S1PR1 and B-cell chronic lymphocytic leukemia: In this study, we showed that the egress receptor, sphingosine-1-phosphate (S1P) receptor 1 (S1PR1), was expressed at low levels in normal germinal centers and CLL lymph nodes in vivo but became upregulated on normal B cells and, to a variable and lesser extent, CLL cells following in vitro incubation in S1P-free medium.