COUP-TFII promotes epithelial-mesenchymal transition by inhibiting miR-34a expression in colorectal cancer

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) expression is upregulated in colorectal cancer and is associated with its progression and a poor prognosis. The aim of the present study was to determine whether COUP-TFII regulates colorectal cancer cell (CRC) invasion and migration by inhibiting microRNA (miR)-34a. Transwell system and wound healing assays were performed to examine cell invasiveness and migration, respectively. Reverse transcription polymerase chain reaction and western blotting were used to detect the RNA and protein levels of target molecules, respectively. The results revealed that COUP-TFII knockdown significantly inhibited CRC invasion and migration. In addition, the expression of miR-34a, a well-known tumor suppressor was revealed to be inversely correlated with COUP-TFII expression. The miR-34a mimic significantly reduced CRC invasion and migration abilities, while the miR-34a inhibitor enhanced CRC invasion and migration activity. There was no significant difference between the negative small interfering RNA and miR-34a inhibitor groups following knockdown of COUP-TFII. Furthermore, western blotting demonstrated that miR-34a mimics inhibited the epithelial-mesenchymal transition (EMT) process of CRCs, while the miR-34a inhibitor had the opposite effect. Taken together, the results demonstrate that miR-34a regulates CRC invasion and migration by examining the mechanism by which COUP-TFII regulates EMT.