As shown by X-ray photography (Figure 6B and 6C) and verified by H&E and TRAP staining (Figure 6D and 6E), breast cancer cells induced osteolytic bone destruction, and RUNX1 T207D overexpression significantly enhanced osteolytic bone destruction compared with control, whereas RUNX1 T207A overexpression markedly reversed the osteolytic bone destruction in limbs. Here, RUNX1 is linked to breast cancer.