Characterization of a novel tumor-derived cytokine. Endothelial-monocyte activating polypeptide II

Integration of EMAP-II-targeted anti-angiogenesis and photodynamic therapy using zinc phthalocyanine nanosystem for enhanced cancer treatment

Angiogenesis provides essential nutrients and oxygen to tumors during tumorigenesis, facilitating invasion and metastasis. Consequently, inhibiting tumor angiogenesis is an established strategy in anti-cancer therapy. In this study, we engineered a dual-function nanosystem with both antiangiogenic and photodynamic properties. We transformed the hydrophobic photosensitizer zinc phthalocyanine (PS) into a hydrophilic form via protein renaturation, resulting in a novel photosensitizer: Monocyte-Activating Polypeptide-II (EMAP-II:PS@NPs). Characterization through dynamic light scattering (DLS) and UV-vis spectroscopy showed that these nanoparticles exhibited uniform size and stability, and enhanced solubility. We further demonstrated that EMAP-II:PS@NPs effectively target tumor vascular endothelia causing intracellular photodynamic cytotoxicity. Notably, EMAP-II:PS@NPs achieved effective ablation of solid tumors at significantly reduced dosages of drugs compared to conventional therapies, due to their potent apoptotic effects on light-exposed cells. This study highlights the potential of combining anti-angiogenic activity with phototherapy, paving the way for innovative cancer treatment strategies.

Functionalized liposomes: an enticing nanocarrier for management of glioma

Glioma is one of the most severe central nervous systems (CNS)-specific tumors, with rapidly growing malignant glial cells accounting for roughly half of all brain tumors and having a poor survival rate ranging from 12 to 15 months. Despite being the most often used technique for glioma therapy, conventional chemotherapy suffers from low permeability of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) to anticancer drugs. When it comes to nanocarriers, liposomes are thought of as one of the most promising nanocarrier systems for glioma treatment. However, owing to BBB tight junctions, non-targeted liposomes, which passively accumulate in most cancer cells primarily via the increased permeability and retention effect (EPR), would not be suitable for glioma treatment. The surface modification of liposomes with various active targeting ligands has shown encouraging outcomes in the recent times by allowing various chemotherapy drugs to pass across the BBB and BBTB and enter glioma cells. This review article introduces by briefly outlining the landscape of glioma, its classification, and some of the pathogenic causes. Further, it discusses major barriers for delivering drugs to glioma such as the BBB, BBTB, and tumor microenvironment. It further discusses modified liposomes such as long-acting circulating liposomes, actively targeted liposomes, stimuli responsive liposomes. Finally, it highlighted the limitations of liposomes in the treatment of glioma and the various actively targeted liposomes undergoing clinical trials for the treatment of glioma.

Endothelial Monocyte-Activating Polypeptide-II Is an Indicator of Severity and Mortality in COVID-19 Patients

Data for predicting the severity and mortality of coronavirus disease 2019 (COVID-19) are limited, and investigations are ongoing. Endothelial monocyte-activating protein II (EMAP-II) is a multifunctional polypeptide with pro-inflammatory properties. EMAP-II is a significant pathogenic component in chronic inflammatory lung diseases and lung injury. In this study, we aimed to assess the potential utility of EMAP-II as a predictor of COVID-19 severity and mortality. This study included 20 healthy volunteers and 60 verified COVID-19 patients. Nasopharyngeal samples from COVID-19-positive subjects and normal volunteers were collected at admission. The nasopharyngeal samples were subjected to EMAP-II real-time polymerase chain reaction (RT-PCR). EMAP-II RNA was not detected in nasopharyngeal swabs of normal controls and mild to asymptomatic COVID-19 patients and was only detectable in severe COVID-19 patients. EMAP-II critical threshold (Ct) was positively associated with lymphocyte percentages and oxygen saturation (p < 0.001) while being negatively associated with age (p = 0.041), serum CRP, ferritin, and D-dimer levels (p < 0.001). EMAP-II Ct cutoff ≤34 predicted a worse outcome in COVID-19 illness, with a sensitivity and specificity of 100%. Our study suggests that EMAP-II could be considered a potential biomarker of COVID-19 severity. EMAP-II can predict the fatal outcome in COVID-19 patients.

EMAP II Expression Is Increased on Peripheral Blood Cells from Non-Hodgkin Lymphoma

Tumor immune evasion is a lineament of cancer. Endothelial monocyte activating polypeptide-II (EMAP II) has been assumed to impact tumor immune escape significantly. EMAP II was first reported in the murine methylcholanthrene A-induced fibrosarcoma supernatant and identified as a tumor-derived cytokine. This study evaluated EMAP II expression in peripheral blood cells and its association with treatment outcome, lactate dehydrogenase (LDH) levels, and clinical criteria in non-Hodgkin's lymphoma (NHL) patients. EMAP II expression on different blood cells obtained from the peripheral blood of 80 NHL patients was evaluated by two-color flow cytometry. The study reported that EMAP II expression was significantly increased in peripheral blood cells in patients with NHL compared to normal volunteers (P < 0.001). Additionally, EMAP II expression levels on blood cells decreased in complete remission (CR) while they increased in relapse. This study showed coexpression of EMAP II and CD36 on peripheral lymphocytes in NHL patients but not in healthy controls (P < 0.001). EMAP II expression on blood cells was associated with increased serum LDH levels. Furthermore, the percentages of EMAP II+/CD36+ peripheral lymphocytes were significantly higher in relapse than in CR and healthy controls. Analyses revealed that higher percentages of EMAP II+CD36+ cells were positively correlated with hepatomegaly, splenomegaly, and an advanced (intermediate and high risk) NHL stage. The results assume that EMAP II might be involved in NHL development and pathogenesis.

Aminoacyl-tRNA synthetases of the multi-tRNA synthetase complex and their role in tumorigenesis

In mammalian cells, 20 aminoacyl-tRNA synthetases (AARS) catalyze the ligation of amino acids to their cognate tRNAs to generate aminoacylated-tRNAs. In higher eukaryotes, 9 of the 20 AARSs, along with 3 auxiliary proteins, join to form the cytoplasmic multi-tRNA synthetase complex (MSC). The complex is absent in prokaryotes, but evolutionary expansion of MSC constituents, primarily by addition of novel interacting domains, facilitates formation of subcomplexes that join to establish the holo-MSC. In some cases, environmental cues direct the release of constituents from the MSC which enables the execution of non-canonical, i.e., "moonlighting", functions distinct from their essential activities in protein translation. These activities are generally beneficial, but can also be deleterious to the cell. Elucidation of the non-canonical activities of several AARSs residing in the MSC suggest they are potential therapeutic targets for cancer, as well as metabolic and neurologic diseases. Here, we describe the role of MSC-resident AARSs in cancer progression, and the factors that regulate their release from the MSC. Also, we highlight recent developments in therapeutic modalities that target MSC AARSs for cancer prevention and treatment.

Systematic expression profiling of neuropathy-related aminoacyl-tRNA synthetases in zebrafish during development

Aminoacyl tRNA synthetases (ARSs) are a group of proteins, acting as transporters to transfer and attach the appropriate amino acids onto their cognate tRNAs for translation. So far, 18 out of 20 cytoplasmic ARSs are reported to be connected to different neuropathy disorders with multi-organ defects that are often accompanied with developmental delays. Thus, it is important to understand functions and impacts of ARSs at the whole organism level. Here, we systematically analyzed the spatiotemporal expression of 14 ars and 2 aimp genes during development in zebrafish that have not be previously reported. Not only in the brain, their dynamic expression patterns in several tissues such as in the muscles, liver and intestine suggest diverse roles in a wide range of development processes in addition to neuronal function, which is consistent with potential involvement in multiple syndrome diseases associated with ARS mutations. In particular, hinted by its robust expression pattern in the brain, we confirmed that aimp1 is required for the formation of cerebrovasculature by a loss-of-function approach. Overall, our systematic profiling data provides a useful basis for studying roles of ARSs during development and understanding their potential functions in the etiology of related diseases.

Role of two aminoacyl-tRNA synthetase associated proteins (Endothelial Monocyte Activating Polypeptides 1 and 2) of Leishmania donovani in chemotaxis of human monocytes

Visceral leishmaniasis is caused by the protozoan parasite Leishmania donovani. It is a fatal form of leishmaniasis prevalent in Indian subcontinent. Since there are no human licensed vaccines available for leishmaniasis, chemotherapeutic drugs remain the only means for combating parasitic infections. We have earlier identified a total of 26 amino-acyl tRNA synthetases (aaRS) along with five stand-alone editing domains and two aaRS-associated proteins in Leishmania donovani. In addition to their canonical role of tRNA aminoacylation, aaRS have been involved in novel functions by acquiring novel domains during evolution. The aaRS-associated proteins have been reported to be analogous to a human cytokine, EMAP II, as they possess a modified version of the heptapeptide motif responsible for the cytokine activity. In this manuscript, we report the characterization of two L. donovani aminoacyl-tRNA synthetase associated proteins which showed a human chemokine like activity. Both the proteins, L. donovani EMAP-1 and EMAP-2, possess a modified form of the heptapeptide motif, which is responsible for cytokine activity in human EMAP-2. LdEMAP-1 and LdEMAP-2 were cloned, expressed, and purified. Both LdEMAP-1 and LdEMAP-2 proteins in the promastigote stage were found to be localized in cytoplasm as confirmed by immunofluorescence. In case of L. donovani infected human THP-1 derived macrophages, secretion of LdEMAP-1 and LdEMAP-2 proteins in the cytosol of the macrophages was observed. The role of LdEMAP-1 and LdEMAP-2 in the aminoacylation of rLdTyrRS was also tested and LdEMAP-2 but not LdEMAP-1 increased the rate of aminoacylation of tyrosyl tRNA synthetase (rLdTyrRS). L. donovani EMAP-1 and EMAP-2 proteins managed to exhibit the capability of attracting human origin cells as determined by chemotaxis assay, and also were able to induce the secretion of cytokines from macrophages like their human counterpart (EMAP II). Our working hypothesis is that both of these proteins might be involved in helping the parasite to establish the infection within the host.

Mechanistic regulation of SPHK1 expression and translocation by EMAP II in pulmonary smooth muscle cells

Phosphorylation of sphingosine by sphingosine kinase 1 (SPHK1) produces the bioactive sphingolipid sphingosine-1-phosphate (S1P), a microvascular and immuno-modulator associated with vascular remodeling in pulmonary arterial hypertension (PAH). The low intracellular concentration of S1P is under tight spatial-temporal control. Molecular mechanisms that mediate S1P burden and S1P regulation of vascular remodeling are poorly understood. Similarities between two early response pro-inflammatory cytokine gene transcript activation profiles, S1P and Endothelial Monocyte Activating Polypeptide II (EMAP II), suggested a strategic link between their signaling pathways. We determined that EMAP II triggers a bimodal phosphorylation, transcriptional regulation and membrane translocation of SPHK1 through a common upstream process in both macrophages and pulmonary artery smooth muscle cells (PASMCs). EMAP II initiates a dual function of ERK1/2: phosphorylation of SPHK1 and regulation of the transcription factor EGR1 that induces expression of SPHK1. Activated ERK1/2 induces a bimodal phosphorylation of SPHK1 which reciprocally increases S1P levels. This identified common upstream signaling mechanism between a protein and a bioactive lipid initiates cell specific downstream signaling representing a multifactorial mechanism that contributes to inflammation and PASMC proliferation which are cardinal histopathological phenotypes of PAH.

Non-canonical functions of human cytoplasmic tyrosyl-, tryptophanyl- and other aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases catalyze the aminoacylation of their cognate tRNAs. Here we review the accumulated knowledge of non-canonical functions of human cytoplasmic aminoacyl-tRNA synthetases, especially tyrosyl- (TyrRS) and tryptophanyl-tRNA synthetase (TrpRS). Human TyrRS and TrpRS have an extra domain. Two distinct cytokines, i.e., the core catalytic "mini TyrRS" and the extra C-domain, are generated from human TyrRS by proteolytic cleavage. Moreover, the core catalytic domains of human TyrRS and TrpRS function as angiogenic and angiostatic factors, respectively, whereas the full-length forms are inactive for this function. It is also known that many synthetases change their localization in response to a specific signal and subsequently exhibit alternative functions. Furthermore, some synthetases function as sensors for amino acids by changing their protein interactions in an amino acid-dependent manner. Further studies will be necessary to elucidate regulatory mechanisms of non-canonical functions of aminoacyl-tRNA synthetases in particular, by analyzing the effect of their post-translational modifications.

A distinct transcriptional profile in response to endothelial monocyte activating polypeptide II is partially mediated by JAK-STAT3 in murine macrophages

Macrophages are important responders to environmental changes such as secreted factors. Among the secreted factors in injured tissues, the highly conserved endothelial monocyte activating polypeptide II (EMAP II) has been characterized to limit vessel formation, to be locally expressed near sites of injury labeling it a "find-me" signal, and to recruit macrophages and neutrophils. The molecular mechanisms mediated by EMAP II within macrophages once they are recruited are unknown. In this study, using a model of partially activated, recruited thioglycollate-elicited peritoneal macrophages, a transient, transcription profile of key functional genes in macrophages exposed to EMAP II was characterized. We found that EMAP II-mediated changes were elicited mainly through signal transducer and activator of transcription 3 (STAT3) as evidenced by increased Y705 phosphorylation and changes in activity and upstream of it, Janus associated kinase (JAK)1/2 upstream. Both inhibition of JAK1/2 and knockdown of Stat3 abrogated a subset of genes that are upregulated by EMAP II. Our results identify a rapid EMAP II-mediated STAT3 activation that coincides with altered pro- and anti-inflammatory gene expression in macrophages.

Hypoxia-induced tumor exosomes promote M2-like macrophage polarization of infiltrating myeloid cells and microRNA-mediated metabolic shift

Developing tumors rapidly outgrow their oxygen supply and are subject to hypoxia, which stimulates hypersecretion of tumor-derived exosomes that promote angiogenesis, metastasis, and immunosuppression, but the molecular mediators of these pathological effects remain poorly defined. Using quantitative proteomics, we identified that exosomes produced by hypoxic tumor cells are highly enriched in immunomodulatory proteins and chemokines including CSF-1, CCL2, FTH, FTL, and TGFβ. Modeling exosome effects on tumor-infiltrating immune cells, we observed a potent ability of these hypoxia-induced vesicles to influence macrophage recruitment and promote M2-like polarization both in vitro and in vivo. In addition, hypoxic, but not normoxic, tumor exosomes enhanced oxidative phosphorylation in bone marrow-derived macrophages via transfer of let-7a miRNA, resulting in suppression of the insulin-Akt-mTOR signaling pathway. Together, these data demonstrate that hypoxia promotes tumor secretion of biomolecule-loaded exosomes that can modify the immunometabolic profile of infiltrating monocyte-macrophages to better evade host immunity and enhance tumor progression.

Aminoacyl tRNA synthetase complex interacting multifunctional protein 1 simultaneously binds Glutamyl-Prolyl-tRNA synthetase and scaffold protein aminoacyl tRNA synthetase complex interacting multifunctional protein 3 of the multi-tRNA synthetase complex

Higher eukaryotes have developed extensive compartmentalization of amino acid (aa) - tRNA coupling through the formation of a multi-synthetase complex (MSC) that is composed of eight aa-tRNA synthetases (ARS) and three scaffold proteins: aminoacyl tRNA synthetase complex interacting multifunctional proteins (AIMP1, 2 and 3). Lower eukaryotes have a much smaller complex while yeast MSC consists of only two ARS (MetRS and GluRS) and one ARS cofactor 1 protein, Arc1p (Simos et al., 1996), the homolog of the mammalian AIMP1. Arc1p is reported to form a tripartite complex with GluRS and MetRS through association of the N-terminus GST-like domains (GST-L) of the three proteins (Koehler et al., 2013). Mammalian AIMP1 has no GST-L domain corresponding to Arc1p N-terminus. Instead, AIMP3, another scaffold protein of 18 kDa composed entirely of a GST-L domain, interacts with Methionyl-tRNA synthetase (MARS) (Quevillon et al., 1999) and Glutamyl-Prolyl-tRNA Synthetase (EPRS) (Cho et al., 2015). Here we report two new interactions between MSC members: AIMP1 binds to EPRS and AIMP1 binds to AIMP3. Interestingly, the interaction between AIMP1 and AIMP3 complex makes it the functional equivalent of a single Arc1p polypeptide in yeast. This interaction is not mapped to AIMP1 N-terminal coiled-coil domain, but rather requires an intact tertiary structure of the entire protein. Since AIMP1 also interacts with AIMP2, all three proteins appear to compose a core docking structure for the eight ARS in the MSC complex.

Endothelial-Monocyte Activating Polypeptide II Suppresses the In Vitro Glioblastoma-Induced Angiogenesis by Inducing Autophagy

The obstacle in delivering therapeutics to glioblastoma (GBM) is tumor-induced angiogenesis which leads to the formation of abnormal vessels and a dysfunctional blood-tumor barrier. Here, we elucidated the effect of endothelial-monocyte activating polypeptide II (EMAP II) on the GBM-induced angiogenesis as well as its potential mechanisms. Our results proved that EMAP II inhibited the viability, mitochondrial membrane potential, migration and tube formation of GBM-induced endothelial cells (GECs) by inducing cell autophagy, demonstrated by cell viability assay, JC-1 staining assay, transwell assay and tube formation assay, respectively. Cell autophagy was induced by EMAP II through the observation of autophagic vacuoles formation and the up-regulation of microtubule-associated protein-1 light chain-3 (LC3)-II and p62/SQSTM1 expression, demonstrated by transmission electron microscopy analysis, immunofluorescence assay and Western blot assay. The activity of PI3K/AKT/mTOR signal pathway could be inhibited by the EMAP II treatment. Furthermore, unfolded protein response (UPR)-related proteins (GRP78, eIF2α, and CHOP) were up-regulated by EMAP II, which suggest that GECs exposed to EMAP II experienced endoplasmic reticulum stress. Further, mechanistic investigations found that EMAP II reduced the miR-96 expression which could directly target the 3'-UTR of these UPR-related proteins, and over-expression of miR-96 inhibited LC3 and p62/SQSTM1 expression by down-regulating these UPR-related proteins in GECs. Moreover, the combination of EMAP II with miR-96 inhibitor showed the inhibitory effect on the viability, migration, and in vitro tube formation of GECs, which are critical for angiogenesis. Taken together, we have demonstrated the fact that EMAP II resulted in the decreased GBM-induced angiogenesis by inducing autophagy, which might contribute to establishing potential strategies for human GBM treatment.

Combination of Endothelial-Monocyte-Activating Polypeptide-II with Temozolomide Suppress Malignant Biological Behaviors of Human Glioblastoma Stem Cells via miR-590-3p/MACC1 Inhibiting PI3K/AKT/mTOR Signal Pathway

This study aims to investigate the effect of Endothelial-Monocyte-Activating Polypeptide-II (EMAP-II) combined with temozolomide (TMZ) upon glioblastoma stem cells (GSCs) and its possible molecular mechanisms. In this study, combination of EMAP-II with TMZ inhibited cell viability, migration and invasion in GSCs, and autophagy inhibitor 3-methyl adenine (3-MA) and chloroquine (CQ) partly reverse the anti-proliferative effect of the combination treatment. Autophagic vacuoles were formed in GSCs after the combination therapy, accompanied with the up-regulation of LC3-II and Beclin-1 as well as the down-regulation of p62/SQSTM1. Further, miR-590-3p was up-regulated and Metastasis-associated in colon cancer 1 (MACC1) was down-regulated by the combination treatment in GSCs; MiR-590-3p overexpression and MACC1 knockdown up-regulated LC3-II and Beclin-1 as well as down-regulated p62/SQSTM1 in GSCs; MACC1 was identified as a direct target of miR-590-3p, mediating the effects of miR-590-3p in the combination treatment. Furthermore, the combination treatment and MACC1 knockdown decreased p-PI3K, p-Akt, p-mTOR, p-S6 and p-4EBP in GSCs; PI3K/Akt agonist insulin-like growth factor-1(IGF-1) partly blocked the effect of the combination treatment. Moreover, in vivo xenograft models, the mice given stable overexpressed miR-590-3p cells and treated with EMAP-II and TMZ had the smallest tumor sizes, besides, miR-590-3p + EMAP-II + TMZ up-regulated the expression level of miR-590-3p, LC3-II and Beclin-1 as well as down-regulated p62/SQSTM1. In conclusion, these results elucidated anovel molecular mechanism of EMAP-II in combination with TMZ suppressed malignant biological behaviors of GSCs via miR-590-3p/MACC1 inhibiting PI3K/AKT/mTOR signaling pathway, and might provide potential therapeutic approaches for human GSCs.

Aminoacyl-tRNA synthetase-interacting multifunctional protein 1 suppresses tumor growth in breast cancer-bearing mice by negatively regulating myeloid-derived suppressor cell functions

Myeloid-derived suppressor cells (MDSCs) are one of the most important cell types that contribute to negative regulation of immune responses in the tumor microenvironment. Recently, aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1), a novel pleiotropic cytokine, was identified as an antitumor protein that inhibits angiogenesis and induces antitumor responses. However, the effect of AIMP1 on MDSCs in the tumor environment remains unclear. In the present study, we demonstrated that AIMP1 significantly inhibited tumor growth in 4T1 breast cancer-bearing mice and reduced MDSCs population of tumor sites and spleens of tumor-bearing mice. AIMP1 reduced expansion of MDSCs from bone marrow-derived cells in the tumor-conditioned media. AIMP1 also negatively regulated suppressive activities of MDSCs by inhibiting IL-6 and NO production, and Arg-1 expression. Furthermore, treatment of breast cancer-bearing mice with AIMP1 decreased the capacity of MDSCs to suppress T cell proliferation and Treg cell induction. Western blot and inhibition experiments showed that downregulation of MDSCs functions by AIMP1 may result from attenuated activation of STATs, Akt, and ERK. These findings indicate that AIMP1 plays an essential role in negative regulation of suppressive functions of MDSCs. Therefore, it has a significant potential as a therapeutic agent for cancer treatment.

Autophagy Induction by Endothelial-Monocyte Activating Polypeptide II Contributes to the Inhibition of Malignant Biological Behaviors by the Combination of EMAP II with Rapamycin in Human Glioblastoma

This study aims to investigate the effect of endothelial-monocyte activating polypeptide II (EMAP II) on human glioblastoma (GBM) cells and glioblastoma stem cells (GSCs) as well as its possible mechanisms. In this study, EMAP II inhibited the cell viability and decreased the mitochondrial membrane potential in human GBM cells and GSCs, and autophagy inhibitor 3-methyl adenine (3-MA) blocked these effects. Autophagic vacuoles were formed in these cells after EMAP II treatment and this phenomenon was blocked by 3-MA. In addition, the up-regulation of microtubule-associated protein-1 light chain-3 (LC3)-II and the down-regulation of autophagic degraded substrate p62/SQSTM1 caused by EMAP II were observed. Cells treated with EMAP-II inhibited the PI3K/Akt/mTOR signal pathway, and PI3K/Akt agonist insulin-like growth factor-1 (IGF-1) blocked the effect of EMAP II on the expression of LC3-II and p62/SQSTM1. Cells exposed to EMAP-II experienced mitophagy and ER stress. Furthermore, the inhibition of cell proliferation, migration and invasion of GBM cells and GSCs were more remarkable by the combination of EMAP II and rapamycin than either agent alone in vitro and in vivo. The current study demonstrated that the cytotoxicity of EMAP II in human GBM cells and GSCs was induced by autophagy, accompanied by the inhibition of PI3K/Akt/mTOR signal pathway, mitophagy and ER stress. The combination of EMAP II with rapamycin demonstrated the inhibitory effect on the malignant biological behaviors of human GBM cells and GSCs in vitro and in vivo.

Molecular and Translational Classifications of DAMPs in Immunogenic Cell Death

The immunogenicity of malignant cells has recently been acknowledged as a critical determinant of efficacy in cancer therapy. Thus, besides developing direct immunostimulatory regimens, including dendritic cell-based vaccines, checkpoint-blocking therapies, and adoptive T-cell transfer, researchers have started to focus on the overall immunobiology of neoplastic cells. It is now clear that cancer cells can succumb to some anticancer therapies by undergoing a peculiar form of cell death that is characterized by an increased immunogenic potential, owing to the emission of the so-called “damage-associated molecular patterns” (DAMPs). The emission of DAMPs and other immunostimulatory factors by cells succumbing to immunogenic cell death (ICD) favors the establishment of a productive interface with the immune system. This results in the elicitation of tumor-targeting immune responses associated with the elimination of residual, treatment-resistant cancer cells, as well as with the establishment of immunological memory. Although ICD has been characterized with increased precision since its discovery, several questions remain to be addressed. Here, we summarize and tabulate the main molecular, immunological, preclinical, and clinical aspects of ICD, in an attempt to capture the essence of this phenomenon, and identify future challenges for this rapidly expanding field of investigation.

The N terminus of pro-endothelial monocyte-activating polypeptide II (EMAP II) regulates its binding with the C terminus, arginyl-tRNA synthetase, and neurofilament light protein

Pro-endothelial monocyte-activating polypeptide II (EMAP II), one component of the multi-aminoacyl tRNA synthetase complex, plays multiple roles in physiological and pathological processes of protein translation, signal transduction, immunity, lung development, and tumor growth. Recent studies have determined that pro-EMAP II has an essential role in maintaining axon integrity in central and peripheral neural systems where deletion of the C terminus of pro-EMAP II has been reported in a consanguineous Israeli Bedouin kindred suffering from Pelizaeus-Merzbacher-like disease. We hypothesized that the N terminus of pro-EMAP II has an important role in the regulation of protein-protein interactions. Using a GFP reporter system, we defined a putative leucine zipper in the N terminus of human pro-EMAP II protein (amino acid residues 1-70) that can form specific strip-like punctate structures. Through GFP punctum analysis, we uncovered that the pro-EMAP II C terminus (amino acids 147-312) can repress GFP punctum formation. Pulldown assays confirmed that the binding between the pro-EMAP II N terminus and its C terminus is mediated by a putative leucine zipper. Furthermore, the pro-EMAP II 1-70 amino acid region was identified as the binding partner of arginyl-tRNA synthetase, a polypeptide of the multi-aminoacyl tRNA synthetase complex. We also determined that the punctate GFP pro-EMAP II 1-70 amino acid aggregate colocalizes and binds to the neurofilament light subunit protein that is associated with pathologic neurofilament network disorganization and degeneration of motor neurons. These findings indicate the structure and binding interaction of pro-EMAP II protein and suggest a role of this protein in pathological neurodegenerative diseases.

Blockade of EMAP II protects cardiac function after chronic myocardial infarction by inducing angiogenesis

Promoting angiogenesis is a key therapeutic target for protection from chronic ischemic cardiac injury. Endothelial-Monocyte-Activating-Polypeptide-II (EMAP II) protein, a tumor-derived cytokine having anti-angiogenic properties in cancer, is markedly elevated following myocardial ischemia. We examined whether neutralization of EMAP II induces angiogenesis and has beneficial effects on myocardial function and structure after chronic myocardial infarction (MI). EMAP II antibody (EMAP II AB), vehicle, or non-specific IgG (IgG) was injected ip at 30 min and 3, 6, and 9 days after permanent coronary artery occlusion in mice. EMAP II AB, compared with vehicle or non-specific antibody, significantly, p<0.05, improved the survival rate after MI, reduced scar size and attenuated the development of heart failure, i.e., left ventricular ejection fraction was significantly higher in EMAP II AB group, fibrosis was reduced by 24%, and importantly, more myocytes were alive in EMAP II AB group in the infarct area. In support of an angiogenic mechanism, capillary density (193/HPF vs. 172/HPF), doubling of the number of proliferating endothelial cells, and angiogenesis related biomarkers were upregulated in mice receiving EMAP II AB treatment as compared to IgG. Furthermore, EMAP II AB prevented EMAP II protein inhibition of in vitro tube formation in HUVECs. We conclude that blockade of EMAP II induces angiogenesis and improves cardiac function following chronic MI, resulting in reduced myocardial fibrosis and scar formation and increased capillary density and preserved viable myocytes in the infarct area.

Plasmacytoid dendritic cells, a role in neoplastic prevention and progression

BACKGROUND

Plasmacytoid dendritic cells (pDCs) are multifunctional bone-marrow-derived immune cells that are key players in bridging the innate and adaptive immune systems. Activation of pDCs through toll-like receptor agonists has proven to be an effective treatment for some neoplastic disorders.

MATERIALS AND METHODS

In this mini-review, we will explore the fascinating contribution of pDCs to neoplastic pathology and discuss their potential utilization in cancer immunotherapy.

RESULTS

Current research suggests that pDCs have cytotoxic potential and can effectively induce apoptosis of tumour-derived cells lines. They are also reported to display tolerogenic function with the ability to suppress T-cell proliferation, analogous to regulatory T cells. In this capacity, they are critical in the suppression of autoimmunity but can be exploited by tumour cells to circumvent the expansion of tumour-specific T cells, thereby allowing tumours to persist.

CONCLUSION

Several forms of skin cancer are successfully treated with the topical drug Imiquimod, which activates pDCs through toll-like receptor 7 engagement. Additionally, pDC-based anticancer vaccines have shown encouraging results for the treatment of melanoma in early trials. Future studies regarding the contributions of pDCs to malignancy will likely afford many opportunities for immunotherapy strategies.

Tumor-associated macrophages as major players in the tumor microenvironment

During tumor progression, circulating monocytes and macrophages are actively recruited into tumors where they alter the tumor microenvironment to accelerate tumor progression. Macrophages shift their functional phenotypes in response to various microenvironmental signals generated from tumor and stromal cells. Based on their function, macrophages are divided broadly into two categories: classical M1 and alternative M2 macrophages. The M1 macrophage is involved in the inflammatory response, pathogen clearance, and antitumor immunity. In contrast, the M2 macrophage influences an anti-inflammatory response, wound healing, and pro-tumorigenic properties. Tumor-associated macrophages (TAMs) closely resemble the M2-polarized macrophages and are critical modulators of the tumor microenvironment. Clinicopathological studies have suggested that TAM accumulation in tumors correlates with a poor clinical outcome. Consistent with that evidence, experimental and animal studies have supported the notion that TAMs can provide a favorable microenvironment to promote tumor development and progression. In this review article, we present an overview of mechanisms responsible for TAM recruitment and highlight the roles of TAMs in the regulation of tumor angiogenesis, invasion, metastasis, immunosuppression, and chemotherapeutic resistance. Finally, we discuss TAM-targeting therapy as a promising novel strategy for an indirect cancer therapy.

tRNA synthetase: tRNA aminoacylation and beyond

The aminoacyl-tRNA synthetases are prominently known for their classic function in the first step of protein synthesis, where they bear the responsibility of setting the genetic code. Each enzyme is exquisitely adapted to covalently link a single standard amino acid to its cognate set of tRNA isoacceptors. These ancient enzymes have evolved idiosyncratically to host alternate activities that go far beyond their aminoacylation role and impact a wide range of other metabolic pathways and cell signaling processes. The family of aminoacyl-tRNA synthetases has also been suggested as a remarkable scaffold to incorporate new domains that would drive evolution and the emergence of new organisms with more complex function. Because they are essential, the tRNA synthetases have served as pharmaceutical targets for drug and antibiotic development. The recent unfolding of novel important functions for this family of proteins offers new and promising pathways for therapeutic development to treat diverse human diseases.

Vascular mediators in chronic lung disease of infancy: role of endothelial monocyte activating polypeptide II (EMAP II)

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of prematurity. Over the years, the BPD phenotype has evolved, but despite various advances in neonatal management approaches, the reduction in the BPD burden is minimal. With the advent of surfactant, glucocorticoids, and new ventilation strategies, BPD has evolved from a disease of structural injury into a new BPD, marked by an arrest in alveolar growth in the lungs of extremely premature infants. This deficient alveolar growth has been associated with a diminution of pulmonary vasculature. Several investigators have described the epithelial / vascular co-dependency and the significant role of crosstalk between vessel formation, alveologenesis, and lung dysplasia's; hence identification and study of factors that regulate pulmonary vascular emergence and inflammation has become crucial in devising effective therapeutic approaches for this debilitating condition. The potent antiangiogenic and proinflammatory protein Endothelial Monocyte Activating Polypeptide II (EMAP II) has been described as a mediator of pulmonary vascular and alveolar formation and its expression is inversely related to the periods of vascularization and alveolarization in the developing lung. Hence the study of EMAP II could play a vital role in studying and devising appropriate therapeutics for diseases of aberrant lung development, such as BPD. Herein, we review the vascular contribution to lung development and the implications that vascular mediators such as EMAP II have in distal lung formation during the vulnerable stage of alveolar genesis.

Extracellular activities of aminoacyl-tRNA synthetases: new mediators for cell-cell communication

Over the last decade, many reports have discussed aminoacyl-tRNA synthetases (ARSs) in extracellular space. Now that so many of them are known to be secreted with distinct activities in the broad range of target cells including endothelial, various immune cells, and fibroblasts, they need to be classified as a new family of extracellular signal mediators. In this chapter the identity of the secreted ARSs, receptors, and their physiological and pathological implications will be described.

Cell proliferation and migration are modulated by Cdk-1-phosphorylated endothelial-monocyte activating polypeptide II

Background

Endothelial-Monocyte Activating Polypeptide (EMAP II) is a secreted protein with well-established anti-angiogenic activities. Intracellular EMAP II expression is increased during fetal development at epithelial/mesenchymal boundaries and in pathophysiologic fibroproliferative cells of bronchopulmonary dysplasia, emphysema, and scar fibroblast tissue following myocardial ischemia. Precise function and regulation of intracellular EMAP II, however, has not been explored to date.

Methodology/Principal Findings

Here we show that high intracellular EMAP II suppresses cellular proliferation by slowing progression through the G2M cell cycle transition in epithelium and fibroblast. Furthermore, EMAP II binds to and is phosphorylated by Cdk1, and exhibits nuclear/cytoplasmic partitioning, with only nuclear EMAP II being phosphorylated. We observed that extracellular secreted EMAP II induces endothelial cell apoptosis, where as excess intracellular EMAP II facilitates epithelial and fibroblast cells migration.

Conclusions/Significance

Our findings suggest that EMAP II has specific intracellular effects, and that this intracellular function appears to antagonize its extracellular anti-angiogenic effects during fetal development and pulmonary disease progression.

Endothelial-monocyte activating polypeptide II disrupts alveolar epithelial type II to type I cell transdifferentiation

Background

Distal alveolar morphogenesis is marked by differentiation of alveolar type (AT)-II to AT-I cells that give rise to the primary site of gas exchange, the alveolar/vascular interface. Endothelial-Monocyte Activating Polypeptide (EMAP) II, an endogenous protein with anti-angiogenic properties, profoundly disrupts distal lung neovascularization and alveolar formation during lung morphogenesis, and is robustly expressed in the dysplastic alveolar regions of infants with Bronchopulmonary dysplasia. Determination as to whether EMAP II has a direct or indirect affect on ATII→ATI trans-differentiation has not been explored.

Method

In a controlled nonvascular environment, an in vitro model of ATII→ATI cell trans-differentiation was utilized to demonstrate the contribution that one vascular mediator has on distal epithelial cell differentiation.

Results

Here, we show that EMAP II significantly blocked ATII→ATI cell transdifferentiation by increasing cellular apoptosis and inhibiting expression of ATI markers. Moreover, EMAP II-treated ATII cells displayed myofibroblast characteristics, including elevated cellular proliferation, increased actin cytoskeleton stress fibers and Rho-GTPase activity, and increased nuclear:cytoplasmic volume. However, EMAP II-treated cells did not express the myofibroblast markers desmin or αSMA.

Conclusion

Our findings demonstrate that EMAP II interferes with ATII → ATI transdifferentiation resulting in a proliferating non-myofibroblast cell. These data identify the transdifferentiating alveolar cell as a possible target for EMAP II's induction of alveolar dysplasia.

Lung endothelial monocyte-activating protein 2 is a mediator of cigarette smoke-induced emphysema in mice

Pulmonary emphysema is a disease characterized by alveolar cellular loss and inflammation. Recently, excessive apoptosis of structural alveolar cells has emerged as a major mechanism in the development of emphysema. Here, we investigated the proapoptotic and monocyte chemoattractant cytokine endothelial monocyte-activating protein 2 (EMAPII). Lung-specific overexpression of EMAPII in mice caused simplification of alveolar structures, apoptosis, and macrophage accumulation, compared with that in control transgenic mice. Additionally, in a mouse model of cigarette smoke-induced (CS-induced) emphysema, EMAPII levels were significantly increased in murine lungs. This upregulation was necessary for emphysema development, as neutralizing antibodies to EMAPII resulted in reduced alveolar cell apoptosis, inflammation, and emphysema-associated structural changes in alveoli and small airways and improved lung function. The mechanism of EMAPII upregulation involved an apoptosis-dependent feed-forward loop, since caspase-3 instillation in the lung markedly increased EMAPII expression, while caspase inhibition decreased its production, even in transgenic EMAPII mice. These findings may have clinical significance, as both current smokers and ex-smoker chronic obstructive pulmonary disease (COPD) patients had increased levels of secreted EMAPII in the bronchoalveolar lavage fluid compared with that of nonsmokers. In conclusion, we suggest that EMAPII perpetuates the mechanism of CS-induced lung emphysema in mice and, given its secretory nature, is a suitable target for neutralization antibody therapy.

Dangerous attraction: phagocyte recruitment and danger signals of apoptotic and necrotic cells

Tissue homeostasis in metazoa requires the rapid and efficient clearance of dying cells by professional or semi-professional phagocytes. Impairment of this finely regulated, fundamental process has been implicated in the development of autoimmune diseases, such as systemic lupus erythematosus. Various studies have provided us a detailed understanding of the interaction between dying cells and phagocytes as well as the current concept that apoptotic cell removal leads to a non- or anti-inflammatory response, whereas necrotic cell removal stimulates a pro-inflammatory reaction. In contrast, our knowledge about the soluble factors released from dying cells is rather limited, although meanwhile it is generally accepted that not only the dying cell itself but also the substances liberated during cell death contribute to the process of corpse clearance and the subsequent immune response. This review article is intended as an up-to-date survey over attraction and danger signals of apoptotic, primary and secondary necrotic cells, their function as chemoattractants in phagocyte recruitment, additional effects on the immune system, and the receptors, which are engaged in this scenario.

Microenvironmental influences of apoptosis in vivo and in vitro

The apoptosis program of physiological cell death elicits a range of non-phlogistic homeostatic mechanisms-"recognition, response and removal"-that regulate the microenvironments of normal and diseased tissues via multiple modalities operating over short and long distances. The molecular mechanisms mediate intercellular signaling through direct contact with neighboring cells, release of soluble factors and production of membrane-delimited fragments (apoptotic bodies, blebs and microparticles) that allow for interaction with host cells over long distances. These processes effect the selective recruitment of mononuclear phagocytes and the specific activation of both phagocytic and non-phagocytic cells. While much evidence is available concerning the mechanisms underlying the recognition and responses of phagocytes that culminate in the engulfment and removal of apoptotic cell bodies, relatively little is yet known about the non-phagocytic cellular responses to the apoptosis program. These responses regulate inflammatory and immune cell activation as well as cell fate decisions of proliferation, differentiation and death. Here, we review current knowledge of these processes, considering especially how apoptotic cells condition the microenvironments of normal and malignant tissues. We also discuss how apoptotic cells that persist in the absence of phagocytic clearance exert inhibitory effects over their viable neighbors, paying particular attention to the specific case of cell cultures and highlighting how new cell-corpse-clearance devices-Dead-Cert Nanoparticles-can significantly improve the efficacy of cell cultures through effective removal of non-viable cells in the absence of phagocytes in vitro.

Pelizaeus-Merzbacher-like disease caused by AIMP1/p43 homozygous mutation

Pelizaeus-Merzbacher disease is an X-linked hypomyelinating leukodystrophy caused by PLP1 mutations. A similar autosomal-recessive phenotype, Pelizaeus-Merzbacher-like disease (PMLD), has been shown to be caused by homozygous mutations in GJC2 or HSPD1. We report a consanguineous Israeli Bedouin kindred with clinical and radiological findings compatible with PMLD in which linkage to PLP1, GJC2, and HSPD1 was excluded. Through genome-wide homozygosity mapping and mutation analysis, we demonstrated in all affected individuals a homozygous frameshift mutation that fully abrogates the main active domain of AIMP1, encoding ARS-interacting multifunctional protein 1. The mutation fully segregates with the disease-associated phenotype and was not found in 250 Bedouin controls. Our findings are in line with the previously demonstrated inability of mutant mice lacking the AIMP1/p43 ortholog to maintain axon integrity in the central and peripheral neural system.

New functions of aminoacyl-tRNA synthetases beyond translation

Over the course of evolution, eukaryotic aminoacyl-tRNA synthetases (aaRSs) progressively incorporated domains and motifs that have no essential connection to aminoacylation reactions. Their accretive addition to virtually all aaRSs correlates with the progressive evolution and complexity of eukaryotes. Based on recent experimental findings focused on a few of these additions and analysis of the aaRS proteome, we propose that they are markers for aaRS-associated functions beyond translation.

Lung self-assembly is modulated by tissue surface tensions

To identify cell-intrinsic properties that facilitate interaction between epithelial endodermal and mesenchymal mesodermal cells during lung morphogenesis, we developed a model of lung self-assembly that mimics fetal lung formation in structure, polarity, vasculature, and extracellular matrix expression. Three-dimensional pulmonary bodies (PBs) spontaneously self-assemble from single-cell suspensions and exhibit liquid-like properties that allow measurements of compaction rate and cohesion, and that may help to specify cellular self-organization. We hypothesized that changes in one or more of these parameters could potentially explain the lung hypoplasia associated with abnormal lung development. We examined the impact of endothelial/monocyte-activating polypeptide (EMAP) II in PBs, because EMAPII is highly expressed in lung hypoplasia. EMAPII significantly increased compaction rate and decreased overall cohesion of PBs composed of both epithelial and mesenchymal cells. Moreover, the effects of EMAPII on compaction and cohesion act exclusively through the mesenchymal cell population by interfering with fibronectin matrix assembly. We also show that EMAPII alters epithelial cell polarity and surfactant protein C expression. Our findings demonstrate, for the first time, that PBs possess liquid-like properties that can help to guide the self-assembly of fetal lungs, and that EMAPII expression can influence both mesenchymal and epithelial cells but through different molecular mechanisms.

Cell Death–Mediated Cleavage of the Attraction Signal p43 in Human Atherosclerosis

Objective— Apoptosis is a key feature of advanced atherosclerotic plaques. Attraction signals such as p43 released from apoptotic cells play a crucial role in the timely removal of the apoptotic remnants by recruiting fresh phagocytes. Here, we sought to determine whether p43 may link apoptosis to inflammation and plaque progression.

Methods and Results— RT-PCR and immunohistochemistry showed that p43 was abundantly expressed in human plaques compared with nonatherosclerotic mammary arteries and colocalized with splicing factor SC-35. Cell culture experiments indicated that p43 expression was associated with enhanced protein translation. On initiation of apoptosis or necrosis, p43 was cleaved by calpains and released as truncated protein p43(apoptosis-released factor [ARF]). Processing of p43 into endothelial monocyte activating polypeptide II was not observed. Full-length p43, but not p43(ARF) or endothelial monocyte activating polypeptide II, activated THP1 monocytes (upregulation of tumor necrosis factor α, interleukin 1β, interleukin 8, macrophage inflammatory protein (MIP)-1α, MIP1β, MIP2α) and endothelial cells (enhanced synthesis of E-selectin, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, tissue factor). The chemotactic activity of p43 or fragments thereof was poor compared with ATP. Treatment of smooth muscle cells with p43 did not induce cell death.

Conclusion— p43 is cleaved during apoptosis by calpains and released as a truncated protein that is harmless for the structure of the plaque.

A genomics method to identify pathogenicity-related proteins. Application to aminoacyl-tRNA synthetase-like proteins

During their extended evolution genes coding for aminoacyl-tRNA synthetases (ARS) have experienced numerous instances of duplication, insertion and deletion of domains. The ARS-related proteins that have resulted from these genetic events are generally known as aminoacyl-tRNA synthetase-like proteins (ARS-like). This heterogeneous group of polypeptides carries out an equally varied number of functions that need not be related to gene translation. Several of these proteins remain uncharacterized. At least 16 different ARS-like proteins have been identified to date, but their functions remain incompletely understood. Here we review the individual phylogenetic distribution of these proteins in bacteria, and apply a new genomics method to determine their potential implication in pathogenicity.

Translation initiation from two in-frame AUGs generates mitochondrial and cytoplasmic forms of the p43 component of the multisynthetase complex

In humans, nine aminoacyl-tRNA synthetases form a stable multiprotein complex with the three auxiliary proteins p18, p38, and p43. The N-terminal moiety of p43 is involved in its anchoring to the complex, and its C-terminal moiety has a potent tRNA binding capacity. The p43 component of the complex is also the precursor of p43(ARF), an apoptosis-released factor, and of p43(EMAPII), the endothelial-monocyte activating polypeptide II. Here we identified a new translation product of the gene of p43, which contains nine additional N-terminal amino acid residues. This gene product is targeted to the mitochondria and accounts for 2% of p43 expressed in human cells. The cytoplasmic and mitochondrial species of p43 are produced from the same mRNA by a mechanism of leaky scanning of the AUG codon at position -27, which is in an unfavorable sequence context for translation initiation. The finding that a mitochondrial species of p43 exists in human cells further exemplifies the multifaceted implications of p43 and opens new perspectives for the understanding of the role of p43 in the apoptotic cell.

A monoclonal rat anti-mouse EMAP II antibody that functionally neutralizes pro- and mature-EMAP II in vitro

EMAP II is an endothelial cell and monocyte activating proinflammatory cytokine, which has been demonstrated to induce endothelial cell apoptosis. In order to analyze its role in disease models linked to inflammation and endothelial cell death, we aimed to develop a neutralizing antibody against mouse EMAP II. Therefore, we generated rat monoclonal anti-mouse EMAP II antibodies by immunization with recombinant full length, mouse pro-EMAP II protein. We could identify by ELISA, hybridoma clones from fusion with mouse myeloma SP2/0 cells which produced antibodies recognizing both full length and mature EMAP II. We further characterized one antibody, M7/1 and demonstrated its ability to detect both EMAP II forms in Western blotting and to neutralize EMAP II directed migration of human peripheral blood monocytes as well as EMAP II induced apoptosis of tumor and endothelial cells. We conclude that this antibody can be useful to both target and analyze murine disease models, in which EMAP II may be involved.

Macrophage inflammatory response to self-assembling rosette nanotubes

Rosette nanotubes (RNTs) are a new class of nanomaterials with significant therapeutic potential. However, societal concerns related to the potential adverse health effects of engineered nanomaterials drew attention towards the investigation of their interaction with the human U937 macrophage cell line. The cells are treated with medium only (control), lysine (50 microg mL(-1)), lysine-functionalized RNTs (RNT-K; 1, 5, and 50 microg mL(-1)), Min-U-Sil quartz microparticles (80 microg mL(-1)), or lipopolysaccharide (1 microg mL(-1)). The supernatant and cells are assayed for cell viability, cytokine protein, and mRNA expression at 1, 6, and 24 h post-treatment. The results indicate that RNT-K activate transcription of proinflammatory genes (interleukin-8 and tumor necrosis factor-alpha (TNF-alpha)) within 1 h, but this effect is not accompanied by protein secretion into the supernatant. The effect of the length of RNTs on human U937 macrophage viability is also investigated. Although both short and long RNT-K exhibit time-dependent effects on TNF-alpha transcription, only the short RNT-K (5 microg mL(-1)) increase TNF-alpha concentration at 6 h relative to the long RNT-K. Moreover, RNT-K (1 and 5 microg mL(-1)) have no effect on cell viability by 24 h. These data indicate that RNT-K do not induce a robust inflammatory response or cytotoxicity in the U937 human macrophage cell line, and therefore could be used for biomedical applications.

Endothelial monocyte activating polypeptide II interferes with VEGF-induced proangiogenic signaling

Endothelial monocyte activating polypeptide II (EMAP II) is a proinflammatory cytokine with antiangiogenic properties. EMAP II functions as a potent inhibitor of primary and metastatic tumor growth, has strong inhibitory effects on endothelial cells (ECs), and can reduce intratumoral expression of the angiogenesis inducer vascular endothelial growth factor (VEGF). VEGF influences EC functions such as proliferation, migration, survival and tube formation. Therapeutic strategies that target VEGF have been demonstrated to reduce the tumor growth. We investigated the effects of EMAP II on VEGF-induced angiogenesis signaling. Primary human fetal lung ECs (HFLECs) and human umbilical vein ECs (HUVECs) were grown in E-Stim medium. Protein binding was analyzed using enzyme-linked immunosorbent assay (ELISA). Protein expression was determined by western blot analysis. EC proliferation and migration was determined using WST-1 reagent and transwell membrane, respectively. EMAP II efficiently and dose dependently binds to VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) as observed by ELISA. B(max) values for VEGFR1 and VEGFR2 were 0.45 and 0.17, respectively. In addition, EMAP II inhibited binding of VEGF to VEGFR1 and VEGFR2. EMAP II significantly reduced VEGF-induced expression of phosphorylated VEGFR1 (in HFLEC and HUVEC) by >50%, and of phosphorylated VEGFR2 (in HUVEC) by 66%. EMAP II also inhibited downstream VEGF signaling. Although VEGF-induced phosphorylation of Akt, Erk1/2, p38 and Raf 2.8-, 1.5-, 2.2- and 3.6-fold, respectively, EMAP II preincubation blocked this induction in phosphorylation to control levels. VEGF-induced EC proliferation 2.5-fold, and EMAP II pretreatment abrogated this effect. Similarly, VEGF-induced EC migration (2.5-fold) was significantly inhibited by EMAP II. These finding suggest that inhibition of VEGF signaling is one possible antiangiogenic mechanism of EMAP II, which may explain its in vivo antitumor activity and delineate therapeutic strategies to enhance anti-VEGF therapy to inhibit tumor growth.

The tumour microenvironment: a novel target for cancer therapy

Cancer therapy is in the midst of a major paradigm shift. Traditionally, cancer treatments have focused on tumour cells. However, studies over the past few decades have demonstrated that cancer is a vastly complex entity with multiple components affecting a tumour's growth, invasion and metastasis. These components, collectively termed the 'tumour microenvironment', include endothelial cells, pericytes, fibroblasts, inflammatory cells, leucocytes and elements of the extracellular matrix (ECM). Biological agents that target components of the tumour microenvironment may provide an interesting alternative to traditional tumour cell-directed therapy. Because of the complexity of the tumour milieu, the most beneficial therapy will likely involve the combination of one or more agents directed at this new target. This review highlights recent preclinical and clinical studies involving agents that target tumour vasculature, leucocytes, pericytes, cancer-associated fibroblasts and ECM components. We pay particular attention to combination therapies targeting multiple components of the tumour microenvironment, and aim to demonstrate that this strategy holds promise for the future of cancer treatment.

The impact of Meth A fibrosarcoma derived EMAP II on dendritic cell migration

Studies have suggested that tumors are capable of modulating dendritic cell (DC) phenotype. A soluble protein produced by certain tumors, endothelial monocyte-activating polypeptide II (EMAP II) has been suggested as an anti-tumor agent based on its anti-angiogenic activity. However, this factor has not been evaluated for effects on DC. In this study, we analyzed the effect of Meth A fibrosarcoma supernatant and recombinant human EMAP II on DC migration. This included the migration of Langerhans cells from mouse ear skin sections and the migration of cells of a dendritic cell line (JAWS II) in a transwell culture system. The results of these studies indicated that EMAP II stimulates the migration of DC. Additional studies showed that the presence of the ascites form of the Meth A tumor led to a decrease in Langerhans cell (LC) numbers in the skin, and this decrease could be partially blocked by neutralizing antibody specific for EMAP II. Subcutaneous injection at the base of the ear of recombinant human EMAP II also led to a decrease in epidermal LC similar to that observed in tumor bearing mice. Together, these results suggest novel roles for EMAP II in modulating the migration of DC and suggest that these effects may modify Meth A tumor/host interactions.

Functional characterization of filamin a interacting protein 1-like, a novel candidate for antivascular cancer therapy

Inhibiting angiogenesis has become a major therapeutic strategy for cancer treatment. To identify common intracellular mediators, we previously analyzed gene expression profiles of endothelial cells after treatment with angiogenesis inhibitors. Filamin A interacting protein 1-like (FILIP1L; previously known as down-regulated in ovarian cancer 1) was identified as one of the genes up-regulated in endothelial cells in response to these inhibitors. However, the expression and function of FILIP1L protein is uncharacterized. Here, we provide the first description of the expression and specific subcellular localization of FILIP1L protein in human tissue. Overexpression of FILIP1L resulted in inhibition of cell proliferation and migration and increased apoptosis. In addition, overexpression of FILIP1L truncation mutants showed differential antiproliferative activity. A COOH terminal truncation mutant (FILIP1LDeltaC103) was more potent than wild-type FILIP1L in mediating this activity. Targeted expression of FILIP1LDeltaC103 in tumor vasculature inhibited tumor growth in vivo. Overall, these findings suggest that the novel protein FILIP1L may be an important mediator of the effects of angiogenesis inhibitors and that FILIP1L has the potential to be an antivascular reagent for cancer therapy.