Sp1 acetylation is associated with loss of DNA binding at promoters associated with cell cycle arrest and cell death in a colon cell line

HDAC6 Enhances Endoglin Expression through Deacetylation of Transcription Factor SP1, Potentiating BMP9-Induced Angiogenesis

Histone deacetylase 6 (HDAC6) plays a crucial role in the acetylation of non-histone proteins and is notably implicated in angiogenesis, though its underlying mechanisms were previously not fully understood. This study conducted transcriptomic and proteomic analyses on vascular endothelial cells with HDAC6 knockdown, identifying endoglin (ENG) as a key downstream protein regulated by HDAC6. This protein is vital for maintaining vascular integrity and plays a complex role in angiogenesis, particularly in its interaction with bone morphogenetic protein 9 (BMP9). In experiments using human umbilical vein endothelial cells (HUVECs), the pro-angiogenic effects of BMP9 were observed, which diminished following the knockdown of HDAC6 and ENG. Western blot analysis revealed that BMP9 treatment increased SMAD1/5/9 phosphorylation, a process hindered by HDAC6 knockdown, correlating with reduced ENG expression. Mechanistically, our study indicates that HDAC6 modulates ENG transcription by influencing promoter activity, leading to increased acetylation of transcription factor SP1 and consequently altering its transcriptional activity. Additionally, the study delves into the structural role of HDAC6, particularly its CD2 domain, in regulating SP1 acetylation and subsequently ENG expression. In conclusion, the present study underscores the critical function of HDAC6 in modulating SP1 acetylation and ENG expression, thereby significantly affecting BMP9-mediated angiogenesis. This finding highlights the potential of HDAC6 as a therapeutic target in angiogenesis-related processes.

GATA-3-dependent Gene Transcription is Impaired upon HDAC Inhibition

PURPOSE

Many peripheral and cutaneous T-cell lymphoma (CTCL) subtypes are poorly responsive to conventional chemotherapeutic agents and associated with dismal outcomes. The zinc finger transcription factor GATA-3 and the transcriptional program it instigates are oncogenic and highly expressed in various T-cell neoplasms. Posttranslational acetylation regulates GATA-3 DNA binding and target gene expression. Given the widespread use of histone deacetylase inhibitors (HDACi) in relapsed/refractory CTCL, we sought to examine the extent to which these agents attenuate the transcriptional landscape in these lymphomas.

EXPERIMENTAL DESIGN

Integrated GATA-3 chromatin immunoprecipitation sequencing and RNA sequencing analyses were performed in complementary cell line models and primary CTCL specimens treated with clinically available HDACi.

RESULTS

We observed that exposure to clinically available HDACi led to significant transcriptional reprogramming and increased GATA-3 acetylation. HDACi-dependent GATA-3 acetylation significantly impaired both its ability to bind DNA and transcriptionally regulate its target genes, thus leading to significant transcriptional reprogramming in HDACi-treated CTCL.

CONCLUSIONS

Beyond shedding new light on the mechanism of action associated with HDACi in CTCL, these findings have significant implications for their use, both as single agents and in combination with other novel agents, in GATA-3-driven lymphoproliferative neoplasms.

Acetate Upregulates GPR43 Expression and Function via PI3K-AKT-SP1 Signaling in Mammary Epithelial Cells during Milk Fat Synthesis

This study investigated the mechanism underlying acetate-induced orphan G-protein-coupled receptor 43 (GPR43) expression and milk fat production. The mammary epithelial cells of dairy cows were treated with acetate, and the effects of GPR43 on acetate uptake and the expression of lipogenesis-related genes were determined by gas chromatography and quantitative polymerase chain reaction (qPCR), respectively. RNAi, inhibitor treatment, and luciferase assay were used to determine the effect of phosphoinositide 3-kinase-protein kinase B-specificity protein 1 (PI3K-AKT-SP1) signaling on acetate-induced GPR43 expression and function. The results showed that GPR43 was highly expressed in lactating cow mammary tissues, which was related to milk fat synthesis. 12 mM acetate significantly increased the GPR43 expression in mammary epithelial cells of dairy cows. In acetate-treated cells, GPR43 overexpression significantly increased the cellular uptake of acetate, the intracellular triacylglycerol (TAG) content, and acetate-induced lipogenesis gene expression. Acetate activated PI3K-AKT signaling and promoted SP1 translocation from the cytosol into the nucleus, where SP1 bound to the GPR43 promoter and upregulated GPR43 transcription. Moreover, the activation of PI3K-AKT-SP1 by acetate facilitated the trafficking of GPR43 from the cytosol to the plasma membrane. In conclusion, acetate upregulated GPR43 expression and function via PI3K-AKT-SP1 signaling in mammary epithelial cells, thereby increasing milk fat synthesis. These results provide an experimental strategy for improving milk lipid synthesis, which is important to the dairy industry.

Lansoprazole as a potent HDAC2 inhibitor for treatment of colorectal cancer: An in-silico analysis and experimental validation

BACKGROUND

Histone deacetylase 2 (HDAC2), belonging to the class I HDAC family, holds significant therapeutic potential as a crucial target for diverse cancer types. As key players in the realm of epigenetic regulatory enzymes, histone deacetylases (HDACs) are intricately involved in the onset and progression of cancer. Consequently, pursuing isoform-specific inhibitors targeting histone deacetylases (HDACs) has garnered substantial interest in both biological and medical circles. The objective of the present investigation was to employ a drug repurposing approach to discover novel and potent HDAC2 inhibitors.

MATERIALS AND METHODS

In this study, our protocol is presented on virtual screening to identify novel potential HDAC2 inhibitors through 3D-QSAR, molecular docking, pharmacophore modeling, and molecular dynamics (MD) simulation. Afterward, In-vitro assays were employed to evaluate the cytotoxicity, apoptosis, and migration of HCT-116 cell lines under treatment of hit compound and valproic acid as a control inhibitor. The expression levels of HDAC2, TP53, BCL2, and BAX were evaluated by QRT-PCR.

RESULTS

RMSD, RMSF, H-bond, and DSSP analysis results confirmed that among bioinformatically selected compounds, lansoprazole exhibited the highest HDAC2 inhibitory potential. Experimental validation revealed that lansoprazole displayed significant antiproliferative activity. The determined IC50 value was 400 ± 2.36 μM. Furthermore, the apoptotic cells ratio concentration-dependently increased under Lansoprazole treatment. Results of the Scratch assay indicated that lansoprazole led to decreasing the migration of CRC cells. Finally, under Lansoprazole treatment the expression level of BCL2 and HDAC2 decreased and BAX and TP53 increased.

CONCLUSION

Taking together the results of the current study indicated that Lansoprazole as a novel HDAC2 inhibitor, could be used as a potential therapeutic agent for the treatment of CRC. Although, further experimental studies should be performed before using this compound in the clinic.

The HDAC2-SP1 Axis Orchestrates Protumor Macrophage Polarization

Tumor-associated macrophages (TAM), including antitumor M1-like TAMs and protumor M2-like TAMs, are transcriptionally dynamic innate immune cells with diverse roles in lung cancer development. Epigenetic regulators are key in controlling macrophage fate in the heterogeneous tumor microenvironment. Here, we demonstrate that the spatial proximity of HDAC2-overexpressing M2-like TAMs to tumor cells significantly correlates with poor overall survival of lung cancer patients. Suppression of HDAC2 in TAMs altered macrophage phenotype, migration, and signaling pathways related to interleukins, chemokines, cytokines, and T-cell activation. In coculture systems of TAMs and cancer cells, suppressing HDAC2 in TAMs resulted in reduced proliferation and migration, increased apoptosis of cancer cell lines and primary lung cancer cells, and attenuated endothelial cell tube formation. HDAC2 regulated the M2-like TAM phenotype via acetylation of histone H3 and transcription factor SP1. Myeloid cell-specific deletion of Hdac2 and pharmacologic inhibition of class I HDACs in four different murine lung cancer models induced the switch from M2-like to M1-like TAMs, altered infiltration of CD4+ and CD8+ T cells, and reduced tumor growth and angiogenesis. TAM-specific HDAC2 expression may provide a biomarker for lung cancer stratification and a target for developing improved therapeutic approaches.

SIGNIFICANCE

HDAC2 inhibition reverses the protumor phenotype of macrophages mediated by epigenetic modulation induced by the HDAC2-SP1 axis, indicating a therapeutic option to modify the immunosuppressive tumor microenvironment.

An antioxidant ameliorates allergic airway inflammation by inhibiting HDAC 1 via HIF-1α/VEGF axis suppression in mice

Histone deacetylase inhibitors (HDACi) are novel class of drugs as they are involved in post translational modification of several proteins involved in signaling pathways related to asthma. HDACi have been reported to elicit protective effects on asthma but the signaling pathways associated with it have not been investigated much. Recently, we have demonstrated that intranasal administrations of Pan-HDAC inhibitors, sodium butyrate and curcumin, which have effectively reduced asthma severity via HDAC1 inhibition in Ovalbumin induced mouse model. Present study aimed to investigate possible pathways by which curcumin and sodium butyrate may minimize asthma pathogenesis via HDAC 1 inhibition. Balb/c mice were exposed (sensitized and challenged) with Ovalbumin to establish allergic asthma model followed by pretreatment of curcumin (5 mg/kg) and sodium butyrate (50 mg/kg) through intranasal route. Effects of curcumin and sodium butyrate on HIF-1α/VEGF signaling through activation of PI3K/Akt axis has been investigated using protein expressions followed by chromatin immunoprecipitation of BCL2 and CCL2 against HDAC1. Molecular docking analysis was also performed to investigate effects of curcumin and butyrate on mucus hypersecretion, goblet cell hyperplasia and airway hyperresponsiveness. Augmented expressions of HDAC-1, HIF-1α, VEGF, p-Akt and p-PI3K were observed in asthmatic group which was suppressed in both the treatments. NRF-2 level was significantly restored by curcumin and butyrate treatments. Protein expressions of p-p38, IL-5 and mRNA expressions of GATA-3 were also reduced in curcumin and butyrate treatment groups. Our findings suggest that curcumin and sodium butyrate may attenuate airway inflammation via down regulation of p-Akt/p-PI3K/HIF-1α/VEGF axis.

Genetic Analysis of HIBM Myopathy-Specific GNE V727M Hotspot Mutation Identifies a Novel COL6A3 Allied Gene Signature That Is Also Deregulated in Multiple Neuromuscular Diseases and Myopathies

The GNE-associated V727M mutation is one of the most prevalent ethnic founder mutations in the Asian HIBM cohort; however, its role in inducing disease phenotype remains largely elusive. In this study, the function of this hotspot mutation was profoundly investigated. For this, V727M mutation-specific altered expression profile and potential networks were explored. The relevant muscular disorder-specific in vivo studies and patient data were further analyzed, and the key altered molecular pathways were identified. Our study found that the GNEV727M mutation resulted in a deregulated lincRNA profile, the majority of which (91%) were associated with a down-regulation trend. Further, in silico analysis of associated targets showed their active role in regulating Wnt, TGF-β, and apoptotic signaling. Interestingly, COL6a3 was found as a key target of these lincRNAs. Further, GSEA analysis showed HIBM patients with variable COL6A3 transcript levels have significant alteration in many critical pathways, including epithelial-mesenchymal-transition, myogenesis, and apoptotic signaling. Interestingly, 12 of the COL6A3 coexpressed genes also showed a similar altered expression profile in HIBM. A similar altered trend in COL6A3 and coexpressed genes were found in in vivo HIBM disease models as well as in multiple other skeletal disorders. Thus, the COL6A3-specific 13 gene signature seems to be altered in multiple muscular disorders. Such deregulation could play a pivotal role in regulating many critical processes such as extracellular matrix organization, cell adhesion, and skeletal muscle development. Thus, investigating this novel COL6A3-specific 13 gene signature provides valuable information for understanding the molecular cause of HIBM and may also pave the way for better diagnosis and effective therapeutic strategies for many muscular disorders.

Mechanism and strategies of immunotherapy resistance in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer in the world. Although there are standard treatment options for CRC, most patients respond poorly to these treatments. Immunotherapies have gradually emerged due to the increasing awareness and understanding of tumor immunity, exhibiting good therapeutic efficacy in various cancers. Immunotherapies include cytokines, immune checkpoint inhibitors (ICIs), and adoptive cell therapies. In particular, ICIs, which are antibodies against cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death 1 (PD-1), or its ligand PD-L1, have been successfully applied clinically for solid tumors, relieving the inhibitory effect of the tumor microenvironment on T cells. However, only a minority of patients with cancer achieve a durable clinical response during immunotherapy. Several factors restrict the efficacy of immunotherapy, leading to the development of drug resistance. In this review, we aimed to discuss the current status of immunotherapy for CRC and elaborate on the mechanisms that mediate resistance to immunotherapy and other potential therapeutic strategies.

SP1 Promotes HDAC4 Expression and Inhibits HMGB1 Expression to Reduce Intestinal Barrier Dysfunction, Oxidative Stress, and Inflammatory Response after Sepsis

As a serious and elusive syndrome caused by infection, sepsis causes a high rate of mortality around the world. Our investigation aims at exploring the role and possible mechanism of specificity protein-1 (SP1) in the development of sepsis. A mouse model of sepsis was established by cecal ligation perforation, and a cellular model was stimulated by lipopolysaccharide (LPS), followed by determination of the SP1 expression. It was determined that SP1 was poorly expressed in the intestinal tissues of septic mice and LPS-treated cells. Next, we examined the interactions among SP1, histone deacetylase 4 (HDAC4), and high mobility group box 1 (HMGB1) and found that SP1 bound to the HDAC4 promoter to upregulate its expression, thereby promoting the deacetylation of HMGB1. Meanwhile, gain- or loss-of-function approaches were applied to evaluate the intestinal barrier dysfunction, oxidative stress, and inflammatory response. Overexpression of SP1 or underexpression of HMGB1 was observed to reduce intestinal barrier dysfunction, oxidative stress, and inflammatory injury. Collectively, these experimental data provide evidence reporting that SP1 could promote the HDAC4-mediated HMGB1 deacetylation to reduce intestinal barrier dysfunction, oxidative stress, and inflammatory response induced by sepsis, providing a novel therapeutic target for sepsis prevention and treatment.

The Role of Bioactive Compounds in Natural Products Extracted from Plants in Cancer Treatment and Their Mechanisms Related to Anticancer Effects

Cancer is one of the greatest causes of death worldwide. With the development of surgery, radiotherapy, and medical agents, the outcomes of cancer patients have greatly improved. However, the underlying mechanisms of cancer are not yet fully understood. Recently, natural products have been proven to be beneficial for various conditions and have played important roles in the development of novel therapies. A substantial amount of evidence indicates that bioactive compounds could improve the outcomes of cancer patients via various pathways, such as endoplasmic reticulum stress, epigenetic modification, and modulation of oxidative stress. Here, we review the current evidence of bioactive compounds in natural products for the treatment of cancer and summarize the underlying mechanisms in this pathological process.

The role of protein acetylation in carcinogenesis and targeted drug discovery

Protein acetylation is a reversible post-translational modification, and is involved in many biological processes in cells, such as transcriptional regulation, DNA damage repair, and energy metabolism, which is an important molecular event and is associated with a wide range of diseases such as cancers. Protein acetylation is dynamically regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) in homeostasis. The abnormal acetylation level might lead to the occurrence and deterioration of a cancer, and is closely related to various pathophysiological characteristics of a cancer, such as malignant phenotypes, and promotes cancer cells to adapt to tumor microenvironment. Therapeutic modalities targeting protein acetylation are a potential therapeutic strategy. This article discussed the roles of protein acetylation in tumor pathology and therapeutic drugs targeting protein acetylation, which offers the contributions of protein acetylation in clarification of carcinogenesis, and discovery of therapeutic drugs for cancers, and lays the foundation for precision medicine in oncology.

In situ delivery of biobutyrate by probiotic Escherichia coli for cancer therapy

Butyrate has a bioactive function to reduce carcinogenesis. To achieve targeted cancer therapy, this study developed bacterial cancer therapy (BCT) with butyrate as a payload. By metabolic engineering, Escherichia coli Nissle 1917 (EcN) was reprogrammed to synthesize butyrate (referred to as biobutyrate) and designated EcN-BUT. The adopted strategy includes construction of a synthetic pathway for biobutyrate and the rational design of central metabolism to increase the production of biobutyrate at the expense of acetate. With glucose, EcN-BUT produced primarily biobutyrate under the hypoxic condition. Furthermore, human colorectal cancer cell was administrated with the produced biobutyrate. It caused the cell cycle arrest at the G1 phase and induced the mitochondrial apoptosis pathway independent of p53. In the tumor-bearing mice, the injected EcN-BUT exhibited tumor-specific colonization and significantly reduced the tumor volume by 70%. Overall, this study opens a new avenue for BCT based on biobutyrate.

Correlation between the expression of cancer stem cell marker BMI1 and glioma prognosis

B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) appears to be essential for promoting certain types of cancer, and its inhibition effectively reduced the stemness of cancer cells. Therefore, this study aimed to investigate the potential role of BMI1 in glioma. To this end, we first investigated BMI1 expression in brain tumors using microarray datasets in ONCOMINE, which indicated that BMI1 levels were not commonly increased in clinical brain tumors. Moreover, survival plots in PROGgeneV2 also showed that BMI1 expression was not significantly associated with reduced survival in glioma patients. Interestingly, stressful serum deprivation and anchorage independence growth conditions led to an increased BMI1 expression in glioma cells. A stress-responsive pathway, HDAC/Sp1, was further identified to regulate BMI1 expression. The HDAC inhibitor vorinostat (SAHA) prevented Sp1 binding to the BMI1 promoter, leading to a decreased expression of BMI1 and attenuating tumor growth of TMZ-resistant glioma xenografts. Importantly, we further performed survival analysis using PROGgeneV2 and found that an elevated expression of HDAC1,3/Sp1/BMI1 but not BMI1 alone showed an increased risk of death in both high- and low-grade glioma patients. Thus, HDAC-mediated Sp1 deacetylation is critical for BMI1 regulation to attenuate stress- and therapy-induced death in glioma cells, and the HDAC/Sp1 axis is more important than BMI1 and appears as a therapeutic target to prevent recurrence of malignant glioma cells persisting after primary therapy.

Selective inhibition of HDAC6 regulates expression of the oncogenic driver EWSR1-FLI1 through the EWSR1 promoter in Ewing sarcoma

Ewing sarcoma (EWS) is an aggressive bone and soft tissue tumor of children and young adults in which the principal driver is a fusion gene, EWSR1-FLI1. Although the essential role of EWSR1-FLI1 protein in the regulation of oncogenesis, survival, and tumor progression processes has been described in-depth, little is known about the regulation of chimeric fusion-gene expression. Here, we demonstrate that the active nuclear HDAC6 in EWS modulates the acetylation status of specificity protein 1 (SP1), consequently regulating the SP1/P300 activator complex binding to EWSR1 and EWSR1-FLI1 promoters. Selective inhibition of HDAC6 impairs binding of the activator complex SP1/P300, thereby inducing EWSR1-FLI1 downregulation and significantly reducing its oncogenic functions. In addition, sensitivity of EWS cell lines to HDAC6 inhibition is higher than other tumor or non-tumor cell lines. High expression of HDAC6 in primary EWS tumor samples from patients correlates with a poor prognosis in two independent series accounting 279 patients. Notably, a combination treatment of a selective HDAC6 and doxorubicin (a DNA damage agent used as a standard therapy of EWS patients) dramatically inhibits tumor growth in two EWS murine xenograft models. These results could lead to suitable and promising therapeutic alternatives for patients with EWS.

Transcription factors in colorectal cancer: molecular mechanism and therapeutic implications

Colorectal cancer (CRC) is a major cause of cancer mortality worldwide, however, the molecular mechanisms underlying the pathogenesis of CRC remain largely unclear. Recent studies have revealed crucial roles of transcription factors in CRC development. Transcription factors essential for the regulation of gene expression by interacting with transcription corepressor/enhancer complexes and they orchestrate downstream signal transduction. Deregulation of transcription factors is a frequent occurrence in CRC, and the accompanying drastic changes in gene expression profiles play fundamental roles in multistep process of tumorigenesis, from cellular transformation, disease progression to metastatic disease. Herein, we summarized current and emerging key transcription factors that participate in CRC tumorigenesis, and highlighted their oncogenic or tumor suppressive functions. Moreover, we presented critical transcription factors of CRC, emphasized the major molecular mechanisms underlying their effect on signal cascades associated with tumorigenesis, and summarized of their potential as molecular biomarkers for CRC prognosis therapeutic response, as well as drug targets for CRC treatment. A better understanding of transcription factors involved in the development of CRC will provide new insights into the pathological mechanisms and reveal novel prognostic biomarkers and therapeutic strategies for CRC.

Increased activation of HDAC1/2/6 and Sp1 underlies therapeutic resistance and tumor growth in glioblastoma

BACKGROUND

Glioblastoma is associated with poor prognosis and high mortality. Although the use of first-line temozolomide can reduce tumor growth, therapy-induced stress drives stem cells out of quiescence, leading to chemoresistance and glioblastoma recurrence. The specificity protein 1 (Sp1) transcription factor is known to protect glioblastoma cells against temozolomide; however, how tumor cells hijack this factor to gain resistance to therapy is not known.

METHODS

Sp1 acetylation in temozolomide-resistant cells and stemlike tumorspheres was analyzed by immunoprecipitation and immunoblotting experiments. Effects of the histone deacetylase (HDAC)/Sp1 axis on malignant growth were examined using cell proliferation-related assays and in vivo experiments. Furthermore, integrative analysis of gene expression with chromatin immunoprecipitation sequencing and the recurrent glioblastoma omics data were also used to further determine the target genes of the HDAC/Sp1 axis.

RESULTS

We identified Sp1 as a novel substrate of HDAC6, and observed that the HDAC1/2/6/Sp1 pathway promotes self-renewal of malignancy by upregulating B cell-specific Mo-MLV integration site 1 (BMI1) and human telomerase reverse transcriptase (hTERT), as well as by regulating G2/M progression and DNA repair via alteration of the transcription of various genes. Importantly, HDAC1/2/6/Sp1 activation is associated with poor clinical outcome in both glioblastoma and low-grade gliomas. However, treatment with azaindolyl sulfonamide, a potent HDAC6 inhibitor with partial efficacy against HDAC1/2, induced G2/M arrest and senescence in both temozolomide-resistant cells and stemlike tumorspheres.

CONCLUSION

Our study uncovers a previously unknown regulatory mechanism in which the HDAC6/Sp1 axis induces cell division and maintains the stem cell population to fuel tumor growth and therapeutic resistance.

The transcription factor Sp1 modulates RNA polymerase III gene transcription by controlling BRF1 and GTF3C2 expression in human cells

Specificity protein 1 (Sp1) is an important transcription factor implicated in numerous cellular processes. However, whether Sp1 is involved in the regulation of RNA polymerase III (Pol III)-directed gene transcription in human cells remains unknown. Here, we first show that filamin A (FLNA) represses Sp1 expression as well as expression of TFIIB-related factor 1 (BRF1) and general transcription factor III C subunit 2 (GTF3C2) in HeLa, 293T, and SaOS2 cell lines stably expressing FLNA-silencing shRNAs. Both BRF1 promoter 4 (BRF1P4) and GTF3C2 promoter 2 (GTF3C2P2) contain putative Sp1-binding sites, suggesting that Sp1 affects Pol III gene transcription by regulating BRF1 and GTF3C2 expression. We demonstrate that Sp1 knockdown inhibits Pol III gene transcription, BRF1 and GTF3C2 expression, and the proliferation of 293T and HeLa cells, whereas Sp1 overexpression enhances these activities. We obtained a comparable result in a cell line in which both FLNA and Sp1 were depleted. These results indicate that Sp1 is involved in the regulation of Pol III gene transcription independently of FLNA expression. Reporter gene assays showed that alteration of Sp1 expression affects BRF1P4 and GTF3C2P2 activation, suggesting that Sp1 modulates Pol III-mediated gene transcription by controlling BRF1 and GTF3C2 gene expression. Further analysis revealed that Sp1 interacts with and thereby promotes the occupancies of TATA box-binding protein, TFIIAα, and p300 at both BRF1P4 and GTF3C2P2. These findings indicate that Sp1 controls Pol III-directed transcription and shed light on how Sp1 regulates cancer cell proliferation.

Linking aberrant chromatin features in chronic lymphocytic leukemia to transcription factor networks

In chronic lymphocytic leukemia (CLL), a diverse set of genetic mutations is embedded in a deregulated epigenetic landscape that drives cancerogenesis. To elucidate the role of aberrant chromatin features, we mapped DNA methylation, seven histone modifications, nucleosome positions, chromatin accessibility, binding of EBF1 and CTCF, as well as the transcriptome of B cells from CLL patients and healthy donors. A globally increased histone deacetylase activity was detected and half of the genome comprised transcriptionally downregulated partially DNA methylated domains demarcated by CTCF. CLL samples displayed a H3K4me3 redistribution and nucleosome gain at promoters as well as changes of enhancer activity and enhancer linkage to target genes. A DNA binding motif analysis identified transcription factors that gained or lost binding in CLL at sites with aberrant chromatin features. These findings were integrated into a gene regulatory enhancer containing network enriched for B‐cell receptor signaling pathway components. Our study predicts novel molecular links to targets of CLL therapies and provides a valuable resource for further studies on the epigenetic contribution to the disease.

Phenethyl Isothiocyanate Exposure Promotes Oxidative Stress and Suppresses Sp1 Transcription Factor in Cancer Stem Cells

Aldehyde dehydrogenase 1 (ALDH1) is a cytosolic marker of cancer stem cells (CSCs), which are a sub-population within heterogeneous tumor cells. CSCs associate with therapy-resistance, self-renewal, malignancy, tumor-relapse, and reduced patient-survival window. ALDH1-mediated aldehyde scavenging helps CSCs to survive a higher level of oxidative stress than regular cancer cells. Cruciferous vegetable-derived phenethyl isothiocyanate (PEITC) selectively induces reactive oxygen species (ROS), leading to apoptosis of cancer cells, but not healthy cells. However, this pro-oxidant role of PEITC in CSCs is poorly understood and is investigated here. In a HeLa CSCs model (hCSCs), the sphere-culture and tumorsphere assay showed significantly enriched ALDH^hi CSCs from HeLa parental cells (p < 0.05). Aldefluor assay and cell proliferation assay revealed that PEITC treatments resulted in a reduced number of ALDH^hi hCSCs in a concentration-dependent manner (p < 0.05). In the ROS assay, PEITC promoted oxidative stress in hCSCs (p ≤ 0.001). Using immunoblotting and flow cytometry techniques, we reported that PEITC suppressed the cancer-associated transcription factor (Sp1) and a downstream multidrug resistance protein (P-glycoprotein) (both, p < 0.05). Furthermore, PEITC-treatment of hCSCs, prior to xenotransplantation in mice, lowered the in vivo tumor-initiating potential of hCSCs. In summary, PEITC treatment suppressed the proliferation of ALDH1 expressing cancer stem cells as well as key factors that are involved with drug-resistance, while promoting oxidative stress and apoptosis in hCSCs.

Elevated histone H3 acetylation and loss of the Sp1-HDAC1 complex de-repress the GM2-synthase gene in renal cell carcinoma

GM2-synthase produces sialic acid-containing glycosphingolipids called gangliosides, and its mRNA overexpression and the gangliosides it generates are linked to tumor progression, migration, and suppression of tumor-specific host immune responses. However, the mechanism underlying GM2-synthase de-repression in renal cell carcinoma (RCC) is poorly understood. Here, we demonstrate that higher GM2-synthase mRNA expression levels in various cancer cells and in human RCC tumors correlate with higher histone acetylation levels (H3K9, H3K14, or both) at region +38/+187 relative to the transcription start site (TSS) of the GM2-synthase gene than in normal kidney epithelial (NKE) cells or healthy adjacent tissues. An increase in GM2-synthase mRNA expression in cells treated with a histone deacetylase (HDAC) inhibitor was accompanied by increased histone acetylation levels at this promoter region. DNA methylation around the TSS was absent in both RCC cell lines and NKE cells. Of note, both the transcription factor Sp1 and corepressor HDAC1 associated with the +38/+187 region when the GM2-synthase gene was repressed in NKE and tumor-adjacent tissues, indicating plausible site-specific repressive roles of HDAC1 and Sp1 in GM2-synthase mRNA expression. Site-directed mutagenesis of the Sp1-binding site within the +38/+187 region relieved repressed luciferase activity of this region by limiting HDAC1 recruitment. Moreover, Sp1 or HDAC1 knock down increased GM2-synthase transcription, and butyrate-mediated activation of GM2-synthase mRNA expression in SK-RC-45 cells was accompanied by Sp1 and HDAC1 loss from the +38/+187 region. Taken together, we have identified an epigenetic mechanism for the de-repression of the GM2-synthase gene in RCC.

Silencing of Transcription Factor Sp1 Promotes SN1 Transporter Regulation by Ammonia in Mouse Cortical Astrocytes

The involvement of the astrocytic SN1 (SNAT3) transporter in ammonia-induced l-glutamine retention was recently documented in mouse-cultured astrocytes. Here we investigated the involvement of specificity protein 1 (Sp1) transcription factor in SN1 regulation in ammonium chloride (“ammonia”)-treated astrocytes. Sp1 expression and its cellular localization were determined using real-time qPCR, Western blot, and confocal microscopy. Sp1 binding to Snat3 promoter was analyzed by chromatin immunoprecipitation. The role of Sp1 in SN1 expression and SN1-mediated [³H]glutamine uptake in ammonia-treated astrocytes was verified using siRNA and mithramycin A. The involvement of protein kinase C (PKC) isoforms in Sp1 level/phosphorylation status was verified using siRNA technology. Sp1 translocation to the nuclei and its enhanced binding to the Snat3 promoter, along with Sp1 dependence of system N-mediated [³H]glutamine uptake, were observed in astrocytes upon ammonia exposure. Ammonia decreased the level of phosphorylated Sp1, and the effect was reinforced by long-term incubation with PKC modulator, phorbol 12-myristate 13-acetate, which is a treatment likely to dephosphorylate Sp1. Furthermore, silencing of the PKCδ isoform appears to enhance the ammonia effect on the Sp1 level. Collectively, the results demonstrate the regulatory role of Sp1 in regulation of SN1 expression and activity in ammonia-treated astrocytes and implicate altered Sp1 phosphorylation status in this capacity.

Effect of Sodium Butyrate on LHX1 mRNA Expression as a Transcription Factor of HDAC8 in Human Colorectal Cancer Cell Lines

BACKGROUND

LHX1 is an important transcription factor for the HDAC8 gene. The aim of this study was to investigate the effect of Sodium Butyrate (SB), as a histone deacetylase inhibitor, on the expression of LHX1 gene in colorectal cancer cell lines.

METHODS

HT-29 and HCT-116 cell lines were treated with 6.25 to 200 mM concentrations of SB at 24, 48, and 72 hr. The cytotoxicity effect on cell viability was evaluated by MTT assay. The 50% Inhibiting Concentration (IC₅₀) was determined graphically. Quantitative real-time PCR was performed to investigate the LHX1 mRNA expression level.

RESULTS

Our study revealed that SB inhibited the proliferation of these cell lines in a concentration and time-dependent manner. The IC₅₀ values for HT-29 cell line were 65, 18.6, and 9.2 mM after 24, 48, and 72 hr of treatment, respectively. The IC₅₀ values for HCT-116 cell line were 35.5, 9.6, and 10 mM after 24, 48, and 72 hr of treatment, respectively. Furthermore, real-time PCR findings demonstrated that the LHX1 mRNA expression in treated HT-29 cell line significantly increased in comparison with untreated cells (p<0.05). However, in treated HCT-116 cell line, SB led to a significant decrease in the level of LHX1 mRNA (p<0.05), as compared to untreated cells.

CONCLUSION

In this study, different effects of SB on LHX1 mRNA expression level were revealed in two distinct human colorectal cancer cell lines.

The histone deacetylase inhibitor panobinostat exerts anticancer effects on esophageal squamous cell carcinoma cells by inducing cell cycle arrest

Esophageal squamous cell carcinoma (ESCC) is a common malignancy without effective therapy. Histone deacetylase inhibitors (HDACIs) have been demonstrated as an emerging class of anticancer drugs for a range of haematological and solid tumours. However, the effect of HDACIs has not yet been investigated on ESCC cells. In this study, HDACIs were initially considered to have anticancer activity for ESCC, due to the high expression of HDAC genes in ESCC cell lines by analysing expression data of 27 ESCC cell lines from the Broad-Novartis Cancer Cell Line Encyclopedia. Next, we used five ESCC cell lines and one normal immortalized esophageal epithelial cell line to screen three HDACIs, panobinostat (LBH589), vorinostat (SAHA), and trichostatin A (TSA), for the ability to inhibit growth. Here, we report that LBH589 more effectively suppressed cell proliferation of ESCC cell lines, in a dose-dependent manner, than TSA and SAHA, as well as had lower toxicity against the SHEE normal immortalized esophageal epithelial cell line. Further experiments indicated that LBH589 treatment significantly inhibited TP53 (mutated TP53) expression, both at the mRNA and protein level, and simultaneously increased p21 and decreased cyclin D1 expression. Taken together, we propose that LBH589 inhibits ESCC cell proliferation mainly through inducing cell cycle arrest by increasing p21 and decreasing cyclin D1 in a p53-independent manner. SIGNIFICANCE OF THE STUDY: In this study, the antitumor activity of HDACIs LBH589, SAHA, and TSA on ESCC was characterized, with LBH589 displaying the most potent anti-proliferative activity while not harming normal immortalized esophageal epithelial cells. Furthermore, we propose that LBH589 exerts its anti-proliferative effect by inducing cell cycle arrest. The ability to specifically target cancer cells indicates therapeutic potential for use of LBH589 in the treatment of ESCC.

MicroRNA-382 inhibits cell growth and migration in colorectal cancer by targeting SP1

BACKGROUND

Emerging evidence showed that microRNAs (miRs) play critical roles in human cancers by functioning as either tumor suppressor or oncogene. MIR-382 was found to function as tumor suppressor in certain cancers. However, the role of MIR-382 in colorectal cancer (CRC) is largely unknown. Specificity protein 1 (SP1) is highly expressed in several cancers including CRC and is correlated with poor prognosis, but it is unclear whether or not MIR-382 can regulate the expression of SP1.

METHODS

MIR-382 expression level was measured by reverse transcription-quantitative polymerase chain reaction. The connection between MIR-382 and SP1 was validated by luciferase activity reporter assay and western blot assay. Cell counting kit-8 assay and wound-healing assay were conducted to investigate the biological functions of MIR-382 in CRC.

RESULTS

In this study, we found MIR-382 expression was downregulated in CRC tissues and cell lines, and the transfection of MIR-382 mimic decreased cell growth and migration. Furthermore, we identified SP1 was a direct target of MIR-382. Overexpression of MIR-382 decreased the expression of SP1, whereas MIR-382 knockdown promoted SP1 expression. We also observed an inversely correlation between MIR-382 and SP1 in CRC tissues. Additionally, we showed that knockdown of SP1 inhibited cell growth and migration and attenuated the effect of MIR-382 inhibitor on cell behaviors.

CONCLUSIONS

In conclusion, the present study describes a potential mechanism underlying a MIR-382/SP1 link contributing to CRC development. Thus, MIR-382 may be able to be developed as a novel treatment target for CRC.

Regulation of Transcription Factor SP1 by the β-Catenin Destruction Complex Modulates Wnt Response

The ubiquitous transcription factor specificity protein 1 (SP1) is heavily modified posttranslationally. These modifications are critical for switching its functions and modulation of its transcriptional activity and DNA binding and stability. However, the mechanism governing the stability of SP1 by cellular signaling pathways is not well understood. Here, we provide biochemical and functional evidence that SP1 is an integral part of the Wnt signaling pathway. We identified a phosphodegron motif in SP1 that is specific to mammals. In the absence of Wnt signaling, glycogen synthase kinase 3β (GSK3β)-mediated phosphorylation and β-TrCP E3 ubiquitin ligase-mediated ubiquitination are required to induce SP1 degradation. When Wnt signaling is on, SP1 is stabilized in a β-catenin-dependent manner. SP1 directly interacts with β-catenin, and Wnt signaling induces the stabilization of SP1 by impeding its interaction with β-TrCP and axin1, components of the destruction complex. Wnt signaling suppresses ubiquitination and subsequent proteosomal degradation of SP1. Furthermore, SP1 regulates Wnt-dependent stability of β-catenin and their mutual stabilization is critical for target gene expression, suggesting a feedback mechanism. Upon stabilization, SP1 and β-catenin cooccupy the promoters of TCFL2/β-catenin target genes. Collectively, this study uncovers a direct link between SP1 and β-catenin in the Wnt signaling pathway.

Inhibition of HDACs-EphA2 Signaling Axis with WW437 Demonstrates Promising Preclinical Antitumor Activity in Breast Cancer

Histone deacetylase inhibitors (HDACi) are small molecules targeting epigenetic enzymes approved for hematologic neoplasms, which have also demonstrated clinical activities in solid tumors. In our present study, we screened our internal compound library and discovered a novel HDACi, WW437, with potent anti-breast cancer ability in vitro and in vivo. WW437 significantly inhibited phosphorylated EphA2 and EphA2 expression. Further study demonstrated WW437 blocked HDACs-EphA2 signaling axis in breast cancer. In parallel, we found that EphA2 expression positively correlates with breast cancer progression; and combined use of WW437 and an EphA2 inhibitor (ALW-II-41-27) exerted more remarkable effect on breast cancer growth than either drug alone. Our findings suggested inhibition of HDACs-EphA2 signaling axis with WW437 alone or in combination with other agents may be a promising therapeutic strategy for advanced breast cancer.

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WW437 is a novel HDACi, which displays potent anticancer activity in breast cancer.

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HDACs-EphA2 signaling axis represents a novel target in breast cancer.

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WW437 is a promising therapeutic agent for advanced breast cancer, alone or in combination with EphA2 inhibitor.

Histone deacetylase inhibitors (HDACi) are small molecules targeting epigenetic enzymes approved for cutaneous T-cell lymphoma (CTCL), peripheral T-cell lymphoma (PTCL) and multiple myeloma (MM) treatment, which have also demonstrated clinical activities in solid tumors, including lung cancer and breast cancer. Herein we report a novel HDACi WW437, which displays potent anticancer activity in both cultured cancer cells and xenograft models. Importantly, our work reveals WW437 significantly blocked the HDACs-EphA2 signaling axis in breast cancer. WW437 exhibited significant inhibitory effects on tumor growth and metastases with little toxicity, and tumors from treated mice showed decreased EphA2 expression, suggesting that EphA2 may be a useful biomarker of response to WW437. We also found that EphA2 expression positively correlates with tumor progression in aggressive breast cancer.

The interferon-stimulated gene TRIM22: A double-edged sword in HIV-1 infection

Infection of target cells by the human immunodeficiency virus type-1 (HIV-1) is hampered by constitutively expressed host cell proteins preventing or curtailing virus replication and therefore defined as "restriction factors". Among them, members of the tripartite motif (TRIM) family have emerged as important players endowed with both antiviral effects and modulatory capacity of the innate immune response. TRIM5α and TRIM19 (i.e. promyelocytic leukemia, PML) are among the best-characterized family members; however, in this review we will focus on the potential role of another family member, i.e. TRIM22, a factor strongly induced by interferon stimulation, in HIV infection in vivo and in vitro in the context of its broader antiviral effects. We will also focus on the potential role of TRIM22 in HIV-1-infected individuals speculating on its dual role in controlling virus replication and more complex role in chronic infection. At the molecular levels, we will review the evidence in favor of a relevant role of TRIM22 as epigenetic inhibitor of HIV-1 transcription acting by preventing the binding of the host cell transcription factor Sp1 to the viral promoter. These evidences suggest that TRIM22 should be considered a potential new player in either the establishment or maintenance of HIV-1 reservoirs of latently infected cells unaffected by combination antiretroviral therapy.

A Novel Hydroxamate-Based Compound WMJ-J-09 Causes Head and Neck Squamous Cell Carcinoma Cell Death via LKB1-AMPK-p38MAPK-p63-Survivin Cascade

Growing evidence shows that hydroxamate-based compounds exhibit broad-spectrum pharmacological properties including anti-tumor activity. However, the precise mechanisms underlying hydroxamate derivative-induced cancer cell death remain incomplete understood. In this study, we explored the anti-tumor mechanisms of a novel aliphatic hydroxamate-based compound, WMJ-J-09, in FaDu head and neck squamous cell carcinoma (HNSCC) cells. WMJ-J-09 induced G2/M cell cycle arrest and apoptosis in FaDu cells. These actions were associated with liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (p38MAPK) activation, transcription factor p63 phosphorylation, as well as modulation of p21 and survivin. LKB1-AMPK-p38MAPK signaling blockade reduced WMJ-J-09’s enhancing effects in p63 phosphorylation, p21 elevation and survivin reduction. Moreover, WMJ-J-09 caused an increase in α-tubulin acetylation and interfered with microtubule assembly. Furthermore, WMJ-J-09 suppressed the growth of subcutaneous FaDu xenografts in vivo. Taken together, WMJ-J-09-induced FaDu cell death may involve LKB1-AMPK-p38MAPK-p63-survivin signaling cascade. HDACs inhibition and disruption of microtubule assembly may also contribute to WMJ-J-09’s actions in FaDu cells. This study suggests that WMJ-J-09 may be a potential lead compound and warrant the clinical development in the treatment of HNSCC.

Occludin regulates glucose uptake and ATP production in pericytes by influencing AMP-activated protein kinase activity

Energetic regulation at the blood-brain barrier is critical for maintaining its integrity, transport capabilities, and brain demands for glucose. However, the underlying mechanisms that regulate these processes are still poorly explored. We recently characterized the protein occludin as a NADH oxidase and demonstrated its influence on the expression and activation of the histone deacetylase SIRT-1. Because SIRT-1 works in concert with AMP-activated protein kinase (AMPK) (AMPK), we investigated the impact of occludin on this metabolic switch. Here we show that in blood-brain barrier pericytes, occludin promotes AMPK expression and activation, influencing the expression of glucose transporters GLUT-1 and GLUT-4, glucose uptake, and ATP content. Furthermore, occludin expression, AMP-dependent protein kinase activity, and glucose uptake were altered under inflammatory (TNFα) and infectious (HIV) conditions. We also show that pericytes share glucose and mitochondria with astrocytes, and that occludin levels modify the ability of pericytes to share those energetic resources. In addition, we demonstrate that murine mitochondria can be transferred from live brain microvessels to energetically impaired human astrocytes, promoting their survival. Our findings demonstrate that occludin plays an important role in blood-brain barrier pericyte metabolism by influencing AMPK protein kinase activity, glucose uptake, ATP production, and by regulating the ability of pericytes to interact metabolically with astrocytes.

Dietary metabolites derived from gut microbiota: critical modulators of epigenetic changes in mammals

The mammalian gastrointestinal tract harbors trillions of commensal microorganisms, collectively known as the microbiota. The microbiota is a critical source of environmental stimuli and, thus, has a tremendous impact on the health of the host. The microbes within the microbiota regulate homeostasis within the gut, and any alteration in their composition can lead to disorders that include inflammatory bowel disease, allergy, autoimmune disease, diabetes, mental disorders, and cancer. Hence, restoration of the gut flora following changes or imbalance is imperative for the host. The low-molecular-weight compounds and nutrients such as short-chain fatty acids, polyamines, polyphenols, and vitamins produced by microbial metabolism of nondigestible food components in the gut actively participate in various epigenomic mechanisms that reprogram the genome by altering the transcriptional machinery of a cell in response to environmental stimuli. These epigenetic modifications are caused by a set of highly dynamic enzymes, notably histone acetylases, deacetylases, DNA methylases, and demethylases, that are influenced by microbial metabolites and other environmental cues. Recent studies have shown that host expression of histone acetylases and histone deacetylases is important for regulating communication between the intestinal microbiota and the host cells. Histone acetylases and deacetylases influence the molecular expression of genes that affect not only physiological functions but also behavioral shifts that occur via neuroepigenetic modifications of genes. The underlying molecular mechanisms, however, have yet to be fully elucidated and thus provide a new area of research. The present review provides insights into the current understanding of the microbiota and its association with mammalian epigenomics as well as the interaction of pathogens and probiotics with host epigenetic machinery.

TIP60 represses telomerase expression by inhibiting Sp1 binding to the TERT promoter

HIV1-TAT interactive protein (TIP60) is a haploinsufficient tumor suppressor. However, the potential mechanisms endowing its tumor suppressor ability remain incompletely understood. It plays a vital role in virus-induced cancers where TIP60 down-regulates the expression of human papillomavirus (HPV) oncoprotein E6 which in turn destabilizes TIP60. This intrigued us to identify the role of TIP60, in the context of a viral infection, where it is targeted by oncoproteins. Through an array of molecular biology techniques such as Chromatin immunoprecipitation, expression analysis and mass spectrometry, we establish the hitherto unknown role of TIP60 in repressing the expression of the catalytic subunit of the human telomerase complex, TERT, a key driver for immortalization. TIP60 acetylates Sp1 at K639, thus inhibiting Sp1 binding to the TERT promoter. We identified that TIP60-mediated growth suppression of HPV-induced cervical cancer is mediated in part due to TERT repression through Sp1 acetylation. In summary, our study has identified a novel substrate for TIP60 catalytic activity and a unique repressive mechanism acting at the TERT promoter in virus-induced malignancies.

WMJ-8-B, a novel hydroxamate derivative, induces MDA-MB-231 breast cancer cell death via the SHP-1-STAT3-survivin cascade

BACKGROUND AND PURPOSE

Histone deacetylase (HDAC) inhibitors have been demonstrate to have broad-spectrum anti-tumour properties and have attracted lots of attention in the field of drug discovery. However, the underlying anti-tumour mechanisms of HDAC inhibitors remain incompletely understood. In this study, we aimed to characterize the underlying mechanisms through which the novel hydroxamate-based HDAC inhibitor, WMJ-8-B, induces the death of MDA-MB-231 breast cancer cells.

EXPERIMENTAL APPROACH

Effects of WMJ-8-B on cell viability, cell cycle distribution, apoptosis and signalling molecules were analysed by the MTT assay, flowcytometric analysis, immunoblotting, reporter assay, chromatin immunoprecipitation analysis and use of siRNAs. A xenograft model was used to determine anti-tumour effects of WMJ-8-B in vivo.

KEY RESULTS

WMJ-8-B induced survivin reduction, G2/M cell cycle arrest and apoptosis in MDA-MB-231 cells. STAT3 phosphorylation, transactivity and its binding to the survivin promoter region were reduced in WMJ-8-B-treated cells. WMJ-8-B activated the protein phosphatase SHP-1 and when SHP-1 signalling was blocked, the effects of WMJ-8-B on STAT3 phosphorylation and survivin levels were abolished. However, WMJ-8-B increased the transcription factor Sp1 binding to the p21 promoter region and enhanced p21 levels. Moreover, WMJ-8-B induced α-tubulin acetylation and disrupted microtubule assembly. Inhibition of HDACs was shown to contribute to WMJ-8-B's actions. Furthermore, WMJ-8-B suppressed the growth of MDA-MB-231 xenografts in mammary fat pads in vivo.

CONCLUSIONS AND IMPLICATIONS

The SHP-1-STAT3-survivin and Sp1-p21 cascades are involved in WMJ-8-B-induced MDA-MB-231 breast cancer cell death. These results also indicate the potential of WMJ-8-B as a lead compound for treatment of breast cancer and warrant its clinical development.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Epi-drugs in combination with immunotherapy: a new avenue to improve anticancer efficacy

Immune checkpoint factors, such as programmed cell death protein-1/2 (PD-1, PD-2) or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) receptors, are targets for monoclonal antibodies (MAbs) developed for cancer immunotherapy. Indeed, modulating immune inhibitory pathways has been considered an important breakthrough in cancer treatment. Although immune checkpoint blockade therapy used to treat malignant diseases has provided promising results, both solid and haematological malignancies develop mechanisms that enable themselves to evade the host immune system. To overcome some major limitations and ensure safety in patients, recent strategies have shown that combining epigenetic modulators, such as inhibitors of histone deacetylases (HDACi) or DNA methyltransferases (DNMTi), with immunotherapeutics can be useful. Preclinical data generated using mouse models strongly support the feasibility and effectiveness of the proposed approaches. Indeed, co-treatment with pan- or class I-selective HDACi or DNMTi improved beneficial outcomes in both in vitro and in vivo studies. Based on the evidence of a pivotal role for HDACi and DNMTi in modulating various components belonging to the immune system, recent clinical trials have shown that both HDACi and DNMTi strongly augmented response to anti-PD-1 immunotherapy in different tumour types. This review describes the current strategies to increase immunotherapy responses, the effects of HDACi and DNMTi on immune modulation, and the advantages of combinatorial therapy over single-drug treatment.

Specificity protein 1: Its role in colorectal cancer progression and metastasis

Specificity protein 1 (Sp1) is a widely expressed transcription factor that plays an important role in the promotion of oncogenes required for tumor survival, progression and metastasis. Sp1 is highly expressed in several cancers including colorectal cancer (CRC) and is related to poor prognosis. Therefore, targeting Sp1 is a rational for CRC therapy. In this review, we will recapitulate the current understanding of Sp1 signaling, its molecular mechanisms, and its potential involvement in CRC growth, progression and metastasis. We will also discuss the current therapeutic drugs for CRC and their mechanism of action via Sp1.

The transcriptional modulator Ifrd1 controls PGC-1α expression under short-term adrenergic stimulation in brown adipocytes

Sympathetic tone activates the function of classical brown adipocytes, which constitutively exist in the brown adipose tissue (BAT), and inducible brown adipocytes (so-called beige adipocytes), which sporadically reside within the white adipose tissue (WAT). Here we identified the transcriptional modulator interferon-related developmental regulator 1 (Ifrd1) as a negative regulator of thermogenic and mitochondrial gene expression in brown adipocytes. Ifrd1 expression was markedly induced by cold exposure and administration of CL-316243 (a β3 adrenergic agonist) in interscapular brown adipose and inguinal subcutaneous WATs, but not in epididymal visceral WAT, in vivo. Adrenergic stimulation also induced Ifrd1 expression in brown adipocytes in a cAMP responsive element binding protein-dependent manner in vitro. CL-316243 injection markedly elevated thermogenic and mitochondrial gene expression, including peroxisome proliferator-activated receptor γ coactivator 1α (Pgc1a) in the subcutaneous WAT of Ifrd1 knockout mice compared with gene expression in wild-type mice. Pgc1a promoter activity enhanced by the transcription factor specificity protein 1 (Sp1) was markedly repressed by co-introduction of Ifrd1 in brown adipocytes, whereas the repression was markedly prevented by the addition of trichostatin A, a histone deacetylase inhibitor. Moreover, adrenergic stimulation induced complex formation between Ifrd1, Sp1 and mSIN3B, which is a component of the SIN complex containing histone deacetylase, in brown adipocytes. These findings, therefore, suggest that Ifrd1 could be a pivotal negative regulator of sympathetic regulation of thermogenic and mitochondrial gene expression in brown adipocytes by interacting with Sp1 and the mSIN3 complex.

Platelet activating factor-induced expression of p21 is correlated with histone acetylation

Ultraviolet (UV)-irradiated keratinocytes secrete the lipid mediator of inflammation, platelet-activating factor (PAF). PAF plays an essential role in UV-induced immune suppression and skin cancer induction. Dermal mast cell migration from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced PAF activates mast cell migration by up-regulating mast cell CXCR4 surface expression. Recent findings indicate that PAF up-regulates CXCR4 expression via histone acetylation. UV-induced PAF also activates cell cycle arrest and disrupts DNA repair, in part by increasing p21 expression. Do epigenetic alterations play a role in p21 up-regulation? Here we show that PAF increases Acetyl-CREB-binding protein (CBP/p300) histone acetyltransferase expression in a time and dose-dependent fashion. Partial deletion of the HAT domain in the CBP gene, blocked these effects. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the p21 promoter. PAF-treatment had no effect on other acetylating enzymes (GCN5L2, PCAF) indicating it is not a global activator of histone acetylation. This study provides further evidence that PAF activates epigenetic mechanisms to affect important cellular processes, and we suggest this bioactive lipid can serve as a link between the environment and the epigenome.

The Role of the Ubiquitously Expressed Transcription Factor Sp1 in Tissue-specific Transcriptional Regulation and in Disease

Sp1 belongs to the 26 member strong Sp/KLF family of transcription factors. It is a paradigm for a ubiquitously expressed transcription factor and is involved in regulating the expression of genes associated with a wide range of cellular processes in mammalian cells. Sp1 can interact with a range of proteins, including other transcription factors, members of the transcription initiation complex and epigenetic regulators, enabling tight regulation of its target genes. In this review, we discuss the mechanisms involved in Sp1-mediated transcriptional regulation, as well as how a ubiquitous transcription factor can be involved in establishing a tissue-specific pattern of gene expression and mechanisms by which its activity may be regulated. We also consider the role of Sp1 in human diseases, such as cancer.

Low-density lipoprotein upregulate SR-BI through Sp1 Ser702 phosphorylation in hepatic cells

Scavenger receptor class B type I (SR-BI) is one of the key proteins in the process of reverse cholesterol transport (RCT), and its major function is to uptake high density lipoprotein (HDL) cholesterol from plasma into liver cells. The regulation of SR-BI expression is important for controlling serum lipid content and reducing the risks of cardiovascular diseases. Here we found that SR-BI expression was significantly increased by LDL in vivo and in vitro, and the transcription factor specific protein 1 (Sp1) plays a critical role in this process. Results from co-immunoprecipitation experiments indicate that the activation of SR-BI was associated with Sp1-recruited protein complexes in the promoter region of SR-BI, where histone acetyltransferase p300 was recruited and histone deacetylase HDAC1 was dismissed. As a result, histone acetylation increased, leading to activation of SR-BI transcription. With further investigation, we found that LDL phosphorylated Sp1 through ERK1/2 pathway, which affected Sp1 protein complexes formation in SR-BI promoter. Using mass spectrometry and site directed mutagenesis, a new Sp1 phosphorylation site Ser702 was defined to be associated with Sp1-HDAC1 interaction and may be important in SR-BI activation, shedding light on the knowledge of delicate mechanism of hepatic HDL receptor SR-BI gene modulation by LDL.

HDAC Inhibitors as Epigenetic Regulators of the Immune System: Impacts on Cancer Therapy and Inflammatory Diseases

Histone deacetylase (HDAC) inhibitors are powerful epigenetic regulators that have enormous therapeutic potential and have pleiotropic effects at the cellular and systemic levels. To date, HDAC inhibitors are used clinically for a wide variety of disorders ranging from hematopoietic malignancies to psychiatric disorders, are known to have anti-inflammatory properties, and are in clinical trials for several other diseases. In addition to influencing gene expression, HDAC enzymes also function as part of large, multisubunit complexes which have many nonhistone targets, alter signaling at the cellular and systemic levels, and result in divergent and cell-type specific effects. Thus, the effects of HDAC inhibitor treatment are too intricate to completely understand with current knowledge but the ability of HDAC inhibitors to modulate the immune system presents intriguing therapeutic possibilities. This review will explore the complexity of HDAC inhibitor treatment at the cellular and systemic levels and suggest strategies for effective use of HDAC inhibitors in biomedical research, focusing on the ability of HDAC inhibitors to modulate the immune system. The possibility of combining the documented anticancer effects and newly emerging immunomodulatory effects of HDAC inhibitors represents a promising new combinatorial therapeutic approach for HDAC inhibitor treatments.

Histone deacetylation contributes to low extracellular superoxide dismutase expression in human idiopathic pulmonary arterial hypertension

Epigenetic mechanisms, including DNA methylation and histone acetylation, regulate gene expression in idiopathic pulmonary arterial hypertension (IPAH). These mechanisms can modulate expression of extracellular superoxide dismutase (SOD3 or EC-SOD), a key vascular antioxidant enzyme, and loss of vascular SOD3 worsens outcomes in animal models of pulmonary arterial hypertension. We hypothesized that SOD3 gene expression is decreased in patients with IPAH due to aberrant DNA methylation and/or histone deacetylation. We used lung tissue and pulmonary artery smooth muscle cells (PASMC) from subjects with IPAH at transplantation and from failed donors (FD). Lung SOD3 mRNA expression and activity was decreased in IPAH vs. FD. In contrast, mitochondrial SOD (Mn-SOD or SOD2) protein expression was unchanged and intracellular SOD activity was unchanged. Using bisulfite sequencing in genomic lung or PASMC DNA, we found the methylation status of the SOD3 promoter was similar between FD and IPAH. Furthermore, treatment with 5-aza-2'-deoxycytidine did not increase PASMC SOD3 mRNA, suggesting DNA methylation was not responsible for PASMC SOD3 expression. Though total histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity, acetylated histones, and acetylated SP1 were similar between IPAH and FD, treatment with two selective class I HDAC inhibitors increased SOD3 only in IPAH PASMC. Class I HDAC3 siRNA also increased SOD3 expression. Trichostatin A, a pan-HDAC inhibitor, decreased proliferation in IPAH, but not in FD PASMC. These data indicate that histone deacetylation, specifically via class I HDAC3, decreases SOD3 expression in PASMC and HDAC inhibitors may protect IPAH in part by increasing PASMC SOD3 expression.

How do tumor cells respond to HDAC inhibition?

It is now well recognized that mutations, deregulated expression, and aberrant recruitment of epigenetic readers, writers, and erasers are fundamentally important processes in the onset and maintenance of many human tumors. The molecular, biological, and biochemical characteristics of a particular class of epigenetic erasers, the histone deacetylases (HDACs), have been extensively studied and small-molecule HDAC inhibitors (HDACis) have now been clinically approved for the treatment of human hemopoietic malignancies. This review explores our current understanding of the biological and molecular effects on tumor cells following HDACi treatment. The predominant responses include induction of tumor cell death and inhibition of proliferation that in experimental models have been linked to therapeutic efficacy. However, tumor cell-intrinsic responses to HDACi, including modulating tumor immunogenicity have also been described and may have substantial roles in mediating the antitumor effects of HDACi. We posit that the field has failed to fully reconcile the biological consequences of exposure to HDACis with the molecular events that underpin these responses, however progress is being made. Understanding the pleiotrophic activities of HDACis on tumor cells will hopefully fast track the development of more potent and selective HDACi that may be used alone or in combination to improve patient outcomes.

Physiological TLR5 expression in the intestine is regulated by differential DNA binding of Sp1/Sp3 through simultaneous Sp1 dephosphorylation and Sp3 phosphorylation by two different PKC isoforms

Toll-like receptor 5 (TLR5) expression in the intestinal epithelial cells (IECs) is critical to maintain health, as underscored by multiple intestinal and extra-intestinal diseases in mice genetically engineered for IEC-specific TLR5 knockout. A gradient of expression exists in the colonic epithelial cells from the cecum to the distal colon. Intriguingly, an identical gradient for the dietary metabolite, butyrate also exists in the luminal contents. However, both being critical for intestinal homeostasis and immune response, no studies examined the role of butyrate in the regulation of TLR5 expression. We showed that butyrate transcriptionally upregulates TLR5 in the IECs and augments flagellin-induced immune responses. Both basal and butyrate-induced transcription is regulated by differential binding of Sp-family transcription factors to the GC-box sequences over the TLR5 promoter. Butyrate activates two different protein kinase C isoforms to dephosphorylate/acetylate Sp1 by serine/threonine phosphatases and phosphorylate Sp3 by ERK-MAPK, respectively. This resulted in Sp1 displacement from the promoter and binding of Sp3 to it, leading to p300 recruitment and histone acetylation, activating transcription. This is the first study addressing the mechanisms of physiological TLR5 expression in the intestine. Additionally, a novel insight is gained into Sp1/Sp3-mediated gene regulation that may apply to other genes.

SENP3 regulates the global protein turnover and the Sp1 level via antagonizing SUMO2/3-targeted ubiquitination and degradation

SUMOylation is recently found to function as a targeting signal for the degradation of substrates through the ubiquitin-proteasome system. RNF4 is the most studied human SUMO-targeted ubiquitin E3 ligase. However, the relationship between SUMO proteases, SENPs, and RNF4 remains obscure. There are limited examples of the SENP regulation of SUMO2/3-targeted proteolysis mediated by RNF4. The present study investigated the role of SENP3 in the global protein turnover related to SUMO2/3-targeted ubiquitination and focused in particular on the SENP3 regulation of the stability of Sp1. Our data demonstrated that SENP3 impaired the global ubiquitination profile and promoted the accumulation of many proteins. Sp1, a cancer-associated transcription factor, was among these proteins. SENP3 increased the level of Sp1 protein via antagonizing the SUMO2/3-targeted ubiquitination and the consequent proteasome-dependent degradation that was mediated by RNF4. De-conjugation of SUMO2/3 by SENP3 attenuated the interaction of Sp1 with RNF4. In gastric cancer cell lines and specimens derived from patients and nude mice, the level of Sp1 was generally increased in parallel to the level of SENP3. These results provided a new explanation for the enrichment of the Sp1 protein in various cancers, and revealed a regulation of SUMO2/3 conjugated proteins whose levels may be tightly controlled by SENP3 and RNF4.

A deterministic oscillatory model of microtubule growth and shrinkage for differential actions of short chain fatty acids

Short-chain fatty acids have distinct effects on cytoskeletal proteins at the level of expression and organisation. We report a new oscillatory, deterministic model which accounts for different actions and predicts response according to fatty acid chain length.

Gut microbiome in health and disease: Linking the microbiome-gut-brain axis and environmental factors in the pathogenesis of systemic and neurodegenerative diseases

The gut microbiome comprises the collective genome of the trillions of microorganisms residing in our gastrointestinal ecosystem. The interaction between the host and its gut microbiome is a complex relationship whose manipulation could prove critical to preventing or treating not only various gut disorders, like irritable bowel syndrome (IBS) and ulcerative colitis (UC), but also central nervous system (CNS) disorders, such as Alzheimer's and Parkinson's diseases. The purpose of this review is to summarize what is known about the gut microbiome, how it is connected to the development of disease and to identify the bacterial and biochemical targets that should be the focus of future research. Understanding the mechanisms behind the activity and proliferation of the gut microbiome will provide us new insights that may pave the way for novel therapeutic strategies.

Histone deacetylase inhibition protects hearing against acute ototoxicity by activating the Nf-κB pathway

Auditory hair cells have repeatedly been shown to be susceptible to ototoxicity from a multitude of drugs including aminoglycoside antibiotics. Here, we found that systemic HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) on adult mice offers almost complete protection against hair cell loss and hearing threshold shifts from acute ototoxic insult from kanamycin potentiated with furosemide. We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration. Rather, SAHA treatment correlated with RelA acetylation (K310) and subsequent activation of the Nf-κB pro-survival pathway leading to expression of pro-survival genes such as Cflar (cFLIP) and Bcl2l1 (Bcl-xL). In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim). These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.

Mechanisms of Histone Deacetylase Inhibitor-Regulated Gene Expression in Cancer Cells

SIGNIFICANCE

Class I and II histone deacetylase inhibitors (HDACis) are approved for the treatment of cutaneous T-cell lymphoma and are undergoing clinical trials as single agents, and in combination, for other hematological and solid tumors. Understanding their mechanisms of action is essential for their more effective clinical use, and broadening their clinical potential.

RECENT ADVANCES

HDACi induce extensive transcriptional changes in tumor cells by activating and repressing similar numbers of genes. These transcriptional changes mediate, at least in part, HDACi-mediated growth inhibition, apoptosis, and differentiation. Here, we highlight two fundamental mechanisms by which HDACi regulate gene expression—histone and transcription factor acetylation. We also review the transcriptional responses invoked by HDACi, and compare these effects within and across tumor types.

CRITICAL ISSUES

The mechanistic basis for how HDACi activate, and in particular repress gene expression, is not well understood. In addition, whether subsets of genes are reproducibly regulated by these agents both within and across tumor types has not been systematically addressed. A detailed understanding of the transcriptional changes elicited by HDACi in various tumor types, and the mechanistic basis for these effects, may provide insights into the specificity of these drugs for transformed cells and specific tumor types.

FUTURE DIRECTIONS

Understanding the mechanisms by which HDACi regulate gene expression and an appreciation of their transcriptional targets could facilitate the ongoing clinical development of these emerging therapeutics. In particular, this knowledge could inform the design of rational drug combinations involving HDACi, and facilitate the identification of mechanism-based biomarkers of response.