miR-30b regulates migration and invasion of human colorectal cancer via SIX1.

CRC (colorectal cancer) is one of the most malignant tumours in both developing and developed countries. It is estimated that 60% of CRC patients have liver metastasis. In the present study, we show that miR-30b is an important regulator in human CRC migration and invasion, which are vital steps in CRC liver metastasis. miR-30b was significantly down-regulated in primary CRC specimens compared with normal tissues. Furthermore, miR-30b was much lower in liver metastasis tissues than in CRCs. We validated SIX1 (SIX homeobox 1), a member of the SIX homeodomain family of transcription factors and an EMT (epithelial-mesenchymal transition)-promoting gene, as the direct target of miR-30b. Forced expression of miR-30b inhibited CRC cell migration and invasion in vitro via its target gene SIX1. Furthermore, an inverse correlation between expression of SIX1 and miR-30b has been observed both in primary CRC specimens and liver metastasis. Taken together, miR-30b plays an important role in mediating metastatic related behaviour in CRC. miR-30b may serve as a potential diagnostic marker and therapeutic target for patients with CRC in the future.