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

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.

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.

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).

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.