cancers Review Overcoming the Immunosuppressive Tumor Microenvironment in Multiple Myeloma Fatih M. Uckun 1,2,3 1 Norris Comprehensive Cancer Center and Childrens Center for Cancer and Blood Diseases, University of Southern California Keck School of Medicine (USC KSOM), Los Angeles, CA 90027, USA;
[email protected] 2 Department of Developmental Therapeutics, Immunology, and Integrative Medicine, Drug Discovery Institute, Ares Pharmaceuticals, St. Paul, MN 55110, USA 3 Reven Pharmaceuticals, Translational Oncology Program, Golden, CO 80401, USA Simple Summary: This article provides a comprehensive review of new and emerging treatment strategies against multiple myeloma that employ precision medicines and/or drugs capable of improving the ability of the immune system to prevent or slow down the progression of multiple myeloma. These rationally designed new treatment methods have the potential to change the therapeutic landscape in multiple myeloma and improve the long-term survival outcome. Abstract: SeverFigurel cellular elements of the bone marrow (BM) microenvironment in multiple myeloma (MM) patients contribute to the immune evasion, proliferation, and drug resistance of MM cells, including myeloid-derived suppressor cells (MDSCs), tumor-associated M2-like, “alter- natively activated” macrophages, CD38+ regulatory B-cells (Bregs), and regulatory T-cells (Tregs). These immunosuppressive elements in bidirectional and multi-directional crosstalk with each other inhibit both memory and cytotoxic effector T-cell populations as well as natural killer (NK) cells. Immunomodulatory imide drugs (IMiDs), protease inhibitors (PI), monoclonal antibodies (MoAb), Citation: Uckun, F.M. Overcoming the Immunosuppressive Tumor adoptive T-cell/NK cell therapy, and inhibitors of anti-apoptotic signaling pathways have emerged as Microenvironment in Multiple promising therapeutic platforms that can be employed in various combinations as part of a rationally Myeloma.