ABSTRACT
We report the development of a potent, selective histone deacetylase 6 (HDAC6) inhibitor. This HDAC6 inhibitor blocks growth of normal and transformed cells but does not induce death of normal cells. The HDAC6 inhibitor alone is as effective as paclitaxel in anticancer activity in tumor-bearing mice.
Subject(s)
Antineoplastic Agents/chemical synthesis , Benzeneacetamides/chemistry , Benzeneacetamides/pharmacology , Histone Deacetylase Inhibitors/chemical synthesis , Histone Deacetylases/genetics , Hydroxamic Acids/chemistry , Hydroxamic Acids/pharmacology , Acetylation/drug effects , Animals , Antineoplastic Agents/chemistry , Cell Death/drug effects , Cell Proliferation/drug effects , Histone Deacetylase 6 , Histone Deacetylase Inhibitors/chemistry , Mice , Molecular Structure , Paclitaxel , Tubulin/metabolismABSTRACT
Development of isoform-selective histone deacetylase (HDAC) inhibitors is important in elucidating the function of individual HDAC enzymes and their potential as therapeutic agents. Among the eleven zinc-dependent HDACs in humans, HDAC6 is structurally and functionally unique. Here, we show that a hydroxamic acid-based small-molecule N-hydroxy-4-(2-[(2-hydroxyethyl)(phenyl)amino]-2-oxoethyl)benzamide (HPOB) selectively inhibits HDAC6 catalytic activity in vivo and in vitro. HPOB causes growth inhibition of normal and transformed cells but does not induce cell death. HPOB enhances the effectiveness of DNA-damaging anticancer drugs in transformed cells but not normal cells. HPOB does not block the ubiquitin-binding activity of HDAC6. The HDAC6-selective inhibitor HPOB has therapeutic potential in combination therapy to enhance the potency of anticancer drugs.
Subject(s)
Histone Deacetylase Inhibitors/chemical synthesis , Histone Deacetylase Inhibitors/pharmacology , Histone Deacetylases/metabolism , Acetylation/drug effects , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Autophagy/drug effects , Cell Line, Transformed/drug effects , Cell Line, Tumor , Cell Survival/drug effects , DNA Breaks, Double-Stranded/drug effects , Doxorubicin/pharmacology , Etoposide/pharmacology , Histone Deacetylase Inhibitors/chemistry , Histones/metabolism , Humans , Hydroxamic Acids/pharmacology , Mice , Trehalose/pharmacology , Tubulin/metabolism , Vorinostat , Xenograft Model Antitumor AssaysABSTRACT
Histone deacetylase (HDAC) inhibitors are a new class of anticancer agents. HDAC inhibitors induce acetylation of histones and nonhistone proteins which are involved in regulation of gene expression and in various cellular pathways including cell growth arrest, differentiation, DNA damage and repair, redox signaling, and apoptosis (Marks, 2010). The U.S. Food and Drug Administration has approved two HDAC inhibitors, vorinostat and romidepsin, for the treatment of cutaneous T-cell lymphoma (Duvic & Vu, 2007; Grant et al., 2010; Marks & Breslow, 2007). Over 20 chemically different HDAC inhibitors are in clinical trials for hematological malignancies and solid tumors. This review considers the mechanisms of resistance to HDAC inhibitors that have been identified which account for the selective effects of these agents in inducing cancer but not normal cell death. These mechanisms, such as functioning Chk1, high levels of thioredoxin, or the prosurvival BCL-2, may also contribute to resistance of cancer cells to HDAC inhibitors.
Subject(s)
Drug Resistance, Neoplasm , Histone Deacetylase Inhibitors/pharmacology , Neoplasm Proteins/antagonists & inhibitors , Neoplasms/drug therapy , Signal Transduction/drug effects , Animals , Histone Deacetylases/chemistry , HumansABSTRACT
Histone deacetylase inhibitors (HDACi) are a new group of anticancer drugs with tumor selective toxicity. Normal cells are relatively resistant to HDACi-induced cell death compared with cancer cells. Previously, we found that vorinostat induces DNA breaks in normal and transformed cells, which normal but not cancer cells can repair. In this study, we found that checkpoint kinase 1 (Chk1), a component of the G2 DNA damage checkpoint, is important in the resistance of normal cells to HDACi in vitro and in vivo. Inhibition of Chk1 activity with Chk1 inhibitor (UCN-01, AZD7762, or CHIR-124) in normal cells increases their sensitivity to HDACi (vorinostat, romidepsin, or entinostat) induced cell death, associated with extensive mitotic disruption. Mitotic abnormalities included loss of sister chromatid cohesion and chromosomal disruption. Inhibition of Chk1 did increase HDACi-induced cell death of transformed cells. Thus, Chk1 is an important factor in the resistance of normal cells, and some transformed cells, to HDACi-induced cell death. Use of Chk1 inhibitors in combination with anticancer agents to treat cancers may be associated with substantial toxicity.
Subject(s)
Drug Resistance , Histone Deacetylase Inhibitors/pharmacology , Protein Kinases/metabolism , Animals , Cell Line, Tumor , Cell Survival/drug effects , Cells, Cultured , Checkpoint Kinase 1 , DNA Damage , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/metabolism , Foreskin/cytology , Histones/metabolism , Humans , Hydroxamic Acids/pharmacology , Immunoblotting , Male , Mice , Protein Kinases/genetics , Quinolines/pharmacology , Quinuclidines/pharmacology , RNA Interference/physiology , Spleen/drug effects , Spleen/metabolism , Staurosporine/analogs & derivatives , Staurosporine/pharmacology , Thiophenes/pharmacology , Urea/analogs & derivatives , Urea/pharmacology , VorinostatABSTRACT
High grade gliomas are aggressive cancers that are not well addressed by current chemotherapies, in large measure because these drugs do not curtail the diffuse invasion of glioma cells into brain tissue surrounding the tumor. Here, we investigate the effects of suberoylanilide hydroxamic acid (SAHA) on glioma cells in 2D and 3D in vitro assays, as SAHA has previously been shown to significantly increase apoptosis, decrease proliferation, and interfere with migration in other cell lines. We find that SAHA has significant independent effects on proliferation, migration, and invasion. These effects are seen in both 2D and 3D culture. In 3D culture, with glioma spheroids embedded in collagen I matrices, SAHA independently limits both glioma invasion and the reorganization of the tumor surroundings that usually proceeds such invasion. The decreased matrix reorganization and invasion is not accompanied by decreased production or activity of matrix-metalloproteases but instead may be related to increased cell-cell adhesion.
Subject(s)
Brain Neoplasms/pathology , Cell Movement/drug effects , Glioma/pathology , Hydroxamic Acids/pharmacology , Neoplasm Invasiveness/prevention & control , 3T3 Cells , Animals , Cell Adhesion , Humans , Mice , Polymerase Chain Reaction , Tumor Cells, Cultured , VorinostatABSTRACT
Microcapsules fabricated by layer-by-layer self-assembly have unique physicochemical properties that make them attractive for drug delivery applications. This study chiefly investigated the biocompatibility of one of the most stable types of microcapsules, those composed of poly-(sodium 4-styrene sulfonate) [PSS] and poly-(allylamine hydrochloride) [PAH], with cells cultured on two-dimensional (2D) substrates and in three-dimensional (3D) matrices. C6 glioma and 3T3 fibroblast cell morphology was observed after 24h of co-culture with PSS/PAH microcapsules on a 2D substrate. Cells were also cultured with four other types of microcapsules, each composed of at least one naturally occurring polyelectrolyte. At microcapsule to cell ratios up to 100:1, it was found that PSS/PAH microcapsules do not affect number of viable cells more substantially than do the other microcapsules investigated. However, differences in number of viable cells were found as a function of microcapsule composition, and our results suggest particular biochemical interactions between cells and internalized microcapsules, rather than mechanical effects, are responsible for these differences. We then investigated the effects of PSS/PAH microcapsules on cells embedded in 3D collagen matrices, which more closely approximate the tumor environments in which microcapsules may be useful drug delivery agents. Matrix structure, cell invasion, and volumetric spheroid growth were investigated, and we show that these microcapsules have a negligible effect on cell invasion and tumor spheroid growth even at high concentration. Taken together, this work suggests that PSS/PAH microcapsules have sufficiently high biocompatibility with at least some cell lines for use as proof of principle drug delivery agents in in vitro studies.
