Caspase inhibition attenuates the uptake of L88 stroma cell–derived exosomes in hematological malignant cells. (A) Percentage of PKH67-positive OPM2 or RPMI cells after 3 hours of incubation with PKH67-labeled L88 cell–derived exosomes that were preincubated with zVAD.fmk or DEVD.fmk. (B) Percentage of MM patient-derived, PKH67-positive cells after 3 hours of incubation with PKH67-labeled L88 cell–derived exosomes, pretreated with the caspase-3 inhibitor z-DEVD.fmk (5 patient samples run in duplicate). (C) Representative confocal microscopy images of MM patient 2 and patient 4 positive cells upon incubation with PKH67-labeled L88 cell–derived exosomes (bar represents 4 µm). (D) Percentage of ALL patient-derived, PKH67-positive cells after 3 hours of incubation with PKH67-labeled L88 cell–derived exosomes, pretreated with the caspase-3 inhibitor DEVD.fmk (1 patient plasma sample, run in duplicate). (E) Percentage of acute myeloid leukemia (AML) patient-derived, PKH67-positive cells after 3 hours of incubation with PKH67-labeled L88 cell–derived exosomes, pretreated with the caspase-3 inhibitor DEVD.fmk (1 patient plasma sample, run in duplicate).