Our findings therefore strongly support the concept that PSMβ5 dysregulation plays a critical role in bortezomib-resistance mechanisms, and provide at our knowledge the first evidence that miR-155, by targeting PSMβ5, may antagonize bortezomib resistance of MM cells; however, taking into account the intrinsic pleiotropic function of miRNAs, we cannot rule out that further oncogenic pathways could be antagonized by miR-155 to elicit its tumor suppressive activity. The gene discussed is PSMB5; the disease is Miyoshi myopathy.