Emerging role of histone deacetylase inhibitors as anti-breast-cancer agents

A prismatic view of the epigenetic-metabolic regulatory axis in breast cancer therapy resistance

Epigenetic regulation established during development to maintain patterns of transcriptional expression and silencing for metabolism and other fundamental cell processes can be reprogrammed in cancer, providing a molecular mechanism for persistent alterations in phenotype. Metabolic deregulation and reprogramming are thus an emerging hallmark of cancer with opportunities for molecular classification as a critical preliminary step for precision therapeutic intervention. Yet, acquisition of therapy resistance against most conventional treatment regimens coupled with tumor relapse, continue to pose unsolved problems for precision healthcare, as exemplified in breast cancer where existing data informs both cancer genotype and phenotype. Furthermore, epigenetic reprograming of the metabolic milieu of cancer cells is among the most crucial determinants of therapeutic resistance and cancer relapse. Importantly, subtype-specific epigenetic-metabolic interplay profoundly affects malignant transformation, resistance to chemotherapy, and response to targeted therapies. In this review, we therefore prismatically dissect interconnected epigenetic and metabolic regulatory pathways and then integrate them into an observable cancer metabolism-therapy-resistance axis that may inform clinical intervention. Optimally coupling genome-wide analysis with an understanding of metabolic elements, epigenetic reprogramming, and their integration by metabolic profiling may decode missing molecular mechanisms at the level of individual tumors. The proposed approach of linking metabolic biochemistry back to genotype, epigenetics, and phenotype for specific tumors and their microenvironment may thus enable successful mechanistic targeting of epigenetic modifiers and oncometabolites despite tumor metabolic heterogeneity.

Mechanistic Sequence of Histone Deacetylase Inhibitors and Radiation Treatment: An Overview

Histone deacetylases inhibitors (HDACis) have shown promising therapeutic outcomes in haematological malignancies such as leukaemia, multiple myeloma, and lymphoma, with disappointing results in solid tumours when used as monotherapy. As a result, combination therapies either with radiation or other deoxyribonucleic acid (DNA) damaging agents have been suggested as ideal strategy to improve their efficacy in solid tumours. Numerous in vitro and in vivo studies have demonstrated that HDACis can sensitise malignant cells to both electromagnetic and particle types of radiation by inhibiting DNA damage repair. Although the radiosensitising ability of HDACis has been reported as early as the 1990s, the mechanisms of radiosensitisation are yet to be fully understood. This review brings forth the various protocols used to sequence the administration of radiation and HDACi treatments in the different studies. The possible contribution of these various protocols to the ambiguity that surrounds the mechanisms of radiosensitisation is also highlighted.

Lectins as a promising therapeutic agent for breast cancer: A review

Efficient treatment of cancer has been a subject of research by scientists for many years. Current treatments for cancer, such as radiotherapy, chemotherapy and surgery have been used in traditional combination therapy, but they have major setbacks like non-specificity, non-responsiveness in certain cancer types towards treatment, tumor recurrence, etc. Epidemiological data has shown that breast cancer accounts for 14% of cancer cases occurring in Indian women. In recent years, scientists have started to focus on the use of natural compounds like lectins obtained from various sources to counter the side effects of traditional therapy. Lectins like Sambucus nigra Agglutinin, Maackia amurensis lectin, Okra lectins, Haliclona caerulea lectin, Sclerotium rolfsii lectin, etc., have been discovered to have both diagnostic and therapeutic potential for breast cancer patients. Lectins have been found to have inhibitory effects on various cancer cell activities such as neo-angiogenesis, causing cell cycle arrest at the G1 phase, and inducing apoptosis. The major idea behind the use of lectins in cancer diagnostics and therapeutics is their capability to bind to glycosylated proteins that are expressed on the cell surface. This review focuses on an exploration of the roles of post-translational modification in cancer cells, especially glycosylation, and the potential of lectins in cancer diagnosis and therapeutics.

Analyzing the fatty acid composition of goat milk and its HDAC inhibitory effects: A rational approach towards understanding the epigenetic impacts of goat milk

Goat milk is a rich source of fatty acids. This study intended to assess the inhibitory potential of goat milk and its extracted fatty acids on histone deacetylases (HDACs). Palmitic acid (C16:0) is the most prevalent saturated fatty acid in goat milk. Goat milk also contains a substantial amount of monounsaturated fatty acids, with oleic acid (C18:1) being the most abundant one. Additionally, the fatty acid profile of goat milk reveals the presence of polyunsaturated fatty acids, including linoleic acid (C18:2) and α-linolenic acid (C18:3n3). Interestingly, the fat extracted from goat milk showed a greater ability to inhibit HDAC enzymes in comparison to the whole milk. These findings, at least to the best of my knowledge, showed the HDAC inhibitory properties of goat milk for the first time, presenting new opportunities for the development of fatty acid-based epigenetic-targeted food products derived from goat milk.

Emerging therapeutic strategy for mitigating cancer progression through inhibition of sirtuin-1 and epithelial-mesenchymal transition

With 8.8 million deaths worldwide, cancer is the major reason for the high rate of fatalities. Malignancy's commencement, progression, development, metastasis, and therapy resistance have all been correlated with the epithelial-to-mesenchymal transition (EMT) pathway. EMT promotes the cancer cells' metastatic spread and starts the development of treatment resistance. Sirtuin-1 (SIRT1) is a histone deacetylase that is important for signaling, cell persistence, and apoptosis. It does this by deacetylating important cell signaling molecules and proteins that are associated with apoptosis. The function of SIRT1 in EMT and cancer progression, as well as the emerging therapeutic strategy of treating cancer through the inhibition of SIRT1 and EMT will be discussed in detail.

The Histone Deacetylase Inhibitory Potential of Chicken Egg Yolk Fat and Their Fatty Acid Composition

Histone deacetylation is a key biochemical event associated with transcriptional regulation. Histone deacetylases (HDACs) mediate the deacetylation of histones. Fatty acids have been reported to function as histone deacetylase inhibitors (HDACi). The present instigation reports the HDAC inhibitory activity of egg yolks and egg yolk-derived fat of country and farm chicken for the first time. Egg yolks and fatty acids derived from both country (CCEF) and farm chicken (FCEF) demonstrated significant HDAC enzyme activity inhibition. Furthermore, egg yolks, CCEF, and FCEF exhibited DPPH free radical scavenging effects. The analysis of fatty acid profiles revealed varying degrees of saturated, mono-, and polyunsaturated fatty acids in the egg yolks. Palmitic acid (C16 : 0) was found to be the most abundant saturated fatty acid in both CCEF and FCEF. Among the monounsaturated fatty acids, oleic acid (C18 : 1) was the most abundant in both CCEF and FCEF. In terms of polyunsaturated fatty acids, a significant difference was observed in the content of linoleic acid (C18 : 2), an omega-6 fatty acid, and docosahexaenoic acid (C22 : 6), an omega-3 fatty acid, between CCEF and FCEF. These findings present exciting prospects for the development of histone deacetylase inhibitors based on egg yolk fat.

Resveratrol exhibits diverse anti-cancer activities through epigenetic regulation of E-cadherin and p21 in triple-negative breast cancer cells

BACKGROUND

Triple-negative breast cancer (TNBC) has an aggressive phenotype and poor outcome, however no specific targeted therapy has been established for TNBC lacking germline BRCA1/2 pathogenic variants. To develop a novel therapeutic strategy, we explored the potential of resveratrol (RSV) for TNBC treatment.

METHODS

We investigated the effects of RSV on malignant phenotypes of TNBC cells as well as on apoptosis induced by ABT263, a specific inhibitor of BCL-2 and BCL-xL, using morphological observation, migration assay, β-galactosidase staining, and Hoechst staining. To elucidate the underlying mechanisms of RSV-mediated effects, expression levels and histone acetylation levels of cadherin 1 (CDH1, E-cadherin) and cyclin dependent kinase inhibitor 1A (CDKN1A, p21) were determined by RT-qPCR, western blotting, and chromatin immunoprecipitation. Furthermore, knockdown analysis was conducted to evaluate the involvement of E-cadherin and/or p21 in RSV potentiation on cytotoxic activity of ABT263.

RESULTS

RSV treatment induced epithelial-like cellular morphology and suppressed the migration capacity in MDA-MB-231 and BT-549-Luc TNBC cells. β-galactosidase-positive cells were increased after RSV treatment, indicating the induction of cellular senescence, in MDA-MB-231 cells but not in BT-549-Luc cells. RSV increased the expression and histone acetylation of CDH1 and CDKN1A in both cells. Interestingly, pre-treatment with RSV enhanced the induction of apoptosis in the ABT263-treated MDA-MB-231 and BT-549-Luc cells, and knockdown of CDKN1A decreased ABT263-induced apoptosis in RSV-treated MDA-MB-231 cells.

CONCLUSIONS

RSV represses the metastatic capacity and enhances the cytotoxic activity of ABT263 in TNBC cells. Our results suggested that RSV can potentially be used as a repressor of metastasis or a sensitizer to ABT263 for TNBC treatment via up-regulation of CDH1 and CDKN1A through epigenetic mechanisms.

Histone 4 lysine 5/12 acetylation enables developmental plasticity of Pristionchus mouth form

Development can be altered to match phenotypes with the environment, and the genetic mechanisms that direct such alternative phenotypes are beginning to be elucidated. Yet, the rules that govern environmental sensitivity vs. invariant development, and potential epigenetic memory, remain unknown. Here, we show that plasticity of nematode mouth forms is determined by histone 4 lysine 5 and 12 acetylation (H4K5/12ac). Acetylation in early larval stages provides a permissive chromatin state, which is susceptible to induction during the critical window of environmental sensitivity. As development proceeds deacetylation shuts off switch gene expression to end the critical period. Inhibiting deacetylase enzymes leads to fixation of prior developmental trajectories, demonstrating that histone modifications in juveniles can carry environmental information to adults. Finally, we provide evidence that this regulation was derived from an ancient mechanism of licensing developmental speed. Altogether, our results show that H4K5/12ac enables epigenetic regulation of developmental plasticity that can be stored and erased by acetylation and deacetylation, respectively.

MIR497HG-Derived miR-195 and miR-497 Mediate Tamoxifen Resistance via PI3K/AKT Signaling in Breast Cancer

Tamoxifen is commonly used for the treatment of patients with estrogen receptor-positive (ER+) breast cancer, but the acquired resistance to tamoxifen presents a critical challenge of breast cancer therapeutics. Recently, long noncoding RNA MIR497HG and its embedded miR-497 and miR-195 are proved to play significant roles in many types of human cancers, but their roles in tamoxifen-resistant breast cancer remain unknown. The results indicate that MIR497HG deficiency induces breast cancer progression and tamoxifen resistance by inducing downregulation of miR-497/195. miR-497/195 coordinately represses five positive PI3K-AKT regulators (MAP2K1, AKT3, BCL2, RAF1, and CCND1), resulting in inhibition of PI3K-AKT signaling, and PI3K-AKT inhibition in tamoxifen-resistant cells restored tamoxifen responsiveness. Furthermore, ER α binds the MIR497HG promoter to activate its transcription in an estrogen-dependent manner. ZEB1 interacts with HDAC1/2 and DNMT3B at the MIR497HG promoter, resulting in promoter hypermethylation and histone deacetylation. The findings reveal that ZEB1-induced MIR497HG depletion contributes to breast cancer progression and tamoxifen resistance through PI3K-AKT signaling. MIR497HG can be used as a biomarker for predicting tamoxifen sensitivity in patients with ER+ breast cancer.

Fatty acids as histone deacetylase inhibitors: old biochemistry tales in a new life sciences town

Histone acetylation is a key epigenetic event. Although the keywords fatty acids, histones, and histone acetylation have a long history in biochemistry, these topics continue to attract much attention among researchers. The acetylation of histones is controlled by the activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). An imbalance in the activities of HATs and HDACs is common in a range of human cancers. Histone deacetylase inhibitors (HDACi) can restore dysregulated histone acetylation profiles in cancer cells and have been identified as promising anti-cancer therapeutics. Short-chain fatty acids mediate anti-cancer effects by inhibiting the activity of HDACs. Recent studies have identified odd-chain fatty acids as novel HDACi. This review summarizes recent findings regarding fatty acids as HDACi in cancer therapy. Teaser: Inhibition of histone deacetylase (HDAC) activity by fatty acids.

Engineered Hybrid Nanosystem for Homologous Targeting of EMT Induced Triple Negative Breast Cancer Cells

The increased mortality rate due to metastatic breast cancer with poor prognosis has raised concern over its effective therapy. Though various therapies and anticancer drugs have been approved, there is still a lack in the targeting of metastatic triple negative breast cancer (TNBC). We have developed a hybrid nanosystem that was synthesized by fusing exosomes from MCF-7 cells and nanovesicles from the MDA MB-231 cells that would be targeted. The developed nanosystem was characterized by various techniques like Western blotting, AFM, FETEM, DLS, CD, and fluorescence spectroscopy. The hybrid system was used for the delivery of an HDAC inhibitor, Trichostatin A (TSA), in combination with lapatinib (a tyrosine kinase inhibitor) for cotherapy of epithelial to mesenchymal transition (EMT) induced TNBC. This targeted cotherapy module had higher efficiency and effectivity in the reduction of metastatic ability and proliferation of EMT induced MDA MB-231 cells as compared to free inhibitor treatment or untargeted cotherapy. Reduction in the expression of the Wnt/β-catenin signaling pathway molecules like β-catenin (by 0.7 fold), Gsk3β (by 0.6 fold), and pGsk-3β (0.3 fold) was observed upon treatment. This subsequently resulted in the suppression of EMT markers, thereby resulting in reversing EMT to MET and suppressing metastatic breast cancer.

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.

Targeting FoxO transcription factors with HDAC inhibitors for the treatment of osteoarthritis

OBJECTIVES

Osteoarthritis (OA) features ageing-related defects in cellular homeostasis mechanisms in articular cartilage. These defects are associated with suppression of forkhead box O (FoxO) transcription factors. FoxO1 or FoxO3 deficient mice show early onset OA while FoxO1 protects against oxidative stress in chondrocytes and promotes expression of autophagy genes and the essential joint lubricant proteoglycan 4 (PRG4). The objective of this study was to identify small molecules that can increase FoxO1 expression.

METHODS

We constructed a reporter cell line with FoxO1 promoter sequences and performed high-throughput screening (HTS) of the Repurposing, Focused Rescue and Accelerated Medchem (ReFRAME) library . Hits from the HTS were validated and function was assessed in human chondrocytes, meniscus cells and synoviocytes and following administration to mice. The most promising hit, the histone deacetylase inhibitor (HDACI) panobinostat was tested in a murine OA model.

RESULTS

Among the top hits were HDACI and testing in human chondrocytes, meniscus cells and synoviocytes showed that panobinostat was the most promising compound as it increased the expression of autophagy genes and PRG4 while suppressing the basal and IL-1β induced expression of inflammatory mediators and extracellular matrix degrading enzymes. Intraperitoneal administration of panobinostat also suppressed the expression of mediators of OA pathogenesis induced by intra-articular injection of IL-1β. In a murine OA model, panobinostat reduced the severity of histological changes in cartilage, synovium and subchondral bone and improved pain behaviours.

CONCLUSION

Panobinostat has a clinically relevant activity profile and is a candidate for OA symptom and structure modification.

Anticancer effects of the HDAC inhibitor, 3β,6β‑dihydroxyurs‑12‑en‑27‑oic acid, in MCF‑7 breast cancer cells via the inhibition of Akt/mTOR pathways

Astilbe chinensis (A. chinensis) is a perennial herb that is used to treat chronic bronchitis and pain. The anticancer activity of 3β,6β‑dihydroxyurs‑12‑en‑27‑oic acid (ACT‑3), a major component isolated from A. chinensis, has not yet been investigated in detail. The purpose of the present study was to investigate the histone deacetylase (HDAC) inhibitory and anticancer activities of ACT‑3 compared with suberoylanilide hydroxamic acid (SAHA) in MCF‑7 human breast cancer cells. The purity of ACT‑3 was determined using high‑performance liquid chromatography. In the present study, the effects of ACT‑3 on anticancer effects of MCF‑7 cells were determined by measuring the level of apoptotic cell death and cell cycle regulator using flow cytometry analysis and western blot analysis, respectively. The effects of ACT‑3 on HDAC enzyme activity were measured using assay kits. ACT‑3 and SAHA increased the levels of acetylated histone H3 and reduced the levels of HDAC1 and HDAC3 in MCF‑7 cells. ACT‑3 significantly decreased the cell viability in a concentration‑dependent manner and induced different morphological changes at high concentrations. ACT‑3 and SAHA significantly inhibited the colony formation in MCF‑7 cells. ACT‑3 inhibited total HDAC activity in a dose‑dependent manner. ACT‑3 significantly reduced the expression levels of cyclin D1 and cyclin‑dependent kinase 4, and upregulated the expression levels of p21^WAF1 and p53. A significant increase in the G1 phase cell population was observed in MCF‑7 cells and ACT‑3 induced apoptosis by reducing the ratio of B‑cell lymphoma‑2 (Bcl‑2)/Bcl‑2‑associated X (Bax) and releasing cleaved caspase 9. Additionally, ACT‑3 significantly increased autophagic cell death by inhibiting the serine‑threonine kinase/mammalian target of the rapamycin pathway. Autophagy induction was confirmed via acridine orange staining. ACT‑3 significantly increased the pERK1/2 and p21 in MCF‑7 cells. Thus, the activated ERK pathway played an important role in cell cycle arrest and apoptosis via ERK‑dependent induction of p21 in MCF‑7 cells. These data indicated that ACT‑3 can be used as a promising anticancer agent to overcome the limitations and reduce the side effects of conventional anticancer drugs.

HDAC7 inhibits cell proliferation via NudCD1/GGH axis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. In the absence of effective molecular markers for TNBC, there is an urgent clinical need for promising therapeutic target for TNBC. Histone deacetylases (HDACs), key regulators for chromatin remodeling and gene expression, have been suggested to play critical roles in cancer development. However, little is known ~the functions and implications of HDACs in TNBC treatment in the future. By analyzing the expression and prognostic significance of HDAC family members in TNBC through TCGA and METABRIC databases, HDAC7 was found to be downregulated in TNBC samples and the survival of patients with lower expression of HDAC7 was shorter. Furthermore, HDAC7 was negatively associated with NudC domain containing 1 (NudCD1) and γ-glutamyl hydrolase (GGH). Loss of NudCD1 or GGH predicted improved overall survival time (OS) of patients with TNBC. In vitro experiments showed that silencing of HDAC7 enhanced TNBC cell proliferation, while overexpression HDAC7 inhibited TNBC cell proliferation. The results of functional experiments confirmed that HDAC7 negatively modulated GGH and NudCD1 expression. Furthermore, decrease of NudCD1 or GGH inhibited cell proliferation. Notably, the HDAC7-NudCD1/GGH axis was found to be associated with NK cell infiltration. Overall, the present study revealed a novel role of HDAC7-NudCD1/GGH axis in TNBC, which might provide a promising treatment strategy for patients with TNBC.

Unconventional protein post-translational modifications: the helmsmen in breast cancer

Breast cancer is the most prevalent malignant tumor and a leading cause of mortality among females worldwide. The tumorigenesis and progression of breast cancer involve complex pathophysiological processes, which may be mediated by post-translational modifications (PTMs) of proteins, stimulated by various genes and signaling pathways. Studies into PTMs have long been dominated by the investigation of protein phosphorylation and histone epigenetic modifications. However, with great advances in proteomic techniques, several other PTMs, such as acetylation, glycosylation, sumoylation, methylation, ubiquitination, citrullination, and palmitoylation have been confirmed in breast cancer. Nevertheless, the mechanisms, effects, and inhibitors of these unconventional PTMs (particularly, the non-histone modifications other than phosphorylation) received comparatively little attention. Therefore, in this review, we illustrate the functions of these PTMs and highlight their impact on the oncogenesis and progression of breast cancer. Identification of novel potential therapeutic drugs targeting PTMs and development of biological markers for the detection of breast cancer would be significantly valuable for the efficient selection of therapeutic regimens and prediction of disease prognosis in patients with breast cancer.

Discovery of 1-Benzhydryl-Piperazine-Based HDAC Inhibitors with Anti-Breast Cancer Activity: Synthesis, Molecular Modeling, In Vitro and In Vivo Biological Evaluation

Isoform-selective histone deacetylase (HDAC) inhibition is promoted as a rational strategy to develop safer anti-cancer drugs compared to non-selective HDAC inhibitors. Despite this presumed benefit, considerably more non-selective HDAC inhibitors have undergone clinical trials. In this report, we detail the design and discovery of potent HDAC inhibitors, with 1-benzhydryl piperazine as a surface recognition group, that differ in hydrocarbon linker. In vitro HDAC screening identified two selective HDAC6 inhibitors with nanomolar IC₅₀ values, as well as two non-selective nanomolar HDAC inhibitors. Structure-based molecular modeling was employed to study the influence of linker chemistry of synthesized inhibitors on HDAC6 potency. The breast cancer cell lines (MDA-MB-231 and MCF-7) were used to evaluate compound-mediated in vitro anti-cancer, anti-migratory, and anti-invasive activities. Experiments on the zebrafish MDA-MB-231 xenograft model revealed that a novel non-selective HDAC inhibitor with a seven-carbon-atom linker exhibits potent anti-tumor, anti-metastatic, and anti-angiogenic effects when tested at low micromolar concentrations.

An Activity-Based Photosensitizer to Reverse Hypoxia and Oxidative Resistance for Tumor Photodynamic Eradication

Photodynamic therapy (PDT) has been a well-accepted clinical treatment for malignant tumors owing to its noninvasiveness and high spatiotemporal selectivity. However, the treatment outcome of current PDT applications is hindered by hypoxia and intracellular oxidative resistance of solid tumors. Recent studies have shown that inhibiting histone deacetylases (HDACs) can induce cell ferroptosis, reverse hypoxia, and elevate oxidative status. Theoretically, the design and synthesis of activity-based photosensitizers that target HDACs can address the bottlenecks of PDT. Herein, the concept of an activity-based photosensitizer is presented for targeting HDACs, which is designed based on a quinoxalinone scaffold through a pharmacophore migration strategy. The developed activity-based photosensitizer can inhibit HDACs, and overcome hypoxia and intracellular oxidative resistance, realizing the full potential of photosensitizers for malignant tumor treatment. The molecular design strategy proposed in this project should provide theoretical guidance for the development of ideal photosensitizers for practical applications.

An assembly-inducing PDC enabling the efficient nuclear delivery of nucleic acid for cancer stem-like cell suppression

Nucleic acid therapy is attracting great attention in diverse clinical translations because of its therapeutic advantages. As a renowned oligonucleotide therapeutical candidate in the clinical stage, AS1411 has shown outstanding tumor suppressing effects; however, its efficient delivery to the cell nucleus is critical for its anticancer effect. Herein, we identified a multifunctional peptide drug conjugate (PDC) as a safe and efficient carrier to achieve the nuclear delivery of AS1411. This PDC consists of the cell penetration peptide RW9, an HDAC inhibitor warhead (peptide C-terminus), and 5-FU (peptide N-terminus), which can coassemble with AS1411 to form nanospheres. The PDC efficiently delivered AS1411 to the nucleus of several types of cancer cells. Moreover, it reversed the stemness of a cancer stem-like cell line. Significantly, due to the assembly-induced accumulation enhancement and retention, a safe single agent concentration of PDC showed unexpected synergy with AS1411 to augment the cancer cell suppression efficiency, exemplified by the downregulation of the stemness-related proteins and the upregulation of apoptosis-related proteins. Therefore, our work presents a powerful strategy for the nuclear delivery of nucleic acid drugs by leveraging cancer-suppressing PDC as assembly inducers, which provides a powerful combination regimen in treating cancer stem-like cells.

A Distinct Chromatin State Drives Therapeutic Resistance in Invasive Lobular Breast Cancer

Most invasive lobular breast cancers (ILC) are of the luminal A subtype and are strongly hormone receptor-positive. Yet, ILC is relatively resistant to tamoxifen and associated with inferior long-term outcomes compared with invasive ductal cancers (IDC). In this study, we sought to gain mechanistic insights into these clinical findings that are not explained by the genetic landscape of ILC and to identify strategies to improve patient outcomes. A comprehensive analysis of the epigenome of ILC in preclinical models and clinical samples showed that, compared with IDC, ILC harbored a distinct chromatin state linked to gained recruitment of FOXA1, a lineage-defining pioneer transcription factor. This resulted in an ILC-unique FOXA1-estrogen receptor (ER) axis that promoted the transcription of genes associated with tumor progression and poor outcomes. The ILC-unique FOXA1-ER axis led to retained ER chromatin binding after tamoxifen treatment, which facilitated tamoxifen resistance while remaining strongly dependent on ER signaling. Mechanistically, gained FOXA1 binding was associated with the autoinduction of FOXA1 in ILC through an ILC-unique FOXA1 binding site. Targeted silencing of this regulatory site resulted in the disruption of the feed-forward loop and growth inhibition in ILC. In summary, ILC is characterized by a unique chromatin state and FOXA1-ER axis that is associated with tumor progression, offering a novel mechanism of tamoxifen resistance. These results underscore the importance of conducting clinical trials dedicated to patients with ILC in order to optimize treatments in this breast cancer subtype.

SIGNIFICANCE

A unique FOXA1-ER axis in invasive lobular breast cancer promotes disease progression and tamoxifen resistance, highlighting a potential therapeutic avenue for clinical investigations dedicated to this disease. See related commentary by Blawski and Toska, p. 3668.

Epigenetic oncogenesis, biomarkers and emerging chemotherapeutics for breast cancer

Breast cancer remains one of the leading causes of cancer-related deaths globally and the most prominent among females, yet with limited effective therapeutic options. Most of the current medications are challenged by various factors including low efficacy, incessant resistance, immune evasion and frequent recurrence of the disease. Further understanding of the prognosis and identification of plausible therapeutic channels thus requires multimodal approaches. In this review, epigenetics studies of several pathways to BC oncogenesis via the inducement of oncogenic changes on relevant markers have been overviewed. Similarly, the counter-epigenetic mechanisms to reverse such changes as effective therapeutic strategies were surveyed. The epigenetic oncogenesis occurs through several pathways, notably, DNMT-mediated hypermethylation of DNA, dysregulated expression for ERα, HER2/ERBB and PR, histone modification, overexpression of transcription factors including the CDK9-cyclin T1 complex and suppression of tumour suppressor genes. Scientifically, the regulatory reversal of the mechanisms constitutes effective epigenetic approaches for mitigating BC initiation, progression and metastasis. These were exhibited at various experimental levels by classical chemotherapeutic agents including some repurposable drugs, endocrine inhibitors, monoclonal antibodies and miRNAs, natural products, metal complexes and nanoparticles. Dozens of the potential candidates are currently in clinical trials while others are still at preclinical experimental stages showing promising anti-BC efficacy. The review presents a model for a wider understanding of epigenetic oncogenic pathways to BC and reveals plausible channels for reversing the unpleasant changes through epigenetic modifications. It advances the science of therapeutic designs for ameliorating the global burden of BC upon further translational studies.

Advances of Epigenetic Biomarkers and Epigenome Editing for Early Diagnosis in Breast Cancer

Epigenetic modifications are known to regulate cell phenotype during cancer progression, including breast cancer. Unlike genetic alterations, changes in the epigenome are reversible, thus potentially reversed by epi-drugs. Breast cancer, the most common cause of cancer death worldwide in women, encompasses multiple histopathological and molecular subtypes. Several lines of evidence demonstrated distortion of the epigenetic landscape in breast cancer. Interestingly, mammary cells isolated from breast cancer patients and cultured ex vivo maintained the tumorigenic phenotype and exhibited aberrant epigenetic modifications. Recent studies indicated that the therapeutic efficiency for breast cancer regimens has increased over time, resulting in reduced mortality. Future medical treatment for breast cancer patients, however, will likely depend upon a better understanding of epigenetic modifications. The present review aims to outline different epigenetic mechanisms including DNA methylation, histone modifications, and ncRNAs with their impact on breast cancer, as well as to discuss studies highlighting the central role of epigenetic mechanisms in breast cancer pathogenesis. We propose new research areas that may facilitate locus-specific epigenome editing as breast cancer therapeutics.

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.

LncRNA ENST869 Targeting Nestin Transcriptional Region to Affect the Pharmacological Effects of Chidamide in Breast Cancer Cells

Breast cancer is one of the leading threats to the health of women. It has the highest incidence and mortality in women worldwide. Although progress has been made in the development and application of anti-breast cancer drugs such as Chidamide and others, the occurrence of drug resistance limits the effective application of chemotherapies. The purpose of this study is to explore the role of LncRNA in the pharmacological effect of Chidamide in breast cancer therapy. The human breast cancer MCF-7 or MDA-MB-231 cells were used as the research cell models. The RNA library screening and high-throughput sequencing comparative analysis was conducted. The binding of LncRNA and its downstream target genes in RNA and protein levels was tested. The results showed that the expression of LncRNA ENST869 in cells treated with Chidamide increased significantly, as demonstrated by real-time PCR and cell viability assay. RNAplex analysis showed that LncRNA ENST869 and Nestin mRNA may interact. RNA interference and Western blot analysis indicated that LncRNA ENST869 could target and regulate the expression of Nestin. Luciferase assay and RNA-protein pulldown showed that LncRNA ENST869 affected Nestin transcription. There might be a highly active binding region of LncRNA ENST869 in regulating Nestin transcriptional activity within the site of 250 bp upstream of the transcription starting point of Nestin. In addition, LncRNA ENST869 did not directly interact with Nestin protein to affect its activity. In conclusion, our results demonstrated that LncRNA ENST869 could affect the function of Nestin in breast cancer cells treated with Chidamide. Nestin is a key player in influencing the pharmacological activity of Chidamide and an essential factor in drug resistance of breast cancer cells.

Assessment of Pharmacological Interactions between SIRT2 Inhibitor AGK2 and Paclitaxel in Different Molecular Subtypes of Breast Cancer Cells

Breast carcinoma (BC) is the most commonly diagnosed type of cancer in women in the world. Although the advances in the treatment of BC patients are significant, numerous side effects, severe toxicity towards normal cells as well as the multidrug resistance (MDR) phenomenon restrict the effectiveness of the therapies used. Therefore, new active compounds which decrease the MDR, extend disease-free survival, thereby ameliorating the effectiveness of the current treatment regimens, are greatly needed. Histone deacetylase inhibitors (HDIs), including sirtuin inhibitors (SIRTi), are the epigenetic antitumor agents which induce a cytotoxic effect in different types of cancer cells, including BC cells. Currently, combined forms of therapy with two or even more chemotherapeutics are promising antineoplastic tools to obtain a better response to therapy and limit adverse effects. Thus, on the one hand, much more effective chemotherapeutics, e.g., sirtuin inhibitors (SIRTi), are in demand; on the other hand, combinations of accepted cytostatics are trialed. Thus, the aim of our research was to examine the combination effects of a renowned cytotoxic drug paclitaxel (PAX) and SIRT2 inhibitor AGK2 on the proliferation and viability of the T47D, MCF7, MDA-MB-231, MDA-MB-468, BT-549 and HCC1937 BC cells. Moreover, cell cycle arrest and apoptosis induction were explored. The type of pharmacological interactions between AGK2 and PAX in different molecular subtypes of BC cells was assessed using the advanced isobolographic method. Our findings demonstrated that the tested active agents singly inhibited viability and proliferation of BC cells as well as induced cell cycle arrest and apoptosis in the cell-dependent context. Additionally, AGK2 increased the antitumor effect of PAX in most BC cell lines. We observed that, depending on the BC cell lines, the combinations of tested drugs showed synergistic, additive or antagonistic pharmacological interaction. In conclusion, our studies demonstrated that the consolidated therapy with the use of AGK2 and PAX can be considered as a potential therapeutic regimen in the personalized cure of BC patients in the future.

Inhibitory activities of grape bioactive compounds against enzymes linked with human diseases

A quest for identification of novel, safe and efficient natural compounds, as additives in the modern food and cosmetic industries, has been prompted by concerns about toxicity and side effects of synthetic products. Plant phenolic compounds are one of the most documented natural products due to their multifarious biological applications. Grape (Vitis vinifera) is an important source of phenolic compounds such as phenolic acids, tannins, quinones, coumarins and, most importantly, flavonoids/flavones. This review crisply encapsulates enzyme inhibitory activities of various grape polyphenols towards different key human-ailment-associated enzymes: xanthine oxidase (gout), tyrosinase (hyperpigmentation), α-amylase and α-glucosidase (diabetes mellitus), pancreatic lipase (obesity), cholinesterase (Alzheimer's disease), angiotensin i-converting enzymes (hypertension), α-synuclein (Parkinson's disease) and histone deacetylase (various diseases). The review also depicts the enzyme inhibitory mechanism of various grape polyphenols and briefly discusses their stature as potential therapeutic and drug development candidates. KEY POINTS: • Nineteen major bioactive polyphenols from the grape/grape products and their disease targets are presented • Sixty-two important polyphenols as enzyme inhibitors from grape/grape products are presented • A thorough description and graphical presentation of biological significance of polyphenols against various diseases.

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.

Epigenetic Reprogramming and Landscape of Transcriptomic Interactions: Impending Therapeutic Interference of Triple-Negative Breast Cancer in Molecular Medicine

The mechanisms governing the development and progression of cancers are believed to be the consequence of hereditary deformities and epigenetic modifications. Accordingly, epigenetics has become an incredible and progressively explored field of research to discover better prevention and therapy for neoplasia, especially triple-negative breast cancer (TNBC). It represents 15-20% of all invasive breast cancers and will, in general, have bellicose histological highlights and poor clinical outcomes. In the early phases of triple-negative breast carcinogenesis, epigenetic deregulation modifies chromatin structure and influences the plasticity of cells. It up-keeps the oncogenic reprogramming of malignant progenitor cells with the acquisition of unrestrained selfrenewal capacities. Genomic impulsiveness in TNBC prompts mutations, copy number variations, as well as genetic rearrangements, while epigenetic remodeling includes an amendment by DNA methylation, histone modification, and noncoding RNAs of gene expression profiles. It is currently evident that epigenetic mechanisms assume a significant part in the pathogenesis, maintenance, and therapeutic resistance of TNBC. Although TNBC is a heterogeneous malaise that is perplexing to describe and treat, the ongoing explosion of genetic and epigenetic research will help to expand these endeavors. Latest developments in transcriptome analysis have reformed our understanding of human diseases, including TNBC at the molecular medicine level. It is appealing to envision transcriptomic biomarkers to comprehend tumor behavior more readily regarding its cellular microenvironment. Understanding these essential biomarkers and molecular changes will propel our capability to treat TNBC adequately. This review will depict the different aspects of epigenetics and the landscape of transcriptomics in triple-negative breast carcinogenesis and their impending application for diagnosis, prognosis, and treatment decision with the view of molecular medicine.

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.

Small-Molecule Inhibitors Overcome Epigenetic Reprogramming for Cancer Therapy

Cancer treatment is a significant challenge for the global health system, although various pharmacological and therapeutic discoveries have been made. It has been widely established that cancer is associated with epigenetic modification, which is reversible and becomes an attractive target for drug development. Adding chemical groups to the DNA backbone and modifying histone proteins impart distinct characteristics on chromatin architecture. This process is mediated by various enzymes modifying chromatin structures to achieve the diversity of epigenetic space and the intricacy in gene expression files. After decades of effort, epigenetic modification has represented the hallmarks of different cancer types, and the enzymes involved in this process have provided novel targets for antitumor therapy development. Epigenetic drugs show significant effects on both preclinical and clinical studies in which the target development and research offer a promising direction for cancer therapy. Here, we summarize the different types of epigenetic enzymes which target corresponding protein domains, emphasize DNA methylation, histone modifications, and microRNA-mediated cooperation with epigenetic modification, and highlight recent achievements in developing targets for epigenetic inhibitor therapy. This article reviews current anticancer small-molecule inhibitors targeting epigenetic modified enzymes and displays their performances in different stages of clinical trials. Future studies are further needed to address their off-target effects and cytotoxicity to improve their clinical translation.

Histone Deacetylase 7 Gene Overexpression Is Associated with Poor Prognosis of Triple-Negative Breast Cancer Patients

Background: Differential expressions of cancer-associated genes, including histone deacetylases (HDACs), were identified in distinctive molecular subtypes of breast cancer. Compared with hormone receptor-positive breast cancer, triple-negative (TNBC, ER-PR-HER2-) is the most aggressive form of breast cancer. Aims: To determine the association of HDAC7 mRNA expression levels with clinicopathological features and patients' survival with TNBC or ER+PR+HER2- breast cancers. Methods: Total RNA was extracted from 61 TNBC and 74 ER+PR+Her2- tumors. Relative gene expression was evaluated by SYBR Green RT-PCR, normalized to glyceraldehyde-3-phosphate dehydrogenase. The HDAC7 mRNA expression was defined as high or low, according to receiver operating characteristic analysis. Kaplan-Meier and Cox regression analyses for overall survival were assessed to evaluate the prognostic relevance of HDAC7 overexpression. Results: The HDAC7 overexpression was predominantly found in invasive ductal carcinomas (p = 0.023), high histologic grade (p = 0.007), and high nuclear grade tumors (p = 0.030). TNBC subtypes had a significantly lower mean HDAC7 gene expression compared with ER+PR+HER2- tumors (p = 0.005). However, HDAC7 overexpression predicted unfavorable survival of TNBC patients (p = 0.003). Multivariate Cox regression analysis indicated that recurrences (hazard ratio [HR] = 5.432, p = 0.003), and HDAC7 overexpression (HR = 9.287, p = 0.033) persisted as independent prognostic factors for poor survival of TNBC patients. Conclusions: HDAC7 mRNA overexpression is associated with poor survival in patients with TNBC tumors.

Emerging Biomarkers and Targeted Therapies in Feline Mammary Carcinoma

Feline mammary carcinoma (FMC) is a common aggressive malignancy with a low survival rate that lacks viable therapeutic options beyond mastectomy. Recently, increasing efforts have been made to understand the molecular mechanisms underlying FMC development, using the knowledge gained from studies on human breast cancer to discover new diagnostic and prognostic biomarkers, thus reinforcing the utility of the cat as a cancer model. In this article, we review the current knowledge on FMC pathogenesis, biomarkers, and prognosis factors and offer new insights into novel therapeutic options for HER2-positive and triple-negative FMC subtypes.

Exploring novel capping framework: high substituent pyridine-hydroxamic acid derivatives as potential antiproliferative agents

PURPOSE

Histone deacetylases (HDACs) play a vital role in the epigenetic regulation of gene expression due to their overexpression in several cancer forms. Therefore, these enzymes are considered as a potential anticancer drug target. Different synthetic and natural structures have been studied as HDACs inhibitors; based on available structural design information, the capping group is important for the biological activity due to the different interactions in the active site entrance. The present study aimed to analyze high substituted pyridine as a capping group, which included carrying out the synthesis, antiproliferative activity analysis, and docking studies of these novel compounds.

METHODS

To achieve the synthesis of these derivatives, four reaction steps were performed, generating desired products 15a-k. Their effects on cell proliferation and gene expression of p21, cyclin D1, and p53 were determined using the sulphorhodamine B (SRB) method and quantitative real-time polymerase chain reaction. The HDAC1, HDAC6, and HDAC8 isoforms were used for performing docking experiments with our 15a-k products.

RESULT

The products 15a-k were obtained in overall yields of 40-71%. Compounds 15j and 15k showed the highest antiproliferative activity in the breast (BT-474 and MDA-MB-231) and prostate (PC3) cancer cell lines at a concentration of 10 µM. These compounds increased p21 mRNA levels and decreased cyclin D1 and p53 gene expression. The docking study showed an increment in the strength, and in the number of interactions performed by the capping moiety of the tested molecules compared with SAHA; interactions displayed are mainly van der Waals, π-stacking, and hydrogen bond.

CONCLUSION

The synthesized compounds 2-thiophene (15j) and 2-furan (15k) pyridine displayed cell growth inhibition, regulation of genes related to cell cycle progression in highly metastatic cancer cell lines. The molecular coupling analysis performed with HDAC1, HDAC6 and HDAC8 showed an increment in the number of interactions performed by the capping moiety and consequently in the strength of the capping group interaction.

Valproic Acid and Breast Cancer: State of the Art in 2021

Valproic acid (2-propylpentanoic acid, VPA) is a short-chain fatty acid, a member of the group of histone deacetylase inhibitors (HDIs). VPA has been successfully used in the treatment of epilepsy, bipolar disorders, and schizophrenia for over 50 years. Numerous in vitro and in vivo pre-clinical studies suggest that this well-known anticonvulsant drug significantly inhibits cancer cell proliferation by modulating multiple signaling pathways. Breast cancer (BC) is the most common malignancy affecting women worldwide. Despite significant progress in the treatment of BC, serious adverse effects, high toxicity to normal cells, and the occurrence of multi-drug resistance (MDR) still limit the effective therapy of BC patients. Thus, new agents which improve the effectiveness of currently used methods, decrease the emergence of MDR, and increase disease-free survival are highly needed. This review focuses on in vitro and in vivo experimental data on VPA, applied individually or in combination with other anti-cancer agents, in the treatment of different histological subtypes of BC.

Identification of epigenetic regulators in the estrogen signaling pathway via siRNA screening

Breast cancer is the most prevalent malignant disease among women across the globe. Notably, estrogen signaling plays a vital role in the progression of estrogen receptor-positive breast cancer. Therefore, targeting epigenetic regulators is a promising therapy for cancer. To identify epigenetic regulators, we conducted a siRNA screening targeting 140 epigenetic genes by which 32 positive and 15 negative regulators of estrogen signaling were obtained. The protein-protein interaction network of the candidate genes was constructed and the topological parameters of the network were calculated. As a result, the top 10 genes with higher MCC (Maximal Clique Centrality) scores were considered as hub genes. Notably, the hub genes all belong to polycomb group genes. The transcription levels of the above genes were compared between breast cancer and normal tissues using the UALCAN database. Then, the survival analysis of the hub genes was conducted using the Kaplan-Meier Plotter online database. Lastly, the effect of hub genes on MCF-7 cell proliferation and ER target gene expression were investigated. These results indicate that PcG genes regulate estrogen signaling and breast cancer development.

Odd-chain fatty acids as novel histone deacetylase 6 (HDAC6) inhibitors

The dysregulation of histone deacetylases (HDACs) is closely associated with tumorigenesis and has emerged as a promising target for anti-cancer drugs. Some odd-chain fatty acids are present in trace levels in human tissue. Despite limited health benefits, there is increasing experimental evidence of nutritional benefits of odd-chain fatty acids. This study examines the effects of five odd-chain fatty acids (valeric, heptanoic, nonanoic, undecanoic, and pentadecanoic acid) as novel HDAC6 inhibitors. Examination of these fatty acids on the proliferation and clonogenic ability in various cancer cell lines revealed that pentadecanoic and undecanoic acid can strongly inhibit cancer cell proliferation. Heptanoic and nonanoic acid showed moderate anti-proliferative effects, while valeric acid demonstrated weak anti-proliferative effects. HDAC6 inhibitory activities were in the order of pentadecanoic acid (C15:0) > undecanoic acid (C11:0) > nonanoic acid (C9:0) > heptanoic acid (C7:0) > valeric acid (C5:0), consistent with the anti-proliferative assay results. All of these fatty acids promoted the acetylation of α-tubulin in MCF-7 breast and A549 lung cancer cells dose-dependently. In-silico molecular docking analysis showed that increasing the aliphatic carbon chain length facilitates binding to HDAC6 residues, which might be important for the inhibitory potential of HDAC6. This study shows the potential utility of odd-chain fatty acids for epigenetic-based cancer therapy.

In silico predictions on the possible mechanism of action of selected bioactive compounds against breast cancer

ABSTRACT

Breast cancer is one of the leading causes of death among women. We employed in silico model to predict the mechanism of actions of selected novel compounds reported against breast cancer using ADMET profiling, drug likeness and molecular docking analyses. The selected compounds were andrographolide (AGP), dipalmitoylphosphatidic acid (DPA), 3-(4-Bromo phenylazo)-2,4-pentanedione (BPP), atorvastatin (ATS), benzylserine (BZS) and 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al (TCD). These compounds largely conform to ADMETlab and Lipinki's rule of drug likeness criteria in addition to their lesser hepatotoxic and mutagenic effects. Docking studies revealed a strong affinity of AGP versus NF-kB (- 6.8 kcal/mol), DPA versus Cutlike-homeobox (- 5.1 kcal/mol), BPP versus Hypoxia inducing factor 1 (- 7.7 kcal/mol), ATS versus Sterol Regulatory Element Binding Protein 2 (- 7.2 kcal/mol), BZS versus Ephrin type-A receptor 2 (- 4.4 kcal/mol) and TCD versus Ying Yang 1 (- 9.4 kcal/mol). Likewise, interaction between the said compounds and respective gene products were evidently observed with strong affinities; AGP versus COX-2 (- 9.6 kcal/mol), DPA versus Fibroblast growth factor receptor (- 5.9 kcal/mol), BPP versus Vascular endothelial growth factor (- 5.8 kcal/mol), ATS versus HMG-COA reductase (- 9.1 kcal/mol), BZS versus L-type amino acid transporter 1 (- 5.3 kcal/mol) and TCD versus Histone deacytylase (- 7.7 kcal/mol), respectively. The compounds might potentially target transcription through inhibition of promoter-transcription factor binding and/or inactivation of final gene product. Thus, findings from this study provide a possible mechanism of action of these xenobiotics to guide in vitro and in vivo studies in breast cancer.

GRAPHIC ABSTRACT

Aberrant HDAC3 expression correlates with brain metastasis in breast cancer patients

BACKGROUND

Brain metastasis is an unsolved clinical problem in breast cancer patients due to its poor prognosis and high fatality rate. Although accumulating evidence has shown that some pan-histone deacetylase (HDAC) inhibitors can relieve breast cancer brain metastasis, the specific HDAC protein involved in this process is unclear. Thus, identifying a specific HDAC protein closely correlated with breast cancer brain metastasis will not only improve our understanding of the functions of the HDAC family but will also help develop a novel target for precision cancer therapy.

METHODS

Immunohistochemical staining of HDAC1, HDAC2, and HDAC3 in 161 samples from breast invasive ductal carcinoma patients, including 63 patients with brain metastasis, was performed using the standard streptavidin-peroxidase method. The relationships between HDAC1, HDAC2, and HDAC3 and overall survival/brain metastasis-free survival/post-brain metastatic survival were evaluated using Kaplan-Meier curves and Cox regression analyses.

RESULTS

HDAC1, HDAC2, and cytoplasmic HDAC3 all displayed typical oncogenic characteristics and were independent prognostic factors for the overall survival of breast cancer patients. Only cytoplasmic HDAC3 was an independent prognostic factor for brain metastasis-free survival. Cytoplasmic expression of HDAC3 was further upregulated in the brain metastases compared with the matched primary tumors, while nuclear expression was downregulated. The HDAC1, HDAC2, and HDAC3 expression levels in the brain metastases were not correlated with survival post-brain metastasis.

CONCLUSIONS

Our studies first demonstrate a critical role for HDAC3 in the brain metastasis of breast cancer patients and it may serve as a promising therapeutic target for the vigorously developing field of precision medicine.

KEY POINTS

Significant findings of the study Cytoplasmic HDAC3 is an independent prognostic factor for the overall survival and brain metastasis-free survival of breast cancer patients. What this study adds Cytoplasmic expression of HDAC3 was further upregulated in the brain metastases compared with the matched primary tumours, while nuclear expression was downregulated.

Molecular docking-based virtual drug screening revealing an oxofluorenyl benzamide and a bromonaphthalene sulfonamido hydroxybenzoic acid as HDAC6 inhibitors with cytotoxicity against leukemia cells

HDAC6 is a crucial epigenetic modifier that plays a vital role in tumor progression and carcinogenesis due to its multiple biological functions. It is a unique member of class-II HDAC enzymes. It possesses two catalytic domains, which function independently of the overall enzyme activity. Up to date, there are only a few selective HDAC6 inhibitors with anti-cancer activity. In this study, 175,204 ligands obtained from the ZINC15 and OTAVAchemical databases were used for virtual drug screening against HDAC6. Molecular docking studies were performed for 100 selected compounds. Furthermore, the top 10 compounds obtained from docking were tested for their efficacy to inhibit the function of HDAC6. Five compounds (N-(9-oxo-9H-fluoren-3-yl)benzamide, 2-hydroxy-5-[(5-oxo-6-phenyl-4,5-dihydro-1,2,4-triazin-3-yl)amino]benzoic acid, 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid, 2-(naphthalen-2-yl)-N-(1H-1,2,3,4-tetrazol-5-yl)cyclopropane-1-carboxamide, and 4-oxa-5,6 diazapentacyclo[10.7.1.0³,⁷.0⁸,²⁰.0¹⁴,¹⁹]icosa-1,3(7),5,8(20),9,11,14,16,18-nonaen-13-one) inhibited enzymatic activity by more than 50 % compared to DMSO as the control. Two candidates, (N-(9-oxo-9H-fluoren-3-yl)benzamide and 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid), were identified with considerable cytotoxicity towards drug-sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Microscale thermophoresis revealed the binding of N-(9-oxo-9H-fluoren-3-yl)benzamide and 5-(4-bromonaphthalene-1-sulfonamido)-2-hydroxybenzoic acid to purified HDAC6 protein. Both compounds induced apoptosis in a dose-dependent manner as analyzed by flow cytometry. In conclusion, we demonstrate for the first time that these two compounds bind to HDAC6, inhibit its function, and exert cytotoxic activity by apoptosis induction.

Hexane Extract of Garcinia quaesita Fruits Induces Apoptosis in Breast Cancer Stem Cells Isolated from Triple Negative Breast Cancer Cell Line MDA-MB-231

Development of therapy resistance is a major clinical issue in breast cancer treatments. Breast cancer stem cells (bCSCs) have a clearly defined role in the development of breast cancer therapy resistance and tumor recurrence. Therefore, discovery of new treatment strategies to circumvent cancer therapy resistance and tumor recurrence by targeting bCSCs is desperately needed. Fruits of many Garcinia species are edible and, possess a range of health benefits. Garcinia quaesita, a species in the genus Garcinia, is endemic to Sri Lanka. Dried fruits of G. quaesita are commonly used to flavor dishes in Sri Lanka. The present study assessed the potential anticancer and apoptotic properties of G. quaesita fruit extracts in bCSCs using WST-1 cell proliferation assay, sphere formation assay, caspase 3/7 assay, real-time PCR and fluorescent and phase-contrast microscopy. DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and FRAP (Ferric Reducing Anti-oxidant Power) assays were used as anti-oxidant assays. The hexane extract of G. quaesita fruits was found to mediate cytotoxicity in bCSCs through induction of apoptosis. Furthermore, the hexane extract showed free radical scavenging ability. This pilot investigation provides a rationale to consume G. quaesita fruits as an anticancer dietary supplement for breast cancer patients.

Association of HDAC8 Expression with Pathological Findings in Triple Negative and Non-Triple Negative Breast Cancer: Implications for Diagnosis

Background:

Previous data have shown the tumorigenicity roles of HDAC8 in breast cancer. More recently, the oncogenic effects of this molecule have been revealed in TNBC. The present study aimed to determine the diagnostic value of HDAC8 for the differentiation of TNBC from nTNBC tumors.

Methods:

A total of 50 cancerous and normal adjacent tumor specimens were obtained, and the clinical and pathological findings of studied subjects were recorded. The expression of HDAC8 gene was determined by qRT-PCR. Also, immunohistochemical staining was performed on tissue samples.

Results:

Our results showed that the expression of HDAC8 in breast cancer tissues was significantly higher than the normal adjacent tissues (p = 0.0011). HDAC8 expression was also observed to be higher in TNBC patients than nTNBC group (p = 0.0013). In addition, in the TNBC group, there was a significant association between the HDAC8 overexpression and tumor characteristics, including tumor size (p = 0.039), lymphatic invasion (p = 0.01), tumor grade (p = 0.02), and perineural invasion (p < 0.05). The cut-off value was fixed at 0.6279 r.u., and the corresponding sensitivity and specificity were found to be 73.91% and 70.37%, respectively.

Conclusion:

According to the findings, among the other markers, HDAC8 oncogene may be used as a potential tumor marker in diagnosis of TNBC tumors.

Ferrocene-containing hybrids as potential anticancer agents: Current developments, mechanisms of action and structure-activity relationships

Cancer is one of the most fatal threatens to human health throughout the world. The major challenges in the control and eradication of cancers are the continuous emergency of drug-resistant cancer and the low specificity of anticancer agents, creating an urgent need to develop novel anticancer agents. Organometallic compounds especially ferrocene derivatives possess remarkable structural and mechanistic diversity, inherent stability towards air, heat and light, low toxicity, low cost, reversible redox, ligand exchange, and catalytic properties, making them promising drug candidates for cancer therapy. Ferrocifen, a ferrocene-phenol hybrid, has demonstrated promising anticancer properties on drug-resistant cancers. Currently, Ferrocifen is in pre-clinical trial against cancers. Obviously, ferrocene moiety is a useful template for the development of novel anticancer agents. This review will provide an overview of ferrocene-containing hybrids with potential application in the treatment of cancers covering articles published between 2010 and 2020. The mechanisms of action, the critical aspects of design and structure-activity relationships are also discussed.

Sp1-mediated epigenetic dysregulation dictates HDAC inhibitor susceptibility of HER2-overexpressing breast cancer

Human epidermal growth factor receptor 2 (HER2/erbB2) is a key driver and therapeutic target for breast cancer. The treatment of HER2-positive breast cancer remains a clinical challenge largely due to the limited understanding of HER2-driving oncogenic signaling and the frequent resistance to simply HER2-targeted therapy. Here, we show that the histone deacetylase inhibitor, trichostatin A (TSA), suppresses HER2-overexpressing breast cancer via upregulation of miR-146a and the resultant repression of its oncogenic targets, interleukin-1 receptor-associated kinase 1 and the chemokine receptor CXCR4. Mechanistically, histone H3K56 acetylation and deacetylation on the MIR146A promoter are catalyzed respectively by the acetyltransferase p300 and histone deacetylase 1 (HDAC1), both of which are recruited to the genomic loci by the transcription factor specificity protein 1 (Sp1). HER2 signaling phosphorylates Sp1 and induces its predominant association with HDAC1, but not p300, leading to histone hypoacetylation and silencing of MIR146A. In addition, the death receptor Fas is similarly downregulated by the aforementioned epigenetic paradigm, indicating its wide involvement in impairing tumor suppressor gene expression. Consequently, TSA synergizes with lapatinib, a tyrosine kinase inhibitor of HER2, to suppress breast cancer in vitro and in rodent models. These findings demonstrate a novel mechanism of HER2-driven carcinogenesis and suggest the applicability of combined HER2 and HDAC targeting in breast cancer therapy.

Targeting miRNAs by histone deacetylase inhibitors (HDACi): Rationalizing epigenetics-based therapies for breast cancer

MicroRNAs (miRNAs) belong to a group of short RNA molecules of ~22 nucleotides that play a significant role in the regulation of gene expression through post-transcriptional regulatory mechanisms. They can directly interact with their target mRNA molecules and induce target gene silencing. Many investigations over the past decade have revealed the involvement of different miRNAs in essential biological events. The expression of a considerable number of miRNAs is tightly regulated through epigenetic events such as histone modifications and DNA methylation. Notably, irregularities in these epigenetic events are associated with aberrant expression of miRNAs in a range of diseases including cancer. Impaired epigenetic events associated with aberrant expression of miRNAs can be pharmacologically modified using chromatin modifying drugs. Numerous pre-clinical and clinical data demonstrate that histone deacetylase inhibitors (HDACi) can re-establish the expression of aberrantly expressed miRNAs in a range of cancer types, rationalizing miRNAs as potential drug targets. This review highlights evidence from investigations assessing the effects of different classes of HDACi on miRNA expression in breast cancer (BC).