Expression Of JMJD2B Research Articles

Histone demethylase JMJD2B-mediated cell proliferation regulated by hypoxia and radiation in gastric cancer cell

Histone modifying factors are functional components of chromatin and play a role in gene regulation. The expression level of JMJD2B, a histone demethylase, is notably up-regulated in cancer tissues. Upregulation of JMJD2B promotes cancer cell proliferation under hypoxic conditions through target gene expression. Here, we describe the patterns of histone methylation and JMJD2B expression under various stressed conditions, such as hypoxia and radiation, in a gastric cancer cell line. JMJD2B expression in AGS cells was actively regulated by hypoxia and radiation. Chromatin immunoprecipitation experiments demonstrated that binding of JMJD2B on the cyclin A1 (CCNA1) promoter resulted in CCNA1 upregulation under hypoxic conditions. Furthermore, we confirmed that AGS cell proliferation was directly affected by JMJD2B and CCNA1 expression by performing experiments with JMJD2B depleted cells. Interestingly, the effects of JMJD2B on cell growth under hypoxia were remarkably repressed after gamma-ray irradiation. These results suggest that JMJD2B may play a central role in gastric cancer cell growth and might constitute a novel therapeutic target to overcome hypoxia-induced radio-resistance, thereby improving the efficiency of radiation therapy.

An epigenetic role for PRL-3 as a regulator of H3K9 methylation in colorectal cancer

ObjectiveThis study investigated the epigenetic role of PRL-3, a key metastasis gene in colorectal cancer (CRC), as a regulator of histone demethylation and the functions of Jumonji domain-containing protein 1B...

The Histone Demethylase JMJD2B Plays an Essential Role in Human Carcinogenesis through Positive Regulation of Cyclin-Dependent Kinase 6

Histone methyltransferases and demethylases are known to regulate transcription by altering the epigenetic marks on histones, but the pathologic roles of their dysfunction in human diseases, such as cancer, still remain to be elucidated. Herein, we show that the histone demethylase JMJD2B is involved in human carcinogenesis. Quantitative real-time PCR showed notably elevated levels of JMJD2B expression in bladder cancers, compared with corresponding nonneoplastic tissues (P < 0.0001), and elevated protein expression was confirmed by immunohistochemistry. In addition, cDNA microarray analysis revealed transactivation of JMJD2B in lung cancer, and immunohistochemical analysis showed protein overexpression in lung cancer. siRNA-mediated reduction of expression of JMJD2B in bladder and lung cancer cell lines significantly suppressed the proliferation of cancer cells, and suppressing JMJD2B expression lead to a decreased population of cancer cells in S phase, with a concomitant increase of cells in G(1) phase. Furthermore, a clonogenicity assay showed that the demethylase activity of JMJD2B possesses an oncogenic activity. Microarray analysis after knockdown of JMJD2B revealed that JMJD2B could regulate multiple pathways which contribute to carcinogenesis, including the cell-cycle pathway. Of the downstream genes, chromatin immunoprecipitation showed that CDK6 (cyclin-dependent kinase 6), essential in G(1)-S transition, was directly regulated by JMJD2B, via demethylation of histone H3-K9 in its promoter region. Expression levels of JMJD2B and CDK6 were significantly correlated in various types of cell lines. Deregulation of histone demethylation resulting in perturbation of the cell cycle, represents a novel mechanism for human carcinogenesis and JMJD2B is a feasible molecular target for anticancer therapy.

Triptolide induces cell-cycle arrest and apoptosis of human multiple myeloma cells in vitro via altering expression of histone demethylase LSD1 and JMJD2B

To elucidate the relationship between triptolide-induced changes in histone methylation and its antitumor effect on human multiple myeloma (MM) cells in vitro. Human multiple myeloma cell line RPMI8226 was used. Apoptosis was evaluated using Annexin-V-FITC/PI-labeled flow cytometry, Hoechst 33258 staining, and transmission electron microscopy. Flow cytometry was used to detect the cell cycle distribution of the apoptotic cells. The presence of the LSD1, JMJD2B, H3K4me2, H3K9me2, and H3K36me2 proteins was verified by Western blot analysis. Semi-quantitative real-time PCR was performed to examine the expression of LSD1 and JMJD2B. Triptolide (10-160 nmol/L) suppressed the proliferation of MM cells in a dose- and time-dependent manner with an IC(50) value of 99.2 ± 9.0 nmol/L at 24 h. Triptolide (50 nmol/L) induced G(0)/G(1) cell cycle arrest in MM cells. The agent (50-150 nmol/L) induced apoptosis of MM cells in a dose-dependent manner. The same concentrations of triptolide suppressed the expression of dimethylated H3K4, dimethylated H3K9 and dimethylated H3K36 by altering the expression of histone demethylase LSD1 and JMJD2B without affecting the expression of histone demethylase LSD1. Triptolide potently inhibits the growth of MM cells via regulating the expression of histone demethylase LSD1 and JMJD2B, which lead to abnormal histone methylation.

Histone demethylase JMJD2B functions as a co-factor of estrogen receptor in breast cancer proliferation and mammary gland development.

Estrogen is a key regulator of normal function of female reproductive system and plays a pivotal role in the development and progression of breast cancer. Here, we demonstrate that JMJD2B (also known as KDM4B) constitutes a key component of the estrogen signaling pathway. JMJD2B is expressed in a high proportion of human breast tumors, and that expression levels significantly correlate with estrogen receptor (ER) positivity. In addition, 17-beta-estradiol (E2) induces JMJD2B expression in an ERα dependent manner. JMJD2B interacts with ERα and components of the SWI/SNF-B chromatin remodeling complex. JMJD2B is recruited to ERα target sites, demethylates H3K9me3 and facilitates transcription of ER responsive genes including MYB, MYC and CCND1. As a consequence, knockdown of JMJD2B severely impairs estrogen-induced cell proliferation and the tumor formation capacity of breast cancer cells. Furthermore, Jmjd2b-deletion in mammary epithelial cells exhibits delayed mammary gland development in female mice. Taken together, these findings suggest an essential role for JMJD2B in the estrogen signaling, and identify JMJD2B as a potential therapeutic target in breast cancer.

The Histone Demethylases JMJD1A and JMJD2B Are Transcriptional Targets of Hypoxia-inducible Factor HIF

Posttranslational histone modifications serve to store epigenetic information and control both nucleosome assembly and recruitment of non-histone proteins. Histone methylation occurs on arginine and lysine residues and is involved in the regulation of gene transcription. A dynamic control of these modifications is exerted by histone methyltransferases and the recently discovered histone demethylases. Here we show that the hypoxia-inducible factor HIF-1alpha binds to specific recognition sites in the genes encoding the jumonji family histone demethylases JMJD1A and JMJD2B and induces their expression. Accordingly, hypoxic cells express elevated levels of JMJD1A and JMJD2B mRNA and protein. Furthermore, we find increased expression of JMJD1A and JMJD2B in renal cancer cells that have lost the von Hippel Lindau tumor suppressor protein VHL and therefore display a deregulated expression of hypoxia-inducible factor. Studies on ectopically expressed JMJD1A and JMJD2B indicate that both proteins retain their histone lysine demethylase activity in hypoxia and thereby might impact the hypoxic gene expression program.

Dynamic Nuclear Organization of the Genome During Fetal Male Germ Cell Development.

In mice, male germ cells enter mitotic arrest at around 13.5 days postcoitum (dpc) and maintain G0/G1 cell cycle stage until after birth. During the mitotic arrest, male germ cells undergo epigenetic reorganization, which is essential for completion of male sex differentiation and reproductive function. We previously showed that when 15.5-19.5 dpc male germ cells are used as donors for nuclear transfer experiments, most of cloned two-cell embryos are developed to blastocysts (Yamazaki et al., 2003). These data indicate that the transition of male germ cells into a G0/G1 cell cycle state increase the reprogramming potential of the genome. Previously, constitutive heterochromatin was thought to be remarkably stable in composition and transcriptionally inert. However, several lines of recent evidence suggest that a global reorganization and spatial clustering of constitutive heterochromatin play a critical role in epigenetic plasticity during cellular differentiation. In this study, we investigated molecular links between the global organization of the genome and the epigenetic plasticity of male germ cells throughout fetal (12.5-19.5 dpc) and neonatal development (4 days postpartum). To reveal the global organization of the genome, constitutive heterochromatin was monitored by DAPI and by immunostaining of histone H3 trimethylated on lysine 9 (H3-triMetK9) and heterochromatin protein 1 (HP1α). The H3-triMetK9 and HP1α stainings were confined to small, discrete foci coincident with DAPI-bright, constitutive heterochromatin in male germ cells at 12.5-13.5 dpc. On the other hand, between 13.5-19.5 dpc, these three stainings showed a diffused, poorly defined regions, and the number of heterochromatin foci significantly decreased. These morphological changes occurred during the transition of male germ cells from mitotic stage into a G0/G1 cell cycle state (13.5-15.5 dpc), and remained constant during G0/G1 cell cycle stage. To assess these global changes at a local level, we compared histone methylation levels at major satellite repeats by chromatin immunoprecipitation analyses. We observed enrichment of H3-triMetK9 across major satellite repeats between 12.5-15.5 dpc, but then observed loss of H3-triMetK9 during 17.5-19.5 dpc. Also, we analyzed the expression profiles of histone methyltransferases (Suv39h1 and Suv39h2), and histone demethylase (Jmjd2b) with real-time RT-PCR. Expression of Suv39h1 and Suv39h2 was downregulated at 15.5 dpc, while the expression of Jmjd2b was upregulated at 17.5 dpc. A marked decrease of H3-triMetK9 levels at major satellite repeats at 17.5 dpc might be caused by preceding loss of the activity of the histone methyltransferases and also the increased activity of the histone demethylase. Taken together, these results showed that constitutive heterochromatin organization is drastically modified at global and local levels during prespermatogenesis. The decrease in epigenetic histone modifications characteristic of heterochromatin suggests that chromatin conformation in male germ cells are globally more open in G0/G1 cell cycle stage compared to mitotically active stage. These chromatin properties of G0/G1 male germ cells might reflect a functionally important hallmark of epigenetic plasticity. (Research was supported by NIH HD042772.)