Epigenetic modulation with HDAC inhibitor CG200745 induces anti-proliferation in non-small cell lung cancer cells

Sodium valproate affects the expression of p16INK4a and p21WAFI/Cip1 cyclin‑dependent kinase inhibitors in HeLa cells

p16INK4a and p21WAF1/Cip1 are cyclin-dependent kinase inhibitors involved in cell cycle control, which can function as oncogenes or tumor suppressors, depending on the context of various extracellular and intracellular signals, and cell type. In human papillomavirus-induced cervical cancer, p16 INK4a shows oncogenic activity and functions as a diagnostic marker of cervical neoplasia, whereas p21 WAF1/Cip1 acts as a tumor suppressor and its downregulation is associated with the progression of malignant transformation. Several histone deacetylase (HDAC) inhibitors promote the positive and negative regulation of a number of genes, including p16 INK4a and p21 WAF1/Cip1; however, the effects of sodium valproate (VPA) on these genes and on the proteins they encode remain uncertain in HeLa cervical cancer cells. In the present study, these effects were investigated in HeLa cells treated with 0.5 or 2 mM VPA for 24 h, using reverse transcription-quantitative PCR, confocal microscopy and western blotting. The results revealed a decrease in the mRNA expression levels of p16 INK4a and a tendency for p16INK4a protein abundance to decrease in the presence of 2 mM VPA. By contrast, an increase in the protein expression levels of p21WAF1/Cip1 was detected in the presence of 0.5 and 2 mM VPA. Furthermore, VPA was confirmed to inhibit HDAC activity and induce global hyperacetylation of histone H3. Notably, VPA was shown to suppress p16 INK4a, a biomarker gene of cervical carcinoma, and to increase the abundance of the tumor suppressor protein p21WAF1/Cip1, thus contributing to the basic knowledge regarding the antitumorigenic potential of VPA. Exploration of epigenetic changes associated with the promoters of p16 INK4a and p21 WAF1/Cip1, such as histone H3 methylation, may provide further information and improve the understanding of these findings.

Emerging therapeutic strategies in cancer therapy by HDAC inhibition as the chemotherapeutic potent and epigenetic regulator

In developing new cancer medications, attention has been focused on novel epigenetic medicines called histone deacetylase (HDAC) inhibitors. Our understanding of cancer behavior is being advanced by research on epigenetics, which also supplies new targets for improving the effectiveness of cancer therapy. Most recently published patents emphasize HDAC selective drugs and multitarget HDAC inhibitors. Though significant progress has been made in emerging HDAC selective antagonists, it is urgently necessary to find new HDAC blockers with novel zinc-binding analogues to avoid the undesirable pharmacological characteristics of hydroxamic acid. HDAC antagonists have lately been explored as a novel approach to treating various diseases, including cancer. The complicated terrain of HDAC inhibitor development is summarized in this article, starting with a discussion of the many HDAC isotypes and their involvement in cancer biology, followed by a discussion of the mechanisms of action of HDAC inhibitors, their current level of development, effect of miRNA, and their combination with immunotherapeutic.

Targeting SMAD-Dependent Signaling: Considerations in Epithelial and Mesenchymal Solid Tumors

SMADs are the canonical intracellular effector proteins of the TGF-β (transforming growth factor-β). SMADs translocate from plasma membrane receptors to the nucleus regulated by many SMAD-interacting proteins through phosphorylation and other post-translational modifications that govern their nucleocytoplasmic shuttling and subsequent transcriptional activity. The signaling pathway of TGF-β/SMAD exhibits both tumor-suppressing and tumor-promoting phenotypes in epithelial-derived solid tumors. Collectively, the pleiotropic nature of TGF-β/SMAD signaling presents significant challenges for the development of effective cancer therapies. Here, we review preclinical studies that evaluate the efficacy of inhibitors targeting major SMAD-regulating and/or -interacting proteins, particularly enzymes that may play important roles in epithelial or mesenchymal compartments within solid tumors.

Targeting epigenetic regulation for cancer therapy using small molecule inhibitors

Cancer cells display pervasive changes in DNA methylation, disrupted patterns of histone posttranslational modification, chromatin composition or organization and regulatory element activities that alter normal programs of gene expression. It is becoming increasingly clear that disturbances in the epigenome are hallmarks of cancer, which are targetable and represent attractive starting points for drug creation. Remarkable progress has been made in the past decades in discovering and developing epigenetic-based small molecule inhibitors. Recently, epigenetic-targeted agents in hematologic malignancies and solid tumors have been identified and these agents are either in current clinical trials or approved for treatment. However, epigenetic drug applications face many challenges, including low selectivity, poor bioavailability, instability and acquired drug resistance. New multidisciplinary approaches are being designed to overcome these limitations, e.g., applications of machine learning, drug repurposing, high throughput virtual screening technologies, to identify selective compounds with improved stability and better bioavailability. We provide an overview of the key proteins that mediate epigenetic regulation that encompass histone and DNA modifications and discuss effector proteins that affect the organization of chromatin structure and function as well as presently available inhibitors as potential drugs. Current anticancer small-molecule inhibitors targeting epigenetic modified enzymes that have been approved by therapeutic regulatory authorities across the world are highlighted. Many of these are in different stages of clinical evaluation. We also assess emerging strategies for combinatorial approaches of epigenetic drugs with immunotherapy, standard chemotherapy or other classes of agents and advances in the design of novel epigenetic therapies.

A phase I/II study of ivaltinostat combined with gemcitabine and erlotinib in patients with untreated locally advanced or metastatic pancreatic adenocarcinoma

This phase I/II study evaluated the safety and efficacy of a new histone deacetylase (HDAC) inhibitor, ivaltinostat, in combination with gemcitabine and erlotinib for advanced pancreatic ductal adenocarcinoma (PDAC). Patients diagnosed with unresectable, histologically confirmed PDAC who had not undergone previous therapy were eligible. Phase I had a 3 + 3 dose escalation design to determine the maximum tolerable dose (MTD) of ivaltinostat (intravenously on days 1, 8 and 15) with gemcitabine (1000 mg/m2 intravenously on days 1, 8 and 15) and erlotinib (100 mg/day, orally) for a 28-day cycle. In phase II, patients received a six-cycle treatment with the MTD of ivaltinostat determined in phase I. The primary endpoint was the objective response rate (ORR). Secondary endpoints included overall survival (OS), disease control rate (DCR) and progression-free survival (PFS). The MTD of ivaltinostat for the phase II trial was determined to be 250 mg/m2 . In phase II, 24 patients were enrolled. The median OS and PFS were 8.6 (95% confidence interval [CI]: 5.3-11.2) and 5.3 months (95% CI: 3.7-5.8). Of the 16 patients evaluated for response, ORR and DCR were 25.0% and 93.8% with a median OS/PFS of 10.8 (95% CI: 8.3-16.7)/5.8 (95% CI: 4.6-6.7) months. Correlative studies showed that mutation burden detected by cfDNA and specific blood markers such as TIMP1, pro-MMP10, PECAM1, proMMP-2 and IGFBP1 were associated with clinical outcomes. Although the result of a small study, a combination of ivaltinostat, gemcitabine and erlotinib appeared to be a potential treatment option for advanced PDAC.

HDAC inhibitors: Targets for tumor therapy, immune modulation and lung diseases

Histone deacetylases (HDACs) are enzymes that play a key role in the epigenetic regulation of gene expression by remodeling chromatin. Inhibition of HDACs is a prospective therapeutic approach for reversing epigenetic alteration in several diseases. In preclinical research, numerous types of HDAC inhibitors were discovered to exhibit powerful and selective anticancer properties. However, such research has revealed that the effects of HDAC inhibitors may be far broader and more intricate than previously thought. This review will provide insight into the HDAC inhibitors and their mechanism of action with special emphasis on the significance of HDAC inhibitors in the treatment of Chronic Obstructive Pulmonary Disease and lung cancer. Nanocarrier-mediated HDAC inhibitor delivery and new approaches for targeting HDACs are also discussed.

Regulating Histone Deacetylase Signaling Pathways of Myeloid-Derived Suppressor Cells Enhanced T Cell-Based Immunotherapy

Immunotherapy has emerged as a promising approach to combat immunosuppressive tumor microenvironment (TME) for improved cancer treatment. FDA approval for the clinical use of programmed death receptor 1/programmed death-ligand 1 (PD-1/PD-L1) inhibitors revolutionized T cell-based immunotherapy. Although only a few cancer patients respond to this treatment due to several factors including the accumulation of immunosuppressive cells in the TME. Several immunosuppressive cells within the TME such as regulatory T cells, myeloid cells, and cancer-associated fibroblast inhibit the activation and function of T cells to promote tumor progression. The roles of epigenetic modifiers such as histone deacetylase (HDAC) in cancer have long been investigated but little is known about their impact on immune cells. Recent studies showed inhibiting HDAC expression on myeloid-derived suppressor cells (MDSCs) promoted their differentiation to less suppressive cells and reduced their immunosuppressive effect in the TME. HDAC inhibitors upregulated PD-1 or PD-L1 expression level on tumor or immune cells sensitizing tumor-bearing mice to anti-PD-1/PD-L1 antibodies. Herein we discuss how inhibiting HDAC expression on MDSCs could circumvent drawbacks to immune checkpoint inhibitors and improve cancer immunotherapy. Furthermore, we highlighted current challenges and future perspectives of HDAC inhibitors in regulating MDSCs function for effective cancer immunotherapy.

Real-world particulate matters induce lung toxicity in rats fed with a high-fat diet: Evidence of histone modifications

Exposure to ambient particulate matters (PMs) has been associated with a variety of lung diseases, and high-fat diet (HFD) was reported to exacerbate PM-induced lung dysfunction. However, the underlying mechanisms for the combined effects of HFD and PM on lung functions remain poorly unraveled. By performing a comparative proteomic analysis, the current study investigated the global changes of histone post-translational modifications (PTMs) in rat lung exposed to long-term, real-world PMs. In result, after PM exposure the abundance of four individual histone PTMs (1 down-regulated and 3 up-regulated) and six combinatorial PTMs (1 down-regulated and 5 up-regulated) were significantly altered in HFD-fed rats while only one individual PTM was changed in rats with normal diet (ND) feeding. Histones H3K18ac, H4K8ac and H4K12ac were reported to be associated with DNA damage response, and we found that these PTMs were enhanced by PM in HFD-fed rats. Together with the elevated DNA damage levels in rat lungs following PM and HFD co-exposure, we demonstrate that PM exposure combined with HFD could induce lung injury through altering more histone modifications accompanied by DNA damage. Overall, these findings will augment our knowledge of the epigenetic mechanisms for pulmonary toxicity caused by ambient PM and HFD exposure.

Evaluation of the Methylation and Acetylation Profiles of Dinitroaniline Herbicides and Resveratrol on the V79 Cell Line

Objectives

Herbicides are among the most widely used pesticide compounds for plant growth control worldwide. Risk assessment of the dinitroaniline-derived herbicides pendimethalin and trifluralin is important for foodborne or other means of exposure. In this study, we aimed to evaluate the methylation and acetylation profiles of pendimethalin and trifluralin, which we have high levels of exposure to in various ways. Furthermore, we also determined the protective effect of resveratrol, an antioxidant compound, against the possible toxic effects of these pesticides.

Materials and Methods

The effects of pendimethalin and trifluralin alone (25, 50, 100 μM) and in combination with resveratrol (100 μM) on DNA methyltransferase (DNMT1) 1, 3a, and 3b; and histone deacetylase (HDAC) 1 and HDAC3 gene expression were evaluated by real-time polymerase chain reaction.

Results

According to the results, pendimethalin caused a significant decrease in DNMT1, 3a, 3b and HDAC expressions at all concentrations, whereas HDAC1 and 3 expression was increased at the concentration of 25 μM, when applied together with resveratrol. There were no changes in DNMT1 or 3b expression levels. Unlike pendimethalin, trifluralin increased DNMT1 expression in a concentration-dependent manner. While DNMT3a and DNMT3b expression levels increased significantly, HDAC1 and 3 expression levels did not change significantly. The expression levels of HDAC1 and HDAC3 increased at all concentrations of trifluralin combination with resveratrol. Moreover, DNMT levels increased at the concentrations of 50 and 100 μM.

Conclusion

Epigenetic gene expression results showed that pendimethalin and trifluralin might cause tissue function loss and chromosome damage as a result of direct effects on cell viability by causing expression level changes in all studied genes. It can also be concluded that the changes that occur in gene expression may induce tumor development. Further studies are needed to elucidate the possible toxicity mechanisms of these herbicides, considering the relationship between epigenetic changes and various diseases.

Small Molecules Targeting HATs, HDACs, and BRDs in Cancer Therapy

Evidence for research over the past decade shows that epigenetic regulation mechanisms run through the development and prognosis of tumors. Therefore, small molecular compounds targeting epigenetic regulation have become a research hotspot in the development of cancer therapeutic drugs. According to the obvious abnormality of histone acetylation when tumors occur, it suggests that histone acetylation modification plays an important role in the process of tumorigenesis. Currently, as a new potential anti-cancer therapeutic drugs, many active small molecules that target histone acetylation regulatory enzymes or proteins such as histone deacetylases (HDACs), histone acetyltransferase (HATs) and bromodomains (BRDs) have been developed to restore abnormal histone acetylation levels to normal. In this review, we will focus on summarizing the changes of histone acetylation levels during tumorigenesis, as well as the possible pharmacological mechanisms of small molecules that target histone acetylation in cancer treatment.

Histone Deacetylase Inhibition in Non-small Cell Lung Cancer: Hype or Hope?

Epigenetic modulation, including acetylation, methylation, phosphorylation, and ubiquitination, plays a pivotal role in regulation of gene expression. Histone acetylation-a balance between the activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs)-is one of the key epigenetic events. Our understanding of the role of HDACs in cancer is evolving. A number of HDAC isoenzymes are overexpressed in a variety of malignancies. Aberrant histone acetylation is associated with dysregulation of tumor suppressor genes leading to development of several solid tumors and hematologic malignancies. Pre-clinical studies have demonstrated that HDAC-1 gene expression is associated with lung cancer progression. Histone hypoacetylation is associated with more aggressive phenotype in adenocarcinoma of the lung. HDAC inhibitors (HDACi) have pleiotropic cellular effects and induce the expression of pro-apoptotic genes/proteins, cause cellular differentiation and/or cell cycle arrest, inhibit angiogenesis, and inhibit transition to a mesenchymal phenotype. Consequently, treatment with HDACi has shown anti-proliferative activity in non-small cell lung cancer (NSCLC) cell lines. Despite promising results in pre-clinical studies, HDACi have shown only modest single agent activity in lung cancer clinical trials. HDAC activation has been implicated as one of the mechanisms causing resistance to chemotherapy, molecularly targeted therapy, and immune checkpoint inhibition. Therefore, there is a growing interest in combining HDACi with these agents to enhance their efficacy or reverse resistance. In this paper, we review the available preclinical and clinical evidence for the use of HDACi in NSCLC. We also review the challenges precluding widespread clinical utility of HDACi as a cancer therapy and future directions.

HDAC Inhibitor, CG-745, Enhances the Anti-Cancer Effect of Anti-PD-1 Immune Checkpoint Inhibitor by Modulation of the Immune Microenvironment

Histone deacetylase inhibitors (HDACis) are well-known epigenetic regulators with therapeutic potential in various diseases. Recent studies have shown that HDACis are involved in immune-mediated anti-cancer effects and may modulate the activity of immunotherapy agents. CG-745, a histone deacetylase inhibitor, has shown anti-cancer effects in pancreatic cancer, colorectal cancer, and non-small cell lung cancer. However, the exact role of CG-745 within the immune system is largely unknown. In this study, we have shown that CG-745 induces microenvironment changes promoting anti-cancer effect of anti-PD-1 antibody in syngeneic mouse models. Specifically, CG-745 induces or extends IL-2 and IFN-γ expression with or without additional stimulation, and increases proliferation of cytotoxic T cells and NK cells, while inhibiting proliferation of regulatory T cells. The analysis of immune cell distribution in the tumor microenvironment and spleen reveals that CG-745 suppresses M2 macrophage polarization and decreases the myeloid-derived suppressor cells. Recent advances in immunotherapy highlight the anti-cancer effects of immune checkpoint inhibitor despite a relatively limited clinical benefit in the subset of patients. Our results indicate that CG-745 enables the synergistic effects of the immune checkpoint inhibitor combination therapy in various cancers by suppressing tumor microenvironment.

Histone deacetylase inhibitor, AR-42, exerts antitumor effects by inducing apoptosis and cell cycle arrest in Y79 cells

Retinoblastoma (RB) is the most common type of intraocular malignant tumor that occurs in childhood. AR-42, a member of a newly discovered class of phenylbutyrate-derived histone deacetylase inhibitors, exerts antitumor effects on many cancers. In the present study, we initially evaluated the effect of AR-42 towards RB cells and explored the underlying mechanism in this disease. Our results found that AR-42 showed powerful antitumor effects at low micromolar concentrations by inhibiting cell viability, blocking cell cycle, stimulating apoptosis in vitro, and suppressing RB growth in a mouse subcutaneous tumor xenograft model. Furthermore, the AKT/nuclear factor-kappa B signaling pathway was disrupted in Y79 cells treated with AR-42. In conclusion, we propose that AR-42 might be a promising drug treatment for RB.

Renoprotective Effect of the Histone Deacetylase Inhibitor CG200745 in DOCA-Salt Hypertensive Rats

The novel histone deacetylase inhibitor CG200745 was initially developed to treat various hematological and solid cancers. We investigated the molecular mechanisms associated with the renoprotective effects of CG200745 using deoxycorticosterone acetate (DOCA)-salt hypertensive (DSH) rats. DOCA strips (200 mg/kg) were implanted into rats one week after unilateral nephrectomy. Two weeks after DOCA implantation, DSH rats were randomly divided into two groups that received either physiological saline or CG200745 (5 mg/kg/day) for another two weeks. The extent of glomerulosclerosis and tubulointerstitial fibrosis was determined by Masson's trichrome staining. The renal expression of fibrosis and inflammatory markers was detected by semiquantitative immunoblotting, a polymerase chain reaction, and immunohistochemistry. Pathological signs such as glomerulosclerosis, tubulointerstitial fibrosis, increased systolic blood pressure, decreased creatinine clearance, and increased albumin-to-creatinine ratios in DSH rats were alleviated by CG200745 treatment compared to those manifestations in positive control animals. Furthermore, this treatment counteracted the increased expression of αSMA, TGF-β1, and Bax, and the decreased expression of Bcl-2 in the kidneys of DSH rats. It also attenuated the increase in the number of apoptotic cells in DSH rats. Thus, CG200745 can effectively prevent the progression of renal injury in DSH rats by exerting anti-inflammatory, anti-fibrotic, and anti-apoptotic effects.

Histone deacetylase inhibitor, CG200745 attenuates renal fibrosis in obstructive kidney disease

Tubulointerstitial fibrosis is a common feature of kidney disease. Histone deacetylase (HDAC) inhibitors have been reported to attenuate renal fibrosis progression. Here, we investigated the effect of CG200745, a novel HDAC inhibitor, on renal fibrosis development in a mouse model of unilateral ureteral obstruction (UUO). To examine the effects of CG200745 on renal fibrosis in UUO, C57BL/6 J male mice were divided into three groups: control, UUO, and CG200745 (30 mg/kg/day)-treated UUO groups. CG 200745 was administered through drinking water for 1 week. Human proximal tubular epithelial (HK-2) cells were also treated with CG200745 (10 µM) with or without TGF-β (2 ng/mL). Seven days after UUO, plasma creatinine did not differ among the groups. However, plasma neutrophil gelatinase-associated lipocalin (NGAL) levels were markedly increased in the UUO group, which were attenuated by CG200745 treatment. UUO kidneys developed marked fibrosis as indicated by collagen deposition and increased α-smooth muscle actin (SMA) and fibronectin expression. CG200745 treatment attenuated these fibrotic responses and suppressed UUO-induced production of transforming growth factor-beta1 (TGF-β) and phosphorylation of Smad-2/3. CG200745 treatment also attenuated UUO-induced inflammation as indicated by the expression of inflammatory markers. Furthermore, CG200745 attenuated phosphorylation of p38 mitogen-activated protein kinase in UUO kidneys. In HK-2 cells, TGF-β induced the expression of α-SMA and fibronectin, which were attenuated by CG200745 cotreatment. These results demonstrate that CG200745, a novel HDAC inhibitor, has a renoprotective effect by suppressing renal fibrosis and inflammation in a UUO mouse model.

Suberoylanilide hydroxamic acid increases anti-cancer effect of tumor necrosis factor-α through up-regulation of TNF receptor 1 in lung cancer cells

Suberoylanilide hydroxamic acid (SAHA) as a histone deacetylase (HDAC) inhibitor has anti-cancer effect. Here, we evaluated the effect of SAHA on HDAC activity and cell growth in many normal lung and cancer cells. We observed that the HDAC activities of lung cancer cells were higher than that of normal lung cells. SAHA inhibited the growth of lung cancer cells regardless of the inhibitory effect on HDAC. This agent induced a G2/M phase arrest and apoptosis, which was accompanied by mitochondrial membrane potential (MMP: ΔΨm) loss in lung cancer cells. However, SAHA did not induce cell death in normal lung cells. All tested caspase inhibitors prevented apoptotic cell death in SAHA-treated A549 and Calu-6 lung cancer cells. Treatment with tumor necrosis factor-alpha (TNF-α) enhanced apoptosis in SAHA-treated lung cancer cells through caspase-8 and caspase-9 activations. Especially, SAHA increased the expression level of TNF-α receptor 1 (TNFR1), especially acetylation of the region of TNFR1 promoter −223/-29 in lung cancer cells. The down-regulation of TNFR1 suppressed apoptosis in TNF-α and SAHA-treated lung cancer cells. In conclusion, SAHA inhibited the growth of lung cancer cells via a G2/M phase arrest and caspase-dependent apoptosis. SAHA also enhanced apoptotic effect of TNF-α in human lung cancer cells through up-regulation of TNFR1. TNF-α may be a key to improve anti-cancer effect of HDAC inhibitors.

CG200745, an HDAC inhibitor, induces anti-tumour effects in cholangiocarcinoma cell lines via miRNAs targeting the Hippo pathway

Cholangiocarcinoma is a devastating malignancy with fatal complications that exhibits low response and resistance to chemotherapy. Here, we evaluated the anticancer effects of CG200745, a novel histone deacetylase inhibitor, either alone or in combination with standard chemotherapy drugs in cholangiocarcinoma cells. CG200745 dose-dependently reduced the viability of cholangiocarcinoma cells in vitro and decreased tumour volume and weight in a xenograft model. Administering CG200745 along with other chemotherapeutic agents including gemcitabine, 5-fluorouracil (5-FU), cisplatin, oxaliplatin, or gemcitabine plus cisplatin further decreased cholangiocarcinoma cell viability, with a combination index < 1 that indicated synergistic action. CG200745 also enhanced the sensitivity of gemcitabine-resistant cells to gemcitabine and 5-FU, thereby decreasing cell viability and inducing apoptosis. This was accompanied by downregulation of YAP, TEAD4, TGF-β2, SMAD3, NOTCH3, HES5, Axl, and Gas6 and upregulation of the miRNAs miR-22-3p, miR-22-5p, miR-194-5p, miR-194-3p, miR-194-5p, miR-210-3p, and miR-509-3p. The Ingenuity Pathway Analysis revealed that CG200745 mainly targets the Hippo signalling pathway by inducing miR-509-3p expression. Thus, CG200745 inhibits cholangiocarcinoma growth in vitro and in vivo, and acts synergistically when administered in combination with standard chemotherapeutic agents, enabling dose reduction. CG200745 is therefore expected to improve the outcome of cholangiocarcinoma patients who exhibit resistance to conventional therapies.

Novel histone deacetylase inhibitor AR-42 exhibits antitumor activity in pancreatic cancer cells by affecting multiple biochemical pathways

OBJECTIVE

Pancreatic cancer is one of the most lethal types of cancer with a 5-year survival rate of ~5%. Histone deacetylases (HDACs) participate in many cellular processes, including carcinogenesis, and pharmacological inhibition of HDACs has emerged as a potential therapeutic strategy. In this study, we explored antitumor activity of the novel HDAC inhibitor AR-42 in pancreatic cancer.

METHODS

Human pancreatic cancer cell lines BxPC-3 and PANC-1 were used in this study. Real-time PCR, RT-PCR, and western blotting were employed to investigate expression of specific genes and proteins, respectively. Translocation of apoptosis-inducing factor was investigated by immunofluorescence and subcellular fractionation. The number of apoptotic cells, cell cycle stages, and reactive oxygen species (ROS) generation levels were determined by flow cytometry. Cell invasiveness was examined by the Matrigel invasion assay. Efficacy of AR-42 in vivo was evaluated by utilizing BxPC-3 xenograft mouse model.

RESULTS

AR-42 inhibited pancreatic cancer cell proliferation by causing G2/M cell cycle arrest via regulating expression levels of genes and proteins involved in cell cycle. AR-42 also induced ROS generation and DNA damage, triggering apoptosis of pancreatic cancer cells via both caspase-3-dependent and caspase-3-independent pathways. In addition, AR-42 increased expression levels of negative regulators of p53 (miR-125b, miR-30d, and miR33), which could contribute to lower expression level of mutant p53 in pancreatic cancer cells. Cell invasion assay showed that AR-42 reduced cancer cell aggressiveness and significantly diminished BxPC-3 xenograft tumor growth in vivo.

CONCLUSION

AR-42, a novel HDAC inhibitor, inhibited pancreatic cancer cells by regulating p53 expression, inducing cell cycle arrest, particularly at the G2/M stage, and activating multiple apoptosis pathways. Additionally, AR-42 inhibited cell invasiveness and potently suppressed pancreatic cancer tumors in vivo. We conclude that by virtue of its multiple mechanisms of action, AR-42 possesses a considerable potential as an antitumor agent in pancreatic cancer.

A novel HDAC inhibitor, CG200745, inhibits pancreatic cancer cell growth and overcomes gemcitabine resistance

Pancreatic cancer is predominantly lethal, and is primarily treated using gemcitabine, with increasing resistance. Therefore, novel agents that increase tumor sensitivity to gemcitabine are needed. Histone deacetylase (HDAC) inhibitors are emerging therapeutic agents, since HDAC plays an important role in cancer initiation and progression. We evaluated the antitumor effect of a novel HDAC inhibitor, CG200745, combined with gemcitabine/erlotinib on pancreatic cancer cells and gemcitabine-resistant pancreatic cancer cells. Three pancreatic cancer-cell lines were used to evaluate the antitumor effect of CG200745 combined with gemcitabine/erlotinib. CG200745 induced the expression of apoptotic proteins (PARP and caspase-3) and increased the levels of acetylated histone H3. CG200745 with gemcitabine/erlotinib showed significant growth inhibition and synergistic antitumor effects in vitro. In vivo, gemcitabine/erlotinib and CG200745 reduced tumor size up to 50%. CG200745 enhanced the sensitivity of gemcitabine-resistant pancreatic cancer cells to gemcitabine, and decreased the level of ATP-binding cassette-transporter genes, especially multidrug resistance protein 3 (MRP3) and MRP4. The novel HDAC inhibitor, CG200745, with gemcitabine/erlotinib had a synergistic anti-tumor effect on pancreatic cancer cells. CG200745 significantly improved pancreatic cancer sensitivity to gemcitabine, with a prominent antitumor effect on gemcitabine-resistant pancreatic cancer cells. Therefore, improved clinical outcome is expected in the future.

Histone deacetylase inhibitor, CG200745, attenuates cardiac hypertrophy and fibrosis in DOCA-induced hypertensive rats

CG200745 is a novel inhibitor of histone deacetylases (HDACs), initially developed for treatment of various hematological and solid cancers. Because it is water-soluble, it can be administered orally. We hypothesized that the HDAC inhibitor, CG200745, attenuates cardiac hypertrophy and fibrosis in deoxycorticosterone acetate (DOCA)-induced hypertensive rats. For establishment of hypertension, 40 mg/kg of DOCA was subcutaneously injected four times weekly into Sprague-Dawley rats. All the rats used in this study including those in the sham group had been unilaterally nephrectomized and allowed free access to drinking water containing 1% NaCl. Systolic blood pressure was measured by the tail-cuff method. Blood chemistry including sodium, potassium, glucose, triglyceride, and cholesterol levels was analyzed. Sections of the heart were visualized after trichrome and hematoxylin and eosin stain. The expression of hypertrophic genes such as atrial natriuretic peptide A (Nppa) and atrial natriuretic peptide B (Nppb) in addition to fibrotic genes such as Collagen-1, Collagen-3, connective tissue growth factor (Ctgf), and Fibronectin were measured by quantitative real-time PCR (qRT-PCR). Injection of DOCA increased systolic blood pressure, heart weight, and cardiac fibrosis, which was attenuated by CG200745. Neither DOCA nor CG200745 affected body weight, vascular contraction and relaxation responses, and blood chemistry. Injection of DOCA increased expression of both hypertrophic and fibrotic genes, which was abrogated by CG200745. These results indicate that CG200745 attenuates cardiac hypertrophy and fibrosis in DOCA-induced hypertensive rats.

Hexavalent Chromium (Cr(VI)) Down-Regulates Acetylation of Histone H4 at Lysine 16 through Induction of Stressor Protein Nupr1

The environmental and occupational carcinogen Hexavalent Chromium (Cr(VI)) has been shown to cause lung cancer in humans when inhaled. In spite of a considerable research effort, the mechanisms of Cr(VI)-induced carcinogenesis remain largely unknown. Nupr1 (nuclear protein 1) is a small, highly basic, and unfolded protein with molecular weight of 8,800 daltons and is induced by a variety of stressors. Studies in animal models have suggested that Nupr1 is a key factor in the development of lung and pancreatic cancers, with little known about the underlying molecular mechanisms. Here we report that the level of Nupr1 is significantly increased in human bronchial epithelial BEAS2B cells following exposure to Cr(VI) through epigenetic mechanisms. Interestingly, Cr(VI) exposure also results in the loss of acetylation at histone H4K16, which is considered a ‘hallmark’ of human cancer. Cr(VI)-induced reduction of H4K16 acetylation appears to be caused by the induction of Nupr1, since (a) overexpression of Nupr1 decreased the levels of both H4K16 acetylation and the histone acetyltransferase MOF (male absent on the first; also known as Kat8, Myst 1), which specifically acetylates H4K16; (b) the loss of acetylation of H4K16 upon Cr(VI) exposure is greatly compromised by knockdown of Nupr1. Moreover, Nupr1-induced reduction of H4K16 acetylation correlates with the transcriptional down-regulation at several genomic loci. Notably, overexpression of Nupr1 induces anchorage-independent cell growth and knockdown of Nupr1 expression prevents Cr(VI)-induced cell transformation. We propose that Cr(VI) induces Nupr1 and rapidly perturbs gene expression by downregulating H4K16 acetylation, thereby contributing to Cr(VI)-induced carcinogenesis.

Chordoma: The Quest for Better Treatment Options

Chordoma is an extremely rare cancer, with an incidence of about one case per million persons per year in the USA and Europe (about 300 and 450 cases per year, respectively). The estimated median overall survival of patients with chordoma is approximately 6–7 years, yielding a rough estimate of chordoma prevalence at about 2000 in the USA and 3000 in Europe. Primary tumor develops along the axial spine between the clivus and sacrum and develops from the residual embryonic notochord. Brachyury (T), a transcription factor required for normal embryonic development, is expressed in the notochord and overexpressed in almost all cases of chordoma. The primary treatment for chordoma is surgical excision with wide local margins, when possible. Radiotherapy also plays a significant role in the adjuvant setting and when surgery is not possible. Unfortunately, in the advanced and/or metastatic setting, where the role of surgery and/or radiation is less clear, treatment options are very limited. To date, there have been no randomized, controlled trials in chordoma that have resulted in defined agents of clinical benefit for systemic treatment. This review briefly describes the natural history and initial treatment of chordoma and focuses on treatment options for advanced disease and potential avenues of research that may lead to improved treatment options in the future.

Epigenetics in Personalized Management of Lung Cancer

In last several years, the focus on the origin and progression of human cancers has shifted from genetic to epigenetic regulation, with particular attention to methylation and acetylation events that have profound effect on the eventual expression of oncogenes and the suppression of tumor suppressors. A few drugs targeting these epigenetic changes have already been approved for treatment, albeit not for lung cancer. With the recent advances in the push towards personalized therapy, questions have been asked about the possible targeting of epigenetic events for personalized lung cancer therapy. Some progress has been made but a lot needs to be done. In this chapter, a succinct review of these topics is provided.

Targeting epigenetic regulations in cancer

Epigenetic regulation of gene expression is a dynamic and reversible process with DNA methylation, histone modifications, and chromatin remodeling. Recently, groundbreaking studies have demonstrated the importance of DNA and chromatin regulatory proteins from different aspects, including stem cell, development, and tumor genesis. Abnormal epigenetic regulation is frequently associated with diseases and drugs targeting DNA methylation and histone acetylation have been approved for cancer therapy. Although the network of epigenetic regulation is more complex than people expect, new potential druggable chromatin-associated proteins are being discovered and tested for clinical application. Here we review the key proteins that mediate epigenetic regulations through DNA methylation, the acetylation and methylation of histones, and the reader proteins that bind to modified histones. We also discuss cancer associations and recent progress of pharmacological development of these proteins.