Diet, Gut Microbiota, and Colorectal Cancer Prevention: A Review of Potential Mechanisms and Promising Targets for Future Research

The Role of the Microbiome on the Pathogenesis and Treatment of Colorectal Cancer

The gut microbiome has long been known to play a role in various aspects of health modulation, including the pathogenesis of colorectal cancer (CRC). With immunotherapy recently emerging as a successful treatment in microsatellite instability high (MSI-high) CRC, and with a newly demonstrated involvement of the gut microbiome in the modulation of therapeutic responses, there has been an explosion of research into the mechanisms of microbial effects on CRC. Harnessing and reprogramming the microbiome may allow for the expansion of these successes to broader categories of CRC, the prevention of CRC in high-risk patients, and the enhancement of standard treatments. In this review, we pull together both well-documented phenomena and recent discoveries that pertain to the microbiome and CRC. We explore the microbial mechanisms associated with CRC pathogenesis and progression, recent advancements in CRC systemic therapy, potential options for diagnosis and prevention, as well as directions for future research.

Colorectal Cancer Screening in a Changing World

Early detection of colorectal neoplasia significantly reduces mortality from colorectal cancer (CRC), and numerous screening options exist. Guidelines for CRC screening from US and international professional societies provide menus of options based on strength of evidence. Despite availability of screening and its proven impact, 40% of guideline-eligible patients are not screened as recommended in the United States. Adherence to or uptake of CRC screening is especially poor among underserved populations, including those with low income and African American and Hispanic populations. Consideration of screening options must not only take into account test performance, but issues of resources and individual versus population benefits.

Characterization of Butyrate-Resistant Colorectal Cancer Cell Lines and the Cytotoxicity of Anticancer Drugs against These Cells

Colorectal cancer (CRC) is the third most common cancer worldwide. The gut microbiota plays a critical role in homeostasis and carcinogenesis. Butyrate, a short-chain fatty acid produced by the gut microbiota, plays a role in intestinal homeostasis and acts as an anticancer agent by inhibiting growth and inducing apoptosis. However, microbiota studies have revealed an abnormally high abundance of butyrate-producing bacteria in patients with CRC and indicated that it leads to chemoresistance. We characterized butyrate resistance in HCT-116 and PMF-K014 CRC cells after treatment with a maximum butyrate concentration of 3.2 mM. The 50% inhibitory concentration of butyrate was increased in butyrate-resistant (BR) cells compared with that in parental (PT) cells. The mechanism of butyrate resistance was initially investigated by determining the expression of butyrate influx- and drug efflux-related genes. We found the increased expression of influx- and efflux-related genes in BR cells compared with that in PT cells. Proteomic data showed both identical and different proteins in PT and BR cells. Further analysis revealed the crossresistance of HCT-116 cells to metformin and oxaliplatin and that of PMF-K014 cells to 5-fluorouracil. Our findings suggest that the acquisition of butyrate resistance induces the development of chemoresistance in CRC cells, which may play an important role in CRC development, treatment, and metastasis.

Cytotoxic effect of metformin on butyrate-resistant PMF-K014 colorectal cancer spheroid cells

Three-dimensional (3D) cell culture models are used in cancer research because they mimic physiological responses in vivo compared with two-dimensional (2D) culture systems. Recently, cross-resistance of butyrate-resistant (BR) cells and chemoresistance in colorectal cancer (CRC) cells have been reported; however, effective treatments for BR cells have not been identified. In this study, we investigated the cytotoxicity of metformin (MET), an anti-diabetic drug, on BR CRC cells in a 3D spheroid culture model. The results demonstrate that MET decreases spheroid size, migration, and spheroid viability, while it increases spheroid death. The molecular mechanism revealed that AMP-activated protein kinase (AMPK) and Akt serine/threonine kinase 1(Akt) were significantly upregulated, whereas the acetyl-CoA-carboxylase (ACC) and mammalian target of rapamycin (mTOR) were downregulated, which led to caspase activation and apoptosis. Our findings show the potential cytotoxicity of MET on CRC-BR cells. The combination of MET and conventional chemotherapeutic drugs should be addressed in further studies to reduce the side effects of standard chemotherapy for CRC.

Cellular Immune Signal Exchange From Ischemic Stroke to Intestinal Lesions Through Brain-Gut Axis

As a vital pivot for the human circulatory system, the brain-gut axis is now being considered as an important channel for many of the small immune molecules’ transductions, including interleukins, interferons, neurotransmitters, peptides, and the chemokines penetrating the mesentery and blood brain barrier (BBB) during the development of an ischemic stroke (IS). Hypoxia-ischemia contributes to pituitary and neurofunctional disorders by interfering with the molecular signal release and communication then providing feedback to the gut. Suffering from such a disease on a long-term basis may cause the peripheral system’s homeostasis to become imbalanced, and it can also lead to multiple intestinal complications such as gut microbiota dysbiosis (GMD), inflammatory bowel disease (IBD), necrotizing enterocolitis (NEC), and even the tumorigenesis of colorectal carcinoma (CRC). Correspondingly, these complications will deteriorate the cerebral infarctions and, in patients suffering with IS, it can even ruin the brain’s immune system. This review summarized recent studies on abnormal immunological signal exchange mediated polarization subtype changes, in both macrophages and microglial cells as well as T-lymphocytes. How gut complications modulate the immune signal transduction from the brain are also elucidated and analyzed. The conclusions drawn in this review could provide guidance and novel strategies to benefit remedies for both IS and relative gut lesions from immune-prophylaxis and immunotherapy aspects.

Cohort profile: The National Colorectal Cancer Cohort (NCRCC) study in China

PURPOSE

The National Colorectal Cancer Cohort (NCRCC) study aims to specifically assess risk factors and biomarkers related to endpoints across the colorectal cancer continuum from the aetiology through survivorship.

PARTICIPANTS

The NCRCC study includes the Colorectal Cancer Screening Cohort (CRCSC), which recruited individuals who were at high risk of CRC between 2016 and 2020 and Colorectal Cancer Patients Cohort (CRCPC), which recruited newly diagnosed patients with CRC between 2015 and 2020. Data collection was based on questionnaires and abstraction from electronic medical record. Items included demographic and lifestyle factors, clinical information, survivorship endpoints and other information. Multiple biospecimens including blood, tissue and urine samples were collected. Participants in CRCSC were followed by a combination of periodic survey every 5 years and annual linkage with regional or national cancer and death registries for at least 10 years. In CRCPC, follow-up was conducted with both active and passive approaches at 6, 12, 18, 24, 36, 48 and 60 months after surgery.

FINDINGS TO DATE

A total of 19 377 participants and 15 551 patients with CRC were recruited in CRCSC and in CRCPC, respectively. In CRCSC, 48.0% were men, and the average age of participants at enrolment was 58.7±8.3 years. In CRCPC, 61.4% were men, and the average age was 60.3±12.3 years with 18.9% of participants under 50 years of age.

FUTURE PLANS

Longitudinal data and biospecimens will continue to be collected. Based on the cohorts, several studies to assess risk factors and biomarkers for CRC or its survivorship will be conducted, ultimately providing research evidence from Chinese population and optimising evidence-based guidelines across the CRC continuum.

The Sulfur Microbial Diet and Risk of Colorectal Cancer by Molecular Subtypes and Intratumoral Microbial Species in Adult Men

INTRODUCTION

We recently described the sulfur microbial diet, a pattern of intake associated with increased gut sulfur-metabolizing bacteria and incidence of distal colorectal cancer (CRC). We assessed whether this risk differed by CRC molecular subtypes or presence of intratumoral microbes involved in CRC pathogenesis (Fusobacterium nucleatum and Bifidobacterium spp.).

METHODS

We performed Cox proportional hazards modeling to examine the association between the sulfur microbial diet and incidence of overall and distal CRC by molecular and microbial subtype in the Health Professionals Follow-Up Study (1986-2012).

RESULTS

We documented 1,264 incident CRC cases among 48,246 men, approximately 40% of whom had available tissue data. After accounting for multiple hypothesis testing, the relationship between the sulfur microbial diet and CRC incidence did not differ by subtype. However, there was a suggestion of an association by prostaglandin synthase 2 (PTGS2) status with a multivariable adjusted hazard ratio for highest vs lowest tertile of sulfur microbial diet scores of 1.31 (95% confidence interval: 0.99-1.74, Ptrend = 0.07, Pheterogeneity = 0.04) for PTGS2-high CRC. The association of the sulfur microbial diet with distal CRC seemed to differ by the presence of intratumoral Bifidobacterium spp. with an adjusted hazard ratio for highest vs lowest tertile of sulfur microbial diet scores of 1.65 (95% confidence interval: 1.14-2.39, Ptrend = 0.01, Pheterogeneity = 0.03) for Bifidobacterium-negative distal CRC. We observed no apparent heterogeneity by other tested molecular markers.

DISCUSSION

Greater long-term adherence to the sulfur microbial diet could be associated with PTGS2-high and Bifidobacterium-negative distal CRC in men. Additional studies are needed to further characterize the role of gut microbial sulfur metabolism and CRC.

Examination of hydrogen cross-feeders using a colonic microbiota model

Background

Hydrogen cross-feeding microbes form a functionally important subset of the human colonic microbiota. The three major hydrogenotrophic functional groups of the colon: sulphate-reducing bacteria (SRB), methanogens and reductive acetogens, have been linked to wide ranging impacts on host physiology, health and wellbeing.

Results

An existing mathematical model for microbial community growth and metabolism was combined with models for each of the three hydrogenotrophic functional groups. The model was further developed for application to the colonic environment via inclusion of responsive pH, host metabolite absorption and the inclusion of host mucins. Predictions of the model, using two existing metabolic parameter sets, were compared to experimental faecal culture datasets. Model accuracy varied between experiments and measured variables and was most successful in predicting the growth of high relative abundance functional groups, such as the Bacteroides, and short chain fatty acid (SCFA) production. Two versions of the colonic model were developed: one representing the colon with sequential compartments and one utilising a continuous spatial representation. When applied to the colonic environment, the model predicted pH dynamics within the ranges measured in vivo and SCFA ratios comparable to those in the literature. The continuous version of the model simulated relative abundances of microbial functional groups comparable to measured values, but predictions were sensitive to the metabolic parameter values used for each functional group. Sulphate availability was found to strongly influence hydrogenotroph activity in the continuous version of the model, correlating positively with SRB and sulphide concentration and negatively with methanogen concentration, but had no effect in the compartmentalised model version.

Conclusions

Although the model predictions compared well to only some experimental measurements, the important features of the colon environment included make it a novel and useful contribution to modelling the colonic microbiota.

An Overview of Gut Microbiota and Colon Diseases with a Focus on Adenomatous Colon Polyps

It is known and accepted that the gut microbiota composition of an organism has an impact on its health. Many studies deal with this topic, the majority discussing gastrointestinal health. Adenomatous colon polyps have a high prevalence as colon cancer precursors, but in many cases, they are hard to diagnose in their early stages. Gut microbiota composition correlated with the presence of adenomatous colon polyps may be a noninvasive and efficient tool for diagnosis with a high impact on human wellbeing and favorable health care costs. This review is meant to analyze the gut microbiota correlated with the presence of adenomatous colon polyps as the first step for early diagnosis, prophylaxis, and treatment.

Food as medicine: targeting the uraemic phenotype in chronic kidney disease

The observation that unhealthy diets (those that are low in whole grains, fruits and vegetables, and high in sugar, salt, saturated fat and ultra-processed foods) are a major risk factor for poor health outcomes has boosted interest in the concept of 'food as medicine'. This concept is especially relevant to metabolic diseases, such as chronic kidney disease (CKD), in which dietary approaches are already used to ameliorate metabolic and nutritional complications. Increased awareness that toxic uraemic metabolites originate not only from intermediary metabolism but also from gut microbial metabolism, which is directly influenced by diet, has fuelled interest in the potential of 'food as medicine' approaches in CKD beyond the current strategies of protein, sodium and phosphate restriction. Bioactive nutrients can alter the composition and metabolism of the microbiota, act as modulators of transcription factors involved in inflammation and oxidative stress, mitigate mitochondrial dysfunction, act as senolytics and impact the epigenome by altering one-carbon metabolism. As gut dysbiosis, inflammation, oxidative stress, mitochondrial dysfunction, premature ageing and epigenetic changes are common features of CKD, these findings suggest that tailored, healthy diets that include bioactive nutrients as part of the foodome could potentially be used to prevent and treat CKD and its complications.

Targeting the gut microbiota by Asian and Western dietary constituents: a new avenue for diabetes

Increasing numerous diabetes annually is a great concern in public health globally. Gut microbiota recently has been suggested to be an emerging organ acting as a critical regulator in diabetes. Notably, gut microbiota is closely affected through an individual's nutrient intake and dietary pattern. Moreover, the metabolites of diets through gut microbiota are closely associated with the development of diabetes. Increasing evidence has established the association of different dietary pattern with alterations of the gut microbiota profile, in particular, the Asian diet and Western diet are typically as essential components linked to the interactions between gut microbiota and induction of obesity which is a significant risk factor for diabetes. In addition, some bacteria-related therapeutic methods including probiotics, dietary short-chain fatty acids immunotherapy, and gut microbiome transfer would be applied in the clinical prevention and control diabetes. Taken together, based on current published observations, the gut microbiota may serve as regulator or targets by the Asian diet and Western diet, contributing to the prevention or induction of diabetes eventually. In general, in the upcoming future, one of the emerging strategies for the prevention and control of diabetes may modulate gut microbiota through precise dietary strategies.

Inflammatory potential of the diet and risk of colorectal cancer in the European Prospective Investigation into Cancer and Nutrition study

Proinflammatory diets are associated with risk of developing colorectal cancer (CRC), however, inconsistencies exist in subsite- and sex-specific associations. The relationship between CRC and combined lifestyle-related factors that contribute toward a low-grade inflammatory profile has not yet been explored. We examined the association between the dietary inflammatory potential and an inflammatory profile and CRC risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. This cohort included 476,160 participants followed-up of 14 years and 5,991 incident CRC cases (3,897 colon and 2,094 rectal tumors). Dietary inflammatory potential was estimated using an Inflammatory Score of the Diet (ISD). An Inflammatory Profile Score (IPS) was constructed, incorporating the ISD, physical activity level and abdominal obesity. The associations between the ISD and CRC and IPS and CRC were assessed using multivariable regression models. More proinflammatory diets were related to a higher CRC risk, particularly for colon cancer; hazard ratio (HR) for highest versus lowest ISD quartile was 1.15 (95% confidence interval [CI] 1.04-1.27) for CRC, 1.24 (95% CI 1.09-1.41) for colon cancer and 0.99 (95% CI 0.83-1.17) for rectal cancer. Associations were more pronounced in men and not significant in women. The IPS was associated with CRC risk, particularly colon cancer among men; HRs for the highest versus lowest IPS was 1.62 (95% CI 1.31-2.01) for colon cancer overall and 2.11 (95% CI 1.50-2.97) for colon cancer in men. Our study shows that more proinflammatory diets and a more inflammatory profile are associated with higher risk of CRC, principally colon cancer and in men.

Metagenomic analysis of gut microbiota modulatory effects of jujube (Ziziphus jujuba Mill.) polysaccharides in a colorectal cancer mouse model

Accumulating evidence has reported that the gut microbiota could play important roles in the occurrence and progression of colorectal cancer.

The BE GONE trial study protocol: a randomized crossover dietary intervention of dry beans targeting the gut microbiome of overweight and obese patients with a history of colorectal polyps or cancer

BACKGROUND

Mouse and human studies support the promise of dry beans to improve metabolic health and to lower cancer risk. In overweight/obese patients with a history of colorectal polyps or cancer, the Beans to Enrich the Gut microbiome vs. Obesity's Negative Effects (BE GONE) trial will test whether and how an increase in the consumption of pre-cooked, canned dry beans within the context of usual diet and lifestyle can enhance the gut landscape to improve metabolic health and reduce cancer risk.

METHODS/DESIGN

This randomized crossover trial is designed to characterize changes in (1) host markers spanning lipid metabolism, inflammation, and obesity-related cancer risk; (2) compositional and functional profiles of the fecal microbiome; and (3) host and microbial metabolites. With each subject serving as their own control, the trial will compare the participant's usual diet with (intervention) and without (control) dry beans. Canned, pre-cooked dry beans are provided to participants and the usual diet continually assessed and monitored. Following a 4-week run-in and equilibration period, each participant provides a total of 5 fasting blood and 6 stool samples over a total period of 16 weeks. The intervention consists of a 2-week ramp-up of dry bean intake to 1 cup/d, which is then continued for an additional 6 weeks. Intra- and inter-individual outcomes are assessed across each crossover period with consideration of the joint or modifying effects of the usual diet and baseline microbiome.

DISCUSSION

The BE GONE trial is evaluating a scalable dietary prevention strategy targeting the gut microbiome of high-risk patients to mitigate the metabolic and inflammatory effects of adiposity that influence colorectal cancer risk, recurrence, and survival. The overarching scientific goal is to further elucidate interactions between diet, the gut microbiome, and host metabolism. Improved understanding of the diet-microbiota interplay and effective means to target these relationships will be key to the future of clinical and public health approaches to cancer and other major diet- and obesity-related diseases.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02843425. First posted July 25, 2016; last verified January 25, 2019.

miR-145-5p restrained cell growth, invasion, migration and tumorigenesis via modulating RHBDD1 in colorectal cancer via the EGFR-associated signaling pathway

miR-145-5p has been reported to be downregulated and described functioning as a tumor suppressive gene in colorectal cancer (CRC), yet its detailed regulatory function and mechanism in malignant progression of the disease have not been thoroughly understood. In our study, miR-145-5p and rhomboid domain containing 1 (RHBDD1) in CRC tissues and cells were examined by qRT-PCR and western blot. MTT, colony formation, wound healing, Transwell invasion, and flow cytometry assays were performed to evaluate the malignant phenotypes of CRC cells. Xenograft tumor, qRT-PCR, and western blot assays were applied to validate the roles and mechanism of miR-145-5p in CRC in vivo. The interaction between miR-145-5p and RHBDD1 was investigated by luciferase reporter assay and western blot. The changes of the EGFR/Raf/MEK/ERK pathway were detected by western blot. We found miR-145-5p was lowly expressed and low miR-145-5p predicted poor prognosis in CRC, while RHBDD1 was greatly enhanced in CRC cells and tissues. RHBDD1 silencing resulted in inhibiting cell proliferative, invasive, and migratory potentials as well as elevating apoptotic ones in CRC cells. miR-145-5p was inversely related with RHBDD1 expression in CRC tissues. miR-145-5p was found to directly bind to RHBDD1 and restrained its expression in CRC cells. miR-145-5p overexpression repressed CRC cell proliferation, invasion, migration and induced apoptosis, and these effects were reversed by RHBDD1 upregulation. Moreover, in CRC xenograft tumor, its growth was impeded by miR-145-5p via suppressing RHBDD1. Furthermore, miR-145-5p inhibited the expression of EGFR, p-MEK1/2 and p-ERK1/2, in vitro and in vivo by targeting RHBDD1. In conclusion, our study revealed that miR-145-5p overexpression inhibited tumorigenesis in CRC by downregulating RHBDD1 via suppressing the EGFR-associated signaling pathway (EGFR/Raf/MEK/ERK cascades).

Bugs, drugs, and cancer: can the microbiome be a potential therapeutic target for cancer management?

Outnumbering our own cells over ten times, gut microbes can even be considered an additional organ. Several studies have explored the association between microbiomes and antitumor drug response. It has been reported that the presence of specific bacteria might modulate cancer progression and the efficacy of anticancer therapeutics. Bacteria-targeting intervention can provide crucial guidance for the design of next-generation antitumor drugs. Here, we review previous findings elucidating the impact of gut microbiomes on cancer treatment and the possible underlying mechanisms. In addition, we examine the role of microbiome manipulation in controlling tumor growth. Finally, we discuss concerns regarding the alteration of the microbiome composition, and the potential approaches to surpass existing limitations.

Targeting gut microbiota with dietary components on cancer: Effects and potential mechanisms of action

Cancers are common chronic diseases worldwide and cause severe health burdens. There have been ongoing debates on the role of gut microbiota in the prevention and management of cancers, thus, it is worthwhile to pay high attention to the impacts of gut microbiota on several cancers, such as colon, liver, and breast cancers. In addition, it has been reported that gut microbiota may also affect the efficacy of cancer chemotherapy and immunotherapy. Among all the factors that influence gut microbiota, diet is the most influential and modifiable. The prebiotics, dietary fibers, short-chain fatty acids, and other bioactive compounds are all important dietary components to assist the growth of beneficial microbiota in the gut, which can protect against cancers and promote human health. Their beneficial effects can be due to the fermentation of dietary fibers, the metabolism of phytochemicals, the synthesis of estrogens, and interactions with chemotherapies and immunotherapies. In order to provide updated information of the relationships among dietary components, gut microbiota, and cancer, in this review, we summarize the reciprocal interactions between dietary components and gut microbiota, and highlight the impacts of dietary components on several common cancers by targeting gut microbiota, with the potential mechanisms of actions also intensively discussed. As a result, this review can be very helpful for healthy people as well as cancer patients to prevent or manage cancers via dietary factor-mediated regulation of gut microbiota.

Olive Oil Effects on Colorectal Cancer

Colorectal cancer is the fourth cause of cancer-related death worldwide. A Mediterranean diet showed protective action against colorectal cancer due to the intake of different substances. Olive oil is a fundamental component of the Mediterranean diet. Olive oil is rich in high-value health compounds (such as monounsaturated free fatty acids, squalene, phytosterols, and phenols). Phenolic compounds exert favourable effects on free radicals, inflammation, gut microbiota, and carcinogenesis. The interaction between gut microbiota and olive oil consumption could modulate colonic microbial composition or activity, with a possible role in cancer prevention. Gut microbiota is able to degrade some substances found in olive oil, producing active metabolites with chemopreventive action. Further clinical research is needed to clarify the beneficial effects of olive oil and its components. A better knowledge of the compounds found in olive oil could lead to the development of nutritional supplements or chemotherapeutic agents with a potential in the prevention and treatment of colorectal cancer.

Hydrogen cross-feeders of the human gastrointestinal tract

Hydrogen plays a key role in many microbial metabolic pathways in the human gastrointestinal tract (GIT) that have an impact on human nutrition, health and wellbeing. Hydrogen is produced by many members of the GIT microbiota, and may be subsequently utilized by cross-feeding microbes for growth and in the production of larger molecules. Hydrogenotrophic microbes fall into three functional groups: sulfate-reducing bacteria, methanogenic archaea and acetogenic bacteria, which can convert hydrogen into hydrogen sulfide, methane and acetate, respectively. Despite different energy yields per molecule of hydrogen used between the functional groups, all three can coexist in the human GIT. The factors affecting the numerical balance of hydrogenotrophs in the GIT remain unconfirmed. There is increasing evidence linking both hydrogen sulfide and methane to GIT diseases such as irritable bowel syndrome, and strategies for the mitigation of such health problems through targeting of hydrogenotrophs constitute an important field for further investigation.

Intestinal microbiota, chronic inflammation, and colorectal cancer

In addition to genetic and epigenetic factors, various environmental factors, including diet, play important roles in the development of colorectal cancer (CRC). Recently, there is increasing interest in the intestinal microbiota as an environmental risk factor for CRC, because diet also influences the composition of the intestinal microbiota. The human intestinal microbiota comprises about 100 trillion microbes. This microbiome thrives on undigested dietary residues in the intestinal lumen and produces various metabolites. It is well known that the dietary risk factors for CRC are mediated by dysbiosis of the intestinal microbiota and their metabolites. In this review, we describe the bacterial taxa associated with CRC, including Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, Escherichia coli, and butyrate-producing bacteria. We also discuss the host-diet interaction in colorectal carcinogenesis.

Underlying Causes and Therapeutic Targeting of the Inflammatory Tumor Microenvironment

Historically, the link between chronic inflammation and cancer has long been speculated. Only more recently, pre-clinical and epidemiologic data as well as clinical evidence all point to the role of the tumor microenvironment as inextricably connected to the neoplastic process. The tumor microenvironment (TME), a complex mix of vasculature, inflammatory cells, and stromal cells is the essential "soil" helping to modulate tumor potential. Increasingly, evidence suggests that chronic inflammation modifies the tumor microenvironment, via a host of mechanisms, including the production of cytokines, pro-inflammatory mediators, angiogenesis, and tissue remodeling. Inflammation can be triggered by a variety of different pressures, such as carcinogen exposure, immune dysfunction, dietary habits, and obesity, as well as genetic alterations leading to oncogene activation or loss of tumor suppressors. In this review, we examine the concept of the tumor microenvironment as related to both extrinsic and intrinsic stimuli that promote chronic inflammation and in turn tumorigenesis. Understanding the common pathways inherent in an inflammatory response and the tumor microenvironment may shed light on new therapies for both primary and metastatic disease. The concept of personalized medicine has pushed the field of oncology to drill down on the genetic changes of a cancer, in the hopes of identifying individually targeted agents. Given the complexities of the tumor microenvironment, it is clear that effective oncologic therapies will necessitate targeting not only the cancer cells, but their dynamic relationship to the tumor microenvironment as well.

miR-6852 serves as a prognostic biomarker in colorectal cancer and inhibits tumor growth and metastasis by targeting TCF7

MicroRNAs (miRs) are have been demonstrated to serve important functions in the genesis of human cancer, including colorectal cancer (CRC). The role of miR-6852 in CRC remains unknown. In this study, it was demonstrated that miR-6852 was underexpressed in CRC tissues compared with adjacent normal tissues. Moreover, the expression of miR-6852 was negatively correlated with CRC metastasis, whereas positively correlated with patient prognosis. It was revealed that the overexpression of miR-6852 significantly inhibited the proliferation and invasion of CRC cells. miR-6852 overexpression reduced CRC cells in the S phase. TCF7 was identified to be a direct target of miR-6852 in CRC cells. Overexpression of miR-6852 significantly inhibited the mRNA and protein levels of TCF7 in CRC cells. Furthermore, TCF7 was highly expressed in CRC tissues and cell lines. TCF7 expression was negatively correlated with miR-6852 levels in CRC tissues. Finally, knockdown of TCF7 significantly suppressed the proliferation and invasion of CRC cells. Taken together, the results of the present study indicated that miR-6852 serves as a tumor suppressor in CRC through targeting TCF7.

Towards a cancer-chemopreventive diet

Commensal microbes engineered to convert natural compounds found in cruciferous vegetables into molecules with anticancer properties prevent carcinogenesis and cause the regression of colorectal cancer in mice fed with a vegetable diet.