Genetic perturbation of IFN-α transcriptional modulators in human endothelial cells uncovers pivotal regulators of angiogenesis

Interferon-a(IFN-a) comprises a family of 13 cytokines involved in the modulation of antiviral, immune,and anticancer responses by orchestrating a complex transcriptional network. The activation of IFN-asig-naling pathway in endothelial cells results in decreased proliferation and migration, ultimately leading tosuppression of angiogenesis. In this study, we knocked-down the expression of seven established or can-didate modulators of IFN-aresponse in endothelial cells to reconstruct a gene regulatory network and toinvestigate the antiangiogenic activity of IFN-a. This genetic perturbation approach, along with the anal-ysis of interferon-induced gene expression dynamics, highlighted a complex and highly interconnectednetwork, in which the angiostatic chemokine C-X-C Motif Chemokine Ligand 10 (CXCL10) was a centralnode targeted by multiple modulators. IFN-a-induced secretion of CXCL10 protein by endothelial cellswas blunted by the silencing of Signal Transducer and Activator of Transcription 1 (STAT1) and ofInterferon Regulatory Factor 1 (IRF1) and it was exacerbated by the silencing of Ubiquitin SpecificPeptidase 18 (USP18).In vitrosprouting assay, which mimicsin vivoangiogenesis, confirmed STAT1 asa positive modulator and USP18 as a negative modulator of IFN-a-mediated sprouting suppression.Our data reveal an unprecedented physiological regulation of angiogenesis in endothelial cells througha tonic IFN-asignaling, whose enhancement could represent a viable strategy to suppress tumorneoangiogenesis.