Activation of CD1d-restricted natural killer T cells can inhibit cancer cell proliferation during chemotherapy by promoting the immune responses in murine mesothelioma

Overcoming resistance to programmed cell death protein 1 (PD-1) blockade with allogeneic invariant natural killer T-cells (iNKT)

Gastric cancer is the 5th most common malignancy worldwide with only 36% of patients with metastatic disease surviving beyond 5 years. Despite therapeutic improvements with the advent of immune checkpoint inhibitors, most patients with gastric cancer develop disease progression related to tumor resistance. Novel immunotherapeutic approaches, including invariant natural killer (iNKT) cells, are in clinical development and represent potential therapeutic options to overcome resistance. AgenT-797 is an allogeneic human unmodified iNKT derived from healthy donors. Activation of iNKT cells by tumor lipid antigens can trigger direct cytotoxicity and promote indirect anti-tumor immune responses such as recruitment and activation of T cells, NK cells, and dendritic cells through secretion of cytokines and IFNγ. We describe immune modulation leading to durable tumor response in a patient with microsatellite instability-high (MSI-H) advanced gastric adenocarcinoma treated with agent-797 after progression on standard chemotherapy and anti-PD-1 therapy.

Pathophysiological roles and applications of glycosphingolipids in the diagnosis and treatment of cancer diseases

Glycosphingolipids (GSLs) are major amphiphilic glycolipids present on the surface of living cell membranes. They have important biological functions, including maintaining plasma membrane stability, regulating signal transduction, and mediating cell recognition and adhesion. Specific GSLs and related enzymes are abnormally expressed in many cancer diseases and affect the malignant characteristics of tumors. The regulatory roles of GSLs in signaling pathways suggest that they are involved in tumor pathogenesis. GSLs have therefore been widely studied as diagnostic markers of cancer diseases and important targets of immunotherapy. This review describes the tumor-related biological functions of GSLs and systematically introduces recent progress in using diverse GSLs and related enzymes to diagnose and treat tumor diseases. Development of drugs and biomarkers for personalized cancer therapy based on GSL structure is also discussed. These advances, combined with recent progress in the preparation of GSLs derivatives through synthetic biology technologies, suggest a strong future for the use of customized GSL libraries in treating human diseases.

CAR-NKT cell therapy: a new promising paradigm of cancer immunotherapy

Today, cancer treatment is one of the fundamental problems facing clinicians and researchers worldwide. Efforts to find an excellent way to treat this illness continue, and new therapeutic strategies are developed quickly. Adoptive cell therapy (ACT) is a practical approach that has been emerged to improve clinical outcomes in cancer patients. In the ACT, one of the best ways to arm the immune cells against tumors is by employing chimeric antigen receptors (CARs) via genetic engineering. CAR equips cells to target specific antigens on tumor cells and selectively eradicate them. Researchers have achieved promising preclinical and clinical outcomes with different cells by using CARs. One of the potent immune cells that seems to be a good candidate for CAR-immune cell therapy is the Natural Killer-T (NKT) cell. NKT cells have multiple features that make them potent cells against tumors and would be a powerful replacement for T cells and natural killer (NK) cells. NKT cells are cytotoxic immune cells with various capabilities and no notable side effects on normal cells. The current study aimed to comprehensively provide the latest advances in CAR-NKT cell therapy for cancers.

Towards a better understanding of human iNKT cell subpopulations for improved clinical outcomes

Invariant natural killer T (iNKT) cells are a unique T lymphocyte population expressing semi-invariant T cell receptors (TCRs) that recognise lipid antigens presented by CD1d. iNKT cells exhibit potent anti-tumour activity through direct killing mechanisms and indirectly through triggering the activation of other anti-tumour immune cells. Because of their ability to induce potent anti-tumour responses, particularly when activated by the strong iNKT agonist αGalCer, they have been the subject of intense research to harness iNKT cell-targeted immunotherapies for cancer treatment. However, despite potent anti-tumour efficacy in pre-clinical models, the translation of iNKT cell immunotherapy into human cancer patients has been less successful. This review provides an overview of iNKT cell biology and why they are of interest within the context of cancer immunology. We focus on the iNKT anti-tumour response, the seminal studies that first reported iNKT cytotoxicity, their anti-tumour mechanisms, and the various described subsets within the iNKT cell repertoire. Finally, we discuss several barriers to the successful utilisation of iNKT cells in human cancer immunotherapy, what is required for a better understanding of human iNKT cells, and the future perspectives facilitating their exploitation for improved clinical outcomes.

Benefits and Challenges of Inhibiting EZH2 in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer that is mainly associated with prior exposure to asbestos fibers. Despite being a rare cancer, its global rate is increasing and the prognosis remains extremely poor. Over the last two decades, despite the constant research of new therapeutic options, the combination chemotherapy with cisplatin and pemetrexed has remained the only first-line therapy for MPM. The recent approval of immune checkpoint blockade (ICB)-based immunotherapy has opened new promising avenues of research. However, MPM is still a fatal cancer with no effective treatments. Enhancer of zeste homolog 2 (EZH2) is a histone methyl transferase that exerts pro-oncogenic and immunomodulatory activities in a variety of tumors. Accordingly, a growing number of studies indicate that EZH2 is also an oncogenic driver in MPM, but its effects on tumor microenvironments are still largely unexplored. This review describes the state-of-the-art of EZH2 in MPM biology and discusses its potential use both as a diagnostic and therapeutic target. We highlight current gaps of knowledge, the filling of which will likely favor the entry of EZH2 inhibitors within the treatment options for MPM patients.

Micellar nanoparticles inhibit breast cancer and pulmonary metastasis by modulating the recruitment and depletion of myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are notorious for their pathological characteristics of immunosuppression and their promoting effect on cancers. They can induce the formation of pre-metastatic niche (PMN) characterized by inflammation, immunosuppression and vascular leakage, and promote pulmonary metastasis of breast cancer. Herein, a tumor targeting c(RGDfk) peptide modified low molecular-weight-heparin-all-trans-retinoic-acid (LMWH-ATRA) micellar nanoparticle loaded with chemotherapeutic drug doxorubicin (DOX) and immune adjuvant α-galactosylceramide (αGC) (RLA/DOX/αGC NP) was developed. The hydrophilic segment LMWH inhibited the recruitment of MDSCs by competitively binding with P-selectin on the surface of vascular endothelial cells (VECs), while the hydrophobic segment ATRA promoted the depletion of MDSCs by inducing their differentiation. Through the modulation of MDSCs, micelles can significantly improve the inflammatory and immunosuppressive microenvironment of the lung and tumor sites, and inhibit the formation of PMN. Not only this, the micelles also produced a synergistic effect with αGC, which effectively improved the anti-tumor immunity of tumor bearing mice and provided a promising therapeutic strategy for breast cancer and pulmonary metastasis.

NK cells and solid tumors: therapeutic potential and persisting obstacles

Natural killer (NK) cells, which are innate lymphocytes endowed with potent cytotoxic activity, have recently attracted attention as potential anticancer therapeutics. While NK cells mediate encouraging responses in patients with leukemia, the therapeutic effects of NK cell infusion in patients with solid tumors are limited. Preclinical and clinical data suggest that the efficacy of NK cell infusion against solid malignancies is hampered by several factors including inadequate tumor infiltration and persistence/activation in the tumor microenvironment (TME). A number of metabolic features of the TME including hypoxia as well as elevated levels of adenosine, reactive oxygen species, and prostaglandins negatively affect NK cell activity. Moreover, cancer-associated fibroblasts, tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells actively suppress NK cell-dependent anticancer immunity. Here, we review the metabolic and cellular barriers that inhibit NK cells in solid neoplasms as we discuss potential strategies to circumvent such obstacles towards superior therapeutic activity.

The Current Landscape of NKT Cell Immunotherapy and the Hills Ahead

Simple Summary

Natural killer T (NKT) cells are a subset of lipid-reactive T cells that enhance anti-tumor immunity. While preclinical studies have shown NKT cell immunotherapy to be safe and effective, clinical studies lack predictable therapeutic efficacy and no approved treatments exist. In this review, we outline the current strategies, challenges, and outlook for NKT cell immunotherapy.

Abstract

NKT cells are a specialized subset of lipid-reactive T lymphocytes that play direct and indirect roles in immunosurveillance and anti-tumor immunity. Preclinical studies have shown that NKT cell activation via delivery of exogenous glycolipids elicits a significant anti-tumor immune response. Furthermore, infiltration of NKT cells is associated with a good prognosis in several cancers. In this review, we aim to summarize the role of NKT cells in cancer as well as the current strategies and status of NKT cell immunotherapy. This review also examines challenges and future directions for improving the therapy.

Triple-modality therapy maximizes antitumor immune responses in a mouse model of mesothelioma

Malignant pleural mesothelioma (MPM) is an intractable disease with an extremely poor prognosis. Our clinical protocol for MPM of subablative radiotherapy (RT) followed by radical surgery achieved better survival compared to other multimodal treatments, but local relapse and metastasis remain a problem. This subablative RT elicits an antitumoral immune response that is limited by the immunosuppressive microenvironment generated by regulatory T (T_reg) cells. The antitumor effect of immunotherapy to simultaneously modulate the immune activation and the immune suppression after subablative RT has not been investigated in MPM. Herein, we demonstrated a rationale to combine interleukin-15 (IL-15) superagonist (IL-15SA) and glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) agonist (DTA-1) with subablative RT in mesothelioma. IL-15SA boosted the systemic expansion of specific antitumoral memory CD8⁺ T cells that were induced by RT in mice. Their effect, however, was limited by the up-regulation and activation of T_reg cells in the radiated tumor microenvironment. Hence, selective depletion of intratumoral T_reg cells through DTA-1 enhanced the benefit of subablative RT in combination with IL-15SA. The addition of surgical resection of the radiated tumor in combination with IL-15SA and DTA-1 maximized the benefit of RT and was accompanied by a reproducible abscopal response in a concomitant tumor model. These data support the development of clinical trials in MPM to test such treatment options for patients with locally advanced or metastatic tumors.

The Immune Microenvironment of Malignant Pleural Mesothelioma: A Literature Review

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumour with a poor prognosis, associated with asbestos exposure. Nowadays, treatment is based on chemotherapy with a median overall survival of less than two years. This review highlights the main characteristics of the immune microenvironment in MPM with special emphasis on recent biological advances. The MPM microenvironment is highly infiltrated by tumour-associated macrophages, mainly M2-macrophages. In line with infiltration by M2-macrophages, which contribute to immune suppression, other effectors of innate immune response are deficient in MPM, such as dendritic cells or natural killer cells. On the other hand, tumour infiltrating lymphocytes (TILs) are also found in MPM, but CD4+ and CD8+ TILs might have decreased cytotoxic effects through T-regulators and high expression of immune checkpoints. Taken together, the immune microenvironment is particularly heterogeneous and can be considered as mainly immunotolerant or immunosuppressive. Therefore, identifying molecular vulnerabilities is particularly relevant to the improvement of patient outcomes and the assessment of promising treatment approaches.

Tumor Immune Microenvironment and Genetic Alterations in Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and fatal disease of the pleural lining. Up to 80% of the MPM cases are linked to asbestos exposure. Even though its use has been banned in the industrialized countries, the cases continue to increase. MPM is a lethal cancer, with very little survival improvements in the last years, mirroring very limited therapeutic advances. Platinum-based chemotherapy in combination with pemetrexed and surgery are the standard of care, but prognosis is still unacceptably poor with median overall survival of approximately 12 months. The genomic landscape of MPM has been widely characterized showing a low mutational burden and the impairment of tumor suppressor genes. Among them, BAP1 and BLM are present as a germline inactivation in a small subset of patients and increases predisposition to tumorigenesis. Other studies have demonstrated a high frequency of mutations in DNA repair genes. Many therapy approaches targeting these alterations have emerged and are under evaluation in the clinic. High-throughput technologies have allowed the detection of more complex molecular events, like chromotripsis and revealed different transcriptional programs for each histological subtype. Transcriptional analysis has also paved the way to the study of tumor-infiltrating cells, thus shedding lights on the crosstalk between tumor cells and the microenvironment. The tumor microenvironment of MPM is indeed crucial for the pathogenesis and outcome of this disease; it is characterized by an inflammatory response to asbestos exposure, involving a variety of chemokines and suppressive immune cells such as M2-like macrophages and regulatory T cells. Another important feature of MPM is the dysregulation of microRNA expression, being frequently linked to cancer development and drug resistance. This review will give a detailed overview of all the above mentioned features of MPM in order to improve the understanding of this disease and the development of new therapeutic strategies.

Decreased invariant natural killer T-cell-mediated antitumor immune response in patients with gastric cancer

Gastric cancer (GC) is the third most common cause of cancer-related death worldwide. Invariant natural killer T (iNKT) cells are innate-like cytotoxic T lymphocytes involved in tumor immune surveillance. They can be activated either through CD1d-presented glycolipid antigens recognized by their invariant T-cell receptor, cytokines or by sensing tumor-associated stress-induced ligands through the natural killer group 2, member D (NKG2D) receptor. Although the number and functionality of iNKT cells may be decreased in several types of cancer, here we show that GC patients presented a mild increase in iNKT cell frequencies and numbers in the blood compared with healthy donors. In GC patients, iNKT cells, expanded in vitro with α-galactosyl ceramide and stimulated with phorbol 12-myristate 13-acetate and ionomycin, produced higher levels of interleukin-2 and transforming growth factor-beta, while their capacity to degranulate remained preserved. Because tumor-derived epithelial cell adhesion molecule-positive epithelial cells did not display surface CD1d, and NKG2D ligands (NKG2DLs) were detected in the gastric tumor milieu, we envisioned a role for NKG2D in iNKT cell functions. Peripheral iNKT cells from GC patients and controls presented similar levels of NKG2D; nevertheless, the percentages of interferon-γ-producing and CD107a-positive iNKT cells from patients were reduced upon challenge with CD1d-negative, NKG2DL-positive K562 cells, suggesting a compromised response by iNKT cells in GC patients, which may not result from impaired NKG2D/NKG2DL signaling. The decreased response of iNKT cells may explain the fact that higher frequencies of circulating iNKT cells did not confer a survival benefit for GC patients. Therefore, functional impairment of iNKT cells in GC may contribute to tumor immune escape and favor disease progression.

Emerging therapies in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare cancer of the pleural surfaces frequently related to asbestos exposure. It is characterized by a poor prognosis even for patients treated with trimodality therapy, including surgery, chemotherapy and radiotherapy. Moreover, the majority of patients are not candidates for surgery due to disease advanced stage or medical comorbidities. For these patients, the survival rate is even lower and few therapeutic options are currently available. Nevertheless, many interesting novel approaches are under investigation, among which immunotherapy represents one of the most promising emerging strategies. In this review, we will discuss the role of new therapeutic options, particularly immunotherapy, and present the results of the most important and promising clinical trials.

Translating mesothelioma molecular genomics and dependencies into precision oncology-based therapies

Malignant pleural mesothelioma (MPM) is a rare, yet lethal asbestos-induced cancer and despite marked efforts to reduce occupational exposure, the incidence has not yet significantly declined. Since 2003, combined treatment with a platinum-based agent and pemetrexed has been the first-line therapy and no effective or approved second-line treatments have emerged. The seemingly slow advance in developing new MPM treatments does not appear to be related to a low level of clinical and pre-clinical research activity. Rather, we suggest that a key hurdle in successfully translating basic discovery into novel MPM therapeutics is the underlying assumption that as a rare cancer, it will also be molecularly and genetically homogeneous. In fact, lung adenocarcinoma and melanoma only benefitted from precision oncology upon full appreciation of the high degree of molecular heterogeneity inherent in these cancers, especially regarding the diversity of oncogenic drivers. Herein, we consider the recent explosion of molecular and genetic information that has become available regarding MPM and suggest ways in which the unfolding landscape may guide identification of novel therapeutic vulnerabilities within subsets of MPM that can be targeted in a manner consistent with the tenets of precision oncology.

MiR-6991-3p is identified as a novel suppressor in the expansion and activation of myeloid-derived suppressor cells in hepatoma-bearing mice

Objective

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of cells derived from bone marrow, which has a significant ability in inhibition of immune cell response. In this study, the role of miR-6991-3p in regulating function of MDSCs was investigated.

Methods

MDSCs were isolated from different tissues of the control and hepatoma-bearing mice, and then expression of miR-6991-3p was detected with qPCR. Then, the miR-6991-3p mimic and inhibitor were respectively transfected into MDSCs, and behaviors of MDSCs were evaluated, including expansion, apoptosis, and production of inflammatory factors. Furthermore, we explored the underlying mechanism from which miR-6991-3p regulated MDSC functions.

Results

Expression miR-6991-3p was markedly decreased in the MDSCs derived from spleen and further decreased in the MDSCs derived from the tumor tissue. MiR-6991-3p mimic transfection suppressed expansion and promoted apoptosis of MDSCs, accompanied by a significant decrease in the production of IL-6 and GM-CSF that are identified as stimulators in MDSC expansion. In contrast, miR-6991-3p inhibitor transfection displayed the opposite effect. miR-6991-3p bound with and negatively regulated expression of LGALS9, a newly identified immune checkpoint gene and activator of STAT3, suppressing production of multiple factors that were customarily used to characterize the activation of MDSCs. MiR-6991-3p-accommodated MDSCs displayed less suppression on T cells, while miR-6991-3p inhibitor enhanced the suppression of MDSCs on T cells.

Conclusion

MiR-6991-3p is identified as a novel suppressor in the expansion and activation of myeloid-derived suppressor cells, which may be regarded as a promising target for modulating the function of MDSCs.

PCC0208009 enhances the anti-tumor effects of temozolomide through direct inhibition and transcriptional regulation of indoleamine 2,3-dioxygenase in glioma models

Indoleamine 2,3-dioxygenase (IDO), which is highly expressed in human glioblastoma and involved in tumor immune escape and resistance to chemotherapy, is clinically correlated with tumor progression and poor clinical outcomes, and is a promising therapeutic target for glioblastoma. IDO inhibitors are marginally efficacious as single-agents; therefore, combination with other therapies holds promise for cancer therapy. The aim of this study was to investigate the anti-tumor effects and mechanisms of the IDO inhibitor PCC0208009 in combination with temozolomide. The effects of PCC0208009 on IDO activity inhibition, and mRNA and protein expression in HeLa cells were observed. In the mouse glioma GL261 heterotopic model, the effects of PCC0208009 on l-kynurenine/tryptophan (Kyn/Trp), tumor growth, flow cytometry for T cells within tumors, and immunohistochemistry for IDO and Ki67 were examined. In the rat glioma C6 orthotopic model, animal survival, flow cytometry for T cells within tumors, and immunohistochemistry for proliferating cell nuclear antigen (PCNA) and IDO were examined. The results show that PCC0208009 is a highly effective IDO inhibitor, not only directly inhibiting IDO activity but also participating in the gene regulation of IDO expression at the transcription and translation levels. PCC0208009 significantly enhanced the anti-tumor effects of temozolomide in GL261 and C6 models, by increasing the percentages of CD3⁺, CD4⁺, and CD8⁺ T cells within tumors and suppressing tumor proliferation. These findings indicate that PCC0208009 can potentiate the anti-tumor efficacy of temozolomide and suggest that combination of IDO inhibitor-based immunotherapy with chemotherapy is a potential strategy for brain tumor treatment.

Putative cancer stem cells may be the key target to inhibit cancer cell repopulation between the intervals of chemoradiation in murine mesothelioma

Background

Cancer cell repopulation during chemotherapy or radiotherapy is a major factor limiting the efficacy of treatment. Cancer stem cells (CSC) may play critical roles during this process. We aim to demonstrate the role of mesothelioma stem cells (MSC) in treatment failure and eventually to design specific target therapies against MSC to improve the efficacy of treatment in malignant mesothelioma.

Methods

Murine mesothelioma AB12 and RN5 cells were used to compare tumorigenicity in mice. The expression of CSC-associated genes was evaluated by quantitative real-time PCR in both cell lines treated with chemo-radiation. Stemness properties of MSC-enriched RN5-EOS-Puro2 cells were characterized with flow cytometry and immunostaining. A MSC-specific gene profile was screened by microarray assay and confirmed thereafter. Gene Ontology analysis of the selected genes was performed by GOMiner.

Results

Tumor growth delay of murine mesothelioma AB12 cells was achieved after each cycle of cisplatin treatment, however, tumors grew back rapidly due to cancer cell repopulation between courses of chemotherapy. Strikingly, a 10-times lower number of irradiated cells in both cell lines led to a similar tumor incidence and growth rate as with untreated cells. The expression of CSC-associated genes such as CD24, CD133, CD90 and uPAR was dramatically up-regulated, while others did not change significantly after chemoradiation. Highly enriched MSC after selection with puromycin displayed an increasing GFP-positive population and showed typical properties of stemness. Comparatively, the proportion of MSC significantly increased after RN5-EOS parental cells were treated with either chemotherapy, γ-ray radiation, or a combination of the two, while MSC showed more resistance to the above treatments. A group of identified genes are most likely MSC-specific, and major pathways related to regulation of cell growth or apoptosis are involved. Upregulation of the gene transcripts Tnfsf18, Serpinb9b, Ly6a, and Nppb were confirmed.

Conclusion

Putative MSC possess the property of stemness showing more resistance to chemoradiation, suggesting that MSC may play critical roles in cancer cell repopulation. Further identification of selected genes may be used to design novel target therapies against MSC, so as to eliminate cancer cell repopulation in mesothelioma.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4354-1) contains supplementary material, which is available to authorized users.

Liposomal formulation of glycosphingolipids from Sphingomonas paucimobilis induces antitumour immunity in mice

Natural Killer T (NKT) cells play an important role in host's anti-tumour immune response. Glycosphingolipids (GSLs) isolated from Sphingomonas paucimobilis have the ability to stimulate NKT cells. In this study, the activity of free GSLs or GSLs-incorporated liposomes (glycosphingosomes) was investigated against dimethyl-α-benzanthracene (DMBA)-induced tumours in mice. The anti-tumour immunity of GSLs- or glycosphingosomes-loaded bone marrow-derived dendritic cells (BMDCs) was investigated in tumour-bearing mice. The Immunotherapeutic potential of co-administration of liposomal doxorubicin (Lip-Dox) and GSLs or glycosphingosomes was assessed by measuring cytokine levels and VEGF in the tumour tissues. Pretreatment with glycosphingosomes significantly delayed the frequency of tumour formation. Immunotherapy with glycosphingosomes-loaded BMDCs increased serum IFN-γ level and survival rate in mice. The effect of immunotherapy was dependent on effector functions of NK cells because the depletion of NK cells abolished the effects of immunotherapy. There was reduced tumour growth with low expression of VEGF in the group of mice treated with glycosphingosomes and Lip-Dox combination. Moreover, the splenocytes secreted higher levels of IFN-γ, IL-12 and lower TGF-β level. The results of this study indicate that glycosphingosomes can induce better antitumour immunity and may be considered a novel formulation in antitumour therapy.

Natural Killer T-cell Immunotherapy in Combination with Chemotherapy-Induced Immunogenic Cell Death Targets Metastatic Breast Cancer

Natural killer T (NKT) cells are glycolipid-reactive lymphocytes that promote cancer control. In previous studies, NKT-cell activation improved survival and antitumor immunity in a postsurgical mouse model of metastatic breast cancer. Herein, we investigated whether NKT-cell activation could be combined with chemotherapeutic agents to augment therapeutic outcomes. Gemcitabine and cyclophosphamide analogues enhanced the potential immunogenicity of 4T1 mammary carcinoma cells by increasing the expression of antigen-presenting molecules (MHC-I, MHC-II, and CD1d) and promoting exposure or release of immunogenic cell death markers (calreticulin, HMGB1, and ATP). In 4T1 primary tumor and postsurgical metastasis models, BALB/c mice were treated with cyclophosphamide or gemcitabine. NKT cells were then activated by transfer of dendritic cells loaded with the glycolipid antigen α-galactosylceramide (α-GalCer). Chemotherapeutic treatments did not impact NKT-cell activation but enhanced recruitment into primary tumors. Cyclophosphamide, gemcitabine, or α-GalCer-loaded dendritic cell monotherapies decreased tumor growth in the primary tumor model and reduced metastatic burden and prolonged survival in the metastasis model. Combining chemotherapeutics with NKT-cell activation therapy significantly enhanced survival, with surviving mice exhibiting attenuated tumor growth following a second tumor challenge. The frequency of myeloid-derived suppressor cells was reduced by gemcitabine, cyclophosphamide, or α-GalCer-loaded dendritic cell treatments; cyclophosphamide also reduced the frequency of regulatory T cells. Individual treatments increased immune cell activation, cytokine polarization, and cytotoxic responses, although these readouts were not enhanced further by combining therapies. These findings demonstrate that NKT-cell activation therapy can be combined with gemcitabine or cyclophosphamide to target tumor burden and enhance protection against tumor recurrence. Cancer Immunol Res; 5(12); 1086-97. ©2017 AACR.

Radio-immunotherapy and chemo-immunotherapy as a novel treatment paradigm in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm with poor outcome. Novel radical radiation techniques using intensity modulated radiation therapy (IMRT) have become an important component of therapy in mesothelioma. Immunotherapy also provides new therapeutic options. However, how best to integrate immunotherapy with standard therapy such as radiation, chemotherapy and surgery remains unknown. A change of paradigm from adjuvant normofractionation to induction accelerated hypofractionated hemithoracic radiation could provide a platform to combine immunotherapy due to the potential benefit of short course high dose radiation on the immune system. Immunotherapy can also be combined with chemotherapy. Although chemotherapy is generally considered immunosuppressive, some chemotherapeutic agents do induce cell death that can be immunogenic and stimulate a specific immune response against the tumor. Immunotherapy could also be used in between cycles of chemotherapy to limit tumor cell repopulation and optimize the results of both treatments. The integration of immunotherapy into a multimodality approach is opening new avenue of treatment for mesothelioma.