Myeloma-derived IL-32γ induced PD-L1 expression in macrophages facilitates immune escape via the PFKFB3-JAK1 axis.

Multiple myeloma (MM) is characterized by an accumulation of monoclonal plasma cells within the bone marrow (BM). Macrophages are an abundant component of myeloma BM microenvironment and support survival of the malignant cells and foster myeloma development and progression by suppression of the immune response. In our previous study, we found that MM patients overexpress pro-inflammatory cytokine interleukin-32 (IL-32). The present study aimed to investigate the role of IL-32 in myeloma progression and mechanisms of IL-32 on macrophages functions. We discovered that the expression of IL-32 was associated with the disease stage in myeloma patients. MM-derived exosomes containing IL-32γ promoted the expression of programmed death-ligand 1(PD-L1) by macrophages, thus promoting immune evasion. Mechanistically, myeloma-secreted IL-32γ acted via proteinase 3 (PR3) to enhance 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) dependent glycolysis and subsequent PD-L1 expression. Moreover, the PFKFB3-Janus kinase 1 (JAK1) axis might contribute to the expression of PD-L1 by macrophages. To sum up, we concluded that IL-32 was a critical mediator in myeloma progression, and targeting IL-32 signaling might be used as a potential strategy for treating myeloma.