A clinical and biological perspective of human myeloid-derived suppressor cells in cancer

Common biological processes and mutual crosstalk mechanisms between cardiovascular disease and cancer

Cancer and cardiovascular disease (CVD) are leading causes of mortality and thus represent major health challenges worldwide. Clinical data suggest that cancer patients have an increased likelihood of developing cardiovascular disease, while epidemiologic studies have shown that patients with cardiovascular disease are also more likely to develop cancer. These observations underscore the increasing importance of studies exploring the mechanisms underlying the interaction between the two diseases. We review their common physiological processes and potential pathophysiological links. We explore the effects of chronic inflammation, oxidative stress, and disorders of fatty acid metabolism in CVD and cancer, and also provide insights into how cancer and its treatments affect heart health, as well as present recent advances in reverse cardio-oncology using a new classification approach.

Management of a Patient with Cardiovascular Disease Should Include Assessment of Primary and Secondary Immunodeficiencies: Part 2-Secondary Immunodeficiencies

BACKGROUND

Cardiovascular diseases are among the most common chronic diseases, generating high social and economic costs. Secondary immunodeficiencies occur more often than primary ones and may result from the co-occurrence of specific diseases, treatment, nutrient deficiencies and non-nutritive bio-active compounds that result from the industrial nutrient practices.

OBJECTIVES

The aim of this article is to present selected secondary immunodeficiencies and their impact on the cardiovascular system.

RESULTS

The treatment of a patient with cardiovascular disease should include an assess-ment for immunodeficiencies, because the immune and cardiovascular systems are closely linked.

CONCLUSIONS

Immune system dysfunctions can significantly affect the course of cardiovascular diseases and their treatment. For this reason, comprehensive care for a patient with cardiovascular disease requires taking into account potential immunodeficiencies, which can have a significant impact on the patient's health.

Study on the mechanism of MDSC-platelets and their role in the breast cancer microenvironment

Myeloid-derived suppressor cells (MDSCs) are key immunosuppressive cells in the tumor microenvironment (TME) that play critical roles in promoting tumor growth and metastasis. Tumor-associated platelets (TAPs) help cancer cells evade the immune system and promote metastasis. In this paper, we describe the interaction between MDSCs and TAPs, including their generation, secretion, activation, and recruitment, as well as the effects of MDSCs and platelets on the generation and changes in the immune, metabolic, and angiogenic breast cancer (BC) microenvironments. In addition, we summarize preclinical and clinical studies, traditional Chinese medicine (TCM) therapeutic approaches, and new technologies related to targeting and preventing MDSCs from interacting with TAPs to modulate the BC TME, discuss the potential mechanisms, and provide perspectives for future development. The therapeutic strategies discussed in this review may have implications in promoting the normalization of the BC TME, reducing primary tumor growth and distant lung metastasis, and improving the efficiency of anti-tumor therapy, thereby improving the overall survival (OS) and progression-free survival (PFS) of patients. However, despite the significant advances in understanding these mechanisms and therapeutic strategies, the complexity and heterogeneity of MDSCs and side effects of antiplatelet agents remain challenging. This requires further investigation in future prospective cohort studies.

Myeloid-derived suppressor cells and tolerogenic dendritic cells are distinctively induced by PI3K and Wnt signaling pathways

Imbalanced immune responses are a prominent hallmark of cancer and autoimmunity. Myeloid cells can be overly suppressive, inhibiting protective immune responses or inactive not controlling autoreactive immune cells. Understanding the mechanisms that induce suppressive myeloid cells, such as myeloid-derived suppressor cells (MDSCs) and tolerogenic dendritic cells (TolDCs), can facilitate the development of immune-restoring therapeutic approaches. MDSCs are a major barrier for effective cancer immunotherapy by suppressing antitumor immune responses in cancer patients. TolDCs are administered to patients to promote immune tolerance with the intent to control autoimmune disease. Here, we investigated the development and suppressive/tolerogenic activity of human MDSCs and TolDCs to gain insight into signaling pathways that drive immunosuppression in these different myeloid subsets. Moreover, monocyte-derived MDSCs (M-MDSCs) generated in vitro were compared to M-MDSCs isolated from head-and-neck squamous cell carcinoma patients. PI3K-AKT signaling was identified as being crucial for the induction of human M-MDSCs. PI3K inhibition prevented the downregulation of HLA-DR and the upregulation of reactive oxygen species and MerTK. In addition, we show that the suppressive activity of dexamethasone-induced TolDCs is induced by β-catenin-dependent Wnt signaling. The identification of PI3K-AKT and Wnt signal transduction pathways as respective inducers of the immunomodulatory capacity of M-MDSCs and TolDCs provides opportunities to overcome suppressive myeloid cells in cancer patients and optimize therapeutic application of TolDCs. Lastly, the observed similarities between generated- and patient-derived M-MDSCs support the use of in vitro-generated M-MDSCs as powerful model to investigate the functionality of human MDSCs.

Here, There, and Everywhere: Myeloid-Derived Suppressor Cells in Immunology

Myeloid-derived suppressor cells (MDSCs) were initially identified in humans and mice with cancer where they profoundly suppress T cell- and NK cell-mediated antitumor immunity. Inflammation is a central feature of many pathologies and normal physiological conditions and is the dominant driving force for the accumulation and function of MDSCs. Therefore, MDSCs are present in conditions where inflammation is present. Although MDSCs are detrimental in cancer and conditions where cellular immunity is desirable, they are beneficial in settings where cellular immunity is hyperactive. Because MDSCs can be generated ex vivo, they are being exploited as therapeutic agents to reduce damaging cellular immunity. In this review, we discuss the detrimental and beneficial roles of MDSCs in disease settings such as bacterial, viral, and parasitic infections, sepsis, obesity, trauma, stress, autoimmunity, transplantation and graft-versus-host disease, and normal physiological settings, including pregnancy and neonates as well as aging. The impact of MDSCs on vaccination is also discussed.

Dominant immune cells in pregnancy and pregnancy complications: T helper cells (TH1/TH2, TH17/Treg cells), NK cells, MDSCs, and the immune checkpoints

Pregnancy problems including recurrent pregnancy loss, repeated implantation failure and pre-eclampsia  are common problems in the reproductive ages. Different reasons such as genetic, immunological, and environmental agents and also infections could develop these complications. In those cases in which the cause of the abortion is diagnosed, the chance of a successful pregnancy is increased by eliminating defective factors. However, in patients with unknown causes, there may be an imbalance in immune cells pattern. As a matter of fact, an inappropriate immune response is often associated with a failed pregnancy. Hence, the focus of treatment is to increase tolerance, not to suppress maternal immune system. These findings are linked to an elevated number of Treg cells and immune checkpoints through normal pregnancy. The present review discusses the balance of myeloid-derived suppressor cells, natural killer cells, T cells, and immune checkpoints, and also targeting them to maintain pregnancy and prevent associated complications.

Crosstalk between angiogenesis and immune regulation in the tumor microenvironment

Cancer creates a complex tumor microenvironment (TME) composed of immune cells, stromal cells, blood vessels, and various other cellular and extracellular elements. It is essential for the development of anti-cancer combination therapies to understand and overcome this high heterogeneity and complexity as well as the dynamic interactions between them within the TME. Recent treatment strategies incorporating immune-checkpoint inhibitors and anti-angiogenic agents have brought many changes and advances in clinical cancer treatment. However, there are still challenges for immune suppressive tumors, which are characterized by a lack of T cell infiltration and treatment resistance. In this review, we will investigate the crosstalk between immunity and angiogenesis in the TME. In addition, we will look at strategies designed to enhance anti-cancer immunity, to convert "immune suppressive tumors" into "immune activating tumors," and the mechanisms by which these strategies enhance effector immune cell infiltration.

Targeted Gene Expression Profiling of Human Myeloid Cells From Blood and Lung Compartments of Patients With Tuberculosis and Other Lung Diseases

Myeloid-derived suppressor cells (MDSC) have been identified in the peripheral blood and granulomas of patients with active TB disease, but their phenotype-, function-, and immunosuppressive mechanism- spectrum remains unclear. Importantly, the frequency and signaling pathways of MDSC at the site of disease is unknown with no indication how this compares to MDSC identified in peripheral blood or to those of related myeloid counterparts such as alveolar macrophages and monocytes. Most phenotypic and functional markers have been described in oncological studies but have not yet been validated in TB. Using a panel of 43 genes selected from pathways previously shown to contribute to tumor-derived MDSC, we set out to evaluate if the expression of these additional functional markers and properties may also be relevant to TB-derived MDSC. Differential expression was investigated between MDSC, alveolar macrophages and monocytes enriched from bronchoalveolar lavage fluid and peripheral blood of patients with active TB, patients with other lung diseases (OLD). Results demonstrated that anatomical compartments may drive compartment-specific immunological responses and subsequent MDSC immunosuppressive functions, demonstrated by the observation that MDSC and/or monocytes from PB alone can discriminate, via hierarchical clustering, between patients with active TB disease and OLD. Our data show that the gene expression patterns of MDSC in peripheral blood and bronchoalveolar lavage fluid do not cluster according to disease states (TB vs OLD). This suggests that MDSC from TB patients may display similar gene expression profiles to those found for MDSC in cancer, but this needs to be validated in a larger cohort. These are important observations for TB research and may provide direction for future studies aimed at repurposing and validating cancer immunotherapies for use in TB.

Reverse cardio-oncology: Exploring the effects of cardiovascular disease on cancer pathogenesis

The field of cardio-oncology has emerged in response to the increased risk of cardiovascular disease (CVD) in patients with cancer. However, recent studies suggest a more complicated CVD-cancer relationship, wherein development of CVD, either prior to or following a cancer diagnosis, can also lead to increased risk of cancer and worse outcomes for patients. In this review, we describe the current evidence base, across epidemiological as well as preclinical studies, which supports the emerging concept of 'reverse-cardio oncology', or CVD-induced acceleration of cancer pathogenesis.

A nomogram-based immunoprofile predicts clinical outcomes for stage II and III human colorectal cancer

An immunoscore for colorectal cancer (CRC) has higher prognostic significance than the TNM staging system. However, the tumor immune microenvironment contains various components that affect clinical prognosis. Therefore, a broader range of immune markers is required to establish an accurate immunoprofile to assess the prognosis of patients with CRC. Using immunohistochemistry combined with multispectral immunohistochemistry and objective assessments, the infiltration of four immune cell types (CD4⁺/CD8⁺/forkhead box p3⁺/CD33⁺ cells), as well as the expression of six co-signaling molecules [programmed cell death 1 (PD1) ligand 1/PD1/T-cell immunoglobulin mucin family member 3/lymphocyte-activating 3/tumor necrosis factor receptor superfamily, member 4/inducible T-cell costimulator] and indoleamine 2,3-dioxygenase 1 were investigated in two independent cohorts of CRC. The patients' overall survival (OS) was evaluated using the Kaplan-Meier method. Using the Cox proportional hazards model, independent prognostic factors of patients were assessed and a nomogram-based immunoprofile system was developed. The predictive ability of the nomogram was determined using a concordance index (C-index) and calibration curve. To facilitate clinical application, a simplified nomogram-based immunoprofile was constructed. Using receiver operating characteristic (ROC) analysis, the predictive accuracy for OS was compared between the immunoprofile and the TNM staging system for patients with stage II/III CRC. According to multivariate analysis for the primary cohort, independent prognostic factors for OS were CD8⁺ tumor-infiltrating lymphocytes, CD33⁺ myeloid-derived suppressor cells and TNM stage, which were included in the nomogram. The C-index of the nomogram for predicting OS was 0.861 (95% CI: 0.796-0.925) for the internal validation and 0.759 (95% CI: 0.714-0.804) for the external validation cohort. The simplified nomogram-based immunoprofile system was able to separate same-stage patients into different risk subgroups, particularly for TNM stage II (P<0.0001) and III (P=0.0002) patients. Pairwise comparison of ROC curves for the immunoprofile and TNM stage systems for patients with stage II/III CRC revealed statistically significant differences (P=0.046) and the Z-statistic value was 1.995. In conclusion, the nomogram-based immunoprofile system provides prognostic accuracy regarding clinical outcomes and is a useful supplement to the TNM staging system for patients with stage II/III CRC.

Evaluation of autophagy mediators in myeloid-derived suppressor cells during human tuberculosis

Myeloid-derived suppressor cells (MDSC) are induced during active TB disease to restore immune homeostasis but instead exacerbate disease outcome due to chronic inflammation. Autophagy, in conventional phagocytes, ensures successful clearance of M.tb. However, autophagy has been demonstrated to induce prolonged MDSC survival. Here we investigate the relationship between autophagy mediators and MDSC in the context of active TB disease and during anti-TB therapy. We demonstrate a significant increase in MDSC frequencies in untreated active TB cases with these MDSC expressing TLR4 and significantly more mTOR and IL-6 than healthy controls, with mTOR levels decreasing during anti-TB therapy. Finally, we show that HMGB1 serum concentrations decrease in parallel with mTOR. These findings suggest a complex interplay between MDSC and autophagic mediators, potentially dependent on cellular localisation and M.tb infection state.

Cystathionine β-synthase mediated PRRX2/IL-6/STAT3 inactivation suppresses Tregs infiltration and induces apoptosis to inhibit HCC carcinogenesis

Background

Hepatocellular carcinoma (HCC) is characterized by inflammation and immunopathogenesis. Accumulating evidence has shown that the cystathionine β-synthase/hydrogen sulfide (CBS/H₂S) axis is involved in the regulation of inflammation. However, roles of CBS in HCC development and immune evasion have not been systematically investigated, and their underlying mechanisms remain elusive. Here, we investigated the roles of CBS in tumor cells and tumor microenvironment of HCC.

Methods

236 HCC samples were collected to detect the expression of CBS, cleaved Caspase-3 and paired related homeobox 2 (PRRX2) and the number of immune cells. HCC cell lines were employed to examine the effects of CBS on cellular viability, apoptosis and signaling in vitro. Cbs heterozygous knockout mice, C57BL/6 mice, nude mice and non-obese diabetic severe combined immunodeficiency mice were used to investigate the in vivo functions of CBS.

Results

Downregulation of CBS was observed in HCC, and low expression of CBS predicted poor prognosis in HCC patients. CBS overexpression dramatically promoted cellular apoptosis in vitro and inhibited tumor growth in vivo. Activation of the Cbs/H₂S axis also reduced the abundance of tumor-infiltrating Tregs, while Cbs deficiency promoted Tregs-mediated immune evasion and boosted tumor growth in Cbs heterozygous knockout mice. Mechanistically, CBS facilitated the expression cleaved Caspase-3 in tumor cells, and on the other hand, suppressed Foxp3 expression in Tregs via inactivating IL-6/STAT3 pathway. As a transcription factor of IL-6, PRRX2 was reduced by CBS. Additionally, miR-24-3p was proven to be an upstream suppressor of CBS in HCC.

Conclusions

Our results indicate the antitumor function of CBS in HCC by inactivation of the PRRX2/IL-6/STAT3 pathway, which may serve as a potential target for HCC clinical immunotherapy.

Cisplatin inhibits frequency and suppressive activity of monocytic myeloid-derived suppressor cells in cancer patients

Cancer immunotherapies have induced long-lasting responses in cancer patients including those with melanoma and head and neck squamous cell carcinoma (HNSCC). However, the majority of treated patients does not achieve clinical benefit from immunotherapy because of systemic tumor-induced immunosuppression. Monocytic myeloid-derived suppressor cells (M-MDSCs) are implicated as key players in inhibiting anti-tumor immune responses and their frequencies are closely associated with tumor progression. Tumor-derived signals, including signaling via STAT3-COX-2, induce the transformation of monocytic precursors into suppressive M-MDSCs. In a retrospective assessment, we observed that survival of melanoma patients undergoing dendritic cell vaccination was negatively associated with blood M-MDSC levels. Previously, it was shown that platinum-based chemotherapeutics inhibit STAT signaling. Here, we show that cisplatin and oxaliplatin treatment interfere with the development of M-MDSCs, potentially synergizing with cancer immunotherapy. In vitro, subclinical doses of platinum-based drugs prevented the generation of COX-2⁺ M-MDSCs induced by tumor cells from melanoma patients. This was confirmed in HNSCC patients where intravenous cisplatin treatment drastically lowered M-MDSC frequency while monocyte levels remained stable. In treated patients, expression of COX-2 and arginase-1 in M-MDSCs was significantly decreased after two rounds of cisplatin, indicating inhibition of STAT3 signaling. In line, the capacity of M-MDSCs to inhibit activated T cell responses ex vivo was significantly decreased after patients received cisplatin. These results show that platinum-based chemotherapeutics inhibit the expansion and suppressive activity of M-MDSCs in vitro and in cancer patients. Therefore, platinum-based drugs have the potential to enhance response rates of immunotherapy by overcoming M-MDSC-mediated immunosuppression.

Metabolic regulation in the immune response to cancer

Metabolic reprogramming in tumor‐immune interactions is emerging as a key factor affecting pro‐inflammatory carcinogenic effects and anticancer immune responses. Therefore, dysregulated metabolites and their regulators affect both cancer progression and therapeutic response. Here, we describe the molecular mechanisms through which microenvironmental, systemic, and microbial metabolites potentially influence the host immune response to mediate malignant progression and therapeutic intervention. We summarized the primary interplaying factors that constitute metabolism, immunological reactions, and cancer with a focus on mechanistic aspects. Finally, we discussed the possibility of metabolic interventions at multiple levels to enhance the efficacy of immunotherapeutic and conventional approaches for future anticancer treatments.

MDSCs, ageing and inflammageing

The challenge of distinguishing between changes attributable to ageing and those attributable to pathology is even greater for the immune system than for many other organs, and this is especially true for myeloid-derived suppressor cells (MDSCs). Hematopoiesis is different in older adults with a bias towards myelopoiesis, and older adults also manifest "inflammageing" exacerbated by disease and contributing to MDSC induction. Hence, at least in humans, one can only investigate MDSCs in the context of ageing and disease states, and not in the context of ageing processes per se. This contribution provides a brief overview of the literature on MDSCs and ageing in humans.

Myeloid-Derived Suppressor Cells in Pregnancy and the Neonatal Period

During pregnancy, the immune systems of mother and offspring are challenged by their close adjacency to balance tolerance and rejection. After birth the neonate has to continue this balance towards its new environment by tolerating commensals while rejecting pathogens and towards its developing tissues to avoid inflammatory damage while overcoming immunosuppression. Our group was the first to link immunosuppressive features of myeloid derived suppressor cells (MDSC) to materno-fetal tolerance, neonatal susceptibility to infection and inflammation control. Here we summarize recent advances in this dynamic field.

Myocardial infarction accelerates breast cancer via innate immune reprogramming

Disruption of systemic homeostasis by either chronic or acute stressors, such as obesity1 or surgery2, alters cancer pathogenesis. Patients with cancer, particularly those with breast cancer, can be at increased risk of cardiovascular disease due to treatment toxicity and changes in lifestyle behaviors3-5. While elevated risk and incidence of cardiovascular events in breast cancer is well established, whether such events impact cancer pathogenesis is not known. Here we show that myocardial infarction (MI) accelerates breast cancer outgrowth and cancer-specific mortality in mice and humans. In mouse models of breast cancer, MI epigenetically reprogrammed Ly6Chi monocytes in the bone marrow reservoir to an immunosuppressive phenotype that was maintained at the transcriptional level in monocytes in both the circulation and tumor. In parallel, MI increased circulating Ly6Chi monocyte levels and recruitment to tumors and depletion of these cells abrogated MI-induced tumor growth. Furthermore, patients with early-stage breast cancer who experienced cardiovascular events after cancer diagnosis had increased risk of recurrence and cancer-specific death. These preclinical and clinical results demonstrate that MI induces alterations in systemic homeostasis, triggering cross-disease communication that accelerates breast cancer.

Exercise and immunometabolic regulation in cancer

Unhealthful lifestyle factors, such as obesity, disrupt organismal homeostasis and accelerate cancer pathogenesis, partly through metabolic and immunological dysregulation. Exercise is a prototypical strategy that maintains and restores homeostasis at the organismal, tissue, cellular and molecular levels and can prevent or inhibit numerous disease conditions, including cancer. Here, we review unhealthful lifestyle factors that contribute to metabolic and immunological dysregulation and drive tumourigenesis, focusing on patient physiology (host)-tissue-tumour microenvironment interactions. We also discuss how exercise may influence distant tissue microenvironments, thereby improving tissue function through both metabolic and immunospecific pathways. Finally, we consider future directions that merit consideration in basic and clinical translational exercise studies.

Imidazo[1,2-b]pyrazole-7-Carboxamide Derivative Induces Differentiation-Coupled Apoptosis of Immature Myeloid Cells Such as Acute Myeloid Leukemia and Myeloid-Derived Suppressor Cells

Chemotherapy-induced differentiation of immature myeloid progenitors, such as acute myeloid leukemia (AML) cells or myeloid-derived suppressor cells (MDSCs), has remained a challenge for the clinicians. Testing our imidazo[1,2-b]pyrazole-7-carboxamide derivative on HL-60 cells, we obtained ERK phosphorylation as an early survival response to treatment followed by the increase of the percentage of the Bcl-xl^bright and pAkt^bright cells. Following the induction of Vav1 and the AP-1 complex, a driver of cellular differentiation, FOS, JUN, JUNB, and JUND were elevated on a concentration and time-dependent manner. As a proof of granulocytic differentiation, the cells remained non-adherent, the expression of CD33 decreased; the granularity, CD11b expression, and MPO activity of HL-60 cells increased upon treatment. Finally, viability of HL-60 cells was hampered shown by the depolarization of mitochondria, activation of caspase-3, cleavage of Z-DEVD-aLUC, appearance of the sub-G1 population, and the leakage of the lactate-dehydrogenase into the supernatant. We confirmed the differentiating effect of our drug candidate on human patient-derived AML cells shown by the increase of CD11b and decrease of CD33+, CD7+, CD206+, and CD38^bright cells followed apoptosis (IC₅₀: 80 nM) after treatment ex vivo. Our compound reduced both CD11b+/Ly6C+ and CD11b+/Ly6G+ splenic MDSCs from the murine 4T1 breast cancer model ex vivo.

A novel methodology of the myeloid-derived suppressor cells (MDSCs) generation with splenic stroma feeder cells

Myeloid-derived suppressor cells (MDSCs) are a significant obstacle for immunotherapy of cancer. It is of great clinical relevance to study the mechanism of MDSCs accumulation in mouse spleens and establish a stable method to obtain high-purity MDSCs in vitro for further research. Here, we established a new method for amplifying a large number of highly pure MDSCs in vitro. To mimic the microenvironment of MDSCs development in vivo, mouse splenic stroma feeder cells and serum-free medium containing granulocyte-macrophage colony stimulating factor (GM-CSF) were used to induce myeloid precursors in mouse bone marrow cells, which differentiate into MDSCs. Development and immunological functions of the cells were monitored both in vivo and in vitro. A total of 4 × 10⁸ MDSCs could be obtained from the bone marrow from one mouse, the ratio of CD11b⁺Gr-1⁺ MDSCs could reach 93.8% ± 3.3% after nine days of culture in vitro. Cultured MDSCs maintained a similar immunophenotype with MDSCs found in tumor-bearing mice. Colony forming assay in vitro and in vivo demonstrated that these were myeloid precursor cells. These cells generated high levels of reactive oxygen species and arginase 1 to prevent proliferation of CD8⁺ T cells in vitro. These also increased regulatory T (Treg) cells in blood while promoting the growth of lymphoma in vivo. In addition, cultured MDSCs effectively inhibited acute graft-versus-host disease (aGVHD). Our findings suggest that mouse splenic stroma plays an important role in the generation of MDSCs and represent a preliminary mechanism for the accumulation of MDSCs in spleens, and thereby lay the foundation for basic research and the clinical application of MDSCs.

Mycobacterium tuberculosis and myeloid-derived suppressor cells: Insights into caveolin rich lipid rafts

Mycobacterium tuberculosis (M.tb) is likely the most successful human pathogen, capable of evading protective host immune responses and driving metabolic changes to support its own survival and growth. Ineffective innate and adaptive immune responses inhibit effective clearance of the bacteria from the human host, resulting in the progression to active TB disease. Many regulatory mechanisms exist to prevent immunopathology, however, chronic infections result in the overproduction of regulatory myeloid cells, like myeloid-derived suppressor cells (MDSC), which actively suppress protective host T lymphocyte responses among other immunosuppressive mechanisms. The mechanisms of M.tb internalization by MDSC and the involvement of host-derived lipid acquisition, have not been fully elucidated. Targeted research aimed at investigating MDSC impact on phagocytic control of M.tb, would be advantageous to our collective anti-TB arsenal. In this review we propose a mechanism by which M.tb may be internalized by MDSC and survive via the manipulation of host-derived lipid sources.

Sequential depletion of myeloid-derived suppressor cells and tumor cells with a dual-pH-sensitive conjugated micelle system for cancer chemoimmunotherapy

Myeloid-derived suppressor cells(MDSCs)are one of the most important immunosuppressive cells in tumor microenvironment, which also promote the development and progression of tumor cells. Nevertheless, due to the different distribution features of MDSCs and tumor cells, selective elimination of MDSCs and tumor cells in tumor microenvironment remain a great challenge. Here we have designed a dual-pH-sensitivity conjugated micelle system (PAH/RGX-104@PDM/PTX) that could deliver liver-X nuclear receptor (LXR) agonist RGX-104 and paclitaxel (PTX) to the perivascular region and tumor cells, respectively. Upon arrival at the acidic tumor microenvironment, the PAH/RGX-104@PDM/PTX undergo structure disintegration and capacitate coinstantaneous release of RGX-104 in the perivascular regions, leaving the intact PTX containing micelles PDM/PTX for tumor deep penetration. The released RGX-104 can be preferentially taken up by leukocytes, endothelial cells and macrophages which are nicely enriched in perivascular regions to active the LXR, and further reduces immunosuppressive MDSC levels. The remained small micelles carrying PTX enable deep tumor penetration as well as rapid specific drug release in the endosomal/lysosomal to kill tumor cells. PAH/RGX-104@PDM/PTX exhibits superior tumor accumulation as well as tumor penetration, and suppresses 74.88% in vivo tumor growth. More importantly, PAH/RGX-104@PDM/PTX has significantly alleviated tumor immunosuppression by eliminating MDSCs and increasing cytotoxic T lymphocytes infiltration. Our studies suggest that the dual-pH-sensitive codelivery nanocarrier not only cause apoptosis of cancer cells but also regulate the tumor immune environment to ultimately enhance the antitumor effect of CTLs through MDSCs depletion.

Dural Cells Release Factors Which Promote Cancer Cell Malignancy and Induce Immunosuppressive Markers in Bone Marrow Myeloid Cells

BACKGROUND

Thirty per cent of cancer patients develop spine metastases with a substantial number leading to spinal cord compression and neurological deficits. Many demonstrate a propensity toward metastasis to the posterior third of the vertebral body. The dura, the outer layer of the meninges, lies in intimate contact with the posterior border of the vertebral body and has been shown to influence adjacent bone. The effects of the dura on bone marrow and cancer cells have not been examined. Understanding the biology of spinal metastasis will provide insights into mechanisms of cancer growth and allow for new treatment strategies.

OBJECTIVE

To examine the extent to which dura influences bone marrow/tumor cell metastatic characteristics.

METHODS

Dura conditioned media (DCM) from primary dura was examined for the ability to stimulate tumor cell proliferation/invasion and to alter bone marrow cell populations. RNA sequencing of dural fibroblasts was performed to examine expression of cytokines and growth factors.

RESULTS

DCM induced a significant increase in invasion and proliferation of multiple tumor cell lines, and of patient-derived primary spinal metastatic cells. DCM also increased the proliferation of bone marrow myeloid cells, inducing expression of immunosuppressive markers. RNA sequencing of dural fibroblasts demonstrated abundant expression of cytokines and growth factors involved in cancer/immune pathways.

CONCLUSION

Factors released by primary dural cells induce proliferation of tumor cells and alter bone marrow to create a fertile environment for tumor growth. The dura therefore may play an important role in the increased incidence of metastases to adjacent bone.

Frequency of Immune Cell Subtypes in Peripheral Blood Correlates With Outcome for Patients With Metastatic Breast Cancer Treated With High-Dose Chemotherapy

BACKGROUND

The frequency of circulating leukocytes has been shown to be a prognostic factor in patients being treated for different types of cancer. In breast cancer, tumor-infiltrating leukocytes may predict patient outcome, but few studies have investigated such associations for circulating leukocytes.

PATIENTS AND METHODS

Multiparametric flow cytometry was used to examine the immunophenotypes of circulating peripheral blood mononuclear cells for 88 patients with metastatic breast cancer, which was then correlated to breast cancer-specific survival. Patients had been treated either with high-dose cyclophosphamide-containing regimens (group 1, n = 51 patients) or high-dose paclitaxel-containing regimens (group 2, n = 37 patients).

RESULTS

The frequency of peripheral blood CD14⁺ monocytes indicated prognosis for patients in group 1 (but not group 2), while higher levels of CD11c⁺ dendritic cells indicated a better prognosis for patients in group 2 (but not group 1). The frequency of a number of different CD4⁺ or CD8⁺ T cell subtypes also predicted prognosis for patients in group 2. For example, patients in group 2 with a higher frequency of circulating CD4⁺ or CD8⁺ naive T cells (CD45RA⁺CD95-CD27⁺CD28⁺) showed a poorer prognosis. In contrast, T cells were not associated with prognosis for patients in group 1.

CONCLUSION

Circulating leukocytes can predict clinical outcome for patients with breast cancer. Prediction of clinical outcome in this cohort of metastatic breast cancer patients was specific to the type of chemotherapy, and this finding is likely to apply to other therapies.

AMPK activation inhibits the functions of myeloid-derived suppressor cells (MDSC): impact on cancer and aging

AMP-activated protein kinase (AMPK) has a crucial role not only in the regulation of tissue energy metabolism but it can also control immune responses through its cooperation with immune signaling pathways, thus affecting immunometabolism and the functions of immune cells. It is known that AMPK signaling inhibits the activity of the NF-κB system and thus suppresses pro-inflammatory responses. Interestingly, AMPK activation can inhibit several major immune signaling pathways, e.g., the JAK-STAT, NF-κB, C/EBPβ, CHOP, and HIF-1α pathways, which induce the expansion and activation of myeloid-derived suppressor cells (MDSC). MDSCs induce an immunosuppressive microenvironment in tumors and thus allow the escape of tumor cells from immune surveillance. Chronic inflammation has a key role in the expansion and activation of MDSCs in both tumors and inflammatory disorders. The numbers of MDSCs also significantly increase during the aging process concurrently with the immunosenescence associated with chronic low-grade inflammation. Increased fatty acid oxidation and lactate produced by aerobic glycolysis are important immunometabolic enhancers of MDSC functions. However, it seems that AMPK signaling regulates the functions of MDSCs in a context-dependent manner. Currently, the activators of AMPK signaling are promising drug candidates for cancer therapy and possibly for the extension of healthspan and lifespan. We will describe in detail the AMPK-mediated regulation of the signaling pathways controlling the expansion and activation of immunosuppressive MDSCs. We will propose that the beneficial effects mediated by AMPK activation, e.g., in cancers and the aging process, could be induced by the inhibition of MDSC functions.

Myeloid-Derived Suppressor Cells: Not Only in Tumor Immunity

Since the realization that immature myeloid cells are powerful modulators of the immune response, many studies on “myeloid-derived suppressor cells” (MDSCs) have documented their ability to promote tumor progression in melanoma and other cancers. Whether MDSCs are induced solely pathologically in tumorigenesis, or whether they also represent physiological immune control mechanisms, is not well-understood, but is particularly important in the light of ongoing attempts to block their activities in order to enhance anti-tumor immunity. Here, we briefly review studies which explore (1) how best to identify MDSCs in the context of cancer and how this compares to other conditions in humans; (2) what the suppressive mechanisms of MDSCs are and how to target them pharmacologically; (3) whether levels of MDSCs with various phenotypes are informative for clinical outcome not only in cancer but also other diseases, and (4) whether MDSCs are only found under pathological conditions or whether they also represent a physiological regulatory mechanism for the feedback control of immunity. Studies unequivocally document that MDSCs strongly influence cancer outcomes, but are less informative regarding their relevance to infection, autoimmunity, transplantation and aging, especially in humans. So far, the results of clinical interventions to reverse their negative effects in cancer have been disappointing; thus, developing differential approaches to modulate MSDCs in cancer and other diseases without unduly comprising any normal physiological function requires further exploration.

Immunosenescence: the potential role of myeloid-derived suppressor cells (MDSC) in age-related immune deficiency

The aging process is associated with chronic low-grade inflammation in both humans and rodents, commonly called inflammaging. At the same time, there is a gradual decline in the functional capacity of adaptive and innate immune systems, i.e., immunosenescence, a process not only linked to the aging process, but also encountered in several pathological conditions involving chronic inflammation. The hallmarks of immunosenescence include a decline in the numbers of naïve CD4+ and CD8+ T cells, an imbalance in the T cell subsets, and a decrease in T cell receptor (TCR) repertoire and signaling. Correspondingly, there is a decline in B cell lymphopoiesis and a reduction in antibody production. The age-related changes are not as profound in innate immunity as they are in adaptive immunity. However, there are distinct functional deficiencies in dendritic cells, natural killer cells, and monocytes/macrophages with aging. Interestingly, the immunosuppression induced by myeloid-derived suppressor cells (MDSC) in diverse inflammatory conditions also targets mainly the T and B cell compartments, i.e., inducing very similar alterations to those present in immunosenescence. Here, we will compare the immune profiles induced by immunosenescence and the MDSC-driven immunosuppression. Given that the appearance of MDSCs significantly increases with aging and MDSCs are the enhancers of other immunosuppressive cells, e.g., regulatory T cells (Tregs) and B cells (Bregs), it seems likely that MDSCs might remodel the immune system, thus preventing excessive inflammation with aging. We propose that MDSCs are potent inducers of immunosenescence.

The role of the P2X7 receptor in myeloid-derived suppressor cells and immunosuppression

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells expanded and recruited from the bone marrow to the periphery or to a specific site of inflammation/infection. MDSC have been described in different pathological conditions including cancer, infections, autoimmunity and obesity. The main function of MDSC is immunosuppression occurring through different mechanisms such as induction of immunosuppressive cells, impairment of lymphocyte homing, free radical production, depletion of amino acids critical for T cell functions, upregulation of ectoenzymes involved in adenosine production and activation of immune regulatory molecules responsible of T cell anergy. A novel immunosuppressive mechanism MDSC-mediated involves the ATP/P2X7 receptor axis that induces the release of immunosuppressive chemokines/cytokines upon triggering with ATP.

Increased circulating GrMyeloid-derived suppressor cells correlated with tumor burden and survival in locally advanced cervical cancer patient

Background: Myeloid-derived suppressor cells (MDSCs) may lead to immune evasion and disease progression in some cancers, but their roles remain to be investigated in cervical cancer. This study aimed to characterize the specific subsets of MDSCs that might be potential indicators for disease progression in cervical cancer patients. Methods: Different subsets of MDSCs were characterized using flow cytometry in blood samples from healthy subjects and cervical cancer patients. T-cell proliferation assay was performed in vitro. Tumor infiltrating CD8+ and FOXP3+ cells were also evaluated by immunostaining on the tumor tissues from patients with early and locally advanced cervical cancer. We further analyzed the relevance of circulating MDSCs to clinicopathological characteristics, patient survival as well as tumor infiltrating lymphocytes. Results: The frequency of circulating GrMDSCs increased correlated with FIGO stage while the percentage of MoMDSCs only elevated in patients with advanced cervical cancers. For patients with early and locally advanced cervical cancer, the frequency of circulating GrMDSCs but not MoMDSCs correlated with clinicopathologic parameters including metastatic lymph nodes, deep stromal invasion and tumor recurrence. The levels of circulating GrMDSCs also negatively correlated with the densities of CD8+ cells in tumor tissues. In vitro assay showed that Gr-MDSCs suppressed the proliferation of autologous T cells. Conclusion: Our study demonstrates that the increased frequency of circulating GrMDSCs is associated with tumor burden and recurrence in early and locally advanced cervical cancer patients, that the GrMDSCs may be potential biomarkers for disease progression cervical cancers.

Expansion and Determination of Antigen-Reactive T Cells by Flow Cytometry

The detection of antigen-reactive T cells has shown great utility for patient clinical monitoring. However, many of the methods commonly used to detect these cells face major limitations, like the predetermination of the given HLA type. The herein described protocol provides a means of overcoming many of the obstacles associated with the use of multimers and other common approaches in this field. In order to be able to detect rare cells which are below the detection limit of direct ex vivo measurement, in the present protocol, antigen-reactive T cells are first expanded in vitro using libraries of overlapping peptides which span the entire protein of interest and consist of 15 amino acid-long peptides that share a 12-amino-acid overlap. This theoretically allows the detection of T cells to any epitope within a protein of interest and consequently does not require the patient's HLA type to be characterized. Furthermore, this method simultaneously detects CD4+ and CD8+ T cells that produce cytokines upon encounter with antigen and thereby provides a functional insight into the behavior of the responding T cells. In our case, we have investigated the pro- or anti-inflammatory cytokines IL-2, IL-5, IL-10, IL-17, TNF-α, and IFN-γ.

Alterations in arginine and energy metabolism, structural and signalling lipids in metastatic breast cancer in mice detected in plasma by targeted metabolomics and lipidomics

Background

The early detection of metastasis based on biomarkers in plasma may improve cancer prognosis and guide treatment. The aim of this work was to characterize alterations in metabolites of the arginine pathway, energy metabolism, and structural and signalling lipids in plasma in the early and late stages of murine breast cancer metastasis.

Methods

Mice were orthotopically inoculated with 4T1 metastatic breast cancer cells, and plasma was analysed along the pulmonary metastasis progression using LC-MS/MS-based targeted metabolomics and lipidomics.

Results

Based on primary tumour growth and pulmonary metastases, 1–2 weeks after 4T1 cancer cell inoculation was defined as an early metastatic stage, and 3–4 weeks after 4T1 cancer cell inoculation was defined as a late metastatic stage. Early metastasis was featured in plasma by a shift of L-arginine metabolism towards arginase (increased ornithine/arginine ratio) and polyamine synthesis (increased putrescine). Late metastasis was reflected in plasma by further progression of changes in the arginine pathway with an additional increase in asymmetric dimethylarginine plasma concentration, as well as by a profound energy metabolism reprogramming towards glycolysis, an accelerated pentose phosphate pathway and a concomitant decrease in tricarboxylic cycle rate (“Warburg effect”). The late but not the early phase of metastasis was also characterized by a different lipid profile pattern in plasma, including a decrease in total phosphatidylcholines, a decrease in diester-bound phospholipid fraction and an increase in lysophospholipids associated with an increase in total sphingomyelins.

Conclusions

The early phase of metastasis in murine 4T1 metastatic breast cancer was associated with plasma metabolome changes characteristic of arginase activation and polyamine synthesis. The late metastasis was reflected in plasma not only by the alterations in arginine pathways but also by a shift towards glycolysis and the pentose pathway, remodelling of structural lipids and activation of lipid signalling, all of which coincided with metastasis progression.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1075-y) contains supplementary material, which is available to authorized users.

Myeloid-derived suppressor cells (MDSCs) in patients with solid tumors: considerations for granulocyte colony-stimulating factor treatment

Myeloid-derived suppressor cells (MDSCs) have been shown to contribute to tumor escape from host immune surveillance and to cancer progression by production of tumor-promoting soluble factors. Granulocyte colony-stimulating factor (G-CSF) is a principle cytokine controlling granulocyte number. Recombinant human G-CSF (rhG-CSF) has become the main therapeutic agent for the treatment of neutropenia and prophylaxis of febrile neutropenia in cancer patients. However, we show here that rhG-CSF triggers accumulation of granulocytic and monocytic subsets. Consequently, we discuss the pharmacological use of granulopoiesis stimulating factors not only in the context of febrile neutropenia but also from the perspective of MDSC-dependent and MDSC-independent mechanisms of immunosuppression and cancer angiogenesis.

Translational Potential of Therapeutics Targeting Regulatory Myeloid Cells in Tuberculosis

Despite recent advances in tuberculosis (TB) drug development and availability, successful antibiotic treatment is challenged by the parallel development of antimicrobial resistance. As a result, new approaches toward improving TB treatment have been proposed in an attempt to reduce the high TB morbidity and mortality rates. Host-directed therapies (HDTs), designed to modulate host immune components, provide an alternative approach for improving treatment outcome in both non-communicable and infectious diseases. Many candidate immunotherapeutics, designed to target regulatory myeloid immune components in cancer, have so far proven to be of value as repurposed HDT in TB. Several of these studies do however lack detailed description of the mechanism or host pathway affected by TB HDT treatment. In this review, we present an argument for greater appreciation of the role of regulatory myeloid cells, such as myeloid-derived suppressor cells (MDSC), as potential targets for the development of candidate TB HDT compounds. We discuss the role of MDSC in the context of Mycobacterium tuberculosis infection and disease, focussing primarily on their specific cellular functions and highlight the impact of HDTs on MDSC frequency and function.

Prognostic role of pretreatment circulating MDSCs in patients with solid malignancies: A meta-analysis of 40 studies

Myeloid-derived suppressor cells (MDSCs) have been shown to contribute to tumor progression, mainly through immune suppression. Inverse correlations have been observed between MDSC levels and patient survival for various malignancies. The purpose of this meta-analysis was to evaluate the prognostic value of pretreatment circulating MDSCs. We searched MEDLINE and EMBASE from their inceptions to September 2017 to identify relevant articles. Using a fixed or random effects model, pooled hazard ratios (HRs) were estimated for overall survival (OS) and combined disease-free survival, progression-free survival, and recurrence-free survival (DFS/PFS/RFS). A total of 40 studies comprising 2721 were included. For solid tumors, high levels of pretreatment circulating MDSCs were significantly associated with worse OS (HR = 1.796, 95% CI = 1.587-2.032) and DFS/PFS/RFS (HR = 2.459, 95% CI = 2.018-2.997). Breast cancer showed the largest association between high MDSC levels and worse OS (pooled HR = 3.053). Elevated MDSCs were also associated with worse OS for mixed-stage tumors (pooled HR = 1.659) and advanced-stage tumors (pooled HR = 2.337). Furthermore, both monocytic-MDSCs (M-MDSCs) and granulocytic or polymorphonuclear (PMN-MDSCs) showed negative associations with survival outcomes. Overall, high levels of pretreatment circulating MDSCs negatively influenced survival in most cancers. Pretreatment circulating MDSCs should be taken into account to further improve prognostic evaluation and develop novel therapeutic strategies.

Blood-based analyses of cancer: Circulating myeloid-derived suppressor cells - is a new era coming?

Progress in cancer treatment made by the beginning of the 21st century has shifted the paradigm from one-size-fits-all to tailor-made treatment. The popular vision, to study solid tumors through the relatively noninvasive sampling of blood, is one of the most thrilling and rapidly advancing fields in global cancer diagnostics. From this perspective, immune-cell analysis in cancer could play a pivotal role in oncology practice. This approach is driven both by rapid technological developments, including the analysis of circulating myeloid-derived suppressor cells (cMDSCs), and by the increasing application of (immune) therapies, the success or failure of which may depend on effective and timely measurements of relevant biomarkers. Although the implementation of these powerful noninvasive diagnostic capabilities in guiding precision cancer treatment is poised to change the ways in which we select and monitor cancer therapy, challenges remain. Here, we discuss the challenges associated with the analysis and clinical aspects of cMDSCs and assess whether the problems in implementing tumor-evolution monitoring as a global tool in personalized oncology can be overcome.

Clinical Relevance and Suppressive Capacity of Human Myeloid-Derived Suppressor Cell Subsets

Purpose: Myeloid-derived suppressor cells (MDSC) are a heterogeneous group of pathologically expanded myeloid cells with immunosuppressive activity. In human disease, three major MDSC subpopulations can be defined as monocytic (M-MDSC), granulocytic [polymorphonuclear-MDSC (PMN-MDSC)], and early stage (e-MDSC), which lacks myeloid lineage markers of the former two subsets. The purpose of this study was to determine and compare the immunosuppressive capacity and clinical relevance of each of these subsets in patients with solid cancer.Experimental Design: The frequency of MDSC subsets in the peripheral blood was determined by flow cytometry in a cohort of 49 patients with advanced head and neck cancer (HNC) and 22 patients with urological cancers. Sorted and purified MDSC subsets were tested in vitro for their T-cell-suppressive capacity. Frequency of circulating MDSC was correlated with overall survival of patients with HNC.Results: A high frequency of PMN-MDSC most strongly correlated with poor overall survival in HNC. T-cell-suppressive activity was higher in PMN-MDSC compared with M-MDSC and e-MDSC. A subset of CD66b⁺/CD11b⁺/CD16⁺ mature PMN-MDSC displayed high expression and activity of arginase I, and was superior to the other subsets in suppressing proliferation and cytokine production of T cells in both cancer types. High levels of this CD11b⁺/CD16⁺ PMN-MDSC, but not other PMN-MDSC subsets, strongly correlated with adverse outcome in HNC.Conclusions: A subset of mature CD11b⁺/CD16⁺ PMN-MDSC was identified as the MDSC subset with the strongest immunosuppressive activity and the highest clinical relevance. Clin Cancer Res; 24(19); 4834-44. ©2018 AACR.

Low levels of intra-tumoural T cells in breast cancer identify clinically frail patients with shorter disease-specific survival

OBJECTIVES

The global health status of older patients with cancer influences their clinical course, but little is known regarding the influence of the immune system on the global health of older patients with cancer. The goal of this study was to assess the relationships between patient fitness/frailty status and survival, and the local tumour immune environment of older patients with breast cancer.

MATERIALS AND METHODS

In a cohort of 58 older patients with breast cancer (over 70 years of age), fluorescence microscopy was used to investigate whether levels of intra-tumoural T cells (CD3+) and granulocytic cells (CD15+) could predict clinical outcome, and/or whether they correlated with patient physical and mental performance as evaluated by comprehensive geriatric assessment.

RESULTS

We observed that patients with higher levels of intra-tumoural T cells were fitter according to a number of clinical health measures including G8 (p = 0.006), Karnofsky Index (p = 0.0372), and Leuven Oncology Frailty Score (LOFS) (p = 0.0187). In contrast, high relative levels of granulocytic cells were found in patients with poorer clinical health (LOFS, p = 0.0474). Furthermore, high levels of T cells but not granulocytic cells were associated with longer breast cancer-specific survival (p = 0.0444).

CONCLUSIONS

This is the first study to show that low relative levels of intra-tumoural T cells are associated with inferior patient fitness. In contrast to T cells, we observed that intra-tumoural granulocytic cells displayed an inverse relationship with patient performance. Further research is needed to determine whether boosting the level of intra-tumoural T cells in older non-fit patients can result in improved outcome.

Inhibiting HSP90 prevents the induction of myeloid-derived suppressor cells by melanoma cells

Metastatic melanoma is the most dangerous form of skin cancer, with an ever-increasing incidence worldwide. Despite encouraging results with immunotherapeutic approaches, long-term survival is still poor. This is likely partly due to tumour-induced immune suppression mediated by myeloid-derived suppressor cells (MDSCs), which were shown to be associated with response to therapy and survival. Thus, identifying pathways responsible for MDSC differentiation may provide new therapeutic targets and improve efficacy of existing immunotherapies. Therefore, we've analysed mechanisms by which tumour cells contribute to the induction of MDSCs. Established melanoma cell lines were pre-treated with inhibitors of different pathways and tested for their capacity to alleviate T cell suppression via MDSC differentiation in vitro. Targeting HSP70/90 in melanoma cells resulted in reduced induction of immune suppressive cells on a phenotypic and functional basis, for which a more potent effect was observed when HSP90 was inhibited under hypoxic conditions. This initial study suggests a novel mechanism in tumour cells responsible for the induction of MDSC in melanoma.

LXR/ApoE Activation Restricts Innate Immune Suppression in Cancer

Therapeutic harnessing of adaptive immunity via checkpoint inhibition has transformed the treatment of many cancers. Despite unprecedented long-term responses, most patients do not respond to these therapies. Immunotherapy non-responders often harbor high levels of circulating myeloid-derived suppressor cells (MDSCs)-an immunosuppressive innate cell population. Through genetic and pharmacological approaches, we uncovered a pathway governing MDSC abundance in multiple cancer types. Therapeutic liver-X nuclear receptor (LXR) agonism reduced MDSC abundance in murine models and in patients treated in a first-in-human dose escalation phase 1 trial. MDSC depletion was associated with activation of cytotoxic T lymphocyte (CTL) responses in mice and patients. The LXR transcriptional target ApoE mediated these effects in mice, where LXR/ApoE activation therapy elicited robust anti-tumor responses and also enhanced T cell activation during various immune-based therapies. We implicate the LXR/ApoE axis in the regulation of innate immune suppression and as a target for enhancing the efficacy of cancer immunotherapy in patients.

S100A9+ MDSC and TAM-mediated EGFR-TKI resistance in lung adenocarcinoma: the role of RELB

Background

Monocytic myeloid-derived suppressor cells (MDSCs), particularly the S100A9+ subset, has been shown initial clinical relevance. However, its role in EGFR-mutated lung adenocarcinoma, especially to EGFR-tyrosine kinase inhibitor (EGFR-TKI) is not clear. In a clinical setting of EGFR mutated lung adenocarcinoma, a role of the MDSC apart from T cell suppression was also investigated.

Results

Blood monocytic S100A9⁺ MDSC counts were higher in lung cancer patients than healthy donors, and were associated with poor treatment response and shorter progression-free survival (PFS). S100A9⁺ MDSCs in PBMC were well correlated to tumor infiltrating CD68⁺ and S100A9⁺ cells, suggesting an origin of TAMs. Patient’s MDMs, mostly from S100A9⁺ MDSC, similar to primary alveolar macrophages from patients, both expressed S100A9 and CD206, attenuated EGFR-TKI cytotoxicity. Microarray analysis identified up-regulation of the RELB signaling genes, confirmed by Western blotting and functionally by RELB knockdown.

Conclusions

In conclusion, blood S100A9⁺ MDSC is a predictor of poor treatment response to EGFR-TKI, possibly via its derived TAMs through activation of the non-canonical NF-κB RELB pathway.

Methods

Patients with activating EGFR mutation lung adenocarcinoma receiving first line EGFR TKIs were prospectively enrolled. Peripheral blood mononuclear cells (PBMCs) were collected for MDSCs analysis and for monocyte-derived macrophages (MDMs) and stored tissue for TAM analysis by IHC. A transwell co-culture system of MDMs/macrophages and H827 cells was used to detect the effect of macrophages on H827 and microarray analysis to explore the underlying molecular mechanisms, functionally confirmed by RNA interference.

CD14+ HLA-DR-/low MDSCs are elevated in the periphery of early-stage breast cancer patients and suppress autologous T cell proliferation

PURPOSE

Despite the recent expansion in the use of immunotherapy for many cancer types, it is still not a standard treatment for breast cancer. Identifying differences in the immune systems of breast cancer patients compared to healthy women might provide insight into potential targets for immunotherapy and thus may assist its clinical implementation.

METHODS

Multi-colour flow cytometry was used to investigate myeloid and lymphoid populations in the peripheral blood of breast cancer patients (n = 40) and in the blood of healthy age-matched women (n = 25). We additionally performed functional testing to identify immune suppressive mechanisms used by circulating CD14+ myeloid cells from breast cancer patients.

RESULTS

Our results show that breast cancer patients have significantly elevated frequencies of cells with the monocytic myeloid-derived suppressor cell (mMDSC) phenotype CD14+ HLA-DR-/low compared with healthy women (p < 0.01). We also observed higher levels of earlier differentiated T cells and correspondingly lower levels of T cells in later stages of differentiation (p < 0.05). These disease-associated differences could already be detected in early-stage breast cancer patients in stages 1 and 2 (n = 33 of 40) (p < 0.05). Levels of circulating T cells correlated with certain clinical features and with patient age (p < 0.05). Functional tests showed that CD14+ myeloid cells from breast cancer patients more potently suppressed autologous T cell proliferation than CD14+ cells from healthy women (p < 0.01). Subsequent investigation determined that suppression was mediated in part by reactive oxygen species, because inhibiting this pathway partially restored T cell proliferation (p < 0.01).

CONCLUSION

Our results highlight the potential importance of cells with mMDSC phenotypes in breast cancer, identifiable already at early stages of disease. This may provide a basis for identifying possible new therapeutic targets to enhance anti-cancer immunity.

Overexpression of Arginase 1 is linked to DNMT3A and TET2 mutations in lower-grade myelodysplastic syndromes and chronic myelomonocytic leukemia

Immune dysregulation is a common feature of myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML), particularly in early stages. However, the genetic basis remains poorly understood. We recently reported that macrophages from mice deficient in tet methylcytosine dioxygenase 2 (Tet2), a model of MDS/CMML, are hyperinflammatory and have increased expression of arginase 1 (Arg1). In macrophages and myeloid derived suppressor cells (MDSCs) expression of Arg1 contributes to T-cell suppression and immune evasion by L-arginine depletion, in the setting of chronic inflammation and cancer. Since human MDS and CMML are driven by TET2 mutations and associated with chronic inflammation, we hypothesized that arginase enzymatic activity and ARG1 expression would be increased in human MDS/CMML bone marrow. Elevated arginase activity was observed in bone marrow mononuclear cells of MDS and CMML patients with lower-grade features. Immunohistochemical studies confirmed that myelomonocytic cells overexpress ARG1. Additionally, mutations in the epigenetic regulators TET2 and DNMT3A corresponded to high ARG1 expression and activity. These findings suggest ARG1 is a biomarker of immune dysregulation in early MDS and CMML. Recent murine findings have implicated Tet2 and Dnmt3a in regulation of innate immunity. Our study suggests similar changes may be driven by human TET2 and DNMT3A mutations.

Increased Levels of Circulating and Tumor-Infiltrating Granulocytic Myeloid Cells in Colorectal Cancer Patients

Increased levels of myeloid cells, especially myeloid-derived suppressor cells (MDSCs), have been reported to correlate with bad prognosis and reduced survival in cancer patients. However, limited data are available on their conclusive phenotypes and their correlation with clinical settings. The aim of this study was to investigate levels and phenotype of myeloid cells in peripheral blood and tumor microenvironment (TME) of colorectal cancer (CRC) patients, compared to blood from healthy donors (HDs) and paired, adjacent non-tumor colon tissue. Flow cytometric analysis was performed to examine the expression of different myeloid markers in fresh peripheral blood samples from CRC patients and HDs, and tissue-infiltrating immune cells from CRC patients. We found significantly higher levels of cells expressing myeloid markers and lacking the expression of major histocompatibility complex class II molecule HLA-DR in blood and tumor of CRC patients. Further analysis revealed that these cells were granulocytic and expressed Arginase 1 indicative of their suppressive phenotype. These expanded cells could be neutrophils or granulocytic MDSCs, and we refer to them as granulocytic myeloid cells (GMCs) due to the phenotypical and functional overlap between these cell subsets. Interestingly, the expansion of peripheral GMCs correlated with higher stage and histological grade of cancer, thereby suggesting their role in cancer progression. Furthermore, an increase in CD33+CD11b+HLA-DR-CD14-CD15- immature myeloid cells was also observed in CRC tumor tissue. Our work shows that GMCs are expanded in circulation and TME of CRC patients, which provides further insights for developing immunotherapeutic approaches targeting these cell subsets to enhance antitumor immune and clinical responses.

Pro-Tumoral Inflammatory Myeloid Cells as Emerging Therapeutic Targets

Since the observation of Virchow, it has long been known that the tumor microenvironment constitutes the soil for the infiltration of inflammatory cells and for the release of inflammatory mediators. Under certain circumstances, inflammation remains unresolved and promotes cancer development. Here, we review some of these indisputable experimental and clinical evidences of cancer related smouldering inflammation. The most common myeloid infiltrate in solid tumors is composed of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs). These cells promote tumor growth by several mechanisms, including their inherent immunosuppressive activity, promotion of neoangiogenesis, mediation of epithelial-mesenchymal transition and alteration of cellular metabolism. The pro-tumoral functions of TAMs and MDSCs are further enhanced by their cross-talk offering a myriad of potential anti-cancer therapeutic targets. We highlight these main pro-tumoral mechanisms of myeloid cells and give a general overview of their phenotypical and functional diversity, offering examples of possible therapeutic targets. Pharmacological targeting of inflammatory cells and molecular mediators may result in therapies improving patient condition and prognosis. Here, we review experimental and clinical findings on cancer-related inflammation with a major focus on creating an inventory of current small molecule-based therapeutic interventions targeting cancer-related inflammatory cells: TAMs and MDSCs.