PARP1 and acute lymphoblastic leukemia: Previous studies investigating the effects of a PARP inhibitor rucaparib in combination with 5-FU in the treatment of acute myeloid leukemia and acute lymphoblastic leukemia found that 5-FU and rucaparib synergize to induce a massive DNA damage ex vivo, measured by expression of phosphorylated histone (γH2AX) (Falzacappa et al., 2015).