Protein content of serum-purified exosomes from patients with colorectal cancer

Tumour cells of colorectal cancer (CRC) release exosomes into the circulation. These exosomes can mediate communication between cells and affect various tumour-related processes in their target cells. Researchers from the Chinese Academy of Medical Sciences present a quantitative proteomics analysis of the exosomes purified from serum of patients with CRC and normal volunteers; data are available via ProteomeXchange with identifier PXD003875. The researchers identified 918 proteins with an overlap of 725 Gene IDs in the Exocarta proteins list.

Compared with the serum-purified exosomes (SPEs) of normal volunteers, they found 36 proteins upregulated and 22 proteins downregulated in the SPEs of CRC patients. Bioinformatics analysis revealed that upregulated proteins are involved in processes that modulate the pretumorigenic microenvironment for metastasis. In contrast, differentially expressed proteins (DEPs) that play critical roles in tumour growth and cell survival were principally downregulated.

Pathway analysis of altered proteins

exosomes

All identified proteins were mapped to related wiki pathway databases. Proteins are represented by boxes labelled with the protein name. Relative protein expression level in SPEs of CRC patients is indicated by different colours. Proteins in grey were not identified in this study. Integrin-mediated cell adhesion pathway

This study demonstrates that SPEs of CRC patients play a pivotal role in promoting the tumour invasiveness, but have minimal influence on putative alterations in tumour survival or proliferation. According to bioinformatics analysis, the researchers speculate that the protein contents of exosomes might be associated with whether they are involved in premetastatic niche establishment or growth and survival of metastatic tumour cells. This information will be helpful in elucidating the pathophysiological functions of tumour-derived exosomes, and aid in the development of CRC diagnostics and therapeutics.

Chen Y, Xie Y, Xu L, Zhan S, Xiao Y, Gao Y, Wu B, Ge W. (2016) Protein content and functional characteristics of serum-purified exosomes from patients with colorectal cancer revealed by quantitative proteomics. Int J Cancer [Epub ahead of print]. [abstract]

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