Overexpression of Cdc25B, an androgen receptor coactivator, in prostate cancer

Unmasking Neuroendocrine Prostate Cancer with a Machine Learning-Driven Seven-Gene Stemness Signature That Predicts Progression

Prostate cancer (PCa) poses a significant global health challenge, particularly due to its progression into aggressive forms like neuroendocrine prostate cancer (NEPC). This study developed and validated a stemness-associated gene signature using advanced machine learning techniques, including Random Forest and Lasso regression, applied to large-scale transcriptomic datasets. The resulting seven-gene signature (KMT5C, DPP4, TYMS, CDC25B, IRF5, MEN1, and DNMT3B) was validated across independent cohorts and patient-derived xenograft (PDX) models. This signature demonstrated strong prognostic value for progression-free, disease-free, relapse-free, metastasis-free, and overall survival. Importantly, the signature not only identified specific NEPC subtypes, such as large-cell neuroendocrine carcinoma, which is associated with very poor outcomes, but also predicted a poor prognosis for PCa cases that exhibit this molecular signature, even when they were not histopathologically classified as NEPC. This dual prognostic and classifier capability makes the seven-gene signature a robust tool for personalized medicine, providing a valuable resource for predicting disease progression and guiding treatment strategies in PCa management.

The BET inhibitor sensitivity is associated with the expression level of CDC25B in pancreatic cancer models

Aim: Cell division cycle 25B (CDC25B) belongs to the CDC25 family of phosphatases that regulate cell cycle progression. CDC25B also contributes to tumor initiation and progression, but no connection between CDC25B levels and drug sensitivity in pancreatic cancer has been reported. Based on our finding that bromodomain and extraterminal domain (BET) inhibitors decrease levels of CDC25B, we aim to compare the sensitivity of models expressing contrasting levels of CDC25B to the BET inhibitor JQ1, in pancreatic cancer cell lines in vitro and in patient-derived xenograft (PDX) models of pancreatic ductal adenocarcinoma (PDAC) in vivo. Methods: We compared the efficacy of the standard of care agent gemcitabine with the BET inhibitor JQ1, using alamarBlue assays to determine IC50s of three pancreatic cancer cell lines in vitro. We used immunohistochemistry (IHC) and immunoblot (IB) to detect CDC25B. We also compared the effect of each agent on the progression of PDX models of PDAC in vivo with contrasting levels of CDC25B. Results: Immunohistochemical data demonstrated that levels of CDC25B differed by ~2- to 5-fold in cell lines and PDX models used. In vitro data showed that the level of CDC25B paralleled sensitivity to JQ1. Similarly, in vivo data showed that tumors with high-level CDC25B were more sensitive to JQ1 than tumors with lower CDC25B. The combination of JQ1 + a pan CDC25 inhibitor was synergistic in gemcitabine-resistant Panc1.gemR cells that had relatively high levels of CDC25B expression compared to parent cells. Conclusion: The data suggest that CDC25B may be an independent indicator of sensitivity to BET inhibitors and that CDC25B may contribute to gemcitabine insensitivity in this tumor type.

Unmasking Neuroendocrine Prostate Cancer with a Machine Learning-Driven 7-Gene Stemness Signature that Predicts Progression

Prostate cancer (PCa) poses a significant global health challenge, particularly due to its progression into aggressive forms like neuroendocrine prostate cancer (NEPC). This study developed and validated a stemness-associated gene signature using advanced machine learning techniques, including Random Forest and Lasso regression, applied to large-scale transcriptomic datasets. The resulting 7-gene signature (KMT5C, MEN1, TYMS, IRF5, DNMT3B, CDC25B and DPP4) was validated across independent cohorts and patient-derived xenograft (PDX) models. The signature demonstrated strong prognostic value for progression-free, disease-free, relapse-free, metastasis-free, and overall survival. Importantly, the signature not only identified specific NEPC subtypes, such as large-cell neuroendocrine carcinoma, which is associated with very poor outcomes, but also predicted a poor prognosis for PCa cases that exhibit this molecular signature, even when they were not histopathologically classified as NEPC. This dual prognostic and classifier capability makes the 7-gene signature a robust tool for personalized medicine, providing a valuable resource for predicting disease progression and guiding treatment strategies in PCa management.

Effective Pharmacophore for CDC25 Phosphatases Enzyme Inhibitors: Newly Synthesized Bromothiazolopyrimidine Derivatives

BACKGROUND

Thiazolopyrimidine analogues are versatile synthetic scaffold possessing wide spectrum of biological interests involving potential anticancer activity.

OBJECTIVE

To report the synthesis of novel bromothiazolopyrimidine derivatives and the study of both molecular modeling and in-vitro anticancer activity.

METHODS

Novel bromothiazolopyrimidine derivatives 5-18 have been prepared from 2-bromo-3-(4- chlorophenyl)-1-(3,4-dimethylphenyl)-propenone 3 as a key starting compound. The anti-cancer activities of the new compounds were evaluated against HepG2, MCF-7, A549 and HCT116 cell lines.

RESULTS

The compounds 16, 17 and 18 showed cytotoxic and growth inhibitory activities on both colon and lung cells. The cytotoxic activities of the novel synthetic compounds 8, 9, 11, 16, 17 and 18 were due to CDC25 phosphatases inhibition as shown by the enzymatic binding assay. Although compounds 8, 9 and 11 have only demonstrated CDC25B phosphatases inhibition.

CONCLUSION

The novel bromothiazolopyrimidine derivatives showed promising in vitro anticancer activities against colon cancer HCT116 and lung cancer A549 cell lines comparable to the anticancer drug doxorubicin.

Molecular Characterisation of Canine Osteosarcoma in High Risk Breeds

Dogs develop osteosarcoma (OSA) and the disease process closely resembles that of human OSA. OSA has a poor prognosis in both species and disease-free intervals and cure rates have not improved in recent years. Gene expression in canine OSAs was compared with non-tumor tissue utilising RNA sequencing, validated by qRT-PCR and immunohistochemistry (n = 16). Polymorphic polyglutamine (polyQ) tracts in the androgen receptor (AR/NR3C4) and nuclear receptor coactivator 3 (NCOA3) genes were investigated in control and OSA patients using polymerase chain reaction (PCR), Sanger sequencing and fragment analysis (n = 1019 Rottweilers, 379 Irish Wolfhounds). Our analysis identified 1281 significantly differentially expressed genes (>2 fold change, p < 0.05), specifically 839 lower and 442 elevated gene expression in osteosarcoma (n = 3) samples relative to non-malignant (n = 4) bone. Enriched pathways and gene ontologies were identified, which provide insight into the molecular pathways implicated in canine OSA. Expression of a subset of these genes (SLC2A1, DKK3, MMP3, POSTN, RBP4, ASPN) was validated by qRTPCR and immunohistochemistry (MMP3, DKK3, SLC2A1) respectively. While little variation was found in the NCOA3 polyQ tract, greater variation was present in both polyQ tracts in the AR, but no significant associations in length were made with OSA. The data provides novel insights into the molecular mechanisms of OSA in high risk breeds. This knowledge may inform development of new prevention strategies and treatments for OSA in dogs and supports utilising spontaneous OSA in dogs to improve understanding of the disease in people.

CircHIPK3 Facilitates the G2/M Transition in Prostate Cancer Cells by Sponging miR-338-3p

Background

Circular RNAs (circRNAs) play a crucial role in gene expression regulation. CircHIPK3 is a circRNA derived from Exon 2 of HIPK3 gene and its role in prostate cancer (PCa) is still unclear.

Methods

CCK8 assays, flow cytometry and colony formation assays were performed to assess the effects of circHIPK3 in PCa cells. Bioinformatics analysis, RNA pull-down assay, RNA immunoprecipitation assay (RIP), and luciferase activity assay were performed to dissect the mechanism underlying circHIPK3-mediated G2/M transition in PCa cells.

Results

CircHIPK3 expression was upregulated in PCa cells and prostate cancer tissues. Overexpression of circHIPK3 or circHIPK3 silencing altered PCa viability, proliferation and apoptosis in vitro. CircHIPK3 could sponge miR-338-3p and inhibit its activity, resulting in increased expression of Cdc25B and Cdc2 in vitro.

Conclusion

CircHIPK3 promotes G2/M transition and induces PCa cell proliferation by sponging miR-338-3p and increasing the expression of Cdc25B and Cdc2. CircHIPK3 may play an oncogenic role in PCa.

TIP5 primes prostate luminal cells for the oncogenic transformation mediated by PTEN-loss

The cell of origin and the temporal order of oncogenic events in tumors play important roles for disease state. This is of particular interest for PCa due to its highly variable clinical outcome. However, these features are difficult to analyze in tumors. We established an in vitro murine PCa organoid model taking into account the cell of origin and the temporal order of events. We found that TIP5 primes luminal prostate cells for Pten-loss mediated oncogenic transformation whereas it is dispensable once the transformation is established. Cross-species transcriptomic analyses revealed a PTEN-loss gene signature that identified a set of aggressive tumors with PTEN-del, or low PTEN expression, and high-TIP5 expression. This paper provides a powerful tool to elucidate PCa mechanisms.

Prostate cancer (PCa) is the second leading cause of cancer death in men. Its clinical and molecular heterogeneities and the lack of in vitro models outline the complexity of PCa in the clinical and research settings. We established an in vitro mouse PCa model based on organoid technology that takes into account the cell of origin and the order of events. Primary PCa with deletion of the tumor suppressor gene PTEN (PTEN-del) can be modeled through Pten-down-regulation in mouse organoids. We used this system to elucidate the contribution of TIP5 in PCa initiation, a chromatin regulator that is implicated in aggressive PCa. High TIP5 expression correlates with primary PTEN-del PCa and this combination strongly associates with reduced prostate-specific antigen (PSA) recurrence-free survival. TIP5 is critical for the initiation of PCa of luminal origin mediated by Pten-loss whereas it is dispensable once Pten-loss mediated transformation is established. Cross-species analyses revealed a PTEN gene signature that identified a group of aggressive primary PCas characterized by PTEN-del, high-TIP5 expression, and a TIP5-regulated gene expression profile. The results highlight the modeling of PCa with organoids as a powerful tool to elucidate the role of genetic alterations found in recent studies in their time orders and cells of origin, thereby providing further optimization for tumor stratification to improve the clinical management of PCa.

Posttranslational regulation of androgen dependent and independent androgen receptor activities in prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer among men in western countries. Androgen receptor (AR) signaling plays key roles in the development of PCa. Androgen deprivation therapy (ADT) remains the standard therapy for advanced PCa. In addition to its ligand androgen, accumulating evidence indicates that posttranscriptional modification is another important mechanism to regulate AR activities during the progression of PCa, especially in castration resistant prostate cancer (CRPC). To date, a number of posttranscriptional modifications of AR have been identified, including phosphorylation (e.g. by CDK1), acetylation (e.g. by p300 and recognized by BRD4), methylation (e.g. by EZH2), ubiquitination (e.g. by SPOP), and SUMOylation (e.g. by PIAS1). These modifications are essential for the maintenance of protein stability, nuclear localization and transcriptional activity of AR. This review summarizes posttranslational modifications that influence androgen-dependent and -independent activities of AR, PCa progression and therapy resistance. We further emphasize that in addition to androgen, posttranslational modification is another important way to regulate AR activity, suggesting that targeting AR posttranslational modifications, such as proteolysis targeting chimeras (PROTACs) of AR, represents a potential and promising alternate for effective treatment of CRPC. Potential areas to be investigated in the future in the field of AR posttranslational modifications are also discussed.

Triggering mitosis

Entry into mitosis is triggered by the activation of cyclin-dependent kinase 1 (Cdk1). This simple reaction rapidly and irreversibly sets the cell up for division. Even though the core step in triggering mitosis is so simple, the regulation of this cellular switch is highly complex, involving a large number of interconnected signalling cascades. We do have a detailed knowledge of most of the components of this network, but only a poor understanding of how they work together to create a precise and robust system that ensures that mitosis is triggered at the right time and in an orderly fashion. In this review, we will give an overview of the literature that describes the Cdk1 activation network and then address questions relating to the systems biology of this switch. How is the timing of the trigger controlled? How is mitosis insulated from interphase? What determines the sequence of events, following the initial trigger of Cdk1 activation? Which elements ensure robustness in the timing and execution of the switch? How has this system been adapted to the high levels of replication stress in cancer cells?

Aberrant localization of signaling proteins in skin cancer: Implications for treatment

Aberrant subcellular localization of signaling proteins can provide cancer cells with advantages such as resistance to apoptotic cell death, increased invasiveness and more rapid proliferation. Nuclear to cytoplasmic shifts in tumor-promoting proteins can lead to worse patient outcomes, providing opportunities to target cancer-specific processes. Herein, we review the significance of dysregulated protein localization with a focus on skin cancer. Altered localization of signaling proteins controlling cell cycle progression or cell death is a common feature of cancer. In some instances, aberrant subcellular localization results in an acquired prosurvival function. Taking advantage of this knowledge reveals novel targets useful in the development of cancer therapeutics.

Protein kinase D1 induces G1-phase cell-cycle arrest independent of Checkpoint kinases by phosphorylating Cell Division Cycle Phosphatase 25

Protein Kinase D1 (PrKD1) functions as a tumor and metastasis suppressor in several human cancers by influencing cell-cycle progression. However, the exact mechanism of cell-cycle regulation by PrKD1 is unclear. Overexpression and ectopic expression of PrKD1 induces G1 arrest in cancer cell lines. Because checkpoint kinases (CHEKs) are known to play a role in progression through the G1 phase, we downregulated CHEK1, which did not overcome the G1 arrest induced by PrKD1. Using in vitro phosphorylation and Western blot assays, we showed that PrKD1 phosphorylates all CDC25 isoforms (known substrates of CHEK kinases), independent from CHEK kinases, suggesting that direct phosphorylation of CDC25 by PrKD1 may be an alternate mechanism of G1 arrest. The study has identified a molecular mechanism for the influence of PrKD1 in cell-cycle progression.

Phosphatases and solid tumors: focus on glioblastoma initiation, progression and recurrences

Phosphatases and cancer have been related for many years now, as these enzymes regulate key cellular functions, including cell survival, migration, differentiation and proliferation. Dysfunctions or mutations affecting these enzymes have been demonstrated to be key factors for oncogenesis. The aim of this review is to shed light on the role of four different phosphatases (PTEN, PP2A, CDC25 and DUSP1) in five different solid tumors (breast cancer, lung cancer, pancreatic cancer, prostate cancer and ovarian cancer), in order to better understand the most frequent and aggressive primary cancer of the central nervous system, glioblastoma.

Design and synthesis of new potent PTP1B inhibitors with the skeleton of 2-substituted imino-3-substituted-5-heteroarylidene-1,3-thiazolidine-4-one: Part I

A new series of 2-substituted imino-3-substituted-5- heteroarylidene-1,3-thiazolidine-4-ones as the potent bidentate PTP1B inhibitors were designed and synthesized in this paper. All of the new compounds were characterized and identified by spectra analysis. The biological screening test against PTP1B showed that some of these compounds have the positive inhibitory activity against PTP1B. The activity of the compounds with 5-substituted pyrrole on 5-postion of 1,3-thiazolidine-4-one are more potent than that of those compounds with 5-substituted pyridine group. Compound 14b, 14h and 14i showed IC50 values of 8.66 μM, 6.83 μM and 6.09 μM against PTP1B, respectively. Docking analysis of these active compounds with PTP1B showed the possible interaction modes of these biheterocyclic compounds with the active sites of PTP1B. The inhibition tests against oncogenetic CDC25B were also conducted on this set of compounds to evaluate the selectivity and possible anti-neoplastic activity. Compound 14b also showed the lowest IC50 of 1.66 μM against CDC25B among all the possible inhibitors, including 14g, 14h, 14i and 15c. Some pharmacological parameters including VolSurf, steric and electric descriptors of all the compounds were calculated to give some hints about the relative relationship with the biological activity. The result of this study might give some light on designing the possible anti-cancer drugs targeting at phosphatases. The most active compound 14i might be used as the lead compound for further structure modification of the new low molecular weight PTP1B inhibitors with the N-containing heterocyclic skeleton.

Effects of Brassicaceae Isothiocyanates on Prostate Cancer

Despite the major progress made in the field of cancer biology, cancer is still one of the leading causes of mortality, and prostate cancer (PCa) is one of the most encountered malignancies among men. The effective management of this disease requires developing better anticancer agents with greater efficacy and fewer side effects. Nature is a large source for the development of chemotherapeutic agents, with more than 50% of current anticancer drugs being of natural origin. Isothiocyanates (ITCs) are degradation products from glucosinolates that are present in members of the family Brassicaceae. Although they are known for a variety of therapeutic effects, including antioxidant, immunostimulatory, anti-inflammatory, antiviral and antibacterial properties, nowadays, cell line and animal studies have additionally indicated the chemopreventive action without causing toxic side effects of ITCs. In this way, they can induce cell cycle arrest, activate apoptosis pathways, increase the sensitivity of resistant PCa to available chemodrugs, modulate epigenetic changes and downregulate activated signaling pathways, resulting in the inhibition of cell proliferation, progression and invasion-metastasis. The present review summarizes the chemopreventive role of ITCs with a particular emphasis on specific molecular targets and epigenetic alterations in in vitro and in vivo cancer animal models.

Phosphatases and kinases regulating CDC25 activity in the cell cycle: clinical implications of CDC25 overexpression and potential treatment strategies

Alterations in the cell-cycle regulatory genes result in uncontrolled cell proliferation leading to several disease conditions. Cyclin-dependent kinases (CDK) and their regulatory subunit, cyclins, are essential proteins in cell-cycle progression. The activity of CDK is regulated by a series of phosphorylation and dephosphorylation at different amino acid residues. Cell Division Cycle-25 (CDC25) plays an important role in transitions between cell-cycle phases by dephosphorylating and activating CDKs. CDC25B and CDC25C play a major role in G2/M progression, whereas CDC25A assists in G1/S transition. Different isomers of CDC25 expressions are upregulated in various clinicopathological situations. Overexpression of CDC25A deregulates G1/S and G2/M events, including the G2 checkpoint. CDC25B has oncogenic properties. Binding to the 14-3-3 proteins regulates the activity and localization of CDC25B. CDC25C is predominantly a nuclear protein in mammalian cells. At the G2/M transition, mitotic activation of CDC25C protein occurs by its dissociation from 14-3-3 proteins along with its phosphorylation at multiple sites within its N-terminal domain. In this article, we critically reviewed the biology of the activation/deactivation of CDC25 by kinases/phosphatases to maintain the level of CDK-cyclin activities and thus the genomic stability, clinical implications due to dysregulation of CDC25, and potential role of CDC25 inhibitors in diseases.

Checkpoint Kinase 2 Negatively Regulates Androgen Sensitivity and Prostate Cancer Cell Growth

Prostate cancer is the second leading cause of cancer death in American men, and curing metastatic disease remains a significant challenge. Nearly all patients with disseminated prostate cancer initially respond to androgen deprivation therapy (ADT), but virtually all patients will relapse and develop incurable castration-resistant prostate cancer (CRPC). A high-throughput RNAi screen to identify signaling pathways regulating prostate cancer cell growth led to our discovery that checkpoint kinase 2 (CHK2) knockdown dramatically increased prostate cancer growth and hypersensitized cells to low androgen levels. Mechanistic investigations revealed that the effects of CHK2 were dependent on the downstream signaling proteins CDC25C and CDK1. Moreover, CHK2 depletion increased androgen receptor (AR) transcriptional activity on androgen-regulated genes, substantiating the finding that CHK2 affects prostate cancer proliferation, partly, through the AR. Remarkably, we further show that CHK2 is a novel AR-repressed gene, suggestive of a negative feedback loop between CHK2 and AR. In addition, we provide evidence that CHK2 physically associates with the AR and that cell-cycle inhibition increased this association. Finally, IHC analysis of CHK2 in prostate cancer patient samples demonstrated a decrease in CHK2 expression in high-grade tumors. In conclusion, we propose that CHK2 is a negative regulator of androgen sensitivity and prostate cancer growth, and that CHK2 signaling is lost during prostate cancer progression to castration resistance. Thus, perturbing CHK2 signaling may offer a new therapeutic approach for sensitizing CRPC to ADT and radiation.

Expression of CDC25A and CDC25B phosphatase proteins in human retinoblastoma and its correlation with clinicopathological parameters

BACKGROUND

CDC25 proteins play a pivotal role in controlling cell proliferation during development and tumorigenesis. The aim of the study is to elucidate the role of CDC25A and CDC25B proteins in retinoblastoma and their association with the clinical and histopathological parameters.

METHODS

One hundred and nine prospective cases of primary enucleated retinoblastomas were included in the present study. Expression of CDC25A and CDC25B proteins was investigated by immunohistochemistry, western blotting and mRNA expression by reverse-transcriptase PCR.

RESULTS

Immunohistochemistry showed CDC25A expression in (57/109) 52.29%, whereas CDC25B expressed in (69/109) 63.30% cases. Western blotting confirmed the immunoreactivity results on representative cases. mRNA expression of CDC25A and CDC25B was found in 29/60 (48.33%) and 35/60 (58.33%) cases, respectively. Expression of CDC25A and CDC25B showed significant correlation with poor tumour differentiation and tumour invasion (p<0.05). There was a statistically significant difference in the overall survival of patients with CDC25B expression (p=0.0270).

CONCLUSIONS

Our results suggest that expression of CDC25B may be used as a potential prognostic marker in the pathogenesis of retinoblastoma. These findings demonstrate an important role of CDC25 phosphatase proteins and inhibition of these proteins may have therapeutic potential in retinoblastoma.

Crosstalk between kinases, phosphatases and miRNAs in cancer

Reversible phosphorylation of proteins, performed by kinases and phosphatases, is the major post translational protein modification in eukaryotic cells. This intracellular event represents a critical regulatory mechanism of several signaling pathways and can be related to a vast array of diseases, including cancer. Cancer research has produced increasing evidence that kinase and phosphatase activity can be compromised by mutations and also by miRNA silencing, performed by small non-coding and endogenously produced RNA molecules that lead to translational repression. miRNAs are believed to target about one-third of human mRNAs while a single miRNA may target about 200 transcripts simultaneously. Regulation of the phosphorylation balance by miRNAs has been a topic of intense research over the last years, spanning topics going as far as cancer aggressiveness and chemotherapy resistance. By addressing recent studies that have shown miRNA expression patterns as phenotypic signatures of cancers and how miRNA influence cellular processes such as apoptosis, cell cycle control, angiogenesis, inflammation and DNA repair, we discuss how kinases, phosphatases and miRNAs cooperatively act in cancer biology.

Chalcones derivatives as potent Cell division cycle 25B phosphatase inhibitors

To discover novel cell division cycle 25 (CDC25) B inhibitors and elucidate the mechanisms of inhibition in cancer cells. Nineteen 2'-hydroxy-4'-isoprenyloxychalcone derivatives (a-s) were evaluated the inhibition CDC25B activity. The enzymatic activities of the CDC25B catalytic domain were determined by monitoring the dephosphorylation of OMFP. Cell growth inhibition was detected by MTT assay. The results showed that sixteen compounds significantly inhibited cycle 25B phosphatase in vitro. Among, three compounds k, r and s had the best inhibition activity and significantly inhibited CDC25B with inhibition rates against CDC25B of 99.95%, 99.75%, and 97.77%, respectively, which is similar to the reference drugs Na3VO4 (98%). Cytotoxic activity assays showed compounds k and r are the potent against HCT116, HeLa, and A549 cells, moreover, compound k delayed the potent tumor inhibitory activity in a colo205 xenograft model in vivo.

The regulatory roles of phosphatases in cancer

The relevance of potentially reversible post-translational modifications required for controlling cellular processes in cancer is one of the most thriving arenas of cellular and molecular biology. Any alteration in the balanced equilibrium between kinases and phosphatases may result in development and progression of various diseases, including different types of cancer, though phosphatases are relatively under-studied. Loss of phosphatases such as PTEN (phosphatase and tensin homologue deleted on chromosome 10), a known tumour suppressor, across tumour types lends credence to the development of phosphatidylinositol 3-kinase inhibitors alongside the use of phosphatase expression as a biomarker, though phase 3 trial data are lacking. In this review, we give an updated report on phosphatase dysregulation linked to organ-specific malignancies.

1,2,4-Triazole/oxime hybrids as new strategy for nitric oxide donors: Synthesis, anti-inflammatory, ulceroginicity and antiproliferative activities

A series of novel nitric oxide (NO) donating triazole/oxime hybrids was prepared and evaluated for their anti-inflammatory activity and antiproliferative activity. Most of the tested compounds showed significant anti-inflammatory activity using carrageenan-induced rat paw edema method compared to indomethacin. Calculation of the ulcer indices and histopathological investigation indicated that the prepared NO-donating oximes exhibited less ulcerogenicity compared to their ketone intermediates and indomethacin. The NO-donating oximes 7i and 7k achieved remarkable cell growth inhibition activity against most of the tested cell lines. Compound 7k was found to be with high selectivity against CNS subpanel with selectivity ratio of 11.99 at GI₅₀ level.

[Pathophysiology and therapy of castration-resistant prostate cancer]

Advanced prostate cancer that progresses under androgen deprivation therapy has long been thought to be refractory to further hormonal treatment. The identification of the mechanism of cancer cells has revolutionized this understanding. Today it is known that castration-resistant prostate cancer (CRPC) still receives signals through the androgen receptor transduction pathways and furthermore is sensitive to hormone therapy. New substances, such as abiraterone, enzalutamide (MDV3100) and TAK 700 target these mechanisms of resistance of cancer cells, stop testosterone production and show not only better tolerance but also effective antitumor activity. Due to the heterogeneity of tumors with cells in varying states of differentiation, the treatment of CRPC with androgen deprivation therapy remains a cornerstone of disease management. To what extent the experimental findings and the recommendations in the guidelines are put into practice was the subject of a survey among urologists analyzing their treatment strategies with CRPC patients.

Posttranslational modification of the androgen receptor in prostate cancer

The androgen receptor (AR) is important in the development of the prostate by regulating transcription, cellular proliferation, and apoptosis. AR undergoes posttranslational modifications that alter its transcription activity, translocation to the nucleus and stability. The posttranslational modifications that regulate these events are of utmost importance to understand the functional role of AR and its activity. The majority of these modifications occur in the activation function-1 (AF1) region of the AR, which contains the transcriptional activation unit 1 (TAU1) and 5 (TAU5). Identification of the modifications that occur to these regions may increase our understanding of AR activation in prostate cancer and the role of AR in the progression from androgen-dependent to castration-resistant prostate cancer (CRPC). Most of the posttranslational modifications identified to date have been determined using the full-length AR in androgen dependent cells. Further investigations into the role of posttranslational modifications in androgen-independent activation of full-length AR and constitutively active splicing variants are warranted, findings from which may provide new therapeutic options for CRPC.

Androgens upregulate Cdc25C protein by inhibiting its proteasomal and lysosomal degradation pathways

Cdc25C is a cell cycle protein of the dual specificity phosphatase family essential for activating the cdk1/Cyclin B1 complex in cells entering into mitosis. Since altered cell cycle is a hallmark of human cancers, we investigated androgen regulation of Cdc25C protein in human prostate cancer (PCa) cells, including androgen-sensitive (AS) LNCaP C-33 cells and androgen-independent (AI) LNCaP C-81 as well as PC-3 cells. In the regular culture condition containing fetal bovine serum (FBS), Cdc25C protein levels were similar in these PCa cells. In a steroid-reduced condition, Cdc25C protein was greatly decreased in AS C-33 cells but not AI C-81 or PC-3 cells. In androgen-treated C-33 cells, the Cdc25C protein level was greatly elevated, following a dose- and a time-dependent manner, correlating with increased cell proliferation. This androgen effect was blocked by Casodex, an androgen receptor blocker. Nevertheless, epidermal growth factor (EGF), a growth stimulator of PCa cells, could only increase Cdc25C protein level by about 1.5-fold. Altered expression of Cdc25C in C-33 cells and PC-3 cells by cDNA and/or shRNA transfection is associated with the corresponding changes of cell growth and Cyclin B1 protein level. Actinomycin D and cycloheximide could only partially block androgen-induced Cdc25C protein level. Treatments with both proteasomal and lysosomal inhibitors resulted in elevated Cdc25C protein levels. Immunoprecipitation revealed that androgens reduced the ubiquitination of Cdc25C proteins. These results show for the first time that Cdc25C protein plays a role in regulating PCa cell growth, and androgen treatments, but not EGF, greatly increase Cdc25C protein levels in AS PCa cells, which is in part by decreasing its degradation. These results can lead to advanced PCa therapy via up-regulating the degradation pathways of Cdc25C protein.

A genome-wide RNA interference screen identifies new regulators of androgen receptor function in prostate cancer cells

The androgen receptor (AR) is a mediator of both androgen-dependent and castration-resistant prostate cancers. Identification of cellular factors affecting AR transcriptional activity could in principle yield new targets that reduce AR activity and combat prostate cancer, yet a comprehensive analysis of the genes required for AR-dependent transcriptional activity has not been determined. Using an unbiased genetic approach that takes advantage of the evolutionary conservation of AR signaling, we have conducted a genome-wide RNAi screen in Drosophila cells for genes required for AR transcriptional activity and applied the results to human prostate cancer cells. We identified 45 AR-regulators, which include known pathway components and genes with functions not previously linked to AR regulation, such as HIPK2 (a protein kinase) and MED19 (a subunit of the Mediator complex). Depletion of HIPK2 and MED19 in human prostate cancer cells decreased AR target gene expression and, importantly, reduced the proliferation of androgen-dependent and castration-resistant prostate cancer cells. We also systematically analyzed additional Mediator subunits and uncovered a small subset of Mediator subunits that interpret AR signaling and affect AR-dependent transcription and prostate cancer cell proliferation. Importantly, targeting of HIPK2 by an FDA-approved kinase inhibitor phenocopied the effect of depletion by RNAi and reduced the growth of AR-positive, but not AR-negative, treatment-resistant prostate cancer cells. Thus, our screen has yielded new AR regulators including drugable targets that reduce the proliferation of castration-resistant prostate cancer cells.

Spongian diterpenoids inhibit androgen receptor activity

Androgen receptor is a ligand-activated transcription factor and a validated drug target for all stages of prostate cancer. Antiandrogens compete with physiologic ligands for androgen receptor ligand-binding domain (LBD). High-throughput screening of a marine natural product library for small molecules that inhibit androgen receptor transcriptional activity yielded the furanoditerpenoid spongia-13(16),-14-dien-19-oic acid, designated terpene 1 (T1). Characterization of T1 and the structurally related semisynthetic analogues (T2 and T3) revealed that these diterpenoids have antiandrogen properties that include inhibition of both androgen-dependent proliferation and androgen receptor transcriptional activity by a mechanism that involved competing with androgen for androgen receptor LBD and blocking essential N/C interactions required for androgen-induced androgen receptor transcriptional activity. Structure-activity relationship analyses revealed some chemical features of T1 that are associated with activity and yielded T3 as the most potent analogue. In vivo, T3 significantly reduced the weight of seminal vesicles, which are an androgen-dependent tissue, thereby confirming the on-target activity of T3. The ability to create analogues of diterpenoids that have varying antiandrogen activity represents a novel class of chemical compounds for the analysis of androgen receptor ligand-binding properties and therapeutic development.

Indirubin, an acting component of indigo naturalis, inhibits EGFR activation and EGF-induced CDC25B gene expression in epidermal keratinocytes

BACKGROUND

Topical indigo naturalis ointment is clinically proved to be an effective therapy for plaque-type psoriasis. Indirubin, as the active component of indigo naturalis, inhibits cell proliferation of epidermal keratinocytes. However, the detailed underlying mechanism is not fully understood.

OBJECTIVE

To further investigate the anti-proliferating effects of indigo naturalis and indirubin on epidermal keratinocytes.

METHODS

The decreased expression of CDC25B in indigo naturalis- or indirubin-treated epidermal keratinocytes, as revealed by cDNA microarray analysis, was studied. The CDC25B expression was examined under different serum concentrations and compared between primary and immortalized keratinocytes. The activation of EGFR and the effect of EGF on the cell proliferation and CDC25B expression were also investigated in epidermal keratinocytes. RT/real-time PCR and western blot method were used to analyze the CDC25B expression at the mRNA and protein levels, respectively.

RESULTS

Indigo naturalis and indirubin were confirmed to down-regulate CDC25B expression significantly at both the mRNA and protein levels. The growth-dependent expression of CDC25B was demonstrated by the increased expression in serum-stimulated and immortalized keratinocytes. The activation of EGF receptor, known to be highly expressed in psoriatic lesions, was inhibited by indigo naturalis or indirubin. The cell proliferation and CDC25B expression of epidermal keratinocytes were induced by EGF alone and confirmed to be inhibited by indigo naturalis or indirubin.

CONCLUSION

Except being a common therapeutic target in various cancers, CDC25B also plays an important role in the hyper-proliferation of epidermal keratinocytes which can be suppressed by anti-psoriatic drug indigo naturalis and its component, indirubin.

Discovery of new inhibitors of Cdc25B dual specificity phosphatases by structure-based virtual screening

Cell division cycle 25 (Cdc25) proteins are highly conserved dual specificity phosphatases that regulate cyclin-dependent kinases and represent attractive drug targets for anticancer therapies. To discover more potent and diverse inhibitors of Cdc25 biological activity, virtual screening was performed by docking 2.1 million compounds into the Cdc25B active site. An initial subset of top-ranked compounds was selected and assayed, and 15 were found to have enzyme inhibition activity at micromolar concentration. Among these, four structurally diverse inhibitors with a different inhibition profile were found to inhibit human MCF-7, PC-3, and K562 cancer cell proliferation and significantly affect the cell cycle progression. A subsequent hierarchical similarity search with the most active reversible Cdc25B inhibitor found led to the identification of an additional set of 19 ligands, three of which were confirmed as Cdc25B inhibitors with IC(50) values of 7.9, 4.2, and 9.9 μM, respectively.

The AR dependent cell cycle: mechanisms and cancer relevance

Prostate cancer cells are exquisitely dependent on androgen receptor (AR) activity for proliferation and survival. As these functions are critical targets of therapeutic intervention for human disease, it is imperative to delineate the mechanisms by which AR engages the cell cycle engine. More than a decade of research has revealed that elegant intercommunication between AR and the cell cycle machinery governs receptor-dependent cellular proliferation, and that perturbations in this process occur frequently in human disease. Here, AR-cell cycle interplay and associated cancer relevance will be reviewed.

Transcriptional repression of Cdc25B by IER5 inhibits the proliferation of leukemic progenitor cells through NF-YB and p300 in acute myeloid leukemia

The immediately-early response gene 5 (IER5) has been reported to be induced by γ-ray irradiation and to play a role in the induction of cell death caused by radiation. We previously identified IER5 as one of the 2,3,4-tribromo-3-methyl-1-phenylphospholane 1-oxide (TMPP)-induced transcriptional responses in AML cells, using microarrays that encompassed the entire human genome. However, the biochemical pathway and mechanisms of IER5 function in regulation of the cell cycle remain unclear. In this study, we investigated the involvement of IER5 in the cell cycle and in cell proliferation of acute myeloid leukemia (AML) cells. We found that the over-expression of IER5 in AML cell lines and in AML-derived ALDH^hi (High Aldehyde Dehydrogenase activity)/CD34⁺ cells inhibited their proliferation compared to control cells, through induction of G2/M cell cycle arrest and a decrease in Cdc25B expression. Moreover, the over-expression of IER5 reduced colony formation of AML-derived ALDH^hi/CD34⁺ cells due to a decrease in Cdc25B expression. In addition, over-expression of Cdc25B restored TMPP inhibitory effects on colony formation in IER5-suppressed AML-derived ALDH^hi/CD34⁺ cells. Furthermore, the IER5 reduced Cdc25B mRNA expression through direct binding to Cdc25B promoter and mediated its transcriptional attenuation through NF-YB and p300 transcriptinal factors. In summary, we found that transcriptional repression mediated by IER5 regulates Cdc25B expression levels via the release of NF-YB and p300 in AML-derived ALDH^hi/CD34⁺ cells, resulting in inhibition of AML progenitor cell proliferation through modulation of cell cycle. Thus, the induction of IER5 expression represents an attractive target for AML therapy.

MicroRNA-148a is down-regulated in human pancreatic ductal adenocarcinomas and regulates cell survival by targeting CDC25B

MicroRNAs (miRNAs: short non-coding RNAs) are emerging as a class of potential novel tumor markers, as their dysregulation is being increasingly reported in various types of cancers. In the present study, we investigated the transcription status of miRNA-148a (miR-148a) in human pancreatic ductal adenocarcinoma (PDAC) and its role in the regulation of the dual specificity protein phosphatase CDC25B. We observed that miR-148a exhibited a significant 4-fold down-regulation in PDAC as opposed to normal pancreatic ductal cells. In addition, we observed that stable lentiviral-mediated overexpression of miR-148a in the pancreatic cancer cell line IMIM-PC2, inhibited tumor cell growth and colony formation. Furthermore, CDC25B was identified as a potential target of miR-148a by in silico analysis using PicTar, Targetscan and miRanda in conjunction with gene ontology analysis. The proposed interaction between miR-148a and the 3' untranslated region (UTR) of CDC25B was verified by in-vitro luciferase assays. We demonstrate that the activity of a luciferase reporter containing the 3'UTR of CDC25B was repressed in the presence of miR-148a mimics, confirming that miR-148a targets the 3'UTR of CDC25B. Finally, CDC25B was down-regulated at the protein level in miR-148a overexpressing IMIM-PC2-cells, and in transiently transfected pancreatic cell lines (as detected by Western blot analysis), as well as in patient tumor samples (as detected by immunohistochemistry). In summary, we identified CDC25B as a novel miR-148a target which may confer a proliferative advantage in PDAC.

Androgen receptor signaling and mutations in prostate cancer

Normal and neoplastic growth of the prostate gland are dependent on androgen receptor (AR) expression and function. Androgenic activation of the AR, in association with its coregulatory factors, is the classical pathway that leads to transcriptional activity of AR target genes. Alternatively, cytoplasmic signaling crosstalk of AR by growth factors, neurotrophic peptides, cytokines or nonandrogenic hormones may have important roles in prostate carcinogenesis and in metastatic or androgen-independent (AI) progression of the disease. In addition, cross-modulation by various nuclear transcription factors acting through basal transcriptional machinery could positively or negatively affect the AR or AR target genes expression and activity. Androgen ablation leads to an initial favorable response in a significant number of patients; however, almost invariably patients relapse with an aggressive form of the disease known as castration-resistant or hormone-refractory prostate cancer (PCa). Understanding critical molecular events that lead PCa cells to resist androgen-deprivation therapy is essential in developing successful treatments for hormone-refractory disease. In a significant number of hormone-refractory patients, the AR is overexpressed, mutated or genomically amplified. These genetic alterations maintain an active presence for a highly sensitive AR, which is responsive to androgens, antiandrogens or nonandrogenic hormones and collectively confer a selective growth advantage to PCa cells. This review provides a brief synopsis of the AR structure, AR coregulators, posttranslational modifications of AR, duality of AR function in prostate epithelial and stromal cells, AR-dependent signaling, genetic changes in the form of somatic and germline mutations and their known functional significance in PCa cells and tissues.

G2/M accumulation in prostate cancer cell line PC-3 is induced by Cdc25 inhibitor 7-chloro-6-(2-morpholin-4-ylethylamino) quinoline-5, 8-dione (DA 3003-2)

Cdc25 phosphatases are dual-specific phosphatases that play a role in cell cycle progression. In many human cancers, Cdc25 phosphatases are overexpressed as compared with normal tissues. In addition, overexpression of Cdc25 phosphatases in prostate cancer is correlated with disease progression. The antiproliferative efficacy of Cdc25 phosphatase inhibitor 7-chloro-6-(2-morpholin-4-ylethylamino) quinoline-5, 8-dione (DA 3003-2) was investigated in the PC-3 asynchronous human prostate cancer cell line using a cell-based assay. The time course changes in cell cycle distribution and the modulation of cell cycle regulators after DA 3003-2 administration were analyzed using the MTT assay. We found that the relative IC(50) of DA 3003-2 was 2-fold lower as compared with its congener (2-mercaptoethanol)-3-methyl-1, 4-naphthoquinone (NSC 672121). Asynchronous PC-3 cells accumulated in the G2/M phase at 24 h after treatment with 10 μM DA 3003-2 or 20 μM NSC 672121, which represent IC(70) concentrations. Treatment of cells with DA 3003-2 caused hyperphosphorylation of Cdc2 tyr(15) in cyclin B(1) and cyclin A complexes. DA 3003-2 did not downregulate the protein expression levels of Cdc25s, cyclins and cyclin-dependent kinases (Cdks). To conclude, after DA 3003-2 administration asynchronous PC-3 cells accumulated in the G2/M phase, with hyperphosphorylation of the G2/M cyclin-Cdk complex.

Overexpression of CDC25B, CDC25C and phospho-CDC25C (Ser216) in vulvar squamous cell carcinomas are associated with malignant features and aggressive cancer phenotypes

BACKGROUND

CDC25 phosphatases are important regulators of the cell cycle. Their abnormal expression detected in a number of tumors implies that their dysregulation is involved in malignant transformation. However, the role of CDC25s in vulvar cancer is still unknown. To shed light on their roles in the pathogenesis and to clarify their prognostic values, expression of CDC25A, CDC25B and CDC25C in a large series of vulvar squamous cell carcinomas were examined.

METHODS

Expression of CDC25A, CDC25B, CDC25C and phosphorylated (phospho)-CDC25C (Ser216) were examined in 300 vulvar carcinomas using immunohistochemistry. Western blot analysis was utilized to demonstrate CDC25s expression in vulvar cancer cell lines. Kinase and phosphatase assays were performed to exclude cross reactivity among CDC25s isoform antibodies.

RESULTS

High nuclear CDC25A and CDC25B expression were observed in 51% and 16% of the vulvar carcinomas, respectively, whereas high cytoplasmic CDC25C expression was seen in 63% of the cases. In cytoplasm, nucleus and cytoplasm/nucleus high phospho-CDC25C (Ser216) expression was identified in 50%, 70% and 77% of the carcinomas, respectively. High expression of CDC25s correlated significantly with malignant features, including poor differentiation and infiltration of vessel for CDC25B, high FIGO stage, presence of lymph node metastases, large tumor diameter, poor differentiation for CDC25C and high FIGO stage, large tumor diameter, deep invasion and poor differentiation for phospho-CDC25C (Ser216). In univariate analysis, high expression of phospho-CDC25C (Ser216) was correlated with poor disease-specific survival (p = 0.04). However, such an association was annulled in multivariate analysis.

CONCLUSIONS

Our results suggest that CDC25C and phospho-CDC25C (Ser216) play a crucial role and CDC25B a minor role in the pathogenesis and/or progression of vulvar carcinomas. CDC25B, CDC25C and phospho-CDC25C (Ser216) were associated with malignant features and aggressive cancer phenotypes. However, the CDC25s isoforms were not independently correlated to prognosis.

Overexpression of CDC25B, CDC25C and phospho-CDC25C (Ser216) in vulvar squamous cell carcinomas are associated with malignant features and aggressive cancer phenotypes

BACKGROUND

CDC25 phosphatases are important regulators of the cell cycle. Their abnormal expression detected in a number of tumors implies that their dysregulation is involved in malignant transformation. However, the role of CDC25s in vulvar cancer is still unknown. To shed light on their roles in the pathogenesis and to clarify their prognostic values, expression of CDC25A, CDC25B and CDC25C in a large series of vulvar squamous cell carcinomas were examined.

METHODS

Expression of CDC25A, CDC25B, CDC25C and phosphorylated (phospho)-CDC25C (Ser216) were examined in 300 vulvar carcinomas using immunohistochemistry. Western blot analysis was utilized to demonstrate CDC25s expression in vulvar cancer cell lines. Kinase and phosphatase assays were performed to exclude cross reactivity among CDC25s isoform antibodies.

RESULTS

High nuclear CDC25A and CDC25B expression were observed in 51% and 16% of the vulvar carcinomas, respectively, whereas high cytoplasmic CDC25C expression was seen in 63% of the cases. In cytoplasm, nucleus and cytoplasm/nucleus high phospho-CDC25C (Ser216) expression was identified in 50%, 70% and 77% of the carcinomas, respectively. High expression of CDC25s correlated significantly with malignant features, including poor differentiation and infiltration of vessel for CDC25B, high FIGO stage, presence of lymph node metastases, large tumor diameter, poor differentiation for CDC25C and high FIGO stage, large tumor diameter, deep invasion and poor differentiation for phospho-CDC25C (Ser216). In univariate analysis, high expression of phospho-CDC25C (Ser216) was correlated with poor disease-specific survival (p = 0.04). However, such an association was annulled in multivariate analysis.

CONCLUSIONS

Our results suggest that CDC25C and phospho-CDC25C (Ser216) play a crucial role and CDC25B a minor role in the pathogenesis and/or progression of vulvar carcinomas. CDC25B, CDC25C and phospho-CDC25C (Ser216) were associated with malignant features and aggressive cancer phenotypes. However, the CDC25s isoforms were not independently correlated to prognosis.

Annexin-A7 protects normal prostate cells and induces distinct patterns of RB-associated cytotoxicity in androgen-sensitive and -resistant prostate cancer cells

The tumor suppressor role of annexin-A7 (ANXA7) was previously demonstrated by cancer susceptibility in Anxa7(+/-)-mice and by ANXA7 loss in human cancers, especially in hormone-resistant prostate tumors. To gain mechanistic insights into ANXA7 tumor suppression, we undertook an in vitro study in which we compared wild-type (WT)-ANXA7 and dominant-negative (DN)-ANXA7 effects to a conventional tumor suppressor p53 in prostate cancer cells with different androgen sensitivity. Unlike p53 (which caused cell growth arrest and apoptosis to a noticeable extent in benign PrEC), WT-ANXA7 demonstrated profound cytotoxicityin androgen-sensitive LNCaP as well as in the androgen-resistant DU145 and PC3 prostate cancer cells, but not in PrEC. In androgen-sensitive LNCaP, WT-ANXA7 decreased low-molecular-weight (LMW) AR protein forms and maintained higher retinoblastoma 1 (RB1)/phospho-RB1 ratio. In contrast, DN-ANXA7 (which lacks phosphatidylserine liposome aggregation properties) increased LMW-AR forms and hyperphosphorylated RB1 that was consistent with the lack of DN-ANXA7 cytotoxicity. According to the microarray-based Ingenuity Pathways Analysis, a major WT-ANXA7 effect in androgen-sensitive LNCaP constituted of upregulation of the RB1-binding transcription factor E2F1 along with its downstream proapoptotic targets such as ASK1 and ASPP2. These results suggested a reversal of the RBdependent repression of the proapoptotic E2F-mediated transcription. However, DN-ANXA7 increased RB1/2 (but not E2F1) expression and induced the proliferation-promoting ERK5, thereby maintaining the RB-dependent repression of E2F-mediated apoptosis in LNcaP. On the other hand, in androgen-resistant cells, WT-ANXA7 tumor suppressor effects involved PTEN and NFkB pathways. Thus, ANXA7 revived the RB-associated cell survival control and overcame androgen resistance and dysfunctional status of major tumor suppressors commonly mutated in prostate cancer. Published 2009 UICC.

LGH00031, a novel ortho-quinonoid inhibitor of cell division cycle 25B, inhibits human cancer cells via ROS generation

AIM

To discover novel cell division cycle 25 (CDC25) B inhibitors and elucidate the mechanisms of inhibition in cancer cells.

METHODS

Cell growth inhibition was detected by MTT assay, the cell cycle was analyzed by flow cytometry, and protein expression and phosphorylation was examined by Western blot analysis.

RESULTS

LGH00031 inhibited CDC25B irreversibly in vitro in a dose-dependent manner, and impaired the proliferation of tumor cell lines. In synchronized HeLa cells, LGH00031 delayed the cell cycle progression at the G(2)/M phase. LGH00031 increased cyclin-dependent kinase 1 (CDK1) tyrosine 15 phosphorylation and cyclin B1 protein level. The activity of LGH00031 against CDC25B in vitro relied on the existence of 1,4-dithiothreitol (DTT) or dihydrolipoic acid and oxygen. The oxygen free radical scavenger catalase and superoxide dismutase reduced the inactivation of CDC25 by LGH00031, confirming that reactive oxygen species (ROS) mediate the inactivation process in vitro. LGH00031 accelerated cellular ROS production in a dose-dependent manner, and N-acetyl cysteine (NAC) markedly decreased the ROS production induced by LGH00031. Correspondingly, the LGH00031-induced decrease in cell viability and cell cycle arrest, cyclin B1 protein level, and phosphorylation of CDK1 tyrosine 15 were also rescued by NAC that decreased ROS production.

CONCLUSION

The activity of LGH00031 at the molecular and cellular level is mediated by ROS.

Development of novel thiazolopyrimidines as CDC25B phosphatase inhibitors

The development of CDC25 phosphatase inhibitors is an interesting approach toward new antitumor agents, as CDC25 play key roles in cell-cycle regulation and are overexpressed in numerous cancers. We previously reported a novel compound belonging to the thiazolopyrimidine family that inhibits CDC25 activity with an IC(50) value of 13 microM and displays cytotoxic properties against HeLa cells. Structural modifications were subsequently conducted on this new pharmacophore which led to a library of 45 thiazolopyrimidines. Regarding the in vitro effects, 14 compounds inhibit CDC25B with IC(50)<20 microM, with the most efficient inhibitor 44 improving the potency to 4.5 microM. Steady-state kinetics were performed and showed a mixed inhibition pattern for all tested compounds. Furthermore, 44 was able to revert the bypass of genotoxicity-induced G(2) arrest upon CDC25B overexpression, indicating that this compound targets the dual-specificity phosphatase in cultured cells. Finally, the cytotoxic activities of the compounds were determined against two human cancer cell lines. The results indicate that the prostatic LNCaP cell line is more sensitive to these derivatives than the pancreatic adenocarcinoma MiaPaCa-2 line. With its interesting enzymatic and cellular properties, compound 44 appears to be a promising CDC25B inhibitor for further development.

Inhibition of overexpressed CDC-25.1 phosphatase activity by flavone in Caenorhabditis elegans

We previously reported that flavone induces embryonic lethality in Caenorhabditis elegans, which appeared to be the result of cell cycle arrest during early embryogenesis. To test this possibility, here we examined whether flavone inhibits the activity of a key cell cycle regulator, CDC-25.1 in C. elegans. A gain-of-function cdc-25.1 mutant, rr31, which exhibits extra cell divisions in intestinal cells, was used to test the inhibitory effects of flavone on CDC-25 activity. Flavone inhibited the extra cell divisions of intestinal cells in rr31, and modifications of flavone reduced the inhibitory effects. The inhibitory effects of flavone on CDC-25.1 were partly, if not completely, due to transcriptional repression.

Toward a molecular understanding of the interaction of dual specificity phosphatases with substrates: insights from structure-based modeling and high throughput screening

Dual-specificity phosphatases (DSPs) are important, but poorly understood, cell signaling enzymes that remove phosphate groups from tyrosine and serine/threonine residues on their substrate. Deregulation of DSPs has been implicated in cancer, obesity, diabetes, inflammation, and Alzheimer's disease. Due to their biological and biomedical significance, DSPs have increasingly become the subject of drug discovery high-throughput screening (HTS) and focused compound library development efforts. Progress in identifying selective and potent DSP inhibitors has, however, been restricted by the lack of sufficient structural data on inhibitor-bound DSPs. The shallow, almost flat, substrate binding sites in DSPs have been a major factor in hampering the rational design and the experimental development of active site inhibitors. Recent experimental and virtual HTS studies, as well as advances in molecular modeling, provide new insights into the potential mechanisms for substrate recognition and binding by this important class of enzymes. We present herein an overview of the progress, along with a brief description of applications to two types of DSPs: Cdc25 and MAP kinase phosphatase (MKP) family members. In particular, we focus on combined computational and experimental efforts for designing Cdc25B and MKP-1 inhibitors and understanding their mechanisms of interactions with their target proteins. These studies emphasize the utility of developing computational models and methods that meet the two major challenges currently faced in structure-based in silico design of lead compounds: the conformational flexibility of the target protein and the entropic contribution to the selection and stabilization of particular bound conformers.

Is Cdc25 a druggable target?

Proper control of cell cycle progression requires the functionality of a small family of activating phosphatases termed Cdc25, which have been implicated in cancer and Alzheimer's disease. These protein tyrosine phosphatases are therefore recognized as attractive molecular targets for small molecules. We review the rationale, approaches, progress and challenges for developing small molecule inhibitors of the Cdc25 family. A number of potential chemical probes are discussed and their characteristics are summarized.

CDC25A functions as a novel Ar corepressor in prostate cancer cells

Androgen receptor (AR) is a ligand-dependent transcription factor and its activity is regulated by numerous AR coregulators. Aberrant expression of AR coregulators in prostate cancer cells has an important role in the development and progression of prostate cancer. We report here that CDC25A, a cell cycle-promoting phosphatase over-expressed in a number of cancers, functions as an AR coregulator suppressing the AR transcriptional activity. In this study, we found that CDC25A is upregulated in human prostate cancer and its expression level is positively associated with the Gleason score and disease metastasis. More importantly, we showed that CDC25A can physically interact with AR through its putative catalytic domain. In addition, ectopic expression of CDC25A in prostate cancer cell lines suppresses PSA and Probasin promoter activities significantly, indicating that CDC25A may function as an AR corepressor. This was further confirmed by knockdown of endogenous CDC25A expression using small interfering RNA (siRNA), which resulted in upregulation of PSA promoter activity. Moreover, a truncated mutant that does not interact with AR fails to suppress the PSA promoter activity, indicating that CDC25A downregulates androgen-responsive promoter by physically interacting with AR. Taken together, our results demonstrated a novel function of CDC25A in the regulation of androgen signaling in human prostate cancer cells.

Overexpression of CDC25B and LAMC2 mRNA and protein in esophageal squamous cell carcinomas and premalignant lesions in subjects from a high-risk population in China

Molecular events associated with the initiation and progression of esophageal squamous cell carcinoma (ESCC) remain poorly understood but likely hold the key to effective early detection approaches for this almost invariably fatal cancer. CDC25B and LAMC2 are two promising early detection candidates emerging from new molecular studies of ESCC. To further elucidate the role of these two genes in esophageal carcinogenesis, we did a series of studies to (a) confirm RNA overexpression, (b) establish the prevalence of protein overexpression, (c) relate protein overexpression to survival, and (d) explore their potential as early detection biomarkers. Results of these studies indicated that CDC25B mRNA was overexpressed (>/=2-fold overexpression in tumor compared with normal) in 64% of the 73 ESCC cases evaluated, whereas LAMC2 mRNA was overexpressed in 89% of cases. CDC25B protein expression was categorized as positive in 59% (144 of 243) of ESCC cases on a tumor tissue microarray, and nonnegative LAMC2 patterns of protein expression were observed in 82% (225 of 275) of cases. Multivariate-adjusted proportional hazard regression models showed no association between CDC25B protein expression score and risk of death [hazard ratio (HR) for each unit increase in expression score, 1.00; P = 0.90]; however, several of the LAMC2 protein expression patterns strongly predicted survival. Using the cytoplasmic pattern as the reference (the pattern with the lowest mortality), cases with a diffuse pattern had a 254% increased risk of death (HR, 3.52; P = 0.007), cases with no LAMC2 expression had a 169% increased risk of death (HR, 2.69; P = 0.009), and cases with a peripheral pattern had a 130% greater risk of death (HR, 2.30; P = 0.02). CDC25B protein expression scores in subjects with esophageal biopsies diagnosed as normal (n = 35), dysplastic (n = 23), or ESCC (n = 32) increased significantly with morphologic progression. For LAMC2, all normal and dysplastic patients had a continuous pattern of protein expression, whereas all ESCCs showed alternative, noncontinuous patterns. This series of studies showed that both CDC25B and LAMC2 overexpress RNA and protein in a significant majority of ESCC cases. The strong relation of LAMC2 pattern of protein expression to survival suggests a role in prognosis, whereas the association of CDC25B with morphologic progression indicates a potential role as an early detection marker.

Discovery of novel Cdc25 phosphatase inhibitors with micromolar activity based on the structure-based virtual screening

Cdc25 phosphatases have been considered as attractive drug targets for anticancer therapy because of the correlation of their overexpression with a wide variety of cancers. We have been able to identify five novel Cdc25 phosphatase inhibitors with micromolar activity by means of a computer-aided drug design protocol involving the homology modeling of Cdc25A and the virtual screening with the automated AutoDock program implementing the effects of ligand solvation in the scoring function. Because the newly discovered inhibitors are structurally diverse and reveal a significant potency with IC 50 values lower than 10 microM, they can be considered for further development by structure-activity relationship studies or de novo design methods. The differences in binding modes of the identified inhibitors in the active sites of Cdc25A and B are discussed in detail.