Intestinal microbiota and colorectal cancer: changes in the intestinal microenvironment and their relation to the disease

Exploring the gut microbiome: A potential biomarker for cancer diagnosis, prognosis, and therapy

The gut microbiome, a complex community of trillions of microorganisms in the intestines, is crucial in maintaining human health. Recent advancements in microbiome research have unveiled a compelling link between the gut microbiome and cancer development and progression. Alterations in the composition and function of the gut microbiome, known as dysbiosis, have been implicated in various types of cancer, including, esophageal, liver, colon, pancreatic, and gastrointestinal. However, the specific gut microbial strains associated with the development or progression of cancers in various tissues remain largely unclear. Here, we summarize current research findings on the gut microbiome of multiple cancers. This review aims to identify key gut microbial targets that closely influence cancer development based on current research findings. To accurately evaluate the effectiveness of the gut microbiome as a clinical tool for cancer, further research is needed to explore its potential as a biomarker and therapeutic strategy.

Robust prediction of colorectal cancer via gut microbiome 16S rRNA sequencing data

Introduction. The study addresses the challenge of utilizing human gut microbiome data for the early detection of colorectal cancer (CRC). The research emphasizes the potential of using machine learning techniques to analyze complex microbiome datasets, providing a non-invasive approach to identifying CRC-related microbial markers.Hypothesis/Gap Statement. The primary hypothesis is that a robust machine learning-based analysis of 16S rRNA microbiome data can identify specific microbial features that serve as effective biomarkers for CRC detection, overcoming the limitations of classical statistical models in high-dimensional settings.Aim. The primary objective of this study is to explore and validate the potential of the human microbiome, specifically in the colon, as a valuable source of biomarkers for colorectal cancer (CRC) detection and progression. The focus is on developing a classifier that effectively predicts the presence of CRC and normal samples based on the analysis of three previously published faecal 16S rRNA sequencing datasets.Methodology. To achieve the aim, various machine learning techniques are employed, including random forest (RF), recursive feature elimination (RFE) and a robust correlation-based technique known as the fuzzy forest (FF). The study utilizes these methods to analyse the three datasets, comparing their performance in predicting CRC and normal samples. The emphasis is on identifying the most relevant microbial features (taxa) associated with CRC development via partial dependence plots, i.e. a machine learning tool focused on explainability, visualizing how a feature influences the predicted outcome.Results. The analysis of the three faecal 16S rRNA sequencing datasets reveals the consistent and superior predictive performance of the FF compared to the RF and RFE. Notably, FF proves effective in addressing the correlation problem when assessing the importance of microbial taxa in explaining the development of CRC. The results highlight the potential of the human microbiome as a non-invasive means to detect CRC and underscore the significance of employing FF for improved predictive accuracy.Conclusion. In conclusion, this study underscores the limitations of classical statistical techniques in handling high-dimensional information such as human microbiome data. The research demonstrates the potential of the human microbiome, specifically in the colon, as a valuable source of biomarkers for CRC detection. Applying machine learning techniques, particularly the FF, is a promising approach for building a classifier to predict CRC and normal samples. The findings advocate for integrating FF to overcome the challenges associated with correlation when identifying crucial microbial features linked to CRC development.

Dandelion root extracts and taraxasterol inhibit LPS‑induced colorectal cancer cell viability by blocking TLR4‑NFκB‑driven ACE2 and TMPRSS2 pathways

Colorectal cancer is the fourth leading cause of cancer-related death worldwide. Notably, abnormalities in intestinal bacteria may contribute to the initiation or progression of colorectal cancer. Lipopolysaccharide (LPS), a bacterial endotoxin, is elevated in patients with colorectal cancer. The present study investigated the protective effects of dandelion root extracts and taraxasterol (TS; a major pharmacologically active compound in dandelion root extracts) on LPS-induced colorectal cancer cell viability, as well as the underlying mechanisms. Cell viability was assessed by MTT assay, and protein and gene expression levels were determined by western blotting and quantitative PCR. It was revealed that LPS at a low dose (0.5 µg/ml) significantly promoted the viability of human colorectal cancer cells but did not affect normal colon epithelial cells. The addition of dandelion root extracts (0.1-1 mg/ml) or TS (0.05-1 µg/ml) was able to reverse the LPS-induced increase in colorectal cancer cell viability and colony formation. Mechanistically, dandelion root extracts or TS may inhibit the LPS-promoted toll-like receptor 4 (TLR4)/NFκB-p65 pathway and transcription levels of pro-inflammatory genes (TNFα, IL4 and IL6). Compared with normal colon epithelial cells, human colorectal cancer cells had higher expression levels of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which could be further enhanced by LPS treatment but this was reversed by co-incubation with dandelion root extracts or TS. In addition, suppression of the TLR4/NFκB-p65 pathway with CLI095 significantly reversed the stimulatory effect of LPS on the expression levels of ACE2 and TMPRSS2, whereas TNFα (10 ng/ml) markedly induced the expression levels of ACE2 and TMPRSS2. In conclusion, the present study suggested that dandelion root extracts and TS could be used as prevention strategies for reversing bacteria-driven colorectal cancer cell viability.

It Is All about Probiotics to Control Cervical Cancer

Cervical cancer (CC) is the fourth most common malignancy in female patients. "Human papillomavirus" (HPV) contamination is a leading cause of all forms of cervical cancer, accounting for an expected 570,000 reported incidents in 2018. Two HPV strains (16 and 18) are responsible for 70% of CC and pre-cancerous cervical abnormalities. CC is one of the foremost reasons for the malignancy death rate in India among women ranging from 30 to 69 years of age in India, responsible for 17% of all cancer deaths. Currently approved cervical cancer treatments are associated with adverse reactions that might harm the lives of women affected by this disease. Consequently, probiotics can play a vital role in the treatment of CC. It is reflected from various studies regarding the role of probiotics in the diagnosis, prevention or treatment of cancer. In this review article, we have discussed the rationale of probiotics for treatment of CC, the role of probiotics as effective adjuvants in anti-cancer therapy and the combined effect of the anti-cancer drug along with probiotics to minimize the side effects due to chemotherapy.

Analysis of the saliva microbiome in patients with immunoglobulin G4-related disease

OBJECTIVES

This article aims to investigate the saliva microbiome in patients with immunoglobulin G4-related disease (IgG4RD) compared with primary Sjögren's syndrome (SS).

METHODS

Saliva samples were collected from 11 IgG4RD and 11 SS patients who visited IMSUT Hospital, The Institute of Medical Science, The University of Tokyo. Deoxyribonucleic acid (DNA) was extracted from the samples, and primers were used to amplify the V3-V4 regions of bacterial and archaeal 16S ribosomal RNA (rRNA) genes, which was then analysed by paired-end sequencing. Amplicon reads were processed using QIIME2 to generate representative sequences. The Greengenes database was used to identify the bacterial flora in each sample and compare them between groups.

RESULTS

The IgG4RD and SS groups exhibited differences in bacterial diversity. Cluster analyses of attributed classification groups by species and disease showed that IgG4RD and SS cases formed individual clusters. Significant differences in relative abundance between IgG4RD and SS were observed for the following organisms: Mogibacterium (P = .0051), Solobacterium moorei (P = .0195), Slackia (P = .0356), and Moryella (P = .0455).

CONCLUSIONS

Salivary microbiome analysis of IgG4RD and SS patients revealed significantly higher relative proportions of Mogibacterium, S. moorei, Slackia, and Moryella bacteria in IgG4RD compared with SS.

Hungatella hathewayi impairs the sensitivity of colorectal cancer cells to 5-FU through decreasing CDX2 expression

Hungatella hathewayi (H. hathewayi), also known as Clostridium hathewayi, has been reported to be accumulated in the colorectal cancer (CRC) samples. In addition, evidence has demonstrated that inoculation with H. hathewayi promotes the proliferation of colonic epithelial cells in mice. Herein, we explored H. hathewayi role in regulating the 5-fluorouracil (5-FU) resistance in CRC cells, and investigated the underlying mechanisms. H. hathewayi abundance in CRC tissues and the corresponding adjacent normal tissues was tested using qRT-PCR. Both parental and 5-FU resistance CRC cell lines were used to assess H. hathewayi role in regulating the 5-FU resistance of CRC cells using CCK-8, flow cytometry and animal experiments. H. hathewayi abundance was significantly increased in CRC tissues, and the high level of H. hathewayi was linked to lower overall survival rate. H. hathewayi treatment significantly weakened 5-FU effects on inhibiting cell growth and inducing cell apoptosis in CRC HCT116 and HT29 cells. In addition, H. hathewayi enhanced the 5-FU resistance of HCT116/5-FU and HT29/5-FU cells (the 5-FU resistance cell lines). In mechanism, H. hathewayi decreased the expression of CDX2, and increased the expression of nuclear accumulation of β-catenin. Overexpression of CDX2 abolished H. hathewayi-mediated enhancement in cell growth and inhibition in cell apoptosis in HCT116/5-FU and HT29/5-FU cells, as well as inhibited the expression and nuclear accumulation of β-catenin. In conclusion, H. hathewayi abundance was increased in CRC tissues, and the high level of H. hathewayi was linked to lower overall survival rate. In mechanisam, H. hathewayi treatment enhanced the 5-FU resistance of CRC cells through modulating CDX2/β-catenin signaling.

Gut microbiota: key facilitator in metastasis of colorectal cancer

Colorectal cancer (CRC) ranks third in terms of incidence among all kinds of cancer. The main cause of death is metastasis. Recent studies have shown that the gut microbiota could facilitate cancer metastasis by promoting cancer cells proliferation, invasion, dissemination, and survival. Multiple mechanisms have been implicated, such as RNA-mediated targeting effects, activation of tumor signaling cascades, secretion of microbiota-derived functional substances, regulation of mRNA methylation, facilitated immune evasion, increased intravasation of cancer cells, and remodeling of tumor microenvironment (TME). The understanding of CRC metastasis was further deepened by the mechanisms mentioned above. In this review, the mechanisms by which the gut microbiota participates in the process of CRC metastasis were reviewed as followed based on recent studies.

Comparison of the effects of probiotic strains (Lactobacillus gasseri, Lactiplantibacillus plantarum, Lactobacillus acidophilus, and Limosilactobacillus fermentum) isolated from human and food products on the immune response of CT26 tumor-bearing mice

This study aimed to compare the effects of the probiotic bacteria, L. gasseri (52b), L. plantarum (M11), L. acidophilus (AC2), and L. fermentum (19SH), isolated from human source and traditional food products on the modulation of the immune system and inflammatory response on BALB/c mouse model bearing CT26 tumor. Five groups of female inbred BALB/c mice were orally administered with the probiotics and their mixes (MIX, at a 1:1 ratio) at varying dosages (1.5 × 108 cfu/ml and 1.2 × 109 cfu/ml) before and after the injection of a subcutaneous CT26 tumor over the course of 38 days via gavage. Finally, their effects on the tumor apoptosis and the cytokine levels in spleen cell cultures were analyzed and compared. M11, MIX, and 52b groups had the greatest levels of interleukin-12 (IL-12) and interferon gamma (IFN-γ) production. The highest production level of granzyme B (GrB) was related to the MIX and 52b groups. Moreover, these groups showed the lowest production level of (IL-4) and transforming growth factor beta (TGF-β). Furthermore, the groups of MIX and 52b demonstrated the greatest amount of lymphocyte proliferation of spleen cells in response to the tumor antigen. The delayed-type hypersensitivity (DTH) response significantly increased in the groups of MIX and 52b compared with the control (p < 0.05). The findings demonstrated that the oral treatment of the human strain (52b) and the combination of these bacteria generated strong T helper type 1 (Th1) immune responses in the tumor tissue of the tumor-bearing mice, which led to the suppression of the tumor development.

Role of Probiotics in the Prevention and Treatment of GIT Cancers: Updated Review

Cancer, one of the leading causes of death worldwide, has been the subject of extensive study by many researchers. Cancer is affected by both genetic and immune system factors in the human body. The gut microbiota plays an important role in the body's capacity to maintain homeostasis. Because of their beneficial effects on human health and their ability to successfully prevent and treat various chronic diseases, such as cancer, probiotics are becoming increasingly important in medicine. A wealth of research has shown that probiotic consumption can significantly helpful in cancer prevention and treatment. The goal of this review is to provide a thorough overview of the research on the function of probiotic bacteria in the prevention and treatment of gastrointestinal cancers.

Prediction model of colorectal cancer (CRC) lymph node metastasis based on intestinal bacteria

BACKGROUND

Lymph node metastasis is the main metastatic mode of CRC. Lymph node metastasis affects patient prognosis.

OBJECTIVE

To screen differential intestinal bacteria for CRC lymph node metastasis and construct a prediction model.

METHODS

First, fecal samples of 119 CRC patients with lymph node metastasis and 110 CRC patients without lymph node metastasis were included for the detection of intestinal bacterial 16S rRNA. Then, bioinformatics analysis of the sequencing data was performed. Community structure and composition analysis, difference analysis, and intragroup and intergroup correlation analysis were conducted between the two groups. Finally, six machine learning models were used to construct a prediction model for CRC lymph node metastasis.

RESULTS

The community richness and the community diversity at the genus level of the two groups were basically consistent. A total of 12 differential bacteria (Agathobacter, Catenibacterium, norank_f__Oscillospiraceae, Lachnospiraceae_FCS020_group, Lachnospiraceae_UCG-004, etc.) were screened at the genus level. Differential bacteria, such as Agathobacter, Catenibacterium, norank_f__Oscillospiraceae, and Lachnospiraceae_FCS020_group, were more associated with no lymph node metastasis in CRC. In the discovery set, the RF model had the highest prediction accuracy (AUC = 1.00, 98.89% correct, specificity = 55.21%, sensitivity = 55.95%). In the test set, SVM model had the highest prediction accuracy (AUC = 0.73, 72.92% correct, specificity = 69.23%, sensitivity = 88.89%). Lachnospiraceae_FCS020_group was the most important variable in the RF model. Lachnospiraceae_UCG - 004 was the most important variable in the SVM model.

CONCLUSION

CRC lymph node metastasis is closely related to intestinal bacteria. The prediction model based on intestinal bacteria can provide a new evaluation method for CRC lymph node metastasis.

The relationship between Clostridium butyricum and colorectal cancer

Gut microbiota dysbiosis is involved in intestinal diseases. The resident microorganisms in the digestive tract contribute to maintenance of gut homeostasis. Some bacterial species have been identified and are suspected to play a role in colorectal cancer (CRC). Many studies have found that Clostridium butyricum has a close relationship with CRC, and the mechanism is becoming increasingly clear. This review discusses the possible relationship between C. butyricum and CRC.

Prospect of bacteria for tumor diagnosis and treatment

In recent decades, the comprehensive cancer treatments including surgery, chemotherapy, and radiotherapy have improved the overall survival rate and quality of life of many cancer patients. However, we are still facing many difficult problems in the cancer treatment, such as unpredictable side effects, high recurrence rate, and poor curative effect. Therefore, the better intervention strategies are needed in this field. In recent years, the role and importance of microbiota in a variety of diseases were focused on as a hot research topic, and the role of some intracellular bacteria of cancer cells in carcinogenesis has recently been discovered. The impact of bacteria on cancer is not limited to their contribution to tumorigenesis, but the overall susceptibility of bacteria to subsequent tumor progression, the development of concurrent infections, and the response to anti-cancer therapy have also been found to be affected. Concerns about the contribution of bacteria in the anti-cancer response have inspired researchers to develop bacteria-based anti-cancer treatments. In this paper, we reviewed the main roles of bacteria in the occurrence and development of tumors, and summarized the mechanism of bacteria in the occurrence, development, and clinical anti-tumor treatment of tumors, providing new insights for the in-depth study of the role of bacteria in tumor diagnosis and treatment. This review aims to provide a new perspective for the development of new technologies based on bacteria to enhance anti-tumor immunotherapy.

The Dark Side of Iron: The Relationship between Iron, Inflammation and Gut Microbiota in Selected Diseases Associated with Iron Deficiency Anaemia—A Narrative Review

Iron is an indispensable nutrient for life. A lack of it leads to iron deficiency anaemia (IDA), which currently affects about 1.2 billion people worldwide. The primary means of IDA treatment is oral or parenteral iron supplementation. This can be burdened with numerous side effects such as oxidative stress, systemic and local-intestinal inflammation, dysbiosis, carcinogenic processes and gastrointestinal adverse events. Therefore, this review aimed to provide insight into the physiological mechanisms of iron management and investigate the state of knowledge of the relationship between iron supplementation, inflammatory status and changes in gut microbiota milieu in diseases typically complicated with IDA and considered as having an inflammatory background such as in inflammatory bowel disease, colorectal cancer or obesity. Understanding the precise mechanisms critical to iron metabolism and the awareness of serious adverse effects associated with iron supplementation may lead to the provision of better IDA treatment. Well-planned research, specific to each patient category and disease, is needed to find measures and methods to optimise iron treatment and reduce adverse effects.

Biological roles of toll-like receptors and gut microbiota in colorectal cancer

Colorectal cancer (CRC) is one of the most considerably common malignancies of the alimentary system, with high mortality and incidence rates.  The present study suggested that the occurrence of CRC is closely related to bacteria, as the large intestine is a gathering place for human micro-organisms. However, the nosogenesis of bacteria leading to tumorigenesis is still obscure. Recently, many studies have reported that toll-like receptors and their related molecular pathways are involved in the process of gut micro-organisms generating CRC. Gut micro-organisms can promote or inhibit the development of CRC via binding to special toll-like receptors. In this paper, the authors review the relationship among toll-like receptors, gut micro-organisms and CRC in order to provide a reference for future tumor immunotherapy and targeted therapy.

Open Reading Frame-3a gene of the 2019 novel coronavirus inhibits the occurrence and development of colorectal cancer

Intestinal microecology is composed of bacteria, fungi and viruses. As a part of intestinal microecology, viruses participate in the occurrence and development of colorectal cancer. The 2019-nCoV was detected in stool samples from patients during COVID-19, suggesting that the 2019-nCoV may be associated with intestinal microecology. However, the relationship of the 2019-nCoV and CRC is unclear. The aim of this study is to explore the role of Open Reading Frame-3a (ORF3a) of the 2019-nCoV in CRC. After the pCDH-CMV-MCS-EF1-Puro vector that provides high expression of ORF3a was transfected into the SW480 CRC cell line, immunofluorescence was used to determine the localization of ORF3a in SW480 cells. The proliferation, migration, invasion, apoptosis, and cell cycle progression of SW480 cells were measured using the Cell Counting Kit-8 (CCK-8), wound healing, Transwell assay, flow cytometry, the TUNEL assay, and propidium iodide single staining. The results showed that ORF3a inhibited the proliferation, invasion, and migration of SW480 cells and induced their apoptosis after 24, 48, 72 h. Meanwhile, ORF3a inhibited the cell cycle and blocked SW480 CRC cells in the G1 phase. In in vivo experiments, high ORF3a expression was associated with decreased tumor volume, tumor weight, relative tumor volume, and tumor activity. ORF3a inhibited the growth and induced apoptosis and necrosis of tumor tissues. Based on this, we demonstrated that ORF3a might play a role in CRC, providing a new direction for the prevention and treatment of CRC.

Bacterial Involvement in Progression and Metastasis of Colorectal Neoplasia

While the gut microbiome is composed of numerous bacteria, specific bacteria within the gut may play a significant role in carcinogenesis, progression, and metastasis of colorectal carcinoma (CRC). Certain microbial species are known to be associated with specific cancers; however, the interrelationship between bacteria and metastasis is still enigmatic. Mounting evidence suggests that bacteria participate in cancer organotropism during solid tumor metastasis. A critical review of the literature was conducted to better characterize what is known about bacteria populating a distant site and whether a tumor depends upon the same microenvironment during or after metastasis. The processes of carcinogenesis, tumor growth and metastatic spread in the setting of bacterial infection were examined in detail. The literature was scrutinized to discover the role of the lymphatic and venous systems in tumor metastasis and how microbes affect these processes. Some bacteria have a potent ability to enhance epithelial-mesenchymal transition, a critical step in the metastatic cascade. Bacteria also can modify the microenvironment and the local immune profile at a metastatic site. Early targeted antibiotic therapy should be further investigated as a measure to prevent metastatic spread in the setting of bacterial infection.

Host microbiomes in tumor precision medicine: how far are we?

The human gut microbiome has received a crescendo of attention in recent years, due to the countless influences on human pathophysiology, including cancer. Research on cancer and anticancer therapy is constantly looking for new hints to improve the response to therapy while reducing the risk of relapse. In this scenario, the gut microbiome and the plethora of microbial-derived metabolites are considered a new opening in the development of innovative anticancer treatments for a better prognosis. This narrative review summarizes the current knowledge on the role of the gut microbiome in the onset and progression of cancer, as well as in response to chemo-immunotherapy. Recent findings regarding the tumor microbiome and its implications for clinical practice are also commented on. Current microbiome-based intervention strategies (i.e., prebiotics, probiotics, live biotherapeutics and fecal microbiota transplantation) are then discussed, along with key shortcomings, including a lack of long-term safety information in patients who are already severely compromised by standard treatments. The implementation of bioinformatic tools applied to microbiomics and other omics data, such as machine learning, has an enormous potential to push research in the field, enabling the prediction of health risk and therapeutic outcomes, for a truly personalized precision medicine.

Commensal Clostridiales strains mediate effective anti-cancer immune response against solid tumors

Despite overall success, T cell checkpoint inhibitors for cancer treatment are still only efficient in a minority of patients. Recently, intestinal microbiota was found to critically modulate anti-cancer immunity and therapy response. Here, we identify Clostridiales members of the gut microbiota associated with a lower tumor burden in mouse models of colorectal cancer (CRC). Interestingly, these commensal species are also significantly reduced in CRC patients compared with healthy controls. Oral application of a mix of four Clostridiales strains (CC4) in mice prevented and even successfully treated CRC as stand-alone therapy. This effect depended on intratumoral infiltration and activation of CD8⁺ T cells. Single application of Roseburia intestinalis or Anaerostipes caccae was even more effective than CC4. In a direct comparison, the CC4 mix supplementation outperformed anti-PD-1 therapy in mouse models of CRC and melanoma. Our findings provide a strong preclinical foundation for exploring gut bacteria as novel stand-alone therapy against solid tumors.

Quxie Capsule Modulating Gut Microbiome and Its Association With T cell Regulation in Patients With Metastatic Colorectal Cancer: Result From a Randomized Controlled Clinical Trial

Aim:

Quxie capsule(QX), a TCM compound, had shown benefit on survival outcomes for metastatic colorectal cancer(mCRC) patients and could inhibit tumor growth through immune regulation. This study aimed to evaluate whether such effect is associated with gut microbiome modulation.

Method:

We conducted a randomized double-blinded placebo controlled clinical trial in Xiyuan Hospital, China Academy of Chinese Medical Sciences. All patients were randomly assigned into QX or placebo control group. Before and after 1-month interventions, we collected patients’ stool samples for microbiome analysis by 16s rRNA sequencing approaches, as well as blood samples to analyze T lymphocyte subsets by flow cytometry methods. Microbiome analysis among groups was done through bioinformation analysis platform. The study had been proved by the ethics committee of Xiyuan Hospital (2016XLA122-1) had been registered on Chinese Clinical Trial Registry (registration number: ChiCTR2000029599). All patients consented before enrollment.

Results:

We randomly assigned 40 patients and 34 were finally analyzed. Among them, 29% were female, with an average age of 63 years old, and 74% had liver or lung metastasis. Both CD4 T(TH) cell and CD8 T(TC) cell counts increased after QX treatment, while TH cells were significantly more in QX than in control group (737 vs 449, P = .024). Microbiome community analysis on Class level showed that the proportion of Actinobacteria declined in the control group, but significantly increased after QX treatments (0.83% vs 4.7%, P = .017). LEfSe analysis showed that after treatments, samples from QX group were highly related with Oscillibacter, Eubacterium, and Lachnospiraceae. RDA analysis showed that after QX interventions, stool samples and microbiome species had relevance with TC/TH cells counts but were not statistically significant. Heatmap analysis on Genus level revealed that after QX treatments, higher amounts of TH cells were significantly associated with less abundance of g_Bifidobacterium (coef. −0.76, P = .002), Collinsella (coef.−0.61, P = .02), Ruminiclostridium_9 (coef. −0.64, P = .01).

Conclusion:

QX capsule could enhance TH cells level among mCRC patients and increase the abundance of gut anticancer bacteria such as Actinobacteria as well as butyrate-producing bacteria such as Lachnospiraceae. These results indicated that QX capsule might have the property of dual effects of antitumor and immunity enhancement, both mediated by the microbiome.

Exploring Gut Microbiota in Patients with Colorectal Disease Based on 16S rRNA Gene Amplicon and Shallow Metagenomic Sequencing

The gastrointestinal tract, the largest human microbial reservoir, is highly dynamic. The gut microbes play essential roles in causing colorectal diseases. In the present study, we explored potential keystone taxa during the development of colorectal diseases in central China. Fecal samples of some patients were collected and were allocated to the adenoma (Group A), colorectal cancer (Group C), and hemorrhoid (Group H) groups. The 16S rRNA amplicon and shallow metagenomic sequencing (SMS) strategies were used to recover the gut microbiota. Microbial diversities obtained from 16S rRNA amplicon and SMS data were similar. Group C had the highest diversity, although no significant difference in diversity was observed among the groups. The most dominant phyla in the gut microbiota of patients with colorectal diseases were Bacteroidetes, Firmicutes, and Proteobacteria, accounting for >95% of microbes in the samples. The most abundant genera in the samples were Bacteroides, Prevotella, and Escherichia/Shigella, and further species-level and network analyses identified certain potential keystone taxa in each group. Some of the dominant species, such as Prevotella copri, Bacteroides dorei, and Bacteroides vulgatus, could be responsible for causing colorectal diseases. The SMS data recovered diverse antibiotic resistance genes of tetracycline, macrolide, and beta-lactam, which could be a result of antibiotic overuse. This study explored the gut microbiota of patients with three different types of colorectal diseases, and the microbial diversity results obtained from 16S rRNA amplicon sequencing and SMS data were found to be similar. However, the findings of this study are based on a limited sample size, which warrants further large-scale studies. The recovery of gut microbiota profiles in patients with colorectal diseases could be beneficial for future diagnosis and treatment with modulation of the gut microbiota. Moreover, SMS data can provide accurate species- and gene-level information, and it is economical. It can therefore be widely applied in future clinical metagenomic studies.

Changes of intestinal flora and miR-10a expression after radical resection of colorectal cancer: Effect of microecological enteral nutrition intervention

BACKGROUND

Radical resection is an important method for the treatment of rectal cancer, but the imbalance of intestinal flora and changes in gene expression caused by surgery are not conducive to the improvement of prognosis. It is of great value to explore the changes of intestinal flora and related gene expression after surgery for the formulation of intervention measures.

AIM

To investigate the changes in intestinal flora and microRNA-10a (miR-10a) expression after radical resection of colorectal cancer, and to analyze the effect of microecological enteral nutrition intervention.

METHODS

From July 2017 to June 2020, 107 patients with colorectal cancer undergoing radical resection at our hospital were selected as research subjects. The intestinal flora and miR-10a expression changes of patients with different intestinal flora were compared, and the relationship between the intestinal flora, miR-10a expression, and dysbacteriosis was analyzed. Microecological enteral nutrition intervention was carried out for patients with intestinal flora disorders, and the intestinal flora and miR-10a expression of patients before and after the intervention were compared. Clinical data, intestinal flora, and miR-10a expression of patients with different curative effects were compared. Factors affecting the efficacy of microecological enteral nutrition intervention were analyzed, as well as the value of intestinal flora and miR-10a expression in evaluation of efficacy of microecological enteral nutrition intervention. The correlation between the intestinal flora and the expression of miR-10a in patients with dysbacteriosis was analyzed.

RESULTS

The numbers of colonies of Lactobacillus, Bifidobacterium, and Eubacterium, and miR-10a expression were higher in patients with normal flora after radical resection of colorectal cancer than those in patients with dysbacteriosis degrees Ⅰ and Ⅱ, and in patients with dysbacteriosis degree Ⅰ than in those with dysbacteriosis degree Ⅱ. The number of Enterococcus was lower in patients with normal flora after radical resection of colorectal cancer than in those with dysbacteriosis degrees Ⅰ and Ⅱ, and in patients with dysbacteriosis degree Ⅰ than in those with dysbacteriosis degree Ⅱ (P < 0.05). As the numbers of Lactobacillus, Bifidobacterium, and Eubacterium, and the expression of miR-10a decreased, and the number of Enterococcus increased, the risk of dysbacteriosis in patients after radical resection of colorectal cancer increased (P < 0.05). The numbers of Lactobacillus, Bifidobacterium, and Eubacterium and miR-10a expression were higher and the number of Enterococcus was lower in patients after microecological enteral nutrition intervention than in patients before intervention (P < 0.05). Age, Duke stage, numbers of Lactobacillus, Bifidobacterium, Enterococcus and Eubacterium after intervention, and miR-10a expression were all significantly correlated with the efficacy of microecological enteral nutrition intervention (P < 0.05). After intervention, the areas under the curves of the intestinal flora and miR-10a expression in evaluating the efficacy of microecological enteral nutrition intervention were both > 0.7.

CONCLUSION

The intestinal flora and miR-10a expression changes after radical resection of colorectal cancer are significantly related to the occurrence of dysbacteriosis. Microecological enteral nutrition intervention can effectively regulate the intestinal flora and miR-10a expression, and the intestinal flora and miR-10a expression can be used as indicators to evaluate the intervention efficacy.

Colorectal Cancer, Gut Microbiota and Traditional Chinese Medicine: A Systematic Review

Based on the study and research on the pathogenesis of colorectal cancer, the types and functions of gut microbiota, and its role in guiding and regulating the occurrence and development of diseases, we have explored the mechanism of traditional Chinese medicine in the treatment of colorectal cancer by regulating the gut microbiota. Genetic variation, abnormal responses of innate and adaptive immunity, mucosal barrier dysfunction, imbalance of intestinal microbial colonization, personal and environmental risk factors are the main pathogenesis of colorectal cancer. The gut microbiota mainly includes Sclerotium (including Clostridium, Enterococcus, Lactobacillus and Ruminococcus) and Bacteroides (including Bacteroides and Prevotella), which have biological antagonism, nutrition for the organism, metabolic abilities, immune stimulation, and ability to shape cancer genes functions to body. The gut microbiota can be related to the health of the host. Current studies have shown that Chinese herbal compound, single medicinal materials, and monomer components can treat colorectal cancer by regulating the gut microbiota, such as Xiaoyaosan can increase the abundance of Bacteroides, Lactobacillus, and Proteus and decrease the abundance of Desulfovibrio and Rickerella. Therefore, studying the regulation and mechanism of gut microbiota on colorectal cancer is of great benefit to disease treatment.

Probiotics in Cancer

In recent years, the consumption of over-the-counter probiotics to promote health has grown rapidly worldwide and become an independent industry. In medicine, various studies have demonstrated that probiotics can help improve the immune system and intestinal health. They are usually safe, but in some rare cases, they may cause concerning adverse reactions. Although the use of probiotics has been widely popularized in the public, the results of many probiotic clinical trials are contradictory. Particularly in cancer patients, the feasibility of probiotic management providing benefits by targeting cancer and lessening anticancer side effects requires further investigation. This review summarizes the interactions between probiotics and the host as well as current knowledge on the pros and cons of utilizing probiotics in cancer patients.

Exploring the Role of Gut Microbiome in Colon Cancer

Dysbiosis of the gut microbiome has been associated with the development of colorectal cancer (CRC). Gut microbiota is involved in the metabolic transformations of dietary components into oncometabolites and tumor-suppressive metabolites that in turn affect CRC development. In a healthy colon, the major of microbial metabolism is saccharolytic fermentation pathways. The alpha-bug hypothesis suggested that oncogenic bacteria such as enterotoxigenic Bacteroides fragilis (ETBF) induce the development of CRC through direct interactions with colonic epithelial cells and alterations of microbiota composition at the colorectal site. Escherichia coli, E. faecalis, F. nucleatum, and Streptococcus gallolyticus showed higher abundance whereas Bifidobacterium, Clostridium, Faecalibacterium, and Roseburia showed reduced abundance in CRC patients. The alterations of gut microbiota may be used as potential therapeutic approaches to prevent or treat CRC. Probiotics such as Lactobacillus and Bifidobacterium inhibit the growth of CRC through inhibiting inflammation and angiogenesis and enhancing the function of the intestinal barrier through the secretion of short-chain fatty acids (SCFAs). Crosstalk between lifestyle, host genetics, and gut microbiota is well documented in the prevention and treatment of CRC. Future studies are required to understand the interaction between gut microbiota and host to the influence and prevention of CRC. However, a better understanding of bacterial dysbiosis in the heterogeneity of CRC tumors should also be considered. Metatranscriptomic and metaproteomic studies are considered a powerful omic tool to understand the anti-cancer properties of certain bacterial strains. The clinical benefits of probiotics in the CRC context remain to be determined. Metagenomic approaches along with metabolomics and immunology will open a new avenue for the treatment of CRC shortly. Dietary interventions may be suitable to modulate the growth of beneficial microbiota in the gut.

The Limits and Avoidance of Biases in Metagenomic Analyses of Human Fecal Microbiota

An increasing body of evidence highlights the role of fecal microbiota in various human diseases. However, more than two-thirds of fecal bacteria cannot be cultivated by routine laboratory techniques. Thus, physicians and scientists use DNA sequencing and statistical tools to identify associations between bacterial subgroup abundances and disease. However, discrepancies between studies weaken these results. In the present study, we focus on biases that might account for these discrepancies. First, three different DNA extraction methods (G’NOME, QIAGEN, and PROMEGA) were compared with regard to their efficiency, i.e., the quality and quantity of DNA recovered from feces of 10 healthy volunteers. Then, the impact of the DNA extraction method on the bacteria identification and quantification was evaluated using our published cohort of sample subjected to both 16S rRNA sequencing and whole metagenome sequencing (WMS). WMS taxonomical assignation employed the universal marker genes profiler mOTU-v2, which is considered the gold standard. The three standard pipelines for 16S RNA analysis (MALT and MEGAN6, QIIME1, and DADA2) were applied for comparison. Taken together, our results indicate that the G’NOME-based method was optimal in terms of quantity and quality of DNA extracts. 16S rRNA sequence-based identification of abundant bacteria genera showed acceptable congruence with WMS sequencing, with the DADA2 pipeline yielding the highest congruent levels. However, for low abundance genera (<0.5% of the total abundance) two pipelines and/or validation by quantitative polymerase chain reaction (qPCR) or WMS are required. Hence, 16S rRNA sequencing for bacteria identification and quantification in clinical and translational studies should be limited to diagnostic purposes in well-characterized and abundant genera. Additional techniques are warranted for low abundant genera, such as WMS, qPCR, or the use of two bio-informatics pipelines.

Dual Role of Bacteria in Carcinoma: Stimulation and Inhibition

Although what unifies the carcinogenic microorganisms has not been determined by multiple studies, the role of bacteria in the development of neoplasms has not been properly elucidated. In this review, we discuss links between the bacterial species and cancer, with focus on immune responses for the stimulation of tumor cells such as induction of inflammation. Finally, we will describe the potential therapeutic strategies of bacteria on target tumors to improve treatment while mitigating adverse reactions. Cancer is a series of genetic changes that transform normal cells into tumor cells. These changes come from several reasons, including smoking, drinking alcohol, sunlight, exposure to chemical or physical factors, and finally chronic infection with microorganisms, including bacteria. In fact, bacterial infections are not carcinogenic, but recently it was discovered that the association between bacteria and cancer is through two mechanisms, the first stimulating chronic inflammation and the second producing carcinogenic metabolites. While bacteria are carcinogenic agents also, they have a dual role eliminating and removing tumor cells. However, the traditional cancer treatments that include chemotherapy, radiotherapy, surgery, and immunotherapy increase the chances of survival, and there are many side effects of these therapies, including the high toxicity of tissues and normal cells, could not penetrate the tumor cells, and resistance of these therapies by tumor cells. Therefore, the world has turned to an alternative solution, which is the use of genetically engineered microorganisms; thus, the use of living bacteria targeting cancerous cells is the unique option to overcome these challenges. Bacterial therapies, whether used alone or combination with chemotherapy, give a positive effect to treat multiple conditions of cancer. Also, bacteria can be used as vectors for drug, gene, or therapy, and this is a great step to treat cancer. Thus, we review the mechanisms underlying the interaction of the microbiota residents with cancer. Cancer-associated bacteria differ from those in healthy human and are linked with gene-expression profile. We also discuss how live bacteria interact with tumor microenvironments to induce tumor regression through colonization and spread. Finally, we provide past and ongoing clinical trials that include bacteria targeting tumors.