In order to confirm the role of CT45A1 in the metastasis of osteosarcoma, the in vivo metastatic assays revealed that the number of mice that showed metastasis following the injection of CT45A1-overexpressing osteosarcoma cells was more than the number of mice that showed metastasis following the injection of the control cells (Fig. 3A), meanwhile lung metastasis occurred more easily in groups with CT45A1 overexpression (Fig. 3B, C). The gene discussed is CT45A1; the disease is osteosarcoma.