Specific Overexpression of Cyclin E·CDK2 in Early Preinvasive and Primary Breast Tumors in Female ACI Rats Induced by Estrogen

Cyclins and cyclin-dependent kinases: from biology to tumorigenesis and therapeutic opportunities

The discussion on cell proliferation cannot be continued without taking a look at the cell cycle regulatory machinery. Cyclin-dependent kinases (CDKs), cyclins, and CDK inhibitors (CKIs) are valuable members of this system and their equilibrium guarantees the proper progression of the cell cycle. As expected, any dysregulation in the expression or function of these components can provide a platform for excessive cell proliferation leading to tumorigenesis. The high frequency of CDK abnormalities in human cancers, together with their druggable structure has raised the possibility that perhaps designing a series of inhibitors targeting CDKs might be advantageous for restricting the survival of tumor cells; however, their application has faced a serious concern, since these groups of serine-threonine kinases possess non-canonical functions as well. In the present review, we aimed to take a look at the biology of CDKs and then magnify their contribution to tumorigenesis. Then, by arguing the bright and dark aspects of CDK inhibition in the treatment of human cancers, we intend to reach a consensus on the application of these inhibitors in clinical settings.

Estrogens—Origin of Centrosome Defects in Human Cancer?

Estrogens are associated with a variety of diseases and play important roles in tumor development and progression. Centrosome defects are hallmarks of human cancers and contribute to ongoing chromosome missegragation and aneuploidy that manifest in genomic instability and tumor progression. Although several mechanisms underlie the etiology of centrosome aberrations in human cancer, upstream regulators are hardly known. Accumulating experimental and clinical evidence points to an important role of estrogens in deregulating centrosome homeostasis and promoting karyotype instability. Here, we will summarize existing literature of how natural and synthetic estrogens might contribute to structural and numerical centrosome defects, genomic instability and human carcinogenesis.

Development of potential inhibitors of cell division protein kinase 2 by ligand based drug design

Cyclin-dependent kinases (CDKs) are commonly known by their role in cell cycle regulation which affects cancer mechanism. In many cancer types, CDKs show extreme activity or CDK inhibiting proteins are dysfunctional. Specifically, CDK2 plays an indispensable role in cell division especially in the G1/S phase and DNA damage repair. Therefore, it is important to find new potential CDK2 inhibitors. In this study, ligand-based drug design is used to design new potential CDK2 inhibitors. Y8 L ligand is obtained from the X-ray crystal structure of human CDK2 (PDB ID: 2XNB) (www.pdb.org) and used as a structure model. By adding hydrophilic and hydrophobic groups to the structure, a training set of 36 molecules is generated. Each molecule examined with Spartan’14 and optimized structures are used for docking to CDK2 structure by AutoDock and AutoDock Vina programs. Ligand-amino acid interactions are analysed with Discovery Studio Visualizer. Van der Waals, Pi-Pi T-shaped, alkyl, pi-alkyl, conventional hydrogen bond and carbon-hydrogen bond interactions are observed. By docking results and viewed interactions, some molecules are identified and discussed as potential CDK2 inhibitors. Additionally, 8 different QSAR descriptors obtained from Spartan’14, Preadmet and ALOGPS 2.1 programs are investigated with multiple linear regulation (MLR) analysis with SPSS program for their impact on affinity value.

Design, Synthesis, Molecular Modeling, Anticancer Studies, and Density Functional Theory Calculations of 4-(1,2,4-Triazol-3-ylsulfanylmethyl)-1,2,3-triazole Derivatives

New conjugates of substituted 1,2,3-triazoles linked to 1,2,4-triazoles were synthesized starting from the appropriate S-propargylated 1,2,4-triazoles 7 and 8. Ligation of 1,2,4-triazoles to the 1,2,3-triazole core was performed through Cu(I)-catalyzed cycloaddition of 1,2,4-triazole-based alkyne side chain 7 and/or 8 with several un/functionalized alkyl- and/or aryl-substituted azides 9-15 to afford the desired 1,4-disubstituted 1,2,3-triazoles 16-27, using both classical and microwave methods. After their spectroscopic characterization (infrared, 1H, 13C nuclear magnetic resonance, and elemental analyses), an anticancer screening was carried out against some cancer cell lines including human colon carcinoma (Caco-2 and HCT116), human cervical carcinoma (HeLa), and human breast adenocarcinoma (MCF-7). The outcomes of this exploration revealed that compounds 17, 22, and 25 had a significant anticancer activity against MCF-7 and Caco-2 cancer cell lines with IC50 values of 0.31 and 4.98 μM, respectively, in relation to the standard reference drug, doxorubicin. Enzyme-docking examination was executed onto cyclin-dependent kinase 2; a promising aim for cancer medication. Synthesized compounds acquiring highest potency showcased superior interactions with the active site residue of the target protein and exhibited minimum binding energy. Finally, the density functional theory (DFT) calculations were carried out to confirm the outcomes of the molecular docking and the experimental findings. The chemical reactivity descriptors such as softness (δ), global hardness (η), electronegativity (χ), and electrophilicity were calculated from the levels of the predicted frontier molecular orbitals and their energy gap. The DFT results and the molecular docking calculation results explained the activity of the most expectedly active compounds 17, 22, and 25.

Reduced RBX1 expression induces chromosome instability and promotes cellular transformation in high-grade serous ovarian cancer precursor cells

Despite high-grade serous ovarian cancer (HGSOC) being the most common and lethal gynecological cancer in women, the early etiological events driving disease development remain largely unknown. Emerging evidence now suggests that chromosome instability (CIN; ongoing changes in chromosome numbers) may play a central role in the development and progression of HGSOC. Importantly, genomic amplification of the Cyclin E1 gene (CCNE1) contributes to HGSOC pathogenesis in ~20% of patients, while Cyclin E1 overexpression induces CIN in model systems. Cyclin E1 levels are normally regulated by the SCF (SKP1-CUL1-FBOX) complex, an E3 ubiquitin ligase that includes RBX1 as a core component. Interestingly, RBX1 is heterozygously lost in ~80% of HGSOC cases and reduced expression corresponds with worse outcomes, suggesting it may be a pathogenic event. Using both short (siRNA) and long (CRISPR/Cas9) term approaches, we show that reduced RBX1 expression corresponds with significant increases in CIN phenotypes in fallopian tube secretory epithelial cells, a cellular precursor of HGSOC. Moreover, reduced RBX1 expression corresponds with increased Cyclin E1 levels and anchorage-independent growth. Collectively, these data identify RBX1 as a novel CIN gene with pathogenic implications for HGSOC.

Synthesis, Biological Assessment, and Structure Activity Relationship Studies of New Flavanones Embodying Chromene Moieties

Novel flavanones that incorporate chromene motifs are synthesized via a one-step multicomponent reaction. The structures of the new chromenes are elucidated by using IR, ¹H-NMR, ¹³C-NMR, ¹H-¹H COSY, HSQC, HMBC, and elemental analysis. The new compounds are screened for their in vitro antimicrobial and cytotoxic activities. The antimicrobial properties are investigated and established against seven human pathogens, employing the agar well diffusion method and the minimum inhibitory concentrations. A majority of the assessed derivatives are found to exhibit significant antimicrobial activities against most bacterial strains, in comparison to standard reference drugs. Moreover, their cytotoxicity is appraised against four different human carcinoma cell lines: human colon carcinoma (HCT-116), human hepatocellular carcinoma (HepG-2), human breast adenocarcinoma (MCF-7), and adenocarcinoma human alveolar basal epithelial cell (A-549). All the desired compounds are subjected to in-silico studies, forecasting their drug likeness, bioactivity, and the absorption, distribution, metabolism, and excretion (ADME) properties prior to their synthetic assembly. The in-silico molecular docking evaluation of all the targeted derivatives is undertaken on gyrase B and the cyclin-dependent kinase. The in-silico predicted outcomes were endorsed by the in vitro studies.

Design, synthesis and molecular docking of novel pyrazolo[1,5-a][1,3,5]triazine derivatives as CDK2 inhibitors

Cyclin Dependent Kinases CDKs unpredictable activity has been accounted for a wide assortment of human malignancies, so it might be conceivable to design pharmacologically relevant ligands that go about as specific and potent inhibitors of CDK2 action. In this respect, a series of novel pyrazolo[1,5-a][1,3,5]triazine derivatives were designed, synthesized and evaluated for CDK2 enzyme inhibitory and anticancer activity. Compounds 9f and 10c showed best CDK2 inhibition among the newly synthesized compounds, with percent inhibition at 82.38%, and 81.96% against CDK2 and IC₅₀ of 1.85 and 2.09 µM, respectively. Additionally, the newly synthesized compounds were tested for their antiproliferative activity against 60 NCI cell lines. Molecular docking revealed the binding mode of these new compounds into the roscovitine binding site of CDK2 enzyme (PDB code: 3ddq). Conclusively, pyrazolotriazine derivatives represent a talented starting point for further study as anticancer drug.

Design, Synthesis and Anticancer Activity of New Thiazole-Tetrazole or Triazole Hybrid Glycosides Targeting CDK-2 via Structure-Based Virtual Screening

Background & Objective:

The target tetrazole glycosides were synthesized by construction of ring system by cycloaddition reaction of benzothiazole-linked nitrile derivative and sodium azide followed by N-glycosylation process and deprotection.

Methods:

The triazole glycosides were prepared by applying click approach involving dipolar cycloaddition of benzothiazole possessing alkyne functionality and different glycosyl azides. The products incorporating acyclic analogs of sugar moieties were synthesized through alkylation using acyclic oxygenated halides.

Results:

The anticancer activity was studied against human breast adenocarcinoma cells (MCF-7) and human normal Retina pigmented epithelium cells (RPE-1). High activities were revealed by three compounds with IC50 values 11.9-16.5 µM compared to doxorubicin (18.6 µM) in addition to other four derivatives with good inhibition activities.

Conclusion:

Enzyme docking investigation was performed into cyclin-dependent kinase 2 (CDK2); a potential target for cancer medication. Compounds which have possessed highest activities revealed good fitting inside the binding site of the protein molecular surface and showed minimum binding energy.

Role of aneuploidy in the carcinogenic process: Part 3 of the report of the 2017 IWGT workgroup on assessing the risk of aneugens for carcinogenesis and hereditary diseases

Aneuploidy is regarded as a hallmark of cancer, however, its role is complex with both pro- and anti-carcinogenic effects evident. In this IWGT review, we consider the role of aneuploidy in cancer biology; cancer risk associated with constitutive aneuploidy; rodent carcinogenesis with known chemical aneugens; and chemotherapy-related malignant neoplasms. Aneuploidy is seen at various stages in carcinogenesis. However, the relationship between induced aneuploidy occurring after exposure and clonal aneuploidy present in tumours is not clear. Recent evidence indicates that the induction of chromosomal instability (CIN), may be more important than aneuploidy per se, in the carcinogenic process. Down Syndrome, trisomy 21, is associated with altered hematopoiesis in utero which, in combination with subsequent mutations, results in an increased risk for acute megakaryoblastic and lymphoblastic leukemias. In contrast, there is reduced cancer risk for most solid tumours in Down Syndrome. Mouse models with high levels of aneuploidy are also associated with increased cancer risk for particular tumours with long latencies, but paradoxically other types of tumour often show decreased incidence. The aneugens reviewed that induce cancer in humans and animals all possess other carcinogenic properties, such as mutagenicity, clastogenicity, cytotoxicity, organ toxicities, hormonal and epigenetic changes which likely account for, or interact with aneuploidy, to cause carcinogenesis. Although the role that aneuploidy plays in carcinogenesis has not been fully established, in many cases, it may not play a primary causative role. Tubulin-disrupting aneugens that do not possess other properties linked to carcinogenesis, were not carcinogenic in rodents. Similarly, in humans, for the tubulin-disrupting aneugens colchicine and albendazole, there is no reported association with increased cancer risk. There is a need for further mechanistic studies on agents that induce aneuploidy, particularly by mechanisms other than tubulin disruption and to determine the role of aneuploidy in pre-neoplastic events and in early and late stage neoplasia.

Targeting cyclin-dependent kinases in human cancers: from small molecules to Peptide inhibitors

Cyclin-dependent kinases (CDK/Cyclins) form a family of heterodimeric kinases that play central roles in regulation of cell cycle progression, transcription and other major biological processes including neuronal differentiation and metabolism. Constitutive or deregulated hyperactivity of these kinases due to amplification, overexpression or mutation of cyclins or CDK, contributes to proliferation of cancer cells, and aberrant activity of these kinases has been reported in a wide variety of human cancers. These kinases therefore constitute biomarkers of proliferation and attractive pharmacological targets for development of anticancer therapeutics. The structural features of several of these kinases have been elucidated and their molecular mechanisms of regulation characterized in depth, providing clues for development of drugs and inhibitors to disrupt their function. However, like most other kinases, they constitute a challenging class of therapeutic targets due to their highly conserved structural features and ATP-binding pocket. Notwithstanding, several classes of inhibitors have been discovered from natural sources, and small molecule derivatives have been synthesized through rational, structure-guided approaches or identified in high throughput screens. The larger part of these inhibitors target ATP pockets, but a growing number of peptides targeting protein/protein interfaces are being proposed, and a small number of compounds targeting allosteric sites have been reported.

Oxidative stress specifically downregulates survivin to promote breast tumour formation

Background:

Breast cancer, a heterogeneous disease has been broadly classified into oestrogen receptor positive (ER+) or oestrogen receptor negative (ER−) tumour types. Each of these tumours is dependent on specific signalling pathways for their progression. While high levels of survivin, an anti-apoptotic protein, increases aggressive behaviour in ER− breast tumours, oxidative stress (OS) promotes the progression of ER+ breast tumours. Mechanisms and molecular targets by which OS promotes tumourigenesis remain poorly understood.

Results:

DETA-NONOate, a nitric oxide (NO)-donor induces OS in breast cancer cell lines by early re-localisation and downregulation of cellular survivin. Using in vivo models of HMLE^HRAS xenografts and E2-induced breast tumours in ACI rats, we demonstrate that high OS downregulates survivin during initiation of tumourigenesis. Overexpression of survivin in HMLE^HRAS cells led to a significant delay in tumour initiation and tumour volume in nude mice. This inverse relationship between survivin and OS was also observed in ER+ human breast tumours. We also demonstrate an upregulation of NADPH oxidase-1 (NOX1) and its activating protein p67, which are novel markers of OS in E2-induced tumours in ACI rats and as well as in ER+ human breast tumours.

Conclusion:

Our data, therefore, suggest that downregulation of survivin could be an important early event by which OS initiates breast tumour formation.