Activation of liver X receptor inhibits the development of pulmonary carcinomas induced by 3-methylcholanthrene and butylated hydroxytoluene in BALB/c mice

Metabolic, toxicological, chemical, and commercial perspectives on esterification of dietary polyphenols: a review

Molecular modifications have been practiced for more than a century and nowadays they are widely applied in food, pharmaceutical, or other industries to manipulate the physicochemical, bioactivity, metabolic/catabolic, and pharmacokinetic properties. Among various structural modifications, the esterification/O-acylation has been well-established in altering lipophilicity and bioactivity of parent bioactive compounds, especially natural polyphenolics, while maintaining their high biocompatibility. Meanwhile, various classic chemical and enzymatic protocols and other recently emerged cell factory technology are being employed as viable esterification strategies. In this contribution, the main motivations of phenolic esterification, including the tendency to replace synthetic alkyl phenolics with safer alternatives in the food industry to improve the bioavailability of phenolics as dietary supplements/pharmaceuticals, are discussed. In addition, the toxicity, metabolism, and commercial application of synthetic and natural phenolics are briefly introduced. Under these contexts, the mechanisms and reaction features of several most prevalent chemical and enzymatic esterification pathways are demonstrated. In addition, insights into the studies of esterification modification of natural phenolic compounds and specific pros/cons of various reaction systems with regard to their practical application are provided.

Activation of CTU2 expression by LXR promotes the development of hepatocellular carcinoma

Cytosolic thiouridylase 2 (CTU2) is an enzyme modifying transfer RNAs post-transcriptionally, which has been implicated in breast cancer and melanoma development. And we found CTU2 participated in hepatocellular carcinoma (HCC) progression here. HepG2 cells as well as xenograft nude mice model were employed to investigate the role of CTU2 in HCC development in vitro and in vivo respectively. Further, we defined CTU2 as a Liver X receptor (LXR) targeted gene, with a typical LXR element in the CTU2 promoter. CTU2 expression was activated by LXR agonist and depressed by LXR knockout. Interestingly, we also found CTU2 took part in lipogenesis by directly enhancing the synthesis of lipogenic proteins, which provided a novel mechanism for LXR regulating lipid synthesis. Meanwhile, lipogenesis was active during cell proliferation, particularly in tumor cells. Reduction of CTU2 expression was related to reduced tumor burden and synergized anti-tumor effect of LXR ligands by inducing tumor cell apoptosis and inhibiting cell proliferation. Taken together, our study identified CTU2 as an LXR target gene. Inhibition of CTU2 expression could enhance the anti-tumor effect of LXR ligand in HCC, identifying CTU2 as a promising target for HCC treatment and providing a novel strategy for the application of LXR agonists in anti-tumor effect.

CD36 inhibition reduces non-small-cell lung cancer development through AKT-mTOR pathway

Lung cancer is the most common cause of cancer-related deaths worldwide and is caused by multiple factors, including high-fat diet (HFD). CD36, a fatty acid receptor, is closely associated with metabolism-related diseases, including cardiovascular disease and cancer. However, the role of CD36 in HFD-accelerated non-small-cell lung cancer (NSCLC) is unclear. In vivo, we fed C57BL/6J wild-type (WT) and CD36 knockout (CD36-/-) mice normal chow or HFD in the presence or absence of pitavastatin 2 weeks before subcutaneous injection of LLC1 cells. In vitro, A549 and NCI-H520 cells were treated with free fatty acids (FFAs) to mimic HFD situation for exploration the underlying mechanisms. We found that HFD promoted LLC1 tumor growth in vivo and that FFAs increased cell proliferation and migration in A549 and NCI-H520 cells. The enhanced cell or tumor growth was inhibited by the lipid-lowering agent pitavastatin, which reduced lipid accumulation. More importantly, we found that plasma soluble CD36 (sCD36) levels were higher in NSCLC patients than those in healthy ones. Compared to that in WT mice, the proliferation of LLC1 cells in CD36-/- mice was largely suppressed, which was further repressed by pitavastatin in HFD group. At the molecular level, we found that CD36 inhibition, either with pitavastatin or plasmid, reduced proliferation- and migration-related protein expression through the AKT/mTOR pathway. Taken together, we demonstrate that inhibition of CD36 expression by pitavastatin or other inhibitors may be a viable strategy for NSCLC treatment.

m6A modification mediates SLC3A2/SLC7A5 translation in 3-methylcholanthrene-induced uroepithelial transformation

3-Methylcholanthracene (3-MC) is one of the most carcinogenic polycyclic aromatic hydrocarbons (PAHs). Long-term exposure to PAHs has been thought of as an important factor in urothelial tumorigenesis. N6-methyladenosine (m6A) exists widely in eukaryotic organisms and regulates the expression level of specific genes by regulating mRNA stability, translation efficiency, and nuclear export efficiency. Currently, the potential molecular mechanisms that regulate m6A modification for 3-MC carcinogenesis remain unclear. Here, we profiled mRNA, m6A, translation and protein level using "-omics" methodologies, including transcriptomes, m6A profile, translatomes, and proteomics in 3-MC-transformed urothelial cells and control cells. The key molecules SLC3A2/SLC7A5 were screened and identified in 3-MC-induced uroepithelial transformation. Moreover, SLC7A5/SLC3A2 promoted uroepithelial cells malignant phenotype in vitro and in vivo. Mechanically, METTL3 and ALKBH5 mediated m6A modification of SLC3A2/SLC7A5 mRNA in 3-MC-induced uroepithelial transformation by upregulating the translation of SLC3A2/SLC7A5. Furthermore, programmable m6A modification of SLC3A2/SLC7A5 mRNA affected the expression of its proteins. Taken together, our results revealed that the m6A modification-mediated SLC3A2/SLC7A5 translation promoted 3-MC-induced uroepithelial transformation, suggesting that targeting m6A modification of SLC3A2/SLC7A5 may be a potential therapeutic strategy for bladder cancer related to PAHs.

IFI44L as a novel epigenetic silencing tumor suppressor promotes apoptosis through JAK/STAT1 pathway during lung carcinogenesis

Numerous evidence showed that the occurrence and development of lung cancer is closely related to environmental pollution. Therefore, new environmental response predictive markers are urgently needed for early diagnosis and screening of lung cancer. Interferon-induced protein 44-like (IFI44L) has been shown to be related in a variety of tumors, but its function and mechanism during lung carcinogenesis still have remained largely unknown. In this study, gene expression and methylation status were analyzed through online tools and malignant transformation models. Differentially expressed cell models and xenograft tumor models were established and used to clarify the gene function. RT-qPCR, western blotting, immunohistochemistry, and co-immunoprecipitation (Co-IP) were used to explore the mechanism. Results showed that IFI44L was dramatically downexpressed during lung carcinogenesis, and its low expression may be attributed to DNA methylation. Overexpression of IFI44L obviously inhibited cell growth and promoted apoptosis. After knockdown of IFI44L expression, the proliferation ability was remarkably increased and the apoptosis was significantly reduced. Functional enrichment showed that IFI44L was involved in apoptosis and JAK/STAT1 signaling pathway, and was highly correlated with downstream molecules. After overexpression of IFI44L, the expression of P-STAT1 and downstream molecules XAF1, OAS1, OAS2 and OAS3 were significantly increased. After knockdown of STAT1 expression, the pro-apoptotic effect of IFI44L was reduced. Co-IP results showed that IFI44L had protein interaction with STAT1. Results proved that IFI44L promoted STAT1 phosphorylation and activated the JAK/STAT1 signaling pathway by directly binding to STAT1 protein, thereby leading to cell apoptosis. Our study revealed that IFI44L promotes cell apoptosis and exerts tumor suppressors by activating the JAK/STAT1 signaling pathway. It further suggests that IFI44L has clinical therapeutic potential and may be a promising biomarker during lung carcinogenesis.

Evaluation of selected antidiabetics in cardiovascular complications associated with cancer cachexia

So far, the cardio-protective potential of antidiabetics is proved, but their effect on cardiovascular complications associated with cancer cachexia is not explored until now. Insulin resistance and glucose intolerance along with systemic inflammation are prominent in cachexia but the potential effect of antidiabetic agents especially those belonging to biguanide, DPP4 inhibitors and SGLT2 on the heart are not studied till now. In present study, the effect of metformin, vildagliptin, teneligliptin, dapagliflozin and empagliflozin on cardiovascular complications associated with cancer cachexia by using B16F1 induced metastatic cancer cachexia and urethane-induced cancer cachexia was studied. These antidiabetic agents proved to be beneficial against cachexia-induced atrophy of the heart, preserved ventricular weights, maintained cardiac hypertrophic index, preserved the wasting of cardiac muscles assessed by HE staining, Masson trichrome staining, periodic acid Schiff staining and picro-Sirius red staining. Altered cardiac gene expression was attenuated after treatment with selected antidiabetics, thus preventing cardiac atrophy. Also, antidiabetic agents treatment improved the serum creatinine kinase MB, Sodium potassium ATPase and collagen in the heart. Reduction in blood pressure and heart rate was observed after treatment with antidiabetic agents. Results of our study show that the selected antidiabetics prove to be beneficial in attenuating the cardiac atrophy and helps in regulation of hemodynamic stauts in cancer cachexia-induced cardiovascular complications. Our study provides some direction towards use of selected antidiabetic agents in the management of cardiovascular complications associated with cancer cachexia and the study outcomes can be useful in desiging clinical trials.

Pre-transplant Transcriptional Signature in Peripheral Blood Mononuclear Cells of Acute Renal Allograft Rejection

Acute rejection (AR) is closely associated with renal allograft dysfunction. Here, we utilised RNA sequencing (RNA-Seq) and bioinformatic methods to characterise the peripheral blood mononuclear cells (PBMCs) of patients with acute renal allograft rejection. Pretransplant blood samples were collected from 32 kidney allograft donors and 42 corresponding recipients with biopsies classified as T cell-mediated rejection (TCMR, n = 18), antibody-mediated rejection (ABMR, n = 5), and normal/non-specific changes (non-AR, n = 19). The patients with TCMR and ABMR were assigned to the AR group, and the patients with normal/non-specific changes (n = 19) were assigned to the non-AR group. We analysed RNA-Seq data for identifying differentially expressed genes (DEGs), and then gene ontology (GO) analysis, Reactome, and ingenuity pathway analysis (IPA), protein—protein interaction (PPI) network, and cell-type enrichment analysis were utilised for bioinformatics analysis. We identified DEGs in the PBMCs of the non-AR group when compared with the AR, ABMR, and TCMR groups. Pathway and GO analysis showed significant inflammatory responses, complement activation, interleukin-10 (IL-10) signalling pathways, classical antibody-mediated complement activation pathways, etc., which were significantly enriched in the DEGs. PPI analysis showed that IL-10, VEGFA, CXCL8, MMP9, and several histone-related genes were the hub genes with the highest degree scores. Moreover, IPA analysis showed that several proinflammatory pathways were upregulated, whereas antiinflammatory pathways were downregulated. The combination of NFSF14+TANK+ANKRD 33 B +HSPA1B was able to discriminate between AR and non-AR with an AUC of 92.3% (95% CI 82.8–100). Characterisation of PBMCs by RNA-Seq and bioinformatics analysis demonstrated gene signatures and biological pathways associated with AR. Our study may provide the foundation for the discovery of biomarkers and an in-depth understanding of acute renal allograft rejection.

DNA methylation and hydroxymethylation associated with gene expression regulatory network during 3-methylcholanthrene induced lung cell malignant transformation

3-methylcholanthrene (3-MCA) is a typical representative PAH. It has strong toxicity and is a typical chemical carcinogen. However, the epigenetic mechanisms underlying 3-MCA-induced tumourigenesis are largely unknown. In this study, a model of the 3-MCA-induced malignant transformation of human bronchial epithelial (HBE) cells was established successfully. The profiles of gene expression and DNA methylation and hydroxymethylation were obtained and analysed with an Illumina HiSeq 4000. A total of 707 genes were found to be significantly up-regulated, and 686 genes were found to be significantly down-regulated. Compared to control cells, 8545 mRNA-associated differentially methylated regions and 15,121 mRNA-associated differentially hydroxymethylated regions in promoters were found to be significantly altered in transformed cells. By using mRNA expression and DNA methylation and hydroxymethylation interaction analysis, 99 differentially expressed genes were identified. Among them, CA9 and EGLN3 were verified to be significantly down-regulated, and CARD6 and LCP1 were shown to be significantly up-regulated, and these genes mainly participated in cell growth, migration and invasion, indicating that these genes were key genes involved in the 3-MCA-induced malignant transformation of HBE cells. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that a large number of differentially expressed genes (DEGs) were involved mainly in RNA polymerase II transcription factor activity, chemical carcinogenesis, base-excision repair (BER), cytokine-cytokine receptor interactions, glycerolipid metabolism, steroid hormone biosynthesis, cAMP signalling pathways and other signalling pathways. Our study suggested that characteristic gene alterations associated with DNA methylation and hydroxymethylation could play important roles in environmental 3-MCA-induced lung carcinogenesis.

Encapsulation of LXR ligand by D-Nap-GFFY hydrogel enhances anti-tumorigenic actions of LXR and removes LXR-induced lipogenesis

Background and purpose: Activation of liver X receptor (LXR) by its ligand T0901317 (T317) enhances interferon-γ (IFNγ) production to inhibit tumor growth. However, induction of severe hypertriglyceridemia and fatty liver by T317 limits its application. The naphthylacetic acid modified D-enantiomeric-glycine-phenylalanine-phenylalanine-tyrosine (D-Nap-GFFY) can form a nanofiber hydrogel which is selectively taken up by antigen-presenting cells (APCs). In this study, we determined if D-Nap-GFFY-encapsulated T317 (D-Nap-GFFY-T317) can potently inhibit tumor growth while having no adverse lipogenic effects on the liver. Methods: We prepared D-Nap-GFFY-T317 nanofiber hydrogel and subcutaneously injected it into IFNγ deficient (IFNγ^-/-) and wild-type (WT) mice with lung carcinoma, either inoculated LLC1 cells or urethane-induced carcinoma. Mice received oral T317 administration were used for comparison. Effects of treatment on tumor growth, lipogenesis and involved mechanisms were investigated. Results: Compared with T317 oral administration, injection of D-Nap-GFFY-T317 more potently inhibited LLC1 tumor growth in mice. The inhibition was dependent on LXR-activated IFNγ expression in APCs. D-Nap-GFFY-T317 increased M1 while reducing M2 type macrophages in tumors. Associated with activation of IFNγ expression, D-Nap-GFFY-T317 enhanced dendritic cell maturation and infiltration into tumors, increased CD3⁺/CD8⁺ cells in tumors, and inhibited tumor angiogenesis. Similarly, D-Nap-GFFY-T317 more potently inhibited growth of urethane-induced lung carcinomas than T317 oral administration. In these two tumor models, T317 oral administration, but not D-Nap-GFFY-T317 injection, activated hepatic lipogenesis and induced fatty liver. Conclusion: Our study demonstrates that D-Nap-GFFY-T317 inhibits lung tumor growth without adverse effects on the liver, indicating the hydrogel-encapsulated LXR ligand might be a novel therapy for tumor treatment.

ER-Negative Breast Cancer Is Highly Responsive to Cholesterol Metabolite Signalling

Interventions that alter cholesterol have differential impacts on hormone receptor positive- and negative-breast cancer risk and prognosis. This implies differential regulation or response to cholesterol within different breast cancer subtypes. We evaluated differences in side-chain hydroxycholesterol and liver X nuclear receptor signalling between Oestrogen Receptor (ER)-positive and ER-negative breast cancers and cell lines. Cell line models of ER-positive and ER-negative disease were treated with Liver X Receptor (LXR) ligands and transcriptional activity assessed using luciferase reporters, qPCR and MTT. Publicly available datasets were mined to identify differences between ER-negative and ER-positive tumours and siRNA was used to suppress candidate regulators. Compared to ER-positive breast cancer, ER-negative breast cancer cells were highly responsive to LXR agonists. In primary disease and cell lines LXRA expression was strongly correlated with its target genes in ER-negative but not ER-positive disease. Expression of LXR’s corepressors (NCOR1, NCOR2 and LCOR) was significantly higher in ER-positive disease relative to ER-negative, and their knock-down equalized sensitivity to ligand between subtypes in reporter, gene expression and viability assays. Our data support further evaluation of dietary and pharmacological targeting of cholesterol metabolism as an adjunct to existing therapies for ER-negative and ER-positive breast cancer patients.

Determination of volatile organic compounds in SW620 colorectal cancer cells and tumor-bearing mice

Early diagnosis and early treatment are important factors in reducing colorectal cancer (CRC) metastasis and mortality. Volatile organic compounds (VOCs) released by the human body have great potential for use in clinical diagnosis and therapeutic monitoring for CRC. The aim of our study was to identify VOCs with high specificity and high sensitivity for CRC and to provide a method for early diagnosis of CRC. Gas chromatography-mass spectrometry (GC-MS) was utilized to analyze metabolites in both the in vivo and in vitro experimental groups. In vivo, VOCs were analyzed in the blood of mice after cell inoculation and tumor resection. In vitro experiments were performed by comparing changes in VOCs in an HCoEpiC cell group, control group, SW620 cell group and Arsenic trioxide + SW620 group. We observed changes in VOCs in a series of CRC SW620 cells in vivo and in vitro. Among these changes, we found that the concentrations of 8 substances, including acetone, increased with tumor growth. Nine substances were found to be significantly elevated in the SW620 cancer cell group compared with the other groups. Only one substance was consumed by the tumor in both the in vivo and in vitro experiments. Our study showed that alkanes, lipids, alcohols, ketones, aldehyde, butylated hydroxytoluene (BHT) and hexamethylcyclotrisiloxane all existed at different levels in SW620 CRC cells compared to those in normal cells. We need more research to further confirm this hypothesis.

Activation of liver X receptor plays a central role in antiviral actions of 25-hydroxycholesterol

Production of 25-hydroxycholesterol (25HC), a potent inhibitor of viral infection, is catalyzed by cholesterol 25-hydroxylase (CH25H). We previously reported that 25HC induced CH25H expression in a liver X receptor (LXR)-dependent manner, implying that LXR can play an important role in antiviral infection. In this study, we determined that activation of LXR by 25HC or synthetic ligands [T0901317 (T317) or GW3965] inhibited infection of herpes simplex virus type 1 (HSV-1) or MLV-(VSV)-GFP in HepG2 cells or RAW 264.7 macrophages. Genetic deletion of LXRα, LXRβ, or CH25H expression in HepG2 cells by CRISPR/Cas9 method increased cell susceptibility to HSV-1 infection and attenuated the inhibition of LXR on viral infection. Lack of interferon (IFN)-γ expression also increased cell susceptibility to viral infection. However, it attenuated, but did not block, the inhibition of LXR on HSV-1 infection. In addition, expression of CH25H, but not IFN-γ, was inversely correlated to cell susceptibility to viral infection and the antiviral actions of LXR. Metabolism of 25HC into 25HC-3-sulfate (25HC3S) by cholesterol sulfotransferase-2B1b moderately reduced the antiviral actions of 25HC because 25HC3S is a weaker inhibitor of HSV-1 infection than 25HC. Furthermore, administration of T317 to BALB/c mice reduced HSV-1 growth in mouse tissues. Taken together, we demonstrate an antiviral system of 25HC with involvement of LXR activation, interaction between CH25H and IFN-γ, and 25HC metabolism.

Time-dependent LXR/RXR pathway modulation characterizes capillary remodeling in inflammatory corneal neovascularization

Inflammation in the normally immune-privileged cornea can initiate a pathologic angiogenic response causing vision-threatening corneal neovascularization. Inflammatory pathways, however, are numerous, complex and are activated in a time-dependent manner. Effective resolution of inflammation and associated angiogenesis in the cornea requires knowledge of these pathways and their time dependence, which has, to date, remained largely unexplored. Here, using a model of endogenous resolution of inflammation-induced corneal angiogenesis, we investigate the time dependence of inflammatory genes in effecting capillary regression and the return of corneal transparency. Endogenous capillary regression was characterized by a progressive thinning and remodeling of angiogenic capillaries and inflammatory cell retreat in vivo in the rat cornea. By whole-genome longitudinal microarray analysis, early suppression of VEGF ligand-receptor signaling and inflammatory pathways preceded an unexpected later-phase preferential activation of LXR/RXR, PPARα/RXRα and STAT3 canonical pathways, with a concurrent attenuation of LPS/IL-1 inhibition of RXR function and Wnt/β-catenin signaling pathways. Potent downstream inflammatory cytokines such as Cxcl5, IL-1β, IL-6 and Ccl2 were concomitantly downregulated during the remodeling phase. Upstream regulators of the inflammatory pathways included Socs3, Sparc and ApoE. A complex and coordinated time-dependent interplay between pro- and anti-inflammatory signaling pathways highlights a potential anti-inflammatory role of LXR/RXR, PPARα/RXRα and STAT3 signaling pathways in resolving inflammatory corneal angiogenesis.

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.

Liver X receptors as potential targets for cancer therapeutics

Liver X receptors (LXRs) are important members of the nuclear receptor family that were originally determined to function in cholesterol transport and the regulation of immune responses. Synthetic LXR ligands have been developed to treat various diseases including diabetes, Alzheimer's disease and atherosclerosis. Previous studies have suggested that LXRs are also involved in numerous types of cancer and are therefore potential targets for cancer therapeutics. The present review summarizes LXR ligands and their mechanisms of action, the effects of LXRs in different types of cancer and their potential applications in clinical treatment. Together, the studies discussed in the present review indicate that LXRs may be potential targets for cancer therapeutics.

Inhibition Role of Atherogenic Diet on Ethyl Carbamate Induced Lung Tumorigenesis in C57BL/6J Mice

With emerging evidence connecting cholesterol dysregulation with disturbed pulmonary homeostasis, we are wondering if diet induced hypercholesterolemia would influence the susceptibility to chemical induced lung tumorigenesis in mice. Six to eight week-old male C57BL/6J mice were fed with either a high-cholesterol atherogenic diet (HCD) or matching normal diet (ND), respectively. Following 3 weeks diet adapting, a multi-dose intraperitoneal injections of ethyl carbamate (urethane, 1 g/kg body weight) were established and lung tumorigenesis assessments were taken after 15 weeks latency period. Compared to the urethane treated ND-fed mice, the HCD-fed mice exhibited significantly decreased lung tumor multiplicity and attenuated pulmonary inflammation, which including reduced influx of leukocytes and down regulated tumor-promoting cyto-/chemokine profile in bronchoalveolar lavage fluid, decreased TLR2/4 expression and NF-κB activation in the lung. As a sensor regulating intracellular cholesterol homeostasis, nuclear receptor LXR-α was up-regulated significantly in the urethane treated HCD-fed mice lungs compared to the ND-fed mice lungs, accompanied with decreased pulmonary free cholesterol content and suppressed tumor cell proliferation. These results suggested that intrapulmonary cholesterol homeostasis, other than systematic cholesterol level, is important in lung tumorigenesis, and LXR activation might partly contribute to the inhibitory role of atherogenic diet on lung tumorigenesis.