In cell lines, including a prolymphocytic leukemia cell line MEC1, both agents as well as thapsigargin induced robust ER stress response which included PERK phosphorylation, XBP1 splicing and CHOP induction, indicating that ER stress response is dysfunctional in CLL [17, 49]. This evidence concerns the gene DDIT3 and B-cell chronic lymphocytic leukemia.