MMP15 and Miyoshi myopathy: In addition to their expression in normal tissues, MMPs are pathologically expressed in the MM BM microenvironment and are involved in the initiation and progression of MM through multiple pathways; these MMPs include MMP-1, MMP-2, MMP-7, MMP-9, MMP-13, MMP-14 and MMP-15 (Supplementary Figure 2).