Antibiotics and risk of breast cancer: up to 9 years of follow-up of 2.1 million women

Association between Antibiotic Use and Subsequent Risk of Breast Cancer: A Nationwide Retrospective Cohort Study in South Korea

Several studies have revealed a possible association between antibiotic use and breast cancer in the Western population of women. However, its association with the Asian population remains unclear. Data utilized in this nationwide population-based retrospective cohort study were obtained from the Korean National Health Insurance Service database. The study population consisted of 4,097,812 women who were followed up from January 1, 2007, to December 31, 2019. Cox proportional hazards regression was utilized to calculate adjusted hazard ratio (aHR) and 95% confidence interval (CI) for the risk of breast cancer according to cumulative days of antibiotic use and the number of antibiotic classes used. It was discovered that women who used antibiotics for more than 365 days had a higher risk of breast cancer (aHR, 1.15; 95% CI, 1.09-1.21) in comparison with those who did not use antibiotics. In addition, an association was found among women who used five or more classes of antibiotics, showing a higher risk of breast cancer (aHR, 1.11; 95% CI, 1.05-1.17) compared with nonusers. Furthermore, compared with antibiotic nonusers, only users of cephalosporins (aHR, 1.09; 95% CI, 1.02-1.17) and lincosamides (aHR, 1.70; 95% CI, 1.20-2.42) had a higher risk of breast cancer. These findings support epidemiologic evidence that long-term use of antibiotics may be associated with a higher risk of breast cancer. This underscores the need for further studies to address the potential for residual confounding, confirm causation, and elucidate the underlying mechanisms. Prevention Relevance: This study found a probable duration-dependent association between antibiotic prescriptions and breast cancer risk. The findings indicate that long-term antibiotic use could be associated with an increased risk of breast cancer and highlight the need for further research to confirm causality and mechanisms.

Interactions between the tumor microbiota and breast cancer

Breast cancer is the most common malignancy in women worldwide. Changes in the microbiota and their metabolites affect the occurrence and development of breast cancer; however, the specific mechanisms are not clear. Gut microbes and their metabolites influence the development of breast cancer by regulating the tumor immune response, estrogen metabolism, chemotherapy, and immunotherapy effects. It was previously thought that there were no microorganisms in breast tissue, but it is now thought that there are microorganisms in breast cancer that can affect the outcome of the disease. This review builds on existing research to comprehensively analyze the role of gut and intratumoral microbiota and their metabolites in the development and metastasis of breast cancer. We also explore the potential function of the microbiota as biomarkers for prognosis and therapeutic response, highlighting the need for further research to clarify the causal relationship between the microbiota and breast cancer. We hope to provide new ideas and directions for the development of new methods for breast cancer treatment.

Roles of Mesenchymal Stem Cells in Breast Cancer Therapy: Engineered Stem Cells and Exosomal Cell-Free Based Therapy

Breast cancer has a high prevalence among women, with a high mortality rate. The number of people who suffer from breast cancer disease is increasing, whereas metastatic cancers are mostly incurable, and existing therapies have unfavorable side effects. For an extended duration, scientists have dedicated their efforts to exploring the potential of mesenchymal stem cells (MSCs) for the treatment of metastatic cancers, including breast cancer. MSCs could be genetically engineered to boost their anticancer potency. Furthermore, MSCs can transport oncolytic viruses, suicide genes, and anticancer medicines to tumors. Extracellular vesicles (EVs) are MSC products that have attracted scientist's attention as a cell-free treatment. This study narratively reviews the current state of knowledge on engineered MSCs and their EVs as promising treatments for breast cancer.

Characterization of immunomodulating agents from Staphylococcus aureus for priming immunotherapy in triple-negative breast cancers

Immunotherapy, specifically immune checkpoint blockade (ICB), has revolutionized the treatment paradigm of triple-negative breast cancers (TNBCs). However, a subset of TNBCs devoid of tumor-infiltrating T cells (TILs) or PD-L1 expression generally has a poor response to immunotherapy. In this study, we aimed to sensitize TNBCs to ICB by harnessing the immunomodulating potential of S. aureus, a breast-resident bacterium. We show that intratumoral injection of spent culture media from S. aureus recruits TILs and suppresses tumor growth in a preclinical TNBC model. We further demonstrate that α-hemolysin (HLA), an S. aureus-produced molecule, increases the levels of CD8+ T cells and PD-L1 expression in tumors, delays tumor growth, and triggers tumor necrosis. Mechanistically, while tumor cells treated with HLA display Gasdermin E (GSDME) cleavage and a cellular phenotype resembling pyroptosis, splenic T cells incubated with HLA lead to selective expansion of CD8+ T cells. Notably, intratumoral HLA injection prior to ICB augments the therapeutic efficacy compared to ICB alone. This study uncovers novel immunomodulatory properties of HLA and suggests that intratumoral administration of HLA could be a potential priming strategy to expand the population of TNBC patients who may respond to ICB.

The effect of an exopolysaccharide probiotic molecule from Bacillus subtilis on breast cancer cells

Introduction

Many well-known risk factors for breast cancer are associated with dysbiosis (an aberrant microbiome). However, how bacterial products modulate cancer are poorly understood. In this study, we investigated the effect of an exopolysaccharide (EPS) produced by the commensal bacterium Bacillus subtilis on breast cancer phenotypes. Although B. subtilis is commonly included in probiotic preparations and its EPS protects against inflammatory diseases, it was virtually unknown whether B. subtilis-derived EPS affects cancer.

Methods

This work investigated effects of EPS on phenotypes of breast cancer cells as a cancer model. The phenotypes included proliferation, mammosphere formation, cell migration, and tumor growth in two immune compromised mouse models. RNA sequencing was performed on RNA from four breast cancer cells treated with PBS or EPS. IKKβ or STAT1 signaling was assessed using pharmacologic or RNAi-mediated knock down approaches.

Results

Short-term treatment with EPS inhibited proliferation of certain breast cancer cells (T47D, MDA-MB-468, HCC1428, MDA-MB-453) while having little effect on others (MCF-7, MDA-MB-231, BT549, ZR-75-30). EPS induced G1/G0 cell cycle arrest of T47D cells while increasing apoptosis of MDA-MB-468 cells. EPS also enhanced aggressive phenotypes in T47D cells including cell migration and cancer stem cell survival. Long-term treatment with EPS (months) led to resistance in vitro and promoted tumor growth in immunocompromised mice. RNA-sequence analysis showed that EPS increased expression of pro-inflammatory pathways including STAT1 and NF-κB. IKKβ and/or STAT1 signaling was necessary for EPS to modulate phenotypes of EPS sensitive breast cancer cells.

Discussion

These results demonstrate a multifaceted role for an EPS molecule secreted by the probiotic bacterium B. subtilis on breast cancer cell phenotypes. These results warrant future studies in immune competent mice and different cancer models to fully understand potential benefits and/or side effects of long-term use of probiotics.

Understanding and harnessing triple-negative breast cancer-related microbiota in oncology

Bacterial inhabitants of the body have the potential to play a role in various stages of cancer initiation, progression, and treatment. These bacteria may be distal to the primary tumour, such as gut microbiota, or local to the tissue, before or after tumour growth. Breast cancer is well studied in this context. Amongst breast cancer types, Triple Negative Breast Cancer (TNBC) is more aggressive, has fewer treatment options than receptor-positive breast cancers, has an overall worse prognosis and higher rates of reoccurrence. Thus, an in-depth understanding of the bacterial influence on TNBC progression and treatment is of high value. In this regard, the Gut Microbiota (GM) can be involved in various stages of tumour progression. It may suppress or promote carcinogenesis through the release of carcinogenic metabolites, sustenance of proinflammatory environments and/or the promotion of epigenetic changes in our genome. It can also mediate metastasis and reoccurrence through interactions with the immune system and has been recently shown to influence chemo-, radio-, and immune-therapies. Furthermore, bacteria have also been found to reside in normal and malignant breast tissue. Several studies have now described the breast and breast tumour microbiome, with the tumour microbiota of TNBC having the least taxonomic diversity among all breast cancer types. Here, specific conditions of the tumour microenvironment (TME) - low O2, leaky vasculature and immune suppression - are supportive of tumour selective bacterial growth. This innate bacterial ability could enable their use as delivery agents for various therapeutics or as diagnostics. This review aims to examine the current knowledge on bacterial relevance to TNBC and potential uses while examining some of the remaining unanswered questions regarding mechanisms underpinning observed effects.

Association of Spironolactone Use With Risk of Cancer: A Systematic Review and Meta-analysis

IMPORTANCE

While originally approved for the management of heart failure, hypertension, and edema, spironolactone is commonly used off label in the management of acne, hidradenitis, androgenetic alopecia, and hirsutism. However, spironolactone carries an official warning from the US Food and Drug Administration regarding potential for tumorigenicity.

OBJECTIVE

To determine the pooled occurrence of cancers, in particular breast and prostate cancers, among those who were ever treated with spironolactone.

DATA SOURCES

PubMed, Cochrane Library, Embase, and Web of Science were searched from inception through June 11, 2021. The search was restricted to studies in the English language.

STUDY SELECTION

Included studies reported the occurrence of cancers in men and women 18 years and older who were exposed to spironolactone.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers (K.B. and H.H.) selected studies, extracted data, and appraised the risk of bias using the Newcastle-Ottawa Scale. Studies were synthesized using random effects meta-analysis.

MAIN OUTCOMES AND MEASURES

Cancer occurrence, with a focus on breast and prostate cancers.

RESULTS

Seven studies met eligibility criteria, with sample sizes ranging from 18 035 to 2.3 million and a total population of 4 528 332 individuals (mean age, 62.6-72.0 years; in the studies without stratification by sex, women accounted for 17.2%-54.4%). All studies were considered to be of low risk of bias. No statistically significant association was observed between spironolactone use and risk of breast cancer (risk ratio [RR], 1.04; 95% CI, 0.86-1.22; certainty of evidence very low). There was an association between spironolactone use and decreased risk of prostate cancer (RR, 0.79; 95% CI, 0.68-0.90; certainty of evidence very low). There was no statistically significant association between spironolactone use and risk of ovarian cancer (RR, 1.52; 95% CI, 0.84-2.20; certainty of evidence very low), bladder cancer (RR, 0.89; 95% CI, 0.71-1.07; certainty of evidence very low), kidney cancer (RR, 0.96; 95% CI, 0.85-1.07; certainty of evidence low), gastric cancer (RR, 1.02; 95% CI, 0.80-1.24; certainty of evidence low), or esophageal cancer (RR, 1.09; 95% CI, 0.91-1.27; certainty of evidence low).

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, spironolactone use was not associated with a substantial increased risk of cancer and was associated with a decreased risk of prostate cancer. However, the certainty of the evidence was low and future studies are needed, including among diverse populations such as younger individuals and those with acne or hirsutism.

Triple-Negative Breast Cancer: A Brief Review About Epidemiology, Risk Factors, Signaling Pathways, Treatment and Role of Artificial Intelligence

Triple-negative breast cancer (TNBC) is a kind of breast cancer that lacks estrogen, progesterone, and human epidermal growth factor receptor 2. This cancer is responsible for more than 15-20% of all breast cancers and is of particular research interest as it is therapeutically challenging mainly because of its low response to therapeutics and highly invasive nature. The non-availability of specific treatment options for TNBC is usually managed by conventional therapy, which often leads to relapse. The focus of this review is to provide up-to-date information related to TNBC epidemiology, risk factors, metastasis, different signaling pathways, and the pathways that can be blocked, immune suppressive cells of the TNBC microenvironment, current and investigation therapies, prognosis, and the role of artificial intelligence in TNBC diagnosis. The data presented in this paper may be helpful for researchers working in the field to obtain general and particular information to advance the understanding of TNBC and provide suitable disease management in the future.

Challenges of repurposing tetracyclines for the treatment of Alzheimer's and Parkinson's disease

The novel antibiotic-exploiting strategy in the treatment of Alzheimer's (AD) and Parkinson's (PD) disease has emerged as a potential breakthrough in the field. The research in animal AD/PD models provided evidence on the antiamyloidogenic, anti-inflammatory, antioxidant and antiapoptotic activity of tetracyclines, associated with cognitive improvement. The neuroprotective effects of minocycline and doxycycline in animals initiated investigation of their clinical efficacy in AD and PD patients which led to inconclusive results and additionally to insufficient safety data on a long-standing doxycycline and minocycline therapy in these patient populations. The safety issues should be considered in two levels; in AD/PD patients (particularly antibiotic-induced alteration of gut microbiota and its consequences), and as a world-wide threat of development of bacterial resistance to these antibiotics posed by a fact that AD and PD are widespread incurable diseases which require daily administered long-lasting antibiotic therapy. Recently proposed subantimicrobial doxycycline doses should be thoroughly explored for their effectiveness and long-term safety especially in AD/PD populations. Keeping in mind the antibacterial activity-related far-reaching undesirable effects both for the patients and globally, further work on repurposing these drugs for a long-standing therapy of AD/PD should consider the chemically modified tetracycline compounds tailored to lack antimicrobial but retain (or introduce) other activities effective against the AD/PD pathology. This strategy might reduce the risk of long-term therapy-related adverse effects (particularly gut-related ones) and development of bacterial resistance toward the tetracycline antibiotic agents but the therapeutic potential and desirable safety profile of such compounds in AD/PD patients need to be confirmed.

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.

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.

Broad-Spectrum Antibiotic Use and Disease Progression in Early-Stage Melanoma Patients: A Retrospective Cohort Study

Animal studies and a few clinical studies have reported mixed findings on the association between antibiotics and cancer incidence. Antibiotics may inhibit tumor cell growth, but could also alter the gut-microbiome-modulated immune system and increase the risk of cancer. Studies that assess how antibiotics affect the progression of cancer are limited. We evaluated the association between broad-spectrum antibiotic use and melanoma progression. We conducted a retrospective cohort study using IQVIA PharMetrics® Plus data (2008-2018). We identified patients with malignant melanoma who underwent wide local excision or Mohs micrographic surgery within 90 days of first diagnosis. Surgery date was the index date. Patients were excluded if they had any other cancer diagnosis or autoimmune disorders in 1 year before the index date ("baseline"). Exposure to broad-spectrum antibiotics was identified in three time windows using three cohorts: 3 months prior to the index date, 1 month after the index date, and 3 months after the index date. The covariates were patients' demographic and clinical characteristics identified in the 1-year baseline period. The patients were followed from the index date until cancer progression, loss of enrollment, or the end of 2 years after the index date. Progression was defined as: (i) any hospice care after surgery, (ii) a new round of treatment for melanoma (surgery, chemotherapy, immunotherapy, targeted therapy, or radiotherapy) 180 days after prior treatment, or (iii) a metastasis diagnosis or a diagnosis of a new nonmelanoma primary cancer at least 180 days after first melanoma diagnosis or prior treatment. A high-dimensional propensity score approach with inverse weighting was used to adjust for the patients' baseline differences. Cox proportional hazard regression was used for estimating the association. The final samples included 3930, 3831, and 3587 patients (mean age: 56 years). Exposure to antibiotics was 16% in the prior-3-months, 22% in the post-1-month, and 22% in the post-3-months. In the pre-3-months analysis, 9% of the exposed group and 9% of the unexposed group had progressed. Antibiotic use was not associated with melanoma progression (HR: 0.81; 95% CI: 0.57-1.14). However, antibiotic use in subsequent 1 month and subsequent 3 months was associated with 31% reduction (HR: 0.69; 95% CI: 0.51-0.92) and 32% reduction (HR: 0.68; 95% CI: 0.51-0.91) in progression, respectively. In this cohort of patients with likely early-stage melanoma cancer, antibiotic use in 1 month and 3 months after melanoma surgery was associated with a lower risk of melanoma progression. Future studies are warranted to validate the findings.

Breast Cancer-Epidemiology, Risk Factors, Classification, Prognostic Markers, and Current Treatment Strategies-An Updated Review

Breast cancer (BC) is the most frequently diagnosed cancer in women worldwide with more than 2 million new cases in 2020. Its incidence and death rates have increased over the last three decades due to the change in risk factor profiles, better cancer registration, and cancer detection. The number of risk factors of BC is significant and includes both the modifiable factors and non-modifiable factors. Currently, about 80% of patients with BC are individuals aged >50. Survival depends on both stage and molecular subtype. Invasive BCs comprise wide spectrum tumors that show a variation concerning their clinical presentation, behavior, and morphology. Based on mRNA gene expression levels, BC can be divided into molecular subtypes (Luminal A, Luminal B, HER2-enriched, and basal-like). The molecular subtypes provide insights into new treatment strategies and patient stratifications that impact the management of BC patients. The eighth edition of TNM classification outlines a new staging system for BC that, in addition to anatomical features, acknowledges biological factors. Treatment of breast cancer is complex and involves a combination of different modalities including surgery, radiotherapy, chemotherapy, hormonal therapy, or biological therapies delivered in diverse sequences.

Neoplasm Reports in Food and Drug Administration Adverse Event Reporting System Following Angiotensin Receptor Blocker Recalls

BACKGROUND

A worldwide voluntary recall of valsartan in July 2018 due to the potential carcinogen N-nitrosodimethylamine received extensive media and public attention. This was followed by more Food and Drug Administration (FDA) recalls regarding other contaminated ARB (angiotensin receptor blocker) products. Our study investigated the association between the FDA recalls and ARB neoplasm adverse events (AEs) reported to the FDA adverse event reporting system.

METHODS

In this cross-sectional study, data were retrospectively collected from the FDA adverse event reporting system database from January 2015 to December 2019. Reporting odds ratios (RORs) were estimated to detect signals of association between ARBs (valsartan, irbesartan, and losartan) and reported neoplasm AEs using negative (amoxicillin and sertraline) and positive (omeprazole and ranitidine) control exposures. The χ² was used to compare categorical variables.

RESULTS

A total of 2 181 524 AEs, including 10 461 nonmetastatic neoplasm AEs were analyzed. Monthly RORs (95% CI) of valsartan-associated neoplasms versus controls (ROR*: valsartan/negative exposures; ROR†: valsartan/omeprazole; and ROR‡: valsartan/ranitidine) showed the highest signals after the recall date in July 2018 (7.64 [4.78-12.19]*; 4.77 [3.36-6.79]†; 4.13 [2.50-6.84]‡) and August 2018 (7.87 [5.19-11.94]*; 5.65 [4.12-7.75]†; and 7.20 [4.46-11.63]‡). In contrast, the highest cancer signals for the irbesartan and losartan recalls detected in March 2019 (4.80*; 4.06†; and 3.38‡) and April 2019 (3.63*; 3.69†; and 2.52‡) respectively, were lower. One-year postrecall reported neoplasm AEs were ≈2-fold higher for valsartan than irbesartan (OR, 1.77 [95% CI, 1.47-2.13], P<0.0001) and losartan (OR, 2.07 [95% CI, 1.85-2.32], P<0.0001). Although all ARBs had the same nitrosamine contamination, we found 1-year postrecall versus prerecall cancer signals for valsartan were 3-fold higher versus control exposures, while the changes in RORs for irbesartan and losartan were only 20-30% higher.

CONCLUSIONS

Significantly more postrecall neoplasms were reported for valsartan, with higher valsartan-associated cancer signals compared with irbesartan and losartan, although they all contained the same carcinogenic contaminant. Extensive media coverage of the FDA valsartan recall may have alarmed patients and generated these abrupt, biologically infeasible cancer signals.

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.

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.

The role of the microbiome in ovarian cancer: mechanistic insights into oncobiosis and to bacterial metabolite signaling

Ovarian cancer is characterized by dysbiosis, referred to as oncobiosis in neoplastic diseases. In ovarian cancer, oncobiosis was identified in numerous compartments, including the tumor tissue itself, the upper and lower female genital tract, serum, peritoneum, and the intestines. Colonization was linked to Gram-negative bacteria with high inflammatory potential. Local inflammation probably participates in the initiation and continuation of carcinogenesis. Furthermore, local bacterial colonies in the peritoneum may facilitate metastasis formation in ovarian cancer. Vaginal infections (e.g. Neisseria gonorrhoeae or Chlamydia trachomatis) increase the risk of developing ovarian cancer. Bacterial metabolites, produced by the healthy eubiome or the oncobiome, may exert autocrine, paracrine, and hormone-like effects, as was evidenced in breast cancer or pancreas adenocarcinoma. We discuss the possible involvement of lipopolysaccharides, lysophosphatides and tryptophan metabolites, as well as, short-chain fatty acids, secondary bile acids and polyamines in the carcinogenesis of ovarian cancer. We discuss the applicability of nutrients, antibiotics, and probiotics to harness the microbiome and support ovarian cancer therapy. The oncobiome and the most likely bacterial metabolites play vital roles in mediating the effectiveness of chemotherapy. Finally, we discuss the potential of oncobiotic changes as biomarkers for the diagnosis of ovarian cancer and microbial metabolites as possible adjuvant agents in therapy.

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.

Gut Microbiota in Cancer Immune Response and Immunotherapy

The gastrointestinal tract (GIT) is the largest immune organ and maintains systemic immune homeostasis in the presence of bacterial challenge. Immune elimination and immune escape are hallmarks of cancer, both of which can be partly bacteria dependent in shaping immunity by mediating host immunomodulation. In addition, host immunity regulates the microbiome by altering bacteria-associated signaling to influence tumor surveillance. Cancer immunotherapy, including immune checkpoint blockade (ICB), appears to have heterogeneous therapeutic effects in different individuals, partially attributed to the microbiota. Thus, the microbiome signature can predict clinical outcomes, prognosis, and immunotherapy responses. In this review, we summarize the intricate crosstalk among the gut microbiome, cancer immune response, and immunotherapy. Interactive modulation of the host microbiota provides new therapeutic strategies to promote anticancer therapy efficacy and/or reduce toxicity.

Indoxylsulfate, a Metabolite of the Microbiome, Has Cytostatic Effects in Breast Cancer via Activation of AHR and PXR Receptors and Induction of Oxidative Stress

Changes to bacterial metabolite-elicited signaling, in oncobiosis associated with breast cancer, plays a role in facilitating the progression of the disease. We show that indoxyl-sulfate (IS), a tryptophan metabolite, has cytostatic properties in models of breast cancer. IS supplementation, in concentrations corresponding to the human serum reference range, suppressed tumor infiltration to the surrounding tissues and metastasis formation in a murine model of breast cancer. In cellular models, IS suppressed NRF2 and induced iNOS, leading to induction of oxidative and nitrosative stress, and, consequently, reduction of cell proliferation; enhanced oxidative and nitrosative stress are crucial in the subsequent cytostasis. IS also suppressed epithelial-to-mesenchymal transition vital for suppressing cellular movement and diapedesis. Furthermore, IS rendered cells hypometabolic, leading to a reduction in aldehyde-dehydrogenase positive cells. Pharmacological inhibition of the pregnane-X receptor using CH223191 and the aryl-hydrocarbon receptor using ketoconazole diminished the IS-elicited effects, suggesting that these receptors were the major receptors of IS in these models. Finally, we showed that increased expression of the human enzymes that form IS (Cyp2E1, Sult1A1, and Sult1A2) is associated with better survival in breast cancer, an effect that is lost in triple negative cases. Taken together, IS, similar to indolepropionic acid (another tryptophan metabolite), has cytostatic properties and higher expression of the metabolic machinery responsible for the formation of IS supports survival in breast cancer.

A Significant Question in Cancer Risk and Therapy: Are Antibiotics Positive or Negative Effectors? Current Answers and Possible Alternatives

Cancer is predominantly considered as an environmental disease caused by genetic or epigenetic alterations induced by exposure to extrinsic (e.g., carcinogens, pollutants, radiation) or intrinsic (e.g., metabolic, immune or genetic deficiencies). Over-exposure to antibiotics, which is favored by unregulated access as well as inappropriate prescriptions by physicians, is known to have led to serious health problems such as the rise of antibiotic resistance, in particular in poorly developed countries. In this review, the attention is focused on evaluating the effects of antibiotic exposure on cancer risk and on the outcome of cancer therapeutic protocols, either directly acting as extrinsic promoters, or indirectly, through interactions with the human gut microbiota. The preponderant evidence derived from information reported over the last 10 years confirms that antibiotic exposure tends to increase cancer risk and, unfortunately, that it reduces the efficacy of various forms of cancer therapy (e.g., chemo-, radio-, and immunotherapy alone or in combination). Alternatives to the current patterns of antibiotic use, such as introducing new antibiotics, bacteriophages or enzybiotics, and implementing dysbiosis-reducing microbiota modulatory strategies in oncology, are discussed. The information is in the end considered from the perspective of the most recent findings on the tumor-specific and intracellular location of the tumor microbiota, and of the most recent theories proposed to explain cancer etiology on the notion of regression of the eukaryotic cells and systems to stages characterized for a lack of coordination among their components of prokaryotic origin, which is promoted by injuries caused by environmental insults.

Indolepropionic Acid, a Metabolite of the Microbiome, Has Cytostatic Properties in Breast Cancer by Activating AHR and PXR Receptors and Inducing Oxidative Stress

Oncobiotic transformation of the gut microbiome may contribute to the risk of breast cancer. Recent studies have provided evidence that the microbiome secretes cytostatic metabolites that inhibit the proliferation, movement, and metastasis formation of cancer cells. In this study, we show that indolepropionic acid (IPA), a bacterial tryptophan metabolite, has cytostatic properties. IPA selectively targeted breast cancer cells, but it had no effects on non-transformed, primary fibroblasts. In cell-based and animal experiments, we showed that IPA supplementation reduced the proportions of cancer stem cells and the proliferation, movement, and metastasis formation of cancer cells. These were achieved through inhibiting epithelial-to-mesenchymal transition, inducing oxidative and nitrosative stress, and boosting antitumor immune response. Increased oxidative/nitrosative stress was due to the IPA-mediated downregulation of nuclear factor erythroid 2-related factor 2 (NRF2), upregulation of inducible nitric oxide synthase (iNOS), and enhanced mitochondrial reactive species production. Increased oxidative/nitrosative stress led to cytostasis and reductions in cancer cell stem-ness. IPA exerted its effects through aryl hydrocarbon receptor (AHR) and pregnane X receptor (PXR) receptors. A higher expression of PXR and AHR supported better survival in human breast cancer patients, highlighting the importance of IPA-elicited pathways in cytostasis in breast cancer. Furthermore, AHR activation and PXR expression related inversely to cancer cell proliferation level and to the stage and grade of the tumor. The fecal microbiome's capacity for IPA biosynthesis was suppressed in women newly diagnosed with breast cancer, especially with stage 0. Bacterial indole biosynthesis showed correlation with lymphocyte infiltration to tumors in humans. Taken together, we found that IPA is a cytostatic bacterial metabolite, the production of which is suppressed in human breast cancer. Bacterial metabolites, among them, IPA, have a pivotal role in regulating the progression but not the initiation of the disease.

Antibiotic use and the risk of breast cancer: A systematic review and dose-response meta-analysis

OBJECTIVE

Oral antibiotics are posed as a possible risk factor for breast cancer. Evidence is insufficient to determine whether the choice of antibiotic class could effect this potential association, and non-linearity has not been studied. We aimed to fill these important knowledge gaps.

METHODS

PubMed, Web of Science, Embase and a trial registry were searched from inception until January 2020, without any restrictions. Additionally, extensive manual searches were undertaken. Random-effects meta-analyses provided pooled risk estimates with 95 % confidence intervals (CI). Dose-response analyses modeling the relationship between number of antibiotic prescriptions and breast cancer risk were extended to non-linear models. Heterogeneity, publication bias and small-study effects were assessed.

RESULTS

Of 7805 identified publications ten were eligible, including 3,719,383 individuals and 84,485 breast cancer cases. The pooled breast cancer risk was modestly increased among individuals who ever used antibiotics (relative risk RR = 1.18, 95 %CI 1.08-1.29), also after excluding the last year prior diagnosis. This excess risk was seen among penicillin (RR = 1.09, 95 %CI 1.01-1.18), tetracycline (RR = 1.13, 95 %CI 1.04-1.24) and nitrofuran users (RR = 1.26, 95 %CI 1.05-1.52), whilst nitroimidazole and metronidazole use (RR = 1.05, 95 %CI 1.00-1.11) indicated for marginal association. No apparent association was found for other antibiotics. Data suggested for a non-linear dose-dependent relationship, with a seemingly protective effect after at least 35 prescriptions. However, these findings might partly be explained by limited power of dose-response analyses.

CONCLUSIONS

The association of antibiotics with breast cancer risk appears to differ between the various antibiotic classes. Whether this association is causal remains unclear, requiring further clarification and mechanistic studies.

The link "Cancer and autoimmune diseases" in the light of microbiota: Evidence of a potential culprit

Evidence establishes that chronic inflammation and autoimmunity are associated with cancer development and patients with a primary malignancy may develop autoimmune-like diseases. Despite immune dysregulation is a common feature of both cancer and autoimmune diseases, precise mechanisms underlying this susceptibility are not clarified and different hypotheses have been proposed, starting from genetic and environmental common features, to intrinsic properties of immune system. Moreover, as the development and use of immunomodulatory therapies for cancer and autoimmune diseases are increasing, the elucidation of this relationship must be investigated in order to offer the best and most secure therapeutic options. The microbiota could represent a potential link between autoimmune diseases and cancer. The immunomodulation role of microbiota is widely recognized and under eubiosis, it orchestrates both the innate and adaptive response of immunity, in order to discriminate and modulate the immune response itself in the most appropriate way. Therefore, a dysbiotic status can alter the immune tonus rendering the host prone to exogenous or endogenous infections, breaking the tolerance against self-components and activating the immune responses in an excessive (i.e. chronic inflammation) or deficient way, favoring the onset of neoplastic and autoimmune diseases.

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.

Oncobiosis and Microbial Metabolite Signaling in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is one of the most lethal cancers in both men and women, with a median five-year survival of around 5%. Therefore, pancreatic adenocarcinoma represents an unmet medical need. Neoplastic diseases, such as pancreatic adenocarcinoma, often are associated with microbiome dysbiosis, termed oncobiosis. In pancreatic adenocarcinoma, the oral, duodenal, ductal, and fecal microbiome become dysbiotic. Furthermore, the pancreas frequently becomes colonized (by Helicobacter pylori and Malassezia, among others). The oncobiomes from long- and short-term survivors of pancreatic adenocarcinoma are different and transplantation of the microbiome from long-term survivors into animal models of pancreatic adenocarcinoma prolongs survival. The oncobiome in pancreatic adenocarcinoma modulates the inflammatory processes that drive carcinogenesis. In this review, we point out that bacterial metabolites (short chain fatty acids, secondary bile acids, polyamines, indole-derivatives, etc.) also have a role in the microbiome-driven pathogenesis of pancreatic adenocarcinoma. Finally, we show that bacterial metabolism and the bacterial metabolome is largely dysregulated in pancreatic adenocarcinoma. The pathogenic role of additional metabolites and metabolic pathways will be identified in the near future, widening the scope of this therapeutically and diagnostically exploitable pathogenic pathway in pancreatic adenocarcinoma.

The Microbiome-Estrogen Connection and Breast Cancer Risk

The microbiome is undoubtedly the second genome of the human body and has diverse roles in health and disease. However, translational progress is limited due to the vastness of the microbiome, which accounts for over 3.3 million genes, whose functions are still unclear. Numerous studies in the past decade have demonstrated how microbiome impacts various organ-specific cancers by altering the energy balance of the body, increasing adiposity, synthesizing genotoxins and small signaling molecules, and priming and regulating immune response and metabolism of indigestible dietary components, xenobiotics, and pharmaceuticals. In relation to breast cancer, one of the most prominent roles of the human microbiome is the regulation of steroid hormone metabolism since endogenous estrogens are the most important risk factor in breast cancer development especially in postmenopausal women. Intestinal microbes encode enzymes capable of deconjugating conjugated estrogen metabolites marked for excretion, pushing them back into the enterohepatic circulation in a biologically active form. In addition, the intestinal microbes also break down otherwise indigestible dietary polyphenols to synthesize estrogen-like compounds or estrogen mimics that exhibit varied estrogenic potency. The present account discusses the potential role of gastrointestinal microbiome in breast cancer development by mediating metabolism of steroid hormones and synthesis of biologically active estrogen mimics.

Modulation of Pulmonary Microbiota by Antibiotic or Probiotic Aerosol Therapy: A Strategy to Promote Immunosurveillance against Lung Metastases

Pulmonary immunological tolerance to inhaled particulates might create a permissive milieu for lung metastasis. Lung microbiota contribute to pulmonary tolerance; here, we explored whether its manipulation via antibiotic or probiotic aerosolization favors immune response against melanoma metastasis. In lungs of vancomycin/neomycin-aerosolized mice, a decrease in bacterial load was associated with reduced regulatory T cells and enhanced T cell and NK cell activation that paralleled a significant reduction of melanoma B16 lung metastases. Reduction of metastases also occurred in lungs transplanted with bacterial isolates from antibiotic-treated lungs. Aerosolized Lactobacillus rhamnosus strongly promoted immunity against B16 lung metastases as well. Furthermore, probiotics or antibiotics improved chemotherapy activity against advanced B16 metastases. Thus, we identify a role for lung microbiota in metastasis and show that its targeting via aerosolization is a therapy that can prevent metastases and enhance responses to chemotherapy.

Untapped "-omics": the microbial metagenome, estrobolome, and their influence on the development of breast cancer and response to treatment

With the advent of next generation sequencing technologies, there is an increasingly complex understanding of the role of gastrointestinal and local breast microbial dysbiosis in breast cancer. In this review, we summarize the current understanding of the microbiome's role in breast carcinogenesis, discussing modifiable risk factors that may affect breast cancer risk by inducing dysbiosis as well as recent sequencing data illustrating breast cancer subtype-specific differences in local breast tissue microbiota. We outline how the 'estrobolome,' the aggregate of estrogen-metabolizing enteric bacterial genes, may affect the risk of developing postmenopausal estrogen receptor-positive breast cancer. We also discuss the microbiome's potent capacity for anticancer therapy activation and deactivation, an important attribute of the gastrointestinal microbiome that has yet to be harnessed clinically.

Demystifying the manipulation of host immunity, metabolism, and extraintestinal tumors by the gut microbiome

The trillions of microorganisms in the gut microbiome have attracted much attention recently owing to their sophisticated and widespread impacts on numerous aspects of host pathophysiology. Remarkable progress in large-scale sequencing and mass spectrometry has increased our understanding of the influence of the microbiome and/or its metabolites on the onset and progression of extraintestinal cancers and the efficacy of cancer immunotherapy. Given the plasticity in microbial composition and function, microbial-based therapeutic interventions, including dietary modulation, prebiotics, and probiotics, as well as fecal microbial transplantation, potentially permit the development of novel strategies for cancer therapy to improve clinical outcomes. Herein, we summarize the latest evidence on the involvement of the gut microbiome in host immunity and metabolism, the effects of the microbiome on extraintestinal cancers and the immune response, and strategies to modulate the gut microbiome, and we discuss ongoing studies and future areas of research that deserve focused research efforts.

The negative impact of antibiotics on outcomes in cancer patients treated with immunotherapy: a new independent prognostic factor?

Immune-checkpoint inhibitors (ICI) now represent the standard of care for several cancer types. In pre-clinical models, absence of an intact gut microbiome negatively impacted ICI efficacy and these findings permitted to unravel the importance of the commensal microbiota in immuno-oncology. Recently, multiple clinical studies including more than 1800 patients in aggregate demonstrated the negative predictive impact of treatments with broad-spectrum antibiotics (ATB) on cancer patients receiving ICI. Altogether, these results have led to the hypothesis that ATB-induced dysbiosis might influence the clinical response through the modulation of the gut microbiome. Controversy still remains, as ATB treatment might simply constitute a surrogate marker of unfit or immunodeficient patients. In this review, we summarize recent publications addressing the impact of the gut microbiome on ICI efficacy, discuss currently available data on the effect of ATB administered in different time-frames respect to ICI initiation, and finally, evoke the therapeutic implications of these findings.

Use of Antibiotics and Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies

The association between antibiotic use and risk of cancer development is unclear, and clinical trials are lacking. We performed a systematic review and meta-analysis of observational studies to assess the association between antibiotic use and risk of cancer. PubMed, the Cochrane Library and EMBASE were searched from inception to 24 February 2019 for studies reporting antibiotic use and subsequent risk of cancer. We included observational studies of adult subjects with previous exposure to antibiotics and available information on incident cancer diagnoses. For each of the eligible studies, data were collected by three reviewers. Risk of cancer was pooled to provide an adjusted odds ratio (OR) with a 95% confidence interval (CI). The primary outcome was the risk of developing cancer in ever versus non-antibiotic users. Cancer risk’s association with antibiotic intake was evaluated among 7,947,270 participants (n = 25 studies). Overall, antibiotic use was an independent risk factor for cancer occurrence (OR 1.18, 95%CI 1.12–1.24, p < 0.001). The risk was especially increased for lung cancer (OR 1.29, 95%CI 1.03–1.61, p = 0.02), lymphomas (OR 1.31, 95%CI 1.13–1.51, p < 0.001), pancreatic cancer (OR 1.28, 95%CI 1.04–1.57, p = 0.019), renal cell carcinoma (OR 1.28, 95%CI 1.1–1.5, p = 0.001), and multiple myeloma (OR 1.36, 95%CI 1.18–1.56, p < 0.001). There is moderate evidence that excessive or prolonged use of antibiotics during a person’s life is associated with slight increased risk of various cancers. The message is potentially important for public health policies because minimizing improper antibiotic use within a program of antibiotic stewardship could also reduce cancer incidence.

Reconsidering the Use of Minocycline in the Preliminary Treatment Regime of Rheumatoid Arthritis

Strong epidemiologic, clinical, and basic science studies have identified a number of factors that may lead to rheumatoid arthritis (RA) onset and progression, particularly involving the complex interplay between genomics, environmental risk factors, the breakdown of immune self-tolerance, and microbiome dysbiosis. A chronic state of inflammation established by infectious agents has long been suspected to set the stage for the development of RA. The purpose of this article is to review the contribution of the gut, lung, and oral microbiomes to the pathogenesis of RA and consider the importance of supplementing the preliminary treatment regime of RA patients with antibiotics, in particular, minocycline. Minocycline has been used in the treatment of RA due to its bacteriostatic, as well as immunomodulatory and anti-inflammatory properties. Ultimately, a short course of antibiotic treatment with minocycline may eliminate pathogenic organisms contributing to the development and progression of RA. 

Potential association between rosacea and cancer: A study in a medical center in southern China

Growing evidence suggests that rosacea increases the risk of systemic diseases, but studies of the relationships between rosacea and cancer are rare. Aimed to assess the relationship between rosacea and cancer, a total of 7548 patients with confirmed internal malignancies and 8340 cancer-free individuals aged 18 years or more were included in this study from November 2015 to October 2017. Clinical characteristics, personal history and laboratory data were recorded when patients were diagnosed with rosacea. Logistic regression analyses were performed to analyze associations between cancer and rosacea. We found rosacea significantly affected more women than men in both cancer and cancer-free group. The data showed there was no relationship between rosacea and lung, gastrointestinal, nasopharyngeal and gynecological cancer. However, rosacea was significantly associated with the increased risk of breast cancer and glioma, but negatively associated with the risk of hematological cancer. Of the 190 female breast cancer patients with rosacea, 98.95% had the erythematotelangiectatic subtype of rosacea, 48.42% had chloasma and 76.31% of them were Fitzpatrick skin type III and IV. In our binary regression model, breast cancer patients with rosacea had a higher prevalence of estrogen receptor-positive status, lower high-density lipoprotein levels and higher low-density lipoprotein than patients with breast cancer but no rosacea. Our findings indicate that rosacea is significantly associated with higher incidence of breast cancer, glioma and lower prevalence of hematological cancer.

Microbiome-Microbial Metabolome-Cancer Cell Interactions in Breast Cancer-Familiar, but Unexplored

Breast cancer is a leading cause of death among women worldwide. Dysbiosis, an aberrant composition of the microbiome, characterizes breast cancer. In this review we discuss the changes to the metabolism of breast cancer cells, as well as the composition of the breast and gut microbiome in breast cancer. The role of the breast microbiome in breast cancer is unresolved, nevertheless it seems that the gut microbiome does have a role in the pathology of the disease. The gut microbiome secretes bioactive metabolites (reactivated estrogens, short chain fatty acids, amino acid metabolites, or secondary bile acids) that modulate breast cancer. We highlight the bacterial species or taxonomical units that generate these metabolites, we show their mode of action, and discuss how the metabolites affect mitochondrial metabolism and other molecular events in breast cancer. These metabolites resemble human hormones, as they are produced in a "gland" (in this case, the microbiome) and they are subsequently transferred to distant sites of action through the circulation. These metabolites appear to be important constituents of the tumor microenvironment. Finally, we discuss how bacterial dysbiosis interferes with breast cancer treatment through interfering with chemotherapeutic drug metabolism and availability.

Cadaverine, a metabolite of the microbiome, reduces breast cancer aggressiveness through trace amino acid receptors

Recent studies showed that changes to the gut microbiome alters the microbiome-derived metabolome, potentially promoting carcinogenesis in organs that are distal to the gut. In this study, we assessed the relationship between breast cancer and cadaverine biosynthesis. Cadaverine treatment of Balb/c female mice (500 nmol/kg p.o. q.d.) grafted with 4T1 breast cancer cells ameliorated the disease (lower mass and infiltration of the primary tumor, fewer metastases, and lower grade tumors). Cadaverine treatment of breast cancer cell lines corresponding to its serum reference range (100–800 nM) reverted endothelial-to-mesenchymal transition, inhibited cellular movement and invasion, moreover, rendered cells less stem cell-like through reducing mitochondrial oxidation. Trace amino acid receptors (TAARs), namely, TAAR1, TAAR8 and TAAR9 were instrumental in provoking the cadaverine-evoked effects. Early stage breast cancer patients, versus control women, had reduced abundance of the CadA and LdcC genes in fecal DNA, both responsible for bacterial cadaverine production. Moreover, we found low protein expression of E. coli LdcC in the feces of stage 1 breast cancer patients. In addition, higher expression of lysine decarboxylase resulted in a prolonged survival among early-stage breast cancer patients. Taken together, cadaverine production seems to be a regulator of early breast cancer.

Lithocholic acid, a bacterial metabolite reduces breast cancer cell proliferation and aggressiveness

Our study aimed at finding a mechanistic relationship between the gut microbiome and breast cancer. Breast cancer cells are not in direct contact with these microbes, but disease could be influenced by bacterial metabolites including secondary bile acids that are exclusively synthesized by the microbiome and known to enter the human circulation. In murine and bench experiments, a secondary bile acid, lithocholic acid (LCA) in concentrations corresponding to its tissue reference concentrations (< 1 μM), reduced cancer cell proliferation (by 10-20%) and VEGF production (by 37%), aggressiveness and metastatic potential of primary tumors through inducing mesenchymal-to-epithelial transition, increased antitumor immune response, OXPHOS and the TCA cycle. Part of these effects was due to activation of TGR5 by LCA. Early stage breast cancer patients, versus control women, had reduced serum LCA levels, reduced chenodeoxycholic acid to LCA ratio, and reduced abundance of the baiH (7α/β-hydroxysteroid dehydroxylase, the key enzyme in LCA generation) gene in fecal DNA, all suggesting reduced microbial generation of LCA in early breast cancer.

Rosacea and its association with enteral microbiota in Korean females

Rosacea is a chronic inflammatory dermatosis affecting the face and eyes. An association between systemic comorbidities and rosacea has been reported, but the link to enteral microbiota is uncertain. We aimed to investigate the link between rosacea and enteral microbiota. A cross-sectional study was performed in a sample of Korean women who participated in a health check-up programme at the Kangbuk Samsung Hospital Health Screening Center between 23 June 2014 and 5 September 2014. The gut microbiome was evaluated by 16S rRNA gene and metagenome sequence analyses. A total of 12 rosacea patients and 251 controls were enrolled. We identified links between rosacea and several changes in gut microbiota: reduced abundance of Peptococcaceae family unknown genus, Methanobrevibacter (genus), Slackia (genus), Coprobacillus (genus), Citrobacter (genus), and Desulfovibrio (genus), and increased abundance of Acidaminococcus (genus), Megasphaera (genus), and Lactobacillales order unknown family unknown genus. A link between rosacea and enteral microbiota was observed in this metagenomic study. A large and elaborate study is needed to confirm these findings and to elucidate the mechanisms involved.

The influence of the commensal microbiota on distal tumor-promoting inflammation

Commensal microbes inhabit barrier surfaces, providing a first line of defense against invading pathogens, aiding in metabolic function of the host, and playing a vital role in immune development and function. Several recent studies have demonstrated that commensal microbes influence systemic immune function and homeostasis. For patients with extramucosal cancers, or cancers occurring distal to barrier surfaces, the role of commensal microbes in influencing tumor progression is beginning to be appreciated. Extrinsic factors such as chronic inflammation, antibiotics, and chemotherapy dysregulate commensal homeostasis and drive tumor-promoting systemic inflammation through a variety of mechanisms, including disruption of barrier function and bacterial translocation, release of soluble inflammatory mediators, and systemic changes in metabolic output. Conversely, it has also been demonstrated that certain immune therapies, immunogenic chemotherapies, and checkpoint inhibitors rely on the commensal microbiota to facilitate anti-tumor immune responses. Thus, it is evident that the mechanisms associated with commensal microbe facilitation of both pro- and anti-tumor immune responses are context dependent and rely upon a variety of factors present within the tumor microenvironment and systemic periphery. The goal of this review is to highlight the various contexts during which commensal microbes orchestrate systemic immune function with a focus on describing possible scenarios where the loss of microbial homeostasis enhances tumor progression.

Microbiome and Anticancer Immunosurveillance

Anticancer immune responses can be considered a desirable form of autoimmunity that may be profoundly shaped by the microbiome. Here, we discuss evidence for the microbiome's influence on anti-tumor immunosurveillance, including those that are indirect and can act at a distance, and we put forward hypotheses regarding mechanisms of how these effects are implemented. These may involve cross-reactivity between microbial and tumor antigens shaping T cell repertoires and/or microbial products stimulating pattern recognition receptors that influence the type and intensity of immune responses. Understanding how the microbiome impacts natural cancer immunosurveillance as well as treatment-induced immune responses will pave the way for more effective therapies and prophylactics.

The Intestinal Microbiome and Estrogen Receptor-Positive Female Breast Cancer

The huge communities of residential microbes, including bacteria, viruses, Archaea, and Eukaryotes, that colonize humans are increasingly recognized as playing important roles in health and disease. A complex populous ecosystem, the human gastrointestinal (GI) tract harbors up to 10(11) bacterial cells per gram of luminal content, whose collective genome, the gut metagenome, contains a vastly greater number of individual genes than the human genome. In health, the function of the microbiome might be considered to be in dynamic equilibrium with the host, exerting both local and distant effects. However, 'disequilibrium' may contribute to the emergence of disease, including malignancy. In this review, we discuss how the intestinal bacterial microbiome and in particular how an 'estrobolome,' the aggregate of enteric bacterial genes capable of metabolizing estrogens, might affect women's risk of developing postmenopausal estrogen receptor-positive breast cancer. Estrobolome composition is impacted by factors that modulate its functional activity. Exploring variations in the composition and activities of the estrobolome in healthy individuals and in women with estrogen-driven breast cancer may lead to development of microbiome-based biomarkers and future targeted interventions to attenuate cancer risk.

Periodontal Disease and Breast Cancer: Prospective Cohort Study of Postmenopausal Women

BACKGROUND

Periodontal disease has been consistently associated with chronic disease; there are no large studies of breast cancer, although oral-associated microbes are present in breast tumors.

METHODS

In the Women's Health Initiative Observational Study, a prospective cohort of postmenopausal women, 73,737 women without previous breast cancer were followed. Incident, primary, invasive breast tumors were verified by physician adjudication. Periodontal disease was by self-report. HRs and 95% confidence intervals (CI) were estimated by Cox proportional hazards, adjusted for breast cancer risk factors. Because the oral microbiome of those with periodontal disease differs with smoking status, we examined associations stratified by smoking.

RESULTS

2,124 incident, invasive breast cancer cases were identified after mean follow-up of 6.7 years. Periodontal disease, reported by 26.1% of women, was associated with increased breast cancer risk (HR 1.14; 95% CI, 1.03-1.26), particularly among former smokers who quit within 20 years (HR 1.36; 95% CI, 1.05-1.77). Among current smokers, the trend was similar (HR 1.32; 95% CI, 0.83-2.11); there were few cases (n = 74) and the CI included the null. The population attributable fraction was 12.06% (95% CI, 1.12-21.79) and 10.90% (95% CI, 10.31-28.94) for periodontal disease among former smokers quitting within 20 years and current smokers, respectively.

CONCLUSION

Periodontal disease, a common chronic inflammatory disorder, was associated with increased risk of postmenopausal breast cancer, particularly among former smokers who quit in the past 20 years.

IMPACT

Understanding a possible role of the oral microbiome in breast carcinogenesis could impact prevention.

Personal history of rosacea and risk of incident cancer among women in the US

BACKGROUND

Rosacea is an inflammatory skin disease. We examined the association between personal history of rosacea and risk of incident cancers.

METHODS

A total of 75 088 whites were included from the Nurses' Health Study II (1991-2011). Information on clinician-diagnosed rosacea and diagnosis year was collected in 2005. All cancers other than basal cell carcinoma (BCC) were confirmed.

RESULTS

During 1 447 205 person-years, we identified 5194 cases with internal malignancies and 5788 with skin cancers. We did not observe significant associations between personal history of rosacea and internal malignancies, except for thyroid cancer (hazard ratio (HR)=1.59, 95% confidence interval (CI)=1.07-2.36). Among skin cancers, personal history of rosacea was associated with an elevated risk of BCC (HR=1.50, 95% CI=1.35-1.67).

CONCLUSIONS

We suggest possible associations between personal history of rosacea and an increased risk of thyroid cancer and BCC. Further studies are warranted to replicate our findings and to explore the underlying mechanisms.

Frequent antibiotic use and second breast cancer events

BACKGROUND

Antibiotic use may be associated with higher breast cancer risk and breast cancer mortality, but no study has evaluated the relation between antibiotic use and second breast cancer events (SBCE).

METHODS

We conducted a retrospective cohort study among women ≥18 years, diagnosed with incident stage I/II breast cancer during 1990-2008. Antibiotic use and covariates were obtained from health plan administrative databases and medical record review. Frequent antibiotic use was defined as ≥4 antibiotic dispensings in any moving 12-month period after diagnosis. Our outcome was SBCE defined as recurrence or second primary breast cancer. We used multivariable Cox proportional hazards models to estimate HR and 95% confidence intervals (CI), accounting for competing risks.

RESULTS

A total of 4,216 women were followed for a median of 6.7 years. Forty percent were frequent antibiotic users and 558 (13%) had an SBCE. Results are suggestive of a modest increased risk of SBCE (HR, 1.15; 95% CI, 0.88-1.50) among frequent antibiotic users compared with nonusers. Any potential increased risk was not supported when we evaluated recent use and past use. We observed no dose-response trends for SBCE with increasing duration of antibiotic use nor did we find evidence for altered SBCE risk in the antibiotic classes studied.

CONCLUSIONS

Frequent antibiotic use may be associated with modestly elevated risk of SBCEs, but the association was not significant.

IMPACT

Additional investigation by antibiotic class and underlying indication are important next steps given the high prevalence of frequent antibiotic use and growing number of breast cancer survivors.

Metronidazole affects breast cancer cell lines

PURPOSE

The aim of our study was to evaluate the impact of metronidazole (MTZ) on cytotoxicity and DNA synthesis in MCF-7 (estrogen receptor positive) and MDA-MB-231 (estrogen receptor negative) breast cancer cell lines.

MATERIAL/METHODS

Toxicity of MTZ was determined by MTT test. MCF-7 and MDA-MB-231 cells were incubated with metronidazole used in different concentrations for 24, 48 and 72 hours. The effect of MTZ on DNA synthesis was measured as [3H]-thymidine incorporation.

RESULTS

We showed that MTZ in concentration 250 μg/ml significantly increases the growth of MCF-7 cell lines after 24 hours of incubation, but it reduces cell viability in concentrations 1 and 10 μg/ml 72 hours after the drug application. Significant increase of MDA-MB-231 cell viability was obtained in MTZ concentration of 250 μg/ml after 24 and 72 hours. The increase of [3H]-thymidine incorporation in MCF-7 cell line treated with MTZ in concentration 250 μg/ml was statistically significant after 24 hours. Great suppression of cell proliferation was obtained in MDA-MB-231 breast cell line after application of the following concentrations of MTZ: 0.1 μg/ml (after 24 hours) and 0.1, 10, 50, 250 μg/ml (after 72h).

CONCLUSIONS

We found that metronidazole exerts different dose- and time- dependent effects on human breast cancer cell lines characterized by presence or absence of estrogen receptors. We suggest that these discrepancies may be influenced by the estrogen signaling.

Antibiotic use and risk of gynecological cancer

OBJECTIVES

Several studies addressed the association between antibiotic use and breast cancer risk. The objective of this study was to assess the association between antibiotic use and risk of cervical, ovarian, and uterine cancer.

STUDY DESIGN

We carried out a population-based case-control study using data from Saskatchewan Health administrative databases (Canada) between the years 1981 and 2000. Cases were matched to 4 controls, using incidence density sampling. The effect of dosage and timing of antibiotic use, over a minimum of 15 years before diagnosis, on cervical, ovarian, or uterine cancer risk was assessed. Number of prescriptions and number of pills were used as exposure definitions. The effect of different classes of antibiotics on cancer risk was also studied.

RESULTS

A total of 1225 cancer cases [192 cervical, 445 ovarian, and 588 uterine] and 4900 matched controls were included in this study. Antibiotic exposure (number of prescriptions) during the period of 1-15 years in the past was significantly associated with a reduced risk of cervical cancer; Relative Risk (RR)=0.40, 0.31, 0.26, and 0.29 for the four exposure quartiles, respectively. No association was found for ovarian or uterine cancer. When number of pills was considered, similar results were found. There was no effect of the timing or class of antibiotic exposure on cervical cancer risk.

CONCLUSIONS

Antibiotic exposure up to 15 years in the past was associated with a decreased risk of cervical cancer. The lack of temporal trends and the absence of class specific effects suggest a non-causal relationship.

Association between antibiotic use and risk of prostate cancer

The association between antibiotics and risk of cancer has been addressed in different studies, most of which were addressing breast cancer. The objective of this study was to assess the association between antibiotics use and risk of prostate cancer. We carried out a population-based case-control study using data from Saskatchewan Health administrative databases (Canada) between the years 1981 and 2000. Cases identified by the Saskatchewan Cancer Agency were matched to 4 controls, using incidence density sampling. The effect of dosage and timing of antibiotic use, over a minimum of 15 years before diagnosis, on prostate cancer risk was assessed. Number of prescriptions and number of tablets were used as exposure definitions. Moreover, the effect of different classes of antibiotics on prostate cancer was also studied. A total of 4,052 prostate cancer cases and 16,208 matched controls were included in this study. Antibiotics exposure (number of prescriptions) during the period of 1-15 years in the past was significantly associated with an increased risk of prostate cancer; RR = 1.69, 2.61, 2.71, and 2.83 for the 4 quartiles, respectively, p-trend = 0.0001. When number of units was taken as the exposure definition, similar results were found. We did not find any effect of the timing or class of antibiotic exposure on prostate cancer risk. We found a dose-dependent association between antibiotics exposure up to 15 years in the past and risk of prostate cancer. However, the lack of temporal trends and the absence of class specific effects suggest a noncausal relationship.