PURPOSE OF REVIEW - This review highlights our current knowledge of oxygen tensions in the bone marrow, and how low oxygen tensions (hypoxia) regulate tumor metastasis to and colonization of the bone marrow.
RECENT FINDINGS - The bone marrow is a relatively hypoxic microenvironment, but oxygen tensions fluctuate throughout the marrow cavity and across the endosteal and periosteal surfaces. Recent advances in imaging have made it possible to better characterize these fluctuations in bone oxygenation, but technical challenges remain. We have compiled evidence from multiple groups that suggests that hypoxia or hypoxia inducible factor (HIF) signaling may induce spontaneous metastasis to the bone and promote tumor colonization of bone, particularly in the case of breast cancer dissemination to the bone marrow. We are beginning to understand oxygenation patterns within the bone compartment and the role for hypoxia and HIF signaling in tumor cell dissemination to the bone marrow, but further studies are warranted.