Glucose-driven histone lactylation promotes the immunosuppressive activity of monocyte-derived macrophages in glioblastoma

Immunosuppressive macrophages restrict anti-cancer immunity in glioblastoma (GBM). Here, we studied the contribution of microglia (MGs) and monocyte-derived macrophages (MDMs) to immunosuppression and mechanisms underlying their regulatory function. MDMs outnumbered MGs at late tumor stages and suppressed T cell activity. Molecular and functional analysis identified a population of glycolytic MDM expressing GLUT1 with potent immunosuppressive activity. GBM-derived factors promoted high glycolysis, lactate, and interleukin-10 (IL-10) production in MDMs. Inhibition of glycolysis or lactate production in MDMs impaired IL-10 expression and T cell suppression. Mechanistically, intracellular lactate-driven histone lactylation promoted IL-10 expression, which was required to suppress T cell activity. GLUT1 expression on MDMs was induced downstream of tumor-derived factors that activated the PERK-ATF4 axis. PERK deletion in MDM abrogated histone lactylation, led to the accumulation of intratumoral T cells and tumor growth delay, and, in combination with immunotherapy, blocked GBM progression. Thus, PERK-driven glucose metabolism promotes MDM immunosuppressive activity via histone lactylation.

Linguistic markers of processing the first months of the pandemic COVID-19: a psycholinguistic analysis of Italian university students' diaries

A longitudinal psycholinguistic study was conducted with 107 students from different Italian universities that produced daily photo-diary entries for two weeks, one at the beginning and the other at the end of the first Italian lockdown period, imposed in view of the rapid dissemination of COVID -19. The task was to take a daily photo accompanied by a short description (text). The texts accompanying the photos were analysed using Linguistic Inquiry and Word Count (LIWC) software to analyze linguistic markers representing psychological processes related to the experience of the pandemic and the lockdown, identifying potential changes in psycholinguistic variables useful for understanding the psychological impact of such harsh and extended restricted living conditions on Italian students. LIWC categories related to negation, anger, cognitive mechanisms, tentative discourse, past, and future increased statistically significantly between the two time points, while word count, prepositions, communication, leisure, and home decreased statistically significantly. While male participants used more articles at both time points, females used more words related to anxiety, social processes, past, and present at T1 and more related to insight at T2. Participants who lived with their partner showed higher scores on negative emotions, affect, positive feelings, anger, optimism, and certainty. Participants from southern Italy tended to describe their experiences from a collective and social perspective rather than an individual perspective. By identifying, discussing, and comparing these phenomena with the broader literature, a spotlight is shed for the first time on the psycholinguistic analysis of students at the national level who faced the first COVID -19 lockdown in Italy.

Distinct Cell Adhesion Signature Defines Glioblastoma Myeloid-Derived Suppressor Cell Subsets

In multiple types of cancer, an increased frequency in myeloid-derived suppressor cells (MDSC) is associated with worse outcomes and poor therapeutic response. In the glioblastoma (GBM) microenvironment, monocytic (m) MDSCs represent the predominant subset. However, the molecular basis of mMDSC enrichment in the tumor microenvironment compared with granulocytic (g) MDSCs has yet to be determined. Here we performed the first broad epigenetic profiling of MDSC subsets to define underlying cell-intrinsic differences in behavior and found that enhanced gene accessibility of cell adhesion programs in mMDSCs is linked to their tumor-accelerating ability in GBM models upon adoptive transfer. Mouse and human mMDSCs expressed higher levels of integrin β1 and dipeptidyl peptidase-4 (DPP-4) compared with gMDSCs as part of an enhanced cell adhesion signature. Integrin β1 blockade abrogated the tumor-promoting phenotype of mMDSCs and altered the immune profile in the tumor microenvironment, whereas treatment with a DPP-4 inhibitor extended survival in preclinical GBM models. Targeting DPP-4 in mMDSCs reduced pERK signaling and their migration towards tumor cells. These findings uncover a fundamental difference in the molecular basis of MDSC subsets and suggest that integrin β1 and DPP-4 represent putative immunotherapy targets to attenuate myeloid cell-driven immune suppression in GBM.

SIGNIFICANCE

Epigenetic profiling uncovers cell adhesion programming as a regulator of the tumor-promoting functions of monocytic myeloid-derived suppressor cells in glioblastoma, identifying therapeutic targets that modulate the immune response and suppress tumor growth.

Biodegradable nanoparticles inhibit tumor growth by altering tumor-associated macrophages and cancer-associated fibroblasts

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Background: The tumor microenvironment (TME) plays a crucial role in tumor growth and progression and has a significant influence on response to therapy. The TME consists of myeloid-derived cells, stroma (e.g. fibroblasts and extracellular matrix (ECM)), and the vasculature that together support tumor growth and progression. Studies in animal models and in humans show that myeloid- derived cells such as myeloid derived suppressor cells (MDSCs) and tumor associated macrophages (TAMs) engage in activities that support tumor growth and progression. These cells also promote immune suppression in the TME that blunts the efficacy of the anti-cancer drugs and immune-targeted therapies such as immune checkpoint inhibitors. In addition to MDSCs, cancer-associated fibroblasts (CAFs) in the TME support tumor progression via production of pro-tumor and pro-angiogenic growth-factors, remodeling of the ECM via production of proteases, and suppression of anti-tumor immune function. CAF abundance in the TME is a negative prognostic factor for several solid tumors and is associated with negative outcomes and poor response to immune-targeted therapies like immune checkpoint inhibitors. ONP-302 nanoparticles fabricated from biodegradable poly (lactic-co-glycolic acid)(PLGA) polymer have been previously described in the literature for the treatment of acute inflammatory conditions via immuno-modulatory effects on myeloid derived cells. Here, we evaluated the efficacy of ONP-302 nanoparticles at inhibiting tumor growth via targeted inhibition of myeloid-derived cells and reshaping of the TME. Methods: ONP-302 anti-tumor efficacy was evaluated in syngeneic mouse tumor models using both immunocompetent and immunodeficient mice. We examined the effect of ONP-302 treatment tumor growth kinetics and effects on the major cellular constituents of the TME such as myeloid-derived cells and CAFs. Results: Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. We found ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Conclusions: Our data indicate that the slowing of tumor growth after ONP-302 treatment is due to disruptions in known signaling pathways involving TAMs and CAFs, pathways typically supporting tumor growth. These data taken in concert indicate the activity of ONP-302 is pleotropic and affects multiple pathways.

ONP-302 Nanoparticles Inhibit Tumor Growth By Altering Tumor-Associated Macrophages And Cancer-Associated Fibroblasts

In this study, we evaluated the ability of negatively charged bio-degradable nanoparticles, ONP- 302, to inhibit tumor growth. Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. Examination of ONP-302 effects on components of the tumor microenvironment (TME) were explored. ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Together, these data support further development of ONP-302 as a novel first-in- class anti-cancer therapeutic that can be used as a single-agent as well as in combination therapies for the treatment of solid tumors due to its ability to modulate the TME.

Myeloid-derived suppressor cells in the era of increasing myeloid cell diversity

Myeloid-derived suppressor cells (MDSCs) are pathologically activated neutrophils and monocytes with potent immunosuppressive activity. They are implicated in the regulation of immune responses in many pathological conditions and are closely associated with poor clinical outcomes in cancer. Recent studies have indicated key distinctions between MDSCs and classical neutrophils and monocytes, and, in this Review, we discuss new data on the major genomic and metabolic characteristics of MDSCs. We explain how these characteristics shape MDSC function and could facilitate therapeutic targeting of these cells, particularly in cancer and in autoimmune diseases. Additionally, we briefly discuss emerging data on MDSC involvement in pregnancy, neonatal biology and COVID-19.

Immune suppressive activity of myeloid-derived suppressor cells in cancer requires inactivation of the type I interferon pathway

Myeloid-derived suppressor cells (MDSC) are pathologically activated neutrophils and monocytes with potent immune suppressive activity. These cells play an important role in accelerating tumor progression and undermining the efficacy of anti-cancer therapies. The natural mechanisms limiting MDSC activity are not well understood. Here, we present evidence that type I interferons (IFN1) receptor signaling serves as a universal mechanism that restricts acquisition of suppressive activity by these cells. Downregulation of the IFNAR1 chain of this receptor is found in MDSC from cancer patients and mouse tumor models. The decrease in IFNAR1 depends on the activation of the p38 protein kinase and is required for activation of the immune suppressive phenotype. Whereas deletion of IFNAR1 is not sufficient to convert neutrophils and monocytes to MDSC, genetic stabilization of IFNAR1 in tumor bearing mice undermines suppressive activity of MDSC and has potent antitumor effect. Stabilizing IFNAR1 using inhibitor of p38 combined with the interferon induction therapy elicits a robust anti-tumor effect. Thus, negative regulatory mechanisms of MDSC function can be exploited therapeutically.

Analysis of classical neutrophils and polymorphonuclear myeloid-derived suppressor cells in cancer patients and tumor-bearing mice

In this study, using single-cell RNA-seq, cell mass spectrometry, flow cytometry, and functional analysis, we characterized the heterogeneity of polymorphonuclear neutrophils (PMNs) in cancer. We describe three populations of PMNs in tumor-bearing mice: classical PMNs, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and activated PMN-MDSCs with potent immune suppressive activity. In spleens of mice, PMN-MDSCs gradually replaced PMNs during tumor progression. Activated PMN-MDSCs were found only in tumors, where they were present at the very early stages of the disease. These populations of PMNs in mice could be separated based on the expression of CD14. In peripheral blood of cancer patients, we identified two distinct populations of PMNs with characteristics of classical PMNs and PMN-MDSCs. The gene signature of tumor PMN-MDSCs was similar to that in mouse activated PMN-MDSCs and was closely associated with negative clinical outcome in cancer patients. Thus, we provide evidence that PMN-MDSCs are a distinct population of PMNs with unique features and potential for selective targeting opportunities.

EGR1 is a gatekeeper of inflammatory enhancers in human macrophages

Monocytes and monocyte-derived macrophages originate through a multistep differentiation process. First, hematopoietic stem cells generate lineage-restricted progenitors that eventually develop into peripheral, postmitotic monocytes. Second, blood-circulating monocytes undergo differentiation into macrophages, which are specialized phagocytic cells capable of tissue infiltration. While monocytes mediate some level of inflammation and cell toxicity, macrophages boast the widest set of defense mechanisms against pathogens and elicit robust inflammatory responses. Here, we analyze the molecular determinants of monocytic and macrophagic commitment by profiling the EGR1 transcription factor. EGR1 is essential for monopoiesis and binds enhancers that regulate monocytic developmental genes such as CSF1R However, differentiating macrophages present a very different EGR1 binding pattern. We identify novel binding sites of EGR1 at a large set of inflammatory enhancers, even in the absence of its binding motif. We show that EGR1 repressive activity results in suppression of inflammatory genes and is mediated by the NuRD corepressor complex.

Myeloid Cells in Glioblastoma Microenvironment

Glioblastoma (GBM) is the most aggressive, malignant primary brain tumor in adults. GBM is notoriously resistant to immunotherapy mainly due to its unique immune microenvironment. High dimensional data analysis reveals the extensive heterogeneity of immune components making up the GBM microenvironment. Myeloid cells are the most predominant contributors to the GBM microenvironment; these cells are critical regulators of immune and therapeutic responses to GBM. Here, we will review the most recent advances on the characteristics and functions of different populations of myeloid cells in GBM, including bone marrow-derived macrophages, microglia, myeloid-derived suppressor cells, dendritic cells, and neutrophils. Epigenetic, metabolic, and phenotypic peculiarities of microglia and bone marrow-derived macrophages will also be assessed. The final goal of this review will be to provide new insights into novel therapeutic approaches for specific targeting of myeloid cells to improve the efficacy of current treatments in GBM patients.

Polymorphonuclear myeloid-derived suppressor cells limit antigen cross-presentation by dendritic cells in cancer

DCs are a critical component of immune responses in cancer primarily due to their ability to cross-present tumor-associated antigens. Cross-presentation by DCs in cancer is impaired, which may represent one of the obstacles for the success of cancer immunotherapies. Here, we report that polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) blocked cross-presentation by DCs without affecting direct presentation of antigens by these cells. This effect did not require direct cell-cell contact and was associated with transfer of lipids. Neutrophils (PMN) and PMN-MDSC transferred lipid to DCs equally well; however, PMN did not affect DC cross-presentation. PMN-MDSC generate oxidatively truncated lipids previously shown to be involved in impaired cross-presentation by DCs. Accumulation of oxidized lipids in PMN-MDSC was dependent on myeloperoxidase (MPO). MPO-deficient PMN-MDSC did not affect cross-presentation by DCs. Cross-presentation of tumor-associated antigens in vivo by DCs was improved in MDSC-depleted or tumor-bearing MPO-KO mice. Pharmacological inhibition of MPO in combination with checkpoint blockade reduced tumor progression in different tumor models. These data suggest MPO-driven lipid peroxidation in PMN-MDSC as a possible non-cell autonomous mechanism of inhibition of antigen cross-presentation by DCs and propose MPO as potential therapeutic target to enhance the efficacy of current immunotherapies for patients with cancer.

Subclinical atherosclerosis and its progression are modulated by PLIN2 through a feed-forward loop between LXR and autophagy

BACKGROUND

Hyperlipidaemia is a major risk factor for cardiovascular disease, and atherosclerosis is the underlying cause of both myocardial infarction and stroke. We have previously shown that the Pro251 variant of perilipin-2 reduces plasma triglycerides and may therefore be beneficial to reduce atherosclerosis development.

OBJECTIVE

We sought to delineate putative beneficial effects of the Pro251 variant of perlipin-2 on subclinical atherosclerosis and the mechanism by which it acts.

METHODS

A pan-European cohort of high-risk individuals where carotid intima-media thickness has been assessed was adopted. Human primary monocyte-derived macrophages were prepared from whole blood from individuals recruited by perilipin-2 genotype or from buffy coats from the Karolinska University hospital blood central.

RESULTS

The Pro251 variant of perilipin-2 is associated with decreased intima-media thickness at baseline and over 30 months of follow-up. Using human primary monocyte-derived macrophages from carriers of the beneficial Pro251 variant, we show that this variant increases autophagy activity, cholesterol efflux and a controlled inflammatory response. Through extensive mechanistic studies, we demonstrate that increase in autophagy activity is accompanied with an increase in liver-X-receptor (LXR) activity and that LXR and autophagy reciprocally activate each other in a feed-forward loop, regulated by CYP27A1 and 27OH-cholesterol.

CONCLUSIONS

For the first time, we show that perilipin-2 affects susceptibility to human atherosclerosis through activation of autophagy and stimulation of cholesterol efflux. We demonstrate that perilipin-2 modulates levels of the LXR ligand 27OH-cholesterol and initiates a feed-forward loop where LXR and autophagy reciprocally activate each other; the mechanism by which perilipin-2 exerts its beneficial effects on subclinical atherosclerosis.

Identification of monocyte-like precursors of granulocytes in cancer as a mechanism for accumulation of PMN-MDSCs

Mastio et al. describe monocytic precursors of granulocytes. These precursors are barely detectable in steady state conditions and are not consequential for differentiation of granulocytes. However, they accumulate in cancer and substantially contribute to PMN-MDSC expansion.

We have identified a precursor that differentiates into granulocytes in vitro and in vivo yet belongs to the monocytic lineage. We have termed these cells monocyte-like precursors of granulocytes (MLPGs). Under steady state conditions, MLPGs were absent in the spleen and barely detectable in the bone marrow (BM). In contrast, these cells significantly expanded in tumor-bearing mice and differentiated to polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). Selective depletion of monocytic cells had no effect on the number of granulocytes in naive mice but decreased the population of PMN-MDSCs in tumor-bearing mice by 50%. The expansion of MLPGs was found to be controlled by the down-regulation of Rb1, but not IRF8, which is known to regulate the expansion of PMN-MDSCs from classic granulocyte precursors. In cancer patients, putative MLPGs were found within the population of CXCR1⁺CD15⁻CD14⁺HLA-DR^−/lo monocytic cells. These findings describe a mechanism of abnormal myelopoiesis in cancer and suggest potential new approaches for selective targeting of MDSCs.

Fatty acid transporter 2 regulates the suppressive functions of PMN-MDSC in cancer

Polymorphonuclear myeloid derived suppressor cells (PMN-MDSC) are critically important for the regulation of immune responses in cancer, promotion of tumor progression, and metastases. PMN-MDSC contribute to the failure of cancer therapies and their presence in cancer patients correlates with a poor prognosis. However, despite the recent advances in understanding of the PMN-MDSC biology, the mechanisms responsible for their suppressive functions are not well defined. The understanding of these mechanisms is critical important for the development of therapeutic strategies for the specific targeting of PMN-MDSC in cancer. Here, we report a massive accumulation of lipids in PMN-MDSC from tumor bearing mice and from cancer patients, compared to normal neutrophils from tumor free mice and healthy donors, respectively. The content of lipids was much higher in PMN-MDSC infiltrating the tumor. The accumulation of lipids was mediated by the exclusive up-regulation of the fatty acid transporter 2 (FATP2) in PMN-MDSC. The deletion of FATP2 abrogated the suppressive activity of PMN-MDSC in spleens and tumors. The selective pharmacological inhibition of FATP2 altered the activity of PMN-MSC and delayed tumor progression in mice. Importantly, FATP2 inhibition in PMN-MDSC favored tumor regression in mice when combined with checkpoint inhibitors. In conclusion, we show that FATP2 regulates the immune suppressive activity of PMN-MDSC and may represent a new target to selectively inhibit the functions of PMN-MDSC and to improve the effect of immunotherapy.

Fatty acid transport protein 2 reprograms neutrophils in cancer

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are pathologically activated neutrophils that are crucial for the regulation of immune responses in cancer. These cells contribute to the failure of cancer therapies and are associated with poor clinical outcomes. Despite recent advances in the understanding of PMN-MDSC biology, the mechanisms responsible for the pathological activation of neutrophils are not well defined, and this limits the selective targeting of these cells. Here we report that mouse and human PMN-MDSCs exclusively upregulate fatty acid transport protein 2 (FATP2). Overexpression of FATP2 in PMN-MDSCs was controlled by granulocyte-macrophage colony-stimulating factor, through the activation of the STAT5 transcription factor. Deletion of FATP2 abrogated the suppressive activity of PMN-MDSCs. The main mechanism of FATP2-mediated suppressive activity involved the uptake of arachidonic acid and the synthesis of prostaglandin E₂. The selective pharmacological inhibition of FATP2 abrogated the activity of PMN-MDSCs and substantially delayed tumour progression. In combination with checkpoint inhibitors, FATP2 inhibition blocked tumour progression in mice. Thus, FATP2 mediates the acquisition of immunosuppressive activity by PMN-MDSCs and represents a target to inhibit the functions of PMN-MDSCs selectively and to improve the efficiency of cancer therapy.

Abstract 5133: Lipids and suppressive functions of MDSC in cancer

Myeloid derived suppressor cells (MDSC) play an important role in the regulation of anti-tumor responses and their presence in cancer patients correlates with a poor prognosis. MDSC contribute to the failure of cancer therapies and favor tumor progression and metastasis. However, despite the recent advances in understanding the biology of MDSC, the mechanisms driving their expansion and suppressive function are not yet well defined. Polymorphonuclear, PMN-MDSC is by far the largest population of MDSC. Here, we found that PMN-MDSC from tumor bearing mice and from cancer patients have higher amount of lipids than their counterpart (neutrophils) in tumor free mice and healthy donors, respectively. The content of lipids in PMN-MDSC was much higher in MDSC infiltrating the tumor, and the accumulation of lipids in PMN-MDSC was caused by the uptake of extracellular lipids. Lipid profile of PMN-MDSC demonstrated accumulation of oxidized fatty acids as part of triglycerides and phospholipids. We demonstrated that fatty acids accumulated by PMN-MDSC are oxidized by myeloperoxidase (MPO) and reactive oxygen species (ROS) generated by Nox2. Genetic ablation of MPO or ROS in MDSC results in a drastic reduction of lipid oxidation and in an impaired ability of MDSC to suppress CD8 T cell responses. In line with these findings, unsaturated fatty acids, highly susceptible to oxidation, favor the expansion of highly suppressive MDSC from hematopoietic progenitors in vitro, contrary to non-oxidizable saturated fatty acids. Together, our data suggest that MDSC have increased ability to pick up lipids from the microenvironment and to oxidize them via their potent oxidative machinery. In turn oxygenated lipids contribute to the suppressive activity of MDSC. In conclusion, the regulation of the oxidation of lipids in MDSC could be an attractive therapeutic strategy in cancer.

Citation Format: Filippo Veglia, Vladimir A. Tyurin, Valerian E. Kagan, Dmitry Gabrilovich. Lipids and suppressive functions of MDSC in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5133.

Integrative studies implicate matrix metalloproteinase-12 as a culprit gene for large-artery atherosclerotic stroke

BACKGROUND

Ischaemic stroke and coronary heart disease are important contributors to the global disease burden and share atherosclerosis as the main underlying cause. Recent evidence from a genome-wide association study (GWAS) suggested that single nucleotide polymorphisms (SNP) near the MMP12 gene at chromosome 11q22.3 were associated with large-vessel ischaemic stroke. Here, we evaluated and extended these results by examining the relationship between MMP12 and atherosclerosis in clinical and experimental studies.

METHODS AND RESULTS

Plasma concentrations of MMP12 were measured at baseline in 3394 subjects with high-risk for cardiovascular disease (CVD) using the Olink ProSeek CVD I array. The plasma MMP12 concentration showed association with incident cardiovascular and cerebrovascular events (130 and 67 events, respectively, over 36 months) and carotid intima-media thickness progression (P = 3.6 × 10^-5 ). A GWAS of plasma MMP12 concentrations revealed that SNPs rs499459, rs613084 and rs1892971 at chr11q22.3 were independently associated with plasma MMP12 (P < 5 × 10^-8 ). The lead SNPs showed associations with mRNA levels of MMP12 and adjacent MMPs in atherosclerotic plaques. MMP12 transcriptomic and proteomic levels were strongly significantly increased in carotid plaques compared with control arterial tissue and in plaques from symptomatic versus asymptomatic patients. By combining immunohistochemistry and proximity ligation assay, we demonstrated that MMP12 localizes to CD68 + macrophages and interacts with elastin in plaques. MMP12 silencing in human THP-1-derived macrophages resulted in reduced macrophage migration.

CONCLUSIONS

Our study supports the notion that MMP12 is implicated in large-artery atherosclerotic stroke, functionally by enhancing elastin degradation and macrophage invasion in plaques.

Dendritic cells in cancer: the role revisited

Dendritic cells (DCs) with their potent antigen presenting ability are long considered as critical factor in antitumor immunity. Despite high potential in promoting antitumor responses, tumor-associated DCs are largely defective in their functional activity and can contribute to immune suppression in cancer. In recent years existence of immune suppressive regulatory DCs in tumor microenvironment was described. Monocytic myeloid derived suppressor cells (M-MDSCs) can contribute to the pool of tumor associated DCs by differentiating to inflammatory DCs (inf-DCs), which appear to have specific phenotype and is critical component of antitumor response. Here we examine the role of inf-DCs along with other DC subsets in the regulation of immune responses in cancer. These novel data expand our view on the role of DCs in cancer and may provide new targets for immunotherapy.

Oxidized lipid bodies block antigen cross-presentation in cancer by preventing trafficking of peptide-MHC class I complexes

Background

Antigen cross presentation is a unique feature of dendritic cells (DCs) and plays an important role in the development of specific CD8+ T cell responses. It is established that the defect in cross-presentation by dendritic cells (DCs) in cancer results in ineffective antitumor immune responses and favors tumor escape. However, the mechanisms behind this phenomenon are unclear.

Results

In this study we found that tumor-derived factors impaired cross-presentation by differentiated conventional DCs without affecting expression of MHC class I, class II, or costimulatory molecules. The ability of DCs to stimulate antigen-specific T cells after loading with short peptide (directly bound to MHC class I) was fully preserved. We found that tumor-derived factors blocked trafficking of peptide-MHC class I (pMHC) complexes to the cell surface. These complexes were found to be entrapped into the lysosomes. This effect was caused by the accumulation of lipid bodies (LB) containing oxidized (ox) triglycerides (TAG) in DCs. Importantly LB containing non-oxidized TAG did not affect cross-presentation. Further experiments have identified the specific molecular mechanism responsible for oxTAG containing LB mediated block of cross-presentation in DCs.

Conclusions

Our results suggest a novel mechanism of regulation of cross-presentation in cancer

Acquired lecithin:cholesterol acyltransferase deficiency as a major factor in lowering plasma HDL levels in chronic kidney disease

OBJECTIVES

It has been suggested that a low plasma high-density lipoprotein cholesterol (HDL-C) level contributes to the high cardiovascular disease risk of patients with chronic kidney disease (CKD), especially those undergoing haemodialysis (HD). The present study was conducted to gain further understanding of the mechanism(s) responsible for the low HDL-C levels in patients with CKD and to separate the impact of HD from that of the underlying CKD.

METHODS

Plasma lipids and lipoproteins, HDL subclasses and various cholesterol esterification parameters were measured in a total of 248 patients with CKD, 198 of whom were undergoing HD treatment and 40 healthy subjects.

RESULTS

Chronic kidney disease was found to be associated with highly significant reductions in plasma HDL-C, unesterified cholesterol, apolipoprotein (apo)A-I, apoA-II and LpA-I:A-II levels in both CKD cohorts (with and without HD treatment). The cholesterol esterification process was markedly impaired, as indicated by reductions in plasma lecithin:cholesterol acyltransferase (LCAT) concentration and activity and cholesterol esterification rate, and by an increase in the plasma preβ-HDL content. HD treatment was associated with a further lowering of HDL levels and impaired plasma cholesterol esterification. The plasma HDL-C level was highly significantly correlated with LCAT concentration (R = 0.438, P < 0.001), LCAT activity (R = 0.243, P < 0.001) and cholesterol esterification rate (R = 0.149, P = 0.031). Highly significant correlations were also found between plasma LCAT concentration and levels of apoA-I (R = 0.432, P < 0.001), apoA-II (R = 0.275, P < 0.001), LpA-I (R = 0.326, P < 0.001) and LpA-I:A-II (R = 0.346, P < 0.001).

CONCLUSION

Acquired LCAT deficiency is a major cause of low plasma HDL levels in patients with CKD, thus LCAT is an attractive target for therapeutic intervention to reverse dyslipidaemia, and possibly lower the cardiovascular disease risk in these patients.

Retinoic acid imprints a mucosal-like phenotype on dendritic cells with an increased ability to fuel HIV-1 infection

The tissue microenvironment shapes the characteristics and functions of dendritic cells (DCs), which are important players in HIV infection and dissemination. Notably, DCs in the gut have the daunting task of orchestrating the balance between immune response and tolerance. They produce retinoic acid (RA), which imprints a gut-homing phenotype and influences surrounding DCs. To investigate how the gut microenvironment impacts the ability of DCs to drive HIV infection, we conditioned human immature monocyte-derived DCs (moDCs) with RA (RA-DCs), before pulsing them with HIV and mixing them with autologous T cells. RA-DCs showed a semimature, mucosal-like phenotype and released higher amounts of TGF-β1 and CCL2. Using flow cytometry, Western blot, and microscopy, we determined that moDCs express the cell adhesion molecule mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1) and that RA increases its expression. MAdCAM-1 was also detected on a small population of DCs in rhesus macaque (Macaca mulata) mesenteric lymph node. RA-DCs formed more DC-T cell conjugates and promoted significantly higher HIV replication in DC-T cell mixtures compared with moDCs. This correlated with the increase in MAdCAM-1 expression. Blocking MAdCAM-1 partially inhibited the enhanced HIV replication. In summary, RA influences DC phenotype, increasing their ability to exacerbate HIV infection. We describe a previously unknown mechanism that may contribute to rapid HIV spread in the gut, a major site of HIV replication after mucosal exposure.

Transrectal doppler ultrasound during prostate biopsy: clinical utility and limitations

OBJECTIVE

To determine the clinical utility and limitations of guided prostate biopsy Power Doppler in patients with elevated serum PSA levels.

MATERIALS AND METHOD

Prospective study. From April 2012 to May 2013, 111 men over 45 years of age with serum PSA level greater than 4.0ng/dl who underwent a transrectal prostate biopsy were included. The hypoechoic nodules in the peripheral region were considered positive on the gray scale. Subsequently, the study was conducted with the Power Doppler, where the vascularization of suspicious images was analyzed for sampling. In addition, samples were taken from the suspected areas when performing the digital rectal examination. We calculated sensitivity, specificity, positive predictive value and negative predictive value of the three tests (digital rectal examination, standard gray scale ultrasound and power Doppler).

RESULTS

Prostate cancer was diagnosed in 48 of the 111 patients (43%). Fifty-nine cases (53%) were defined as positive with the Power Doppler. Of these, 39 (66%) corresponded to a diagnosis of prostate adenocarcinoma. The Power Doppler was positive in 39 cases of the 48 patients diagnosed with cancer and the gray scale ultrasound was positive in 31 cases. Overall sensitivity of the power Doppler was 81%, specificity 68%, PPV 66% and NPV 82%, which was higher compared to the other methods (P<.05).

CONCLUSION

Currently, prostate biopsy using Power Doppler does not seem to identify prostate cancer with sufficient accuracy to omit the guided systematic biopsy gray scale, the combined use of these methods being preferable.

In vivo prostacyclin biosynthesis and effects of different aspirin regimens in patients with essential thrombocythaemia

Essential thrombocythaemia (ET) is characterised by enhanced platelet generation and thrombosis. Once daily (od) aspirin incompletely inhibits platelet thromboxane (TX)A2 production in ET. A twice daily (bid) dosing is necessary to fully inhibit TXA2. Whether this dosing regimen affects in vivo prostacyclin (PGI2) biosynthesis is unknown. PGI2 biosynthesis was characterised in 50 ET patients on enteric-coated (EC) aspirin 100 mg od, by measuring its urinary metabolite, 2,3-dinor-6-keto-PGF1α (PGI-M). Moreover, in a crossover study 22 patients poorly responsive to standard aspirin based on serum TXB2 levels (≥4 ng/ml) were randomised to different seven-day aspirin regimens: EC aspirin 100 mg od, 100 mg bid, 200 mg od, or plain aspirin 100 mg od. PGI-M measured 24 hours after the last aspirin intake (EC, 100 mg od) was similar in patients and healthy subjects both on (n=10) and off (n=30) aspirin. PGI-M was unrelated to in vivo TXA2 biosynthesis, and not affected by EC aspirin 100 mg bid or 200 mg od as compared to EC 100 mg od. PGI2 biosynthesis in aspirin-treated ET patients appears unrelated to TXA2 biosynthesis, and not affected by an improved aspirin regimen, demonstrating its vascular safety for future trials.

Oxidized lipids block antigen cross-presentation by dendritic cells in cancer

Cross-presentation is one of the main features of dendritic cells (DCs), which is critically important for the development of spontaneous and therapy-inducible antitumor immune responses. Patients, at early stages of cancer, have normal presence of DCs. However, the difficulties in the development of antitumor responses in patients with low tumor burden raised the question of the mechanisms of DC dysfunction. In this study, we found that, in differentiated DCs, tumor-derived factors blocked the cross-presentation of exogenous Ags without inhibiting the Ag presentation of endogenous protein or peptides. This effect was caused by intracellular accumulation of different types of oxidized neutral lipids: triglycerides, cholesterol esters, and fatty acids. In contrast, the accumulation of nonoxidized lipids did not affect cross-presentation. Oxidized lipids blocked cross-presentation by reducing the expression of peptide-MHC class I complexes on the cell surface. Thus, this study suggests the novel role of oxidized lipids in the regulation of cross-presentation.

LDL oxidative modification and carotid atherosclerosis: results of a multicenter study

OBJECTIVE

Serum LDL conjugated diene concentration is a marker of oxidative modification of LDL. We investigated the relationship between LDL conjugated dienes and cross-sectional subclinical atherosclerosis assessed by carotid IMT in high-risk subjects of a multicenter study.

METHODS

Serum LDL conjugated dienes and ultrasonographically assessed carotid intima-media thickness (IMT(mean), IMT(max) and IMT(mean-max)) were available for 553 subjects from Finland, France, Italy, the Netherlands, and Sweden.

RESULTS

In multivariate regression analysis, gender (p < 0.001), age (p < 0.001), systolic blood pressure (IMT(mean), p = 0.01; IMT(mean-max), p = 0.05) and serum LDL conjugated dienes (p = 0.02 for both IMT(mean) and IMT(mean-max)) were the strongest determinants of IMT variation, adjusted for study center, ultrasound videotape reader and serum LDL cholesterol. Pack-years of smoking, added into the regression model, did not destroy the significant association between increased serum LDL conjugated dienes and IMT. Ratio of LDL conjugated dienes to LDL particle cholesterol was higher in subjects of Northern recruiting centers than of Southern centers (r = 0.39, p < 0.0001).

CONCLUSIONS

There was a cross-sectional association between in vivo increased LDL oxidative modification and subclinical atherosclerosis after adjustment for traditional risk factors. The subjects in Northern countries of Europe had more oxidatively modified lipids per cholesterol in LDL particle than subjects in Southern countries.

HER2-based recombinant immunogen to target DCs through FcγRs for cancer immunotherapy

Dendritic cell (DC)-based immunotherapy is an attractive approach to induce long lasting antitumor effector cells aiming to control cancer progression. DC targeting is a critical step in the design of DC vaccines in order to optimize delivery and processing of the antigen, and several receptors have been characterized for this purpose. In this study, we employed the FcγRs to target DCs both in vitro and in vivo. We designed a recombinant molecule (HER2-Fc) composed of the immunogenic sequence of the human tumor-associated antigen HER2 (aa 364–391) and the Fc domain of a human IgG₁. In a mouse model, HER2-Fc cDNA vaccination activated significant T cell-mediated immune responses towards HER2 peptide epitopes as detected by IFN-γ ELIspot and induced longer tumor latency as compared to Ctrl-Fc-vaccinated control mice. Human in vitro studies indicated that the recombinant HER2-Fc immunogen efficiently targeted human DCs through the FcγRs resulting in protein cross-processing and in the activation of autologous HER2-specific CD8⁺ T cells from breast cancer patients.

Polyclonal Treg cells enhance the activity of a mucosal adjuvant

The efficacy of vaccines can be greatly improved by adjuvants that enhance and modify the magnitude and the duration of the immune response. Several approaches to design rational adjuvants are based on the suppression of regulatory T-cell (Treg) function. Here, we evaluated whether removal or addition of Treg at the time of vaccination with tetanus toxoid and the mucosal adjuvant cholera toxin (CT), would affect immune responses. We found that depletion/inactivation of CD4(+)CD25(+) Treg, either by treatment of BALB/c mice with anti-CD25 monoclonal antibodies or by adoptive transfer of CD4(+)CD25(-) T lymphocytes depleted of CD4(+)CD25(+) Treg into nu/nu mice, impaired antibody production after mucosal immunization in the presence of CT. Conversely, transfer of polyclonal, but not Ag-specific, CD4(+)CD25(+)Foxp3(+) Treg to normal BALB/c mice enhanced CT-induced antibody responses. An increased titer of both immunoglobulin IgG1 and IgG2a antibody subclasses was found, however, the ratio between IgG1/IgG2a with or without polyclonal Treg was comparable, suggesting that polyclonal Treg influence the magnitude, but not the quality of the immune response. Recipients of polyclonal Treg that had been immunized with CT had an increased number of Ag-specific CD4(+) T cells with an activated phenotype (CD44(hi)) in the draining lymph nodes. This accumulation of Ag-specific CD4(+) T lymphocytes could favour the germinal centre formation and may promote T-dependent B-cell responses. Overall, our study indicates that Foxp3(+) Treg can not only function as suppressor cells but also as helper T cells, depending on the type of immune response being evaluated and the microenvironment in which the response is generated.

Impact of dietary regimen on the duration of cow's milk allergy: a random allocation study

BACKGROUND

The impact of diet on cow's milk allergy (CMA) duration and whether exposure to residual amounts of cow's milk protein influences the onset of tolerance are unknown.

OBJECTIVE

To prospectively assess the dietary factors influencing disease duration in a randomized cohort.

METHODS

We randomly switched the formula of symptomatic patients from the Milan Cow's Milk Allergy Cohort to one of three treatment groups according to the quarterly rotation of rice hydrolysate formula, extensively hydrolysed cow's milk formula and soy-based formula. In this intention-to-treat, randomized analysis, a hazard ratio (HR) estimation model was used to analyse dietary impact on disease duration.

RESULTS

Seventy-two children aged a mean of 14.1+/-8.6 months at diagnosis were followed up for a median of 26 months. Fifty-one reached tolerance at a mean of 34.1+/-15.2 months. The mean duration of disease was 40.2+/-4.8 months with milk hydrolysate, 24.3+/-3.6 months with rice and 24.3+/-2.6 months with soy. Dietary choice independently predicted shorter duration of disease [adjusted HRs 3.09 (P=0.007) for rice, 2.54 (P=0.02) for soy, both against milk hydrolysate]. In 50 children not co-sensitized to soy, diet choice impacted the duration of disease more strongly [adjusted HRs 8.02 (P=0.006) for rice, 6.53 (P=0.015) for soy, both against milk hydrolysate].

DISCUSSION

Patients not exposed to cow's milk protein residue achieve cow's milk tolerance earlier than patients who follow an extensively hydrolysed cow's milk diet. This may be due to residual antigenicity in hydrolysed milks. As the effect of dietary intervention is stronger in patients not sensitized to soy, we infer that when atopic disease has progressed to multiple sensitizations, the elimination of allergenic exposure may not be sufficient to reduce the duration of CMA.

Persistence of CCR5 usage among primary human immunodeficiency virus isolates of individuals receiving intermittent interleukin-2

OBJECTIVE

To investigate the impact of intermittent interleukin-2 (IL-2) plus combination antiretroviral therapy (cART) on HIV-1 entry co-receptor use.

METHODS

Primary HIV-1 isolates were obtained from 54 HIV-1-positive individuals at baseline and after 12 months using co-cultivation of peripheral blood mononuclear cells (PBMC) with activated PBMC of HIV-negative healthy donors. HIV-1 co-receptor use was determined on U87-CD4 cells.

RESULTS

Fourteen out of the 21 (67%) IL-2-treated individuals harbouring a primary CCR5-dependent (R5) HIV-1 isolate at baseline confirmed an R5 virus isolation after 12 months in contrast to 3 out of 7 (43%) of those receiving cART only. After 12 months, only 1 R5X4 HIV-1 isolate was obtained from 21 cART+IL-2-treated individuals infected with an R5 virus at entry (5%) vs. 2/7 (29%) patients receiving cART alone, as confirmed by a 5-year follow-up on some individuals.

CONCLUSIONS

Intermittent IL-2 administration plus cART may prevent evolution towards CXCR4 usage in individuals infected with R5 HIV-1.

Markers of inflammation, thrombosis and endothelial activation correlate with carotid IMT regression in stable coronary disease after atorvastatin treatment

BACKGROUND AND AIMS

MIAMI is a prospective multicenter clinical study designed to investigate the relationship between changes in carotid intima-media thickness (C-IMT) and changes in circulating markers of inflammation, thrombosis and endothelial activation in stable coronary patients treated for 20+/-3.7 months with 20mg/day atorvastatin.

METHODS AND RESULTS

Eighty-five subjects had their C-IMT, blood lipids and soluble markers measured at baseline, at the 12th month and at the end of the study. Almost all soluble markers decreased upon treatment except for high-sensitivity C-reactive protein (hs-CRP), interleukin-18 (IL-18), tissue factor pathway inhibitor-free (TFPI-free) and soluble vascular cell adhesion molecules-1 (sVCAM-1) which did not change significantly, and interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and soluble CD40 ligand (sCD40L) which increased. sCD40L, fibrinogen, tissue factor pathway inhibitor-total (TFPI-total), soluble intercellular adhesion molecules-1 (sICAM-1), sE-selectin, interleukin-8 (IL-8) and von Willebrand factor (vWF) changed significantly even after application of the Bonferroni correction for multiple comparisons. Changes in lipids did not correlate with C-IMT regression either when considered singly or when combined in a lipid score. Changes in soluble markers correlated poorly with C-IMT regression when analyzed singly, but strongly when combined in relevant composite scores (inflammation/coagulation score, endothelial activation score, soluble markers score and total score).

CONCLUSION

In patients with stable coronary artery disease treated with moderate doses of atorvastatin, carotid IMT regression correlated with changes of inflammation, thrombosis and endothelial activation profiles.