Bioinformatics analysis reveals link between alternative complement cascade pathway and colorectal cancer liver metastasis

Abstract

Background Colorectal cancer (CRC) has a high incidence mortality rate and is characterized by liver metastasis, which is the main cause of CRC patient death. In this study, a transcriptome sequencing dataset (GSE81558) from the integrated Gene Expression Omnibus database was evaluated to gain new insights into the pathogenesis of CRC and potential therapeutic targets. Methods All raw data were processed using R and screened for differentially expressed genes (DEGs) using LIMMA software. In-depth Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted and visualized using R and Cytoscape software. Protein‒protein interactions (PPIs) associated with the DEGs were assessed using the Search Tool for the Retrieval of Interacting Genes/Proteins database. A mouse model of CRC liver metastasis of CRC was used to verify key associated signaling pathways. Results The GO biological processes (BPs) and KEGG pathway analyses revealed that DEGs between the normal colon and CRC samples were mainly involved in the cell cycle and the P53 signaling pathway, which regulate the cell cycle and alter tumor signaling pathways. The 10 hub genes identified by PPI were cell cycle-related. In CRC versus and CRC liver metastasis samples, the GO BPs were mainly associated with platelets and coagulation, and the KEGG pathways were mainly enriched in the complement and coagulation cascades and drug metabolism. The PPI hub genes were blood protein-related, such as ALB, AHSG, and APOH, or plasma protease inhibitors, such as SERPINC1. To confirm bioinformatics analysis results, we used wild-type (WT), C4 (an important molecule in the classical and lectin complement cascade pathways), and complement factor B (fB, an important molecule in the alternative complement cascade pathway) knockout (KO) mice to construct a CRC liver metastasis model. Compared with WT mice, fB-KO mice demonstrated significantly reduced liver metastasis and inflammation, while there was no difference in C4-KO mice. Conclusion Bioinformatics analyses revealed that the complement cascade is related to CRC liver metastasis and that the cell cycle is related to CRC. The role of the alternative complement pathway in CRC liver metastasis was confirmed in mice, indicating that this pathway is a potential therapeutic target in CRC liver metastasis and providing a theoretical basis for further research.