Fig. 7: DNA damage in ASNase-treated malignant B cells revealed their sensitivity to the PARP1/2 inhibitor, Olaparib.

a Total protein extract prepared from Eµ-Myc cells (#506 or #688) cultivated for 10 h in Asn-free medium, supplemented (+) or not (−) with Asn (0.37 mM) alone or in combination with ASNase (0.003 IU/ml), was immunoblotted using an anti-poly(ADP-ribose) antibody. Treatment with H₂O₂ (0.5 mM) for 5 min was used as a positive control. The samples derive from the same experiments but different gels for poly(ADP)-ribose, ERK2 and another for ATF4 were processed in parallel. b, c Percentage of dead Eµ-Myc cells (DAPI+) treated for 24 h with DMSO, ASNase (0.003 IU/ml) and/or the PARP inhibitor Olaparib (at indicated concentrations) in Asn-containing medium. (b, from #506 cells, n = 3 independent experiments; c, from #688, n = 5 independent experiments). d Percentage of dead Eµ-Myc (#688) cells (DAPI+) treated with DMSO, ASNase (0.003 IU/ml) and/or Olaparib (0.3 µM) for 24 h in Asn-containing medium and in the presence (+) or absence (−) of the caspase inhibitor qVD-OPh (20 µM) (n = 3 experiments). e, f Four-day proliferation of Eµ-Myc (#506) cells (e) and of Eµ-Myc (#688) cells (f) treated with DMSO, ASNase (0.003 IU/ml) and/or Olaparib (0.3 µM) in Asn-containing medium (n = 5 independent experiments). g Schematic representation of in vivo co-treatment with ASNase/Olaparib. h Body weight of Eµ-Myc (#506) cells-bearing C57BL/6 mice from the start of treatment (day 7 post tumor cell inoculation) (n = 10 mice/group). i Survival curves of WT C57BL/6 mice intravenously injected with Eµ-Myc (#506) cells and treated 7 days later with Vehicle, Olaparib (daily), ASNase (every 48 h) or their combination, for several weeks, until lymphoma development reached endpoint (n = 10 mice/group). Data are expressed as mean ± SD (b–f) ± SEM (h). P-values are from 2-way Anova followed by Tukey’s test (b–f), log-rank test (i) and indicated as ns, not significant; *, p < 0.05; **, p < 0.01; ***, p < 0.001 ****, p < 0.0001. For detailed individual P-value, please refer to the Source data table.