Association between the gut microbiota and patient responses to cancer immune checkpoint inhibitors

Gut and local microbiota in patients with cancer: increasing evidence and potential clinical applications

In recent years, cancer research has highlighted the role of disrupted microbiota in carcinogenesis and cancer recurrence. However, microbiota may also interfere with drug metabolism, influencing the efficacy of cancer drugs, especially immunotherapy, and modulating the onset of adverse events. Intestinal micro-organisms can be altered by external factors, such as use of antibiotics, proton pump inhibitors treatment, lifestyle and the use of prebiotics or probiotics. The aim of our review is to provide a picture of the current evidence about preclinical and clinical data of the role of gut and local microbiota in malignancies and its potential clinical role in cancer treatments. Standardization of microbiota sequencing approaches and its modulating strategies within prospective clinical trials could be intriguing for two aims: first, to provide novel potential biomarkers both for early cancer detection and for therapeutic effectiveness; second, to propose personalized and "microbiota-tailored" treatment strategies.

The Interplay between Medical Plants and Gut Microbiota in Cancer

The gut microbiota is a dynamic community of bacteria distributed in the gastroenteric tract and changes in response to diseases, diet, use of antibiotics and probiotics, hygiene status, and other environmental factors. Dysbiosis, a disruption of the normal crosstalk between the host and the microbes, is associated with obesity, diabetes, cancer, and cardiovascular diseases, is linked to a reduction of anti-inflammatory bacteria like Lactobacillus and Roseburia, and to an increase in the growth of proinflammatory species like Ruminococcus gnavus and Bacteroidetes. Some plants possess anticancer properties and various studies have reported that some of these are also able to modulate the gut microbiota. The aim of this work is to evaluate the crucial relationship between medical plants and gut microbiota and the consequences on the onset and progression of cancer. In vivo studies about hematological malignancies showed that beta-glucans tie to endogenous antibeta glucan antibodies and to iC3b, an opsonic fragment of the central complement protein C3, leading to phagocytosis of antibody-targeted neoplastic cells and potentiation of the cytotoxic activity of the innate immune system if administered together with monoclonal antibodies. In conclusion, this review suggests the potential use of medical plants to improve gut dysbiosis and assist in the treatment of cancer.

Predictive significance of body composition indices in patients with head and neck squamous cell carcinoma treated with nivolumab: A multicenter retrospective study

BACKGROUND

The identification of predictive factors is imperative for identifying patients with optimal responses to nivolumab. We aimed to determine whether body composition parameters can predict treatment outcomes in patients with head and neck squamous cell carcinoma (HNSCC) treated with nivolumab.

METHOD

We performed a multicenter retrospective chart review of patients with recurrent and/or metastatic HNSCC treated with nivolumab between 2017 and 2020. Computed tomography images and anthropometric measures were used to determine the skeletal muscle index (SMI), subcutaneous adipose index, visceral adipose index (VAI), and body mass index. Objective response, overall survival (OS), progression-free survival (PFS), and severe immune-related adverse events (irAEs) were the main outcomes. Odds ratios (ORs) and hazard ratios (HRs) for low-index groups compared with high-index groups were calculated for these outcomes.

RESULTS

Our study comprised 114 patients with a median follow-up period of 23.1 months. Low SMI and low VAI were significantly associated with poor disease control [OR: 0.39, 95% confidence interval (CI): 0.15-0.97] and poor response (OR: 0.38, 95% CI: 0.15-0.94), respectively. Low SMI independently predicted poor OS (HR: 2.06, 95% CI: 1.16-3.67), poor PFS (HR: 1.74, 95% CI: 1.04-2.92), and increased incidence of irAEs (OR: 6.00, 95% CI: 1.04-34.61). Low VAI independently predicted poor PFS (HR 2.07, 95% CI: 1.15-3.73).

CONCLUSION

The SMI and VAI are predictive factors of nivolumab therapy in patients with HNSCC. Body composition indices should be assessed before nivolumab treatment for achieving optimal responses to nivolumab.

Gut Metabolites and Breast Cancer: The Continuum of Dysbiosis, Breast Cancer Risk, and Potential Breast Cancer Therapy

The complex association between the gut microbiome and cancer development has been an emerging field of study in recent years. The gut microbiome plays a crucial role in the overall maintenance of human health and interacts closely with the host immune system to prevent and fight infection. This review was designed to draw a comprehensive assessment and summary of recent research assessing the anticancer activity of the metabolites (produced by the gut microbiota) specifically against breast cancer. In this review, a total of 2701 articles were screened from different scientific databases (PubMed, Scopus, Embase and Web of Science) with 72 relevant articles included based on the predetermined inclusion and exclusion criteria. Metabolites produced by the gut microbial communities have been researched for their health benefits and potential anticancer activity. For instance, the short-chain fatty acid, butyrate, has been evaluated against multiple cancer types, including breast cancer, and has demonstrated anticancer potential via various molecular pathways. Similarly, nisin, a bacteriocin, has presented with a range of anticancer properties primarily against gastrointestinal cancers, with nominal evidence supporting its use against breast cancer. Comparatively, a natural purine nucleoside, inosine, though it has not been thoroughly investigated as a natural anticancer agent, has shown promise in recent studies. Additionally, recent studies demonstrated that gut microbial metabolites influence the efficacy of standard chemotherapeutics and potentially be implemented as a combination therapy. Despite the promising evidence supporting the anticancer action of gut metabolites on different cancer types, the molecular mechanisms of action of this activity are not well established, especially against breast cancer and warrant further investigation. As such, future research must prioritise determining the dose-response relationship, molecular mechanisms, and conducting animal and clinical studies to validate in vitro findings. This review also highlights the potential future directions of this field.

Analysis of interactions of immune checkpoint inhibitors with antibiotics in cancer therapy

The discovery of immune checkpoint inhibitors, such as PD-1/PD-L1 and CTLA-4, has played an important role in the development of cancer immunotherapy. However, immune-related adverse events often occur because of the enhanced immune response enabled by these agents. Antibiotics are widely applied in clinical treatment, and they are inevitably used in combination with immune checkpoint inhibitors. Clinical practice has revealed that antibiotics can weaken the therapeutic response to immune checkpoint inhibitors. Studies have shown that the gut microbiota is essential for the interaction between immune checkpoint inhibitors and antibiotics, although the exact mechanisms remain unclear. This review focuses on the interactions between immune checkpoint inhibitors and antibiotics, with an in-depth discussion about the mechanisms and therapeutic potential of modulating gut microbiota, as well as other new combination strategies.

An oral cancer vaccine using a Bifidobacterium vector suppresses tumor growth in a syngeneic mouse bladder cancer model

Cancer immunotherapy using immune-checkpoint inhibitors (ICIs) such as PD-1/PD-L1 inhibitors has been well established for various types of cancer. Monotherapy with ICIs, however, can achieve a durable response in only a subset of patients. There is a great unmet need for the ICI-resistant-tumors. Since patients who respond to ICIs should have preexisting antitumor T cell response, combining ICIs with cancer vaccines that forcibly induce an antitumor T cell response is a reasonable strategy. However, the preferred administration sequence of the combination of ICIs and cancer vaccines is unknown. In this study, we demonstrated that combining an oral WT1 cancer vaccine using a Bifidobacterium vector and following anti-PD-1 antibody treatment eliminated tumor growth in a syngeneic mouse model of bladder cancer. This vaccine induced T cell responses specific to multiple WT1 epitopes through the gut immune system. Moreover, in a tumor model poorly responsive to an initial anti-PD-1 antibody, this vaccine alone significantly inhibited the tumor growth, whereas combination with continuous anti-PD-1 antibody could not inhibit the tumor growth. These results suggest that this oral cancer vaccine alone or as an adjunct to anti-PD-1 antibody could provide a novel treatment option for patients with advanced urothelial cancer including bladder cancer.

PD-L1, TMB, and other potential predictors of response to immunotherapy for hepatocellular carcinoma: how can they assist drug clinical trials?

INTRODUCTION

Hepatocellular carcinoma (HCC) represents the sixth most commonly diagnosed malignancy worldwide, accounting for millions of deaths annually. Despite immune checkpoint inhibitors (ICIs) reported important results, only a minority of HCC patients benefit from these treatments, and the identification of predictive biomarkers of response still remains a highly unmet need.

AREAS COVERED

Herein, we provide a timely overview of available evidence on biochemical predictors of response to immunotherapy in advanced HCC patients; we speculate on how PD-L1, TMB, and other emerging biomarkers could assist drug clinical trials in the near future. A literature search was conducted in June 2021 using Pubmed/Medline, Cochrane library, and Scopus databases.

EXPERT OPINION

Reliable predictors of response to ICIs are of pivotal importance to allow a proper stratification and selection of HCC patients that could derive more benefit from immunotherapy. Well-designed, multicenter clinical trials specifically focused on predictive biomarkers are warranted in this setting, where most of evidence currently derives from retrospective, single-center studies with small sample size.

The Role of Gut Microbiota in Overcoming Resistance to Checkpoint Inhibitors in Cancer Patients: Mechanisms and Challenges

The introduction of immune checkpoint inhibitors has constituted a major revolution in the treatment of patients with cancer. In contrast with the traditional cytotoxic therapies that directly kill tumor cells, this treatment modality enhances the ability of the host’s immune system to recognize and target cancerous cells. While immune checkpoint inhibitors have been effective across multiple cancer types, overcoming resistance remains a key area of ongoing research. The gut microbiota and its role in cancer immunosurveillance have recently become a major field of study. Gut microbiota has been shown to have direct and systemic effects on cancer pathogenesis and hosts anti-tumor immune response. Many studies have also shown that the host microbiota profile plays an essential role in the response to immunotherapy, especially immune checkpoint inhibitors. As such, modulating this microbial environment has offered a potential path to overcome the resistance to immune checkpoint inhibitors. In this review, we will talk about the role of microbiota in cancer pathogenesis and immune-system activity. We will also discuss preclinical and clinical studies that have increased our understanding about the roles and the mechanisms through which microbiota influences the response to treatment with immune checkpoint inhibitors.

Impact of the Gut Microbiota Balance on the Health-Disease Relationship: The Importance of Consuming Probiotics and Prebiotics

Gut microbiota is a group of microorganisms that are deposited throughout the entire gastrointestinal tract. Currently, thanks to genomic tools, studies of gut microbiota have pointed towards the understanding of the metabolism of important bacteria that are not cultivable and their relationship with human homeostasis. Alterations in the composition of gut microbiota could explain, at least in part, some epidemics, such as diabetes and obesity. Likewise, dysbiosis has been associated with gastrointestinal disorders, neurodegenerative diseases, and even cancer. That is why several studies have recently been focused on the direct relationship that these types of conditions have with the specific composition of gut microbiota, as in the case of the microbiota-intestine-brain axis. In the same way, the control of microbiota is related to the diet. Therefore, this review highlights the importance of gut microbiota, from its composition to its relationship with the human health-disease condition, as well as emphasizes the effect of probiotic and prebiotic consumption on the balance of its composition.

The Association Between Inflammation and Immunosuppression: Implications for ICI Biomarker Development

Evasion of immune destruction is considered one of the hallmarks of cancer. Chronic inflammation can enable immune escape by suppressing immune surveillance and permitting the development of tumors and creating a tumor microenvironment that sustains cancer. This includes generating mechanisms that prevent the effectiveness of anti-tumor treatment including immune checkpoint inhibitor therapy. In this review, we explore the interplay of inflammation and immunosuppression, their effects on the tumor microenvironment, and their implications for immune checkpoint inhibitor therapy particularly in the context of predictive biomarkers for their use.

Food, Nutrition, Physical Activity and Microbiota: Which Impact on Lung Cancer?

Lung cancer still represents the leading cause of cancer-related death, globally. Likewise, malnutrition and inactivity represent a major risk for loss of functional pulmonary capacities influencing overall lung cancer severity. Therefore, the adhesion to an appropriate health lifestyle is crucial in the management of lung cancer patients despite the subtype of cancer. This review aims to summarize the available knowledge about dietary approaches as well as physical activity as the major factors that decrease the risk towards lung cancer, and improve the response to therapies. We discuss the most significant dietary schemes positively associated to body composition and prognosis of lung cancer and the main molecular processes regulated by specific diet schemes, functional foods and physical activity, i.e., inflammation and oxidative stress. Finally, we report evidence demonstrating that dysbiosis of lung and/or gut microbiome, as well as their interconnection (the gut–lung axis), are strictly related to dietary patterns and regular physical activity playing a key role in lung cancer formation and progression, opening to the avenue of modulating the microbiome as coadjuvant therapy. Altogether, the evidence reported in this review highlights the necessity to consider non-pharmacological interventions (nutrition and physical activity) as effective adjunctive strategies in the management of lung cancer.