Immunotherapy in Colorectal Cancer: Potential of Fecal Transplant and Microbiota-augmented Clinical Trials

Transfer of modified gut viromes improves symptoms associated with metabolic syndrome in obese male mice

Metabolic syndrome encompasses amongst other conditions like obesity and type-2 diabetes and is associated with gut microbiome (GM) dysbiosis. Fecal microbiota transplantation (FMT) has been explored to treat metabolic syndrome by restoring the GM; however, concerns on accidentally transferring pathogenic microbes remain. As a safer alternative, fecal virome transplantation (FVT, sterile-filtrated feces) has the advantage over FMT in that mainly bacteriophages are transferred. FVT from lean male donors have shown promise in alleviating the metabolic effects of high-fat diet in a preclinical mouse study. However, FVT still carries the risk of eukaryotic viral infections. To address this, recently developed methods are applied for removing or inactivating eukaryotic viruses in the viral component of FVT. Modified FVTs are compared with unmodified FVT and saline in a diet-induced obesity model on male C57BL/6 N mice. Contrasted with obese control, mice administered a modified FVT (nearly depleted for eukaryotic viruses) exhibits enhanced blood glucose clearance but not weight loss. The unmodified FVT improves liver pathology and reduces the proportions of immune cells in the adipose tissue with a non-uniform response. GM analysis suggests that bacteriophage-mediated GM modulation influences outcomes. Optimizing these approaches could lead to the development of safe bacteriophage-based therapies targeting metabolic syndrome through GM restoration.

Dissecting the role of the gut microbiome and fecal microbiota transplantation in radio- and immunotherapy treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers and poses a major burden on the human health worldwide. At the moment, treatment of CRC consists of surgery in combination with (neo)adjuvant chemotherapy and/or radiotherapy. More recently, immune checkpoint blockers (ICBs) have also been approved for CRC treatment. In addition, recent studies have shown that radiotherapy and ICBs act synergistically, with radiotherapy stimulating the immune system that is activated by ICBs. However, both treatments are also associated with severe toxicity and efficacy issues, which can lead to temporary or permanent discontinuation of these treatment programs. There's growing evidence pointing to the gut microbiome playing a role in these issues. Some microorganisms seem to contribute to radiotherapy-associated toxicity and hinder ICB efficacy, while others seem to reduce radiotherapy-associated toxicity or enhance ICB efficacy. Consequently, fecal microbiota transplantation (FMT) has been applied to reduce radio- and immunotherapy-related toxicity and enhance their efficacies. Here, we have reviewed the currently available preclinical and clinical data in CRC treatment, with a focus on how the gut microbiome influences radio- and immunotherapy toxicity and efficacy and if these treatments could benefit from FMT.

Predictive Biomarkers for Checkpoint Inhibitor Immune-Related Adverse Events

Immune-checkpoint inhibitors (ICIs) are antagonists of inhibitory receptors in the immune system, such as the cytotoxic T-lymphocyte-associated antigen-4, the programmed cell death protein-1 and its ligand PD-L1, and they are increasingly used in cancer treatment. By blocking certain suppressive pathways, ICIs promote T-cell activation and antitumor activity but may induce so-called immune-related adverse events (irAEs), which mimic traditional autoimmune disorders. With the approval of more ICIs, irAE prediction has become a key factor in improving patient survival and quality of life. Several biomarkers have been described as potential irAE predictors, some of them are already available for clinical use and others are under development; examples include circulating blood cell counts and ratios, T-cell expansion and diversification, cytokines, autoantibodies and autoantigens, serum and other biological fluid proteins, human leucocyte antigen genotypes, genetic variations and gene profiles, microRNAs, and the gastrointestinal microbiome. Nevertheless, it is difficult to generalize the application of irAE biomarkers based on the current evidence because most studies have been retrospective, time-limited and restricted to a specific type of cancer, irAE or ICI. Long-term prospective cohorts and real-life studies are needed to assess the predictive capacity of different potential irAE biomarkers, regardless of the ICI type, organ involved or cancer site.

Association of Helicobacter pylori infection with survival outcomes in advanced gastric cancer patients treated with immune checkpoint inhibitors

Background

Accumulating evidence has revealed that the gut microbiota influences the effectiveness of immune checkpoint inhibitors (ICIs) in cancer patients. As a part of the human microbiome, Helicobacter pylori (H. pylori) was reported to be associated with reduced effectiveness of anti-PD1 immunotherapy in patients with non-small-cell lung cancer (NSCLC). Gastric cancer is more closely related to H. pylori, so we conducted a retrospective analysis to verify whether the association of H. pylori and effectiveness is applicable to advanced gastric cancer (AGC) patients.

Material and methods

AGC patients who had evidence of H. pylori and received anti-PD-1 antibodies were enrolled in the study. The differences in the disease control rate (DCR), overall survival (OS) and progression-free survival (PFS) between the H. pylori-positive group and the negative group were compared.

Results

A total of 77 patients were included in this study; 34 patients were H. pylori positive, and the prevalence of H. pylori infection was 44.2%. Compared with the H. pylori-negative group, patients in the H. pylori-positive group had a higher risk of nonclinical response to anti-PD-1 antibody, with an OR of 2.91 (95% CI: 1.13–7.50). Patients in the H. pylori-negative group had a longer OS and PFS than those in the positive group, with an estimated median OS of 17.5 months vs. 6.2 months (HR = 2.85, 95% CI: 1.70–4.78; P = 0.021) and a median PFS of 8.4 months vs. 2.7 months (HR = 3.11, 95% CI: 1.96–5.07, P = 0.008). Multivariate analysis indicated that H. pylori infection was independently associated with PFS (HR = 1.90, 95% CI: 1.10–3.30; P = 0.022).

Conclusion

Our study unveils for the first time that H. pylori infection is associated with the outcome of immunotherapy for AGC patients. Multicenter, large sample and prospective clinical studies are needed to verify the association.

Effect of gut microbiota in the colorectal cancer and potential target therapy

The symbiotic interaction between gut microbiota and the digestive tract is an important factor in maintaining the intestinal environment balance. Colorectal cancer (CRC) is a complex disease involving the interaction between tumour cells and a large number of microorganisms. The microbiota is involved in the occurrence, development and prognosis of colorectal cancer. Several microbiota species have been studied, such as Fusobacterium nucleatum (F. nucleatum), Enterotoxigenic Bacteroides fragilis (ETBF), Streptococcus bovis (S. bovis), Lactobacillus, and Bifidobacterium. Studies about the interaction between microbiota and CRC were retrieved from Embase, PubMed, Ovid and Web of Science up to 21 Oct 2021. This review expounded on the effect of microbiota on CRC, especially the dysregulation of bacteria and carcinogenicity. The methods of gut microbiota modifications representing novel prognostic markers and innovative therapeutic strategies were also described.

The Human Virome: Viral Metagenomics, Relations with Human Diseases, and Therapeutic Applications

The human body is colonized by a wide range of microorganisms. The field of viromics has expanded since the first reports on the detection of viruses via metagenomic sequencing in 2002. With the continued development of reference materials and databases, viral metagenomic approaches have been used to explore known components of the virome and discover new viruses from various types of samples. The virome has attracted substantial interest since the outbreak of the coronavirus disease 2019 (COVID-19) pandemic. Increasing numbers of studies and review articles have documented the diverse virome in various sites in the human body, as well as interactions between the human host and the virome with regard to health and disease. However, there have been few studies of direct causal relationships. Viral metagenomic analyses often lack standard references and are potentially subject to bias. Moreover, most virome-related review articles have focused on the gut virome and did not investigate the roles of the virome in other sites of the body in human disease. This review presents an overview of viral metagenomics, with updates regarding the relations between alterations in the human virome and the pathogenesis of human diseases, recent findings related to COVID-19, and therapeutic applications related to the human virome.

Encouraging probiotics for the prevention and treatment of immune-related adverse events in novel immunotherapies against malignant glioma

Among the malignant tumors in the central nervous system (CNS), glioma is the most challenging tumor to the public society, which accounts for the majority of intracranial malignant tumors with impaired brain function. In general, conventional therapies are still unable to provide an effective cure. However, novel immunotherapies have changed the treatment scene giving patients a greater potential to attain long term survival, improved quality of life. Having shown favorable results in solid tumors, those therapies are now at a cancer research hotspot, which could even shrink the growth of glioma cells without causing severe complications. However, it is important to recognize that the therapy may be occasionally associated with noteworthy adverse action called immune-related adverse events (IRAEs) which have emerged as a potential limitation of the therapy. Multiple classes of mediators have been developed to enhance the ability of immune system to target malignant tumors including glioma but may also be associated with the IRAEs. In addition, it is probable that it would take long time after the therapy to exhibit severe immune-related disorders. Gut microbiota could play an integral role in optimal immune development and/or appropriate function for the cancer therapy, which is a vital component of the multidirectional communication between immune system, brain, and gut, also known as gut-brain-immune axis. Here, we show the potential effects of the gut-brain-immune axis based on an "engram theory" for the innovative treatment of IRAEs.

Personalized Immunotherapy in Colorectal Cancers: Where Do We Stand?

Colorectal cancer (CRC) is the second leading cause of cancer death in the world. Immunotherapy using monoclonal antibodies, immune-checkpoint inhibitors, adoptive cell therapy, and cancer vaccines has raised great hopes for treating poor prognosis metastatic CRCs that are resistant to the conventional therapies. However, high inter-tumor and intra-tumor heterogeneity hinder the success of immunotherapy in CRC. Patients with a similar tumor phenotype respond differently to the same immunotherapy regimen. Mutation-based classification, molecular subtyping, and immunoscoring of CRCs facilitated the multi-aspect grouping of CRC patients and improved immunotherapy. Personalized immunotherapy using tumor-specific neoantigens provides the opportunity to consider each patient as an independent group deserving of individualized immunotherapy. In the recent decade, the development of sequencing and multi-omics techniques has helped us classify patients more precisely. The expansion of such advanced techniques along with the neoantigen-based immunotherapy could herald a new era in treating heterogeneous tumors such as CRC. In this review article, we provided the latest findings in immunotherapy of CRC. We elaborated on the heterogeneity of CRC patients as a bottleneck of CRC immunotherapy and reviewed the latest advances in personalized immunotherapy to overcome CRC heterogeneity.

The gastrointestinal microbiota in colorectal cancer cell migration and invasion

Colorectal carcinoma is the third most common cancer in developed countries and the second leading cause of cancer-related mortality. Interest in the influence of the intestinal microbiota on CRC emerged rapidly in the past few years, and the close presence of microbiota to the tumour mass creates a unique microenvironment in CRC. The gastrointestinal microbiota secrete factors that can contribute to CRC metastasis by influencing, for example, epithelial-to-mesenchymal transition. Although the role of EMT in metastasis is well-studied, mechanisms by which gastrointestinal microbiota contribute to the progression of CRC remain poorly understood. In this review, we will explore bacterial factors that contribute to the migration and invasion of colorectal carcinoma and the mechanisms involved. Bacteria involved in the induction of metastasis in primary CRC include Fusobacterium nucleatum, Enterococcus faecalis, enterotoxigenic Bacteroides fragilis, Escherichia coli and Salmonella enterica. Examples of prominent bacterial factors secreted by these bacteria include Fusobacterium adhesin A and Bacteroides fragilis Toxin. Most of these factors induce EMT-like properties in carcinoma cells and, as such, contribute to disease progression by affecting cell-cell adhesion, breakdown of the extracellular matrix and reorganisation of the cytoskeleton. It is of utmost importance to elucidate how bacterial factors promote CRC recurrence and metastasis to increase patient survival. So far, mainly animal models have been used to demonstrate this interplay between the host and microbiota. More human-based models are needed to study the mechanisms that promote migration and invasion and mimic the progression and recurrence of CRC.

Bacterial Extracellular Vesicles in Gastrointestinal Tract Cancer: An Unexplored Territory

Bacterial extracellular vesicles are membrane-enclosed, lipid bi-layer nanostructures that carry different classes of biomolecules, such as nucleic acids, lipids, proteins, and diverse types of small molecular metabolites, as their cargo. Almost all of the bacteria in the gut secrete extracellular vesicles to assist them in competition, survival, material exchange, host immune modulation, infection, and invasion. The role of gut microbiota in the development, progression, and pathogenesis of gastrointestinal tract (GIT) cancer has been well documented. However, the possible involvement of bacterial extracellular vesicles (bEVs) in GIT cancer pathophysiology has not been given due attention. Studies have illustrated the ability of bEVs to cross physiological barriers, selectively accumulate near tumor cells, and possibly alter the tumor microenvironment (TME). A systematic search of original published works related to bacterial extracellular vesicles on gastrointestinal cancer was performed for this review. The current systemic review outlines the possible impact of gut microbiota derived bEVs in GIT cancer in light of present-day understanding. The necessity of using advanced sequencing technologies, such as genetic, proteomic, and metabolomic investigation methodologies, to facilitate an understanding of the interrelationship between cancer-associated bacterial vesicles and gastrointestinal cancer is also emphasized. We further discuss the clinical and pharmaceutical potential of bEVs, along with future efforts needed to understand the mechanism of interaction of bEVs in GIT cancer pathogenesis.

Advances and new frontiers for immunotherapy in colorectal cancer: Setting the stage for neoadjuvant success?

Immunotherapy in the metastatic setting has drastically altered the landscape of treatment for various types of malignancy, including colorectal cancer. The category of immune checkpoint inhibitors has especially emerged as a class of therapy predicated on a more comprehensive understanding of immune cell-cancer cell regulation and evolution of the tumor microenvironment over time. Strategies including adoptive cellular therapies, tumor vaccines, and antibodies have also demonstrated the ability to enhance antitumor immunity. In this article, we provide a comprehensive review of the current landscape of immunotherapeutic strategies in colorectal cancer and provide insight into how these strategies may evolve in the next decade and be adapted to more localized forms of cancers of the colon and rectum. We provide particular focus on various combination approaches under investigation for reversing cancer-induced immunosuppression, especially in mismatch repair-proficient/microsatellite-stable colorectal tumors. Finally, we summarize current understanding on a recently identified integral factor in local immune regulation, the colonic microbiome. The aim of this article is to identify current challenges and barriers to improvement and to specify opportunities for applying knowledge in the immunotherapy sphere to rational design of clinical trials intended to improve survival and related outcomes in patients treated in the neoadjuvant setting.

Precision strategies for cancer treatment by modifying the tumor-related bacteria

Research on the roles of the bacteria in tumor development and progression is a rapidly emerging field. Increasing evidence links bacteria with the modification of the tumor immune microenvironment, which greatly influences the antitumor response. In view of the individual immune effects of various bacteria in various tumors, developing personalized bacteria-modulating therapy may be a key to successful antitumor treatment. This review emphasizes the critical role of the bacteria in immune regulation, including both the tumor bacteria and gut bacteria. Aiming at tumor-related bacteria, we focus on various precise modulation strategies and discuss their impact and potential for tumor suppression. Finally, engineered bacteria with tumor-targeting ability could achieve precise delivery of various payloads into tumors, acting as a precision tool. Therefore, a precise tumor-related bacteria therapy may be a promising approach to suppress the development of tumors, as well as an adjuvant therapy to improve the antitumor efficacy of other approaches. KEY POINTS: • The mini-review updates the knowledge on complex effect of bacteria in TME. • Insight into the interaction and adjustment of bacteria in gut for TME. • Prospects and limitations of bacteria-related personalized therapy in the clinical anticancer therapy.

Bacillus subtilis BSH has a protective effect on Salmonella infection by regulating the intestinal flora structure in chickens

Salmonellosis is a worldwide zoonotic disease that poses a serious threat to the reproduction of livestock and poultry and the health of young animals. Probiotics including Bacillus species, have received increasing attention as a substitute for antibiotics. In this study, chicks infected with Salmonella were fed feed supplemented with the BSH to observe the pathological changes in the liver, detect the number of viable bacteria in the liver and spleen, and record the death of the chicks. The results showed that BSH could reduce the pathological changes in the liver and the invasion of Salmonella into the liver and spleen of chicks. In addition, the survival rate of chicks in the BSH experimental group was 60%, while that in the infected control group was 26%, indicating that BSH had a protective effect on chicks infected with Salmonella. Finally, the fecal microflora of 9-day-old chicks was analyzed by 16S rRNA high-throughput sequencing. The results showed that Salmonella infection could cause intestinal flora changes, while BSH could alleviate this change. In addition, BSH also promoted the proliferation of Lactobacillus salivarius in the cecum of chick. This study emphasized that BSH has anti- Salmonella infection effects in chickens and can be used as a candidate microecological preparation strain.

Treating Colorectal Cancer with Immunotherapy: Implications for Single versus Combination Therapy

PURPOSE OF REVIEW

Colorectal cancer (CRC) is the second leading cause of cancer-associated deaths in the United States, with most metastatic cases subsequently turning refractory to standard chemotherapy. One of the promising current interventions is immunotherapy that relies on harnessing the body's immune mechanisms to kill the cancer cells. The aim of this review is to highlight the implications of single versus combination immunotherapy and identify the molecular features and mutations that enhance or deter responsiveness.

RECENT FINDINGS

Based on current findings, responsiveness is associated with deficiency of mismatch repair (dMMR) genes or presence of microsatellite instability (MSI-high), with high immunoscore and tumor-mutational burden contributing to better efficacy while BRAF mutation conferring no significant effect. Combination immunotherapy demonstrates better efficacy in treating MSI-high CRC compared to single agent immunotherapy or chemotherapy.

SUMMARY

Given improved responsiveness and overall survival, there is potential for immunotherapy to change the standard of care for metastatic CRC. Furthermore, stratifying the patients by their molecular features and mutation status is critical for establishing care.