Accordingly, K145, an inhibitor of sphingosine kinase 2 (SphK2), triggered MM cell death through UPR activation; moreover, the concomitant treatment of K145, a SphK2 inhibitor, together with bortezomib reactivated bortezomib sensitivity of drug-resistant MM cells [118]. This evidence concerns the gene SPHK2 and Miyoshi myopathy.