CBX4 and osteosarcoma: Secondly, regarding the invasion and metastasis of osteosarcoma, studies have shown that overexpression of chromobox protein homolog 4 (CBX4) in osteosarcoma cell lines and tissues leads to the recruitment of GCN5 to the Runx2 promoter, upregulating Runx2 at the transcriptional level and thus promoting tumor metastasis.