Correlation of bone marrow angiogenesis and mast cells with tryptase activity in myelodysplastic syndromes

Adipocytes, mast cells and angiogenesis

Healthy adipose tissue contains a wide variety of innate and adaptive immune cells, including macrophages, dendritic cells, mast cells, eosinophils, neutrophils, and lymphocytes. Numerous signaling molecules in the adipose microenvironment can positively or negatively modulate angiogenic processes, regulate the interaction between the vascular system and adipocytes, and participate in tumor progression. Mast cells are involved in the new formation or metabolism of fat, are present in abundant quantities in fatty tissue, among fat cells, and a number of mediators released from mast cells play a role in adipogenesis. Moreover, mast cells produce several pro-angiogenic factors and are involved in tumor angiogenesis. In this context, the angiogenic effect might be amplified when the adipocytes and mast cells act in concert, and treatment of adipose tissue- and mast cell-associated cancers with anti-angiogenic drugs may represent an alternative or adjuvant strategy for the treatment of these tumors.

Mast cells: A double-edged sword in cancer

Mast cells (MCs), a type of innate immune cells, are derived from myeloid stem cells, sometimes known as mastocytes or labrocytes, and contain many granules rich in histamine and heparin. The mentioned cells are able to release various mediators such as cytokines, leukotrienes, and a large number of proteases into the environment. Many studies and experiments have established the infiltration of MCs into the tumor site. However, the findings are highly controversial to determine whether these immune cells contribute to the growth and development of the tumor or cause anti-tumor immune responses. Various studies have revealed that MCs have a pro-tumorigenic or anti-tumorigenic role depending on the type of cancer, the degree of tumor progression, and the location of these immune cells in the tumor bulk. Although these types of immune cells cause angiogenesis and tumor progression in some cancers, they have a significant anti-tumor role in some other types of cancers. In general, although a number of studies have specified the protective role of MCs in cancers, the increased number of MCs in the blood and microenvironment of tumors, as well as the increased level of angiogenesis and tumor progression, has been indicated in another array of studies. The function of MCs against or in favor of the cancers still requires further investigations to more accurately and specifically determine the role of MCs in the cancers. The function of MCs in tumors and their various roles in case of exposure to the cancer cells have been addressed in the present review. The concluding section of the present study recommends a number of methods for modification of MCs in cancer immunotherapy.

Mast Cells and Angiogenesis in Human Plasma Cell Malignancies

Bone marrow angiogenesis plays an important role in the pathogenesis and progression of hematological malignancies. It is well known that tumor microenvironment promotes tumor angiogenesis, proliferation, invasion, and metastasis, and also mediates mechanisms of therapeutic resistance. An increased number of mast cells has been demonstrated in angiogenesis associated with hematological tumors. In this review we focused on the role of mast cells in angiogenesis in human plasma cell malignancies. In this context, mast cells might act as a new target for the adjuvant treatment of these tumors through the selective inhibition of angiogenesis, tissue remodeling and tumor-promoting molecules, permitting the secretion of cytotoxic cytokines and preventing mast cell-mediated immune suppression.

The dual role of mast cells in tumor fate

The exact role of mast cells in tumor growth is not clear and multifaceted. In some cases, mast cells stimulate while in others inhibit this process. This dual role may be explained to some extent by the huge number of bioactive molecules stored in mast cell granules, as well as differences between tumor microenvironment, tumor type, and tumor phase of development.

Mast cells and cancer

Mast cells (MCs) are a potent proangiogenic factor in tumors, they product several pro-angiogenic factors such as fibroblast growth factor 2 (FGF-2), vascular epithelial growth factor (VEGF), tryptase and chymase. Tryptase is a serine protease classified as α-tryptase and β-tryptase, both produced by MCs. Tryptase degrades the tissues, playing an important role in angiogenesis and in the development of metastases. Serum tryptase increases with age, with increased damage to cells and risk of developing a malignancy and it could be considered the expression of a fundamental role of MCs in tumor growth or, on the contrary, in the antitumor response. Many biomarkers have been developed in clinical practice for improving diagnosis and prognosis of some neoplasms. Elevated tryptase levels are found in subgroups of patients with haematologic and solid cancers. In the current review, we want to update the perspectives of tryptase as a potential biomarker in daily practice in different neoplasms.

Spatial distribution of mast cells around vessels and glands in human gastric carcinoma

The spatial distribution of mast cells inside the tumor stroma has been little investigated. In this study, we have evaluated tumor mast cells (MCs) distribution in gastric cancer through the analysis of the morphological features of the spatial patterns generated by these cells, including size, shape, and architecture of the cell pattern. The pattern of distribution of tryptase- and chymase-positive MCs around the blood vessels and gastric glands in human gastric adenocarcinoma samples was investigated by immunohistochemical techniques and by introducing a quantitative approach to characterize the spatial distribution of MCs. In human gastric cancer, both chymase-positive MC and vessels exhibited significant deviations from randomness for what it concerns their spatial relationship with gastric parenchyma. As indicated by cell-to-gland distances shorter than expected by chance, in grade II samples a preferential localization of chymase-positive MC near the gastric glands was observed. Interestingly, the same type of spatial association was exhibited by vessels in grade IV samples, where vessel-to-gland distances shorter than expected by chance were observed. These two findings allow to speculate about a sequence of events in which a subpopulation of MC is first recruited around gastric parenchyma to drive the subsequent development of a vascular support to the tissue.

Colorectal cancer-promoting activity of the senescent peritoneal mesothelium

Gastrointestinal cancers metastasize into the peritoneal cavity in a process controlled by peritoneal mesothelial cells (HPMCs). In this paper we examined if senescent HPMCs can intensify the progression of colorectal (SW480) and pancreatic (PSN-1) cancers in vitro and in vivo. Experiments showed that senescent HPMCs stimulate proliferation, migration and invasion of SW480 cells, and migration of PSN-1 cells. When SW480 cells were injected i.p. with senescent HPMCs, the dynamics of tumor formation and vascularization were increased. When xenografts were generated using PSN-1 cells, senescent HPMCs failed to favor their growth. SW480 cells subjected to senescent HPMCs displayed up-regulated expression of transcripts for various pro-cancerogenic agents as well as increased secretion of their products. Moreover, they underwent an epithelial-mesenchymal transition in the Smad 2/3-Snail1-related pathway. The search for mediators of senescent HPMC activity showed that increased SW480 cell proliferation was stimulated by IL-6, migration by CXCL8 and CCL2, invasion by IL-6, MMP-3 and uPA, and epithelial-mesenchymal transition by TGF-β1. Secretion of these agents by senescent HPMCs was increased in an NF-κB- and p38 MAPK-dependent mechanism. Collectively, our findings indicate that in the peritoneum senescent HPMCs may create a metastatic niche in which critical aspects of cancer progression become intensified.

Non-random spatial relationships between mast cells and microvessels in human endometrial carcinoma

Mast cells (MCs) accumulate in the stroma surrounding tumors, where they secrete angiogenic cytokines and proteases, and an increased number of MCs have been demonstrated in angiogenesis associated with solid and hematological tumors. The aim of this study is to contribute to the knowledge of distribution of MCs in tumors, investigating the pattern of distribution of tryptase-positive MCs around the blood vessels in human endometrial carcinoma samples by introducing a quantitative approach to characterize their spatial distribution. The results have shown that in human endometrial cancer bioptic specimens the spatial distribution of MCs shows significant deviation from randomness as compared with control group in which, instead, the spatial distribution of MCs is consistent with a random distribution. These findings confirm that MCs enhance tumor angiogenesis and their preferential localization along blood vessels and sites of new vessel formation sustaining the suggestion for an association between MCs and angiogenesis. However, this spatial association between vessels and MCs might simply reflect migrating MCs from the blood stream at vessel growing sites.

Mast cells: potential positive and negative roles in tumor biology

Mast cells are immune cells that reside in virtually all vascularized tissues. Upon activation by diverse mechanisms, mast cells can secrete a broad array of biologically active products that either are stored in the cytoplasmic granules of the cells (e.g., histamine, heparin, various proteases) or are produced de novo upon cell stimulation (e.g., prostaglandins, leukotrienes, cytokines, chemokines, and growth factors). Mast cells are best known for their effector functions during anaphylaxis and acute IgE-associated allergic reactions, but they also have been implicated in a wide variety of processes that maintain health or contribute to disease. There has been particular interest in the possible roles of mast cells in tumor biology. In vitro studies have shown that mast cells have the potential to influence many aspects of tumor biology, including tumor development, tumor-induced angiogenesis, and tissue remodeling, and the shaping of adaptive immune responses to tumors. Yet, the actual contributions of mast cells to tumor biology in vivo remain controversial. Here, we review some basic features of mast cell biology with a special emphasis on those relevant to their potential roles in tumors. We discuss how using in vivo tumor models in combination with models in which mast cell function can be modulated has implicated mast cells in the regulation of host responses to tumors. Finally, we summarize data from studies of human tumors that suggest either beneficial or detrimental roles for mast cells in tumors.

Tryptase, a novel angiogenic factor stored in mast cell granules

Human mast cells (MCs) are a rich reservoir of neutral proteases, packed in large amounts in their granules and comprising a high fraction of all cellular proteins. Among these proteases, tryptase is involved in angiogenesis after its release from activated MC granules, as it has been demonstrated in different in vitro and in vivo assays. Moreover, tryptase-positive MCs increase in number and vascularization increases in a linear fashion in different solid and hematological tumors. This complex interplay between MCs and tumor angiogenesis have led to consider the therapeutic use of angiogenesis inhibitors, which specifically target the angiogenic activity of tryptase, such as gabexate mesilate and nafamostat mesilate, two inhibitors of trypsin-like serine proteases.

Targeting mast cells tryptase in tumor microenvironment: a potential antiangiogenetic strategy

Angiogenesis is a complex process finely regulated by the balance between angiogenesis stimulators and inhibitors. As a result of proangiogenic factors overexpression, it plays a crucial role in cancer development. Although initially mast cells (MCs) role has been defined in hypersensitivity reactions and in immunity, it has been discovered that MCs have a crucial interplay on the regulatory function between inflammatory and tumor cells through the release of classical proangiogenic factors (e.g., vascular endothelial growth factor) and nonclassical proangiogenic mediators granule-associated (mainly tryptase). In fact, in several animal and human malignancies, MCs density is highly correlated with tumor angiogenesis. In particular, tryptase, an agonist of the proteinase-activated receptor-2 (PAR-2), represents one of the most powerful angiogenic mediators released by human MCs after c-Kit receptor activation. This protease, acting on PAR-2 by its proteolytic activity, has angiogenic activity stimulating both human vascular endothelial and tumor cell proliferation in paracrine manner, helping tumor cell invasion and metastasis. Based on literature data it is shown that tryptase may represent a promising target in cancer treatment due to its proangiogenic activity. Here we focused on molecular mechanisms of three tryptase inhibitors (gabexate mesylate, nafamostat mesylate, and tranilast) in order to consider their prospective role in cancer therapy.

Possible biological and translational significance of mast cells density in colorectal cancer

Mast cells (MCs), located ubiquitously near blood vessels, are descended from CD34⁺ hematopoietic stem cells. Initially, although their role has been well defined in hypersensitivity reactions, the discovery of their sharing in both innate and adaptive immunity has allowed to redefine their crucial interplay on the regulatory function between inflammatory and tumor cells through the release of mediators granule-associated (mainly tryptase and vascular endothelial growth factor). In particular, in several animal and human malignancies it has been well demonstrated that activated c-Kit receptor (c-KitR) and tryptase (an agonist of the proteinase-activated receptor-2) take pivotal part in tumor angiogenesis after the MCs activation, contributing to tumor cells invasion and metastasis. In this review, we focused on crucial MCs density (MCD) role in colorectal cancer (CRC) development and progression angiogenesis-mediated; then, we will analyze the principal studies that have focused on MCD as possible prognostic factor. Finally, we will consider a possible role of MCD as novel therapeutic target mainly by c-KitR tyrosine kinase inhibitors (imatinib, masitinib) and tryptase inhibitors (gabexate and nafamostat mesylate) with the aim to prevent CRC progression.

The role of inflammatory cells in angiogenesis in multiple myeloma

Both innate and adaptive immune cells are involved in the mechanisms of endothelial cell proliferation, migration and activation, via production and release of a large spectrum of pro-angiogenic mediators, thus creating the specific microenvironment that favors increased rate of tissue vascularization. In this article, we focus on the immune cell component of the angiogenic process occurring during multiple myeloma progression. We also provide information on some anti-angiogenic properties of immune cells that may be applied for a potential pharmacological use as anti-angiogenic agents in the disease treatment.

Mast cells and macrophages exert beneficial and detrimental effects on tumor progression and angiogenesis

Mast cells and macrophages are critical regulators of inflammation and immunological response in the tumor microenvironment. Increased number of mast cells and macrophages have been reported to correlate with poor prognosis in numerous solid and hematological tumors. In contrast to their pro-tumorigenic role, mast cells and macrophages have shown also anti-tumorigenic effect in certain malignancies, for example by supporting cancer rejection. Thus, mast cells and macrophages can exert both detrimental and beneficial effects on tumor progression. Mast cell- and macrophages-derived growth factors able to promote tumor development and angiogenesis include TNF-α, TGF-β1, FGF-2, VEGF, PDGF, IL-8, osteopontin, and NGF. On the contrary, mast cell- and macrophages-produced cytokines that may participate in anti-tumor response include IL-1, IL-2, IL-4, IL-10, and IFN-γ. It is to note that mast cells and macrophages may also show beneficial and detrimental effects in the same cancer depending on the tumor stage.

Tryptase serum levels in patients suffering from hepatocellular carcinoma undergoing intra-arterial chemoembolization: Possible predictive role of response to treatment

Tryptase is a serin protease stored in mast cell granules that has recently been found to be involved in tumor angiogenesis. Data from experimental tumor models have suggested that prior to the onset of angiogenesis mast cells were accumulated near tumor cells and were required for the macroscopic expansion and metastatic spread of primary tumor cells. Hepatocellular cancer (HCC) is a well-established, highly angiogenesis-dependent hypervascular tumor. The aim of this preliminary study was to assess tryptase serum levels in 30 HCC patients prior and subsequent to hepatic transarterial chemoembolization (TACE). In this study, patients with intermediate stage (B) HCC, according to the Barcelona Clinic Liver Cancer (BCLC) staging classification, were enrolled. Additional patient features were adequate liver functional reserve and A or B status, according to the Child-Pugh classification. Tryptase levels were measured using the UniCAP-Tryptase fluoroimmunoassay. TACE was performed by loading doxorubicin on microspheres. The mean ± standard deviation (SD) tryptase level pre-TACE was 7.74±3.62 μg/l, and post-TACE 4.67±2.79 μg/l. A statistically significant difference (P<0.001) was detected, using the Student's t-test, between pre- and post-TACE tryptase level concentrations. No correlations were found between tryptase levels and other important clinicopathological features of patients. This is the first preliminary study analyzing the potential significance of serum tryptase levels in HCC patients. The results demonstrated higher serum tryptase levels in HCC patients, suggesting tryptase release from HCC tissue. As expected, after TACE, serum tryptase levels were decreased. Therefore, we suggested that tryptase was a potential biomarker of response to TACE treatment in HCC patients.

The mandibular ridge oral mucosa model of stromal influences on the endothelial tip cells: an immunohistochemical and TEM study

This study aimed to evaluate by immunohistochemistry and transmission electron microscopy (TEM) the morphological features of the oral mucosa endothelial tip cells (ETCs) and to determine the immune and ultrastructural patterns of the stromal nonimmune cells which could influence healing processes. Immune labeling was performed on bioptic samples obtained from six edentulous patients undergoing surgery for dental implants placement; three normal samples were collected from patients prior to the extraction of the third mandibular molar. The antibodies were tested for CD34, CD117(c-kit), platelet derived growth factor receptor-alpha (PDGFR-α), Mast Cell Tryptase, CD44, vimentin, CD45, CD105, alpha-smooth muscle actin, FGF2, Ki67. In light microscopy, while stromal cells (StrCs) of the reparatory and normal oral mucosa, with a fibroblastic appearance, were found positive for a CD34/CD44/CD45/CD105/PDGFR-α/vimentin immune phenotype, the CD117/c-kit labeling led to a positive stromal reaction only in the reparatory mucosa. In TEM, non-immune StrCs presenting particular ultrastructural features were identified as circulating fibrocytes (CFCs). Within the lamina propria CFCs were in close contact with ETCs. Long processes of the ETCs were moniliform, and hook-like collaterals were arising from the dilated segments, suggestive for a different stage migration. Maintenance and healing of oral mucosa are so supported by extensive processes of angiogenesis, guided by ETCs that, in turn, are influenced by the CFCs that populate the stromal compartment both in normal and reparatory states. Therefore, CFCs could be targeted by specific therapies, with pro- or anti-angiogenic purposes.

Mast cells, angiogenesis and cancer

Mast cells (MCs) were first described by Paul Ehrlich 1 in his doctoral thesis. MCs have long been implicated in the pathogenesis of allergic reactions and certain protective responses to parasites. As most tumors contain inflammatory cell infiltrates, which often include plentiful MCs, the question as to the possible contribution of MCs to tumor development has progressively been emerging. In this chapter, the specific involvement of MCs in tumor biology and tumor fate will be considered, with particular emphasis on the capacity of these cells to stimulate tumor growth by promoting angiogenesis and lymphangiogenesis. Data from experimental carcinogenesis and from different tumor settings in human pathology will be summarized. Information to be presented will suggest that MCs may serve as a novel therapeutic target for cancer treatment.

Mast cells, angiogenesis, and tumour growth

Accumulation of mast cells (MCs) in tumours was described by Ehrlich in his doctoral thesis. Since this early account, ample evidence has been provided highlighting participation of MCs to the inflammatory reaction that occurs in many clinical and experimental tumour settings. MCs are bone marrow-derived tissue-homing leukocytes that are endowed with a panoply of releasable mediators and surface receptors. These cells actively take part to innate and acquired immune reactions as well as to a series of fundamental functions such as angiogenesis, tissue repair, and tissue remodelling. The involvement of MCs in tumour development is debated. Although some evidence suggests that MCs can promote tumourigenesis and tumour progression, there are some clinical sets as well as experimental tumour models in which MCs seem to have functions that favour the host. One of the major issues linking MCs to cancer is the ability of these cells to release potent pro-angiogenic factors. This review will focus on the most recent acquisitions about this intriguing field of research. This article is part of a Special Issue entitled: Mast cells in inflammation.

Mast cells and angiogenesis in gastric carcinoma

Previous studies have shown that increased vascularity is associated with haematogenous metastasis and poor prognosis in gastric cancer. The role of mast cells in gastric cancer angiogenesis has not been clarified completely. In this study, we correlated microvascular density and tryptase- and chymase-positive mast cells with histopathological type in gastric cancer. Specimens of primary gastric adenocarcinomas obtained from 30 patients who had undergone curative gastrectomy were investigated immunohistochemically by using anti-CD31 antibody to stain endothelial cells and anti-tryptase and anti-chymase antibodies to stain mast cells. The results showed that stage IV gastric carcinoma has a higher degree of vascularization than other stages and that both tryptase- and chymase-positive mast cells increase in parallel with malignancy grade even if the density of chymase-positive mast cells was significantly lower than the density of tryptase-positive mast cells and is highly correlated with the extent of angiogenesis. This study has demonstrated that mast cell density correlates with angiogenesis and progression of patients with gastric carcinoma. Understanding the mechanisms of gastric cancer angiogenesis provides a basis for a rational approach to the development of an antiangiogenic therapy in patients with this malignancy.

A comparative study of the spatial distribution of mast cells and microvessels in the foetal, adult human thymus and thymoma

Mast cells (MCs) are widely distributed in human and animal tissues and have been shown to play an important role in angiogenesis in normal and pathological conditions. Few data are available about the relationship between MCs and blood vessels in the normal human thymus, and there are virtually no data about their distribution and significance in thymoma. The aim of this study was to analyse the spatial distribution of MCs and microvessels in the normal foetal and adult thymus and thymoma. Twenty biopsy specimens of human thymus, including foetal and adult normal thymus and thymoma were analysed. Double staining with CD34 and mast cell tryptase was used to count both mast cells and microvessels in the same fields. Computer-assisted image analysis was performed to characterize the spatial distribution of MCs and blood vessels in selected specimens. Results demonstrated that MCs were localized exclusively to the medulla. Their number was significantly higher in thymoma specimens as compared with adult and foetal normal specimens respectively. In contrast the microvessel area was unchanged. The analysis of the spatial distribution and relationship between MCs and microvessels revealed that only in the thymoma specimens was there a significant spatial association between MCs and microvessels. Overall, these data suggest that MCs do not contribute significantly to the development of the vascular network in foetal and adult thymus, whereas in thymoma they show a close relationship to blood vessels. This could be an expression of their involvement not only in endothelial cells but also in tumour cell proliferation.

Immune cells and angiogenesis

Both innate and adaptive immune cells are involved in the mechanisms of endothelial cell proliferation, migration and activation, through the production and release of a large spectrum of pro-angiogenic mediators. These may create the specific microenvironment that favours an increased rate of tissue vascularization. In this review, we will focus on the immune cell component of the angiogenic process in inflammation and tumour growth. As angiogenesis is the result of a net balance between the activities exerted by positive and negative regulators, we will also provide information on some antiangiogenic properties of immune cells that may be utilized for a potential pharmacological use as antiangiogenic agents in inflammation as well as in cancer.

Mast cells and angiogenesis in haematological malignancies

Tumor cells are surrounded by an infiltrate of inflammatory cells, namely lymphocytes, neutrophils, macrophages and mast cells (MCs). Increasing evidence indicates that MCs play a role in tumor growth and tumor-related angiogenesis in both solid and haematological tumors. In this review article, we discuss the involvement of MCs in angiogenesis in haematological malignancies and suggest that MCs might act as a new target for the adjuvant treatment of these tumors through the selective inhibition of angiogenesis.

The controversial role of mast cells in tumor growth

Mast cells (MCs) were first described by Paul Ehrlich (Beiträge zur Theorie und Praxis der Histologischen Färbung, Thesis, Leipzig University, 1878). They have long been implicated in the pathogenesis of allergic reactions and protective responses to parasites. However, their functional role has been found to be complex and multifarious. MCs are also involved in various cell-mediated immune reactions and found in tissues from multiple disease sites, and as a component of the host reaction to bacteria, parasite, and even virus infections. They also participate in angiogenic and tissue repair processes after injury. The importance of a possible functional link between chronic inflammation and cancer has long been recognized. As most tumors contain inflammatory cell infiltrates, which often include plentiful MCs, a possible contribution of these cells to tumor development has emerged. In this review, general biology of mast cells, their development, anatomical distribution, and phenotype as well as their secretory products will first be discussed. The specific involvement of MCs in tumor biology and tumor fate will then be considered, with particular emphasis on their capacity to stimulate tumor growth by promoting angiogenesis and lymphangiogenesis. Finally, it is suggested that mast cells may serve as a novel therapeutic target for cancer treatment.

Angiogenesis and mast cells in human breast cancer sentinel lymph nodes with and without micrometastases

AIMS

An increasing number of mast cells have been reported in angiogenesis associated with solid and haematopoietic tumours. Data concerning the number of mast cells in neoplastic lymph nodes and their relationship with microvessel density are controversial. The aim was to correlate the extent of angiogenesis with the number of mast cells reactive with tryptase in biopsy specimens of sentinel lymph nodes with and without micrometastases obtained from patients with breast cancer.

METHODS AND RESULTS

Specimens from sentinel lymph nodes obtained from 80 patients (40 with and 40 without micrometastases) were investigated immunohistochemically by using anti-CD31 and anti-tryptase antibodies. Angiogenesis, measured as microvessel counts, increased in parallel with the number of tryptase-positive mast cells and their values were significantly higher in lymph nodes with micrometastases compared with those without.

CONCLUSIONS

Tryptase-positive mast cells may contribute, at least in part, to angiogenesis occurring in sentinel lymph nodes with micrometastases from patients with breast cancer.

Tryptase- and leptin-positive mast cells correlate with vascular density in uterine leiomyomas

OBJECTIVE

In vitro and in vivo studies have linked mast cell (MC) degranulation and activation with angiogenesis and neovascularization. This assumption is partially supported by the close anatomical association between MC and the vasculature and the recruitment of these cells during tumor growth. The aim of this study was to correlate the extent of angiogenesis with the number of MC expressing tryptase and leptin in human leiomyomas.

STUDY DESIGN

Tissues from human leiomyomas and control specimens were investigated immunohistochemically, using murine monoclonal antibodies against the endothelial cell marker CD31, leptin, and the MC marker tryptase.

RESULTS

Angiogenesis, measured as microvessel counts, was highly correlated with MC tryptase- and leptin-positive cell counts.

CONCLUSION

These data suggest that angiogenesis in leiomyomas is correlated to expression of tryptase in MC granules and provide for the first time evidence of a putative role of leptin, also contained in MC secretory granules, in MC-dependent angiogenesis.

Expression and functions of the vascular endothelial growth factors and their receptors in human basophils

Angiogenesis is a multistep complex phenomenon critical for several inflammatory and neoplastic disorders. Basophils, normally confined to peripheral blood, can infiltrate the sites of chronic inflammation. In an attempt to obtain insights into the mechanism(s) underlying human basophil chemotaxis and its role in inflammation, we have characterized the expression and function of vascular endothelial growth factors (VEGFs) and their receptors in these cells. Basophils express mRNA for three isoforms of VEGF-A (121, 165, and 189) and two isoforms of VEGF-B (167 and 186). Peripheral blood and basophils in nasal polyps contain VEGF-A localized in secretory granules. The concentration of VEGF-A in basophils was 144.4 +/- 10.8 pg/10(6) cells. Immunologic activation of basophils induced the release of VEGF-A. VEGF-A (10-500 ng/ml) induced basophil chemotaxis. Supernatants of activated basophils induced an angiogenic response in the chick embryo chorioallantoic membrane that was inhibited by an anti-VEGF-A Ab. The tyrosine kinase VEGFR-2 (VEGFR-2/KDR) mRNA was expressed in basophils. These cells also expressed mRNA for the soluble form of VEGFR-1 and neuropilin (NRP)1 and NRP2. Flow cytometric analysis indicated that basophils express epitopes recognized by mAbs against the extracellular domains of VEGFR-2, NRP1, and NRP2. Our data suggest that basophils could play a role in angiogenesis and inflammation through the expression of several forms of VEGF and their receptors.

Angiogenesis in relation to clinical stage, apoptosis and prognostic score in myelodysplastic syndromes

The International Prognostic Scoring System (IPSS), based on the number of cytopenias, percentage of bone marrow blasts and cytogenetics, is an important prognostic tool for patients with myelodysplastic syndrome (MDS). In addition, factors such as high bone marrow cellularity and lactate dehydrogenase levels have been associated with an adverse outcome, spontaneously and after chemotherapy. Recently, increased bone marrow angiogenesis, measured as, e.g. microvascular density (MVD), was reported to be more intense in high-risk than in low-risk MDS. To assess the prognostic role of MVD in MDS, a cohort of 56 patients, thoroughly investigated for various clinical and morphological parameters, were followed-up for survival > or =60 months after the diagnostic analysis. As a group MDS patients had higher MVD compared to healthy controls (p<0.02). The highest median MVD value was observed in the RAEB group, but there was no overall significant difference between the FAB groups. No significant correlations were observed between MVD and peripheral blood counts, bone marrow cellularity, percentage of bone marrow blasts and CD34 positive cells, apoptotic index (TUNEL), proliferation index (MIB-1), erythroid index, FAB group and IPSS score. MVD was not correlated to overall survival. In contrast, bone marrow blast count <5%, low or normal cellularity, as well as a high erythroid index, indicated a favorable survival. Thus, our data do not support an important prognostic role of angiogenesis, reflected by microvessel density, in the myelodysplastic syndromes.

Neovascularization and mast cells with tryptase activity increase simultaneously with pathologic progression in human endometrial cancer

OBJECTIVE

In vitro and in vivo studies have linked mast cell (MC) degranulation and activation with angiogenesis and neovascularization. This assumption is partially supported by the close anatomic association between MC and the vasculature and the recruitment of these cells during tumor growth. The aim of this study was to correlate the extent of angiogenesis with the number of MC expressing tryptase in human endometrial adenocarcinoma.

STUDY DESIGN

Tissues from human endometrial hyperplasia and endometrial adenocarcinoma were investigated immunohistochemically, using 2 murine monoclonal antibodies against the endothelial cell marker CD31 and the MC marker tryptase.

RESULTS

Angiogenesis, measured as microvessel counts, was highly correlated with MC tryptase-positive cell counts and that these parameters increase in agreement with tumor progression.

CONCLUSION

These results suggest that angiogenesis in endometrial cancer increases with tumor progression and that angiogenic tryptase secreted by host MC cooperate in its induction.

Mast cell contribution to angiogenesis related to tumour progression

The current wisdom is that tumours are endowed with an angiogenic capability and that their growth, invasion and metastasis are angiogenesis dependent. It is now well documented that neoplastic cells are influenced by their microenvironment and vice versa. The specific organ microenvironment determines the extent of cancer cell proliferation, angiogenesis, invasion and survival. Tumour cells are surrounded by an infiltrate of inflammatory cells, namely lymphocytes, neutrophils, macrophages and mast cells (MCs), which communicate via a complex network of intercellular signalling pathways, mediated by surface adhesion molecules, cytokines and their receptors. This review article summarizes: (i) the MC mediators involved in angiogenesis; (ii) the experimental evidence concerning the role played by MCs in angiogenesis; (iii) the list of solid and haematological tumours in which a close relationship between angiogenesis, tumour progression and MCs has been demonstrated; (iv) the circumstances in which MCs are a critical source of angiogenic factors in vivo, and in such cases, the signals that regulate their production and secretion that need to be determined as a prelude to the elaboration of new therapeutic strategies associated with MC presence and activation.

Relation between bone marrow angiogenesis and serum levels of angiogenin in patients with myelodysplastic syndromes

Angiogenesis is implicated in the progression of myelodysplastic syndromes (MDS). Bone marrow microvascular density (MVD), serum angiogenin (ANG) and interleukin 6 (IL-6) were measured in 67 patients with untreated MDS. MVD, ANG and IL-6 were significantly higher in the patient group as a whole when compared to controls (P < 0.01). MVD and ANG were significantly higher in subtypes with a high-risk for leukemic transformation (RAEB, RAEB-t and CMML) than in low-risk subtypes (RA and RARS) (P < 0.01). In the MDS group, a positive correlation was found between ANG and IL-6 (P < 0.001) and also between MVD and IL-6 (P < 0.05). Using multivariate analysis, only IL-6 displayed independent prognostic value and was inversely related to MDS survival.

Role of human mast cells and basophils in bronchial asthma

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.

Prostaglandin E2 induces degranulation-independent production of vascular endothelial growth factor by human mast cells

Mast cells accumulate in large numbers at angiogenic sites, where they have been shown to express a number of proangiogenic factors, including vascular endothelial growth factor (VEGF-A). PGE(2) is known to strongly promote angiogenesis and is found in increased levels at sites of chronic inflammation and around solid tumors. The expression pattern of VEGF and the regulation of VEGF-A by PGE(2) were examined in cord blood-derived human mast cells (CBMC). CBMC expressed mRNA for five isoforms of VEGF-A and other members of the VEGF family (VEGF-B, VEGF-C, and VEGF-D) with strong expression of the most potent secretory isoforms. PGE(2) was a very strong inducer of VEGF-A(121/165) production by CBMC and also elevated VEGF-A mRNA expression. The amount of VEGF-A(121/165) protein production induced by PGE(2) was 4-fold greater than that induced by IgE-mediated activation of CBMC. Moreover, the response to PGE(2) as well as to other cAMP-elevating agents such as forskolin and salbutamol was observed under conditions that were not associated with mast cell degranulation. CBMC expressed substantial levels of the EP(2) receptor, but not the EP(4) receptor, when examined by flow cytometry. In contrast to other reported PGE(2)-mediated effects on mast cells, VEGF-A(121/165) production occurred via activation of the EP(2) receptor. These data suggest a role for human mast cells as a potent source of VEGF(121/165) in the absence of degranulation, and may provide new opportunities to regulate angiogenesis at mast cell-rich sites.

Angiogenesis in acute and chronic lymphocytic leukemia

The bone marrow microenvironment plays a crucial role in leukemogenesis. Recent studies suggest that its vascularity changes significantly during this process and that angiogenic factors are of major importance in leukemia. This review summarizes the literature concerning the relationship between angiogenesis and the progression of acute and chronic lymphocytic leukemia. It is becoming increasingly evident that agents which interfere with angiogenesis also block tumor progression and anti-angiogenic management has become a prominent aspect of pre-clinical and clinical assessment. Recent applications of anti-angiogenic agents which interfere with or block leukemia progression are reviewed.

A possible role of tryptase in angiogenesis in the brain of mdx mouse, a model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is characterized by muscle degeneration and affects the CNS. Dystrophin is absent in muscle and CNS of both DMD patients and mdx mouse, a model of DMD. While the involvement of vascular compartment in DMD was poorly investigated, some studies suggested a role for mast cells (MC). Tryptase, contained in the MC granules, stimulates angiogenesis in vitro and in vivo. We demonstrated for the first time a correlation between the extent of angiogenesis and the number of tryptase-positive neurons and microvessels and suggest that the tryptase contained in the neurons and in the endothelial cells of the mdx mouse brain may be involved in the regulation of angiogenesis taking place in mdx mouse.

Low mast cell density in the human duodenal mucosa from chronic inflammatory duodenal bowel disorders is associated with defective villous architecture

BACKGROUND

Mast cells (MC) have recently been implicated in the processes of tissue homeostasis, remodeling and repair.

DESIGN

In this study, the total and tryptase-reactive mast cell populations were quantified in the duodenal mucosa of 27 subjects suffering from chronic inflammatory bowel disorders. Mast cell density was both related to the general villous architecture (normal or defective) and to the microvascular density in the duodenal mucosa.

RESULTS

Total mast cell and tryptase-positive mast cell subpopulation densities were found to be significantly reduced in the samples with defective villous architecture in comparison with those exhibiting a normal villous profile. In these last samples, a relevant proportion of mucosal mast cells exhibited ultrastructural features of secretory activity, in particular piecemeal degranulation. Finally, no correlation was established between microvascular density and tryptase activity, as it has been previously demonstrated in other pathological conditions.

CONCLUSIONS

Overall, these findings indicate a significant correlation between mast cell density and the duodenal mucosal architecture.

Tumor vascularity and tryptase-positive mast cells correlate with a poor prognosis in melanoma

BACKGROUND

The importance of angiogenesis in melanoma has been controversial and is not homogeneous. Mast cell density (MCD) is highly correlated with the extent of both normal and pathological angiogenesis, such as that in chronic inflammatory diseases and tumours.

METHODS

We evaluated the prognostic significance of tumour microvascular density (MVD) and MCD in 25 advanced melanoma patients after resection and a 4-5-year follow up: 48% of the patients were alive and free of metastases (good prognostic subgroup); 16% had developed regional nodal metastases (intermediate prognostic subgroup); and 36% had died (poor prognostic subgroup). Tissues samples were investigated immunohistochemically to count microvessels and mast cells with an antifactor VIII and an antitryptase antibody, respectively.

RESULTS

Immunohistological staining showed a higher number of microvessels and mast cells in melanoma lesions of poor prognosis as compared with intermediate prognosis and with good prognosis, respectively.

CONCLUSIONS

These data agree with those showing a close relationship between MCD and angiogenesis during tumour progression and demonstrate, for the first time, a prognostic significance of MCD in human melanoma.