Regulation of the androgen receptor by SET9-mediated methylation

Androgen receptor post-translational modifications and their implications for pathology

A major mechanism to modulate the biological activities of the androgen receptor (AR) involves a growing number of post-translational modifications (PTMs). In this review we summarise the current knowledge on the structural and functional impact of PTMs that affect this major transcription factor. Next, we discuss the cross-talk between these different PTMs and the presence of clusters of modified residues in the AR protein. Finally, we discuss the implications of these covalent modifications for the aetiology of diseases such as spinal and bulbar muscular atrophy (Kennedy's disease) and prostate cancer, and the perspectives for pharmacological intervention.

Regulating Androgen Receptor Function in Prostate Cancer: Exploring the Diversity of Post-Translational Modifications

Androgen receptor (AR) transcriptional activity significantly influences prostate cancer (PCa) progression. In addition to ligand stimulation, AR transcriptional activity is also influenced by a variety of post-translational modifications (PTMs). A number of oncogenes and tumor suppressors have been observed leveraging PTMs to influence AR activity. Subjectively targeting these post-translational modifiers based on their impact on PCa cell proliferation is a rapidly developing area of research. This review elucidates the modifiers, contextualizes the effects of these PTMs on AR activity, and connects these cellular interactions to the progression of PCa.

Acetylation of nuclear receptors in health and disease: an update

Lysine acetylation is a common reversible post-translational modification of proteins that plays a key role in regulating gene expression. Nuclear receptors (NRs) include ligand-inducible transcription factors and orphan receptors for which the ligand is undetermined, which together regulate the expression of genes involved in development, metabolism, homeostasis, reproduction and human diseases including cancer. Since the original finding that the ERα, AR and HNF4 are acetylated, we now understand that the vast majority of NRs are acetylated and that this modification has profound effects on NR function. Acetylation sites are often conserved and involve both ordered and disordered regions of NRs. The acetylated residues function as part of an intramolecular signalling platform intersecting phosphorylation, methylation and other modifications. Acetylation of NR has been shown to impact recruitment into chromatin, co-repressor and coactivator complex formation, sensitivity and specificity of regulation by ligand and ligand antagonists, DNA binding, subcellular distribution and transcriptional activity. A growing body of evidence in mice indicates a vital role for NR acetylation in metabolism. Additionally, mutations of the NR acetylation site occur in human disease. This review focuses on the role of NR acetylation in coordinating signalling in normal physiology and disease.

Methylation of the JMJD2B epigenetic regulator differentially affects its ability to coactivate the ETV1 and JUN transcription factors

OBJECTIVES

Jumonji C domain-containing (JMJD) 2B (JMJD2B) is a transcriptional cofactor and histone demethylase that is involved in prostate cancer formation. However, how its function is regulated by posttranslational modification has remained elusive. Hence, we examined if JMJD2B would be regulated by lysine methylation.

METHODS

Through in vitro methylation assays and Western blotting with methyl-lysine specific antibodies, we analyzed lysine methylation within JMJD2B. Identified methylated lysine residues were mutated to arginine residues and the respective impact on JMJD2B transcriptional activity measured with a reporter gene assay in human LNCaP prostate cancer cells.

RESULTS

We discovered that JMJD2B is methylated on up to six different lysine residues. Further, we identified the suppressor of variegation 3-9/enhancer of zeste/trithorax (SET) domain-containing protein 7/9 (SET7/9) as the methyltransferase being responsible for this posttranslational modification. Mutating the methylation sites in JMJD2B to arginine residues led to diminished coactivation of the Ju-nana (JUN) transcription factor, which is a known oncogenic protein in prostate tumors. In contrast, methylation of JMJD2B had no impact on its ability to coactivate another transcription factor associated with prostate cancer, the DNA-binding protein E26 transformation-specific (ETS) variant 1 (ETV1). Consistent with a potential joint action of JMJD2B, SET7/9 and JUN in prostate cancer, the expression of JMJD2B in human prostate tumors was positively correlated with both SET7/9 and JUN levels.

CONCLUSIONS

The identified SET7/9-mediated methylation of JMJD2B appears to impact its cooperation with selected interacting transcription factors in prostate cancer cells. Given the implicated roles of JMJD2B beyond prostate tumorigenesis, SET7/9-mediated methylation of JMJD2B possibly also influences the development of other cancers, while its impairment might have relevance for obesity or a global developmental delay that can be elicited by reduced JMJD2B activity.

(R)-PFI-2 Analogues as Substrates and Inhibitors of Histone Lysine Methyltransferase SETD7

(R)-PFI-2 is a histone substrate-competitive inhibitor of the human histone lysine monomethyltransferase SETD7. Aimed at developing potent inhibitors of SETD7 that can also act as small molecule substrates, we replaced the pyrrolidine ring of (R)-PFI-2 with several side chains bearing nucleophilic functional groups. We explored the inhibitory activity of 20 novel (R)-PFI-2 analogues, and found that the most potent analogue has a hydroxyethyl side chain (7). SETD7's ability to catalyse methylation of (R)-PFI-2-based small molecules was evaluated by mass spectrometric assays, and we observed efficient methylation of analogues bearing lysine mimicking nucleophilic amines. The optimal side chain was found to be an aminoethyl group (1), which was surprisingly also dimethylated by SETD7. The work demonstrates that small molecules can act as both substrates and inhibitors of biomedically important SETD7.

Mechanistic Insights on Localized to Metastatic Prostate Cancer Transition and Therapeutic Opportunities

Prostate cancer is the most common non-cutaneous cancer among American men. Multiple mechanisms are involved in tumorigenesis and progression to metastases. While androgen deprivation therapy remains the cornerstone of treatment, progression to castration-resistant disease becomes inevitable. Aberrant pathway activations of PI3K/AKT due to PTEN loss, epithelial-mesenchymal transition pathways, homologous recombination repair, and DNA repair pathway mechanisms of resistance and cross-talk lead to opportunities for therapeutic targeting in metastatic castration-resistant prostate cancer. This review focuses on mechanisms of progression and key trials that evaluate the drugs and combinations that exploit these pathways.

Methylation of the epigenetic JMJD2D protein by SET7/9 promotes prostate tumorigenesis

How the function of the JMJD2D epigenetic regulator is regulated or whether it plays a role in prostate cancer has remained elusive. We found that JMJD2D was overexpressed in prostate tumors, stimulated prostate cancer cell growth and became methylated by SET7/9 on K427. Mutation of this lysine residue in JMJD2D reduced the ability of DU145 prostate cancer cells to grow, invade and form tumors and elicited extensive transcriptomic changes. This included downregulation of CBLC, a ubiquitin ligase gene with hitherto unknown functions in prostate cancer, and upregulation of PLAGL1, a transcription factor with reported tumor suppressive characteristics in the prostate. Bioinformatic analyses indicated that CBLC expression was elevated in prostate tumors. Further, downregulation of CBLC largely phenocopied the effects of the K427 mutation on DU145 cells. In sum, these data have unveiled a novel mode of regulation of JMJD2D through lysine methylation, illustrated how this can affect oncogenic properties by influencing expression of the CBLC gene, and established a pro-tumorigenic role for CBLC in the prostate. A corollary is that JMJD2D and CBLC inhibitors could have therapeutic benefits in the treatment of prostate and possibly other cancers.

SET7/9-mediated methylation affects oncogenic functions of histone demethylase JMJD2A

The histone demethylase JMJD2A/KDM4A facilitates prostate cancer development, yet how JMJD2A function is regulated has remained elusive. Here, we demonstrate that SET7/9-mediated methylation on 6 lysine residues modulated JMJD2A. Joint mutation of these lysine residues suppressed JMJD2A's ability to stimulate the MMP1 matrix metallopeptidase promoter upon recruitment by the ETV1 transcription factor. Mutation of just 3 methylation sites (K505, K506, and K507) to arginine residues (3xR mutation) was sufficient to maximally reduce JMJD2A transcriptional activity and also decreased its binding to ETV1. Introduction of the 3xR mutation into DU145 prostate cancer cells reduced in vitro growth and invasion and also severely compromised tumorigenesis. Consistently, the 3xR genotype caused transcriptome changes related to cell proliferation and invasion pathways, including downregulation of MMP1 and the NPM3 nucleophosmin/nucleoplasmin gene. NPM3 downregulation phenocopied and its overexpression rescued, to a large degree, the 3xR mutation in DU145 cells, suggesting that NPM3 was a seminal downstream effector of methylated JMJD2A. Moreover, we found that NPM3 was overexpressed in prostate cancer and might be indicative of disease aggressiveness. SET7/9-mediated lysine methylation of JMJD2A may aggravate prostate tumorigenesis in a manner dependent on NPM3, implying that the SET7/9→JMJD2A→NPM3 axis could be targeted for therapy.

SETD7 functions as a transcription repressor in prostate cancer via methylating FOXA1

Dysregulation of histone lysine methyltransferases and demethylases is one of the major mechanisms driving the epigenetic reprogramming of transcriptional networks in castration-resistant prostate cancer (CRPC). In addition to their canonical histone targets, some of these factors can modify critical transcription factors, further impacting oncogenic transcription programs. Our recent report demonstrated that LSD1 can demethylate the lysine 270 of FOXA1 in prostate cancer (PCa) cells, leading to the stabilization of FOXA1 chromatin binding. This process enhances the activities of the androgen receptor and other transcription factors that rely on FOXA1 as a pioneer factor. However, the identity of the methyltransferase responsible for FOXA1 methylation and negative regulation of the FOXA1-LSD1 oncogenic axis remains unknown. SETD7 was initially identified as a transcriptional activator through its methylation of histone 3 lysine 4, but its function as a methyltransferase on nonhistone substrates remains poorly understood, particularly in the context of PCa progression. In this study, we reveal that SETD7 primarily acts as a transcriptional repressor in CRPC cells by functioning as the major methyltransferase targeting FOXA1-K270. This methylation disrupts FOXA1-mediated transcription. Consistent with its molecular function, we found that SETD7 confers tumor suppressor activity in PCa cells. Moreover, loss of SETD7 expression is significantly associated with PCa progression and tumor aggressiveness. Overall, our study provides mechanistic insights into the tumor-suppressive and transcriptional repression activities of SETD7 in mediating PCa progression and therapy resistance.

Lysine N-methyltransferase SETD7 promotes bladder cancer progression and immune escape via STAT3/PD-L1 cascade

Background: The immunotherapy sensitivity of patients with bladder cancer (BCa) remains low. As the role of protein methylation in tumorigenesis and development becomes clearer, the role of lysine N-methyltransferase SET domain containing 7 (SETD7) in the progression and immune escape of BCa is worth studying. Methods: The correlation between lysine methyltransferase family and prognosis or immunotheray sensitivity of BCa patients were analyzed, and SETD7 was screened out because of the significant correlation between its expression and survival data or immunotherapy sensitivity. The expression of SETD7 in BCa tissues and cell lines were explored. The functions of SETD7 were investigated by proliferation and migration assays. The role of SETD7 in BCa immune escape was validated by analyzing the correlation between SETD7 expression and tumor microenvironment (TME)-related indicators. The results were further confirmed by conducting BCa cell-CD8+ T cell co-culture assays and tumorigenesis experiment in human immune reconstitution NOG mice (HuNOG mice). Bioinformatic prediction, CO-IP, qRT-PCR, and western blot were used to validate the SETD7/STAT3/PD-L1 cascade. Results: SETD7 was highly expressed in BCa, and it was positively associated with high histological grade and worse prognosis. SETD7 promoted the proliferation and migration of BCa cells. The results of bioinformatics, in vitro co-culture, and in vivo tumorigenesis assays showed that SETD7 could inhibit the chemotoxis and cytotoxicity of CD8+ T cells in BCa TME. Mechanistically, bioinformatics analysis, CO-IP assay, qRT-PCR, and western blot results indicated that SETD7 could increase the expression of PD-L1 via binding and promoting STAT3. Conclusions: Taken together, SETD7 indicated poor prognosis and promoted the progression and immune escape of BCa cells. It has great potential to act as a new indicator for BCa diagnosis and treatment, especially immunotherapy.

Methyltransferase Set7/9 as a Multifaceted Regulator of ROS Response

Reactive oxygen species (ROS) induce multiple signaling cascades in the cell and hence play an important role in the regulation of the cell's fate. ROS can cause irreversible damage to DNA and proteins resulting in cell death. Therefore, finely tuned regulatory mechanisms exist in evolutionarily diverse organisms that are aimed at the neutralization of ROS and its consequences with respect to cellular damage. The SET domain-containing lysine methyltransferase Set7/9 (KMT7, SETD7, SET7, SET9) post-translationally modifies several histones and non-histone proteins via monomethylation of the target lysines in a sequence-specific manner. In cellulo, the Set7/9-directed covalent modification of its substrates affects gene expression, cell cycle, energy metabolism, apoptosis, ROS, and DNA damage response. However, the in vivo role of Set7/9 remains enigmatic. In this review, we summarize the currently available information regarding the role of methyltransferase Set7/9 in the regulation of ROS-inducible molecular cascades in response to oxidative stress. We also highlight the in vivo importance of Set7/9 in ROS-related diseases.

Epigenetic Modifications in Prostate Cancer Metastasis and Microenvironment

The gradual evolution of prostate tissue from benign tumor to malignant lesion or distant metastasis is driven by intracellular epigenetic changes and the tumor microenvironment remodeling. With the continuous study of epigenetic modifications, these tumor-driving forces are being discovered and are providing new treatments for cancer. Here we introduce the classification of epigenetic modification and highlight the role of epigenetic modification in tumor remodeling and communication of the tumor microenvironment.

The catalytic domains of all human KDM5 JmjC demethylases catalyse N-methyl arginine demethylation

The demethylation of Nε -methyllysine residues on histones by Jumonji-C lysine demethylases (JmjC-KDMs) has been established. A subset of JmjC-KDMs has also been reported to have Nω -methylarginine residue demethylase (RDM) activity. Here, we describe biochemical screening studies, showing that the catalytic domains of all human KDM5s (KDM5A-KDM5D), KDM4E and, to a lesser extent, KDM4A/D, have both KDM and RDM activities with histone peptides. Ras GTPase-activating protein-binding protein 1 peptides were shown to be RDM substrates for KDM5C/D. No RDM activity was observed with KDM1A and the other JmjC-KDMs tested. The results highlight the potential of JmjC-KDMs to catalyse reactions other than Nε -methyllysine demethylation. Although our study is limited to peptide fragments, the results should help guide biological studies investigating JmjC functions.

The epigenetic function of androgen receptor in prostate cancer progression

Androgen and androgen deprivation (castration) therapies, including androgen receptor antagonists, are clinically used to treat patients with prostate cancer. However, most hormone-dependent prostate cancer patients progress into a malignant state with loss of hormone-dependency, known as castration (drug)-resistant prostate cancer (CRPC), after prolong androgen-based treatments. Even in the CRPC state with irreversible malignancy, androgen receptor (AR) expression is detectable. An epigenetic transition to CRPC induced by the action of AR-mediated androgen could be speculated in the patients with prostate cancer. Androgen receptors belongs to the nuclear receptor superfamily with 48 members in humans, and acts as a ligand-dependent transcriptional factor, leading to local chromatin reorganization for ligand-dependent gene regulation. In this review, we discussed the transcriptional/epigenetic regulatory functions of AR, with emphasis on the clinical applications of AR ligands, AR protein co-regulators, and AR RNA coregulator (enhancer RNA), especially in chromatin reorganization, in patients with prostate cancer.

SETD7 Expression Is Associated with Breast Cancer Survival Outcomes for Specific Molecular Subtypes: A Systematic Analysis of Publicly Available Datasets

SETD7 is a lysine N-methyltransferase that targets many proteins important in breast cancer (BC). However, its role and clinical significance remain unclear. Here, we used online tools and multiple public datasets to explore the predictive potential of SETD7 expression (high or low quartile) considering BC subtype, grade, stage, and therapy. We also investigated overrepresented biological processes associated with its expression using TCGA-BRCA data. SETD7 expression was highest in the Her2 (ERBB2)-enriched molecular subtype and lowest in the basal-like subtype. For the basal-like subtype specifically, higher SETD7 was consistently correlated with worse recurrence-free survival (p < 0.009). High SETD7-expressing tumours further exhibited a higher rate of ERBB2 mutation (20% vs. 5%) along with a poorer response to anti-Her2 therapy. Overall, high SETD7-expressing tumours showed higher stromal and lower immune scores. This was specifically related to higher counts of cancer-associated fibroblasts and endothelial cells, but lower B and T cell signatures, especially in the luminal A subtype. Genes significantly associated with SETD7 expression were accordingly overrepresented in immune response processes, with distinct subtype characteristics. We conclude that the prognostic value of SETD7 depends on the BC subtype and that SETD7 may be further explored as a potential treatment-predictive marker for immune checkpoint inhibitors.

The Epigenetic Regulation of Nonhistone Proteins by SETD7: New Targets in Cancer

Epigenetic modifications are essential mechanism by which to ensure cell homeostasis. One such modification is lysine methylation of nonhistone proteins by SETD7, a mono-methyltransferase containing SET domains. SETD7 methylates over 30 proteins and is thus involved in various classical pathways. As such, SETD7 has been implicated in both the basic functions of normal tissues but also in several pathologies, such as cancers. In this review, we summarize the current knowledge of SETD7 substrates, especially transcriptional-related proteins and enzymes, and their putative roles upon SETD7-mediated methylation. We focus on the role of SETD7 in cancers, and speculate on the possible points of intervention and areas for future research.

Exploring the Role of Posttranslational Modifications in Spinal and Bulbar Muscular Atrophy

Spinal and Bulbar Muscular Atrophy (SBMA) is an X-linked adult-onset progressive neuromuscular disease that affects the spinal and bulbar motor neurons and skeletal muscles. SBMA is caused by expansion of polymorphic CAG trinucleotide repeats in the Androgen Receptor (AR) gene, resulting in expanded glutamine tract in the AR protein. Polyglutamine (polyQ) expansion renders the mutant AR protein toxic, resulting in the formation of mutant protein aggregates and cell death. This classifies SBMA as one of the nine known polyQ diseases. Like other polyQ disorders, the expansion of the polyQ tract in the AR protein is the main genetic cause of the disease; however, multiple other mechanisms besides the polyQ tract expansion also contribute to the SBMA disease pathophysiology. Posttranslational modifications (PTMs), including phosphorylation, acetylation, methylation, ubiquitination, and SUMOylation are a category of mechanisms by which the functionality of AR has been found to be significantly modulated and can alter the neurotoxicity of SBMA. This review summarizes the different PTMs and their effects in regulating the AR function and discusses their pathogenic or protective roles in context of SBMA. This review also includes the therapeutic approaches that target the PTMs of AR in an effort to reduce the mutant AR-mediated toxicity in SBMA.

A Systematic Review to Define the Multi-Faceted Role of Lysine Methyltransferase SETD7 in Cancer

Histone–lysine N-methyltransferase SETD7 regulates a variety of cancer-related processes, in a tissue-type and signalling context-dependent manner. To date, there is no consensus regarding SETD7´s biological functions, or potential for cancer diagnostics and therapeutics. In this work, we summarised the literature on SETD7 expression and function in cancer, to identify the contexts where SETD7 expression and targeting can lead to improvements in cancer diagnosis and therapy. The most studied cancers were found to be lung and osteosarcoma followed by colorectal and breast cancers. SETD7 mRNA and/or protein expression in human cancer tissue was evaluated using public databases and/or in-house cohorts, but its prognostic significance remains inconclusive. The most studied cancer-related processes regulated by SETD7 were cell proliferation, apoptosis, epithelial-mesenchymal transition, migration and invasion with special relevance to the pRb/E2F-1 pathway. SETD7 consistently prevented epithelial to mesenchymal transition in different cancer types, and inhibition of its function appears to be associated with improved response to DNA-damaging agents in most of the analysed studies. Stabilising mutations in SETD7 target proteins prevent their methylation or promote other competing post-translational modifications that can override the SETD7 effect. This indicates that a clear discrimination of these mutations and competing signalling pathways must be considered in future functional studies.

Computational identification of new potential transcriptional partners of ERRα in breast cancer cells: specific partners for specific targets

Estrogen related receptors are orphan members of the nuclear receptor superfamily acting as transcription factors (TFs). In contrast to classical nuclear receptors, the activities of the ERRs are not controlled by a natural ligand. Regulation of their activities thus relies on availability of transcriptional co-regulators. In this paper, we focus on ERRα, whose involvement in cancer progression has been broadly demonstrated. We propose a new approach to identify potential co-activators, starting from previously identified ERRα-activated genes in a breast cancer (BC) cell line. Considering mRNA gene expression from two sets of human BC cells as major endpoint, we used sparse partial least squares modeling to uncover new transcriptional regulators associated with ERRα. Among them, DDX21, MYBBP1A, NFKB1, and SETD7 are functionally relevant in MDA-MB-231 cells, specifically activating the expression of subsets of ERRα-activated genes. We studied SET7 in more details and showed its co-localization with ERRα and its ERRα-dependent transcriptional and phenotypic effects. Our results thus demonstrate the ability of a modeling approach to identify new transcriptional partners from gene expression. Finally, experimental results show that ERRα cooperates with distinct co-regulators to control the expression of distinct sets of target genes, thus reinforcing the combinatorial specificity of transcription.

Androgen Receptor-Mediated Transcription in Prostate Cancer

Androgen receptor (AR)-mediated transcription is critical in almost all stages of prostate cancer (PCa) growth and differentiation. This process involves a complex interplay of coregulatory proteins, chromatin remodeling complexes, and other transcription factors that work with AR at cis-regulatory enhancer regions to induce the spatiotemporal transcription of target genes. This enhancer-driven mechanism is remarkably dynamic and undergoes significant alterations during PCa progression. In this review, we discuss the AR mechanism of action in PCa with a focus on how cis-regulatory elements modulate gene expression. We explore emerging evidence of genetic variants that can impact AR regulatory regions and alter gene transcription in PCa. Finally, we highlight several outstanding questions and discuss potential mechanisms of this critical transcription factor.

The Role of Lysine Methyltransferase SET7/9 in Proliferation and Cell Stress Response

Lysine-specific methyltransferase 7 (KMT7) SET7/9, aka Set7, Set9, or SetD7, or KMT5 was discovered 20 years ago, yet its biological role remains rather enigmatic. In this review, we analyze the particularities of SET7/9 enzymatic activity and substrate specificity with respect to its biological importance, mostly focusing on its two well-characterized biological functions: cellular proliferation and stress response.

Proteome-wide identification of non-histone lysine methylation in tomato during fruit ripening

INTRODUCTION

Histone and non-histone methylations are important post-translational modifications in plants. Histone methylation plays a crucial role in regulating chromatin structure and gene expression. However, the involvement of non-histone methylation in plant biological processes remains largely unknown.

METHODS

The methylated substrates and methylation sites during tomato fruit ripening were identified by LC-MS/MS. Bioinformatics of lysine methylated proteins was conducted to analyze the possible role of methylated proteins. The effects of methylation modification on protein functions were preliminarily investigated by site-directed mutation simulation.

RESULTS

A total of 241 lysine methylation (mono-, di- and trimethylation) sites in 176 proteins were identified with two conserved methylation motifs: xxxxxxExxx_K_xxxExxxxxx and xxxxxxExxx_K_xxxxxxxxxx. These methylated proteins were mainly related to fruit ripening and senescence, oxidation reduction process, signal transduction, stimulus and stress responses, and energy metabolism. Three representative proteins, thioredoxin (Trx), glutathione S-transferase T1 (GST T1), and NADH dehydrogenase (NOX), were selected to investigate the effect of methylation modifications on protein activity. Mimicking demethylation led to decreased Trx activity but increased GST T1 and NOX activities. In addition, RT-qPCR exhibited that the expression of many genes that encode proteins subjected to methylation was upregulated during fruit ripening.

CONCLUSION

Our study suggests that tomato fruit ripening undergo non-histone lysine methylation, which may participate in the regulation of fruit ripening. It is the first report of methyl proteome profiling of non-histone lysine in horticultural crops.

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.

Nonhistone Lysine Methylation as a Protein Degradation Signal

Protein degradation is a fundamental feature of cellular life, and malfunction of this process is implicated in human disease. Ubiquitin tagging is the best characterized mechanism of targeting a protein for degradation; however, there are a growing number of distinct mechanisms which have also been identified that carry out this essential function. For example, covalent tagging of proteins with sequestosome-1 targets them for selective autophagy. Degradation signals are not exclusively polypeptides such as ubiquitin, NEDD8, and sequestosome-1. Phosphorylation, acetylation, and methylation are small covalent additions that can also direct protein degradation. The diversity of substrate sequences and overlap with other pleotrophic functions for these smaller signaling moieties has made their characterization more challenging. However, these small signals might be responsible for orchestrating a large portion of the protein degradation activity in the cell. As such, there has been increasing interest in lysine methylation and associated lysine methyltransferases (KMTs), beyond canonical histone protein modification, in mediating protein degradation in a variety of contexts. This review focuses on the current evidence for lysine methylation as a protein degradation signal with a detailed discussion of the class of enzymes responsible for this phenomenon.

Non-histone methylation of SET7/9 and its biological functions

BACKGROUND

(su(var)-3-9,enhancer-of-zeste,trithorax) domain-containing protein 7/9 (SET7/9) is a member of the protein lysine methyltransferases (PLMTs or PKMTs) family. It contains a SET domain. Recent studies demonstrate that SET7/9 methylates both lysine 4 of histone 3 (H3-K4) and lysine(s) of non-histone proteins, including transcription factors, tumor suppressors, and membrane-associated receptors.

OBJECTIVE

This article mainly reviews the non-histone methylation effects of SET7/9 and its functions in tumorigenesis and development.

METHODS

PubMed was screened for this information.

RESULTS

SET7/9 plays a key regulatory role in various biological processes such as cell proliferation, transcription regulation, cell cycle, protein stability, cardiac morphogenesis, and development. In addition, SET7/9 is involved in the pathogenesis of hair loss, breast cancer progression, human carotid plaque atherosclerosis, chronic kidney disease, diabetes, obesity, ovarian cancer, prostate cancer, hepatocellular carcinoma, and pulmonary fibrosis.

CONCLUSION

SET7/9 is an important methyltransferase, which can catalyze the methylation of a variety of proteins. Its substrates are closely related to the occurrence and development of tumors.

Histone H3K4 Methyltransferases as Targets for Drug-Resistant Cancers

The KMT2 (MLL) family of proteins, including the major histone H3K4 methyltransferase found in mammals, exists as large complexes with common subunit proteins and exhibits enzymatic activity. SMYD, another H3K4 methyltransferase, and SET7/9 proteins catalyze the methylation of several non-histone targets, in addition to histone H3K4 residues. Despite these structural and functional commonalities, H3K4 methyltransferase proteins have specificity for their target genes and play a role in the development of various cancers as well as in drug resistance. In this review, we examine the overall role of histone H3K4 methyltransferase in the development of various cancers and in the progression of drug resistance. Compounds that inhibit protein-protein interactions between KMT2 family proteins and their common subunits or the activity of SMYD and SET7/9 are continuously being developed for the treatment of acute leukemia, triple-negative breast cancer, and castration-resistant prostate cancer. These H3K4 methyltransferase inhibitors, either alone or in combination with other drugs, are expected to play a role in overcoming drug resistance in leukemia and various solid cancers.

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.

MLL5, a histone modifying enzyme, regulates androgen receptor activity in prostate cancer cells by recruiting co-regulators, HCF1 and SET1

In prostate cancer, the androgen receptor (AR) transcription factor is a major regulator of cell proliferation and metastasis. To identify new AR regulators, we focused on Mixed lineage leukemia 5 (MLL5), a histone-regulating enzyme, because significantly higher MLL5 expression was detected in prostate cancer tissues than in matching normal tissues. When we expressed shRNAs targeting MLL5 gene in prostate cancer cell line, the growth rate and AR activity were reduced compared to those in control cells, and migration ability of the knockdown cells was reduced significantly. To determine the molecular mechanisms of MLL5 on AR activity, we proved that AR physically interacted with MLL5 and other co-factors, including SET-1 and HCF-1, using an immunoprecipitation method. The chromatin immunoprecipitation analysis showed reduced binding of MLL5, co-factors, and AR enzymes to AR target gene promoters in MLL5 shRNA-expressing cells. Histone H3K4 methylation on the AR target gene promoters was reduced, and H3K9 methylation at the same site was increased in MLL5 knockdown cells. Finally, xenograft tumor formation revealed that reduction of MLL5 in prostate cancer cells retarded tumor growth. Our results thus demonstrate the important role of MLL5 as a new epigenetic regulator of AR in prostate cancer.

ACK1-AR and AR-HOXB13 signaling axes: epigenetic regulation of lethal prostate cancers

The androgen receptor (AR) is a critical transcription factor in prostate cancer (PC) pathogenesis. Its activity in malignant cells is dependent on interactions with a diverse set of co-regulators. These interactions fluctuate depending on androgen availability. For example, the androgen depletion increases the dependence of castration-resistant PCs (CRPCs) on the ACK1 and HOXB13 cell survival pathways. Activated ACK1, an oncogenic tyrosine kinase, phosphorylates cytosolic and nuclear proteins, thereby avoiding the inhibitory growth consequences of androgen depletion. Notably, ACK1-mediated phosphorylation of histone H4, which leads to epigenetic upregulation of AR expression, has emerged as a critical mechanism of CRPC resistance to anti-androgens. This resistance can be targeted using the ACK1-selective small-molecule kinase inhibitor (R)- 9b. CRPCs also deploy the bromodomain and extra-terminal domain protein BRD4 to epigenetically increase HOXB13 gene expression, which in turn activates the MYC target genes AURKA/AURKB. HOXB13 also facilitates ligand-independent recruitment of the AR splice variant AR-V7 to chromatin, compensating for the loss of the chromatin remodeling protein, CHD1, and restricting expression of the mitosis control gene HSPB8. These studies highlight the crosstalk between AR-ACK1 and AR-HOXB13 pathways as key mediators of CRPC recurrence.

Impact of taxanes on androgen receptor signaling

The development and progression of metastatic castration-resistant prostate cancer is the major challenge in the treatment of advanced prostate cancer. The androgen receptor signaling pathway remains active in metastatic castration-resistant prostate cancer. Docetaxel and cabazitaxel are the first- and second-line chemotherapy, respectively, for patients with metastatic castration-resistant prostate cancer. These two taxanes, in general, function by (i) inhibiting mitosis and inducing apoptosis and (ii) preventing microtubule-dependent cargo trafficking. In prostate cancer, taxanes have been reported to inhibit the nuclear translocation and activity of the androgen receptor. However, whether this is attainable or not clinically remains controversial. In this review, we will provide a comprehensive view of the effects of taxanes on androgen receptor signaling in prostate cancer.

Isoform-Specific Lysine Methylation of RORα2 by SETD7 Is Required for Association of the TIP60 Coactivator Complex in Prostate Cancer Progression

The retinoid acid-related orphan receptor α (RORα), a member of the orphan nuclear receptor superfamily, functions as an unknown ligand-dependent transcription factor. RORα was shown to regulate a broad array of physiological processes such as Purkinje cell development in the cerebellum, circadian rhythm, lipid and bone metabolism, inhibition of inflammation, and anti-apoptosis. The human RORα gene encodes at least four distinct isoforms (RORα1, -2, -3, -4), which differ only in their N-terminal domain (NTD). Two isoforms, RORα2 and 3, are not expressed in mice, whereas RORα1 and 4 are expressed both in mice and humans. In the present study, we identified the specific NTD of RORα2 that enhances prostate tumor progression and proliferation via lysine methylation-mediated recruitment of coactivator complex pontin/Tip60. Upregulation of the RORα2 isoform in prostate cancers putatively promotes tumor formation and progression. Furthermore, binding between coactivator complex and RORα2 is increased by lysine methylation of RORα2 because methylation permits subsequent interaction with binding partners. This methylation-dependent activation is performed by SET domain containing 7 (SETD7) methyltransferase, inducing the oncogenic potential of RORα2. Thus, post-translational lysine methylation of RORα2 modulates oncogenic function of RORα2 in prostate cancer. Exploration of the post-translational modifications of RORα2 provides new avenues for the development of tumor-suppressive therapeutic agents through modulating the human isoform-specific tumorigenic role of RORα2.

A novel CRISPR-engineered prostate cancer cell line defines the AR-V transcriptome and identifies PARP inhibitor sensitivities

Resistance to androgen receptor (AR)-targeted therapies in prostate cancer (PC) is a major clinical problem. A key mechanism of treatment resistance in advanced PC is the generation of alternatively spliced forms of the AR termed AR variants (AR-Vs) that are refractory to targeted agents and drive tumour progression. Our understanding of how AR-Vs function is limited due to difficulties in distinguishing their discriminate activities from full-length AR (FL-AR). Here we report the development of a novel CRISPR-derived cell line which is a derivative of CWR22Rv1 cells, called CWR22Rv1-AR-EK, that has lost expression of FL-AR, but retains all endogenous AR-Vs. From this, we show that AR-Vs act unhindered by loss of FL-AR to drive cell growth and expression of androgenic genes. Global transcriptomics demonstrate that AR-Vs drive expression of a cohort of DNA damage response genes and depletion of AR-Vs sensitises cells to ionising radiation. Moreover, we demonstrate that AR-Vs interact with PARP1 and PARP2 and are dependent upon their catalytic function for transcriptional activation. Importantly, PARP blockade compromises expression of AR-V-target genes and reduces growth of CRPC cell lines suggesting a synthetic lethality relationship between AR-Vs and PARP, advocating the use of PARP inhibitors in AR-V positive PC.

FOXO1 degradation via G9a-mediated methylation promotes cell proliferation in colon cancer

Posttranslational modifications of the Forkhead family transcription factor, FOXO1, have been known to have important regulatory implications in its diverse activities. Several types of modifications of FOXO1, including acetylation, phosphorylation, and ubiquitination, have been reported. However, lysine methylation of FOXO1 has not yet been identified. Here, we reported that FOXO1 is methylated by G9a at K273 residue in vitro and in vivo. Methylation of FOXO1 by G9a increased interaction between FOXO1 and a specific E3 ligase, SKP2, and decreased FOXO1 protein stability. In addition, G9a expression was increased by insulin and resulted in insulin-mediated FOXO1 degradation by K273 methylation. Tissue array analysis indicated that G9a was overexpressed and FOXO1 levels decreased in human colon cancer. Cell proliferation assays revealed that G9a-mediated FOXO1 methylation increased colon cancer cell proliferation. Fluorescence-activated cell sorting (FACS) analysis indicated that apoptosis rates were higher in the presence of FOXO1 than in FOXO1 knock-out cells. Furthermore, we found that G9a protein levels were elevated and FOXO1 protein levels were decreased in human colon cancer patients tissue samples. Here, we report that G9a specific inhibitor, BIX-01294, can regulate cell proliferation and apoptosis by inhibiting G9a-mediated FOXO1 methylation.

Lysine methylation signaling of non-histone proteins in the nucleus

Lysine methylation, catalyzed by protein lysine methyltransferases (PKMTs), is a central post-translational modification regulating many signaling pathways. It has direct and indirect effects on chromatin structure and transcription. Accumulating evidence suggests that dysregulation of PKMT activity has a fundamental impact on the development of many pathologies. While most of these works involve in-depth analysis of methylation events in the context of histones, in recent years, it has become evident that methylation of non-histone proteins also plays a pivotal role in cell processes. This review highlights the importance of non-histone methylation, with focus on methylation events taking place in the nucleus. Known experimental platforms which were developed to identify new methylation events, as well as examples of specific lysine methylation signaling events which regulate key transcription factors, are presented. In addition, the role of these methylation events in normal and disease states is emphasized.

Lysine methylation of transcription factors in cancer

Protein lysine methylation is a critical and dynamic post-translational modification that can regulate protein stability and function. This post-translational modification is regulated by lysine methyltransferases and lysine demethylases. Recent studies using mass-spectrometric techniques have revealed that in addition to histones, a great number of transcription factors are also methylated, often at multiple sites and to different degrees (mono-, di-, trimethyl lysine). The biomedical significance of transcription factor methylation in human diseases, including cancer, has been explored recently. Some studies have demonstrated that interfering with transcription factor lysine methylation both in vitro and in vivo can inhibit cancer cell proliferation, thereby reversing tumor progression. The inhibitors targeting lysine methyltransferases and lysine demethylases have been under development for the past two decades, and may be used as potential anticancer agents in the clinic. In this review, we focus on the current findings of transcription factor lysine methylation, and the effects on both transcriptional activity and target gene expression. We outlined the biological significance of transcription factor lysine methylation on tumor progression and highlighted its clinical value in cancer therapy.

Histone Methyltransferase Setd7 Regulates Nrf2 Signaling Pathway by Phenethyl Isothiocyanate and Ursolic Acid in Human Prostate Cancer Cells

SCOPE

This study aims to investigate the role of the epigenetic regulator SET domain-containing lysine methyltransferase 7 (Setd7) in regulating the antioxidant Nrf2 pathway in prostate cancer (PCa) cells and examines the effects of two phytochemicals, phenethyl isothiocyanate (PEITC) and ursolic acid (UA).

METHODS AND RESULTS

Lentivirus-mediated shRNA knockdown of Setd7 in LNCaP and PC-3 cells decreases the expression of downstream Nrf2 targets, such as NAD(P)H: quinone oxidoreductase 1 (Nqo1) and glutathione S-transferase theta 2 (Gstt2). Downregulation of Setd7 decreases soft agar colony formation ability of PCa cells. Knockdown of Setd7 increases reactive oxygen species (ROS) generation. Furthermore, Setd7 knockdown attenuates Nqo1 and Gstt2 expression in response to H2 O2 challenge, whereas increased DNA damage is observed in Setd7 knockdown cells in comet assay. Interestingly, Setd7 expression could be induced by the dietary phytochemicals PEITC and UA. Chromatin immunoprecipitation (ChIP) assays show that Setd7 knockdown decreased H3K4me1 enrichment in the Nrf2 and Gstt2 promoter regions, while PEITC and UA treatments elevated the enrichment.

CONCLUSION

Taken together, these results indicate that Setd7 knockdown decreases Nrf2 and Nrf2-target genes expression and that PEITC and UA induce Setd7 expression, which activates the Nrf2/antioxidant response element (ARE) signaling pathway and protects DNA from oxidative damage.

Development of Novel Inhibitors for Histone Methyltransferase SET7/9 based on Cyproheptadine

The histone methyltransferase SET7/9 methylates not only histone but also non-histone proteins as substrates, and therefore, SET7/9 inhibitors are considered candidates for the treatment of diseases. Previously, our group identified cyproheptadine, used clinically as a serotonin receptor antagonist and histamine receptor (H1) antagonist, as a novel scaffold of the SET7/9 inhibitor. In this work, we focused on dibenzosuberene as a substructure of cyproheptadine and synthesized derivatives with various functional groups. Among them, the compound bearing a 2-hydroxy group showed the most potent activity. On the other hand, a 3-hydroxy group or another hydrophilic functional group such as acetamide decreased the activity. Structural analysis clarified a rationale for the improved potency only by tightly restricted location and type of the hydrophilic group. In addition, a SET7/9 loop, which was only partially visible in the complex with cyproheptadine, became more clearly visible in the complex with 2-hydroxycyproheptadine. These results are expected to be helpful for further structure-based development of SET7/9 inhibitors.

Chemical and Biochemical Perspectives of Protein Lysine Methylation

Protein lysine methylation is a distinct posttranslational modification that causes minimal changes in the size and electrostatic status of lysine residues. Lysine methylation plays essential roles in regulating fates and functions of target proteins in an epigenetic manner. As a result, substrates and degrees (free versus mono/di/tri) of protein lysine methylation are orchestrated within cells by balanced activities of protein lysine methyltransferases (PKMTs) and demethylases (KDMs). Their dysregulation is often associated with neurological disorders, developmental abnormalities, or cancer. Methyllysine-containing proteins can be recognized by downstream effector proteins, which contain methyllysine reader domains, to relay their biological functions. While numerous efforts have been made to annotate biological roles of protein lysine methylation, limited work has been done to uncover mechanisms associated with this modification at a molecular or atomic level. Given distinct biophysical and biochemical properties of methyllysine, this review will focus on chemical and biochemical aspects in addition, recognition, and removal of this posttranslational mark. Chemical and biophysical methods to profile PKMT substrates will be discussed along with classification of PKMT inhibitors for accurate perturbation of methyltransferase activities. Semisynthesis of methyllysine-containing proteins will also be covered given the critical need for these reagents to unambiguously define functional roles of protein lysine methylation.

Identification and Characterizations of Novel, Selective Histone Methyltransferase SET7 Inhibitors by Scaffold Hopping- and 2D-Molecular Fingerprint-Based Similarity Search

SET7, serving as the only histone methyltransferase that monomethylates 'Lys-4' of histone H3, has been proved to function as a key regulator in diverse biological processes, such as cell proliferation, transcriptional network regulation in embryonic stem cell, cell cycle control, protein stability, heart morphogenesis and development. What's more, SET7 is involved inthe pathogenesis of alopecia aerate, breast cancer, tumor and cancer progression, atherosclerosis in human carotid plaques, chronic renal diseases, diabetes, obesity, ovarian cancer, prostate cancer, hepatocellular carcinoma, and pulmonary fibrosis. Therefore, there is urgent need to develop novel SET7 inhibitors. In this paper, based on DC-S239 which has been previously reported in our group, we employed scaffold hopping- and 2D fingerprint-based similarity searches and identified DC-S285 as the new hit compound targeting SET7 (IC₅₀ = 9.3 μM). Both radioactive tracing and NMR experiments validated the interactions between DC-S285 and SET7 followed by the second-round similarity search leading to the identification ofDC-S303 with the IC₅₀ value of 1.1 μM. In cellular level, DC-S285 retarded tumor cell proliferation and showed selectivity against MCF7 (IC₅₀ = 21.4 μM), Jurkat (IC₅₀ = 2.2 μM), THP1 (IC₅₀ = 3.5 μM), U937 (IC₅₀ = 3.9 μM) cell lines. Docking calculations suggested that DC-S303 share similar binding mode with the parent compoundDC-S239. What's more, it presented good selectivity against other epigenetic targets, including SETD1B, SETD8, G9a, SMYD2 and EZH2. DC-S303 can serve as a drug-like scaffold which may need further optimization for drug development, and can be used as chemical probe to help the community to better understand the SET7 biology.

LSD1 demethylates HIF1α to inhibit hydroxylation and ubiquitin-mediated degradation in tumor angiogenesis

Lysine-specific demethylase 1 (LSD1), which has been considered as a potential therapeutic target in human cancer, has been known to regulate many biological functions through its non-histone substrates. Although LSD1-induced hypoxia-inducible factor alpha (HIF1α) demethylation has recently been proposed, the effect of LSD1 on the relationship between HIF1α post-translational modifications (PTMs) and HIF1α-induced tumor angiogenesis remains to be elucidated. Here, we identify a new methylation site of the HIF1α protein antagonized by LSD1 and the interplay between HIF1α protein methylation and other PTMs in regulating tumor angiogenesis. LSD1 demethylates HIF1α at lysine (K) 391, which protects HIF1α against ubiquitin-mediated protein degradation. LSD1 also directly suppresses PHD2-induced HIF1α hydroxylation, which has a mutually dependent interplay with Set9-mediated HIF1α methylation. Moreover, the HIF1α acetylation that occurs in a HIF1α methylation-dependent manner is inhibited by the LSD1/NuRD complex. HIF1α stabilized by LSD1 cooperates with CBP and MTA1 to enhance vascular endothelial growth factor (VEGF)-induced tumor angiogenesis. Thus, LSD1 is a key regulator of HIF1α/VEGF-mediated tumor angiogenesis by antagonizing the crosstalk between PTMs involving HIF1α protein degradation.

Opposite Effects of SET7/9 on Apoptosis of Human Acute Myeloid Leukemia Cells and Lung Cancer Cells

SET7/9 is a protein lysine methyltransferases (PLMTs or PKMTs) which methylates both histone H3K4 and non-histone proteins including transcriptional factors, tumor suppressors, and membrane-associated receptors. Methylation of these proteins alters protein activity and leads to changes in cellular behavior and a series of biological processes. This study aims to investigate the role of SET7/9 in human acute myeloid leukemia (AML) and non-small-cell lung cancer (NSCLC). We examined the expression of SET7/9 in AML cells and NSCLC cells and detected the methylation status of the SET7/9 promoter region. To evaluate the effect of SET7/9 expression changes on cell apoptosis, cell apoptosis rates were determined after SET7/9 overexpression or down-regulation. Our results showed that SET7/9 induces apoptosis of AML cells and inhibits apoptosis of NSCLC cells, suggesting differential effects of SET7/9 on cellular apoptosis and carcinogenesis depending on different cancer types and genetic contexts. Furthermore, we also demonstrated that SET7/9 suppresses cell apoptosis via modulation of E2F1 under circumstance of p53 deficiency in NSCLC cells.

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.

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.

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.