Pomalidomide Promotes the Maturation of Healthy Donors and Multiple Myeloma Patients Derived-Dendritic Cells

Abstract: Objective To investigate the effect of pomalidomide on the maturation of monocyte derived dendritic cells (moDCs) from healthy donors (HDs) and multiple myeloma (MM) patients. Method Peripheral blood mononuclear cells (PBMCs) were isolated from the peripheral blood of HDs and MM patients. The generation of moDCs from monocytes in PBMCs was conducted by the incubation of 7 days in a medium consisting of RPMI 1640 medium, 5% human serum, 800U/mL GM-CSF, 500U/mL IL-4, 100U/mL penicillin and 0.1mg/mL streptomycin. During this period, the incubation system was administrated with pomalidomide at 10 µM or 1×PBS as the control group. On the 8 ^th day, cells were harvested, and the immunophenotyping of cells were analyzed by the flow cytometry. The CD80+CD86+ cell population in total cells is gated as DCs in the FACS analyzing system. Then, the median fluorescence intensity (MFI) of surface markers CD40 and HLA-DR as well as the proportion of CD40+ DCs and HLA-DR+ DCs in total DCs were analyzed respectively. In addition, supernatant from the incubation system with or without pomalidomide administration was collected and detected for the concentration of cytokines IL-12, TNF-α and MIP-1α. Results The proportion of CD80+CD86+ cells in total cells was higher in HD group (n=15) than in MM patient group (n=11), but there was no statistically significant difference (93.49%±6.43% vs 77.04%±27.17%, P=0.094). When analyzing all the HD-derived moDCs (n=15), pomalidomide significantly enhanced the MFI of CD40 (P=0.003) and HLA-DR (P=0.040) on moDCs when compared with the control group. Meanwhile, the proportion of CD40+ DCs (P=0.008) and HLA-DR+ DCs (P=0.032) in total DCs was significantly higher in pomalidomide group than in control group. When analyzing all MM patients-derived moDCs (n=11), pomalidomide significantly enhanced the MFI of CD40 (P=0.047) and HLA-DR (P=0.006) on moDCs when compared with the control group. Meanwhile, the proportion of HLA-DR+ DCs in total DCs was significantly higher in pomalidomide group than in the control group (P=0.000). Moreover, pomalidomide treated HD-derived moDCs (n=8) produced 192% IL-12 (P=0.020), 110% TNF-α (P=0.006) and 112% MIP-1α (P=0.055) of untreated moDCs. However, when analyzing MM patients-derived moDCs (n=10), the expression of IL-12 (P=0.458), TNF-α (P=0.377) and MIP-1α (P=0.248) from moDCs showed no significant difference between pomalidomide group and the control group. Conclusions Pomalidomide at 10 µM can promote the maturation of both HD-derived moDCs and MM patients-derived moDCs. Pomalidomide shows potential to be a DC adjuvant for DC-based therapeutic strategies, such as DC vaccine and DC cell-therapy in MM.

Key words: Pomalidomide; Monocyte derived Dendritic Cells; Multiple Myeloma; DC Adjuvant