Abstract: Abstract: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. 

Key words: colorectal neoplasms, exosome, heat shock, immunotherapy