Microbiome Assisted Tumor Microenvironment: Emerging Target of Breast Cancer

Bacterial metabolites: Effects on the development of breast cancer and therapeutic efficacy (Review)

Evidence suggests that various gut metabolites significantly impact breast cancer (BC) and its treatment. However, the underlying mechanisms remain poorly understood and require further investigation. In the present study, the current literature was reviewed to evaluate the roles of microbial metabolites in the development of BC and its response to treatment. Microbial metabolites, including secondary bile acids, short-chain fatty acids, amino acid metabolites, lipopolysaccharide, nisin and pyocyanin, serve crucial roles in the BC microenvironment. Microbial metabolites promote BC invasion, metastasis and recurrence by facilitating cellular movement, epithelial-mesenchymal transition, cancer stem cell function and diapedesis. Furthermore, certain metabolites, such as trimethylamine N-oxide and L-norvaline, can alter the pharmacokinetics of chemotherapeutic drugs. The present review highlights the possible involvement of microbial metabolites and bacteriocins in BC carcinogenesis, development and metastasis. These metabolites could provide new insights for BC treatment strategies and are considered potential therapeutic targets.

Integrated spatial multi-omics profiling of Fusobacterium nucleatum in breast cancer unveils its role in tumour microenvironment modulation and cancer progression

Tumour-associated microbiota are integral components of the tumour microenvironment (TME). However, previous studies on intratumoral microbiota primarily rely on bulk tissue analysis, which may obscure their spatial distribution and localized effects. In this study, we applied in situ spatial-profiling technology to investigate the spatial distribution of intratumoral microbiota in breast cancer and their interactions with the local TME. Using 5R 16S rRNA gene sequencing and RNAscope FISH/CISH on patients' tissue, we identified significant spatial heterogeneity in intratumoral microbiota, with Fusobacterium nucleatum (F. nucleatum) predominantly localized in tumour cell-rich areas. GeoMx digital spatial profiling (DSP) revealed that regions colonized by F. nucleatum exhibit significant influence on the expression of RNAs and proteins involved in proliferation, migration and invasion. In vitro studies indicated that co-culture with F. nucleatum significantly stimulates the proliferation and migration of breast cancer cells. Integrative spatial multi-omics and co-culture transcriptomic analyses highlighted the MAPK signalling pathways as key altered pathways. By intersecting these datasets, VEGFD and PAK1 emerged as critical upregulated proteins in F. nucleatum-positive regions, showing strong positive correlations with MAPK pathway proteins. Moreover, the upregulation of VEGFD and PAK1 by F. nucleatum was confirmed in co-culture experiments, and their knockdown significantly reduced F. nucleatum-induced proliferation and migration. In conclusion, intratumoral microbiota in breast cancer exhibit significant spatial heterogeneity, with F. nucleatum colonization markedly altering tumour cell protein expression to promote progression and migration. These findings provide novel perspectives on the role of microbiota in breast cancer, identify potential therapeutic targets, and lay the foundation for future cancer treatments. KEY POINTS: Intratumoral Fusobacterium nucleatum exhibits significant spatial heterogeneity within breast cancer tissues. F. nucleatum colonization alters the expression of key proteins involved in tumour progression and migration. The MAPK signalling pathway is a critical mediator of F. nucleatum-induced breast cancer cell proliferation and migration. VEGFD and PAK1 are potential therapeutic targets to mitigate F. nucleatum-induced tumour progression.

Tumor Microenvironment Targeted by Polysaccharides in Cancer Prevention: Expanding Roles of Gut Microbiota and Metabolites

Since the development of immune checkpoint inhibitors (ICIs), immunotherapy has been widely used as a novel cancer treatment. However, the efficacy of tumor immunotherapy is largely dependent on the tumor microenvironment (TME). The high degree of heterogeneity within TME remains a major obstacle to acquire satisfactory therapeutic. Emerging studies suggest that gut microbiota is becoming an important regulator of TME. Polysaccharides as tumor immunotherapeutic agents or immune adjuvants not only exhibit antitumor activity by targeting gut microbiota, but also expand their role in the tumor immunotherapy by remodeling TME. To date, the mechanism by which polysaccharides targeting TME for tumor prevention via gut microbiota has not been deeply investigated. In this review, recent advances in the regulation of TME by polysaccharides through gut microbiota were systematically outlined, and the challenges and possible solutions in the clinical application of TME-targeted polysaccharides were discussed. Exploring the relationship between polysaccharides and TME from the perspective of gut microbiota may provide new ideas for the application of polysaccharides in tumor immunotherapy. This is a new area with major challenges that deserve further exploration.

Pan-Cancer Insights: A Study of Microbial Metabolite Receptors in Malignancy Dynamics

BACKGROUND/OBJECTIVES

The role of the gut microbiome in cancer biology has become an increasingly prominent area of research, particularly regarding the role of microbial metabolites and their receptors (MMRs). These metabolites, through the various gut-organ axes, have been proven to influence several pathogenetic mechanisms. This study conducted a comprehensive pan-cancer analysis of MMR transcriptomic profiles across twenty-three cancer types, exploring the mechanisms through which they can influence cancer development and progression.

METHODS

Utilizing both cancer cell lines from CCLE (Cancer Cell Line Encyclopedia) and human tumor samples from TCGA (The Cancer Gene Atlas), we analyzed 107 MMRs interacting with microbial metabolites such as short-chain fatty acids, bile acids, indole derivatives, and others while studying their interactions with key known cancer genes.

RESULTS

Our results revealed that certain MMRs, such as GPR84 and serotonin receptors, are consistently upregulated in various malignancies, while others, like ADRA1A, are frequently downregulated, suggesting diverse roles in cancer pathophysiology. Furthermore, we identified significant correlations between MMR expression and cancer hallmark genes and pathways, including immune evasion, proliferation, and metastasis.

CONCLUSIONS

These findings suggest that the interactions between microbial metabolites and MMRs may serve as potential biomarkers for cancer diagnosis, prognosis, and therapy, highlighting their therapeutic potential. This study underscores the significance of the microbiota-cancer axis and provides novel insights into microbiome-based strategies for cancer treatment.

Multilevel Mechanisms of Cancer Drug Resistance

Cancer drug resistance represents one of the most significant challenges in oncology and manifests through multiple interconnected molecular and cellular mechanisms. Objective: To provide a comprehensive analysis of multilevel processes driving treatment resistance by integrating recent advances in understanding genetic, epigenetic, and microenvironmental factors. This is a systematic review of the recent literature focusing on the mechanisms of cancer drug resistance, including genomic studies, clinical trials, and experimental research. Key findings include the following: (1) Up to 63% of somatic mutations can be heterogeneous within individual tumors, contributing to resistance development; (2) cancer stem cells demonstrate enhanced DNA repair capacity and altered metabolic profiles; (3) the tumor microenvironment, including cancer-associated fibroblasts and immune cell populations, plays a crucial role in promoting resistance; and (4) selective pressure from radiotherapy drives the emergence of radioresistant phenotypes through multiple adaptive mechanisms. Understanding the complex interplay between various resistance mechanisms is essential for developing effective treatment strategies. Future therapeutic approaches should focus on combination strategies that target multiple resistance pathways simultaneously, guided by specific biomarkers.

The impact of intestinal and mammary microbiomes on breast cancer development: A review on the microbiota and oestrobolome roles in tumour microenvironments

Microbiota affects carcinogenesis by altering energy equilibrium, increasing fat mass, synthesizing small signaling molecules, and formulating and regulating immune response and indigestible food ingredient, xenobiotic, and pharmaceutical compound metabolism. The intestinal microbiome can moderate oestrogen and other steroid hormone metabolisms, and secrete bioactive metabolites that are important for tumour microenvironment. Specifically, the breast tissue microbiome could become altered and lead to breast cancer development. The study of oestrobolome, the microbiomic component that metabolizes oestrogens, can contribute to better breast cancer understanding and subsequent treatment. Investigating oestrobolome-related oestrogen metabolism mechanisms in immune system regulation can shed light on how intestinal microorganisms regulate tumour microenvironment. Intestinal and regional breast microbiomes can determine treatment lines and serve as possible biomarkers for breast cancer. The aim of this study is to summarise current evidence on the role of microbiome in breast cancer progression with particular interest in therapeutic and diagnostic implementation.

The Influence of Microbiota on Breast Cancer: A Review

Breast cancer remains one of the leading causes of death among women worldwide, and recent research highlights its growing connection to alterations in the microbiota. This review delves into the intricate relationship between microbiotas and breast cancer, exploring its presence in healthy breast tissue, its changes during cancer progression, and its considerable impact on both the tumor microenvironment (TME) and the tumor immune microenvironment (TIME). We extensively analyze how the microbiota influences cancer growth, invasion, metastasis, resistance to drugs, and the evasion of the immune system, with a special focus on its effects on the TIME. Furthermore, we investigate distinct microbial profiles associated with the four primary molecular subtypes of breast cancer, examining how the microbiota in tumor tissues compares with that in adjacent normal tissues. Emerging studies suggest that microbiotas could serve as valuable diagnostic and prognostic biomarkers, as well as targets for therapy. This review emphasizes the urgent need for further research to improve strategies for breast cancer prevention, diagnosis, and treatment. By offering a detailed examination of the microbiota's critical role in breast cancer, this review aims to foster the development of novel microbiota-based approaches for managing the disease.

The emerging tumor microbe microenvironment: From delineation to multidisciplinary approach-based interventions

Intratumoral microbiota has become research hotspots, and emerges as a non-negligent new component of tumor microenvironments (TME), due to its powerful influence on tumor initiation, metastasis, immunosurveillance and prognosis despite in low-biomass. The accumulations of microbes, and their related components and metabolites within tumor tissues, endow TME with additional pluralistic features which are distinct from the conventional one. Therefore, it's definitely necessary to comprehensively delineate the sophisticated landscapes of tumor microbe microenvironment, as well as their functions and related underlying mechanisms. Herein, in this review, we focused on the fields of tumor microbe microenvironment, including the heterogeneity of intratumor microbiota in different types of tumors, the controversial roles of intratumoral microbiota, the basic features of tumor microbe microenvironment (i.e., pathogen-associated molecular patterns (PAMPs), typical microbial metabolites, autophagy, inflammation, multi-faceted immunomodulation and chemoresistance), as well as the multidisciplinary approach-based intervention of tumor microbiome for cancer therapy by applying wild-type or engineered live microbes, microbiota metabolites, antibiotics, synthetic biology and rationally designed biomaterials. We hope our work will provide valuable insight to deeply understand the interplay of cancer-immune-microbial, and facilitate the development of microbes-based tumor-specific treatments.

The ways Fusobacterium nucleatum translocate to breast tissue and contribute to breast cancer development

Breast cancer is among the most prevalent malignancies in women worldwide. Epidemiological findings suggested that periodontal diseases may be associated with breast cancer, among which Fusobacterium nucleatum is considered an important cross-participant. In this work, we comprehensively summarize the known mechanisms of how F. nucleatum translocates to, colonizes in mammary tumors, and promotes the carcinogenesis. Specifically, F. nucleatum translocates to mammary tissue through the mammary-intestinal axis, direct nipple contact, and hematogenous transmission. Subsequently, F. nucleatum takes advantage of fusobacterium autotransporter protein 2 to colonize breast cancer and uses virulence factors fusobacterium adhesin A and lipopolysaccharide to promote proliferation. Moreover, the upregulated matrix metalloproteinase-9 induced by F. nucleatum does not only trigger the inflammatory response but also facilitates the tumor-promoting microenvironment. Aside from the pro-inflammatory effect, F. nucleatum may also be engaged in tumor immune evasion, which is achieved through the action of virulence factors on immune checkpoint receptors highly expressed on T cells, natural killer cells, and tumor-infiltrating lymphocytes. Taking breast cancer as an example, more relevant research studies may expand our current knowledge of how oral microbes affect systemic health. Hopefully, exploring these mechanisms in depth could provide new strategies for safer and more effective biologic and targeted therapies targeted at breast cancer.

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.

Environmental insults and compensative responses: when microbiome meets cancer

Tumor microenvironment has recently been ascribed a new hallmark-the polymorphic microbiome. Accumulating evidence regarding the tissue specific territories of tumor-microbiome have opened new and interesting avenues. A pertinent question is regarding the functional consequence of the interface between host-microbiome and cancer. Given microbial communities have predominantly been explored through an ecological perspective, it is important that the foundational aspects of ecological stress and the fight to 'survive and thrive' are accounted for tumor-micro(b)environment as well. Building on existing evidence and classical microbial ecology, here we attempt to characterize the ecological stresses and the compensative responses of the microorganisms inside the tumor microenvironment. What insults would microbes experience inside the cancer jungle? How would they respond to these insults? How the interplay of stress and microbial quest for survival would influence the fate of tumor? This work asks these questions and tries to describe this underdiscussed ecological interface of the tumor and its microbiota. It is hoped that a larger scientific thought on the importance of microbial competition sensing vis-à-vis tumor-microenvironment would be stimulated.

Association between Tumor Microbiome and Hypoxia across Anatomic Subsites of Head and Neck Cancers

Purpose/Objective(s): Microbiome has been shown to affect tumorigenesis by promoting inflammation. However, the association between the upper aerodigestive microbiome and head and neck squamous cell carcinoma (HNSCC) is not well established. Hypoxia is a modifiable factor associated with poor radiation response. Our study analyzed the HNSCC tumor samples from The Cancer Genome Atlas (TCGA) to investigate the relationship between different HNSCC tumor subsites, hypoxia, and local tumor microbiome composition. Results: A total of 357 patients were included [Oral cavity (OC) = 226, Oropharynx (OPx) = 53, and Larynx/Hypopharynx (LHPx) = 78], of which 12.8%, 71.7%, and 10.3%, respectively, were HPV positive. The mean (SD) hypoxia scores were 30.18 (11.10), 24.31 (14.13), and 29.53 (12.61) in OC, OPx, and LHPx tumors, respectively, with higher values indicating greater hypoxia. The hypoxia score was significantly higher for OC tumors compared to OPx (p = 0.044) and LHPx (p = 0.002). There was no significant correlation between hypoxia and HPV status. Pseudomonas sp. in OC, Actinomyces sp. and Sulfurimonas sp. in OPx, and Filifactor, Pseudomonas and Actinomyces sp. in LHPx had the strongest association with the hypoxia score. Materials/Methods: Tumor RNAseq samples from TCGA were processed, and the R package “tmesig” was used to calculate gene expression signature, including the Buffa hypoxia (BH) score, a validated hypoxia signature using 52 hypoxia-regulated genes. Microbe relative abundances were modeled with primary tumor location and a high vs. low tertile BH score applying a gamma-distributed generalized linear regression using the “stats” package in R, with adjusted p-value < 0.05 considered significant. Conclusions: In our study, oral cavity tumors were found to be more hypoxic compared to other head and neck subsites, which could potentially contribute to their radiation resistance. For each subsite, distinct microbial populations were over-represented in hypoxic tumors in a subsite-specific manner. Further studies focusing on an association between microbiome, hypoxia, and patient outcomes are warranted.

Tumor microbiome - an integral part of the tumor microenvironment

The tumor microenvironment (TME) plays a significant role in tumor progression and cancer cell survival. Besides malignant cells and non-malignant components, including immune cells, elements of the extracellular matrix, stromal cells, and endothelial cells, the tumor microbiome is considered to be an integral part of the TME. Mounting evidence from preclinical and clinical studies evaluated the presence of tumor type-specific intratumoral bacteria. Differences in microbiome composition between cancerous tissues and benign controls suggest the importance of the microbiome-based approach. Complex host-microbiota crosstalk within the TME affects tumor cell biology via the regulation of oncogenic pathways, immune response modulation, and interaction with microbiota-derived metabolites. Significantly, the involvement of tumor-associated microbiota in cancer drug metabolism highlights the therapeutic implications. This review aims to summarize current knowledge about the emerging role of tumor microbiome in various types of solid malignancies. The clinical utility of tumor microbiome in cancer progression and treatment is also discussed. Moreover, we provide an overview of clinical trials evaluating the role of tumor microbiome in cancer patients. The research focusing on the communication between the gut and tumor microbiomes may bring new opportunities for targeting the microbiome to increase the efficacy of cancer treatment and improve patient outcomes.

Tumor microenvironment-related multigene prognostic prediction model for breast cancer

BACKGROUND

Breast cancer is an invasive disease with complex molecular mechanisms. Prognosis-related biomarkers are still urgently needed to predict outcomes of breast cancer patients.

METHODS

Original data were download from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). The analyses were performed using perl-5.32 and R-x64-4.1.1.

RESULTS

In this study, 1086 differentially expressed genes (DEGs) were identified in the TCGA cohort; 523 shared DEGs were identified in the TCGA and GSE10886 cohorts. Eight subtypes were estimated using non-negative matrix factorization clustering with significant differences seen in overall survival (OS) and progression-free survival (PFS) (P < 0.01). Univariate Cox analysis and least absolute shrinkage and selection operator (LASSO) regression analysis were performed to develop a related risk score related to the 17 DEGs; this score separated breast cancer into low- and high-risk groups with significant differences in survival (P < 0.01) and showed powerful effectiveness (TCGA all group: 1-year area under the curve [AUC] = 0.729, 3-year AUC = 0.778, 5-year AUC = 0.781). A nomogram prediction model was constructed using non-negative matrix factorization clustering, the risk score, and clinical characteristics. Our model was confirmed to be related with tumor microenvironment. Furthermore, DEGs in high-risk breast cancer were enriched in histidine metabolism (normalized enrichment score [NES] = 1.49, P < 0.05), protein export (NES = 1.58, P < 0.05), and steroid hormone biosynthesis signaling pathways (NES = 1.56, P < 0.05).

CONCLUSIONS

We established a comprehensive model that can predict prognosis and guide treatment.

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.

Pathogen-Induced Epigenetic Modifications in Cancers: Implications for Prevention, Detection and Treatment of Cancers in Africa

Cancer is a major public health burden worldwide. Tumor formation is caused by multiple intrinsic and extrinsic factors. Many reports have demonstrated a positive correlation between the burden of infectious pathogens and the occurrence of cancers. However, the mechanistic link between pathogens and cancer development remains largely unclear and is subject to active investigations. Apart from somatic mutations that have been widely linked with various cancers, an appreciable body of knowledge points to alterations of host epigenetic patterns as key triggers for cancer development. Several studies have associated various infectious pathogens with epigenetic modifications. It is therefore plausible to assume that pathogens induce carcinogenesis via alteration of normal host epigenetic patterns. Thus, Africa with its disproportionate burden of infectious pathogens is threatened by a dramatic increase in pathogen-mediated cancers. To curb the potential upsurge of such cancers, a better understanding of the role of tropical pathogens in cancer epigenetics could substantially provide resources to improve cancer management among Africans. Therefore, this review discusses cancer epigenetic studies in Africa and the link between tropical pathogens and cancer burden. In addition, we discuss the potential mechanisms by which pathogens induce cancers and the opportunities and challenges of tropical pathogen-induced epigenetic changes for cancer prevention, detection and management.