Western blot analysis was done according to published methods [28 (link),29 (link)]. Briefly, the lung tissues or cells were extracted with cell lysis reagent (Sigma, St. Louis, MO, USA ). Then, protein samples were separated with 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Proteins were transferred to a polyvinylidene fluoride (PVDF) membrane (Millipore, Bedford, MA, USA). The PVDF membrane was incubated in 5% bovine serum albumin (BSA) for 2 h. After 3 washes with Tris-buffered saline containing Tween-20 (TBST), the PVDF membrane was incubated with E-cadherin, β-actin, P-ERK1/2 and ERK1/2 antibodies (Cell Signaling Technology, Danvers, USA) separately overnight at 4°C. The PVDF membrane was then washed with TBST 3 times followed by incubation with HRP-conjugated secondary antibodies (Cell Signaling Technology, Danvers, USA) for 2 h at room temperature. After 3 washes with TBST, immunoreactive bands were visualized using chemiluminescence detection reagents (Bio-Rad Laboratories, Redmond, USA). The signal intensities of bands were quantified by using ImageJ software.