A novel, macrophage migration inhibitory factor suicide substrate inhibits motility and growth of lung cancer cells

The C-terminal Region of D-DT Regulates Molecular Recognition for Protein-Ligand Complexes

Systematic analysis of molecular recognition is critical for understanding the biological function of macromolecules. For the immunomodulatory protein D-dopachrome tautomerase (D-DT), the mechanism of protein-ligand interactions is poorly understood. Here, 17 carefully designed protein variants and wild type (WT) D-DT were interrogated with an array of complementary techniques to elucidate the structural basis of ligand recognition. Utilization of a substrate and two selective inhibitors with distinct binding profiles offered previously unseen mechanistic insights into D-DT-ligand interactions. Our results demonstrate that the C-terminal region serves a key role in molecular recognition via regulation of the active site opening, protein-ligand interactions, and conformational flexibility of the pocket's environment. While our study is the first comprehensive analysis of molecular recognition for D-DT, the findings reported herein promote the understanding of protein functionality and enable the design of new structure-based drug discovery projects.

Macrophage migration inhibitory factor blockade reprograms macrophages and disrupts prosurvival signaling in acute myeloid leukemia

The malignant microenvironment plays a major role in the development of resistance to therapies and the occurrence of relapses in acute myeloid leukemia (AML). We previously showed that interactions of AML blasts with bone marrow macrophages (MΦ) shift their polarization towards a protumoral (M2-like) phenotype, promoting drug resistance; we demonstrated that inhibiting the colony-stimulating factor-1 receptor (CSF1R) repolarizes MΦ towards an antitumoral (M1-like) phenotype and that other factors may be involved. We investigated here macrophage migration inhibitory factor (MIF) as a target in AML blast survival and protumoral interactions with MΦ. We show that pharmacologically inhibiting MIF secreted by AML blasts results in their apoptosis. However, this effect is abrogated when blasts are co-cultured in close contact with M2-like MΦ. We next demonstrate that pharmacological inhibition of MIF secreted by MΦ, in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF), efficiently reprograms MΦ to an M1-like phenotype that triggers apoptosis of interacting blasts. Furthermore, contact with reprogrammed MΦ relieves blast resistance to venetoclax and midostaurin acquired in contact with CD163+ protumoral MΦ. Using intravital imaging in mice, we also show that treatment with MIF inhibitor 4-IPP and GM-CSF profoundly affects the tumor microenvironment in vivo: it strikingly inhibits tumor vasculature, reduces protumoral MΦ, and slows down leukemia progression. Thus, our data demonstrate that MIF plays a crucial role in AML MΦ M2-like protumoral phenotype that can be reversed by inhibiting its activity and suggest the therapeutic targeting of MIF as an avenue towards improved AML treatment outcomes.

MIF contribution to progressive brain diseases

Progressive brain diseases create a huge social and economic burden on modern societies as a major cause of disability and death. Incidence of brain diseases has a significantly increasing trend and merits new therapeutic strategies. At the base of many progressive brain malfunctions is a process of unresolved, chronic inflammation. Macrophage migration inhibitory factor, MIF, is an inflammatory mediator that recently gained interest of neuro-researchers due to its varied effects on the CNS such as participation of nervous system development, neuroendocrine functions, and modulation of neuroinflammation. MIF appears to be a candidate as a new biomarker and target of novel therapeutics against numerous neurologic diseases ranging from cancer, autoimmune diseases, vascular diseases, neurodegenerative pathology to psychiatric disorders. In this review, we will focus on MIF's crucial role in neurological diseases such as multiple sclerosis (MS), Alzheimer's disease (AD) and glioblastoma (GBM).

Phosphorylation of MIF by PIP4K2a is necessary for cilia biogenesis

Primary cilia are microtubule-based organelles that play important roles in development and tissue homeostasis. Macrophage migration inhibitory factor (MIF) has long been recognized as a secreted cytokine in the pathogenesis of various human diseases, including cancer and autosomal dominant polycystic kidney disease (ADPKD). Unlike other cytokines, unique functional characteristics of intracellular MIF have emerged. In this study, we show that MIF is localized and formed a ring like structure at the proximal end of centrioles, where it regulates cilia biogenesis through affecting 1) the recruitment of TTBK2 to basal body and the removal of CP110 from mother centriole, 2) the accumulation of CEP290 at centriolar satellites, and 3) the trafficking of intraflagellar transport (IFT) related proteins. We also show that MIF functions as a novel transcriptional factor to regulate the expression of genes related to ciliogenesis via binding on the promotors of those genes. MIF also binds chromatin and regulates transcription of genes involved in diverse homeostatic signaling pathways. We identify phosphatidylinositol-5-phosphate 4-kinase type 2 alpha (PIP4K2a) as an upstream regulator of MIF, which interacts with and phosphorylates MIF at S91 to increase its interaction with 14-3-3ζ, resulting in its nuclear translocation and transcription regulation. This study suggests that MIF is a key player in cilia biogenesis and a novel transcriptional regulator in homeostasis, which forward our understanding of how MIF is able to carry out several nonoverlapping functions.

Infection and inflammation stimulate expansion of a CD74+ Paneth cell subset to regulate disease progression

Paneth cells (PCs), a specialized secretory cell type in the small intestine, are increasingly recognized as having an essential role in host responses to microbiome and environmental stresses. Whether and how commensal and pathogenic microbes modify PC composition to modulate inflammation remain unclear. Using newly developed PC-reporter mice under conventional and gnotobiotic conditions, we determined PC transcriptomic heterogeneity in response to commensal and invasive microbes at single cell level. Infection expands the pool of CD74+ PCs, whose number correlates with auto or allogeneic inflammatory disease progressions in mice. Similar correlation was found in human inflammatory disease tissues. Infection-stimulated cytokines increase production of reactive oxygen species (ROS) and expression of a PC-specific mucosal pentraxin (Mptx2) in activated PCs. A PC-specific ablation of MyD88 reduced CD74+ PC population, thus ameliorating pathogen-induced systemic disease. A similar phenotype was also observed in mice lacking Mptx2. Thus, infection stimulates expansion of a PC subset that influences disease progression.

Suppression of epithelial proliferation and tumorigenesis by immunoglobulin A

Immunoglobulin A (IgA) is the most abundant antibody isotype produced across mammals and plays a specialized role in mucosal homeostasis 1 . Constantly secreted into the lumen of the intestine, IgA binds commensal microbiota to regulate their colonization and function 2,3 , with unclear implications for health. IgA deficiency is common in humans but is difficult to study due to its complex etiology and comorbidities 4-8 . Using genetically and environmentally controlled mice, here we show that IgA-deficient animals have a baseline alteration in the colon epithelium that increases susceptibility to multiple models of colorectal cancer. Transcriptome, imaging, and flow cytometry-based analyses revealed that, in the absence of IgA, colonic epithelial cells induce antibacterial factors and accelerate cell cycling in response to the microbiota. Oral treatment with IgA was sufficient to suppress aberrant epithelial proliferation independently of bacterial binding, suggesting that IgA provides a feedback signal to epithelial cells in parallel with its known roles in microbiome shaping. In a primary colonic organoid culture system, IgA directly suppresses epithelial growth. Conversely, the susceptibility of IgA-deficient mice to colorectal cancer was reversed by Notch inhibition to suppress the absorptive colonocyte developmental program, or by inhibition of the cytokine MIF, the receptor for which was upregulated in stem cells of IgA-deficient animals. These studies demonstrate a homeostatic function for IgA in tempering physiological epithelial responses to microbiota to maintain mucosal health.

Downregulation of PDCD4 through STAT3/ATF6/autophagy mediates MIF-induced PASMCs proliferation/migration and vascular remodeling

To address the molecular mechanisms underlying macrophage migration inhibitory factor (MIF) induced pulmonary artery smooth muscle cells (PASMCs) proliferation, migration and vascular remodeling in pulmonary hypertension (PH), primary cultured rat PASMCs and monocrotaline (MCT)-induced rats with PH were applied in the present study. The results showed that MIF increased signal transducer and activator of transcription 3 (STAT3) phosphorylation, and then stimulated activating transcription factor 6 (ATF6) activation, subsequently triggered autophagy activation, which further led to programmed cell death factor 4 (PDCD4) lysosomal degradation, and eventually promoted PASMCs proliferation/migration. In lung tissues of MCT rats, MIF protein expression was elevated, phosphorylation of STAT3 and activation of ATF6 were increased, activation of autophagy was evident, and reduction of PDCD4 was observed. Intervention with MIF inhibitor 4-Iodo-6-phenylpyrimidine (4-IPP), ATF6 blocker melatonin or autophagy inhibitor chloroquine, confirmed the in vitro interaction among MIF, STAT3, ATF6, autophagy and PDCD4 in MCT induced rats with PH. Targeting MIF/STAT3/ATF6/autophagy/PDCD4 axis effectively prevented the development of PH by suppressing PASMCs proliferation and vascular remodeling. In conclusions, we demonstrate that MIF activates the STAT3/ATF6/autophagy cascade and then degrades PDCD4 leading to PASMCs proliferation/migration and pulmonary vascular remodeling, suggesting that intervention this axis might have potential value in management of PH.

Macrophage migration inhibitory factor exacerbates asthmatic airway remodeling via dynamin-related protein 1-mediated autophagy activation

BACKGROUND

Macrophage migration inhibitory factor (MIF) and GTPase dynamin-related protein 1 (Drp1)-dependent aberrant mitochondrial fission are closely linked to the pathogenesis of asthma. However, it is unclear whether Drp1-mediated mitochondrial fission and its downstream targets mediate MIF-induced proliferation of airway smooth muscle cells (ASMCs) in vitro and airway remodeling in chronic asthma models. The present study aims to clarify these issues.

METHODS

In this study, primary cultured ASMCs and ovalbumin (OVA)-induced asthmatic rats were applied. Cell proliferation was detected by CCK-8 and EdU assays. Western blotting was used to detect extracellular signal-regulated kinase (ERK) 1/2, Drp1, autophagy-related markers and E-cadherin protein phosphorylation and expression. Inflammatory cytokines production, airway reactivity test, histological staining and immunohistochemical staining were conducted to evaluate the development of asthma. Transmission electron microscopy was used to observe the mitochondrial ultrastructure.

RESULTS

In primary cultured ASMCs, MIF increased the phosphorylation level of Drp1 at the Ser616 site through activation of the ERK1/2 signaling pathway, which further activated autophagy and reduced E-cadherin expression, ultimately leading to ASMCs proliferation. In OVA-induced asthmatic rats, MIF inhibitor 4-iodo-6-phenylpyrimidine (4-IPP) treatment, suppression of mitochondrial fission by Mdivi-1 or inhibiting autophagy with chloroquine phosphate (CQ) all attenuated the development of airway remodeling.

CONCLUSIONS

The present study provides novel insights that MIF promotes airway remodeling in asthma by activating autophagy and degradation of E-cadherin via ERK/Drp1 signaling pathway, suggesting that targeting MIF/ERK/Drp1 might have potential therapeutic value for the prevention and treatment of asthma.

MIF is a critical regulator of mononuclear phagocytic infiltration in hepatocellular carcinoma

Immunotherapy targeting tumor-associated macrophages (TAMs) is a promising approach to treating cancer. However, the limited drug targets and ambiguous mechanisms impede the development of clinical immunotherapy strategies. To elucidate the underlying processes involved in mononuclear phagocyte (MNP) infiltration and phenotypic changes in hepatocellular carcinoma (HCC), we integrated single-cell RNA-sequencing data from 100,030 cells derived from patients with HCC and healthy individuals and compared the phenotypes and origins of the MNPs in the tumor core, tumor periphery, adjacent normal tissue, and healthy liver samples. Using machine learning and multi-omics analyses, we identified 445 infiltration-associated genes and potential drug targets affecting this process. Through in vitro experiments, we found that the expression of macrophage migration inhibitory factor (MIF) is the upstream regulator of secreted phosphoprotein 1 (SPP1) and promote migration in TAMs. Our findings also indicate that MIF promotes tumor metastasis and invasion and is a promising potential target for treating HCC.

Macrophage Migration Inhibitory Factor contributes to drive phenotypic and functional macrophages activation in response to Toxoplasma gondii infection

Cytokines are small molecules secreted by numerous cells. Macrophage Migration Inhibitory Factor (MIF) is a cytokine initially described due to its function of inhibiting random macrophage migration. Currently, new functions have been described for MIF, such as stimulating inflammatory functions in response to infections by microorganisms including, Toxoplasma gondii. However, the primordial MIF function related to macrophages has been little addressed. The main purpose of the study was to recapitulate MIF function on macrophages in response to T. gondii infection. To achieve this goal, peritoneal macrophages were collected from C57BL/6WT and Mif1^-/- mice after recruitment with thioglycolate. Macrophages were cultured, treated with 4-Iodo-6-phenylpyrimidine (4-IPP), and infected or not by T. gondii for 24 h. Following this, the culture supernatant was collected for cytokine, urea and nitrite analysis. In addition, macrophages were evaluated for phagocytic activity and T. gondii proliferation rates. Results demonstrated that T. gondii infection triggered an increase in MIF production in the WT group as well as an increase in the secretion of IL-10, TNF, IFN-γ, IL-6 and IL-17 in the WT and Mif1^-/- macrophages. Regarding the comparison between groups, it was detected that Mif1^-/- macrophages secreted more IL-10 compared to WT. On the other hand, the WT macrophages produced greater amounts of TNF, IFN-γ, IL-6 and IL-17. Urea production was more pronounced in Mif1^-/- macrophages while nitrite production was higher in WT macrophages. T. gondii showed a greater ability to proliferate in Mif1^-/- macrophages and these cells also presented enhanced phagocytic activity. In conclusion, T. gondii infection induces macrophage activation inciting cytokine production. In presence of MIF, T. gondii infected macrophages produce pro-inflammatory cytokines compatible with the M1 activation profile. MIF absence caused a dramatic reduction in pro-inflammatory cytokines that are balanced by increased levels of urea and anti-inflammatory cytokines. These macrophages presented increased phagocytic capacity and shared features activation with the M2 profile.

4-Iodo-6-phenylpyrimidine (4-IPP) suppresses fibroblast-like synoviocyte- mediated inflammation and joint destruction associated with rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic immune-mediated inflammatory disease that significantly impacts patients' quality of life. Fibroblast-like synovial cells (FLSs) within the synovial intima exhibit "tumor-like" properties such as increased proliferation, migration, and invasion. Activation of FLSs and secretion of pro-inflammation factors result in pannus formation and cartilage destruction. As an inhibitor of the cytokine, macrophage migration inhibitory factor (MIF), 4-Iodo-6-phenylpyrimidine (4-IPP) has been shown to reduce cell proliferation, migration, invasion, and the secretion of pro-inflammatory mediators in a variety of diseases. However, the usefulness of 4-IPP for RA treatment has not been assessed and was the purpose of this study. In vitro, 4-IPP was demonstrated to inhibit proliferation, migration, and invasion of RA FLSs, as well as the expression of pro-inflammatory cytokines. 4-IPP was also shown to inhibit MIF-induced phosphorylation of ERK, JNK, and p38, as well as reduce expression of COX2 and PGE2. In order to efficiently deliver 4-IPP to anatomical RA sites, we developed lactic-co-glycolic acid (PLGA) nanospheres, which not only protected 4-IPP from degradation but also controlled the release of 4-IPP. 4-IPP/PLGA nanospheres had potent anti-inflammatory activity and a high degree of biosafety. Results showed that local 4-IPP concentration was increased by nanosphere delivery, effectively reducing the inflammatory microenvironment as well as synovial inflammation, joint swelling, and cartilage destruction in a collagen-induced rheumatoid arthritis (CIA) rat model. Therefore, 4-IPP nanospheres are a sustained-release delivery system that may be an effective therapeutic strategy for RA treatment.

Role of MIF1/MIF2/CD74 interactions in bladder cancer

Macrophage migration inhibitory factor (MIF1) is a pleiotropic cytokine involved in inflammation and cancer. Genetic knockout of Mif1 in the validated N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) model of bladder cancer (BCa) resulted in stage arrest at non-muscle-invasive disease in prior studies. Small-molecule inhibition of MIF1 reduced cancer-associated outcomes, but it did not fully recapitulate genetic models. D-dopachrome tautomerase (gene symbol DDT), commonly referred to as MIF2, is a functional homolog of MIF1, and both MIF1 and MIF2 can bind the cell surface receptor CD74 on multiple cell types to initiate a signaling cascade. It has been proposed that this interaction mediates part of the protumorigenic effects of MIF1 and MIF2 and may explain the discordance in prior studies. We hypothesized that MIF2 functions redundantly with MIF1 in BCa development and progression. The Cancer Genome Atlas (TCGA) analysis indicated MIF and DDT expression were increased in BCa patients compared to control. 4-Iodopyridine (4-IPP), a combined MIF1/MIF2 inhibitor, was more efficacious than ISO-1, a MIF1-only inhibitor, in preventing cellular proliferation in BCa cell lines. To evaluate these findings in vivo, wild-type (WT) and Mif1^-/- animals were exposed to 0.05% BBN in drinking water for 16 weeks to initiate tumorigenesis and then evaluated over the subsequent 4 weeks for tumor formation and progression in the presence or absence of 4-IPP. 4-IPP reduced bladder weights in WT animals and bladder weights/tumor stage in Mif1^-/- animals. To determine whether MIF1/MIF2 functioned through CD74 in BCa, WT or Cd74^-/- animals were used in the same BBN model. Although these animals were partially protected against BBN-induced BCa, 4-IPP did not enhance this effect. In conclusion, our data suggest that MIF2 mechanistically functions in a similar protumorigenic manner to MIF1, and this is at least partially through CD74. Dual inhibition of MIF homologs is more efficacious at reducing tumor burden in this model of BCa. © 2022 The Pathological Society of Great Britain and Ireland.

Anti-macrophage migration inhibitory factor (MIF) activity of ibudilast: A repurposing drug attenuates the pathophysiology of leptospirosis

To develop the macrophage migration inhibitory factor (MIF) directed therapeutic approach for the treatment of leptospirosis, we identified potential MIF inhibitors by screening 10 essential tautomerase inhibition classes of chemical compounds and 7 existing anti-inflammatory and anti-microbial drugs. Dopachrome tautomerase assay was performed to measure the anti-MIF activity of selected compounds. Among 17 chemical compounds, ibudilast, an anti-inflammatory agent showed the MIF tautomerase IC50 value at a very lower concentration (9.5 ± 5.6 μM) which is considered similar to the IC50 of standard MIF antagonist, ISO-1 (6.2 ± 3.8 μM) with non-significant cytotoxicity. The in vitro analysis of the therapeutic potential of MIF inhibitor revealed that ibudilast significantly reduced the leptospiral lipopolysaccharide (LPS) mediated expression of inflammatory mediators such as intercellular adhesion molecule (ICAM), p38 and p44/42 mitogen-activated protein kinase (MAPK), inflammatory cytokines, and decreased the reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm) loss and cell death of LPS treated THP-1 cells. In vivo analysis demonstrated that the administration of anti-MIF Ibudilast significantly reduced the histopathological changes, downregulates the pro-inflammatory cytokines, and protects the leptospiral BALB/c model from lethality by increasing the survival rate from 25% to 66%. Finally, the biocompatibility of the evaluated anti-MIF compound was explored by cytotoxicity, hemocompatibility, and cell death assay. Ibudilast showed no significant cytotoxicity and hemolytic activity was noticed even at the higher concentration of ≤50 μM and ≥250 μM, when compared with the positive control, 0.1% Triton X-100; no significant cell death was observed at ≤50 μM concentration of Ibudilast in THP-1 cells. From these lines of evidence, we propose that Ibudilast may be a great MIF targeting repurposing drug for reliable supportive treatment of severe leptospirosis.

D-dopachrome tautomerase in cardiovascular and inflammatory diseases-A new kid on the block or just another MIF?

Macrophage migration inhibitory factor (MIF) as well as its more recently described structural homolog D-dopachrome tautomerase (D-DT), now also termed MIF-2, are atypical cytokines and chemokines with key roles in host immunity. They also have an important pathogenic role in acute and chronic inflammatory conditions, cardiovascular diseases, lung diseases, adipose tissue inflammation, and cancer. Although our mechanistic understanding of MIF-2 is relatively limited compared to the extensive body of evidence available for MIF, emerging data suggests that MIF-2 is not only a functional phenocopy of MIF, but may have differential or even oppositional activities, depending on the disease and context. In this review, we summarize and discuss the similarities and differences between MIF and MIF-2, with a focus on their structures, receptors, signaling pathways, and their roles in diseases. While mainly covering the roles of the MIF homologs in cardiovascular, inflammatory, autoimmune, and metabolic diseases, we also discuss their involvement in cancer, sepsis, and chronic obstructive lung disease (COPD). A particular emphasis is laid upon potential mechanistic explanations for synergistic or cooperative activities of the MIF homologs in cancer, myocardial diseases, and COPD as opposed to emerging disparate or antagonistic activities in adipose tissue inflammation, metabolic diseases, and atherosclerosis. Lastly, we discuss potential future opportunities of jointly targeting MIF and MIF-2 in certain diseases, whereas precision targeting of only one homolog might be preferable in other conditions. Together, this article provides an update of the mechanisms and future therapeutic avenues of human MIF proteins with a focus on their emerging, surprisingly disparate activities, suggesting that MIF-2 displays a variety of activities that are distinct from those of MIF.

MIF/CXCR4 signaling axis contributes to survival, invasion, and drug resistance of metastatic neuroblastoma cells in the bone marrow microenvironment

BACKGROUND

The bone marrow (BM) is the most common site of dissemination in patients with aggressive, metastatic neuroblastoma (NB). However, the molecular mechanisms underlying the aggressive behavior of NB cells in the BM niche are still greatly unknown. In the present study, we explored biological mechanisms that play a critical role in NB cell survival and progression in the BM and investigated potential therapeutic targets.

METHODS

Patient-derived bone marrow (BM) primary cultures were generated using fresh BM aspirates obtained from NB patients. NB cell lines were cultured in the presence of BM conditioned media containing cell-secreted factors, and under low oxygen levels (1% O₂) to mimic specific features of the BM microenvironment of high-risk NB patients. The BM niche was explored using cytokine profiling assays, cell migration-invasion and viability assays, flow cytometry and analysis of RNA-sequencing data. Selective pharmacological inhibition of factors identified as potential mediators of NB progression within the BM niche was performed in vitro and in vivo.

RESULTS

We identified macrophage migration inhibitory factor (MIF) as a key inflammatory cytokine involved in BM infiltration. Cytokine profiling and RNA-sequencing data analysis revealed NB cells as the main source of MIF in the BM, suggesting a potential role of MIF in tumor invasion. Exposure of NB cells to BM-conditions increased NB cell-surface expression of the MIF receptor CXCR4, which was associated with increased cell viability, enhanced migration-invasion, and activation of PI3K/AKT and MAPK/ERK signaling pathways. Moreover, subcutaneous co-injection of NB and BM cells enhanced tumor engraftment in mice. MIF inhibition with 4-IPP impaired in vitro NB aggressiveness, and improved drug response while delayed NB growth, improving survival of the NB xenograft model.

CONCLUSIONS

Our findings suggest that BM infiltration by NB cells may be mediated, in part, by MIF-CXCR4 signaling. We demonstrate the antitumor efficacy of MIF targeting in vitro and in vivo that could represent a novel therapeutic target for patients with disseminated high-risk NB.

Discovery of novel MIF inhibitors that attenuate microglial inflammatory activation by structures-based virtual screening and in vitro bioassays

Macrophage migration inhibitory factor (MIF) is a pluripotent pro-inflammatory cytokine and is related to acute and chronic inflammatory responses, immune disorders, tumors, and other diseases. In this study, an integrated virtual screening strategy and bioassays were used to search for potent MIF inhibitors. Twelve compounds with better bioactivity than the prototypical MIF-inhibitor ISO-1 (IC₅₀ = 14.41 μM) were identified by an in vitro enzymatic activity assay. Structural analysis revealed that these inhibitors have novel structural scaffolds. Compound 11 was then chosen for further characterization in vitro, and it exhibited marked anti-inflammatory efficacy in LPS-activated BV-2 microglial cells by suppressing the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs). Our findings suggest that MIF may be involved in the regulation of microglial inflammatory activation and that small-molecule MIF inhibitors may serve as promising therapeutic agents for neuroinflammatory diseases.

Construction of a Novel Ferroptosis-Related Gene Signature for Predicting Survival of Patients With Lung Adenocarcinoma

Lung adenocarcinoma (LUAD) is the most diagnosed subtype of lung cancer; ferroptosis is widely involved in the pathological cell death associated with various cancers, including lung cancer. However, the comprehensive relationship between ferroptosis and LUAD is little known in molecular levels until now. In the present study, 513 LUAD patients could be aggregated into three clusters by consensus clustering based on RNA sequencing data of 291 ferroptosis-related genes (FRGs) in The Cancer Genome Atlas (TCGA) database; cluster2 had significant survival advantage compared to the other two clusters. A novel prognostic model of 8 differential FRGs was constructed to effectively divide LUAD patients into high- or low-risk group according to the risk scores by the Cox and LASSO regression analyses. The overall survival of LUAD patients in the high-risk group was significantly worse in the TCGA and GEO cohorts. Moreover, patients with radiation therapy or high clinical stage had obviously higher risk scores. We validated the differential mRNA and protein expression of four FRGs in paired tumor and normal samples from our clinical cohort. Our study constructed a novel FRG signature to predict the prognosis of LUAD patients, which might provide a new prognostic tool and potential therapeutic targets for LUAD.

Destabilization of macrophage migration inhibitory factor by 4-IPP reduces NF-κB/P-TEFb complex-mediated c-Myb transcription to suppress osteosarcoma tumourigenesis

BACKGROUND

As an inflammatory factor and oncogenic driver protein, the pleiotropic cytokine macrophage migration inhibitory factor (MIF) plays a crucial role in the osteosarcoma microenvironment. Although 4-iodo-6-phenylpyrimidine (4-IPP) can inactivate MIF biological functions, its anti-osteosarcoma effect and molecular mechanisms have not been investigated. In this study, we identified the MIF inhibitor 4-IPP as a specific double-effector drug for osteosarcoma with both anti-tumour and anti-osteoclastogenic functions.

METHODS

The anti-cancer effects of 4-IPP were evaluated by wound healing assay, cell cycle analysis, colony formation assay, CCK-8 assay, apoptosis analysis, and Transwell migration/invasion assays. Through the application of a luciferase reporter, chromatin immunoprecipitation assays, and immunofluorescence and coimmunoprecipitation analyses, the transcriptional regulation of the NF-κB/P-TEFb complex on c-Myb- and STUB1-mediated proteasome-dependent MIF protein degradation was confirmed. The effect of 4-IPP on tumour growth and metastasis was assessed using an HOS-derived tail vein metastasis model and subcutaneous and orthotopic xenograft tumour models.

RESULTS

In vitro, 4-IPP significantly reduced the proliferation and metastasis of osteosarcoma cells by suppressing the NF-κB pathway. 4-IPP hindered the binding between MIF and CD74 as well as p65. Moreover, 4-IPP inhibited MIF to interrupt the formation of downstream NF-κB/P-TEFb complexes, leading to the down-regulation of c-Myb transcription. Interestingly, the implementation of 4-IPP can mediate small molecule-induced MIF protein proteasomal degradation via the STUB1 E3 ligand. However, 4-IPP still interrupted MIF-mediated communication between osteosarcoma cells and osteoclasts, thus promoting osteoclastogenesis. Remarkably, 4-IPP strongly reduced HOS-derived xenograft osteosarcoma tumourigenesis and metastasis in an in vivo mouse model.

CONCLUSIONS

Our findings demonstrate that the small molecule 4-IPP targeting the MIF protein exerts an anti-osteosarcoma effect by simultaneously inactivating the biological functions of MIF and promoting its proteasomal degradation. Direct destabilization of the MIF protein with 4-IPP may be a promising therapeutic strategy for treating osteosarcoma.

The IL-25-dependent tuft cell circuit driven by intestinal helminths requires macrophage migration inhibitory factor (MIF)

Macrophage migration inhibitory factor (MIF) is a key innate immune mediator with chemokine- and cytokine-like properties in the inflammatory pathway. While its actions on macrophages are well-studied, its effects on other cell types are less understood. Here we report that MIF is required for expansion of intestinal tuft cells during infection with the helminth Nippostrongylus brasiliensis. MIF-deficient mice show defective innate responses following infection, lacking intestinal epithelial tuft cell hyperplasia or upregulation of goblet cell RELMβ, and fail to expand eosinophil, type 2 innate lymphoid cell (ILC2) and macrophage (M2) populations. Similar effects were observed in MIF-sufficient wild-type mice given the MIF inhibitor 4-IPP. MIF had no direct effect on epithelial cells in organoid cultures, and MIF-deficient intestinal stem cells could generate tuft cells in vitro in the presence of type 2 cytokines. In vivo the lack of MIF could be fully compensated by administration of IL-25, restoring tuft cell differentiation and goblet cell expression of RELM-β, demonstrating its requirement upstream of the ILC2-tuft cell circuit. Both ILC2s and macrophages expressed the MIF receptor CXCR4, indicating that MIF may act as an essential co-factor on both cell types to activate responses to IL-25 in helminth infection.

4-Iodopyrimidine Labeling Reveals Nuclear Translocation and Nuclease Activity for Both MIF and MIF2*

Macrophage migration inhibitory factor (MIF) and its homolog MIF2 (also known as D‐dopachrome tautomerase or DDT) play key roles in cell growth and immune responses. MIF and MIF2 expression is dysregulated in cancers and neurodegenerative diseases. Accurate and convenient detection of MIF and MIF2 will facilitate research on their roles in cancer and other diseases. Herein, we report the development and application of a 4‐iodopyrimidine based probe 8 for the selective labeling of MIF and MIF2. Probe 8 incorporates a fluorophore that allows in situ imaging of these two proteins. This enabled visualization of the translocation of MIF2 from the cytoplasm to the nucleus upon methylnitronitrosoguanidine stimulation of HeLa cells. This observation, combined with literature on nuclease activity for MIF, enabled the identification of nuclease activity for MIF2 on human genomic DNA.

Macrophage migration inhibitory factor (MIF): A multifaceted cytokine regulated by genetic and physiological strategies

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine encoded within a functionally polymorphic genetic locus. MIF was initially recognized as a cytokine generated by activated T cells, but in recent days it has been identified as a multipotent key cytokine secreted by many other cell types involved in immune response and physiological processes. MIF is a highly conserved 12.5 kDa secretory protein that is involved in numerous biological processes. The expression and secretion profile of MIF suggests that MIF to be ubiquitously and constitutively expressed in almost all mammalian cells and is vital for numerous physiological processes. MIF is a critical upstream mediator of host innate and adaptive immunity and survival pathways resulting in the clearance of pathogens thus playing a protective role during infectious diseases. On the other hand, MIF being an immune modulator accelerates detrimental inflammation, promotes cancer metastasis and progression, thus worsening disease conditions. Several reports demonstrated that genetic and physiological factors, including MIF gene polymorphisms, posttranslational regulations, and receptor binding control the functional activities of MIF. Taking into consideration the multi-faceted role of MIF both in physiology and pathology, we thought it is timely to review and summarize the expressional and functional regulation of MIF, its functional mechanisms associated with its beneficial and pathological roles, and MIF-targeting therapies. Thus, our review will provide an overview on how MIF is regulated, its response, and the potency of the therapies that target MIF.

MIF as a biomarker and therapeutic target for overcoming resistance to proteasome inhibitors in human myeloma

Multiple myeloma (MM) remains largely incurable despite significant advances in biotherapy and chemotherapy. The development of drug resistance is a major problem in MM management. Macrophage migration inhibitory factor (MIF) expression was significantly higher in purified MM cells from relapsed patients than those with sustained response, and MM patients with high MIF had significantly shorter progression-free survival (PFS) and overall survival (OS). MM cell lines also express high levels of MIF, and knocking out MIF made them more sensitive to proteasome inhibitor (PI)-induced apoptosis not observed with other chemotherapy drugs. Mechanistic studies showed that MIF protects MM cells from PI-induced apoptosis by maintaining mitochondrial function via suppression of superoxide production in response to PIs. Specifically, MIF, in the form of a homotrimer, acts as a chaperone for superoxide dismutase 1 (SOD1) to suppress PI-induced SOD1 misfolding and to maintain SOD1 activity. MIF inhibitor 4-iodo-6-phenylpyrimidine and homotrimer disrupter ebselen, which do not kill MM cells, enhanced PI-induced SOD1 misfolding and loss of function, resulting in significantly more cell death in both cell lines and primary MM cells. More importantly, inhibiting MIF activity in vivo displayed synergistic antitumor activity with PIs and resensitized PI-resistant MM cells to treatment. In support of these findings, gene-profiling data showed a significantly negative correlation between MIF and SOD1 expression and response to PI treatment in patients with MM. This study shows that MIF plays a crucial role in MM sensitivity to PIs and suggests that targeting MIF may be a promising strategy to (re)sensitize MM to the treatment.

Extracellular MIF, but not its homologue D-DT, promotes fibroblast motility independently of its receptor complex CD74/CD44

Macrophage migration inhibitory factor (MIF) and its homologue D-dopachrome tautomerase (D-DT) are widely expressed pro-inflammatory cytokines with chemokine-like functions that coordinate a wide spectrum of biological activities, such as migration. Here, we biotin-tagged intracellular MIF/D-DT in vivo to identify important cytosolic interactors and found a plethora of actin cytoskeleton-associated proteins. Although the receptor complex between CD74 and CD44 (CD74/CD44) is essential for signalling transduction in fibroblasts via extracellular MIF/D-DT, our interactome data suggested direct effects. We, thus, investigated whether MIF/D-DT can modulate cell migration independently of CD74/CD44. To distinguish between receptor- and non-receptor-mediated motility, we used fibroblasts that are either deficient or that express CD74/CD44 proteins, and treated them with recombinant MIF/D-DT. Interestingly, only MIF could stimulate chemokinesis in the presence or absence of CD74/CD44. The pro-migratory effects of MIF depended on lipid raft/caveolae-mediated but not clathrin-mediated endocytosis, on its tautomerase activity and, probably, on its thiol protein oxidoreductase activity. As MIF treatment restrained actin polymerisation in vitro, our findings establish a new intracellular role for MIF/D-DT in driving cell motility through modulation of the actin cytoskeleton.

Macrophage migration inhibitory factor inhibits neutrophil apoptosis by inducing cytokine release from mononuclear cells

The chemokine-like inflammatory cytokine macrophage migration inhibitory factor (MIF) is a pivotal driver of acute and chronic inflammatory conditions, cardiovascular disease, autoimmunity, and cancer. MIF modulates the early inflammatory response through various mechanisms, including regulation of neutrophil recruitment and fate, but the mechanisms and the role of the more recently described MIF homolog MIF-2 (D-dopachrome tautomerase; D-DT) are incompletely understood. Here, we show that both MIF and MIF-2/D-DT inhibit neutrophil apoptosis. This is not a direct effect, but involves the activation of mononuclear cells, which secrete CXCL8 and other prosurvival mediators to promote neutrophil survival. Individually, CXCL8 and MIF (or MIF-2) did not significantly inhibit neutrophil apoptosis, but in combination they elicited a synergistic response, promoting neutrophil survival even in the absence of mononuclear cells. The use of receptor-specific inhibitors provided evidence for a causal role of the noncognate MIF receptor CXCR2 expressed on both monocytes and neutrophils in MIF-mediated neutrophil survival. We suggest that the ability to inhibit neutrophil apoptosis contributes to the proinflammatory role ascribed to MIF, and propose that blocking the interaction between MIF and CXCR2 could be an important anti-inflammatory strategy in the early inflammatory response.

MIF-Dependent Control of Tumor Immunity

Initially identified as a T lymphocyte-elicited inhibitor of macrophage motility, macrophage migration inhibitory factor (MIF) has since been found to be expressed by nearly every immune cell type examined and overexpressed in most solid and hematogenous malignant cancers. It is localized to both extracellular and intracellular compartments and physically interacts with more than a dozen different cell surface and intracellular proteins. Although classically associated with and characterized as a mediator of pro-inflammatory innate immune responses, more recent studies demonstrate that, in malignant disease settings, MIF contributes to anti-inflammatory, immune evasive, and immune tolerant phenotypes in both innate and adaptive immune cell types. This review will summarize the studies describing MIF in tumor-specific innate and adaptive immune responses and attempt to reconcile these various pleiotropic functions in normal physiology.

Explicating the Pivotal Pathogenic, Diagnostic, and Therapeutic Biomarker Potentials of Myeloid-Derived Suppressor Cells in Glioblastoma

Glioblastoma (GBM) is a malignant and aggressive central nervous tumor that originates from astrocytes. These pathogenic astrocytes divide rapidly and are sustained by enormous network of blood vessels via which they receive requisite nutrients. It well proven that GBM microenvironment is extremely infiltrated by myeloid-derived suppressor cells (MDSCs). MDSCs are a heterogeneous cluster of immature myeloid progenitors. They are key mediates in immune suppression as well as sustenance glioma growth, invasion, vascularization, and upsurge of regulatory T cells via different molecules. MDSCs are often elevated in the peripheral blood of patients with GBM. MDSCs in the peripheral blood as well as those infiltrating the GBM microenvironment correlated with poor prognosis. Also, an upsurge in circulating MDSCs in the peripheral blood of patients with GBM was observed compared to benign and grade I/II glioma patients. GBM patients with good prognosis presented with reduced MDSCs as well as augmented dendritic cells. Almost all chemotherapeutic medication for GBM has shown no obvious improvement in overall survival in patients. Nevertheless, low-dose chemotherapies were capable of suppressing the levels of MDSCs in GBM as well as multiple tumor models with metastatic to the brain. Thus, MDSCs are potential diagnostic as well as therapeutic biomarkers for GBM patients.

Astragalus Polysaccharide (PG2) Suppresses Macrophage Migration Inhibitory Factor and Aggressiveness of Lung Adenocarcinoma Cells

Astragalus membranaceus is the most popular traditional Chinese medicine for managing vital energy deficiency. Its injectable polysaccharide PG2 has been used for relieving cancer-related fatigue, and PG2 has immune-modulatory and anti-inflammatory effects. In this study, we explored the effects of PG2 in lung adenocarcinoma A549 and CL1-2 cells and investigated its anticancer activity, and the results were validated in severe combined immunodeficiency (SCID) mice. Although PG2 did not inhibit the growth of these cells, it dose-dependently suppressed their migration and invasion, accompanied by reduced vimentin and AXL and induced epithelial cadherin (E-cadherin) expression. Regarding the underlying molecular mechanism, PG2 treatment reduced the macrophage migration inhibitory factor (MIF), an inflammatory cytokine that promotes the epithelial-mesenchymal transition and aggressiveness of cancer cells. Consistent with the previous finding that MIF regulates matrix metalloproteinase-13 (MMP-13) and AMP-activated protein kinase (AMPK), treatment with PG2 reduced MMP-13 and activated AMPK in A549 and CL1-2 cells in this study. In SCID mice injected with A549 cells through the tail vein, intraperitoneal injection with PG2 reduced lung and abdominal metastases in parallel with decreased immunohistochemical staining of AXL, vimentin, MMP-13, and MIF in the tumor. Collectively, data revealed a potential application of PG2 in integrative cancer treatment through the suppression of MIF in cancer cells and their aggressiveness.

The transcriptional signature associated with human motile cilia

Cilia are complex microtubule-based organelles essential to a range of processes associated with embryogenesis and tissue homeostasis. Mutations in components of these organelles or those involved in their assembly may result in a diverse set of diseases collectively known as ciliopathies. Accordingly, many cilia-associated proteins have been described, while those distinguishing cilia subtypes are poorly defined. Here we set out to define genes associated with motile cilia in humans based on their transcriptional signature. To define the signature, we performed network deconvolution of transcriptomics data derived from tissues possessing motile ciliated cell populations. For each tissue, genes coexpressed with the motile cilia-associated transcriptional factor, FOXJ1, were identified. The consensus across tissues provided a transcriptional signature of 248 genes. To validate these, we examined the literature, databases (CilDB, CentrosomeDB, CiliaCarta and SysCilia), single cell RNA-Seq data, and the localisation of mRNA and proteins in motile ciliated cells. In the case of six poorly characterised signature genes, we performed new localisation experiments on ARMC3, EFCAB6, FAM183A, MYCBPAP, RIBC2 and VWA3A. In summary, we report a set of motile cilia-associated genes that helps shape our understanding of these complex cellular organelles.

Glioblastoma Myeloid-Derived Suppressor Cell Subsets Express Differential Macrophage Migration Inhibitory Factor Receptor Profiles That Can Be Targeted to Reduce Immune Suppression

The application of tumor immunotherapy to glioblastoma (GBM) is limited by an unprecedented degree of immune suppression due to factors that include high numbers of immune suppressive myeloid cells, the blood brain barrier, and T cell sequestration to the bone marrow. We previously identified an increase in immune suppressive myeloid-derived suppressor cells (MDSCs) in GBM patients, which correlated with poor prognosis and was dependent on macrophage migration inhibitory factor (MIF). Here we examine the MIF signaling axis in detail in murine MDSC models, GBM-educated MDSCs and human GBM. We found that the monocytic subset of MDSCs (M-MDSCs) expressed high levels of the MIF cognate receptor CD74 and was localized in the tumor microenvironment. In contrast, granulocytic MDSCs (G-MDSCs) expressed high levels of the MIF non-cognate receptor CXCR2 and showed minimal accumulation in the tumor microenvironment. Furthermore, targeting M-MDSCs with Ibudilast, a brain penetrant MIF-CD74 interaction inhibitor, reduced MDSC function and enhanced CD8 T cell activity in the tumor microenvironment. These findings demonstrate the MDSC subsets differentially express MIF receptors and may be leveraged for specific MDSC targeting.

Regulation of MIF Enzymatic Activity by an Allosteric Site at the Central Solvent Channel

In proteins with multiple functions, such as macrophage migration inhibitory factor (MIF), the study of its intramolecular dynamic network can offer a unique opportunity to understand how a single protein is able to carry out several nonoverlapping functions. A dynamic mechanism that controls the MIF-induced activation of CD74 was recently discovered. In this study, the regulation of tautomerase activity was explored. The catalytic base Pro1 is found to form dynamic communications with the same allosteric node that regulates CD74 activation. Signal transmission between the allosteric and catalytic sites take place through intramolecular aromatic interactions and a hydrogen bond network that involves residues and water molecules of the MIF solvent channel. Once thought to be a consequence of trimerization, a regulatory function for the solvent channel is now defined. These results provide mechanistic insights into the regulation of catalytic activity and the role of solvent channel water molecules in MIF catalysis.

Immune modulation by the macrophage migration inhibitory factor (MIF) family: D-dopachrome tautomerase (DDT) is not (always) a backup system

Human macrophage migration inhibition factor (MIF) is a protein with cytokine and chemokine properties that regulates a diverse range of physiological functions related to innate immunity and inflammation. Most research has focused on the role of MIF in different inflammatory diseases. D-dopachrome tautomerase (DDT), a different molecule with structural similarities to MIF, which shares receptors and biological functions, has recently been reported, but little is known about its roles and mechanisms. In this review, we sought to understand the similarities and differences between these molecules by summarizing what is known about their different structures, receptors and mechanisms regulating their expression and biological activities with an emphasis on immunological aspects.

Macrophage Migration Inhibitory Factor (MIF) Is Essential for Type 2 Effector Cell Immunity to an Intestinal Helminth Parasite

Immunity to intestinal helminths is known to require both innate and adaptive components of the immune system activated along the Type 2 IL-4R/STAT6-dependent pathway. We have found that macrophage migration inhibitory factor (MIF) is essential for the development of effective immunity to the intestinal helminth Heligmosomoides polygyrus, even following vaccination which induces sterile immunity in wild-type mice. A chemical inhibitor of MIF, 4-IPP, was similarly found to compromise anti-parasite immunity. Cellular analyses found that the adaptive arm of the immune response, including IgG1 antibody responses and Th2-derived cytokines, was intact and that Foxp3+ T regulatory cell responses were unaltered in the absence of MIF. However, MIF was found to be an essential cytokine for innate cells, with ablated eosinophilia and ILC2 responses, and delayed recruitment and activation of macrophages to the M2 phenotype (expressing Arginase 1, Chil3, and RELM-α) upon infection of MIF-deficient mice; a macrophage deficit was also seen in wild-type BALB/c mice exposed to 4-IPP. Gene expression analysis of intestinal and lymph node tissues from MIF-deficient and -sufficient infected mice indicated significantly reduced levels of Arl2bp, encoding a factor involved in nuclear localization of STAT3. We further found that STAT3-deficient macrophages expressed less Arginase-1, and that mice lacking STAT3 in the myeloid compartment (LysMCrexSTAT3fl/fl) were unable to reject a secondary infection with H. polygyrus. We thus conclude that in the context of a Type 2 infection, MIF plays a critical role in polarizing macrophages into the protective alternatively-activated phenotype, and that STAT3 signaling may make a previously unrecognized contribution to immunity to helminths.

A selective small-molecule inhibitor of macrophage migration inhibitory factor-2 (MIF-2), a MIF cytokine superfamily member, inhibits MIF-2 biological activity

Cytokine macrophage migration inhibitory factor-2 (MIF-2 or D-dopachrome tautomerase) is a recently characterized second member of the MIF cytokine superfamily in mammalian genomes. MIF-2 shares pro-inflammatory and tumorigenic properties with the clinical target MIF (MIF-1), but the precise contribution of MIF-2 to immune physiology or pathology is unclear. Like MIF-1, MIF-2 has intrinsic keto-enol tautomerase activity and mediates biological functions by engaging the cognate, common MIF family receptor CD74. Evidence that the catalytic site of MIF family cytokines has a structural role in receptor binding has prompted exploration of tautomerase inhibitors as potential biological antagonists and therapeutic agents, although few catalytic inhibitors inhibit receptor activation. Here we describe the discovery and biochemical characterization of a selective small-molecule inhibitor of MIF-2. An in silico screen of 1.6 million compounds targeting the MIF-2 tautomerase site yielded several hits for potential catalytic inhibitors of MIF-2 and identified 4-(3-carboxyphenyl)-2,5-pyridinedicarboxylic acid (4-CPPC) as the most functionally potent compound. We found that 4-CPPC has an enzymatic IC₅₀ of 27 μm and 17-fold selectivity for MIF-2 versus MIF-1. An in vitro binding assay for MIF-1/MIF-2 to the CD74 ectodomain (sCD74) indicated that 4-CPPC inhibits MIF-2-CD74 binding in a dose-dependent manner (0.01-10 μm) without influencing MIF-1-CD74 binding. Notably, 4-CPPC inhibited MIF-2-mediated activation of CD74 and reduced CD74-dependent signal transduction. These results open opportunities for development of more potent and pharmacologically auspicious MIF-2 inhibitors to investigate the distinct functions of this MIF family member in vivo.

Macrophage Migration Inhibitory Factor Is a Molecular Determinant of the Anti-EGFR Monoclonal Antibody Cetuximab Resistance in Human Colorectal Cancer Cells

Background: The clinical impact of the monoclonal antibody cetuximab targeting the EGFR in colorectal cancer (CRC) is widely recognized. Nevertheless, the onset of cetuximab resistance is a serious issue that limits the effectiveness of this drug in targeted therapies. Unraveling the molecular players involved in cancer resistance is the first step towards the identification of alternative signaling pathways that can be targeted to circumvent resistance mechanisms restoring the efficacy of therapeutic treatments in a tailored manner. Methods: By applying a nanoLC-MS/MS TMT isobaric labeling-based approach, we have delineated a molecular hallmark of cetuximab-resistance in CRC. Results: We identified macrophage migration inhibitory factor (MIF) as a molecular determinant capable of triggering cancer resistance in sensitive human CRC cells. Blocking the MIF axis in resistant cells by a selective MIF inhibitor restores cell sensitivity to cetuximab. The combined treatment with cetuximab and the MIF inhibitor further enhanced cell growth inhibition in CRC resistant cell lines with a synergistic effect depending on inhibition of key downstream effectors of the MAPK and AKT signaling pathways. Conclusions: Collectively, our results suggest the association of MIF signaling and its dysregulation to cetuximab drug resistance, paving the way to the development of personalized combination therapies targeting the MIF axis.

Macrophage migration inhibitory factor (MIF) as a therapeutic target for rheumatoid arthritis and systemic lupus erythematosus

Introduction. Macrophage migration inhibitory factor (MIF) is a pleiotropic inflammatory cytokine with upstream regulatory roles in innate and adaptive immunity and is implicated in the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Several classes of MIF inhibitors such as small molecule inhibitors and peptide inhibitors are in clinical development. Areas covered. The role of MIF in the pathogenesis of RA and SLE is examined; the authors review the structure, physiology and signaling characteristics of MIF and the related cytokine D-DT/MIF-2. The preclinical and clinical trial data for MIF inhibitors are also reviewed; information was retrieved from PubMed and ClinicalTrials.gov using the keywords MIF, D-DT/MIF-2, CD74, CD44, CXCR2, CXCR4, Jab-1, rheumatoid arthritis, systemic lupus erythematosus, MIF inhibitor, small molecule, anti-MIF, anti-CD74, and peptide inhibitor. Expert opinion. Studies in mice and in humans demonstrate the therapeutic potential of MIF inhibition for RA and SLE. MIF- directed approaches could be particularly efficacious in patients with high expression MIF genetic polymorphisms. In patients with RA and SLE and high expression MIF alleles, targeted MIF inhibition could be a precision medicine approach to treatment. Anti-MIF pharmacotherapies could also be steroid-sparing in patients with chronic glucocorticoid dependence or refractory autoimmune disease.

Macrophage migration inhibitory factor (MIF) inhibitor 4-IPP suppresses osteoclast formation and promotes osteoblast differentiation through the inhibition of the NF-κB signaling pathway

Current pharmacological intervention for the treatment of osteolytic bone diseases such as osteoporosis focuses on the prevention of excessive osteoclastic bone resorption but does not enhance osteoblast-mediated bone formation. In our study, we have shown that 4-iodo-6-phenylpyrimidine (4-IPP), an irreversible inhibitor of macrophage migration inhibitory factor (MIF), can inhibit receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis and potentiate osteoblast-mediated mineralization and bone nodule formation in vitro. Mechanistically, 4-IPP inhibited RANKL-induced p65 phosphorylation and nuclear translocation by preventing the interaction of MIF with thioredoxin-interacting protein-p65 complexes. This led to the suppression of late osteoclast marker genes such as nuclear factor of activated T cells cytoplasmic 1, resulting in impaired osteoclast formation. In contrast, 4-IPP potentiated osteoblast differentiation and mineralization also through the inhibition of the p65/NF-κB signaling cascade. In the murine model of pathologic osteolysis induced by titanium particles, 4-IPP protected against calvarial bone destruction. Similarly, in the murine model of ovariectomy-induced osteoporosis, 4-IPP treatment ameliorated the bone loss associated with estrogen deficiency by reducing osteoclastic activities and enhancing osteoblastic bone formation. Collectively, these findings provide evidence for the pharmacological targeting of MIF for the treatment of osteolytic bone disorders.-Zheng, L., Gao, J., Jin, K., Chen, Z., Yu, W., Zhu, K., Huang, W., Liu, F., Mei, L., Lou, C., He, D. Macrophage migration inhibitory factor (MIF) inhibitor 4-IPP suppresses osteoclast formation and promotes osteoblast differentiation through the inhibition of the NF-κB signaling pathway.

Macrophage Migration Inhibitory Factor Regulates U1 Small Nuclear RNP Immune Complex-Mediated Activation of the NLRP3 Inflammasome

OBJECTIVE

High-expression alleles of macrophage migration inhibitory factor (MIF) are linked genetically to the severity of systemic lupus erythematosus (SLE). The U1 small nuclear RNP (snRNP) immune complex containing U1 snRNP and anti-U1 snRNP antibodies, which are found in patients with SLE, activates the NLRP3 inflammasome, comprising NLRP3, ASC, and procaspase 1, in human monocytes, leading to the production of interleukin-1β (IL-1β). This study was undertaken to investigate the role of the snRNP immune complex in up-regulating the expression of MIF and its interface with the NLRP3 inflammasome.

METHODS

MIF, IL-1β, NLRP3, caspase 1, ASC, and MIF receptors were analyzed by enzyme-linked immunosorbent assay, Western blotting, quantitative polymerase chain reaction, and cytometry by time-of-flight mass spectrometry (CytoF) in human monocytes incubated with or without the snRNP immune complex. MIF pathway responses were probed with the novel small molecule antagonist MIF098.

RESULTS

The snRNP immune complex induced the production of MIF and IL-1β from human monocytes. High-dimensional, single-cell CytoF analysis established that MIF regulates activation of the NLRP3 inflammasome, including findings of a quantitative relationship between MIF and its receptors and IL-1β levels in the monocytes. MIF098, which blocks MIF binding to its cognate receptor, suppressed the production of IL-1β, the up-regulation of NLRP3, which is a rate-limiting step in NLRP3 inflammasome activation, and the activation of caspase 1 in snRNP immune complex-stimulated human monocytes.

CONCLUSION

The U1 snRNP immune complex is a specific stimulus of MIF production in human monocytes, with MIF having an upstream role in defining the inflammatory characteristics of activated monocytes by regulating NLRP3 inflammasome activation and downstream IL-1β production. These findings provide mechanistic insight and a therapeutic rationale for targeting MIF in subgroups of lupus patients, such as those classified as high genotypic MIF expressers or those with anti-snRNP antibodies.

Role of MIF and D-DT in immune-inflammatory, autoimmune, and chronic respiratory diseases: from pathogenic factors to therapeutic targets

Macrophage migration inhibitory factor (MIF) is a protein that acts as a cytokine-, enzyme-, endocrine- and chaperon-like molecule. It binds to the cell-surface receptor CD74 in association with CD44, which activates the downstream signal transduction pathway. In addition, MIF acts also as a noncognate ligand for C-X-C chemokine receptor type 2 (CXCR2), type 4 (CXCR4), and type 7 (CXCR7). Recently, D-dopachrome tautomerase (D-DT), a second member of the MIF superfamily, was identified. From a pharmacological and clinical point of view, the nonredundant biological properties of MIF and D-DT anticipate potential synergisms from their simultaneous inhibition. Here, we focus on the role of MIF and D-DT in human immune-inflammatory, autoimmune, and chronic respiratory diseases, providing an update on the progress made in the identification of specific small-molecule inhibitors of these proteins.

Oral squamous carcinoma cells promote macrophage polarization in an MIF-dependent manner

BACKGROUND

Tumor-associated macrophages (TAMs) are important determinants of intratumoral immune evasion, neoangiogenesis, extracellular matrix remodeling and dysregulated tumor cell proliferation. Our prior studies revealed that macrophage-derived, but not tumor cell-derived, macrophage migration inhibitory factor (MIF), is an important determinant of TAM alternative activation and M2 polarization.

AIM

Because MIF is historically thought to initiate signaling via a receptor-dependent, outside-in mode of action, we wished to investigate the specific contributions of tumor-derived vs. macrophage-derived MIF to M2 marker expression during macrophage polarization.

DESIGN

Murine oral squamous cell-carcinoma cells (SCCVII) were co-cultured with either the RAW 264.7 mouse macrophage cell line or mouse primary bone marrow-derived macrophages in the context of MIF genetic loss/inhibition individually or in combination each cell type.

METHODS

Twelve well Transwell plates were used to co-culture SCCVII cells and RAW 264.7, MIF+/+ or MIF-/- macrophages treated with/without the small molecule MIF inhibitor, 4-iodo-6-phenylpyrimidine and incubated in the presence or absence of interleukin (IL-4) for 48 h. Macrophages were analyzed by quantitative real-time polymerase chain reaction and/or immunoblotting for relative macrophage polarization marker expression.

RESULTS

IL-4 treatment synergizes with SCCVII co-culture in inducing the expression of macrophage M2 markers and loss or inhibition of macrophage-derived MIF significantly reduces both IL-4 alone and IL-4/SCCVII co-culture-induced macrophage M2 marker expression.

CONCLUSION

These studies identify an important and dominant requirement for macrophage MIF in maximal Th2-cytokine and oral squamous carcinoma cell-induced macrophage polarization and M2 marker expression.

Macrophage Inhibitory Factor-1 (MIF-1) controls the plasticity of multiple myeloma tumor cells

Multiple Myeloma (MM) is the second most common hematological malignancy with a median survival of 5–10 years. While current treatments initially cause remission, relapse almost always occurs, leading to the hypothesis that a chemotherapy-resistant cancer stem cell (CSC) remains dormant, and undergoes self-renewal and differentiation to reestablish disease. Our finding is that the mature cancer cell (CD138+, rapidly proliferating and chemosensitive) has developmental plasticity; namely, the ability to dedifferentiate back into its own chemoresistant CSC progenitor, the CD138–, quiescent pre-plasma cell. We observe multiple cycles of differentiation and dedifferentiation in the absence of niche or supportive accessory cells, suggesting that soluble cytokines secreted by the MM cells themselves are responsible for this bidirectional interconversion and that stemness and chemoresistance are dynamic characteristics that can be acquired or lost and thus may be targetable. By examining cytokine secretion of CD138- and CD138+ RPMI-8226 cells, we identified that concomitant with interconversion, Macrophage Migration Inhibitory Factor (MIF-1) is secreted. The addition of a small molecule MIF-1 inhibitor (4-IPP) or MIF-1 neutralizing antibodies to CD138+ cells accelerated dedifferentiation back into the CD138- progenitor, while addition of recombinant MIF-1 drove cells towards CD138+ differentiation. A similar increase in the CD138- population is seen when MM tumor cells isolated from primary bone marrow aspirates are cultured in the presence of 4-IPP. As the CD138+ MM cell is chemosensitive, targeting MIF-1 and/or the pathways that it regulates could be a viable way to modulate stemness and chemosensitivity, which could in turn transform the treatment of MM.

Macrophage migration inhibitory factor promotes resistance to MEK blockade in KRAS mutant colorectal cancer cells

Although MEK blockade has been highlighted as a promising antitumor drug, it has poor clinical efficacy in KRAS mutant colorectal cancer (CRC). Several feedback systems have been described in which inhibition of one intracellular pathway leads to activation of a parallel signaling pathway, thereby decreasing the effectiveness of single‐MEK targeted therapies. Here, we investigated a bypass mechanism of resistance to MEK inhibition in KRAS CRC. We found that KRAS mutant CRC cells with refametinib, MEK inhibitor, induced MIF secretion and resulted in activation of STAT3 and MAPK. MIF knockdown by siRNA restored sensitivity to refametinib in KRAS mutant cells. In addition, combination with refametinib and 4‐IPP, a MIF inhibitor, effectively reduced the activity of STAT3 and MAPK, more than single‐agent treatment. As a result, combined therapy was found to exhibit a synergistic growth inhibitory effect against refametinib‐resistant cells by inhibition of MIF activation. These results reveal that MIF‐induced STAT3 and MAPK activation evoked an intrinsic resistance to refametinib. Our results provide the basis for a rational combination strategy against KRAS mutant colorectal cancers, predicated on the understanding of cross talk between the MEK and MIF pathways.

Small-molecule inhibitors of macrophage migration inhibitory factor (MIF) as an emerging class of therapeutics for immune disorders

Macrophage migration inhibitory factor (MIF) is an important cytokine for which an increasing number of functions is being described in the pathogenesis of inflammation and cancer. Nevertheless, the availability of potent and druglike MIF inhibitors that are well-characterized in relevant disease models remains limited. Development of highly potent and selective small-molecule MIF inhibitors and validation of their use in relevant disease models will advance drug discovery. In this review, we provide an overview of recent advances in the identification of MIF as a pharmacological target in the pathogenesis of inflammatory diseases and cancer. We also give an overview of the current developments in the discovery and design of small-molecule MIF inhibitors and define future aims in this field.

Pathogenic role for macrophage migration inhibitory factor in glioblastoma and its targeting with specific inhibitors as novel tailored therapeutic approach

Macrophage Migration Inhibitory Factor (MIF) is a pro-inflammatory cytokine expressed by a variety of cell types. Although MIF has been primarily studied for its role in the pathogenesis of autoimmune diseases, it has also been shown to promote tumorigenesis and it is over expressed in various malignant tumors. MIF is able to induce angiogenesis, cell cycle progression, and to block apoptosis. As tailored therapeutic approaches for the inhibition of endogenous MIF are being developed, it is important to evaluate the role of MIF in individual neoplastic conditions that may benefit from specific MIF inhibitors. Along with this line, in this paper, we have reviewed the evidence of the involvement of MIF in the etiopathogenesis and progression of glioblastoma and the preclinical data suggesting the possible use of specific MIF inhibition as a potential novel therapeutic strategy for brain tumors.

Role of macrophage migration inhibitory factor in head and neck cancer and novel therapeutic targets: A systematic review

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in systemic, autoimmune, and inflammatory diseases, such as obesity, rheumatoid arthritis, and systemic lupus erythematosus. For the 2 past decades, MIF has been reported to participate in carcinogenesis, disease prognosis, tumor cell proliferation, invasion, and tumor-induced angiogenesis in many cancers. The purpose of this article is to review published experimental and clinical data for MIF and its involvement in upper aerodigestive tract cancers. Based on the current literature, we propose a biomolecular model describing the mechanisms underlying the involvement of MIF in the initiation, progression, apoptosis, and proliferation of head and neck tumor cells. In reference to this model, potential therapeutic approaches based on the use of MIF antagonists and neutralizing antibodies are described. It is concluded that MIF is a promising target for future therapeutic strategies, both with and without chemoradiation strategies.

Modulating glioma-mediated myeloid-derived suppressor cell development with sulforaphane

Glioblastoma is the most common primary tumor of the brain and has few long-term survivors. The local and systemic immunosuppressive environment created by glioblastoma allows it to evade immunosurveillance. Myeloid-derived suppressor cells (MDSCs) are a critical component of this immunosuppression. Understanding mechanisms of MDSC formation and function are key to developing effective immunotherapies. In this study, we developed a novel model to reliably generate human MDSCs from healthy-donor CD14+ monocytes by culture in human glioma-conditioned media. Monocytic MDSC frequency was assessed by flow cytometry and confocal microscopy. The resulting MDSCs robustly inhibited T cell proliferation. A cytokine array identified multiple components of the GCM potentially contributing to MDSC generation, including Monocyte Chemoattractive Protein-1, interleukin-6, interleukin-8, and Macrophage Migration Inhibitory Factor (MIF). Of these, Macrophage Migration Inhibitory Factor is a particularly attractive therapeutic target as sulforaphane, a naturally occurring MIF inhibitor derived from broccoli sprouts, has excellent oral bioavailability. Sulforaphane inhibits the transformation of normal monocytes to MDSCs by glioma-conditioned media in vitro at pharmacologically relevant concentrations that are non-toxic to normal leukocytes. This is associated with a corresponding increase in mature dendritic cells. Interestingly, sulforaphane treatment had similar pro-inflammatory effects on normal monocytes in fresh media but specifically increased immature dendritic cells. Thus, we have used a simple in vitro model system to identify a novel contributor to glioblastoma immunosuppression for which a natural inhibitor exists that increases mature dendritic cell development at the expense of myeloid-derived suppressor cells when normal monocytes are exposed to glioma conditioned media.

Reprint of: The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.

Macrophage migration inhibitory factor interacts with thioredoxin-interacting protein and induces NF-κB activity

The nuclear factor kappa B (NF-κB) pathway is pivotal in controlling survival and apoptosis of cancer cells. Macrophage migration inhibitory factor (MIF), a cytokine that regulates the immune response and tumorigenesis under inflammatory conditions, is upregulated in various tumors. However, the intracellular functions of MIF are unclear. In this study, we found that MIF directly interacted with thioredoxin-interacting protein (TXNIP), a tumor suppressor and known inhibitor of NF-κB activity, and MIF significantly induced NF-κB activation. MIF competed with TXNIP for NF-κB activation, and the intracellular MIF induced NF-κB target genes, including c-IAP2, Bcl-xL, ICAM-1, MMP2 and uPA, by inhibiting the interactions between TXNIP and HDACs or p65. Furthermore, we identified the interaction motifs between MIF and TXNIP via site-directed mutagenesis of their cysteine (Cys) residues. Cys⁵⁷ and Cys⁸¹ of MIF and Cys³⁶ and Cys¹²⁰ of TXNIP were responsible for the interaction. MIF reversed the TXNIP-induced suppression of cell proliferation and migration. Overall, we suggest that MIF induces NF-κB activity by counter acting the inhibitory effect of TXNIP on the NF-κB pathway via direct interaction with TXNIP. These findings reveal a novel intracellular function of MIF in the progression of cancer.

The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, ‎protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.