Role of the Cysteine 81 Residue of Macrophage Migration Inhibitory Factor as a Molecular Redox Switch.

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory and tumor-promoting cytokine that occurs in two redox-dependent immunologically distinct conformational isoforms. The disease-related structural isoform of MIF (oxMIF) can be specifically and predominantly detected in the circulation of patients with inflammatory diseases and in tumor tissue, whereas the ubiquitously expressed isoform of MIF (redMIF) is abundantly expressed in healthy and diseased subjects. In this article, we report that cysteine 81 within MIF serves as a "switch cysteine" for the conversion of redMIF to oxMIF. Modulating cysteine 81 by thiol reactive agents leads to significant structural rearrangements of the protein, resulting in a decreased ß-sheet content and an increased random coil content, but maintaining the trimeric quaternary structure. This conformational change in the MIF molecule enables binding of oxMIF-specific antibodies BaxB01 and BaxM159, which showed beneficial activity in animal models of inflammation and cancer. Crystal structure analysis of the MIF-derived EPCALCS peptide, bound in its oxMIF-like conformation by the Fab fragment of BaxB01, revealed that this peptide adopts a curved conformation, making the central thiol protein oxidoreductase motif competent to undergo disulfide shuffling. We conclude that redMIF might reflect a latent zymogenic form of MIF, and formation of oxMIF leads to a physiologically relevant, i.e., enzymatically active, state.

Selective Targeting of a Disease-Related Conformational Isoform of Macrophage Migration Inhibitory Factor Ameliorates Inflammatory Conditions.

Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine and counterregulator of glucocorticoids, is a potential therapeutic target. MIF is markedly different from other cytokines because it is constitutively expressed, stored in the cytoplasm, and present in the circulation of healthy subjects. Thus, the concept of targeting MIF for therapeutic intervention is challenging because of the need to neutralize a ubiquitous protein. In this article, we report that MIF occurs in two redox-dependent conformational isoforms. We show that one of the two isoforms of MIF, that is, oxidized MIF (oxMIF), is specifically recognized by three mAbs directed against MIF. Surprisingly, oxMIF is selectively expressed in the plasma and on the cell surface of immune cells of patients with different inflammatory diseases. In patients with acute infections or chronic inflammation, oxMIF expression correlated with inflammatory flare-ups. In addition, anti-oxMIF mAbs alleviated disease severity in mouse models of acute and chronic enterocolitis and improved, in synergy with glucocorticoids, renal function in a rat model of crescentic glomerulonephritis. We conclude that oxMIF represents the disease-related isoform of MIF; oxMIF is therefore a new diagnostic marker for inflammation and a relevant target for anti-inflammatory therapy.

Pretargeted Radioimmunotherapy with the Novel Anti-oxMIF/HSG Bispecific Antibody ON105 Results in Significant Tumor Regression in Murine Models of Cancer.

Radioimmunotherapy (RIT) uses monoclonal antibodies to deliver radionuclides to cancer cells or the tumor microenvironment and has shown promise in treating localized and diffuse tumors. Although RIT agents have gained FDA/EMA approval for certain hematologic malignancies, effectiveness of RIT in treating solid tumors remains limited. In this study, we present PreTarg-it®, a novel approach for pretargeted RIT, providing optimized delivery of payloads in a two-step regimen. The effectiveness of PreTarg-it® is demonstrated by a powerful combination of ON105, a novel bispecific antibody against both oxidized macrophage migration inhibitory factor (oxMIF) and the histamine-succinyl-glycyl (HSG) hapten, as the first component and the radioactively labeled DOTA-di-HSG peptide as the second component in murine models of cancer. Mice bearing either subcutaneous mouse colorectal CT26 or human pancreatic CFPAC-1 tumors received an i.v. injection of ON105. After ON105 had accumulated in the tumor and cleared from circulation to approximately 1% to 3% of its peak concentration, 177Lu-DOTA-di-HSG peptide was administered. A single PreTarg-it® treatment cycle resulted in tumor regression when mice bearing CT26 tumors were given the highest treatment dose with a pretargeting delay of 3 days. Administered with a 5-day interval, the highest dose arrested tumor growth in both CT26 syngrafts and CFPAC-1 xenografts. In all cases, the highest treatment dose resulted in 100% survival at the study endpoint, whereas the control cohorts showed 0% and 60% survival in the CT26 and CFPAC-1 models, respectively. Therefore, PreTarg-it® holds potential as a novel and potent therapy for patients with hard-to-treat solid tumors, such as pancreatic cancer, as well as those with late-stage malignancies.

Pretargeted radioimmunotherapy with the novel anti-oxMIF/HSG bispecific antibody ON105 results in significant tumor regression in murine models of cancer.

Radioimmunotherapy (RIT) uses mAbs to deliver radionuclides to cancer cells or the tumor microenvironment and has shown promise in treating localized and diffuse tumors. While RIT agents have gained FDA/EMA approval for certain hematological malignancies, effectiveness of RIT in treating solid tumors remains limited. Here we present PreTarg-it®, a novel approach for pretargeted radioimmunotherapy, providing optimized delivery of payloads in a two-step regimen. The effectiveness of PreTarg-it® is demonstrated by a powerful combination of ON105, a novel bispecific antibody against both oxMIF and the histamine-succinyl-glycyl (HSG) hapten, as the first component and the radioactively labeled DOTA-di-HSG peptide as the second component in murine models of cancer. Mice bearing either subcutaneous mouse colorectal CT26 or human pancreatic CFPAC-1 tumors received an intravenous injection of ON105. After ON105 had accumulated in the tumor and cleared from circulation to approximately 1-3% of its peak concentration, 177Lu-DOTA-di-HSG peptide was administered. A single PreTarg-it® treatment cycle resulted in tumor regression when mice bearing CT26 tumors were given the highest treatment dose with a pretargeting delay of three days. Administered with a 5-day interval, the highest dose arrested tumor growth in both CT26 syngrafts and CFPAC-1 xenografts. In all cases, the highest treatment dose resulted in 100% survival at the study endpoint whereas the control cohorts showed 0% and 60% survival in the CT26 and CFPAC-1 models, respectively. Therefore, PreTarg-it® holds potential as a novel and potent therapy for patients with hard-to-treat solid tumors such as pancreatic cancer, as well as those with late-stage malignancies.

Redox-dependent plasticity of oxMIF facilitates its interaction with CD74 and therapeutic antibodies.

MIF is a ubiquitous protein involved in proinflammatory processes, which undergoes an oxidation-driven conformational change to oxidized (ox)MIF. We demonstrate that hypochlorous acid, produced by neutrophil-released myeloperoxidase (MPO) under inflammatory conditions, effectively oxidizes MIF into the oxMIF isoform, which is specifically recognized by the anti-oxMIF therapeutic antibody, ON104. NMR investigation of MIF oxidized by the MPO system revealed increased flexibility throughout the MIF structure, including at several catalytic and allosteric sites. Mass spectrometry of MPO-oxMIF revealed methionines as the primary site of oxidation, whereas Pro2 and Tyr99/100 remained almost unmodified. ELISA, SPR and cell-based assays demonstrated that structural changes caused by MPO-driven oxidation promoted binding of oxMIF to its receptor, CD74, which does not occur with native MIF. These data reveal the environment and modifications that facilitate interactions between MIF and its pro-inflammatory receptor, and a route for therapeutic intervention targeting the oxMIF isoform.

Targeting of oxidized Macrophage Migration Inhibitory Factor (oxMIF) with antibody ON104 attenuates the severity of glomerulonephritis.

The oxidized form of Macrophage Migration Inhibitory Factor (oxMIF) has been identified as the disease-related isoform of MIF, exerting pathological functions in inflamed tissue. In this study, we aimed to explore the in vivo effects of the neutralizing anti-oxMIF antibody ON104 in a rat model of crescentic glomerulonephritis (CGN), to better understand its disease modifying activities. WKY rats received a single intravenous injection of a rabbit nephrotoxic serum (NTS), targeting rat glomerular basement membrane to induce CGN. On day 4 and day 6, ON104 was given intraperitoneally (i.p.) and on day 8 urine, blood and kidney tissue were collected. ON104 substantially attenuated the severity of CGN demonstrated by reduced proteinuria, hematuria, as well as lower levels of kidney injury molecule (KIM)-1. ON104 treatment preserved the glomerular morphology and suppressed crescent formation, a hallmark of the disease. On the cellular level, oxMIF neutralization by ON104 strongly reduced the number of macrophages and neutrophils within the inflamed kidneys. In vitro, we identified human neutrophils, but not monocytes, as main producers of oxMIF among total peripheral cells. The present study demonstrates that oxMIF is a pertinent therapeutic target in a model of CGN which mechanistically resembles human immune mediated CGN. In this model, neutralization of oxMIF by ON104 leads to an improvement in both urinary abnormalities and histological pathological characteristics of the disease. ON104, thus has the potential to become a novel disease-modifying drug for the treatment of glomerulonephritis and other inflammatory kidney diseases.

Neutralization of macrophage migration inhibitory factor (MIF) by fully human antibodies correlates with their specificity for the ß-sheet structure of MIF.

The macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that recently emerged as an attractive therapeutic target for a variety of diseases. A diverse panel of fully human anti-MIF antibodies was generated by selection from a phage display library and extensively analyzed in vitro. Epitope mapping studies identified antibodies specific for linear as well as structural epitopes. Experimental animal studies revealed that only those antibodies binding epitopes within amino acids 50-68 or 86-102 of the MIF molecule exerted protective effects in models of sepsis or contact hypersensitivity. Within the MIF protein, these two binding regions form a ß-sheet structure that includes the MIF oxidoreductase motif. We therefore conclude that this ß-sheet structure is a crucial region for MIF activity and a promising target for anti-MIF antibody therapy.

The newly engineered monoclonal antibody ON104, targeting the oxidized Macrophage Migration Inhibitory Factor (oxMIF), ameliorates clinical and histopathological signs of collagen-induced arthritis.

Macrophage Migration Inhibitory Factor (MIF) is a pleiotropic inflammatory cytokine that emerged as a pivotal regulator in the pathogenesis of several autoimmune diseases including rheumatoid arthritis (RA). MIF occurs in two immunologically distinct conformational isoforms, indicated as reduced (redMIF) and oxidized MIF (oxMIF) where the latter exerts disease-related activities. In this study we demonstrate the presence of circulating oxMIF in RA patients and investigate the in vivo effects of an oxMIF-neutralizing antibody in a murine model of RA. By advanced antibody engineering we generated the fully human anti-oxMIF antibody ON104 with abolished effector functions. The therapeutic potential of ON104 was tested in a model of Collagen-Induced Arthritis (CIA) in DBA/1j mice. At disease onset, the mice received ON104 twice a week for three weeks. Clinical symptoms were assessed daily, and histological examinations of the joints were performed at the end of the study. Antibody ON104, specifically targeting human and murine oxMIF, is highly affine and does not elicit effector functions in vitro. The treatment of CIA mice with ON104 profoundly modulated disease progression with marked amelioration of clinical signs of arthritis that was associated with reduced synovial and cartilage damage and reduced F4/80-positive macrophages in the joints. These data prove that oxMIF is a relevant target in a well-known model of human RA and its specific neutralization by the antibody ON104 ameliorates clinical and histological signs of the disease in the so-treated mice. Thus, ON104 represents a new and promising treatment option for RA and possibly other autoimmune diseases.

Preclinical Evaluation of ON203, A Novel Bioengineered mAb Targeting Oxidized Macrophage Migration Inhibitory Factor as an Anticancer Therapeutic.

High levels of macrophage migration inhibitory factor (MIF) in patients with cancer are associated with poor prognosis. Its redox-dependent conformational isoform, termed oxidized MIF (oxMIF), is a promising tumor target due to its selective occurrence in tumor lesions and at inflammatory sites. A first-generation anti-oxMIF mAb, imalumab, was investigated in clinical trials in patients with advanced solid tumors, where it was well tolerated and showed signs of efficacy. However, imalumab has a short half-life in humans, increased aggregation propensity, and an unfavorable pharmacokinetic profile. Here, we aimed to optimize imalumab by improving its physicochemical characteristics and boosting its effector functions. Point mutations introduced into the variable regions reduced hydrophobicity and the antibodies' aggregation potential, and increased plasma half-life and tumor accumulation in vivo, while retaining affinity and specificity to oxMIF. The introduction of mutations into the Fc region known to increase antibody-dependent cellular cytotoxicity resulted in enhanced effector functions of the novel antibodies in vitro, whereas reduced cytokine release from human peripheral blood mononuclear cells in the absence of target antigen by the engineered anti-oxMIF mAb ON203 versus imalumab reveals a favorable in vitro safety profile. In vivo, ON203 mAb demonstrated superior efficacy over imalumab in both prophylactic and established prostate cancer (PC3) mouse xenograft models. In summary, our data highlight the potential of the second-generation anti-oxMIF mAb ON203 as a promising immunotherapy for patients with solid tumors, warranting clinical evaluation.

OxMIF: a druggable isoform of macrophage migration inhibitory factor in cancer and inflammatory diseases.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with a pleiotropic spectrum of biological functions implicated in the pathogenesis of cancer and inflammatory diseases. MIF is constitutively present in several cell types and non-lymphoid tissues and is secreted after acute stress or inflammation. MIF triggers the release of proinflammatory cytokines, overrides the anti-inflammatory effects of glucocorticoids, and exerts chemokine function, resulting in increased migration and recruitment of leukocytes into inflamed tissue. Despite this, MIF is a challenging target for therapeutic intervention because of its ubiquitous nature and presence in the circulation and tissue of healthy individuals. Oxidized MIF (oxMIF) is an immunologically distinct disease-related structural isoform found in the plasma and tissues of patients with inflammatory diseases and in solid tumor tissues. MIF converts to oxMIF in an oxidizing, inflammatory environment. This review discusses the biology and activity of MIF and the potential for autoimmune disease and cancer modification by targeting oxMIF. Anti-oxMIF antibodies reduce cancer cell invasion/migration, angiogenesis, proinflammatory cytokine production, and ERK and AKT activation. Anti-oxMIF antibodies also elicit apoptosis and alter immune cell function and/or migration. When co-administered with a glucocorticoid, anti-oxMIF antibodies produced a synergistic response in inflammatory models. Anti-oxMIF antibodies therefore counterregulate biological activities attributed to MIF. oxMIF expression has been observed in inflammatory diseases (eg, sepsis, psoriasis, asthma, inflammatory bowel disease, and systemic lupus erythematosus) and oxMIF has been detected in ovarian, colorectal, lung, and pancreatic cancers. In contrast to MIF, oxMIF is specifically detected in plasma and/or tissues of diseased patients, but not in healthy individuals. Therefore, as a druggable isoform of MIF, oxMIF represents a potential new therapeutic target in inflammatory diseases and cancer. Fully human, monoclonal anti-oxMIF antibodies have been shown to selectively bind oxMIF in preclinical and phase I studies; however, additional clinical assessments are necessary to validate their use as either a monotherapy or in combination with standard-of-care regimens (ie, immunomodulatory agents/checkpoint inhibitors, anti-angiogenic drugs, chemotherapeutics, and glucocorticoids).

A chemically defined production process for highly attenuated poxviruses.

Highly attenuated poxviruses are promising vectors for protective and therapeutic vaccines. These vectors do not replicate in human cells and can therefore be safely given even to immunocompromised recipients. They can accommodate very large inserts and provide strong stimulation of the immune system against the vectored antigen. Disadvantages include that very high numbers of infectious units are required per dose for full efficacy. Because they are difficult to produce, improved cellular substrates and processes are urgently needed to facilitate programs intended to reach a large number of vaccinees. We have developed a fully scalable and very efficient chemically-defined production process for modified vaccinia Ankara (MVA), canarypox (CNPV, strain ALVAC) and fowlpox viruses (FPV) based on a continuous cell line.

Optimization of an Antibody Light Chain Framework Enhances Expression, Biophysical Properties and Pharmacokinetics.

Efficacy, safety, and manufacturability of therapeutic antibodies are influenced by their biopharmaceutical and biophysical properties. These properties can be optimized by library approaches or rationale protein design. Here, we employed a protein engineering approach to modify the variable domain of the light chain (VL) framework of an oxidized macrophage migration inhibitory factor (oxMIF)-specific antibody. The amendment of the antibody sequence was based on homology to human germline VL genes. Three regions or positions were identified in the VL domain-L1-4, L66, L79-and mutated independently or in combination to match the closest germline V gene. None of the mutations altered oxMIF specificity or affinity, but some variants improved thermal stability, aggregation propensity, and resulted in up to five-fold higher expression. Importantly, the improved biopharmaceutical properties translated into a superior pharmacokinetic profile of the antibody. Thus, optimization of the V domain framework can ameliorate the biophysical qualities of a therapeutic antibody candidate, and as result its manufacturability, and also has the potential to improve pharmacokinetics.

Pharmacokinetics, disease-modifying activity, and safety of an experimental therapeutic targeting an immunological isoform of macrophage migration inhibitory factor, in rat glomerulonephritis.

New therapeutic agents are needed to overcome the toxicity and suboptimal efficacy observed in current treatment of glomerulonephritis (GN). BaxB01 is a fully human monoclonal antibody targeting a disease-related immunologically distinct isoform of Macrophage migration Inhibitory Factor (MIF), designated oxidized MIF (oxMIF) and locally expressed in inflammatory conditions. We report the pharmacokinetic profile of BaxB01, and its dose and exposure-related disease-modifying activity in experimentally induced rat GN. BaxB01 bound to rat oxMIF with high affinity and reduced rat macrophage migration in vitro. After intravenous administration in rats, BaxB01 demonstrated favorable pharmacokinetics, with a half-life of up to nine days. Disease modification was dose-related (≥ 10mg/kg) as demonstrated by significantly reduced proteinuria and diminished histopathological glomerular crescent formation. Importantly, a single dose was sufficient to establish an exposure-related, anti-inflammatory milieu via amelioration of glomerular cellular inflammation. Pharmacodynamic modeling corroborated these findings, consistently predicting plasma exposures that were effective in attenuating both anti-inflammatory activity and reducing loss of kidney function. This pharmacologic benefit on glomerular function and structure was sustained during established disease, while correlation analyses confirmed a link between the antibody's anti-inflammatory activity and reduced crescent formation in individual rats. Finally, safety assessment in rats showed that the experimental therapeutic was well tolerated without signs of systemic toxicity or negative impact on kidney function. These data define therapeutically relevant exposures correlated with mechanism-based activity in GN, while toxicological evaluation suggests a large therapeutic index and provides evidence for achieving safe and effective exposure to a MIF isoform-directed therapeutic in nephritis-associated disease.

Rapid and transient activation of the ERK MAPK signalling pathway by macrophage migration inhibitory factor (MIF) and dependence on JAB1/CSN5 and Src kinase activity.

Macrophage migration inhibitory factor (MIF) is a 12.5 kD polypeptide that serves as a critical regulator of cell functions such as gene expression, proliferation or apoptosis. However, the signal transduction pathways through which MIF takes part in cellular regulation are only incompletely understood. MIF leads to CD74-dependent "sustained" activation of ERK1/2 MAPK, but MIF's role in "transient" ERK activation and the involved upstream pathways are unknown. Here we report that the transient ERK pathway was markedly activated by MIF. This effect involved the phosphorylation and activation of Raf-1, MEK, ERK, and Elk-1. Of note, rapid and transient ERK phosphorylation by MIF was measurable in MIF-deficient cells, suggesting that MIF acted in a non-autocrine fashion. Applying the inhibitor genistein, a tyrosine kinase (TPK) activity was identified as a critical upstream signalling event in MIF-induced transient ERK signalling. Experiments using the Src kinase inhibitor PP2 indicated that the involved TPK was a Src-type tyrosine kinase. A role for an upstream Src kinase was proven by applying Src-deficient cells which did not exhibit transient ERK activation upon treatment with MIF, but in which MIF-induced ERK signalling could be restored by re-expressing Src. Intriguingly, JAB1/CSN5, a signalosome component, cellular binding protein of MIF and regulator of cell proliferation and survival, had a marked, yet dual, effect on MIF-induced ERK signalling. JAB1 overexpression inhibited sustained, but not transient, ERK phosphorylation. By contrast, JAB1-knock-down by siRNA revealed that minimum JAB1 levels were necessary for transient activation of ERK by MIF. In conclusion, MIF rapidly and transiently activates the ERK pathway, an effect that has not been recognized previously. This signalling pathway involves the upstream activation of a Src-type kinase and is co-regulated by the cellular MIF binding protein JAB1/CSN5. Our study thus has unravelled a novel MIF-driven signalling pathway and an intricate regulatory system involving extra- and possibly intracellular MIF, and which likely critically participates in controlling cell proliferation and survival.

Oxidized macrophage migration inhibitory factor is a potential new tissue marker and drug target in cancer.

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine, which was shown to be upregulated in cancers and to exhibit tumor promoting properties. Unlike other cytokines, MIF is ubiquitously present in the circulation and tissue of healthy subjects. We recently described a previously unrecognized, disease-related isoform of MIF, designated oxMIF, which is present in the circulation of patients with different inflammatory diseases. In this article, we report that oxMIF is also linked to different solid tumors as it is specifically expressed in tumor tissue from patients with colorectal, pancreatic, ovarian and lung cancer. Furthermore, oxMIF can be specifically targeted by a subset of phage display-derived fully human, monoclonal anti-MIF antibodies (mAbs) that were shown to neutralize pro-tumorigenic activities of MIF in vivo. We further demonstrate that anti-oxMIF mAbs sensitize human cancer cell lines (LNCaP, PC3, A2780 and A2780ADR) to the action of cytotoxic drugs (mitoxantrone, cisplatin and doxorubicin) in vitro and in an A2780 xenograft mouse model of ovarian cancer. We conclude that oxMIF is the disease related isoform of MIF in solid tumors and a potential new diagnostic marker and drug target in cancer.

Stabilization of atherosclerotic plaques by blockade of macrophage migration inhibitory factor after vascular injury in apolipoprotein E-deficient mice.

BACKGROUND: Macrophage migration inhibitory factor (MIF), a cytokine that controls cell-mediated inflammatory responses, is upregulated in atherogenesis; however, its functional contribution to lesion development has not been evaluated. METHODS AND RESULTS: We studied the role of MIF on neointima lesion formation after wire-induced injury of carotid arteries in apolipoprotein E-deficient (apoE(-/-)) mice. Immunohistochemistry revealed that MIF expression was detectable in endothelial cells before injury and upregulated in smooth muscle cells (SMCs) 24 hours after endothelial denudation. Three weeks after injury, MIF was predominantly found in endothelial cells and macrophage-derived foam cells. Neutralizing MIF with a monoclonal antibody resulted in a marked reduction of neointimal macrophages and inhibited transformation of macrophages into foam cells. Conversely, the content of SMCs and of collagen in the neointima were increased, amounting to a slight but not significant reduction in neointima and media size after 3 weeks of MIF monoclonal antibody treatment. Notably, serum levels of the cytokines IL-2, IL-4, IL-6, IL-10, and tumor necrosis factor were increased in MIF monoclonal antibody-treated mice. In vitro flow assays revealed that MIF pretreatment of aortic endothelium enhanced monocyte recruitment and that the monocyte arrest induced by oxidized LDL is mediated by endothelial MIF, as shown by monoclonal antibody inhibition. CONCLUSIONS: Inhibition of MIF resulted in a shift in the cellular composition of neointimal plaques toward a stabilized phenotype with reduced macrophage/foam cell content and increased SMC content. This might be attributable to a reduction of monocyte recruitment mediated by endothelial MIF.

Binding of JAB1/CSN5 to MIF is mediated by the MPN domain but is independent of the JAMM motif.

Macrophage migration inhibitory factor (MIF) binds to c-Jun activation domain binding protein-1 (JAB1)/subunit 5 of COP9 signalosome (CSN5) and modulates cell signaling and the cell cycle through JAB1. The binding domain of JAB1 responsible for binding to MIF is unknown. We hypothesized that the conserved Mpr1p Pad1p N-terminal (MPN) domain of JAB1 may mediate binding to MIF. In fact, yeast two hybrid (YTH) and in vitro translation/coimmunoprecipitation (CoIP) analysis showed that a core MPN domain, which did not cover the functional JAB1/MPN/Mov34 metalloenzyme (JAMM) deneddylase sequence, binds to MIF comparable to full-length JAB1. YTH and pull-down analysis in conjunction with nanobead affinity matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry demonstrated that MIF(50-65) and MPN are sufficient to mediate MIF-JAB1 interaction, respectively. Finally, endogenous CoIP of MIF-CSN6 complexes from mammalian cells demonstrated that MPN is responsible for MIF-JAB1 binding in vivo, and, as CSN6 does not contain a functional JAMM motif, confirmed that the interaction does not require JAMM.

Link between macrophage migration inhibitory factor and cellular redox regulation.

Macrophage migration inhibitory factor (MIF) is an evolutionary conserved 12.5-kDa protein mediator with multiple functions in innate and acquired immunity. Upon leaderless secretion, MIF acts as a typical inflammatory cytokine, but there is no structural homology between MIF and any of the known cytokine protein families. Also, MIF is unique among cytokines in that it exhibits certain endocrine properties and has enzymatic activity. The catalytic thiol-protein oxidoreductase (TPOR) activity of MIF is mediated by a Cys-Ala-Leu-Cys active site between residues 57 and 60 that can undergo reversible intramolecular disulfide formation. Such a redox motif is typically found in TPORs of the thioredoxin (Trx) family of proteins. MIF seems to act as a disulfide reductase, and structure-function analyses of the redox site indicate that this activity is not only observed in vitro, but plays a role in cellular redox homeostasis, apoptosis inhibition, MIF-mediated monocyte/macrophage activation, and possibly the modulation of the activity of MIF-binding proteins. In this Forum review, the biochemical and biological evidence for a role of the TPOR activity for various MIF functions is summarized and discussed. In particular, the marked functional homologies with Trx proteins, the MIF redox/MHC II link, and recent attempts to discern the intra- versus extracellular roles of the MIF TPOR activity are dealt with.

Human anti-macrophage migration inhibitory factor antibodies inhibit growth of human prostate cancer cells in vitro and in vivo.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine, originally discovered for its eponymous effect and now known for pleiotropic biologic properties in immunology and oncology. Circulating MIF levels are elevated in several types of human cancer including prostate cancer. MIF is released presumably by both stromal and tumor cells and enhances malignant growth and metastasis by diverse mechanisms, such as stimulating tumor cell proliferation, suppressing apoptotic death, facilitating invasion of the extracellular matrix, and promoting angiogenesis. Recently described fully human anti-MIF antibodies were tested in vitro and in vivo for their ability to influence growth rate and invasion of the human PC3 prostate cancer cell line. In vitro, the selected candidate antibodies BaxG03, BaxB01, and BaxM159 reduced cell growth and viability by inhibiting MIF-induced phosphorylation of the central kinases p44/42 mitogen-activated protein kinase [extracellular signal-regulated kinase-1 and -2 (ERK1/2)] and protein kinase B (AKT). Incubation of cells in the presence of the antibodies also promoted activation of caspase-3/7. The antibodies furthermore inhibited MIF-promoted invasion and chemotaxis as transmigration through Matrigel along a MIF gradient was impaired. In vivo, pharmacokinetic parameters (half-life, volume of distribution, and bioavailability) of the antibodies were determined and a proof-of-concept was obtained in a PC3-xenograft mouse model. Treatment with human anti-MIF antibodies blunted xenograft tumor growth in a dose-dependent manner. We therefore conclude that the anti-MIF antibodies described neutralize some of the key tumor-promoting activities of MIF and thus limit tumor growth in vivo.

The cytokine macrophage migration inhibitory factor reduces pro-oxidative stress-induced apoptosis.

The cytokine macrophage migration inhibitory factor (MIF) exhibits pro- and anti-inflammatory activities and regulates cell proliferation and survival. We investigated the effects of MIF on apoptosis. As MIF exhibits oxidoreductase activity and participates in regulating oxidative cell stress, we studied whether MIF could affect oxidative stress-induced apoptosis. We demonstrated that MIF exhibits antiapoptotic activity in various settings. MIF suppressed camptothecin-induced apoptosis in HeLa and Kym cells and HL-60 promyeloblasts. Both exogenous MIF and endogenous MIF, induced following overexpression through tetracycline (tet) gene induction, led to significant suppression of apoptosis. Apoptosis reduction by MIF was also observed in T cells. A role for MIF in redox stress-induced apoptosis was addressed by comparing the effects of rMIF with those of the oxidoreductase mutant C60SMIF. Endogenous overexpression of C60SMIF was similar to that of MIF, but C60SMIF did not suppress apoptosis. Exogenous rC60SMIF inhibited apoptosis. A role for MIF in oxidative stress-induced apoptosis was directly studied in HL-60 leukocytes and tet-regulated HeLa cells following thiol starvation or diamide treatment. MIF protected these cells from redox stress-induced apoptosis and enhanced cellular glutathione levels. As overexpressed C60SMIF did not protect tet-regulated HeLa cells from thiol starvation-induced apoptosis, it seems that the redox motif of MIF is important for this function. Finally, overexpression of MIF inhibited phosphorylation of endogenous c-Jun induced by thiol starvation, indicating that MIF-based suppression of apoptosis is mediated through modulation of c-Jun N-terminal kinase activity. Our findings show that MIF has potent antiapoptotic activities and suggest that MIF is a modulator of pro-oxidative stress-induced apoptosis.