Angiogenesis, or the formation of new blood vessels out of pre-existing capillaries, is a sequence of events that is fundamental to many physiologic and pathologic processes such as cancer, ischemic diseases, and chronic inflammation. With the identification of several proangiogenic molecules such as the vascular endothelial cell growth factor, the fibroblast growth factors (like in FGFs), and the angiopoietins, and the recent description of specific inhibitors of angiogenesis such as platelet factor-4, angiostatin, endostatin, and vasostatin, it is recognized that therapeutic interference with vasculature formation offers a tool for clinical applications in various pathologies. Whereas inhibition of angiogenesis can prevent diseases with excessive vessel growth such as cancer, diabetes retinopathy, and arthritis, stimulation of angiogenesis would be beneficial in the treatment of diseases such as coronary artery disease and critical limb ischemia in diabetes. In this review we highlight the current knowledge on angiogenesis regulation and report on the recent findings in angiogenesis research and clinical studies. We also discuss the potentials, limitations, and challenges within this field of research, in light of the development of new therapeutic strategies for diseases in which angiogenesis plays an important role.

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Angiogenesis: Potentials for Pharmacologic Intervention in the Treatment of Cancer, Cardiovascular Diseases, and Chronic Inflammation

Infantile hemangiomas are endothelial tumors that grow rapidly in the first year of life and regress slowly during early childhood. Although hemangiomas are well-known vascular lesions, little is known about the mechanisms that cause the excessive endothelial cell proliferation in these most common tumors of infancy. To investigate the molecular basis of hemangioma, we isolated endothelial cells from several proliferative-phase lesions and showed that these cells are clonal and exhibit abnormal properties in vitro (E. Boye, Y. Yu, G. Paranya, J. B. Mulliken, B. R. Olsen, J. Bischoff: Clonality and altered behavior of endothelial cells from hemangiomas. J Clin Invest 2001, 107:745–752). Here, we analyzed mRNA expression patterns of genes required for angiogenesis, including members of the vascular endothelial growth factor (VEGF)/VEGF receptor family and the angiopoietin/Tie family, in hemangioma-derived and normal endothelial cells. KDR, Flt-1, Tie1, Tie2, and angiopoietin-2 (Ang2) were strongly expressed in cultured hemangioma-derived endothelial cells and in hemangioma tissue. In contrast, there was little expression of angiopoietin-1 (Ang1) or VEGF. We found Tie2 mRNA and protein up-regulated with a concomitant increase in cellular responsiveness to Ang1 in most hemangioma-derived endothelial cells. Ang2 mRNA was down-regulated in response to serum in hemangioma-derived endothelial cells, but not in normal endothelial cells, suggesting altered regulation. These findings implicate Tie2 and its ligands Ang1 and Ang2 in the pathogenesis of hemangioma.

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Increased Tie2 Expression, Enhanced Response to Angiopoietin-1, and Dysregulated Angiopoietin-2 Expression in Hemangioma-Derived Endothelial Cells

OBJECTIVES. Oral systemic corticosteroids are the mainstay of treatment for problematic hemangiomas; however, current information is based on anecdotal experience and retrospective studies. We aimed to determine whether systemic steroids are efficacious in proliferating hemangioma and to compare the efficacy and safety of 2 corticosteroid treatment modalities. PATIENTS AND METHODS. Twenty patients with problematic hemangiomas of infancy were randomly assigned to either daily oral prednisolone or monthly intravenous pulses of methylprednisolone. Their clinical outcomes (improvement using a visual analog score) and adverse events were compared at 3 months from baseline and 1 year of age. Data on possible surrogate markers of angiogenesis were available for the first 3 months. RESULTS. At 3 months, orally treated patients had a median visual analog score of 70 compared with 12 in the intravenous group. This response pattern was similar at the patients9 first birthday: 50.0 vs −1.5. Additional treatment beyond 3 months was needed for 65% of the patients (7 in the intravenous and 6 in the oral group). Six of 8 patients with impaired vision at enrollment had an improved function at 1 year (4 patients in the intravenous group and 3 patients in the oral group). Of the 4 surrogate markers of angiogenesis measured (plasma basic fibroblast growth factor, vascular endothelial growth factor, vascular cellular adhesion molecule 1, endoglin, and urine basic fibroblast growth factor), the only 2 that decreased over time were vascular cellular adhesion molecule 1 and endoglin. Patients in the oral group had a higher rate of adverse effects, such as hypertension (18.6% vs 13.1%), abnormal cortisol (78% vs 60%), and growth retardation. CONCLUSIONS. Systemic corticosteroids are efficacious in stopping the proliferation of hemangiomas. The oral corticosteroids offered more clinical and biological benefit than the pulse steroids with higher risk of adverse effects.

Oral Versus High-Dose Pulse Corticosteroids for Problematic Infantile Hemangiomas: A Randomized, Controlled Trial

Vascular tumors of infancy and childhood: beyond capillary hemangioma.

Background: Increased angiogenesis and eventual involution are major characteristics of neonatal hemangiomas. The mechanism to explain this transition is not completely understood.



Methods: To determine the nature of these changes, endothelial cells were isolated from eight hemangiomas and the growth characteristics and morphology of these cells were compared to cells isolated from normal fetal and neonatal skin. Three cells lines were further characterized by analyzing protein expression with immunhistochemistry and FACS analysis.



Results: Hemangioma endothelial cells converted to a spindle-shaped morphology similar to that of fetal endothelial cells whereas neonatal endothelial cells maintained their characteristic epithelioid morphology. While neonatal, hemangioma and fetal endothelial cells continued to express platelet-endothelial cell adhesion molecule-1 (PECAM-1) and von Willebrand factor (vWf), hemangioma and fetal cells expressed both proteins at a lower level and in a distribution distinct from normal neonatal endothelial cells. Neonatal endothelial cells continued to express epithelial specific Type IV collagen, while hemangioma and fetal endothelial cells produced interstitial Type I collagen.



Conclusions: Both cell morphology and protein expression of neonatal hemangioma endothelial cells were more characteristic of embryonic microvascular endothelial cells than that of postembryonic cells demonstrating a similarity in these two cell types and suggesting a dysfunction in the normal growth and maturation of endothelial cells in this tumor.

In vitro characteristics of neonatal hemangioma endothelial cells: similarities and differences between normal neonatal and fetal endothelial cells

Cellular adhesion molecules are newly identified mediators of angiogenesis. Infantile hemangiomas, characterized in the early stages by a proliferation of poorly differentiated vessels followed in the late stages by a vascular differentiation and regression of the tumor, represent an interesting model to study angiogenesis. We studied by immunohistochemistry the distribution of HLA-DR and three adhesion molecules ICAM-3, E-selectin and VCAM-1 on endothelial cells in different stages of vessel differentiation in infantile hemangiomas. We found high levels of ICAM-3 expression on proliferating vessels, while its expression was low or undetectable on well differentiated vessels. A different set of E-selectin antibodies showed a more heterogenous pattern of distribution and VCAM-1 antigens were found in both proliferating and differentiated vessels. HLA-DR expression on endothelial cells was inversely correlated to the vascular differentiation. Our results are consistent with the hypothesis that ICAM-3 plays a role in the early stages of vessel formation. Our results also suggest that variation of E-selectin and HLA-DR expression may be related either to vessel differentiation or may reflect the acquisition of an activated endothelial cell status.

ICAM-3 and E-selectin endothelial cell expression differentiate two phases of angiogenesis in infantile hemangiomas.

Large congenital melanocytic naevi (LCMN) represent the main risk factor for development of melanoma in childhood. This retrospective study of 10 cases of melanoma in patients with LCMN used fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) (6 cases) to elucidate the clinical, histological, and cytogenetic characteristics of this rare disorder. Six melanomas were found within the LCMN, the others in lymph nodes, subcutis and brain. The LCMN was located on the trunk in 8 cases, with satellite naevi in 6 cases. Two distinct groups emerged: 5 melanomas that developed before the age of 10 years and the other after 20 years. The mortality rate was 60% and clearly correlated with clinical stage at diagnosis. Histological diagnosis was difficult in only 2 patients in whom neither immunohistochemistry nor FISH were helpful. Otherwise, CGH showed a high number of chromosomal aberrations leading to a formal diagnosis.

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Malignant Melanoma Arising in Patients with a Large Congenital Melanocytic Naevus: Retrospective Study of 10 Cases with Cytogenetic Analysis.

Verrucous hemangioma or verrucous venous malformation is a superficial venous malformation frequently misdiagnosed as a lymphatic malformation because of its classical hyperkeratotic appearance. Clinical characteristics of VVM were studied in patients with a histologically confirmed VVM, and validated in a prospective study of 18 patients. VVM was made of separated vascular elements with irregular shape, in a linear disposition, with variable thickness and keratosis. Its specific vascular pattern consisting of an erythematous patch with scattered small red to violet dots was easily identified using dermoscopy. In many cases, the typical clinical presentation of verrucous hemangioma is sufficient to establish the diagnosis and a biopsy may not be required.

Bertrand Chrétien-Marquet

Papers

ICAM-3 and E-selectin endothelial cell expression differentiate two phases of angiogenesis in infantile hemangiomas.

Malignant Melanoma Arising in Patients with a Large Congenital Melanocytic Naevus: Retrospective Study of 10 Cases with Cytogenetic Analysis.

Verrucous hemangioma (also known as verrucous venous malformation): A vascular anomaly frequently misdiagnosed as a lymphatic malformation