BMSCs protect MM cells from apoptosis induced by Sant7 or an anti-gp130 mAb.

The IL-6–dependent MM cell line INA-6 (A) and primary MM cells derived from 4 different patients (B) were treated with Sant7 (50 μg/mL) or with a blocking anti-gp130 mAb (100 μg/mL) either (with 2 ng/mL IL-6) in the absence or presence of primary BMSCs derived from 3 different donors (see “Materials and methods”). After incubation periods of 3 days (INA-6) or up to 7 days (primary MM cells), apoptosis was analyzed by annexin V-FITC/PI staining. Fraction of viable cells, negative for both annexin V and PI, is indicated as percentage of untreated control (A) or as percentage of total cells (B). SDs of 3 independently performed experiments (INA-6/BMSC#1, INA-6/BMSC#2, INA-6/BMSC#3) are shown in panel A). Panel A: ● indicates +BMSCs; ■, −BMSCs. Panel B: ░ indicates patient 1; ▩, patient 2; ▪, patient 3; and ▧, patient 4.