Histone deacetylase inhibitor (SAHA) and repression of EZH2 synergistically inhibit proliferation of gallbladder carcinoma

Chemical perturbations impacting histone acetylation govern colorectal cancer differentiation

Dysregulated epigenetic programs that restrict differentiation, reactivate fetal genes, and confer phenotypic plasticity are critical to colorectal cancer (CRC) development. By screening a small molecule library targeting epigenetic regulators using our dual reporter system, we found that inhibiting histone deacetylase (HDAC) 1/2 promotes CRC differentiation and anti-tumor activity. Comprehensive biochemical, chemical, and genetic experiments revealed that on-target blockade of the HDAC1/2 catalytic domain mediated the differentiated phenotype. Unbiased profiling of histone posttranslational modifications induced by HDAC1/2 inhibition nominated acetylation of specific histone lysine residues as potential regulators of differentiation. Genome-wide assessment of implicated marks indicated that H3K27ac gains at HDAC1/2-bound regions associated with open chromatin and upregulation of differentiation genes upon HDAC1/2 inhibition. Disrupting H3K27ac by degrading acetyltransferase EP300 rescued HDAC1/2 inhibitor-mediated differentiation of a patient-derived CRC model using single cell RNA-sequencing. Genetic screens revealed that DAPK3 contributes to CRC differentiation induced by HDAC1/2 inhibition. These results highlight the importance of specific chemically targetable histone modifications in governing cancer cell states and epigenetic reprogramming as a therapeutic strategy in CRC.

Exposure to the extremely low-frequency electromagnetic field induces changes in the epigenetic regulation of gene expression in the endometrium

Increasing technological development results in more sources of the extremely low-frequency electromagnetic field (ELF-EMF), which is recognized as an environmental risk factor. The results of the past study indicate that the ELF-EMF can affect the level of DNA methylation. The study aimed to determine whether the ELF-EMF induces changes in epigenetic regulation of gene expression in the endometrium of pigs during the peri-implantation period. Endometrial slices (100 ± 5 mg) collected on days 15-16 of pregnancy were exposed in vitro to the ELF-EMF at a frequency of 50 Hz for 2 h of treatment duration. To determine the impact of the ELF-EMF on elements of epigenetic regulations involved in DNA methylation, histone modification, and microRNA biogenesis in the endometrium, the DNMT1 and DNMT3a; EZH2, UHRF1, and MBD1; DICER1 and DGCR8 mRNA transcript and protein abundance were analyzed using Real-Time PCR and Western blot, respectively. Moreover, EED and SUZ12 mRNA transcript, global DNA methylation, and the activity of histone deacetylase (HDAC) were analyzed. The changes in the abundance of DNMT1 and DNMT3a, EZH2 mRNA transcript and protein, EED and SUZ12 mRNA transcript, global DNA methylation level, HDAC activity, and the abundance of proteins involved in microRNA biogenesis evoked by the ELF-EMF in the endometrium were observed. The ELF-EMF possesses the potential to alter epigenetic regulation of gene expression in the porcine endometrium. Observed alterations may be the reason for changes in the transcriptomic profile of the endometrium exposed to the ELF-EMF which in turn may disrupt biological processes in the uterus during peri-implantation.

The roles of epigenetic regulation in cholangiocarcinogenesis

Cholangiocarcinoma (CCA), a heterogeneous malignancy of bile duct epithelial cells, is characterized by aggressiveness, difficult diagnosis, and poor prognosis due to limited understanding and lack of effective therapeutic strategies. Genetic and epigenetic alterations accumulated in CCA cells can cause the aberrant regulation of oncogenes and tumor suppressors. Epigenetic alterations with histone modification, DNA methylation, and noncoding RNA modulation are associated with the carcinogenesis of CCA. Mutation or silencing of genes by various mechanisms can be a frequent event during CCA development. Alterations in histone acetylation/deacetylation at the posttranslational level, DNA methylation at promoters, and noncoding RNA regulation contribute to the heterogeneity of CCA and drive tumor development. In this review article, we mainly focus on the roles of epigenetic regulation in cholangiocarcinogenesis. Alterations in epigenetic modification can be potential targets for the therapeutic management of CCA, and epigenetic targets may become diagnostic biomarkers of CCA.

Hedgehog pathway orchestrates the interplay of histone modifications and tailors combination epigenetic therapies in breast cancer

Epigenetic therapies that cause genome-wide epigenetic alterations, could trigger local interplay between different histone marks, leading to a switch of transcriptional outcome and therapeutic responses of epigenetic treatment. However, in human cancers with diverse oncogenic activation, how oncogenic pathways cooperate with epigenetic modifiers to regulate the histone mark interplay is poorly understood. We herein discover that the hedgehog (Hh) pathway reprograms the histone methylation landscape in breast cancer, especially in triple-negative breast cancer (TNBC). This facilitates the histone acetylation caused by histone deacetylase (HDAC) inhibitors and gives rise to new therapeutic vulnerability of combination therapies. Specifically, overexpression of zinc finger protein of the cerebellum 1 (ZIC1) in breast cancer promotes Hh activation, facilitating the switch of H3K27 methylation (H3K27me) to acetylation (H3K27ac). The mutually exclusive relationship of H3K27me and H3K27ac allows their functional interplay at oncogenic gene locus and switches therapeutic outcomes. Using multiple in vivo breast cancer models including patient-derived TNBC xenograft, we show that Hh signaling-orchestrated H3K27me and H3K27ac interplay tailors combination epigenetic drugs in treating breast cancer. Together, this study reveals the new role of Hh signaling-regulated histone modifications interplay in responding to HDAC inhibitors and suggests new epigenetically-targeted therapeutic solutions for treating TNBC.

Evaluation of Tazemetostat as a Therapeutically Relevant Substance in Biliary Tract Cancer

Biliary tract cancer (BTC) is a gastrointestinal malignancy associated with a poor survival rate. Current therapies encompass palliative and chemotherapeutic treatment as well as radiation therapy, which results in a median survival of only one year due to standard therapeutic ineffectiveness or resistance. Tazemetostat is an FDA-approved inhibitor of enhancer of Zeste homolog 2 (EZH2), a methyltransferase involved in BTC tumorigenesis via trimethylation of histone 3 at lysine 27 (H3K27me3), an epigenetic mark associated with silencing of tumor suppressor genes. Up to now, there are no data available regarding tazemetostat as a possible treatment option against BTC. Therefore, the aim of our study is a first-time investigation of tazemetostat as a potential anti-BTC substance in vitro. In this study, we demonstrate that tazemetostat affects cell viability and the clonogenic growth of BTC cells in a cell line-dependent manner. Furthermore, we found a strong epigenetic effect at low concentrations of tazemetostat, which was independent of the cytotoxic effect. We also observed in one BTC cell line that tazemetostat increases the mRNA levels and protein expression of the tumor suppressor gene Fructose-1,6-bisphosphatase 1 (FBP1). Interestingly, the observed cytotoxic and epigenetic effects were independent of the mutation status of EZH2. To conclude, our study shows that tazemetostat is a potential anti-tumorigenic substance in BTC with a strong epigenetic effect.

HDAC Screening Identifies the HDAC Class I Inhibitor Romidepsin as a Promising Epigenetic Drug for Biliary Tract Cancer

Simple Summary

Biliary tract cancer (BTC) is a rare disease with dismal outcomes. Therefore, the investigation of new therapeutic targets is urgently required. In this study, we demonstrate that histone deacetylases (HDACs) are expressed in BTC cell lines and that treatment of BTC cells with different HDAC class inhibitors reduces cell viability. Specifically, we found that BTC cells are vulnerable to the HDAC class I inhibitor romidepsin. Treatment with romidepsin resulted in apoptotic cell death of BTC cells and reduced HDAC activity. Furthermore, romidepsin augmented the cytotoxic effect of the standard chemotherapeutic cisplatin. HDAC class I proteins were also expressed in BTC patient samples. We detected that BTC patients with high HDAC-2-expressing tumors showed a significantly shorter survival. In summary, we were able to demonstrate that BTC cells are vulnerable to HDAC inhibition and that the HDAC class I inhibitor romidepsin might be a promising anti-BTC substance.

Abstract

Inhibition of histone deacetylases (HDACs) is a promising anti-cancer approach. For biliary tract cancer (BTC), only limited therapeutic options are currently available. Therefore, we performed a comprehensive investigation of HDAC expression and pharmacological HDAC inhibition into a panel of eight established BTC cell lines. The screening results indicate a heterogeneous expression of HDACs across the studied cell lines. We next tested the effect of six established HDAC inhibitors (HDACi) covering pan- and class-specific HDACis on cell viability of BTC cells and found that the effect (i) is dose- and cell-line-dependent, (ii) does not correlate with HDAC isoform expression, and (iii) is most pronounced for romidepsin (a class I HDACi), showing the highest reduction in cell viability with IC₅₀ values in the low-nM range. Further analyses demonstrated that romidepsin induces apoptosis in BTC cells, reduces HDAC activity, and increases acetylation of histone 3 lysine 9 (H3K9Ac). Similar to BTC cell lines, HDAC 1/2 proteins were heterogeneously expressed in a cohort of resected BTC specimens (n = 78), and their expression increased with tumor grading. The survival of BTC patients with high HDAC-2-expressing tumors was significantly shorter. In conclusion, HDAC class I inhibition in BTC cells by romidepsin is highly effective in vitro and encourages further in vivo evaluation in BTC. In situ assessment of HDAC 2 expression in BTC specimens indicates its importance for oncogenesis and/or progression of BTC as well as for the prognosis of BTC patients.

Expression of Human epidermal growth factor receptor 2, Survivin, Enhancer of zeste homolog -2, Cyclooxygenase-2, p53 and p16 molecular markers in Gall bladder carcinoma

INTRODUCTION:

Gallbladder cancer exhibits striking variability in the global rates, reaching epidemic levels for some regions and ethnicities. The basis of its variability resides in differences in environmental exposure and intrinsic genetic predisposition to carcinogenesis. There is little information present regarding genetic and molecular alterations in gall bladder cancer (GBC). We, therefore, have evaluated the molecular marker expression in GBC and studied their correlation with clinicopathological staging.

MATERIALS AND METHODS:

This prospective observational study was conducted on newly diagnosed GBC patients from July 2017 to July 2020. After complete staging workup, the GBC biopsy samples paraffin block was tested for molecular markers estrogen receptor (ER), progesterone receptor (PR), p53, p16, Human epidermal growth factor receptor 2 (HER 2-neu), Survivin, Enhancer of zeste homolog-2 (EZH2), and Cyclooxygenase-2 (COX-2) expression by immunohistochemistry.

RESULTS:

Fifty newly diagnosed patients of carcinoma gall bladder were included in the present study. Age was ranged from 29 – 69 years (mean 53.42). p53 was the most common positive marker in 74% of patients, survivin in 58%, COX-2 in 44%, and p16 in 42% whereas Her 2 neu and EZH-2 were positive in 16% of patients each. None of the patients of GBC were ER or PR positive. There was a significant difference between the various groups in terms of the distribution of histological grade and Her 2 neu (χ² = 9.886, P = 0.014) but not with other markers. Furthermore, there was a significant difference in terms of distribution of p16 and p53 with stage (χ² = 7.017, P = 0.037 and χ² = 5.861, P = 0.033) respectively.

CONCLUSIONS:

The present study shows the expression of molecular markers Her2 neu, p53, p16, survivin, COX-2, and EZH-2 in GBC. Now the time has come, and it is also the need of the day to establish early biomarkers of this highly lethal malignancy. It can be used in future for the detection of disease in the early phase and targeted therapy.

Recent developments in epigenetic cancer therapeutics: clinical advancement and emerging trends

Epigenetic drug discovery field has evidenced significant advancement in the recent times. A plethora of small molecule inhibitors have progressed to clinical stage investigations and are being explored exhaustively to ascertain conclusive benefits in diverse malignancies. Literature precedents indicates that substantial amount of efforts were directed towards the use of epigenetic tools in monotherapy as well as in combination regimens at the clinical level, however, the preclinical/preliminary explorations were inclined towards the identification of prudent approaches that can leverage the anticancer potential of small molecule epigenetic inhibitors as single agents only. This review article presents an update of FDA approved epigenetic drugs along with the epigenetic inhibitors undergoing clinical stage investigations in different cancer types. A detailed discussion of the pragmatic strategies that are expected to steer the progress of the epigenetic therapy through the implementation of emerging approaches such as PROTACS and CRISPR/Cas9 along with logical ways for scaffold fabrication to selectively approach the enzyme isoforms in pursuit of garnering amplified antitumor effects has been covered. In addition, the compilation also presents the rational strategies for the construction of multi-targeting scaffold assemblages employing previously identified pharmacophores as potential alternatives to the combination therapy.

Fucoidan induces ROS-dependent epigenetic modulation in cervical cancer HeLa cell

Fucoidan is a sulfated polysaccharide obtained from marine algae and known for various pharmacological activities. In this study, we investigated the effect of Fucoidan on cell viability, redox balance, cytoskeletal component F-actin, HDAC inhibition, autophagy, and senescence phenomenon in human cervical cancer HeLa cell line in comparison to positive control suberoylanilide hydroxamic acid by flow cytometry, fluorescence microscopy, and western blotting. Our observations revealed that Fucoidan exposure induces cytotoxicity in HeLa cells via ROS and mitochondrial superoxide generation and loss of ATP. Colorimetrical studies suggested that Fucoidan impairs the function of HDAC expression. Fucoidan treatment also contributes to the change in the granularity of cells, senescence-associated heterochromatin foci formation that leads to senescence in HeLa cells. Moreover, we visualize that Fucoidan exhibits autophagosomes formation with monodansylcadaverine, and flow cytometry analysis by acridine orange further substantiates that Fucoidan triggers autophagy in HeLa cells. Additionally, the changes in the expression of proteins p21, p16, BECN1, and HDAC1 were seen as markers of senescence, autophagy, and HDAC inhibition by FACS and immunoblotting. Molecular docking study validates Fucoidan-HDAC1 association in corroboration with the experimental data. Collectively, these mechanistic studies demonstrated that Fucoidan could be a therapeutic molecule for targeting HDACs in cervical cancer.

Modulation of mTOR and epigenetic pathways as therapeutics in gallbladder cancer

Gallbladder cancer (GBC) is the most common malignancy of the biliary tract, with extremely dismal prognosis. Limited therapeutic options are available for GBC patients. We used whole-exome sequencing of human GBC to identify the ErbB and epigenetic pathways as two vulnerabilities in GBC. We screened two focused small-molecule libraries that target these two pathways using GBC cell lines and identified the mTOR inhibitor INK-128 and the histone deacetylase (HDAC) inhibitor JNJ-26481585 as compounds that inhibited proliferation at low concentrations. Both significantly suppressed tumor growth and metastases in mouse models. Both synergized with the standard of care chemotherapeutic agent gemcitabine in cell lines and in mouse models. Furthermore, the activation of the mTOR pathway, measured by immunostaining for phosphorylated mTOR and downstream effector S6K1, is correlated with poor prognosis in GBC. Phosphorylated mTOR or p-S6K1 in clinical samples is an independent indicator for overall survival in GBC patients. Taken together, our findings suggest that mTOR inhibitors and HDAC inhibitors can serve as potential therapeutics for GBC, and the phosphorylation of mTOR and S6K1 may serve as biomarkers for GBC.

Enhancer of Zeste Homolog 2 (EZH2) in Malignant Progression of Gallbladder Carcinoma

PURPOSE

Data related to the role of epigenetic modifications in gallbladder carcinoma (GBC) is limited. We intended to assess the role of crucial epigenetic modifiers pertaining to histone modification and DNA-methylation system in gallbladder carcinogenesis.

METHODS

The expression of EZH2, H3K27me3, and DNA methyltransferases (DNMTs) was analyzed by immunohistochemistry in cases of GBC (n = 39), gallbladder dysplasia (GBD, n = 12), and benign mucosa (BM, n = 16). A semi-quantitative scoring system was used for assessing the immunohistochemical expression.

RESULTS

The expression of EZH2 was significantly higher in cases of GBC than GBD (p value 0.001). The cases of BM were negative. Its expression was also higher in poorly differentiated tumors and positively correlated with the proliferative activity (MIB-1 labeling index) (p value 0.03 and 0.01, respectively). There was no significant difference in the expression levels of H3K27me3, DNMT-1, and DNMT-3B among GBC, GBD, and BM cases. Although GBC cases with strong EZH2 expression showed a shorter overall survival, the difference was not statistically significant.

CONCLUSION

This study highlights the crucial role of the key epigenetic regulators EZH2 in the pathobiology and evolution of gallbladder carcinogenesis. Given the reversibility of epigenetic alterations, EZH2 may be a novel therapeutic target for gallbladder carcinogenesis.

Recent advances in small molecular modulators targeting histone deacetylase 6

Histone deacetylase 6 (HDAC6) is a unique isozyme in the HDAC family with various distinguished characters. HDAC6 is predominantly localized in the cytoplasm and has several specific nonhistone substrates, such as α-tubulin, cortactin, Hsp90, tau and peroxiredoxins. Accumulating evidence reveals that targeting HDAC6 may serve as a promising therapeutic strategy for the treatment of cancers, neurological disorders and immune diseases, making the development of HDAC6 inhibitors particularly attractive. Recently, multitarget drug design and proteolysis targeting chimera technology have also been applied in the discovery of novel small molecular modulators targeting HDAC6. In this review, we briefly describe the structural features and biological functions of HDAC6 and discuss the recent advances in HDAC6 modulators, including selective inhibitors, chimeric inhibitors and proteolysis targeting chimeras for multiple therapeutic purposes.

Long Non-Coding RNAs in Biliary Tract Cancer-An Up-to-Date Review

The term long non-coding RNA (lncRNA) describes non protein-coding transcripts with a length greater than 200 base pairs. The ongoing discovery, characterization and functional categorization of lncRNAs has led to a better understanding of the involvement of lncRNAs in diverse biological and pathological processes including cancer. Aberrant expression of specific lncRNA species was demonstrated in various cancer types and associated with unfavorable clinical characteristics. Recent studies suggest that lncRNAs are also involved in the development and progression of biliary tract cancer, a rare disease with high mortality and limited therapeutic options. In this review, we summarize current findings regarding the manifold roles of lncRNAs in biliary tract cancer and give an overview of the clinical and molecular consequences of aberrant lncRNA expression as well as of underlying regulatory functions of selected lncRNA species in the context of biliary tract cancer.

Role of Histone Deacetylases in Carcinogenesis: Potential Role in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly invasive and metastatic form of carcinoma with bleak prognosis due to limited therapies, frequent relapse, and chemotherapy resistance. There is an urgent need to identify the molecular regulators of CCA in order to develop novel therapeutics and advance diseases diagnosis. Many cellular proteins including histones may undergo a series of enzyme-mediated post-translational modifications including acetylation, methylation, phosphorylation, sumoylation, and crotonylation. Histone deacetylases (HDACs) play an important role in regulating epigenetic maintenance and modifications of their targets, which in turn exert critical impacts on chromatin structure, gene expression, and stability of proteins. As such, HDACs constitute a group of potential therapeutic targets for CCA. The aim of this review was to summarize the role that HDACs perform in regulating epigenetic changes, tumor development, and their potential as therapeutic targets for CCA.

Histone Deacetylases and Histone Deacetylase Inhibitors: Molecular Mechanisms of Action in Various Cancers

Epigenetic modifications such as histone modification play an important role in tumorigenesis. There are several evidence that histone deacetylases (HDACs) play a key role in cancer induction and progression by histone deacetylation. Besides, histone acetylation is being accessed as a therapeutic target because of its role in regulating gene expression. HDAC inhibitors (HDACIs) are a family of synthetic and natural compounds that differ in their target specificities and activities. They affect markedly cancer cells, inducing cell differentiation, cell cycle arrest and cell death, reduction of angiogenesis, and modulation of the immune system. Here, we summarize the mechanisms of HDACs and the HDACIs in several cancers. An online search of different sources such as PubMed, ISI, and Scopus was performed to find available data on mechanisms and pathways of HDACs and HDACIs in different cancers. The result indicated that HDACs induce cancer through multiple mechanisms in various tissues. This effect can be inhibited by HDACIs which affect cancer cell by different pathways such as cell differentiation, cell cycle arrest, and cell death. In conclusion, these findings indicate that the HDACs play a major role in carcinogenesis through various pathways, and HDACIs can inhibit HDAC activity by multiple mechanisms resulting in cell cycle arrest, cell growth inhibition, and apoptosis induction.

BRD4 inhibitor and histone deacetylase inhibitor synergistically inhibit the proliferation of gallbladder cancer in vitro and in vivo

Gallbladder cancer (GBC) is the most common malignancy of the bile duct and has a high mortality rate. Here, we demonstrated that BRD4 inhibitor JQ1 and histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) synergistically inhibited the GBC cells in vitro and in vivo. Our results showed that cotreatment with JQ1 and SAHA significantly inhibited proliferation, cell viability and metastasis, and induced apoptosis and G2/M arrest in GBC cells, with only minor effects in benign cells. In vivo, tumor volumes and weights of GBC xenograft models were significantly decreased after treatment with JQ1 or SAHA; meanwhile, the cotreatment showed the strongest effect. Further study indicated that the above anticancer effects was associated with the downregulation of BRD4 and suppression of PI3K/AKT and MAPK/ERK pathways. These findings highlight JQ1 and SAHA as potential therapeutic agents and their combination as a promising therapeutic strategy for GBC.

Circulating EZH2-positive T cells are decreased in multiple sclerosis patients

BACKGROUND

Recent studies in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis (MS), suggest an involvement of the histone methyltransferase enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) in important processes such as cell adhesion and migration.

METHODS

Here, we aimed to expand these initial observations by investigating the role of EZH2 in MS. mRNA expression levels for EZH2 were measured by real-time PCR in peripheral blood mononuclear cells (PBMC) from 121 MS patients (62 untreated and 59 receiving treatment) and 24 healthy controls.

RESULTS

EZH2 expression levels were decreased in PBMC from untreated patients compared to that from controls, and treatment significantly upregulated EZH2 expression. Expression of miR-124 was increased in MS patients compared to controls. Blood immunophenotyping revealed EZH2 expression mostly restricted to CD4+ and CD8+ T cells, and circulating EZH2+ CD4+ and CD8+ T cells were decreased in untreated MS patients compared to controls. CD8+ T cells expressing EZH2 exhibited a predominant central memory phenotype, whereas EZH2+ CD4+ T cells were of effector memory nature, and both T cell subsets produced TNF-α. EZH2+ T cells were enriched in the cerebrospinal fluid compartment compared to blood and were found in chronic active lesions from MS patients. EZH2 inhibition and microarray analysis in PBMC was associated with significant downregulation of key T cell adhesion molecules.

CONCLUSION

These findings suggest a role of EZH2 in the migration of T cells in MS patients. The observation of TNF-α expression by CD4+ and CD8+ T cells expressing EZH2 warrants additional studies to explore more in depth the pathogenic potential of EZH2+-positive cells in MS.

Histone Deacetylase Inhibitors Synergize with Catalytic Inhibitors of EZH2 to Exhibit Antitumor Activity in Small Cell Carcinoma of the Ovary, Hypercalcemic Type

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare but extremely lethal malignancy that mainly impacts young women. SCCOHT is characterized by a diploid genome with loss of SMARCA4 and lack of SMARCA2 expression, two mutually exclusive ATPases of the SWI/SNF chromatin-remodeling complex. We and others have identified the histone methyltransferase EZH2 as a promising therapeutic target for SCCOHT, suggesting that SCCOHT cells depend on the alternation of epigenetic pathways for survival. In this study, we found that SCCOHT cells were more sensitive to pan-HDAC inhibitors compared with other ovarian cancer lines or immortalized cell lines tested. Pan-HDAC inhibitors, such as quisinostat, reversed the expression of a group of proteins that were deregulated in SCCOHT cells due to SMARCA4 loss, leading to growth arrest, apoptosis, and differentiation in vitro and suppressed tumor growth of xenografted tumors of SCCOHT cells. Moreover, combined treatment of HDAC inhibitors and EZH2 inhibitors at sublethal doses synergistically induced histone H3K27 acetylation and target gene expression, leading to rapid induction of apoptosis and growth suppression of SCCOHT cells and xenografted tumors. Therefore, our preclinical study highlighted the therapeutic potential of combined treatment of HDAC inhibitors with EZH2 catalytic inhibitors to treat SCCOHT.

Small molecule epigenetic screen identifies novel EZH2 and HDAC inhibitors that target glioblastoma brain tumor-initiating cells

Glioblastoma (GBM) is the most lethal and aggressive adult brain tumor, requiring the development of efficacious therapeutics. Towards this goal, we screened five genetically distinct patient-derived brain-tumor initiating cell lines (BTIC) with a unique collection of small molecule epigenetic modulators from the Structural Genomics Consortium (SGC). We identified multiple hits that inhibited the growth of BTICs in vitro, and further evaluated the therapeutic potential of EZH2 and HDAC inhibitors due to the high relevance of these targets for GBM. We found that the novel SAM-competitive EZH2 inhibitor UNC1999 exhibited low micromolar cytotoxicity in vitro on a diverse collection of BTIC lines, synergized with dexamethasone (DEX) and suppressed tumor growth in vivo in combination with DEX. In addition, a unique brain-penetrant class I HDAC inhibitor exhibited cytotoxicity in vitro on a panel of BTIC lines and extended survival in combination with TMZ in an orthotopic BTIC model in vivo. Finally, a combination of EZH2 and HDAC inhibitors demonstrated synergy in vitro by augmenting apoptosis and increasing DNA damage. Our findings identify key epigenetic modulators in GBM that regulate BTIC growth and survival and highlight promising combination therapies.

Epithelial-to-mesenchymal transition in gallbladder cancer: from clinical evidence to cellular regulatory networks

Gallbladder cancer (GBC), with late diagnosis, rapid disease progression and early metastasis, is a highly aggressive malignant tumor found worldwide. Patients with GBC have poor survival, low curative resection rates and early recurrence. For such a lethal tumor, uncovering the mechanisms and exploring new strategies to prevent tumor progression and metastasis are critically important. Epithelial-to-mesenchymal transition (EMT) has a prominent role in the early steps of tumor progression and metastasis by initiating polarized epithelial cell transition into motile mesenchymal cells. Accumulating evidence suggests that EMT can be modulated by the cooperation of multiple mechanisms affecting common targets. Signaling pathways, transcriptional and post-transcriptional regulation and epigenetic alterations are involved in the stepwise EMT regulatory network in GBC. Loss of epithelial markers, acquisition of mesenchymal markers and dysregulation of EMT-inducing transcription factors (EMT-TFs) have been observed and are associated with the clinicopathology and prognosis of GBC patients. Therefore, EMT may be a detectable and predictable event for predicting GBC progression and metastasis in the clinic. In this review, we will provide an overview of EMT from the clinical evidence to cellular regulatory networks that have been studied thus far in clinical and basic GBC studies.

Novel combination of histone methylation modulators with therapeutic synergy against acute myeloid leukemia in vitro and in vivo

Acute myeloid leukemia (AML) is a hematological malignancy with rapid disease progression and often becomes lethal without treatment. Development of effective new therapies is essential to improve the clinical outcome of AML patients. Enhancer of zeste homolog 2 (EZH2) and lysine specific demethylase 1 (LSD1) play important roles in epigenetic regulation and their altered expressions have been observed in cancer. Although EZH2 and LSD1 have opposite histone methylation functions, we found that both enzymes were paradoxically up-regulated in AML cells. Importantly, a combined inhibition of EZH2 and LSD1 resulted in a synergistic activity against AML in vitro and in vivo. Such synergy was mechanistically correlated with up-regulation of H3K4me1/2 and H3K9Ac and down-regulation of H3K27me3, leading to a decrease of anti-apoptotic protein Bcl-2. These epigenetic alterations also compromised the mitochondrial respiration capacity and glycolytic activity and resulted in ATP depletion, a key event contributing to the potent cytotoxic effect of the drug combination. Taken together, our work identified a novel therapeutic approach against AML by combining two small molecules that inhibit different histone methylation-modulating proteins with apparently opposite enzyme activities. Such a new drug combination strategy likely has significant clinical implications since epigenetic modulators are currently in clinical trials.

Long non-coding RNA MINCR promotes gallbladder cancer progression through stimulating EZH2 expression

The regulation of MYC-regulated long non-coding RNAs has been reported to contribute to certain types of cancers. However, the role of MYC-induced long non-coding RNA (MINCR) in the tumorigenesis of gallbladder cancer (GBC) is still largely unknown. In this study, we discovered that MINCR was markedly upregulated in GBC tissues compared with adjacent normal tissues. High MINCR expression levels in GBC were positively associated with tumor volume and lymph node metastasis and were negatively correlated with overall survival (OS). Upregulation of MINCR and enhancer of zeste homolog 2 (EZH2) in GBC coincided with the downregulation of miR-26a-5p in GBC. Mechanistically, MINCR/miR-26a-5p/EZH2 axis was found to be involved in cell proliferation, cell invasive and apoptosis in GBC cells. Moreover, knockdown of MINCR suppressed cell proliferation, decreased S-phase cell numbers, increased cell apoptosis, and inhibited cell invasion by inhibiting the epithelial-mesenchymal transition (EMT) phenomenon in GBC cells. In vivo, tumor volumes were significantly decreased in the MINCR silencing group compared with those in the control group. These results demonstrated that MINCR could potentially be a therapeutic target as well as a prognostic marker in GBC.

Combined inhibition of EZH2 and histone deacetylases as a potential epigenetic therapy for non-small-cell lung cancer cells

Recent discoveries have revealed that human cancer involves aberrant epigenetic alterations. We and others have previously shown that the histone methyltransferase EZH2, the catalytic subunit of polycomb repressive complex 2 (PRC2), is frequently overexpressed in non‐small‐cell lung cancer (NSCLC) and that an EZH2 inhibitor, 3‐deazaneplanocin A, inhibits the proliferation of NSCLC cells. Transcriptional silencing by EZH2 was recently shown to be required for the activity of histone deacetylases (HDACs) that interact with another PRC2 protein, EED. To develop a more effective epigenetic therapy for NSCLC, we determined the effects of co‐treatment with 3‐deazaneplanocin A and the HDAC inhibitor vorinostat (SAHA) in NSCLC cells. The co‐treatment synergistically suppressed the proliferation of all tested NSCLC cell lines, regardless of their epidermal growth factor receptor (EGFR) status. The synergistic effect was associated with slightly decreased histone H3 lysine 27 trimethylation, modestly increased histone acetylation, and the depletion of EZH2 and other PRC2 proteins. The co‐treatment resulted in an accumulation of p27Kip1, decrease in cyclin A, and increased apoptotic fraction in an additive/synergistic manner. Interestingly, the co‐treatment strongly suppressed EGFR signaling, not only in EGFR‐wild‐type NSCLC cells, but also in EGFR‐mutant cells, mainly through dephosphorylation of EGFR. Furthermore, the co‐treatment suppressed the in vivo tumor growth of EGFR‐mutant, EGFR–tyrosine kinase‐resistant H1975 cells more effectively than did each agent alone, without visible toxicity. These results suggest that the combined pharmacological targeting of EZH2 and HDACs may provide more effective epigenetic therapeutics for NSCLC.

Histone deacetylase inhibitor screening identifies HC toxin as the most effective in intrahepatic cholangiocarcinoma cells

Histone deacetylases (HDACs) are highly expressed in intrahepatic cholangiocarcinoma (ICC) and are associated with poor prognosis of these patients. The aim of the present study was to explore the inhibitory effects of HDAC inhibitors on ICC cells and identify effective and sensitive drugs for ICC. Effects of 34 HDAC inhibitors were screened through two rounds of cell viability assays, and HC toxin, a cyclic tetrapeptide first isolated from the secondary metabolite of Helminthosporium carbonum, exhibited an antitumor activity superior to that of the other HDAC inhibitors and gemcitabine. The mechanisms involved in the inhibitory effects of HC toxin on CCLP-1 cells were investigated by cell counting, colony formation assay, cell morphological observation, real-time PCR, western blotting and flow cytometry. It was demonstrated that HC toxin inhibited the cell proliferation and clone formation ability of the CCLP-1 cells. HC toxin increased the acetyl-histone H4 level and this was associated with the inhibitory effect of HC toxin on the CCLP-1 cells. We also found that HC toxin reduced the level of HDAC1 protein in a post-transcriptional manner. Morphological observation showed multiple morphological changes and indicated the possibility of cell differentiation owing to HC toxin. With increasing concentration of HC toxin, the cell cycle was gradually arrested at the G0/G1 stage and the percentage of apoptotic cells increased which was not mainly through the caspase-3-dependent ways. These results indicated that HC toxin was the most effective among the various HDAC inhibitors with multiple functions in the suppression of ICC in vitro. Thus, HC may be a potential chemotherapeutic for ICC.

Mutual regulation between CHD5 and EZH2 in hepatocellular carcinoma

Chromodomain helicase DNA binding protein 5 (CHD5) acts as a tumor suppressor in many cancers. In the present study, we demonstrated that reduced levels of CHD5 in hepatocellular carcinoma (HCC) tissues were significantly associated with metastasis and poor prognosis. Gain-of-function assays revealed that CHD5 suppressed motility and invasion of HCC cells. Subsequent investigations showed that CHD5 was epigenetically silenced by polycomb repressive complex 2 (PRC2)-mediated the trimethylation of histone H3 at lysine 27 (H3K27me3) in HCC cells. Furthermore, overexpression of CHD5 repressed enhancer of zeste homolog 2 (EZH2) and activated PRC2 target genes, such as p16 and p21. Chromatin immunoprecipitation and luciferase reporter assays also showed that CHD5 and EZH2 bind to each other's promoters and inhibit transcription. These findings uncovered, for the first time, a mutual suppression regulation between CHD5 and EZH2, which may provide new insights into their potential therapeutic significance for HCC.

HDAC Inhibition for the Treatment of Epithelioid Sarcoma: Novel Cross Talk Between Epigenetic Components

Epithelioid sarcoma is a rare neoplasm uniquely comprised of cells exhibiting both mesenchymal and epithelial features. Having propensity for local and distant recurrence, it poses a diagnostic dilemma secondary to pathologic complexity. Patients have dismal prognosis due to lack of effective therapy. HDAC inhibitors (HDACi) exhibit marked antitumor effects in various malignancies. The studies here demonstrate that pan-HDAC inhibitors constitute novel therapeutics versus epithelioid sarcoma. Human ES cells (VAESBJ, HS-ES, Epi-544) were studied in preclinical models to evaluate HDACi effects. Immunoblot and RT-PCR were used to evaluate expression of acetylated tubulin, histones H3/H4, EZH2 upon HDACi. MTS and clonogenic assays were used to assess the impact of HDACi on cell growth. Cell culture assays were used to evaluate the impact of HDACi and EZH2-specific siRNA inhibition on cell-cycle progression and survival. Unbiased gene array analysis was used to identify the impact of HDACi on epithelioid sarcoma gene expression. Xenografts were used to evaluate epithelioid sarcoma tumor growth in response to HDACi. HDAC inhibition increased target protein acetylation and abrogated cell growth and colony formation in epithelioid sarcoma cells. HDACi induced G(2) cell-cycle arrest and marked apoptosis, and reduced tumor growth in xenograft models. HDACi induced widespread gene expression changes, and EZH2 was significantly downregulated. EZH2 knockdown resulted in abrogated cell growth in vitro.

IMPLICATIONS

The current study suggests a clinical role for HDACi in human epithelioid sarcoma, which, when combined with EZH2 inhibitors, could serve as a novel therapeutic strategy for epithelioid sarcoma patients. Future investigations targeting specific HDAC isoforms along with EZH2 may potentially maximizing treatment efficacy.

Nrf2 status affects tumor growth, HDAC3 gene promoter associations, and the response to sulforaphane in the colon

Background

The dietary agent sulforaphane (SFN) has been reported to induce nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2)-dependent pathways as well as inhibiting histone deacetylase (HDAC) activity. The current investigation sought to examine the relationships between Nrf2 status and HDAC expression in preclinical and translational studies.

Results

Wild type (WT) and Nrf2-deficient (Nrf2^−/+) mice were treated with the colon carcinogen 1,2-dimethylhydrazine (DMH) followed by 400 ppm SFN in the diet (n = 35 mice/group). WT mice were more susceptible than Nrf2^−/+ mice to tumor induction in the colon. Tumors from WT mice had higher HDAC levels globally and locally on genes such as cyclin-dependant kinase inhibitor 2a (Cdkn2a/p16) that were dysregulated during tumor development. The average tumor burden was reduced by SFN from 62.7 to 26.0 mm³ in WT mice and from 14.6 to 11.7 mm³ in Nrf2^−/+ mice. The decreased antitumor activity of SFN in Nrf2^−/+ mice coincided with attenuated Cdkn2a promoter interactions involving HDAC3. HDAC3 knockdown in human colon cancer cells recapitulated the effects of SFN on p16 induction. Human subjects given a broccoli sprout extract supplement (200 μmol SFN equivalents), or reporting more than five cruciferous vegetable servings per week, had increased p16 expression that was inversely associated with HDAC3 in circulating peripheral blood mononuclear cells (PBMCs) and in biopsies obtained during screening colonoscopy.

Conclusions

Nrf2 expression varies widely in both normal human colon and human colon cancers and likely contributes to the overall rate of tumor growth in the large intestine. It remains to be determined whether this influences global HDAC protein expression levels, as well as local HDAC interactions on genes dysregulated during human colon tumor development. If corroborated in future studies, Nrf2 status might serve as a biomarker of HDAC inhibitor efficacy in clinical trials using single agent or combination modalities to slow, halt, or regress the progression to later stages of solid tumors and hematological malignancies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0132-y) contains supplementary material, which is available to authorized users.

Histone Deacetylase Inhibitors Inhibit the Proliferation of Gallbladder Carcinoma Cells by Suppressing AKT/mTOR Signaling

Gallbladder carcinoma is an aggressive malignancy with high mortality mainly due to the limited potential for curative resection and its resistance to chemotherapeutic agents. Here, we show that the histone deacetylase inhibitors (HDACIs) trichostatin-A (TSA) and suberoylanilide hydroxamic acid (SAHA) reduce the proliferation and induce apoptosis of gallbladder carcinoma cells by suppressing the AKT/mammalian target of rapamycin (mTOR) signaling. Gallbladder carcinoma SGC-996 cells were treated with different concentrations of TSA and SAHA for different lengths of time. Cell proliferation and morphology were assessed with MTT assay and microscopy, respectively. Cell cycle distribution and cell apoptosis were analyzed with flow cytometry. Western blotting was used to detect the proteins related to apoptosis, cell cycle, and the AKT/mTOR signaling pathway. Our data showed that TSA and SAHA reduced SGC-996 cell viability and arrested cell cycle at the G1 phase in a dose- and time-dependent manner. TSA and SAHA promoted apoptosis of SGC-996 cells, down-regulated the expression of cyclin D1, c-Myc and Bmi1, and decreased the phosphorylation of AKT, mTOR p70S6K1, S6 and 4E-BP1. Additionally, the mTOR inhibitor rapamycin further reduced the cell viability of TSA- and SAHA-treated SGC-996 cells and the phosphorylation of mTOR, whereas the mTOR activator 1,2-dioctanoyl-sn-glycero-3-phosphate (C8-PA) exerted the opposite influence. Our results demonstrate that histone deacetylase inhibitors (HDACIs) suppress the proliferation of gallbladder carcinoma cell via inhibition of AKT/mTOR signaling. These findings offer a mechanistic rationale for the application of HDACIs in gallbladder carcinoma treatment.

Structure and function insights into the NuRD chromatin remodeling complex

Transcription regulation through chromatin compaction and decompaction is regulated through various chromatin-remodeling complexes such as nucleosome remodeling and histone deacetylation (NuRD) complex. NuRD is a 1 MDa multi-subunit protein complex which comprises many different subunits, among which histone deacetylases HDAC1/2, ATP-dependent remodeling enzymes CHD3/4, histone chaperones RbAp46/48, CpG-binding proteins MBD2/3, the GATAD2a (p66α) and/or GATAD2b (p66β) and specific DNA-binding proteins MTA1/2/3. Here, we review the currently known crystal and NMR structures of these subunits, the functional data and their relevance for biomedical research considering the implication of NuRD subunits in cancer and various other diseases. The complexity of this macromolecular assembly, and its poorly understood mode of interaction with the nucleosome, the repeating unit of chromatin, illustrate that this complex is a major challenge for structure-function relationship studies which will be tackled best by an integrated biology approach.

Luotonin-A based quinazolinones cause apoptosis and senescence via HDAC inhibition and activation of tumor suppressor proteins in HeLa cells

A series of novel quinazolinone hybrids were synthesized by employing click chemistry and evaluated for anti-proliferative activities against MCF-7, HeLa and K562 cell lines. Among these cell lines, HeLa cells were found to respond effectively to these quinazolinone hybrids with IC50 values ranging from 5.94 to 16.45 μM. Some of the hybrids (4q, 4r, 4e, 4k, 4t, 4w) with promising anti-cancer activity were further investigated for their effects on the cell cycle distribution. FACS analysis revealed the G1 cell cycle arrest nature of these hybrids. Further to assess the senescence inducing ability of these compounds, a senescence associated β-gal assay was performed. The senescence inducing nature of these compounds was supported by the effect of hybrid (4q) on p16 promoter activity, the marker for senescence. Moreover, cells treated with most effective compound (4q) show up-regulation of p53, p21 and down-regulation of HDAC-1, HDAC-2, HDAC-5 and EZH2 mRNA levels. Docking results suggest that, the triazole nitrogen showed Zn(+2) mediated interactions with the histidine residue of HDACs.

The role of polycomb repressive complexes in biliary tract cancer

INTRODUCTION

Polycomb group proteins are major epigenetic regulators that modify histone tails. They are organized in two multi-protein complexes called polycomb repressive complex (PRC) 1 and 2. Aberrant PRC activity is known to contribute to the development and aggressiveness of many cancers. Biliary tract cancer (BTC) is a rare malignancy associated with high chemoresistance and poor clinical outcome. Here we review the role of the PRC complexes and the effects of RNAi and drug-mediated inhibition of PRC1 and PRC2 in BTC.

AREAS COVERED

This review gives a short overview of the composition, biochemical functions and oncogenic role of PRC complexes. We then focus on and summarize the results of current studies that address the role of PRC in BTC. Finally, we discuss options and results of therapeutic targeting of PRC in BTC.

EXPERT OPINION

Pharmacological inhibition of the two PRC complexes seems to be a promising strategy for treatment of BTC. To date, only few studies have addressed the therapeutic effect of PRC inhibition in BTC. Therefore, it will be important to test established PRC inhibitors, such as DZNep, as well as newly developed drugs, for example, PTC209, to gain more insight into the role of the PRC complexes in BTC and potentially to develop new therapeutic strategies.

PCI-24781 down-regulates EZH2 expression and then promotes glioma apoptosis by suppressing the PIK3K/Akt/mTOR pathway

PCI-24781 is a novel histone deacetylase inhibitor that inhibits tumor proliferation and promotes cell apoptosis. However, it is unclear whether PCI-24781 inhibits Enhancer of Zeste 2 (EZH2) expression in malignant gliomas. In this work, three glioma cell lines were incubated with various concentrations of PCI-24781 (0, 0.25, 0.5, 1, 2.5 and 5 μM) and analyzed for cell proliferation by the MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay and colony formation, and cell cycle and apoptosis were assessed by flow cytometry. The expression of EZH2 and apoptosis-related proteins was assessed by western blotting. Malignant glioma cells were also transfected with EZH2 siRNA to examine how PCI-24781 suppresses tumor cells. EZH2 was highly expressed in the three glioma cell lines. Incubation with PCI-24781 reduced cell proliferation and increased cell apoptosis by down-regulating EZH2 in a concentration-dependent manner. These effects were simulated by EZH2 siRNA. In addition, PCI-24781 or EZH2 siRNA accelerated cell apoptosis by down-regulating the expression of AKT, mTOR, p70 ribosomal protein S6 kinase (p70s6k), glycogen synthase kinase 3A and B (GSK3a/b) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). These data suggest that PCI-24781 may be a promising therapeutic agent for treating gliomas by down-regulating EZH2 which promotes cell apoptosis by suppressing the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of the rapamycin (mTOR) pathway.

Histone deacetylases and their inhibitors as potential therapeutic drugs for cholangiocarcinoma - cell line findings

Histone deacetylation mediated by histone deacetylases (HDACs) has been reported as one of the epigenetic mechanisms associated with tumorigenesis. The poor responsiveness of anticancer drugs found with cholangiocarcinoma (CCA) leads to short survival rate. We aimed to investigate mRNA expression of HDACs class I and II, and the effect of HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA), in CCA in vitro. Expression of HDACs was studied in CCA cell lines (M213, M214 and KKU-100) and an immortal cholangiocyte (MMNK1) by semi-quantitative reverse transcription-PCR. SAHA and VPA, as well as a classical chemotherapeutic drug 5-fluorouracil (5-FU) were used in this study. Cell proliferation was determined by sulforhodamine assay. IC50 and IC20 were then analyzed for each agent and cell line. Moreover, synergistic potential of VPA or SAHA in combination with 5-FU at subtoxic dose (IC20) of each agent was also evaluated. Statistic difference of HDACs expression or cell proliferation in each experimental condition was analyzed by Student's t-test. The result demonstrated that HDACs were expressed in all studied cell types. Both SAHA and VPA inhibited cell proliferation in a dose-dependent manner. Interestingly, KKU-100 which was less sensitive to classical chemotherapeutic 5-FU was highly sensitive to HDAC inhibitors. Simultaneous combination of subtoxic doses of HDAC inhibitors and 5-FU significantly inhibited cell proliferation in CCA cell lines compared to single agent treatment (P ≤ 0.01), while sequentially combined treatments were less effective. The present study showed inhibitory effects of HDACIs on cell proliferation in CCA cell lines, with synergistic antitumor potential demonstrated by simultaneous combination of VPA or SAHA with 5-FU, suggesting a novel alternative therapeutic strategy in effective treatment of CCA.

A single nucleotide polymorphism in EZH2 predicts overall survival rate in patients with cholangiocarcinoma

Cholangiocarcinoma (CCA) is a deadly disease arising from the malignant transformation of cholangiocytes. Enhancer of zeste homolog 2 (EZH2) is overexpressed in poorly differentiated CCA. Functional single nucleotide polymorphisms (SNPs) in this gene may affect the role of EZH2 in cholangiocarcinogenesis and chemoresistance. The aim of the current study was to evaluate the correlation between EZH2 SNPs and clinical outcome. Using PROMO3.0, GeneCard and MicroSNiper, 4 EZH2 SNPs with functional relevance in CCA were selected in silico. These SNPs were studied in genomic DNA extracted from the blood samples of 75 patients with advanced CCA, who were treated with epirubicin-cisplatin-xeloda (ECX regimen). SNP genotyping was performed with specific PCR assays. The rs887569 TT genotype was correlated with a significantly longer overall survival (OS; TT vs. CT-CC, P=0.026). Moreover, the TT genotype revealed a trend toward a significant association with a reduced risk of mortality (HR, 0.59; 95% CI, 0.33-1.05; P=0.075), by multivariate analysis. These results support future studies on the role of rs887569 EZH2 SNP as a possible predictive marker of OS in advanced CCA patients.

Modulating autophagy: a strategy for cancer therapy

Autophagy is a process in which long-lived proteins, damaged cell organelles, and other cellular particles are sequestered and degraded. This process is important for maintaining the cellular microenvironment when the cell is under stress. Many studies have shown that autophagy plays a complex role in human diseases, especially in cancer, where it is known to have paradoxical effects. Namely, autophagy provides the energy for metabolism and tumor growth and leads to cell death that promotes tumor suppression. The link between autophagy and cancer is also evident in that some of the genes that regulate Carcinogenesis, oncogenes and tumor suppressor genes, participate in or impact the autophagy process. Therefore, modulating autophagy will be a valuable topic for cancer therapy. Many studies have shown that autophagy can inhibit the tumor growth when autophagy modulators are combined with radiotherapy and/or chemotherapy. These findings suggest that autophagy may be a potent target for cancer therapy.

Overexpression of histone deacetylase 2 predicts unfavorable prognosis in human gallbladder carcinoma

As important regulators of chromatin, histone deacetylases (HDACs) are involved in silencing tumor suppressor genes. HDAC2, a member of HDACs, has been demonstrated to be implicated in the development and progression of various human malignancies; however, its expression and role in human primary gallbladder carcinoma (PGC) are not fully understood. Therefore, we conducted this study to address this problem. The subjects were 136 patients underwent resection for PGC. Immunostainings for HDAC2 were performed on these archival tissues. The correlation of HDAC2 expression with clinicopathological characteristics including survival was analyzed. HDAC2 was positively expressed in the nucleus of tumor cells in 86.0 % (117/136) of PGC but not in the normal epithelium of the gallbladder. Additionally, there was a significant difference in the incidence of positive nodal metastasis between high and low HDAC2 expression groups (P = 0.001). The incidences of advanced clinical stage (P = 0.005) and pathologic T stage (P < 0.001), and higher histologic grade (P < 0.001) were respectively higher in the high HDAC2 expression group than in the low group. Moreover, univariate and multivariate analyses revealed the high HDAC2 expression to be an independent prognostic factor for both overall and disease-free survival of patients with PGC. High HDAC2 expression was correlated with a high incidence of lymph node metastasis and aggressive tumor progression of PGC. It also was an independent prognostic factor for poorer overall and disease-free survival in patients. Therefore, detection of HDAC2 expression may help us screen patients at increased risk of malignant behavior for PGC.

The therapeutic effect of histone deacetylase inhibitor PCI-24781 on gallbladder carcinoma in BK5.erbB2 mice

BACKGROUND & AIMS

Gallbladder carcinoma (GBCa), a type of biliary tract cancer (BTC), has proven challenging to treat, demonstrating the need for more effective therapeutic strategies. In our current study, we examined the therapeutic effects of the histone deacetylase (HDAC) inhibitor PCI-24781 against GBCa that developed in BK5.erbB2 mice.

METHODS

PCI-24781 [50 mg/kg/day] and control solutions were administered to BK5.erbB2 mice for 4 weeks. The therapeutic effect of PCI-24781 was evaluated by ultrasound biomicroscopy (USBM) throughout the experiment and histological analyses at the end of the experiment. To investigate potential mechanisms underlining the therapeutic effects of PCI-24781 on GBCa in BK5.erbB2 mice, PCI-24781-treated gallbladders were subjected to Western blot and RT-PCR analysis. The inhibitory effect of PCI-24781 on the growth of BTC cells was compared to the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and gemcitabine. To study the role of miRNAs in GBCa tumorigenesis, the expression profile of 368 miRNAs in GBCas from BK5.erbB2 (both treated and untreated) and wild type mice was analyzed.

RESULTS

Treatment of BK5.erbB2 mice with PCI-24781 for 1 month prevented 79% of GBCa cases from progression and showed a clinical effect in 47% of cases. We also confirmed a potent inhibitory effect on tumor cell growth in human BTC cell lines treated with PCI-24781. This effect was associated with downregulation of ErbB2 mRNA and ErbB2 protein/activity and upregulation of acetylated histone and acetylated tubulin. Treatment with PCI-24781 resulted in decreased expression of Muc4, an intramembrane ligand for ErbB2, in BTC cells. PCI-24781 had more effects on growth inhibition of BTC cells than SAHA. In addition, PCI-24781 effectively inhibited the growth of gemcitabine-resistant cells. miRNA profiling revealed that the expression of several miRNAs was significantly altered in GBCa in the BK5.erbB2 mouse compared to normal gallbladder, including upregulated miR21, which was downregulated by PCI-24781.

CONCLUSIONS

These results indicate that PCI-24781 potently inhibits the growth of BTC cells by decreasing ErbB2 expression and activity as well as regulating altered miRNA expression. PCI-24781 may have a potential value as a novel chemotherapeutic agent against human BTC in which ErbB2 is overexpressed.

Immunohistochemical characteristics and malignant progression of hepatic cystic neoplasms in comparison with pancreatic counterparts

The recent World Health Organization classification for tumors of the digestive system defined grossly and histologically hepatic mucinous cystic neoplasms and intraductal papillary neoplasms of the bile duct separately. In this study, the immunohistochemical features of intraductal papillary neoplasm of the bile duct (19 cases) and hepatic mucinous cystic neoplasm (5 cases) were characterized and compared with those of similar pancreatic lesions, intraductal papillary mucinous neoplasm of the pancreas (12 cases), and pancreatic mucinous cystic neoplasm (6 cases) and with those of other biliary cystic lesions, peribiliary cysts (10 cases). Intraductal papillary neoplasm of the bile duct and intraductal papillary mucinous neoplasm of the pancreas frequently expressed cytokeratin 7; mucin core proteins 1, 2, 5AC, and 6; trypsin; and amylase. Hepatic and pancreatic mucinous cystic neoplasms frequently expressed cytokeratin 7, mucin core proteins 1 and 5AC, estrogen receptor, progesterone receptor, trypsin, and amylase. Estrogen and progesterone receptors were expressed in the subepithelial stromal cells. The groups with intraductal papillary neoplasm of the bile duct and intraductal papillary mucinous neoplasm of the pancreas were different from the groups with hepatic and pancreatic mucinous cystic neoplasm with respect to several phenotypes reflecting gastric and intestinal metaplasia and also the lack of expression of estrogen and progesterone receptors. The Ki-67 and p53 labeling indexes increased significantly with the malignant progression of intraductal papillary neoplasm of the bile duct and intraductal papillary mucinous neoplasm of the pancreas. The p16 labeling index decreased and EZH2 labeling index increased significantly with the malignant progression of intraductal papillary neoplasm of the bile duct and intraductal papillary mucinous neoplasm of the pancreas. In conclusion, intraductal papillary neoplasm of the bile duct and hepatic mucinous cystic neoplasm might be regarded as biliary counterparts of intraductal papillary mucinous neoplasm of the pancreas and pancreatic mucinous cystic neoplasm, respectively, and the mucinous cystic neoplasm and intraductal papillary neoplasm groups differed from each other. Labeling indexes of Ki-67, p53, p16, and EZH2 were comparable in intraductal papillary neoplasm of the bile duct and intraductal papillary mucinous neoplasm of the pancreas along with their malignant progression, suggesting a common carcinogenic process of the tumors.

EZH2 silencing with RNAi enhances irradiation-induced inhibition of human lung cancer growth in vitro and in vivo

Non-small cell lung cancer (NSCLC) has a high mortality rate and poor prognosis. The aim of the present study was to silence EZH2 and explore the antitumor effect of small interfering RNA (siRNA)-EZH2 in combination with radiotherapy, which is a main treatment for NSCLC. The results showed that irradiation in the presence of siRNA-EZH2 arrested A549 cells in the G(0) and G(1) phases, delayed cell cycle progression and effectively inhibited cell proliferation, compared with cells that received radiotherapy alone. The combined therapy enhanced the percentage of apoptotic A549 cells in vitro and reduced the tumor size, in addition to increasing the survival rate in tumor xenograft experiments. This study demonstrates the antitumor activity of ionizing radiation therapy in combination with siRNA-EZH2 in NSCLC, both in vitro and in vivo, as well as providing a scientific rationale for targeting EZH2 to enhance the sensitivity of cancer to radiotherapy in NSCLC patients.

Cellular senescence and tumor suppressor gene p16

Cellular senescence is an irreversible arrest of cell growth. Biochemical and morphological changes occur during cellular senescence, including the formation of a unique cellular morphology such as flattened cytoplasm. Function of mitochondria, endoplasmic reticulum and lysosomes are affected resulting in the inhibition of lysosomal and proteosomal pathways. Cellular senescence can be triggered by a number of factors including, aging, DNA damage, oncogene activation and oxidative stress. While the molecular mechanism of senescence involves p16 and p53 tumor suppressor genes and telomere shortening, this review is focused on the mechanism of p16 control. The p16-mediated senescence acts through the retinoblastoma (Rb) pathway inhibiting the action of the cyclin dependant kinases leading to G1 cell cycle arrest. Rb is maintained in a hypophosphorylated state resulting in the inhibition of transcription factor E2F1. Regulation of p16 expression is complex and involves epigenetic control and multiple transcription factors. PRC1 (Pombe repressor complex (1) and PRC2 (Pombe repressor complex (2) proteins and histone deacetylases play an important role in the promoter hypermethylation for suppressing p16 expression. While transcription factors YY1 and Id1 suppress p16 expression, transcription factors CTCF, Sp1 and Ets family members activate p16 transcription. Senescence occurs with the inactivation of suppressor elements leading to the enhanced expression of p16.

(-)-Epigallocatechin-3-gallate and DZNep reduce polycomb protein level via a proteasome-dependent mechanism in skin cancer cells

Polycomb group (PcG) protein-dependent histone methylation and ubiquitination drives chromatin compaction leading to reduced tumor suppressor expression and increased cancer cell survival. Green tea polyphenols and S-adenosylhomocysteine (AdoHcy) hydrolase inhibitors are important candidate chemopreventive agents. Previous studies indicate that (-)-epigallocatechin-3-gallate (EGCG), a potent green tea polyphenol, suppresses PcG protein level and skin cancer cell survival. Inhibition of AdoHcy hydrolase with 3-deazaneplanocin A (DZNep) inhibits methyltransferases by reducing methyl group availability. In the present study, we examine the impact of EGCG and DZNep cotreatment on skin cancer cell function. EGCG and DZNep, independently and in combination, reduce the level of PcG proteins including Ezh2, eed, Suz12, Mel18 and Bmi-1. This is associated with reduced H3K27me3 and H2AK119ub formation, histone modifications associated with closed chromatin. Histone deacetylase 1 level is also reduced and acetylated H3 formation is increased. These changes are associated with increased tumor suppressor expression and reduced cell survival and are partially reversed by vector-mediated maintenance of Bmi-1 level. The reduction in PcG protein level is associated with increased ubiquitination and is reversed by proteasome inhibitors, suggesting proteasome-associated degradation.

Epigenetic silencing of HIV-1 by the histone H3 lysine 27 methyltransferase enhancer of Zeste 2

Latent HIV proviruses are silenced as the result of deacetylation and methylation of histones located at the viral long terminal repeat (LTR). Inhibition of histone deacetylases (HDACs) leads to the reemergence of HIV-1 from latency, but the contribution of histone lysine methyltransferases (HKMTs) to maintaining HIV latency remains uncertain. Chromatin immunoprecipitation experiments using latently infected Jurkat T-cell lines demonstrated that the HKMT enhancer of Zeste 2 (EZH2) was present at high levels at the LTR of silenced HIV proviruses and was rapidly displaced following proviral reactivation. Knockdown of EZH2, a key component of the Polycomb repressive complex 2 (PRC2) silencing machinery, and the enzyme which is required for trimethyl histone lysine 27 (H3K27me3) synthesis induced up to 40% of the latent HIV proviruses. In contrast, there was less than 5% induction of latent proviruses following knockdown of SUV39H1, which is required for H3K9me3 synthesis. Knockdown of EZH2 also sensitized latent proviruses to external stimuli, such as T-cell receptor stimulation, and slowed the reversion of reactivated proviruses to latency. Similarly, cell populations that responded poorly to external stimuli carried HIV proviruses that were enriched in H3K27me3 and relatively depleted in H3K9me3. Treating latently infected cells with the HKMT inhibitor 3-deazaneplanocin A, which targets EZH2, led to the reactivation of silenced proviruses, whereas chaetocin and BIX01294 showed only minimal reactivation activities. These findings suggest that PRC2-mediated silencing is an important feature of HIV latency and that inhibitors of histone methylation may play a useful role in induction strategies designed to eradicate latent HIV pools.

Enhancer of zeste homolog 2 (EZH2) in pediatric soft tissue sarcomas: first implications

Soft tissue sarcomas of childhood are a group of heterogeneous tumors thought to be derived from mesenchymal stem cells. Surgical resection is effective only in about 50% of cases and resistance to conventional chemotherapy is often responsible for treatment failure. Therefore, investigations on novel therapeutic targets are of fundamental importance. Deregulation of epigenetic mechanisms underlying chromatin modifications during stem cell differentiation has been suggested to contribute to soft tissue sarcoma pathogenesis. One of the main elements in this scenario is enhancer of zeste homolog 2 (EZH2), a methyltransferase belonging to the Polycomb group proteins. EZH2 catalyzes histone H3 methylation on gene promoters, thus repressing genes that induce stem cell differentiation to maintain an embryonic stem cell signature. EZH2 deregulated expression/function in soft tissue sarcomas has been recently reported. In this review, an overview of the recently reported functions of EZH2 in soft tissue sarcomas is given and the hypothesis that its expression might be involved in soft tissue sarcomagenesis is discussed. Finally, the therapeutic potential of epigenetic therapies modulating EZH2-mediated gene repression is considered.

Transcriptional regulation of cellular senescence

Cellular senescence is an irreversible arrest of proliferation. It is activated when a cell encounters stress such as DNA damage, telomere shortening or oncogene activation. Like apoptosis, it impedes tumour progression and acts as a barrier that pre-neoplastic cells must overcome during their evolution toward the full tumourigenic state. This review focuses on the role of transcriptional regulators in the control of cellular senescence, explores how their function is perturbed in cancer and discusses the potential to harness this knowledge for future cancer therapies.