Olaparib targets proliferating lymphoid cells. (A) Percentage of BrdU-positive cells significantly decreases 7 days after exposure to increasing doses of olaparib in Granta-519 cells. (B) Effect of continued olaparib exposure on proliferation of ATM null cells. After 7 days exposure to 3μM olaparib, Granta519 (top), PGA-ATMsh (middle), and PGA-GFPsh (bottom), cells were reseeded at a low number and then continuously exposed to either 0μM or 3μM olaparib for an additional 2 weeks.