Natural killer cell immunotherapy against multiple myeloma: Progress and possibilities

Multiple myeloma (MM) is a complex aggressive mature B-cell malignancy. Although with the wide application of chemotherapy drugs, it remains incurable and the vast majority of patients relapse. Natural killer (NK) cells, also known as CD56⁺ CD3^- large granular lymphocytes, are cytotoxic innate immune cells against MM without prior sensitization steps. NK cell-based immunotherapy is extensively promising in a wide range of clinical settings. It is worthy of note that some novel drugs such as monoclonal antibodies (mAbs), proteasome inhibitors (PIs), and immunomodulators (IMiDs) directly or indirectly activate NK cells to enhance their antitumor activity, and the combined regimens significantly improve the prognosis of MM patients. In this review, we summarize recent findings that support a role for NK cells in the pathogenesis of MM and outline innovative approaches in the implementation of NK cell-based immunotherapy against MM.