Arylstibonic acids are potent and isoform-selective inhibitors of Cdc25a and Cdc25b phosphatases

6-Regioisomeric 5,8-quinolinediones as potent CDC25 inhibitors against colorectal cancers

Precise and accurate control of cell cycle progression is required to maintain cell identity and proliferation. Failing to keep it will lead to genome instability and tumorigenesis. Cell Division Cycle 25 (CDC25) phosphatases are the key to regulating the activity of the master cell cycle controller, cyclin-dependent kinases (CDKs). Dysregulation of CDC25 has been shown to associate with several human malignancies. Here, we reported a series of derivatives of the CDC25 inhibitor, NSC663284, bearing quinones as core scaffolds and morpholin alkylamino side chains. Among these derivatives, the cytotoxic activity of the 6-isomer of 5,8-quinolinedione derivatives (6b, 16b, 17b, and 18b) displayed higher potency against colorectal cancer (CRC) cells. Compound 6b possessed the most antiproliferative activity, with IC₅₀ values of 0.59 μM (DLD1) and 0.44 μM (HCT116). The treatment of compound 6b resulted in a remarkable effect on cell cycle progression, blocking S-phase progression in DLD1 cells straight away while slowing S-phase progression and accumulated cells in the G₂/M phase in HCT116 cells. Furthermore, we showed that compound 6b inhibited CDK1 dephosphorylation and H4K20 methylation in cells. The treatment with compound 6b induced DNA damage and triggered apoptosis. Our study identifies compound 6b as a potent CDC25 inhibitor that induces genome instability and kills cancer cells through an apoptotic pathway, deserving further investigation to fulfill its candidacy as an anti-CRC agent.

Discrete Molecular Aggregates Based on ZnII and SbIII/V Ions Displaying Efficient Antibacterial and Antioxidant Properties

The reactions of [Zn₃Cl₂(3,5-Me₂PzH)₄(t-BuPO₃)₂] with organostibonic acid in varying reaction conditions have been investigated. Single-crystal X-ray diffraction studies reveal the formation of [Zn₂(p-ClC₆H₄Sb)₂(O)₂(OCH₃)₂(t-BuPO₃)₃(py)₂] (1), [Zn₂(p-ClC₆H₄Sb^V)₄(Sb^III)₂(O)₈(t-BuPO₃H)₄(t-BuPO₃)₂(py)₂Cl₂] (2), and [Zn₂(RSb)₄(O)₄(OCH₃)₄(t-BuPO₃)₄(py)₂], where R = p-ClC₆H₄ (3) and R = p-iPrC₆H₄ (4), respectively. Interestingly, in the synthesis of 2, complete dearylation of organoantimony moieties followed by C-F bond formation, a reduction from Sb (V) to Sb (III), and Sb···Cl weak intermolecular interactions have been observed. ESI-MS studies suggested that clusters 1-4 maintained their structural integrity in the solution state also. Solution NMR studies (¹H, ³¹P, and ¹³C) support well the observed solid-state structures. 1-4 were tested for antibacterial activity using a microdilution assay. 1 and 4 showed the best activity with lower MIC values (0.78-6.25 μg/mL) against all the tested pathogens. The total antioxidant activity of 1-4 was evaluated through the phosphomolybdenum assay, which showed a total antioxidant activity ranging from 28.96 to 86.46 mg AAE/g compound with the ascorbic acid standard.

Stibonic acids and related stibonate-phosphonate clusters: Synthesis, characterization and bioactivity evaluation

The reaction of 4-(azobenzene)phenylstibonic acid with t-butylphosphonic acid led to the isolation of the tetranuclear oxo-hydroxo antimony cluster of formulae [(4-azobenzene-C₆H₄Sb)₄(OH)₄(^tBuPO₃)₆] (C1). The reaction of (p-t-butyl phenyl stibonic acid with phenyl phosphonic acid resulted in the isolation of complex with formulae [(p-t-BuC₆H₄Sb)₄(O)₂(PhPO₃)₄(PhPO₃H)₄] (C2). Based upon the initial results from docking studies, parent stibonic acids, t-butyl-phenylstibonic acid, p-isopropylphenylstibonic acid, 4-azobenzenephenylstibonic acid, and the derived tetranuclear organoantimonate-phosphonate clusters were screened against different cancer cell lines, various Gram-positive and Gram-Negative bacteria and mycobacteria for possible bioactivity profile.

Medicinal chemistry insights into novel CDC25 inhibitors

Cell division cycle 25 (CDC25) phosphatases, a kind of cell cycle regulators, have become an attractive target for drug discovery, as they have been found to be over-expressed in various human cancer cells. Several CDC25 inhibitors have achieved significant attention in clinical trials with possible mechanistic actions. Prompted by the significance of CDC25 inhibitors with medicinal chemistry prospect, it is an apt time to review the various drug discovery methods involved in CDC25 drug discovery including high throughput screening (HTS), virtual screening (VS), fragment-based drug design, substitution decorating approach, structural simplification approach and scaffold hopping method to seek trends and identify promising new avenues of CDC25 drug discovery.

Cross-Species Complementation of Nonessential Yeast Genes Establishes Platforms for Testing Inhibitors of Human Proteins

Cross-species complementation can be used to generate humanized yeast, which is a valuable resource with which to model and study human biology. Humanized yeast can be used as an in vivo platform to screen for chemical inhibition of human protein drug targets. To this end, we report the systematic complementation of nonessential yeast genes implicated in chromosome instability (CIN) with their human homologs. We identified 20 human-yeast complementation pairs that are replaceable in 44 assays that test rescue of chemical sensitivity and/or CIN defects. We selected a human-yeast pair (hFEN1/yRAD27), which is frequently overexpressed in cancer and is an anticancer therapeutic target, to perform in vivo inhibitor assays using a humanized yeast cell-based platform. In agreement with published in vitro assays, we demonstrate that HU-based PTPD is a species-specific hFEN1 inhibitor. In contrast, another reported hFEN1 inhibitor, the arylstibonic acid derivative NSC-13755, was determined to have off-target effects resulting in a synthetic lethal phenotype with yRAD27-deficient strains. Our study expands the list of human-yeast complementation pairs to nonessential genes by defining novel cell-based assays that can be utilized as a broad resource to study human drug targets.

Insights into the interaction of high potency inhibitor IRC-083864 with phosphatase CDC25

CDC25 phosphatases play a crucial role in cell cycle regulation. They have been found to be over-expressed in various human tumours and to be valuable targets for cancer treatment. Here, we report the first model of binding of the most potent CDC25 inhibitor to date, the bis-quinone IRC-083864, into CDC25B obtained by combining molecular modeling and NMR studies. Our study provides new insights into key interactions of the catalytic site inhibitor and CDC25B in the absence of any available experimental structure of CDC25 with a bound catalytic site inhibitor. The docking model reveals that IRC-083864 occupies both the active site and the inhibitor binding pocket of the CDC25B catalytic domain. NMR saturation transfer difference and WaterLOGSY data indicate the binding zones of the inhibitor and support the docking model. Probing interactions of analogues of the two quinone units of IRC-083864 with CDC25B demonstrate that IRC-083864 competes with each monomer. Proteins 2017; 85:593-601. © 2016 Wiley Periodicals, Inc.

Synthesis of unsaturated phosphatidylinositol 4-phosphates and the effects of substrate unsaturation on SopB phosphatase activity

In this paper evidence is presented that the fatty acid component of an inositide substrate affects the kinetic parameters of the lipid phosphatase Salmonella Outer Protein B (SopB). A succinct route was used to prepare the naturally occurring enantiomer of phosphatidylinositol 4-phosphate (PI-4-P) with saturated, as well as singly, triply and quadruply unsaturated, fatty acid esters, in four stages: (1) The enantiomers of 2,3:5,6-O-dicyclohexylidene-myo-inositol were resolved by crystallisation of their di(acetylmandelate) diastereoisomers. (2) The resulting diol was phosphorylated regio-selectively exclusively on the 1-O using the new reagent tri(2-cyanoethyl)phosphite. (3) With the 4-OH still unprotected, the glyceride was coupled using phosphate tri-ester methodology. (4) A final phosphorylation of the 4-O, followed by global deprotection under basic then acidic conditions, provided PI-4-P bearing a range of sn-1-stearoyl, sn-2-stearoyl, -oleoyl, -γ-linolenoyl and arachidonoyl, glycerides. Enzymological studies showed that the introduction of cis-unsaturated bonds has a measurable influence on the activity (relative Vmax) of SopB. Mono-unsaturated PI-4-P exhibited a five-fold higher activity, with a two-fold higher KM, over the saturated substrate, when presented in DOPC vesicles. Poly-unsaturated PI-4-P showed little further change with respect to the singly unsaturated species. This result, coupled with our previous report that saturated PI-4-P has much higher stored curvature elastic stress than PI, supports the hypothesis that the activity of inositide phosphatase SopB has a physical role in vivo.