ABSTRACT
PURPOSE: Transcriptional silencing of tumor suppressor genes by aberrant methylation of CpG islands plays a crucial role in the development of human cancers. We comprehensively examined the methylation status of several tumor suppressor genes in osteosarcoma with a special focus on the RUNX3 gene. MATERIALS AND METHODS: Methylation-specific polymerase chain reaction (MSP) was performed for osteosarcoma tissues and their cell lines. MSP and RT-PCR for the RUNX3 gene were performed in the tumor-derived cell lines and the immortalized cell lines. The demethylating agent 5-aza-2' deoxycytidine was used in the SaOS-2 cell line to reverse the methylation status. RESULTS: Hypermethylation of the RUNX3 gene was observed in 60% (24 of 40) of the osteosarcoma tissues, whereas other tumor suppressor genes showed very low methylation. Thirteen of 30 (43%) tumor-derived cell lines, and U-2OS and SaOS-2 showed hypermethylation of the RUNX3 gene on MSPCR. However, RUNX3 was expressed in the SaOS-2 cell line, as determined by RT-PCR, and the expression was augmented by treatment with 5-aza-2' deoxycytidine. CONCLUSION: Our study suggests that aberrant methylation is an important mechanism of RUNX3 down-regulation in osteosarcoma. This data may have potential significance in developing a potential therapeutic target for osteosarcoma.