These disappointing results may well be related to the fact that bortezomib and other proteasome inhibitors (e.g. MG-132 and epoxomicin) also induce Mcl-1 accumulation notably in CLL cells: this would decrease the proteasome inhibitors' apoptotic response and thus therapeutic efficacy [68]. Here, MCL1 is linked to B-cell chronic lymphocytic leukemia.