Macrophage migration inhibitory factor is secreted by rhabdomyosarcoma cells, modulates tumor metastasis by binding to CXCR4 and CXCR7 receptors and inhibits recruitment of cancer-associated fibroblasts

Endothelial Pim3 kinase protects the vascular barrier during lung metastasis

Endothelial cells (ECs) form a tissue-specific barrier for disseminating cancer cells in distant organs. However, the molecular regulation of the ECs in the metastatic niche remains unclear. Here, we analyze using scRNA-Seq, the transcriptional reprogramming of lung ECs six hours after the arrival of melanoma cells in mouse lungs. We discover a reactive capillary EC cluster (rCap) that increases from general capillary ECs in response to infiltrating cancer cells. rCap is enriched for angiogenic and inflammatory pathways and is also found in human lung datasets. The JAK-STAT activated oncogenic Pim3 kinase is a marker of rCap, being upregulated in spontaneous metastasis models. Notably, PIM inhibition increases vascular leakage and metastatic colonization and impairs the EC barrier by decreasing the junctional cadherin-5 and catenins α, β and δ. These results highlight the pulmonary endothelium's plasticity and its protection by PIM3, which may impair the efficacy of PIM inhibitors in cancer therapies.

Constitutive activity of an atypical chemokine receptor revealed by inverse agonistic nanobodies

Chemokine stimulation of atypical chemokine receptor 3 (ACKR3) does not activate G proteins but recruits arrestins. It is a chemokine scavenger that indirectly influences responses by restricting the availability of CXCL12, an agonist shared with the canonical receptor CXCR4. ACKR3 is upregulated in numerous disorders. Due to limited insights in chemokine-activated ACKR3 signaling, it is unclear how ACKR3 contributes to pathological phenotypes. One explanation may be that high constitutive activity of ACKR3 drives non-canonical signaling through a basal receptor state. Here we characterize the constitutive action of ACKR3 using novel inverse agonistic nanobodies to suppress basal activity. These new tools promote an inactive receptor conformation which decreased arrestin engagement and inhibited constitutive internalization. Basal, non-chemotactic, breast cancer cell motility was also suppressed, suggesting a role for ACKR3 in this process. The basal receptor activity in pathophysiology may provide a new therapeutic approach for targeting ACKR3.

Gastrointestinal stromal tumors regulate macrophage M2 polarization through the MIF/CXCR4 axis to immune escape

Purpose

The infiltration of immune cells and their roles of the infiltrating-immune cells in gastrointestinal stromal tumor (GIST) is still unclear. We aimed to discover the infiltration cell types and the relationship between the infiltrating-immune cells and the progression of GIST.

Experimental design

Single-cell RNA sequencing were performed to discover types of the infiltrating-immune cells and to analyze CellChat between cells. Immunohistochemistry of 80 GIST samples were used to clarify the relation between macrophages and recurrence risk. In vitro, flow cytometry and Real-time PCR were performed to uncover a potential mechanism of tumor cell regulation of macrophages.

Results

Tumor cells, macrophages, and T-cells were the predominant cell types. The MIF/CXCR4 axis was the most common ligand-receptor interaction between macrophages and tumor cells. As the risk increased, expression levels of CD68, CD206, MIF, and CXCR4 gradually increased. In vitro, we found that GIST882 was able to secrete MIF and GIST882 cell supernatant upregulated M2 polarization. Real-time PCR showed that expression levels of IL-10 mRNA and Arginase-1 mRNA were also the highest in the GIST882 cell supernatant group.

Conclusions

These findings identify that macrophages are the most abundant infiltrating cells in GIST. The MIF/CXCR4 axis is the most common ligand-receptor interaction between macrophages and tumor cells. GIST cells can regulate macrophage M2 polarization through the MIF/CXCR4 axis.

EAF2 Downregulation Recruits Tumor-associated Macrophages in Prostate Cancer through Upregulation of MIF

BACKGROUND

The role of tumor inflammatory microenvironment in the advancement of cancer, particularly prostate cancer, is widely acknowledged. ELL-associated factor 2 (EAF2), a tumor suppressor that has been identified in the prostate, is often downregulated in prostate cancer. Earlier investigations have shown that mice with EAF2 gene knockout exhibited a substantial infiltration of inflammatory cells into the prostatic stroma.

METHODS

A cohort comprising 38 patients who had been diagnosed with prostate cancer and subsequently undergone radical prostatectomy (RP) was selected. These patients were pathologically graded according to the Gleason scoring system and divided into two groups. The purpose of this selection was to investigate the potential correlation between EAF2 and CD163 using immunohistochemistry (IHC) staining. Additionally, in vitro experimentation was conducted to verify the relationship between EAF2 expression, macrophage migration and polarization.

RESULTS

Our study demonstrated that in specimens of human prostate cancer, the expression of EAF2 was notably downregulated, and this decrease was inversely associated with the number of CD163-positive macrophages that infiltrated the cancerous tissue. Cell co-culture experiments revealed that the chemotactic effect of tumor cells towards macrophages was intensified and that macrophages differentiated into tumor-associated macrophages (TAMs) when EAF2 was knocked out. Additionally, the application of cytokine protein microarray showed that the expression of chemokine macrophage migration inhibitory factor (MIF) increased after EAF2 knockout.

CONCLUSIONS

Our findings suggested that EAF2 was involved in the infiltration of CD163-positive macrophages in prostate cancer via MIF.

The role of macrophage migration inhibitory factor family and CD74 in the pathogenesis of melanoma

Melanoma is an aggressive tumour with poor prognosis that arises from the malignant transformation of melanocytes. Over the past few decades, intense research into the pathogenesis of melanoma has led to the development of BRAF and immune checkpoint inhibitors, including antibodies against programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), which have shown clinically significant efficacy. However, some tumours do not respond to these therapies initially or become treatment resistant. Most melanoma tissues appear to possess biological characteristics that allow them to evade these treatments, and identifying these characteristics is one of the major challenges facing cancer researchers. One such characteristic that has recently gained attention is the role of macrophage migration inhibitory factor (MIF) and its receptor CD74. This review outlines the cellular and molecular functions of CD74, MIF and their family of proteins. We then review their roles in tumours based on previous reports, highlight their pathological significance in melanoma and discuss their potential as therapeutic targets.

Exploring the anti-inflammatory activity of sulforaphane

Dysregulation of innate immune responses can result in chronic inflammatory conditions. Glucocorticoids, the current frontline therapy, are effective immunosuppressive drugs but come with a trade-off of cumulative and serious side effects. Therefore, alternative drug options with improved safety profiles are urgently needed. Sulforaphane, a phytochemical derived from plants of the brassica family, is a potent inducer of phase II detoxification enzymes via nuclear factor-erythroid factor 2-related factor 2 (NRF2) signaling. Moreover, a growing body of evidence suggests additional diverse anti-inflammatory properties of sulforaphane through interactions with mediators of key signaling pathways and inflammatory cytokines. Multiple studies support a role for sulforaphane as a negative regulator of nuclear factor kappa-light chain enhancer of activated B cells (NF-κB) activation and subsequent cytokine release, inflammasome activation and direct regulation of the activity of macrophage migration inhibitory factor. Significantly, studies have also highlighted potential steroid-sparing activity for sulforaphane, suggesting that it may have potential as an adjunctive therapy for some inflammatory conditions. This review discusses published research on sulforaphane, including proposed mechanisms of action, and poses questions for future studies that might help progress our understanding of the potential clinical applications of this intriguing molecule.

Hallmarks of Cancer Affected by the MIF Cytokine Family

New diagnostic methods and treatments have significantly decreased the mortality rates of cancer patients, but further improvements are warranted based on the identification of novel tumor-promoting molecules that can serve as therapeutic targets. The macrophage migration inhibitory factor (MIF) family of cytokines, comprising MIF and DDT (also known as MIF2), are overexpressed in almost all cancer types, and their high expressions are related to a worse prognosis for the patients. MIF is involved in 9 of the 10 hallmarks of cancer, and its inhibition by antibodies, nanobodies, or small synthetic molecules has shown promising results. Even though DDT is also proposed to be involved in several of the hallmarks of cancer, the available information about its pro-tumoral role and mechanism of action is more limited. Here, we provide an overview of the involvement of both MIF and DDT in cancer, and we propose that blocking both cytokines is needed to obtain the maximum anti-tumor response.

Targeted therapies and checkpoint inhibitors in sarcoma

Sarcomas are defined as a group of mesenchymal malignancies with over 100 heterogeneous subtypes. As a rare and difficult to diagnose entity, micrometastasis is already present at the time of diagnosis in many cases. Current treatment practice of sarcomas consists mainly of surgery, (neo)adjuvant chemo- and/or radiotherapy. Although the past decade has shown that particular genetic abnormalities can promote the development of sarcomas, such as translocations, gain-of-function mutations, amplifications or tumor suppressor gene losses, these insights have not led to established alternative treatment strategies so far. Novel therapeutic concepts with immunotherapy at its forefront have experienced some remarkable success in different solid tumors while their impact in sarcoma remains limited. In this review, the most common immunotherapy strategies in sarcomas, such as immune checkpoint inhibitors, targeted therapy and cytokine therapy are concisely discussed. The programmed cell death (PD)-1/PD-1L axis and apoptosis-inducing cytokines, such as TNF-related apoptosis-inducing ligand (TRAIL), have not yielded the same success like in other solid tumors. However, in certain sarcoma subtypes, e.g. liposarcoma or undifferentiated pleomorphic sarcoma, encouraging results in some cases when employing immune checkpoint inhibitors in combination with other treatment options were found. Moreover, newer strategies such as the targeted therapy against the ancient cytokine macrophage migration inhibitory factor (MIF) may represent an interesting approach worth investigation in the future.

Bone Marrow Macrophages Induce Inflammation by Efferocytosis of Apoptotic Prostate Cancer Cells via HIF-1α Stabilization

The clearance of apoptotic cancer cells by macrophages, known as efferocytosis, fuels the bone-metastatic growth of prostate cancer cells via pro-inflammatory and immunosuppressive processes. However, the exact molecular mechanisms remain unclear. In this study, single-cell transcriptomics of bone marrow (BM) macrophages undergoing efferocytosis of apoptotic prostate cancer cells revealed a significant enrichment in their cellular response to hypoxia. Here, we show that BM macrophage efferocytosis increased hypoxia inducible factor-1alpha (HIF-1α) and STAT3 phosphorylation (p-STAT3 at Tyr705) under normoxic conditions, while inhibitors of p-STAT3 reduced HIF-1α. Efferocytosis promoted HIF-1α stabilization, reduced its ubiquitination, and induced HIF-1α and p-STAT3 nuclear translocation. HIF-1α stabilization in efferocytic BM macrophages resulted in enhanced expression of pro-inflammatory cytokine MIF, whereas BM macrophages with inactive HIF-1α reduced MIF expression upon efferocytosis. Stabilization of HIF-1α using the HIF-prolyl-hydroxylase inhibitor, Roxadustat, enhanced MIF expression in BM macrophages. Furthermore, BM macrophages treated with recombinant MIF protein activated NF-κB (p65) signaling and increased the expression of pro-inflammatory cytokines. Altogether, these findings suggest that the clearance of apoptotic cancer cells by BM macrophages triggers p-STAT3/HIF-1α/MIF signaling to promote further inflammation in the bone tumor microenvironment where a significant number of apoptotic cancer cells are present.

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 confers survival advantage to pancreatic CAFs by suppressing interferon pathway-induced p53-dependent apoptosis

The presence of activated pancreatic stellate cells (PSCs) in the pancreatic ductal adenocarcinoma (PDAC) microenvironment plays a significant role in cancer progression. Macrophage migration inhibitory factor (MIF) is overexpressed in PDAC tissues and expressed by both cancer and stromal cells. The pathophysiological role of MIF in PDAC-associated fibroblasts or PSCs is yet to be elucidated. Here we report that the PSCs of mouse or cancer-associated fibroblast cells (CAFs) of human expresses MIF and its receptors, whose expression gets upregulated upon LPS or TNF-α stimulation. In vitro functional experiments showed that MIF significantly conferred a survival advantage to CAFs/PSCs upon growth factor deprivation. Genetic or pharmacological inhibition of MIF also corroborated these findings. Further, co-injection of mouse pancreatic cancer cells with PSCs isolated from Mif-/- or Mif+/+ mice confirmed the pro-survival effect of MIF in PSCs and also demonstrated the pro-tumorigenic role of MIF expressed by CAFs in vivo. Differential gene expression analysis and in vitro mechanistic studies indicated that MIF expressed by activated CAFs/PSCs confers a survival advantage to these cells by suppression of interferon pathway induced p53 dependent apoptosis.

TA-MSCs, TA-MSCs-EVs, MIF: their crosstalk in immunosuppressive tumor microenvironment

As an important component of the immunosuppressive tumor microenvironment (TME), it has been established that mesenchymal stem cells (MSCs) promote the progression of tumor cells. MSCs can directly promote the proliferation, migration, and invasion of tumor cells via cytokines and chemokines, as well as promote tumor progression by regulating the functions of anti-tumor immune and immunosuppressive cells. MSCs-derived extracellular vesicles (MSCs-EVs) contain part of the plasma membrane and signaling factors from MSCs; therefore, they display similar effects on tumors in the immunosuppressive TME. The tumor-promoting role of macrophage migration inhibitory factor (MIF) in the immunosuppressive TME has also been revealed. Interestingly, MIF exerts similar effects to those of MSCs in the immunosuppressive TME. In this review, we summarized the main effects and related mechanisms of tumor-associated MSCs (TA-MSCs), TA-MSCs-EVs, and MIF on tumors, and described their relationships. On this basis, we hypothesized that TA-MSCs-EVs, the MIF axis, and TA-MSCs form a positive feedback loop with tumor cells, influencing the occurrence and development of tumors. The functions of these three factors in the TME may undergo dynamic changes with tumor growth and continuously affect tumor development. This provides a new idea for the targeted treatment of tumors with EVs carrying MIF inhibitors.

Germinal Center-Related G Protein-Coupled Receptors in Antibody-Mediated Autoimmune Skin Diseases: from Basic Research to Clinical Trials

Germinal center (GC) reaction greatly contributes to the humoral immune response, which begins in lymph nodes or other secondary lymphoid organs after follicular B cells are activated by T-dependent antigens. The GCs then serve as a platform for follicular B cells to complete clonal expansion and somatic hypermutation and then interact with follicular dendritic cells (FDC) and follicular helper T cells (Tfh). Through the interaction between the immune cells, significant processes of the humoral immune response are accomplished, such as antibody affinity maturation, class switching, and production of memory B cells and plasma cells. Cell positioning during the GC reaction is mainly mediated by the chemokine receptors and lipid receptors, which both belong to G protein-coupled receptors (GPCRs) family. There are some orphan GPCRs whose endogenous ligands are unclear yet contribute to the regulation of GC reaction as well. This review will give an introduction on the ligands and functions of two types of GC-relating GPCRs-chemokine receptors like CXCR4 and CXCR5, as well as emerging de-orphanized GPCRs like GPR183, GPR174, and P2RY8. The roles these GPCRs play in several antibody-mediated autoimmune skin diseases will be also discussed, including systemic lupus erythematosus (SLE), pemphigus, scleroderma, and dermatomyositis. Besides, GPCRs are excellent drug targets due to the unique structure and vital functions. Therefore, this review is aimed at providing readers with a focused knowledge about the role that GPCRs play in GC reaction, as well as in provoking the development of GPCR-targeting agents for immune-mediated diseases besides autoimmune diseases.

The key players of parthanatos: opportunities for targeting multiple levels in the therapy of parthanatos-based pathogenesis

Parthanatos is a form of regulated cell death involved in the pathogenesis of many diseases, particularly neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis. Parthanatos is a multistep cell death pathway cascade that involves poly (ADP-ribose) polymerase 1 (PARP-1) overactivation, PAR accumulation, PAR binding to apoptosis-inducing factor (AIF), AIF release from the mitochondria, nuclear translocation of the AIF/macrophage migration inhibitory factor (MIF) complex, and MIF-mediated large-scale DNA fragmentation. All the key players in the parthanatos pathway are pleiotropic proteins with diverse functions. An in-depth understanding of the structure-based activity of the key factors, and the biochemical mechanisms of parthanatos, is crucial for the development of drugs and therapeutic strategies. In this review, we delve into the key players of the parthanatos pathway and reveal the multiple levels of therapeutic opportunities for treating parthanatos-based pathogenesis.

Bioinformatics prediction and experimental verification identify MAD2L1 and CCNB2 as diagnostic biomarkers of rhabdomyosarcoma

Background

Rhabdomyosarcoma (RMS) is a malignant soft-tissue tumour. In recent years, the tumour microenvironment (TME) has been reported to be associated with the development of tumours. However, the relationship between the occurrence and development of RMS and TME is unclear. The purpose of this study is to identify potential tumor microenvironment-related biomarkers in rhabdomyosarcoma and analyze their molecular mechanisms, diagnostic and prognostic significance.

Methods

We first applied bioinformatics method to analyse the tumour samples of 125 patients with rhabdomyosarcoma (RMS) from the Gene Expression Omnibus database (GEO). Differential genes (DEGs) that significantly correlate with TME and the clinical staging of tumors were extracted. Immunohistochemistry (IHC) was applied to validate the expression of mitotic arrest deficient 2 like 1 (MAD2L1) and cyclin B2 (CCNB2) in RMS tissue. Then, we used cell function and molecular biology techniques to study the influence of MAD2L1 and CCNB2 expression levels on the progression of RMS.

Results

Bioinformatics results show that the RMS TME key genes were screened, and a TME-related tumour clinical staging model was constructed. The top 10 hub genes were screened through the establishment of a protein–protein interaction (PPI) network, and then Gene Expression Profiling Interactive Analysis (GEPIA) was conducted to measure the overall survival (OS) of the 10 hub genes in the sarcoma cases in The Cancer Genome Atlas (TCGA). Six DEGs of statistical significance were acquired. The relationship between these six differential genes and the clinical stage of RMS was analysed. Further analysis revealed that the OS of RMS patients with high expression of MAD2L1 and CCNB2 was worse and the expression of MAD2L1 and CCNB2 was related to the clinical stage of RMS patients. Gene set enrichment analysis (GSEA) revealed that the genes in MAD2L1 and CCNB2 groups with high expression were mainly related to the mechanism of tumour metastasis and recurrence. In the low-expression MAD2L1 and CCNB2 groups, the genes were enriched in the metabolic and immune pathways. Immunohistochemical results also confirmed that the expression levels of MAD2L1 (30/33, 87.5%) and CCNB2 (33/33, 100%) were remarkably higher in RMS group than in normal control group (0/11, 0%). Moreover, the expression of CCNB2 was related to tumour size. Downregulation of MAD2L1 and CCNB2 suppressed the growth, invasion, migration, and cell cycling of RMS cells and promoted their apoptosis. The CIBERSORT immune cell fraction analysis indicated that the expression levels of MAD2L1 and CCNB2 affected the immune status in the TME.

Conclusions

The expression levels of MAD2L1 and CCNB2 are potential indicators of TME status changes in RMS, which may help guide the prognosis of patients with RMS and the clinical staging of tumours.

Bone marrow-derived mesenchymal stem cells promote Helicobacter pylori-associated gastric cancer progression by secreting thrombospondin-2

Objectives

Bone marrow‐derived cells (BMDCs), especially mesenchymal stem cells (MSCs), may be involved in the development of Helicobacter pylori‐associated gastric cancer (GC) in mice, but the specific mechanism remains unclear, and evidence from human studies is lacking.

Materials and Methods

To verify the role of BM‐MSCs in H pylori‐associated GC, green fluorescent protein (GFP)‐labelled BM‐MSCs were transplanted into the subserosal layers of the stomach in a mouse model of chronic H pylori infection. Three months post‐transplantation, the mice were sacrificed, and the gastric tissues were subjected to histopathological and immunofluorescence analyses. In addition, we performed fluorescence in situ hybridization (FISH) and immunofluorescence analyses of gastric tissue from a female patient with H pylori infection and a history of acute myeloid leukaemia who received a BM transplant from a male donor.

Results

In mice with chronic H pylori infection, GFP‐labelled BM‐MSCs migrated from the serous layer to the mucosal layer and promoted GC progression. The BM‐MSCs differentiated into pan‐cytokeratin‐positive epithelial cells and α‐smooth muscle actin‐positive cancer‐associated fibroblasts (CAFs) by secreting the protein thrombospondin‐2. FISH analysis of gastric tissue from the female patient revealed Y‐chromosome‐positive cells. Immunofluorescence analyses further confirmed that Y‐chromosome‐positive cells showed positive BM‐MSCs marker. These results suggested that allogeneic BMDCs, including BM‐MSCs, can migrate to the stomach under chronic H pylori infection.

Conclusions

Taken together, these findings imply that BM‐MSCs participate in the development of chronic H pylori‐associated GC by differentiating into both gastric epithelial cells and CAFs.

Polyfunctionality of the CXCR4/CXCL12 axis in health and disease: Implications for therapeutic interventions in cancer and immune-mediated diseases

Historically the chemokine receptor CXCR4 and its canonical ligand CXCL12 are associated with the bone marrow niche and hematopoiesis. However, CXCL12 exhibits broad tissue expression including brain, thymus, heart, lung, liver, kidney, spleen, and bone marrow. CXCR4 can be considered as a node which is integrating and transducing inputs from a range of ligand-receptor interactions into a responsive and divergent network of intracellular signaling pathways that impact multiple cellular processes such as proliferation, migration, and stress resistance. Dysregulation of the CXCR4/CXCL12 axis and consequent fundamental cellular processes, are associated with a panoply of disease. This review frames the polyfunctionality of the receptor at a molecular, physiological, and pathophysiological levels. Transitioning our perspective of this axis from a single gene/protein:single function model to a polyfunctional signaling cascade highlights the potential for finer therapeutic intervention and cautions against a reductionist approach.

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.

Rhabdomyosarcoma Cells Produce Their Own Extracellular Matrix With Minimal Involvement of Cancer-Associated Fibroblasts: A Preliminary Study

BACKGROUND

The interplay between neoplastic cells and surrounding extracellular matrix (ECM) is one of the determinant elements for cancer growth. The remodeling of the ECM by cancer-associated fibroblasts (CAFs) shapes tumor microenvironment by depositing and digesting ECM proteins, hence promoting tumor growth and invasion. While for epithelial tumors CAFs are well characterized, little is known about the stroma composition of mesenchymal cancers, such as in rhabdomyosarcoma (RMS), the most common soft tissue sarcoma during childhood and adolescence. The aim of this work is to identify the importance of CAFs in specifying RMS microenvironment and the role of these stromal cells in RMS growth.

METHODS

We assessed in two dimensional (2D) and three dimensional (3D) systems the attraction between RMS cells and fibroblasts using epithelial colon cancer cell line as control. CAFs were studied in a xenogeneic mouse model of both tumor types and characterized in terms of fibroblast activation protein (FAP), mouse PDGFR expression, metalloproteases activation, and ECM gene and protein expression profiling.

RESULTS

In 2D model, the rate of interaction between stromal and malignant cells was significantly lower in RMS with respect to colon cancer. Particularly, in 3D system, RMS spheroids tended to dismantle the compact aggregate when grown on the layer of stromal cells. In vivo, despite the well-formed tumor mass, murine CAFs were found in low percentage in RMS xenogeneic samples.

CONCLUSIONS

Our findings support the evidence that, differently from epithelial cancers, RMS cells are directly involved in their own ECM remodeling, and less dependent on CAFs support for cancer cell growth.

The Role of Tumor Microenvironment in Multiple Myeloma Development and Progression

Simple Summary

Multiple Myeloma (MM) is a hematologic malignancy caused by aberrant plasma cell proliferation in the bone marrow (BM) and constitutes the second most common hematological disease after non-Hodgkin lymphoma. The disease progression is drastically regulated by the immunosuppressive tumor microenvironment (TME) generated by soluble factors and different cells that naturally reside in the BM. This microenvironment does not remain unchanged and alterations favor cancer dissemination. Despite therapeutic advances over the past 15 years, MM remains incurable and therefore understanding the elements that control the TME in MM would allow better-targeted therapies to cure this disease. In this review, we discuss the main events and changes that occur in the BM milieu during MM development.

Abstract

Multiple myeloma (MM) is a hematologic cancer characterized by clonal proliferation of plasma cells in the bone marrow (BM). The progression, from the early stages of the disease as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to MM and occasionally extramedullary disease, is drastically affected by the tumor microenvironment (TME). Soluble factors and direct cell–cell interactions regulate MM plasma cell trafficking and homing to the BM niche. Mesenchymal stromal cells, osteoclasts, osteoblasts, myeloid and lymphoid cells present in the BM create a unique milieu that favors MM plasma cell immune evasion and promotes disease progression. Moreover, TME is implicated in malignant cell protection against anti-tumor therapy. This review describes the main cellular and non-cellular components located in the BM, which condition the immunosuppressive environment and lead the MM establishment and progression.

Macrophage migration inhibitory factor modulates cytokine expression in the trophoblast cell line HTR-8/SVneo

Extravillous trophoblasts are specific placental cells that invade the uterine stroma and spiral arteries modifying and adjusting them to pregnancy. Many pregnancy pathologies are associated with impairment of this process, including preeclampsia and intrauterine growth restriction, among others. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that is abundant at the fetomaternal interface. Previous results from our group showed that MIF participates in trophoblast invasion and modulates the expression of molecules known to mediate stromal and endovascular trophoblast invasion. In this study we investigated the possibility that MIF could act as a regulator of cytokines known to modulate trophoblast invasion using the normal extravillous trophoblast-derived cell line HTR-8/SVneo. Expression of trophoblast MIF was attenuated by MIF mRNA-specific small interfering RNAs. Cytokine expression was assessed at the mRNA and protein levels using real-time quantitative polymerase chain reaction and flow cytometry respectively. Knockdown of MIF led to a significant decrease in mRNA for IL-1β (IL1B) and IL-8 (CXCL8) and interleukin (IL)-8 protein. The addition of recombinant human MIF to cell culture medium increased IL-6 after 24h treatment and IL-6 and IL-8 after 72h treatment. Cell viability was not affected by MIF silencing or rhMIF treatment. The results of this study imply that at least some of the effects of MIF on trophoblast invasion could be mediated through autocrine or paracrine modulation of trophoblast cytokine production.

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.

Sarcoma treatment in the era of molecular medicine

Sarcomas are heterogeneous and clinically challenging soft tissue and bone cancers. Although constituting only 1% of all human malignancies, sarcomas represent the second most common type of solid tumors in children and adolescents and comprise an important group of secondary malignancies. More than 100 histological subtypes have been characterized to date, and many more are being discovered due to molecular profiling. Owing to their mostly aggressive biological behavior, relative rarity, and occurrence at virtually every anatomical site, many sarcoma subtypes are in particular difficult-to-treat categories. Current multimodal treatment concepts combine surgery, polychemotherapy (with/without local hyperthermia), irradiation, immunotherapy, and/or targeted therapeutics. Recent scientific advancements have enabled a more precise molecular characterization of sarcoma subtypes and revealed novel therapeutic targets and prognostic/predictive biomarkers. This review aims at providing a comprehensive overview of the latest advances in the molecular biology of sarcomas and their effects on clinical oncology; it is meant for a broad readership ranging from novices to experts in the field of sarcoma.

Dynamical modeling predicts an inflammation-inducible CXCR7+ B cell precursor with potential implications in lymphoid blockage pathologies

Background

The blockage at the early B lymphoid cell development pathway within the bone marrow is tightly associated with hematopoietic and immune diseases, where the disruption of basal regulatory networks prevents the continuous replenishment of functional B cells. Dynamic computational models may be instrumental for the comprehensive understanding of mechanisms underlying complex differentiation processes and provide novel prediction/intervention platforms to reinvigorate the system.

Methods

By reconstructing a three-module regulatory network including genetic transcription, intracellular transduction, and microenvironment communication, we have investigated the early B lineage cell fate decisions in normal and pathological settings. The early B cell differentiation network was simulated as a Boolean model and then transformed, using fuzzy logic, to a continuous model. We tested null and overexpression mutants to analyze the emergent behavior of the network. Due to its importance in inflammation, we investigated the effect of NFkB induction at different early B cell differentiation stages.

Results

While the exhaustive synchronous and asynchronous simulation of the early B cell regulatory network (eBCRN) reproduced the configurations of the hematopoietic progenitors and early B lymphoid precursors of the pathway, its simulation as a continuous model with fuzzy logics suggested a transient IL-7R⁺ ProB-to-Pre-B subset expressing pre-BCR and a series of dominant B-cell transcriptional factors. This conspicuous differentiating cell population up-regulated CXCR7 and reduced CXCR4 and FoxO1 expression levels. Strikingly, constant but intermediate NFkB signaling at specific B cell differentiation stages allowed stabilization of an aberrant CXCR7⁺ pre-B like phenotype with apparent affinity to proliferative signals, while under constitutive overactivation of NFkB, such cell phenotype was aberrantly exacerbated from the earliest stage of common lymphoid progenitors. Our mutant models revealed an abnormal delay in the BCR assembly upon NFkB activation, concomitant to sustained Flt3 signaling, down-regulation of Ebf1, Irf4 and Pax5 genes transcription, and reduced Ig recombination, pointing to a potential lineage commitment blockage.

Discussion

For the first time, an inducible CXCR7^hi B cell precursor endowed with the potential capability of shifting central lymphoid niches, is inferred by computational modeling. Its phenotype is compatible with that of leukemia-initiating cells and might be the foundation that bridges inflammation with blockage-related malignancies and a wide range of immunological diseases. Besides the predicted differentiation impairment, inflammation-inducible phenotypes open the possibility of newly formed niches colonized by the reported precursor. Thus, emergent bone marrow ecosystems are predicted following a pro-inflammatory induction, that may lead to hematopoietic instability associated to blockage pathologies.

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.

The effect of the macrophage migration inhibitory factor (MIF) on excisional wound healing in vivo

Background: The macrophage migration inhibitory factor (MIF) has been determined as a cytokine exerting a multitude of effects in inflammation and angiogenesis. Earlier studies have indicated that MIF may also be involved in wound healing and flap surgery. Methods: We investigated the effect of MIF in an excisional wound model in wildtype, Mif^-/- and recombinant MIF treated mice. Wound closure rates as well as the macrophage marker Mac-3, the pro-inflammatory cytokine tumor necrosis factor α (TNFα) and the pro-angiogenic factor von Willebrand factor (vWF) were measured. Finally, we used a flap model in Mif^-/- and WT mice with an established perfusion gradient to identify MIF's contribution in flap perfusion. Results: In the excision wound model, we found reduced wound healing after MIF injection, whereas Mif deletion improved wound healing. Furthermore, a reduced expression of Mac-3, TNFα and vWF in Mif^-/- mice was seen when compared to WT mice. In the flap model, Mif^-/- knockout mice showed mitigated flap perfusion with lower hemoglobin content and oxygen saturation as measured by O₂C measurements when compared to WT mice. Conclusions: Our data suggest an inhibiting effect of MIF in wound healing with increased inflammation and perfusion. In flaps, by contrast, MIF may contribute to flap vascularization.

The role of MIF in chronic lung diseases: looking beyond inflammation

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has been associated with many diseases. Most studies found in literature describe MIF as a proinflammatory cytokine involved in chronic inflammatory conditions, but evidence from last years suggests that many of its key effects are not directly related to inflammation. In fact, MIF is constitutively expressed in most human tissues and in some cases in high levels, which does not reflect the pattern of expression of a classic proinflammatory cytokine. Moreover, MIF is highly expressed during embryonic development and decreases during adulthood, which point toward a more likely role as growth factor. Accordingly, MIF knockout mice develop age-related spontaneous emphysema, suggesting that MIF presence (e.g., in younger individuals and wild-type animals) is part of a healthy lung. In view of this new line of evidence, we aimed to review data on the role of MIF in the pathogenesis of chronic lung diseases.

Carcinoma and Sarcoma Microenvironment at a Glance: Where We Are

Cells and extracellular matrix (ECM) components represent the multifaceted and dynamic environment that distinguishes each organ. Cancer is characterized by the dysregulation of the composition and structure of the tissues, giving rise to the tumor milieu. In this review, we focus on the microenvironmental analysis of colorectal cancer (CRC) and rhabdomyosarcoma (RMS), two different solid tumors. While a lot is known about CRC environment, for RMS, this aspect is mostly unexplored. Following the example of the more complete CRC microenvironmental characterization, we collected and organized data on RMS for a better awareness of how tissue remodeling affects disease progression.

C-X-C Chemokine Receptor Type 7 (CXCR-7) Expression in Invasive Ductal Carcinoma of Breast in Association with Clinicopathological Features

C-X-C chemokine receptor type 7 (CXCR-7) is an atypical receptor for chemokines whose role in different stages of carcinogenesis has been evaluated in breast cancer cell lines and animal models. Moreover, it has been demonstrated to be a target of regulation by the tumor suppressor microRNA (miR)-100. In the present study, we assessed CXCR-7 expression in 60 breast cancer patients in association with clinicopathological and demographic data of patients. We also extracted the results of our previous work on miR-100 expression in the same cohort of patients to assess the correlation between miR-100 and CXCR-7 expression levels. Transcript levels of CXCR-7 were significantly higher in tumoral tissues compared with adjacent non-cancerous tissues (ANCTs) (Tumoral vs. ANCTs: 3.64 ± 1.8 vs. 0.73 ± 1.3, P = 0.000). A significant negative correlation was detected between CXCR-7 protein and miR-100 transcript levels (r = -0.526, P < 0.05). High CXCR-7 mRNA levels were significantly associated with tumor size (P = 0.01). Besides, high protein levels were more prevalent in higher TNM stages (P = 0.000). Moreover, high CXCR-7 protein levels were significantly associated with ER (P = 0.005) and PR (P = 0.02) status. The present work provides further evidence for the role of CXCR-7 in breast cancer and proposes the elimination of inhibitory effects of miR-100 on CXCR-7 expression as a mechanism for its up-regulation in breast cancer tissues.

Molecular Players in Hematologic Tumor Cell Trafficking

The trafficking of neoplastic cells represents a key process that contributes to progression of hematologic malignancies. Diapedesis of neoplastic cells across endothelium and perivascular cells is facilitated by adhesion molecules and chemokines, which act in concert to tightly regulate directional motility. Intravital microscopy provides spatio-temporal views of neoplastic cell trafficking, and is crucial for testing and developing therapies against hematologic cancers. Multiple myeloma (MM), chronic lymphocytic leukemia (CLL), and acute lymphoblastic leukemia (ALL) are hematologic malignancies characterized by continuous neoplastic cell trafficking during disease progression. A common feature of these neoplasias is the homing and infiltration of blood cancer cells into the bone marrow (BM), which favors growth and survival of the malignant cells. MM cells traffic between different BM niches and egress from BM at late disease stages. Besides the BM, CLL cells commonly home to lymph nodes (LNs) and spleen. Likewise, ALL cells also infiltrate extramedullary organs, such as the central nervous system, spleen, liver, and testicles. The α4β1 integrin and the chemokine receptor CXCR4 are key molecules for MM, ALL, and CLL cell trafficking into and out of the BM. In addition, the chemokine receptor CCR7 controls CLL cell homing to LNs, and CXCR4, CCR7, and CXCR3 contribute to ALL cell migration across endothelia and the blood brain barrier. Some of these receptors are used as diagnostic markers for relapse and survival in ALL patients, and their level of expression allows clinicians to choose the appropriate treatments. In CLL, elevated α4β1 expression is an established adverse prognostic marker, reinforcing its role in the disease expansion. Combining current chemotherapies with inhibitors of malignant cell trafficking could represent a useful therapy against these neoplasias. Moreover, immunotherapy using humanized antibodies, CAR-T cells, or immune check-point inhibitors together with agents targeting the migration of tumor cells could also restrict their survival. In this review, we provide a view of the molecular players that regulate the trafficking of neoplastic cells during development and progression of MM, CLL, and ALL, together with current therapies that target the malignant cells.

Rhabdomyosarcoma and Extraosseous Ewing Sarcoma

Rhabdomyosarcoma (RMS) is a malignant tumor that represents the most common form of pediatric soft tissue sarcoma. It arises from mesenchymal origin and forms part of the group of small round blue cell tumors of childhood. It has a constant annual incidence of 4.5 cases per 1,000,000 children. The known histological diagnosis of the two major subtypes (embryonal and alveolar) has been recently enhanced by tumor biological markers and molecular differentiation diagnostic tools that have improved not only the updated classification based on risk stratification, but also the treatment approach based on the clinical group. Ewing sarcoma (ES) is a round cell tumor, highly malignant and poorly differentiated that is currently the second most common malignant bone tumor in children. In rare instances, it develops from an extraskeletal origin, classified as extraosseous Ewing sarcoma (EES). We provide an updated, evidence-based and comprehensive review of the molecular diagnosis, clinical and diagnostic approach and a multidisciplinary medical and surgical management according to the latest standard of care for the treatment of pediatric RMS and EES.

Chemosensitivity is differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes in acute lymphoblastic leukemia with MLL gene rearrangements

Although recent advances in chemotherapy have markedly improved outcome of acute lymphoblastic leukemia (ALL), infantile ALL with MLL gene rearrangements (MLL+ALL) is refractory to chemotherapy. We have shown that specific cytokines FLT3 ligand and TGFβ1 both of which are produced from bone marrow stromal cells synergistically induced MLL+ALL cells into chemo-resistant quiescence, and that treatment of MLL+ALL cells with inhibitors against FLT3 and/or TGFβ1 receptor partially but significantly converts them toward chemo-sensitive. In the present study, we showed that MLL+ALL cells expressed CXCR4 and CXCR7, both receptors for the same chemokine stromal cell derived factor-1 (SDF-1), but their biological events were differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes and particularly exerted an opposite effect for determining chemo-sensitivity of MLL+ALL cells; enhancement via the SDF-1/CXCR4 axis vs. suppression via the SDF-1/CXCR7 axis. Because cytosine-arabinoside-induced apoptosis of MLL+ALL cells was inhibited by pretreatment with the CXCR4 inhibitor but rather accelerated by pretreatment with the CXCR7 inhibitor, an application of the CXCR7 inhibitor may become a good treatment option in future for MLL+ALL patients. MLL+ALL has a unique gene profile distinguishable from other types of ALL and AML, and should be investigated separately in responses to biological active agents including chemokine inhibitors.

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.

Targeting the MIF/CXCR7/AKT Signaling Pathway in Castration-Resistant Prostate Cancer

Although androgen deprivation therapy (ADT) is an effective treatment for metastatic prostate cancer, incurable castration-resistant prostate cancer (CRPC) inevitably develops. Importantly, androgen receptor (AR) continues to be critical for prostate cancer growth and progression after ADT. One of the underlying molecular mechanisms is derepression of AR-repressed genes involved in cell cycle and proliferation after ADT. Here, the data demonstrate that C-X-C chemokine receptor type 7 (CXCR7), a seven-transmembrane G-protein-coupled chemokine receptor, is an AR-repressed gene and is upregulated after ADT. AR directly regulates CXCR7 using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) gene editing. Macrophage migration inhibitory factor (MIF) was identified as a ligand for CXCR7, which induces expression of cell-cycle genes through activating AKT signaling pathway. Previous studies have been focused on chemokine CXCL12 and its receptor CXCR4 in mediating metastasis of various cancer types, including prostate cancer. The critical roles of CXCL12/CXCR4 axis in the interaction between cancer cells and their microenvironment render it a promising therapeutic target in cancer treatment. The data suggest that the MIF/CXCR7/AKT pathway drives CRPC growth and metastasis independent of the CXCL12/CXCR4 axis. Furthermore, CXCR7 blockade in combination with anti-androgen enzalutamide inhibits CRPC tumor growth and potentially prevents metastasis. Notably, both MIF and CXCR7 are overexpressed in CRPC patient specimens and therefore are attractive therapeutic targets for these patients. IMPLICATIONS: This work suggests that CXCR7 plays more important roles than CXCR4 in CRPC progression; thus, targeting CXCR7 in combination with anti-androgen is a promising therapeutic approach for metastatic CRPC.

Interaction Between Macrophage Migration Inhibitory Factor and CD74 in Human Immunodeficiency Virus Type I Infected Primary Monocyte-Derived Macrophages Triggers the Production of Proinflammatory Mediators and Enhances Infection of Unactivated CD4+ T Cells

Understanding the mechanisms of human immunodeficiency virus type I (HIV-1) pathogenesis would facilitate the identification of new therapeutic targets to control the infection in face of current antiretroviral therapy limitations. CD74 membrane expression is upregulated in HIV-1-infected cells and the magnitude of its modulation correlates with immune hyperactivation in HIV-infected individuals. In addition, plasma level of the CD74 activating ligand macrophage migration inhibitory factor (MIF) is increased in infected subjects. However, the role played by MIF/CD74 interaction in HIV pathogenesis remains unexplored. Here, we studied the effect of MIF/CD74 interaction on primary HIV-infected monocyte-derived macrophages (MDMs) and its implications for HIV immunopathogenesis. Confocal immunofluorescence analysis of CD74 and CD44 (the MIF signal transduction co-receptor) expression indicated that both molecules colocalized at the plasma membrane specifically in wild-type HIV-infected MDMs. Treatment of infected MDMs with MIF resulted in an MIF-dependent increase in TLR4 expression. Similarly, there was a dose-dependent increase in the production of IL-6, IL-8, TNFα, IL-1β, and sICAM compared to the no-MIF condition, specifically from infected MDMs. Importantly, the effect observed on IL-6, IL-8, TNFα, and IL-1β was abrogated by impeding MIF interaction with CD74. Moreover, the use of a neutralizing αMIF antibody or an MIF antagonist reverted these effects, supporting the specificity of the results. Treatment of unactivated CD4⁺ T-cells with MIF-treated HIV-infected MDM-derived culture supernatants led to enhanced permissiveness to HIV-1 infection. This effect was lost when CD4⁺ T-cells were treated with supernatants derived from infected MDMs in which CD74/MIF interaction had been blocked. Moreover, the enhanced permissiveness of unactivated CD4⁺ T-cells was recapitulated by exogenous addition of IL-6, IL-8, IL-1β, and TNFα, or abrogated by neutralizing its biological activity using specific antibodies. Results obtained with BAL and NL4-3 HIV laboratory strains were reproduced using transmitted/founder primary isolates. This evidence indicated that MIF/CD74 interaction resulted in a higher production of proinflammatory cytokines from HIV-infected MDMs. This caused the generation of an inflammatory microenvironment which predisposed unactivated CD4⁺ T-cells to HIV-1 infection, which might contribute to viral spreading and reservoir seeding. Overall, these results support a novel role of the MIF/CD74 axis in HIV pathogenesis that deserves further investigation.

CXCR7 Targeting and Its Major Disease Relevance

Chemokine receptors are the target of small peptide chemokines. They play various important roles in physiological and pathological processes. CXCR7, later renamed ACKR3, is a non-classical seven transmembrane-spanning receptor whose function as a signaling or non-signaling scavenger/decoy receptor is currently under debate. Even for cell signaling mechanisms, there has been inconsistency on whether CXCR7 couples to G-proteins or β-arrestins. Several reasons may contribute to this uncertainty or controversy. In one hand, it has been neglected that CXCR7 has more than five natural ligands and unfortunately, most of the prior research only studied SDF-1 (CXCL12) and/or I-TAC (CXCL11); on the other hand, there are mounting evidence supporting ligand and tissue bias for receptor signaling, but limited such information is available for CXCR7. In this review we focus on summarizing the endogenous and exogenous ligands of CXCR7, the main diseases related to CXCR7 and the biased signaling events happening on CXCR7. These three aspects of CXCR7 pharmacologic properties may explain why the contradicting opinions of whether CXCR7 is a signaling or non-signaling receptor exist. Further, potential new direction and perspective for the study of CXCR7 biology and pharmacology are highlighted.

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 MIF/CD74 signaling pathway in the development of pleural mesothelioma

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine implicated in acute and chronic inflammatory diseases. MIF is overexpressed in various tumors. It displays a number of functions that provide a direct link between the process of inflammation and tumor growth. Our group recently identified the MIF-receptor CD74 as an independent prognostic factor for overall survival in patients with malignant pleural mesothelioma.

In the present study, we compared the levels of expression of MIF and CD74 in different human mesothelioma cell lines and investigated their physiopathological functions in vitro and in vivo.

Human mesothelioma cells expressed more CD74 and secreted less MIF than non tumoral MeT5A cells, suggesting a higher sensitivity to MIF. In mesothelioma cells, high MIF levels were associated with a high multiplication rate of cells. In vitro, reduction of MIF or CD74 levels in both mesothelioma cell lines showed that the MIF/CD74 signaling pathway promoted tumor cell proliferation and protected MPM cells from apoptosis. Finally, mesothelioma cell lines expressing high CD74 levels had a low tumorigenic potential after xenogeneic implantation in athymic nude mice.

All these data highlight the complexity of the MIF/CD74 signaling pathway in the development of mesothelioma.

Hepatocyte-derived macrophage migration inhibitory factor mediates alcohol-induced liver injury in mice and patients

BACKGROUND & AIMS

Macrophage migration inhibitory factor (MIF) is a multi-potent cytokine that contributes to the inflammatory response to injury. MIF is expressed by multiple cell types; however, the cellular source and actions of MIF in alcoholic liver disease (ALD) are not well known. Here we tested the hypothesis that non-myeloid cells, specifically hepatocytes, are an important cellular source of MIF in ALD.

METHODS

MIF expression was measured in HuH7 and differentiated THP-1 cells in response to ethanol. Ethanol-induced liver injury was assessed in C57BL/6 (WT) and Mif^-/- bone marrow chimeras. MIF was measured in peripheral and suprahepatic serum, as well as visualized by immunohistochemistry in liver biopsies, from patients with alcoholic hepatitis (AH).

RESULTS

HuH7 hepatocytes, but not THP-1 macrophages, released MIF in response to ethanol challenge in culture. In chimeric mice expressing MIF in non-myeloid cells (Mif^-/-→WT), chronic ethanol feeding increased ALT/AST, hepatic steatosis, and expression of cytokine/chemokine mRNA. In contrast, chimeric mice not expressing MIF in non-myeloid cells (WT→Mif^-/-) were protected from ethanol-induced liver injury. Immunohistochemical staining of liver biopsies from patients with AH revealed a predominant localization of MIF to hepatocytes. Interestingly, the concentration of MIF in suprahepatic serum, but not peripheral serum, was positively correlated with clinical indicators of disease severity and with an increased risk of mortality in patients with AH.

CONCLUSIONS

Taken together, these data provide evidence that hepatocyte-derived MIF is critical in the pathogenesis of ALD in mice and likely contributes to liver injury in patients with AH. Lay summary: Alcoholic liver disease is a major cause of preventable mortality worldwide, and lacks specific pharmacological therapies. Recent studies have recognized that macrophage migration inhibitor factor (MIF) has a critical role in the inflammatory response to liver damage. However, the cells that produce this protein are still unknown. Our present findings reveal that hepatocytes, the main cell type in the liver, are primarily responsible for MIF production in response to alcohol, which promotes liver injury. Our study suggests that drugs inhibiting MIF production could be beneficial in treating patients with liver disease due to excessive alcohol consumption.

Macrophage migration inhibitory factor promotes tumor aggressiveness of esophageal squamous cell carcinoma via activation of Akt and inactivation of GSK3β

The pleiotropic pro-inflammatory cytokine, macrophage migration inhibitory factor (MIF), represents an important link between chronic inflammation and tumorigenesis. Although accumulating evidence demonstrates that MIF overexpression is implicated in the development and progression of multiple cancers, including esophageal squamous cell carcinoma (ESCC), the molecular mechanisms underlying its tumor-promoting roles in ESCC remain unclear. In the present study, we observed that MIF is overexpressed in ESCC and correlated significantly with lymph node metastasis, advanced clinical stage, and poor survival of ESCC. MIF knockdown attenuated the proliferation, migration, and invasion of ESCC cells in vitro and in vivo. Moreover, blockage of MIF expression decreased the activation of the Akt, MEK/ERK, and NF-κB pathways and enhanced sensitivity to apoptosis. Meanwhile, repression of MIF expression resulted in activation of glycogen synthase kinase 3 beta (GSK3β) and subsequent decrease of active β-catenin, as well as its downstream targets including cyclin D1, matrix metalloproteinase (MMP)-7, c-myc, and c-Jun. Collectively, our results provided mechanistic insights into the tumor-promoting role of MIF in ESCC, and suggested that MIF represents a potential therapeutic target for treatment of ESCC.

Harnessing CXCR4 antagonists in stem cell mobilization, HIV infection, ischemic diseases, and oncology

CXCR4 antagonists (e.g., Plerixafor^TM ) have been successfully validated as stem cell mobilizers for peripheral blood stem cell transplantation. Applications of the CXCR4 antagonists have heralded the era of cell-based therapy and opened a potential therapeutic horizon for many unmet medical needs such as kidney injury, ischemic stroke, cancer, and myocardial infarction. In this review, we first introduce the central role of CXCR4 in diverse cellular signaling pathways and discuss its involvement in several disease progressions. We then highlight the molecular design and optimization strategies for targeting CXCR4 from a large number of case studies, concluding that polyamines are the preferred CXCR4-binding ligands compared to other structural options, presumably by mimicking the highly positively charged natural ligand CXCL12. These results could be further justified with computer-aided docking into the CXCR4 crystal structure wherein both major and minor subpockets of the binding cavity are considered functionally important. Finally, from the clinical point of view, CXCR4 antagonists could mobilize hematopoietic stem/progenitor cells with long-term repopulating capacity to the peripheral blood, promising to replace surgically obtained bone marrow cells as a preferred source for stem cell transplantation.

Macrophage migration inhibitory factor (MIF) is induced by cytotoxic drugs and is involved in immune escape and migration in childhood rhabdomyosarcoma

Macrophage migration inhibitory factor (MIF) is known to be involved in oncogenic transformation, tumour progression, and immunosuppression and is overexpressed in many solid tumours, including paediatric rhabdomyosarcoma (RMS). We investigated the function of MIF in RMS during treatment with cytotoxic drugs. RMS cell lines were analysed by flow cytometry, immunofluorescence staining, and ELISA. We demonstrated the overexpression of MIF in RMS cells and the enhanced expression and secretion after treatment with cytotoxic agents. Migration assays of RMS cells revealed that inhibitors of MIF (ISO-1, Ant.III 4-IPP, Ant.V, sulforaphane (SF)) and blocking antibodies caused reduced migration, indicating a role for MIF in metastatic invasion. Additionally, we investigated the function of MIF in immune escape. The development of a population containing immunosuppressive myeloid-derived suppressor cells was promoted by incubation in conditioned medium of RMS cells comprising MIF and was reversed by MIF inhibitors but not by antibodies. Although most inhibitors may restore immune activity, Ant.III and 10 µM SF disturbed T cell proliferation in a CFSE assay, whereas T cell proliferation was not reduced by 3 µM SF, ISO-1 or antibodies. However, the inhibition of MIF by blocking antibodies did not increase the killing activity of allogenic PBMCs co-cultured with RMS cells. Our results reveal that MIF may be involved in an immune escape mechanism and demonstrate the involvement of MIF in immunogenic cell death during treatment with cytotoxic drugs. Targeting MIF may contribute to the restoration of immune sensitivity and the control of migration and metastatic invasion.

MIF, a controversial cytokine: a review of structural features, challenges, and opportunities for drug development

INTRODUCTION

Macrophage migration inhibitory factor (MIF) has emerged as a promising drug target in diseases including sepsis, rheumatoid arthritis, and cancer. MIF has multiple properties that favor development of specific, targeted therapies: it is expressed broadly among human cells, has noted roles in diverse inflammatory and oncological processes, and has intrinsic enzymatic activity amenable to high-throughput screening. Despite these advantages, anti-MIF therapy remains well behind other cytokine-targeted therapeutics, with no small molecules in the pipeline for clinical development and anti-MIF antibodies only recently beginning clinical trials. Areas covered: In this review we summarize current literature regarding MIF structure and function-including challenges and controversies that have arisen in studies of anti-MIF therapeutics-and propose a strategy for development of clinically relevant anti-MIF drugs. Expert opinion: We believe that the field of anti-MIF therapeutics would benefit from capitalizing on the protein's multiple assets while acknowledging their flaws. The tautomerase enzymatic site of MIF may not be active biologically, but can nonetheless offer a high-throughput method to highlight molecules of interest that can affect its other, frequently intertwined bioactivities. Future work should also focus on developing more robust assays for MIF bioactivity that can be used for second-pass screening and specificity studies.

Identification of Iguratimod as an Inhibitor of Macrophage Migration Inhibitory Factor (MIF) with Steroid-sparing Potential

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has been implicated in a broad range of inflammatory and oncologic diseases. MIF is unique among cytokines in terms of its release profile and inflammatory role, notably as an endogenous counter-regulator of the anti-inflammatory effects of glucocorticoids. In addition, it exhibits a catalytic tautomerase activity amenable to the design of high affinity small molecule inhibitors. Although several classes of these compounds have been identified, biologic characterization of these molecules remains a topic of active investigation. In this study, we used in vitro LPS-driven assays to characterize representative molecules from several classes of MIF inhibitors. We determined that MIF inhibitors exhibit distinct profiles of anti-inflammatory activity, especially with regard to TNFα. We further investigated a molecule with relatively low anti-inflammatory activity, compound T-614 (also known as the anti-rheumatic drug iguratimod), and found that, in addition to exhibiting selective MIF inhibition in vitro and in vivo, iguratimod also has additive effects with glucocorticoids. Furthermore, we found that iguratimod synergizes with glucocorticoids in attenuating experimental autoimmune encephalitis, a model of multiple sclerosis. Our work identifies iguratimod as a valuable new candidate for drug repurposing to MIF-relevant diseases, including multiple sclerosis.

Rhabdomyosarcoma

A malignant tumor of striated muscle origin, rhabdomyosarcoma (RMS) is a childhood tumor that has benefited from nearly 30 years of multimodality therapy, culminating in a >70% overall 5-year survival. Prognosis for RMS is dependent on primary tumor site, age, completeness of resection, presence and number of metastatic sites, histology, and biology of the tumor cells. Multimodality treatment is based on risk stratification according to pre-treatment stage, postoperative group, histology, and site. Unique to RMS is the concept of postoperative clinical grouping that assesses the completeness of disease resection and takes into account lymph node evaluation at both the regional and metastatic basins. At all sites, if complete operative resection of disease is accomplished, including microscopic disease, survival is improved. Therefore, the surgeon plays a vital role in determining risk stratification for treatment, local control of the primary tumor and overall outcome for the patient with RMS.

Does it make sense to target one tumor cell chemotactic factor or its receptor when several chemotactic axes are involved in metastasis of the same cancer?

The major problem with cancer progression and anti-cancer therapy is the inherent ability of cancer cells to migrate and establish distant metastases. This ability to metastasize correlates with the presence in a growing tumor of cells with a more malignant phenotype, which express certain cancer stem cell markers. The propensity of malignant cells to migrate and their resistance to radio-chemotherapy somewhat mimics the properties of normal developmentally early stem cells that migrate during organogenesis in the developing embryo. In the past, several factors, including cell migration-promoting cytokines, chemokines, growth factors, bioactive lipids, extracellular nucleotides, and even H(+) ions, were found to influence the metastasis of cancer cells. This plethora of pro-migratory factors demonstrates the existence of significant redundancy in the chemoattractants for cancer cells. In spite of this obvious fact, significant research effort has been dedicated to demonstrating the crucial involvement of particular pro-metastatic factor-receptor axes and the development of new drugs targeting one receptor or one chemoattractant. Based on our own experience working with a model of metastatic rhabdomyosarcoma as well as the work of others, in this review we conclude that targeting a single receptor-ligand pro-metastatic axis will not effectively prevent metastasis and that we should seek other more effective therapeutic options.