Fig. 1.

PARP inhibition increases FdUrd-induced Chk1 and Chk2 activation and causes persistent DNA damage. OVCAR-8 cells were treated with 2 μM FdUrd and 3 μM ABT-888. After 24 h of incubation, one set of cells (labeled 24 h, lanes 2–4) was collected. The second set of cells (labeled 24 + 24 h, lanes 5–7) was washed after 24 h to remove FdUrd, and 3 μM ABT-888 was readded to samples that initially contained ABT-888. These cells were then cultured an additional 24 h. A, cell lysates were immunoblotted for the indicated antigens. B, cells were stained to detect phospho-Ser139-H2AX (P-H2AX) and analyzed by flow cytometry. P, phospho; HSP90, heat shock protein 90.