Androgen Receptor in Hormone Receptor-Positive Breast Cancer.

Breast cancer subtypes expressing hormone receptors (HR+ BCa) have a good prognosis and respond to first-line endocrine therapy (ET). However, the majority of HR+ BCa patients exhibit intrinsic or acquired ET resistance (ET-R) and rapid onset of incurable metastatic BCa. With the failure of conventional ET, limited targeted therapy exists for ET-R HR+ BCa patients. The androgen receptor (AR) in HR-negative BCa subtypes is emerging as an attractive alternative target for therapy. The AR drives Luminal AR (LAR) triple-negative breast cancer progression, and LAR patients consistently exhibit positive clinical benefits with AR antagonists in clinical trials. In contrast, the function of the AR in HR+ BCa is more conflicting. AR in HR+ BCa correlates with a favorable prognosis, and yet, the AR supports the development of ET-R BCa. While AR antagonists were ineffective, ongoing clinical trials with a selective AR modulator have shown promise for HR+ BCa patients. To understand the incongruent actions of ARs in HR+ BCa, the current review discusses how the structure and post-translational modification impact AR function. Additionally, completed and ongoing clinical trials with FDA-approved AR-targeting agents for BCa are presented. Finally, we identify promising investigational small molecules and chimera drugs for future HR+ BCa therapy.

Constitutively active androgen receptor supports the metastatic phenotype of endocrine-resistant hormone receptor-positive breast cancer.

BACKGROUND: Hormone receptor positive (HR+) breast cancer (BCa) is the most frequently diagnosed subtype. Acquired and intrinsic resistance to conventional endocrine therapy (ET) commonly occurs and prompts incurable metastatic disease. Hence, ET-resistant (ET-R) HR+ BCa presents a therapeutic challenge. Previous studies show elevated androgen receptor (AR) that supports resistance to ET tamoxifen and correlates with HR+ BCa metastasis. Yet surprisingly, studies with AR-blocker enzalutamide (Enz) in ET-R HR+ BCa present conflicting results. We now report that a constitutively active, unique from canonical Enz-targeted, AR accumulates in endocrine resistant HR+ BCa cells. METHODS: AR protein profiles in acquired and intrinsic ET-R HR + -BCa were defined with cell-free modification tests, in-house in-vivo SUMOylation assays, and PLA imaging. Genomic activity of native AR and modified-AR mimetic was tested with reporter assays and limited transcriptome analysis. Spheroid growth and migration studies were used to evaluate inhibitory actions of Enz and combinatorial therapy. RESULTS: Sustained higher molecular weight SUMO-modified AR (SUMO-AR) persists in acquired and intrinsic ET-R BCa cell lines. Concurrently, SUMO isoforms and global SUMO-modified proteome also accumulates in the same cell lines. We identified AR as a novel substrate for the SUMO-E3 ligase HSPB1/Hsp27. Independent of ligand, SUMO-AR is resilient to ubiquitin-mediated proteasomal degradation, enriched in the nucleus, readily chromatin-bound, and transcriptionally active. Constitutive SUMO-AR initiates a gene-expression profile that favors epithelial-mesenchymal transition. Enz combined with a SUMO inhibitor attenuates migration and metastatic phenotype of ET-R HR+ BCa. CONCLUSION: Targeting both unmodified and SUMO-modified AR prevents the metastatic progression of HR+ BCa with ET-R. Video abstract.

ß-catenin links von Hippel-Lindau to aurora kinase A and loss of primary cilia in renal cell carcinoma.

von Hippel-Lindau (VHL) gene mutations are associated with clear cell renal cell carcinoma (ccRCC). A hallmark of ccRCC is loss of the primary cilium. Loss of this key organelle in ccRCC is caused by loss of VHL and associated with increased Aurora kinase A (AURKA) and histone deacetylase 6 (HDAC6) activities, which drive disassembly of the primary cilium. However, the underlying mechanism by which VHL loss increases AURKA levels has not been clearly elucidated, although it has been suggested that hypoxia-inducible factor-1α (HIF-1α) mediates increased AURKA expression in VHL-null cells. By contrast, we found that elevated AURKA expression is not increased by HIF-1α, suggesting an alternate mechanism for AURKA dysregulation in VHL-null cells. We report here that AURKA expression is driven by ß-catenin transcription in VHL-null cells. In a panel of RCC cell lines, we observed nuclear accumulation of ß-catenin and increased AURKA signaling to HDAC6. Moreover, HIF-1α inhibited AURKA expression by inhibiting ß-catenin transcription. VHL knockdown activated ß-catenin and elevated AURKA expression, decreased primary cilia formation, and caused significant shortening of cilia length in cells that did form cilia. The ß-catenin responsive transcription inhibitor iCRT14 reduced AURKA levels and rescued ciliary defects, inducing a significant increase in primary cilia formation in VHL-deficient cells. These data define a role for ß-catenin in regulating AURKA and formation of primary cilia in the setting of VHL deficiency, opening new avenues for treatment with ß-catenin inhibitors to rescue ciliogenesis in ccRCC.

Differential expression of SUMO-specific protease 7 variants regulates epithelial-mesenchymal transition.

Two Sentrin/small ubiquitin-like modifier (SUMO)-specific protease 7 (SENP7) variants are naturally expressed in breast epithelia. Breast cancer (BCa) onset down-regulates the short SENP7 splice variant (SENP7S) and enhances the long transcript (SENP7L). Here, we show that SENP7L induction promotes gene expression profiles that favor aberrant proliferation and initiate epithelial-mesenchymal transition (EMT). SENP7L exhibits an interaction domain for the epigenetic remodeler heterochromatin protein 1 α (HP1α) and isopeptidase activity against SUMO-modified HP1α. Loss of this interaction domain, as observed with SENP7S, favors HP1α SUMOylation. SUMOylated HP1α is enriched at E2F-responsive and mesenchymal gene promoters, silences transcription of these genes, and promotes cellular senescence. Elevated SENP7L renders HP1α hypo-SUMOylated, which relieves transcriptional repression of the same genes and concurrently decreases transcription of epithelial-promoting genes via an HP1α-independent mechanism. Consequently, SENP7L levels correlate with EMT, motility, and invasiveness of BCa cells. Stable knockdown of elevated SENP7L levels lessens the dissemination of highly metastatic BCa cells to the lungs from primary implantation sites in in vivo studies. Thus, differential splicing of the SENP7 regulates either tumor suppression or progression.

SumoPred-PLM: human SUMOylation and SUMO2/3 sites Prediction using Pre-trained Protein Language Model.

SUMOylation is an essential post-translational modification system with the ability to regulate nearly all aspects of cellular physiology. Three major paralogues SUMO1, SUMO2 and SUMO3 form a covalent bond between the small ubiquitin-like modifier with lysine residues at consensus sites in protein substrates. Biochemical studies continue to identify unique biological functions for protein targets conjugated to SUMO1 versus the highly homologous SUMO2 and SUMO3 paralogues. Yet, the field has failed to harness contemporary AI approaches including pre-trained protein language models to fully expand and/or recognize the SUMOylated proteome. Herein, we present a novel, deep learning-based approach called SumoPred-PLM for human SUMOylation prediction with sensitivity, specificity, Matthew's correlation coefficient, and accuracy of 74.64%, 73.36%, 0.48% and 74.00%, respectively, on the CPLM 4.0 independent test dataset. In addition, this novel platform uses contextualized embeddings obtained from a pre-trained protein language model, ProtT5-XL-UniRef50 to identify SUMO2/3-specific conjugation sites. The results demonstrate that SumoPred-PLM is a powerful and unique computational tool to predict SUMOylation sites in proteins and accelerate discovery.

Liver X Receptor Inverse Agonist GAC0001E5 Impedes Glutaminolysis and Disrupts Redox Homeostasis in Breast Cancer Cells.

Liver X receptors (LXRs) are members of the nuclear receptor family of ligand-dependent transcription factors which regulate the expression of lipid and cholesterol metabolism genes. Moreover, LXRs and their ligands have been shown to inhibit tumor growth in a variety of cancers. We have previously identified the small molecule compound GAC0001E5 (1E5) as an LXR inverse agonist and a potent inhibitor of pancreatic cancer cells. Transcriptomic and metabolomic studies showed that 1E5 disrupts glutamine metabolism, an essential metabolic pathway commonly reprogrammed during malignant transformation, including in breast cancers. To determine the role of LXRs and potential application of 1E5 in breast cancer, we examined LXR expression in publicly available clinical samples, and found that LXR expression is elevated in breast tumors as compared to normal tissues. In luminal A, endocrine therapy-resistant, and triple-negative breast cancer cells, 1E5 exhibited LXR inverse agonist and "degrader" activity and strongly inhibited cell proliferation and colony formation. Treatments with 1E5 downregulated the transcription of key glutaminolysis genes, and, correspondingly, biochemical assays indicated that 1E5 lowered intracellular glutamate and glutathione levels and increased reactive oxygen species. These results indicate that novel LXR ligand 1E5 is an inhibitor of glutamine metabolism and redox homeostasis in breast cancers and suggest that modulating LXR activity and expression in tumor cells is a promising strategy for targeting metabolic reprogramming in breast cancer therapeutics.

Exosc9 Initiates SUMO-Dependent lncRNA TERRA Degradation to Impact Telomeric Integrity in Endocrine Therapy Insensitive Hormone Receptor-Positive Breast Cancer.

Long, noncoding RNAs (lncRNAs) are indispensable for normal cell physiology and, consequently, are tightly regulated in human cells. Yet, unlike mRNA, substantially less is known about the mechanisms for lncRNA degradation. It is important to delineate the regulatory control of lncRNA degradation, particularly for lncRNA telomeric repeat-containing RNA (TERRA), as the TERRA-telomere R-loops dictate cell cycle progression and genomic stability. We now report that the exosome complex component Exosc9 degrades lncRNA TERRA in human mammary epithelial cells. Heterochromatin protein 1 alpha (HP1α) recruits Exosc9 to the telomeres; specifically, the SUMO-modified form of HP1α supports interaction with Exosc9 and, as previously reported, lncRNA TERRA. The telomeric enrichment of Exosc9 is cell cycle-dependent and consistent with the loss of telomeric TERRA in the S/G2 phase. Elevated Exosc9 is frequently observed and drives the growth of endocrine therapy-resistant (ET-R) HR+ breast cancer (BCa) cells. Specifically, the knockdown of Exosc9 inversely impacts telomeric R-loops and the integrity of the chromosome ends of ET-R cells. Consistently, Exosc9 levels dictate DNA damage and the sensitivity of ET-R BCa cells to PARP inhibitors. In this regard, Exosc9 may serve as a promising biomarker for predicting the response to PARP inhibitors as a targeted monotherapy for ET-R HR+ BCa.

SENP1 induces prostatic intraepithelial neoplasia through multiple mechanisms.

SUMOylation has been shown to modulate DNA replication/repair, cell cycle progression, signal transduction, and the hypoxic response. SUMO (small ubiquitin-like modifier)-specific proteases regulate SUMOylation, but how changes in the expression of these proteases contribute to physiological and/or pathophysiological events remains undefined. Here, we show that SENP1 (sentrin/SUMO-specific protease 1) is highly expressed in human prostate cancer specimens and correlates with hypoxia-inducing factor 1alpha (HIF1alpha) expression. Mechanistic studies in a mouse model indicate that androgen-driven expression of murine SENP1 leads to HIF1alpha stabilization, enhanced vascular endothelial growth factor production, and angiogenesis. Further pathological assessment of the mouse indicates that SENP1 overexpression induces transformation of the normal prostate gland and gradually facilitates the onset of high-grade prostatic intraepithelial neoplasia. Consistent with cell culture studies, SENP1 enhances prostate epithelial cell proliferation via modulating the androgen receptor and cyclin D(1). These results demonstrate that deSUMOylation plays a critical role in prostate pathogenesis through induction of HIF1alpha-dependent angiogenesis and enhanced cell proliferation.

The in vivo functions of desumoylating enzymes.

This chapter reviews the current literature to highlight the biological mechanisms mediated via the enzymatic actions of the SUMO-specific protease family. All members of this cysteine protease family express isopeptidase activity to deSUMOylate conjugated cellular protein targets. Here, we discuss how SUMO proteases discriminate amongst the SUMOylated targets based on subcellular localization and conjugated SUMO isoform. Several signal transduction pathways modulate endogenous levels of the deSUMOylating enzymes to regulate cell growth, cell cycle progression and gene transcription. The ability of specific proteases to mediate these cellular events is presented. In addition, we examine cases in which aberrant SUMO protease expression affects normal embryonic development, carcinogenesis and the onset of additional pathophysiological conditions.

The ERß4 variant induces transformation of the normal breast mammary epithelial cell line MCF-10A; the ERß variants ERß2 and ERß5 increase aggressiveness of TNBC by regulation of hypoxic signaling.

Triple negative breast cancer (TNBC) still remains a challenge to treat in the clinic due to a lack of good targets for treatment. Although TNBC lacks expression of ERα, the expression of ERß and its variants are detected quite frequently in this cancer type and can represent an avenue for treatment. We show that two of the variants of ERß, namely ERß2 and ERß5, control aggressiveness of TNBC by regulating hypoxic signaling through stabilization of HIF-1α. RNA-seq of patient derived xenografts (PDX) from TNBC shows expression of ERß2, ERß4 and ERß5 variants in more than half of the samples. Furthermore, expression of ERß4 in the immortalized, normal mammary epithelial cell line MCF-10A that is resistant to tumorsphere formation caused transformation and development of tumorspheres. By contrast, ERß1, ERß2 or ERß5 were unable to support tumorsphere formation. We have previously shown that all variants except ERß1 stabilize HIF-1α but only ERß4 appears to have the ability to transform normal mammary epithelial cells, pointing towards a unique property of ERß4. We propose that ERß variants may be good diagnostic tools and also serve as novel targets for treatment of breast cancer.

The presence of beta2-adrenoceptors sensitizes alpha2A-adrenoceptors to desensitization after chronic epinephrine treatment.

BACKGROUND: In addition to the regulation of blood pressure, alpha2- and beta-adrenoceptor (AR) subtypes play an important role in the modulation of noradrenergic neurotransmission in the human CNS and PNS. Several studies suggest that the alpha2-AR responsiveness in cells and tissues after chronic epinephrine (EPI) or norepinephrine (NE) exposure may vary, depending on the beta-AR activity present there. Recently, we reported that in BE(2)-C human neuroblastoma cells (endogenously expressing alpha2A- and beta2-AR), chronic EPI treatment (300 nM) produced a dramatic beta-adrenoceptor-dependent desensitization of the alpha2A-AR response. The aim of this study is to determine if stable addition of a beta2-AR to a second neuroblastoma cell line (SH-SY5Y), that normally expresses only alpha2A-ARs that are not sensitive to 300 nM EPI exposure, would suddenly render alpha2A-ARs in that cell line sensitive to treatment with the same EPI concentration. METHODS: These studies employed RT-PCR, receptor binding and inhibition of cAMP accumulation to confirm alpha2-AR subtype expression. Stable clones of SH-SY5Y cells transfected to stably express functional beta2-ARs (SHbeta2AR4) were selected to compare sensitivity of alpha2-AR to EPI in the presence or absence of beta2-ARs. RESULTS: A series of molecular, biochemical and pharmacological studies indicated that the difference between the cell lines could not be attributed to alpha2-AR heterogeneity. We now report that after transfection of functional beta2-AR into SH-SY5Y cells (SHbeta2AR4), chronic treatment with modest levels of EPI desensitizes the alpha2A-AR. This effect results from a beta2-AR dependent down-regulation of native alpha2A-ARs by EPI accompanied by enhanced translocation of GRK2 and GRK3 to the membrane (required for GRK-mediated phosphorylation of agonist-occupied receptors). CONCLUSION: This study further supports the hypothesis that the presence of the beta-AR renders the alpha2A-AR more susceptible to desensitization with physiological levels of EPI.

SENP1 regulates PTEN stability to dictate prostate cancer development.

SUMO protease SENP1 is elevated in multiple carcinomas including prostate cancer (PCa). SENP1 exhibits carcinogenic properties; it promotes androgen receptor-dependent and -independent cell proliferation, stabilizes HIF1α, increases VEGF, and supports angiogenesis. However, mice expressing an androgen-responsive promoter driven SENP1-transgene (SENP1-Tg) develop high-grade prostatic intraepithelial neoplasia, but not carcinoma. We now show that tumor suppressive PTEN signaling is induced in SENP1-Tg to enhance prostate epithelial cell apoptosis. SENP1 blocks SUMO1-dependent ubiquitylation and degradation of PTEN. In the absence of SENP1, SUMO1-modified PTEN is sequestered in the cytosol, where binding to ubiquitin-E3 ligase WWP2 occurs. Concurrently, WWP2 is also SUMOylated, which potentiates its interaction with PTEN. Thus, SENP1 directs ubiquitin-E3-substrate association to control PTEN stability. PTEN serves as a barrier for SENP1-mediated prostate carcinogenesis as SENP1-Tg mice develop invasive carcinomas only after PTEN reduction. Hence, SENP1 modulates multiple facets of carcinogenesis and may serve as a target specifically for aggressive PTEN-deficient PCa.

Novel SUMO-Protease SENP7S Regulates ß-catenin Signaling and Mammary Epithelial Cell Transformation.

SUMO post-translational modification of proteins or SUMOylation ensures normal cell function. Disruption of SUMO dynamics prompts various pathophysiological conditions, including cancer. The burden of deSUMOylating the large SUMO-proteome rests on 6 full-length mammalian SUMO-proteases or SENP. While multiple SENP isoforms exist, the function of these isoforms remains undefined. We now delineate the biological role of a novel SENP7 isoform SENP7S in mammary epithelial cells. SENP7S is the predominant SENP transcript in human mammary epithelia but is significantly reduced in precancerous ductal carcinoma in situ and all breast cancer subtypes. Like other SENP family members, SENP7S has SUMO isopeptidase activity but unlike full-length SENP7L, SENP7S is localized in the cytosol. In vivo, SUMOylated ß-catenin and Axin1 are both SENP7S-substrates. With knockdown of SENP7S in mammary epithelial cells, Axin1-ß-catenin interaction is lost and ß-catenin escapes ubiquitylation-dependent proteasomal degradation. SUMOylated ß-catenin accumulates at the chromatin and activates multiple oncogenes. Hence, non-tumorigenic MCF10-2A cells with reduced SENP7S exhibit greater cell proliferation and anchorage-dependent growth. SENP7S depletion directly potentiates tumorigenic properties of MCF10-2A cells with induction of anchorage-independent growth and self-renewal in 3D-spheroid conditions. Collectively, the results identify SENP7S as a novel mediator of ß-catenin signaling and normal mammary epithelial cell physiology.

Isolation of In Vivo SUMOylated Chromatin-Bound Proteins.

SUMO posttranslational modification directs gene transcription and epigenetic programming to support normal cell function. The dynamic nature of SUMO-modification makes it difficult to identify endogenous protein substrates. Isolation of chromatin-bound SUMO targets is exceptionally challenging, as conventional immunoprecipitation assays are inefficient at concentrating this protein population. This chapter describes a protocol that effectively precipitates chromatin-associated fractions of SUMOylated heterochromatin protein 1α in cultured cells. Techniques to enrich endogenous SUMO substrates at the chromatin are also demonstrated and discussed. This approach could be adapted to evaluate chromatin-bound SUMO targets in additional in vivo systems.

SUMOylated ORC2 Recruits a Histone Demethylase to Regulate Centromeric Histone Modification and Genomic Stability.

Origin recognition complex 2 (ORC2), a subunit of the ORC, is essential for DNA replication initiation in eukaryotic cells. In addition to a role in DNA replication initiation at the G1/S phase, ORC2 has been shown to localize to the centromere during the G2/M phase. Here, we show that ORC2 is modified by small ubiquitin-like modifier 2 (SUMO2), but not SUMO1, at the G2/M phase of the cell cycle. SUMO2-modification of ORC2 is important for the recruitment of KDM5A in order to convert H3K4me3 to H3K4me2, a "permissive" histone marker for α-satellite transcription at the centromere. Persistent expression of SUMO-less ORC2 led to reduced α-satellite transcription and impaired pericentric heterochromatin silencing, which resulted in re-replication of heterochromatin DNA. DNA re-replication eventually activated the DNA damage response, causing the bypass of mitosis and the formation of polyploid cells. Thus, ORC2 sustains genomic stability by recruiting KDM5A to maintain centromere histone methylation in order to prevent DNA re-replication.

SUMOylation of HP1α supports association with ncRNA to define responsiveness of breast cancer cells to chemotherapy.

Epigenetic reprogramming allows cancer cells to bypass normal checkpoints and potentiate aberrant proliferation. Several chromatin regulators are subject to reversible SUMO-modification but little is known about how SUMOylation of chromatin-remodelers modulates the cancer epigenome. Recently, we demonstrated that SUMO-protease SENP7L is upregulated in aggressive BCa and maintains hypoSUMOylated heterochromatin protein 1-α (HP1α). Canonical models define HP1α as a "reader" of repressive H3K9m3 marks that supports constitutive heterochromatin. It is unclear how SUMOylation affects HP1α function in BCa cells. This report shows HP1α SUMO-dynamics are closely regulated in a complex with SENP7L and SUMO-E3 Polycomb-2 (PC2/CBX4). This complex accumulates at H3K9m3 sites, hypoSUMOylates HP1α and PC2, and reduces PC2's SUMO-E3 activity. HyperSUMO conditions cause complex dissociation, SUMOylation of PC2 and HP1α, and recruitment of SUMOylated HP1α to multiple DNA-repair genes including Rad51C. SUMOylated HP1α's enrichment at euchromatin requires chromatin-bound non-coding RNA (ncRNA), reduces Rad51C protein, and increases DNA-breaks in BCa cells. Hence, HP1α SUMOylation and consistently low SENP7L increase efficacy of DNA-damaging chemotherapeutic agents. BCa patients on chemotherapy that express low SENP7L exhibit greater survival rates than patients with high SENP7L. Collectively, these studies suggest that SUMOylated HP1α is a critical epigenetic-regulator of DNA-repair in BCa that could define chemotherapy responsiveness.

Identification of the molecular basis of doxorubicin-induced cardiotoxicity.

Doxorubicin is believed to cause dose-dependent cardiotoxicity through redox cycling and the generation of reactive oxygen species (ROS). Here we show that cardiomyocyte-specific deletion of Top2b (encoding topoisomerase-IIß) protects cardiomyocytes from doxorubicin-induced DNA double-strand breaks and transcriptome changes that are responsible for defective mitochondrial biogenesis and ROS formation. Furthermore, cardiomyocyte-specific deletion of Top2b protects mice from the development of doxorubicin-induced progressive heart failure, suggesting that doxorubicin-induced cardiotoxicity is mediated by topoisomerase-IIß in cardiomyocytes.

SUMO Losing Balance: SUMO Proteases Disrupt SUMO Homeostasis to Facilitate Cancer Development and Progression.

Small ubiquitin-like modifiers (SUMO) conjugation to cellular proteins is a reversible posttranslational modification that mediates the protein's function, subcellular localization, and/or expression. The SUMO proteases (SENP) deconjugate modified proteins and thus are critical for maintaining the level of SUMOylated and un-SUMOylated substrates required for normal physiology. Altered expression of SENPs is observed in several carcinomas. This review focuses on how the change in SENP levels disturbs SUMO homeostasis and contributes to cancer development and progression. We reported that one member of the SENP family, SENP1 can transform normal prostate epithelia to a dysplasic state and directly modulate several oncogenic pathways in prostate cells, including AR, c-Jun, and Cyclin D1. Assessment of tissue from human prostate cancer patients indicates elevated mRNA levels of SENP1 and the SUMO2/3 deconjugating enzyme, SENP3. The induction of SENP3 in cancer cells initiates the angiogenic pathway; specifically SENP3 regulates the transcriptional activity of hypoxia-inducible factor 1α (HIF1α) via deSUMOylation of the co-regulatory protein p300. Unlike prostate cancer, enhanced SUMOylation is favored with onset of breast cancer and correlated with the reduced SENP6 mRNA levels found in several breast cancer tissue arrays. Preventing enhanced SUMO conjugation of cellular substrates in breast cancer cells reduces tumorigenesis. Hence, distortion of SUMO equilibrium contributes to both the initiation and progression of cancer, specifically in prostate and breast cancers. The deSUMOylation machinery may be key to restoring balance to the SUMO system and hence serve as ideal targets for therapeutic agents.

Induction of the SUMO-specific protease 1 transcription by the androgen receptor in prostate cancer cells.

Prostate cancer, the most frequently diagnosed carcinoma in males, is readily modulated via the transcriptional activity of androgen receptors. Our recent publication reported that androgen receptor-dependent transcription is significantly elevated with expression of the human sentrin/SUMO-specific protease (SENP1) in the androgen-sensitive human prostate cancer cell line (LNCaP). In situ hybridization studies indicated an elevation of SENP1 message in prostatic intraepithelial neoplasia and prostate cancer lesions as compared with normal prostate epithelia. This study aimed to delineate the mechanism for the regulation of SENP1 message and to determine the pathophysiological consequence of SENP1 induction with respect to prostate cancer. Real-time PCR confirmed the elevation of SENP1 mRNA in prostate cancer cells as compared with normal prostate epithelial cells. Chronic androgen exposure of LNCaP cells prompted an enhancement in the SENP1 transcript selectively. This androgen-mediated augmentation of SENP1 was absent with co-administration of the androgen receptor antagonist bicalutamide and in androgen receptor-negative prostate cancer PC-3 cells, indicating an androgen receptor-dependent event. Activation of the androgen receptor was required for binding an identified androgen response element and positively regulating SENP1 promoter activity. Abrogation of elevated SENP1 mRNA in prostate cancer cells significantly decreased androgen-mediated cell growth. Because increased SENP1 expression directly modulated androgen receptor-dependent cell proliferation and transcription, SENP1 could play an important role in prostate carcinogenesis.