Biomolecular markers and involution of hemangiomas.

BACKGROUND/PURPOSE: Vascular anomalies are a diverse set of lesions with distinct clinical behaviors, whose biomolecular characteristics are largely undefined. Common hemangiomas proliferate during the first year of life, then involute at a variable pace over several years. Other vascular tumors may involute much more quickly (rapidly involuting congenital hemangiomas [RICH]), not at all (lymphatic malformation), or display malignant behavior (angiosarcoma). Key cytokines driving angiogenesis include vascular endothelial growth factor (VEGF) family members/receptors (placental growth factor [PIGF], VEGF-A, and VEGF-C) and angiopoietins. The authors hypothesized that involuting hemangiomas would display biologic markers distinctly different from noninvoluting vascular lesions. METHODS: Six patient samples were analyzed: (1) RICH, (2) proliferating hemangioma, (3) involuting hemangioma, (4) tufted angioma, (5) hepatic angiosarcoma, and (6) lymphatic malformation. Detailed examination of endothelial/vascular mural cell status was performed by fluorescent double-label immunostaining using specific markers (PECAM-1, alphaSMA) in combination with markers of proliferation (anti-phospho-histone H3) or apoptosis (TUNEL). Expression of PIGF, VEGF-A, VEGF-C, and Ang-1 was localized by in situ hybridization. RESULTS: Involuting/proliferating common hemangiomas demonstrated vasculature with abundant vascular mural cells (alphaSMA+); in contrast, alphaSMA(+) cells were rare in RICH vessels. Endothelial apoptosis was increased dramatically, but proliferation was unchanged during involution. VEGF-A was expressed in all lesions except lymphatic malformation, which displayed VEGF-C and Ang-1 upregulation. Strikingly, PIGF expression was increased markedly in the lesions predicted to involute/actively involuting but was virtually absent from noninvoluting tumors. CONCLUSIONS: Vessel architecture and endothelial/vascular mural cell status differed between lesions, differentiating even common versus rapidly involuting hemangioma and corresponded to clinical involution. VEGF-A expression characterized endothelial-derived lesions, whereas VEGF-C marked lymphatic-derived cells. PIGF expression occurred only in vascular anomalies predicted to involute or actively involuting, a pattern potentially linked to PIGF function as a conditional antagonist of VEGF-A. Thus, distinct patterns of morphology and angiogenic factor expression characterize vascular anomalies with different clinical behaviors.

Anti-VEGF antibody in experimental hepatoblastoma: suppression of tumor growth and altered angiogenesis.

BACKGROUND: Hepatoblastoma is the most common primary hepatic malignancy of childhood, frequently presenting as advanced disease. Vascular endothelial growth factor (VEGF) is an endothelial mitogen and survival factor critical to growth and angiogenesis in many human cancers. Inhibition of VEGF effectively suppresses tumorigenesis in multiple experimental models. The authors hypothesized that anti-VEGF antibody would alter vascular architecture and impede tumor growth in experimental hepatoblastoma. METHODS: The Institutional Animal Care and Use Committee of Columbia University approved all protocols. Xenografts were established in athymic mice by intrarenal injection of cultured human hepatoblastoma cells. Anti-VEGF antibody (100 microg/dose) or vehicle was administered intraperitoneally 2 times per week for 5 weeks. At week 6, 10 control/treated mice were killed and remaining animals maintained without treatment until week 8. Tumor weights were compared by Kruskal-Wallis analysis, and vascular alterations ascertained by fluorescein angiography and specific immunostaining. RESULTS: Anti-VEGF antibody significantly inhibited tumor growth at 6 weeks (1.85 g +/- 0.60 control, 0.05 +/- 0.03 antibody, P <.0003). In comparison with controls, treated xenografts showed decreased vascularity and dilated surviving vessels with prominent vascular smooth muscle elements. CONCLUSIONS: Specific anti-VEGF therapy inhibits neoangiogenesis and significantly suppresses tumor growth in experimental hepatoblastoma. Surviving vasculature displays dilation and increased vascular smooth muscle. Anti-VEGF agents may represent new therapeutic alternatives for children with advanced disease.

Regression of established tumors and metastases by potent vascular endothelial growth factor blockade.

Vascular endothelial growth factor (VEGF) is a critical promoter of blood vessel growth during embryonic development and tumorigenesis. To date, studies of VEGF antagonists have primarily focused on halting progression in models of minimal residual cancer. Consistent with this focus, recent clinical trials suggest that blockade of VEGF may impede cancer progression, presumably by preventing neoangiogenesis. However, VEGF is also a key mediator of endothelial-vascular mural cell interactions, a role that may contribute to the integrity of mature vessels in advanced tumors. Here, we report that high-affinity blockade of VEGF, using the recently described VEGF-Trap, abolishes mature, preexisting vasculature in established xenografts. Eradication of vasculature is followed by marked tumor regression, including regression of lung micrometastases. Thus, the contribution of relatively low levels of VEGF to vessel integrity may be critical to maintenance of even very small tumor masses. Potent blockade of VEGF may provide a new therapeutic option for patients with bulky, metastatic cancers.