A Vacca

Bone marrow angiogenesis and mast cell density increase simultaneously with progression of human multiple myeloma

SummaryImmunohistochemical, cytochemical and ultrastructural data showing vivid angiogenesis and numerous mast cells (MCs) in the bone marrow of 24 patients with active multiple myeloma (MM) compared with 34 patients with non-active MM and 22 patients with monoclonal gammopathy of undetermined significance (MGUS) led us to hypothesize that angiogenesis parallels progression of MM, and that MCs participate in its induction via angiogenic factors in their secretory granules.

Angiogenesis extent and macrophage density increase simultaneously with pathological progression in B-cell non-Hodgkin’s lymphomas

SummaryNode biopsies of 30 benign lymphadenopathies and 71 B-cell non-Hodgkin’s lymphomas (B-NHLs) were investigated for microvessel and macrophage counts using immunohistochemistry and morphometric analysis. Both counts were significantly higher in B-NHL. Moreover, when these were grouped into low-grade and high-grade lymphomas, according to the Kiel classification and Working Formulation (WF), statistically significant higher counts were found in the high-grade tumours. Immunohistochemistry and electron microscopy revealed a close spatial association between microvessels and macrophages. Overall, the results suggest that, in analogy to what has already been shown in solid tumours, angiogenesis occurring in B-NHLs increases with tumour progression, and that macrophages promote the induction of angiogenesis via the release of their angiogenic factors.

The history of the angiogenic switch concept

Spontaneously arising tumor cells are not usually angiogenic at first. The phenotypic switch to angiogenesis is usually accomplished by a substet that induces new capillaries that then converge toward the tumor. The switch clearly involves more than simple upregulation of angiogenic activity and is thought to be the result of a net balance of positive and negative regulators. Tumor growth is although to require disruption of this balance and hence this switch must turned on for cancer progression. Progenitor endothelial cells, the crosstalk between angiogenic factors and their receptors and the interaction between vasculogenesis and lymphangiogenesis are all factors that may contribute to the switch. Its promotion is also the outcome of genetic instability resulting in the emergence of tumor cell lines. This review describes the history of the angiogenic switch illustrated in the literature and with particular reference to the three transgenic mouse models, namely RIP1-TAG2, keratin-14 (K14) (human papilloma virus) HPV16 and papilloma virus, used for stage-specific assessment of the effects of antiangiogenic and antitumorigenic agents.

Importance of the bone marrow microenvironment in inducing the angiogenic response in multiple myeloma

Tumor microenvironment is essential for tumor cell proliferation, angiogenesis, invasion and metastasis through its provision of survival signals, secretion of growth and pro-angiogenic factors, and direct adhesion molecule interactions. This review examines its importance in the induction of an angiogenic response in multiple myeloma (MM). The encouraging results of preclinical and clinical trials in which MM has been treated by targeting the tumor microenvironment are also discussed.

In vivo activation of JAK2/STAT-3 pathway during angiogenesis induced by GM-CSF

Besides the regulation of hematopoiesis, granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) induces the expression of a functional program in cultured endothelial cells (ECs) related to angiogenesis and to the their survival in bone marrow microenvironment. ECs express the specific GM‐CSF receptor that signals through the recruitment and the activation of Janus kinase (JAK)2 (Soldi et al., Blood 89, 863–872, 1987). We now report that GM‐CSF in vivo induces angiogenesis and activates JAK‐2 and signal transducers and activators of transcription (STAT)‐3. This cytokine has an angiogenetic activity in chick chorioallantoic membrane (CAM) without recruitment of inflammatory cells and induces vessel sprouting from chicken aorta rings. When added to CAM, subnanomolar concentrations of GM‐CSF cause a rapid phosphorylation in tyrosine residues of JAK‐2 persisting at least for 10 min. Furthermore, we show that signal transducers and activators of transcription (STAT)‐3, but not STAT‐5, also are phosphorylated for 30 min after GM‐CSF stimulation. AG‐490, a JAK‐2 inhibitor, reduced in a dose‐dependent manner the angiogenic effect of GM‐CSF in CAM. These findings provide the first evidence that the JAK‐2/STAT‐3 pathway is activated in vivo and participates in vessel formation triggered by GM‐CSF.

Inhibition of endothelial cell functions and of angiogenesis by the metastasis inhibitor NAMI-A

NAMI-A is a ruthenium-based compound with selective anti-metastasis activity in experimental models of solid tumours. We studied whether this activity was dependent on anti-angiogenic ability of NAMI-A. We thus investigated its in vitro effects on endothelial cell functions necessary for angiogenesis to develop, as well as its in vivo effects in the chick embryo chorioallantoic membrane model. Endothelial cell proliferation, chemotaxis, and secretion of the matrix-degrading enzyme metalloproteinase-2 were inhibited by NAMI-A in a dose-dependent manner, and without morphologic signs of cell apoptosis or necrosis. Lastly, NAMI-A displayed a dose-dependent in vivo anti-angiogenic activity in the chorioallantoic membrane model. These data suggest that the anti-angiogenic activity of NAMI-A can contribute to its anti-metastatic efficacy in mice bearing malignant solid tumours.

Vasculogenic mimicry by bone marrow macrophages in patients with multiple myeloma

Bone marrow macrophages of patients with active and nonactive multiple myeloma (MM), monoclonal gammopathies of undetermined significance (MGUS) and benign anemia (controls) were stimulated for 7 days with vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), and analysed for the expression of endothelial cell (EC) markers by reverse transcription (RT)–PCR, real-time RT–PCR, western blot and immunofluorescence. Their vasculogenic ability was investigated in vitro in a Matrigel assay and in vivo on bone marrow biopsies through dual immunofluorescence and confocal laser microscopy. Active MM macrophages exposed to VEGF and bFGF acquired EC markers and formed capillary-like structures mimicking paired bone marrow ECs (multiple myeloma patient-derived endothelial cells, MMECs), with major responsiveness compared to macrophages from nonactive MM, MGUS or controls. Bone marrow biopsies of active MM harbored ‘mosaic’ vessels, being formed by MMECs, EC-like macrophages and macrophages themselves. These figures were rare in nonactive MM and absent in MGUS or controls. Our data indicate that macrophages contribute to build neovessels in active MM through vasculogenic mimicry, and this ability proceeds parallel to progression of the plasma cell tumors. Macrophages may be a target for the MM antivascular treatment.

Do mast cells help to induce angiogenesis in B-cell non-Hodgkin's lymphomas?

Morphological and morphometric data showing a higher number of mast cells (MCs) in the stroma of B-cell non-Hodgkins lymphomas (B-NHL) than in benign lymphadenopathies are presented in support of the suggestion that angiogenesis during the progression of B-NHL may be partly mediated by angiogenic factors in their secretory granules.

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

Bone marrow samples from 30 patients with myelodysplastic syndromes (MDS) grouped according to the International Prognostic Scoring System for MDS were investigated for counts of microvessels, total metachromatic mast cells (MC) and MC expressing tryptase, an angiogenesis-inducing molecule. Counts were higher in patients with a poor prognosis. The observation of a high correlation between microvessel counts and both total metachromatic and tryptase-reactive MC in all samples suggests that angiogenesis in MDS increases with their progression and that MC may intervene in the angiogenic response in MDS through tryptase contained in their secretory granules.

Crosstalk between angiogenesis and lymphangiogenesis in tumor progression

Extensive studies have identified reliable markers of lymphatic endothelial cells, and mechanisms and molecules that regulate development and growth of the lymphatic vessels. Vascular endothelial growth factors (VEGF)-C and VEGF-D, and their cognate receptor tyrosine kinase, VEGF receptor-3 (VEGFR-3), are critical regulators of lymphangiogenesis. By binding to its endothelial cell surface receptors VEGFR-1 and VEGFR-2, VEGF-A mediates vascular leakage, endothelial proliferation and migration. Angiopoietin-2 (Ang-2) is expressed at sites of blood vessel remodeling and invasion, and factors that induce angiogenesis in vivo, such as VEGF-A, upregulate Ang-2 in endothelial cells. In this review, we summarize the literature concerning the crosstalk between angiogenesis and lymphangiogenesis in tumor progression, that is, involvement of VEGF-C, VEGF-D and VEGFR-3 in angiogenesis, and the role played by VEGF-A and Ang-2 in lymphangiogenesis, respectively.