SPHK2 and plasma cell myeloma: In agreement with previous reports [61] along with our recent study [62], it was suggested that knockdown of SphK2 with siRNA or inhibition of SphK2 activity with the selective pharmacological drugs reduces cancer cell growth, migration, and invasion [61–68], induces apoptosis by accumulating proapoptotic ceramides [63, 64, 69, 70], and promotes proteasomal inhibitor-mediated ER stress resulting in myeloma cell death [71, 72].