Fig. 2.
The combination of olaparib and palbociclib results in irreversible lethal DNA damage and redistribution of the cell cycle. a (Left) Representative images at different treatment time points of BRCAmut/TNBC cells stained with DAPI, γH2AX and RAD51. (Up) MDA-MD-436 cells treated with olaparib alone. (Down) HCC1937 cells treated with olaparib alone or olaparib plus palbociclib. (Right) The signal intensity of γH2AX and RAD51 in cells changing over time. Scale bar, 7.5 μm. b Quantitative reverse transcription PCR analysis of RAD51 mRNA expression in BRCAmut/TNBC cells treated with drugs as indicated in (a) for 72 h. c Efficiency of homologous recombination (HR) in U2OS cells treated with vehicle, 20 μM olaparib, 5 μM palbociclib or their combination for 72 h; n = 3 independent assays. d The percentage of cells in different phases of the cell cycle was analysed by flow cytometry. The treatment of cells was as described in (a). The p-value here is the t-test of the G2 + M phase of each group relative to the control group. e The effect of different sequential application was tested in colony formation assays. The effect of 6-day olaparib followed by 6-day palbociclib (O-P) and its reverse (P-O) effect were tested in HCC1937 cells. (Left) Pattern diagram of sequential administration. (Middle) Representative images of colony formation assays. (Right) Quantification of colony formation. Student’s t-test; ***p < 0.001, **p < 0.01, *p < 0.05; ns, not significant. The data are presented as the means ± SEMs. Con: Control; Ola: Olaparib; Palb: Palbociclib