Evaluation of the Therapeutic Potential of the Novel Isotype Specific HDAC Inhibitor 4SC-202 in Urothelial Carcinoma Cell Lines

Deciphering the interplay of histone post-translational modifications in cancer: Co-targeting histone modulators for precision therapy

Chromatin undergoes dynamic regulation through reversible histone post-translational modifications (PTMs), orchestrated by "writers," "erasers," and "readers" enzymes. Dysregulation of these histone modulators is well implicated in shaping the cancer epigenome and providing avenues for precision therapies. The approval of six drugs for cancer therapy targeting histone modulators, along with the ongoing clinical trials of numerous candidates, represents a significant advancement in the field of precision medicine. Recently, it became apparent that histone PTMs act together in a coordinated manner to control gene expression. The intricate crosstalk of histone PTMs has been reported to be dysregulated in cancer, thus emerging as a critical factor in the complex landscape of cancer development. This formed the foundation of the swift emergence of co-targeting different histone modulators as a new strategy in cancer therapy. This review dissects how histone PTMs, encompassing acetylation, phosphorylation, methylation, SUMOylation and ubiquitination, collaboratively influence the chromatin states and impact cellular processes. Furthermore, we explore the significance of histone modification crosstalk in cancer and discuss the potential of targeting histone modification crosstalk in cancer management. Moreover, we underscore the significant strides made in developing dual epigenetic inhibitors, which hold promise as emerging candidates for effective cancer therapy.

New synergistic combination therapy approaches with HDAC inhibitor quisinostat, cisplatin or PARP inhibitor talazoparib for urothelial carcinoma

Urothelial carcinoma (UC) urgently requires new therapeutic options. Histone deacetylases (HDAC) are frequently dysregulated in UC and constitute interesting targets for the development of alternative therapy options. Thus, we investigated the effect of the second generation HDAC inhibitor (HDACi) quisinostat in five UC cell lines (UCC) and two normal control cell lines in comparison to romidepsin, a well characterized HDACi which was previously shown to induce cell death and cell cycle arrest. In UCC, quisinostat led to cell cycle alterations, cell death induction and DNA damage, but was well tolerated by normal cells. Combinations of quisinostat with cisplatin or the PARP inhibitor talazoparib led to decrease in cell viability and significant synergistic effect in five UCCs and platinum-resistant sublines allowing dose reduction. Further analyses in UM-UC-3 and J82 at low dose ratio revealed that the mechanisms included cell cycle disturbance, apoptosis induction and DNA damage. These combinations appeared to be well tolerated in normal cells. In conclusion, our results suggest new promising combination regimes for treatment of UC, also in the cisplatin-resistant setting.

Strategies that regulate LSD1 for novel therapeutics

Histone methylation plays crucial roles in regulating chromatin structure and gene transcription in epigenetic modifications. Lysine-specific demethylase 1 (LSD1), the first identified histone demethylase, is universally overexpressed in various diseases. LSD1 dysregulation is closely associated with cancer, viral infections, and neurodegenerative diseases, etc., making it a promising therapeutic target. Several LSD1 inhibitors and two small-molecule degraders (UM171 and BEA-17) have entered the clinical stage. LSD1 can remove methyl groups from histone 3 at lysine 4 or lysine 9 (H3K4 or H3K9), resulting in either transcription repression or activation. While the roles of LSD1 in transcriptional regulation are well-established, studies have revealed that LSD1 can also be dynamically regulated by other factors. For example, the expression or activity of LSD1 can be regulated by many proteins that form transcriptional corepressor complexes with LSD1. Moreover, some post-transcriptional modifications and cellular metabolites can also regulate LSD1 expression or its demethylase activity. Therefore, in this review, we will systematically summarize how proteins involved in the transcriptional corepressor complex, various post-translational modifications, and metabolites act as regulatory factors for LSD1 activity.

LSD1 in drug discovery: From biological function to clinical application

Lysine-specific demethylase 1 (LSD1) is a flavin adenine dinucleotide (FAD) dependent monoamine oxidase (MAO) that erases the mono-, and dimethylation of histone 3 lysine 4 (H3K4), resulting in the suppression of target gene transcriptions. Besides, it can also demethylate some nonhistone substrates to regulate their biological functions. As reported, LSD1 is widely upregulated and plays a key role in several kinds of cancers, pharmacological or genetic ablation of LSD1 in cancer cells suppresses cell aggressiveness by several distinct mechanisms. Therefore, numerous LSD1 inhibitors, including covalent and noncovalent, have been developed and several of them have entered clinical trials. Herein, we systemically reviewed and discussed the biological function of LSD1 in tumors, lymphocytes as well as LSD1-targeting inhibitors in clinical trials, hoping to benefit the field of LSD1 and its inhibitors.

GSE1 links the HDAC1/CoREST co-repressor complex to DNA damage

Post-translational modifications of histones are important regulators of the DNA damage response (DDR). By using affinity purification mass spectrometry (AP-MS) we discovered that genetic suppressor element 1 (GSE1) forms a complex with the HDAC1/CoREST deacetylase/demethylase co-repressor complex. In-depth phosphorylome analysis revealed that loss of GSE1 results in impaired DDR, ATR signalling and γH2AX formation upon DNA damage induction. Altered profiles of ATR target serine-glutamine motifs (SQ) on DDR-related hallmark proteins point to a defect in DNA damage sensing. In addition, GSE1 knock-out cells show hampered DNA damage-induced phosphorylation on SQ motifs of regulators of histone post-translational modifications, suggesting altered histone modification. While loss of GSE1 does not affect the histone deacetylation activity of CoREST, GSE1 appears to be essential for binding of the deubiquitinase USP22 to CoREST and for the deubiquitination of H2B K120 in response to DNA damage. The combination of deacetylase, demethylase, and deubiquitinase activity makes the USP22-GSE1-CoREST subcomplex a multi-enzymatic eraser that seems to play an important role during DDR. Since GSE1 has been previously associated with cancer progression and survival our findings are potentially of high medical relevance.

A review of progress in o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities for cancer therapy

Histone deacetylases, as a new class of anticancer targets, could maintain homeostasis by catalyzing histone deacetylation and play important roles in regulating the expression of target genes. Due to the fact that simultaneous intervention with dual tumor related targets could improve treatment effects, researches on innovative design of dual-target drugs are underway. HDAC is known as a "sensitizer" for the synergistic effects with other anticancer-target drugs because of its flexible structure design. The synergistic effects of HDAC inhibitor and other target inhibitors usually show enhanced inhibitory effects on tumor cells, and also provide new strategies to overcome multidrug resistance. Many research groups have reported that simultaneously inhibiting HDAC and other targets, such as tubulin, EGFR, could enhance the therapeutic effects. The o-aminobenzamide group is often used as a ZBG group in the design of HDAC inhibitors with potent antitumor effects. Given the prolonged inhibitory effects and reduced toxic side effects of HDAC inhibitors using o-aminobenzamide as the ZBG group, the o-aminobenzamide group is expected to become a more promising alternative to hydroxamic acid. In fact, o-aminobenzamide-based dual inhibitors of HDAC with different chemical structures have been extensively prepared and reported with synergistic and enhanced anti-tumor effects. In this work, we first time reviewed the rational design, molecular docking, inhibitory activities and potential application of o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities in cancer therapy, which might provide a reference for developing new and more effective anticancer drugs.

Domatinostat Targets the FOXM1-Survivin Axis to Reduce the Viability of Ovarian Cancer Cells Alone and in Combination with Chemotherapeutic Agents

The deregulation of the FOXM1 transcription factor is a key molecular alteration in ovarian cancer, contributing to the development and progression of ovarian cancer via activation of the target genes. As such, FOXM1 is a highly attractive therapeutic target in the treatment of ovarian cancer, but there has been no clinically tested FOXM1 inhibitor to date. We investigated in this study the effects of domatinostat, a class I-selective HDAC inhibitor currently in the clinical stage of development as a cancer therapeutic, on the expression of FOXM1 and viability of ovarian cancer cells. Cell viability, as well as protein and mRNA expression of FOXM1 and its transcriptional target survivin, was examined after domatinostat treatment of TOV21G and SKOV3 ovarian cancer cell lines in the absence or presence of cisplatin and paclitaxel. The effect of FOXM1 knockdown on survivin expression and those of genetic and pharmacological inhibition of survivin alone or in combination with the chemotherapeutic agents on cell viability were also examined. Domatinostat reduced the protein and mRNA expression of FOXM1 and survivin and also the viability of ovarian cancer cells alone and in combination with cisplatin or paclitaxel at clinically relevant concentrations. Knockdown experiments showed survivin expression was dependent on FOXM1 in ovarian cancer cells. Survivin inhibition was sufficient to reduce the viability of ovarian cancer cells alone and in combination with the chemotherapeutic agents. Our findings suggest that domatinostat, which effectively targets the FOXM1-survivin axis required for the viability of ovarian cancer cells, is a promising option for the treatment of ovarian cancer.

Lysine-Specific Demethylase 1 Promises to Be a Novel Target in Cancer Drug Resistance: Therapeutic Implications

Chemotherapy, targeted therapy, and immunotherapy are effective against most tumors, but drug resistance remains a barrier to successful treatment. Lysine-specific demethylase 1 (LSD1), a member of histone demethylation modifications, can regulate invasion, metastasis, apoptosis, and immune escape of tumor cells, which are associated with tumorigenesis and tumor progression. Recent studies suggest that LSD1 ablation regulates resensitivity of tumor cells to anticarcinogens containing immune checkpoint inhibitors (ICIs) via multiple upstream and downstream pathways. In this review, we describe the recent findings about LSD1 biology and its role in the development and progression of cancer drug resistance. Further, we summarize LSD1 inhibitors that have a reversal or resensitive effect on drug resistance and discuss the possibility of targeting LSD1 in combination with other agents to surmount resistance.

A novel mitochondria-related gene signature in esophageal carcinoma: prognostic, immune, and therapeutic features

Esophageal carcinoma (ESCA) is a common and lethal malignant tumor worldwide. The mitochondrial biomarkers were useful in finding significant prognostic gene modules associated with ESCA owing to the role of mitochondria in tumorigenesis and progression. In the present work, we obtained the transcriptome expression profiles and corresponding clinical information of ESCA from The Cancer Genome Atlas (TCGA) database. Differential expressed genes (DEGs) were overlapped with 2030 mitochondria-related genes to get mitochondria-related DEGs. The univariate cox regression, Least Absolute Shrinkage and Selection Operator (LASSO) regression, and multivariate cox regression were sequentially used to define the risk scoring model for mitochondria-related DEGs, and its prognostic value was verified in the external datasets GSE53624. Based on the risk score, ESCA patients were divided into high- and low-risk groups. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were performed to further investigate the difference between low- and high-risk groups at the gene pathway level. CIBERSORT was used to evaluate immune cell infiltration. The mutation difference between high- and low-risk groups was compared by using the R package "Maftools". Cellminer was used to assess the association between the risk scoring model and drug sensitivity. As the most important outcome of the study, a 6-gene risk scoring model (APOOL, HIGD1A, MAOB, BCAP31, SLC44A2, and CHPT1) was constructed from 306 mitochondria-related DEGs. Pathways including the "hippo signaling pathway" and "cell-cell junction" were enriched in the DEGs between high and low groups. According to CIBERSORT, samples with high-risk scores demonstrated a higher abundance of CD4⁺ T cells, NK cells, M0 and M2 macrophages, and a lower abundance of M1 macrophages. The immune cell marker genes were correlated with the risk score. In mutation analysis, the mutation rate of TP53 was significantly different between the high- and low-risk groups. Drugs with a strong correlation with the risk model were selected. In conclusion, we focused on the role of mitochondria-related genes in cancer development and proposed a prognostic signature for individualized integrative assessment.

Therapeutic strategies of dual-target small molecules to overcome drug resistance in cancer therapy

Despite some advances in targeted therapeutics of human cancers, curative cancer treatment still remains a tremendous challenge due to the occurrence of drug resistance. A variety of underlying resistance mechanisms to targeted cancer drugs have recently revealed that the dual-target therapeutic strategy would be an attractive avenue. Compared to drug combination strategies, one agent simultaneously modulating two druggable targets generally shows fewer adverse reactions and lower toxicity. As a consequence, the dual-target small molecule has been extensively explored to overcome drug resistance in cancer therapy. Thus, in this review, we focus on summarizing drug resistance mechanisms of cancer cells, such as enhanced drug efflux, deregulated cell death, DNA damage repair, and epigenetic alterations. Based upon the resistance mechanisms, we further discuss the current therapeutic strategies of dual-target small molecules to overcome drug resistance, which will shed new light on exploiting more intricate mechanisms and relevant dual-target drugs for future cancer therapeutics.

Epigenetic Priming and Development of New Combination Therapy Approaches

Muscle-invasive urothelial carcinoma of the bladder (MIBC) has been treated with cisplatin-based chemotherapy for over 30 years. With the advent of immune checkpoint inhibitors, antibody drug conjugates and FGFR3 inhibitors new therapeutic options have been approved for patients with urothelial carcinoma (UC) and are still under investigation regarding association between patients' response and recently defined molecular subtypes. Unfortunately, similar to chemotherapy, only a fraction of UC patients responds to these new treatment approaches. Thus, either further new efficacious therapeutic options for treatment of individual subtypes or new approaches to overcome treatment resistance and to increase patients' response to standard of care treatment are needed.Epigenetic modifications of DNA and chromatin are known to mediate cellular plasticity or treatment resistance, and the responsible epigenetic regulators are frequently mutated or aberrantly expressed in UC. Thus, these enzymes provide targets for novel drug combination therapies to "episensitize" toward approved standard therapies by epigenetic priming. In general, these epigenetic regulators comprise writers and erasers like DNA methyltransferases and DNA demethylases (for DNA methylation), histone methyltransferases and histone demethylases (for histone methylation), as well as acetyl transferases and histone deacetylases (for histone and nonhistone acetylation). Such modifications, e.g., acetyl groups, are recognized by further epigenetic reader proteins, e.g., like the bromodomain and extra-terminal domain (BET) family proteins that often interact in multi-protein complexes and finally regulate chromatin conformation and transcriptional activity.Concurringly, epigenetic regulators target a plethora of cellular functions. Their pharmaceutical inhibitors often inhibit enzymatic activity of more than one isoenzyme or may have further noncanonical cytotoxic effects. Thus, analysis of their functions in UC pathogenesis as well as of the antineoplastic capacity of corresponding inhibitors alone or in combination with other approved drugs should follow a multidimensional approach. Here, we present our standard approach to analyze cellular effects of new epigenetic inhibitors on UC cells alone to define their potency and to conclude on putative reasonable combination therapy partners. We further describe our approach to identify efficacious synergistic combination therapies (e.g., with cisplatin or PARP inhibitors) that may have reduced normal toxicity through dose reduction, which can then be further analyzed in animal experiments. This approach may also serve as prototype for the preclinical evaluation of other epigenetic treatment approaches.

4SC-202 exerts an anti-tumor effect in cervical cancer by targeting PRLR signaling pathway

The aim of the present study is to investigate whether 4SC-202, a selective class I histone deacetylase inhibitor (HDACi), plays an anti-tumor role in cervical cancer (CC) by targeting prolactin receptor (PRLR). CCK-8 and colony formation assays were used to evaluate the effects of 4SC-202 on the proliferation of CC cells in vitro. Effects of 4SC-202 on the cell cycle distribution and apoptosis in SiHa cells were determined by flow cytometry and western blotting, respectively. Immunofluorescence, western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were performed to detect the activities of PRLR-related pathways and PRLR expression in CC cells. A xenograft tumor model in nude mice was established to examine effects of 4SC-202 on the tumor growth, apoptosis and PRLR-related pathways in vivo. The biochemical analyzer and H&E staining were used to detect the serum biochemical indexes and organ toxicity. 4SC-202 inhibited the proliferation of CC cells (SiHa, HeLa, and CaSki) in vitro in a time- and dose-dependent manner. SiHa cells were treated with 1 or 5 µM 4SC-202 for 72 h and then subjected to various functional assays. The assays showed that 4SC-202 significantly induced G2/M phase arrest and apoptosis, while inhibiting the activities of PRLR-related pathways and PRLR expression. In addition, 4SC-202 reduced tumor growth and induced apoptosis in vivo. 4SC-202 down-regulated the expression of PRLR and activities of PRLR-related pathways in the mouse model, displayed no effects on serum biochemical indicators and caused no toxicity to mouse organs. This finding suggests that 4SC-202 may serve as a novel therapeutic agent for CC.

HDAC Class I Inhibitor Domatinostat Preferentially Targets Glioma Stem Cells over Their Differentiated Progeny

Cancer stem cells (CSCs) are in general characterized by higher resistance to cell death and cancer therapies than non-stem differentiated cancer cells. However, we and others have recently revealed using glioma stem cells (GSCs) as a model that, unexpectedly, CSCs have specific vulnerabilities that make them more sensitive to certain drugs compared with their differentiated counterparts. We aimed in this study to discover novel drugs targeting such Achilles’ heels of GSCs as anti-GSC drug candidates to be used for the treatment of glioblastoma, the most therapy-resistant form of brain tumors. Here we report that domatinostat (4SC-202), a class I HDAC inhibitor, is one such candidate. At concentrations where it showed no or minimal growth inhibitory effect on differentiated GSCs and normal cells, domatinostat effectively inhibited the growth of GSCs mainly by inducing apoptosis. Furthermore, GSCs that survived domatinostat treatment lost their self-renewal capacity. These results suggested that domatinostat is a unique drug that selectively eliminates GSCs not only physically by inducing cell death but also functionally by inhibiting their self-renewal. Our findings also imply that class I HDACs and/or LSD1, another target of domatinostat, may possibly have a specific role in the maintenance of GSCs and therefore could be an attractive target in the development of anti-GSC therapies.

Reduction of Metastasis via Epigenetic Modulation in a Murine Model of Metastatic Triple Negative Breast Cancer (TNBC)

This study investigates the effects of a dual selective Class I histone deacetylase (HDAC)/lysine-specific histone demethylase 1A (LSD1) inhibitor known as 4SC-202 (Domatinostat) on tumor growth and metastasis in a highly metastatic murine model of Triple Negative Breast Cancer (TNBC). 4SC-202 is cytotoxic and cytostatic to the TNBC murine cell line 4T1 and the human TNBC cell line MDA-MB-231; the drug does not kill the normal breast epithelial cell line MCF10A. Furthermore, 4SC-202 reduces cancer cell migration. In vivo studies conducted in the syngeneic 4T1 model, which closely mimics human TNBC in terms of sites of metastasis, reveal reduced tumor burden and lung metastasis. The mechanism of action of 4SC-202 may involve effects on cancer stem cells (CSC) which can self-renew and form metastatic lesions. Approximately 5% of the total 4T1 cell population grown in three-dimensional scaffolds had a distinct CD44^high/CD24^low CSC profile which decreased after treatment. Bulk transcriptome (RNA) sequencing analyses of 4T1 tumors reveal changes in metastasis-related pathways in 4SC-202-treated tumors, including changes to expression levels of genes implicated in cell migration and cell motility. In summary, 4SC-202 treatment of tumors from a highly metastatic murine model of TNBC reduces metastasis and warrants further preclinical studies.

Complexities in the role of acetylation dynamics in modifying inducible gene activation parameters

High levels of histone acetylation are associated with the regulatory elements of active genes, suggesting a link between acetylation and gene activation. We revisited this model, in the context of EGF-inducible gene expression and found that rather than a simple unifying model, there are two broad classes of genes; one in which high lysine acetylation activity is required for efficient gene activation, and a second group where the opposite occurs and high acetylation activity is inhibitory. We examined the latter class in more detail using EGR2 as a model gene and found that lysine acetylation levels are critical for several activation parameters, including the timing of expression onset, and overall amplitudes of the transcriptional response. In contrast, DUSP1 responds in the canonical manner and its transcriptional activity is promoted by acetylation. Single cell approaches demonstrate heterogenous activation kinetics of a given gene in response to EGF stimulation. Acetylation levels modify these heterogenous patterns and influence both allele activation frequencies and overall expression profile parameters. Our data therefore point to a complex interplay between acetylation equilibria and target gene induction where acetylation level thresholds are an important determinant of transcriptional induction dynamics that are sensed in a gene-specific manner.

Selective Targeting of Class I Histone Deacetylases in a Model of Human Osteosarcoma

Dysregulation of histone deacetylases (HDACs) is associated with the pathogenesis of human osteosarcoma, which may present an epigenetic vulnerability as well as a therapeutic target. Domatinostat (4SC-202) is a next-generation class I HDAC inhibitor that is currently being used in clinical research for certain cancers, but its impact on human osteosarcoma has yet to be explored. In this study, we report that 4SC-202 inhibits osteosarcoma cell growth in vitro and in vivo. By analyzing cell function in vitro, we show that the anti-tumor effect of 4SC-202 involves the combined induction of cell-cycle arrest at the G2/M phase and apoptotic program, as well as a reduction in cell invasion and migration capabilities. We also found that 4SC-202 has little capacity to promote osteogenic differentiation. Remarkably, 4SC-202 revised the global transcriptome and induced distinct signatures of gene expression in vitro. Moreover, 4SC-202 decreased tumor growth of established human tumor xenografts in immunodeficient mice in vivo. We further reveal key targets regulated by 4SC-202 that contribute to tumor cell growth and survival, and canonical signaling pathways associated with progression and metastasis of osteosarcoma. Our study suggests that 4SC-202 may be exploited as a valuable drug to promote more effective treatment of patients with osteosarcoma and provide molecular insights into the mechanism of action of class I HDAC inhibitors.

Dissecting Histone Deacetylase 3 in Multiple Disease Conditions: Selective Inhibition as a Promising Therapeutic Strategy

The acetylation of histone and non-histone proteins has been implicated in several disease states. Modulation of such epigenetic modifications has therefore made histone deacetylases (HDACs) important drug targets. HDAC3, among various class I HDACs, has been signified as a potentially validated target in multiple diseases, namely, cancer, neurodegenerative diseases, diabetes, obesity, cardiovascular disorders, autoimmune diseases, inflammatory diseases, parasitic infections, and HIV. However, only a handful of HDAC3-selective inhibitors have been reported in spite of continuous efforts in design and development of HDAC3-selective inhibitors. In this Perspective, the roles of HDAC3 in various diseases as well as numerous potent and HDAC3-selective inhibitors have been discussed in detail. It will surely open up a new vista in the discovery of newer, more effective, and more selective HDAC3 inhibitors.

Research progress of dual inhibitors targeting crosstalk between histone epigenetic modulators for cancer therapy

Abnormal epigenetics is a critical hallmark of human cancers. Anticancer drug discovery directed at histone epigenetic modulators has gained impressive advances with six drugs available for cancer therapy and numerous other candidates undergoing clinical trials. However, limited therapeutic profile, drug resistance, narrow safety margin, and dose-limiting toxicities pose intractable challenges for their clinical utility. Because histone epigenetic modulators undergo intricate crosstalk and act cooperatively to shape an aberrant epigenetic profile, co-targeting histone epigenetic modulators with a different mechanism of action has rapidly emerged as an attractive strategy to overcome the limitations faced by the single-target epigenetic inhibitors. In this review, we summarize in detail the crosstalk of histone epigenetic modulators in regulating gene transcription and the progress of dual epigenetic inhibitors targeting this crosstalk.

Design, synthesis, and biological evaluation of novel dual inhibitors targeting lysine specific demethylase 1 (LSD1) and histone deacetylases (HDAC) for treatment of gastric cancer

LSD1 and HDAC are physical and functional related to each other in various human cancers and simultaneous pharmacological inhibition of LSD1 and HDAC exerts synergistic anti-cancer effects. In this work, a series of novel LSD1/HDAC bifunctional inhibitors with a styrylpyridine skeleton were designed and synthesized based on our previously reported LSD1 inhibitors. The representative compounds 5d and 5m showed potent activity against LSD1 and HDAC at both molecular and cellular level and displayed high selectivity against MAO-A/B. Moreover, compounds 5d and 5m demonstrated potent antiproliferative activities against MGC-803 and HCT-116 cancer cell lines. Notably, compound 5m showed superior in vitro anticancer potency against a panel of gastric cancer cell lines than ORY-1001 and SP-2509 with IC₅₀ values ranging from 0.23 to 1.56 μM. Compounds 5d and 5m significantly modulated the expression of Bcl-2, Bax, Vimentin, ZO-1 and E-cadherin, induced apoptosis, reduced colony formation and suppressed migration in MGC-803 cancer cells. In addition, preliminary absorption, distribution, metabolism, excretion (ADME) studies revealed that compounds 5d and 5m showed acceptable metabolic stability in human liver microsomes with minimal inhibition of cytochrome P450s (CYPs). Those results indicated that compound 5m could be a promising lead compound for further development as a therapeutic agent in gastric cancers via LSD1 and HDAC dual inhibition.

4sc-202 and Ink-128 cooperate to reverse the epithelial to mesenchymal transition in OSCC

Treatment of oral squamous cell carcinoma remains a challenge due to a high incidence of treatment resistance, which is followed by tumor recrudescence and metastasis to the lymph nodes. Thus, it is important to explore novel inhibitors of OSCC. Here, we aimed to identify drugs that may cooperate with histone deacetylase inhibitors to reverse the EMT, inhibit EMT and cell migration and invasion, and contribute to therapeutic efficacy. We found that treatment with 4sc-202 potently reversed the EMT and thereby inhibited cell migration and invasion in vitro, in part by inducing expression of the FoxO1 tumor-suppressor gene. Furthermore, 4sc-202 also synergized with Ink-128 to inhibit tumor migration and invasion in vitro. Mechanistically, 4sc-202 induced FoxO1 expression, whereas Ink-128 promoted nuclear translocation of FoxO1. Our findings indicated that FoxO1 might reverse the EMT by interacting with Twist1 in OSCC. In conclusion, we identified an effective combination therapy involving class I histone deacetylase and mammalian target of rapamycin complex 1/2 inhibition that effectively blocked the EMT of tumor cells by upregulating FoxO1 expression to inhibit Twist1 transcription. These data have implications for developing new targets for early diagnosis and treatment of OSCC.

Epigenetic Treatment of Urothelial Carcinoma Cells Sensitizes to Cisplatin Chemotherapy and PARP Inhibitor Treatment

Simple Summary

Muscle-invasive urothelial carcinoma of the bladder (UC) is treated with chemotherapies based on the DNA-damaging drug cisplatin, which only works temporarily due to the development of drug resistance. In this study, we show that it may be possible to overcome such resistances by treating the cancer cells with specific epigenetic drugs. We investigated the “epidrug” PLX51107 that inhibits the chromatin regulator BRD4 (Bromodomain Containing 4). PLX51107 inhibited cell growth, caused DNA damage, and blocked DNA repair response in UC cells. Concomitant application of PLX51107 with cisplatin or the drug talazoparib, interfering with DNA repair, caused cell death very efficiently. PLX51107 thus sensitizes UC cells to other drugs and may allow therapy with novel effective anti-tumor drugs like talazoparib that normally only work in a small proportion of patients with specific gene mutations. These results may help to improve current standard therapy and to develop new treatment options urgently required for UC patients.

Abstract

Muscle-invasive urothelial carcinoma (UC) is treated with cisplatin-based chemotherapy, which is only moderately efficient, mostly due to development of resistance. New therapy approaches are therefore urgently needed. Epigenetic alterations due to frequent mutations in epigenetic regulators contribute to development of the disease and to treatment resistance, and provide targets for novel drug combination therapies. Here, we determined the cytotoxic impact of the second-generation bromodomain protein inhibitor (BETi) PLX51107 on UC cell lines (UCC) and normal HBLAK control cells. PLX51107 inhibited proliferation, induced apoptosis, and acted synergistically with the histone deacetylase inhibitor romidepsin. While PLX51107 caused significant DNA damage, DNA damage signaling and DNA repair were impeded, a state defined as BRCAness. Accordingly, the drug strongly synergized with cisplatin more efficiently than romidepsin, and with the PARP inhibitor talazoparib to inhibit proliferation and induce cell death in UCC. Thus, a BETi can be used to “episensitize” UC cells to cytotoxic chemotherapy and inhibitors of DNA repair by inducing BRCAness in non BRCA1/2 mutated cancers. In clinical applications, the synergy between PLX51107 and other drugs should permit significant dosage reductions to minimize effects on normal tissues.

Downregulation of Cell Cycle and Checkpoint Genes by Class I HDAC Inhibitors Limits Synergism with G2/M Checkpoint Inhibitor MK-1775 in Bladder Cancer Cells

Since genes encoding epigenetic regulators are often mutated or deregulated in urothelial carcinoma (UC), they represent promising therapeutic targets. Specifically, inhibition of Class-I histone deacetylase (HDAC) isoenzymes induces cell death in UC cell lines (UCC) and, in contrast to other cancer types, cell cycle arrest in G2/M. Here, we investigated whether mutations in cell cycle genes contribute to G2/M rather than G1 arrest, identified the precise point of arrest and clarified the function of individual HDAC Class-I isoenzymes. Database analyses of UC tissues and cell lines revealed mutations in G1/S, but not G2/M checkpoint regulators. Using class I-specific HDAC inhibitors (HDACi) with different isoenzyme specificity (Romidepsin, Entinostat, RGFP966), cell cycle arrest was shown to occur at the G2/M transition and to depend on inhibition of HDAC1/2 rather than HDAC3. Since HDAC1/2 inhibition caused cell-type-specific downregulation of genes encoding G2/M regulators, the WEE1 inhibitor MK-1775 could not overcome G2/M checkpoint arrest and therefore did not synergize with Romidepsin inhibiting HDAC1/2. Instead, since DNA damage was induced by inhibition of HDAC1/2, but not of HDAC3, combinations between inhibitors of HDAC1/2 and of DNA repair should be attempted.

Clinical efficiency of epigenetic drugs therapy in bone malignancies

A great interest in the scientific community is focused on the improvement of the cure rate in patients with bone malignancies that have a poor response to the first line of therapies. Novel treatments currently include epigenetic compounds or molecules targeting epigenetic-sensitive pathways. Here, we offer an exhaustive review of such agents in these clinical settings. Carefully designed preclinical studies selected several epigenetic drugs, including inhibitors of DNA methyltransferase (DNMTIs), such as Decitabine, histone deacetylase classes I-II (HDACIs), as Entinostat, Belinostat, lysine-specific histone demethylase (LSD1), as INCB059872 or FT-2102 (Olutasidenib), inhibitors of isocitrate dehydrogenases, and enhancer of zeste homolog 2 (EZH2), such as EPZ6438 (Tazemetostat) To enhance the therapeutic effect, the prevalent approach in phase II trial is the association of these epigenetic drug inhibitors, with targeted therapy or immune checkpoint blockade. Optimization of drug dosing and regimens of Phase II trials may improve the clinical efficiency of such novel therapeutic approaches against these devastating cancers.

Metformin Combined with 4SC-202 Inhibited the Migration and Invasion of OSCC via STAT3/TWIST1

Background

Oral squamous cell carcinoma (OSCC), the most common epithelial malignant neoplasm in the head and neck, characterizes with local infiltration and metastasis of lymph nodes. The five-year survival rate of OSCC remains low despite the advances in clinical methods. Thus, it is necessary to develop a new effective therapeutic scheme for OSCC. Our previous results showed that metformin and 4SC-202 synergistically promoted the intrinsic apoptosis of OSCC in vitro and in vivo, but the effects on invasion and migration remained unclear.

Methods

Human OSCC cell lines HSC6 and CAL33 were cultured with metformin (16 mM) or/and 4SC-202 (0.4 μM) for 72 h. STAT3 inhibitor S31-201 was applied at concentration of 60 μM for 48 h. Wound-healing assays and transwell assays were used to determine the invasion and migration ability of OSCC. qRT-PCR and Western blot were performed to detect mRNA levels and protein levels.

Results

Metformin or/and 4SC-202 suppressed the migration and invasion of OSCC cells. Importantly, the expression of TWIST1 was suppressed by metformin and 4SC-202, while the invasion and migration inhibitory effects of metformin and 4SC-202 were countered by the overexpression of TWIST1. In addition, the phosphorylation level of STAT3 decreased after the administration of metformin or/and 4SC-202. Furthermore, inhibition of STAT3 by S31-201 suppressed the expression of TWIST1 and led to a decline in migration and invasion of OSCC, while overexpression of TWIST1 attenuated these effects.

Conclusion

Metformin and 4SC-202 suppressed the invasion and migration of OSCC through inhibition of STAT3/TWIST1, and this scheme can serve as a novel therapeutic strategy for OSCC.

Histone deacetylase inhibitor MPT0B291 suppresses Glioma Growth in vitro and in vivo partially through acetylation of p53

Background: Histone deacetylase (HDAC) inhibitors have emerged as a new class of anti-tumor agents for various types of tumors, including glioblastoma.

Methods and results: We found that a novel HDAC inhibitor, MPT0B291, significantly reduced the cell viability and increased cell death of human and rat glioma cell lines, but not in normal astrocytes. We also demonstrated that MPT0B291 suppressed proliferation by inducing G1 phase cell cycle arrest and increased apoptosis in human and rat glioma cell lines by flow cytometry and immunocytochemistry. We further investigated the anti-tumor effects of MPT0B291 in xenograft (mouse) and allograft (rat) models. The IVIS200 images and histological analysis indicated MPT0B291 (25 mg/kg, p. o.) reduced tumor volume. Mechanistically, MPT0B291 increased phosphorylation and acetylation/activation of p53 and increased mRNA levels of the apoptosis related genes PUMA, Bax, and Apaf1 as well as increased protein level of PUMA, Apaf1 in C6 cell line. The expression of cell cycle related gene p21 was also increased and Cdk2, Cdk4 were decreased by MPT0B291.

Conclusion: Our study highlights the anti-tumor efficacy of a novel compound MPT0B291 on glioma growth.

Tranylcypromine Based Lysine-Specific Demethylase 1 Inhibitor: Summary and Perspective

Histone lysine-specific demethylase 1 (LSD1/KDM1A) has become an important and promising anticancer target since it was first identified in 2004 and specially demethylates lysine residues of histone H3K4me1/2 and H3K9me1/2. LSD1 is ubiquitously overexpressed in diverse cancers, and abrogation of LSD1 results in inhibition of proliferation, invasion, and migration in cancer cells. Over the past decade, a number of biologically active small-molecule LSD1 inhibitors have been developed. To date, six trans-2-phenylcyclopropylamine (TCP)-based LSD1 inhibitors (including TCP, ORY-1001, GSK-2879552, INCB059872, IMG-7289, and ORY-2001) that covalently bind to the flavin adenine dinucleotide (FAD) within the LSD1 catalytic cavity have already entered into clinical trials. Here, we provide an overview about the structures, activities, and structure-activity relationship (SAR) of TCP-based LSD1 inhibitors that mainly covers the literature from 2008 to date. The opportunities, challenges, and future research directions in this emerging and promising field are also discussed.

Dual inhibitors of histone deacetylases and other cancer-related targets: A pharmacological perspective

Epigenetic enzymes histone deacetylases (HDACs) are clinically validated anticancer drug targets which have been studied intensively in the past few decades. Although several drugs have been approved in this field, they are still limited to a subset of hematological malignancies (in particular T-cell lymphomas), with therapeutic potential not fully realized and the drug-resistance occurred after a certain period of use. To maximize the therapeutic potential of these classes of anticancer drugs, and to extend their application to solid tumors, numerous combination therapies containing an HDACi and an anticancer agent from other mechanisms are currently ongoing in clinical trials. Recently, dual targeting strategy comprising the HDACs component has emerged as an alternative approach for combination therapies. In this perspective, we intend to gather all HDACs-containing dual inhibitors related to cancer therapy published in literature since 2015, classify them into five categories based on targets' biological functions, and discuss the rationale why dual acting agents should work better than combinatorial therapies using two separate drugs. The article discusses the pharmacological aspects of these dual inhibitors, including in vitro biological activities, pharmacokinetic studies, in vivo efficacy studies, as well as available clinical trials. The review of the current status and advances should provide better analysis for future opportunities and challenges of this field.

4SC-202 induces apoptosis in myelodysplastic syndromes and the underlying mechanism

Epigenetic modifications play crucial roles in regulating the self-renewal and differentiation of hematopoiesis. 4SC-202, a novel inhibitor of histone lysine-specific demethylase 1 (LSD1) and class I histone deacetylases (HDACs), is a potential therapeutic agent to treat myelodysplastic syndrome (MDS). However, it remains unclarified of the mechanism of 4SC-202. In the study, we found that 4SC-202 treatment could inhibit cell viability, induce apoptosis and cause G2/M cell cycle arrest in MDS cell line SKM-1. Heme oxygenase-1 (HO-1) was correlated with disease progression and chemotherapy resistance. Here, we reported that 4SC-202 could down-regulate the expression of HO-1, and up-regulation of HO-1 could significantly attenuate the 4SC-202-induced apoptosis in SKM-1 cells. In addition, the activation of NF-κB pathway was suppressed by 4SC-202, while up-regulation of HO-1 significantly weakened the 4SC-202-induced suppression of the NF-κB pathway, thereby attenuating the efficacy of 4SC-202. However, down-regulation of HO-1 enhanced the sensitivity of 4SC-202 against SKM-1 cells. Moreover, SKM-1 cells were transfected with HO-1 overexpression lentivirus, subsequently injected into the tail vein of NOD/SCID mice, followed by administration of 4SC-202 in mice. As a result, up-regulation HO-1 could partially attenuate 4SC-202-suppressed MDS cells growth in NOD/SCID mice. In conclusion, 4SC-202 could induce apoptosis via the NF-κB pathway, and our present finding may provide a novel therapeutic strategy for MDS.

Analysis of Dual Class I Histone Deacetylase and Lysine Demethylase Inhibitor Domatinostat (4SC-202) on Growth and Cellular and Genomic Landscape of Atypical Teratoid/Rhabdoid

Central nervous system atypical teratoid/rhabdoid tumors (ATRTs) are rare and aggressive tumors with a very poor prognosis. Current treatments for ATRT include resection of the tumor, followed by systemic chemotherapy and radiation therapy, which have toxic side effects for young children. Gene expression analyses of human ATRTs and normal brain samples indicate that ATRTs have aberrant expression of epigenetic markers including class I histone deacetylases (HDAC’s) and lysine demethylase (LSD1). Here, we investigate the effect of a small molecule epigenetic modulator known as Domatinostat (4SC-202), which inhibits both class I HDAC’s and Lysine Demethylase (LSD1), on ATRT cell survival and single cell heterogeneity. Our findings suggest that 4SC-202 is both cytotoxic and cytostatic to ATRT in 2D and 3D scaffold cell culture models and may target cancer stem cells. Single-cell RNA sequencing data from ATRT-06 spheroids treated with 4SC-202 have a reduced population of cells overexpressing stem cell-related genes, including SOX2. Flow cytometry and immunofluorescence on 3D ATRT-06 scaffold models support these results suggesting that 4SC-202 reduces expression of cancer stem cell markers SOX2, CD133, and FOXM1. Drug-induced changes to the systems biology landscape are also explored by multi-omics enrichment analyses. In summary, our data indicate that 4SC-202 has both cytotoxic and cytostatic effects on ATRT, targets specific cell sub-populations, including those with cancer stem-like features, and is an important potential cancer therapeutic to be investigated in vivo.

Anti-tumor effects of the histone deacetylase inhibitor vorinostat on canine urothelial carcinoma cells

Canine urothelial carcinoma (cUC) is the most common tumor of the lower urinary tract in dogs. Although chemotherapy and radical surgery have improved the overall survival, most dogs with cUC succumb to metastasis or recurrence. Therefore, the development of an effective systematic therapy is warranted. In this study, a comprehensive drug screening test using a cUC cell line was performed and the anti-tumor effect of a histone deacetylase (HDAC) inhibitor was evaluated. Comprehensive drug screening was performed on cUC cells. Based on this screening, the anti-proliferation effect of vorinostat, an HDAC inhibitor clinically applied in humans, was evaluated using several cUC cell lines in sulforhodamine B and flow cytometry assays. Western blot analysis was also performed to evaluate the degree of acetylation of histone H3 as well as the expression and phosphorylation of cell cycle-related molecules. The anti-tumor effect of vorinostat in vivo was evaluated using a xenograft model. Finally, immunohistochemistry was performed on acetyl-histone H3 in cUC and the relationship between the degree of acetylation and prognosis was examined using Kaplan–Meier survival analysis. Drug screening revealed that HDAC inhibitors consistently inhibited the growth of cUC cells. Vorinostat inhibited the growth of 6 cUC cell lines in a dose-dependent manner and induced G0/G1 cell cycle arrest. Western blot analysis showed that vorinostat mediated the acetylation of histone H3, the dephosphorylation of p-Rb, and the upregulation of p21 upon exposure to vorinostat. Furthermore, inhibition of tumor growth was observed in the xenograft model. In clinical cUC cases, neoplastic urothelium showed significant deacetylation of histones compared to the normal control, where lower histone acetylation levels were associated with a poor prognosis. In conclusion, the therapeutic potential of vorinostat was demonstrated in cUC. Histone deacetylation may be related to cUC tumor progression.

Urinary expression of genes involved in DNA methylation and histone modification for diagnosis of bladder cancer in patients with asymptomatic microscopic haematuria

The aim of the present study was to identify and test a urine marker panel of genes involved in DNA methylation and histone modification for the detection of urothelial carcinoma of the bladder (UCB). RNA samples obtained from the voided urine of 227 patients with asymptomatic microscopic haematuria (AMH) were analysed. Gene array analysis was performed on 18 randomly selected cDNA samples, which revealed that histone deacetylase 9 (HDAC9), HDAC3, tRNA (cytosine-5-)-methyltransferase1 and DNA methyltransferase 1 were differentially expressed between patients with UCB and control subjects. Subsequently, reverse transcription-quantitative polymerase chain reaction analysis was employed to test the performance of the identified four-gene panel on the remaining 209 cDNA samples. In this targeted discovery cohort, all four genes were significantly associated with UCB on univariable analyses [each odds ratio (OR) >2, P<0.05], but only HDAC3 was significant following multivariable analysis (OR=2.8, P=0.011). The addition of HDAC3 to a base risk factor model improved its accuracy by 1.4%. These data suggest that urinary HDAC3 is associated with the presence of UCB in patients with AMH; however, HDAC3 improved the accuracy of the established risk factors only to a marginal extent.

Metformin and 4SC-202 synergistically promote intrinsic cell apoptosis by accelerating ΔNp63 ubiquitination and degradation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common and aggressive epithelial tumor in the head and neck region with a rising incidence. Despite the advances in basic science and clinical research, the overall survival rate of OSCC remains low. Thus finding novel effective therapeutic agents for OSCC is necessary. In this study, we investigated the effects and mechanisms of combined metformin and 4SC-202 in OSCC. Our results showed that metformin and 4SC-202 synergistically suppressed the proliferation and promoted the intrinsic apoptosis of OSCC cells in vitro and in vivo. Importantly, the proteasome inhibitor MG132 impeded the ΔNp63-decreasing effects after metformin and 4SC-202 treatment, indicating that metformin and 4SC-202 could promote the degradation of ΔNp63 protein. Moreover, ubiquitination level of ΔNp63 increased after metformin or/and 4SC-202 administration. Furthermore, we revealed that ΔNp63 mediated anticancer effects of metformin and 4SC-202, as overexpression or suppression of ΔNp63 could attenuate or facilitate the apoptosis rate of OSCC under metformin or/and 4SC-202 treatment. Collectively, metformin and 4SC-202 synergistically promote intrinsic apoptosis through accelerating ubiquitin-mediated degradation of ΔNp63 in OSCC, and this co-treatment can serve as a potential therapeutic scheme for OSCC.

Combined class I histone deacetylase and mTORC1/C2 inhibition suppresses the initiation and recurrence of oral squamous cell carcinomas by repressing SOX2

Treatment of oral squamous cell carcinoma (OSCC) remains a challenge because of the lack of effective early treatment strategies and high incidence of relapse. Here, we showed that combined 4SC-202 (a novel selective class I HDAC inhibitor) and INK128 (a selective mTORC1/C2 inhibitor) treatment exhibited synergistic effects on inhibiting cell growth, sphere-forming ability, subcutaneous tumor formation and ALDH1⁺ cancer stem cells (CSCs) in OSCC. The initiation of OSCC was significantly inhibited by combined treatment in 4NQO-induced rat model. In addition, upregulated SOX2 was associated with advanced and metastatic tumors in OSCC patients and was responsible for the drug-resistance property of OSCC cells. The inhibitory effect of combined treatment on cell viability and ALDH1⁺ CSCs were attenuated by SOX2 verexpression. Furthermore, combined treatment can effectively overcome chemoresistance and inhibit the growth of recurrent OSCC in vitro and in vivo. Mechanistically, 4SC-202 and INK128 repressed SOX2 expression through miR-429/miR-1181-mediated mRNA degradation and preventing cap-dependent mRNA translation, respectively. These results suggest that combined class I histone deacetylase and mTORC1/C2 inhibition suppresses the carcinogenesis and recurrence of OSCC by repressing SOX2.

HDAC1 knockdown inhibits invasion and induces apoptosis in non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is a common malignant tumor. Although the abnormal expression and potential clinical prognostic value of histone deacetylase 1 (HDAC1) were recently discovered in many kinds of cancer, the roles and molecular mechanisms of HDAC1 in NSCLC is still limited. The CCK-8 assay is used to evaluate the viability of NSCLC cells. Downregulation of HDAC1 by shRNA. The TUNEL assay was used to evaluate the role of HDAC1 in NSCLC apoptosis. To evaluate the role of HDAC1 in NSCLC cells migration, the Boyden chamber transwell assay and wound healing assay were used. To evaluate the cells invasion, the matrigel precoated Transwell assay was used. Enzyme-linked immunosorbent assays (ELISAs) were used to detect the level of vascular endothelial growth factor (VEGF) and IL-8 in NSCLC. To investigate the role of HDAC1 in angiogenesis, the tube formation assay was investigated. In this study, we showed that HDAC1 expression was elevated in NSCLC lines compared to that in normal liver cells LO2. Furthermore, downregulation of HDAC1 inhibited cell proliferation, prevented cell migration, decreased cell invasion, reduced tumor angiogenesis and induced cell apoptosis. In summary, HDAC1 may be regarded as a potential indicator for NSCLC patient treatment.

Elucidating the mechanism of action of domatinostat (4SC-202) in cutaneous T cell lymphoma cells

Background

Targeting epigenetic modifiers is effective in cutaneous T cell lymphoma (CTCL). However, there is a need for further improvement of this therapeutic approach. Here, we compared the mode of action of romidepsin (FK228), an established class I histone deacetylase inhibitor, and domatinostat (4SC-202), a novel inhibitor of class I HDACs, which has been reported to also target the lysine-specific histone demethylase 1A (LSD1).

Methods

We performed MTS assays and flow cytometric analyses of propidium iodide or annexin V-stained cells to assess drug impact on cellular proliferation, cell cycle distribution, and survival. Histone acetylation and methylation as well as caspase activation was analyzed by immunoblot. Gene expression analysis was performed using NanosString technology. Knockdown and knockout of LSD1 was achieved with shRNA and CRISPR/Cas9, respectively, while the CRISPR/Cas9 synergistic activation mediator system was used to induce expression of endogenous HDACs and LSD1. Furthermore, time-lapse fluorescence microscopy and an in vitro tubulin polymerization assay were applied.

Results

While FK228 as well as 4SC-202 potently induced cell death in six different CTCL cell lines, only in the case of 4SC-202 death was preceded by an accumulation of cells in the G2/M phase of the cell cycle. Surprisingly, apoptosis and accumulation of cells with double DNA content occurred already at 4SC-202 concentrations hardly affecting histone acetylation and methylation, and provoking significantly less changes in gene expression compared to biologically equivalent doses of FK228. Indeed, we provide evidence that the 4SC-202-induced G2/M arrest in CTCL cells is independent of de novo transcription. Furthermore, neither enforced expression of HDAC1 nor knockdown or knockout of LSD1 affected the 4SC-202-induced effects. Since time-lapse microscopy revealed that 4SC-202 could affect mitotic spindle formation, we performed an in vitro tubulin polymerization assay revealing that 4SC-202 can directly inhibit microtubule formation.

Conclusions

We demonstrate that 4SC-202, a drug currently tested in clinical trials, effectively inhibits growth of CTCL cells. The anti-cancer cell activity of 4SC-202 is however not limited to LSD1-inhibition, modulation of histone modifications, and consecutive alteration of gene expression. Indeed, the compound is also a potent microtubule-destabilizing agent.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0719-4) contains supplementary material, which is available to authorized users.

Histone Deacetylase Inhibitors and Phenotypical Transformation of Cancer Cells

Histone deacetylase inhibitors (HDIs) are a group of potent epigenetic drugs which have been investigated for their therapeutic potential in various clinical disorders, including hematological malignancies and solid tumors. Currently, several HDIs are already in clinical use and many more are on clinical trials. HDIs have shown efficacy to inhibit initiation and progression of cancer cells. Nevertheless, both pro-invasive and anti-invasive activities of HDIs have been reported, questioning their impact in carcinogenesis. The aim of this review is to compile and discuss the most recent findings on the effect of HDIs on the epithelial-mesenchymal transition (EMT) process in human cancers. We have summarized the impact of HDIs on epithelial (E-cadherin, β-catenin) and mesenchymal (N-cadherin, vimentin) markers, EMT activators (TWIST, SNAIL, SLUG, SMAD, ZEB), as well as morphology, migration and invasion potential of cancer cells. We further discuss the use of HDIs as monotherapy or in combination with existing or novel anti-neoplastic drugs in relation to changes in EMT.

Effects of novel HDAC inhibitors on urothelial carcinoma cells

Background

Histone deacetylase inhibitors (HDACi) are promising anti-cancer drugs that could also be employed for urothelial carcinoma (UC) therapy. It is unclear, however, whether inhibition of all 11 zinc-dependent HDACs or of individual enzymes is more efficacious and specific. Here, we investigated the novel HDACi 19i (LMK235) with presumed preferential activity against class IIA HDAC4/5 in comparison to the pan-HDACi vorinostat (SAHA) and the HDAC4-specific HDACi TMP269 in UC cell lines with basal expression of HDAC4 and characterized two HDAC4-overexpressing UC cell lines.

Methods

Cytotoxic concentrations 50% (CC₅₀s) for HDACi were determined by MTT assay and high-content analysis-based fluorescent live/dead assay in UC cell lines with different expression of HDAC4 and as well as in normal urothelial cell cultures, HBLAK and HEK-293 cell lines. Effects of HDACis were analyzed by flow cytometry; molecular changes were followed by qRT-PCR and Western blots. UC lines overexpressing HDAC4 were established by lentiviral transduction. Inhibitor activity profiles of HDACi were obtained by current state in vitro assays, and docking analysis was performed using an updated crystal structure of HDAC4.

Results

In UC cell lines, 19i CC₅₀s ranged around 1 μM; control lines were similarly or less sensitive. Like SAHA, 19i increased the G2/M-fraction, disturbed mitosis, and elicited apoptosis or in some cells senescence. Thymidylate synthase expression was diminished, and p21^CIP1 was induced; global histone acetylation and α-tubulin acetylation also increased. In most cell lines, 19i as well as SAHA induced HDAC5 and HDAC4 mRNAs while rather repressing HDAC7. UC cell lines overexpressing HDAC4 were not significantly less sensitive to 19i. Reevaluation of the in vitro HDAC isoenzyme activity inhibition profile of 19i and its docking to HDAC4 using current assays suggested rather low activity against class IIA HDACs. The specific class IIA HDAC inhibitor TMP269 impeded proliferation of UC cell lines only at concentrations > 10 μM.

Conclusions

Anti-neoplastic effects of 19i on UC cells appear to be exerted by targeting class I HDACs. In fact, HDAC4 may rather impede UC growth. Our results suggest that targeting of class IIA HDACs 4/5 may not be optimal for UC therapy. Moreover, our investigation provides further evidence for cross-regulation of class IIA HDACs by class I HDACs.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0531-y) contains supplementary material, which is available to authorized users.

The Multiple Myeloma Drug Pipeline-2018: A Review of Small Molecules and Their Therapeutic Targets

Treatment of multiple myeloma (MM), a neoplasm of plasma cells, formerly dependent on alkylating drugs, corticosteroids, and autologous stem cell transplantation, has changed dramatically in the past 20 years because 3 new classes of small molecule drugs (arbitrarily defined as having a molecular weight of < 900 kDa)-immunomodulators, proteasome inhibitors, and histone deacetylase blockers-have been introduced for the disease. Therapeutic options for MM expanded further in 2015 when 2 new monoclonal antibodies (daratumumab and elotuzumab) were approved by the Food and Drug Administration for MM. Although MM remains incurable, the cumulative effect of these advances has resulted in a near-doubling of the 5-year survival rate since the late 1980s. Despite these advances, therapy for MM continues to pose substantial challenges because resistance to therapy frequently develops, and relapse and recurrence are all too common. The present review focused on the pipeline for new small molecules in various stages of development and their associated cellular targets. In addition to newer versions of alkylators, immunomodulators, proteasome inhibitors, and histone deacetylase inhibitors, the present review considered the prospects for adding new classes of small molecules to the MM armamentarium, which offer the potential for oral efficacy, relative simplicity of preparation, and prospects for improvement in the cost-to-benefit ratio. Included are agents that affect myeloma epigenetics and the ubiquitination-proteasome system and the unfolded protein response, apoptotic mechanisms, chromosomal abnormalities, nuclear protein transport, and various kinases involved in cellular signaling pathways.

Combined inhibition of BET proteins and class I HDACs synergistically induces apoptosis in urothelial carcinoma cell lines

Background

New efficient therapies for urothelial carcinoma (UC) are urgently required. Small-molecule drugs targeting chromatin regulators are reasonable candidates because these regulators are frequently mutated or deregulated in UC. Indeed, in previous work, Romidepsin, which targets class I histone deacetylases (HDAC), efficiently killed UC cells, but did not elicit canonical apoptosis and affected benign urothelial cells indiscriminately. Combinations of HDAC inhibitors with JQ1, an inhibitor of bromodomain-containing acetylation reader proteins like BRD4, which promote especially the transcription of pro-tumorigenic genes, have shown efficacy in several tumor types. We therefore investigated the effects of combined Romidepsin and JQ1 treatment on UC and benign urothelial control cells.

Results

JQ1 alone induced cell cycle arrest, but only limited apoptosis in eight UC cell lines with strongly varying IC₅₀ values between 0.18 and 10 μM. Comparable effects were achieved by siRNA-mediated knockdown of BRD4. Romidepsin and JQ1 acted in a synergistic manner across all UC cell lines, efficiently inhibiting cell cycle progression, suppressing clonogenic growth, and inducing caspase-dependent apoptosis. Benign control cells were growth-arrested without apoptosis induction, but retained long-term proliferation capacity. In UC cells, anti-apoptotic and oncogenic factors Survivin, BCL-2, BCL-XL, c-MYC, EZH2 and SKP2 were consistently downregulated by the drug combination and AKT phosphorylation was diminished. Around the transcriptional start sites of these genes, the drug combination enhanced H3K27 acetylation, but decreased H3K4 trimethylation. The cell cycle inhibitor CDKN1C/p57^KIP2 was dramatically induced at mRNA and protein levels. However, Cas9-mediated CDKN1C/p57^KIP2 knockout did not rescue UC cells from apoptosis.

Conclusion

Our results demonstrate significant synergistic effects on induction of apoptosis in UC cells by the combination treatment with JQ1 and Romidepsin, but only minor effects in benign cells. Thus, this study established a promising new small-molecule combination therapy approach for UC.

Electronic supplementary material

The online version of this article (10.1186/s13148-017-0434-3) contains supplementary material, which is available to authorized users.

Epigenetic Treatment Options in Urothelial Carcinoma

Mutations, dysregulation, and dysbalance of epigenetic regulators are especially frequent in urothelial carcinoma (UC) compared to other malignancies. Accordingly, targeting epigenetic regulators may provide a window of opportunity particularly in anticancer therapy of UC. In general, these epigenetic regulators comprise DNA methyltransferases and DNA demethylases (for DNA methylation), histone methyltransferases, and histone demethylases (for histone methylation) as well as acetyl transferases and histone deacetylases (for histone and non-histone acetylation).As epigenetic regulators target a plethora of cellular functions and available inhibitors often inhibit enzymatic activity of more than one isoenzyme or may have further off-target effects, analysis of their functions in UC pathogenesis as well as of the antineoplastic capacity of according inhibitors should follow a multidimensional approach.Here, we present our standard approach for the analysis of the cellular and molecular functions of individual HDAC enzymes, their suitability as treatment targets and for the evaluation of isoenzyme-specific HDAC inhibitors regarding their antineoplastic efficacy. This approach may also serve as prototype for the preclinical evaluation of other epigenetic treatment approaches.

Histone deacetylase class-I inhibition promotes epithelial gene expression in pancreatic cancer cells in a BRD4- and MYC-dependent manner

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer with a particularly dismal prognosis. Histone deacetylases (HDAC) are epigenetic modulators whose activity is frequently deregulated in various cancers including PDAC. In particular, class-I HDACs (HDAC 1, 2, 3 and 8) have been shown to play an important role in PDAC. In this study, we investigated the effects of the class I-specific HDAC inhibitor (HDACi) 4SC-202 in multiple PDAC cell lines in promoting tumor cell differentiation. We show that 4SC-202 negatively affects TGFβ signaling and inhibits TGFβ-induced epithelial-to-mesenchymal transition (EMT). Moreover, 4SC-202 markedly induced p21 (CDKN1A) expression and significantly attenuated cell proliferation. Mechanistically, genome-wide studies revealed that 4SC-202-induced genes were enriched for Bromodomain-containing Protein-4 (BRD4) and MYC occupancy. BRD4, a well-characterized acetyllysine reader, has been shown to play a major role in regulating transcription of selected subsets of genes. Importantly, BRD4 and MYC are essential for the expression of a subgroup of genes induced by class-I HDACi. Taken together, our study uncovers a previously unknown role of BRD4 and MYC in eliciting the HDACi-mediated induction of a subset of genes and provides molecular insight into the mechanisms of HDACi action in PDAC.

Targeting class I histone deacetylases by the novel small molecule inhibitor 4SC-202 blocks oncogenic hedgehog-GLI signaling and overcomes smoothened inhibitor resistance

Aberrant activation of Hedgehog (HH)/GLI signaling is causally involved in numerous human malignancies, including basal cell carcinoma (BCC) and medulloblastoma. HH pathway antagonists targeting smoothened (SMO), an essential effector of canonical HH/GLI signaling, show significant clinical success in BCC patients and have recently been approved for the treatment of advanced and metastatic BCC. However, rapid and frequent development of drug resistance to SMO inhibitors (SMOi) together with severe side effects caused by prolonged SMOi treatment call for alternative treatment strategies targeting HH/GLI signaling downstream of SMO. In this study, we report that 4SC-202, a novel clinically validated inhibitor of class I histone deacetylases (HDACs), efficiently blocks HH/GLI signaling. Notably, 4SC-202 treatment abrogates GLI activation and HH target gene expression in both SMOi-sensitive and -resistant cells. Mechanistically, we propose that the inhibition of HDACs 1/2/3 is crucial for targeting oncogenic HH/GLI signaling, and that class I HDAC inhibitors either in combination with SMOi or as second-line therapy may improve the treatment options for HH-associated malignancies with SMOi resistance.

4SC-202 as a Potential Treatment for the Pediatric Brain Tumor Medulloblastoma

This project involves an examination of the effect of the small molecule inhibitor 4SC-202 on the growth of the pediatric brain cancer medulloblastoma. The small molecule inhibitor 4SC-202 significantly inhibits the viability of the pediatric desmoplastic cerebellar human medulloblastoma cell line DAOY, with an IC₅₀ = 58.1 nM, but does not affect the viability of noncancerous neural stem cells (NSC). 4SC-202 exposure inhibits hedgehog expression in the DAOY cell line. Furthermore, microarray analysis of human medulloblastoma patient tumors indicate significant upregulation of key targets in the Hedgehog signaling pathway and Protein Tyrosine Kinase (PTK7).

Applying the chicken embryo chorioallantoic membrane assay to study treatment approaches in urothelial carcinoma

BACKGROUND

Rapid development of novel treatment options demands valid preclinical screening models for urothelial carcinoma (UC). The translational value of high-throughput drug testing using 2-dimensional (2D) cultures is limited while for xenograft models handling efforts and costs often become prohibitive for larger-scale drug testing. Therefore, we investigated to which extent the chicken chorioallantoic membrane (CAM) assay might provide an alternative model to study antineoplastic treatment approaches for UC.

METHODS

The ability of 8 human UC cell lines (UCCs) to form tumors after implantation on CAMs was investigated. Epithelial-like RT-112 and mesenchymal-like T-24 UCCs in cell culture or as CAM tumors were treated with cisplatin alone or combined with histone deacetylase inhibitors (HDACi) romidepsin and suberanilohydroxamic acid. Tumor weight, size, and bioluminescence activity were monitored; tumor specimens were analyzed by histology and immunohistochemistry. Western blotting and quantitative real time polymerase chain reaction were used to measure protein and mRNA expression.

RESULTS

UCCs were reliably implantable on the CAM, but tumor development varied among cell lines. Expression of differentiation markers (E-cadherin, vimentin, CK5, CK18, and CK20) was similar in CAM tumors and 2D cultures. Cellular phenotypes also remained stable after recultivation of CAM tumors in 2D cultures. Bioluminescence images correlated with tumor weight. Cisplatin and HDACi decreased weight and growth of CAM tumors in a dose-dependent manner, but HDACi treatment acted less efficiently as in 2D cultures, especially on its typically associated molecular markers. Synergistic effects of HDACi and subsequent cisplatin treatment on UCCs were neither detected in 2D cultures nor detected in CAM tumors.

CONCLUSION

Our results demonstrate that the CAM assay is a useful tool for studying tumor growth and response to conventional anticancer drugs under 3D conditions, especially cytotoxic drugs as cisplatin. With some limitations, it might serve as a cost- and time-effective preclinical screening assay for novel therapeutic approaches before further assessment in expensive and cumbersome animal models.

Stepwise assembly of functional C-terminal REST/NRSF transcriptional repressor complexes as a drug target

In human cells, thousands of predominantly neuronal genes are regulated by the repressor element 1 (RE1)-silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF). REST/NRSF represses transcription of these genes in stem cells and non-neuronal cells by tethering corepressor complexes. Aberrant REST/NRSF expression and intracellular localization are associated with cancer and neurodegeneration in humans. To date, detailed molecular analyses of REST/NRSF and its C-terminal repressor complex have been hampered largely by the lack of sufficient amounts of purified REST/NRSF and its complexes. Therefore, the aim of this study was to express and purify human REST/NRSF and its C-terminal interactors in a baculovirus multiprotein expression system as individual proteins and coexpressed complexes. All proteins were enriched in the nucleus, and REST/NRSF was isolated as a slower migrating form, characteristic of nuclear REST/NRSF in mammalian cells. Both REST/NRSF alone and its C-terminal repressor complex were functionally active in histone deacetylation and histone demethylation and bound to RE1/neuron-restrictive silencer element (NRSE) sites. Additionally, the mechanisms of inhibition of the small-molecule drugs 4SC-202 and SP2509 were analyzed. These drugs interfered with the viability of medulloblastoma cells, where REST/NRSF has been implicated in cancer pathogenesis. Thus, a resource for molecular REST/NRSF studies and drug development has been established.