Cryo-EM structure of the CDK2-cyclin A-CDC25A complex.

The cell division cycle 25 phosphatases CDC25A, B and C regulate cell cycle transitions by dephosphorylating residues in the conserved glycine-rich loop of CDKs to activate their activity. Here, we present the cryo-EM structure of CDK2-cyclin A in complex with CDC25A at 2.7 Å resolution, providing a detailed structural analysis of the overall complex architecture and key protein-protein interactions that underpin this 86 kDa complex. We further identify a CDC25A C-terminal helix that is critical for complex formation. Sequence conservation analysis suggests CDK1/2-cyclin A, CDK1-cyclin B and CDK2/3-cyclin E are suitable binding partners for CDC25A, whilst CDK4/6-cyclin D complexes appear unlikely substrates. A comparative structural analysis of CDK-containing complexes also confirms the functional importance of the conserved CDK1/2 GDSEID motif. This structure improves our understanding of the roles of CDC25 phosphatases in CDK regulation and may inform the development of CDC25-targeting anticancer strategies.

Targeting cyclin-dependent kinase 2 CDK2: Insights from molecular docking and dynamics simulation - A systematic computational approach to discover novel cancer therapeutics.

Global public health is confronted with significant challenges due to the prevalence of cancer and the emergence of treatment resistance. This work focuses on the identification of cyclin-dependent kinase 2 (CDK2) through a systematic computational approach to discover novel cancer therapeutics. A ligand-based pharmacophore model was initially developed using a training set of seven potent CDK2 inhibitors. The obtained most robust model was characterized by three features: one donor (|Don|) and two acceptors (|Acc|). Screening this model against the ZINC database resulted in identifying 108 hits, which underwent further molecular docking studies. The docking results indicated binding affinity, with energy values ranging from -6.59 kcal mol⁻¹ to -7.40 kcal mol⁻¹ compared to the standard Roscovitine. The top 10 compounds (Z1-Z10) selected from the docking data were further screened for ADMET profiling, ensuring their compliance with pharmacokinetic and toxicological criteria. The top 3 compounds (Z1-Z3) chosen from the docking were subjected to Density Functional Theory (DFT) studies. They revealed significant variations in electronic properties, providing insights into the reactivity, stability, and polarity of these compounds. Molecular dynamics simulations confirmed the stability of the ligand-protein complexes, with acceptable RMSD and RMSF values. Specifically, compound Z1 demonstrated stability, around 2.4 Å, and maintained throughout the 100 ns simulation period with minimal conformational changes, stable RMSD, and consistent protein-ligand interactions.

Molecular docking and MD simulation studies of 4-thiazol-N-(pyridin-2-yl)pyrimidin-2-amine derivatives as novel inhibitors targeted to CDK2/4/6.

PURPOSE: Nowadays, cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have been approved for treating metastatic breast cancer and have achieved inspiring curative effects. But some discoveries have indicated that CDK 4/6 are not the requisite factors in some cell types because CDK2 partly compensates for the inhibition of CDK4/6. Thus, it is urgent to design CDK2/4/6 inhibitors for significantly enhancing their potency. This study aims to explore the mechanism of the binding of CDK2/4/6 kinases and their inhibitors to design novel CDK2/4/6 inhibitors for significantly enhancing their potency in different kinds of cancers. MATERIALS AND METHODS: A series of 72 disparately functionalized 4-substituted N-phenylpyrimidin-2-amine derivatives exhibiting potent inhibitor activities against CDK2, CDK4 and CDK6 were collected to apply to this research. The total set of these derivatives was divided into a training set (54 compounds) and a test set (18 compounds). The derivatives were constructed through the sketch molecule module in SYBYL 6.9 software. A Powell gradient algorithm and Tripos force field were used to calculate the minimal structural energy and the minimized structure was used as the initial conformation for molecular docking. By the means of 3D-QSAR models, partial least squares (PLS) analysis, molecular dynamics (MD) simulations and binding free energy calculations, we can find the relationship between structure and biological activity. RESULTS: In this study, we used molecular docking, 3D-QSAR and molecular dynamics simulation methods to comprehensively analyze the interaction and structure-activity relationships of 72 new CDK2/4/6 inhibitors. We used detailed statistical data to reasonably verify the constructed 3D-QSAR models for three receptors (q2 of CDK2 = 0.714, R2pred = 0.764, q2 = 0.815; R2pred of CDK4 = 0.681, q2 = 0.757; R2pred of CDK6 = 0.674). MD simulations and decomposition energy analysis validated the reasonability of the docking results and identified polar interactions as crucial factors that influence the different bioactivities of the studied inhibitors of CDK2/4/6 receptors, especially the electrostatic interactions of Lys33/35/43 and Asp145/158/163. The nonpolar interaction with Ile10/12/19 was also critical for the differing potencies of the CDK2/4/6 inhibitors. We concluded that the following probably enhanced the bioactivity against CDK2/4/6 kinases: (1) electronegative groups at the N1-position and electropositive and moderate-sized groups at ring E; (2) electrogroups featured at R2; (3) carbon atoms at the X-position or ring C replaced by a benzene ring; and (4) an electrogroup as R4. CONCLUSION: Previous studies, to our knowledge, only utilized a single approach of 3D-QSAR and did not integrate this method with other sophisticated techniques such as molecular dynamics simulations to discover new potential inhibitors of CDK2, CDK4, or CDK6. So we applied the intergenerational technology, such as 3D-QSAR technology, molecular docking simulation techniques, molecular dynamics simulations and MMPBSA19/MMGBSA20-binding free energy calculations to statistically explore the correlations between the structure with biological activities. The constructed 3D-QSAR models of the three receptors were reasonable and confirmed by the excellent statistical data. We hope the results obtained from this work will provide some useful references for the development of novel CDK2/4/6 inhibitors.

Exploring the mechanism of action of spirooxindoles as a class of CDK2 inhibitors: a structure-based computational approach.

Cyclin-dependent kinase 2 (CDK2) regulates cell cycle checkpoints in the synthesis and mitosis phases and plays a pivotal role in cancerous cell proliferation. The activation of CDK2, influenced by various protein signaling pathways, initiates the phosphorylation process. Due to its crucial role in carcinogenesis, CDK2 is a druggable hotspot target to suppress cancer cell proliferation. In this context, several studies have identified spirooxindoles as an effective class of CDK2 inhibitors. In the present study, three spirooxindoles (SOI1, SOI2, and SOI3) were studied to understand their inhibitory mechanism against CDK2 through a structure-based approach. Molecular docking and molecular dynamics (MD) simulations were performed to explore their interactions with CDK2 at the molecular level. The calculated binding free energy for the spirooxindole-based CDK2 inhibitors aligned well with experimental results regarding CDK2 inhibition. Energy decomposition (ED) analysis identified key binding residues, including I10, G11, T14, R36, F82, K89, L134, P155, T158, Y159, and T160, in the CDK2 active site and T-loop phosphorylation. Molecular mechanics (MM) energy was identified as the primary contributor to stabilizing inhibitor binding in the CDK2 protein structure. Furthermore, the analysis of binding affinity revealed that the inhibitor SOI1 binds more strongly to CDK2 compared to the other inhibitors under investigation. It demonstrated a robust interaction with the crucial residue T160 in the T-loop phosphorylation site, responsible for kinase activation. These insights into the inhibitory mechanism are anticipated to contribute to the development of potential CDK2 inhibitors using the spirooxindole scaffold.

Cymbopogon proximus phytochemicals induce S-phase arrest in A549 lung cancer cell lines via CDK2/cyclin A2 inhibition: gas chromatography-mass spectrometry and molecular docking analyses.

Cymbopogon proximus comprises several phytoconstituent classes that are reported to possess anticancer activity; however, studies on the anticancer potentials of the plant are lacking. C. proximus was extracted using solvents with increasing polarity. In-vitro cytotoxic activity of C. proximus extracts was examined against liver (HepG2), lung (A549), prostate (PC3), and bone (MG63) cell lines using MTT assay in comparison to doxorubicin. Flow cytometry was used to analyze the cell cycle for identification of the phase of inhibition. Chemical composition of the most active fraction was examined using the GC/MS technique. Molecular docking was used to explore the mechanism of cytotoxicity against A549, and the results were confirmed by Western blot analysis. Petroleum ether fraction was the highly effective fraction against A549 with IC50 = 14.02 ± 2.79. GC/MS analysis of Pet.Eth led to the identification of nine compounds in unsaponifiable matter and 27 components in the saponifiable fraction. Di-N-octyl phthalate, 3-ß-hydroxylean-11.13(18)-dien-30-oic acid methyl ester, elemol hydrocarbons, linoelaidic acid and linoleic acid demonstrated the lowest docking binding scores and similar binding modes against CDK2 as compared to that attained by the native ligand R-Roscovitine "CDK2 ATP inhibitor". Western blot analysis demonstrated that CDK2/cyclinA2 protein expression has been suppressed in A549 cell lines by Pet.Eth fraction.

Slower CDK4 and faster CDK2 activation in the cell cycle.

Dysregulation of cyclin-dependent kinases (CDKs) impacts cell proliferation, driving cancer. Here, we ask why the cyclin-D/CDK4 complex governs cell cycle progression through the longer G1 phase, whereas cyclin-E/CDK2 regulates the shorter G1/S phase transition. We consider available experimental cellular and structural data including cyclin-E's high-level burst, sustained duration of elevated cyclin-D expression, and explicit solvent molecular dynamics simulations of the inactive monomeric and complexed states, to establish the conformational tendencies along the landscape of the distinct activation scenarios of cyclin-D/CDK4 and cyclin-E/CDK2 in the G1 phase and G1/S transition of the cell cycle, respectively. These lead us to propose slower activation of cyclin-D/CDK4 and rapid activation of cyclin-E/CDK2. We provide the mechanisms through which this occurs, offering innovative CDK4 drug design considerations. Our insightful mechanistic work addresses a compelling cell cycle regulation question and illuminates the distinct activation speeds between the G1 and the G1/S phases, which are crucial for function.

Discovery of macrocyclic CDK2/4/6 inhibitors with improved potency and DMPK properties through a highly efficient macrocyclic drug design platform.

Cyclin-dependent kinases (CDKs) are critical cell cycle regulators that are often overexpressed in tumors, making them promising targets for anti-cancer therapies. Despite substantial advancements in optimizing the selectivity and drug-like properties of CDK inhibitors, safety of multi-target inhibitors remains a significant challenge. Macrocyclization is a promising drug discovery strategy to improve the pharmacological properties of existing compounds. Here we report the development of a macrocyclization platform that enabled the highly efficient discovery of a novel, macrocyclic CDK2/4/6 inhibitor from an acyclic precursor (NUV422). Using dihedral angle scan and structure-based, computer-aided drug design to select an optimal ring-closing site and linker length for the macrocycle, we identified compound 8 as a potent new CDK2/4/6 inhibitor with optimized cellular potency and safety profile compared to NUV422. Our platform leverages both experimentally-solved as well as generative chemistry-derived macrocyclic structures and can be deployed to streamline the design of macrocyclic new drugs from acyclic starting compounds, yielding macrocyclic compounds with enhanced potency and improved drug-like properties.

kinCSM: Using graph-based signatures to predict small molecule CDK2 inhibitors.

Protein phosphorylation acts as an essential on/off switch in many cellular signaling pathways. This has led to ongoing interest in targeting kinases for therapeutic intervention. Computer-aided drug discovery has been proven a useful and cost-effective approach for facilitating prioritization and enrichment of screening libraries, but limited effort has been devoted providing insights on what makes a potent kinase inhibitor. To fill this gap, here we developed kinCSM, an integrative computational tool capable of accurately identifying potent cyclin-dependent kinase 2 (CDK2) inhibitors, quantitatively predicting CDK2 ligand-kinase inhibition constants (pKi ) and classifying different types of inhibitors based on their favorable binding modes. kinCSM predictive models were built using supervised learning and leveraged the concept of graph-based signatures to capture both physicochemical properties and geometry properties of small molecules. CDK2 inhibitors were accurately identified with Matthew's Correlation Coefficients (MCC) of up to 0.74, and inhibition constants predicted with Pearson's correlation of up to 0.76, both with consistent performances of 0.66 and 0.68 on a nonredundant blind test, respectively. kinCSM was also able to identify the potential type of inhibition for a given molecule, achieving MCC of up to 0.80 on cross-validation and 0.73 on the blind test. Analyzing the molecular composition of revealed enriched chemical fragments in CDK2 inhibitors and different types of inhibitors, which provides insights into the molecular mechanisms behind ligand-kinase interactions. kinCSM will be an invaluable tool to guide future kinase drug discovery. To aid the fast and accurate screening of CDK2 inhibitors, kinCSM is freely available at https://biosig.lab.uq.edu.au/kin_csm/.

Advances in Pyrazole Based Scaffold as Cyclin-dependent Kinase 2 Inhibitors for the Treatment of Cancer.

The transformation of a normal cell into a tumor cell is one of the initial steps in cell cycle deregulation. The cell cycle is regulated by cyclin-dependent kinases (CDKs) that belong to the protein kinase family. CDK2 is an enchanting target for specific genotype tumors since cyclin E is selective for CDK2 and the deregulation of specific cancer types. Thus, CDKs inhibitor, specifically CDK2/cyclin A-E, has the potential to be a valid cancer target as per the currently undergoing clinical trials. Most of the pyrazole scaffolds have shown selectivity and potency for CDK2 inhibitors. This review aims at examining pyrazole and pyrazole fused with other heterocyclic rings for antiproliferative activity. Based on the in vitro and molecular docking studies, the most potent analogues for CDK2 inhibition are exhibited by IC50 value. Moreover, the review emphasizes the various lead analogs of pyrazole hybrids which can be very potent and selective for anti-cancer drugs.

Exploring multi-target inhibitors using in silico approach targeting cell cycle dysregulator-CDK proteins.

Cyclin-dependent kinases (CDKs) belong to a family of multifunctional enzymes that control cell cycle modifications, transcription, and cell proliferation. Their dysfunctions result in different diseases like cancer making them an important drug target in oncology and beyond. The present study aims at identifying the selective inhibitors for ATP binding site in CDK proteins (CDK1, CDK2, CDK4, and CDK5) following a multi-target drug designing approach. Significant challenges lie in identifying the selective inhibitor for the ATP binding site as this region is highly conserved in all protein kinases. Molecular docking coupled with molecular dynamics simulation and free energy of binding calculations (MMPBSA/MMGBSA) were used to identify the potent competitive ATP binding site inhibitors. All the four proteins were docked against the library of drug-like compounds and the outcomes of the docking study were further analyzed by Molecular dynamics (total of 6µs) and MMPB/GBSA techniques. Five different inhibitors for structurally distant protein kinases, i.e. CDK1, CDK2, CDK4, and CDK5 are identified with the binding energy (ΔGbind-PB) in the range -18.24 to -28.43Kcal/mol. Mechanistic complexities associated with the binding of the inhibitor are unraveled by carefully analyzing the MD trajectories. It is observed that certain residues (Lys33, Asp127, Asp145, Tyr15, Gly16, Asn144) and regions are critical for the retention of inhibitors in active pocket, and significant conformational changes take place in the active site region as well as its neighbor following the entry of the ligand inside active pocket as inferred by RMSD and RMSF. It is observed that LIG3 and LIG4 are the best possible inhibitors as reflected from their high binding energy, interaction pattern, and their retention inside the active pocket. This study will facilitate the process of multi-target drug designing against CDK proteins and can be used in the development of potential therapeutics against different diseases.

Classical MD and metadynamics simulations on back-pocket binders of CDK2 and VEGFR2: a guidepost to design novel small-molecule dual inhibitors.

Cyclin-Dependent Kinase 2 (CDK2) and Vascular-Endothelial Growth Factor Receptor 2 (VEGFR2) are promising targets for the design of novel inhibitors in anticancer therapeutics. In a recent work, our group designed a set of potential dual inhibitors predicted to occupy an allosteric back pocket near the active site of both enzymes, but their dynamic and unbinding behavior was unclear. Here, we used molecular dynamics (MD) and metadynamics (meta-D) simulations to study two of these virtual candidates (herein called IQ2 and IQ3). Their binding mode was predicted to be similar to that observed in LQ5 and BAX, well-known back-pocket binders of CDK2 and VEGFR2, respectively, including H-bonding with critical residues such as Leu83/Cys113 and Asp145/Asp190 (but excepting H-bonding with Glu51/Glu111) in CDK2/VEGFR2, correspondingly. Likewise, while LQ5 and BAX unbound through the allosteric channel as expected for type-IIA inhibitors, IQ2 and IQ3 unbound via the ATP channel (except for CDK2-IQ2) as expected for type-I½A inhibitors. Interestingly, a C-C single/double bond difference between IQ2/IQ3, respectively, resulted associated with differences in the AS/T loop flexibility observed for CDK2. These insights will help developing scaffold modifications during an optimization stage, serving as a starting point to develop dual kinase inhibitors in challenging biological targets with a promising anticancer potential.Communicated by Ramaswamy H. Sarma.

Tanshinone IIA suppresses the progression of lung adenocarcinoma through regulating CCNA2-CDK2 complex and AURKA/PLK1 pathway.

Lung adenocarcinoma (LUAD) belongs to a subgroup of non-small cell lung cancer (NSCLC) with an increasing incidence all over the world. Tanshinone IIA (TSA), an active compound of Salvia miltiorrhiza Bunge., has been found to have anti-tumor effects on many tumors, but its anti-LUAD effect and its mechanism have not been reported yet. In this study, bio-information analysis was applied to characterize the potential mechanism of TSA on LUA, biological experiments were used to verify the mechanisms involved. TCGA, Pubchem, SwissTargetPrediction, Venny2.1.0, STRING, DAVID, Cytoscape 3.7.2, Omicshare, GEPIA, RSCBPDB, Chem Draw, AutoDockTools, and PyMOL were utilized for analysis in the bio-information analysis and network pharmacology. Our experiments in vitro focused on the anti-LUAD effects and mechanisms of TSA on LUAD cells (A549 and NCI-H1975 cells) via MTT, plate cloning, Annexin V-FITC and PI dual staining, flow cytometry, and western blot assays. A total of 64 differentially expressed genes (DEGs) of TSA for treatment of LUAD were screened out. Gene ontology and pathway analysis revealed characteristic of the DEGs network. After GEPIA-based DEGs confirmation, 46 genes were considered having significant differences. Further, 10 key DEGs (BTK, HSD11B1, ADAM33, TNNC1, THRA, CCNA2, AURKA, MIF, PLK1, and SORD) were identified as the most likely relevant genes from overall survival analysis. Molecular Docking results showed that CCNA2, CDK2 and PLK1 had the lowest docking energy. MTT and plate cloning assays results showed that TSA inhibited the proliferation of LUAD cells in a concentration-dependent manner. Annexin V-FITC and PI dual staining and flow cytometry assays results told that TSA promoted the apoptosis of the two LUAD cells in different degrees, and induced cycle arrest in the G1/S phase. Western blot results showed that TSA significantly down-regulated the expression of CCNA2, CDK2, AURKA, PLK1, and p-ERK. In summary, TSA could suppress the progression of LUAD by inducing cell apoptosis and arresting cell cycle, and these were done by regulating CCNA2-CDK2 complex and AURKA/PLK1 pathway. These findings are the first to demonstrate the molecular mechanism of TSA in treatment of LUAD combination of network bio-information analysis and biological experiments in vitro.

Discovery of New Pyrazolopyridine, Furopyridine, and Pyridine Derivatives as CDK2 Inhibitors: Design, Synthesis, Docking Studies, and Anti-Proliferative Activity.

New pyridine, pyrazoloyridine, and furopyridine derivatives substituted with naphthyl and thienyl moieties were designed and synthesized starting from 6-(naphthalen-2-yl)-2-oxo-4-(thiophen-2-yl)-1,2-dihydropyridine-3-carbonitrile (1). The chloro, methoxy, cholroacetoxy, imidazolyl, azide, and arylamino derivatives were prepared to obtain the pyridine--C2 functionalized derivatives. The derived pyrazolpyridine-N-glycosides were synthesized via heterocyclization of the C2-thioxopyridine derivative followed by glycosylation using glucose and galactose. The furopyridine derivative 14 and the tricyclic pyrido[3',2':4,5]furo[3,2-d]pyrimidine 15 were prepared via heterocyclization of the ester derivative followed by a reaction with formamide. The newly synthesized compounds were evaluated for their ability to in vitro inhibit the CDK2 enzyme. In addition, the cytotoxicity of the compounds was tested against four different human cancer cell lines (HCT-116, MCF-7, HepG2, and A549). The CDK2/cyclin A2 enzyme inhibitory results revealed that pyridone 1, 2-chloro-6-(naphthalen-2-yl)-4-(thiophen-2-yl)nicotinonitrile (4), 6-(naphthalen-2-yl)-4-(thiophen-2-yl)-1H-pyrazolo[3,4-b]pyridin-3-amine (8), S-(3-cyano-6-(naphthaen-2-yl)-4-(thiophen-2-yl)pyridin-2-yl) 2-chloroethanethioate (11), and ethyl 3-amino-6-(naphthalen-2-yl)-4-(thiophen-2-yl)furo[2,3-b]pyridine-2-carboxylate (14) are among the most active inhibitors with IC50 values of 0.57, 0.24, 0.65, 0.50, and 0.93 µM, respectively, compared to roscovitine (IC50 0.394 µM). Most compounds showed significant inhibition on different human cancer cell lines (HCT-116, MCF-7, HepG2, and A549) with IC50 ranges of 31.3-49.0, 19.3-55.5, 22.7-44.8, and 36.8-70.7 µM, respectively compared to doxorubicin (IC50 40.0, 64.8, 24.7 and 58.1 µM, respectively). Furthermore, a molecular docking study suggests that most of the target compounds have a similar binding mode as a reference compound in the active site of the CDK2 enzyme. The structural requirements controlling the CDK2 inhibitory activity were determined through the generation of a statistically significant 2D-QSAR model.

Chemical profiling, antiviral and antiproliferative activities of the essential oil of Phlomis aurea Decne grown in Egypt.

Here, we investigated the chemical composition of the edible Phlomis aurea oil and its anticancer potential on three human cancer cell lines, as well as its antiviral activity against Herpes simplex-1 (HSV-1). Exploring Phlomis aurea Decne essential oil by gas chromatography coupled with mass spectrometry (GC/MS) revealed the presence of four major components: germacrene D (51.56%), trans-ß-farnesene (11.36%), α-pinene (22.96%) & limonene (6.26%). An antiproliferative effect, as determined by the MTT assay, against human hepatic, breast and colon cancer cell lines, manifested IC50 values of 10.14, 328.02, & 628.43 µg mL-1, respectively. Cytotoxicity assay of the Phlomis oil against Vero cell lines revealed a safe profile within the range of 50 µg ml-1. Phlomis essential oil induced the apoptosis of HepG2 cells through increasing cell accumulation in sub G1 & G2/M phases, decreasing both S & G0/G1 phases of the cell cycle, triggering both caspases-3 &-9, and inhibiting cyclin dependent kinase-2 (CDK2). The antiviral activity of the oil against HSV-1 was investigated using the plaque reduction assay, which showed 80% of virus inhibition. Moreover, the molecular docking in silico study of the four major chemical constituents of the oil at the CDK2 binding site demonstrated marked interactions with the ATP-binding site residues through alkyl & Pi-alkyl interactions. Cell cycle distribution of HepG2 cells was studied using flow cytometry to highlight the apoptotic mechanistic approaches by measuring caspases-3 &-9 and CDK2 activities. Thus, the edible Phlomis oil can be regarded as a candidate for in vivo studies to prove that it is a promising natural antiviral/anticancer agent.

Discovery of New Coumarin-Based Lead with Potential Anticancer, CDK4 Inhibition and Selective Radiotheranostic Effect: Synthesis, 2D & 3D QSAR, Molecular Dynamics, In Vitro Cytotoxicity, Radioiodination, and Biodistribution Studies.

Novel 6-bromo-coumarin-ethylidene-hydrazonyl-thiazolyl and 6-bromo-coumarin-thiazolyl-based derivatives were synthesized. A quantitative structure activity relationship (QSAR) model with high predictive power r2 = 0.92, and RMSE = 0.44 predicted five compounds; 2b, 3b, 5a, 9a and 9i to have potential anticancer activities. Compound 2b achieved the best ΔG of -15.34 kcal/mol with an affinity of 40.05 pki. In a molecular dynamic study 2b showed an equilibrium at 0.8 Å after 3.5 ns, while flavopiridol did so at 0.5 Å after the same time (3.5 ns). 2b showed an IC50 of 0.0136 µM, 0.015 µM, and 0.054 µM against MCF-7, A-549, and CHO-K1 cell lines, respectively. The CDK4 enzyme assay revealed the significant CDK4 inhibitory activity of compound 2b with IC50 of 0.036 µM. The selectivity of the newly discovered lead compound 2b toward localization in tumor cells was confirmed by a radioiodination biological assay that was done via electrophilic substitution reaction utilizing the oxidative effect of chloramine-t. 131I-2b showed good in vitro stability up to 4 h. In solid tumor bearing mice, the values of tumor uptake reached a height of 5.97 ± 0.82%ID/g at 60 min p.i. 131I-2b can be considered as a selective radiotheranostic agent for solid tumors with promising anticancer activity.

BF3-OEt2 Catalyzed C3-Alkylation of Indole: Synthesis of Indolylsuccinimidesand Their Cytotoxicity Studies.

A simple and efficient BF3-OEt2 promoted C3-alkylation of indole has been developed to obtain3-indolylsuccinimidesfrom commercially available indoles and maleimides, with excellent yields under mild reaction conditions. Furthermore, anti-proliferative activity of these conjugates was evaluated against HT-29 (Colorectal), Hepg2 (Liver) and A549 (Lung) human cancer cell lines. One of the compounds, 3w, having N,N-Dimethylatedindolylsuccinimide is a potent congener amongst the series with IC50 value 0.02 µM and 0.8 µM against HT-29 and Hepg2 cell lines, respectively, and compound 3i was most active amongst the series with IC50 value 1.5 µM against A549 cells. Molecular docking study and mechanism of reaction have briefly beendiscussed. This method is better than previous reports in view of yield and substrate scope including electron deficient indoles.

Dynamic Docking Using Multicanonical Molecular Dynamics: Simulating Complex Formation at the Atomistic Level.

Multicanonical molecular dynamics (McMD)-based dynamic docking has been applied to predict the native binding configurations for several protein receptors and their ligands. Due to the enhanced sampling capabilities of McMD, it can exhaustively sample bound and unbound ligand configurations, as well as receptor conformations, and thus enables efficient sampling of the conformational and configurational space, not possible using canonical MD simulations. As McMD samples a wide configurational space, extensive analysis is required to study the diverse ensemble consisting of bound and unbound structures. By projecting the reweighted ensemble onto the first two principal axes obtained via principal component analysis of the multicanonical ensemble, the free energy landscape (FEL) can be obtained. Further analysis produces representative structures positioned at the local minima of the FEL, where these structures are then ranked by their free energy. In this chapter, we describe our dynamic docking methodology, which has successfully reproduced the native binding configuration for small compounds, medium-sized compounds, and peptide molecules.

Discriminative SKP2 Interactions with CDK-Cyclin Complexes Support a Cyclin A-Specific Role in p27KIP1 Degradation.

The SCFSKP2 ubiquitin ligase relieves G1 checkpoint control of CDK-cyclin complexes by promoting p27KIP1 degradation. We describe reconstitution of stable complexes containing SKP1-SKP2 and CDK1-cyclin B or CDK2-cyclin A/E, mediated by the CDK regulatory subunit CKS1. We further show that a direct interaction between a SKP2 N-terminal motif and cyclin A can stabilize SKP1-SKP2-CDK2-cyclin A complexes in the absence of CKS1. We identify the SKP2 binding site on cyclin A and demonstrate the site is not present in cyclin B or cyclin E. This site is distinct from but overlapping with features that mediate binding of p27KIP1 and other G1 cyclin regulators to cyclin A. We propose that the capacity of SKP2 to engage with CDK2-cyclin A by more than one structural mechanism provides a way to fine tune the degradation of p27KIP1 and distinguishes cyclin A from other G1 cyclins to ensure orderly cell cycle progression.

Cytotoxicity, Docking Study of New Fluorinated Fused Pyrimidine Scaffold: Thermal and Microwave Irradiation Synthesis.

BACKGROUND: Azolopyrimidines are imposed on the arena of drugs treated for cancer. The urgent need to discover new selective anticancer agents, paved the way to explore the antitumor significance of such fused systems. From the synthetic point of view, Microwave facilitated technique for synthesis is very strongly associated with green method in chemistry field. AIM: Our aim is to synthesize bioactive compounds using docking simulation run by MOE program to explore the binding mode of the most active enzyme inhibitor among the target compounds. METHODS: In addition to the use of conventional heating, the MARS system of CEM utilized for Microwave irradiation that is equipped with a multi-mode platform with a magnetic stirring plate and a rotor that allows the parallel processing of many vessels per batch. All the synthesized compounds were tested for their anticancer activity against hepatic cancer (HepG-2), breast cancer (MCF-7) and colon cancer (HCT-116). Screening against the cancer cell lines was performed, using doxorubicin as a reference drug. Docking studies were conducted using MOE software. RESULTS: A novel series of fluorinated fused-pyrimidine namely, pyrazolopyrimidine, triazolopyrimidine and pyrimidobenzimidazole were designed and synthesized conventionally and under microwave irradiations. The mechanistic pathways as well as the structure of all products were debated and demonstrated based on all possible spectral data. In-vitro examination of the novel prepared derivatives versus the three different human cancer cell lines [hepatic cancer (HepG-2), breast cancer (MCF-7) and colon cancer (HCT-116)] was evaluated to estimate their actual activity. CONCLUSION: We have developed a simple, facile, and efficient procedure for the formation of new series of azolopyrimidines. All spectra of all products were investigated deliberately to confirm their structures. The anti-cancer activity has been examined against three cancer cell lines e.g. HepG-2, MCF-7 and HCT116. Molecular modeling study was carried out in order to rationalize the in vitro anti-tumor results.

Synthesis, In Silico Prediction and In Vitro Evaluation of Antitumor Activities of Novel Pyrido[2,3-d]pyrimidine, Xanthine and Lumazine Derivatives.

Ethyl 5-arylpyridopyrimidine-6-carboxylates 3a-d were prepared as a one pot three component reaction via the condensation of different aromatic aldehydes and ethyl acetoacetate with 6-amino-1-benzyluracil 1a under reflux condition in ethanol. Additionally, condensation of ethyl 2-(2-hydroxybenzylidene) acetoacetate with 6-amino-1-benzyluracil in DMF afforded 6-acetylpyridopyrimidine-7-one 3e; a facile, operationally, simple and efficient one-pot synthesis of 8-arylxanthines 6a-f is reported by refluxing 5,6-diaminouracil 4 with aromatic aldehydes in DMF. Moreover, 6-aryllumazines 7a-d was obtained via the reaction of 5,6-diaminouracil with the appropriate aromatic aldehydes in triethyl orthoformate under reflux condition. The synthesized compounds were characterized by spectral (1H-NMR, 13C-NMR, IR and mass spectra) and elemental analyses. The newly synthesized compounds were screened for their anticancer activity against lung cancer A549 cell line. Furthermore, a molecular-docking study was employed to determine the possible mode of action of the synthesized compounds against a group of proteins highly implicated in cancer progression, especially lung cancer. Docking results showed that compounds 3b, 6c, 6d, 6e, 7c and 7d were the best potential docked compounds against most of the tested proteins, especially CDK2, Jak2, and DHFR proteins. These results are in agreement with cytotoxicity results, which shed a light on the promising activity of these novel six heterocyclic derivatives for further investigation as potential chemotherapeutics.