Characterizing functional DNA damage and response caused by the combination of CHK1 and WEE1 inhibitors in ovarian and breast cancer models

We proposed to quantify reduction of functional DNA damage response (DDR) mechanisms caused by the combination of CHK1 and WEE1 inhibitors. Survival of cells and tumor growth in-vitro and in-vivo caused by the combination of the CHK1 inhibitor SRA737 and the WEE1 inhibitor adavosertib was studied in OVCAR3 and MDA-MB 436 cells. Functional DNA damage was quantified using in vitro cell free DNA assays. The combination of SRA737 and adavosertib caused significant reduction of survival of cells and DNA damage in-vitro and growth inhibition in-vivo. Studies using functional DDR assays found significant changes in the functional capacity of OVCAR3 but not MDA-MB 436 cells to repair DNA damage using multiple mechanisms including intra strand cross link repair, nucleotide excision repair, homologous recombination and non-homologous end joining. This study, for the first time provides a mechanistic insight into differences in the reduction in functional capacity of cells to repair DNA when exposed to CHK1 and WEE1 inhibitors. The combination of the CHK1 inhibitor SRA737 and WEE1 inhibitor adavosertib causes growth inhibition in-vitro and in-vivo, but differential functional inhibition of DDR in the models studied.