MERTK and melanoma: The LC model contains nine soluble signaling molecules, many of which have been linked to melanoma biology: TNF-α (36), TGF-β (37), IL-1β (38), canonical WNT ligands and the soluble frizzled inhibitor DKK (39), ligands of the CSF1 receptor CSF1 (40) and IL-34 (41), and Tyro3, Axl, and MerTK (TAM) receptor ligands Pros1 and Gas6 (42).