Chandrabose Karthikeyan

Bio: Chandrabose Karthikeyan is an academic researcher from Rajiv Gandhi Proudyogiki Vishwavidyalaya. The author has contributed to research in topics: Apoptosis & Quantitative structure–activity relationship. The author has an hindex of 17, co-authored 58 publications receiving 950 citations. Previous affiliations of Chandrabose Karthikeyan include Indira Gandhi National Tribal University & Shri Govindram Seksaria Institute of Technology and Science.

Advances in Chalcones with Anticancer Activities

Abstract: Chalcones are naturally occurring compounds exhibiting broad spectrum biological activities including anticancer activity through multiple mechanisms. Literature on anticancer chalcones highlights the employment of three pronged strategies, namely; structural manipulation of both aryl rings, replacement of aryl rings with heteroaryl scaffolds, molecular hybridization through conjugation with other pharmacologically interesting scaffolds for enhancement of anticancer properties. Methoxy substitutions on both the aryl rings (A and B) of the chalcones, depending upon their positions in the aryl rings appear to influence anticancer and other activities. Similarly, heterocyclic rings either as ring A or B in chalcones, also influence the anticancer activity shown by this class of compounds. Hybrid chalcones formulated by chemically linking chalcones to other prominent anticancer scaffolds such as pyrrol[2,1-c][1,4]benzodiazepines, benzothiazoles, imidazolones have demonstrated synergistic or additive pharmacological activities. The successful application of these three pronged strategies for discovering novel anticancer agents based on chalcone scaffold has resulted in many novel and chemically diverse chalcones with potential therapeutic application for many types of cancer. This review summarizes the concerted efforts expended on the design and development of anticancer chalcones recorded in recent literature and also provides an overview of the patents published in this area between 2007 and 2014 (WO2013022951, WO201201745 & US2012029489).

Human CDC2-Like Kinase 1 (CLK1): A Novel Target for Alzheimer’s Disease

Abstract: The cdc2-like kinases (CLKs) are an evolutionarily conserved group of dual specificity kinases belonging to the CMGC (cyclin-dependent kinases (CDKs), mitogen-activated protein kinases (MAP kinases), glycogen synthase kinases (GSK) and CDK-like kinases). The CLK family consists of four isoforms namely CLK1, CLK2, CLK3 and CLK4. The human CLK1 encoded protein comprises 454 amino acids and the catalytic domain of CLK1 exhibits the typical protein kinase fold. CLK1 has been shown to autophosphorylate on serine, threonine and tyrosine residues and phosphorylate exogenous substrates on serine and threonine residues. CLK1 plays an important role in the regulation of RNA splicing through phosphorylation of members of the serine and arginine-rich (SR) family of splicing factors. CLK1 is involved in the pathophysiology of Alzheimer's disease by phosphorylating the serine residue in SR proteins. Nuclear speckles of the nucleoplasm contain the stored form of SR proteins and are moderately responsible for the choice of splicing sites during pre-mRNA splicing. Hence, the inhibition of CLK1 can be used as a therapeutic strategy for Alzheimer's disease. Many natural and synthetic molecules are reported to possess CLK1 inhibitory activity. Some specific examples are Marine alkaloid Leucettamine B and KH-CB19. Leucettamine B is a potent inhibitor of CLK1 (15 nM), Dyrk1A (40 nM), and Dyrk2 (35 nM) and a moderate inhibitor of CLK3 (4.5 µM) whereas KH-CB19 is a highly specific and potent inhibitor of the CLK1/CLK4. X-ray crystallographic studies have revealed the binding mode of marine sponge metabolite hymenialdisine and a dichloroindolyl enamino nitrile (KH-CB19) to CLK1. This review focuses on the role of CLKs in the pathophysiology of Alzheimer's disease and therapeutic potential of targeting CLK1 in Alzheimer's disease drug discovery and development. In addition, the recent developments in drug discovery efforts targeting human CLK1 are also highlighted.

A novel benzimidazole derivative, MBIC inhibits tumor growth and promotes apoptosis via activation of ROS-dependent JNK signaling pathway in hepatocellular carcinoma.

Abstract: // Xiaoyun Dai 1, * , Lingzhi Wang 1, 2, * , Amudha Deivasigamni 3, * , Chung Yeng Looi 4 , Chandrabose Karthikeyan 5 , Piyush Trivedi 5 , Arunachalam Chinnathambi 6 , Sulaiman Ali Alharbi 6 , Frank Arfuso 7 , Arunasalam Dharmarajan 7 , Boon Cher Goh 1, 2, 8 , Kam Man Hui 3, 9, 10, 11 , Alan Prem Kumar 1, 2, 12, 13 , Mohd Rais Mustafa 4 , Gautam Sethi 1, 6, 14 1 Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 2 Cancer Science Institute of Singapore, Centre for Translational Medicine, Singapore 3 Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre, Singapore 4 Department of Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia 5 School of Pharmaceutical Sciences, Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal, India 6 Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia, 7 Stem Cell and Cancer Biology Laboratory, School of Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth WA, Australia 8 Department of Haematology-Oncology, National University Health System, Singapore 9 Institute of Molecular and Cell Biology, A*STAR, Biopolis Drive Proteos, Singapore 10 Cancer and Stem Cell Biology Program, Duke–National University of Singapore Graduate Medical School, Singapore 11 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 12 Curtin Medical School, Faculty of Health Sciences, Curtin University, Perth WA, Australia 13 Department of Biological Sciences, University of North Texas, Denton, Texas, USA 14 School of Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth WA, Australia * These authors contributed equally to this work Correspondence to: Gautam Sethi, email: phcgs@nus.edu.sg Kam Man Hui, email: cmrhkm@nccs.com.sg Mohd Rais Mustafa, email: rais@nm.edu.my Alan Prem Kumar, email: csiapk@nus.edu.sg Keywords: MBIC, HCC, JNK, ROS, apoptosis Received: July 27, 2016 Accepted: December 15, 2016 Published: January 12, 2017 ABSTRACT A prior screening programme carried out using MTT assay by our group identified a series of novel benzimidazole derivatives, among which Methyl 2-(5-fluoro-2-hydroxyphenyl)-1H- benzo[d]imidazole-5-carboxylate (MBIC) showed highest anticancer efficacy compared to that of chemotherapeutic agent, cisplatin. In the present study, we found that MBIC inhibited cell viability in different hepatocellular carcinoma (HCC) cell lines without exerting significant cytotoxic effects on normal liver cells. Annexin V-FITC/PI flow cytometry analysis and Western blotting results indicated that MBIC can induce apoptosis in HCC cells, which was found to be mediated through mitochondria associated proteins ultimately leading to the activation of caspase-3. The exposure to MBIC also resulted in remarkable impairment of HCC cell migration and invasion. In addition, treatment with MBIC led to a rapid generation of reactive oxygen species (ROS) and substantial activation of c-Jun-N-terminal kinase (JNK). The depletion of ROS by N-Acetyl cysteine (NAC) partially blocked MBIC-induced apoptosis and JNK activation in HCC cells. Finally, MBIC significantly inhibited tumor growth at a dose of 25 mg/kg in an orthotopic HCC mouse model. Taken together, these results demonstrate that MBIC may inhibit cell proliferation via ROS-mediated activation of the JNK signaling cascade in HCC cells.

Chalcone: A Privileged Structure in Medicinal Chemistry.

Abstract: Privileged structures have been widely used as an effective template in medicinal chemistry for drug discovery. Chalcone is a common simple scaffold found in many naturally occurring compounds. Many chalcone derivatives have also been prepared due to their convenient synthesis. These natural products and synthetic compounds have shown numerous interesting biological activities with clinical potentials against various diseases. This review aims to highlight the recent evidence of chalcone as a privileged scaffold in medicinal chemistry. Multiple aspects of chalcone will be summarized herein, including the isolation of novel chalcone derivatives, the development of new synthetic methodologies, the evaluation of their biological properties, and the exploration of the mechanisms of action as well as target identification. This review is expected to be a comprehensive, authoritative, and critical review of the chalcone template to the chemistry community.

Role of Reactive Oxygen Species in Cancer Progression: Molecular Mechanisms and Recent Advancements.

Abstract: Reactive oxygen species (ROS) play a pivotal role in biological processes and continuous ROS production in normal cells is controlled by the appropriate regulation between the silver lining of low and high ROS concentration mediated effects. Interestingly, ROS also dynamically influences the tumor microenvironment and is known to initiate cancer angiogenesis, metastasis, and survival at different concentrations. At moderate concentration, ROS activates the cancer cell survival signaling cascade involving mitogen-activated protein kinase/extracellular signal-regulated protein kinases 1/2 (MAPK/ERK1/2), p38, c-Jun N-terminal kinase (JNK), and phosphoinositide-3-kinase/ protein kinase B (PI3K/Akt), which in turn activate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), matrix metalloproteinases (MMPs), and vascular endothelial growth factor (VEGF). At high concentrations, ROS can cause cancer cell apoptosis. Hence, it critically depends upon the ROS levels, to either augment tumorigenesis or lead to apoptosis. The major issue is targeting the dual actions of ROS effectively with respect to the concentration bias, which needs to be monitored carefully to impede tumor angiogenesis and metastasis for ROS to serve as potential therapeutic targets exogenously/endogenously. Overall, additional research is required to comprehend the potential of ROS as an effective anti-tumor modality and therapeutic target for treating malignancies.

Ruthenium-catalyzed direct oxidative alkenylation of arenes through twofold C–H bond functionalization

Abstract: Significant progress has been accomplished in direct olefinations through twofold C–H bond functionalization of arenes and heteroarenes employing readily accessible, selective and relatively inexpensive ruthenium catalysts. Particularly, ruthenium(II) complexes have allowed challenging direct double C–H/C–H bond alkenylations of arenes with ample scope. These catalysts set the stage for step-economical C–H/C–H bond functionalization with electron-rich as well as electron-deficient arenes and heteroarenes, and, thereby, provide versatile access to diversely decorated styrenes.

Metabolism and function of phenazines in bacteria: impacts on the behavior of bacteria in the environment and biotechnological processes

Abstract: Phenazines constitute a large group of nitrogen-containing heterocyclic compounds produced by a diverse range of bacteria. Both natural and synthetic phenazine derivatives are studied due their impacts on bacterial interactions and biotechnological processes. Phenazines serve as electron shuttles to alternate terminal acceptors, modify cellular redox states, act as cell signals that regulate patterns of gene expression, contribute to biofilm formation and architecture, and enhance bacterial survival. Phenazines have diverse effects on eukaryotic hosts and host tissues, including the modification of multiple host cellular responses. In plants, phenazines also may influence growth and elicit induced systemic resistance. Here, we discuss emerging evidence that phenazines play multiple roles for the producing organism and contribute to their behavior and ecological fitness.