BAP18 coactivates androgen receptor action and promotes prostate cancer progression

BAP18 acting as a novel peroxisome proliferator-activated receptor α co-regulator contributes to hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is a common malignancy worldwide with a poor prognosis. The therapeutic outcomes of HCC patients are urgently needed to be improved, and predictive biomarkers for the optimal treatment selection remains to be further defined. In the present study, our results showed that BPTF-associated protein of 18 KDa (BAP18) was highly expressed in HCC tissues. In cultured HCC cells, BAP18 regulated a subset of down-stream genes involved in different functions, particularly including peroxisome proliferator-activated receptor (PPAR) pathway and lipid metabolism. Furthermore, BAP18 co-activated PPARα-mediated transactivation and facilitated the recruitment of nucleosome acetyltransferase of H4 (NuA4)/tat interacting protein 60 (TIP60) complex, thereby increasing histone H4 acetylation on stearoyl-CoA desaturase 1 (SCD1) loci. In addition, BAP18 promoted HCC cell proliferation, increased intracellular lipid levels and enhanced cell survival under the metabolic stress conditions, such as glucose limitation or tyrosine kinase inhibitors (TKIs) treatment. Importantly, higher BAP18 expression was positively correlated with the postoperative recurrence and the poor disease-free survival in clinical patients receiving sorafenib treatment. Altogether, we discovered that BAP18 plays an oncogenic role in the survival and proliferation of HCC cells, and BAP18 may serve as a predictive biomarker for adjunct TKIs treatment in patients with HCC, and further facilitate the precise treatment.

MTTLm6A: A multi-task transfer learning approach for base-resolution mRNA m6A site prediction based on an improved transformer

N6-methyladenosine (m6A) is a crucial RNA modification involved in various biological activities. Computational methods have been developed for the detection of m6A sites in Saccharomyces cerevisiae at base-resolution due to their cost-effectiveness and efficiency. However, the generalization of these methods has been hindered by limited base-resolution datasets. Additionally, RMBase contains a vast number of low-resolution m6A sites for Saccharomyces cerevisiae, and base-resolution sites are often inferred from these low-resolution results through post-calibration. We propose MTTLm6A, a multi-task transfer learning approach for base-resolution mRNA m6A site prediction based on an improved transformer. First, the RNA sequences are encoded by using one-hot encoding. Then, we construct a multi-task model that combines a convolutional neural network with a multi-head-attention deep framework. This model not only detects low-resolution m6A sites, it also assigns reasonable probabilities to the predicted sites. Finally, we employ transfer learning to predict base-resolution m6A sites based on the low-resolution m6A sites. Experimental results on Saccharomyces cerevisiae m6A and Homo sapiens m1A data demonstrate that MTTLm6A respectively achieved area under the receiver operating characteristic (AUROC) values of 77.13% and 92.9%, outperforming the state-of-the-art models. At the same time, it shows that the model has strong generalization ability. To enhance user convenience, we have made a user-friendly web server for MTTLm6A publicly available at http://47.242.23.141/MTTLm6A/index.php.

MYSM1 acts as a novel co-activator of ERα to confer antiestrogen resistance in breast cancer

Endocrine resistance is a crucial challenge in estrogen receptor alpha (ERα)-positive breast cancer (BCa). Aberrant alteration in modulation of E2/ERα signaling pathway has emerged as the putative contributor for endocrine resistance in BCa. Herein, we demonstrate that MYSM1 as a deubiquitinase participates in modulating ERα action via histone and non-histone deubiquitination. MYSM1 is involved in maintenance of ERα stability via ERα deubiquitination. MYSM1 regulates relevant histone modifications on cis regulatory elements of ERα-regulated genes, facilitating chromatin decondensation. MYSM1 is highly expressed in clinical BCa samples. MYSM1 depletion attenuates BCa-derived cell growth in xenograft models and increases the sensitivity of antiestrogen agents in BCa cells. A virtual screen shows that the small molecule Imatinib could potentially interact with catalytic MPN domain of MYSM1 to inhibit BCa cell growth via MYSM1-ERα axis. These findings clarify the molecular mechanism of MYSM1 as an epigenetic modifier in regulation of ERα action and provide a potential therapeutic target for endocrine resistance in BCa.

BAP18 facilitates CTCF-mediated chromatin accessible to regulate enhancer activity in breast cancer

The estrogen receptor alpha (ERα) signaling pathway is a crucial target for ERα-positive breast cancer therapeutic strategies. Co-regulators and other transcription factors cooperate for effective ERα-related enhancer activation. Recent studies demonstrate that the transcription factor CTCF is essential to participate in ERα/E2-induced enhancer transactivation. However, the mechanism of how CTCF is achieved remains unknown. Here, we provided evidence that BAP18 is required for CTCF recruitment on ERα-enriched enhancers, facilitating CTCF-mediated chromatin accessibility to promote enhancer RNAs transcription. Consistently, GRO-seq demonstrates that the enhancer activity is positively correlated with BAP18 enrichment. Furthermore, BAP18 interacts with SMARCA1/BPTF to accelerate the recruitment of CTCF to ERα-related enhancers. Interestingly, BAP18 is involved in chromatin accessibility within enhancer regions, thereby increasing enhancer transactivation and enhancer-promoter looping. BAP18 depletion increases the sensitivity of anti-estrogen and anti-enhancer treatment in MCF7 cells. Collectively, our study indicates that BAP18 coordinates with CTCF to enlarge the transactivation of ERα-related enhancers, providing a better understanding of BAP18/CTCF coupling chromatin remodeling and E-P looping in the regulation of enhancer transcription.

Yeast-based evolutionary modeling of androgen receptor mutations and natural selection

Cancer progression is associated with the evolutionary accumulation of genetic mutations that are biologically significant. Mutations of the androgen receptor (AR) are associated with the development of prostate cancer (PCa) by responding to non-androgenic hormones, and the lack of annotations in their responsiveness to hormone ligands remains a daunting challenge. Here, we have used a yeast reporter system to quickly evaluate the responsiveness of all fifty clinical AR mutations to a variety of steroidal ligands including dihydrotestosterone (DHT), 17β-estradiol (E2), progesterone (PROG), and cyproterone acetate (CPA). Based on an AR-driven reporter that synthesizes histidine, a basic amino acid required for yeast survival and propagation, the yeast reporter system enabling clonal selection was further empowered by combining with a random DNA mutagenesis library to simulate the natural evolution of AR gene under the selective pressures of steroidal ligands. In a time-frame of 1-2 weeks, 19 AR mutants were identified, in which 11 AR mutants were validated for activation by tested steroidal compounds. The high efficiency of our artificial evolution strategy was further evidenced by a sequential selection that enabled the discovery of multipoint AR mutations and evolution directions under the pressure of steroidal ligands. In summary, our designer yeast is a portable reporter module that can be readily adapted to streamline high-throughput AR-compound screening, used as a PCa clinical reference, and combined with additional bioassay systems to further extend its potential.

Ubiquitin-specific peptidase 14 maintains estrogen receptor α stability via its deubiquitination activity in endometrial cancer

USP14 deubiquitinates ERα to maintain its stability in ECEndometrial cancer (EC) is one of the common gynecological malignancies of which the incidence has been rising for decades. It is considered that continuously unopposed estrogen exposure is the main risk factor for EC initiation. Thus, exploring the modulation of estrogen/estrogen receptor α (ERα) signaling pathway in EC would be helpful to well understand the mechanism of EC development and find the potential target for EC therapy. Ubiquitin-specific peptidase 14 (USP14), a member of the proteasome-associated deubiquitinating enzyme family, plays a crucial role in a series of tumors. However, the function of USP14 in EC is still elusive. Here, our results have demonstrated that USP14 is highly expressed in EC tissues compared with that in normal endometrial tissues, and higher expression of USP14 is positively correlated with poor prognosis. Moreover, USP14 maintains ERα stability through its deubiquitination activity. Our results further demonstrate that USP14 depletion decreases the expression of ERα-regulated genes in EC-derived cell lines. Moreover, knockdown of USP14 or USP14-specific inhibitor treatment significantly suppresses cell growth and migration in EC cell lines or in mice. We further provide the evidence to show that the effect of USP14 on EC cell growth, if not all, at least is partially related to ERα pathway. Our study provides new sights for USP14 to be a potential therapeutic target for the treatment of EC, especially for EC patients with fertility preservation needs.

Chromatin complexes subunit BAP18 promotes triple-negative breast cancer progression through transcriptional activation of oncogene S100A9

Triple-negative breast cancer (TNBC) is a highly lethal disease due to aggressive clinical phenotype and the lack of validated therapeutic targets. Our recent quantitative proteomic analysis of 90 cases of TNBC tissues and 72 cases of matched adjacent normal tissues revealed that the expression levels of BPTF-associated protein of 18 KDa (BAP18), a component of the MLL1 and NURF chromatin complexes, were upregulated in TNBC tissues relative to normal tissues. However, the biological function and the underlying mechanism of BAP18 in TNBC progression remain unexplored. Here, we report that BAP18 promoted TNBC cell proliferation, migration, and invasion in vitro and xenograft tumor growth and lung colonization in vivo. Mechanistic investigations revealed that S100 calcium-binding protein A9 (S100A9), a member of the S100 protein family that is frequently upregulated in breast tumors and acts as an oncogenic driver in breast cancer progression, was a downstream target gene of BAP18. BAP18 was recruited to histone H3 trimethylation at lysine 4 (H3K4me3)-marked promoter of S100A9 and enhanced its promoter activities. Notably, knockdown of BAP18 by short hairpin RNA in TNBC cells suppressed xenograft tumor growth in mice, the noted effect was partially reverted by re-expression of S100A9 in BAP18-depleted cells. Taken together, these results suggest that BAP18 promotes TNBC progression through, at least in part, transcriptional activation of oncogene S100A9, and represents a potential therapeutic target for TNBC.

The Ash2l SDI Domain Is Required to Maintain the Stability and Binding of DPY30

ASH2L and DPY30 are important for the assembly and catalytic activity of the complex associated with SET1 (COMPASS), which catalyzes histone methylation and regulates gene expression. However, the regulations among COMPASS components are not fully understood. Here, we leveraged a mouse model and cell lines to observe the outcome of Ash2l depletion and found a significant decrease in DPY30. Analyzing ASH2L ChIP-seq and RNA-seq data excluded transcriptional and translational regulation of ASH2L to DPY30. The decrease in DPY30 was further attributed to the degradation via the ubiquitin-mediated proteasomal pathway. We also verified that three amino acids in the ASH2L Sdc1 DPY30 interaction (SDI) domain are essential for the recognition and binding of DPY30. Lastly, we unexpectedly observed that overexpression of DPY30 in Ash2l-depleted cells rescued the decrease in Ccnd1 and the abnormal cell cycle, which indicates that DPY30 can participate in other complexes to regulate gene expression. Overall, our results, for the first time, reveal that the existence of DPY30 relies on the binding with ASH2L, with degradation of DPY30 via the ubiquitin-proteasome system, and they further indicate that the function of DPY30 can be independent of ASH2L.

RNF8 up-regulates AR/ARV7 action to contribute to advanced prostate cancer progression

Androgen receptor (AR) signaling drives prostate cancer (PC) progression. Androgen deprivation therapy (ADT) is temporally effective, whereas drug resistance inevitably develops. Abnormal expression of AR/ARV7 (the most common AR splicing variant) is critical for endocrine resistance, while the detailed mechanism is still elusive. In this study, bioinformatics and immunohistochemical analyses demonstrate that RNF8 is high expressed in PC and castration-resistant PC (CRPC) samples and the expression of RNF8 is positively correlated with the Gleason score. The high expression of RNF8 in PCs predicts a poor prognosis. These results provide a potential function of RNF8 in PC progression. Furthermore, the mRNA expression of RNF8 is positively correlated with that of AR in PC. Mechanistically, we find that RNF8 upregulates c-Myc-induced AR transcription via altering histone modifications at the c-Myc binding site within the AR gene. RNF8 also acts as a co-activator of AR, promoting the recruitment of AR/ARV7 to the KLK3 (PSA) promoter, where RNF8 modulates histone modifications. These functions of RNF8 are dependent on its E3 ligase activity. RNF8 knockdown further reduces AR transactivation and PSA expression in CRPC cells with enzalutamide treatment. RNF8 depletion restrains cell proliferation and alleviates enzalutamide resistance in CRPC cells. Our findings indicate that RNF8 may be a potential therapeutic target for endocrine resistance in PC.

Opportunity knocks for uncovering the new function of an understudied nucleosome remodeling complex member, the bromodomain PHD finger transcription factor, BPTF

Nucleosome remodeling provides access to genomic DNA for recruitment of the transcriptional machinery to mediate gene expression. The aberrant function of nucleosome remodeling complexes has been correlated to human cancer, making them emerging therapeutic targets. The bromodomain PHD finger transcription factor, BPTF, is the largest member of the human nucleosome remodeling factor NURF. Over the last five years, BPTF has become increasingly identified as a protumorigenic factor, prompting investigations into the molecular mechanisms associated with BPTF function. Despite a druggable bromodomain, small molecule discovery is at an early stage. Here we highlight recent investigations into the biology being discovered for BPTF, chemical biology approaches used to study its function, and small molecule inhibitors being designed as future chemical probes and therapeutics.

Expression and potential role of CXCL5 in the pathogenesis of intrauterine adhesions

Objective

C-X-C motif chemokine ligand 5 (CXCL5), a member of the chemokine family, is associated with remodeling of connective tissues. However, its role in formation of intrauterine adhesions (IUA) remains unclear. We aimed to investigate the expression and mechanism underlying the role of CXCL5 in IUA.

Methods

Expression of CXCL5 in IUA was detected by immunohistochemistry in a rat model of IUA and by real-time PCR and western blotting in patients with IUA. The protein levels of matrix metalloproteinase 9 (MMP9) and transcription factor p65 in human endometrial cells were assessed by western blotting after CXCL5 overexpression.

Results

Protein expression of CXCL5 was significantly decreased in the endometria of IUA rats compared with that of control and sham-operated rats. Real-time PCR and western blotting in patients with IUA showed similar results to those from the rat model. After overexpression, CXCL5 significantly upregulated expression of MMP9 and slightly upregulated expression of p65 in human endometrial cells.

Conclusions

CXCL5 plays an important role in IUA formation after endometrial injury. We propose a molecular mechanism to explain formation of IUA, including downregulation of MMP9 by low CXCL5 expression. These findings provide valuable information for the prevention and targeted therapy of IUA.

The function of BAP18 on modulation of androgen receptor action in luteinized granulosa cells from normal weight women with and without PCOS

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in reproductive-age women. In this study, BPTF associated protein of 18 kDa (BAP18) is decreased in luteinized granulosa cells (GCs) from PCOS women. BAP18 depletion significantly decreases CYP19A1 expression levels, leading to an abrogation in transfer capacity of androgen to estrogen in GCs. Also, BAP18 knockdown delays cell cycle G1 to S phase transition and induces cell apoptosis to decrease GCs proliferation. We also provide evidence showing BAP18 interacts with androgen receptor (AR) and enhances AR-mediated transactivation in GCs. Results indicate that AR or BAP18 recruits to androgen response elements (AREs) of CYP19A1 and FSHR, which are putative AR-induced genes in GCs. BAP18 interacts with Sp1 transcription factor and co-recruits to the promoter region of AR gene, resulting in AR transactivation in GCs. Taken together, these data provide new insights on the pathophysiology of PCOS.

PRPF6 promotes androgen receptor/androgen receptor-variant 7 actions in castration-resistant prostate cancer cells

Androgen receptor (AR) and its variants play vital roles in development and progression of prostate cancer. To clarify the mechanisms involved in the enhancement of their actions would be crucial for understanding the process in prostate cancer and castration-resistant prostate cancer transformation. Here, we provided the evidence to show that pre-mRNA processing factor 6 (PRPF6) acts as a key regulator for action of both AR full length (AR-FL) and AR variant 7 (AR-V7), thereby participating in the enhancement of AR-FL and AR-V7-induced transactivation in prostate cancer. In addition, PRPF6 is recruited to cis-regulatory elements in AR target genes and associates with JMJD1A to enhance AR-induced transactivation. PRPF6 also promotes expression of AR-FL and AR-V7. Moreover, PRPF6 depletion reduces tumor growth in prostate cancer-derived cell lines and results in significant suppression of xenograft tumors even under castration condition in mouse model. Furthermore, PRPF6 is obviously highly expressed in human prostate cancer samples. Collectively, our results suggest PRPF6 is involved in enhancement of oncogenic AR signaling, which support a previously unknown role of PRPF6 during progression of prostate cancer and castration-resistant prostate cancers.

An H3K4me3 reader, BAP18 as an adaptor of COMPASS-like core subunits co-activates ERα action and associates with the sensitivity of antiestrogen in breast cancer

Estrogen receptor alpha (ERα) signaling pathway is essential for ERα-positive breast cancer progression and endocrine therapy resistance. Bromodomain PHD Finger Transcription Factor (BPTF) associated protein of 18kDa (BAP18) has been recognized as a crucial H3K4me3 reader. However, the whole genomic occupation of BAP18 and its biological function in breast cancer is still elusive. Here, we found that higher expression of BAP18 in ERα-positive breast cancer is positively correlated with poor prognosis. ChIP-seq analysis further demonstrated that the half estrogen response elements (EREs) and the CCCTC binding factor (CTCF) binding sites are the significant enrichment sites found in estrogen-induced BAP18 binding sites. Also, we provide the evidence to demonstrate that BAP18 as a novel co-activator of ERα is required for the recruitment of COMPASS-like core subunits to the cis-regulatory element of ERα target genes in breast cancer cells. BAP18 is recruited to the promoter regions of estrogen-induced genes, accompanied with the enrichment of the lysine 4-trimethylated histone H3 tail (H3K4me3) in the presence of E2. Furthermore, BAP18 promotes cell growth and associates the sensitivity of antiestrogen in ERα-positive breast cancer. Our data suggest that BAP18 facilitates the association between ERα and COMPASS-like core subunits, which might be an essential epigenetic therapeutic target for breast cancer.

ATXN7L3 positively regulates SMAD7 transcription in hepatocellular carcinoma with growth inhibitory function

Background

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide, with unmet need for the pharmacological therapy. The functions of ATXN7L3 in HCC progression are not known.

Methods

RNA sequence, quantitative real-time PCR, and western blot were performed to detect gene expression. Chromatin immunoprecipitation was performed to detect possible mechanisms. Immunohistochemical stain was performed to examine the protein expression. Colony formation, cell growth curve and xenograft tumor experiments were performed to examine cell growth in vitro and in vivo.

Findings

ATXN7L3 functions as a coactivator for ERα-mediated transactivation in HCC cells, thereby contributing to enhanced SMAD7 transcription. ATXN7L3 is recruited to the promoter regions of SMAD7 gene, thereby regulating histone H2B ubiquitination level, to enhance the transcription of SMAD7. A series of genes regulated by ATXN7L3 were identified. Moreover, ATXN7L3 participates in suppression of tumor growth. In addition, ATXN7L3 is lower expressed in HCC samples, and the lower expression of ATXN7L3 positively correlates with poor clinical outcome in patients with HCC.

Interpretation

This study demonstrated that ATXN7L3 is a novel regulator of SMAD7 transcription, subsequently participating in inhibition of tumor growth in HCC, which provides an insight to support a previously unknown role of ATXN7L3 in HCC progression.

Fund

This work was funded by 973 Program Grant from the Ministry of Science and Technology of China (2013CB945201), National Natural Science Foundation of China (31871286, 81872015, 31701102, 81702800, 81902889), Foundation for Special Professor of Liaoning Province, Natural Science Foundation of Liaoning Province (No.20180530072); China Postdoctoral Science Foundation (2019M651164).

Splicing factor PRPF6 upregulates oncogenic androgen receptor signaling pathway in hepatocellular carcinoma

Androgen receptor (AR) signaling is considered to be crucial for the pathogenesis of hepatocellular carcinoma (HCC) with obvious sexual dimorphism. Pre‐mRNA processing factor 6 (PRPF6) was identified as a coactivator of AR. However, the molecular mechanism underlying the modulation function of PRPF6 on AR‐mediated transcriptional activity in HCC needs to be further clarified. In this study, we analyzed data from The Cancer Genome Atlas to show that PRPF6 is highly expressed in HCC. . Our data indicated that PRPF6 interacts with AR/AR splice variants (AR‐Vs) and upregulates AR/AR splice variant 7‐mediated transcriptional activity even without dihydrotestosterone treatment. We observed that AR is obviously induced by androgen treatment and is mainly expressed in the nucleus in HCC‐derived cell lines. Moreover, overexpression of PRPF6 enhances AR expression accompanied with the increase of AR‐Vs expression. We provided evidence that PRPF6 participates in upregulating AR self‐transcription. PRPF6 facilitates the recruitment of AR to the androgen responsive element region of the AR gene. Finally, PRPF6 depletion inhibits cell proliferation in HCC cells and mouse xenografts. Taken together, our results suggest that PRPF6 as a splicing factor enhances AR self‐transcription, thereby coactivating oncogenic AR/AR‐Vs actions in HCC.

BAP18 is involved in upregulation of CCND1/2 transcription to promote cell growth in oral squamous cell carcinoma

BACKGROUND

As a reader of histone H3K4me3, BPTF associated protein of 18 kDa (BAP18) is involved in modulation of androgen receptor action in prostate cancer. However, the function of BAP18 on oral squamous cell carcinoma (OSCC) and its molecular mechanism remains to be elusive.

METHODS

OSCC-derived cell lines carrying silenced BAP18 were established by Lentiviral infection. Quantitative PCR (qPCR), western blot, and ChIP assay were performed to detect gene transcription regulation and the possible mechanism. Colony formation, cell growth curve and xenograft tumor experiments were performed to examine cell growth and proliferation.

FINDINGS

Our study demonstrated that BAP18 was highly expressed in OSCC samples compared with that in benign. BAP18 depletion obviously influenced the expression of a series of genes, including cell cycle-related genes. We thus provided the evidence to demonstrate that BAP18 depletion significantly decreases CCND1 and CCND2 (CCND1/2) transcription. In addition, BAP18 is recruited to the promoter regions of CCND1/2, thereby facilitating the recruitment of the core subunits of MLL1 complex to the same regions, to increase histone H3K4me3 levels. Furthermore, BAP18 depletion delayed G1-S phase transition and inhibited cell growth in OSCC-derived cell lines.

INTERPRETATION

This study suggests that BAP18 is involved in modulation of CCND1/2 transcription and promotes OSCC progression. BAP18 could be a potential target for OSCC treatment and diagnosis. FUND: This work was funded by National Natural Science Foundation of China (31871286, 81872015, 31701102, 81702800, 81902889), Foundation for Special Professor of Liaoning Province, and Supported project for young technological innovation-talents in Shenyang (No. RC170541).

Expression and potential role of SNF5 in endometrial carcinoma

Background

SNF5 is a key protein in regulating cell proliferation and apoptosis in various cancers. However, the physiological roles of SNF5 in Endometrial carcinoma (EC), which is one of the most frequent malignancies of the female reproduction worldwide, remains unclear. This study aims to investigate the role of SNF5 and its correlation with clinicopathologic characteristics in EC.

Methods

We performed immunohistochemistry to detect the SNF5 expression in 46 endometrial carcinomas and 20 normal endometrium (non-EC) specimens, as well as analyzed the correlations between SNF5 expression and clinicopathologic features of patients using a statistics software (GraphPad Prism V6.0). Western blotting had been used to confirm the protein level of SNF5 in endometrial tissues. In addition, we evaluated the correlations between SNF5 and p21 in EC.

Results

The positive immunostaining rate for SNF5 in EC and non-EC specimens were 65% (30/46) and 25% (5/20) respectively, and the expression of SNF5 was dramatically increased in EC compared with the normal endometrium (P < 0.01). The overexpression of SNF5 was associated with the PR levels, but not with age, FIGO stage, grade, lymphatic metastasis, myometrial invasion or ER status. Knockdown of SNF5 inhibits the expression of p21.

Conclusions

Our results indicate that SNF5 plays an important role of promoting oncogenesis in EC. These findings open up the possibility for various novel and effective combination therapies targeting SNF5 in the EC.

Histone acetyltransferase MOF is involved in suppression of endometrial cancer and maintenance of ERα stability

Histone acetyltransferase MOF is involved in active transcription regulation through histone H4K16 acetylation. MOF is downexpressed in a number of human tumors, but biological function of MOF in endometrial cancer has not been fully defined. The estrogen receptor α (ERα) is a transcription factor that regulates estrogen-stimulated cell proliferation in hormone-responsive tumors. However, ERα expression is decreased in grade III ECa samples and high expression of ERα is associated with long disease-free survival in ECa. The molecular mechanism for these observations is still unclear. Here we demonstrate knockdown of MOF promotes ECa cell growth and proliferation in vitro and in vivo. Clinical evidence indicates that expression MOF is decreased and positively correlated with that of ERα in ECa tissues. Furthermore, MOF physically interacts with ERα and modulates ERα stability in ECa cells. In addition, MOF modulates expression of a subset of endogenous genes regulated by ERα. Taken together, our results define MOF as a potential tumor suppressor in ECa participates in maintenance of ERα protein stability and regulation of ERα action.

Androgen receptor: what we know and what we expect in castration-resistant prostate cancer

Androgen deprivation therapy is an important therapy for prostate cancer (PCa) in aging men. Under the background of castration, it is inevitable that prostate cancer will develop into castration-resistant prostate cancer (CRPC), which has a high mortality rate, after 2-3 years. Androgen receptor (AR) plays a key role in PCa development and is essential to CRPC. More recent research studies have reported that the development of CRPC is largely due to altered mechanisms related to AR, so it is important for us to understand the roles of AR and detailed AR-related mechanisms in CRPC. The multiple AR-related mechanisms promoting the development of CRPC are as follows: (1) enhanced transformation and increased synthesis of intratumoral androgen; (2) AR overexpression, which enables CRPC to be hypersensitive to low levels of androgen; (3) AR cofactors, which enhanced AR transactivation; (4) AR-spliced variants, which mediated downstream gene expression without androgen; (5) the interaction between the AR pathway and classic tumor-related pathways; and» (6) AR mutations, which reduced AR specificity and enhanced AR transcription.

Bromodomain-containing proteins in prostate cancer

Several oncogenic factors have been involved in prostate cancer progression. However, therapeutic approaches still focus on suppression of androgen receptor (AR) signaling. In fact, whereas the full-length AR incorporates a ligand-binding domain, which has become a drug target for competitive inhibitors, other transcription factors often do not have tractable binding pockets that aid drug development. Consequently drug development efforts have turned to transcription co-regulators, often chromatin-modifying enzymes or factors that bind to epigenetic modifications to chromatin. Bromodomain (BRD)-containing proteins fall into the latter category and significant progress has been made in developing small molecule inhibitors that target a particular subgroup of BRD-containing proteins known as the Bromodomain and extra-terminal (BET) family proteins. These inhibitors have proven particularly effective in inactivating c-Myc in lymphoma but more recently members of the BET family have also been identified as AR-interacting proteins raising the prospect of using these inhibitors as an alternative strategy for targeting AR-driven cancers. In this review we will provide an overview of BRD-containing proteins and the potential for exploiting them as biomarkers and drug targets in prostate cancer.

The role of CREB3L4 in the proliferation of prostate cancer cells

The incidence of prostate cancer (PC) is growing rapidly throughout the world, in probable association with the adoption of western style diets. Thus, understanding the molecular pathways triggering the development of PC is crucial for both its prevention and treatment. Here, we investigated the role of the metabolism-associated protein, CREB3L4, in the proliferation of PC cells. CREB3L4 was upregulated by the synthetic androgen, R1881, in LNCaP PC cells (an androgen-dependent cell line). Knockdown of CREB3L4 resulted in decreased androgen-dependent PC cell growth. LNCaP cells transfected with siCREB3L4 underwent G2/M arrest, with upregulation of the proteins cyclin B1, phospho-CDK1, p21^Waf1/Cip1, and INCA1, and downregulation of cyclin D1. Moreover, depletion of CREB3L4 resulted in significantly decreased expression of a subset of androgen-receptor (AR) target genes, including PSA, FKBP5, HPGD, KLK2, and KLK4. We also demonstrated that CREB3L4 directly interacts with the AR, and increases the binding of AR to androgen response elements (AREs). We also identified a role for the unfolded protein response (and its surrogate, IRE1α), in activating CREB3L4. Cumulatively, we postulate that CREB3L4 expression is mediated by an AR-IRE1α axis, but is also directly regulated by AR-to-ARE binding. Thus, our study demonstrates that CREB3L4 plays a key role in PC cell proliferation, which is promoted by both AR and IRE1α.

The HIF/PHF8/AR axis promotes prostate cancer progression

Recent studies provide strong evidence that the androgen receptor (AR) signaling pathway remains active in castration-resistant prostate cancer (CRPC). However, the underlying mechanisms are not well understood. In this study, we demonstrate that plant homeo domain finger protein 8 (PHF8 )interacts with and functions as an essential histone demethylase activity-dependent AR coactivator. Furthermore, we demonstrate that the expression of PHF8 is induced by hypoxia in various prostate cancer cell lines. Knockdown of either hypoxia-inducible factor HIF2α or HIF1α almost completely abolished hypoxia-induced PHF8 expression. Importantly, we observed that PHF8 is highly expressed in clinical androgen deprived prostate cancer samples and expression of PHF8 correlates with increased levels of HIF1α and HIF2α. Moreover, elevated PHF8 is associated with higher grade prostate cancers and unfavorable outcomes. Our findings support a working model in which hypoxia in castrated prostate cancer activates HIF transcription factors which then induces PHF8 expression. The elevated PHF8 in turn promotes the AR signaling pathway and prostate cancer progression. Therefore, the HIF/PHF8/AR axis could serve as a potential biomarker for CRPC and is also a promising therapeutic target in combating CRPC.