Carcinogenesis and therapeutics: the microbiota perspective

Targeting the gut microbiota to alleviate chemotherapy-induced toxicity in cancer

Despite ongoing breakthroughs in novel anticancer therapies, chemotherapy remains a mainstream therapeutic modality in different types of cancer. Unfortunately, chemotherapy-related toxicity (CRT) often leads to dose limitation, and even results in treatment termination. Over the past few years, accumulating evidence has indicated that the gut microbiota is extensively engaged in various toxicities initiated by chemotherapeutic drugs, either directly or indirectly. The gut microbiota can now be targeted to reduce the toxicity of chemotherapy. In the current review, we summarized the clinical relationship between the gut microbiota and CRT, as well as the critical role of the gut microbiota in the occurrence and development of CRT. We then summarized the key mechanisms by which the gut microbiota modulates CRT. Furthermore, currently available strategies to mitigate CRT by targeting the gut microbiota were summarized and discussed. This review offers a novel perspective for the mitigation of diverse chemotherapy-associated toxic reactions in cancer patients and the future development of innovative drugs or functional supplements to alleviate CRT via targeting the gut microbiota.

Effects of a Nutraceutical Treatment on the Intestinal Microbiota of Sled Dogs

Dog sledding is the main discipline of working dogs on snow, consisting of a team of dogs pulling a sled under the guidance of the owner. To carry out this sport, dogs must have adequate nutrition and vitamin and antioxidant supplementation to ensure that the physical effort is optimal. The present study evaluated the effect that sporting activity and stress have on the canine intestinal microbiota by dividing the dogs into two groups: a control group that did not take any nutraceutical products and the treated group to which a nutraceutical product was administered. The nutraceutical administered in this study is used in all cases of canine intestinal dysbiosis in which it is essential to quickly restore a balanced intestinal microbiota. The results obtained show that in dogs not taking the nutraceutical, there is an increase in bacteria, such as Streptococcus spp. and E. coli, considered enteropathogenic to the detriment of beneficial bacterial species such as Faecalibacterium spp., Turicibacter spp., Blautia spp., Fusobacterium spp., and Clostridium hiranonis. Instead, the group of dogs treated with nutraceutical displays a lower amount of enteropathogenic bacteria and a great increase in the other bacterial species considered beneficial for the animal's health. The results obtained in the present study show that Microbiotal cane® can be used in dogs subject to intense sporting activity by preventing severe alterations at intestinal ecosystem levels by maintaining intestinal bacterial composition as balanced as possible.

Friend or Foe: Exploring the Relationship between the Gut Microbiota and the Pathogenesis and Treatment of Digestive Cancers

Digestive cancers are among the leading causes of cancer death in the world. However, the mechanisms of cancer development and progression are not fully understood. Accumulating evidence in recent years pointing to the bidirectional interactions between gut dysbiosis and the development of a specific type of gastrointestinal cancer is shedding light on the importance of this "unseen organ"-the microbiota. This review focuses on the local role of the gut microbiota imbalance in different digestive tract organs and annexes related to the carcinogenic mechanisms. Microbiota modulation, either by probiotic administration or by dietary changes, plays an important role in the future therapies of various digestive cancers.

The role of gut microbiota and probiotics in preventing, treating, and boosting the immune system in colorectal cancer

The gut microbiome plays a significant role in developing colorectal cancer (CRC). The gut microbiome usually acts as a protective barrier against harmful pathogens and infections in the intestine, while also regulating inflammation by affecting the human immune system. The gut microbiota and probiotics play a role not only in intestinal inflammation associated with tumor formation but also in regulating anti-cancer immune response. As a result, they associated with tumor progression and the effectiveness of anti-cancer therapies. Research indicates that gut microbiota and probiotics can be used as biomarkers to predict the impact of immunotherapy and enhance its efficacy in treating CRC by regulating it. This review examines the importance of gut microbiota and probiotics in the development and progression of CRC, as well as their synergistic impact on anti-cancer treatments.

Gut microbial dysbiosis in the pathogenesis of leukemia: an immune-based perspective

Leukemias are a set of clonal hematopoietic malignant diseases that develop in the bone marrow. Several factors influence leukemia development and progression. Among these, the gut microbiota is a major factor influencing a wide array of its processes. The gut microbial composition is linked to the risk of tumor development and the host's ability to respond to treatment, mostly due to the immune-modulatory effects of their metabolites. Despite such strong evidence, its role in the development of hematologic malignancies still requires attention of investigators worldwide. In this review, we make an effort to discuss the role of host gut microbiota-immune crosstalk in leukemia development and progression. Additionally, we highlight certain recently developed strategies to modify the gut microbial composition that may help to overcome dysbiosis in leukemia patients in the near future.

Dynamic Changes of the Gut Microbiota and Its Functional Metagenomic Potential during the Development of Non-Small Cell Lung Cancer

The gut microbiota plays a significant role in tumor pathogenesis by regulating the host metabolism and immune response, and there are few studies focused on tracking changes in the gut microbiota from the onset of lung cancer. Therefore, the aim of our study is combining preclinical and clinical research to thoroughly analyze the signatures of fecal microbiota in lung cancer, which will be useful for early diagnosis and predicting the therapeutic efficacy of lung cancer. The first part of this study analyzed the fecal metagenomic differences between patients with non-small cell lung cancer and healthy subjects, and the second part of this work constructed a murine lung cancer model to monitor changes in mouse fecal metagenomics and T cell immunology during lung cancer progression. We found that the fecal microbiota was altered in both humans and mice with lung cancer, characterized by a significantly reduced microbial diversity and number of beneficial microbes, with increases in potential pathogens. The fecal level of Akkermansia muciniphila and the gut metabolic module of the secondary bile acid metabolism were diminished in both humans and mice with lung cancer compared with healthy subjects. Splenomegaly was observed in the lung cancer mice. Flow cytometer analysis of the splenocytes revealed substantial alterations in the proportions of T cell subsets in the lung cancer mice, characterized by significant increases in CD4+Foxp3+CD25+ T regulatory cells (p < 0.05) while significant decreases in CD3+ T cells (p < 0.001), CD4+ T cells (p < 0.001), and the CD4+/CD8+ ratio (p < 0.01). Vertical and longitudinal analyses of the fecal microbiota of the two mouse groups identified some lung cancer biomarkers (including Acutalibacter timonensis, Lachnospiraceae bacterium NSJ-38 sp014337195, etc.). The fecal microbiota of the lung cancer mice had a reduced metagenomic potential for neurotransmitters (melatonin, γ-aminobutyric acid, and histamine) compared with healthy mice. In summary, this study found that the diversity, structure, and composition of gut microbiota vary between cancer and healthy conditions, ultimately leading to changes in the potential for functional metagenomics.

The cross talk of ubiquitination and chemotherapy tolerance in colorectal cancer

Ubiquitination, a highly adaptable post-translational modification, plays a pivotal role in maintaining cellular protein homeostasis, encompassing cancer chemoresistance-associated proteins. Recent findings have indicated a potential correlation between perturbations in the ubiquitination process and the emergence of drug resistance in CRC cancer. Consequently, numerous studies have spurred the advancement of compounds specifically designed to target ubiquitinates, offering promising prospects for cancer therapy. In this review, we highlight the role of ubiquitination enzymes associated with chemoresistance to chemotherapy via the Wnt/β-catenin signaling pathway, epithelial-mesenchymal transition (EMT), and cell cycle perturbation. In addition, we summarize the application and role of small compounds that target ubiquitination enzymes for CRC treatment, along with the significance of targeting ubiquitination enzymes as potential cancer therapies.

Alterations in the gut microbiota and their metabolites in human intestinal epithelial cells of patients with colorectal cancer

BACKGROUND

The gut microbiota has become one of the main risk factors for the formation and development of colorectal cancer (CRC). CRC intensification may be due to the microbial pathogens' colonization and their released metabolites. Here, we analyzed Bacteroidetes and Clostridia bacteria in CRC patients and studied bacterial metabolome in cancerous tissues compared to their adjacent normal tissues.

METHODS AND RESULTS

The population of selected bacteria in biopsy specimens of 30 patients with CRC was studied by RT-qPCR. The mutagenicity and cytotoxicity effects of microbiota metabolites were evaluated by Ames test and MTT Assay, respectively. Moreover, gene expression in carcinogenic pathways was studied by RT-qPCR, and genes with different expressions in tumor and non-tumor tissues were diagnosed. Based on microbiota analysis, the relative abundance of Clostridia and C. difficile was significantly higher in CRC tissue, whereas C. perfringens showed higher relative abundance in normal tissue. AIMES test confirmed the proliferation and mutagenicity effects of the bacterial metabolites in CRC patients. Significant upregulation of C-Myc, GRB2, IL-8, EGFR, PI3K, and AKT and downregulation of ATM were observed in CRC samples compared to the control.

CONCLUSIONS

The influence of bacterial metabolites on inflammation and altered expression of genes in the cell signaling pathways was observed. The findings confirm the role gut microbiota composition and bacterial metabolites as key players in CRC onset and development.

Investigating the Influence of Gut Microbiota-related Metabolites in Gastrointestinal Cancer

Gastrointestinal (GI) cancer is a major health concern due to its prevalence, impact on well-being, high mortality rate, economic burden, and potential for prevention and early detection. GI cancer research has made remarkable strides in understanding biology, risk factors, and treatment options. An emerging area of research is the gut microbiome's role in GI cancer development and treatment response. The gut microbiome, vital for digestion, metabolism, and immune function, is increasingly linked to GI cancers. Dysbiosis and alterations in gut microbe composition may contribute to cancer development. Scientists study how specific bacteria or microbial metabolites influence cancer progression and treatment response. Modulating the gut microbiota shows promise in enhancing treatment efficacy and preventing GI cancers. Gut microbiota dysbiosis can impact GI cancer through inflammation, metabolite production, genotoxicity, and immune modulation. Microbes produce metabolites like short-chain fatty acids, bile acids, and secondary metabolites. These affect host cells, influencing processes like cell proliferation, apoptosis, DNA damage, and immune regulation, all implicated in cancer development. This review explores the latest research on gut microbiota metabolites and their molecular mechanisms in GI cancers. The hope is that this attempt will help in conducting other relevant research to unravel the precise mechanism involved, identify microbial signatures associated with GI cancer, and develop targets.

Non-pathogenic microbiota accelerate age-related CpG Island methylation in colonic mucosa

DNA methylation is an epigenetic process altered in cancer and ageing. Age-related methylation drift can be used to estimate lifespan and can be influenced by extrinsic factors such as diet. Here, we report that non-pathogenic microbiota accelerate age-related methylation drift in the colon when compared with germ-free mice. DNA methylation analyses showed that microbiota and IL10KO were associated with changes in 5% and 4.1% of CpG sites, while mice with both factors had 18% alterations. Microbiota, IL10KO, and their combination altered 0.4%, 0.4%, and 4% of CpG island methylation, respectively. These are comparable to what is seen in colon cancer. Ageing changes were accelerated in the IL10KO mice with microbiota, and the affected genes were more likely to be altered in colon cancer. Thus, the microbiota affect DNA methylation of the colon in patterns reminiscent of what is observed in ageing and colorectal cancer.

Microbiota, Diet and Acute Leukaemia: Tips and Tricks on Their Possible Connections

Acute leukaemia is probably one of the most recurrent cancers in children and younger adults, with an incidence of acute lymphoblastic leukaemia in 80% of cases and an incidence of acute myeloid leukaemia in 15% of cases. Yet, while incidence is common in children and adolescents, acute leukaemia is a rare disease whose aetiology still requires further analysis. Many studies have investigated the aetiology of acute leukaemia, reporting that the formation of gut microbiota may be modified by the start and development of many diseases. Considering that in patients affected by acute lymphoblastic leukaemia, there is an inherent disequilibrium in the gut microbiota before treatment compared with healthy patients, increasing evidence shows how dysbiosis of the gut microbiota provokes an inflammatory immune response, contributing to the development of cancer. Our analysis suggeststhe key role of gut microbiota in the modulation of the efficacy of leukaemia treatment as well as in the progress of many cancers, such as acute leukaemia. Therefore, in this paper, we present an examination of information found in literature regarding the role of dietary factors and gut microbiota alterations in the development of leukaemia and suggest possible future preventive and therapeutic strategies.

Progress in the diagnosis of lymph node metastasis in rectal cancer: a review

Historically, the chief focus of lymph node metastasis research has been molecular and clinical studies of a few essential pathways and genes. Recent years have seen a rapid accumulation of massive omics and imaging data catalyzed by the rapid development of advanced technologies. This rapid increase in data has driven improvements in the accuracy of diagnosis of lymph node metastasis, and its analysis further demands new methods and the opportunity to provide novel insights for basic research. In fact, the combination of omics data, imaging data, clinical medicine, and diagnostic methods has led to notable advances in our basic understanding and transformation of lymph node metastases in rectal cancer. Higher levels of integration will require a concerted effort among data scientists and clinicians. Herein, we review the current state and future challenges to advance the diagnosis of lymph node metastases in rectal cancer.

Gut microbes involvement in gastrointestinal cancers through redox regulation

Gastrointestinal (GI) cancers are among the most common and lethal cancers worldwide. GI microbes play an important role in the occurrence and development of GI cancers. The common mechanisms by which GI microbes may lead to the occurrence and development of cancer include the instability of the microbial internal environment, secretion of cancer-related metabolites, and destabilization of the GI mucosal barrier. In recent years, many studies have found that the relationship between GI microbes and the development of cancer is closely associated with the GI redox level. Redox instability associated with GI microbes may induce oxidative stress, DNA damage, cumulative gene mutation, protein dysfunction and abnormal lipid metabolism in GI cells. Redox-related metabolites of GI microbes, such as short-chain fatty acids, hydrogen sulfide and nitric oxide, which are involved in cancer, may also influence GI redox levels. This paper reviews the redox reactions of GI cells regulated by microorganisms and their metabolites, as well as redox reactions in the cancer-related GI microbes themselves. This study provides a new perspective for the prevention and treatment of GI cancers.

A gut bacterial signature in blood and liver tissue characterizes cirrhosis and hepatocellular carcinoma

BACKGROUND

HCC is the leading cause of cancer in chronic liver disease. A growing body of experimental mouse models supports the notion that gut-resident and liver-resident microbes control hepatic immune responses and, thereby, crucially contribute to liver tumorigenesis. However, a comprehensive characterization of the intestinal microbiome in fueling the transition from chronic liver disease to HCC in humans is currently missing.

METHODS

Here, we profiled the fecal, blood, and liver tissue microbiome of patients with HCC by 16S rRNA sequencing and compared profiles to nonmalignant cirrhotic and noncirrhotic NAFLD patients.

RESULTS

We report a distinct bacterial profile, defined from 16S rRNA gene sequences, with reduced α-and β-diversity in the feces of patients with HCC and cirrhosis compared to NAFLD. Patients with HCC and cirrhosis exhibited an increased proportion of fecal bacterial gene signatures in the blood and liver compared to NAFLD. Differential analysis of the relative abundance of bacterial genera identified an increased abundance of Ruminococcaceae and Bacteroidaceae in blood and liver tissue from both HCC and cirrhosis patients compared to NAFLD. Fecal samples from cirrhosis and HCC patients both showed a reduced abundance for several taxa, including short-chain fatty acid-producing genera, such as Blautia and Agathobacter. Using paired 16S rRNA and transcriptome sequencing, we identified a direct association between gut bacterial genus abundance and host transcriptome response within the liver tissue.

CONCLUSIONS

Our study indicates perturbations of the intestinal and liver-resident microbiome as a critical determinant of patients with cirrhosis and HCC.

Gut microbiota mediated the individualized efficacy of Temozolomide via immunomodulation in glioma

BACKGROUND

Temozolomide (TMZ) is the preferred chemotherapy strategy for glioma therapy. As a second-generation alkylating agent, TMZ provides superior oral bio-availability. However, limited response rate (less than 50%) and high incidence of drug resistance seriously restricts TMZ's application, there still lack of strategies to increase the chemotherapy sensitivity.

METHODS

Luci-GL261 glioma orthotopic xenograft model combined bioluminescence imaging was utilized to evaluate the anti-tumor effect of TMZ and differentiate TMZ sensitive (S)/non-sensitive (NS) individuals. Integrated microbiomics and metabolomics analysis was applied to disentangle the involvement of gut bacteria in TMZ sensitivity. Spearman's correlation analysis was applied to test the association between fecal bacteria levels and pharmacodynamics indices. Antibiotics treatment combined TMZ treatment was used to confirm the involvement of gut microbiota in TMZ response. Flow cytometry analysis, ELISA and histopathology were used to explore the potential role of immunoregulation in gut microbiota mediated TMZ response.

RESULTS

Firstly, gut bacteria composition was significantly altered during glioma development and TMZ treatment. Meanwhile, in vivo anti-cancer evaluation suggested a remarkable difference in chemotherapy efficacy after TMZ administration. Moreover, 16s rRNA gene sequencing and non-targeted metabolomics analysis revealed distinct different gut microbiota and immune infiltrating state between TMZ sensitive and non-sensitive mice, while abundance of differential gut bacteria and related metabolites was significantly correlated with TMZ pharmacodynamics indices. Further verification suggested that gut microbiota deletion by antibiotics treatment could accelerate glioma development, attenuate TMZ efficacy and inhibit immune cells (macrophage and CD8α⁺ T cell) recruitment.

CONCLUSIONS

The current study confirmed the involvement of gut microbiota in glioma development and individualized TMZ efficacy via immunomodulation, hence gut bacteria may serve as a predictive biomarker as well as a therapeutic target for clinical TMZ application.

Detection of Microorganisms in Body Fluid Samples

Next-generation sequencing (NGS) has been widely applied to the identification of microbiome in body fluids. The methodology of 16S rRNA amplicon sequencing is simple, fast, and cost-effective. It overcomes the problem that some microorganisms cannot be isolated or cultured. Low abundant bacteria can also be amplified and sequenced, but the resolution of classification can hardly reach species or sub-species level; moreover, this methodology is mainly used to identify bacterial populations, and other microorganisms like viruses or fungi cannot be sequenced. On the other hand, the microbiome profiling obtained by shotgun metagenomic sequencing is more comprehensive with better resolution, and more accurate classification can be expected due to higher coverage of genomic sequences from microorganisms. By combining the capture-based method with metagenomic sequencing, we can further enrich and detect low abundant microorganisms and identify the viral integration sites in host gDNA at once.

Using whole-genome sequencing (WGS) to plot colorectal cancer-related gut microbiota in a population with varied geography

BACKGROUND

Colorectal cancer (CRC) is a multifactorial disease with genetic and environmental factors. Regional differences in risk factors are an important reason for the different incidences of CRC in different regions.

OBJECTIVE

The goal was to clarify the intestinal microbial composition and structure of CRC patients in different regions and construct CRC risk prediction models based on regional differences.

METHODS

A metagenomic dataset of 601 samples from 6 countries in the GMrepo and NCBI databases was collected. All whole-genome sequencing (WGS) data were annotated for species by MetaPhlAn2. We obtained the relative abundance of species composition at the species level and genus level. The MicrobiotaProcess package was used to visualize species composition and PCA. LEfSe analysis was used to analyze the differences in the datasets in each region. Spearman correlation analysis was performed for CRC differential species. Finally, the CRC risk prediction model was constructed and verified in each regional dataset.

RESULTS

The composition of the intestinal bacterial community varied in different regions. Differential intestinal bacteria of CRC in different regions are inconsistent. There was a common diversity of bacteria in all six countries, such as Peptostreptococcus stomatis and Fusobacterium nucleatum at the species level. Peptostreptococcus stomatis (species level) and Peptostreptococcus (genus level) are important CRC-related bacteria that are related to other bacteria in different regions. Region has little influence on the accuracy of the CRC risk prediction model. Peptostreptococcus stomatis is an important variable in CRC risk prediction models in all regions.

CONCLUSION

Peptostreptococcus stomatis is a common high-risk pathogen of CRC worldwide, and it is an important variable in CRC risk prediction models in all regions. However, regional differences in intestinal bacteria had no significant impact on the accuracy of the CRC risk prediction model.

Gut microbiota in acute leukemia: Current evidence and future directions

Gut microbiota includes a large number of microorganisms inhabiting the human gastrointestinal tract, which show a wide range of physiological functions, including digestion, metabolism, immunity, neural development, etc., and are considered to play an increasingly important role in health and disease. A large number of studies have shown that gut microbiota are closely associated with the onset and development of several diseases. In particular, the interaction between gut microbiota and cancer has recently attracted scholars' attention. Acute leukemia (AL) is a common hematologic malignancy, especially in children. Microbiota can affect hematopoietic function, and the effects of chemotherapy and immunotherapy on AL are noteworthy. The composition and diversity of gut microbiota are important factors that influence and predict the complications and prognosis of AL after chemotherapy or hematopoietic stem cell transplantation. Probiotics, prebiotics, fecal microbiota transplantation, and dietary regulation may reduce side effects of leukemia therapy, improve response to treatment, and improve prognosis. This review concentrated on the role of the gut microbiota in the onset and development of AL, the response and side effects of chemotherapy drugs, infection during treatment, and therapeutic efficacy. According to the characteristics of gut microbes, the applications and prospects of microbial preparations were discussed.

Understanding the cross-talk between human microbiota and gastrointestinal cancer for developing potential diagnostic and prognostic biomarkers

The interaction between gut microbes and gastrointestinal (GI) tract carcinogenesis has always attracted researchers' attention to identify therapeutic targets or potential prognostic biomarkers. Various studies have suggested that the microbiota do show inflammation and immune dysregulation, which led to carcinogenesis in GI tract. In this review, we have focused on the role of microbes present in the gut, intestine, or faeces in GI tract cancers, including esophageal cancer, gastric cancer, and colorectal cancer. Herein, we have discussed the importance of the microbes and their metabolites, which could serve as diagnostic biomarkers for cancer detection, especially in the early stage, and prognostic markers. To maximize the effect of the treatment strategies, an accurate evaluation of the prognosis is imperative for clinicians. There is a vast difference in the microbiota profiles within a population and across the populations depending upon age, diet, lifestyle, genetic makeup, use of antibiotics, and environmental factors. Therefore, the diagnostic efficiency of the microbial markers needs to be further validated. A deeper understanding of the GI cancer and the host microbiota is needed to acquire pivotal information about disease status.

Live Biotherapeutic Lactococcus lactis GEN3013 Enhances Antitumor Efficacy of Cancer Treatment via Modulation of Cancer Progression and Immune System

Simple Summary

Recent studies, which have revealed the strong relationship between gut microbiota and tumor progression, have driven the clinical application of microbiome-based treatments to increase the efficacy of anticancer therapies. In particular, the genome-editing Lactococcus lactis, which activates the host immune system by expressing immune-boosting cytokines or metabolites, is a candidate for microbiome treatment. While Lactococcus lactis has so far been studied in terms of its recombinant forms, we investigated the anticancer effects of the strain-specific Lactococcus lactis GEN3013 itself. In vitro cytotoxicity tests showed that L. lactis GEN3013 inhibited the cell growth of various human and murine cancer cell lines. Consistent with the in vitro results, L. lactis GEN3013 showed antitumor effects and enhanced the therapeutic efficacy of both chemotherapy and immunotherapy in syngeneic mice. In addition, the host immune system was activated both locally and systemically by the combinatorial treatment of L. lactis GEN3013 with chemotherapy and immunotherapy. For these reasons, we suggest that L. lactis GEN3013 could be utilized as a novel biotherapeutic agent for cancer treatment.

Abstract

The gut microbiota is responsible for differential anticancer drug efficacies by modulating the host immune system and the tumor microenvironment. Interestingly, this differential effect is highly strain-specific. For example, certain strains can directly suppress tumor growth and enhance antitumor immunity; however, others do not have such an effect or even promote tumor growth. Identifying effective strains that possess antitumor effects is key for developing live biotherapeutic anticancer products. Here, we found that Lactococcus lactis GEN3013 inhibits tumor growth by regulating tumor angiogenesis and directly inducing cancer cell death. Moreover, L. lactis GEN3013 enhanced the therapeutic effects of oxaliplatin and the PD-1 blockade. Comprehensive immune profiling showed that L. lactis GEN3013 augmented cytotoxic immune cell populations, such as CD4⁺ T cells, CD8⁺ effector T cells, and NK cells in the tumor microenvironment. Our results indicate that L. lactis GEN3013 is a promising candidate for potentiating cancer treatment in combination with current standard therapy.

Intestinal microbiota modulates pancreatic carcinogenesis through intratumoral natural killer cells

Preclinical data demonstrate that the gut microbiota can promote pancreatic ductal adenocarcinoma (PDAC), but mechanisms remain unclear. We hypothesized that intestinal microbiota alters anti-tumor innate immunity response to facilitate PDAC progression. Human PDAC L3.6pl cells were heterotopically implanted into Rag1^-/- mice after microbiota depletion with antibiotics, while syngeneic murine PDAC Pan02 cells were implanted intrapancreatic into germ-free (GF) C57BL/6 J mice. Natural killer (NK) cells and their IFNγ expression were quantitated by flow cytometry. NK cells were depleted in vivo using anti-Asialo GM1 antibody to confirm the role of NK cells. Bacteria-free supernatant from SPF and GF mice feces was used to test its effect on NK-92MI cell anti-tumor response in vitro. SPF and ex-GF mice (reconstituted with SPF microbiota) developed larger PDAC tumors with decreased NK cell tumor infiltration and IFNγ expression versus GF-Rag1^-/-. Microbiota-induced PDAC tumorigenesis was attenuated by antibiotic exposure, a process reversed following NK cell depletion in both Rag1^-/- and C57BL/6 J mice. Compared to GF, SPF-Rag1^-/- abiotic stool culture supernatant inhibited NK-92MI cytotoxicity, migration, and anti-cancer related gene expression. Gut microbiota promotes PDAC tumor progression through modulation of the intratumoral infiltration and activity of NK cells.

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.

Gut microbiome in gastrointestinal cancer: a friend or foe?

The impact of the gut microbiome on host health is becoming increasingly recognized. To date, there is growing evidence that the complex characteristics of the microbial community play key roles as potential biomarkers and predictors of responses in cancer therapy. Many studies have shown that altered commensal bacteria lead to cancer susceptibility and progression in diverse pathways. In this review, we critically assess the data for gut microbiota related to gastrointestinal cancer, including esophageal, gastric, pancreatic, colorectal cancer, hepatocellular carcinoma and cholangiocarcinoma. Importantly, the underlying mechanisms of gut microbiota involved in cancer occurrence, prevention and treatment are elucidated. The purpose of this review is to provide novel insights for applying this understanding to the development of new therapeutic strategies in gastrointestinal cancer by targeting the microbial community.

The Relationship Between Microbial Community and Breast Cancer

Breast cancer (BC) is the most common cancer in women and the leading cause of cancer-related deaths in women worldwide. Recent research studies have shown that the intestinal flora is related to the occurrence and progression of BC. Notably, some evidence identifies a unique microbial community in breast tissue, a site previously thought to be sterile. In addition, breast tumors have their own specific microbial community, distinct from normal mammary gland tissue, and all of them may result from intestinal flora. Some microbial community in breast tissue may lead to the occurrence and development of BC. This review focuses on the relationship between the microbial community and breast cancer, which will lay a solid theoretical foundation for further understanding the local microenvironment of BC and developing effective targeted therapeutic drugs.

Characterization of Some Microorganisms from Human Stool Samples and Determination of Their Effects on CT26 Colorectal Carcinoma Cell Line

The present study aimed to isolate and identify the potential probiotic, pathobiont, and pathogenic microorganisms in the stool samples of 12 healthy individuals and evaluate their in vitro effects on cancer formation. A total of 83 strains were isolated from the stool samples and identified using MALDI-Biotyper. Fourteen of the isolates were identified as Candida spp., three isolates were identified as Cryptococcus neoformans, 55 isolates were identified as lactic acid bacteria, and the remaining isolates belonged to different 11 bacterial genera. Important microbial properties for cancer prevention and some probiotic properties were examined. All strains maintained their viability under acidic conditions and in media containing bile salts. Of the bacterial strains, 62.5% were resistant to ampicillin, chloramphenicol, gentamicin, erythromycin, kanamycin, penicillin, streptomycin, tetracycline, and vancomycin. All yeast strains were resistant to ketoconazole and susceptible to nystatin. The susceptibility of the strains to fluconazole, voriconazole, amphotericin B, and itraconazole varied. Fifty-nine percent of the strains produced EPS and 21.7% showed proteolytic activity (PA). Of the strains, 15.7% both produced exopolysaccharides (EPS) and had PA. The antioxidant activity (AOA) varied depending on the strains. The pathobiont and pathogenic microorganisms promoted tumor formation, while potential probiotic microorganisms had a suppressive effect on tumor formation (P > 0.01). One yeast (Candida kefyr MK17) and three lactic acid bacteria strains (Lacticaseibacillus paracasei MK73, Lactiplantibacillus plantarum MK55, Limosilactobacillus mucosae MK45) have superior potential thanks to their anticarcinogenic properties as well as tolerance to gastrointestinal tract conditions. Stool samples of each individual contain various potential probiotic, pathobiont, and pathogenic microorganisms.

Mechanisms Involved in Gut Microbiota Regulation of Skeletal Muscle

Skeletal muscle is one of the largest organs in the body and is essential for maintaining quality of life. Loss of skeletal muscle mass and function can lead to a range of adverse consequences. The gut microbiota can interact with skeletal muscle by regulating a variety of processes that affect host physiology, including inflammatory immunity, protein anabolism, energy, lipids, neuromuscular connectivity, oxidative stress, mitochondrial function, and endocrine and insulin resistance. It is proposed that the gut microbiota plays a role in the direction of skeletal muscle mass and work. Even though the notion of the gut microbiota-muscle axis (gut-muscle axis) has been postulated, its causal link is still unknown. The impact of the gut microbiota on skeletal muscle function and quality is described in detail in this review.

Intestinal Barrier Dysfunction in Fatty Liver Disease: Roles of Microbiota, Mucosal Immune System, and Bile Acids

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of progressive liver diseases ranging from simple steatosis to steatohepatitis and fibrosis. Globally, NAFLD is the leading cause of morbidity and mortality associated with chronic liver disease, and NAFLD patients are at a higher risk of developing cirrhosis and hepatocellular carcinoma. While there is a consensus that inflammation plays a key role in promoting NAFLD progression, the underlying mechanisms are not well understood. Recent clinical and experimental evidence suggest that increased hepatic translocation of gut microbial antigens, secondary to diet-induced impairment of the intestinal barrier may be important in driving hepatic inflammation in NAFLD. Here, we briefly review various endogenous and exogenous factors influencing the intestinal barrier and present recent advances in our understanding of cellular and molecular mechanisms underlying intestinal barrier dysfunction in NAFLD.

Influence of Natural Polysaccharides on Intestinal Microbiota in Inflammatory Bowel Diseases: An Overview

The incidence of inflammatory bowel disease (IBD) has increased in recent years. Considering the potential side effects of conventional drugs, safe and efficient treatment methods for IBD are required urgently. Natural polysaccharides (NPs) have attracted considerable attention as potential therapeutic agents for IBD owing to their high efficiency, low toxicity, and wide range of biological activities. Intestinal microbiota and their fermentative products, mainly short-chain fatty acids (SCFAs), are thought to mediate the effect of NPs in IBDs. This review explores the beneficial effects of NPs on IBD, with a special focus on the role of intestinal microbes. Intestinal microbiota exert alleviation effects via various mechanisms, such as increasing the intestinal immunity, anti-inflammatory activities, and intestinal barrier protection via microbiota-dependent and microbiota-independent strategies. The aim of this paper was to document evidence of NP–intestinal microbiota-associated IBD prevention, which would be helpful for guidance in the treatment and management of IBD.

Roles of Microbiota in Cancer: From Tumor Development to Treatment

Cancer as a second leading cause of death arises from multifactorial pathology. The association of microbiota and their products with various pathologic conditions including cancer is receiving significant attention over the past few years. Mounting evidence showed that human microbiota is an emerging target in tumor onset, progression, prevention, and even diagnosis. Accordingly, modulating this composition might influence the response to tumor therapy and therapeutic resistance as well. Through this review, one could conceive of complex interaction between the microbiome and cancer in either positive or negative manner by which may hold potential for finding novel preventive and therapeutic strategies against cancer.

Aluminum induced intestinal dysfunction via mechanical, immune, chemical and biological barriers

Aluminum is the most abundant metal element in the Earth's crust, which exists naturally in the form of aluminum compounds. Aluminum is mainly absorbed through the gastrointestinal tract, which varies with different aluminum compounds. During this process, aluminum could induce the disruption of intestinal mucosa barrier. However, its underlying mechanism has not been elucidated yet. Previous studies have reported that aluminum can firstly promote the apoptosis of intestinal epithelial cells, destroy the structure of tight-junction proteins, and increase the intestinal permeability, injuring the mechanical barrier of gut. Also, it can induce the activation of immune cells to secrete inflammatory factors, and trigger immune responses, interfering with immune barrier. Moreover, aluminum treatment can regulate intestinal composition and bio-enzyme activity, impairing the function of chemical barrier. In addition, aluminum accumulation can induce an imbalance of the intestinal flora, inhibit the growth of beneficial bacteria, and promote the proliferation of harmful bacteria, which ultimately disrupting biological barrier. Collectively, aluminum may do extensive damage to intestinal barrier function covering mechanical barrier, immune barrier, chemical barrier and biological barrier.

Evolutionary dynamics in Barrett oesophagus: implications for surveillance, risk stratification and therapy

Cancer development is a dynamic evolutionary process characterized by marked intratumoural heterogeneity at the genetic, epigenetic and phenotypic levels. Barrett oesophagus, the pre-malignant condition to oesophageal adenocarcinoma (EAC), is an exemplary system to longitudinally study the evolution of malignancy. Evidence has emerged of Barrett oesophagus lesions pre-programmed for progression to EAC many years before clinical detection, indicating a considerable window for therapeutic intervention. In this Review, we explore the mechanisms underlying clonal expansion and contraction that establish the Barrett oesophagus clonal mosaicism over time and space and discuss intrinsic genotypic and extrinsic environmental drivers that direct the evolutionary trajectory of Barrett oesophagus towards a malignant phenotype. We propose that understanding and exploiting the evolutionary dynamics of Barrett oesophagus will identify novel therapeutic targets, improve prognostic tools and offer the opportunity for personalized surveillance programmes geared to prevent progression to EAC.

A comprehensive update: gastrointestinal microflora, gastric cancer and gastric premalignant condition, and intervention by traditional Chinese medicine

With the recent upsurge of studies in the field of microbiology, we have learned more about the complexity of the gastrointestinal microecosystem. More than 30 genera and 1000 species of gastrointestinal microflora have been found. The structure of the normal microflora is relatively stable, and is in an interdependent and restricted dynamic equilibrium with the body. In recent years, studies have shown that there is a potential relationship between gastrointestinal microflora imbalance and gastric cancer (GC) and precancerous lesions. So, restoring the balance of gastrointestinal microflora is of great significance. Moreover, intervention in gastric premalignant condition (GPC), also known as precancerous lesion of gastric cancer (PLGC), has been the focus of current clinical studies. The holistic view of traditional Chinese medicine (TCM) is consistent with the microecology concept, and oral TCM can play a two-way regulatory role directly with the microflora in the digestive tract, restoring the homeostasis of gastrointestinal microflora to prevent canceration. However, large gaps in knowledge remain to be addressed. This review aims to provide new ideas and a reference for clinical practice.

Dietary spinach reshapes the gut microbiome in an Apc-mutant genetic background: mechanistic insights from integrated multi-omics

Complex interrelationships govern the dynamic interactions between gut microbes, the host, and exogenous drivers of disease outcome. A multi-omics approach to cancer prevention by spinach (SPI) was pursued for the first time in the polyposis in rat colon (Pirc) model. SPI fed for 26 weeks (10% w/w, freeze-dried in the diet) exhibited significant antitumor efficacy and, in the Apc-mutant genetic background, β-catenin remained highly overexpressed in adenomatous polyps. However, in both wild type and Apc-mutant rats, increased gut microbiome diversity after SPI consumption coincided with reversal of taxonomic composition. Metagenomic prediction implicated linoleate and butanoate metabolism, tricarboxylic acid cycle, and pathways in cancer, which was supported by transcriptomic and metabolomic analyses. Thus, tumor suppression by SPI involved marked reshaping of the gut microbiome along with changes in host RNA-miRNA networks. When colon polyps were compared with matched normal-looking tissues via metabolomics, anticancer outcomes were linked to SPI-derived linoleate bioactives with known anti-inflammatory/ proapoptotic mechanisms, as well as N-aceto-2-hydroxybutanoate, consistent with altered butanoate metabolism stemming from increased α-diversity of the gut microbiome. In colon tumors from SPI-fed rats, L-glutamate and N-acetylneuraminate also were reduced, implicating altered mitochondrial energetics and cell surface glycans involved in oncogenic signaling networks and immune evasion. In conclusion, a multi-omics approach to cancer prevention by SPI provided mechanistic support for linoleate and butanoate metabolism, as well as tumor-associated changes in L-glutamate and N-acetylneuraminate. Additional factors, such as the fiber content, also warrant further investigation with a view to delaying colectomy and drug intervention in at-risk patients.

Oral nanomedicine for modulating immunity, intestinal barrier functions, and gut microbiome

The gastrointestinal tract (GIT) affects not only local diseases in the GIT but also various systemic diseases. Factors that can affect the health and disease of both GIT and the human body include 1) the mucosal immune system composed of the gut-associated lymphoid tissues and the lamina propria, 2) the intestinal barrier composed of mucus and intestinal epithelium, and 3) the gut microbiota. Selective delivery of drugs, including antigens, immune-modulators, intestinal barrier enhancers, and gut-microbiome manipulators, has shown promising results for oral vaccines, immune tolerance, treatment of inflammatory bowel diseases, and other systemic diseases, including cancer. However, physicochemical and biological barriers of the GIT present significant challenges for successful translation. With the advances of novel nanomaterials, oral nanomedicine has emerged as an attractive option to not only overcome these barriers but also to selectively deliver drugs to the target sites in GIT. In this review, we discuss the GIT factors and physicochemical and biological barriers in the GIT. Furthermore, we present the recent progress of oral nanomedicine for oral vaccines, immune tolerance, and anti-inflammation therapies. We also discuss recent advances in oral nanomedicine designed to fortify the intestinal barrier functions and modulate the gut microbiota and microbial metabolites. Finally, we opine about the future directions of oral nano-immunotherapy.

Gut microbiota and renin-angiotensin system: a complex interplay at local and systemic levels

Gut microbiota is a potent biological modulator of many physiological and pathological states. The renin-angiotensin system (RAS), including the local gastrointestinal RAS (GI RAS), emerges as a potential mediator of microbiota-related effects. The RAS is involved in cardiovascular system homeostasis, water-electrolyte balance, intestinal absorption, glycemic control, inflammation, carcinogenesis, and aging-related processes. Ample evidence suggests a bidirectional interaction between the microbiome and RAS. On the one hand, gut bacteria and their metabolites may modulate GI and systemic RAS. On the other hand, changes in the intestinal habitat caused by alterations in RAS may shape microbiota metabolic activity and composition. Notably, the pharmacodynamic effects of the RAS-targeted therapies may be in part mediated by the intestinal RAS and changes in the microbiome. This review summarizes studies on gut microbiota and RAS physiology. Expanding the research on this topic may lay the foundation for new therapeutic paradigms in gastrointestinal diseases and multiple systemic disorders.

The gut microbiome and efficacy of cancer immunotherapy

Cancer treatment has been deeply changed by immunotherapy, achieving unprecedented improvement in overall and progression-free survival in several advanced and metastatic cancers. Currently, immune checkpoint inhibitor (ICI) antibodies against cytotoxic T-lymphocyte antigen (CTLA-4) and programmed death/ligand 1 (PD-1/PD-L1) are being tested and approved for different tumors, ranging from melanoma to lung carcinoma. However, only a subgroup of patients can reach treatment benefits and long-term responses, and reliable biomarkers that can accurately predict clinical responses to immunotherapy are still unidentified. In the last decade, accumulating evidence seems to suggest the gut microbiota as one of the modulators that can alter the efficacy and toxicity of immunotherapy drugs (as well as chemotherapeutics), mainly acting through the local and systemic immune system. Herein, we reviewed the highly dynamic and complex microbiome-immune system interface, its bidirectional relationship with cancer immunotherapies, and explored the future possibilities and risks in manipulating the gut microbiome.

Protein lysine crotonylation: past, present, perspective

Lysine crotonylation has been discovered in histone and non-histone proteins and found to be involved in diverse diseases and biological processes, such as neuropsychiatric disease, carcinogenesis, spermatogenesis, tissue injury, and inflammation. The unique carbon–carbon π-bond structure indicates that lysine crotonylation may use distinct regulatory mechanisms from the widely studied other types of lysine acylation. In this review, we discussed the regulation of lysine crotonylation by enzymatic and non-enzymatic mechanisms, the recognition of substrate proteins, the physiological functions of lysine crotonylation and its cross-talk with other types of modification. The tools and methods for prediction and detection of lysine crotonylation were also described.

Relationship between microsatellite status and immune microenvironment of colorectal cancer and its application to diagnosis and treatment

Due to advances in understanding the immune microenvironment of colorectal cancer (CRC), microsatellite classification (dMMR/MSI-H and pMMR/MSS) has become a key biomarker for the diagnosis and treatment of CRC patients and therefore has important clinical value. Microsatellite status is associated with a variety of clinicopathological features and affects drug resistance and the prognosis of patients. CRC patients with different microsatellite statuses have different compositions and distributions of immune cells and cytokines within their tumor microenvironments (TMEs). Therefore, there is great interest in reversing or reshaping CRC TMEs to transform immune tolerant "cold" tumors into immune sensitive "hot" tumors. This requires a thorough understanding of differences in the immune microenvironments of MSI-H and MSS type tumors. This review focuses on the relationship between CRC microsatellite status and the immune microenvironment. It focuses on how this relationship has value for clinical application in diagnosis and treatment, as well as exploring the limitations of its current application.

Research progress on gut microbiota in patients with gastric cancer, esophageal cancer, and small intestine cancer

The pathogenesis of gut microbiota in humans can be indicated due to the wide application of techniques, such as 16S rRNA sequencing. Presently, several studies have found a significant difference in fecal flora between normal individuals and patients with gastric cancer. Although clinical research on the feedback mechanism of gastric flora and gut microbiota is lacking, clarifying the relationship between gut microbiota and the characteristics of cancer is significant for the early diagnosis of gastric cancer. This study was conducted to review the results of several studies in the past 5 years and analyze the intestinal bacteria in patients with gastric cancer and compare them with those in patients with esophageal and small intestine cancers. It was found that the gut microbiota in patients with gastric cancer was similar to that in patients with esophageal cancer. However, making an analysis and comparing the gut microbiota in patients with small intestine and gastric cancers was impossible due to the low incidence of small intestinal cancer. Our review summarized the research progress on using the gut microbiota for early screening for gastric cancer, and the results of this study will provide a further direction in this field. KEY POINTS: • We reviewed several relative mechanisms of the gut microbiota related to gastric cancer. • The gut microbiota in gastric, esophageal, and small intestine cancers are significantly different in types and quantity, and we have provided some tips for further research. • A prospective review of sequencing methods and study results on the gut microbiota in gastric, esophageal, and small intestine cancers was described.

Emerging applications of bacteria as antitumor agents

Bacteria are associated with the human body and colonize the gut, skin, and mucous membranes. These associations can be either symbiotic or pathogenic. In either case, bacteria derive more benefit from their host. The ability of bacteria to enter and survive within the human body can be exploited for human benefit. They can be used as a vehicle for delivering or producing bioactive molecules, such as toxins and lytic enzymes, and eventually for killing tumor cells. Clostridium and Salmonella have been shown to infect and survive within the human body, including in tumors. There is a need to develop genetic circuits, which enable bacterial cells to carry out the following activities: (i) escape the human immune system, (ii) invade tumors, (iii) multiply within the tumorous cells, (iv) produce toxins via quorum sensing at low cell densities, and (v) express suicide genes to undergo cell death or cell lysis after the tumor has been lysed. Thus, bacteria have the potential to be exploited as anticancer agents.

Transmissive Single-Pixel Microscopic Imaging through Scattering Media

Microscopic imaging is of great significance for medical diagnosis. However, due to the strong scattering and absorption of tissue, the implementation of non-invasive microscopic imaging is very difficult. Traditional single-pixel microscopes, based on reflective optical systems, provide an alternative solution for scattering media imaging. Here, the single-pixel microscope with transmissive liquid crystal modulation is proposed. The microscopic ability of the proposed microscope is calibrated. The multi-spectral microscopic imaging of the object is demonstrated. The transmissive imaging of the object behind the scattering media is analyzed. The proposed prototype of the transmissive single-pixel microscope is expected to be applied in microscopic imaging through scattering media and medical imaging.

Modeling colorectal cancers using multidimensional organoids

Organoids have revolutionized cancer research as highly adaptable models that enable an array of experimental techniques to interrogate tissue morphology and function. Because they preserve the genetic, phenotypic, and behavioral traits of their source tissue, organoids have gained traction as the most relevant models for drug discovery, tracking therapeutic response and for personalized medicine. As organoids are indisputably becoming a mainstay of cancer research, this review specifically addresses how colon-derived organoids can be perfected as multidimensional, scalable, reproducible models of healthy, pre-neoplastic and neoplastic conditions of the colon and for use in high-throughput "Phase-0" human clinical trials-in-a-dish.

The potential role of nontyphoidal salmonellosis in gastric cancer: a nationwide matched cohort study

BACKGROUND

The research is to explore the association between nontyphoidal salmonellosis (NTS) and subsequent gastric cancer.

METHODS

We conducted a retrospective study by analyzing hospitalization dataset from the National Health Insurance Research Database in Taiwan. Patients aged 20 years and older with NTS (n = 9 097) admitted between January 1, 2000, and December 31, 2012, were enrolled and followed up until December 31, 2013. The primary outcome was the incidence of gastric cancer. Cox proportional hazards regression was used to estimate the risk of malignancy, accounting for the competing risk of death. In addition, we conducted a sensitivity analysis by propensity score matching and exclusion of malignancy within 1 year observation to minimize measurable confounding and protopathic bias. Negative controls were applied to examine the presence of possible unmeasured confounders in the study.

RESULTS

The study included 18 194 patients (9097 in each NTS and non-NTS group). The median follow-up time was 7 years. The incidence density rate of gastric cancer was 0.72 per 1000 person-years for the NTS group and 0.40 per 1000 person-years for the non-NTS group. The NTS group had a modestly higher risk of gastric cancer (aHR, 2.02; 95% CI 1.18-3.45) than the non-NTS group. The sensitivity analyses revealed consistent results.

CONCLUSIONS

Patients with NTS are associated with increased risk of subsequent gastric cancer compared with non-NTS patients. Future research is needed to examine whether NTS is parallel, reactive or causative to gastric cancer.

Microbiome or Infections: Amyloid-Containing Biofilms as a Trigger for Complex Human Diseases

The human microbiota is the community of microorganisms that live upon or within their human host. The microbiota consists of various microorganisms including bacteria, fungi, viruses, and archaea; the gut microbiota is comprised mostly of bacteria. Many bacterial species within the gut microbiome grow as biofilms, which are multicellular communities embedded in an extracellular matrix. Studies have shown that the relative abundances of bacterial species, and therefore biofilms and bacterial byproducts, change during progression of a variety of human diseases including gastrointestinal, autoimmune, neurodegenerative, and cancer. Studies have shown the location and proximity of the biofilms within the gastrointestinal tract might impact disease outcome. Gram-negative enteric bacteria secrete the amyloid curli, which makes up as much as 85% of the extracellular matrix of enteric biofilms. Curli mediates cell-cell attachment and attachment to various surfaces including extracellular matrix components such as fibronectin and laminin. Structurally, curli is strikingly similar to pathological and immunomodulatory human amyloids such as amyloid-β, which has been implicated in Alzheimer's disease, α-synuclein, which is involved in Parkinson's disease, and serum amyloid A, which is secreted during the acute phase of inflammation. The immune system recognizes both bacterial amyloid curli and human amyloids utilizing the same receptors, so curli also induces inflammation. Moreover, recent work indicates that curli can participate in the self-assembly process of pathological human amyloids. Curli is found within biofilms of commensal enteric bacteria as well as invasive pathogens; therefore, evidence suggests that curli contributes to complex human diseases. In this review, we summarize the recent findings on how bacterial biofilms containing curli participate in the pathological and immunological processes in gastrointestinal diseases, systemic autoimmune diseases, and neurodegenerative diseases.

A tumor microenvironment-specific gene expression signature predicts chemotherapy resistance in colorectal cancer patients

Studies have shown that tumor microenvironment (TME) might affect drug sensitivity and the classification of colorectal cancer (CRC). Using TME-specific gene signature to identify CRC subtypes with distinctive clinical relevance has not yet been tested. A total of 18 "bulk" RNA-seq datasets (total n = 2269) and four single-cell RNA-seq datasets were included in this study. We constructed a "Signature associated with FOLFIRI resistant and Microenvironment" (SFM) that could discriminate both TME and drug sensitivity. Further, SFM subtypes were identified using K-means clustering and verified in three independent cohorts. Nearest template prediction algorithm was used to predict drug response. TME estimation was performed by CIBERSORT and microenvironment cell populations-counter (MCP-counter) methods. We identified six SFM subtypes based on SFM signature that discriminated both TME and drug sensitivity. The SFM subtypes were associated with distinct clinicopathological, molecular and phenotypic characteristics, specific enrichments of gene signatures, signaling pathways, prognosis, gut microbiome patterns, and tumor lymphocytes infiltration. Among them, SFM-C and -F were immune suppressive. SFM-F had higher stromal fraction with epithelial-to-mesenchymal transition phenotype, while SFM-C was characterized as microsatellite instability phenotype which was responsive to immunotherapy. SFM-D, -E, and -F were sensitive to FOLFIRI and FOLFOX, while SFM-A, -B, and -C were responsive to EGFR inhibitors. Finally, SFM subtypes had strong prognostic value in which SFM-E and -F had worse survival than other subtypes. SFM subtypes enable the stratification of CRC with potential chemotherapy response thereby providing more precise therapeutic options for these patients.