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

The impact of dysregulation SUMOylation on prostate cancer

Prostate cancer (PCa) remains one of the most common malignancies in men, with its development and progression being governed by complex molecular pathways. SUMOylation, a post-translational modification (PTM) that involves the covalent attachment of small ubiquitin-like modifier (SUMO) proteins to target substrates, has emerged as a critical regulator of various cellular processes such as transcription, DNA repair, cell cycle progression, and apoptosis. Emerging evidence reveals that abnormal SUMOylation may contribute to PCa pathogenesis, and notably, SUMO-associated enzymes are commonly dysregulated in PCa. This review explores the mechanisms by which SUMOylation is implicated in the regulation of key pathways, and summary aberrant expression of SUMO-related enzymes or SUMOylation sites mutations of substrtes in PCa, as well as the therapeutic implications of targeting the SUMO-related enzymes in PCa treatment.

EHD1 impaired decidualization of endometrial stromal cells in recurrent implantation failure: role of SENP1 in modulating progesterone receptor signalling†

Recurrent implantation failure (RIF) patients exhibit poor endometrial receptivity and abnormal decidualization with reduced effectiveness and exposure to progesterone, which is an intractable clinical problem. However, the associated molecular mechanisms remain elusive. We found that EH domain containing 1 (EHD1) expression was abnormally elevated in RIF and linked to aberrant endometrial decidualization. Here we show that EHD1 overexpressed in human endometrial stromal cells significantly inhibited progesterone receptor (PGR) transcriptional activity and the responsiveness to progesterone. No significant changes were observed in PGR mRNA levels, while a significant decrease in progesterone receptor B (PRB) protein level. Indeed, EHD1 binds to the PRB protein, with the K388 site crucial for this interaction. Overexpression of EHD1 promotes the SUMOylation and ubiquitination of PRB, leading to the degradation of the PRB protein. Supplementation with the de-SUMOylated protease SENP1 ameliorated EHD1-repressed PRB transcriptional activity. To establish a functional link between EHD1 and the PGR signalling pathway, sg-EHD1 were utilized to suppress EHD1 expression in HESCs from RIF patients. A significant increase in the expression of prolactin and insulin-like growth factor-binding protein 1 was detected by interfering with the EHD1. In conclusion, we demonstrated that abnormally high expression of EHD1 in endometrial stromal cells attenuated the activity of PRB associated with progesterone resistance in a subset of women with RIF.

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.

Emerging role of SENP1 in tumorigenesis and cancer therapy

Acting as a cysteine protease, small ubiquitin-like modifier (SUMO)/sentrin-specific protease1 (SENP1) involved in multiple physiological and pathological processes through processing the precursor SUMO protein into mature form and deSUMOylating target protein. It has been reported that SENP1 is highly expressed and plays a carcinogenic role in various cancers. In this paper, we mainly explore the function and mechanism of SENP1 in tumor cell proliferation, apoptosis, invasion, metastasis, stemness, angiogenesis, metabolism and drug resistance. Furthermore, the research progress of SENP1 inhibitors for cancer treatment is introduced. This study aims to provide theoretical references for cancer therapy by targeting SENP1.

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

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

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.

Regulation of SUMOylation on RNA metabolism in cancers

Post-translational modifications of proteins play very important roles in regulating RNA metabolism and affect many biological pathways. Here we mainly summarize the crucial functions of small ubiquitin-like modifier (SUMO) modification in RNA metabolism including transcription, splicing, tailing, stability and modification, as well as its impact on the biogenesis and function of microRNA (miRNA) in particular. This review also highlights the current knowledge about SUMOylation regulation in RNA metabolism involved in many cellular processes such as cell proliferation and apoptosis, which is closely related to tumorigenesis and cancer progression.

Recent research and development of inhibitors targeting sentrin-specific protease 1 for the treatment of cancers

Small ubiquitin-like modifier (SUMO)/sentrin-specific protease 1 (SENP1), is a cysteine protease that promotes SUMO maturation and deSUMOylation of target proteins and regulates transcription factors or co-regulatory factors to mediate gene transcription. Many studies have shown that SENP1 is the driving factor for a multitude of cancers including prostate cancer, liver cancer, and breast cancer. Inhibition of SENP1 activity has been proved to inhibit the survival, proliferation, invasion, and migration of cancer cells, and increase their chemical and radiation sensitivity. Therefore, SENP1 is a promising anti-tumor target. At present, peptide inhibitors of SENP1 have entered clinical trials. Recently, many small molecule compounds and natural products were synthesized and identified as SENP1 inhibitors, and showed good tumor inhibitory activity in vitro and in vivo. This review summarizes the structure, physiological function, and role of SENP1 in tumorigenesis and development, focusing on the design and discovery of small molecule inhibitors of SENP1 from the perspective of medicinal chemistry, providing ideas for the development and research of small molecule inhibitors of SENP1 in the future.

The SUMO protease SENP1 promotes aggressive behaviors of high HIF2α expressing renal cell carcinoma cells

While an important role for the SUMO protease SENP1 is recognized in multiple solid cancers, its role in renal cell carcinoma (RCC) pathogenesis, particularly the most dominant subtype, clear cell RCC (ccRCC), is poorly understood. Here we show that a combination of high HIF2α and SENP1 expression in ccRCC samples predicts poor patient survival. Using ccRCC cell models that express high HIF2α but low SENP1, we show that overexpression of SENP1 reduces sumoylation and ubiquitination of HIF2α, increases HIF2α transcriptional activity, and enhances expression of genes associated with cancer cell invasion, stemness and epithelial-mesenchymal transition. Accordingly, ccRCC cells with high HIF2α and SENP1 showed increased invasion and sphere formation in vitro, and local invasion and metastasis in vivo. Finally, SENP1 overexpression caused high HIF2α ccRCC cells to acquire resistance to a clinical mTOR inhibitor, everolimus. These results reveal a combination of high SENP1 and HIF2α expression gives particularly poor prognosis for ccRCC patients and suggest that SENP1 may be an attractive new target for treating metastatic RCC (mRCC).

Both SUMOylation and ubiquitination of TFE3 fusion protein regulated by androgen receptor are the potential target in the therapy of Xp11.2 translocation renal cell carcinoma

Background

The aggressiveness of renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2 translocation RCC [Xp11.2 tRCC]) is age‐dependent, which is similar to the overall trend of reproductive endocrine hormones. Therefore, this study focused on the effect and potential mechanism of androgen and androgen receptor (AR) on the progression of Xp11.2 tRCC.

Methods

The effects of androgen and AR on the proliferation and migration of Xp11.2 tRCC cells were first evaluated utilising Xp11.2 tRCC cell lines and tissues. Because Transcription factor enhancer 3 (TFE3) fusion proteins play a key role in Xp11.2 tRCC, we focused on the regulatory role of AR and TFE3 expression and transcriptional activity.

Results

When Xp11.2 tRCC cells were treated with dihydrotestosterone, increased cell proliferation, invasion and migration were observed. Compared with clear cell RCC, the positive rate of AR in Xp11.2 tRCC tissues was higher, and its expression was negatively associated with the progression‐free survival of Xp11.2 tRCC. Further studies revealed that AR could positively regulate the transcriptional activity of TFE3 fusion proteins by small ubiquitin‐related modifier (SUMO)‐specific protease 1, inducing the deSUMOylation of TFE3 fusion. On the other hand, UCHL1 negatively regulated by AR plays a role in the deubiquitination degradation of the PRCC‐TFE3 fusion protein. Therefore, the combination of the AR inhibitor MDV3100 and the UCHL1 inhibitor 6RK73 was effective in delaying the progression of Xp11.2 tRCC, especially PRCC‐TFE3 tRCC.

Conclusions

Androgen and AR function as facilitators in Xp11.2 tRCC progression and may be a novel therapeutic target for Xp11.2 tRCC.

The combined use of AR antagonist MDV3100 and UCHL1 inhibitor 6RK73 increased both the SUMOylation and ubiquitination of the PRCC‐TFE3 fusion protein

Therapeutic Potential of Targeting the SUMO Pathway in Cancer

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

SENP1-mediated deSUMOylation of JAK2 regulates its kinase activity and platinum drug resistance

The JAK2/STAT pathway is hyperactivated in many cancers, and such hyperactivation is associated with a poor clinical prognosis and drug resistance. The mechanism regulating JAK2 activity is complex. Although translocation of JAK2 between nucleus and cytoplasm is an important regulatory mechanism, how JAK2 translocation is regulated and what is the physiological function of this translocation remain largely unknown. Here, we found that protease SENP1 directly interacts with and deSUMOylates JAK2, and the deSUMOylation of JAK2 leads to its accumulation at cytoplasm, where JAK2 is activated. Significantly, this novel SENP1/JAK2 axis is activated in platinum-resistant ovarian cancer in a manner dependent on a transcription factor RUNX2 and activated RUNX2/SENP1/JAK2 is critical for platinum-resistance in ovarian cancer. To explore the application of anti-SENP1/JAK2 for treatment of platinum-resistant ovarian cancer, we found SENP1 deficiency or treatment by SENP1 inhibitor Momordin Ic significantly overcomes platinum-resistance of ovarian cancer. Thus, this study not only identifies a novel mechanism regulating JAK2 activity, but also provides with a potential approach to treat platinum-resistant ovarian cancer by targeting SENP1/JAK2 pathway.

Kochiae Fructus, the Fruit of Common Potherb Kochia scoparia (L.) Schrad: A Review on Phytochemistry, Pharmacology, Toxicology, Quality Control, and Pharmacokinetics

Kochiae Fructus (KF) is the fruit of an annual potherb Kochia scoparia (Linn.) Schrad and has been traditionally used for the treatment of diseases in the skin, eyes, and urinary tract for thousands of years in China. Recent studies have showed its anti-inflammatory, antifungal, antiallergic, and antipruritogenic effects to clarify the mechanisms of these actions. Meanwhile, its other effects, such as anticancer, hypoglycemic, and hepatoprotective effects, also have been reported. The achievement of these therapeutic effects is contributed by its chemical constituents. A total of 153 compounds have been identified in KF, mainly including triterpenoids, flavonoids, carbohydrates, amino acids, organic acids, and essential oils. Momordin Ic is the representative triterpene glycoside compound, which is used as a phytochemical marker for the quality control of Kochiae Fructus. The research on toxicity is insufficient, and only one article reported that the LD₅₀ was 7.15 ± 0.03 g/kg for water extract of KF after oral administration in KM mice. In addition, the pharmacokinetic study was carried out on momordin Ic with linear pharmacokinetic characteristics. Above all, this review provides comprehensive information about Kochiae Fructus and may provide the theoretic foundation of its clinical application and further development.

Identification of novel anti-cancer agents, applying in silico method for SENP1 protease inhibition

The SENP1 (Sentrin-Specific Protease1) is essential for desumoylation. SENP1 plays an essential role in many diseases such as cardiovascular disease, diabetes and cancer via targeting GATA2, NEMO, Pin1, SMAD4 and HIF-1α for deSUMOylation. Considering that, over expression of SENP1 was reported in cancer, thus an optional inhibitor of SENP1 can restitute the balance to the skewed system of SUMO and act as an effective therapeutic agent. The purpose of this study was to select and to sort inhibitors with a stronger binding affinity with SENP1. Molecular docking of SENP1 with natural compounds including Gallic acid, Caffeic acid, Thymoquinone, Thymol, Betaine, Alkannin, Ellagic acid, Betanin, Shikonin, Betanidin and Momordin IC was performed using AutoDock 4, then docking complexes for molecular dynamics (MD) simulation with GROMACS 4.6.5 were applied. Results with RMSD, RMSF, SASA, DSSP, gyrate, H-bond, ADMET and TOPKAT measurements, binding energy and structural features were surveyed. Among those, Gallic acid has shown the most significant results including RMSD and RMSF plots with high stability, high hydrogen bonds, high binding energy and the highest intermolecular bonds with SENP1. Gallic acid demonstrated strong connections and results of toxicity better than Momordin as control. Gallic acid is a phenolic compound which affects several pharmacological and biochemical pathways and has strong antioxidant, anti-inflammatory, antimutagenic and anticancer properties. Further research can improve the appropriate use of plant products drastically. Basic, pre-clinical and clinical research on Gallic acid may provide a roadmap for its ultimate application in the field of cancer prevention.Communicated by Ramaswamy H. Sarma.

SUMO: From Bench to Bedside

Sentrin/small ubiquitin-like modifier (SUMO) is protein modification pathway that regulates multiple biological processes, including cell division, DNA replication/repair, signal transduction, and cellular metabolism. In this review, we will focus on recent advances in the mechanisms of disease pathogenesis, such as cancer, diabetes, seizure, and heart failure, which have been linked to the SUMO pathway. SUMO is conjugated to lysine residues in target proteins through an isopeptide linkage catalyzed by SUMO-specific activating (E1), conjugating (E2), and ligating (E3) enzymes. In steady state, the quantity of SUMO-modified substrates is usually a small fraction of unmodified substrates due to the deconjugation activity of the family Sentrin/SUMO-specific proteases (SENPs). In contrast to the complexity of the ubiquitination/deubiquitination machinery, the biochemistry of SUMOylation and de-SUMOylation is relatively modest. Specificity of the SUMO pathway is achieved through redox regulation, acetylation, phosphorylation, or other posttranslational protein modification of the SUMOylation and de-SUMOylation enzymes. There are three major SUMOs. SUMO-1 usually modifies a substrate as a monomer; however, SUMO-2/3 can form poly-SUMO chains. The monomeric SUMO-1 or poly-SUMO chains can interact with other proteins through SUMO-interactive motif (SIM). Thus SUMO modification provides a platform to enhance protein-protein interaction. The consequence of SUMOylation includes changes in cellular localization, protein activity, or protein stability. Furthermore, SUMO may join force with ubiquitin to degrade proteins through SUMO-targeted ubiquitin ligases (STUbL). After 20 yr of research, SUMO has been shown to play critical roles in most, if not all, biological pathways. Thus the SUMO enzymes could be targets for drug development to treat human diseases.

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.

Divergent Modulation of Proteostasis in Prostate Cancer

Proteostasis regulates key cellular processes such as cell proliferation, differentiation, transcription, and apoptosis. The mechanisms by which proteostasis is regulated are crucial and the deterioration of cellular proteostasis has been significantly associated with tumorigenesis since it specifically targets key oncoproteins and tumor suppressors. Prostate cancer (PCa) is the second most common cause of cancer death in men worldwide. Androgens mediate one of the most central signaling pathways in all stages of PCa via the androgen receptor (AR). In addition to their regulation by hormones, PCa cells are also known to be highly secretory and are particularly prone to ER stress as proper ER function is essential. Alterations in various complex signaling pathways and cellular processes including cell cycle control, transcription, DNA repair, apoptosis, cell adhesion, epithelial-mesenchymal transition (EMT), and angiogenesis are critical factors influencing PCa development through key molecular changes mainly by posttranslational modifications in PCa-related proteins, including AR, NKX3.1, PTEN, p53, cyclin D1, and p27. Several ubiquitin ligases like MDM2, Siah2, RNF6, CHIP, and substrate-binding adaptor SPOP; deubiquitinases such as USP7, USP10, USP26, and USP12 are just some of the modifiers involved in the regulation of these key proteins via ubiquitin-proteasome system (UPS). Some ubiquitin-like modifiers, especially SUMOs, have been also closely associated with PCa. On the other hand, the proteotoxicity resulting from misfolded proteins and failure of ER adaptive capacity induce unfolded protein response (UPR) that is an indispensable signaling mechanism for PCa development. Lastly, ER-associated degradation (ERAD) also plays a crucial role in prostate tumorigenesis. In this section, the relationship between prostate cancer and proteostasis will be discussed in terms of UPS, UPR, SUMOylation, ERAD, and autophagy.

Noncovalent structure of SENP1 in complex with SUMO2

SUMOylation is a post-translational modification in which a small ubiquitin-like molecule (SUMO) is appended to substrate proteins and is known to influence myriads of biological processes. A delicate interplay between several families of SUMOylation proteins and their substrates ensures the proper level of SUMOylation required for normal cell function. Among the SUMO proteins, SUMO2 is known to form mono-SUMOylated proteins and engage in poly-SUMO chain formation, while sentrin-specific protease 1 (SENP1) is a key enzyme in regulating both events. Determination of the SENP1-SUMO2 interaction is therefore necessary to better understand SUMOylation. In this regard, the current paper reports the noncovalent structure of SENP1 in complex with SUMO2, which was refined to a resolution of 2.62 Å with R and Rfree values of 22.92% and 27.66%, respectively. The structure shows that SENP1-SUMO2 complex formation is driven largely by polar interactions and limited hydrophobic contacts. The essential C-terminal motif (QQTGG) of SUMO2 is stabilized by a number of specific bonding interactions that enable it to protrude into the catalytic triad of SENP1 and provide the arrangement necessary for maturation of SUMO and deSUMOylation activity. Overall, the structure shows a number of structural details that pinpoint the basis of SENP1-SUMO2 complex formation.

Small-Molecule Inhibitors Targeting Protein SUMOylation as Novel Anticancer Compounds

SUMOylation, one of post-translational modifications, is covalently modified on lysine residues of a target protein through an enzymatic cascade reaction similar to protein ubiquitination. Along with identification of many SUMOylated proteins, protein SUMOylation has been proven to regulate multiple biologic activities including transcription, cell cycle, DNA repair, and innate immunity. The dysregulation of protein SUMOylation and deSUMOylation modification is linked with carcinogenesis and tumor progression. The SUMOylation-associated enzymes are usually elevated in various cancers, which function as cancer biomarkers to relate to poor outcomes for patients. Considering the significance of protein SUMOylation in regulating diverse biologic functions in cancer progression, numerous small-molecule inhibitors targeting protein SUMOylation pathway are developed as potentially clinical anticancer therapeutics. Here, we systematically summarize the latest progresses of associations of small ubiquitin-like modifier (SUMO) enzymes with cancers and small-molecular inhibitors against human cancers by targeting SUMOylation enzymes. We also compared the pros and cons of several special anticancer inhibitors targeting SUMO pathway. As more efforts are invested in this field, small-molecule inhibitors targeting the SUMOylation modification pathway are promising for development into novel anticancer drugs.

The post-translational modification, SUMOylation, and cancer (Review)

SUMOylation is a reversible post-translational modification which has emerged as a crucial molecular regulatory mechanism, involved in the regulation of DNA damage repair, immune responses, carcinogenesis, cell cycle progression and apoptosis. Four SUMO isoforms have been identified, which are SUMO1, SUMO2/3 and SUMO4. The small ubiquitin-like modifier (SUMO) pathway is conserved in all eukaryotes and plays pivotal roles in the regulation of gene expression, cellular signaling and the maintenance of genomic integrity. The SUMO catalytic cycle includes maturation, activation, conjugation, ligation and de-modification. The dysregulation of the SUMO system is associated with a number of diseases, particularly cancer. SUMOylation is widely involved in carcinogenesis, DNA damage response, cancer cell proliferation, metastasis and apoptosis. SUMO can be used as a potential therapeutic target for cancer. In this review, we briefly outline the basic concepts of the SUMO system and summarize the involvement of SUMO proteins in cancer cells in order to better understand the role of SUMO in human disease.

Momordin Ic, a new natural SENP1 inhibitor, inhibits prostate cancer cell proliferation

SUMO-specific protease 1 (SENP1), a member of the de-SUMOylation protease family, is elevated in prostate cancer (PCa) cells and is involved in PCa pathogenesis. Momordin Ιc (Mc), a natural pentacyclic triterpenoid, inhibited SENP1 in vitro, as reflected by reduced SENP1C-induced cleavage of SUMO2-ΔRanGAP1. Mc also altered the thermal stability of SENP1 in a newly developed cellular thermal shift assay, indicating that Mc directly interacts with SENP1 in PCa cells. Consistent with SENP1 inhibition, Mc increased SUMOylated protein levels, which was further confirmed by the accumulation of two known SUMOylated proteins, hypoxia inducible factor-1a and nucleus accumbens associated protein 1 in PC3 cells. Compared to LNCaP and normal prostate epithelial RWPE-1 cells, PC3 cells had higher levels of SENP1 mRNA and were more sensitive to Mc-induced growth inhibition. Mc also reduced SENP1 mRNA levels in PCa cells. Overexpression of SENP1 rescued PC3 cells from Mc-induced apoptosis. Finally, Mc suppressed cell proliferation and induced cell death in vivo in a xenograft PC3 tumor mouse model. These findings demonstrate that Mc is a novel SENP1 inhibitor with potential therapeutic value for PCa. Investigation of other pentacyclic triterpenoids may aid in the development of novel SENP1 inhibitor drugs.

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.

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 HIF1a, 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.

SUMO and the robustness of cancer

Post-translational protein modification by small ubiquitin-like modifier (SUMO), termed sumoylation, is an important mechanism in cellular responses to stress and one that appears to be upregulated in many cancers. Here, we examine the role of sumoylation in tumorigenesis as a possibly necessary safeguard that protects the stability and functionality of otherwise easily misregulated gene expression programmes and signalling pathways of cancer cells.

The prognostic value of SUMO1/Sentrin specific peptidase 1 (SENP1) in prostate cancer is limited to ERG-fusion positive tumors lacking PTEN deletion

Background

Posttranscriptional protein modification by SUMOylation plays an important role in tumor development and progression. In the current study we analyzed prevalence and prognostic impact of the de-SUMOylation enzyme SENP1 in prostate cancer.

Methods

SENP1 expression was analyzed by immunohistochemistry on a tissue microarray containing more than 12,400 prostate cancer specimens. Results were compared to tumor phenotype, ERG status, genomic deletions of 3p, 5q, 6q and PTEN, and biochemical recurrence.

Results

SENP1 immunostaining was detectable in 34.5 % of 9,516 interpretable cancers and considered strong in 7.3 %, moderate in 14.9 % and weak in 12.3 % of cases. Strong SENP1 expression was linked to advanced pT stage (p < 0.0001), high Gleason grade (p < 0.0001), positive lymph node status (p = 0.0019), high pre-operative PSA levels (p = 0.0037), and PSA recurrence (p < 0.0001). SENP1 expression was strongly associated with positive ERG fusion status as determined by both in situ hybridization (FISH) and immunohistochemistry as well as with PTEN deletions. Detectable SENP1 immunostaining was found in 41 % of ERG positive and in 47 % of PTEN deleted cancers but in only 30 % of ERG negative and 30 % of PTEN non-deleted cancers (p < 0.0001 each). Deletions of 3p, 5q, and 6q were unrelated to SENP1 expression. Subset analyses revealed that the prognostic impact of SENP1 expression was solely driven by the subgroup of ERG positive, PTEN undeleted cancers. In this subgroup, the prognostic role of SENP1 expression was independent of the preoperative PSA level, tumor stage, Gleason grade, and the status of the resection margin.

Conclusions

SENP1 expression has strong prognostic impact in a molecularly defined subset of cancers. This is per se not surprising as the biologic impact of each individual molecular event is likely to be dependent on its cellular environment. However, such findings challenge the concept of finding clinically relevant molecular signatures that are equally applicable to all prostate cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1555-8) contains supplementary material, which is available to authorized users.

SUMO-Specific Protease 2 (SENP2) Is an Important Regulator of Fatty Acid Metabolism in Skeletal Muscle

Small ubiquitin-like modifier (SUMO)-specific proteases (SENPs) that reverse protein modification by SUMO are involved in the control of numerous cellular processes, including transcription, cell division, and cancer development. However, the physiological function of SENPs in energy metabolism remains unclear. Here, we investigated the role of SENP2 in fatty acid metabolism in C2C12 myotubes and in vivo. In C2C12 myotubes, treatment with saturated fatty acids, like palmitate, led to nuclear factor-κB-mediated increase in the expression of SENP2. This increase promoted the recruitment of peroxisome proliferator-activated receptor (PPAR)δ and PPARγ, through desumoylation of PPARs, to the promoters of the genes involved in fatty acid oxidation (FAO), such as carnitine-palmitoyl transferase-1 (CPT1b) and long-chain acyl-CoA synthetase 1 (ACSL1). In addition, SENP2 overexpression substantially increased FAO in C2C12 myotubes. Consistent with the cell culture system, muscle-specific SENP2 overexpression led to a marked increase in the mRNA levels of CPT1b and ACSL1 and thereby in FAO in the skeletal muscle, which ultimately alleviated high-fat diet-induced obesity and insulin resistance. Collectively, these data identify SENP2 as an important regulator of fatty acid metabolism in skeletal muscle and further implicate that muscle SENP2 could be a novel therapeutic target for the treatment of obesity-linked metabolic disorders.

Tumor-suppressive microRNA-145 induces growth arrest by targeting SENP1 in human prostate cancer cells

Prostate cancer (PCa) prevails as the most commonly diagnosed malignancy in men and the third leading cause of cancer-related deaths in developed countries. One of the distinct characteristics of prostate cancer is overexpression of the small ubiquitin-like modifier (SUMO)-specific protease 1 (SENP1), and the upregulation of SENP1 contributes to the malignant progression and cell proliferation of PCa. Previous studies have shown that the expression of microRNA-145 (miRNA-145) was extensively deregulated in PCa cell lines and primary clinical prostate cancer samples. Independent target prediction methods have indicated that the 3′-untranslated region of SENP1 mRNA is a potential target of miR-145. Here we found that low expression of miR-145 was correlated with high expression of SENP1 in PCa cell line PC-3. The transient introduction of miR-145 caused cell cycle arrest in PC-3 cells, and the opposite effect was observed when miR-145 inhibitor was transfected. Further studies revealed that the SENP1 3′-untranslated region was a regulative target of miR-145 in vitro. MicroRNA-145 also suppressed tumor formation in vivo in nude mice. Taken together, miR-145 plays an important role in tumorigenesis of PCa through interfering SENP1.

Roles of ubiquitination and SUMOylation on prostate cancer: mechanisms and clinical implications

The initiation and progression of human prostate cancer are highly associated with aberrant dysregulations of tumor suppressors and proto-oncogenes. Despite that deletions and mutations of tumor suppressors and aberrant elevations of oncogenes at the genetic level are reported to cause cancers, emerging evidence has revealed that cancer progression is largely regulated by posttranslational modifications (PTMs) and epigenetic alterations. PTMs play critical roles in gene regulation, cellular functions, tissue development, diseases, malignant progression and drug resistance. Recent discoveries demonstrate that ubiquitination and SUMOylation are complicated but highly-regulated PTMs, and make essential contributions to diseases and cancers by regulation of key factors and signaling pathways. Ubiquitination and SUMOylation pathways can be differentially modulated under various stimuli or stresses in order to produce the sustained oncogenic potentials. In this review, we discuss some new insights about molecular mechanisms on ubiquitination and SUMOylation, their associations with diseases, oncogenic impact on prostate cancer (PCa) and clinical implications for PCa treatment.

Overview on the complexity of androgen receptor-targeted therapy for prostate cancer

In the past decades, the field of prostate cancer (PCa) biology has developed exponentially and paralleled with that has been the growing interest in translation of laboratory findings into clinical practice. Based on overwhelming evidence of high impact research findings which support the underlying cause of insufficient drug efficacy in patients progressing on standard androgen deprivation therapy (ADT) is due to persistent activation of the androgen receptor (AR) signaling axis. Therefore, newer agents must be discovered especially because newer ADT such as abiraterone and enzalutamide are becoming ineffective due to rapid development of resistance to these agents. High-throughput technologies are generating massive and highly dimensional genetic variation data that has helped in developing a better understanding of the dynamic repertoire of AR and AR variants. Full length AR protein and its variants modulate a sophisticated regulatory system to orchestrate cellular responses. We partition this multicomponent review into subsections addressing the underlying mechanisms of resistance to recent therapeutics, positive and negative regulators of AR signaling cascade, and how SUMOylation modulates AR induced transcriptional activity. Experimentally verified findings obtained from cell culture and preclinical studies focusing on the potential of natural agents in inhibiting mRNA/protein levels of AR, nuclear accumulation and enhanced nuclear export of AR are also discussed. We also provide spotlight on molecular basis of enzalutamide resistance with an overview of the strategies opted to overcome such resistance. AR variants are comprehensively described and different mechanisms that regulate AR variant expression are also discussed. Reconceptualization of phenotype- and genotype-driven studies have convincingly revealed that drug induced resistance is a major stumbling block in standardization of therapy. Therefore, we summarize succinctly the knowledge of drug resistance especially to ADT and potential avenues to overcome such resistance for improving the treatment outcome of PCa patients.

Higher androgen bioactivity is associated with excessive erythrocytosis and chronic mountain sickness in Andean Highlanders: a review

Populations living at high altitudes (HA), particularly in the Peruvian Central Andes, are characterised by presenting subjects with erythrocytosis and others with excessive erythrocytosis (EE)(Hb>21 g dl(-1) ). EE is associated with chronic mountain sickness (CMS), or lack of adaptation to HA. Testosterone is an erythropoietic hormone and it may play a role on EE at HA. The objective of the present review was to summarise findings on role of serum T levels on adaptation at HA and genes acting on this process. Men at HA without EE have higher androstenedione levels and low ratio androstenedione/testosterone than men with EE, suggesting low activity of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and this could be a mechanism of adaptation to HA. Higher conversion of dehydroepiandrosterone to testosterone in men with EE suggests nigher 17beta-HSD activity. Men with CMS at Peruvian Central Andes have two genes SENP1, and ANP32D with higher transcriptional response to hypoxia relative to those without. SUMO-specific protease 1 (SENP1) is an erythropoiesis regulator, which is essential for the stability and activity of hypoxia-inducible factor 1 (HIF-1α) under hypoxia. SENP1 reverses the hormone-augmented SUMOylation of androgen receptor (AR) increasing the transcription activity of AR.In conclusion, increased androgen activity is related with CMS.

SUMO-specific protease 1 regulates pancreatic cancer cell proliferation and invasion by targeting MMP-9

SUMOylation is a dynamic process which can be reversed by a family of sentrin/SUMO-specific protease (SENPs). Recently, SENP1, a member of SENPs family was shown to have a pro-oncogenic role in many types of cancer. Here, we showed that SENP1 was upregulated in pancreatic ductal adenocarcinoma (PDAC) tissues compared with adjacent normal tissues. Moreover, clinical data showed that SENP1 was positively associated with lymph node metastasis and TNM stage. Furthermore, knockdown of SENP1 by SENP1-siRNA inhibited pancreatic cancer cell proliferation, migration, and invasion, suggesting that SENP1 played an important role in PDAC progression and metastasis. Mechanistically, silencing of SENP1 results in downregulation of MMP-9, which is pivotal for PDAC cell growth and migration. Taken together, these results suggest that SENP1 may serve as a potential novel diagnostic and therapeutic target of PDAC.

Network analysis of ChIP-Seq data reveals key genes in prostate cancer

Background

Prostate cancer (PC) is the second most common cancer among men in the United States, and it imposes a considerable threat to human health. A deep understanding of its underlying molecular mechanisms is the premise for developing effective targeted therapies. Recently, deep transcriptional sequencing has been used as an effective genomic assay to obtain insights into diseases and may be helpful in the study of PC.

Methods

In present study, ChIP-Seq data for PC and normal samples were compared, and differential peaks identified, based upon fold changes (with P-values calculated with t-tests). Annotations of these peaks were performed. Protein–protein interaction (PPI) network analysis was performed with BioGRID and constructed with Cytoscape, following which the highly connected genes were screened.

Results

We obtained a total of 5,570 differential peaks, including 3,726 differentially enriched peaks in tumor samples and 1,844 differentially enriched peaks in normal samples. There were eight significant regions of the peaks. The intergenic region possessed the highest score (51%), followed by intronic (31%) and exonic (11%) regions. The analysis revealed the top 35 highly connected genes, which comprised 33 differential genes (such as YWHAQ, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein and θ polypeptide) from ChIP-Seq data and 2 differential genes retrieved from the PPI network: UBA52 (ubiquitin A-52 residue ribosomal protein fusion product 1) and SUMO2 (SMT3 suppressor of mif two 3 homolog 2) .

Conclusions

Our findings regarding potential PC-related genes increase the understanding of PC and provides direction for future research.

Electronic supplementary material

The online version of this article (doi:10.1186/s40001-014-0047-7) contains supplementary material, which is available to authorized users.

Aberrant sumoylation signaling evoked by reactive oxygen species impairs protective function of Prdx6 by destabilization and repression of its transcription

Loss of the cytoprotective protein peroxiredoxin 6 (Prdx6) in cells that are aging or under oxidative stress is known to be linked to the pathobiology of many age-related diseases. However, the mechanism by which Prdx6 activity goes awry is largely unknown. Using Prdx6-deficient (Prdx6(-/-) ) cells as a model for aging or redox active cells, human/mouse lens epithelial cells (LECs) facing oxidative stress and aging lenses, we found a significant increase in the levels of small ubiquitin-like modifier (Sumo)1 conjugates. These cells displayed increased levels of Sumo1 and reduced the expression of Prdx6. Specifically, we observed that Prdx6 is a target for aberrant sumoylation signaling, and that Sumo1 modification reduces its cellular abundance. LECs overexpressing Sumo1 showed reduced expression and activity of Prdx6 and its transactivator specificity protein 1 (Sp1), mRNA and protein with increased levels of reactive oxygen species; those cells were vulnerable to oxidative stress-induced cell death. A significant reduction in Prdx6, Sp1 protein and mRNA expression was observed in redox active Prdx6(-/-) cells and in aging lenses/LECs. The reduction was correlated with increased expression of Sumo1 and enrichment of the inactive form (dimeric) of Sumo-specific protease (Senp)1. Experiments with Sumo1-fused Prdx6 and Prdx6 promoter-linked to chloramphenicol acetyltransferase reporter gene constructs indicated that Sumo1 dysregulated Prdx6 activity by reducing its abundance and attenuating its transcription; in contrast, the delivery of Senp1 or Prdx6 reversed the process. The data show that reactive oxygen species-evoked aberrant sumoylation signaling affects Prdx6 activity by reducing Prdx6 abundance, as well as transcription. The findings of the present study may provide a foundation for a strategy to repair deleterious oxidative signaling generated by a reduced activity of Prdx6.

15-LOX-1 suppression of hypoxia-induced metastatic phenotype and HIF-1α expression in human colon cancer cells

The expression of 15-lipoxygenase-1 (15-LOX-1) is downregulated in colon cancer and other major cancers, and 15-LOX-1 reexpression in cancer cells suppresses colonic tumorigenesis. Various lines of evidence indicate that 15-LOX-1 expression suppresses premetastatic stages of colonic tumorigenesis; nevertheless, the role of 15-LOX-1 loss of expression in cancer epithelial cells in metastases continues to be debated. Hypoxia, a common feature of the cancer microenvironment, promotes prometastatic mechanisms such as the upregulation of hypoxia-inducible factor (HIF)-1α, a transcriptional master regulator that enhances cancer cell metastatic potential, angiogenesis, and tumor cell invasion and migration. We have, therefore, tested whether restoring 15-LOX-1 in colon cancer cells affects cancer cells' hypoxia response that promotes metastasis. We found that 15-LOX-1 reexpression in HCT116, HT29LMM, and LoVo colon cancer cells inhibited survival, vascular endothelial growth factor (VEGF) expression, angiogenesis, cancer cell migration and invasion, and HIF-1α protein expression and stability under hypoxia. These findings demonstrate that 15-LOX-1 expression loss in cancer cells promotes metastasis and that therapeutically targeting ubiquitous 15-LOX-1 loss in cancer cells has the potential to suppress metastasis.

Exploring the desumoylation process of SENP1: a study combined MD simulations with QM/MM calculations on SENP1-SUMO1-RanGAP1

The small ubiquitin-related modifier (SUMO)-specific protease (SENP) processes SUMOs to mature forms and deconjugates them from various modified substrates. Loss of the equilibrium from desumoylation catalyzed by abnormal SENP1 is associated with cancers and transcription factor activity. In spite of the significant role of SENP1, the molecular basis of its desumoylation remains unclear. Here, MD simulations and QM/MM methods are combined to investigate the catalytic mechanism of desumoylation. The results showed that substrate SUMO1-RanGAP1 fitted into the catalytic pocket of SENP1 by the break of internal hydrophobic interactions and the isomerization of isopeptide from trans to cis. After that, the nucleophilic sulfur anion of Cys603 in SENP1 attacked the carbonyl carbon of Gly97 of SUMO1 to trigger the reaction, and then a tetrahedral intermediate and an acyl-enzyme intermediate were generated in turn, leading to the final release of enzyme SENP1 and two products, free SUMO1 and RanGAP1. In the process, nucleophilic attack was identified as the rate-determining step with a potential energy barrier of 20.2 kcal/mol. These results are in agreement with experimental data from mutagenesis and other experiments. Our findings elucidate the catalytic mechanism of SENP1 with its substrate and may provide a better understanding of SENP desumoylation. In particular, we have identified key residues in SENP1 needed for desumoylation that might be beneficial for the design of novel inhibitors of SENP1-related diseases.

Dissecting Major Signaling Pathways throughout the Development of Prostate Cancer

Prostate cancer (PCa) is one of the most common malignancies found in males. The development of PCa involves several mutations in prostate epithelial cells, usually linked to developmental changes, such as enhanced resistance to apoptotic death, constitutive proliferation, and, in some cases, to differentiation into an androgen deprivation-resistant phenotype, leading to the appearance of castration-resistant PCa (CRPCa), which leads to a poor prognosis in patients. In this review, we summarize recent findings concerning the main deregulations into signaling pathways that will lead to the development of PCa and/or CRPCa. Key mutations in some pathway molecules are often linked to a higher prevalence of PCa, by directly affecting the respective cascade and, in some cases, by deregulating a cross-talk node or junction along the pathways. We also discuss the possible environmental and nonenvironmental inducers for these mutations, as well as the potential therapeutic strategies targeting these signaling pathways. A better understanding of how some risk factors induce deregulation of these signaling pathways, as well as how these deregulated pathways affect the development of PCa and CRPCa, will further help in the development of new treatments and prevention strategies for this disease.

Function and regulation of SUMO proteases

Covalent attachment of small ubiquitin-like modifier (SUMO) to proteins is highly dynamic, and both SUMO-protein conjugation and cleavage can be regulated. Protein desumoylation is carried out by SUMO proteases, which control cellular mechanisms ranging from transcription and cell division to ribosome biogenesis. Recent advances include the discovery of two novel classes of SUMO proteases, insights regarding SUMO protease specificity, and revelations of previously unappreciated SUMO protease functions in several key cellular pathways. These developments, together with new connections between SUMO proteases and the recently discovered SUMO-targeted ubiquitin ligases (STUbLs), make this an exciting period to study these enzymes.

Down-regulation of SENP1 expression increases apoptosis of Burkitt lymphoma cells

OBJECTIVE

To investigate the effect of down-regulation of Sentrin/SUMO-specific protease 1 (SENP1) expression on the apoptosis of human Burkitt lymphoma cells (Daudi cells) and potential mechanisms.

METHODS

Short hairpin RNA (shRNA) targeting SENP1 was designed and synthesized and then cloned into a lentiviral vector. A lentiviral packaging plasmid was used to transfect Daudi cells (sh-SENP1-Daudi group). Daudi cells without transfection (Daudi group) and Daudi cells transfected with blank plasmid (sh-NC-Daudi group) served as control groups. Flow cytometry was performed to screen GFP positive cells and semiquantitative PCR and Western blot assays were employed to detect the inference efficiency. The morphology of cells was observed under a microscope before and after transfection. Fluorescence quantitative PCR and Western blot assays were conducted to measure the mRNA and protein expression of apoptosis related molecules (caspase-3, 8 and 9). After treatment with COCl2 for 24 h, the mRNA and protein expression of hypoxia inducible factor -1α (HIF-1α) was determined.

RESULTS

Sequencing showed the expression vectors of shRNA targeting SENP1 to be successfully constructed. Following screening of GFP positive cells by FCM, semiqualitative PCR showed the interference efficiency was 79.2±0.026%. At 48 h after transfection, the Daudi cells became shrunken, had irregular edges and presented apoptotic bodies. Western blot assay revealed increase in expression of caspase-3, 8 and 9 with prolongation of transfection (P<0.05). Following hypoxia treatment, mRNA expression of HIF-1α remained unchanged in three groups (P>0.05) but the protein expression of HIF-1α markedly increased (P<0.05). However, in the sh-SENP1-Daudi group, the protein expression of HIF-1α remained unchanged.

CONCLUSION

SENP1-shRNA can efficiently inhibit SENP1 expression in Daudi cells. SENP1 inhibition may promote cell apoptosis. These findings suggest that SENP1 may serve as an important target in the gene therapy of Burkitts lymphoma.

Transcriptional repression of estrogen receptor α signaling by SENP2 in breast cancer cells

Estrogen receptors (ERs) are ligand-activated transcription factors involved in many physiological and pathological processes, including breast cancer. Their activity is fine-tuned by posttranslational modifications, notably sumoylation. In the present study, we investigated the role of the small ubiquitin-related modifier (SUMO) protease, SUMO1/sentrin/suppressor of Mif 2-specific peptidase 2 (SENP2), in the regulation of ERα activity. We first found SENP2 to significantly repress estradiol-induced transcriptional activity in breast cancer cells (MCF7 and T47D). This effect was observed with a reporter plasmid and on endogenous genes such as TFF1 and CTSD, which were shown to recruit SENP2 in chromatin immunoprecipitation experiments. Using glutathione S-transferase pull-down, coimmunoprecipitation and proximity ligation assays, SENP2 was found to interact with ERα and this interaction to be mediated by the amino-terminal region of the protease and the hinge region of the receptor. Interestingly, we demonstrated that ERα repression by SENP2 is independent of its SUMO protease activity and requires a transcriptional repressive domain located in the amino-terminal end of the protease. Using small interfering RNA assays, we evidenced that this domain recruits the histone deacetylase 3 (HDAC3), to be fully active. Furthermore, using both overexpression and knockdown strategies, we showed that SENP2 robustly represses estrogen-dependent and independent proliferation of MCF7 cells. We provided evidence that this effect requires both the proteolytic and transcriptional activities of SENP2. Altogether, our study unravels a new property for a SUMO protease and identifies SENP2 as a classical transcription coregulator.

Dynamic regulation of steroid hormone receptor transcriptional activity by reversible SUMOylation

Transcription complexes containing steroid hormone receptors (SRs) have been well characterized at selected canonical target genes. More recently, the advent of whole genome technologies has allowed for complete SR transcriptome analyses in diverse cell types and in response to a variety of cellular stimuli. These types of studies have revealed little overlap between the tissue or cell type-specific transcriptomes of a given SR, suggesting that all SRs are highly context-dependent transcription factors. However, the mechanisms controlling SR promoter selectivity have not been fully elucidated. Many factors may influence SR promoter selectivity, including chromatin structure, cofactor availability, and posttranslational modifications to SRs and/or their numerous coregulators; this review focuses on the impact that covalent attachment of small ubiquitin-like modifier (SUMO) moieties to SRs (i.e., SUMOylation) have on the transcriptional regulation of SR target genes.

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-IIβ) 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-IIβ in cardiomyocytes.

Detection of differentially expressed genes and association with clinicopathological features in laryngeal squamous cell carcinoma

Head and neck cancer is a significant health problem worldwide. Early detection and prediction of prognosis will improve patient survival and quality of life. The aim of this study was to identify genes differentially expressed between laryngeal cancer and the corresponding normal tissues as potential biomarkers. A total of 36 patients with laryngeal squamous cell carcinoma were recruited. Four of these cases were randomly selected for cDNA microarray analysis of the entire genome. Using semi-quantitative RT-PCR and western blot analysis, the differential expression of genes and their protein products, respectively, between laryngeal cancer tissues and corresponding adjacent normal tissues was verified in the remaining 32 cases. The expression levels of these genes and proteins were investigated for associations with clinicopathological parameters taken from patient data. The cDNA microarray analysis identified 349 differentially expressed genes between tumor and normal tissues, 112 of which were upregulated and 237 were downregulated in tumors. Seven genes and their protein products were then selected for validation using RT-PCR and western blot analysis, respectively. The data demonstrated that the expression of SENP1, CD109, CKS2, LAMA3, ITGAV and ITGB8 was increased, while LAMA2 was downregulated in laryngeal cancer compared with the corresponding normal tissues. Associations between the expression of these genes and clinicopathological data from the patients were also established, including age, tumor classification, stage, differentiation and lymph node metastasis. Our current study provides the first evidence that these seven genes may be differentially expressed in laryngeal squamous cell carcinoma and also associated with clinicopathological data. Future study is required to further confirm whether detection of their expression can be used as biomarkers for prediction of patient survival or potential treatment targets.

The in vivo role of androgen receptor SUMOylation as revealed by androgen insensitivity syndrome and prostate cancer mutations targeting the proline/glycine residues of synergy control motifs

The androgen receptor (AR) mediates the effects of male sexual hormones on development and physiology. Alterations in AR function are central to reproductive disorders, prostate cancer, and Kennedy disease. AR activity is influenced by post-translational modifications, but their role in AR-based diseases is poorly understood. Conjugation by small ubiquitin-like modifier (SUMO) proteins at two synergy control (SC) motifs in AR exerts a promoter context-dependent inhibitory role. SC motifs are composed of a four-amino acid core that is often preceded and/or followed by nearby proline or glycine residues. The function of these flanking residues, however, has not been examined directly. Remarkably, several AR mutations associated with oligospermia and androgen insensitivity syndrome map to Pro-390, the conserved proline downstream of the first SC motif in AR. Similarly, mutations at Gly-524, downstream of the second SC motif, were recovered in recurrent prostate cancer samples. We now provide evidence that these clinically isolated substitutions lead to a partial loss of SC motif function and AR SUMOylation that affects multiple endogenous genes. Consistent with a structural role as terminators of secondary structure elements, substitution of Pro-390 by Gly fully supports both SC motif function and SUMOylation. As predicted from the functional properties of SC motifs, the clinically isolated mutations preferentially enhance transcription driven by genomic regions harboring multiple AR binding sites. The data support the view that alterations in AR SUMOylation play significant roles in AR-based diseases and offer novel SUMO-based therapeutic opportunities.

SUMO-specific protease 1 promotes prostate cancer progression and metastasis

SUMO-specific protease 1 (SENP1) is a member of de-SUMOylation protease family and has an important role in the regulation of androgen receptor-dependent transcription and hypoxia signaling. This activity profile of SENP1 prompted us to investigate whether SENP1 is involved in the pathogenesis of prostate cancer. In previous studies, we have detected the overexpression of SENP1 in both precancerous prostate intraepithelial neoplasia (PIN) lesions and prostate cancer tissue samples from patients. Whereas our whole-animal model has demonstrated that SENP1 induction is critical for prostate cell transformation, the role of SENP1 in prostate cancer progression is still unknown. In this study, we show that SENP1 expression directly correlates with prostate cancer aggressiveness and reccurrence, by analyzing more than 150 prostate cancer specimens. Modulating SENP1 level dictates colony formation of prostate cancer cell lines, tumor growth in nude mice and also prostate cancer cell migration and invasion. Silencing SENP1 level in highly metastatic prostate cancer cells perturbs their ability to metastasize to the bone and initiates secondary tumors. Mechanistically, the expression of two critical bone remodeling proteins, matrix metalloproteinase 2 (MMP2) and MMP9, is regulated by SENP1 through the HIF1α signaling pathway. All these results show the contribution of SENP1 to the progression of prostate cancer, and suggest that SENP1 may be a prognostic marker and a therapeutic target for metastasis in prostate cancer patients.

Triptolide inhibits the proliferation of prostate cancer cells and down-regulates SUMO-specific protease 1 expression

Recently, traditional Chinese medicine and medicinal herbs have attracted more attentions worldwide for its anti-tumor efficacy. Celastrol and Triptolide, two active components extracted from the Chinese herb Tripterygium wilfordii Hook F (known as Lei Gong Teng or Thunder of God Vine), have shown anti-tumor effects. Celastrol was identified as a natural 26 s proteasome inhibitor which promotes cell apoptosis and inhibits tumor growth. The effect and mechanism of Triptolide on prostate cancer (PCa) is not well studied. Here we demonstrated that Triptolide, more potent than Celastrol, inhibited cell growth and induced cell death in LNCaP and PC-3 cell lines. Triptolide also significantly inhibited the xenografted PC-3 tumor growth in nude mice. Moreover, Triptolide induced PCa cell apoptosis through caspases activation and PARP cleavage. Unbalance between SUMOylation and deSUMOylation was reported to play an important role in PCa progression. SUMO-specific protease 1 (SENP1) was thought to be a potential marker and therapeutical target of PCa. Importantly, we observed that Triptolide down-regulated SENP1 expression in both mRNA and protein levels in dose-dependent and time-dependent manners, resulting in an enhanced cellular SUMOylation in PCa cells. Meanwhile, Triptolide decreased AR and c-Jun expression at similar manners, and suppressed AR and c-Jun transcription activity. Furthermore, knockdown or ectopic SENP1, c-Jun and AR expression in PCa cells inhibited the Triptolide anti-PCa effects. Taken together, our data suggest that Triptolide is a natural compound with potential therapeutic value for PCa. Its anti-tumor activity may be attributed to mechanisms involving down-regulation of SENP1 that restores SUMOylation and deSUMOyaltion balance and negative regulation of AR and c-Jun expression that inhibits the AR and c-Jun mediated transcription in PCa.

The Role of the Small Ubiquitin-Related Modifier (SUMO) Pathway in Prostate Cancer

SUMO (small ubiquitin-related modifier) conjugation is a reversible three-step process of protein post-translational modifications mediating protein-protein interactions, subcellular compartmentalization and regulation of transcriptional events. Among divergent transcription factors regulated by SUMOylation and deSUMOylation, the androgen receptor (AR) is of exceptional significance, given its established role in prostate carcinogenesis. The enzymes of the SUMO pathway can have diverse effects on AR transcriptional activity, either via direct modification of the AR or through modification of AR co-regulators. Accumulating in vitro and in vivo evidence implicates the SUMO pathway in AR-dependent signaling. Prostate cancer cell proliferation and hypoxia-induced angiogenesis are also regulated by the SUMO pathway, through an AR-independent mechanism. Thus, an important role has been revealed for members of the SUMO pathway in prostate cancer (PCa) development and progression, offering new therapeutic targets.

ETV1, 4 and 5: an oncogenic subfamily of ETS transcription factors

The homologous ETV1, ETV4 and ETV5 proteins form the PEA3 subfamily of ETS transcription factors. In Ewing tumors, chromosomal translocations affecting ETV1 or ETV4 are an underlying cause of carcinogenesis. Likewise, chromosomal rearrangements of the ETV1, ETV4 or ETV5 gene occur in prostate tumors and are thought to be one of the major driving forces in the genesis of prostate cancer. In addition, these three ETS proteins are implicated in melanomas, breast and other types of cancer. Complex posttranslational modifications govern the activity of PEA3 factors, which can promote cell proliferation, motility and invasion. Here, we review evidence for a role of ETV1, 4 and 5 as oncoproteins and describe modes of their action. Modulation of their activation or interaction with cofactors as well as inhibiting crucial target gene products may ultimately be exploited to treat various cancers that are dependent on the PEA3 group of ETS transcription factors.