USP9X and malignant peripheral nerve sheath tumor: In all MPNST cell lines tested, but most prominently in the T265-2c cell line, Mcl-1 knock-down-induced death displayed features of apoptosis such as increased annexin V staining and decreased mitochondrial membrane potential but, as in Usp9X knock-down cells, broad caspase inhibition did not protect MPNST cells from Mcl-1 knock-down-induced death.