Limiting oxidative DNA damage reduces microbe-induced colitis-associated colorectal cancer. Nat Commun. 2020;11:1802. [PMID: 32286276 PMCID: PMC7156452 DOI: 10.1038/s41467-020-15549-6]

Gut microbiota and gastrointestinal tumors: insights from a bibliometric analysis

Introduction

Despite the growing number of studies on the role of gut microbiota in treating gastrointestinal tumors, the overall research trends in this field remain inadequately characterized.

Methods

A bibliometric analysis was conducted using publications retrieved from the Web of Science Core Collection (up to September 30, 2024). Analytical tools including VOSviewer, CiteSpace, and an online bibliometric platform were employed to evaluate trends and hotspots.

Results

Analysis of 1,421 publications revealed significant geographical disparities in research output, with China and the United States leading contributions. Institutionally, the University of Adelaide, Zhejiang University, and Shanghai Jiao Tong University were prominent contributors. Authorship analysis identified Hannah R. Wardill as the most prolific author, while the International Journal of Molecular Sciences emerged as a leading journal. Rapidly growing frontiers include "proliferation," "inhibition," "immunotherapy," "drug delivery," and "tumorigenesis."

Discussion

This study provides a comprehensive overview of research trends and highlights emerging directions, aiming to advance scientific and clinical applications of gut microbiota in gastrointestinal tumor therapy.

Dietary fibre counters the oncogenic potential of colibactin-producing Escherichia coli in colorectal cancer

Diet, microbiome, inflammation and host genetics have been linked to colorectal cancer development; however, it is not clear whether and how these factors interact to promote carcinogenesis. Here we used Il10-/- mice colonized with bacteria previously associated with colorectal cancer: enterotoxigenic Bacteroides fragilis, Helicobacter hepaticus or colibactin-producing (polyketide synthase-positive (pks+)) Escherichia coli and fed either a low-carbohydrate (LC) diet deficient in soluble fibre, a high-fat and high-sugar diet, or a normal chow diet. Colonic polyposis was increased in mice colonized with pks+ E. coli and fed the LC diet. Mechanistically, mucosal inflammation was increased in the LC-diet-fed mice, leading to diminished colonic PPAR-γ signalling and increased luminal nitrate levels. This promoted both pks+ E. coli growth and colibactin-induced DNA damage. PPAR-γ agonists or supplementation with dietary soluble fibre in the form of inulin reverted inflammatory and polyposis phenotypes. The pks+ E. coli also induced more polyps in mismatch-repair-deficient mice by inducing a senescence-associated secretory phenotype. Moreover, oncogenic effects were further potentiated by inflammatory triggers in the mismatch-repair-deficient model. These data reveal that diet and host genetics influence the oncogenic potential of a common bacterium.

Combining gut microbiota modulation and immunotherapy: A promising approach for treating microsatellite stable colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and lethal cancers worldwide, ranking third in incidence and second in mortality. While immunotherapy has shown promise in patients with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H), its effectiveness in proficient mismatch repair (pMMR) or microsatellite stable (MSS) CRC remains limited. Recent advances highlight the gut microbiota as a potential modulator of anti-tumor immunity. The gut microbiome can significantly influence the efficacy of immune checkpoint inhibitors (ICIs), especially in pMMR/MSS CRC, by modulating immune responses and systemic inflammation. This review explores the role of the gut microbiota in pMMR/MSS CRC, the mechanisms by which it may enhance immunotherapy, and current strategies for microbiota modulation. We discuss the potential benefits of combining microbiota-targeting interventions with immunotherapy to improve treatment outcomes for pMMR/MSS CRC patients.

Mitochondrial defects and metabolic vulnerabilities in Lynch syndrome-associated MSH2-deficient endometrial cancer

Lynch syndrome (LS), caused by inherited mutations in DNA mismatch repair genes, including MSH2, carries a 60% lifetime risk of developing endometrial cancer (EC). Beyond hypermutability, mechanisms driving LS-associated EC (LS-EC) remain unclear. We investigated MSH2 loss in EC pathogenesis using a mouse model (PR-Cre Msh2LoxP/LoxP, abbreviated Msh2KO), primary cell lines, human tissues, and human EC cells with isogenic MSH2 knockdown. By 8 months, 58% of Msh2KO mice developed endometrial atypical hyperplasia (AH), a precancerous lesion. At 12-16 months, 50% of Msh2KO mice exhibited either AH or ECs with histologic similarities to human LS-ECs. Transcriptomic profiling of EC from Msh2KO mice revealed mitochondrial dysfunction-related pathway changes. Subsequent studies in vitro and in vivo revealed mitochondrial dysfunction based on 2 mechanisms: mitochondrial content reduction and structural disruptions in retained mitochondria. Human LS-ECs also exhibited mitochondrial content reduction compared with non-LS-ECs. Functional studies demonstrated metabolic reprogramming of MSH2-deficient EC, including reduced oxidative phosphorylation and increased susceptibility to glycolysis suppression. These findings identified mitochondrial dysfunction and metabolic disruption as consequences of MSH2 deficiency in EC. Mitochondrial and metabolic aberrations should be evaluated as biomarkers for endometrial carcinogenesis or risk stratification and represent potential targets for cancer interception in women with LS.

Intratumor microbiota and colorectal cancer: Comprehensive and lucid review

As a key component of tumor microenvironment, the microbiota has gradually played a key role in cancer research. Particularly in colorectal cancer, the specific population of microbiota within the tumor shows a strong association with the tumor type. Although the existence and potential role of microbiota in tumors have been recognized, the specific associations between the microbiota and tumor tissue and the mechanism of action still need to be further explored. This paper reviews the discovery, origin, and emerging role of the intratumor microbiota in the immune microenvironment and systematically outlines the oncogenic and metastasis-promoting strategies of the intratumor microbiota. Moreover, it comprehensively and holistically evaluates therapeutic strategies and prognostic performance on the basis of the intratumor microbiota, with the goal of providing strong support for future research and clinical practice.

Investigating the role of the intratumoral microbiome in thyroid cancer development and progression

The intratumoral microbiome (ITM) is in the spotlight due to its possible contribution to the initiation, progression, and invasion of a wide range of cancers. Its precise contribution to cancer tumorigenesis is still elusive, though. Thyroid cancer(TC), the ninth leading cause of cancer globally and the most prevalent endocrine malignancy with a rapidly rising incidence among all cancers, has attracted much attention nowadays. Still, the association between the tumor's microbiome and TC progression and development is an evolving area of investigation with significant consequences for disease understanding and intervention. Therefore, this review offers an appropriate perspective on this emerging concept in TC based on prior studies on the ITM among the most common tumors worldwide, concentrating on TC. Moreover, information on the origin of the ITM and practical methods can pave the way for researchers to opt for the most appropriate method for further investigations on the ITM more accurately.

Intratumoral Microbiota: Insights from Anatomical, Molecular, and Clinical Perspectives

The human microbiota represents a heterogeneous microbial community composed of several commensal, symbiotic, and even pathogenic microorganisms colonizing both the external and internal body surfaces. Despite the term "microbiota" being commonly used to identify microorganisms inhabiting the gut, several pieces of evidence suggest the presence of different microbiota physiologically colonizing other organs. In this context, several studies have also confirmed that microbes are integral components of tumor tissue in different types of cancer, constituting the so-called "intratumoral microbiota". The intratumoral microbiota is closely related to the occurrence and development of cancer as well as to the efficacy of anticancer treatments. Indeed, intratumoral microbiota can contribute to carcinogenesis and metastasis formation as some microbes can directly cause DNA damage, while others can induce the activation of proinflammatory responses or oncogenic pathways and alter the tumor microenvironment (TME). All these characteristics make the intratumoral microbiota an interesting topic to investigate for both diagnostic and prognostic purposes in order to improve the management of cancer patients. This review aims to gather the most recent data on the role of the intratumoral microbiota in cancer development, progression, and response to treatment, as well as its potential diagnostic and prognostic value.

Multifunctional MnGA Nanozymes for the Treatment of Ulcerative Colitis by Reducing Intestinal Inflammation and Regulating the Intestinal Flora

In ulcerative colitis (UC), the formation of an inflammatory environment is due to the combined effects of excess production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), overproduction of proinflammatory cytokines, and disruption of immune system function. There are many kinds of traditional drugs for the clinical treatment of UC, but long-term drug use can cause toxic side effects and drug resistance and can also reduce patient compliance and other drawbacks. Hence, in light of the clinical challenges associated with UC, including the limitations of existing treatments, intense adverse reactions and the development of resistance to medications, no novel therapeutic agents that offer effective relief and maintain a high level of biosafety are urgently needed. Although many anti-inflammatory nanomedicines have been developed by researchers, the development of efficient and nontoxic nanomedicines is still a major challenge in clinical medicine. Using the natural product gallic acid and the metal compound manganese chloride, a highly effective and nontoxic multifunctional nanoenzyme was developed for the treatment of UC. Nanozymes can effectively eliminate ROS and RNS to reduce the inflammation of intestinal epithelial cells caused by oxidation, facilitate the restoration of the intestinal epithelial barrier through the upregulation of tight junction protein expression, and balance the intestinal microbiota to maintain the stability of the intestinal environment. Using a rodent model designed to mimic UC, we monitored body weight, colon length, the spleen index, and the degree of tissue damage and demonstrated that manganese gallate (MnGA) nanoparticles can reduce intestinal inflammation by clearing ROS and active nitrogen. Intestinal flora sequencing revealed that MnGA nanoparticles could regulate the intestinal flora, promote the growth of beneficial bacteria and decrease the levels of detrimental bacteria within the intestinal tract in a mouse model of UC. Thus, MnGA nanoparticles can maintain the balance of the intestinal flora. This study demonstrated that MnGA nanoparticles are excellent antioxidant and effective anti-inflammatory agents, have good biosafety, and can effectively treat UC.

Bioengineering of glucan coated silver nanoparticles as dynamic biomedical compound; in vitro and in vivo studies

The use of silver nanoparticles (AgNPs) gaining importance for the treatment of microbial infections and are in great demand due to their efficient broad antibacterial action but there is only one problem that silver nanoparticles can cause tissue damage. Therefore, the present study evaluated antimicrobial potential and intricacy of glucan coated silver nanoparticles in comparison with free silver nanoparticles. In this study, glucan coated silver nanoparticles (Glucan-AgNPs) by using Pleurotus spps. were characterized for their antimicrobial, minimum inhibitory concentration (MIC), biofilm inhibition, mutagenicity potential, hemolytic activities and histological examination through in vitro and in vivo analysis. The liver, kidney, intestine, and skin tissues were examined to gauge the adverse effects of the treatment method's toxicity by silver deposition. The results of this study have shown that mushroom's glucan extracted from Pleurotus spps. are excellent reducing agent and due to their best capping ability they reduce the toxicity of AgNPs and enhance their antimicrobial activities. The highest zone of inhibition was observed by Glucan-AgNPs from P. ostreatus (24 mm) against S. aureus while least zone of inhibition was resulted from Glucan-AgNPs from P. sapidus (14 mm) against B. subtilis. The results for biofilm inhibition showed excellent biofilm inhibition ability of Glucan-AgNPs. In results, maximum inhibition 95.2 % was observed by Glucan-AgNPs from P. ostreatus against S. aureus, while minimum inhibition 79.2 % by Glucan-AgNPs of P. sapidus against E. coli. Furthermore, Glucan-AgNPs treated mice showed no deposition and damage in the organs. Glucan-AgNPs has a higher efficacy in treating microbial infection.

Beyond the Gut: The intratumoral microbiome's influence on tumorigenesis and treatment response

The intratumoral microbiome (TM) refers to the microorganisms in the tumor tissues, including bacteria, fungi, viruses, and so on, and is distinct from the gut microbiome and circulating microbiota. TM is strongly associated with tumorigenesis, progression, metastasis, and response to therapy. This paper highlights the current status of TM. Tract sources, adjacent normal tissue, circulatory system, and concomitant tumor co-metastasis are the main origin of TM. The advanced techniques in TM analysis are comprehensively summarized. Besides, TM is involved in tumor progression through several mechanisms, including DNA damage, activation of oncogenic signaling pathways (phosphoinositide 3-kinase [PI3K], signal transducer and activator of transcription [STAT], WNT/β-catenin, and extracellular regulated protein kinases [ERK]), influence of cytokines and induce inflammatory responses, and interaction with the tumor microenvironment (anti-tumor immunity, pro-tumor immunity, and microbial-derived metabolites). Moreover, promising directions of TM in tumor therapy include immunotherapy, chemotherapy, radiotherapy, the application of probiotics/prebiotics/synbiotics, fecal microbiome transplantation, engineered microbiota, phage therapy, and oncolytic virus therapy. The inherent challenges of clinical application are also summarized. This review provides a comprehensive landscape for analyzing TM, especially the TM-related mechanisms and TM-based treatment in cancer.

Effects of intratumoral microbiota on tumorigenesis, anti-tumor immunity, and microbe-based cancer therapy

Intratumoral microbiota (IM) has emerged as a significant component of the previously thought sterile tumor microenvironment (TME), exerting diverse functions in tumorigenesis and immune modulation. This review outlines the historical background, classification, and diversity of IM, elucidating its pivotal roles in oncogenicity, cancer development, and progression, alongside its influence on anti-tumor immunity. The signaling pathways through which IM impacts tumorigenesis and immunity, including reactive oxygen species (ROS), β-catenin, stimulator of interferon genes (STING), and other pathways [NF-κB, Toll-like receptor (TLR), complement, RhoA/ROCK, PKR-like ER kinase (PERK)], are discussed comprehensively. Furthermore, we briefly introduce the clinical implications of IM, emphasizing its potential as a target for novel cancer therapies, diagnostic biomarkers, and prognostic indicators. Notably, microbe-based therapeutic strategies such as fecal microbiome transplantation (FMT), probiotics regulation, bacteriotherapy, bacteriophage therapy, and oncolytic virotherapy are highlighted. These strategies hold promise for enhancing the efficacy of current cancer treatments and warrant further exploration in clinical settings.

Transformation of colitis and colorectal cancer: a tale of gut microbiota

Intestinal inflammation modifies host physiology to promote the occurrence of colorectal cancer (CRC), as seen in colitis-associated CRC. Gut microbiota is crucial in cancer progression, primarily by inducing intestinal chronic inflammatory microenvironment, leading to DNA damage, chromosomal mutation, and alterations in specific metabolite production. Therefore, there is an increasing interest in microbiota-based prevention and treatment strategies, such as probiotics, prebiotics, microbiota-derived metabolites, and fecal microbiota transplantation. This review aims to provide valuable insights into the potential correlations between gut microbiota and colitis-associated CRC, as well as the promising microbiota-based strategies for colitis-associated CRC.

Path to bacteriotherapy: From bacterial engineering to therapeutic perspectives

The major reason for the failure of conventional therapies is the heterogeneity and complexity of tumor microenvironments (TMEs). Many malignant tumors reprogram their surface antigens to evade the immune surveillance, leading to reduced antigen-presenting cells and hindered T-cell activation. Bacteria-mediated cancer immunotherapy has been extensively investigated in recent years. Scientists have ingeniously modified bacteria using synthetic biology and nanotechnology to enhance their biosafety with high tumor specificity, resulting in robust anticancer immune responses. To enhance the antitumor efficacy, therapeutic proteins, cytokines, nanoparticles, and chemotherapeutic drugs have been efficiently delivered using engineered bacteria. This review provides a comprehensive understanding of oncolytic bacterial therapies, covering bacterial design and the intricate interactions within TMEs. Additionally, it offers an in-depth comparison of the current techniques used for bacterial modification, both internally and externally, to maximize their therapeutic effectiveness. Finally, we outlined the challenges and opportunities ahead in the clinical application of oncolytic bacterial therapies.

Antioxidant Role of Probiotics in Inflammation-Induced Colorectal Cancer

Colorectal cancer (CRC) continues to be a significant contributor to global morbidity and mortality. Emerging evidence indicates that disturbances in gut microbial composition, the formation of reactive oxygen species (ROS), and the resulting inflammation can lead to DNA damage, driving the pathogenesis and progression of CRC. Notably, bacterial metabolites can either protect against or contribute to oxidative stress by modulating the activity of antioxidant enzymes and influencing signaling pathways that govern ROS-induced inflammation. Additionally, microbiota byproducts, when supplemented through probiotics, can affect tumor microenvironments to enhance treatment efficacy and selectively mediate the ROS-induced destruction of CRC cells. This review aims to discuss the mechanisms by which taxonomical shifts in gut microbiota and related metabolites such as short-chain fatty acids, secondary bile acids, and trimethylamine-N-oxide influence ROS concentrations to safeguard or promote the onset of inflammation-mediated CRC. Additionally, we focus on the role of probiotic species in modulating ROS-mediated signaling pathways that influence both oxidative status and inflammation, such as Nrf2-Keap1, NF-κB, and NLRP3 to mitigate carcinogenesis. Overall, a deeper understanding of the role of gut microbiota on oxidative stress may aid in delaying or preventing the onset of CRC and offer new avenues for adjunct, CRC-specific therapeutic interventions such as cancer immunotherapy.

Multiplex spatial omics reveals changes in immune-epithelial crosstalk during inflammation and dysplasia development in chronic IBD patients

Patients with long-standing inflammatory bowel disease (IBD) face an increased risk of developing colitis-associated cancer (CAC). Although IBD-induced prolonged inflammation seems to be involved in CAC pathogenesis, the specific molecular changes that contribute remain unknown. Here, we applied digital spatial RNA profiling, RNAscope, and imaging mass cytometry to examine paired uninflamed, inflamed, and early dysplastic mucosa of patients with IBD. We observed robust type 3 (IL-17) responses during inflammation, accompanied by elevated JAK-STAT signaling and phosphorylated STAT3 (P-STAT3) levels, with both inflamed and dysplastic mucosa displaying immune cell activation. Higher stromal P-STAT3 was detected in uninflamed and inflamed mucosa of patients who eventually developed dysplasia. CD8a+ T cells did not infiltrate inflamed or dysplastic epithelial regions in these patients, while control patients showed elevated CD8a in inflamed mucosa. Our study reveals distinct inflammatory patterns throughout CAC development, marked by an activated IL-17 pathway, engaged STAT3, and diminished cytotoxic T cell infiltration.

Sea Cucumber Viscera Processed by Protease Hydrolysis Combined with Cordyceps militaris Fermentation Protect Caco-2 Cells against Oxidative Damage via Enhancing Antioxidant Capacity, Activating Nrf2/HO-1 Pathway and Improving Cell Metabolism

Excessive reactive oxygen species (ROS) may lead to oxidative damage and metabolic disorder. The pathogenesis of human bowel inflammation is closely related to oxidative damage of intestinal epithelial cells caused by ROS. This study aimed to explore the high-value utilization of the byproducts of sea cucumber in antioxidant food for colitis prevention. The technology of protease hydrolysis combined with Cordyceps militaris fermentation was used to obtain fermented sea cucumber viscera protease hydrolysates (FSVHs). The results revealed that FSVH could enhance antioxidant capacity and alleviate oxidative damage and apoptosis by activating the Nrf2/HO-1 pathway and triggering the self-protection immune mechanisms. Moreover, the FSVH supplementation could upregulate antioxidant-related metabolic pathways of Caco-2 cells such as glutathione metabolism, confirming the enhanced antioxidant capacity of damaged cells. In summary, FSVH could exert protective effects on Caco-2 cells in response to oxidative damage, providing a promising prospect for sea cucumber resource utilization and colitis prevention.

Broadening oncological boundaries: the intratumoral microbiota

The microbiota of solid tumors was identified >100 years ago; however, heterogeneous composition and diversity have been revealed only recently. Growing evidence has suggested that several functional mechanisms of the intratumoral microbiota affect tumorigenesis and progression, suggesting that the intratumoral microbiota is a promising biomarker for multiple cancers. The low biomass of the intratumoral microbiota poses a major challenge to related research, thus necessitating the use of a multiple-modality integrated framework to resolve this dilemma. Advanced techniques such as single-cell sequencing provide significant clues, and the gradual optimization of functional experiments and culture-based methods enables deeper investigation of the underlying mechanisms involved. In this review, we outline the current state of research on the intratumoral microbiota and describe the challenges and comprehensive strategies for future research.

Low-dose dimethylfumarate attenuates colitis-associated cancer in mice through M2 macrophage polarization and blocking oxidative stress

Colitis-associated cancer (CAC) is an aggressive subtype of colorectal cancer that can develop in ulcerative colitis patients and is driven by chronic inflammation and oxidative stress. Current chemotherapy for CAC, based on 5-fluorouracil and oxalipltin, is not fully effective and displays severe side effects, prompting the search for alternative therapies. Dimethylfumarate (DMF), an activator of the nuclear factor erythroid 2-related factor 2 (NRF2), is a potent antioxidant and immunomodelatrory drug used in the treatment of multiple sclerosis and showed a strong anti-inflammatory effect on experimental colitis. Here, we investigated the chemotherapeutic effect of DMF on an experimental model of CAC. Male NMRI mice were given two subcutaneous injections of 1,2 Dimethylhydrazine (DMH), followed by three cycles of dextran sulfate sodium (DSS). Low-dose (DMF30) and high-dose of DMF (DMF100) or oxaliplatin (OXA) were administered from the 8th to 12th week of the experiment, and then the colon tissues were analysed histologically and biochemically. DMH/DSS induced dysplastic aberrant crypt foci (ACF), oxidative stress, and severe colonic inflammation, with a predominance of pro-inflammatory M1 macrophages. As OXA, DMF30 reduced ACF multiplicity and crypt dysplasia, but further restored redox status, and reduced colitis severity by shifting macrophages towards the anti-inflammatory M2 phenotype. Surprisingly, DMF100 exacerbated ACF multiplicity, oxidative stress, and colon inflammation, likely through NRF2 and p53 overexpression in colonic inflammatory cells. DMF had a dual effect on CAC. At low dose, DMF is chemotherapeutic and acts as an antioxidant and immunomodulator, whereas at high dose, DMF is pro-oxidant and exacerbates colitis-associated cancer.

Exploiting bacteria for cancer immunotherapy

Immunotherapy has revolutionized the treatment of cancer but continues to be constrained by limited response rates, acquired resistance, toxicities and high costs, which necessitates the development of new, innovative strategies. The discovery of a connection between the human microbiota and cancer dates back 4,000 years, when local infection was observed to result in tumour eradication in some individuals. However, the true oncological relevance of the intratumoural microbiota was not recognized until the turn of the twentieth century. The intratumoural microbiota can have pivotal roles in both the pathogenesis and treatment of cancer. In particular, intratumoural bacteria can either promote or inhibit cancer growth via remodelling of the tumour microenvironment. Over the past two decades, remarkable progress has been made preclinically in engineering bacteria as agents for cancer immunotherapy; some of these bacterial products have successfully reached the clinical stages of development. In this Review, we discuss the characteristics of intratumoural bacteria and their intricate interactions with the tumour microenvironment. We also describe the many strategies used to engineer bacteria for use in the treatment of cancer, summarizing contemporary data from completed and ongoing clinical trials. The work described herein highlights the potential of bacteria to transform the landscape of cancer therapy, bridging ancient wisdom with modern scientific innovation.

Nfe2l2/NRF2 Deletion Attenuates Tumorigenesis and Increases Bacterial Diversity in a Mouse Model of Lynch Syndrome

Lynch syndrome (LS) is the most prevalent heritable form of colorectal cancer. Its early onset and high lifetime risk for colorectal cancer emphasize the necessity for effective chemoprevention. NFE2L2 (NRF2) is often considered a potential druggable target, and many chemopreventive compounds induce NRF2. However, although NRF2 counteracts oxidative stress, it is also overexpressed in colorectal cancer and may promote tumorigenesis. In this study, we evaluated the role of NRF2 in the prevention of LS-associated neoplasia. We found increased levels of NRF2 in intestinal epithelia of mice with intestinal epithelium-specific Msh2 deletion (MSH2ΔIEC) compared with C57BL/6 (wild-type) mice, as well as an increase in downstream NRF2 targets NAD(P)H dehydrogenase (quinone 1) and glutamate-cysteine ligase catalytic subunit. Likewise, NRF2 levels were increased in human MSH2-deficient LS tumors compared with healthy human controls. In silico analysis of a publicly accessible RNA sequencing LS dataset also found an increase in downstream NRF2 targets. Upon crossing MSH2ΔIEC with Nrf2null (MSH2ΔIECNrf2null) mice, we unexpectedly found reduced tumorigenesis in MSH2ΔIECNrf2null mice compared with MSH2ΔIEC mice after 40 weeks, which occurred despite an increase in oxidative damage in MSH2ΔIECNrf2null mice. The loss of NRF2 impaired proliferation as seen by Ki67 intestinal staining and in organoid cultures. This was accompanied by diminished WNT/β-catenin signaling, but apoptosis was unaffected. Microbial α-diversity increased over time with the loss of NRF2 based upon 16S rRNA gene amplicon sequencing of murine fecal samples. Altogether, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. Activation of NRF2 may not be a feasible strategy for chemoprevention in LS. Prevention Relevance: Patients with LS have an early onset and high lifetime risk for colorectal cancer. In this study, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. This suggests that NRF2 may not be a tumor suppressor in this specific context.

Methodologies for the detection and sequencing of the epigenetic-like oxidative DNA modification, 8-oxo-7,8-dihydroguanine

The human genome is constantly threatened by endogenous and environmental DNA damaging agents that can induce a variety of chemically modified DNA lesions including 8-oxo-7,8-dihydroguanine (OG). Increasing evidence has indicated that OG is not only a biomarker for oxidative DNA damage but also a novel epigenetic-like modification involved in regulation of gene expression in mammalian cells. Here we summarize the recent progress in OG research focusing on the following points: (i) the mechanism of OG production in organisms and its biological consequences in cells, (ii) the accurate identification of OG in low-abundance genomes and complex biological backgrounds, (iii) the development of OG sequencing methods. These studies will be helpful for further understanding of the molecular mechanisms of OG-induced mutagenesis and its potential roles in human development and diseases such as cancer.

Mitochondrial defects and metabolic vulnerabilities in Lynch syndrome-associated MSH2-deficient endometrial cancer

Lynch syndrome (LS) is defined by inherited mutations in DNA mismatch repair genes, including MSH2, and carries 60% lifetime risk of developing endometrial cancer (EC). Beyond hypermutability, specific mechanisms for LS-associated endometrial carcinogenesis are not well understood. Here, we assessed the effects of MSH2 loss on EC pathogenesis using a novel mouse model (PR-Cre Msh2 flox/flox , abbreviated Msh2KO), primary cell lines established from this model, human tissues, and human EC cell lines with isogenic MSH2 knockdown. Beginning at eight months of age, 30% of Msh2KO mice exhibited endometrial atypical hyperplasia (AH), a precancerous lesion. At 12 to 16 months of age, 47% of Msh2KO mice exhibited either AH or ECs with histologic features similar to human LS-related ECs. Transcriptomic profiling of EC from Msh2KO mice revealed a transcriptomic signature for mitochondrial dysfunction. Studies in vitro and in vivo revealed mitochondrial dysfunction based upon two mechanisms: marked mitochondrial content reduction, along with pronounced disruptions to the integrity of retained mitochondria. Human LS-related ECs also exhibited mitochondrial content reduction compared with non-LS-related ECs. Functional studies revealed metabolic reprogramming of MSH2-deficient EC cells in vitro , including reduced oxidative phosphorylation and increased susceptibility to glycolysis suppression. We are the first to identify mitochondrial dysfunction and metabolic disruption as a consequence of MSH2 deficiency-related EC. Mitochondrial and metabolic aberrations should be evaluated as novel biomarkers for endometrial carcinogenesis or risk stratification and could serve as targets for cancer interception in women with LS.

Significance

This is the first study to report mitochondrial dysfunction contributing to MSH2-deficient endometrial cancer development, identifying a noncanonical pathway for MSH2 deficient carcinogenesis, which also imparts vulnerability to metabolic targeting.

Unveiling intratumoral microbiota: An emerging force for colorectal cancer diagnosis and therapy

Microbes, including bacteria, viruses, fungi, and other eukaryotic organisms, are commonly present in multiple organs of the human body and contribute significantly to both physiological and pathological processes. Nowadays, the development of sequencing technology has revealed the presence and composition of the intratumoral microbiota, which includes Fusobacterium, Bifidobacteria, and Bacteroides, and has shed light on the significant involvement in the progression of colorectal cancer (CRC). Here, we summarized the current understanding of the intratumoral microbiota in CRC and outline the potential translational and clinical applications in the diagnosis, prevention, and treatment of CRC. We focused on reviewing the development of microbial therapies targeting the intratumoral microbiota to improve the efficacy and safety of chemotherapy and immunotherapy for CRC and to identify biomarkers for the diagnosis and prognosis of CRC. Finally, we emphasized the obstacles and potential solutions to translating the knowledge of the intratumoral microbiota into clinical practice.

The Cross-talk Between Intestinal Microbiota and MDSCs Fuels Colitis-associated Cancer Development

Intestinal chronic inflammation is associated with microbial dysbiosis and accumulation of various immune cells including myeloid-derived suppressor cells (MDSC), which profoundly impact the immune microenvironment, perturb homeostasis and increase the risk to develop colitis-associated colorectal cancer (CAC). However, the specific MDSCs-dysbiotic microbiota interactions and their collective impact on CAC development remain poorly understood. In this study, using a murine model of CAC, we demonstrate that CAC-bearing mice exhibit significantly elevated levels of highly immunosuppressive MDSCs, accompanied by microbiota alterations. Both MDSCs and bacteria that infiltrate the colon tissue and developing tumors can be found in close proximity, suggesting intricate MDSC-microbiota cross-talk within the tumor microenvironment. To investigate this phenomenon, we employed antibiotic treatment to disrupt MDSC-microbiota interactions. This intervention yielded a remarkable reduction in intestinal inflammation, decreased MDSC levels, and alleviated immunosuppression, all of which were associated with a significant reduction in tumor burden. Furthermore, we underscore the causative role of dysbiotic microbiota in the predisposition toward tumor development, highlighting their potential as biomarkers for predicting tumor load. We shed light on the intimate MDSCs-microbiota cross-talk, revealing how bacteria enhance MDSC suppressive features and activities, inhibit their differentiation into mature beneficial myeloid cells, and redirect some toward M2 macrophage phenotype. Collectively, this study uncovers the role of MDSC-bacteria cross-talk in impairing immune responses and promoting tumor growth, providing new insights into potential therapeutic strategies for CAC.

SIGNIFICANCE

MDSCs-dysbiotic bacteria interactions in the intestine play a crucial role in intensifying immunosuppression within the CAC microenvironment, ultimately facilitating tumor growth, highlighting potential therapeutic targets for improving the treatment outcomes of CAC.

Enterohemorrhagic Escherichia coli effector EspF triggers oxidative DNA lesions in intestinal epithelial cells

Attaching/effacing (A/E) pathogens induce DNA damage and colorectal cancer by injecting effector proteins into host cells via the type III secretion system (T3SS). EspF is one of the T3SS-dependent effector proteins exclusive to A/E pathogens, which include enterohemorrhagic Escherichia coli. The role of EspF in the induction of double-strand breaks (DSBs) and the phosphorylation of the repair protein SMC1 has been demonstrated previously. However, the process of damage accumulation and DSB formation has remained enigmatic, and the damage response is not well understood. Here, we first showed a compensatory increase in the mismatch repair proteins MutS homolog 2 (MSH2) and MSH6, as well as poly(ADP-ribose) polymerase 1, followed by a dramatic decrease, threatening cell survival in the presence of EspF. Flow cytometry revealed that EspF arrested the cell cycle at the G2/M phase to facilitate DNA repair. Subsequently, 8-oxoguanine (8-oxoG) lesions, a marker of oxidative damage, were assayed by ELISA and immunofluorescence, which revealed the accumulation of 8-oxoG from the cytosol to the nucleus. Furthermore, the status of single-stranded DNA (ssDNA) and DSBs was confirmed. We observed that EspF accelerated the course of DNA lesions, including 8-oxoG and unrepaired ssDNA, which were converted into DSBs; this was accompanied by the phosphorylation of replication protein A 32 in repair-defective cells. Collectively, these findings reveal that EspF triggers various types of oxidative DNA lesions with impairment of the DNA damage response and may result in genomic instability and cell death, offering novel insight into the tumorigenic potential of EspF.IMPORTANCEOxidative DNA lesions play causative roles in colitis-associated colon cancer. Accumulating evidence shows strong links between attaching/effacing (A/E) pathogens and colorectal cancer (CRC). EspF is one of many effector proteins exclusive to A/E pathogens with defined roles in the induction of oxidative stress, double-strand breaks (DSBs), and repair dysregulation. Here, we found that EspF promotes reactive oxygen species generation and 8-oxoguanine (8-oxoG) lesions when the repair system is activated, contributing to sustained cell survival. However, infected cells exposed to EspF presented 8-oxoG, which results in DSBs and ssDNA accumulation when the cell cycle is arrested at the G2/M phase and the repair system is defective or saturated by DNA lesions. In addition, we found that EspF could intensify the accumulation of nuclear DNA lesions through oxidative and replication stress. Overall, our work highlights the involvement of EspF in DNA lesions and DNA damage response, providing a novel avenue by which A/E pathogens may contribute to CRC.

The microbial landscape of colorectal cancer

Colorectal cancer (CRC) is a substantial source of global morbidity and mortality in dire need of improved prevention and treatment strategies. As our understanding of CRC grows, it is becoming increasingly evident that the gut microbiota, consisting of trillions of microorganisms in direct interface with the colon, plays a substantial role in CRC development and progression. Understanding the roles that individual microorganisms and complex microbial communities play in CRC pathogenesis, along with their attendant mechanisms, will help yield novel preventive and therapeutic interventions for CRC. In this Review, we discuss recent evidence concerning global perturbations of the gut microbiota in CRC, associations of specific microorganisms with CRC, the underlying mechanisms by which microorganisms potentially drive CRC development and the roles of complex microbial communities in CRC pathogenesis. While our understanding of the relationship between the microbiota and CRC has improved in recent years, our findings highlight substantial gaps in current research that need to be filled before this knowledge can be used to the benefit of patients.

Genotoxin-producing Salmonella enterica induces tissue-specific types of DNA damage and DNA damage response outcomes

Introduction

Typhoid toxin-expressing Salmonella enterica causes DNA damage in the intestinal mucosa in vivo, activating the DNA damage response (DDR) in the absence of inflammation. To understand whether the tissue microenvironment constrains the infection outcome, we compared the immune response and DDR patterns in the colon and liver of mice infected with a genotoxigenic strain or its isogenic control strain.

Methods

In situ spatial transcriptomic and immunofluorescence have been used to assess DNA damage makers, activation of the DDR, innate immunity markers in a multiparametric analysis.

Result

The presence of the typhoid toxin protected from colonic bacteria-induced inflammation, despite nuclear localization of p53, enhanced co-expression of type-I interferons (IfnbI) and the inflammasome sensor Aim2, both classic features of DNA-break-induced DDR activation. These effects were not observed in the livers of either infected group. Instead, in this tissue, the inflammatory response and DDR were associated with high oxidative stress-induced DNA damage.

Conclusions

Our work highlights the relevance of the tissue microenvironment in enabling the typhoid toxin to suppress the host inflammatory response in vivo.

Carcinogenic risk in the biliary epithelium of children with congenital biliary dilatation via the DNA damage repair pathway

PURPOSES

Congenital biliary dilatation (CBD) is a high-risk factor for biliary tract cancer (BTC). We previously reported the potential for carcinogenesis in the biliary epithelium of patients with CBD. In this study, we investigated potential carcinogenetic pathways, focusing on the DNA damage repair response, in children with CBD and compared the findings with those in adults.

METHODS

We enrolled 6 children with CBD and 10 adults with CBD without BTC who underwent extrahepatic bile duct resections, plus 4 control patients who underwent pancreaticoduodenectomy for non-biliary cancer. Levels of phosphorylated histone H2AX (γH2AX), MRE11, and Ku-70 in the biliary tract epithelium were evaluated by immunohistochemistry.

RESULTS

The levels of γH2AX, MRE11, and Ku-70 were significantly higher in the gallbladder epithelium and bile duct epithelium of both children and adults than in controls.

CONCLUSIONS

Children and adults with CBD might develop BTC via the DNA damage repair pathway, as evidenced by increased γH2AX, MRE11, and Ku-70 expression.

pH/enzyme dual sensitive Gegenqinlian pellets coated with Bletilla striata polysaccharide membranes for the treatment of ulcerative colitis

Gegen Qinlian Decoction, derived from Zhang Zhongjing's Treatise on Typhoid Fever, has been widely used in the treatment of various common diseases, frequently-occurring diseases and difficult and complicated diseases, such as ulcerative colitis. In this study, Bletilla striata polysaccharide (BSP) was innovatively used as a film coating material to prepare Gegen Qinlian pellets with dual sensitivity of pH enzyme for the treatment of ulcerative colitis. BSP has the ability to repair the inflamed colon mucosa and can produce synergistic effects, while avoiding the adverse therapeutic effects caused by the early release of drugs from a single pH-sensitive pellets in the small intestine. The prepared pellets have a uniform particle size, good roundness, a particle size range from 0.8 mm to 1.0 mm, and a particle yield is 85.6 %. The results of in vitro release showed that ES-BSP pellets hardly released drugs in the pH range of 1.2-6.8. However, in the colon mimic fluid containing specific enzymes, the drug release was significantly accelerated, demonstrating the sensitivity of the pellets to pH enzymes. In vivo and ex vivo fluorescence imaging of small animals showed that Gegen Qinlian pellets with dual sensitivity of pH enzyme remained longer in the colon compared with pH-sensitive pellets. In vivo pharmacodynamics study showed that the Gegen Qinlian pellets with dual sensitivity of pH enzyme had a better therapeutic effect in the rat model of the ulcerative colon than the commercially available Gegenqinlian pellets in the control group.

Colonic expression of glutathione S-transferase alpha 4 and 4-hydroxynonenal adducts is correlated with the pathology of murine colitis-associated cancer

Chronic inflammation-induced oxidative stress is an important driving force for developing colitis-associated cancer (CAC). 4-hydroxynonenal (4-HNE) is a highly reactive aldehyde derived from lipid peroxidation of ω-6 polyunsaturated fatty acids that contributes to colorectal carcinogenesis. Glutathione S-transferase alpha 4 (Gsta4) specifically conjugates glutathione to 4-HNE and thereby detoxifies 4-HNE. The correlation of these oxidative biomarkers with the pathological changes in CAC is, however, unclear. In this study, we investigated the expression of Gsta4 and 4-HNE adducts in azoxymethane/dextran sulfate sodium (AOM/DSS)-induced murine CAC, and analyzed the correlations of 4-HNE and Gsta4 with inflammatory cytokines and the pathological scores in the colon biopsies. Real-time quantitative PCR showed that expression of IL6, TNFα, and Gsta4 sequentially increased in colon tissues for mice treated with DSS for 1, 2, and 3 cycles, respectively. Moreover, immunohistochemical staining showed remarkably increased expression of 4-HNE adducts, Gsta4, TNFα, and IL6 in the colon biopsies after 3 cycles of DSS treatment. Correlation analysis demonstrated that 4-HNE adducts in the colon biopsies were positively correlated with Gsta4 expression. Additionally, the expression of Gsta4 and 4-HNE adducts were strongly correlated with the pathological changes of colon, as well as the expression of TNFα and IL6 in colon tissues. These results provide evidence for the association of oxidative biomarkers Gsta4 and 4-HNE with the pathological changes of CAC and may help developing novel histopathological biomarkers and prevention targets for CAC.

Involvement of the human microbiome in frequent cancers, current knowledge and carcinogenesis mechanisms

The human body is home to a complex microbial community, living in symbiosis. However, when an imbalance occurs, known as dysbiosis, it can lead to organic diseases such as cancers. Helicobacter pylori is commonly recognized as the causative agent of gastric cancer. Numerous studies have explored the potential role of other microorganisms in cancers. For example, the role of intestinal microbiota in the hepatocellular carcinoma formation and progression, the microbiota in breast cancer and the interaction between the microbiome and TP53 in human lung carcinogenesis. In this review, we highlight the latest findings on the microbiome involved in the most common cancers and the suggested mechanisms of carcinogenesis.

Current perspectives of mitochondria-targeted antioxidants in cancer prevention and treatment

Oxidative stress nearly always accompanies all stages of cancer development. At the early stages, antioxidants may help to reduce reactive oxygen species (ROS) production and exhibit anticarcinogenic effects. In the later stages, ROS involvement becomes more complex. On the one hand, ROS are necessary for cancer progression and epithelial-mesenchymal transition. On the other hand, antioxidants may promote cancer cell survival and may increase metastatic frequency. The role of mitochondrial ROS in cancer development remains largely unknown. This paper reviews experimental data on the effects of both endogenous and exogenous antioxidants on cancerogenesis focusing on the development and application of mitochondria-targeted antioxidants. We also discuss the prospects for antioxidant cancer therapy, focusing on the use of mitochondria-targeted antioxidants.

Genetic heterogeneity of colorectal cancer and the microbiome

In 2020, the International Agency for Research on Cancer and the World Health Organization's GLOBOCAN database ranked colorectal cancer (CRC) as the third most common cancer in the world. Most cases of CRC (> 95%) are sporadic and develop from colorectal polyps that can progress to intramucosal carcinoma and CRC. Increasing evidence is accumulating that the gut microbiota can play a key role in the initiation and progression of CRC, as well as in the treatment of CRC, acting as an important metabolic and immunological regulator. Factors that may determine the microbiota role in CRC carcinogenesis include inflammation, changes in intestinal stem cell function, impact of bacterial metabolites on gut mucosa, accumulation of genetic mutations and other factors. In this review, I discuss the major mechanisms of the development of sporadic CRC, provide detailed characteristics of the bacteria that are most often associated with CRC, and analyze the role of the microbiome and microbial metabolites in inflammation initiation, activation of proliferative activity in intestinal epithelial and stem cells, and the development of genetic and epigenetic changes in CRC. I consider long-term studies in this direction to be very important, as they open up new opportunities for the treatment and prevention of CRC.

Seminars in immunology special issue: Nutrition, microbiota and immunity The unexplored microbes in health and disease

Functional characterization of the microbiome's influence on host physiology has been dominated by a few characteristic example strains that have been studied in detail. However, the extensive development of methods for high-throughput bacterial isolation and culture over the past decade is enabling functional characterization of the broader microbiota that may impact human health. Characterizing the understudied majority of human microbes and expanding our functional understanding of the diversity of the gut microbiota could enable new insights into diseases with unknown etiology, provide disease-predictive microbiome signatures, and advance microbial therapeutics. We summarize high-throughput culture-dependent platforms for characterizing bacterial strain function and host-interactions. We elaborate on the importance of these technologies in facilitating mechanistic studies of previously unexplored microbes, highlight new opportunities for large-scale in vitro screens of host-relevant microbial functions, and discuss the potential translational applications for microbiome science.

Xanthones from Gentianella acuta (Michx.) Hulten Ameliorate Colorectal Carcinoma via the PI3K/Akt/mTOR Signaling Pathway

Colorectal carcinoma (CRC) is a kind of malignant tumor closely related to ulcerative colitis. Xanthone derivatives are one of the most promising therapeutic drugs which have been used in phase I/II clinical trials for cancer therapy. Our previous study indicated that the aerial parts of Gentianella acuta Michx. Hulten (GA) was rich in xanthones and showed a good therapeutic effect on ulcerative colitis in mice, suggesting that GA xanthones might have some therapeutic or ameliorative effects on CRC. However, no relevant study has been reported. This study aims to find the effective substances of GA inhibiting CRC and clarify their mechanism. Solvent extraction, column chromatographic separation, and LC-MS analysis were used to characterize the 70% EtOH extract of GA and track xanthones abundant fraction XF. MTT assay was carried out to clarify the activity of GA fractions; the result showed XF to be the main active fraction. LC-MS analysis was executed to characterize XF, 38 xanthones were identified. Network pharmacology prediction, in vitro activity screening, and molecular docking assay were combined to predict the potential mechanism; the PI3K/Akt/mTOR signaling pathway was found to be most important. Western blot assay on the main active xanthones 1,3,5-trihydroxyxanthone (16), 1,3,5,8-tetrahydroxyxanthone (17), 1,5,8-trihydroxy-3-methoxyxanthone (18), and 1,7-dihydroxy-3,8-dimethoxyxanthone (19) was used to verify the above prediction; these xanthones were found to inhibit the PI3K/Akt/mTOR signaling pathway, and 17 played a significant role among them through Western blot assay using PI3K/AKT/mTOR agonist IGF-1. In conclusion, this study demonstrated that GA xanthones were effective compounds of GA inhibiting CRC by regulating PI3K/Akt/mTOR signaling pathway transduction, at least. Importantly, 1,3,5,8-tetrahydroxyxanthone (17), the most abundant active xanthone in GA, might be a candidate drug for CRC.

Ultra-small polydopamine nanomedicine-enabled antioxidation against senescence

Senescence is a cellular response characterized by cells irreversibly stopping dividing and entering a state of permanent growth arrest. One of the underlying pathophysiological causes of senescence is the oxidative stress-induced damage, indicating that eliminating the reactive oxygen and nitrogen species (RONS) may be beneficial to prevent and/or alleviate senescence. Herein, we developed ultra-small polydopamine nanoparticles (UPDA NPs) with superoxide dismutase (SOD)/catalase (CAT) enzyme-mimic activities, featuring broad-spectrum RONS-scavenging capability for inducing cytoprotective effects against RONS-mediated damage. The engineered UPDA NPs can restore senescence-related renal function, tissue homeostasis, fur density, and motor ability in mice, potentially associated with the regulation of multiple genes involved in lipid metabolism, mitochondrial function, energy homeostasis, telomerase activity, neuroprotection, and inflammatory responses. Importantly, the dietary UPDA NPs can enhance the antioxidant capacity, improve the climbing ability, and prolong the lifespan of Drosophila. Notably, UPDA NPs possess excellent biocompatibility stemming from the ultra-small size, ensuring quick clearance out of the body. These findings reveal that UPDA NPs can delay aging through reducing oxidative stress and provide a paradigm and practical strategy for treating senescence and senescence-related diseases.

Intratumoral microbiota: roles in cancer initiation, development and therapeutic efficacy

Microorganisms, including bacteria, viruses, fungi, and other eukaryotes, play critical roles in human health. An altered microbiome can be associated with complex diseases. Intratumoral microbial components are found in multiple tumor tissues and are closely correlated with cancer initiation and development and therapy efficacy. The intratumoral microbiota may contribute to promotion of the initiation and progression of cancers by DNA mutations, activating carcinogenic pathways, promoting chronic inflammation, complement system, and initiating metastasis. Moreover, the intratumoral microbiota may not only enhance antitumor immunity via mechanisms including STING signaling activation, T and NK cell activation, TLS production, and intratumoral microbiota-derived antigen presenting, but also decrease antitumor immune responses and promote cancer progression through pathways including upregulation of ROS, promoting an anti-inflammatory environment, T cell inactivation, and immunosuppression. The effect of intratumoral microbiota on antitumor immunity is dependent on microbiota composition, crosstalk between microbiota and the cancer, and status of cancers. The intratumoral microbiota may regulate cancer cell physiology and the immune response by different signaling pathways, including ROS, β-catenin, TLR, ERK, NF-κB, and STING, among others. These viewpoints may help identify the microbiota as diagnosis or prognosis evaluation of cancers, and as new therapeutic strategy and potential therapeutic targets for cancer therapy.

Implication of gut microbes and its metabolites in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer with a significant impact on loss of life. In 2020, nearly 1.9 million new cases and over 9,35,000 deaths were reported. Numerous microbes that are abundant in the human gut benefit host physiology in many ways. Although the underlying mechanism is still unknown, their association appears to be crucial in the beginning and progression of CRC. Diet has a significant impact on the microbial composition and may increase the chance of getting CRC. Increasing evidence points to the gut microbiota as the primary initiator of colonic inflammation, which is connected to the development of colonic tumors. However, it is unclear how the microbiota contributes to the development of CRCs. Patients with CRC have been found to have dysbiosis of the gut microbiota, which can be identified by a decline in commensal bacterial species, such as those that produce butyrate, and a concurrent increase in harmful bacterial populations, such as opportunistic pathogens that produce pro-inflammatory cytokines. We believe that using probiotics or altering the gut microbiota will likely be effective tools in the fight against CRC treatment.

PURPOSE

In this review, we revisited the association between gut microbiota and colorectal cancer whether cause or effect. The various factors which influence gut microbiome in patients with CRC and possible mechanism in relation with development of CRC.

CONCLUSION

The clinical significance of the intestinal microbiota may aid in the prevention and management of CRC.

Regulatory Components of Oxidative Stress and Inflammation and Their Complex Interplay in Carcinogenesis

Cancer progression is closely linked to oxidative stress (OS) inflammation. OS is caused by an imbalance between the amount of reactive oxygen species produced and antioxidants present in the body. Excess ROS either oxidizes biomolecules or activates the signaling cascade, resulting in inflammation. Immune cells secrete cytokines and chemokines when inflammation is activated. These signaling molecules attract a wide range of immune cells to the site of infection or oxidative stress. Similarly, increased ROS production by immune cells at the inflamed site causes oxidative stress in the affected area. A review on the role of oxidative stress and inflammation in cancer-related literature was conducted to obtain data. All of the information gathered was focused on the current state of oxidative stress and inflammation in various cancers. After gathering all relevant information, a narrative review was created to provide a detailed note on oxidative stress and inflammation in cancer. Proliferation, differentiation, angiogenesis, migration, invasion, metabolic changes, and evasion of programmed cell death are all aided by OS and inflammation in cancer. Imbalance between reactive oxygen species (ROS) and antioxidants lead to oxidative stress that damages macromolecules (nucleic acids, lipids and proteins). It causes breakdown of the biological signaling cascade. Prolonged oxidative stress causes inflammation by activating transcription factors (NF-κB, p53, HIF-1α, PPAR-γ, Nrf2, AP-1) that alter the expression of many other genes and proteins, including growth factors, tumor-suppressor genes, oncogenes, and pro-inflammatory cytokines, resulting in cancer cell survival. The present review article examines the complex relationship between OS and inflammation in certain types of cancer (colorectal, breast, lung, bladder, and gastric cancer).

Oral fullerene tablets for colorectal cancer therapy based on modulation of tumor inflammatory microenvironments

The development and progression of colorectal cancer (CRC) are highly dependent on the long-term inflammatory microenvironment with immune dysregulation in the colorectum. However, effective therapeutics are limited to targeting CRC. Here, we developed oral fullerene tablets (OFTs) that can act directly on the colorectal site by oral administration and reduce the inflammatory state at the tumor site for effective CRC therapy. In detail, OFTs scavenged reactive oxygen species (ROS), restrained the mutation of the wild-type P53, inhibited the activation of the inflammatory pathway nuclear factor-κB (NF-κB) and the signal transducer and activator of transcription 3 (STAT3) in the colorectum of CRC mice. Subsequently, OFTs could greatly reduce the infiltration of pro-inflammatory M1 macrophages and neutrophils at the tumor site, restoring the inflammatory microenvironment and immune homeostasis in the colorectal region, and ultimately achieving the inhibition of CRC. In addition, there were no significant toxic side effects of the long-term administration of OFTs. Our work provides an effective oral therapeutic strategy for CRC therapy by modulating the colorectal tumor inflammatory microenvironment and sheds light on the route for oral nano-materials in the clinical treatment of CRC.

Dysbiosis: The first hit for digestive system cancer

Gastrointestinal cancer may be associated with dysbiosis, which is characterized by an alteration of the gut microbiota. Understanding the role of gut microbiota in the development of gastrointestinal cancer is useful for cancer prevention and gut microbiota-based therapy. However, the potential role of dysbiosis in the onset of tumorigenesis is not fully understood. While accumulating evidence has demonstrated the presence of dysbiosis in the intestinal microbiota of both healthy individuals and patients with various digestive system diseases, severe dysbiosis is often present in patients with digestive system cancer. Importantly, specific bacteria have been isolated from the fecal samples of these patients. Thus, the association between dysbiosis and the development of digestive system cancer cannot be ignored. A new model describing this relationship must be established. In this review, we postulate that dysbiosis serves as the first hit for the development of digestive system cancer. Dysbiosis-induced alterations, including inflammation, aberrant immune response, bacteria-produced genotoxins, and cellular stress response associated with genetic, epigenetic, and/or neoplastic changes, are second hits that speed carcinogenesis. This review explains the mechanisms for these four pathways and discusses gut microbiota-based therapies. The content included in this review will shed light on gut microbiota-based strategies for cancer prevention and therapy.

Colorectal Cancer in Ulcerative Colitis: Mechanisms, Surveillance and Chemoprevention

Patients with ulcerative colitis (UC) are at a two- to three-fold increased risk of developing colorectal cancer (CRC) than the general population based on population-based data. UC-CRC has generated a series of clinical problems, which are reflected in its worse prognosis and higher mortality than sporadic CRC. Chronic inflammation is a significant contributor to the development of UC-CRC, so comprehending the relationship between the proinflammatory factors and epithelial cells together with downstream signaling pathways is the core to elucidate the mechanisms involved in developing of CRC. Clinical studies have shown the importance of early prevention, detection and management of CRC in patients with UC, and colonoscopic surveillance at regular intervals with multiple biopsies is considered the most effective way. The use of endoscopy with targeted biopsies of visible lesions has been supported in most populations. In contrast, random biopsies in patients with high-risk characteristics have been suggested during surveillance. Some of the agents used to treat UC are chemopreventive, the effects of which will be examined in cancers in UC in a population-based setting. In this review, we outline the current state of potential risk factors and chemopreventive recommendations in UC-CRC, with a specific focus on the proinflammatory mechanisms in promoting CRC and evidence for personalized surveillance.

Design of Diselenide-Bridged Hyaluronic Acid Nano-antioxidant for Efficient ROS Scavenging to Relieve Colitis

Overproduction of reactive oxygen species (ROS), a key characteristic of inflammatory bowel disease (IBD), is responsible for dysregulation of signal transduction, inflammatory response, and DNA damage, which ultimately leads to disease progression and deterioration. Thus, ROS scavenging has become a promising strategy to navigate IBD. Inspired by the targeting capability of hyaluronic acid (HA) to CD44-overexpressed inflammatory cells together with the redox regulation capacity of diselenide compounds, we developed an oral nanoformulation, i.e., diselenide-bridged hyaluronic acid nanogel (SeNG), with a view to treat colitis through a ROS scavenging mechanism. Our data demonstrated that SeNG specifically accumulated in colitis tissue that was mediated by highly efficient CD44-HA interaction. This has allowed us to demonstrate a significant anti-inflammatory effect in an acute colitis mouse model induced by dextran sulfate sodium and trinitrobenzenesulfonic acid. Mechanistically, we continued to show SeNG reduced the ROS level via both direct elimination and up-regulation of the Nrf2/HO-1 signal pathway. Collectively, our work provides proof-of-principle evidence for a SeNG-mediated nano-antioxidant strategy, by which colitis could be effectively managed.

Human Colon Cancer-Derived Clostridioides difficile Strains Drive Colonic Tumorigenesis in Mice

Defining the complex role of the microbiome in colorectal cancer and the discovery of novel, protumorigenic microbes are areas of active investigation. In the present study, culturing and reassociation experiments revealed that toxigenic strains of Clostridioides difficile drove the tumorigenic phenotype of a subset of colorectal cancer patient-derived mucosal slurries in germ-free ApcMin/+ mice. Tumorigenesis was dependent on the C. difficile toxin TcdB and was associated with induction of Wnt signaling, reactive oxygen species, and protumorigenic mucosal immune responses marked by the infiltration of activated myeloid cells and IL17-producing lymphoid and innate lymphoid cell subsets. These findings suggest that chronic colonization with toxigenic C. difficile is a potential driver of colorectal cancer in patients.

SIGNIFICANCE

Colorectal cancer is a leading cause of cancer and cancer-related deaths worldwide, with a multifactorial etiology that likely includes procarcinogenic bacteria. Using human colon cancer specimens, culturing, and murine models, we demonstrate that chronic infection with the enteric pathogen C. difficile is a previously unrecognized contributor to colonic tumorigenesis. See related commentary by Jain and Dudeja, p. 1838. This article is highlighted in the In This Issue feature, p. 1825.

Interaction between microbiota and immunity and its implication in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the world. Besides genetic causes, colonic inflammation is one of the major risk factors for CRC development, which is synergistically regulated by multiple components, including innate and adaptive immune cells, cytokine signaling, and microbiota. The complex interaction between CRC and the gut microbiome has emerged as an important area of current CRC research. Metagenomic profiling has identified a number of prominent CRC-associated bacteria that are enriched in CRC patients, linking the microbiota composition to colitis and cancer development. Some microbiota species have been reported to promote colitis and CRC development in preclinical models, while a few others are identified as immune modulators to induce potent protective immunity against colitis and CRC. Mechanistically, microbiota regulates the activation of different immune cell populations, inflammation, and CRC via crosstalk between innate and adaptive immune signaling pathways, including nuclear factor kappa B (NF-κB), type I interferon, and inflammasome. In this review, we provide an overview of the potential interactions between gut microbiota and host immunity and how their crosstalk could synergistically regulate inflammation and CRC, thus highlighting the potential roles and mechanisms of gut microbiota in the development of microbiota-based therapies to prevent or alleviate colitis and CRC.

Microbiota in Tumors: From Understanding to Application

Microbes with complex functions have been found to be a potential component in tumor microenvironments. Due to their low biomass and other obstacles, intratumor microbiota is poorly understood. Mucosal sites and normal adjacent tissues are important sources of intratumor microbiota, while hematogenous spread also leads to the invasion of microbes. Intratumor microbiota affects the progression of tumors through several mechanisms, such as DNA damage, activation of oncogenic pathways, induction of immunosuppression, and metabolization of drugs. Notably, in different types of tumors, the composition and abundance of intratumor microbiota are highly heterogeneous and may play different roles in the progression of tumors. Because of the concern in this field, several techniques such as omics and immunological methods have been used to study intratumor microbiota. Here, recent progress in this field is reviewed, including the potential sources of intratumor microbiota, their functions and related mechanisms, and their heterogeneity. Techniques that can be used to study intratumor microbiota are also discussed. Moreover, research is summarized into the development of strategies that can be used in antitumor treatment and prospects for possible future research in this field.

Delivery of therapeutic carbon monoxide by gas-entrapping materials

Carbon monoxide (CO) has long been considered a toxic gas but is now a recognized bioactive gasotransmitter with potent immunomodulatory effects. Although inhaled CO is currently under investigation for use in patients with lung disease, this mode of administration can present clinical challenges. The capacity to deliver CO directly and safely to the gastrointestinal (GI) tract could transform the management of diseases affecting the GI mucosa such as inflammatory bowel disease or radiation injury. To address this unmet need, inspired by molecular gastronomy techniques, we have developed a family of gas-entrapping materials (GEMs) for delivery of CO to the GI tract. We show highly tunable and potent delivery of CO, achieving clinically relevant CO concentrations in vivo in rodent and swine models. To support the potential range of applications of foam GEMs, we evaluated the system in three distinct disease models. We show that a GEM containing CO dose-dependently reduced acetaminophen-induced hepatocellular injury, dampened colitis-associated inflammation and oxidative tissue injury, and mitigated radiation-induced gut epithelial damage in rodents. Collectively, foam GEMs have potential paradigm-shifting implications for the safe therapeutic use of CO across a range of indications.

Loss of MMR and TGFBR2 Increases the Susceptibility to Microbiota-Dependent Inflammation-Associated Colon Cancer

BACKGROUND AND AIMS

Mutations in DNA mismatch repair (MMR) genes are causative in Lynch syndrome and a significant proportion of sporadic colorectal cancers (CRCs). MMR-deficient (dMMR) CRCs display increased mutation rates, with mutations frequently accumulating at short repetitive DNA sequences throughout the genome (microsatellite instability). The TGFBR2 gene is one of the most frequently mutated genes in dMMR CRCs. Therefore, we generated an animal model to study how the loss of both TGFBR2 signaling impacts dMMR-driven intestinal tumorigenesis in vivo and explore the impact of the gut microbiota.

METHODS

We generated VCMsh2/Tgfbr2 mice in which Msh2loxP and Tgfbr2loxP alleles are inactivated by Villin-Cre recombinase in the intestinal epithelium. VCMsh2/Tgfbr2 mice were analyzed for their rate of intestinal cancer development and for the mutational spectra and gene expression profiles of tumors. In addition, we assessed the impact of chemically induced chronic inflammation and gut microbiota composition on colorectal tumorigenesis.

RESULTS

VCMsh2/Tgfbr2 mice developed small intestinal adenocarcinomas and CRCs with histopathological features highly similar to CRCs in Lynch syndrome patients. The CRCs in VCMsh2/Tgfbr2 mice were associated with the presence of colitis and displayed genetic and histological features that resembled inflammation-associated CRCs in human patients. The development of CRCs in VCMsh2/Tgfbr2 mice was strongly modulated by the gut microbiota composition, which in turn was impacted by the TGFBR2 status of the tumors.

CONCLUSIONS

Our results demonstrate a synergistic interaction between MMR and TGFBR2 inactivation in inflammation-associated colon tumorigenesis and highlight the crucial impact of the gut microbiota on modulating the incidence of inflammation-associated CRCs.

Inflammatory bowel disease and carcinogenesis

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer mortality worldwide. Colitis-associated colorectal cancer (CAC) is a subtype of CRC associated with inflammatory bowel disease (IBD). It is well known that individuals with IBD have a 2-3 times higher risk of developing CRC than those who do not, rendering CAC a major cause of death in this group. Although the etiology and pathogenesis of CAC are incompletely understood, animal models of chronic inflammation and human cohort data indicate that changes in the intestinal environment, including host response dysregulation and gut microbiota perturbations, may contribute to the development of CAC. Genomic alterations are a hallmark of CAC, with patterns that are distinct from those in sporadic CRC. The discovery of the biological changes that underlie the development of CAC is ongoing; however, current data suggest that chronic inflammation in IBD increases the risk of developing CAC. Therefore, a deeper understanding of the precise mechanisms by which inflammation triggers genetic alterations and disrupts intestinal homeostasis may provide insight into novel therapeutic strategies for the prevention of CAC.