The target of miR-155 was predicted by the online database Targetscan 7.2 [http://www.targetscan.org/vert_72/ (28 (link))]. The 3'UTR of TGFBR2 containing the predicted miR-155 specific binding site was amplified by PCR from genomic DNA, and inserted into the pMIR-REPORT™ luciferase reporter vector (Thermo Fisher Scientific, Inc.) to obtain the wild-type luciferase reporter plasmid p-TGFBR2-wt. PCR was performed using the following thermocycling conditions: 94˚C for 2 min, followed by 35 cycles of 94˚C for 2 sec, 60˚C for 60 sec and 72˚C for 1 min. The PCR products were amplified using cDNA and fused to the firefly luciferase gene of the pGL3-control plasmid (Promega Corporation) with the restriction enzyme sites of KpnI and XhoI. Two site mutations were introduced to WT-TGFBR2-3'-UTR to construct the mutant (MUT) TGFBR2-3'-UTR using a Quick Site-directed mutation kit (Agilent Technologies, Inc.). The cells were co-transfected with pGL3 constructions including 200 ng pGL3-WT-TGFBR2 and 200 ng pGL3-Mut-TGFBR2, 10 nM miR-NC or 10 nM miR-155 mimics and 26 ng pRL-TK in 24-well plates using Lipofectamine® 2000 (Invitrogen, USA). At 24 h of transfection, luciferase activity (firefly and Renilla) was determined using the dual-luciferase reporter assay system (Promega, USA).