MIR31 and adenocarcinoma: We established HEC-50B cells overexpressing MIR31 by introducing precursor-MIR31 using lentivirus vectors because the MIR31 expression level of HEC-50B was modest among the several adenocarcinoma cell lines analyzed (Additional file 1: Figure S1) and lentivirus vectors can be efficiently transfected into this cell line (HEC-50B mock and MIR31).