Fig. 6. Induction of cell cycle arrest and apoptosis by ATL and olaparib.

a, b Flow cytometry analysis of cell cycle distribution. Treatment by the combination of 10 μM ATL and 10 μM olaparib (Ola) caused progressive accumulation of PC-3 cells in the S and G₂/M phases within the first 48 h, and then the G₂/M but not the S population started to fall, meanwhile, the sub-G₁ population increased steadily. c Western blot analysis of phosphorylated H3. The levels of H3-pS10 in PC-3 cells decreased sharply after treatment by the combination of 10 μM ATL and 10 μM olaparib (Ola) for 12 h and longer, indicating that the cells in the G₂/M population were in early-to-mid G₂ phase. d Western blot analysis of cleaved caspase 3. Treatment by the combination of 10 μM ATL and 10 μM olaparib (Ola) caused a rapidly progressive increase in the levels of cleaved caspase 3 in the PC-3 cell line. e Flow cytometry analysis of apoptosis in PC-3 cells. Treatment by the combination of 10 μM ATL and 10 μM olaparib (Ola) caused a time-dependent increase in Annexin V-positive cells, most of which were propidium iodide (PI) negative, indicating they were in early apoptosis. The pan-caspase inhibitor Z-VAD-FMK suppressed the increase in Annexin V-positive cells.