Orally delivered microencapsulated probiotic formulation favorably impacts polyp formation in APC (Min/+) model of intestinal carcinogenesis

Targeting beta-catenin signaling for prevention of colorectal cancer - Nutraceutical, drug, and dietary options

Progressive up-regulation of β-catenin signaling is very common in the transformation of colorectal epithelium to colorectal cancer (CRC). Practical measures for opposing such signaling hence have potential for preventing or slowing such transformation. cAMP/PKA activity in colon epithelium, as stimulated by COX-2-generated prostaglandins and β2-adrenergic signaling, boosts β-catenin activity, whereas cGMP/PKG signaling has the opposite effect. Bacterial generation of short-chain fatty acids (as supported by unrefined high-carbohydrate diets, berberine, and probiotics), dietary calcium, daily aspirin, antioxidants opposing cox-2 induction, and nicotine avoidance, can suppress cAMP production in colonic epithelium, whereas cGMP can be boosted via linaclotides, PDE5 inhibitors such as sildenafil or icariin, and likely high-dose biotin. Selective activation of estrogen receptor-β by soy isoflavones, support of adequate vitamin D receptor activity with UV exposure or supplemental vitamin D, and inhibition of CK2 activity with flavanols such as quercetin, can also oppose β-catenin signaling in colorectal epithelium. Secondary bile acids, the colonic production of which can be diminished by low-fat diets and berberine, can up-regulate β-catenin activity by down-regulating farnesoid X receptor expression. Stimulation of PI3K/Akt via insulin, IGF-I, TLR4, and EGFR receptors boosts β-catenin levels via inhibition of glycogen synthase-3β; plant-based diets can down-regulate insulin and IGF-I levels, exercise training and leanness can keep insulin low, anthocyanins and their key metabolite ferulic acid have potential for opposing TLR4 signaling, and silibinin is a direct antagonist for EGFR. Partially hydrolyzed phytate can oppose growth factor-mediated down-regulation of β-catenin by inhibiting Akt activation. Multifactorial strategies for safely opposing β-catenin signaling can be complemented with measures that diminish colonic mutagenesis and DNA hypomethylation - such as avoidance of heme-rich meat and charred or processed meats, consumption of phase II-inductive foods and nutraceuticals (e.g., Crucifera), and assurance of adequate folate status.

Probiotic immunonutrition impacts on colon cancer immunotherapy and prevention

The important role of the immune system in treating cancer has attracted the attention of researchers to the emergence of oncology research. Immunotherapy has shown that the immune system is important in the fight against cancer. The challenge has led researchers to analyze the impact of immunotherapy on improving the status of the immune system, modifying the resulting safety response, reducing toxicity, and improving the results. This study aimed to discuss the potential mechanisms of probiotics in preventing colon cancer. The mechanisms include the change in intestinal microbiota, the metabolic activity of microbiota, the binding and degradation of the carcinogenic compounds present in the lumen of the intestine, the production of compounds with anticancer activity, immune system modification, intestinal dysfunction, changes in host physiology, and inhibition of cell proliferation and induction of apoptosis in cancerous cells. By contrast, very few reports have shown the harmful effects of oral probiotic supplements. According to available evidence, further studies on probiotics are needed, especially in identifying bacterial species with anticancer potential, studying the survival of the strains after passing the digestive tract, reviewing potential side effects in people with a weak immune system, and ultimately consuming and repeating its use. This study emphasizes that the nutritional formula can modulate inflammatory and immune responses in cancer patients. This effect reduces acute toxicity, although the pathways and measurement of this immune response are unclear. Nutrition safety is an emerging field in oncology, and further research is required.

The role of the gut microbiota and probiotics associated with microbial metabolisms in cancer prevention and therapy

Cancer is the second leading cause of elevated mortality worldwide. Thus, the development of drugs and treatments is needed to enhance the survival rate of the cancer-affected population. Recently, gut microbiota research in the healthy development of the human body has garnered widespread attention. Many reports indicate that changes in the gut microbiota are strongly associated with chronic inflammation-related diseases, including colitis, liver disease, and cancer within the intestine and the extraintestinal tract. Different gut bacteria are vital in the occurrence and development of tumors within the gut and extraintestinal tract. The human gut microbiome has significant implications for human physiology, including metabolism, nutrient absorption, and immune function. Moreover, diet and lifestyle habits are involved in the evolution of the human microbiome throughout the lifetime of the host and are involved in drug metabolism. Probiotics are a functional food with a protective role in cancer development in animal models. Probiotics alter the gut microbiota in the host; thus, beneficial bacterial activity is stimulated, and detrimental activity is inhibited. Clinical applications have revealed that some probiotic strains could reduce the occurrence of postoperative inflammation among cancer patients. An association network was constructed by analyzing the previous literature to explore the role of probiotics from the anti-tumor perspective. Therefore, it provides direction and insights for research on tumor treatment.

Cellular Carcinogenesis: Role of Polarized Macrophages in Cancer Initiation

Simple Summary

Inflammation is a hallmark of many cancers. Macrophages are key participants in innate immunity and important drivers of inflammation. When chronically polarized beyond normal homeostatic responses to infection, injury, or aging, macrophages can express several pro-carcinogenic phenotypes. In this review, evidence supporting polarized macrophages as endogenous sources of carcinogenesis is discussed. In addition, the depletion or modulation of macrophages by small molecule inhibitors and probiotics are reviewed as emerging strategies in cancer prevention.

Abstract

Inflammation is an essential hallmark of cancer. Macrophages are key innate immune effector cells in chronic inflammation, parainflammation, and inflammaging. Parainflammation is a form of subclinical inflammation associated with a persistent DNA damage response. Inflammaging represents low-grade inflammation due to the dysregulation of innate and adaptive immune responses that occur with aging. Whether induced by infection, injury, or aging, immune dysregulation and chronic macrophage polarization contributes to cancer initiation through the production of proinflammatory chemokines/cytokines and genotoxins and by modulating immune surveillance. This review presents pre-clinical and clinical evidence for polarized macrophages as endogenous cellular carcinogens in the context of chronic inflammation, parainflammation, and inflammaging. Emerging strategies for cancer prevention, including small molecule inhibitors and probiotic approaches, that target macrophage function and phenotype are also discussed.

Kefir modulates gut microbiota and reduces DMH-associated colorectal cancer via regulation of intestinal inflammation in adulthood offsprings programmed by neonatal overfeeding

Obesity is associated with chronic inflammation, intestinal dysbiosis, and colorectal cancer risk. The anti-cancer effects of kefir are highlighted. Here, lactating Wistar rats were divided into: Normal litter (NL); Kefir normal litter (KNL); Small litter (SL); Kefir small litter (KSL). The NL and SL groups received 1 mL of water/day; KNL and KSL received kefir milk daily (10⁸ CFU/mL) during lactation. After weaning, the pups continued to receive the same treatments until 60 days. At 67 days old, colorectal carcinogenesis was induced through intraperitoneal injection of 1,2-dimethylhydrazine. At 240 days, visceral adipose tissue was higher in SL compared to NL, KNL, and KSL. Kefir intake was found to suppress the number of tumors in both KNL and KSL groups (-100% and -71.43%; p < 0.01, respectively). IL-1β, IL-6, TNF-α, and NO levels in the colon were higher in the NL and SL compared to the KNL and KSL. The gut microbiota in cecal samples of SL was enriched with Alloprevotella, Acinetobacter, and Bacteroides. In contrast, the cecal contents of KSL and KNL were higher Romboutsia. Thus, neonatal overfeeding leads to greater adiposity, inflammation and number of colon tumors in adulthood. Early-life nutrition based on kefir reverted these alterations.

Familial adenomatous polyposis and changes in the gut microbiota: New insights into colorectal cancer carcinogenesis

Patients with familial adenomatous polyposis (FAP), an autosomal dominant hereditary colorectal cancer syndrome, have a lifetime risk of developing cancer of nearly 100%. Recent studies have pointed out that the gut microbiota could play a crucial role in the development of colorectal adenomas and the consequent progression to colorectal cancer. Some gut bacteria, such as Fusobacterium nucleatum, Escherichia coli, Clostridium difficile, Peptostreptococcus, and enterotoxigenic Bacteroides fragilis, could be implicated in colorectal carcinogenesis through different mechanisms, including the maintenance of a chronic inflammatory state, production of bioactive tumorigenic metabolites, and DNA damage. Studies using the adenomatous polyposis coliMin/+ mouse model, which resembles FAP in most respects, have shown that specific changes in the intestinal microbial community could influence a multistep progression, the intestinal "adenoma-carcinoma sequence", which involves mucosal barrier injury, low-grade inflammation, activation of the Wnt pathway. Therefore, modulation of gut microbiota might represent a novel therapeutic target for patients with FAP. Administration of probiotics, prebiotics, antibiotics, and nonsteroidal anti-inflammatory drugs could potentially prevent the progression of the adenoma-carcinoma sequence in FAP. The aim of this review was to summarize the best available knowledge on the role of gut microbiota in colorectal carcinogenesis in patients with FAP.

Gut Microbiota: Influence on Carcinogenesis and Modulation Strategies by Drug Delivery Systems to Improve Cancer Therapy

Gut microbiota have close interactions with the host. It can affect cancer progression and the outcomes of cancer therapy, including chemotherapy, immunotherapy, and radiotherapy. Therefore, approaches toward the modulation of gut microbiota will enhance cancer prevention and treatment. Modern drug delivery systems (DDS) are emerging as rational and promising tools for microbiota intervention. These delivery systems have compensated for the obstacles associated with traditional treatments. In this review, the essential roles of gut microbiota in carcinogenesis, cancer progression, and various cancer therapies are first introduced. Next, advances in DDS that are aimed at enhancing the efficacy of cancer therapy by modulating or engineering gut microbiota are highlighted. Finally, the challenges and opportunities associated with the application of DDS targeting gut microbiota for cancer prevention and treatment are briefly discussed.

Preclinical and clinical relevance of probiotics and synbiotics in colorectal carcinogenesis: a systematic review

CONTEXT

Recent evidence suggests that modulation of the gut microbiota may help prevent colorectal cancer.

OBJECTIVE

The aim of this systematic review was to investigate the role of probiotics and synbiotics in the prevention of colorectal cancer and to clarify potential mechanisms involved.

DATA SOURCES

The PubMed, ScienceDirect, and LILACS databases were searched for studies conducted in humans or animal models and published up to August 15, 2018.

STUDY SELECTION

Clinical trials and placebo-controlled experimental studies that evaluated the effects of probiotics and synbiotics in colorectal cancer and cancer associated with inflammatory bowel disease were included. Of 247 articles identified, 31 remained after exclusion criteria were applied. A search of reference lists identified 5 additional studies, for a total of 36 included studies.

DATA EXTRACTION

Two authors independently assessed risk of bias of included studies and extracted data. Data were pooled by type of study, ie, preclinical or clinical.

RESULTS

The results showed positive effects of probiotics and synbiotics in preventing colorectal cancer. The main mechanisms identified were alterations in the composition and metabolic activity of the intestinal microbiota; reduction of inflammation; induction of apoptosis and inhibition of tumor growth; modulation of immune responses and cell proliferation; enhanced function of the intestinal barrier; production of compounds with anticarcinogenic activity; and modulation of oxidative stress.

CONCLUSIONS

Probiotics or synbiotics may help prevent colorectal cancer, but additional studies in humans are required to better inform clinical practice.

Preclinical Evidence of Probiotics in Colorectal Carcinogenesis: A Systematic Review

BACKGROUND

Colorectal cancer, the second major cause of cancer deaths, imposes a major health burden worldwide. There is growing evidence that supports that the use of probiotics is effective against various diseases, especially in gastrointestinal diseases, including the colorectal cancer, but the differences between the strains, dose, and frequency used are not yet clear.

AIMS

To perform a systematic review to compile the results of studies carried out in animal models and investigated the effect of probiotics on colorectal carcinogenesis.

METHODS

Studies were selected in PubMed/MEDLINE and Scopus according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Search filters were developed using three parameters: probiotics, colorectal cancer, and animal model.

RESULTS

From a structured search, we discovered 34 original articles and submitted them to a risk of bias analysis using SYRCLE's tool. The studies show a great diversity of models, most were conducted in rats (55.8%) and used 1,2 dimethylhydrazine as the drug to induce colorectal carcinogenesis (61.7%). The vast majority of trials investigated Lactobacillus (64%) and Bifidobacterium (29.4%) strains. Twenty-six (86.6%) studies found significant reduction in lesions or tumors in the animals that received probiotics. The main methodological limitation was the insufficient amount of information for the adequate reproducibility of the trials, which indicated a high risk of bias due to incomplete characterization of the experimental design.

CONCLUSIONS

The different probiotics' strains showed anti-carcinogenic effect, reduced the development of lesions and intestinal tumors, antioxidant and immunomodulatory activity, and reduced fecal bacterial enzymes.

Modulation of Anti-Tumour Immune Responses by Probiotic Bacteria

There is a growing amount of evidence to support the beneficial role of a balanced intestinal microbiota, or distinct members thereof, in the manifestation and progression of malignant tumours, not only in the gastrointestinal tract but also in distant tissues as well. Intriguingly, bacterial species have been demonstrated to be indispensable modulatory agents of widely-used immunotherapeutic or chemotherapeutic regiments. However, the exact contribution of commensal bacteria to immunity, as well as to neoplasia formation and response to treatment, has not been fully elucidated, and most of the current knowledge acquired from animal models has yet to be translated to human subjects. Here, recent advances in understanding the interaction of gut microbes with the immune system and the modulation of protective immune responses to cancer, either naturally or in the context of widely-used treatments, are reviewed, along with the implications of these observations for future therapeutic approaches. In this regard, bacterial species capable of facilitating optimal immune responses against cancer have been surveyed. According to the findings summarized here, we suggest that strategies incorporating probiotic bacteria and/or modulation of the intestinal microbiota can be used as immune adjuvants, aiming to optimize the efficacy of cancer immunotherapies and conventional anti-tumour treatments.

Disease managing capacities and mechanisms of host effects of lactic acid bacteria

Consumption of lactic acid bacteria (LAB) has been suggested to confer health-promoting effects on the host. However, effects of LABs have been reported to be species- and strain-specific and the mechanisms involved are subjects of discussion. Here, the possible mechanisms by which LABs induce antipathogenic, gut barrier enhancing and immune modulating effects in consumers are reviewed. Specific strains for which it has been proven that health is improved by these mechanisms are discussed. However, most strains probably act via several or combinations of mechanisms depending on which effector molecules they express. Current insight is that these effector molecules are either present on the cell wall of LAB or are excreted. These molecules are reviewed as well as the ligand binding receptors in the host. Also postbiotics are discussed. Finally, we provide an overview of the efficacy of LABs in combating infections caused by Helicobacter pylori, Salmonella, Escherichia coli, Streptococcus pneumoniae, and influenza virus, in controlling gut inflammatory diseases, in managing allergic disorders, and in alleviating cancer.

Oral supplementation with lactobacilli to prevent colorectal cancer in preclinical models

Colorectal cancer (CRC) is still a major threat for public health, as it is the third most common cancer in men and the second in women and it ranks second among tumors in terms of mortality. Evidence from the last decades emphasizes the complex role of gut microbial composition in CRC development. Historically, it is believed that dairy products, a source of lactobacilli and other lactic acid bacteria, are beneficial for human health and help in preventing CRC. We searched online literature for trials evaluating the preventive role of lactobacilli in CRC animal models. Most of selected studied assessed a relevant role of lactobacilli in preventing CRC and precursor lesions. Mechanisms through which this effect was achieved are supposed to regard immunomodulation, regulation of apoptosis, gut microbial modulation, genes expression, reduction of oxidative stress and others. Lactobacilli oral supplementation is reported to be effective in preventing CRC in animal models, even if the underlying mechanisms of action are still not fully understood.

A novel polyphenolic prebiotic and probiotic formulation have synergistic effects on the gut microbiota influencing Drosophila melanogaster physiology

The gut microbiota is a vast community of synergistic bacterial species providing health benefits to the host. Imbalances in the gut microbiota (dysbiosis) due to diet, antibiotic use, age and stress contribute to disease development including diabetes, obesity, colon cancer, inflammatory bowel disease, inflammaging and neurodegeneration. Fortunately, a probiotic regime with a diet rich in prebiotics may reverse dysbiosis promoting health and wellness in age. The current study designs, optimizes and tests a novel probiotic and synbiotic formulation consisting of three metabolically active probiotics Lactobacillus plantarum, Lactobacillus fermentum and Bifidobacteria infantis together with a novel polyphenol-rich prebiotic, Triphala. The prebiotic action of Triphala was characterized using in vitro batch cultures, Drosophila melanogaster and a simulated model of the human gastrointestinal tract (SHIME) where in each model, Triphala supported growth of beneficial bacteria while inhibiting pathogenic species. Neither Triphala at 0.5% w/v nor the individual probiotics at 5.0 × 10⁸ to 7.5 × 10⁹ CFU/ml demonstrated toxicity in Drosophila. Interestingly, motility was combinatorially enhanced by the probiotic and synbiotic formulations reflecting the beneficial variations in the gut microbiota. Altogether, the present study shows that probiotics and synbiotics in combination are more effective at modulating the gut microbiota and eliciting biological effects than their components.

Probiotics-mediated suppression of cancer

PURPOSE OF REVIEW

Probiotics can be used as an adjuvant for cancer prevention or/and treatment through their abilities to modulate intestinal microbiota and host immune response. Although most of the recent reviews have focused on the potential role of probiotics against colon cancer, only few of them include the probiotic effect on extraintestinal cancers. The present review covers the most important findings from the literature published during the past 20 months (from January 2015 to August 2016) regarding the probiotics-mediated suppression of both gastrointestinal and extraintestinal cancers and the underlying mechanisms.

RECENT FINDINGS

A comprehensive literature search in Pubmed, Science direct and Google scholar databases was conducted to locate all relevant articles that investigated the effect of probiotics on prevention/treatment of both gastrointestinal and extraintestinal cancers. Different mechanisms for the beneficial effects of probiotics against cancer were also discussed, mainly via modulation of gut microbiota which thereby influences host metabolism and immunity.

SUMMARY

Despite laboratory-based studies having demonstrated encouraging outcomes that probiotics possess antitumor effects, the benefits should not be exaggerated before we get more results from human clinical trials. These are very important before the medical community can accept the use of probiotics as an alternative therapy for cancer control.

Anticancer effects of the microbiome and its products

The human gut microbiome modulates many host processes, including metabolism, inflammation, and immune and cellular responses. It is becoming increasingly apparent that the microbiome can also influence the development of cancer. In preclinical models, the host response to cancer treatment has been improved by modulating the gut microbiome; this is known to have an altered composition in many diseases, including cancer. In addition, cancer treatment with microbial agents or their products has the potential to shrink tumours. However, the microbiome could also negatively influence cancer prognosis through the production of potentially oncogenic toxins and metabolites by bacteria. Thus, future antineoplastic treatments could combine the modulation of the microbiome and its products with immunotherapeutics and more conventional approaches that directly target malignant cells.