Relationship between Bone Marrow PD-1 and PD-L1 Expression and the Presence of Osteolytic Bone Disease in Multiple Myeloma Patients

Abstract Alterations of the bone marrow (BM) immune-microenvironment characterize the progression of monoclonal gammopathies and the development of osteolytic bone disease in multiple myeloma (MM). MM patients exhibit immune dysfunctions as impaired dendritic, NK and T cells, whereas the onset of MM osteolytic lesions is associated to an increased prevalence of Th17 cells. Recently, the pathophysiological role of the programmed cell death protein 1 (PD-1)/PD-1 ligand (PD-L1) pathway together with an increase of myeloid derived suppressor cells (MDSCs) in the induction of tumor tolerance and immune evasion has been underlined with a therapeutic relevance. However, unclear data on the express…