FUNCTIONALLY ACTIVE MYELOID-DERIVED SUPPRESSOR CELLS ARE INCREASED AFTER LENALIDOMIDE PLUS DEXAMETHASONE TREATMENT IN PREVIOUSLY UNTREATED MULTIPLE MYELOMA PATIENTS

Sborník

Background. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature cells and reported to be expanded in pathological conditions including cancer, infectious diseases and some autoimmune diseases. Recently, a large number of studies showed MDSCs expansion and their suppressive function in tumor models and non-hematological malignancies. Multiple myeloma (MM) is a plasma cell malignancy associated with immunological impairments. Aims. To evaluate frequency of MDSCs and their suppressive function in MM patients at baseline and after lenalidomide plus dexamethasone (LD) treatment. Patients and Methods. A cohort of 16 untreated MM patients was included after obtaining signed informed consent forms according to Helsinki declaration. Median age of the studied cohort was 60 years (range, 36-67). According to international staging system (ISS) patients were staged as: ISS1, 8/16 (50%); ISS2, 5/16 (31%); and ISS3, 3/16 (19%). All patients received LD for 4 cycles as induction therapy (lenalidomide, 25mg on days 1-21; dexamethasone, 40mg on days 1, 8, 15, 22). Using multi-parameter flow cytometry (CD4- FITC, CD11b-PE, CD33-PerCpCy5.5, CD14-PECy7, HLA-DR-APC and CD8- PB), we assessed MDSCs, total lymphocytes, CD4 and CD8 T cells from PB of MM patients at baseline and after each LD treatment cycle. As controls, 11 healthy volunteers (HVs) PB samples were also assessed. Functional activity of MDSCs was studied using CFSE based T cell proliferation assays from 4 MM patients (3 untreated and 1 LD treated) and 3 HVs. Further, we profiled supernatants from proliferation assays for pro-inflammatory (IFN-γ, TNF-α) and immunosuppressive (IL-10) cytokines. Results. MDSCs were identified as CD33+CD11b+CD14-HLADR-. Frequency of MDSCs was significantly increased and total lymphocytes were reduced in MM patients at baseline compared to HVs (median% of MDSCs, 0.33 vs.0.08; P=0.001 and median% of lymphocytes, 16.10 vs. 36.13; P=0.01). However, baseline CD4 and CD8 T cells from MM patients did not differ significantly from HVs. When we compared MDSCs from baseline and post-LD treatment, significant increase was observed after the 4th cycle but similar frequency was observed after 1-3 cycles (median% of MDSCs, 0.33 vs. 0.57; P=0.033). Functional studies revealed that MDSCs from MM patients and HVs suppressed CD3 T cell proliferation in concentration dependent manner (1:1, 1:5, 0:1). Suppressive function of MDSCs was comparable between HVs, untreated and LD treated patients. Cytokine data from MM and HVs showed that in the presence of MDSCs in proliferation assays, the level of IFN-γ, TNF-α and IL-10 was reduced significantly compared to proliferation assays without MDSCs (P=0.05). Comparison of MM and HVs cytokine data from proliferation assays (in presence or absence of MDSCs) showed no significant difference in the level of IFN-γ and TNF-α. But IL-10 level was 3-fold increased in proliferation assays (without MDSCs) from MM patients compared to HVs (mean pg/ml: 960.88 vs. 368.36; P=0.045). Conclusions. Our findings suggest that MDSCs are expanded and functional in MM. LD treatment in MM did not reduce MDSCs and their suppressive function. Expansion of these cells might enhance immune suppression in MM and thereby progress the disease.This study was supported by GACRGAP304/10/1395, MSM0021622434, LC06027, IGA: NS10406 and NS10408.

Haematologica, 2012; 97(s1):  110