Ishikawa and HEC1-A cells were selected for cell transfection. Short hairpin RNAs for circSMAD2 (sh-circSMAD2#1, sh-circSMAD2#2, sh-circSMAD2#3) or the control sh-NC were constructed by Invitrogen (Carlsbad, CA, USA). MiR-1277-5p mimics, miR-1277-5p inhibitors, siRNA of MFGE8, pcDNA-MFGE8 and their corresponding negative controls were obtained from Sangon (Shanghai, China). Then cell transfection was carried our using Lipofectamine 2000 (Invitrogen).