In line with the role of BCR signal in PIM1 regulation, a BTK inhibitor, ibrutinib, decreased expression of PIM1 in murine TCL1‐192 cells xenografted to SCID mice.8 Taken together, these observations indicate that induction of PIM kinases in CLL is controlled by microenvironment signals. This evidence concerns the gene PIM1 and B-cell chronic lymphocytic leukemia.