Targeted Inactivation of HDAC2 Restores p16INK4a Activity and Exerts Antitumor Effects on Human Gastric Cancer

DNA methylation drives a new path in gastric cancer early detection: Current impact and prospects

Gastric cancer (GC) is one of the most common and deadly cancers worldwide. Early detection offers the best chance for curative treatment and reducing its mortality. However, the optimal population-based early screening for GC remains unmet. Aberrant DNA methylation occurs in the early stage of GC, exhibiting cancer-specific genetic and epigenetic changes, and can be detected in the media such as blood, gastric juice, and feces, constituting a valuable biomarker for cancer early detection. Furthermore, DNA methylation is a stable epigenetic alteration, and many innovative methods have been developed to quantify it rapidly and accurately. Nonetheless, large-scale clinical validation of DNA methylation serving as tumor biomarkers is still lacking, precluding their implementation in clinical practice. In conclusion, after a critical analysis of the recent existing literature, we summarized the evolving roles of DNA methylation during GC occurrence, expounded the newly discovered noninvasive DNA methylation biomarkers for early detection of GC, and discussed its challenges and prospects in clinical applications.

Upregulation of E-cadherin by the combination of methionine restriction and HDAC2 intervention for inhibiting gastric carcinoma metastasis

Invasion and metastasis are the leading causes of death in individuals with malignant tumors, including gastric cancer. In this study, we aim to explore the effect and related mechanisms of methionine restriction (MR) on gastric carcinoma metastasis. In the MR cell model, gastric carcinoma cells are cultured in the MR medium, and in the animal model, BALB/c nude rodents are administered with a methionine-free diet after receiving injections of MKN45 cells into the caudal vein. Transwell assay is used to detect cell invasion and migration. Chromatin immunoprecipitation is performed to investigate the levels of H3K9me2, H3K27Ac, and H3K27me3 in the E-cadherin promoter. The results show that MR inhibits gastric carcinoma cell migration, invasion, and lung metastasis. MR increases E-cadherin while reducing the H3K27me3 level in the E-cadherin promoter. E-cadherin expression in gastric carcinoma cells is adversely regulated by HDAC2. Overexpressing HDAC2 reduces the H3K27Ac level in the E-cadherin promoter, while interfering with HDAC2 increases the H3K27Ac level. HDAC2 interference under MR conditions further upregulates E-cadherin expression and inhibits gastric carcinoma cell migration, invasion, and lung metastasis. MR combined with HDAC2 interference promotes E-cadherin expression by mediating the methylation and acetylation of E-cadherin, thus inhibiting the invasion, migration, and lung metastasis of gastric carcinoma cells. Our study provides a new theoretical basis for the inhibitory effect of MR on gastric cancer.

HDAC2 as a Target for developing Anti-cancer Drugs

Histone deacetylases (HDACs) deacetylate histones H3 and H4. An imbalance between histone acetylation and deacetylation can lead to various diseases. HDAC2 is present in the nucleus. It plays a critical role in modifying chromatin structures and regulates the expression of various genes by functioning as a transcriptional regulator. The roles of HDAC2 in tumorigenesis and anti-cancer drug resistance are discussed in this review. Several reports suggested that HDAC2 is a prognostic marker of various cancers. The roles of microRNAs (miRNAs) that directly regulate the expression of HDAC2 in tumorigenesis are also discussed in this review. This review also presents HDAC2 as a valuable target for developing anti-cancer drugs.

Protein acylation: mechanisms, biological functions and therapeutic targets

Metabolic reprogramming is involved in the pathogenesis of not only cancers but also neurodegenerative diseases, cardiovascular diseases, and infectious diseases. With the progress of metabonomics and proteomics, metabolites have been found to affect protein acylations through providing acyl groups or changing the activities of acyltransferases or deacylases. Reciprocally, protein acylation is involved in key cellular processes relevant to physiology and diseases, such as protein stability, protein subcellular localization, enzyme activity, transcriptional activity, protein-protein interactions and protein-DNA interactions. Herein, we summarize the functional diversity and mechanisms of eight kinds of nonhistone protein acylations in the physiological processes and progression of several diseases. We also highlight the recent progress in the development of inhibitors for acyltransferase, deacylase, and acylation reader proteins for their potential applications in drug discovery.

Histone Deacetylase Functions in Gastric Cancer: Therapeutic Target?

Gastric cancer (GC) is one of the most aggressive cancers. Therapeutic treatments are based on surgery combined with chemotherapy using a combination of platinum-based agents. However, at metastatic stages of the disease, survival is extremely low due to late diagnosis and resistance mechanisms to chemotherapies. The development of new classifications has not yet identified new prognostic markers for clinical use. The studies of epigenetic processes highlighted the implication of histone acetylation status, regulated by histone acetyltransferases (HATs) and by histone deacetylases (HDACs), in cancer development. In this way, inhibitors of HDACs (HDACis) have been developed and some of them have already been clinically approved to treat T-cell lymphoma and multiple myeloma. In this review, we summarize the regulations and functions of eighteen HDACs in GC, describing their known targets, involved cellular processes, associated clinicopathological features, and impact on survival of patients. Additionally, we resume the in vitro, pre-clinical, and clinical trials of four HDACis approved by Food and Drug Administration (FDA) in cancers in the context of GC.

Potential of histone deacetylase inhibitors in the control and regulation of prostate, breast and ovarian cancer

Histone deacetylases (HDACs) are enzymes that play a role in chromatin remodeling and epigenetics. They belong to a specific category of enzymes that eliminate the acetyl part of the histones’ -N-acetyl lysine, causing the histones to be wrapped compactly around DNA. Numerous biological processes rely on HDACs, including cell proliferation and differentiation, angiogenesis, metastasis, gene regulation, and transcription. Epigenetic changes, specifically increased expression and activity of HDACs, are commonly detected in cancer. As a result, HDACi could be used to develop anticancer drugs. Although preclinical outcomes with HDACs as monotherapy have been promising clinical trials have had mixed results and limited success. In both preclinical and clinical trials, however, combination therapy with different anticancer medicines has proved to have synergistic effects. Furthermore, these combinations improved efficacy, decreased tumor resistance to therapy, and decreased toxicity. In the present review, the detailed modes of action, classification of HDACs, and their correlation with different cancers like prostate, breast, and ovarian cancer were discussed. Further, the different cell signaling pathways and the structure-activity relationship and pharmaco-toxicological properties of the HDACi, and their synergistic effects with other anticancer drugs observed in recent preclinical and clinical studies used in combination therapy were discussed for prostate, breast, and ovarian cancer treatment.

IFITM3 promotes malignant progression, cancer stemness and chemoresistance of gastric cancer by targeting MET/AKT/FOXO3/c-MYC axis

Background

Targeting the HGF/MET signaling pathway has been a viable therapeutic strategy for various cancer types due to hyperactivation of HGF/MET axis occurs frequently that leads to detrimental cancer progression and recurrence. Deciphering novel molecule mechanisms underlying complex HGF/MET signaling network is therefore critical to development of effective therapeutics for treating MET-dependent malignancies.

Results

Using isobaric mass tag-based quantitative proteomics approach, we identified IFITM3, an interferon-induced transmembrane protein that was highly expressed in micro-dissected gastric cancer (GC) tumor regions relative to adjacent non-tumor epithelia. Analyses of GC clinical specimens revealed that expression IFITM3 was closely correlated to advanced pathological stages. IFITM3 has been reported as a PIP3 scaffold protein that promotes PI3K signaling. In present study, we unprecedentedly unraveled that IFITM3 associated with MET and AKT to facilitate HGF/MET mediated AKT signaling crosstalk in suppressing FOXO3, consequently leading to c-MYC mediated GC progression. In addition, gene ontology analyses of the clinical GC cohort revealed significant correlation between IFITM3-associated genes and targets of c-MYC, which is a crucial downstream effector of HGF/MET pathway in cancer progression. Moreover, we demonstrated ectopic expression of IFITM3 suppressed FOXO3 expression, consequently led to c-MYC induction to promote tumor growth, cell metastasis, cancer stemness as well as chemoresistance. Conversely, depletion of IFITM3 resulted in suppression of HGF triggered cellular growth and migration via inhibition of AKT/c-MYC signaling in GC.

Conclusions

In summary, our present study unveiled a novel regulatory mechanism for c-MYC-driven oncogenesis underlined by IFITM3-mediated signaling crosstalk between MET associated AKT signaling cascade.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00858-8.

Design, synthesis and biological evaluation of novel o-aminobenzamide derivatives as potential anti-gastric cancer agents in vitro and in vivo

Although gastric cancer has become a major public health problem, oral agents applied in clinics for gastric cancer therapy are scarce. Therefore, to explore new oral chemical entities with high efficiency and low toxicity, 41 o-aminobenzamide derivatives based on the scaffolds of MS-275 and SAHA were designed, synthesized, and evaluated for their anti-gastric cancer abilities in vitro and in vivo. Structure-activity relationships were discussed, leading to the identification of compounds F8 (IC₅₀ = 0.28 μM against HGC-27 cell) and T9 (IC₅₀ = 1.84 μM against HGC-27 cell) with improved cytotoxicity, anti-gastric cancer proliferation potency, induction of cell apoptosis and cell cycle arrest ability, inhibition of cell migration and invasion. What is worth mentioning is that compound F8 was more efficient and less toxic than the positive drug capecitabine in vivo on the HGC-27-xenograft model. Meanwhile, compound F8 exhibited suitable pharmacokinetic properties and less acute toxicity (LD₅₀ > 1000 mg/kg). Besides, western blotting analysis, IHC analysis, differentially expressed proteins analysis and ABPP experiment indicated that compound F8 could modulate molecular pathways involved in apoptosis and cell cycle progression. Consequently, compound F8 is a strong candidate for the development of human gastric cancer therapy.

Comparative differential cytotoxicity of clinically used SERMs in human cancer lines of different origin and its predictive molecular docking studies of key target genes involved in cancer progression and treatment responses

SERMS like Tamoxifene, 5-hydroxy tamoxifene, raloxifene and endoxifene has been used for the treatment of hormonal imbalances and dependent cancers owing to their action via Estrogen receptors as in the treatment of estrogen sensitive breast cancers. Due to the adverse side effects, modifications and development of the existing or newer SERMS has always been of immense interest. Ormeloxifene, a SERM molecule manufactured by HLL Lifecare Ltd, India as birth control under the trade names Saheli, Novex, and Novex-DS which is also investigated against mastalgia, fibro-adenoma and abnormal uterine bleeding. Anti-cancer effects have been reported in estrogen dependent and independent cancers which shows its wide scope to be implemented in cancer therapy. Current investigation is a comprehensive effort to find the cytotoxic potential of Ormeloxifene in comparison with clinically used four SERMS in twenty six cancer cell lines of different origin using Adriamycin as positive control. Also the computational studies pertaining to selected target/ligand with respect to tumor progression, development, treatment responses and apoptosis. The studies proved effective cytotoxicity of Ormeloxifene on cancer cell lines with lower TGI, GI50 and LC50 values which are significantly comparable. Also the in silico studies proved that the docking score of the compound suggests the interaction of the compound which could tightly regulate key target genes controlling cancer like ER, EGFR kinase, EGFR-cSRC, HDAC-2, PARP-1 and BRAF. This study brings out the superior efficacy of Ormeloxifene compared to other SERMS with proven safety profile to be repositioned as an anti-cancer drug to treat diverse cancer types.

Histone deacetylase 2 selective inhibitors: A versatile therapeutic strategy as next generation drug target in cancer therapy

Acetylation and deacetylation of histone and several non-histone proteins are the two important processes amongst the different modes of epigenetic modulation that are involved in regulating cancer initiation and development. Abnormal expression of histone deacetylases (HDACs) is often reported in various types of cancers. Few pan HDAC inhibitors have been approved for use as therapeutic interventions for cancer treatment including vorinostat, belinostat and panobinostat. However, not all the HDAC isoforms are abnormally expressed in certain cancers, such as in the case of, ovarian cancer where overexpression of HDAC1-3, lung cancer where overexpression of HDAC 1 and 3 and gastric cancer where overexpression of HDAC2 is seen. Therefore, pan-inhibition of HDAC is not an efficient way to combat cancer via HDAC inhibition. Hence, isoform-selective HDAC inhibition can be one of the best therapeutic strategies in the treatment of cancer. In this context since aberrant expression of HDAC2 largely contributes to cancer progression by silencing pro-apoptotic protein expressions such as NOXA and APAF1 (caspase 9-activating proteins) and inactivation of tumor suppressor p53, HDAC2 specific inhibitors may help to develop not only the direct targets but also indirect targets that are crucial for tumor development. However, to develop a HDAC2 specific and potent inhibitor, extensive knowledge of its structure and specific functions is essential. The present review updates details on the structural features, physiological functions, and roles of HDAC2 in different types of cancer, emphasizing the challenges and status of the development of HDAC2 selective inhibitors against various types of cancer.

Effect of vorinostat on INK4 family and HDACs 1, 2, and 3 in pancreatic cancer and hepatocellular carcinoma

Background and purpose:

In mammalian cells, several distinct surveillance systems, named cell cycle checkpoints, can interrupt normal cell-cycle progression. The cyclin-dependent kinases are negatively regulated by proteins of cyclin-dependent kinases inhibitors comprising INK4 and Cip/Kip families. Histone deacetylation induced by histone deacetylases (HDACs) inactivates the INK4 and Cip/Kip families lead to cancer induction. HDAC inhibitors (HDACIs) have been indicated to be potent inducers of differentiation, growth arrest, and apoptotic induction. Vorinostat (suberoylanilide hydroxamic acid, SAHA), as an HDACI, is reported to be useful in various cancers. Previously, we reported the effect of trichostatin A on hepatocellular carcinoma and also vorinostat on colon cancer cell lines. The current study was aimed to investigate the effect of vorinostat on p16INK4a, p14ARF, p15INK4b, and class I HDACs 1, 2, and 3 gene expression, cell growth inhibition, and apoptosis induction in pancreatic cancer AsPC-1 and hepatocellular carcinoma LCL-PI 11 cell lines.

Experimental approach:

The AsPC-1 and LCL-PI 11 cell lines were cultured and treated with vorinostat. To determine, viability, apoptosis, and the relative expression level of p16INK4a, p14ARF, p15INK4b, class I HDACs 1, 2, and 3 genes, MTT assay, cell apoptosis assay, and RT-qPCR were performed, respectively.

Findings/Results:

Vorinostat significantly inhibited cell growth, induced apoptosis, increased p16INK4a, p14ARF, p15INK4b, and decreased class I HDACs 1, 2, and 3 gene expression.

Conclusion and implications:

Vorinostat can reactivate the INK4 family through inhibition of class I HDACs 1, 2, and 3 genes activity.

Histone deacetylase 2: A potential therapeutic target for cancer and neurodegenerative disorders

Histone deacetylases (HDACs) have been implicated in a number of diseases including cancer, cardiovascular disorders, diabetes mellitus, neurodegenerative disorders and inflammation. For the treatment of epigenetically altered diseases such as cancer, HDAC inhibitors have made a significant progress in terms of development of isoform selective inhibitiors. Isoform specific HDAC inhibitors have less adverse events and better safety profile. A HDAC isoform i.e., HDAC2 demonstrated significant role in the development of variety of diseases, mainly involved in the cancer and neurodegenerative disorders. Discovery and development of selective HDAC2 inhibitors have a great potential for the treatment of target diseases. In the present compilation, we have reviewed the role of HDAC2 in progression of cancer and neurodegenerative disorders, and information on the drug development opportunities for selective HDAC2 inhibition.

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.

Function and regulation annotation of up-regulated long non-coding RNA LINC01234 in gastric cancer

Background

Accumulated evidences indicate that long non‐coding RNAs (lncRNAs) participate in many biological mechanisms. Moreover, it acts as an essential regulator in various human diseases such as gastric cancer (GC). Nevertheless, the comprehensive regulatory roles and clinical significance of most lncRNAs in GC are not fully understood.

Methods

In this research, our aim was to investigate the underlying mechanism of lncRNA LINC01234 in GC. Firstly, the usage of qRT‐PCR helped to establish expression pattern of LINC01234 in GC tissues. Following this, appropriate statistical tests were applied to analyze the relation between expression level and clinicopathological factors. Ultimately, potential functions and regulatory network of LINC01234 were concluded via GSEA and a series of bioinformatics tools or databases, respectively.

Results

Consequently, at the end of research we found LINC01234 is up‐regulated in GC tissues in comparison with adjacent normal tissues. Furthermore, its expression level is correlated with differentiation of patients with GC. It is also important to highlight bioinformatics analysis revealed that LINC01234 is involved in cancer‐associated pathways such as cell cycle and mismatch repair. Also, regulatory network of LINC01234 presented a probability in the involvement of tumorigenesis through regulating cancer‐associated genes.

Conclusion

Overall, our results suggested that LINC01234 may play a crucial role in GC.

Histone deacetylase inhibitors differentially regulate c-Myc expression in retinoblastoma cells

Retinoblastoma (RB) is the most prevalent childhood intraocular cancer type. Previous studies have demonstrated that c-myc (a proto-oncogene) is associated with tumorigenesis. However, at present, the influence of the expression profile and bioactivity of c-Myc on RB occurrence and progression is yet to be characterised. Notably, the present study demonstrated that c-myc is downregulated in the RB cell line WERI-Rb1. However, treatment with the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) was revealed to significantly upregulate the expression of c-Myc mRNA and protein in WERI-Rb1 cells. Moreover, TSA increased the activity of the c-myc promoter in WERI-Rb1 cells, and the expression of c-Myc was also regulated by other HDAC inhibitors, including vorinostat (SAHA), valproic acid sodium salt (VPA) and entinostat. Notably, although c-myc was silenced in the Y79 cell line, the HDAC inhibitor TSA did not induce upregulation of mRNA and protein in Y79 cells. By contrast, certain HDAC inhibitors (TSA, VPA and SAHA) were discovered to significantly decrease the activity of the c-myc promoter in Y79 cells. Furthermore, the current data indicated that exogenous c-myc expression has a mild inhibitory effect on WERI-Rb1 and Y79 cell viability. Therefore, the present study revealed novel insights into the expression mechanism and bioactivity of c-Myc in RB cells.

Identification of HDAC9 as a viable therapeutic target for the treatment of gastric cancer

Histone deacetylase inhibitors (HDACis) are a new class of anticancer drugs confirmed to have good therapeutic effects against gastric cancer (GC) in preclinical experiments, but most HDACis are non-selective (pan-HDACis), with highly toxic side effects. Therefore, it is necessary to screen HDAC family members that play key roles in GC as therapeutic targets to reduce toxic side effects. In this study, we evaluated the targeting specificity of the HDACi suberoylanilide hydroxamic acid (SAHA) for GC via fluorescence molecular imaging (FMI). In vitro FMI results showed that SAHA had higher binding affinity for GC cells than for normal gastric cells. In vivo FMI of gastric tumor-bearing mice confirmed that SAHA can be enriched in GC tissues. However, there was also a high-concentration distribution in normal organs such as the stomach and lungs, suggesting potential side effects. In addition, we found that among the HDAC family members, HDAC9 was the most significantly upregulated in GC cells, and we verified this upregulation in GC tissues. Further experiments confirmed that knockdown of HDAC9 inhibits cell growth, reduces colony formation, and induces apoptosis and cell cycle arrest. These results suggest that HDAC9 has an oncogenic role in GC. Moreover, HDAC9 siRNA suppressed GC tumor growth and enhanced the antitumor efficacy of cisplatin in GC treatment by inhibiting the proliferation and inducing the apoptosis of GC cells in vitro and in vivo. Our findings suggest that the development of HDAC9-selective HDACis is a potential approach to improve the efficacy of chemotherapy and reduce systemic toxicity.

Inhibiting histone deacetylase 9 (HDAC9), a protein that regulates gene expression, reduces stomach cancer cell growth. The efficacy of current treatments for stomach cancer is limited. Although HDACs have emerged as promising therapeutic targets, non-selective HDAC inhibitors can cause severe side effects. Shigang Ding at Peking University Third Hospital in Beijing, China, and colleagues found that human stomach cancer cells have significantly higher levels of HDAC9 than other members of the HDAC family and that high HDAC9 levels are associated with reduced patient survival. Interfering with the production of HDAC9 protein improved the efficacy of the chemotherapeutic drug cisplatin in mice with stomach cancer. The authors suggest that selective HDAC9 inhibitors could help to improve the survival of patients with this type of cancer.

p53 at the Crossroads between Different Types of HDAC Inhibitor-Mediated Cancer Cell Death

Cancer is a complex genetic and epigenetic-based disease that has developed an armada of mechanisms to escape cell death. The deregulation of apoptosis and autophagy, which are basic processes essential for normal cellular activity, are commonly encountered during the development of human tumors. In order to assist the cancer cell in defeating the imbalance between cell growth and cell death, histone deacetylase inhibitors (HDACi) have been employed to reverse epigenetically deregulated gene expression caused by aberrant post-translational protein modifications. These interfere with histone acetyltransferase- and deacetylase-mediated acetylation of both histone and non-histone proteins, and thereby exert a wide array of HDACi-stimulated cytotoxic effects. Key determinants of HDACi lethality that interfere with cellular growth in a multitude of tumor cells are apoptosis and autophagy, which are either mutually exclusive or activated in combination. Here, we compile known molecular signals and pathways involved in the HDACi-triggered induction of apoptosis and autophagy. Currently, the factors that determine the mode of HDACi-elicited cell death are mostly unclear. Correspondingly, we also summarized as yet established intertwined mechanisms, in particular with respect to the oncogenic tumor suppressor protein p53, that drive the interplay between apoptosis and autophagy in response to HDACi. In this context, we also note the significance to determine the presence of functional p53 protein levels in the cancer cell. The confirmation of the context-dependent function of autophagy will pave the way to improve the benefit from HDACi-mediated cancer treatment.

Activation of PAR4 Upregulates p16 through Inhibition of DNMT1 and HDAC2 Expression via MAPK Signals in Esophageal Squamous Cell Carcinoma Cells

A previous study showed that a downexpression of protease-activated receptor 4 (PAR4) is associated with the development of esophageal squamous cell carcinoma (ESCC). In this study, we explored the relationship between PAR4 activation and the expression of p16, and elucidated the underlying mechanisms in PAR4 inducing the tumor suppressor role in ESCC. ESCC cell lines (EC109 and TE-1) were treated with PAR4-activating peptide (PAR4-AP). Immunohistochemistry for DNA methyltransferase 1 (DNMT1) and histone deacetylase 2 (HDAC2) was performed in 26 cases of ESCC tissues. We found that DNMT1 and HDAC2 immunoreactivities in ESCC were significantly higher than those in adjacent noncancerous tissues. PAR4 activation could suppress DNMT1 and HDAC2, as well as increase p16 expressions, whereas silencing PAR4 dramatically increased HDAC2 and DNMT1, as well as reduced p16 expressions. Importantly, the chromatin immunoprecipitation-PCR (ChIP-PCR) data indicated that treatment of ESCC cells with PAR4-AP remarkably suppressed DNMT1 and HDAC2 enrichments on the p16 promoter. Furthermore, we demonstrated that activation of PAR4 resulted in an increase of p38/ERK phosphorylation and activators for p38/ERK enhanced the effect of PAR4 activation on HDAC2, DNMT1, and p16 expressions, whereas p38/ERK inhibitors reversed these effects. Moreover, we found that activation of PAR4 in ESCC cells significantly inhibited cell proliferation and induced apoptosis. These findings suggest that PAR4 plays a potential tumor suppressor role in ESCC cells and represents a potential therapeutic target of this disease.

Epigenetic inactivation of tumour suppressor coding and non-coding genes in human cancer: an update

Cancer cells undergo many different alterations during their transformation, including genetic and epigenetic events. The controlled division of healthy cells can be impaired through the downregulation of tumour suppressor genes. Here, we provide an update of the mechanisms in which epigenetically altered coding and non-coding tumour suppressor genes are implicated. We will highlight the importance of epigenetics in the different molecular pathways that lead to enhanced and unlimited capacity of division, genomic instability, metabolic shift, acquisition of mesenchymal features that lead to metastasis, and tumour plasticity. We will briefly describe these pathways, focusing especially on genes whose epigenetic inactivation through DNA methylation has been recently described, as well as on those that are well established as being epigenetically silenced in cancer. A brief perspective of current clinical therapeutic approaches that can revert epigenetic inactivation of non-coding tumour suppressor genes will also be given.

Epigenetic Contribution of High-Mobility Group A Proteins to Stem Cell Properties

High-mobility group A (HMGA) proteins have been examined to understand their participation as structural epigenetic chromatin factors that confer stem-like properties to embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and cancer stem cells (CSCs). The function of HMGA was evaluated in conjunction with that of other epigenetic factors such as histones and microRNAs (miRs), taking into consideration the posttranscriptional modifications (PTMs) of histones (acetylation and methylation) and DNA methylation. HMGA proteins were coordinated or associated with histone and DNA modification and the expression of the factors related to pluripotency. CSCs showed remarkable differences compared with ESCs and iPSCs.

2,4‑Di‑tert‑butylphenol, a potential HDAC6 inhibitor, induces senescence and mitotic catastrophe in human gastric adenocarcinoma AGS cells

The natural product 2,4‑di‑tert‑butylphenol (DTBP) has a wide spectrum of biological functions, including anticancer activities, although the underlying mechanisms are poorly understood. Here, we found that DTBP induces senescence in human gastric adenocarcinoma AGS cells as evidenced by upregulation of p21 and Rb and increased β‑galactosidase activity. DTBP also induces mitotic catastrophe and generates multinucleated cells, which is accompanied by an increase in the proportion of polymerized tubulin, possibly caused by inhibition of HDAC6 enzyme activity. In silico docking analysis showed that DTBP docked at the entrance of the ligand-binding pocket of the HDAC6 enzyme. Accordingly, DTBP represents a promising lead structure for the development of HDAC6 inhibitors, with an improvement in specificity conferred by modification of the cap group. We propose for the first time that the underlying mechanism of the anticancer activity of DTBP is attributed to inhibition of HDAC6 activity.

MicroRNA-31 Function as a Suppressor Was Regulated by Epigenetic Mechanisms in Gastric Cancer

Gastric cancer is one of the most lethal malignancies worldwide. The aberrant expression of microRNA-31 (miR-31) has been reported in gastric cancer; however, its regulation mechanisms are still unclear. Here, we confirmed that miR-31 expression was significantly decreased in gastric cancer tissue and cell lines. Ectopic expression of miR-31 potentially suppresses proliferation and induced early apoptosis in gastric cancer cells. Furthermore, miR-31 expression was regulated as a result of epigenetic mechanisms. The downregulation of miR-31 was associated with promoter DNA methylation status in gastric cancer and cell lines. Moreover, we found that HDAC2 was the direct target of miR-31 by binding to 3′-UTR from the results of luciferase reporter assays, qRT-PCR, and western blotting. HDAC2 played an activation role in tumor growth, whose expression is upregulated and inversely associated with miR-31 levels. All the results suggested that miR-31 function as a crucial tumor suppressor was regulated by epigenetic mechanisms in gastric cancer. We found an epigenetic pathway loop, DNA methylation-miRNA expression-target gene-tumor progression in gastric cancer, and also provided implications for molecular diagnosis and therapeutics of gastric malignancies by detecting miR-31 as a potential target.

MicroRNA-495-3p functions as a tumor suppressor by regulating multiple epigenetic modifiers in gastric carcinogenesis

MicroRNAs (miRNAs) engage in complex interactions with the machinery that controls the transcriptome and concurrently target multiple mRNAs. Here, we demonstrate that microRNA-495-3p (miR-495-3p) functions as a potent tumor suppressor by governing ten oncogenic epigenetic modifiers (EMs) in gastric carcinogenesis. From the large cohort transcriptome datasets of gastric cancer (GC) patients available from The Cancer Genome Atlas (TCGA) and the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO), we were able to recapitulate 15 EMs as significantly overexpressed in GC among the 51 EMs that were previously reported to be involved in cancer progression. Computational target prediction yielded miR-495-3p, which targets as many as ten of the 15 candidate oncogenic EMs. Ectopic expression of miRNA mimics in GC cells caused miR-495-3p to suppress ten EMs, and inhibited tumor cell growth and proliferation via caspase-dependent and caspase-independent cell death processing. In addition, in vitro metastasis assays showed that miR-495-3p plays a role in the metastatic behavior of GC cells by regulating SLUG, vimentin, and N-cadherin. Furthermore, treatment of GC cells with 5-aza-2'-deoxcytidine restored miR-495-3p expression; sequence analysis revealed hypermethylation of the miR-495-3p promoter region in GC cells. A negative regulatory loop is proposed, whereby DNMT1, among ten oncogenic EMs, regulates miR-495-3p expression via hypermethylation of the miR-495-3p promoter. Our findings suggest that the functional loss or suppression of miR-495-3p triggers overexpression of multiple oncogenic EMs, and thereby contributes to malignant transformation and growth of gastric epithelial cells. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

CRISPR-mediated HDAC2 disruption identifies two distinct classes of target genes in human cells

The transcriptional functions of the class I histone deacetylases (HDACs) HDAC1 and HDAC2 are mainly viewed as both repressive and redundant based on murine knockout studies, but they may have additional independent roles and their physiological functions in human cells are not as clearly defined. To address the individual epigenomic functions of HDAC2, here we utilized CRISPR-Cas9 to disrupt HDAC2 in human cells. We find that while HDAC2 null cells exhibited signs of cross-regulation between HDAC1 and HDAC2, specific epigenomic phenotypes were still apparent using RNA-seq and ChIP assays. We identified specific targets of HDAC2 repression, and defined a novel class of genes that are actively expressed in a partially HDAC2-dependent manner. While HDAC2 was required for the recruitment of HDAC1 to repressed HDAC2-gene targets, HDAC2 was dispensable for HDAC1 binding to HDAC2-activated targets, supporting the notion of distinct classes of targets. Both active and repressed classes of gene targets demonstrated enhanced histone acetylation and methylation in HDAC2-null cells. Binding of the HDAC1/2-associated SIN3A corepressor was altered at most HDAC2-targets, but without a clear pattern. Overall, our study defines two classes of HDAC2 targets in human cells, with a dependence of HDAC1 on HDAC2 at one class of targets, and distinguishes unique functions for HDAC2.

Inhibitory effects of 1,25(OH)2D3 on the proliferation of hepatocellular carcinoma cells through the downregulation of HDAC2

The inhibitory effects of 1,25(OH)2D3 on the proliferation of a variety of cancer cell lines have been extensively reported. However, the underlying mechanisms remain largely unknown. In the present study, the effects of 1,25(OH)2D3 on the in vitro proliferation of human hepatocellular carcinoma HepG2 cells and the mechanism involved were investigated. Flow cytometry and MTT assay revealed that 1,25(OH)2D3 inhibited cell proliferation in vitro. Western blotting and real-time PCR indicated that 1,25(OH)2D3 upregulated the expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and attenuated that of histone deacetylase 2 (HDAC2). Knockdown of HDAC2 completely mimicked the effects of 1,25(OH)2D3 on PTEN gene expression. The influence of 1,25(OH)2D3 on PTEN expression was reversed in the cells treated with a recombinant pEGFP-LV2-HDAC2 plasmid. Akt phosphorylation, which was downregulated by 1,25(OH)2D3 treatment, was promoted by HDAC2 overexpression. These findings revealed that 1,25(OH)2D3 inhibited cell growth possibly by HDAC2-mediated PTEN upregulation, Akt deactivation, and inhibition of the PI3K/Akt signaling pathway.

Human transporters, PEPT1/2, facilitate melatonin transportation into mitochondria of cancer cells: An implication of the therapeutic potential

Melatonin is present in virtually all organisms from bacteria to mammals, and it exhibits a broad spectrum of biological functions, including synchronization of circadian rhythms and oncostatic activity. Several functions of melatonin are mediated by its membrane receptors, but others are receptor-independent. For the latter, melatonin is required to penetrate membrane and enters intracellular compartments. However, the mechanism by which melatonin enters cells remains debatable. In this study, it was identified that melatonin and its sulfation metabolites were the substrates of oligopeptide transporter (PEPT) 1/2 and organic anion transporter (OAT) 3, respectively. The docking analysis showed that the binding of melatonin to PEPT1/2 was attributed to their low binding energy and suitable binding conformation in which melatonin was embedded in the active site of PEPT1/2 and fitted well with the cavity in three-dimensional space. PEPT1/2 transporters play a pivotal role in melatonin uptake in cells. Melatonin's membrane transportation via PEPT1/2 renders its oncostatic effect in malignant cells. For the first time, PEPT1/2 were identified to localize in the mitochondrial membrane of human cancer cell lines of PC3 and U118. PEPT1/2 facilitated the transportation of melatonin into mitochondria. Melatonin accumulation in mitochondria induced apoptosis of PC3 and U118 cells. Thus, PEPT1/2 can potentially be used as a cancer cell-targeted melatonin delivery system to improve the therapeutic effects of melatonin in cancer treatment.

Histone deacetylases function as novel potential therapeutic targets for cancer

Diverse cellular functions, including tumor suppressor gene expression, DNA repair, cell proliferation and apoptosis, are regulated by histone acetylation and deacetylation. Histone deacetylases (HDACs) are enzymes involved in remodeling of chromatin by deacetylating the lysine residues. They play a pivotal role in epigenetic regulation of gene expression. Dysregulation of HDACs and aberrant chromatin acetylation and deacetylation have been implicated in the pathogenesis of various diseases, including cancer. Histone deacetylases have become a target for the development of drugs for treating cancer because of their major contribution to oncogenic cell transformation. Overexpression of HDACs correlates with tumorigenesis. Previous work showed that inhibition of HDACs results in apoptosis and the inhibition of cell proliferation in multiple cells. A significant number of HDAC inhibitors have been developed in the past decade. These inhibitors have strong anticancer effects in vitro and in vivo, inducing growth arrest, differentiation, and programmed cell death, inhibiting cell migration, invasion, and metastasis, and suppressing angiogenesis. In addition, HDAC-mediated deacetylation alters the transcriptional activity of nuclear transcription factors, including p53, E2F, c-Myc, and nuclear factor-κB, as well as the extracellular signal-regulated kinase1/2, phosphatidylinositol 3-kinase, Notch, and Wnt signaling pathways. This review highlights the role of HDACs in cancer pathogenesis and, more importantly, that HDACs are potential novel therapeutic targets.

HDACs and HDAC Inhibitors in Cancer Development and Therapy

Over the last several decades, it has become clear that epigenetic abnormalities may be one of the hallmarks of cancer. Posttranslational modifications of histones, for example, may play a crucial role in cancer development and progression by modulating gene transcription, chromatin remodeling, and nuclear architecture. Histone acetylation, a well-studied posttranslational histone modification, is controlled by the opposing activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). By removing acetyl groups, HDACs reverse chromatin acetylation and alter transcription of oncogenes and tumor suppressor genes. In addition, HDACs deacetylate numerous nonhistone cellular substrates that govern a wide array of biological processes including cancer initiation and progression. This review will discuss the role of HDACs in cancer and the therapeutic potential of HDAC inhibitors (HDACi) as emerging drugs in cancer treatment.

Recombinant human alpha fetoprotein synergistically potentiates the anti-cancer effects of 1'-S-1'-acetoxychavicol acetate when used as a complex against human tumours harbouring AFP-receptors

Purpose

Previous in vitro and in vivo studies have reported that 1′-S-1′-acetoxychavicol acetate (ACA) isolated from rhizomes of the Malaysian ethno-medicinal plant Alpinia conchigera Griff (Zingiberaceae) induces apoptosis-mediated cell death in tumour cells via dysregulation of the NF-κB pathway. However there were some clinical development drawbacks such as poor in vivo solubility, depreciation of biological activity upon exposure to an aqueous environment and non-specific targeting of tumour cells. In the present study, all the problems above were addressed using the novel drug complex formulation involving recombinant human alpha fetoprotein (rhAFP) and ACA.

Experimental Design

To study the synergistic effect of both agents on human cancer xenografts, athymic nude (Nu/Nu) mice were used and treated with various combination regimes intraperitoneally. Serum levels of tumour markers for carcinoembryonic antigen (CEA) and prostate specific antigen (PSA) were assessed using sandwich ELISA. IHC and Western blotting were also conducted on in vivo tumour biopsies to investigate the involvement of NF-κB regulated genes and inflammatory biomarkers. Quantification and correlation between drug efficacies and AFP-receptors were done using IF-IC and Pearson's correlation analysis.

Results

Mice exposed to combined treatments displayed higher reductions in tumour volume compared to stand alone agents, consistent with in vitro cytotoxicity assays. Milder signs of systemic toxicity, such as loss in body weight and inflammation of vital organs were also demonstrated compared to stand alone treatments. Tumour marker levels were consistent within all rhAFP/ACA treatment groups where levels of CEA and PSA were initially elevated upon commencement of treatment, and consecutively reduced corresponding to a decrease in tumour bulk volume. Both IHC and Western blotting results indicated that the combined action of rhAFP/ACA was not only able to down-regulate NF-κB activation, but also reduce the expression of NF-κB regulated genes and inflammatory biomarkers. The efficacy of rhAFP/ACA complex was also found to be weakly negatively correlated to the level of surface AFP-receptors between tumour types.

Conclusions

This drug complex formulation shows great therapeutic potential against AFP-receptor positive tumours, and serves as a basis to overcome insoluble and non-specific anti-neoplastic molecules.

Histone Deacetylases and Their Regulatory MicroRNAs in Hepatocarcinogenesis

A growing body of evidence suggests that epigenetic modifications are promising potential mechanisms in cancer research. Among the molecules that mediate epigenetic mechanisms, histone deacetylases (HDACs) are critical regulators of gene expression that promote formation of heterochromatin by deacetylating histone and non-histone proteins. Aberrant regulation of HDACs contributes to malignant transformation and progression in a wide variety of human cancers, including hepatocellular carcinoma (HCC), gastric cancer, lung cancer, and other cancers. Thus, the roles of HDACs have been extensively studied because of their potential as therapeutic targets. However, the underlying mechanism leading to deregulation of individual HDACs remains largely unknown. Some reports have suggested that functional microRNAs (miRNAs) modulate epigenetic effector molecules including HDACs. Here, we describe the oncogenic or tumor suppressive functions of HDAC families and their regulatory miRNAs governing HDAC expression in hepatocarcinogenesis.

MicroRNA-221 governs tumor suppressor HDAC6 to potentiate malignant progression of liver cancer

BACKGROUND & AIMS

Most common reason behind changes in histone deacetylase (HDAC) function is its overexpression in cancer. However, among HDACs in liver cancer, HDAC6 is uniquely endowed with a tumor suppressor, but the mechanism underlying HDAC6 inactivation has yet to be uncovered.

METHODS

Microarray profiling and target prediction programs were used to identify miRNAs targeting HDAC6. A series of inhibitors, activators and siRNAs was introduced to validate regulatory mechanisms for microRNA-221-3p (miR-221) governing HDAC6 in hepatocarcinogenesis.

RESULTS

Comprehensive miRNA profiling analysis identified seven putative endogenous miRNAs that are significantly upregulated in hepatocellular carcinoma (HCC). While miR-221 was identified as a suppressor of HDAC6 by ectopic expression of miRNA mimics in Dicer knockdown cells, targeted-disruption of miR-221 repressed cancer cell growth through derepressing HDAC6 expression. Suppression of HDAC6 via miR-221 was induced by JNK/c-Jun signaling in liver cancer cells but not in normal hepatic cells. Additionally, cytokine-induced NF-κBp65 independently regulated miR-221, thereby suppressing HDAC6 expression in HCC cells. HCC tissues derived from chemical-induced rat and H-ras12V transgenic mice liver cancer models validated that JNK/c-Jun activation and NF-κBp65 nuclear translocation are essential for the transcription of miR-221 leading to repression of HDAC6 in HCC.

CONCLUSIONS

Our findings suggest that the functional loss or suppression of the tumor suppressor HDAC6 is caused by induction of miR-221 through coordinated JNK/c-Jun- and NF-κB-signaling pathways during liver tumorigenesis, providing a novel target for the molecular treatment of liver malignancies.

UHRF1 promotes proliferation of gastric cancer via mediating tumor suppressor gene hypermethylation

Epigenetic changes play significant roles in cancer development. UHRF1, an epigenetic regulator, has been shown to be overexpressed and to coordinate tumor suppressor gene (TSG) silencing in several cancers. In a previous study, we found that UHRF1 promoted gastric cancer (GC) invasion and metastasis. However, the role and underlying mechanism of UHRF1 in GC carcinogenesis remain largely unknown. In the present study, we investigated UHRF1 expression and function in GC proliferation and explored its downstream regulatory mechanism. The results demonstrated that UHRF1 overexpression was an independent and significant predictor of GC prognosis. Downregulation of UHRF1 suppressed GC proliferation and growth in vitro and in vivo, and UHRF1 upregulation showed opposite effects. Furthermore, downregulation of UHRF1 reactivated 7 TSGs, including CDX2, CDKN2A, RUNX3, FOXO4, PPARG, BRCA1 and PML, via promoter demethylation. These results provide insight into the GC proliferation process, and suggest that targeting UHRF1 represents a new therapeutic approach to block GC development.

Silencing HO-1 sensitizes SKM-1 cells to apoptosis induced by low concentration 5-azacytidine through enhancing p16 demethylation

Heme oxygenase-1 was reported previously as a resistance target on acute myelocytic leukemia (AML). We found that HO-1 was resistant to 5-azacytidine (AZA) treatment of myelodysplastic syndrome (MDS), and explored further the relative mechanisms. Patient bone marrow mononuclear cells (n=48) diagnosed as different levels of MDS were collected. Cell growth was evaluated by MTT assay; cell cycle and apoptosis were detected by flow cytometry; mRNA expression was assessed by real-time PCR, protein expression was analyzed through western blotting. Methylation was assessed by MSP. The survival time, and weight of mice were recorded. HO-1 overexpression was observed in SKM-1 cells after AZA treatment comparing to other cell lines. The HO-1 expression in MDS patients with high-risk was higher than in low-risk patients. After HO-1 was silenced by lentivirus-mediated siRNA, the proliferation of SKM-1 cells was effectively inhibited by low concentration AZA, and the cell cycle was arrested in the G0/G1 phase. Upregulation of p16 and changing of p16-relative cell cycle protein was observed after silencing HO-1 in AZA treated SKM-1 cells. In addition, DNMT1 was downregulated following the decrease of HO-1 expression. In vivo, silencing HO-1 inhibited SKM-1 cell growth induced by AZA in a NOD/SCID mouse model. Silencing HO-1 sensitized SKM-1 cells toward AZA, which may be attributed to the influence of HO-1 on AZA-induced p16 demethylation. HO-1 may be one of the targets that enhance the therapeutic effects of AZA on MDS malignant transformation inspiring new treatment methods for high-risk and very high-risk MDS patients in clinical practice.

Epigenetics of gastric cancer

Epigenetic changes frequently occur in human gastric cancer. Gene promoter region hypermethylation, genomic global hypomethylation, histone modifications, and alterations of noncoding RNAs are major epigenetic changes in gastric cancer. As a key risk factor of gastric cancer, H. pylori infection is an independent predictive indicator of gene methylation. A growing number of epigenetic studies in gastric cancer have provided lots of potential diagnostic and prognostic markers and therapeutic targets.

Histone deacetylase 2 controls p53 and is a critical factor in tumorigenesis

Histone deacetylase 2 (HDAC2) regulates biological processes by deacetylation of histones and non-histone proteins. HDAC2 is overexpressed in numerous cancer types, suggesting general cancer-relevant functions of HDAC2. In human tumors the TP53 gene encoding p53 is frequently mutated and wild-type p53 is often disarmed. Molecular pathways inactivating wild-type p53 often remain to be defined and understood. Remarkably, current data link HDAC2 to the regulation of the tumor suppressor p53 by deacetylation and to the maintenance of genomic stability. Here, we summarize recent findings on HDAC2 overexpression in solid and hematopoietic cancers with a focus on mechanisms connecting HDAC2 and p53 in vitro and in vivo. In addition, we present an evidence-based model that integrates molecular pathways and feedback loops by which p53 and further transcription factors govern the expression and the ubiquitin-dependent proteasomal degradation of HDAC2 and of p53 itself. Understanding the interactions between p53 and HDAC2 might aid in the development of new therapeutic approaches against cancer.

Melittin restores PTEN expression by down-regulating HDAC2 in human hepatocelluar carcinoma HepG2 cells

Melittin is a water-soluble toxic peptide derived from the venom of the bee. Although many studies show the anti-tumor activity of melittin in human cancer including glioma cells, the underlying mechanisms remain elusive. Here the effect of melittin on human hepatocelluar carcinoma HepG2 cell proliferation in vitro and further mechanisms was investigated. We found melittin could inhibit cell proliferation in vitro using Flow cytometry and MTT method. Besides, we discovered that melittin significantly downregulated the expressions of CyclinD1 and CDK4. Results of western Blot and Real-time PCR analysis indicated that melittin was capable to upregulate the expression of PTEN and attenuate histone deacetylase 2 (HDAC2) expression. Further studies demonstrated that knockdown of HDAC2 completely mimicked the effects of melittin on PTEN gene expression. Conversely, it was that the potential utility of melittin on PTEN expression was reversed in cells treated with a recombinant pEGFP-C2-HDAC2 plasmid. In addition, treatment with melittin caused a downregulation of Akt phosphorylation, while overexpression of HDAC2 promoted Akt phosphorylation. These findings suggested that the inhibitory of cell growth by melittin might be led by HDAC2-mediated PTEN upregulation, Akt inactivation, and inhibition of the PI3K/Akt signaling pathways.

Cross-communication between histone H3 and H4 acetylation and Akt-mTOR signalling in prostate cancer cells

Molecular tumour targeting has significantly improved anti-cancer protocols. Still, the addition of molecular targeting to the treatment regime has not led to a curative breakthrough. Combined mammalian target of Rapamycin (mTOR) and histone deacetylase (HDAC) inhibition has been shown not only to enhance anti-tumour potential, but also to prevent resistance development seen under mono-drug therapy. This investigation was designed to evaluate whether cross-communication exists between mTOR signalling and epigenetic events regulated by HDAC. DU-145 prostate cancer cells were treated with insulin-like growth factor (IGF) to activate the Akt-mTOR cascade or with the HDAC-inhibitor valproic acid (VPA) to induce histone H3 and H4 acetylation (aH3, aH4). Subsequently, mTOR, Rictor, Raptor, p70s6k, Akt (all: total and phosphorylated), H3 and H4 (total and acetylated) were analysed by western blotting. Both techniques revealed a link between mTOR and the epigenetic machinery. IGF activated mTOR, Rictor, Raptor, p70s6k and Akt, but also enhanced aH3 and aH4. Inversely, IGFr blockade and knock-down blocked the Akt-mTOR axis, but simultaneously diminished aH3 and aH4. VPA treatment up-regulated histone acetylation, but also activated mTOR-Akt signalling. HDAC1 and 2 knock-down revealed that the interaction with the mTOR system is initiated by histone H3 acetylation. HDAC-mTOR communication, therefore, is apparent whereby tumour-promoting (Akt/mTOR^high, aH3/aH4^low) and tumour-suppressing signals (Akt/mTOR^low, aH3/aH4^high) are activated in parallel. Combined use of an HDAC- and mTOR inhibitor might then diminish pro-tumour effects triggered by the HDAC- (Akt/mTOR^high) or mTOR inhibitor (aH3/aH4^low) alone.

Differential expression of histone deacetylase and acetyltransferase genes in gastric cancer and their modulation by trichostatin A

Gastric cancer is still the second leading cause of cancer-related death worldwide, even though its incidence and mortality have declined over the recent few decades. Epigenetic control using histone deacetylase inhibitors, such as trichostatin A (TSA), is a promising cancer therapy. This study aimed to assess the messenger RNA (mRNA) levels of three histone deacetylases (HDAC1, HDAC2, and HDAC3), two histone acetyltransferases (GCN5 and PCAF), and two possible targets of these histone modifiers (MYC and CDKN1A) in 50 matched pairs of gastric tumors and corresponding adjacent nontumors samples from patients with gastric adenocarcinoma, as well as their correlations and their possible associations with clinicopathological features. Additionally, we evaluated whether these genes are sensitive to TSA in gastric cancer cell lines. Our results demonstrated downregulation of HDAC1, PCAF, and CDKN1A in gastric tumors compared with adjacent nontumors (P < 0.05). On the other hand, upregulation of HDAC2, GCN5, and MYC was observed in gastric tumors compared with adjacent nontumors (P < 0.05). The mRNA level of MYC was correlated to HDAC3 and GCN5 (P < 0.05), whereas CDKN1A was correlated to HDAC1 and GCN5 (P < 0.05 and P < 0.01, respectively). In addition, the reduced expression of PCAF was associated with intestinal-type gastric cancer (P = 0.03) and TNM stages I/II (P = 0.01). The increased expression of GCN5 was associated with advanced stage gastric cancer (P = 0.02) and tumor invasion (P = 0.03). The gastric cell lines treated with TSA showed different patterns of histone deacetylase and acetyltransferase mRNA expression, downregulation of MYC, and upregulation of CDKN1A. Our findings suggest that alteration of histone modifier genes play an important role in gastric carcinogenesis, contributing to MYC and CDKN1A deregulation. In addition, all genes studied here are modulated by TSA, although this modulation appears to be dependent of the genetic background of the cell line.

HDAC2 provides a critical support to malignant progression of hepatocellular carcinoma through feedback control of mTORC1 and AKT

Aberrant regulation of histone deacetylase 2 (HDAC2) contributes to malignant progression in various cancers, but the underlying mechanism leading to the activation of oncogenic HDAC2 remains unknown. In this study, we show that HDAC2 expression is upregulated in a large cohort of patients with human hepatocellular carcinoma, and that high expression of HDAC2 was significantly associated with poor prognosis of patients with hepatocellular carcinoma. We found that mTORC1/NF-κBp50 signaling is necessary for the growth factor-induced HDAC2 and is sustained in hepatocellular carcinoma, but not in normal hepatic cells. Growth factor-induced mTORC1 activates the nuclear translocation of NF-κBp50, where it binds to the intragenic sequences of the HDAC2 gene and promotes its transcription. Hepatocellular carcinoma tissues derived from chemical-induced mouse and rat liver cancer models validated that mTORC1 activation and NF-κBp50 nuclear translocation are essential for the transcriptional activation of oncogenic HDAC2 in hepatocellular carcinoma. In addition, we demonstrate that HDAC2 is required to maintain mTORC1 activity by stabilizing the mTOR/RAPTOR complex. Elevated expression of HDAC2 triggers a positive feedback loop that activates AKT phosphorylation via the transcriptional modulation of phosphoinositide signaling molecules. Bioinformatics analysis of HDAC2 signature and immunoblot analysis of mesenchymal genes also evidenced that HDAC2 plays a role in the malignant behavior of tumor cells by Snail induction and simultaneously E-cadherin suppression in hepatocellular carcinoma cells. These findings establish a molecular mechanism responsible for the activation of oncogenic HDAC2, which explains how growth factor-induced HDAC2 maintains mitogenic signaling and function during hepatocellular malignant progression and provide a novel strategy for therapeutic intervention in liver cancer. Cancer Res; 74(6); 1728-38. ©2014 AACR.

Identification of proteins related to epigenetic regulation in the malignant transformation of aberrant karyotypic human embryonic stem cells by quantitative proteomics

Previous reports have demonstrated that human embryonic stem cells (hESCs) tend to develop genomic alterations and progress to a malignant state during long-term in vitro culture. This raises concerns of the clinical safety in using cultured hESCs. However, transformed hESCs might serve as an excellent model to determine the process of embryonic stem cell transition. In this study, ITRAQ-based tandem mass spectrometry was used to quantify normal and aberrant karyotypic hESCs proteins from simple to more complex karyotypic abnormalities. We identified and quantified 2583 proteins, and found that the expression levels of 316 proteins that represented at least 23 functional molecular groups were significantly different in both normal and abnormal hESCs. Dysregulated protein expression in epigenetic regulation was further verified in six pairs of hESC lines in early and late passage. In summary, this study is the first large-scale quantitative proteomic analysis of the malignant transformation of aberrant karyotypic hESCs. The data generated should serve as a useful reference of stem cell-derived tumor progression. Increased expression of both HDAC2 and CTNNB1 are detected as early as the pre-neoplastic stage, and might serve as prognostic markers in the malignant transformation of hESCs.

The molecular balancing act of p16(INK4a) in cancer and aging

p16(INK4a), located on chromosome 9p21.3, is lost among a cluster of neighboring tumor suppressor genes. Although it is classically known for its capacity to inhibit cyclin-dependent kinase (CDK) activity, p16(INK4a) is not just a one-trick pony. Long-term p16(INK4a) expression pushes cells to enter senescence, an irreversible cell-cycle arrest that precludes the growth of would-be cancer cells but also contributes to cellular aging. Importantly, loss of p16(INK4a) is one of the most frequent events in human tumors and allows precancerous lesions to bypass senescence. Therefore, precise regulation of p16(INK4a) is essential to tissue homeostasis, maintaining a coordinated balance between tumor suppression and aging. This review outlines the molecular pathways critical for proper p16(INK4a) regulation and emphasizes the indispensable functions of p16(INK4a) in cancer, aging, and human physiology that make this gene special.