Development of a multiparameter flow cytometric assay as a potential biomarker for homologous recombination deficiency in @entity1 with high-grade serous XXXX .

@entity1 @entity43 @entity15124 @entity3003 @entity9190 @entity6545
OBJECTIVES: @entity9190 inhibitors (PARPi) are a novel class of drugs with activity in @entity1 with acquired or germline homologous recombination (HR) deficiency-associated high-grade serous @entity43 (HGSOC). We hypothesized that measuring yH2AX as an indicator of DNA double-strand breaks (DSB), and @entity15124 or @entity6545 as an indicator of DSB repair, would reflect HR status and predict response to PARPi-based therapy. Our aim was to develop and use high-throughput multiparametric flow cytometry to quantify yH2AX with @entity15124 or @entity6545 in PBMCs as a readily available surrogate. METHODS: Healthy donor PBMCs were used for assay development and optimization. We validated induction of yH2AX, @entity15124 and @entity6545 by staining with fluorophore-conjugated antibodies. The multiparameter flow cytometric method was applied to PBMC samples from recurrent HGSOC @entity1 who were treated with PARPi, olaparib and @entity3003 . RESULTS: Stimulation was necessary for quantification of a DNA damage response to olaparib/ @entity3003 in healthy donor PBMCs. The flow cytometric protocol could not distinguish between cytoplasmic and nuclear @entity6545 , erroneously indicating activation in response to injury. Thus, @entity15124 was selected as the marker of DSB repair. PBMCs from 15 recurrent HGSOC @entity1 were then examined. @entity1 who did not respond to PARPi therapy had a significantly higher pre-treatment level of yH2AX (p  =  0.01), and a higher ratio of yH2AX/ @entity15124 (11.0 [3.5-13.2] v. 3.3 [2.8-9.9], p  <  0.03) compared with responders. CONCLUSIONS: We successfully developed and applied a multiparameter flow cytometry assay to measure yH2AX and @entity15124 in PBMCs. Prospective studies will be required to validate this surrogate biomarker assay as a potential predictive biomarker of PARPi-based therapy.
