Human prostate cancer selectively metastasizes to the bone with mechanisms that are partially unknown. RAGE is a receptor overexpressed by prostate cancer cells whose expression correlates with the capacity of colonizing the bone marrow microenvironment. Proteinase 3 (PR3) is a serine protease produced and released by myeloid cells, and has been identified as a RAGE-interacting protein. Using high resolution confocal microscopy, it was found that soluble PR3 (red) accumulates at the surface of prostate cancer cells overexpressing RAGE (green). This result supports further evidence of heterotypic cell-cell interactions between prostate cancer cells expressing RAGE and hematopoietic cells expressing PR3. For more details, see article by Kolonin and colleagues on page 3144.