INTRODUCTIONrnBone is a mechanosensitive organ, and it constantly remodels itself using mechanical loading as one of its major cues.1 Osteocytes are the most abundant type of cells in the bone matrix, and they act as mechanosensors and induce load-driven bone remodeling.2 While mechanical loading activates many load-sensitive genes via a wide spectrum of signaling pathways, little is known about the potential effects of mechanical stimulation on tumor-osteocyte communication. Osteocyte-mediated loading effects are potentially different from those observed in tumor cells that directly receive mechanical stimulation.3-5 In this study, we examined the interactions between osteocytes and migratory breast cancer cells in the presence and absence of mechanical stimulation in vitro and in vivo.