CXCL1 and osteosarcoma: In consideration of the fact that HPAECs-secreted CXCL1 recruits osteosarcoma cells and contributes to lung metastasis, and our findings showing that VCAM-1 expression is positively correlated with CXCR2 in osteosarcoma tissue, we analyzed VCAM-1 expression after HPAECs CM treatment.