Characterization of exosomes and MVs from tumor cells. Exosomes and MVs, collected by differential centrifugation, were characterized by TEM (A) and western blot (C). The size of MVs was determined by TEM on 25 measurements from MB-MDA-231 cells and 25 measurements from MCF7 cells. (B) The size of exosomes was determined from 20 measurements from MD-MBA-231 cells, 15 measurements from MCF7 cells, and 15 measurements from A549 cells. Results are presented as mean ± SEM. (C) Cell lysates, exosomes, and MVs (30 μg) from each cell line were analyzed by western blotting for TSG101, CD81, and actinin-4. One representative blot is shown for each cell line. Each blot was repeated 3 times with different samples. ****P ≤ .0001, Mann-Whitney U test (1 tailed).