Intestinal Microbiota in Colorectal Adenoma-Carcinoma Sequence

Abstract

Background: Most colorectal cancer (CRC) cases are sporadic and develop along the adenoma-carcinoma sequence. Intestinal microbial dysbiosis is involved in the development of colorectal cancer. However, there are still no absolute markers predicting the progression from adenoma to carcinoma. This study aimed to investigate the characteristics of intestinal microbiota in patients with colorectal adenoma and carcinoma and its correlations with clinical characteristics.

Methods: Fecal samples were collected from 154 patients with CRC, 20 patients with colorectal adenoma (AD) and 199 healthy controls. To analyze the differences in the intestinal microbiota, 16S rRNA gene sequencing was conducted.

Results: At the genus level, there were four significantly different genera among the three groups, namely Acidaminococcus, Alloprevotella, Mycoplasma, and Sphingobacterium, while Acidaminococcus significantly decreased with the order of Control-AD-CRC (P < 0.05). In addition, Parvimonas, Peptostreptococcus, Prevotella, Butyricimonas, Alistipes, and Odoribacter were the key genera in the network of colorectal adenoma/carcinoma-associated bacteria. The top 10 most important species, including Butyricimonas synergistica, Agrobacterium larrymoorei, Bacteroides plebeius, Lachnospiraceae bacterium feline oral taxon 001, Clostridium scindens, Prevotella heparinolytica, bacterium LD2013, Streptococcus mutans, Lachnospiraceae bacterium 19gly4, and Eubacterium hallii, showed the best performance in distinguishing AD from CRC (AUC = 85.54%, 95% CI: 78.83-92.25%). The clinicopathologic features, including age, gender, tumor location, differentiation degree, and TNM stage, were identified to be closely linked to the intestinal microbiome in CRC.

Conclusion: Several intestinal bacteria changed along the adenoma-carcinoma sequence and might be the potential markers for the diagnosis and treatment of colorectal adenoma/carcinoma. Intestinal microbiota characteristics in CRC should account for the host factors.

Keywords: 16S rRNA; adenoma-carcinoma sequence; colorectal adenoma; colorectal cancer; intestinal microbiota.

FIGURE 1

(A) Venn diagram illustrating the total, unique, and shared number of OTUs predicted for AD and CRC group datasets; (B) Rarefaction curve of OTU; (C) Species accumulation boxplot.

FIGURE 2

(A) Box plot based on Good’s coverage; (B) Alpha diversity analysis based on the Chao1 index in the AD and CRC group (P = 0.95); (C) Alpha diversity analysis based on the Shannon index in the AD and CRC group (P = 0.74).

FIGURE 3

(A) Principal coordinates analysis (PCoA) based on weighted unifrac distance matrix in the AD and CRC group [Pr (> F) = 0.33]; (B) Non-metric multidimensional scaling (NMDS) based on weighted unifrac distance matrix in the AD and CRC group (stress = 0.202); (C) Beta diversity analysis by weighted UniFrac distance in the AD and CRC group (P = 0.88); (D) Principal coordinates analysis (PCoA) based on weighted unifrac distance matrix among Control, AD, and CRC group; (E) Non-metric multidimensional scaling (NMDS) based on weighted unifrac distance matrix among Control, AD, and CRC group (stress = 0.123).

FIGURE 4

(A) Venn diagram illustrating the total, unique, and shared number of significant pairwise difference at the genus level among the Control, AD, and CRC groups; (B) The relative abundance of the significant changed genera among the three groups; (C) Microbial association network for colorectal adenoma/carcinoma-associated genera; (D) Receiver operating curve (ROC) by Random Forest analysis for distinguishing AD patients from CRC; (E) Mean Decrease Accuracy (MDA) coefficients of the 10 most important species in distinguishing AD patients from CRC; (F) Mean Decrease Gini (MDG) coefficients of the 10 most important species in distinguishing patients with AD from patients with CRC.

FIGURE 5

Association between fecal microbiota and CRC clinical characteristics. (A) The correlation heatmap between intestinal microbiota and age of patients with CRC; (B) The correlation heatmap between intestinal microbiota and gender of patients with CRC; (C) The correlation heatmap between intestinal microbiota and the tumor location; (D) The correlation heatmap between intestinal microbiota and tumor stage.