Potential role of intratumor bacteria in mediating tumor resistance to the chemotherapeutic drug gemcitabine

Metagenome association study of the gut microbiome revealed biomarkers linked to chemotherapy outcomes in locally advanced and advanced lung cancer

Background

The gut microbiome is important in the development and immunotherapy efficacy of lung cancer. However, the relationship between the intestinal flora and chemotherapy outcomes remains unclear and was investigated in this study.

Methods

We analyzed baseline stool samples from patients with locally advanced and advanced lung cancer before chemotherapy treatment, through metagenomics of the gut microbiota. The composition, diversity, function, and metabolic pathway analysis were compared among patients with different clinical outcomes.

Results

From 64 patients, 33 responded to treatment (responders) and 31 did not (nonresponders). Streptococcus mutans and Enterococcus casseliflavus were enriched in responders (P < 0.05), while 11 bacteria including Leuconostoc lactis and Eubacterium siraeum were enriched in nonresponders (P < 0.05) by variance analysis. Responders were associated with significantly higher Acidobacteria and Granulicella, while Streptococcus oligofermentans, Megasphaera micronuciformis, and Eubacterium siraeum were more abundant in nonresponders by Lefse analysis. Streptococcus mutans and Enterococcus casseliflavus were further identified as bacterial markers relevant to responders using unsupervised clustering, and Leuconostoc lactis and Eubacterium siraeum were related to nonresponders. The L‐glutamate degradation VIII pathway was enriched in responders (P = 0.014), and the C4 photosynthetic carbon assimilation cycle, reductive TCA cycle I, and hexitol fermentation to lactate, formate, ethanol, and acetate were enriched in nonresponders (P < 0.05). Additionally, significant associations of bacterial species with clinical phenotypes were observed by Spearman correlation analysis.

Conclusions

The specific gut microbiome of patients with lung cancer might be connected to the clinical outcomes of chemotherapy.

Key points

The impact of modulating the gastrointestinal microbiota in cancer patients

Gastrointestinal microbiota is vastly deregulated in cancer patients due to different factors, but the exact mechanisms of interaction between cancer and microbiome are still poorly understood. Current evidence suggests that alterations in the composition of the microbiota may affect efficacy and toxicity of anti-cancer therapies. Recent preclinical and clinical studies demonstrate different mechanisms and outcomes of deregulation of gut microbiome, and investigate effects of modulating gastrointestinal microbiota in cancer patients. This paper reviews effects of altered microbiome on anti-cancer management, including antibiotics, chemotherapy and immunotherapy, as well as possible outcomes of modulating altered microbiome by probiotics or faecal microbiome transplantation in cancer patients.

Emerging role of bacterial extracellular vesicles in cancer

Shedding of microbial extracellular vesicles constitutes a universal mechanism for inter-kingdom and intra-kingdom communication that is conserved among prokaryotic and eukaryotic microbes. In this review we delineate fundamental aspects of bacterial extracellular vesicles (BEVs) including their biogenesis, cargo composition, and interactions with host cells. We critically examine the evidence that BEVs from the host gut microbiome can enter the circulatory system to disseminate to distant organs and tissues. The potential involvement of BEVs in carcinogenesis is evaluated and future research ideas explored. We further discuss the potential of BEVs in microbiome-based liquid biopsies for cancer diagnostics and bioengineering strategies for cancer therapy.

Microbiota Effects on Carcinogenesis: Initiation, Promotion, and Progression

Carcinogenesis is a multistep process by which normal cells acquire genetic and epigenetic changes that result in cancer. In combination with host genetic susceptibility and environmental exposures, a prominent procarcinogenic role for the microbiota has recently emerged. In colorectal cancer (CRC), three nefarious microbes have been consistently linked to cancer development: (a) Colibactin-producing Escherichia coli initiates carcinogenic DNA damage, (b) enterotoxigenic Bacteroides fragilis promotes tumorigenesis via toxin-induced cell proliferation and tumor-promoting inflammation, and (c) Fusobacterium nucleatum enhances CRC progression through two adhesins, Fap2 and FadA, that promote proliferation and antitumor immune evasion and may contribute to metastases. Herein, we use these three prominent microbes to discuss the experimental evidence linking microbial activities to carcinogenesis and the specific mechanisms driving this stepwise process. Precisely defining mechanisms by which the microbiota impacts carcinogenesis at each stage is essential for developing microbiota-targeted strategies for the diagnosis, prognosis, and treatment of cancer.

The role of gut microbiota in cancer treatment: friend or foe?

The gut microbiota has been implicated in cancer and shown to modulate anticancer drug efficacy. Altered gut microbiota is associated with resistance to chemo drugs or immune checkpoint inhibitors (ICIs), whereas supplementation of distinct bacterial species restores responses to the anticancer drugs. Accumulating evidence has revealed the potential of modulating the gut microbiota to enhance the efficacy of anticancer drugs. Regardless of the valuable findings by preclinical models and clinical data of patients with cancer, a more thorough understanding of the interactions of the microbiota with cancer therapy helps researchers identify novel strategy for cancer prevention, stratify patients for more effective treatment and reduce treatment complication. In this review, we discuss the scientific evidence on the role of gut microbiota in cancer treatment, and highlight the latest knowledge and technologies leveraged to target specific bacteria that contribute to tumourigenesis. First, we provide an overview of the role of the gut microbiota in cancer, establishing the links between bacteria, inflammation and cancer treatment. Second, we highlight the mechanisms used by distinct bacterial species to modulate cancer growth, immune responses, as well as the efficacy of chemotherapeutic drugs and ICIs. Third, we demonstrate various approaches to modulate the gut microbiota and their potential in translational research. Finally, we discuss the limitations of current microbiome research in the context of cancer treatment, ongoing efforts to overcome these challenges and future perspectives.

Microenvironmental Determinants of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) belongs to the most lethal solid tumors in humans. A histological hallmark feature of PDAC is the pronounced tumor microenvironment (TME) that dynamically evolves during tumor progression. The TME consists of different non-neoplastic cells such as cancer-associated fibroblasts, immune cells, endothelial cells, and neurons. Furthermore, abundant extracellular matrix components such as collagen and hyaluronic acid as well as matricellular proteins create a highly dynamic and hypovascular TME with multiple biochemical and physical interactions among the various cellular and acellular components that promote tumor progression and therapeutic resistance. In recent years, intensive research efforts have resulted in a significantly improved understanding of the biology and pathophysiology of the TME in PDAC, and novel stroma-targeted approaches are emerging that may help to improve the devastating prognosis of PDAC patients. However, none of anti-stromal therapies has been approved in patients so far, and there is still a large discrepancy between multiple successful preclinical results and subsequent failure in clinical trials. Furthermore, recent findings suggest that parts of the TME may also possess tumor-restraining properties rendering tailored therapies even more challenging.

Association between the use of antibiotics and efficacy of gemcitabine plus nab-paclitaxel in advanced pancreatic cancer

It is unclear whether the use of antibiotics is related to the efficacy of gemcitabine plus nab-paclitaxel (GnP). Therefore, we investigated the association between the use of antibiotics and efficacy of GnP.We conducted a retrospective single center study from January 2014 to December 2018 in Hokkaido University Hospital.Ninety-nine patients were eligible for the study. Thirty-seven used antibiotics (U) and 62 did not use antibiotics (NU) during GnP therapy. In the U group, 15 patients used β-lactam antibiotics, 21 used new quinolones, and 1 used carbapenem. The median progression-free survival was 5.8 and 2.7 months (hazards ratio [HR] .602, 95% confidence interval [CI] .391-.928, P = .022) and the median overall survival was 11.0 and 8.4 months (HR .768, 95% CI .491-1.202, P = .248) in the U and not use antibiotics groups, respectively. Antibiotic use (HR .489, 95% CI .287-.832, P = .008) and locally advanced pancreatic cancer (HR 1.808, 95% CI 1.051-3.112, P = .032) were independent prognostic factors for progression-free survival.Antibiotic use was associated with a higher efficacy of GnP, and therefore, it may be employed as a novel treatment strategy.

Simple synthesis of multifunctional photosensitizers for mitochondrial and bacterial imaging and photodynamic anticancer and antibacterial therapy

Photosensitizers (PSs), a critical drug administered for successful photodynamic therapy (PDT), have been well researched regarding their anticancer or bactericidal capability with high precision and low invasiveness. Although traditional PSs have been explored either in photodynamic anticancer or in antibiosis, they usually require synthesis with multiple steps, harsh synthetic conditions, and a complicated purification process for a single targeted product. Therefore, developing new multifunctional PSs with a simple synthesis and reactant flexibility which combine mitochondrial and bacterial imaging, efficient photodynamic anticancer and antibacterial effects is of the utmost urgency and of great importance for clinical applications. Herein, a large structural investigation of isoquinolinium-based PSs synthesized by a simple Rh-catalysed annulation reaction with high yields is presented. These lipophilic cationic PSs have a tunable photophysical property. LIQ-6 was found to perform not only as an ideal mitochondria targeting probe but also an effective cancer cell killing PS, and moreover, a tracker for bacterial imaging and ablation. LIQ-6 can be used to image a wide range of cancer cells and to monitor the photo-induced cell apoptosis, and simultaneously, it can also image and be a photodynamic germicide for both Gram-positive and Gram-negative bacteria. Furthermore, LIQ-6 shows great effectiveness in the wound healing process, showing its ability to be an ideal PS in vivo as well. This contribution is believed to offer a new platform for the construction of a theragnostic system for future practical applications in biology and biomedicine.

The Pancreatic Microbiome is Associated with Carcinogenesis and Worse Prognosis in Males and Smokers

Simple Summary

The cancer microbiome has been suggested to be closely involved in the immune dysregulation that leads to carcinogenesis. Given that pancreatic adenocarcinoma (PAAD) is one of the most lethal cancers, it is important to identify features of the microbiome that may contribute to more deadly PAAD tumors. In this study, we analyzed PAAD patient RNA-sequencing data from The Cancer Genome Atlas (TCGA) to correlate abundance of intra-pancreatic microbes to dysregulation of immune and cancer-associated genes and pathways. We discovered that the presence of several bacteria species within PAAD tumors is linked to metastasis and immune suppression. Furthermore, we found that the increased prevalence and poorer prognosis of PAAD in males and smokers are linked to the presence of potentially cancer-promoting or immune-inhibiting microbes. Further study into the roles of these microbes in PAAD is imperative for understanding how a pro-tumor microenvironment may be treated to limit cancer progression.

Abstract

An intra-pancreatic microbiota was recently discovered in several prominent studies. Since pancreatic adenocarcinoma (PAAD) is one of the most lethal cancers worldwide, and the intratumor microbiome was found to be a significant contributor to carcinogenesis in other cancers, this study aims to characterize the PAAD microbiome and elucidate how it may be associated with PAAD prognosis. We further explored the association between the intra-pancreatic microbiome and smoking and gender, which are both risk factors for PAAD. RNA-sequencing data from The Cancer Genome Atlas (TCGA) were used to infer microbial abundance, which was correlated to clinical variables and to cancer and immune-associated gene expression, to determine how microbes may contribute to cancer progression. We discovered that the presence of several bacteria species within PAAD tumors is linked to metastasis and immune suppression. This is the first large-scale study to report microbiome-immune correlations in human pancreatic cancer samples. Furthermore, we found that the increased prevalence and poorer prognosis of PAAD in males and smokers are linked to the presence of potentially cancer-promoting or immune-inhibiting microbes. Further study into the roles of these microbes in PAAD is imperative for understanding how a pro-tumor microenvironment may be treated to limit cancer progression.

Gut Microbes' Impact on Oncogenic Drivers: Location Matters

Recent work by Kadosh et al. (2020) suggests that mutant p53 activity in gut epithelia is influenced by local production of microbial metabolites. The switch of p53 from tumor suppressor to oncogene is location-dependent and is impacted by microbially derived gallic acid.

Cellular Mechanisms Accounting for the Refractoriness of Colorectal Carcinoma to Pharmacological Treatment

Simple Summary

Colorectal cancer (CRC) causes a high number (more than 800,000) of deaths worldwide each year. Better methods for early diagnosis and the development of strategies to enhance the efficacy of the therapeutic approaches used to complement or substitute surgical removal of the tumor are urgently needed. Currently available pharmacological armamentarium provides very moderate benefits to patients due to the high resistance of tumor cells to respond to anticancer drugs. The present review summarizes and classifies into seven groups the cellular and molecular mechanisms of chemoresistance (MOC) accounting for the failure of CRC response to the pharmacological treatment.

Abstract

The unsatisfactory response of colorectal cancer (CRC) to pharmacological treatment contributes to the substantial global health burden caused by this disease. Over the last few decades, CRC has become the cause of more than 800,000 deaths per year. The reason is a combination of two factors: (i) the late cancer detection, which is being partially solved by the implementation of mass screening of adults over age 50, permitting earlier diagnosis and treatment; (ii) the inadequate response of advanced unresectable tumors (i.e., stages III and IV) to pharmacological therapy. The latter is due to the existence of complex mechanisms of chemoresistance (MOCs) that interact and synergize with each other, rendering CRC cells strongly refractory to the available pharmacological regimens based on conventional chemotherapy, such as pyrimidine analogs (5-fluorouracil, capecitabine, trifluridine, and tipiracil), oxaliplatin, and irinotecan, as well as drugs targeted toward tyrosine kinase receptors (regorafenib, aflibercept, bevacizumab, cetuximab, panitumumab, and ramucirumab), and, more recently, immune checkpoint inhibitors (nivolumab, ipilimumab, and pembrolizumab). In the present review, we have inventoried the genes involved in the lack of CRC response to pharmacological treatment, classifying them into seven groups (from MOC-1 to MOC-7) according to functional criteria to identify cancer cell weaknesses. This classification will be useful to pave the way for developing sensitizing tools consisting of (i) new agents to be co-administered with the active drug; (ii) pharmacological approaches, such as drug encapsulation (e.g., into labeled liposomes or exosomes); (iii) gene therapy interventions aimed at restoring the impaired function of some proteins (e.g., uptake transporters and tumor suppressors) or abolishing that of others (such as export pumps and oncogenes).

Microbiota and Cancer: The Emerging Beneficial Role of Bifidobacteria in Cancer Immunotherapy

Many intestinal bacteria are believed to be involved in various inflammatory and immune processes that influence tumor etiology because of their metabolic properties and their ability to alter the microbiota homeostasis. Although many functions of the microbiota are still unclear, there is compelling experimental evidence showing that the intestinal microbiota is able to modulate carcinogenesis and the response to anticancer therapies, both in the intestinal tract and other body sites. Among the wide variety of gut-colonizing microorganisms, various species belonging to the Bifidobacterium genus are believed to elicit beneficial effects on human physiology and on the host-immune system. Recent findings, based on preclinical mouse models and on human clinical trials, have demonstrated the impact of gut commensals including bifidobacteria on the efficacy of tumor-targeting immunotherapy. Although the underlying molecular mechanisms remain obscure, bifidobacteria and other microorganisms have become a promising aid to immunotherapeutic procedures that are currently applied to treat cancer. The present review focuses on strategies to recruit the microbiome in order to enhance anticancer responses and develop therapies aimed at fighting the onset and progression of malignancies.

T-Cell Immunity in Pancreatic Cancer

Worldwide, approximately half a million people are diagnosed with pancreatic cancer every year, with mortality rates of more than 90%. T cells within pancreatic tumors are generally infrequent and incapable of eliciting antitumor immunity. Thus, pancreatic cancer is considered an "immunologically cold" tumor. However, recent studies clearly show that when T-cell immunity in pancreatic cancer is sufficiently induced, T cells become effective weapons. This fact suggests that to improve pancreatic cancer patients' clinical outcomes, we need to unveil the complex immune biology of this disease. In this review, we discuss the elements of tumor immunogenicity in the specific context of pancreatic malignancy.

The gut microbiome and potential implications for early-onset colorectal cancer

Recently, there has been an unexpected trend toward increased incidence of colorectal cancer in younger individuals, particularly distal colon and rectal cancer in those under age 50. There is evidence to suggest that the human gut microbiome may play a role in carcinogenesis. The microbiome is dynamic and varies with age, geography, ethnicity and diet. Certain bacteria such as Fusobacterium nucleatum have been implicated in the development of colorectal and other gastrointestinal cancers. Recent data suggest that bacteria can alter the inflammatory and immune environment, influencing carcinogenesis, lack of treatment response and prognosis. Studies to date focus on older patients. Because the microbiome varies with age, it could be a potential explanation for the rise in early-onset colorectal cancer.

A pilot clinical trial of the cytidine deaminase inhibitor tetrahydrouridine combined with decitabine to target DNMT1 in advanced, chemorefractory pancreatic cancer

DNA methyltransferase 1 (DNMT1) is scientifically validated as a molecular target to treat chemo-resistant pancreatic ductal adenocarcinoma (PDAC). Results of clinical studies of the pyrimidine nucleoside analog decitabine to target DNMT1 in PDAC have, however, disappointed. One reason is high expression in PDAC of the enzyme cytidine deaminase (CDA), which catabolizes decitabine within minutes. We therefore added tetrahydrouridine (THU) to inhibit CDA with decitabine. In this pilot clinical trial, patients with advanced chemorefractory PDAC ingested oral THU ~10 mg/kg/day combined with oral decitabine ~0.2 mg/kg/day, for 5 consecutive days, then 2X/week. We treated 13 patients with extensively metastatic chemo-resistant PDAC, including 8 patients (62%) with ascites: all had received ≥ 1 prior therapies including gemcitabine/nab-paclitaxel in 9 (69%) and FOLFIRINOX in 12 (92%). Median time on THU/decitabine treatment was 35 days (range 4-63). The most frequent treatment-attributable adverse event was anemia (n=5). No deaths were attributed to THU/decitabine. Five patients had clinical progressive disease (PD) prior to week 8. Eight patients had week 8 evaluation scans: 1 had stable disease and 7 PD. Median overall survival was 3.1 months. Decitabine systemic exposure is expected to decrease neutrophil counts; however, neutropenia was unexpectedly mild. To identify reasons for limited systemic decitabine effect, we measured plasma CDA enzyme activity in PDAC patients, and found a > 10-fold increase in those with metastatic vs resectable PDAC. We concluded that CDA activity is increased not just locally but also systemically in metastatic PDAC, suggesting a need for even higher CDA-inhibitor doses than used here.

Radiation Therapy-Induced Changes of the Nasopharyngeal Commensal Microbiome in Nasopharyngeal Carcinoma Patients

PURPOSE

The human commensal microbiome has been suggested to be involved in the regulation of response to anticancer therapies. However, little is known regarding changes in commensal microbes in patients with cancer during radiation therapy. We conducted a prospective, longitudinal proof-of-concept cohort study with patients with newly diagnosed nasopharyngeal carcinoma (NPC) who underwent radiation therapy-based treatment.

METHODS AND MATERIALS

Nasopharyngeal swabs were collected before radiation therapy, twice per week during radiation therapy, and after radiation therapy. The nasopharyngeal microbiome was assessed using 16S rRNA amplicon sequencing. A patient's response to treatment was measured 3 months after the completion of radiation therapy as a short-term clinical outcome. In total, 39 NPC patients with 445 nasopharyngeal samples were analyzed.

RESULTS

There was stable temporal change in the community structure of the nasopharyngeal microbiome among patients with NPC during treatment (P = .0005). Among 73 abundant amplicon sequence variants (ASVs), 7 ASVs assigned to genus Corynebacterium decreased significantly during the treatment (W-statistic >80%); 23 ASVs showed statistically significant changes in the ratio of abundance between early and late responders during treatment (false discovery rate <0.05).

CONCLUSIONS

This study addressed stable temporal change in the nasopharyngeal microbiome among patients with NPC during radiation therapy-based treatment and provided preliminary evidence of an association with a short-term clinical outcome.

Bacterial lipopolysaccharide as negative predictor of gemcitabine efficacy in advanced pancreatic cancer - translational results from the AIO-PK0104 Phase 3 study

Background

Gram-negative bacteria mediated gemcitabine resistance in pre-clinical models. We determined if intratumoural lipopolysaccharide (LPS) detection by immunohistochemistry is associated with outcome in advanced pancreatic ductal adenocarcinoma (PDAC) treated with gemcitabine and non-gemcitabine containing 1st-line chemotherapy.

Methods

We examined LPS on tumour tissue from 130 patients treated within the randomised AIO-PK0104 trial and a validation cohort (n = 113) and analysed the association of LPS detection to patient outcome according to treatment subgroups.

Results

In 24% of samples from the AIO-PK0104 study LPS was detected; in LPS-positive patients median OS was 4.4 months, compared to 7.3 months with LPS negative tumours (HR 1.732, p = 0.010). A difference in OS was detected in 1st-line gemcitabine-treated patients (n = 71; HR 2.377, p = 0.002), but not in the non-gemcitabine treatment subgroup (n = 59; HR 1.275, p = 0.478). Within the validation cohort, the LPS positivity rate was 23%, and LPS detection was correlated with impaired OS in the gemcitabine subgroup (n = 94; HR 1.993, p = 0.008) whereas no difference in OS was observed in the non-gemcitabine subgroup (n = 19; HR 2.596, p = 0.219).

Conclusions

The detection of intratumoural LPS as surrogate marker for gram-negative bacterial colonisation may serve as a negative predictor for gemcitabine efficacy in advanced PDAC.

Clinical trial registry

The Clinical trial registry identifier is NCT00440167.

Intracellular Porphyromonas gingivalis Promotes the Tumorigenic Behavior of Pancreatic Carcinoma Cells

Porphyromonas gingivalis is a member of the dysbiotic oral microbiome associated with oral inflammation and periodontal disease. Intriguingly, epidemiological studies link P. gingivalis to an increased risk of pancreatic cancer. Given that oral bacteria are detected in human pancreatic cancer, and both mouse and human pancreata harbor microbiota, we explored the involvement of P. gingivalis in pancreatic tumorigenesis using cell lines and a xenograft model. Live P. gingivalis induced proliferation of pancreatic cancer cells; however, surprisingly, this effect was independent of Toll-like receptor 2, the innate immune receptor that is engaged in response to P. gingivalis on other cancer and immune cells, and is required for P. gingivalis to induce alveolar bone resorption. Instead, we found that P. gingivalis survives inside pancreatic cancer cells, a trait that can be enhanced in vitro and is increased by hypoxia, a central characteristic of pancreatic cancer. Increased tumor cell proliferation was related to the degree of intracellular persistence, and infection of tumor cells with P. gingivalis led to enhanced growth in vivo. To the best of our knowledge, this study is the first to demonstrate the direct effect of exposure to P. gingivalis on the tumorigenic behavior of pancreatic cancer cell lines. Our findings shed light on potential mechanisms underlying the pancreatic cancer–periodontitis link.

Regulation and modulation of antitumor immunity in pancreatic cancer

Pancreatic ductal adenocarcinoma carries a dismal prognosis, and outcomes have improved little with modern therapeutics. Checkpoint-based immunotherapy has failed to elicit responses in the vast majority of patients with pancreatic cancer. Alongside tumor cell-intrinsic mechanisms associated with oncogenic KRAS-induced inflammation, the tolerogenic myeloid cell infiltrate has emerged as a critical impediment to adaptive antitumor immune responses. Furthermore, the discovery of an intratumoral microbiome and the elucidation of host-microbe interactions that curtail antitumor immunity also present opportunities for intervention. Here we review the mechanisms of immunotherapy resistance in pancreatic ductal adenocarcinoma and discuss strategies to directly augment T cell responses in parallel with myeloid cell- and microbiome-targeted approaches that may enable immune-mediated control of this malignancy.

Strain-level epidemiology of microbial communities and the human microbiome

The biological importance and varied metabolic capabilities of specific microbial strains have long been established in the scientific community. Strains have, in the past, been largely defined and characterized based on microbial isolates. However, the emergence of new technologies and techniques has enabled assessments of their ecology and phenotypes within microbial communities and the human microbiome. While it is now more obvious how pathogenic strain variants are detrimental to human health, the consequences of subtle genetic variation in the microbiome have only recently been exposed. Here, we review the operational definitions of strains (e.g., genetic and structural variants) as they can now be identified from microbial communities using different high-throughput, often culture-independent techniques. We summarize the distribution and diversity of strains across the human body and their emerging links to health maintenance, disease risk and progression, and biochemical responses to perturbations, such as diet or drugs. We list methods for identifying, quantifying, and tracking strains, utilizing high-throughput sequencing along with other molecular and “culturomics” technologies. Finally, we discuss implications of population studies in bridging experimental gaps and leading to a better understanding of the health effects of strains in the human microbiome.

Bidirectional interaction between intestinal microbiome and cancer: opportunities for therapeutic interventions

Gut microbiota composition influences the balance between human health and disease. Increasing evidence suggests the involvement of microbial factors in regulating cancer development, progression, and therapeutic response. Distinct microbial species have been implicated in modulating gut environment and architecture that affects cancer therapy outcomes. While some microbial species offer enhanced cancer therapy response, others diminish cancer treatment efficacy. In addition, use of antibiotics, often to minimize infection risks in cancer, causes intestinal dysbiosis and proves detrimental. In this review we discuss the role of gut microbiota in cancer development and therapy. We also provide insights into future strategies to manipulate the microbiome and gut epithelial barrier to augment therapeutic responses while minimizing toxicity or infection risks.

Biomarker discovery and beyond for diagnosis of bladder diseases

Molecular biosignatures of altered cellular landscapes and functions have been casually linked with pathological conditions, which imply the promise of biomarkers specific to bladder diseases, such as bladder cancer and other dysfunctions. Urinary biomarkers are particularly attractive due to costs, time, and the minimal and noninvasive efforts acquiring urine. The evolution of omics platforms and bioinformatics for analyzing the genome, epigenome, transcriptome, proteome, lipidome, metabolome, etc., have enabled us to develop more sensitive and disease-specific biomarkers. These discoveries broaden our understanding of the complex biology and pathophysiology of bladder diseases, which can ultimately be translated into the clinical setting. In this short review, we will discuss current efforts on identification of promising urinary biomarkers of bladder diseases and their roles in diagnosis and monitoring. With these considerations, we also aim to provide a prospective view of how we can further utilize these bladder biomarkers in developing ideal and smart medical devices that would be applied in the clinic.

Characterization of B cell-mediated PD-1/PD-L1 interaction in pancreatic cancer patients

Pancreatic ductal adenocarcinoma (PDAC) is a common type of pancreatic cancer with one of the worst survival rate of all malignancies. Recent studies have identified that immunosuppressive B cells could employ the PD-1/PD-L1 pathway to suppress antitumour T cell responses; hence, we examined the expression and function of PD-L1 in B cells. We found that the PD-L1 expression was significantly enriched in tumour-infiltrating (TI) B cells than in peripheral blood (PB) B cells from the same patients. Additionally, the PB B cells from stage III and stage IV PDAC patients presented significantly higher PD-L1 than the PB B cells from healthy controls. High PD-L1 expression in PB B cells could be achieved by stimulation via CpG and less effectively via anti-BCR plus CD40L, but not by coculture with pancreatic cancer cell lines in vitro. Also, STAT1 and STAT3 inhibition significantly suppressed PD-L1 upregulation in stimulated B cells. CpG-stimulated PB B cells could inhibit the IFN-γ expression and proliferation of CD8 T cells in a PD-L1-dependent manner. Also, TI CD8 T cells incubated with whole TI B cells presented significantly lower IFN-γ expression and lower proliferation, than TI CD8 T cells incubated with PD-L1+  cell-depleted TI B cells, suggesting that PD-L1+  B cells could also suppress CD8 T cells in the tumour. Overall, this study identified that B cells could suppress CD8 T cells via PD-L1 expression, indicating a novel pathway of immuno-regulation in pancreatic cancer.

The pint- sized powerhouse: Illuminating the mighty role of the gut microbiome in improving the outcome of anti- cancer therapy

Cancer persists as a major health catastrophe and a leading cause of widespread mortality across every nation. Research of several decades has increased our understanding of the pivotal pathways and key players of the host during tumor development and progression, which has enabled generation of precision therapeutics with improved efficacy. Despite such tremendous advancements in our combat against this fatal disease, a majority of the cancer patients suffer from poor tumor- free survival owing to the increased incidence of recurrent tumor. This is primarily due to the development of resistance against contemporary anti- cancer strategies. Recent studies have pointed towards the involvement of the human symbiotic gut microbiota in regulating the outcome of chemotherapy and immunotherapy. It does so primarily by modulating the metabolism of the drugs and host immune response, thereby enhancing the efficacy and ameliorating the toxicity. The interactions between the therapeutic agents, microbial community and host immunity may provide a new avenue for the clinical management of cancer. In addition, consumption of dietary pro-, pre- and synbiotics has been recognized to confer protection against tumor genesis and also promote improved response to traditional tumor suppressive strategies. Naturally, the use of various combinatorial regimes containing dietary supplements that improve the gut microbiome in amalgamation with conventional cancer treatment methods may significantly augment the therapeutic outcome of cancer patients and circumnavigate the resistance mechanisms that confound traditional therapies. In this review, we have summarized the role of the gut microbiome, which is the largest assembly of commensals within the human body, in regulating the efficacy and toxicity of various existing anti- cancer therapies including chemotherapy, immunotherapy and surgery. Furthermore, we have discussed how novel strategies integrating the application of probiotics, prebiotics, synbiotics and antibiotics in combination with the aforementioned anti- cancer modules manipulate the gut microbiota and, therefore, augment their therapeutic outcome. Together, such innovative anti- tumorigenic approaches may prove highly effective in improving the prognosis of cancer patients.

Jab1-siRNA Induces Cell Growth Inhibition and Cell Cycle Arrest in Gall Bladder Cancer Cells via Targeting Jab1 Signalosome

BACKGROUND

The aberrant alteration in Jab1 signalosome (COP9 Signalosome Complex Subunit 5) has been proven to be associated with the progression of several carcinomas. However the specific role and mechanism of action of Jab1 signalosome in carcinogenesis of gall bladder cancer (GBC) are poorly understood.

OBJECTIVE

The main objective of our study was to elucidate the role and mechanism of Jab1 signalosome in gall bladder cancer by employing siRNA.

METHODS

Jab1 overexpression was identified in gall bladder cancer tissue sample. The role of Jab1-siRNA approach in cell growth inhibition and apoptotic induction was then examined by RT-PCR, Western Blotting, MTT, ROS, Hoechst and FITC/Annexin-V staining.

RESULTS

In the current study, we have shown that overexpression of Jab1 stimulated the proliferation of GBC cells; whereas downregulation of Jab1 by using Jab1-siRNA approach resulted incell growth inhibition and apoptotic induction. Furthermore, we found that downregulation of Jab1 induces cell cycle arrest at G1 phase and upregulated the expression of p27, p53 and Bax gene. Moreover, Jab1-siRNA induces apoptosis by enhancing ROS generation and caspase-3 activation. In addition, combined treatment with Jab1-siRNA and gemicitabine demonstrated an enhanced decline in cell proliferation which further suggested increased efficacy of gemcitabine at a very lower dose (5μM) in combination with Jab1-siRNA.

CONCLUSION

In conclusion, our study strongly suggests that targeting Jab1 signalosome could be a promising therapeutic target for the treatment of gall bladder cancer.

Characterization of the human tumor microbiome reveals tumor-type specific intra-cellular bacteria

Many characteristics of cancer such as proliferation, survival, progression, immunogenicity, sensitivity, and resistance to therapy are not just endogenously driven by the tumor cells themselves, but are greatly affected by their interaction with the components of their microenvironment. In our recent report, we comprehensively characterized the bacterial content of solid tumors, which is strongly related to tumor type and subtype, largely presenting as metabolically-active and intra-cellular. Our integration with clinical patient data indicates potential avenues of cross-talk between the tumors and their bacterial counterparts paving the way for a deeper understanding of the physiological/biological context of the tumor and how to harness bacteria in therapy settings.

The microbiome in pancreatic diseases: Recent advances and future perspectives

The human microbiota exerts multiple physiological functions such as the regulation of metabolic and inflammatory processes. High-throughput sequencing techniques such as next-generation sequencing have become widely available in preclinical and clinical settings and have exponentially increased our knowledge about the microbiome and its interaction with host cells and organisms. There is now emerging evidence that microorganisms also contribute to inflammatory and neoplastic diseases of the pancreas. This review summarizes current clinical and translational microbiome studies in acute and chronic pancreatitis as well as pancreatic cancer and provides evidence that the microbiome has a high potential for biomarker discovery. Furthermore, the intestinal and pancreas-specific microbiome may also become an integrative part of diagnostic and therapeutic approaches of pancreatic diseases in the near future.

Microbiome dysbiosis in cancer: Exploring therapeutic strategies to counter the disease

Cancer being a multiplex disease which involves many genomic and physiological alterations that occur consistently in the cancerous tissue, making the treatment and management of the disease even more complicated. The human gut microbiota (GM) harbors collective genomes of microbes comprising of trillions of bacteria along with fungi, archaea, and viruses that have the tendency to affect the development and progression of cancer. Moreover, inter-microbial interactions, diversity and distinct differences among the GM populations could influence the course of disease, making the microbiome an ideal target or to be modulated in such a way so as to improve cancer therapeutics with better efficacy and reduced toxicity. Current review focuses upon exploring the association of gut microbiota with the progression of cancer for which a structured search of bibliographic databases for peer-reviewed research literature has been carried out using focused review questions and inclusion/exclusion criteria. Through this review one could envisage a wide-spectrum role of microbiota in maintaining host metabolism, immune homeostasis paving the way for an anticancer diagnostic and therapeutic solution that has the potential to counter the menace of anti-cancer drug resistance as well.

Can we harness the microbiota to enhance the efficacy of cancer immunotherapy?

There is currently much interest in defining how the microbiota shapes immune responses in the context of cancer. Various studies in both mice and humans have associated particular commensal species with better (or worse) outcomes in different cancer types and following treatment with cancer immunotherapies. However, the mechanisms involved remain ill-defined and even controversial. In this Viewpoint, Nature Reviews Immunology has invited six eminent scientists in the field to share their thoughts on the key questions and challenges for the field.

Differential immune microenvironmental features of microsatellite-unstable colorectal cancers according to Fusobacterium nucleatum status

It has been suggested that Fusobacterium nucleatum (Fn) may differentially impact tumor immune responses according to microsatellite instability (MSI) status in colorectal cancers (CRCs). We aimed to reveal the detailed relationship between intratumoral Fn and immune microenvironmental features in MSI-high CRCs. A total of 126 MSI-high CRCs were subjected to analyses for intratumoral Fn DNA load using quantitative PCR and for densities of tumor-infiltrating immune cells, including CD3⁺ T cells, CD4⁺ T cells, CD8⁺ T cells, FoxP3⁺ T cells, CD68⁺ macrophages, CD163⁺ macrophages, and CD177⁺ neutrophils, at invasive margin (IM) and center of tumor (CT) areas using computational image analysis of immunohistochemistry. Based on the Fn load, the 126 MSI-high CRCs were classified into Fn-high, -low, and -negative subgroups. The Fn-high subset of MSI-high CRCs was significantly correlated with larger tumor size and advanced invasion depth (p = 0.017 and p = 0.034, respectively). Compared with the Fn-low/negative subgroup, Fn-high tumors demonstrated significantly lower density of FoxP3⁺ cells in both IM and CT areas (p = 0.002 and p = 0.003, respectively). Additionally, Fn-high was significantly associated with elevated CD163⁺ cell to CD68⁺ cell ratio in only CT areas of MSI-high CRCs (p = 0.028). In conclusion, the Fn-enriched subset of MSI-high CRCs is characterized by increased tumor growth and invasion and distinct immune microenvironmental features, including decreased FoxP3⁺ T cells throughout the tumor and increased proportion of M2-polarized macrophages in the tumor center. These findings collectively support that Fn may be linked to pro-tumoral immune responses in MSI-high CRCs.

Meta-analysis of randomized clinical trials of adjuvant chemotherapy for resected biliary tract cancers

BACKGROUND

This meta-analysis was performed by analyzing randomized controlled trials (RCTs) to assess the potential prognostic value of adjuvant chemotherapy (ACT) for patients with resected biliary tract cancers (BTCs).

METHODS

PubMed, EMBASE, and the Cochrane Library were searched for relevant articles published. Only RCTs affected by tumors of gallbladder, intrahepatic, perihilar, and distal bile ducts were considered. Data were pooled using a random-effects model. The primary endpoint of the study was overall survival (OS).

RESULTS

The study identified 1192 patients who met the inclusion and exclusion criteria. ACT had nearly reached a significant better OS (HR, 0.88; 95% CI, 0.77-1.01; P = 0.07) and achieved a significant better RFS (HR, 0.83; 95% CI, 0.69-0.99; P = 0.04). The effectiveness of ACT for OS was significantly modified by fluorouracil-based ACT (HR, 0.83; 95% CI, 0.70-0.99; P = 0.04), but not by gemcitabine-based ACT (HR, 0.91; 95% CI, 0.74-1.12; P = 0.36). The survival benefit was also not modified by primary disease site, resection margin status, and lymph node status.

CONCLUSIONS

ACT is correlated with favorable relapse-free survival compared with non-ACT for resected BTCs patients. Fluorouracil-based ACT could be viewed as a standard practice for resected BTCs patients regardless of the primary cancer site, lymph node or margin status.

Antibacterial Use Is Associated with an Increased Risk of Hematologic and Gastrointestinal Adverse Events in Patients Treated with Gemcitabine for Stage IV Pancreatic Cancer

BACKGROUND

Preclinical evidence has demonstrated that common intratumor bacteria metabolize the chemotherapeutic drug gemcitabine. The significance of this bacterial metabolism pathway, relative to the known metabolic pathways by host enzymes, is not known. We hypothesized that bacterial metabolism is clinically significant and that "knockdown" by antibacterial therapy has the unintended effect of increasing the effective dose of gemcitabine, thereby increasing the risk for gemcitabine-associated toxicities.

MATERIALS AND METHODS

We reanalyzed the comparator arm of the MPACT trial (NCT01442974), made available through Project Data Sphere, LLC (CEO Roundtable on Cancer's Life Sciences Consortium, Cary, NC; www.projectdatasphere.org). In this arm, 430 patients with metastatic pancreatic adenocarcinoma were treated with gemcitabine. We used the Anderson-Gill survival model to compare the risk of developing an adverse event after antibacterial prescription with time unexposed to antibacterials. Adverse events of grade 3 and greater were considered at three levels of granularity: all aggregated into one endpoint, aggregated by class, and taken individually. Antibiotic exposures were analyzed in aggregate as well as by class.

RESULTS

Antibacterial exposure was associated with an increased risk of adverse events (hazard ratio [HR]: 1.77; confidence interval [CI]: 1.46-2.14), any hematologic adverse event (HR: 1.64; CI: 1.26-2.13), and any gastrointestinal adverse event (HR: 2.14; CI: 1.12-4.10) but not a constitutional (HR: 1.33; CI: 0.611-2.90) or hepatologic adverse event (HR: 0.99; CI: 0.363-2.71). Among specific adverse events, antibacterial exposure was associated with an increased risk of anemia (HR: 3.16; CI: 1.59-6.27), thrombocytopenia (HR: 2.52; CI: 1.31-4.85), leukopenia (HR: 3.91; CI: 1.46-10.5), and neutropenia (HR: 1.53; CI: 1.07-2.17) but not any other specific adverse events.

CONCLUSION

Antibacterial exposure was associated with an increased risk of gemcitabine-associated, dose-limiting adverse events, including aggregate hematologic and gastrointestinal events, as well as four specific hematologic adverse events, suggesting that intratumor bacteria may be responsible for a clinically significant portion of gemcitabine metabolism. Alternative avenues of evidence will be necessary to confirm this preliminary finding and assess its generalizability. There is plentiful opportunity for similar analyses on other clinical trial data sets, where gemcitabine or other biomimetic small molecules were used.

IMPLICATIONS FOR PRACTICE

Patients treated with gemcitabine for metastatic pancreatic ductal adenocarcinoma have an increased rate of gemcitabine-associated toxicity during and after antibiotic therapy. This observation is consistent with preclinical evidence that intratumor bacteria metabolize gemcitabine to an inactive form. Further research is needed to determine whether this observation merits any changes in clinical practice.

The Microbiome in Immuno-oncology

The field of cancer therapy has been revolutionized through the use of immunotherapy, and treatment with these therapies now spans from early to late stage, and even into prevention. However, there are still a significant proportion of patients who do not derive long-term benefit from monotherapy and even combined therapy regimens, and novel approaches are needed to enhance therapeutic responses. Additionally, ideal biomarkers of response to immunotherapy are lacking and are critically needed. An emerging area of interest in immuno-oncology (IO) is the microbiome, which refers to the collection of microbes (and their genomes) that inhabit an individual and live in symbiosis. There is now evidence that these microbes (particularly those within the gut) impact host physiology and can impact responses to immunotherapy. The field of microbiome research in immuno-oncology is quickly emerging, with the potential use of the microbiome (in the gut as well as in the tumor) as a biomarker for response to IO as well as a therapeutic target. Notably, the microbiome may even have a role in toxicity to therapy. The state of the science in microbiome and IO are discussed and caveats and future directions are outlined to provide insights as we move forward as a field.

Environmental Remediation of Antineoplastic Drugs: Present Status, Challenges, and Future Directions

The global burden of cancer is on the rise, and as a result, the number of therapeutics administered for chemotherapy is increasing. The occupational exposure, recalcitrant nature and ecotoxicological toxicity of these therapeutics, referred to as antineoplastic (ANP) drugs, have raised concerns about their safe remediation. This review provides an overview of the environmental source of ANPs agents, with emphasis on the currently used remediation approaches. Outpatient excreta, hospital effluents, and waste from pharmaceutical industries are the primary source of ANP waste. The current review describes various biotic and abiotic methods used in the remediation of ANP drugs in the environment. Abiotic methods often generate transformation products (TPs) of unknown toxicity. In this light, obtaining data on the environmental toxicity of ANPs and its TPs is crucial to determine their toxic effect on the ecosystem. We also discuss the biodegradation of ANP drugs using monoculture of fungal and bacterial species, and microbial consortia in sewage treatment plants. The current review effort further explores a safe and sustainable approach for ANP waste treatment to replace existing chemical and oxidation intensive treatment approaches. To conclude, we assess the possibility of integrating biotic and abiotic methods of ANP drug degradation.

Gut Microbiome Modulation Via Fecal Microbiota Transplant to Augment Immunotherapy in Patients with Melanoma or Other Cancers

PURPOSE OF REVIEW

We review emerging evidence regarding the impact of gut microbes on antitumor immunity, and ongoing efforts to translate this in clinical trials.

RECENT FINDINGS

Pre-clinical models and human cohort studies support a role for gut microbes in modulating overall immunity and immunotherapy response, and numerous trials are now underway exploring strategies to modulate gut microbes to enhance responses to cancer therapy. This includes the use of fecal microbiota transplant (FMT), which is being used to treat patients with Clostridium difficile infection among other non-cancer indications. The use of FMT is now being extended to modulate gut microbes in patients being treated with cancer immunotherapy, with the goal of enhancing responses and/or to ameliorate toxicity. However, significant complexities exist with such an approach and will be discussed herein. Data from ongoing studies of FMT in cancer will provide critical insights for optimization of this approach.

Gut microbiota contributes towards immunomodulation against cancer: New frontiers in precision cancer therapeutics

The microbiota influences human health and the development of diverse diseases, including cancer. Microbes can influence tumor initiation and development in either a positive or negative manner. In addition, the composition of the gut microbiota affects the efficacy and toxicity of cancer therapeutics as well as therapeutic resistance. The striking impact of microbiota on oncogenesis and cancer therapy provides compelling evidence to support the notion that manipulating microbial networks represents a promising strategy for treating and preventing cancer. Specific microbes or the microbial ecosystem can be modified via a multiplicity of processes, and therapeutic methods and approaches have been evolving. Microbial manipulation can be applied as an adjunct to traditional cancer therapies such as chemotherapy and immunotherapy. Furthermore, this approach displays great promise as a stand-alone therapy following the failure of standard therapy. Moreover, such strategies may also benefit patients by avoiding the emergence of toxic side effects that result in treatment discontinuation. A better understanding of the host-microbial ecosystem in patients with cancer, together with the development of methodologies for manipulating the microbiome, will help expand the frontiers of precision cancer therapeutics, thereby improving patient care. This review discusses the roles of the microbiota in oncogenesis and cancer therapy, with a focus on efforts to harness the microbiota to fight cancer.

Functionalization of Ti substrate with pH-responsive naringin-ZnO nanoparticles for the reconstruction of large bony after osteosarcoma resection

After bone tumor resection, the large bony deficits are commonly reconstructed with Ti-based metallic endoprosthesis, which provide immediate stable fixation and allow early ambulation and weight bearing. However, when used in osteosarcoma resection, Ti implant-relative infection and tumor recurrence were recognized as the two critical factors for implantation failure. Hence, in this work, a novel zinc oxide nanoparticle decorating with naringin was prepared and immobilized onto Ti substrate. The drugs delivery profiles proved that in the bacterial infection and Warburg effect of osteosarcoma-induced acidic condition, naringin and Zn²⁺ can be released easily from the functional Ti substrate. The anti-osteosarcoma and antibacterial assay showed the delivered naringin and Zn²⁺ can induce a remarkable increase of oxidative stress in bacteria (Escherichia coli and Staphylococcus aureus) and osteosarcoma (Saos-2 cells) by producing reactive oxygen species (ROS). Accumulation of ROS results in damage of bacterial biofilm and bacterial membrane, leading to the leakage of bacterial RNA and DNA. Meanwhile, the increase of ROS induces osteosarcoma cell apoptosis by activating ROS/extracellular signal-regulated kinase signaling pathway. Furthermore, in vitro cellular experiments, including cell viability, alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization level, indicated that the functional Ti substrate exhibited great potential for osteoblasts proliferation and differentiation. Hence, this study provides a simple and promising strategy of developing multifunctional Ti-based implants for the reconstruction of large bony after osteosarcoma resection.

Antibiotics Improve the Treatment Efficacy of Oxaliplatin-Based but Not Irinotecan-Based Therapy in Advanced Colorectal Cancer Patients

Background

Oxaliplatin and irinotecan are generally used to treat advanced colorectal cancer (CRC) patients. Antibiotics improve the cytotoxicity of oxaliplatin but not irinotecan in a colon cancer cell line in vitro. This study retrospectively assessed whether antibiotics improve the treatment efficacy of oxaliplatin- but not irinotecan-based therapy in advanced CRC patients. Patients and Methods. The medical records of 220 advanced CRC patients who underwent oxaliplatin- or irinotecan-based therapy were retrospectively reviewed. The oxaliplatin and irinotecan groups were further divided into antibiotic-treated (group 1) and antibiotic-untreated (group 2) subgroups.

Results

In oxaliplatin groups 1 and 2, the response rate (RR) was 58.2% and 30.2%, while the disease control rate (DCR) was 92.5% and 64.2%, respectively; the median progression-free survival (PFS) was 10.5 months (95% confidence interval (CI) = 7.5–12.2) and 7.0 months (95% CI = 17.0–26.0), respectively, and the median overall survival (OS) was 23.8 months (95% CI = 5.1–9.1) and 17.4 months (95% CI = 13.1–24.9), respectively. In irinotecan groups 1 and 2, the RR was 17.8% and 20.0%, while the DCR was 75.6% and 69.1%, respectively; the median PFS was 8.2 months (95% CI = 6.2–12.7) and 7.9 months (95% CI = 12.0–23.0), respectively, and the median OS was 16.8 months (95% CI = 5.9–10.6) and 13.1 months (95% CI = 10.4–23.7), respectively.

Conclusion

To improve the treatment efficacy of oxaliplatin-based therapy in advanced CRC patients, adding antibiotics is a potential therapeutic option.

The microbiome in pediatric oncology

The human microbiome comprises a diverse set of microorganisms, which play a mostly cooperative role in processes such as metabolism and host defense. Next-generation genomic sequencing of bacterial nucleic acids now can contribute a much broader understanding of the diverse organisms composing the microbiome. Emerging evidence has suggested several roles of the microbiome in pediatric hematology/oncology, including susceptibility to infectious diseases, immune response to neoplasia, and contributions to the tumor microenvironment as well as changes to the microbiome from chemotherapy and antibiotics with unclear consequences. In this review, the authors have examined the evidence of the role of the microbiome in pediatric hematology/oncology, discussed how the microbiome may be modulated, and suggested key questions in need of further exploration.

The human tumor microbiome is composed of tumor type-specific intracellular bacteria

Bacteria were first detected in human tumors more than 100 years ago, but the characterization of the tumor microbiome has remained challenging because of its low biomass. We undertook a comprehensive analysis of the tumor microbiome, studying 1526 tumors and their adjacent normal tissues across seven cancer types, including breast, lung, ovary, pancreas, melanoma, bone, and brain tumors. We found that each tumor type has a distinct microbiome composition and that breast cancer has a particularly rich and diverse microbiome. The intratumor bacteria are mostly intracellular and are present in both cancer and immune cells. We also noted correlations between intratumor bacteria or their predicted functions with tumor types and subtypes, patients' smoking status, and the response to immunotherapy.

Gut microbiota modulation: a novel strategy for prevention and treatment of colorectal cancer

Research about the role of gut microbiome in colorectal cancer (CRC) is a newly emerging field of study. Gut microbiota modulation, with the aim to reverse established microbial dysbiosis, is a novel strategy for prevention and treatment of CRC. Different strategies including probiotics, prebiotics, postbiotics, antibiotics, and fecal microbiota transplantation (FMT) have been employed. Although these strategies show promising results, mechanistically by correcting microbiota composition, modulating innate immune system, enhancing gut barrier function, preventing pathogen colonization and exerting selective cytotoxicity against tumor cells, it should be noted that they are accompanied by risks and controversies that can potentially introduce clinical complications. During bench-to-bedside translation, evaluation of risk-and-benefit ratio, as well as patient selection, should be carefully performed. In view of the individualized host response to gut microbiome intervention, developing personalized microbiome therapy may be the key to successful clinical treatment.

The promise and challenge of cancer microbiome research

Many microbial agents have been implicated as contributors to cancer genesis and development, and the search to identify and characterize new cancer-related organisms is ongoing. Modern developments in methodologies, especially culture-independent approaches, have accelerated and driven this research. Recent work has shed light on the multifaceted role that the community of organisms in and on the human body plays in cancer onset, development, detection, treatment, and outcome. Much remains to be discovered, however, as methodological variation and functional testing of statistical correlations need to be addressed for the field to advance.

Intervention strategies for microbial therapeutics in cancer immunotherapy

Immunotherapies have drastically improved clinical outcomes in a wide range of malignancies. Nevertheless, patient responses remain highly variable, and reliable biomarkers that predict responses accurately are not yet fully understood. Compelling evidence from preclinical studies and observational data from clinical cohorts have shown that commensal microorganisms that reside in the human gastrointestinal tract, collectively termed the ‘microbiome’, can actively modify responses to chemotherapeutic agents and immunotherapies by influencing host immunosurveillance. Notably, microbial correlates are largely context specific, and response signatures may vary by patient population, geographic location and type of anticancer treatment. Therefore, the incongruence of beneficial microbiome signatures across studies, along with an emerging understanding of the mechanisms underlying the interactions between the microbiome, metabolome and host immune system, highlight a critical need for additional comprehensive and standardized multi-omics studies. Future research should consider key host factors, such as diet and use of medication, in both preclinical animal models and large-scale, multicenter clinical trials. In addition, there is a strong rationale to evaluate the microbiome as a tumor-extrinsic biomarker of clinical outcomes and to test the therapeutic potential of derived microbial products (e.g. defined microbial consortia), with the eventual goal of improving the efficacy of existing anticancer treatments. This review discusses the importance of the microbiome from the perspective of cancer immunotherapies, and outlines future steps that may contribute to wide-ranging clinical and translational benefits that may improve the health and quality of life of patients with cancer.

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The gut microbiome impacts the outcomes of cancer treatment by influencing host immunosurveillance.

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Modulation of microbiota represents a novel therapeutic strategy to improve responses.

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Incongruent beneficial bacterial signatures complicate the design of modulators.

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Reverse translation processes can be used to characterize candidate bacteria.

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Rationally designed microbial consortia catalyze transition to a healthy ecology.

[Gut Microbiota and Pancreatobiliary System]

The gut microbiota is part of the human body that is involved in body metabolism and the occurrence of various diseases. Detecting and analyzing their genetic information (microbiome) is as important as analyzing human genes. The core microbiome, the key functional genes shared by all humans, helps better understand the physiology of the human body. Information on the gut microbiome of a diseased person can help diagnose and treat disease. The pancreatobiliary system releases functional antimicrobial substances, such as bile acids and antimicrobial peptides, which affect the gut microbiota directly. In response, the gut microbiota influences pancreatobiliary secretion by controlling the generation and emission of substances through indirect signaling. This crosstalk maintains homeostasis of the pancreatobiliary system secretion and microbiota. Dysbiosis and disease can occur if this fails to work properly. Bile acid therapy has been used widely and may affect the microbial environment in the intestine. An association of the gut microbiota has been reported in many cases of pancreatobiliary diseases, including malignant tumors. Traditionally, most pancreatobiliary diseases are accompanied by infections from the gut microbiota, which is an important target for treatment. The pancreatobiliary system can control its function through physical and drug therapy. This may be a new pioneering field in the study or treatment of the gut microbiota.