Detection and clinical significance of peripheral blood myeloid-derived suppressor cells in patients with multiple myeloma.

Myeloid-derived suppressor cells (MDSCs) are immunosuppressive cells whose levels in peripheral blood are elevated in multiple myeloma (MM) and are closely associated with disease progression and treatment response. This study used flow cytometry to assess MDSC proportions in peripheral blood mononuclear cells from 26 MM patients and 5 with nutritional anemia. T-test and 1-way analysis of variance were used for statistics. The correlation between MDSCs and M protein type, light chain subtype, risk stratification, and disease stage was also investigated. Compared to controls, MM patients had significantly higher levels of granulocytic (G-MDSC) and monocytic (M-MDSC) subsets (P < .05). G-MDSC levels were notably increased in light chain MM (9.23 ± 2.02) compared to IgG (4.06 ± 2.85, P = .004) and IgA subtypes (2.83 ± 2.14, P = .001). M-MDSC levels were significantly higher in κ light chain MM (3.11 ± 3.16) than in λ subtype (1.17 ± 0.74, P = .023). No significant correlation was found between MDSC subsets and risk stratification (G-MDSC: R = 0.13, P = .53; M-MDSC: R = 0.12, P = .57). Patients with relapsed MM showed elevated M-MDSC levels (mean 1.18) compared to controls (mean 0.57, P = .04), and patients with remission MM showed elevated M-MDSC levels (mean 2.58) compared to controls (mean 0.57, P = .01). While G-MDSC levels showed no significant difference (P > .05). After 2 treatment courses, both M-MDSC (1.23 ± 0.53 vs 2.76 ± 3.42, P = .03) and G-MDSC (1.09 ± 0.93 vs 5.57 ± 2.38, P < .001) levels significantly decreased. MDSCs are elevated in MM, and G-MDSC is positively associated with specific M protein subtypes and disease progression. Regulating MDSC expression may offer a novel strategy for MM treatment.