KDR and systemic sclerosis: Notably, several soluble growth factor receptors involved in fibrosis and vasculopathy were significantly downregulated (FDR < 5%) in SSc patients, including three epithelial growth factor receptors (EGFR, ERBB2, and ERBB3), VEGFR2 (the main receptor for VEGF, a key growth factor in angiogenesis), as well as TGFBR3 and PDGF-R-alpha (both key receptors in fibrotic response [26]).