SPP1 and neoplasm: Consistent with the data in Fig. 4d, the number of metastatic cells as assessed by immunohistochemical staining of CD4 in the liver was significantly increased in TL-OmI/WT MEF-inoculated mice compared with TL-OmI-inoculated mice, and the absence of OPN in the co-inoculated MEFs resulted in a lower number of tumor cells in the liver (Fig. 4e).