Lithocholic acid upregulates uPAR and cell invasiveness via MAPK and AP-1 signaling in colon cancer cells

The bacterial metabolite, lithocholic acid, has antineoplastic effects in pancreatic adenocarcinoma

Lithocholic acid (LCA) is a secondary bile acid. LCA enters the circulation after bacterial synthesis in the gastrointestinal tract, reaches distantly located cancer cells, and influences their behavior. LCA was considered carcinogenic, but recent studies demonstrated that LCA has antitumor effects. We assessed the possible role of LCA in pancreatic adenocarcinoma. At the serum reference concentration, LCA induced a multi-pronged antineoplastic program in pancreatic adenocarcinoma cells. LCA inhibited cancer cell proliferation and induced mesenchymal-to-epithelial (MET) transition that reduced cell invasion capacity. LCA induced oxidative/nitrosative stress by decreasing the expression of nuclear factor, erythroid 2-like 2 (NRF2) and inducing inducible nitric oxide synthase (iNOS). The oxidative/nitrosative stress increased protein nitration and lipid peroxidation. Suppression of oxidative stress by glutathione (GSH) or pegylated catalase (pegCAT) blunted LCA-induced MET. Antioxidant genes were overexpressed in pancreatic adenocarcinoma and decreased antioxidant levels correlated with better survival of pancreatic adenocarcinoma patients. Furthermore, LCA treatment decreased the proportions of cancer stem cells. Finally, LCA induced total and ATP-linked mitochondrial oxidation and fatty acid oxidation. LCA exerted effects through the farnesoid X receptor (FXR), vitamin D receptor (VDR), and constitutive androstane receptor (CAR). LCA did not interfere with cytostatic agents used in the chemotherapy of pancreatic adenocarcinoma. Taken together, LCA is a non-toxic compound and has antineoplastic effects in pancreatic adenocarcinoma.

Dissecting the role of the gut microbiome and fecal microbiota transplantation in radio- and immunotherapy treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers and poses a major burden on the human health worldwide. At the moment, treatment of CRC consists of surgery in combination with (neo)adjuvant chemotherapy and/or radiotherapy. More recently, immune checkpoint blockers (ICBs) have also been approved for CRC treatment. In addition, recent studies have shown that radiotherapy and ICBs act synergistically, with radiotherapy stimulating the immune system that is activated by ICBs. However, both treatments are also associated with severe toxicity and efficacy issues, which can lead to temporary or permanent discontinuation of these treatment programs. There's growing evidence pointing to the gut microbiome playing a role in these issues. Some microorganisms seem to contribute to radiotherapy-associated toxicity and hinder ICB efficacy, while others seem to reduce radiotherapy-associated toxicity or enhance ICB efficacy. Consequently, fecal microbiota transplantation (FMT) has been applied to reduce radio- and immunotherapy-related toxicity and enhance their efficacies. Here, we have reviewed the currently available preclinical and clinical data in CRC treatment, with a focus on how the gut microbiome influences radio- and immunotherapy toxicity and efficacy and if these treatments could benefit from FMT.

Beneficial insights into postbiotics against colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and life-threatening cancer types with limited therapeutic options worldwide. Gut microbiota has been recognized as the pivotal determinant in maintaining gastrointestinal (GI) tract homeostasis, while dysbiosis of gut microbiota contributes to CRC development. Recently, the beneficial role of postbiotics, a new concept in describing microorganism derived substances, in CRC has been uncovered by various studies. However, a comprehensive characterization of the molecular identity, mechanism of action, or routes of administration of postbiotics, particularly their role in CRC, is still lacking. In this review, we outline the current state of research toward the beneficial effects of gut microbiota derived postbiotics against CRC, which will represent the key elements of future precision-medicine approaches in the development of novel therapeutic strategies targeting gut microbiota to improve treatment outcomes in CRC.

Gut Microbiota in Colorectal Cancer: Biological Role and Therapeutic Opportunities

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths worldwide. While CRC is thought to be an interplay between genetic and environmental factors, several lines of evidence suggest the involvement of gut microbiota in promoting inflammation and tumor progression. Gut microbiota refer to the ~40 trillion microorganisms that inhabit the human gut. Advances in next-generation sequencing technologies and metagenomics have provided new insights into the gut microbial ecology and have helped in linking gut microbiota to CRC. Many studies carried out in humans and animal models have emphasized the role of certain gut bacteria, such as Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli, in the onset and progression of CRC. Metagenomic studies have opened up new avenues for the application of gut microbiota in the diagnosis, prevention, and treatment of CRC. This review article summarizes the role of gut microbiota in CRC development and its use as a biomarker to predict the disease and its potential therapeutic applications.

(-)-Epigallocatechin-3-Gallate Prevents IL-1β-Induced uPAR Expression and Invasiveness via the Suppression of NF-κB and AP-1 in Human Bladder Cancer Cells

(-)-Epigallocatechin-3-O-gallate (EGCG), a primary green tea polyphenol, has powerful iron scavengers, belongs to the family of flavonoids with antioxidant properties, and can be used to prevent cancer. Urokinase-type plasminogen activator receptors (uPARs) are glycosylphosphatidylinositol (GPI)-anchored cell membrane receptors that have crucial roles in cell invasion and metastasis of several cancers including bladder cancer. The mechanism of action of EGCG on uPAR expression has not been reported clearly yet. In this study, we investigated the effect of EGCG on interleukin (IL)-1β-induced cell invasion and uPAR activity in T24 human bladder cancer cells. Interestingly, nuclear factor (NF)-κB and activator protein (AP)-1 transcription factors were critically required for IL-1β-induced high uPAR expression, and EGCG suppressed the transcriptional activity of both the ERK1/2 and JNK signaling pathways with the AP-1 subunit c-Jun. EGCG blocked the IL-1β-stimulated reactive oxygen species (ROS) production, in turn suppressing NF-κB signaling and anti-invasion effects by inhibiting uPAR expression. These results suggest that EGCG may exert at least part of its anticancer effect by controlling uPAR expression through the suppression of ERK1/2, JNK, AP-1, and NF-κB.

Cholecystectomy promotes the development of colorectal cancer by the alternation of bile acid metabolism and the gut microbiota

The incidence and mortality of colorectal cancer (CRC) have been markedly increasing worldwide, causing a tremendous burden to the healthcare system. Therefore, it is crucial to investigate the risk factors and pathogenesis of CRC. Cholecystectomy is a gold standard procedure for treating symptomatic cholelithiasis and gallstone diseases. The rhythm of bile acids entering the intestine is altered after cholecystectomy, which leads to metabolic disorders. Nonetheless, emerging evidence suggests that cholecystectomy might be associated with the development of CRC. It has been reported that alterations in bile acid metabolism and gut microbiota are the two main reasons. However, the potential mechanisms still need to be elucidated. In this review, we mainly discussed how bile acid metabolism, gut microbiota, and the interaction between the two factors influence the development of CRC. Subsequently, we summarized the underlying mechanisms of the alterations in bile acid metabolism after cholecystectomy including cellular level, molecular level, and signaling pathways. The potential mechanisms of the alterations on gut microbiota contain an imbalance of bile acid metabolism, cellular immune abnormality, acid-base imbalance, activation of cancer-related pathways, and induction of toxin, inflammation, and oxidative stress.

Lithocholic acid inhibits gallbladder cancer proliferation through interfering glutaminase-mediated glutamine metabolism

Lithocholic acid (LCA), one of the most common metabolic products of bile acids (BAs), is originally synthesized in the liver, stored in the gallbladder, and released to the intestine, where it assists absorption of lipid-soluble nutrients. LCA has recently emerged as a powerful reagent to inhibit tumorigenesis; however, the anti-tumor activity and molecular mechanisms of LCA in gallbladder cancer (GBC) remain poorly acknowledged. Here, we analyzed serum levels of LCA in human GBC and found that LCA was significantly downregulated in these patients, and reduced LCA levels were associated with poor clinical outcomes. Treatment of xenografts with LCA impeded tumor growth. Furthermore, LCA treatment in GBC cell lines decreased glutaminase (GLS) expression, glutamine (Gln) consumption, and GSH/GSSG and NADPH/NADP⁺ ratios, leading to cellular ferroptosis. In contrast, GLS overexpression in tumor cells fully restored GBC proliferation and decreased ROS imbalance, thus suppressing ferroptosis. Our findings reveal that LCA functions as a tumor-suppressive factor in GBC by downregulating GLS-mediated glutamine metabolism and subsequently inducing ferroptosis. This study may offer a new therapeutic strategy tailored to improve the treatment of GBC.

Interaction between microbiota and immunity and its implication in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the world. Besides genetic causes, colonic inflammation is one of the major risk factors for CRC development, which is synergistically regulated by multiple components, including innate and adaptive immune cells, cytokine signaling, and microbiota. The complex interaction between CRC and the gut microbiome has emerged as an important area of current CRC research. Metagenomic profiling has identified a number of prominent CRC-associated bacteria that are enriched in CRC patients, linking the microbiota composition to colitis and cancer development. Some microbiota species have been reported to promote colitis and CRC development in preclinical models, while a few others are identified as immune modulators to induce potent protective immunity against colitis and CRC. Mechanistically, microbiota regulates the activation of different immune cell populations, inflammation, and CRC via crosstalk between innate and adaptive immune signaling pathways, including nuclear factor kappa B (NF-κB), type I interferon, and inflammasome. In this review, we provide an overview of the potential interactions between gut microbiota and host immunity and how their crosstalk could synergistically regulate inflammation and CRC, thus highlighting the potential roles and mechanisms of gut microbiota in the development of microbiota-based therapies to prevent or alleviate colitis and CRC.

Role of bile acids and their receptors in gastrointestinal and hepatic pathophysiology

Bile acids (BAs) can regulate their own metabolism and transport as well as other key aspects of metabolic homeostasis via dedicated (nuclear and G protein-coupled) receptors. Disrupted BA transport and homeostasis results in the development of cholestatic disorders and contributes to a wide range of liver diseases, including nonalcoholic fatty liver disease and hepatocellular and cholangiocellular carcinoma. Furthermore, impaired BA homeostasis can also affect the intestine, contributing to the pathogenesis of irritable bowel syndrome, inflammatory bowel disease, and colorectal and oesophageal cancer. Here, we provide a summary of the role of BAs and their disrupted homeostasis in the development of gastrointestinal and hepatic disorders and present novel insights on how targeting BA pathways might contribute to novel treatment strategies for these disorders.

Secondary Bile Acids and Tumorigenesis in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common and deadly cancers in the world and is a typical inflammatory tumor. In recent years, the incidence of CRC has been increasing year by year. There is evidence that the intake of high-fat diet and overweight are associated with the incidence of CRC, among which bile acids play a key role in the pathogenesis of the disease. Studies on the relationship between bile acid metabolism and the occurrence of CRC have gradually become a hot topic, improving the understanding of metabolic factors in the etiology of colorectal cancer. Meanwhile, intestinal flora also plays an important role in the occurrence and development of CRC In this review, the classification of bile acids and their role in promoting the occurrence of CRC are discussed, and we highlights how a high-fat diet affects bile acid metabolism and destroys the integrity of the intestinal barrier and the effects of gut bacteria.

Targeting the gut and tumor microbiota in cancer

Microorganisms within the gut and other niches may contribute to carcinogenesis, as well as shaping cancer immunosurveillance and response to immunotherapy. Our understanding of the complex relationship between different host-intrinsic microorganisms, as well as the multifaceted mechanisms by which they influence health and disease, has grown tremendously-hastening development of novel therapeutic strategies that target the microbiota to improve treatment outcomes in cancer. Accordingly, the evaluation of a patient's microbial composition and function and its subsequent targeted modulation represent key elements of future multidisciplinary and precision-medicine approaches. In this Review, we outline the current state of research toward harnessing the microbiome to better prevent and treat cancer.

The role of bile acids in carcinogenesis

Bile acids are soluble derivatives of cholesterol produced in the liver that subsequently undergo bacterial transformation yielding a diverse array of metabolites. The bulk of bile acid synthesis takes place in the liver yielding primary bile acids; however, other tissues have also the capacity to generate bile acids (e.g. ovaries). Hepatic bile acids are then transported to bile and are subsequently released into the intestines. In the large intestine, a fraction of primary bile acids is converted to secondary bile acids by gut bacteria. The majority of the intestinal bile acids undergo reuptake and return to the liver. A small fraction of secondary and primary bile acids remains in the circulation and exert receptor-mediated and pure chemical effects (e.g. acidic bile in oesophageal cancer) on cancer cells. In this review, we assess how changes to bile acid biosynthesis, bile acid flux and local bile acid concentration modulate the behavior of different cancers. Here, we present in-depth the involvement of bile acids in oesophageal, gastric, hepatocellular, pancreatic, colorectal, breast, prostate, ovarian cancer. Previous studies often used bile acids in supraphysiological concentration, sometimes in concentrations 1000 times higher than the highest reported tissue or serum concentrations likely eliciting unspecific effects, a practice that we advocate against in this review. Furthermore, we show that, although bile acids were classically considered as pro-carcinogenic agents (e.g. oesophageal cancer), the dogma that switch, as lower concentrations of bile acids that correspond to their serum or tissue reference concentration possess anticancer activity in a subset of cancers. Differences in the response of cancers to bile acids lie in the differential expression of bile acid receptors between cancers (e.g. FXR vs. TGR5). UDCA, a bile acid that is sold as a generic medication against cholestasis or biliary surge, and its conjugates were identified with almost purely anticancer features suggesting a possibility for drug repurposing. Taken together, bile acids were considered as tumor inducers or tumor promoter molecules; nevertheless, in certain cancers, like breast cancer, bile acids in their reference concentrations may act as tumor suppressors suggesting a Janus-faced nature of bile acids in carcinogenesis.

Piperine Attenuates Lithocholic Acid-Stimulated Interleukin-8 by Suppressing Src/EGFR and Reactive Oxygen Species in Human Colorectal Cancer Cells

Piperine, a natural alkaloidal pungent product present in pepper plants, possesses the properties of anti-inflammatory and anti-metastasis. Lithocholic acid is a monohydroxy-5beta-cholanic acid with an alpha-hydroxy substituent at position 3; it is a secondary bile acid that plays a pivotal role in fat absorption, and has been discovered to mediate colorectal cancer (CRC) cell invasion and migration. However, the effect of piperine on angiogenesis has been poorly investigated. In the current study, we examined the role of piperine on LCA-stimulated angiogenesis by measuring interleukin-8 (IL-8) expression; moreover, we revealed the potential molecular mechanisms in CRC cells. Here, we showed that piperine inhibited LCA-stimulated endothelial EA.hy926 cell angiogenesis in a conditioned medium obtained from colorectal HCT-116 cells. Experiments with an IL-8 neutralizer showed that IL-8 present in the conditioned medium was the major angiogenic factor. Piperine inhibited LCA-stimulated ERK1/2 and AKT via the Src/EGFR-driven ROS signaling pathway in the colorectal cell line (HCT-116). Through mutagenesis and inhibitory studies, we revealed that ERK1/2 acted as an upstream signaling molecule in AP-1 activation, and AKT acted as an upstream signaling molecule in NF-κB activation, which in turn attenuated IL-8 expression. Taken together, we demonstrated that piperine blocked LCA-stimulated IL-8 expression by suppressing Src and EGFR in human CRC HCT-116 cells, thus remarkably attenuating endothelial EA.hy926 cell tube formation.

Research Progress of Bile Acids in Cancer

Bile acids (BAs) were originally known as detergents to facilitate the digestion and absorption of lipids. And our current knowledge of BAs has been extended to potential carcinogenic or cancer suppressor factors due to constant research. In fact, BAs were regarded as a tumor promoters as early as the 1940s. Differential bile acid signals emitted by various bile acid profiles can produce distinct pathophysiological traits, thereby participating in the occurrence and development of tumors. Nevertheless, in recent years, more and more studies have noticed the value of BAs as therapeutic targets. And several studies have applied BAs as a therapeutic agent for various diseases including cancer. Based on the above evidence, we acknowledge that the role of BAs in cancer has yet to be exploited, although considerable efforts have been made to probe the functions of BAs. In this review, we describe the characteristics of BAs as a double-edged sword in cancer, hoping to provide references for future cancer treatments.

Bile acids as regulatory molecules and potential targets in metabolic diseases

Bile acids are important hydroxylated steroids that are synthesized in the liver from cholesterol for intestinal absorption of lipids and other fatty-nutrient. They also display remarkable and immense functions such as regulating immune responses, managing the apoptosis of cells, participating in glucose metabolism, and so on. Some bile acids were used for the treatment or prevention of diseases such as gallstones, primary biliary cirrhosis, and colorectal cancer. Meanwhile, the accumulation of toxic bile acids leads to apoptosis, necrosis, and inflammation. Alteration of bile acids metabolism, as well as the gut microbiota that interacted with bile acids, contributes to the pathogenesis of metabolic diseases. Therefore, the purpose of this review is to summarize the current functions and pre-clinical or clinical applications of bile acids, and to further discuss the alteration of bile acids in metabolic disorders as well as the manipulation of bile acids metabolism as potential therapeutic targets.

Gut Microbiota Profiles in Early- and Late-Onset Colorectal Cancer: A Potential Diagnostic Biomarker in the Future

BACKGROUND

Researchers believe the role of gut microbiota dysbiosis in the raised incidence of early-onset colorectal cancer (EOCRC). The development of EOCRC may be associated with microbiota dysbiosis either dependently or independently (combined with other risk factors).

SUMMARY

Recently, the rising of incidence and mortality of EOCRC have been noted. Some researchers are looking for risk factors influencing this fact. They hypothesize that it may be because of microbiota dysbiosis. Microbiota dysbiosis has been known to promote cancer development through immunity dysregulation and chronic inflammation. Microbiomes profile in late-onset colorectal cancer (LOCRC) among older patients has been documented, but there is still lack of data about microbial profiles among younger colorectal cancer (CRC) patients. This review tries to explain microbial profiles differences between EOCRC and LOCRC as a potential diagnostic biomarker in the future, and whether microbiota can have a role in EOCRC genesis. Key Messages: Microbiota does vary with age, and EOCRC may be associated with colonization of some specific bacteria. Further studies about gut microbiota profiles in EOCRC and LOCRC may provide a new insight on diagnostic biomarker of CRC.

Lithocholic Acid Induces miR21, Promoting PTEN Inhibition via STAT3 and ERK-1/2 Signaling in Colorectal Cancer Cells

Micro-RNA-21 (miR-21) is a vital regulator of colorectal cancer (CRC) progression and has emerged as a potential therapeutic target in CRC treatment. Our study using real-time PCR assay found that a secondary bile acid, lithocholic acid (LCA), stimulated the expression of miR21 in the CRC cell lines. Promoter activity assay showed that LCA strongly stimulated miR21 promoter activity in HCT116 cells in a time- and dose-dependent manner. Studies of chemical inhibitors and miR21 promoter mutants indicated that Erk1/2 signaling, AP-1 transcription factor, and STAT3 are major signals involved in the mechanism of LCA-induced miR21 in HCT116 cells. The elevation of miR21 expression was upstream of the phosphatase and tensin homolog (PTEN) inhibition, and CRC cell proliferation enhancement that was shown to be possibly mediated by PI3K/AKT signaling activation. This study is the first to report that LCA affects miR21 expression in CRC cells, providing us with a better understanding of the cancer-promoting mechanism of bile acids that have been described as the very first promoters of CRC progression.

Sialyltransferase Inhibitors Suppress Breast Cancer Metastasis

We report the synthesis and evaluation of a series of cell-permeable and N- versus O-selective sialyltransferase inhibitors. Inhibitor design entailed the functionalization of lithocholic acid at C(3) and at the cyclopentane ring side chain. Among the series, FCW34 and FCW66 were shown to inhibit MDA-MB-231 cell migration as effectively as ST3GALIII-gene knockdown did. FCW34 was shown to inhibit tumor growth, reduce angiogenesis, and delay cancer cell metastasis in animal models. Furthermore, FCW34 inhibited vessel development and suppressed angiogenic activity in transgenic zebrafish models. Our results provide clear evidence that FCW34-induced sialyltransferase inhibition reduces cancer cell metastasis by decreasing N-glycan sialylation, thus altering the regulation of talin/integrin/FAK/paxillin and integrin/NFκB signaling pathways.

Microbiota-Derived Metabolites in Tumor Progression and Metastasis

Microbial communities and human cells, through a dynamic crosstalk, maintain a mutualistic relationship that contributes to the maintenance of cellular metabolism and of the immune and neuronal systems. This dialogue normally occurs through the production and regulation of hormonal intermediates, metabolites, secondary metabolites, proteins, and toxins. When the balance between host and microbiota is compromised, the dynamics of this relationship change, creating favorable conditions for the development of diseases, including cancers. Microbiome metabolites can be important modulators of the tumor microenvironment contributing to regulate inflammation, proliferation, and cell death, in either a positive or negative way. Recent studies also highlight the involvement of microbiota metabolites in inducing epithelial-mesenchymal transition, thus favoring the setup of the metastatic niche. An investigation of microbe-derived metabolites in "liquid" human samples, such as plasma, serum, and urine, provide further information to clarify the relationship between host and microbiota.

Cholic Acid Stimulates MMP-9 in Human Colon Cancer Cells via Activation of MAPK, AP-1, and NF-κB Activity

Matrix metalloproteinase-9 (MMP-9) plays a crucial role in cell invasion and cancer metastasis. In this study, we showed that cholic acid (CA), a major primary bile acid, can induce MMP-9 expression in colon cancer HT29 and SW620 cells. CA increased reactive oxygen species (ROS) production and also activated phosphorylation of ERK1/2, JNK, and p38 MAPK. Specific inhibitors and mutagenesis studies showed that ERK1/2 and JNK functioned as upstream signals in the activation of AP-1, and p38 MAPK functioned as an upstream signal in the activation of NF-κB. N-acetyl-L-cysteine (NAC, an ROS scavenger) and diphenyleneiodonium chloride (DPI, an NADPH oxidase inhibitor) inhibited CA-induced activation of ERK1/2, JNK, and p38 MAPK, indicating that ROS production by NADPH oxidase could be the furthest upstream signal in MMP-9 expression. Colon cancer cells pretreated with CA showed remarkably enhanced invasiveness. Such enhancement was partially abrogated by MMP-9-neutralizing antibodies. These results demonstrate that CA could induce MMP-9 expression via ROS-dependent ERK1/2, JNK-activated AP-1, and p38-MAPK-activated NF-κB signaling pathways, which in turn stimulate cell invasion in human colon cancer cells.

Bile acid bio-nanoencapsulation improved drug targeted-delivery and pharmacological effects via cellular flux: 6-months diabetes preclinical study

The antilipidemic drug, probucol (PB), has demonstrated potential applications in Type 2 diabetes (T2D) through its protective effects on pancreatic β-cells. PB has poor solubility and bioavailability, and despite attempts to improve its oral delivery, none has shown dramatic improvements in absorption or antidiabetic effects. Preliminary data has shown potential benefits from bile acid co-encapsulation with PB. One bile acid has shown best potential improvement of PB oral delivery (ursodeoxycholic acid, UDCA). This study aimed to examine PB and UDCA microcapsules (with UDCA microcapsules serving as control) in terms of the microcapsules’ morphology, biological effects ex vivo, and their hypoglycemic and antilipidemic and anti-inflammatory effects in vivo. PBUDCA and UDCA microcapsules were examined in vitro (formulation studies), ex vivo and in vivo. PBUDCA microcapsules exerted positive effects on β-cells viability at hyperglycemic state, and brought about hypoglycemic and anti-inflammatory effects on the prediabetic mice. In conclusion, PBUDCA co-encapsulation have showed beneficial therapeutic impact of dual antioxidant-bile acid effects in diabetes treatment.

Metformin inhibits lithocholic acid-induced interleukin 8 upregulation in colorectal cancer cells by suppressing ROS production and NF-kB activity

Metformin, an inexpensive, well-tolerated oral agent that is a commonly used first-line treatment for type 2 diabetes, has become the focus of intense research as a potential anticancer agent. In this study, we describe the inhibitory effect of metformin in interleukin 8 (IL-8) upregulation by lithocholic acid (LCA) in HCT116 colorectal cancer (CRC) cells. Pharmacological inhibition studies indicated that reactive oxygen species (ROS) were involved in LCA-induced IL-8 upregulation through activation of the transcription factor NF-κB. Metformin was demonstrated to block LCA-stimulated ROS production, in turn suppressing NF-κB signaling that was critical for IL-8 upregulation. An NADPH oxidase assay proved that the inhibitory effect of metformin on ROS production was derived from its strong suppression of NADPH oxidase, a key producer of ROS in cells. Compared with conditioned media (CM) derived from HCT116 cells treated with LCA, CM derived from HCT116 cells pretreated with metformin and then treated with LCA lost all stimulatory effect on endothelial cell proliferation and tubelike formation. In conclusion, metformin inhibited NADPH oxidase, which in turn suppressed ROS production and NF-κB activation to prevent IL-8 upregulation stimulated by LCA; this prevention thus obstructed endothelial cell proliferation and tubelike formation.

Microbiota in cancer development and treatment

PURPOSE

Human microbiota comprises of a variety of organisms ranging from bacterial species to viruses, fungi, and protozoa which are present on the epidermal and mucosal barriers of the body. It plays a key role in health and survival of the host by regulation of the systemic functions. Its apparent functions in modulation of the host immune system, inducing carcinogenesis and regulation of the response to the cancer therapy through a variety of mechanisms such as bacterial dysbiosis, production of genotoxins, pathobionts, and disruption of the host metabolism are increasingly becoming evident.

METHODS

Different electronic databases such as PubMed, Google Scholar, and Web of Science were searched for relevant literature which has been reviewed in this article.

RESULTS

Characterization of the microbiome particularly gut microbiota, understanding of the host-microbiota interactions, and its potential for therapeutic exploitation are necessary for the development of novel anticancer therapeutic strategies with better efficacy and lowered off-target side effects.

CONCLUSION

In this review, the role of microbiota is explained in carcinogenesis, mechanisms of microbiota-mediated carcinogenesis, and role of gut microbiota in modulation of cancer therapy.

Role of bile acids in colon carcinogenesis

Bile acids (BAs) are cholesterol derivatives synthesized in the liver and then secreted into the intestine for lipid absorption. There are numerous scientific reports describing BAs, especially secondary BAs, as strong carcinogens or promoters of colon cancers. Firstly, BAs act as strong stimulators of colorectal cancer (CRC) initiation by damaging colonic epithelial cells, and inducing reactive oxygen species production, genomic destabilization, apoptosis resistance, and cancer stem cells-like formation. Consequently, BAs promote CRC progression via multiple mechanisms, including inhibiting apoptosis, enhancing cancer cell proliferation, invasion, and angiogenesis. There are diverse signals involved in the carcinogenesis mechanism of BAs, with a major role of epidermal growth factor receptor, and its down-stream signaling, involving mitogen-activated protein kinase, phosphoinositide 3-kinase/Akt, and nuclear factor kappa-light-chain-enhancer of activated B cells. BAs regulate numerous genes including the human leukocyte antigen class I gene, p53, matrix metalloprotease, urokinase plasminogen activator receptor, Cyclin D1, cyclooxygenase-2, interleukin-8, and miRNAs of CRC cells, leading to CRC promotion. These evidence suggests that targeting BAs is an efficacious strategies for CRC prevention and treatment.

Dysbiosis of gut microbiota in promoting the development of colorectal cancer

Gastrointestinal microbiome, containing at least 100 trillion bacteria, resides in the mucosal surface of human intestine. Recent studies show that perturbations in the microbiota may influence physiology and link to a number of diseases, including colon tumorigenesis. Colorectal cancer (CRC), the third most common cancer, is the disease resulting from multi-genes and multi-factors, but the mechanistic details between gut microenvironment and CRC remain poorly characterized. Thanks to new technologies such as metagenome sequencing, progress in large-scale analysis of the genetic and metabolic profile of gut microbial has been possible, which has facilitated studies about microbiota composition, taxonomic alterations and host interactions. Different bacterial species and their metabolites play critical roles in the development of CRC. Also, microbiota is important in the inflammatory response and immune processes deregulation during the development and progression of CRC. This review summarizes current studies regarding the association between gastrointestinal microbiota and the development of CRC, which provides insights into the therapeutic strategy of CRC.

Lithocholic Acid Stimulates IL-8 Expression in Human Colorectal Cancer Cells Via Activation of Erk1/2 MAPK and Suppression of STAT3 Activity

The secondary bile acid lithocholic acid (LCA), an established tumor promoter, has been implicated in colorectal cancer (CRC) metastasis. Overexpression of interleukin-8 (IL-8) has been detected in CRC, and it contributes to poor prognosis. However, the effect of LCA on IL-8 expression is still undefined. In this study, we observed that LCA treatment induced IL-8 expression in CRC HCT116 cells. Pharmacological inhibition and mutagenesis studies indicated that Erk1/2 is critical for LCA-induced IL-8 expression. Furthermore, LCA reduced the phosphorylation of STAT3, and the STAT3 inhibitor Stattic, accelerated LCA-induced IL-8 expression, suggesting that STAT3 is involved in LCA-induced IL-8 expression. Activation of Erk1/2 functioned as an upstream signal of the STAT3 suppression induced by LCA. In conclusion, LCA activated Erk1/2 and in turn, suppressed STAT3 phosphorylation to induce IL-8 expression in HCT116 cells, thus stimulating endothelial cell proliferation and tube like formation. J. Cell. Biochem. 118: 2958-2967, 2017. © 2017 Wiley Periodicals, Inc.

Constitutive and Inducible Expression of Invasion-related Factors in PC-3 Prostate Cancer Cells

Background:

Tumor growth and invasion are interconnected with the tumor microenvironment. Overexpression of genes that regulate cancer cell invasion by growth factors, cytokines, and lipid factors can affect cancer aggressiveness. A comparative gene expression analysis between highly invasive and low invasive cells revealed that various genes are differentially expressed in association with invasive potential. In this study, we selected variant PC-3 prostate cancer cell sublines and discovered critical molecules that contributed to their invasive potential.

Methods:

The high invasive and low invasive variant PC-3 cell sublines were obtained by serial selection following Matrigel-coated Transwell invasion and were characterized by Transwell invasion, luciferase reporter assay, and Rhotekin pull-down assay. Lysophosphatidic acid (LPA) was added to the cultures to observe the response to this extracellular stimulus. The essential molecules related with cancer invasiveness were detected with Northern blotting, quantitative reverse transcription-polymerase chain reaction, and cDNA microarray.

Results:

Highly invasive PC-3 cells showed higher nuclear factor kappa B (NF-κB), activator protein 1 (AP-1) and RhoA activities than of low invasive PC-3 cells. LPA promoted cancer invasion through NF-κB, AP-1, and RhoA activities. Thrombospondin-1, interleukin-8, kallikrein 6, matrix metalloproteinase-1, and tissue factor were overexpressed in the highly invasive PC-3 variant cells and further upregulated by LPA stimulation.

Conclusions:

The results suggest that the target molecules are involved in invasiveness of prostate cancer. These molecules may have clinical value for anti-invasion therapy by serving as biomarkers for the prediction of aggressive cancers and the detection of pharmacological inhibitors.

Effects of high-fat diet on 1,2-dimethylhydrazine-induced aberrant crypt foci and colorectal tumours in rats

Obesity is one of the leading causes of numerous types of cancer. The present study investigated the impact of a high-fat diet on 1,2-dimethylhydrazine (DMH)-induced colorectal cancer (CRC) in F344 rats. A total of 16 male F344 rats aged 4 weeks were randomly divided into two groups (8 rats/group). Rats in group A were fed a basal diet with a moderate fat (MF) content, while rats in group B were fed a high-fat diet. Upon reaching 5 weeks of age, the rats were injected subcutaneously with DMH (20 mg/kg body weight). DMH was administered once a week for 8 consecutive weeks. All the rats were sacrificed 34 weeks after the first DMH injection and dissected to obtain samples of colorectal tissues. The tissues were examined under a microscope for the presence of aberrant crypt foci (ACFs) and subjected to histopathological analysis. The results showed that at the end of the 34-week experiment, body weights and visceral fat levels were significantly higher in the high-fat diet group compared to the basal diet group. In addition, the incidences of colorectal ACF, adenoma and adenocarcinoma were markedly elevated in the high-fat diet group compared to the basal diet group. These results indicate that the consumption of a high-fat diet promotes the development and progression of CRC and the control of fat intake may prevent CRC.

Downregulation of galectin-3 causes a decrease in uPAR levels and inhibits the proliferation, migration and invasion of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related mortality worldwide. Galectin-3 (Gal-3), a multifunctional β-galactoside-binding protein, is highly expressed and associated with the prognosis of HCC. However, the functions of Gal-3 in HCC cells are not fully understood. To address the function of Gal-3 in HCC cells, we used small interfering RNA (siRNA) to knock down Gal-3 expression in HepG2, an HCC cell line. We found that in vitro the silencing of Gal-3 decreased the proliferative activity, colony formation ability, migratory and invasive potential of HepG2 cells. The silencing of Gal-3 significantly decreased the mRNA and protein levels of urokinase-type plasminogen activator receptor (uPAR) as well as uPAR's downstream signaling transduction pathway, including phosphorylation of AKT. Furthermore, the downregulation of Gal-3 by siRNA resulted in significantly decreased activity of the MEK/ERK signaling pathway, and the treatment of HepG2 cells with MEK/ERK inhibitor U0126 significantly reduced the mRNA and protein levels of uPAR. Taken together, our results suggest that Gal-3 modulates uPAR expression via the MEK/ERK pathway, and that Gal-3 may be a potential therapeutic target for the treatment of HCC.

Update on inflammatory bowel disease in patients with primary sclerosing cholangitis

Patients with primary sclerosing cholangitis (PSC) complicated by inflammatory bowel disease (IBD) represent a distinct subset of patients with unique characteristics, which have serious clinical implications. The aim of this literature review was to shed light to the obscure clinical and molecular aspects of the two diseases combined utilizing current data available and putting issues of diagnosis and treatment into perspective. The prevalence of IBD, mainly ulcerative colitis in PSC patients is estimated to be 21%-80%, dependent on screening programs and nationality. PSC-associated colitis is likely to be extensive, characterized by rectal sparing, backwash ileitis, and generally mild symptoms. It is also more likely to progress to colorectal malignancy, making it imperative for clinicians to maintain a high level of suspicion when tackling PSC patients. There is no optimal surveillance strategy but current guidelines advocate that colonoscopy is necessary at the time of PSC diagnosis with annual endoscopic follow-up. Random biopsies have been criticized and a shift towards targeted biopsies using chromoendoscopy, laser endomicroscopy and narrow-band imaging has been noted. Techniques directed towards genetic mutations instead of histological abnormalities hold promise for easier, more accurate diagnosis of dysplastic lesions. Chemopreventive measures against colorectal cancer have been sought in these patients. Ursodeoxycholic acid seemed promising at first but subsequent studies yielded conflicting results showing anticarcinogenic effects in low doses (8-15 mg/kg per day) and carcinogenic properties in high doses (15-30 mg/kg per day).

GEP100 regulates epidermal growth factor-induced MDA-MB-231 breast cancer cell invasion through the activation of Arf6/ERK/uPAR signaling pathway

GEP100, a guanine nucleotide exchanging factor (GEF) for Arf6, plays a pivotal role in promoting breast cancer cell invasion both in vitro and in vivo. However, the precise mechanism for GEP100-mediated cell invasion is still poorly understood. In this study, we found that down-regulation of endogenous GEP100 in MDA-MB-231 cells significantly inhibited EGF-induced cell invasion, which was rescued by over-expression of ectopic GEP100. EGF increased Arf6 activity, ERK phosphorylation, and uPAR expression in a time dependent manner. Additionally, blocking Arf6 with Arf6 siRNA largely abolished EGF-induced cell invasion. GEP100 siRNA or Arf6 siRNA suppressed EGF-induced ERK activity and uPAR expression. Furthermore, blocking ERK signaling with U0126, a specific inhibitor for MEK, markedly inhibited EGF-induced uPAR expression and consequently cell invasion. Inhibition of uPAR expression by uPAR siRNA also significantly abolished EGF-induced cell invasion. Taken together, this study illustrates that GEP100 regulates an Arf6/ERK/uPAR signaling cascade in EGF-induced breast cancer cell invasion. These findings could provide a rationale for designing new therapies based on inhibition of breast cancer metastasis.

Pro-apoptotic role of the MEK/ERK pathway in ursodeoxycholic acid-induced apoptosis in SNU601 gastric cancer cells

Ursodeoxycholic acid (UDCA) has been regarded as a suppressor of gastrointestinal cancer, but the mechanisms underlying its antitumor effects are not fully understood. Previously, we reported the antitumor effect of UDCA by demonstrating that UDCA induces apoptosis of gastric cancer cells. Bile acids are known to activate the ERK pathway and ERK is a representative oncogenic kinase in cancer cells. Here, we investigated the role of ERK in UDCA-induced gastric cancer cell apoptosis. We found that UDCA enhanced the phosphorylation of ERK1/2 and MEK1/2. The prevention of MEK by the pharmacologic inhibitors PD98059 and U0126, resulted in decreased UDCA-induced apoptosis as shown by the reduction of apoptotic body formation, caspase-8 activity, and caspase-3, -6 and PARP cleavage, indicating that ERK exerts pro-apoptotic activity upon exposure to UDCA. In addition, U0126 reduced UDCA-triggered TNF-related apoptosis-inducing ligand receptor 2 (TRAIL-R2/DR5) expression. In gene silencing studies, we observed that RNA interference of ERK2 decreased apoptosis and reduced DR5 overexpression. Lipid raft disrupting agent, methyl-β-cyclodextrin, blunted the phosphorylation of ERK1/2, indicating that ERK activation is regulated in a lipid raft-dependent manner. On the other hand, tumor-promoting bile acid, deoxycholic acid (DCA), also phosphorylated ERK in SNU601 cells. However, the DCA-triggered ERK pathway exerted anti-apoptotic function in the cells. Suppression of the ERK pathway enhanced DCA-induced apoptosis, and ERK activation was observed to be lipid raft-independently controlled. These results indicated that UDCA and DCA may cause differential responses in gastric cancer cells through the ERK signaling molecule. Thus, ERK activation may be a possible mechanism by which UDCA and DCA represent differential activities in gastrointestinal cancer.

High-dose ursodeoxycholic acid is associated with the development of colorectal neoplasia in patients with ulcerative colitis and primary sclerosing cholangitis

OBJECTIVES

Some studies have suggested that ursodeoxycholic acid (UDCA) may have a chemopreventive effect on the development of colorectal neoplasia in patients with ulcerative colitis (UC) and primary sclerosing cholangitis (PSC). We examined the effects of high-dose (28-30 mg/kg/day) UDCA on the development of colorectal neoplasia in patients with UC and PSC.

METHODS

Patients with UC and PSC enrolled in a prior, multicenter randomized placebo-controlled trial of high-dose UDCA were evaluated for the development of colorectal neoplasia. Patients with UC and PSC who received UDCA were compared with those who received placebo. We reviewed the pathology and colonoscopy reports for the development of low-grade or high-grade dysplasia or colorectal cancer.

RESULTS

Fifty-six subjects were followed for a total of 235 patient years. Baseline characteristics (including duration of PSC and UC, medications, patient age, family history of colorectal cancer, and smoking status) were similar for both the groups. Patients who received high-dose UDCA had a significantly higher risk of developing colorectal neoplasia (dysplasia and cancer) during the study compared with those who received placebo (hazard ratio: 4.44, 95% confidence interval: 1.30-20.10, P=0.02).

CONCLUSIONS

Long-term use of high-dose UDCA is associated with an increased risk of colorectal neoplasia in patients with UC and PSC.

MSP-induced RON activation upregulates uPAR expression and cell invasiveness via MAPK, AP-1 and NF-κB signals in gastric cancer cells

Overexpression of recepteur d'Origine nantais (RON) and urokinase plasminogen activator receptor (uPAR) have been observed in human gastric cancers. However, the interaction between RON and uPAR in gastric cancer is unclear. The present study investigated the effect of macrophage-stimulating protein (MSP, the RON ligand) on uPAR expression and the underlying signal pathways in human gastric cancer AGS cells. uPAR messenger RNA expression was induced by MSP in a time- and concentration-dependent manner. MSP also induced uPAR promoter activity. The introduction of RON-specific small interfering RNA (siRNA) significantly affected the MSP-induced uPAR transcription. Deleted and site-directed mutagenesis studies demonstrated the involvement of the binding sites of transcription factor nuclear factor-kappaB (NF-κB) and activator protein (AP)-1 in the MSP-induced uPAR expression. Studies with expression vectors encoding mutated-type NF-κB signaling molecules and AP-1 decoy confirmed that NF-κB and AP-1 were essential for the MSP-induced uPAR expression. In addition, MSP induced the activation of extracellular signal-regulated kinase-1/2 (Erk-1/2), c-Jun amino terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Dominant-negative mutants (K97M and TAM67) and specific inhibitors of Erk-1/2 and JNK were able to suppress the MSP-induced uPAR expression. AGS cells pretreated with MSP showed a remarkably enhanced invasiveness, which was partially abrogated by siRNA-targeted RON and uPAR-neutralizing antibodies. The above results suggest that MSP induces uPAR expression via MAPK, AP-1 and NF-κB signaling pathways and, in turn, stimulates cell invasiveness in human gastric cancer AGS cells.