PTEN and osteosarcoma: The present study cultured the MG-63 osteosarcoma cell line and treated the cells with different concentrations of the methylation inhibitor 5-Zac to detect the expression levels of the PTEN protein, the mRNA transcription levels of the PTEN gene, and the influence of the methylation status of the GC site that binds to the transcription factors Myc and Sp1 in the PTEN promoter.