IL-6 and fibronectin-mediated adherence fail to protect MM cells from apoptosis induced by Bay 11-7082/UCN-01. (A) MM cells were exposed to 200 nM UCN-0110 + 4 μM (U266) or 1 μM (MM.1S) Bay 11-7082 in the presence or absence of 100 ng/mL IL-6 for 24 hours, after which the percentage of apoptotic cells was determined by examining Wright-Giemsa-stained cytospin preparations. (B) MM.1S cells were seeded into 96-well plates coated with 50 μg/mL human cellular fibronectin, as described in “Materials and methods.” Adherent cells and cells in suspension were separately exposed to 10 μM dexamethasone or 200 nM UCN-01 + 1 μM Bay 11-7082 for 24 hours, after which the extent of apoptosis was determined as described for panel A. ^*Significantly lower than values for cells in suspension (P < .01). (C) Parental 8226 cells, and their Dox40- and LR5-resistant counterparts were exposed to 1 μM Bay 11-7082 ± 200 nM UCN-01 for 24 to 48 hours, after which the percentage of apoptotic cells was determined as described. (A-C) Values represent means ± SD for 3 separate experiments performed in triplicate. (D) CD138⁺ and CD138^- cells were isolated from the bone marrow of 2 patients with MM (designated as patients 1 and 2), as described in “Materials and methods.” Cells were exposed to 1 μM Bay 11-7082 ± 200 nM UCN-01. After 24-hour treatment, the extent of apoptosis was determined by evaluating Wright-Giemsa-stained cytospin preparations. Parallel studies were performed using the CD138^- cell population. Values represent means ± SDs for 10 randomly selected fields encompassing more than 500 cells.