Unraveling the roles of extracellular vesicles in the colorectal tumor microenvironment

Colorectal cancer (CRC) remains a global health challenge, yet the lack of reliable biomarkers hinders early detection and improved patient outcomes. Further challenges arise due to the paucity of information about the tumor microenvironment (TME) that promotes tumor progression and metastasis. Extracellular vesicles (EVs), which carry molecular fingerprints of the parent cell, facilitate intercellular communication within the TME. This study aimed to leverage EVs as a tool to gain comprehensive insights into the TME and identify potential biomarkers for CRC. Tissue-derived EVs were successfully extracted from 123 fresh tissue samples (tumor, paired adjacent healthy mucosa, and inflammatory control) and characterized by transmission electron microscopy, nanoparticle tracking analysis, super-resolution microscopy, and bead-based flow cytometry. EVs from tumor tissues (CRC-TISSUE-EVs) had distinct surface marker profiles compared to EVs from healthy colonic tissues (HC-TISSUE-EVs), highlighting the different cellular composition and interactions in the TME. CRC-TISSUE-EVs displayed enrichment of platelet activation (CD42a, CD62p, CD142), angiogenesis (CD31), myeloid (CD11c, CD14, HLA-DR), and lymphoid (CD24, CD25, CD40, CD86) markers, while HC-TISSUE-EVs showed upregulation of cell activation (CD69, HLA-ABC) and tissue-specific markers (CD29, CD44, CD146). Notably, CRC-TISSUE-EVs exhibited downregulation of the NK cell marker (CD56) and upregulation of Treg (CD25) marker, suggesting potential immune escape mechanisms. Evaluation of biomarker potential revealed CD42a, CD56, CD44, and CD146 as promising candidates for CRC detection with high sensitivity and specificity. For prognosis, HLA-DR emerged as the best positive risk marker, while HLA-ABC, CD146, CD44, and CD56 were indicated as negative risk markers. Principal component analysis confirmed the ability of the tissue-derived EV surface markers to discriminate between CRC and healthy states, reinforcing their diagnostic value. Furthermore, CRC-TISSUE-EVs have also been demonstrated to enhance the malignancy of CRC cells in vitro, implicating their functional role in tumor progression. Altogether, this study provides novel insights into the role of EVs in the CRC TME and highlights their potential as biomarkers for CRC detection and monitoring.