Steroid therapy of a proliferating hemangioma: histochemical and molecular changes.

OBJECTIVES: Hemangioma is a primary tumor of the microvasculature in which angiogenesis is initially excessive, followed by regression of the newly formed vessels. Intervention is necessary in up to 20% of cases, high-dose systemic or intralesional steroids being the first-line treatment. As the mechanism of action of steroids is unknown, we undertook an investigation of the cellular and molecular effects of their action. STUDY DESIGN: A unique opportunity to study the effect of steroid treatment was presented when biopsy material was obtained from an infant with an ulcerated proliferating hemangioma before and after intralesional triamcinolone injection, which resulted in an accelerated regression of the lesion. Histochemical quantitation of mast cells, molecular analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) for 7 growth factor transcripts and differential display RT-PCR (DD RT-PCR) were conducted. RESULTS: After steroid therapy, the mast cell number increased (untreated = 2.22 +/-.27 [standard error of the mean ¿SEM¿]; treated = 8.7 +/-.71 [SEM] mast cells per field, respectively; P <.0001; n = 40 fields for each group), and the transcriptional expression of cytokines: platelet-derived growth factor-A and -B; interleukin-6; transforming growth factor-beta1 and -beta3 decreased, while that of basic fibroblast growth factor (bFGF) and vascular endothelial cell growth factor remained unaltered. Elevated urinary bFGF levels noted in cases of proliferating hemangioma, persisted even after steroid treatment. Using DD RT-PCR an amplicon that shared 100% sequence homology with the human mitochondrial cytochrome b gene was detected in the hemangioma biopsy after steroid treatment. CONCLUSIONS: The regression of this hemangioma subsequent to steroid therapy was accompanied by a significant increase in mast cell density, reduced transcription of several cytokines, and an enhanced expression of the mitochondrial cytochrome b gene.

Clusterin/apoJ expression during the development of hemangioma.

Hemangioma is the most common tumor of infancy. This vascular tumor is characterized by an initial rapid proliferation followed by an inevitable regression. The life cycle of hemangioma is divided into proliferative, involuting, and involuted phases. The cellular and molecular mechanisms responsible for controlling the biological behavior of hemangioma are largely unknown. Differential display analysis using mRNA isolated from biopsy specimens representative of the 3 different phases showed increased expression of clusterin/apoJ (clust/apoJ) in the involuting samples. Clust/apoJ is a multifunctional glycoprotein that has been associated with apoptosis. Reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry showed that both the transcription and protein expression of clust/apoJ were increased in hemangioma as the tumor progressed from the proliferative to the involuting and involuted phases. This suggests that clust/apoJ is involved in regulating apoptosis during the spontaneous regression of hemangioma. It has been suggested that mast cells (MC) play a role in the regression of hemangioma. The increase in the number and proportion of clust/ apoJ-positive MC with progression of hemangioma, along with the localization of clust/apoJ to MC granules, supports this hypothesis. We suggest that MC may be synthesizing/releasing this apoptotic modulator, leading to the regression of the tumor. Better understanding of the pathogenesis of hemangioma by identification of the relevant factors involved in its regression such as clust/apoJ will result in the development of novel therapies for this condition and tumors that do not undergo spontaneous regression.

Altered mitochondrial cytochrome b gene expression during the regression of hemangioma.

Hemangioma is a primary tumor of microvasculature. Its development typically exhibits a proliferative phase followed by an involuting phase that continues into the involuted phase. Although apoptosis has been reported, the mechanisms regulating the spontaneous regression of hemangioma are largely unknown. The authors recently demonstrated up-regulation of the mitochondrial cytochrome b gene in hemangioma associated with steroid-induced regression. The present study investigated whether a similar change occurred during spontaneous regression. Biopsy material was obtained from 11 patients with hemangiomas at different phases of development. In one of these patients, a biopsy was taken from the proliferative, involuting, and involuted areas of the hemangioma. In another patient, a biopsy was taken before and 5 weeks after the intralesional administration of steroids. From each tissue specimen, RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction analysis by use of specific primers for the human mitochondrial cytochrome b gene. Semiquantitative reverse transcriptase-polymerase chain reaction analysis revealed that the strongest expression of the mitochondrial cytochrome b transcripts was in specimens taken from hemangiomas in the involuting phase compared with those from the proliferative and involuted phases. The authors concluded that mitochondrial cytochrome b is associated with both the spontaneous and the steroid-induced regression of hemangioma, probably by regulating apoptosis.