Finally, osteopontin was expressed in ~ 45% of cells in the bone marrow of bones of tumor-bearing mice injected with MDA-MB-231GFP/Luc2 cells plus EO-231 cells, but was expressed in only ~ 17% of cells in the bone marrow of tumor-bearing mice injected with MDA-MB-231GFP/Luc2 cells alone (Fig. 4). Here, SPP1 is linked to neoplasm.