Lysine-specific demethylase 1 is strongly expressed in poorly differentiated neuroblastoma: implications for therapy

LSD1-mediated epigenetic modification contributes to proliferation and metastasis of colon cancer

BACKGROUND

Emerging evidence has demonstrated that lysine-specific demethylase 1 (LSD1) has an important role in many pathological processes of cancer cells, such as carcinogenesis, proliferation and metastasis. In this study, we characterised the role and molecular mechanisms of LSD1 in proliferation and metastasis of colon cancer.

METHODS

We evaluated the correlation of LSD1, CDH-1 and CDH-2 with invasiveness of colon cancer cells, and investigated the roles of LSD1 in proliferation, invasion and apoptosis of colon cancer cells. We further investigated the mechanisms of LSD1-mediated metastasis of colon cancer.

RESULTS

Lysine-specific demethylase 1 was upregulated in colon cancer tissues, and the high LSD1 expression was significantly associated with tumour-node-metastasis (TNM) stages and distant metastasis. Functionally, inhibition of LSD1 impaired proliferation and invasiveness, and induced apoptosis of colon cancer cells in vitro. The LSD1 physically interacted with the promoter of CDH-1 and decreased dimethyl histone H3 lysine 4 (H3K4) at this region, downregulated CDH-1 expression, and consequently contributed to colon cancer metastasis.

CONCLUSION

Lysine-specific demethylase 1 downregulates the expression of CDH-1 by epigenetic modification, and consequently promotes metastasis of colon cancer cells. The LSD1 antagonists might be a useful strategy to suppress metastasis of colon cancer.

Lysine-specific demethylase 1 (LSD1/KDM1A) contributes to colorectal tumorigenesis via activation of the Wnt/β-catenin pathway by down-regulating Dickkopf-1 (DKK1) [corrected]

We collected paired samples of tumor and adjacent normal colorectal tissues from 22 patients with colorectal carcinoma to compare the differences in the expression of lysine specific demethylase 1 (LSD1) in these two tissues. The results showed that in 19 paired samples (86.4%), LSD1 is more highly expressed in tumor tissue than in normal tissue. To explore the role of LSD1 in colorectal tumorigenesis, we used somatic cell gene targeting to generate an LSD1 knockout (KO) HCT 116 human colorectal cancer cell line as a research model. The analysis of phenotypic changes showed that LSD1 KO colorectal cancer cells are less tumorigenic, both in vivo and in vitro. The differential expression analysis of the cells by mRNA sequencing (RNA-Seq) yielded 2,663 differentially expressed genes, and 28 of these genes had highly significant differences (Q <0.01). We then selected the 4 colorectal cancer-related genes ADM, DKK1, HAS3 and SMURF2 for quantitative real-time PCR verification. The results showed that the differences in the expression of ADM, DKK1 and HAS3 were consistent with those measured using the RNA-Seq data. As DKK1 was the gene with the most significant differential expression, we analyzed the key proteins of the DKK1-related Wnt/β-catenin signaling pathway and found that, after knocking out LSD1, the amount of free β-catenin translocated to the nucleus was significantly reduced and that the transcription of the signaling pathway target gene c-Myc was down-regulated. Our studies show that LSD1 activates the Wnt/β-catenin signaling pathway by down-regulating the pathway antagonist DKK1, which may be one of the mechanisms leading to colorectal tumorigenesis.

High expression of lysine-specific demethylase 1 correlates with poor prognosis of patients with esophageal squamous cell carcinoma

Recent studies have elucidated the role of lysine-specific demethylase 1 (LSD1), a member of the histone demethylases, in epigenetic regulation of tumor suppressing/promoting genes and neoplastic growth. However, the expression of LSD1 in patients with esophageal squamous cell carcinoma (ESCC) is still unknown. Here, we reported that LSD1 expression was elevated in cancerous tissue and correlated with lymph node metastasis and poorer overall survival in patients with ESCC. Compared to EC109 cells, LSD1 expression was unregulated in aggressive cancer cell lines KYSE450 and KYSE150. Knockdown of LSD1 using lentivirus delivery of LSD1-specific shRNA abrogated the migration and invasion of ESCC cells in vitro. Further, a LSD1 inhibitor, tranylcypromine, suppressed H3K4me2 demethylation and attenuated cellular motility and invasiveness in a dose-dependent manner. Taken together, these data suggested that LSD1 was a potential prognostic maker and may be a molecular target for inhibiting invasion and metastasis in ESCC.

Effects of the monoamine oxidase inhibitors pargyline and tranylcypromine on cellular proliferation in human prostate cancer cells

Chemotherapy is one of the therapeutic strategies that has been used for the inhibition of cancer cell proliferation in several types of cancer, including prostate cancer. Although monoamine oxidase (MAO) inhibitors, phytoestrogen and antioxidants used in chemotherapy have been systematically studied, their effects on cancer cell growth remain to be fully understood. The purpose of this study was to investigate the effects of the MAO inhibitors, pargyline and tranylcypromine on cell survival in human prostate carcinoma (LNCaP-LN3) cells. After treating LNCaP-LN3 cells with pargyline or tranylcypromine, we examined cell proliferation, cell cycle pattern, apoptosis and the expression levels of apoptosis-related genes. The proliferation of cells exposed to pargyline decreased in a dose- and time-dependent manner, while tranylcypromine-treated cells showed the opposite results. Treatment with pargyline significantly induced cell cycle arrest at the G1 phase compared to the control and tranylcypromine-treated cells. In addition, pargyline induced an increase in the cell death rate by promoting apoptosis; however, tranylcypromine had no effect on LNCaP-LN3 cells. Based on our results, we suggest that pargyline is more powerful than tranylcypromine for the treatment of human prostate cancer.

Formaldehyde in brain: an overlooked player in neurodegeneration?

Formaldehyde is an environmental pollutant that is also generated in substantial amounts in the human body during normal metabolism. This aldehyde is a well-established neurotoxin that affects memory, learning, and behavior. In addition, in several pathological conditions, including Alzheimer's disease, an increase in the expression of formaldehyde-generating enzymes and elevated levels of formaldehyde in brain have been reported. This article gives an overview on the current knowledge on the generation and metabolism of formaldehyde in brain cells as well as on formaldehyde-induced alterations in metabolic processes. Brain cells have the potential to generate and to dispose formaldehyde. In culture, both astrocytes and neurons efficiently oxidize formaldehyde to formate which can be exported or further oxidized. Although moderate concentrations of formaldehyde are not acutely toxic for brain cells, exposure to formaldehyde severely affects their metabolism as demonstrated by the formaldehyde-induced acceleration of glycolytic flux and by the rapid multidrug resistance protein 1-mediated export of glutathione from both astrocytes and neurons. These formaldehyde-induced alterations in the metabolism of brain cells may contribute to the impaired cognitive performance observed after formaldehyde exposure and to the neurodegeneration in diseases that are associated with increased formaldehyde levels in brain.

SNAI1-mediated epithelial-mesenchymal transition confers chemoresistance and cellular plasticity by regulating genes involved in cell death and stem cell maintenance

Tumor cells at the tumor margin lose epithelial properties and acquire features of mesenchymal cells, a process called epithelial-to-mesenchymal transition (EMT). Recently, features of EMT were shown to be linked to cells with tumor-founding capability, so-called cancer stem cells (CSCs). Inducers of the EMT include several transcription factors, such as Snail (SNAI1) and Slug (SNAI2), as well as the secreted transforming growth factor (TGFß). In the present study, we found that EMT induction in MCF10A cells by stably expressing SNAI1 contributed to drug resistance and acquisition of stem/progenitor-like character as shown by increased cell population for surface marker CD44(+)/CD24(-) and mammosphere forming capacity. Using a microarray approach, we demonstrate that SNAI1 overexpression results in a dramatic change in signaling pathways involved in the regulation of cell death and stem cell maintenance. We showed that NF-κB/MAPK signaling pathways are highly activated in MCF10A-SNAI1 cells by IL1ß stimulation, leading to the robust induction in IL6 and IL8. Furthermore, MCF10A-SNAI1 cells showed enhanced TCF/ß-catenin activity responding to the exogenous Wnt3a treatment. However, EMT-induced stem/progenitor cell activation process is tightly regulated in non-transformed MCF10A cells, as WNT5A and TGFB2 are strongly upregulated in MCF10A-SNAI1 cells antagonizing canonical Wnt pathway. In summary, our data provide new molecular findings how EMT contributes to the enhanced chemoresistance and the acquisition of stem/progenitor-like character by regulating signaling pathways.

Positive expression of LSD1 and negative expression of E-cadherin correlate with metastasis and poor prognosis of colon cancer

BACKGROUND

The first identified lysine-specific demethylase, LSD1, plays an important role in the metastatic progression of several types of cancer.

AIMS

The aim of this study was to investigate LSD1, E-cadherin, and N-cadherin expression in colon cancer specimens and their clinical significance.

METHODS

The expression of LSD1, E-cadherin, and N-cadherin in colon cancer specimens was determined by immunohistochemistry, and the relationship between the expression of the respective molecules and clinicopathological characteristics was analyzed.

RESULTS

The positive expression rates of LSD1, E-cadherin, and N-cadherin in colon cancer specimens were 66.7 % (72/108), 85.2 % (92/108), and 41.7 % (45/108), respectively. LSD1 was significantly more highly expressed in colon cancer specimens classified as high TNM stage lesions and with distant metastasis (P < 0.05). Further analysis demonstrated that LSD1 expression was positively correlated with lymph node and distant metastases (P < 0.05). However, E-cadherin expression was significantly downregulated in colon cancer specimens classified as high TNM stage lesions and with distant metastasis (P < 0.05), whereas the expression of N-cadherin did not differ significantly according to clinical and pathological characteristics (P > 0.05). Correlation analysis revealed that LSD1 expression was negatively correlated with E-cadherin expression (r s = -0.318, P = 0.001), but not evidently correlated with N-cadherin expression (r s = 0.182, P = 0.06). Colon cancer specimens with positive LSD1 expression and negative E-cadherin expression were correlated with significantly lower overall survival.

CONCLUSIONS

LSD1 showed a significantly higher expression, in contrast to the significantly lower expression of E-cadherin, in colon cancer specimens classified as high TNM stage lesions and with distant metastasis. Positive expression of LSD1 and negative expression of E-cadherin may be predictors of a worse colon cancer prognosis.

The KDM1A histone demethylase is a promising new target for the epigenetic therapy of medulloblastoma

Background

Medulloblastoma is a leading cause of childhood cancer-related deaths. Current aggressive treatments frequently lead to cognitive and neurological disabilities in survivors. Novel targeted therapies are required to improve outcome in high-risk medulloblastoma patients and quality of life of survivors. Targeting enzymes controlling epigenetic alterations is a promising approach recently bolstered by the identification of mutations in histone demethylating enzymes in medulloblastoma sequencing efforts. Hypomethylation of lysine 4 in histone 3 (H3K4) is also associated with a dismal prognosis for medulloblastoma patients. Functional characterization of important epigenetic key regulators is urgently needed.

Results

We examined the role of the H3K4 modifying enzyme, KDM1A, in medulloblastoma, an enzyme also associated with malignant progression in the closely related tumor, neuroblastoma. Re-analysis of gene expression data and immunohistochemistry of tissue microarrays of human medulloblastomas showed strong KDM1A overexpression in the majority of tumors throughout all molecular subgroups. Interestingly, KDM1A knockdown in medulloblastoma cell lines not only induced apoptosis and suppressed proliferation, but also impaired migratory capacity. Further analyses revealed bone morphogenetic protein 2 (BMP2) as a major KDM1A target gene. BMP2 is known to be involved in development and differentiation of granule neuron precursor cells (GNCPs), one potential cell of origin for medulloblastoma. Treating medulloblastoma cells with the specific KDM1A inhibitor, NCL-1, significantly inhibited growth in vitro.

Conclusion

We provide the first evidence that a histone demethylase is functionally involved in the regulation of the malignant phenotype of medulloblastoma cells, and lay a foundation for future evaluation of KDM1A-inihibiting therapies in combating medulloblastoma.

The histone LSD1 demethylase in stemness and cancer transcription programs

DNA and histone chromatin modifying enzymes play a crucial role in chromatin remodeling in several biological processes. Lysine-specific demethylase 1 (LSD1), the first identified histone demethylase, is a relevant player in the regulation of a broad spectrum of biological processes including development, cellular differentiation, embryonic pluripotency and cancer. Here, we review recent insights on the role of LSD1 activity in chromatin regulatory complexes, its functional role in the epigenetic changes during embryonic development, in the establishment and maintenance of stemness and during cancer progression.

Roles of histone methyl-modifying enzymes in development and progression of cancer

Retroviral insertional mutagenesis in mice is considered a powerful forward genetic strategy to identify disease genes involved in cancer. Our high-throughput screens led to frequent identification of the genes encoding the enzymes engaged in histone lysine methylation. Histone methylation can positively or negatively impact on gene transcription, and then fulfill important roles in developmental control and cell-fate decisions. A tremendous amount of progress has accelerated the characterization of histone methylations and the enzymes that regulate them. Deregulation of these histone methyl-modifying enzymes has been increasingly recognized as a hallmark of cancer in the last few years. However, in most cases, we have only limited understanding for the molecular mechanisms by which these enzymes contribute to cancer development and progression. In this review, we summarize the current knowledge regarding some of the best-validated examples of histone lysine methyltransferases and demethylases associated with oncogenesis and discuss their potential mechanisms of action.

A hypomorphic lsd1 allele results in heart development defects in mice

Lysine-specific demethylase 1 (Lsd1/Aof2/Kdm1a), the first enzyme with specific lysine demethylase activity to be described, demethylates histone and non-histone proteins and is essential for mouse embryogenesis. Lsd1 interacts with numerous proteins through several different domains, most notably the tower domain, an extended helical structure that protrudes from the core of the protein. While there is evidence that Lsd1-interacting proteins regulate the activity and specificity of Lsd1, the significance and roles of such interactions in developmental processes remain largely unknown. Here we describe a hypomorphic Lsd1 allele that contains two point mutations in the tower domain, resulting in a protein with reduced interaction with known binding partners and decreased enzymatic activity. Mice homozygous for this allele die perinatally due to heart defects, with the majority of animals suffering from ventricular septal defects. Molecular analyses revealed hyperphosphorylation of E-cadherin in the hearts of mutant animals. These results identify a previously unknown role for Lsd1 in heart development, perhaps partly through the control of E-cadherin phosphorylation.

Loss of LSD1 (lysine-specific demethylase 1) suppresses growth and alters gene expression of human colon cancer cells in a p53- and DNMT1(DNA methyltransferase 1)-independent manner

Epigenetic silencing of gene expression is important in cancer. Aberrant DNA CpG island hypermethylation and histone modifications are involved in the aberrant silencing of tumour-suppressor genes. LSD1 (lysine-specific demethylase 1) is a H3K4 (histone H3 Lys⁴) demethylase associated with gene repression and is overexpressed in multiple cancer types. LSD1 has also been implicated in targeting p53 and DNMT1 (DNA methyltransferase 1), with data suggesting that the demethylating activity of LSD1 on these proteins is necessary for their stabilization. To examine the role of LSD1 we generated LSD1 heterozygous (LSD1^+/−) and homozygous (LSD1^−/−) knockouts in the human colorectal cancer cell line HCT116. The deletion of LSD1 led to a reduced cell proliferation both in vitro and in vivo. Surprisingly, the knockout of LSD1 in HCT116 cells did not result in global increases in its histone substrate H3K4me2 (dimethyl-H3K4) or changes in the stability or function of p53 or DNMT1. However, there was a significant difference in gene expression between cells containing LSD1 and those null for LSD1. The results of the present study suggested that LSD1 is critical in the regulation of cell proliferation, but also indicated that LSD1 is not an absolute requirement for the stabilization of either p53 or DNMT1.

Epigenetic therapy: use of agents targeting deacetylation and methylation in cancer management

The emergence of epigenetic mechanisms as key regulators of gene expression has led to dramatic advances in understanding cancer biology. Driven by complex layers that include aberrant DNA methylation and histone modification, epigenetic aberrations have emerged as critical processes that disrupt cellular machinery and homeostasis. Recent discoveries have already translated into successful clinical trials and improved patient care, with several agents approved for hematologic disease and others undergoing study. As the field matures, substantial challenges persist that will require resolution. These include the need to decipher more fully the interplay between the epigenetic and genetic machinery, patient selection and improving treatment efficacy in solid tumors, and optimizing combination therapies to counteract chemoresistance and minimize adverse effects. Here, we review recent progress in epigenetic treatments and consider their implications for future cancer therapy.

The re-expression of the epigenetically silenced e-cadherin gene by a polyamine analogue lysine-specific demethylase-1 (LSD1) inhibitor in human acute myeloid leukemia cell lines

Aberrant epigenetic silencing of tumor suppressor genes is a common feature observed during the transformation process of many cancers, including those of hematologic origin. Histone modifications, including acetylation, phosphorylation, and methylation, collaborate with DNA CpG island methylation to regulate gene expression. The dynamic process of histone methylation is the latest of these epigenetic modifications to be described, and the identification and characterization of LSD1 as a demethylase of lysine 4 of histone H3 (H3K4) has confirmed that both the enzyme and the modified histone play important roles as regulators of gene expression. LSD1 activity contributes to the suppression of gene expression by demethylating promoter-region mono- and dimethyl-H3K4 histone marks that are associated with active gene expression. As most post-translational modifications are reversible, the enzymes involved in the modification of histones have become targets for chemotherapeutic intervention. In this study, we examined the effects of the polyamine analogue LSD1 inhibitor 2d (1,15-bis{N (5)-[3,3-(diphenyl)propyl]-N(1)-biguanido}-4,12-diazapentadecane) in human acute myeloid leukemia (AML) cell lines. In each line studied, 2d evoked cytotoxicity and inhibited LSD1 activity, as evidenced by increases in the global levels of mono- and di-methylated H3K4 proteins. Global increases in other chromatin modifications were also observed following exposure to 2d, suggesting a broad response to this compound with respect to chromatin regulation. On a gene-specific level, treatment with 2d resulted in the re-expression of e-cadherin, a tumor suppressor gene frequently silenced by epigenetic modification in AML. Quantitative chromatin immunoprecipitation analysis of the e-cadherin promoter further confirmed that this re-expression was concurrent with changes in both active and repressive histone marks that were consistent with LSD1 inhibition. As hematologic malignancies have demonstrated promising clinical responses to agents targeting epigenetic silencing, this polyamine analogue LSD1 inhibitor presents an exciting new avenue for the development of novel therapeutic agents for the treatment of AML.

Context-specific regulation of cancer epigenomes by histone and transcription factor methylation

Altered expression or activity of histone lysine methylases and demethylases in cancer lead to aberrant chromatin modification patterns, which contribute to uncontrolled cell proliferation via cancer-specific deregulation of gene expression programs or the induction of genome instability. Several transcription factors that regulate growth-associated genes undergo lysine methylation, expanding the repertoire of regulatory targets modulated by histone-methylating enzymes during tumorigenesis. In certain specific tumor types or specific physiological conditions, these enzymes may trigger chromatin structure and/or transcription factor activity changes that result in opposite effects on cancer initiation or progression. The mechanisms of such context-specific dual functions and those involved in the crosstalk between factor and histone modifications are subject to extensive research, which is beginning to shed light into this novel level of complexity of cancer-related epigenetic pathways.

Transcriptional corepressors in cancer: emerging targets for therapeutic intervention

The normal cell transcriptional process entails a high degree of combinatorial effects and time-dependent "flexibility" to translate cellular signaling into differential gene expression levels. Transcriptional corepressors can function as histone-modifying enzymes to regulate epigenetic events, modulate chromatin structure, and hence control transcriptional activity. Various corepressor complexes have been described; qualitative and quantitative alterations of corepressors can crucially influence the transcriptional output of both normal and malignant cells. Because these molecules can exert epigenetic control of tumorigenic signaling pathways, they can be considered potential regulators of cancer cell-related phenomena. Alterations of the expression level and/or function of transcriptional corepressors have been reported in a wide range of human cancers; thus, corepressors may present rational therapeutic targets as well as potential biomarkers of response to selective therapeutic interventions. Deeper insights into the context-specific and time-specific physical connections among transcription factors, coregulators, and gene regulatory elements, as well as epigenetic modifications, and their interactions, can enhance the capacity to interfere with small molecules that may restore the normal transcriptome/interactome in a cancer cell. There are several conceivable mechanisms of corepressor targeting in cancer that create enthusiasm. However, design, discovery, and testing of such innovative treatment approaches require extensive elaboration before they can achieve practical implementation in the clinic.

Lysine-specific demethylase 1 in breast cancer cells contributes to the production of endogenous formaldehyde in the metastatic bone cancer pain model of rats

Background

Bone cancer pain seriously affects the quality of life of cancer patients. Our previous study found that endogenous formaldehyde was produced by cancer cells metastasized into bone marrows and played an important role in bone cancer pain. However, the mechanism of production of this endogenous formaldehyde by metastatic cancer cells was unknown in bone cancer pain rats. Lysine-specific demethylase 1 (LSD1) is one of the major enzymes catalyzing the production of formaldehyde. The expression of LSD1 and the concentration of formaldehyde were up-regulated in many high-risk tumors.

Objective

This study aimed to investigate whether LSD1 in metastasized MRMT-1 breast cancer cells in bone marrows participated in the production of endogenous formaldehyde in bone cancer pain rats.

Methodology/Principal Findings

Concentration of the endogenous formaldehyde was measured by high performance liquid chromatography (HPLC). Endogenous formaldehyde dramatically increased in cultured MRMT-1 breast cancer cells in vitro, in bone marrows and sera of bone cancer pain rats, in tumor tissues and sera of MRMT-1 subcutaneous vaccination model rats in vivo. Formaldehyde at a concentration as low as the above measured (3 mM) induced pain behaviors in normal rats. The expression of LSD1 which mainly located in nuclei of cancer cells significantly increased in bone marrows of bone cancer pain rats from 14 d to 21 d after inoculation. Furthermore, inhibition of LSD1 decreased the production of formaldehyde in MRMT-1 cells in vitro. Intraperitoneal injection of LSD1 inhibitor pargyline from 3 d to 14 d after inoculation of MRMT-1 cancer cells reduced bone cancer pain behaviors.

Conclusion

Our data in the present study, combing our previous report, suggested that in the endogenous formaldehyde-induced pain in bone cancer pain rats, LSD1 in metastasized cancer cells contributed to the production of the endogenous formaldehyde.

MiR-137 functions as a tumor suppressor in neuroblastoma by downregulating KDM1A

Neuroblastoma is the most common extracranial solid tumor of childhood, and accounts for ∼15% of all childhood cancer deaths. The histone demethylase, lysine-specific demethylase 1 (KDM1A, previously known as LSD1), is strongly expressed in neuroblastomas, and overexpression correlates with poor patient prognosis. Inducing differentiation in neuroblastoma cells has previously been shown to down regulate KDM1A, and siRNA-mediated KDM1A knockdown inhibited neuroblastoma cell viability. The microRNA, miR-137, has been reported to be downregulated in several human cancers, and KDM1A mRNA was reported as a putative target of miR-137 in colon cancer. We hypothesized that miR-137 might have a tumor-suppressive role in neuroblastoma mediated via downregulation of KDM1A. Indeed, low levels of miR-137 expression in primary neuroblastomas correlated with poor patient prognosis. Re-expressing miR-137 in neuroblastoma cell lines increased apoptosis and decreased cell viability and proliferation. KDM1A mRNA was repressed by miR-137 in neuroblastoma cells, and was validated as a direct target of miR-137 using reporter assays in SHEP and HEK293 cells. Furthermore, siRNA-mediated KDM1A knockdown phenocopied the miR-137 re-expression phenotype in neuroblastoma cells. We conclude that miR-137 directly targets KDM1A mRNA in neuroblastoma cells, and activates cell properties consistent with tumor suppression. Therapeutic strategies to re-express miR-137 in neuroblastomas could be useful to reduce tumor aggressiveness.

JARID2 is a direct target of the PAX3-FOXO1 fusion protein and inhibits myogenic differentiation of rhabdomyosarcoma cells

Rhabdomyosarcomas (RMS) are the most frequent soft-tissue sarcoma in children and characteristically show features of developing skeletal muscle. The alveolar subtype is frequently associated with a PAX3-FOXO1 fusion protein that is known to contribute to the undifferentiated myogenic phenotype of RMS cells. Histone methylation of lysine residues controls developmental processes in both normal and malignant cell contexts. Here we show that JARID2, which encodes a protein known to recruit various complexes with histone-methylating activity to their target genes, is significantly overexpressed in RMS with PAX3-FOXO1 compared with the fusion gene-negative RMS (t-test; P < 0.0001). Multivariate analyses showed that higher JARID2 levels are also associated with metastases at diagnosis, independent of fusion gene status and RMS subtype (n = 120; P = 0.039). JARID2 levels were altered by silencing or overexpressing PAX3-FOXO1 in RMS cell lines with and without the fusion gene, respectively. Consistent with this, we demonstrated that JARID2 is a direct transcriptional target of the PAX3-FOXO1 fusion protein. Silencing JARID2 resulted in reduced cell proliferation coupled with myogenic differentiation, including increased expression of Myogenin (MYOG) and Myosin Light Chain (MYL1) in RMS cell lines representative of both the alveolar and embryonal subtypes. Induced myogenic differentiation was associated with a decrease in JARID2 levels and this phenotype could be rescued by overexpressing JARID2. Furthermore, we that showed JARID2 binds to and alters the methylation status of histone H3 lysine 27 in the promoter regions of MYOG and MYL1 and that the interaction of JARID2 at these promoters is dependent on EED, a core component of the polycomb repressive complex 2 (PRC2). Therefore, JARID2 is a downstream effector of PAX3-FOXO1 that maintains an undifferentiated myogenic phenotype that is characteristic of RMS. JARID2 and other components of PRC2 may represent novel therapeutic targets for treating RMS patients.

Low p14ARF expression in neuroblastoma cells is associated with repressed histone mark status, and enforced expression induces growth arrest and apoptosis

The TP53 tumor suppressor pathway is abrogated by TP53 mutations in the majority of human cancers. Increased levels of wild-type TP53 in aggressive neuroblastomas appear paradox but are tolerated by tumor cells due to co-activation of the TP53 ubiquitin ligase, MDM2. The role of the MDM2 antagonist, p14(ARF), in controlling the TP53-MDM2 balance in neuroblastoma is unresolved. In the present study, we show that conditional p14(ARF) expression substantially suppresses viability, clonogenicity and anchorage-independent growth in p14(ARF)-deficient or MYCN-amplified neuroblastoma cell lines. Furthermore, ectopic 14(ARF) expression induced accumulation of cells in the G1 phase and apoptosis, which was paralleled by accumulation of TP53 and its targets. Comparative genomic hybridization analysis of 193 primary neuroblastomas detected one homozygous deletion of CDKN2A (encoding both p14(ARF) and p16(INK4A)) and heterozygous loss of CDKN2A in 22% of tumors. Co-expression analysis of p14(ARF) and its transactivator, E2F1, in a set of 68 primary tumors revealed only a weak correlation, suggesting that further regulatory mechanisms govern p14(ARF) expression in neuroblastomas. Intriguingly, analyses utilizing chromatin immunoprecipitation revealed different histone mark-defined epigenetic activity states of p14(ARF) in neuroblastoma cell lines that correlated with endogenous p14(ARF) expression but not with episomal p14(ARF) promoter reporter activity, indicating that the native chromatin context serves to epigenetically repress p14(ARF) in neuroblastoma cells. Collectively, the data pinpoint p14(ARF) as a critical factor for efficient TP53 response in neuroblastoma cells and assign p14(ARF) as a neuroblastoma suppressor candidate that is impaired by genomic loss and epigenetic repression.

The lysine specific demethylase-1 (LSD1/KDM1A) regulates VEGF-A expression in prostate cancer

Recurrent prostate cancer remains a major clinical challenge. The lysine specific demethylase-1 (LSD1/KDM1A), together with the JmjC domain-containing JMJD2A and JMJD2C proteins, have emerged as critical regulators of histone lysine methylation. The LSD1-JMJD2 complex functions as a transcriptional co-regulator of hormone activated androgen and estrogen receptors at specific gene promoters. LSD1 also regulates DNA methylation and p53 function. LSD1 is overexpressed in numerous cancers including prostate cancer through an unknown mechanism. We investigated expression of the LSD1 and JMJD2A in malignant human prostate specimens. We correlated LSD1 and JMJD2A expression with known mediators of prostate cancer progression: VEGF-A and cyclin A1. We show that elevated expression of LSD1, but not JMJD2A, correlates with prostate cancer recurrence and with increased VEGF-A expression. We show that functional depletion of LSD1 expression using siRNA in prostate cancer cells decreases VEGF-A and blocks androgen induced VEGF-A, PSA and Tmprss2 expression. We demonstrate that pharmacological inhibition of LSD1 reduces proliferation of both androgen dependent (LnCaP) and independent cell lines (LnCaP: C42, PC3). We show a direct mechanistic link between LSD1 over-expression and increased activity of pro-angiogenic pathways. New therapies targeting LSD1 activity should be useful in the treatment of hormone dependent and independent prostate cancer.

Altered histone modifications in cancer

In human health and disease the choreographed actions of a wide armory of transcription factors govern the regulated expression of coding and nonprotein coding genes. These actions are central to human health and are evidently aberrant in cancer. Central components of regulated gene expression are a variety of epigenetic mechanisms that include histone modifications. The post-translational modifications of histones are widespread and diverse, and appear to be spatial--temporally regulated in a highly intricate manner. The true functional consequences of these patterns of regulation are still emerging. Correlative evidence supports the idea that these patterns are distorted in malignancy on both a genome-wide and a discrete gene loci level. These patterns of distortion also often reflect the altered expression of the enzymes that control these histone states. Similarly gene expression patterns also appear to reflect a correlation with altered histone modifications at both the candidate loci and genome-wide level. Clarity is emerging in resolving these relationships between histone modification status and gene expression -patterns. For example, altered transcription factor interactions with the key co-activator and co-repressors, which in turn marshal many of the histone-modifying enzymes, may distort regulation of histone modifications at specific gene loci. In turn these aberrant transcriptional processes can trigger other altered epigenetic events such as DNA methylation and underline the aberrant and specific gene expression patterns in cancer. Considered in this manner, altered expression and recruitment of histone-modifying enzymes may underline the distortion to transcriptional responsiveness observed in malignancy. Insight from understanding these processes addresses the challenge of targeted epigenetic therapies in cancer.

Overexpression of lysine specific demethylase 1 predicts worse prognosis in primary hepatocellular carcinoma patients

AIM: To investigate the clinicopathological features and prognostic value of lysine specific demethylase 1 (LSD1) in hepatocellular carcinoma (HCC).

METHODS: We examined LSD1 expression in 60 paired liver cancer tissues and adjacent noncancerous tissues by quantitative real time polymerase chain reaction (qRT-PCR) and Western blotting. In addition, we analyzed LSD1 expression in 198 HCC samples by immunohistochemistry. The relationship between LSD1 expression, clinicopathological features and patient survival was investigated.

RESULTS: Immunohistochemistry, Western blotting, and qRT-PCR consistently confirmed LSD1 overexpression in HCC tissues compared to adjacent non-neoplastic tissues (P < 0.01). Additionally, immunostaining showed more LSD1-positive cells in the higher tumor stage (T3-4) and tumor grade (G3) than in the lower tumor stage (T1-2, P < 0.001) and tumor grade (G1-2, P < 0.001), respectively. Moreover, HCC patients with high LSD1 expression had significantly lower 5-year overall survival rates (P < 0.001) and lower 5-year disease-free survival rates (P < 0.001), respectively. A Cox proportional hazards model further demonstrated that LSD1 over-expression was an independent predictor of poor prognosis for both 5-year disease-free survival [hazards ratio (HR) = 1.426, 95%CI: 0.672-2.146, P < 0.001] and 5-year overall survival (HR = 2.456, 95%CI: 1.234-3.932, P < 0.001) in HCC.

CONCLUSION: Our data suggest for the first time that the overexpression of LSD1 protein in HCC tissues indicates tumor progression and predicts poor prognosis.

Flavin-dependent enzymes in cancer prevention

Statistical studies have demonstrated that various agents may reduce the risk of cancer's development. One of them is activity of flavin-dependent enzymes such as flavin-containing monooxygenase (FMO)(GS-OX1), FAD-dependent 5,10-methylenetetrahydrofolate reductase and flavin-dependent monoamine oxidase. In the last decade, many papers concerning their structure, reaction mechanism and role in the cancer prevention were published. In our work, we provide a more in-depth analysis of flavin-dependent enzymes and their contribution to the cancer prevention. We present the actual knowledge about the glucosinolate synthesized by flavin-containing monooxygenase (FMO)(GS-OX1) and its role in cancer prevention, discuss the influence of mutations in FAD-dependent 5,10-methylenetetrahydrofolate reductase on the cancer risk, and describe FAD as an important cofactor for the demethylation of histons. We also present our views on the role of riboflavin supplements in the prevention against cancer.

Epigenetic changes in pediatric solid tumors: promising new targets

Cancer is being reinterpreted in the light of recent discoveries related to the histone code and the dynamic nature of epigenetic regulation and control of gene programs during development, as well as insights gained from whole cancer genome sequencing. Somatic mutations in or deregulated expression of genes that encode chromatin-modifying enzymes are being identified with high frequency. Nowhere is this more relevant than in pediatric embryonal solid tumors. A picture is emerging that shows that classic genetic alterations associated with these tumors ultimately converge on the epigenome to dysregulate developmental programs. In this review, we relate how alterations in components of the transcriptional machinery and chromatin modifier genes contribute to the initiation and progression of pediatric solid tumors. We also discuss how dramatic progress in our understanding of the fundamental mechanisms that contribute to epigenetic deregulation in cancer is providing novel avenues for targeted cancer therapy.

LIN28B induces neuroblastoma and enhances MYCN levels via let-7 suppression

LIN28B regulates developmental processes by modulating microRNAs (miRNAs) of the let-7 family. A role for LIN28B in cancer has been proposed but has not been established in vivo. Here, we report that LIN28B showed genomic aberrations and extensive overexpression in high-risk neuroblastoma compared to several other tumor entities and normal tissues. High LIN28B expression was an independent risk factor for adverse outcome in neuroblastoma. LIN28B signaled through repression of the let-7 miRNAs and consequently resulted in elevated MYCN protein expression in neuroblastoma cells. LIN28B-let-7-MYCN signaling blocked differentiation of normal neuroblasts and neuroblastoma cells. These findings were fully recapitulated in a mouse model in which LIN28B expression in the sympathetic adrenergic lineage induced development of neuroblastomas marked by low let-7 miRNA levels and high MYCN protein expression. Interference with this pathway might offer therapeutic perspectives.

Involvement of histone demethylase LSD1 in short-time-scale gene expression changes during cell cycle progression in embryonic stem cells

The histone demethylase LSD1, a component of the CoREST (corepressor for element 1-silencing transcription factor) corepressor complex, plays an important role in the downregulation of gene expression during development. However, the activities of LSD1 in mediating short-time-scale gene expression changes have not been well understood. To reveal the mechanisms underlying these two distinct functions of LSD1, we performed genome-wide mapping and cellular localization studies of LSD1 and its dimethylated histone 3 lysine 4 (substrate H3K4me2) in mouse embryonic stem cells (ES cells). Our results showed an extensive overlap between the LSD1 and H3K4me2 genomic regions and a correlation between the genomic levels of LSD1/H3K4me2 and gene expression, including many highly expressed ES cell genes. LSD1 is recruited to the chromatin of cells in the G(1)/S/G(2) phases and is displaced from the chromatin of M-phase cells, suggesting that LSD1 or H3K4me2 alternatively occupies LSD1 genomic regions during cell cycle progression. LSD1 knockdown by RNA interference or its displacement from the chromatin by antineoplastic agents caused an increase in the levels of a subset of LSD1 target genes. Taken together, these results suggest that cell cycle-dependent association and dissociation of LSD1 with chromatin mediates short-time-scale gene expression changes during embryonic stem cell cycle progression.

Drosophila LSD1-CoREST demethylase complex regulates DPP/TGFβ signaling during wing development

The choice and timing of specific developmental pathways in organogenesis are determined by tissue-specific temporal and spatial cues that are acted upon to impart unique cellular and compartmental identities. A consequence of cellular signaling is the rapid transcriptional reprogramming of a wide variety of target genes. To overcome intrinsic epigenetic chromatin barriers to transcription modulation, histone modifying and remodeling complexes are employed. The deposition or erasure of specific covalent histone modifications, including acetylation, methylation, and ubiquitination are essential features of gene activation and repression. We have found that the activity of a specific class of histone demethylation enzymes is required for the specification of vein cell fates during Drosophila wing development. Genetic tests revealed that the Drosophila LSD1-CoREST complex is required for proper cell specification through regulation of the DPP/TGFβ pathway. An important finding from this analysis is that LSD1-CoREST functions through control of rhomboid expression in an EGFR-independent pathway.

Overexpression of LSD1 in hepatocellular carcinoma: a latent target for the diagnosis and therapy of hepatoma

The aim of this study was to investigate the expression of LSD1 in human hepatocellular carcinoma (HCC) cell lines and HCC samples. In this study, we examined LSD1 expression in 60 paired liver cancer tissues and adjacent noncancerous tissues by Western blot. In addition, we analyzed LSD1 expression in 198 HCC samples by immunohistochemistry. The relationship between LSD1 expression and clinicopathological features was investigated. The HCC cell line SMMC-7721 was transfected with LSD1 siRNA expressing plasmids. We subsequently examined in vitro cell growth using the MTT assay and anchorage-independent growth through a soft-agar colony-formation assay. In addition, the expression levels of Bcl-2 and c-Myc were also examined. Immunohistochemistry and Western blotting consistently confirmed LSD1 overexpression in HCC tissues compared with adjacent non-neoplastic tissues (P < 0.01). Additionally, immunostaining showed more LSD1-positive cells in the higher tumor stage (T3-4) and tumor grade (G3) than in the lower tumor stage (T1-2, P < 0.001) and tumor grade (G1-2, P < 0.001). Knockdown of LSD1 expression in HCC cells led to decreased cell proliferation. The expression of Bcl-2 and c-Myc were down-regulated after transfection of LSD1 siRNA into HCC cell line SMMC-7721. In conclusion, because LSD1 was overexpressed in HCC and has an important role in the development of HCC, LSD1 could be a latent target in the diagnosis and therapy of HCC.

Epigenetic control and cancer: the potential of histone demethylases as therapeutic targets

The development of cancer involves an immense number of factors at the molecular level. These factors are associated principally with alterations in the epigenetic mechanisms that regulate gene expression profiles. Studying the effects of chromatin structure alterations, which are caused by the addition/removal of functional groups to specific histone residues, are of great interest as a promising way to identify markers for cancer diagnosis, classify the disease and determine its prognosis, and these markers could be potential targets for the treatment of this disease in its different forms. This manuscript presents the current point of view regarding members of the recently described family of proteins that exhibit histone demethylase activity; histone demethylases are genetic regulators that play a fundamental role in both the activation and repression of genes and whose expression has been observed to increase in many types of cancer. Some fundamental aspects of their association with the development of cancer and their relevance as potential targets for the development of new therapeutic strategies at the epigenetic level are discussed in the following manuscript.

LSD1 inhibition: a therapeutic strategy in cancer?

INTRODUCTION

The role of epigenetic dysfunction in cancer is increasingly appreciated. This has raised the question as to whether enzymes that regulate the structure and function of chromatin might represent novel therapeutic targets. The histone demethylase LSD1 is one such candidate and novel, potent inhibitors are under development.

AREAS COVERED

The literature on LSD1 (also known as KDM1A, AOF2, BHC110 or KIAA0601) was identified in Pubmed and is herein discussed. Areas covered include the structure and enzymatic activity of LSD1, its role in chromatin regulatory complexes, its functional roles in normal and malignant tissue, pharmacological inhibitors of its activity and their putative therapeutic roles.

EXPERT OPINION

Pre-clinical data supporting a therapeutic role for LSD1 inhibitors are most encouraging in acute myeloid leukaemia, although optimal dosing strategies and beneficial combinations with other agents remain unclear. Studies making use of potent, selective LSD1 inhibitors active in the nanomolar range are required to establish therapeutic indications in other subtypes of haematological malignancy, and in solid tumours.

Elevated expression of LSD1 (Lysine-specific demethylase 1) during tumour progression from pre-invasive to invasive ductal carcinoma of the breast

Background

Lysine-specific demethylase1 (LSD1) is a nuclear protein which belongs to the aminooxidase-enzymes playing an important role in controlling gene expression. It has also been found highly expressed in several human malignancies including breast carcinoma. Our aim was to detect LSD1 expression also in pre-invasive neoplasias of the breast. In the current study we therefore analysed LSD1 protein expression in ductal carcinoma in situ (DCIS) in comparison to invasive ductal breast cancer (IDC).

Methods

Using immunohistochemistry we systematically analysed LSD1 expression in low grade DCIS (n = 27), intermediate grade DCIS (n = 30), high grade DCIS (n = 31) and in invasive ductal breast cancer (n = 32). SPSS version 18.0 was used for statistical analysis.

Results

LSD1 was differentially expressed in DCIS and invasive ductal breast cancer. Interestingly, LSD1 was significantly overexpressed in high grade DCIS versus low grade DCIS. Differences in LSD1 expression levels were also statistically significant between low/intermediate DCIS and invasive ductal breast carcinoma.

Conclusions

LSD1 is also expressed in pre-invasive neoplasias of the breast. Additionally, there is a gradual increase of LSD1 expression within tumour progression from pre-invasive DCIS to invasive ductal breast carcinoma. Therefore upregulation of LSD1 may be an early tumour promoting event.

An overview of phenylcyclopropylamine derivatives: biochemical and biological significance and recent developments

trans-2-Phencylcyclopropylamine (2-PCPA), a potent, clinically used antidepressant, affects monoamine neurotransmitter levels by inhibiting the main metabolizing enzymes, monoamine oxidases (MAOs). However, the antidepressant action of this compound was not fully explained by its effects on MAOs due to its wide variety of biological effects. 2-PCPA also affects depression-associated pathophysiological pathways, and linked with increased levels of trace amines in brain, upregulation of GABAB receptors (where GABA is gamma amino butyric acid), modulation of phospholipid metabolism, and interference with various cytochrome P450 (CYP) enzymes. Consequently, despite its adverse effects and limited clinical applicability, 2-PCPA has attracted interest as a structural scaffold for the development of mechanism-based inhibitors of various enzymes, including lysine-specific demethylase 1 (LSD1), which is a possible target for cancer chemotherapy. In the recent years, many reports have appeared in the literature based on 2-PCPA scaffold and their potential medicinal implications. This review mainly focuses on the medicinal chemistry aspects including drug design, structure-activity relationships (SAR), biological and biochemical properties, and mechanism of actions of 2-PCPA and its derivatives. Furthermore, we also highlight recent advance in this area and discuss their future applications for beneficial therapeutic effects.

Oncoepigenomics: making histone lysine methylation count

Increasing studies show that methylation of histone lysine residues is implicated in the development and progression of varying disease states such as schizophrenia, diabetes, and multiple human cancers. Targeting the specific enzymes responsible for these processes has fueled global investigation into the understanding and correction of epigenetic pathology. This review aims to assemble a timely account of the current progress against chromatin-modifying histone lysine methyltransferases (KMTs) and demethylases (KDMs) to inform ongoing and future efforts into this promising field. In particular, we report on their role in tumor growth and progression and the development of small molecules that modulate these enzymes.

The role of histone demethylases in cancer therapy

Reversible histone methylation has emerged in the last few years as an important mechanism of epigenetic regulation. Histone methyltransferases and demethylases have been identified as contributing factors in the development of several diseases, especially cancer. Therefore, they have been postulated to be new drug targets with high therapeutic potential. Here, we review histone demethylases with a special focus on their potential role in oncology drug discovery. We present an overview over the different classes of enzymes, their biochemistry, selected data on their role in physiology and already available inhibitors.

Targeting the PELP1-KDM1 axis as a potential therapeutic strategy for breast cancer

INTRODUCTION

The estrogen receptor (ER) co-regulator proline glutamic acid and leucine-rich protein 1 (PELP1) is a proto-oncogene that modulates epigenetic changes on ER target gene promoters via interactions with lysine-specific histone demethylase 1 (KDM1). In this study, we assessed the therapeutic potential of targeting the PELP1-KDM1 axis in vivo using liposomal (1,2-dioleoyl-sn-glycero-3-phosphatidylcholine; DOPC) siRNA to downregulate PELP1 expression and KDM1 inhibitors, pargyline and N-((1S)-3-(3-(trans-2-aminocyclopropyl)phenoxy)-1-(benzylcarbamoyl)propyl)benzamide using preclinical models.

METHODS

Preclinical xenograft models were used to test the efficacy of drugs in vivo. Ki-67 and terminal deoxynucleotidyl transferase dUTP nick end-labeling immunohistochemical analysis of epigenetic markers was performed on tumor tissues. The in vitro effect of PELP1-KDM axis blockers was tested using proliferation, reporter gene, chromatin immunoprecipitation and real-time RT-PCR assays. The efficacy of the KDM1 targeting drugs alone or in combination with letrozole and tamoxifen was tested using therapy-resistant model cells.

RESULTS

Treatment of ER-positive xenograft-based breast tumors with PELP1-siRNA-DOPC or pargyline reduced tumor volume by 58.6% and 62%, respectively. In a postmenopausal model, in which tumor growth is stimulated solely by local estrogen synthesis, daily pargyline treatment reduced tumor volume by 78%. Immunohistochemical analysis of excised tumors revealed a combined decrease in cellular proliferation, induction of apoptosis and upregulation of inhibitory epigenetic modifications. Pharmacological inhibition of KDM1 in vitro increased inhibitory histone mark dimethylation of histone H3 at lysine 9 (H3K9me2) and decreased histone activation mark acetylation of H3K9 (H3K9Ac) on ER target gene promoters. Combining KDM1 targeting drugs with current endocrine therapies substantially impeded growth and restored sensitivity of therapy-resistant breast cancer cells to treatment.

CONCLUSION

Our results suggest inhibition of PELP1-KDM1-mediated histone modifications as a potential therapeutic strategy for blocking breast cancer progression and therapy resistance.

LSD1/CoREST is an allosteric nanoscale clamp regulated by H3-histone-tail molecular recognition

The complex of lysine-specific demethylase-1 (LSD1/KDM1A) with its corepressor protein CoREST is an exceptionally relevant target for epigenetic drugs. Here, we provide insight into the local and global changes of LSD1/CoREST conformational dynamics that occur upon H3 binding on the basis of a total cumulative time of one microsecond molecular dynamics simulation. The LSD1/CoREST complex functions as an allosteric nanoscale-binding clamp, which is regulated by substrate binding. In the unbound state, LSD1/CoREST reversibly visits clamp states that are more open or significantly more closed compared with the available X-ray crystal structures. The Lys triad of residues Lys355, Lys357, and Lys359 gates the entrance of the H3 pocket. H3 binding shifts the pocket breathing dynamics toward open, higher-volume states while reducing the overall flexibility of the LSD1/CoREST nanoscale clamp. We show that the H3 pocket is an allosteric site for the regulation of the rotation of the amino oxidase domain with respect to the Tower domain. The allosteric mechanism relies on the specific reduction of nanoscale domain rotation upon local H3-tail binding. Instead, clamp opening/closing motions that do not involve domain rotation only reduce in amplitude yet are dominant in the bound state. Overall, our data suggest that the H3 binding pocket is a central target site to (i) switch off LSD1 amino oxidase activity, thus H3-tail demethylation; (ii) block the competitive binding of transcription factors; and (iii) prevent chromatin anchoring to LSD1/CoREST. This study underscores the importance of receptor flexibility for future epigenetic drug discovery.

Lysine-specific demethylase 1 restricts hematopoietic progenitor proliferation and is essential for terminal differentiation

Lysine (K)-specific demethylase 1A (LSD1/KDM1A) has been identified as a potential therapeutic target in solid cancers and more recently in acute myeloid leukemia. However, the potential side effects of a LSD1-inhibitory therapy remain elusive. Here, we show, with a newly established conditional in vivo knockdown model, that LSD1 represents a central regulator of hematopoietic stem and progenitor cells. LSD1 knockdown (LSD1-kd) expanded progenitor numbers by enhancing their proliferative behavior. LSD1-kd led to an extensive expansion of granulomonocytic, erythroid and megakaryocytic progenitors. In contrast, terminal granulopoiesis, erythropoiesis and platelet production were severely inhibited. The only exception was monopoiesis, which was promoted by LSD1 deficiency. Importantly, we showed that peripheral blood granulocytopenia, monocytosis, anemia and thrombocytopenia were reversible after LSD1-kd termination. Extramedullary splenic hematopoiesis contributed to the phenotypic reversion, and progenitor populations remained expanded. LSD1-kd was associated with the upregulation of key hematopoietic genes, including Gfi1b, Hoxa9 and Meis1, which are known regulators of the HSC/progenitor compartment. We also demonstrated that LSD1-kd abrogated Gfi1b-negative autoregulation by crossing LSD1-kd with Gfi1b:GFP mice. Taken together, our findings distinguish LSD1 as a critical regulator of hematopoiesis and point to severe, but reversible, side effects of a LSD1-targeted therapy.

Targeting transcription factor corepressors in tumor cells

By being the "integration" center of transcriptional control as they move and target transcription factors, corepressors fine-tune the epigenetic status of the nucleus. Many of them utilize enzymatic activities to modulate chromatin through histone modification or chromatin remodeling. The clinical and etiological relevance of the corepressors to neoplastic growth is increasingly being recognized. Aberrant expression or function (both loss and gain of) of corepressors has been associated with malignancy and contribute to the generation of transcriptional "inflexibility" manifested as distorted signaling along certain axes. Understanding and predicting the consequences of corepressor alterations in tumor cells has diagnostic and prognostic value, and also have the capacity to be targeted through selective epigenetic regimens. Here, we evaluate corepressors with the most promising therapeutic potential based on their physiological roles and involvement in malignant development, and also highlight areas that can be exploited for molecular targeting of a large proportion of clinical cancers and their complications.

The epigenetics of renal cell tumors: from biology to biomarkers

Renal cell tumors (RCT) collectively constitute the third most common type of genitourinary neoplasms, only surpassed by prostate and bladder cancer. They comprise a heterogeneous group of neoplasms with distinctive clinical, morphological, and genetic features. Epigenetic alterations are a hallmark of cancer cells and their role in renal tumorigenesis is starting to emerge. Aberrant DNA methylation, altered chromatin remodeling/histone onco-modifications and deregulated microRNA expression not only contribute to the emergence and progression of RCTs, but owing to their ubiquity, they also constitute a promising class of biomarkers tailored for disease detection, diagnosis, assessment of prognosis, and prediction of response to therapy. Moreover, due to their dynamic and reversible properties, those alterations represent a target for epigenetic-directed therapies. In this review, the current knowledge about epigenetic mechanisms and their altered status in RCT is summarized and their envisaged use in a clinical setting is also provided.

The histone demethylase KDM1A sustains the oncogenic potential of MLL-AF9 leukemia stem cells

Using a mouse model of human MLL-AF9 leukemia, we identified the lysine-specific demethylase KDM1A (LSD1 or AOF2) as an essential regulator of leukemia stem cell (LSC) potential. KDM1A acts at genomic loci bound by MLL-AF9 to sustain expression of the associated oncogenic program, thus preventing differentiation and apoptosis. In vitro and in vivo pharmacologic targeting of KDM1A using tranylcypromine analogs active in the nanomolar range phenocopied Kdm1a knockdown in both murine and primary human AML cells exhibiting MLL translocations. By contrast, the clonogenic and repopulating potential of normal hematopoietic stem and progenitor cells was spared. Our data establish KDM1A as a key effector of the differentiation block in MLL leukemia, which may be selectively targeted to therapeutic effect.

MYCN and ALKF1174L are sufficient to drive neuroblastoma development from neural crest progenitor cells

Neuroblastoma is an embryonal tumor with a heterogeneous clinical course. The tumor is presumed to be derived from the neural crest, but the cells of origin remain to be determined. To date, few recurrent genetic changes contributing to neuroblastoma formation, such as amplification of the MYCN oncogene and activating mutations of the ALK oncogene, have been identified. The possibility to model neuroblastoma in mice allows investigation of the cell of origin hypothesis in further detail. Here we present the evidence that murine neural crest progenitor cells can give rise to neuroblastoma upon transformation with MYCN or ALK(F1174L). For this purpose we used JoMa1, a multipotent neural crest progenitor cell line, which is kept in a viable and undifferentiated state by a tamoxifen-activated c-Myc transgene (c-MycER(T)). Expression of MYCN or ALK(F1174L), one of the oncogenic ALK variants identified in primary neuroblastomas, enabled these cells to grow independently of c-MycER(T) activity in vitro and caused formation of neuroblastoma-like tumors in vivo in contrast to parental JoMa1 cells and JoMa1 cells-expressing TrkA or GFP. Tumorigenicity was enhanced upon serial transplantation of tumor-derived cells, and tumor cells remained susceptible to the MYC-inhibitor, NBT-272, indicating that cell growth depended on functional MYCN. Our findings support neural crest progenitor cells as the precursor cells of neuroblastoma, and indicate that neuroblastomas arise as their malignant progeny.