Histone deacetylase inhibitor FK228 suppresses the Ras-MAP kinase signaling pathway by upregulating Rap1 and induces apoptosis in malignant melanoma

Histone deacetylases in the regulation of cell death and survival mechanisms in resistant BRAF-mutant cancers

Small-molecule BRAF inhibitors (e.g., vemurafenib and dabrafenib) and MEK (MAPK/ERK) kinases inhibitors (e.g., trametinib) have distinctly improved the survival of patients suffering from BRAF-mutant cancers such as melanomas. However, the emergence of resistance to BRAF and MEK inhibitor-based melanoma therapy, as well as the reduced sensitivity of other BRAF-mutant cancers such as CRC, poses a considerable clinical problem. For instance, the reactivation of MAPK/ERK signaling hampering cell death induction mechanisms was responsible for BRAF inhibitor resistance, which can be correlated with distinct post-translational and epigenetic processes. Histone deacetylases (HDACs) are prominent epigenetic drug targets and some HDAC inhibitors have already been clinically approved for the therapy of various blood cancers. In addition, several HDACs were identified, which also play a crucial role in the drug resistance of BRAF-mutant cancers. Consequently, inhibition of HDACs was described as a promising approach to overcome resistance. This review summarizes the influence of HDACs (Zn2+-dependent HDACs and NAD+-dependent sirtuins) on BRAF-mutant cancers and BRAF inhibitor resistance based on upregulated survival mechanisms and the prevention of tumor cell death. Moreover, it outlines reasonable HDAC-based strategies to circumvent BRAF-associated resistance mechanisms based on downregulated cell death mechanisms.

Hippocampal transcriptomic analyses reveal the potential antiapoptotic mechanism of a novel anticonvulsant agent Q808 on pentylenetetrazol-induced epilepsy in rats

Brain apoptosis is one of the main causes of epileptogenesis. The antiapoptotic effect and potential mechanism of Q808, an innovative anticonvulsant chemical, have never been reported. In this study, the seizure stage and latency to reach stage 2 of pentylenetetrazol (PTZ) seizure rat model treated with Q808 were investigated. The morphological change and neuronal apoptosis in the hippocampus were detected by hematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining, respectively. The hippocampal transcriptomic changes were observed using RNA sequencing (RNA-seq). The expression levels of hub genes were verified by quantitative reverse-transcription PCR (qRT-PCR). Results revealed that Q808 could allay the seizure score and prolong the stage 2 latency in seizure rats. The morphological changes of neurons and the number of apoptotic cells in the DG area were diminished by Q808 treatment. RNA-seq analysis revealed eight hub genes, including Map2k3, Nfs1, Chchd4, Hdac6, Siglec5, Slc35d3, Entpd1, and LOC103690108, and nine hub pathways among the control, PTZ, and Q808 groups. Hub gene Nfs1 was involved in the hub pathway sulfur relay system, and Map2k3 was involved in the eight remaining hub pathways, including Amyotrophic lateral sclerosis, Cellular senescence, Fc epsilon RI signaling pathway, GnRH signaling pathway, Influenza A, Rap1 signaling pathway, TNF signaling pathway, and Toll-like receptor signaling pathway. qRT-PCR confirmed that the mRNA levels of these hub genes were consistent with the RNA-seq results. Our findings might contribute to further studies exploring the new apoptosis mechanism and actions of Q808.

Givinostat-Liposomes: Anti-Tumor Effect on 2D and 3D Glioblastoma Models and Pharmacokinetics

Glioblastoma is the most common and aggressive brain tumor, associated with poor prognosis and survival, representing a challenging medical issue for neurooncologists. Dysregulation of histone-modifying enzymes (HDACs) is commonly identified in many tumors and has been linked to cancer proliferation, changes in metabolism, and drug resistance. These findings led to the development of HDAC inhibitors, which are limited by their narrow therapeutic index. In this work, we provide the proof of concept for a delivery system that can improve the in vivo half-life and increase the brain delivery of Givinostat, a pan-HDAC inhibitor. Here, 150-nm-sized liposomes composed of cholesterol and sphingomyelin with or without surface decoration with mApoE peptide, inhibited human glioblastoma cell growth in 2D and 3D models by inducing a time- and dose-dependent reduction in cell viability, reduction in the receptors involved in cholesterol metabolism (from -25% to -75% of protein levels), and reduction in HDAC activity (-25% within 30 min). In addition, liposome-Givinostat formulations showed a 2.5-fold increase in the drug half-life in the bloodstream and a 6-fold increase in the amount of drug entering the brain in healthy mice, without any signs of overt toxicity. These features make liposomes loaded with Givinostat valuable as potential candidates for glioblastoma therapy.

Identification and bioinformatics analysis of differentially expressed milk exosomal microRNAs in milk exosomes of heat-stressed Holstein cows

In summer, heat stress is one of the primary reasons for the compromised health and low milk productivity of dairy cows. Hyperthermia affects milk synthesis and secretion in the mammary glands of dairy cows. As molecules for intercellular communication, milk-derived exosomes carry genetic material, proteins, and lipids, playing a crucial role in mammary tissue growth and milk synthesis in dairy cows. The aim of this study was to explore the milk exosomal miRNA profile of heat-stressed and normal Holstein cows. We isolated and identified milk exosomes to screening for differentially expressed miRNAs using small RNA sequencing. Then, TargetScan and miRanda algorithms were used to predict the putative targets of the differentially expressed miRNAs, whereas GO and KEGG pathway enrichment analyses were performed for the differentially expressed miRNA-target genes. Our results showed that 215 miRNAs were significantly differentially expressed in heat-stressed milk exosomes, of which one was upregulated and 214 were significantly downregulated. GO and KEGG enrichment analyses indicated that differentially expressed miRNAs might play a role in apoptosis, autophagy, and the p38 MAPK pathway. qRT-PCR assay verified that the expression of miRNAs was consistent with the sequencing results, warranting further verification of their specific targets of action. In conclusion, changes in the miRNA expression profile of milk exosomes indicated the role of exosomal miRNAs in regulating heat stress resistance and apoptosis in dairy cows. Our results suggested that milk-derived exosomal miRNAs could increase mammary gland resistance to heat stress, thereby enhancing milk synthesis in dairy cows.

Down-regulated HDAC3 elevates microRNA-495-3p to restrain epithelial-mesenchymal transition and oncogenicity of melanoma cells via reducing TRAF5

MicroRNAs (miRNAs) are emerging biomarkers in biological processes and the role of miR‐495‐3p has been identified in melanoma, while the detailed molecular mechanisms remain to be further explored. We aim to explore the effect of histone deacetylase 3 (HDAC3) and miR‐495‐3p on epithelial‐mesenchymal transition (EMT) and oncogenicity of melanoma cells by regulating tumour necrosis factor receptor‐associated factor 5 (TRAF5). Levels of HDAC3, miR‐495‐3p and TRAF5 in melanoma tissues and pigmented nevus tissues were determined, and the predictive roles of HDAC3 and miR‐495‐3p in prognosis of melanoma patients were measured. The melanoma cells were screened and transfected with relative oligonucleotides and plasmids, and the expression of HDAC3, miR‐495‐3p and TRAF5, and phenotypes of melanoma cells were gauged by a series of assays. The relations between HDAC3 and miR‐495‐3p, and between miR‐495‐3p and TRAF5 were confirmed. HDAC3 and TRAF5 were increased while miR‐495‐3p was decreased in melanoma cells and tissues, and the low expression of miR‐495‐3p as well as high expression of HDAC3 indicated a poor prognosis of melanoma patients. Inhibited HDAC3 elevated miR‐495‐3p to suppress EMT and oncogenicity of melanoma cells by reducing TRAF5. HDAC3 particularly bound to miR‐495‐3p and TRAF5 was the target gene of miR‐495‐3p. Our results revealed that down‐regulated HDAC3 elevates miR‐495‐3p to suppress malignant phenotypes of melanoma cells by inhibiting TRAF5, thereby repressing EMT progression of melanoma cells. This study may provide novel targets for melanoma treatment.

[Research Progress of Epigenetics in Pathogenesis and Treatment of Malignant Tumors]

表观遗传学修饰与肿瘤的发生发展密切相关，其主要通过DNA甲基化、组蛋白修饰、非编码RNA调控和染色质结构重构等方式对基因功能和表达水平进行调控，从而影响肿瘤的进展。目前针对表观遗传学的药物已经逐渐应用于恶性肿瘤的治疗，常见的药物类型包括DNA甲基转移酶抑制剂和组蛋白去乙酰化酶抑制剂，但此类药物仍存在诸多不足之处广泛的临床应用仍需要进一步的研究，令人鼓舞的是表观遗传药物与多种抗肿瘤药物联合应用已表现出巨大的应用潜力。本文就表观遗传学在恶性肿瘤的发生发展机制和相关药物的新进展进行了综述。

A pan-cancer analysis of driver gene mutations, DNA methylation and gene expressions reveals that chromatin remodeling is a major mechanism inducing global changes in cancer epigenomes

Background

Recent large-scale cancer sequencing studies have discovered many novel cancer driver genes (CDGs) in human cancers. Some studies also suggest that CDG mutations contribute to cancer-associated epigenomic and transcriptomic alterations across many cancer types. Here we aim to improve our understanding of the connections between CDG mutations and altered cancer cell epigenomes and transcriptomes on pan-cancer level and how these connections contribute to the known association between epigenome and transcriptome.

Method

Using multi-omics data including somatic mutation, DNA methylation, and gene expression data of 20 cancer types from The Cancer Genome Atlas (TCGA) project, we conducted a pan-cancer analysis to identify CDGs, when mutated, have strong associations with genome-wide methylation or expression changes across cancer types, which we refer as methylation driver genes (MDGs) or expression driver genes (EDGs), respectively.

Results

We identified 32 MDGs, among which, eight are known chromatin modification or remodeling genes. Many of the remaining 24 MDGs are connected to chromatin regulators through either regulating their transcription or physically interacting with them as potential co-factors. We identified 29 EDGs, 26 of which are also MDGs. Further investigation on target genes’ promoters methylation and expression alteration patterns of these 26 overlapping driver genes shows that hyper-methylation of target genes’ promoters are significantly associated with down-regulation of the same target genes and hypo-methylation of target genes’ promoters are significantly associated with up-regulation of the same target genes.

Conclusion

This finding suggests a pivotal role for genetically driven changes in chromatin remodeling in shaping DNA methylation and gene expression patterns during tumor development.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0425-z) contains supplementary material, which is available to authorized users.

Up-regulation of NSP3 by Oligomeric Aβ Accelerates Neuronal Death Through Cas-independent Rap1A Activation

β-Amyloid (Aβ) plays an important role in the early pathogenesis of Alzheimer's disease (AD). In vitro studies have demonstrated that Aβ oligomers induce hippocampal and neocortical neuronal death. However the neurotoxic mechanisms by which soluble Aβ oligomers cause neuronal damage and death remain to be fully elucidated. To this end, we analyzed the gene expression profile of rat cerebral cortical neurons treated with Aβ oligomers in vitro. Aβ treatment induced the expression of novel SH2-containing protein 3 (NSP3), an adaptor molecule interacting with Cas family proteins. NSP3 expression was upregulated not only in oligomeric-Aβ-treated cultured neurons but also in the neocortex of aged Tg2576 mice. NSP3 overexpression in cultured cortical neurons accelerated neuronal death. The C-terminal region of NSP3 unbound to a Cas protein was necessary for the NSP3-induced acceleration of neuronal death, as was Cas-independent Rap1A activation downstream of NSP3. Moreover, NSP3 RNAi knockdown partially rescued Aβ-oligomer-treated neurons. These results indicate that NSP3 upregulation by soluble Aβ oligomers may accelerate neuronal death via Cas-independent Rap1A activation, implicating NSP3 in the pathogenesis of AD.

Sirt1 Protects against Oxidative Stress-Induced Apoptosis in Fibroblasts from Psoriatic Patients: A New Insight into the Pathogenetic Mechanisms of Psoriasis

Psoriasis, a multisystem chronic disease characterized by abnormal keratinocyte proliferation, has an unclear pathogenesis where systemic inflammation and oxidative stress play mutual roles. Dermal fibroblasts, which are known to provide a crucial microenvironment for epidermal keratinocyte function, represented the selected experimental model in our study which aimed to clarify the potential role of SIRT1 in the pathogenetic mechanisms of the disease. We firstly detected the presence of oxidative stress (lipid peroxidation and total antioxidant capacity), significantly reduced SIRT1 expression level and activity, mitochondrial damage and apoptosis (caspase-3, -8 and -9 activities) in psoriatic fibroblasts. Upon SIRT1 activation, redox balance was re-established, mitochondrial function was restored and apoptosis was no longer evident. Furthermore, we examined p38, ERK and JNK activation, which was strongly altered in psoriatic fibroblasts, in response to SIRT1 activation and we measured caspase-3 activity in the presence of specific MAPK inhibitors demonstrating the key role of the SIRT1 pathway against apoptotic cell death via MAPK modulation. Our results clearly demonstrate the involvement of SIRT1 in the protective mechanisms related to fibroblast injury in psoriasis. SIRT1 activation exerts an active role in restoring both mitochondrial function and redox balance via modulation of MAPK signaling. Hence, SIRT1 can be proposed as a specific tool for the treatment of psoriasis.

Small Molecules Modulate Chromatin Accessibility to Promote NEUROG2-Mediated Fibroblast-to-Neuron Reprogramming

Pro-neural transcription factors and small molecules can induce the reprogramming of fibroblasts into functional neurons; however, the immediate-early molecular events that catalyze this conversion have not been well defined. We previously demonstrated that neurogenin 2 (NEUROG2), forskolin (F), and dorsomorphin (D) can reprogram fibroblasts into functional neurons with high efficiency. Here, we used this model to define the genetic and epigenetic events that initiate an acquisition of neuronal identity. We demonstrate that NEUROG2 is a pioneer factor, FD enhances chromatin accessibility and H3K27 acetylation, and synergistic transcription activated by these factors is essential to successful reprogramming. CREB1 promotes neuron survival and acts with NEUROG2 to upregulate SOX4, which co-activates NEUROD1 and NEUROD4. In addition, SOX4 targets SWI/SNF subunits and SOX4 knockdown results in extensive loss of open chromatin and abolishes reprogramming. Applying these insights, adult human glioblastoma cell and skin fibroblast reprogramming can be improved using SOX4 or chromatin-modifying chemicals.

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NEUROG2 acts as a pioneer factor to drive neuronal reprogramming

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ATAC-, ChIP-, and RNA-seq profiling reveals genome-wide mechanisms for reprogramming

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SOX4 is a critical mediator of chromatin remodeling during reprogramming

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SOX4 or FK228 can enhance adult human glioblastoma and skin fibroblast reprogramming

Evaluation of surrogate tissues as indicators of drug activity in a melanoma skin model

The development of novel cancer treatments is a challenging task, partly because results from model systems often fail to predict drug efficacy in humans, and also tumors are often inaccessible for biochemical analysis, preventing effective monitoring of drug activity in vivo. Utilizing a model system, we evaluated the use of drug-induced DNA damage in surrogate tissues as indicators of drug efficacy. Samples of a commercially available melanoma skin model (Mattek MLNM-FT-A375) containing keratinocyte and fibroblast layers with melanoma nodules were subjected to various chemotherapeutic regimens for one, four, or eight days. At these times they were analyzed for DNA double-stranded breaks (γH2AX foci) and apoptosis (TUNEL). A wide range of drug responses in both tumor and normal tissues were observed and cataloged. For the melanoma, the most common drug response was apoptosis. The basal keratinocyte layer, which was the most reliable indicator of drug response in the melanoma skin model, responded with γH2AX foci formation that was abrupt and transient. The relationships between tumor and surrogate tissue drug responses are complex, indicating that while surrogate tissue drug responses may be useful clinical tools, careful control of variables such as the timing of sampling may be important in interpreting the results.

Histone deacetylase inhibitor, Romidepsin (FK228) inhibits endometrial cancer cell growth through augmentation of p53-p21 pathway

OBJECTIVE

Romidepsin (FK228), a Histone Deacetylase (HDAC) inhibitor, has been used for anti-cancer therapies. However, the anti-cancer effect of FK228 and its underlying mechanism in endometrial carcinoma (EC) have not been studied. The aime of this study was to investigate the anti-cancer effects of FK228 and the associated mechanism(s) in EC.

METHODS

Ishikawa and HEC-1-A endometrial cancer cells were treated with 8nM concentration of FK228 and cell growth was measured by XTT assay. The cell cycle distribution and cell death were measured by flow cytometry, immunofluorescence, respectively. The mNRA and protein expressions were analyzed by quantitative RT-PCR and western blot, respectively.

RESULTS

Based on assays carried out in EC cell lines, it was observed that FK228 inhibited EC cell proliferation in a dose and time-dependent manner. Furthermore, following treatment with FK228 for 48h, there were significant induction of apoptosis and cell cycle arrest at G0/G1 phase in EC cells. Moreover, FK228 treatment significantly increased the mRNA and protein expressions of p53, p21, cleaved caspases such as 3, 7 and 8 and PARP. Further, FK228 treatment increased the levels of acetylated histone H3 and H4 that confirms the HDAC inhibition.

CONCLUSION

In conclusion, FK228 inhibits EC tumor cell proliferation and induces apoptosis by activation caspase/PARP via the induction of p53/p21 signaling cascades, suggesting that FK228 is a potential therapeutic agent for EC.

Treatment of resistant metastatic melanoma using sequential epigenetic therapy (decitabine and panobinostat) combined with chemotherapy (temozolomide)

Purpose

To explore the safety and tolerability of combining two epigenetic drugs: decitabine (a DNA methyltransferase inhibitor) and panobinostat (a histone deacetylase inhibitor), with chemotherapy with temozolomide (an alkylating agent). The purpose of such combination is to evaluate the use of epigenetic priming to overcome resistance of melanoma to chemotherapy.

Methods

A Phase I clinical trial enrolling patients aged 18 years or older, with recurrent or unresectable stage III or IV melanoma of any site. This trial was conducted with full Institutional Review Board approval and was registered with the National Institutes of Health under the clinicaltrials.gov identifier NCT00925132. Patients were treated with subcutaneous decitabine 0.1 or 0.2 mg/kg three times weekly for 2 weeks (starting on day 1), in combination with oral panobinostat 10, 20, or 30 mg every 96 h (starting on day 8), and oral temozolomide 150 mg/m²/day on days 9 through 13. In cycle 2, temozolomide was increased to 200 mg/m²/day if neutropenia or thrombocytopenia had not occurred. Each cycle lasted 6 weeks, and patients could receive up to six cycles. Patients who did not demonstrate disease progression were eligible to enter a maintenance protocol with combination of weekly panobinostat and thrice-weekly decitabine until tumor progression, unacceptable toxicity, or withdrawal of consent.

Results

Twenty patients were initially enrolled, with 17 receiving treatment. The median age was 56 years. Eleven (65 %) were male, and 6 (35 %) were female. Eleven (64.7 %) had cutaneous melanoma, 4 (23.5 %) had ocular melanoma, and 2 (11.8 %) had mucosal melanoma. All patients received at least one treatment cycle and were evaluable for toxicity. Patients received a median of two 6-week treatment cycles (range 1–6). None of the patients experienced DLT. MTD was not reached. Adverse events attributed to treatment included grade 3 lymphopenia (24 %), anemia (12 %), neutropenia (12 %), and fatigue (12 %), as well as grade 2 leukopenia (30 %), neutropenia (23 %), nausea (23 %), and lymphopenia (18 %). The most common reason for study discontinuation was disease progression.

Conclusions

This triple agent of dual epigenetic therapy in combination with traditional chemotherapy was generally well tolerated by the cohort and appeared safe to be continued in a Phase II trial. No DLTs were observed, and MTD was not reached.

The therapeutic potential of class I selective histone deacetylase inhibitors in ovarian cancer

Epithelial ovarian cancer remains the deadliest gynecologic malignancy. Despite advances in treatment, new approaches are needed. Histone deacetylases (HDACs) are a family of enzymes that regulate gene expression by removing acetyl groups from lysine residues on histones and non-histone proteins. Inhibition of HDACs with small molecules has led to the development of histone deacetylase inhibitors (HDACi) that are in clinical use, primarily for hematologic malignancies. Although clinical trials with HDACi as single agents in solid tumors have been disappointing, data from independent labs and recent work by our group show that class I selective HDACi have potent anti-tumor effects in pre-clinical models of ovarian cancer. This review summarizes the role of HDACs in ovarian cancer and the potential niche for selective class I HDACi, particularly HDAC3 in ovarian cancer therapy.

SIRT1 regulates MAPK pathways in vitiligo skin: insight into the molecular pathways of cell survival

Vitiligo is an acquired and progressive hypomelanotic disease that manifests as circumscribed depigmented patches on the skin. The aetiology of vitiligo remains unclear, but recent experimental data underline the interactions between melanocytes and other typical skin cells, particularly keratinocytes. Our previous results indicate that keratinocytes from perilesional skin show the features of damaged cells. Sirtuins (silent mating type information regulation 2 homolog) 1, well-known modulators of lifespan in many species, have a role in gene repression, metabolic control, apoptosis and cell survival, DNA repair, development, inflammation, neuroprotection and healthy ageing. In the literature there is no evidence for SIRT1 signalling in vitiligo and its possible involvement in disease progression. Here, biopsies were taken from the perilesional skin of 16 patients suffering from non-segmental vitiligo and SIRT1 signalling was investigated in these cells. For the first time, a new SIRT1/Akt, also known as Protein Kinase B (PKB)/mitogen-activated protein kinase (MAPK) signalling has been revealed in vitiligo. SIRT1 regulates MAPK pathway via Akt-apoptosis signal-regulating kinase-1 and down-regulates pro-apoptotic molecules, leading to decreased oxidative stress and apoptotic cell death in perilesional vitiligo keratinocytes. We therefore propose SIRT1 activation as a novel way of protecting perilesional vitiligo keratinocytes from damage.

HDAC inhibitors induce tumor-cell-selective pro-apoptotic transcriptional responses

The identification of recurrent somatic mutations in genes encoding epigenetic enzymes has provided a strong rationale for the development of compounds that target the epigenome for the treatment of cancer. This notion is supported by biochemical studies demonstrating aberrant recruitment of epigenetic enzymes such as histone deacetylases (HDACs) and histone methyltransferases to promoter regions through association with oncogenic fusion proteins such as PML-RARα and AML1-ETO. HDAC inhibitors (HDACi) are potent inducers of tumor cell apoptosis; however, it remains unclear why tumor cells are more sensitive to HDACi-induced cell death than normal cells. Herein, we assessed the biological and molecular responses of isogenic normal and transformed cells to the FDA-approved HDACi vorinostat and romidepsin. Both HDACi selectively killed cells of diverse tissue origin that had been transformed through the serial introduction of different oncogenes. Time-course microarray expression profiling revealed that normal and transformed cells transcriptionally responded to vorinostat treatment. Over 4200 genes responded differently to vorinostat in normal and transformed cells and gene ontology and pathway analyses identified a tumor-cell-selective pro-apoptotic gene-expression signature that consisted of BCL2 family genes. In particular, HDACi induced tumor-cell-selective upregulation of the pro-apoptotic gene BMF and downregulation of the pro-survival gene BCL2A1 encoding BFL-1. Maintenance of BFL-1 levels in transformed cells through forced expression conferred vorinostat resistance, indicating that specific and selective engagement of the intrinsic apoptotic pathway underlies the tumor-cell-selective apoptotic activities of these agents. The ability of HDACi to affect the growth and survival of tumor cells whilst leaving normal cells relatively unharmed is fundamental to their successful clinical application. This study provides new insight into the transcriptional effects of HDACi in human donor-matched normal and transformed cells, and implicates specific molecules and pathways in the tumor-selective cytotoxic activity of these compounds.

Histone deacetylase inhibitors suppress mechanical stress-induced expression of RUNX-2 and ADAMTS-5 through the inhibition of the MAPK signaling pathway in cultured human chondrocytes

OBJECTIVE

To investigate the inhibitory effects and the regulatory mechanisms of histone deacetylase (HDAC) inhibitors on mechanical stress-induced gene expression of runt-related transcription factor (RUNX)-2 and adisintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5 in human chondrocytes.

METHODS

Human chondrocytes were seeded in stretch chambers at a concentration of 5 × 10(4)cells/chamber. Cells were pre-incubated with or without HDAC inhibitors (MS-275 or trichostatin A; TSA) for 12h, followed by uniaxial cyclic tensile strain (CTS) (0.5Hz, 10% elongation), which was applied for 30 min using the ST-140-10 system (STREX, Osaka, Japan). Total RNA was extracted and the expression of RUNX-2, ADAMTS-5, matrix metalloproteinase (MMP)-3, and MMP-13 at the mRNA and protein levels were examined by real-time polymerase chain reaction (PCR) and immunocytochemistry, respectively. The activation of diverse mitogen-activated protein kinase (MAPK) pathways with or without HDAC inhibitors during CTS was examined by western blotting.

RESULTS

HDAC inhibitors (TSA: 10 nM, MS-275: 100 nM) suppressed CTS-induced expression of RUNX-2, ADAMTS-5, and MMP-3 at both the mRNA and protein levels within 1h. CTS-induced activation of p38 MAPK (p38), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) MAPKs was downregulated by both HDAC inhibitors.

CONCLUSION

The CTS-induced expression of RUNX-2 and ADAMTS-5 was suppressed by HDAC inhibitors via the inhibition of the MAPK pathway activation in human chondrocytes. The results of the current study suggested a novel therapeutic role for HDAC inhibitors against degenerative joint disease such as osteoarthritis.

Aggressiveness of human melanoma xenograft models is promoted by aneuploidy-driven gene expression deregulation

Melanoma is a devastating skin cancer characterized by distinct biological subtypes. Besides frequent mutations in growth- and survival-promoting genes like BRAF and NRAS, melanomas additionally harbor complex non-random genomic alterations. Using an integrative approach, we have analysed genomic and gene expression changes in human melanoma cell lines (N=32) derived from primary tumors and various metastatic sites and investigated the relation to local growth aggressiveness as xenografts in immuno-compromised mice (N=22). Although the vast majority >90% of melanoma models harbored mutations in either BRAF or NRAS, significant differences in subcutaneous growth aggressiveness became obvious. Unsupervised clustering revealed that genomic alterations rather than gene expression data reflected this aggressive phenotype, while no association with histology, stage or metastatic site of the original melanoma was found. Genomic clustering allowed separation of melanoma models into two subgroups with differing local growth aggressiveness in vivo. Regarding genes expressed at significantly altered levels between these subgroups, a surprising correlation with the respective gene doses (>85% accordance) was found. Genes deregulated at the DNA and mRNA level included well-known cancer genes partly already linked to melanoma (RAS genes, PTEN, AURKA, MAPK inhibitors Sprouty/Spred), but also novel candidates like SIPA1 (a Rap1GAP). Pathway mining further supported deregulation of Rap1 signaling in the aggressive subgroup e.g. by additional repression of two Rap1GEFs. Accordingly, siRNA-mediated down-regulation of SIPA1 exerted significant effects on clonogenicity, adherence and migration in aggressive melanoma models. Together our data suggest that an aneuploidy-driven gene expression deregulation drives local aggressiveness in human melanoma.

SIRT1 modulates MAPK pathways in ischemic-reperfused cardiomyocytes

SIRT1, an ubiquitous NAD(+)-dependent deacetylase that plays a role in biological processes such as longevity and stress response, is significantly activated in response to reactive oxygen species (ROS) production. Resveratrol (Resv), an important activator of SIRT1, has been shown to exert major health benefits in diseases associated with oxidative stress. In ischemia-reperfusion (IR) injury, a major role has been attributed to the mitogen-activated protein kinase (MAPK) pathway, which is upregulated in response to a variety of stress stimuli, including oxidative stress. In neonatal rat ventricular cardiomyocytes subjected to simulated IR, the effect of Resv-induced SIRT1 activation and the relationships with the MAPK pathway were investigated. Resv-induced SIRT1 overexpression protected cardiomyocytes from oxidative injury, mitochondrial dysfunction, and cell death induced by IR. For the first time, we demonstrate that SIRT1 overexpression positively affects the MAPK pathway-via Akt/ASK1 signaling-by reducing p38 and JNK phosphorylation and increasing ERK phosphorylation. These results reveal a new protective mechanism elicited by Resv-induced SIRT1 activation in IR tissues and suggest novel potential therapeutic targets to manage IR-induced cardiac dysfunction.

Histone deacetylase inhibitors enhance the apoptotic activity of insulin-like growth factor binding protein-3 by blocking PKC-induced IGFBP-3 degradation

Overexpression of insulin-like growth factor binding protein (IGFBP)-3 induces apoptosis of cancer cells. However, preexisting resistance to IGFBP-3 could limit its antitumor activities. This study characterizes the efficacy and mechanism of the combination of recombinant IGFBP-3 (rIGFBP-3) and HDAC inhibitors to overcome IGFBP-3 resistance in a subset of non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC) cells. The effects of the combination of rIGFBP-3 and a number of HDAC inhibitors on cell proliferation and apoptosis were assessed in vitro and in vivo by using the MTT assay, a flow cytometry-based TUNEL assay, Western blot analyses and the NSCLC xenograft tumor model. Combined treatment with HDAC inhibitors and rIGFBP-3 had synergistic antiproliferative effects accompanied by increased apoptosis rates in a subset of NSCLC and HNSCC cell lines in vitro. Moreover, combined treatment with depsipeptide and rIGFBP-3 completely suppressed tumor growth and increased the apoptosis rate in vivo in H1299 NSCLC xenografts. Evidence suggests that HDAC inhibitors increased the half-life of rIGFBP-3 protein by blocking protein kinase C (PKC)-mediated phosphorylation and degradation of rIGFBP-3. In addition, combined treatment of IGFBP-3 with an HDAC inhibitor facilitates apoptosis through upregulation of rIGFBP-3 stability and Akt signaling inhibition. The ability of HDAC inhibitors to decrease PKC activation may enhance apoptotic activities of rIGFBP-3 in NSCLC cells in vitro and in vivo. These results indicated that combined treatment with HDAC inhibitor and rIGFBP-3 could be an effective treatment strategy for NSCLC and HNSCC with highly activated PKC.

Preclinical validation of AR42, a novel histone deacetylase inhibitor, as treatment for vestibular schwannomas

OBJECTIVES/HYPOTHESIS

Recent studies indicate that vestibular schwannomas (VSs) rely on phosphatidylinositol 3-kinase/AKT activation to promote cell proliferation and survival; therefore, targeting AKT may provide new therapeutic options. We have previously shown that AR42, a novel histone deacetylase inhibitor, potently suppresses VS growth in vitro at doses correlating with AKT inactivation. The objectives of the current study were translational: 1) to examine the end biologic effects of AR42 on tumor growth in vivo, 2) to validate AKT as its in vivo molecular target, 3) to determine whether AR42 penetrates the blood-brain barrier (BBB), and 4) to study the pharmacotoxicity profile of AR42.

STUDY DESIGN

In vivo mouse studies.

METHODS

AR42 was dosed orally in murine schwannoma allografts and human VS xenografts. Magnetic resonance imaging was used to quantify changes in tumor volume, and intracellular molecular targets were analyzed using immunohistochemistry. BBB penetration was assayed, and both blood-chemistry measurements and histology studies were used to evaluate toxicity.

RESULTS

Growth of schwannoma implants was dramatically decreased by AR42 at doses correlating with AKT dephosphorylation, cell cycle arrest, and apoptosis. AR42 penetrated the BBB, and wild-type mice fed AR42 for 6 months behaved normally and gained weight appropriately. Blood-chemistry studies and organ histology performed after 3 and 6 months of AR42 treatment demonstrated no clinically significant abnormalities.

CONCLUSIONS

AR42 suppresses schwannoma growth at doses correlating with AKT pathway inhibition. This orally bioavailable drug penetrates the BBB, is well tolerated, and represents a novel candidate for translation to human VS clinical trials.

Born to be alive: a role for the BCL-2 family in melanoma tumor cell survival, apoptosis, and treatment

The global incidence of melanoma has dramatically increased during the recent decades, yet the advancement of primary and adjuvant therapies has not kept a similar pace. The development of melanoma is often centered on cellular signaling that hyper-activates survival pathways, while inducing a concomitant blockade to cell death. Aberrations in cell death signaling not only promote tumor survival and enhanced metastatic potential, but also create resistance to anti-tumor strategies. Chemotherapeutic agents target melanoma tumor cells by inducing a form of cell death called apoptosis, which is governed by the BCL-2 family of proteins. The BCL-2 family is comprised of anti-apoptotic proteins (e.g., BCL-2, BCL-xL, and MCL-1) and pro-apoptotic proteins (e.g., BAK, BAX, and BIM), and their coordinated regulation and function are essential for optimal responses to chemotherapeutics. Here we will discuss what is currently known about the mechanisms of BCL-2 family function with a focus on the signaling pathways that maintain melanoma tumor cell survival. Importantly, we will critically evaluate the literature regarding how chemotherapeutic strategies directly impact on BCL-2 family function and offer several suggestions for future regimens to target melanoma and enhance patient survival.

HDAC inhibitors augment cytotoxic activity of rituximab by upregulating CD20 expression on lymphoma cells

Anti-CD20 antibody rituximab is now essential for the treatment of CD20-positive B-cell lymphomas. Decreased expression of CD20 is one of the major mechanisms underlying both innate and acquired resistance to rituximab. In this study, we show that histone deacetylase (HDAC) inhibitors augment the cytotoxic activity of rituximab by enhancing the surface expression of CD20 antigen on lymphoma cells. HDAC inhibitors, valproic acid (VPA) and romidepsin, increased CD20 expression at protein and mRNA levels in B-cell lymphoma cell lines with relatively low CD20 expression levels. The VPA-mediated increase in CD20 expression occurred at 1 m, which is clinically achievable and safe, but insufficient for inducing cell death. Chromatin immunoprecipitation assays revealed that HDAC inhibitors transactivated the CD20 gene through promoter hyperacetylation and Sp1 recruitment. HDAC inhibitors potentiated the activity of rituximab in complement-dependent cytotoxic assays. In mouse lymphoma models, HDAC inhibitors enhanced CD20 expression along with histone hyperacetylation in transplanted cells, and acted synergistically with rituximab to retard their growth. The combination with HDAC inhibitors may serve as an effective strategy to overcome rituximab resistance in B-cell lymphomas.

F-actin-binding domain of c-Abl regulates localized phosphorylation of C3G: role of C3G in c-Abl-mediated cell death

The c-Abl tyrosine kinase maintains cellular homeostasis through its ability to regulate apoptosis and actin dynamics. In vivo, c-Abl activity is stringently regulated and mechanisms involved are not fully understood. Here, we identified the Rap1 guanine nucleotide exchange factor, C3G (RapGEF1), as a substrate and an effector of c-Abl-mediated functions. Ectopic expression of c-Abl in mammalian cell lines, known to induce apoptosis, resulted in phosphorylation of endogenous C3G on Y504 coincident with cell detachment and chromatin condensation. Phosphorylation of C3G coincided with restricted c-Abl activation in regions rich in actin, and was dependent on cellular F-actin dynamics. Unlike C3G or c-Abl, p-C3G was resistant to detergent extraction, suggesting its enhanced affinity for the cytoskeleton. Localized C3G phosphorylation and coincidence with cells undergoing cell death was dependent on F-actin-binding domain (FABD) of c-Abl. Activation of endogenous c-Abl by oxidative stress was associated with phosphorylation of cellular C3G on Y504. Inhibition of C3G expression and function using RNAi or dominant-negative approaches inhibited c-Abl-mediated cell death. These findings identify C3G as a novel target of c-Abl and also show that FABD of c-Abl is essential for regulation of its restricted activation to induce apoptosis.

Epigenetics of human cutaneous melanoma: setting the stage for new therapeutic strategies

Cutaneous melanoma is a very aggressive neoplasia of melanocytic origin with constantly growing incidence and mortality rates world-wide. Epigenetic modifications (i.e., alterations of genomic DNA methylation patterns, of post-translational modifications of histones, and of microRNA profiles) have been recently identified as playing an important role in melanoma development and progression by affecting key cellular pathways such as cell cycle regulation, cell signalling, differentiation, DNA repair, apoptosis, invasion and immune recognition. In this scenario, pharmacologic inhibition of DNA methyltransferases and/or of histone deacetylases were demonstrated to efficiently restore the expression of aberrantly-silenced genes, thus re-establishing pathway functions. In light of the pleiotropic activities of epigenetic drugs, their use alone or in combination therapies is being strongly suggested, and a particular clinical benefit might be expected from their synergistic activities with chemo-, radio-, and immuno-therapeutic approaches in melanoma patients. On this path, an important improvement would possibly derive from the development of new generation epigenetic drugs characterized by much reduced systemic toxicities, higher bioavailability, and more specific epigenetic effects.

Histone deacetylases are critical targets of bortezomib-induced cytotoxicity in multiple myeloma

Bortezomib is now widely used for the treatment of multiple myeloma (MM); however, its action mechanisms are not fully understood. Despite the initial results, recent investigations have indicated that bortezomib does not inactivate nuclear factor-kappaB activity in MM cells, suggesting the presence of other critical pathways leading to cytotoxicity. In this study, we show that histone deacetylases (HDACs) are critical targets of bortezomib, which specifically down-regulated the expression of class I HDACs (HDAC1, HDAC2, and HDAC3) in MM cell lines and primary MM cells at the transcriptional level, accompanied by reciprocal histone hyperacetylation. Transcriptional repression of HDACs was mediated by caspase-8-dependent degradation of Sp1 protein, the most potent transactivator of class I HDAC genes. Short-interfering RNA-mediated knockdown of HDAC1 enhanced bortezomib-induced apoptosis and histone hyperacetylation, whereas HDAC1 overexpression inhibited them. HDAC1 overexpression conferred resistance to bortezomib in MM cells, and administration of the HDAC inhibitor romidepsin restored sensitivity to bortezomib in HDAC1-overexpressing cells both in vitro and in vivo. These results suggest that bortezomib targets HDACs via distinct mechanisms from conventional HDAC inhibitors. Our findings provide a novel molecular basis and rationale for the use of bortezomib in MM treatment.

A novel histone deacetylase inhibitor Chidamide induces apoptosis of human colon cancer cells

Many studies have demonstrated that histone deacetylase (HDAC) inhibitors induce various tumor cells to undergo apoptosis, and such inhibitors have been used in different clinical trials against different human cancers. In this study, we designed and synthesized a novel HDAC inhibitor, Chidamide. We showed that Chidamide was able to increase the acetylation levels of histone H3 and to inhibit the PI3K/Akt and MAPK/Ras signaling pathways, which resulted in arresting colon cancer cells at the G1 phase of the cell cycle and promoting apoptosis. As a result, the proliferation of colon cancer cells was suppressed in vitro. Our data support the potential application of Chidamide as an anticancer agent in treating colon cancer. Future studies are needed to demonstrate its in vivo efficacy.

Epigenetics in human melanoma

BACKGROUND

Recent technological advances have allowed us to examine the human genome in greater detail than ever before. This has opened the door to an improved understanding of the gene expression patterns involved with cancer.

METHODS

A review of the literature was performed to determine the role of epigenetic modifications in human melanoma. We focused the search on histone deacetylation, methylation of gene promoter regions, demethylation of CpG islands, and the role of microRNA. We examined the relationship between human melanoma epigenetics and their importance in tumorigenesis, tumor progression, and inhibition of metastasis. The development and clinical application of select pharmacologic agents are also discussed.

RESULTS

We identified several articles that have extensively studied the role of epigenetics in melanoma, further elucidating the complex processes involved in gene regulation and expression. Several new agents directly affect epigenetic mechanisms in melanoma, with divergent affects on the metastatic potential of melanoma.

CONCLUSIONS

Epigenetic mechanisms have emerged as having a central role in gene regulation of human melanoma, including the identification of several putative tumor suppressor genes and oncogenes. Further research will focus on the development of novel therapeutics that will likely target and alter such epigenetic changes.

Romidepsin inhibits Ras-dependent growth transformation of NIH 3T3 fibroblasts and RIE-1 epithelial cells independently of Ras signaling inhibition

Background

Despite intensive effort, currently no effective anti-Ras therapies have successfully reached clinical application. Previous studies suggest that the histone deacetylatse (HDAC) inhibitor romidepsin, which is currently in clinical trials for the treatment of multiple malignancies, can block Ras-dependent signaling and growth transformation. These studies suggest that mutational activation of Ras may be a useful biomarker for sensitivity to romidepsin and that the anti-tumor activity of this HDAC inhibitor may involve inhibition of Ras effector-mediated signaling.

Results

To rigorously assess romidepsin as an antagonist of Ras, we utilized two well-characterized cell models for Ras transformation. We found that romidepsin blocked the anchorage-dependent and -independent growth of NIH 3T3 fibroblasts and RIE-1 epithelial cells transformed by all three Ras isoforms. However, romidepsin treatment also blocked growth transformation caused by other oncoproteins (B-Raf and ErbB2/Neu), suggesting that romidepsin is not selective for Ras. We also observed striking differences in romidepsin-mediated growth inhibition between transformed NIH 3T3 fibroblasts compared to RIE-1 epithelial cells, suggesting that the mechanism by which romidepsin blocks transformation is dependent on cellular context. Finally, we found that romidepsin did not inhibit Ras activation of the ERK and AKT effector pathways in NIH 3T3 and RIE-1 cells, suggesting that romidepsin does not directly antagonize Ras.

Conclusion

Taken together, our results suggest that romidepsin is not selective for Ras-transformed cells and that the anti-tumor activity of romidepsin is not due to direct inhibition of Ras function.

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, diminishes lymphoproliferation in the Fas -deficient MRL/lpr(-/-) murine model of autoimmune lymphoproliferative syndrome (ALPS)

OBJECTIVE

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of apoptosis, often presenting in childhood. Similarly, MRL/lpr(-/-) mice homozygous for Fas mutations develop an ALPS-like disease with autoimmunity, lymphadenopathy, splenomegaly, and expansion of double-negative T cells. Currently, there are no proven therapies with adequate safety margins for sustained abolition of the lymphoproliferation associated with ALPS. We sought to test the ability of valproic acid (VPA), a histone deacetylase inhibitor, to induce apoptosis and inhibit lymphoproliferation.

MATERIALS AND METHODS

Human peripheral blood mononuclear cells from patients with ALPS and normal controls were tested in vitro to determine the efficacy of VPA at inducing cell death. VPA was used in vivo to control lymphoproliferation in MRL/lpr(-/-) mice, a model for ALPS.

RESULTS

VPA induced cell death in vitro, and was partially inhibited by the pan caspase inhibitor, Z-VAD-FMK. MRL/lpr(-/-) mice treated with VPA for 8 weeks showed significant reductions in spleen and lymph node weights and cellularity compared to controls. A concomitant decrease in double-negative T cells was observed in the spleen, lymph nodes, and peripheral blood. Serum levels of VPA peaked 1 hour after injection, and a 2.5-fold increase in histone acetylation was observed in the spleen at 4 hours after injection.

CONCLUSION

Based on our data, VPA is effective at reducing lymphoproliferation in mice, and is currently being studied in a clinical trial as a lympholytic agent in patients with ALPS.

Epigenetics of cutaneous melanoma

Tumorigenesis is traditionally thought to be caused by the imbalance between oncogenes and tumor-suppressor genes. Epigenetics is a recently described phenomenon that uses an alternative mechanism to explain the transcriptional inactivation of tumor-suppressor genes predominantly by hypermethylation of the promoter regions. Hypermethylation of these regions has been described extensively in many neoplasms, including cutaneous melanoma. Histone modification, primarily by acetylation and deacetylation, is a current potential target for melanoma therapy, but more research is required to understand the mechanisms involved and the therapeutic effectiveness of regimens involving these agents. These mechanisms not only are important for understanding the origin and progression of neoplasms but also have important potential therapeutic implications. Understanding the epigenetic mechanisms involved in melanoma can provide valuable information with significant implications in diagnosis, treatment, and prevention.

Transactivation of RON receptor tyrosine kinase by interaction with PDGF receptor beta during steady-state growth of human mesangial cells

Although it is well known that platelet-derived growth factor (PDGF) causes mesangial cell proliferation (presumably contributing to progression of glomerular disease), targeted inhibition of the PDGF receptor system has shown only limited efficacy against glomerular diseases. To examine whether this discrepancy is due to the involvement of other pathways, we used phosphorylated receptor tyrosine kinase arrays and found that RON (recepteur d'origine nantais) was phosphorylated while the PDGF receptor was dephosphorylated (thus inactive) in human mesangial cells (HMCs) at the time of cell cycle entry. Further, RON remained active during steady-state growth. Activation of RON was independent of its canonical ligand, macrophage-stimulating protein, but was mediated by transactivation from the PDGF-engaged PDGF receptor. Following stimulation with PDGF we found that the two receptors physically interacted. Knockdown of RON by siRNA increased the number of apoptotic cells without affecting the rate of DNA synthesis, suggesting that RON has anti-apoptotic functions. Immunohistochemical analysis found phosphorylated RON in glomerular lesions of patients with IgA nephropathy but not those with minimal change nephrotic syndrome, a disease not associated with mesangial proliferation. These results suggest that RON is involved in mesangial cell proliferation under both physiological and pathological conditions, and may be a relevant target for therapeutic intervention.

SIRT1 overexpression antagonizes cellular senescence with activated ERK/S6k1 signaling in human diploid fibroblasts

Sir2, a NAD-dependent deacetylase, modulates lifespan in yeasts, worms and flies. The SIRT1, mammalian homologue of Sir2, regulates signaling for favoring survival in stress. But whether SIRT1 has the function to influence cell viability and senescence under non-stressed conditions in human diploid fibroblasts is far from unknown. Our data showed that enforced SIRT1 expression promoted cell proliferation and antagonized cellular senescence with the characteristic features of delayed Senescence-Associated beta-galactosidase (SA-beta-gal) staining, reduced Senescence-Associated Heterochromatic Foci (SAHF) formation and G1 phase arrest, increased cell growth rate and extended cellular lifespan in human fibroblasts, while dominant-negative SIRT1 allele (H363Y) did not significantly affect cell growth and senescence but displayed a bit decreased lifespan. Western blot results showed that SIRT1 reduced the expression of p16(INK4A) and promoted phosphorylation of Rb. Our data also exposed that overexpression of SIRT1 was accompanied by enhanced activation of ERK and S6K1 signaling. These effects were mimicked in both WI38 cells and 2BS cells by concentration-dependent resveratrol, a SIRT1 activator. It was noted that treatment of SIRT1-.transfected cells with Rapamycin, a mTOR inhibitor, reduced the phosphorylation of S6K1 and the expression of Id1, implying that SIRT1-induced phosphorylation of S6K1 may be partly for the decreased expression of p16(INK4A) and promoted phosphorylation of Rb in 2BS. It was also observed that the expression of SIRT1 and phosphorylation of ERK and S6K1 was declined in senescent 2BS. These findings suggested that SIRT1-promoted cell proliferation and antagonized cellular senescence in human diploid fibroblasts may be, in part, via the activation of ERK/ S6K1 signaling.

Improved total synthesis of the potent HDAC inhibitor FK228 (FR-901228)

A scaleable synthesis of the potent histone deacetylase (HDAC) inhibitor FK228 is described. A reliable strategy for preparing the key beta-hydroxy mercapto heptenoic acid partner was accomplished in nine steps and 13% overall yield. A Noyori asymmetric hydrogen-transfer reaction established the hydroxyl stereochemistry in >99:1 er via the reduction of a propargylic ketone.

Transcriptional modulation using HDACi depsipeptide promotes immune cell-mediated tumor destruction of murine B16 melanoma

With melanoma, as with many other malignancies, aberrant transcriptional repression is a hallmark of refractory cancer. To restore gene expression, use of a histone deacetylase inhibitor (HDACi) is expected to be effective. Our recent DNA micro-array analysis showed that the HDACi depsipeptide (FK228) significantly enhances gp100 antigen expression. Herein, we demonstrate that depsipeptide promotes tumor-specific T-cell-mediated killing of B16/F10 murine melanoma cells. First, by a quantitative assay of caspase-3/7 activity, a sublethal dose of depsipeptide was determined (ED50: 5 nM), in which p21(Waf1/Cip1) and Fas were sufficiently evoked concomitantly with histone H3 acetylation. Second, the sublethal dose of depsipeptide treatment with either a recombinant Fas ligand or tumor-specific T cells synergistically enhanced apoptotic cell death in B16/F10 cells in vitro. Furthermore, we found that depsipeptide increased levels of perforin in T cells. Finally, in vivo metastatic growth of B16/F10 in the lung was significantly inhibited by a combination of depsipeptide treatment and immune cell adoptive transfer from immunized mice using irradiated B16 cells and gp100-specific (Pmel-1) TCR transgenic mice (P<0.05, vs cell transfer alone). Consequently, employment of a transcriptional modulation strategy using HDACis might prove to be a useful pretreatment for human melanoma immunotherapy.

Ras-associated protein-1 regulates extracellular signal-regulated kinase activation and migration in melanoma cells: two processes important to melanoma tumorigenesis and metastasis

Melanoma is one of the most devastating malignancies with a rising incidence and lack of effective treatments for advanced disease. Constitutive activation of the mitogen-activated protein kinase (MAPK) pathway and altered expression of alpha(v)beta(3) integrin are critical for melanoma development and progression. Ras-associated protein-1 (Rap1), a Ras family member of the small GTPases, has emerged as a key mediator in these two important processes. In this study, we have shown Rap1 activation in cells derived from two human metastatic melanomas and also in three of seven cutaneous metastatic melanoma tissues. We found increased extracellular signal-regulated kinase (ERK) activity in the tumors with detected Rap1 activity that interestingly harbored neither BRAF nor N-Ras mutation, suggesting a role for Rap1 in ERK activation in vivo. We also showed Rap1 and ERK activation by both hepatocyte growth factor (HGF) and 8CPT-2Me-cAMP (an activator of Epac, a Rap1 guanine nucleotide exchange factor) in two human melanoma cell lines. In addition, the activation of ERK by HGF was reduced, at least in part, by small interfering RNAs against Rap1 and a dominant-negative Rap1. Finally, a functional role for Rap1 activation was shown by Rap1-induced alpha(v)beta(3) integrin activation and consequent increased melanoma cell migration in vitro. Taken together, these results show that Rap1 is involved in the activation of MAPK pathway and integrin activation in human melanoma and suggest a potential role for Rap1 in melanoma tumorigenesis and metastasis.

Telomerase expression and cell proliferation in ovarian cancer cells induced by histone deacetylase inhibitors

OBJECTIVE

Telomerase is composed primarily of catalytic subunit (hTERT) and RNA template (hTERC). Histone deacetylase (HDAC) inhibitors are known to modulate transcription and change the expression of hTERT and hTERC mRNA and telomerase activity in several types of cancer cells, but it is unclear if there is a similar effect in ovarian cancer cells.

METHOD

The present study was designed to evaluate the effects of HDAC inhibitors on hTERT and hTERC mRNA expression in ovarian cancer cells. SK-V-3 cells were treated with the HDAC inhibitors, trichostatinA (TSA) and sodium butyrate (NaB); the expression of hTERC and hTERT mRNA and telomerase activity were evaluated by RT-PCR and TRAP assay, respectively.

RESULTS

In SK-OV-3 cells, TSA and NaB inhibited cell proliferation and induced apoptosis. The expression of hTERT and hTERT mRNA was not suppressed even after treatment with 1.0 microM TSA and 6 mM NaB, respectively. The telomerase activity was not changed by either TSA or NaB.

CONCLUSION

Histone deacetylase inhibitors inhibited cell proliferation and induced apoptosis, but had no effect on the expression of hTERC and hTERT mRNA and on telomerase activity.

Pro-apoptotic activity of oncogenic H-Ras for histone deacetylase inhibitor to induce apoptosis of human cancer HT29 cells

PURPOSE

To verify the pro-apoptotic activity of oncogenic H-Ras in the increased susceptibility of human cancer cells to histone deacetylase inhibitor (HDACI).

METHODS

The pro-apoptotic activity of oncogenic H-Ras(V12) was verified by its ability to increase susceptibility of human colorectal adenocarcinoma HT29 cells to HDACI for inducing apoptosis and growth inhibition, assayed by various methods. The mode of action of HDACI FR901228 was studied by its ability to modulate protein phosphorylation, acetylation, and expression levels in various signaling pathways, measured by Western blot analysis.

RESULTS

Activation of caspase-3, -7, and -8, and serine protease by FR901228 was facilitated by oncogenic H-Ras to induce apoptosis. Expression of H-Ras(V12) changed the intrinsic modulation of Raf in cells responding to FR901228 treatment. Both p21( Cip1 ) and p27( Kip1 ) were induced in FR901228-treated cells arrested in either the G0/G1 or G2/M phase of the cell cycle. Deacetylation of FR901228-induced acetylation of core histones was accelerated by H-Ras(V12) in cells undergoing apoptosis.

CONCLUSION

Expression of H-Ras(V12) increased susceptibility of HT29 cells to HDACI FR901228 and Trichostatin A for inducing apoptosis. The pro-apoptotic activity of H-Ras(V12) responding to HDACI indicates a potential value of this new class of anticancer agents in treating Ras-related human cancers.

Epigenetic events in malignant melanoma

Irreversible changes in the DNA sequence, including chromosomal deletions or amplification, activating or inactivating mutations in genes, have been implicated in the development and progression of melanoma. However, increasing attention is being turned towards the participation of 'epigenetic' events in melanoma progression that do not affect DNA sequence, but which nevertheless may lead to stable inherited changes in gene expression. Epigenetic events including histone modifications and DNA methylation play a key role in normal development and are crucial to establishing the correct program of gene expression. In contrast, mistargeting of such epigenetic modifications can lead to aberrant patterns of gene expression and loss of anti-cancer checkpoints. Thus, to date at least 50 genes have been reported to be dysregulated in melanoma by aberrant DNA methylation and accumulating evidence also suggests that mistargetting of histone modifications and altered chromatin remodeling activities will play a key role in melanoma. This review gives an overview of the many different types of epigenetic modifications and their involvement in cancer and especially in melanoma development and progression.

Cytotoxic effects of histone deacetylase inhibitor FK228 (depsipeptide, formally named FR901228) in combination with conventional anti-leukemia/lymphoma agents against human leukemia/lymphoma cell lines

FK228 is a novel antitumor depsipeptide that inhibits histone deacetylases and restores the expression of genes aberrantly suppressed in cancer cells. This agent was shown to have broad antitumor activity in preclinical studies, and is currently under phase I/II evaluations. Because of its wide spectrum of actions, it is reasonable to consider the combination with other anticancer drugs in clinical application. We studied the cytotoxic interaction of FK228 in combination with conventional antileukemic agents using human promyelocytic leukemia HL60, Philadelphia chromosome-positive (Ph(+)) chronic myelogenous leukemia KU-812, T-cell lymphoblastic leukemia MOLT3 and Burkitt's lymphoma Raji cell lines. For the combination of FK228 and imatinib, Ph(+) leukemia KU812, K562 and TCC-S cell lines were used. The cells were exposed simultaneously to FK228 and other agents for 4 days. Cell growth inhibition was determined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. We used the isobologram method of Steel and Peckham to evaluate the cytotoxic interaction at the concentration of drugs that produced 80% cell growth inhibition (IC(80)). FK228 showed an additive effect with cytarabine, carboplatin, doxorubicin, etoposide, 4-hydroperoxy-cyclophosphamide, 6-mercaptopurine and SN-38 (active metabolite of irinotecan) in all cell lines studied. FK228 with methotrexate and vincristine showed an antagonistic effect in three and one of the four cell lines, respectively. FK228 was additive with imatinib in all three Ph(+) leukemia cells. Our findings suggest that FK228 is a promising candidate for combining with most anticancer agents except for methotrexate and vincristine, which produce suboptimal effects.