Figure 1.

BMMSC-mediated resistance against KHYG-1 NK cells and DR5-agonistic antibodies. (A) LUC-transduced MM1.s and RPMI-8226 cell lines were cultured in the absence or presence of BMMSCs and treated with serial E:T ratios of KHYG-1 NK cells. MM cell survival was determined by BLI, 24 hours after treatment. Results are representative of 3 independent assays. Error bars represent means with SEM of triplicate cultures. (B) The MM1.s cell line (left) and BMMNC samples from 5 MM patients (right) were cultured in the absence or presence of BMMSCs. MM1.s was treated for 24 hours with 1 µg/mL drozitumab and PBMCs from healthy donors (n = 5). BMMNC samples were treated with 10 µg/mL drozitumab (circles) or TRA-8 (triangles) for 24 hours. Viable MM1.s cells were enumerated by BLI and viable CD138⁺ CD38⁺ CD45^dim patient MM cells were enumerated by flow cytometry. Bars represent the median values. The statistical differences between the culture conditions without versus with BMMSCs were calculated using unpaired (A) or paired (B) t-tests (*P < 0.05; **P < 0.001; ****P < 0.0001). ns = not significant; BMMNC = bone marrow mononuclear cells; BMMSC = bone marrow mesenchymal stromal cell; LUC = Luciferase; MM = multiple myeloma; PBMC = peripheral blood mononuclear cell.