Bone is the preferred metastasis site for many cancer cell types, including breast and prostate cancers.It is a challenge to study the biology behind cancer bone metastasis in vitro, largely due to the paucity of suitable co-culture models and experimental tools.A new Coming Osteo Assay Surface (COAS) has been developed with an inorganic bone mimetic coating on polystyrene surface.On the surface, we have demonstrated osteoclast bone resorption in the coculture of osteoclasts differentiated from RAW 264.7 cells with prostate cancer PC-3 cells or breast cancer MDAMB-231 cells.In addition, this surface has also been found suitable for primary osteoclast differentiation and bone resorption, osteoblast differentiation, co-culture ofosteoclasts and osteoblasts, and osteoporosis drug testing.Therefore,not only can the COAS provide a substrate for bone cell assays, but also a physiologically relevant bone microenvironment for the study of bone metastatic cancer in vitro.Dr.Hongwei Hanna Rao, Ph.D., presently is a Senior Research Scientist at Corning Incorporated, New York, USA.She got her M.Sc and Ph.D.in Neuroscience at the University of Provence,France, postdoctoral training at Princeton University, USA.Before joining Corning Incorporated in 2005, she was an Assistant Professor at the Bone Research Center, University of Pittsburgh, USA.