Idelalisib treatment is associated with decreased expression of L-selectin on circulating CLL cells in vivo. (A) Graph represents the MFIR of L-selectin on CLL cells from patients (n = 6) under idelalisib treatment (−, before treatment; +, under treatment). Paired t test; *P < .05. (B) Rolling and sticking fractions of calcein-labeled CLL cells from a patient with bulky disease are shown before treatment, and at 3 or 7 weeks under idelalisib treatment. Mean ± SD, venular order III (n = 3), order IV (n = 4), order V (n = 3-4). Unpaired t test; *P < .05, **P < .01. (C) Data represent the percentages of CLL cells rolling at or below a given velocity (V_roll). The median velocity of cells before treatment, and at week 3 or week 7 was 69.59, 475.1, and 299.8 µm.s⁻¹, respectively, in order IV and 51.27, 247.2, and 185.9 µm.s⁻¹, respectively, in order V (19 to 30 cells per venular order were analyzed). Mann-Whitney test; ***P < .001. (D) Graph represents the MFIR of L-selectin on CLL cells from patients (n = 5) incubated ex vivo with (+) or without (−) idelalisib during 4 hours. Paired t test. (E) MFIR of L-selectin on CLL cells from 2 different patients, incubated ex vivo with (+) or without (−) idelalisib, during the indicated time (hours). Mean ± SEM, n = 3 experimental replicates. Data are representative of 3 independent experiments.