Background: Surgery remains the most important treatment strategy for solid tumors, such as colorectal cancer (CRC); However, a number of studies have suggested that surgical stress contributes to tumor recurrence or distant metastases. Extracellular vesicles (EVs), which contain a rich variety of RNAs with specialized functions and clinical applications, have been shown to be an indicator for diagnosis and prognosis of cancers. The effect of surgical stress on the landscape and characteristics of EV long RNA (exLR) in human blood, however, remains largely unknown.
Methods: We present an optimized strategy for exLR sequencing (exLR-seq) the plasma from three patients with CRC at 4 time points (before surgery [T0], after extubation [T1], 1 day after surgery [T2], and 3 days after surgery [T4]). The “Limma” R package was used to evaluate the dynamic changes of mRNAs and long non-coding (lnc)RNAs from EVs. We also constructed a protein–protein interaction (PPI) network of hub genes and predicted biological processes, cellular components, and molecular functions of gene ontology (GO) functional analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway.
Results: We observed a sufficient number of exLRs, including 12,924 mRNAs and 2196 lncRNAs. Both mRNAs and lncRNAs underwent dynamic changes during the peri-operative period. Compared with T0, there were 110 mRNAs differentially expressed after extubation, 60 differentially expressed genes（DEGs）1 day after surgery, and 50 DEGs 3 days after surgery. A total of 11 genes changed at all 3 time points and were related to regulation of the membrane potential, receptor complex, and passive transmembrane transporter activity. In addition, 22 lncRNAs were differentially expressed after extubation (T1). Nineteen lncRNAs were differentially expressed between T0 and T2, and 38 lncRNAs were differentially expressed between T0 and T3. In addition, we found that only 3 lncRNAs changed at 3 time points. Interestingly, blood exLRs reflected the tissue origins and relative fractions of different immune cell types. EVs from CD8+ T，CD4+ memory T, and NK cells decreased after surgery and the absolute quality of EVs from immune cells decreased as well.
Conclusion: In summary, this study demonstrated abundant exLRs in human plasma and the dynamic changes of these exLRs and exLRs originating from CD8+ T and CD4+ memory T cells were reduced during the peri-operative period.