Increased CD14(+)HLA-DR (-/low) myeloid-derived suppressor cells correlate with extrathoracic metastasis and poor response to chemotherapy in non-small cell lung cancer patients

A circulating subpopulation of monocytic myeloid-derived suppressor cells as an independent prognostic/predictive factor in untreated non-small lung cancer patients

Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of cells with immunosuppressive properties and might confer to worse prognosis in cancer patients. The presence of phenotypically newly described subpopulations of MDSCs and their association with the clinical outcome were investigated in non-small cell lung cancer (NSCLC) patients. The percentages and correlation between MDSCs and distinct immune cells in the peripheral blood of 110 chemotherapy-naive patients before treatment and healthy controls were investigated using flow cytometry. Two monocytic [CD14(+)CD15(-)CD11b(+)CD33(+)HLA-DR(-)Lin(-) and CD14(+)CD15(+)CD11b(+)CD33(+)HLA-DR(-)Lin(-)] and a granulocytic [CD14(-)CD15(+)CD11b(+)CD33(+)HLA-DR(-)Lin(-)] subpopulations of MDSCs were identified, expressing inducible nitric oxide synthase, and reactive oxygen species, respectively. Increased percentages of both monocytic-MDSCs' subpopulations were inversely correlated to dendritic/monocyte levels (P ≤ 0.04), while granulocytic-MDSCs were inversely correlated to CD4(+) T cells (P = 0.006). Increased percentages of monocytic-MDSCs were associated with worse response to treatment (P = 0.02) and patients with normal levels of CD14(+)CD15(+)CD11b(+)CD33(+)HLA-DR(-)Lin(-) had longer overall survival and progression free-survival compared to those with high levels (P = 0.008 and P = 0.005, resp.). Multivariate analysis revealed that the increased percentages of CD14(+)CD15(+)CD11b(+)CD33(+)HLA-DR(-)Lin(-) MDSCs were independently associated with decreased progression free-survival and overall survival. The data provide evidence that increased percentages of new monocytic-MDSCs' subpopulations in advanced NSCLC patients are associated with an unfavourable clinical outcome.

Myeloid-derived suppressor cells regulate immune response in patients with chronic hepatitis B virus infection through PD-1-induced IL-10

Although myeloid-derived suppressor cells (MDSCs) are well known for their immunosuppressive function in several pathological conditions, the role of MDSCs in hepatitis B virus infection remains obscure. In this study, we investigated the frequency and function of MDSCs in the peripheral blood and liver of 91 chronic hepatitis B (CHB) patients. A higher percentage of MDSCs, defined as CD14(+)HLA-DR(-/low), was detected in peripheral blood of CHB patients than that of the healthy controls. Moreover, high expression of programmed death 1 (PD-1) and secretion of IL-10 in this population were determined. The frequency of MDSCs was positively correlated with serum viral load, but it was negatively correlated with liver inflammatory injury. These cells were also abundant in liver tissue of CHB patients and were related to necroinflammatory activity. Furthermore, we found that these cells could suppress hepatitis B virus-specific CD8(+) T cell response, including reduced proliferation and IFN-γ production, and inhibit degranulation of CD8(+) T cells, including reduced production of granzyme B and perforin. Importantly, PD-1-induced IL-10 production by MDSCs was responsible for the suppressive activity. To our knowledge, for the first time our study proved that CD14(+)HLA-DR(-/low)PD-1(+) MDSCs in CHB patients contribute to an inadequate immune response against the virus and lead to chronic infection, which represents a potential target for therapeutic intervention.

Regulation of tumor metastasis by myeloid-derived suppressor cells

Accumulation of pathologically activated immature myeloid cells with potent immune-suppressive activity is one of the major immunological hallmarks of cancer. In recent years, it became clear that in addition to their immune-suppressive activity, myeloid-derived suppressor cells (MDSCs) influence tumor progression in a variety of ways. They are directly implicated in the promotion of tumor metastases by participating in the formation of premetastatic niches, promoting angiogenesis and tumor cell invasion. In this review, we discuss recent data describing various roles of MDSCs in the formation of tumor metastases.

The preoperative lymphocyte to monocyte ratio predicts clinical outcomes in patients with stage II/III gastric cancer

Recently, lymphocyte to monocyte ratio (LMR) has been reported to be associated with clinical outcomes in some types of cancer but has not been explored in gastric cancer. In this study, we analyzed the association between LMR and clinical outcomes in stage II/III gastric cancer patients. Preoperative LMR calculated from peripheral lymphocyte and monocyte with corresponding clinical features from 426 stage II/III gastric cancer patients was noted. Kaplan-Meier method and Cox regression model were applied for overall survival (OS) and recurrence-free survival (RFS). Related with smaller tumor size (p<0.001), increased LMR could predict better OS [hazard ratio (HR), 0.688; 95% confidence interval (CI), 0.521-0.908, p=0.008] and was borderline significantly associated with better RFS (HR, 0.775; 95% CI, 0.592-1.01, p=0.06) in stage II/III gastric cancer patients through multivariable analysis. Subgroup analyses revealed that except stage III patients for RFS which yielded borderline significance (p=0.052), lower LMR was associated with poor clinical outcomes for patients regardless of different stages or whether the patients received adjuvant chemotherapy. The elevated preoperative LMR level was a significant favorable factor in the prognosis of stage II/III gastric cancer patients, especially for those with stage II. However, further validation of our findings is warranted.

Computational algorithm-driven evaluation of monocytic myeloid-derived suppressor cell frequency for prediction of clinical outcomes

Evaluation of myeloid-derived suppressor cells (MDSC), a cell type implicated in T-cell suppression, may inform immune status. However, a uniform methodology is necessary for prospective testing as a biomarker. We report the use of a computational algorithm-driven analysis of whole blood and cryopreserved samples for monocytic MDSC (m-MDSC) quantity that removes variables related to blood processing and user definitions. Applying these methods to samples from patients with melanoma identifies differing frequency distribution of m-MDSC relative to that in healthy donors. Patients with a pretreatment m-MDSC frequency outside a preliminary definition of healthy donor range (<14.9%) were significantly more likely to achieve prolonged overall survival following treatment with ipilimumab, an antibody that promotes T-cell activation and proliferation. m-MDSC frequencies were inversely correlated with peripheral CD8(+) T-cell expansion following ipilimumab. Algorithm-driven analysis may enable not only development of a novel pretreatment biomarker for ipilimumab therapy, but also prospective validation of peripheral blood m-MDSCs as a biomarker in multiple disease settings.

Tumour-induced immune suppression: role of inflammatory mediators released by myelomonocytic cells

Tumour-induced immune dysfunction is a serious challenge to immunotherapy for cancer, and intact adaptive and innate cellular immunity is key to its success. Myelomonocytic cells have a central role in this immune suppression, and tumour-associated macrophages, eosinophils, neutrophils and myeloid-derived suppressor cells have all been shown to be of major importance. These myelomonocytic cells secrete a broad repertoire of inflammatory mediators providing them with powerful tools to inhibit tumour-reactive T cells and natural killer cells; free oxygen radicals including reactive oxygen species and NO, arginase, indoleamine 2,3-dioxygenase, prostaglandins, the pro-inflammatory heterodimer S100A8/9 and cytokines, such as granulocyte-macrophage colony-stimulating factor and transforming growth factor-β, have proven particularly potent in suppressing antitumour cellular immunity. Determining which of these factors prevail in individual cancer patients and designing methods aimed at neutralization or inhibition of their effects on target tissues have the potential to greatly enhance the clinical efficacy of immunotherapy.

Myeloid regulatory cells in tumor spreading and metastasis

Development of metastasis is determined by both the accretion of essential changes in cancerous cells and by their communications with different stromal elements in the tumor microenvironment. Specifically, inflammatory response and emergence of immune regulatory cells, such and myeloid regulatory cells (macrophages, dendritic cells, neutrophils, myeloid-derived suppressor cells) and lymphoid regulatory cells (regulatory T, B and NK cells) to the tumor site have been reported to support tumor growth in addition to spreading and metastasis. Every phase of tumor progression, from its initiation through metastatic expansion, is endorsed by interaction between malignant and immune cells mediated by a number of growth factors, cytokines, proteases and other molecules that modify the tumor microenvironment. Invasion and metastasis depend on intratumoral vascularization, alterations of the basement membrane and degradation of the extracellular matrix for tumor cell spreading, invasion and extravasation into the blood and lymphatic vessels. The consequent dissemination of cancerous cells to distant tissues and organs necessitates a trafficking through the vasculature, which is promoted by further interactions with cells of the immune system, including myeloid regulatory cells. Moreover, the formation of the pre-metastatic niche and specific metastasis organ tropism is also regulated and controlled by bone marrow-derived hematopoietic immune progenitor cells, immature myeloid cells and certain cytokines, chemokines and growth factors derived from tumor and immune cells, which amend the local microenvironment of the organ or tissue to promote adhesion and survival of circulating cancerous cells. Although the potential role for myeloid regulatory cells in tumor spreading and development of pre-metastatic niche has been suggested, the concept still requires further supportive experimental and clinical data, as well as data related to specific factors and mechanisms responsible for myeloid regulatory cell functioning at malignant sites.

Molecular pathways: myeloid complicity in cancer

Cancer-induced inflammation results in accumulation of myeloid cells. These myeloid cells include progenitors and progeny of monocytes, granulocytes, macrophages, and dendritic cells. It has become increasingly evident that tumor-dependent factors can condition myeloid cells toward an immunosuppressive and protumorigenic phenotype. Thus, myeloid cells are not simply bystanders in malignancy or barometers of disease burden. Reflecting their dynamic and plastic nature, myeloid cells manifest a continuum of cellular differentiation and are intimately involved at all stages of neoplastic progression. They can promote tumorigenesis through both immune-dependent and -independent mechanisms and can dictate response to therapies. A greater understanding of the inherent plasticity and relationships among myeloid subsets is needed to inform therapeutic targeting. New clinical trials are being designed to modulate the activities of myeloid cells in cancer, which may be essential to maximize the efficacy of both conventional cytotoxic and immune-based therapies for solid tumors. Clin Cancer Res; 20(20); 5157-70. ©2014 AACR.

Mapping the immunosuppressive environment in uterine tumors: implications for immunotherapy

The major hurdle for cancer vaccines to be effective is posed by tumor immune evasion. Several common immune mechanisms and mediators are exploited by tumors to avoid immune destruction. In an attempt to shed more light on the immunosuppressive environment in uterine tumors, we analyzed the presence of PD-L1, PD-L2, B7-H4, indoleamine 2,3-dioxygenase (IDO), galectin-1, galectin-3, arginase-1 activity and myeloid-derived suppressor cell (MDSC) infiltration. IDO, PD-L1, PD-L2 and B7-H4 were analyzed by immunohistochemistry. PD-L2 was mostly expressed at low levels in these tumors. We found high IDO expression in 21 % of endometrial carcinoma samples and in 14 % of uterine sarcoma samples. For PD-L1 and B7-H4, we found high expression in 92 and 90 % of endometrial cancers, respectively, and in 100 and 92 % of the sarcomas. Galectin-1 and 3 were analyzed in tissue lysates by ELISA, but we did not find an increase in both molecules in tumor lysates compared with benign tissues. We detected expression of galectin-3 by fibroblasts, immune cells and tumor cells in single-cell tumor suspensions. In addition, we noted a highly significant increase in arginase-1 activity in endometrial carcinomas compared with normal endometria, which was not the case for uterine sarcomas. Finally, we could demonstrate MDSC infiltration in fresh tumor suspensions from uterine tumors. These results indicate that the PD-1/PD-L1 interaction and B7-H4 could be possible targets for immune intervention in uterine cancer patients as well as mediation of MDSC function. These observations are another step toward the implementation of inhibitors of immunosuppression in the treatment of uterine cancer patients.

Cancer Vaccines in the World of Immune Suppressive Monocytes (CD14(+)HLA-DR(lo/neg) Cells): The Gateway to Improved Responses

Dendritic cells are an important target in cancer immunotherapy based on their critical role in antigen presentation and response to tumor development. The capacity of dendritic cells to stimulate anti-tumor immunity has led investigators to use these cells to mediate anti-tumor responses in a number of clinical trials. However, these trials have had mixed results. The typical method for generation of ex vivo dendritic cells starts with the purification of CD14(+) cells. Our studies identified a deficiency in the ability to generate mature dendritic cell using CD14(+) cells from cancer patients that corresponded with an increased population of monocytes with altered surface marker expression (CD14(+)HLA-DR(lo/neg)). Further studies identified systemic immune suppression and increased concentrations of CD14(+)HLA-DR(lo/neg) monocytes capable of inhibiting T-cell proliferation and DC maturation. Together, these findings strongly suggest that protocols aimed at immune stimulation via monocytes/dendritic cells, if optimized on normal monocytes or in systems without these suppressive monocytes, are unlikely to engender effective DC maturation in vitro or efficiently trigger DC maturation in vivo. This highlights the importance of developing optimal protocols for stimulating DCs in the context of significantly altered monocyte phenotypes often seen in cancer patients.

Myeloid-derived suppressor cells in cancer: therapeutic, predictive, and prognostic implications

Immune evasion is a hallmark of cancer. While there are multiple different mechanisms that cancer cells employ, myeloid-derived suppressor cells (MDSCs) are one of the key drivers of tumor-mediated immune evasion. MDSCs begin as myeloid cells recruited to the tumor microenvironment, where they are transformed into potent immunosuppressive cells. However, our understanding of the clinical relevance of MDSCs in cancer patients has significantly lagged behind the preclinical literature in part due to the absence of a cognate molecule present in mice, as well as to the considerable heterogeneity of MDSCs. However, if one evaluates the clinical literature through the filter of clinically robust endpoints, such as overall survival, three important phenotypes emerge: promyelocytic, monocytic, and granulocytic. Based on these studies, MDSCs have clear prognostic importance in multiple solid tumors, and emerging data support the utility of circulating MDSCs as a predictive marker for cancer immunotherapy, and even as an early leading marker for predicting clinical response to systemic chemotherapy in patients with advanced solid tumors. More recent preclinical data in immunosuppressed murine models suggest that MDSCs play an important role in tumor progression and the metastatic process that is independent of their immunosuppressive properties. Consequently, targeting MDSCs either in combination with cancer immunotherapy or independently as part of an approach to inhibit the metastatic process appears to be a very clinically promising strategy. We review different approaches to target MDSCs that could potentially be tested in future clinical trials in cancer patients.

Breaking immunotolerance of tumors: a new perspective for dendritic cell therapy

The use of dendritic cells (DC) in cancer immunotherapy is based on their potent abilities to present antigens, so they can act as 'natural adjuvants' to enhance immunogenicity of tumor antigens and stimulate specific cytotoxic T-cells. Large amounts of DC can be generated from bone marrow, neonatal cord blood, and peripheral blood CD34(+) hematopoietic stem cells, or from peripheral blood monocytes. The DC can then be pulsed with tumor antigens and re-infused. In vitro, antigen-pulsed DC can stimulate allogeneic T-cell proliferation and induction of autologous specific cytotoxic T-cells; in vivo, the cells inhibit the growth of tumors or protect hosts (i.e. mice) from development of inoculated tumors. The results of preliminary clinical trials have shown that DC vaccines are safe and elicit immune responses; however, the rates of clinical responses are low. It has become quite clear that one key reason for unsatisfactory clinical results is tumor-induced immunosuppression. Among the factors contributing to this type of immunosuppression are populations of regulatory cells including: T-regulatory (T(reg)) cells, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), and DC expressing 2,3-dioxygenase indoleamine (IDO-DC). This review presents an overview of the current understanding about populations of regulatory cells and the most current research efforts directed to overcome immunosuppressive activity due to the tumor microenvironment.

New Approaches in Immunotherapy for the Treatment of Lung Cancer

Despite the several advances in the last few years into treatment of advanced lung cancer, the 5-year survival remains extremely low. New therapeutic strategies are currently under investigation, and immunotherapy seems to offer a promising treatment alternative. In the last decade, therapeutic cancer vaccines in lung cancer have been rather disappointing, mainly due to the lack of efficient predictive biomarkers. A better refinement of the patient population that might respond to treatment might finally lead to a success story. For the first time, the immune checkpoint inhibitors are demonstrating sustained antitumor response and improved survival and they may be the first immunotherapeutics available for patients with lung cancer.

The proportion and function of peripheral myeloid-derived suppressor cells do not correlate with systemic inflammation in chronic obstructive pulmonary disease

Myeloid-derived suppressor cells (MDSC) have been implicated in the regulation of chronic inflammation. Chronic obstructive pulmonary disease (COPD) involves persistent inflammation, but the role of MDSC has not been explored. Here, proportions of MDSC (CD14(-)HLA-DR(-)CD33(+)CD11b(+) cells) were quantified in peripheral blood mononuclear cells (PBMC) isolated from patients with 'stable' COPD (n = 12), smokers with no evidence of COPD (n = 11) and healthy non-smokers (n = 11). The proportions of MDSC were similar in all groups. MDSC function was assessed by comparing T-cell and cytokine responses of whole and MDSC-depleted PBMC stimulated with Staphylococcus enterotoxin-B (SEB). Depletion of MDSC did not enhance CD4(+) or CD8(+) T-cell activation and proliferation, or alter IFNγ and IL-17 production in response to SEB. However production of TGFβ decreased after depletion of MDSC, so MDSC may be a source of this cytokine. In conclusion, COPD was not associated with perturbations in the proportion or function of MDSC in peripheral blood.