Myeloid-Derived Suppressor Cells in Patients with Multiple Myeloma and Monoclonal Gammopathy of Undetermined Significance.

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of cells of myeloid origin, and include immature macrophages, granulocytes, dendritic cells (DC) and other myeloid cells. In mice, are phenotypically characterized as CD11b+Gr-1+. Humans MDSC have an immature phenotype, including lineage negative (Lin-), CD14-, HLA-DR-, CD15+, CD34+, CD11b+, CD33+, and CD13+ cells. MDSC impair T-cell functions through secretion immunosuppressive cytokines, perturbation of the arginine metabolism by inducible nitric oxide synthase (iNOS), up-regulation of reactive oxygen species (ROS), therefore are considered an important tumor escape mechanism. These cells, also promote tumor-dependent angiogenesis as well as tumor metastasis, and to provide tumor resistance to antiangiogenic drugs. Their accumulation has been described in the peripheral blood of patients affected by breast, lung, renal and neck carcinoma, melanoma, chronic infections, inflammatory diseases, and traumatic stress.

We investigate MSDC in patients with multiple myeloma (MM) and monoclonal gammopathy undetermined significance (MGUS) by flow cytometry

We studied 22 patients with MM at diagnosis, 20 patients with MGUS, and 10 healthy controls (HC).

we observed that patients with MGUS showed the same number of MDSC (CD11b+,CD13+,CD34+,CD14-,CD45+) in the peripheral blood compared to HC (1,90±1,03/mmc, p=0,23). On the contrary, patients affected by MM showed a significant increase of MDSC vs HC (6,80±8,79/mmc vs 1,45± 0,98/mmc, p=0,003).

Our results suggest that these myeloid-derived suppressor cells, through their mechanisms immunesuppressive and proangiogenesis, could be involved in the progression of MGUS towards overt MM.

No relevant conflicts of interest to declare.