The natural product CCR5 antagonist anibamine and its analogs as anti-prostate cancer agents

Phytochemicals in Inhibition of Prostate Cancer: Evidence from Molecular Mechanisms Studies

Prostate cancer is one of the leading causes of death for men worldwide. The development of resistance, toxicity, and side effects of conventional therapies have made prostate cancer treatment become more intensive and aggressive. Many phytochemicals isolated from plants have shown to be tumor cytotoxic. In vitro laboratory studies have revealed that natural compounds can affect cancer cell proliferation by modulating many crucial cellular signaling pathways frequently dysregulated in prostate cancer. A multitude of natural compounds have been found to induce cell cycle arrest, promote apoptosis, inhibit cancer cell growth, and suppress angiogenesis. In addition, combinatorial use of natural compounds with hormone and/or chemotherapeutic drugs seems to be a promising strategy to enhance the therapeutic effect in a less toxic manner, as suggested by pre-clinical studies. In this context, we systematically reviewed the currently available literature of naturally occurring compounds isolated from vegetables, fruits, teas, and herbs, with their relevant mechanisms of action in prostate cancer. As there is increasing data on how phytochemicals interfere with diverse molecular pathways in prostate cancer, this review discusses and emphasizes the implicated molecular pathways of cell proliferation, cell cycle control, apoptosis, and autophagy as important processes that control tumor angiogenesis, invasion, and metastasis. In conclusion, the elucidation of the natural compounds' chemical structure-based anti-cancer mechanisms will facilitate drug development and the optimization of drug combinations. Phytochemicals, as anti-cancer agents in the treatment of prostate cancer, can have significant health benefits for humans.

Research Trends and Regulation of CCL5 in Prostate Cancer

Prostate cancer (PCa) is considered as the most common cancer of urologic neoplasms, and its development and prognosis are associated with many factors. Chemokine receptor signaling combine with advances in advanced clinicopathological characteristics have provided new insights into the molecular landscape of prostate cancer. Chemokine (C-C motif) ligand 5 (CCL5) is an important member of the CC subfamily of chemokines. The expression of chemokine CCL5 is positively correlated with poor prognostic features in patients with PCa. Current study suggested that CCL5/CCR5 axis plays a significant role in the proliferation, metastasis, angiogenesis, drug resistance of prostate cancer cells and promotes self-renewal of prostate cancer stem cells (PCSCs). Due to the major domination in CCL5 by prostate cancer and the high cancer-specific mortality with prostate cancer, research on the CCL5/CCR5 axis effective antagonists is widespread application. However, challenges for precision oncology of CCL5/CCR5 axis and effective antagonists in CRPC remain. Herein, we summarized the crucial role of CCL5 in promoting the development of PCa and discussed the antitumor application of the antagonists of CCL5/CCR5 axis.

Anibamine and Its Analogues: Potent Antiplasmodial Agents from Aniba citrifolia

In our continuing search for novel natural products with antiplasmodial activity, an extract of Aniba citrifolia was found to have good activity, with an IC₅₀ value less than 1.25 μg/mL. After bioassay-directed fractionation, the known indolizinium alkaloid anibamine (1) and the new indolizinium alkaloid anibamine B (2) were isolated as the major bioactive constituents, with antiplasmodial IC₅₀ values of 0.170 and 0.244 μM against the drug-resistant Dd2 strain of Plasmodium falciparum. The new coumarin anibomarin A (3), the new norneolignan anibignan A (5), and six known neolignans (7-12) were also obtained. The structures of all the isolated compounds were determined based on analyses of 1D and 2D NMR spectroscopic and mass spectrometric data, and the absolute configuration of anibignan A (5) was assigned from its ECD spectrum. Evaluation of a library of 28 anibamine analogues (13-40) indicated that quaternary charged analogues had IC₅₀ values as low as 58 nM, while uncharged analogues were inactive or significantly less active. Assessment of the potential effects of anibamine and its analogues on the intraerythrocytic stages and morphological development of P. falciparum revealed substantial activity against ring stages for compounds with two C-10 side chains, while those with only one C-10 side chain exhibited substantial activity against trophozoite stages, suggesting different mechanisms of action.

Facile one-pot synthesis of 2,3-dihydro-1H-indolizinium derivatives by rhodium(iii)-catalyzed intramolecular oxidative annulation via C–H activation: application to ficuseptine synthesis

Various substituted indolizidinium, quinolizinium and pyrido[1,2-a]azepinium salts were synthesized from benzaldehydes (α,β-unsaturated aldehydes) and alkyne–amines via Rh-catalyzed C–H activation.

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.

Simple Indolizidine and Quinolizidine Alkaloids

This review of simple indolizidine and quinolizidine alkaloids (i.e., those in which the parent bicyclic systems are in general not embedded in polycyclic arrays) is an update of the previous coverage in Volume 55 of this series (2001). The present survey covers the literature from mid-1999 to the end of 2013; and in addition to aspects of the isolation, characterization, and biological activity of the alkaloids, much emphasis is placed on their total synthesis. A brief introduction to the topic is followed by an overview of relevant alkaloids from fungal and microbial sources, among them slaframine, cyclizidine, Steptomyces metabolites, and the pantocins. The important iminosugar alkaloids lentiginosine, steviamine, swainsonine, castanospermine, and related hydroxyindolizidines are dealt with in the subsequent section. The fourth and fifth sections cover metabolites from terrestrial plants. Pertinent plant alkaloids bearing alkyl, functionalized alkyl or alkenyl substituents include dendroprimine, anibamine, simple alkaloids belonging to the genera Prosopis, Elaeocarpus, Lycopodium, and Poranthera, and bicyclic alkaloids of the lupin family. Plant alkaloids bearing aryl or heteroaryl substituents include ipalbidine and analogs, secophenanthroindolizidine and secophenanthroquinolizidine alkaloids (among them septicine, julandine, and analogs), ficuseptine, lasubines, and other simple quinolizidines of the Lythraceae, the simple furyl-substituted Nuphar alkaloids, and a mixed quinolizidine-quinazoline alkaloid. The penultimate section of the review deals with the sizable group of simple indolizidine and quinolizidine alkaloids isolated from, or detected in, ants, mites, and terrestrial amphibians, and includes an overview of the "dietary hypothesis" for the origin of the amphibian metabolites. The final section surveys relevant alkaloids from marine sources, and includes clathryimines and analogs, stellettamides, the clavepictines and pictamine, and bis(quinolizidine) alkaloids.

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.

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 (125)I-gp120 in binding to the chemokine receptor CCR5, with an IC(50) = 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.

Design and synthesis of a bivalent ligand to explore the putative heterodimerization of the mu opioid receptor and the chemokine receptor CCR5

The bivalent ligand approach has been utilized not only to study the underlying mechanism of G protein-coupled receptors dimerization and/or oligomerization, but also to enhance ligand affinity and/or selectivity for potential treatment of a variety of diseases by targeting this process. Substance abuse and addiction have made both the prevention and the treatment of human immunodeficiency virus (HIV) infection more difficult to tackle. Morphine, a mu opioid receptor (MOR) agonist, can accelerate HIV infection through up-regulating the expression of the chemokine receptor CCR5, a well-known co-receptor for HIV invasion to the host cells and this has been extensively studied. Meanwhile, two research groups have described the putative MOR-CCR5 heterodimers in their independent studies. The purpose of this paper is to report the design and synthesis of a bivalent ligand to explore the biological and pharmacological process of the putative MOR-CCR5 dimerization phenomenon. The developed bivalent ligand thus contains two distinct pharmacophores linked through a spacer; ideally one of which will interact with the MOR and the other with the CCR5. Naltrexone and Maraviroc were selected as the pharmacophores to generate such a bivalent probe. The overall reaction route to prepare this bivalent ligand was convergent and efficient, and involved sixteen steps with moderate to good yields. The preliminary biological characterization showed that the bivalent compound 1 retained the pharmacological characteristics of both pharmacophores towards the MOR and the CCR5 respectively with relatively lower binding affinity, which tentatively validated our original molecular design.

Regio- and stereoselective syntheses of the natural product CCR5 antagonist anibamine and its three olefin isomers

The syntheses of the natural product anibamine and its three olefin isomers have been achieved concisely and efficiently via highly regio- and stereoselective reactions. The crucial steps included a regioselective palladium-catalyzed alkynylation by Sonogashira coupling and a stereoselective Suzuki coupling. Further conformation analyses and in vitro calcium mobilization studies were carried out to characterize the compounds' biological properties.