Histone deacetylase (HDAC)6 is a member of the class IIb HDAC family. This enzyme is zinc-dependent and mainly localized in the cytoplasm. HDAC6 is a unique isoenzyme with two functional catalytic ...domains and specific physiological roles. Indeed, HDAC6 deacetylates various substrates including α-tubulin and HSP90α, and is involved in protein trafficking and degradation, cell shape and migration. Consequently, deregulation of HDAC6 activity was associated to a variety of diseases including cancer, neurodegenerative diseases and pathological autoimmune response. Therefore, HDAC6 represents an interesting potential therapeutic target. In this review, we discuss structural features of this histone deacetylase, regulation of its expression and activity, biological functions, implication in human disease initiation and progression. Finally will describe novel and selective HDAC6 inhibitors.
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Alterations of the epigenetic machinery, affecting multiple biological functions, represent a major hallmark enabling the development of tumors. Among epigenetic regulatory proteins, ...histone deacetylase (HDAC)6 has emerged as an interesting potential therapeutic target towards a variety of diseases including cancer. Accordingly, this isoenzyme regulates many vital cellular regulatory processes and pathways essential to physiological homeostasis, as well as tumor multistep transformation involving initiation, promotion, progression and metastasis. In this review, we will consequently discuss the critical implications of HDAC6 in distinct mechanisms relevant to physiological and cancerous conditions, as well as the anticancer properties of synthetic, natural and natural-derived compounds through the modulation of HDAC6-related pathways.
Core histone acetylation is a key prerequisite for chromatin decondensation and plays a pivotal role in regulation of chromatin structure, function and dynamics. The addition of acetyl groups ...disturbs histone/DNA interactions in the nucleosome and alters histone/histone interactions in the same or adjacent nucleosomes. Acetyl groups can also provide binding sites for recruitment of bromodomain (BRD)-containing non-histone readers and regulatory complexes to chromatin allowing them to perform distinct downstream functions. The presence of a particular acetylation pattern influences appearance of other histone modifications in the immediate vicinity forming the "histone code". Although the roles of the acetylation of particular lysine residues for the ongoing chromatin functions is largely studied, the epigenetic inheritance of histone acetylation is a debated issue. The dynamics of local or global histone acetylation is associated with fundamental cellular processes such as gene transcription, DNA replication, DNA repair or chromatin condensation. Therefore, it is an essential part of the epigenetic cell response to processes related to internal and external signals.
Arsenic ranks as the number one toxic environmental contaminant. In humans, arsenic exposure is associated with various forms of cancer, cardiovascular and skin diseases, neuropathies of the central ...nervous system, and genotoxic and immunotoxic effects. Although a well recognized human carcinogen, arsenic itself is not a potent mutagen and has been thought to act through epigenetic mechanisms that modify DNA methylation patterns, perhaps in conjunction with DNA-damaging agents. To develop preliminary support for a more thorough examination of this hypothesis, we have measured the effect of submicromolar and low-micromolar concentrations of arsenite on the methylation status of DNA and the biochemical reactions that regulate it. We find that arsenic causes the depletion of
S-adenosylmethionine, the main cellular methyl donor, and represses the expression of the DNA methyltransferase genes
DNMT1 and
DNMT3A. Possibly as a consequence of these two complementary mechanisms, long-term exposure to arsenic results in DNA hypomethylation.
Highlights • 4-HBA derivatives inhibit HDAC activities and lead to increased protein acetylation. • 4-HBA derivatives display anti-tumor activities against solid and non-solid cancer cells. • Cancer ...cells are more sensitive to 4-HBA treatments than normal cells.
Highlights • Deregulation of the epigenetic machinery is a hallmark of cancer. • Natural marine compounds possess epigenetic modulatory activities. • Natural marine compounds provide potent ...anti-cancer drugs. • Epigenetic activity of largazole, psammaplin, trichostatin, azumamide are described.
Despite considerable scientific progress, the burden of cancer in our society remains a major public health problem. Tumorigenesis is recognized as a complex and multistep process that involves the ...accumulation of successive transformational events with multi-factorial etiology. Nevertheless, such events result in the acquisition of key hallmark characteristics that are shared by all cancer cells. Accumulating evidence indicates that, besides genetic alterations, epigenetic mechanisms (heritable changes in gene expression caused by modifications in chromatin structure without alterations of DNA sequence) are implicated in the acquisition of malignant phenotype. The potential reversibility of epigenetic alterations linked to tumorigenesis offers a promising avenue for therapeutic intervention. This review focuses on the epigenetic regulation of the cancer hallmarks and the foreseeable use of epigenetic drugs to target these features as a promising strategy for anti-cancer therapy. Based on this body of evidence, we believe that epigenetic deregulations can affect virtually all cell functions and therefore therapeutic approaches with epigenetic drugs could allow multi-target approach against the hallmarks of cancer.
In addition to its demethylating properties, 2′-deoxy-5-azacytidine (DAC) induces cell cycle arrest, differentiation, cell sensitization to chemotherapy, and cell death. However, the mechanisms by ...which DAC induces antiproliferation via these processes and how they are interconnected remain unclear. In this study, we found that a clinically relevant concentration of DAC triggered erythroid and megakaryocytic differentiation in the human chronic myeloid leukemia (CML) K-562 and MEG-01 cell lines, respectively. In addition, cells showed a marked increase in cell size in both cell lines and a more adhesive cell profile for MEG-01. Furthermore, DAC treatment induced cellular senescence and autophagy as shown by β-galactosidase staining and by autophagosome formation, respectively. After prolonged DAC treatment, phosphatidyl serine exposure, nuclear morphology analysis, and caspase cleavage revealed an activation of mitochondrial-dependent apoptosis in CML cells. This activation was accompanied by a decrease of anti-apoptotic proteins and an increase of calpain activity. Finally, we showed that combinatory treatment of relatively resistant CML with DAC and either conventional apoptotic inducers or with an histone deacetylase inhibitor increased synergistically apoptosis. We therefore conclude that induction of differentiation, senescence, and autophagy in CML are a key in cell sensitization and DAC-induced apoptosis.
Imatinib became the standard treatment for chronic myeloid leukemia (CML) about 20 years ago, which was a major breakthrough in stabilizing the pathology and improving the quality of life of ...patients. However, the emergence of resistance to imatinib and other tyrosine kinase inhibitors leads researchers to characterize new therapeutic targets. Several studies have highlighted the role of histone deacetylase 6 (HDAC6) in various pathologies, including cancer. This protein effectively intervenes in cellular activities by its primarily cytoplasmic localization. In this review, we will discuss the molecular characteristics of the HDAC6 protein, as well as its overexpression in CML leukemic stem cells, which make it a promising therapeutic target for the treatment of CML.
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