Suppressed NFAT-dependent VEGFR1 expression and constitutive VEGFR2 signaling in infantile hemangioma

Infantile hemangiomas are localized and rapidly growing regions of disorganized angiogenesis. We demonstrate that expression of VEGFR1 in hemangioma endothelial cells (hemEC) and tissue is only 10−20% of that in controls. Low VEGFR1 levels result in VEGF-dependent activation of VEGFR2 and downstream pathways. We show that VEGFR1 transcription is NFAT-dependent, and that low VEGFR1 expression in hemEC is caused by reduced activity of a pathway involving β1 integrin, the integrin-like receptor TEM8, VEGFR2 and NFAT. In a subset of individuals with hemangioma, we find missense mutations in VEGFR2 or TEM8. Further studies indicate that the mutations result in increased interaction between VEGFR2, TEM8 and β1 integrin and inhibition of integrin activity. Normalization of the constitutive VEGFR2-signaling in hemEC with soluble VEGFR1 and antibodies that block VEGF or stimulate β1 integrin suggests that local administration of these or similar agents may be effective in hemangioma treatment.