SPP1 and breast cancer: To investigate the spatial relationship between breast cancer cells, endosteal surfaces and bone microvessels, 30 μm thick tibial sections of long bones, isolated from 6-week and 12-week old animals 6 days following tumour cell injection, were stained with antibodies against endomucin (a pan-endothelial marker to visualise the entire capillary network), the bone marker osteopontin and human CD29 and CD59 (markers expressed on the human tumour cells).