Overexpression of DDR2 increases Snail1 protein expression. (A) TPC-1 cells transfected with DDR2 vector or control vector were subjected to Snail1, Snail2, Twist1 and ZEB1. (B) TPC-1 cells transfected with DDR2 siRNA or control siRNA were subjected to western blotting for Snail1, Snail2, Twist1 and ZEB1 (C) RT-qPCR results of Snail1 in TPC-1 cells transfected with DDR2 vector or control vector. (D) RT-qPCR results of Snail1 in TPC-1 cells transfected with DDR2 siRNA or control siRNA. (E) TPC-1 cells transfected with DDR2 siRNA or control siRNA were incubated with 5 ng/ml of TGF-β for 48 h. The Snail1 protein level was detected by western blotting. (F) TPC-1 cells transfected with DDR2 siRNA or control siRNA were incubated with 2 µg/ml collagen I for 48 h. The Snail1 protein level was detected by western blotting. (G) TPC-1 cells transfected with DDR2 vector or control vector were transduced with Snail1 siRNA. The protein level of Snail1, E-cadherin and Vimentin was detected by western blotting. **P<0.01. RT-qPCR, reverse transcription-quantitative polymerase chain reaction; DDR2, discoidin domain receptor tyrosine kinase 2; si, small interfering; TGF, transforming growth factor; ZEB, zinc finger E-box binding homeobox 1.