Anti-prostate Cancer Agents Research Articles

Abstract 3652: Development of novel chemical inhibitors targeting the N-terminal domain (NTD) of androgen receptor variants as anti-prostate cancer agents

Abstract The androgen receptor (AR) signaling is a driver of prostate cancer. Current therapeutic strategy for advanced prostate cancer is to suppress the AR signaling by androgen deprivation therapy (ADT) via castration and by antiandrogens to stop androgens from working. However, prostate cancer cells are very versatile in circumventing the ADT and reactivate the AR via multiple mechanisms, resulting in lethal castration-resistant prostate cancer (CRPC). An alarming problem is the emergence of AR variants that lack the ligand-binding domain (such as AR-V7) in CRPC patients, which are constitutively active without the need for androgens. Studies revealed that AR-v7 expression level was correlated with the risk of tumor recurrence after radical prostatectomy and was associated with short patient survival. In addition, mutations in full-length AR is another important mechanism of aberrant AR activation in CRPC cells. Recently, it was found that the F876L mutation is sufficient to confer enzalutamide resistance in cell lines and xenograft model. The AR F876L mutant is detected in CRPC patients treated with an enzalutamide analogue (ARN-509). The AR W741C mutant was detected in CRPC patient treated with bicalutamide and was found to be paradoxically activated by bicalutamide. In this project, we propose to develop novel AR inhibitors that target the AR N-terminal domain (NTD). The rationale for this has at least three fold: i) All of the FDA-approved antiandrogens are targeting the AR-LBD and thereby all of them are inactive against AR-v7; ii) All of the known mechanisms that could account for AR reactivation in CRPC cells are critically depending on the AR-NTD to reactivate AR; and iii) Among the NTD, DNA-binding domain (DBD) and LBD domains, the NTD is the most different domain between the AR and other members of steroid receptors. By a panel of in vitro assays, we have discovered a series of compounds that target the AR-NTD and potently inhibit all forms of the AR variants in our assays, including AR-V7, the wild-type and multiple clinically-relevant mutants of full-length ARs. Our inhibitors showed selectivity towards AR as they are inactive against the close homology proteins within the same steroid family (such as GR and PR). This project could lead to novel AR-NTD inhibitors as drug candidates for treating CRPC patients who have acquired resistance to AR-LBD-directed therapies, such as enzalutamide and abiraterone. Citation Format: Jian Hui Wu. Development of novel chemical inhibitors targeting the N-terminal domain (NTD) of androgen receptor variants as anti-prostate cancer agents. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3652. doi:10.1158/1538-7445.AM2015-3652

Abstract 3661: Development of novel small-molecule inhibitors of ETS oncoproteins as anti-prostate cancer agents

Abstract Currently advanced prostate cancer is treated by suppressing androgen receptor (AR) signaling. Since AR could be activated via multiple mechanisms, inhibition of one or two of these mechanisms could be initially effective, but drug resistance can rapidly develop due to kick-in of other AR-activating mechanisms, resulting in lethal castration-resistant prostate cancer (CRPC). The therapeutic effects of all of the currently available AR-targeting agents are short-lived. To achieve long lasting therapeutic effect for prostate cancer, it appears we need to get out of the box of AR. Here, we propose to develop chemical inhibitors of oncogenic protein ERG, which is an ETS transcriptional factor. The rationale for inhibiting ERG as a possible treatment for prostate cancer has two folds: i) ERG plays a critical role in prostate cancer initiation and progression, and ii) Half of all prostate cancer patients are TMPRSS2-ERG fusion positive, which result in high level of ERG oncoprotein. ERG is a transcriptional factor that directly regulates EZH2, oncogene c-Myc and tumor suppressor Nkx3.1 and many other targets in prostate cancer. ERG cooperates with PI3K/AKT and AR in tumor initiation. ERG knockdown inhibits tumor growth in xenograft of VCaP cells. To date, accumulated studies in patients and experimental models have indicated that ERG overexpression as a result of TMPRSS2-ERG fusion plays a critical role in prostate cancer initiation and progression. However, ERG protein has no obvious functional sites or enzymatic activity to be inhibited and is considered ‘undruggable’. In contrast to such view, our laboratory has recently discovered a novel chemical inhibitor of ERG by combining virtual screening and reporter assay. We have built a structural model of ERG DBD and identified a putative binding-site for virtual screening study. We discovered a novel compound, which substantially inhibits ERG-dependent reporter activity in HEK293 cells and inhibits expression of ERG-regulated genes, such as EZH2 and c-Myc, in VCaP cells. We further showed that our compound inhibits proliferation of VCaP cells, and disrupts association of ERG with its essential coactivator PARP1 by co-IP assay. Surface Plasmon Resonance (SPR) analysis has confirmed that our compound has direct binding with recombinant ERG protein. As recent studies indicated that advanced prostate cancer with TMPRSS2-ERG fusion have substantial higher tendency to metastasize to lymph nodes, ERG inhibitors could be an effective therapeutics to prevent this progression. Importantly, ERG inhibitors could be effective therapeutics for advanced prostate cancer. Citation Format: Xiaohong Tian. Development of novel small-molecule inhibitors of ETS oncoproteins as anti-prostate cancer agents. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3661. doi:10.1158/1538-7445.AM2015-3661

Exploration on natural product anibamine side chain modification toward development of novel CCR5 antagonists and potential anti-prostate cancer agents.

Prostate cancer is one of the leading causes of death among males in the world. Prostate cancer cells have been shown to express upregulated chemokine receptor CCR5, a G protein-coupled receptor (GPCR) that relates to the inflammation process. Anibamine, a natural product containing a pyridine ring and two aliphatic side chains, was shown to carry a binding affinity of 1 μM at CCR5 as an antagonist with potential anti-cancer activity. However, it is not drug-like according to the Lipinski's rule of five mainly due to its two long aliphatic side chains. In our effort to improve its drug-like property, a series of anibamine derivatives were designed and synthesized by placement of aromatic side chains through an amide linkage to the pyridine ring. The newly synthesized compounds were tested for their CCR5 affinity and antagonism, and potential anti-proliferation activity against prostate cancer cell lines. Basal cytotoxicity was finally studied for compounds showing potent anti-proliferation activity. It was found that compounds with hydrophobic substitutions on the aromatic systems seemed to carry more promising CCR5 binding and prostate cancer cell proliferation inhibition activities.

Dual targeting of mTORC1 and mTORC2 by INK-128 potently inhibits human prostate cancer cell growth in vitro and in vivo.

Both mammalian target of rapamycin (mTOR) complexes 1 and 2 (mTORC1/2) are often over-activated in prostate cancer cells and are associated with cancer progression. In the current study, we evaluated the potential anti-prostate cancer activity of INK-128, an ATP-competitive mTORC1/2 dual inhibitor, both in vitro and in vivo. Our results showed that INK-128 exerted potent anti-proliferative activity in established (PC-3 and LNCaP lines) and primary (patient-derived) human prostate cancer cells by inducing cell apoptosis. The latter was evidenced by increase of annexin V percentage, formation of cytoplasmic histone-associated DNA fragments, and cleavage of caspase-3. INK-128-induced prostate cancer cell apoptosis and cytotoxicity were alleviated upon pretreatment of cells with the pan-caspase inhibitor z-VAD-FMK or the specific caspase-3 inhibitor z-DVED-FMK. At the molecular level, INK-18 blocked mTORC1/2 activation in PC-3 cells and LNCaP cells and downregulated mTOR-regulated genes including cyclin D1, hypoxia-inducible factor 1α (HIF-1α), and HIF-2α. ERK-MAPK activation and androgen receptor expression were, however, not affected by INK-128 treatment. In vivo, oral administration of INK-128 significantly inhibited growth of PC-3 xenografts in nude mice. The preclinical results of this study suggest that INK-128 could be further investigated as a promising anti-prostate cancer agent.

Computer-aided molecular design of (E)-N-Aryl-2-ethene-sulfonamide analogues as microtubule targeted agents in prostate cancer

Microtubules are tube-shaped, filamentous and cytoskeletal proteins that are essential in all eukaryotic cells. Microtubule is an attractive and promising target for anticancer agents. In this study, three-dimensional quantitative structure activity relationships (3D-QSAR) including comparative molecular field analysis, CoMFA, and comparative molecular similarity indices analysis, CoMSIA, were performed on a set of 45 (E)-N-Aryl-2-ethene-sulfonamide analogues as microtubule-targeted anti-prostate cancer agents. Automated grid potential analysis, AutoGPA module in Molecular Operating Environment 2009.10 (MOE) as a new 3D-QSAR approach with the pharmacophore-based alignment was carried out on the same dataset. AutoGPA-based 3D-QSAR model yielded better prediction parameters than CoMFA and CoMSIA. Based on the contour maps generated from the models, some key features were identified in (E)-N-Aryl-2-arylethene-sulfonamide analogues that were responsible for the anti-cancer activity. Virtual screening was performed based on pharmacophore modeling and molecular docking to identify the new inhibitors from ZINC database. Seven top ranked compounds were found based on Gold score fitness function. In silico ADMET studies were performed on compounds retrieved from virtual screening in compliance with the standard ranges.

Curcumin-based anti-prostate cancer agents.

Prostate cancer possesses the highest occurrence rate and is the second-paramount disease that causes cancer-affiliated death among men in the United States. Approximately 30,000 men die each year of castration-resistant prostate cancer due to the inevitable progression of resistance to first-line treatment with docetaxel. The safety profile of dietary curcumin in humans has been well-documented, and its therapeutic prospect in treating prostate cancer, especially for castration-resistant prostate cancer, has been evidenced in several cell culture systems and human xenograft mouse models. The critical disadvantage of curcumin as a drug candidate is its low bioavailability caused by poor water solubility and rapid in vivo metabolism. Curcumin is characteristic of regulating multiple targets, representing a good example for the philosophy to search for multitargeted drugs in the realm of drug design and drug development. This feature, together with its potential in treating castration-resistant prostate cancer and its safety profile, enables curcumin to serve as an ideal lead compound for the design and syntheses of curcumin-based agents with improved potential for the clinical therapies of prostate cancer. Several researches aiming to improve its bioavailability and potency resulted in the discovery and development of a wealth of curcumin-based compounds with an enhanced anticancer potential and/or an improved pharmacokinetic profile. This review starts with a brief summarization of the prospect of curcumin in treating prostate cancer and its mechanisms of action, then provides an in-depth overview of current development of curcumin-based anti-prostate cancer agents and their structure-activity relationships, and ends with the syntheses and pharmacokinetic studies of curcumin.

Synthesis and evaluation of linear furanocoumarins as potential anti-breast and anti-prostate cancer agents

A series of 22 furanocoumarin derivatives were synthesized and evaluated for cytotoxicity against breast cancer (MCF-7 and MDA-MB-231) and prostate cancer (PC-3) cell lines along with normal cell line. Several analogs were synthesized by replacing prenyl moiety with alkyl, aromatic, and heteroaromatic functionality to study the structure–activity relationship. Compounds 20 and 22 with adamantoylamino, diprenylamino and substituted benzene sulfonamide substituents showed potent antiproliferative activity in MCF-7 cell line with IC50 values of 0.48 and 0.53 µM, respectively. Both the compounds showed higher IC50 value in MCF-10A cell lines indicating nontoxicity in normal cell lines.

Androgen receptor antagonists and anti-prostate cancer activities of some newly synthesized substituted fused pyrazolo-, triazolo- and thiazolo-pyrimidine derivatives.

A series of substituted pyrazole, triazole and thiazole derivatives (2–13) were synthesized from 1-(naphtho[1,2-d]thiazol-2-yl)hydrazine as starting material and evaluated as androgen receptor antagonists and anti-prostate cancer agents. The newly synthesized compounds showed potent androgen receptor antagonists and anti-prostate cancer activities with low toxicity (lethal dose 50 (LD50)) comparable to Bicalutamide as reference drug. The structures of newly synthesized compounds were confirmed by IR, 1H-NMR, 13C-NMR, and MS spectral data and elemental analysis. The detailed synthesis, spectroscopic data, LD50 values and pharmacological activities of the synthesized compounds are reported.

Androprostamines A and B, the new anti-prostate cancer agents produced by Streptomyces sp. MK932-CF8.

Androgen receptor (AR) is a validated target in all clinical states of prostate cancer. Androprostamines A and B, the new inhibitors of androgen receptor, were isolated from Streptomyces sp. MK932-CF8. Their structures were determined by the spectroscopic analysis, degradation studies and synthesis. Androprostamines showed potent inhibitory effect against androgen-dependent growth of human prostate cancer cells without cytotoxicity and repressed the androgen-induced expression of AR-regulated genes.

Magnolol Causes Alterations in the Cell Cycle in Androgen Insensitive Human Prostate Cancer Cells In Vitro by Affecting Expression of Key Cell Cycle Regulatory Proteins

Prostate cancer, one of the most common cancers in the Western world, affects many men worldwide. This study investigated the effects of magnolol, a compound found in the roots and bark of the magnolia tree Magnolia officinalis, on the behavior of 2 androgen insensitive human prostate cancer cell lines, DU145 and PC3, in vitro. Magnolol, in a 24-h exposure at 40 and 80 μM, was found to be cytotoxic to cells. Magnolol also affected cell cycle progression of DU145 and PC3 cells, resulting in alterations to the cell cycle and subsequently decreasing the proportion of cells entering the G2/M-phase of the cell cycle. Magnolol inhibited the expression of cell cycle regulatory proteins including cyclins A, B1, D1, and E, as well as CDK2 and CDK4. Protein expression levels of pRBp107 decreased and pRBp130 protein expression levels increased in response to magnolol exposure, whereas p16INK4a, p21, and p27 protein expression levels were apparently unchanged post 24-h exposure. Magnolol exposure at 6 h did increase p27 protein expression levels. This study has demonstrated that magnolol can alter the behavior of androgen insensitive human prostate cancer cells in vitro and suggests that magnolol may have potential as a novel anti-prostate cancer agent.

SRJ23, a new semisynthetic andrographolide derivative: in vitro growth inhibition and mechanisms of cell cycle arrest and apoptosis in prostate cancer cells.

3,19-(3-Chloro-4-fluorobenzylidene)andrographolide (SRJ23), a new semisynthetic derivative of andrographolide (AGP), exhibited selectivity against prostate cancer cells in the US National Cancer Institute (NCI) in vitro anti-cancer screen. Herein, we report the in vitro growth inhibition and mechanisms of cell cycle arrest and apoptosis induced by SRJ23. 3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used in assessing in vitro growth inhibition of compounds against prostate cancer (PC-3, DU-145 and LNCaP) and mouse macrophage (RAW 264.7) cell lines. Flow cytometry was utilised to analyse cell cycle distribution, whereas fluorescence microscopy was performed to determine morphological cell death. DNA fragmentation and annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) flow cytometry were done to confirm apoptosis induced by SRJ23. Quantitation of cell cycle and apoptotic regulatory proteins were determined by immunoblotting. AGP and SRJ23 selectively inhibited the growth of prostate cancer cells compared with RAW 264.7 cells at low micromolar concentrations; however, SRJ23 was more potent. Mechanistically, SRJ23-treated PC-3 cells displayed down-regulation of cyclin-dependent kinase (CDK) 1 without affecting levels of CDK4 and cyclin D1. However, SRJ23 induced down-regulation of CDK4 and cyclin D1 but without affecting CDK1 in DU145 and LNCaP cell lines. DNA histogram analysis revealed that the SRJ23 induced G2/M in PC-3 cells but G1 arrest in DU-145 and LNCaP cells. Morphologically, both compounds induced predominantly apoptosis, which was further confirmed by DNA fragmentation and annexin V-FITC staining. The DNA fragmentation was inhibited in the presence of caspase 8 inhibitor (Z-IETD-FMK). Apoptosis was associated with an increase in caspase 8 expression and activation. This thought to have induced cleavage of Bid into t-Bid. Additionally, increased expression and activation of caspase 9 and Bax proteins were apparent, with a concomitant down-regulation of Bcl-2 protein. Similar apoptosis cascade of events was observed in SRJ23-treated DU145 and LNCaP cell lines. SRJ23 inhibited the growth of prostate cancer cells by inducing G2/M and G1 arrest via down-regulation of CDK1, and CDK4 and cyclin, respectively, and initiated caspase-8-mediated mitochondrial apoptosis. Taken together, these data support the potential of this compound as a new anti-prostate cancer agent.

Design, syntheses, and characterization of piperazine based chemokine receptor CCR5 antagonists as anti prostate cancer agents

Chemokine receptor CCR5 plays an important role in the pro-inflammatory environment that aids in the proliferation of prostate cancer cells. Previously, a series of CCR5 antagonists containing a piperidine ring core skeleton were designed based upon the proposed CCR5 antagonist pharmacophore from molecular modeling studies. The developed CCR5 antagonists were able to antagonize CCR5 at a micromolar level and inhibit the proliferation of metastatic prostate cancer cell lines. In order to further explore the structure–activity-relationship of the pharmacophore identified, the molecular scaffold was expanded to contain a piperazine ring as the core. A number of compounds that were synthesized showed promising anti prostate cancer activity and reasonable cytotoxicity profiles based on the biological characterization.

Novel phenolic inhibitors of the sarco/endoplasmic reticulum calcium ATPase: identification and characterization by quantitative structure–activity relationship modeling and virtual screening

Inhibitors of the sarco/endoplasmic reticulum calcium ATPase (SERCA) are valuable research tools and hold promise as a new generation of anti-prostate cancer agents. Based on previously determined potencies of phenolic SERCA inhibitors, we created quantitative structure–activity relationship (QSAR) models using three independent development strategies. The obtained QSAR models facilitated virtual screens of several commercial compound collections for novel inhibitors. Sixteen compounds were subsequently evaluated in SERCA activity inhibition assays and 11 showed detectable potencies in the micro- to millimolar range. The experimental results were then incorporated into a comprehensive master QSAR model, whose physical interpretation by partial least squares analysis revealed that properly positioned substituents at the central phenyl ring capable of forming hydrogen bonds and of undergoing hydrophobic interactions were prerequisites for effective SERCA inhibition. The established SAR was in good agreement with findings from previous structural studies, even though it was obtained independently using standard QSAR methodologies.

Synthesis of bufalin derivatives with inhibitory activity against prostate cancer cells

Bufalin possesses a strong anti-cancer effect, but the cardiac toxicity targeting the Na+, K+-ATPase limits its application. Here, two bufalin derivatives, bufadienolactam (1) and secobufalinamide (2), were synthesised by treating bufalin with ammonium acetate in dimethylformamide solution. Their structures were elucidated by extensive spectroscopic methods. The structure of compound 2 was further confirmed by single-crystal X-ray diffraction analysis. Compounds 1 and 2 expressed strong inhibitory activities against androgen-dependent prostate cancer cells (IC50 values about 10 μM), but only weak inhibition on Na+, K+-ATPase (Ki about 70 μM), indicating that they might be potential anti-prostate cancer agents without severe cardiac toxicity.

Design and synthesis of optically pure 3-aryl-6-methyl-2-thioxotetrahydropyrimidin-4(1H)-ones as anti-prostate cancer agents

3-Aryl-6-methyl-2-thioxotetrahydropyrimidin-4(1H)-ones were designed and synthesized as a new class of anti-prostate cancer agents.

Glionitrin A, a New Diketopiperazine Disulfide, Activates ATM-ATR-Chk1/2 <i>via</i> 53BP1 Phosphorylation in DU145 Cells and Shows Antitumor Effect in Xenograft Model

In a recent study, we isolated the diketopiperazine disulfide glionitrin A from the co-culture broth of a mine drainage-derived fungus (Aspergillus fumigatus KMC901) and bacterium (Sphingomonas KMK001). Here, we investigated the antitumor activity of glionitrin A and its underlying molecular mechanisms in human prostate cancer DU145 cells. Glionitrin A showed significant cytotoxicity, promoting cell cycle arrest and apoptosis. Glionitrin A-treated cells exhibited elevated levels of phospho-histone 2AX (Ser139), a marker of DNA damage, and accumulated in both S phase and G2/M phase due to the activation of checkpoints associated with the ataxia-telangiectasia-mutated and ataxia-telangiectasia-mutated-Rad3-related Chk1/2 pathway downstream of p53-binding protein 1 phosphorylation at Ser1778. In addition, glionitrin A induced apoptosis through both caspase-dependent and -independent pathways. Glionitrin A activated caspase-8, -9 and -3 and also released endonuclease G from the mitochondria to the nucleus in a dose-dependent manner. Our in vivo study performed in nude mice bearing xenografts of DU145 cells showed that glionitrin A dramatically reduced the tumor volume by an average of 38.2% (5 mg/kg, per os (p.o.)) and 71.3% (10 mg/kg, p.o.) at 27 d after the beginning of treatment. Taken together, these findings provide a detailed description of the mechanism underlying the biological activity of the new natural product glionitrin A, which has the potential to be developed as an anti-prostate cancer agent.

Design, syntheses, and characterization of pharmacophore based chemokine receptor CCR5 antagonists as anti prostate cancer agents

Accumulating evidence has shown multiple roles that chemokine receptor CCR5 may play to promote the progression of several types of cancer. The mechanism of such promotion is believed to involve chronic inflammation that creates a microenvironment which enhances tumor survival. Therefore, blocking CCR5 function with an antagonist may provide a novel treatment of cancers such as prostate cancer. Currently, several CCR5 antagonists are available, but all have been optimized for their inhibitory activity on HIV-1 cellular membrane invasion process rather than inhibition on cytoplasmic signaling pathways. Thus, there is need to develop CCR5 antagonists focusing on blockage of CCR5 downstream signaling and inhibition of CCR5 related prostate cancer proliferation and progression. In this report, a pharmacophore analysis was conducted based on docking studies of several known CCR5 antagonists in a CCR5 homology model. A unique structural skeleton for CCR5 antagonist was constructed and functionalized, resulting in a new series of small molecules to be synthesized and characterized. A combination of CCR5 calcium flux inhibition, anti prostate cancer cell proliferation, basal cytotoxicity, and in vivo animal model studies were applied to screen the newly synthesized compounds. Results from this study provided a potential lead compound for future CCR5 antagonist development focusing on prostate cancer therapy.

Design and Synthesis of 4-(4-Benzoylaminophenoxy)phenol Derivatives As Androgen Receptor Antagonists.

We report the design and synthesis of novel 4-(4-benzoylaminophenoxy)phenol derivatives that bind to the androgen receptor (AR) ligand-binding domain and exhibit potent androgen-antagonistic activity. Compound 22 is one of the most potent of these derivatives, inhibiting the dihydrotestosterone-promoted growth of SC-3 cell line bearing wild-type AR (IC50 0.75 μM), LNCaP cell line bearing T877A-mutated AR (IC50 0.043 μM), and 22Rv1 cell line bearing H874Y-mutated AR (IC50 0.22 μM). Structure-activity relationship studies confirmed that the pharmacophore of these novel AR antagonists is distinct from the nitro- or cyano-substituted anilide substructure of other nonsteroidal AR antagonists. This novel pharmacophore is expected to provide a basis for designing new antiprostate cancer agents.

Crystal Structures of the Free and Ligand-Bound FK1–FK2 Domain Segment of FKBP52 Reveal a Flexible Inter-Domain Hinge

The human Hsp90 co-chaperone FKBP52 belongs to the family of FK506-binding proteins, which act as peptidyl-prolyl isomerases. FKBP52 specifically enhances the signaling of steroid hormone receptors, modulates ion channels and regulates neuronal outgrowth dynamics. In turn, small-molecule ligands of FKBP52 have been suggested as potential neurotrophic or anti-prostate cancer agents. The usefulness of available ligands is however limited by a lack of selectivity. The immunophilin FKBP52 is composed of three domains, an FK506-binding domain with peptidyl-prolyl isomerase activity, an FKBP-like domain of unknown function and a TPR-clamp domain, which recognizes the C-terminal peptide of Hsp90 with high affinity. The herein reported crystal structures of FKBP52 reveal that the short linker connecting the FK506-binding domain and the FKBP-like domain acts as a flexible hinge. This enhanced flexibility and its modulation by phosphorylation might explain some of the functional antagonism between the closely related homologs FKBP51 and FKBP52. We further present two co-crystal structures of FKBP52 in complex with the prototypic ligand FK506 and a synthetic analog thereof. These structures revealed the molecular interactions in great detail, which enabled in-depth comparison with the corresponding complexes of the other cytosolic FKBPs, FKBP51 and FKBP12. The observed subtle differences provide crucial insights for the rational design of ligands with improved selectivity for FKBP52.

Structure activity relationship studies of natural product chemokine receptor CCR5 antagonist anibamine toward the development of novel anti prostate cancer agents

Recent studies have indicated that the CCR5 chemokine receptor may be a potential target for treating prostate cancer. Thus, development of CCR5 antagonists may provide novel prostate cancer therapy. Anibamine, a novel pyridine quaternary alkaloid isolated from Aniba sp., was found to effectively compete with 125I-gp120 in binding to the chemokine receptor CCR5, with an IC50 = 1 μM. Anibamine is the first natural product reported as a CCR5 antagonist, and thus provides a novel structural skeleton unique from other lead compounds that have generally been identified from high-throughput screening efforts. In order to refine the lead compound's structure and improve the therapeutic index of anibamine derivatives as potential anti prostate cancer agents, the approach of “deconstruction–reconstruction–elaboration” was applied in the structure–activity relationship studies of this work. Here, we report the design, syntheses and anti prostate cancer activities of anibamine and 17 analogues. The results from the in vitro and in vivo studies described here show that this class of compounds has potential to provide novel leads as anti prostate cancer agents.