Changes of Intestinal Microflora in Colorectal Cancer Patients after Surgical Resection and Chemotherapy

Abstract

Objective. The change of bacterial flora structure in colorectal cancer (CRC) patients after treatment is not clear. The aim of this study was to explore the change and function of intestinal microflora in CRC before and after treatment. Method. The 16S conserved region V3+V4 of intestinal flora obtained from CRC patients was sequenced and analyzed. Alpha and beta diversity indices were used to analyze the abundance and structure of gut flora. FAPROTAX, BugBase, and Tax4Fun software were used to analyze the species phenotypes and Kyoto Encyclopedia of Genes and Genomes Ontology (KO) function pathways. Results. Total abundance and structure of species in CRC patients were significantly increased compared with healthy people (control group) ( $P<0.05$ ), but there was no significant difference between CRC patients before and after treatment ( $P>0.05$ ). There was significant difference in relative abundance of bacteria at different levels (phylum, class, order, family, genus, and species) between the CRC group with after operation (CRC_O group) and chemotherapy (CRC_C group) treatment, particularly Prevotellaceae_UCG-001, Akkermansia, Fusicatenibacter, Tyzzerella_4, Megamonas, etc. in genus level. The KO function analysis showed that most of the bacteria with differences were mainly involved in the biosynthesis of lipopolysaccharide (Megamonas, Megasphaera, and Ruminococcus torques_group), protein digestion and absorption, renin-angiotensin system pathway (Akkermansia, Eubacterium_ruminantium_group, and Eubacterium_nodatum_group genus), adipocytokine signaling pathway and peroxisome pathway (Tyzzerella_4, Phascolarctobacterium, Ruminococcus_gnavus_group), and so on. Conclusion. The abundance of intestinal microflora in CRC patients was increased significantly contrasted to healthy people, and surgery and chemotherapy were hard to reduce this phenomenon. Megamonas was involved in lipopolysaccharide biosynthesis and carcinogenesis in colorectal cancer. Surgery and drug treatment did not reduced lipopolysaccharide biosynthesis but increased the number of probiotic Akkermansia population and reduced the pathogenic bacteria Tyzzerella_4, participate in adipocytokine signaling pathway, and affect metabolism.