Displaying publications 1 - 20 of 52 in total

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  1. Elucidating the dynamic remodelling of Escherichia coli interactome in different growth conditions using multiplex co-fractionation MS (mCF-MS)
    Low TY
    Proteomics, 2023 Nov;23(21-22):e2300209.
    PMID: 37986683 DOI: 10.1002/pmic.202300209
    Most proteins function by forming complexes within a dynamic interconnected network that underlies various biological mechanisms. To systematically investigate such interactomes, high-throughput techniques, including CF-MS, have been developed to capture, identify, and quantify protein-protein interactions (PPIs) on a large scale. Compared to other techniques, CF-MS allows the global identification and quantification of native protein complexes in one setting, without genetic manipulation. Furthermore, quantitative CF-MS can potentially elucidate the distribution of a protein in multiple co-elution features, informing the stoichiometries and dynamics of a target protein complex. In this issue, Youssef et al. (Proteomics 2023, 00, e2200404) combined multiplex CF-MS and a new algorithm to study the dynamics of the PPI network for Escherichia coli grown under ten different conditions. Although the results demonstrated that most proteins remained stable, the authors were able to detect disrupted interactions that were growth condition specific. Further bioinformatics analyses also revealed the biophysical properties and structural patterns that govern such a response.
  2. Identification and Quantification of Affinity-Purified Proteins with MaxQuant, Followed by the Discrimination of Nonspecific Interactions with the CRAPome Interface
    Lee PY, Low TY
    Methods Mol Biol, 2023;2690:299-310.
    PMID: 37450156 DOI: 10.1007/978-1-0716-3327-4_25
    Affinity purification coupled to mass spectrometry (AP-MS) is a powerful method to analyze protein-protein interactions (PPIs). The AP-MS approach provides an unbiased analysis of the entire protein complex and is useful to identify indirect interactors. However, reliable protein identification from the complex AP-MS experiments requires appropriate control of false identifications and rigorous statistical analysis. Another challenge that can arise from AP-MS analysis is to distinguish bona fide interacting proteins from the non-specifically bound endogenous proteins or the "background contaminants" that co-purified by the bait experiments. In this chapter, we will first describe the protocol for performing in-solution trypsinization for the samples from the AP experiment followed by LC-MS/MS analysis. We will then detail the MaxQuant workflow for protein identification and quantification for the PPI data derived from the AP-MS experiment. Finally, we describe the CRAPome interface to process the data by filtering against contaminant lists, score the interactions and visualize the protein interaction networks.
  3. Tandem Affinity Purification (TAP) of Interacting Prey Proteins with FLAG- and HA-Tagged Bait Proteins
    Low TY, Lee PY
    Methods Mol Biol, 2023;2690:69-80.
    PMID: 37450137 DOI: 10.1007/978-1-0716-3327-4_6
    Proteins often interact with each other to form complexes and play functional roles in almost all cellular processes. The study of protein-protein interactions is therefore critical to understand protein function and biological pathways. Affinity Purification coupled with Mass Spectrometry (AP-MS) is an invaluable technique for identifying the interaction partners in protein complexes. In this approach, the protein of interest is fused to an affinity tag, followed by the expression and purification of the fusion protein. The affinity-purified sample is then analyzed by mass spectrometry to identify the interaction partners of the bait proteins. In this chapter, we detail the protocol for tandem affinity purification (TAP) based on the use of the FLAG (a fusion tag with peptide sequence DYKDDDDK) and hemagglutinin (HA) peptide epitopes. The immunoprecipitation using dual-affinity tags offers the advantage of increasing the specificity of the purification with lower nonspecific-background interactions.
  4. Probing the endogenous peptidomes of cancer for biomarkers: A new endeavor
    Lee PY, Low TY, Jamal R
    Adv Clin Chem, 2018 12 27;88:67-89.
    PMID: 30612607 DOI: 10.1016/bs.acc.2018.10.004
    The life span of cancer patients can be prolonged with appropriate therapies if detected early. Mass screening for early detection of cancer, however, requires sensitive and specific biomarkers obtainable from body fluids such as blood or urine. To date, most biomarker discovery programs focus on the proteome rather than the endogenous peptidome. It has been long-established that tumor cells and stromal cells produce tumor resident proteases (TRPs) to remodel the surrounding tumor microenvironment in support of tumor progression. In fact, proteolytic products of TRPs have been shown to correlate with malignant behavior. Being of low molecular weight, these unique peptides can pass through the endothelial barrier of the vasculature into the bloodstream. As such, the cancer peptidome has increasingly become a focus for biomarker discovery. In this review, we discuss on the various aspects of the peptidome in cancer biomarker research.
  5. The evolution of two-dimensional gel electrophoresis - from proteomics to emerging alternative applications
    Lee PY, Saraygord-Afshari N, Low TY
    J Chromatogr A, 2020 Mar 29;1615:460763.
    PMID: 31836310 DOI: 10.1016/j.chroma.2019.460763
    Two-dimensional gel electrophoresis (2-DE) is a technique that has been widely applied in a variety of proteomics studies. It is capable of resolving complex protein mixtures into individual protein spots based on their isoelectric point and molecular weight, enabling large-scale analysis of protein expression patterns for deciphering their changes in different biological conditions. 2-DE is a powerful tool that empowers researchers to perform differential qualitative and quantitative proteome analysis and is particularly advantageous for characterizing protein isoforms and post-translationally modified proteins. Despite its popularity as the workhorse for proteomics in the past few decades, it has been gradually displaced by the more sophisticated and high-performance mass spectrometry-based methods. However, there are several variations of the 2-DE technique that have emerged as promising approaches that shine new light on specific niches that 2-DE could still contribute. In this review, we first provide an overview of the applications of 2-DE, its merits and pitfalls in the current proteomic research arena, followed by a discussion on several alternative approaches for potential future applications.
  6. A recent update on small-molecule kinase inhibitors for targeted cancer therapy and their therapeutic insights from mass spectrometry-based proteomic analysis
    Lee PY, Yeoh Y, Low TY
    FEBS J, 2023 Jun;290(11):2845-2864.
    PMID: 35313089 DOI: 10.1111/febs.16442
    Kinases are key regulatory signalling proteins governing numerous essential biological processes and cellular functions. Dysregulation of many protein kinases is associated with cancer initiation and progression. Given their crucial roles, there has been increasing interest in harnessing kinases as prospective drug targets for cancer. In recent decades, numerous small-molecule kinase inhibitors have been developed and revolutionized the cancer treatment landscape. Despite their great potential, challenges remain in developing highly selective and effective kinase inhibitors, with toxicity and resistance issues frequently arising. In this review, we first provide an overview of the role of kinases in carcinogenesis and describe the current progress with small-molecule kinase inhibitors that have been approved for clinical use. We then discuss the application of mass spectrometry (MS)-based proteomics strategies to help in the design of kinase inhibitors. Finally, we discuss the challenges and outlook concerning MS-based proteomics techniques for kinase drug research.
  7. On the critical importance of meticulous data extraction for meta-analysis of genetic association study
    Low TY, Chin KY, Tan SC
    Arch Physiol Biochem, 2023 Dec;129(4):1007-1008.
    PMID: 33689514 DOI: 10.1080/13813455.2021.1890132
  8. Fulltext Using the Proteomics Toolbox to Resolve Topology and Dynamics of Compartmentalized cAMP Signaling
    Kovanich D, Low TY, Zaccolo M
    Int J Mol Sci, 2023 Feb 28;24(5).
    PMID: 36902098 DOI: 10.3390/ijms24054667
    cAMP is a second messenger that regulates a myriad of cellular functions in response to multiple extracellular stimuli. New developments in the field have provided exciting insights into how cAMP utilizes compartmentalization to ensure specificity when the message conveyed to the cell by an extracellular stimulus is translated into the appropriate functional outcome. cAMP compartmentalization relies on the formation of local signaling domains where the subset of cAMP signaling effectors, regulators and targets involved in a specific cellular response cluster together. These domains are dynamic in nature and underpin the exacting spatiotemporal regulation of cAMP signaling. In this review, we focus on how the proteomics toolbox can be utilized to identify the molecular components of these domains and to define the dynamic cellular cAMP signaling landscape. From a therapeutic perspective, compiling data on compartmentalized cAMP signaling in physiological and pathological conditions will help define the signaling events underlying disease and may reveal domain-specific targets for the development of precision medicine interventions.
  9. Fulltext Revisiting the Roles of Pro-Metastatic EpCAM in Cancer
    Mohtar MA, Syafruddin SE, Nasir SN, Low TY
    Biomolecules, 2020 02 07;10(2).
    PMID: 32046162 DOI: 10.3390/biom10020255
    Epithelial cell adhesion molecule (EpCAM) is a cell surface protein that was discovered as a tumour marker of epithelial origins nearly four decades ago. EpCAM is expressed at basal levels in the basolateral membrane of normal epithelial cells. However, EpCAM expression is upregulated in solid epithelial cancers and stem cells. EpCAM can also be found in disseminated tumour cells and circulating tumour cells. Various OMICs studies have demonstrated that EpCAM plays roles in several key biological processes such as cell adhesion, migration, proliferation and differentiation. Additionally, EpCAM can be detected in the bodily fluid of cancer patients suggesting that EpCAM is a pathophysiologically relevant anti-tumour target as well as being utilized as a diagnostic/prognostic agent for a variety of cancers. This review will focus on the structure-features of EpCAM protein and discuss recent evidence on the pathological and physiological roles of EpCAM in modulating cell adhesion and signalling pathways in cancers as well as deliberating the clinical implication of EpCAM as a therapeutic target.
  10. Probing the colorectal cancer proteome for biomarkers: Current status and perspectives
    Lee PY, Chin SF, Low TY, Jamal R
    J Proteomics, 2018 09 15;187:93-105.
    PMID: 29953962 DOI: 10.1016/j.jprot.2018.06.014
    Colorectal cancer (CRC) is one of the most prevalent malignancies worldwide. Biomarkers that can facilitate better clinical management of CRC are in high demand to improve patient outcome and to reduce mortality. In this regard, proteomic analysis holds a promising prospect in the hunt of novel biomarkers for CRC and in understanding the mechanisms underlying tumorigenesis. This review aims to provide an overview of the current progress of proteomic research, focusing on discovery and validation of diagnostic biomarkers for CRC. We will summarize the contributions of proteomic strategies to recent discoveries of protein biomarkers for CRC and also briefly discuss the potential and challenges of different proteomic approaches in biomarker discovery and translational applications.
  11. Corrigendum to "Probing the colorectal cancer proteome for biomarkers: Current status and perspectives" [J Proteomics Vol. 187 (2018) 93-105]
    Lee PY, Chin SF, Low TY, Jamal R
    J Proteomics, 2019 Feb 10;192:383.
    PMID: 30213519 DOI: 10.1016/j.jprot.2018.08.017
  12. Connecting Proteomics to Next-Generation Sequencing: Proteogenomics and Its Current Applications in Biology
    Low TY, Mohtar MA, Ang MY, Jamal R
    Proteomics, 2019 05;19(10):e1800235.
    PMID: 30431238 DOI: 10.1002/pmic.201800235
    Understanding the relationship between genotypes and phenotypes is essential to disentangle biological mechanisms and to unravel the molecular basis of diseases. Genes and proteins are closely linked in biological systems. However, genomics and proteomics have developed separately into two distinct disciplines whereby crosstalk among scientists from the two domains is limited and this constrains the integration of both fields into a single data modality of useful information. The emerging field of proteogenomics attempts to address this by building bridges between the two disciplines. In this review, how genomics and transcriptomics data in different formats can be utilized to assist proteogenomics application is briefly discussed. Subsequently, a much larger part of this review focuses on proteogenomics research articles that are published in the last five years that answer two important questions. First, how proteogenomics can be applied to tackle biological problems is discussed, covering genome annotation and precision medicine. Second, the latest developments in analytical technologies for data acquisition and the bioinformatics tools to interpret and visualize proteogenomics data are covered.
  13. Plasma/serum proteomics: depletion strategies for reducing high-abundance proteins for biomarker discovery
    Lee PY, Osman J, Low TY, Jamal R
    Bioanalysis, 2019 Oct;11(19):1799-1812.
    PMID: 31617391 DOI: 10.4155/bio-2019-0145
    Plasma and serum are widely used for proteomics-based biomarker discovery. However, analysis of these biofluids is highly challenging due to the complexity and wide dynamic range of their proteomes. Notably, highly abundant proteins tend to obscure the detection of potential biomarkers that are usually of lower concentrations. Among the strategies to resolve this problem are: depletion of high-abundance proteins, enrichment of low abundant proteins of interest and prefractionation. In this review, we focus on current and emerging depletion techniques used to enhance the detection and identification of the less abundant proteins in plasma and serum. We discuss the applications and contributions of these methods to proteomics analysis of plasma and serum alongside their limitations and future perspectives.
  14. Fulltext Regulation of signal transduction pathways in colorectal cancer: implications for therapeutic resistance
    Yeoh Y, Low TY, Abu N, Lee PY
    PeerJ, 2021;9:e12338.
    PMID: 34733591 DOI: 10.7717/peerj.12338
    Resistance to anti-cancer treatments is a critical and widespread health issue that has brought serious impacts on lives, the economy and public policies. Mounting research has suggested that a selected spectrum of patients with advanced colorectal cancer (CRC) tend to respond poorly to both chemotherapeutic and targeted therapeutic regimens. Drug resistance in tumours can occur in an intrinsic or acquired manner, rendering cancer cells insensitive to the treatment of anti-cancer therapies. Multiple factors have been associated with drug resistance. The most well-established factors are the emergence of cancer stem cell-like properties and overexpression of ABC transporters that mediate drug efflux. Besides, there is emerging evidence that signalling pathways that modulate cell survival and drug metabolism play major roles in the maintenance of multidrug resistance in CRC. This article reviews drug resistance in CRC as a result of alterations in the MAPK, PI3K/PKB, Wnt/β-catenin and Notch pathways.
  15. Biomarkers for colorectal cancer chemotherapy: Recent updates and future perspective
    Lee PY, Md Azhan FS, Low TY
    Malays J Pathol, 2023 Dec;45(3):317-331.
    PMID: 38155375
    During the last few decades, the treatment options available for patients with metastatic colorectal cancer (mCRC) have undergone continuous improvements, transitioning from conventional chemotherapy to targeted therapy. These therapeutic innovations have led to significant improvements in patient clinical outcomes. However, there remains a need to improve the outcome for many CRC patients. Chemotherapy remains a cornerstone of CRC treatment, but the wide variability in tumour response and adverse reactions to chemotherapy poses a challenge to cancer treatment management. As a result, there is an unmet need to identify predictive biomarkers of chemotherapeutic response to guide treatment decisions. In this review, we summarise the conventional biomarkers used to predict chemotherapy responses in CRC and provide an overview of emerging predictive biomarkers based on the current understanding of the molecular biology of treatment response. Finally, we explore the challenges and future prospects of biomarker discovery to improve the prediction of patient response and ensure optimal treatment management for patients with metastatic CRC.
  16. Fulltext More Than Meets the Eye: Revisiting the Roles of Heat Shock Factor 4 in Health and Diseases
    Syafruddin SE, Ling S, Low TY, Mohtar MA
    Biomolecules, 2021 Mar 31;11(4).
    PMID: 33807297 DOI: 10.3390/biom11040523
    Cells encounter a myriad of endogenous and exogenous stresses that could perturb cellular physiological processes. Therefore, cells are equipped with several adaptive and stress-response machinery to overcome and survive these insults. One such machinery is the heat shock response (HSR) program that is governed by the heat shock factors (HSFs) family in response towards elevated temperature, free radicals, oxidants, and heavy metals. HSF4 is a member of this HSFs family that could exist in two predominant isoforms, either the transcriptional repressor HSFa or transcriptional activator HSF4b. HSF4 is constitutively active due to the lack of oligomerization negative regulator domain. HSF4 has been demonstrated to play roles in several physiological processes and not only limited to regulating the classical heat shock- or stress-responsive transcriptional programs. In this review, we will revisit and delineate the recent updates on HSF4 molecular properties. We also comprehensively discuss the roles of HSF4 in health and diseases, particularly in lens cell development, cataract formation, and cancer pathogenesis. Finally, we will posit the potential direction of HSF4 future research that could enhance our knowledge on HSF4 molecular networks as well as physiological and pathophysiological functions.
  17. Secretion of pro-oncogenic AGR2 protein in cancer
    Moidu NA, A Rahman NS, Syafruddin SE, Low TY, Mohtar MA
    Heliyon, 2020 Sep;6(9):e05000.
    PMID: 33005802 DOI: 10.1016/j.heliyon.2020.e05000
    Anterior gradient-2 (AGR2) protein mediates the formation, breakage and isomerization of disulphide bonds during protein maturation in the endoplasmic reticulum (ER) and contributes to the homoeostasis of the secretory pathway. AGR2 promotes tumour development and metastasis and its elevated expression is almost completely restricted to malignant tumours. Interestingly, this supposedly ER-resident protein can be localised to other compartments of cancer cells and can also be secreted into the extracellular milieu. There are emerging evidences that describe the gain-of-function activities of the extracellular AGR2, particularly in cancer development. Here, we reviewed studies detailing the expression, pathological and physiological roles associated with AGR2 and compared the duality of localization, intracellular and extracellular, with special emphasis on the later. We also discussed the possible mechanisms of AGR2 secretion as well as deliberating the functional impacts of AGR2 in cancer settings. Last, we deliberate the current therapeutic strategies and posit the potential use AGR2, as a prognosis and diagnosis marker in cancer.
  18. Analyzing the Secretome of Gut Microbiota as the Next Strategy For Early Detection of Colorectal Cancer
    Megat Mohd Azlan PI, Chin SF, Low TY, Neoh HM, Jamal R
    Proteomics, 2019 05;19(10):e1800176.
    PMID: 30557447 DOI: 10.1002/pmic.201800176
    Dysbiosis of gut microbiome can contribute to inflammation, and subsequently initiation and progression of colorectal cancer (CRC). Throughout these stages, various proteins and metabolites are secreted to the external environment by microorganisms or the hosts themselves. Studying these proteins may help enhance our understanding of the host-microorganism relationship or they may even serve as useful biomarkers for CRC. However, secretomic studies of gut microbiome of CRC patients, until now, are scarcely performed. In this review article, the focus is on the roles of gut microbiome in CRC, the current findings on CRC secretome are highlighted, and the emerging challenges and strategies to drive forward this area of research are addressed.
  19. Signatures of gene expression, DNA methylation and microRNAs of hepatocellular carcinoma with vascular invasion
    Sulaiman SA, Abu N, Ab-Mutalib NS, Low TY, Jamal R
    Future Oncol, 2019 Aug;15(22):2603-2617.
    PMID: 31339048 DOI: 10.2217/fon-2018-0909
    Aim: Micro and macro vascular invasion (VI) are known as independent predictors of tumor recurrence and poor survival after surgical treatment of hepatocellular carcinoma (HCC). Here, we aimed to re-analyze The Cancer Genome Atlas of liver hepatocellular carcinoma datasets to identify the VI-expression signatures. Materials & methods: We filtered The Cancer Genome Atlas liver hepatocellular carcinoma (LIHC) datasets into three groups: no VI (NVI = 198); micro VI (MIVI = 89) and macro VI (MAVI = 16). We performed differential gene expression, methylation and microRNA analyses. Results & conclusion: We identified 12 differentially expressed genes and 55 differentially methylated genes in MAVI compared with no VI. The GPD1L gene appeared in all of the comparative analyses. Higher GPD1L expression was associated with VI and poor outcomes in the HCC patients.
  20. A dose-response and meta-analysis of dehydroepiandrosterone (DHEA) supplementation on testosterone levels: perinatal prediction of randomized clinical trials
    Li Y, Ren J, Li N, Liu J, Tan SC, Low TY, et al.
    Exp Gerontol, 2020 11;141:111110.
    PMID: 33045358 DOI: 10.1016/j.exger.2020.111110
    BACKGROUND: Dehydroepiandrosterone (DHEA) has been aggressively sold as a dietary supplement to boost testosterone levels although the impact of DHEA supplementation on testosterone levels has not been fully established. Therefore, we performed a systematic review and meta-analysis of RCTs to investigate the effect of oral DHEA supplementation on testosterone levels.

    METHODS: A systematic literature search was performed in Scopus, Embase, Web of Science, and PubMed databases up to February 2020 for RCTs that investigated the effect of DHEA supplementation on testosterone levels. The estimated effect of the data was calculated using the weighted mean difference (WMD). Subgroup analysis was performed to identify the source of heterogeneity among studies.

    RESULTS: Overall results from 42 publications (comprising 55 arms) demonstrated that testosterone level was significantly increased after DHEA administration (WMD: 28.02 ng/dl, 95% CI: 21.44-34.60, p = 0.00). Subgroup analyses revealed that DHEA increased testosterone level in all subgroups, but the magnitude of increment was higher in females compared to men (WMD: 30.98 ng/dl vs. 21.36 ng/dl); DHEA dosage of ˃50 mg/d compared to ≤50 mg/d (WMD: 57.96 ng/dl vs. 19.43 ng/dl); intervention duration of ≤12 weeks compared to ˃12 weeks (WMD: 44.64 ng/dl vs. 19 ng/dl); healthy participants compared to postmenopausal women, pregnant women, non-healthy participants and androgen-deficient patients (WMD: 52.17 ng/dl vs. 25.04 ng/dl, 16.44 ng/dl and 16.47 ng/dl); and participants below 60 years old compared to above 60 years old (WMD: 31.42 ng/dl vs. 23.93 ng/dl).

    CONCLUSION: DHEA supplementation is effective for increasing testosterone levels, although the magnitude varies among different subgroups. More study needed on pregnant women and miscarriage.

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