VCAM1 and neoplasm: The VLA-4 and VCAM1 axis regulates HSC homing, dormancy and mobilization.20,21 Recently, the Varner group showed that VLA4 is expressed by MDSCs, playing key roles in recruitment to tumor tissues, angiogenesis, and immunosuppressive activity.22–25 We subsequently tested whether the VLA-4 (α4β1 integrin) and VCAM1 axis plays a role in MDSC mobilization from the bone marrow into the circulation.