Investigation of the association between the fecal microbiota and breast cancer in postmenopausal women: a population-based case-control pilot study

Roles of Microbiota in Cancer: From Tumor Development to Treatment

Cancer as a second leading cause of death arises from multifactorial pathology. The association of microbiota and their products with various pathologic conditions including cancer is receiving significant attention over the past few years. Mounting evidence showed that human microbiota is an emerging target in tumor onset, progression, prevention, and even diagnosis. Accordingly, modulating this composition might influence the response to tumor therapy and therapeutic resistance as well. Through this review, one could conceive of complex interaction between the microbiome and cancer in either positive or negative manner by which may hold potential for finding novel preventive and therapeutic strategies against cancer.

Obesity and breast cancer: Preventive and therapeutic possibilities for bariatric surgery

Breast cancer is the most common and second deadliest malignancy in women. With rising obesity rates and building evidence for a strong association with obesity, the incidence of breast cancer can be expected to increase. Weight loss reduces breast cancer risk, the mechanisms of which are still poorly understood. As an effective therapy for obesity, bariatric surgery may be a powerful tool in breast cancer prevention and treatment. This review details the potential physiologic mechanisms that may underlie this association, as well as recently published studies that reinforce the link between bariatric surgery and a reduction in incident breast cancer. The use of bariatric surgery as an adjunct therapy in endometrial cancer also raises the potential for similar use in select breast cancer patients. Despite the expanding potential applications of bariatric surgery in this field, publications to date have been strictly observational, highlighting a need for future clinical trials.

Next-generation probiotics - do they open new therapeutic strategies for cancer patients?

Gut microbiota and its association with cancer development/treatment has been intensively studied during the past several years. Currently, there is a growing interest toward next-generation probiotics (NGPs) as therapeutic agents that alter gut microbiota and impact on cancer development. In the present review we focus on three emerging NGPs, namely Faecalibacterium prausnitzii, Akkermansia muciniphila, and Bacteroides fragilis as their presence in the digestive tract can have an impact on cancer incidence. These NGPs enhance gastrointestinal immunity, maintain intestinal barrier integrity, produce beneficial metabolites, act against pathogens, improve immunotherapy efficacy, and reduce complications associated with chemotherapy and radiotherapy. Notably, the use of NGPs in cancer patients does not have a long history and, although their safety remains relatively undefined, recently published data has shown that they are non-toxigenic. Notwithstanding, A. muciniphila may promote colitis whereas enterotoxigenic B. fragilis stimulates chronic inflammation and participates in colorectal carcinogenesis. Nevertheless, the majority of B. fragilis strains provide a beneficial effect to the host, are non-toxigenic and considered as the best current NGP candidate. Overall, emerging studies indicate a beneficial role of these NGPs in the prevention of carcinogenesis and open new promising therapeutic options for cancer patients.

Human Microbiota and Immunotherapy in Breast Cancer - A Review of Recent Developments

Breast cancer (BC) is the most common malignancy and the second cause of cancer-specific death in women from high-income countries. Infectious agents are the third most important risk factor for cancer incidence after tobacco and obesity. Dysbiosis emerged as a key player that may influence cancer development, treatment, and prognosis through diverse biological processes. Metastatic BC has a highly variable clinical course, and more recently, immune checkpoint inhibitors (ICIs) have become an emerging therapy in BC. Even with standardised treatment protocols, patients do not respond similarly, reflecting each individual´s heterogeneity, unique BC features, and tumour microenvironment. However, there is insufficient data regarding predictive factors of response to available treatments for BC. The microbiota could be a crucial piece of the puzzle to anticipate better individual BC risk and prognosis, pharmacokinetics, pharmacodynamics, and clinical efficacy. In recent years, it has been shown that gut microbiota may modulate cancer treatments' efficacy and adverse effects, and it is also apparent that both cancer itself and anticancer therapies interact with gut microbiota bidirectionally. Moreover, it has been proposed that certain gut microbes may protect the host against inappropriate inflammation and modulate the immune response. Future clinical research will determine if microbiota may be a prognostic and predictive factor of response to ICI and/or its side effects. Also, modulation of microbiota can be used to improve outcomes in BC patients. In this review, we discuss the potential implications of metabolomics and pharmacomicrobiomics that might impact BC immunotherapy treatment.

Emerging Interrelationship Between the Gut Microbiome and Cellular Senescence in the Context of Aging and Disease: Perspectives and Therapeutic Opportunities

The significance of diversity, composition, and functional attributes of the gut microbiota in shaping human health is well recognized. Studies have shown that gut microbiota is closely linked to human aging, and changes in the gut microbiome can predict human survival and longevity. In addition, a causal relationship between gut microbiota dysbiosis and chronic age-related disorders is also becoming apparent. Recent advances in our understanding of the cellular and molecular aspects of biological aging have revealed a cellular senescence-centric view of the aging process. However, the association between the gut microbiome and cellular senescence is only beginning to be understood. The present review provides an integrative view of the evolving relationship between the gut microbiome and cellular senescence in aging and disease. Evidence relating to microbiome-mediated modulation of senescent cells, as well as senescent cells-mediated changes in intestinal homeostasis and diseases, have been discussed. Unanswered questions and future research directions have also been deliberated to truly ascertain the relationship between the gut microbiome and cellular senescence for developing microbiome-based age-delaying and longevity-promoting therapies.

Host microbiomes in tumor precision medicine: how far are we?

The human gut microbiome has received a crescendo of attention in recent years, due to the countless influences on human pathophysiology, including cancer. Research on cancer and anticancer therapy is constantly looking for new hints to improve the response to therapy while reducing the risk of relapse. In this scenario, the gut microbiome and the plethora of microbial-derived metabolites are considered a new opening in the development of innovative anticancer treatments for a better prognosis. This narrative review summarizes the current knowledge on the role of the gut microbiome in the onset and progression of cancer, as well as in response to chemo-immunotherapy. Recent findings regarding the tumor microbiome and its implications for clinical practice are also commented on. Current microbiome-based intervention strategies (i.e., prebiotics, probiotics, live biotherapeutics and fecal microbiota transplantation) are then discussed, along with key shortcomings, including a lack of long-term safety information in patients who are already severely compromised by standard treatments. The implementation of bioinformatic tools applied to microbiomics and other omics data, such as machine learning, has an enormous potential to push research in the field, enabling the prediction of health risk and therapeutic outcomes, for a truly personalized precision medicine.

The Association Between Breast Density and Gut Microbiota Composition at 2 Years Post-Menarche: A Cross-Sectional Study of Adolescents in Santiago, Chile

The gut microbiome has been linked to breast cancer via immune, inflammatory, and hormonal mechanisms. We examined the relation between adolescent breast density and gut microbial composition and function in a cohort of Chilean girls. This cross-sectional study included 218 female participants in the Growth and Obesity Cohort Study who were 2 years post-menarche. We measured absolute breast fibroglandular volume (aFGV) and derived percent FGV (%FGV) using dual energy X-ray absorptiometry. All participants provided a fecal sample. The gut microbiome was characterized using 16S ribosomal RNA sequencing of the V3-V4 hypervariable region. We examined alpha diversity and beta diversity across terciles of %FGV and aFGV. We used MaAsLin2 for multivariable general linear modeling to assess differential taxa and predicted metabolic pathway abundance (MetaCyc) between %FGV and aFGV terciles. All models were adjusted for potential confounding variables and corrected for multiple comparisons. The mean %FGV and aFGV was 49.5% and 217.0 cm³, respectively, among study participants. Similar median alpha diversity levels were found across %FGV and aFGV terciles when measured by the Shannon diversity index (%FGV T1: 4.0, T2: 3.9, T3: 4.1; aFGV T1: 4.0, T2: 4.0, T3: 4.1). %FGV was associated with differences in beta diversity (R^{2 =}0.012, p=0.02). No genera were differentially abundant when comparing %FGV nor aFGV terciles after adjusting for potential confounders (q > 0.56 for all genera). We found no associations between predicted MetaCyc pathway abundance and %FGV and aFGV. Overall, breast density measured at 2 years post-menarche was not associated with composition and predicted function of the gut microbiome among adolescent Chilean girls.

Microbiota of Breast Tissue and Its Potential Association with Regional Recurrence of Breast Cancer in Korean Women

Recent studies have reported dysbiosis of the microbiome in breast tissue collected from patients with breast cancer and the association between the microbiota and disease progression. However, the role of the microbiota in breast tissue remains unclear, possibly due to the complexity of breast cancer and various factors, including racial and geographical differences, influencing microbiota in breast tissue. Here, to determine the potential role of microbiota in breast tumor tissue, we analyzed 141 tissue samples based on three different tissue types (tumor, adjacent normal, and lymph node tissues) from the same patients with breast cancer in Korea. The microbiota was not simply distinguishable based on tissue types. However, the microbiota could be divided into two cluster types, even within the same tissue type, and the clinicopathologic factors were differently correlated in the two cluster types. Risk of regional recurrence was also significantly different between the microbiota cluster types (p = 0.014). In predicted function analysis, the pentose and glucuronate interconversions were significantly different between the cluster types (q < 0.001), and Enterococcus was the main genus contributing to these differences (q < 0.01). Results showed that the microbiota of breast tissue could interact with the host and influence the risk of regional recurrence. Although further studies would be recommended to validate our results, this study could expand our understanding on the breast tissue microbiota, and the results might be applied to develop novel prediction methods and treatments for patients with breast cancer.

Intestinal Microbiota in Postmenopausal Breast Cancer Patients and Controls

Simple Summary

Besides the already known factors that increase the risk of breast cancer, like hormonal treatment, heredity, and obesity, growing evidence exists that intestinal microbiota can influence breast cancer carcinogenesis. Current clinical information into the role of the intestinal microbiota in breast cancer patients is limited. This study aimed to see whether there are differences in intestinal microbiota richness, diversity, and composition between oestrogen receptor positive breast cancer patients and controls. We concluded that the intestinal microbiota richness, diversity, and composition were not different between breast cancer patients and postmenopausal controls. An increased relative abundance of Dialister and Veillonellaceae was observed in breast cancer patients scheduled for adjuvant treatment, which might be caused by a relative decrease in other bacteria due to surgery associated factors rather than an absolute increase. For future studies, we strongly advise a more homogeneous group of breast cancer patients of preferably treatment-naive patients.

Abstract

Background: Previous preclinical and clinical research has investigated the role of intestinal microbiota in carcinogenesis. Growing evidence exists that intestinal microbiota can influence breast cancer carcinogenesis. However, the role of intestinal microbiota in breast cancer needs to be further investigated. This study aimed to identify the microbiota differences between postmenopausal breast cancer patients and controls. Patients and methods: This prospective cohort study compared the intestinal microbiota richness, diversity, and composition in postmenopausal histologically proven ER+/HER2- breast cancer patients and postmenopausal controls. Patients scheduled for (neo)adjuvant adriamycin, cyclophosphamide (AC), and docetaxel (D), or endocrine therapy (tamoxifen) were prospectively enrolled in a multicentre cohort study in the Netherlands. Patients collected a faecal sample and completed a questionnaire before starting systemic cancer treatment. Controls, enrolled from the National Dutch Breast Cancer Screening Programme, also collected a faecal sample and completed a questionnaire. Intestinal microbiota was analysed by amplicon sequencing of the 16S rRNA V4 gene region. Results: In total, 81 postmenopausal ER+/HER2- breast cancer patients and 67 postmenopausal controls were included, resulting in 148 faecal samples. Observed species richness, Shannon index, and overall microbial community structure were not significantly different between breast cancer patients and controls. There was a significant difference in overall microbial community structure between breast cancer patients scheduled for adjuvant treatment, neoadjuvant treatment, and controls at the phylum (p = 0.042) and genus levels (p = 0.015). Dialister (p = 0.001) and its corresponding family Veillonellaceae (p = 0.001) were higher in patients scheduled for adjuvant treatment, compared to patients scheduled for neoadjuvant treatment. Additional sensitivity analysis to correct for the potential confounding effect of prophylactic antibiotic use, indicated no differences in microbial community structure between patients scheduled for neoadjuvant systemic treatment, adjuvant systemic treatment, and controls at the phylum (p = 0.471) and genus levels (p = 0.124). Conclusions: Intestinal microbiota richness, diversity, and composition are not different between postmenopausal breast cancer patients and controls. The increased relative abundance of Dialister and Veillonellaceae was observed in breast cancer patients scheduled for adjuvant treatment, which might be caused by a relative decrease in other bacteria due to prophylactic antibiotic administration rather than an absolute increase.

The involvement of oncobiosis and bacterial metabolite signaling in metastasis formation in breast cancer

Breast cancer, the most frequent cancer in women, is characterized by pathological changes to the microbiome of breast tissue, the tumor, the gut, and the urinary tract. Changes to the microbiome are determined by the stage, grade, origin (NST/lobular), and receptor status of the tumor. This year is the 50th anniversary of when Hill and colleagues first showed that changes to the gut microbiome can support breast cancer growth, namely that the oncobiome can reactivate excreted estrogens. The currently available human and murine data suggest that oncobiosis is not a cause of breast cancer, but can support its growth. Furthermore, preexisting dysbiosis and the predisposition to cancer are transplantable. The breast's and breast cancer's inherent microbiome and the gut microbiome promote breast cancer growth by reactivating estrogens, rearranging cancer cell metabolism, bringing about a more inflammatory microenvironment, and reducing the number of tumor-infiltrating lymphocytes. Furthermore, the gut microbiome can produce cytostatic metabolites, the production of which decreases or blunts breast cancer. The role of oncobiosis in the urinary tract is largely uncharted. Oncobiosis in breast cancer supports invasion, metastasis, and recurrence by supporting cellular movement, epithelial-to-mesenchymal transition, cancer stem cell function, and diapedesis. Finally, the oncobiome can modify the pharmacokinetics of chemotherapeutic drugs. The microbiome provides novel leverage on breast cancer that should be exploited for better management of the disease.

Exploring the Impact of the Microbiome on Neuroactive Steroid Levels in Germ-Free Animals

Steroid hormones are essential biomolecules for human physiology as they modulate the endocrine system, nervous function and behaviour. Recent studies have shown that the gut microbiota is directly involved in the production and metabolism of steroid hormones in the periphery. However, the influence of the gut microbiota on levels of steroids acting and present in the brain (i.e., neuroactive steroids) is not fully understood. Therefore, using liquid chromatography–tandem mass spectrometry, we assessed the levels of several neuroactive steroids in various brain areas and the plasma of germ-free (GF) male mice and conventionally colonized controls. The data obtained indicate an increase in allopregnanolone levels associated with a decrease in those of 5α-androstane-3α, 17β-diol (3α-diol) in the plasma of GF mice. Moreover, an increase of dihydroprogesterone and isoallopregnanolone in the hippocampus, cerebellum, and cerebral cortex was also reported. Changes in dihydrotestosterone and 3α-diol levels were also observed in the hippocampus of GF mice. In addition, an increase in dehydroepiandrosterone was associated with a decrease in testosterone levels in the hypothalamus of GF mice. Our findings suggest that the absence of microbes affects the neuroactive steroids in the periphery and the brain, supporting the evidence of a microbiota-mediated modulation of neuroendocrine pathways involved in preserving host brain functioning.

From Microbiome to Inflammation: The Key Drivers of Cervical Cancer

Cervical cancer is the third leading cause of cancer-related death worldwide. Microbes and hosts form a mutually beneficial symbiosis relationship, and various parts of the host body are microbial habitats. Microbes can trigger inflammation in certain parts of the host body, contributing to cervical cancer development. This article reviews the relationship between cervicovaginal microbes, inflammation and cervical cancer, and discusses the effect of some key cervical microbes on cervical cancer. Finally, probiotic therapy and immunotherapy are summarized.

Gut Microbiota: A Potential Target for Cancer Interventions

The gut microbiota plays a crucial role in many physiological processes in the human body. Dysbiosis can disrupt the intestinal barrier and alter metabolism and immune responses, leading to the development of diseases. Over the past few decades, evidence has accumulated linking changes in the composition of the gut microbiota to dozens of seemingly unrelated conditions, including cancer. Overall, the gut microbiota mainly affects the occurrence and development of cancer by damaging host DNA, forming and maintaining a pro-inflammatory environment, and affecting host immune responses. In addition, the gut microbiota can also affect the efficacy and toxicity of chemotherapy, radiotherapy, and immunotherapy. Scientists attempt to improve the efficacy and decrease the toxicity of these treatment modalities by fine-tuning the gut microbiota. The aim of this review is to assist researchers and clinicians in developing new strategies for the detection and treatment of tumors by providing the latest information on the intestinal microbiome and cancer, as well as exploring potential application prospects and mechanisms of action.

Comparison of the Gut Microbiota in Patients with Benign and Malignant Breast Tumors: A Pilot Study

The microbiome plays diverse roles in many diseases and can potentially contribute to cancer development. Breast cancer is the most commonly diagnosed cancer in women worldwide. Thus, we investigated whether the gut microbiota differs between patients with breast carcinoma and those with benign tumors. The DNA of the fecal microbiota community was detected by Illumina sequencing and the taxonomy of 16S rRNA genes. The α-diversity and β-diversity analyses were used to determine richness and evenness of the gut microbiota. Gene function prediction of the microbiota in patients with benign and malignant carcinoma was performed using PICRUSt. There was no significant difference in the α-diversity between patients with benign and malignant tumors (P = 3.15e-1 for the Chao index and P = 3.1e-1 for the ACE index). The microbiota composition was different between the 2 groups, although no statistical difference was observed in β-diversity. Of the 31 different genera compared between the 2 groups, level of only Citrobacter was significantly higher in the malignant tumor group than that in benign tumor group. The metabolic pathways of the gut microbiome in the malignant tumor group were significantly different from those in benign tumor group. Furthermore, the study establishes the distinct richness of the gut microbiome in patients with breast cancer with different clinicopathological factors, including ER, PR, Ki-67 level, Her2 status, and tumor grade. These findings suggest that the gut microbiome may be useful for the diagnosis and treatment of malignant breast carcinoma.

Effect of Microbiota in the Development of Breast Cancer

Breast cancer is the most frequent cancer among women and causes the greatest number of cancer-related death among women all over the world. It approximately accounts for 15% of all cancer death. The human microbiota is the term applied to the aggregate of microbes that live in different habitats of living organisms 'bodies, including the gut, skin, vagina, and mouth, as well as nose, conjunctiva, pharynx, and urethra, among others. Increasing evidence is pointing to the role of the microbiome in the occurrence and development of a variety of cancers. Intestinal microbiome imbalance is related to the occurrence of gastrointestinal tumors, such as esophageal, gastric, colorectal, and gallbladder cancer. The present study aimed to identify the role of microbiota in the development of breast cancer. The women with breast cancer (n=130) in this study were in the age range of 25-75 years. The study was conducted in Kirkuk city of Iraq from September 10, 2019, to March 15, 2020. The control group included 20 women diagnosed with benign breast lesions in the age range 25-75 years, who matched the women in the patient group. Blood samples and breast tissue samples were taken from patients with breast cancer and benign breast lesions. Blood samples were examined through immunological methods, enzyme-linked immunosorbent assay (ELISA) was adopted for the detection of interleukin-19 (IL-19). Breast tissue samples were taken from breast cancer and benign breast lesions patients to isolate and identify bacteria. Based on the obtained results, only 6 out of 30 (20%) cultured breast tissue samples from women with breast cancer showed bacterial growth. In total, 4 (67%) and 2(33%) of these 6 positive cultures were Escherichia coli was and Staphylococcus aureus, respectively, and this relation was statistically significant. However, no bacterial growth was observed on the cultured breast tissue samples taken from women with benign breast lesions. Moreover, the difference between women with a positive and negative result of bacterial culture and stages of breast cancer was statistically non-significant. It is worth mentioning that 50 % of women with breast cancer and bacterial growth were within the age range of 40-49 year. The present study revealed that the difference between women with breast cancer and those with benign breast lesions was statistically highly significant according to the place of residence. In addition, the mean level of IL-19 among women with breast cancer was lower than that in women with benign breast lesions, and this relation was statistically highly significant.

Antibiotic-induced disturbances of the gut microbiota result in accelerated breast tumor growth

The gut microbiota's function in regulating health has seen it linked to disease progression in several cancers. However, there is limited research detailing its influence in breast cancer (BrCa). This study found that antibiotic-induced perturbation of the gut microbiota significantly increases tumor progression in multiple BrCa mouse models. Metagenomics highlights the common loss of several bacterial species following antibiotic administration. One such bacteria, Faecalibaculum rodentium, rescued this increased tumor growth. Single-cell transcriptomics identified an increased number of cells with a stromal signature in tumors, and subsequent histology revealed an increased abundance of mast cells in the tumor stromal regions. We show that administration of a mast cell stabilizer, cromolyn, rescues increased tumor growth in antibiotic treated animals but has no influence on tumors from control cohorts. These findings highlight that BrCa-microbiota interactions are different from other cancers studied to date and suggest new research avenues for therapy development.

Circulating microbiome DNA: An emerging paradigm for cancer liquid biopsy

Dysbiosis of the human microbiome has long been reported to be closely associated with various cancers. Accumulating studies have shown that microbial dysbiosis can accelerate tumorigenesis through tumor-promoting inflammation, DNA damage, and inducing immune evasion. Differential composition of microbiome could be novel biomarkers for cancer detection or biomarkers of successful immunotherapy. More importantly, emerging evidence demonstrates that alterations of circulating microbiome DNA (cmDNA) could serve as promising noninvasive biomarkers for cancer detection. It has been reported that distinct circulating bacterial DNA could distinguish prostate cancer, lung cancer, and melanoma patients from healthy populations. Therefore, in this review, we summarized current literature on microbial biomarkers for cancer detection and unraveled the potential of cmDNA as a promising cancer detection tool.

Targeting obesity-related dysfunction in hormonally driven cancers

Obesity is a risk factor for at least 13 different types of cancer, many of which are hormonally driven, and is associated with increased cancer incidence and morbidity. Adult obesity rates are steadily increasing and a subsequent increase in cancer burden is anticipated. Obesity-related dysfunction can contribute to cancer pathogenesis and treatment resistance through various mechanisms, including those mediated by insulin, leptin, adipokine, and aromatase signalling pathways, particularly in women. Furthermore, adiposity-related changes can influence tumour vascularity and inflammation in the tumour microenvironment, which can support tumour development and growth. Trials investigating non-pharmacological approaches to target the mechanisms driving obesity-mediated cancer pathogenesis are emerging and are necessary to better appreciate the interplay between malignancy, adiposity, diet and exercise. Diet, exercise and bariatric surgery are potential strategies to reverse the cancer-promoting effects of obesity; trials of these interventions should be conducted in a scientifically rigorous manner with dose escalation and appropriate selection of tumour phenotypes and have cancer-related clinical and mechanistic endpoints. We are only beginning to understand the mechanisms by which obesity effects cell signalling and systemic factors that contribute to oncogenesis. As the rates of obesity and cancer increase, we must promote the development of non-pharmacological lifestyle trials for the treatment and prevention of malignancy.

The Role of Gut Microbial β-Glucuronidase in Estrogen Reactivation and Breast Cancer

Over the past decade, the gut microbiota has received considerable attention for its interactions with the host. Microbial β-glucuronidase generated by this community has hence aroused concern for its biotransformation activity to a wide range of exogenous (foreign) and endogenous compounds. Lately, the role of gut microbial β-glucuronidase in the pathogenesis of breast cancer has been proposed for its estrogen reactivation activity. This is plausible considering that estrogen glucuronides are the primary products of estrogens' hepatic phase II metabolism and are subject to β-glucuronidase-catalyzed hydrolysis in the gut via bile excretion. However, research in this field is still at its very preliminary stage. This review outlines the biology of microbial β-glucuronidase in the gastrointestinal tract and elaborates on the clues to the existence of microbial β-glucuronidase-estrogen metabolism-breast cancer axis. The research gaps in this field will be discussed and possible strategies to address these challenges are suggested.

Commensal microbiota in the digestive tract: a review of its roles in carcinogenesis and radiotherapy

The human microflora is a complex ecosystem composed of diverse microorganisms mainly distributed in the epidermal and mucosal habitats of the entire body, including the mouth, lung, intestines, skin, and vagina. These microbial communities are involved in many essential functions, such as metabolism, immunity, host nutrition, and diseases. Recent studies have focused on the microbiota associated with cancers, particularly the oral and intestinal microbiota. Radiotherapy, the most effective cytotoxic modality available for solid tumors, contributes to the treatment of cancer patients. Mounting evidence supports that the microbiota plays pivotal roles in the efficacy and prognosis of tumor radiotherapy. Here, we review current research on the microbiota and cancer development, and describe knowledge gaps in the study of radiotherapy and the microbiota. Better understanding of the effects of the microbiome in tumorigenesis and radiotherapy will shed light on future novel prevention and treatment strategies based on modulating the microbiome in cancer patients.

Gut Microbiota Dynamics during Chemotherapy in Epithelial Ovarian Cancer Patients Are Related to Therapeutic Outcome

Simple Summary

This pilot study on the trajectory of the gut microbiota (GM) in patients with epithelial ovarian cancer undergoing neoadjuvant and adjuvant chemotherapy highlighted peculiar dynamics associated with the therapeutic outcome. In particular, platinum-resistant patients showed a marked temporal reduction in GM diversity and increased instability with loss of health-associated taxa and increased proportions of lactate-producing microorganisms compared to those sensitive to platinum. These potential GM signatures of therapeutic failure are detectable within the first half of chemotherapy cycles, suggesting that early integrated treatments also aimed at modulating GM could influence therapeutic outcome. Further studies in larger cohorts combining multiple omics and possibly animal models are urgently needed for in-depth mechanistic understanding.

Abstract

Epithelial ovarian cancer (EOC) is one of the most lethal and silent gynecological tumors. Despite appropriate surgery and chemotherapy, relapse occurs in over half of patients with a poor prognosis. Recently, the gut microbiota (GM) was hypothesized to influence the efficacy of anticancer therapies, but no data are available in EOC. Here, by 16S rRNA gene sequencing and inferred metagenomics, we profiled the GM of EOC patients at diagnosis and reconstructed its trajectory along the course of neoadjuvant or adjuvant chemotherapy up to follow-up. Compared to healthy subjects, the GM of EOC patients appeared unbalanced and severely affected by chemotherapy. Strikingly, discriminating patterns were identified in relation to the therapeutic response. Platinum-resistant patients showed a marked temporal reduction in GM diversity and increased instability with loss of health-associated taxa and increased proportions of Coriobacteriaceae and Bifidobacterium. Notably, most of these microorganisms are lactate producers, suggesting increased lactate production as supported by inferred metagenomics. In contrast, the GM of platinum-sensitive patients appeared overall more diverse and stable and enriched in lactate utilizers from the Veillonellaceae family. In conclusion, we identified potential GM signatures of therapeutic outcome in EOC patients, which could open up new opportunities for cancer prognosis and treatment.

Faecal Microbiota Composition Varies between Patients with Breast Cancer and Healthy Women: A Comparative Case-Control Study

The intestinal microbiota plays an essential role in many diseases, such as obesity, irritable bowel disease (IBD), and cancer. This study aimed to characterize the faecal microbiota from early-stage breast cancer (BC) patients and healthy controls. Faeces from newly diagnosed breast cancer patients, mainly for an invasive carcinoma of no specific type (HR⁺ and HER2⁻), before any therapeutic treatment and healthy controls were collected for metabarcoding analyses. We show that the Shannon index, used as an index of diversity, was statistically lower in the BC group compared to that of controls. This work highlights a reduction of microbial diversity, a relative enrichment in Firmicutes, as well as a depletion in Bacteroidetes in patients diagnosed with early BC compared to those of healthy women. A tendency towards a decreased relative abundance of Odoribacter sp., Butyricimonas sp., and Coprococcus sp. was observed. This preliminary study suggests that breast cancer patients may differ from healthy subjects in their intestinal bacterial composition.

Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies

BACKGROUND

Epidemiologic studies examining the relations between dairy product and calcium intakes and breast cancer have been inconclusive, especially for tumor subtypes.

OBJECTIVE

To evaluate the associations between intakes of specific dairy products and calcium and risk of breast cancer overall and for subtypes defined by estrogen receptor (ER) status.

METHOD

We pooled the individual-level data of over 1 million women who were followed for a maximum of 8-20 years across studies. Associations were evaluated for dairy product and calcium intakes and risk of incident invasive breast cancer overall (n = 37,861 cases) and by subtypes defined by ER status. Study-specific multivariable hazard ratios (HRs) were estimated and then combined using random-effects models.

RESULTS

Overall, no clear association was observed between the consumption of specific dairy foods, dietary (from foods only) calcium, and total (from foods and supplements) calcium, and risk of overall breast cancer. Although each dairy product showed a null or very weak inverse association with risk of overall breast cancer (P, test for trend >0.05 for all), differences by ER status were suggested for yogurt and cottage/ricotta cheese with associations observed for ER-negative tumors only (pooled HR = 0.90, 95% CI: 0.83, 0.98 comparing ≥60 g/d with <1 g/d of yogurt and 0.85, 95% CI: 0.76, 0.95 comparing ≥25 g/d with <1 g/d of cottage/ricotta cheese). Dietary calcium intake was only weakly associated with breast cancer risk (pooled HR = 0.98, 95% CI: 0.97, 0.99 per 350 mg/d).

CONCLUSION

Our study shows that adult dairy or calcium consumption is unlikely to associate with a higher risk of breast cancer and that higher yogurt and cottage/ricotta cheese intakes were inversely associated with the risk of ER-negative breast cancer, a less hormonally dependent subtype with poor prognosis. Future studies on fermented dairy products, earlier life exposures, ER-negative breast cancer, and different racial/ethnic populations may further elucidate the relation.

Role of Gut Microbiota Dysbiosis in Breast Cancer and Novel Approaches in Prevention, Diagnosis, and Treatment

Breast cancer is the most common cause of cancer-related deaths in women. Breast cancer is still a major cause of morbidity and mortality among women despite all the available diagnostic and treatment modalities. The gut microbiota has drawn keen interest as an additional environmental risk factor in breast cancer, especially in sporadic cases. This article explores factors that disrupt the normal gut microbial composition and the role of gut microbial dysbiosis in the development of breast cancer. We finalized 40 relevant articles after searching Pubmed and Google Scholar using regular keywords and the Medical Subject Headings (MeSH) strategy. Gut microbiota dysbiosis has been shown to play a role in the development of breast cancer via estrogen-dependent mechanisms and non-estrogen-dependent mechanisms involving the production of microbial-derived metabolites, immune regulation, and effects on DNA. The gut microbiota influence estrogen metabolism hence estrogen levels. The metabolites that have demonstrated anticancer properties include lithocholic acid, butyrate, and cadaverine. New approaches targeting the gut microbiota have come up and may yield new advances in the prevention, diagnosis, and treatment of breast cancer. They include the use of prebiotics, probiotics, and hormone supplements to restore normobiosis in the prevention and treatment of breast cancer.

Exploring the impact of gut microbiota and diet on breast cancer risk and progression

There is emerging evidence that resident microbiota communities, that is, the microbiota, play a key role in cancer outcomes and anticancer responses. Although this has been relatively well studied in colorectal cancer and melanoma, other cancers, such as breast cancer (BrCa), have been largely overlooked to date. Importantly, many of the environmental factors associated with BrCa incidence and progression are also known to impact the microbiota, for example, diet and antibiotics. Here, we explore BrCa risk factors from large epidemiology studies and microbiota associations, and more recent studies that have directly profiled BrCa patients' gut microbiotas. We also discuss how in vivo studies have begun to unravel the immune mechanisms whereby the microbiota may influence BrCa responses, and finally we examine how diet and specific nutrients are also linked to BrCa outcomes. We also consider future research avenues and important considerations with respect to study design and implementation, and we highlight some of the important unresolved questions, which currently limit our overall understanding of the mechanisms underpinning microbiota-BrCa responses.

Distinct Changes in Gut Microbiota Are Associated with Estradiol-Mediated Protection from Diet-Induced Obesity in Female Mice

A decrease in ovarian estrogens in postmenopausal women increases the risk of weight gain, cardiovascular disease, type 2 diabetes, and chronic inflammation. While it is known that gut microbiota regulates energy homeostasis, it is unclear if gut microbiota is associated with estradiol regulation of metabolism. In this study, we tested if estradiol-mediated protection from high-fat diet (HFD)-induced obesity and metabolic changes are associated with longitudinal alterations in gut microbiota in female mice. Ovariectomized adult mice with vehicle or estradiol (E2) implants were fed chow for two weeks and HFD for four weeks. As reported previously, E2 increased energy expenditure, physical activity, insulin sensitivity, and whole-body glucose turnover. Interestingly, E2 decreased the tight junction protein occludin, suggesting E2 affects gut epithelial integrity. Moreover, E2 increased Akkermansia and decreased Erysipleotrichaceae and Streptococcaceae. Furthermore, Coprobacillus and Lactococcus were positively correlated, while Akkermansia was negatively correlated, with body weight and fat mass. These results suggest that changes in gut epithelial barrier and specific gut microbiota contribute to E2-mediated protection against diet-induced obesity and metabolic dysregulation. These findings provide support for the gut microbiota as a therapeutic target for treating estrogen-dependent metabolic disorders in women.

Structure and Dynamics of the Breast Tissue Microbiomes Under Tumor Influences: An Approach With Neutral, Near-Neutral, and Niche-Neutral Hybrid Models

The structure and dynamics of breast tissue bacteria can have far-reaching influences on women’s health, particularly on breast tumor development. However, there is little understanding on the ecological processes that shape the structure and dynamics of breast tissue bacteria. Here, we fill the gap by applying three metacommunity models for investigating the community assembly and diversity maintenance, including Sloan near neutral model, Harris et al. multisite neutral and Tang & Zhou niche-neutral hybrid models to reanalyze the 16S-rRNA sequencing datasets of 23 healthy, 12 benign tumor, and 33 malignant tumor tissue samples. First, we found that, at the community/metacommunity levels, the mechanisms of bacteria assembly and diversity maintenance of breast tissue bacteria were moderately influenced by stochastic drifts of bacteria demography (division, death, and dispersal of bacterial cells). At species level, on average, approximately 10 and 5% species were above (positively selected) and below (negatively selected) neutral, respectively. Furthermore, malignant tumor may raise the positively selected species up to 17%. Second, malignant tumor appears to inhibit microbial dispersal as evidenced by lowered migration rates, compared with the migration in normal and benign tumor tissues. These theoretic findings can be inspirational for further investigating the relationships between tissue bacteria and breast tumor progression/development.

Diet Alters Entero-Mammary Signaling to Regulate the Breast Microbiome and Tumorigenesis

Obesity and poor diet often go hand-in-hand, altering metabolic signaling and thereby impacting breast cancer risk and outcomes. We have recently demonstrated that dietary patterns modulate mammary microbiota populations. An important and largely open question is whether the microbiome of the gut and mammary gland mediates the dietary effects on breast cancer. To address this, we performed fecal transplants between mice on control or high-fat diets (HFD) and recorded mammary tumor outcomes in a chemical carcinogenesis model. HFD induced protumorigenic effects, which could be mimicked in animals fed a control diet by transplanting HFD-derived microbiota. Fecal transplants altered both the gut and mammary tumor microbiota populations, suggesting a link between the gut and breast microbiomes. HFD increased serum levels of bacterial lipopolysaccharide (LPS), and control diet-derived fecal transplant reduced LPS bioavailability in HFD-fed animals. In vitro models of the normal breast epithelium showed that LPS disrupts tight junctions (TJ) and compromises epithelial permeability. In mice, HFD or fecal transplant from animals on HFD reduced expression of TJ-associated genes in the gut and mammary gland. Furthermore, infecting breast cancer cells with an HFD-derived microbiome increased proliferation, implicating tumor-associated bacteria in cancer signaling. In a double-blind placebo-controlled clinical trial of patients with breast cancer administered fish oil supplements before primary tumor resection, dietary intervention modulated the microbiota in tumors and normal breast tissue. This study demonstrates a link between the gut and breast that mediates the effect of diet on cancer. SIGNIFICANCE: This study demonstrates that diet shifts the microbiome in the gut and the breast tumor microenvironment to affect tumorigenesis, and oral dietary interventions can modulate the tumor microbiota in patients with breast cancer. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/14/3890/F1.large.jpg.

Nutritional Interventions Targeting Gut Microbiota during Cancer Therapies

The gut microbiome is increasingly being recognized for its influence on intestinal and extra-intestinal disorders such as cancer. Today, diet is the most studied environmental modulator of gut microbiota, capable of altering or improving it in terms of richness and diversity. Recent evidence from several preclinical and clinical trials suggested that gut microbiota composition could modulate cancer therapies (toxicities, treatment responses) and vice versa. This review highlights the latest research on the bidirectional associations between gut microbiota and cancer. We also dissect the role of gut microbiota during cancer therapies in terms of toxicity and treatment response and, in turn, how cancer therapies could impact gut microbiota composition and functions. In this context, we summarize the state-of-the-art research regarding the role of various nutritional interventions-prebiotics, dietary strategies, and dietary restrictions-as cutting-edge possibilities to modulate gut microbiota during cancer therapies.

Association of gut microbiomes with lung and esophageal cancer: a pilot study

Gut microbiota, especially human pathogens, has been shown to be involved in the occurrence and development of cancer. Esophageal squamous cell carcinoma and lung cancer are two malignant cancers, and their relationship with gut microbiota is still unclear. Virulence factor database (VFDB) is an integrated and comprehensive online resource for curating information about human pathogens. Here, based on VFDB database, we analyzed the differences of bacteria at genus level in the gut of patients with esophageal squamous cell carcinoma, lung cancer, and healthy controls. We proposed the possible cancer-associated bacteria in gut and put forward their possible effects. Apart from this, principal coordinate analysis (PCoA) and analysis of similarities (ANSOIM) suggested that some bacteria in the gut can be used as potential biomarkers to screen esophageal squamous cell carcinoma and lung cancer, and their effectiveness was preliminary verified. The relative abundance of Klebsiella and Streptococcus can be used to distinguish patients with esophageal squamous cell carcinoma and lung cancer from healthy controls. The absolute abundance of Klebsiella can further distinguish patients with esophageal squamous cell carcinoma from patients with lung cancer. In particular, the relative abundance of Fusobacterium can directly distinguish between patients with esophageal squamous cell carcinoma and healthy controls. Additionally, the absolute abundance of Haemophilus can distinguish lung cancer from healthy controls. Our study provided a new way based on VFDB database to explore the relationship between gut microbiota and cancer, and initially proposed a feasible cancer screening method.

Cancer-fighting potentials of algal polysaccharides as nutraceuticals

Cancer has been listed as one of the world's five incurable diseases by the World Health Organization and causes tens of thousands of deaths every year. Unfortunately, anticancer agents either show limited efficacy or show serious side effects. The algae possess high nutritional value and their polysaccharides have a variety of biological activities, especially anti-cancer and immunomodulatory properties. Algal polysaccharides exert anti-cancer effects by inducing apoptosis, cell cycle arrest, anti-angiogenesis, and regulating intestinal flora and immune function. Algal polysaccharides can be combined with nanoparticles and other drugs to reduce the side effects caused by chemotherapy and increase the anticancer effects. This review shows the signal pathways related to the anti-cancer mechanisms of algal polysaccharides, including their influence on intestinal flora and immune regulation, the application of nanoparticles, and the effects on combination therapy and clinical trials of cancer treatments.

Tumor-related Microbiome in the Breast Microenvironment and Breast Cancer

Despite the significant progress in diagnosis and treatment over the past years in the understanding of breast cancer pathophysiology, it remains one of the leading causes of mortality worldwide among females. Novel technologies are needed to improve better diagnostic and therapeutic approaches, and to better understand the role of tumor-environment microbiome players involved in the progression of this disease. The gut environment is enriched with over 100 trillion microorganisms, which participate in metabolic diseases, obesity, and inflammation, and influence the response to therapy. In addition to the direct metabolic effects of the gut microbiome, accumulating evidence has revealed that a microbiome also exists in the breast and in breast cancer tissue. This microbiome enriched in the breast environment and the tumor microenvironment may modulate effects potentially associated with carcinogenesis and therapeutic interventions in breast tissue, which to date have not been properly acknowledged. Herein, we review the most recent works associated with the population dynamics of breast microbes and explore the significance of the microbiome on diagnosis, tumor development, response to chemotherapy, endocrine therapy, and immunotherapy. To overcome the low reproducibility of evaluations of tumor-related microbiome, sequencing technical escalation and machine deep learning algorithms may be valid for standardization of assessment for breast-related microbiome and their applications as powerful biomarkers for prognosis and predictive response in the future.

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

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

Associations of fecal microbial profiles with breast cancer and nonmalignant breast disease in the Ghana Breast Health Study

The gut microbiota may play a role in breast cancer etiology by regulating hormonal, metabolic and immunologic pathways. We investigated associations of fecal bacteria with breast cancer and nonmalignant breast disease in a case-control study conducted in Ghana, a country with rising breast cancer incidence and mortality. To do this, we sequenced the V4 region of the 16S rRNA gene to characterize bacteria in fecal samples collected at the time of breast biopsy (N = 379 breast cancer cases, N = 102 nonmalignant breast disease cases, N = 414 population-based controls). We estimated associations of alpha diversity (observed amplicon sequence variants [ASVs], Shannon index, and Faith's phylogenetic diversity), beta diversity (Bray-Curtis and unweighted/weighted UniFrac distance), and the presence and relative abundance of select taxa with breast cancer and nonmalignant breast disease using multivariable unconditional polytomous logistic regression. All alpha diversity metrics were strongly, inversely associated with odds of breast cancer and for those in the highest relative to lowest tertile of observed ASVs, the odds ratio (95% confidence interval) was 0.21 (0.13-0.36; Ptrend < .001). Alpha diversity associations were similar for nonmalignant breast disease and breast cancer grade/molecular subtype. All beta diversity distance matrices and multiple taxa with possible estrogen-conjugating and immune-related functions were strongly associated with breast cancer (all Ps < .001). There were no statistically significant differences between breast cancer and nonmalignant breast disease cases in any microbiota metric. In conclusion, fecal bacterial characteristics were strongly and similarly associated with breast cancer and nonmalignant breast disease. Our findings provide novel insight into potential microbially-mediated mechanisms of breast disease.

Intricate Connections between the Microbiota and Endometriosis

Imbalances in gut and reproductive tract microbiota composition, known as dysbiosis, disrupt normal immune function, leading to the elevation of proinflammatory cytokines, compromised immunosurveillance and altered immune cell profiles, all of which may contribute to the pathogenesis of endometriosis. Over time, this immune dysregulation can progress into a chronic state of inflammation, creating an environment conducive to increased adhesion and angiogenesis, which may drive the vicious cycle of endometriosis onset and progression. Recent studies have demonstrated both the ability of endometriosis to induce microbiota changes, and the ability of antibiotics to treat endometriosis. Endometriotic microbiotas have been consistently associated with diminished Lactobacillus dominance, as well as the elevated abundance of bacterial vaginosis-related bacteria and other opportunistic pathogens. Possible explanations for the implications of dysbiosis in endometriosis include the Bacterial Contamination Theory and immune activation, cytokine-impaired gut function, altered estrogen metabolism and signaling, and aberrant progenitor and stem-cell homeostasis. Although preliminary, antibiotic and probiotic treatments have demonstrated efficacy in treating endometriosis, and female reproductive tract (FRT) microbiota sampling has successfully predicted disease risk and stage. Future research should aim to characterize the "core" upper FRT microbiota and elucidate mechanisms behind the relationship between the microbiota and endometriosis.

Using dynamic cell communication improves treatment strategies of breast cancer

Several insights from the clinical treatment of breast cancer patients have revealed that only a portion of patients achieve the expected curative effect after traditional targeted therapy, that surgical treatment may promote the development of cancer metastasis, and that the optimal combination of neoadjuvant chemotherapy and traditional treatment is not clear. Therefore, a more precise classification of breast cancer and selection of treatment methods should be undertaken to improve the efficacy of clinical treatment. In the clinical treatment of breast cancer, cell communication molecules are often selected as therapeutic targets. However, various cell communications are not static. Their dynamic changes are related to communicating cells, communicating molecules, and various intertwined internal and external environmental factors. Understanding the dynamic microenvironment can help us improve therapeutic efficacy and provide new ways to more accurately determine the cancer status. Therefore, this review describes multiple types of cellular communication in the breast cancer microenvironment and incorporates internal and external environmental factors as variable signaling factors in cell communication. Using dynamic and developmental concepts, we summarize the functional changes in signaling molecules and cells to aid in the diagnosis and treatment of breast cancer.

Comparative analysis of excretion of six major compounds of Polygonum orientale L. extract in urine, feces and bile under physiological and myocardial ischemia conditions in rats using UPLC-MS/MS

Polygonum orientale L. is a traditional Chinese medicine having extensive pharmacological activities including antimyocardial ischemia (MI) injury properties. Isoorientin, orientin, vitexin, quercitrin, astragalin and protocatechuic acid are the main compounds in P. orientale extract. The aim of this study was to establish an ultra-performance liquid chromatography-tandem mass spectrometry method for the determination of the content of these compounds in urine, feces and bile samples simultaneously and application of the method in a comparative excretion study in normal and MI model rats after oral administration of P. orientale extract. Chromatographic seperation was conducted on an Agilent Eclipse Plus C₁₈ column with the mobile phase consisting of 0.1% formic acid-acetonitrile and 0.1% formic acid-water. Negative ion multiple reaction monitoring mode was used for quantification. The six compounds had good linearity (r ≥ 0.9921) and acceptable accuracy ranging from 10.10 to -5.82% The relative standard deviations of within-day precision and inter-day precision were <10.45 and 13.44%, respectively. The extraction recovery of the six analytes ranged from 80.31 to 101.47% and the matrix effect was 82.56-102.88%, indicating that the preparations of sample collected form urine, feces and bile were stable throughout analysis. The excretion amount of the six analytes increased in both normal and MI model rats' urine, feces and bile in a 24 h period and became stable between 36 and 48 h after administration. The total excretion rate of six compounds was <5% in urine, feces and bile of normal and MI model rats. The excretion peak period for all compounds in MI rats was slower than that in normal rats. This excretion study provides insights for further application and research on P. orientale.

Gut Microbiota and Gynecological Cancers: A Summary of Pathogenetic Mechanisms and Future Directions

Over the past 20 years, important relationships between the microbiota and human health have emerged. A link between alterations of microbiota composition (dysbiosis) and cancer development has been recently demonstrated. In particular, the composition and the oncogenic role of intestinal bacterial flora has been extensively investigated in preclinical and clinical studies focusing on gastrointestinal tumors. Overall, the development of gastrointestinal tumors is favored by dysbiosis as it leads to depletion of antitumor substances (e.g., short-chain fatty acids) produced by healthy microbiota. Moreover, dysbiosis leads to alterations of the gut barrier, promotes a chronic inflammatory status through activation of toll-like receptors, and causes metabolic and hormonal dysregulations. However, the effects of these imbalances are not limited to the gastrointestinal tract and they can influence gynecological tumor carcinogenesis as well. The purpose of this Review is to provide a synthetic update about the mechanisms of interaction between gut microbiota and the female reproductive tract favoring the development of neoplasms. Furthermore, novel therapeutic approaches based on the modulation of microbiota and their role in gynecological oncology are discussed.

Combined hormonal contraceptives are associated with minor changes in composition and diversity in gut microbiota of healthy women

Recent human and animal studies have found associations between gut microbiota composition and serum levels of sex hormones, indicating that they could be an important factor in shaping the microbiota. However, little is known about the effect of regular hormonal fluctuations over the menstrual cycle or CHC-related changes of hormone levels on gut microbiota structure, diversity and dynamics. The aim of this study was to investigate the effect of CHCs on human gut microbiota composition. The effect of CHC pill intake on gut microbiota composition was studied in a group of seven healthy pre-menopausal women using the CHC pill, compared to the control group of nine age-matched healthy women that have not used hormonal contraceptives in the 6 months prior to the start of the study. By analysing the gut microbiota composition in both groups during one menstrual cycle, we found that CHC usage is associated with a minor decrease in gut microbiota diversity and differences in the abundance of several bacterial taxa. These results call for further investigation of the mechanisms underlying hormonal and hormonal contraceptive-related changes of the gut microbiota and the potential implications of these changes for women's health.

Gut Microbiota as Potential Biomarker and/or Therapeutic Target to Improve the Management of Cancer: Focus on Colibactin-Producing Escherichia coli in Colorectal Cancer

Simple Summary

Gut microbiota is emerging as new diagnostic and prognostic marker and/or therapeutic target to improve the management of cancer. This review aims to summarize microbial signatures that have been associated with digestive and other cancers. We report the clinical relevance of these microbial markers to predict the response to cancer therapy. Among these biomarkers, colibactin-producing E. coli are prevalent in the colonic mucosa of patients with colorectal cancer and they promote colorectal carcinogenesis in several pre-clinical models. Here we discuss the promising use of colibactin-producing E. coli as a new predictive factor and a therapeutic target in colon cancer management.

Abstract

The gut microbiota is crucial for physiological development and immunological homeostasis. Alterations of this microbial community called dysbiosis, have been associated with cancers such colorectal cancers (CRC). The pro-carcinogenic potential of this dysbiotic microbiota has been demonstrated in the colon. Recently the role of the microbiota in the efficacy of anti-tumor therapeutic strategies has been described in digestive cancers and in other cancers (e.g., melanoma and sarcoma). Different bacterial species seem to be implicated in these mechanisms: F. nucleatum, B. fragilis, and colibactin-associated E. coli (CoPEC). CoPEC bacteria are prevalent in the colonic mucosa of patients with CRC and they promote colorectal carcinogenesis in susceptible mouse models of CRC. In this review, we report preclinical and clinical data that suggest that CoPEC could be a new factor predictive of poor outcomes that could be used to improve cancer management. Moreover, we describe the possibility of using these bacteria as new therapeutic targets.

Health benefits of edible mushroom polysaccharides and associated gut microbiota regulation

Edible mushrooms have been an important part of the human diet for thousands of years, and over 100 varieties have been cultivated for their potential human health benefits. In recent years, edible mushroom polysaccharides (EMPs) have been studied for their activities against obesity, inflammatory bowel disease (IBD), and cancer. Particularly, accumulating evidence on the exact causality between these health risks and specific gut microbiota species has been revealed and characterized, and most of the beneficial health effects of EMPs have been associated with its reversal impacts on gut microbiota dysbiosis. This demonstrates the key role of EMPs in decreasing health risks through gut microbiota modulation effects. This review article compiles and summarizes the latest studies that focus on the health benefits and underlying functional mechanisms of gut microbiota regulation via EMPs. We conclude that EMPs can be considered a dietary source for the improvement and prevention of several health risks, and this review provides the theoretical basis and technical guidance for the development of novel functional foods with the utilization of edible mushrooms.

Gut microbial differences in breast and prostate cancer cases from two randomised controlled trials compared to matched cancer-free controls

Implicated in several chronic diseases, the gastrointestinal microbiome is hypothesised to influence carcinogenesis. We compared faecal microbiota of newly diagnosed treatment-naïve overweight and obese cancer patients and matched controls. Cases were enrolled in presurgical weight-loss trials for breast (NCT02224807) and prostate (NCT01886677) cancers and had a body mass index (BMI) ≥25 kg/m². Cancer-free controls were matched 1:1 by age (±5 years), race, gender, and BMI (±5 kg/m²). All participants provided faecal samples; isolated bacterial DNA were PCR amplified at the V4 region of the 16S rRNA gene and analysed using the QIIME pipeline. Tests compared cases versus controls, then separately by gender. Microbial alpha-diversity and beta-diversity were assessed, and relative abundance of Operational Taxonomic Units (OTU's) were compared at the genus level, with false discovery rate (FDR) correction. 22 overweight and obese cancer patients were matched with 22 cancer-free controls, with an average BMI of 30.5±4.3 kg/m², age 54.4±5.3 years, and 54.5% were black. Fourteen matches were made between breast cancer cases and healthy female controls, and 8 matches were made with prostate cancer cases and healthy male controls. Comparison of all cases and controls revealed no differences in alpha diversity, though prostate cancer patients had higher Chao1 (P=0.006) and Observed Species (P=0.036) than cancer-free males. Beta-diversity metrics were significantly different between cases and controls (P<0.03 for all tests in whole sample and in men), though only unweighted Unifrac was different in women (P=0.005). Kruskal Wallis tests indicated significant differences among 16 genera in all matches, 9 in female, and 51 in male. This study suggests the faecal microbiota of treatment-naive breast and prostate cancer patients differs from controls, though larger samples are needed to substantiate these findings. Trial registration: NIH Clinical Trials, NCT01886677, NCT02224807, registered 26 June 2013, 25 Aug 2014 (respectively) - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT01886677; https://clinicaltrials.gov/ct2/show/NCT02224807.

Taxamat: Automated biodiversity data management tool - Implications for microbiome studies

Working with biodiversity data is a computationally intensive process. Numerous applications and services provide options to deal with sequencing and taxonomy data. Professional statistics software are also available to analyze these type of data. However, in-between the two processes there is a huge need to curate biodiversity sample files. Curation involves creating summed abundance values for chosen taxonomy ranks, excluding certain taxa from analysis, and finally merging and downsampling data files. Very few tools, if any, offer a solution to this problem, thus we present Taxamat, a simple data management application that allows for curation of biodiversity data files before they can be imported to other statistics software. Taxamat is a downloadable application for automated curation of biodiversity data featuring taxonomic classification, taxon filtering, sample merging, and downsampling. Input and output files are compatible with most widely used programs. Taxamat is available on the web at http://www.taxamat.com either as a single executable or as an installable package for Microsoft Windows platforms.

The lung microbiota in Korean patients with non-tuberculous mycobacterial pulmonary disease

Background

The microbiota of the lower respiratory tract in patients with non-tuberculous mycobacterial pulmonary disease (NTM-PD) has not been fully evaluated. We explored the role of the lung microbiota in NTM-PD by analyzing protected specimen brushing (PSB) and bronchial washing samples from patients with NTM-PD obtained using a flexible bronchoscope.

Results

Bronchial washing and PSB samples from the NTM-PD group tended to have fewer OTUs and lower Chao1 richness values compared with those from the control group. In both bronchial washing and PSB samples, beta diversity was significantly lower in the NTM-PD group than in the control group (P = 2.25E-6 and P = 4.13E-4, respectively). Principal component analysis showed that the PSBs and bronchial washings exhibited similar patterns within each group but differed between the two groups. The volcano plots indicated differences in several phyla and genera between the two groups.

Conclusions

The lower respiratory tract of patients with NTM-PD has a unique microbiota distribution that is low in richness/diversity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02141-1.

Exploring the Potential of Breast Microbiota as Biomarker for Breast Cancer and Therapeutic Response

Breast cancer tissue contains its own unique microbiota. Emerging preclinical data indicates that breast microbiota dysbiosis contributes to breast cancer initiation and progression. Furthermore, the breast microbiota may be a promising biomarker for treatment selection and prognosis. Differences in breast microbiota composition have been found between breast cancer subtypes and disease severities that may contribute to immunosuppression, enabling tumor cells to evade immune destruction. Interactions between breast microbiota, gut microbiota, and immune system are proposed, all forming potential targets to increase therapeutic efficacy. In addition, because the gut microbiota affects the host immune system and systemic availability of estrogen and bile acids known to influence tumor biology, gut microbiota modulation could be used to manipulate breast microbiota composition. Identifying breast and gut microbial compositions that respond positively to certain anticancer therapeutics could significantly reduce cancer burden. Additional research is needed to unravel the complexity of breast microbiota functioning and its interactions with the gut and the immune system. In this review, developments in the understanding of breast microbiota and its interaction with the immune system and the gut microbiota are discussed. Furthermore, the biomarker potential of breast microbiota is evaluated in conjunction with possible strategies to target microbiota in order to improve breast cancer treatment.

Approaching precision medicine by tailoring the microbiota

Accumulating evidence has revealed the link between the microbiota and various human diseases. Advances in high-throughput sequencing technologies have identified some consistent disease-associated microbial features, leading to the emerging concept of microbiome-based therapeutics. However, it is also becoming clear that there are considerable variations in the microbiota among patients with the same disease. Variations in the microbial composition and function contribute to substantial differences in metabolic status of the host via production of a myriad of biochemically and functionally different microbial metabolites. Indeed, compelling evidence indicates that individuality of the microbiome may result in individualized responses to microbiome-based therapeutics and other interventions. Mechanistic understanding of the role of the microbiota in diseases and drug metabolism would help us to identify causal relationships and thus guide the development of microbiome-based precision or personalized medicine. In this review, we provide an overview of current efforts to use microbiome-based interventions for the treatment of diseases such as cancer, neurological disorders, and diabetes to approach precision medicine.

The onco-immunological implications of Fusobacterium nucleatum in breast cancer

Breast cancer is a leading cause of death worldwide and a better understanding of this disease is needed to improve treatment outcomes. Recent evidence indicates that bacterial dysbiosis is associated with breast cancer, but the bacteria involved remain poorly characterised. Furthermore, an association between periodontal disease, characterised by oral dysbiosis, and breast cancer have also been discovered, but the mechanisms responsible for this association remains to be elucidated. The oral bacterium involved in periodontal disease, Fusobacterium nucleatum, have recently been detected in human breast tumour tissue and it promoted tumour growth and metastatic progression in a mouse model. The mechanisms of how F. nucleatum might colonise breast tissue and how it might promote tumour progression has not been fully elucidated yet. Here we discuss the breast tumour microbiota, its colonisation by F. nucleatum, possible mechanisms by which F. nucleatum might promote breast cancer progression and how this might impact breast cancer treatment. Literature indicates that F. nucleatum might promote breast cancer progression through activating the Toll-like receptor 4 pathway and by supressing the immune system. This results in cell growth and treatment resistance through autophagy as well as immune evasion. Targeted treatment directed at F. nucleatum combined with immunotherapy and autophagy inhibitors might therefore be a feasible treatment strategy for breast cancer patients.

Immune Checkpoint Inhibitors in Triple Negative Breast Cancer Treatment: Promising Future Prospects

Immunotherapy has emerged as the fifth pillar of cancer treatment alongside surgery, radiotherapy, chemotherapy, and targeted therapy. Immune checkpoint inhibitors are the current superheroes of immunotherapy, unleashing a patient's own immune cells to kill tumors and revolutionizing cancer treatment in a variety of cancers. Although breast cancer was historically believed to be immunologically silent, treatment with immune checkpoint inhibitors has been shown to induce modest responses in metastatic breast cancer. Given the inherent heterogeneity of breast tumors, this raised the question whether certain breast tumors might benefit more from immune-based interventions and which cancer cell-intrinsic and/or microenvironmental factors define the likelihood of inducing a potent and durable anti-tumor immune response. In this review, we will focus on triple negative breast cancer as immunogenic breast cancer subtype, and specifically discuss the relevance of tumor mutational burden, the plethora and diversity of tumor infiltrating immune cells in addition to the immunoscore, the presence of immune checkpoint expression, and the microbiome in defining immune checkpoint blockade response. We will highlight the current immune checkpoint inhibitor treatment options, either as monotherapy or in combination with standard-of-care treatment modalities such as chemotherapy and targeted therapy. In addition, we will look into the potential of immunotherapy-based combination strategies using immune checkpoint inhibitors to enhance both innate and adaptive immune responses, or to establish a more immune favorable environment for cancer vaccines. Finally, the review will address the need for unambiguous predictive biomarkers as one of the main challenges of immune checkpoint blockade. To conclude, the potential of immune checkpoint blockade for triple negative breast cancer treatment could be enhanced by exploration of aforementioned factors and treatment strategies thereby providing promising future prospects.

Human Microbiota and Breast Cancer-Is There Any Relevant Link?-A Literature Review and New Horizons Toward Personalised Medicine

Breast cancer (BC) is the most common malignancy and the second cause of cancer-specific death in women from high-income countries. Recently, gut microbiota dysbiosis emerged as a key player that may directly and/or indirectly influence development, treatment, and prognosis of BC through diverse biological processes: host cell proliferation and death, immune system function, chronic inflammation, oncogenic signalling, hormonal and detoxification pathways. Gut colonisation occurs during the prenatal period and is later diversified over distinct phases throughout life. In newly diagnosed postmenopausal BC patients, an altered faecal microbiota composition has been observed compared with healthy controls. Particularly, β-glucuronidase bacteria seem to modulate the enterohepatic circulation of oestrogens and their resorption, increasing the risk of hormone-dependent BC. Moreover, active phytoestrogens, short-chain fatty acids, lithocholic acid, and cadaverine have been identified as bacterial metabolites influencing the risk and prognosis of BC. As in gut, links are also being made with local microbiota of tumoural and healthy breast tissues. In breast microbiota, different microbial signatures have been reported, with distinct patterns per stage and biological subtype. Total bacterial DNA load was lower in tumour tissue and advanced-stage BC when compared with healthy tissue and early stage BC, respectively. Hypothetically, these findings reflect local dysbiosis, potentially creating an environment that favours breast tumour carcinogenesis (oncogenic trigger), or the natural selection of microorganisms adapted to a specific microenvironment. In this review, we discuss the origin, composition, and dynamic evolution of human microbiota, the links between gut/breast microbiota and BC, and explore the potential implications of metabolomics and pharmacomicrobiomics that might impact BC development and treatment choices toward a more personalised medicine. Finally, we put in perspective the potential limitations and biases regarding the current microbiota research and provide new horizons for stronger accurate translational and clinical studies that are needed to better elucidate the complex network of interactions between host, microorganisms, and drugs in the field of BC.