Mesenchymal Stromal Cells: Regulators of Immune Response in Hematological Malignancies

The Bone Marrow (BM) microenvironment plays a key role in regulating the maturation of precursors of myeloid and B lymphoid cells. This microenvironment is composed of several types of cells among which Mesenchymal Stromal Cells (MSC) can be considered as a major component. Indeed, these elements produce several extracellular matrix proteins involved in triggering signals to precursors cells; furthermore, MSC posses the high plasticity to differentiate into other cell components present within BM as osteocytes and adipocytes which regulate the composition of the microenvironment. MSC can display an immunoregulatory activity leading to the impairment of recognition of leukemic transformed cells. There are preclinical and clinical evidences that treatment with Immunomodulatory Drugs (IMiDs) in multiple myeloma and aminobisphosphonates in different hematological malignancies can trigger an efficient immune response; this response can hit both tumor and stromal cell component of the BM. Herein, we briefly summarize the more recent advances on how and what MSC can regulate anti-leukemic immune response and which drugs would be employed to render MSC immunostimulatory rather than immunosuppressive.