Virulent Bacteria as Inflammatory and Immune Co-Factor in Colon Carcinogenesis: Evidence From Two Monozygotic Patients and Validation in CRC Patient and Healthy Cohorts

Abstract

Colorectal carcinoma (CRC) is a common disease, the incidence of which is increasing according to Western lifestyle; it remains to have a poor prognosis. Western nutriments are presumed to induce mild inflammation within the colonic mucosa, resulting in the accumulation of DNA alterations in colonocytes through a multistage carcinogenesis process. This suggests that most CRCs are related to the environment. Of interest, fecal microbiota composition has been shown yielding a novel approach regarding how environment changes may impact health and disease. Here, we compare whole shotgun metagenomic gut microbiota of two monozygotic twin sisters, one of whom is suffering from an advance colorectal tumor with a profound disequilibrium of the composition of the gut microbiota due to the overexpression of virulent bacteria such as E. coli, Shigella, and Clostridium species in the colon cancer patient's feces contrasting with low levels of bacterial species such as Faecalibacterium and Akkermansia usually enriched in the healthy adults' microbial flora. The disequilibrium in microbiota of the CRC patient's feces as compared to her monozygotic twin sister is linked to inflammatory and immune cell infiltrates in the patient's colonic tissue. We speculate on the role of microbiota disequilibrium on the immune-tolerant cell infiltrate within CRCs.

Trial registration: ClinicalTrials.gov NCT01270360.

Keywords: cancer; colon; immune cells; microbiota; virulent bacteria.

Figure 1

Levels of bacteria sequences, as assigned by whole metagenome sequencing [for methods see (Zeller et al., 2014; Sobhani et al., 2019)], by using the diamond software (MEGAN6) program and referring to the complete NCBI non-redundant protein database in two monozygotic twin sisters. The raw data are compared with values from our prospective cohorts, including patients with invasive CRC and those with precancerous polyps in the colon. The mean (a) and median values (b) in the adenomatous cohorts (n = 47), and the mean (c) and median values (d) in the CRC patient cohort (n = 187) are indicated for each bacteria; discontinued horizontal bars fit with the median value in the CRC patient cohort; FR-901 and FR-902 are the design code numbers of the CRC patient and her monozygotic sister, respectively.

Figure 2

Levels of cytokines and chemokines’ transcripts, as assessed by qRT-PCR in normal and neoplastic (polyps and CRC) colonic tissues in two monozygotic sisters (in reference to housekeeping genes; for methods, see Le Gouvello et al., 2008). FR-901 and FR-902 are the design code numbers of the CRC patient and her monozygotic sister, respectively; P1 and P2 are design polyps in the no-CRC patient.

Figure 3

Few inflammatory and immune cells were detected in the homologous normal colonic mucosa, compared to the tumoral tissue, in the patient with CRC (FR.901) (A–F). No active immune cells were detected in her monozygotic twin sister’s polyps (FR.902P20) (G, H). Notably, the IL17 TH pathway is involved in CD4+ Foxp3+ IL-17+ cells, which were expanded in both CRC and adenomatous patients, with a trend towards elevated immunostained cells in CRC tissues.