Histone deacetylase 6 (HDAC6) is an unique subtype of histone deacetylases with two tandem deacetylase domains and substrate specificity for non-histone proteins. It is involved in many important physiological and pathological processes and has become a promising therapeutic target in recent decades. Different kinds of potent HDAC6-selective inhibitors have been reported around the world. This paper reviews the progress in the study of structure and functions of HDAC6 as well as the development of HDAC6-selective inhibitors.
Histone Deacetylase Inhibitors ; pharmacology ; Histone Deacetylases ; chemistry ; Humans ; Substrate Specificity

PURPOSE: Histone deacetylase inhibitors (HDIs) are emerging as potentially useful components of anticancer therapy and their radiosensitizing effects have become evident. Specific HDIs are now available that preferentially inhibit specific HDAC classes; TSA inhibits Class I and II HDACs, and SK7041 inhibits Class I HDACs. MATERIALS AND METHODS: We tested the differential radiosensitization induced by two different classes of HDIs in HeLa cells. We next tested the hypothesis that p53 expression in cancer cells may influence the susceptibility to HDIs by using pharmacologic modification of the p53 status under an isogenic background. RESULTS: It is interesting that p53 expression in the HeLa cells clearly increased the degree of radiosensitization by TSA compared to that of the class I specific inhibitor SK7041. This suggests that p53 may, in part, be responsible for the mechanistic role for the greater radiosensitization induced by Class I & II inhibitors compared to that of the class I specific inhibitors. Thus, these studies are useful in distinguishing between events mediated solely by the Class I HDACs versus those events involving the other classes of HDACs as well. CONCLUSION: The anticancer efficacy of targeting Class I and II HDACs, in conjunction with radiation therapy, may be further enhanced by the restoration of p53 expression.
HeLa Cells* ; Histone Deacetylase Inhibitors ; Humans ; Radiation-Sensitizing Agents

As a crucial part of epigenetic regulation, the histone modification catalyzed by histone modification enzymes can alter the chromatin structure and modulate the gene expression. The role of histone modification in disease pathogenesis, especially in tumorigenesis, has become a research hotspot. The deregulation of histone modification, such as the overexpression and gain-of-function mutations of histone methyltransferase EZH2, the inactive mutations of histone methyltransferase MLL2, histone acetyltransferase CREBBP and EP300 are crucial for the development of hematological neoplasms. Some of Epi-drugs such as HDAC inhibitors, EZH2 inhibitors, are already clinically used, some are still in basic research stage, which are important field of new drug development for hematological neoplasms. In this review, the researches advances of basic medical sciences and clinical applications of aberrant histone modifications in hematological neoplasms are summarized.
Cell Transformation, Neoplastic ; Epigenesis, Genetic ; Hematologic Neoplasms ; Histone Deacetylase Inhibitors ; Histone-Lysine N-Methyltransferase ; Histones ; Humans

Mice ; Animals ; Acetylation ; NF-kappa B/metabolism* ; Histone Deacetylases/metabolism* ; Inflammation ; Histone Deacetylase Inhibitors

BACKGROUNDPlacental multidrug resistance-associated protein 2 (MRP2), encoded by ABCC2 gene in human, plays a significant role in regulating drugs' transplacental transfer rates. Studies on placental MRP2 regulation could provide more therapeutic targets for individualized and safe pharmacotherapy during pregnancy. Currently, the roles of epigenetic mechanisms in regulating placental drug transporters are still unclear. This study aimed to investigate the effect of histone deacetylases (HDACs) inhibition on MRP2 expression in the placental trophoblast cell line and to explore whether HDAC1/2/3 are preliminarily involved in this process.

METHODSThe human choriocarcinoma-derived trophoblast cell line (Bewo cells) was treated with the HDAC inhibitors-trichostatin A (TSA) at different concentration gradients of 0.5, 1.0, 3.0, and 5.0 μmol/L. Cells were harvested after 24 and 48 h treatment. Small interfering RNA (siRNA) specific for HDAC1/HDAC2/HDAC3 or control siRNA was transfected into cells. Total HDAC activity was detected by colorimetric assay kits. HDAC1/2/3/ABCC2 messenger RNA (mRNA) and protein expressions were determined by real-time quantitative polymerase chain reaction and Western-blot analysis, respectively. Immunofluorescence for MRP2 protein expression was visualized and assessed using an immunofluorescence microscopy and ImageJ software, respectively.

RESULTSTSA could inhibit total HDAC activity and HDAC1/2/3 expression in company with increase of MRP2 expression in Bewo cells. Reduction of HDAC1 protein level was noted after 24 h of TSA incubation at 1.0, 3.0, and 5.0 μmol/L (vs. vehicle group, all P < 0.001), accompanied with dose-dependent induction of MRP2 expression (P = 0.045 for 1.0 μmol/L, P = 0.001 for 3.0 μmol/L, and P < 0.001 for 5.0 μmol/L), whereas no significant differences in MRP2 expression were noted after HDAC2/3 silencing. Fluorescent micrograph images of MRP2 protein were expressed on the cell membrane. The fluorescent intensities of MRP2 in the control, HDAC2, and HDAC3 siRNA-transfected cells were week, and no significant differences were noticed among these three groups (all P > 0.05). However, MRP2 expression was remarkably elevated in HDAC1 siRNA-transfected cells, which displayed an almost 3.19-fold changes in comparison with the control siRNA-transfected cells (P < 0.001).

CONCLUSIONSHDACs inhibition could up-regulate placental MRP2 expression in vitro, and HDAC1 was probably to be involved in this process.

Cell Line ; Histone Deacetylase 1 ; metabolism ; Histone Deacetylase 2 ; metabolism ; Histone Deacetylase Inhibitors ; pharmacology ; Histone Deacetylases ; metabolism ; Humans ; Hydroxamic Acids ; pharmacology ; Microscopy, Fluorescence ; Multidrug Resistance-Associated Proteins ; genetics ; metabolism ; RNA, Messenger ; Trophoblasts ; cytology ; metabolism

Histone deacetylase (HDAC) inhibitors are considered novel agents for cancer chemotherapy. We previously investigated MHY219, a new HDAC inhibitor, and its potent anticancer activity in human prostate cancer cells. In the present study, we evaluated MHY219 molecular mechanisms involved in the regulation of prostate cancer cell migration. Similar to suberanilohydroxamic acid (SAHA), MHY219 inhibited HDAC1 enzyme activity in a dose-dependent manner. MHY219 cytotoxicity was higher in LNCaP (IC50=0.67 muM) than in DU145 cells (IC50=1.10 muM) and PC3 cells (IC50=5.60 muM) after 48 h of treatment. MHY219 significantly inhibited the HDAC1 protein levels in LNCaP and DU145 cells at high concentrations. However, inhibitory effects of MHY219 on HDAC proteins levels varied based on the cell type. MHY219 significantly inhibited LNCaP and DU145 cells migration by down-regulation of matrix metalloprotease-1 (MMP-1) and MMP-2 and induction of tissue inhibitor of metalloproteinases-1 (TIMP-1). These results suggest that MHY219 may potentially be used as an anticancer agent to block cancer cell migration through the repression of MMP-1 and MMP-2, which is related to the reduction of HDAC1.
Cell Movement ; Down-Regulation ; Drug Therapy ; Histone Deacetylase Inhibitors* ; Histone Deacetylases* ; Histones* ; Humans* ; Matrix Metalloproteinases ; Prostate* ; Prostatic Neoplasms* ; Repression, Psychology

The incidence of thyroid cancer is growing the fastest among all cancers in the United States, especially in women. The number of patients with thyroid neoplasm is part of an even larger number of patients who often need to undergo an operation to exclude a cancer diagnosis. While differentiated thyroid cancer (papillary thyroid cancer and follicular thyroid cancer) accounts for most cases of thyroid cancer and has a relatively good prognosis, effective treatments for patients with de-differentiated and anaplastic thyroid cancer are still gravely needed. Despite progress in the identification of genetic changes in thyroid cancer, the impact of aberrant epigenetic alterations on thyroid cancer remains to be fully elucidated. Understanding of the roles of epigenetic changes in thyroid cancer could open new opportunities for the identification of innovative molecular targets for novel treatment modalities, especially for anaplastic thyroid cancer for which treatment is very limited. This article briefly reviews the studies that exemplify the potential for and promise of using epigenetic regulators in the treatment of thyroid cancer.
Diagnosis ; Epigenomics* ; Female ; Histone Deacetylase Inhibitors ; Histone Deacetylases ; Humans ; Incidence ; Prognosis ; Thyroid Carcinoma, Anaplastic ; Thyroid Gland* ; Thyroid Neoplasms* ; United States

PURPOSE: Ataxia-telangiectasia mutated (ATM) kinase regulates diverse cellular DNA damage responses, including genome surveillance, cell growth, and gene expression. While the role of histone acetylation/deacetylation in gene expression is well established, little is known as to whether this modification can activate an ATM-dependent signal pathway, and whether this modification can thereby be implicated in an ATM-mediated DNA damage response. MATERIALS AND METHODS: Formation of H2AXgamma foci was examined in HeLa and U2OS cells following treatment with a histone deacetylase inhibitor, Trichostatin A (TSA). We determine an ATM-dependency of the TSA-induced DNA damage signal pathway using isogenic A-T (ATM square) and control (ATM+) cells. We monitored the phosphorylation of ATM, an ATM-downstream effector kinase, Chk2, and H2AXgamma to detect the activation of the ATM-dependent DNA damage signal pathway. RESULTS: Exposure of cells to TSA results in the formation of H2AXgamma foci in HeLa and U2OS cells. The TSA-induced formation of H2AXgamma foci occurs in an ATM-dependent manner. TSA induces phosphorylation of serine 1981 of ATM, accumulation of phosphorylated H2AX and Chk2, and formation of H2AX foci, in a manner analogous to genotoxic DNA damage. CONCLUSION: In this work, we show that TSA induces a DNA damage signaling pathway in an ATM-dependent manner. These results suggest that ATM can respond to altered histone acetylation induced by the histone deacetylase inhibitor, TSA.
Acetylation ; Ataxia Telangiectasia ; DNA Damage* ; DNA* ; Gene Expression ; Genome ; Histone Deacetylase Inhibitors* ; Histone Deacetylases* ; Histones* ; Phosphorylation ; Phosphotransferases ; Serine ; Signal Transduction*

Cells that have endogenous multipotent properties can be used as a starting source for the generation of induced pluripotent cells (iPSC). In addition, small molecules associated with epigenetic reprogramming are also widely used to enhance the multi- or pluripotency of such cells. Skin-derived precursor cells (SKPs) are multipotent, sphere-forming and embryonic neural crest-related precursor cells. These cells can be isolated from a juvenile or adult mammalian dermis. SKPs are also an efficient starting cell source for reprogramming and the generation of iPSCs because of the high expression levels of Sox2 and Klf4 in these cells as well as their endogenous multipotency. In this study, valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, was tested in the generation of iPSCs as a potential enhancer of the reprogramming potential of SKPs. SKPs were isolated from the back skins of 5-6 week old C57BL/6 X DBA/2 F1 mice. After passage 3, the SKPs was treated with 2 mM of VPA and the quantitative real time RT-PCR was performed to quantify the expression of Oct4 and Klf4 (pluripotency specific genes), and Snai2 and Ngfr (neural crest specific genes). The results show that Oct4 and Klf4 expression was decreased by VPA treatment. However, there were no significant changes in neural crest specific gene expression following VPA treatment. Hence, although VPA is one of the most potent of the HDAC inhibitors, it does not enhance the reprogramming of multipotent skin precursor cells in mice.
Adult ; Animals ; Dermis ; Epigenomics ; Gene Expression ; Histone Deacetylase Inhibitors ; Histone Deacetylases ; Histones ; Humans ; Mice ; Neural Crest ; Skin ; Valproic Acid

Histone modification is an important mechanism in oncogenesis and development of hematologic malignancies. Acetylation of lysine residues on histones and opening chromatin are correlated with activation of genes, whereas lysine residues methylation can result in either activation or repression on expressions of chromatin. The main point of all is deacetylation of histone mediated by histone deacetylases (HDACs). HDAC inhibitors are divided into 4 categories: short-chain fatty acids, hydroxamic acids, cyclic tetrapeptides and benzamides, owning different mechanisms in HDAC inhibition. Many kinds of I/II phase clinical tests showed that all these HDAC inhibitors have obviously therapeutic efficacies in treatment of hematologic malignancies with low poisons. Combination of HDAC inhibitors with DNA demethylation drugs can decrease DNA methylation, increase histone acetylation and recover antioncogene expression. As important parts of epigenetics, histone acetylation and HDAC inhibitors possess positive prospects in treatment of hematologic malignancies. In this review the advances of study on mechanisms of histone modification, HDAC inhibitors and their use in treatment of hematologic malignancies are summarized.
Acetylation ; Hematologic Neoplasms ; drug therapy ; Histone Deacetylase Inhibitors ; therapeutic use ; Histone Deacetylases ; genetics ; Histones ; chemistry ; genetics ; metabolism