NSG1 and esophageal squamous cell carcinoma: In order to deepen our understanding of the potential role of NSG1-induced activation of the TGF-β/Smad signaling pathway in ESCC cell invasion and migration, we exposed NSG1-overexpressing ESCC cells to SB-431542 (25 μM) - a highly selective TGF-β inhibitor, and si-smad2.