Studies on human myeloma cell lines (HMCLs) discovered that CD138+PD-L1+ cells show a more aggressive phenotype, with increased proliferation rate and resistance to conventional anti-MM therapies, as dexamethasone, melphalan and bortezomib, mediated by the activation of PI3K/AKT signaling pathway [34,35]. Here, CD274 is linked to Miyoshi myopathy.