Coactivator MYST1 regulates nuclear factor-κB and androgen receptor functions during proliferation of prostate cancer cells

Androgen Receptor-Interacting Proteins in Prostate Cancer Development and Therapy Resistance

Endocrine therapy for prostate cancer is based on the use of drugs that diminish androgen concentration and androgen receptor (AR) signaling inhibitors and is limited by the functional consequences of AR point mutations and increased expression of constitutively active receptors. Many coactivators (>280) interact with different AR regions. Most studies have determined the expression of coactivators and their effects in the presence of increasing concentrations of androgen or the antiandrogen enzalutamide. The p160 group of coactivators (SRC-1, SRC-2, and SRC-3) is highly expressed in prostate cancer and contributes to ligand-dependent activation of the receptor in models that represent therapy-sensitive and therapy-resistant cell lines. The transcriptional coactivators p300 and CREB-binding protein (CBP) are implicated in the regulation of a large number of cellular events, such as proliferation, apoptosis, migration, and invasion. AR coactivators also may predict biochemical and clinical recurrence. The AR coactivator expression, which is enhanced in enzalutamide resistance, includes growth regulating estrogen receptor binding 1 (GREB1) and GATA-binding protein 2 (GATA2). Several coactivators also activate AR-unrelated signaling pathways, such as those of insulin-like growth factors, which inhibit apoptosis in cancer cells. They are expressed in multiple models of resistance to therapy and can be targeted by various inhibitors in vitro and in vivo. The role of the glucocorticoid receptor in endocrine therapy-resistant prostate cancer has been documented previously. Specific coactivators may interact with the glucocorticoid receptor, thus contributing to therapy failure.

The interaction between the histone acetyltransferase complex Hat1-Hat2 and transcription factor AmyR provides a molecular brake to regulate amylase gene expression

The chromatin structure is generally regulated by chromatin remodelers and histone modifiers, which affect DNA replication, repair, and levels of transcription. The first identified histone acetyltransferase was Hat1/KAT1, which belongs to lysine (K) acetyltransferases. The catalytic subunit Hat1 and the regulatory subunit Hat2 make up the core HAT1 complex. In this study, the results of tandem affinity purification and mass spectrometry and bimolecular fluorescence complementation proved that the Penicillium oxalicum PoHat1-Hat2 is the transcriptional cofactor of the sequence-specific transcription factor PoAmyR, a transcription activator essential for the transcription of amylase gene. ChIP-qPCR results demonstrated that the complex PoHat1-Hat2 is recruited by PoAmyR to the promoters of prominent amylase genes Poamy13A and Poamy15A and performs histone H4 lysine12 acetylation. The result of the yeast two-hybrid test indicated that PoHat2 is the subunit that directly interacts with PoAmyR. PoHat1-Hat2 acts as the molecular brake of the PoAmyR-regulating transcription of amylase genes. A putative model for amylase gene regulation by PoAmyR-Hat2-Hat1 was constructed. Our paper is the first report that the Hat1-Hat2 complex acts as a cofactor for sequence-specific TF to regulate gene expression and explains the mechanism of TF AmyR regulating amylase genes expression.

MOF negatively regulates estrogen receptor α signaling via CUL4B-mediated protein degradation in breast cancer

Estrogen receptor α (ERα) is the dominant tumorigenesis driver in breast cancer (BC), and ERα-positive BC (ERα+ BC) accounts for more than two-thirds of BC cases. MOF (males absent on the first) is a highly conserved histone acetyltransferase that acetylates lysine 16 of histone H4 (H4K16) and several non-histone proteins. Unbalanced expression of MOF has been identified, and high MOF expression predicted a favorable prognosis in BC. However, the association of MOF with ERα and the regulatory mechanisms of MOF in ERα signaling remain elusive. Our study revealed that the expression of MOF is negatively correlated with that of ERα in BC. In ERα+ BC cells, MOF overexpression downregulated the protein abundance of ERα in both cytoplasm and nucleus, thus attenuating ERα-mediated transactivation as well as cellular proliferation and in vivo tumorigenicity of BC cells. MOF promoted ERα protein degradation through CUL4B-mediated ubiquitin–proteasome pathway and induced HSP90 hyperacetylation that led to the loss of chaperone protection of HSP90 to ERα. We also revealed that suppression of MOF restored ERα expression and increased the sensitivity of ERα-negative BC cells to tamoxifen treatment. These results provide a new insight into the tumor-suppressive role of MOF in BC via negatively regulating ERα action, suggesting that MOF might be a potential therapeutic target for BC.

TIP60 buffers acute stress response and depressive behaviour by controlling PPARγ-mediated transcription

Tat-interacting protein 60 (TIP60) as nuclear receptors (NRs) coregulator, acts as a tumor suppressor and also has promising therapeutic potential to target Alzheimer's disease. Stress has been implicated in many psychiatric disorders, and these disorders are characterized by impairments in cognitive function. Until now, there are no experimental data available on the regulatory effect of TIP60 in acute stress and depression. There is also no definitive explanation on which specific modulation of target gene expression is achieved by TIP60. Here, we identify TIP60 as a novel positive regulator in response to acute restraint stress (ARS) and a potentially effective target of antidepressants. Firstly, we discovered increased hippocampal TIP60 expressions in the ARS model. Furthermore, using the TIP60 inhibitor, MG149, we proved that TIP60 function correlates with behavioral and synaptic activation in the two-hour ARS. Secondly, the lentivirus vector (LV)-TIP60^{overexpression (OE)} was injected into the hippocampus prior to the chronic restraint stress (CRS) experiments and it was found that over-expressed TIP60 compensates for TIP60 decrease and improves depression index in CRS. Thirdly, through the intervention of TIP60 expression in vitro, we established the genetic regulation of TIP60 on synaptic proteins, confirmed the TIP60 function as a specific coactivator for PPARγ and found that the PPARγ-mediated TIP60 function modulates transcriptional activation of synaptic proteins. Finally, the LV-TIP60^OE and PPARγ antagonist, GW9662, were both administered in the CRS model and the data indicated that blocking PPARγ significantly weakened the protective effect of TIP60 against the CRS-induced depression. Conclusively, these findings together support TIP60 as a novel positive factor in response to acute stress and interacts with PPARγ to modulate the pathological mechanism of CRS-induced depression.

Inflammation induced by lipopolysaccharide advanced androgen receptor expression and epithelial-mesenchymal transition progress in prostatitis and prostate cancer

Background

To explore the mechanism of prostatic inflammation on prostate cancer (PCa) by comparing the changes of prostate epithelial cells and PCa cells in an inflammatory environment.

Methods

First, immunohistochemistry (IHC) was used to compare the level of expression of TNF-α, IL-1β, IL-6, and TGF-β between benign prostatic hyperplasia (BPH), prostatitis, and PCa. Then primary prostate epithelial cells were sampled from patients who were suspected of PCa and had histological prostatitis (HP) confirmed by pathological biopsy. Lipopolysaccharide (LPS) or BAY11-7082 were used to investigate the change of androgen receptor (AR) and AR-mediated transcription, epithelial-mesenchymal transition (EMT) in primary prostate epithelial cells, and lymph node carcinoma of the prostate (LNCap) cells.

Results

TNF-α, IL-1β, IL-6, and TGF-β were significantly increased in HP and PCa compared with those in BPH patients. The proliferation of primary prostate epithelial cells and LNCap cells got the inflection point at LPS 10 µg/mL. In an inflammatory environment with 10 µg/mL LPS, both primary prostate epithelial cell and LNCap cell viability increased, and AR, AR-mediated transcription, and EMT processes were significantly increased. Inhibitors of NF-κB with 10 nM BAY11-7082 decreased AR, AR-mediated transcription, and EMT processes.

Conclusions

NF-κB regulates AR expression and EMT in prostatitis and PCa, and NF-κB inhibitors may have potential therapeutic value.

Lysine Acetyltransferases and Their Role in AR Signaling and Prostate Cancer

The development and growth of a normal prostate gland, as well as its physiological functions, are regulated by the actions of androgens through androgen receptor (AR) signaling which drives multiple cellular processes including transcription, cellular proliferation, and apoptosis in prostate cells. Post-translational regulation of AR plays a vital role in directing its cellular activities via modulating its stability, nuclear localization, and transcriptional activity. Among various post-translational modifications (PTMs), acetylation is an essential PTM recognized in AR and is governed by the regulated actions of acetyltransferases and deacetyltransferases. Acetylation of AR has been identified as a critical step for its activation and depending on the site of acetylation, the intracellular dynamics and activity of the AR can be modulated. Various acetyltransferases such as CBP, p300, PCAF, TIP60, and ARD1 that are known to acetylate AR, may directly coactivate the AR transcriptional function or help to recruit additional coactivators to functionally regulate the transcriptional activity of the AR. Aberrant expression of acetyltransferases and their deregulated activities have been found to interfere with AR signaling and play a key role in development and progression of prostatic diseases, including prostate cancer (PCa). In this review, we summarized recent research advances aimed at understanding the role of various lysine acetyltransferases (KATs) in the regulation of AR activity at the level of post-translational modifications in normal prostate physiology, as well as in development and progression of PCa. Considering the critical importance of KATs in modulating AR activity in physiological and patho-physiological context, we further discussed the potential of targeting these enzymes as a therapeutic option to treat AR-related pathology in combination with hormonal therapy.

Deacetylation of Transcription Factors in Carcinogenesis

Reversible Nε-lysine acetylation/deacetylation is one of the most common post-translational modifications (PTM) of histones and non-histone proteins that is regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs). This epigenetic process is highly involved in carcinogenesis, affecting histone and non-histone proteins' properties and their biological functions. Some of the transcription factors, including tumor suppressors and oncoproteins, undergo this modification altering different cell signaling pathways. HDACs deacetylate their targets, which leads to either the upregulation or downregulation of proteins involved in the regulation of cell cycle and apoptosis, ultimately influencing tumor growth, invasion, and drug resistance. Therefore, epigenetic modifications are of great clinical importance and may constitute a new therapeutic target in cancer treatment. This review is aimed to present the significance of HDACs in carcinogenesis through their influence on functions of transcription factors, and therefore regulation of different signaling pathways, cancer progression, and metastasis.

Lack of MOF Decreases Susceptibility to Hypoxia and Promotes Multidrug Resistance in Hepatocellular Carcinoma via HIF-1α

Hypoxia-inducible factor-1α (HIF-1α) promotes oncogenesis in hepatocellular carcinoma and is functionally linked to cell proliferation, chemoresistance, metastasis and angiogenesis. It has been confirmed that the low expression level of Males absent on the first (MOF) in hepatocellular carcinoma leads to poor prognosis of patients. However, potential regulatory mechanisms of MOF in response to hypoxia remain elusive. Our results demonstrate that MOF expression is negatively associated with HIF-1α expression in hepatocellular carcinoma tissues and in response to chloride-mimicked hypoxia in hepatocellular carcinoma cell lines. MOF regulates HIF-1α mRNA expression and also directly binds to HIF-1α to mediate HIF-1α N-terminal lysine acetylation, ubiquitination and degradation, with downstream effects on MDR1 levels. Functional inactivation of MOF enhances HIF-1α stability and causes cell tolerance to hypoxia that is insensitive to histone deacetylase inhibitor treatment. Dysfunction of MOF in hepatocellular carcinoma cells also results in chemoresistance to trichostatin A, sorafenib and 5-fluorouracil via HIF-1α. Our results suggest that MOF regulates hypoxia tolerance and drug resistance in hepatocellular carcinoma cells by modulating both HIF-1α mRNA expression and N-terminal acetylation of HIF-1α, providing molecular insight into MOF-dependent oncogenic function of hepatocellular carcinoma cells.

MOF upregulates the estrogen receptor α signaling pathway by its acetylase activity in hepatocellular carcinoma

The histone acetyltransferase MOF (KAT8) is mainly involved in the acetylation of histone H4 at lysine 16 (H4K16) and some non‐histone proteins. The MOF expression level is significantly reduced in many cancers, however the biological function of MOF and its underlying mechanism are still elusive in hepatocellular carcinoma (HCC). Estrogen receptor α (ERα) has been considered as a tumor suppressor in HCC. Here, we demonstrated that MOF expression is significantly reduced in HCC samples, and is positively correlated with that of ERα. MOF interacts with ERα, and participates in acetylation of ERα at K266, K268, K299, thereby inhibiting ERα ubiquitination to maintain the stability of ERα. In addition, MOF participates in the upregulation of ERα‐mediated transactivation. Depletion of MOF significantly promotes cell growth, migration, and invasion in HCC cell lines. Taken together, our results provide new insights to understand the mechanism underlying the modulation function of MOF on ERα action in HCC, suggesting that MOF might be a potential therapeutic target for HCC.

The Biological Significance of Targeting Acetylation-Mediated Gene Regulation for Designing New Mechanistic Tools and Potential Therapeutics

The molecular interplay between nucleosomal packaging and the chromatin landscape regulates the transcriptional programming and biological outcomes of downstream genes. An array of epigenetic modifications plays a pivotal role in shaping the chromatin architecture, which controls DNA access to the transcriptional machinery. Acetylation of the amino acid lysine is a widespread epigenetic modification that serves as a marker for gene activation, which intertwines the maintenance of cellular homeostasis and the regulation of signaling during stress. The biochemical horizon of acetylation ranges from orchestrating the stability and cellular localization of proteins that engage in the cell cycle to DNA repair and metabolism. Furthermore, lysine acetyltransferases (KATs) modulate the functions of transcription factors that govern cellular response to microbial infections, genotoxic stress, and inflammation. Due to their central role in many biological processes, mutations in KATs cause developmental and intellectual challenges and metabolic disorders. Despite the availability of tools for detecting acetylation, the mechanistic knowledge of acetylation-mediated cellular processes remains limited. This review aims to integrate molecular and structural bases of KAT functions, which would help design highly selective tools for understanding the biology of KATs toward developing new disease treatments.

Post-Translational Modifications That Drive Prostate Cancer Progression

While a protein primary structure is determined by genetic code, its specific functional form is mostly achieved in a dynamic interplay that includes actions of many enzymes involved in post-translational modifications. This versatile repertoire is widely used by cells to direct their response to external stimuli, regulate transcription and protein localization and to keep proteostasis. Herein, post-translational modifications with evident potency to drive prostate cancer are explored. A comprehensive list of proteome-wide and single protein post-translational modifications and their involvement in phenotypic outcomes is presented. Specifically, the data on phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and lipidation in prostate cancer and the enzymes involved are collected. This type of knowledge is especially valuable in cases when cancer cells do not differ in the expression or mutational status of a protein, but its differential activity is regulated on the level of post-translational modifications. Since their driving roles in prostate cancer, post-translational modifications are widely studied in attempts to advance prostate cancer treatment. Current strategies that exploit the potential of post-translational modifications in prostate cancer therapy are presented.

The Versatility of Sirtuin-1 in Endocrinology and Immunology

Sirtuins belong to the class III family of NAD-dependent histone deacetylases (HDAC) and are involved in diverse physiological processes that range from regulation of metabolism and endocrine function to coordination of immunity and cellular responses to stress. Sirtuin-1 (SIRT1) is the most well-studied family member and has been shown to be critically involved in epigenetics, immunology, and endocrinology. The versatile roles of SIRT1 include regulation of energy sensing metabolic homeostasis, deacetylation of histone and non-histone proteins in numerous tissues, neuro-endocrine regulation via stimulation of hypothalamus-pituitary axes, synthesis and maintenance of reproductive hormones via steroidogenesis, maintenance of innate and adaptive immune system via regulation of T- and B-cell maturation, chronic inflammation and autoimmune diseases. Moreover, SIRT1 is an appealing target in various disease contexts due to the promise of pharmacological and/or natural modulators of SIRT1 activity within the context of endocrine and immune-related disease models. In this review we aim to provide a broad overview on the role of SIRT1 particularly within the context of endocrinology and immunology.

Nuclear Localization Is Not Required for Tip60 Tumor Suppressor Activity in Breast and Lung Cancer Cells

The Tip60 lysine acetyltransferase is a tumor suppressor in most cancers but an oncogene in prostate and gastric cancer. Tip60 is commonly found in the nucleus, where it acetylates proteins involved in transcription, DNA repair, and chromatin; however, it has also been shown to acetylate cytoplasmic targets. In this study, we investigated the relationship between Tip60 localization and breast and lung cancer. In cell fractionation experiments, cancer-derived cell lines showed a shift from nuclear to cytoplasmic endogenous Tip60 compared with cell lines derived from normal cells. With immunofluorescence, we observed four different localization patterns of overexpressed Tip60 and found that cancer cells had increased cytoplasmic localization of Tip60 compared with HEK-293 cells. The addition of a nuclear localization signal (NLS) increased the number of cells containing nuclear Tip60, whereas mutation of a putative endogenous NLS increased the number of cells with cytoplasmic Tip60. Overexpression of Tip60 increased cancer cell line sensitivity to paclitaxel regardless of changes in localization. These results suggest that dysregulation of Tip60 in breast and lung cancer is not limited to reduced expression but may also involve subcellular localization.

Epigenetic activation of the small GTPase TCL contributes to colorectal cancer cell migration and invasion

TC10-like (TCL) is a small GTPase that has been implicated in carcinogenesis. Elevated TCL expression has been observed in many different types of cancers although the underlying epigenetic mechanism is poorly understood. Here we report that TCL up-regulation was associated with high malignancy in both human colorectal cancer biopsy specimens and in cultured colorectal cancer cells. Hypoxia, a pro-metastatic stimulus, up-regulated TCL expression in HT-29 cells. Further studies revealed that myocardin-related transcription factor A (MRTF-A) promoted migration and invasion of HT-29 cells in a TCL-dependent manner. MRTF-A directly bound to the proximal TCL promoter in response to hypoxia to activate TCL transcription. Chromatin immunoprecipitation (ChIP) assay showed that hypoxia stimulation specifically enhanced acetylation of histone H4K16 surrounding the TCL promoter, which was abolished by MRTF-A depletion or inhibition. Mechanistically, MRTF-A interacted with and recruited the H4K16 acetyltransferase hMOF to the TCL promoter to cooperatively regulate TCL transcription. hMOF depletion or inhibition attenuated hypoxia-induced TCL expression and migration/invasion of HT-29 cells. In conclusion, our data identify a novel MRTF-A-hMOF-TCL axis that contributes to colorectal cancer metastasis.

TNF-α regulates diabetic macrophage function through the histone acetyltransferase MOF

A critical component of wound healing is the transition from the inflammatory phase to the proliferation phase to initiate healing and remodeling of the wound. Macrophages are critical for the initiation and resolution of the inflammatory phase during wound repair. In diabetes, macrophages display a sustained inflammatory phenotype in late wound healing characterized by elevated production of inflammatory cytokines, such as TNF-α. Previous studies have shown that an altered epigenetic program directs diabetic macrophages toward a proinflammatory phenotype, contributing to a sustained inflammatory phase. Males absent on the first (MOF) is a histone acetyltransferase (HAT) that has been shown be a coactivator of TNF-α signaling and promote NF-κB-mediated gene transcription in prostate cancer cell lines. Based on MOF's role in TNF-α/NF-κB-mediated gene expression, we hypothesized that MOF influences macrophage-mediated inflammation during wound repair. We used myeloid-specific Mof-knockout (Lyz2Cre Moffl/fl) and diet-induced obese (DIO) mice to determine the function of MOF in diabetic wound healing. MOF-deficient mice exhibited reduced inflammatory cytokine gene expression. Furthermore, we found that wound macrophages from DIO mice had elevated MOF levels and higher levels of acetylated histone H4K16, MOF's primary substrate of HAT activity, on the promoters of inflammatory genes. We further identified that MOF expression could be stimulated by TNF-α and that treatment with etanercept, an FDA-approved TNF-α inhibitor, reduced MOF levels and improved wound healing in DIO mice. This report is the first to our knowledge to define an important role for MOF in regulating macrophage-mediated inflammation in wound repair and identifies TNF-α inhibition as a potential therapy for the treatment of chronic inflammation in diabetic wounds.

Targeting epigenetic regulators for cancer therapy: mechanisms and advances in clinical trials

Epigenetic alternations concern heritable yet reversible changes in histone or DNA modifications that regulate gene activity beyond the underlying sequence. Epigenetic dysregulation is often linked to human disease, notably cancer. With the development of various drugs targeting epigenetic regulators, epigenetic-targeted therapy has been applied in the treatment of hematological malignancies and has exhibited viable therapeutic potential for solid tumors in preclinical and clinical trials. In this review, we summarize the aberrant functions of enzymes in DNA methylation, histone acetylation and histone methylation during tumor progression and highlight the development of inhibitors of or drugs targeted at epigenetic enzymes.

MYST1/KAT8 contributes to tumor progression by activating EGFR signaling in glioblastoma cells

With short survival time, glioblastoma (GBM) is the most malignant tumor in the central nervous system. Recently, epigenetic enzymes play essential roles in the regulation of tumorigenesis and cancer development of GBM. However, little is known about MYST1/KAT8/MOF, a histone acetylation enzyme, in GBM. The present study shows that MYST1 promotes GBM progression through activating epidermal growth factor receptor (EGFR) signaling. MYST1 expression was increased in GBM and was negatively correlated with prognosis in patients with glioma and GBM. Knockdown of MYST1 reduced cell proliferation and BrdU incorporation in LN229, U87, and A172 GBM cells. Besides, MYST1 downregulation also induced cell cycle arrest at G2M phase, as well as the reduced expression of CDK1, Cyclin A, Cyclin B1, and increased expression of p21^CIP1/Waf1. Meanwhile, Self‐renewal capability in vitro and tumorigenecity in vivo were also impaired after MYST1 knockdown. Importantly, MYST1 expression was lowly expressed in mesenchymal subtype of GBM and was positively correlated with EGFR expression in a cohort from The Cancer Genome Atlas. Western blot subsequently confirmed that phosphorylation and activation of p‐Try1068 of EGFR, p‐Ser473 of AKT and p‐Thr202/Tyr204 of Erk1/2 were also decreased by MYST1 knockdown. Consistent with the results above, overexpression of MYST1 promoted GBM growth and activated EGFR signaling in vitro and in vivo. In addition, erlotinib, a US Food and Drug Administration approved cancer drug which targets EGFR, was able to rescue MYST1‐promoted cell proliferation and EGFR signaling pathway. Furthermore, the transcription of EGF, an EFGR ligand, was shown to be positively regulated by MYST1 possibly via H4K16 acetylation. Our findings elucidate MYST1 as a tumor promoter in GBM and an EGFR activator, and may be a potential drug target for GBM treatment.

Tat-interactive Protein-60KDA (TIP60) Regulates the Tumorigenesis of Lung Cancer In Vitro

Histone acetyltransferases (HATs) play vital functions in the tumorigenesis of many solid organ malignancies. We previously screened a human HATs cDNA library and identified Tat-interactive protein-60KDa (TIP60) as a candidate critical HATs in the origination of lung cancer. In this study, our data suggested that overexpression of TIP60 inhibited the cell viability of A549 and H1299 cells since day 2. Compared to the control group, the viability of these two lung cancer cells was inhibited by 25% and 19% at day 6 with the overexpression of TIP60. It increased by 36% and 26% when TIP60 was knockdown for 6 days. The invasion ability of these two cells was also restrained when TIP60 was overexpressed. While knockdown of TIP60 had the opposite effect. Inhibition of TIP60 significantly promoted the expression of molecules in AKT signaling pathway especially c-Myc. Furthermore, compared to paired tumor-adjacent tissue, lung cancer tumors had low expression of TIP60. Therefore, we concluded that TIP60 might inhibit the viability and invasion ability of lung cancer cells through down-regulation of AKT signaling pathway.

Exploiting Epigenetic Alterations in Prostate Cancer

Prostate cancer affects an increasing number of men worldwide and is a leading cause of cancer-associated deaths. Beside genetic mutations, many epigenetic alterations including DNA and histone modifications have been identified in clinical prostate tumor samples. They have been linked to aberrant activity of enzymes and reader proteins involved in these epigenetic processes, leading to the search for dedicated inhibitory compounds. In the wake of encouraging anti-tumor efficacy results in preclinical models, epigenetic modulators addressing different targets are now being tested in prostate cancer patients. In addition, the assessment of microRNAs as stratification biomarkers, and early clinical trials evaluating suppressor microRNAs as potential prostate cancer treatment are being discussed.

An Ω-3 fatty acid desaturase-expressing gene attenuates prostate cancer proliferation by cell cycle regulation

Previous studies have reported that Ω-6 and Ω-3 fatty acids have opposing effects on cancer development. Consuming high levels of long-chain Ω-3 polyunsaturated fatty acids (PUFAs) has been shown to reduce prostate cancer risk and increase chemotherapy sensitivity. The sdd17 gene encodes an Ω-3 fatty acid desaturase, which converts arachidonic acid into eicosapentaenoic acid (EPA). However, little is known regarding the function of the sdd17 gene in tumor cells in vitro. In the present study, prostate cancer cells were infected with the msdd17 gene, which allowed the endogenous production of Ω-3 PUFAs. The cells that expressed the msdd17 gene had high levels of long-chain Ω-3 PUFAs compared with the control cells. Expression of the msdd17 gene significantly inhibited prostate cancer cell proliferation. EPA exposure and msdd17 gene transfection each induced G2 cell cycle arrest and reduced E2F transcription factor 1 expression in prostate cancer cells. These results suggest that msdd17 gene transfection suppressed prostate cancer cell proliferation and induced G2 cell cycle arrest.

PR-957, a selective inhibitor of immunoproteasome subunit low-MW polypeptide 7, attenuates experimental autoimmune neuritis by suppressing Th17-cell differentiation and regulating cytokine production

Experimental autoimmune neuritis (EAN) is a CD4⁺ T-cell-mediated autoimmune inflammatory demyelinating disease of the peripheral nervous system. It has been replicated in an animal model of human inflammatory demyelinating polyradiculoneuropathy, Guillain-Barré syndrome. In this study, we evaluated the therapeutic efficacy of a selective inhibitor of the immunoproteasome subunit, low-MW polypeptide 7 (PR-957) in rats with EAN. Our results showed that PR-957 significantly delayed onset day, reduced severity and shortened duration of EAN, and alleviated demyelination and inflammatory infiltration in sciatic nerves. In addition to significantly regulating expression of the cytokine profile, PR-957 treatment down-regulated the proportion of proinflammatory T-helper (T_h)17 cells in sciatic nerves and spleens of rats with EAN. Data presented show the role of PR-957 in the signal transducer and activator of transcription 3 (STAT3) pathway. PR-957 not only decreased expression of IL-6 and IL-23 but also led to down-regulation of STAT3 phosphorylation in CD4⁺ T cells. Regulation of the STAT3 pathway led to a reduction in retinoid-related orphan nuclear receptor γ t and IL-17 production. Furthermore, reduction of STAT3 phosphorylation may have directly suppressed T_h17-cell differentiation. Therefore, our study demonstrates that PR-957 could potently alleviate inflammation in rats with EAN and that it may be a likely candidate for treating Guillain-Barré syndrome.-Liu, H., Wan, C., Ding, Y., Han, R., He, Y., Xiao, J., Hao, J. PR-957, a selective inhibitor of immunoproteasome subunit low-MW polypeptide 7, attenuates experimental autoimmune neuritis by suppressing T_h17-cell differentiation and regulating cytokine production.

Molecular and Cellular Changes During Cancer Progression Resulting From Genetic and Epigenetic Alterations

Tumorigenesis is a complex process that involves a persistent dismantling of cellular safeguards and checkpoints. These molecular and cellular changes that accumulate over months or decades lead to a change in the fundamental identity of a cell as it transitions from normal to malignant. In this chapter, we will examine some of the molecular changes in the evolving relationship between the genome and epigenome and highlight some of the key changes that occur as normal cells progress to tumor cells. For many years tumorigenesis was almost exclusively attributed to mutations in protein-coding genes. This notion that mutations in protein-coding genes were a fundamental driver of tumorigenesis enabled the development of several novel therapeutics that targeted the mutant protein or overactive pathway responsible for driving a significant portion of the tumor growth. However, because many therapeutic challenges remained in the face of these advances, it was clear that other pieces to the puzzle had yet to be discovered. Advances in molecular and genomics techniques continued and the study of epigenetics began to expand and helped reshape the view that drivers of tumorigenesis extended beyond mutations in protein-coding genes. Studies in the field of epigenetics began to identify aberrant epigenetic marks which created altered chromatin structures and enabled protein expression in tissues that defied rules governing tissue-specificity. Not only were epigenetic alterations found to enable overexpression of proto-oncogenes, they also led to the silencing of tumor suppressor genes. With these discoveries, it became clear that tumor growth could be stimulated by much more than mutations in protein-coding genes. In fact, it became increasingly clear that much of the human genome, while transcribed, did not lead to proteins. This discovery further led to studies that began to uncover the role of noncoding RNAs in regulating chromatin structure, gene transcription, and tumor biology. In this chapter, some of the key alterations in the genome and epigenome will be explored, and some of the cancer therapies that were developed as a result of these discoveries will be discussed.

KAT8 Regulates Androgen Signaling in Prostate Cancer Cells

Androgen receptor (AR) plays pivotal roles in prostate cancer. Upon androgen stimulation, AR recruits the Protein kinase N1 (PKN1), which phosphorylates histone H3 at threonine 11, with subsequent recruitment of tryptophan, aspartic acid (WD) repeat-containing protein 5 (WDR5) and the su(var)3-9, enhancer of zeste, trithorax/mixed-lineage leukemia (SET1/MLL) histone methyltransferase complex to promote AR target gene activation and prostate cancer cell growth. However, the underlying mechanisms of target gene activation and cell growth subsequent to WDR5 recruitment are not well understood. Here, we demonstrate an epigenetic cross talk between histone modifications and AR target gene regulation. We discovered that K(lysine) acetyltransferase 8 (KAT8), a member of the MOZ, YBF2/SAS2, and TIP 60 protein 1 (MYST) family of histone acetyltransferases that catalyzes histone H4 lysine 16 acetylation, colocalized with WDR5 at AR target genes, resulting in hormone-dependent gene activation in prostate cancer cells. PKN1 or WDR5 knockdown severely inhibited KAT8 association with AR target genes and histone H4 lysine 16 acetylation upon androgen treatment. Knockdown of KAT8 significantly decreased AR target gene expression and prostate cancer cell proliferation. Collectively, these data describe a trans-histone modification pathway involving PKN1/histone H3 threonine 11 phosphorylation followed by WDR5/MLL histone methyltransferase and KAT8/histone acetyltransferase recruitment to effect androgen-dependent gene activation and prostate cancer cell proliferation.

BAP18 coactivates androgen receptor action and promotes prostate cancer progression

BPTF associated protein of 18 kDa (BAP18) has been reported as a component of MLL1-WDR5 complex. However, BAP18 is an uncharacterized protein. The detailed biological functions of BAP18 and underlying mechanisms have not been defined. Androgen receptor (AR), a member of transcription factor, plays an essential role in prostate cancer (PCa) and castration-resistant prostate cancer (CRPC) progression. Here, we demonstrate that BAP18 is identified as a coactivator of AR in Drosophilar experimental system and mammalian cells. BAP18 facilitates the recruitment of MLL1 subcomplex and AR to androgen-response element (ARE) of AR target genes, subsequently increasing histone H3K4 trimethylation and H4K16 acetylation. Knockdown of BAP18 attenuates cell growth and proliferation of PCa cells. Moreover, BAP18 depletion results in inhibition of xenograft tumor growth in mice even under androgen-depletion conditions. In addition, our data show that BAP18 expression in clinical PCa samples is higher than that in benign prostatic hyperplasia (BPH). Our data suggest that BAP18 as an epigenetic modifier regulates AR-induced transactivation and the function of BAP18 might be targeted in human PCa to promote tumor growth and progression to castration-resistance.

Androgen Receptor Coactivators in Regulation of Growth and Differentiation in Prostate Cancer

Androgen receptor (AR) is a key factor in regulation of growth and differentiation in normal and malignant prostate. Endocrine therapies for prostate cancer include inhibition of androgen production either by analogs of luteinizing hormone releasing hormone or abiraterone acetate and/or use of anti-androgens such as hydroxyflutamide, bicalutamide, and enzalutamide. Castration therapy-resistant cancer develops inevitably in patients who undergo treatment. AR coactivators are proteins which interact with one or more regions of the AR thus enhancing its function. Although several functions of AR coactivators may be redundant, specific functions have been identified and analyzed. The p160 group of coactivators, SRC-1, -2, and -3 not only potentiate the activation of the AR, but are also implicated in potentiation of function of insulin-like growth factor-I and activation of the Akt pathway. Transcriptional integrators p300 and CBP are up-regulated by androgen ablation and may influence antagonist/agonist balance of non-steroidal anti-androgens. A therapy approach designed to target p300 in prostate cancer revealed its role in regulation of proliferation of migration of androgen-sensitive and -insensitive prostate cancer cells. Coactivators p300 and SRC-1 are required for AR activation by interleukin-6 (IL-6), a cytokine that is overexpressed in castration therapy-resistant prostate cancer. Some coactivators, such as Vav3, are involved in regulation of transcriptional activity of truncated AR, which emerge during endocrine thrapy. Stimulation of cellular migration and invasion by AR coactivators has also been described. Translational studies with aim to introduce anti-AR coactivator therapy have not been successfully implemented in the clinic so far.

Aberrant lysine acetylation in tumorigenesis: Implications in the development of therapeutics

The 'language' of covalent histone modifications translates environmental and cellular cues into gene expression. This vast array of post-translational modifications on histones are more than just covalent moieties added onto a protein, as they also form a platform on which crucial cellular signals are relayed. The reversible lysine acetylation has emerged as an important post-translational modification of both histone and non-histone proteins, dictating numerous epigenetic programs within a cell. Thus, understanding the complex biology of lysine acetylation and its regulators is essential for the development of epigenetic therapeutics. In this review, we will attempt to address the complexities of lysine acetylation in the context of tumorigenesis, their role in cancer progression and emphasize on the modalities developed to target lysine acetyltransferases towards cancer treatment.

Dichotomy in the Epigenetic Mark Lysine Acetylation is Critical for the Proliferation of Prostate Cancer Cells

The dynamics of lysine acetylation serve as a major epigenetic mark, which regulates cellular response to inflammation, DNA damage and hormonal changes. Microarray assays reveal changes in gene expression, but cannot predict regulation of a protein function by epigenetic modifications. The present study employs computational tools to inclusively analyze microarray data to understand the potential role of acetylation during development of androgen-independent PCa. The data revealed that the androgen receptor interacts with 333 proteins, out of which at least 92 proteins were acetylated. Notably, the number of cellular proteins undergoing acetylation in the androgen-dependent PCa was more as compared to the androgen-independent PCa. Specifically, the 32 lysine-acetylated proteins in the cellular models of androgen-dependent PCa were mainly involved in regulating stability as well as pre- and post-processing of mRNA. Collectively, the data demonstrate that protein lysine acetylation plays a crucial role during the transition of androgen-dependent to -independent PCa, which importantly, could also serve as a functional axis to unravel new therapeutic targets.