Effects of ABT-888 on MM-cell survival, PARP1/2 activity, and DNA damage. (A) Effect of ABT-888 on MM-cell survival. Cells were treated with 0-20μM ABT-888 for 72 hours and viability was determined by annexin V/PI staining. Results shown here are representative of 3 independent experiments. (B-C) Protein levels of PAR polymers and γ-H2AX (p-Ser139-H2AX) (B) and p-ATM and ATM (C) after ABT-888 treatment in MM cell lines. Representative blot of PAR, γ-H2AX, p-ATM, and ATM both before and after 5μM ABT treatment is shown. (D-E) Effects of ABT-888 on γ-H2AX foci formation induced by ABT-888 (5μM) over time in OPM2 and MM1S MM cells and detected by immunofluorescent microscopy. Image acquisition was performed with an epifluorescence microscope (BX51; Olympus) and multispectral color camera (Nuance FX; CRi) with a 60× magnification lens and oil immersion.