From this report, although co-inhibition of PSMB5 and PSMB7 on Btz-resistant cells was not tested in our study, dual inhibition of CT-L and T-L activities, rather than single inhibition, is indispensable for triggering excessive ER stress and sequential fatal cell stress in Btz-resistant MM cells. This evidence concerns the gene PSMB7 and Miyoshi myopathy.