Furthermore, Western blot analysis showed that p-Smad2 expression were down-regulated after treatment with SB431542 (Fig. 2C, G., K), Band densitometry analysis showed significant differences in SB431542-treated ESCC cells as compared with controls (Fig. 2 D, H, L, P<0.05). The gene discussed is SMAD2; the disease is esophageal squamous cell carcinoma.