Acetate Induces Growth Arrest in Colon Cancer Cells Through Modulation of Mitochondrial Function

Putrescine Supplementation Limits the Expansion of pks+ Escherichia coli and Tumor Development in the Colon

Escherichia coli that harbor the polyketide synthase (pks) genomic island produce colibactin and are associated with sporadic colorectal cancer development. Given the considerable prevalence of pks+ bacteria in healthy individuals, we sought to identify strategies to limit the growth and expansion of pks+ E. coli. We found that culture supernatants of the probiotic strain E. coli Nissle 1917 were able to inhibit the growth of the murine pathogenic strain pks+ E. coli NC101 (EcNC101). We performed a nontargeted analysis of the metabolome in supernatants from several E. coli strains and identified putrescine as a potential postbiotic capable of suppressing EcNC101 growth in vitro. The effect of putrescine supplementation was then evaluated in the azoxymethane/dextran sulfate sodium mouse model of colorectal cancer in mice colonized with EcNC101. Putrescine supplementation inhibited the growth of pks+ E. coli, reduced the number and size of colonic tumors, and downmodulated the release of inflammatory cytokines in the colonic lumen. Additionally, putrescine supplementation led to shifts in the composition and function of gut microbiota, characterized by an increase in the Firmicutes/Bacteroidetes ratio and enhanced acetate production. The effect of putrescine was further confirmed in vitro using a pks+ E. coli strain isolated from a patient with colorectal cancer. These results suggest that probiotic-derived metabolites can be used as an alternative to live bacteria in individuals at risk of developing colorectal cancer due to the presence of pks+ bacteria in their colon.

SIGNIFICANCE

Putrescine supplementation inhibits the growth of cancer-promoting bacteria in the gut, lowers inflammation, and reduces colon cancer development. The consumption of healthy foods rich in putrescine may be a potential prophylactic approach for individuals at risk of developing colorectal cancer due to the presence of pks+ bacteria in their colon.

The Crucial Roles of Diet, Microbiota, and Postbiotics in Colorectal Cancer

PURPOSE OF REVIEW

Colorectal cancer is the second deadliest cancer in the world, and its prevalence has been increasing alarmingly in recent years. After researchers discovered the existence of dysbiosis in colorectal cancer, they considered the use of probiotics in the treatment of colorectal cancer. However, for various reasons, including the low safety profile of probiotics in susceptible and immunocompromised patient5s, and the risk of developing antibiotic resistance, researchers have shifted their focus to non-living cells, their components, and metabolites. This review aims to comprehensively evaluate the literature on the effects of diet, microbiota, and postbiotics on colorectal cancer and the future of postbiotics.

RECENT FINDINGS

The link between diet, gut microbiota, and colorectal cancer has been established primarily as a relationship rather than a cause-effect relationship. The gut microbiota can convert gastrointestinal tract and dietary factors into either onco-metabolites or tumor suppressor metabolites. There is serious dysbiosis in the microbiota in colorectal cancer. Postbiotics appear to be promising agents in the prevention and treatment of colorectal cancer. It has been shown that various postbiotics can selectively induce apoptosis in CRC, inhibit cell proliferation, growth, invasion, and migration, modulate the immune system, suppress carcinogenic signaling pathways, maintain intestinal epithelial integrity, and have a synergistic effect with chemotherapy drugs. However, it is also reported that some postbiotics are ineffective and may be risky in terms of safety profile in some patients. Many issues need to be researched about postbiotics. Large-scale, randomized, double-blind clinical studies are needed.

NREP, transcriptionally upregulated by HIF-1α, aggravates breast cancer cell growth and metastasis by promoting glycolysis

Breast cancer (BC) poses a great threat to women's health. Neuronal regeneration related protein (NREP) is a multifunctional protein that is involved in embryonic development, regeneration, and human disease. However, the biological function of NREP in tumors is rarely reported and its role in BC remains unknown. Bioinformatics analysis showed that NREP is highly expressed and closely correlated with poor survival in BC patients. Under hypoxic conditions, NREP was upregulated in BC cells, and this promotion was reversed by hypoxia-inducible factor HIF-1α suppression. Luciferase reporter system and chromatin immunoprecipitation assays confirmed that HIF-1α directly binds to the promoter of NREP to increase the transcriptional activity of NREP. NREP suppression inhibited cell proliferation, arrested the cell cycle at the G1/S phase, and promoted apoptosis and caspase-3 activity in BC cells. Suppression of NREP decreased the tube formation ability of HUVECs. In addition, NREP downregulation showed an inhibition effect on cell migration, invasion, and EMT of BC cells. In NREP overexpressed cells, all these changes were reversed. In vivo, animal experiments also confirmed that NREP promotes BC tumor growth and metastasis. In addition, NREP promoted cellular glycolysis and enhanced the levels of glucose consumption, ATP, lactate production, and glucose transporters expression in NREP-overexpressed BC cells. In summary, our results demonstrated that NREP could be transcriptional activated by HIF-1α, which may aggravate BC tumor growth and metastasis by promoting cellular glycolysis. This result suggested that NREP may play an essential part in BC progression.

The emerging role of hypoxia and environmental factors in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and debilitating disorder characterized by inflammation of the gastrointestinal tract. Despite extensive research, the exact cause of IBD remains unknown, hampering the development of effective therapies. However, emerging evidence suggests that hypoxia, a condition resulting from inadequate oxygen supply, plays a crucial role in intestinal inflammation and tissue damage in IBD. Hypoxia-inducible factors (HIFs), transcription factors that regulate the cellular response to low oxygen levels, have gained attention for their involvement in modulating inflammatory processes and maintaining tissue homeostasis. The two most studied HIFs, HIF-1α and HIF-2α, have been implicated in the development and progression of IBD. Toxicological factors encompass a wide range of environmental and endogenous agents, including dietary components, microbial metabolites, and pollutants. These factors can profoundly influence the hypoxic microenvironment within the gut, thereby exacerbating the course of IBD and fostering the progression of colitis-associated colorectal cancer. This review explores the regulation of hypoxia signaling at the molecular, microenvironmental, and environmental levels, investigating the intricate interplay between toxicological factors and hypoxic signaling in the context of IBD, focusing on its most concerning outcomes: intestinal fibrosis and colorectal cancer.

BRD9 status is a major contributor for cysteine metabolic remodeling through MST and EAAT3 modulation in malignant melanoma

Cutaneous melanoma (CM) is the most aggressive skin cancer, showing globally increasing incidence. Hereditary CM accounts for a significant percentage (5-15 %) of all CM cases. However, most familial cases remain without a known genetic cause. Even though, BRD9 has been associated to CM as a susceptibility gene. The molecular events following BRD9 mutagenesis are still not completely understood. In this study, we disclosed BRD9 as a key regulator in cysteine metabolism and associated altered BRD9 to increased cell proliferation, migration and invasiveness, as well as to altered melanin levels, inducing higher susceptibility to melanomagenesis. It is evident that BRD9 WT and mutated BRD9 (c.183G>C) have a different impact on cysteine metabolism, respectively by inhibiting and activating MPST expression in the metastatic A375 cell line. The effect of the mutated BRD9 variant was more evident in A375 cells than in the less invasive WM115 line. Our data point out novel molecular and metabolic mechanisms dependent on BRD9 status that potentially account for the increased risk of developing CM and enhancing CM aggressiveness. Moreover, our findings emphasize the role of cysteine metabolism remodeling in melanoma progression and open new queues to follow to explore the role of BRD9 as a melanoma susceptibility or cancer-related gene.

Probiotic-Derived Bioactive Compounds in Colorectal Cancer Treatment

Colorectal cancer (CRC) is a multifactorial disease with increased morbidity and mortality rates globally. Despite advanced chemotherapeutic approaches for the treatment of CRC, low survival rates due to the regular occurrence of drug resistance and deleterious side effects render the need for alternative anticancer agents imperative. Accumulating evidence supports that gut microbiota imbalance precedes the establishment of carcinogenesis, subsequently contributing to cancer progression and response to anticancer therapy. Manipulation of the gut microbiota composition via the administration of probiotic-derived bioactive compounds has gradually attained the interest of scientific communities as a novel therapeutic strategy for CRC. These compounds encompass miscellaneous metabolic secreted products of probiotics, including bacteriocins, short-chain fatty acids (SCFAs), lactate, exopolysaccharides (EPSs), biosurfactants, and bacterial peptides, with profound anti-inflammatory and antiproliferative properties. This review provides a classification of postbiotic types and a comprehensive summary of the current state of research on their biological role against CRC. It also describes how their intricate interaction with the gut microbiota regulates the proper function of the intestinal barrier, thus eliminating gut dysbiosis and CRC development. Finally, it discusses the future perspectives in precision-medicine approaches as well as the challenges of their synthesis and optimization of administration in clinical studies.

Integrative bioinformatics analysis of ACS enzymes as candidate prognostic and diagnostic biomarkers in colon adenocarcinoma

Background and purpose

Acyl-CoA synthetase (ACS) enzymes play an important role in the activation of fatty acids. While many studies have found correlations between the expression levels of ACS enzymes with the progression, growth, and survival of cancer cells, their role and expression patterns in colon adenocarcinoma are still greatly unknown and demand further investigation.

Experimental approach

The expression data of colon adenocarcinoma samples were downloaded from the Cancer Genome Atlas (TCGA) database. Normalization and differential expression analysis were performed to identify differentially expressed genes (DEGs). Gene set enrichment analysis was applied to identify top enriched genes from ACS enzymes in cancer samples. Gene ontology and protein-protein interaction analyses were performed for the prediction of molecular functions and interactions. Survival analysis and receiver operating characteristic test (ROC) were performed to find potential prognostic and diagnostic biomarkers.

Findings/Results

ACSL6 and ACSM5 genes demonstrated more significant differential expression and LogFC value compared to other ACS enzymes and also achieved the highest enrichment scores. Gene ontology analysis predicted the involvement of top DEGs in fatty acids metabolism, while protein-protein interaction network analysis presented strong interactions between ACSLs, ACSSs, ACSMs, and ACSBG enzymes with each other. Survival analysis suggested ACSM3 and ACSM5 as potential prognostic biomarkers, while the ROC test predicted stronger diagnostic potential for ACSM5, ACSS2, and ACSF2 genes.

Conclusion and implications

Our findings revealed the expression patterns, prognostic, and diagnostic biomarker potential of ACS enzymes in colon adenocarcinoma. ACSM3, ACSM5, ACSS2, and ACSF2 genes are suggested as possible prognostic and diagnostic biomarkers.

Acss2/HIF-2 signaling facilitates colon cancer growth and metastasis

The microenvironment of solid tumors is characterized by oxygen and glucose deprivation. Acss2/HIF-2 signaling coordinates essential genetic regulators including acetate-dependent acetyl CoA synthetase 2 (Acss2), Creb binding protein (Cbp), Sirtuin 1 (Sirt1), and Hypoxia Inducible Factor 2α (HIF-2α). We previously shown in mice that exogenous acetate augments growth and metastasis of flank tumors derived from fibrosarcoma-derived HT1080 cells in an Acss2/HIF-2 dependent manner. Colonic epithelial cells are exposed to the highest acetate levels in the body. We reasoned that colon cancer cells, like fibrosarcoma cells, may respond to acetate in a pro-growth manner. In this study, we examine the role of Acss2/HIF-2 signaling in colon cancer. We find that Acss2/HIF-2 signaling is activated by oxygen or glucose deprivation in two human colon cancer-derived cell lines, HCT116 and HT29, and is crucial for colony formation, migration, and invasion in cell culture studies. Flank tumors derived from HCT116 and HT29 cells exhibit augmented growth in mice when supplemented with exogenous acetate in an Acss2/HIF-2 dependent manner. Finally, Acss2 in human colon cancer samples is most frequently localized in the nucleus, consistent with it having a signaling role. Targeted inhibition of Acss2/HIF-2 signaling may have synergistic effects for some colon cancer patients.

Short-chain fatty acids reprogram metabolic profiles with the induction of reactive oxygen species production in human colorectal adenocarcinoma cells

Short-chain fatty acids (SCFAs) exhibit anticancer activity in cellular and animal models of colon cancer. Acetate, propionate, and butyrate are the three major SCFAs produced from dietary fiber by gut microbiota fermentation and have beneficial effects on human health. Most previous studies on the antitumor mechanisms of SCFAs have focused on specific metabolites or genes involved in antitumor pathways, such as reactive oxygen species (ROS) biosynthesis. In this study, we performed a systematic and unbiased analysis of the effects of acetate, propionate, and butyrate on ROS levels and metabolic and transcriptomic signatures at physiological concentrations in human colorectal adenocarcinoma cells. We observed significantly elevated levels of ROS in the treated cells. Furthermore, significantly regulated signatures were involved in overlapping pathways at metabolic and transcriptomic levels, including ROS response and metabolism, fatty acid transport and metabolism, glucose response and metabolism, mitochondrial transport and respiratory chain complex, one-carbon metabolism, amino acid transport and metabolism, and glutaminolysis, which are directly or indirectly linked to ROS production. Additionally, metabolic and transcriptomic regulation occurred in a SCFAs types-dependent manner, with an increasing degree from acetate to propionate and then to butyrate. This study provides a comprehensive analysis of how SCFAs induce ROS production and modulate metabolic and transcriptomic levels in colon cancer cells, which is vital for understanding the mechanisms of the effects of SCFAs on antitumor activity in colon cancer.

Gut microbiota-derived short-chain fatty acids regulate gastrointestinal tumor immunity: a novel therapeutic strategy?

Tumor immune microenvironment (TIME), a tumor-derived immune component, is proven to be closely related to the development, metastasis, and recurrence of tumors. Gut microbiota and its fermented-metabolites short-chain fatty acids (SCFAs) play a critical role in maintaining the immune homeostasis of gastrointestinal tumors. Consisting mainly of acetate, propionate, and butyrate, SCFAs can interact with G protein-coupled receptors 43 of T helper 1 cell or restrain histone deacetylases (HDACs) of cytotoxic T lymphocytes to exert immunotherapy effects. Studies have shed light on SCFAs can mediate the differentiation and function of regulatory T cells, as well as cytokine production in TIME. Additionally, SCFAs can alter epigenetic modification of CD8⁺ T cells by inhibiting HDACs to participate in the immune response process. In gastrointestinal tumors, the abundance of SCFAs and their producing bacteria is significantly reduced. Direct supplementation of dietary fiber and probiotics, or fecal microbiota transplantation to change the structure of gut microbiota can both increase the level of SCFAs and inhibit tumor development. The mechanism by which SCFAs modulate the progression of gastrointestinal tumors has been elucidated in this review, aiming to provide prospects for the development of novel immunotherapeutic strategies.

Establishment of a platform for measuring mitochondrial oxygen consumption rate for cardiac mitochondrial toxicity

The heart has an abundance of mitochondria since cardiac muscles require copious amounts of energy for providing continuous blood through the circulatory system, thereby implying that myocardial function is largely reliant on mitochondrial energy. Thus, cardiomyocytes are susceptible to mitochondrial dysfunction and are likely targets of mitochondrial toxic drugs. Various methods have been developed to evaluate mitochondrial toxicity by evaluating toxicological mechanisms, but an optimized and standardized assay for cardiomyocytes remains unmet. We have therefore attempted to standardize the evaluation system for determining cardiac mitochondrial toxicity, using AC16 human and H9C2 rat cardiomyocytes. Three clinically administered drugs (acetaminophen, amiodarone, and valproic acid) and two anticancer drugs (doxorubicin and tamoxifen) which are reported to have mitochondrial effects, were applied in this study. The oxygen consumption rate (OCR), which directly reflects mitochondrial function, and changes in mRNA levels of mitochondrial respiratory complex I to complex V, were analyzed. Our results reveal that exposure to all five drugs results in a concentration-dependent decrease in the basal and maximal levels of OCR in AC16 cells and H9C2 cells. In particular, marked reduction in the OCR was observed after treatment with doxorubicin. The reduction in OCR after exposure to mitochondrial toxic drugs was found to be associated with reduced mRNA expression in the mitochondrial respiratory complexes, suggesting that the cardiac mitochondrial toxicity of drugs is majorly due to dysfunction of mitochondrial respiration. Based on the results of this study, we established and standardized a protocol to measure OCR in cardiomyocytes. We expect that this standardized evaluation system for mitochondrial toxicity can be applied as basic data for establishing a screening platform to evaluate cardiac mitochondrial toxicity of drugs, during the developmental stage of new drug discovery.

Mitochondrial Function and Microbial Metabolites as Central Regulators of Intestinal Immune Responses and Cancer

Energy and anabolic metabolism are essential for normal cellular homeostasis but also play an important role in regulating immune responses and cancer development as active immune and cancer cells show an altered metabolic profile. Mitochondria take a prominent position in these metabolic reactions. First, most key energetic reactions take place within or in conjunction with mitochondria. Second, mitochondria react to internal cues from within the cell but also to external cues originating from the microbiota, a vast diversity of associated microorganisms. The impact of the microbiota on host physiology has been largely investigated in the last decade revealing that the microbiota contributes to the extraction of calories from the diet, energy metabolism, maturation of the immune system and cellular differentiation. Thus, changes in the microbiota termed dysbiosis have been associated with disease development including metabolic diseases, inflammation and cancer. Targeting the microbiota to modulate interactions with the mitochondria and cellular metabolism to delay or inhibit disease development and pathogenesis appears an attractive therapeutic approach. Here, we summarize recent advances in developing the therapeutic potential of microbiota-mitochondria interactions for inflammation and cancer.

The short-chain fatty acid acetate modulates epithelial-to-mesenchymal transition

Normal tissue and organ morphogenesis requires epithelial cell plasticity and conversion to a mesenchymal phenotype through a tightly regulated process: epithelial-to-mesenchymal transition (EMT). Alterations of EMT go far beyond cell-lineage segregation and contribute to pathologic conditions such as cancer. EMT is subject to intersecting control pathways; however, EMT's metabolic mechanism remains poorly understood. Here, we demonstrate that transforming growth factor β (TGF-β)-induced EMT is accompanied by decreased fatty acid oxidation (FAO) and reduced acetyl-coenzyme A (acetyl-CoA) levels. Acetyl-CoA is a central metabolite and the sole donor of acetyl groups to acetylate key proteins. Further, the short-chain fatty acid acetate increases acetyl-CoA levels-robustly inhibiting EMT and cancer cell migration. Acetate can restore EMT-associated α-tubulin acetylation levels, increasing microtubule stability. Transcriptome profiling and flow cytometric analysis show that acetate inhibits the global gene expression program associated with EMT and the EMT-associated G1 cell cycle arrest. Taken together, these results demonstrate that acetate is a potent metabolic regulator of EMT and that therapeutic manipulation of acetate metabolism could provide the basis for treating a wide range of EMT-linked pathological conditions, including cancer.

Mucus sialylation determines intestinal host-commensal homeostasis

Intestinal mucus forms the first line of defense against bacterial invasion while providing nutrition to support microbial symbiosis. How the host controls mucus barrier integrity and commensalism is unclear. We show that terminal sialylation of glycans on intestinal mucus by ST6GALNAC1 (ST6), the dominant sialyltransferase specifically expressed in goblet cells and induced by microbial pathogen-associated molecular patterns, is essential for mucus integrity and protecting against excessive bacterial proteolytic degradation. Glycoproteomic profiling and biochemical analysis of ST6 mutations identified in patients show that decreased sialylation causes defective mucus proteins and congenital inflammatory bowel disease (IBD). Mice harboring a patient ST6 mutation have compromised mucus barriers, dysbiosis, and susceptibility to intestinal inflammation. Based on our understanding of the ST6 regulatory network, we show that treatment with sialylated mucin or a Foxo3 inhibitor can ameliorate IBD.

N-acetyl l-aspartate and Triacetin modulate tumor suppressor MicroRNA and class I and II HDAC gene expression induce apoptosis in Glioblastoma cancer cells in vitro

Glioblastoma multiforme (GBM), grade IV glioma and is aggressive, malignant primary brain cancer. Altered expression and activity of epigenetic proteins such as histone deacetylases (HDACs) are involved in GBM metastasis. Also, acetates are important to brain metabolites that regulate cell proliferation and apoptosis. Here, we have examined the effect of the acetates on the cell-cycle. U87MG cancer cells treated with N-acetyl l-aspartate (NAA) and sodium acetate have exhibited G1 phase cell-cycle arrest whereas U87MG cells treated with Triacetin (TA), and potassium acetate has induced G2/M cell cycle arrest. We have observed inhibition of histone deacetylase (HDAC) mRNA levels in acetate treated U87MG cells. Interestingly, acetates-treated U87MG cells have shown a significant reduction in the mRNA level of class II HDACs than class I HDACs. Acetate treated cells have exhibited an enhanced expression of various microRNAs such as miR-15b, miR-92, miR-101, miR-155, miR-199, miR-200, miR-223, miR-16, and miR-17 that are involved in the inhibition of cancer cell proliferation, invasion, migration, and angiogenesis. Further, these acetate molecules regulate genes involved in mammalian target of rapamycin complex 2 (mTORC2) such as mammalian stress-activated protein kinase-interacting protein (mSIN1), protein observed with Rictor 2 (Protor 2), and protein kinase C α (PKCα). The present study reveals the possible involvement of the mTORC2 complex during acetate-mediated HDAC inhibition, as well as microRNA modulation. Furthermore, molecular modeling studies were employed to understand the binding mode of these acetate molecules to mTOR, Rapamycin-insensitive companion of mammalian target of rapamycin (Rictor), and HDAC-8 proteins. Thus in this study, we have identified the pivotal role of acetates in the modulation of mTOR complex, epigenetic genes and provide structural as well as functional insights that will help in future drug discovery against GBM cancer therapy.