Idelalisib-resistant CLL cells are sensitive to CC-115 treatment. (A) CLL cells obtained from a patient clinically sensitive to idelalisib (−) and CLL cells obtained after the patient became resistant to idelalisib (idelalisib-resistant) were pretreated with 1 µM CC-115 or 1 µM idelalisib and stimulated with αIgM for 20 minutes. Protein lysates were probed for pS6 (S240/244), pERK (T202/204), and actin as loading control. (B) CLL cells obtained from a patient clinically sensitive to idelalisib (−) and CLL cells obtained after the patient became resistant to idelalisib (idelalisib-resistant) were cultured on CD40L-expressing fibroblast in the presence or absence of 1 µM CC-115 or idelalisib for 24 hours. Protein lysates were probed for pAKT (S473), pERK (T202/204), pS6 (S240/244), and actin as loading control. (C) CLL cells from 2 patients that became resistant to idelalisib (idelalisib-resistant) and samples that response to idelalisib treatment (−) were incubated with 0. 1 to 10 μM CC-115 for 48 hours. Viability was assessed by DiOC6/PI staining, and specific apoptosis was calculated.