Histone Hyperacetylation Research Articles

Modulation of Tumor Suppressor Genes by Histone Deacetylase Inhibitors in Cancer Therapy

Histone deacetylase (HDAC) inhibitors have emerged as promising therapeutics for various cancers due to their ability to modulate gene expression profiles and restore normal cellular functions. Among the key targets of HDAC inhibitors are tumor suppressor genes, which play crucial roles in regulating cell cycle progression, apoptosis, and DNA repair. However, despite their therapeutic potential, HDAC inhibitors come with significant drawbacks. These include off-target effects that can lead to unintended alterations in gene expression, toxicity to normal cells, and the development of drug resistance in some cancer patients. Additionally, the non-specific nature of some HDAC inhibitors can result in side effects such as fatigue, gastrointestinal disturbances, and hematological toxicity, limiting their clinical utility. This review provides a comprehensive overview of the impact of HDAC inhibitors on tumor suppressor genes in cancer therapy. We discussed the mechanisms by which HDAC inhibitors regulate the expression of tumor suppressor genes, including p53, p21, BRCA1, PTEN, and others, through histone hyperacetylation and chromatin remodeling. Furthermore, we described the therapeutic implications of HDAC inhibitor-induced modulation of tumor suppressor genes in various cancer types, highlighting the potential for combination therapies and personalized treatment approaches. Understanding the interplay between HDAC inhibitors and tumor suppressor genes is critical for optimizing the efficacy of HDAC inhibitor-based therapies and advancing precision medicine in oncology.

Proteolysis targeting chimera extracellular vesicles for therapeutic development treating triple negative breast cancer.

Proteolysis targeting chimeras (PROTACs) are an emerging targeted cancer therapy approach, but wide-spread clinical use of PROTAC is limited due to poor cell targeting and penetration, and instability in vivo. To overcome such issues and enhance the in vivo efficacy of PROTAC drugs, microfluidic droplet-based electroporation (µDES) was developed as a novel extracellular vesicle (EVs) transfection system, which enables the high-efficient PROTAC loading and effective delivery in vivo. Our previously developed YX968 PROTAC drug had shown the selectively degradation of HDAC3 and 8, which effectively suppresses the growth of breast tumor cell lines, including MDA-MB-231 triple negative breast cancer (TNBC) line, via dual degradation without provoking a global histone hyperacetylation. In this study, we demonstrated that µDES-based PROTAC loading in EVs significantly enhanced therapeutic function of PROTAC drug in vivo in the TNBC breast tumor mouse model. NSG mice with pre-established MDA-MB-231 tumors and treated with intraperitoneal injection of EVs for tumor inhibition study, which showed significantly higher HDAC 3 and 8 degradation efficiency and tumor inhibition than PROTAC only group. The liver, spleen, kidney, lung, heart, and brain were collected for safety testing, which exhibited improved toxicity. The EV delivery of PROTAC drug enhances drug stability and bioavailability in vivo, transportability, and drug targeting ability, which fills an important gap in current development of PROTAC therapeutic functionality in vivo and clinical translation. This novel EV-based drug transfection and delivery strategy could be applicable to various therapeutics for enhancing in vivo delivery, efficacy, and safety.

Nucleosome remodeler exclusion by histone deacetylation enforces heterochromatic silencing and epigenetic inheritance

Heterochromatin enforces transcriptional gene silencing and can be epigenetically inherited, but the underlying mechanisms remain unclear. Here, we show that histone deacetylation, a conserved feature of heterochromatin domains, blocks SWI/SNF subfamily remodelers involved in chromatin unraveling, thereby stabilizing modified nucleosomes that preserve gene silencing. Histone hyperacetylation, resulting from either the loss of histone deacetylase (HDAC) activity or the direct targeting of a histone acetyltransferase to heterochromatin, permits remodeler access, leading to silencing defects. The requirement for HDAC in heterochromatin silencing can be bypassed by impeding SWI/SNF activity. Highlighting the crucial role of remodelers, merely targeting SWI/SNF to heterochromatin, even in cells with functional HDAC, increases nucleosome turnover, causing defective gene silencing and compromised epigenetic inheritance. This study elucidates a fundamental mechanism whereby histone hypoacetylation, maintained by high HDAC levels in heterochromatic regions, ensures stable gene silencing and epigenetic inheritance, providing insights into genome regulatory mechanisms relevant to human diseases.

Exploration of Hydrazide-Based HDAC8 PROTACs for the Treatment of Hematological Malignancies and Solid Tumors.

HDAC8 can mediate signals by using its enzymatic or nonenzymatic functions, which are expected to be critical for various types of cancer. Herein, we employed proteolysis targeting chimera (PROTAC) technology to target the enzymatic as well as the nonenzymatic functions of HDAC8. A potent and selective HDAC8 PROTAC Z16 (CZH-726) with low nanomolar DC50 values in various cell lines was identified. Interestingly, Z16 induced structural maintenance of chromosomes protein 3 (SMC3) hyperacetylation at low concentrations and histone hyperacetylation at high concentrations, which can be explained by HDAC8 degradation and off-target HDAC inhibition, respectively. Notably, Z16 potently inhibited proliferation of various cancer cell lines and the antiproliferative mechanisms proved to be cell-type-dependent, which, to a large extent, is due to off-target HDAC inhibition. In conclusion, we report a hydrazide-based HDAC8 PROTAC Z16, which can be used as a probe to investigate the biological functions of HDAC8.

Dysregulated expression of cholesterol biosynthetic genes in Alzheimer's disease alters epigenomic signatures of hippocampal neurons

Aging is the main risk factor of cognitive neurodegenerative diseases such as Alzheimer's disease, with epigenome alterations as a contributing factor. Here, we compared transcriptomic/epigenomic changes in the hippocampus, modified by aging and by tauopathy, an AD-related feature. We show that the cholesterol biosynthesis pathway is severely impaired in hippocampal neurons of tauopathic but not of aged mice pointing to vulnerability of these neurons in the disease. At the epigenomic level, histone hyperacetylation was observed at neuronal enhancers associated with glutamatergic regulations only in the tauopathy. Lastly, a treatment of tau mice with the CSP-TTK21 epi-drug that restored expression of key cholesterol biosynthesis genes counteracted hyperacetylation at neuronal enhancers and restored object memory. As acetyl-CoA is the primary substrate of both pathways, these data suggest that the rate of the cholesterol biosynthesis in hippocampal neurons may trigger epigenetic-driven changes, that may compromise the functions of hippocampal neurons in pathological conditions.

Identification of a new bisindolinone arresting IGROV1 cells proliferation

In an initial screening, a series of novel Knoevenagel adducts were submitted to the National Cancer Institute for evaluation of antitumor activity in human cell lines. In particular, compound 5f showed remarkable selectivity against IGROV1, an ovarian cancer cell line, without affecting healthy human fibroblast cells. Analyses of cytotoxicity, cell proliferation, cell migration, epigenetic changes, gene expression, and DNA damage were performed to obtain detailed information about its antitumor properties. Our results show that 5f causes proliferation arrest, decrease in motility, histone hyperacetylation, downregulation of cyclin D1 and α5 subunit of integrin β1 gene transcription. In addition, 5f treatment reduces transcript and protein levels of cyclin D1, which increases sensitivity to ionizing radiation and results in DNA damage comparable to cyclin D1 gene silencing.

Abstract 3236: Discovery of hydrazide-based HDAC8 selective PROTACs

Abstract HDAC8 plays crucial roles in biological processes and is a highly desirable target for therapeutic interventions. However, due to the conserved catalytic domain among HDACs, developing specific inhibitors for these isozymes has proven challenging. HDAC8 also has deacetylase-independent activity which cannot be blocked by an inhibitor. Previously we reported the discoveries of a potent HDAC3 degrader XZ9002 and an HDAC3/8 dual degrader YX968. In this study, we carried out further optimizations based on the warhead of YX968 through rational design, which led to the discovery of YX862 and YL246, novel hydrazide-based HDAC8 selective PROTAC degraders with single-digit nanomolar DC50 and excellent selectivity. We demonstrated that the degradation of HDAC8 affects its non-histone substrates; however, it does not trigger profound histone hyper-acetylation and gene expression alteration, highlighting the unique role of HDAC8. The PROTACs developed in this study are well-characterized HDAC8 degraders without triggering pan-HDAC inhibition which represent valuable tool compounds for exploring the biological and therapeutic potential of HDAC8 in cancers and beyond. Citation Format: Yufeng Xiao, Yi Liu, Nikee Awasthee, Chengcheng Meng, Michael He, Seth Hale, Rashmi Karki, Zongtao Lin, Robert Kridel, Daiqing Liao, Guangrong Zheng. Discovery of hydrazide-based HDAC8 selective PROTACs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3236.

Romidepsin exhibits anti-esophageal squamous cell carcinoma activity through the DDIT4-mTORC1 pathway.

Esophageal squamous cell carcinoma (ESCC) is one of the most common human malignancies worldwide and is associated with high morbidity and mortality. Current treatment options are limited, highlighting the need for development of novel effective agents. Here, a high-throughput drug screening (HTS) was performed using ESCC cell lines in both two- and three-dimensional culture systems to screen compounds that have anti-ESCC activity. Our screen identified romidepsin, a histone deactylase inhibitor, as a potential anti-ESCC agent. Romidepsin treatment decreased cell viability, induced apoptosis and cell cycle arrest in ESCC cell lines, and these findings were confirmed in ESCC cell line-derived xenografted (CDX) mouse models. Mechanically, romidepsin induced transcriptional upregulation of DNA damage-inducible transcript 4 (DDIT4) gene by histone hyperacetylation at its promoter region, leading to the inhibition of mammalian target of rapamycin complex 1 (mTORC1) pathway. Furthermore, romidepsin exhibited better efficacy and safety compared to the conventional therapeutic drugs in ESCC patient-derived xenografted (PDX) mouse models. These data indicate that romidepsin may be a novel option for anti-ESCC therapy.

Hyperacetylated histone H4 is a source of carbon contributing to lipid synthesis.

Histone modifications commonly integrate environmental cues with cellular metabolic outputs by affecting gene expression. However, chromatin modifications such as acetylation do not always correlate with transcription, pointing towards an alternative role of histone modifications in cellular metabolism. Using an approach that integrates mass spectrometry-based histone modification mapping and metabolomics with stable isotope tracers, we demonstrate that elevated lipids in acetyltransferase-depleted hepatocytes result from carbon atoms derived from deacetylation of hyperacetylated histone H4 flowing towards fatty acids. Consistently, enhanced lipid synthesis in acetyltransferase-depleted hepatocytes is dependent on histone deacetylases and acetyl-CoA synthetase ACSS2, but not on the substrate specificity of the acetyltransferases. Furthermore, we show that during diet-induced lipid synthesis the levels of hyperacetylated histone H4 decrease in hepatocytes and in mouse liver. In addition, overexpression of acetyltransferases can reverse diet-induced lipogenesis by blocking lipid droplet accumulation and maintaining the levels of hyperacetylated histone H4. Overall, these findings highlight hyperacetylated histones as a metabolite reservoir that can directly contribute carbon to lipid synthesis, constituting a novel function of chromatin in cellular metabolism.

Acetyl-CoA production by Mediator-bound 2-ketoacid dehydrogenases boosts de novo histone acetylation and is regulated by nitric oxide

Histone-modifying enzymes depend on the availability of cofactors, with acetyl-coenzyme A (CoA) being required for histone acetyltransferase (HAT) activity. The discovery that mitochondrial acyl-CoA-producing enzymes translocate to the nucleus suggests that high concentrations of locally synthesized metabolites may impact acylation of histones and other nuclear substrates, thereby controlling gene expression. Here, we show that 2-ketoacid dehydrogenases are stably associated with the Mediator complex, thus providing a local supply of acetyl-CoA and increasing the generation of hyper-acetylated histone tails. Nitric oxide (NO), which is produced in large amounts in lipopolysaccharide-stimulated macrophages, inhibited the activity of Mediator-associated 2-ketoacid dehydrogenases. Elevation of NO levels and the disruption of Mediator complex integrity both affected de novo histone acetylation within a shared set of genomic regions. Our findings indicate that the local supply of acetyl-CoA generated by 2-ketoacid dehydrogenases bound to Mediator is required to maximize acetylation of histone tails at sites of elevated HAT activity.

A comprehensive characterisation of phaeochromocytoma and paraganglioma tumours through histone protein profiling, DNA methylation and transcriptomic analysis genome wide

BackgroundPhaeochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours. Pathogenic variants have been identified in more than 15 susceptibility genes; associated tumours are grouped into three Clusters, reinforced by their transcriptional profiles. Cluster 1A PPGLs have pathogenic variants affecting enzymes of the tricarboxylic acid cycle, including succinate dehydrogenase. Within inherited PPGLs, these are the most common. PPGL tumours are known to undergo epigenetic reprograming, and here, we report on global histone post-translational modifications and DNA methylation levels, alongside clinical phenotypes.ResultsOut of the 25 histone post-translational modifications examined, Cluster 1A PPGLs were distinguished from other tumours by a decrease in hyper-acetylated peptides and an increase in H3K4me2. DNA methylation was compared between tumours from individuals who developed metastatic disease versus those that did not. The majority of differentially methylated sites identified tended to be completely methylated or unmethylated in non-metastatic tumours, with low inter-sample variance. Metastatic tumours by contrast consistently had an intermediate DNA methylation state, including the ephrin receptor EPHA4 and its ligand EFNA3. Gene expression analyses performed to identify genes involved in metastatic tumour behaviour pin-pointed a number of genes previously described as mis-regulated in Cluster 1A tumours, as well as highlighting the tumour suppressor RGS22 and the pituitary tumour-transforming gene PTTG1.ConclusionsCombined transcriptomic and DNA methylation analyses revealed aberrant pathways, including ones that could be implicated in metastatic phenotypes and, for the first time, we report a decrease in hyper-acetylated histone marks in Cluster 1 PPGLs.

Histone acetylation regulates ORMDL3 expression-mediated NLRP3 inflammasome overexpression during RSV-allergic exacerbation mice.

Whether respiratory syncytial virus (RSV) infection in early life may induce orosomucoid 1-like protein 3 (ORMDL3) and lead to NOD-like receptor protein 3 (NLRP3) inflammasome overexpression in asthma, which could be alleviated by the inhibition of HAT p300. First, we explored the relationship between RSV, ORMDL3, and recurrent wheezing in the future through clinical data of infants with RSV-induced bronchiolitis. Then, we used bronchial epithelium transformed with Ad12-SV40 2B (BEAS-2B) and an asthmatic mouse model of repeated RSV infection and OVA sensitization and challenge (rRSV + OVA) in early life to assess the effects of ORMDL3 on NLRP3 inflammasome and that of histone acetylation on ORMDL3 regulation. ORMDL3 overexpression is the independent risk factor of recurrent wheezing in RSV-bronchiolitis follow-up. In BEAS-2B, ORMDL3-induced NLRP3 inflammasome expression. BEAS-2B infected by RSV resulted in overexpression of ORMDL3 and NLRP3 inflammasome and histone hyperacetylation, while ORMDL3-small interfering RNA and C646 interfered could decrease NLRP3 inflammasome. ORMDL3 overexpression in mouse lung increased NLRP3 inflammasome. The expression of ORMDL3 and NLRP3 inflammasome significantly increased, with histone hyperacetylation in the lung in rRSV + OVA mice. p300 and acetylH3 bound to ORMDL3 promoter. In C646 + rRSV + OVA mice, C646 alleviated lung inflammation and overexpression of ORMDL3 and NLRP3 inflammasome. RSV activated ORMDL3 overexpression through histone hyperacetylation and induced NLRP3 inflammasome expression.

Hydroxamate-based compounds are potent inhibitors of Toxoplasma gondii HDAC biological activity.

Toxoplasmosis is a critical health issue for immune-deficient individuals and the offspring of newly infected mothers. It is caused by a unicellular intracellular parasite called Toxoplasma gondii that is found worldwide. Although efficient drugs are commonly used to treat toxoplasmosis, serious adverse events are common. Therefore, new compounds with potent anti-T. gondii activity are needed to provide better suited treatments. We have tested compounds designed to target specifically histone deacetylase enzymes. Among the 55 compounds tested, we identified three compounds showing a concentration of drug required for 50% inhibition (IC50) in the low 100 nM range with a selectivity index of more than 100. These compounds are not only active at inhibiting the growth of the parasite in vitro but also at preventing some of the consequences of the acute disease in vivo. Two of these hydroxamate based compound also induce a hyper-acetylation of the parasite histones while the parasitic acetylated tubulin level remains unchanged. These findings suggest that the enzymes regulating histone acetylation are potent therapeutic targets for the treatment of acute toxoplasmosis.

Discovery of Novel Fedratinib-Based HDAC/JAK/BRD4 Triple Inhibitors with Remarkable Antitumor Activity against Triple Negative Breast Cancer.

Multitarget HDAC inhibitors capable of simultaneously blocking the BRD4-LIFR-JAK1-STAT3 signaling pathway hold great potential for the treatment of TNBC and other solid tumors. Herein, novel Fedratinib-based multitarget HDAC inhibitors were rationally designed, synthesized, and biologically evaluated, among which compound 25ap stood out as a potent HDAC/JAK/BRD4 triple inhibitor. Satisfyingly, compound 25ap led to concurrent inhibition of HDACs and the BRD4-LIFR-JAK1-STAT3 signaling pathway, which was validated by hyper-acetylation of histone and α-tubulin, hypo-phosphorylation of STAT3, downregulation of LIFR, MCL-1, and c-Myc in MDA-MB-231 cells. The multitarget effects of 25ap contributed to its robust antitumor response, including potent antiproliferative activity, remarkable apoptosis-inducing activity, and inhibition of colony formation. Notably, 25ap possessed an acceptable therapeutic window between normal and cancerous cells, desirable in vitro metabolic stability in mouse microsome, and sufficient in vivo exposure via intraperitoneal administration. Additionally, the in vivo antitumor potency of 25ap was demonstrated in an MDA-MB-231 xenograft model.

Altered Smooth Muscle Cell Histone Acetylome by the SPHK2/S1P Axis Promotes Pulmonary Hypertension.

Epigenetic regulation of vascular remodeling in pulmonary hypertension (PH) is poorly understood. Transcription regulating, histone acetylation code alters chromatin accessibility to promote transcriptional activation. Our goal was to identify upstream mechanisms that disrupt epigenetic equilibrium in PH. Human pulmonary artery smooth muscle cells (PASMCs), human idiopathic pulmonary arterial hypertension (iPAH):human PASMCs, iPAH lung tissue, failed donor lung tissue, human pulmonary microvascular endothelial cells, iPAH:PASMC and non-iPAH:PASMC RNA-seq databases, NanoString nCounter, and cleavage under targets and release using nuclease were utilized to investigate histone acetylation, hyperacetylation targets, protein and gene expression, sphingolipid activation, cell proliferation, and gene target identification. SPHK2 (sphingosine kinase 2) knockout was compared with control C57BL/6NJ mice after 3 weeks of hypoxia and assessed for indices of PH. We identified that Human PASMCs are vulnerable to the transcription-promoting epigenetic mediator histone acetylation resulting in alterations in transcription machinery and confirmed its pathological existence in PH:PASMC cells. We report that SPHK2 is elevated as much as 20-fold in iPAH lung tissue and is elevated in iPAH:PASMC cells. During PH pathogenesis, nuclear SPHK2 activates nuclear bioactive lipid S1P (sphingosine 1-phosphate) catalyzing enzyme and mediates transcription regulating histone H3K9 acetylation (acetyl histone H3 lysine 9 [Ac-H3K9]) through EMAP (endothelial monocyte activating polypeptide) II. In iPAH lungs, we identified a 4-fold elevation of the reversible epigenetic transcription modulator Ac-H3K9:H3 ratio. Loss of SPHK2 inhibited hypoxic-induced PH and Ac-H3K9 in mice. We discovered that pulmonary vascular endothelial cells are a priming factor of the EMAP II/SPHK2/S1P axis that alters the acetylome with a specificity for PASMC, through hyperacetylation of histone H3K9. Using cleavage under targets and release using nuclease, we further show that EMAP II-mediated SPHK2 has the potential to modify the local transcription machinery of pluripotency factor KLF4 (Krüppel-like factor 4) by hyperacetylating KLF4 Cis-regulatory elements while deletion and targeted inhibition of SPHK2 rescues transcription altering Ac-H3K9. SPHK2 expression and its activation of the reversible histone H3K9 acetylation in human pulmonary artery smooth muscle cell represent new therapeutic targets that could mitigate PH vascular remodeling.

Design, synthesis and biological evaluation of pyrimidine base hydroxamic acid derivatives as dual JMJD3 and HDAC inhibitors

The Jumonji domain-containing protein demethylase 3 (JMJD3) and histone deacetylase (HADC) are related to various cancers and regard as antitumor targets for drug discovery. In this study, based on rational drug design strategy, we designed and synthesized a series of pyrimidine derivatives with hydroxamic acid as novel dual JMJD3 and HDAC inhibitors for synergistic cancer treatment. Compound A5b exhibited inhibitory potency against JMJD3 and HDAC1/6 simultaneously and favorable cytotoxicity against human cancer cells such as A549 and U937. Furthermore, mechanistic studies showed that A5b treatment in A549 cells increased the hypermethylation of histone H3K27 and hyperacetylation of H3K9, suppressed clonogenicity, migration and invasion of cancer cells. Besides, A5b induced apoptosis via the cleavage of caspase-7 and PARP, and G1 cell cycle arrest via upregulated p21 expression. All these results suggested that A5b was the first dual inhibitor against JMJD3 and HDAC and can be a potential compound for cancer therapy.

Recruitment of the Histone Variant MacroH2A1 to the Pericentric Region Occurs upon Chromatin Relaxation and Is Responsible for Major Satellite Transcriptional Regulation.

Heterochromatin formation plays a pivotal role in regulating chromatin organization and influences nuclear architecture and genome stability and expression. Amongst the locations where heterochromatin is found, the pericentric regions have the capability to attract the histone variant macroH2A1. However, the factors and mechanisms behind macroH2A1 incorporation into these regions have not been explored. In this study, we probe different conditions that lead to the recruitment of macroH2A1 to pericentromeric regions and elucidate its underlying functions. Through experiments conducted on murine fibroblastic cells, we determine that partial chromatin relaxation resulting from DNA damage, senescence, or histone hyper-acetylation is necessary for the recruitment of macroH2A1 to pericentric regions. Furthermore, macroH2A1 is required for upregulation of noncoding pericentric RNA expression but not for pericentric chromatin organization. Our findings shed light on the functional rather than structural significance of macroH2A1 incorporation into pericentric chromatin.

HDAC3 and HDAC8 PROTAC dual degrader reveals roles of histone acetylation in gene regulation

HDAC3 and HDAC8 have critical biological functions and represent highly sought-after therapeutic targets. Because histone deacetylases (HDACs) have a very conserved catalytic domain, developing isozyme-selective inhibitors remains challenging. HDAC3/8 also have deacetylase-independent activity, which cannot be blocked by conventional enzymatic inhibitors. Proteolysis-targeting chimeras (PROTACs) can selectively degrade a target enzyme, abolishing both enzymatic and scaffolding function. Here, we report a novel HDAC3/8 dual degrader YX968 that induces highly potent, rapid, and selective degradation of both HDAC3/8 without triggering pan-HDAC inhibitory effects. Unbiased quantitative proteomic experiments confirmed its high selectivity. HDAC3/8 degradation by YX968 does not induce histone hyperacetylation and broad transcriptomic perturbation. Thus, histone hyperacetylation may be a major factor for altering transcription. YX968 promotes apoptosis and kills cancer cells with a high potency invitro. YX968 thus represents a new probe for dissecting the complex biological functions of HDAC3/8.

Intermittent Fasting Sustainably Improves Glucose Tolerance in Normal Weight Male Mice Through Histone Hyperacetylation

Abstract To explore the mechanism by which intermittent fasting (IF) exerts prolonged effects after discontinuation, we examined mice that had been subjected to 4 cycles of fasting for 72 hours and ad libitum feeding for 96 hours per week (72hIF), followed by 4 weeks of ad libitum feeding, focusing on expression of genes for lipid metabolism in the skeletal muscle and histone acetylation in the promoter region. The 72hIF regimen resulted in metabolic remodeling, characterized by enhanced lipid utilization and mitochondrial activation in the muscle. This long-term IF (72hIF) caused stronger metabolic effects than alternate day fasting (24hIF) wherein fasting and refeeding are repeated every 24 hours. Upregulation of lipid oxidation genes and an increase in oxygen utilization were sustained even at 4 weeks after discontinuation of 72hIF, associated with histone hyperacetylation of the promoter region of uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) genes. An increase in leucine owing to fasting-induced muscle degradation was suggested to lead to the histone acetylation. These findings support the previously unappreciated notion that sustainable promotion of histone acetylation in lipid oxidation genes of the muscle and adipose tissues during and after IF may contribute to sustained metabolic effects of IF.

HDAC inhibitor SB939 potentiates TRAIL-induced apoptosis in colorectal cancer cells.

Colorectal cancer (CRC) displays noticeable resistance to chemotherapeutic drugs or innovative tumor cell apoptosis-inducing agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Thus, sensitizers are needed to enhance the effects of TRAIL-based cancer therapies. Elevated tumor cell death has been reported when various HDAC inhibitors are administered with TRAIL in various human cancers; however, SB939-TRAIL combined treatment has not been reported. In this study, we determined the ability of SB939 and TRAIL, as single agents or in combination, to inhibit the growth and survival of colorectal cancer cells. Our results demonstrated the effects of SB939 and TRAIL on cell viability, apoptosis, and morphological changes in HT-29 cells. SB939 treatment induces hyper-acetylation of histones and death receptors (DR) by activating MAPK proteins in a dose- and time-dependent manner. The ability of SB939 to sensitize HT-29 cells suggests that SB939 can induce essential changes in cell signaling pathways. Thus, the pan-HDAC inhibitor SB939 sensitizes TRAIL-induced apoptosis via up-regulation of DR5, and SB939-TRAIL combined treatment may target the MAPK pathways and serve as an effective therapeutic strategy against CRC.