GAS6 and posterior cortical atrophy: Taken together, these results support a model of osteoblast-mediated PCa cellular dormancy through Gas6 and TGF-β signaling in marrow (Fig. 9); Gas6 produced by osteoblasts binds to Axl expressed by disseminated PCa cells, and its signaling induces expression of both TGF-β ligands (TGF-β1and TGF-β2) and their receptors (TGFBR2 and TGFBR3).