The Role of the Gut Microbiome in Colorectal Cancer

Identification of KRAS mutation-associated gut microbiota in colorectal cancer and construction of predictive machine learning model

Gut microbiota has demonstrated an increasingly important role in the onset and development of colorectal cancer (CRC). Nonetheless, the association between gut microbiota and KRAS mutation in CRC remains enigmatic. We conducted 16S rRNA sequencing on stool samples from 94 CRC patients and employed the linear discriminant analysis effect size algorithm to identify distinct gut microbiota between KRAS mutant and KRAS wild-type CRC patients. Transcriptome sequencing data from nine CRC patients were transformed into a matrix of immune infiltrating cells, which was then utilized to explore KRAS mutation-associated biological functions, including Gene Ontology items and Kyoto Encyclopedia of Genes and Genomes pathways. Subsequently, we analyzed the correlations among these KRAS mutation-associated gut microbiota, host immunity, and KRAS mutation-associated biological functions. At last, we developed a predictive random forest (RF) machine learning model to predict the KRAS mutation status in CRC patients, based on the gut microbiota associated with KRAS mutation. We identified a total of 26 differential gut microbiota between both groups. Intriguingly, a significant positive correlation was observed between Bifidobacterium spp. and mast cells, as well as between Bifidobacterium longum and chemokine receptor CX3CR1. Additionally, we also observed a notable negative correlation between Bifidobacterium and GOMF:proteasome binding. The RF model constructed using the KRAS mutation-associated gut microbiota demonstrated qualified efficacy in predicting the KRAS phenotype in CRC. Our study ascertained the presence of 26 KRAS mutation-associated gut microbiota in CRC and speculated that Bifidobacterium may exert an essential role in preventing CRC progression, which appeared to correlate with the upregulation of mast cells and CX3CR1 expression, as well as the downregulation of GOMF:proteasome binding. Furthermore, the RF model constructed on the basis of KRAS mutation-associated gut microbiota exhibited substantial potential in predicting KRAS mutation status in CRC patients.IMPORTANCEGut microbiota has emerged as an essential player in the onset and development of colorectal cancer (CRC). However, the relationship between gut microbiota and KRAS mutation in CRC remains elusive. Our study not only identified a total of 26 gut microbiota associated with KRAS mutation in CRC but also unveiled their significant correlations with tumor-infiltrating immune cells, immune-related genes, and biological pathways (Gene Ontology items and Kyoto Encyclopedia of Genes and Genomes pathways). We speculated that Bifidobacterium may play a crucial role in impeding CRC progression, potentially linked to the upregulation of mast cells and CX3CR1 expression, as well as the downregulation of GOMF:Proteasome binding. Furthermore, based on the KRAS mutation-associated gut microbiota, the RF model exhibited promising potential in the prediction of KRAS mutation status for CRC patients. Overall, the findings of our study offered fresh insights into microbiological research and clinical prediction of KRAS mutation status for CRC patients.

TCM syndrome differentiation in colorectal cancer patients assisted by differences in gut microbiota: An exploratory study

Objective

To explore the difference in gut microbiota between different traditional Chinese Medicine (TCM) syndromes in patients with colorectal cancer (CRC) and its internal relationship.

Methods

From June 2020 to August 2021, 109 colorectal cancer patients with a clear pathological diagnosis who had not yet undergone surgery or chemotherapy were classified according to the TCM syndrome classification, and the feces samples of 109 patients with preoperative colorectal cancer were collected. 16s rRNA gene sequencing was used to determine gut microbiota diversity and abundance in CRC patients with different TCM syndrome, and LEfSe analysis was made to screen different TCM syndrome for differential representative microbiota.

Results

109 patients were divided into 5 syndromes by TCM syndrome classification, which were Liver and Kidney Yin Deficiency Syndrome (LKYDS, n = 19), Spleen Deficient Qi Stagnation Syndrome (SDQSS, n = 30), Stasis and Poison Obstruction Syndrome (SPOS, n = 17), Damp-Heat Syndrome (DHS, n = 30), Qi and Blood Deficiency Syndrome (QBDS, n = 13). Alpha diversity index showed significant differences among the five groups of TCM syndromes, with Shannon index being highest in the SDQSS group and lowest in the LKYDS (p = 0.003). ACE index being highest in the SDQSS group and lowest in the SPOS (p = 0.010). PD whole tree index being highest in the SDQSS group and lowest in the SPOS (p = 0.017). Similarly, beta diversity showed significant differences among the five groups of TCM syndromes, with principal coordinate analysis (PCo1 = 31.86 %, PCo2 = 5.62 %) showing separation and coincidence between the groups, and Adonis group differences showing coincidence between the QBDS-LKYDS (p = 0.702), QBDS-DHS (p = 0.133), and SDQSS-DHS (p = 0.260) groups. LEfSe analysis revealed that the representative microbiota of DHS patients was Dialister sp Marseille P5638 (LDA = 3.05, p＜0.001), the representative microbiota of SPOS patients was Oscillospirales (LDA = 4.78, p = 0.029), the representative microbiota of SDQSS patients was Selenomonadaceae (LDA = 3.94, p = 0.003), the representative microbiota of LKYDS patients was Dialister (LDA = 4.19, p = 0.001), and the representative microbiota of QBDS patients was Akkermansia muciniphila (LDA = 4.23, p = 0.006).

Conclusions

There are significant differences in gut microbiota between different TCM syndromes in CRC patients. The five microbiota, Dialister sp Marseille P5638, Oscillospirales, Selenomonadaceae, Dialister, and Akkermansia muciniphila, may be differential markers of TCM syndrome in CRC and are expected to be one of the bases for accurate TCM syndrome differentiation of CRC.

Differences in tissue-associated bacteria between metastatic and non-metastatic colorectal cancer

Background and aims

Accumulated evidence indicates that the intestinal microbiota plays crucial roles in the initiation and progression of colorectal cancer (CRC). However, the effects of the tissue-associated microbiota on CRC metastasis are poorly defined. The aim of this study was to explore the differences in bacteria between metastatic and non-metastatic CRC tissues and identify potential bacterial species that associate with CRC metastasis.

Methods

16S rDNA amplicon high-throughput sequencing was used to test the intestinal tissue-associated microbiota in patients with metastatic CRC (n = 48) and non-metastatic CRC (n = 44). The microbial diversity and differential species were analysed by standard microbiological methods, and then the differential bacteria were confirmed by qPCR. Receiver operating characteristic (ROC) curves were plotted to evaluate the ability of the differential bacteria in predicting the metastasis of CRC. In addition, the microbial compositions of tumor-adjacent tissues from the metastatic and non-metastatic CRC groups were analysed.

Results

The α- or β-diversity of microbial community between the metastatic and non-metastatic CRC groups did not exhibit significant differences. However, some bacterial abundances between two groups showed significant differences. At the phylum level, Bacteroidota and Desulfobacterota were significantly higher in the metastatic group than in the non-metastatic group, while Proteobacteria was significantly decreased in the metastatic group. At the genus level, Bacteroides (mainly composed of Bacteroides fragilis and Bacteroides uniformis) was significantly higher in the metastatic group than in the non-metastatic group, while Streptococcus and Escherichia-Shigella were significantly decreased. The ROC curves of the selected bacteria showed area under the curve (AUC) values ranging from 0.598 to 0.69; when CEA and the selected bacteria were combined, the AUC values increased from 0.678 to 0.705. In addition, the bacterial composition of tumor-adjacent tissues from the metastatic and non-metastatic CRC groups were also different, and the differential bacteria were consistent with those between metastatic and non-metastatic CRC tumor tissues.

Conclusion

The bacterial composition of tumor and tumor adjacent tissue from the metastatic CRC group was different from that of the non-metastatic CRC group; in particular, Bacteroides was increased, and Streptococcus was decreased. These findings are helpful to further reveal the mechanism of CRC metastasis and provide new ideas for the clinical diagnosis and treatment of CRC metastasis.

Lacticaseibacillus rhamnosus—A Promising Tool for Colorectal Cancer Treatment

Probiotic strains such as Lactobacillus spp. are already known for their beneficial effect on human health and new research supports their role in colon cancer prevention and treatment. The current study reports the effect of different concentrations of Lacticaseibacillus rhamnosus (LGG, 106–109 CFU/mL), alone or in association with 5-fluorouracil (5-FU, 10 μM), tested against normal HaCaT cells, HT-29 colorectal adenocarcinoma and HCT-116 colorectal carcinoma cell lines. The underlying cytotoxic effect was further investigated. LGG treatment of HT-29 and HCT-116 cells caused a variety of apoptotic-related nuclear morphological changes, as revealed by DAPI staining. ELISA studies showed that LGG treatment increased caspase-3 activity and pro-apoptotic BAX protein levels while decreasing anti-apoptotic Bcl-2 protein levels and the proto-oncogene Cyclin D1. A more detailed examination of the mitochondrial function revealed that high concentrations of LGG can impair mitochondrial function in HT-29 and HCT-116 cancer cells. All of these findings suggest that LGG has a pro-apoptotic, mitochondrial-targeted, cytotoxic effect on both colon cancer cell lines studied.

The Pivotal Role of the Gut Microbiome in Colorectal Cancer

Simple Summary

Colorectal cancer is a common form of cancer observed globally. It is thought that the gut microbiome may play a pivotal role in the development and progression of colorectal cancer in patients. Furthermore, current treatment strategies may lead to a variety of side effects, and chemotherapeutic resistance is observed. Consequently, new types of treatments should be considered, including post/pre/synbiotics and fecal microbiota transfer, which may be able to restore gut microbial dysbiosis.

Abstract

Colorectal cancer is the third most diagnosed cancer worldwide and the second most prevalent cause of cancer-related mortality. It is believed that alterations within the gut microbiome may impact the development and progression of cancer. Additionally, the diet an individual maintains and the amount of alcohol consumed can alter the microbiome, thus impacting the development of colorectal cancer. A diet focused on fiber intake is considered beneficial, as it contains short-chain fatty acids such as butyrate, which have antitumor properties. Furthermore, current treatment strategies, such as chemotherapy, have various side effects. In this review, we discuss the role of the gut microbiome and oral bacteria in relation to colorectal cancer. We also deliberate on the role of diet and alcohol consumption in the development of colorectal cancer. Moreover, the influence of the various metabolites within the gut and the importance of gut inflammation in the development of colorectal cancer are explained. Finally, potential therapies such as fecal microbiota transfer and post/prebiotics are elaborated on. To further comprehend risk factors in the development of colorectal cancer, future studies are warranted to determine the precise mechanisms of action between the gut microbiome and carcinogenesis in order to develop therapies that may target gut microbial dysbiosis.

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.

Controlling the uncontrolled variation in the diet induced obese mouse by microbiomic characterization

Group sizes in an animal study are calculated from estimates on variation, effect, power and significance level. Much of the variation in glucose related parameters of the diet-induced obese (DIO) mouse model is due to inter-individual variation in gut microbiota composition. In addition, standard tandem repeats (STRs) in the non-coding DNA shows that inbred mice are not always homogenic. C57BL/6NTac (B6NTac) mice from Taconic and C57BL/6NRj (B6NRj) mice from Janvier Labs were fed a high calorie diet and treated with liraglutide. The fecal microbiota was sequenced before high-calorie feeding (time 1) and after diet-induced obesity instantly before liraglutide treatment (time 2) and mice were divided into clusters on the basis of their microbiota. Although liraglutide in both sub-strains alleviated glucose intolerance and reduced body weight, in a one-way ANOVA a borderline reduction in glycosylated hemoglobin (HbA1c) could only be shown in B6NTac mice. However, if the microbiota clusters from time 1 or time 2 were incorporated in a two-way ANOVA, the HbA1c effect was significant in B6NTac mice in both analyses, while this did not change anything in B6NRj mice. In a one-way ANOVA the estimated group size needed for a significant HbA1c effect in B6NTac mice was 42, but in two-way ANOVAs based upon microbiota clusters of time 1 or time 2 it was reduced to 21 or 12, respectively. The lowering impact on glucose tolerance was also powered by incorporation of microbiota clusters of both times in both sub-strains. B6NRj had up to six, while B6NTac had maximum three alleles in some of their STRs. In B6NRj mice in 28.8% of the STRs the most prevalent allele had a gene frequency less than 90%, while this was only 6.6% in the B6NTac mice. However, incorporation of the STRs with the highest number of alleles or the most even distribution of frequencies in two-way ANOVAs only had little impact on the outcome of data evaluation. It is concluded that the inclusion of microbiota clusters in a two-way ANOVA in the evaluation of the glucose related effects of an intervention in the DIO mouse model might be an efficient tool for increasing power and reducing group sizes in mouse sub-strains, if these have a microbiota, which influences these parameters.

Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms

This is a narrative review of the evidence supporting vitamin D’s anticancer actions. The first section reviews the findings from ecological studies of cancer with respect to indices of solar radiation, which found a reduced risk of incidence and mortality for approximately 23 types of cancer. Meta-analyses of observational studies reported the inverse correlations of serum 25-hydroxyvitamin D [25(OH)D] with the incidence of 12 types of cancer. Case-control studies with a 25(OH)D concentration measured near the time of cancer diagnosis are stronger than nested case-control and cohort studies as long follow-up times reduce the correlations due to changes in 25(OH)D with time. There is no evidence that undiagnosed cancer reduces 25(OH)D concentrations unless the cancer is at a very advanced stage. Meta-analyses of cancer incidence with respect to dietary intake have had limited success due to the low amount of vitamin D in most diets. An analysis of 25(OH)D-cancer incidence rates suggests that achieving 80 ng/mL vs. 10 ng/mL would reduce cancer incidence rates by 70 ± 10%. Clinical trials have provided limited support for the UVB-vitamin D-cancer hypothesis due to poor design and execution. In recent decades, many experimental studies in cultured cells and animal models have described a wide range of anticancer effects of vitamin D compounds. This paper will review studies showing the inhibition of tumor cell proliferation, dedifferentiation, and invasion together with the sensitization to proapoptotic agents. Moreover, 1,25-(OH)₂D₃ and other vitamin D receptor agonists modulate the biology of several types of stromal cells such as fibroblasts, endothelial and immune cells in a way that interferes the apparition of metastases. In sum, the available mechanistic data support the global protective action of vitamin D against several important types of cancer.

Roles of gut microbiota in colorectal carcinogenesis providing a perspective for early diagnosis and treatment

Colorectal cancer (CRC) is the third most prevalent malignant neoplasm in the world. CRC is influenced by both environmental and genetic factors. Through toxin-mediated DNA damage and promotion of persistent dysregulated inflammation, the gut microbiota plays a crucial role in the development of CRC. In this review, we discussed the correlation between the bacterial microbiota and CRC carcinogenesis as well as the mechanism by which Streptococcus bovis/gallolyticus, Fusobacterium nucleatum, Bacteroides fragilis, and Escherichia coli can cause CRC.

Obesity and inflammation: colorectal cancer engines

The prevalence of obesity continues to increase to the extent that it became a worldwide pandemic. An accumulating body of evidence has associated obesity with the development of different types of cancer, including colorectal cancer, which is a notorious disease with a high mortality rate. At the molecular level, colorectal cancer is a heterogenous disease characterized by a myriad of genetic and epigenetic alterations associated with various forms of genomic instability (detailed in Supplementary Materials). Recently, the microenvironment has emerged as a major factor in carcinogenesis. Our aim is to define the different molecular alterations leading to the development of colorectal cancer in obese patients with a focus on the role of the microenvironment in carcinogenesis. We also highlight all existent molecules in clinical trials that target the activated pathways in obesity-associated colorectal cancer, whether used as single treatments or in combination. Obesity predisposes to colorectal cancer via creating a state of chronic inflammation with dysregulated adipokines, inflammatory mediators, and other factors such as immune cell infiltration. A unifying theme in obesity-mediated colorectal cancer is the activation of the PI3K/AKT, mTOR/MAPK, and STAT3 signaling pathways. Different inhibitory molecules towards these pathways exist, increasing the therapeutic choice of obesity-associated colon cancer. However, obese patients are more likely to suffer from chemotherapy overdosing. Preventing obesity through maintaining a healthy and active lifestyle remains to be the best remedy.

The brain-gut axis in gastrointestinal cancers

Recent developments have given more credence into the brain-gut-microbiota axis and its role in the development of tumor genesis. The microbiota have multiple functions including maintenance of the epithelial barrier, immune response, digestion, cortisol regulation, and control of neurotransmitters and their metabolism [e.g., serotonin, dopamine, noradrenaline and gamma-Aminobutyric Acid (GABA)]. Changes in gut microbiota can interfere with homeostasis leading to dysbiosis microbiota, which is linked to colorectal cancer. Microbiota composition can cause pronounced effect on medical interventions including medications, chemotherapy, and radiation. Altered primary immune system is associated with microbiota disassociation and development of colorectal cancer. This article reviews the current research in brain-gut axis with focus on microbiota and its role in the development of gastrointestinal cancers. We conducted a literature review on PubMed, Cochrane, and Science direct using English language. We begin by reviewing the brain-gut axis and its function and then discuss its effect on the development of gastrointestinal cancers. We reviewed 70 manuscripts and found association between microbiota dysfunction and development of colorectal cancers predisposing to psychiatric manifestations. Lasting disturbances in the microbiota can lead to systemic inflammation with implications on disease development or treatment modifications. These disruptions of the intestinal flora can play an important role in the pathogenesis of cancers. Most psychological reactions to cancer are similar across cancer types but each cancer when examined individually has its own unique features associated with it. Correlation between fear of recurrence and the level of pathological distress is viewed as an indicator of overall adjustment to cancer survival.

The role of microbiome in colorectal carcinogenesis and its clinical potential as a target for cancer treatment

The role of gut microbiome-intestinal immune complex in the development of colorectal cancer and its progression is well recognized. Accordingly, certain microbial strains tend to colonize or vanish in patients with colorectal cancer. Probiotics, prebiotics, and synbiotics are expected to exhibit both anti-tumor effects and chemopreventive effects during cancer treatment through mechanisms such as xenometabolism, immune interactions, and altered eco-community. Microbial modulation can also be safely used to prevent complications during peri-operational periods of colorectal surgery. A deeper understanding of the role of intestinal microbiota as a target for colorectal cancer treatment will lead the way to a better prognosis for colorectal cancer patients.

Metformin and Probiotics in the Crosstalk between Colitis-Associated Colorectal Cancer and Diabetes in Mice

The co-occurrence of colorectal cancer (CRC) and diabetes mellitus along with inflammation and dismicrobism has been frequently reported. Several studies shed light on the antioncogenic potential of metformin on colorectal carcinogenesis. This study aimed to demonstrate that metformin in association with probiotics acts in a synergic effect in breaking the crosstalk, thus inhibiting CRC progression, improving diabetes, and reducing inflammation. Ninety-six male Balb/c mice, 6–8 weeks old, were divided into 16 control and experimental groups to assess the effect of the different treatments and combinations at the clinical, histological, and molecular levels. Metformin and probiotics showed beneficial outcomes on CRC and diabetes, alone and most importantly in combination. Their effects were exerted by inhibiting the inflammatory process whereby a downregulation of IL-6 and TNF-α as well as oxidative stress were depicted. The characterization of the effects of probiotics and metformin on CRC and diabetes sheds light on the role of inflammation and microbiota in this crosstalk. Deciphering the downstream signaling pathways elicited by these compounds will help in developing new effective targeted treatment modalities.

Alterations in the Gut Microbiome and Suppression of Histone Deacetylases by Resveratrol Are Associated with Attenuation of Colonic Inflammation and Protection Against Colorectal Cancer

Inflammatory bowel disease (IBD) is known to significantly increase the risk for development of colorectal cancer (CRC), suggesting inflammation and cancer development are closely intertwined. Thus, agents that suppress inflammation may prevent the onset of cancer. In the current study, we used resveratrol, an anti-inflammatory stilbenoid, to study the role of microbiota in preventing inflammation-driven CRC. Resveratrol treatment in the azoxymethane (AOM) and dextran sodium sulphate (DSS) CRC murine model caused an increase in anti-inflammatory CD4 + FOXP3 + (Tregs) and CD4 + IL10 + cells, a decrease in proinflammatory Th1 and Th17 cells, and attenuated CRC development. Gut microbial profile studies demonstrated that resveratrol altered the gut microbiome and short chain fatty acid (SCFA), with modest increases in n-butyric acid and a potential butyrate precursor isobutyric acid. Fecal transfer from resveratrol-treated CRC mice and butyrate supplementation resulted in attenuation of disease and suppression of the inflammatory T cell response. Data also revealed both resveratrol and sodium butyrate (BUT) were capable of inhibiting histone deacetylases (HDACs), correlating with Treg induction. Analysis of The Cancer Genome Atlas (TCGA) datasets revealed increased expression of Treg-specific transcription factor FoxP3 or anti-inflammatory IL-10 resulted in an increase in 5-year survival of patients with CRC. These data suggest that alterations in the gut microbiome lead to an anti-inflammatory T cell response, leading to attenuation of inflammation-driven CRC.

Effect and mechanism of vitamin D on the development of colorectal cancer based on intestinal flora disorder

BACKGROUND

To investigate the correlation between the level of circulating vitamin D and the development of colorectal cancer (CRC) and to clarify the effect and mechanism of vitamin D on the development of CRC.

METHODS

Serum samples from 63 patients with CRC (CRC group) and 61 healthy volunteers (normal group) were collected. Azoxymethane + dextran sodium sulfate-induced CRC mouse model and dietary models with different doses of vitamin D were established to verify whether vitamin D supplementation could reverse the occurrence and development of CRC at the overall animal level. Intestinal barrier integrity and microbial defense response were evaluated by detection of intestinal flora and expression of related genes.

RESULTS

In the clinical serum samples, compared with the normal group, the level of 25 (OH) D3 in the CRC group was relatively low (P < 0.01), which was consistent with the clinical situation in mice. Vitamin D deficiency aggravated the deterioration of enteritis and intestinal cancer in CRC mice, whereas the overall condition of CRC mice improved after vitamin D supplementation. Vitamin D has a significant regulatory effect on the homeostasis of the intestinal flora, particularly in the regulation of intestinal probiotics, Akkermansia muciniphila-mediated colon barrier integrity.

CONCLUSIONS

Vitamin D deficiency is closely related to the high incidence of CRC, and vitamin D supplementation can inhibit the occurrence and development of CRC. Vitamin D plays a role in the reversal of CRC mainly through the regulation of intestinal flora, especially the regulation of A. muciniphila-mediated colon barrier integrity.

Driver Gene Mutations and Epigenetics in Colorectal Cancer

OBJECTIVE

The majority of patients with colorectal cancer are diagnosed with locally advanced and/or disseminated disease, and treatment options include surgery in combination with cytotoxic chemotherapy regimens, biologics, and/or radiotherapy. Thus, colorectal cancer remains a heavy burden on society and health care systems.Mounting evidence show that driver gene mutations play only part of the role in carcinogenesis. Epigenetics are strongly implicated in initiation and progression of colorectal cancer along with major players such as intestinal microbiotic dysbiosis and chronic mucosal inflammation.To assess phenotypic changes in proteins and gene expression, multigene expression signatures based on sequencing techniques have been developed to hopefully improve predictors of the tumor profile, immune response, and therapeutic outcomes. Our objective was to review current advances in the field and to update surgeons and academics on driver gene mutations and epigenetics in colorectal cancer.

BACKGROUND AND METHODS

This is a narrative review studying relevant research published in the PUBMED database from 2012-2018.

RESULTS AND CONCLUSION

Increased understanding of the molecular biology will improve options to characterize colorectal cancer with regard to mutations and molecular pathways, including microsatellite instability, epigenetics, microbiota, and microenvironment. Research will inevitably improve risk group stratification and targeted treatment approaches.Epigenetic profiling and epigenetic modulating drugs will increase risk stratification, increase accessibility for DNA targeting chemotherapeutics and reduce cytotoxic drug resistance.New generation antibiotics such as biofilm inhibitors and quorum sensing inhibitors are being developed to target the carcinogenetic impact of colonic dysbiosis and inflammation.

The Effects of Neoadjuvant Treatment on the Tumor Microenvironment in Rectal Cancer: Implications for Immune Activation and Therapy Response

BACKGROUND

Because more than one neoadjuvant treatment is available for advanced rectal cancer, the aim of this study was to compare the differential clinical and pathologic effects of different combinations of chemoradiation regimens, treatment sequencing, and timing to surgery on patient outcomes.

PATIENTS AND METHODS

Between January 2015 and October 2018, 126 newly diagnosed patients with rectal cancer with magnetic resonance imaging-based cT3-4 or N+ rectal disease for curative-intent treatment received 1 of 4 neoadjuvant regimens, followed by immediate surgery or delayed surgery. Whole post-neoadjuvant surgical specimens were assessed by 3-dimensional digital whole-tumor microarray imaging and immunostaining in pathology to analyze the global tumor pathologic regression grades, residual tumor distribution patterns, the extent of lymphovascular permeation, lymph node positivity, and the overall density of lymphocyte infiltration in the tumor microenvironment. These factors were further examined to identify possible correlations with clinical outcomes.

RESULTS

Among the 4 neoadjuvant treatment groups, including 2 conventional regimens, we found a significant increase of stromal CD3+ and CD8+ immune infiltrates in the postneoadjuvant tumor microenvironment in the 3 groups with delayed surgery after different chemoradiation regimens compared with the group with immediate surgery after a short course of RT alone. Independent of neoadjuvant chemoradiation regimens, the post-induction high-intermediate-low stromal-infiltrating CD8+ T-cell densities corresponded to tumor regression grades, distant metastasis rates, and disease-free survival and were prognostic factors for the further stratification of patients with American Joint Committee on Cancer stage III rectal cancer into different risk groups after surgery.

CONCLUSION

The effectiveness of induction strategies on tumor remission and disease recurrence in advanced rectal cancer was significantly correlated with an enhanced cytotoxic immune response in the tumor microenvironment.

Curcumin and colorectal cancer: An update and current perspective on this natural medicine

Colorectal cancer (CRC) is one of most common malignancies worldwide and its incidence is still growing. In spite of recent advances in targeted therapies, their clinical efficacy has been limited, non-curative and unaffordable. A growing body of literature indicates that CRC is a multi-modal disease, where a variety of factors within the tumor microenvironment play a significant role in its pathogenesis. For instance, imbalance in gut microbial profiles and impaired intestinal barrier function contribute to the overall intestinal inflammation and initiation of CRC. Moreover, persistent chronic inflammation favors a tumor microenvironment for the growth of cancer. In addition, autophagy or 'self-eating' is a surveillance mechanism involved in the degradation of cellular constituents that are generated under stressful conditions. Cancer stem cells (CSCs), on the other hand, engage in the onset of CRC and are able to endow cancer cells with chemo-resistance. Furthermore, the aberrant epigenetic alterations promote CRC. These evidences highlight the need for multi-targeted approaches that are not only safe and inexpensive but offer a more effective alternative to current generation of targeted drugs. Curcumin, derived from the plant Curcuma longa, represents one such option that has a long history of its use for a variety of chronic disease including cancer, in Indian ayurvedic and traditional Chinese medicine. Scientific evidence over the past few decades have overwhelmingly shown that curcumin exhibits a multitude of anti-cancer activities orchestrated through key signaling pathways associated with cancer. In this article, we will present a current update and perspective on this natural medicine - incorporating the basic cellular mechanisms it effects and the current state of clinical evidence, challenges and promise for its use as a cancer preventative and potential adjunct together with modern therapies for CRC patients.

Lysates of Lactobacillus acidophilus combined with CTLA-4-blocking antibodies enhance antitumor immunity in a mouse colon cancer model

Previous reports have suggested that many gut microbiomes were associated with the development of colorectal cancer (CRC), and could modulate response to numerous forms of cancer therapy, including checkpoint blockade immunotherapy. Here we evaluated the protective efficacy of Lactobacillus acidophilus (L. acidophilus) cell lysates combined with an anti-CTL antigen-4 blocking antibody (CTLA-4 mAb) in syngeneic BALB/c mice CRC models induce by a single intraperitoneal injection of 10 mg/kg azoxymethane (AOM), followed by three cycles of 2% dextran sulfate sodium (DSS) in drinking water. In contrast to CTLA-4 mAb monotherapy, L. acidophilus lysates could attenuate the loss of body weight and the combined administration significantly protected mice against CRC development, which suggested that the lysates enhanced antitumor activity of CTLA-4 mAb in model mice. The enhanced efficacy was associated with the increased CD8 + T cell, increased effector memory T cells (CD44 + CD8 + CD62L+), decreased Treg (CD4 + CD25 + Foxp3+) and M2 macrophages (F4/80 + CD206+) in the tumor microenvironment. In addition, our results revealed that L. acidophilus lysates had an immunomodulatory effect through inhibition the M2 polarization and the IL-10 expressed levels of LPS-activated Raw264.7 macrophages. Finally, the 16S rRNA gene sequencing of fecal microbiota demonstrated that the combined administration significantly inhibited the abnormal increase in the relative abundance of proteobacteria and partly counterbalance CRC-induced dysbiosis in model mice. Overall, these data support promising clinical possibilities of L. acidophilus lysates with CTLA-4 mAb in cancer patients and the hypothesis that probiotics help shape the anticancer immune response.

Evaluation and comparison of short chain fatty acids composition in gut diseases

BACKGROUND

An altered (dysbiosis) and unhealthy status of the gut microbiota is usually responsible for a reduction of short chain fatty acids (SCFAs) concentration. SCFAs obtained from the carbohydrate fermentation processes are crucial in maintaining gut homeostasis and their determination in stool samples could provide a faster, reliable and cheaper method to highlight the presence of an intestinal dysbiosis and a biomarker for various gut diseases. We hypothesize that different intestinal diseases, such as celiac disease (CD), adenomatous polyposis (AP) and colorectal cancer (CRC) could display a particular fecal SCFAs' signature.

AIM

To compare the fecal SCFAs' profiles of CD, AP, CRC patients and healthy controls, using the same analytical method.

METHODS

In this cross-sectional study, we defined and compared the SCFAs' concentration in fecal samples of 9 AP, 16 CD, 19 CRC patients and 16 healthy controls (HC). The SCFAs' analysis were performed using a gas-chromatography coupled with mass spectrometry method. Data analysis was carried out using Wilcoxon rank-sum test to assess pairwise differences of SCFAs' profiles, partial least squares-discriminate analysis (PLS-DA) to determine the status membership based on distinct SCFAs' profiles, and Dirichlet regression to determine factors influencing concentration levels of SCFAs.

RESULTS

We have not observed any difference in the SCFAs' amount and composition between CD and healthy control. On the contrary, the total amount of SCFAs was significantly lower in CRC patients compared to HC (P = 0.044) and CD (P = 0.005). Moreover, the SCFAs' percentage composition was different in CRC and AP compared to HC. In detail, HC displayed higher percentage of acetic acid (P value = 1.3 × 10-6) and a lower amount of butyric (P value = 0.02192), isobutyric (P value = 7.4 × 10-5), isovaleric (P value = 0.00012) and valeric (P value = 0.00014) acids compared to CRC patients. AP showed a lower abundance of acetic acid (P value = 0.00062) and higher percentages of propionic (P value = 0.00433) and isovaleric (P value = 0.00433) acids compared to HC. Moreover, AP showed higher levels of propionic acid (P value = 0.03251) and a lower level of isobutyric acid (P value = 0.00427) in comparison to CRC. The PLS-DA model demonstrated a significant separation of CRC and AP groups from HC, although some degree of overlap was observed between CRC and AP.

CONCLUSION

Analysis of fecal SCFAs shows the potential to provide a non-invasive means of diagnosis to detect patients with CRC and AP, while CD patients cannot be discriminated from healthy subjects.

The Molecular Hallmarks of the Serrated Pathway in Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. It includes different subtypes that differ in their clinical and prognostic features. In the past decade, in addition to the conventional adenoma-carcinoma model, an alternative multistep mechanism of carcinogenesis, namely the “serrated pathway”, has been described. Approximately, 15 to 30% of all CRCs arise from neoplastic serrated polyps, a heterogeneous group of lesions that are histologically classified into three morphologic categories: hyperplastic polyps, sessile serrated adenomas/polyps, and the traditional serrated adenomas/polyps. Serrated polyps are characterized by genetic (BRAF or KRAS mutations) and epigenetic (CpG island methylator phenotype (CIMP)) alterations that cooperate to initiate and drive malignant transformation from normal colon mucosa to polyps, and then to CRC. The high heterogeneity of the serrated lesions renders their diagnostic and pathological interpretation difficult. Hence, novel genetic and epigenetic biomarkers are required for better classification and management of CRCs. To date, several molecular alterations have been associated with the serrated polyp-CRC sequence. In addition, the gut microbiota is emerging as a contributor to/modulator of the serrated pathway. This review summarizes the state of the art of the genetic, epigenetic and microbiota signatures associated with serrated CRCs, together with their clinical implications.

E-cadherin Beyond Structure: A Signaling Hub in Colon Homeostasis and Disease

E-cadherin is the core component of epithelial adherens junctions, essential for tissue development, differentiation, and maintenance. It is also fundamental for tissue barrier formation, a critical function of epithelial tissues. The colon or large intestine is lined by an epithelial monolayer that encompasses an E-cadherin-dependent barrier, critical for the homeostasis of the organ. Compromised barriers of the colonic epithelium lead to inflammation, fibrosis, and are commonly observed in colorectal cancer. In addition to its architectural role, E-cadherin is also considered a tumor suppressor in the colon, primarily a result of its opposing function to Wnt signaling, the predominant driver of colon tumorigenesis. Beyond these well-established traditional roles, several studies have portrayed an evolving role of E-cadherin as a signaling epicenter that regulates cell behavior in response to intra- and extra-cellular cues. Intriguingly, these recent findings also reveal tumor-promoting functions of E-cadherin in colon tumorigenesis and new interacting partners, opening future avenues of investigation. In this Review, we focus on these emerging aspects of E-cadherin signaling, and we discuss their implications in colon biology and disease.

Analysis of Fusobacterium nucleatum and Streptococcus gallolyticus in saliva of colorectal cancer patients

Aim: The aim of the study was to examine the prevalence and amount of Fusobacterium nucleatum (Fn), Porphyromonas gingivalis (Pg) and Streptococcus gallolyticus (Sg) in the saliva of colorectal cancer (CRC) patients and controls. Methods: PCR analyses performed in 71 CRC patients and 77 controls. Results: Saliva samples of patients had higher amounts of Fn (p = 0.001) and Sg (p < 0.001) compared with controls. Amount of Fn and Sg were lower in the microsatellite instability (+) group. Evaluation of salivary Sg amount by receiver operating characteristics analysis found to have diagnostic value for CRC (AUC: 0.84, 95% CI: 0.72-0.96). Conclusion: We found higher amounts of Fn and Sg in the saliva of CRC patients. Salivary Sg could helpful in distinction of CRC.

Relationship between intestinal microorganisms and T lymphocytes in colorectal cancer

Colorectal cancer (CRC) is a common type of malignant cancer worldwide. Recent studies have identified the gut microbiota as the origin of CRC, and T lymphocyte-mediated immune functions have been shown to play an important role in this disease. By summarizing previous literature, we found that Fusobacterium nucleatum may protect CRC from immune cell attack by inhibiting T cells and influencing the production of many chemokines and cytokines. Some bacterial metabolites and probiotics have been shown to participate in the regulation of CRC through T cell-mediated molecular pathways. To visualize the relevant data, an association network of intestinal microorganisms and T lymphocytes associated with CRC was constructed. This work may provide direction for - and insight into - further research on the relationship between intestinal microorganisms and T lymphocytes in CRC.

Probiotics and Colon Cancer

Literature has recently highlighted the enormous scientific interest on the relationship between the gut microbiota and colon cancer, and how the use of some selected probiotics can have a future impact on the adverse events which occur during this disease. Although there is no clear evidence to claim that probiotics are effective in people with cancer, recent reviews have found that probiotics can significantly reduce the incidence of diarrhea and the average frequency of daily bowel movements. However, most of this evidence needs to be more clinically convincing and further discussed. Undoubtedly, some probiotics, when properly dosed and administered, can have a strong rebalance effect on the gut microbiota and as a consequence a possible positive action on immune modulation of the gastrointestinal tract and on inflammation of the intestinal mucosa. Many recent findings indeed support the hypothesis that the daily use of some selected probiotics can be a feasible approach to effectively protect patients against the risk of some severe consequences due to radiation therapy or chemotherapy. This paper aims to review the most recent articles in order to consider a possible adjuvant approach for the use of certain well-balanced probiotics to help prevent colon cancer and the adverse effects caused by related therapies.

The Interplay between Immunity and Microbiota at Intestinal Immunological Niche: The Case of Cancer

The gut microbiota is central to the pathogenesis of several inflammatory and autoimmune diseases. While multiple mechanisms are involved, the immune system clearly plays a special role. Indeed, the breakdown of the physiological balance in gut microbial composition leads to dysbiosis, which is then able to enhance inflammation and to influence gene expression. At the same time, there is an intense cross-talk between the microbiota and the immunological niche in the intestinal mucosa. These interactions may pave the way to the development, growth and spreading of cancer, especially in the gastro-intestinal system. Here, we review the changes in microbiota composition, how they relate to the immunological imbalance, influencing the onset of different types of cancer and the impact of these mechanisms on the efficacy of traditional and upcoming cancer treatments.