Small molecule HDAC inhibitors: Promising agents for breast cancer treatment

Targeting epigenetic deregulations for the management of esophageal carcinoma: recent advances and emerging approaches

Ranking from seventh in incidence to sixth in mortality, esophageal carcinoma is considered a severe malignancy of food pipe. Later-stage diagnosis, drug resistance, and a high mortality rate contribute to its lethality. Esophageal squamous cell carcinoma and esophageal adenocarcinoma are the two main histological subtypes of esophageal carcinoma, with squamous cell carcinoma alone accounting for more than eighty percent of its cases. While genetic anomalies are well known in esophageal cancer, accountability of epigenetic deregulations is also being explored for the recent two decades. DNA methylation, histone modifications, and functional non-coding RNAs are the crucial epigenetic players involved in the modulation of different malignancies, including esophageal carcinoma. Targeting these epigenetic aberrations will provide new insights into the development of biomarker tools for risk stratification, early diagnosis, and effective therapeutic intervention. This review discusses different epigenetic alterations, emphasizing the most significant developments in esophageal cancer epigenetics and their potential implication for the detection, prognosis, and treatment of esophageal carcinoma. Further, the preclinical and clinical status of various epigenetic drugs has also been reviewed.

Recent histone deacetylase inhibitors in cancer therapy

Cancer metastasis increases the complexity of the disease and escalates patient mortality. Traditional chemotherapy has been associated with low efficacy and marked side effects. Studies pivot toward histone deacetylase (HDAC) enzymes and inhibitors because they are critical for chromatin structure, gene regulation, and cellular activities that are linked to metastasis and cancer progression. HDAC inhibitors (HDACi) can alter gene expression patterns and can lead to cell-cycle arrest and apoptosis in neoplastic cells. Several HDACi drugs like vorinostat, romidepsin, panobinostat, and belinostat are approved by the Food and Drug Administration. China and Japan have approved the use of tucidinostat, a new subtype-selective HDACi that inhibits class 1 HDAC1, HDAC2, HDAC3, as well as class 2b HDAC10. These drugs have shown promising results in the treatment of multiple carcinoma including cervical cancer, T-cell lymphoma, brain cancer, and breast cancer. This review highlights the HDACi classes, the mechanism of action of these inhibitors, their preclinical and clinical efficacy, and the latest clinical trials and patents used in cancer therapeutics. Overall, this review focuses on patents and clinical trials data from 2019 onward to give a better viewpoint on current trends in HDACis as chemotherapy agents.

2-Substituted 1,5-benzothiazepine-based HDAC inhibitors exert anticancer activities on human solid and acute myeloid leukemia cell lines

Herein, we report the development of a new series of histone deacetylase inhibitors (HDACi) containing a 2-substituted 1,5-benzothiazepine scaffold. First, a virtual combinatorial library (∼1.6 × 103 items) was built according to a convenient synthetic route, and then it was submitted to molecular docking experiments on seven HDACs isoforms belonging to classes I and II. Integrated computational filters were used to select the most promising ones that were synthesized through an optimized approach, also amenable to generating both racemic and enantioenriched benzothiazepine-based derivatives. The obtained compounds showed potent HDAC inhibitory activity, especially those containing the sulphone moiety, endowed with IC50 in the nanomolar range. In addition, in vitro outcomes of our synthesized compounds demonstrated a cytotoxic effect on U937 and HCT116 cell lines and an arrest in the G2/M phase (13 ≤ IC50 ≤ 18 µM). Finally, Western blot analyses outlined the modulation of the histone acetyl markers such as H3K9/14, acetyl-tubulin, and the apoptotic indicator p21 in both cancer cell lines, disclosing a good HDAC inhibitor activity exerted by the designed items. Given the key role of HDACs in many cellular pathways, which makes these enzymes appealing and "hot" drug targets, our findings highlighted the importance of these 2-substituted 1,5-benzothiazepine-based compounds (both in the reduced and oxidized version) for the development of novel epidrugs.

Vaccines in Breast Cancer: Challenges and Breakthroughs

Breast cancer is a problem for women's health globally. Early detection techniques come in a variety of forms ranging from local to systemic and from non-invasive to invasive. The treatment of cancer has always been challenging despite the availability of a wide range of therapeutics. This is either due to the variable behaviour and heterogeneity of the proliferating cells and/or the individual's response towards the treatment applied. However, advancements in cancer biology and scientific technology have changed the course of the cancer treatment approach. This current review briefly encompasses the diagnostics, the latest and most recent breakthrough strategies and challenges, and the limitations in fighting breast cancer, emphasising the development of breast cancer vaccines. It also includes the filed/granted patents referring to the same aspects.

Design, synthesis, and biological evaluation of novel HDAC inhibitors with a 3-(benzazol-2-yl)quinoxaline framework

A series of novel histone deacetylase (HDAC) inhibitors derived from 3-(benzazol-2-yl)quinoxaline derivatives were designed and synthesized by a pharmacophore fusion strategy. In vitro results showed that most of the synthesized compounds exhibited good anti-proliferative activity. Among them, compound 10c showed the most potent cytotoxicity, especially in HCT-116 cells with an IC50 value of 0.91 μM much superior to Vorinostat (5.66 μM). 10c was also found to induce cell apoptosis, arrest the cell cycle at G2/M phase, induce the generation of reactive oxygen species and inhibit cell invasion and migration in HCT-116 cells. Further studies revealed that 10c could up-regulate the acetylation levels of H3 and α-tubulin, exhibit significant Topo I inhibition and induce the release of related apoptotic biomarkers. These results highlight the great potential of 10c to become a promising anti-cancer HDAC inhibitor.

Emerging Intrinsic Therapeutic Targets for Metastatic Breast Cancer

Breast cancer is now the most common cancer worldwide, and it is also the main cause of cancer-related death in women. Survival rates for female breast cancer have significantly improved due to early diagnosis and better treatment. Nevertheless, for patients with advanced or metastatic breast cancer, the survival rate is still low, reflecting a need for the development of new therapies. Mechanistic insights into metastatic breast cancer have provided excellent opportunities for developing novel therapeutic strategies. Although high-throughput approaches have identified several therapeutic targets in metastatic disease, some subtypes such as triple-negative breast cancer do not yet have an apparent tumor-specific receptor or pathway to target. Therefore, exploring new druggable targets in metastatic disease is a high clinical priority. In this review, we summarize the emerging intrinsic therapeutic targets for metastatic breast cancer, including cyclin D-dependent kinases CDK4 and CDK6, the PI3K/AKT/mTOR pathway, the insulin/IGF1R pathway, the EGFR/HER family, the JAK/STAT pathway, poly(ADP-ribose) polymerases (PARP), TROP-2, Src kinases, histone modification enzymes, activated growth factor receptors, androgen receptors, breast cancer stem cells, matrix metalloproteinases, and immune checkpoint proteins. We also review the latest development in breast cancer immunotherapy. Drugs that target these molecules/pathways are either already FDA-approved or currently being tested in clinical trials.

Epigenetic Regulation in Breast Cancer: Insights on Epidrugs

Breast cancer remains a common cause of cancer-related death in women. Therefore, further studies are necessary for the comprehension of breast cancer and the revolution of breast cancer treatment. Cancer is a heterogeneous disease that results from epigenetic alterations in normal cells. Aberrant epigenetic regulation is strongly associated with the development of breast cancer. Current therapeutic approaches target epigenetic alterations rather than genetic mutations due to their reversibility. The formation and maintenance of epigenetic changes depend on specific enzymes, including DNA methyltransferases and histone deacetylases, which are promising targets for epigenetic-based therapy. Epidrugs target different epigenetic alterations, including DNA methylation, histone acetylation, and histone methylation, which can restore normal cellular memory in cancerous diseases. Epigenetic-targeted therapy using epidrugs has anti-tumor effects on malignancies, including breast cancer. This review focuses on the importance of epigenetic regulation and the clinical implications of epidrugs in breast cancer.

Current trends in development of HDAC-based chemotherapeutics

BACKGROUND

Histone deacetylases (HDACs) are one of the essential epigenetic targets in cancer treatment. These enzymes play key roles in post-translation modification (PTM) and gene expression, and consequently, their inhibitors are about to find their place in pharmacotherapy. Most of the currently approved HDAC inhibitors (HDACIs) are wide-spectrum with poor clinical outcomes and numerous side effects. Therefore, new generations of HDAC-based chemotherapeutics with better clinical outcomes are emerging, e.g., isoform-selective inhibitors, multitargeted HDACIs, as well as HDAC degraders.

AIM

The review intended to introduce drug design approaches which were used for designing novel agents which can be beneficial in the process of finding new and more effective HDACI-based therapeutics.

METHODS

PubMed and other databases were searched for literature regarding the structure-function of HDAC isoforms, and strategies used to design HDAC inhibitors. Also, all clinical trials available from the ClinicalTrials site for years 2021-2022 were investigated.

KEY FINDINGS

It is expected that the future of drug discovery projects in HDAC field will concentrate mostly on issues such as isoform-selectivity, multitargeted HDAC inhibitors and HDAC degraders. Deeper knowledge of the 3D structure of HDACs complexed with inhibitors and extensive delineation of biological roles of HDACs are needed for efficient investigations leading to the discovery of novel potent inhibitors.

SIGNIFICANCE

Histone deacetylases (HDACs) are one of the important epigenetic targets in cancer treatment drug discovery. Comprehending the structure of HDAC isoforms along with applied drug design strategies can inspire new ideas.

Histone deacetylase inhibitor givinostat has ameliorative effect in the colitis model

Purpose:

To investigate the effect of givinostat treatment in acetic acid-induced ulcerative colitis model in rats.

Methods:

Thirty male Wistar albino rats were used. Rats were randomly divided into three equal groups, and colitis was induced on 20 rats by rectal administration of %4 solutions of acetic acid. Twenty rats with colitis were randomly divided into two groups. %0.9 NaCl (saline) solution was administered intraperitoneally to the first group of rats (saline group, n=10) at the dose of 1 mL/kg/day. Givinostat was administered intraperitoneally to the second group rats (Givinostat group, n=10) at the dose of 5 mg/kg/day. Samples were collected for biochemical analysis. Colon was removed for histopathological and biochemical examinations.

Results:

Plasma tumor necrosis factor-α (TNF-α), pentraxin-3 (PTX-3), and malondialdehyde levels were significantly decreased in the givinostat group compared to the saline group (p<0.05, p<0.001, and p<0.001 respectively; p<0.001, p<0.001, and p<0.001, respectively). Colon TNF-α and prostaglandin F2 alpha (PGF-2) levels were significantly decreased (p<0.05, and p<0.001, respectively). The givinostat group had a significantly lower histologic score than saline group (p<0.001, and p<0.001, respectively).

Conclusions:

Givinostat, a good protector and regenerator of tissue and an anti-inflammatory agent, may be involved in the treatment of colitis in the future.

Additive pharmacological interaction between sirtuin inhibitor cambinol and paclitaxel in MCF7 luminal and MDA-MB-231 triple-negative breast cancer cells

Background

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related death in women worldwide. Sirtuin inhibitors (SIRTi), belonging to the histone deacetylase inhibitors group (HDIs), are potent epigenetic drugs that have been investigated for therapeutic use in different clinical disorders, including hematological malignancies and solid tumors.

Methods

The influence of cambinol (CAM; SIRTi) used individually or in combination with standard chemotherapeutic paclitaxel (PAX) on viability (MTT assay), proliferation (BrdU assay), induction of apoptosis and cell cycle arrest (FACS analysis) was determined in MCF7 luminal and MDA-MB-231 triple-negative breast cancer (TNBC) cells. The types of pharmacological drug–drug interaction between CAM and PAX were determined by an exact and rigorous pharmacodynamic method—an isobolography, to determine the presence of synergism, addition or antagonism between analyzed drugs using a variety of fixed-dose ratios.

Results

The combination of CAM and PAX at a fixed ratio of 1:1 exerted additive interaction in the viability of MCF7 and MDA-MB-231 BC cells. Both active agents used separately reduced viability and proliferation of BC cells as well as induced apoptosis and cell cycle arrest. These effects were much more evident in MCF7 than in MDA-MB-231 BC cells. Additionally, CAM combined with PAX increased anti-cancer activity compared to PAX used alone.

Conclusion

CAM might be considered a potential therapeutic agent individually or in combined therapy with PAX against luminal or TNBC.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00393-w.

Target-based in-silico screening of basil polysaccharides against different epigenetic targets responsible for breast cancer

PURPOSE

Breast cancer (BC) is one of the leading types of cancer found in women. One of the causes reported for BC is improper regulation of epigenetic modifications. Various epigenetic targets such as histone deacetylases (HDAC) and histone acetyltransferases (HAT) regulate many types of cancer, including BC. Basil is known to possess anti-cancer properties; however, the role of its polysaccharides against different epigenetic targets is still not very clear. Therefore, the molecular docking method is used to find out the binding potential of the BPSs against different epigenetic targets responsible for BC.

METHODS

All the basil polysaccharides (BPSs) were screened against the diverse epigenetic targets reported for BC (HDAC1-2, 4-8, and HAT) using molecular docking studies alongwith swissADME studies to check the drug likeliness of the BPSs.

RESULTS

It was found that glucosamine ring, glucosamine linear, glucuronic acid linear, rhamnose linear, glucuronic acid ring, galactose ring, mannose, glucose, and xylose were exhibited consistent binding potential against the epigenetic targets (HDAC1, HDAC2, HDAC4, HDAC5, HDAC6, HDAC7, HDAC8, and HAT,) responsible for BC.

CONCLUSION

This is the first report where BPSs were reported against these epigenetic targets. These studies can help to understand the underlying mechanism of BPSs used against epigenetic targets for BC. These results can be further validated experimentally to confirm their potential as a promising inhibitor against the epigenetic targets (HDAC1-2, 4-8, and HAT) having a role in BC.

Combining histone deacetylase inhibitors (HDACis) with other therapies for cancer therapy

Histone deacetylases (HDACs) play an important role in regulating the expression of genes involved in tumorigenesis and tumor maintenance, and hence they have been considered as key targets in cancer therapy. As a novel category of antitumor agents, histone deacetylase inhibitors (HDACis) can induce cell cycle arrest, apoptosis, and differentiation in cancer cells, ultimately combating cancer. Although in the United States, the use of HDACis for the treatment of certain cancers has been approved, the therapeutic efficacy of HDACis as a single therapeutic agent in solid tumorshas been unsatisfactory and drug resistance may yet occur. To enhance therapeutic efficacy and limit drug resistance, numerous combination therapies involving HDACis in synergy with other antitumor therapies have been studied. In this review, we describe the classification of HDACs. Moreover, we summarize the antitumor mechanism of the HDACis for targeting key cellular processes of cancers (cell cycle, apoptosis, angiogenesis, DNA repair, and immune response). In addition, we outline the major developments of other antitumor therapies in combination with HDACis, including chemotherapy, radiotherapy, phototherapy, targeted therapy, and immunotherapy. Finally, we discuss the current state and challenges of HDACis-drugs combinations in future clinical studies, with the aim of optimizing the antitumor effect of such combinations.

Anticancer activity of N-heteroaryl acetic acid salts against breast cancer; in silico and in vitro investigation

BACKGROUND

The present research was performed to assess N-heteroaryl acetic acid salts' anticancer activity against the breast cancer cell in order to introduce new inhibitory agents for histone deacetylase.

METHODS AND RESULTS

A molecular docking simulation was performed to design the rational novel compounds. Afterward, the best compounds were selected for synthesis. The cytotoxic effects and mechanism of action have been studied via (Methyl Thiazol-Tetrazolium) MTT assay. Flow cytometry and gene expression analyses were performed to introduce an effective acetic acid derivative as an anticancer agent. Molecular docking simulations demonstrated that all compounds have the best interaction with histone deacetylase. The fold changes of Bcl-2, Bak, Bim, Caspase-3, and Caspase-8 gene expressions were investigated and compared with reference gene using real-time PCR. The cytotoxic studies showed the best anticancer activity of 4-benzyl-1-(carboxymethyl) pyridinium bromide (compound 2) with a low IC₅₀ value (32 µM, p < 0.05). Also, the best anti HDAC activity was obtained for compound 2 with IC50 value of 1.1 µM. Furthermore, this compound showed a high percentage of apoptosis among all tested compounds after 72 h incubation which was associated with the significant increase in mRNA level of Bim, Bax, Bak, Caspase-3, and Caspase-8 and the considerable decrease in Bcl2 gene expression.

CONCLUSION

These results suggest that compound 2 with the benzyl ring could be an effective anticancer compound for further investigation in breast cancer treatment.

Experimental models of endocrine responsive breast cancer: strengths, limitations, and use

Breast cancers characterized by expression of estrogen receptor-alpha (ER; ESR1) represent approximately 70% of all new cases and comprise the largest molecular subtype of this disease. Despite this high prevalence, the number of adequate experimental models of ER+ breast cancer is relatively limited. Nonetheless, these models have proved very useful in advancing understanding of how cells respond to and resist endocrine therapies, and how the ER acts as a transcription factor to regulate cell fate signaling. We discuss the primary experimental models of ER+ breast cancer including 2D and 3D cultures of established cell lines, cell line- and patient-derived xenografts, and chemically induced rodent models, with a consideration of their respective general strengths and limitations. What can and cannot be learned easily from these models is also discussed, and some observations on how these models may be used more effectively are provided. Overall, despite their limitations, the panel of models currently available has enabled major advances in the field, and these models remain central to the ability to study mechanisms of therapy action and resistance and for hypothesis testing that would otherwise be intractable or unethical in human subjects.

Lysosome activable polymeric vorinostat encapsulating PD-L1KD for a combination of HDACi and immunotherapy

PD-1/PD-L1 blocking therapy has become one of the most promising methods in the field of tumor treatment. However, it encounters the challenge of immune escape due to the exhaustion of T cells. Studies have shown that the epigenetic regulation drug histone deacetylase inhibitor (HDACi) may be able to reverse exhausted T cells by changing the epigenetic transcription program. Therefore, the combination of epigenetic therapy and PD-1/PD-L1 blockade therapy is expected to reverse the immune escape, whereas the overriding goal should aim at the spontaneous release and synergy of PD-1/PD-L1 blocking siRNA and HDACi. In this study, we develop PDDS{polyethylene glycol-b-asparaginate(diethylenetriamine-vorinostat), (PEG-b-P[Asp(DET-SAHA)_n] PPDS)}encapsulating siRNA-PD-L1to provide micelles siRNA-PD-L1-loaded micelles (siRNA@PPDS). Transmission electron microscope (TEM) images demonstrate that siRNA@PPDS micelles presented spherical morphology with a size of about 120 nm; hydrodynamic data analysis indicates pH sensitivity of siRNA@PPDS micelles. The experiments reveal that siRNA@PPDS micelles could be well uptaken by the tumor cells to silence the expression of PD-L1 protein in a dose-dependent manner; compared with the free SAHA, the SAHA-loaded micelles PPDS show higher cytotoxicity to induce tumor cell apoptosis and block cell cycle in G1 phase on melanoma-bearing mice, siRNA@PPDS has shown outstanding inhibition of tumor growth and pulmonary metastasis. By comprehensively activating the immune system, lysosome activable polymeric vorinostat encapsulating PD-L1KD for the combination therapy of PD-L1-KD and HDACIs can be an effective strategy to reverse the unresponsiveness of immune checkpoint inhibitors and a promising treatment to inhibit tumor growth, recurrence, and metastasis in clinic.

Epigenetics and therapeutic targets in gastrointestinal malignancies

Gastrointestinal (GI) malignancies account for substantial mortality and morbidity worldwide. They are generally promoted by dysregulated signal transduction and epigenetic pathways, which are controlled by specific enzymes. Recent studies demonstrated that histone deacetylases (HDACs) together with DNA methyltransferases (DNMTs) have crucial roles in the signal transduction/epigenetic pathways in GI regulation. In this review, we discuss various enzyme targets and their functional mechanisms responsible for the regulatory processes of GI malignancies. We also discuss the epigenetic therapeutic targets that are mainly facilitated by DNMT and HDAC inhibitors, which have functional consequences and clinical outcomes for GI malignancies.

CXCL1 Clone Evolution Induced by the HDAC Inhibitor Belinostat Might Be a Favorable Prognostic Indicator in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer due to its lack of treatment options. Patients with TNBC frequently develop resistance to chemotherapy. As epigenetic-based antineoplastic drugs, histone deacetylase inhibitors (HDACis) have achieved particular efficacy in lymphoma but are less efficacious in solid tumors, and the resistance mechanism remains poorly understood. In this study, the GSE129944 microarray dataset from the Gene Expression Omnibus database was downloaded, and fold changes at the transcriptome level of a TNBC line (MDA-MB-231) after treatment with belinostat were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to identify the critical biological processes. Construction and analysis of the protein-protein interaction (PPI) network were performed to screen candidate genes related to cancer prognosis. A total of 465 DEGs were identified, including 240 downregulated and 225 upregulated genes. The cytokine-cytokine receptor pathway was identified as being significantly changed. Furthermore, the expression of CXCL1 was implicated as a favorable factor in the overall survival of breast cancer patients. With in vitro approaches, we also showed that belinostat could induce the expression of CXCL1 in another 2 TNBC cell lines (BT-549 and HCC-1937). We speculate that belinostat-induced CXCL1 expression could be one of the results of the stress clone evolution of cells after HDACi treatment. These findings provide new insights into clone evolution during HDACi treatment, which might guide us to a novel perspective that various mutation-targeted treatments should be implemented during the whole treatment cycle.

Small-molecule inhibitors of breast cancer-related targets: Potential therapeutic agents for breast cancer

Despite dramatic advances in cancer research and therapy, breast cancer remains a tricky health problem and represents a top biomedical research priority. Nowadays, breast cancer is still the leading cause of malignancy-related deaths in women, and incidence and mortality rates of it are expected to increase significantly the next years. Currently more and more researchers are interested in the study of breast cancer by its arising in young women. The common treatment options of breast cancer are chemotherapy, immunotherapy, hormone therapy, surgery, and radiotherapy. Most of them require chemical agents, such as PARP inhibitors, CDK4/6 inhibitors, and HER2 inhibitors. Recent studies suggest that some targets or pathways, including BRD4, PLK1, PD-L1, HDAC, and PI3K/AKT/mTOR, are tightly related to the occurrence and development of breast cancer. This article reviews the interplay between these targets and breast cancer and summarizes the progress of current research on small molecule inhibitors of these anti-breast cancer targets. The review aims to provide structural and theoretical basis for designing novel anti-breast cancer agents.

Senescent thyroid tumor cells promote their migration by inducing the polarization of M2-like macrophages

PURPOSE

An in-depth understanding of the mechanism of thyroid cancer progression will help identify patients with thyroid cancer with a high risk of recurrence and metastasis. Although studies have pointed out that the senescence of thyroid tumor cells may stimulate TAMs and cause a series of changes. However, the role of TAMs in aging thyroid cancer cells is still unknown. The aim of this study was to investigate the function of TAMs in aging thyroid cancer cells.

METHODS

We conducted in vitro model studies based on the K1 cell line to induce tumor cell senescence and study its effect on the differentiation of macrophages, flow cytometry was used to confirm polarization of macrophages, transwell assay was used to confirm changes of invasion and migration of tumor cells.

RESULT

Our data indicate that aging thyroid tumor cell lines trigger the polarization of M2-like macrophages, accompanied by increased expression of CCL17, CCL18, IL-18, and TGFβ1. This event is caused by the activation of the NFκB pathway upregulation of CXCL2 and CXCL3 is related. Further studies have shown that differentiated M2-like macrophages promote tumor cell migration (but have no effect on cell proliferation).

CONCLUSION

Our study indicating that the interaction between tumor and TAMs also occurs in the advanced stages of thyroid tumors and will lead to faster tumors progress.

Histone Deacetylase Inhibitors from Marine Invertebrates

Histone deacetylases (HDACs) are key components of the epigenetic machinery controlling gene expression. They are involved in chromatin remodeling events via post-translational histone modifications but may also act on nonhistone proteins, influencing many fundamental cellular processes. Due to the key involvement of HDACs in serious human pathologies, including cancer, HDAC inhibitors (HDACis) have received increased attention in recent years. It is known that marine invertebrates produce significant amounts of secondary metabolites showing active pharmacological properties and an extensive spectrum of biomedical applications. The aim of this review is to gather selected studies that report the extraction and identification of marine invertebrate-derived compounds that possess HDACi properties, grouping the producing species according to their taxonomic hierarchy. The molecular, biochemical, and/or physiological aspects, where available, and modes of action of these naturally occurring HDACis will be recapitulated, taking into consideration their possible utilization for the future design of analogs with increased bioavailability and efficacy, less toxicity, and, also, higher isoform selectivity.

Perspectives on the Role of Histone Modification in Breast Cancer Progression and the Advanced Technological Tools to Study Epigenetic Determinants of Metastasis

Metastasis is a complex process that involved in various genetic and epigenetic alterations during the progression of breast cancer. Recent evidences have indicated that the mutation in the genome sequence may not be the key factor for increasing metastatic potential. Epigenetic changes were revealed to be important for metastatic phenotypes transition with the development in understanding the epigenetic basis of breast cancer. Herein, we aim to present the potential epigenetic drivers that induce dysregulation of genes related to breast tumor growth and metastasis, with a particular focus on histone modification including histone acetylation and methylation. The pervasive role of major histone modification enzymes in cancer metastasis such as histone acetyltransferases (HAT), histone deacetylases (HDACs), DNA methyltransferases (DNMTs), and so on are demonstrated and further discussed. In addition, we summarize the recent advances of next-generation sequencing technologies and microfluidic-based devices for enhancing the study of epigenomic landscapes of breast cancer. This feature also introduces several important biotechnologists for identifying robust epigenetic biomarkers and enabling the translation of epigenetic analyses to the clinic. In summary, a comprehensive understanding of epigenetic determinants in metastasis will offer new insights of breast cancer progression and can be achieved in the near future with the development of innovative epigenomic mapping tools.

Cannabinoid Receptor Subtype 2 (CB2R) in a Multitarget Approach: Perspective of an Innovative Strategy in Cancer and Neurodegeneration

The cannabinoid receptor subtype 2 (CB2R) represents an interesting and new therapeutic target for its involvement in the first steps of neurodegeneration as well as in cancer onset and progression. Several studies, focused on different types of tumors, report a promising anticancer activity induced by CB2R agonists due to their ability to reduce inflammation and cell proliferation. Moreover, in neuroinflammation, the stimulation of CB2R, overexpressed in microglial cells, exerts beneficial effects in neurodegenerative disorders. With the aim to overcome current treatment limitations, new drugs can be developed by specifically modulating, together with CB2R, other targets involved in such multifactorial disorders. Building on successful case studies of already developed multitarget strategies involving CB2R, in this Perspective we aim at prompting the scientific community to consider new promising target associations involving HDACs (histone deacetylases) and σ receptors by employing modern approaches based on molecular hybridization, computational polypharmacology, and machine learning algorithms.

Reactive Oxygen Species-Mediated Mitochondrial Dysfunction Triggers Sodium Valproate-Induced Cytotoxicity in Human Colorectal Adenocarcinoma Cells

BACKGROUND

Colorectal cancer (CRC) is one of the frequently diagnosed cancers worldwide. Currently used chemotherapeutic drugs have several side effects. Histone deacetylase (HDAC) enzyme inhibitors possess potential anti-cancer effects. Therefore, we investigated the cytotoxic potential of sodium valproate, a HDAC inhibitor in human colorectal adenocarcinoma (HT-29) cells.

METHODS

MTT assay was used to analyze the cytotoxicity of HT-29 cells. Intracellular reactive oxygen species (ROS) induction was evaluated by dichloro-dihydro-fluorescein diacetate staining. Dual staining with acridine orange/ethidium bromide was used to investigate the morphology-related apoptotic cell death. Mitochondrial membrane potential was analyzed by rhodamine 123 staining. E-cadherin protein expression was examined by immunofluorescence staining.

RESULTS

Sodium valproate at 2 and 4 mM/mL treatments significantly induced cytotoxicity. Increased intracellular ROS expression was observed in the cells treated with sodium valproate. This treatment also induced mitochondrial dissipation, apoptosis-related morphological damage, and E-cadherin expression in HT-29 cells.

CONCLUSIONS

Our present results suggest that sodium valproate is cytotoxic to HT-29 cells due to its pro-oxidative and apoptosis inducing potential. Sodium valproate can be used as an adjuvant along with standard chemotherapeutic agents in CRC patients after necessary in vivo and clinical studies.

EpCAM-Targeted 3WJ RNA Nanoparticle Harboring Delta-5-Desaturase siRNA Inhibited Lung Tumor Formation via DGLA Peroxidation

Knocking down delta-5-desaturase (D5D) expression by D5D small interfering RNA (siRNA) has been reported that could redirect the cyclooxygenase-2 (COX-2)-catalyzed dihomo-γ-linolenic acid (DGLA) peroxidation from producing prostaglandin E2 to 8-hydroxyoctanoic acid (8-HOA), resulting in the inhibition of colon and pancreatic cancers. However, the effect of D5D siRNA on lung cancer is still unknown. In this study, by incorporating epithelial cell adhesion molecule (EpCAM) aptamer and validated D5D siRNA into the innovative three-way junction (3WJ) RNA nanoparticle, target-specific accumulation and D5D knockdown were achieved in the lung cancer cell and mouse models. By promoting the 8-HOA formation from the COX-2-catalyzed DGLA peroxidation, the 3WJ-EpCAM-D5D siRNA nanoparticle inhibited lung cancer growth in vivo and in vitro. As a potential histone deacetylases inhibitor, 8-HOA subsequently inhibited cancer proliferation and induced apoptosis via suppressing YAP1/TAZ nuclear translocation and expression. Therefore, this 3WJ-RNA nanoparticle could improve the targeting and effectiveness of D5D siRNA in lung cancer therapy.

Histone modifications in epigenetic regulation of cancer: Perspectives and achieved progress

Epigenetic changes associated with histone modifications play an important role in the emergence and maintenance of the phenotype of various cancer types. In contrast to direct mutations in the main DNA sequence, these changes are reversible, which makes the development of inhibitors of enzymes of post-translational histone modifications one of the most promising strategies for the creation of anticancer drugs. To date, a wide variety of histone modifications have been found that play an important role in the regulation of chromatin state, gene expression, and other nuclear events. This review examines the main features of the most common and studied epigenetic histone modifications with a proven role in the pathogenesis of a wide range of malignant neoplasms: acetylation / deacetylation and methylation / demethylation of histone proteins, as well as the role of enzymes of the HAT / HDAC and HMT / HDMT families in the development of oncological pathologies. The data on the relationship between histone modifications and certain types of cancer are presented and discussed. Special attention is devoted to the consideration of various strategies for the development of epigenetic inhibitors. The main directions of the development of inhibitors of histone modifications are analyzed and effective strategies for their creation are identified and discussed. The most promising strategy is the use of multitarget drugs, which will affect multiple molecular targets of cancer. A critical analysis of the current status of approved epigenetic anticancer drugs has also been performed.

Elucidating the molecular signaling pathways of WAVE3

Cancer metastasis is a complex, multistep process that requires tumor cells to evade from the original site and form new tumors at a distant site or a different organ, often via bloodstream or the lymphatic system. Metastasis is responsible for more than 90% of cancer-related deaths. WAVE3 belongs to the Wiskott-Aldrich syndrome protein (WASP) family, which regulate actin cytoskeleton remodeling as well as several aspects of cell migration, invasion, and metastasis. In fact, WAVE3 has been established as a driver of tumor progression and metastasis in cancers from several origins, including triple negative breast cancers (TNBCs), which are classified as the most lethal subtype of breast cancer, due to their resistance to standard of care therapy and highly metastatic behavior. In this review, we will attempt to summarize the recent advances that have been made to understand how WAVE3 contributes to the molecular mechanisms that control cancer progression and metastasis. We will also review the signaling pathways that are involved in the regulation of WAVE3 expression and function to identify potential therapeutic options targeted against WAVE3 for the treatment of patients with metastatic tumors.

Precision-engineered reporter cell lines reveal ABCG2 regulation in live lung cancer cells

Expression of the ABCG2 multidrug transporter is a marker of cancer stem cells and a predictor of recurrent malignant disease. Understanding how human ABCG2 expression is modulated by pharmacotherapy is crucial in guiding therapeutic recommendations and may aid rational drug development. Genome edited reporter cells are useful in investigating gene regulation and visualizing protein activity in live cells but require precise targeting to preserve native regulatory regions. Here, we describe a fluorescent reporter assay that allows the noninvasive assessment of ABCG2 regulation in human lung adenocarcinoma cells. Using CRISPR-Cas9 gene editing coupled with homology-directed repair, we targeted an EGFP coding sequence to the translational start site of ABCG2, generating ABCG2 knock-out and in situ tagged ABCG2 reporter cells. Using the engineered cell lines, we show that ABCG2 is upregulated by a number of anti-cancer medications, HDAC inhibitors, hypoxia-mimicking agents and glucocorticoids, supporting a model in which ABCG2 is under the control of a general stress response. To our knowledge, this is the first description of a fluorescent reporter assay system designed to follow the endogenous regulation of a human ABC transporter in live cells. The information gained may guide therapy recommendations and aid rational drug design.

Pracinostat (SB939), a histone deacetylase inhibitor, suppresses breast cancer metastasis and growth by inactivating the IL-6/STAT3 signalling pathways

AIMS

Histone deacetylases inhibitors have shown favorable antitumor activity in clinical investigations. In the present study, we assessed the effects of a novel hydroxamic acid-based HDAC inhibitor, SB939, on breast cancer metastasis and tumor growth and characterized the underlying molecular mechanisms.

MAIN METHODS

MTS, Wound-healing, and Transwell chamber invasion assays were used to detect the inhibition effects of SB939 on proliferation, migration, and invasion of breast cancer cells. Western blot, cellular immunofluorescence, and EMSA were used to explore the molecular mechanism of SB939 in suppressing breast cancer metastasis. MDA-MB-231 subcutaneous tumor-bearing model of nude mice and the spontaneous metastasis model of breast cancer were both applied to verify in vivo anti-tumor growth and anti-metastatic effects.

KEY FINDINGS

Our results demonstrated that SB939 at 0.5-1 μmol/L markedly impaired the chemotactic motility of breast cancer cells. SB939 reversed epithelial-mesenchymal transition (EMT) process, as evidenced by upregulation E-cadherin expression and downregulation expressions of N-cadherin and vimentin through increasing the levels of ac-histone H3 and H4 and drecreasing the expressiongs of HDAC 5 and 4. This cascade inhibition mediated by SB939 was well interpreted by inactivating phosphorylation of STAT3, blocking its DNA-binding activity, and decreasing the expressions of STAT3-dependent target genes, including MMP2 and MMP9. Furhtermore, we found that SB939 significantly inhibited breast cancer metastasis and tumor growth in vivo and showed superior anti-tumor properties compared with SAHA in two breast cancer animal models.

SIGNIFICANCE

Our findings indicate that SB939 may be an effective therapeutic option for treating advanced breast cancer.

Development of Coumarin-Based Hydroxamates as Histone Deacetylase Inhibitors with Antitumor Activities

Histone deacetylases (HDACs) have been proved to be promising targets for the treatment of cancer, and five histone deacetylase inhibitors (HDACis) have been approved on the market for the treatment of different lymphomas. In our previous work, we designed a series of novel coumarin-containing hydroxamate HDACis, among which compounds 6 and 7 displayed promising activities against tumor growth. Based on a molecular docking study, we further developed 26 additional analogues with the aim to improve activity of designed compounds. Several of these new derivatives not only showed excellent HDAC1 inhibitory effects, but also displayed significant growth inhibitory activities against four human cancer cell lines. Representative compounds, 13a and 13c, showed potent anti-proliferative activities against solid tumor cell lines with IC50 values of 0.36-2.91 M and low cytotoxicity against Beas-2B and L-02 normal cells. Immunoblot analysis revealed that 13a and 13c dose-dependently increased the acetylation of histone H3 and H4. Importantly, the two compounds displayed much better anti-metastatic effects than SAHA against the MDA-MB-231 cell line. Moreover, 13a and 13c arrested MDA-MB-231 cells at G2/M phase and induced MDA-MB-231 cell apoptosis. Finally, the molecular docking study rationalized the high potency of compound 13c.

Histone Deacetylases and their Inhibitors in Cancer Epigenetics

Histone deacetylases (HDAC) and histone deacetylase inhibitors (HDACi) have greatly impacted the war on cancer. Their role in epigenetics has significantly altered the development of anticancer drugs used to treat the most rare, persistent forms of cancer. During transcription, HDAC and HDACi are used to regulate the genetic mutations found in cancerous cells by removing and/or preventing the removal of the acetyl group on specific histones. This activity determines the relaxed or condensed conformation of the nucleosome, changing the accessibility zones for transcription factors. These modifications lead to other biological processes for the cell, including cell cycle progression, proliferation, and differentiation. Each HDAC and HDACi class or group has a distinctive mechanism of action that can be utilized to halt the progression of cancerous cell growth. While the use of HDAC- and HDACi-derived compounds are relatively new in treatment of cancers, they have a proven efficacy when the appropriately utilized. This following manuscript highlights the mechanisms of action utilized by HDAC and HDACi in various cancer, their role in epigenetics, current drug manufacturers, and the impact predicative modeling systems have on cancer therapeutic drug discovery.