GAS6 and neoplasm: Interestingly, however, EO771 Xkr8 knockout cells did not show apparent defects in tumor cell proliferation (Fig. 1D) or tumor-sphere formation in Matrigel, as shown by tumor sphere size (Fig. 1E) and tumor sphere count (Fig. 1F), or defects in the immediate Gas6-mediated activation of p-Akt through Axl (Fig. S3B), suggesting that Xkr8 does not impinge on the cell-intrinsic oncogenic features of these cells in cell culture.