Fig. 7: Inhibition of the alpha/delta isoforms of PI3K is required to induce cell death of senescent tumor cells.

Proliferating and senescent (day 7 after γIR) HCT116 (A, B, E), MCF-7 (C, F) and A549 (D) cells were treated with PX-866 (3, 10 and 30 µM, orange bars in all panels) or other inhibitors for 24 h before cell death induction was quantified by determining released LDH activity in the cell culture supernatant. In (A), autophagy-modulating inhibitors such as Torin-2 (0.1, 0.5 and 1 µM, targets mTOR) and SAR405 (1, 5 and 10 µM, targets Vps34, the only class III PI3K) were tested in addition to PX-866. In (B), the dual Pan-PI3K/mTOR inhibitor BEZ235 was analyzed. In B–D, the pan-PI3K inhibitor BAY80-6946 was employed. In (E, F), the PI3K-alpha-inhibitor BYL-719 and the PI3K-delta-inhibitor CAL-101 were used either alone or together in two different concentrations (3 and 10 µM for BYL-719, 1 and 10 µM for CAL-101). Please note, that for a better comparison the data bars for the solvent control (DMSO) as well as for PX-866 (in orange) are included as a reference in all graphs. In a similar manner, the results for A549 treated with DMSO and PX-866 (D) is also shown in Fig. 3C. A gray line was used in all panels to demonstrate the level of released LDH activity in senescent cells without any other treatment. The data shown in all panels are the mean ± SD of at least three independent experiments. Individual data points are represented in the bar charts by small black squares. n.s. not significant, *p < 0.05, **p < 0.01, ***p < 0.001.