Regulation of a novel androgen receptor target gene, the cyclin B1 gene, through androgen-dependent E2F family member switching

Genetic and biological drivers of prostate cancer disparities in Black men

Black men with prostate cancer have historically had worse outcomes than white men with prostate cancer. The causes of this disparity in outcomes are multi-factorial, but a potential basis is that prostate cancers in Black men are biologically distinct from prostate cancers in white men. Evidence suggests that genetic and ancestral factors, molecular pathways involving androgen and non-androgen receptor signalling, inflammation, epigenetics, the tumour microenvironment and tumour metabolism are contributing factors to the racial disparities observed. Key genetic and molecular pathways linked to prostate cancer risk and aggressiveness have potential clinical relevance. Describing biological drivers of prostate cancer disparities could inform efforts to improve outcomes for Black men with prostate cancer.

Potential Therapeutic Targets for Luminal Androgen Receptor Breast Cancer: What We Know so Far

Luminal Androgen Receptor Breast Cancers (LAR BCs) are characterized by a triple negative phenotype and by the expression of Androgen Receptor (AR), coupled with luminal-like genomic features. This unique BC subtype, accounting for about 10% of all triple negative BC, has raised considerable interest given its ill-defined clinical behavior and the chance to exploit AR as a therapeutic target. The complexity of AR activity in BC cells, as revealed by decades of mechanistic studies, holds promise to offer additional therapeutic options beyond mere AR inhibition. Indeed, preclinical and translational evidence showed that several pathways and mediators, including PI3K/mToR, HER2, BRCA1, cell cycle and immune modulation, can be tackled in LAR BCs. Moving from bench to bedside, several clinical trials tested anti-androgen therapies in LAR BCs, but their results are inconsistent and often disappointing. More recently, studies exploring combinations of anti-androgen agents with other targeted therapies have been designed and are currently ongoing. While the results from these trials are awaited, a concerted effort will be needed to find the biological vulnerabilities of LAR BCs which may disclose new and effective therapeutic targets, eventually improving patients' outcomes.

The role of cyclins in the development and progression of prostate cancer

The role of cyclins in hormone-dependent neoplasms is crucial in the development of the disease that is resistant to first-line therapy, as the example of breast cancer shows. However, in prostate cancer, cyclins are studied to a lesser extent. There are some well-described molecular pathways, including cyclins A1 and D1 signaling, however the role of other cyclins, e.g., D2, D3, E, and H, still requires further investigation. Recent studies indicate that cyclins regulate various cellular processes, not only the cell cycle. Furthermore, they remain in cross-talk with many other signaling pathways, e.g., MAPK/ERK, PI3K/Akt, and Notch. The androgen signaling axis, which is pivotal in prostate cancer progression, interferes with cyclin pathways at many levels. This article summarizes current knowledge on the influence of cyclins on prostate cancer progression by describing interactions between the androgen receptor and cyclins, as well as mechanisms underlying the development of resistance to currently used therapies.

Deep Learning-Based Multi-Omics Integration Robustly Predicts Relapse in Prostate Cancer

Objective

Post-operative biochemical relapse (BCR) continues to occur in a significant percentage of patients with localized prostate cancer (PCa). Current stratification methods are not adequate to identify high-risk patients. The present study exploits the ability of deep learning (DL) algorithms using the H2O package to combine multi-omics data to resolve this problem.

Methods

Five-omics data from 417 PCa patients from The Cancer Genome Atlas (TCGA) were used to construct the DL-based, relapse-sensitive model. Among them, 265 (63.5%) individuals experienced BCR. Five additional independent validation sets were applied to assess its predictive robustness. Bioinformatics analyses of two relapse-associated subgroups were then performed for identification of differentially expressed genes (DEGs), enriched pathway analysis, copy number analysis and immune cell infiltration analysis.

Results

The DL-based model, with a significant difference (P = 6e-9) between two subgroups and good concordance index (C-index = 0.767), were proven to be robust by external validation. 1530 DEGs including 678 up- and 852 down-regulated genes were identified in the high-risk subgroup S2 compared with the low-risk subgroup S1. Enrichment analyses found five hallmark gene sets were up-regulated while 13 were down-regulated. Then, we found that DNA damage repair pathways were significantly enriched in the S2 subgroup. CNV analysis showed that 30.18% of genes were significantly up-regulated and gene amplification on chromosomes 7 and 8 was significantly elevated in the S2 subgroup. Moreover, enrichment analysis revealed that some DEGs and pathways were associated with immunity. Three tumor-infiltrating immune cell (TIIC) groups with a higher proportion in the S2 subgroup (p = 1e-05, p = 8.7e-06, p = 0.00014) and one TIIC group with a higher proportion in the S1 subgroup (P = 1.3e-06) were identified.

Conclusion

We developed a novel, robust classification for understanding PCa relapse. This study validated the effectiveness of deep learning technique in prognosis prediction, and the method may benefit patients and prevent relapse by improving early detection and advancing early intervention.

Comprehensive analysis of the functional and prognostic value of E2F transcription factors in human prostate cancer through data mining and experimental validation

Background

A growing body of evidence shows that E2F transcription factors play a significant role in the tumorigenesis of prostate cancer. However, their functional and prognostic value has not been fully illustrated. Therefore, we used bioinformatics methods to further analyze the possible roles of E2F transcription factors in the development and progression of prostate cancer.

Methods

We explored the expression levels of E2F transcription factors using data from The Cancer Genome Atlas (TCGA) and Oncomine database in paired and unpaired samples. The clinical correlation and prognostic value of E2F transcription factors were assessed. Using the R package “pROC”, we judged the diagnostic value of E2F transcription factors. The online website tool cBioPortal was also employed to find possible gene alterations of E2F transcription factors in samples from TCGA. The R package “clusterprofiler” was used to conduct functional analysis. Moreover, we also used the Tumor Immune Estimation Resource to search for the associations between E2F transcription factors and the infiltration levels of 6 kinds of immune cells. Finally, quantitative real-time polymerase chain reaction (PCR) was conducted to validate the expression levels of E2F transcription factors in human paired prostate tissues.

Results

E2F1/2/3/5 messenger RNA (mRNA) expression levels were higher in prostate cancer tissues than in normal tissues, while E2F4 and E2F6 mRNA expression levels were lower (P<0.05). All E2F transcription factors were associated with clinical parameters. Kaplan-Meier analysis revealed that E2F1/4/6/8 were notably associated with the overall survival of patients with prostate cancer (P<0.05). Receiver operating characteristic (ROC) curve results showed that except for E2F7, the other E2F transcription factors had diagnostic value for prostate cancer (P<0.05). We further found close associations between E2F transcription factors and the infiltration levels of immune cells. The results of quantitative real-time PCR were consistent with those from public databases.

Conclusions

E2F transcription factor family members are differentially expressed in prostate cancer and are significantly related to the prognosis of patients, suggesting that they may be adopted as biomarkers for prognosis prediction and the treatment of prostate cancer.

The androgen receptor inhibits transcription of GPER1 by preventing Sp1 and Sp3 from binding to the promoters in prostate cancer cells

G-1, a GPER1 agonist, was shown to inhibit the growth of castration-resistant mouse xenografts but not their parental androgen-dependent tumors. It is currently unknown how the androgen receptor (AR) represses GPER1 expression. Here, we found that two GPER1 mRNA variants (GPER1v2 and GPER1v4) were transcriptionally repressed, not via transcript destabilization, by the androgen-activated AR. Although no AR binding was found in all active promoters near GPER1, data from promoter assays suggested that both variants' promoters were inhibited by androgen treatment. Site-directed mutagenesis on Sp1/Sp3 binding sites revealed their role in supporting the basal expression of GPER1. Knockdown of Sp1 and Sp3 together but not separately repressed GPER1 expression whereas overexpression of both Sp1 and Sp3 together was required to alleviate AR repression of GPER1. Based on the chromatin immunoprecipitation data, Sp3 was found to bind to the promoters prior to the binding of Sp1 and RNA polymerase II. However, the binding of all three transcription factors was inhibited by DHT treatment. Concordantly, DHT treatment induced nuclear interactions between AR and Sp1 or Sp3. Taken together, these results indicate that AR represses transcription of GPER1 by binding to Sp1 and Sp3 independently to prevent their transactivation of the GPER1 promoters.

Hsa-mir-3163 and CCNB1 may be potential biomarkers and therapeutic targets for androgen receptor positive triple-negative breast cancer

Breast cancer (BC) is the most common malignancy in female, but the role of androgen receptor (AR) in triple-negative breast cancer (TNBC) is still unclear. This study aimed to exam the performance of innovative biomarkers for AR positive TNBC in diagnosis and therapies. Four datasets (GSE42568, GSE45827, GSE54002 and GSE76124) were analyzed by bioinformatic methods and the differential expression genes (DEGs) between the AR positive TNBC tissues and normal tissues were firstly identified by limma package and Venn diagrams. Next, Gene Ontologies (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to explore the relationship between these DEGs. Then, the Protein-protein interaction (PPI) network was constructed. CytoHubba and bioinformatic approaches including Molecular Complex Detection (MCODE), Gene Expression Profiling Interactive Analysis (GEPIA), the Kaplan–Meier (KM) plotter and The Human Pro-tein Atlas (THPA) were used to identify the hub genes. Lastly, a miRNA-hub-gene regulatory axis was constructed by use of Target Scan database and ENCORI database. As a result, a total of 390 common DEGs were identified, including 250 up-regulated and 140 down-regulated. GO and KEGG enrichment analysis showed that the up-regulated DEGs were mostly enriched in the cell division, mitotic nuclear division, nucleosome, midbody, protein heterodimerization activity, cadherin binding involved in cell−cell adhesion, systemic lupus erythematosus and alcoholism, while the down-regulated DEGs were mainly enriched in carbohydrate metabolic process, extracellular space, extracellular region, zinc ion binding and microRNAs in cancer. Then, 13 hub genes (CCNB2, FOXM1, HMMR, MAD2L1, RRM2, TPX2, TYMS, CEP55, AURKA, CCNB1, CDK1, TOP2A, PBK) were selected. The survival analysis revealed that only CCNB1 was associated with significantly poor survival (P <0.05) in TNBC patients. Finally, we found that hsa-miR-3163 took part in the regulation of CCNB1 and constructed a potential hsa-miR-3163-CCNB1 regulatory axis. The results of current study suggest that CCNB1 and hsa-miR-3163 may serve as highly potential prognostic markers and therapeutic targets for AR positive TNBC. Our findings may make contributions to the diagnosis and therapies of AR positive TNBC.

Histone Demethylase KDM7A Regulates Androgen Receptor Activity, and Its Chemical Inhibitor TC-E 5002 Overcomes Cisplatin-Resistance in Bladder Cancer Cells

Histone demethylase KDM7A regulates many biological processes, including differentiation, development, and the growth of several cancer cells. Here, we have focused on the role of KDM7A in bladder cancer cells, especially under drug-resistant conditions. When the KDM7A gene was knocked down, bladder cancer cell lines showed impaired cell growth, increased cell death, and reduced rates of cell migration. Biochemical studies revealed that KDM7A knockdown in the bladder cancer cells repressed the activity of androgen receptor (AR) through epigenetic regulation. When we developed a cisplatin-resistant bladder cancer cell line, we found that AR expression was highly elevated. Upon treatment with TC-E 5002, a chemical inhibitor of KDM7A, the cisplatin-resistant bladder cancer cells, showed decreased cell proliferation. In the mouse xenograft model, KDM7A knockdown or treatment with its inhibitor reduced the growth of the bladder tumor. We also observed the upregulation of KDM7A expression in patients with bladder cancer. The findings suggest that histone demethylase KDM7A mediates the growth of bladder cancer. Moreover, our findings highlight the therapeutic potential of the KMD7A inhibitor, TC-E 5002, in patients with cisplatin-resistant bladder cancer.

The Role of Crosstalk between AR3 and E2F1 in Drug Resistance in Prostate Cancer Cells

Background: Drug resistance is one of the most prevalent causes of death in advanced prostate cancer patients. Combination therapies that target cancer cells via different mechanisms to overcome resistance have gained increased attention in recent years. However, the optimal drug combinations and the underlying mechanisms are yet to be fully explored. Aim and methods: The aim of this study is to investigate drug combinations that inhibit the growth of drug-resistant cells and determine the underlying mechanisms of their actions. In addition, we also established cell lines that are resistant to combination treatments and tested new compounds to overcome the phenomenon of double drug-resistance. Results: Our results show that the combination of enzalutamide (ENZ) and docetaxel (DTX) effectively inhibit the growth of prostate cancer cells that are resistant to either drug alone. The downregulation of transcription factor E2F1 plays a crucial role in cellular inhibition in response to the combined therapy. Notably, we found that the androgen receptor (AR) variant AR3 (a.k.a. AR-V7), but not AR full length (AR-FL), positively regulates E2F1 expression in these cells. E2F1 in turn regulates AR3 and forms a positive regulatory feedforward loop. We also established double drug-resistant cell lines that are resistant to ENZ+DTX combination therapy and found that the expression of both AR3 and E2F1 was restored in these cells. Furthermore, we identified that auranofin, an FDA-approved drug for the treatment of rheumatoid arthritis, overcame drug resistance and inhibited the growth of drug-resistant prostate cancer cells both in vitro and in vivo. Conclusion and significance: This proof-of-principle study demonstrates that targeting the E2F1/AR3 feedforward loop via a combination therapy or a multi-targeting drug could circumvent castration resistance in prostate cancer.

Selective repression of the Drosophila cyclin B promoter by retinoblastoma and E2F proteins

The Cyclin B1 gene encodes a G2/M cyclin that is deregulated in various human cancers, however, the transcriptional regulation of this gene is incompletely understood. The E2F and retinoblastoma family of proteins are involved in this gene's regulation, but there is disagreement on which of the E2F and retinoblastoma proteins interact with the promoter to regulate this gene. Here, we dissect the promoter region of the Drosophila CycB gene, and study the role of Rbf and E2F factors in its regulation. This gene exhibits remarkable features that distinguish it from G1/S regulated promoters, such as PCNA. The promoter is comprised of modular elements with dedicated repressor and activator functions, including a segment spanning the first intron that interferes with a 5' activator element. A highly active minimal promoter (-464, +100) is repressed by the Rbf1 retinoblastoma protein, but much more potently repressed by the Rbf2 protein, which has been linked in other studies to control of cell growth genes. Unlike many other cell-cycle genes, which are activated by E2F1 and repressed by E2F2, CycB is potently activated by E2F2, and repressed by E2F1. Although the bulk of Rbf binding is associated with a region 5' of the core promoter, E2F and retinoblastoma proteins functionally interact with the basal promoter region, in part through a conserved E2F site at -80 bp. The specific regulatory requirements of this late cell cycle promoter appear to be linked to the unique activities of E2F and retinoblastoma family members acting on a complex cis-regulatory circuit.

The conflicting role of E2F1 in prostate cancer: A matter of cell context or interpretational flexibility?

The transcription factor E2F1 plays a crucial role in mediating multiple cancer hallmark capabilities that regulate cell cycle, survival, apoptosis, metabolism, and metastasis. Aberrant activation of E2F1 is closely associated with a poor clinical outcome in various human cancers. However, E2F1 has conflictingly been reported to exert tumor suppressive activity, raising a question as to the nature of its substantive role in the control of cell fate. In this review, we summarize deregulated E2F1 activity and its role in prostate cancer. We highlight the recent advances in understanding the molecular mechanism by which E2F1 regulates the development and progression of prostate cancer, providing insight into how cell context or data interpretation shapes the role of E2F1 in prostate cancer. This review will aid in translating biomedical knowledge into therapeutic strategies for prostate cancer.

Epigenetic regulation of lung cancer cell proliferation and migration by the chromatin remodeling protein BRG1

Malignant lung cancer cells are characterized by uncontrolled proliferation and migration. Aberrant lung cancer cell proliferation and migration are programmed by altered cancer transcriptome. The underlying epigenetic mechanism is unclear. Here we report that expression levels of BRG1, a chromatin remodeling protein, were significantly up-regulated in human lung cancer biopsy specimens of higher malignancy grades compared to those of lower grades. Small interfering RNA mediated depletion or pharmaceutical inhibition of BRG1 suppressed proliferation and migration of lung cancer cells. BRG1 depletion or inhibition was paralleled by down-regulation of cyclin B1 (CCNB1) and latent TGF-β binding protein 2 (LTBP2) in lung cancer cells. Further analysis revealed that BRG1 directly bound to the CCNB1 promoter to activate transcription in response to hypoxia stimulation by interacting with E2F1. On the other hand, BRG1 interacted with Sp1 to activate LTBP2 transcription. Mechanistically, BRG1 regulated CCNB1 and LTBP2 transcription by altering histone modifications on target promoters. Specifically, BRG1 recruited KDM3A, a histone H3K9 demethylase, to remove dimethyl H3K9 from target gene promoters thereby activating transcription. KDM3A knockdown achieved equivalent effects as BRG1 silencing by diminishing lung cancer proliferation and migration. Of interest, BRG1 directly activated KDM3A transcription by forming a complex with HIF-1α. In conclusion, our data unveil a novel epigenetic mechanism whereby malignant lung cancer cells acquired heightened ability to proliferate and migrate. Targeting BRG1 may yield effective interventional strategies against malignant lung cancers.

Transcriptional repression by androgen receptor: roles in castration-resistant prostate cancer

Androgen receptor (AR), a hormonal transcription factor, plays important roles during prostate cancer progression and is a key target for therapeutic interventions. While androgen-deprivation therapies are initially successful in regressing prostate tumors, the disease ultimately comes back as castration-resistant prostate cancer (CRPC) or at the late stage as neuroendocrine prostate cancer (NEPC). CRPC remains largely dependent on hyperactive AR signaling in the milieu of low androgen, while NEPC is negative of AR expression but positive of many AR-repressed genes. Recent technological advances in genome-wide analysis of transcription factor binding sites have revealed an unprecedented set of AR target genes. In addition to its well-known function in activating gene expression, AR is increasingly known to also act as a transcriptional repressor. Here, we review the molecular mechanisms by which AR represses gene expression. We also summarize AR-repressed genes that are aberrantly upregulated in CRPC and NEPC and represent promising targets for therapeutic intervention.

A Protoplast Transient Expression System to Enable Molecular, Cellular, and Functional Studies in Phalaenopsis orchids

The enigmatic nature of the specialized developmental programs of orchids has fascinated plant biologists for centuries. The recent releases of orchid genomes indicate that orchids possess new gene families and family expansions and contractions to regulate a diverse suite of developmental processes. However, the extremely long orchid life cycle and lack of molecular toolkit have hampered the advancement of orchid biology research. To overcome the technical difficulties and establish a platform for rapid gene regulation studies, in this study, we developed an efficient protoplast isolation and transient expression system for Phalaenopsis aphrodite. This protocol was successfully applied to protein subcellular localization and protein-protein interaction studies. Moreover, it was confirmed to be useful in delineating the PaE2F/PaDP-dependent cell cycle pathway and studying auxin response. In summary, the established orchid protoplast transient expression system provides a means to functionally characterize orchid genes at the molecular level allowing assessment of transcriptome responses to transgene expression and widening the scope of molecular studies in orchids.

Androgen Signaling in Esophageal Adenocarcinoma Cell Lines In Vitro

BACKGROUND

We showed previously that nuclear localization of the androgen receptor (AR) and expression of the androgen-responsive gene FK506-binding protein 5 (FKBP5) in esophageal adenocarcinoma (EAC) tissues were associated with decreased patient survival, suggesting a role for androgens in this cancer.

AIM

To investigate the effect of the AR ligand 5α-dihydrotestosterone (DHT) on AR-expressing EAC cell lines in vitro.

METHODS AND RESULTS

In tissue resection specimens from EAC patients, FKBP5 expression was positively associated with proliferation as measured by Ki-67 expression. We stably transduced AR into three AR-negative EAC cell lines, OE33, JH-EsoAd1, and OE19, to investigate androgen signaling in vitro. In the AR-expressing cell lines, 10 nM DHT, the concentration typically used to study AR signaling, induced changes in the expression of androgen-responsive genes and inhibited proliferation by inducing cell cycle arrest and senescence. At lower DHT concentrations near the half maximal inhibitory concentration (IC50), the AR-expressing cell lines proliferated and there were changes in the expression of androgen-responsive genes. In direct co-culture with cancer-associated fibroblast-like PShTert myofibroblasts, 10 nM DHT induced changes in the expression of androgen-responsive genes but did not inhibit proliferation.

CONCLUSIONS

This is the first study to show that EAC cell lines respond to androgen in vitro. Proliferation together with the expression of androgen-responsive genes was dependent on the concentration of DHT, or the presence of a permissive microenvironment, consistent with observations in the tissues. These findings are consistent with a role for androgen signaling in EAC.

ACSL4 promotes prostate cancer growth, invasion and hormonal resistance

Increases in fatty acid metabolism have been demonstrated to promote the growth and survival of a variety of cancers, including prostate cancer (PCa). Here, we examine the expression and function of the fatty acid activating enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), in PCa. Ectopic expression of ACSL4 in ACSL4-negative PCa cells increases proliferation, migration and invasion, while ablation of ACSL4 in PCa cells expressing endogenous ACSL4 reduces cell proliferation, migration and invasion. The cell proliferative effects were observed both in vitro, as well as in vivo. Immunohistochemical analysis of human PCa tissue samples indicated ACSL4 expression is increased in malignant cells compared with adjacent benign epithelial cells, and particularly increased in castration-resistant PCa (CRPC) when compared with hormone naive PCa. In cell lines co-expressing both ACSL4 and AR, proliferation was independent of exogenous androgens, suggesting that ACSL4 expression may lead to CRPC. In support for this hypothesis, ectopic ACSL4 expression induced resistance to treatment with Casodex, via decrease in apoptosis. Our studies further indicate that ACSL4 upregulates distinct pathway proteins including p-AKT, LSD1 and β-catenin. These results suggest ACSL4 could serve as a biomarker and potential therapeutic target for CRPC.

miR-762 promotes porcine immature Sertoli cell growth via the ring finger protein 4 (RNF4) gene

A growing number of reports have revealed that microRNAs (miRNAs) play critical roles in spermatogenesis. Our previous study showed that miR-762 is differentially expressed in immature and mature testes of Large White boars. Our present data shows that miR-762 directly binds the 3′ untranslated region (3′UTR) of ring finger protein 4 (RNF4) and down-regulates RNF4 expression. A single nucleotide polymorphism (SNP) in the RNF4 3′UTR that is significantly associated with porcine sperm quality traits leads to a change in the miR-762 binding ability. Moreover, miR-762 promotes the proliferation of and inhibits apoptosis in porcine immature Sertoli cells, partly by accelerating DNA damage repair and by reducing androgen receptor (AR) expression. Taken together, these findings suggest that miR-762 may play a role in pig spermatogenesis by regulating immature Sertoli cell growth.

Resveratrol inhibits cell cycle progression by targeting Aurora kinase A and Polo-like kinase 1 in breast cancer cells

The Aurora protein kinase (AURKA) and the Polo-like kinase-1 (PLK1) activate the cell cycle, and they are considered promising druggable targets in cancer therapy. However, resistance to chemotherapy and to specific small‑molecule inhibitors is common in cancer patients; thus alternative therapeutic approaches are needed to overcome clinical resistance. Here, we showed that the dietary compound resveratrol suppressed the cell cycle by targeting AURKA and PLK1 kinases. First, we identified genes modulated by resveratrol using a genome-wide analysis of gene expression in MDA-MB-231 breast cancer cells. Transcriptional profiling indicated that 375 genes were modulated at 24 h after resveratrol intervention, whereas 579 genes were regulated at 48 h. Of these, 290 genes were deregulated in common at 24 and 48 h. Interestingly, a significant decrease in the expression of genes involved in the cell cycle, DNA repair, cytoskeleton organization, and angiogenesis was detected. In particular, AURKA and PLK1 kinases were downregulated by resveratrol at 24 h. In addition the BRCA1 gene, an AURKA/PLK1 inhibitor, was upregulated at 24 h of treatment. Moreover, two well-known resveratrol effectors, cyclin D1 (CCND1) and cyclin B1 (CCNB1), were also repressed at both times. Congruently, we found that resveratrol impaired G1/S phase transition in both MDA-MB-231 and MCF-7 cells. By western blot assays, we confirmed that resveratrol suppressed AURKA, CCND1 and CCNB1 at 24 and 48 h. In summary, we showed for the first time that resveratrol regulates cell cycle progression by targeting AURKA and PLK1. Our findings highlight the potential use of resveratrol as an adjuvant therapy for breast cancer.

Pan-cancer analyses of the nuclear receptor superfamily

Nuclear receptors (NR) act as an integrated conduit for environmental and hormonal signals to govern genomic responses, which relate to cell fate decisions. We review how their integrated actions with each other, shared co-factors and other transcription factors are disrupted in cancer. Steroid hormone nuclear receptors are oncogenic drivers in breast and prostate cancer and blockade of signaling is a major therapeutic goal. By contrast to blockade of receptors, in other cancers enhanced receptor function is attractive, as illustrated initially with targeting of retinoic acid receptors in leukemia. In the post-genomic era large consortia, such as The Cancer Genome Atlas, have developed a remarkable volume of genomic data with which to examine multiple aspects of nuclear receptor status in a pan-cancer manner. Therefore to extend the review of NR function we have also undertaken bioinformatics analyses of NR expression in over 3000 tumors, spread across six different tumor types (bladder, breast, colon, head and neck, liver and prostate). Specifically, to ask how the NR expression was distorted (altered expression, mutation and CNV) we have applied bootstrapping approaches to simulate data for comparison, and also compared these NR findings to 12 other transcription factor families. Nuclear receptors were uniquely and uniformly downregulated across all six tumor types, more than predicted by chance. These approaches also revealed that each tumor type had a specific NR expression profile but these were most similar between breast and prostate cancer. Some NRs were down-regulated in at least five tumor types (e.g. NR3C2/MR and NR5A2/LRH-1)) whereas others were uniquely down-regulated in one tumor (e.g. NR1B3/RARG). The downregulation was not driven by copy number variation or mutation and epigenetic mechanisms maybe responsible for the altered nuclear receptor expression.

Integrative genomic analysis in K562 chronic myelogenous leukemia cells reveals that proximal NCOR1 binding positively regulates genes that govern erythroid differentiation and Imatinib sensitivity

To define the functions of NCOR1 we developed an integrative analysis that combined ENCODE and NCI-60 data, followed by in vitro validation. NCOR1 and H3K9me3 ChIP-Seq, FAIRE-seq and DNA CpG methylation interactions were related to gene expression using bootstrapping approaches. Most NCOR1 combinations (24/44) were associated with significantly elevated level expression of protein coding genes and only very few combinations related to gene repression. DAVID's biological process annotation revealed that elevated gene expression was uniquely associated with acetylation and ETS binding. A matrix of gene and drug interactions built on NCI-60 data identified that Imatinib significantly targeted the NCOR1 governed transcriptome. Stable knockdown of NCOR1 in K562 cells slowed growth and significantly repressed genes associated with NCOR1 cistrome, again, with the GO terms acetylation and ETS binding, and significantly dampened sensitivity to Imatinib-induced erythroid differentiation. Mining public microarray data revealed that NCOR1-targeted genes were significantly enriched in Imatinib response gene signatures in cell lines and chronic myelogenous leukemia (CML) patients. These approaches integrated cistrome, transcriptome and drug sensitivity relationships to reveal that NCOR1 function is surprisingly most associated with elevated gene expression, and that these targets, both in CML cell lines and patients, associate with sensitivity to Imatinib.

EWS-FLI1 employs an E2F switch to drive target gene expression

Cell cycle progression is orchestrated by E2F factors. We previously reported that in ETS-driven cancers of the bone and prostate, activating E2F3 cooperates with ETS on target promoters. The mechanism of target co-regulation remained unknown. Using RNAi and time-resolved chromatin-immunoprecipitation in Ewing sarcoma we report replacement of E2F3/pRB by constitutively expressed repressive E2F4/p130 complexes on target genes upon EWS-FLI1 modulation. Using mathematical modeling we interrogated four alternative explanatory models for the observed EWS-FLI1/E2F3 cooperation based on longitudinal E2F target and regulating transcription factor expression analysis. Bayesian model selection revealed the formation of a synergistic complex between EWS-FLI1 and E2F3 as the by far most likely mechanism explaining the observed kinetics of E2F target induction. Consequently we propose that aberrant cell cycle activation in Ewing sarcoma is due to the de-repression of E2F targets as a consequence of transcriptional induction and physical recruitment of E2F3 by EWS-FLI1 replacing E2F4 on their target promoters.

Stromal androgen receptor in prostate development and cancer

The androgen receptor (AR) in stromal cells contributes significantly to the development and growth of prostate during fetal stages as well as during prostate carcinogenesis and cancer progression. During prostate development, stromal AR induces and promotes epithelial cell growth, as observed from tissue recombinant and mouse knockout studies. During prostate carcinogenesis and progression, the stromal cells begin to lose AR expression as early as at the stage of high-grade prostatic intraepithelial neoplasia. The extent of loss of stromal AR is directly proportional to the degree of differentiation (Gleason grade) and progression of prostate cancer (PCa). Co-culture studies suggested that stromal AR inhibits the growth of malignant epithelial cells, possibly through expression of certain paracrine factors in the presence of androgens. This functional reversal of stromal AR, from growth promotion during fetal prostate development to mediating certain growth-inhibiting effects in cancer, explains to some extent the reason that loss of AR expression in stromal cells may be crucial for development of resistance to androgen ablation therapy for PCa. From a translational perspective, it generates the need to re-examine the current therapeutic options and opens a fundamental new direction for therapeutic interventions, especially in advanced PCa.

Androgen receptor promotes the oncogenic function of overexpressed Jagged1 in prostate cancer by enhancing cyclin B1 expression via Akt phosphorylation

The Jagged1, a Notch signaling pathway ligand, had been shown to have a positive correlation with prostate cancer development. Our study for Jagged1 expression in 218 prostate cancer tissue samples also supports this conclusion. However, the detailed molecular mechanism of Jagged1 in promoting the progression of prostate cancer is still unclear. Through cell proliferation examination, androgen receptor (AR) was found to promote the oncogenic function of Jagged1 to enhance the cell proliferation rate by comparing four prostate cancer cell lines, LNCaP, LAPC4, DU145, and PC3, which was further validated through analyzing the survival of 118 patients treated with androgen-deprivation therapy (ADT) with different expression levels of Jagged1 and AR. More importantly, our data showed that Jagged1 combined with AR could increase the phosphorylation level of Akt and, in turn, phosphorylated Akt plays an important role in regulating the expression level of cyclin B1 by interacting with AR and increasing the transcriptional activity of AR. These data indicate that prostate cancer progression regulated by Jagged1 can be dramatically enhanced by combining with AR through promoting Akt activity.

IMPLICATIONS

This study could benefit our clinical treatments for patients with prostate cancer with overexpressed Jagged1 by targeting AR and Akt.

Mini-review: androgen receptor phosphorylation in prostate cancer

Androgen receptor (AR) plays an important role in the tumorigenesis and progression of prostate cancer (PCa), and is the primary therapeutic target for PCa treatment. AR activity can be regulated via phosphorylation at multiple phosphorylation sites within the protein. Modifications by phosphorylation alter AR function, including its cellular localization, stability and transcriptional activity, ultimately leading to changes in cancer cell biology and disease progression. Here we present a brief overview of AR phosphorylation sites in PCa, focusing on functional roles of phospho-AR (p-AR) species, relevance in PCa disease progression, and potential as biomarkers and/or therapeutic targets through the use of kinase inhibitors. Additionally, recent evidence has shown the important role of AR activity in the cancer associated stroma on PCa growth and progression. The phosphorylation status of epithelial and stromal AR may be distinct; however, the current data available on stromal AR phosphorylation is limited. Further research will determine global view on the synergistic effects of phosphorylation across multiple AR sites in both epithelial and stromal cells and validate whether together they can be used as prognostic markers and/or effective therapeutic targets for PCa.

Targeting amino acid transport in metastatic castration-resistant prostate cancer: effects on cell cycle, cell growth, and tumor development

BACKGROUND

L-type amino acid transporters (LATs) uptake neutral amino acids including L-leucine into cells, stimulating mammalian target of rapamycin complex 1 signaling and protein synthesis. LAT1 and LAT3 are overexpressed at different stages of prostate cancer, and they are responsible for increasing nutrients and stimulating cell growth.

METHODS

We examined LAT3 protein expression in human prostate cancer tissue microarrays. LAT function was inhibited using a leucine analog (BCH) in androgen-dependent and -independent environments, with gene expression analyzed by microarray. A PC-3 xenograft mouse model was used to study the effects of inhibiting LAT1 and LAT3 expression. Results were analyzed with the Mann-Whitney U or Fisher exact tests. All statistical tests were two-sided.

RESULTS

LAT3 protein was expressed at all stages of prostate cancer, with a statistically significant decrease in expression after 4-7 months of neoadjuvant hormone therapy (4-7 month mean = 1.571; 95% confidence interval = 1.155 to 1.987 vs 0 month = 2.098; 95% confidence interval = 1.962 to 2.235; P = .0187). Inhibition of LAT function led to activating transcription factor 4-mediated upregulation of amino acid transporters including ASCT1, ASCT2, and 4F2hc, all of which were also regulated via the androgen receptor. LAT inhibition suppressed M-phase cell cycle genes regulated by E2F family transcription factors including critical castration-resistant prostate cancer regulatory genes UBE2C, CDC20, and CDK1. In silico analysis of BCH-downregulated genes showed that 90.9% are statistically significantly upregulated in metastatic castration-resistant prostate cancer. Finally, LAT1 or LAT3 knockdown in xenografts inhibited tumor growth, cell cycle progression, and spontaneous metastasis in vivo.

CONCLUSION

Inhibition of LAT transporters may provide a novel therapeutic target in metastatic castration-resistant prostate cancer, via suppression of mammalian target of rapamycin complex 1 activity and M-phase cell cycle genes.

Targeting stromal androgen receptor suppresses prolactin-driven benign prostatic hyperplasia (BPH)

Stromal-epithelial interaction plays a pivotal role to mediate the normal prostate growth, the pathogenesis of benign prostatic hyperplasia (BPH), and prostate cancer development. Until now, the stromal androgen receptor (AR) functions in the BPH development, and the underlying mechanisms remain largely unknown. Here we used a genetic knockout approach to ablate stromal fibromuscular (fibroblasts and smooth muscle cells) AR in a probasin promoter-driven prolactin transgenic mouse model (Pb-PRL tg mice) that could spontaneously develop prostate hyperplasia to partially mimic human BPH development. We found Pb-PRL tg mice lacking stromal fibromuscular AR developed smaller prostates, with more marked changes in the dorsolateral prostate lobes with less proliferation index. Mechanistically, prolactin mediated hyperplastic prostate growth involved epithelial-stromal interaction through epithelial prolactin/prolactin receptor signals to regulate granulocyte macrophage-colony stimulating factor expression to facilitate stromal cell growth via sustaining signal transducer and activator of transcription-3 activity. Importantly, the stromal fibromuscular AR could modulate such epithelial-stromal interacting signals. Targeting stromal fibromuscular AR with the AR degradation enhancer, ASC-J9(®), led to the reduction of prostate size, which could be used in future therapy.

Proto-oncogene activity of melanoma antigen-A11 (MAGE-A11) regulates retinoblastoma-related p107 and E2F1 proteins

Melanoma antigen-A11 (MAGE-A11) is a low-abundance, primate-specific steroid receptor coregulator in normal tissues of the human reproductive tract that is expressed at higher levels in prostate cancer. Increased expression of MAGE-A11 enhances androgen receptor transcriptional activity and promotes prostate cancer cell growth. Further investigation into the mechanisms of MAGE-A11 function in prostate cancer demonstrated interactions with the retinoblastoma-related protein p107 and Rb tumor suppressor but no interaction with p130 of the Rb family. MAGE-A11 interaction with p107 was associated with transcriptional repression in cells with low MAGE-A11 and transcriptional activation in cells with higher MAGE-A11. Selective interaction of MAGE-A11 with retinoblastoma family members suggested the regulation of E2F transcription factors. MAGE-A11 stabilized p107 by inhibition of ubiquitination and linked p107 to hypophosphorylated E2F1 in association with the stabilization and activation of E2F1. The androgen receptor and MAGE-A11 modulated endogenous expression of the E2F1-regulated cyclin-dependent kinase inhibitor p27(Kip1). The ability of MAGE-A11 to increase E2F1 transcriptional activity was similar to the activity of adenovirus early oncoprotein E1A and depended on MAGE-A11 interactions with p107 and p300. The immunoreactivity of p107 and MAGE-A11 was greater in advanced prostate cancer than in benign prostate, and knockdown with small inhibitory RNA showed that p107 is a transcriptional activator in prostate cancer cells. These results suggest that MAGE-A11 is a proto-oncogene whose increased expression in prostate cancer reverses retinoblastoma-related protein p107 from a transcriptional repressor to a transcriptional activator of the androgen receptor and E2F1.

Functional domains of androgen receptor coactivator p44/Mep50/WDR77and its interaction with Smad1

p44/MEP50/WDR77 has been identified as a coactivator of androgen receptor (AR), with distinct growth suppression and promotion function in gender specific endocrine organs and their malignancies. We dissected the functional domains of p44 for protein interaction with transcription factors, transcriptional activation, as well as the functional domains in p44 related to its growth inhibition in prostate cancer. Using a yeast two-hybrid screen, we identified a novel transcription complex AR-p44-Smad1, confirmed for physical interaction by co-immunoprecipitaion and functional interaction with luciferase assays in human prostate cancer cells. Yeast two-hybrid assay revealed that the N-terminal region of p44, instead of the traditional WD40 domain at the C-terminus, mediates the interaction among p44, N-terminus of AR and full length Smad1. Although both N and C terminal domains of p44 are necessary for maximum AR transcriptional activation, the N terminal fragment of p44 alone maintains the basic effect on AR transcriptional activation. Cell proliferation assays with N- and C- terminal deletion mutations indicated that the central portion of p44 is required for nuclear p44 mediated prostate cancer growth inhibition.

Cell cycle-regulatory cyclins and their deregulation in oral cancer

Oral cancer is a growth-related disorder, and cyclins are the prime regulators of cell division. Cyclins are associated with the pathogenesis of oral cancer and are considered valuable biomarkers for diagnosis and prognosis. These important molecules are regulated in many ways to achieve a gain in function and are involved in promoting neoplastic growth. While the causes of most cyclin overexpression are varied, these cyclins may be induced by buccal mucosal insult mainly with carcinogens that alter various pathways propelling oral cancer. Substantial experimental evidences support a link between oncogenic signaling pathways and the deregulation of cyclins in oral cancer. This review focuses on the mechanisms by which cyclins are regulated and promote oral oncogenesis.

Inhibition of Plk1 and Cyclin B1 expression results in panobinostat-induced G₂ delay and mitotic defects

The development of clinically useful histone deacetylase inhibitors has expanded greatly. In a preclinical study, we showed that panobinostat (LBH589) inhibits cell cycle progression of human head and neck squamous cell carcinoma (HNSCC) cell lines at G₂/M and an associated decrease in expression of particular genes required for passage through G₂ and mitosis. In this study we sought to analyse the mechanistic underpinnings of panobinostat-induced growth arrest. HNSCC cell lines were synchronised and progression through mitosis monitored. We demonstrate that panobinostat causes a marked G₂ delay and mitotic defects. A loss of G₂-specific Plk1 and Cyclin B1 expression and co-incident increase in p21(Waf1/Cip1) expression is also shown. Furthermore, we show a significant loss of E2F1 recruitment to the promoters of these genes in response to panobinostat treatment. These data provide mechanistic evidence of panobinostat-induced cell cycle arrest and highlight its potential as a chemotherapeutic agent for HNSCC.