S1PR1 and B-cell chronic lymphocytic leukemia: This study therefore provides novel insight into the mobilizing effects of BCR signaling inhibitors, and, in particular, allows us to propose that the CLL cell–mobilizing effect of idelalisib results, at least in part, from reversal of BCR-mediated repression of S1PR1 expression on the malignant cells leading to enhanced egress from affected lymph nodes, whereas the mobilizing effect of ibrutinib is mediated by blockade of integrin-mediated signals required for tissue entry and retention.