MERTK and neoplasm: In addition, tumor-secreted PROS1 can bind to MER and TYRO3 on macrophages and suppress their ability to express an M1, inflammatory and anti-tumor phenotype [120], and binding of GAS6 and PROS1 to phosphatidylserine exposed on the outer membrane leaflet of apoptotic cells can activate TAM receptors on macrophages and stimulate uptake of the dying cells (efferocytosis), which also reduces inflammation in the TME [121].