scholarly journals Kynurenine Monooxygenase Expression and Activity in Human Astrocytomas

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 2028
Author(s):  
Gustavo Ignacio Vázquez Cervantes ◽  
Benjamín Pineda ◽  
Daniela Ramírez Ortega ◽  
Alelí Salazar ◽  
Dinora Fabiola González Esquivel ◽  
...  
Keyword(s):  
Protein Expression ◽  
Mrna Expression ◽  
Cell Lines ◽  
Kynurenine Pathway ◽  
Primary Brain Tumor ◽  
Rate Limiting Step ◽  
Tryptophan Catabolism ◽  
Tryptophan Oxidation ◽  
Rate Limiting ◽  
Expression And Activity

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. The enzyme indoleamine-2,3-dioxygenase (IDO), which participates in the rate-limiting step of tryptophan catabolism through the kynurenine pathway (KP), is associated with poor prognosis in patients with GBM. The metabolites produced after tryptophan oxidation have immunomodulatory properties that can support the immunosuppressor environment. In this study, mRNA expression, protein expression, and activity of the enzyme kynurenine monooxygenase (KMO) were analyzed in GBM cell lines (A172, LN-18, U87, U373) and patient-derived astrocytoma samples. KMO mRNA expression was assessed by real-time RT-qPCR, KMO protein expression was evaluated by flow cytometry and immunofluorescence, and KMO activity was determined by quantifying 3-hydroxykynurenine by HPLC. Heterogenous patterns of both KMO expression and activity were observed among the GBM cell lines, with the A172 cell line showing the highest KMO expression and activity. Higher KMO mRNA expression was observed in glioma samples than in patients diagnosed with only a neurological disease; high KMO mRNA expression was also observed when using samples from patients with GBM in the TCGA program. The KMO protein expression was localized in GFAP+ cells in tumor tissue. These results suggest that KMO is a relevant target to be explored in glioma since it might play a role in supporting tumor metabolism and immune suppression.

scholarly journals Tryptophan 2,3-Dioxygenase Expression Identified in Murine Decidual Stromal Cells Is Not Essential for Feto-Maternal Tolerance

2020 ◽  
Vol 11 ◽  
Author(s):  
Delia Hoffmann ◽  
Tereza Dvorakova ◽  
Florence Schramme ◽  
Vincent Stroobant ◽  
Benoit J. Van den Eynde
Keyword(s):  
Stromal Cells ◽  
Kynurenine Pathway ◽  
Immune Rejection ◽  
Cell Type ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Tryptophan Catabolism ◽  
Maternal Tolerance ◽  
Rate Limiting

Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO) catalyze the rate-limiting step of tryptophan catabolism along the kynurenine pathway, which has important immuno suppressive properties, particularly in tumor cells and dendritic cells. The prominent expression of IDO1 in the placenta also suggested a role in preventing immune rejection of fetal tissues, and pharmacological inhibition of IDO1 induced abortion of allogeneic fetuses in mice. However, this was later challenged by the lack of rejection of allogeneic fetuses in IDO1-KO mice, suggesting that other mechanisms may compensate for IDO1 deficiency. Here we investigated whether TDO could contribute to feto-maternal tolerance and compensate for IDO1 deficiency in IDO1-KO mice. Expression of TDO mRNA was previously detected in placental tissues. We developed a new chimeric rabbit anti-TDO antibody to confirm TDO expression at the protein level and identify the positive cell type by immunohistochemistry in murine placenta. We observed massive TDO expression in decidual stromal cells, starting at day E3.5, peaking at day E6.5 then declining rapidly while remaining detectable until gestation end. IDO1 was also induced in decidual stromal cells, but only at a later stage of gestation when TDO expression declined. To determine whether TDO contributed to feto-maternal tolerance, we mated TDO-KO and double IDO1-TDO-KO females with allogeneic males. However, we did not observe reduced fertility. These results suggest that, despite its expression in decidual stromal cells, TDO is not a dominant mechanism of feto-maternal tolerance able to compensate for the absence of IDO1. Redundant additional mechanisms of immunosuppression likely take over in these KO mice. The massive expression of TDO during decidualization might suggest a role of TDO in angiogenesis or vessel tonicity, as previously described for IDO1.

scholarly journals Exploitation of the IDO Pathway in the Therapy of Rheumatoid Arthritis

2013 ◽  
Vol 6s1 ◽  
pp. IJTR.S11737 ◽  
Author(s):  
Richard O. Williams
Keyword(s):  
Rheumatoid Arthritis ◽  
Anthranilic Acid ◽  
Kynurenine Pathway ◽  
Gene Encoding ◽  
Rate Limiting Step ◽  
Tryptophan Metabolites ◽  
Synthetic Derivative ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Draining Lymph Nodes

Indoleamine 2,3-dioxygenase (IDO) is the first and rate-limiting step along the kynurenine pathway and is thought to play a key role in immune homeostasis through depletion of tryptophan and accumulation of kynurenines. In this review we summarize recent research into the possibility of harnessing the IDO pathway for the therapy of rheumatoid arthritis. Inhibition of IDO activity, or knockout of the gene encoding IDO, was shown to cause an increase in the severity of collagen-induced arthritis, an animal model of rheumatoid arthritis. The increased severity of disease was associated with elevated numbers of pathogenic Th1 and Th17 cells in the joints and draining lymph nodes. In another study, analysis of the kinetics of expression of downstream kynurenine pathway enzymes during the course of arthritis revealed a potential role for tryptophan metabolites in resolution of arthritis. Furthermore, the therapeutic administration of L-kynurenine or [3,4-dimethoxycinnamonyl]-anthranilic acid (a synthetic derivative of 3-hydroxy-anthranilic acid) significantly reduced both clinical and histological progression of experimental arthritis. These findings raise the possibility of exploiting the IDO pathway for the therapy of autoimmune disease.

Oxidation of L-tryptophan in biology: a comparison between tryptophan 2,3-dioxygenase and indoleamine 2,3-dioxygenase

2009 ◽  
Vol 37 (2) ◽  
pp. 408-412 ◽  
Author(s):  
Sara A. Rafice ◽  
Nishma Chauhan ◽  
Igor Efimov ◽  
Jaswir Basran ◽  
Emma Lloyd Raven
Keyword(s):  
Structural Information ◽  
Recombinant Expression ◽  
Kynurenine Pathway ◽  
Expression Systems ◽  
Indoleamine 2,3 Dioxygenase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
The Family ◽  
And Function ◽  
Rate Limiting

The family of haem dioxygenases catalyse the initial oxidative cleavage of L-tryptophan to N-formylkynurenine, which is the first, rate-limiting, step in the L-kynurenine pathway. In the present paper, we discuss and compare structure and function across the family of haem dioxygenases by focusing on TDO (tryptophan 2,3-dioxygenase) and IDO (indoleamine 2,3-dioxygenase), including a review of recent structural information for both enzymes. The present paper describes how the recent development of recombinant expression systems has informed our more detailed understanding of the substrate binding, catalytic activity and mechanistic properties of these haem dioxygenases.

Bromodomain Inhibition By OTX015 Regulates c-MYC and HEXIM1 in a Panel of Human Acute Leukemia Cell Lines

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5957-5957
Author(s):  
Marie-Magdelaine Coudé ◽  
Thorsten Braun ◽  
Jeannig Berrou ◽  
Mélanie Dupont ◽  
Raphael Itzykson ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Expression ◽  
Mrna Expression ◽  
Rna Polymerase Ii ◽  
Cell Lines ◽  
Leukemia Cell ◽  
K562 Cells ◽  
Antileukemic Activity ◽  
Protein Levels ◽  
Gene And Protein Expression

Abstract Background: The bromodomain-containing protein 4 (BRD4) activates the transcription elongation factor b (P-TEFb) which regulates RNA polymerase II. Conversely, hexamethylene bisacetamide (HMBA) inducible protein 1 (HEXIM1) inactivates P-TEFb. BRD4/HEXIM1 interplay influences cell cycle progression and tumorigenesis. It has been widely demonstrated that BRD4 knockdown or inhibition by JQ1 is associated with c-MYC downregulation and antileukemic activity. We recently reported that the small molecule BRD2/3/4 inhibitor OTX015 (Oncoethix, Lausanne, Switzerland), currently in clinical development, mimics the effects of JQ1 (Braun et al, ASH 2013). We evaluated the effect of OTX015 on c-MYC, BRD2/3/4, and HEXIM1 in human in vitro leukemic models. Methods: c-MYC, BRD2/3/4 and HEXIM1 expression was assessed in six acute myeloid leukemia (AML; K562, HL-60, NB4, NOMO-1, KG1, OCI-AML3) and two acute lymphoid leukemia (ALL; JURKAT and RS4-11) cell lines after exposure to 500 nM OTX015. Quantitative RT-PCR and Western blotting were performed at different time points (24-72h). A heatmap was computed with R-software. Results: c-MYC RNA levels were ubiquitously downregulated in all AML and ALL cell lines after 24h exposure to OTX015 (Figure 1). c-MYC protein levels decreased to a variable extent at 24-72h in all cell lines evaluated other than KG1. BRD2, BRD3 and BRD4 mRNA expression was significantly decreased in K562 cells (known to be OTX015-resistant) after 48h exposure to OTX015 but was increased in HL60 and NOMO-1 cells, while minimal to no increases were observed in other cell lines. OTX015 induced a decrease in BRD2 protein expression in most cell lines, but not in K562 cells. In contrast, decreased BRD4 protein expression was only seen in the OCI-AML3, NB4 and K562 cell lines. BRD3 protein levels were not modified after OTX015 exposure in all cell lines evaluated other than KG1. HEXIM1 mRNA expression increased after 24h exposure to 500 nM OTX015 in all cell lines except OTX015-resistant K562 cells in which the increase was considered insignificant (less than two-fold). Increases in HEXIM1 protein levels were observed in OCI-AML3, JURKAT and RS4-11 cell lines at 24-72h but not in K562 cells. Conclusion: Taken together, these results show that BRD inhibition by OTX015 modulates HEXIM1 gene and protein expression, in addition to c-MYC decrease and BRD variations. HEXIM1 upregulation seems to be restricted to OTX015-sensitive cell lines and was not significantly affected in OTX015-resistant K562 cells. Further studies are needed to clarify the role of HEXIM1 in antileukemic activity of BRD inhibitors. Figure 1: Heatmap of gene expression after exposure to 500 nM OTX015 for 24 or 48h in AML and ALL cell lines. Repression in blue. Overexpression in red. Figure 1:. Heatmap of gene expression after exposure to 500 nM OTX015 for 24 or 48h in AML and ALL cell lines. Repression in blue. Overexpression in red. Disclosures Riveiro: OTD: Employment. Herait:OncoEthix: Employment. Dombret:OncoEthix: Research Funding.

Hypoxia Drives AML Proliferation in the Bone Marrow Microenvironment Via Macrophage Inhibitory Factor

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1721-1721
Author(s):  
Amina M Abdul-Aziz ◽  
Manar S Shafat ◽  
Lyubov Zaitseva ◽  
Matthew J Lawes ◽  
Stuart A Rushworth ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Protein Expression ◽  
Mrna Expression ◽  
Cell Lines ◽  
Bone Marrow Microenvironment ◽  
Inhibitory Factor ◽  
Bone Marrow Niche ◽  
Hematopoietic Stem ◽  
Hypoxic Conditions

Abstract Introduction Hypoxia is an important component of the bone marrow microenvironment and the hematopoietic stem cell niche. Studies have shown that hypoxia contributes to the development and maintenance of acute myeloid leukemia (AML) cells within the bone marrow microenvironment. Hypoxia is principally maintained by members of the hypoxia-inducible factor (HIF), in particular HIF1a and its target genes, including MIF. We have previously shown that AML cells express constitutively high macrophage migration inhibitory factor (MIF) which drives IL-8 expression by the BM-MSC which in turn supports AML cell survival and proliferation. The aim of the present study is to determine if there is a connection between the role of hypoxia in regulating AML survival and MIF survival signals. Furthermore we investigate the role BM-MSC in regulating the hypoxic response. Methods Primary AML and BM-MSC were isolated from AML patients following informed consent and under approval from the UK National Research Ethics Service (LRCEref07/H0310/146). AML cell lines and primary AML blasts were cultured under normoxic (20% oxygen) or hypoxic conditions (1% oxygen) for 4 - 24 hours, mRNA expression of MIF, HIF1a, VEGF and IL-8 were determined by RT-PCR. MIF and IL-8 protein was determined using target specific ELISA. HIF1a protein expression was determined by western blotting. Hypoxia-mimetic agents, cobalt chloride (CoCl2) and desferrioxamine (DFO) were used. Cell proliferation was determines using CellTiter Glo and trypan blue exclusion. CFU-assays were performed using complete methylcellulose media. Results To determine If MIF is regulated by HIF1a in AML cells, we mimicked hypoxic conditions using CoCl2 and DFO in AML cells. Both CoCl2 and DFO upregulate MIF transcription and protein expression in OCI-AML3 cell lines and in primary AML blasts. Moreover, hypoxia increases both MIF mRNA expression and MIF chemokine expression compared to normoxic conditions. Lentiviral mediated knockdown of MIF in AML cells show significantly reduced cell proliferation and colony formation in methylcellulose media. Recombinant MIF induced interleukin-8 in AML blasts and the MIF inhibitor blocked MIF induced IL-8 release. Lentiviral mediated KD of HIF1a decreased MIF expression in human AML cells and a significant reduced their proliferative capacity. Finally we found that hypoxia increased MIF in AML blasts which was further increased when in co-culture with BM-MSC. Conclusions The results reported here suggest that hypoxia significantly affects the expression of the survival cytokine MIF in AML blasts. Furthermore, we show that BM-MSC regulate HIF1a induced MIF expression in AML under hypoxic conditions. We propose this hypoxia regulated HIF1a/MIF axis is essential to blast survival in the bone marrow niche. Disclosures Rushworth: Infinity Pharmaceuticals: Research Funding.

scholarly journals High Expression of LTBP2 Contributes to Poor Prognosis in Colorectal Cancer Patients and Correlates with the Mesenchymal Colorectal Cancer Subtype

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Ying Huang ◽  
Guihua Wang ◽  
Chunmei Zhao ◽  
Rong Geng ◽  
Shu Zhang ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Overall Survival ◽  
Protein Expression ◽  
Mrna Expression ◽  
Cell Lines ◽  
Critical Role ◽  
Prognostic Significance ◽  
Poor Overall Survival ◽  
Expression Levels ◽  
Mrna And Protein Expression

Colorectal cancer (CRC) is a complex and heterogeneous disease with four consensus molecular subtypes (CMS1-4). LTBP2 is a member of the fibrillin/LTBP super family and plays a critical role in tumorigenesis by activating TGF-β in the CMS4 CRC subtype. So far, the expression and prognostic significance of LTBP2 in CRC remains obscure. In this study, we aimed to analyze the mRNA and protein expression levels of LTBP2 in CRC tissues and then estimate their values as a potential prognostic biomarker. We detected the mRNA expression of LTBP2 in 28 cases of fresh CRC tissues and 4 CRC cell lines and the protein expression of LTBP2 in 483 samples of CRC tissues, matched tumor-adjacent tissues, and benign colorectal diseases. LTBP2 protein expression was then correlated to patients’ clinical features and overall survival. Both LTBP2 mRNA and protein expression levels in CRC tissues were remarkably superior to those in adjacent normal colorectal tissues (P=0.0071 and P<0.001, respectively), according to TCGA dataset of CRC. High LTBP2 protein expression was correlated with TNM stage (P<0.001), T stage (P<0.001), N stage (P<0.001), and M stage (P<0.001). High LTBP2 protein expression was related to poor overall survival in CRC patients and was an independent prognostic factor for CRC. LTBP2 mRNA expression was especially higher in the CMS4 subtype (P<0.001), which was confirmed in CRC cell lines. Our data suggested that LTBP2 may act as an oncogene in the development of colorectal cancer and have important significance in predicting CRC prognosis. LTBP2 could be a novel biomarker and potential therapeutic target for mesenchymal colorectal cancer and can improve the outcome of high-risk CRC.

scholarly journals Citrus Flavanone Naringenin Induces Browning and Brown Adipogenesis: Role of PPARgamma

2021 ◽  
Vol 5 (Supplement_2) ◽  
pp. 382-382
Author(s):  
Yang Yang ◽  
Xinyun Xu ◽  
Haley Overby ◽  
Kelsey Hildreth ◽  
Ling Zhao
Keyword(s):  
Protein Expression ◽  
Mrna Expression ◽  
Cell Lines ◽  
Differentiation Markers ◽  
Beneficial Effects ◽  
Funding Sources ◽  
White Adipocytes ◽  
Oil Red O ◽  
Brown Adipogenesis

Abstract Objectives Browning of white adipose tissue and brown adipogenesis induced by PPARg agonists have shown beneficial effects on obesity and associated metabolic disorders. Naringenin, a citrus flavanone, is a promising nutrient for obesity prevention partially through PPARg activation. We previously reported that naringenin significantly enhanced the isoproterenol (ISO)-stimulated thermogenesis by upregulating Ucp1 and Pgc1α in 3T3-L1 cell lines (murine white adipocytes). However, the effects of naringenin on browning and brown adipogenesis and its mechanisms have not been fully explored. We aim to investigate the effects of naringenin on browning and brown adipogenesis and its potential mechanisms in vitro. Methods Murine primary stromal white preadipocytes and murine brown preadipocytes were treated with 10 microM naringenin. PPARg knockdown (PPARg-KD) and scrambled nontargeting control (SCR) in 3T3-L1 cell lines and murine brown preadipocytes were generated and treated with naringenin (10 microM). Oil red o staining was performed to quantify lipid accumulation corresponding to the level of differentiation and the brown adipogenesis. mRNA and protein expression of candidate genes involved in thermogenesis and differentiation were analyzed by qRT-PCR and western blot, respectively. Results In murine primary stromal white adipocytes, naringenin significantly increased Ucp1 mRNA expression at the basal state and significantly enhanced the ISO-stimulated upregulation of Ucp1 and Pgc1α mRNA expression. PPARg-KD significantly blocked the naringenin-induced upregulation of Ucp1 and Pgc1α mRNA. In addition, naringenin significantly promoted the differentiation of brown preadipocytes as determined by oil red o lipid staining. Consistently, protein expression of general differentiation markers including FABP4, HSL, PLIN, and ATGL and thermogenic markers UCP1 and PGC1 α were significantly increased by naringenin, which was significantly attenuated by PPARg knockdown. Conclusions Combined with our previous study showing that naringenin transactivated PPARg using reporter assays, we demonstrated that naringenin induced browning of primary stromal white adipocytes and promoted brown adipogenesis through PPARg activation. Funding Sources The work was supported by funding from NIH.

Glutathione and Glutathione Utilizing Enzymes Are Key Determinants in the Sensitivity of Myeloma Cells to Arsenic Trioxide as Well as Its Mechanism of Action.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 5143-5143
Author(s):  
Delia Gutman ◽  
Alejo Morales ◽  
Jennifer M. McCafferty ◽  
Emilio Volz ◽  
Tatiana Eguizabal ◽  
...  
Keyword(s):  
Cell Death ◽  
Arsenic Trioxide ◽  
Cell Lines ◽  
Mechanism Of Action ◽  
De Novo ◽  
Single Agent ◽  
Building Blocks ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Abstract Arsenic trioxide (ATO, Trisenox) is currently being tested in clinical trials as a single agent or in combination with other agents that have activity in multiple myeloma (MM). We and others have demonstrated that glutathione (GSH) levels can influence the ability of ATO to induce cell death in MM cell lines/patient samples and based on these data have initiated a trial to test the safety and efficacy of the combination of ATO and ascorbic acid for the treatment of refractory/relapsed MM. Therefore we performed expression profiling on 4 MM cell lines treated with ATO over a 48 timecourse. Affymetrix Hu133 2.0 plus arrays were hybridized and up to 7035 out of 54,675 probe sets displayed a change and up to 1546 probes sets displayed 2 fold or greater changes compared to untreated cells at 6 hrs. By only looking at genes that increased in all four cell lines we restricted our search to less than 365 probes sets at any given time point. Interestingly the cells appear to have initiated several pathways that are consistent with an attempt to enhance GSH synthesis. Upregulation of transporters of cysteine (xCT) and glycine (Glyt1) as well as enzymes that convert methionine to cysteine (cystathionase) and serine to glycine (serine hydroxymethyl transferase-1) was observed. Moreover the rate-limiting step of the glutathione salvage pathway gamma-glutamyltransferase is also upregulated. Together this suggests an increase in the building blocks for GSH that can be used for de novo synthesis. The rate limiting step for this reaction is performed by gamma-glutamate cysteine ligase which both the catalytic and modifier subunits are upregulated. GSH can also be regenerated from GSSG by glutathione reductase (GR) in an NADPH-dependent fashion. Both GR and the NADPH generating malic enzyme are also upregulated following treatment with ATO. While consistent with our previous findings the data do not provide much insight as to how the GSH is utilized. The only GSH utilizing enzyme that was observed to be upregulated were the cytosolic and mitochondrial forms of glutaredoxin. Glutathione peroxidase (GPx) activity is not altered by ATO treatment. However GPx baseline expression and activity do correlate with sensitivity of MM cell lines to ATO. We also determined GSTP1 activity in the cells and found that it was expressed in 4/5 MM cell lines tested. In contrast to GPx, GSTP1 baseline expression did not correlate with sensitivity to ATO. However this pattern of expression correlated with our previous findings regarding these cells demonstrating differences in caspase dependence of ATO-induced cell death. The one line that did not express GSTP1, RPMI 8226, also utilizes caspase-independent mechanisms of cell death. Transfection of the GSTP1A allele into these cells could render cells more resistant to ATO-induced apoptosis at concentrations of ATO that are not likely to be achieved in patients. Interestingly transfection of the GSTP1B allele could not render cells more resistant, however like GSTP1A it resulted in inhibition of the caspase-independent pathway. Taken together these data confirm that GSH is an important modulator of ATO therapy and that GPx expression may determine the sensitivity of cells to ATO while GSTP1 can affect the mechanism of action by which ATO-induces apoptosis.

scholarly journals Restoration of Epigenetically Silenced Sulfatase 1 Expression by 5-Aza-2′-Deoxycytidine Sensitizes Hepatocellular Carcinoma Cells to Chemotherapy-Induced Apoptosis

2015 ◽  
Vol 3 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Abdirashid Shire ◽  
Gwen Lomberk ◽  
Jin-Ping Lai ◽  
Hongzhi Zou ◽  
Norihiko Tsuchiya ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Dna Methylation ◽  
Protein Expression ◽  
Mrna Expression ◽  
Cell Lines ◽  
Gene Copy ◽  
Drug Induced ◽  
Sulfatase Activity ◽  
Induced Apoptosis ◽  
Hcc Cells

Background: Hepatocellular carcinoma (HCC) is the second most frequent cause of cancer death worldwide. Sulfatase 1 (SULF1) functions as a tumor suppressor in HCC cell lines in vitro but also has an oncogenic effect in some HCCs in vivo. Aim: The purpose of this study was to examine the mechanisms regulating SULF1 and its function in HCC. Methods: First, SULF1 mRNA and protein expression were examined. Second, we examined SULF1 gene copy numbers in HCC cells. Third, we assessed whether DNA methylation or methylation and/or acetylation of histone marks on the promoter regulate SULF1 expression. Finally, we examined the effect of 5-aza-2′-deoxycytidine (5-Aza-dC) on sulfatase activity and drug-induced apoptosis. Results: SULF1 mRNA was downregulated in nine of eleven HCC cell lines, but only in six of ten primary tumors. SULF1 mRNA correlated with protein expression. Gene copy number assessment by fluorescence in situ hybridization showed intact SULF1 alleles in low-SULF1-expressing cell lines. CpG island methylation in the SULF1 promoter and two downstream CpG islands did not show an inverse correlation between DNA methylation and SULF1 expression. However, chromatin immunoprecipitation showed that the SULF1 promoter acquires a silenced chromatin state in low-SULF1-expressing cells through an increase in di/trimethyl-K9H3 and trimethyl-K27H3 and a concomitant loss of activating acetyl K9, K14H3 marks. 5-Aza-dC restored SULF1 mRNA expression in SULF1-negative cell lines, with an associated increase in sulfatase activity and sensitization of HCC cells to cisplatin-induced apoptosis. Conclusion: SULF1 gene silencing in HCC occurs through histone modifications on the SULF1 promoter. Restoration of SULF1 mRNA expression by 5-Aza-dC sensitized HCC cells to drug-induced apoptosis.

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