Discovery of novel phosphatidylcholine-specific phospholipase C drug-like inhibitors as potential anticancer agents

Screening and separation of natural anticancer active ingredients related to phospholipase C

Based on the specific binding of drug molecules to cell membrane receptors, a screening and separation method for active compounds of natural products was established by combining phospholipase C (PLC) sensitized hollow fiber microscreening by a solvent seal with high-performance liquid chromatography technology. In the process, the factors affecting the screening were optimized. Under the optimal screening conditions, we screened honokiol (HK), magnolol (MG), negative control drug carbamazepine, and positive control drug amentoflavone, the repeatability of the method was tested. The PLC activity was determined before and after the screening. Experimental results showed that the sensitization factors of PLC of HK and MG were 61.0 and 48.5, respectively, and amentoflavone was 15.0, carbamazepine could not bind to PLC. Moreover, the molecular docking results were consistent with this measurement, indicating that HK and MG could be combined with PLC, and they were potential interacting components with PLC. This method used organic solvent to seal the PLC greatly ensuring the activity, so this method had the advantage of integrating separation, and purification with screening, it not only exhibited good reproducibility and high sensitivity but was also suitable for screening the active components in natural products by various targets in vitro.

Metal-Free Late-Stage Alkylation of Tryptophan and Tryptophan-Containing Peptides with 1,3-Dithiane Derivatives

Late-stage diversification of structurally complex peptides has enormous potential for drug discovery and molecular imaging. We report a simple, metal-free, late-stage reductive C2 alkylation of tryptophan and tryptophan-containing peptides using readily available 1,3-dithianes. This alkylation protocol has a wide substrate scope and an excellent tolerance for reactive functional groups.

Phosphatidylcholine-Specific Phospholipase C as a Promising Drug Target

Phosphatidylcholine-specific phospholipase C (PC-PLC) is an enzyme that catalyzes the formation of the important secondary messengers phosphocholine and diacylglycerol (DAG) from phosphatidylcholine. Although PC-PLC has been linked to the progression of many pathological conditions, including cancer, atherosclerosis, inflammation and neuronal cell death, studies of PC-PLC on the protein level have been somewhat neglected with relatively scarce data. To date, the human gene expressing PC-PLC has not yet been found, and the only protein structure of PC-PLC that has been solved was from Bacillus cereus (PC-PLCBc). Nonetheless, there is evidence for PC-PLC activity as a human functional equivalent of its prokaryotic counterpart. Additionally, inhibitors of PC-PLCBc have been developed as potential therapeutic agents. The most notable classes include 2-aminohydroxamic acids, xanthates, N,N'-hydroxyureas, phospholipid analogues, 1,4-oxazepines, pyrido[3,4-b]indoles, morpholinobenzoic acids and univalent ions. However, many medicinal chemistry studies lack evidence for their cellular and in vivo effects, which hampers the progression of the inhibitors towards the clinic. This review outlines the pathological implications of PC-PLC and highlights current progress and future challenges in the development of PC-PLC inhibitors from the literature.

Tricyclodecan-9-yl-Xanthogenate (D609): Mechanism of Action and Pharmacological Applications

Tricyclodecan-9-yl xanthogenate (D609) is a synthetic tricyclic compound possessing a xanthate group. This xanthogenate compound is known for its diverse pharmacological properties. Over the last three decades, many studies have reported the biological activities of D609, including antioxidant, antiapoptotic, anticholinergic, anti-tumor, anti-inflammatory, anti-viral, anti-proliferative, and neuroprotective activities. Its mechanism of action is extensively attributed to its ability to cause the competitive inhibition of phosphatidylcholine (PC)-specific phospholipase C (PC-PLC) and sphingomyelin synthase (SMS). The inhibition of PCPLC or SMS affects secondary messengers with a lipidic nature, i.e., 1,2-diacylglycerol (DAG) and ceramide. Various in vitro/in vivo studies suggest that PCPLC and SMS inhibition regulate the cell cycle, block cellular proliferation, and induce differentiation. D609 acts as a pro-inflammatory cytokine antagonist and diminishes Aβ-stimulated toxicity. PCPLC enzymatic activity essentially requires Zn²⁺, and D609 might act as a potential chelator of Zn²⁺, thereby blocking PCPLC enzymatic activity. D609 also demonstrates promising results in reducing atherosclerotic plaque formation, post-stroke cerebral infarction, and cancer progression. The present compilation provides a comprehensive mechanistic insight into D609, including its chemistry, mechanism of action, and regulation of various pharmacological activities.

Development of 2-Morpholino-N-hydroxybenzamides as anti-proliferative PC-PLC inhibitors

Phosphatidylcholine-specific phospholipase C (PC-PLC) is a key enzyme involved in the metabolism of the mammalian phospholipid phosphatidylcholine into secondary messengers diacylglycerol (DAG) and phosphocholine. DAG and phosphocholine have been identified to amplify various cellular processes involved in oncogenesis such as proliferation, cell-cycle activation, differentiation and motility, therefore making PC-PLC a potential target for novel anti-cancer treatments. The current literature standard for PC-PLC inhibition, tricyclodecan-9-yl-potassium xanthate (D609), has been shown to arrest proliferation in multiple cancer cell lines, however, it is not drug-like resulting in low aqueous stability, making it a poor drug candidate. 2-Morpholinobenzoic acids have been shown to have improved PC-PLC inhibitory activity compared to D609, with molecular modelling identifying chelation of the carboxylic acid to catalytic Zn²⁺ ions in the PC-PLC active site being a key interaction. In this study, the carboxylic acid motif was replaced with a hydroxamic acid to strengthen the Zn²⁺ interaction. It was found that the hydroxamic acid derivatives displayed PC-PLC inhibitory activity similar, or better, than D609. Furthermore, these novel inhibitors had potent anti-proliferative activity in MDA-MB-231 and HCT-116 cancer cell lines, far greater than D609 and previous 2-morpholinobenzoic acids.

Synthesis, Characterization and In Vitro Evaluation of Novel 5-Ene-thiazolo[3,2-b][1,2,4]triazole-6(5H)-ones as Possible Anticancer Agents

The present paper is devoted to the search for drug-like molecules with anticancer properties using the thiazolo[3,2-b][1,2,4]triazole-6-one scaffold. A series of 24 novel thiazolo-[3,2-b][1,2,4]triazole-6-ones with 5-aryl(heteryl)idene- and 5-aminomethylidene-moieties has been synthesized employing three-component and three-stage synthetic protocols. A mixture of Z/E-isomers was obtained in solution for the synthesized 5-aminomethylidene-thiazolo[3,2-b]-[1,2,4]triazole-6-ones. The compounds have been studied for their antitumor activity in the NCI 60 lines screen. Some compounds present excellent anticancer properties at 10 μM. Derivatives 2h and 2i were the most active against cancer cell lines without causing toxicity to normal somatic (HEK293) cells. A preliminary SAR study had been performed for the synthesized compounds.

An optimised MALDI-TOF assay for phosphatidylcholine-specific phospholipase C

The Bacillus cereus phosphatidylcholine-specific phospholipase C (PC-PLCBc) is an enzyme that catalyses the hydrolysis of phosphatidylcholines into phosphocholine and 1,2-diacylglycerols. PC-PLCBc has found applications in both the food industry and in medicinal chemistry. Herein, we report our work in the development and optimisation of a matrix assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry-based assay to monitor PC-PLCBc activity. The use of one-phase and two-phase reaction systems to assess the inhibition of PC-PLCBc with different structural classes of inhibitors was compared. We also highlighted the advantage of our assay over the commonly used commercially available Amplex Red assay. This method will also be applicable to work on the activity and inhibition of other phospholipases.

Structure-based discovery of small molecule APC-Asef interaction inhibitors: In silico approaches and molecular dynamics simulations

Colorectal cancer, which is considered one of the leading causes of mortality worldwide, develops through the formation of benign polyps on the inner colon or rectum wall. Truncations in adenomatous polyposis coli (APC) gene lead to the spread of the disease in the entire colon region when combined with the guanine nucleotide exchange factor (GEF) Asef. A series of peptidomimetic agents were previously discovered as protein-protein interaction inhibitors that can target the APC-Asef interface. Structure-based virtual screening (SBVS), using a set of docking methods combined with molecular dynamics simulations, was carried out to identify new small drug-like agents. After the initial screening process, compounds with diverse chemical scaffolds and direct interaction with Arg549 and other active site residues were chosen and subjected to induce fit. The amide functional group found in the ligand hit structures showed strong interactions with Arg549, leading to observable conformational changes that allow suitable positioning within the peptide binding site. Furthermore, the pH-specific MD simulations of the top hit 838 within the APC-Asef binding site depicted significant interactions required for biochemical recognition in changing microenvironment. Predicted inhibitory constant (Ki) values and binding free energies of hits further described the significance of the amide group over the other chemical scaffolds. This combination of in silico approaches provides key insights for colorectal drug discovery programs targeting the APC-Asef interaction. Graphical abstract The common active site residues involved in interaction with ligands.