Single-cell transcriptomic analysis of NK cell dynamics in myeloma patients reveal persistent reduction of cytotoxic NK cells from diagnosis to relapse

Single-cell transcriptomics was performed to investigate the bone marrow NK cell compartment of myeloma patients at diagnosis (n=19), during treatment (n=21) and at relapse (n=6). The bone marrow of myeloma patients is characterized by a reduction in conventional cytotoxic NK cells that persists throughout treatment. We show in 20% of newly diagnosed myeloma patients that an altered balance between cytotoxic and cytokine-producing NK cells translates into a reduced cytotoxic ability in response to therapeutic antibodies. The relative loss of cytotoxic NK cells persists at relapse and is accompanied by an expansion of IFN-responsive NK cells. These findings reveal previously unappreciated alterations in bone marrow NK cell composition and highlight the importance of understanding the bone marrow immune system in patients receiving immunotherapies.