Proliferative hemangiomas: Analysis of cytokine gene expression and angiogenesis

Hemangiomas are benign vascular tumors of childhood that can lead to disfig urement and/or life-threatening consequences. The pathogenesis of hemangiom a formation is likely to involve increased angiogenesis. Basic fibroblast g rowth factor and vascular endothelial growth factor are cytokines that stim ulate angiogenesis in multiple in vivo and in vitro models. Proliferative h emangiomas have been found to have elevated levels of basic fibroblast grow th factor and vascular endothelial growth factor protein, but the gene expr ession of these cytokines in human specimens has not been previously studie d. We examined the gene expression and spatial distribution of basic fibrob last growth factor and vascular endothelial growth factor messenger RNA in proliferative versus involuted human hemangioma specimens using nonisotopic in situ hybridization techniques. Thirteen hemangioma specimens were harvested during initial surgical excisi on. In situ hybridization was performed on frozen sections of both prolifer ative and involuted hemangioma specimens using genetically engineered antis ense probes specific for basic fibroblast growth factor and vascular endoth elial growth factor messenger RNA. Controls were an interleukin-6 sense seq uence and a transforming growth factor-beta 1 antisense sequence. A large number of cells within the specimens of proliferative hemangiomas r evealed localized gene expression of basic fibroblast growth factor and vas cular endothelial growth factor messenger RNA (626 +/- 129 and 1660 +/- 371 cells/mm(2), respectively). The majority of the cells were endothelial in origin. In contrast, involuted hemangioma specimens revealed significantly lower numbers of cells staining positive for basic fibroblast growth factor and vascular endothelial growth factor messenger RNA (44 +/- 11 and 431 +/ - 76 cells/mm(2), respectively; p < 0.05). Transforming growth factor-beta 1 messenger RNA was slightly more expressed by involuted hemangiomas (117 /- 30 cells/mm(2)). There were very low levels of transforming growth facto r-beta 1 gene expression from proliferative hemangiomas (37 +/- 24 cells/mm (2); p < 0.02). These data demonstrate that (1) in situ hybridization allows identification and relative quantitation of cells expressing messenger RNA for specific g rowth factors in human hemangioma specimens; (2) basic fibroblast growth fa ctor and vascular endothelial growth factor messenger RNA are up-regulated in proliferative hemangiomas; and (3) transforming growth factor-beta 1 mes senger RNA remains low in both proliferative and involuted hem angiomas. Be cause basic fibroblast growth factor and vascular endothelial growth factor messenger RNA have been implicated in the pathobiology of human hemangioma formation, biochemical modulation of these angiogenic cytokines may eventu ally help inhibit proliferation and promote regression of hemangiomas.