Wee Han Ang

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Organization: National University of Singapore , Singapore
Department: Department of Chemistry
Title: (PhD)

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Co-reporter:Mun Juinn Chow;Mohammad Alfiean;Giorgia Pastorin;Christian Gaiddon
Chemical Science (2010-Present) 2017 vol. 8(Issue 5) pp:3641-3649
Publication Date(Web):2017/05/03
DOI:10.1039/C7SC00497D
Multidrug resistance is a major impediment to chemotherapy and limits the efficacies of conventional anticancer drugs. A strategy to bypass multidrug resistance is to develop new drug candidates capable of inducing apoptosis-independent programmed cell death. However, cellular pathways implicated in alternative programmed cell death are not well-elucidated and multifactorial, making a target-based discovery approach a challenge. Here, we show that a coordination-directed three-component assembly and phenotypic screening strategy could be employed as a viable alternative for the identification of apoptosis-independent organoruthenium anticancer agents. Through an on-plate synthesis and screening of 195 organoruthenium complexes against apoptosis-sensitive and -resistant cancers, we identified two apoptosis-independent hits. Subsequent validation of the two hits showed a lack of induction of apoptotic biomarkers, a caspase-independent activity and an equal efficacy in both apoptosis-sensitive and -resistant colorectal cancers. This validated their apoptosis-independent modes-of-action, paving the way as potential candidates for the treatment of highly-refractory cancer phenotypes.
Co-reporter:Angela Sîrbu;Oleg Palamarciuc;Maria V. Babak;Jia Min Lim;Kateryna Ohui;Eva A. Enyedy;Sergiu Shova;Denisa Darvasiová;Peter Rapta;Vladimir B. Arion
Dalton Transactions 2017 vol. 46(Issue 12) pp:3833-3847
Publication Date(Web):2017/03/21
DOI:10.1039/C7DT00283A
A series of water-soluble sodium salts of 3-formyl-4-hydroxybenzenesulfonic acid thiosemicarbazones (or sodium 5-sulfonate-salicylaldehyde thiosemicarbazones) containing different substituents at the terminal nitrogen atom (H, Me, Et, Ph) and their copper(II) complexes have been prepared and characterised by elemental analysis, spectroscopic techniques (IR, UV-vis, 1H NMR), ESI mass spectrometry, X-ray crystallography and cyclic voltammetry. The proligands and their copper(II) complexes exhibit moderate water solubility and good stability in aqueous environment, determined by investigating their proton dissociation and complex formation equilibria. The copper(II) complexes showed moderate anticancer activity in established human cancer cell lines, while the proligands were devoid of cytotoxicity. The anticancer activity of the copper(II) complexes correlates with their ability to induce ROS accumulation in cells, consistent with their redox potentials within the biological window, triggering the activation of antioxidation defense mechanisms in response to the ROS insult. These studies pave the way for the investigation of ROS-inducing copper(II) complexes as prospective antiproliferative agents in cancer chemotherapy.
Co-reporter:Mun Juinn Chow, Cynthia Licona, Giorgia Pastorin, Georg Mellitzer, Wee Han Ang and Christian Gaiddon  
Chemical Science 2016 vol. 7(Issue 7) pp:4117-4124
Publication Date(Web):01 Mar 2016
DOI:10.1039/C6SC00268D
Multidrug resistance (MDR) is a major impediment to the success of chemotherapy in many cancer types. One particular MDR mechanism is the inherent or acquired adaptation of the cellular survival pathways that render malignant cells resistant to apoptotic cell death. Since most drugs act through apoptosis, compounds capable of inducing alternative forms of programmed cell death (PCD) can potentially be harnessed to bypass MDR. We investigated two organoruthenium complexes, RAS-1H and RAS-1T, and demonstrated that although they both induced non-apoptotic PCD through ER stress pathways, their modes-of-action were drastically different despite modest structural variations. RAS-1T acted through ROS-mediated ER stress while RAS-1H was ROS-independent. We further showed that they were more efficacious against apoptosis-resistant cells compared to clinical drugs including oxaliplatin. This work provides the basis for underpinning ER stress modulation using metal complexes to bypass apoptosis resistance.
Co-reporter:Mun Juinn Chow; Maria V. Babak; Daniel Yuan Qiang Wong; Giorgia Pastorin; Christian Gaiddon
Molecular Pharmaceutics 2016 Volume 13(Issue 7) pp:2543-2554
Publication Date(Web):May 13, 2016
DOI:10.1021/acs.molpharmaceut.6b00348
p53 is a key tumor suppressor gene involved in key cellular processes and implicated in cancer therapy. However, it is inactivated in more than 50% of all cancers due to mutation or overexpression of its negative regulators. This leads to drug resistance and poor chemotherapeutic outcome as most clinical drugs act via a p53-dependent mechanism of action. An attractive strategy to circumvent this resistance would be to identify new anticancer drugs that act via p53-independent mode of action. In the present study, we identified 9 Ru (II)-Arene Schiff-base (RAS) complexes able to induce p53-independent cytotoxicity and discuss structural features that are required for their p53-independent activity. Increasing hydrophobicity led to an increase in cellular accumulation in cells with a corresponding increase in efficacy. We further showed that all nine complexes demonstrated p53-independent activity. This was despite significant differences in their physicochemical properties, suggesting that the iminoquinoline ligand, a common structural feature for all the complexes, is required for the p53-independent activity.
Co-reporter:Daniel Yuan Qiang Wong, Jun Han Lim and Wee Han Ang  
Chemical Science 2015 vol. 6(Issue 5) pp:3051-3056
Publication Date(Web):16 Mar 2015
DOI:10.1039/C5SC00015G
It is well-recognized that the failure of many chemotherapeutics arises due to an inability to induce apoptosis. Most cancers acquire a myriad of pro-survival adaptations, and the vast heterogeneity and accumulation of multiple often unrelated anti-apoptotic signaling pathways have been a major stumbling block towards the development of conventional chemotherapeutics, which can overcome drug resistance. We have developed highly potent and selective HER2-targeted Pt(IV) prodrugs bearing anti-HER2/neu peptides that induce targeted necrosis as a novel strategy to circumvent apoptosis-resistance. These Pt(IV)–peptide conjugates exhibit a unique biphasic mode of cytotoxicity comprising rapid killing of cancer cells via necrosis in the first phase followed by an extended and gradual phase of delayed cell death. We demonstrate that these Pt(IV)–peptide prodrugs are more potent than their Pt(II) congeners in direct cell-killing and exhibit comparable long-term inhibition of proliferative capacity and with greater selectivity against HER2-positive cancer cells.
Co-reporter:Xinyan Bi, Giulia Adriani, Yang Xu, Sabyasachi Chakrabortty, Giorgia Pastorin, Han Kiat Ho, Wee Han Ang, and Yinthai Chan
Analytical Chemistry 2015 Volume 87(Issue 20) pp:10292
Publication Date(Web):September 18, 2015
DOI:10.1021/acs.analchem.5b01942
The salient optical properties of highly luminescent semiconductor nanocrystals render them ideal fluorophores for clinical diagnostics, therapeutics, and highly sensitive biochip applications. Microfluidic systems allow miniaturization and integration of multiple biochemical processes in a single device and do not require sophisticated diagnostic tools. Herein, we describe a microfluidic system that integrates RNA extraction, reverse transcription to cDNA, amplification and detection within one integrated device to detect histidine decarboxylase (HDC) gene directly from human white blood cells samples. When anisotropic semiconductor nanorods (NRs) were used as the fluorescent probes, the detection limit was found to be 0.4 ng of total RNA, which was much lower than that obtained using spherical quantum dots (QDs) or organic dyes. This was attributed to the large action cross-section of NRs and their high probability of target capture in a pull-down detection scheme. The combination of large scale integrated microfluidics with highly fluorescent semiconductor NRs may find widespread utility in point-of-care devices and multitarget diagnostics.
Co-reporter:Jun Xiang Ong, Jian Yu Yap, Siew Qi Yap, Wee Han Ang
Journal of Inorganic Biochemistry 2015 Volume 153() pp:272-278
Publication Date(Web):December 2015
DOI:10.1016/j.jinorgbio.2015.10.002
•Pt-selective rhodamine probes synthesized for structure–activity relationship studies•Activation by co-operative binding between recognition and fluorophore motifs•Thiospirolactam scaffold significantly enhances reactivity towards Pt(II) complexes.•Thionylated probe distinguishes Pt(II) complexes from their parental Pt(IV) prodrugs.Fluorescence microscopy has emerged as an attractive technique for imaging intracellular Pt species arising from exposure to clinical anticancer drugs such as cisplatin. A rhodamine-B based fluorogenic probe termed Rho-DDTC can be activated selectively in the presence of Pt(II) compounds, and possesses the ability to discriminate Pt(II) species from Pt(IV) carboxylate prodrug complexes, thereby providing a unique platform to investigate the reduction of these Pt(IV) complexes after cell entry. In this report, we seek to establish the mechanism of activation of Rho-DDTC through a structure–activity relationship study on its structural analogues.The mechanism of activation of rhodamine B-based fluorogenic probes termed Rho-DDTC by Pt(II) complexes was investigated through a structure–activity relationship study on its structural analogues.
Co-reporter:Daniel Yuan Qiang Wong;Wendy Wei Fang Ong; Wee Han Ang
Angewandte Chemie 2015 Volume 127( Issue 22) pp:6583-6587
Publication Date(Web):
DOI:10.1002/ange.201500934

Abstract

There is compelling evidence suggesting that the immune-modulating effects of many conventional chemotherapeutics, including platinum-based agents, play a crucial role in achieving clinical response. One way in which chemotherapeutics can engage a tumor-specific immune response is by triggering an immunogenic mode of tumor cell death (ICD), which then acts as an “anticancer vaccine”. In spite of being a mainstay of chemotherapy, there has not been a systematic attempt to screen both existing and upcoming Pt agents for their ICD ability. A library of chemotherapeutically active Pt agents was evaluated in an in vitro phagocytosis assay, and no correlation between cytotoxicity and phagocytosis was observed. A PtII N-heterocyclic carbene complex was found to display the characteristic hallmarks of a type II ICD inducer, namely focused oxidative endoplasmic reticulum (ER) stress, calreticulin exposure, and both HMGB1 and ATP release, and thus identified as the first small-molecule immuno-chemotherapeutic agent.

Co-reporter:Daniel Yuan Qiang Wong;Wendy Wei Fang Ong; Wee Han Ang
Angewandte Chemie International Edition 2015 Volume 54( Issue 22) pp:6483-6487
Publication Date(Web):
DOI:10.1002/anie.201500934

Abstract

There is compelling evidence suggesting that the immune-modulating effects of many conventional chemotherapeutics, including platinum-based agents, play a crucial role in achieving clinical response. One way in which chemotherapeutics can engage a tumor-specific immune response is by triggering an immunogenic mode of tumor cell death (ICD), which then acts as an “anticancer vaccine”. In spite of being a mainstay of chemotherapy, there has not been a systematic attempt to screen both existing and upcoming Pt agents for their ICD ability. A library of chemotherapeutically active Pt agents was evaluated in an in vitro phagocytosis assay, and no correlation between cytotoxicity and phagocytosis was observed. A PtII N-heterocyclic carbene complex was found to display the characteristic hallmarks of a type II ICD inducer, namely focused oxidative endoplasmic reticulum (ER) stress, calreticulin exposure, and both HMGB1 and ATP release, and thus identified as the first small-molecule immuno-chemotherapeutic agent.

Co-reporter:Chee Fei Chin, Siew Qi Yap, Jian Li, Giorgia Pastorin and Wee Han Ang  
Chemical Science 2014 vol. 5(Issue 6) pp:2265-2270
Publication Date(Web):07 Feb 2014
DOI:10.1039/C3SC53106F
Combination therapy is an effective strategy to enhance the efficacy of single-agent chemotherapy and delay onset of chemoresistance. However, differences in the pharmacokinetic profiles of the drug constituents can complicate the implementation of combination regimens in a clinical setting. Nanomaterials can overcome these limitations by offering a unified platform for targeted and synchronous delivery of multiple drugs, although exact ratiometric loading cannot be assured using conventional encapsulation techniques. An approach was conceived with the goal of delivering exact stoichiometric proportions of cisplatin and doxorubicin against endometrial adenocarcinoma using tumour-targeting multi-walled carbon nanotubes entrapping an inert Pt(IV) prodrug. Activation of the Pt(IV) prodrug after cell entry, synchronously releases molar equivalents of hydrophilic cisplatin and doxorubicin from the hydrophobic confines, thereby achieving ratiometric delivery of these mechanistically-complementary drug entities.
Co-reporter:Sia Lee Yoong, Bin Sheng Wong, Qi Ling Zhou, Chee Fei Chin, Jian Li, Thirumalai Venkatesan, Han Kiat Ho, Victor Yu, Wee Han Ang, Giorgia Pastorin
Biomaterials 2014 35(2) pp: 748-759
Publication Date(Web):
DOI:10.1016/j.biomaterials.2013.09.036
Co-reporter:Jian Li, Aakansha Pant, Chee Fei Chin, Wee Han Ang, Cécilia Ménard-Moyon, Tapas R. Nayak, Dan Gibson, Sundara Ramaprabhu, Tomasz Panczyk, Alberto Bianco, Giorgia Pastorin
Nanomedicine: Nanotechnology, Biology and Medicine 2014 Volume 10(Issue 7) pp:1465-1475
Publication Date(Web):October 2014
DOI:10.1016/j.nano.2014.01.004
Carbon nanotubes (CNTs) are promising drug delivery systems due to their external functionalizable surface and their hollowed cavity that can encapsulate several bioactive molecules. In this study, the chemotherapeutic drug cisplatin or an inert platinum(IV) complex were entrapped inside functionalized-multi-walled-CNTs and intravenously injected into mice to investigate the influence of CNTs on the biodistribution of Pt-based molecules. The platinum levels in vital organs suggested that functionalized-CNTs did not affect cisplatin distribution, while they significantly enhanced the accumulation of Pt(IV) sample in some tissues (e.g. in the lungs, suggesting their potential application in lung cancer therapy) and reduced both kidney and liver accumulation (thus decreasing eventual nephrotoxicity, a typical side effect of cisplatin). Concurrently, CNTs did not induce any intrinsic abnormal immune response or inflammation, as confirmed by normal cytokine levels and histological evaluations. Therefore, functionalized nanotubes represent an efficient nano-carrier to improve accumulation of Pt species in targeted tissues/organs.From the Clinical EditorIn this preclinical study functionalized carbon nanotubes are reported to be safe and efficient for targeted delivery of platinum-containing compounds in rodents. Approaches like this may improve the treatment of specific cancers, since platinum based chemotherapies are commonly used, yet limited by toxicity and relatively poor target tissue concentration.The chemotherapeutic drug cisplatin or its derivative platinum(IV) complex were entrapped inside functionalized-multi-walled carbon nanotubes and then intravenously injected into mice to investigate the influence of the nanotubes on the biodistribution of Pt-based molecules. The amino-functionalized nanotubes significantly enhanced the accumulation of Pt(IV) sample in the lungs, and reduced both kidney and liver accumulation.
Co-reporter:Daniel Yuan Qiang Wong;Charmian Hui Fang Yeo; Wee Han Ang
Angewandte Chemie 2014 Volume 126( Issue 26) pp:6870-6874
Publication Date(Web):
DOI:10.1002/ange.201402879

Abstract

There is growing consensus that the clinical therapeutic efficacy of some chemotherapeutic agents depends on their off-target immune-modulating effects. Pt anticancer drugs have previously been identified to be potent immunomodulators of both the innate and the adaptive immune system. Nevertheless, there has been little development in the rational design of Pt-based chemotherapeutic agents to exploit their immune-activating capabilities. The FPR1/2 formyl peptide receptors are highly expressed in immune cells, as well as in many metastatic cancers. Herein, we report a rationally designed multimodal PtIV prodrug containing a FPR1/2-targeting peptide that combines chemotherapy with immunotherapy to achieve therapeutic synergy and demonstrate the feasibility of this approach.

Co-reporter:Daniel Yuan Qiang Wong;Charmian Hui Fang Yeo; Wee Han Ang
Angewandte Chemie International Edition 2014 Volume 53( Issue 26) pp:6752-6756
Publication Date(Web):
DOI:10.1002/anie.201402879

Abstract

There is growing consensus that the clinical therapeutic efficacy of some chemotherapeutic agents depends on their off-target immune-modulating effects. Pt anticancer drugs have previously been identified to be potent immunomodulators of both the innate and the adaptive immune system. Nevertheless, there has been little development in the rational design of Pt-based chemotherapeutic agents to exploit their immune-activating capabilities. The FPR1/2 formyl peptide receptors are highly expressed in immune cells, as well as in many metastatic cancers. Herein, we report a rationally designed multimodal PtIV prodrug containing a FPR1/2-targeting peptide that combines chemotherapy with immunotherapy to achieve therapeutic synergy and demonstrate the feasibility of this approach.

Co-reporter:Dr. Diego Montagner;Siew Qi Yap;Dr. Wee Han Ang
Angewandte Chemie International Edition 2013 Volume 52( Issue 45) pp:11785-11789
Publication Date(Web):
DOI:10.1002/anie.201305734
Co-reporter:Dr. Priyankar Paira;Mun Juinn Chow;Gopalakrishnan Venkatesan;Vamsi Krishna Kosaraju;Dr. Siew Lee Cheong;Karl-Norbert Klotz;Dr. Wee Han Ang;Assoc. Giorgia Pastorin
Chemistry - A European Journal 2013 Volume 19( Issue 25) pp:8321-8330
Publication Date(Web):
DOI:10.1002/chem.201203291

Abstract

Human A3 adenosine receptor (hA3AR) is a membrane-bound G protein-coupled receptor implicated in a number of severe pathological conditions, including cancer, in which it acts as a potential therapeutic target. To derive structure–activity relationships on pyrazolo–triazolo–pyrimidine (PTP)-based A3AR antagonists, we developed a new class of organometallic inhibitors through replacement of the triazolo moiety with an organoruthenium fragment. The objective was to introduce by design structural diversity into the PTP scaffold in order to tune their binding efficacy toward the target receptor. These novel organoruthenium antagonists displayed good aquatic stability and moderate binding affinity toward the hA3 receptor in the low micromolar range. The assembly of these complexes through a template-driven approach with selective ligand replacement at the metal center to control their steric and receptor-binding properties is discussed.

Co-reporter:Dr. Diego Montagner;Siew Qi Yap;Dr. Wee Han Ang
Angewandte Chemie 2013 Volume 125( Issue 45) pp:12001-12005
Publication Date(Web):
DOI:10.1002/ange.201305734
Co-reporter:Jian Li, Siew Qi Yap, Chee Fei Chin, Quan Tian, Sia Lee Yoong, Giorgia Pastorin and Wee Han Ang  
Chemical Science 2012 vol. 3(Issue 6) pp:2083-2087
Publication Date(Web):28 Mar 2012
DOI:10.1039/C2SC01086K
Platinum-based anticancer drugs constitute some of most effective chemotherapeutic regimes, but they are limited by high toxicities and severe side-effects arising from premature aquation and non-specific interactions. Macromolecular delivery agents can be used to shield platinum drugs from adventitious binding and as a platform to attach targeting groups, as a strategy to mitigate some of these limitations. An approach was conceived to utilise carbon nanotubes as a protective shell for stable platinum(IV) prodrugs entrapped within its inner cavities. An inert and strongly hydrophobic platinum(IV) complex was designed for entrapment within multiwalled carbon nanotubes via hydrophobic–hydrophobic interactions. Upon chemical reduction, the drug was converted to its cytotoxic and hydrophilic form and released from the carrier, via a drastic reversal in hydrophobicity, for DNA-binding. This simple method of hydrophobic entrapment and controlled release by chemical reduction and hydrophobicity reversal, exploiting the Pt(IV) scaffold as a prodrug, could form the basis of other delivery strategies for targeted delivery of platinum drugs into cancer cells.
Co-reporter:Quan Tian, Winnie Wong, Yang Xu, Yinthai Chan, Han Kiat Ho, Giorgia Pastorin and Wee Han Ang  
Chemical Communications 2012 vol. 48(Issue 44) pp:5467-5469
Publication Date(Web):10 Apr 2012
DOI:10.1039/C2CC30680H
A sensitive and versatile detection scheme based on quantum dot immobilisation on a solid support through bio-orthogonal PCR amplification and labelling has been developed for detection and quantification of gene targets in complex DNA mixtures.
Co-reporter:Chee Fei Chin ; Quan Tian ; Magdiel Inggrid Setyawati ; Wanru Fang ; Emelyn Sue Qing Tan ; David Tai Leong
Journal of Medicinal Chemistry 2012 Volume 55(Issue 17) pp:7571-7582
Publication Date(Web):August 9, 2012
DOI:10.1021/jm300580y
Platinum(II) anticancer drug cisplatin is one of the most important chemotherapeutic agents in clinical use but is limited by its high toxicity and severe side effects. Platinum(IV) anticancer prodrugs can overcome these limitations by resisting premature aquation and binding to essential plasma proteins. Structure–activity relationship studies revealed a link between the efficacy of platinum(IV) complexes with the nature of their axial ligands, which can be modified to enhance the properties of the prodrug. The existing paradigm of employing platinum(IV) complexes with symmetrical axial carboxylate ligands does not fully exploit their vast potential. A new approach was conceived to control properties of platinum(IV) prodrugs using contrasting axial ligands via sequential acylation. We report a novel class of asymmetric platinum(IV) carboxylates based on the cisplatin template containing both hydrophilic and lipophilic ligands on the same scaffold designed to improve their aqueous properties and enhance their efficacy against cancer cells in vitro.
Co-reporter:Jun Xiang Ong, Chun Wei Yap, and Wee Han Ang
Inorganic Chemistry 2012 Volume 51(Issue 22) pp:12483-12492
Publication Date(Web):November 2, 2012
DOI:10.1021/ic301884j
Protein tyrosine phosphatases (PTPs) belong to a large family of important regulatory enzymes involved in vital mammalian signaling pathways. Selective inhibitors of PTPs are highly valuable from a therapeutic standpoint given their association with various pathological conditions. One such target is PTP-1B which has previously been linked to diabetes and cancer. However, developing a selective inhibitor against PTP-1B has proven to be daunting because the enzyme shares a high degree of structural homology with TC-PTP, an essential PTP involved in modulating immune functions. To address this challenge, a series of organoruthenium complexes was developed to bind at the PTP substrate-binding site while simultaneously target the peripheral structural space. By capitalizing on the potential difference in the structural environment proximal to the active site between different PTPs, selectivity toward PTP-1B over TC-PTP was improved, paving the way for organoruthenium complexes as selective PTP-1B metalloinhibitors.
Co-reporter:Daniel Yuan Qiang Wong, Jia Yi Lau and Wee Han Ang  
Dalton Transactions 2012 vol. 41(Issue 20) pp:6104-6111
Publication Date(Web):15 Feb 2012
DOI:10.1039/C2DT30264K
Platinum(II) anticancer drugs are among the most effective and often used chemotherapeutic drugs. In recent years, there has been increasing interest in exploiting inert platinum(IV) scaffolds as a prodrug strategy to mitigate the limitations of platinum(II) anticancer complexes. In this prodrug strategy, the axial ligands are released concomitantly upon intracellular reduction to the active platinum(II) congener, offering the possibility of conjugating bioactive co-drugs which may synergistically enhance cytotoxicity on cancer cells. Existing techniques of tethering bioactive molecules to the axial positions of platinum(IV) prodrugs suffer from limited scope, poor yields and low reliability. This report explores the applications of current chemoselective ligation chemistries to platinum(IV) anticancer complexes with the aim of addressing the aforementioned limitations. Here, we describe the synthesis of a platinum(IV) complex bearing an aromatic aldehyde functionality and explored the scope of imine ligation with various hydrazide and aminooxy functionalized substrates. As a proof of concept, we tethered a six sequence long peptide mimetic (AMVSEF) of the anti-inflammatory protein, ANXA1.
Co-reporter:Yu Qian Tan, Paul J. Dyson, and Wee Han Ang
Organometallics 2011 Volume 30(Issue 21) pp:5965-5971
Publication Date(Web):October 8, 2011
DOI:10.1021/om200783r
Ruthenium–arene complexes bearing the 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]decane ligand, namely, RAPTA compounds, are widely investigated as potential antimetastatic agents for cancer therapy. Although much evidence points toward covalent binding with essential protein biomolecules as the key determinant of their activity, the exact biological targets of RAPTA remain elusive. To address this current gap in understanding, RAPTA compounds derivatized with acetal groups via a pendant chain to the arene ligand were developed as a functional probe for selective postlabeling and tagging of covalent RAPTA adducts in cancer cells.
Co-reporter:Dai Thien Nhan Tram, Hao Wang, Sigit Sugiarto, Tao Li, Wee Han Ang, Chengkuo Lee, Giorgia Pastorin
Biotechnology Advances (December 2016) Volume 34(Issue 8) pp:1275-1288
Publication Date(Web):December 2016
DOI:10.1016/j.biotechadv.2016.09.003
Co-reporter:Mun Juinn Chow ; Cynthia Licona ; Daniel Yuan Qiang Wong ; Giorgia Pastorin ; Christian Gaiddon
Journal of Medicinal Chemistry () pp:
Publication Date(Web):2017-2-22
DOI:10.1021/jm500455p
The structural diversity of metal scaffolds makes them a viable alternative to traditional organic scaffolds for drug design. Combinatorial chemistry and multicomponent reactions, coupled with high-throughput screening, are useful techniques in drug discovery, but they are rarely used in metal-based drug design. We report the optimization and validation of a new combinatorial, metal-based, three-component assembly reaction for the synthesis of a library of 442 Ru–arene Schiff-base (RAS) complexes. These RAS complexes were synthesized in a one-pot, on-a-plate format using commercially available starting materials under aqueous conditions. The library was screened for their anticancer activity, and several cytotoxic lead compounds were identified. In particular, [(η6-1,3,5-triisopropylbenzene)RuCl(4-methoxy-N-(2-quinolinylmethylene)aniline)]Cl (4) displayed low micromolar IC50 values in ovarian cancers (A2780, A2780cisR), breast cancer (MCF7), and colorectal cancer (HCT116, SW480). The absence of p53 activation or changes in IC50 value between p53+/+ and p53–/– cells suggests that 4 and possibly the other lead compounds may act independently of the p53 tumor suppressor gene frequently mutated in cancer.
Co-reporter:Angela Sîrbu, Oleg Palamarciuc, Maria V. Babak, Jia Min Lim, Kateryna Ohui, Eva A. Enyedy, Sergiu Shova, Denisa Darvasiová, Peter Rapta, Wee Han Ang and Vladimir B. Arion
Dalton Transactions 2017 - vol. 46(Issue 12) pp:NaN3847-3847
Publication Date(Web):2017/02/27
DOI:10.1039/C7DT00283A
A series of water-soluble sodium salts of 3-formyl-4-hydroxybenzenesulfonic acid thiosemicarbazones (or sodium 5-sulfonate-salicylaldehyde thiosemicarbazones) containing different substituents at the terminal nitrogen atom (H, Me, Et, Ph) and their copper(II) complexes have been prepared and characterised by elemental analysis, spectroscopic techniques (IR, UV-vis, 1H NMR), ESI mass spectrometry, X-ray crystallography and cyclic voltammetry. The proligands and their copper(II) complexes exhibit moderate water solubility and good stability in aqueous environment, determined by investigating their proton dissociation and complex formation equilibria. The copper(II) complexes showed moderate anticancer activity in established human cancer cell lines, while the proligands were devoid of cytotoxicity. The anticancer activity of the copper(II) complexes correlates with their ability to induce ROS accumulation in cells, consistent with their redox potentials within the biological window, triggering the activation of antioxidation defense mechanisms in response to the ROS insult. These studies pave the way for the investigation of ROS-inducing copper(II) complexes as prospective antiproliferative agents in cancer chemotherapy.
Co-reporter:Mun Juinn Chow, Mohammad Alfiean, Giorgia Pastorin, Christian Gaiddon and Wee Han Ang
Chemical Science (2010-Present) 2017 - vol. 8(Issue 5) pp:NaN3649-3649
Publication Date(Web):2017/02/28
DOI:10.1039/C7SC00497D
Multidrug resistance is a major impediment to chemotherapy and limits the efficacies of conventional anticancer drugs. A strategy to bypass multidrug resistance is to develop new drug candidates capable of inducing apoptosis-independent programmed cell death. However, cellular pathways implicated in alternative programmed cell death are not well-elucidated and multifactorial, making a target-based discovery approach a challenge. Here, we show that a coordination-directed three-component assembly and phenotypic screening strategy could be employed as a viable alternative for the identification of apoptosis-independent organoruthenium anticancer agents. Through an on-plate synthesis and screening of 195 organoruthenium complexes against apoptosis-sensitive and -resistant cancers, we identified two apoptosis-independent hits. Subsequent validation of the two hits showed a lack of induction of apoptotic biomarkers, a caspase-independent activity and an equal efficacy in both apoptosis-sensitive and -resistant colorectal cancers. This validated their apoptosis-independent modes-of-action, paving the way as potential candidates for the treatment of highly-refractory cancer phenotypes.
Co-reporter:Mun Juinn Chow, Cynthia Licona, Giorgia Pastorin, Georg Mellitzer, Wee Han Ang and Christian Gaiddon
Chemical Science (2010-Present) 2016 - vol. 7(Issue 7) pp:NaN4124-4124
Publication Date(Web):2016/03/01
DOI:10.1039/C6SC00268D
Multidrug resistance (MDR) is a major impediment to the success of chemotherapy in many cancer types. One particular MDR mechanism is the inherent or acquired adaptation of the cellular survival pathways that render malignant cells resistant to apoptotic cell death. Since most drugs act through apoptosis, compounds capable of inducing alternative forms of programmed cell death (PCD) can potentially be harnessed to bypass MDR. We investigated two organoruthenium complexes, RAS-1H and RAS-1T, and demonstrated that although they both induced non-apoptotic PCD through ER stress pathways, their modes-of-action were drastically different despite modest structural variations. RAS-1T acted through ROS-mediated ER stress while RAS-1H was ROS-independent. We further showed that they were more efficacious against apoptosis-resistant cells compared to clinical drugs including oxaliplatin. This work provides the basis for underpinning ER stress modulation using metal complexes to bypass apoptosis resistance.
Co-reporter:Daniel Yuan Qiang Wong, Jia Yi Lau and Wee Han Ang
Dalton Transactions 2012 - vol. 41(Issue 20) pp:NaN6111-6111
Publication Date(Web):2012/02/15
DOI:10.1039/C2DT30264K
Platinum(II) anticancer drugs are among the most effective and often used chemotherapeutic drugs. In recent years, there has been increasing interest in exploiting inert platinum(IV) scaffolds as a prodrug strategy to mitigate the limitations of platinum(II) anticancer complexes. In this prodrug strategy, the axial ligands are released concomitantly upon intracellular reduction to the active platinum(II) congener, offering the possibility of conjugating bioactive co-drugs which may synergistically enhance cytotoxicity on cancer cells. Existing techniques of tethering bioactive molecules to the axial positions of platinum(IV) prodrugs suffer from limited scope, poor yields and low reliability. This report explores the applications of current chemoselective ligation chemistries to platinum(IV) anticancer complexes with the aim of addressing the aforementioned limitations. Here, we describe the synthesis of a platinum(IV) complex bearing an aromatic aldehyde functionality and explored the scope of imine ligation with various hydrazide and aminooxy functionalized substrates. As a proof of concept, we tethered a six sequence long peptide mimetic (AMVSEF) of the anti-inflammatory protein, ANXA1.
Co-reporter:Chee Fei Chin, Siew Qi Yap, Jian Li, Giorgia Pastorin and Wee Han Ang
Chemical Science (2010-Present) 2014 - vol. 5(Issue 6) pp:NaN2270-2270
Publication Date(Web):2014/02/07
DOI:10.1039/C3SC53106F
Combination therapy is an effective strategy to enhance the efficacy of single-agent chemotherapy and delay onset of chemoresistance. However, differences in the pharmacokinetic profiles of the drug constituents can complicate the implementation of combination regimens in a clinical setting. Nanomaterials can overcome these limitations by offering a unified platform for targeted and synchronous delivery of multiple drugs, although exact ratiometric loading cannot be assured using conventional encapsulation techniques. An approach was conceived with the goal of delivering exact stoichiometric proportions of cisplatin and doxorubicin against endometrial adenocarcinoma using tumour-targeting multi-walled carbon nanotubes entrapping an inert Pt(IV) prodrug. Activation of the Pt(IV) prodrug after cell entry, synchronously releases molar equivalents of hydrophilic cisplatin and doxorubicin from the hydrophobic confines, thereby achieving ratiometric delivery of these mechanistically-complementary drug entities.
Co-reporter:Daniel Yuan Qiang Wong, Jun Han Lim and Wee Han Ang
Chemical Science (2010-Present) 2015 - vol. 6(Issue 5) pp:NaN3056-3056
Publication Date(Web):2015/03/16
DOI:10.1039/C5SC00015G
It is well-recognized that the failure of many chemotherapeutics arises due to an inability to induce apoptosis. Most cancers acquire a myriad of pro-survival adaptations, and the vast heterogeneity and accumulation of multiple often unrelated anti-apoptotic signaling pathways have been a major stumbling block towards the development of conventional chemotherapeutics, which can overcome drug resistance. We have developed highly potent and selective HER2-targeted Pt(IV) prodrugs bearing anti-HER2/neu peptides that induce targeted necrosis as a novel strategy to circumvent apoptosis-resistance. These Pt(IV)–peptide conjugates exhibit a unique biphasic mode of cytotoxicity comprising rapid killing of cancer cells via necrosis in the first phase followed by an extended and gradual phase of delayed cell death. We demonstrate that these Pt(IV)–peptide prodrugs are more potent than their Pt(II) congeners in direct cell-killing and exhibit comparable long-term inhibition of proliferative capacity and with greater selectivity against HER2-positive cancer cells.
Co-reporter:Jian Li, Siew Qi Yap, Chee Fei Chin, Quan Tian, Sia Lee Yoong, Giorgia Pastorin and Wee Han Ang
Chemical Science (2010-Present) 2012 - vol. 3(Issue 6) pp:NaN2087-2087
Publication Date(Web):2012/03/28
DOI:10.1039/C2SC01086K
Platinum-based anticancer drugs constitute some of most effective chemotherapeutic regimes, but they are limited by high toxicities and severe side-effects arising from premature aquation and non-specific interactions. Macromolecular delivery agents can be used to shield platinum drugs from adventitious binding and as a platform to attach targeting groups, as a strategy to mitigate some of these limitations. An approach was conceived to utilise carbon nanotubes as a protective shell for stable platinum(IV) prodrugs entrapped within its inner cavities. An inert and strongly hydrophobic platinum(IV) complex was designed for entrapment within multiwalled carbon nanotubes via hydrophobic–hydrophobic interactions. Upon chemical reduction, the drug was converted to its cytotoxic and hydrophilic form and released from the carrier, via a drastic reversal in hydrophobicity, for DNA-binding. This simple method of hydrophobic entrapment and controlled release by chemical reduction and hydrophobicity reversal, exploiting the Pt(IV) scaffold as a prodrug, could form the basis of other delivery strategies for targeted delivery of platinum drugs into cancer cells.
Co-reporter:Quan Tian, Winnie Wong, Yang Xu, Yinthai Chan, Han Kiat Ho, Giorgia Pastorin and Wee Han Ang
Chemical Communications 2012 - vol. 48(Issue 44) pp:NaN5469-5469
Publication Date(Web):2012/04/10
DOI:10.1039/C2CC30680H
A sensitive and versatile detection scheme based on quantum dot immobilisation on a solid support through bio-orthogonal PCR amplification and labelling has been developed for detection and quantification of gene targets in complex DNA mixtures.
1-Naphthalenamine, N-(2-quinolinylmethylene)-
1,4-Cyclohexadiene-1-propanal
1H-Pyrazole-4-carbonitrile, 3-amino-1-(3-phenylpropyl)-
5H-PYRAZOLO[3,4-D]PYRIMIDIN-5-AMINE, 2,4-DIHYDRO-4-IMINO-2-METHYL-
L-histidine decarboxylase type iii-S*from lactoba
Platinum, diamminedichlorodihydroxy-, (OC-6-33)-
3-(1,4-CYCLOHEXADIEN-1-YL)-1-PROPANOL
azane,2-methylpyridine,platinum(2+),dichloride
Hydrogen cation
N-(4-cyano-1-methyl-1H-pyrazol-3-yl)-Methanimidic acid ethyl ester