S1PR1 and melanoma: Persistent non-canonical STAT3 activation by the G-coupled protein receptor S1PR1 (sphingosine-1-phosphate receptor 1) in myeloid cells has been linked to the formation of a lung premetastatic niche in bladder cancer and melanoma models through the induction of factors that are associated with suppressive immune cell recruitment, invasion, angiogenesis, and tumor survival [163].