Inhibition of endothelial cell proliferation by platelet factor-4 involves a unique action on S phase progression

DNA damage repair in megakaryopoiesis: molecular and clinical aspects

INTRODUCTION

Endogenous DNA damage is a significant factor in the damage of hematopoietic cells. Megakaryopoiesis is one of the pathways of hematopoiesis that ends with the production of platelets and plays the most crucial role in hemostasis. Despite the presence of efficient DNA repair mechanisms, some endogenous lesions can lead to mutagenic alterations, disruption of pathways of hematopoiesis including megakaryopoiesis and potentially result in human diseases.

AREAS COVERED

The complex regulation of DNA repair mechanisms plays a central role in maintaining genomic integrity during megakaryopoiesis and influences platelet production efficiency and quality. Moreover, anomalies in DNA repair processes are involved in several diseases associated with megakaryopoiesis, including myeloproliferative disorders and thrombocytopenia.

EXPERT OPINION

In the era of personalized medicine, diagnosing diseases related to megakaryopoiesis can only be made with a complete assessment of their molecular aspects to provide physicians with critical molecular data for patient management and to identify the subset of patients who could benefit from targeted therapy.

Platelets and (Lymph)angiogenesis

The formation of new blood and lymphatic vessels is essential for both the development of multicellular organisms and (patho)physiological processes like wound repair and tumor growth. In the 1990s, circulating blood platelets were first postulated to regulate tumor angiogenesis by interacting with the endothelium and releasing angiogenic regulators from specialized α granules. Since then, many studies have validated the contributions of platelets to tumor angiogenesis, while uncovering novel roles for platelets in other angiogenic processes like wound resolution and retinal vascular disease. Although the majority of (lymph)angiogenesis occurs during development, platelets appear necessary for lymphatic but not vascular growth, implying their particular importance in pathological cases of adult angiogenesis. Future work is required to determine whether drugs targeting platelet production or function offer a clinically relevant tool to limit detrimental angiogenesis.

Strategies to better treat glioblastoma: antiangiogenic agents and endothelial cell targeting agents

Glioblastoma multiforme (GBM) is the most prevalent and aggressive form of glioma, with poor prognosis and high mortality rates. As GBM is a highly vascularized cancer, antiangiogenic therapies to halt or minimize the rate of tumor growth are critical to improving treatment. In this review, antiangiogenic therapies, including small-molecule drugs, nucleic acids and proteins and peptides, are discussed. The authors further explore biomaterials that have been utilized to increase the bioavailability and bioactivity of antiangiogenic factors for better antitumor responses in GBM. Finally, the authors summarize the current status of biomaterial-based targeting moieties that target endothelial cells in GBM to more efficiently deliver therapeutics to these cells and avoid off-target cell or organ side effects.

Angiodrastic Chemokines in Colorectal Cancer: Clinicopathological Correlations

Aim

To study the expression of angiodrastic chemokines in colorectal tumors and correlate findings with clinicopathological parameters and survival.

Methods

The proangiogenic factor VEGF, the angiogenic chemokines CXCL8 and CXCL6, and the angiostatic chemokine CXCL4 were measured by ELISA in tumor and normal tissue of 35 stage II and III patients and correlated with the histopathology markers Ki67, p53, p21, bcl2, EGFR, and MLH1 and 5-year survival. The Wilcoxon and chi-square tests were used for statistical comparisons.

Results

There was a significant increase of CXCL6 (p = 0.005) and VEGF (p = 0.003) in cancerous tissue compared to normal. Patients with lower levels of CXCL8 and CXCL4 lived significantly longer. Patients with loss of EGFR expression had higher levels of CXCL8 while p21 loss was associated with higher levels of CXCL6. Chemokine levels were not correlated with TNM or Dukes classification. Strong expression of p53 was accompanied by decreased survival.

Conclusions

(1) The angiogenic factors CXCL6 and VEGF are increased in colorectal cancer tissue with no association with the clinical stage of the disease or survival. (2) However, increased levels of tissue CXCL8 and CXCL4 are associated with poor survival. (3) Strong expression of p53 is found in patients with poor survival.

Cellular and Molecular Changes in MNU-Induced Breast Tumours Injected with PF4 or bFGF

Background: Angiogenic activity has been considered to reflect important molecular events during breast tumour development. The present study concerned cellular and molecular changes of MNU-induced breast tumours subjected to promotion and suppression of angiogenesis. Methods: Female Sprague Dawley rats at the age of 21 days received MNU at the dose 70 mg/kg of body weight by intraperitoneal injection. Three months post-carcinogen initiation, mammary tumours were palpated and their growth was monitored. When the tumour diameter reached 1.0 ± 0.05 cm, rats were given bFGF or PF4 intratumourally at a dose of 10 μg/tumour. Entire palpable tumour were subsequently excised and subjected to histology examination, IHC staining, and RT-PCR. Results: No critical morphological changes were observed between pro-angiogenic factor, bFGF, and control groups. However, increase of tumour size with more necrotic and diffuse areas was notable in tumours after anti-angiogenic PF4 intervention. ER and PR mRNA expression was significantly up- and down-regulated in bFGF and PF4 groups, respectively. The trends were significantly associated with peri- and intratumoural MVD counts. However, irrespective of whether we promoted or inhibited angiogenesis, the expression of EGFR and ERBB2 continued to be significantly increased but this was not significantly associated with the MVD score. No significant differences in E-cadherin and LR gene expression were noted between intervention and control groups. Conclusion: ER and PR receptor expression shows consistent responses when tumour angiogenesis is manipulated either positively or negatively. Our study adds to current understanding that not only do we need to target hormonal receptors, as presently practiced, but we also need to target endothelial receptors to successfully treat breast cancer.

Anti-CXCL4 monoclonal antibody accelerates telogen to anagen transition and attenuates apoptosis of the hair follicle in mice

Although hair loss or alopecia is a common disease, its exact mechanisms are not yet well understood. The present study investigated the hypothesis that the homeostatic regulation of genes during hair regeneration may participate in hair loss, based on the cyclicity of hair growth. A cluster of such genes was identified by an expression gene-array from the dorsal skin in a depilated mouse model, and CXCL4 was identified as a significantly regulated gene during the hair regeneration process. To elucidate the function of CXCL4 in hair growth, CXCL4 activity was blocked by the administration of an anti-CXCL4 monoclonal antibody (mAb). Histomorphometric analysis indicated that anti-CXCL4 mAb induced an earlier anagen phase and delayed hair follicle regression, in contrast with that in the control group. Moreover, CXCL4 mAb upregulated the transcription levels of several hair growth-related genes, including Lef1, Wnt10b, Bmp4 and Bmp2. In addition, CXCL4 mAb increased the levels of the proliferation-related protein PCNA and Bcl-2 during the anagen phase, while it reduced the expression of pro-apoptotic protein Bax and cleaved caspase-3 during the catagen phase. These findings reveal that CXCL4 plays an important role in hair growth, and that blockade of CXCL4 activity promotes hair growth.

CXCR2 and CXCL4 regulate survival and self-renewal of hematopoietic stem/progenitor cells

The regulation of hematopoietic stem cell (HSC) survival and self-renewal within the bone marrow (BM) niche is not well understood. We therefore investigated global transcriptomic profiling of normal human HSC/hematopoietic progenitor cells [HPCs], revealing that several chemokine ligands (CXCL1-4, CXCL6, CXCL10, CXCL11, and CXCL13) were upregulated in human quiescent CD34(+)Hoescht(-)Pyronin Y(-) and primitive CD34(+)38(-), as compared with proliferating CD34(+)Hoechst(+)Pyronin Y(+) and CD34(+)38(+) stem/progenitor cells. This suggested that chemokines might play an important role in the homeostasis of HSCs. In human CD34(+) hematopoietic cells, knockdown of CXCL4 or pharmacologic inhibition of the chemokine receptor CXCR2, significantly decreased cell viability and colony forming cell (CFC) potential. Studies on Cxcr2(-/-) mice demonstrated enhanced BM and spleen cellularity, with significantly increased numbers of HSCs, hematopoietic progenitor cell-1 (HPC-1), HPC-2, and Lin(-)Sca-1(+)c-Kit(+) subpopulations. Cxcr2(-/-) stem/progenitor cells showed reduced self-renewal capacity as measured in serial transplantation assays. Parallel studies on Cxcl4 demonstrated reduced numbers of CFC in primary and secondary assays following knockdown in murine c-Kit(+) cells, and Cxcl4(-/-) mice showed a decrease in HSC and reduced self-renewal capacity after secondary transplantation. These data demonstrate that the CXCR2 network and CXCL4 play a role in the maintenance of normal HSC/HPC cell fates, including survival and self-renewal.

Recombinant adeno-associated virus-delivered anginex inhibits angiogenesis and growth of HUVECs by regulating the Akt, JNK and NF-κB signaling pathways

Anginex is an artificial synthetic small molecule β-sheet-forming peptide shown to have anti-angiogenesis and antitumor effects in various solid tumors. However, its molecular mechanism remains largely unclear and efficient delivery methods for anginex remains to be developed. We report on the development of recombinant adeno-associated virus (rAAV2)-delivered anginex and the underlying mechanism of anti-angiogenesis and antitumor effects of anginex. We have successfully developed the rAAV2 vector to efficiently express anginex (rAAV2‑anginex). Transduction of rAAV2-anginex significantly induced apoptosis, and inhibited the proliferation, migration, invasion and tube formation of human umbilical vein endothelial cells in vitro. Western blot analysis revealed that rAAV2‑anginex inhibited the phosphorylation of Akt, while inducing the phosphorylation of JNK and activation of the NF-κB signaling pathway. In an in vivo CAM assay and xenograft model of SKOV3, rAAV2-anginex significantly reduced microvessel density (MVD) and vascular endothelial growth factor 165 (VEGF165), as demonstrated by immunohistochemistry analysis. Importantly, rAAV2-anginex inhibited tumor growth in an ovarian cancer SKOV3 cell nude mouse xenograft model. Our results suggest that rAAV2-anginex may inhibit tumor angiogenesis and growth through regulating Akt, JNK and NF-κB signaling pathways.

Specific molecular signatures predict decitabine response in chronic myelomonocytic leukemia

Myelodysplastic syndromes and chronic myelomonocytic leukemia (CMML) are characterized by mutations in genes encoding epigenetic modifiers and aberrant DNA methylation. DNA methyltransferase inhibitors (DMTis) are used to treat these disorders, but response is highly variable, with few means to predict which patients will benefit. Here, we examined baseline differences in mutations, DNA methylation, and gene expression in 40 CMML patients who were responsive or resistant to decitabine (DAC) in order to develop a molecular means of predicting response at diagnosis. While somatic mutations did not differentiate responders from nonresponders, we identified 167 differentially methylated regions (DMRs) of DNA at baseline that distinguished responders from nonresponders using next-generation sequencing. These DMRs were primarily localized to nonpromoter regions and overlapped with distal regulatory enhancers. Using the methylation profiles, we developed an epigenetic classifier that accurately predicted DAC response at the time of diagnosis. Transcriptional analysis revealed differences in gene expression at diagnosis between responders and nonresponders. In responders, the upregulated genes included those that are associated with the cell cycle, potentially contributing to effective DAC incorporation. Treatment with CXCL4 and CXCL7, which were overexpressed in nonresponders, blocked DAC effects in isolated normal CD34+ and primary CMML cells, suggesting that their upregulation contributes to primary DAC resistance.

Association between preeclampsia and the CXC chemokine family (Review)

Preeclampsia is a major cause of maternal and perinatal mortality and morbidity, characterized by gestational hypertension, proteinuria, systemic endothelial cell activation and an exaggerated inflammatory response. The precise cause of preeclampsia is not currently known; however, it is widely accepted that the pathogenesis of preeclampsia involves inadequate trophoblast invasion, leading to generalized endothelial dysfunction and an exaggerated inflammatory response. Chemokines are a superfamily of structurally similar proteins that mediate cell recruitment, angiogenesis, immunity and stem cell trafficking. CXC chemokines are a family of cytokines, unique in their ability to behave in a disparate manner in the regulation of angiogenesis. The CXC chemokine family further divides into two subfamilies; CXC ELR+, which promotes angiogenesis, and CXC ELR-, which inhibits angiogenesis. Furthermore, CXC chemokines are involved in the pathogenesis of various conditions, including malignant tumors, wound repair, chronic inflammation, atherosclerosis and potentially preeclampsia.

Antiphospholipid antibodies attenuate endothelial repair and promote neointima formation in mice

Background

Antiphospholipid syndrome patients have antiphospholipid antibodies (aPLs) that promote thrombosis, and they have increased cardiovascular disease risk. Although the basis for the thrombosis has been well delineated, it is not known why antiphospholipid syndrome patients also have an increased prevalence of nonthrombotic vascular occlusion. The aims of this work were to determine if aPLs directly promote medial hypertrophy or neointima formation in mice and to identify the underlying mechanisms.

Methods and Results

Medial hypertrophy and neointima formation invoked by carotid artery endothelial denudation were evaluated in mice administered normal human IgG or aPLs. While aPLs had no effect on medial hypertrophy, they caused exaggerated neointima development. This was related to an aPL‐induced impairment in reendothelialization post denudation, and scratch assays in cell culture revealed that there are direct effects of aPLs on endothelium that retard cell migration. Further experiments showed that aPL antagonism of endothelial migration and repair is mediated by antibody recognition of β2‐glycoprotein I, apolipoprotein E receptor 2, and a decline in bioavailable NO. Consistent with these mechanisms, the adverse impacts of aPLs on reendothelialization and neointima formation were fully prevented by the NO donor molsidomine.

Conclusions

APLs blunt endothelial repair, and there is related aPL‐induced exaggeration in neointima formation after endothelial injury in mice. The initiating process entails NO deficiency mediated by β2‐glycoprotein I recognition by aPLs and apolipoprotein E receptor 2. The modulation of endothelial apolipoprotein E receptor 2 function or NO bioavailability may represent new interventions to prevent the nonthrombotic vascular occlusion and resulting cardiovascular disorders that afflict antiphospholipid syndrome patients.

Vascular endothelial growth factor (VEGF) and platelet (PF-4) factor 4 inputs modulate human microvascular endothelial signaling in a three-dimensional matrix migration context

The process of angiogenesis is under complex regulation in adult organisms, particularly as it often occurs in an inflammatory post-wound environment. As such, there are many impacting factors that will regulate the generation of new blood vessels which include not only pro-angiogenic growth factors such as vascular endothelial growth factor, but also angiostatic factors. During initial postwound hemostasis, a large initial bolus of platelet factor 4 is released into localized areas of damage before progression of wound healing toward tissue homeostasis. Because of its early presence and high concentration, the angiostatic chemokine platelet factor 4, which can induce endothelial anoikis, can strongly affect angiogenesis. In our work, we explored signaling crosstalk interactions between vascular endothelial growth factor and platelet factor 4 using phosphotyrosine-enriched mass spectrometry methods on human dermal microvascular endothelial cells cultured under conditions facilitating migratory sprouting into collagen gel matrices. We developed new methods to enable mass spectrometry-based phosphorylation analysis of primary cells cultured on collagen gels, and quantified signaling pathways over the first 48 h of treatment with vascular endothelial growth factor in the presence or absence of platelet factor 4. By observing early and late signaling dynamics in tandem with correlation network modeling, we found that platelet factor 4 has significant crosstalk with vascular endothelial growth factor by modulating cell migration and polarization pathways, centered around P38α MAPK, Src family kinases Fyn and Lyn, along with FAK. Interestingly, we found EphA2 correlational topology to strongly involve key migration-related signaling nodes after introduction of platelet factor 4, indicating an influence of the angiostatic factor on this ambiguous but generally angiogenic signal in this complex environment.

Role of platelet chemokines, PF-4 and CTAP-III, in cancer biology

With the recent addition of anti-angiogenic agents to cancer treatment, the angiogenesis regulators in platelets are gaining importance. Platelet factor 4 (PF-4/CXCL4) and Connective tissue activating peptide III (CTAP-III) are two platelet-associated chemokines that modulate tumor angiogenesis, inflammation within the tumor microenvironment, and in turn tumor growth. Here, we review the role of PF-4 and CTAP-III in the regulation of tumor angiogenesis; the results of clinical trial using recombinant PF-4 (rPF-4); and the use of PF-4 and CTAP-III as cancer biomarkers.

Advances and prospects of anginex as a promising anti-angiogenesis and anti-tumor agent

Anginex, a novel artificial cytokine-like peptide (βpep-25), is designed by using basic folding principles and incorporating short sequences from the β-sheet domains of anti-angiogenic agents, including platelet factor-4 (PF4), interleukin-8 (IL-8), and bactericidal-permeability increasing protein 1 (BP1). Anginex can specially block the adhesion and migration of the angiogenically activated endothelial cells (ECs), leading to apoptosis and ultimately to the inhibition of angiogenesis and tumor growth. In vitro and in vivo studies have proved its inhibitory effects on the formation of new blood vessels and tumor growth even though the mechanism is not clear. The inhibitory effects of anginex can be enhanced when it is applied in combination with other therapies, such as chemotherapy, radiotherapy and other anti-angiogenic agents. The limitations of anginex, including poor stability, short half life, complicated synthesis and low purity, have been conquered by modifying its structure or designing novel compound anginex and recombinant anginex, which makes possible the clinical application of anginex. Here, we summarize the basic and preclinical trials of anginex and discuss the prospects of anginex in clinical application. We come to the conclusion that anginex and compound or recombinant anginex can be used as effective anti-angiogenic agents.

Platelet factor 4 induces cell apoptosis by inhibition of STAT3 via up-regulation of SOCS3 expression in multiple myeloma

Platelet factor 4 (PF4) is an angiostatic chemokine that suppresses tumor growth and metastasis. We previously revealed frequent transcriptional silencing of PF4 in multiple myeloma, but the functional roles of this chemokine are still unknown. We studied the apoptotic effects of PF4 on myeloma cell lines and primary myeloma in vitro, and investigated the involved signaling pathway. The in vivo effects were also studied using a mouse model. PF4 not only suppressed myeloma-associated angiogenesis, but also inhibited growth and induced apoptosis in myeloma cells. We found that PF4 negatively regulated STAT3 and concordantly inhibited constitutive and interleukin-6-induced phosphorylation of STAT3, and down-regulated the expression of STAT3 target genes (Mcl-1, survivin and VEGF). Overexpression of constitutively activated STAT3 could rescue PF4-induced apoptotic effects. Furthermore, we found that PF4 induced the expression of SOCS3, a STAT3 inhibitor, and gene silencing of SOCS3 abolished its ability to inhibit STAT3 activation, suggesting a critical role of SOCS3 in PF4-induced STAT3 inhibition. Knockdown of LRP1, a putative PF4 receptor, could also abolish PF4-induced apoptosis and STAT3 inhibition. Finally, the tumor growth inhibitory effect of PF4 was confirmed by in vivo mouse models. Immunostaining of rabbit bone xenografts from PF4-treated mice showed induction of apoptosis of myeloma cells and inhibition of angiogenesis, which was associated with suppression of STAT3 activity. Together, our preclinical data indicate that PF4 may be a potential new targeting agent for the treatment of myeloma.

The role of CXC chemokines and their receptors in the progression and treatment of tumors

Chemokines are a class of functional chemotactic peptides that contribute to a number of tumor-related processes. They are functionally defined as soluble factors that are able to control the directional migration of leukocytes, in particular, during infection and inflammation. It appears, however, that the biological effects mediated by chemokines are far more complex, and virtually all cells, including many tumor cell types, can express chemokines and chemokine receptors. A growing body of evidence indicates that they also contribute to a number of tumor-related processes, such as tumor cell growth, angiogenesis/angiostasis, local invasion, and mediate organ-specific metastases of cancer. The CXC chemokine class is a subfamily of a large family of chemokines. During the occurrence and development of tumor cells, this chemokine class is often accompanied by a series of molecular and biological changes. The CXC chemokine subfamily is closely related to the body's immune response to tumors and biological behaviors of tumors. In this paper, CXC chemokines and their role in the progression and treatment of tumors will be reviewed.

Rapid angiogenesis onset after discontinuation of sunitinib treatment of renal cell carcinoma patients

PURPOSE

To investigate the angiogenic changes in primary tumor tissue of renal cell carcinoma (RCC) patients treated with VEGF-targeted therapy.

EXPERIMENTAL DESIGN

Phase II trials of VEGF pathway-targeted therapy given before cytoreductive surgery were carried out with metastatic RCC patients with the primary tumor in situ to investigate the necessity of nephrectomy. Primary tumor tissues were obtained and assessed for angiogenesis parameters. Results were compared with similar analyses on untreated tumors.

RESULTS

Sunitinib or bevacizumab pretreatment resulted in a significant reduction of microvessel density in the primary tumor. Also, an increase in vascular pericyte coverage was found in sunitinib-pretreated tumors, consistent with efficient angiogenesis inhibition. Expression of several key regulators of angiogenesis was found to be suppressed in pretreated tissues, among which VEGFR-1 and VEGFR-2, angiopoietin-1 and angiopoietin-2 and platelet-derived growth factor-B. In addition, apoptosis in tumor and endothelial cells was induced. Interestingly, in sunitinib-pretreated tissues a dramatic increase of the number of proliferating endothelial cells was observed, which was not the case in bevacizumab-pretreated tumors. A positive correlation with the interval between halting the therapy and surgery was found, suggesting a compensatory angiogenic response caused by the discontinuation of sunitinib treatment.

CONCLUSION

This study describes, for the first time, the angiostatic response in human primary renal cancers at the tissue level upon treatment with VEGF-targeted therapy. Discontinuation of treatment with tyrosine kinase inhibitors leads to accelerated endothelial cell proliferation. The results of this study contribute important data to the ongoing discussion on the discontinuation of treatment with kinase inhibitors.

Megakaryocytes, malignancy and bone marrow vascular niches

Dynamic interactions between hematopoietic cells and their specialized bone marrow microenvironments, namely the vascular and osteoblastic 'niches', regulate hematopoiesis. The vascular niche is conducive for thrombopoiesis and megakaryocytes may, in turn, regulate the vascular niche, especially in supporting vascular and hematopoietic regeneration following irradiation or chemotherapy. A role for platelets in tumor growth and metastasis is well established and, more recently, the vascular niche has also been implicated as an area for preferential homing and engraftment of malignant cells. This article aims to provide an overview of the dynamic interactions between cellular and molecular components of the bone marrow vascular niche and the potential role of megakaryocytes in bone marrow malignancy.

Signaling pathways governing tumor angiogenesis

Angiogenesis is regulated by the highly coordinated function of various proteins with pro- and antiangiogenic functions. Proangiogenic factors include vascular endothelial growth factor (VEGF), fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, transforming growth factor, angiopoietins, and several chemokines; antiangiogenic factors include thrombospondin-1, angiostatin, and endostatin. Matrix metalloproteinases display a dual role in vascular development. Notch signaling affects remodeling of the primary vascular network of uniformly sized vessels into functionally and morphologically distinct arteries, veins, and capillaries. Tumors, described as 'wounds that never heal', lose the appropriate balance among these factors. Although VEGF-targeted therapies are showing promise, new angiogenesis targets are needed to make additional gains. Here, we highlight recent advances in our understanding of the regulation of tumor angiogenesis and discuss the potential of molecular targeting as a new therapeutic approach.

The role of chemokines and their receptors in angiogenesis

Chemokines are a vertebrate-specific group of small molecules that regulate cell migration and behaviour in diverse contexts. So far, around 50 chemokines have been identified in humans, which bind to 18 different chemokine receptors. These are members of the seven-transmembrane receptor family. Initially, chemokines were identified as modulators of the immune response. Subsequently, they were also shown to regulate cell migration during embryonic development. Here, we discuss the influence of chemokines and their receptors on angiogenesis, or the formation of new blood vessels. We highlight recent advances in our understanding of how chemokine signalling might directly influence endothelial cell migration. We furthermore examine the contributions of chemokine signalling in immune cells during this process. Finally, we explore possible implications for disease settings, such as chronic inflammation and tumour progression.

Regulation of angiostatic chemokines driven by IL-12 and IL-27 in human tumors

Chemokines have pleiotropic effects in regulating immunity, angiogenesis, and tumor growth. CXC and CC chemokine families members and their receptors are able to exert a proangiogenic or an antiangiogenic effect in experimental models and in human tumors. In this review article, we have summarized literature data and our studies concerning the angiostatic activity of chemokines. Their angiostatic activity may be a result of a direct effect on the biological functions of endothelial cells and/or an effect on tumor cells inhibiting their capability to stimulate new blood vessel formation. Moreover, chemokines have a pro- and antitumor effect within the tumor microenvironment by regulating immune cell infiltration and its antitumor activities. We have focused our interest on the role of IL-12 and IL-27 in solid and hematological tumors, and we have suggested and discussed their potential use as antiangiogenic agents in the treatment of such tumors.

Role of endothelial chemokines and their receptors during inflammation

Chemokines are a large group of small cytokines known for their chemotactic ability to regulate the recruitment of leukocytes to sites of inflammation. This occurs through the binding of chemokines to their receptors located on the leukocyte that results in cellular changes such as actin rearrangement and cell shape, which allow for the migration of the leukocyte. In addition to regulating leukocyte function, it is now becoming apparent that other nonhematopoetic cells, such as smooth muscle cells and endothelial cells, can also be regulated by chemokines. Studies within the past 10 years has demonstrated the presence of various chemokine receptors on endothelial cells as well as the ability of chemokines to activate these receptors resulting in various cellular responses including migration, proliferation, and cellular activation. The purpose of this review is to highlight the research that has been done to date demonstrating the important role for chemokines in regulating endothelial function during various inflammatory conditions associated with angiogenesis, homeostasis, and leukocyte transmigration. This review will focus specifically on the role of the endothelium in mediating chemokine effects associated with wound healing, atherosclerosis, and autoimmune diseases, conditions where leukocyte recruitment and angiogenesis play a major role. Recent progress in the development and implementation of therapeutics agents against these small molecules, or their receptors, will also be addressed.

The role of the CXC chemokines platelet factor-4 (CXCL4/PF-4) and its variant (CXCL4L1/PF-4var) in inflammation, angiogenesis and cancer

Chemokines are chemotactic cytokines which recruit leukocytes to inflammatory sites. They also affect tumor development and metastasis by acting as growth factor, by attracting pro- or anti-tumoral leukocytes or by influencing angiogenesis. Platelet factor-4 (CXCL4/PF-4) was the first chemokine shown to inhibit angiogenesis. CXCL4L1/PF-4var, recently isolated from thrombin-stimulated platelets, differing from authentic CXCL4/PF-4 in three carboxy-terminally located amino acids, was found to be more potent than CXCL4/PF-4 in inhibiting angiogenesis and tumor growth. Both glycosaminoglycans (GAG) and CXCR3 are implicated in the activities of the PF-4 variants. This report reviews the current knowledge on the role of CXCL4/PF-4 and CXCL4L1/PF-4var in physiological and pathological processes. In particular, the role of CXCL4/PF-4 in cancer, heparin-induced thrombocytopenia and atherosclerosis is described.

CXC chemokine ligand 4 (CXCL4) down-regulates CC chemokine receptor expression on human monocytes

During acute inflammation, monocytes are essential in abolishing invading micro-organisms and encouraging wound healing. Recruitment by CC chemokines is an important step in targeting monocytes to the inflamed tissue. However, cell surface expression of the corresponding chemokine receptors is subject to regulation by various endogenous stimuli which so far have not been comprehensively identified. We report that the platelet-derived CXC chemokine ligand 4 (CXCL4), a known activator of human monocytes, induces down-regulation of CC chemokine receptors (CCR) 1, -2, and -5, resulting in drastic impairment of monocyte chemotactic migration towards cognate CC chemokine ligands (CCL) for these receptors. Interestingly, CXCL4-mediated down-regulation of CCR1, CCR2 and CCR5 was strongly dependent on the chemokine's ability to stimulate autocrine/paracrine release of TNF-α. In turn, TNF-α induced the secretion CCL3 and CCL4, two chemokines selective for CCR1 and CCR5, while the secretion of CCR2-ligand CCL2 was TNF-α-independent. Culture supernatants of CXCL4-stimulated monocytes as well as chemokine-enriched preparations thereof reproduced CXCL4-induced CCR down-regulation. In conclusion, CXCL4 may act as a selective regulator of monocyte migration by stimulating the release of autocrine, receptor-desensitizing chemokine ligands. Our results stress a co-ordinating role for CXCL4 in the cross-talk between platelets and monocytes during early inflammation.

Chemokines as mediators of tumor angiogenesis and neovascularization

Chemokines are a superfamily of structurally homologous heparin-binding proteins that influence tumor growth and metastasis. Several members of the CXC and CC chemokine families are potent inducers of neovascularization, whereas a subset of the CXC chemokines are potent inhibitors. In this paper, we review the current literature regarding the role of chemokines as mediators of tumor angiogenesis and neovascularization.

Serum protein signature may improve detection of ductal carcinoma in situ of the breast

Ductal carcinoma in situ (DCIS) of the breast is part of a spectrum of preinvasive lesions that originate within normal breast tissue and progress to invasive breast cancer. The detection of DCIS is important for the reduction of mortality from breast cancer, but the diagnosis of preinvasive breast tumors is hampered by the lack of an adequate detection method. To identify the changes in protein expression during the initial stage of tumorigenesis and to identify the presence of new DCIS markers, we analysed serum from 60 patients with breast cancer and 60 normal controls using mass spectrometry. A 23-protein index was generated that correctly distinguishes the DCIS and control groups with sensitivities and specificities in excess of 80% in two independent cohorts. Two candidate peptides were purified and identified as platelet factor 4 (PF-4) and complement C3a(desArg) anaphylatoxin (C3a(desArg)) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In an independent serum set of 165 patients, PF-4 and C3a(desArg) were significantly upregulated in DCIS compared with non-cancerous controls, as validated using western blot and enzyme-linked immunosorbent assay. We conclude that our serum protein-based test, used in conjunction with image-based screening practices, could improve the sensitivity and specificity of breast cancer detection.

Chemokines as mediators of neovascularization

Chemokines are a superfamily of homologous heparin-binding proteins, first described for their role in recruiting leukocytes to sites of inflammation. Chemokines have since been recognized as key factors mediating both physiological and pathological neovascularization in such diverse clinical settings as malignancy, wound repair, chronic fibroproliferative disorders, myocardial ischemia, and atherosclerosis. Members of the CXC chemokine family, structurally defined as containing the ELR amino acid motif, are potent inducers of angiogenesis, whereas another subset of the CXC chemokines inhibits angiogenesis. In addition, CCL2, a CC chemokine ligand, has been implicated in arteriogenesis. In this article, we review the current literature on the role of chemokines as mediators of neovascularization.

Platelet factor 4 (CXC chemokine ligand 4) differentially regulates respiratory burst, survival, and cytokine expression of human monocytes by using distinct signaling pathways

Platelet factor 4 (PF4; CXCL4) is an abundant platelet alpha-granule CXC chemokine with unique functions. Although lacking a chemotactic activity, PF4 initiates a signal transduction cascade in human monocytes leading to the induction of a broad spectrum of acute and delayed functions including phagocytosis, respiratory burst, survival, and the secretion of cytokines. Surprisingly, although these monocyte functions are well defined, only very limited information exists on the specific signaling pathways that are involved in the regulation of these biological responses. By using specific inhibitors and direct phosphorylation/activation studies, we show in the present study that PF4-mediated respiratory burst is dependent on a very rapid activation of PI3K, Syk, and p38 MAPK. Moreover, monocyte survival and differentiation instead is controlled by a delayed activation of Erk, with an activity peak after 6 h of stimulation. The inhibition of Erk completely reverted PF4-mediated protection against apoptosis. Finally, even though JNK is rapidly activated in PF4-treated monocytes, it is dispensable for the regulation of survival and respiratory burst. However, PF4-induced up-regulation of chemokine and cytokine mRNA and protein requires a sustained activation of JNK and Erk. Taken together, PF4-stimulated immediate monocyte functions (oxygen radical formation) are regulated by p38 MAPK, Syk, and PI3K, whereas delayed functions (survival and cytokine expression) are controlled by Erk and JNK.

NMR solution structure of the angiostatic peptide anginex

Anginex, a designed peptide 33mer, is known to function both as an antiangiogenic and bactericidal agent. Solving the NMR solution structure of the peptide is key to understand better its structure-activity relationships and to design more bioactive peptides and peptide mimetics. However, structure elucidation of anginex has been elusive due to subunit exchange-induced resonance broadening. Here, we found that performing NMR structural studies in a micellar environment abolishes exchange broadening and allows the structure of anginex to be determined. Anginex folds in an amphipathic, three-stranded antiparallel beta-sheet conformation with functionally key hydrophobic residues lying on one face of the beta-sheet and positively charged, mostly lysine residues, lying on the opposite face. Structural comparison is made with a homologous, yet relatively inactive peptide, betapep-28. These results contribute to the design of peptidomimetics of anginex for therapeutic use against angiogenically-related diseases like cancer, as well as infectious diseases.

Antiangiogenesis therapy using a novel angiogenesis inhibitor, anginex, following radiation causes tumor growth delay

BACKGROUND

The present study investigated whether treatment with anginex, a novel antiangiogenic peptide, could block re-vascularization after radiation treatment.

METHODS

A squamous cell (SCCVII) xenograft tumor mouse model was employed to assess the effects of anginex given post-radiation on tumor growth, microvessel density (MVD), and oxygen levels. The oxygen status was determined by the partial pressure of O2.

RESULTS

Tumors in untreated mice increased threefold in 7.0 days, anginex-treated tumors (10 mg/kg intraperitoneal, twice) required 7.3 +/- 0.9 days, and tumors exposed to 8-Gy radiation increased threefold over 11 days. Combination treatment of anginex and radiation caused the tumors to grow threefold in 16.1 +/- 1.6 days, a delay which was significant and deemed supra-additive. Oxygen levels in tumors treated by stand-alone or combination therapies were significantly reduced; for example from 19.5 +/- 4.9 mmHg in controls to 9.7 +/- 1.9 mmHg in combination-treated, size-matched tumors. In addition, immunohistochemistry showed a decrease in MVD in the tumors treated with anginex, radiation, or the combination. These results suggest that a combination of anginex and radiation can greatly affect the amount of functional vasculature in tumors and prolong radiation-induced tumor regression.

CONCLUSION

Antiangiogenesis therapy with anginex, in addition to radiotherapy, will be useful by blocking angiogenesis-dependent regrowth of vessels.

Roles of platelet factor 4 in hematopoiesis and angiogenesis

Platelet factor 4 (PF4) has been recognized as a physiological inhibitor of megakaryocytopoiesis and angiogenesis for two decades. Structure-function studies have shown that the DLQ determinant in position 54-56 is necessary for megakaryocytic inhibition whereas mutations of these residues into ELR sequence and more importantly, into DLR sequence, induce a stronger inhibitory activity of peptide p47-70 on angiogenesis. The alpha-helix region of peptides may participate in the fixation of the effector to its cellular receptor and the other important structural domains would activate the receptor. In vivo, PF4 and its related peptides can protect hematopoiesis from chemotherapy by enhancing cell viability and suppress tumor growth through anti-angiogenic pathway. Several PF4 fragments and modified molecules exhibit antiangiogenesis properties and may become an alternative for further therapeutic angiogenesis.

Application of surface enhanced laser desorption ionization time-of-flight mass spectrometry technology in the diagnosis of hepatocellular carcinoma

AIM: To explore tumor markers for the diagnosis of hepatocellular carcinoma (HCC) through detecting the serum protein spectrum differently expressed between hepatitis B virus (HBV) carriers and HCC patients.

METHODS: We detected the serum protein spectrum in 27 HCC patients, 27 HBV carriers and 25 healthy controls using surface enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS) technique, and the diagnosis model was established through analyzing the detected data by biomarker patterns software (BPS) 5.0.

RESULTS: The protein peaks, which could discriminate HBV carriers from HCC patients and healthy individuals, as well as healthy individuals from HCC patients, were detected. A diagnosis model based on the detected data was established with the specificity of 93%, 96%, 84%, and sensitivity of 85%, 96%, 89%, respectively. In addition, the 8141-Da protein in HCC patients had a higher expression than that in HBV carriers (P < 10^-5); the expression of 3448-Da protein was higher both in HCC patients and HBV carriers than that in healthy controls (P < 10^-5), but it had no significant difference between HCC patients and HBV carriers (P > 0.05), indicating that 3448-Da protein might be a potential marker for HBV infection; 7771-Da protein was differently expressed between the three groups of patients.

CONCLUSION: With a high specificity and sensitivity, the detection of serum protein spectrum can be performed easily and quickly by SELDI-TOF-MS technique, which provides a serological way for the diagnosis of HCC.

Mitogen-Activated Protein Kinase Pathway Activation by the CD6 Lymphocyte Surface Receptor

CD6 is a cell surface receptor primarily expressed on immature thymocytes and mature T and B1a lymphocytes. Through its binding to activated leukocyte cell adhesion molecule (ALCAM/CD166), CD6 is considered to play an important role in lymphocyte development and activation. Accordingly, CD6 associates with the TCR/CD3 complex and colocalizes with it at the center of the mature immunological synapse on T lymphocytes. Moreover, the CD6-ALCAM interaction has been shown to be critical for proper immunological synapse maturation and T cell proliferative responses. However, the precise biological effects of CD6 ligation and its signaling pathway are still not well understood. The present study shows that CD6 ligation with three different specific mAbs (161.8, SPV-L14.2, and MAE1-C10) induces time- and dose-dependent activation of ERK1/2 on normal and leukemic human T cells. This effect was also observed upon CD6 ligation with a chimerical ALCAM protein (ALCAM-Fc). The C-terminal cytoplasmic region of CD6, as well as Src tyrosine kinases, was critical for CD6-induced ERK1/2 activation. Synergistic effects were observed upon coligation of the TCR/CD3 complex with CD6. The ligation of CD6 induced the transcriptional activation of reporter genes under the control of the c-Fos serum responsive element and AP-1. Accordingly, CD6-mediated activation of p38 and JNK was also observed. These findings indicate that the CD6-ALCAM interaction results in activation of the three MAPK cascades, likely influencing the dynamic balance that determines whether resting or activated lymphocytes survive or undergo apoptosis.

Neutrophil adhesion to endothelial cells induced by platelet factor 4 requires sequential activation of Ras, Syk, and JNK MAP kinases

Signal transduction mechanisms associated with neutrophil activation by platelet factor 4 (PF4; CXCL4) are as yet poorly characterized. In a recent report, we showed that PF4-induced neutrophil functions (such as adhesion and secondary granule exocytosis) involve the activation of Src-kinases. By analyzing intracellular signals leading to adherence, we here demonstrate by several lines of evidence that in addition to Src-kinases, PF4 signaling involves the monomeric GTPase Ras, the tyrosine kinase Syk, and the MAP kinase JNK. Furthermore, on stimulation, GTPases Rac2 and RhoA were activated, and each was translocated to a different membrane compartment. As shown by inhibitor studies, Rac2 and JNK are located downstream of Syk and Ras. Most intriguingly, the latter 2 elements appear to control the activity of Rac2 and JNK independently of each other at different phases of the activation process. Although a first phase of Rac2 and JNK activation of up to 5 minutes is initiated by Ras, the second phase (5-30 minutes) depends predominantly on the activity of Syk. In summary, we describe that coordinated activity of Syk, Ras, and JNK mediates neutrophil adhesion to endothelial cells and that PF4 induces sequential activation of these elements.

CXC chemokines in angiogenesis

CXC chemokines display pleiotropic effects in immunity, regulating angiogenesis, and mediating organ-specific metastases of cancer. In the context of angiogenesis, CXC chemokines are a unique family of cytokines, known for their ability to behave in a disparate manner in the regulation of angiogenesis. Members that contain the 'ELR' motif are potent promoters of angiogenesis, and mediate their angiogenic activity via binding and activating CXCR2 on endothelium. In contrast, members, in general, those are inducible by interferons and lack the ELR motif (ELR-) are potent inhibitors of angiogenesis, and bind to CXCR3 on endothelium. This review will discuss the biology of these angiogenic and angiostatic CXC chemokines and discuss their disparate angiogenic activity in the context of a variety of disorders.

Discovery of novel biomarkers by microarray analysis of peripheral blood mononuclear cell gene expression in benzene-exposed workers

Benzene is an industrial chemical and component of gasoline that is an established cause of leukemia. To better understand the risk benzene poses, we examined the effect of benzene exposure on peripheral blood mononuclear cell (PBMC) gene expression in a population of shoe-factory workers with well-characterized occupational exposures using microarrays and real-time polymerase chain reaction (PCR). PBMC RNA was stabilized in the field and analyzed using a comprehensive human array, the U133A/B Affymetrix GeneChip set. A matched analysis of six exposed-control pairs was performed. A combination of robust multiarray analysis and ordering of genes using paired t-statistics, along with bootstrapping to control for a 5% familywise error rate, was used to identify differentially expressed genes in a global analysis. This resulted in a set of 29 known genes being identified that were highly likely to be differentially expressed. We also repeated these analyses on a smaller subset of 508 cytokine probe sets and found that the expression of 19 known cytokine genes was significantly different between the exposed and the control subjects. Six genes were selected for confirmation by real-time PCR, and of these, CXCL16, ZNF331, JUN, and PF4 were the most significantly affected by benzene exposure, a finding that was confirmed in a larger data set from 28 subjects. The altered expression was not caused by changes in the makeup of the PBMC fraction. Thus, microarray analysis along with real-time PCR confirmation reveals that altered expressions of CXCL16, ZNF331, JUN, and PF4 are potential biomarkers of benzene exposure.

Interferon-inducible protein 9 (CXCL11)-induced cell motility in keratinocytes requires calcium flux-dependent activation of mu-calpain

Keratinocyte migration is critical to reepithelialization during wound repair. The motility response is promoted by growth factors, cytokines, and cytokines produced in the wound bed, including those that activate the epidermal growth factor (EGF) receptor. The Alu-Leu-Arg-negative CXC chemokine interferon-inducible protein 9 (IP-9; also known as CXCL11, I-TAC, beta-R1, and H-174) is produced by keratinocytes in response to injury. As keratinocytes also express the receptor, CXCR3, this prompted us to examine the role and molecular mechanism by which IP-9 regulates keratinocyte motility. Unexpectedly, as CXCR3 liganding blocks growth factor-induced motility in fibroblasts, IP-9 alone promoted motility in undifferentiated keratinocytes (37 +/- 6% of the level of the highly motogenic EGF) as determined in a two-dimensional in vitro wound healing assay. IP-9 even enhanced EGF-induced motility in undifferentiated keratinocytes (116 +/- 5%; P < 0.05 compared to EGF alone), suggesting two separate mechanisms of action. IP-9-increased motility and -decreased adhesiveness required the intracellular protease calpain. The increases in both motility and calpain activity by IP-9 were blocked by pharmacological and molecular inhibition of phospholipase C-beta3 and chelation of calcium, which prevented an intracellular calcium flux. Molecular downregulation or RNA interference-mediated depletion of mu-calpain (calpain 1) but not M-calpain (calpain 2) blocked IP-9-induced calpain activation and motility. In accord with elimination of IP-9-induced de-adhesion, RNA interference-mediated depletion of calpain 1 but not calpain 2 prevented cleavage of the focal adhesion component focal adhesion kinase and disassembly of vinculin aggregates. In comparison, EGF-induced motility of the same undifferentiated keratinocytes requires the previously described extracellular signal-regulated kinase to the M-calpain pathway. These data demonstrate that while both EGF- and IP-9-induced motility in keratinocytes requires calpain activity, the isoform of calpain triggered depends on the nature of the receptor for the particular ligand. Interestingly, physiological nonapoptotic calcium fluxes were capable of activating mu-calpain, implying that the calcium requirement of mu-calpain for activation is attained during cell signaling. This is also the first demonstration of differential activation of the two ubiquitous calpain isoforms in the same cell by different signals.

Platelet Factor 4 and Interleukin-8 CXC Chemokine Heterodimer Formation Modulates Function at the Quaternary Structural Level

The apparent complexity of biology increases as more biomolecular interactions that mediate function become known. We have used NMR spectroscopy and molecular modeling to provide direct evidence that tetrameric platelet factor-4 (PF4) and dimeric interleukin-8 (IL8), two members of the CXC chemokine family, readily interact by exchanging subunits and forming heterodimers via extension of their antiparallel beta-sheet domains. We further demonstrate using functional assays that PF4/IL8 heterodimerization has a direct and significant consequence on the biological activity of both chemokines. Formation of heterodimers enhances the anti-proliferative effect of PF4 on endothelial cells in culture, as well as the IL8-induced migration of CXCR2 vector-transfected Baf3 cells. These results suggest that CXC chemokine biology, and perhaps cytokine biology in general, may be functionally modulated at the molecular level by formation of heterodimers. This concept, in turn, has implications for designing chemokine/cytokine variants with modified biological properties.

Heparin Accelerates Pulmonary Artery Development in Neonate Rabbits

Pulmonary vascular resistance drops sharply within a few minutes after birth for the survival of neonates. A majority of this resistance is caused by "pulmonary vascular bed" or vessel lacking smooth muscle cells. Heparin is known to promote proliferation and development of endothelial cells and to subsequently decrease their overall vascular resistance, but its detailed features remained unknown. Therefore, in this study we treated neonatal rabbits with heparin, protamine (antagonist of heparin), or saline, and evaluated histopathological features of vascular endothelial cells using two different types of computer assisted image analysis, i.e., CAS200 and NIH image. These two systems detected the percentage of vascular endothelial area per fields (VA) and CD31-positive area per total area of tissue following subtraction of background stain. CD31 was used as an endothelial cell marker. Heparin treated rabbits were associated with significant decrement of pulmonary/systemic artery pressure (Pp/Ps) (21.0 +/- 6.0%) compared to protamine (29.9 +/- 6.1%) or saline (29.4 +/- 3.0%) treated animals. The values of VA obtained by the two image analyses (CAS200 and NIH image) were significantly increased in heparin treated animals (38.4 +/- 3.2% determined by CAS200 and 24.0 +/- 1.3% by NIH image) compared to protamine (30.2 +/- 3.9% and 19.2 +/- 1.8%) or saline (33.2 +/- 1.5% and 20.8 +/- 3.8%) treated animals on 14th day of treatment. The present study indicates that heparin accelerates pulmonary vascular bed development probably by increasing the number and volume of endothelial cells, which subsequently contributes to the decrease in pulmonary vascular resistance.

Recent developments in the inhibition of angiogenesis: examples from studies on platelet factor-4 and the VEGF/VEGFR system

Inhibition of angiogenesis is an important strategy to block tumor growth and invasion. We discuss herein results from our ongoing investigations on platelet factor-4 (PF-4) and the VEGF/VEGFR system. Platelet factor-4 (PF-4) is an anti-angiogenic ELR-negative chemokine. PF-4 inhibits endothelial cell proliferation and migration, and angiogenesis in vitro and in vivo. We have studied the structure and anti-angiogenic activities of a C-terminal fragment of PF-4 named PF-4 CTF. This molecule retains anti-angiogenic activity, blocks the interaction of angiogenesis factors with their receptors and may also be improved by mutation or domain-swapping. It seems, therefore, to be a good candidate for further development. Furthermore, we have developed a cyclic vascular endothelial growth inhibitor (Cyclo VEGI) from the structure of VEGF-A. In aqueous solution, cyclo-VEGI adopts an alpha helix conformation. Cyclo-VEGI inhibits binding of iodinated VEGF(165) to endothelial cells and angiogenesis. Furthermore, cyclo-VEGI significantly blocks the growth of established intracranial glioma in nude and syngeneic mice and improves survival.

Platelet factor 4 disrupts the intracellular signalling cascade induced by vascular endothelial growth factor by both KDR dependent and independent mechanisms

The mechanism by which the CXC chemokine platelet factor 4 (PF-4) inhibits endothelial cell proliferation is unclear. The heparin-binding domains of PF-4 have been reported to prevent vascular endothelial growth factor 165 (VEGF(165)) and fibroblast growth factor 2 (FGF2) from interacting with their receptors. However, other studies have suggested that PF-4 acts via heparin-binding independent interactions. Here, we compared the effects of PF-4 on the signalling events involved in the proliferation induced by VEGF(165), which binds heparin, and by VEGF(121), which does not. Activation of the VEGF receptor, KDR, and phospholipase Cgamma (PLCgamma) was unaffected in conditions in which PF-4 inhibited VEGF(121)-induced DNA synthesis. In contrast, VEGF(165)-induced phosphorylation of KDR and PLCgamma was partially inhibited by PF-4. These observations are consistent with PF-4 affecting the binding of VEGF(165), but not that of VEGF(121), to KDR. PF-4 also strongly inhibited the VEGF(165)- and VEGF(121)-induced mitogen-activated protein (MAP) kinase signalling pathways comprising Raf1, MEK1/2 and ERK1/2: for VEGF(165) it interacts directly or upstream from Raf1; for VEGF(121), it acts downstream from PLCgamma. Finally, the mechanism by which PF-4 may inhibit the endothelial cell proliferation induced by both VEGF(121) and VEGF(165), involving disruption of the MAP kinase signalling pathway downstream from KDR did not seem to involve CXCR3B activation.

Suppression of tumor growth by viral vector-mediated gene transfer of N-terminal truncated platelet factor 4

Platelet factor four (PF4), an inhibitor of endothelial cell proliferation in vitro, inhibits angiogenesis and tumor growth in vivo in experimental animals. The present study was designed to determine whether gene therapy-mediated expression of a form of PF4 lacking 16 amino acids of N-terminus from tumor cells could inhibit angiogenesis and tumor growth in vivo. Two replication-defective recombinant retroviral vectors were constructed. One encodes human PF4 (rRV-PF4) and the other encodes the N-truncated peptide (rRVp17-70). These vectors were then used to transduce KB cells, a human head and neck squamous carcinoma cell line. Expression of PF4 and p17-70 transgenes was confirmed by Western blot analysis. In vitro, both rRV-PF4 and rRVp17-70 were able to inhibit selectively the proliferation of human umbilical vascular endothelial cells (HUVEC) but not KB cells. In vivo activity was assessed by injecting 10(7) KB cells subcutaneously into nude mice and by monitoring subsequent tumor growth, xenograft vascular histochemistry, and animal survival. Viral vector-mediated cDNA transfer of PF4 and p17-70 resulted in inhibiting solid tumors through an anti-angiogenic action in vivo. Our data indicate that targeting tumor angiogenesis using viral-mediated gene transfer of full-length and N-terminal truncated PF4 represents a promising strategy for cancer gene therapy.

Cancer immunotherapy with chemoattractant peptides

The chemokine/chemokine receptor network is an essential part of an intricate system of immunosurveillance and homeostasis, it promotes or suppresses neovascularization, affects and regulates directly or indirectly growth and metastasis of malignant cells. Numerous studies have been conducted to harness this network as therapeutic agents for cancer to redress the chemokine balance and control angiogenesis and tumour growth and metastasis. Second generation of immunotherapeutics and chemoattractant-based vaccines use chemokines and chemoattractant peptides to elicit antitumor immunity by a specific targeting and modulating subsets of effector leukocytes, including professional antigen presenting cells.

Design of a partial peptide mimetic of anginex with antiangiogenic and anticancer activity

Based on structure-activity relationships of the angiostatic beta-sheet-forming peptide anginex, we have designed a mimetic, 6DBF7, which inhibits angiogenesis and tumor growth in mice. 6DBF7 is composed of a beta-sheet-inducing dibenzofuran (DBF)-turn mimetic and two short key amino acid sequences from anginex. This novel antiangiogenic molecule is more effective in vivo than parent anginex. In a mouse xenograft model for ovarian carcinoma, 6DBF7 is observed to reduce tumor growth by up to 80%. It is suggested that the activity is based on antiangiogenesis, because in vitro tube formation is inhibited, and because treatment of tumor-bearing mice led to a significant reduction in microvessel density within the tumor. This partial peptide mimetic is the first endothelial cell-specific molecule designed as a substitute for an angiostatic inhibitory peptide.