Targeting NF-κB in infantile hemangioma-derived stem cells reduces VEGF-A expression

Infantile hemangioma (IH) is a most common tumor of infancy. Using infantile hemangioma-derived stem cells (HemSCs), we recently demonstrated that corticosteroids suppress the expression of VEGF-A, monocyte chemoattractant protein-1 (MCP-1), urokinase plasminogen activator receptor (uPAR), and interleukin-6 (IL-6); each of these are known targets of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappa B). In the present study, we examined the expression of these NF-kappa B target genes in IH tissue specimens and the effect of NF-kappa B regulation on the expression of pro-angiogenic cytokines, and in particular VEGF-A, in HemSCs. RNA extracted from IH tissue and hemangioma-derived stem cells (HemSCs) was used to analyze NF-kappa B target gene expression by reverse transcription-quantitative PCR (RT-qPCR). The effects of NF-kappa B blockade were examined in HemSCs. Immunostaining, immunoblotting and ELISA were used to assess protein expression. MCP-1, uPAR, and IL-6 were found to be differentially expressed in proliferating versus involuting IH. Corticosteroids suppressed NF-kappa B activity of HemSCs. Velcade (Bortezomib), a proteosome inhibitor that can indirectly inhibit NF-kappa B, impaired HemSCs viability and expression of pro-angiogenic factors. Furthermore, specific inhibition of NF-kappa B resulted in suppression of VEGF-A. We demonstrate expression of NF-kappa B target genes in proliferating IH. In addition, we show that the expression of several pro-angiogenic factors in HemSCs, and in particular VEGF-A, is regulated by NF-B activity.