HIF-2α increases CXCL12 expression by MM cell lines [54] which, in turn, reduces CXCR4 cell-surface levels on MM cells [35], forming a feedback loop that leads to a decrease in CXCR4 signalling and a desensitisation to exogenous CXCL12 [35]. Here, CXCL12 is linked to Miyoshi myopathy.