Prognostic and biological significance of the proangiogenic factor EGFL7 in acute myeloid leukemia.

Epithelial growth factor-like 7 (EGFL7) is a protein that is secreted by endothelial cells and plays an important role in angiogenesis. Although EGFL7 is aberrantly overexpressed in solid tumors, its role in leukemia has not been evaluated. Here, we report that levels of both EGFL7 mRNA and EGFL7 protein are increased in blasts of patients with acute myeloid leukemia (AML) compared with normal bone marrow cells. High EGFL7 mRNA expression associates with lower complete remission rates, and shorter event-free and overall survival in older (age ≥60 y) and younger (age <60 y) patients with cytogenetically normal AML. We further show that AML blasts secrete EGFL7 protein and that higher levels of EGFL7 protein are found in the sera from AML patients than in sera from healthy controls. Treatment of patient AML blasts with recombinant EGFL7 in vitro leads to increases in leukemic blast cell growth and levels of phosphorylated AKT. EGFL7 blockade with an anti-EGFL7 antibody reduced the growth potential and viability of AML cells. Our findings demonstrate that increased EGFL7 expression and secretion is an autocrine mechanism supporting growth of leukemic blasts in patients with AML.

AntAngioCOOL: computational detection of anti-angiogenic peptides.

BACKGROUND: Angiogenesis inhibition research is a cutting edge area in angiogenesis-dependent disease therapy, especially in cancer therapy. Recently, studies on anti-angiogenic peptides have provided promising results in the field of cancer treatment. METHODS: A non-redundant dataset of 135 anti-angiogenic peptides (positive instances) and 135 non anti-angiogenic peptides (negative instances) was used in this study. Also, 20% of each class were selected to construct an independent test dataset (see Additional files 1, 2). We proposed an effective machine learning based R package (AntAngioCOOL) to predict anti-angiogenic peptides. We have examined more than 200 different classifiers to build an efficient predictor. Also, more than 17,000 features were extracted to encode the peptides. RESULTS: Finally, more than 2000 informative features were selected to train the classifiers for detecting anti-angiogenic peptides. AntAngioCOOL includes three different models that can be selected by the user for different purposes; it is the most sensitive, most specific and most accurate. According to the obtained results AntAngioCOOL can effectively suggest anti-angiogenic peptides; this tool achieved sensitivity of 88%, specificity of 77% and accuracy of 75% on the independent test set. AntAngioCOOL can be accessed at https://cran.r-project.org/ . CONCLUSIONS: Only 2% of the extracted descriptors were used to build the predictor models. The results revealed that physico-chemical profile is the most important feature type in predicting anti-angiogenic peptides. Also, atomic profile and PseAAC are the other important features.

Redundant angiogenic signaling and tumor drug resistance.

Angiogenesis research in the past two decades has contributed significantly towards understanding the molecular pathophysiology of cancer progression and inspired target-oriented research and pharma industry for the development of novel anti-angiogenic agents. Currently, over eleven drugs targeting angiogenesis have been approved by the FDA for the treatment of various malignancies. Of the registered anti-angiogenic clinical trials until the end of 2017 (ClinicalTrials.gov), over 47% were completed, 10% were terminated, 3% withdrawn, over 0.5% were suspended and only 4 trials have culminated in FDA approval for marketing. On the one hand, the clinical benefits of anti-angiogenic drugs prompted the development of novel anti-angiogenic agents. On the other hand, however, a plethora of recent studies demonstrated the emergence of tumor drug resistance towards currently used anti-angiogenic therapeutics. Series of preclinical and clinical studies have highlighted the enigma of drug resistance with functional bypass pathways, and identified compensatory or alternative angiogenic mechanisms assuring tumor growth in the midst of an anti-angiogenic stress environment. In the present review the classical literature of such redundant angiogenic pathways in concert with the key angiogenic factors and specialized cells involved in anti-angiogenic escape mechanisms is described. A strategic discourse regarding increasing tumor drug resistance and future modalities for anti-angiogenic therapy is also discussed in view of recent advances.

Targeting human vasohibin-2 by a neutralizing monoclonal antibody for anti-cancer treatment.

There are two members of the vasohibin (VASH) family, VASH1 and VASH2. VASH1 is expressed mainly in endothelial cells to inhibit angiogenesis, whereas VASH2 is expressed mainly in cancer cells to stimulate tumor growth. The aim of the present study was to establish neutralizing monoclonal antibody (mAb) against human VASH2 and apply it as an anti-cancer treatment. We previously raised mAb against several synthetic peptides of hVASH1, and found that one of them exhibited neutralizing activity against hVASH1. Because of the similarity in the amino acid sequences between VASH1 and VASH2, we hypothesized that they shared the bioactive center. When we mutated four amino acids within the region, the mutant VASH2 lost its pro-angiogenic activity. Therefore, we raised mAb against a synthetic peptide overlapping the mutated amino acids of hVASH2, and isolated one clone (1760) that almost completely inhibited the stimulatory effect of hVASH2 on the migration of and tube formation by endothelial cells. When we used this clone 1760 antibody for cancer treatment, the peritoneal injection of it inhibited both tumor growth and angiogenesis in a mouse xenograft model of human cancer cells. In terms of anti-tumor activity, 25 mg/kg of clone 1760 was equivalent to 5 mg/kg of bevacizmab. From these results, we propose the targeting of human VASH2 with neutralizing mAb as a new strategy for cancer treatment.

Specific chemotherapeutic agents induce metastatic behaviour through stromal- and tumour-derived cytokine and angiogenic factor signalling.

Recent studies reveal that chemotherapy can enhance metastasis due to host responses, such as augmented expression of adhesion molecules in endothelial cells and increased populations of myeloid cells. However, it is still unclear how tumour cells contribute to this process. Here, we observed that paclitaxel and carboplatin accelerated lung metastasis in tumour-bearing mice, while doxorubicin and fluorouracil did not. Mechanistically, paclitaxel and carboplatin induced similar changes in cytokine and angiogenic factors. Increased levels of CXCR2, CXCR4, S1P/S1PR1, PlGF and PDGF-BB were identified in the serum or primary tumour tissues of tumour-bearing mice treated by paclitaxel. The serum levels of CXCL1 and PDGF-BB and the tissue level of CXCR4 were also elevated by carboplatin. On the other hand, doxorubicin and fluorouracil did not induce such changes. The chemotherapy-induced cytokine and angiogenic factor changes were also confirmed in gene expression datasets from human patients following chemotherapy treatment. These chemotherapy-enhanced cytokines and angiogenic factors further induced angiogenesis, destabilized vascular integrity, recruited BMDCs to metastatic organs and mediated the proliferation, migration and epithelial-to-mesenchymal transition of tumour cells. Interestingly, inhibitors of these factors counteracted chemotherapy-enhanced metastasis in both tumour-bearing mice and normal mice injected intravenously with B16F10-GFP cells. In particular, blockade of the SDF-1α-CXCR4 or S1P-S1PR1 axes not only compromised chemotherapy-induced metastasis but also prolonged the median survival time by 33.9% and 40.3%, respectively. The current study delineates the mechanism of chemotherapy-induced metastasis and provides novel therapeutic strategies to counterbalance pro-metastatic effects of chemo-drugs via combination treatment with anti-cytokine/anti-angiogenic therapy.

Angiogenic factors as potential drug target: efficacy and limitations of anti-angiogenic therapy.

Formation of new blood vessels (angiogenesis) has been demonstrated to be a basic prerequisite for sustainable growth and proliferation of tumor. Several growth factors, cytokines, small peptides and enzymes support tumor growth either independently or in synergy. Decoding the crucial mechanisms of angiogenesis in physiological and pathological state has remained a subject of intense interest during the past three decades. Currently, the most widely preferred approach for arresting tumor angiogenesis is the blockade of vascular endothelial growth factor (VEGF) pathway; however, the clinical usage of this modality is still limited by several factors such as adverse effects, toxicity, acquired drug resistance, and non-availability of valid biomarkers. Nevertheless, angiogenesis, being a normal physiological process imposes limitations in maneuvering it as therapeutic target for tumor angiogenesis. The present review offers an updated relevant literature describing the role of well-characterized angiogenic factors, such as VEGF, basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), placenta growth factor (PLGF), hepatocyte growth factor/scatter factor (HGF/SF) and angiopoetins (ANGs) in regulating tumor angiogenesis. We have also attempted to discuss tumor angiogenesis with a perspective of 'an attractive target with emerging challenges', along with the limitations and present status of anti-angiogenic therapy in the current state-of-the-art.

Synthesis and Evaluation of New 4-Chloro-2-(3-chloro-4-fluorophenyl)-5-(aliphatic/cyclic saturated amino)pyridazin-3(2H)-one Derivatives as Anticancer, Antiangiogenic, and Antioxidant Agents.

Pyridazinones are widely recognized as versatile scaffolds with a wide spectrum of biological activities. In the present work, a series of new 4-chloro-2-(3-chloro-4-fluorophenyl)-5-(aliphatic/cyclic saturated amino)pyridazin-3(2H)-one derivatives 4a-i were synthesized and characterized by spectral techniques. The inhibitory effects of the synthesized compounds 4a-i on the viability of three human cancer cell lines, HEP3BPN 11 (liver), MDA 453 (breast), and HL 60 (leukemia), were assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay. Among the compounds 4a-i screened, 4g and 4i exhibited inhibitory activity very close to the standard methotrexate; therefore, these lead compounds were further tested for their potential to inhibit the proangiogenic cytokines involved in tumor progression. Compound 4g was found to be a potent antiangiogenic agent against TNFα, VEGF, FGFb, and TGFß, whereas 4i showed potent antiangiogenic activity against TNFα, VEGF, FGFb, and leptin. All the compounds 4a-i were screened for their antioxidant activities using 2,2-diphenyl-1-picryl hydrazine (DPPH), OH, and superoxide anion radicals. Compound 4f showed better OH radical scavenging activity than the standard ascorbic acid.

Angiogenic and signalling proteins correlate with sensitivity to sequential treatment in renal cell cancer.

BACKGROUND: We aimed to study key signalling proteins involved in angiogenesis and proliferation on the response to inhibitors of tyrosine kinases and mammalian target of rapamycin in first- and in second-line treatment of renal cell carcinoma (RCC). METHODS: In a panel of human RCC tumours, in vitro and in nude mice, we evaluated the effect of sunitinib, sorafenib and everolimus, alone and in sequence, on tumour growth and expression of signalling proteins involved in proliferation and resistance to treatment. RESULTS: We demonstrated that, as single agents, sunitinib, sorafenib and everolimus share similar activity in inhibiting cell proliferation, signal transduction and vascular endothelial growth factor (VEGF) secretion in different RCC models, both in vitro and in tumour xenografts. Pre-treatment with sunitinib reduced the response to subsequent sunitinib and sorafenib but not to everolimus. Inability by sunitinib to persistently inhibit HIF-1, VEGF and pMAPK anticipated treatment resistance in xenografted tumours. After first-line sunitinib, second-line treatment with everolimus was more effective than either sorafenib or rechallenge with sunitinib in interfering with signalling proteins, VEGF and interleukin-8, translating into a significant advantage in tumour growth inhibition and mice survival. CONCLUSION: We demonstrated that a panel of angiogenic and signalling proteins can correlate with the onset of resistance to sunitinib and the activity of everolimus in second line.

IL-17 contributes to angiogenesis in rheumatoid arthritis.

Angiogenesis is an early and a critical event in the pathogenesis of rheumatoid arthritis (RA). Neovascularization is dependent on endothelial cell activation, migration and proliferation, and inhibition of angiogenesis may provide a novel therapeutic approach in RA. In this study, we document a novel role of IL-17 in mediating angiogenesis. Local expression of IL-17 in mouse ankles increases vascularity. We further demonstrate that IL-17 is angiogenic by showing its ability to promote blood vessel growth in Matrigel plugs in vivo. Additionally, IL-17, in concentrations present in the RA joint, induces human lung microvascular endothelial cell (HMVEC) migration mediated through the PI3K/AKT1 pathway. Furthermore, suppression of the PI3K pathway markedly reduces IL-17-induced tube formation. We also show that both IL-17-induced HMVEC chemotaxis and tube formation are mediated primarily through IL-17 receptor C. Neutralization of either IL-17 in RA synovial fluids or IL-17 receptor C on HMVECs significantly reduces the induction of HMVEC migration by RA synovial fluid. Finally, RA synovial fluid immunoneutralized with anti-IL-17 and antivascular endothelial growth factor does not reduce HMVEC migration beyond the effect detected by immunodepleting each factor alone. These observations identify a novel function for IL-17 as an angiogenic mediator in RA, supporting IL-17 as a therapeutic target in RA.

Signaling pathways modulated by miRNAs in breast cancer angiogenesis and new therapeutics.

MicroRNAs (miRNAs) act as oncogenes or tumor suppressors by suppressing the expression of target genes, some of which are engaged in angiogenic signaling pathways directly or indirectly. Tumor development and metastasis are dependent on angiogenesis, and it is the main reason for the poor prognosis of cancer patients. New blood vessels are formed from pre-existing vessels when angiogenesis occurs. Thus, it is essential to develop primary tumors and the spread of cancer to surrounding tissues. MicroRNAs (miRNAs) are small noncoding RNAs involved in various biological processes. They can bind to the 3'-UTR of their target genes and prevent them from expressing. MiRNAs control the activity of endothelial cells (ECs) through altering many biological pathways, which plays a key role in cancer progression and angiogenesis. Recent findings revealed that tumor-derived extracellular vesicles participated directly in the control of tumor angiogenesis by delivering miRNAs to ECs. miRNAs recently show great promise in cancer therapies to inhibit angiogenesis. In this study, we showed the miRNA-regulated signaling pathways in tumor angiogenesis with highlighting the anti-angiogenic therapy response and miRNA delivery methods that have been used to inhibit angiogenesis in both in vivo and in vitro studies.

Preliminary studies of the effects of vascular adhesion protein-1 inhibitors on experimental corneal neovascularization.

Vascular adhesion protein-1 (VAP-1) controls the adhesion of lymphocytes to endothelial cells and is upregulated at sites of inflammation. Moreover, it expresses amine oxidase activity, due to the sequence identity with semicarbazide-sensitive amine oxidase. Recent studies indicate a significant role for VAP-1 in neovascularization, besides its contribution to inflammation. Pathological blood vessel development in severe ocular diseases (such as diabetes, age-related macula degeneration, trauma and infections) might lead to decreased visual acuity and finally to blindness, yet there is no clear consensus as to its appropriate treatment. In the present case study, the effects of two VAP-1 inhibitors on experimentally induced corneal neovascularization in rabbits were compared with the effects of a known inhibitor of angiogenesis, bevacizumab, an anti-vascular endothelial growth factor antibody. In accordance with recent literature data, the results of the preliminary study reported here indicate that the administration of VAP-1 inhibitors is a potentially valuable therapeutic option in the treatment of corneal neovascularization.

The role of macrophage-derived IL-1 in induction and maintenance of angiogenesis.

Inflammation and angiogenesis are pivotal processes in the progression of many diseases, including malignancies. A hypoxic microenvironment often results in a milieu of proinflammatory and proangiogenic cytokines produced by infiltrating cells. We assessed the role of macrophage-derived hypoxia-associated cytokines in promoting inflammation and angiogenesis. Supernatants of macrophages, stimulated under hypoxia with or without an inflammatory stimulus (LPS), promoted angiogenesis when incorporated into Matrigel plugs. However, neutralization of IL-1 in the supernatants, particularly IL-1beta, completely abrogated cell infiltration and angiogenesis in Matrigel plugs and reduced vascular endothelial growth factor (VEGF) levels by 85%. Similarly, supernatants from macrophages of IL-1beta knockout mice did not induce inflammatory or angiogenic responses. The importance of IL-1 signaling in the host was demonstrated by the dramatic reduction of inflammatory and angiogenic responses in Matrigel plugs that contained macrophage supernatants from control mice which had been implanted in IL-1 receptor type I knockout mice. Myeloid cells infiltrating into Matrigel plugs were of bone marrow origin and represented the major source of IL-1 and other cytokines/chemokines in the plugs. Cells of endothelial lineage were the main source of VEGF and were recruited mainly from neighboring tissues, rather than from the bone marrow. Using the aortic ring sprouting assay, it was shown that in this experimental system, IL-1 does not directly activate endothelial cell migration, proliferation and organization into blood vessel-like structures, but rather activates infiltrating cells to produce endothelial cell activating factors, such as VEGF. Thus, targeting IL-1beta has the potential to inhibit angiogenesis in pathological situations and may be of considerable clinical value.

Improvement of antiangiogenic cancer therapy by understanding the mechanisms of angiogenic factor interplay and drug resistance.

Several antiangiogenic agents, including bevacizumab, sunitinib, and sorafenib, which mainly target the VEGF signaling system, have been approved for the treatment of human cancers. These drugs have been paired with conventional chemotherapeutic agents to treat different types of cancers, including colorectal and lung cancers; however, the patient response rate and resultant increase in overall survival time have been rather modest. The current antiangiogenic regimen is far from optimal. Improvements of therapeutic efficacy and minimization of adverse effects and drug resistance are urgent tasks that are most likely to be resolved by understanding the molecular mechanisms underlying tumor angiogenesis. The aim of this article is to discuss these clinically related issues, to highlight several recent examples of the complex interplays between tumor-produced angiogenic factors, and to propose a new paradigm for improvement of therapeutic intervention of tumor angiogenesis.

The angiogenic switch in carcinogenesis.

Coined in the late eighties, the term "angiogenic switch" refers to a time-restricted event during tumor progression where the balance between pro- and anti-angiogenic factors tilts towards a pro-angiogenic outcome, resulting in the transition from dormant avascularized hyperplasia to outgrowing vascularized tumor and eventually to malignant tumor progression. The molecular players and mechanisms underlying the angiogenic switch have been intensely investigated. In particular, a large number of pro-angiogenic factors and angiogenic inhibitors activated and repressed, respectively, in their activities during the angiogenic switch have been identified and characterized. Part of this research has lead to the development of various pro- and anti-angiogenic therapies that are currently tested in clinical trials or are already in clinical use. More recently, transgenic mouse models of cancer have been instrumental in revealing that inflammatory responses within the tumor microenvironment are critically contributing to the onset of tumor angiogenesis. These mouse models closely recapitulate multistage carcinogenesis in cancer patients and represent reliable tools to study the molecular and cellular players implicated in the onset and maintenance of tumor angiogenesis. Furthermore, they also offer the opportunity to assess the efficacy of novel anti-angiogenic cancer therapies and the nature of developing resistance mechanisms. These experiments have provided first important concepts to improve anti-angiogenic therapy and thus directly contribute to their translation to the clinical setting.

Angiogenesis and vasculogenesis in rheumatoid arthritis.

PURPOSE OF REVIEW: Angiogenesis is the formation of new capillaries from pre-existing vessels, whereas vasculogenesis is de-novo capillary formation from endothelial precursor cells (EPCs). Current understanding of the role of angiogenesis and vasculogenesis in rheumatoid arthritis (RA) and possibilities of therapeutic intervention should be summarized. RECENT FINDINGS: There have been many recent studies on the role of the hypoxia and hypoxia-inducible factor (HIF)-vascular endothelial growth factor (VEGF)-angiopoietin axis in angiogenesis associated with RA. The role of additional growth factors, chemokines, cytokines, matrix components and adhesion molecules has been further characterized. Macrophage migration inhibitory factor (MIF) may link inflammation, angiogenesis and atherosclerosis. Junctional adhesion molecules (JAMs) and focal adhesion kinases (FAKs) have recently been implicated in inflammatory angiogenesis. Novel information regarding the role of serum amyloid A (SAA) and sphingosine kinase has become available. Most of these angiogenic factors have recently been targeted using various techniques and arthritis models. Whereas angiogenesis is abundant in RA, there is defective EPC function and vasculogenesis leading to atherosclerosis and vascular disease in arthritis. Treatment with EPCs already under investigation in vascular diseases may also be attempted in RA. SUMMARY: Targeting angiogenesis and restoration of vasculogenesis may be beneficial for the therapy and outcome of RA.

Reexpression of ARHI inhibits tumor growth and angiogenesis and impairs the mTOR/VEGF pathway in hepatocellular carcinoma.

The Ras-related tumor suppressor gene aplasia Ras homolog member I (ARHI) is frequently downregulated in many types of cancer, including hepatocellular carcinoma (HCC). In this study, we sought to explore the therapeutic implications of ARHI reconstitution in the treatment of HCC. We generated stable cell lines overexpressing ARHI in Hep3B and SK-Hep1 cells, both of which lack endogenous ARHI. The effects of ARHI reexpression on tumor growth and angiogenesis were assessed. Given the key role of mammalian target of rapamycin (mTOR) signaling in HCC progression, we also tested whether ARHI overexpression affected the mTOR pathway. Forced expression of ARHI resulted in a significant inhibition of the proliferation of both Hep3B and SK-Hep1 cells compared to control cells (P<0.01). Cell cycle analysis revealed a G0-G1 arrest induced by ARHI reexpression. Moreover, ARHI reexpression significantly retarded Hep3B xenograft growth in vivo, and caused a marked reduction in tumor angiogenesis assessed by CD31-stained microvessel count. Western blot analysis of the xenografts showed that ARHI overexpression substantially reduced the phosphorylation of two mTOR substrates, S6K1 and 4E-BP1, indicative of an inactivation of the mTOR pathway. Accompanying with the mTOR inactivation, the angiogenic factors, hypoxia-inducible factor 1 alpha and vascular endothelial growth factor, were significantly downregulated. These data highlighted an important role for ARHI in controlling HCC growth and angiogenesis, therefore offering a possible therapeutic strategy against this malignancy.

Tumor Development and Angiogenesis in Adult Brain Tumor: Glioblastoma.

Angiogenesis is the growth of new capillaries from the preexisting blood vessels. Glioblastoma (GBM) tumors are highly vascularized tumors, and glioma growth depends on the formation of new blood vessels. Angiogenesis is a complex process involving proliferation, migration, and differentiation of vascular endothelial cells (ECs) under the stimulation of specific signals. It is controlled by the balance between its promoting and inhibiting factors. Various angiogenic factors and genes have been identified that stimulate glioma angiogenesis. Therefore, attention has been directed to anti-angiogenesis therapy in which glioma proliferation is inhibited by inhibiting the formation of new tumor vessels using angiogenesis inhibitory factors and drugs. Here, in this review, we highlight and summarize the various molecular mediators that regulate GBM angiogenesis with focus on recent clinical research on the potential of exploiting angiogenic pathways as a strategy in the treatment of GBM patients.

Disease modifying and antiangiogenic activity of 2-methoxyestradiol in a murine model of rheumatoid arthritis.

BACKGROUND: A critical component of disease progression in rheumatoid arthritis (RA) involves neovascularization associated with pannus formation. 2-methoxyestradiol (2ME2) is a naturally occurring molecule with no known physiologic function, although at pharmacologic concentrations it has antiproliferative and antiangiogenic activities. We investigated the impact of orally administered 2ME2 on the initiation and development of proliferative synovitis using the anti-collagen monoclonal antibodies (CAIA) model. METHODS: Severe polyarticular arthritis was induced in Balb/c female mice by administration of 2 mg of a monoclonal antibody cocktail intravenously into the tail vein of mice. Twenty-four hours following monoclonal antibody administration, mice were injected with 25 microg of LPS (E. coli strain 0111:B4) via the intraperitoneal route. Treatment with 2ME2 (100, 75, 50, 25, 10, 1 mg/kg, p.o., daily), or vehicle control began 24 hrs following LPS challenge and continued to day 21. Hind limbs were harvested, sectioned and evaluated for DMARD activity and general histopathology by histomorphometric analysis and immunohistochemistry (vWF staining). In a separate study, different dosing regimens of 2ME2 (100 mg/kg; q.d. vs q.w. vs q.w. x 2) were evaluated. The effect of treatment with 2ME2 on gene expression of inflammatory cytokines and angiogenic growth factors in the joint space was evaluated 5 and 14 days after the induction of arthritis. RESULTS: Mice treated with 2ME2 beginning 24 hours post anti-collagen monoclonal antibody injection, showed a dose-dependent inhibition in mean arthritic scores. At study termination (day 21), blinded histomorphometric assessments of sectioned hind limbs demonstrated decreases in synovial inflammation, articular cartilage degradation, pannus formation, osteoclast activity and bone resorption. At the maximal efficacious dosing regimen (100 mg/kg/day), administration of 2ME2 resulted in total inhibition of the study parameters and prevented neovascularization into the joint. Examination of gene expression on dissected hind limbs from mice treated for 5 or 14 days with 2ME2 showed inhibition of inflammatory cytokine message for IL-1beta, TNF-alpha, IL-6 and IL-17, as well as the angiogenic cytokines, VEGF and FGF-2. CONCLUSION: These data demonstrate that in the CAIA mouse model of RA, 2ME2 has disease modifying activity that is at least partially attributable to the inhibition of neovascular development. Further, the data suggests new mechanistic points of intervention for 2ME2 in RA, specifically inhibition of inflammatory mediators and osteoclast activity.

Protein kinase Ds promote tumor angiogenesis through mast cell recruitment and expression of angiogenic factors in prostate cancer microenvironment.

BACKGROUND: Mast cells are being increasingly recognized as critical components in the tumor microenvironment. Protein Kinase D (PKD) is essential for the progression of prostate cancer, but its role in prostate cancer microenvironment remains poorly understood. METHODS: The expression of PKD, mast cells and microvessel density were examined by IHC. The clinical significance was determined by statistical analyses. The biological function of PKD and the underlying mechanisms were investigated using in vitro and in vivo models. RESULTS: PKD2/3 contributed to MCs recruitment and tumor angiogenesis in the prostate cancer microenvironment. Clinical data showed that increased activation of PKD at Ser744/748 in prostate cancer was correlated with mast cell infiltration and microvascular density. PKD2/3 silencing of prostate cancer cells markedly decreased MCs migration and tube formation of HUVEC cells. Moreover, PKD2/3 depletion not only reduced SCF, CCL5 and CCL11 expression in prostate cancer cells but also inhibited angiogenic factors in MCs. Conversely, exogenous SCF, CCL5 and CCL11 reversed the effect on MCs migration inhibited by PKD2/3 silencing. Mechanistically, PKD2/3 interacted with Erk1/2 and activated Erk1/2 or NF-κB signaling pathway, leading to AP-1 or NF-κB binding to the promoter of scf, ccl5 and ccl11. Finally, PKD-specific inhibitor significantly reduced tumor volume and tumor growth in mice bearing RM-1 prostate cancer cells, which was attributed to attenuation of mast cell recruitment and tumor angiogenesis. CONCLUSIONS: These results demonstrate a novel PKDs function that contributes to tumor angiogenesis and progression through mast cells recruitment in prostate cancer microenvironment.