MiR-218 promotes apoptosis of U2OS osteosarcoma cells through targeting BIRC5.

ABSTRACT

OBJECTIVE: Baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5) is a member of apoptosis inhibition family which suppresses caspase activity. Osteosarcoma tissues have significantly higher BIRC5 and lower microRNA-218 (miR-218) level than adjacent tissues, indicating tumor suppressor role of miR-218 in osteosarcoma. Bioinformatics analysis showed satisfactory targeting correlation between miR-218 and 3'-UTR of BIRC5 mRNA. This study, thus, investigated if dysregulation of miR-218 and BIRC5 affected apoptosis of osteosarcoma cells U2OS. PATIENTS AND METHODS: A total of 42 osteosarcoma patients were collected for tumor and adjacent tissues to compare miR-218 and BIRC5 expressions. Dual-luciferase reporter gene assay examined targeted regulation between miR-218 and BIRC5. In vitro cultured U2OS cells were treated with miR-218 mimic and/or si-BIRC5. Caspase-3 activity was measured by spectrometry while flow cytometry was used to test cell apoptosis, plus protein expression assay by Western blot assay. RESULTS: Compared to adjacent tissues, osteosarcoma tissues had significantly depressed miR-218 expression and elevated BIRC5 expression (p<0.05). miR-21 targeted 3'-UTR of BIRC5 to suppress its expression. The elevation of miR-218 and/or silencing BIRC5 significantly depressed BRIC5-induced inhibition on caspase-5, and facilitated U2OS cell apoptosis (p<0.05). CONCLUSIONS: We observed that miR-218 was significantly down-regulated in osteosarcoma tissues, which had elevated BIRC5 expression. MiR-218 targeted and inhibited BIRC5 expression, weakened caspase-5 inhibition by BIRC5, and facilitated U2OS osteosarcoma cell apoptosis.