MiR-335 functions as a tumor suppressor and regulates survivin expression in osteosarcoma.

OBJECTIVE Previous studies have shown that miR-335 plays an anti-tumor role in several types of cancer. However, whether it is able to regulate the tumorigenesis of osteosarcoma (OS) has not been fully investigated. The present study was designed to study its potential role in regulating apoptosis of OS cells. MATERIALS AND METHODS The expression of miR-335 in a total of 18 paired OS tumor tissues and adjacent non-cancerous tissues was measured by Real-time PCR, and its different expression in OS cell lines was also measured. The effect of miR-335 on apoptosis was measured by MTT assay, caspase-3 activity assay and TUNEL assay. The effect of survivin inhibition on apoptosis of OS cells was determined by MTT assay and western blot. Luciferase reporter assay and western blot were conducted to confirm the relationship between miR-335 and the 3'UTR of survivin mRNA. RESULTS MiR-335 expression was found to be significantly downregulated in OS tumor tissues and OS cell lines. Overexpression of miR-335 led to decreased cell viability and increased apoptosis. MiR-335 directly targeted the 3'UTR of survivin mRNA and suppressed survivin gene expression, and inhibition of survivin exhibited similar effects to miR-335 overexpression. CONCLUSIONS MiR-335 might function as a tumor suppressor in OS, and downregulation of miR-335 in OS cells contributes to the decreased apoptotic potential of OS cells through derepression of survivin.