MiR-23a functions as a tumor suppressor in osteosarcoma.

BACKGROUND: Osteosarcoma is the most common primary bone malignancy in children and adolescents, and the pathogenesis of this cancer remains unclear. Therefore, the discovery of new biomarkers for the diagnosis, prognosis, and treatment of osteosarcoma remains an important but unmet clinical need.
METHOD: Quantitative real-time PCR was carried out to examine the expression of miR-23a. Methylation-specific PCR was performed to evaluate the DNA methylation status of the miR-23a promoter. Cell proliferation, migration, and invasion were examined by cell counting assays, wound healing assays, and cell invasion assays, respectively. Western blot analysis and luciferase reporter assays were performed to identify miR-23 target genes. Nude mice were used to investigate the function of miR-23a in vivo.
RESULTS: The expression of miR-23a was decreased in osteosarcoma cells and tissues compared to normal controls. The promoter region of the miR-23a gene was hypermethylated in osteosarcoma cells, and demethylase treatment increased the expression of miR-23a. The ectopic expression of miR-23a led to retarded proliferation, migration, and invasion of osteosarcoma cells, whereas the depletion of miR-23a resulted in the opposite effects. MiR-23a suppressed the transcription of RUNX2 and CXCL12 by binding to the 3' UTRs of these mRNAs. The cellular function of miR-23a is RUNX2/CXCL12-dependent, and the overexpression of RUNX2 or CXCL12 rescued the impaired cell growth, migration, and invasion induced by miR-23a. Nude mouse experiments indicated that miR-23a may inhibit the proliferation of osteosarcoma cells in vivo.
CONCLUSION: We identified miR-23a as a tumor suppressor in osteosarcoma. Our data clarify the mechanism of osteosarcoma progression and demonstrated the potential for exploiting miR-23a as a diagnostic marker for osteosarcoma.