Circulating microvesicles (cMVs) are 40-100nm membrane-bound structures that play an important role in several biologic processes,
including angiogenesis and immune modulation. cMV levels are known to change in response to certain pathologies, and specific subpopulations of cMV can be isolated using antibodies targeted to membrane proteins specific for the secreting cells. We examined whether the levels of specific cMV subpopulations are altered in patients with a disease, specifically breast cancer. In order to characterize individual cancer-associated microvesicles (MVs), advanced breast cancer MVs were compared with normal control MVs. Circulating microvesicles were isolated from breast cancer patients and non-cancer control patients, stained with fluorochrome-conjugated antibodies, and analyzed using flow cytometry. Tumor-specific antibodies were paired with process-specific markers, such as DLL4 and VEGFR2 for angiogenic cMVs, CTLA4 and FasL for immunosuppressive cMV, and CD80 or CD83 for immunostimulatory cMV, to identify and characterize cMV subpopulations.