Histone deacetylase inhibitor, Trichostatin A, activates p21WAF1/CIP1 expression through downregulation of c-myc and release of the repression of c-myc from the promoter in human cervical cancer cells

Suberanilohydroxamic acid (SAHA), a HDAC inhibitor, suppresses the effect of Treg cells by targeting the c-Myc/CCL1 pathway in glioma stem cells and improves PD-L1 blockade therapy

PURPOSE

A strong immunosuppressive tumor microenvironment (TME) represents the major barrier responsible for the failure of current immunotherapy approaches in treating Glioblastoma Multiforme (GBM). Within the TME, the regulatory T cells (Tregs) exert immunosuppressive effects on CD8+ T cell - mediated anti-cancer immune killing. Consequently, targeting and inhibiting their immunosuppressive function emerges as an effective therapeutic strategy for GBM. The present study aimed to investigate the mechanisms and effects of Suberanilohydroxamic Acid (SAHA), a histone deacetylase inhibitor, on immunosuppressive Tregs.

METHODS

The tumor-infiltrating immune cells in the immunocompetent GBM intracranial implanted xenograft mouse model were analyzed by immunohistochemistry and flow cytometry techniques. The mRNA expressions were assessed through the RT-qPCR method, while the related protein expressions were determined using western blot, ELISA, immunofluorescence (IF), and flow cytometry techniques. The relationship between c-Myc and C-C motif Chemokine Ligand 1 (CCL1) promotor was validated through a dual-luciferase reporter assay system and chromatin immunoprecipitation.

RESULTS

SAHA suppressed effectively tumor growth and extended significantly overall survival in the immunocompetent GBM intracranial xenograft mouse model. Additionally, it promoted the infiltration of CD8+ T lymphocytes while suppressed the infiltration of CD4+ CD25+ Tregs. Furthermore, SAHA enhanced anti-PD-L1 immune therapy in the intracranial xenograft of mice. Mechanistically, SAHA exerted its effects by inhibiting histone deacetylase 2 (HDAC2), thereby suppressing the binding between c-Myc and the CCL1 promotor.

CONCLUSION

SAHA inhibited the binding of c-Myc with the CCL1 promoter and then suppressed the transcription of CCL1.Additionally, it effectively blocked the interplay of CCL1-CCR8, resulting in reduced activity of Tregs and alleviation of tumor immunosuppression.

Profiling of Circulating Tumor Cells for Screening of Selective Inhibitors of Tumor-Initiating Stem-Like Cells

A critical barrier to effective cancer therapy is the improvement of drug selectivity, toxicity, and reduced recurrence of tumors expanded from tumor-initiating stem-like cells (TICs). The aim is to identify circulating tumor cell (CTC)-biomarkers and to identify an effective combination of TIC-specific, repurposed federal drug administration (FDA)-approved drugs. Three different types of high-throughput screens targeting the TIC population are employed: these include a CD133 (+) cell viability screen, a NANOG expression screen, and a drug combination screen. When combined in a refined secondary screening approach that targets Nanog expression with the same FDA-approved drug library, histone deacetylase (HDAC) inhibitor(s) combined with all-trans retinoic acid (ATRA) demonstrate the highest efficacy for inhibition of TIC growth in vitro and in vivo. Addition of immune checkpoint inhibitor further decreases recurrence and extends PDX mouse survival. RNA-seq analysis of TICs reveals that combined drug treatment reduces many Toll-like receptors (TLR) and stemness genes through repression of the lncRNA MIR22HG. This downregulation induces PTEN and TET2, leading to loss of the self-renewal property of TICs. Thus, CTC biomarker analysis would predict the prognosis and therapy response to this drug combination. In general, biomarker-guided stratification of HCC patients and TIC-targeted therapy should eradicate TICs to extend HCC patient survival.

The Emerging Role of Histone Deacetylase Inhibitors in Cervical Cancer Therapy

Cervical carcinoma is one of the most common cancers among women globally. Histone deacetylase inhibitors (HDACIs) constitute anticancer drugs that, by increasing the histone acetylation level in various cell types, induce differentiation, cell cycle arrest, and apoptosis. The aim of the current review is to study the role of HDACIs in the treatment of cervical cancer. A literature review was conducted using the MEDLINE and LIVIVO databases with a view to identifying relevant studies. By employing the search terms "histone deacetylase" and "cervical cancer", we managed to identify 95 studies published between 2001 and 2023. The present work embodies the most up-to-date, comprehensive review of the literature centering on the particular role of HDACIs as treatment agents for cervical cancer. Both well-established and novel HDACIs seem to represent modern, efficacious anticancer drugs, which, alone or in combination with other treatments, may successfully inhibit cervical cancer cell growth, induce cell cycle arrest, and provoke apoptosis. In summary, histone deacetylases seem to represent promising future treatment targets in cervical cancer.

Pharmacological Properties of Trichostatin A, Focusing on the Anticancer Potential: A Comprehensive Review

Trichostatin A (TSA), a natural derivative of dienohydroxamic acid derived from a fungal metabolite, exhibits various biological activities. It exerts antidiabetic activity and reverses high glucose levels caused by the downregulation of brain-derived neurotrophic factor (BDNF) expression in Schwann cells, anti-inflammatory activity by suppressing the expression of various cytokines, and significant antioxidant activity by suppressing oxidative stress through multiple mechanisms. Most importantly, TSA exhibits potent inhibitory activity against different types of cancer through different pathways. The anticancer activity of TSA appeared in many in vitro and in vivo investigations that involved various cell lines and animal models. Indeed, TSA exhibits anticancer properties alone or in combination with other drugs used in chemotherapy. It induces sensitivity of some human cancers toward chemotherapeutical drugs. TSA also exhibits its action on epigenetic modulators involved in cell transformation, and therefore it is considered an epidrug candidate for cancer therapy. Accordingly, this work presents a comprehensive review of the most recent developments in utilizing this natural compound for the prevention, management, and treatment of various diseases, including cancer, along with the multiple mechanisms of action. In addition, this review summarizes the most recent and relevant literature that deals with the use of TSA as a therapeutic agent against various diseases, emphasizing its anticancer potential and the anticancer molecular mechanisms. Moreover, TSA has not been involved in toxicological effects on normal cells. Furthermore, this work highlights the potential utilization of TSA as a complementary or alternative medicine for preventing and treating cancer, alone or in combination with other anticancer drugs.

Dissecting Histone Deacetylase 3 in Multiple Disease Conditions: Selective Inhibition as a Promising Therapeutic Strategy

The acetylation of histone and non-histone proteins has been implicated in several disease states. Modulation of such epigenetic modifications has therefore made histone deacetylases (HDACs) important drug targets. HDAC3, among various class I HDACs, has been signified as a potentially validated target in multiple diseases, namely, cancer, neurodegenerative diseases, diabetes, obesity, cardiovascular disorders, autoimmune diseases, inflammatory diseases, parasitic infections, and HIV. However, only a handful of HDAC3-selective inhibitors have been reported in spite of continuous efforts in design and development of HDAC3-selective inhibitors. In this Perspective, the roles of HDAC3 in various diseases as well as numerous potent and HDAC3-selective inhibitors have been discussed in detail. It will surely open up a new vista in the discovery of newer, more effective, and more selective HDAC3 inhibitors.

Activation of β-Catenin Signaling and its Crosstalk With Estrogen and Histone Deacetylases in Human Uterine Fibroids

CONTEXT

Uterine fibroids (UF) are the most common benign tumor of the myometrium (MM) in women of reproductive age. However, the mechanism underlying the pathogenesis of UF is largely unknown.

OBJECTIVE

To explore the link between nuclear β-catenin and UF phenotype and β-catenin crosstalk with estrogen and histone deacetylases (HDACs).

DESIGN

Protein/RNA levels of β-catenin (CTNNB1 gene), its responsive markers cyclin D1 and c-Myc, androgen receptor (AR), p27, and class-I HDACs were measured in matched UF/MM tissues or cell populations. The effects of chemical inhibition/activation and genetic knockdown of CTNNB1 on UF phenotype were measured. The anti-UF effect of 2 HDAC inhibitors was evaluated.

MAIN OUTCOME MEASURE

β-catenin nuclear translocation in response to β-catenin inhibition/activation, estrogen, and HDAC inhibitors in UF cells.

RESULTS

UF tissues/cells showed significantly higher expression of nuclear β-catenin, cyclin D1, c-Myc, and HDACs 1, 2, 3, and 8 than MM. Estradiol induced β-catenin nuclear translocation and consequently its responsive genes in both MM and UF cells, while an estrogen receptor antagonist reversed this induction effect. Treatment with β-catenin or HDAC inhibitors led to dose-dependent growth inhibition, while Wnt3a treatment increased proliferation compared with control. Chemical inhibition of β-catenin decreased cyclin D1 and c-Myc expression levels, while β-catenin activation increased expression of the same markers. Genetic knockdown of CTNNB1 resulted in a marked decrease in β-catenin, cyclin D1, c-Myc, and AR expression. Treatment of UF cells with HDAC inhibitors decreased nuclear β-catenin, cyclin D1, and c-Myc expression. Moreover, HDAC inhibitors induced apoptosis of UF cells and cell cycle arrest.

CONCLUSION

β-catenin nuclear translocation contributes to UF phenotype, and β-catenin signaling is modulated by estradiol and HDAC activity.

Tumor Necrosis Factor Receptor-Associated Factor 6 Promotes Hepatocarcinogenesis by Interacting With Histone Deacetylase 3 to Enhance c-Myc Gene Expression and Protein Stability

The oncogene c-Myc is aberrantly expressed and plays a key role in malignant transformation and progression of hepatocellular carcinoma (HCC). Here, we report that c-Myc is significantly up-regulated by tumor necrosis factor receptor-associated factor 6 (TRAF6), an E3 ubiquitin ligase, in hepatocarcinogenesis. High TRAF6 expression in clinical HCC samples correlates with poor prognosis, and the loss of one copy of the Traf6 gene in Traf6^+/- mice significantly impairs liver tumorigenesis. Mechanistically, TRAF6 first interacts with and ubiquitinates histone deacetylase 3 (HDAC3) with K63-linked ubiquitin chains, which leads to the dissociation of HDAC3 from the c-Myc promoter and subsequent acetylation of histone H3 at K9, thereby epigenetically enhancing the mRNA expression of c-Myc. Second, the K63-linked ubiquitination of HDAC3 impairs the HDAC3 interaction with c-Myc and promotes c-Myc protein acetylation, which thereby enhances c-Myc protein stability by inhibiting carboxyl terminus of heat shock cognate 70-kDa-interacting protein-mediated c-Myc ubiquitination and degradation. Importantly, TRAF6/HDAC3/c-Myc signaling is also primed in hepatitis B virus-transgenic mice, unveiling a critical role for a mechanism in inflammation-cancer transition. In clinical specimens, TRAF6 positively correlates with c-Myc at both the mRNA and protein levels, and high TRAF6 and c-Myc expression is associated with an unfavorable prognosis, suggesting that TRAF6 collaborates with c-Myc to promote human hepatocarcinogenesis. Consistently, curbing c-Myc expression by inhibition of TRAF6 activity with a TRAF6 inhibitor peptide or the silencing of c-Myc by small interfering RNA significantly suppressed tumor growth in mice. Conclusion: These findings demonstrate the oncogenic potential of TRAF6 during hepatocarcinogenesis by modulating TRAF6/HDAC3/c-Myc signaling, with potential implications for HCC therapy.

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.

MYC competes with MiT/TFE in regulating lysosomal biogenesis and autophagy through an epigenetic rheostat

Coordinated regulation of the lysosomal and autophagic systems ensures basal catabolism and normal cell physiology, and failure of either system causes disease. Here we describe an epigenetic rheostat orchestrated by c-MYC and histone deacetylases that inhibits lysosomal and autophagic biogenesis by concomitantly repressing the expression of the transcription factors MiT/TFE and FOXH1, and that of lysosomal and autophagy genes. Inhibition of histone deacetylases abates c-MYC binding to the promoters of lysosomal and autophagy genes, granting promoter occupancy to the MiT/TFE members, TFEB and TFE3, and/or the autophagy regulator FOXH1. In pluripotent stem cells and cancer, suppression of lysosomal and autophagic function is directly downstream of c-MYC overexpression and may represent a hallmark of malignant transformation. We propose that, by determining the fate of these catabolic systems, this hierarchical switch regulates the adaptive response of cells to pathological and physiological cues that could be exploited therapeutically.

Genes related to lysosomal and autophagic systems are transcriptionally regulated by the Mit/TFE family of transcription factors. Here the authors show that MYC, in association with HDACs, suppresses the expression of lysosomal and autophagy genes by competing with the Mit/TFE transcription factors for occupancy of their target gene promoters.

Inhibition of class I HDACs attenuates renal interstitial fibrosis in a murine model

Renal interstitial fibrosis is the most common of all the forms of chronic kidney disease (CKD). Research has shown that histone deacetylases (HDACs) participate in the process leading to renal fibrosis. However, the effects of class I HDAC inhibitors on the mechanisms of onset and progression of renal interstitial fibrosis are still unclear. Here, we present the effects and mechanisms of action of FK228 (a selective inhibitor of class I HDACs) in the murine model of unilateral ureteral obstruction (UUO) and in vitro models. We investigated the antifibrotic role of FK228 in a murine model of UUO. We used two key effector cell populations, rat renal interstitial fibroblasts and renal tubular epithelial cells exposed to recombinant transforming growth factor-beta 1 (TGF-β1), to explore the mechanistic pathways among in vitro models. The results indicated that FK228 significantly suppressed the production of extracellular matrix (ECM) in both in vivo and in vitro models. FK228 inhibited renal fibroblast activation and proliferation and increased the acetylation of histone H3. We found that FK228 also inhibited the small mothers against decapentaplegic (Smad) and non-Smad signaling pathways. So FK228 could significantly suppress renal interstitial fibrosis via Smad and non-Smad pathways. FK228 may be the basis for a new and effective medicine for alleviating renal fibrosis in the future.

Genomic insult oriented mitochondrial instability and proliferative hindrance in the bone marrow of aplastic mice including stem/progenitor population

Aplastic anemia is the bone marrow failure condition characterized by the development of hypocellularity in both marrow and peripheral blood compartments. Anti-tumor chemotherapeutic agents often exert secondary effect on hematopoietic system leading to aplastic anemia by marrow failure. The precise mechanisms behind the marrow ablative effects of the drugs remain yet to be established. The present study holds a mechanistic approach to unveil the mystery. Aplastic anemia was generated in mice with the administration of busulfan and cyclophosphamide followed by the characterization of the disease with peripheral blood hemogram, histopathological and cytochemical examinations of bone marrow. To gain deep knowledge about the molecular mechanisms of the hematopoietic disruption, cytotoxicity assay, DNA damage measurement, apoptosis study, replicative senescence analysis, redox balance study, mitochondrial membrane potential change assessment, flowcytometric expressional analysis of p21, p53, ATM, Chk-2, Necdin, Gfi-1, c-myc, KU-80 and Sod-2 were done with marrow hematopoietic stem/ progenitor cells (HSPCs). Severe blood pancytopenia and marrow hypocellularity was found in aplastic mice. Proliferative hindrance and apoptosis of marrow cells were identified as the cause behind the hematopoietic catastrophe. The genotoxic effects of the drugs triggered chromatin damage and induced replicative senescence in aplastic HSPCs by upregulating p21 in a p53 independent manner. Moreover, accumulation of genomic insults also caused apoptotic elimination of marrow cells due to disruption of mitochondrial membrane potential by generating redox imbalance. The study established the underlying mechanisms behind hematopoietic disruption during drug induced marrow aplasia. Outcome of the study may be helpful in successful designing of therapeutic strategies for the disease concerned.

Suppression of c-Myc and RRM2 expression in pancreatic cancer cells by the sphingosine kinase-2 inhibitor ABC294640

Pancreatic cancer remains extremely difficult to treat, with the average lifespan following diagnosis being only 3-6 months, resulting in a death to incidence ratio of 0.94. A major reason for this high mortality rate is resistance to the main chemotherapeutic agent used to treat this disease, gemcitabine. Alterations in nucleoside and gemcitabine metabolism, specifically over-expression of ribonucleotide reductase, have been implicated as a major mechanism of resistance to this drug. Here, we show that inhibition of sphingosine kinase-2 by the specific inhibitor ABC294640 is synergistically cytotoxic with gemcitabine toward three human pancreatic cancer cell lines. Treatment with ABC294640 results in decreased expression of both RRM2 and MYC in all three cell lines. Additionally, expression of c-Myc protein and phosphorylation of Rb at S780 both decrease in a dose-dependent manner in response to ABC294640, while acetylation of H3-K9 and p21 levels increase. Pretreatment with the protein phosphatase 1 inhibitor okadaic acid or the ceramide synthase inhibitor fumonisin B1 fails to prevent the effects of ABC294640 on Rb phosphorylation. These data indicate a role for sphingosine kinase-2 in E2F and c-Myc mediated transcription through alteration of histone acetylation and p21 expression. These effects of ABC294640 suggest that it may be an effective agent for pancreatic cancer, particularly in combination with gemcitabine.

Role of peroxiredoxin2 downregulation in recurrent miscarriage through regulation of trophoblast proliferation and apoptosis

Peroxiredoxin (Prdx) 2 is an antioxidant protein that utilizes its redox-sensitive cysteine groups to reduce hydrogen peroxide molecules and protect cells against oxidative damage from reactive oxygen species (ROS). However, its function in trophoblasts at the maternal-fetal interface has not been clarified yet. In this study, significantly lower Prdx2 expression was found in the first-trimester villous cytotrophoblasts of patients with recurrent miscarriage (RM) than in cytotrophoblasts from healthy controls. Further, Prdx2 knockdown inhibited proliferation and increased apoptosis of trophoblast cells. The reason for this may be an increase in the level of cellular ROS after knockdown of Prdx2, which may subsequently lead to an increase in the expression of phosphorylated p53 (p-p53) and p38-MAPK/p21. Prdx2 knockdown also impaired the fusion of BeWo cells induced by forskolin. Bioinformatics analysis identified a c-Myc-binding site in the Prdx2 promoter region, and chromatin immunoprecipitation verified that c-Myc directly bound to a site in this locus. Suppression and overexpression of c-Myc resulted in reduction and increase of Prdx2 expression respectively. Furthermore, we demonstrated that c-Myc was downregulated in the first-trimester cytotrophoblasts of patients with RM, and its downregulation is also related with inhibited cell proliferation, increased apoptosis, as well as upregulated p21 expression and p-p53/p53 ratio. Our findings indicate that Prdx2 might have an important role in the regulation of trophoblast proliferation and apoptosis during early pregnancy, and that its expression is mediated by c-Myc. Thus, these two proteins may be involved in the pathogenesis of RM and may represent potential therapeutic targets.

Transcription factor AP-2β suppresses cervical cancer cell proliferation by promoting the degradation of its interaction partner β-catenin

Transcription factor AP-2β mediates the transcription of a number of genes implicated in mammalian development, cell proliferation, and carcinogenesis. Although the expression pattern of AP-2β has been analyzed in cervical cancer cell lines, the functions and molecular mechanism of AP-2β are unknown. Here, we found that AP-2β significantly inhibits TCF/LEF reporter activity. Moreover, AP-2β and β-catenin interact both in vitro through GST pull-down assays and in vivo by co-immunoprecipitation. We further identified the interaction regions to the DNA-binding domain of AP-2β and the 1-9 Armadillo repeats of β-catenin. Moreover, AP-2β binds with β-TrCP and promotes the degradation of endogenous β-catenin via the proteasomal degradation pathway. Immunohistochemistry analysis revealed a negative correlation between the two proteins in cervical cancer tissues and cell lines. Finally, functional analysis showed that AP-2β suppresses cervical cancer cell growth in vitro and in vivo by inhibiting the expression of Wnt downstream genes. Taken together, these findings demonstrated that AP-2β functions as a novel inhibitor of the Wnt/β-catenin signaling pathway in cervical cancer.

Enhancement of pomalidomide anti-tumor response with ACY-241, a selective HDAC6 inhibitor

Thalidomide-based Immunomodulatory Drugs (IMiDs^®), including lenalidomide and pomalidomide, are effective therapeutics for multiple myeloma. These agents have been approved with, or are under clinical development with, other targeted therapies including proteasome inhibitors, αCD38 monoclonal antibodies, as well as histone deacetylase (HDAC) inhibitors for combination therapy. HDAC inhibitors broadly targeting Class I and IIb HDACs have shown potent preclinical efficacy but have frequently demonstrated an undesirable safety profile in combination therapy approaches in clinical studies. Therefore, development of more selective HDAC inhibitors could provide enhanced efficacy with reduced side effects in combination with IMiDs^® for the treatment of B-cell malignancies, including multiple myeloma. Here, the second generation selective HDAC6 inhibitor citarinostat (ACY-241), with a more favorable safety profile than non-selective pan-HDAC inhibitors, is shown to synergize with pomalidomide in in vitro assays through promoting greater apoptosis and cell cycle arrest. Furthermore, utilizing a multiple myeloma in vivo murine xenograft model, combination treatment with pomalidomide and ACY-241 leads to increased tumor growth inhibition. At the molecular level, combination treatment with ACY-241 and pomalidomide leads to greater suppression of the pro-survival factors survivin, Myc, and IRF4. The results presented here demonstrate synergy between pomalidomide and ACY-241 in both in vitro and in vivo preclinical models, providing further impetus for clinical development of ACY-241 for use in combination with IMiDs for patients with multiple myeloma and potentially other B-cell malignancies.

Hydroxylated-graphene quantum dots induce cells senescence in both p53-dependent and -independent manner

The numerous particular chemical/physical properties make graphene quantum dots (GQDs) attractive for various biomedical applications such as drug delivery, bioimaging and tumor photodynamic therapy (PDT). In the present study, the critical roles of hydroxyl-modified GQDs (OH-GQDs) on lung carcinoma A549 (wild type p53) and H1299 (p53-null) cells were investigated. Our data showed that a medium concentration (50 μg mL-1) of OH-GQDs significantly decreased the viability of A549 and H1299 cells. OH-GQDs treatment enhanced intracellular reactive oxygen species (ROS) generation. Furthermore, we found that treatment with ROS scavenger N-acetylcysteine (NAC) at least partially abolished the cytotoxic effect of OH-GQDs on A549 and H1299 cells. Hydroxylated GQDs lead to G0-G1 arrest and cells senescence. Signal pathway analysis revealed that OH-GQDs activated the expression of p21 in both a p53-dependent and -independent manner. Consistent with this, OH-GQDs could also inhibit the phosphorylation of Rb in both A549 and H1299 cells. These findings provide valuable information for the consideration of biomedical application of GQDs in the future.

Ricolinostat plus lenalidomide, and dexamethasone in relapsed or refractory multiple myeloma: a multicentre phase 1b trial

BACKGROUND

Histone deacetylase (HDAC) inhibitors are an important new class of therapeutics for treating multiple myeloma. Ricolinostat (ACY-1215) is the first oral selective HDAC6 inhibitor with reduced class I HDAC activity to be studied clinically. Motivated by findings from preclinical studies showing potent synergistic activity with ricolinostat and lenalidomide, our goal was to assess the safety and preliminary activity of the combination of ricolinostat with lenalidomide and dexamethasone in relapsed or refractory multiple myeloma.

METHODS

In this multicentre phase 1b trial, we recruited patients aged 18 years or older with previously treated relapsed or refractory multiple myeloma from five cancer centres in the USA. Inclusion criteria included a Karnofsky Performance Status score of at least 70, measureable disease, adequate bone marrow reserve, adequate hepatic function, and a creatinine clearance of at least 50 mL per min. Exclusion criteria included previous exposure to HDAC inhibitors; previous allogeneic stem-cell transplantation; previous autologous stem-cell transplantation within 12 weeks of baseline; active systemic infection; malignancy within the last 5 years; known or suspected HIV, hepatitis B, or hepatitis C infection; a QTc Fridericia of more than 480 ms; and substantial cardiovascular, gastrointestinal, psychiatric, or other medical disorders. We gave escalating doses (from 40-240 mg once daily to 160 mg twice daily) of oral ricolinostat according to a standard 3 + 3 design according to three different regimens on days 1-21 with a conventional 28 day schedule of oral lenalidomide (from 15 mg [in one cohort] to 25 mg [in all other cohorts] once daily) and oral dexamethasone (40 mg weekly). Primary outcomes were dose-limiting toxicities, the maximum tolerated dose of ricolinostat in this combination, and the dose and schedule of ricolinostat recommended for further phase 2 investigation. Secondary outcomes were the pharmacokinetics and pharmacodynamics of ricolinostat in this combination and the preliminary anti-tumour activity of this treatment. The trial is closed to accrual and is registered at ClinicalTrials.gov, number NCT01583283.

FINDINGS

Between July 12, 2012, and Aug 20, 2015, we enrolled 38 patients. We observed two dose-limiting toxicities with ricolinostat 160 mg twice daily: one (2%) grade 3 syncope and one (2%) grade 3 myalgia event in different cohorts. A maximum tolerated dose was not reached. We chose ricolinostat 160 mg once daily on days 1-21 of a 28 day cycle as the recommended dose for future phase 2 studies in combination with lenalidomide 25 mg and dexamethasone 40 mg. The most common adverse events were fatigue (grade 1-2 in 14 [37%] patients; grade 3 in seven [18%]) and diarrhoea (grade 1-2 in 15 [39%] patients; grade 3 in two [5%]). Our pharmacodynamic studies showed that at clinically relevant doses, ricolinostat selectively inhibits HDAC6 while retaining a low and tolerable level of class I HDAC inhibition. The pharmacokinetics of ricolinostat and lenalidomide were not affected by co-administration. In a preliminary assessment of antitumour activity, 21 (55% [95% CI 38-71]) of 38 patients had an overall response.

INTERPRETATION

The findings from this study provide preliminary evidence that ricolinostat is a safe and well tolerated selective HDAC6 inhibitor, which might partner well with lenalidomide and dexamethasone to enhance their efficacy in relapsed or refractory multiple myeloma.

FUNDING

Acetylon Pharmaceuticals.

Identification of a gene expression driven progression pathway in myxoid liposarcoma

Aim: to investigate the events involved in the progression of myxoid liposarcoma (MLS).

Gene expression profiling and immunohistochemical/biochemical analyses were applied to specimens representative of the opposite ends of the MLS spectrum: pure myxoid (ML) and pure round cell (RC) liposarcomas.

The analyses revealed the involvement of both coding and non coding RNAs (SNORDs located in DLK1-DIO3 region) and support a model of stepwise progression mainly driven by epigenetic changes involving tumour vascular supply and tumoral cellular component. In this model, a switch in the vascular landscape from a normal to a pro-angiogenic signature and the silencing of DLK1-DIO3 region mark the progression from ML to RC in concert with the acquisition by the latter of the over-expression of YY1/C-MYC/HDAC2, together with over-expression of genes involved in cell proliferation and stemness: MKNK2, MSX1 and TRIM71.

Taken together, these findings strongly suggest that to progress from ML to RC liposarcoma the cells have to overcome the epigenetic silencing restriction point in order to reset their new stem-like differentiation signature. Our findings provide a first attempt at identifying the missing links between ML and RC liposarcomas, that may also have broader applications in other clinico-pathological settings characterised by a spectrum of progression.

CDKN1A histone acetylation and gene expression relationship in gastric adenocarcinomas

CDKN1A is a tumor suppressor gene involved in gastric carcinogenesis and is a potential target for histone deacetylase inhibitor-based therapies. Upregulation of CDKN1A is generally observed in several cell lines after histone deacetylase inhibitor treatment; however, little is known about the histone acetylation status associated with this gene in clinical samples, including gastric tumor tissue samples. Therefore, our goal was to quantify the H3K9 and H4K16 acetylation levels associated with three CDKN1A regions in 21 matched pairs of gastric adenocarcinoma and corresponding adjacent non-tumor samples by chromatin immunoprecipitation and to correlate these data with the gene expression. Our results demonstrated that the -402, -20, and +182 CDKN1A regions showed a significantly increased acetylation level in at least one of the histones evaluated (p < 0.05, for all comparisons), and these levels were positively correlated in gastric tumors. However, an inverse correlation was detected between both H3K9 and H4K16 acetylation at the -402 CDKN1A region and mRNA levels in gastric tumors (r = -0.51, p = 0.02; r = -0.60, p < 0.01, respectively). Furthermore, increased H4K16 acetylation at the -20 CDKN1A region was associated with gastric tumors of patients without lymph node metastasis (p = 0.04). These results highlight the complexity of these processes in gastric adenocarcinoma and contribute to a better understanding of CDKN1A regulation in carcinogenesis.

Rational combination treatment with histone deacetylase inhibitors and immunomodulatory drugs in multiple myeloma

Immunomodulatory drugs (IMiDs) thalidomide, lenalidomide (Len) and pomalidomide trigger anti-tumor activities in multiple myeloma (MM) by targetting cereblon and thereby impacting IZF1/3, c-Myc and IRF4. Histone deacetylase inhibitors (HDACi) also downregulate c-Myc. We therefore determined whether IMiDs with HDACi trigger significant MM cell growth inhibition by inhibiting or downregulating c-Myc. Combination treatment of Len with non-selective HDACi suberoylanilide hydroxamic acid or class-I HDAC-selective inhibitor MS275 induces synergic cytotoxicity, associated with downregulation of c-Myc. Unexpectedly, we observed that decreased levels of cereblon (CRBN), a primary target protein of IMiDs, was triggered by these agents. Indeed, sequential treatment of MM cells with MS275 followed by Len shows less efficacy than simultaneous treatment with this combination. Importantly ACY1215, an HDAC6 inhibitor with minimal effects on class-I HDACs, together with Len induces synergistic MM cytotoxicity without alteration of CRBN expression. Our results showed that only modest class-I HDAC inhibition is able to induce synergistic MM cytotoxicity in combination with Len. These studies may provide the framework for utilizing HDACi in combination with Len to both avoid CRBN downregulation and enhance anti-MM activities.

Epigenetic and molecular mechanisms underlying the antileukemic activity of the histone deacetylase inhibitor belinostat in human acute promyelocytic leukemia cells

Therapeutic strategies targeting histone deacetylase (HDAC) inhibition have become promising in many human malignancies. Belinostat (PXD101) is a hydroxamate-type HDAC inhibitor tested in phase I and II clinical trials in solid tumors and hematological cancers. However, little is known about the use of belinostat for differentiation therapy against acute myelogenous leukemia. Here, we characterize the antileukemia activity of belinostat as a single drug and in combination with all-trans-retinoic acid (RA) in promyelocytic leukemia HL-60 and NB4 cells. Belinostat exerted dose-dependent growth-inhibitory or proapoptotic effects, promoting cell cycle arrest at the G0/G1 or the S transition. Apoptosis was accompanied by activation of caspase 3, degradation of PARP-1, and cell cycle-dependent changes in the expression of survivin, cyclin E1, and cyclin A2. Belinostat induced a dose-dependent reduction in the expression of EZH2 and SUZ12, HDAC-1, HDAC-2, and histone acetyltransferase PCAF (p300/CBP-associated factor). Belinostat increased acetylation of histone H4, H3 at K9 and H3 at K16 residues in a dose-dependent manner, but did not reduce trimethylation of H3 at K27 at proapoptotic doses. Combined treatment with belinostat and RA dose dependently accelerated and reinforced granulocytic differentiation, accompanied by changes in the expression of CD11b, C/EBPα (CCAAT/enhancer binding protein-α), and C/EBPε. Our results concluded the usefulness of belinostat, as an epigenetic drug, for antileukemia and differentiation therapy.

The expression of p21 is upregulated by forkhead box A1/2 in p53-null H1299 cells

The expression of the cell cycle inhibitor p21 is increased in response to various stimuli and stress signals through p53-dependent and independent pathways. We demonstrate in this study that forkhead box A1/2 (FOXA1/2) is a crucial transcription factor in the activation of p21 transcription via direct binding to the p21 promoter in p53-null H1299 lung carcinoma cells. In addition, histone deacetylase inhibitor trichostatin A (TSA)-mediated upregulation of p21 expression was repressed by knockdown of FOXA1/2 in H1299 cells. Consequently, these results suggest that FOXA1/2 is required for p53-independent p21 expression.

Histone deacetylase inhibitor (HDACI) mechanisms of action: emerging insights

Initially regarded as "epigenetic modifiers" acting predominantly through chromatin remodeling via histone acetylation, HDACIs, alternatively referred to as lysine deacetylase or simply deacetylase inhibitors, have since been recognized to exert multiple cytotoxic actions in cancer cells, often through acetylation of non-histone proteins. Some well-recognized mechanisms of HDACI lethality include, in addition to relaxation of DNA and de-repression of gene transcription, interference with chaperone protein function, free radical generation, induction of DNA damage, up-regulation of endogenous inhibitors of cell cycle progression, e.g., p21, and promotion of apoptosis. Intriguingly, this class of agents is relatively selective for transformed cells, at least in pre-clinical studies. In recent years, additional mechanisms of action of these agents have been uncovered. For example, HDACIs interfere with multiple DNA repair processes, as well as disrupt cell cycle checkpoints, critical to the maintenance of genomic integrity in the face of diverse genotoxic insults. Despite their pre-clinical potential, the clinical use of HDACIs remains restricted to certain subsets of T-cell lymphoma. Currently, it appears likely that the ultimate role of these agents will lie in rational combinations, only a few of which have been pursued in the clinic to date. This review focuses on relatively recently identified mechanisms of action of HDACIs, with particular emphasis on those that relate to the DNA damage response (DDR), and discusses synergistic strategies combining HDACIs with several novel targeted agents that disrupt the DDR or antagonize anti-apoptotic proteins that could have implications for the future use of HDACIs in patients with cancer.

Targeting cardiac fibroblasts to treat fibrosis of the heart: focus on HDACs

Cardiac fibrosis is implicated in numerous physiologic and pathologic conditions, including scar formation, heart failure and cardiac arrhythmias. However the specific cells and signaling pathways mediating this process are poorly understood. Lysine acetylation of nucleosomal histone tails is an important mechanism for the regulation of gene expression. Additionally, proteomic studies have revealed that thousands of proteins in all cellular compartments are subject to reversible lysine acetylation, and thus it is becoming clear that this post-translational modification will rival phosphorylation in terms of biological import. Acetyl groups are conjugated to lysine by histone acetyltransferases (HATs) and removed from lysine by histone deacetylases (HDACs). Recent studies have shown that pharmacologic agents that alter lysine acetylation by targeting HDACs have the remarkable ability to block pathological fibrosis. Here, we review the current understanding of cardiac fibroblasts and the fibrogenic process with respect to the roles of lysine acetylation in the control of disease-related cardiac fibrosis. Potential for small molecule HDAC inhibitors as anti-fibrotic therapeutics that target cardiac fibroblasts is highlighted. This article is part of a Special Issue entitled "Myocyte-Fibroblast Signalling in Myocardium."

Low expression of long noncoding XLOC_010588 indicates a poor prognosis and promotes proliferation through upregulation of c-Myc in cervical cancer

OBJECTIVE

The identification and investigation of cancer-associated long non-coding RNAs are important for understanding the molecular biology of cancer. The aim of the present study was to examine the expression pattern of lncRNA XLOC_010588 in cervical cancer and to evaluate its biological role and clinical significance in tumor progression.

METHODS

We examined the expression of XLOC_010588 in 218 cervical cancer tissues and matched 218 adjacent normal tissues using real-time qRT-PCR. Over-expression and RNA interference approaches were used to investigate the biological functions of XLOC_010588. The effect of XLOC_010588 on proliferation was evaluated by MTT and BrdU assays. Western blot assays were used to investigate the molecular mechanism by which XLOC_010588 increases cervical cancer cell proliferation.

RESULTS

The results showed that XLOC_010588 expression in cervical cancer was significantly downregulated. Decreased XLOC_010588 expression was correlated with FIGO stage, tumor size and SCC-Ag. Moreover, cervical cancer patients with XLOC_010588 lower expression have shown poorer prognosis. Multivariate Cox regression analyses showed that XLOC_010588 expression served as an independent predictor for overall survival. Ectopic expression of XLOC_010588 inhibited the proliferation of HeLa and SiHa cells. By contrast, knockdown of XLOC_010588 promoted the growth of HCC94 cells. Western blot assays confirmed that XLOC_010588 physically associates with c-Myc, consequently decreasing the expression of c-Myc. The expression of XLOC_010588 and c-Myc is strongly correlated in cervical cancer tissues.

CONCLUSION

These results suggested that XLOC_010588 plays a pivotal role in cervical cancer cell proliferation via decreasing c-Myc expression and implicated the potential application of XLOC_010588 in cervical cancer therapy.

Class I HDACs regulate angiotensin II-dependent cardiac fibrosis via fibroblasts and circulating fibrocytes

Fibrosis, which is defined as excessive accumulation of fibrous connective tissue, contributes to the pathogenesis of numerous diseases involving diverse organ systems. Cardiac fibrosis predisposes individuals to myocardial ischemia, arrhythmias and sudden death, and is commonly associated with diastolic dysfunction. Histone deacetylase (HDAC) inhibitors block cardiac fibrosis in pre-clinical models of heart failure. However, which HDAC isoforms govern cardiac fibrosis, and the mechanisms by which they do so, remains unclear. Here, we show that selective inhibition of class I HDACs potently suppresses angiotensin II (Ang II)-mediated cardiac fibrosis by targeting two key effector cell populations, cardiac fibroblasts and bone marrow-derived fibrocytes. Class I HDAC inhibition blocks cardiac fibroblast cell cycle progression through derepression of the genes encoding the cyclin-dependent kinase (CDK) inhibitors, p15 and p57. In contrast, class I HDAC inhibitors block agonist-dependent differentiation of fibrocytes through a mechanism involving repression of ERK1/2 signaling. These findings define novel roles for class I HDACs in the control of pathological cardiac fibrosis. Furthermore, since fibrocytes have been implicated in the pathogenesis of a variety of human diseases, including heart, lung and kidney failure, our results suggest broad utility for isoform-selective HDAC inhibitors as anti-fibrotic agents that function, in part, by targeting these circulating mesenchymal cells.

HSPC111 governs breast cancer growth by regulating ribosomal biogenesis

Activation of c-Myc plays a decisive role in the development of many human cancers. As a transcription factor, c-Myc facilitates cell growth and proliferation by directly transcribing a multitude of targets, including rRNAs and ribosome proteins. However, how to elucidate the deregulation of rRNAs and ribosome proteins driven by c-Myc in cancer remains a significant challenge and thus warrants close investigation. In this report, a crucial role for the HSPC111 (NOP16) multiprotein complex in governing ribosomal biogenesis and tumor growth was determined. It was discovered that enhanced HSPC111 expression paralleled the upregulation of c-Myc and was directly regulated by c-Myc in breast cancer cells. Knockdown of HSPC111 dramatically reduced the occurrence of tumorigenesis in vivo, and largely restrained tumor cell growth in vitro and in vivo. In stark contrast, HSPC111 overexpression significantly promoted tumor cell growth. Biochemically, it was demonstrated that RNA 3'-phosphate cyclase (RTCD1/RTCA) interacted with HSPC111, and RTCD1 was involved in the HSPC111 multiprotein complex in regulating rRNA production and ribosomal biogenesis. Moreover, HSPC111 and RTCD1 synergistically modulated cell growth and cellular size through commanding rRNA synthesis and ribosome assembly coupled to protein production. Finally, overall survival analysis revealed that concomitant upregulation of HSPC111 and RTCD1 correlated with the worst prognosis in a breast cancer cohort.

IMPLICATIONS

Inhibition of HSPC111-dependent ribosomal biosynthesis and protein synthesis is a promising therapeutic strategy to diminish breast cancer tumor progression.

Incompatible effects of p53 and HDAC inhibition on p21 expression and cell cycle progression

Nutlin-3 selectively activates p53 by inhibiting the interaction of this tumor suppressor with its negative regulator murine double minute 2 (mdm2), while trichostatin A (TSA) is one of the most potent histone deacetylase (HDAC) inhibitors currently available. As both Nutlin-3 and TSA increase the levels of the cell cycle inhibitor p21(cip1/waf1) in cells, we investigated whether a combination of these compounds would further augment p21 levels. Contrary to expectations, we found that short-term exposure to Nutlin-3 and TSA in combination did not have an additive effect on p21 expression. Instead, we observed that activation of p53 prevented the ability of TSA to increase p21 levels. Furthermore, TSA inhibited Nutlin-3-induced expression of p53-dependent mRNAs including P21. This negative effect of TSA on Nutlin-3 was significantly less pronounced in the case of hdm2, another p53 downstream target. Aside from suggesting a model to explain these incompatible effects of Nutlin-3 and TSA, we discuss the implications of our findings in cancer therapy and cell reprogramming.

Histone deacetylase inhibitor induction of epithelial-mesenchymal transitions via up-regulation of Snail facilitates cancer progression

Histone deacetylase inhibitors (HDACIs) are now emerging as a new class of anticancer drugs. Some of them have been used in clinical treatment for tumors, most impressively in the hematological tumors. But their single-agent activities in epithelial-derived tumors are limited. The mechanisms of these actions of HDACIs are not yet well understood. In this study, it was found for the first time that HDACIs were able to induce epithelial-mesenchymal transitions (EMT) which is believed to trigger tumor cell invasion and metastasis. We show that HDACIs induce fibroblast-like morphology, up-regulate Snail and Vimentin and down-regulate E-cadherin in epithelial cell-derived tumor cell lines. It demonstrates that HDACI treatment enhances further Snail acetylation and reduces its ubiquitylation, and induces Snail transcription as well as Snail nuclear translocation in CNE2 cells. Snail knockdown by siRNAs prevents the change in cell morphology and Vimentin up-regulation in response to HDACIs. The results suggested that Snail plays an important role in the HDACI-induced EMT. It is very crucial for a better understanding of clinical therapeutical failure of HDACIs in the patients with epithelial cell-derived cancers. Therefore, our results indicate that more attention should be paid to the cancer treatment using HDACIs due to the fact that it will enhance the spread risks of cancer cells to facilitate cancer progression and it is very important to select appropriate drugs for different tumors.

TSA suppresses miR-106b-93-25 cluster expression through downregulation of MYC and inhibits proliferation and induces apoptosis in human EMC

Histone deacetylase (HDAC) inhibitors are emerging as a novel class of anti-tumor agents and have manifested the ability to decrease proliferation and increase apoptosis in different cancer cells. A significant number of genes have been identified as potential effectors responsible for the anti-tumor function of HDAC inhibitor. However, the molecular mechanisms of these HDAC inhibitors in this process remain largely undefined. In the current study, we searched for microRNAs (miRs) that were affected by HDAC inhibitor trichostatin (TSA) and investigated their effects in endometrial cancer (EMC) cells. Our data showed that TSA significantly inhibited the growth of EMC cells and induced their apoptosis. Among the miRNAs that altered in the presence of TSA, the miR-106b-93-25 cluster, together with its host gene MCM7, were obviously down-regulated in EMC cells. p21 and BIM, which were identified as target genes of miR-106b-93-25 cluster, increased in TSA treated tumor cells and were responsible for cell cycle arrest and apoptosis. We further identified MYC as a regulator of miR-106b-93-25 cluster and demonstrated its down-regulation in the presence of TSA resulted in the reduction of miR-106b-93-25 cluster and up-regulation of p21 and BIM. More important, we found miR-106b-93-25 cluster was up-regulated in clinical EMC samples in association with the overexpression of MCM7 and MYC and the down-regulation of p21 and BIM. Thus our studies strongly indicated TSA inhibited EMC cell growth and induced cell apoptosis and cell cycle arrest at least partially through the down-regulation of the miR-106b-93-25 cluster and up-regulation of it's target genes p21 and BIM via MYC.

The molecular classification of medulloblastoma: driving the next generation clinical trials

PURPOSE OF REVIEW

Most children diagnosed with cancer today are expected to be cured. Medulloblastoma, the most common pediatric malignant brain tumor, is an example of a disease that has benefitted from advances in diagnostic imaging, surgical techniques, radiation therapy and combination chemotherapy over the past decades. It was an incurable disease 50 years ago, but approximately 70% of children with medulloblastoma are now cured of their disease. However, the pace of increasing the cure rate has slowed over the past 2 decades, and we have likely reached the maximal benefit that can be achieved with cytotoxic therapy and clinical risk stratification. Long-term toxicity of therapy also remains significant. To increase cure rates and decrease long-term toxicity, there is great interest in incorporating biologic 'targeted' therapy into treatment of medulloblastoma, but this will require a paradigm shift in how we classify and study disease.

RECENT FINDINGS

Using genome-based high-throughput analytic techniques, several groups have independently reported methods of molecular classification of medulloblastoma within the past year. This has resulted in a working consensus to view medulloblastoma as four molecular subtypes, including wingless-type murine mammary tumor virus integration site (WNT) pathway subtype, Sonic Hedgehog pathway subtype and two less well defined subtypes (groups C and D).

SUMMARY

Novel classification and risk stratification based on biologic subtypes of disease will form the basis of further study in medulloblastoma and identify specific subtypes that warrant greater research focus.

The tumor suppressor role of CTCF

CTCF is an evolutionary conserved and ubiquitously expressed protein that binds thousands of sites in the human genome. Ectopic expression of CTCF in various normal and tumoral human cell lines inhibits cell division and clonogenicity, with the consequence to consider CTCF a potential tumor-suppressor factor. In this review article, we focused on the molecular mechanisms engaged by CTCF to modulate the expression of several key-regulators of differentiation, cellular senescence, cell cycle control and progression, whose expression is frequently altered in tumors. Moreover, we discussed common features of CTCF at each tumor-related DNA-binding sequence, such as protein-partners, post-translational modifications, and distinctive epigenetic marks establishment. The investigation of the molecular mechanisms engaged by CTCF to modulate tumor-related genes emphasizes the cell-type dependency of its tumor suppressor role. Indeed, the ability of CTCF to bind their promoters strictly depends by cell-type features as DNA methylation, BORIS-binding and post-translational modifications as PARYlation.

Histone deacetylase inhibitors sensitize human non-small cell lung cancer cells to ionizing radiation through acetyl p53-mediated c-myc down-regulation

INTRODUCTION

Histone deacetylase inhibitors (HDACIs) induce growth arrest and apoptosis in cancer cells. In addition to their intrinsic anticancer properties, HDACIs modulate cellular responses to ionizing radiation (IR). We examined the molecular mechanism(s) associated with the radiosensitizing effects of HDACIs in human lung cancer cells.

METHODS

Lung cancer cells were pretreated with the appropriate concentrations of suberoylanilide hydroxamic acid or trichostatin A. After 2 hours, cells were irradiated with various doses of γ-IR, and then we performed 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, fluorescence-activated cell sorting analysis, clonogenic assay, and Western blotting to detect cell viability or apoptosis and changes of specific proteins expression levels.

RESULTS

In this study, we showed that HDACIs (including suberoylanilide hydroxamic acid and trichostatin A) and IR synergistically trigger cell death in human non-small cell lung cancer cells. Cell viability and clonogenic survival were markedly decreased in cultures cotreated with HDACIs and IR. Interestingly, p53 acetylation at lysine 382 was significantly increased, and c-myc expression simultaneously down-regulated in cotreated cells. Radiosensitization by HDACIs was inhibited on transfection with small interfering RNA against p53 and c-myc overexpression, supporting the involvement of p53 and c-myc in this process. Furthermore, c-myc down-regulation and apoptotic cell death coinduced by IR and HDACI were suppressed in cells transfected with mutant K382R p53 and C135Y p53 displaying loss of acetylation at lysine 382 and DNA-binding activity, respectively.

CONCLUSIONS

Our results collectively demonstrate that the degree of radiosensitization by HDACIs is influenced by acetyl p53-mediated c-myc down-regulation.

C/EBPα and PU.1 are involved in distinct differentiation responses of acute promyelocytic leukemia HL-60 and NB4 cells via chromatin remodeling

C/EBPα and PU.1 are the basic transcription factors that control differentiation-related genes, including granulocyte- colony-stimulating factor (G-CSFR) and human neutrophil elastase (HNE). Here, we analyzed a role of C/EBPα and PU.1 in human acute leukemia cell lines, HL-60 and NB4, in association with a modified chromatin structure by histone deacetylase inhibitors, FK228, sodium phenyl butyrate and vitamin B3. We found that sodium phenyl butyrate alone and 6h-pretreatment with phenyl butyrate or FK228 before the induction of differentiation with all-trans-retinoic acid in the presence of vitamin B3 effectively accelerated and enhanced differentiation to granulocytes in HL-60 but not in NB4 cells as detected by NBT test and the expression of CD11b and CD114 (G-CSFR) using flow cytometric analysis. HDACIs induced a time- and dose-dependent accumulation of hyper-acetylated histone H4 in both cell lines with the delay in NB4 cells. Time-dependent different induction of HL-60 and NB4 cell differentiation was paralleled by the activation of C/EBPα and PU.1 binding to the G-CSFR and the HNE promoters in electrophoretic mobility shift assay. Chromatin immunoprecipitation analysis revealed histone H4 acetylation in the G-CSF receptor promoter at the C/EBPα binding site in HL-60 but not in NB4 cells under the combined treatment. The results indicate that epigenetic events, such as histone acetylation, are involved in the activity modulation of the key transcription factors responsible for the induction of granulocytic differentiation in promyelocytic leukemia cells.

Epigenetic tools in potential anticancer therapy

Human cancer represents a heterogeneous group of diseases that are driven by progressive genetic and epigenetic abnormalities. The latter alterations involve hypermethylation and hypomethylation of DNA, and changed patterns of histone modification, with resultant remodeling of the chromatin structure that cause deregulation of the transcription activity of many genes. Unlike the remarkable progress in understanding the processes by which DNA methyltransferases can regulate gene expression and histone deacetylases can induce alteration of chromatin structure, the roles of epigenetic events in tumors remain insufficiently explained. In contrast to genetic changes, the epigenetic alterations in cancer cells can be reversed by the inhibition of DNA methylation and histone deacetylation. Therefore, many inhibition agents for re-expression, predominantly of tumor-suppressor genes, have been identified and tested in laboratory models and numerous clinical trials. Despite in-vitro evidence that a single drug can lead to reactivation of methylated genes, inhibitors of DNA methyltransferases and histone deacetylases have been investigated in combination, or together with cytotoxic chemotherapy, radiotherapy, immunotherapy, or hormonal therapy to improve the therapeutic effect. Ongoing trials are recognizing that the identification of a target group of patients who are more likely to respond to the epigenetic therapy, defining of an optimal dose and schedule of treatment, and the development of more specific inhibitors with minimal unwanted side effects are necessary. Thus, new combinations of anticancer agents, including epigenetic modulators, may lead to a more effective control of cancer.

p53-independent induction of G1 arrest and p21WAF1/CIP1 expression by ascofuranone, an isoprenoid antibiotic, through downregulation of c-Myc

Ascofuranone has been shown to have antitumor activity, but the precise molecular mechanism by which it inhibits the proliferation of cancer cells remains unclear. Here, we study the effects of ascofuranone on cell cycle progression in human cancer cells and find that ascofuranone induces G(1) arrest without cytoxicity with upregulation of p53 and p21(WAF1/CIP1) while downregulating c-Myc and G(1) cyclins. Chromatin immunoprecipitation assay and RNA interference studies with cells deficient in p53 and p21 show that ascofuranone induces p21(WAF1/CIP1) expression and subsequent G(1) arrest through the release of p21(WAF1/CIP1) promoter from c-Myc-mediated transcriptional repression, independent of p53. Ascofuranone-induced p21(WAF1/CIP1) associates with CDK2 and prevents CDK2-cyclin E complex formation, leading to the inactivation of E2F transcriptional activity. These results suggest that ascofuranone upregulates p21(WAF1/CIP1) through p53-independent suppression of c-Myc expression, leading to cytostatic G(1) arrest. Thus, ascofuranone represents a unique natural antitumor compound that targets c-Myc independent of p53.

Cytotoxicity mediated by histone deacetylase inhibitors in cancer cells: mechanisms and potential clinical implications

Aberrant expression of epigenetic regulators of gene expression contributes to initiation and progression of cancer. During recent years, considerable research efforts have focused on the role of histone acetyltransferases (HATs) and histone deacetylases (HDACs) in cancer cells, and the identification of pharmacologic agents that modulate gene expression via inhibition of HDACs. The following review highlights recent studies pertaining to HDAC expression in cancer cells, the plieotropic mechanisms by which HDAC inhibitors (HDACi) mediate antitumor activity, and the potential clinical implications of HDAC inhibition as a strategy for cancer therapy.

Chfr is linked to tumour metastasis through the downregulation of HDAC1

Chfr is a ubiquitin ligase that functions in the mitotic checkpoint by delaying entry into metaphase in response to mitotic stress. It has been suggested that Chfr is a tumour suppressor as Chfr is frequently silenced in human cancers. To better understand how Chfr activity relates to cell-cycle progression and tumorigenesis, we sought to identify Chfr-interacting proteins using affinity purification combined with mass spectrometry. Histone deacetylase 1 (HDAC1), which represses transcription by deacetylating histones, was newly isolated as a Chfr-interacting protein. Chfr binds and downregulates HDAC1 by inducing its polyubiquitylation, both in vitro and in vivo. Ectopic expression of Chfr in cancer cells that normally do not express it results in downregulation of HDAC1, leading to upregulation of the Cdk inhibitor p21(CIP1/WAF1) and the metastasis suppressors KAI1 and E-cadherin. Coincident with these changes, cells arrest in the G1 phase of the cell cycle and become less invasive. Collectively, our data suggest that Chfr functions as a tumour suppressor by regulating HDAC1.

HLA antigen changes in malignant cells: epigenetic mechanisms and biologic significance

Changes in classical and nonclassical HLA class I as well as HLA class II antigens have been identified in malignant lesions. These changes, which are described in this review are believed to play a major role in the clinical course of the disease since both HLA class I and class II antigens are critical to the interaction between tumor cells and components of both innate and adaptive immune system. Abnormalities in HLA antigen expression in malignant cells, which range in frequency from 0-90%, are caused by distinct mechanisms. They include defects in beta(2)-microglobulin (beta(2)m) synthesis, loss of the gene(s) encoding HLA antigen heavy chain(s), mutations, which inhibit HLA antigen heavy chain transcription or translation, defects in the regulatory mechanisms, which control HLA antigen expression and/or abnormalities in one or more of the antigen processing, machinery (APM) components. More recently, epigenetic events associated with tumor development and progression have been found to underlie changes in HLA antigen, APM component, costimulatory molecule and tumor antigen (TA) expression in malignant cells. The types of epigenetic modifications that may occur in normal and malignant cells as well as their role in changes in HLA antigen expression by malignant cells have been reviewed. The epigenetic events associated with alterations in HLA antigen expression may be clinically relevant as, in some cases, they have been shown to impair the recognition of tumor cells by components of the adaptive immune system. The functional relevance and potential clinical significance of these epigenetic alterations have been addressed. Finally, unlike genetic alterations, epigenetic modifications can, in some cases, be reversed with pharmacologic agents that induce DNA hypomethylation or inhibit histone deacetylation. Therefore, strategies to overcome epigenetic modifications underlying changes in HLA antigen expression in malignant cells have been discussed.

Modulation of the cyclin-dependent kinase inhibitor p21(WAF1/Cip1) gene by Zac1 through the antagonistic regulators p53 and histone deacetylase 1 in HeLa Cells

Zac1 is a novel seven-zinc finger protein which possesses the ability to bind specifically to GC-rich DNA elements. Zac1 not only promotes apoptosis and cell cycle arrest but also acts as a transcriptional cofactor for p53 and a number of nuclear receptors. Our previous study indicated that the enhancement of p53 activity by Zac1 is much more pronounced in HeLa cells compared with other cell lines tested. This phenomenon might be due to the coactivator effect of Zac1 on p53 and the ability of Zac1 to reverse E6 inhibition of p53. In the present study, we showed that Zac1 acted synergistically with either p53 or a histone deacetylase inhibitor, trichostatin A, to enhance p21(WAF1/Cip1) promoter activity. We showed that Zac1 physically interacted with some nuclear receptor corepressors such as histone deacetylase 1 (HDAC1) and mSin3a, and the induction of p21(WAF1/Cip1) gene and protein by Zac1 was suppressed by either overexpressing HDAC1 or its deacetylase-dead mutant. In addition, our data suggest that trichostatin A-induced p21(WAF1/Cip1) protein expression might be mediated through a p53-independent and HDAC deacetylase-independent pathway. Taken together, our data suggest that Zac1 might be involved in regulating the p21(WAF1/Cip1) gene and protein expression through its protein-protein interaction with p53 and HDAC1 in HeLa cells.

Trichostatin A causes p53 to switch oxidative-damaged colorectal cancer cells from cell cycle arrest into apoptosis

Many studies aim at improving therapeutic efficacy by combining strategies with oxidative stress-inducing drugs and histone deacetylase (HDAC) inhibitors in colorectal cancer. As p53 and p21^WAF1 are essential in oxidative stress-induced DNA damage, we investigated epigenetic regulation of p21^WAF1 promoter. Firstly, HCT116 p53⁺/⁺ and p53⁻/⁻ colorectal cancer cells were treated with H₂O₂ for 6 hrs and 24 hrs (early/late response). Chromatin immunoprecipitation revealed transcriptional transactivation of p21^WAF1 in HCT116 p53⁺/⁺ cells as shown by increased binding of p53 and acetylated H4 around two p21^WAF1 promoter sites, the responsible element (RE) and the Sp1 site, while both proteins bound preferentially on the RE. Interestingly, H3 was not involved, suggesting H4-specific transactivation of the p21^WAF1 promoter. H₂O₂ addition resulted in G₂/M arrest of both HCT116 cell lines without significant cell death. To investigate whether a HDAC inhibitor strengthens G₂/M arrest, we pretreated cells with Trichostatin A (TSA). In HCT116 p53⁺/⁺ cells, we found (i) remarkably increased acetylated H4 around both p21^WAF1 promoter regions, especially at the Sp1 site; (ii) increased acetylation of p53 at lysines 320 and 382;(iii) displacement of HDAC1 from the Sp1 site, thus inhibiting its repression effect and increasing p53 binding.p53 seems to trigger H4-acetylation around the p21^WAF1 promoter because there was nearly no H4 acetylation in HCT116 p53⁻/⁻ cells. For the first time we show that there is a time-dependent TSA mode of action with increased p53-dependent histone H4 acetylation at the p21^WAF1 promoter in early response, and decreased acetylation in late response. Reduced p53-triggered transactivation of p21^WAF1 in late response allows cells to re-enter cell cycle, and TSA causes p53 to simultaneously induce apoptosis.

Acetylation of non-histone proteins modulates cellular signalling at multiple levels

This review focuses on the posttranslational acetylation of non-histone proteins, which determines vital regulatory processes. The recruitment of histone acetyltransferases and histone deacetylases to the transcriptional machinery is a key element in the dynamic regulation of genes controlling cellular proliferation and differentiation. A steadily growing number of identified acetylated non-histone proteins demonstrate that reversible lysine acetylation affects mRNA stability, and the localisation, interaction, degradation and function of proteins. Interestingly, most non-histone proteins targeted by acetylation are relevant for tumourigenesis, cancer cell proliferation and immune functions. Therefore inhibitors of histone deacetylases are considered as candidate drugs for cancer therapy. Histone deacetylase inhibitors alter histone acetylation and chromatin structure, which modulates gene expression, as well as promoting the acetylation of non-histone proteins. Here, we summarise the complex effects of dynamic alterations in the cellular acetylome on physiologically relevant pathways.

Aging and induced senescence as factors in the pathogenesis of lung emphysema

Classically, the development of emphysema in chronic obstructive pulmonary disease is believed to involve inflammation induced by cigarette smoke and leukocyte activation, including oxidant-antioxidant and protease-antiprotease imbalances. While there is substantial evidence for this, additional aspects have been suggested by a number of clinical and experimental observations. Smokers exhibit signs of premature aging, particularly obvious in the skin. The link between aging and chronic disease is well-known, e.g., for the brain and musculoskeletal or cardiovascular system, as well as the clinical link between malnutrition and emphysema, and the experimental link to caloric restriction. Interestingly, this intervention also increases lifespan, in parallel with alterations in metabolism, oxidant burden and endocrine signaling. Of special interest is the observation that, even in the absence of an inflammatory environment, lung fibroblasts from patients with emphysema show persistent alterations, possibly based on epigenetic mechanisms. The importance of these mechanisms for cellular reprogramming and response patterns, individual risk profile and therapeutic options is becoming increasingly recognized. The same applies to cellular senescence. Recent findings from patients and experimental models open novel views into the arena of gene-environment interactions, including the role of systemic alterations, cellular stress, telomeres, CDK inhibitors such as p16, p21, pRb, PI3K, mTOR, FOXO transcription factors, histone modifications, and sirtuins. This article aims to outline this emerging picture and to stimulate the identification of challenging questions. Such insights also bear implications for the long-term course of the disease in relation to existing or future therapies and the exploration of potential lung regeneration.

Valproic acid inhibits the growth of cervical cancer both in vitro and in vivo

Valproic acid (VPA), a well-known anti-convulsant, is currently under extensive evaluation as an anti-cancer agent. It is known to exert its anti-cancer effect mainly by inhibiting the enzyme histone deacetylase I. In our study, we investigated the effects of VPA on cervical cancer both in vitro and in vivo cancer models. We examined the effects of acute VPA (0, 1.2, 2.4, 5.0 mM) treatment on cell proliferation in cervical cancer cell lines HeLa, SiHa and Ca Ski and histone acetylation, p21 and p53 gene expression in HeLa cell line. We also investigated the effect of chronic VPA administration in tumour xenograft growth studies. Our results show that with acute treatment, VPA can increase the expression of net histone H3 acetylation and up-regulate p21 expression with no effect on p53 expression. Chronic administration of VPA had a net cytostatic effect that resulted in a statistically significant reduction of tumour growth and improved survival advantages in tumour xenografts studies. Furthermore, we also demonstrated that VPA has a direct anti-angiogenic effect in tumour studies and could potentially be a promising candidate for further cervical cancer trails.