Deregulated expression of selected histone methylases and demethylases in prostate carcinoma

A novel small molecule ZYZ384 targeting SMYD3 for hepatocellular carcinoma via reducing H3K4 trimethylation of the Rac1 promoter

SMYD3 (SET and MYND domain-containing 3) is a histone lysine methyltransferase highly expressed in different types of cancer(s) and is a promising epigenetic target for developing novel antitumor therapeutics. No selective inhibitors for this protein have been developed for cancer treatment. Therefore, the current study describes developing and characterizing a novel small molecule ZYZ384 screened and synthesized based on SMYD3 structure. Virtual screening was initially used to identify a lead compound and followed up by modification to get the novel molecules. Several technologies were used to facilitate compound screening about these novel molecules' binding affinities and inhibition activities with SMYD3 protein; the antitumor activity has been assessed in vitro using various cancer cell lines. In addition, a tumor-bearing nude mice model was established, and the activity of the selected molecule was determined in vivo. Both RNA-seq and chip-seq were performed to explore the antitumor mechanism. This work identified a novel small molecule ZYZ384 targeting SMYD3 with antitumor activity and impaired hepatocellular carcinoma tumor growth by reducing H3K4 trimethylation of the Rac1 promoter triggering the tumor cell cycle arrest through the AKT pathway.

KDM4B mutations in human cancers

Homologous recombination (HR) is essential for repair of DNA double-strand breaks (DSBs) and restart of stalled or collapsed replication forks. Most cancers are characterized by mutations in components of the DSB repair pathways. Redundant DSB repair pathways exist in eukaryotes from yeast to humans and recent evidence has shown that complete loss of HR function appears to be lethal. Recent evidence has also shown that cancer cells with mutations in one DSB repair pathway can be killed by inhibiting one or more parallel pathways, a strategy that is currently aggressively explored as a cancer therapy. KDM4B is a histone demethylase with pleiotropic functions, which participates in preparing DSBs for repair by contributing to chromatin remodeling. In this report we carried out a pan-cancer analysis of KDM4B mutations with the goal of understanding their distribution and interaction with other DSB genes. We find that although KDM4B mutations co-occur with DSB repair genes, most KDM4B mutations are not drivers or pathogenic. A sequence conservation analysis from yeast to humans shows that highly conserved residues are resistant to mutation. Finally, all mutations occur in a heterozygous state. A single mutation, R986L, was predicted to significantly affect protein structure using computational modeling. This analysis suggests that KDM4B makes contributions to DSB repair but is not a key player.

Histone methyltransferase SUV39H2 regulates apoptosis and chemosensitivity in prostate cancer through AKT/FOXO signaling pathway

Prostate cancer (PCa) is one of the most common malignant tumors that exhibit both chemoresistance and recurrence. SUV39H2 is highly expressed in many types of human tumors, but its role in the development and progression of PCa has never been clarified. The aim of this study is to elucidate the role of SUV39H2 in the development and progression of PCa, its association with the AKT/FOXO signaling pathway, and its potential implications for PCa diagnosis and treatment. SUV39H2 expression was analyzed in The Cancer Genome Atlas (TCGA) and genotype tissue expression pan-cancer data. The TCGA database was evaluated for SUV39H2 enrichment and its correlation to immune cell infiltration. SUV39H2 levels in PCa tissues and control tissues were determined in 30 patients using qPCR and IHC. Clinical relevance was assessed via The Cancer Genome Atlas (TCGA). In vitro assessments including colony formation assays, Western Blot analysis, CCK-8 assays, and flow cytometry were utilized to establish SUV39H2's contribution to PCa cell growth. The influence of SUV39H2 on PC3 and DU145 cell proliferation was assessed through a cell line-derived xenograft model. Sphere formation assays and qPCR were employed to delineate SUV39H2's role in PCa stemness and chemosensitivity. In vitro macrophage polarization assays provided insights into SUV39H2's association with M2 macrophages, while enrichment analysis shed light on its role in FOXO signaling. PCa tissues expressed higher levels of SUV39H2 than normal tissues. By knocking down SUV39H2, PCa cells were made more chemosensitive to docetaxel and cell proliferation and stemness were inhibited. Additionally, SUV39H2 knockdown significantly inhibited in vivo PCa cell growth and inhibited the polarization of macrophages. Furthermore, SUV39H2 was found to regulate AKT/FOXO signaling by increasing Akt and FOXO3a phosphorylation. Our findings highlight SUV39H2's role in PCa cell apoptosis and chemosensitivity mainly by regulating the AKT/FOXO signaling pathway and suggest that SUV39H2 could be a potential target for PCa diagnosis and treatment.

Therapeutic m6A Eraser ALKBH5 mRNA-Loaded Exosome-Liposome Hybrid Nanoparticles Inhibit Progression of Colorectal Cancer in Preclinical Tumor Models

Although therapeutic targets have been developed for colorectal cancer (CRC) therapy, the therapeutic effects are not ideal and the survival rate for CRC patients remains poor. Therefore, it is crucial to recognize a specific target and develop an efficacious delivery system for CRC therapy. Herein, we demonstrate that reduced ALKBH5 mediates aberrant m⁶A modification and tumor progression in CRC. Mechanically, histone deacetylase 2-mediated H3K27 deacetylation inhibits ALKBH5 transcription in CRC, whereas ectopic ALKBH5 expression decreases tumorigenesis of CRC cells and protects mice from colitis-associated tumor development. Further, METTL14/ALKBH5/IGF2BPs combine to modulate JMJD8 stability in an m⁶A-dependent manner, which increases glycolysis and accelerates the development of CRC by enhancing the enzymatic activity of PKM2. Moreover, ALKBH5 mRNA-loaded folic acid-modified exosome-liposome hybrid nanoparticles were synthesized and significantly inhibit the progression of CRC in preclinical tumor models by modulating the ALKBH5/JMJD8/PKM2 axis and inhibiting glycolysis. Overall, our research confirms the crucial function of ALKBH5 in regulating the m⁶A status in CRC and provides a direct preclinical approach for using ALKBH5 mRNA nanotherapeutics for CRC.

DNA Methyltransferase 1 Targeting Using Guadecitabine Inhibits Prostate Cancer Growth by an Apoptosis-Independent Pathway

Epigenetic alterations such as DNA methylation and histone modifications are implicated in repressing several tumor suppressor genes in prostate cancer progression. In this study, we determined the anti-prostate cancer effect of a small molecule drug guadecitabine (gDEC) that inhibits/depletes the DNA methylation writer DNA methyltransferase 1 (DNMT1). gDEC inhibited prostate cancer cell growth and proliferation in vitro without activating the apoptotic cascade. Molecular studies confirmed DNMT1 depletion and modulated epithelial-mesenchymal transition markers E-cadherin and β-catenin in several prostate cancer cell lines (LNCaP, 22Rv1, and MDA PCa 2b). gDEC treatment also significantly inhibited prostate tumor growth in vivo in mice (22Rv1, MDA PCa 2b, and PC-3 xenografts) without any observed toxicities. gDEC did not impact the expression of androgen receptor (AR) or AR-variant 7 (AR-V7) nor sensitize the prostate cancer cells to the anti-androgen enzalutamide in vitro. In further investigating the mechanism of cytoreduction by gDEC, a PCR array analyses of 84 chromatin modifying enzymes demonstrated upregulation of several lysine-specific methyltransferases (KMTs: KMT2A, KMT2C, KMT2E, KMT2H, KMT5A), confirmed by additional expression analyses in vitro and of harvested xenografts. Moreover, gDEC treatment increased global histone 3 lysine 4 mono-and di-methylation (H3K4me1 and H3K4me2). In sum, gDEC, in addition to directly depleting the corepressor DNMT1, upregulated KMT activating epigenetic enzymes, activating terminal epithelial program activation, and prostate cancer cell cycling exits independent of apoptosis.

H3 histone methylation landscape in male urogenital cancers: from molecular mechanisms to epigenetic biomarkers and therapeutic targets

During the last decades, male urogenital cancers (including prostate, renal, bladder and testicular cancers) have become one of the most frequently encountered malignancies affecting all ages. While their great variety has promoted the development of various diagnosis, treatment and monitoring strategies, some aspects such as the common involvement of epigenetic mechanisms are still not elucidated. Epigenetic processes have come into the spotlight in the past years as important players in the initiation and progression of tumors, leading to a plethora of studies highlighting their potential as biomarkers for diagnosis, staging, prognosis, and even as therapeutic targets. Thus, fostering research on the various epigenetic mechanisms and their roles in cancer remains a priority for the scientific community. This review focuses on one of the main epigenetic mechanisms, namely, the methylation of the histone H3 at various sites and its involvement in male urogenital cancers. This histone modification presents a great interest due to its modulatory effect on gene expression, leading either to activation (e.g., H3K4me3, H3K36me3) or repression (e.g., H3K27me3, H3K9me3). In the last few years, growing evidence has demonstrated the aberrant expression of enzymes that methylate/demethylate histone H3 in cancer and inflammatory diseases, that might contribute to the initiation and progression of such disorders. We highlight how these particular epigenetic modifications are emerging as potential diagnostic and prognostic biomarkers or targets for the treatment of urogenital cancers.

Targeting Epigenetic Changes Mediated by Members of the SMYD Family of Lysine Methyltransferases

A comprehensive understanding of the mechanisms involved in epigenetic changes in gene expression is essential to the clinical management of diseases linked to the SMYD family of lysine methyltransferases. The five known SMYD enzymes catalyze the transfer of donor methyl groups from S-adenosylmethionine (SAM) to specific lysines on histones and non-histone substrates. SMYDs family members have distinct tissue distributions and tissue-specific functions, including regulation of development, cell differentiation, and embryogenesis. Diseases associated with SMYDs include the repressed transcription of SMYD1 genes needed for the formation of ion channels in the heart leading to heart failure, SMYD2 overexpression in esophageal squamous cell carcinoma (ESCC) or p53-related cancers, and poor prognosis associated with SMYD3 overexpression in more than 14 types of cancer including breast cancer, colon cancer, prostate cancer, lung cancer, and pancreatic cancer. Given the importance of epigenetics in various pathologies, the development of epigenetic inhibitors has attracted considerable attention from the pharmaceutical industry. The pharmacologic development of the inhibitors involves the identification of molecules regulating both functional SMYD SET (Suppressor of variegation, Enhancer of Zeste, Trithorax) and MYND (Myeloid-Nervy-DEAF1) domains, a process facilitated by available X-ray structures for SMYD1, SMYD2, and SMYD3. Important leads for potential pharmaceutical agents have been reported for SMYD2 and SMYD3 enzymes, and six epigenetic inhibitors have been developed for drugs used to treat myelodysplastic syndrome (Vidaza, Dacogen), cutaneous T-cell lymphoma (Zoinza, Isrodax), and peripheral T-cell lymphoma (Beleodag, Epidaza). The recently demonstrated reversal of SMYD histone methylation suggests that reversing the epigenetic effects of SMYDs in cancerous tissues may be a desirable target for pharmacological development.

LSD1/PRMT6-targeting gene therapy to attenuate androgen receptor toxic gain-of-function ameliorates spinobulbar muscular atrophy phenotypes in flies and mice

Spinobulbar muscular atrophy (SBMA) is caused by CAG expansions in the androgen receptor gene. Androgen binding to polyQ-expanded androgen receptor triggers SBMA through a combination of toxic gain-of-function and loss-of-function mechanisms. Leveraging cell lines, mice, and patient-derived specimens, we show that androgen receptor co-regulators lysine-specific demethylase 1 (LSD1) and protein arginine methyltransferase 6 (PRMT6) are overexpressed in an androgen-dependent manner specifically in the skeletal muscle of SBMA patients and mice. LSD1 and PRMT6 cooperatively and synergistically transactivate androgen receptor, and their effect is enhanced by expanded polyQ. Pharmacological and genetic silencing of LSD1 and PRMT6 attenuates polyQ-expanded androgen receptor transactivation in SBMA cells and suppresses toxicity in SBMA flies, and a preclinical approach based on miRNA-mediated silencing of LSD1 and PRMT6 attenuates disease manifestations in SBMA mice. These observations suggest that targeting overexpressed co-regulators can attenuate androgen receptor toxic gain-of-function without exacerbating loss-of-function, highlighting a potential therapeutic strategy for patients with SBMA.

Discovery of cysteine-targeting covalent histone methyltransferase inhibitors

Post-translational methylation of histone lysine or arginine residues by histone methyltransferases (HMTs) plays crucial roles in gene regulation and diverse physiological processes and is implicated in a plethora of human diseases, especially cancer. Therefore, histone methyltransferases have been increasingly recognized as potential therapeutic targets. Consequently, the discovery and development of histone methyltransferase inhibitors have been pursued with steadily increasing interest over the past decade. However, the disadvantages of limited clinical efficacy, moderate selectivity, and propensity for acquired resistance have hindered the development of HMTs inhibitors. Targeted covalent modification represents a proven strategy for kinase drug development and has gained increasing attention in HMTs drug discovery. In this review, we focus on the discovery, characterization, and biological applications of covalent inhibitors for HMTs with emphasis on advancements in the field. In addition, we identify the challenges and future directions in this fast-growing research area of drug discovery.

Epigenetic (De)regulation in Prostate Cancer

Prostate cancer (PCa) is a heterogeneous disease exhibiting both genetic and epigenetic deregulations. Epigenetic alterations are defined as changes not based on DNA sequence, which include those of DNA methylation, histone modification, and chromatin remodeling. Androgen receptor (AR) is the main driver for PCa and androgen deprivation therapy (ADT) remains a backbone treatment for patients with PCa; however, ADT resistance almost inevitably occurs and advanced diseases develop termed castration-resistant PCa (CRPC), due to both genetic and epigenetic changes. Due to the reversible nature of epigenetic modifications, inhibitors targeting epigenetic factors have become promising anti-cancer agents. In this chapter, we focus on recent studies about the dysregulation of epigenetic regulators crucially involved in the initiation, development, and progression of PCa and discuss the potential use of inhibitors targeting epigenetic modifiers for treatment of advanced PCa.

Drawing a line between histone demethylase KDM5A and KDM5B: their roles in development and tumorigenesis

Distinct epigenetic modifiers ensure coordinated control over genes that govern a myriad of cellular processes. Growing evidence shows that dynamic regulation of histone methylation is critical for almost all stages of development. Notably, the KDM5 subfamily of histone lysine-specific demethylases plays essential roles in the proper development and differentiation of tissues, and aberrant regulation of KDM5 proteins during development can lead to chronic developmental defects and even cancer. In this review, we adopt a unique perspective regarding the context-dependent roles of KDM5A and KDM5B in development and tumorigenesis. It is well known that these two proteins show a high degree of sequence homology, with overlapping functions. However, we provide deeper insights into their substrate specificity and distinctive function in gene regulation that at times divert from each other. We also highlight both the possibility of targeting KDM5A and KDM5B to improve cancer treatment and the limitations that must be overcome to increase the efficacy of current drugs.

Lysine demethylase 5A promotes prostate adenocarcinoma progression by suppressing microRNA-330-3p expression and activating the COPB2/PI3K/AKT axis in an ETS1-dependent manner

Lysine demethylase 5A (KDM5A) is a histone demethylase frequently involved in cancer progression. This research aimed to explore the function of KDM5A in prostate adenocarcinoma (PRAD) and the molecular mechanism. KDM5A was highly expressed in collected PRAD tissues and acquired PRAD cells. High KDM5A expression was correlated with reduced survival and poor prognosis of patients with PRAD. Knockdown of KDM5A suppressed the proliferation, colony formation, migration, and invasiveness of PRAD cells and reduced angiogenesis ability of endothelial cells. Downstream molecules implicated in KDM5A mediation were predicted using integrated bioinformatic analyses. KDM5A enhanced ETS proto-oncogene 1 (ETS1) expression through demethylation of H3K4me2 at its promoter. ETS1 suppressed the transcription activity of miR-330-3p, and either further ETS1 overexpression or miR-330-3p inhibition blocked the functions of KDM5A knockdown in PRAD. miR-330-3p targeted coatomer protein complex subunit β2 (COPB2) mRNA. Downregulation of miR-330-3p restored the expression of COPB2 and activated the PI3K/AKT pathway in PRAD. The results in vitro were reproduced in vivo where KDM5A downregulation suppressed the growth and metastasis of xenograft tumors in nude mice. In conclusion, this study demonstrated that KDM5A promoted PRAD by suppressing miR-330-3p and activating the COPB2/PI3K/AKT axis in an ETS1-dependent manner.

Clinical prognostic value of the SMYD2/3 as new epigenetic biomarkers in solid cancer patients: a systematic review and meta-analysis

BACKGROUND

SET and MYND domain-containing protein (SMYD) family with methyltransferase activity is involved in cancer progression. This novel meta-analysis aimed to evaluate the association of SMYD family with the clinical and survival outcomes in solid cancer patients.

METHODS

We systematically searched Embase, PubMed, Scopus and Web of Science to select relevant articles. Hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals were extracted. Heterogeneity was evaluated by chi-square-based Q and I2 tests, while publication bias by funnel plots and Egger's test.

RESULTS

Thirty-two articles (4,826 patients) met inclusion criteria. SMYD2/3 overexpression was statistically associated with poor overall survival (HR = 1.794, P < 0.001), disease/relapse/progression-free survival (HR = 2.114, P < 0.001), disease/cancer-specific survival (HR = 3.220, P = 0.003), larger tumor size (OR = 1.963, P < 0.001), advanced TNM stage (OR = 2.066, P < 0.001), lymph node metastasis (OR = 2.054, P < 0.001), and distant metastasis (OR = 1.978, P = 0.004). Subgroup analysis showed more significant association between SMYD2 overexpression and reduced survival outcomes than that in SMYD3. Conversely, the relationship between SMYD3 and various clinicopathologic factors was stronger compared to SMYD2.

CONCLUSION

Enhanced SMYD2/3 expression may be an unfavorable clinical prognostic factor in different solid cancer types.

Progression of prostate cancer reprograms MYC-mediated lipid metabolism via lysine methyltransferase 2A

BACKGROUND

The activities of MYC, the androgen receptor, and its associated pioneer factors demonstrate substantial reprogramming between early and advanced prostate cancer. Although previous studies have shown a shift in cellular metabolic requirements associated with prostate cancer progression, the epigenetic regulation of these processes is incompletely described. Here, we have integrated chromatin immunoprecipitation sequencing (ChIP-seq) and whole-transcriptome sequencing to identify novel regulators of metabolism in advanced prostate tumors characterized by elevated MYC activity.

RESULTS

Using ChIP-seq against MYC, HOXB13, and AR in LNCaP cells, we observed redistribution of co-bound sites suggestive of differential KMT2A activity as a function of MYC expression. In a cohort of 177 laser-capture microdissected foci of prostate tumors, KMT2A expression was positively correlated with MYC activity, AR activity, and HOXB13 expression, but decreased with tumor grade severity. However, KMT2A expression was negatively correlated with these factors in 25 LuCaP patient-derived xenograft models of advanced prostate cancer and 99 laser-capture microdissected foci of metastatic castration-resistant prostate cancer. Stratified by KMT2A expression, ChIP-seq against AR and HOXB13 in 15 LuCaP patient-derived xenografts showed an inverse association with sites involving genes implicated in lipid metabolism, including the arachidonic acid metabolic enzyme PLA2G4F. LuCaP patient-derived xenograft models grown as organoids recapitulated the inverse association between KMT2A expression and fluorine-18 labeled arachidonic acid uptake in vitro.

CONCLUSIONS

Our study demonstrates that the epigenetic activity of transcription factor oncogenes exhibits a shift during prostate cancer progression with distinctive phenotypic effects on metabolism. These epigenetically driven changes in lipid metabolism may serve as novel targets for the development of novel imaging agents and therapeutics.

JMJD family proteins in cancer and inflammation

The occurrence of cancer entails a series of genetic mutations that favor uncontrollable tumor growth. It is believed that various factors collectively contribute to cancer, and there is no one single explanation for tumorigenesis. Epigenetic changes such as the dysregulation of enzymes modifying DNA or histones are actively involved in oncogenesis and inflammatory response. The methylation of lysine residues on histone proteins represents a class of post-translational modifications. The human Jumonji C domain-containing (JMJD) protein family consists of more than 30 members. The JMJD proteins have long been identified with histone lysine demethylases (KDM) and histone arginine demethylases activities and thus could function as epigenetic modulators in physiological processes and diseases. Importantly, growing evidence has demonstrated the aberrant expression of JMJD proteins in cancer and inflammatory diseases, which might serve as an underlying mechanism for the initiation and progression of such diseases. Here, we discuss the role of key JMJD proteins in cancer and inflammation, including the intensively studied histone lysine demethylases, as well as the understudied group of JMJD members. In particular, we focused on epigenetic changes induced by each JMJD member and summarized recent research progress evaluating their therapeutic potential for the treatment of cancer and inflammatory diseases.

Expression, Prognostic Value, and Functional Mechanism of the KDM5 Family in Pancreatic Cancer

Background: The histone lysine demethylase KDM5 family is an important epigenetic state-modifying enzyme family. Increasing evidence supports that epigenetic abnormalities in the KDM5 family are related to multiple cancers in humans. However, the role of the KDM5 family in pancreatic cancer is not clear, and related research is very scarce.

Methods: R software, Kaplan–Meier Plotter, cBioPortal, TIMER, LinkedOmics, STRING, Metascape, TISIDB, and the GSCA Lite online tool were utilized for bioinformatics analysis.

Results: KDM5A/B/C was significantly overexpressed in many kinds of tumor tissues, including pancreatic adenocarcinoma (PAAD), while the expression of KDM5D was significantly downregulated. The high expression of KDM5A/B/C was related to poor clinical features, such as worse treatment efficacy, higher tumor grade, and more advanced clinical stage. Patients with a family history of breast cancer and melanoma, history of drinking or history chronic pancreatitis were more likely to have KDM5A/B/C gene abnormalities, which were related to a variety of adverse clinical features. The results of gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) pathway analyses of the KDM5 family and its 800 co-expressed genes showed that many gene terms related to cell proliferation, migration and many carcinogenic pathways. Notably, we found that the expression level of KDM5A/B/C was positively correlated with the expression of multiple key driver genes such as KRAS, BRCA1, and BRCA2 etc. In addition, PPI network analysis showed KDM5 family proteins have strong interactions with histone deacetylase family 1 (HDAC1), which could modify the lysines of histone H3, and co-act on many pathways, including the “longevity-regulating pathway” and “Notch signaling pathway”. Moreover, the upregulation of KDM5A/B/C expression was associated with an increase in the infiltration of B cells, CD8⁺ T cells and other infiltrating immune lymphocytes and the expression levels of immune molecules such as NT5E and CD274. Interestingly, the overexpression of KDM5A/C was also corelated with reduced sensitivity of pancreatic cancer cells to many kinds of pancreatic cancer-targeting or chemotherapeutic drugs, including axitinib and gemcitabine.

Conclusion: KDM5 family members may be prognostic markers and new therapeutic targets for patients with pancreatic cancer.

The Emerging Role of PRMT6 in Cancer

Protein arginine methyltransferase 6 (PRMT6) is a type I PRMT that is involved in epigenetic regulation of gene expression through methylating histone or non-histone proteins, and other processes such as alternative splicing, DNA repair, cell proliferation and senescence, and cell signaling. In addition, PRMT6 also plays different roles in various cancers via influencing cell growth, migration, invasion, apoptosis, and drug resistant, which make PRMT6 an anti-tumor therapeutic target for a variety of cancers. As a result, many PRMT6 inhibitors are being utilized to explore their efficacy as potential drugs for various cancers. In this review, we summarize the current knowledge on the function and structure of PRMT6. At the same time, we highlight the role of PRMT6 in different cancers, including the differentiation of its promotive or inhibitory effects and the underlying mechanisms. Apart from the above, current research progress and the potential mechanisms of PRMT6 behind them were also summarized.

The Diverse Roles of Histone Demethylase KDM4B in Normal and Cancer Development and Progression

Histone methylation status is an important process associated with cell growth, survival, differentiation and gene expression in human diseases. As a member of the KDM4 family, KDM4B specifically targets H1.4K26, H3K9, H3K36, and H4K20, which affects both histone methylation and gene expression. Therefore, KDM4B is often regarded as a key intermediate protein in cellular pathways that plays an important role in growth and development as well as organ differentiation. However, KDM4B is broadly defined as an oncoprotein that plays key roles in processes related to tumorigenesis, including cell proliferation, cell survival, metastasis and so on. In this review, we discuss the diverse roles of KDM4B in contributing to cancer progression and normal developmental processes. Furthermore, we focus on recent studies highlighting the oncogenic functions of KDM4B in various kinds of cancers, which may be a novel therapeutic target for cancer treatment. We also provide a relatively complete report of the progress of research related to KDM4B inhibitors and discuss their potential as therapeutic agents for overcoming cancer.

How Protein Methylation Regulates Steroid Receptor Function

Steroid receptors (SRs) are members of the nuclear hormonal receptor family, many of which are transcription factors regulated by ligand binding. SRs regulate various human physiological functions essential for maintenance of vital biological pathways, including development, reproduction, and metabolic homeostasis. In addition, aberrant expression of SRs or dysregulation of their signaling has been observed in a wide variety of pathologies. SR activity is tightly and finely controlled by post-translational modifications (PTMs) targeting the receptors and/or their coregulators. Whereas major attention has been focused on phosphorylation, growing evidence shows that methylation is also an important regulator of SRs. Interestingly, the protein methyltransferases depositing methyl marks are involved in many functions, from development to adult life. They have also been associated with pathologies such as inflammation, as well as cardiovascular and neuronal disorders, and cancer. This article provides an overview of SR methylation/demethylation events, along with their functional effects and biological consequences. An in-depth understanding of the landscape of these methylation events could provide new information on SR regulation in physiology, as well as promising perspectives for the development of new therapeutic strategies, illustrated by the specific inhibitors of protein methyltransferases that are currently available.

Structure, Activity and Function of the Protein Arginine Methyltransferase 6

Members of the protein arginine methyltransferase (PRMT) family methylate the arginine residue(s) of several proteins and regulate a broad spectrum of cellular functions. Protein arginine methyltransferase 6 (PRMT6) is a type I PRMT that asymmetrically dimethylates the arginine residues of numerous substrate proteins. PRMT6 introduces asymmetric dimethylation modification in the histone 3 at arginine 2 (H3R2me2a) and facilitates epigenetic regulation of global gene expression. In addition to histones, PRMT6 methylates a wide range of cellular proteins and regulates their functions. Here, we discuss (i) the biochemical aspects of enzyme kinetics, (ii) the structural features of PRMT6 and (iii) the diverse functional outcomes of PRMT6 mediated arginine methylation. Finally, we highlight how dysregulation of PRMT6 is implicated in various types of cancers and response to viral infections.

Epigenetic Editing in Prostate Cancer: Challenges and Opportunities

Epigenome editing consists of fusing a predesigned DNA recognition unit to the catalytic domain of a chromatin modifying enzyme leading to the introduction or removal of an epigenetic mark at a specific locus. These platforms enabled the study of the mechanisms and roles of epigenetic changes in several research domains such as those addressing pathogenesis and progression of cancer. Despite the continued efforts required to overcome some limitations, which include specificity, off-target effects, efficacy, and longevity, these tools have been rapidly progressing and improving.Since prostate cancer is characterized by multiple genetic and epigenetic alterations that affect different signalling pathways, epigenetic editing constitutes a promising strategy to hamper cancer progression. Therefore, by modulating chromatin structure through epigenome editing, its conformation might be better understood and events that drive prostate carcinogenesis might be further unveiled.This review describes the different epigenome engineering tools, their mechanisms concerning gene's expression and regulation, highlighting the challenges and opportunities concerning prostate cancer research.

F-Box Protein FBXW17-Mediated Proteasomal Degradation of Protein Methyltransferase PRMT6 Exaggerates CSE-Induced Lung Epithelial Inflammation and Apoptosis

Chronic obstructive pulmonary disease (COPD) is a chronic debilitating lung disease, characterized by progressive airway inflammation and lung structural cell death. Cigarette smoke is considered the most common risk factor of COPD pathogenesis. Understanding the molecular mechanisms of persistent inflammation and epithelial apoptosis induced by cigarette smoke would be extremely beneficial for improving the treatment and prevention of COPD. A histone methyl modifier, protein arginine N-methyltransferase 6 (PRMT6), is reported to alleviate cigarette smoke extract (CSE)-induced emphysema through inhibiting inflammation and cell apoptosis. However, few studies have focused on the modulation of PRMT6 in regulating inflammation and cell apoptosis. In this study, we showed that protein expression of PRMT6 was aberrantly decreased in the lung tissue of COPD patients and CSE-treated epithelial cells. FBXW17, a member of the Skp1-Cullin-F-box (SCF) family of E3 ubiquitin ligases, selectively bound to PRMT6 in nuclei to modulate its elimination in the proteasome system. Proteasome inhibitor or silencing of FBXW17 abrogated CSE-induced PRMT6 protein degradation. Furthermore, negative alteration of FBXW17/PRMT6 signaling lessened the proapoptotic and proinflammatory effects of CSE in lung epithelial cells. Our study, therefore, provides a potential therapeutic target against the airway inflammation and cell death in CS-induced COPD.

Huaier Extract Inhibits Prostate Cancer Growth via Targeting AR/AR-V7 Pathway

The androgen receptor (AR) plays a pivotal role in prostatic carcinogenesis, and it also affects the transition from hormone sensitive prostate cancer (HSPC) to castration-resistant prostate cancer (CRPC). Particularly, the persistent activation of the androgen receptor and the appearance of androgen receptor splicing variant 7 (AR-V7), could partly explain the failure of androgen deprivation therapy (ADT). In the present study, we reported that huaier extract, derived from officinal fungi, has potent antiproliferative effects in both HSPC and CRPC cells. Mechanistically, huaier extract downregulated both full length AR (AR-FL) and AR-V7 mRNA levels via targeting the SET and MYND domain-containing protein 3 (SMYD3) signaling pathway. Huaier extract also enhanced proteasome-mediated protein degradation of AR-FL and AR-V7 by downregulating proteasome-associated deubiquitinase ubiquitin-specific protease 14 (USP14). Furthermore, huaier extract inhibited AR-FL/AR-V7 transcriptional activity and their nuclear translocation. More importantly, our data demonstrated that huaier extract could re-sensitize enzalutamide-resistant prostate cancer cells to enzalutamide treatment in vitro and in vivo models. Our work revealed that huaier extract could be effective for treatment of prostate cancer either as monotherapy or in combination with enzalutamide.

The emerging role of KDM5A in human cancer

Histone methylation is a key posttranslational modification of chromatin, and its dysregulation affects a wide array of nuclear activities including the maintenance of genome integrity, transcriptional regulation, and epigenetic inheritance. Variations in the pattern of histone methylation influence both physiological and pathological events. Lysine-specific demethylase 5A (KDM5A, also known as JARID1A or RBP2) is a KDM5 Jumonji histone demethylase subfamily member that erases di- and tri-methyl groups from lysine 4 of histone H3. Emerging studies indicate that KDM5A is responsible for driving multiple human diseases, particularly cancers. In this review, we summarize the roles of KDM5A in human cancers, survey the field of KDM5A inhibitors including their anticancer activity and modes of action, and the current challenges and potential opportunities of this field.

Activation of the KDM5A/miRNA-495/YTHDF2/m6A-MOB3B axis facilitates prostate cancer progression

Background

Accumulating evidence supports that lysine-specific demethylase 5 (KDM5) family members act as oncogenic drivers. This study was performed to elucidate the potential effects of KDM5A on prostate cancer (PCa) progression via the miR-495/YTHDF2/m6A-MOB3B axis.

Methods

The expression of KDM5A, miR-495, YTHDF2 and MOB3B was validated in human PCa tissues and cell lines. Ectopic expression and knockdown experiments were developed in PCa cells to evaluate their effects on PCa cell proliferation, migration, invasion and apoptosis. Mechanistic insights into the interaction among KDM5A, miR-495, YTHDF2 and MOB3B were obtained after dual luciferase reporter, ChIP, and PAR-CLIP assays. Me-RIP assay was used to determine m6A modification level of MOB3B mRNA in PCa cells. Mouse xenograft models of PCa cells were also established to monitor the tumor growth.

Results

KDM5A was highly expressed in human PCa tissues and cell lines. Upregulated KDM5A stimulated PCa cell proliferation, migration and invasion, but reduced cell apoptosis. Mechanistically, KDM5A, as a H3K4me3 demethylase, bound to the miR-495 promoter, which led to inhibition of its transcription and expression. As a target of miR-495, YTHDF2 could inhibit MOB3B expression by recognizing m6A modification of MOB3B mRNA and inducing mRNA degradation. Furthermore, KDM5A was found to downregulate MOB3B expression, consequently augmenting PCa cell proliferation, migration and invasion in vitro and promoting tumor growth in vivo via the miR-495/YTHDF2 axis.

Conclusion

In summary, our study highlights the potential of histone demethylase KDM5A activity in enhancing PCa progression, and suggests KDM5A as a promising target for PCa treatment.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13046-020-01735-3.

The Promise for Histone Methyltransferase Inhibitors for Epigenetic Therapy in Clinical Oncology: A Narrative Review

Epigenetic processes are essential for normal development and the maintenance of tissue-specific gene expression in mammals. Changes in gene expression and malignant cellular transformation can result from disruption of epigenetic mechanisms, and global disruption in the epigenetic landscape is a key feature of cancer. The study of epigenetics in cancer has revealed that human cancer cells harbor both genetic alterations and epigenetic abnormalities that interplay at all stages of cancer development. Unlike genetic mutations, epigenetic aberrations are potentially reversible through epigenetic therapy, providing a therapeutically relevant treatment option. Histone methyltransferase inhibitors are emerging as an epigenetic therapy approach with great promise in the field of clinical oncology. The recent accelerated approval of the enhancer of zeste homolog 2 (EZH2; also known as histone-lysine N-methyltransferase EZH2) inhibitor tazemetostat for metastatic or locally advanced epithelioid sarcoma marks the first approval of such a compound for the treatment of cancer. Many other histone methyltransferase inhibitors are currently in development, some of which are being tested in clinical studies. This review focuses on histone methyltransferase inhibitors, highlighting their potential in the treatment of cancer. We also discuss the role for such epigenetic drugs in overcoming epigenetically driven drug resistance mechanisms, and their value in combination with other therapeutic approaches such as immunotherapy.

Discovery of a First-in-Class Protein Arginine Methyltransferase 6 (PRMT6) Covalent Inhibitor

Protein arginine methyltransferase 6 (PRMT6) plays important roles in several biological processes associated with multiple cancers. Well-characterized potent, selective, and cell-active PRMT6 inhibitors are invaluable tools for testing biological and therapeutic hypotheses. Although there are several known reversible PRMT6 inhibitors, covalent PRMT6 inhibitors have not been reported. Based on a cocrystal structure of PRMT6-MS023 (a type I PRMT inhibitor), we discovered the first potent and cell-active irreversible PRMT6 inhibitor, 4 (MS117). The covalent binding mode of compound 4 to PRMT6 was confirmed by mass spectrometry and kinetic studies and by a cocrystal structure. Compound 4 did not covalently modify other closely related PRMTs, potently inhibited PRMT6 in cells, and was selective for PRMT6 over other methyltransferases. We also developed two structurally similar control compounds, 5 (MS167) and 7 (MS168). We provide these valuable chemical tools to the scientific community for further studying PRMT6 physiological and pathophysiological functions.

Advances in histone demethylase KDM4 as cancer therapeutic targets

The KDM4 subfamily H3K9 histone demethylases are epigenetic regulators that control chromatin structure and gene expression by demethylating histone H3K9, H3K36, and H1.4K26. The KDM4 subfamily mainly consists of four proteins (KDM4A-D), all harboring the Jumonji C domain (JmjC) but with differential substrate specificities. KDM4A-C proteins also possess the double PHD and Tudor domains, whereas KDM4D lacks these domains. KDM4 proteins are overexpressed or deregulated in multiple cancers, cardiovascular diseases, and mental retardation and are thus potential therapeutic targets. Despite extensive efforts, however, there are very few KDM4-selective inhibitors. Defining the exact physiological and oncogenic functions of KDM4 demethylase will provide the foundation for the discovery of novel potent inhibitors. In this review, we focus on recent studies highlighting the oncogenic functions of KDM4s and the interplay between KDM4-mediated epigenetic and metabolic pathways in cancer. We also review currently available KDM4 inhibitors and discuss their potential as therapeutic agents for cancer treatment.

Peptidic transition state analogues as PRMT inhibitors

Protein arginine N-methyltransferases (PRMTs) methylate arginine residues in target proteins using the ubiquitous methyl donor S-adenosyl-l-methionine (AdoMet) as a cofactor. PRMTs play important roles in both healthy and disease states and as such inhibition of PRMTs has gained increasing interest. A primary challenge in the development of PRMT inhibitors is achieving specificity for the PRMT of interest as the active sites are highly conserved for all nine members of the PRMT family. Notably, PRMTs show very little redundancy in vivo due to their specific sets of protein substrates. However, relatively little is known about the interactions of PRMTs with their protein substrates that drive this substrate specificity. We here describe the extended application of a methodology recently developed in our group for the production of peptide-based transition state mimicking PRMT inhibitors. Using this approach, an adenosine moiety, mimicking that of the AdoMet cofactor, is covalently linked to the guanidine side chain of a target arginine residue contained in a peptidic fragment derived from a PRMT substrate protein. Using this approach, histone H4 tail peptide-based transition state mimics were synthesized wherein the adenosine group was linked to the Arg3 residue. H4R3 is a substrate for multiple PRMTs, including PRMT1 and PRMT6. The inhibition results obtained with these new H4-based transition state mimics show low micromolar IC₅₀ values against PRMT1 and PRMT6, indicating that the methodology is applicable to the broader family of PRMTs.

The Oncogenic Potential of SUV39H2: A Comprehensive and Perspective View

Epigenetic modifications at the histone level have attracted significant attention because of their roles in tumorigenesis. Suppressor of variegation 3-9 homolog 2 (SUV39H2, also known as KMT1B) is a member of the SUV39 subfamily of lysine methyltransferases (KMTs) that plays a significant role in histone H3-K9 di-/tri-methylation, transcriptional regulation and cell cycle. Overexpressions of SUV39H2 at gene, mRNA and protein levels are known to be associated with a range of cancers: leukemia, lymphomas, lung cancer, breast cancer, colorectal cancer, gastric cancer, hepatocellular cancer and so on. Accumulating evidence indicates that SUV39H2 acts as an oncogene and contributes to the initiation and progression of cancers. It could, therefore, be a promising target for anti-cancer treatment. In this review, we focus on the dysregulation of SUV39H2 in cancers, including its clinical prognostic predictor role, molecular mechanism involved in cancer occurrence and development, relevant inhibitors against cancer, and its epigenetic modification interaction with immunotherapy. A better understanding of the SUV39H2 will be beneficial to the development of molecular-targeted therapies in cancer.

SMYD3 promoter hypomethylation is associated with the risk of colorectal cancer

AIM

SMYD3 encodes histone lysine methyltransferase. The goal of our study was to investigate the association between SMYD3 methylation and colorectal cancer (CRC).

MATERIALS & METHODS

SMYD3 methylation was measured by quantitative methylation-specific PCR method in 117 pairs of CRC tumor and para-tumor tissues.

RESULTS

Significantly lower SMYD3 methylation was observed in CRC tumor tissues than para-tumor tissues (p = 0.002). Further subgroup analysis by clinical features showed that significantly lower SMYD3 methylation were only observed in the CRC patients with tumors of moderately and well differentiation, positive lymph node metastasis, and stage III + IV.

CONCLUSION

Our work reported for the first time that SMYD3 promoter hypomethylation was associated with CRC.

Significant association of PRMT6 hypomethylation with colorectal cancer

BACKGROUND

Protein arginine N-methyltransferase 6 (PRMT6) was deemed to be indispensable in the variety of biological processes. Upregulated PRMT6 was found in various human diseases including cancer. Herein, we investigated the performance of PRMT6 methylation in the diagnosis for CRC.

METHODS

A quantitative methylation-specific polymerase chain reaction (qMSP) method was used to measure PRMT6 promoter methylation. The percentage of methylated reference (PMR) was applied to represent gene methylation level.

RESULTS

Our data indicated that PRMT6 promoter methylation levels were significantly lower in CRC tissues than those in paired nontumor tissues (median PMR: 36.93% vs 63.12%, P = 1E-6) and normal intestinal tissues (median PMR: 36.93% vs 506.55%, P = 8E-12). We further examined the potential role of PRMT6 hypomethylation by the receiver operating characteristic (ROC) curve. Our results showed that the area under the curve (AUC) was 0.644 (95% CI = 0.596-0.733) between CRC tissues and paired nontumor tissues, 0.958 (95% CI = 0.919-0.998) between CRC tissues and normal intestinal tissues, and 0.899 (95% CI = 0.825-0.972) between paired nontumor tissues and normal intestinal tissues.

CONCLUSION

Our study firstly indicated that the hypomethylation of PRMT6 promoter could be a novel diagnostic biomarker for CRC.

A multiplatform approach identifies miR-152-3p as a common epigenetically regulated onco-suppressor in prostate cancer targeting TMEM97

Background

Prostate cancer (PCa) is a major cause of morbidity and mortality in men worldwide. MicroRNAs are globally downregulated in PCa, especially in poorly differentiated tumors. Nonetheless, the underlying mechanisms are still elusive. Herein, using combined analysis of microRNAs expression and genomewide DNA methylation, we aimed to identify epigenetically downregulated microRNAs in PCa.

Results

We found that miR-152-3p was underexpressed in PCa and that lower expression levels were associated with promoter hypermethylation in accordance with TCGA dataset analysis. Functional in vitro assays suggest that miR-152-3p suppresses cell viability and invasion potential, whereas it promotes cell cycle arrest at S and G2/M phases. Additionally, miR-152-3p expression was associated with longer disease-free survival in PCa patients from TCGA. Finally, TMEM97, which is overexpressed in PCa, was identified as a novel miR-152-3p target gene.

Conclusions

Our findings demonstrate the advantages of using a combinatory approach to identify microRNAs downregulated due to aberrant promoter methylation. MiR-152-3p downregulation and promoter methylation was found to be prevalent in primary PCa, which impairs its role in control of cell viability, cell cycle regulation and invasion.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0475-2) contains supplementary material, which is available to authorized users.

Histone methyltransferase PRMT6 plays an oncogenic role of in prostate cancer

Prostate cancer (PCa) is a major cause of morbidity and mortality. Until now the specific role of histone methyltransferases (HMTs) deregulated expression/activity in PCa is poorly understood. Herein we aimed to uncover the potential oncogenic role of PRMT6 in prostate carcinogenesis. PRMT6 overexpression was confirmed in PCa, at transcript and protein level. Stable PRMT6 knockdown in PC-3 cells attenuated malignant phenotype, increasing apoptosis and decreasing cell viability, migration and invasion. PRMT6 silencing was associated with decreased H3R2me2a levels and increased MLL and SMYD3 expression. PRMT6 silencing increased p21, p27 and CD44 and decreased MMP-9 expression and was associated with PI3K/AKT/mTOR downregulation and increased AR signaling pathway. In Sh-PRMT6 cells, AR restored expression might re-sensitized cells to androgen deprivation therapy, impacting in clinical management of castration-resistant PCa (CRPC). PRMT6 plays an oncogenic role in PCa and predicts for more clinically aggressive disease, constituting a potential target for patients with CRPC.

Histone demethylase KDM5A inhibits glioma cells migration and invasion by down regulating ZEB1

Malignant gliomas are highly lethal cancers worldwide as tumor cells infiltrate to healthy brain tissue invariably. Histone demethylase KDM5A as an oncogene or tumor suppressor in cancer still has been controversial. KDM5A may have a different function in different type cancer cells. However, the specific roles of KDM5A in the progression of glioma remain undiscovered. In this study, we found that compared with primary glioma, metastasis glioma had low KDM5A levels. Besides, lower KDM5A levels were linked to poor survival in glioma cancer patients, indicating that KDM5A is a new prognostic marker for glioma cancer. KDM5A knockdown increases the invasive abilities of glioma cancer cells and changes the EMT markers. A mechanism, KDM5A suppressing the expression of ZEB1, and its catalytic activity is indispensable for anti-invasive function. Our study revealed that histone demethylase KDM5A exerts anti-invasiveness function partly through repressing oncogenic ZEB1 expression by mediating H3K4 demethylation. We also demonstrate that ZEB1 play a crucial role in KDM5A induced function. In summary, in this study, we showed that KDM5A has a crucial role in glioma and therefore may serve as a novel therapeutic target and prognostic marker in glioma.

High immunoexpression of Ki67, EZH2, and SMYD3 in diagnostic prostate biopsies independently predicts outcome in patients with prostate cancer

INTRODUCTION

Overtreatment is a major concern in patients with prostate cancer (PCa). Prognostic biomarkers discriminating indolent from aggressive disease in prostate biopsy are urgently needed. We aimed to evaluate the prognostic value of Ki67, EZH2, LSD1, and SMYD3 immunoexpression in diagnostic biopsies from a cohort of PCa patients with long term follow-up.

MATERIALS AND METHODS

A series of 189 consecutive prostate biopsies diagnosed with PCa (1997-2001) in a cancer center was included in the study, with follow-up last updated in November 2016. Biopsies were reviewed and graded according to 2016 WHO criteria. Immunohistochemistry was performed in the most representative block. Nuclear staining was assessed using digital image analysis. Study outcomes included disease-specific, disease-free, and progression-free survival. Statistical analysis was tabulated using SPSS version 22.0. Survival curves and hazard ratios (HRs) were estimated using Kaplan-Meyer and Cox-regression models, respectively. Statistical significance was set at P<0.05.

RESULTS

The proportion of patients who completed the study was 177/189 (94%). In univariable analysis, high Ki67, EZH2, and SMYD3 immunoexpression associated with significantly worse disease-specific survival (HR = 1.86, 95% CI: 1.05-3.29; HR = 1.87, 95% CI: 1.10-3.27; HR = 2.68, 95% CI: 1.02-7.92). In multivariable analysis, the 3 biomarkers displayed significantly worse DSS adjusted for CAPRA score (HR = 1.78, 95% CI: 1.01-3.16; HR = 1.93, 95% CI: 1.12-3.32; HR = 2.71, 95% CI: 1.04-7.10). Among patients with low/intermediate risk CAPRA score, high Ki67 immunoexpression identified those more prone to experience disease recurrence (HR = 9.20, 95% CI: 1.27-66.44) and progression (HR = 2.97, 95% CI: 1.05-8.43).

CONCLUSIONS

High Ki67, EZH2, and SMYD3 immunoexpression, adjusted for standard clinicopathological parameters, independently predicts outcome in patients with PCa, at diagnosis. This might assist in discriminating indolent from aggressive PCa, improving treatment selection.

JMJD8 is a novel endoplasmic reticulum protein with a JmjC domain

Jumonji C (JmjC) domain-containing proteins have been shown to regulate cellular processes by hydroxylating or demethylating histone and non-histone targets. JMJD8 belongs to the JmjC domain-only family that was recently shown to be involved in angiogenesis and TNF-induced NF-κB signaling. Here, we employed bioinformatic analysis and immunofluorescence microscopy to examine the physiological properties of JMJD8. We demonstrated that JMJD8 localizes to the lumen of endoplasmic reticulum and that JMJD8 forms dimers or oligomers in vivo. Furthermore, we identified potential JMJD8-interacting proteins that are known to regulate protein complex assembly and protein folding. Taken together, this work demonstrates that JMJD8 is the first JmjC domain-containing protein found in the lumen of the endoplasmic reticulum that may function in protein complex assembly and protein folding.

Ganoderma lucidum polysaccharide inhibits prostate cancer cell migration via the protein arginine methyltransferase 6 signaling pathway

Prostate cancer is one of the most common types of malignant tumor of men worldwide and the incidence and mortality rate is gradually increasing. At present, the molecular mechanisms of growth and migration in human prostate cancer have not been completely elucidated. Studies have demonstrated that Ganoderma lucidum polysaccharides (GLP) can inhibit cancer. Therefore the present study investigated the effect and molecular mechanism of GLP on cell growth and migration of LNCaP human prostate cancer cells. LNCaP cells were transfected with either a protein arginine methyltransferase 6 (PRMT6) overexpression plasmid or PRMT6 small interfering (si)RNA. The cell growth and migration, and the expression of PRMT6 signaling-associated proteins, were investigated following treatment with 5 and 20 µg/ml GLP. The results demonstrated that GLP inhibited cell growth, induced cell cycle arrest, decreased PRMT6, cyclin-dependent kinase 2 (CDK2), focal adhesion kinase (FAK) and steroid receptor coactivator, (SRC) expression, and increased p21 expression in LNCaP cells, as determined by using a Coulter counter, flow cytometry, and reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. Furthermore, GLP significantly inhibited cell migration, as determined by Transwell migration and scratch assays, and altered CDK2, FAK, SRC and p21 expression in LNCaP cells transfected with the PRMT6 overexpression plasmid. By contrast, PRMT6 knockdown by siRNA reduced the effect of GLP on cell migration. These results indicate that GLP was effective in inhibiting cell growth, the cell cycle and cell migration, and the suppressive effect of GLP on cell migration may occur via the PRMT6 signaling pathway. Therefore, it is suggested that GLP may act as a tumor suppressor with applications in the treatment of prostate cancer. The results of the present study provide both the preliminary theoretical and experimental basis for the investigation of GLP as a therapeutic agent.

Epigenetic Signature: A New Player as Predictor of Clinically Significant Prostate Cancer (PCa) in Patients on Active Surveillance (AS)

Widespread prostate-specific antigen (PSA) testing notably increased the number of prostate cancer (PCa) diagnoses. However, about 30% of these patients have low-risk tumors that are not lethal and remain asymptomatic during their lifetime. Overtreatment of such patients may reduce quality of life and increase healthcare costs. Active surveillance (AS) has become an accepted alternative to immediate treatment in selected men with low-risk PCa. Despite much progress in recent years toward identifying the best candidates for AS in recent years, the greatest risk remains the possibility of misclassification of the cancer or missing a high-risk cancer. This is particularly worrisome in men with a life expectancy of greater than 10–15 years. The Prostate Cancer Research International Active Surveillance (PRIAS) study showed that, in addition to age and PSA at diagnosis, both PSA density (PSA-D) and the number of positive cores at diagnosis (two compared with one) are the strongest predictors for reclassification biopsy or switching to deferred treatment. However, there is still no consensus upon guidelines for placing patients on AS. Each institution has its own protocol for AS that is based on PRIAS criteria. Many different variables have been proposed as tools to enrol patients in AS: PSA-D, the percentage of freePSA, and the extent of cancer on biopsy (number of positive cores or percentage of core involvement). More recently, the Prostate Health Index (PHI), the 4 Kallikrein (4K) score, and other patient factors, such as age, race, and family history, have been investigated as tools able to predict clinically significant PCa. Recently, some reports suggested that epigenetic mapping differs significantly between cancer patients and healthy subjects. These findings indicated as future prospect the use of epigenetic markers to identify PCa patients with low-grade disease, who are likely candidates for AS. This review explores literature data about the potential of epigenetic markers as predictors of clinically significant disease.

Inhibitors of Protein Methyltransferases and Demethylases

Post-translational modifications of histones by protein methyltransferases (PMTs) and histone demethylases (KDMs) play an important role in the regulation of gene expression and transcription and are implicated in cancer and many other diseases. Many of these enzymes also target various nonhistone proteins impacting numerous crucial biological pathways. Given their key biological functions and implications in human diseases, there has been a growing interest in assessing these enzymes as potential therapeutic targets. Consequently, discovering and developing inhibitors of these enzymes has become a very active and fast-growing research area over the past decade. In this review, we cover the discovery, characterization, and biological application of inhibitors of PMTs and KDMs with emphasis on key advancements in the field. We also discuss challenges, opportunities, and future directions in this emerging, exciting research field.

Androgen receptor regulation by histone methyltransferase Suppressor of variegation 3-9 homolog 2 and Melanoma antigen-A11

Androgen receptor (AR) transcriptional activity depends on interactions between the AR NH₂-terminal region and transcriptional coregulators. A yeast two-hybrid screen of a human testis library using predicted α-helical NH₂-terminal fragment AR-(370-420) as bait identified suppressor of variegation 3-9 homolog 2 (SUV39H2) histone methyltransferase as an AR interacting protein. SUV39H2 interaction with AR and the AR coregulator, melanoma antigen-A11 (MAGE-A11), was verified in two-hybrid, in vitro glutathione S-transferase affinity matrix and coimmunoprecipitation assays. Fluorescent immunocytochemistry colocalized SUV39H2 and AR in the cytoplasm without androgen, in the nucleus with androgen, and with MAGE-A11 in the nucleus independent of androgen. Chromatin immunoprecipitation using antibodies raised against SUV39H2 demonstrated androgen-dependent recruitment of AR and SUV39H2 to the androgen-responsive upstream enhancer of the prostate-specific antigen gene. SUV39H2 functioned cooperatively with MAGE-A11 to increase androgen-dependent AR transcriptional activity. SUV39H2 histone methyltransferase is an AR coactivator that increases androgen-dependent transcriptional activity through interactions with AR and MAGE-A11.

Epigenetic therapy in urologic cancers: an update on clinical trials

Epigenetic dysregulation is one of many factors that contribute to cancer development and progression. Numerous epigenetic alterations have been identified in urologic cancers including histone modifications, DNA methylation changes, and microRNA expression. Since these changes are reversible, efforts are being made to develop epigenetic drugs that restore the normal epigenetic patterns of cells, and many clinical trials are already underway to test their clinical potential. In this review we analyze multiple clinical trials (n=51) that test the efficacy of these drugs in patients with urologic cancers. The most frequently used epigenetic drugs were histone deacetylase inhibitors followed by antisense oligonucleotides, DNA methyltransferase inhibitors and histone demethylase inhibitors, the last of which are only being tested in prostate cancer. In more than 50% of the clinical trials considered, epigenetic drugs were used as part of combination therapy, which achieved the best results. The epigenetic regulation of some cancers is still matter of research but will undoubtedly open a window to new therapeutic approaches in the era of personalized medicine. The future of therapy for urological malignancies is likely to include multidrug regimens in which epigenetic modifying drugs will play an important role.

P110β Inhibition Reduces Histone H3K4 Di-Methylation in Prostate Cancer

INTRODUCTION AND AIMS

Epigenetic alteration plays a major role in the development and progression of human cancers, including prostate cancer. Histones are the key factors in modulating gene accessibility to transcription factors and post-translational modification of the histone N-terminal tail including methylation is associated with either transcriptional activation (H3K4me2) or repression (H3K9me3). Furthermore, phosphoinositide 3-kinase (PI3 K) signaling and the androgen receptor (AR) are the key determinants in prostate cancer development and progression. We recently showed that prostate-targeted nano-micelles loaded with PI3 K/p110beta specific inhibitor TGX221 blocked prostate cancer growth in vitro and in vivo. Our objective of this study was to determine the role of PI3 K signaling in histone methylation in prostate cancer, with emphasis on histone H3K4 methylation.

METHODS

PI3 K non-specific inhibitor LY294002 and p110beta-specific inhibitor TGX221 were used to block PI3 K/p110beta signaling. The global levels of H3K4 and H3K9 methylation in prostate cancer cells and tissue specimens were evaluated by Western blot assay and immunohistochemical staining. A synthetic androgen R1881 was used to stimulate AR activity in prostate cancer cells. A castration-resistant prostate cancer (CRPC) specific human tissue microarray (TMA) was used to assess the global levels of H3K4me2 methylation by immunostaining approach.

RESULTS

Our data revealed that H3K4me2 levels were significantly elevated after androgen stimulation. With RNA silencing and pharmacology approaches, we further defined that inhibition of PI3 K/p110beta activity through gene-specific knocking down and small chemical inhibitor TGX221 abolished androgen-stimulated H3K4me2 methylation. Consistently, prostate cancer-targeted delivery of TGX221 in vivo dramatically reduced the global levels of H3K4me2 as assessed by immunohistochemical staining on tissue section of mouse xenografts from CRPC cell lines 22RV1 and C4-2. Finally, immunostaining data revealed a strong H3K4me2 immunosignal in CRPC tissues compared to primary tumors and benign prostate tissues.

CONCLUSIONS

Taken together, our results suggest that PI3 K/p110beta-dependent signaling is involved in androgen-stimulated H3K4me2 methylation in prostate cancer, which might be used as a novel biomarker for disease prognosis and targeted therapy. Prostate 77:299-308, 2017. © 2016 Wiley Periodicals, Inc.

Epigenomic Regulation of Androgen Receptor Signaling: Potential Role in Prostate Cancer Therapy

Androgen receptor (AR) signaling remains the major oncogenic pathway in prostate cancer (PCa). Androgen-deprivation therapy (ADT) is the principle treatment for locally advanced and metastatic disease. However, a significant number of patients acquire treatment resistance leading to castration resistant prostate cancer (CRPC). Epigenetics, the study of heritable and reversible changes in gene expression without alterations in DNA sequences, is a crucial regulatory step in AR signaling. We and others, recently described the technological advance Chem-seq, a method to identify the interaction between a drug and the genome. This has permitted better understanding of the underlying regulatory mechanisms of AR during carcinogenesis and revealed the importance of epigenetic modifiers. In screening for new epigenomic modifiying drugs, we identified SD-70, and found that this demethylase inhibitor is effective in CRPC cells in combination with current therapies. The aim of this review is to explore the role of epigenetic modifications as biomarkers for detection, prognosis, and risk evaluation of PCa. Furthermore, we also provide an update of the recent findings on the epigenetic key processes (DNA methylation, chromatin modifications and alterations in noncoding RNA profiles) involved in AR expression and their possible role as therapeutic targets.

Therapeutical potential of deregulated lysine methyltransferase SMYD3 as a safe target for novel anticancer agents

INTRODUCTION

SET and MYND domain containing-3 (SMYD3) is a member of the lysine methyltransferase family of proteins, and plays an important role in the methylation of various histone and non-histone targets. Proper functioning of SMYD3 is very important for the target molecules to determine their different roles in chromatin remodeling, signal transduction and cell cycle control. Due to the abnormal expression of SMYD3 in tumors, it is projected as a prognostic marker in various solid cancers. Areas covered: Here we elaborate on the general information, structure and the pathological role of SMYD3 protein. We summarize the role of SMYD3-mediated protein interactions in oncology pathways, mutational effects and regulation of SMYD3 in specific types of cancer. The efficacy and mechanisms of action of currently available SMYD3 small molecule inhibitors are also addressed. Expert opinion: The findings analyzed herein demonstrate that aberrant levels of SMYD3 protein exert tumorigenic effects by altering the epigenetic regulation of target genes. The partial involvement of SMYD3 in some distinct pathways provides a vital opportunity in targeting cancer effectively with fewer side effects. Further, identification and co-targeting of synergistic oncogenic pathways is suggested, which could provide much more beneficial effects for the treatment of solid cancers.

Epigenetic disruption of miR-130a promotes prostate cancer by targeting SEC23B and DEPDC1

MicroRNAs (miRNAs) are small, non-coding RNAs that mediate post-transcriptional gene silencing, fine tuning gene expression. In an initial screen, miRNAs were found to be globally down-regulated in prostate cancer (PCa) cell lines and primary tumours. Exposure of PCa cell lines to a demethylating agent, 5-Aza-CdR resulted in an increase in the expression levels of miRNAs in general. Using stringent filtering criteria miR-130a was identified as the most promising candidate and selected for validation analyses in our patient series. Down-regulation of miR-130a was associated with promoter hypermethylation. MiR-130a methylation levels discriminated PCa from non-malignant tissues (AUC = 0.956), and urine samples revealed high specificity for non-invasive detection of patients with PCa (AUC = 0.89). Additionally, repressive histone marks were also found in the promoter of miR-130a. Over-expression of miR-130a in PCa cells reduced cell viability and invasion capability, and increased apoptosis. Putative targets of miR-130a were assessed by microarray expression profiling and DEPD1C and SEC23B were selected for validation. Silencing of both genes resembled the effect of over-expressing miR-130a in PCa cells. Our data indicate that miR-130a is an epigenetically regulated miRNA involved in regulation of key molecular and phenotypic features of prostate carcinogenesis, acting as a tumour suppressor miRNA.