Tumour-associated macrophages as a novel target of VEGI-251 in cancer therapy.

Tumour-associated macrophages (TAMs), which possess M2-like characters and are derived from immature monocytes in the circulatory system, represent a predominant population of inflammatory cells in solid tumours. TAM infiltration in tumour microenvironment can be used as an important prognostic marker in many cancer types and is a potential target for cancer prevention or treatment. VEGI-251 not only is involved in the inhibition of tumour angiogenesis, but also participates in the regulation of host immunity. This work aimed to investigate the involvement of VEGI-251 in the regulation of specific antitumour immunity. We found that recombinant human VEGI-251(rhVEGI-251) efficiently mediated the elimination of TAMs in tumour tissue in mice, and induced apoptosis of purified TAMs in vitro. During this process, caspase-8 and caspase-3 were activated, leading to PARP cleavage and apoptosis. Most importantly, we further elucidated the mechanism underlying VEGI-251-triggered TAM apoptosis, which suggests that ASK1, an intermediate component of the VEGI-251, activates the JNK pathway via TRAF2 in a potentially DR3-dependent manner in the process of TAM apoptosis. Collectively, our findings provide new insights into the basic mechanisms underlying the actions of VEGI-251 that might lead to future development of antitumour therapeutic strategies using VEGI-251 to target TAMs.

VEGI174 protein and its functional domain peptides exert antitumour effects on renal cell carcinoma.

Vascular endothelial growth inhibitor (VEGI) has been identified as an anti­angiogenic cytokine. However, the effects of VEGI174 protein, and its functional domain peptides V7 and V8, on renal cell carcinoma (RCC) remain unknown. In the present study, the protein and peptides were biosynthesised as experimental agents. The A498 and 786­O RCC cell lines, and an established mouse xenograft model, were separately treated with VEGI174, V7 or V8. Cellular functions, including proliferation, migration and invasion, were subsequently detected. Cell migration and invasion were monitored using the xCELLigence system. Furthermore, tumour growth and mouse behaviours, including mobility, appetite and body weight, were assessed. The results demonstrated that VEGI174, V7 and V8 inhibited the proliferation, migration and invasion of A498 and 786­O cell lines when administered at concentrations of 1 and 100 pM, 10 nM and 1 µM. The inhibitory effects exhibited dose­ and time­dependent antitumour activity. Furthermore, VEGI174, V7 and V8 inhibited tumour growth in A498 and 786­O xenograft mice. In the A498 xenografts, the tumour growth inhibition (TGI) rates in the VEGI174­, V7­ and V8­treated groups were 71, 20 and 31%, respectively. In the 786­O xenografts, the TGI rates in the VEGI174­, V7­ and V8­treated groups were 34, 26 and 31%, respectively. There was no significant loss in body weight and no cases of mortality were observed for all treated mice. In conclusion, VEGI174, V7 and V8 exhibited potential antitumour effects and were well tolerated in vivo. V7 and V8, as functional domain peptides of the VEGI174 protein, may be studied for the future treatment of RCC.

Hydrogen/deuterium exchange mass spectrometry and computational modeling reveal a discontinuous epitope of an antibody/TL1A Interaction.

TL1A, a tumor necrosis factor-like cytokine, is a ligand for the death domain receptor DR3. TL1A, upon binding to DR3, can stimulate lymphocytes and trigger secretion of proinflammatory cytokines. Therefore, blockade of TL1A/DR3 interaction may be a potential therapeutic strategy for autoimmune and inflammatory diseases. Recently, the anti-TL1A monoclonal antibody 1 (mAb1) with a strong potency in blocking the TL1A/DR3 interaction was identified. Here, we report on the use of hydrogen/deuterium exchange mass spectrometry (HDX-MS) to obtain molecular-level details of mAb1's binding epitope on TL1A. HDX coupled with electron-transfer dissociation MS provided residue-level epitope information. The HDX dataset, in combination with solvent accessible surface area (SASA) analysis and computational modeling, revealed a discontinuous epitope within the predicted interaction interface of TL1A and DR3. The epitope regions span a distance within the approximate size of the variable domains of mAb1's heavy and light chains, indicating it uses a unique mechanism of action to block the TL1A/DR3 interaction.

Vascular endothelial growth inhibitor 174 and its functional domains inhibit epithelial-mesenchymal transition in renal cell carcinoma cells in vitro.

The present study was carried out to investigate the effects of vascular endothelial growth inhibitor 174 (VEGI174) and its functional domains (V7 and V8) on epithelial­mesenchymal transition (EMT) in renal cell carcinoma (RCC) cells in vitro. The RCC cell lines A498 and 786­O were used in this study. Based on our preliminary study, we selected full­length VEGI174 and its functional domains (V7 and V8) as the target genes in this study. Plasmids containing VEGI174, V7 or V8 transgenes were constructed and transfected into A498 and 786­O cell lines. Cytological activity was tested during cell culture. Quantitative PCR and western blot analysis were performed to determine the expression levels of EMT markers (E­cadherin, vimentin, ß­catenin and Slug). Overexpression of VEGI174, V7 or V8 did not have a significant influence on cell viability (P>0.05). The mRNA level of E­cadherin was significantly upregulated, while that of vimentin was downregulated in A498VEGIexp, A498V7exp, A498V8exp, 786­OVEGIexp, 786­OV7exp and 786­OV8exp cells compared with the cells containing the empty plasmid controls (P<0.05). The western blot results showed that changes in protein expression levels were consistent with the changes in mRNA expression. Both the mRNA and protein expression levels of ß­catenin and Slug were downregulated in the A498VEGIexp, A498V7exp, A498V8exp, 786­OVEGIexp, 786­OV7exp and 786­OV8exp cells. In conclusion, overexpression of VEGI174, V7 or V8 inhibited EMT in A498 and 786­O cells. Notably, V7 and V8 are two effective functional domains of VEGI174 that have the potential to be studied for peptide synthesis and the treatment of RCC.

Death receptor 3 signaling enhances proliferation of human regulatory T cells.

Exploiting regulatory T cells (Tregs) to control aberrant immune reactions is a promising therapeutic approach, but is hampered by their relative paucity. In mice, activation of death receptor 3 (DR3), a member of the TNF-receptor superfamily (TNFRSF), increases Treg frequency and efficiently controls exuberant immune activation. For human Tregs, neither DR3 expression nor potential functions have been described. Here, we show that human Tregs express DR3 and demonstrate DR3-mediated activation of p38, ERK, and NFκB. DR3 stimulation enhances Treg expansion ex vivo while retaining their suppressive capacity. In summary, our results establish a functional role for DR3 signaling in human Tregs and could potentially help to tailor Treg-based therapies.

In vivo NIRF imaging-guided delivery of a novel NGR-VEGI fusion protein for targeting tumor vasculature.

Pathological angiogenesis is crucial in tumor growth, invasion and metastasis. Previous studies demonstrated that the vascular endothelial growth inhibitor (VEGI), a member of the tumor necrosis factor superfamily, can be used as a potent endogenous inhibitor of tumor angiogenesis. Molecular probes containing the asparagine-glycine-arginine (NGR) sequence can specifically bind to CD13 receptor which is overexpressed on neovasculature and several tumor cells. Near-infrared fluorescence (NIRF) optical imaging for targeting tumor vasculature offers a noninvasive method for early detection of tumor angiogenesis and efficient monitoring of response to anti-tumor vasculature therapy. The aim of this study was to develop a new NIRF imaging probe on the basis of an NGR-VEGI protein for the visualization of tumor vasculature. The NGR-VEGI fusion protein was prepared from prokaryotic expression, and its function was characterized in vitro. The NGR-VEGI protein was then labeled with a Cy5.5 fluorophore to afford Cy5.5-NGR-VEGI probe. Using the NIRF imaging technique, we visualized and quantified the specific delivery of Cy5.5-NGR-VEGI protein to subcutaneous HT-1080 fibrosarcoma tumors in mouse xenografts. The Cy5.5-NGR-VEGI probe exhibited rapid HT-1080 tumor targeting, and highest tumor-to-background contrast at 8 h post-injection (pi). Tumor specificity of Cy5.5-NGR-VEGI was confirmed by effective blocking of tumor uptake in the presence of unlabeled NGR-VEGI (20 mg/kg). Ex vivo NIRF imaging further confirmed in vivo imaging findings, demonstrating that Cy5.5-NGR-VEGI displayed an excellent tumor-to-muscle ratio (18.93 ± 2.88) at 8 h pi for the non-blocking group and significantly reduced ratio (4.92 ± 0.75) for the blocking group. In conclusion, Cy5.5-NGR-VEGI provided highly sensitive, target-specific, and longitudinal imaging of HT-1080 tumors. As a novel theranostic protein, Cy5.5-NGR-VEGI has the potential to improve cancer treatment by targeting tumor vasculature.

Immunobiology of TNFSF15 and TNFRSF25.

TNFRSF25 is an understudied broad-acting T cell costimulator with high homology to TNFR1, however, the overall role of this receptor in T cell immunobiology is unclear. Ligation of TNFRSF25 by its monogamous ligand, TNFSF15 (TL1A), leads to recruitment of TNFR-associated factor 2 and TNFR-associated death domain in primary T cells with downstream activation of both NFκB as well as the PI3K/Akt axis. These signaling pathways are dependent upon coordinated engagement of the T cell receptor and interleukin-2 receptor and leads to the constitutive proliferation of CD4+FoxP3+ regulatory T cells (Treg) as a result of tonic exposure to self-antigen. Concurrent activation of CD4+ or CD8+ conventional T cell clones is dependent upon the availability of cognate foreign antigen. Here, we provide a review of both the literature and our work on this receptor and propose that the overall function of TL1A signaling to TNFRSF25 in T cells is to provide simultaneous costimulation of foreign-antigen-specific effector T cells and pre-existing Treg in order to focus the clonality of effector immunity to pathogen-derived antigens and reduce the risk of bystander inflammation toward self- or endogenous microbial antigens.

Approaches to efficient production of recombinant angiogenesis inhibitor rhVEGI-192 and characterization of its structure and antiangiogenic function.

Methods to prepare pure, bioactive recombinant human vascular endothelial growth inhibitor (rhVEGI), a potent inhibitor of angiogenesis potentially applicable in antiangiogenic cancer therapy, are in urgent demand for preclinical investigation as well as future clinical trials of the protein. Here, we report expression and purification of rhVEGI-192, a recombinant VEGI isoform, comparatively using host strains BL21 (DE3) pLysS and Origami B (DE3) with IPTG-induction and autoinduction techniques. Our study identified that a combined use of Origami B (DE3) strain and autoinduction expression system gave rise to a high yield of purified rhVEGI-192 at 105.38 mg/L culture by immobilized-metal affinity chromatography on Ni-NTA column. The antiangiogenic activity was effectively restored after the insoluble fractions being dissolved in 8M urea and subsequently subjected to a gradient-dialysis refolding process. Functional tests demonstrated that the purified rhVEGI-192 potently inhibited endothelial growth, induced endothelial apoptosis and suppressed neovascularization in chicken chorioallantoic membrane, indicating that the developed method allows preparation of rhVEGI-192 with high yield, solubility, and bioactivity. Most importantly, our study also demonstrates that VEGI-192 is capable of forming polymeric structure, which is possibly required for its antiangiogenic activity.

Biochemical and structural characterization of the human TL1A ectodomain.

TNF-like 1A (TL1A) is a newly described member of the TNF superfamily that is directly implicated in the pathogenesis of autoimmune diseases, including inflammatory bowel disease, atherosclerosis, and rheumatoid arthritis. We report the crystal structure of the human TL1A extracellular domain at a resolution of 2.5 A, which reveals a jelly-roll fold typical of the TNF superfamily. This structural information, in combination with complementary mutagenesis and biochemical characterization, provides insights into the binding interface and the specificity of the interactions between TL1A and the DcR3 and DR3 receptors. These studies suggest that the mode of interaction between TL1A and DcR3 differs from other characterized TNF ligand/receptor complexes. In addition, we have generated functional TL1A mutants with altered disulfide bonding capability that exhibit enhanced solution properties, which will facilitate the production of materials for future cell-based and whole animal studies. In summary, these studies provide insights into the structure and function of TL1A and provide the basis for the rational manipulation of its interactions with cognate receptors.

X-ray crystal structure of TNF ligand family member TL1A at 2.1A.

The TNF family has been one of the most intensively studied protein families in the past two decades and it has rapidly expanded through the era of genomics and bioinformatics. However, the structural basis of the functional and interactional similarities and differences of this family is poorly understood. TL1A is a recently identified TNF family member that has received increasing attention. Here, the crystal structure of human TL1A is reported. TL1A forms a homotrimer with each monomer assuming a jellyroll beta-sandwich fold. The CD loop in TL1A is the longest among the TNF ligand members with known structure and the AA' loop in TL1A is the second longest after that in TRAIL, where part of it is disordered. Both these loops are known to participate in receptor binding in TNFbeta/LTalpha. The AA' loop may be very different in other TL1A variants if the overall fold is to be preserved.

Purification and crystallization of recombinant human TNF-like ligand TL1A.

TL1A is a recently discovered TNF-like ligand. Because of the interests in the structural basis of the specificity of the bindings of the TNF ligands to the TNF receptors, we sought to crystallize the mature soluble form of human TL1A. To prepare recombinant human TL1A, the coding sequence for mature human soluble TL1A (aa72-aa251) was cloned into Escherichia coli expression vector pDEST14 and the protein was purified in a succession of immobilized metal affinity, hydrophobic interaction, ion exchange and size exclusion chromatography, indicating that mature TL1A may have a metal ligand. The functional activity of recombinant TL1A was confirmed by its ability to bind to DcR3, a soluble decoy receptor of the TNF receptor family that has been previously reported to bind to TL1A. Single crystals of TL1A were obtained in a screen with a crystal screen kit using the hanging-drop vapor diffusion method. Diffraction quality crystals were grown after optimization. TL1A crystals belong to the tetragonal space group P4(1)2(1)2, with unit cell parameter of a=b=116.734, c=118.927A. The TL1A crystals diffracted to at least 3.2A. Self-rotation functions showed that there are three molecules in the asymmetry unit. Assuming an average partial specific volume of 0.74cm(3)g(-1) for proteins, the water content of the crystal is 62.8%. A preliminary molecular replacement solution was obtained with three TL1A molecules in the asymmetric unit. The three protomers are related by a non-crystallographic 3-fold axis, like those of other TNF ligand family members.

Functional characterization of tumor necrosis factor superfamily 15 (TNFSF15) induced by lipopolysaccharides and Eimeria infection.

A full-length cDNA encoding chicken tumor necrosis factor superfamily 15 (TNFSF15) was isolated and its functional role was investigated. TNFSF15 transcripts were primarily expressed in spleen, liver, intestinal intraepithelial lymphocytes (IEL), peripheral blood lymphocytes and bursa. In vitro infection of HTC macrophages with three species of Eimeria sporozoites induced TNFSF15 gene expression. In vivo experiments revealed that TNFSF15 gene was highly increased following primary infections with Eimeria acervulina or Eimeria maxima. In contrast, no consistent changes in transcript levels were seen following primary infection with Eimeria tenella, or following secondary infection with any of the three Eimeria species. Following infection with E. acervulina and E. maxima, TNFSF15 transcripts were primarily expressed in intestinal CD4(+) and TCR2(+) IEL, respectively. A dose-dependent cytotoxic effect of recombinant TNFSF15 protein was observed on HTC and LSCC-RP9 tumor cells. These results indicate that TNFSF15 plays an important role in local inflammatory response to Eimeria.