Figure 5. PI3Kδ and PKCβ activities are involved in the stroma-induced resistance of CLL cells to ATO.
(A) 2 × 105 CLL cells were incubated for 1 h with or without the indicated inhibitors and cultured with HS-27A stromal cells. After 2 h at 37°C, 2 μM ATO was added or not, and cells further incubated for 24 h. Cell viability was determined by flow cytometry. LY, LY294002; Tric, Triciribine; Bis I, Bisindolylmaleimide I; UO, UO126; NF-κB-i, NF-κB inhibitor. The inhibitory effect of UO126 and PP2 was confirmed by Western blotting. (B, C) 2 × 105 CLL cells were treated for 1 h with the indicated concentrations of idelalisib (B) or sotrastaurin (C) and cultured on HS-27A cells, in the absence or presence of 2 μM ATO. UO was used as control in these experiments. After 24 h, cell viability was determined by flow cytometry. (D, E) Combination index values for the interaction of 2 μM ATO with various concentrations of idelalisib (Idela) (D) or sotrastaurin (Sotras) (E) were calculated using the CompuSyn software. Graphs represent the means of five different experiments, each with a different CLL sample. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001.