Studies [52,136] have confirmed that the CXCR4/CXCL12 axis plays a particularly critical role in MM cell proliferation, invasion, and chemoresistance; in addition, CXCR4 also plays a pleiotropic role in the expansion and colonization of MM cells in the BM and in the homing, adhesion, invasion, migration, and mobilization of MM cells out of the BM. This evidence concerns the gene CXCR4 and Miyoshi myopathy.