Isolation and characterization of circulating micro(nano)vesicles in the plasma of colorectal cancer patients and their interactions with tumor cells.

Micro(nano)vesicles (MV) are regarded as important messengers in cell-to-cell communication. There is also evidence for their pivotal role in cancer progression. Circulating MV are of different body cells origin, including tumor cell‑derived MV (TMV) in cancer patients. Determination of circulating TMV is of importance because of their potential diagnostic and therapeutic applications. In the present study, an analysis of circulating MV in colorectal cancer (CRC) patients was undertaken. Plasma from healthy donors was used as the control. In order to define MV characteristics, two plasma fractions: obtained by sequential centrifugation at 15,000 x g (MV15) and 50,000 x g (MV50) were used for analysis. The two fractions possessed a large range of sizes: 70(80)-1,300(1,400) nm and the most common particles with sizes 70-90 nm, both in patients and controls. Atomic force microscopy images of MV50 revealed a heterogeneous population of particles with different shapes and sizes. MV15 contained an increased level of CD41+ and CD61+ particles, suggesting their platelet origin. No difference between patients and controls was observed. A more precise analysis of MV50 showed the increased level of particles expressing EGFR (HER-1/Erb B1), HER-2/neu and Mucin1 (MUC1), suggesting their tumor origin. The total level of MV50‑expressing EGFR, HER-2/neu and MUC1 was enhanced in CRC patients. MV50 both of patients and controls attached to a colon cancer cell line (SW480) and to isolated blood monocytes at 2 h and were engulfed at 24 h. This uptake showed the lack of specificity. Thus, apart from the direct delivery of MV to the tumor site by plasma, monocytes carrying MV may also be involved in their transportation. Taken together, the presented data indicate that MV15 contain mainly platelet‑derived particles, while MV50 from CRC patients are enriched in TMV. Interaction of MV with cancer cells may pin-point their role in communication between tumor cells, resulting in molecular cargo exchange between them.