Introduction
Extracellular vesicles (EVs) are essential mediators of intercellular signalling within the tumour microenvironment (TME), influencing cancer development and progression. Circulating monocytes may encounter tumour-derived EVs in the bloodstream or after entering the TME. Within the TME, monocytes and their derivatives, macrophages, can exhibit both tumour-promoting and tumour-suppressive properties. Interactions with rectal cancer (RC) EVs (RC-EVs) may predispose circulating monocytes towards phenotypes that promote a favourable TME for tumour survival. This study investigated the effects of RC-EVs on monocytes from healthy volunteers.
Methods
This study was approved by the Health and Disability Committee (15/CEN/143), and all participants provided written informed consent. Plasma samples were collected from RC patients (stage II-III) prior to neoadjuvant therapy. EVs were isolated from plasma and from the RC cell line SW837 using qEV SEC columns. EVs were quantified by TRPS, imaged using cryo-SEM, and protein contents were characterised by Western Blot. RC-EVs were co-cultured with monocytes from healthy volunteers, and changes in gene and protein expression were assessed by RT-qPCR and spectral flow cytometry.
Results
Western blots confirmed the presence of EV-associated markers CD63 and TSG101, and cyro-SEM showed spherical vesicles ranging from 40–300nm. RC-EVs modulated mRNA expression of genes related to pro- and anti-inflammatory functions, inflammasomes, and pattern recognition receptors in healthy monocytes. Relative to Dummy-EVs, SW837-EVs significantly increased CASP5 expression (0.71-fold) and decreased NOD1 expression (1.41-fold). Monocyte surface markers were also measured.
Summary/Conclusion
RC-EVs altered gene expression in primary human monocytes, suggesting RC-EVs may affect the inflammatory properties of circulating monocytes.