Fig. 2

PARP1 inhibition restored CDK4/6i sensitivity. A–B. The 3 siRNA sequences in MCF7AR cells showed that PARP1 silencing restored sensitivity to abemaciclib. C. Overexpression of PARP1 restored abemaciclib sensitivity. D–G. Olaparib treatment promoted cell sensitivity to abemaciclib in 4 breast cancer cell lines. H–I. The combined therapy showed a synergistic antitumor effect by crystal violet staining assay. J. The cell cycle assay showed that G1 phase increased remarkably when treatment with combined therapy. K–L. The combined therapy induced cell apoptosis significantly in the flow cytometry assay. M–N. The fluorescence level of p-H2AX was upregulated simultaneously with PARP1 levels in MCF7 cells treated with abemaciclib. Orange represents p-H2AX, red represents p-YB-1 and blue represents DAPI. O–P. EdU can incorporate the replicated DNA molecule by replacing T-thymine during cell proliferation. Q. The enrichment in the DNA repair pathway when MCF7 cells were treated with abemaciclib. The results presented have been repeated in 3 biological replicates. Data, means ± SEMs, *, P < 0.05, **, P < 0.01, ***, P < 0.001