Pectin supplement significantly enhanced the anti-PD-1 efficacy in tumor-bearing mice humanized with gut microbiota from patients with colorectal cancer

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.

Global research on the crosstalk between intestinal microbiome and colorectal cancer: A visualization analysis

Background

Increasing evidence has shown that the intestinal microbiome (IM) is highly linked to colorectal cancer (CRC). To investigate scientific output, identify highly cited papers, and explore research hotspots and trends in the field of IM/CRC, we conducted a bibliometric and visualized analysis.

Methods

A bibliographic search regarding IM/CRC research (2012-2021) was implemented on October 17, 2022. The terms attached to IM and CRC were searched for in the titles (TI), abstracts (AB), and author keywords (AK). The main information was extracted from the Web of Science Core Collection (WoSCC). Biblioshiny from R packages and VOSviewer were used for data visualization.

Results

A total of 1725 papers related to IM/CRC were retrieved. Publications on IM/CRC have grown rapidly from 2012 to 2021. China and the United States were in the leading position for publications in this field and made the most significant contributions to IM/CRC research. Shanghai Jiao Tong University and Harvard University were the most productive institutions. The high-yield authors were Yu Jun and Fang Jing Yuan. The International Journal of Molecular Sciences published the most papers, whereas Gut had the most citations. Historical citation analysis showed the evolution of IM/CRC research. Current status and hotspots were highlighted using keyword cluster analysis. The hot topics include the effect of IM on tumorigenesis, the effect of IM on CRC treatment, the role of IM in CRC screening, the mechanisms of IM involvement in CRC, and IM modulation for CRC management. Some topics, such as chemotherapy, immunotherapy, Fusobacterium nucleatum and short-chain fatty acids could be the focus of IM/CRC research in the coming years.

Conclusion

This research evaluated the global scientific output of IM/CRC research and its quantitative features, identified some significant papers, and gathered information on the status and trends of IM/CRC research, which may shape future paths for academics and practitioners.

The effects of traditional Chinese medicine and dietary compounds on digestive cancer immunotherapy and gut microbiota modulation: A review

Digestive tract-related cancers account for four of the top ten high-risk cancers worldwide. In recent years, cancer immunotherapy, which exploits the innate immune system to attack tumors, has led to a paradigm shifts in cancer treatment. Gut microbiota modification has been widely used to regulate cancer immunotherapy. Dietary compounds and traditional Chinese medicine (TCM) can alter the gut microbiota and its influence on toxic metabolite production, such as the effect of iprindole on lipopolysaccharide (LPS), and involvement in various metabolic pathways that are closely associated with immune reactions. Therefore, it is an effective strategy to explore new immunotherapies for gastrointestinal cancer to clarify the immunoregulatory effects of different dietary compounds/TCMs on intestinal microbiota. In this review, we have summarized recent progress regarding the effects of dietary compounds/TCMs on gut microbiota and their metabolites, as well as the relationship between digestive cancer immunotherapy and gut microbiota. We hope that this review will act as reference, providing a theoretical basis for the clinical immunotherapy of digestive cancer via gut microbiota modulation.

Role of Gut Microbiome in Immune Regulation and Immune Checkpoint Therapy of Colorectal Cancer

Colorectal cancer (CRC) is one of the most frequent gastrointestinal malignant tumors worldwide. Immune checkpoint therapies (ICTs) have been proven to be a reliable treatment for some subtypes of CRC. Gut microbiome is closely involved in intestinal carcinogenesis through the regulation of local immune and inflammation of colonic mucosa. Numerous studies have demonstrated that the immunotherapeutic efficacy of CRC and other kinds of cancer is influenced by the immunosuppressive microenvironment constituted by intestinal microbiome and their metabolites. This Review will discuss the recent advances in how gut microbiome can modify the immune microenvironment and its potential role in ICTs of CRC.

Gut microbiome in tumorigenesis and therapy of colorectal cancer

Colorectal cancer (CRC) is the malignant tumor with the highest incidence in the digestive system, and the gut microbiome plays a crucial role in CRC tumorigenesis and therapy. The gastrointestinal tract is the organ harboring most of the microbiota in humans. Changes in the gut microbiome in CRC patients suggest possible host-microbe interactions, thereby hinting the potential tumorigenesis, which provides new perspective for preventing, diagnosing, or treating CRC. In this review, we discuss the effects of gut microbiome dysbiosis on CRC, and reveal the mechanisms by which gut microbiome dysbiosis leads to CRC. Gut microbiome modulation with the aim to reverse the established gut microbial dysbiosis is a novel strategy for the prevention and treatment of CRC. In addition, this review summarizes that probiotic antagonize CRC tumorigenesis by protecting intestinal barrier function, inhibiting cancer cell proliferation, resisting oxidative stress, and enhancing host immunity. Finally, we highlight clinical applications of the gut microbiome, such as gut microbiome analysis-based biomarker screening and prediction, and microbe modulation-based CRC prevention, treatment enhancement, and treatment side effect reduction. This review provides the reference for the clinical application of gut microbiome in the prevention and treatment of CRC.

Emerging roles of the gut microbiota in cancer immunotherapy

Gut microbiota represents a hidden treasure vault encompassing trillions of microorganisms that inhabit the intestinal epithelial barrier of the host. In the past decade, numerous in-vitro, animal and clinical studies have revealed the profound roles of gut microbiota in maintaining the homeostasis of various physiological functions, especially immune modulation, and remarkable differences in the configuration of microbial communities between cancers and healthy individuals. In addition, although considerable efforts have been devoted to cancer treatments, there remain many patients succumb to their disease with the incremental cancer burden worldwide. Nevertheless, compared with the stability of human genome, the plasticity of gut microbiota renders it a promising opportunity for individualized treatment. Meanwhile, burgeoning findings indicate that gut microbiota is involved in close interactions with the outcomes of diverse cancer immunotherapy protocols, including immune checkpoint blockade therapy, allogeneic hematopoietic stem cell transplantation, and chimeric antigen receptor T cell therapy. Here, we reviewed the evidence for the capacity of gut microflora to modulate cancer immunotherapies, and highlighted the opportunities of microbiota-based prognostic prediction, as well as microbiotherapy by targeting the microflora to potentiate anticancer efficacy while attenuating toxicity, which will be pivotal to the development of personalized cancer treatment strategies.

The potential role of short chain fatty acids improving ex vivo T and CAR-T cell fitness and expansion for cancer immunotherapies

Adoptive cell therapies, like tumor-infiltrating lymphocytes or chimeric antigen receptor T cells, have become an important immunotherapeutic approach against cancer. One of the main struggles of T cell immunotherapies is how to obtain the most effective T cell phenotype, persistence, and differentiation potential to infuse into patients. Adjusting the T cell ex vivo cell culture conditions is a key factor to increase and improve the efficacy of cellular immunotherapies. In this review, we have summarized the ex vivo impact of short chain fatty acids, a group of gut microbiota derived metabolites, on T cell culture and expansion for immunotherapies. There is a complex gut microbiota-immune system interaction that can affect antitumor immunotherapy efficacy. Indeed, gut microbiota derived metabolites can modulate different biological functions in the immune system local and systemically.

Gut microbiota-derived short-chain fatty acids regulate gastrointestinal tumor immunity: a novel therapeutic strategy?

Tumor immune microenvironment (TIME), a tumor-derived immune component, is proven to be closely related to the development, metastasis, and recurrence of tumors. Gut microbiota and its fermented-metabolites short-chain fatty acids (SCFAs) play a critical role in maintaining the immune homeostasis of gastrointestinal tumors. Consisting mainly of acetate, propionate, and butyrate, SCFAs can interact with G protein-coupled receptors 43 of T helper 1 cell or restrain histone deacetylases (HDACs) of cytotoxic T lymphocytes to exert immunotherapy effects. Studies have shed light on SCFAs can mediate the differentiation and function of regulatory T cells, as well as cytokine production in TIME. Additionally, SCFAs can alter epigenetic modification of CD8⁺ T cells by inhibiting HDACs to participate in the immune response process. In gastrointestinal tumors, the abundance of SCFAs and their producing bacteria is significantly reduced. Direct supplementation of dietary fiber and probiotics, or fecal microbiota transplantation to change the structure of gut microbiota can both increase the level of SCFAs and inhibit tumor development. The mechanism by which SCFAs modulate the progression of gastrointestinal tumors has been elucidated in this review, aiming to provide prospects for the development of novel immunotherapeutic strategies.

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.

The antitumour effects of caloric restriction are mediated by the gut microbiome

Calorie restriction (CR) and intermittent fasting (IF) without malnutrition reduce the risk of cancer development. Separately, CR and IF can also lead to gut microbiota remodelling. However, whether the gut microbiota has a role in the antitumour effect related to CR or IF is still unknown. Here we show that CR, but not IF, protects against subcutaneous MC38 tumour formation through a mechanism that is dependent on the gut microbiota in female mice. After CR, we identify enrichment of Bifidobacterium through 16S rRNA sequencing of the gut microbiome. Moreover, Bifidobacterium bifidum administration is sufficient to rescue the antitumour effect of CR in microbiota-depleted mice. Mechanistically, B. bifidum mediates the CR-induced antitumour effect through acetate production and this effect is also dependent on the accumulation of interferon-γ⁺CD8⁺ T cells in the tumour microenvironment. Our results demonstrate that CR can modulate the gut taxonomic composition, which should be of oncological significance in tumour growth kinetics and cancer immunosurveillance.

Gut microbiota alteration after cholecystectomy contributes to post-cholecystectomy diarrhea via bile acids stimulating colonic serotonin

Post-cholecystectomy diarrhea (PCD) is highly prevalent among outpatients with cholecystectomy, and gut microbiota alteration is correlated with it. However, how and to what extent changed fecal bacteria contributes to diarrhea are still unrevealed. Humanized gut microbiome mice model by fecal microbiota transplantation was established to explore the diarrhea-inducible effects of gut microbiota. The role of microbial bile acids (BAs) metabolites was identified by UPLC/MS and the underlying mechanisms were investigated with selective inhibitors and antagonists as probes. These mice transplanted with fecal microbiome of PCD patients (PCD mice) exhibited significantly enhanced gastrointestinal motility and elevated fecal water content, compared with these mice with fecal microbiome of NonPCD patients and HC. In analyzing gut microbiota, tryptophan metabolism was enriched in PCD microbiome. In addition, overabundant serotonin in serum and colon, along with elevated biosynthesis gene and reduced reuptake gene, and highly expressed 5-HT receptors (5-HTRs) in colon of PCD mice were found, but not in small intestine. Notably, diarrheal phenotypes in PCD mice were depleted by tryptophan hydroxylase 1 inhibitor (LX1606) and 5-HTRs selective antagonists (alosetron and GR113808). Furthermore, increased microbial secondary BAs metabolites of DCA, HDCA and LCA were revealed in feces of PCD mice and they were found responsible for stimulating 5-HT level in vitro and in vivo. Intriguingly, blocking BAs-conjugated TGR5/TRPA1 signaling pathway could significantly alleviate PCD. In conclusion, altered gut microbiota after cholecystectomy contributes to PCD by promoting secondary BAs in colon, which stimulates colonic 5-HT and increases colon motility.

Pectin in Metabolic Liver Disease

Alterations in the composition of the gut microbiota (dysbiosis) are observed in nutritional liver diseases, including non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) and have been shown to be associated with the severity of both. Editing the composition of the microbiota by fecal microbiota transfer or by application of probiotics or prebiotics/fiber in rodent models and human proof-of-concept trials of NAFLD and ALD have demonstrated its possible contribution to reducing the progression of liver damage. In this review, we address the role of a soluble fiber, pectin, in reducing the development of liver injury in NAFLD and ALD through its impact on gut bacteria.

Targeting the gut microbiota for cancer therapy

Growing evidence suggests that the gut microbiota modulates the efficacy and toxicity of cancer therapy, most notably immunotherapy and its immune-related adverse effects. The poor response to immunotherapy in patients treated with antibiotics supports this influential role of the microbiota. Until recently, results pertaining to the identification of the microbial species responsible for these effects were incongruent, and relatively few studies analysed the underlying mechanisms. A better understanding of the taxonomy of the species involved and of the mechanisms of action has since been achieved. Defined bacterial species have been shown to promote an improved response to immune-checkpoint inhibitors by producing different products or metabolites. However, a suppressive effect of Gram-negative bacteria may be dominant in some unresponsive patients. Machine learning approaches trained on the microbiota composition of patients can predict the ability of patients to respond to immunotherapy with some accuracy. Thus, interest in modulating the microbiota composition to improve patient responsiveness to therapy has been mounting. Clinical proof-of-concept studies have demonstrated that faecal microbiota transplantation or dietary interventions might be utilized clinically to improve the success rate of immunotherapy in patients with cancer. Here, we review recent advances and discuss emerging strategies for microbiota-based cancer therapies.

Multi-Time-Point Fecal Sampling in Human and Mouse Reveals the Formation of New Homeostasis in Gut Microbiota after Bowel Cleansing

Polyethylene glycol (PEG) is one of the most commonly used bowel cleansing methods. Although the safety of PEG for bowel cleansing has been proven, its impact on intestinal microbiota has not been clearly explained, especially in terms of the dynamic changes in intestinal microbiota after PEG bowel cleansing, and there are no consistent results. In this study, stool samples were collected from 12 participants at six time points before and after bowel cleansing. We obtained data on the microbiota of these samples using 16S rRNA gene sequencing and analysis. The data revealed that the structure and composition of the microbiota changed greatly approximately 7 d after intestinal cleansing. The analysis of the dynamic changes in the microbiota showed that the change was most significant at day 3, but the internal structure of the microbiota was similar to that before bowel cleansing. A comparison of the most significantly changed microbiota at different time points before and after bowel cleansing revealed four bacteria: Bacteroides, Roseburia, Eubacterium, and Bifidobacterium. We also established a humanized mouse model to simulate human bowel cleansing using PEG. The results showed that the mouse model achieved similar effects to human bowel cleansing, but its recovery speed was one stage earlier than that of humans. These findings suggest that the intestinal microbiota after bowel cleansing initially underwent a short-term change and then actively returned to its initial status. The results on key bacteria and establishment of mouse models can provide a reference for subsequent research on bowel cleansing.

The impact of the microbiome in cancer: Targeting metabolism of cancer cells and host

Abnormal metabolic alterations of cancer cells and the host play critical roles in the occurrence and development of tumors. Targeting cancer cells and host metabolism can provide novel diagnosis indicators and intervention targets for tumors. In recent years, it has been found that gut microbiota is involved in the metabolism of the host and cancer cells. Increasingly, gut microbiome and their metabolites have been demonstrated great influence on the tumor formation, prognosis and treatment. Specific gut microbial composition and metabolites are associated with the status of tumor in the host. Interventions on the gut microbiota can exert the protective effects on the tumor, through the manipulation of structure and its related metabolites. This may be the new approach to improve the efficacy of tumor prevention and treatment. Here, we discuss the effects and the underlying mechanisms of gut microbiota and microbial-derived metabolites in tumor progression and treatment.

A study on the method and effect of the construction of a humanized mouse model of fecal microbiota transplantation

The gestation period is critical for the health of the mother and fetus. Malnutrition or over nutrition during pregnancy may cause gestational diseases that can result in adverse pregnancy outcomes. Fecal microbiota transplantation (FMT) can be used to re-establish new gut microbiota to treat a variety of diseases and construct a model to investigate the nutritional health during pregnancy. Therefore, this study investigated whether human-derived gut microbiota during pregnancy could colonize the intestines of mice. Moreover, we determined the time and method of intervention for FMT. Based on this information, a humanized mouse model of FMT was constructed to simulate the human intestinal microecology during pregnancy, and serve as a useful animal model for the study of nutritional health and disease during pregnancy. Germ-free (GF) and specific pathogen free (SPF) C57BL/6J mice were selected for humanized gestational FMT and the transplantation outcomes were evaluated. The results demonstrated that the gestational intestinal microbiota colonized the intestines of mice, allowing researchers to construct a humanized mouse model of gestational FMT. The main intestinal flora of the gestational period were transplanted into GF mice, with the gestational flora being similar to the flora of GF mice after transplantation. However, antibiotics could not eliminate the original microbial flora in SPF mice, and the flora was complex and variable after FMT with little increase in abundance. Background flora had a significant impact on the outcomes assessment. The results were better in GF mice than in SPF mice, and after microbiota transplantation, a superior effect was observed on day 21 compared to days 7 and 14.

Gut Microbiota and Tumor Immune Escape: A New Perspective for Improving Tumor Immunotherapy

The gut microbiota is a large symbiotic community of anaerobic and facultative aerobic bacteria inhabiting the human intestinal tract, and its activities significantly affect human health. Increasing evidence has suggested that the gut microbiome plays an important role in tumor-related immune regulation. In the tumor microenvironment (TME), the gut microbiome and its metabolites affect the differentiation and function of immune cells regulating the immune evasion of tumors. The gut microbiome can indirectly influence individual responses to various classical tumor immunotherapies, including immune checkpoint inhibitor therapy and adoptive immunotherapy. Microbial regulation through antibiotics, prebiotics, and fecal microbiota transplantation (FMT) optimize the composition of the gut microbiome, improving the efficacy of immunotherapy and bringing a new perspective and hope for tumor treatment.

Facts and Hopes for Gut Microbiota Interventions in Cancer Immunotherapy

Immune checkpoint inhibitors (ICI) targeting cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD-1) proteins transformed the management of advanced cancers. Many tumor-intrinsic factors modulate immunological and clinical responses to such therapies, but ample evidence also implicates the gut microbiome in responses. The gut microbiome, comprising the bacteria, archaea, fungi, and viruses that live in the human digestive tract, is an established determinant of host immunity, but its impact on response to ICI therapy in mice and humans with cancer has only recently been appreciated. Therapeutic interventions to optimize microbiota composition to improve immunotherapy outcomes show promise in mice and humans with cancer. In this review, we discuss the rationale for gut microbiome-based cancer therapies, the results from early-phase clinical trials, and possible future developments.

Effect and Mechanism of Pharmaceutical Excipients on Berberine to Alleviate Ulcerative Colitis via Regulating Gut Microbiota

Background: Various potential effect of drugs on alleviating diseases by regulating intestinal microbiome as well as the pharmaceutical excipients on gut microbiota has been revealed. However, the interaction between them is rarely investigated. Methods: Histological analysis, immunohistochemistry analysis, enzyme-linked immunosorbent assay (ELISA) analysis, RT-qPCR, and 16S rRNA analysis were utilized to explore the effect mechanism of the five excipients including hydroxypropyl methylcellulose (HPMC) F4M, Eudragit (EU) S100, chitosan (CT), pectin (PT), and rheum officinale polysaccharide (DHP) on berberine (BBR) to cure UC. Results: The combined BBR with PT and DHP group exhibited better therapeutic efficacy of UC with significantly increased colon length, and decreased hematoxylin-eosin (H&E) scores than other groups. Furthermore, the expression of tight junction ZO-1 and occludin in colon tissue were upregulated, and claudin-2 was downregulated. Ultimately, the serum content of tumor necrosis (TNF)-α, interleukin (IL)-1β, and IL-6 was decreased. Moreover, the combined BBR with PT significantly promoted the restoration of gut microbiota. The relative abundance of Firmicutes and Lactobacillus was significantly increased by the supplement of PT and DHP, and the relative abundance of Proteobacteria was downregulated. Conclusions: Our study may provide a new perspective that the selection of pharmaceutical excipients could be a crucial factor affecting the drugs’ therapeutic efficiency outcome.

Gut microbiota: An emerging therapeutic approach of herbal medicine for prevention of colorectal cancer

The gut dysbiosis has emerged as a prominent player in the pathogenesis and development of colorectal cancer (CRC), which in turn intensifies dysregulated gut microbiota composition and inflammation. Since most drugs are given orally, this dysbiosis directly and indirectly impinges the absorption and metabolism of drugs in the gastrointestinal tract, and subsequently affects the clinical outcome of patients with CRC. Herbal medicine, including the natural bioactive products, have been used traditionally for centuries and can be considered as novel medicinal sources for anticancer drug discovery. Due to their various structures and pharmacological effects, natural products have been found to improve microbiota composition, repair intestinal barrier and reduce inflammation in human and animal models of CRC. This review summarizes the chemo-preventive effects of extracts and/or compounds derived from natural herbs as the promising antineoplastic agents against CRC, and will provide innovative strategies to counteract dysregulated microbiota and improve the lives of CRC patients.

New insights into natural products that target the gut microbiota: Effects on the prevention and treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignant carcinomas. CRC is characterized by asymptomatic onset, and most patients are already in the middle and advanced stages of disease when they are diagnosed. Inflammatory bowel disease (IBD) and the inflammatory-cancer transformation of advanced colorectal adenoma are the main causes of CRC. There is an urgent need for effective prevention and intervention strategies for CRC. In recent years, rapid research progress has increased our understanding of gut microbiota. Meanwhile, with the deepening of research on the pathogenesis of colorectal cancer, gut microbiota has been confirmed to play a direct role in the occurrence and treatment of colorectal cancer. Strategies to regulate the gut microbiota have potential value for application in the prevention and treatment of CRC. Regulation of gut microbiota is one of the important ways for natural products to exert pharmacological effects, especially in the treatment of metabolic diseases and tumours. This review summarizes the role of gut microbiota in colorectal tumorigenesis and the mechanism by which natural products reduce tumorigenesis and improve therapeutic response. We point out that the regulation of gut microbiota by natural products may serve as a potential means of treatment and prevention of CRC.

Colorectal Cancer and Microbiota Modulation for Clinical Use. A Systematic Review

Colorectal cancer (CRC) is one of the top contributors to the global burden of cancer incidence and mortality, with both genetic and environmental factors contributing to its etiology. Environmental factors may be the cause of up to 60% of the risk of developing CRC, with gut microbiota being a crucial modifiable risk factor. The microbial ecosystem plays a vital role in CRC prevention and antitumoral response through modulation of the immune system and production of short-chain fatty acids. Numerous approaches have been followed to modify the gut microbiota in order to reduce the risk of cancer development, improve treatment efficacy, and reduce side effects. This study aims to perform a systematic analysis of the published literature to elucidate whether microbiota modulation through pre-, pro-, and symbiotic treatment and/or nutritional intervention can be beneficial for patients diagnosed with CRC. Our analysis finds that some prebiotics, mainly in the form of oligo- and polysaccharides, probiotics such as lactic strain producers of short-chain fatty acids, and consumption of a Mediterranean plant-based diet may be beneficial for patients diagnosed with CRC. However, there is a need for clinical data which evaluate the modulation of gut microbiota in a safe and effective manner.

Microbiome in cancer: An exploration of carcinogenesis, immune responses and immunotherapy

Cancer is a major disease endangering human health. More and more studies have shown that microorganisms play an extremely important role in the occurrence, development and treatment of tumors. As a very promising tumor treatment strategy, immunotherapy has also been proved to have a great relationship with microorganisms. Here, the authors review the contribution of the microbiota to cancer and the research on its impact on cancer immunotherapy. We also highlight the possible mechanism of their interaction and outlined the potential application of microbiota in tumor immunotherapy.

Therapeutic approaches to colorectal cancer via strategies based on modulation of gut microbiota

Colorectal cancer (CRC) ranks third in terms of global incidence and second in terms of death toll among malignant tumors. Gut microbiota are involved in the formation, development, and responses to different treatments of CRC. Under normal physiological conditions, intestinal microorganisms protect the intestinal mucosa, resist pathogen invasion, and regulate the proliferation of intestinal mucosal cells via a barrier effect and inhibition of DNA damage. The composition of gut microbiota and the influences of diet, drugs, and gender on the composition of the intestinal flora are important factors in the early detection of CRC and prediction of the results of CRC treatment. Regulation of gut microbiota is one of the most promising new strategies for CRC treatment, and it is essential to clarify the effect of gut microbiota on CRC and its possible mechanisms to facilitate the prevention and treatment of CRC. This review discusses the role of gut microbiota in the pathogenesis of CRC, the potential of gut microbiota as biomarkers for CRC, and therapeutic approaches to CRC based on the regulation of gut microbiota. It might provide new ideas for the use of gut microbiota in the prevention and treatment of CRC in the near future and thus reduce the incidence of CRC.

Microbial short-chain fatty acids: a strategy to tune adoptive T cell therapy

The gut microbiota and its metabolites have been shown to play a pivotal role in the regulation of metabolic, endocrine and immune functions. Though the exact mechanism of action remains to be fully elucidated, available knowledge supports the ability of microbiota-fermented short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, to influence epigenetic and metabolic cascades controlling gene expression, chemotaxis, differentiation, proliferation, and apoptosis in several non-immune and immune cell subsets. While used as preferred metabolic substrates and sources of energy by colonic gut epithelial cells, most recent evidence indicates that these metabolites regulate immune functions, and in particular fine-tune T cell effector, regulatory and memory phenotypes, with direct in vivo consequences on the efficacy of chemotherapy, radiotherapy and immunotherapy. Most recent data also support the use of these metabolites over the course of T cell manufacturing, paving the way for refined adoptive T cell therapy engineering. Here, we review the most recent advances in the field, highlighting in vitro and in vivo evidence for the ability of SCFAs to shape T cell phenotypes and functions.

Clinical management of metastatic colorectal cancer in the era of precision medicine

Colorectal cancer (CRC) represents approximately 10% of all cancers and is the second most common cause of cancer deaths. Initial clinical presentation as metastatic CRC (mCRC) occurs in approximately 20% of patients. Moreover, up to 50% of patients with localized disease eventually develop metastases. Appropriate clinical management of these patients is still a challenging medical issue. Major efforts have been made to unveil the molecular landscape of mCRC. This has resulted in the identification of several druggable tumor molecular targets with the aim of developing personalized treatments for each patient. This review summarizes the improvements in the clinical management of patients with mCRC in the emerging era of precision medicine. In fact, molecular stratification, on which the current treatment algorithm for mCRC is based, although it does not completely represent the complexity of this disease, has been the first significant step toward clinically informative genetic profiling for implementing more effective therapeutic approaches. This has resulted in a clinically relevant increase in mCRC disease control and patient survival. The next steps in the clinical management of mCRC will be to integrate the comprehensive knowledge of tumor gene alterations, of tumor and microenvironment gene and protein expression profiling, of host immune competence as well as the application of the resulting dynamic changes to a precision medicine-based continuum of care for each patient. This approach could result in the identification of individual prognostic and predictive parameters, which could help the clinician in choosing the most appropriate therapeutic program(s) throughout the entire disease journey for each patient with mCRC. CA Cancer J Clin. 2022;72:000-000.

Fatty Acids as a Tool to Boost Cancer Immunotherapy Efficacy

Although immunotherapy represents one of the most potent therapeutic anti-cancer approaches, only a limited number of patients shows clinical benefit. Recent evidence suggests that patients' nutritional status plays a major role in immunotherapy outcome. Fatty acids are essential in a balanced diet and well-known to influence the immune response. Moreover, short-chain fatty acids (SCFAs) show beneficial effects in metabolic disorders as well as in cancer and polyunsaturated fatty acids (PUFAs) contribute to body weight and fat free mass preservation in cancer patients. In line with these data, several studies imply a role for SCFAs and PUFAs in boosting the outcome of immunotherapy. In this review, we specifically focus on mechanistic data showing that SCFAs modulate the immunogenicity of tumor cells and we discuss the direct effects of SCFAs and PUFAs on the immune system in the context of cancer. We provide preclinical and clinical evidence indicating that SCFAs and PUFAs may have the potential to boost immunotherapy efficacy. Finally, we describe the challenges and address opportunities for successful application of nutritional interventions focusing on SCFAs and PUFAs to increase the therapeutic potential of immunotherapeutic approaches for cancer.

Intratumor microbiome in cancer progression: current developments, challenges and future trends

Cancer is a complicated disease attributed to multifactorial changes, which causes difficulties with treatment strategies. Various factors have been regarded as the main contributors, and infectious etiological factors have recently attracted interest. Several microbiomes contribute to carcinogenesis, cancer progression, and modulating cancer treatment by inducing cancerous epithelial cells and chronic inflammation. Most of our knowledge on the role of microbiota in tumor oncogenesis and clinical efficiency is associated with the intestinal microbiome. However, compelling evidence has also confirmed the contribution of the intratumor microbiome in cancer. Indeed, the findings of clinical tumor samples, animal models, and studies in vitro have revealed that many intratumor microbiomes promote tumorigenesis and immune evasion. In addition, the intratumor microbiome participates in regulating the immune response and even affects the outcomes of cancer treatment. This review summarizes the interplay between the intratumor microbiota and cancer, focusing on the contribution and mechanism of intratumor microbiota in cancer initiation, progression, and potential applications to cancer therapy.

Can Natural Products be Used to Overcome the Limitations of Colorectal Cancer Immunotherapy?

Colorectal cancer (CRC) is a common cancer of the digestive system that endangers human health. Immunotherapy is widely used in the treatment of patients with cancer. Some patients with dMMR/MSI-H CRC benefit from treatments that use immune checkpoint inhibitors, but most CRC patients are not sensitive to immunotherapy. Furthermore, internal resistance and immune escape lead to a reduced immunotherapy response. Therefore, the development of an effective combination therapy to improve the response rate to immunotherapy is a goal of cancer research. Natural products are potential candidates for comprehensive cancer treatments due to their wide range of immunomodulatory effects through multifactorial underlying mechanisms. In this review, we summarize the challenges in the treatment of CRC and assess the immunomodulatory effects of natural products and their active components. Our work suggests that natural products represent potential options for combined CRC immunotherapy.

Lacticaseibacillus paracasei sh2020 induced antitumor immunity and synergized with anti-programmed cell death 1 to reduce tumor burden in mice

The gut microbiota was emerging as critical regulatory elements in shaping the outcome of cancer immunotherapy. However, the underlying mechanisms by which the gut commensal species enhance antitumor immunity remain largely unexplored. Here, we show that the gut microbiota from healthy individuals conferred considerable sensitivity to anti-PD-1 in the colorectal cancer (CRC) tumor-bearing mice, whereas gut microbiota from CRC patients failed to do so. By 16S rRNA gene sequencing, we identified Lactobacillus that was significantly increased in the mice with good response to anti-PD-1, and significantly correlated with anti-tumor immunity. After a series of screening, we isolated a novel Lacticaseibacillus strain, named L. paracasei sh2020. L. paracasei sh2020 showed the most notable anti-tumor immunity in the mice with gut dysbiosis. Mechanistically, the antitumor immune response elicited by L. paracasei sh2020 was dependent on CD8⁺ T cell. In vitro and in vivo studies revealed that L. paracasei sh2020 stimulation triggered the upregulated expression of CXCL10 in the tumors and subsequently enhanced CD8⁺ T cell recruitment. Meanwhile, the modulation of gut microbiota caused by L. paracasei sh2020 enhanced its antitumor effect and gut barrier function. Overall, our study offered novel insights into the mechanism by which gut microbiota shaped the outcome of cancer immunotherapy and, more importantly, the novel strain L. paracasei sh2020 might serve as an easy and effective way to promote anti-PD-1 effect in clinical practice.

Structural features and anticancer mechanisms of pectic polysaccharides: A review

The anticancer activity of pectic polysaccharides (PPs) was proved by numerous studies, and which also indicated that the bioactivity of PPs was closely related to its complicated structures. Based on the summary and analysis about structure characteristics and corresponding enzymatic process of the reported PPs, the anticancer mechanism and related structural features were systematically clarified. It was found that not only the direct effects on the cancer cells by proliferation inhibition or apoptosis, but also the regulation of immune system, gut microbiota and gut metabolism as indirect effects, jointly played important roles in the anticancer of PPs. Nevertheless, during the study of PPs as promising anticancer components, the exact structure-function relationship, digestion process in vivo, and comprehensive action mechanism are still not well understanding. With the unveiling of the proposed issues, it is believed that PPs are promising to be exploited as effective cancer therapy/adjunctive therapy drugs or functional foods.

Gut microbiota correlates with antitumor activity in patients with mCRC and NSCLC treated with cetuximab plus avelumab

Gut microbiota is involved in immune modulation and immune checkpoint inhibitors (ICIs) efficacy. Single‐arm phase II CAVE‐mCRC and CAVE‐LUNG clinical trials investigated cetuximab + avelumab combination in RAS wild‐type (WT) metastatic colorectal cancer (mCRC) and chemo‐refractory nonsmall cell lung cancer (NSCLC) patients, respectively. A comprehensive gut microbiota genetic analysis was done in basal fecal samples of 14 patients from CAVE‐mCRC trial with circulating tumor DNA (ctDNA) RAS/BRAF WT and microsatellite stable (MSS) disease. Results were validated in a cohort of 10 patients from CAVE‐Lung trial. 16S rRNA sequencing revealed 23 027 bacteria species in basal fecal samples of 14 patients from CAVE‐mCRC trial. In five long‐term responding patients (progression‐free survival [PFS], 9‐24 months) significant increases in two butyrate‐producing bacteria, Agathobacter M104/1 (P = .018) and Blautia SR1/5 (P = .023) were found compared to nine patients with shorter PFS (2‐6 months). A significantly better PFS was also observed according to the presence or absence of these species in basal fecal samples. For Agathobacter M104/1, median PFS (mPFS) was 13.5 months (95% confidence interval [CI], 6.5‐20.5 months) vs 4.6 months (95% CI, 1.8‐7.4 months); P = .006. For Blautia SR1/5, mPFS was 5.9 months (95% CI, 2.2‐9.7 months) vs 3.6 months (95% CI, 3.3‐4.0 months); P = .021. Similarly, in CAVE‐Lung validation cohort, Agathobacter M104/1 and Blautia SR1/5 expression were associated with PFS according to their presence or absence in basal fecal samples. Agathobacter and Blautia species could be potential biomarkers of outcome in mCRC, and NSCLC patients treated with cetuximab + avelumab. These findings deserve further investigation.

The Anti-Cancer Effects of Red-Pigmented Foods: Biomarker Modulation and Mechanisms Underlying Cancer Progression

Cancer is one the most malignant diseases that is a leading cause of death worldwide. Vegetables and fruits contain beneficial nutrients such as vitamins, minerals, folates, dietary fibers, and various natural bioactive compounds. These can prevent the pathological processes of many cancers and reduce cancer related mortality. Specifically, the anti-cancer effect of vegetables and fruits is largely attributable to the natural bioactive compounds present within them. A lot of bioactive compounds have very specific colors with pigments and the action of them in the human body varies by their color. Red-pigmented foods, such as apples, oranges, tomatoes, cherries, grapes, berries, and red wine, have been widely reported to elicit beneficial effects and have been investigated for their anti-tumor, anti-inflammatory, and antioxidative properties, as well as anti-cancer effect. Most of the anti-cancer effects of bioactive compounds in red-pigmented foods arise from the suppression of cancer cell invasion and metastasis, as well as the induction of apoptosis and cell cycle arrest. In this review, we assessed publications from the last 10 years and identified 10 bioactive compounds commonly studied in red-pigmented foods: lycopene, anthocyanin, β-carotene, pectin, betaine, rutin, ursolic acid, kaempferol, quercetin, and myricetin. We focused on the mechanisms and targets underlying the anti-cancer effect of the compounds and provided rationale for further investigation of the compounds to develop more potent anti-cancer treatment methods.

Disordered Gut Microbiota Correlates With Altered Fecal Bile Acid Metabolism and Post-cholecystectomy Diarrhea

Post-cholecystectomy diarrhea (PCD) is a common complication of gallbladder removal, and gut microbiota changes have been determined in PCD patients. Bile acid diarrhea (BAD) is supposed to be the main pathogenic factor for PCD due to the disrupted fecal bile acid metabolism in diarrheal patients. However, the profiling of bile acid metabolite alteration in PCD is unclear and whether changed gut microbiota and fecal bile acid metabolism are correlated is also underdetermined. The fecal bile acid metabolites from fecal samples were profiled by targeted UPLC/MS (ultra-high-performance liquid chromatography coupled with a triple-quadrupole mass spectrometer) and the composition of fecal bile acid metabolites in PCD patients was demonstrated to be distinct from those in Non-PCD and HC groups. In addition, the quantification of bile acid excretion in feces of diarrheal patients was significantly elevated. Furthermore, 16S rRNA sequencing results revealed that PCD patients had the lowest operational taxonomic units (OTU) and significant reduction in microbial richness and evenness. Bacterial composition was remarkably shifted in PCD patients, which mainly lay in dominated phyla Firmicutes and Bacteroidota. Besides, the co-abundance network among genus bacteria declined in PCD. Among the genera, Prevotella, Enterococcus, and Erysipelotrichaceae_UCG-003 were enriched, but Alistipes, Bacteroides, Ruminococcus, and Phascolarctobacterium were reduced. Moreover, these disease-linked genera were closely associated with several diarrheal phenotypes. Notably, changed bile acid metabolites exhibited strong correlations with gut microbiota as well. Conclusively, this study reveals associations between PCD-linked microbes and bile acid metabolites, which may synergistically correlate to postoperative diarrhea.

The microbiome, gastrointestinal cancer, and immunotherapy

The gastrointestinal tract greatly contributes to global cancer burden and cancer-related deaths. The microbiota represents the population of microorganisms that live in and around the body, located primarily in the gastrointestinal tract. The microbiota has been implicated in colorectal cancer development and progression, but its role in cancer therapy for the gastrointestinal tract is less defined, especially for extra-intestinal cancers. In this review, we discuss the past 5 years of research into microbial involvement in immune-related therapies for colorectal, pancreatic, hepatic, and gastric cancers, with the goal of highlighting recent advances and new areas for investigation in this field.

Directing T-Cell Immune Responses for Cancer Vaccination and Immunotherapy

Cancer vaccination and immunotherapy revolutionised the treatment of cancer, a result of decades of research into the immune system in health and disease. However, despite recent breakthroughs in treating otherwise terminal cancer, only a minority of patients respond to cancer immunotherapy and some cancers are largely refractive to immunotherapy treatment. This is due to numerous issues intrinsic to the tumour, its microenvironment, or the immune system. CD4+ and CD8+ αβ T-cells emerged as the primary effector cells of the anti-tumour immune response but their function in cancer patients is often compromised. This review details the mechanisms by which T-cell responses are hindered in the setting of cancer and refractive to immunotherapy, and details many of the approaches under investigation to direct T-cell function and improve the efficacy of cancer vaccination and immunotherapy.

Natural Products with Activity against Lung Cancer: A Review Focusing on the Tumor Microenvironment

Lung cancer is one of the most prevalent malignancies worldwide. Despite the undeniable progress in lung cancer research made over the past decade, it is still the leading cause of cancer-related deaths and continues to challenge scientists and researchers engaged in searching for therapeutics and drugs. The tumor microenvironment (TME) is recognized as one of the major hallmarks of epithelial cancers, including the majority of lung cancers, and is associated with tumorigenesis, progression, invasion, and metastasis. Targeting of the TME has received increasing attention in recent years. Natural products have historically made substantial contributions to pharmacotherapy, especially for cancer. In this review, we emphasize the role of the TME and summarize the experimental proof demonstrating the antitumor effects and underlying mechanisms of natural products that target the TME. We also review the effects of natural products used in combination with anticancer agents. Moreover, we highlight nanotechnology and other materials used to enhance the effects of natural products. Overall, our hope is that this review of these natural products will encourage more thoughts and ideas on therapeutic development to benefit lung cancer patients.

Ultrafine Jujube Powder Enhances the Infiltration of Immune Cells during Anti-PD-L1 Treatment against Murine Colon Adenocarcinoma

Simple Summary

While modulating gut microbiota using dietary intervention with natural nutrients has proven to be effective in improving the response rate of immune checkpoint inhibitors (ICIs), the underpinning mechanism is poorly understood. This work demonstrates that the oral administration of ultrafine jujube powder (JP) let to a significant alteration of gut microbiota, an increased abundance of Clostridiales, including Ruminococcaceae and Lachnospiraceae, an elevated SCFA production, an intensified infiltration of CD8⁺ T cells to the tumor microenvironment, and a greatly improved response of anti-PD-L1 treatment against murine colon adenocarcinoma. Moreover, the size of the JP particles had a significant impact on the abovementioned attributes. The present study demonstrates that dietary intervention with nutrients is highly effective in modulating the gut microbiota for an improved immune checkpoint blockage therapy.

Abstract

Whereas dietary intervention with natural nutrients plays an important role in activating the immune response and holds unprecedented application potential, the underpinning mechanism is poorly understood. The present work was dedicated to comprehensively examine the effects of ultrafine jujube powder (JP) on the gut microbiota and, consequentially, the effects associated with the response rate to anti-PD-L1 treatment against murine colon adenocarcinoma. A murine colon adenocarcinoma model with anti-PD-L1 immunotherapy was established to evaluate how dietary interventions affect the microbiota. In vitro and in vivo experiments confirmed the role of SCFAs in the immune response. Oral administration of JP greatly improves the response of anti-PD-L1 treatment against murine colon adenocarcinoma. Such an improvement is associated with the alteration of gut microbiota which leads to an increased abundance of Clostridiales, including Ruminococcaceae and Lachnospiraceae, an elevated SCFA production, and an intensified infiltration of CD8⁺ T cells to the tumor microenvironment. This work demonstrates that JP is particularly effective in modulating the gut microbiota for an improved immune checkpoint blockage therapy by boosting cytotoxic CD8⁺ T cells in tumor-infiltrating lymphocytes. The experimental findings of the present study are helpful for the development of dietary intervention methods for cancer immunotherapy using natural nutrients.