Analysis of PARPi-induced p-H2AX in CyclinA2- and CyclinA2+ subsets in DDR wild type or mutant cell lines distinguishes distinct levels of HRR deficiency including haploinsufficiency. (A) Flow plot examples of p-H2AX vs. CyclinA2 in untreated or 48 h PARPi AZD2281 (6 μg/mL) treated BRCA1+/+, BRCA1+/- and BRCA2-/- cell lines. (B) PARPi AZD2281 +/- temozolomide (2 μg/mL)-induced p-H2AX in CyclinA2- or CyclinA2+ subsets (columns) after treatment for 48 or 72 hr (rows) for cell lines of known HRR status (BRCA1+/+, squares; BRCA1+/-, circles; BRCA2-/-, crosses; Cell line panel 2, Materials and methods). Mean average Log2Fold values from two independent experiments are shown. T-test p-valuescomparing BRCA1+/+and BRCA1+/- cell lines are shown for each condition with significant (p < .05) indicated by an asterisk (*). Analysis of AZD2281 +/- temozolomide treatment in CyclinA2+ cells demonstrates highest p-H2AX induction in the BRCA2-/- cell line, medium induction in BRCA1+/- cell lines and lowest induction in BRCA1+/+ cell lines.