Intestinal microbiota reduces genotoxic endpoints induced by high-energy protons

The Function and Molecular Mechanism of Commensal Microbiome in Promoting Malignant Progression of Lung Cancer

The human commensal microbiome existing in an internal environment is relatively consistent with that of the host. The presence of bacterial dysbiosis, on the other hand, promptly results in the termination of this symbiotic association. The altered microbial structure in the lung may be responsible for the development of lung cancer by controlling the host's inflammatory response and influencing a variety of immunological pathways. More and more studies have pointed to the fact that the commensal microbiota plays a vital role in both the development of tumors and the body's response to lung cancer treatment. Microbiome dysbiosis, genotoxicity, virulence effect, and epigenetic dysregulations are some of the potential mechanisms that may lie behind the process of tumorigenesis that is mediated by microbiome. Other potential mechanisms include regulating host immune activity through a variety of pathogenic factors, dysregulating host metabolism as a result of microbiome alterations, and microbiome dysbiosis. In this historical overview, we go through some of the more recent mechanistic discoveries into the biological processes that are involved in lung cancer that are caused by bacteria. Without a question, obtaining a greater knowledge of the dynamic link between the lung microbiome and lung cancer has the potential to inspire the development of innovative early detection and customized treatment methods for lung cancer.

Particle Radiation Side-Effects: Intestinal Microbiota Composition Shapes Interferon-γ-Induced Osteo-Immunogenicity

Microbiota can both negatively and positively impact radiation-induced bone loss. Our prior research showed that compared to mice with conventional gut microbiota (CM), mice with restricted gut microbiota (RM) reduced inflammatory tumor necrosis factor (TNF) in bone marrow, interleukin (IL)-17 in blood, and chemokine (C-C motif) ligand 20 (CCL20) in bone marrow under anti-IL-17 treatment. We showed that Muribaculum intestinale was more abundant in intestinal epithelial cells (IECs) from the small intestine of female RM mice and positively associated with augmented skeletal bone structure. Female C57BL/6J pun RM mice, which were injected with anti-IL-17 antibody one day before exposure to 1.5 Gy 28Si ions of 850 MeV/u, showed high trabecular numbers in tibiae at 6 weeks postirradiation. Irradiated CM mice were investigated for lower interferon-γ and IL-17 levels in the small intestine than RM mice. IL-17 blockage resulted in bacterial indicator phylotypes being different between both microbiota groups before and after irradiation. Analysis of the fecal bacteria were performed in relation to bone quality and body weight, showing reduced tibia cortical thickness in irradiated CM mice (-15%) vs. irradiated RM mice (-9.2%). Correlation analyses identified relationships among trabecular bone parameters (TRI-BV/TV, Tb.N, Tb.Th, Tb.Sp) and Bacteroides massiliensis, Muribaculum sp. and Prevotella denticola. Turicibacter sp. was found directly correlated with trabecular separation in anti-IL-17 treated mice, whereas an unidentified Bacteroidetes correlated with trabecular thickness in anti-IL-17 neutralized and radiation-exposed mice. We demonstrated radiation-induced osteolytic damage to correlate with bacterial indicator phylotypes of the intestinal microbiota composition, and these relationships were determined from the previously discovered dose-dependent particle radiation effects on cell proliferation in bone tissue. New translational approaches were designed to investigate dynamic changes of gut microbiota in correlation with conditions of treatment and disease as well as mechanisms of systemic side-effects in radiotherapy.

A Minireview on Gastrointestinal Microbiota and Radiosusceptibility

Gastrointestinal (GI) microbiota maintains a symbiotic relationship with the host and plays a key role in modulating many important biological processes and functions of the host, such as metabolism, inflammation, immune and stress response. It is becoming increasingly apparent that GI microbiota is susceptible to a wide range of environmental factors and insults, for examples, geographic location of birth, diet, use of antibiotics, and exposure to radiation. Alterations in GI microbiota link to various diseases, including radiation-induced disorders. In addition, GI microbiota composition could be used as a biomarker to estimate radiosusceptibility and radiation health risk in the host. In this minireview, we summarized the documented studies on radiation-induced alterations in GI microbiota and the relationship between GI microbiota and radiosusceptibility of the host, and mainly discussed the possible mechanisms underlying GI microbiota influencing the outcome of radiation response in humans and animal models. Furthermore, we proposed that GI microbiota manipulation may be used to reduce radiation injury and improve the health of the host.

Intestinal bacterial indicator phylotypes associate with impaired DNA double-stranded break sensors but augmented skeletal bone micro-structure

Intestinal microbiota are considered a sensor for molecular pathways, which orchestrate energy balance, immune responses, and cell regeneration. We previously reported that microbiota restriction promoted higher levels of systemic radiation-induced genotoxicity, proliferative lymphocyte activation, and apoptotic polarization of metabolic pathways. Restricted intestinal microbiota (RM) that harbors increased abundance of Lactobacillus johnsonii (LBJ) has been investigated for bacterial communities that correlated radiation-induced genotoxicity. Indicator phylotypes were more abundant in RM mice and increased in prevalence after whole body irradiation in conventional microbiota (CM) mice, while none of the same ten most abundant phylotypes were different in abundance between CM mice before and after heavy ion irradiation. Muribaculum intestinale was detected highest in female small intestines in RM mice, which were lacking Ureaplasma felinum compared with males, and thus these bacteria could be contributing to the differential amounts of radiation-induced systemic genotoxicity between the CM and RM groups. Helicobacter rodentium and M.intestinale were found in colons in the radiation-resistant CM phenotype. While the expression of interferon-γ was elevated in the small intestine, and lower in blood in CM mice, high-linear energy transfer radiation reduced transforming growth factor-β with peripheral interleukin (IL)-17 in RM mice, particularly in females. We found that female RM mice showed improved micro-architectural bone structure and anti-inflammatory radiation response compared with CM mice at a delayed phase 6 weeks postexposure to particle radiation. However, microbiota restriction reduced inflammatory markers of tumor necrosis factor in marrow, when IL-17 was reduced by intraperitoneal injection of IL-17 neutralizing antibody.

Microbial Alterations and Risk Factors of Breast Cancer: Connections and Mechanistic Insights

Breast cancer-related mortality remains high worldwide, despite tremendous advances in diagnostics and therapeutics; hence, the quest for better strategies for disease management, as well as the identification of modifiable risk factors, continues. With recent leaps in genomic technologies, microbiota have emerged as major players in most cancers, including breast cancer. Interestingly, microbial alterations have been observed with some of the established risk factors of breast cancer, such as obesity, aging and periodontal disease. Higher levels of estrogen, a risk factor for breast cancer that cross-talks with other risk factors such as alcohol intake, obesity, parity, breastfeeding, early menarche and late menopause, are also modulated by microbial dysbiosis. In this review, we discuss the association between known breast cancer risk factors and altered microbiota. An important question related to microbial dysbiosis and cancer is the underlying mechanisms by which alterations in microbiota can support cancer progression. To this end, we review the involvement of microbial metabolites as effector molecules, the modulation of the metabolism of xenobiotics, the induction of systemic immune modulation, and altered responses to therapy owing to microbial dysbiosis. Given the association of breast cancer risk factors with microbial dysbiosis and the multitude of mechanisms altered by dysbiotic microbiota, an impaired microbiome is, in itself, an important risk factor.

The power of small changes: Comprehensive analyses of microbial dysbiosis in breast cancer

Disparate occurrence of breast cancer remains an intriguing question since only a subset of women with known risk factors develop cancer. Recent studies suggest an active role of local and distant microbiota in breast cancer initiation, progression, and overall prognosis. A dysbiotic microbiota predisposes the body to develop cancer by inducing genetic instability, initiating DNA damage and proliferation of the damaged progeny, eliciting favorable immune response, metabolic dysregulation and altered response to therapy. In this review, we present our analyses of the existing datasets and discuss the local dysbiosis observed in breast cancer patients and different aspects of breast carcinogenesis that can be potentially influenced by local breast microbiota. Striking differences between microbial community compositions in breast of cancer patients compared to healthy individuals were noted. Differences in microbiome were also apparent between benign and malignant disease and between nipple aspirate fluid of healthy individuals and breast survivors. We also discuss the identification of distinct bacterial, fungal, viral as well as parasite signatures for breast cancer. These microbes are capable of producing numerous secondary metabolites that can act as signaling mediators effecting breast cancer progression. We review how microbes potentially alter response to therapy affecting drug metabolism, pharmacokinetics, anti-tumor effects and toxicity. In conclusion, breast harbors a community of microbes that can communicate with the host cells inducing downstream signaling pathways and modulating various aspects of breast cancer growth and metastatic progression and an improved understanding of microbial dysbiosis can potentially reduce breast cancer risk and improve outcomes of breast cancer patients. The human microbiome, now referred to as, the "forgotten organ" contains a metagenome that is 100-fold more diverse compared to the human genome, thereby, is critically associated with human health [1,2]. With the revelations of the human microbiome project and advent of deep sequencing techniques, a plethora of information has been acquired in recent years. Body sites like stomach, bladder and lungs, once thought to be sterile, are now known to harbor millions of indigenous microbial species. Approximately 80% of the healthy microbiome consists of Firmicutes and Bacteroidetes accompanied by Verrucomicrobia, Actinobacteria, Proteobacteria, Tenericutes and Cyanobacteria [2-7]. The role of microbiome in diabetes, obesity and even neurodegenerative diseases was greatly appreciated in the last decade [1,7-14] and now it has been established that microbiome significantly contributes to many organ specific cancers [1,15,16].

A More Robust Gut Microbiota in Calorie-Restricted Mice Is Associated with Attenuated Intestinal Injury Caused by the Chemotherapy Drug Cyclophosphamide

Improving the gut microbiota via calorie restriction is beneficial for human health. Our findings showed differential responses between calorie-restricted mice and ad libitum-fed mice. Compared with the ad libitum-fed mice, the calorie-restricted mice were less susceptible to cyclophosphamide side effects otherwise observed on the gut integrity and its microbiota. These results show the potential benefits of manipulating the gut microbiota with CR prior to cancer chemotherapy.

Cyclophosphamide (CTX) is widely used in cancer chemotherapy, but it often induces mucositis, in which the disruption of the gut microbiota might play a pivotal role. Whether the manipulation of the gut microbiota can be used as a strategy to improve CTX-induced mucositis remains to be studied. Here we observed the effects of a 4-week calorie restriction (CR) on CTX-induced mucositis. Compared with ad libitum-fed mice, CR mice showed significantly less mucositis in response to CTX, including lower intestinal permeability, less bacterial translocation, higher number of epithelial stem cells, and less epithelium damage. CTX induced significant shifts of the gut microbiota of the gut microbiota in ad libitum-fed control mice. In contrast, CR mice showed no significant change in their gut microbiota in responding to CTX treatment. CR significantly enriched the gut microbiota in Lactobacillus and Lachnospiraceae which are known to mitigate inflammation and improve gut barrier function. These findings suggest that CR remodeled gut microbiota is more robust and may contribute to attenuate the side effects of cyclophosphamide, which supports the concept that cancer chemotherapy would benefit from strategies targeting the gut microbiota.

Caulerpa lentilliferapolysaccharides enhance the immunostimulatory activity in immunosuppressed mice in correlation with modulating gut microbiota

Caulerpa lentilliferapolysaccharides could serve as novel prebiotics and immunostimulators, since they improve the immune-related factors and modulate the gut microbiota in cytoxan-induced immunosuppressed mice.

Induction and modulation of genotoxicity by the bacteriome in mammals

The living environment is a multilevel physical and chemical xenobiotic complex with potentially mutagenic effects and health risks. In addition to inorganic exposures, all terrestrial and aquatic living forms interact with microbiota as selectively established communities of bacteria, viruses and fungi. Along these lines, the human organism should then be considered a "meta-organism" with complex dynamics of interaction between the environment and microbiome. Bacterial communities within the microbiome, bacteriome, by its mass, symbiotic or competitive position and composition are in a fragile balance with the host organisms and have a crucial impact on their homeostasis. Bacteriome taxonomic composition is modulated by age, sex and host genetic profile and may be changed by adverse environmental exposures and life style factors such as diet or drug intake. A changed and/or misbalanced bacteriome has genotoxic potential with significant impact on the pathogenesis of acute, chronic and neoplastic diseases in the host organism. Bacteria may produce genotoxins, express a variety of pathways in which they generate free radicals or affect DNA repair causing genome damage, cell cycle arrest and apoptosis, modulate immune response and launch carcinogenesis in the host organism. Future investigations should focus on the interplay between exposure to xenobiotics and bacteriome composition, immunomodulation caused by misbalanced bacteriome, impact of the environment on bacteriome composition in children and its lifelong effect on health risks.

Space-type radiation induces multimodal responses in the mouse gut microbiome and metabolome

BACKGROUND

Space travel is associated with continuous low dose rate exposure to high linear energy transfer (LET) radiation. Pathophysiological manifestations after low dose radiation exposure are strongly influenced by non-cytocidal radiation effects, including changes in the microbiome and host gene expression. Although the importance of the gut microbiome in the maintenance of human health is well established, little is known about the role of radiation in altering the microbiome during deep-space travel.

RESULTS

Using a mouse model for exposure to high LET radiation, we observed substantial changes in the composition and functional potential of the gut microbiome. These were accompanied by changes in the abundance of multiple metabolites, which were related to the enzymatic activity of the predicted metagenome by means of metabolic network modeling. There was a complex dynamic in microbial and metabolic composition at different radiation doses, suggestive of transient, dose-dependent interactions between microbial ecology and signals from the host's cellular damage repair processes. The observed radiation-induced changes in microbiota diversity and composition were analyzed at the functional level. A constitutive change in activity was found for several pathways dominated by microbiome-specific enzymatic reactions like carbohydrate digestion and absorption and lipopolysaccharide biosynthesis, while the activity in other radiation-responsive pathways like phosphatidylinositol signaling could be linked to dose-dependent changes in the abundance of specific taxa.

CONCLUSIONS

The implication of microbiome-mediated pathophysiology after low dose ionizing radiation may be an unappreciated biologic hazard of space travel and deserves experimental validation. This study provides a conceptual and analytical basis of further investigations to increase our understanding of the chronic effects of space radiation on human health, and points to potential new targets for intervention in adverse radiation effects.

ROS-modulated therapeutic approaches in cancer treatment

PURPOSE

Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells.

METHODS

We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed.

RESULTS

This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy.

CONCLUSION

Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.

Microbiota: a key orchestrator of cancer therapy

The microbiota is composed of commensal bacteria and other microorganisms that live on the epithelial barriers of the host. The commensal microbiota is important for the health and survival of the organism. Microbiota influences physiological functions from the maintenance of barrier homeostasis locally to the regulation of metabolism, haematopoiesis, inflammation, immunity and other functions systemically. The microbiota is also involved in the initiation, progression and dissemination of cancer both at epithelial barriers and in sterile tissues. Recently, it has become evident that microbiota, and particularly the gut microbiota, modulates the response to cancer therapy and susceptibility to toxic side effects. In this Review, we discuss the evidence for the ability of the microbiota to modulate chemotherapy, radiotherapy and immunotherapy with a focus on the microbial species involved, their mechanism of action and the possibility of targeting the microbiota to improve anticancer efficacy while preventing toxicity.

Enterococcus hirae and Barnesiella intestinihominis Facilitate Cyclophosphamide-Induced Therapeutic Immunomodulatory Effects

The efficacy of the anti-cancer immunomodulatory agent cyclophosphamide (CTX) relies on intestinal bacteria. How and which relevant bacterial species are involved in tumor immunosurveillance, and their mechanism of action are unclear. Here, we identified two bacterial species, Enterococcus hirae and Barnesiella intestinihominis that are involved during CTX therapy. Whereas E. hirae translocated from the small intestine to secondary lymphoid organs and increased the intratumoral CD8/Treg ratio, B. intestinihominis accumulated in the colon and promoted the infiltration of IFN-γ-producing γδT cells in cancer lesions. The immune sensor, NOD2, limited CTX-induced cancer immunosurveillance and the bioactivity of these microbes. Finally, E. hirae and B. intestinihominis specific-memory Th1 cell immune responses selectively predicted longer progression-free survival in advanced lung and ovarian cancer patients treated with chemo-immunotherapy. Altogether, E. hirae and B. intestinihominis represent valuable "oncomicrobiotics" ameliorating the efficacy of the most common alkylating immunomodulatory compound.

Chemopreventive Metabolites Are Correlated with a Change in Intestinal Microbiota Measured in A-T Mice and Decreased Carcinogenesis

Intestinal microbiota play a significant role in nutrient metabolism, modulation of the immune system, obesity, and possibly in carcinogenesis, although the underlying mechanisms resulting in disease or impacts on longevity caused by different intestinal microbiota are mostly unknown. Herein we use isogenic Atm-deficient and wild type mice as models to interrogate changes in the metabolic profiles of urine and feces of these mice, which are differing in their intestinal microbiota. Using high resolution mass spectrometry approach we show that the composition of intestinal microbiota modulates specific metabolic perturbations resulting in a possible alleviation of a glycolytic phenotype. Metabolites including 3-methylbutyrolactone, kyneurenic acid and 3-methyladenine known to be onco-protective are elevated in Atm-deficient and wild type mice with restricted intestinal microbiota. Thus our approach has broad applicability to study the direct influence of gut microbiome on host metabolism and resultant phenotype. These results for the first time suggest a possible correlation of metabolic alterations and carcinogenesis, modulated by intestinal microbiota in A-T mice.

Low-dose irradiation affects the functional behavior of oral microbiota in the context of mucositis

The role of host-microbe interactions in the pathobiology of oral mucositis is still unclear; therefore, this study aimed to unravel the effect of irradiation on behavioral characteristics of oral microbial species in the context of mucositis. Using various experimental in vitro setups, the effects of irradiation on growth and biofilm formation of two Candida spp., Streptococcus salivarius and Klebsiella oxytoca in different culture conditions were evaluated. Irradiation did not affect growth of planktonic cells, but reduced the number of K. oxytoca cells in newly formed biofilms cultured in static conditions. Biofilm formation of K. oxytoca and Candida glabrata was affected by irradiation and depended on the culturing conditions. In the presence of mucins, these effects were lost, indicating the protective nature of mucins. Furthermore, the Galleria melonella model was used to study effects on microbial virulence. Irradiated K. oxytoca microbes were more virulent in G. melonella larvae compared to the nonirradiated ones. Our data indicate that low-dose irradiation can have an impact on functional characteristics of microbial species. Screening for pathogens like K. oxytoca in the context of mucosits could be useful to allow early detection and immediate intervention.

Evidence from Animal Models: Is a Restricted or Conventional Intestinal Microbiota Composition Predisposing to Risk for High-LET Radiation Injury?

Intestinal microbiota affect cell responses to ionizing radiation at the molecular level and can be linked to the development of the immune system, controlled cell death or apoptosis. We have developed a microbiota mouse model and report here that high-linear energy transfer (LET) radiation induced the repair of chromosomal DNA lesions more efficiently in conventional than in restricted intestinal microbiota mice. Based on different phylotype densities after whole-body irradiation, bacterial indicator phylotypes were found to be more abundant in restricted in microbiota than in conventional microbiota. Genotoxic phenotypes of irradiated restricted and conventional microbiota mice were compared with ataxia telangiectasia-deficient restricted and conventional microbiota mice, respectively. Those indicator phylotypes, including Bacteroides (Gram-negative bacterium cTPY-13), Barnesiella intestinihominis and others, which were identified in nonirradiated restricted microbiota mice, increase in radiation-exposed conventional microbiota along with a reduction of persistent DNA double-strand breaks in blood lymphocytes. The dynamic change of phylotype abundances elucidated a feedback mechanism and effect of intestinal microbiota composition on the adaptive response to high-LET radiation. Several other bacterial phylotypes ( Helicobacter hepaticus , Helicobacter spp and others) were found to be more abundant in conventional than restricted microbiota. In this commentary, mouse models used in cancer research and radiotherapy for the study on the effects of intestinal microbiota composition on normal tissue radiation response are characterized and discussed. Highlights of this commentary: 1. Restricted microbiota phylotypes were correlated with persistent DNA double-strand breaks (DSBs) and were found to orchestrate onco-protective controlled cell death after radiation; 2. Restricted microbiota composition reduced proinflammatory extracellular-stimulated immune responses, but specifically increased anti-neoplastic cytolytic memory CD8(+) T cells by low taxonomic diversity and 3. DNA damage repair efficiency induced by a model of conventional microbiota most likely initiates an adaptive response to radiation through microbiota-induced intestinal sub-symptomatic inflammation.

High-throughput 16S rRNA gene sequencing reveals alterations of mouse intestinal microbiota after radiotherapy

The mammalian gastrointestinal tract harbors a highly complex microbial community that comprises hundreds of different types of bacterial cells. The gastrointestinal microbiota plays an important role in the function of the host intestine. Most cancer patients undergoing pelvic irradiation experience side effects such as diarrhea; however, little is currently known about the effects of irradiation on the microorganisms colonizing the mucosal surfaces of the gastrointestinal tract. The aim of this study was to investigate the effects of gamma irradiation on the compositions of the large and small intestinal microbiotas. The gut microbiotas in control mice and mice receiving irradiation treatment were characterized by high-throughput sequencing of the bacterial 16S rRNA gene. Irradiation treatment induced significant alterations in the bacterial compositions of the large and small intestines at the genus level. Unexpectedly, irradiation treatment increased the number of operational taxonomic units in the small intestine but not the large intestine. In particular, irradiation treatment increased the level of the genera Alistipes in the large intestine and increased the level of the genus Corynebacterium in the small intestine. By contrast, compared with that in the corresponding control group, the level of the genera Prevotella was lower in the irradiated large intestine, and the level of the genera Alistipes was lower in the irradiated small intestine. Overall, the data presented here reveal the potential microbiological effects of pelvic irradiation on the gastrointestinal tracts of cancer patients.

Gastric and enterohepatic helicobacters other than Helicobacter pylori

During the past year, research on non-Helicobacter pylori species has intensified. H. valdiviensis was isolated from wild birds, and putative novel species have been isolated from Bengal tigers and Australian marsupials. Various genomes have been sequenced: H. bilis, H. canis, H. macacae, H. fennelliae, H. cetorum, and H. suis. Several studies highlighted the virulence of non-H. pylori species including H. cinaedi in humans and hyperlipidemic mice or H. macacae in geriatric rhesus monkeys with intestinal adenocarcinoma. Not surprisingly, increased attention has been paid to the position of Helicobacter species in the microbiota of children and animal species (mice, chickens, penguins, and migrating birds). A large number of experimental studies have been performed in animal models of Helicobacter induced typhlocolitis, showing that the gastrointestinal microbial community is involved in modulation of host pathways leading to chronic inflammation. Animal models of H. suis, H. heilmannii, and H. felis infection have been used to study the development of severe inflammation-related pathologies, including gastric MALT lymphoma and adenocarcinoma.