PARP cleavage and cell cycle profile of MM cells exposed to GW654652. (A) GW654652 induces proteolytic cleavage of PARP. MM.1S cells were treated with GW654652 for 24 and 48 hours, followed by immunoblot analysis of the lysates with anti-PARP antibody. (B) Cell cycle profile of MM cells exposed to GW654652. U266 cells were cultured for 48 hours in the presence of GW654652 (1 and 5 μg/mL). Cultures in media alone served as negative control. Cells were stained with propidium iodide, and cell cycle profile was determined using flow cytometry.