EGR1 and systemic sclerosis: Other extracellular signals which are relevant to SSc [such as PDGF, hypoxia, HGF, or LPS (bacterial LPS), oxidative stress, thrombin, LPA, ultraviolet light, cigarette smoke, mechanical strength, ischemia-reperfusion, and T-cell receptor ligature] have been shown to increase Egr-1 expression (373).