ERN1 and acute lymphoblastic leukemia: Furthermore, the strong ERN-1 gene expression caused by ixazomib as a single agent and by the dual treatment depicts that the TKI effect on this part of the cell is only minimal and implies that a major part of the response of Ph+ ALL cells to proteasome inhibitors is mediated through the UPR, enabling a synergistic effect between both drugs in BV-173.