The Regional Specificity of Mucosa-Associated Microbiota in Patients with Distal Colorectal Cancer

Streptococcus anginosus: the potential role in the progression of gastric cancer

Gastric cancer (GC) is among the most common and aggressive malignancies worldwide, characterized by a poor prognosis. Research on its pathogenesis and progression continues to evolve. Streptococcus anginosus (S. anginosus, SA) is a Gram-positive coccus commonly found in the oral cavity and upper respiratory tract, serving as a commensal bacterium in the oral, gastrointestinal, and genitourinary tracts. It is frequently associated with abscess formation in various organs and tissues, as well as other purulent infections. In recent years, S. anginosus has gained increasing attention for its role in GC progression, potentially leading to chronic gastric inflammation and precancerous lesions, and ultimately promoting the development of GC. Emerging evidence indicates a strong association between S. anginosus and the malignant progression and unfavorable prognosis of GC. This review summarizes the role and underlying mechanisms of S. anginosus in GC and proposes that S. anginosus plays a pivotal role in its initiation and progression, underscoring its potential therapeutic significance.

Altered microbiota of rectal mucosa in rectal cancer patients

BACKGROUND

With advances in sequencing techniques, microbiota dysbiosis and pathogenic microbes that accelerate colorectal cancer progression have been identified and widely reported. However, few studies have focused on the microbiota taxa of rectal mucus in rectal cancer (RC) patients. Here, we analyzed the composition and characteristics of the rectal mucosa microbiota of RC patients from Wenzhou city, China, and compared the results with those of healthy controls.

AIM

To explore the changes in the characteristics of the rectal mucosal flora associated with RC, and identify biomarkers of microbe taxa for RC.

METHODS

Rectal mucosa samples from a Chinese cohort of 72 recently diagnosed RC patients and 71 healthy controls were obtained. A validation cohort, which included 22 RC patients and 60 healthy controls, was also established. Changes in the rectal mucosal flora were observed by cultivation, 16S ribosomal DNA gene sequencing analysis and quantitative polymerase chain reaction analysis.

RESULTS

The 16S ribosomal DNA results demonstrated that RC patients presented increased bacterial community richness and alpha diversity as well as an altered rectal mucosal microbiota, with depletion of Proteobacteria and Thermi and enrichment of Bacteroidetes and Fusobacteria in cancerous mucosal tissues (CM) and enrichment of Firmicutes and Cyanobacteria in adjacent noncancerous mucosal tissues (AM). The culture results showed that the mean loads of Escherichia coli, Bifidobacterium, Enterococcus, and Lactobacillus were significantly reduced in RC patients. The ratios of Prevotella to Ruminococcus [areas under the receiver operating curve: 0.795 in AM vs normal control mucosa (NM), 0.77 in CM vs NM] and of Prevotella stercorea to Propionibacterium acnes (areas under the receiver operating curve: 0.808 in AM vs NM, 0.843 in CM vs NM) exhibited excellent abilities to differentiate between healthy controls and RC patients.

CONCLUSION

RC patients have an altered rectal mucosal microbiota, and the ratio of Prevotella to Ruminococcus or the ratio of Prevotella stercorea to Propionibacterium acnes may serve as a marker for RC diagnosis.

Reduced Abundance of Phocaeicola in Mucosa-associated Microbiota Is Associated with Distal Colorectal Cancer Metastases Possibly through an Altered Local Immune Environment

Objectives

The aim of this study was to identify the microbiota whose decrease in tumor area was associated with the metastatic process of distal colorectal cancer (CRC).

Methods

Twenty-eight consecutive patients with distal CRC undergoing surgical resection in our hospital were enrolled. Microbiota in 28 specimens from surgically resected colorectal cancers were analyzed using 16S ribosomal ribonucleic acid gene amplicon sequencing and the relative abundance (RA) of microbiota was evaluated. The densities of tumor-infiltrating lymphocytes (TIL) and tumor associated macrophages (TAM) in the colorectal cancers were immunohistochemically evaluated.

Results

Phocaeicola was the most abundant microbiota in normal mucosa. The RA of Phocaeicola in tumor tissues tended to be lower than that in normal mucosa although the difference was not significant (p=0.0732). The RA of Phocaeicola at tumor sites did not correlate either with depth of tumor invasion (pT-stage) or tumor size, however they were significantly reduced in patients with nodal metastases (p<0.05) and those with distant metastases (p<0.001). The RA of Phocaeicola at tumor sites showed positive correlation with the densities of CD3(+) or CD8(+) TIL. Since P. vulgatus was the most dominant species (47%) of the Phocaeicola, the RA of P. vulgatus and CRC metastasis and its association with TIL and TAM were also investigated. P. vulgatus showed a similar trend to genus Phocaeicola but was not statistically significant.

Conclusions

A relative reduction of Phocaeicola attenuates the local anti-tumor immune response in distal CRC, which may facilitate metastatic spread.

Progress in research of gut microbiota in colorectal cancer

The human gut microbiota is a large and complex microbial community that is linked to human health and disease. Intestinal homeostasis is dependent on the tight interplay between the host and gut microbiota. Moreover, the gut microbiota plays an important role in digestion and metabolism. In recent years, the gut microbiota is still the most studied topic, and numerous studies have shown that the gut microbiota is closely related to colorectal cancer. In this paper, we will review the relationship between the gut microbiota and colorectal cancer pathogenesis, prevention, and treatment, with an aim to provide some new ideas for the research of colorectal cancer.

Fusobacterium nucleatum and colorectal cancer: From phenomenon to mechanism

Colorectal cancer(CRC) is the third most frequent malignant tumor. The gut microbiome acts as a vital component of CRC etiology. Fusobacterium nucleatum(Fn) is a key member of colorectal cancer-associated bacteria. But we lack a systematic and in-depth understanding on its role in CRC evolution. In this article, We reviewed the abundance changes and distribution of Fn in CRC occurrence and development, potential effect of Fn in the initiation of CRC, the source of intratumoral Fn and the cause of its tropism to CRC. In addition, We described the mechanism by which Fn promotes the malignant biological behavior of CRC, affects CRC response to therapy, and shapes the tumor immune microenvironment in great detail. Based on the relationship between Fn and CRC, we proposed strategies for CRC prevention and treatment, and discussed the feasibility and limitations of specific cases, to gain insights into further basic and clinical research in the future.