Advances and Challenges of HDAC Inhibitors in Cancer Therapeutics

HBI-8000, HUYABIO Lead Clinical Program, Is a Selective Histone Deacetylase Inhibitor With Therapeutic Benefits in Leukemia and in Solid Tumors

HBI-8000 is a small molecule inhibitor of class I HDACs and has been approved for the treatment of PTCL, ATL and, in combination with exemestane, in a subpopulation of breast cancer. Given the roles of HDACs in normal and cancerous cells, there are currently multiple clinical trials, by HUYABIO International, to test the efficacy of HBI-8000 in monotherapy or in combination settings in leukemias and in solid tumors. The current review is focused on the applications of HDACi HBI-8000 in cancer therapy and its potential in combination with DDR agents.

YTHDF2 promotes multiple myeloma cell proliferation via STAT5A/MAP2K2/p-ERK axis

Multiple myeloma (MM) is still incurable partially due to lacking effective therapeutic targets. Aberrant N6-methyladenosine (m6A) RNA modification plays a vital role in many cancers, however few researches are executed in MM. We first screened the m6A-related genes in MM patient cohorts and correlated these genes with patient outcomes. We found that YTHDF2, a well-recognized m6A reader, was increased in MM patients and associated with poor outcomes. Decreased YTHDF2 expression hampered MM cell proliferation in vitro and in vivo, while enforced YTHDF2 expression reversed those effects. The analyses of m6A-RIP-seq and RIP-PCR indicated that STAT5A was the downstream target of YTHDF2, which was binding to the m6A modification site of STAT5A to promote its mRNA degradation. ChIP-seq and PCR assays revealed that STAT5A suppressed MM cell proliferation by occupying the transcription site of MAP2K2 to decrease ERK phosphorylation. In addition, we confirmed that YTHDF2 mediated the unphosphorylated form of STAT5A to inhibit the expression of MAP2K2/p-ERK. In conclusion, our study highlights that YTHDF2/STAT5A/MAP2K2/p-ERK axis plays a key role in MM proliferation and targeting YTHDF2 may be a promising therapeutic strategy.

HDAC Inhibitors: Innovative Strategies for Their Design and Applications

Histone deacetylases (HDACs) are a large family of epigenetic metalloenzymes that are involved in gene transcription and regulation, cell proliferation, differentiation, migration, and death, as well as angiogenesis. Particularly, disorders of the HDACs expression are linked to the development of many types of cancer and neurodegenerative diseases, making them interesting molecular targets for the design of new efficient drugs and imaging agents that facilitate an early diagnosis of these diseases. Thus, their selective inhibition or degradation are the basis for new therapies. This is supported by the fact that many HDAC inhibitors (HDACis) are currently under clinical research for cancer therapy, and the Food and Drug Administration (FDA) has already approved some of them. In this review, we will focus on the recent advances and latest discoveries of innovative strategies in the development and applications of compounds that demonstrate inhibitory or degradation activity against HDACs, such as PROteolysis-TArgeting Chimeras (PROTACs), tumor-targeted HDACis (e.g., folate conjugates and nanoparticles), and imaging probes (positron emission tomography (PET) and fluorescent ligands).

MeCOM: A Method for Comparing Three-Dimensional Metalloenzyme Active Sites

Since metalloenzymes are a large collection of metal ion(s) dependent enzymes, comparison analyses of metalloenzyme active sites are critical for metalloenzyme de novo design, function investigation, and inhibitor development. Here, we report a method named MeCOM for comparing metalloenzyme active sites. It is characterized by metal ion(s) centric active site recognition and three-dimensional superimposition using α-carbon or pharmacophore features. The test results revealed that for the given metalloenzymes, MeCOM could effectively recognize the active sites, extract active site features, and superimpose the active sites; it also could correctly identify similar active sites, differentiate dissimilar active sites, and evaluate the similarity degree. Moreover, MeCOM showed potential to establish new associations between structurally distinct metalloenzymes by active site comparison. MeCOM is freely available at https://mecom.ddtmlab.org.

Blocking autophagy overcomes resistance to dual histone deacetylase and proteasome inhibition in gynecologic cancer

Histone deacetylase (HDAC) inhibitors and proteasome inhibitors have been approved by the FDA for the treatment of multiple myeloma and lymphoma, respectively, but have not achieved similar activity as single agents in solid tumors. Preclinical studies have demonstrated the activity of the combination of an HDAC inhibitor and a proteasome inhibitor in a variety of tumor models. However, the mechanisms underlying sensitivity and resistance to this combination are not well-understood. This study explores the role of autophagy in adaptive resistance to dual HDAC and proteasome inhibition. Studies focus on ovarian and endometrial gynecologic cancers, two diseases with high mortality and a need for novel treatment approaches. We found that nanomolar concentrations of the proteasome inhibitor ixazomib and HDAC inhibitor romidepsin synergistically induce cell death in the majority of gynecologic cancer cells and patient-derived organoid (PDO) models created using endometrial and ovarian patient tumor tissue. However, some models were not sensitive to this combination, and mechanistic studies implicated autophagy as the main mediator of cell survival in the context of dual HDAC and proteasome inhibition. Whereas the combination of ixazomib and romidepsin reduces autophagy in sensitive gynecologic cancer models, autophagy is induced following drug treatment of resistant cells. Pharmacologic or genetic inhibition of autophagy in resistant cells reverses drug resistance as evidenced by an enhanced anti-tumor response both in vitro and in vivo. Taken together, our findings demonstrate a role for autophagic-mediated cell survival in proteasome inhibitor and HDAC inhibitor-resistant gynecologic cancer cells. These data reveal a new approach to overcome drug resistance by inhibiting the autophagy pathway.

HDAC8 suppresses the epithelial phenotype and promotes EMT in chemotherapy-treated basal-like breast cancer

BACKGROUND

Basal-like breast cancer (BLBC) is one of the most aggressive malignant diseases in women with an increased metastatic behavior and poor prognosis compared to other molecular subtypes of breast cancer. Resistance to chemotherapy is the main cause of treatment failure in BLBC. Therefore, novel therapeutic strategies counteracting the gain of aggressiveness underlying therapy resistance are urgently needed. The epithelial-to-mesenchymal transition (EMT) has been established as one central process stimulating cancer cell migratory capacity but also acquisition of chemotherapy-resistant properties. In this study, we aimed to uncover epigenetic factors involved in the EMT-transcriptional program occurring in BLBC cells surviving conventional chemotherapy.

RESULTS

Using whole transcriptome data from a murine mammary carcinoma cell line (pG-2), we identified upregulation of Hdac4, 7 and 8 in tumor cells surviving conventional chemotherapy. Subsequent analyses of human BLBC patient datasets and cell lines established HDAC8 as the most promising factor sustaining tumor cell viability. ChIP-sequencing data analysis identified a pronounced loss of H3K27ac at regulatory regions of master transcription factors (TFs) of epithelial phenotype like Gata3, Elf5, Rora and Grhl2 upon chemotherapy. Interestingly, impairment of HDAC8 activity reverted epithelial-TFs levels. Furthermore, loss of HDAC8 activity sensitized tumor cells to chemotherapeutic treatments, even at low doses.

CONCLUSION

The current study reveals a previously unknown transcriptional repressive function of HDAC8 exerted on a panel of transcription factors involved in the maintenance of epithelial cell phenotype, thereby supporting BLBC cell survival to conventional chemotherapy. Our data establish HDAC8 as an attractive therapeutically targetable epigenetic factor to increase the efficiency of chemotherapeutics.

Design, synthesis and biological evaluation of novel o-aminobenzamide derivatives as potential anti-gastric cancer agents in vitro and in vivo

Although gastric cancer has become a major public health problem, oral agents applied in clinics for gastric cancer therapy are scarce. Therefore, to explore new oral chemical entities with high efficiency and low toxicity, 41 o-aminobenzamide derivatives based on the scaffolds of MS-275 and SAHA were designed, synthesized, and evaluated for their anti-gastric cancer abilities in vitro and in vivo. Structure-activity relationships were discussed, leading to the identification of compounds F8 (IC₅₀ = 0.28 μM against HGC-27 cell) and T9 (IC₅₀ = 1.84 μM against HGC-27 cell) with improved cytotoxicity, anti-gastric cancer proliferation potency, induction of cell apoptosis and cell cycle arrest ability, inhibition of cell migration and invasion. What is worth mentioning is that compound F8 was more efficient and less toxic than the positive drug capecitabine in vivo on the HGC-27-xenograft model. Meanwhile, compound F8 exhibited suitable pharmacokinetic properties and less acute toxicity (LD₅₀ > 1000 mg/kg). Besides, western blotting analysis, IHC analysis, differentially expressed proteins analysis and ABPP experiment indicated that compound F8 could modulate molecular pathways involved in apoptosis and cell cycle progression. Consequently, compound F8 is a strong candidate for the development of human gastric cancer therapy.

Histone deacetylases: A novel class of therapeutic targets for pancreatic cancer

Pancreatic cancer is the seventh leading cause of cancer death worldwide, with a low 5-year survival rate. Novel agents are urgently necessary to treat the main pathological type, known as pancreatic ductal carcinoma (PDAC). The dysregulation of histone deacetylases (HDACs) has been identified in association with PDAC, which can be more easily targeted by small molecular inhibitors than gene mutations and may represent a therapeutic breakthrough for PDAC. However, the contributions of HDACs to PDAC remain controversial, and pharmacokinetic challenges have limited the application of HDAC inhibitors (HDACis) in PDAC. This review summarizes the mechanisms associated with success and failure of HDACis in PDAC and discusses the recent progress made in HDACi development and application, such as combination therapies designed to enhance efficacy. More precise strategies involving HDACis might eventually improve the outcomes of PDAC treatment.

The role of protein acetylation in carcinogenesis and targeted drug discovery

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

Potent Hydrazide-Based HDAC Inhibitors with a Superior Pharmacokinetic Profile for Efficient Treatment of Acute Myeloid Leukemia In Vivo

As "Michael acceptors" may induce promiscuous responses in mammalian cells by reacting with various proteins, we modified the cinnamamide of our previous hydrazide-based HDAC inhibitors (HDACIs) to deactivate the Michael reaction. Representative compound 11h is 2-5 times more potent than lead compound 17 in both HDAC inhibitory activity (IC₅₀ = 0.43-3.01 nM) and cell-based antitumor assay (IC₅₀ = 19.23-61.04 nM). The breakthrough in the pharmacokinetic profile of 11h (oral bioavailability: 112%) makes it a lead-in-class oral active agent, validated in the in vivo anti-AML study (4 mg/kg p.o., TGI = 78.9%). Accumulated AcHH3 and AcHH4 levels in tumor tissue directly correlate with the in vivo efficacy, as panobinostat with lower AcHH3 and AcHH4 levels than 11h displays limited activity. To the best of our knowledge, this work contributes the first report of in vivo antitumor activity of hydrazide-based HDACIs. The outstanding pharmacokinetic/pharmacodynamic and antitumor activity of 11h could potentially extend the clinical application of current HDACIs.

Epigenetic modulation of antitumor immunity for improved cancer immunotherapy

Epigenetic mechanisms play vital roles not only in cancer initiation and progression, but also in the activation, differentiation and effector function(s) of immune cells. In this review, we summarize current literature related to epigenomic dynamics in immune cells impacting immune cell fate and functionality, and the immunogenicity of cancer cells. Some important immune-associated genes, such as granzyme B, IFN-γ, IL-2, IL-12, FoxP3 and STING, are regulated via epigenetic mechanisms in immune or/and cancer cells, as are immune checkpoint molecules (PD-1, CTLA-4, TIM-3, LAG-3, TIGIT) expressed by immune cells and tumor-associated stromal cells. Thus, therapeutic strategies implementing epigenetic modulating drugs are expected to significantly impact the tumor microenvironment (TME) by promoting transcriptional and metabolic reprogramming in local immune cell populations, resulting in inhibition of immunosuppressive cells (MDSCs and Treg) and the activation of anti-tumor T effector cells, professional antigen presenting cells (APC), as well as cancer cells which can serve as non-professional APC. In the latter instance, epigenetic modulating agents may coordinately promote tumor immunogenicity by inducing de novo expression of transcriptionally repressed tumor-associated antigens, increasing expression of neoantigens and MHC processing/presentation machinery, and activating tumor immunogenic cell death (ICD). ICD provides a rich source of immunogens for anti-tumor T cell cross-priming and sensitizing cancer cells to interventional immunotherapy. In this way, epigenetic modulators may be envisioned as effective components in combination immunotherapy approaches capable of mediating superior therapeutic efficacy.

USP53 activated by H3K27 acetylation regulates cell viability, apoptosis, and metabolism in esophageal carcinoma via the AMPK signaling pathway

Esophageal carcinoma (ESCA) is a leading cause of cancer death worldwide, despite an overall decline in the incidence of new cases. However, knowledge of gene expression signatures for risk and prognosis stratification of ESCA is inadequate. Thus, identifying novel molecular biomarkers and therapeutic targets for ESCA might improve its prognosis and treatment. The current study investigated the role of ubiquitin-specific peptidase 53 (USP53), a member of the USP family that exhibits deubiquitinating activity, in ESCA and showed that USP53 is downregulated in ESCA tissues, indicating poor prognosis. USP53 suppresses the proliferation and growth of ESCA cells in vitro and in vivo, whereas its knockdown exerts opposite effects. AMP-activated protein kinase inhibitor reverses the effects of USP53 knockdown. USP53 also inhibits glycolysis, oxidative metabolism, and mitochondrial dynamics. H3K27 acetylation increases USP53 expression by binding to its promoter region. Our study reveals that USP53 is activated by H3K27 acetylation and suppresses ESCA progression by regulating cell growth and metabolism. USP53 is therefore a promising target for ESCA treatment.

Inhibition of HDACs Suppresses Cell Proliferation and Cell Migration of Gastric Cancer by Regulating E2F5 Targeting BCL2

(1) Background: Gastric cancer (GC) is the most common high death-rate cancer type worldwide, with an enhanced prevalence and increased rate of mortality. Although significant evidence on surgery strategy has been generated for the treatment of GC, conclusions are still uncertain regarding profound metastatic or persevering gastric cancer. Therefore, it is essential to develop novel and effective biomarkers or therapeutic targets for the diagnosis of GC. Histone deacetylations (HDACs) are important epigenetic regulators that control the aberrant transcription of critical genes that are mainly involved in cell proliferation, cell migration, regulation of the cell cycle, and different signal pathways. (2) Methods: Expression analysis of HDACs family members and E2F5 in gastric cancer cell lines was determined by RT-PCR and Western blotting. The cell proliferation was determined through an MTT assay. Cell migration was determined using a wound-healing assay. Flow cytometry experiments were used to determine cell-cycle analysis. The statistical software OriginPro 2015 (OriginLab, Northampton, MA, USA) was used to analyze data. A p value of < 0.05 was regarded as significant. (3) Results: The present study shows that E2F5 expression is upregulated in GC cancer cell lines compared to normal cell lines, and is positively associated with the level of HDACs and BCL2. HDACi and knocking down of E2F5 as tumor suppressors inhibited cell proliferation, migration invasion, and blocked the cell cycle in gastric cancer cells by suppressing BCL2. The results conclude that the anticancer mechanism of HDACi was determined by regulating E2F5 via targeting BCL2. (4) Conclusions: Our results suggest that the HDAC–E2F5–BCL2 signaling axis might be a novel potential biomarker in gastric cancer.

Utilization of cyanopyridine in design and synthesis of first-in-class anticancer dual acting PIM-1 kinase/HDAC inhibitors

Herein, we report design and synthesis of twenty-one dual PIM-1/HDAC inhibitors utilizing 3-cyanopyridines as a novel cap moiety linked with aliphatic /aromatic linker bearing carboxylic acid 3a-g, hydroxamic acid 4a-g or 2-aminoanilide moieties 5a-g as zinc-binding group. Most of the target hybrids revealed promising growth inhibition according to one dose NCI protocol against 60 cancer cell lines. Meanwhile, hydroxamic acids 4b, 4d and 4e displayed strong and broad-spectrum activity against nine tumor subpanels tested (GI₅₀ 0.176-8.87 μM); 4d displayed strong antiproliferative activity with GI₅₀ ≤ 3 μM against different cancer cell lines (GI₅₀ range from 0.325 to 2.9 μM). Furthermore, 4a, 4d-4g and 5f manifested a high inhibitory activity against HDACs 1 and 6 isozymes; 4g, displayed potent HDAC 1 and 6 inhibitory activity (45.01 ± 2.1 and 19.78 ± 1.1 nM) more than the reference SAHA (51.54 ± 2.4 and 21.38 ± 1.2 nM, respectively), while 4f was more potent (30.09 ± 1.4 nM) than SAHA against HDAC 1 and less potent (30.29 ± 1.7 nM) than SAHA against HDAC 6. Hybrids 4b, 4d, 4e and 4f exhibited potent PIM-1 inhibitory activity; 4d showed comparable activity to quercetin (IC₅₀ of 343.87 ± 16.6 and 353.76 ± 17.1 nM, respectively); it exhibited pre G1 apoptosis and arrest cell cycle at G2/M phase. Moreover, it revealed good binding into pocket of HDACs 1,6 and PIM-1 kinase enzymes with good correlation with biological results. Moreover, 4b, 4d and 4e had reasonable drug-likeness properties according to Lipinski's rule. However, multitarget inhibitor of PIM-1/HDAC is a promising strategy in anticancer drug discovery; the most potent hybrids require further in vivo and clinical investigations.

Astragaloside IV Reduces OxLDL-Induced BNP Overexpression by Regulating HDAC

Effective drug intervention is the most important method to improve the prognosis, improve the quality of life, and prolong the life of patients with heart failure. This study aimed to explore the protective effect of astragaloside IV on myocardial cell injury induced by oxidized low-density lipoprotein (OxLDL) and its regulatory mechanism on the increase of brain natriuretic peptide (BNP) caused by myocardial cell injury. The model of myocardial cell injury, protection, and histone deacetylase (HDAC) inhibition in HL-1 mice was established by OxLDL treatment, astragaloside IV intervention, and UF010 coincubation. The effects of OxLDL and astragaloside IV on apoptosis were detected by flow cytometry. The expression level of BNP mRNA and protein in cells was investigated by real-time fluorescence quantification, western blot, and enzyme-linked immunosorbent assay. HDAC activity in nucleus was calibrated by fluorescence absorption intensity. Enzyme-linked immunosorbent assay (ELISA) was applied to test eNOS level in myocardial cells. OxLDL significantly promoted apoptosis, upregulated BNP mRNA, increased BNP protein level inside and outside cells, and decreased eNOS level. Compared with OxLDL treatment group, apoptosis decreased, BNP mRNA expression level decreased, BNP protein concentration decreased, and eNOS level increased significantly combined with low and high concentration astragaloside IV treatment group. HDAC activity significantly increased in OxLDL treatment group and significantly decreased after combined incubation with low and high concentrations of astragaloside IV. Inhibition of HDAC significantly increased eNOS level and decreased BNP protein level. In conclusion, astragaloside IV can reverse the low level of eNOS caused by OxLDL by regulating HDAC activity to protect myocardial cells from oxide damage, which is manifested by the decrease of BNP concentration.

Discovery of novel tubulin/HDAC dual-targeting inhibitors with strong antitumor and antiangiogenic potency

A novel series of cis-diphenylethene and benzophenone derivatives as tubulin/HDAC dual-targeting inhibitors were designed and synthesized. Among them, compound 28g exhibited the most potent antiproliferative activities against six different human cancer cell lines, 28g could not only inhibited tubulin polymerization, disrupted cellular microtubule networks but also selectively inhibited class IIa HDACs, especially HDAC7 activity. Further molecular docking demonstrated 28g could occupy the binding pockets of tubulin and HDAC7 meanwhile. Cellular mechanism studies revealed that 28g could induce G2/M phase arrest by down-regulated expression of p-cdc2 and cell apoptosis by regulating mitochondrial membrane potential, reactive oxygen species (ROS) levels and apoptosis-related proteins (PARP, Caspase families) in a dose-dependent manner. Importantly, 28g significantly inhibited HUVEC tube formation, proliferation, migration and invasion. The inhibitory effect against angiogenesis in vivo was confirmed by zebrafish xenograft. Furthermore, 28g could effectively suppress the proliferation and metastasis of MGC-803 cells in vitro and in zebrafish xenograft. All above results indicated that 28g can act as a promising antitumor and antiangiogenic agent via targeting tubulin and class IIa HDACs.

Regulation of epigenetic homeostasis in uveal melanoma and retinoblastoma

Uveal melanoma (UM) and retinoblastoma (RB), which cause blindness and even death, are the most frequently observed primary intraocular malignancies in adults and children, respectively. Epigenetic studies have shown that changes in the epigenome contribute to the rapid progression of both UM and RB following classic genetic changes. The loss of epigenetic homeostasis plays an important role in oncogenesis by disrupting the normal patterns of gene expression. The targetable nature of epigenetic modifications provides a unique opportunity to optimize treatment paradigms and establish new therapeutic options for both UM and RB with these aberrant epigenetic modifications. We aimed to review the research findings regarding relevant epigenetic changes in UM and RB. Herein, we 1) summarize the literature, with an emphasis on epigenetic alterations, including DNA methylation, histone modifications, RNA modifications, noncoding RNAs and an abnormal chromosomal architecture; 2) elaborate on the regulatory role of epigenetic modifications in biological processes during tumorigenesis; and 3) propose promising therapeutic candidates for epigenetic targets and update the list of epigenetic drugs for the treatment of UM and RB. In summary, we endeavour to depict the epigenetic landscape of primary intraocular malignancy tumorigenesis and provide potential epigenetic targets in the treatment of these tumours.

A Novel Hydroxamic Acid-Based Curcumin Derivative as Potent Histone Deacetylase Inhibitor for the Treatment of Glioblastoma

Glioblastoma (GBM) is one of the most common primary and deadliest malignant brain tumor with chemoresistance and poor prognosis. There is a lack of effective chemotherapeutic drug for the treatment of GBM. In this work, we reported the preparation of a histone deacetylase (HDAC) inhibitor, DMC-HA, from the structural modification of natural product curcumin. DMC-HAs were tested in an HDAC inhibition assay and an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cytotoxicity. It showed potent inhibition of HDAC1–2 and HDAC6 with IC₅₀ values in the submicromolar concentration range. DMC-HA significantly inhibited the proliferation of human glioblastoma U87 cells and mediated apoptosis of U87 cells in a dose- and time-dependent manner. In addition, DMC-HA elevated the acetylation level of histone H3 in U87 cells. Pharmacokinetic studies showed that DMC-HA possessed acceptable pharmacokinetic profiles, accompanied with certain brain permeability. Lastly, we showed that DMC-HA suppressed the growth of tumor in U87 tumor xenograft model in vivo with no obvious toxicity. These results demonstrate that DMC-HA has the potential to be developed as a chemotherapeutic drug for GBM patients.

Bacterial Lipopolysaccharide Augmented Malignant Transformation and Promoted the Stemness in Prostate Cancer Epithelial Cells

Purpose

To study bacterial lipopolysaccharide (LPS)-induced cancer stem-like transformation and to investigate the inhibitory effect of Trichostatin A (TSA) on the malignant transformation through targeting p-Stat3 signaling.

Methods

2D, 3D, and serum-free suspension culture system were used to study LPS-induced malignant transformation in series malignant grade of prostate cancer (PCa) epithelial cells. Flow cytometry assay and RT-PCR were utilized to evaluate the CD44⁺CD133⁺ stem cell population, the expression of inflammatory cytokines and series tumor stemness biomarkers. Meanwhile, Western blot was used to analyze the alteration of cell signaling associated-molecules by treatment with TSA, an original antifungal antibiotic and a panel inhibitor of histone deacetylase.

Results

Our study found that LPS promoted the migration, invasion and stem-like tumoroshpere forming in multiple PCa cell lines including DU145, PC3, 22RV1, LNCaP. LPS also enriched CD44⁺CD133⁺ stem cell population and increased the expression of series tumor stemness biomarkers (e.g., CD44, CD133, SOX-2, α-intergrin, Nestin, etc.). TSA was found to prevent tumor cell migration, invasion and tumorosphere forming in DU145 and PC3 cells with increasing tumor suppressive Maspin and reducing both phosphorylation of Stat3 (p-Stat3) and pro-oncogene c-Myc expression in LPS-treated DU145 cells. Furthermore, blocking Stat3 signaling pathway by treatment with TSA and/or small molecule compound Stattic of an p-Stat3 inhibitor effectively abrogated LPS-induced tumorosphere forming with decrease of IL-6, IL-8 and stemness biomarkers CD44, SOX-2 expression.

Conclusion

Our data demonstrated that the inflammatory agent of bacterial LPS augmented malignant transformation and promoted the cancerous stemness in PCa epithelial cells. TSA could prevent, at least in part, the LPS-induced malignant transformation by targeting p-Stat3/c-Myc signaling pathway and reducing inflammatory IL-6, IL-8. In addition, the assay of LPS-induced tumorosphere forming could serve as a simple and an easy handling method for targeting cancer stem cells drug screening in vitro in clinical practice.

Design, Synthesis, In Vitro Anticancer Evaluation and Molecular Modelling Studies of 3,4,5-Trimethoxyphenyl-Based Derivatives as Dual EGFR/HDAC Hybrid Inhibitors

Recently, combining histone deacetylase (HDAC) inhibitors with chemotherapeutic drugs or agents, in particular epidermal growth factor receptor (EGFR) inhibitors, is considered to be one of the most encouraging strategy to enhance the efficacy of the antineoplastic agents and decrease or avoid drug resistance. Therefore, in this work, based on introducing 3,4,5-trimethoxy phenyl group as a part of the CAP moiety, in addition to incorporating 4-6 aliphatic carbons linker and using COOH or hydroxamic acid as ZBG, 12 novel EGFR/HDAC hybrid inhibitors 2a-c, 3a-c, 4a-c and 5a-c were designed, constructed, and evaluated for their anticancer activities against 4 cancer cell lines (HepG2, MCF-7, HCT116 and A549). Among all, hybrids with hydroxamic acid 4a-c and 5a, exhibited the highest inhibition against all cancer cell lines with IC50 ranging from 0.536 to 4.892 μM compared to Vorinostat (SAHA) with IC50 ranging from 2.43 to 3.63 μM and Gefitinib with IC50 ranging from 1.439 to 3.366 μM. Mechanistically, the most potent hybrids 4a-c and 5a were further tested for their EGFR and HDACs inhibitory activities. The findings disclosed that hybrid 4b displayed IC50 = 0.063 µM on the target EGFR enzyme which is slightly less potent than the standard Staurosporine (IC50 = 0.044 µM). Furthermore, hybrid 4b showed less HDAC inhibitory activity IC50 against HDAC1 (0.148), 2 (0.168), 4 (5.852), 6 (0.06) and 8 (2.257) than SAHA. In addition, the investigation of apoptotic action of the most potent hybrid 4b showed a significant increase in Bax level up to 3.75-folds, with down-regulation in Bcl2 to 0.42-fold, compared to the control. Furthermore, hybrid 4b displayed an increase in the levels of Caspases 3 and 8 by 5.1 and 3.15 folds, respectively. Additionally, the cell cycle analysis of hybrid 4b revealed that it showed programmed cell death and cell cycle arrest at G1/S phase. Moreover, all these outcomes together with the molecular docking study recommended the rationalized target hybrids 4a-c and 5a, particularly 4b, may be considered to be promising lead candidates for discovery of novel anticancer agents via dual inhibition of both EGFR/HDAC enzymes.

β-Carboline tethered cinnamoyl 2-aminobenzamides as class I selective HDAC inhibitors: Design, synthesis, biological activities and modelling studies

The effect of β-carboline motif as cap for HDAC inhibitors containing cinnamic acid as linker and benzamides as zinc binding group was examined in this study. A series of β-carboline-cinnamide conjugates have been synthesized and evaluated for their HDAC inhibitory activity and in vitro cytotoxicity against different human cancer cell lines. Almost all the compounds exhibited superior HDAC inhibitory activity than the standard drug Entinostat for in vitro enzymatic assay. Among the tested compounds, 7h displayed a noteworthy potency with an IC₅₀ value of 0.70 ± 0.15 µM against HCT-15 cell line when compared to the standard drug Entinostat (IC₅₀ of 3.87 ± 0.62 µM). The traditional apoptosis assays such as nuclear morphological alterations, AO/EB, DAPI, and Annexin-V/PI staining revealed the antiproliferative activity of 7h while depolarization of mitochondrial membrane potential by JC-1 was observed in dose-dependent manner. Cell cycle analysis also unveiled the typical accumulation of cells in G₂M phase and sub-G₁/S phase arrest. In addition, immunoblot analysis for compound 7h on HCT-15 indicated selective inhibition of the protein expression of class I HDAC 2 and 3 isoforms. Molecular docking analysis of compound 7h revealed that it can prominent binding with the active pocket of the HDAC 2. These finding suggest that the compound 7h can be a promising lead candidate for further investigation in the development of novel anti-cancer drug potentially inhibiting HDACs.

HDAC2/3 inhibitor MI192 mitigates oligodendrocyte loss and reduces microglial activation upon injury: A potential role of epigenetics

Background:

During development, oligodendrocyte (OL) lineage cells are susceptible to injury, leading to life-long clinical neurodevelopmental deficits, which lack effective treatments. Drugs targeting epigenetic modifications that inhibit histone deacetylases (HDACs) protect from many clinical neurodegenerative disorders.

Aim:

This study aimed to investigate the therapeutic potential of histone deacetylase 2/3 (HDAC2/3) inhibitor MI192 on white matter (WM) pathology in a model of neonatal rat brain injury.

Methods:

Wistar rats (8.5-day-old, n = 32) were used to generate brain tissues. The tissues were cultured and then randomly divided into four groups and treated as following: group I (sham); the tissues were cultured under normoxia, group II (vehicle); DMSO only, group III (injury, INJ); the tissues were exposed to 20 minutes oxygen-glucose deprivation (OGD) insult, and group IV (INJ + MI192); the tissues were subjected to the OGD insult and then treated with the MI192 inhibitor. On culture day 10, the tissues were fixed for biochemical and histological examinations.

Results:

The results showed that inhibition of HDAC2/3 activity alleviated WM pathology. Specifically, MI192 treatment significantly reduced cell death, minimized apoptosis, and mitigates the loss of the MBP⁺ OLs and their precursors (NG₂⁺ OPCs). Additionally, MI192 decreased the density of reactive microglia (OX−42⁺). These findings demonstrate that the inhibition of HDAC2/3 activity post-insult alleviates WM pathology through mechanism(s) including preserving OL lineage cells and suppressing microglial activation.

Conclusion:

The findings of this study suggest that HDAC2/3 inhibition is a rational strategy to preserve WM or reverse its pathology upon newborn brain injury.

Intravitreal HDAC Inhibitor Belinostat Effectively Eradicates Vitreous Seeds Without Retinal Toxicity In Vivo in a Rabbit Retinoblastoma Model

Purpose

Current melphalan-based regimens for intravitreal chemotherapy for retinoblastoma vitreous seeds are effective but toxic to the retina. Thus, alternative agents are needed. Based on the known biology of histone deacetylases (HDACs) in the retinoblastoma pathway, we systematically studied whether the HDAC inhibitor belinostat is a viable, molecularly targeted alternative agent for intravitreal delivery that might provide comparable efficacy, without toxicity.

Methods

In vivo pharmacokinetic experiments in rabbits and in vitro cytotoxicity experiments were performed to determine the 90% inhibitory concentration (IC₉₀). Functional toxicity by electroretinography and structural toxicity by optical coherence tomography (OCT), OCT angiography, and histopathology were evaluated in rabbits following three injections of belinostat 350 µg (2× IC₉₀) or 700 µg (4× IC₉₀), compared with melphalan 12.5 µg (rabbit equivalent of the human dose). The relative efficacy of intravitreal belinostat versus melphalan to treat WERI-Rb1 human cell xenografts in rabbit eyes was directly quantified. RNA sequencing was used to assess belinostat-induced changes in RB cell gene expression.

Results

The maximum nontoxic dose of belinostat was 350 µg, which caused no reductions in electroretinography parameters, retinal microvascular loss on OCT angiography, or retinal degeneration. Melphalan caused severe retinal structural and functional toxicity. Belinostat 350 µg (equivalent to 700 µg in the larger human eye) was equally effective at eradicating vitreous seeds in the rabbit xenograft model compared with melphalan (95.5% reduction for belinostat, P < 0.001; 89.4% reduction for melphalan, P < 0.001; belinostat vs. melphalan, P = 0.10). Even 700 µg belinostat (equivalent to 1400 µg in humans) caused only minimal toxicity. Widespread changes in gene expression resulted.

Conclusions

Molecularly targeted inhibition of HDACs with intravitreal belinostat was equally effective as standard-of-care melphalan but without retinal toxicity. Belinostat may therefore be an attractive agent to pursue clinically for intravitreal treatment of retinoblastoma.

NO-HDAC dual inhibitors

HDAC inhibitors and NO donors have both demonstrated independently broad therapeutic potential in a variety of diseases. Borretto et al. presented the topic of NO-HDAC dual inhibitors for the first time in 2013 as an attractive new topic. Here we collected the general structure of all synthesized NO-HDAC dual inhibitors, lead compounds, synthesis methods and biological features of the most potent dual NO-HDAC inhibitor in each category with the intention of assisting in the synthesis and optimization of new drug-like compounds for diverse diseases. Based on studies done so far, NO-HDAC dual inhibitors have displayed satisfactory results against wound healing (3), heart hypertrophy (3), inflammatory, cardiovascular, neuromuscular illnesses (11a-11e) and cancer (6a-6o, 9a-9d, 10a-10d, 16 and 17). NO-HDAC dual inhibitors can have high therapeutic potential for various diseases due to their new properties, NO properties, HDAC inhibitor properties and also due to the effects of NO on HDAC enzymes.

Analyzing mRNAsi-Related Genes Identifies Novel Prognostic Markers and Potential Drug Combination for Patients with Basal Breast Cancer

Basal breast cancer subtype is the worst prognosis subtypes among all breast cancer subtypes. Recently, a new tumor stemness index-mRNAsi is found to be able to measure the degree of oncogenic differentiation of tissues. The mRNAsi involved in a variety of cancer processes is derived from the innovative application of one-class logistic regression (OCLR) machine learning algorithm to the whole genome expression of various stem cells and tumor cells. However, it is largely unknown about mRNAsi in basal breast cancer. Here, we find that basal breast cancer carries the highest mRNAsi among all four subtypes of breast cancer, especially 385 mRNAsi-related genes are positively related to the high mRNAsi value in basal breast cancer. This high mRNAsi is also closely related to active cell cycle, DNA replication, and metabolic reprogramming in basal breast cancer. Intriguingly, in the 385 genes, TRIM59, SEPT3, RAD51AP1, and EXO1 can act as independent protective prognostic factors, but CTSF and ABHD4B can serve as independent bad prognostic factors in patients with basal breast cancer. Remarkably, we establish a robust prognostic model containing the 6 mRNAsi-related genes that can effectively predict the survival rate of patients with the basal breast cancer subtype. Finally, the drug sensitivity analysis reveals that some drug combinations may be effectively against basal breast cancer via targeting the mRNAsi-related genes. Taken together, our study not only identifies novel prognostic biomarkers for basal breast cancers but also provides the drug sensitivity data by establishing an mRNAsi-related prognostic model.

Histone Deacetylase (HDAC)-1, -2, -4, and -6 in Uveal Melanomas: Associations with Clinicopathological Parameters and Patients' Survival

Simple Summary

Histone Deacetylases (HDACs) have been reportedly associated with tumor development and progression in several types of human malignancy, being currently investigated as potential targets of anti-cancer therapy. The aim of this study is to assess the clinical significance and prognostic role of the of HDAC-1, -2, -4, and -6 immunohistochemical expression, in 75 uveal melanoma (UM) cases. HDACs are differentially expressed in UMs, HDAC-2 being the most frequently expressed isoform, whereas cytoplasmic expression of class I HDAC isoforms is also observed. Additionally, HDAC-1 was associated with increased tumor size, HDAC-6 with mitotic index, and HDAC-2 with epithelioid cell morphology and presence of tumor-infiltrating lymphocytes, both parameters of adverse prognosis. Moreover, our data support a significant association of HDAC-2 with patients’ improved OS. These findings suggest that HDACs, and especially HDAC-2, may be implicated in the formation and progression of UM.

Abstract

Background: Uveal melanoma (UM) represents the most common primary intraocular malignancy in adults, exerting high metastatic potential and poor prognosis. Histone deacetylases (HDACs) play a key role in carcinogenesis, and HDAC inhibitors (HDACIs) are currently being explored as anti-cancer agents in clinical settings. The aim of this study was to evaluate the clinical significance of HDAC-1, -2, -4, and -6 expression in UM. Methods: HDAC-1, -2, -4, and -6 expression was examined immunohistochemically in 75 UM tissue specimens and was correlated with tumors’ clinicopathological characteristics, the presence of tumor-infiltrating lymphocytes (TILS), as well as with our patients’ overall survival (OS). Results: HDAC-2 was the most frequently expressed isoform (66%), whereas we confirmed in addition to the expected nuclear expression the presence of cytoplasmic expression of class I HDAC isoforms, namely HDAC-1 (33%) and HDAC-2 (9.5%). HDAC-4 and -6 expression was cytoplasmic. HDAC-1 nuclear expression was associated with increased tumor size (p = 0.03), HDAC-6 with higher mitotic index (p = 0.03), and nuclear HDAC-2 with epithelioid cell morphology (p = 0.03) and presence of tumor-infiltrating lymphocytes (p = 0.04). The association with the remaining parameters including Monosomy 3 was not significant. Moreover, the presence as well as the nuclear expression pattern of HDAC-2 were correlated with patients’ improved OS and remained significant in multivariate survival analysis. Conclusions: These findings provide evidence for a potential role of HDACs and especially HDAC-2 in the biological mechanisms governing UM evolution and progression.

Fungal Lysine Deacetylases in Virulence, Resistance, and Production of Small Bioactive Compounds

The growing number of immunocompromised patients begs for efficient therapy strategies against invasive fungal infections. As conventional antifungal treatment is increasingly hampered by resistance to commonly used antifungals, development of novel therapy regimens is required. On the other hand, numerous fungal species are industrially exploited as cell factories of enzymes and chemicals or as producers of medically relevant pharmaceuticals. Consequently, there is immense interest in tapping the almost inexhaustible fungal portfolio of natural products for potential medical and industrial applications. Both the pathogenicity and production of those small metabolites are significantly dependent on the acetylation status of distinct regulatory proteins. Thus, classical lysine deacetylases (KDACs) are crucial virulence determinants and important regulators of natural products of fungi. In this review, we present an overview of the members of classical KDACs and their complexes in filamentous fungi. Further, we discuss the impact of the genetic manipulation of KDACs on the pathogenicity and production of bioactive molecules. Special consideration is given to inhibitors of these enzymes and their role as potential new antifungals and emerging tools for the discovery of novel pharmaceutical drugs and antibiotics in fungal producer strains.

The roles of epigenetics in cancer progression and metastasis

Cancer metastasis remains a major clinical challenge for cancer treatment. It is therefore crucial to understand how cancer cells establish and maintain their metastatic traits. However, metastasis-specific genetic mutations have not been identified in most exome or genome sequencing studies. Emerging evidence suggests that key steps of metastasis are controlled by reversible epigenetic mechanisms, which can be targeted to prevent and treat the metastatic disease. A variety of epigenetic mechanisms were identified to regulate metastasis, including the well-studied DNA methylation and histone modifications. In the past few years, large scale chromatin structure alterations including reprogramming of the enhancers and chromatin accessibility to the transcription factors were shown to be potential driving force of cancer metastasis. To dissect the molecular mechanisms and functional output of these epigenetic changes, it is critical to use advanced techniques and alternative animal models for interdisciplinary and translational research on this topic. Here we summarize our current understanding of epigenetic aberrations in cancer progression and metastasis, and their implications in developing new effective metastasis-specific therapies.

Non-Hydroxamate Zinc-Binding Groups as Warheads for Histone Deacetylases

Histone deacetylases (HDACs) remove acetyl groups from acetylated lysine residues and have a large variety of substrates and interaction partners. Therefore, it is not surprising that HDACs are involved in many diseases. Most inhibitors of zinc-dependent HDACs (HDACis) including approved drugs contain a hydroxamate as a zinc-binding group (ZBG), which is by far the biggest contributor to affinity, while chemical variation of the residual molecule is exploited to create more or less selectivity against HDAC isozymes or other metalloproteins. Hydroxamates have a propensity for nonspecificity and have recently come under considerable suspicion because of potential mutagenicity. Therefore, there are significant concerns when applying hydroxamate-containing compounds as therapeutics in chronic diseases beyond oncology due to unwanted toxic side effects. In the last years, several alternative ZBGs have been developed, which can replace the critical hydroxamate group in HDACis, while preserving high potency. Moreover, these compounds can be developed into highly selective inhibitors. This review aims at providing an overview of the progress in the field of non-hydroxamic HDACis in the time period from 2015 to present. Formally, ZBGs are clustered according to their binding mode and structural similarity to provide qualitative assessments and predictions based on available structural information.

Treatment strategies for glucose-6-phosphate dehydrogenase deficiency: past and future perspectives

Glucose-6-phosphate dehydrogenase (G6PD) maintains redox balance in a variety of cell types and is essential for erythrocyte resistance to oxidative stress. G6PD deficiency, caused by mutations in the G6PD gene, is present in ~400 million people worldwide, and can cause acute hemolytic anemia. Currently, there are no therapeutics for G6PD deficiency. We discuss the role of G6PD in hemolytic and nonhemolytic disorders, treatment strategies attempted over the years, and potential reasons for their failure. We also discuss potential pharmacological pathways, including glutathione (GSH) metabolism, compensatory NADPH production routes, transcriptional upregulation of the G6PD gene, highlighting potential drug targets. The needs and opportunities described here may motivate the development of a therapeutic for hematological and other chronic diseases associated with G6PD deficiency.

Recent Progresses in Conjugation with Bioactive Ligands to Improve the Anticancer Activity of Platinum Compounds

Platinum (Pt) drugs, including cisplatin, are widely used for the treatment of solid tumors. Despite the clinical success, side effects and occurrence of resistance represent major limitations to the use of clinically available Pt drugs. To overcome these problems, a variety of derivatives have been designed and synthetized. Here, we summarize the recent progress in the development of Pt(II) and Pt(IV) complexes with bioactive ligands. The development of Pt(II) and Pt(IV) complexes with targeting molecules, clinically available agents, and other bioactive molecules is an active field of research. Even if none of the reported Pt derivatives has been yet approved for clinical use, many of these compounds exhibit promising anticancer activities with an improved pharmacological profile. Thus, planning hybrid compounds can be considered as a promising approach to improve the available Pt-based anticancer agents and to obtain new molecular tools to deepen the knowledge of cancer progression and drug resistance mechanisms.

The Impact of Epigenetic Modifications on Adaptive Resistance Evolution in Glioblastoma

Glioblastoma (GBM) is a highly lethal cancer that is universally refractory to the standard multimodal therapies of surgical resection, radiation, and chemotherapy treatment. Temozolomide (TMZ) is currently the best chemotherapy agent for GBM, but the durability of response is epigenetically dependent and often short-lived secondary to tumor resistance. Therapies that can provide synergy to chemoradiation are desperately needed in GBM. There is accumulating evidence that adaptive resistance evolution in GBM is facilitated through treatment-induced epigenetic modifications. Epigenetic alterations of DNA methylation, histone modifications, and chromatin remodeling have all been implicated as mechanisms that enhance accessibility for transcriptional activation of genes that play critical roles in GBM resistance and lethality. Hence, understanding and targeting epigenetic modifications associated with GBM resistance is of utmost priority. In this review, we summarize the latest updates on the impact of epigenetic modifications on adaptive resistance evolution in GBM to therapy.

Unraveling the Epigenetic Role and Clinical Impact of Histone Deacetylases in Neoplasia

Histone deacetylases (HDACs) have long been implicated in tumorigenesis and tumor progression demonstrating their important participation in neoplasia. Therefore, numerous studies have been performed, highlighting the mechanism of HDACs action in tumor cells and demonstrating the potential role of HDAC inhibitors in the treatment of different cancer types. The outcome of these studies further delineated and strengthened the solid role that HDACs and epigenetic modifications exert in neoplasia. These results have spread promise regarding the potential use of HDACs as prospective therapeutic targets. Nevertheless, the clinical significance of HDAC expression and their use as biomarkers in cancer has not been extensively elucidated. The aim of our study is to emphasize the clinical significance of HDAC isoforms expression in different tumor types and the correlations noted between the clinicopathological parameters of tumors and patient outcomes. We further discuss the obstacles that the next generation HDAC inhibitors need to overcome, for them to become more potent.

Comprehensive analysis of a new prognosis signature based on histone deacetylases in clear cell renal cell carcinoma

Histone deacetylases (HDAC) family is vital for tumorigenesis and tumor progression. However, the exact role of the HDAC family in clear cell renal cell carcinoma (ccRCC) remains unclear. Based on The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and The Human Protein Atlas (HPA) database, we investigated and validated the expression profile, clinical significance and prognostic value of HDAC family members in ccRCC. Moreover, we further explored the correlation between HDACs and tumor microenvironment, tumor stemness, drug activity and immune subtype. The HDAC8, HDAC10, and HDAC11 manifested potential clinical value for prognosis, and the correlation analyses reveals underlying molecular mechanisms, which deserve further investigation for ccRCC. This Integrated bioinformatics analysis, based on transcriptomics and proteomics, implied that HDAC8, HDAC10, and HDAC11 may serve as potential molecular biomarkers and therapeutic targets for ccRCC, but some underlying molecular mechanisms still need to be elucidated.

Exploring epigenetic and microRNA approaches for γ-globin gene regulation

Therapeutic interventions aimed at inducing fetal hemoglobin and reducing the concentration of sickle hemoglobin is an effective approach to ameliorating acute and chronic complications of sickle cell disease, exemplified by the long-term use of hydroxyurea. However, there remains an unmet need for the development of additional safe and effective drugs for single agent or combination therapy for individuals with β-hemoglobinopathies. Regulation of the γ-globin to β-globin switch is achieved by chromatin remodeling at the HBB locus on chromosome 11 and interactions of major DNA binding proteins, such as KLF1 and BCL11A in the proximal promoters of the globin genes. Experimental evidence also supports a role of epigenetic modifications including DNA methylation, histone acetylation/methylation, and microRNA expression in γ-globin gene silencing during development. In this review, we will critically evaluate the role of epigenetic mechanisms in γ-globin gene regulation and discuss data generated in tissue culture, pre-clinical animal models, and clinical trials to support drug development to date. The question remains whether modulation of epigenetic pathways will produce sufficient efficacy and specificity for fetal hemoglobin induction and to what extent targeting these pathways form the basis of prospects for clinical therapy.

HDAC Inhibitors: Dissecting Mechanisms of Action to Counter Tumor Heterogeneity

Intra-tumoral heterogeneity presents a major obstacle to cancer therapeutics, including conventional chemotherapy, immunotherapy, and targeted therapies. Stochastic events such as mutations, chromosomal aberrations, and epigenetic dysregulation, as well as micro-environmental selection pressures related to nutrient and oxygen availability, immune infiltration, and immunoediting processes can drive immense phenotypic variability in tumor cells. Here, we discuss how histone deacetylase inhibitors, a prominent class of epigenetic drugs, can be leveraged to counter tumor heterogeneity. We examine their effects on cellular processes that contribute to heterogeneity and provide insights on their mechanisms of action that could assist in the development of future therapeutic approaches.

A novel moniliformin derivative as pan-inhibitor of histone deacetylases triggering apoptosis of leukemia cells

New and potent agents that evade multidrug resistance (MDR) and inhibit epigenetic modifications are of great interest in cancer drug development. Here, we describe that a moniliformin derivative (IUPAC name: 3-(naphthalen-2-ylsulfanyl)-4-{[(2Z)-1,3,3-trimethyl-2,3-dihydro-1H-indol-2-ylidene]methyl}cyclobut-3-ene-1,2-dione; code: MCC1381) bypasses P-gp-mediated MDR. Using transcriptomics, we identified a large number of genes significantly regulated in response to MCC1381, which affected the cell cycle and disturbed cellular death and survival. The potential targets of MCC1381 might be histone deacetylases (HDACs) as predicted by SwissTargetPrediction. In silico studies confirmed that MCC1381 presented comparable affinity with HDAC1, 2, 3, 6, 8 and 11. Besides, the inhibition activity of HDACs was dose-dependently inhibited by MCC1381. Particularly, a strong binding affinity was observed between MCC1381 and HDAC6 by microscale thermophoresis analysis. MCC1381 decreased the expression of HDAC6, inversely correlated with the increase of acetylated HDAC6 substrates, acetylation p53 and α-tubulin. Furthermore, MCC1381 arrested the cell cycle at the G₂/M phase, induced the generation of reactive oxygen species and collapse of the mitochondrial membrane potential. MCC1381 exhibited in vivo anti-cancer activity in xenografted zebrafish. Collectively, MCC1381 extended cytotoxicity towards P-gp-resistant leukemia cancer cells and may act as a pan-HDACs inhibitor, indicating that MCC1381 is a novel candidate for cancer therapy.

Imidazoles as Potential Anticancer Agents: An Update on Recent Studies

Nitrogen-containing heterocyclic rings are common structural components of marketed drugs. Among these heterocycles, imidazole/fused imidazole rings are present in a wide range of bioactive compounds. The unique properties of such structures, including high polarity and the ability to participate in hydrogen bonding and coordination chemistry, allow them to interact with a wide range of biomolecules, and imidazole-/fused imidazole-containing compounds are reported to have a broad spectrum of biological activities. This review summarizes recent reports of imidazole/fused imidazole derivatives as anticancer agents appearing in the peer-reviewed literature from 2018 through 2020. Such molecules have been shown to modulate various targets, including microtubules, tyrosine and serine-threonine kinases, histone deacetylases, p53-Murine Double Minute 2 (MDM2) protein, poly (ADP-ribose) polymerase (PARP), G-quadraplexes, and other targets. Imidazole-containing compounds that display anticancer activity by unknown/undefined mechanisms are also described, as well as key features of structure-activity relationships. This review is intended to provide an overview of recent advances in imidazole-based anticancer drug discovery and development, as well as inspire the design and synthesis of new anticancer molecules.

Beyond DNA-targeting in Cancer Chemotherapy. Emerging Frontiers - A Review

Modern anti-cancer drugs target DNA specifically for rapid division of malignant cells. One downside of this approach is that they also target other rapidly dividing healthy cells, such as those involved in hair growth leading to serious toxic side effects and hair loss. Therefore, it would be better to develop novel agents that address cellular signaling mechanisms unique to cancerous cells, and new research is now focussing on such approaches. Although the classical chemotherapy area involving DNA as the set target continues to produce important findings, nevertheless, a distinctly discernible emerging trend is the divergence from the cisplatin operation model that uses the metal as the primary active center of the drug. Many successful anti-cancer drugs present are associated with elevated toxicity levels. Cancers also develop immunity against most therapies and the area of cancer research can, therefore, be seen as an area with a high unaddressed need. Hence, ongoing work into cancer pathogenesis is important to create accurate preclinical tests that can contribute to the development of innovative drugs to manage and treat cancer. Some of the emergent frontiers utilizing different approaches include nanoparticles delivery, use of quantum dots, metal complexes, tumor ablation, magnetic hypothermia and hyperthermia by use of Superparamagnetic Iron oxide Nanostructures, pathomics and radiomics, laser surgery and exosomes. This review summarizes these new approaches in good detail, giving critical views with necessary comparisons. It also delves into what they carry for the future, including their advantages and disadvantages.

Phase I Study and Pilot Efficacy Analysis of Entinostat, a Novel Histone Deacetylase Inhibitor, in Chinese Postmenopausal Women with Hormone Receptor-Positive Metastatic Breast Cancer

BACKGROUND

Previous clinical trials have demonstrated that entinostat in combination with exemestane had good tolerability and significant clinical efficacy in patients with advanced hormone receptor positive (HR+) and HER2 negative (HER2-) metastatic breast cancer (MBC) in the USA. However, no clinical trials have been conducted in Chinese populations.

OBJECTIVE

To investigate the safety, pharmacokinetics, and pilot efficacy of entinostat with or without exemestane in Chinese postmenopausal patients with locally advanced or metastatic HR+ /HER2- MBC.

PATIENTS AND METHODS

Nineteen patients received entinostat for 4 weeks (dose-limiting toxicity (DLT) observation stage) at 3, 5, or 7 mg/week, with a "3+3" dose-escalation design and in combination with exemestane thereafter (extended treatment stage: entinostat, 3 or 5 mg/week; exemestane, 25 mg/day). An additional 21 patients were enrolled to assess the entinostat (5 mg) plus exemestane (25 mg) pharmacokinetic profile and potential efficacy.

RESULTS

The peak entinostat serum concentration and area under the curve increased dose proportionally, without significant interaction between entinostat and exemestane. Entinostat was well tolerated at all doses. The most common grade 3/4 adverse effects (AEs) included neutropenia (31.6%) and thrombocytopenia (15.8%). In the DLT observation stage, grade 3/4 AEs accounted for 16.7% in the 5 mg group with one suspicious DLT (G3 ventricular tachycardia) and 33.3% in the 7 mg group. In the extended treatment stage, 2/16 patients achieved partial response and three patients experienced stable disease (> 12 weeks). The median progression-free survival was 9.41 months for the additional 21 patients, who experienced grade 3/4 AEs of neutropenia (38%), thrombocytopenia (9.5%), anemia (9.5%), and fatigue (9.5%).

CONCLUSION

Entinostat with exemestane showed reasonable safety, tolerability, and encouraging efficacy in Chinese patients with HR+/HER2- MBC. These results support further evaluation in a randomized, double-blind Phase III study with a weekly 5 mg entinostat dose in a Chinese population.

TRIAL REGISTRATION

NCT02833155.

Pharmaco-transcriptomic correlation analysis reveals novel responsive signatures to HDAC inhibitors and identifies Dasatinib as a synergistic interactor in small-cell lung cancer

BACKGROUND

Histone acetylation/deacetylase process is one of the most studied epigenetic modifications. Histone deacetylase inhibitors (HDACis) have shown clinical benefits in haematological malignancies but failed in solid tumours due to the lack of biomarker-driven stratification.

METHODS

We perform integrative pharmaco-transcriptomic analysis by correlating drug response profiles of five pan-HDACis with transcriptomes of solid cancer cell lines (n=659) to systematically identify generalizable gene signatures associated with HDACis sensitivity and resistance. The established signatures are then applied to identify cancer subtypes that are potentially sensitive or resistant to HDACis, and drugs that enhance the efficacy of HDACis. Finally, the reproductivity of the established HDACis signatures is evaluated by multiple independent drug response datasets and experimental assays.

FINDINGS

We successfully delineate generalizable gene signatures predicting sensitivity (containing 46 genes) and resistance (containing 53 genes) to all five HDACis, with their reproductivity confirmed by multiple external sources and independent internal assays. Using the gene signatures, we identify low-grade glioma harbouring isocitrate dehydrogenase 1/2 (IDH1/2) mutation and non-YAP1-driven subsets of small-cell lung cancer (SCLC) that particularly benefit from HDACis monotherapy. Further, based on the resistance gene signature, we identify clinically-approved Dasatinib as a synthetic lethal drug with HDACi, synergizing in inducing apoptosis and reactive oxygen species on a panel of SCLC. Finally, Dasatinib significantly enhances the therapeutic efficacy of Vorinostat in SCLC xenografts.

INTERPRETATION

Our work establishes robust gene signatures predicting HDACis sensitivity/resistance in solid cancer and uncovers combined Dasatinib/HDACi as a synthetic lethal combination therapy for SCLC.

FUNDING

This work was supported by the National Natural Science Foundation of China (82072570 to F. Yao; 82002941 to B. Sun).

Efficient Synthesis and Bioevaluation of Novel Dual Tubulin/Histone Deacetylase 3 Inhibitors as Potential Anticancer Agents

Novel dual HDAC3/tubulin inhibitors were designed and efficiently synthesized by combining the pharmacophores of SMART (tubulin inhibitor) and MS-275 (HDAC inhibitor), among which compound 15c was found to be the most potent and balanced HDAC3/tubulin dual inhibitor with high HDAC3 activity (IC50 = 30 nM) and selectivity (SI > 1000) as well as excellent antiproliferative potency against various cancer cell lines, including an HDAC-resistant gastric cancer cell line (YCC3/7) with IC50 values in the range of 30-144 nM. Compound 15c inhibited B16-F10 cancer cell migration and colony formation. In addition, 15c demonstrated significant in vivo antitumor efficacy in a B16-F10 melanoma tumor model with a better TGI (70.00%, 10 mg/kg) than that of the combination of MS-275 and SMART. Finally, 15c presented a safe cardiotoxicity profile and did not cause nephro-/hepatotoxicity. Collectively, this work shows that compound 15c represents a novel tubulin/HDAC3 dual-targeting agent deserving further investigation as a potential anticancer agent.

Defects in Macrophage Reprogramming in Cancer Therapy: The Negative Impact of PD-L1/PD-1

Classically activated M1 macrophages and alternatively activated M2 macrophages are two polarized subsets of macrophages at the extreme ends of a constructed continuum. In the field of cancer research, M2 macrophage reprogramming is defined as the repolarization of pro-tumoral M2 to anti-tumoral M1 macrophages. It is known that colony-stimulating factor 1 (CSF1)/CSF1 receptor (CSF1R) and CSF2/CSF2R signaling play important roles in macrophage polarization. Targeting CSF1/CSF1R for M2 macrophage reprogramming has been widely performed in clinical trials for cancer therapy. Other targets for M2 macrophage reprogramming include Toll-like receptor 7 (TLR7), TLR8, TLR9, CD40, histone deacetylase (HDAC), and PI3Kγ. Although macrophages are involved in innate and adaptive immune responses, M1 macrophages are less effective at phagocytosis and antigen presenting, which are required properties for the activation of T cells and eradication of cancer cells. Similar to T and dendritic cells, the “functionally exhausted” status might be attributed to the high expression of programmed death-ligand 1 (PD-L1) or programmed cell death protein 1 (PD-1). PD-L1 is expressed on both M1 and M2 macrophages. Macrophage reprogramming from M2 to M1 might increase the expression of PD-L1, which can be transcriptionally activated by STAT3. Macrophage reprogramming or PD-L1/PD-1 blockade alone is less effective in the treatment of most cancers. Since PD-L1/PD-1 blockade could make up for the defect in macrophage reprogramming, the combination of macrophage reprogramming and PD-L1/PD-1 blockade might be a novel treatment strategy for cancer therapy.

Polymerized vorinostat mediated photodynamic therapy using lysosomal spatiotemporal synchronized drug release complex

A combination of photodynamic therapy (PDT) and histone deacetylase inhibitor (HDACis) could potentiate single-mode anti-tumor activity of HDACis or PDT to inhibit tumor relapse and metastasis. However, poor solubility and heterogeneity in cellular uptake and tissue distribution hamper the dual mode antitumor effect. For a controlled drug release of photosensitizers and HDACis in cytoplasm, photosensitizer pyropheophorbide-a (Pyro) encapsulated in polymer polyethylene glycol-b-poly (asparaginyl-vorinostat) (simplified as Pyro@FPPS) are fabricated to achieve their lysosomal spatiotemporal synchronized release. With HDACis modeling PDT in vitro and in vivo, it seems that polymerized Vorinostat encapsulated photosensitizers significantly inhibited the tumor proliferation and metastasis by spatiotemporal synchronized drugs release, and Pyro@FPPS reported here reveals a promising prospect to exert drugs' synergistic effect in a spatiotemporal synchronized manner and can be an effective strategy to inhibit tumor growth, recurrence and metastasis in clinic.

Genetic Alterations in Gliomas Remodel the Tumor Immune Microenvironment and Impact Immune-Mediated Therapies

High grade gliomas are malignant brain tumors that arise in the central nervous system, in patients of all ages. Currently, the standard of care, entailing surgery and chemo radiation, exhibits a survival rate of 14-17 months. Thus, there is an urgent need to develop new therapeutic strategies for these malignant brain tumors. Currently, immunotherapies represent an appealing approach to treat malignant gliomas, as the pre-clinical data has been encouraging. However, the translation of the discoveries from the bench to the bedside has not been as successful as with other types of cancer, and no long-lasting clinical benefits have been observed for glioma patients treated with immune-mediated therapies so far. This review aims to discuss our current knowledge about gliomas, their molecular particularities and the impact on the tumor immune microenvironment. Also, we discuss several murine models used to study these therapies pre-clinically and how the model selection can impact the outcomes of the approaches to be tested. Finally, we present different immunotherapy strategies being employed in clinical trials for glioma and the newest developments intended to harness the immune system against these incurable brain tumors.

Latency Reversing Agents: Kick and Kill of HTLV-1?

Human T-cell leukemia virus type 1 (HTLV-1), the cause of adult T-cell leukemia/lymphoma (ATLL), is a retrovirus, which integrates into the host genome and persistently infects CD4⁺ T-cells. Virus propagation is stimulated by (1) clonal expansion of infected cells and (2) de novo infection. Viral gene expression is induced by the transactivator protein Tax, which recruits host factors like positive transcription elongation factor b (P-TEFb) to the viral promoter. Since HTLV-1 gene expression is repressed in vivo by viral, cellular, and epigenetic mechanisms in late phases of infection, HTLV-1 avoids an efficient CD8⁺ cytotoxic T-cell (CTL) response directed against the immunodominant viral Tax antigen. Hence, therapeutic strategies using latency reversing agents (LRAs) sought to transiently activate viral gene expression and antigen presentation of Tax to enhance CTL responses towards HTLV-1, and thus, to expose the latent HTLV-1 reservoir to immune destruction. Here, we review strategies that aimed at enhancing Tax expression and Tax-specific CTL responses to interfere with HTLV-1 latency. Further, we provide an overview of LRAs including (1) histone deacetylase inhibitors (HDACi) and (2) activators of P-TEFb, that have mainly been studied in context of human immunodeficiency virus (HIV), but which may also be powerful in the context of HTLV-1.

Characterization of Renal Cell Carcinoma Heterotypic 3D Co-Cultures with Immune Cell Subsets

Two-dimensional cell culture-based platforms are easy and reproducible, however, they do not resemble the heterotypic cell-cell interactions or the complex tumor microenvironment. These parameters influence the treatment response and the cancer cell fate. Platforms to study the efficacy of anti-cancer treatments and their impact on the tumor microenvironment are currently being developed. In this study, we established robust, reproducible, and easy-to-use short-term spheroid cultures to mimic clear cell renal cell carcinoma (ccRCC). These 3D co-cultures included human endothelial cells, fibroblasts, immune cell subsets, and ccRCC cell lines, both parental and sunitinib-resistant. During spheroid formation, cells induce the production and secretion of the extracellular matrix. We monitored immune cell infiltration, surface protein expression, and the response to a treatment showing that the immune cells infiltrated the spheroid co-cultures within 6 h. Treatment with an optimized drug combination or the small molecule-based targeted drug sunitinib increased immune cell infiltration significantly. Assessing the therapeutic potential of this drug combination in this platform, we revealed that the expression of PD-L1 increased in 3D co-cultures. The cost- and time-effective establishment of our 3D co-culture model and its application as a pre-clinical drug screening platform can facilitate the treatment validation and clinical translation.

Recent developments of HDAC inhibitors: Emerging indications and novel molecules

The histone deacetylase (HDAC) enzymes, a class of epigenetic regulators, are historically well established as attractive therapeutic targets. During investigation of trends within clinical trials, we have identified a high number of clinical trials involving HDAC inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 32 agents with HDAC-inhibiting properties, of which 29 were found to interact with the HDAC enzymes as their primary therapeutic target. In this review, we provide an overview of the clinical drug development highlighting the recent advances and provide analysis of specific trials and, where applicable, chemical structures. We found haematologic neoplasms continue to represent the majority of clinical indications for this class of drugs; however, it is clear that there is an ongoing trend towards diversification. Therapies for non-oncology indications including HIV infection, muscular dystrophies, inflammatory diseases as well as neurodegenerative diseases such as Alzheimer's disease, frontotemporal dementia and Friedreich's ataxia are achieving promising clinical progress. Combinatory regimens are proving to be useful to improve responsiveness among FDA-approved agents; however, it often results in increased treatment-related toxicities. This analysis suggests that the indication field is broadening through a high number of clinical trials while several fields of preclinical development are also promising.

Advancements in practical and scientific bioanalytical approaches to metabolism studies in drug development

Advancement in metabolism profiling approaches and bioanalytical techniques has been revolutionized over the last two decades. Different in vitro and in vivo approaches along with advanced bioanalytical techniques are enabling the accurate qualitative and quantitative analysis of metabolites. This review summarizes various modern in vitro and in vivo approaches for executing metabolism studies with special emphasis on the recent advancement in the field. Advanced bioanalytical techniques, which can be employed in metabolism studies, have been discussed suggesting their particular application based on specific study objectives. This article can efficiently guide the researchers to scientifically plan metabolism studies and their bioanalysis during drug development programs taking advantage of a detailed understanding of instances of failure in the past.

HDAC6 inhibitor WT161 performs anti-tumor effect on osteosarcoma and synergistically interacts with 5-FU

BACKGROUND

WT161, as a selective HDAC6 inhibitor, has been shown to play anti-tumor effects on several kinds of cancers. The aim of the present study is to explore the roles of WT161 in osteosarcoma and its underlying mechanisms.

METHODS

The anti-proliferative effect of WT161 on osteosarcoma cells was examined using MTT assay and colony formation assay. Cell apoptosis was analyzed using flow cytometer. The synergistic effect was evaluated by isobologram analysis using CompuSyn software. The osteosarcoma xenograft models were established to evaluate the anti-proliferative effect of WT161 in vivo.

RESULTS

WT161 suppressed the cell growth and induced apoptosis of osteosarcoma cells in a dose- and time-dependent manner. Mechanistically, we found that WT161 treatment obviously increased the protein level of PTEN and decreased the phosphorylation level of protein kinase-B (AKT). More importantly, WT161 showed synergistic inhibition with 5-FU on osteosarcoma cells in vitro and in vivo.

CONCLUSIONS

These results indicate that WT161 inhibits the growth of osteosarcoma through PTEN and has a synergistic efficiency with 5-FU.