CXCR6 and neoplasm: Apart from the classical forward signaling via CXCR6, the transmembrane CXCL16 form may also mediate signaling on its own, either upon binding its soluble CXCL16 (inverse signaling) or upon binding of its receptor CXCR6 (reverse signaling), inducing proliferation and survival, as well as migration in tumor cells.