Lysine-specific Demethylase 1 Gene Research Articles

Lysine-Specific Demethylase 1 Affects the Progression of Papillary Thyroid Carcinoma via HIF1α and microRNA-146a.

Lysine-specific demethylase 1 (LSD1) stabilizes hypoxia-inducible factor 1α (HIF1α) to advance tumor progression, while HIF1α functions as a transcription factor to increase the expression of microRNA-146a (miR-146a). We aim to investigate whether LSD1 affects the development of papillary thyroid carcinoma (PTC) via HIF1α and miR-146a. In vitro assays were performed with Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines. In vivo assays were conducted with established xenograft tumors in nude mice. This study was conducted at our lab. PTC tissues and corresponding adjacent normal tissues were obtained from 45 patients hospitalized in Sun Yat-Sen Memorial Hospital. Assays were conducted using Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines, as well as 50 male BALB/c nude mice. Cells were transfected with sh-LSD1, sh-GABPA, oe-LSD1, oe-HIF1α, miR-146a mimic, and miR-146a inhibitor. In addition, K1 cells expressing lv-oe-LSD1, lv-miR-146a inhibitor, lv-oe-LSD1 or miR-146a inhibitor were injected into the right side of the mice. LSD1 gene and protein expression patterns were analyzed in 45 clinical PTC tissue samples. Expression of LSD1, HIF1α, miR-146a, and GA-binding protein transcription factor alpha (GABPA), as well as their effects on PTC. LSD1 was highly expressed in clinical PTC tissues. LSD1 stabilized HIF1α and inhibited the degradation of its ubiquitin proteasome. HIF1α was enriched in the promoter region of miR-146a, an upregulated miRNA in PTC. HIF1α increased miR-146a expression to promote PTC progression in vitro, which was achieved by inhibiting GABPA, a target gene of miR-146a. LSD1 upregulated miR-146a to enhance the development and metastasis of PTC in nude mice. Our results show that LSD1 functions as an oncogene in PTC by upregulating HIF1α and miR-146a, elucidating an understanding of undefined mechanisms associated with tumor progression in PTC.

LSD1 Inhibitor 4SC-202 Inducing Apoptosis in Myelodysplastic Syndrome Cells Via NF-κb-HO-1 Pathway

Aims: Human histone lysine-specific demethylase 1(LSD1) inhibit gene transcription and thereby block myeloid differentiation, apoptosis and cell cycle in AML. 4SC-202, a novel inhibitor of LSD1, is potential therapeutic agent for treating Myelodysplastic syndrome, while its mechanism of action remains unclear. M ainly method : In the study, LSD1 and HO-1 gene expression were detected in MDS/AML patients. After MDS cell line SKM-1 was treated with 4SC-202, cell viability, apoptosis and cell cycle were detected by CCK-8 or FACS. Lastly, western blotting analyzed that the agent caused the change of the related cellular function protein in SKM-1 cells. K ey findings: We found that LSD1 and HO-1 were overexpression in MDS/AML patients. LSD1 inhibitor 4SC-202 inhibited cell viability. The agent induced apoptosis by up-regulated BAX and cleaved caspase3/9 as well as down-regulated BCL-2, arrested cell cycle in the G2/M phase by down-regulated CDK1 and up-regulated p21, as well as inhibited activation of the NF-κB pathway and decreased HO-1. LSD1 and HO-1 expression were decreased after exposure with the NF-κB inhibitor OBY11-7082. Silencing LSD1 by LSD1 siRNA hardly caused apoptosis in SKM-1 cells, while the combination of Bay11-7082 and silencing LSD1 significantly decreased LSD1 and HO-1 expression and further increased apoptosis. While up-regulated HO-1 significantly limited the 4SC-202-induced down-regulation of BCL-2, up-regulation of cleaved caspase 3/9 and suppressed activation of NF-κB pathway as well as thereby attenuated the agent efficacy. S ignificant : In conclusion, LSD1 inhibitor 4SC-202 induced apoptosis through the NF-κB-mediated HO-1 pathway. LSD1 might be a potential target for the treatment of MDS. Disclosures No relevant conflicts of interest to declare.

Expression of lysine-specific demethylase 1 in hepatocellular carcinoma tissues and its effect on cell proliferation and invasion

Objective To investigate the expression of lysine-specific demethylase 1 (LSD1) in hepatocellular carcinoma tissues, and to explore the effects of down-regulation of LSD1 gene expression on proliferation and invasion of human hepatoma HepG2 cells. Methods A total of 91 cases of hepatocellular carcinoma undergoing elective surgery in our hospital and Henan Cancer Hospital were selected. Immunohistochemistry was used to detect the expression of LSD1 protein in hepatocellular carcinoma tissues and adjacent tissues. Human hepatoma HepG2 cells were cultured and divided into LSD1 interference sequence group, negative control group and blank group. Real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) was used to detect the expression of LSD1 gene in cells. Methyl thiazol tetrazolium (MTT) assay was used to detect cell proliferation. Transwell chamber was used to detect cell invasion. Western blotting was used to detect the expression of LSD1, Snail, E-cadherin and N-cadherin proteins in cells. Results The positive expression rate of LSD1 protein in hepatocellular carcinoma tissues was 81.32%, which was significantly higher than that in adjacent tissues (35.16%, P<0.01). The expression of LSD1 protein in hepatocellular carcinoma tissues was related to the degree of differentiation, TNM staging and vascular invasion (P<0.05). The relative expression level of LSD1 mRNA in LSD1 interference sequence group was 1.19±0.10, which was significantly lower than that in the negative control group and blank group (2.29±0.14 and 2.34±0.11, P<0.05). The absorbance (A) values at 24, 48, 72 and 96 h in the LSD1 interference sequence group were 0.23±0.05, 0.32±0.08, 0.38±0.08 and 0.52±0.03, respectively, which were significantly lower than those in the negative control group (0.38±0.08, 0.49±0.05, 0.67±0.04 and 0.77±0.10) and blank group (0.33±0.03, 0.52±0.09, 0.70±0.08 and 0.78±0.07, P<0.05). The number of invasive cells in the LSD1 interference sequence group was (86.3±3.9), which was significantly less than that in the negative control group (110.6±9.4) and the blank group (117.7±7.0, P<0.05). The relative expression levels of LSD1, Snail, and N-cadherin proteins in the LSD1 interference sequence group were (0.25±0.03, 0.30±0.02 and 0.32±0.03), which were significantly lower than those in the negative control group (0.77±0.06, 0.76±0.10 and 0.67±0.04) and blank group (0.84±0.14, 0.74±0.07 and 0.69±0.06, P<0.05), and the relative expression level of E-cadherin protein (0.71±0.05) was significantly higher than in the negative control group (0.37±0.02) and blank group (0.34±0.04, P<0.05). Conclusion LSD1 protein was highly expressed in hepatocellular carcinoma tissues, and might play an important role in the proliferation and invasion of human hepatoma HepG2 cells through epithelial-mesenchymal transition. Key words: Carcinoma, hepatocellular; Lysine-specific demethylase 1; Proliferation; Invasion; Epithelial-mesenchymal transition

Silencing of LSD1 gene modulates histone methylation and acetylation and induces the apoptosis of JeKo-1 and MOLT-4 cells.

Lysine-specific demethylase 1 (LSD1) has been identified and biochemically characterized in epigenetics; however, the pathological roles of its dysfunction in mantle cell lymphoma (MCL) and T-cell acute lymphoblastic leukemia remain to be elucidated. In this study, we evaluated LSD1, and histone H3 lysine 4 (H3K4)me1 and H3K4me2 expression in patients with MCL and silenced LSD1 in JeKo-1 and MOLT-4 cells, in order to define its role in JeKo-1 and MOLT-4 cell proliferation and apoptosis. We retrospectively analyzed the protein expression of LSD1, and mono- and dimethylated H3K4 (H3K4me1 and H3K4me2), and cyclin D1 and Ki67 in 30 cases of MCL by immunohistochemistry. The correlation of LSD1, H3K4me1 and H3K4me2 with Ki67 was determined by statistical analysis. LSD1 was silenced by small interfering RNA (siRNA). Cell apoptosis and cell proliferation were detected by flow cytometry and 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) assay. The protein expression levels of LSD1, histone methylated H3K4, histone acetylated H3, cyclin D1, apoptotic proteins, p15 and DNA methyltransferase 1 (DNMT1) were examined by western blot analysis. We demonstrated that LSD1 was upregulated, and that H3K4me1 and H3K4me2 were downregulated in the cases with MCL, compared to those with proliferative lymphadenitis (p<0.05). LSD1 positively correlated with Ki67 in MCL [Cohen's kappa (κ)=0.667, p<0.01]. There was no significant correlation between H3K4me1 and H3K4me2, and Ki67 (κ=−0.182, p>0.05, κ=−0.200, p>0.05). The silencing of LSD1 decreased the levels of the apoptosis-related proteins, Bcl-2, pro-caspase-3 and C-myc, and decreased those of DNMT1 and increased p15, and resulted in the loss of cell viability and the induction apoptosis. The silencing of LSD1 increased the expression of H3K4me1 and H3K4me2, and histone acetylated H3 in the JeKo-1 and MOLT-4 cells. LSD1 siRNA also decreased cyclin D1 expression in the JeKo-1 cells. On the whole, our findings demonstrate that the overexpression of LSD1 may be associated with the pathogenesis in MCL. We demonstrated that the silencing of LSD1 is capable of removing the mono- and dimethyl groups from H3K4, and upregulating the histone acetylation of H3 in JeKo-1 and MOLT-4 cells. The silencing of LSD1 inhibited cell growth and induced cell apoptosis. Of note, in JeKo-1 cells, the silencing of LSD1 decreased cyclin D1 expression, which is one of the genes that contribute to the pathogenesis of MCL. LSD1 may thus be a possible therapeutic target in MCL and acute lymphoblastic leukemia MOLT-4 cells.

LSD1 Substrate Binding and Gene Expression Are Affected by HDAC1-Mediated Deacetylation.

Lysine Specific Demethylase 1 (LSD1) catalyzes the demethylation of histone 3 to regulate gene expression. With a fundamental role in gene regulation, LSD1 is involved in multiple cellular processes, including embryonic development, cell proliferation, and metastasis. Significantly, LSD1 is overexpressed in multiple cancers and has emerged as a potential anticancer drug target. LSD1 is typically found in association with another epigenetic enzyme, histone deacetylase (HDAC). HDAC and LSD1 inhibitor compounds have been tested as combination anticancer agents. However, the functional link between LSD1 and HDAC has yet to be understood in detail. Here, we used a substrate trapping strategy to identify cellular substrates of HDAC1. Using inactive HDAC1 mutants, we identified LSD1 as an HDAC1 substrate. HDAC1 mediated deacetylation of LSD1 at K374 in the substrate binding lobe, which affected the histone 3 binding and gene expression activity of LSD1. The mechanistic link between HDAC1 and LSD1 established here suggests that HDAC inhibitors influence LSD1 activity, which will ultimately guide drug design targeting epigenetic enzymes.

Abstract P117: Lysine Specific Demethylase-1 Deficiency Accelerates the Development of Renal Damage and Hypertension During Long Term Exposure to Sodium

Long term exposure to salt is a demonstrated risk factor for hypertension (HT), as well as cardiovascular and renal (CVR) outcomes. We recently proposed a novel contributor to the etiology of salt-mediated HT: the Lysine Specific Demethylase-1 (LSD1). We showed that LSD1 deficiency (in mice) and LSD1 gene variants (in humans) associate - in response to short term (one week) of sodium loading - with dysregulated renal sodium handling, volume expansion and HT, and RAAS dysfunction. However, the timeline and severity of these changes during long term exposure to sodium, and the protective effects of sodium restriction in LSD1 deficient states have yet to be determined. This study aimed (1) to evaluate the timing of onset for changes in CVR health during long term sodium loading in LSD1 deficient mice and (2) to assess whether a low salt (LS) diet can prevent these effects. LSD1 heterozygous (HET) and WT mice were randomized to high salt (HS) or LS and followed longitudinally for 6 months. BP, plasma aldosterone (Aldo) and albumin/creatinine ratios (A/C) were assessed monthly. The SBP (mm Hg) increased progressively during the study, and reached significance on the 5 th and 6 th month for HS-HET and HS-WT (141±4 and 134±3, respectively, both p&lt;0.05 vs. baseline) but not for LS-HET and LS-WT (128±6 and 120±6, respectively). The SBP effects were driven by a significant interaction between genotype and age (p&lt;0.05). Similar results were obtained for DBP (p&lt;0.05), suggesting a volume mediated effect. HS plasma Aldo was appropriately suppressed. The A/C (μg/mg) was progressively increased in both HS groups, one month prior to the BP change. Namely, A/C reached significance on the 4 th and 5 th month for HS-HET and HS-WT (46±4 and 48±9, respectively, both p&lt;0.05 vs. baseline). The LS diet prevented these changes in both genotypes. Our novel study shows that long term exposure to HS induces kidney damage followed by BP increase, and that these changes are initiated earlier in the LSD1 HET, suggesting LSD1 as a critical component of mechanisms involved in CVR health. Moreover, long term sodium restriction prevented the development of both target organ damage and HT in this model, suggesting that this dietary intervention may be particularly efficient in human carriers of LSD1 gene variants.

Abstract 966: LSD1 functions as a global androgen receptor coactivator and is a therapeutic target in prostate cancer

Abstract Androgen receptor (AR) plays a pivotal role in prostate cancer (PCa) and remains critical for more aggressive castration-resistant PCa (CRPC) through transactivation of multiple genes. Although CRPC is generally responsive to further CYP17A1 inhibition (abiraterone) or more potent AR antagonist (enzalutamide) treatments, patients treated with these agents still relapse within 1-2 years, and high levels of AR and AR regulated genes in many of these relapsed tumors indicate that AR activity has again been restored. Therefore, there remains a need for further novel AR targeted therapies. Initially identified as a component in the REST complex that functions as a transcriptional suppressor, Lysine Specific Demethylase 1 (LSD1) removes the methyl group from histone 3 lysine 4 (H3K4me1 and 2), and turns off the marks of active transcription. Our recent genome-wide integrated analysis of LSD1 and AR chromatin bindings and gene expression profiles indicates that LSD1 is broadly associated with AR regulated enhancers, and LSD1 functions as a coactivator on AR-stimulated genes through demethylating novel histone or nonhistone substrates in addition to H3K4me. LSD1 is also associated with FOXA1 at AR regulated enhancer sites, and an LSD1-FOXA1 interaction enhances binding of both proteins at these sites. These results clearly demonstrated LSD1 as a therapeutic target in prostate cancer. We then accessed if LSD1 enzymatic activity is required for its global AR coactivator function. AR transcription activity is significantly impaired in cells overexpressing a catalytic-deficient LSD1 mutant. In addition, this mutant also decreased FOXA1 binding on AR-regulated enhancers. We then selected of a panel of LSD1 inhibitors (a few of them have been used in clinical trials for lung cancer and leukemia) to assess the effects on AR activity and PCa cell growth. Inhibition of LSD1 consistently impaired AR activity through abrogating acetylated H3K27 at AR-regulated enhancers. LSD1 inhibitor also decreased FOXA1 binding prior to androgen stimulation. While most of inhibitors showed relatively low efficacy in PCa cells (&amp;gt;50μM), LSD1-C12 is highly potent and specific at μM range to dramatically decrease AR activity and PCa cell growth. Overall, our study suggests that the AR coactivator function of LSD1 depends on its enzymatic activity and targeting LSD1 with more specific and potent inhibitors is a promising therapeutic approach to treat PCa. Furthermore, understanding the mechanism of LSD1 coactivator function will potentially advance PCa therapy by targeting LSD1. Citation Format: Shuai Gao, Yanfei Gao, Hansen He, Myles Brown, Steve Balk, Changmeng Cai. LSD1 functions as a global androgen receptor coactivator and is a therapeutic target in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 966. doi:10.1158/1538-7445.AM2015-966

Overexpression of lysine-specific demethylase 1 in ovarian endometriomas and its inhibition reduces cellular proliferation, cell cycle progression, and invasiveness

To investigate whether lysine-specific demethylase 1 (LSD1) is aberrantly expressed in endometriomas and whether treatment with tranylcypromine, an LSD1 inhibitor, has any effect on cell viability, cell cycle, and invasiveness. Laboratory study using human tissues. Academic hospital. Forty-two ectopic endometrial tissue samples, their homologue eutopic endometrial tissue samples, and 70 control endometrial tissue samples. Immunohistochemistry analysis of LSD1 of all human tissue samples, and Western blot analysis, quantitative real-time reverse-transcription polymerase chain reaction analysis, cell viability assay, cell cycle analysis, and invasion assay of eutopic and ectopic endometriotic stromal cells and normal endometrial stromal cells. Immunostaining levels of LSD1, gene and protein expression levels, cell viability, cell cycles, and invasiveness. The expression of the LSD1 gene and protein in endometriosis was elevated. Treatment of endometriotic stromal cells with tranylcypromine statistically significantly reduced the cellular proliferation, cell cycle progression, and invasiveness. Because DNA and histones are intimately intertwined and work in concert in transcription regulation, conceivably histone demethylation activity of LSD1 could be wide ranging. The inhibition of LSD1 activity by tranylcypromine and the resultant inhibition of proliferation, cell cycle progression, and invasiveness suggest that LSD1 may be a candidate therapeutic target for endometriosis.

Lysine-specific demethylase 1-mediated demethylation of histone H3 lysine 9 contributes to interleukin 1β-induced microsomal prostaglandin E synthase 1 expression in human osteoarthritic chondrocytes.

IntroductionMicrosomal prostaglandin E synthase 1 (mPGES-1) catalyzes the terminal step in the biosynthesis of PGE2, a critical mediator in the pathophysiology of osteoarthritis (OA). Histone methylation plays an important role in epigenetic gene regulation. In this study, we investigated the roles of histone H3 lysine 9 (H3K9) methylation in interleukin 1β (IL-1β)-induced mPGES-1 expression in human chondrocytes.MethodsChondrocytes were stimulated with IL-1β, and the expression of mPGES-1 mRNA was evaluated using real-time RT-PCR. H3K9 methylation and the recruitment of the histone demethylase lysine-specific demethylase 1 (LSD1) to the mPGES-1 promoter were evaluated using chromatin immunoprecipitation assays. The role of LSD1 was further evaluated using the pharmacological inhibitors tranylcypromine and pargyline and small interfering RNA (siRNA)-mediated gene silencing. The LSD1 level in cartilage was determined by RT-PCR and immunohistochemistry.ResultsThe induction of mPGES-1 expression by IL-1β correlated with decreased levels of mono- and dimethylated H3K9 at the mPGES-1 promoter. These changes were concomitant with the recruitment of the histone demethylase LSD1. Treatment with tranylcypromine and pargyline, which are potent inhibitors of LSD1, prevented IL-1β-induced H3K9 demethylation at the mPGES-1 promoter and expression of mPGES-1. Consistently, LSD1 gene silencing with siRNA prevented IL-1β-induced H3K9 demethylation and mPGES-1 expression, suggesting that LSD1 mediates IL-1β-induced mPGES-1 expression via H3K9 demethylation. We show that the level of LSD1 was elevated in OA compared to normal cartilage.ConclusionThese results indicate that H3K9 demethylation by LSD1 contributes to IL-1β-induced mPGES-1 expression and suggest that this pathway could be a potential target for pharmacological intervention in the treatment of OA and possibly other arthritic conditions.

Characterization of lysine‐specific demethylase 1 (LSD1) as a potential olfactory receptor regulator

Mouse olfactory sensory neurons (OSNs) express a variety of over 1000 odorant receptor (OR) genes located throughout the genome. Previous studies have shown that each OSN expresses only one OR gene out of the &gt;;1000 possible genes and that the expressed locus lacks an H3K9 trimethylation mark. Lysine specific demethylase 1 (LSD1) is a candidate demethylase that may play a role in the epigenetic pathway of OR gene regulation. Preliminary immunofluorescence experiments have shown that LSD1 displays three phenotypes throughout the cell cycle. LSD1 exhibits a broad, diffuse nuclear staining or a highly localized, punctate nuclear expression pattern. Some punctate nuclei exhibit one distinct compartment of LSD1. Cell synchronization experiments show a significantly higher incidence of punctate LSD1 during G2/M phase and a higher frequency of the distinct LSD1 phenotype during telophase. One possible model suggests that all OR loci are initially silenced by trimethylation and that distinct signals represent active LSD1 complexes which derepress a gene locus for future expression. DNA immuno‐FISH experiments show that active OR gene clusters co‐localize with LSD1 distinct and punctate signals within the nucleus of cycling OP6 cells occasionally, while the control, actin, does not co‐localize with LSD1 in cycling cells. Co‐localization would suggest possible LSD1 and OR gene interaction, in which LSD1 may function in the derepression of the expressed OR locus.

Molecular Cloning, Tissue Expression, and Analysis with Genome DNA Methylation of Porcine LSD1 Gene

Lysine-specific demethylase 1 (LSD1) functioned as a demethyl methylase gene, underlying a wide range of biological processes, including cancer, cell apoptosis, differentiation, and development. To further understand the functions of the porcine LSD1 gene, we first obtained cDNA sequence of porcine LSD1 gene, using in silico cloning method. We further found that the porcine LSD1 gene has two transcripts, in which cDNA sequences are 2,716 and 2,656 bp, ORF are 2,622 and 2,562 bp, respectively. Then, RT-PCR analysis showed that the LSD1 gene is expressed in various tissues and relatively higher in the tissues of ovary, kidney, and spleen. Besides, the LSD1 gene was expressed higher in the growth nonage and peaked at 3 days in muscle tissue. Meanwhile, the expression of two transcript variants of LSD1 gene presented the same change trend. Besides, the level of DNA methylation was approximately fourfold higher in a 3-day muscle than in an old pig (180 days), significantly positive related to the gene expression of LSD1 (R = 0.9362, P < 0.05), and declined with growing age. Cloning, expression pattern, and analysis with genome DNA methylation of porcine LSD1 gene laid a foundation to clarify the molecular mechanisms of porcine growth and development and also for further work on animal breeding.

Lysine-Specific Demethylase 1: An Epigenetic Regulator of Salt-Sensitive Hypertension

Hypertension (HTN) represents a complex heritable disease in which environmental factors may directly affect gene function via epigenetic mechanisms. The aim of this study was to test the hypothesis that dietary salt influences the activity of a histone-modifying enzyme, lysine-specific demethylase 1 (LSD-1), which in turn is associated with salt-sensitivity of blood pressure (BP). Animal and human studies were performed. Salt-sensitivity of LSD-1 expression was assessed in wild-type (WT) and LSD-1 heterozygote knockout (LSD-1(+/-)) mice. Clinical relevance was tested by multivariate associations between single-nuclear polymorphisms (SNPs) in the LSD-1 gene and salt-sensitivity of BP, with control of dietary sodium, in a primary African-American hypertensive cohort and two replication hypertensive cohorts (Caucasian and Mexican-American). LSD-1 expression was modified by dietary salt in WT mice with lower levels associated with liberal salt intake. LSD-1(+/-) mice expressed lower LSD-1 protein levels than WT mice in kidney tissue. Similar to LSD-1(+/-) mice, African-American minor allele carriers of two LSD-1 SNPs displayed greater change in systolic BP (SBP) in response to change from low to liberal salt diet (rs671357, P = 0.01; rs587168, P = 0.005). This association was replicated in the Hispanic (rs587168, P = 0.04) but not the Caucasian cohort. Exploratory analyses demonstrated decreased serum aldosterone concentrations in African-American minor allele carriers similar to findings in the LSD-1(+/-) mice, decreased α-EnaC expression in LSD-1(+/-) mice, and impaired renovascular responsiveness to salt loading in minor allele carriers. The results of this translational research study support a role for LSD-1 in the pathogenesis of salt-sensitive HTN.

HDAC and LSD1 Inhibitors Synergize to Induce Cell Death in Acute Leukemia Cells

Abstract 1427Histone deacetylase inhibitors (HDACi) are a class of emerging epigenetic therapies which are being used to treat cancer. Two HDACi (vorinostat and romidepsin) are FDA approved for cutaneous T-cell lymphoma. HDACi have been employed in clinical trials for acute leukemia, but single agent activity has been limited. Improved efficacy is observed when combined with other anticancer agents. In the current study we addressed acute leukemia models using vorinostat, a pan-HDACi that inhibits HDAC class I, II, and IV and entinostat, a newer HDACi that inhibits HDAC class I more specifically. These HDACi were combined with inhibition of another histone modifying enzyme: lysine specific demethylase 1 (LSD1). The LSD1 gene encodes a favin-dependent monoamine oxidase, which demethylates mono- and di-methylated lysines, specifically lysines 4 and 9 on histone 3 (H3K4 and H3K9), thus it is also involved in gene regulation through post-translational histone modification. LSD1 overexpression has been linked to human carcinogenesis in bladder carcinomas, lung cancer, and poorly differentiated neuroblastoma. However, it has not been studied in hematologic malignancies. Because LSD1 is structurally similar to monoamine oxidase (MAO), it has been shown that nonselective MAO inhibitors also inhibit LSD1. Here we employed tranylcypromine, a monoamine oxidase inhibitor (MAOi), as an irreversible LSD1 inhibitor. Recently published work from our laboratory has shown synergistic effects of combined HDAC and LSD1 inhibition in brain tumors (glioblastoma multiforme). Similar results have been published in breast cancer cells, but no work has been done in hematological malignancies. The objective of this study was to investigate the possible synergy of HDAC and LSD1 inhibitors in acute leukemia cells. LSD1 protein expression in several leukemia cells lines was analyzed by Western blot analysis. LSD1 was expressed in all leukemia cell lines tested, which included T-cell ALL (Jurkat, Sub-T1, MOLT4), B-cell ALL (JM-1,697), and Philadelphia chromosome positive ALL (Z33, Z119, Z181). To determine whether synergy exists between HDACi and LSD1 inhibitors, Jurkat cells were exposed to different concentrations of tranylcypromine and vorinostat or entinostat. After 24 hr, DNA fragmentation was assessed by propidium iodide (PI) staining followed by flow cytometric analysis. A combination index (CI) less than 1.0 is representative of synergism as measured by Calcusyn software. Results showed a synergistic effect on DNA fragmentation when combining the 2.5 μM dose of vorinostat with a range of tranylcypromine doses (1 mM CI= 0.78, 1.5 mM CI= 0.49, and 2 mM CI= 0.39). The same effect was observed with the combination of 2.5 μM entinostat with 2 mM tranylcypromine (CI=0.52). Viability studies performed with the same drug concentrations in conbination also showed statistically significant cell death. Additional acute leukemia cell lines, 697 and MOLT-4, also demonstrated significantly increased cell death with the combination relative to treatment with either agent alone. Since these agents inhibit histone deacetylation and lysine demethylation, we tested whether these histone modifications were promoted by combination treatment. Jurkat cell lysates were generated by acid extraction of histones and Western blot analysis was conducted. We demonstrated that in fact histone acetylation was increased with combination treatment, indicating that these modifications coordinately regulate each other in acute leukemia cells. A molecular target for LSD1 is p53, a tumor suppressor protein whose activity is regulated by lysine methylation and demethylation. Western blot analysis showed that p53 is downregulated in leukemia cells after exposure to the combination of HDAC and LSD1 inhibitors. Future studies will address if p53 downregulation is a trigger for the synergistic cell death. Taken together, our data shows the efficacy of combining LSD1 inhibitors with HDAC inhibitors in multiple acute leukemia models. Since tranylcypromine is also a FDA-approved agent, these results urge the design of a feasible and effective clinical trial combining LSD1 and HDAC inhibitors for acute leukemia. Disclosures:No relevant conflicts of interest to declare.

Role of the Lysine-Specific Demethylase 1 in the Proinflammatory Phenotype of Vascular Smooth Muscle Cells of Diabetic Mice

Insulin resistance and type 2 diabetes are major risk factors for vascular complications. Vascular smooth muscle cells (VSMCs) derived from db/db mice, an established mouse model of type 2 diabetes, displayed enhanced inflammatory gene expression and proatherogenic responses. We examined the hypothesis that aberrant epigenetic chromatin events may the underlying mechanism for this persistent dysfunctional behavior and "memory" of the diabetic cells. Chromatin immunoprecipitation assays showed that levels of histone H3 lysine 4 dimethylation (H3K4me2), a key chromatin mark associated with active gene expression, were significantly elevated at the promoters of the inflammatory genes monocyte chemoattractant protein-1 and interleukin-6 in db/db VSMCs relative to db/+ cells. Tumor necrosis factor-alpha-induced inflammatory gene expression, H3K4me2 levels, and recruitment of RNA polymerase II at the gene promoters were also enhanced in db/db VSMCs, demonstrating the formation of open chromatin poised for transcriptional activation in diabetes. On the other hand, protein levels of lysine-specific demethylase1 (LSD1), which negatively regulates H3K4 methylation and its occupancy at these gene promoters, were significantly reduced in db/db VSMCs. High glucose (25 mmol/L) treatment of human VSMCs also increased inflammatory genes with parallel increases in promoter H3K4me2 levels and reduced LSD1 recruitment. LSD1 gene silencing with small interfering RNAs significantly increased inflammatory gene expression and enhanced VSMC-monocyte binding in nondiabetic VSMCs. In contrast, overexpression of LSD1 in diabetic db/db VSMCs inhibited their enhanced inflammatory gene expression. These results demonstrate novel functional roles for LSD1 and H3K4 methylation in VSMCs and inflammation. Dysregulation of their actions may be a major mechanism for vascular inflammation and metabolic memory associated with diabetic complications.