Abstract
In this study Next-Generation Sequencing (NGS) was used to analyze and compare human microbiota from three different compartments, i.e., saliva, feces, and cancer tissue (CT), of a selected cohort of 10 Italian patients with colorectal cancer (CRC) vs. 10 healthy controls (saliva and feces). Furthermore, the Fusobacterium nucleatum abundance in the same body site was investigated through real-time quantitative polymerase chain reaction (qPCR) to assess the association with CRC. Differences in bacterial composition, F. nucleatum abundance in healthy controls vs. CRC patients, and the association of F. nucleatum with clinical parameters were observed. Taxonomic analysis based on 16S rRNA gene, revealed the presence of three main bacterial phyla, which includes about 80% of reads: Firmicutes (39.18%), Bacteroidetes (30.36%), and Proteobacteria (10.65%). The results highlighted the presence of different bacterial compositions; in particular, the fecal samples of CRC patients seemed to be enriched with Bacteroidetes, whereas in the fecal samples of healthy controls Firmicutes were one of the major phyla detected though these differences were not statistically significant. The CT samples showed the highest alpha diversity values. These results emphasize a different taxonomic composition of feces from CRC compared to healthy controls. Despite the low number of samples included in the study, these results suggest the importance of microbiota in the CRC progression and could pave the way to the development of therapeutic interventions and novel microbial-related diagnostic tools in CRC patients.
Highlights
Colorectal cancer (CRC) is the third most frequent tumor worldwide and is considered as the fourth leading cause of cancer deaths (Rowland, 2009), accounting for about 1.2 million new cases and 600,000 deaths per year
Differences in bacterial community composition were assessed using the analysis of similarity (ANOSIM function with 1,000 permutations)
The different body sites showed different bacterial compositions (R = 0.834, P = 0.001), along with feces samples coming from controls and CRC patients (R = 0.201, P = 0.005)
Summary
Colorectal cancer (CRC) is the third most frequent tumor worldwide and is considered as the fourth leading cause of cancer deaths (Rowland, 2009), accounting for about 1.2 million new cases and 600,000 deaths per year. The CRC etiology is still not fully understood, but the development of colorectal carcinogenesis is a heterogeneous progression with different sets of genetic and epigenetic variations, and is influenced by dietary patterns, environmental conditions, host immunity, and microbial adhesion (as reviewed in Russo et al, 2016). The association between some bacteria with the initiation and progression of neoplasia, e.g., Helicobacter pylori to gastric cancer (Amedei et al, 2014), has been well-established. This infection is the cause of approximately 5.5% of all cancers (Parkin, 2006). The obtained results suggested that the breakdown of the intestinal microbiota structure could promote carcinogenesis and CRC development
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