Rational development of histone deacetylase inhibitors as anticancer agents: a review

Potential therapies targeting nuclear metabolic regulation in cancer

The interplay between genetic alterations and metabolic dysregulation is increasingly recognized as a pivotal axis in cancer pathogenesis. Both elements are mutually reinforcing, thereby expediting the ontogeny and progression of malignant neoplasms. Intriguingly, recent findings have highlighted the translocation of metabolites and metabolic enzymes from the cytoplasm into the nuclear compartment, where they appear to be intimately associated with tumor cell proliferation. Despite these advancements, significant gaps persist in our understanding of their specific roles within the nuclear milieu, their modulatory effects on gene transcription and cellular proliferation, and the intricacies of their coordination with the genomic landscape. In this comprehensive review, we endeavor to elucidate the regulatory landscape of metabolic signaling within the nuclear domain, namely nuclear metabolic signaling involving metabolites and metabolic enzymes. We explore the roles and molecular mechanisms through which metabolic flux and enzymatic activity impact critical nuclear processes, including epigenetic modulation, DNA damage repair, and gene expression regulation. In conclusion, we underscore the paramount significance of nuclear metabolic signaling in cancer biology and enumerate potential therapeutic targets, associated pharmacological interventions, and implications for clinical applications. Importantly, these emergent findings not only augment our conceptual understanding of tumoral metabolism but also herald the potential for innovative therapeutic paradigms targeting the metabolism-genome transcriptional axis.

Shifts in Intestinal Metabolic Profile Among Kidney Transplantation Recipients with Antibody-Mediated Rejection

Background

Antibody-mediated rejection (AMR) is emerging as the main cause of graft loss after kidney transplantation. Our previous study revealed the gut microbiota alternation associated with AMR in kidney transplant recipients, which was predicted to affect the metabolism-related pathways.

Methods

To further investigate the shifts in intestinal metabolic profile among kidney transplantation recipients with AMR, fecal samples from kidney transplant recipients and patients with end-stage renal disease (ESRD) were subjected to untargeted LC-MS-based metabolomics.

Results

A total of 86 individuals were enrolled in this study, including 30 kidney transplantation recipients with AMR, 35 kidney transplant recipients with stable renal function (KT-SRF), and 21 participants with ESRD. Fecal metabolome in patients with ESRD and kidney transplantation recipients with KT-SRF were parallelly detected as controls. Our results demonstrated that intestinal metabolic profile of patients with AMR differed significantly from those with ESRD. A total of 172 and 25 differential metabolites were identified in the KT-AMR group, when compared with the ESRD group and the KT-SRF group, respectively, and 14 were common to the pairwise comparisons, some of which had good discriminative ability for AMR. KEGG pathway enrichment analysis demonstrated that the different metabolites between the KT-AMR and ESRD groups or between KT-AMR and KT-SRF groups were significantly enriched in 33 or 36 signaling pathways, respectively.

Conclusion

From the metabolic point of view, our findings may provide key clues for developing effective diagnostic biomarkers and therapeutic targets for AMR after kidney transplantation.

Potential of histone deacetylase inhibitors for the therapy of ovarian cancer

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemotherapy increase patient mortality. Accumulating evidence demonstrates that histone modifications play a key role in cancerization and progression. Histone deacetylases is associated with chromatin condensed structure and transcriptional repression and play a role in chromatin remodeling and epigenetics. Histone deacetylases are promising targets for therapeutic interventions intended to reverse aberrant epigenetic associated with cancer. Therefore, histone deacetylases inhibitors could be used as anti-cancer drugs. Preclinical studies have shown promising outcomes of histone deacetylases inhibitors in ovarian cancer while clinical trials have had mixed results and limited success as monotherapy. Therefore, combination therapy with different anticancer drugs for synergistic effects and newly selective histone deacetylases inhibitors development for lower toxicity are hot issues now. In this review, we summarize the latest studies on the classification and mechanisms of action of histone deacetylase and the clinical application of their inhibitors as monotherapy or combination therapy in ovarian cancer.

Probiotics and gut microbiota: mechanistic insights into gut immune homeostasis through TLR pathway regulation

Consumption of probiotics as a useful functional food improves the host's wellbeing, and, when paired with prebiotics (indigestible dietary fibre/carbohydrate), often benefits the host through anaerobic fermentation.

Phase 1 trial of entinostat as monotherapy and combined with exemestane in Japanese patients with hormone receptor-positive advanced breast cancer

Background

Entinostat is an oral inhibitor of class I histone deacetylases intended for endocrine therapy-resistant patients with hormone receptor-positive (HR+) advanced or metastatic breast cancer (BC). We examined the safety, efficacy, and pharmacokinetics of entinostat monotherapy and combined entinostat/exemestane in Japanese patients.

Methods

This phase 1 study (3 + 3 dose-escalation design) enrolled postmenopausal women with advanced/metastatic HR+ BC previously treated with nonsteroidal aromatase inhibitors. Dose-limiting toxicities (DLTs) of entinostat monotherapy (3 mg/qw, 5 mg/qw, or 10 mg/q2w) and entinostat+exemestane (5 mg/qw + 25 mg/qd) were assessed. Pharmacokinetics, lysine acetylation (Ac-K), and T-cell activation markers were measured at multiple time points.

Results

Twelve patients were enrolled. No DLTs or grade 3–5 adverse events (AEs) occurred. Drug-related AEs (≥ 2 patients) during DLT observation were hypophosphatemia, nausea, and platelet count decreased. Six patients (50%) achieved stable disease (SD) for ≥ 6 months, including one treated for > 19 months. Median progression-free survival was 13.9 months (95% CI 1.9–not calculable); median overall survival was not reached. Area under the plasma concentration-time curve and Ac-K in peripheral blood CD19+ B cells increased dose-proportionally. The changing patterns of entinostat concentrations and Ac-K levels were well correlated. T-cell activation markers increased over time; CD69 increased more in patients with SD ≥ 6 months vs. SD < 6 months.

Conclusions

Entinostat monotherapy and combined entinostat/exemestane were well tolerated in Japanese patients, with no additional safety concerns compared with previous reports. The correlation between pharmacokinetics and Ac-K in peripheral blood CD19+ B cells, and also T-cell activation markers, merits further investigation.

Trial registration

JAPIC Clinical Trial Information, JapicCTI-153066. Registered 12 November 2015. ClinicalTrials.gov, NCT02623751. Registered 8 December 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08973-4.

Relevant pharmacological interactions between alkylating agents and antiepileptic drugs: Preclinical and clinical data

Seizures are relatively common in cancer patients, and co-administration of chemotherapeutic and antiepileptic drugs (AEDs) is highly probable and necessary in many cases. Nonetheless, clinically relevant interactions between chemotherapeutic drugs and AEDs are rarely summarized and pharmacologically described. These interactions can cause insufficient tumor and seizure control or lead to unforeseen toxicity. This review focused on pharmacokinetic and pharmacodynamic interactions between alkylating agents and AEDs, helping readers to make a rational choice of treatment optimization, and thus improving patients' quality of life. As an example, phenobarbital, phenytoin, and carbamazepine, by increasing the hepatic metabolism of cyclophosphamide, ifosfamide and busulfan, yield smaller peak concentrations and a reduced area under the plasma concentration-time curve (AUC) of the prodrugs; alongside, the maximum concentration and AUC of their active products were increased with the possible onset of severe adverse drug reactions. On the other side, valproic acid, acting as histone deacetylase inhibitor, showed synergistic effects with temozolomide when tested in glioblastoma. The present review is aimed at providing evidence that may offer useful suggestions for rational pharmacological strategies in patients with seizures symptoms undertaking alkylating agents. Firstly, clinicians should avoid the use of enzyme-inducing AEDs in combination with alkylating agents and prefer the use of AEDs, such as levetiracetam, that have a low or no impact on hepatic metabolism. Secondly, a careful therapeutic drug monitoring of both alkylating agents and AEDs (and their active metabolites) is necessary to maintain therapeutic ranges and to avoid serious adverse reactions.

Advances in Pyrazole Based Scaffold as Cyclin-Dependent Kinase 2 Inhibitors for the Treatment of Cancer

The transformation of a normal cell into a tumor cell is one of the initial steps in cell cycle deregulation. The cell cycle is regulated by cyclin-dependent kinases (CDKs) that belong to the protein kinase family. CDK2 is an enchanting target for specific genotypes tumors since cyclin E is selective for CDK2 and the deregulation of specific cancer forms. Thus, CDKs inhibitor specifically CDK2/cyclin A-E has the potential to be a valid cancer target as per the currently undergoing clinical trials. Mostly pyrazole scaffolds have shown selectivity and potency for CDK2 inhibitors. This review demonstrates pyrazole and pyrazole fused with other heterocyclic rings for anti-proliferative activity. Based on the in vitro and molecular docking studies, the IC50 value of various hybrids is revealed to display the most potent analogs for CDK2 inhibition. Thus, the review emphasizes various lead analogs of pyrazole hybrids which can be found to be very potent and selective for anti-cancer drugs.

Latency Reversing Agents: Kick and Kill of HTLV-1?

Human T-cell leukemia virus type 1 (HTLV-1), the cause of adult T-cell leukemia/lymphoma (ATLL), is a retrovirus, which integrates into the host genome and persistently infects CD4⁺ T-cells. Virus propagation is stimulated by (1) clonal expansion of infected cells and (2) de novo infection. Viral gene expression is induced by the transactivator protein Tax, which recruits host factors like positive transcription elongation factor b (P-TEFb) to the viral promoter. Since HTLV-1 gene expression is repressed in vivo by viral, cellular, and epigenetic mechanisms in late phases of infection, HTLV-1 avoids an efficient CD8⁺ cytotoxic T-cell (CTL) response directed against the immunodominant viral Tax antigen. Hence, therapeutic strategies using latency reversing agents (LRAs) sought to transiently activate viral gene expression and antigen presentation of Tax to enhance CTL responses towards HTLV-1, and thus, to expose the latent HTLV-1 reservoir to immune destruction. Here, we review strategies that aimed at enhancing Tax expression and Tax-specific CTL responses to interfere with HTLV-1 latency. Further, we provide an overview of LRAs including (1) histone deacetylase inhibitors (HDACi) and (2) activators of P-TEFb, that have mainly been studied in context of human immunodeficiency virus (HIV), but which may also be powerful in the context of HTLV-1.

Comparative QM/MM Molecular Dynamics and Umbrella Sampling Simulations: Interaction of the Zinc-Bound Intermediate Gem-Diolate Trapoxin A Inhibitor and Acetyl-l-lysine Substrate with Histone Deacetylase 8

Targeting the genetic material without destruction is a priority to develop safe anticancer drugs. Histone deacetylase 8 (HDAC8), which is proved to be involved in carcinogenesis, is an enzyme associated with the chromatin for post-translational deacetylation of acetylated lysine. In this study, HDAC8 co-crystallized with the intermediate state tetrapeptide Trapoxin A (TA) inhibitor and the holoenzyme are utilized to find their conformational ensembles. Furthermore, the co-crystallized intermediate gem-diolate TA was used to find optimum interactions with the active site residues by conventional molecular dynamics (MD) simulation and QM/MM umbrella sampling. Finally, the intermediate state of the acetyl-l-lysine substrate was explored by QM/MM steered MD and compared to the binding of the intermediate state of the inhibitor. This research showed that HDAC8 is flexible and exists in conformational ensembles in its holoenzyme state. Binding of the intermediate state TA stabilizes its conformation. The optimum binding to the active site of HDAC8 for structures of gem-diolate TA (intermediate state) and acetyl-l-lysine (intermediate state) was determined according to the corresponding energy profiles. The use of these models will aid in the design of potentially reversible, potent, and selective inhibitors of HDAC8 for cancer treatment.

The role of HDAC11 in obesity-related metabolic disorders: A critical review

At present, metabolic diseases, such as obesity and diabetes, have become the world's top health threats. These diseases are closely related to the abnormal development and function of adipocytes and metabolic inflammation associated with obesity. Histone deacetylase 11 (HDAC11), with a relatively unique structure and function in the HDAC family, plays a vital role in regulating cell growth, migration, and cell death. Currently, research on new key regulatory functions of HDAC11 in metabolic homeostasis is receiving more and more attention, and HDAC11 has also become a potential therapeutic target in the treatment of obesity and obesity-related diseases. Here, we summarized the latest literature on the role of HDAC11 in regulating the progress of obesity-related metabolic disorders.

Bromodomain and BET family proteins as epigenetic targets in cancer therapy: their degradation, present drugs, and possible PROTACs

Alteration in the pattern of epigenetic marking leads to cancer, neurological disorders, inflammatory problems etc. These changes are due to aberration in histone modification enzymes that function as readers, writers and erasers. Bromodomains (BDs) and BET proteins that recognize acetylation of chromatin regulate gene expression. To block the function of any of these BrDs and/or BET protein can be a controlling agent in disorders such as cancer. BrDs and BET proteins are now emerging as targets for new therapeutic development. Traditional drugs like enzyme inhibitors and protein–protein inhibitors have many limitations. Recently Proteolysis-Targeting Chimeras (PROTACs) have become an advanced tool in therapeutic intervention as they remove disease causing proteins. This review provides an overview of the development and mechanisms of PROTACs for BRD and BET protein regulation in cancer and advanced possibilities of genetic technologies in therapeutics.

Alteration in the pattern of epigenetic marking leads to cancer, neurological disorders, inflammatory problems etc.

Chidamide increases the sensitivity of refractory or relapsed acute myeloid leukemia cells to anthracyclines via regulation of the HDAC3 -AKT-P21-CDK2 signaling pathway

BACKGROUND

Induction therapy for acute myeloid leukemia (AML) is an anthracycline-based chemotherapy regimen. However, many patients experience a relapse or exhibit refractory disease (R/R). There is an urgent need for more effective regimens to reverse anthracycline resistance in these patients.

METHODS

In this paper, Twenty-seven R/R AML patients with anthracycline resistance consecutively received chidamide in combination with anthracycline-based regimen as salvage therapy at the Chinese PLA General Hospital.

RESULTS

Of the 27 patients who had received one course of salvage therapy, 13 achieved a complete response and 1 achieved a partial response. We found that the HDAC3-AKT-P21-CDK2 signaling pathway was significantly upregulated in anthracycline-resistant AML cells compared to non-resistant cells. AML patients with higher levels of HDAC3 had lower event-free survival (EFS) and overall survival (OS) rates. Moreover, anthracycline-resistant AML cells are susceptible to chidamide, a histone deacetylase inhibitor which can inhibit cell proliferation, increase cell apoptosis and induce cell-cycle arrest in a time- and dose-dependent manner. Chidamide increases the sensitivity of anthracycline-resistant cells to anthracycline drugs, and these effects are associated with the inhibition of the HDAC3-AKT-P21-CDK2 signaling pathway.

CONCLUSION

Chidamide can increase anthracycline drug sensitivity by inhibiting HDAC3-AKT-P21-CDK2 signaling pathway, thus demonstrating the potential for application.

Recent Progress in Histone Deacetylase Inhibitors as Anticancer Agents

Histone Deacetylase (HDAC) inhibitors are a relatively new class of anti-cancer agents that play important roles in epigenetic or non-epigenetic regulation, inducing death, apoptosis, and cell cycle arrest in cancer cells. Recently, their use has been clinically validated in cancer patients resulting in the approval by the FDA of four HDAC inhibitors, vorinostat, romidepsin, belinostat and panobinostat, used for the treatment of cutaneous/peripheral T-cell lymphoma and multiple myeloma. Many more HDAC inhibitors are at different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. Also, clinical trials of several HDAC inhibitors for use as anti-cancer drugs (alone or in combination with other anti-cancer therapeutics) are ongoing. In the intensifying efforts to discover new, hopefully, more therapeutically efficacious HDAC inhibitors, molecular modelingbased rational drug design has played an important role. In this review, we summarize four major structural classes of HDAC inhibitors (hydroxamic acid derivatives, aminobenzamide, cyclic peptide and short-chain fatty acids) that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

Epileptogenesis and oncogenesis: An antineoplastic role for antiepileptic drugs in brain tumours?

The first description of epileptic seizures due to brain tumours occurred in 19th century. Nevertheless, after over one hundred years, scientific literature is still lacking on how epilepsy and its treatment can affect tumour burden, progression and clinical outcomes. In patients with brain tumours, epilepsy dramatically impacts their quality of life (QoL). Even antiepileptic therapy seems to affect tumor lesion development. Numerous studies suggest that certain actors involved in epileptogenesis (inflammatory changes, glutamate and its ionotropic and metabotropic receptors, GABA-A and its GABA-AR receptor, as well as certain ligand- and voltage-gated ion channel) may also contribute to tumorigenesis. Although some antiepileptic drugs (AEDs) are known operating on such mechanisms underlying epilepsy and tumor development, few preclinical and clinical studies have tried to investigate them as targets of pharmacological tools acting to control both phenomena. The primary aim of this review is to summarize known determinants and pathophysiological mechanisms of seizures, as well as of cell growth and spread, in patients with brain tumors. Therefore, a special focus will be provided on the anticancer effects of commonly prescribed AEDs (including levetiracetam, valproic acid, oxcarbazepine and others), with an overview of both preclinical and clinical data. Potential clinical applications of this finding are discussed.

A class of Pt(iv) triple-prodrugs targeting nucleic acids, thymidylate synthases and histone deacetylases

A Pt(iv)-triple-prodrug, comprising VPA, 5-FU, regulated TS, HDAC, and γH2AX, showing higher efficiency and lower toxicity than cisplatin.

Divergent Access to Histone Deacetylase Inhibitory Cyclopeptides via a Late-Stage Cyclopropane Ring Cleavage Strategy. Short Synthesis of Chlamydocin

A unified step-economical strategy for accessing histone deacetylase inhibitory peptides is proposed, based on the late-stage installation of multiple zinc-binding functionalities via the cleavage of the strained cyclopropane ring in the common pluripotent cyclopropanol precursor. The efficacy of the proposed diversity-oriented approach has been validated by short stereoselective synthesis of natural product chlamydocin, containing a challenging-to-install fragment of (2S,9S)-2-amino-8-oxo-9,10-epoxydecanoic acid (Aoe) and a range of its analogues, derivatives of 2-amino-8-oxodecanoic and 2-aminosuberic acids.

Epigenetic Regulation of TRAIL Signaling: Implication for Cancer Therapy

One of the main characteristics of carcinogenesis relies on genetic alterations in DNA and epigenetic changes in histone and non-histone proteins. At the chromatin level, gene expression is tightly controlled by DNA methyl transferases, histone acetyltransferases (HATs), histone deacetylases (HDACs), and acetyl-binding proteins. In particular, the expression level and function of several tumor suppressor genes, or oncogenes such as c-Myc, p53 or TRAIL, have been found to be regulated by acetylation. For example, HATs are a group of enzymes, which are responsible for the acetylation of histone proteins, resulting in chromatin relaxation and transcriptional activation, whereas HDACs by deacetylating histones lead to chromatin compaction and the subsequent transcriptional repression of tumor suppressor genes. Direct acetylation of suppressor genes or oncogenes can affect their stability or function. Histone deacetylase inhibitors (HDACi) have thus been developed as a promising therapeutic target in oncology. While these inhibitors display anticancer properties in preclinical models, and despite the fact that some of them have been approved by the FDA, HDACi still have limited therapeutic efficacy in clinical terms. Nonetheless, combined with a wide range of structurally and functionally diverse chemical compounds or immune therapies, HDACi have been reported to work in synergy to induce tumor regression. In this review, the role of HDACs in cancer etiology and recent advances in the development of HDACi will be presented and put into perspective as potential drugs synergizing with TRAIL's pro-apoptotic potential.

Targeting stem cells in the realm of drug-resistant breast cancer

Since its first documentation, breast cancer (BC) has been a conundrum that ails millions of women every year. This cancer has been well studied by researchers all over the world, which has improved the patient outcome significantly. There are many diagnostic markers to identify the disease, but early detection and then subclassification of this cancer remain dubious. Even after the correct diagnosis, more than half the patients come back with a more aggressive and metastatic tumor. The underpinning mechanism that governs the resistance includes over-amplification of receptors, mutations in key gene targets, and activation of different signaling. A plethora of drugs have been devised that have shown promising results in clinical settings. However, in recent times, the role played by cancer stem cells in disease progression and their interaction in mediating the resistance to cellular insults have come into the limelight. As breast cancer stem cells (BCSCs) are dormant in nature, it is highly likely that they fail to directly respond to the cytotoxic drugs which are meant for ablating rapidly proliferating cells. Furthermore, the absence of well-characterized, drug-able surface markers to date, has limited the application of targeted therapies in complete eradication of the disease. In this review, our intent is to discuss versatile therapeutics in practice followed by discussing the upcoming therapy strategies in the pipeline for BC. Furthermore, we focus on the roles played by BCSCs in mediating the resistance, and therefore, the aspects of new therapeutics against BCSCs under development that may ease the burden in future has also been discussed.

Anti-plasmodial activity of sodium acetate in Plasmodium berghei-infected mice

Background

Continuous increase in drug resistance has hindered the control of malaria infection and resulted in multi-drug-resistant parasite strains. This, therefore, intensifies the search for alternative treatments with no or less side effects. Several histone deacetylase inhibitors have been characterised to possess anti-malaria activity; however, their further development as anti-malaria agents has not recorded much success. The present study investigated the anti-plasmodial activity of sodium acetate in Plasmodium berghei-infected mice, aiming at finding a better alternative source of malaria chemotherapy.

Methods

Thirty female Swiss albino mice were randomly distributed into six groups. Groups A (uninfected control) and B (infected control) received only distilled water. Group C (artesunate control) were infected and treated orally with 4 mg/kg artesunate on the first day, and subsequently 2 mg/kg artesunate. Groups D, E and F were infected and orally treated with 50, 100 and 200 mg/kg sodium acetate, respectively.

Results

Sodium acetate significantly lowered parasitaemia (p<0.05) after 4 days post-treatment, and the parasite inhibition rate of 68.5% at 50 mg/kg compared favourably with the 73.3% rate of artesunate. Similarly, administration of 50 mg/kg sodium acetate improved serum total cholesterol relatively better than artesunate. Our results also revealed that sodium acetate does not interfere with liver function, as there was no significant difference (p>0.05) in the serum activities of aspartate aminotransferase and alanine aminotransferase in both infected treated and uninfected mice.

Conclusions

This study shows that sodium acetate may be a safe alternative source of anti-malaria drugs. Its effect on the serum total cholesterol also predicts its ability in correcting malaria-induced metabolic syndromes.

Alterations in histone acetylation following exposure to 60Co γ-rays and their relationship with chromosome damage in human lymphoblastoid cells

Chromosome damage is related to DNA damage and erroneous repair. It can cause cell dysfunction and ultimately induce carcinogenesis. Histone acetylation is crucial for regulating chromatin structure and DNA damage repair. Ionizing radiation (IR) can alter histone acetylation. However, variations in histone acetylation in response to IR exposure and the relationship between histone acetylation and IR-induced chromosome damage remains unclear. Hence, this study investigated the variation in the total acetylation levels of H3 and H4 in human lymphocytes exposed to 0-2 Gy ⁶⁰Co γ-rays. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, was added to modify the histone acetylation state of irradiated cells. Then, the total acetylation level, enzyme activity, dicentric plus centric rings (dic + r) frequencies, and micronucleus (MN) frequencies of the treated cells were analyzed. Results indicated that the acetylation levels of H3 and H4 significantly decreased at 1 and 24 h, respectively, after radiation exposure. The acetylation levels of H3 and H4 in irradiated groups treated with SAHA were significantly higher than those in irradiated groups that were not treated with SAHA. SAHA treatment inhibited HDAC activity in cells exposed to 0-1 Gy ⁶⁰Co γ-rays. SAHA treatment significantly decreased dic + r/cell and MN/cell in cells exposed to 0.5 or 1.0 Gy ⁶⁰Co γ-rays relative to that in cells that did not receive SAHA treatment. In conclusion, histone acetylation is significantly affected by IR and is involved in chromosome damage induced by ⁶⁰Co γ-radiation.

Triple action Pt(iv) derivatives of cisplatin: a new class of potent anticancer agents that overcome resistance

A series of triple action Pt(iv) prodrugs was designed to test the hypothesis that multi-action compounds, where each bioactive moiety intervenes in several cellular processes, might be more effective than a single agent at killing cancer cells. In particular, "triple action" Pt(iv) derivatives of cisplatin, where the axial ligands are inhibitors of cyclooxygenase (COXi), histone deacetylase (HDACi) or pyruvate dehydrogenase kinase (PDKi) were developed. All compounds, ctc-[Pt(NH₃)₂(COXi)(PDKi)Cl₂], ctc-[Pt(NH₃)₂(COXi)(HDACi)Cl₂] and ctc-[Pt(NH₃)₂(HDACi)(PDKi)Cl₂], where COXi = aspirin or ibuprofen, PDKi = dichloroacetate and HDACi = valproate or phenylbutyrate, were significantly more cytotoxic than cisplatin against all cell lines of an in-house panel of human cancer cells. They were particularly effective against thyroid and pancreatic cancer cells in monolayer cytotoxicity tests. Remarkably, in 3D spheroid cancer cell cultures, some triple action compounds showed an antitumor potency up to 50-fold higher than cisplatin against a KRAS mutated pancreatic cancer cell line (PSN-1 cells). Standard biochemical assays classically employed to explore structure activity relationships of platinum drugs, such as cellular uptake and binding to potential biological targets (DNA, HDAC, mitochondria, and COX), do not provide linear correlations with the overall cytotoxicity data. We observed a preferential induction of ROS production and of an anti-mitochondrial effect in cancer cells compared to rapidly dividing non-cancerous cells. Thus, we propose that these new triple action Pt(iv) derivatives of cisplatin are a novel and interesting class of potent and selective cytotoxic agents.

Insights into structural features of HDAC1 and its selectivity inhibition elucidated by Molecular dynamic simulation and Molecular Docking

Histone deacetylases (HDACs) are a family of proteins whose main function is the removal of acetyl groups from lysine residues located on histone and non-histone substrates, which regulates gene transcription and other activities in cells. HDAC1 dysfunction has been implicated in cancer development and progression; thus, its inhibition has emerged as a new therapeutic strategy. Two additional metal binding sites (Site 1 and Site 2) in HDACs have been described that are primarily occupied by potassium ions, suggesting a possible structural role that affects HDAC activity. In this work, we explored the structural role of potassium ions in Site 1 and Site 2 and how they affect the interactions of compounds with high affinities for HDAC1 (AC1OCG0B, Chlamydocin, Dacinostat and Quisinostat) and SAHA (a pan-inhibitor) using molecular docking and molecular dynamics (MD) simulations in concert with a Molecular-Mechanics-Generalized-Born-Surface-Area (MMGBSA) approach. Four models were generated: one with a potassium ion (K⁺) in both sites (HDAC1_k), a second with K⁺ only at site 1 (HDAC1_ks1), a third with K⁺ only at site 2 (HDAC1_ks2) and a fourth with no K⁺ (HDAC1_wk). We found that the presence or absence of K⁺ not only impacted the structural flexibility of HDAC1, but also its molecular recognition, consistent with experimental findings. These results could therefore be useful for further structure-based drug design studies addressing new HDAC1 inhibitors.

New 5-Aryl-Substituted 2-Aminobenzamide-Type HDAC Inhibitors with a Diketopiperazine Group and Their Ameliorating Effects on Ischemia-Induced Neuronal Cell Death

We previously synthesized new 5-thienyl-substituted 2-aminobenzamide-type HDAC1, 2 inhibitors with the (4-ethyl-2,3-dioxopiperazine-1-carboxamido) methyl group. K-560 (1a) protected against neuronal cell death in a Parkinson’s disease model by up-regulating the expression of XIAP. This finding prompted us to design new K-560-related compounds. We examined the structure activity relationship (SAR) for the neuronal protective effects of newly synthesized and known K-560 derivatives after cerebral ischemia. Among them, K-856 (8), containing the (4-methyl-2,5-dioxopiperazin-1-yl) methyl group, exhibited a promising neuronal survival activity. The SAR study strongly suggested that the attachment of a monocyclic 2,3- or 2,5-diketopiperazine group to the 2-amino-5-aryl (but not 2-nitro-5-aryl) scaffold is necessary for K-560-related compounds to exert a potent neuroprotective effect.

Trichostatin A inhibits radiation-induced epithelial-to-mesenchymal transition in the alveolar epithelial cells

Radiation-induced pneumonitis and fibrosis are major complications following thoracic radiotherapy. Epithelial-to-mesenchymal transition (EMT) plays an important role in tissue injury leading to organ fibrosis, including lung. Our previous studies have reported that radiation can induce EMT in the type II alveolar epithelial cells in both in vitro and in vivo. HDAC inhibitors are a new family of anti-cancer agents currently being used in several clinical trials. In addition to their intrinsic anti-tumor properties, HDAC inhibition is also important in other human diseases, including fibrosis and radiation-induced damage. In this study, we evaluated the effect of Trichostatin A (TSA), a HDAC inhibitor, on radiation-induced EMT in type II alveolar epithelial cells (RLE-6TN). Pre-treatment of RLE-6TN cells with TSA inhibited radiation-induced EMT-like morphological alterations including elevated protein level of α-SMA and Snail, reduction of E-cadherin expression, enhanced phosphorylation of GSK3β and ERK1/2, increased generation of ROS. Radiation enhanced the protein level of TGF-β1, which was blocked by N-acetylcysteine, an antioxidant. Treating cells with SB-431542, TGF-β1 type I receptor inhibitor, diminished radiation-induced alterations in the protein levels of p-GSK-3β, Snail-1 and α-SMA, suggesting a regulatory role of TGF-β1 in EMT. Pre-incubation of cells with TSA showed significant decrease in the level of TGF-β1 compared to radiation control. Collectively, these results demonstrate that i] radiation-induced EMT in RLE-6TN cells is mediated by ROS/MEK/ERK and ROS/TGF-β1 signaling pathways and ii] the inhibitory role of TSA in radiation-induced EMT appears to be due, at least in part, to its action of blocking ROS and TGF-β1 signaling.

The role of HDAC2 in chromatin remodelling and response to chemotherapy in ovarian cancer

Chromatin undergoes structural changes in response to extracellular and environmental signals. We observed changes in nuclear morphology in cancer tissue biopsied after chemotherapy and hypothesised that these DNA damage-induced changes are mediated by histone deacetylases (HDACs). Nuclear morphological changes in cell lines (PE01 and PE04 models) and a xenograft model (OV1002) were measured in response to platinum chemotherapy by image analysis of nuclear texture. HDAC2 expression increased in PEO1 cells treated with cisplatin at 24h, which was accompanied by increased expression of heterochromatin protein 1 (HP1). HDAC2 and HP1 expression were also increased after carboplatin treatment in the OV1002 carboplatin-sensitive xenograft model but not in the insensitive HOX424 model. Expression of DNA damage response pathways (pBRCA1, γH2AX, pATM, pATR) showed time-dependent changes after cisplatin treatment. HDAC2 knockdown by siRNA reduced HP1 expression, induced DNA double strand breaks (DSB) measured by γH2AX, and interfered with the activation of DNA damage response induced by cisplatin. Furthermore, HDAC2 depletion affected γH2AX foci formation, cell cycle distribution, and apoptosis triggered by cisplatin, and was additive to the inhibitory effect of cisplatin in cell lines. By inhibiting expression of HDAC2, reversible alterations in chromatin patterns during cisplatin treatment were observed. These results demonstrate quantifiable alterations in nuclear morphology after chemotherapy, and implicate HDAC2 in higher order chromatin changes and cellular DNA damage responses in ovarian cancer cells in vitro and in vivo.

Valproic acid, compared to other antiepileptic drugs, is associated with improved overall and progression-free survival in glioblastoma but worse outcome in grade II/III gliomas treated with temozolomide

Valproic acid (VPA) is an anti-epileptic drug with properties of a histone deacetylase inhibitor (HDACi). HDACi play a key role in epigenetic regulation of gene expression and have been increasingly used as anticancer agents. Recent studies suggest that VPA is associated with improved survival in high-grade gliomas. However, effects on lower grade gliomas have not been examined. This study investigates whether use of VPA correlates with tumor grade, histological progression, progression-free and overall survival (OS) in grade II, III, and IV glioma patients. Data from 359 glioma patients (WHO II-IV) treated with temozolomide plus an antiepileptic drug (VPA or another antiepileptic drug) between January 1997 and June 2013 at the Massachusetts General Hospital was analyzed retrospectively. After confounder adjustment, VPA was associated with a 28 % decrease in hazard of death (p = 0.031) and a 28 % decrease in the hazard of progression or death (p = 0.015) in glioblastoma. Additionally, VPA dose correlated with reduced hazard of death by 7 % (p = 0.002) and reduced hazard of progression or death by 5 % (p < 0.001) with each 100 g increase in total dose. Conversely, in grade II and III gliomas VPA was associated with a 118 % increased risk of tumor progression or death (p = 0.014), and every additional 100 g of VPA raised the hazard of progression or death by 4 %, although not statistically significant (p = 0.064). Moreover, grade II and III glioma patients taking VPA had 2.17 times the risk of histological progression (p = 0.020), although this effect was no longer significant after confounder adjustment. In conclusion, VPA was associated with improved survival in glioblastoma in a dose-dependent manner. However, in grade II and III gliomas, VPA was linked to histological progression and decrease in progression-free survival. Prospective evaluation of VPA treatment for glioma patients is warranted to confirm these findings.

Design and development of sulfonylurea derivatives as zinc metalloenzyme modulators

Sulfonylurea derivatives are zinc metalloenzyme modulators.

The Effect of MGCD0103 on CYP450 Isoforms Activity of Rats by Cocktail Method

MGCD0103, an isotype-selective histone deacetylase inhibitor (HDACi), has been clinically evaluated for the treatment of hematologic malignancies and advanced solid tumors, alone and in combination with standard-of-care agents. In order to investigate the effects of MGCD0103 on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of human CYP2B1, CYP1A2, CYP2C11, CYP2D6, CYP3A4, and CYP2C9. The rats were randomly divided into MGCD0103 group (Low, Medium, and High) and control group. The MGCD0103 group rats were given 20, 40, and 80 mg/kg (Low, Medium, and High) MGCD0103 by continuous intragastric administration for 7 days. Six probe drugs, bupropion, phenacetin, tolbutamide, metoprolol, testosterone, and omeprazole, were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS. Statistical pharmacokinetics difference for tolbutamide in rats were observed by comparing MGCD0103 group with control group. Continuous 7-day intragastric administration of MGCD0103 slightly induces the activities of CYP2C11 of rats.

The synergic effect of vincristine and vorinostat in leukemia in vitro and in vivo

Background

Combination therapy is a key strategy for minimizing drug resistance, a common problem in cancer therapy. The microtubule-depolymerizing agent vincristine is widely used in the treatment of acute leukemia. In order to decrease toxicity and chemoresistance of vincristine, this study will investigate the effects of combination vincristine and vorinostat (suberoylanilide hydroxamic acid (SAHA)), a pan-histone deacetylase inhibitor, on human acute T cell lymphoblastic leukemia cells.

Methods

Cell viability experiments were determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and cell cycle distributions as well as mitochondria membrane potential were analyzed by flow cytometry. In vitro tubulin polymerization assay was used to test tubulin assembly, and immunofluorescence analysis was performed to detect microtubule distribution and morphology. In vivo effect of the combination was evaluated by a MOLT-4 xenograft model. Statistical analysis was assessed by Bonferroni’s t test.

Results

Cell viability showed that the combination of vincristine and SAHA exhibited greater cytotoxicity with an IC₅₀ value of 0.88 nM, compared to each drug alone, 3.3 and 840 nM. This combination synergically induced G₂/M arrest, followed by an increase in cell number at the sub-G₁ phase and caspase activation. Moreover, the results of vincristine combined with an HDAC6 inhibitor (tubastatin A), which acetylated α-tubulin, were consistent with the effects of vincristine/SAHA co-treatment, thus suggesting that SAHA may alter microtubule dynamics through HDAC6 inhibition.

Conclusion

These findings indicate that the combination of vincristine and SAHA on T cell leukemic cells resulted in a change in microtubule dynamics contributing to M phase arrest followed by induction of the apoptotic pathway. These data suggest that the combination effect of vincristine/SAHA could have an important preclinical basis for future clinical trial testing.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0176-7) contains supplementary material, which is available to authorized users.

Treatment of chronic kidney diseases with histone deacetylase inhibitors

Histone deacetylases (HDACs) induce deacetylation of both histone and non-histone proteins and play a critical role in the modulation of physiological and pathological gene expression. Pharmacological inhibition of HDAC has been reported to attenuate progression of renal fibrogenesis in obstructed kidney and reduce cyst formation in polycystic kidney disease. HDAC inhibitors (HDACis) are also able to ameliorate renal lesions in diabetes nephropathy, lupus nephritis, aristolochic acid nephropathy, and transplant nephropathy. The beneficial effects of HDACis are associated with their anti-fibrosis, anti-inflammation, and immunosuppressant effects. In this review, we summarize recent advances on the treatment of various chronic kidney diseases with HDACis in pre-clinical models.

An unbiased approach to identify endogenous substrates of "histone" deacetylase 8

Despite being extensively characterized structurally and biochemically, the functional role of histone deacetylase 8 (HDAC8) has remained largely obscure due in part to a lack of known cellular substrates. Herein, we describe an unbiased approach using chemical tools in conjunction with sophisticated proteomics methods to identify novel non-histone nuclear substrates of HDAC8, including the tumor suppressor ARID1A. These newly discovered substrates of HDAC8 are involved in diverse biological processes including mitosis, transcription, chromatin remodeling, and RNA splicing and may help guide therapeutic strategies that target the function of HDAC8.

Trichostatin A induces mesenchymal-like morphological change and gene expression but inhibits migration and colony formation in human cancer cells

Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl from lysine residues in histones and other proteins, which results in gene transcriptional repression and subsequent changes in signaling events. HDACs inhibitors (HDACIs) have been used to reverse the aberrant epigenetic changes associated with cancer. However, the effects of HDACIs on epithelial-mesenchymal transition (EMT) in human cancer cells remain unclear. EMT is a fundamental process governing morphogenesis in multicellular organisms and promotes cancer invasion and metastasis. In this study, human cancer cells were treated with the HDACI trichostatin A (TSA). TSA was found to induce mesenchymal‑like morphological changes in BGC-823 human gastric cancer and MCF-7 breast cancer cells, and increase the expression levels of the mesenchymal markers Vimentin and Twist. However, the expression levels of the epithelial cell marker E-cadherin were also increased in response to TSA treatment, while cell migration was reduced by TSA. Furthermore, TSA decreased cancer cell colony formation in BGC-823 and MCF-7 cells, and led to the deregulation of β-catenin, a critical signaling molecule involved in EMT. In conclusion, the results suggested that TSA exhibits dual functions in EMT induction and inhibition in human cancer cells, but the detailed mechanisms require further investigation.

Emerging roles of lactic acid bacteria in protection against colorectal cancer

Colorectal cancer (CRC) is the third leading cause of cancer deaths worldwide and the fourth most common cancer diagnosed among men and women in the United States. Considering the risk factors of CRC, dietary therapy has become one of the most effective approaches in reducing CRC morbidity and mortality. The use of probiotics is increasing in popularity for both the prevention and treatment of a variety of diseases. As the most common types of microbes used as probiotics, lactic acid bacteria (LAB) are comprised of an ecologically diverse group of microorganisms united by formation of lactic acid as the primary metabolite of sugar metabolism. LAB have been successfully used in managing diarrhea, food allergies, and inflammatory bowel disease. LAB also demonstrated a host of properties in preventing colorectal cancer development by inhibiting initiation or progression through multiple pathways. In this review, we discuss recent insights into cellular and molecular mechanisms of LAB in CRC prevention including apoptosis, antioxidant DNA damages, immune responses, and epigenetics. The emerging experimental findings from clinical trials as well as the proposed mechanisms of gut microbiota in carcinogenesis will also be briefly discussed.

Potential role of histone deacetylase inhibitors in the treatment of advanced non-small-cell lung cancer

SUMMARY 

Histones are highly alkaline proteins of cell nuclei that package and order DNA into structural units called nucleosomes. The balance between the acetylation and deacetylation of hystones is mediated by two different sets of enzymes: histone acetyltransferases and histone deacetylases (HDACs). HDAC inhibitors, a novel class of anticancer agents, acting by regulating chromatin structure and function, induce acetylation of histones, which ultimately results in apoptosis and cell cycle arrest, modulate anticancer immunity and inhibition of angiogenesis. HDAC inhibitors are being clinically investigated for the treatment of several hematological and solid tumors. The potential role of HDAC inhibitors in the treatment of advanced non-small-cell lung cancer patients, including their clinical effectiveness and future developments, is discussed here.

Influence of bacteria on epigenetic gene control

Cellular information is inherited by daughter cells through epigenetic routes in addition to genetic routes. Epigenetics, which is primarily mediated by inheritable DNA methylation and histone post-translational modifications, involves changes in the chromatin structure important for regulating gene expression. It is widely known that epigenetic control of gene expression plays an essential role in cell differentiation processes in vertebrates. Furthermore, because epigenetic changes can occur reversibly depending on environmental factors in differentiated cells, they have recently attracted considerable attention as targets for disease prevention and treatment. These environmental factors include diet, exposure to bacteria or viruses, and air pollution, of which this review focuses on the influence of bacteria on epigenetic gene control in a host. Host-bacterial interactions not only occur upon pathogenic bacterial infection but also continuously exist between commensal bacteria and the host. These bacterial stimuli play an essential role in various biological responses involving external stimuli and in maintaining physiological homeostasis by altering epigenetic markers and machinery.

Histone deacetylase inhibitors and epigenetic modifications as a novel strategy in renal cell carcinoma

Recent investigations of renal cell carcinoma (RCC) have revealed several epigenetic modifications, as well as alterations in the genes and enzymes that regulate these changes. Preclinical models have revealed that histone gene modifiers and epigenetic alterations may play a critical role in RCC tumorigenesis. Specific changes in DNA methylation and mutations of histone modifiers have been identified and may be associated with an aggressive phenotype. In addition, the potential of reversing the effects of these enzymes and hence reversing the cellular epigenetic landscape to a "normal phenotype" have led to an increasing interest in developing targeted chromatin remodeling agents. However, the translation of the understanding of these changes to the clinic for the treatment of RCC has posed significant challenges, partly due to tumor heterogeneity. This review describes the aberrant histone and DNA alterations recently reported in RCC and highlights the potential targeted chromatin remodeling therapies in the management of this disease.

Epigenetic modulators mitigate angiogenesis through a complex transcriptomic network

In this review, we summarize the knowledge pertaining to the role of epigenetics in the regulation of angiogenesis. In particular, we show that lysine acetylation and cytosine methylation are important transcriptional regulators of angiogenic genes in endothelial cells. Lysine acetylation and cytosine methylation inhibitors idiosyncratically tune the transcriptome and affect expression of key modulators of angiogenesis such as VEGF and eNOS. Transcriptomic profiling also reveals a series of novel genes that are concomitantly affected by epigenetic modulators. The reversibility and overall tolerability of currently available epigenetic inhibitors open up the prospect of therapeutic intervention in pathologies where angiogenesis is exacerbated. This type of multitargeted strategy has the major advantage of overcoming the compensatory feedback mechanisms that characterize single anti-angiogenic factors.

Adverse reactions to targeted and non-targeted chemotherapeutic drugs with emphasis on hypersensitivity responses and the invasive metastatic switch

More than 100 drugs are used to treat the many different cancers. They can be divided into agents with relatively broad, non-targeted specificity and targeted drugs developed on the basis of a more refined understanding of individual cancers and directed at specific molecular targets on different cancer cells. Individual drugs in both groups have been classified on the basis of their mechanism of action in killing cancer cells. The targeted drugs include proteasome inhibitors, toxic chimeric proteins and signal transduction inhibitors such as tyrosine kinase (non-receptor and receptor), serine/threonine kinase, histone deacetylase and mammalian target of rapamycin inhibitors. Increasingly used targeted vascular (VEGF) and platelet-derived endothelial growth factor blockade can provoke a range of pathological consequences. Many of the non-targeted drugs are cytotoxic, suppressing haematopoiesis as well as provoking cutaneous eruptions and vascular, lung and liver injury. Cytotoxic side effects of the targeted drugs occur less often and usually with less severity, but they show their own unusual adverse effects including, for example, a lengthened QT interval, a characteristic papulopustular rash, nail disorders and a hand-foot skin reaction variant. The term hypersensitivity is widely used across a number of disciplines but not always with the same definition in mind, and the terminology needs to be standardised. This is particularly apparent in cancer chemotherapy where anti-neoplastic drug-induced thrombocytopenia, neutropenia, anaemia, vascular disorders, liver injury and lung disease as well as many dermatological manifestations sometimes have an immune basis. The most insidious of all adverse consequences of targeted therapies, however, are tumour adaptation, increased malignancy and the invasive metastatic switch seen with anti-angiogenic drugs that inhibit the VEGF-A pathway. Adverse reactions to 44 non-targeted and 33 targeted, frequently used, chemotherapeutic drugs are presented together with discussions of diagnosis, premedications, desensitizations and importance of understanding the mechanisms underlying the various drug-induced reactions. There is need for wide-ranging acceptance of what constitutes a hypersensitivity reaction and for allergists to be more involved in the diagnosis, treatment and prevention of chemotherapeutic drug-induced hypersensitivity reactions.

Photoreactive "nanorulers" detect a novel conformation of full length HDAC3-SMRT complex in solution

Histone deacetylase 3 (HDAC3) is a promising epigenetic drug target for multiple therapeutic applications. Direct interaction between the Deacetylase Activating Domain of the silencing mediator for retinoid or thyroid-hormone receptors (SMRT-DAD) is required for activation of enzymatic activity of HDAC3. The structure of this complex and the nature of interactions with HDAC inhibitors in solution are unknown. Using novel photoreactive HDAC probes, "nanorulers", we determined the distance between the catalytic site of the full-length HDAC3 and SMRT-DAD in solution at physiologically relevant conditions and found it to be substantially different from that predicted by the X-ray model with a Δ379-428 aa truncated HDAC3. Further experiments indicated that in solution this distance might change in response to chemical stimuli, while the enzymatic activity remained unaffected. These observations were further validated by Saturation Transfer Difference (STD) NMR experiments. We propose that the observed changes in the distance are an important part of the histone code that remains to be explored. Mapping direct interactions and distances between macromolecules with such "nanorulers" as a function of cellular events facilitates better understanding of basic biology and ways for its manipulation in a cell- and tissue-specific manner.

HDAC inhibitor DWP0016 activates p53 transcription and acetylation to inhibit cell growth in U251 glioblastoma cells

Here we report a hydroacid named DWP0016, which exhibited HDAC inhibition and induced p53 acetylation in U251 glioblastoma cells. DWP0016 effectively inhibited the cell growth of U251 cells and other four carcinoma cell lines but did not affect the normal cells. Cell cycle distribution analysis showed DWP0016 arrested at G1 phase cell cycle dose-dependently in U251 cells. DWP0016 induced caspase-dependent and independent apoptosis in U251 cells, which was identified by flow cytometry analysis, caspases activity analysis, Western blotting assay, and caspases inhibition. Mechanisms research suggested that DWP0016 activated transcription and acetylation of tumor suppressor p53. DWP0016 regulated p300, CBP, and PCAF to facilitate p53 acetylation at lys382 in U251 cells. In addition, activation of p53 by DWP0016 promoted PUMA to catalyze mitochondrial pathway. Besides, siRNA assay indicated p53 was the key gene to induce growth inhibition, cell cycle arrest, and apoptosis in DWP0016 treated U251 cells. Conclusively, our results show DWP0016 is a potent HDAC inhibitor and the anti-tumor activity is consistent with its intended p53 activation mechanisms. These findings indicate the promising antitumor potential of DWP0016 for further glioblastoma treatment applications.

Resveratrol as a pan-HDAC inhibitor alters the acetylation status of histone [corrected] proteins in human-derived hepatoblastoma cells

The polyphenolic alcohol resveratrol has demonstrated promising activities for the prevention and treatment of cancer. Different modes of action have been described for resveratrol including the activation of sirtuins, which represent the class III histone deacetylases (HDACs). However, little is known about the activity of resveratrol on the classical HDACs of class I, II and IV, although these classes are involved in cancer development or progression and inhibitors of HDACs (HDACi) are currently under investigation as promising novel anticancer drugs. We could show by in silico docking studies that resveratrol has the chemical structure to inhibit the activity of different human HDAC enzymes. In vitro analyses of overall HDAC inhibition and a detailed HDAC profiling showed that resveratrol inhibited all eleven human HDACs of class I, II and IV in a dose-dependent manner. Transferring this molecular mechanism into cancer therapy strategies, resveratrol treatment was analyzed on solid tumor cell lines. Despite the fact that hepatocellular carcinoma (HCC) is known to be particularly resistant against conventional chemotherapeutics, treatment of HCC with established HDACi already has shown promising results. Testing of resveratrol on hepatoma cell lines HepG2, Hep3B and HuH7 revealed a dose-dependent antiproliferative effect on all cell lines. Interestingly, only for HepG2 cells a specific inhibition of HDACs and in turn a histone hyperacetylation caused by resveratrol was detected. Additional testing of human blood samples demonstrated a HDACi activity by resveratrol ex vivo. Concluding toxicity studies showed that primary human hepatocytes tolerated resveratrol, whereas in vivo chicken embryotoxicity assays demonstrated severe toxicity at high concentrations. Taken together, this novel pan-HDACi activity opens up a new perspective of resveratrol for cancer therapy alone or in combination with other chemotherapeutics. Moreover, resveratrol may serve as a lead structure for chemical optimization of bioavailability, pharmacology or HDAC inhibition.

Epigenetic modifications of prostate-derived Ets transcription factor in breast cancer cells

The importance of epigenetic alterations such as DNA methylation, histone modification and nucleosome remodeling in breast cancer is well established. Epigenetic alterations are reversible, and much research has been focused on understanding these alterations with the aim of developing effective therapies. Prostate-derived Ets factor (PDEF) is a member of the Ets family of transcription factors and has long been under investigation for its key role in tumor development and progression. To date, no studies have been conducted to elucidate the epigenetic modifications of PDEF in cancer progression. Using breast and prostate cancer cells, we investigated the effect of the methylation inhibitor 5' azacytidine (AZA) on the expression of PDEF in these cells. The inhibition of methylation observed was specific to breast cancer cells as experiments with prostate cells did not exhibit any significant change. Notably, the expression of p21, a cyclin-dependent kinase (CDK) inhibitor 1 and also a target gene of PDEF, was found to be positively correlated with PDEF expression following 5'AZA treatment. Inhibition of methylation led to a decrease in the proliferation rate of MDA-MB-468 cells as revealed by MTT proliferation assay. Other epigenetic alterations such as histone modifications were not observed in these breast cancer cells following treatment with specific HDAC inhibitors. Our data suggest the possibility of epigenetic modification of PDEF due to DNA methylation and involvement of the cell cycle inhibitor p21. Future studies on the epigenetic alterations of PDEF in correlation with p21 or other targets may facilitate the development of effective therapies for the treatment of breast cancer.