Joining up the scattered anticancer knowledge on auraptene and umbelliprenin: a meta-analysis

Auraptene (AUR) and umbelliprenin (UMB) are naturally occurring prenylated coumarins that have demonstrated promising anticancer effects across various human cancer cell lines. This meta-analysis aimed to systematically assess, compare, and quantify the anticancer efficacy of AUR and UMB by synthesizing evidence from in vitro studies. A comprehensive literature search identified 27 eligible studies investigating AUR or UMB against cancer cells. Mixed-effects models revealed significant negative associations between coumarin dose and viability for AUR (est. = - 2.27) and UMB (est. = - 3.990), underscoring their dose-dependent cytotoxicity. Meta-regression indicated slightly higher potency for UMB over AUR, potentially due to increased lipophilicity imparted by additional isoprenyl units. Machine learning approaches identified coumarin dose and cancer type as the most influential determinants of toxicity, while treatment duration and the specific coumarin displayed weaker effects. Moderate (AUR) to substantial (UMB) between-study heterogeneity was detected, although the findings proved robust. In summary, this meta-analysis establishes AUR and UMB as promising natural anticancer candidates with clear dose-toxicity relationships across diverse malignancies. The structural insights and quantifications of anticancer efficacy can inform forthcoming efforts assessing therapeutic potential in pre-clinical models and human trials.

Reversible translocation of acyl-CoA:cholesterol acyltransferase (ACAT) between the endoplasmic reticulum and vesicular structures

The enzyme acyl-CoA:cholesterol acyltransferase (ACAT) is normally localized in the endoplasmic reticulum (ER) where it can esterify cholesterol for storage in lipid droplets and/or the formation of lipoproteins. Here, we report that ACAT can translocate from the ER into vesicular structures in response to different ACAT inhibitors. The translocation was fast (within minutes), reversible and occurred in different cell types. Interestingly, oleic acid was able to fasten the re-translocation from vesicles back into the reticular ER network. The process of ACAT translocation could also be induced by cyclodextrins, cholesterol, lanosterol (but not 4-cholestene-3 one), 25-hydroxycholesterol, and by certain stress stimuli such as hyperosmolarity (sucrose treatment), temperature change, or high-density cultivation. In vitro esterification showed that ACAT remains fully active after it has been translocated to vesicles in response to hyperosmotic sucrose treatment of the cells. The translocation process was not accompanied by changes in the electrophoretic mobility of ACAT, even after chemical crosslinking. Interestingly, the protein synthesis inhibitor cycloheximide showed a stimulating effect on ACAT activity and prevented the translocation of ACAT from the ER into vesicles.

Targeting Sterol O-Acyltransferase/Acyl-CoA:Cholesterol Acyltransferase (ACAT): A Perspective on Small-Molecule Inhibitors and Their Therapeutic Potential

Sterol O-acyltransferase (SOAT) is a membrane-bound enzyme that aids the esterification of cholesterol and fatty acids to cholesterol esters. SOAT has been studied extensively as a potential drug target, since its inhibition can serve as an alternative to statin therapy. Two SOAT isozymes that have discrete functions in the human body, namely, SOAT1 and SOAT2, have been characterized. Over three decades of research has focused on candidate SOAT1 inhibitors with unsatisfactory results in clinical trials. Recent research has focused on targeting SOAT2 selectively. In this perspective, we summarize the literature covering various SOAT inhibitory agents and discuss the design, structural requirements, and mode of action of SOAT inhibitors.

LDL Promotes Disorders in β-Cell Cholesterol Metabolism, Implications on Insulin Cellular Communication Mediated by EVs

Dyslipidemia is described as a hallmark of metabolic syndrome, promoting a stage of metabolic inflammation (metainflammation) that could lead to misbalances in energetic metabolism, contributing to insulin resistance, and modifying intracellular cholesterol pathways and the renin–angiotensin system (RAS) in pancreatic islets. Low-density lipoprotein (LDL) hypercholesterolemia could disrupt the tissue communication between Langerhans β-cells and hepatocytes, wherein extracellular vesicles (EVs) are secreted by β-cells, and exposition to LDL can impair these phenomena. β-cells activate compensatory mechanisms to maintain insulin and metabolic homeostasis; therefore, the work aimed to characterize the impact of LDL on β-cell cholesterol metabolism and the implication on insulin secretion, connected with the regulation of cellular communication mediated by EVs on hepatocytes. Our results suggest that β-cells can endocytose LDL, promoting an increase in de novo cholesterol synthesis targets. Notably, LDL treatment increased mRNA levels and insulin secretion; this hyperinsulinism condition was associated with the transcription factor PDX-1. However, a compensatory response that maintains basal levels of intracellular calcium was described, mediated by the overexpression of calcium targets PMCA1/4, SERCA2, and NCX1, together with the upregulation of the unfolded protein response (UPR) through the activation of IRE1 and PERK arms to maintain protein homeostasis. The LDL treatment induced metainflammation by IL-6, NF-κB, and COX-2 overexpression. Furthermore, LDL endocytosis triggered an imbalance of the RAS components. LDL treatment increased the intracellular levels of cholesterol on lipid droplets; the adaptive β-cell response was portrayed by the overexpression of cholesterol transporters ABCA1 and ABCG1. Therefore, lipotoxicity and hyperinsulinism induced by LDL were regulated by the natural compound auraptene, a geranyloxyn coumarin modulator of cholesterol-esterification by ACAT1 enzyme inhibition. EVs isolated from β-cells impaired insulin signaling via mTOR/p70S6Kα in hepatocytes, a phenomenon regulated by auraptene. Our results show that LDL overload plays a novel role in hyperinsulinism, mechanisms associated with a dysregulation of intracellular cholesterol, lipotoxicity, and the adaptive UPR, which may be regulated by coumarin-auraptene; these conditions explain the affectations that occur during the initial stages of insulin resistance.

Assessment of the diagnostic and prognostic relevance of ACAT1 and CE levels in plasma, peritoneal fluid and tumor tissue of epithelial ovarian cancer patients - a pilot study

Background

Abnormal accumulation of acyl-CoA cholesterol acyltransferase-1 (ACAT1) and ACAT1-mediated cholesterol esterified with fatty acids (CE) contribute to cancer progression in various cancers. Our findings of increased CE and ACAT1 levels in epithelial ovarian cancer (EOC) cell lines prompted us to investigate whether such an increase occurs in primary clinical samples obtained from human subjects diagnosed with EOC. We evaluated the diagnostic/prognostic potential of ACAT1 and CE in EOC by: 1) assessing ACAT1 and CE levels in plasma, peritoneal fluid, and ovarian/tumor tissues; 2) assessing diagnostic performance by Receiver Operating Characteristic (ROC) analysis; and 3) comparing expression of ACAT1 and CE with that of tumor proliferation marker, Ki67.

Methods

ACAT1 protein levels in plasma, peritoneal fluid and tissue were measured via enzyme-linked immunosorbent assay. Tissue expression of ACAT1 and Ki67 proteins were confirmed by immunohistochemistry and mRNA transcript levels were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR). CE levels were assessed in plasma, peritoneal fluid (colorimetric assay) and in tissue (thin layer chromatography).

Results

Preoperative levels of ACAT1 and CE on the day of surgery were significantly higher in tissue and peritoneal fluid from EOC patients vs. the non-malignant group, which included subjects with benign tumors and normal ovaries; however, no significant differences were observed in plasma. In tissue and peritoneal fluid, positive correlations were observed between CE and ACAT1 levels, as well as between ACAT1/CE and Ki67.

Conclusions

ACAT1 and CE accumulation may be linked to the aggressive potential of EOC; therefore, these mediators may be useful biomarkers for EOC prognosis and target-specific treatments.

Pharmacologic and genetic inhibition of cholesterol esterification enzymes reduces tumour burden: A systematic review and meta-analysis of preclinical models

Cholesterol esterification proteins Sterol-O acyltransferases (SOAT) 1 and 2 are emerging prognostic markers in many cancers. These enzymes utilise fatty acids conjugated to coenzyme A to esterify cholesterol. Cholesterol esterification is tightly regulated and enables formation of lipid droplets that act as storage organelles for lipid soluble vitamins and minerals, and as cholesterol reservoirs. In cancer, this provides rapid access to cholesterol to maintain continual synthesis of the plasma membrane. In this systematic review and meta-analysis, we summarise the current depth of understanding of the role of this metabolic pathway in pan-cancer development. A systematic search of PubMed, Scopus, Web of Science, and Cochrane Library for preclinical studies identified eight studies where cholesteryl ester concentrations were compared between tumour and adjacent-normal tissue, and 24 studies where cholesterol esterification was blocked by pharmacological or genetic approaches. Tumour tissue had a significantly greater concentration of cholesteryl esters than non-tumour tissue (p < 0.0001). Pharmacological or genetic inhibition of SOAT was associated with significantly smaller tumours of all types (p ≤ 0.002). SOAT inhibition increased tumour apoptosis (p = 0.007), CD8 + lymphocyte infiltration and cytotoxicity (p ≤ 0.05), and reduced proliferation (p = 0.0003) and metastasis (p < 0.0001). Significant risk of publication bias was found and may have contributed to a 32% overestimation of the meta-analysed effect size. Avasimibe, the most frequently used SOAT inhibitor, was effective at doses equivalent to those previously reported to be safe and tolerable in humans. This work indicates that SOAT inhibition should be explored in clinical trials as an adjunct to existing anti-neoplastic agents.

Expression of SR-B1 receptor in breast cancer cell lines, MDAMB-468 and MCF-7: Effect on cell proliferation and apoptosis

OBJECTIVES

High-density lipoprotein (HDL) is necessary for proliferation of several cells. The growth of many kinds of cells, such as breast cancer cells (BCC) is motivated by HDL. Cellular uptake of cholesterol from HDL which increases cell growth is facilitated by scavenger receptors of the B class (SR-BI). The proliferative effect of HDL might be mediated by this receptor. It is also believed that HDL has an anti-apoptotic effect on various cell types and promotes cell growth. This study was designed to investigate SR-BI expression, proliferation and apoptotic effect of HDL on human BCC lines, MCF-7 and MDA-MB-468.

MATERIALS AND METHODS

Real-time-PCR method was used to evaluate expression of SR-BI, and cholesterol concentration was measured using a cholesterol assay kits (Pars AZ moon, Karaj, Iran). Cell viability was assessed using the MTT test. To identify cell apoptosis, the annexin V-FITC staining test and caspase-9 activity assay were applied.

RESULTS

Treatment of both cell lines (MCF-7, MDA-MB-468) with HDL results in augmentation of SR-BI mRNA expression and also elevation of the intracellular cholesterol (P<0.01). HDL induced cell proliferation, cell cycle progression, and prevented activation of caspase-9 (P<0.05). We also demonstrated that inhibition of SR-B1 by BLT-1 could reduce cell proliferation, and induction of SR-B1 receptor by quercetin increased HDL-induced proliferation in both cell lines (P<0.05).

CONCLUSION

It can be concluded that alteration in HDL levels by SR-B1 activator (Quercetin) or inhibitor (BLT-1) may affect BCC growth and apoptosis induction.

A Review of Auraptene as an Anticancer Agent

Auraptene is a bioactive monoterpene coumarin isolated from Citrus aurantium and Aegle marmelos that belong to the Rutaceae family. Auraptene can modulate intracellular signaling pathways that control cell growth, inflammation and apoptosis and can exert pharmacological properties such as anti-bacterial, anti-fungal, antileishmania and anti-oxidant activity. Auraptene had inhibitory and chemo-preventive effects on the proliferation, tumorigenesis and growth of several cancer cell lines through increase in the activity of glutathione S-transferase, formation of DNA adducts and reduction of the number of aberrant crypt foci. Auraptene exhibits anticancer effects via targeting different cell signaling pathways such as cytokines, genes modulating cellular proliferation, growth factors, transcription factors and apoptosis. The present review is a detailed survey of scientific researches on the cytotoxicity and anticancer activity of Auraptene on cancer cells and tumor bearing animals.

Signaling pathways essential for triple-negative breast cancer stem-like cells

Since the discovery of breast cancer stem cells (CSCs), a significant effort has been made to identify and characterize these cells. It is a generally believe that CSCs play an important role in cancer initiation, therapy resistance, and progression of triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with poor prognosis. Thus, therapies targeting these cells would be a valuable addition to standard treatments that primarily target more differentiated, rapidly dividing TNBC cells. Although several cell surface and intracellular proteins have been described as biomarkers for CSCs, none of these are specific to this population of cells. Recent research is moving toward cellular signaling pathways as targets and biomarkers for CSCs. The WNT pathway, the nuclear factor-kappa B (NF-κB) pathway, and the cholesterol biosynthesis pathway have recently been identified to play a key role in proliferation, survival, and differentiation of CSCs, including those of breast cancer. In this review, we assess recent findings related to these three pathways in breast CSC, with particular focus on TNBC CSCs, and discuss how targeting these pathways, in combination with current standard of care, might prove effective and improve the prognosis of TNBC patients.

pH-Responsive Fluorescence Enhanced Nanogel for Targeted Delivery of AUR and CDDP Against Breast Cancer

Introduction

Auraptene (AUR), a natural bioactive prenyloxy coumarin, is a highly pleiotropic molecule that can bind to the MT1 receptor and can effectively reduce the proliferation and migration of breast cancer cells. Cisplatin (CDDP), as the first synthetic platinum-based anticancer drug, is widely used in the clinic due to its definite mechanism and therapeutic effect on diverse tumors. However, both of AUR and CDDP exhibit some disadvantages when used alone, including poor solubility, low bioavailability, lack of selectivity and systemic toxicity when they are used singly.

Methods

Therefore, the biodegradable materials hyaluronic acid (HA) and β-cyclodextrin derivative (mono-(6-amino-mono-6-deoxy)-β-CD, CD) were employed as carriers to load AUR and CDDP to form nanogel (^CDDPHA-CD@AUR) capable of dual-targeted delivery and synergistic therapy for breast cancer and cell imaging.

Results

With the help of the CDDP-crosslinked CD-loaded structure, the newly synthesized nanogel exhibited excellent physiological stability and fluorescence effects. The release of AUR and CDDP was affected by the pH value, which was beneficial to the selective release in the tumor microenvironment. Cell experiments in vitro demonstrated that the nanogel could be selectively internalized by MCF-7 cells and exhibited low cytotoxicity to HK-2 cells. Antitumor experiments in vivo showed that the nanogel have better antitumor effects and lower systemic toxicity.

Conclusion

Based on these, the nanogel loaded with AUR and CDDP have the potential for targeted delivery against breast cancer.

Apolipoprotein-mediated regulation of lipid metabolism induces distinctive effects in different types of breast cancer cells

BACKGROUND

The highest incidence of breast cancer is in the Western world. Several aspects of the Western lifestyle are known risk factors for breast cancer. In particular, previous studies have shown that cholesterol levels can play an important role in the regulation of tumor progression.

METHODS

In the present study, we modulated cholesterol metabolism in the human breast cancer cell lines MCF-7 and MDA-MB-231 using a genetic approach. Apolipoprotein A-I (apoA-I) and apolipoprotein E (apoE) were expressed in these cell lines to modulate cholesterol metabolism. The effects of these apolipoproteins on cancer cell properties were examined.

RESULTS

Our results show that both apolipoproteins can regulate cholesterol metabolism and can control the epithelial-to-mesenchymal transition process. However, these effects were different depending on the cell type. We show that expressing apoA-I or apoE stimulates proliferation, migration, and tumor growth of MCF-7 cells. However, apoA-I or apoE reduces proliferation and migration of MDA-MB-231 cells.

CONCLUSIONS

These data suggest that modulating sterol metabolism may be most effective at limiting tumor progression in models of triple-negative cancers.

Role of de novo cholesterol synthesis enzymes in cancer

Despite extensive research in the cancer field, cancer remains one of the most prevalent diseases. There is an urgent need to identify specific targets that are safe and effective for the treatment of cancer. In recent years, cancer metabolism has come into the spotlight in cancer research. Lipid metabolism, especially cholesterol metabolism, plays a critical role in membrane synthesis as well as lipid signaling in cancer. This review focuses on the contribution of the de novo cholesterol synthesis pathway to tumorigenesis, cancer progression and metastasis. In conclusion, cholesterol metabolism could be an effective target for novel anticancer treatment.

Spinach consumption ameliorates the gut microbiota and dislipaemia in rats with diet-induced non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is defined as the accumulation of fat in liver cells, which causes serious health consequences. Animal and human studies suggest that the gut microbiota plays a role in the pathogenesis of NAFLD. Here, we investigated whether spinach consumption could ameliorate high-fat-diet-induced disturbances in certain intestinal bacterial groups and products derived from their metabolism, such as short-chain fatty acids (SCFAs) and microbial phenolic catabolites. Attention is also paid to blood lipids and glucose. In the study, a rat model of high-fat-diet-induced NAFLD was used. There were six experimental groups: NC (normal diet), NB (normal diet + 2.5% spinach), NA (normal diet + 5% spinach), HC (high-fat diet), HB (high-fat diet + 2.5% spinach) and HA (high-fat diet + 5% spinach). The rats consumed these diets for five weeks, and after that, they were sacrificed and plasma, urine, intestinal content, faeces and liver samples were taken. Biochemical parameters were analyzed in plasma, phenolic catabolites were quantified in the faeces, urine, plasma and liver by UPLC-ESI-MS/MS, and the analysis of the microbiota and SCFAs in the intestinal content was performed by qPCR and GLC. Consumption of a high-fat diet caused NAFLD and dislipaemia and altered the gut microbiota and the pattern of SCFAs and phenolic gut microbial catabolites. Supplementation with spinach partially ameliorated some alterations induced by the high-fat diet, in particular by increasing the Lactobacillus counts, reducing the fasting glucose and total and LDL-cholesterol and preventing excess liver cholesterol accumulation, thereby improving the values of the steatosis biomarkers.

Biomolecular Targets of Oxyprenylated Phenylpropanoids and Polyketides

Oxyprenylated secondary metabolites (e.g. phenylpropanoids and polyketides) represent a rare class of natural compounds. Over the past two decades, this group of phytochemicals has become a topic of intense research activity by several teams worldwide due to their in vitro and in vivo pharmacological activities, and to their great therapeutic and nutraceutical potential for the chemoprevention of acute and chronic diseases affecting humans. Such investigations have provided evidence that oxyprenylated secondary metabolites are able to interact with several biological targets at different levels accounting for their observed anticarcinogenic, anti-inflammatory, neuroprotective, immunomodulatory, antihypertensive, and metabolic effects. The aim of the present contribution is to provide a detailed survey of the so far reported data on the capacities of selected oxyprenylated phenylpropanoids and polyketides to trigger receptors, enzymes, and other types of cellular factors for which they exhibit a high degree of affinity and therefore evoke specific responses. With respect to the rather small amounts of these compounds available from natural sources, their chemical synthesis is also highlighted.

Insulin promotes progression of colon cancer by upregulation of ACAT1

Background

Insulin resistant and the progression of cancer is closely related. The aim of this study was to  investigate the effect of insulin on the proliferation and migration of colon cancer cells and its underlying mechanism.

Methods

Colon carcinoma tissues from the 80 cases of colon cancer patients were collected. Immunohistochemistry was used to detect the expression of acyl coenzyme A: cholesterol acyltransferase1 (ACAT1), and we analyzed the correlation between hyperglycemia and ACAT1, hyperglycemia and metastasis. CCK8 assay and transwell assay were used to investigate the effect of different concentrations of insulin and ACAT1siRNA on human colon cancer cell line HT-29. ACAT1 mRNA expression and protein level in HT-29 cells were determined by real-time quantitative PCR and western blotting, respectively.

Results

Biopsies from patients with colon carcinoma showed hyperglycemia links ACAT1, lymph nodes metastasis and distant metastasis. Insulin markedly promoted cell proliferation and migration in human colon cancer HT-29 cells. Moreover, ACAT1mRNA expression and protein level were increased by insulin. ACAT1siRNA resulted in a complete inhibition of the ACAT1 mRNA expression. Consequently insulin-triggered cell proliferation and migration on colon cancer cells were inhibited.

Conclusion

The progression of colon cancer has a positive correlation with hyperinsulinemia. Insulin-triggered cell proliferation and metastatic effects on colorectal cancer cells are mediated by ACAT1. Therefore, insulin could promote colon cancer progression by upregulation of ACAT1, which maybe is a potential therapeutic target for colon cancer.

Bryonolic Acid Blocks Cancer Cell Clonogenicity and Invasiveness through the Inhibition of Fatty Acid: Cholesteryl Ester Formation

Bryonolic acid (BrA) is a pentacyclic triterpene present in several plants used in African traditional medicine such as Anisophyllea dichostyla R. Br. Here we investigated the in vitro anticancer properties of BrA. We report that BrA inhibits acyl-coA: cholesterol acyl transferase (ACAT) activity in rat liver microsomes in a concentration-dependent manner, blocking the biosynthesis of the cholesterol fatty acid ester tumour promoter. We next demonstrated that BrA inhibits ACAT in intact cancer cells with an IC₅₀ of 12.6 ± 2.4 µM. BrA inhibited both clonogenicity and invasiveness of several cancer cell lines, establishing that BrA displays specific anticancer properties. BrA appears to be more potent than the other pentacyclic triterpenes, betulinic acid and ursolic acid studied under similar conditions. The inhibitory effect of BrA was reversed by exogenous addition of cholesteryl oleate, showing that ACAT inhibition is responsible for the anticancer effect of BrA. This report reveals new anticancer properties for BrA.

Hepatoprotection of auraptene from peels of citrus fruits against thioacetamide-induced hepatic fibrosis in mice by activating farnesoid X receptor

Auraptene protects against hepatic fibrosis.

Dendrogenin A drives LXR to trigger lethal autophagy in cancers

Dendrogenin A (DDA) is a newly discovered cholesterol metabolite with tumor suppressor properties. Here, we explored its efficacy and mechanism of cell death in melanoma and acute myeloid leukemia (AML). We found that DDA induced lethal autophagy in vitro and in vivo, including primary AML patient samples, independently of melanoma Braf status or AML molecular and cytogenetic classifications. DDA is a partial agonist on liver-X-receptor (LXR) increasing Nur77, Nor1, and LC3 expression leading to autolysosome formation. Moreover, DDA inhibited the cholesterol biosynthesizing enzyme 3β-hydroxysterol-Δ^8,7-isomerase (D8D7I) leading to sterol accumulation and cooperating in autophagy induction. This mechanism of death was not observed with other LXR ligands or D8D7I inhibitors establishing DDA selectivity. The potent anti-tumor activity of DDA, its original mechanism of action and its low toxicity support its clinical evaluation. More generally, this study reveals that DDA can direct control a nuclear receptor to trigger lethal autophagy in cancers.

Safety evaluation of auraptene in rats in acute and subacute toxicity studies

Auraptene (AUR) is a natural, bioactive, monoterpene coumarin ether. It has anti-inflammatory, anti-carcinogenic, anti-bacterial, neuroprotective, and hepatoprotective properties. The aim of the present study was to assess the acute and subacute toxicity of oral administration of AUR in rats by evaluating clinical signs, haematology, biochemical factors, pathological changes and immune-toxicity. Acute administration of AUR in doses of 125, 250, 500, 1000 and 2000 mg/kg body weight had no mortality or clinical signs in a period of two days. To evaluate subacute toxicity, AUR was administrated for 28 days by oral gavage in doses of 125 and 250 mg/kg. There were significant differences in the haematological and biochemical data of the treated and untreated groups. However, almost all haematological differences were within normal reference ranges. Subacute administration of AUR showed no toxic histopathological effects on organ tissue. Evaluation of immune-toxicity also revealed no significant differences between treatment and untreated groups.

Synergy of Dendritic Cell Vaccines and Avasimibe in Treatment of Head and Neck Cancer in Mice

BACKGROUND The main purpose of this study was to explore the antitumor effect and mechanisms of ACAT1 inhibitor combined with CSCs-DC vaccine. MATERIAL AND METHODS We isolated HNSCC CSCs and gained CSCs antigens, then used CSCs antigens to load dendritic cells (DC) and generated a CSCs-DC vaccine. We treated mice after surgical excision of established SCC7 tumors with CSCs-DC vaccine and/or ACAT1 inhibitor, and recorded local tumor relapse and host survival. T cells and B cells were harvested from mice treated with CSCs-DC vaccine and/or ACAT1 inhibitor. We tested antibody production and the death rate of CSCs killed by T cells. RESULTS The tumors in the combined treatment group were smaller than in all other groups (P<0.01). The average survival time of the combined treatment group was 82 days and was the longest of all groups. Analysis of IgG levels secreted by B cell and CTL activity in spleens of mice found that results of the combined treatment group were the highest, and the results of the CSCs-DC group were lower than in the combined treatment group. The ACAT1 inhibitor group results were lower than in the CSCs-DC group and the combined treatment group results, but higher than in the PBS group, and the difference was statistically significant. CONCLUSIONS ACAT1 inhibitor enhanced the therapeutic effect of CSCs-DC vaccine in the treatment of the mouse HNSCC postoperative recurrence model. ACAT1 may play an important role in cancer immunotherapy.

Efficacy of hyperthermia in human colon adenocarcinoma cells is improved by auraptene

Colon adenocarcinoma is one of the most common cancers worldwide, and resistance to current therapeutic modalities is a serious drawback in its treatment. Auraptene is a natural coumarin with considerable anticancer effects. The goal of this study was to introduce a novel combinatorial approach for treatment against colon adenocarcinoma cells. To do so, HT29 cells were pretreated with nontoxic auraptene and then hyperthermia was induced. Afterwards, the viability of the cells was assessed, changes induced in the cell cycle were analyzed, and the expression patterns of candidate genes were studied. Results from the MTT assay demonstrated significant (p < 0.01) decreases in cell viability when 20 μg/mL auraptene was used for 72 h, heat shock was induced, and cells were allowed to recover for 24 h. Flow cytometry analysis also indicated considerable changes in the distribution of cells between the sub-G₁/G₁ and G₂/M phases of cell cycle after the combinatorial treatment. Real-time RT-PCR studies revealed significant (p < 0.01) up-regulation of P21 in the cells pretreated with auraptene after heat shock, whereas no significant change was observed in HSP27 expression. Our findings not only indicate, for the first time, that the efficacy of hyperthermia was improved by auraptene pretreatment, but also suggest that this coumarin could be used in the future to achieve more effective therapeutic outcomes.

The interaction of auraptene and other oxyprenylated phenylpropanoids with glucose transporter type 4

BACKGROUND

Glucose transporter 4 (GLUT4) is firmly established to play a pivotal role in glucose metabolism and in particular in modulating the insulin-stimulated glucose transport in several tissues, such as skeletal muscle and adipose tissue. Stimulation of GLUT4 by insulin results in its translocation to the plasma membrane, activation of several kinases, and finally in a large glucose influx into cells.

PURPOSE

In this study we investigated the modulating properties of four biologically active oxyprenylated ferulic acid and umbelliferone derivatives and of their unprenylated parent compounds on GLUT-4 mediated glucose uptake and translocation.

METHODS

Oxyprenylated phenylpropanoids have been synthesized in high yields and purity by already reported methodologies. All the synthesized chemicals were tested for their capacity to modulate GLUT4 mediated glucose uptake and GLUT4 translocation in L6 rat skeletal myoblasts in the concentration range 0.1 - 10 µM. Insulin (0.1 µM) was used as positive control. Western blot analysis was employed to assess if GLUT4 translocation occurred prior to increase of glucose uptake. Statistical analyses were carried out by the Dunnett multiple comparison test.

RESULTS

4'-Geranyloxyferulic acid (GOFA), 7-isopentenyloxycoumarin, and auraptene (7-geranyloxycoumarin) increased glucose uptake in a concentration-dependent manner, and significant increases were observed at 0.1 µM for GOFA, and 10 µM for 7-isopentenyloxycoumarin, and auraptene. These products also were able to significantly promote the translocation of GLUT4 to the plasma membrane of L6 myotubes. After treatment with compounds for 15 min, the incorporated amounts of GOFA, 7-isopentenyloxucoumarin, and auraptene were 0.15, 0.32, and 1.77 nmols/60-mm culture dish, respectively. A sample of raw Italian propolis, found to be rich in GOFA and auraptene, was also seen to mimic insulin-effect in the concentration range 0.01 - 1.0 mg/ml.

CONCLUSIONS

Among the compounds assayed, auraptene showed to possess potentialities to be a potent activator of both translocation of GLUT4 and glucose influx into skeletal muscle cells with the highest bioavailability among effective compounds. Its capacity to modulate sugar metabolism, coupled to its presence in edible Citrus fruits, can be regarded as an additional reason to account for the already known stimulating properties of some vegetable (e.g. bitter orange).

Reactive oxygen species dependent phosphorylation of the liver kinase B1/AMP activated protein kinase/ acetyl-CoA carboxylase signaling is critically involved in apoptotic effect of lambertianic acid in hepatocellular carcinoma cells

Though lambertianic acid (LA) is reported to have hypolipidemic activity in liver, its underlying anticancer mechanism is poorly understood so far. Thus, in the present study, apoptotic mechanism of LA was elucidated in HepG2 and SK-Hep1 hepatocellular carcinoma (HCC) cells. Here LA increased cytotoxicity, sub-G1 population and Annexin V/PI positive cells in two HCC cells. Also, LA cleaved caspase-3 and poly(ADP-ribose) polymerase (PARP), activated phosphorylation of liver kinase B1 (LKB1)/AMP activated protein kinase (AMPK)/ acetyl-CoA carboxylase (ACC) pathway and also suppressed antiapoptotic proteins such as phosphorylation of Akt/ mammalian target of rapamycin (mTOR) and the expression of B cell lymphoma-2 (Bcl-2)/ B-cell lymphoma-extra large (Bcl-xL) and cyclooxygenase-2 (COX-2) in two HCC cells. Furthermore, LA generated reactive oxygen species (ROS) in HepG2 cells and AMPK inhibitor compound C or ROS inhibitor N-acetyl-L-cysteine (NAC) blocked the apoptotic ability of LA to cleave PARP or increase sub G1 population in HepG2 cells. Consistently, cleavages of PARP and caspase-3 were induced by LA only in AMPK^+/+ MEF cells, but not in AMPK^-/- MEF cells. Also, immunoprecipitation (IP) revealed that phosphorylation of LKB1/AMPK through their binding was enhanced in LA treated HepG2 cells. Overall, these findings suggest that ROS dependent phosphorylation of LKB1/AMPK/ACC signaling is critically involved in LA induced apoptosis in HCCs.

Auraptene Induces Apoptosis via Myeloid Cell Leukemia 1-Mediated Activation of Caspases in PC3 and DU145 Prostate Cancer Cells

Although auraptene, a prenyloxy coumarin from Citrus species, was known to have anti-oxidant, anti-bacterial, antiinflammatory, and anti-tumor activities, the underlying anti-tumor mechanism of auraptene in prostate cancers is not fully understood to date. Thus, in the present study, we have investigated the anti-tumor mechanism of auraptene mainly in PC3 and DU145 prostate cancer cells, because auraptene suppressed the viability of androgen-independent PC3 and DU145 prostate cancer cells better than androgen-sensitive LNCaP cells. Also, auraptene notably increased sub-G1 cell population and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells as features of apoptosis in two prostate cancer cells compared with untreated control. Consistently, auraptene cleaved poly(ADP-ribose) polymerase, activated caspase-9 and caspase-3, suppressed the expression of anti-apoptotic proteins, including Bcl-2 and myeloid cell leukemia 1 (Mcl-1), and also activated pro-apoptotic protein Bax in both prostate cancer cells. However, Mcl-1 overexpression reversed the apoptotic effect of auraptene to increase sub-G1 population and induce caspase-9/3 in both prostate cancer cells. Taken together, the results support scientific evidences that auraptene induces apoptosis in PC3 and DU145 prostate cancer cells via Mcl-1-mediated activation of caspases as a potent chemopreventive agent for prostate cancer prevention and treatment. Copyright © 2017 John Wiley & Sons, Ltd.

Auraptene Attenuates Malignant Properties of Esophageal Stem-Like Cancer Cells

The high incidence of esophageal squamous cell carcinoma has been reported in selected ethnic populations including North of Iran. Low survival rate of esophageal carcinoma is partially due to the presence of stem-like cancer cells with chemotherapy resistance. In the current study, we aimed to determine the effects of auraptene, an interesting dietary coumarin with various biological activities, on malignant properties of stem-like esophageal squamous cell carcinoma, in terms of sensitivity to anticancer drugs and expression of specific markers. To do so, the half maximal inhibitory concentration values of auraptene, cisplatin, paclitaxel, and 5-fluorouracil were determined on esophageal carcinoma cells (KYSE30 cell line). After administrating combinatorial treatments, including nontoxic concentrations of auraptene + cisplatin, paclitaxel, or 5-fluorouracil, sensitivity of cells to chemical drugs and also induced apoptosis were assessed. In addition, quantitative real-time polymerase chain reaction was used to study changes in the expression of tumor suppressor proteins 53 and 21 ( P53 and P21), cluster of differentiation 44 ( CD44), and B cell-specific Moloney murine leukemia virus integration site 1 ( BMI-1) upon treatments. Results of thiazolyl blue assay revealed that auraptene significantly ( P < .05) increased toxicity of cisplatin, paclitaxel, and 5-fluorouracil in KYSE30 cells, specifically 72 hours after treatment. Conducting an apoptosis assay using flow cytometry also confirmed the synergic effects of auraptene. Results of quantitative real-time polymerase chain reaction revealed significant ( P < .05) upregulation of P53 and P21 upon combinatorial treatments and also downregulation of CD44 and BMI-1 after auraptene administration. Current study provided evidence, for the first time, that auraptene attenuates the properties of esophageal stem-like cancer cells through enhancing sensitivity to chemical agents and reducing the expression of CD44 and BMI-1 markers.

Molecular and Biochemical Analysis of the Estrogenic and Proliferative Properties of Vitamin E Compounds

Tocols are vitamin E compounds that include tocopherols (TPs) and tocotrienols (TTs). These lipophilic compounds are phenolic antioxidants and are reportedly able to modulate estrogen receptor β (ERβ). We investigated the molecular determinants that control their estrogenicity and effects on the proliferation of breast cancer cells. Docking experiments highlighted the importance of the tocol phenolic groups for their interaction with the ERs. Binding experiments confirmed that they directly interact with both ERα and ERβ with their isoforms showing potencies in the following order: δ-tocols > γ-tocols > α-tocols. We also found that tocols activated the transcription of an estrogen-responsive reporter gene that had been stably transfected into cells expressing either ERα or ERβ. The role of the phenolic group in tocol-ER interaction was further established using δ-tocopherylquinone, the oxidized form of δ-TP, which had no ER affinity and did not induce ER-dependent transcriptional modulation. Tocol activity also required the AF1 transactivation domain of ER. We found that both δ-TP and δ-TT stimulated the expression of endogenous ER-dependent genes. However, whereas δ-TP induced the proliferation of ER-positive breast cancer cells but not ER-negative breast cancer cells, δ-TT inhibited the proliferation of both ER-positive and ER-negative breast cancer cells. These effects of δ-TT were found to act through the down regulation of HMG-CoA reductase (HMGR) activity, establishing that ERs are not involved in this effect. Altogether, these data show that the reduced form of δ-TP has estrogenic properties which are lost when it is oxidized, highlighting the importance of the redox status in its estrogenicity. Moreover, we have shown that δ-TT has antiproliferative effects on breast cancer cells independently of their ER status through the inhibition of HMGR. These data clearly show that TPs can be discriminated from TTs according to their structure.

Auraptene and Its Role in Chronic Diseases

Auraptene (7-geranyloxycoumarin) is the best known and most abundant prenyloxycoumarin present in nature. It is synthesized by various plant species, mainly those of the Rutaceae and Umbeliferae (Apiaceae) families, comprising many edible fruits and vegetables such as lemons, grapefruit and orange. Auraptene has shown a remarkable effect in the prevention of degenerative diseases, in particular it has been reported to be one the most promising known natural chemopreventive agents against several types of cancer. The aim of this chapter is to review the effects of auraptene in the prevention and treatment of different chronic diseases.

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

Intratumor cholesteryl ester accumulation is associated with human breast cancer proliferation and aggressive potential: a molecular and clinicopathological study

BACKGROUND

The metabolic effect of intratumor cholesteryl ester (CE) in breast cancer remains poorly understood. The objective was to analyze the relationship between intratumor CE content and clinicopathological variables in human breast carcinomas.

METHODS

We classified 30 breast carcinoma samples into three subgroups: 10 luminal-A tumors (ER+/PR+/Her2-), 10 Her-2 tumors (ER-/PR-/Her2+), and 10 triple negative (TN) tumors (ER-/PR-/Her2-). We analyzed intratumor neutral CE, free cholesterol (FC) and triglyceride (TG) content by thin layer chromatography after lipid extraction. RNA and protein levels of lipid metabolism and invasion mediators were analyzed by real time PCR and Western blot analysis.

RESULTS

Group-wise comparisons, linear regression and logistic regression models showed a close association between CE-rich tumors and higher histologic grade, Ki-67 and tumor necrosis. CE-rich tumors displayed higher mRNA and protein levels of low-density lipoprotein receptor (LDLR) and scavenger receptor class B member 1 (SCARB1). An increased expression of acetyl-Coenzyme A acetyltransferase 1 (ACAT1) in CE-rich tumors was also reported.

CONCLUSIONS

Intratumor CE accumulation is intimately linked to proliferation and aggressive potential of breast cancer tumors. Our data support the link between intratumor CE content and poor clinical outcome and open the door to new antitumor interventions.

Scavenger receptor class B type I regulates cellular cholesterol metabolism and cell signaling associated with breast cancer development

Introduction

Previous studies have identified cholesterol as an important regulator of breast cancer development. High-density lipoprotein (HDL) and its cellular receptor, the scavenger receptor class B type I (SR-BI) have both been implicated in the regulation of cellular cholesterol homeostasis, but their functions in cancer remain to be established.

Methods

In the present study, we have examined the role of HDL and SR-BI in the regulation of cellular signaling pathways in breast cancer cell lines and in the development of tumor in a mouse xenograft model.

Results

Our data show that HDL is capable of stimulating migration and can activate signal transduction pathways in the two human breast cancer cell lines, MDA-MB-231 and MCF7. Furthermore, we also show that knockdown of the HDL receptor, SR-BI, attenuates HDL-induced activation of the phosphatidylinositol 3-kinase (PI3K)/protein Kinase B (Akt) pathway in both cell lines. Additional investigations show that inhibition of the PI3K pathway, but not that of the mitogen-activated protein kinase (MAPK) pathway, could lead to a reduction in cellular proliferation in the absence of SR-BI. Importantly, whereas the knockdown of SR-BI led to decreased proliferation and migration in vitro, it also led to a significant reduction in tumor growth in vivo. Most important, we also show that pharmacological inhibition of SR-BI can attenuate signaling and lead to decreased cellular proliferation in vitro. Taken together, our data indicate that both cholesteryl ester entry via HDL-SR-BI and Akt signaling play an essential role in the regulation of cellular proliferation and migration, and, eventually, tumor growth.

Conclusions

These results identify SR-BI as a potential target for the treatment of breast cancer.

Dendrogenin A arises from cholesterol and histamine metabolism and shows cell differentiation and anti-tumour properties

We previously synthesized dendrogenin A and hypothesized that it could be a natural metabolite occurring in mammals. Here we explore this hypothesis and report the discovery of dendrogenin A in mammalian tissues and normal cells as an enzymatic product of the conjugation of 5,6α-epoxy-cholesterol and histamine. Dendrogenin A was not detected in cancer cell lines and was fivefold lower in human breast tumours compared with normal tissues, suggesting a deregulation of dendrogenin A metabolism during carcinogenesis. We established that dendrogenin A is a selective inhibitor of cholesterol epoxide hydrolase and it triggered tumour re-differentiation and growth control in mice and improved animal survival. The properties of dendrogenin A and its decreased level in tumours suggest a physiological function in maintaining cell integrity and differentiation. The discovery of dendrogenin A reveals a new metabolic pathway at the crossroads of cholesterol and histamine metabolism and the existence of steroidal alkaloids in mammals.

It has been hypothesized that the steroidal alkaloid dendrogenin A (DDA) is a natural metabolite. de Medina et al. show that DDA is produced in mammalian tissues from 5,6α-epoxy-cholesterol and histamine metabolism, and that the compound displays cell differentiation and anti-tumour activities.

5,6-Epoxy-cholesterols contribute to the anticancer pharmacology of tamoxifen in breast cancer cells

Tamoxifen (Tam) is a selective estrogen receptor modulator (SERM) that remains one of the major drugs used in the hormonotherapy of breast cancer (BC). In addition to its SERM activity, we recently showed that the oxidative metabolism of cholesterol plays a role in its anticancer pharmacology. We established that these effects were not regulated by the ER but by the microsomal antiestrogen binding site/cholesterol-5,6-epoxide hydrolase complex (AEBS/ChEH). The present study aimed to identify the oxysterols that are produced under Tam treatment and to define their mechanisms of action. Tam and PBPE (a selective AEBS/ChEH ligand) stimulated the production and the accumulation of 5,6α-epoxy-cholesterol (5,6α-EC), 5,6α-epoxy-cholesterol-3β-sulfate (5,6-ECS), 5,6β-epoxy-cholesterol (5,6β-EC) in MCF-7 cells through a ROS-dependent mechanism, by inhibiting ChEH and inducing sulfation of 5,6α-EC by SULT2B1b. We showed that only 5,6α-EC was responsible for the induction of triacylglycerol (TAG) biosynthesis by Tam and PBPE, through the modulation of the oxysterol receptor LXRβ. The cytotoxicity mediated by Tam and PBPE was triggered by 5,6β-EC through an LXRβ-independent route and by 5,6-ECS through an LXRβ-dependent mechanism. The importance of SULT2B1b was confirmed by its ectopic expression in the SULT2B1b(-) MDA-MB-231 cells, which became sensitive to 5,6α-EC, Tam or PBPE at a comparable level to MCF-7 cells. This study established that 5,6-EC metabolites contribute to the anticancer pharmacology of Tam and highlights a novel signaling pathway that points to a rationale for re-sensitizing BC cells to Tam and AEBS/ChEH ligands.

Quantitative evaluation of auraptene and umbelliferone, chemopreventive coumarins in citrus fruits, by HPLC-UV-FL-MS

An analytical strategy, based on the development of two HPLC methods with spectrophotometric (UV), spectrofluorometric (FL), and mass spectrometric (MS) detection, has been developed to investigate the presence of and to quantitate two important chemopreventive coumarins, auraptene and umbelliferone, in foodstuffs. The analytes were determined in fruits, and fruit parts, of plants belonging to the Citrus , Poncirus , and Fortunella genera, to test their nutraceutical potential. The method validation has been carried out according to international guidelines, with good results in terms of precision (RSD < 6.9%) and extraction yields (>91%). Application to the quantitative analysis of auraptene and umbelliferone in several kinds of citrus fruits was successful, providing reliable and consistent data. Exploiting three different kinds of detection, the analytical methodology proposed herein has been demonstrated to be sound but versatile, as well as reliable. Performances and results were compared and always found in good agreement among themselves. Thus, this approach is suitable for the identification and simultaneous quantitation of auraptene and umbelliferone in citrus fruits, with the aim of evaluating their nutraceutical potential.

Effects of Auraptene on IGF-1 Stimulated Cell Cycle Progression in the Human Breast Cancer Cell Line, MCF-7

Auraptene is being investigated for its chemopreventive effects in many models of cancer including skin, colon, prostate, and breast. Many mechanisms of action including anti-inflammatory, antiproliferative, and antiapoptotic effects are being suggested for the chemopreventive properties of auraptene. We have previously shown in the N-methylnitrosourea induced mammary carcinogenesis model that dietary auraptene (500 ppm) significantly delayed tumor latency. The delay in time to tumor corresponded with a significant reduction in cyclin D1 protein expression in the tumors. Since cyclin D1 is a major regulator of cell cycle, we further studied the effects of auraptene on cell cycle and the genes related to cell cycle in MCF-7 cells. Here we show that auraptene significantly inhibited IGF-1 stimulated S phase of cell cycle in MCF-7 cells and significantly changed the transcription of many genes involved in cell cycle.

Cholesterol and breast cancer development

Breast cancer is the most commonly occurring type of cancer in the world. Among the environmental factors believed to be responsible for this phenomenon, cholesterol has recently received considerable attention. Epidemiologic studies have provided inconclusive results, indicating that there may be a relationship between abnormal plasma cholesterol levels and breast cancer risk. However, more compelling evidence has been obtained in laboratory studies, and they indicate that cholesterol is capable of regulating proliferation, migration, and signaling pathways in breast cancer. In vivo studies have also indicated that plasma cholesterol levels can regulate tumor growth in mouse models. The recognition of cholesterol as a factor contributing to breast cancer development identifies cholesterol and its metabolism as novel targets for cancer therapy.

Surprising unreactivity of cholesterol-5,6-epoxides towards nucleophiles

We recently established that drugs used for the treatment and the prophylaxis of breast cancers, such as tamoxifen, were potent inhibitors of cholesterol-5,6-epoxide hydrolase (ChEH), which led to the accumulation of 5,6α-epoxy-cholesterol (5,6α-EC) and 5,6β-epoxy-cholesterol (5,6β-EC). This could be considered a paradox because epoxides are known as alkylating agents with putative carcinogenic properties. We report here that, as opposed to the carcinogen styrene-oxide, neither of the ECs reacted spontaneously with nucleophiles. Under catalytic conditions, 5,6β-EC remains unreactive whereas 5,6α-EC gives cholestan-3β,5α-diol-6β-substituted compounds. These data showed that 5,6-ECs are stable epoxides and unreactive toward nucleophiles in the absence of a catalyst, which contrasts with the well-known reactivity of aromatic and aliphatic epoxides. These data rule out 5,6-EC acting as spontaneous alkylating agents. In addition, these data support the existence of a stereoselective metabolism of 5,6α-EC.

Differences in gene expression profiles and carcinogenesis pathways between colon and rectal cancer

OBJECTIVE

Colon cancer is more common in the USA and Europe than that in China, for reasons that are unclear. The aim of this study was to investigate the differences in gene expression profiles and carcinogenesis pathways between colon and rectal cancer.

METHODS

Expression profiling of primary tumor tissues from 12 colon and 12 rectal cancers was performed using oligonucleotide microarray analysis. All samples were strictly matched by clinical features. Bioinformatic analyses such as the Kyoto Encyclopedia of Genes and Genomes were used to identify genes and pathways specifically associated with colon or rectal cancers.

RESULTS

A total of 824 genes were differentially expressed in colon and rectal cancers. All differential gene interactions in the Signal-Net were analyzed. More genes were differentially expressed and included in the Signal-Net for rectal than colon cancer. Of the genes differentially expressed between colon and rectal cancer, S100P, the Reg family, ACTN1, CAMK2G and ACAT1 were the most significantly altered. Genes involved in the cell cycle pathway were present in rectal and colon cancers, but were more important in rectal cancer. The p53 and metabolic signaling pathways were significantly different in colon and rectal cancers. Gene expression profiles differed between colon and rectal cancer, with metabolic pathways being more important in rectal cancer.

CONCLUSION

The oncogenesis of rectal cancer may be more complex than that of colon cancer. Some genes could be new biomarkers for distinguishing between these two cancers.