HDAC6 siRNA inhibits proliferation and induces apoptosis of HeLa cells and its related molecular mechanism

Ricolinostat suppresses proliferation, promotes apoptosis, and enhances the antiproliferative activity of topoisomerase inhibitors in cervical cancer cells

Ricolinostat has been found to exhibit anticancer effects alone and in combination with various chemotherapeutic drugs in several cancer types. However, to the best of our knowledge, the efficacy of ricolinostat in cervical cancer is still not investigated. Therefore, in this study, we evaluated the effect of ricolinostat in cervical cancer alone and in combination with topoisomerase inhibitors. The effect of ricolinostat on cervical cancer cells was assessed using MTT, cell-cycle arrest, Annexin V/PI staining assay, reactive oxygen species (ROS) measurement, and western blot analysis. The antiproliferative effect of ricolinostat in combination with topoisomerase inhibitors was assessed using the MTT assay and synergism was computed using "CompuSyn" software. We found that ricolinostat inhibited proliferation, and induced G2/M phase arrest and apoptosis in cervical cancer cells. We further found that ricolinostat treatment resulted in increased ROS production, decreased Bcl-xL expression, and induced p21 expression. We also investigated the effect of ricolinostat in combination with topotecan and etoposide in cervical cancer cells. Ricolinostat was found to significantly enhance the antiproliferative activity of both, topotecan and etoposide, in cervical cancer cells in a concentration-dependent manner. In conclusion, our study showed that ricolinostat suppressed proliferation by inducing G2/M phase arrest and promoted apoptosis in cervical cancer cells, indicating that ricolinostat may be a promising antitumor agent in cervical cancer. Also, ricolinostat and topotecan/etoposide combination are synergistic in cervical cancer cells.

HDAC6 Degradation Inhibits the Growth of High-Grade Serous Ovarian Cancer Cells

Simple Summary

The objective of this study was, firstly, to investigate the relationship between Histone deacetylase 6 (HDAC6) expression and survival in patients with ovarian cancer and, secondly, to test the effects of histone deacetylase 6 (HDAC6) inhibition on ovarian cancer cells in vitro. A meta-analysis of the correlation between HDAC6 gene expression and survival was performed on 3573 ovarian tumors from 19 datasets showed that high HDAC6 gene expression was associated with a decreased risk of death. Knockdown of HDAC6 gene expression with small interfering RNA (siRNA) and protein expression with a HDAC6 targeting protein degrader decreased ovarian cell proliferation, migration, and viability. Conversely, the selective inhibition of HDAC6 catalytic activity did not produce a robust inhibition of HDAC6 protein function. In summary, we demonstrated, for the first time, that HDAC6 over-expression in ovarian cancers is a favorable prognostic marker. We provide evidence to suggest that inhibition of HDAC6 catalytic activity has limited efficacy as a monotherapy in ovarian cancers.

Abstract

Histone deacetylase 6 (HDAC6) is a unique histone deacetylating enzyme that resides in the cell cytoplasm and is linked to the modulation of several key cancer related responses, including cell proliferation and migration. The promising anti-cancer response of the first-generation HDAC6 catalytic inhibitors continues to be assessed in clinical trials, although its role in high grade serous ovarian cancer is unclear. This study investigated HDAC6 tumor expression by immunohistochemistry in high-grade serous ovarian cancer (HGSOC) tissue samples and a meta-analysis of HDAC6 gene expression in ovarian cancer from publicly available data. The pharmacological activity of HDAC6 inhibition was assessed in a patient-derived model of HGSOC. HDAC6 was found to be highly expressed in HGSOC tissue samples and in the patient-derived HGSOC cell lines where higher HDAC6 protein and gene expression was associated with a decreased risk of death (hazard ratio (HR) 0.38, (95% confidence interval (CI), 0.16–0.88; p = 0.02); HR = 0.88 (95% CI, 0.78–0.99; p = 0.04)). Similarly, the multivariate analysis of HDAC6 protein expression, adjusting for stage, grade, and cytoreduction/cytoreductive surgery was associated with a decreased risk of death (HR = 0.19 (95% CI, 0.06–0.55); p = 0.002). Knock-down of HDAC6 gene expression with siRNA and protein expression with a HDAC6 targeting protein degrader decreased HGSOC cell proliferation, migration, and viability. Conversely, the selective inhibition of HDAC6 with the catalytic domain inhibitor, Ricolinostat (ACY-1215), inhibited HDAC6 deacetylation of α-tubulin, resulting in a sustained accumulation of acetylated α-tubulin up to 24 h in HGSOC cells, did not produce a robust inhibition of HDAC6 protein function. Inhibition of HGSOC cell proliferation by ACY-1215 was only achieved with significantly higher and non-selective doses of ACY-1215. In summary, we demonstrated, for the first time, that HDAC6 over-expression in HGSOC and all ovarian cancers is a favorable prognostic marker. We provide evidence to suggest that inhibition of HDAC6 catalytic activity with first generation HDAC6 inhibitors has limited efficacy as a monotherapy in HGSOC.

Isoflurane promotes proliferation of squamous cervical cancer cells through mTOR-histone deacetylase 6 pathway

This study investigated the effect of isoflurane on the proliferation of squamous cervical cancer cells, with focus on histone deacetylase 6 that is closely related to carcinogenesis. Squamous cervical cancer cells SiHa and Caski were exposed to 1%, 2%, or 3% isoflurane for 2 h, respectively. Cell proliferation was measured with the cell counting kit (CCK-8) assay and determined by BrdU assay. Expression of histone deacetylase 6, phospho-AKT, phospho-mTOR, and proliferating cell nuclear antigen (PCNA) was assessed by Western blot. In order to block the histone deacetylase 6 (HDAC6) expression, siRNA transfection was performed. Isoflurane significantly promoted the proliferation of both SiHa and Caski cells, accompanied by upregulation of PCNA protein expression. Isoflurane increased the level of histone deacetylase 6 protein expression in both cells, and knockdown of histone deacetylase 6 attenuated the pro-proliferation effects of isoflurane. Additionally, activation of AKT/mTOR was found after isoflurane treatment, and mTOR inhibition abolished isoflurane-induced histone deacetylase 6 expression. However, inhibition of AKT phosphorylation had no effect on the expression of histone deacetylase 6 mediated by isoflurane. In conclusion, Isoflurane enhanced proliferation of cervical cancer cells through upregulation of histone deacetylase 6, which was associated with mTOR-dependent pathway, but not AKT-mediated pathway.

Molecular docking-based virtual drug screening revealing an oxofluorenyl benzamide and a bromonaphthalene sulfonamido hydroxybenzoic acid as HDAC6 inhibitors with cytotoxicity against leukemia cells

HDAC6 is a crucial epigenetic modifier that plays a vital role in tumor progression and carcinogenesis due to its multiple biological functions. It is a unique member of class-II HDAC enzymes. It possesses two catalytic domains, which function independently of the overall enzyme activity. Up to date, there are only a few selective HDAC6 inhibitors with anti-cancer activity. In this study, 175,204 ligands obtained from the ZINC15 and OTAVAchemical databases were used for virtual drug screening against HDAC6. Molecular docking studies were performed for 100 selected compounds. Furthermore, the top 10 compounds obtained from docking were tested for their efficacy to inhibit the function of HDAC6. Five compounds (N-(9-oxo-9H-fluoren-3-yl)benzamide, 2-hydroxy-5-[(5-oxo-6-phenyl-4,5-dihydro-1,2,4-triazin-3-yl)amino]benzoic acid, 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid, 2-(naphthalen-2-yl)-N-(1H-1,2,3,4-tetrazol-5-yl)cyclopropane-1-carboxamide, and 4-oxa-5,6 diazapentacyclo[10.7.1.0³,⁷.0⁸,²⁰.0¹⁴,¹⁹]icosa-1,3(7),5,8(20),9,11,14,16,18-nonaen-13-one) inhibited enzymatic activity by more than 50 % compared to DMSO as the control. Two candidates, (N-(9-oxo-9H-fluoren-3-yl)benzamide and 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid), were identified with considerable cytotoxicity towards drug-sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Microscale thermophoresis revealed the binding of N-(9-oxo-9H-fluoren-3-yl)benzamide and 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid to purified HDAC6 protein. Both compounds induced apoptosis in a dose-dependent manner as analyzed by flow cytometry. In conclusion, we demonstrate for the first time that these two compounds bind to HDAC6, inhibit its function, and exert cytotoxic activity by apoptosis induction.

Sevoflurane Enhances Proliferation, Metastatic Potential of Cervical Cancer Cells via the Histone Deacetylase 6 Modulation In Vitro

Background

Sevoflurane is commonly used for cervical cancer surgery, but its effect on cervical cancer cell biology remains unclear. This mechanistic study explores how sevoflurane affects the proliferation and metastatic potential of immortalized cervical cancer cell lines.

Methods

Cultured cervical cancer Caski and HeLa lines were exposed to 1, 2, or 3% sevoflurane for 2 or 4 h. Cell proliferation was determined through the Kit-8 assay and Ki-67 immunofluorescent staining. Cell migration and invasion were evaluated with the Transwell assay. Immunofluorescent staining and Western blot analysis were used to identify sevoflurane-induced morphological and biochemical changes.

Results

Sevoflurane exposure for either 2 or 4 h significantly increased HeLa cell proliferation in a time- and concentration-dependent manner to be 106 ± 2.7% and 107 ± 1.4% relative to the controls (n = 10; P = 0.036; P = 0.022) at 24 h after exposure and to be 106 ± 2.2% and 106 ± 1.7% relative to the controls (n = 10; P = 0.031; P = 0.023) at the highest concentration of 3% sevoflurane studied, respectively, but not Caski cells. Sevoflurane promoted invasion ability (1.63 ± 0.14 and 1.92 ± 0.12 relative to the controls) and increased cell size (1.69 ± 0.21 and 1.76 ± 0.13 relative to the controls) of Caski and HeLa cells (n = 6; all P < 0.001), respectively. Sevoflurane increased histone deacetylase 6 expression in both cells, and histone deacetylase 6 knockdown abolished the prometastatic effects of sevoflurane. Sevoflurane also induced deacetylation of α-tubulin in a histone deacetylase 6–dependent manner. The protein kinase B (AKT) or extracellular regulated protein kinase (ERK1/2) phosphorylation inhibition attenuated sevoflurane-induced histone deacetylase 6 expression.

Conclusions

Sevoflurane enhanced proliferation, migration, and invasion of immortalized cervical cancer cells, which was likely associated with increasing histone deacetylase 6 expression caused by phosphatidylinositide 3-kinase/AKT- and ERK1/2-signaling pathway activation.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

HDAC6 differentially regulates autophagy in stem-like versus differentiated cancer cells

Cancer stem-like cells (CSCs), a small population of pluripotent cells residing within heterogeneous tumor mass, remain highly resistant to various chemotherapies as compared to the differentiated cancer cells. It is being postulated that CSCs possess unique molecular mechanisms, such as autophagic homeostasis, that allow CSCs to withstand the therapeutic assaults. Here we demonstrate that HDAC6 inhibition differentially modulates macroautophagy/autophagy in CSCs as compared to that of differentiated cancer cells. Using human and murine CSC models and differentiated cells, we show that the inhibition or knockdown (KD) of HDAC6 decreases CSC pluripotency by downregulating major pluripotency factors POU5F1, NANOG and SOX2. This decreased HDAC6 expression increases ACTB, TUBB3 and CSN2 expression and promotes differentiation in CSCs in an apoptosis-independent manner. Mechanistically, HDAC6 KD in CSCs decreases pluripotency by promoting autophagy, whereas the inhibition of pluripotency via retinoic acid treatment, POU5F1 or autophagy-related gene (ATG7 and ATG12) KD in CSCs decreases HDAC6 expression and promotes differentiation. Interestingly, HDAC6 KD-mediated CSC growth inhibition is further enhanced in the presence of autophagy inducers Tat-Beclin 1 peptide and rapamycin. In contrast to the results observed in CSCs, HDAC6 KD in differentiated breast cancer cells downregulates autophagy and increases apoptosis. Furthermore, the autophagy regulator p-MTOR, upstream negative regulators of p-MTOR (TSC1 and TSC2) and downstream effectors of p-MTOR (p-RPS6KB and p-EIF4EBP1) are differentially regulated in CSCs versus differentiated cancer cells following HDAC6 KD. Overall these data identify the differential regulation of autophagy as a molecular link behind the differing chemo-susceptibility of CSCs and differentiated cancer cells.

Down-regulation of histone deacetylase 4, -5 and -6 as a mechanism of synergistic enhancement of apoptosis in human lung cancer cells treated with the combination of a synthetic retinoid, Am80 and green tea catechin

(-)-Epigallocatechin gallate (EGCG), a green tea catechin, acts as a synergist with various anticancer drugs, including retinoids. Am80 is a synthetic retinoid with a different structure from all-trans-retinoic acid: Am80 is now clinically utilized as a new drug for relapsed and intractable acute promyelocytic leukemia patients. Our experiments showed that the combination of EGCG and Am80 synergistically induced both apoptosis in human lung cancer cell line PC-9 and up-regulated expressions of growth arrest and DNA damage-inducible gene 153 (GADD153), death receptor 5, and p21^waf1 genes in the cells. To understand the mechanisms of synergistic anticancer activity of the combination, we gave special attention to the lysine acetylation of proteins. Proteomic analysis using nanoLC-ESI-MS/MS revealed that PC-9 cells treated with the combination contained 331 acetylated proteins, while nontreated cells contained 553 acetylated proteins, and 59 acetylated proteins were found in both groups. Among them, the combination increased acetylated-p53 and acetylated-α-tubulin through reduction of histone deacetylase (HDAC) activity in cytosol fraction, although the levels of acetylation in histones H3 or H4 did not change, and the combination reduced protein levels of HDAC4, -5 and -6 by 20% to 80%. Moreover, we found that a specific inhibitor of HDAC4 and -5 strongly induced p21^waf1 gene expression, and that of HDAC6 induced both GADD153 and p21^waf1 gene expression, which resulted in apoptosis. All results demonstrate that EGCG in combination with Am80 changes levels of acetylation in nonhistone proteins via down-regulation of HDAC4, -5 and -6 and stimulates apoptotic induction.

Both HDAC5 and HDAC6 are required for the proliferation and metastasis of melanoma cells

Background

Histone deacetylase (HDAC) inhibitors are widely used in clinical investigation as novel drug targets. For example, panobinostat and vorinostat have been used to treat patients with melanoma. However, HDAC inhibitors are small-molecule compounds without a specific target, and their mechanism of action is unclear. Therefore, it is necessary to investigate which HDACs are required for the proliferation and metastasis of melanoma cells.

Methods

We used overexpression and knocking down lentivirus to clarify the influence of HDAC5 and HDAC6 in melanoma development. Also, we introduced stable HDAC5 or HDAC6 knockdown cells into null mice and found that the knockdown cells were unable to form solid tumors. Finally, we tested HDAC5 and HDAC6 expression and sub-location in clinical melanoma tissues and tumor adjacent tissues.

Results

In this study, and found that HDAC5 and HDAC6 were highly expressed in melanoma cells but exhibited low expression levels in normal skin cells. Furthermore, we knocked down HDAC5 or HDAC6 in A375 cells and demonstrated that both HDAC5 and HDAC6 contributed to the proliferation and metastasis of melanoma cells.

Conclusions

This study demonstrated both HDAC5 and HDAC6 were required for melanoma cell proliferation and metastasis through different signaling pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0753-0) contains supplementary material, which is available to authorized users.

TRPM2 mediates histone deacetylase inhibition-induced apoptosis in bladder cancer cells

PURPOSE

Inhibition of histone deacetylase (HDAC) activity results in growth arrest and apoptosis in multiple types of cancer cells. It has been well established that p21 is responsible for HDAC inhibitor (HDACi)-induced growth inhibition, while the mechanism underlying HDACi-elicited apoptosis in bladder cancer cells remains largely unknown.

METHODS

In this study, the apoptotic response to HDACi (trichostatin A and sodium butyrate) with different concentrations was determined by flow cytometry analysis and real-time polymerase chain reaction was conducted to examine the TRPM2 (Transient receptor potential cation channel, subfamily M, member 2) expression change on HDACi treatment. TRPM2 knockdown and overexpression were performed to investigate the role of TRPM2 in HDACi-induced apoptosis. The mechanism of HDACi-elicited upregulation of TRPM2 was studied by chromatin-immunoprecipitation.

RESULTS

HDACi efficiently induced cell apoptosis and TRPM2 upregulation in a time- and dose-dependent manner in T24 bladder cancer cells. Functional analysis revealed that TRPM2 overexpression promotes apoptosis of T24 cells. Conversely, TRPM2 depletion remarkably antagonized HDACi-induced apoptosis. Furthermore, HDAC inhibition-elicited TRPM2 upregulation is caused by the increase of acetylated H3K9 (H3K9Ac) enrichment in TRPM2 promoter.

CONCLUSIONS

These data suggest that the HDACi-elicited upregulation of TRPM2 expression is required for HDACi-induced apoptosis in bladder cancer cells and that HDACi activated the enrichment of H3K9Ac-represented permissive chromatin in TRPM2 promoter.

Limited efficacy of specific HDAC6 inhibition in urothelial cancer cells

Epigenetic modifiers such as histone deacetylases (HDACs) have come into focus as novel drug targets for cancer therapy due to their functional role in tumor progression. Since common pan-HDAC inhibitors have adverse side effects and minor anti-cancer activity against solid tumors, enzyme-specific inhibitors were developed. HDAC6 is especially well-suited for specific inhibition due to its unique domain structure and mode of action and has been suggested to provide an exceptionally suitable target for cancer therapy. However, expression and function of HDACs have been insufficiently studied in urothelial cancers (UC), a disease urgently requiring new therapeutic approaches. The present study sought to evaluate HDAC6 as a target for treatment of urothelial cancers with enzyme-specific inhibitors. We observed moderate HDAC6 overexpression in urothelial cancer tissues and a broad range of expression in urothelial cancer cell lines. In the cell lines Tubacin was the most potent inhibitor, compared with Tubastatin and ST-80, but still active only at high micromolar concentrations. HDAC6 expression levels correlated poorly with sensitivity to enzyme inhibition. Combined treatments with heat shock, HSP90 inhibition by 17-AAG, proteasome inhibition by bortezomib, or DNA-damaging agents did not result in significant synergistic effects. Experiments with siRNA-mediated knockdown further underlined that urothelial cancer cells do not critically depend on HDAC6 expression for survival.