In addition, previous studies shows leukocytes can be educated to upregulate the expression of Mer's ligand GAS6 in a Mer-dependent manner once they are recruited into tumor microenvironment [43], thus supporting a model in which Mer signaling induces GAS6 expression in tumor-associated macrophages, creating positive feed-forward signaling acting on tumor cells and tumor-associated macrophages through Mer [42]. Here, GAS6 is linked to neoplasm.