through activation of RAS signaling pathway. Furthermore, we demonstrated that hypoxia induced factor 1 (HIF-1A) can regulate the expression of OSBPL3 via binding to the hypoxia response element (HRE) in the promoter of OSBPL3. In summary, Upregulation of OSBPL3 by HIF1A promotes colorectal cancer progression through activation of RAS signaling pathway. This novel mechanism provides a comprehensive understanding of both OSBPL3 and the RAS signaling pathway in the progression of CRC and indicates that the HIF1A–OSBPL3–RAS axis is a potential target for early therapeutic intervention in CRC progression.

RNA Nanotechnology-Mediated Cancer Immunotherapy

RNA molecules (e.g., siRNA, microRNA, and mRNA) have shown tremendous potential for immunomodulation and cancer immunotherapy. They can activate both innate and adaptive immune system responses by silencing or upregulating immune-relevant genes. In addition, mRNA-based vaccines have recently been actively pursued and tested in cancer patients, as a form of treatment. Meanwhile, various nanomaterials have been developed to enhance RNA delivery to the tumor and immune cells. In this review article, we summarize recent advances in the development of RNA-based therapeutics and their applications in cancer immunotherapy. We also highlight the variety of nanoparticle platforms that have been used for RNA delivery to elicit anti-tumor immune responses. Finally, we provide our perspectives of potential challenges and opportunities of RNA-based nanotherapeutics in clinical translation towards cancer immunotherapy.

Corticosteroid inhibits differentiation of palmar fibromatosis-derived stem cells (FSCs) through downregulation of transforming growth factor-β1 (TGF-β1)

Treatment for musculoskeletal fibromatosis remains challenging. Surgical excision for fibromatosis is the standard therapy but recurrence remains high. Corticosteroids, an anti-fibrogenic compound, have been used to treat early stage palmar fibromatosis, but the mechanism is unknown. We investigated the inhibitory mechanism effect of corticosteroids in the murine model of fibromatosis nodule as well as in cultured FSCs. Quantitative reverse transcription/polymerase chain reaction (PCR) analysis and immunofluorescence (IF) staining for markers of myofibroblasts (α-smooth muscle actin and type III collagen) were used to examine the effect of dexamethasone on myofibroblasic differentiation of FSCs both in vitro and in vivo. Transforming growth factor-β1 (TGF-β1) signaling and its downstream targets were examined using western blot analysis. TGF-β1 expression in FSCs before and after dexamethasone treatment was compared. In addition, inhibition of TGF-β1 expression was examined using RNA interference (RNAi) on FSCs, both in vitro and in vivo. Treating FSCs with dexamethasone inhibited FSCs’ myofibroblastic differentiation in vitro. Treating FSCs with dexamethasone before or after implantation further inhibited formation of fibromatosis nodules. Dexamethasone suppressed expression of TGF-β1 and pSmad2/3 by FSCs in vitro. TGF-β1 knockdown FSCs showed reducing myofibroblastic differentiation both in vitro and in vivo. Finally, addition of TGF-β1 abolished dexamethasone-mediated inhibition of myofibroblastic differentiation. Dexamethasone inhibits the myofibroblastic differentiated potential of FSCs both in vitro and in vivo through inhibition of TGF-β1 expression in FSCs. TGF-β1 plays a key role in myofibroblastic differentiation.

Strategies to Improve the Efficacy of Dendritic Cell-Based Immunotherapy for Melanoma

Melanoma is a highly aggressive form of skin cancer that frequently metastasizes to vital organs, where it is often difficult to treat with traditional therapies such as surgery and radiation. In such cases of metastatic disease, immunotherapy has emerged in recent years as an exciting treatment option for melanoma patients. Despite unprecedented successes with immune therapy in the clinic, many patients still experience disease relapse, and others fail to respond at all, thus highlighting the need to better understand factors that influence the efficacy of antitumor immune responses. At the heart of antitumor immunity are dendritic cells (DCs), an innate population of cells that function as critical regulators of immune tolerance and activation. As such, DCs have the potential to serve as important targets and delivery agents of cancer immunotherapies. Even immunotherapies that do not directly target or employ DCs, such as checkpoint blockade therapy and adoptive cell transfer therapy, are likely to rely on DCs that shape the quality of therapy-associated antitumor immunity. Therefore, understanding factors that regulate the function of tumor-associated DCs is critical for optimizing both current and future immunotherapeutic strategies for treating melanoma. To this end, this review focuses on advances in our understanding of DC function in the context of melanoma, with particular emphasis on (1) the role of immunogenic cell death in eliciting tumor-associated DC activation, (2) immunosuppression of DC function by melanoma-associated factors in the tumor microenvironment, (3) metabolic constraints on the activation of tumor-associated DCs, and (4) the role of the microbiome in shaping the immunogenicity of DCs and the overall quality of anti-melanoma immune responses they mediate. Additionally, this review highlights novel DC-based immunotherapies for melanoma that are emerging from recent progress in each of these areas of investigation, and it discusses current issues and questions that will need to be addressed in future studies aimed at optimizing the function of melanoma-associated DCs and the antitumor immune responses they direct against this cancer.

TGF-β1-silenced leukemia cell-derived exosomes target dendritic cells to induce potent anti-leukemic immunity in a mouse model

Tumor-derived exosomes (TEX) can induce a specific antitumor immune response and have been developed as a promising tumor vaccine. Despite promising preclinical data, TEX exhibit relatively low efficacy and limited clinical benefit in clinical trials. In the present study, we investigated whether exosomes from the TGF-β1 silenced L1210 cells (LEXTGF-β1si) can enhance the efficacy of DC-based vaccines. We silenced TGF-β1 in L1210 cells with a lentiviral shRNA vector and prepared the LEXTGF-β1si. It was shown that LEXTGF-β1si can significantly decrease TGF-β1 expression of dendritic cells (DC) and effectively promote their maturation and immune function. In addition, DC pulsed with LEXTGF-β1si (DCLEX-TGF-β1si) more effectively promoted CD4+ T cell proliferation in vitro and Th1 cytokine secretion and induced tumor-specific CTL response. This response was higher in potency compared to that noted by the other two formulations. Moreover, DCLEX-TGF-β1si inhibited tumor growth more efficiently than other formulations did as the preventive or therapeutic tumor vaccine. Accordingly, these findings revealed that DCLEX-TGF-β1si induced a more potent antigen-specific anti-leukemic immunity than DC pulsed with exosomes from non-manipulated L1210 cells. This indicated that the targeting of DC by LEXTGF-β1si may be used as a promising approach for leukemia immunotherapy.

Intratumoral Lentivector-Mediated TGF-β1 Gene Downregulation As a Potent Strategy for Enhancing the Antitumor Effect of Therapy Composed of Cyclophosphamide and Dendritic Cells

Vaccination with dendritic cells (DCs) stimulated with tumor antigens can induce specific cellular immune response that recognizes a high spectrum of tumor antigens. However, the ability of cancer cells to produce immunosuppressive factors drastically decreases the antitumor activity of DCs. The main purpose of the study was to improve the effectiveness of DC-based immunotherapy or chemoimmunotherapy composed of cyclophosphamide (CY) and DCs by application of lentivectors (LVs)-encoding short hairpin RNA specific for TGF-β1 (shTGFβ1 LVs). We observed that s.c. inoculation of both MC38 cells with silenced expression of TGF-β1 (MC38/shTGF-β1) and direct intratumoral application of shTGFβ1 LVs contributed to reduction of suppressor activity of myeloid cells and Tregs in tumor. Contrary to expectations, in mice bearing wild tumor, the application of shTGFβ1 LVs prior to vaccination with bone marrow-derived DC stimulated with tumor antigens (BMDC/TAg) did not influence myeloid-derived suppressor cell (MDSC) infiltration into tumor. As a result, we observed only minor MC38 tumor growth inhibition (TGI) accompanied by systemic antitumor response activation comparable to that obtained for negative control (shN). However, when the proposed scheme was complemented by pretreatment with a low dose of CY, we noticed high MC38 TGI together with decreased number of MDSCs in tumor and induction of Th1-type response. Moreover, in both schemes of treatment, LVs (shTGFβ1 as well as shN) induced high influx of CTLs into tumor associated probably with the viral antigen introduction into tumor microenvironment. Concluding, the application of shTGFβ1 LVs alone or in combination with DC-based vaccines is not sufficient for long-lasting elimination of suppression in tumor. However, simultaneous reduction of TGF-β1 in tumor microenvironment and its remodeling by pretreatment with a low dose of CY facilitates the settlement of peritumorally inoculated DCs and supports them in restoration and activation of a potent antitumor response.

Anti-PD-1 inhibits Foxp3+ Treg cell conversion and unleashes intratumoural effector T cells thereby enhancing the efficacy of a cancer vaccine in a mouse model

The co-inhibitory molecule PD-1 suppresses T cell responses and has been targeted in the treatment of cancer. Here, we examined the role of PD-1 in regulating the balance between regulatory and effector T cells and whether blocking PD-1 could enhance tumour vaccine-induced protective immunity. A significantly higher proportion of tumour-resident T cells expressed PD-1 and Foxp3 compared with T cells in the tumour circulation or draining lymph nodes, and this correlated with a lower frequency of IFN-γ- and TNF-secreting CD8 T cells. Blocking PD-1 with a specific antibody reduced Foxp3+ regulatory T (Treg) cell induction and enhanced proliferation, cytokine production, and tumour killing by CD8 T cells. Treatment of CT26 tumour-bearing mice with anti-PD-1 in combination with a vaccine, comprising heat-shocked irradiated tumour cells and a TLR 7/8 agonist, significantly reduced tumour growth and enhanced survival. Furthermore, surviving mice resisted tumour re-challenge. The rejection of tumours in mice treated with the anti-PD-1 vaccine combination was associated with a reduction in tumour-infiltrating Treg cells and enhancement of IFN-γ-secreting CD8 T cells. Our findings demonstrate that high PD-1 expression correlates with increased tumour-infiltrating Treg cells and reduced effector T cells and that when combined with a potent antigen-adjuvant combination, blocking PD-1 effectively enhances anti-tumour immunity.

Dysregulation of TGFβ1 Activity in Cancer and Its Influence on the Quality of Anti-Tumor Immunity

TGFβ1 is a pleiotropic cytokine that exhibits a variety of physiologic and immune regulatory functions. Although its influence on multiple cell types is critical for the regulation of numerous biologic processes in the host, dysregulation of both TGFβ1 expression and activity is frequently observed in cancer and contributes to various aspects of cancer progression. This review focuses on TGFβ1’s contribution to tumor immune suppression and escape, with emphasis on the influence of this regulatory cytokine on the differentiation and function of dendritic cells and T cells. Clinical trials targeting TGFβ1 in cancer patients are also reviewed, and strategies for future therapeutic interventions that build on our current understanding of immune regulation by TGFβ1 are discussed.

Advances in inducing adaptive immunity using cell-based cancer vaccines: Clinical applications in pancreatic cancer

The incidence of pancreatic ductal adenocarcinoma (PDA) is on the rise, and the prognosis is extremely poor because PDA is highly aggressive and notoriously difficult to treat. Although gemcitabine- or 5-fluorouracil-based chemotherapy is typically offered as a standard of care, most patients do not survive longer than 1 year. Therefore, the development of alternative therapeutic approaches for patients with PDA is imperative. As PDA cells express numerous tumor-associated antigens that are suitable vaccine targets, one promising treatment approach is cancer vaccines. During the last few decades, cell-based cancer vaccines have offered encouraging results in preclinical studies. Cell-based cancer vaccines are mainly generated by presenting whole tumor cells or dendritic cells to cells of the immune system. In particular, several clinical trials have explored cell-based cancer vaccines as a promising therapeutic approach for patients with PDA. Moreover, chemotherapy and cancer vaccines can synergize to result in increased efficacies in patients with PDA. In this review, we will discuss both the effect of cell-based cancer vaccines and advances in terms of future strategies of cancer vaccines for the treatment of PDA patients.

The impact of dendritic cell-tumor fusion cells on cancer vaccines - past progress and future strategies

Dendritic cells (DCs) are potent antigen-presenting cells that can be used in cancer vaccines. Thus, various strategies have been developed to deliver tumor-associated antigens via DCs. One strategy includes administering DC-tumor fusion cells (DC-tumor FCs) to induce antitumor immune responses in cancer patients. However, clinical trials using this strategy have fallen short of expectations. Several factors might limit the efficacy of these anticancer vaccines. To induce efficient antitumor immune responses and enhance potential clinical benefits, DC-tumor FC-based cancer vaccines require manipulations that improve immunogenicity for both DCs and whole tumor cells. This review addresses recent progress in improving clinical outcomes using DC-tumor FC-based cancer vaccines.

Cell fusion between dendritic cells and whole tumor cells

We have developed cell fusion vaccines generated with dendritic cells (DCs) and whole tumor cells to induce antigen-specific antitumor immunity. This approach allows DCs to be exposed to the entire repertoire of tumor-associated antigens (TAAs) originally expressed by the tumor cell, to process them endogenously, and to present antigenic epitopes thought the MHC class I and class II pathways to activate both CD8+ and CD4+ T cells, respectively. The therapeutic efficacy of DC/tumor fusion cell vaccines requires the improved immunogenicity of both cells. Here, we describe the strategy to generate DC/tumor fusion cells.

[Accumulation-associated protein gene and TGF-beta 1 affects the formation of lung cancer-related biological material Staphylococcus epidermidis biofilm]

背景与目的

研究聚集相关蛋白（accumulation-associated protein, Aap）基因及转化生长因子β1（TGF-β1）对肺癌相关生物材料表皮葡萄球菌（SE）生物膜形成的影响。

方法

种属鉴定分离临床肺癌患者植入材料感染表皮葡萄球菌株，PCR法检测生物膜形成相关基因Aap，检测表皮葡萄球菌Aap基因株生物形成能力。密度梯度法提取非小细胞肺癌患者外周血单个核细胞，与人肺腺癌细胞A549在不同浓度（10 ng/mL, 20 ng/mL, 40 ng/mL）TGF-β1共培养30 h后，取上清液分别加入SE Aap+株、SE Aap-株下与医用硅橡胶培养30 h，半定量粘附试验测各组细菌生物膜形成的情况，扫描电镜观察材料表面生物膜微观情况。

结果

Aap基因的与表皮葡萄球菌生物膜的形成密切相关（P < 0.01）。在（10 ng/mL, 20 ng/mL, 40 ng/mL）TGF-β1浓度组医用硅橡胶表面SE Aap+生物膜的厚度大于空白组（P < 0.01）。SE Aap+株在TGF-β1浓度组间生物膜的厚度无明显差异（P > 0.05）。在不同浓度TGF-β1因子刺激下SE Aap-株均不能形成明显细菌生物膜。

结论

在肺癌患者植入材料引起感染中表皮葡萄球菌Aap基因表达阳性株较易形成细菌生物膜，TGF-β1对SE Aap阳性形成细菌生物膜有一定促进作用。

Enhancement of antitumor activity by combination of tumor lysate-pulsed dendritic cells and celecoxib in a rat glioma model

Using dendritic cell (DC)-based vaccines for treatment of gliomas has emerged as a meaningful and feasible treatment approach for inducing long-term survival, but this approach so far has failed to generate significant clinical responses. In the present study, we demonstrated that glioma lysate-pulsed DCs in combination with celecoxib, a selective cyclooxygenase 2 (COX-2) inhibitor, showed more significantly enhanced antitumor activity with increased apoptosis of tumor cells, reduced neovascularization, and developed a strong cytotoxic T lymphocyte (CTL) response in tumor-bearing rats. Celecoxib may reduce production of prostaglandin E2 and modulate the balance between T helper 1 (Th1) cytokines and T helper 2 (Th2) cytokines by increasing the pivotal Thl cytokine interleukin-12 and reducing Th2 cytokine interleukin-10. Taken together, our results demonstrated that selective inhibition of COX-2 using celecoxib combined with DC-based immunotherapy could act as an important novel strategy for improving future treatment of malignant gliomas.

Immunosuppressive networks and checkpoints controlling antitumor immunity and their blockade in the development of cancer immunotherapeutics and vaccines

Vaccines that promote protective adaptive immune responses have been successfully developed against a range of infectious diseases, and these are normally administered prior to exposure with the relevant virus or bacteria. Adaptive immunity also plays a critical role in the control of tumors. Immunotherapeutics and vaccines that promote effector T cell responses have the potential to eliminate tumors when used in a therapeutic setting. However, the induction of protective antitumor immunity is compromised by innate immunosuppressive mechanisms and regulatory cells that often dominate the tumor microenvironment. Recent studies have shown that blocking these suppressor cells and immune checkpoints to allow induction of antitumor immunity is a successful immunotherapeutic modality for the treatment of cancer. Furthermore, stimulation of innate and consequently adaptive immune responses with concomitant inhibition of immune suppression, especially that mediated by regulatory T (Treg) cells, is emerging as a promising approach to enhance the efficacy of therapeutic vaccines against cancer. This review describes the immunosuppressive mechanisms controlling antitumor immunity and the novel strategies being employed to design effective immunotherapeutics against tumors based on inhibition of suppressor cells or blockade of immune checkpoints to allow induction of more potent effector T cell responses. This review also discusses the potential of using a combination of adjuvants with inhibition of immune checkpoint or suppressor cells for therapeutic vaccines and the translation of pre-clinical studies to the next-generation vaccines against cancer in humans.

Strategies to improve the immunogenicity of anticancer vaccines based on dendritic cell/malignant cell fusions

The rationale for fusing dendritic cells (DCs) with whole tumor cells to generate anticancer vaccines resides in the fact that the former operate as potent antigen-presenting cells, whereas the latter express a constellation of tumor-associated antigens (TAAs). Although the administration of DC/malignant cell fusions to cancer patients is safe and this immunotherapeutic intervention triggers efficient tumor-specific T-cell responses in vitro, a limited number of objective clinical responses to DC/cancer cell fusions has been reported thus far. This review discusses novel approaches to improve the immunogenicity of DC/malignant cell fusions as anticancer vaccines.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or "assault" signals stemming from the underlying immune disorder. The "policing" activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or “assault” signals stemming from the underlying immune disorder. The “policing” activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Blocking retinoic acid receptor-α enhances the efficacy of a dendritic cell vaccine against tumours by suppressing the induction of regulatory T cells

The immune system has evolved regulatory mechanisms to control immune responses to self-antigens. Regulatory T (Treg) cells play a pivotal role in maintaining immune tolerance, but tumour growth is associated with local immunosuppression, which can subvert effector immune responses. Indeed, the induction and recruitment of Treg cells by tumours is a major barrier in the development of effective immunotherapeutics and vaccines against cancer. Retinoic acid (RA) has been shown to promote conversion of naïve T cells into Treg cells. This study addresses the hypothesis that blocking RA receptor alpha (RARα) may enhance the efficacy of a tumour vaccine by inhibiting the induction of Treg cells. We found that RA significantly enhanced TGF-β-induced expression of Foxp3 on naïve and committed T cells in vitro and that this was blocked by an antagonist of RARα (RARi). In addition, RARi significantly suppressed TGF-β and IL-10 and enhanced IL-12 production by dendritic cells (DC) in response to killed tumour cells or TLR agonists. Furthermore, RARi augmented the efficacy of an antigen-pulsed and TLR-activated DC vaccine, significantly attenuating growth of B16 tumours in vivo and enhancing survival of mice. This protective effect was associated with significant reduction in tumour-infiltrating FoxP3(+) and IL-10(+) Treg cells and a corresponding increase in tumour-infiltrating CD4(+) and CD8(+) T cells that secreted IFN-γ. Our findings demonstrate that RARα is an important target for the development of effective anti-tumour immunotherapeutics and for improving the efficacy of cancer vaccines.

Improved immunogenicity of fusions between ethanol-treated cancer cells and dendritic cells exposed to dual TLR stimulation

Tumor-derived transforming growth factor β1 (TGFβ1) generally abrogates the immunogenicity of dendritic cells (DCs) fused to whole cancer cells. We have recently revealed that ethanol-treated neoplastic cells fused to DCs exposed to 2 Toll-like receptor agonists efficiently induce cytotoxic T lymphocytes via TGFβ1 blockade and the production of interleukin-12.

Inhibition of transforming growth factor-β release from tumor cells reduces their motility associated with epithelial-mesenchymal transition

The high level of transforming growth factor‑β (TGF‑β) in tumor tissue, which is primarily released from tumor cells, helps maintain their metastatic nature and exacerbates the creation of a pro-tumor microenvironment. Although the strategy of targeting TGF‑β in cancer therapy has shown promise, its effects remain limited. In the present study, we focused on tumor cells as sources of TGF‑β release, and hypothesized that inhibition of their TGF‑β release could suppress their epithelial-mesenchymal transition (EMT)-associated metastatic nature and inactivate the induction of suppressor immune cells. To investigate this hypothesis, LLC1 cells, a mouse lung cancer cell line, were cultured with the TGF‑β release inhibitor tranilast and the motility of LLC1 cells was examined. Furthermore, to examine whether inhibition of TGF‑β release influences the induction of regulatory T (Treg) cells, spleen cells from normal mice were cultured in medium in which LLC1 cells had been cultured with tranilast. The results showed that tranilast inhibited the release of TGF‑β1 from LLC1 cells without affecting their proliferation. Inhibition of TGF‑β1 release suppressed the invasive activity of LLC1 cells, but enhanced their activity to adhere. mRNA levels of Slug and Twist were decreased in LLC1 cells, whereas levels of E‑cadherin were recovered. Treg cells were less frequently induced by medium in which LLC1 cells had been cultured with tranilast. Taken together, inhibition of TGF‑β1 release dampens the metastatic nature of LLC1 cells through the downregulation of EMT and possesses the possibility to improve antitumor immune responses through suppression of Treg cell induction. These findings provide a new rationale for development of TGF‑β‑targeted molecular immunotherapy against cancer.

Immune modulation by genetic modification of dendritic cells with lentiviral vectors

Our work over the past eight years has focused on the use of HIV-1 lentiviral vectors (lentivectors) for the genetic modification of dendritic cells (DCs) to control their functions in immune modulation. DCs are key professional antigen presenting cells which regulate the activity of most effector immune cells, including T, B and NK cells. Their genetic modification provides the means for the development of targeted therapies towards cancer and autoimmune disease. We have been modulating with lentivectors the activity of intracellular signalling pathways and co-stimulation during antigen presentation to T cells, to fine-tune the type and strength of the immune response. In the course of our research, we have found unexpected results such as the surprising immunosuppressive role of anti-viral signalling pathways, and the close link between negative co-stimulation in the immunological synapse and T cell receptor trafficking. Here we review our major findings and put them into context with other published work.

Augmentation of antitumor immunity by fusions of ethanol-treated tumor cells and dendritic cells stimulated via dual TLRs through TGF-β1 blockade and IL-12p70 production

The therapeutic efficacy of fusion cell (FC)-based cancer vaccine generated with whole tumor cells and dendritic cells (DCs) requires the improved immunogenicity of both cells. Treatment of whole tumor cells with ethanol resulted in blockade of immune-suppressive soluble factors such as transforming growth factor (TGF)-β1, vascular endothelial growth factor, and IL-10 without decreased expression of major histocompatibility complex (MHC) class I and the MUC1 tumor-associated antigen. Moreover, the ethanol-treated tumor cells expressed “eat-me” signals such as calreticulin (CRT) on the cell surface and released immunostimulatory factors such as heat shock protein (HSP)90α and high-mobility group box 1 (HMGB1). A dual stimulation of protein-bound polysaccharides isolated from Coriolus versicolor (TLR2 agonist) and penicillin-inactivated Streptococcus pyogenes (TLR4 agonist) led human monocyte-derived DCs to produce HSP90α and multiple cytokines such as IL-12p70 and IL-10. Interestingly, incorporating ethanol-treated tumor cells and TLRs-stimulated DCs during the fusion process promoted fusion efficiency and up-regulated MHC class II molecules on a per fusion basis. Moreover, fusions of ethanol-treated tumor cells and dual TLRs-stimulated DCs (E-tumor/FCs) inhibited the production of multiple immune-suppressive soluble factors including TGF-β1 and up-regulated the production of IL-12p70 and HSP90α. Most importantly, E-tumor/FCs activated T cells capable of producing high levels of IFN-γ, resulting in augmented MUC1-specific CTL induction. Collectively, our results illustrate the synergy between ethanol-treated whole tumor cells and dual TLRs-stimulated DCs in inducing augmented CTL responses in vitro by FC preparations. The alternative system is simple and may provide a platform for adoptive immunotherapy.

siRNA and cancer immunotherapy

Immunotherapeutic approaches have been gaining attention in the field of cancer treatment because of their possible ability to eradicate cancer cells as well as metastases by recruiting the host immune system. On the other hand, RNA-based therapeutics with the ability to silence expression of specific targets are currently under clinical investigation for various disorders including cancer. As the mechanisms of tumor evasion from the host immune system are versatile, different molecules have the capacity to be targeted by RNAi technology in order to enhance the immune response against tumors. This technology has been used to silence specific targets in tumor cells, as well as immune cells in cancer cell lines, animal models and clinical trials. siRNAs can also stimulate innate immune responses through activation of Toll-like receptors. Although currently clinical trials of the application of siRNA in cancer immunotherapy are few, it is predicted that in future this technology will be used broadly in cancer treatment.

Influence of tumors on protective anti-tumor immunity and the effects of irradiation

Innate and adaptive immunity plays important roles in the development and progression of cancer and it is becoming apparent that tumors can influence the induction of potentially protective responses in a number of ways. The prevalence of immunoregulatory T cell populations in the circulation and tumors of patients with cancer is increased and the presence of these cells appears to present a major barrier to the induction of tumor immunity. One aspect of tumor-mediated immunoregulation which has received comparatively little attention is that which is directed toward natural killer (NK) cells, although evidence that the phenotype and function of NK cell populations are modified in patients with cancer is accumulating. Although the precise mechanisms underlying these localized and systemic immunoregulatory effects remain unclear, tumor-derived factors appear, in part at least, to be involved. The effects could be manifested by an altered function and/or via an influence on the migratory properties of individual cell subsets. A better insight into endogenous immunoregulatory mechanisms and the capacity of tumors to modify the phenotype and function of innate and adaptive immune cells might assist the development of new immunotherapeutic approaches and improve the management of patients with cancer. This article reviews current knowledge relating to the influence of tumors on protective anti-tumor immunity and considers the potential influence that radiation-induced effects might have on the prevalence, phenotype, and function of innate and adaptive immune cells in patients with cancer.

Transforming growth factor-β gene silencing using adenovirus expressing TGF-β1 or TGF-β2 shRNA

Tumor cells secrete a variety of cytokines to outgrow and evade host immune surveillance. In this context, transforming growth factor-β1 (TGF-β1) is an extremely interesting cytokine because it has biphasic effects in cancer cells and normal cells. TGF-β1 acts as a growth inhibitor in normal cells, whereas it promotes tumor growth and progression in tumor cells. Overexpression of TGF-β1 in tumor cells also provides additional oncogenic activities by circumventing the host immune surveillance. Therefore, this study ultimately aimed to test the hypothesis that suppression of TGF-β1 in tumor cells by RNA interference can have antitumorigenic effects. However, we demonstrated here that the interrelation between TGF-β isotypes should be carefully considered for the antitumor effect in addition to the selection of target sequences with highest efficacy. The target sequences were proven to be highly specific and effective for suppressing both TGF-β1 mRNA and protein expression in cells after infection with an adenovirus expressing TGF-β1 short hairpin RNA (shRNA). A single base pair change in the shRNA sequence completely abrogated the suppressive effect on TGF-β1. Surprisingly, the suppression of TGF-β1 induced TGF-β3 upregulation, and the suppression of TGF-β2 induced another unexpected downregulation of both TGF-β1 and TGF-β3. Taken together, this information may prove useful when considering the design for a novel cancer immunogene therapy.

Developmental plasticity of murine and human Foxp3(+) regulatory T cells

Murine and human CD4(+) regulatory T (Treg) cells expressing the Forkhead box p3 (Foxp3) transcription factor represent a distinct, highly differentiated CD4(+) T cell lineage that is programmed for dominant self-tolerance and control of immune responses against a variety of foreign antigens. Sustained Foxp3 expression in these cells drives the differentiation of a regulatory phenotype and ensures the stability of their suppressive functions under a variety of inflammatory settings. Some recent studies have challenged this premise and advanced the notion that Foxp3(+) Treg cells manifest a high degree of functional plasticity that enables them to adapt and reprogram into effector-like T cells in response to various inflammatory stimuli. The concept of Treg cell plasticity remains highly contentious, with a high degree of variation in measured plasticity potential observed under different experimental conditions. In this chapter, we propose a unifying model of Treg cell plasticity, which hypothesizes that the stable fates of regulatory and effector T (Teff) cell lineages allow transient plasticity into the alternative lineage under a discrete set of microenvironmental influences associated with, respectively, the initiation and resolution phases of infection. This model utilizes a theoretical framework consistent with the requirements for effective immune regulation and accounts for both the extraordinary long-term stability of Treg cells and the observed fate plasticity.

Induced and natural regulatory T cells in human cancer

INTRODUCTION

Evidence suggests that FOXP3(+)CD25(high)CD4(+) regulatory T cells (Treg) which accumulate in cancer may have beneficial or unfavorable effects on prognosis. The presence in tumor-associated inflammatory infiltrates of two subsets of Treg with distinct phenotypic and functional profiles might explain these conflicting observations.

AREAS COVERED

Human inducible (i) Treg arising by tumor-driven conversion of conventional CD4(+) T cells are highly suppressive, therapy-resistant Treg which down-regulate anti-tumor immune responses, promoting tumor growth. Natural (n) Treg, normally responsible for maintaining peripheral tolerance, control cancer-associated inflammation, which favors tumor progression. This division of labor between nTreg and iTreg is not absolute, and overlap may be common. Nevertheless, iTreg play a critical and major role in cancer and cancer therapy. The tumor microenvironment determines the type, frequency and suppression levels of accumulating Treg.

EXPERT OPINION

In cancer, a selective removal or silencing of iTreg and not of nTreg should be a therapeutic goal. However, the implementation of this challenging strategy requires further studies of cellular and molecular crosstalk among immune cells in the tumor microenvironment.