ADORA3 activation promotes goblet cell differentiation via enhancing HMGCS2-mediated ketogenesis in ulcerative colitis.

ADORA3 is mainly expressed in intestinal tract, and has the potential to promote the expression of mucin 2 (MUC2), the function-related factor of goblet cells, under asthma conditions. This study aims to confirm the induction and mechanisms of ADORA3 activation on goblet cells in ulcerative colitis (UC). A significant decrease in ADORA3 expression was found in mucosal biopsies from UC patients and in the colons of colitis mice. This reduction correlated negatively with disease severity and positively with goblet cell number. ADORA3 activation mitigated dextran sulfate sodium (DSS)-induced colitis and facilitated ATOH1-mediated goblet cell differentiation in both in vivo and in vitro. Metabolomics analysis unveiled that ADORA3 activation bolstered ketogenesis, leading to elevated levels of the metabolite BHB. Subsequently, BHB heightened the activity of HDAC1/2, augmenting histone acetylation at the H3K9ac site within the promoter region of the ATOH1 gene. Furthermore, the reason for ADORA3 activation to enhance ketogenesis was attributed to controlling the competitive binding among ß-arrestin2, SHP1 and PPARγ. This results in the non-ligand-dependent activation of PPARγ, thereby promoting the transcription of HMGCS2. The exact mechanisms by which ADORA3 promoted goblet cell differentiation and alleviated UC were elucidated using MRS1191 and shHMGCS2 plasmid. Collectively, ADORA3 activation promoted goblet cell differentiation and alleviated UC by enhancing ketogenesis via the "BHB-HDAC1/2-H3K9ac" pathway.

A novel lncRNA LOC101928222 promotes colorectal cancer angiogenesis by stabilizing HMGCS2 mRNA and increasing cholesterol synthesis.

BACKGROUND: Metastasis is the leading cause of mortality in patients with colorectal cancer (CRC) and angiogenesis is a crucial factor in tumor invasion and metastasis. Long noncoding RNAs (lncRNAs) play regulatory functions in various biological processes in tumor cells, however, the roles of lncRNAs in CRC-associated angiogenesis remain to be elucidated in CRC, as do the underlying mechanisms. METHODS: We used bioinformatics to screen differentially expressed lncRNAs from TCGA database. LOC101928222 expression was assessed by qRT-PCR. The impact of LOC101928222 in CRC tumor development was assessed both in vitro and in vivo. The regulatory mechanisms of LOC101928222 in CRC were investigated by cellular fractionation, RNA-sequencing, mass spectrometric, RNA pull-down, RNA immunoprecipitation, RNA stability, and gene-specific m6A assays. RESULTS: LOC101928222 expression was upregulated in CRC and was correlated with a worse outcome. Moreover, LOC101928222 was shown to promote migration, invasion, and angiogenesis in CRC. Mechanistically, LOC101928222 synergized with IGF2BP1 to stabilize HMGCS2 mRNA through an m6A-dependent pathway, leading to increased cholesterol synthesis and, ultimately, the promotion of CRC development. CONCLUSIONS: In summary, these findings demonstrate a novel, LOC101928222-based mechanism involved in the regulation of cholesterol synthesis and the metastatic potential of CRC. The LOC101928222-HMGCS2-cholesterol synthesis pathway may be an effective target for diagnosing and managing CRC metastasis.

[Inhibition of Lung Squamous Cancer Target HMGCS1 Promotes Cellular Ferroptosis].

BACKGROUND: Targeted therapies are ineffective in lung squamous cancer (LUSC), and the low response rate of immunotherapy hampers its application in LUSC, so it is urgent to explore new strategies for LUSC treatment. Ferroptosis plays an important role in tumour suppression. The aim of this study was to investigate the role and mechanism of targeting 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1) in regulating ferroptosis in LUSC cells, in order to provide a new research direction for LUSC therapy. METHODS: The expression of HMGCS1 in LUSC was analysed by The Cancer Genome Atlas (TCGA) and Clinical Proteomic Tumor Analysis Consortium (CPTAC) online databases; the relationship between HMGCS1 and survival time of lung cancer was analysed by the Kaplan-Meier Plotter online survival database; the expression level of HMGCS1 in LUSC tissues was verified by immunohistochemistry. After interfering with HMGCS1 expression by small interfering RNA (siRNA), cell activity and cell migration ability were detected by CCK8 and Transwell assay; apoptosis was detected by flow cytometry after interfering with HMGCS1 or after treatment with the HMGCS1 inhibitor of hymeglusin; Fe2+, reactive oxygen species (ROS) and lipid peroxidation levels were detected by flow cytometry and high-content confocal fluorescence imaging systems, respectively in SKMES cells after inhibition of HMGCS1; and Western blot was performed to detect the expression of ACSL4, GPX4 and SLC7A11, which are markers of the ferroptosis pathway after inhibition of HMGCS1. RESULTS: HMGCS1 mRNA and protein levels were significantly high in LUSC; siRNA interference with HMGCS1 expression inhibited the proliferative activity and migration ability of LUSC cells, but had no significant effect on apoptosis. Interference with HMGCS1 or treatment with the HMGCS1 inhibitor of hymeglusin significantly promoted intracellular Fe2+, ROS and lipid peroxidation levels in SKMES cells, and induced ferroptosis in LUSC cells; Western blot assay showed that inhibition of HMGCS1 significantly promoted the expression of ACSL4. CONCLUSIONS: Inhibition of HMGCS1, a target of LUSC, promotes ferroptosis in lung cancer cells and provides a research basis for screening new therapeutic targets for LUSC.

Induction of resistance to neurotrophic tropomyosin-receptor kinase inhibitors by HMGCS2 via a mevalonate pathway.

INTRODUCTION: A neurotrophic tropomyosin receptor kinase (NTRK)-tyrosine kinase inhibitor (TKI) has shown dramatic efficacy against malignant tumors harboring an NTRK fusion gene. However, almost all tumors eventually acquire resistance to NTRK-TKIs. METHOD: To investigate the mechanism of resistance to NTRK-TKIs, we established cells resistant to three types of NTRK-TKIs (larotrectinib, entrectinib, and selitrectinib) using KM12 colon cancer cells with a TPM3-NTRK1 rearrangement. RESULT: Overexpression of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) was observed in three resistant cells (KM12-LR, KM12-ER, and KM12-SR) by microarray analysis. Lower expression of sterol regulatory element-binding protein 2 (SREBP2) and peroxisome proliferator activated receptor α (PPARα) was found in two cells (KM12-ER and KM12-SR) in which HMGCS2 was overexpressed compared to the parental KM12 and KM12-LR cells. In resistant cells, knockdown of HMGCS2 using small interfering RNA improved the sensitivity to NTRK-TKI. Further treatment with mevalonolactone after HMGCS2 knockdown reintroduced the NTRK-TKI resistance. In addition, simvastatin and silibinin had a synergistic effect with NTRK-TKIs in resistant cells, and delayed tolerance was observed after sustained exposure to clinical concentrations of NTRK-TKI and simvastatin in KM12 cells. In xenograft mouse models, combination treatment with entrectinib and simvastatin reduced resistant tumor growth compared with entrectinib alone. CONCLUSION: These results suggest that HMGCS2 overexpression induces resistance to NTRK-TKIs via the mevalonate pathway in colon cancer cells. Statin inhibition of the mevalonate pathway may be useful for overcoming this mechanistic resistance.

BET inhibition decreases HMGCS2 and sensitizes resistant pancreatic tumors to gemcitabine.

Efforts to develop targetable molecular bases for drug resistance for pancreatic ductal adenocarcinoma (PDAC) have been equivocally successful. Using RNA-seq and ingenuity pathway analysis we identified that the superpathway of cholesterol biosynthesis is upregulated in gemcitabine resistant (gemR) tumors using a unique PDAC PDX model with resistance to gemcitabine acquired in vivo. Analysis of additional in vitro and in vivo gemR PDAC models showed that HMG-CoA synthase 2 (HMGCS2), an enzyme involved in cholesterol biosynthesis and rate limiting in ketogenesis, is overexpressed in these models. Mechanistic data demonstrate the novel findings that HMGCS2 contributes to gemR and confers metastatic properties in PDAC models, and that HMGCS2 is BRD4 dependent. Further, BET inhibitor JQ1 decreases levels of HMGCS2, sensitizes PDAC cells to gemcitabine, and a combination of gemcitabine and JQ1 induced regressions of gemR tumors in vivo. Our data suggest that decreasing HMGCS2 may reverse gemR, and that HMGCS2 represents a useful therapeutic target for treating gemcitabine resistant PDAC.

Restoration of HMGCS2-mediated ketogenesis alleviates tacrolimus-induced hepatic lipid metabolism disorder.

Tacrolimus, one of the macrolide calcineurin inhibitors, is the most frequently used immunosuppressant after transplantation. Long-term administration of tacrolimus leads to dyslipidemia and affects liver lipid metabolism. In this study, we investigated the mode of action and underlying mechanisms of this adverse reaction. Mice were administered tacrolimus (2.5 mg·kg-1·d-1, i.g.) for 10 weeks, then euthanized; the blood samples and liver tissues were collected for analyses. We showed that tacrolimus administration induced significant dyslipidemia and lipid deposition in mouse liver. Dyslipidemia was also observed in heart or kidney transplantation patients treated with tacrolimus. We demonstrated that tacrolimus did not directly induce de novo synthesis of fatty acids, but markedly decreased fatty acid oxidation (FAO) in AML12 cells. Furthermore, we showed that tacrolimus dramatically decreased the expression of HMGCS2, the rate-limiting enzyme of ketogenesis, with decreased ketogenesis in AML12 cells, which was responsible for lipid deposition in normal hepatocytes. Moreover, we revealed that tacrolimus inhibited forkhead box protein O1 (FoxO1) nuclear translocation by promoting FKBP51-FoxO1 complex formation, thus reducing FoxO1 binding to the HMGCS2 promoter and its transcription ability in AML12 cells. The loss of HMGCS2 induced by tacrolimus caused decreased ketogenesis and increased acetyl-CoA accumulation, which promoted mitochondrial protein acetylation, thereby resulting in FAO function inhibition. Liver-specific HMGCS2 overexpression via tail intravenous injection of AAV8-TBG-HMGCS2 construct reversed tacrolimus-induced mitochondrial protein acetylation and FAO inhibition, thus removing the lipid deposition in hepatocytes. Collectively, this study demonstrates a novel mechanism of liver lipid deposition and hyperlipidemia induced by long-term administration of tacrolimus, resulted from the loss of HMGCS2-mediated ketogenesis and subsequent FAO inhibition, providing an alternative target for reversing tacrolimus-induced adverse reaction.

Perfluorooctanesulfonic acid exposure leads to downregulation of 3-hydroxy-3-methylglutaryl-CoA synthase 2 expression and upregulation of markers associated with intestinal carcinogenesis in mouse intestinal tissues.

Perfluorooctanesulfonic acid (PFOS) is a widely recognized environment pollutant known for its high bioaccumulation potential and a long elimination half-life. Several studies have shown that PFOS can alter multiple biological pathways and negatively affect human health. Considering the direct exposure to the gastrointestinal (GI) tract to environmental pollutants, PFOS can potentially disrupt intestinal homeostasis. However, there is limited knowledge about the effect of PFOS exposure on normal intestinal tissues, and its contribution to GI-associated diseases remains to be determined. In this study, we examined the effect of PFOS exposure on the gene expression profile of intestinal tissues of C57BL/6 mice using RNAseq analysis. We found that PFOS exposure in drinking water significantly downregulates mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a rate-limiting ketogenic enzyme, in intestinal tissues of mice. We found that diets containing the soluble fibers inulin and pectin, which are known to be protective against PFOS exposure, were ineffective in reversing the downregulation of HMGCS2 expression in vivo. Analysis of intestinal tissues also demonstrated that PFOS exposure leads to upregulation of proteins implicated in colorectal carcinogenesis, including ß-catenin, c-MYC, mTOR and FASN. Consistent with the in vivo results, PFOS exposure leads to downregulation of HMGCS2 in mouse and human normal intestinal organoids in vitro. Furthermore, we show that shRNA-mediated knockdown of HMGCS2 in a human normal intestinal cell line resulted in increased cell proliferation and upregulation of key proliferation-associated proteins such as cyclin D, survivin, ERK1/2 and AKT, along with an increase in lipid accumulation. In summary, our results suggest that PFOS exposure may contribute to pathological changes in normal intestinal cells via downregulation of HMGCS2 expression and upregulation of pro-carcinogenic signaling pathways that may increase the risk of colorectal cancer development.

Downregulation of HMGCS2 mediated AECIIs lipid metabolic alteration promotes pulmonary fibrosis by activating fibroblasts.

BACKGROUND: Abnormal lipid metabolism has recently been reported as a crucial signature of idiopathic pulmonary fibrosis (IPF). However, the origin and biological function of the lipid and possible mechanisms of increased lipid content in the pathogenesis of IPF remains undetermined. METHODS: Oil-red staining and immunofluorescence analysis were used to detect lipid accumulation in mouse lung fibrosis frozen sections, Bleomycin-treated human type II alveolar epithelial cells (AECIIs) and lung fibroblast. Untargeted Lipid omics analysis was applied to investigate differential lipid species and identified LysoPC was utilized to treat human lung fibroblasts and mice. Microarray and single-cell RNA expression data sets identified lipid metabolism-related differentially expressed genes. Gain of function experiment was used to study the function of 3-hydroxy-3-methylglutaryl-Coa Synthase 2 (HMGCS2) in regulating AECIIs lipid metabolism. Mice with AECII-HMGCS2 high were established by intratracheally delivering HBAAV2/6-SFTPC- HMGCS2 adeno-associated virus. Western blot, Co-immunoprecipitation, immunofluorescence, site-directed mutation and flow cytometry were utilized to investigate the mechanisms of HMGCS2-mediated lipid metabolism in AECIIs. RESULTS: Injured AECIIs were the primary source of accumulated lipids in response to Bleomycin stimulation. LysoPCs released by injured AECIIs could activate lung fibroblasts, thus promoting the progression of pulmonary fibrosis. Mechanistically, HMGCS2 was decreased explicitly in AECIIs and ectopic expression of HMGCS2 in AECIIs using the AAV system significantly alleviated experimental mouse lung fibrosis progression via modulating lipid degradation in AECIIs through promoting CPT1A and CPT2 expression by interacting with PPARα. CONCLUSIONS: These data unveiled a novel etiological mechanism of HMGCS2-mediated AECII lipid metabolism in the genesis and development of pulmonary fibrosis and provided a novel target for clinical intervention.

Liver-Derived Ketogenesis via Overexpressing HMGCS2 Promotes the Recovery of Spinal Cord Injury.

The liver is the major ketogenic organ of the body, and ketones are reported to possess favorable neuroprotective effects. This study aims to elucidate whether ketone bodies generated from the liver play a critical role in bridging the liver and spinal cord. Mice model with a contusive spinal cord injury (SCI) surgery is established, and SCI induces significant histological changes in mice liver. mRNA-seq of liver tissue shows the temporal changes of ketone bodies-related genes, ß-hydroxybutyrate dehydrogenase (BDH1) and solute carrier family 16 (monocarboxylic acid transporters), member 6 (SLC16A6). Then, an activated ketogenesis model is created with adult C57BL/6 mice receiving the tail intravenous injection of GPAAV8-TBG-Mouse-Hmgcs2-CMV- mCherry -WPRE (HMGCS2liver ) and mice receiving equal AAV8-Null being the control group (Vectorliver ). Then, the mice undergo either a contusive SCI or sham surgery. The results show that overexpression of HMG-CoA synthase (Hmgcs2) in mice liver dramatically alleviates SCI-mediated pathological changes and promotes ketogenesis in the liver. Amazingly, liver-derived ketogenesis evidently alleviates neuron apoptosis and inflammatory microglia activation and improves the recovery of motor function of SCI mice. In conclusion, a liver-spinal cord axis can be bridged via ketone bodies, and enhancing the production of the ketone body within the liver has neuroprotective effects on traumatic SCI.

Compartmentalized activities of HMGCS1 control cervical cancer radiosensitivity.

The underlying mechanisms by which cellular metabolism affects cervical cancer cell radiosensitivity remain poorly understood. Here, we found that loss of 3-hydroxy-3-methylglutaryl coenzyme A synthase 1 (HMGCS1), a key enzyme catalyzing the conversion of acetoacetyl-CoA to HMG-CoA in the cholesterol biosynthesis pathway, sensitizes the cervical cancer cells to radiation. We observed a compartmentalized cellular distribution of HMGCS1 in nuclei, cytosol, and mitochondria of cervical cancer cells and found that cytosolic HMGCS1 and mitochondrial HMGCS1 contribute together to the regulation of radiosensitivity. Mechanistically, we show that cytosolic HMGCS1 regulates radiosensitivity via manipulating the cholesterol metabolism, while mitochondrial HMGCS1 controls mitochondrial gene expression, thereby sustaining the mitochondrial function of cervical cancer cells. Together, our study identifies HMGCS1 as a novel regulator of radiosensitivty in cervical cancer cells, providing a molecular link between altered cholesterol metabolism, mitochondrial respiration, and radiosensitivity. Thus, targeting HMGCS1 may improve the therapeutic outcome of cervical cancer radiotherapy.

HMGCS2 Mediation of Ketone Levels Affects Sorafenib Treatment Efficacy in Liver Cancer Cells.

Primary liver cancer is the fifth leading death of cancers in men, and hepatocellular carcinoma (HCC) accounts for approximately 90% of all primary liver cancer cases. Sorafenib is a first-line drug for advanced-stage HCC patients. Sorafenib is a multi-target kinase inhibitor that blocks tumor cell proliferation and angiogenesis. Despite sorafenib treatment extending survival, some patients experience side effects, and sorafenib resistance does occur. 3-Hydroxymethyl glutaryl-CoA synthase 2 (HMGCS2) is the rate-limiting enzyme for ketogenesis, which synthesizes the ketone bodies, ß-hydroxybutyrate (ß-HB) and acetoacetate (AcAc). ß-HB is the most abundant ketone body which is present in a 4:1 ratio compared to AcAc. Recently, ketone body treatment was found to have therapeutic effects against many cancers by causing metabolic alternations and cancer cell apoptosis. Our previous publication showed that HMGCS2 downregulation-mediated ketone body reduction promoted HCC clinicopathological progression through regulating c-Myc/cyclin D1 and caspase-dependent signaling. However, whether HMGCS2-regulated ketone body production alters the sensitivity of human HCC to sorafenib treatment remains unclear. In this study, we showed that HMGCS2 downregulation enhanced the proliferative ability and attenuated the cytotoxic effects of sorafenib by activating expressions of phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-P38, and p-AKT. In contrast, HMGCS2 overexpression decreased cell proliferation and enhanced the cytotoxic effects of sorafenib in HCC cells by inhibiting ERK activation. Furthermore, we showed that knockdown HMGCS2 exhibited the potential migratory ability, as well as decreasing zonula occludens protein (ZO)-1 and increasing c-Myc expression in both sorafenib-treated Huh7 and HepG2 cells. Although HMGCS2 overexpression did not alter the migratory effect, expressions of ZO-1, c-Myc, and N-cadherin decreased in sorafenib-treated HMGCS2-overexpressing HCC cells. Finally, we investigated whether ketone treatment influences sorafenib sensitivity. We showed that ß-HB pretreatment decreased cell proliferation and enhanced antiproliferative effect of sorafenib in both Huh7 and HepG2 cells. In conclusion, this study defined the impacts of HMGCS2 expression and ketone body treatment on influencing the sorafenib sensitivity of liver cancer cells.

TET2 deficiency sensitizes tumor cells to statins by reducing HMGCS1 expression.

TET2 (ten-eleven-translocation) protein is a Fe(II)- and α-ketoglutarate-dependent dioxygenase that catalyzes DNA demethylation to regulate gene expression. While TET2 gene is frequently mutated in hematological cancer, its enzymatic activity is also compromised in various solid tumors. Whether TET2 deficiency creates vulnerability for cancer cells has not been studied. Here we reported that TET2 deficiency is associated with the change of lipid metabolism processes in acute myeloid leukemia (AML) patient. We demonstrate that statins, the inhibitors of ß-Hydroxy ß-methylglutaryl-CoA (HMG-CoA) reductase and commonly used cholesterol-lowering medicines, significantly sensitize TET2 deficient tumor cells to apoptosis. TET2 directly regulates the expression of HMG-CoA synthase (HMGCS1) by catalyzing demethylation on its promoter region, and conversely TET2 deficiency leads to significant down-regulation of HMGCS1 expression and the mevalonate pathway. Consistently, overexpression of HMGCS1 in TET2-deficient cells rescues statin-induced apoptosis. We further reveal that decrease of geranylgeranyl diphosphate (GGPP), an intermediate metabolite in the mevalonate pathway, is responsible for statin-induced apoptosis. GGPP shortage abolishes normal membrane localization and function of multiple small GTPases, leading to cell dysfunction. Collectively, our study reveals a vulnerability in TET2 deficient tumor and a potential therapeutic strategy using an already approved safe medicine.

Antidiabetic drug metformin suppresses tumorigenesis through inhibition of mevalonate pathway enzyme HMGCS1.

Metformin, an antidiabetic drug, shows some potent antitumor effects. However, the molecular mechanism of metformin in tumor suppression has not been clarified. Here, we provided evidence using in vitro and in vivo data that metformin inhibited mevalonate pathway by downregulation of 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1), a key enzyme in this pathway. Our results further demonstrated that metformin downregulated HMGCS1 expression through inhibition of transcription factor nuclear factor E2-related factor 2. In addition, we determined that HMGCS1 was highly expressed in human liver and lung cancer tissues and associated with lower survival rates. In summary, our study indicated that metformin suppresses tumorigenesis through inhibition of the nuclear factor E2-related factor 2-HMGCS1 axis, which might be a potential target in cancer prevention and treatment.

An acetate-independent pathway for isopropanol production via HMG-CoA in Escherichia coli.

Isopropanol has a good potential as a new fuel substitution. In the model biosynthesis pathway of isopropanol synthesis, acetoacetyl-CoA is converted to acetoacetate by acetoacetyl-CoA transferases, which requires an acetate molecule as a substrate. Herein, a novel isopropanol synthesis pathway based on mammalian ketone metabolic pathway was developed. In this pathway, acetoacetyl-CoA is condensed with acetyl-CoA to generate 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) by HMG-CoA synthase, and then catalyzed by HMG-CoA lyase to generate acetoacetate. This process is acetate-independent. Under the same experimental system using glycerol as carbon source, the E. coli strain MG::ISOP1 containing the novel pathway produced 11.7 times more isopropanol than the strain MG::ISOP0 containing the model pathway. The pta-ackA knockout mutant strain MG∆pta-ackA::ISOP1, which reduced the conversion of acetyl-CoA to acetate, further increased the production from 76 mg/L to 360 mg/L. In another strategy, knocking out atoDA to block the acetoacetate degradation pathway in strain MG∆atoDA::ISOP1 increased the production to 680 mg/L. By knocking out both of pta-ackA and atoDA, strain MGΔpta-ackAΔatoDA::ISOP1 produced 964 mg/L of isopropanol, which was 12.7 times that of MG::ISOP1. This study indicated that the novel pathway is competent for isopropanol synthesis, and provides a new perspective for biosynthesis of isopropanol.

Pan-cancer analysis reveals the oncogenic role of 3-hydroxy-3-methylglutaryl-CoA synthase 1.

BACKGROUND: Emerging studies reveals that 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1) plays vital oncogenic roles in a broad spectrum of human cancers, but there is no pan-cancer evidence on the relationship between HMGCS1 and various tumor types. AIM: To explore the potential role of HMGCS1 across various tumor types based on big clinical data. METHODS: We conducted a pan-cancer analysis across more than 30 tumor types, based on the most comprehensive database available, including TCGA, GSCA, clinical proteomic tumor analysis consortium, Kaplan-Meier Plotter dataset, GEPIA2, TIMER2, STRING, and GDSC dataset. RESULTS: HMGCS1 was highly expressed and negatively correlated with the prognosis in most cancer types. The infiltration levels of cancer associated fibroblast and CD8+ T-cell were closely associated with HMGCS1 expression. Amplification was the most common genetic alteration of HMGCS1 in different cancers, while the frequency of mutation was low. Besides, ACAT2 and MVD were closely correlated and bind to HMGCS1. Pathway enrichment analysis indicated that HMGCS1 was actively involved in steroid biosynthesis. Moreover, high HMGCS1 expression could reduce the sensitivity to most drugs in the GDSC dataset. CONCLUSIONS: Our study revealed the potential oncogenic role of HMGCS1 in cancers.

PXR Suppresses PPARα-Dependent HMGCS2 Gene Transcription by Inhibiting the Interaction between PPARα and PGC1α.

BACKGROUND: PXR is a xenobiotic-responsive nuclear receptor that controls the expression of drug-metabolizing enzymes. Drug-induced activation of PXR sometimes causes drug-drug interactions due to the induced metabolism of co-administered drugs. Our group recently reported a possible drug-drug interaction mechanism via an interaction between the nuclear receptors CAR and PPARα. As CAR and PXR are structurally and functionally related receptors, we investigated possible crosstalk between PXR and PPARα. METHODS: Human hepatocyte-like HepaRG cells were treated with various PXR ligands, and mRNA levels were determined by quantitative reverse transcription PCR. Reporter assays using the HMGCS2 promoter containing a PPARα-binding motif and mammalian two-hybrid assays were performed in HepG2 or COS-1 cells. RESULTS: Treatment with PXR activators reduced the mRNA levels of PPARα target genes in HepaRG cells. In reporter assays, PXR suppressed PPARα-dependent gene expression in HepG2 cells. In COS-1 cells, co-expression of PGC1α, a common coactivator of PPARα and PXR, enhanced PPARα-dependent gene transcription, which was clearly suppressed by PXR. Consistently, in mammalian two-hybrid assays, the interaction between PGC1α and PPARα was attenuated by ligand-activated PXR. CONCLUSION: The present results suggest that ligand-activated PXR suppresses PPARα-dependent gene expression by inhibiting PGC1α recruitment.

Epigenetic inactivation of hydroxymethylglutaryl CoA synthase reduces ketogenesis and facilitates tumor cell motility in clear cell renal carcinoma.

Previously, we have reported that the dysregulation of ketogenesis plays an important role in the carcinogenesis of clear cell renal cell carcinoma (ccRCC). Here, we demonstrate decreased expression of the HMGCS2 gene in ccRCC, a critical enzyme for the synthesis of the ketone body ß-hydroxybutyrate (ß-OHB). We found that the reduced transcription of the HMGCS2 gene in ccRCC cells was significantly correlated to a higher relative methylation rate in its promotor region. The higher methylation rate in the region of the transcription start site and 1st exon of the HMGCS2 gene was, in turn, correlated with a worse clinical outcome for patients. The transcription of HMGCS2 was possible to restore by treatment with 5-aza-2'-deoxycytidine and with the histone deacetylase inhibitor ß-OHB. Therefore, the low levels of the HMGCS2 enzyme in ccRCC may be the consequence of hypermethylation of the HMGCS2 promotor. The ensuing reduction in the ketone body levels further suppresses the transcription of HMGCS2 via a feedback loop. Ectopic expression of HMGCS2 attenuates the migration and invasion of ccRCC but does not affect the proliferative capacity of ccRCC cells in vitro. In addition, we showed that ectopic expression of HMGCS2 boosts the intracellular levels of ß-OHB and that exogenously applied ß-OHB suppresses the motility and invasion of ccRCC. Our study reveals crosstalk between genes that regulate metabolism and their metabolites, thus providing a better understanding of the epigenetic mechanism involved in ccRCC carcinogenesis and suggesting opportunities for metabolic therapy of tumors. Initially, we suggest that the mRNA level of HMGCS2 could serve as a potentially valuable diagnostic (AUC = 0.918, p < 0.001) and prognostic biomarker.

circHMGCS1-016 reshapes immune environment by sponging miR-1236-3p to regulate CD73 and GAL-8 expression in intrahepatic cholangiocarcinoma.

BACKGROUND: Accumulating evidence indicates that circRNAs may serve as essential regulators in the progression of several human cancers, but the function and mechanism of circRNAs in intrahepatic cholangiocarcinoma (ICC) are largely unknown. METHODS: RNA-seq was used to assess differentially expressed circRNAs between 4 ICC and peritumor tissues. Quantitative RT-PCR and in situ hybridization were used to determine the circHMGCS1-016 expression in ICC tissues. The function and mechanism of circHMGCS1-016 were further identified via in vivo experiments. The clinical characteristics and prognostic significance of circHMGCS1-016 were analyzed by a retrospective study. The functions of circHMGCS1-016 were assessed via modifying circRNA expression in ICC cells. Moreover, the molecular mechanisms of circHMGCS1-016 in ICC cells were explored by circRNA precipitation, miRNA immunoprecipitation, SILAC and luciferase reporter assays. RESULTS: We identified that compared with peritumor tissues, ICC tissues expressed hsa_circ_0008621 (circHMGCS1-016) high by RNA-seq, which was further identified by qRT-PCR and in situ hybridization. Moreover, the expression of circHMGCS1-016 was revealed to be associated with survival and recurrence of ICC patients. By regulating circHMGCS1-016 expression, we found that elevated circHMGCS1-016 promoted ICC development both in vitro and in vivo. By SILAC and circRNA-pull down, we demonstrated that circHMGCS1-016 induced ICC cell invasion and reshaped the tumor immune microenvironment via the miR-1236-3p/CD73 and GAL-8 axis. In ICC tissues, we uncovered that a high level of circHMGCS1-016 was positively associated with CD73 and GAL-8 expression and negatively related to the CD8+ T cells infiltration, which was further validated by establishing a humanized mouse tumor model. Importantly, we displayed that ICC patients with high levels of circHMGCS1-016 in tumor tissues benefited less from anti-PD1 treatment compared to those with low levels of circHMGCS1-016. CONCLUSIONS: CircHMGCS1-016 is a forceful contributor in ICC development and immune tolerance via miR-1236-3p/CD73 and GAL-8 axis. CircHMGCS1-016 can be explored as a new potential biomarker and therapeutic target for PD1-resistant ICC.

FOSL1 promotes cholangiocarcinoma via transcriptional effectors that could be therapeutically targeted.

BACKGROUND & AIMS: Cholangiocarcinoma (CCA) is a neoplasia of the biliary tract driven by genetic, epigenetic and transcriptional mechanisms. Herein, we investigated the role of the transcription factor FOSL1, as well as its downstream transcriptional effectors, in the development and progression of CCA. METHODS: FOSL1 was investigated in human CCA clinical samples. Genetic inhibition of FOSL1 in human and mouse CCA cell lines was performed in in vitro and in vivo models using constitutive and inducible short-hairpin RNAs. Conditional FOSL1 ablation was done using a genetically engineered mouse (GEM) model of CCA (mutant KRAS and Trp53 knockout). Follow-up RNA and chromatin immunoprecipitation (ChIP) sequencing analyses were carried out and downstream targets were validated using genetic and pharmacological inhibition. RESULTS: An inter-species analysis of FOSL1 in CCA was conducted. First, FOSL1 was found to be highly upregulated in human and mouse CCA, and associated with poor patient survival. Pharmacological inhibition of different signalling pathways in CCA cells converged on the regulation of FOSL1 expression. Functional experiments showed that FOSL1 is required for cell proliferation and cell cycle progression in vitro, and for tumour growth and tumour maintenance in both orthotopic and subcutaneous xenograft models. Likewise, FOSL1 genetic abrogation in a GEM model of CCA extended mouse survival by decreasing the oncogenic potential of transformed cholangiocytes. RNA and ChIP sequencing studies identified direct and indirect transcriptional effectors such as HMGCS1 and AURKA, whose genetic and pharmacological inhibition phenocopied FOSL1 loss. CONCLUSIONS: Our data illustrate the functional and clinical relevance of FOSL1 in CCA and unveil potential targets amenable to pharmacological inhibition that could enable the implementation of novel therapeutic strategies. LAY SUMMARY: Understanding the molecular mechanisms involved in cholangiocarcinoma (bile duct cancer) development and progression stands as a critical step for the development of novel therapies. Through an inter-species approach, this study provides evidence of the clinical and functional role of the transcription factor FOSL1 in cholangiocarcinoma. Moreover, we report that downstream effectors of FOSL1 are susceptible to pharmacological inhibition, thus providing new opportunities for therapeutic intervention.

Construction of Decision Trees Based on Gene Expression Omnibus Data to Classify Bladder Cancer and Its Subtypes.

BACKGROUND Bladder cancer is a malignant tumor of the genitourinary system. Different subtypes of bladder cancer have different treatment methods and prognoses. Therefore, identifying hub genes affecting other genes is of great significance for the treatment of bladder cancer. MATERIAL AND METHODS We obtained expression profiles from the GSE13507 and GSE77952 datasets from the Gene Expression Omnibus database. First, principal component analysis was used to identify the difference in gene expression in different types of tissues. Differential expression analysis was used to find the differentially expressed genes between normal and tumor tissues, and between tumors with and without muscle infiltration. Further, based on differentially expressed genes, we constructed 2 decision trees for differentiating between tumor and normal tissues, and between muscle-infiltrating and non-muscle-infiltrating tumor tissues. A receiver operating characteristic curve was used to evaluate the prediction effect of the decision trees. RESULTS FAM107A and C8orf4 showed significantly lower expression in bladder cancer tissues than in normal tissues. Regarding muscle infiltration, CTHRC1 showed lower expression and HMGCS2 showed higher expression in non-muscle-infiltrating samples than in those with muscle infiltration. We constructed 2 decision trees for differentiating between tumor and normal tissue, and between tissues with and without muscle infiltration. Both decision trees showed good prediction results. CONCLUSIONS These newly discovered hub genes will be helpful in understanding the occurrence and development of different subtypes of bladder cancer, and will provide new therapeutic targets and biomarkers for bladder cancer.