The immunosuppressive tumour network: myeloid-derived suppressor cells, regulatory T cells and natural killer T cells

Myeloid derived suppressor cells in chronic myeloid leukemia

The suppression of the immune system creates a permissive environment for development and progression of cancer. One population of immunosuppressive cells that have become the focus of intense study is myeloid derived suppressor cells (MDSCs), immature myeloid cells able to induce immune-escape, angiogenesis, and tumor progression. Two different subpopulations have been identified and studied: granulocytic and monocytic MDSCs, with a different immunophenotype and immunosuppressive properties. Recently, an accumulation of both Gr-MDSCs and Mo-MDSCs cells has been found in the peripheral blood of chronic myeloid leukemia (CML) patients. They are part of the tumor clone showing BCR/ABL expression. Imatinib therapy decreases both MDSCs and arginase 1 levels to normal ones. This review will focus on actual knowledge for human MDSCs and their immunosuppressive activity in CML patients, with a critical attention to comparison of Gr-MDSCs and polymorphonuclear cells (PMNs). We will then suggest the monitoring of MDSCs in patients who have discontinued tyrosine kinase inhibitors (TKIs) therapy to evaluate if their increase could correlate with disease relapse.

Exosomes - structure, biogenesis and biological role in non-small-cell lung cancer

Many different cells produce and release membraneous microvesicles (MV) or exosomes into their microenvironment. Exosomes represent a specific subtype of secreted derived vesicles which are defined as homogenous vesicles of 30-100 nm lined by a lipid bilayer, which contain a specific set of proteins, lipids, and nucleic acids. There are clear evidences that they serve as important biological signals messengers and carriers in physiological as well as in pathological processes. Those derived from tumours (tumour-derived exosomes, TD-exosomes) function as protumourigenic factors that can mediate intercellular communication in the tumour microenvironment and also contribute to cancer progression. The main functions of exosomes in the cancer microenvironment include the following: promotion of primary cancer growth, stimulation of angiogenesis, activation of stromal fibroblasts, sculpting the cancer ECM, generation of a premetastatic niche and suppression of host immune response. Exosomes have recently emerged as potentially promising diagnostic and prognostic biomarkers in cancer and other diseases. This article is a summary of information about the structure and origin of exosomes and also indicates the importance of exosomes and microRNAs in lung cancer. The role of exosomes in NSCLC is little known, and its explanation requires thorough research.

MicroRNAs as mediators and communicators between cancer cells and the tumor microenvironment

Cancer cells grow in an environment comprised of multiple components that support tumor growth and contribute to therapy resistance. Major cell types in the tumor microenvironment are fibroblasts, endothelial cells and infiltrating immune cells all of which communicate with cancer cells. One way that these cell types promote cancer progression is by altering the expression of microRNAs (miRNAs), small noncoding RNAs that negatively regulate protein expression, either in the cancer cells or in the associated normal cells. Changes in miRNA expression can be brought about by direct interaction between the stromal cells and cancer cells, by paracrine factors secreted by any of the cell types or even through direct communication between cells through secreted miRNAs. Understanding the role of miRNAs in the complex interactions between the tumor and cells in its microenvironment is necessary if we are to understand tumor progression and devise new treatments.

The nitric oxide radical scavenger carboxy-PTIO reduces the immunosuppressive activity of myeloid-derived suppressor cells and potentiates the antitumor activity of adoptive cytotoxic T lymphocyte immunotherapy

Adoptive immunotherapy with cytotoxic T lymphocytes (CTLs) can result in robust and durable antitumor responses. Tumor-infiltrating CTLs produce IFNγ and mediate antitumor activity, but they simultaneously induce counter-regulatory immunosuppressive mechanisms in the tumor by recruiting monocytic myeloid-derived suppressor cells (MDSCs) that limit their proliferation and effector function. Using a murine model of adoptive immunotherapy for B16 melanoma, we developed a strategy to augment CTL activity by downregulating immunosuppression by MDSCs. Intravenous injection of transgenic pmel-1 CTLs into tumor-bearing mice, resulted in their infiltration into the tumor, but this was accompanied by the accumulation of large numbers of monocytic MDSCs (M-MDSCs). These cells hampered CTL function and reduced their numbers in the tumor. We determined that one mechanism responsible for this immunosuppression was the production of nitric oxide (NO) by MDSCs in the tumor. Therefore, mice were given the NO scavenger carboxy-PTIO (C-PTIO) on the day after CTL transfer. This led to the restoration of impaired proliferative capacity and function of the CTLs, resulting in sustained suppression of tumor growth. Thus, we conclude that CTL therapy can be improved by counter-acting immunosuppression. Targeting NO, one mediator of the immunosuppressive activity of M-MDSCs, may be an appropriate strategy to restore impaired CTL function and improve the efficacy of immunotherapy.

CD14-expressing cancer cells establish the inflammatory and proliferative tumor microenvironment in bladder cancer

Nonresolving chronic inflammation at the neoplastic site is consistently associated with promoting tumor progression and poor patient outcomes. However, many aspects behind the mechanisms that establish this tumor-promoting inflammatory microenvironment remain undefined. Using bladder cancer (BC) as a model, we found that CD14-high cancer cells express higher levels of numerous inflammation mediators and form larger tumors compared with CD14-low cells. CD14 antigen is a glycosyl-phosphatidylinositol (GPI)-linked glycoprotein and has been shown to be critically important in the signaling pathways of Toll-like receptor (TLR). CD14 expression in this BC subpopulation of cancer cells is required for increased cytokine production and increased tumor growth. Furthermore, tumors formed by CD14-high cells are more highly vascularized with higher myeloid cell infiltration. Inflammatory factors produced by CD14-high BC cells recruit and polarize monocytes and macrophages to acquire immune-suppressive characteristics. In contrast, CD14-low BC cells have a higher baseline cell division rate than CD14-high cells. Importantly, CD14-high cells produce factors that further increase the proliferation of CD14-low cells. Collectively, we demonstrate that CD14-high BC cells may orchestrate tumor-promoting inflammation and drive tumor cell proliferation to promote tumor growth.

Microencapsulation of tumor lysates and live cell engineering with MIP-3α as an effective vaccine

The combination of several potential strategies so as to develop new tumor vaccines is an attractive field of translational medicine. Pulsing tumor lysates with dendritic cells (DCs), in-vivo attraction of DCs by macrophage inflammatory protein 3α (MIP-3α), and reversion of the tumor suppressive microenvironment have been tested as strategies to develop tumor vaccines. In this study, we generated an alginate microsphere (named PaLtTcAdMIP3α) that encapsulated tumor lysates, live tumor cells engineering with a recombinant MIP-3α adenovirus and BCG. We used PaLtTcAdMIP3α as a model vaccine to test its antitumor activities. Our results showed that PaLtTcAdMIP3α expressed and excreted MIP-3α, which effectively attracted DCs ex vivo and in vivo. Injection of PaLtTcAdMIP3α into tumor-bearing mice effectively induced both therapeutic and prophylactic antitumor immunities in CT26, Meth A, B16-F10 and H22 models, but without any ensuing increase in adverse effects. Both tumor-specific cellular and humoral immune responses, especially the CD8(+) T cell-dependent cytotoxic T immunity, were found in the mice injected with PaLtTcAdMIP3α. The anti-tumor activity was abrogated completely by depletion of CD8(+) and partially by CD4(+) T lymphocytes. In addition, the number of IFN-γ-producing CD8(+) T cells in spleen and tumor tissues was significantly increased; but the number of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) in tumor tissues was decreased. These data strongly suggest that a combination of multi-current-using strategies such as the novel approach of using our PaLtTcAdMIP3α microspheres could be an effective tumor model vaccine.

Efferocytosis creates a tumor microenvironment supportive of tumor survival and metastasis

Programmed cell death, or apoptosis, occurs in nearly all tissues of all multi-cellular organisms. In order to avoid leakage of intracellular contents, which could generate tissue damaging inflammation, apoptotic cells are cleared from tissues by phagocytes, which then dispatch the engulfed dying cell through the lysosomal pathway. Phagocytic clearance of apoptotic cells is referred to as efferocytosis. One key feature of efferocytosis is the production and release of wound healing cytokines by the phagocyte, which acts to resolve inflammation, and promote tissue repair. Phagocytic engulfment of apoptotic cells coupled with cytokine modulation aimed at immune suppression ensures that physiological programmed cell death does not induce inflammation and tissue damage. However, cytokines involved in wound healing and immune suppression are notorious for their role in the tumor microenvironment, increasing tumor cell motility and promoting evasion of anti-tumor immunity. Therefore, current and future studies aimed at targeting important players of efferocytosis should reveal new and efficacious therapeutic approaches for limiting cancer progression and relapse.

The TLR4 agonist fibronectin extra domain A is cryptic, exposed by elastase-2; use in a fibrin matrix cancer vaccine

Fibronectin (FN) is an extracellular matrix (ECM) protein including numerous fibronectin type III (FNIII) repeats with different functions. The alternatively spliced FN variant containing the extra domain A (FNIII EDA), located between FNIII 11 and FNIII 12, is expressed in sites of injury, chronic inflammation, and solid tumors. Although its function is not well understood, FNIII EDA is known to agonize Toll-like receptor 4 (TLR4). Here, by producing various FN fragments containing FNIII EDA, we found that FNIII EDA's immunological activity depends upon its local intramolecular context within the FN chain. N-terminal extension of the isolated FNIII EDA with its neighboring FNIII repeats (FNIII 9-10-11) enhanced its activity in agonizing TLR4, while C-terminal extension with the native FNIII 12-13-14 heparin-binding domain abrogated it. In addition, we reveal that an elastase 2 cleavage site is present between FNIII EDA and FNIII 12. Activity of the C-terminally extended FNIII EDA could be restored after cleavage of the FNIII 12-13-14 domain by elastase 2. FN being naturally bound to the ECM, we immobilized FNIII EDA-containing FN fragments within a fibrin matrix model along with antigenic peptides. Such matrices were shown to stimulate cytotoxic CD8⁺ T cell responses in two murine cancer models.

Intra-adrenal murine TH-MYCN neuroblastoma tumors grow more aggressive and exhibit a distinct tumor microenvironment relative to their subcutaneous equivalents

In around half of the patients with neuroblastoma (NBL), the primary tumor is located in one of the adrenal glands. We have previously reported on a transplantable TH-MYCN model of subcutaneous (SC) growing NBL in C57Bl/6 mice for immunological studies. In this report, we describe an orthotopic TH-MYCN transplantable model where the tumor cells were injected intra-adrenally (IA) by microsurgery. Strikingly, 9464D cells grew out much faster in IA tumors compared to the subcutis. Tumors were infiltrated by equal numbers of lymphocytes and myeloid cells. Within the myeloid cell population, however, tumor-infiltrating macrophages were more abundant in IA tumors compared to SC tumors and expressed lower levels of MHC class II, indicative of a more immunosuppressive phenotype. Using 9464D cells stably expressing firefly luciferase, enhanced IA tumor growth could be confirmed using bioluminescence. Collectively, these data show that the orthotopic IA localization of TH-MYCN cells impacts the NBL tumor microenvironment, resulting in a more stringent NBL model to study novel immunotherapeutic approaches for NBL.

The immunocytokine NHS-IL12 as a potential cancer therapeutic

Targeted delivery of IL-12 might turn this cytokine into a safer, more effective cancer therapeutic. Here we describe a novel immunocytokine, NHS-IL12, consisting of two molecules of IL-12 fused to a tumor necrosis-targeting human IgG1 (NHS76). The addition of the human IgG1 moiety resulted in a longer plasma half-life of NHS-IL12 than recombinant IL-12, and a selective targeting to murine tumors in vivo. Data from both in vitro assays using human PBMCs and in vivo primate studies showed that IFN-gamma production by immune cells is attenuated following treatment with the immunocytokine, suggesting an improved toxicity profile than seen with recombinant IL-12 alone. NHS-IL12 was superior to recombinant IL-12 when evaluated as an anti-tumor agent in three murine tumor models. Mechanistic studies utilizing immune cell subset-depleting antibodies, flow cytometric methods, and in vitro cytotoxicity and ELISA assays all indicated that the anti-tumor effects of NHS-IL12 were primarily CD8+ T cell-dependent and likely IL-12-mediated. Combining NHS-IL12 treatment with a cancer vaccine, radiation, or chemotherapy resulted in greater anti-tumor effects than each individual therapy alone. These preclinical findings provide a rationale for the clinical testing of this immunocytokine, both as a single agent and in combination with vaccines, radiation and chemotherapy.

Effectiveness of immune therapy combined with chemotherapy on the immune function and recurrence rate of cervical cancer

The aim of this study was to compare the immune function of patients with cervical cancer and the cancer recurrence rate in patients treated with biological immune therapy combined with chemotherapy or with chemotherapy only. A total of 79 postoperative patients with cervical cancer participated in the present study. They were randomly divided into a control group and an experimental group. Patients in the control group were treated with cisplatin chemotherapy. Patients in the experimental group were treated with dendritic cell-cytokine-induced killer (DC-CIK) cells combined with cisplatin chemotherapy. The CD3⁺, CD4⁺, CD8⁺, CD16⁺, CD56⁺ and CD4⁺CD25⁺ cell ratios in peripheral blood, and the expression levels of perforin, granzyme B (GraB) and CD107a of peripheral blood mononuclear cells (PBMCs) in all patients prior to and following treatment were observed. The changes of immune function and recurrence rate between these two groups prior to and following treatment were compared. Prior to treatment, the lymphocyte ratio had no significant difference between the two groups (P>0.05). Following treatment, the lymphocyte ratio in the experimental group was significantly higher than that in the control group (P<0.05). The positive expression levels of perforin, GraB and CD107a of PBMCs in the experimental group following treatment were significantly higher than those prior to treatment and those of the control group (P<0.05). The cumulative recurrence rate in the experimental group was significantly lower than that in the control group (P<0.05). In conclusion, in postoperative patients with cervical cancer, treatment with DC-CIK cells combined with cisplatin chemotherapy significantly improved the immune function, reduced the recurrence rate and prolonged the survival time of the patients.

Overcoming tumor immune evasion with an unique arbovirus

Combining dendritic cell vaccination with the adjuvant effect of a strain of dengue virus may be a way to overcome known tumor immune evasion mechanisms. Dengue is unique among viruses as primary infections carry lower mortality than the common cold, but secondary infections carry significant risk of hypovolemic shock. While current immuno-therapies rely on a single axis of attack, this approach combines physiological (hyperthermic reduction of tumor perfusion), immunological (activation of effector cells of the adaptive and innate immune system), and apoptosis-inducing pathways (sTRAIL) to destroy tumor cells. The premise of using multiple mechanisms of action in synergy with a decline in the ability of the tumor cells to employ resistance methods suggests the potential of this combination approach in cancer immunotherapy.

Repurposing drugs in oncology (ReDO)-cimetidine as an anti-cancer agent

Cimetidine, the first H₂ receptor antagonist in widespread clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical and clinical studies for a number of different cancer types. These data are summarised and discussed in relation to a number of distinct mechanisms of action. Based on the evidence presented, it is proposed that cimetidine would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of cimetidine as an anti-cancer therapeutic is warranted. Furthermore, there is compelling evidence that cimetidine administration during the peri-operative period may provide a survival benefit in some cancers. A number of possible combinations with other drugs are discussed in the supplementary material accompanying this paper.

Detailed characterization of tumor infiltrating lymphocytes in two distinct human solid malignancies show phenotypic similarities

Background

We examined the phenotype and function of lymphocytes collected from the peripheral blood (PBL) and tumor (TIL) of patients with two different solid malignancies: colorectal cancer liver metastases (CRLM) and ovarian cancer (OVC).

Methods

Tumor and corresponding peripheral blood were collected from 16 CRLM and 22 OVC patients; immediately following resection they were processed and analyzed using a multi-color flow cytometry panel. Cytokine mRNA from purified PBL and TIL CD4⁺ T cells were also analyzed by qPCR.

Results

Overall, we found similar changes in the phenotypic and cytokine profiles when the TIL were compared to PBL from patients with two different malignancies. The percentage of Treg (CD4⁺/CD25⁺/FoxP3⁺) in PBL and TIL was similar: 8.1% versus 10.2%, respectively in CRLM patients. However, the frequency of Treg in primary OVC TIL was higher than PBL: 19.2% versus 4.5% (p <0.0001). A subpopulation of Treg expressing HLA-DR was markedly increased in TIL compared to PBL in both tumor types, CRLM: 69.0% versus 31.7% (p = 0.0002) and OVC 74.6% versus 37.0% (p <0.0001), which suggested preferential Treg activation within the tumor. The cytokine mRNA profile showed that IL-6, a cytokine known for its immunosuppressive properties through STAT3 upregulation, was increased in TIL samples in patients with OVC and CRLM. Both TIL populations also contained a significantly higher proportion of activated CD8⁺ T cells (HLA-DR⁺/CD38⁺) compared to PBL (CRLM: 30.2% vs 7.7%, (p = 0.0012), OVC: 57.1% vs 12.0%, (p <0.0001)).

Conclusion

This study demonstrates that multi-color flow cytometry of freshly digested tumor samples reveals phenotypic differences in TIL vs PBL T cell sub-populations. The TIL composition in primary and metastatic tumors from two distinct histologies were remarkably similar, showing a greater proportion of activated/suppressive Treg (HLA-DR⁺, CD39⁺, CTLA-4⁺ and Helios⁺) and activated cytotoxic T cells (CD8⁺/HLA-DR⁺/CD38⁺) when compared to PBL and an increase in IL-6 mRNA from CD4 TIL.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-014-0038-9) contains supplementary material, which is available to authorized users.

Selective colorectal cancer cell lysates enhance the immune function of mature dendritic cells in vitro

The aim of the present study was to determine the most effective antigen with which to mature dendritic cells (DCs). The immune function of DCs loaded with lysates from three different colorectal cancer cell lines was compared. DCs were induced using granulocyte macrophage colony‑stimulating factor, interleukin (IL)‑4 and tumor necrosis factor-α from the peripheral blood mononuclear cells of patients with colorectal cancer, and loaded with lysates from Colo320, SW480 and SW620 colorectal cancer cell lines, respectively. Autogenous T cells were co‑cultured with mature DCs. Surface markers and the secretory function of mature DCs and stimulated T cells were then analyzed. MTT assays were used to evaluate the killing capacity of autogenous cytotoxic T lymphocytes (CTLs). Compared with control, cluster of differentiation (CD)1a, CD83 and CD86, and human leukocyte antigen‑DR expression levels were significantly higher in DCs matured using cancer cell lysates. In addition, IL‑12 secretion levels were elevated. Autogenous T cells stimulated with DCs that were matured using cancer cell lysates showed a higher proliferation capacity, increased interferon-γ secretion levels and stronger cytotoxic abilities compared with control cells. Among the three cell lines, SW480 lysates were most effective at promoting DC and T cell function. The results showed that SW480 lysates are more efficient than Colo320 and SW620 lysates in inducing DC immune function and activating the antitumor function of autogenous T cells.

Increased monocytic CD14⁺HLADRlow/- myeloid-derived suppressor cells in obesity

Obesity is associated with numerous immunological disorders. The present study investigated the proportion and phenotype of myeloid‑derived suppressor cells (MDSCs) in the plasma of obese subjects and the association of these cells with the level of liver enzymes. Certain features of the immune response in obese subjects were examined by analyzing the expression of T cell receptor‑ζ (TCRζ) molecules on the surface of T cells. The expression and secretion of S100A9, a possible marker for MDSCs, were detected in the peripheral blood of obese subjects and compared with levels in lean controls. Results showed that the percentage of monocytic MDSCs, with the phenotype CD33+CD11b+CD14+HLADRlow/‑, was significantly increased in obese subjects compared with lean controls. The circulating level of monocytic MDSCs was positively correlated with the levels of liver enzymes in serum. The expression of the TCRζ molecule in the resting T cells was significantly lower in obese individuals than that of lean controls. The expression of S100A9 was detected in the majority of monocytes in peripheral blood mononulear cells, but no difference was identified in the frequency of CD14+S100A9+ cells between the obese and lean groups. However, the plasma level of S100A8/9 was significantly increased in obese compared with lean subjects. These observations suggested that the increased frequency of CD33+CD11b+CD14+HLADRlow/‑ cells may be responsible for the impaired T‑cell function and liver injury observed in obesity.

Myeloid-derived suppressor cells: paradoxical roles in infection and immunity

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature suppressor cells that are generated due to aberrant myelopoiesis under pathological conditions. Although MDSCs have been recognized for more than 20 years under the guise of different monikers, these particular populations of myeloid cells gained more attention recently due to their immunosuppressive properties, which halt host immune responses to growing cancers or overwhelming infections. While MDSCs may contribute to immune homeostasis after infection or tissue injury by limiting excessive inflammatory processes, their expansion may be at the expense of pathogen elimination and thus may lead to disease persistence. Therefore, MDSCs may be either damaging or obliging to the host by attenuating, for example, antitumor or anti-infectious immune responses. In this review, we recapitulate the biological and immunological aspects of MDSCs, including their generation, distribution, trafficking and the factors involved in their activation, expansion, suppressive functions, and interplay between MDSCs and regulatory T cells, with a focus on the perspectives of infection and inflammation.

Interleukin-17 mediated inflammatory responses are required for ultraviolet radiation-induced immune suppression

Ultraviolet radiation (UVR) induces immunosuppression and is a major factor for development of skin cancer. Numerous efforts have been made to determine mechanisms for UVR-induced immunosuppression and to develop strategies for prevention and treatment of UVR-induced cancers. In the current study, we use IL-17 receptor (IL-17R) deficient mice to examine whether IL-17 mediated responses have a role in UVB (290-320)-induced immunosuppression of contact hypersensitivity responses. Results demonstrate that IL-17 mediated responses are required for UVB-induced immunosuppression of contact hypersensitivity responses. The systemic immune suppression and development of regulatory T cells are inhibited in UVB-treated IL-17R deficient mice compared to wild-type animals. The deficiency in IL-17R inhibits the infiltration and development of a tolerogenic myeloid cell population in UVB-treated skin, which expresses CD11b and Gr-1 and produces reactive oxygen species. We speculate that the development of the tolerogenic myeloid cells is dependent on IL-17-induced chemokines and inflammatory mediators in UVB-treated skin. The inhibition of the tolerogenic myeloid cells may be attributed to the suppression of regulatory T cells in UVR-treated IL-17R(-/-) mice. The findings may be exploited to new strategies for prevention and treatment of UVR-induced skin diseases and cancers.

Induction of Bcl-xL-specific cytotoxic T lymphocytes in mice

The induction of active immunity against tumour-associated antigens to prevent relapse of cancer is a promising approach but has so far shown only low efficacy. This low efficacy may in part be due to clonal escape of tumour cell variants by the downregulation of antigen expression or inflammation-induced dedifferentiation. Identification of novel tumour-associated antigens that at the same time are essential for continued tumour cell survival is thus critical for the development of active cancer vaccinations. At the same time, identification of novel endogenous murine tumour antigens will help improve preclinical development of cancer immunotherapy. The anti-apoptotic protein Bcl-xL has been suggested to be such an essential tumour antigen, but the lack of well-defined murine epitopes have delayed preclinical studies of Bcl-xL-targeting cancer vaccines. Here, we report the identification of two novel murine tumour-associated epitopes TAYQSFEQV and AFFSFGGAL derived from mouse Bcl-xL. Dendritic cell (DC)-based vaccination induced CD8(+) T cells capable of producing IFN-γ upon restimulation with these epitopes. Thus, our data may benefit the design of future immunotherapy strategies by providing a preclinical model for cancer vaccination with an endogenous tumour antigen that can be combined with other cancer treatments.

Tumor-derived osteopontin suppresses antitumor immunity by promoting extramedullary myelopoiesis

Extramedullary myelopoiesis occurs commonly in tumor-bearing animals and is known to lead to accumulation of peripheral myeloid-derived suppressor cells (MDSC), which play an important role in immune escape. However, the cellular and molecular mechanisms by which tumors induce extramedullary myelopoiesis are poorly understood. In this study, we found that osteopontin expressed by tumor cells enhances extramedullary myelopoiesis in a CD44-dependent manner through the Erk1/2-MAPK pathway. Osteopontin-mediated extramedullary myelopoiesis was directly associated with increased MDSCs in tumor-bearing hosts. More importantly, osteopontin silencing in tumor cells delayed both tumor growth and extramedullary myelopoiesis, while the same treatment did not affect tumor growth in vitro. Finally, treatment with an antibody against osteopontin inhibited tumor growth and synergized with cell-based immunotherapeutic vaccines in mediating antitumor immunity. Our findings unveil a novel immunosuppressive role for tumor-derived osteopontin and offer a rationale for its therapeutic targeting in cancer treatment.

MDSCs: the final frontier of the microenvironment in CLL?

In this issue of Blood, Jitschin et al identify increased numbers of myeloid-derived suppressor cells (MDSCs) in untreated patients with chronic lymphocytic leukemia (CLL) suppressing T cells and inducing regulatory T cells (T(regs)), resulting in impaired immune responses.

Different subsets of natural killer T cells may vary in their roles in health and disease

Natural killer T cells (NKT) can regulate innate and adaptive immune responses. Type I and type II NKT cell subsets recognize different lipid antigens presented by CD1d, an MHC class-I-like molecule. Most type I NKT cells express a semi-invariant T-cell receptor (TCR), but a major subset of type II NKT cells reactive to a self antigen sulphatide use an oligoclonal TCR. Whereas TCR-α dominates CD1d-lipid recognition by type I NKT cells, TCR-α and TCR-β contribute equally to CD1d-lipid recognition by type II NKT cells. These variable modes of NKT cell recognition of lipid-CD1d complexes activate a host of cytokine-dependent responses that can either exacerbate or protect from disease. Recent studies of chronic inflammatory and autoimmune diseases have led to a hypothesis that: (i) although type I NKT cells can promote pathogenic and regulatory responses, they are more frequently pathogenic, and (ii) type II NKT cells are predominantly inhibitory and protective from such responses and diseases. This review focuses on a further test of this hypothesis by the use of recently developed techniques, intravital imaging and mass cytometry, to analyse the molecular and cellular dynamics of type I and type II NKT cell antigen-presenting cell motility, interaction, activation and immunoregulation that promote immune responses leading to health versus disease outcomes.

Ribavirin enhances myeloid-derived suppressor cell differentiation through CXCL9/10 downregulation

Elevation of myeloid-derived suppressor cells (MDSCs) was observed in some viral infectious diseases. In this study, we studied whether ribavirin, a widely used clinical antiviral drug, could impact the differentiation of human MDSCs in vitro. Flow cytometric analysis showed that ribavirin treatment (5-20 µg/ml) significantly enhanced the differentiation of monocytic MDSCs in a dose-dependent manner. The ribavirin-generated MDSCs were immune-suppressive toward autologous T cells. The mRNA expression of some cytokines was further examined by quantitative reverse transcription polymerase chain reaction. We observed a significant down-regulation of chemokine (C-X-C motif) ligand 9 (CXCL9) and CXCL10 mRNA in ribavirin-generated MDSCs, when compared with control. Peripheral blood mononuclear cells from clinical chronic hepatitis C patients subjected to ribavirin therapy also displayed a similar suppression in CXCL9/10 mRNA expression. Administration of recombinant CXCL9/10 proteins clearly counteracted the effect of ribavirin on MDSCs. In summary, this study showed that ribavirin enhanced human MDSCs differentiation in vitro, which may be attribute to the down-regulation of CXCL9/10 expression.

The Measure of DAMPs and a role for S100A8 in recruiting suppressor cells in breast cancer lung metastasis

To determine whether there was a relationship between damage associated molecular pattern molecule (DAMP) expression and recruitment of suppressor cells to sites of metastasis we measured relative expression of DAMPs, regulatory T cells (Tregs), and myeloid derived suppressor cells (MDSC) in mice at various stages of breast cancer progression using the 4T1 model. Although S100A8 was expressed at relatively low levels in the tumor cells, expression was 100-fold higher in the lung and liver which are common sites of metastasis for this tumor. Despite the relatively high level of S100A8 expression in the lungs of naïve mice, the level of expression increased further and was significantly elevated after only 7 days of tumor growth. The same pattern was observed for MDSC, and both S100A8 and MDSC expression peaked in the lungs of mice following 21 days of tumor growth. Characterization of MDSC from the lungs revealed expression of RAGE, and the cells were capable of migrating in a dose-dependent manner toward S100A8. In addition, the MDSC expressed low levels of MHC Class I, MHC Class II, CD80, and secreted TGF-β. Taken together, these data suggest that expression of S100A8 in the lungs may facilitate recruitment of MDSC, which may in turn aid in establishing a metastatic niche capable of suppressing a localized immune response.

Neuropilin-1+ regulatory T cells promote skin allograft survival and modulate effector CD4+ T cells phenotypic signature

During allograft rejection, several immune cell types, including dendritic cells, CD4(+) and CD8(+) T cells among others, recirculate between the graft and the nearest draining lymph node, resulting in immunity against the 'foreign' tissue. Regulatory CD4(+) T cells are critical for controlling the magnitude of the immune response and may act to promote or maintain tolerance. They are characterized by the expression of CD25 and Foxp3, and more recently, Neuropilin-1 (Nrp1). The role of these suppressor cells during allograft rejection is not well understood. Our work shows that during graft rejection, there is an increase in the frequency of total CD4(+) T cells expressing Nrp1, but the expression of this molecule is downregulated in the regulatory CD4(+) T-cell compartment. Interestingly, the expression of the transcription factor Eos, which renders cell function stability, is also reduced. In adoptive transfer experiments, we observed that during allograft rejection: (i) natural regulatory CD4(+) T cells maintain high levels of Nrp1 expression, (ii) effector CD4(+) T cells (Nrp1(-)) become Nrp1(+)Eos(+) and (iii) the transfer of regulatory CD4(+) T cells (Nrp1(+)) can promote allograft survival, and also enhance the gain of Nrp1 and Eos on T-effector cells. Together, these data suggest that rejection occurs, at least in part, through the loss of Nrp1 expression on regulatory CD4(+) T cells, their stability or both. Additionally, the transfer of regulatory CD4(+) T cells (based on Nrp1 expression) permits the acceptance of the allograft, placing Nrp1 as a new target for immune therapy.

An autologous leukemia cell vaccine prevents murine acute leukemia relapse after cytarabine treatment

Acute leukemias with adverse prognostic features carry a high relapse rate without allogeneic stem cell transplantation (allo-SCT). Allo-SCT has a high morbidity and is precluded for many patients because of advanced age or comorbidities. Postremission therapies with reduced toxicities are urgently needed. The murine acute leukemia model C1498 was used to study the efficacy of an intravenously administered vaccine consisting of irradiated leukemia cells loaded with the natural killer T (NKT)-cell agonist α-galactosylceramide (α-GalCer). Prophylactically, the vaccine was highly effective at preventing leukemia development through the downstream activities of activated NKT cells, which were dependent on splenic langerin(+)CD8α(+) dendritic cells and which led to stimulation of antileukemia CD4(+) and CD8(+) T cells. However, hosts with established leukemia received no protective benefit from the vaccine, despite inducing NKT-cell activation. Established leukemia was associated with increases in regulatory T cells and myeloid-derived suppressor cells, and the leukemic cells themselves were highly suppressive in vitro. Although this suppressive environment impaired both effector arms of the immune response, CD4(+) T-cell responses were more severely affected. When cytarabine chemotherapy was administered prior to vaccination, all animals in remission posttherapy were protected against rechallenge with viable leukemia cells.

From bench to bedside: immunotherapy for prostate cancer

The mainstay therapeutic strategy for metastatic castrate-resistant prostate cancer (CRPC) continues to be androgen deprivation therapy usually in combination with chemotherapy or androgen receptor targeting therapy in either sequence, or recently approved novel agents such as Radium 223. However, immunotherapy has also emerged as an option for the treatment of this disease following the approval of sipuleucel-T by the FDA in 2010. Immunotherapy is a rational approach for prostate cancer based on a body of evidence suggesting these cancers are inherently immunogenic and, most importantly, that immunological interventions can induce protective antitumour responses. Various forms of immunotherapy are currently being explored clinically, with the most common being cancer vaccines (dendritic-cell, viral, and whole tumour cell-based) and immune checkpoint inhibition. This review will discuss recent clinical developments of immune-based therapies for prostate cancer that have reached the phase III clinical trial stage. A perspective of how immunotherapy could be best employed within current treatment regimes to achieve most clinical benefits is also provided.

Molecular mimicry and clonal deletion: A fresh look

In this article, I trace the historic background of clonal deletion and molecular mimicry, two major pillars underlying our present understanding of autoimmunity and autoimmune disease. Clonal deletion originated as a critical element of the clonal selection theory of antibody formation in order to explain tolerance of self. If we did have complete clonal deletion, there would be major voids, the infamous "black holes", in our immune repertoire. For comprehensive, protective adaptive immunity, full deletion is necessarily a rare event. Molecular mimicry, the sharing of epitopes among self and non-self antigens, is extraordinary common and provides the evidence that complete deletion of self-reactive clones is rare. If molecular mimicry were not common, protective adaptive immunity could not be all-encompassing. By taking a fresh look at these two processes together we can envision their evolutionary basis and understand the need for regulatory devices to prevent molecular mimicry from progressing to autoimmune disease.

Genetic engineering of hematopoiesis for targeted IFN-α delivery inhibits breast cancer progression

The immunosuppressive tumor microenvironment represents a major hurdle to cancer therapy. We developed a gene transfer strategy into hematopoietic stem cells (HSCs) to target transgene expression to tumor-infiltrating monocytes/macrophages. Using a combination of transcriptional and microRNA-mediated control, we achieved selective expression of an interferon-α (IFN-α) transgene in differentiated monocytes of human hematochimeric mice. We show that IFN-α transgene expression does not impair engraftment and long-term multilineage repopulation of NSG (NOD/LtSz-scidIL2Rγ(null)) mice by transplanted human HSCs. By providing a source of human cytokines in the mice, we improved the functional reconstitution of human myeloid, natural killer, and T cell lineages, and achieved enhanced immune-mediated clearance of transplanted human breast tumors when hematopoiesis was engineered for tumor-targeted IFN-α expression. By applying our strategy to mouse breast cancer models, we achieved inhibition of tumor progression and experimental metastases in an autologous setting, likely through enhanced generation of effector T cells and their recruitment to the neoplastic tissues. By forcing IFN-α expression in tumor-infiltrating macrophages, we blunted their innate protumoral activity and reprogrammed the tumor microenvironment toward more effective dendritic cell activation and immune effector cell cytotoxicity. Overall, our studies validate the feasibility, safety, and therapeutic potential of a new cancer gene therapy strategy, and open the way to test this approach as adjuvant therapy in advanced breast cancer patients.

Vaccine-elicited CD8+ T cells cure mesothelioma by overcoming tumor-induced immunosuppressive environment

Eradicating malignant tumors by vaccine-elicited host immunity remains a major medical challenge. To date, correlates of immune protection remain unknown for malignant mesothelioma. In this study, we demonstrated that antigen-specific CD8(+) T-cell immune response correlates with the elimination of malignant mesothelioma by a model PD-1-based DNA vaccine. Unlike the nonprotective tumor antigen WT1-based DNA vaccines, the model vaccine showed complete and long-lasting protection against lethal mesothelioma challenge in immunocompetent BALB/c mice. Furthermore, it remained highly immunogenic in tumor-bearing animals and led to therapeutic cure of preexisting mesothelioma. T-cell depletion and adoptive transfer experiments revealed that vaccine-elicited CD8(+) T cells conferred to the protective efficacy in a dose-dependent way. Also, these CD8(+) T cells functioned by releasing inflammatory IFNγ and TNFα in the vicinity of target cells as well as by initiating TRAIL-directed tumor cell apoptosis. Importantly, repeated DNA vaccinations, a major advantage over live-vectored vaccines with issues of preexisting immunity, achieve an active functional state, not only preventing the rise of exhausted PD-1(+) and Tim-3(+) CD8(+) T cells but also suppressing tumor-induced myeloid-derived suppressive cells and Treg cells, with the frequency of antigen-specific CD8(+) T cells inversely correlating with tumor mass. Our results provide new insights into quantitative and qualitative requirements of vaccine-elicited functional CD8(+) T cells in cancer prevention and immunotherapy.

Dissecting the regulatory microenvironment of a large animal model of non-Hodgkin lymphoma: evidence of a negative prognostic impact of FOXP3+ T cells in canine B cell lymphoma

The cancer microenvironment plays a pivotal role in oncogenesis, containing a number of regulatory cells that attenuate the anti-neoplastic immune response. While the negative prognostic impact of regulatory T cells (Tregs) in the context of most solid tissue tumors is well established, their role in lymphoid malignancies remains unclear. T cells expressing FOXP3 and Helios were documented in the fine needle aspirates of affected lymph nodes of dogs with spontaneous multicentric B cell lymphoma (BCL), proposed to be a model for human non-Hodgkin lymphoma. Multivariable analysis revealed that the frequency of lymph node FOXP3⁺ T cells was an independent negative prognostic factor, impacting both progression-free survival (hazard ratio 1.10; p = 0.01) and overall survival (hazard ratio 1.61; p = 0.01) when comparing dogs showing higher than the median FOXP3 expression with those showing the median value of FOXP3 expression or less. Taken together, these data suggest the existence of a population of Tregs operational in canine multicentric BCL that resembles thymic Tregs, which we speculate are co-opted by the tumor from the periphery. We suggest that canine multicentric BCL represents a robust large animal model of human diffuse large BCL, showing clinical, cytological and immunophenotypic similarities with the disease in man, allowing comparative studies of immunoregulatory mechanisms.

A clinical perspective on the role of chronic inflammation in gastrointestinal cancer

Chronic inflammation has been identified as an important risk factor for the development of malignancy, and knowledge about its molecular and cellular mechanisms is increasing. Several chronic inflammatory diseases of the gastrointestinal tract are important as risk factors for malignancy and have been studied in detail. In this review, we summarize important molecular mechanisms in chronic inflammation and highlight established and potential links between chronic inflammation and gastrointestinal cancer. In addition, we present the role of chronic inflammation in numerous tumors within the gastrointestinal tract as well as the relevant pathways or epidemiologic observations linking the pathogenesis of these tumors to inflammation.

Human cell-based artificial antigen-presenting cells for cancer immunotherapy

Adoptive T-cell therapy, where anti-tumor T cells are first prepared in vitro, is attractive since it facilitates the delivery of essential signals to selected subsets of anti-tumor T cells without unfavorable immunoregulatory issues that exist in tumor-bearing hosts. Recent clinical trials have demonstrated that anti-tumor adoptive T-cell therapy, i.e. infusion of tumor-specific T cells, can induce clinically relevant and sustained responses in patients with advanced cancer. The goal of adoptive cell therapy is to establish anti-tumor immunologic memory, which can result in life-long rejection of tumor cells in patients. To achieve this goal, during the process of in vitro expansion, T-cell grafts used in adoptive T-cell therapy must be appropriately educated and equipped with the capacity to accomplish multiple, essential tasks. Adoptively transferred T cells must be endowed, prior to infusion, with the ability to efficiently engraft, expand, persist, and traffic to tumor in vivo. As a strategy to consistently generate T-cell grafts with these capabilities, artificial antigen-presenting cells have been developed to deliver the proper signals necessary to T cells to enable optimal adoptive cell therapy.

Lysosomal acid lipase is critical for myeloid-derived suppressive cell differentiation, development, and homeostasis

Lysosomal acid lipase (LAL) cleaves cholesteryl esters (CE) and triglycerides (TG) to generate cholesterol and free fatty acid in lysosomes of cells. The downstream metabolic products of fatty acids are ligands for activation of peroxisome proliferator-activated receptor gamma (PPARγ). Accumulation of CEs and TGs is resulted from lack of functional LAL in lysosomes of cells, especially in myeloid cells. One characteristic phenotype in LAL knock-out (lal-/-) mice is systemic elevation of myeloid-derived suppressive cells (MDSCs). MDSCs infiltrate into multiple distal organs, alter T cell development, and suppress T cell proliferation and lymphokine production in lal-/- mice, which lead to severe pathogeneses in multiple organs. The gene transcriptional profile analysis in MDSCs from the bone marrow has identified multiple defects responsible for MDSCs malformation and malfunction in lal-/- mice, including G protein signaling, cell cycles, glycolysis metabolism, mitochondrial bioenergetics, mTOR pathway etc. In a separate gene transcriptional profile analysis in the lung of lal-/- mice, matrix metalloproteinase 12 (MMP12) and apoptosis inhibitor 6 (Api6) are highly overexpressed due to lack of ligand synthesis for PPARγ. PPARγ negatively regulates MMP12 and Api6. Blocking the PPAR signaling by overexpression of a dominant negative PPARγ (dnPPARγ) form, or overexpressing MMP12 or Api6 in myeloid or lung epithelial cells in inducible transgenic mouse models results in elevated MDSCs and inflammation-induced tumorigenesis. These studies demonstrate that LAL and its downstream effectors are critical for MDSCs development, differentiation and malfunction.

Sweet escape: sialic acids in tumor immune evasion

Sialic acids represent a family of sugar molecules derived from neuraminic acid that frequently terminate glycan chains and contribute to many biological processes. Already five decades ago, aberrantly high expression of sialic acids has been proposed to protect cancer cells from recognition and eradication by the immune system. Today, increased understanding at the molecular level demonstrates the broad immunomodulatory capacity of tumor-derived sialic acids that is, at least in part, mediated through interactions with immunoinhibitory Siglec receptors. Here we will review current studies from a sialic acid sugar perspective showing that tumor-derived sialic acids disable major killing mechanisms of effector immune cells, trigger production of immune suppressive cytokines and dampen activation of antigen-presenting cells and subsequent induction of anti-tumor immune responses. Furthermore, strategies to modulate sialic acid expression in cancer cells to improve cancer immunotherapy will be discussed.

Systemic Platelet-activating Factor Receptor Activation Augments Experimental Lung Tumor Growth and Metastasis

Pro-oxidative stressors including cigarette smoke (CS) generate novel lipids with platelet-activated factor-receptor (PAF-R) agonistic activity mediate systemic immunosuppression, one of the most recognized events in promoting carcinogenesis. Our previous studies have established that these oxidized-PAF-R-agonists augment murine B16F10 melanoma tumor growth in a PAF-R-dependent manner because of its effects on host immunity. As CS generates PAF-R agonists, the current studies sought to determine the impact of PAF-R agonists on lung cancer growth and metastasis. Using the murine Lewis Lung Carcinoma (LLC1) model, we demonstrate that treatment of C57BL/6 mice with a PAF-R agonist augments tumor growth and lung metastasis in a PAF-R-dependent manner as these findings were not seen in PAF-R-deficient mice. Importantly, this effect was because of host rather than tumor cells PAF-R dependent as LLC1 cells do not express functional PAF-R. These findings indicate that experimental lung cancer progression can be modulated by the PAF system.

Immune consequences of kinase inhibitors in development, undergoing clinical trials and in current use in melanoma treatment

Metastatic malignant melanoma is a frequently fatal cancer. In recent years substantial therapeutic progress has occurred with the development of targeted kinase inhibitors and immunotherapeutics. Targeted therapies often result in rapid clinical benefit however responses are seldom durable. Immune therapies can result in durable disease control but responses may not be immediate. Optimal cancer therapy requires both rapid and durable cancer control and this can likely best be achieved by combining targeted therapies with immunotherapeutics. To achieve this, a detailed understanding of the immune consequences of the various kinase inhibitors, in development, clinical trial and currently used to treat melanoma is required.

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.

Ultrasound induced cancer immunotherapy

Recently, the use of ultrasound (US) has been shown to have potential in cancer immunotherapy. High intensity focused US destruction of tumors may lead to immunity forming in situ in the body by immune cells being exposed to the tumor debris and immune stimulatory substances that are present in the tumor remains. Another way of achieving anti-cancer immune responses is by using US in combination with microbubbles and nanobubbles to deliver genes and antigens into cells. US leads to bubble destruction and the forces released to direct delivery of the substances into the cytoplasm of the cells thus circumventing the natural barriers. In this way tumor antigens and antigen-encoding genes can be delivered to immune cells and immune response stimulating genes can be delivered to cancer cells thus enhancing immune responses. Combination of bubbles with cell-targeting ligands and US provides an even more sophisticated delivery system whereby the therapy is not only site specific but also cell specific. In this review we describe how US has been used to achieve immunity and discuss the potential and possible obstacles in future development.

Clinical impact of tumor-infiltrating inflammatory cells in primary small cell esophageal carcinoma

Primary small cell esophageal carcinoma is a rare and aggressive type of gastrointestinal cancer with poor prognosis. In the present study, the impact of tumour infiltrating inflammatory cells on clinico-pathological characteristics and the patients' prognosis were analysed. A total of 36 small cell esophageal carcinomas, 19 adjacent normal tissues and 16 esophageal squamous cell carcinoma samples were collected. Qualified pathologists examined eosinophils, neutrophils, lymphocytes and macrophages on histochemical slides. The infiltration of eosinophils and macrophages in small cell esophageal carcinoma was significantly increased as compared with tumor adjacent normal tissues, and was significantly less in esophageal squamous cell carcinoma. Macrophage count was significantly associated with (p = 0.015) lymph node-stage in small cell esophageal carcinoma. When we grouped patients into two groups by counts of infiltrated inflammatory cells, Kaplan-Meier analysis revealed that high macrophage infiltration group (p = 0.004) and high eosinophil infiltration group (p = 0.027) had significantly enhanced survival. In addition, multivariate analysis unveiled that eosinophil count (p = 0.002) and chemotherapy (Yes vs. No, p = 0.001) were independent prognostic indicators. Taken together, infiltration of macrophages and eosinophils into the solid tumor appear to be important in the progression of small cell esophageal carcinoma and patients' prognosis.

Effects of gastric cancer cells on the differentiation of Treg cells

The aim of this study was evaluated the prevalence of Treg cells in peripheral blood in patients with gastric cancer, and investigate the effect of gastric cancer cells on their differentiation. ELISA was employed to assess the concentrations of TGF-β and IL-10 in gastric cancer patients' serum. Then, mouse gastric cancer cells were co-cultured with T lymphocytes or T lymphocytes + anti-TGF-β. Flow cytometric analysis and RT-PCR were then performed to detect Treg cells and TGF-β and IL-10 expression in gastric cancer cells. Our data showed that the expression of TGF-β and IL-10 in the patients with gastric cancer was increased compared to the case with healthy donors. The population of Treg cells and the expression levels of TGF-β and IL-10 in the co-culture group were much higher than in the control group (18.6% vs 9.5%) (P<0.05). Moreover, the population of Treg cells and the expression levels of TGF-β and IL-10 in the co-culture systerm were clearly decreased after addition of anti-TGF-β (7.7% vs 19.6%) (P<0.01). In conclusion, gastric cancer cells may induce Treg cell differentiation through TGF-β, and further promote immunosuppression.

Deletion of CD24 impairs development of heat shock protein gp96-driven autoimmune disease through expansion of myeloid-derived suppressor cells

CD24 binds to and suppresses inflammation triggered by danger-associated molecular patterns such as heat shock proteins (HSPs) and high-mobility group box 1. Paradoxically, CD24 has been shown to enhance autoimmune disease. In this study, we attempt to reconcile this paradox by deletion of CD24 (24KO) in a lupus-like disease model driven by forced expression of HSP gp96 at the cell surface (transgenic mice [tm]). As expected, tm24KO mice showed increased CD11c(+) dendritic cell activation coupled to a significant increase in dendritic cell-specific IL-12 production compared with tm mice. However, tm24KO mice showed less CD4 T cell activation and peripheral inflammatory cytokine production in comparison with tm mice. We characterized an enhanced immune suppressive milieu in tm24KO mice distinguished by increased TGF-β and greater regulatory T cell-suppressive capacity. We found greater absolute numbers of myeloid-derived suppressor cells (MDSCs) in tm24KO mice and showed that the Ly6C(+) MDSC subset had greater suppressive capacity from tm24KO mice. Deletion of CD24 in tm mice led to diminished lupus-like pathology as evidenced by anti-nuclear Ab deposition and glomerulonephritis. Finally, we show that expanded MDSC populations were mediated by increased free high-mobility group box 1 in tm24KO mice. Thus, the deletion of CD24 in an HSP-driven model of autoimmunity led to the unexpected development of regulatory T cell and MDSC populations that augmented immune tolerance. Further study of these populations as possible negative regulators of inflammation in the context of autoimmunity is warranted.

A phase ΙI study of five peptides combination with oxaliplatin-based chemotherapy as a first-line therapy for advanced colorectal cancer (FXV study)

BACKGROUND

We previously conducted a phase I trial for advanced colorectal cancer (CRC) using five HLA-A*2402-restricted peptides, three derived from oncoantigens and two from vascular endothelial growth factor (VEGF) receptors, and confirmed safety and immunological responses. To evaluate clinical benefits of cancer vaccination treatment, we conducted a phase II trial using the same peptides in combination with oxaliplatin-based chemotherapy as a first-line therapy.

METHODS

The primary objective of the study was the response rates (RR). Progression free survival (PFS), overall survival (OS), and immunological parameters were evaluated as secondary objective. The planned sample size was more than 40 patients for both HLA2402-matched and -unmatched groups. All patients received a cocktail of five peptides (3 mg each) mixed with 1.5 ml of IFA which was subcutaneously administered weekly for the first 12 weeks followed by biweekly administration. Presence or absence of the HLA-A*2402 genotype were used for classification of patients into two groups.

RESULTS

Between February 2009 and November 2012, ninety-six chemotherapy naïve CRC patients were enrolled under the masking of their HLA-A status. Ninety-three patients received mFOLFOX6 and three received XELOX. Bevacizumab was added in five patients. RR was 62.0% and 60.9% in the HLA-A*2402-matched and -unmatched groups, respectively (p=0.910). The median OS was 20.7 months in the HLA-A*2402-matched group and 24.0 months in the unmatched group (log-rank, p=0.489). In subgroup with a neutrophil/lymphocyte ratio (NLR) of <3.0, patients in the HLA-matched group did not survive significantly longer than those in the unmatched group (log-rank, p=0.289) but showed a delayed response.

CONCLUSIONS

Although no significance was observed for planned statistical efficacy endpoints, a delayed response was observed in subgroup with a NLR of <3.0. Biomarkers such as NLR might be useful for selecting patients with a better treatment outcome by the vaccination.

TRIAL REGISTRATION

Trial registration: UMIN000001791.