Antitumor Activity of Pyridocarbazole and Benzopyridoindole Derivatives that Inhibit Protein Kinase CK2

Bioactivities and Action Mechanisms of Ellipticine Derivatives Reported Prior to 2023

Currently, natural products are one of the priceless options for finding novel chemical pharmaceutical entities. Ellipticine is a naturally occurring alkaloid isolated from the leaves of Ochrosia elliptica Labill. Ellipticine and its derivatives are characterized by multiple biological activities. The purpose of this review was to provide a critical and systematic assessment of ellipticine and its derivatives as bioactive molecules over the last 60 years. Publications focused mainly on the total synthesis of alkaloids of this type without any evaluation of bioactivity have been excluded. We have reviewed papers dealing with the synthesis, bioactivity evaluation and mechanism of action of ellipticine and its derivatives. It was found that ellipticine and its derivatives showed cytotoxicity, antimicrobial ability, and anti-inflammatory activity, among which cytotoxicity toward cancer cell lines was the most investigated aspect. The inhibition of DNA topoisomerase II was the most relevant mechanism for cytotoxicity. The PI3K/AKT pathway, p53 pathway, and MAPK pathway were also closely related to the antiproliferative ability of these compounds. In addition, the structure-activity relationship was deduced, and future prospects were outlined. We are confident that these findings will lay a scientific foundation for ellipticine-based drug development, especially for anticancer agents.

Formulation and Investigation of CK2 Inhibitor-Loaded Alginate Microbeads with Different Excipients

The aim of this study was to formulate and characterize CK2 inhibitor-loaded alginate microbeads via the polymerization method. Different excipients were used in the formulation to improve the penetration of an active agent and to stabilize our preparations. Transcutol® HP was added to the drug-sodium alginate mixture and polyvinylpyrrolidone (PVP) was added to the hardening solution, alone and in combination. To characterize the formulations, mean particle size, scanning electron microscopy analysis, encapsulation efficiency, swelling behavior, an enzymatic stability test and an in vitro dissolution study were performed. The cell viability assay and permeability test were also carried out on the Caco-2 cell line. The anti-oxidant and anti-inflammatory effects of the formulations were finally evaluated. The combination of Transcutol® HP and PVP in the formulation of sodium alginate microbeads could improve the stability, in vitro permeability, anti-oxidant and anti-inflammatory effects of the CK2 inhibitor.

S16020 pyridocarbazole derivatives display high activity to lung cancer cells

BACKGROUND

Despite the dynamic development of medicine, globally cancer diseases remain the second leading cause of death. Therefore, there is a strong necessity to improve chemotherapy regimens and search for new anticancer agents. Pyridocarbazoles are compounds with confirmed antitumor properties based on multimodal mechanisms, i.a. DNA intercalation and topoisomerase II-DNA complex inhibition. One of them, S16020, displayed a wide spectrum of activity.

OBJECTIVE

The aim of the study was to investigate the antitumor potency of six S16020 derivatives, synthesized according to the SAR (structure-activity relationship) method.

METHODS

The biological evaluation included influence on cancer cell viability, proliferation, and migration, as well as P-glycoprotein activity. NHDF, A549, MCF-7, LoVo, and LoVo/DX cell lines were used in the study.

RESULTS

All derivatives displayed low toxicity to normal (NHDF) cells at 1 and 2 µM (≤ 20% of cell growth inhibition). The highest reduction in cell viability was noted in A549 cells which was accompanied by significant disruption of cells proliferation and motility. Compound 1 exhibited the strongest cytotoxic, antiproliferative, and antimigratory effects, higher than the reference olivacine. A significant reduction in P-glycoprotein activity was found for derivatives 6 and 1.

CONCLUSION

S16020 derivatives could be considered as potential candidates for new anticancer drugs.

Simultaneous CK2/TNIK/DYRK1 inhibition by 108600 suppresses triple negative breast cancer stem cells and chemotherapy-resistant disease

Triple negative breast cancer (TNBC) remains challenging because of heterogeneous responses to chemotherapy. Incomplete response is associated with a greater risk of metastatic progression. Therefore, treatments that target chemotherapy-resistant TNBC and enhance chemosensitivity would improve outcomes for these high-risk patients. Breast cancer stem cell-like cells (BCSCs) have been proposed to represent a chemotherapy-resistant subpopulation responsible for tumor initiation, progression and metastases. Targeting this population could lead to improved TNBC disease control. Here, we describe a novel multi-kinase inhibitor, 108600, that targets the TNBC BCSC population. 108600 treatment suppresses growth, colony and mammosphere forming capacity of BCSCs and induces G2M arrest and apoptosis of TNBC cells. In vivo, 108600 treatment of mice bearing triple negative tumors results in the induction of apoptosis and overcomes chemotherapy resistance. Finally, treatment with 108600 and chemotherapy suppresses growth of pre-established TNBC metastases, providing additional support for the clinical translation of this agent to clinical trials.

Protein kinase 2 (CK2): a potential regulator of immune cell development and function in cancer

Protein kinase CK2, formally known as casein kinase II, is ubiquitously expressed and highly conserved serine/threonine or tyrosine kinase enzyme that regulates diverse signaling pathways responsible for cellular processes (i.e., cell proliferation and apoptosis) via interactions with over 500 known substrates. The enzyme's physiological interactions and cellular functions have been widely studied, most notably in the blood and solid malignancies. CK2 has intrinsic role in carcinogenesis as overexpression of CK2 subunits (α, α`, and β) and deregulation of its activity have been linked to various forms of cancers. CK2 also has extrinsic role in cancer stroma or in the tumor microenvironment (TME) including the immune cells. However, very few research studies have focused on extrinsic role of CK2 in regulating immune responses as a therapeutic alternative for cancer. The following review discusses CK2's regulation of key signaling events [Nuclear factor kappa B (NF-κB), Janus kinase/signal transducer and activators of transcription (JAK/STAT), Hypoxia inducible factor-1alpha (HIF-1α), Cyclooygenase-2 (COX-2), Extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK), Notch, Protein kinase B/AKT, Ikaros and Wnt] that can influence the development and function of immune cells in cancer. Potential clinical trials using potent CK2 inhibitors will facilitate and improve the treatment of human malignancies.

Two Antagonistic Microtubule Targeting Drugs Act Synergistically to Kill Cancer Cells

Paclitaxel is a microtubule stabilizing agent and a successful drug for cancer chemotherapy inducing, however, adverse effects. To reduce the effective dose of paclitaxel, we searched for pharmaceutics which could potentiate its therapeutic effect. We screened a chemical library and selected Carba1, a carbazole, which exerts synergistic cytotoxic effects on tumor cells grown in vitro, when co-administrated with a low dose of paclitaxel. Carba1 targets the colchicine binding-site of tubulin and is a microtubule-destabilizing agent. Catastrophe induction by Carba1 promotes paclitaxel binding to microtubule ends, providing a mechanistic explanation of the observed synergy. The synergistic effect of Carba1 with paclitaxel on tumor cell viability was also observed in vivo in xenografted mice. Thus, a new mechanism favoring paclitaxel binding to dynamic microtubules can be transposed to in vivo mouse cancer treatments, paving the way for new therapeutic strategies combining low doses of microtubule targeting agents with opposite mechanisms of action.

Alternaria toxins as casein kinase 2 inhibitors and possible consequences for estrogenicity: a hybrid in silico/in vitro study

Emerging mycotoxins produced by Alternaria spp. were previously reported to exert cytotoxic, genotoxic, but also estrogenic effects in human cells. The involved mechanisms are very complex and not fully elucidated yet. Thus, we followed an in silico target fishing approach to extend knowledge on the possible biological targets underlying the activity of alternariol, taken as the signature compound of Alternaria toxins. Combining ligand-based screening and structure-based modeling, the ubiquitous casein kinase 2 (CK2) was identified as a potential target for the compound. This result was validated in a cell-free in vitro CK2 activity assay, where alternariol inhibited CK2 with an IC₅₀ of 707 nM. As CK2 was recently discussed to influence estrogen receptor (ER) transcription and DNA-binding affinity, we assessed a potential impact on the mRNA levels of ERα or ERβ by qRT-PCR and on nuclear localization of the receptors by confocal microscopy, using estrogen-sensitive Ishikawa cells as a model. While AOH did not affect the transcription of ERα or ERβ, an increase in nuclear localization of ERα after incubation with 10 µM AOH was observed. However, this effect might be due to ER binding affinity and therefore estrogenicity of AOH. Furthermore, in silico docking simulation revealed not only AOH, but also a number of other Alternaria toxins as potential inhibitors of CK2, including alternariol monomethyl ether and the perylene quinone derivative altertoxin II (ATX-II). These findings were representatively confirmed in vitro for the perylene quinone derivative altertoxin II, which was found to inhibit the kinase with an IC₅₀ of 5.1 µM. Taken together, we propose CK2 inhibition as an additional mechanism to consider in future studies for alternariol and several other Alternaria toxins.

Synthetic Optimization of Ellipticine and Antitumor Activity of Novel Hexacyclic Derivatives of Ellipticine

Background:

For decades, a great deal of research work has been done to synthesize ellipticine and its derivatives because of their potential antitumor properties and anti-HIV activities. However, the resonance structures in different media, a low level of solubility at physiological pH and systemic toxicity have prevented the use of ellipticine as a therapeutic agent. Besides, the low yield and complex steps of ellipticine synthesis limit its application.

Methods:

A high-yield synthetic procedure of ellipticine has been optimized, and the total yield was up to 50% without silica gel column chromatography. Novel hexacyclic ellipticine derivatives were synthesized by coupling ellipticine with o-aminobenzoic acid. Their cytotoxicities against HCT116, MGC803, HT29 and MCF-7 tumor cells were evaluated.

Results:

The synthesis process of ellipticine was optimized, and the total yield of the synthetic route was increased to 50% through several operation steps optimization. Fourteen ellipticine hexacyclic derivatives were synthesized. The synthetic compounds were screened for anti-tumor activity in vivo and in vitro, and some of the derivatives had good anti-tumor activity.

Conclusion:

Compared with ellipticine, the compound 1l showed higher antitumor activity and better tolerance to tumor models. The compound 1l treatment increased the percentage of late apoptotic cells from 3.1% (DMSO) to 21.6% (20.0 μM) in NCI-H460 cells. It also was observed the effect of 1l on G2 phase arrest was similar as that of ellipticine. The mechanism of action indicated compound 1l could be a topoisomerase IIα poison. These studies provided the basis for the pharmacodynamics and toxicology of ellipticine, and further clarifies the structureactivity relationship of antitumor activity of ellipticine.

Carbazole scaffolds in cancer therapy: a review from 2012 to 2018

For over half a century, the carbazole skeleton has been the key structural motif of many biologically active compounds including natural and synthetic products. Carbazoles have taken an important part in all the existing anti-cancer drugs because of their discovery from a large variety of organisms, including bacteria, fungi, plants, and animals. In this article, we specifically explored the literature from 2012 to 2018 on the anti-tumour activities reported to carbazole derivatives and we have critically collected the most significant data. The most described carbazole anti-tumour agents were classified according to their structure, starting from the tricyclic–carbazole motif to fused tetra-, penta-, hexa- and heptacyclic carbazoles. To date, three derivatives are available on the market and approved in cancer therapy.

Role of protein kinase CK2 in antitumor drug resistance

Drug resistance represents the major reason of pharmacological treatment failure. It is supported by a broad spectrum of mechanisms, whose molecular bases have been frequently correlated to aberrant protein phosphorylation. CK2 is a constitutively active protein kinase which phosphorylates hundreds of substrates; it is expressed in all cells, but its level is commonly found higher in cancer cells, where it plays anti-apoptotic, pro-migration and pro-proliferation functions. Several evidences support a role for CK2 in processes directly responsible of drug resistance, such as drug efflux and DNA repair; moreover, CK2 intervenes in signaling pathways which are crucial to evade drug response (as PI3K/AKT/PTEN, NF-κB, β-catenin, hedgehog signaling, p53), and controls the activity of chaperone machineries fundamental in resistant cells. Interestingly, a panel of specific and effective inhibitors of CK2 is available, and several examples are known of their efficacy in resistant cells, with synergistic effect when used in combination with conventional drugs, also in vivo. Here we analyze and discuss evidences supporting the hypothesis that CK2 targeting represents a valuable strategy to overcome drug resistance.

2-Aminothiazole Derivatives as Selective Allosteric Modulators of the Protein Kinase CK2. 1. Identification of an Allosteric Binding Site

CK2 is a ubiquitous Ser/Thr protein kinase involved in the control of various signaling pathways and is known to be constitutively active. In the present study, we identified aryl 2-aminothiazoles as a novel class of CK2 inhibitors, which displayed a non-ATP-competitive mode of action and stabilized an inactive conformation of CK2 in solution. Enzyme kinetics studies, STD NMR, circular dichroism spectroscopy, and native mass spectrometry experiments demonstrated that the compounds bind in an allosteric pocket outside the ATP-binding site. Our data, combined with molecular docking studies, strongly suggested that this new binding site was located at the interface between the αC helix and the flexible glycine-rich loop. A first hit optimization led to compound 7, exhibiting an IC₅₀ of 3.4 μM against purified CK2α in combination with a favorable selectivity profile. Thus, we identified a novel class of CK2 inhibitors targeting an allosteric pocket, offering great potential for further optimization into anticancer drugs.

Protein Kinase CK2, a Potential Therapeutic Target in Carcinoma Management

The Protein kinase CK2 (formerly known as casein kinase 2) is a highly conserved serine/ threonine kinase overexpressed in various human carcinomas and its high expression often correlates with poor prognosis. CK2 protein is localized in the nucleus of many tumor cells and correlates with clinical features in many cases. Increased expression of CK2 in mice results in the development of various types of carcinomas (both solids and blood related tumors, such as (breast carcinoma, lymphoma, etc), which reveals its carcinogenic properties. CK2 plays essential roles in many key biological processes related to carcinoma, including cell apoptosis, DNA damage responses and cell cycle regulation. CK2 has become a potential anti-carcinoma target. Various CK2 inhibitors have been developed with anti-neoplastic properties against a variety of carcinomas. Some CK2 inhibitors have showed good results in in vitro and pre-clinical models, and have even entered in clinical trials. This article will review effects of CK2 and its inhibitors on common carcinomas in in vitro and pre-clinical studies.

Novel halogenated pyrido[2,3-a]carbazoles with enhanced aromaticity as potent anticancer and antioxidant agents: rational design and microwave assisted synthesis

Design and synthesis a series of pyrido[2,3-a]carbazoles for their anticancer and antioxidant activity.

Transition-Metal-Free Access to Pyridocarbazoles from 2-Alkynylindole-3-carbaldehydes via Azomethine Ylide

An efficient approach for the synthesis of functionalized tetrahydro-pyrido/quinolinocarbazoles from 2-alkynylindole-3-carbaldehydes and l-proline utilizing a metal-free decarboxylative cyclization, ring expansion, and ring contraction strategy via the generation of azomethine ylide was developed. The reaction of 2-alkynylindole-3-carbaldehydes with l-thioproline leads to the formation of γ-carbolines. By virtue of this expedient method, a diverse range of biologically active heteroannulated carbazoles can be synthesized efficiently.

Unexpected Binding Mode of a Potent Indeno[1,2-b]indole-Type Inhibitor of Protein Kinase CK2 Revealed by Complex Structures with the Catalytic Subunit CK2α and Its Paralog CK2α'

Protein kinase CK2, a member of the eukaryotic protein kinase superfamily, is associated with cancer and other human pathologies and thus an attractive drug target. The indeno[1,2-b]indole scaffold is a novel lead structure to develop ATP-competitive CK2 inhibitors. Some indeno[1,2-b]indole-based CK2 inhibitors additionally obstruct ABCG2, an ABC half transporter overexpressed in breast cancer and co-responsible for drug efflux and resistance. Comprehensive derivatization studies revealed substitutions of the indeno[1,2-b]indole framework that boost either the CK2 or the ABCG2 selectivity or even support the dual inhibition potential. The best indeno[1,2-b]indole-based CK2 inhibitor described yet (IC₅₀ = 25 nM) is 5-isopropyl-4-(3-methylbut-2-enyl-oxy)-5,6,7,8-tetrahydroindeno[1,2-b]indole-9,10-dione (4p). Herein, we demonstrate the membrane permeability of 4p and describe co-crystal structures of 4p with CK2α and CK2α′, the paralogs of human CK2 catalytic subunit. As expected, 4p occupies the narrow, hydrophobic ATP site of CK2α/CK2α′, but surprisingly with a unique orientation: its hydrophobic substituents point towards the solvent while its two oxo groups are hydrogen-bonded to a hidden water molecule. An equivalent water molecule was found in many CK2α structures, but never as a critical mediator of ligand binding. This unexpected binding mode is independent of the interdomain hinge/helix αD region conformation and of the salt content in the crystallization medium.

CK2 in Cancer: Cellular and Biochemical Mechanisms and Potential Therapeutic Target

CK2 genes are overexpressed in many human cancers, and most often overexpression is associated with worse prognosis. Site-specific expression in mice leads to cancer development (e.g., breast, lymphoma) indicating the oncogenic nature of CK2. CK2 is involved in many key aspects of cancer including inhibition of apoptosis, modulation of signaling pathways, DNA damage response, and cell cycle regulation. A number of CK2 inhibitors are now available and have been shown to have activity against various cancers in vitro and in pre-clinical models. Some of these inhibitors are now undergoing exploration in clinical trials as well. In this review, we will examine some of the major cancers in which CK2 inhibition has promise based on in vitro and pre-clinical studies, the proposed cellular and signaling mechanisms of anti-cancer activity by CK2 inhibitors, and the current or recent clinical trials using CK2 inhibitors.

Intercalative DNA binding of the marine anticancer drug variolin B

Variolin B is a rare marine alkaloid that showed promising anti-cancer activity soon after its isolation. It acts as a cyclin-dependent kinase inhibitor, although the precise mechanism through which it exerts the cytotoxic effects is still unknown. The crystal structure of a variolin B bound to a DNA forming a pseudo-Holliday junction shows that this compound can also contribute, through intercalative binding, to either the formation or stabilization of multi-stranded DNA forms.

Increased expression of protein kinase CK2α correlates with poor patient prognosis in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is one of the deadly gynecological malignancies. The function of protein kinase CK2α (CK2α) in EOC is still unknown. Our study aimed to investigate the relationship between the protein expression of CK2α and the tumor progression, the prognosis of human EOC. In this study, we analyzed the expression levels of CK2α through Western blot, using EOC cell lines like A2780, HO8910, COV644, OVCAR3, SKOV3, and the primary normal ovarian surface epithelial (NOSE) cells. Furthermore, OVCAR3 and SKOV3 EOC cells were employed as a cellular model to study the role of CK2α on cell growth, migration, invasion, apoptosis, and cell cycle distribution. In addition, we investigated CK2α protein expression in tumor tissues from patients with EOC by immunohistochemistry and analyzed the association between CK2α expression and clinicopathologic parameters and prognosis of EOC patients. And we found that compared with NOSE cells, CK2α protein expression was increased in A2780, HO8910, OVCAR3, and SKOV3 ovarian cancer cell lines. Decreased CK2α expression suppressed OVCAR3 and SKOV3 cell growth and induced more apoptosis. CK2α knockdown using specific siRNAs inhibited migration and invasion ability of OVCAR3 and SKOV3 cells. In addition, high CK2α protein expression was found in 68.4% (80/117) of EOC patients. Increased CK2α expression of was significantly correlated with FIGO staging and peritoneal cytology. Patients with higher CK2α expression had a significantly poorer overall survival compared with those with lower CK2α expression. Multi-variate Cox regression analysis proved that increased CK2α expression was an independent prognostic marker for EOC. Taken together, our data displayed that CK2α may play a role in tumor aggressive behavior of EOC and could be used as a marker for predicting prognosis of EOC patient. High CK2α expression might predict poor patient survival.

Screening of Pharmacologically Active Small Molecule Compounds Identifies Antifungal Agents Against Candida Biofilms

Candida species have emerged as important and common opportunistic human pathogens, particularly in immunocompromised individuals. The current antifungal therapies either have toxic side effects or are insufficiently effect. The aim of this study is develop new small-molecule antifungal compounds by library screening methods using Candida albicans, and to evaluate their antifungal effects on Candida biofilms and cytotoxic effects on human cells. Wild-type C. albicans strain SC5314 was used in library screening. To identify antifungal compounds, we screened a small-molecule library of 1,280 pharmacologically active compounds (LOPAC(1280TM)) using an antifungal susceptibility test (AST). To investigate the antifungal effects of the hit compounds, ASTs were conducted using Candida strains in various growth modes, including biofilms. We tested the cytotoxicity of the hit compounds using human gingival fibroblast (hGF) cells to evaluate their clinical safety. Only 35 compounds were identified by screening, which inhibited the metabolic activity of C. albicans by >50%. Of these, 26 compounds had fungistatic effects and nine compounds had fungicidal effects on C. albicans. Five compounds, BAY11-7082, BAY11-7085, sanguinarine chloride hydrate, ellipticine and CV-3988, had strong fungicidal effects and could inhibit the metabolic activity of Candida biofilms. However, BAY11-7082, BAY11-7085, sanguinarine chloride hydrate and ellipticine were cytotoxic to hGF cells at low concentrations. CV-3988 showed no cytotoxicity at a fungicidal concentration. Four of the compounds identified, BAY11-7082, BAY11-7085, sanguinarine chloride hydrate and ellipticine, had toxic effects on Candida strains and hGF cells. In contrast, CV-3988 had fungicidal effects on Candida strains, but low cytotoxic effects on hGF cells. Therefore, this screening reveals agent, CV-3988 that was previously unknown to be antifungal agent, which could be a novel therapies for superficial mucosal candidiasis.

Casein kinases as potential therapeutic targets

INTRODUCTION

The conventional term 'casein kinase' (CK) denotes three classes of kinases - CK1, CK2 and Golgi-CK (G-CK)/Fam20C (family with sequence similarity 20, member C) - sharing the ability to phoshorylate casein in vitro, but otherwise unrelated to each other. All CKs have been reported to be implicated in human diseases, and reviews individually dealing with the druggability of CK1 and CK2 are available. Our aim is to provide a comparative analysis of the three classes of CKs as therapeutic targets.

AREAS COVERED

CK2 is the CK for which implication in neoplasia is best documented, with the survival of cancer cells often relying on its overexpression. An ample variety of cell-permeable CK2 inhibitors have been developed, with a couple of these now in clinical trials. Isoform-specific CK1 inhibitors that are expected to play a beneficial role in oncology and neurodegeneration have been also developed. In contrast, the pathogenic potential of G-CK/Fam20C is caused by its loss of function. Activators of Fam20C, notably sphingolipids and their analogs, may prove beneficial in this respect.

EXPERT OPINION

Optimization of CK2 and CK1 inhibitors will prove useful to develop new therapeutic strategies for treating cancer and neurodegenerative disorders, while the design of potent activators of G-CK/Fam20C will provide a new tool in the fields of bio-mineralization and hypophosphatemic diseases.

Chemical Library Screening and Structure-Function Relationship Studies Identify Bisacodyl as a Potent and Selective Cytotoxic Agent Towards Quiescent Human Glioblastoma Tumor Stem-Like Cells

Cancer stem-like cells reside in hypoxic and slightly acidic tumor niches. Such microenvironments favor more aggressive undifferentiated phenotypes and a slow growing "quiescent state" which preserves them from chemotherapeutic agents that essentially target proliferating cells. Our objective was to identify compounds active on glioblastoma stem-like cells, including under conditions that mimick those found in vivo within this most severe and incurable form of brain malignancy. We screened the Prestwick Library to identify cytotoxic compounds towards glioblastoma stem-like cells, either in a proliferating state or in more slow-growing "quiescent" phenotype resulting from non-renewal of the culture medium in vitro. Compound effects were assessed by ATP-level determination using a cell-based assay. Twenty active molecules belonging to different pharmacological classes have thus been identified. Among those, the stimulant laxative drug bisacodyl was the sole to inhibit in a potent and specific manner the survival of quiescent glioblastoma stem-like cells. Subsequent structure-function relationship studies led to identification of 4,4'-dihydroxydiphenyl-2-pyridyl-methane (DDPM), the deacetylated form of bisacodyl, as the pharmacophore. To our knowledge, bisacodyl is currently the only known compound targeting glioblastoma cancer stem-like cells in their quiescent, more resistant state. Due to its known non-toxicity in humans, bisacodyl appears as a new potential anti-tumor agent that may, in association with classical chemotherapeutic compounds, participate in tumor eradication.

Synthesis, Biological Evaluation and Molecular Modeling of Substituted Indeno[1,2-b]indoles as Inhibitors of Human Protein Kinase CK2

Due to their system of annulated 6-5-5-6-membered rings, indenoindoles have sparked great interest for the design of ATP-competitive inhibitors of human CK2. In the present study, we prepared twenty-one indeno[1,2-b]indole derivatives, all of which were tested in vitro on human CK2. The indenoindolones 5a and 5b inhibited human CK2 with an IC₅₀ of 0.17 and 0.61 µM, respectively. The indeno[1,2-b]indoloquinone 7a also showed inhibitory activity on CK2 at a submicromolar range (IC₅₀ = 0.43 µM). Additionally, a large number of indenoindole derivatives was evaluated for their cytotoxic activities against the cell lines 3T3, WI-38, HEK293T and MEF.

Optimizing CIGB-300 intralesional delivery in locally advanced cervical cancer

BACKGROUND

We conducted a phase 1 trial in patients with locally advanced cervical cancer by injecting 0.5 ml of the CK2-antagonist CIGB-300 in two different sites on tumours to assess tumour uptake, safety, pharmacodynamic activity and identify the recommended dose.

METHODS

Fourteen patients were treated with intralesional injections containing 35 or 70 mg of CIGB-300 in three alternate cycles of three consecutive days each before standard chemoradiotherapy. Tumour uptake was determined using (99)Tc-radiolabelled peptide. In situ B23/nucleophosmin was determined by immunohistochemistry.

RESULTS

Maximum tumour uptake for CIGB-300 70-mg dose was significantly higher than the one observed for 35 mg: 16.1 ± 8.9 vs 31.3 ± 12.9 mg (P = 0.01). Both, AUC24h and biological half-life were also significantly higher using 70 mg of CIGB-300 (P < 0.001). Unincorporated CIGB-300 diffused rapidly to blood and was mainly distributed towards kidneys, and marginally in liver, lungs, heart and spleen. There was no DLT and moderate allergic-like reactions were the most common systemic side effect with strong correlation between unincorporated CIGB-300 and histamine levels in blood. CIGB-300, 70 mg, downregulated B23/nucleophosmin (P = 0.03) in tumour specimens.

CONCLUSION

Intralesional injections of 70 mg CIGB-300 in two sites (0.5 ml per injection) and this treatment plan are recommended to be evaluated in phase 2 studies.

[Strength and specificity of the CMBA screening platform for bioactive molecules discovery]

Used as powerful chemical probes in Life science fundamental research, the application potential of new bioactive molecular entities includes but extends beyond their development as therapeutic drugs in pharmacology. In this review, we wish to point out the methodology of chemical libraries screening on living cells or purified proteins at the CMBA academic platform of Grenoble Alpes University, and strategies employed to further characterize the selected bioactive molecules by phenotypic profiling on human cells. Multiple application fields are concerned by the screening activity developed at CMBA with bioactive molecules previously selected for their potential as tools for fundamental research purpose, therapeutic candidates to treat cancer or infection, or promising compounds for production of bioenergy.

Casein kinase 2α regulates glioblastoma brain tumor-initiating cell growth through the β-catenin pathway

Glioblastoma (GBM) is the most common and fatal primary brain tumor in humans and it is essential that new and better therapies are developed to treat this disease. Previous research suggests that casein kinase 2 (CK2), may be a promising therapeutic target for GBMs. CK2 has enhanced expression or activity in numerous cancers, including GBM and it has been demonstrated that inhibitors of CK2 regressed tumor growth in GBM xenograft mouse models. Our studies demonstrate that the CK2 subunit, CK2α, is overexpressed in and plays an important role in regulating brain tumor initiating cells (BTIC) in GBM. Initial studies showed that two GBM cell lines (U87-MG and U138) transduced with CK2α had enhanced proliferation and anchorage-independent growth. Inhibition of CK2α using siRNA or small molecule inhibitors (TBBz, CX-4945) reduced cell growth and decreased tumor size and increased the survival rate in GBM xenograft mouse models. We also verified that inhibition of CK2α decreased the activity of a well-known GBM initiating cell regulator, β-catenin. Loss of CK2α decreased two β-catenin-regulated genes that are involved in GBM initiating cell growth, OCT4 and NANOG. To determine the importance of CK2α in GBM stem cell maintenance, we reduced CK2α activity in primary GBM samples and tumor spheres derived from GBM patients. We discovered that loss of CK2α activity reduced the sphere forming capacity of BTIC and decreased numerous GBM stem cell markers including CD133, CD90, CD49f, and A2B5. Our study suggests that CK2α is involved in GBM tumorigenesis by maintaining BTIC through the regulation of β-catenin.

Casein kinase: the triple meaning of a misnomer

The term 'casein kinase' has been widely used for decades to denote protein kinases sharing the ability to readily phosphorylate casein in vitro. These fall into three main classes: two of them, later renamed as protein kinases CK1 (casein kinase 1, also known as CKI) and CK2 (also known as CKII), are pleiotropic members of the kinome functionally unrelated to casein, whereas G-CK, or genuine casein kinase, responsible for the phosphorylation of casein in the Golgi apparatus of the lactating mammary gland, has only been identified recently with Fam20C [family with sequence similarity 20C; also known as DMP-4 (dentin matrix protein-4)], a member of the four-jointed family of atypical protein kinases, being responsible for the phosphorylation of many secreted proteins. In hindsight, therefore, the term 'casein kinase' is misleading in every instance; in the case of CK1 and CK2, it is because casein is not a physiological substrate, and in the case of G-CK/Fam20C/DMP-4, it is because casein is just one out of a plethora of its targets, and a rather marginal one at that. Strikingly, casein kinases altogether, albeit representing a minimal proportion of the whole kinome, appear to be responsible for the generation of up to 40-50% of non-redundant phosphosites currently retrieved in human phosphopeptides database. In the present review, a short historical explanation will be provided accounting for the usage of the same misnomer to denote three unrelated classes of protein kinases, together with an update of our current knowledge of these pleiotropic enzymes, sharing the same misnomer while playing very distinct biological roles.

Cytotoxic activity of the casein kinase 2 inhibitor CX-4945 against T-cell acute lymphoblastic leukemia: targeting the unfolded protein response signaling

Constitutively active casein kinase 2 (CK2) signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL). CK2 phosphorylates PTEN (phosphatase and tensin homolog) tumor suppressor, resulting in PTEN stabilization and functional inactivation. Downregulation of PTEN activity has an impact on PI3K/Akt/mTOR signaling, which is of fundamental importance for T-ALL cell survival. These observations lend compelling weight to the application of CK2 inhibitors in the therapy of T-ALL. Here, we have analyzed the therapeutic potential of CX-4945-a novel, highly specific, orally available, ATP-competitive inhibitor of CK2α. We show that CX-4945 treatment induced apoptosis in T-ALL cell lines and patient T lymphoblasts. CX-4945 downregulated PI3K/Akt/mTOR signaling in leukemic cells. Notably, CX-4945 affected the unfolded protein response (UPR), as demonstrated by a significant decrease in the levels of the main UPR regulator GRP78/BIP, and led to apoptosis via upregulation of the ER stress/UPR cell death mediators IRE1α and CHOP. In vivo administration of CX-4945 to a subcutaneous xenotransplant model of human T-ALL significantly delayed tumor growth. Our findings indicate that modulation of the ER stress/UPR signaling through CK2 inhibition could be exploited for inducing apoptosis in T-ALL cells and that CX-4945 may be an efficient treatment for those T-ALLs displaying upregulation of CK2α/PI3K/Akt/mTOR signaling.

Targeting protein kinase CK2 suppresses prosurvival signaling pathways and growth of glioblastoma

PURPOSE

Gliomas are the most frequently occurring primary malignancies in the brain, and glioblastoma is the most aggressive of these tumors. Protein kinase CK2 is composed of two catalytic subunits (α and/or α') and two β regulatory subunits. CK2 suppresses apoptosis, promotes neoangiogenesis, and enhances activation of the JAK/STAT, NF-κB, PI3K/AKT, Hsp90, Wnt, and Hedgehog pathways. Aberrant activation of the NF-κB, PI3K/AKT, and JAK/STAT-3 pathways is implicated in glioblastoma progression. As CK2 is involved in their activation, the expression and function of CK2 in glioblastoma was evaluated.

EXPERIMENTAL DESIGN AND RESULTS

Analysis of 537 glioblastomas from The Cancer Genome Atlas Project demonstrates the CSNK2A1 gene, encoding CK2α, has gene dosage gains in glioblastoma (33.7%), and is significantly associated with the classical glioblastoma subtype. Inhibition of CK2 activity by CX-4945, a selective CK2 inhibitor, or CK2 knockdown by siRNA suppresses activation of the JAK/STAT, NF-κB, and AKT pathways and downstream gene expression in human glioblastoma xenografts. On a functional level, CX-4945 treatment decreases the adhesion and migration of glioblastoma cells, in part through inhibition of integrin β1 and α4 expression. In vivo, CX-4945 inhibits activation of STAT-3, NF-κB p65, and AKT, and promotes survival of mice with intracranial human glioblastoma xenografts.

CONCLUSIONS

CK2 inhibitors may be considered for treatment of patients with glioblastoma.

[Small compounds libraries: a research tool for chemical biology]

Obtaining and screening collections of small molecules remain a challenge for biologists. Recent advances in analytical techniques and instrumentation now make screening possible in academia. The history of the creation of such public or commercial collections and their accessibility is related. It shows that there is interest for an academic laboratory involved in medicinal chemistry, chemogenomics or "chemical biology" to organize its own collection and make it available through existing networks such as the French National chimiothèque or the European partner network "European Infrastructure of open screening platforms for Chemical Biology" EU-OpenScreen under construction.

Claulansine F suppresses apoptosis induced by sodium nitroprusside in PC12 cells

Reactive oxygen species (ROS) are known to be involved in many neurodegenerative diseases. This study assessed the effect of Claulansine F, a new carbazole isolated from Clausena lansium, on sodium nitroprusside (SNP)-treated rat pheochromocytoma PC12 cells. First, it was found that Claulansine F showed more potential on inhibiting the programmed death of PC12 cells than edaravone by cell viability, morphologic observation, and flow cytometric analysis. Further results also showed that Claulansine F attenuated the production of total intracellular ROS formation and lipid peroxidation in PC12 cells, inhibited the mitochondrial membrane potential (MMP) loss, and prevented the programmed cell death event via the P53/Bcl-2 family pathway. Its protective effect was likely medicated by the hydroxyl radical (·OH) scavenging ability, as it appeared to be not involved in the natural antioxidant system. These results suggested a promising potential for Claulansine F as a ROS scavenger in pathologies, where an oxidative stress is involved.

Design, synthesis and evaluation of 2-phenylisothiazolidin-3-one-1,1-dioxides as a new class of human protein kinase CK2 inhibitors

The synthesis and in vitro evaluation of 40 new 2-phenylisothiazolidin-3-one-1,1-dioxide derivatives are described. The optimization based on biological screening data and molecular modeling resulted in a 10-fold increase in inhibitory activity compared with previously reported inhibitors of this class and led to the identification of 3-{[2-chloro-4-(1,1-dioxido-3-oxoisothiazolidin-2-yl)benzoyl]amino}benzoic acid, a potent inhibitor of human protein kinase CK2 (ІC₅₀ = 1.5 μM).

Protein kinase CK2 inhibitors: a patent review

INTRODUCTION

CK2 is a pleiotropic, ubiquitous and constitutively active protein kinase, localized in both cytosolic and nuclear compartments, where it catalyzes the phosphorylation of hundreds of proteins. CK2 is generally described as a tetramer composed of two catalytic (α and/or α') and two regulatory subunits (β), however, the free α/α' subunits are catalytically active by themselves. CK2 plays a key role in several physiological and pathological processes and has been connected to many neoplastic, inflammatory, autoimmune and infectious disorders. In the last 20 years, several inhibitors of CK2 have been discovered though only one of these, CX-4945, has recently entered into Phase II clinical trials as potential anticancer drug.

AREAS COVERED

The main objective of the present review is to describe the development of CK2 activity modulators over the years according to the timeline of their patent registration.

EXPERT OPINION

CK2 was discovered in 1954, but the first patent on CK2 modulators was deposited only 50 years later, in 2004. However, in the last 5 years an increasing number of patents on CK2 inhibitors have been registered, reflecting an increased interest in this kind of drug candidates and their possible therapeutic applications.

Hydrosoluble benzo[e]pyridoindolones as potent inhibitors of aurora kinases

Aurora kinases play an essential role in mitotic progression and are potentially druggable targets in cancer therapy. We identified benzo[e]pyridoindoles (BePI) as powerful aurora kinase inhibitors. Their efficiency was demonstrated both in enzymatic inhibition studies and in cell culture assays. New BePI molecules were synthesized, and a structure-activity relationship study was conducted with the aim of improving the activity and solubility of the lead compound. Tetracyclic BePI derivatives are characterized by a particular curved shape, and the presence of an oxo group on the pyridine ring was found to be required for aurora kinase B inhibition. New hydrosoluble benzo[e]pyridoindolones were subsequently designed, and their efficacy was tested by a combination of cell-cycle analysis and time-lapse experiments in live cells. The most active BePI derivative, 13 b, inhibited the cell cycle, drove cells to polyploidy, and eventually induced apoptosis. It exhibited high antiproliferative activity in HeLa cells with an IC(50) value of 63 nM. Relative to compounds tested in clinical trials, this antiproliferative potency places 13 b among the top 10 aurora kinase inhibitors. Our results justify further in vivo evaluation in preclinical animal models of cancer.

Effects of the CK2 inhibitors CX-4945 and CX-5011 on drug-resistant cells

CK2 is a pleiotropic protein kinase, which regulates many survival pathways and plays a global anti-apoptotic function. It is highly expressed in tumor cells, and is presently considered a promising therapeutic target. Among the many inhibitors available for this kinase, the recently developed CX-4945 and CX-5011 have proved to be very potent, selective and effective in inducing cell death in tumor cells; CX-4945 has recently entered clinical trials. However, no data are available on the efficacy of these compounds to overcome drug resistance, a major reasons of cancer therapy failure. Here we address this point, by studying their effects in several tumor cell lines, each available as variant R resistant to drug-induced apoptosis, and normal-sensitive variant S. We found that the inhibition of endogenous CK2 was very similar in S and R treated cells, with more than 50% CK2 activity reduction at sub-micromolar concentrations of CX-4945 and CX-5011. A consequent apoptotic response was induced both in S and R variants of each pairs. Moreover, the combined treatment of CX-4945 plus vinblastine was able to sensitize to vinblastine R cells that are otherwise almost insensitive to this conventional antitumor drug. Consistently, doxorubicin accumulation in multidrug resistant (MDR) cells was greatly increased by CX-4945.

In summary, we demonstrated that all the R variants are sensitive to CX-4945 and CX-5011; since some of the treated R lines express the extrusion pump Pgp, often responsible of the MDR phenotype, we can also conclude that the two inhibitors can successfully overcome the MDR phenomenon.

The anticancer multi-kinase inhibitor dovitinib also targets topoisomerase I and topoisomerase II

Dovitinib (TKI258/CHIR258) is a multi-kinase inhibitor in phase III development for the treatment of several cancers. Dovitinib is a benzimidazole-quinolinone compound that structurally resembles the bisbenzimidazole minor groove binding dye Hoechst 33258. Dovitinib bound to DNA as shown by its ability to increase the DNA melting temperature and by increases in its fluorescence spectrum that occurred upon the addition of DNA. Molecular modeling studies of the docking of dovitinib into an X-ray structure of a Hoechst 33258-DNA complex showed that dovitinib could reasonably be accommodated in the DNA minor groove. Because DNA binders are often topoisomerase I (EC 5.99.1.2) and topoisomerase II (EC 5.99.1.3) inhibitors, the ability of dovitinib to inhibit these DNA processing enzymes was also investigated. Dovitinib inhibited the catalytic decatenation activity of topoisomerase IIα. It also inhibited the DNA-independent ATPase activity of yeast topoisomerase II which suggested that it interacted with the ATP binding site. Using isolated human topoisomerase IIα, dovitinib stabilized the enzyme-cleavage complex and acted as a topoisomerase IIα poison. Dovitinib was also found to be a cellular topoisomerase II poison in human leukemia K562 cells and induced double-strand DNA breaks in K562 cells as evidenced by increased phosphorylation of H2AX. Finally, dovitinib inhibited the topoisomerase I-catalyzed relaxation of plasmid DNA and acted as a cellular topoisomerase I poison. In conclusion, the cell growth inhibitory activity and the anticancer activity of dovitinib may result not only from its ability to inhibit multiple kinases, but also, in part, from its ability to target topoisomerase I and topoisomerase II.