The quorum sensing peptides PhrG, CSP and EDF promote angiogenesis and invasion of breast cancer cells in vitro

Stress in the microbiome-immune crosstalk

The gut microbiota exerts a mutualistic interaction with the host in a fragile ecosystem and the host intestinal, neural, and immune cells. Perturbations of the gastrointestinal track composition after stress have profound consequences on the central nervous system and the immune system. Reciprocally, brain signals after stress affect the gut microbiota highlighting the bidirectional communication between the brain and the gut. Here, we focus on the potential role of inflammation in mediating stress-induced gut-brain changes and discuss the impact of several immune cells and inflammatory molecules of the gut-brain dialogue after stress. Understanding the impact of microbial changes on the immune system after stress might provide new avenues for therapy.

Exploring the Role of the Gut and Intratumoral Microbiomes in Tumor Progression and Metastasis

Cancer cell dissemination involves invasion, migration, resistance to stressors in the circulation, extravasation, colonization, and other functions responsible for macroscopic metastases. By enhancing invasiveness, motility, and intravasation, the epithelial-to-mesenchymal transition (EMT) process promotes the generation of circulating tumor cells and their collective migration. Preclinical and clinical studies have documented intensive crosstalk between the gut microbiome, host organism, and immune system. According to the findings, polymorphic microbes might play diverse roles in tumorigenesis, cancer progression, and therapy response. Microbial imbalances and changes in the levels of bacterial metabolites and toxins promote cancer progression via EMT and angiogenesis. In contrast, a favorable microbial composition, together with microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), can attenuate the processes of tumor initiation, disease progression, and the formation of distant metastases. In this review, we highlight the role of the intratumoral and gut microbiomes in cancer cell invasion, migration, and metastatic ability and outline the potential options for microbiota modulation. As shown in murine models, probiotics inhibited tumor development, reduced tumor volume, and suppressed angiogenesis and metastasis. Moreover, modulation of an unfavorable microbiome might improve efficacy and reduce treatment-related toxicities, bringing clinical benefit to patients with metastatic cancer.

Cell Fate: What's Evolution Got to Do With It?

Theoretical frameworks concerning cell fate typically center on proximate causes to explain how cells know what type they are meant to become. While major advances in cell fate theory have been achieved by these mechanism-focused frameworks, there are some aspects of cell decision-making that require an evolutionary interpretation. While mechanistic biologists sometimes turn to evolutionary theory to gain insights about cell fate (cancer is a good example), it is not entirely clear in cell fate theory what insights evolutionary theory can add, and why in some cases it is required for understanding cell fate. In this perspective we draw on our work on cellular mortality to illustrate how evolutionary theory provides an explanation for death being selected as one of the potential cell fates. Using our hypothesis for why some microbes in a community choose death as their fate, we suggest that some insights in cell fate theory are inaccessible to a theoretical framework that focuses solely on proximate causes.

Case Report: Resolution of high grade anal squamous intraepithelial lesion with antibiotics proposes a new role for syphilitic infection in potentiation of HPV-associated ASCC

Introduction

Human Papillomavirus (HPV) is the primary risk factor for the development of anal intraepithelial neoplasia (AIN) and is a leading risk factor for anogenital squamous cell carcinoma (ASCC). Despite common shared risk factors for both HPV and syphilis, co-infection is not well documented, and the role of syphilitic infection in HPV-associated AIN and ASCC potentiation is not defined.

Case description/methods

A 72-year-old single male presented with complaints of mild rectal pain and intermittent rectal bleeding. A flexible sigmoidoscopy was performed, and a firm 4.5cm x 3cm perianal mass was detected and superficially biopsied. Pathology findings demonstrated evidence of a high grade squamous intraepithelial lesion (HGSIL, AIN II/III/AIS) with viral cytopathic effect, consistent with HPV infection. Much of the biopsied lesion showed acanthotic squamous mucosa with intraepithelial neutrophils and abundant submucosal plasma cells, suggesting possible syphilitic involvement. Subsequent immunohistochemical staining for p16 as a surrogate marker for HPV was positive, as was an immunohistochemical stain for spirochetes, supportive of co-infection with Treponema pallidum pallidum (T. pallidum), the causative agent in venereal syphilis. The patient was referred to an infectious disease specialist for syphilitic infection and was treated with penicillin with surprisingly complete resolution of the lesion. EUAs were performed 2- and 3-months following treatment without lesion recurrence. However, one year following diagnosis, a flexible sigmoidoscopy revealed a 5 mm recurrent HPV-related low-grade AIN 1 lesion at the dentate line.

Discussion

Resolution of the lesion by antibiotic treatment for syphilitic infection suggested that co-infection by T. pallidum may potentiate HPV-associated squamous cell carcinoma based on histological findings. Findings from this case, as well as a review of bacterial involvement and potentiation in various cancers, are reviewed here. Such findings offer new insight regarding the role of STI-associated bacteria and HPV co-infection in the establishment of AIN and may additionally propose new treatment modalities for ASCC.

Exploring the complex role of gut microbiome in the development of precision medicine strategies for targeting microbial imbalance-induced colon cancer

The gut microbiome has been increasingly recognized as a key player in the development and progression of colon cancer. Alterations in the gut microbiota, known as dysbiosis, can lead to a variety of medical issues. Microbial adaptation through signals and small molecules can enhance pathogen colonization and modulate host immunity, significantly impacting disease progression. Quorum sensing peptides and molecules have been linked to the progression of colon cancer. Various interventions, such as fecal microbiota transplantation, probiotics, prebiotics, synbiotics, and antibiotics, have been used to reverse dysbiosis with mixed results and potential side effects. Thus, a personalized approach to treatment selection based on patient characteristics, such as individual gut microbiota manipulation, is necessary to prevent and treat diseases like colon cancer. With advances in metagenomic sequencing and other omics technologies, there has been a growing interest in developing precision medicine strategies for microbial imbalance-induced colon cancer. This review serves as a comprehensive synthesis of current knowledge on the gut microbiome involvement in colon cancer. By exploring the potential of utilizing the gut microbiome as a target for precision medicine, this review underscores the exciting opportunities that lie ahead. Although challenges exist, the integration of microbiome data into precision medicine approaches has the potential to revolutionize the management of colon cancer, providing patients with more personalized and effective treatment options.

Intratumor microbiome: selective colonization in the tumor microenvironment and a vital regulator of tumor biology

The polymorphic microbiome has been proposed as a new hallmark of cancer. Intratumor microbiome has been revealed to play vital roles in regulating tumor initiation and progression, but the regulatory mechanisms have not been fully uncovered. In this review, we illustrated that similar to other components in the tumor microenvironment, the reside and composition of intratumor microbiome are regulated by tumor cells and the surrounding microenvironment. The intratumor hypoxic, immune suppressive, and highly permeable microenvironment may select certain microbiomes, and tumor cells may directly interact with microbiome via molecular binding or secretions. Conversely, the intratumor microbiomes plays vital roles in regulating tumor initiation and progression via regulating the mutational landscape, the function of genes in tumor cells and modulating the tumor microenvironment, including immunity, inflammation, angiogenesis, stem cell niche, etc. Moreover, intratumor microbiome is regulated by anti-cancer therapies and actively influences therapy response, which could be a therapeutic target or engineered to be a therapy weapon in the clinic. This review highlights the intratumor microbiome as a vital component in the tumor microenvironment, uncovers potential mutual regulatory mechanisms between the tumor microenvironment and intratumor microbiome, and points out the ongoing research directions and drawbacks of the research area, which should broaden our view of microbiome and enlighten further investigation directions.

Gut colonization with an obesity-associated enteropathogenic microbe modulates the premetastatic niches to promote breast cancer lung and liver metastasis

Introduction

Obesity, an independent risk factor for breast cancer growth and metastatic progression, is also closely intertwined with gut dysbiosis; and both obese state and dysbiosis promote each other. Enteric abundance of Bacteroides fragilis is strongly linked with obesity, and we recently discovered the presence of B. fragilis in malignant breast cancer. Given that enterotoxigenic B. fragilis or ETBF, which secretes B. fragilis toxin (BFT), has been identified as a procarcinogenic microbe in breast cancer, it is necessary to examine its impact on distant metastasis and underlying systemic and localized alterations promoting metastatic progression of breast cancer.

Methods

We used syngeneic mammary intraductal (MIND) model harboring gut colonization with ETBF to query distant metastasis of breast cancer cells. Alterations in the immune network and cytokines/chemokines in the tumor microenvironment and distant metastatic sites were examined using flow cytometry, immunohistochemistry, and multiplex arrays.

Results

ETBF infection initiates a systemic inflammation aiding in the establishment of the premetastatic niche formation in vital organs via increased proinflammatory and protumorigenic cytokines like IL17A, IL17E, IL27p28, IL17A/F, IL6, and IL10 in addition to creating a prometastatic immunosuppressive environment in the liver and lungs rich in myeloid cells, macrophages, and T regulatory cells. It induces remodeling of the tumor microenvironment via immune cell and stroma infiltration, increased vasculogenesis, and an EMT-like response, thereby encouraging early metastatic dissemination ready to colonize the conducive environment in liver and lungs of the breast tumor-bearing mice.

Discussion

In this study, we show that enteric ETBF infection concomitantly induces systemic inflammation, reshapes the tumor immune microenvironment, and creates conducive metastatic niches to potentiate early dissemination and seeding of metastases to liver and lung tissues in agreement with the "seed and soil hypothesis." Our results also support the ETBF-induced "parallel model" of metastasis that advocates for an early dissemination of tumor cells that form metastatic lesions independent of the primary tumor load.

Quorum Sensing in Oral Biofilms: Influence on Host Cells

Quorum sensing molecules (QSMs) in the oral cavity regulate biofilm formation, the acquisition of iron, stress responses, and the expression of virulence factors. However, knowledge of the direct QSM-host interactions in the oral environment is limited, although their understanding could provide greater insight into the cross-kingdom communication occurring during oral disease development. This review aims to explore the literature on oral QSM-host interactions and to highlight areas of advancement in this field. The studies included in this review encompass an array of cell types and oral QSMs, with particular emphasis on immune cells and their relationship to periodontal diseases. It can be inferred from the current literature that QSMs are utilised by host cells to detect bacterial presence and, in the majority of cases, elicit an immune response towards the environmental QSMs. This may provide a base to target QSMs as a novel treatment of oral diseases. However, N-acyl homoserine lactone (AHL) detection methods remain an area for development, through which a greater understanding of the influence of oral QSMs on host cells could be achieved.

The gut microbiota in breast cancer development and treatment: The good, the bad, and the useful!

Regardless of the global progress in early diagnosis and novel therapeutic regimens, breast carcinoma poses a devastating threat, and the advances are somewhat marred by high mortality rates. Breast cancer risk prediction models based on the known risk factors are extremely useful, but a large number of breast cancers develop in women with no/low known risk. The gut microbiome exerts a profound impact on the host health and physiology and has emerged as a pivotal frontier in breast cancer pathogenesis. Progress in metagenomic analysis has enabled the identification of specific changes in the host microbial signature. In this review, we discuss the microbial and metabolomic changes associated with breast cancer initiation and metastatic progression. We summarize the bidirectional impact of various breast cancer-related therapies on gut microbiota and vice-versa. Finally, we discuss the strategies to modulate the gut microbiota toward a more favorable state that confers anticancer effects.

Targeting the gut microbiota for cancer therapy

Growing evidence suggests that the gut microbiota modulates the efficacy and toxicity of cancer therapy, most notably immunotherapy and its immune-related adverse effects. The poor response to immunotherapy in patients treated with antibiotics supports this influential role of the microbiota. Until recently, results pertaining to the identification of the microbial species responsible for these effects were incongruent, and relatively few studies analysed the underlying mechanisms. A better understanding of the taxonomy of the species involved and of the mechanisms of action has since been achieved. Defined bacterial species have been shown to promote an improved response to immune-checkpoint inhibitors by producing different products or metabolites. However, a suppressive effect of Gram-negative bacteria may be dominant in some unresponsive patients. Machine learning approaches trained on the microbiota composition of patients can predict the ability of patients to respond to immunotherapy with some accuracy. Thus, interest in modulating the microbiota composition to improve patient responsiveness to therapy has been mounting. Clinical proof-of-concept studies have demonstrated that faecal microbiota transplantation or dietary interventions might be utilized clinically to improve the success rate of immunotherapy in patients with cancer. Here, we review recent advances and discuss emerging strategies for microbiota-based cancer therapies.

Microbiome systems biology advancements for natural well-being

Throughout the years all data from epidemiological, physiological and omics have suggested that the microbial communities play a considerable role in modulating human health. The population of microorganisms residing in the human intestine collectively known as microbiota presents a genetic repertoire that is higher in magnitude than the human genome. They play an essential role in host immunity and neuronal signaling. Rapid enhancement of sequence based screening and development of humanized gnotobiotic model has sparked a great deal of interest among scientists to probe the dynamic interactions of the commensal bacteria. This review focuses on systemic analysis of the gut microbiome to decipher the complexity of the host-microbe intercommunication and gives a special emphasis on the evolution of targeted precision medicine through microbiome engineering. In addition, we have also provided a comprehensive description of how interconnection between metabolism and biochemical reactions in a specific organism can be obtained from a metabolic network or a flux balance analysis and combining multiple datasets helps in the identification of a particular metabolite. The review highlights how genetic modification of the critical components and programming the resident microflora can be employed for targeted precision medicine. Inspite of the ongoing debate on the utility of gut microbiome we have explored on the probable new therapeutic avenues like FMT (Fecal microbiota transplant) can be utilized. This review also recapitulates integrating human-relevant 3D cellular models coupled with computational models and the metadata obtained from interventional and epidemiological studies may decipher the complex interactome of diet-microbiota-disease pathophysiology. In addition, it will also open new avenues for the development of therapeutics derived from microbiome or implementation of personalized nutrition. In addition, the identification of biomarkers can also help towards the development of new diagnostic tools and eventually will lead to strategic management of the disease. Inspite of the ongoing debate on the utility of the gut microbiome we have explored how probable new therapeutic avenues like FMT (Fecal microbiota transplant) can be utilized. This review also summarises integrating human-relevant 3D cellular models coupled with computational models and the metadata obtained from interventional and epidemiological studies may decipher the complex interactome of diet- microbiota-disease pathophysiology. In addition, it will also open new avenues for the development of therapeutics derived from the microbiome or implementation of personalized nutrition. In addition, the identification of biomarkers can also help towards the development of new diagnostic tools and eventually will lead to strategic management of disease.

Bacterial infection-driven lymphomagenesis

PURPOSE OF REVIEW

The first convincing evidence for a causal relationship between bacterial infection and lymphomagenesis came from the link between gastric lymphoma and chronic Helicobacter pylori gastritis. This review will summarize the current epidemiological, clinical, and biological evidence of a causative role of bacteria in the development of malignant lymphomas, particularly, the extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue type.

RECENT FINDINGS

Other microorganisms have been associated with specific extranodal lymphoma sites with variable and not always definitive, evidence, including Chlamydia psittaci , Borrelia burgdorferi , Campylobacter jejuni and, most recently, Coxiella Burnetii . According to most plausible models, lymphoma growth is a consequence of continuous antigenic stimulation induced by chronic infection. However, some evidence of a direct oncogenic role of H. pylori has been provided, too.

SUMMARY

Lymphomas are not the result of a single cause but multifactorial diseases, influenced by a variety of genetic and environmental elements. Hence, ascertaining the specific contribution of bacterial infections is not always easy. Nevertheless, the eradication of the associated chronic infection may result in sustained lymphoma regression. Moreover, the association between infections and lymphoma may offer opportunities for reducing lymphoma incidence by preventing the predisposing infections or treating them early.

Modulating Microbiota as a New Strategy for Breast Cancer Prevention and Treatment

Breast cancer (BC) is the most common cancer in women in the United States. There has been an increasing incidence and decreasing mortality rate of BC cases over the past several decades. Many risk factors are associated with BC, such as diet, aging, personal and family history, obesity, and some environmental factors. Recent studies have shown that healthy individuals and BC patients have different microbiota composition, indicating that microbiome is a new risk factor for BC. Gut and breast microbiota alterations are associated with BC prognosis. This review will evaluate altered microbiota populations in gut, breast tissue, and milk of BC patients, as well as mechanisms of interactions between microbiota modulation and BC. Probiotics and prebiotics are commercially available dietary supplements to alleviate side-effects of cancer therapies. They also shape the population of human gut microbiome. This review evaluates novel means of modulating microbiota by nutritional treatment with probiotics and prebiotics as emerging and promising strategies for prevention and treatment of BC. The mechanistic role of probiotic and prebiotics partially depend on alterations in estrogen metabolism, systematic immune regulation, and epigenetics regulation.

The quorum sensing peptide EntF* promotes colorectal cancer metastasis in mice: a new factor in the host-microbiome interaction

Background

Colorectal cancer, one of the most common malignancies worldwide, is associated with a high mortality rate, mainly caused by metastasis. Comparative metagenome-wide association analyses of healthy individuals and cancer patients suggest a role for the human intestinal microbiota in tumor progression. However, the microbial molecules involved in host-microbe communication are largely unknown, with current studies mainly focusing on short-chain fatty acids and amino acid metabolites as potential mediators. Quorum sensing peptides are not yet considered in this context since their presence in vivo and their ability to affect host cells have not been reported so far.

Results

Here, we show that EntF*, a metabolite of the quorum sensing peptide EntF produced by Enterococcus faecium, is naturally present in mice bloodstream. Moreover, by using an orthotopic mouse model, we show that EntF* promotes colorectal cancer metastasis in vivo, with metastatic lesions in liver and lung tissues. In vitro tests suggest that EntF* regulates E-cadherin expression and consequently the epithelial-mesenchymal transition, via the CXCR4 receptor. In addition, alanine-scanning analysis indicates that the first, second, sixth, and tenth amino acid of EntF* are critical for epithelial-mesenchymal transition and tumor metastasis.

Conclusion

Our work identifies a new class of molecules, quorum sensing peptides, as potential regulators of host-microbe interactions. We prove, for the first time, the presence of a selected quorum sensing peptide metabolite in a mouse model, and we demonstrate its effects on colorectal cancer metastasis. We believe that our work represents a starting point for future investigations on the role of microbiome in colorectal cancer metastasis and for the development of novel bio-therapeutics in other disease areas.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01317-z.

3-oxo-C12:2-HSL, quorum sensing molecule from human intestinal microbiota, inhibits pro-inflammatory pathways in immune cells via bitter taste receptors

In the gut ecosystem, microorganisms regulate group behaviour and interplay with the host via a molecular system called quorum sensing (QS). The QS molecule 3-oxo-C12:2-HSL, first identified in human gut microbiota, exerts anti-inflammatory effects and could play a role in inflammatory bowel diseases where dysbiosis has been described. Our aim was to identify which signalling pathways are involved in this effect. We observed that 3-oxo-C12:2-HSL decreases expression of pro-inflammatory cytokines such as Interleukine-1β (− 35%) and Tumor Necrosis Factor-α (TNFα) (− 40%) by stimulated immune RAW264.7 cells and decreased TNF secretion by stimulated PBMC in a dose-dependent manner, between 25 to 100 µM. Transcriptomic analysis of RAW264.7 cells exposed to 3-oxo-C12:2-HSL, in a pro-inflammatory context, highlighted JAK-STAT, NF-κB and TFN signalling pathways and we confirmed that 3-oxo-C12:2-HSL inhibited JAK1 and STAT1 phosphorylation. We also showed through a screening assay that 3-oxo-C12:2-HSL interacted with several human bitter taste receptors. Its anti-inflammatory effect involved TAS2R38 as shown by pharmacologic inhibition and led to an increase in intracellular calcium levels. We thus unravelled the involvement of several cellular pathways in the anti-inflammatory effects exerted by the QS molecule 3-oxo-C12:2-HSL.

A Tryptophan Metabolite of the Microbiota Improves Neovascularization in Diabetic Limb Ischemia

Diabetes mellitus (DM) is accompanied by a series of macrovascular and microvascular injuries. Critical limb ischemia is the most severe manifestation of peripheral artery disease (PAD) caused by DM and is almost incurable. Therapeutic modulation of angiogenesis holds promise for the prevention of limb ischemia in diabetic patients with PAD. However, no small-molecule drugs are capable of promoting diabetic angiogenesis. An endogenous tryptophan metabolite, indole-3-aldehyde (3-IAld), has been found to have proangiogenic activity in endothelial cells. Nevertheless, the role of 3-IAld in diabetic angiogenesis remains unknown. Here, we found that 3-IAld ameliorated high glucose-induced mitochondrial dysfunction, decreasing oxidative stress and apoptosis and thus improving neovascularization.

Importance of crosstalk between the microbiota and the neuroimmune system for tissue homeostasis

The principal function of inflammation is cellular defence against ‘danger signals’ such as tissue injury and pathogen infection to maintain the homeostasis of the organism. The initiation and progression of inflammation are not autonomous as there is substantial evidence that inflammation is known to be strongly influenced by ‘neuroimmune crosstalk’, involving the production and expression of soluble signalling molecules that interact with cell surface receptors. In addition, microbiota have been found to be involved in the development and function of the nervous and immune systems and play an important role in health and disease. Herein, we provide an outline of the mechanisms of neuroimmune communication in the regulation of inflammation and immune response and then provide evidence for the involvement of microbiota in the development and functions of the host nervous and immune systems. It appears that the nervous and immune systems in multicellular organisms have co‐evolved with the microbiota, such that all components are in communication to maximise the ability of the organism to adapt to a wide range of environmental stresses to maintain or restore tissue homeostasis.

Microbiome in cancer: Role in carcinogenesis and impact in therapeutic strategies

Cancer is the world's second-leading cause of death, and the involvement of microbes in a range of diseases, including cancer, is well established. The gut microbiota is known to play an important role in the host's health and physiology. The gut microbiota and its metabolites may activate immunological and cellular pathways that kill invading pathogens and initiate a cancer-fighting immune response. Cancer is a multiplex illness, characterized by the persistence of several genetic and physiological anomalies in malignant tissue, complicating disease therapy and control. Humans have coevolved with a complex bacterial, fungal, and viral microbiome over millions of years. Specific long-known epidemiological links between certain bacteria and cancer have recently been grasped at the molecular level. Similarly, advances in next-generation sequencing technology have enabled detailed research of microbiomes, such as the human gut microbiome, allowing for the finding of taxonomic and metabolomic linkages between the microbiome and cancer. These investigations have found causative pathways for both microorganisms within tumors and bacteria in various host habitats far from tumors using direct and immunological procedures. Anticancer diagnostic and therapeutic solutions could be developed using this review to tackle the threat of anti-cancer medication resistance as well through the wide-ranging involvement of the microbiota in regulating host metabolic and immunological homeostasis. We reviewed the significance of gut microbiota in cancer initiation as well as cancer prevention. We look at certain microorganisms that may play a role in the development of cancer. Several bacteria with probiotic qualities may be employed as bio-therapeutic agents to re-establish the microbial population and trigger a strong immune response to remove malignancies, and further study into this should be conducted.

Roles of Microbiota in Cancer: From Tumor Development to Treatment

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

The 3D in vivo chorioallantoic membrane model and its role in breast cancer research

PURPOSE

We aimed to evaluate the role of the chorioallantoic membrane model (CAM) in breast cancer research.

METHODS

The following is an overview of the use of the CAM in the field of breast cancer research based on a PubMed literature query.

RESULTS

The CAM is a 3D in vivo model that can be used for the analysis of tumor growth, biology and angiogenesis of primary tumor tissue or tumor cell lines. The CAM model has been used in breast cancer research for drug testing, migration assays and the evaluation of vascularization, amongst others. The CAM model is a valuable method that offers a better imitation of the physiological phenomena compared to 2D or 3D in vitro models.

CONCLUSION

The CAM model has primarily and successfully been utilized for the assessment of the tumor biology of established breast cancer cell lines. Further, the CAM model is a promising method to analyze patient derived primary tumor material and could be used as a "patient-specific 3D-tumor-therapy-model" for the cost-efficient evaluation of anti-cancer drugs to find the optimal treatment for breast cancer patients.

Streptococcal bacterial components in cancer therapy

The incidence rate of cancer is steadily increasing all around the world, and there is an urgent need to develop novel and more effective treatment strategies. Recently, bacterial therapy has been investigated as a new approach to target cancer, and is becoming a serious option. Streptococcus strains are among the most common and well-studied virulent bacteria that cause a variety of human infections. Everyone has experienced a sore throat during their lifetime, or has been asymptomatically colonized by streptococci. The ability of Streptococcus bacteria to fight cancer was discovered more than 100 years ago, and over the years has undergone clinical trials, but the mechanism is not yet completely understood. Recently, several animal models and human clinical trials have been reported. Streptococcal strains can have an intrinsic anti-tumor activity, or can activate the host immune system to fight the tumor. Bacteria can selectively accumulate and proliferate in the hypoxic regions of solid tumors. Moreover, the bacteria can be genetically engineered to secrete toxins or enzymes that can specifically attack the tumors.

Microbiome Crosstalk in Immunotherapy and Antiangiogenesis Therapy

The human body and its microbiome constitute a highly delicate system. The gut microbiome participates in the absorption of the host's nutrients and metabolism, maintains the microcirculation, and modulates the immune response. Increasing evidence shows that gut microbiome dysbiosis in the body not only affects the occurrence and development of tumors but also tumor prognosis and treatment. Microbiome have been implicated in tumor control in patients undergoing anti- angiogenesis therapy and immunotherapy. In cases with unsatisfactory responses to chemotherapy, radiotherapy, and targeted therapy, appropriate adjustment of microbes abundance is considered to enhance the treatment response. Here, we review the current research progress in cancer immunotherapy and anti- angiogenesis therapy, as well as the unlimited potential of their combination, especially focusing on how the interaction between intestinal microbiota and the immune system affects cancer pathogenesis and treatment. In addition, we discuss the effects of microbiota on anti-cancer immune response and anti- angiogenesis therapy, and the potential value of these interactions in promoting further research in this field.

Dietary polyphenol and microbiota interactions in the context of prostate health

Recent data strongly indicate a relationship between prostate health and gut microbiota, in which composition and physiological function strictly depend on dietary patterns. The bidirectional interplay of foods containing polyphenols, such as ellagitannins, condensed tannins, lignans, isoflavones, and prenylated flavonoids with human gut microbiota, has been proven to contribute to their impact on prostate health. Considering the attributed role of dietary polyphenols in the prevention of prostate diseases, this paper aims to critically review the studies concerning the influence of polyphenols' postbiotic metabolites on processes associated with the pathophysiology of prostate diseases. Clinical, in vivo, and in vitro studies on polyphenols have been juxtaposed with the current knowledge regarding their pharmacokinetics, microbial metabolism, and potential interactions with microbiota harboring different niches of the human organism. Directions of future research on dietary polyphenols regarding their interaction with microbiota and prostate health have been indicated.

Microbiome Assisted Tumor Microenvironment: Emerging Target of Breast Cancer

The microbiome assisted tumor microenvironment (TME) supports the tumors by modulating multiple mechanisms. Recent studies reported that microbiome dysbiosis is the main culprit of immune suppressive phenotypes of TME. Further, it has been documented that immune suppressive stimulate metastatic phenotype in TME via modulating signaling pathways, cell differentiation, and innate immune response. This review aims at providing comprehensive developments in microbiome and breast TME interface. The combination of microbiome and breast cancer, breast TME and microbiome or microbial dysbiosis, microbiome and risk of breast cancer, microbiome and phytochemicals or anticancer drugs were as used keywords to retrieve literature from PubMed, Google scholar, Scopus, Web of Science from 2015 onwards. Based on the literature, we presented the impact of TME assisted microbiome dysbiosis and estrobolome in breast cancer risk, drug resistance, and antitumor immunity. We have discussed the influence of antibiotics on the breast microbiome. we also presented the possible dietary phytochemicals that target microbiome dysbiosis to restore the tumor suppression immune environment in breast TME. We presented the microbiome as a possible marker for breast cancer diagnosis. This study will help in the identification of microbiome as a novel target and diagnostic markers and phytochemicals and microbiome metabolites for breast cancer treatment.

PapRIV, a BV-2 microglial cell activating quorum sensing peptide

Quorum sensing peptides (QSPs) are bacterial peptides produced by Gram-positive bacteria to communicate with their peers in a cell-density dependent manner. These peptides do not only act as interbacterial communication signals, but can also have effects on the host. Compelling evidence demonstrates the presence of a gut-brain axis and more specifically, the role of the gut microbiota in microglial functioning. The aim of this study is to investigate microglial activating properties of a selected QSP (PapRIV) which is produced by Bacillus cereus species. PapRIV showed in vitro activating properties of BV-2 microglia cells and was able to cross the in vitro Caco-2 cell model and reach the brain. In vivo peptide presence was also demonstrated in mouse plasma. The peptide caused induction of IL-6, TNFα and ROS expression and increased the fraction of ameboid BV-2 microglia cells in an NF-κB dependent manner. Different metabolites were identified in serum, of which the main metabolite still remained active. PapRIV is thus able to cross the gastro-intestinal tract and the blood–brain barrier and shows in vitro activating properties in BV-2 microglia cells, hereby indicating a potential role of this quorum sensing peptide in gut-brain interaction.

Emerging applications of bacteria as antitumor agents

Bacteria are associated with the human body and colonize the gut, skin, and mucous membranes. These associations can be either symbiotic or pathogenic. In either case, bacteria derive more benefit from their host. The ability of bacteria to enter and survive within the human body can be exploited for human benefit. They can be used as a vehicle for delivering or producing bioactive molecules, such as toxins and lytic enzymes, and eventually for killing tumor cells. Clostridium and Salmonella have been shown to infect and survive within the human body, including in tumors. There is a need to develop genetic circuits, which enable bacterial cells to carry out the following activities: (i) escape the human immune system, (ii) invade tumors, (iii) multiply within the tumorous cells, (iv) produce toxins via quorum sensing at low cell densities, and (v) express suicide genes to undergo cell death or cell lysis after the tumor has been lysed. Thus, bacteria have the potential to be exploited as anticancer agents.

Role of microbiota-derived short-chain fatty acids in cancer development and prevention

Following cancer, cells in a particular tissue can no longer respond to the factors involved in controlling cell survival, differentiation, proliferation, and death. In recent years, it has been indicated that alterations in the gut microbiota components, intestinal epithelium, and host immune system are associated with cancer incidence. Also, it has been demonstrated that the short-chain fatty acids (SCFAs) generated by gut microbiota are vitally crucial in cell homeostasis as they contribute to the modulation of histone deacetylases (HDACs), resulting effected cell attachment, immune cell immigration, cytokine production, chemotaxis, and the programmed cell death. Therefore, the manipulation of SCFA levels in the intestinal tract by alterations in the microbiota structure can be potentially taken into consideration for cancer treatment/prevention. In the current study, we will explain the most recent findings on the detrimental or protective roles of SFCA (particularly butyrate, propionate, and acetate) in several cancers, including bladder, colon, breast, stomach, liver, lung, pancreas, and prostate cancers.

Potential Impacts of Prebiotics and Probiotics in Cancer Prevention

BACKGROUND

Cancer is a serious problem throughout the world. The pathophysiology of cancer is multifactorial and is also related to gut microbiota. Intestinal microbes are the useful resident of the healthy human. They play various aspects of human health including nutritional biotransformation, flushing of the pathogens, toxin neutralization, immune response, and onco-suppression. Disruption in the interactions among the gut microbiota, intestinal epithelium, and the host immune system are associated with gastrointestinal disorders, neurodegenerative diseases, metabolic syndrome, and cancer. Probiotic bacteria (Lactobacillus spp., Bifidobacterium spp.) have been regarded as beneficial to health and shown to play a significant role in immunomodulation and displayed preventive role against obesity, diabetes, liver disease, inflammatory bowel disease, tumor progression, and cancer.

OBJECTIVE

The involvement of gut microorganisms in cancer development and prevention has been recognized as a balancing factor. The events of dysbiosis emphasize metabolic disorder and carcinogenesis. The gut flora potentiates immunomodulation and minimizes the limitations of usual chemotherapy. The significant role of prebiotics and probiotics on the improvement of immunomodulation and antitumor properties has been considered.

METHODS

I had reviewed the literature on the multidimensional activities of prebiotics and probiotics from the NCBI website database PubMed, Springer Nature, Science Direct (Elsevier), Google Scholar database to search relevant articles. Specifically, I had focused on the role of prebiotics and probiotics in immunomodulation and cancer prevention.

RESULTS

Prebiotics are the nondigestible fermentable sugars that selectively influence the growth of probiotic organisms that exert immunomodulation over the cancerous growth. The oncostatic properties of bacteria are mediated through the recruitment of cytotoxic T cells, natural killer cells, and oxidative stress-induced apoptosis in the tumor microenvironment. Moreover, approaches have also been taken to use probiotics as an adjuvant in cancer therapy.

CONCLUSION

The present review has indicated that dysbiosis is the crucial factor in many pathological situations including cancer. Applications of prebiotics and probiotics exhibit the immune-surveillance as oncostatic effects. These events increase the possibilities of new therapeutic strategies for cancer prevention.

Microbes as Medicines: Harnessing the Power of Bacteria in Advancing Cancer Treatment

Conventional anti-cancer therapy involves the use of chemical chemotherapeutics and radiation and are often non-specific in action. The development of drug resistance and the inability of the drug to penetrate the tumor cells has been a major pitfall in current treatment. This has led to the investigation of alternative anti-tumor therapeutics possessing greater specificity and efficacy. There is a significant interest in exploring the use of microbes as potential anti-cancer medicines. The inherent tropism of the bacteria for hypoxic tumor environment and its ability to be genetically engineered as a vector for gene and drug therapy has led to the development of bacteria as a potential weapon against cancer. In this review, we will introduce bacterial anti-cancer therapy with an emphasis on the various mechanisms involved in tumor targeting and tumor suppression. The bacteriotherapy approaches in conjunction with the conventional cancer therapy can be effective in designing novel cancer therapies. We focus on the current progress achieved in bacterial cancer therapies that show potential in advancing existing cancer treatment options and help attain positive clinical outcomes with minimal systemic side-effects.

Bacterial cross talk with gut microbiome and its implications: a short review

Human gut microbiota exists in a complicated symbiotic relationship which postulates to impact health and disease conditions on the host. Interestingly, the gut microbiome shows different mechanisms to regulate host physiology and metabolism including cell-to-cell communications. But microbiota imbalance is characterized to change in the host normal functioning and lead to the development and progression of major human diseases. Therefore, the direct cross talk through the microbial metabolites or peptides suggests the evidence of host health and disease. Recent reports highlight the adaptation signals/small molecules promoting microbial colonization which allows modulating immunity of host and leads to pathogen colonization. Moreover, quorum sensing peptides are also evident in the involvement of host disease conditions. Here, we review the current understanding of the gut microbiota cross talk with mammalian cells through metabolites and peptides. These studies are providing insight into the prediction of signature molecules which significantly provide information for the understanding of the interaction for precision medicine applications.

Significance of human microbiome in breast cancer: Tale of an invisible and an invincible

The human microbiome is a mysterious treasure of the body playing endless important roles in the well-being of the host metabolism, digestion, and immunity. On the other hand, it actively participates in the development of a variety of pathological conditions including cancer. With the Human Microbiome Project initiative, metagenomics, and next-generation sequencing technologies in place, the last decade has witnessed immense explorations and investigations on the enigmatic association of breast cancer with the human microbiome. However, the connection between the human microbiome and breast cancer remains to be explored in greater detail. In fact, there are several emerging questions such as whether the host microbiota contributes to disease initiation, or is it a consequence of the disease is an irrevocably important question that demands a valid answer. Since the microbiome is an extremely complex community, gaps still remain on how this vital microbial organ plays a role in orchestrating breast cancer development. Nevertheless, undeniable evidence from studies has pinpointed the presence of specific microbial elements of the breast and gut to play a role in governing breast cancer. It is still unclear if an alteration in microbiome/dysbiosis leads to breast cancer or is it vice versa. Though specific microbial signatures have been detected to be associated with various breast cancer subtypes, the structure and composition of a core "healthy" microbiome is yet to be established. Probiotics seem to be a promising antidote for targeted prevention and treatment of breast cancer. Interestingly, these microbial communities can serve as potential biomarkers for prognosis, diagnosis, and treatment of breast cancer, thereby leading to the rise of a completely new era of personalized medicine. This review is a humble attempt to summarize the research findings on the human microbiome and its relation to breast cancer.

Influence of Blood Collection Methods and Long-Term Plasma Storage on Quorum-Sensing Peptide Stability

Finding adequate biomarkers for rapid and accurate disease detection, prognosis, and therapy is increasingly important. Quorum-sensing peptides are herein a new emerging group, produced by bacteria, fungi, protozoa, and viruses, with blood being the most straightforward sample type to detect/quantitate them. However, detailed information about suitable blood sample collection methods and storage conditions for measuring these quorum-sensing peptides hampers further clinical research and development. Here, we first tested the time-dependent stability of a set of chemically diverse quorum-sensing peptides, spiked in blood at different temperatures (4, 21, and 37 °C) in four different ethylenediamine tetraacetic acid (EDTA)-containing plasma tubes (with different protein-stabilizing additives) over a period of up to 7.5 h. Next, we determined the storage stability of these quorum-sensing peptides in plasma at different temperatures (4, -35, and -80 °C). UPLC/MS-MS was used to selectively detect and quantify the spiked quorum-sensing peptides. The results of this study indicate that a cost-effective tube, designed for traditional proteomics and stored at 4 °C, is the preferred collection condition when quorum-sensing peptides need to be detected/quantified in human plasma. When the tubes are handled at room temperature (21 °C), a more specialized tube is required. Long-term storage of plasma samples, even under low-temperature conditions (-80 °C), indicates rapid degradation of certain quorum-sensing peptides.

Bacteria as a double-action sword in cancer

Bacteria have long been known as one of the primary causative agents of cancer, however, recent studies suggest that they can be used as a promising agent in cancer therapy. Because of the limitations that conventional treatment faces due to the specific pathophysiology and the tumor environment, there is a great need for the new anticancer therapeutic agents. Bacteriotherapy utilizes live, attenuated strains or toxins, peptides, bacteriocins of the bacteria in the treatment of cancer. Moreover, they are widely used as a vector for delivering genes, peptides, or drugs to the tumor target. Interestingly, it was found that their combination with the conventional therapeutic approaches may enhance the treatment outcome. In the genome editing era, it is feasible to develop a novel generation of therapeutic bacteria with fewer side effects and more efficacy for cancer therapy. Here we review the current knowledge on the dual role of bacteria in the development of cancer as well as cancer therapy.

Microbiome and host crosstalk: A new paradigm to cancer therapy

The commensal microbiome of humans has co-evolved for thousands of years. The microbiome regulates human health and is also linked to several diseases, including cancer. The advances in next-generation sequencing have significantly contributed to our understanding of the microbiome and its association with cancer and cancer therapy. Recent studies have highlighted a close relationship of the microbiome to the pharmacological effect of chemotherapy and immunotherapy. The chemo-drugs usually interfere with the host immune system and reduces the microbiome diversity inside the body, which in turn leads to decreased efficacy of these drugs. The human microbiome, specifically the gut microbiome, increases the potency of chemo-drugs through metabolism, enzymatic degradation, ecological differences, and immunomodulation. Recent research exploits the involvement of microbiome to shape the efficacy and decrease the toxicity of these chemo-drugs. In this review, we have highlighted the recent development in understanding the relationship of the human microbiome with cancer and also emphasize on various roles of the microbiome in the modulation of cancer therapy. Additionally, we also summarize the ongoing research focussed on the improved efficacy of chemotherapy and immunotherapy using the host microbiome.

Efficacy of Moxifloxacin plus Treatment of Physician's Choice in Patients with Metastatic Breast Cancer

LESSONS LEARNED

Moxifloxacin plus continuation of the previous treatment of physician's choice shows promising efficacy in patients with metastatic breast cancer. The addition of moxifloxacin shows well-tolerated toxicities.

BACKGROUND

Recent studies have confirmed bacterial infection as an important contributor in cancer. Elimination of tumor-associated microbes may lead to a reduction in tumors and improved survival. Moxifloxacin is an orally administrated fourth-generation quinolone with broad-spectrum coverage against tumor-associated bacteria.

METHODS

In this study, we assessed the efficacy and safety of moxifloxacin in combination with treatment of physician's choice (TPC) in patients with metastatic breast cancer (MBC). In this single-arm, phase II study, we recruited 30 patients with MBC who had a trend toward disease progression (stable disease [SD] with increased tumor size) during TPC before enrollment at Sun Yat-sen University Cancer Center between January 1 and July 30, 2018. Eligible patients were given moxifloxacin once daily at a dose of 400 mg from days 1 to 7 of a 28-day cycle, in addition to continuing to receive the therapy previously selected by their physicians. Tumor response was determined according to RECIST (version 1.1). Progression-free survival (PFS) was calculated using the Kaplan-Meier method.

RESULTS

The concomitant use of moxifloxacin and previous TPC yielded a median PFS of 6.6 months (95% confidence interval [CI]: 4.0-9.1) and a 1-year PFS of 25.9% (95% CI: 10.0%-41.9%). Objective responses were achieved in seven (23.3%, 95% CI: 7.3%-39.4%) patients. The clinical benefit rate was 46.7% (95% CI: 27.7%-65.6%). No grade 4 adverse events (AEs) and four grade 3 AEs were observed, none of which were considered to have definite relation to moxifloxacin.

CONCLUSION

The combination of moxifloxacin with previous TPC shows promising efficacy and well-tolerated toxicities in patients with MBC.

Microbiome, bile acids, and obesity: How microbially modified metabolites shape anti-tumor immunity

Bile acids (BAs) are known facilitators of nutrient absorption but recent paradigm shifts now recognize BAs as signaling molecules regulating both innate and adaptive immunity. Bile acids are synthesized from cholesterol in the liver with subsequent microbial modification and fermentation adding complexity to pool composition. Bile acids act on several receptors such as Farnesoid X Receptor and the G protein-coupled BA receptor 1 (TGR5). Interestingly, BA receptors (BARs) are expressed on immune cells and activation either by BAs or BAR agonists modulates innate and adaptive immune cell populations skewing their polarization toward a more tolerogenic anti-inflammatory phenotype. Intriguingly, recent evidence also suggests that BAs promote anti-tumor immune response through activation and recruitment of tumoricidal immune cells such as natural killer T cells. These exciting findings have redefined BA signaling in health and disease wherein they may suppress inflammation on the one hand, yet promote anti-tumor immunity on the other hand. In this review, we provide our readers with the most recent understanding of the interaction of BAs with the host microbiome, their effect on innate and adaptive immunity in health and disease with a special focus on obesity, bariatric surgery-induced weight loss, and immune checkpoint blockade in cancer.

Microbiome and Breast Cancer: New Role for an Ancient Population

There are many risk factors associated with breast cancer (BC) such as the familial history of BC, using hormone replacement therapy, obesity, personal habits, and other clinical factors; however, not all BC cases are attributed to these risk factors. Recent researches show a correlation between patient microbiome and BC suggested as a new risk factor. The present review article aimed at evaluating the role of the microbiome as a risk factor in the occurrence of BC, investigating the proposed mechanisms of interaction between the microbiome and human genes involved in BC, and assessing the impact of the altered composition of breast, gut, and milk microbiome in the physiological status of normal breast as well as cancerous or non-cancerous breast lesions. The study also evaluated the growing evidence that these altered populations may hinder chemotherapeutic treatment. The role of microbiome in the development and maintenance of inflammation, estrogen metabolism, and epigenetic alterations was properly investigated. Finally, clinical and therapeutic applications of the microbiome- e.g., probiotics, microbiome genome modulation, and engineered microbiome enzymes in the management of BC were reviewed.

Bacteria and cancer: Different sides of the same coin

Conventional cancer therapies such as chemotherapy, radiation therapy, and immunotherapy due to the complexity of cancer have been unsuccessful in the complete eradication of tumor cells. Thus, there is a need for new therapeutic strategies toward cancer. Recently, the therapeutic role of bacteria in different fields of medicine and pharmaceutical research has attracted attention in recent decades. Although several bacteria are notorious as cancer-causing agents, recent research revealed intriguing results suggesting the bacterial potential in cancer therapy. Thus, bacterial cancer therapy is an alternative anticancer approach that has promising results on tumor cells in-vivo. Moreover, with the aid of genetic engineering, some natural or genetically modified bacterial strains can directly target hypoxic regions of tumors and secrete therapeutic molecules leading to cancer cell death. Additionally, stimulation of immune cells by bacteria, bacterial cancer DNA vaccine and antitumor bacterial metabolites are other therapeutic applications of bacteria in cancer therapy. The present study is a comprehensive review of different aspects of bacterial cancer therapy alone and in combination with conventional methods, for improving cancer therapy.

Cho W, Soleimanpour S. Bacteriotherapy in Breast Cancer

Breast cancer is the second most common cause of cancer-related mortality among women around the world. Conventional treatments in the fight against breast cancer, such as chemotherapy, are being challenged regarding their effectiveness. Thus, strategies for the treatment of breast cancer need to be continuously refined to achieve a better patient outcome. We know that a number of bacteria are pathogenic and some are even associated with tumor development, however, recent studies have demonstrated interesting results suggesting some bacteria may have potential for cancer therapy. Therefore, the therapeutic role of bacteria has aroused attention in medical and pharmaceutical studies. Furthermore, genetic engineering has been used in bacterial therapy and may led to greater efficacy with few side effects. Some genetically modified non-pathogenic bacterial species are more successful due to their selectivity for cancer cells but with low toxicity for normal cells. Some live, attenuated, or genetically modified bacterias are capable to multiply in tumors and inhibit their growth. This article aims to review the role of bacteria and their products including bacterial peptides, bacteriocins, and toxins for the treatment of breast cancer.

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The Potential Role of Quorum Sensing in Clonal Growth and Subsequent Expansion of Bone Marrow Stromal Cell Strains in Culture

Clonal development (clonogenicity) is an inherent property of a subset of postnatal bone marrow (BM) adherent stromal mesenchymal stem cells (MSCs) from which a multipotent progeny develops in culture. Our data suggest that clonogenicity and BM-MSC expansion are two distinct biological events. This hypothesis is based on the following observations: (1) the beginning of clonal growth is a property strictly dependent on serum and independent of the social context, (2) the expansion of individual clone is influenced by events deriving from a social context during initial growth, (3) clonogenic cells grown in a social context in presence of serum can emancipate themselves to generate a secondary different progeny, and (4) the ability of socially generated clones to develop an inherent potential for further growth suggests that quorum sensing may operate in BM-MSC cultures and determine the potential growth of clonal strains.

The significance of microbiome in personalized medicine

Considering the important role of microbiome, many of current investigations have focused on its beneficial aspects. Although, research explores new dimensions of the impact of microbiome and examines the differences in patients and healthy individuals for identifying biomarker patterns, but limited information is available, and investigation in this field seems to be of great value. On the other hand, new therapeutic approaches, called personalized medicine, have opened a new window in medical science, and the association between microbiome and personalized medicine seems to be one of the most interesting aspects of the subsequent research, and has a pivotal perspective on the treatment of diseases such as cancer. Accordingly, given the novelty of the relationship between these two axes, there are very few studies in this regard. The presence of specific strains may have the ability to modulate cancer progression and therapeutics; this increases the likelihood of precision medicine in relation to microbiota, in terms of treatment and prognosis, and therefore, microbiota is a next generation medicine and may develop a novel therapeutic action in this field.

The effect of breastmilk and saliva combinations on the in vitro growth of oral pathogenic and commensal microorganisms

Neonates are exposed to microbes in utero and at birth, thereby establishing their microbiota (healthy microbial colonisers). Previously, we reported significant differences in the neonatal oral microbiota of breast-fed and formula-fed babies after first discovering a primal metabolic mechanism that occurs when breastmilk (containing the enzyme xanthine oxidase) and neonatal saliva (containing highly elevated concentrations of the substrates for xanthine oxidase: xanthine and hypoxanthine). The interaction of neonatal saliva and breast milk releases antibacterial compounds including hydrogen peroxide, and regulates the growth of bacteria. Using a novel in vitro experimental approach, the current study compared the effects of this unique metabolic pathway on a range of bacterial species and determined the period of time that microbial growth was affected. We demonstrated that microbial growth was inhibited predominately, immediately and for up to 24 hr following breastmilk and saliva mixing; however, some microorganisms were able to recover and continue to grow following exposure to these micromolar amounts of hydrogen peroxide. Interestingly, growth inhibition was independent of whether the organisms possessed a catalase enzyme. This study further confirms that this is one mechanism that contributes to the significant differences in the neonatal oral microbiota of breast-fed and formula-fed babies.

The role of bacteria in cancer therapy - enemies in the past, but allies at present

In recent decades, bacteria’s therapeutic role has aroused attention in medicinal and pharmaceutical research. While bacteria are considered among the primary agents for causing cancer, recent research has shown intriguing results suggesting that bacteria can be effective agents for cancer treatment – they are the perfect vessels for targeted cancer therapy. Several bacterial strains/species have been discovered to possess inherent oncolytic potentials to invade and colonize solid tumors in vivo. The therapeutic strategy of using bacteria for treating cancer is considered to be effective; however, the severe side effects encountered during the treatment resulted in the abandonment of the therapy. State-of-the-art genetic engineering has been recently applied to bacteria therapy and resulted in a greater efficacy with minimum side effects. In addition, the anti-cancer potential of tumor-targeting bacteria through oral administration circumvents the use of the intravenous route and the associated adverse effects. This review aims to provide a comprehensive summary of the latest literature on the role of bacteria in cancer treatment.

Screening of quorum sensing peptides for biological effects in neuronal cells

Quorum sensing peptides (QSP) are an important class of bacterial peptides which can have an effect on human host cells. These peptides are used by bacteria to communicate with each other. Some QSP are able to cross the blood-brain barrier and reach the brain parenchyma. However, nothing is known about the effects of these peptides in the brain. Therefore, 85 quorum sensing peptides were screened on six different neuronal cell lines using MTT toxicity, neurite differentiation, cytokine production and morphology as biological outcomes. This primary screening resulted in 22 peptides with effects observed on neuronal cell lines, indicating a possible role in the gut-brain axis. Four peptides (Q138, Q143, Q180 and Q212) showed induction of neurite outgrowth while two peptides (Q162 and Q208) inhibited NGF-induced neurite outgrowth in PC12 cells. Eight peptides (Q25, Q135, Q137, Q146, Q151, Q165, Q208 and Q298) induced neurite outgrowth in human SH-SY5Y neuroblastoma cells. Two peptides (Q13 and Q52) were toxic for SH-SY5Y cells and one (Q123) for BV-2 microglia cells based on the MTT assay. Six peptides had an effect on BV-2 microglia, Q180, Q184 and Q191 were able to induce IL-6 expression and Q164, Q192 and Q208 induced NO production. Finally, Q75 and Q147 treated C8D1A astrocytes demonstrated a higher fraction of round cells. Overall, these in vitro screening study results indicate for the first time possible effects of QSP on neuronal cells.