PD184352/UCN-01–induced apoptosis proceeds via IL-6– and IGF-1–independent pathways in MM cells.

8226 (A), H929 (B), and U266 (C) MM cells were exposed to 10 μM PD184352 + 150 nM UCN-01 or 10 μM dexamethasone for 24 to 72 hours in the presence or absence of 100 ng/mL IL-6, after which the loss of viability, reflected by MTS dye reduction, was determined as described in “Materials and methods.” Alternatively, cells were exposed to PD184352 + UCN-01 for 24 or 48 hours in the presence or absence of 400 ng/mL IGF-1, after which the percentage of apoptotic cells was determined (D) by examining Wright-Giemsa–stained specimens as described in “Materials and methods.” For panels A, B, and C: ▪ indicates PD + UCN; ■, PD + UCN + IL-6; ▾, Dex; ▿, DEX + IL-6. For panel D: ■ indicates control; ▪, PD + UCN; ▨, PD + UCN + IGF-1. In all cases, values represent the means ± SD for 3 separate experiments performed in triplicate.