GAS6 and posterior cortical atrophy: Based on these results, we examined how the bone marrow microenvironment responds to GAS6 overexpression by PCa cells and whether the CSC phenotype is affected in vivo. For these studies, the CD133+/CD44+ populations present in DTC populations were examined following isolation by FACS from mouse bone marrow 24 hours after i.c. injection of PCaControl cells or PCaGAS6OE cells (Figure 2D).