Preparation of exosomes derived from colorectal carcinoma cells and their effects of promoting proliferation on mononuclear cells

Objective: To separate and identify the exosomes from colorectal carcinoma cells and to preliminarily study their immunological characteristics, and to provide basis for the application of exosomes in colorectal carcinoma immunotherapy. Methods: The normal exosomes and heat shock exosomes of HCT116 and SW480 cells were separated by ultracentrifugation and purified by 220 nm microspore film. The morphology of exosomes were observed under transmission electron microscope. The protein compositions of cells and exosomes were analyzed by SDS-PAGE method. The promoting function of exosomes in proliferation of peripheral blood monouclear cells (PBMCs) was detected. Results: Under transmission electron microscope, the normal exosomes and heat shock exosomes had similar appearance. They were either spherical or oval membrane vesicles, whose diameters were about 50-100 nm. The results of SDS-PAGE showed the differences of protein compositions between colorectal cell lysates and exosomes derived from colorectal carcinoma cells. Compared with untreated and heat shock treated colorectal carcinoma cells, the exosomes had stronger promotion effect on PBMCs proliferation (P < 0.05). The proliferaton of PBMCs could be reinforced with heat shock(P<0.05). Conclusion: For separation and identification of the exosomes derived from colorectal carcinoma cells, the method of ultracentrifugation and filtration is simple and feasible. The differences of protein composition between colorectal cell lysates and exosomes may be the major reason of their differences in immunological characteristics. The immuogenicity of exosomes could be enhanced by treating the cells with heat shock.