KPT-330+CS arrests cells in S phase and inhibits DNA damage repair. (A) Cell-cycle profile of CS, KPT-330, and KPT-330+CS–treated unsynchronized JeKo-1 cells. The KPT-330+CS treatment arrests cells at S phase (blue filled arrow) and induces cell death (blue hollow arrow). (B) Cell-cycle profiles of KPT-330+CS–treated JeKo-1 cells assessed at different time points from release after G₁-phase synchronization. Blue filled arrow indicates progression of S-phase arrest with time and blue hollow arrow indicates fraction of cell death. (C) γ-H2AX foci (green) formed in JeKo-1 cells following KPT-330+CS treatment of 24 hours. Images were obtained from a Zeiss LSM 780 confocal microscope at ×100 magnification (D) Immunoblot assessing γ-H2AX and Rad51 in JeKo-1 cells following KPT-330+CS treatment. (E) Comet assay indicated DNA damage (comet tail) in JeKo-1 cells treated with KPT-330+CS for 24 hours. Images were obtained from Zeiss LSM 780 confocal microscope at ×10 magnification after staining with SYBR gold DNA stain (red square denotes cells additionally magnified 2×). (F) HRD assessment following respective drug treatments. Y-axis represents percent GFP⁺ cells assessed through flow cytometry. The GFP⁺ cell signifies the degree of HR proficiency. (G)Viability assessment of JeKo-1 cells through Annexin V/PI assay following 48 hours of incubation with respective drug concentrations; KPT-330 (0.5 µM), and CS (3 mM) and olaparib (10 µM). **P = .0016. The paired Student t test was used to compare all continuous variables. A value of P < .05 was considered statistically significant.