Vorinostat interferes with the signaling transduction pathway of T-cell receptor and synergizes with phosphoinositide-3 kinase inhibitors in cutaneous T-cell lymphoma

Development of New Nanoniosome Carriers for Vorinostat: Evaluation of Anticancer Efficacy In Vitro

Vorinostat (VST) is a chemotherapeutic agent administrated for various types of cancers. However, it suffers from side effects and chemoresistance that reduce its application. Different nanoniosomes comprised Span 20, 60, 65 and 80 were prepared by the thin film hydration method and loaded with VST. The nanoniosomes were physicochemically characterized using particle size analysis and field emission scanning electron microscopy. The best formulation that was prepared using Span 65 (VST-NN-S65) included vesicle size of 127 nm with a narrow size distribution. VST-NN-S65 had an entrapment efficiency and loading capacity of 81.3 ± 5.1 and 32.0 ± 3.9 %, respectively. Drug release rate measurements showed that 90 % of VST was liberated within 1 h. Cytotoxicity assessments of VST-NN-S65 in HeLa and MCF7 cells indicated significant improvement in the effectiveness of VST, compared to the VST suspension. For VST-NN-S65, IC50 values of 26.3 and 6.6 μg mL-1 were obtained for HeLa and MCF7 cell lines, respectively. In situ apoptosis detection by the TUNEL assay revealed that apoptosis mainly occurred in the cell lines.

Immunobiology and treatment of cutaneous T-cell lymphoma

INTRODUCTION

Primary cutaneous T cell lymphomas (CTCL) are a heterogenous group of non-Hodgkin lymphomas derived from skin-homing T cells. These include mycosis fungoides and its leukemic variant Sezary syndrome, as well as the CD30+ lymphoproliferative disorders.

AREAS COVERED

In this review, we provide a summary of the current literature on CTCL, with a focus on the immunopathogenesis and treatment of mycosis fungoides and Sezary syndrome.

EXPERT OPINION

Recent advances in immunology have provided new insights into the biology of malignant T cells. This in turn has led to the development of new therapies that modulate the immune system to facilitate tumor clearance or target specific aspects of tumor biology.

Stage-related increase in PIM2 expression in mycosis fungoides

The oncogene PIM2 is upregulated in several malignancies but has never been investigated in mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). PIM2 is a well-known oncogene and is regulated by cell signaling pathways like the JAK/STAT- and NF-kB-pathway, key regulators in the pathogenesis of CTCL. The aim of this study was to examine the role of PIM2 in MF. PIM2 gene expression was measured in 81 formalin-fixed paraffin-embedded skin biopsies from patients with MF and 46 control biopsies from healthy skin (HS) and benign inflammatory skin disease (BID). Validation of PIM2 protein expression was performed on selected biopsies with immunohistochemical staining. We found a significant difference in gene expression levels between both early stage MF and HS (p < 0.0001), and BID (p < 0.0001). In addition, the PIM2 gene expression was higher in advanced-stage MF compared to early stage disease (p = 0.0001). No significant difference in gene expression levels was found between patients with and without disease progression. In conclusion, we found PIM2 expression is significantly increased in MF compared to controls, and in advanced-stage MF compared to early stage MF. These findings could potentially have diagnostic value in discriminating early stage MF from BID.

Targeting Histone Deacetylases 6 in Dual-Target Therapy of Cancer

Histone deacetylases (HDACs) are the major regulators of the balance of acetylation of histone and non-histone proteins. In contrast to other HDAC isoforms, HDAC6 is mainly involved in maintaining the acetylation balance of many non-histone proteins. Therefore, the overexpression of HDAC6 is associated with tumorigenesis, invasion, migration, survival, apoptosis and growth of various malignancies. As a result, HDAC6 is considered a promising target for cancer treatment. However, none of selective HDAC6 inhibitors are in clinical use, mainly because of the low efficacy and high concentrations used to show anticancer properties, which may lead to off-target effects. Therefore, HDAC6 inhibitors with dual-target capabilities represent a new trend in cancer treatment, aiming to overcome the above problems. In this review, we summarize the advances in tumor treatment with dual-target HDAC6 inhibitors.

Quatramer™ encapsulation of dual-targeted PI3-Kδ/HDAC6 inhibitor, HSB-510, suppresses growth of breast cancer

Multiple studies have shown that the progression of breast cancer depends on multiple signaling pathways, suggesting that therapies with multitargeted anticancer agents will offer improved therapeutic benefits through synergistic effects in inhibiting cancer growth. Dual-targeted inhibitors of phosphoinositide 3-kinase (PI3-K) and histone deacetylase (HDAC) have emerged as promising cancer therapy candidates. However, poor aqueous solubility and bioavailability limited their efficacy in cancer. The present study investigates the encapsulation of a PI3-Kδ/HDAC6 dual inhibitor into hybrid block copolymers (polylactic acid-methoxy polyethylene glycol; polylactic acid-polyethylene glycol-polypropylene glycol-polyethylene glycol-polylactic acid) (HSB-510) as a delivery system to target PI3-Kδ and HDAC6 pathways in breast cancer cells. The prepared HSB-510 showed an average diameter of 96 ± 3 nm, a zeta potential of -17 ± 2 mV, and PDI of ˂0.1 with a slow and sustained release profile of PI3-Kδ/HDAC6 inhibitors in a nonphysiological buffer. In vitro studies with HSB-510 have demonstrated substantial growth inhibition of breast cancer cell lines, MDA-MB-468, SUM-149, MCF-7, and Ehrlich ascites carcinoma (EAC) as well as downregulation of phospho-AKT, phospho-ERK, and c-Myc levels. Importantly, bi-weekly treatment of Balb/c wild-type mice harboring EAC cells with HSB-510 at a dose of 25 mg/kg resulted in significant tumor growth inhibition. The treatment with HSB-510 was without any significant effect on the body weights of the mice. These results demonstrate that a novel Quatramer encapsulation of a PI3-Kδ/HDAC6 dual inhibitor (HSB-510) represents an approach for the successful targeting of breast cancer and potentially other cancer types.

Differential Response of Mycosis Fungoides Cells to Vorinostat

Mycosis fungoides (MF) is the most common form of cutaneous T-cell lymphoma (CTCL) and is characterized by epidermotrophism of malignant CD4+ T-lymphocytes. When MF advances to a recurrent stage, patients require treatment with systemic therapies such as vorinostat, a histone deacetylase inhibitor. While vorinostat has been shown to exhibit anti-tumor activity in MF, its exact molecular mechanism has yet to be fully discerned. In the present study, we examined the transcriptomic and proteomic profiles of vorinostat treatment in two MF cell lines, Myla 2059 and HH. We find that vorinostat downregulates CTLA-4, CXCR4, and CCR7 in both cell lines, but its effect on several key pathways differs between the two MF cell lines. For example, vorinostat upregulates CCL5, CCR5, and CXCL10 expression in Myla cells but downregulates CCL5 and CXCL10 expression in HH cells. Furthermore, vorinostat upregulates IFN-γ and IL-23 signaling and downregulates IL-6, IL-7, and IL-15 signaling in Myla cells but does not affect these pathways in HH cells. Although Myla and HH represent established MF cell lines, their distinct tumor origin from separate patients demonstrates that inherent phenotypic variations within the disease persist, underscoring the importance of using a variety of MF cells in the preclinical development of MF therapeutics.

Harnessing the immune system in the treatment of cutaneous T cell lymphomas

Cutaneous T cell lymphomas are a rare subset of non-Hodgkin's lymphomas with predilection for the skin with immunosuppressive effects that drive morbidity and mortality. We are now appreciating that suppression of the immune system is an important step in the progression of disease. It should come as no surprise that therapies historically and currently being used to treat these cancers have immune modulating functions that impact disease outcomes. By understanding the immune effects of our therapies, we may better develop new agents that target the immune system and improve combinatorial treatment strategies to limit morbidity and mortality of these cancers. The immune modulating effect of therapeutic drugs in use and under development for cutaneous T cell lymphomas will be reviewed.

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.

Exploring the oncogenic and therapeutic target potential of the MYB-TYK2 fusion gene in B-cell acute lymphoblastic leukemia

TYK2-rearrangements have recently been identified in high-risk acute lymphoblastic leukemia (HR-ALL) cases and are associated with poor outcome. Current understanding of the leukemogenic potential and therapeutic targetability of activating TYK2 alterations in the ALL setting is unclear, thus further investigations are warranted. Consequently, we developed in vitro, and for the first time, in vivo models of B-cell ALL from a patient harboring the MYB-TYK2 fusion gene. These models revealed JAK/STAT signaling activation and the oncogenic potential of the MYB-TYK2 fusion gene in isolation. High throughput screening identified the HDAC inhibitor, vorinostat and the HSP90 inhibitor, tanespimycin plus the JAK inhibitor, cerdulatinib as the most effective agents against cells expressing the MYB-TYK2 alteration. Evaluation of vorinostat and cerdulatinib in pre-clinical models of MYB-TYK2-rearranged ALL demonstrated that both drugs exhibited anti-leukemic effects and reduced the disease burden in treated mice. Importantly, these findings indicate that activating TYK2 alterations can function as driver oncogenes rather than passenger or secondary events in disease development. In addition, our data provide evidence for use of vorinostat and cerdulatinib in the treatment regimens of patients with this rare yet aggressive type of high-risk ALL that warrants further investigation in the clinical setting.

Vorinostat in autophagic cell death: A critical insight into autophagy-mediated, -associated and -dependent cell death for cancer prevention

Histone deacetylases (HDACs) inhibit the acetylation of crucial autophagy genes, thereby deregulating autophagy and autophagic cell death (ACD) and facilitating cancer cell survival. Vorinostat, a broad-spectrum pan-HDAC inhibitor, inhibits the deacetylation of key autophagic markers and thus interferes with ACD. Vorinostat-regulated ACD can have an autophagy-mediated, -associated or -dependent mechanism depending on the involvement of apoptosis. Molecular insights revealed that hyperactivation of the PIK3C3/VPS34-BECN1 complex increases lysosomal disparity and enhances mitophagy. These changes are followed by reduced mitochondrial biogenesis and by secondary signals that enable superactivated, nonselective or bulk autophagy, leading to ACD. Although the evidence is limited, this review focuses on molecular insights into vorinostat-regulated ACD and describes critical concepts for clinical translation.

Functional Depletion of HSP72 by siRNA and Quercetin Enhances Vorinostat-Induced Apoptosis in an HSP72-Overexpressing Cutaneous T-Cell Lymphoma Cell Line, Hut78

Histone deacetylase inhibitors (HDACis) are one of the therapeutic options for cutaneous T-cell lymphoma (CTCL), but they have limited effects. We previously demonstrated that HSP72 overexpression is associated with chemoresistance to HDACis in lymphoma cells. The purpose of this study was to investigate whether the functional depletion of HSP72 enhances the effect of the HDACi vorinostat. First, we established a stable HSP72-knockdown CTCL cell line and confirmed the influence of HSP72 reduction on the antitumor effects of vorinostat. Next, we studied the effect of quercetin, an inhibitor of HSP72, on the antineoplastic effects of vorinostat. In five CTCL cell lines examined, HSP72 expression was highest in Hut78 cells, and HSP72 knockdown enhanced vorinostat-induced apoptosis in these cells. Low-dose quercetin reduced HSP72 expression, increased HDAC activity, and enhanced vorinostat-induced suppression of Hut78 cell proliferation. A single low dose of quercetin induced G2 arrest and only slightly increased the sub-G1 cell fraction. Quercetin also significantly enhanced vorinostat-induced apoptosis, caspase-3, caspase-8, and caspase-9 activity, and the loss of mitochondrial membrane potential. HSP72 knockdown enhanced vorinostat-induced apoptosis in an HSP72-overexpressing CTCL cell line, and thus, quercetin may be a suitable candidate for combination therapy with vorinostat in clinical settings.

The contributory roles of histone deacetylases (HDACs) in hematopoiesis regulation and possibilities for pharmacologic interventions in hematologic malignancies

Although the definitive role of epigenetic modulations in a wide range of hematologic malignancies, spanning from leukemia to lymphoma and multiple myeloma, has been evidenced, few articles reviewed the task. Given the high accessibility of histone deacetylase (HDACs) to necessary transcription factors involved in hematopoiesis, this review aims to outline physiologic impacts of these enzymes in normal hematopoiesis, and also to outline the original data obtained from international research laboratories on their regulatory role in the differentiation and maturation of different hematopoietic lineages. Questions on how aberrant expression of HDACs contributes to the formation of hematologic malignancies are also responded, because these classes of enzymes have a respectable share in the development, progression, and recurrence of leukemia, lymphoma, and multiple myeloma. The last section provides a special focus on the therapeutic perspectiveof HDACs inhibitors, either as single agents or in a combined-modal strategy, in these neoplasms. In conclusion, optimizing the dose and the design of more patient-tailored inhibitors, while maintaining low toxicity against normal cells, will help improve clinical outcomes of HDAC inhibitors in hematologic malignancies.

Novel Suberoylanilide Hydroxamic Acid Analogs Inhibit Angiogenesis and Induce Apoptosis in Breast Cancer Cells

BACKGROUND

Histone deacetylases (HDACs) are the enzymes that catalyze the removal of the acetyl group from lysine residues and regulate several biological processes. Suberoylanilide hydroxamic acid (SAHA) is a notable HDAC inhibitor that exhibited remarkable anti-proliferative efficiency by alleviating gene regulation against solid and hematologic cancers.

AIM

The aim of this study was to develop new chemotherapeutic agents for breast cancer treatment, therefore, a novel series of Suberoylanilide hydroxamic acid (SAHA) analogs were investigated as anticancer agents.

METHODS

We designed and synthesized a novel series of analogs derived from SAHA by substituting alkyl, alkoxy, halo, and benzyl groups at different positions of the phenyl ring. The newly synthesized analogs were assessed for their cytotoxic potential against four human cancer cell lines in comparison with healthy cell lines, using several biological assays.

RESULTS

SAHA analogs displayed significant cytotoxic potential with IC50 values ranging from 1.6 to 19.2 µM in various tumor cell lines. Among these analogs, 2d (containing 3-chloro, 4-floro substitutions on phenyl moiety), 2h (containing 3,4-di chloro substitutions on phenyl moiety), and 2j (containing 4-chloro, 3-methyl substitutions on phenyl moiety) showed significant cytotoxic potential with IC50 values ranging from 1.6 to 1.8 µM in MCF-7 (breast carcinoma) cell line. More importantly, these analogs were found to be non-toxic towards healthy primary human hepatocytes (PHH) and mouse fibroblast cells (NIH3T3), which represent their tumor selectivity. These analogs were further analyzed for their effect on cell migration, BrdU incorporation, Annexin V-FITC and cell cycle arrest (Sub-G1 phase). Remarkably, analogs 2d, 2h, and 2j displayed significant HDAC inhibition than the parent SAHA molecule. Further studies also confirmed that these SAHA analogs are efficient in inducing apoptosis, as they regulated the expression of several proteins involved in mitochondrial or intrinsic apoptosis pathways. Findings in the Chick Chorioallantoic Membrane (CAM) assay studies revealed anti-angiogenic properties of the currently described SAHA analogs.

CONCLUSION

From anti-proliferative study results, it is clearly evident that 3,4-substitution at the SAHA phenyl ring improves the anti-proliferative activity of SAHA. Based on these findings, we presume that the synthesized novel SAHA analogs could be potential therapeutic agents in treating breast cancer.

Epigenetics in the Pathogenesis and Treatment of Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphomas (CTCLs) comprise a group of heterogeneous diseases involving malignant T cells. The pathogenesis and etiology of CTCL are still unclear, although a large number of genetic and epidemiological studies on CTCL have been conducted. Most CTCLs have an indolent course, making early diagnosis difficult. Once large-cell transformation occurs, CTCL progresses to more aggressive types, resulting in an overall survival of less than five years. Epigenetic drugs, which have shown certain curative effects, have been selected as third-line drugs in patients with relapsing and refractory CTCL. Many studies have also identified epigenetic biomarkers from tissues and peripheral blood of patients with CTCL and suggested that epigenetic changes play a role in malignant transformation and histone deacetylase inhibitor (HDACi) resistance in CTCL. Single-cell sequencing has been applied in CTCL studies, revealing heterogeneity in CTCL malignant T cells. The mechanisms of HDACi resistance have also been described, further facilitating the discovery of novel HDACi targets. Despite the heterogeneity of CTCL disease and its obscure pathogenesis, more epigenetic abnormalities have been gradually discovered recently, which not only enables us to understand CTCL disease further but also improves our understanding of the specific role of epigenetics in the pathogenesis and treatment. In this review, we discuss the recent discoveries concerning the pathological roles of epigenetics and epigenetic therapy in CTCL.

Kinome profiling analysis identified Src pathway as a novel therapeutic target in combination with histone deacetylase inhibitors for cutaneous T-cell lymphoma

BACKGROUND

Histone deacetylase inhibitors (HDACi) are used to treat patients with cutaneous T-cell lymphoma (CTCL), but they show limited efficacy. Hence, combination therapies should be explored to enhance the effectiveness of HDACis.

OBJECTIVE

This study was conducted to identify novel therapeutic targets that can be combined with HDACis for treating CTCL.

METHODS

We performed a global kinome profiling assay of three CTCL cell lines (HH, MJ, and Hut78) with three HDACis (romidepsin, vorinostat, and belinostat) using the PamChip® microarray. The three cell lines were co-treated with romidepsin and an inhibitor against the tyrosine kinase pathway.

RESULTS

Principal component analysis revealed that kinome expression patterns were mainly related to the cell origin and were not affected by the drugs. Few kinases were commonly activated by the HDACis. Most identified kinases were Src-associated molecules, such as annexin A2, embryonal Fyn-associated substrate, and progesterone receptor. Phosphorylated Src was not observed in any untreated cell lines, whereas Src phosphorylation was detected in two of the three cell lines after HDACi treatment. Ponatinib, a Src inhibitor, significantly enhanced romidepsin-induced apoptosis not only in HH, MJ, and Hut78 cells, but also in Myla and SeAx CTCL cell lines.

CONCLUSION

The Src pathway is a possible target for combination therapy involving HDACis for CTCL.

Multitarget Inhibition of Histone Deacetylase (HDAC) and Phosphatidylinositol-3-kinase (PI3K): Current and Future Prospects

The discovery of histone deacetylase (HDAC) inhibitors is a hot topic in the medicinal chemistry community regarding cancer research. This is related primarily to two factors: success in the clinic, e. g., the four FDA-approved HDAC inhibitors, and strong versatility to combine their pharmacophoric features to design new hybrid compounds with multitarget profiles. Thus, the selection of adequate pharmacophores to combine, i. e., combining targets that can result in a synergistic effect, is desirable, as it increases the probability of discovering a new useful therapeutic strategy. In this work, we highlight the design of multitarget HDAC/PI3K inhibitors. Although this approach is still in its early stages, many significant works have described the design and pharmacological evaluation of this new promising class of multitarget inhibitors, where compound CUDC-907, which is already in clinical trials, stands out. Therefore, the question emerges of whether there still space for the design and evaluation of new multitarget HDAC/PI3K inhibitors. When considering the selectivity profile of the described multitarget compounds, the answer appears to be in the affirmative, especially since the first examples of compounds with a certain selectivity profile only recently appeared in 2020.

Resistance to histone deacetylase inhibitors confers hypersensitivity to oncolytic reovirus therapy

Despite the promising antilymphoma activity of histone deacetylase (HDAC) inhibitors as a drug class, resistance is a significant clinical issue. Elucidating the molecular mechanisms driving HDAC inhibitor resistance and/or the specific targets that are altered in drug-resistant cells may facilitate the development of strategies that overcome drug resistance and are more effective for refractory patients. We generated novel T-cell lymphoma (TCL) cell line models of acquired resistance to the HDAC inhibitor belinostat to identify potential effective therapies. Belinostat-resistant cells displayed significant cross-resistance to other HDAC inhibitors including romidepsin, panobinostat, and vorinostat. Consistent with a lack of sensitivity to HDAC inhibitors, the resistant cells failed to induce increased acetylated histones. Drug-resistant cells featured significantly decreased expression of the key antiviral mediators IRF1 and STAT1. On the basis of these findings, we investigated the efficacy of the clinical formulation of reovirus (Reolysin) in parental and drug-resistant models. Our investigation revealed that HDAC inhibitor-resistant cells displayed enhanced vulnerability to reovirus replication and cell death in both in vitro and in vivo models compared with their parental counterparts. Importantly, Reolysin also significantly increased the antilymphoma activity of belinostat in HDAC inhibitor-resistant cells. Our data demonstrate that Reolysin alone or in combination with belinostat is a novel therapeutic strategy to treat TCL patients who develop resistance to HDAC inhibitors.

Dual inhibition of HDAC and tyrosine kinase signaling pathways with CUDC-907 attenuates TGFβ1 induced lung and tumor fibrosis

TGFβ1 signaling is a critical driver of collagen accumulation in pulmonary fibrotic diseases and a well-characterized regulator of cancer associated fibroblasts (CAF) activation in lung cancer. Myofibroblasts induced by TGFβ1 and other factors are key players in the pathogenesis of lung fibrosis and tumor. Tremendous attention has been gained to targeting myofibroblasts in order to inhibit the progression of fibrosis and myofibroblast-induced tumor progression and metastasis. Here we determined the therapeutic efficacy of simultaneously targeting PI3K and HDAC pathways in lung myofibroblasts and CAF with a single agent and to evaluate biomarkers of treatment response. CUDC-907 is a first-in-class compound, functioning as a dual inhibitor of HDACs and PI3K/AKT pathway. We investigated its effects in counteracting the activity of TGFβ1-induced myofibroblasts/CAF in regard to cell proliferation, migration, invasion, apoptosis in vitro antifibrosis efficiency in vivo. We found that CUDC-907 inhibited myofibroblasts/CAF cell proliferation, migration and apoptosis in a dose-dependent manner and caused cell cycle arrest at G1-S phase. CUDC-907 not only inhibited myofibroblasts markers expression, but also significantly inhibited the phosphorylation level of AKT, mTOR, Smad2/3, and promoted acetylation of histones. Furthermore, the observed inhibitory effect was also confirmed in bleomycin-induced mice lung fibrosis and nude mouse transplanted tumor model. Overall, these data suggest that dual inhibition of HDAC and the tyrosine kinase signaling pathways with CUDC-907 is a promising treatment strategy for TGFβ1-induced lung and tumor fibrosis.

Recent Update of HDAC Inhibitors in Lymphoma

Modulating epigenetic modification has been recognized for over a decade as an effective therapeutic approach to cancer and many studies of histone deacetylase (HDAC), one of the best known epigenetic modulators, have been published. HDAC modulates cell proliferation and angiogenesis and plays an essential role in cell growth. Research shows that up-regulated HDACs are present in many cancer types and synthetic or natural HDAC inhibitors have been used to silence overregulated HDACs. Inhibiting HDACs may cause arrest of cell proliferation, angiogenesis reduction and cell apoptosis. Recent studies indicate that HDAC inhibitors can provide a therapeutic effect in various cancers, such as B-cell lymphoma, leukemia, multiple myeloma and some virus-associated cancers. Some evidence has demonstrated that HDAC inhibitors can increase the expression of immune-related molecules leading to accumulation of CD8 + T cells and causing unresponsive tumor cells to be recognized by the immune system, reducing tumor immunity. This may be a solution for the blockade of PD-1. Here, we review the emerging development of HDAC inhibitors in various cancer treatments and reduction of tumor immunity.

Current status of histone deacetylase inhibitors in cutaneous T-cell lymphoma

Cutaneous T cell lymphoma (CTCL) is a non-Hodgkin's lymphoma with a heterogenous presentation and highly variable disease course. The most common subtypes of CTCL are mycosis fungoides (MF) and Sézary Syndrome (SS). Treatment varies based on the stage of the disease with skin directed therapies typically utilized for early stage disease, and systemic therapies employed for more advanced disease. There are few highly effective treatments available, and systemic therapies have limited response rates. Histone deacetylase inhibitors have emerged as mainstream treatments for MF/SS over the past several years. Here, we discuss the mechanism of action of histone deacetylase inhibitors in relation to the pathogenesis of MF/SS, evaluate the clinical trials that led to Food and Drug Administration approval of two of the histone deacetylase inhibitors for MF/SS and describe the results for those still under investigation. Additionally, we discuss the potential for combination therapies in order to optimize outcomes of treatment with histone deacetylase inhibitors.

Selective inhibition of HDAC6 sensitizes cutaneous T-cell lymphoma to PI3K inhibitors

Histone deacetylase (HDAC) inhibitors, approved for the treatment of cutaneous T-cell lymphoma (CTCL), are non-selective agents associated with an unsatisfactory response and considerable side-effects. Targeting single HDAC isoforms is considered to provide novel therapeutic options. HDAC6 is overexpressed in primary samples from patients with CTCL and preclinical studies using transgenic mice that spontaneously develop a CTCL-like disease, have suggested that combinations including HDAC6 inhibitors may be successful in the treatment of CTCL. PI3K inhibition is currently being tested in clinical trials for CTCL with promising results. Since HDAC6 is known to diminish the activity of Akt via its deacetylation, the aim of the present study was to evaluate the therapeutic potential of selective HDAC6 inhibitors in combination with PI3K inhibitors in CTCL. Through the genetic and pharmacological inhibition of HDAC6, it was demonstrated that combining HDAC6 with PI3K inhibition may be an attractive therapeutic option for patients with CTCL.

In Vitro and In Vivo Effects of the Polymyxin-Vorinostat Combination Therapy Against Multidrug-Resistant Gram-Negative Pathogens

With the stagnancy of antibiotics development, polymyxins have become the last defense for treatment of multidrug-resistant (MDR) Gram-negative bacteria, whereas the effect of polymyxin monotherapy is limited by resistance. The objective of this study was to evaluate the effects of polymyxin B (PMNB)-vorinostat (SAHA) combination therapy against Gram-negative pathogens in vitro and in vivo. The antibacterial activities of PMNB and SAHA were evaluated by susceptibility testing. The synergistic effect was assessed by checkerboard tests and time-killing kinetics experiments. Cellular morphology studies and reactive oxygen species (ROS) assay were conducted to explore potential mechanisms. Also, Galleria mellonella models were made to evaluate the antibacterial effects in vivo. PMNB-SAHA had the synergistic effect against all tested isolates, reducing >2 log₁₀ colony-forming units (CFU)/mL at 40 minutes, and showed more powerful antibacterial effects than PMNB alone in the 24-hour window. Cellular morphology study showed the change of membrane and disruption of integrity. ROS assay showed more oxidative stress in combination than PMNB or SAHA monotherapy. In animal models, PMNB-SAHA showed a higher survival rate than that of monotherapy. This study is the first to report the synergistic antibacterial effect of PMNB-SAHA therapy against MDR Gram-negative bacteria. Further clinical research is needed to confirm the results.

Design, Synthesis, and Pharmacological Evaluation of First-in-Class Multitarget N-Acylhydrazone Derivatives as Selective HDAC6/8 and PI3Kα Inhibitors

Targeting histone deacetylases (HDACs) and phosphatidylinositol 3-kinases (PI3Ks) is a very promising approach for cancer treatment. This manuscript describes the design, synthesis, in vitro pharmacological profile, and molecular modeling of a novel class of N-acylhydrazone (NAH) derivatives that act as HDAC6/8 and PI3Kα dual inhibitors. The surprising selectivity for PI3Kα may be related to differences in the conformation in the active site. Cellular studies showed that these compounds act in HDAC6 inhibition and the PI3/K/AKT/mTOR pathway. The compounds that are selective for inhibition of HDAC6/8 and inhibit PI3Kα show potential for the treatment of cancer.

Impaired T cell proliferation by ex vivo BET-inhibition impedes adoptive immunotherapy in a murine melanoma model

Activation of naïve CD8+ T cells stimulates proliferation and differentiation into cytotoxic T-lymphocytes (CTLs). Adoptive T Cell Therapy (ACT) involves multiple rounds of ex vivo activation to generate enough CTLs for reinfusion into patients, but this drives differentiation into terminal effector T cells. Less differentiated CTL populations, such as stem cell memory T cells, are more ideal candidates for ACT because of increased self-renewal and persistent properties. Ex vivo targeting of T cell differentiation with epigenetic modifiers is a potential strategy to improve cytotoxic T-lymphocyte (CTL) generation for ACT. We established a pipeline to assess the effects of epigenetic modifiers on CD8+ T cell proliferation, differentiation, and efficacy in a preclinical melanoma model. Single treatment with epigenetic modifiers inhibited T cell proliferation in vitro, producing CD44hiCD62Lhi effector-like T cells rather than a stem cell memory T cell phenotype. Most epigenetic modifying agents had no significant effect on ACT efficacy with the notable exception of the bromodomain and extraterminal (BET)-inhibitor JQ1 which was associated with a decrease in efficacy compared to unmodified T cells. These findings reveal the complexity of epigenetic targeting of T cell differentiation, highlighting the need to precisely define the epigenetic targeting strategies to improve CTL generation for ACT.

Cancer genome landscape: a radiologist's guide to cancer genome medicine with imaging correlates

The introduction of high throughput sequence analysis in the past decade and the decrease in sequencing costs has made available an enormous amount of genomic data. These data have shaped the landscape of cancer genome, which encompasses mutations determining tumorigenesis, the signaling pathways involved in cancer growth, the tumor heterogeneity, and its role in development of metastases. Tumors develop acquiring a series of driver mutations over time. Of the many mutated genes present in cancer, only few specific mutations are responsible for invasiveness and metastatic potential, which, in many cases, have characteristic imaging appearance. Ten signaling pathways, each with targetable components, have been identified as responsible for cancer growth. Blockage of any of these pathways form the basis for molecular targeted therapies, which are associated with specific pattern of response and toxicities. Tumor heterogeneity, responsible for the different mutation pattern of metastases and primary tumor, has been classified in intratumoral, intermetastatic, intrametastatic, and interpatient heterogeneity, each with specific imaging correlates. The purpose of this article is to introduce the key components of the landscapes of cancer genome and their imaging counterparts, describing the types of mutations associated with tumorigenesis, the pathways of cancer growth, the genetic heterogeneity involved in metastatic disease, as well as the current challenges and opportunities for cancer genomics research.

Long non-coding RNAs and latent HIV - A search for novel targets for latency reversal

The latent cellular reservoir of HIV is recognized as the major barrier to cure from HIV infection. Long non-coding RNAs (lncRNAs) are more tissue and cell type-specific than protein coding genes, and may represent targets of choice for HIV latency reversal. Using two in vitro primary T-cell models, we identified lncRNAs dysregulated in latency. PVT1 and RP11-347C18.3 were up-regulated in common between the two models, and RP11-539L10.2 was down-regulated. The major component of the latent HIV reservoir, memory CD4+ T-cells, had higher expression of these lncRNAs, compared to naïve T-cells. Guilt-by-association analysis demonstrated that lncRNAs dysregulated in latency were associated with several cellular pathways implicated in HIV latency establishment and maintenance: proteasome, spliceosome, p53 signaling, and mammalian target of rapamycin (MTOR). PVT1, RP11-347C18.3, and RP11-539L10.2 were down-regulated by latency reversing agents, suberoylanilide hydroxamic acid and Romidepsin, suggesting that modulation of lncRNAs is a possible secondary mechanism of action of these compounds. These results will facilitate prioritization of lncRNAs for evaluation as targets for HIV latency reversal. Importantly, our study provides insights into regulatory function of lncRNA during latent HIV infection.

CUDC‑907 reverses pathological phenotype of keloid fibroblasts in vitro and in vivo via dual inhibition of PI3K/Akt/mTOR signaling and HDAC2

Keloids are benign skin tumors with a high recurrence rate following surgical excision. Abnormal intracellular signaling is one of the key mechanisms involved in its pathogenesis. Over-activated phosphoinositide 3-kinase/RAC-alpha serine/threonine-protein kinase/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway and overproduction of histone deacetylases 2 (HDAC2) have also been observed in keloid fibroblasts (KFs). The present study aimed to explore the possibility of reversing the KF pathological phenotype using CUDC-907, a dual inhibitor of PI3K/Akt/mTOR pathway and HDACs. KFs and keloid xenografts were treated with CUDC-907 to examine its inhibitory effects on the pathological activities of KFs in vitro and in vivo. CUDC-907 inhibited cell proliferation, migration, invasion and extracellular matrix deposition of in vitro cultured KFs and also suppressed collagen accumulation and disrupted the capillaries of keloid explants ex vivo and in vivo. A mechanistic study of CUDC-907 revealed the initiation of cell cycle arrest at G2/M phase along with the enhanced expression of cyclin-dependent kinase inhibitor 1 and decreased expression of cyclin B in cells treated with CUDC-907. CUDC-907 not only inhibited AKT and mTOR phosphorylation and promoted the acetylation of histone H3, but also significantly inhibited the phosphorylation levels of Smad2/3 and Erk. These preclinical data demonstrating its anti-keloid effects suggest that CUDC-907 may represent a candidate drug for systemic keloid therapy.

The role of aurora A and polo-like kinases in high-risk lymphomas

High-risk lymphomas (HRLs) are associated with dismal outcomes and remain a therapeutic challenge. Recurrent genetic and molecular alterations, including c-myc expression and aurora A kinase (AAK) and polo-like kinase-1 (PLK1) activation, promote cell proliferation and contribute to the highly aggressive natural history associated with these lymphoproliferative disorders. In addition to its canonical targets regulating mitosis, the AAK/PLK1 axis directly regulates noncanonical targets, including c-myc. Recent studies demonstrate that HRLs, including T-cell lymphomas and many highly aggressive B-cell lymphomas, are dependent upon the AAK/PLK1 axis. Therefore, the AAK/PLK1 axis has emerged as an attractive therapeutic target in these lymphomas. In addition to reviewing these recent findings, we summarize the rationale for targeting AAK/PLK1 in high-risk and c-myc-driven lymphoproliferative disorders.

Integrative microRNA and gene expression analysis identifies new drug repurposing candidates for fetal hemoglobin induction in β-hemoglobinopathies

Therapeutic induction of fetal hemoglobin (HbF) is one of the most promising approaches to ameliorate the severity of hemoglobinopathies like β-thalassemia and sickle cell anemia. Although several pharmacological agents have been investigated for HbF induction in adults, the majority of these are associated with significant side-effects. While drug repurposing is known to open new doors for the use of approved drugs in unexplored clinical conditions, the primary challenge lies in identifying such candidates. In this study, we aimed to identify repurposing candidates for HbF induction using a novel in silico approach utilizing microRNA-pathway-drug relationships. A computational drug repurposing strategy identified several unique candidates for HbF induction; among which Curcumin, Ginsenoside, Valproate, and Vorinostat were found to be most suitable for future trials. This study identified new drug repurposing candidates for HbF induction and demonstrates an easily adaptable methodology that can be used for other pathophysiological conditions.

Histone deacetylase inhibitors induce complex host responses that contribute to differential potencies of these compounds in HIV reactivation

Histone deacetylase (HDAC) inhibitors (HDACis) have been widely tested in clinical trials for their ability to reverse HIV latency but have yielded only limited success. One HDACi, suberoylanilide hydroxamic acid (SAHA), exhibits off-target effects on host gene expression predicted to interfere with induction of HIV transcription. Romidepsin (RMD) has higher potency and specificity for class I HDACs implicated in maintaining HIV provirus in the latent state. More robust HIV reactivation has indeed been achieved with RMD use ex vivo than with SAHA; however, reduction of viral reservoir size has not been observed in clinical trials. Therefore, using RNA-Seq, we sought to compare the effects of SAHA and RMD on gene expression in primary CD4+ T cells. Among the genes whose expression was modulated by both HDACi agents, we identified genes previously implicated in HIV latency. Two genes, SMARCB1 and PARP1, whose modulation by SAHA and RMD is predicted to inhibit HIV reactivation, were evaluated in the major maturation subsets of CD4+ T cells and were consistently either up- or down-regulated by both HDACi compounds. Our results indicate that despite having different potencies and HDAC specificities, SAHA and RMD modulate an overlapping set of genes, implicated in HIV latency regulation. Some of these genes merit exploration as additional targets to improve the therapeutic outcomes of "shock and kill" strategies. The overall complexity of HDACi-induced responses among host genes with predicted stimulatory or inhibitory effects on HIV expression likely contributes to differential HDACi potencies and dictates the outcome of HIV reactivation.

Histone Deacetylases (HDACs) Guided Novel Therapies for T-cell lymphomas

T-cell lymphomas are a heterogeneous group of cancers with different pathogenesis and poor prognosis. Histone deacetylases (HDACs) are epigenetic modifiers that modulate many key biological processes. In recent years, HDACs have been fully investigated for their roles and potential as drug targets in T-cell lymphomas. In this review, we have deciphered the modes of action of HDACs, HDAC inhibitors as single agents, and HDACs guided combination therapies in T-cell lymphomas. The overview of HDACs on the stage of T-cell lymphomas, and HDACs guided therapies both as single agents and combination regimens endow great opportunities for the cure of T-cell lymphomas.

Dying to Be Noticed: Epigenetic Regulation of Immunogenic Cell Death for Cancer Immunotherapy

Immunogenic cell death (ICD) activates both innate and adaptive arms of the immune system during apoptotic cancer cell death. With respect to cancer immunotherapy, the process of ICD elicits enhanced adjuvanticity and antigenicity from dying cancer cells and consequently, promotes the development of clinically desired antitumor immunity. Cancer ICD requires the presentation of various "hallmarks" of immunomodulation, which include the cell-surface translocation of calreticulin, production of type I interferons, and release of high-mobility group box-1 and ATP, which through their compatible actions induce an immune response against cancer cells. Interestingly, recent reports investigating the use of epigenetic modifying drugs as anticancer therapeutics have identified several connections to ICD hallmarks. Epigenetic modifiers have a direct effect on cell viability and appear to fundamentally change the immunogenic properties of cancer cells, by actively subverting tumor microenvironment-associated immunoevasion and aiding in the development of an antitumor immune response. In this review, we critically discuss the current evidence that identifies direct links between epigenetic modifications and ICD hallmarks, and put forward an otherwise poorly understood role for epigenetic drugs as ICD inducers. We further discuss potential therapeutic innovations that aim to induce ICD during epigenetic drug therapy, generating highly efficacious cancer immunotherapies.

Metabolomic Profiling Reveals Cellular Reprogramming of B-Cell Lymphoma by a Lysine Deacetylase Inhibitor through the Choline Pathway

Despite the proven clinical antineoplastic activity of histone deacetylase inhibitors (HDACI), their effect has been reported to be lower than expected in B-cell lymphomas. Traditionally considered as “epigenetic drugs”, HDACI modify the acetylation status of an extensive proteome, acting as general lysine deacetylase inhibitors (KDACI), and thus potentially impacting various branches of cellular metabolism. Here, we demonstrate through metabolomic profiling of patient plasma and cell lines that the KDACI panobinostat alters lipid metabolism and downstream survival signaling in diffuse large B-cell lymphomas (DLBCL). Specifically, panobinostat induces metabolic adaptations resulting in newly acquired dependency on the choline pathway and activation of PI3K signaling. This metabolic reprogramming decreased the antineoplastic effect of panobinostat. Conversely, inhibition of these metabolic adaptations resulted in superior anti-lymphoma effect as demonstrated by the combination of panobinostat with a choline pathway inhibitor. In conclusion, our study demonstrates the power of metabolomics in identifying unknown effects of KDACI, and emphasizes the need for a better understanding of these drugs in order to achieve successful clinical implementation.

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Lysine deacetylase inhibitor (KDACI) treatment alters choline metabolism in B-cell lymphoma patients.

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KDACI-treated lymphoma cells acquire PI3K pathway dependency via increased choline kinase A (CHKA) activity.

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Targeting the acquired choline dependency improves the anti-lymphoma effect of KDACI.

Pera et al. explored the effects of the lysine deacetylase inhibitor panobinostat in the metabolism of patients with lymphoma. They demonstrated that panobinostat alters choline metabolism leading to PI3K pathway activation. Their findings revealed the mechanism behind the anti-lymphoma activity of dual lysine deacetylase/PI3K inhibitors, and uncovered a novel therapeutic strategy based on targeting choline pathway following panobinostat treatment.

Histone modifier gene mutations in peripheral T-cell lymphoma not otherwise specified

Due to heterogeneous morphological and immunophenotypic features, approximately 50% of peripheral T-cell lymphomas are unclassifiable and categorized as peripheral T-cell lymphomas, not otherwise specified. These conditions have an aggressive course and poor clinical outcome. Identification of actionable biomarkers is urgently needed to develop better therapeutic strategies. Epigenetic alterations play a crucial role in tumor progression. Histone modifications, particularly methylation and acetylation, are generally involved in chromatin state regulation. Here we screened the core set of genes related to histone methylation (KMT2D, SETD2, KMT2A, KDM6A) and acetylation (EP300, CREBBP) and identified 59 somatic mutations in 45 of 125 (36.0%) patients with peripheral T-cell lymphomas, not otherwise specified. Histone modifier gene mutations were associated with inferior progression-free survival time of the patients, irrespective of chemotherapy regimens, but an increased response to the histone deacetylase inhibitor chidamide. In vitro, chidamide significantly inhibited the growth of EP300-mutated T-lymphoma cells and KMT2D-mutated T-lymphoma cells when combined with the hypomethylating agent decitabine. Mechanistically, decitabine acted synergistically with chidamide to enhance the interaction of KMT2D with transcription factor PU.1, regulated H3K4me-associated signaling pathways, and sensitized T-lymphoma cells to chidamide. In a xenograft KMT2D-mutated T-lymphoma model, dual treatment with chidamide and decitabine significantly retarded tumor growth and induced cell apoptosis through modulation of the KMT2D/H3K4me axis. Our work thus contributes to the understanding of aberrant histone modification in peripheral T-cell lymphomas, not otherwise specified and the stratification of a biological subset that can benefit from epigenetic treatment.

Ruxolitinib combined with vorinostat suppresses tumor growth and alters metabolic phenotype in hematological diseases

JAK-2 dysregulation plays an important role as an oncogenic driver, and is thus a promising therapeutic target in hematological malignancies. Ruxolitinib is a pyrrolo[2.3-d]pyrimidine derivative with inhibitory activity against JAK1 and JAK2, moderate activity against TYK2, and minor activity against JAK3. Vorinostat is an HDAC inhibitor that reduces JAK-2 expression, thus affecting JAK-2 mRNA expression and increasing JAK-2 proteasomal deterioration. Here we hypothesized that the combination of ruxolitinib and vorinostat could have synergistic effects against hematological disease. We tested combinations of low doses of ruxolitinib and vorinostat in 12 cell lines, and observed highly synergistic cytotoxic action in six cell lines, which was maintained for up to 120 h in the presence of stromal cells. The sensitivity of the six cell lines may be explained by the broad effects of the drug combination, which can affect various targets. Treatment with the combination of ruxolitinib and vorinostat appeared to induce a possible reversal of the Warburg effect, with associated ROS production, apoptotic events, and growth inhibition. Decreased glucose metabolism may have markedly sensitized the six more susceptible cell lines to combined treatment. Therapeutic inhibition of the JAK/STAT pathway seems to offer substantial anti-tumor benefit, and combined therapy with ruxolitinib and vorinostat may represent a promising novel therapeutic modality for hematological neoplasms.

Vorinostat and Mithramycin A in combination therapy as an interesting strategy for the treatment of Sézary T lymphoma: a transcriptomic approach

SAHA (vorinostat) is a histone deacetylase inhibitor approved by the USA Food and Drug Administration (FDA) for treating advanced refractory cutaneous T cell lymphomas. As SAHA alters the expression of many genes under control of the Sp1 transcription factor, we examined the effect of its association with the FDA-approved anticancer antibiotic Mithramycin A (MTR, plicamycin), a competitive inhibitor of Sp1 binding to DNA. Sézary syndrome (SS) cells, expanded ex vivo from peripheral blood mononuclear cells of 4 patients, were tested for their sensitivity to the drugs regarding cytotoxicity and differential responsive gene expression. Multivariate statistical methods were used to identify genes whose expression is altered by SAHA, MTR, and the synergist effect of the two drugs. MTR, like SAHA, induced the apoptosis of SS cells, while the two drugs in combination showed clear synergy or potentiation. Expression data stressed a likely important role of additive or synergistic epigenetic modifications in the combined effect of the two drugs, while direct inhibition of Sp1-dependent transcription seemed to have only limited impact. Ontological analysis of modified gene expression suggested that the two drugs, either independently or synergistically, counteracted many intertwined pro-survival pathways deregulated in SS cells, resistance of these tumors to intrinsic and extrinsic apoptosis, abnormal adhesion migration, and invasive properties, as well as immunosuppressive behavior. Our findings provide preliminary clues on the individual and combined effects of SAHA and MTR in SS cells and highlight a potential therapeutic interest of this novel pair of drugs for treatment of SS patients.

Epigenetics in fibrosis

Fibrosis is a common and important disease. It is a pathological state due to excessive scar formation mediated by an increase in activated fibroblasts that express alpha smooth muscle actin and copious amounts of extracellular matrix molecules. Epigenetics is an area of research that encompasses three main mechanisms: methylation, histone modifications to the tails of histones and also non-coding RNAs including long and short non-coding RNAs. These three mechanisms all seek to regulate gene expression without a change in the underlying DNA sequence. In recent years an explosion of research, aided by deep sequencing technology becoming available, has demonstrated a role for epigenetics in fibrosis, either organ specific like lung fibrosis or more widespread as in systemic sclerosis. While the great majority of epigenetic work in fibrosis is centered on histone codes, more recently the non-coding RNAs have been examined in greater detail. It is known that one modification can affect the other and cross-talk among all three adds a new layer of complexity. This review aims to examine the role of epigenetics in fibrosis, evaluating all three mechanisms, and to suggest possible areas where epigenetics could be targeted therapeutically.

Epigenetic Modulation as a Therapeutic Prospect for Treatment of Autoimmune Rheumatic Diseases

Systemic inflammatory rheumatic diseases are considered as autoimmune diseases, meaning that the balance between recognition of pathogens and avoidance of self-attack is impaired and the immune system attacks and destroys its own healthy tissue. Treatment with conventional Disease Modifying Antirheumatic Drugs (DMARDs) and/or Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) is often associated with various adverse reactions due to unspecific and toxic properties of those drugs. Although biologic drugs have largely improved the outcome in many patients, such drugs still pose significant problems and fail to provide a solution to all patients. Therefore, development of more effective treatments and improvements in early diagnosis of rheumatic diseases are badly needed in order to increase patient's functioning and quality of life. The reversible nature of epigenetic mechanisms offers a new class of drugs that modulate the immune system and inflammation. In fact, epigenetic drugs are already in use in some types of cancer or cardiovascular diseases. Therefore, epigenetic-based therapeutics that control autoimmunity and chronic inflammatory process have broad implications for the pathogenesis, diagnosis, and management of rheumatic diseases. This review summarises the latest information about potential therapeutic application of epigenetic modification in targeting immune abnormalities and inflammation of rheumatic diseases.

HR23b expression is a potential predictive biomarker for HDAC inhibitor treatment in mesenchymal tumours and is associated with response to vorinostat

Histone deacetylases (HDAC) are key players in epigenetic regulation of gene expression and HDAC inhibitor (HDACi) treatment seems to be a promising anticancer therapy in many human tumours, including soft tissue sarcomas. HR23b has been shown to be a potential biomarker for sensitivity to HDACi therapy in cutaneous T‐cell lymphoma and hepatocellular carcinoma. We aimed to evaluate HR23b as a candidate biomarker for HDACi response in sarcomas and gastrointestinal stromal tumours (GIST). Therefore, HR23b expression was analysed comprehensively by western blot in sarcoma and GIST cell lines covering all major clinically relevant subtypes. MTT assay and ApoTox‐Glo^TM Triplex assay were performed after treatment with vorinostat, belinostat, mocetinostat and entinostat. HR23b protein expression was measured under HDACi treatment. Furthermore, HR23b expression levels were immunohistochemically determined in a large set of 523 clinical samples from sarcoma and GIST patients. Western blot analyses showed that sarcomas differ significantly in their expression of HR23b protein. All HDACi were able to regulate proliferation and apoptosis in vitro. Sensitivity to vorinostat correlated significantly with HR23b protein expression. Immunohistochemical prevalence screening in clinical samples of relevant adult‐type tumours revealed that 12.5% of sarcomas (among them malignant peripheral nerve sheath tumours, pleomorphic liposarcomas, leiomyosarcomas, dedifferentiated liposarcomas, synovial sarcomas and angiosarcomas) and 23.2% of GIST show high HR23b expression. Therefore, HDACi have antiproliferative and proapoptotic effects in sarcomas depending on the expression level of HR23b. These findings suggest that HR23b represents a candidate biomarker for HDACi sensitivity in certain sarcoma types and in GIST.

Human ATP-Binding Cassette Transporter ABCG2 Confers Resistance to CUDC-907, a Dual Inhibitor of Histone Deacetylase and Phosphatidylinositol 3-Kinase

CUDC-907 is a novel, dual-acting small molecule compound designed to simultaneously inhibit the activity of histone deacetylase (HDAC) and phosphatidylinositol 3-kinase (PI3K). Treatment with CUDC-907 led to sustained inhibition of HDAC and PI3K activity, inhibition of RAF-MEK-MAPK signaling pathway, and inhibition of cancer cell growth. CUDC-907 is currently under evaluation in phase I clinical trials in patients with lymphoma or multiple myeloma, and in patients with advanced solid tumors. However, the risk of developing acquired resistance to CUDC-907 can present a significant therapeutic challenge to clinicians in the future and should be investigated. The overexpression of ATP-binding cassette (ABC) drug transporter ABCB1, ABCC1, or ABCG2 is one of the most common mechanisms of developing multidrug resistance (MDR) in cancers and a major obstacle in chemotherapy. In this study, we reveal that ABCG2 reduces the intracellular accumulation of CUDC-907 and confers significant resistance to CUDC-907, which leads to reduced activity of CUDC-907 to inhibit HDAC and PI3K in human cancer cells. Moreover, although CUDC-907 affects the transport function of ABCG2, it was not potent enough to reverse drug resistance mediated by ABCG2 or affect the expression level of ABCG2 in human cancer cells. Taken together, our findings indicate that ABCG2-mediated CUDC-907 resistance can have serious clinical implications and should be further investigated. More importantly, we demonstrate that the activity of CUDC-907 in ABCG2-overexpressing cancer cells can be restored by inhibiting the function of ABCG2, which provides support for the rationale of combining CUDC-907 with modulators of ABCG2 to improve the pharmacokinetics and efficacy of CUDC-907 in future treatment trials.

Mixed effects of suberoylanilide hydroxamic acid (SAHA) on the host transcriptome and proteome and their implications for HIV reactivation from latency

Suberoylanilide hydroxamic acid (SAHA) has been assessed in clinical trials as part of a "shock and kill" strategy to cure HIV-infected patients. While it was effective at inducing expression of HIV RNA ("shock"), treatment with SAHA did not result in a reduction of reservoir size ("kill"). We therefore utilized a combined analysis of effects of SAHA on the host transcriptome and proteome to dissect its mechanisms of action that may explain its limited success in "shock and kill" strategies. CD4+ T cells from HIV seronegative donors were treated with 1μM SAHA or its solvent dimethyl sulfoxide (DMSO) for 24h. Protein expression and post-translational modifications were measured with iTRAQ proteomics using ultra high-precision two-dimensional liquid chromatography-tandem mass spectrometry. Gene expression was assessed by Illumina microarrays. Using limma package in the R computing environment, we identified 185 proteins, 18 phosphorylated forms, 4 acetylated forms and 2982 genes, whose expression was modulated by SAHA. A protein interaction network integrating these 4 data types identified the HIV transcriptional repressor HMGA1 to be upregulated by SAHA at the transcript, protein and acetylated protein levels. Further functional category assessment of proteins and genes modulated by SAHA identified gene ontology terms related to NFκB signaling, protein folding and autophagy, which are all relevant to HIV reactivation. In summary, SAHA modulated numerous host cell transcripts, proteins and post-translational modifications of proteins, which would be expected to have very mixed effects on the induction of HIV-specific transcription and protein function. Proteome profiling highlighted a number of potential counter-regulatory effects of SAHA with respect to viral induction, which transcriptome profiling alone would not have identified. These observations could lead to a more informed selection and design of other HDACi with a more refined targeting profile, and prioritization of latency reversing agents of other classes to be used in combination with SAHA to achieve more potent induction of HIV expression.

Romidepsin in peripheral and cutaneous T-cell lymphoma: mechanistic implications from clinical and correlative data

Romidepsin is an epigenetic agent approved for the treatment of patients with cutaneous or peripheral T-cell lymphoma (CTCL and PTCL). Here we report data in all patients treated on the National Cancer Institute 1312 trial, demonstrating long-term disease control and the ability to retreat patients relapsing off-therapy. In all, 84 patients with CTCL and 47 with PTCL were enrolled. Responses occurred early, were clinically meaningful and of very long duration in some cases. Notably, patients with PTCL receiving romidepsin as third-line therapy or later had a comparable response rate (32%) of similar duration as the total population (38%). Eight patients had treatment breaks of 3.5 months to 10 years; in four of six patients, re-initiation of treatment led to clear benefit. Safety data show slightly greater haematological and constitutional toxicity in PTCL. cDNA microarray studies show unique individual gene expression profiles, minimal overlap between patients, and both induction and repression of gene expression that reversed within 24 h. These data argue against cell death occurring as a result of an epigenetics-mediated gene induction programme. Together this work supports the safety and activity of romidepsin in T-cell lymphoma, but suggests a complex mechanism of action.

Targeting Histone Deacetylases in Diseases: Where Are We?

SIGNIFICANCE

Epigenetic inactivation of pivotal genes involved in cell growth is a hallmark of human pathologies, in particular cancer. Histone acetylation balance obtained through opposing actions of histone deacetylases (HDACs) and histone acetyltransferases is one epigenetic mechanism controlling gene expression and is, thus, associated with disease etiology and progression. Interfering pharmacologically with HDAC activity can correct abnormalities in cell proliferation, migration, vascularization, and death.

RECENT ADVANCES

Histone deacetylase inhibitors (HDACi) represent a new class of cytostatic agents that interfere with the function of HDACs and are able to increase gene expression by indirectly inducing histone acetylation. Several HDACi, alone or in combination with DNA-demethylating agents, chemopreventive, or classical chemotherapeutic drugs, are currently being used in clinical trials for solid and hematological malignancies, and are, thus, promising candidates for cancer therapy.

CRITICAL ISSUES

(i) Non-specific (off-target) HDACi effects due to activities unassociated with HDAC inhibition. (ii) Advantages/disadvantages of non-selective or isoform-directed HDACi. (iii) Limited number of response-predictive biomarkers. (iv) Toxicity leading to dysfunction of critical biological processes.

FUTURE DIRECTIONS

Selective HDACi could achieve enhanced clinical utility by reducing or eliminating the serious side effects associated with current first-generation non-selective HDACi. Isoform-selective and pan-HDACi candidates might benefit from the identification of biomarkers, enabling better patient stratification and prediction of response to treatment.

PIM kinases: an overview in tumors and recent advances in pancreatic cancer

The PIM kinases represent a family of serine/threonine kinases, which is composed of three different members (PIM1, PIM2 and PIM3). Aberrant expression of PIM kinases is observed in variety of tumors, including pancreatic cancer. The PIM kinases play pivotal roles in the regulation of cell cycle, apoptosis, properties of stem cells, metabolism, autophagy, drug resistance and targeted therapy. The roles of PIM kinases in pancreatic cancer include the regulation of proliferation, apoptosis, cell cycle, formation, angiogenesis and prediction prognosis. Blocking the activities of PIM kinases could prevent pancreatic cancer development. PIM kinases may be a novel target for cancer therapy.

Vorinostat synergizes with ridaforolimus and abrogates the ridaforolimus-induced activation of AKT in synovial sarcoma cells

Background

Curative treatments for patients with metastatic synovial sarcoma (SS) do not exist, and such patients have a poor prognosis. We explored combinations of molecularly-targeted and cytotoxic agents to identify synergistic treatment combinations in SS cells.

Methods

Two SS cell lines (HS-SY-II and SYO-I) were treated with single agents or combinations of molecularly targeted therapies (HDAC inhibitor, vorinostat; mTOR inhibitor, ridaforolimus) and cytotoxic agents. After 72 hours, cell viability was measured using the MTS cell proliferation assay. Combination Indices (CI) were calculated to determine whether each combination was synergistic, additive, or antagonistic. Western Blot analysis assessed alterations in total and phospho-AKT protein levels in response to drug treatment.

Results

We determined the single-agent IC₅₀ for ridaforolimus, vorinostat, doxorubicin, and melphalan in HS-SY-II and SYO-I. Synergism was apparent in cells co-treated with ridaforolimus and vorinostat: CI was 0.28 and 0.63 in HS-SY-II and SYO-I, respectively. Ridaforolimus/doxorubicin and ridaforolimus/melphalan exhibited synergism in both cell lines. An additive effect was observed with combination of vorinostat/doxorubicin in both cell lines. Vorinostat/melphalan was synergistic in HS-SY-II and additive in SYO-I. Western blot analysis demonstrated that ridaforolimus increased pAKT-ser473 levels; this effect was abrogated by vorinostat co-treatment.

Conclusions

The combination of ridaforolimus and vorinostat demonstrates in vitro synergism in SS. Addition of vorinostat abrogated ridaforolimus-induced AKT activation. Since AKT activation is a possible mechanism of resistance to mTOR inhibitors, adding vorinostat (or another HDAC inhibitor) may be a route to circumvent AKT-mediated resistance to mTOR inhibitors.

Predicting the structures of complexes between phosphoinositide 3-kinase (PI3K) and romidepsin-related compounds for the drug design of PI3K/histone deacetylase dual inhibitors using computational docking and the ligand-based drug design approach

Predictions of the three-dimensional (3D) structures of the complexes between phosphoinositide 3-kinase (PI3K) and two inhibitors were conducted using computational docking and the ligand-based drug design approach. The obtained structures were refined by structural optimizations and molecular dynamics (MD) simulations. The ligands were located deep inside the ligand binding pocket of the p110α subunit of PI3K, and the hydrogen bond formations and hydrophobic effects of the surrounding amino acids were predicted. Although rough structures were obtained for the PI3K-inhibitor complexes before the MD simulations, the refinement of the structures by these simulations clarified the hydrogen bonding patterns of the complexes.

Suberoylanilide hydroxamic acid (SAHA)-induced dynamics of a human histone deacetylase protein interaction network

Histone deacetylases (HDACs) are targets for cancer therapy. Suberoylanilide hydroxamic acid (SAHA) is an HDAC inhibitor approved by the U.S. Food and Drug Administration for the treatment of cutaneous T-cell lymphoma. To obtain a better mechanistic understanding of the Sin3/HDAC complex in cancer, we extended its protein-protein interaction network and identified a mutually exclusive pair within the complex. We then assessed the effects of SAHA on the disruption of the complex network through six homologous baits. SAHA perturbs multiple protein interactions and therefore compromises the composition of large parts of the Sin3/HDAC network. A comparison of the effect of SAHA treatment on gene expression in breast cancer cells to a knockdown of the ING2 subunit indicated that a portion of the anticancer effects of SAHA may be attributed to the disruption of ING2's association with the complex. Our dynamic protein interaction network resource provides novel insights into the molecular mechanism of SAHA action and demonstrates the potential for drugs to rewire networks.