Gut Microbiota Promotes Tumor Growth in Mice by Modulating Immune Response

Unveiling the intratumoral microbiota within cancer landscapes

Recent advances in cancer research have unveiled a significant yet previously underappreciated aspect of oncology: the presence and role of intratumoral microbiota. These microbial residents, encompassing bacteria, fungi, and viruses within tumor tissues, have been found to exert considerable influence on tumor development, progression, and the efficacy of therapeutic interventions. This review aims to synthesize these groundbreaking discoveries, providing an integrated overview of the identification, characterization, and functional roles of intratumoral microbiota in cancer biology. We focus on elucidating the complex interactions between these microorganisms and the tumor microenvironment, highlighting their potential as novel biomarkers and therapeutic targets. The purpose of this review is to offer a comprehensive understanding of the microbial dimension in cancer, paving the way for innovative approaches in cancer diagnosis and treatment.

Current and future immunotherapeutic approaches in pancreatic cancer treatment

Pancreatic cancer is a major cause of cancer-related death, but despondently, the outlook and prognosis for this resistant type of tumor have remained grim for a long time. Currently, it is extremely challenging to prevent or detect it early enough for effective treatment because patients rarely exhibit symptoms and there are no reliable indicators for detection. Most patients have advanced or spreading cancer that is difficult to treat, and treatments like chemotherapy and radiotherapy can only slightly prolong their life by a few months. Immunotherapy has revolutionized the treatment of pancreatic cancer, yet its effectiveness is limited by the tumor's immunosuppressive and hard-to-reach microenvironment. First, this article explains the immunosuppressive microenvironment of pancreatic cancer and highlights a wide range of immunotherapy options, including therapies involving oncolytic viruses, modified T cells (T-cell receptor [TCR]-engineered and chimeric antigen receptor [CAR] T-cell therapy), CAR natural killer cell therapy, cytokine-induced killer cells, immune checkpoint inhibitors, immunomodulators, cancer vaccines, and strategies targeting myeloid cells in the context of contemporary knowledge and future trends. Lastly, it discusses the main challenges ahead of pancreatic cancer immunotherapy.

Gut microbiome-mediated monocytes promote liver metastasis

The gut microbiome plays an important role in tumor growth by regulating immune cell function. However, the role of the gut microbiome-mediated monocytes in liver metastasis remains unclear. In this study, we found that fecal microbiome transplantation (FMT) from the stool of patients with liver metastasis (LM) significantly promoted liver metastasis compared with healthy donors (HD). Monocytes were upregulated in liver tissues by the CCL2/CCR2 axis in LM patients' stool transplanted mouse model. CCL2/CCR2 inhibition and monocyte depletion significantly suppress liver metastasis. FMT using LM patients' stool enhanced the plasma lipopolysaccharides (LPS) concentration. The LPS/TLR4 signaling pathway is crucial for gut microbiome-mediated liver metastasis. These results indicated that monocytes contribute to liver metastasis via the CCL2/CCR2 axis.

Interaction between intestinal flora and gastric cancer in tumor microenvironment

Gastric Cancer (GC) is a prevalent malignancy globally and is the third leading cause of cancer-related deaths. Recent researches focused on the correlation between intestinal flora and GC. Studies indicate that bacteria can influence the development of gastrointestinal tumors by releasing bacterial extracellular vesicles (BEVs). The Tumor microenvironment (TME) plays an important role in tumor survival, with the interaction between intestinal flora, BEVs, and TME directly impacting tumor progression. Moreover, recent studies have demonstrated that intestinal microflora and BEVs can modify TME to enhance the effectiveness of antitumor drugs. This review article provides an overview and comparison of the biological targets through which the intestinal microbiome regulates TME, laying the groundwork for potential applications in tumor diagnosis, treatment, and prognosis.

Role of T cells in liver metastasis

The liver is a major metastatic site (organ) for gastrointestinal cancers (such as colorectal, gastric, and pancreatic cancers) as well as non-gastrointestinal cancers (such as lung, breast, and melanoma cancers). Due to the innate anatomical position of the liver, the apoptosis of T cells in the liver, the unique metabolic regulation of hepatocytes and other potential mechanisms, the liver tends to form an immunosuppressive microenvironment and subsequently form a pre-metastatic niche (PMN), which can promote metastasis and colonization by various tumor cells(TCs). As a result, the critical role of immunoresponse in liver based metastasis has become increasingly appreciated. T cells, a centrally important member of adaptive immune response, play a significant role in liver based metastases and clarifying the different roles of the various T cells subsets is important to guide future clinical treatment. In this review, we first introduce the predisposing factors and related mechanisms of liver metastasis (LM) before introducing the PMN and its transition to LM. Finally, we detail the role of different subsets of T cells in LM and advances in the management of LM in order to identify potential therapeutic targets for patients with LM.

Targeted modulation of gut and intra-tumor microbiota to improve the quality of immune checkpoint inhibitor responses

Immune checkpoint inhibitor (ICI) therapies, such as those blocking the interaction of PD-1 with its ligands, can restore the immune-killing function of T cells. However, ICI therapy is clinically beneficial in only a small number of patients, and it is difficult to predict post-treatment outcomes, thereby limiting its widespread clinical use. Research suggests that gut microbiota can regulate the host immune system and affect cancer progression and treatment. Moreover, the effectiveness of immunotherapy is related to the composition of the patient's gut microbiota; different gut microbial strains can either activate or inhibit the immune response. However, the importance of the microbial composition within the tumor has not been explored until recently. This study describes recent advances in the crosstalk between microbes in tumors and gut microbiota, which can modulate the tumor microbiome by directly translocating into the tumor and altering the tumor microenvironment. This study focused on the potential manipulation of the tumor and gut microbiota using fecal microbiota transplantation (FMT), probiotics, antimicrobials, prebiotics, and postbiotics to enrich immune-boosting bacteria while decreasing unfavorable bacteria to proactively improve the efficacy of ICI treatments. In addition, the use of genetic technologies and nanomaterials to modify microorganisms can largely optimize tumor immunotherapy and advance personalized and precise cancer treatment.

The Effect of Intratumor Heterogeneity in Pancreatic Ductal Adenocarcinoma Progression and Treatment

BACKGROUND AND OBJECTIVES

Pancreatic cancer is one of the most lethal malignancies. Even though many substantial improvements in the survival rates for other major cancer forms were made, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Even more, no standard classification system for pancreatic cancer is based on cellular biomarkers. This review will discuss and provide updates about the role of stem cells in the progression of PC, the genetic changes associated with it, and the promising biomarkers for diagnosis.

MATERIALS AND METHODS

The search process used PubMed, Cochrane Library, and Scopus databases to identify the relevant and related articles. Articles had to be published in English to be considered.

RESULTS

The increasing number of studies in recent years has revealed that the diversity of cancer-associated fibroblasts is far greater than previously acknowledged, which highlights the need for further research to better understand the various cancer-associated fibroblast subpopulations. Despite the huge diversity in pancreatic cancer, some common features can be noted to be shared among patients. Mutations involving CDKN2, P53, and K-RAS can be seen in a big number of patients, for example. Similarly, some patterns of genes and biomarkers expression and the level of their expression can help in predicting cancer behavior such as metastasis and drug resistance. The current trend in cancer research, especially with the advancement in technology, is to sequence everything in hopes of finding disease-related mutations.

CONCLUSION

Optimizing pancreatic cancer treatment requires clear classification, understanding CAF roles, and exploring stroma reshaping approaches.

Leveraging genomic signatures of oral microbiome-associated antibiotic resistance genes for diagnosing pancreatic cancer

Growing evidence has increasingly suggested a potential linkage between the oral microbiome and various diseases, including pancreatic ductal adenocarcinoma (PDAC). However, the utilization of gene-level information derived from the oral microbiome for diagnosing PDAC remains unexplored. In this study, we sought to investigate the novel potential of leveraging genomic signatures associated with antibiotic resistance genes (ARGs) within the oral microbiome for the diagnosis of PDAC. By conducting an analysis of oral microbiome samples obtained from PDAC patients, we successfully identified specific ARGs that displayed distinct sequence abundance profiles correlated with the presence of PDAC. In the healthy group, three ARGs were found to be enriched, whereas 21 ARGs were enriched in PDAC patients. Remarkably, these ARGs from oral microbiome exhibited promising diagnostic capabilities for PDAC (AUROC = 0.79), providing a non-invasive and early detection method. Our findings not only provide novel modal data for diagnosing PDAC but also shed light on the intricate interplay between the oral microbiome and PDAC.

Heterogeneous changes in gut and tumor microbiota in patients with pancreatic cancer: insights from clinical evidence

BACKGROUND

Pancreatic cancer is the foremost contributor to cancer-related deaths globally, and its prevalence continues to rise annually. Nevertheless, the underlying mechanisms behind its development remain unclear and necessitate comprehensive investigation.

METHODS

In this study, a total of 29 fresh stool samples were collected from patients diagnosed with pancreatic cancer. The gut microbial data of healthy controls were obtained from the SRA database (SRA data number: SRP150089). Additionally, 28 serum samples and diseased tissues were collected from 14 patients with confirmed pancreatic cancer and 14 patients with chronic pancreatitis. Informed consent was obtained from both groups of patients. Microbial sequencing was performed using 16s rRNA.

RESULTS

The results showed that compared with healthy controls, the species abundance index of intestinal flora in patients with pancreatic cancer was increased (P < 0.05), and the number of beneficial bacteria at the genus level was reduced (P < 0.05). Compared with patients with chronic pancreatitis, the expression levels of CA242 and CA199 in the serum of patients with pancreatic cancer were increased (P < 0.05). The bacterial richness index of tumor microorganisms in patients with pancreatic cancer increased, while the diversity index decreased(P < 0.05). Furthermore, there was a change in the species composition at the genus level. Additionally, the expression level of CA242 was found to be significantly positively correlated with the relative abundance of Acinetobacter(P < 0.05).

CONCLUSION

Over all, the expression levels of serum tumor markers CA242 and CA19-9 in patients with pancreatic cancer are increased, while the beneficial bacteria in the intestine and tumor microenvironment are reduced and pathogenic bacteria are increased. Acinetobacter is a specific bacterial genus highly expressed in pancreatic cancer tissue.

Gut Mycobiota Dysbiosis Is Associated with Melanoma and Response to Anti-PD-1 Therapy

Recent research indicates that gut microbiota may be vital in the advancement of melanoma. In this study, we found that melanoma patients exhibited a distinct gut mycobiota structure compared with healthy participants. Candida albicans, Candida dubliniensis, and Neurospora crassa were more abundant in samples from patients with melanoma, whereas Saccharomyces cerevisiae and Debaryomyces hansenii were less abundant. During anti-PD-1 treatment, the relative amount of Malassezia restricta and C. albicans increased. A higher level of Saccharomyces paradoxus was associated with a positive response to anti-PD-1 treatment, whereas a higher level of Tetrapisispora blattae was associated with a lack of clinical benefits. High levels of M. restricta and C. albicans, elevated serum lactate dehydrogenase, and being overweight were linked to increased risk of melanoma progression and poorer response to anti-PD-1 treatment. Thus, this study has revealed melanoma-associated mycobiome dysbiosis, characterized by altered fungal composition and fungi species associated with a higher risk of melanoma progression, identifying a role for the gut mycobiome in melanoma progression.

Pathological significance of heme oxygenase-1 as a potential tumor promoter in heme-induced colorectal carcinogenesis

The significance of the heme-metabolizing enzyme heme oxygenase-1 (HMOX1) in the pathogenesis of colorectal cancer (CRC) has not been fully explored. HMOX1 cytoprotection is imperative to limit oxidative stress. However, its roles in preventing carcinogenesis in response to high levels of heme are not thoroughly understood. This study reviews various mechanisms associated with the paradoxical role of HMOX1, which is advantageous for tumor growth, refractoriness, and survival of cancer cells amid oxidative stress in heme-induced CRC. The alternate role of HMOX1 promotes cell proliferation and metastasis through immune modulation and angiogenesis. Inhibiting HMOX1 has been found to reverse tumor promotion. Thus, HMOX1 acts as a conditional tumor promoter in CRC pathogenesis.

An investigation for phylogenetic characterization of human Pancreatic cancer microbiome by 16SrDNA Sequencing and Bioinformatics techniques

Pancreatic cancer is a significant public health concern, with increasing incidence rates and limited treatment options. Recent studies have highlighted the role of the human microbiome, particularly the gut microbiota, in the development and progression of this disease. Microbial dysbiosis, characterized by alterations in the composition and function of the gut microbiota, has been implicated in pancreatic carcinogenesis through mechanisms involving chronic inflammation, immune dysregulation, and metabolic disturbances. Researchers have identified specific microbial signatures associated with pancreatic cancer, offering potential biomarkers for early detection and prognostication. By leveraging advanced sequencing and bioinformatics tools, scientists have delineated differences in the gut microbiota between pancreatic cancer patients and healthy individuals, providing insights into disease pathogenesis and potential diagnostic strategies. Moreover, the microbiome holds promise as a therapeutic target in pancreatic cancer treatment. Interventions aimed at modulating the microbiome, such as probiotics, prebiotics, and fecal microbiota transplantation, have demonstrated potential in enhancing the efficacy of existing cancer therapies, including chemotherapy and immunotherapy. These approaches can influence immune responses, alter tumor microenvironments, and sensitize tumors to treatment, offering new avenues for improving patient outcomes and overcoming therapeutic resistance. Overall, understanding the complex interplay between the microbiome and pancreatic cancer is crucial for advancing our knowledge of disease mechanisms and identifying innovative therapeutic strategies. Here we report phylogenetic analysis of the 16S microbial sequences of the pancreatic cancer mice microbiome and corresponding age matched healthy mice microbiome. We successfully identified differentially abundance of microbiota in the pancreatic cancer.

Nanomaterials-Involved Tumor-Associated Macrophages' Reprogramming for Antitumor Therapy

Tumor-associated macrophages (TAMs) play pivotal roles in tumor development. As primary contents of tumor environment (TME), TAMs secrete inflammation-related substances to regulate tumoral occurrence and development. There are two kinds of TAMs: the tumoricidal M1-like TAMs and protumoral M2-like TAMs. Reprogramming TAMs from immunosuppressive M2 to immunocompetent M1 phenotype is considered a feasible way to improve immunotherapeutic efficiency. Notably, nanomaterials show great potential for biomedical fields due to their controllable structures and properties. There are many types of nanomaterials that exhibit great regulatory activities for TAMs' reprogramming. In this review, the recent progress of nanomaterials-involved TAMs' reprogramming is comprehensively discussed. The various nanomaterials for TAMs' reprogramming and the reprogramming strategies are summarized and introduced. Additionally, the challenges and perspectives of TAMs' reprogramming for efficient therapy are discussed, aiming to provide inspiration for TAMs' regulator design and promote the development of TAMs-mediated immunotherapy.

Association between the gut microbiota, inflammatory factors, and colorectal cancer: evidence from Mendelian randomization analysis

Background

Colorectal cancer (CRC) is one of the most common malignant tumors primarily affecting individuals over the age of 50 years. Recent studies have suggested that the dysbiosis of the gut microbiota, a community of microorganisms in the human gut, is closely associated with the occurrence and development of CRC. Additionally, inflammatory factors (IFs) have also been reported to play a significant role in the development of CRC. However, the causal relationships between the gut microbiota, IFs, and CRC remain unclear.

Methods

In this study, we performed Mendelian randomization (MR) analysis using publicly available genome-wide association study (GWAS) data to explore the causal relationship between the gut microbiota, IFs, and CRC. The gut microbiota GWAS data were obtained from the MiBioGen study, while the IFs GWAS data were derived from the comprehensive analysis of three independent cohorts. Causal relationship analysis was conducted using appropriate instrumental variables (IVs) and statistical models.

Results

MR analysis of the gut microbiota and CRC revealed a negative correlation between the Lachnospiraceae species in the gut and CRC risk, while a positive correlation was observed between Porphyromonadaceae species, Lachnospiraceae UCG010 genus, Lachnospira genus, and Sellimonas genus in the gut, and CRC risk. Additionally, we observed a causal relationship between IL-10 and CRC risk. These findings suggest that the dysbiosis of the gut microbiota might be associated with an increased risk of CRC and that specific bacterial groups may play a crucial role in the occurrence and development of CRC.

Conclusion

Using MR analysis, this study revealed the causal relationships between the gut microbiota, IFs, and CRC. The negative correlation between the Lachnospiraceae species in the gut and CRC risk, as well as the causal relationship between IL-10 and CRC, provide important clues for the potential roles of gut microbiota regulation and inflammatory factor control in the prevention and treatment of CRC.

Postbiotic butyrate: role and its effects for being a potential drug and biomarker to pancreatic cancer

Postbiotics are produced by microbes and have recently gained importance in the field of oncology due to their beneficial effects to the host, effectiveness against cancer cells, and their ability to suppress inflammation. In particular, butyrate dominates over all other postbiotics both in quantity and anticancer properties. Pancreatic cancer (PC), being one of the most malignant and lethal cancers, reported a decreased 5-year survival rate in less than 10% of the patients. PC causes an increased mortality rate due to its inability to be detected at an early stage but still a promising strategy for its diagnosis has not been achieved yet. It is necessary to diagnose Pancreatic cancer before the metastatic progression stage. The available blood biomarkers lack accurate and proficient diagnostic results. Postbiotic butyrate is produced by gut microbiota such as Rhuminococcus and Faecalibacterium it is involved in cell signalling pathways, autophagy, and cell cycle regulation, and reduction in butyrate concentration is associated with the occurrence of pancreatic cancer. The postbiotic butyrate is a potential biomarker that could detect PC at an early stage, before the metastatic progression stage. Thus, this review focused on the gut microbiota butyrate's role in pancreatic cancer and the immuno-suppressive environment, its effects on histone deacetylase and other immune cells, microbes in major butyrate synthesis pathways, current biomarkers in use for Pancreatic Cancer.

Genetically predicted gut microbiome and risk of oral cancer

PURPOSE

Mounting evidence suggests a possible link between gut microbiome and oral cancer, pointing to some potential modifiable targets for disease prevention. In the present study, Mendelian randomization (MR) was used to explore whether there was a causal link between gut microbiome and oral cancer.

METHODS

The single nucleotide polymorphisms (SNPs) significantly associated with gut microbiome were served as instrumental variables. MR analyses were performed using genetic approaches such as inverse variance weighting (IVW), MR Egger and weighted median, with IVW as the primary approach, supplemented by MR Egger and weighted median. Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and MR-Egger regression were used to detect the presence of horizontal pleiotropy and identify outlier SNPs.

RESULTS

Causal effect estimates indicated that genetically predicted abundance of Prevotellaceae was associated with higher risk of oral cancer (odds ratio (OR) 1.80, 95% confidence interval (CI) 1.16-2.81, p = 0.009). There was no evidence of notable heterogeneity and horizontal pleiotropy.

CONCLUSION

Genetically derived estimates suggest that Prevotellaceae may be associated with the risk of oral cancer. Such robust evidence should be given priority in future studies and explore the underlying mechanisms.

The role of the gut microbiome in gastrointestinal cancers

The gut microbiota present in the human digestive system is incredibly varied and is home to trillions of microorganisms. The gut microbiome is shaped at birth, while numerous genetic, dietary, and environmental variables primarily influence the microbiome composition. The importance of gut microbiota on host health is becoming more widely acknowledged. Digestion, intestinal permeability, and immunological and metabolism responses can all be affected by changes in the composition and function of the gut microbiota. There is mounting evidence that the microbial population's complex traits are important biomarkers and indicators of patient outcomes in cancer and its therapies. Numerous studies have demonstrated that changed commensal gut microorganisms contribute to the development and spread of cancer through various routes. Despite the ongoing controversy surrounding the gut microbiome and gastrointestinal cancer, accumulating evidence points to a potentially far more intricate connection than a simple cause-and-effect relationship. SIMPLE SUMMARY: Due to their high frequency and fatality rate, gastrointestinal cancers are regarded as a severe public health issue with complex medical and economic burdens. The gut microbiota may directly or indirectly interact with existing therapies like immunotherapy and chemotherapy, affecting how well a treatment works. The gut microbiome influences the immune response's activity, function, and development. Generally, certain gut bacteria impact the antitumor actions during cancer by creating particular metabolites or triggering T-cell responses. Yet, certain bacterial species have been found to promote cellular proliferation and metastasis in cancer, and comprehending these interactions in the context of cancer may help identify possible treatment targets. Notwithstanding the improvements in the field, additional research is still required to comprehend the underlying processes, examine the effects on existing therapies, and pinpoint certain bacteria and immune cells that can cause this interaction.

Impact of intratumoral microbiome on tumor immunity and prognosis in human pancreatic ductal adenocarcinoma

BACKGROUND

Recent evidence suggests that the presence of microbiome within human pancreatic ductal adenocarcinoma (PDAC) tissue potentially influences cancer progression and prognosis. However, the significance of tumor-resident microbiome remains unclear. We aimed to elucidate the impact of intratumoral bacteria on the pathophysiology and prognosis of human PDAC.

METHODS

The presence of intratumoral bacteria was assessed in 162 surgically resected PDACs using quantitative polymerase chain reaction (qPCR) and in situ hybridization (ISH) targeting 16S rRNA. The intratumoral microbiome was explored by 16S metagenome sequencing using DNA extracted from formalin-fixed paraffin-embedded tissues. The profile of intratumoral bacteria was compared with clinical information, pathological findings including tumor-infiltrating T cells, tumor-associated macrophage, fibrosis, and alterations in four main driver genes (KRAS, TP53, CDKN2A/p16, SMAD4) in tumor genomes.

RESULTS

The presence of intratumoral bacteria was confirmed in 52 tumors (32%) using both qPCR and ISH. The 16S metagenome sequencing revealed characteristic bacterial profiles within these tumors, including phyla such as Proteobacteria and Firmicutes. Comparison of bacterial profiles between cases with good and poor prognosis revealed a significant positive correlation between a shorter survival time and the presence of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus. The abundance of these bacteria was correlated with a decrease in the number of tumor-infiltrating T cells positive for CD4, CD8, and CD45RO.

CONCLUSIONS

Intratumoral infection of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus is correlated with the suppressed anti-PDAC immunity and poor prognosis.

Microbiota in colorectal cancer related to liver metastasis

The prevalence of colorectal cancer (CRC) is increasing annually and metastasis is the principal cause of death in patients with CRC, with the liver being the most frequently affected site. Many studies have shown a strong interplay between the gut flora, particularly Fusobacterium nucleatum (F. nucleatum), Escherichia coli, and Bacteroides fragilis, and the development of gut tumors. Some strains can induce gut inflammation and produce toxins that directly harm gut epithelial cells, ultimately accelerating the onset and progression of CRC. However, little clinical evidence exists on the specific interplay between the gut microflora and colorectal cancer liver metastasis (CRLM). Some research showed the existence of viable F. nucleatum in distant metastasis of CRC. Subsequently, gut microbiota products, such as lipopolysaccharides, sodium butyrate, and protein cathepsin K, were also found to affect the development of CRC. This article summarizes the mechanism and research status of the interplay between gut microflora and CRLM, discusses the importance of gut microflora in the treatment of CRLM, and proposes a new approach to understanding the mechanism of CRLM and potential treatments for the microbiome. It is anticipated that the gut microbiota will be a formidable therapeutic and prophylactic tool for treating and preventing CRLM.

Involvement of the Gut Microbiome in the Local and Systemic Immune Response to Pancreatic Ductal Adenocarcinoma

The systemic and local immunosuppression exhibited by pancreatic ductal adenocarcinoma (PDAC) contributes significantly to its aggressive nature. There is a need for a greater understanding of the mechanisms behind this profound immune evasion, which makes it one of the most challenging malignancies to treat and thus one of the leading causes of cancer death worldwide. The gut microbiome is now thought to be the largest immune organ in the body and has been shown to play an important role in multiple immune-mediated diseases. By summarizing the current literature, this review examines the mechanisms by which the gut microbiome may modulate the immune response to PDAC. Evidence suggests that the gut microbiome can alter immune cell populations both in the peripheral blood and within the tumour itself in PDAC patients. In addition, evidence suggests that the gut microbiome influences the composition of the PDAC tumour microbiome, which exerts a local effect on PDAC tumour immune infiltration. Put together, this promotes the gut microbiome as a promising route for future therapies to improve immune responses in PDAC patients.

Astaxanthin exerts an adjunctive anti-cancer effect through the modulation of gut microbiota and mucosal immunity

This study aimed to investigate the function of gut microbiota in astaxanthin's adjuvant anticancer effects. Our prior research demonstrated that astaxanthin enhanced the antitumor effects of sorafenib by enhancing the body's antitumor immune response; astaxanthin also regulated the intestinal flora composition of tumor-bearing mice. However, it is presently unknown whether this beneficial effect is dependent on the gut microbiota. We first used broad-spectrum antibiotics to eradicate gut microbiota of tumor-bearing mice, followed by the transplantation of fecal microbiota. The results of this study indicate that the beneficial effects of astaxanthin when combined with molecular targeting are dependent on the presence of intestinal microbiota. Astaxanthin facilitates the infiltration of CD8+ T lymphocytes into the tumor microenvironment and increases Granzyme B production by modulating the intestinal flora. Therefore, it strengthens the body's anti-tumor immune response and synergistically boosts the therapeutic efficacy of drugs. Astaxanthin stimulates the production of cuprocytes and mucus in the intestines by promoting the proliferation of Akkermansia. In addition, astaxanthin enhances the intestinal mucosal immunological function. Our research supports the unique ability of astaxanthin to sustain intestinal flora homeostasis and its function as a dietary immune booster for individuals with tumors.

Bacteroides and related species: The keystone taxa of the human gut microbiota

Microbial communities play a significant role in maintaining ecosystems in a healthy homeostasis. Presently, in the human gastrointestinal tract, there are certain taxonomic groups of importance, though there is no single species that plays a keystone role. Bacteroides spp. are known to be major players in the maintenance of eubiosis in the human gastrointestinal tract. Here we review the critical role that Bacteroides play in the human gut, their potential pathogenic role outside of the gut, and their various methods of adapting to the environment, with a focus on data for B. fragilis and B. thetaiotaomicron. Bacteroides are anaerobic non-sporing Gram negative organisms that are also resistant to bile acids, generally thriving in the gut and having a beneficial relationship with the host. While they are generally commensal organisms, some Bacteroides spp. can be opportunistic pathogens in scenarios of GI disease, trauma, cancer, or GI surgery, and cause infection, most commonly intra-abdominal infection. B. fragilis can develop antimicrobial resistance through multiple mechanisms in large part due to its plasticity and fluid genome. Bacteroidota (formerly, Bacteroidetes) have a very broad metabolic potential in the GI microbiota and can rapidly adapt their carbohydrate metabolism to the available nutrients. Gastrointestinal Bacteroidota species produce short-chain fatty acids such as succinate, acetate, butyrate, and occasionally propionate, as the major end-products, which have wide-ranging and many beneficial influences on the host. Bacteroidota, via bile acid metabolism, also play a role in in colonization-resistance of other organisms, including Clostridioides difficile, and maintenance of gut integrity.

Microbiomes in pancreatic cancer can be an accomplice or a weapon

Recently, several investigations have linked the microbiome to pancreatic cancer progression. It is critical to reveal the role of different microbiomes in the occurrence, development, and treatment of pancreatic cancer. The current review summarizes the various microbiota types in pancreatic cancer while updating and supplementing the mechanisms of the representative gut, pancreatic, and oral microbiota, and their metabolites during its pathogenesis and therapeutic intervention. Several novel strategies have been introduced based on the tumor-associated microbiome to optimize the early diagnosis and prognosis of pancreatic cancer. The pros and cons involving different microbiomes in treating pancreatic cancer are discussed. The microbiome-related clinical trials for pancreatic cancer theranostics are outlined. This convergence of cutting-edge knowledge will provide feasible ideas for developing innovative therapies against pancreatic cancer.

Forces at play: exploring factors affecting the cancer metastasis

Metastatic disease, a leading and lethal indication of deaths associated with tumors, results from the dissemination of metastatic tumor cells from the site of primary origin to a distant organ. Dispersion of metastatic cells during the development of tumors at distant organs leads to failure to comply with conventional treatments, ultimately instigating abrupt tissue homeostasis and organ failure. Increasing evidence indicates that the tumor microenvironment (TME) is a crucial factor in cancer progression and the process of metastatic tumor development at secondary sites. TME comprises several factors contributing to the initiation and progression of the metastatic cascade. Among these, various cell types in TME, such as mesenchymal stem cells (MSCs), lymphatic endothelial cells (LECs), cancer-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), T cells, and tumor-associated macrophages (TAMs), are significant players participating in cancer metastasis. Besides, various other factors, such as extracellular matrix (ECM), gut microbiota, circadian rhythm, and hypoxia, also shape the TME and impact the metastatic cascade. A thorough understanding of the functions of TME components in tumor progression and metastasis is necessary to discover new therapeutic strategies targeting the metastatic tumor cells and TME. Therefore, we reviewed these pivotal TME components and highlighted the background knowledge on how these cell types and disrupted components of TME influence the metastatic cascade and establish the premetastatic niche. This review will help researchers identify these altered components' molecular patterns and design an optimized, targeted therapy to treat solid tumors and restrict metastatic cascade.

Gut epithelial Interleukin-17 receptor A signaling can modulate distant tumors growth through microbial regulation

Microbes influence cancer initiation, progression and therapy responsiveness. IL-17 signaling contributes to gut barrier immunity by regulating microbes but also drives tumor growth. A knowledge gap remains regarding the influence of enteric IL-17-IL-17RA signaling and their microbial regulation on the behavior of distant tumors. We demonstrate that gut dysbiosis induced by systemic or gut epithelial deletion of IL-17RA induces growth of pancreatic and brain tumors due to excessive development of Th17, primary source of IL-17 in human and mouse pancreatic ductal adenocarcinoma, as well as B cells that circulate to distant tumors. Microbial dependent IL-17 signaling increases DUOX2 signaling in tumor cells. Inefficacy of pharmacological inhibition of IL-17RA is overcome with targeted microbial ablation that blocks the compensatory loop. These findings demonstrate the complexities of IL-17-IL-17RA signaling in different compartments and the relevance for accounting for its homeostatic host defense function during cancer therapy.

Microbiome as a biomarker and therapeutic target in pancreatic cancer

Studying the effects of the microbiome on the development of different types of cancer has recently received increasing research attention. In this context, the microbial content of organs of the gastrointestinal tract has been proposed to play a potential role in the development of pancreatic cancer (PC). Proposed mechanisms for the pathogenesis of PC include persistent inflammation caused by microbiota leading to an impairment of antitumor immune surveillance and altered cellular processes in the tumor microenvironment. The limited available diagnostic markers that can currently be used for screening suggest the importance of microbial composition as a non-invasive biomarker that can be used in clinical settings. Samples including saliva, stool, and blood can be analyzed by 16 s rRNA sequencing to determine the relative abundance of specific bacteria. Studies have shown the potentially beneficial effects of prebiotics, probiotics, antibiotics, fecal microbial transplantation, and bacteriophage therapy in altering microbial diversity, and subsequently improving treatment outcomes. In this review, we summarize the potential impact of the microbiome in the pathogenesis of PC, and the role these microorganisms might play as biomarkers in the diagnosis and determining the prognosis of patients. We also discuss novel treatment methods being used to minimize or prevent the progression of dysbiosis by modulating the microbial composition. Emerging evidence is supportive of applying these findings to improve current therapeutic strategies employed in the treatment of PC.

Roles of microbiota in pancreatic cancer development and treatment

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with poor prognosis. This is due to the fact that most cases are only diagnosed at an advanced and palliative disease stage, and there is a high incidence of therapy resistance. Despite ongoing efforts, to date, the mechanisms underlying PDAC oncogenesis and its poor responses to treatment are still largely unclear. As the study of the microbiome in cancer progresses, growing evidence suggests that bacteria or fungi might be key players both in PDAC oncogenesis as well as in its resistance to chemo- and immunotherapy, for instance through modulation of the tumor microenvironment and reshaping of the host immune response. Here, we review how the microbiota exerts these effects directly or indirectly via microbial-derived metabolites. Finally, we further discuss the potential of modulating the microbiota composition as a therapy in PDAC.

The Interaction of Microbiome and Pancreas in Acute Pancreatitis

Acute pancreatitis (AP) is a common acute abdomen disease characterized by the pathological activation of digestive enzymes and the self-digestion of pancreatic acinar cells. Secondary infection and sepsis are independent prognosticators for AP progression and increased mortality. Accumulating anatomical and epidemiological evidence suggests that the dysbiosis of gut microbiota affects the etiology and severity of AP through intestinal barrier disruption, local or systemic inflammatory response, bacterial translocation, and the regulatory role of microbial metabolites in AP patients and animal models. Recent studies discussing the interactions between gut microbiota and the pancreas have opened new scopes for AP, and new therapeutic interventions that target the bacteria community have received substantial attention. This review concentrates on the alterations of gut microbiota and its roles in modulating gut-pancreas axis in AP. The potential therapies of targeting microbes as well as the major challenges of applying those interventions are explored. We expect to understand the roles of microbes in AP diagnosis and treatment.

Getting off tract: contributions of intraorgan microbiota to cancer in extraintestinal organs

The gastrointestinal ecosystem has received the most attention when examining the contributions of the human microbiome to health and disease. This concentration of effort is logical due to the overwhelming abundance of microbes in the gut coupled with the relative ease of sampling compared with other organs. However, the intestines are intimately connected to multiple extraintestinal organs, providing an opportunity for homeostatic microbial colonisation and pathogenesis in organs traditionally thought to be sterile or only transiently harbouring microbiota. These habitats are challenging to sample, and their low microbial biomass among large amounts of host tissue can make study challenging. Nevertheless, recent findings have shown that many extraintestinal organs that are intimately linked to the gut harbour stable microbiomes, which are colonised from the gut in selective manners and have highlighted not just the influence of the bacteriome but that of the mycobiome and virome on oncogenesis and health.

Exploring the Role of the Gut and Intratumoral Microbiomes in Tumor Progression and Metastasis

Cancer cell dissemination involves invasion, migration, resistance to stressors in the circulation, extravasation, colonization, and other functions responsible for macroscopic metastases. By enhancing invasiveness, motility, and intravasation, the epithelial-to-mesenchymal transition (EMT) process promotes the generation of circulating tumor cells and their collective migration. Preclinical and clinical studies have documented intensive crosstalk between the gut microbiome, host organism, and immune system. According to the findings, polymorphic microbes might play diverse roles in tumorigenesis, cancer progression, and therapy response. Microbial imbalances and changes in the levels of bacterial metabolites and toxins promote cancer progression via EMT and angiogenesis. In contrast, a favorable microbial composition, together with microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), can attenuate the processes of tumor initiation, disease progression, and the formation of distant metastases. In this review, we highlight the role of the intratumoral and gut microbiomes in cancer cell invasion, migration, and metastatic ability and outline the potential options for microbiota modulation. As shown in murine models, probiotics inhibited tumor development, reduced tumor volume, and suppressed angiogenesis and metastasis. Moreover, modulation of an unfavorable microbiome might improve efficacy and reduce treatment-related toxicities, bringing clinical benefit to patients with metastatic cancer.

The Prospect of Harnessing the Microbiome to Improve Immunotherapeutic Response in Pancreatic Cancer

Pancreatic ductal adenocarcinoma cancer (PDAC) is projected to become the second leading cause of cancer-related death in the United States by 2030. Patients are often diagnosed with advanced disease, which explains the dismal 5-year median overall survival rate of ~12%. Immunotherapy has been successful in improving outcomes in the past decade for a variety of malignancies, including gastrointestinal cancers. However, PDAC is historically an immunologically "cold" tumor, one with an immunosuppressive environment and with restricted entry of immune cells that have limited the success of immunotherapy in these tumors. The microbiome, the intricate community of microorganisms present on and within humans, has been shown to contribute to many cancers, including PDAC. Recently, its role in tumor immunology and response to immunotherapy has generated much interest. Herein, the current state of the interaction of the microbiome and immunotherapy in PDAC is discussed with a focus on needed areas of study in order to harness the immune system to combat pancreatic cancer.

Microbiota in cancer: molecular mechanisms and therapeutic interventions

The diverse bacterial populations within the symbiotic microbiota play a pivotal role in both health and disease. Microbiota modulates critical aspects of tumor biology including cell proliferation, invasion, and metastasis. This regulation occurs through mechanisms like enhancing genomic damage, hindering gene repair, activating aberrant cell signaling pathways, influencing tumor cell metabolism, promoting revascularization, and remodeling the tumor immune microenvironment. These microbiota-mediated effects significantly impact overall survival and the recurrence of tumors after surgery by affecting the efficacy of chemoradiotherapy. Moreover, leveraging the microbiota for the development of biovectors, probiotics, prebiotics, and synbiotics, in addition to utilizing antibiotics, dietary adjustments, defensins, oncolytic virotherapy, and fecal microbiota transplantation, offers promising alternatives for cancer treatment. Nonetheless, due to the extensive and diverse nature of the microbiota, along with tumor heterogeneity, the molecular mechanisms underlying the role of microbiota in cancer remain a subject of intense debate. In this context, we refocus on various cancers, delving into the molecular signaling pathways associated with the microbiota and its derivatives, the reshaping of the tumor microenvironmental matrix, and the impact on tolerance to tumor treatments such as chemotherapy and radiotherapy. This exploration aims to shed light on novel perspectives and potential applications in the field.

Causal effect between gut microbiota and pancreatic cancer: a two-sample Mendelian randomization study

BACKGROUND

Gut microbiota (GM) comprises a vast and diverse community of microorganisms, and recent studies have highlighted the crucial regulatory roles of various GM and their secreted metabolites in pancreatic cancer (PC). However, the causal relationship between GM and PC has yet to be confirmed.

METHODS

In the present study, we used two-sample Mendelian randomization (MR) analysis to investigate the causal effect between GM and PC, with genome-wide association study (GWAS) from MiBioGen consortium as an exposure factor and PC GWAS data from FinnGen as an outcome factor. Inverse variance weighted (IVW) was used as the primary method for this study.

RESULTS

At the genus level, we observed that Senegalimassilia (OR: 0.635, 95% CI: 0.403-0.998, P = 0.049) exhibited a protective effect against PC, while Odoribacter (OR:1.899, 95%CI:1.157-3.116, P = 0.011), Ruminiclostridium 9(OR:1.976,95%CI:1.128-3.461, P = 0.017), Ruminococcaceae (UCG011)(OR:1.433, 95%CI:1.072-1.916, P = 0.015), and Streptococcus(OR:1.712, 95%CI:1.071-1.736, P = 0.025) were identified as causative factors for PC. Additionally, sensitivity analysis, Cochran's Q test, the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO), and MR-Egger regression indicated no heterogeneity, horizontal pleiotropy, or reverse causality between GM and PC.

CONCLUSIONS

Our analysis establishes a causal effect between specific GM and PC, which may provide new insights into the potential pathogenic mechanisms of GM in PC and the assignment of effective therapeutic strategies.

Microbiota-Accessible Boron-Containing Compounds in Complex Regional Pain Syndrome

The microbiota-gut-brain axis has garnered increasing attention in recent years for its role in various health conditions, including neuroinflammatory disorders like complex regional pain syndrome (CRPS). CRPS is a debilitating condition characterized by chronic neuropathic pain, and its etiology and pathophysiology remain elusive. Emerging research suggests that alterations in the gut microbiota composition and function could play a significant role in CRPS development and progression. Our paper explores the implications of microbiota in CRPS and the potential therapeutic role of boron (B). Studies have demonstrated that individuals with CRPS often exhibit dysbiosis, with imbalances in beneficial and pathogenic gut bacteria. Dysbiosis can lead to increased gut permeability and systemic inflammation, contributing to the chronic pain experienced in CRPS. B, an essential trace element, has shown promise in modulating the gut microbiome positively and exerting anti-inflammatory effects. Recent preclinical and clinical studies suggest that B supplementation may alleviate neuropathic pain and improve CRPS symptoms by restoring microbiota balance and reducing inflammation. Our review highlights the complex interplay between microbiota, inflammation, and neuropathic pain in CRPS and underscores the potential of B as a novel therapeutic approach to target the microbiota-gut-brain axis, offering hope for improved management of this challenging condition.

Gut Lactobacillus contribute to the progression of breast cancer by affecting the anti-tumor activities of immune cells in the TME of tumor-bearing mice

Studies have proven that gut microbiota dysbiosis may influence the carcinogenesis and outcomes of multiple cancers. However, it is still unclear whether gut microbiota dysbiosis affect the progression of breast cancer, especially triple-negative breast cancer. In the present study, by using gut microbiota dysbiosis murine model established by treatment of mice with streptomycin, we found Lactobacillus and the metabolite-lactic acid are the pivotal factors for 4T1 tumor progression. In fact, streptomycin-treated mice exhibited slower tumor growth, in parallel with less abundance of Lactobacillus in the gut. Supplementation with Lactobacillus resulted in a rapid tumor growth, following a decrease in the expression of mRNAs for anti-tumor-related factors but an increase in the M2 polarization. The elevated percentages of IFN-γ-producing CD4+T cells and CD8+T cells in the tumor microenvironment of streptomycin-treated tumor-bearing mice may be vanished by supplementation of Lactobacillus. It seems likely that lactobacillus-mediated pro-tumor effect is related to the production of lactic acid. A decrease in the levels of lactic acid in the cecal feces and tumor tissues were observed in streptomycin-treated tumor bearing mice. However, supplementation of Lactobacillus can restore streptomycin-reduced concentration of lactic acid in the tumor tissues, suggesting that gut Lactobacillus are the source of lactic acid. Bioinformatics analysis result suggests high concentration of lactic acid in tumor sites may be related to the diminished anti-tumor immunity in the TME. This study reveals a correlation between gut Lactobacillus and tumor progression in a murine 4T1 tumor model, providing experimental evidence for clinical treatment of breast cancer.

Alarming correlation between multidrug-resistant bacteriobilia and morbidity after pancreatic surgery

BACKGROUND

Pancreatic surgery is characterized by high morbidity and mortality. Biliary colonization may affect clinical outcomes in these patients.

AIMS

This study aimed to verify whether bacteriobilia and multidrug resistance (MDR) detected during and after pancreatic surgery may have an impact on post-operative outcomes.

METHODS

Data from patients undergoing pancreatic surgery involving bile duct transection (2016-2022) in two high-volume centers were analyzed in relationship to overall morbidity, major morbidity and mortality after pancreato-duodenectomy (PD) or total pancreatectomy (TP). Simple and multivariable regressions were used.

RESULTS

227 patients submitted to PD (n=129) or TP (n=98) were included. Of them, 133 had preoperative biliary drainage (BD; 56.6%), mostly with the employment of endoscopic stents (91.7%). Bacteriobilia was detected in 111 patients (48.9%), and remarkably, observed in patients with BD (p=0.001). In addition, 25 MDR pathogens were identified (22.5%), with a significant prevalence in patients with BD. Multivariable regression analysis showed BD was strongly related to MDR isolation (odds ratio [OR]: 5.61; p=0.010). MDR isolation was the main factor linked to a higher number of major complications (OR: 2.75; p=0.041), including major infection complications (OR: 2.94; p=0.031).

CONCLUSIONS

Isolation of MDR from biliary swab during PD or TP significantly increases the risk of a worse post-operative outcome. Pre-operative precautions could improve patient safety.

Lactobacillus casei combined with Lactobacillus reuteri alleviate pancreatic cancer by inhibiting TLR4 to promote macrophage M1 polarization and regulate gut microbial homeostasis

BACKGROUND

Pancreatic cancer is a highly lethal disease with no effective treatments. Lactobacillus casei (L. casei) and Lactobacillus reuteri (L. reuteri) exhibited therapeutic effects on several cancers, but their roles in pancreatic cancer are unknown. This study aims to explore how L. casei & L. reuteri influence pancreatic cancer and the underlying mechanisms.

METHODS

Pancreatic cancer cells were treated with L. casei & L. reuteri and co-cultured with macrophages in a transwell system in vitro. Pancreatic cancer xenograft model was established and L. casei & L. reuteri was used to treat mice in vivo. MTT, CCK-8 assay or immunohistochemical staining were used to determine the proliferation of pancreatic cancer cells or tumor tissues. Transwell assay was applied to test the migration and invasion of pancreatic cells. RT-qPCR was utilized to assess TLR4 and MyD88 expressions in pancreatic cells or tumor tissues. WB, immunofluorescence staining, or flow cytometry was used to evaluate the M1/M2 polarization of macrophages. Besides, the composition of gut microbiota of tumor-bearing mice was determined by 16 S rRNA sequencing, and ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) untargeted metabolomics was used to evaluate the metabolic profiles of feces.

RESULTS

L. casei & L. reuteri inhibited the proliferation, migration, invasion of pancreatic cancer cells and pancreatic cancer cell-induced M2 polarization of macrophages by suppressing TLR4. Meanwhile, L. casei & L. reuteri repressed pancreatic cancer growth and promoted M1 macrophage polarization. Besides, L. casei & L. reuteri reduced fecal Alloprevotella and increased fecal azelate and glutamate in nude mice, while TLR4 inhibitor TAK-242 increased Clostridia UCG-014, azelate, uridine, methionine sulfoxide, oxypurinol, and decreased glyceryl monoester in the feces of pancreatic tumor-bearing mice. Fecal oxypurinol and glyceryl monoester levels were positively or negatively associated with gut Clostridia UCG-014 abundance, respectively.

CONCLUSION

L. casei & L. reuteri alleviate pancreatic cancer by inhibiting TLR4 to promote macrophage M1 polarization and regulate gut microbial homeostasis.

Pancreatic Exocrine Insufficiency and the Gut Microbiome in Pancreatic Cancer: A Target for Future Diagnostic Tests and Therapies?

Pancreatic exocrine insufficiency (PEI) is common amongst pancreatic cancer patients and is associated with poorer treatment outcomes. Pancreatic enzyme replacement therapy (PERT) is known to improve outcomes in pancreatic cancer, but the mechanisms are not fully understood. The aim of this narrative literature review is to summarise the current evidence linking PEI with microbiome dysbiosis, assess how microbiome composition may be impacted by PERT treatment, and look towards possible future diagnostic and therapeutic targets in this area. Early evidence in the literature reveals that there are complex mechanisms by which pancreatic secretions modulate the gut microbiome, so when these are disturbed, as in PEI, gut microbiome dysbiosis occurs. PERT has been shown to return the gut microbiome towards normal, so called rebiosis, in animal studies. Gut microbiome dysbiosis has multiple downstream effects in pancreatic cancer such as modulation of the immune response and the response to chemotherapeutic agents. It therefore represents a possible future target for future therapies. In conclusion, it is likely that the gut microbiome of pancreatic cancer patients with PEI exhibits dysbiosis and that this may potentially be reversible with PERT. However, further human studies are required to determine if this is indeed the case.

Repeated Social Defeat Stress Induces an Inflammatory Gut Milieu by Altering the Mucosal Barrier Integrity and Gut Microbiota Homeostasis

Background

Posttraumatic stress disorder (PTSD) is a mental health condition triggered by exposure to traumatic events in an individual's life. Patients with PTSD are also at a higher risk for comorbidities. However, it is not well understood how PTSD affects human health and/or promotes the risk for comorbidities. Nevertheless, patients with PTSD harbor a proinflammatory milieu and dysbiotic gut microbiota. Gut barrier integrity helps to maintain normal gut homeostasis and its dysregulation promotes gut dysbiosis and inflammation.

Methods

We used a mouse model of repeated social defeat stress (RSDS), a preclinical model of PTSD. Behavioral studies, metagenomics analysis of the microbiome, gut permeability assay (on mouse colon, using an Ussing chamber), immunoblotting, and immunohistochemical analyses were performed. Polarized intestinal epithelial cells and 3-dimensional crypt cultures were used for mechanistic analysis.

Results

The RSDS mice harbor a heightened proinflammatory gut environment and microbiota dysbiosis. The RSDS mice further showed significant dysregulation of gut barrier functions, including transepithelial electrical resistance, mucin homeostasis, and antimicrobial responses. RSDS mice also showed a specific increase in intestinal expression of claudin-2, a tight junction protein, and epinephrine, a stress-induced neurotransmitter. Treating intestinal epithelial cells or 3-dimensional cultured crypts with norepinephrine or intestinal luminal contents (fecal contents) upregulated claudin-2 expression and inhibited transepithelial electrical resistance.

Conclusions

Traumatic stress induces dysregulation of gut barrier functions, which may underlie the observed gut microbiota changes and proinflammatory gut milieu, all of which may have an interdependent effect on the health and increased risk of comorbidities in patients with PTSD.

Advances in the role of gut microbiota in the regulation of the tumor microenvironment (Review)

As a protector of human health, the gut microbiota plays an important role in the development of the immune system during childhood, and the regulation of dietary habits, metabolism and immune system during adulthood. Dysregulated gut flora is not pathogenic, but it can weaken the protective effect of the immune system and cause various diseases. The tumor microenvironment is a physiological environment formed during tumor growth, which provides nutrients and growth factors necessary for tumor growth. As an important factor affecting the tumor microenvironment, the intestinal microflora affects the development of tumors through the mechanisms of gut and microflora metabolites, gene toxins and signaling pathways. The present article aimed to review the components and mechanisms of action, clinical applications, and biological targets of gut microbiota in the regulation of the tumor microenvironment. The present review provides novel insights for the future use of intestinal flora, to regulate the tumor microenvironment, to intervene in the occurrence, development, treatment and prognosis of tumors.

A new strategy for treating colorectal cancer: Regulating the influence of intestinal flora and oncolytic virus on interferon

Colorectal cancer (CRC) has the third highest incidence and the second highest mortality in the world, which seriously affects human health, while current treatments methods for CRC, including systemic therapy, preoperative radiotherapy, and surgical local excision, still have poor survival rates for patients with metastatic disease, making it critical to develop new strategies for treating CRC. In this article, we found that the gut microbiota can modulate the signaling pathways of cancer cells through direct contact with tumor cells, generate inflammatory responses and oxidative stress through interactions between the innate and adaptive immune systems, and produce diverse metabolic combinations to trigger specific immune responses and promote the initiation of systemic type I interferon (IFN-I) and anti-viral immunity. In addition, oncolytic virus-mediated immunotherapy for regulating oncolytic virus can directly lyse tumor cells, induce the immune activity of the body, interact with interferon, inhibit the anti-viral effect of IFN-I, and enhance the anti-tumor effect of IFN-II. Interferon plays an important role in the anti-tumor process. We put forward that exploring the effects of intestinal flora and oncolytic virus on interferon to treat CRC is a promising therapeutic option.

The correlation between gut and intra-tumor microbiota and PDAC: Etiology, diagnostics and therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is one of the lethal cancers in the world and its 5-year survival rate is <10%. Due to the unique TME and dense tissue structure, its curative efficacy is far from satisfactory，the immunotherapy is even more invalid. According to the recent studies, the gut and tumor microbiota have been proved to play a key role in the development, progression and prognosis of PDAC. Based on the differences of microbiome composition observed in PDAC patients and normal pancreas, many researches have been made focusing on the latent communication between gut and intra-tumor microbiota and PDAC. In this review, we will demonstrate the potential mechanism of the oncogenic effects of GM and IM and their crucial effects on modulating the TME. Besides, we focus on their interaction with chemotherapeutic and immunotherapeutic drugs and inducing the drug resistance, thus enlightening the promising role to be used to monitor the occurrence of PDAC, accurately modulate the immune environment to promote the therapeutic efficacy and predict the prognosis.

Advances in Immunotherapeutics in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) accounts for up to 95% of all pancreatic cancer cases and is the seventh-leading cause of cancer death. Poor prognosis is a result of late presentation, a lack of screening tests and the fact some patients develop resistance to chemotherapy and radiotherapy. Novel therapies like immunotherapeutics have been of recent interest in pancreatic cancer. However, this field remains in its infancy with much to unravel. Immunotherapy and other targeted therapies have yet to yield significant progress in treating PDAC, primarily due to our limited understanding of the disease immune mechanisms and its intricate interactions with the tumour microenvironment (TME). In this review we provide an overview of current novel immunotherapies which have been studied in the field of pancreatic cancer. We discuss their mechanisms, evidence available in pancreatic cancer as well as the limitations of such therapies. We showcase the potential role of combining novel therapies in PDAC, postulate their potential clinical implications and the hurdles associated with their use in PDAC. Therapies discussed with include programmed death checkpoint inhibitors, Cytotoxic T-lymphocyte-associated protein 4, Chimeric Antigen Receptor-T cell therapy, oncolytic viral therapy and vaccine therapies including KRAS vaccines, Telomerase vaccines, Gastrin Vaccines, Survivin-targeting vaccines, Heat-shock protein (HSP) peptide complex-based vaccines, MUC-1 targeting vaccines, Listeria based vaccines and Dendritic cell-based vaccines.

The role of the symbiotic microecosystem in cancer: gut microbiota, metabolome, and host immunome

The gut microbiota is not just a simple nutritional symbiosis that parasitizes the host; it is a complex and dynamic ecosystem that coevolves actively with the host and is involved in a variety of biological activities such as circadian rhythm regulation, energy metabolism, and immune response. The development of the immune system and immunological functions are significantly influenced by the interaction between the host and the microbiota. The interactions between gut microbiota and cancer are of a complex nature. The critical role that the gut microbiota plays in tumor occurrence, progression, and treatment is not clear despite the already done research. The development of precision medicine and cancer immunotherapy further emphasizes the importance and significance of the question of how the microbiota takes part in cancer development, progression, and treatment. This review summarizes recent literature on the relationship between the gut microbiome and cancer immunology. The findings suggest the existence of a "symbiotic microecosystem" formed by gut microbiota, metabolome, and host immunome that is fundamental for the pathogenesis analysis and the development of therapeutic strategies for cancer.

Factors impacting the benefits and pathogenicity of Th17 cells in the tumor microenvironment

Tumor development is closely associated with a complex tumor microenvironment, which is composed of tumor cells, blood vessels, tumor stromal cells, infiltrating immune cells, and associated effector molecules. T helper type 17 (Th17) cells, which are a subset of CD4+ T cells and are renowned for their ability to combat bacterial and fungal infections and mediate inflammatory responses, exhibit context-dependent effector functions. Within the tumor microenvironment, different molecular signals regulate the proliferation, differentiation, metabolic reprogramming, and phenotypic conversion of Th17 cells. Consequently, Th17 cells exert dual effects on tumor progression and can promote or inhibit tumor growth. This review aimed to investigate the impact of various alterations in the tumor microenvironment on the antitumor and protumor effects of Th17 cells to provide valuable clues for the exploration of additional tumor immunotherapy strategies.

Intestinal Flora in Chemotherapy Resistance of Biliary Pancreatic Cancer

Biliary pancreatic malignancy has an occultic onset, a high degree of malignancy, and a poor prognosis. Most clinical patients miss the opportunity for surgical resection of the tumor. Systemic chemotherapy is still one of the important methods for the treatment of biliary pancreatic malignancies. Many chemotherapy regimens are available, but their efficacy is not satisfactory, and the occurrence of chemotherapy resistance is a major reason leading to poor prognosis. With the advancement of studies on intestinal flora, it has been found that intestinal flora is correlated with and plays an important role in chemotherapy resistance. The application of probiotics and other ways to regulate intestinal flora can improve this problem. This paper aims to review and analyze the research progress of intestinal flora in the chemotherapy resistance of biliary pancreatic malignancies to provide new ideas for treatment.

Molecular and metabolic regulation of immunosuppression in metastatic pancreatic ductal adenocarcinoma

Immunosuppression is a hallmark of pancreatic ductal adenocarcinoma (PDAC), contributing to early metastasis and poor patient survival. Compared to the localized tumors, current standard-of-care therapies have failed to improve the survival of patients with metastatic PDAC, that necessecitates exploration of novel therapeutic approaches. While immunotherapies such as immune checkpoint blockade (ICB) and therapeutic vaccines have emerged as promising treatment modalities in certain cancers, limited responses have been achieved in PDAC. Therefore, specific mechanisms regulating the poor response to immunotherapy must be explored. The immunosuppressive microenvironment driven by oncogenic mutations, tumor secretome, non-coding RNAs, and tumor microbiome persists throughout PDAC progression, allowing neoplastic cells to grow locally and metastasize distantly. The metastatic cells escaping the host immune surveillance are unique in molecular, immunological, and metabolic characteristics. Following chemokine and exosomal guidance, these cells metastasize to the organ-specific pre-metastatic niches (PMNs) constituted by local resident cells, stromal fibroblasts, and suppressive immune cells, such as the metastasis-associated macrophages, neutrophils, and myeloid-derived suppressor cells. The metastatic immune microenvironment differs from primary tumors in stromal and immune cell composition, functionality, and metabolism. Thus far, multiple molecular and metabolic pathways, distinct from primary tumors, have been identified that dampen immune effector functions, confounding the immunotherapy response in metastatic PDAC. This review describes major immunoregulatory pathways that contribute to the metastatic progression and limit immunotherapy outcomes in PDAC. Overall, we highlight the therapeutic vulnerabilities attributable to immunosuppressive factors and discuss whether targeting these molecular and immunological "hot spots" could improve the outcomes of PDAC immunotherapies.

HGF/c-Met pathway inhibition combined with chemotherapy increases cytotoxic T-cell infiltration and inhibits pancreatic tumour growth and metastasis

Pancreatic cancer (PC) is a deadly cancer with a high mortality rate. The unique characteristics of PC, including desmoplasia and immunosuppression, have made it difficult to develop effective treatment strategies. Pancreatic stellate cells (PSCs) play a crucial role in the progression of the disease by interacting with cancer cells. One of the key mediators of PSC - cancer cell interactions is the hepatocyte growth factor (HGF)/c-MET pathway. Using an immunocompetent in vivo model of PC as well as in vitro experiments, this study has shown that a combined approach using HGF/c-MET inhibitors to target stromal-tumour interactions and chemotherapy (gemcitabine) to target cancer cells effectively decreases tumour volume, EMT, and stemness, and importantly, eliminates metastasis. Notably, HGF/c-MET inhibition decreases TGF-β secretion by cancer cells, resulting in an increase in cytotoxic T-cell infiltration, thus contributing to cancer cell death in tumours. HGF/c-MET inhibition + chemotherapy was also found to normalise the gut microbiome and improve gut microbial diversity. These findings provide a strong platform for assessment of this triple therapy (HGF/c-MET inhibition + chemotherapy) approach in the clinical setting.

The Role of Microbiota in Pancreatic Cancer

Pancreatic cancer (PC) has an unfavorable prognosis with few effective therapeutic options. This has led researchers to investigate the possible links between microbiota and PC. A disrupted gut microbiome can lead to chronic inflammation, which is involved in the pathogenesis of PC. In addition, some bacterial strains can produce carcinogens that promote the growth of cancer cells. Research has also focused on pancreatic and oral microbiota. Changes in these microbiota can contribute to the development and progression of PC. Furthermore, patients with periodontal disease have an increased risk of developing PC. The potential use of microbiota as a prognostic marker or to predict patients' responses to chemotherapy or immunotherapy is also being explored. Overall, the role of microbiota-including the gut, pancreatic, and oral microbiota-in PC is an active research area. Understanding these associations could lead to new diagnostic and therapeutic targets for this deadly disease.

Microbial Influences on Immune Checkpoint Inhibitor Response in Melanoma: The Interplay between Skin and Gut Microbiota

Immunotherapy has revolutionized the treatment of melanoma, but its limitations due to resistance and variable patient responses have become apparent. The microbiota, which refers to the complex ecosystem of microorganisms that inhabit the human body, has emerged as a promising area of research for its potential role in melanoma development and treatment response. Recent studies have highlighted the role of microbiota in influencing the immune system and its response to melanoma, as well as its influence on the development of immune-related adverse events associated with immunotherapy. In this article, we discuss the complex multifactorial mechanisms through which skin and gut microbiota can affect the development of melanoma including microbial metabolites, intra-tumor microbes, UV light, and the immune system. In addition, we will discuss the pre-clinical and clinical studies that have demonstrated the influence of different microbial profiles on response to immunotherapy. Additionally, we will explore the role of microbiota in the development of immune-mediated adverse events.