Proteomic analysis of microvesicles derived from human colorectal cancer ascites.

The presence of malignant ascites in the peritoneal cavity is a poor prognostic indicator of low survival rate. Various cancer cells, including those of colorectal cancer (CRC), release microvesicles (exosomes) into surrounding tissues and peripheral circulation including malignant ascites. Although recent progress has revealed that microvesicles play multiple roles in tumor progression, the protein composition and the pathological function of malignant ascites-derived microvesicles are still unknown. Here, we report the first global proteomic analyses of highly purified microvesicles derived from human CRC ascites. With 1-D SDS-PAGE and nano-LC-MS/MS analyses, we identified a total of 846 microvesicular proteins from ascites of three CRC patients with high confidence; 384 proteins were identified in at least two patients. We identified proteins that might function in tumor progression via disruption of epithelial polarity, migration, invasion, tumor growth, immune modulation, and angiogenesis. Furthermore, we identified several potential diagnostic markers of CRC including colon-specific surface antigens. Our proteomic analyses will help to elucidate diverse functions of microvesicles in cancer progression and will aid in the development of novel diagnostic tools for CRC.