Caspase-3 is present and active in L88 exosomes. (A) Western blot analysis of the indicated proteins in L88 whole cell lysates and exosomes. (B) Caspase 3/7 activity assay performed in L88 cell–derived exosomes ± caspase inhibitors z-VAD.fmk or z-DEVD.fmk (mean ± standard deviation [SD], n = 3). ***P < .001. NT, not treated; U.A., units arbitrary. (C) Western blot analysis of L88 cell–derived exosomes treated with zVAD.fmk or DEVD.fmk and probed for the indicated proteins. (D) Western blot analysis of MCF-7 (pcDNA3.1 or caspase-3) transfected cells for the indicated proteins. (E) Caspase-3/7 activity assay performed in MCF-7–transfected cells treated with doxorubicin (mean ± SD, n = 3). (F) Western blot analysis in exosomes isolated from MCF-7–transfected cells for the indicated proteins.