Displaying publications 1 - 20 of 109 in total

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  1. Organotypic culture of human amnion cells in air-liquid interface as a potential substitute for skin regeneration
    Fatimah SS, Chua K, Tan GC, Azmi TI, Tan AE, Abdul Rahman H
    Cytotherapy, 2013 Aug;15(8):1030-41.
    PMID: 23830235 DOI: 10.1016/j.jcyt.2013.05.003
    The aim of the present study was to evaluate the effects of air-liquid interface on the differentiation potential of human amnion epithelial cells (HAECs) to skin-like substitute in organotypic culture.
  2. Augmentation of angiogenic and endothelial associated gene expression by EDM50 in human chorion-derived stem cells
    Manzor NF, Chua KH, Tan GC, Tan AE, Abdul Rahman H
    Med J Malaysia, 2008 Jul;63 Suppl A:11-2.
    PMID: 19024960
    The objective of this study was to investigate the angiogenic potential of human chorion-derived stem cells (CDSC) cultured in medium containing bFGF and VEGF (EDM50). Total RNA was extracted from cells cultured in FD+10% FBS and EDM50. Quantitative RT-PCR was carried out to score the differential mRNA expression of genes involve in angiogenesis and endothelial differentiation. Our finding demonstrated that all angiogenic and endothelial associated genes were expressed higher in EDM50. Expression level of ANG-1, eNOS and VEGFR2 were significantly higher in EDM50 compared to FD+10% FBS. Our results suggested that human CDSC cultured in EDM50 can be used for angiogenesis purpose in regenerative medicine.
  3. Fulltext NK/T cell lymphoma associated with peripheral eosinophilia
    Yap E, Wan Jamaluddin WF, Tumian NR, Mashuri F, Mohammed F, Tan GC, et al.
    Malays J Pathol, 2014 Dec;36(3):201-5.
    PMID: 25500520 MyJurnal
    NK/T cell lymphoma, nasal type is an aggressive and uncommon malignancy. Disease that occurs outside of the aerodigestive tract exhibits an even more aggressive clinical behaviour and does not respond as well to conventional therapy compared to its nasal counterpart. We report such a case of NK/T cell lymphoma, nasal type, that presented as an anterior chest wall mass, arising from the left pectoralis muscle. An interesting feature we wish to highlight is the associated eosinophilia that corresponded to disease activity, exhibiting fluctuations with surgical resection and chemotherapy. To the best of our knowledge this is the third reported case of NK/T cell lymphoma that is associated with peripheral eosinophilia. Our case highlights the role of certain NK cell subsets that play a major role in eosinophilic activation in NK/T lymphomas and calls for more research into further classification of this disease by virtue of its NK cell subsets.
  4. Intrathyroidal oxyphilic parathyroid carcinoma: A potential diagnostic caveat in cytology?
    Wong YP, Sharifah NA, Tan GC, Gill AJ, Ali SZ
    Diagn Cytopathol, 2016 May 26.
    PMID: 27229757 DOI: 10.1002/dc.23493
    Oxyphilic (oncocytic) parathyroid lesions are very uncommon and their cytological features are rarely described. Due to the similarities in anatomical location and indistinguishable cytomorphological features, these lesions are easily confused with neoplastic and non-neoplastic thyroid lesions on fine needle aspiration (FNA). The diagnosis becomes more challenging in cases of unusual intrathyroidal location of the parathyroid lesions in the absence of clinical evidence of hyperparathyroidism, which simulate thyroid nodules clinically. We describe a case of intrathyroidal oxyphilic parathyroid carcinoma in a 66-year-old female, who presented with a dominant left "thyroid" nodule. FNA smears were cellular, comprising predominantly of oxyphilic cells arranged in papillary-like architecture with occasional nuclear grooves, which was mistaken for oncocytic variant of papillary carcinoma of the thyroid. The histological diagnosis of oxyphilic parathyroid "adenoma" was made following total thyroidectomy. The tumor, unfortunately, recurred 7 years later with associated multiple lung metastases. When dealing with thyroid lesions comprising predominantly of oncocytic cells, one should consider oxyphilic parathyroid neoplasms as one of the differential diagnosis. In difficult equivocal cases, a panel of immunocytochemical stains (PTH, GATA3, TTF-1, PAX8, and thyroglobulin) can be helpful. In addition, a combination of valuable clinical, radiological, and laboratory data, including serum calcium and parathyroid hormone levels are key to arriving at an accurate cytological diagnosis. Diagn. Cytopathol. 2016. © 2016 Wiley Periodicals, Inc.
  5. Aldosterone-Producing Adenomas: Histopathology-Genotype Correlation and Identification of a Novel CACNA1D Mutation
    Tan GC, Negro G, Pinggera A, Tizen Laim NMS, Mohamed Rose I, Ceral J, et al.
    Hypertension, 2017 07;70(1):129-136.
    PMID: 28584016 DOI: 10.1161/HYPERTENSIONAHA.117.09057
    Mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D, and CTNNB1 are thought to cause the excessive autonomous aldosterone secretion of aldosterone-producing adenomas (APAs). The histopathology of KCNJ5 mutant APAs, the most common and largest, has been thoroughly investigated and shown to have a zona fasciculata-like composition. This study aims to characterize the histopathologic spectrum of the other genotypes and document the proliferation rate of the different sized APAs. Adrenals from 39 primary aldosteronism patients were immunohistochemically stained for CYP11B2 to confirm diagnosis of an APA. Twenty-eight adenomas had sufficient material for further analysis and were target sequenced at hot spots in the 5 causal genes. Ten adenomas had a KCNJ5 mutation (35.7%), 7 adenomas had an ATP1A1 mutation (25%), and 4 adenomas had a CACNA1D mutation (14.3%). One novel mutation in exon 28 of CACNA1D (V1153G) was identified. The mutation caused a hyperpolarizing shift of the voltage-dependent activation and inactivation and slowed the channel's inactivation kinetics. Immunohistochemical stainings of CYP17A1 as a zona fasciculata cell marker and Ki67 as a proliferation marker were used. KCNJ5 mutant adenomas showed a strong expression of CYP17A1, whereas ATP1A1/CACNA1D mutant adenomas had a predominantly negative expression (P value =1.20×10-4). ATP1A1/CACNA1D mutant adenomas had twice the nuclei with intense staining of Ki67 than KCNJ5 mutant adenomas (0.7% [0.5%-1.9%] versus 0.4% [0.3%-0.7%]; P value =0.04). Further, 3 adenomas with either an ATP1A1 mutation or a CACNA1D mutation had >30% nuclei with moderate Ki67 staining. In summary, similar to KCNJ5 mutant APAs, ATP1A1 and CACNA1D mutant adenomas have a seemingly specific histopathologic phenotype.
  6. Fulltext Prevalence and Histopathological Characteristics of KCNJ5 Mutant Aldosterone-Producing Adenomas in a Multi-Ethnic Malaysian Cohort
    Mohideen SK, Mustangin M, Kamaruddin NA, Muhammad R, Jamal ARA, Sukor N, et al.
    Front Endocrinol (Lausanne), 2019;10:666.
    PMID: 31636604 DOI: 10.3389/fendo.2019.00666
    Studies on excised adrenals from primary aldosteronism patients have found that somatic mutations in KCNJ5 frequently cause excess aldosterone production in the culprit aldosterone-producing adenoma (APA). KCNJ5 mutant APAs were reported to be peculiarly overrepresented among young females and in Oriental cohorts, compared to their older male, or Caucasian counterparts. These larger APAs were also reported to have similarities with the zona fasciculata (ZF) in the adrenal both from the steroid production profile and the morphology of the cell. We therefore aimed to corroborate these findings by characterizing the APAs from a multi-ethnic Malaysian cohort. The prevalence of KCNJ5 mutations was estimated through targeted DNA sequencing of KCNJ5 in 54 APAs. Confirmation of APA sample acquisition was performed by CYP11B2 immunohistochemistry (IHC) staining. The ZF steroid production profile was based on the ZF enzyme CYP17A1 IHC staining, and ZF cell morphology was based on a high cytoplasm to nucleus ratio. Seventeen (31.5%) APAs studied, harbored a KCNJ5 mutation. No female over-representation was seen in this cohort though females were found to have a higher expression of CYP11B2 than males (p = 0.009; Mann-Whitney U test). Age at adrenalectomy correlated negatively with the percentage of ZF-like cells in the APA (p = 0.01; Spearman's rho) but not with the KCNJ5 genotype. KCNJ5 mutant APAs had a high percentage of ZF-like cells (and high CYP17A1 expression) but so did the wild-type APAs. In summary, prevalence of KCNJ5 mutant APAs in this cohort was similar to other Caucasian cohorts, however, over-representation of females did not occur, which is similar to some studies in Oriental cohorts.
  7. Implementation of the International Academy of Cytology Yokohama standardized reporting for breast cytopathology: An 8-year retrospective study
    Wong YP, Vincent James EP, Mohammad Azhar MAA, Krishnamoorthy Y, Zainudin NA, Zamara F, et al.
    Diagn Cytopathol, 2021 Jun;49(6):718-726.
    PMID: 33629823 DOI: 10.1002/dc.24731
    BACKGROUND: The International Academy of Cytology (IAC) Yokohama reporting system was recently proposed to serve as a standardized diagnostic platform for the cytological interpretation of breast fine needle aspiration biopsy (FNAB). Five cytological categories were suggested, linked to a certain risk of malignancy (ROM). The aim of this study was to assess the potency of this newly proposed reporting guideline, with a review of literatures.

    METHODS: This is a retrospective study over 8-year duration in which all the breast FNABs performed in our institution were recategorized in accordance to the IAC Yokohama reporting system. Kappa coefficient was used to evaluate the agreement between the proposed cytological category and corresponding histological diagnosis, with the level of significance set at 5%. Cyto-histopathological correlation and its diagnostic performance were also assessed.

    RESULTS: A total of 1136 breast FNABs were analyzed, including 31 repeat FNABs. Of these, 521 (47.1%) cases had matched histopathological results. Respective ROM for each category was: "insufficient" 13.6%, "benign" 0.4%, "atypical" 25.0%, "suspicious" 85.7%, and "malignant" 100%. There was substantial agreement (κ=0.757) between cytology and histopathological results. Our data revealed a high-diagnostic specificity, sensitivity, positive and negative predictive value of 99.3% (95% CI: 97.6%-99.9%), 94.2% (95% CI: 87.9%-97.9%), 98.0% (95% CI: 92.5%-99.5%), 98.0% (95% CI: 96.1%-99.1%) respectively when both the "suspicious" and "malignant" cases were considered as positive tests, with area under the curve of 0.993.

    CONCLUSIONS: The IAC Yokohama system is a reliable, evidence-based, and standardized reporting system that helps to facilitate communication among cytopathologists, radiologists, and surgeons toward individualized patient management.

  8. Fulltext Somatic mutations of CADM1 in aldosterone-producing adenomas and gap junction-dependent regulation of aldosterone production
    Wu X, Azizan EAB, Goodchild E, Garg S, Hagiyama M, Cabrera CP, et al.
    Nat Genet, 2023 Jun;55(6):1009-1021.
    PMID: 37291193 DOI: 10.1038/s41588-023-01403-0
    Aldosterone-producing adenomas (APAs) are the commonest curable cause of hypertension. Most have gain-of-function somatic mutations of ion channels or transporters. Herein we report the discovery, replication and phenotype of mutations in the neuronal cell adhesion gene CADM1. Independent whole exome sequencing of 40 and 81 APAs found intramembranous p.Val380Asp or p.Gly379Asp variants in two patients whose hypertension and periodic primary aldosteronism were cured by adrenalectomy. Replication identified two more APAs with each variant (total, n = 6). The most upregulated gene (10- to 25-fold) in human adrenocortical H295R cells transduced with the mutations (compared to wildtype) was CYP11B2 (aldosterone synthase), and biological rhythms were the most differentially expressed process. CADM1 knockdown or mutation inhibited gap junction (GJ)-permeable dye transfer. GJ blockade by Gap27 increased CYP11B2 similarly to CADM1 mutation. Human adrenal zona glomerulosa (ZG) expression of GJA1 (the main GJ protein) was patchy, and annular GJs (sequelae of GJ communication) were less prominent in CYP11B2-positive micronodules than adjacent ZG. Somatic mutations of CADM1 cause reversible hypertension and reveal a role for GJ communication in suppressing physiological aldosterone production.
  9. Fulltext Tracheal agenesis: a rare cause of unsuccessful tracheal intubation during resuscitation
    Iszuari M, Mazita A, Tan GC, Hayati AR, Shareena I, Cheah FC
    Med J Malaysia, 2010 Dec;65(4):317-8.
    PMID: 21901957
    Tracheal agenesis is a rare congenital airway anomaly that usually results in a fatal outcome. The diagnosis is usually made through post-mortem examination. In the current literature, there has been no reported long-term survival although a few reports claimed prolongation of life of several hours to days. This condition is commonly associated with premature birth, polyhydramnios and a male predominance. In 90% of the cases, it is associated with multiple cardiovascular, gastrointestinal and genitourinary tract anomalies which are incompatible with life. We report a case of a premature newborn with severe respiratory distress, absent cry and cyanosis soon after birth. Attempts at endotracheal intubation failed as it was no possible to negotiate the tube beyond the vocal cords. Needle cricothyrotomy and attempted tracheostomy also failed to secure the airway. The diagnosis was confirmed at post-mortem examination.
  10. Gardnerella vaginalis in perinatology: An overview of the clinicopathological correlation
    Wong YP, Tan GC, Wong KK, Anushia S, Cheah FC
    Malays J Pathol, 2018 Dec;40(3):267-286.
    PMID: 30580358
    Gardnerella vaginalis (GV) is a facultatively anaerobic gram-variable bacillus and is the major organism involved in bacterial vaginosis. GV-associated bacterial vaginosis has been associated with adverse pregnancy outcomes include preterm parturition and subclinical chorioamnionitis. Inflammatory response induced by GV presents paediatric problems as well. Studies had shown that increased levels of proinflammatory cytokines include TNF-α, IL-1β and IL-6 following fetal inflammatory response syndrome secondary to GV-induced intrauterine infection may result in the development of periventricular leukomalacia and bronchopulmonary dysplasia in the infected fetus. There is increasing evidence that GV-associated BV infection serves as a risk factor for long-term neurological complications, such as cerebral palsy and learning disability. GV is fastidious and could elude conventional detection methods such as bacterial cultures. With current more sophisticated molecular biology detection methods, its role and pathogenic effects have been shown to have a greater impact on intrauterine inflammation and fetal/neonatal infection. This review gives an overview on the characteristics of GV and its virulence properties. Its detrimental role in causing unfavourable GV-related perinatal outcomes, with emphasis on the possible mechanistic pathways is discussed. The discovery of disease mechanisms allows the building of a strong platform where further research on innovative therapies can be based on, for instance, an anti-TLR monoclonal antibody as therapeutic agent to halt inflammation-precipitate adverse perinatal outcomes.
  11. Fulltext Targeted inactivation of Salmonella Agona metabolic genes by group II introns and in vivo assessment of pathogenicity and anti-tumour activity in mouse model
    Gwee CP, Khoo CH, Yeap SK, Tan GC, Cheah YK
    PeerJ, 2019;7:e5989.
    PMID: 30671294 DOI: 10.7717/peerj.5989
    The fight against cancer has been a never-ending battle. Limitations of conventional therapies include lack of selectivity, poor penetration and highly toxic to the host. Using genetically modified bacteria as a tumour therapy agent has gained the interest of scientist from the past few decades. Low virulence and highly tolerability of Salmonella spp. in animals and humans make it as the most studied pathogen with regards to anti-tumour therapy. The present study aims to construct a genetically modified S. Agona auxotroph as an anti-tumour agent. LeuB and ArgD metabolic genes in ΔSopBΔSopD double knockout S. Agona were successfully knocked out using a Targetron gene knockout system. The knockout was confirmed by colony PCR and the strains were characterized in vitro and in vivo. The knockout of metabolic genes causes significant growth defect in M9 minimal media. Quadruple knockout ΔSopBΔSopDΔLeuBΔArgD (BDLA) exhibited lowest virulence among all of the strains in all parameters including bacterial load, immunity profile and histopathology studies. In vivo anti-tumour study on colorectal tumour bearing-BALB/c mice revealed that all strains of S. Agona were able to suppress the growth of the large solid tumour as compared with negative control and ΔLeuBΔArgD (LA) and BDLA auxotroph showed better efficacy. Interestingly, higher level of tumour growth suppression was noticed in large tumour. However, multiple administration of bacteria dosage did not increase the tumour suppression efficacy. In this study, the virulence of BDLA knockout strain was slightly reduced and tumour growth suppression efficacy was successfully enhanced, which provide a valuable starting point for the development of S. Agona as anti-tumour agent.
  12. Small interfering RNA silencing of interleukin-6 in mesenchymal stromal cells inhibits multiple myeloma cell growth
    Teoh HK, Chong PP, Abdullah M, Sekawi Z, Tan GC, Leong CF, et al.
    Leuk. Res., 2016 Jan;40:44-53.
    PMID: 26626206 DOI: 10.1016/j.leukres.2015.10.004
    Studies demonstrated that mesenchymal stromal cells (MSC) from bone marrow stroma produced high concentration of interleukin-6 (IL-6) that promoted multiple myeloma cell growth. In view of the failure of IL-6 monoclonal antibody therapy to demonstrate substantial clinical responses in early clinical trials, more effective methods are needed in order to disrupt the favourable microenvironment provided by the bone marrow stroma. In this study, we evaluated the short interfering RNA (siRNA)-mediated silencing of IL-6 in MSC and the efficacy of these genetically modified MSC, with IL-6 suppression, on inhibition of U266 multiple myeloma cell growth. IL-6 mRNA and protein were significantly suppressed by 72h post IL-6 siRNA transfection without affecting the biological properties of MSC. Here we show significant inhibition of cell growth and IL-6 production in U266 cells co-cultured with MSC transfected with IL-6 siRNA when compared to U266 cells co-cultured with control MSC. We also show that the tumour volume and mitotic index of tumours in nude mice co-injected with U266 and MSC transfected with IL-6 siRNA were significantly reduced compared to tumours of mice co-injected with control MSC. Our results suggest potential use of RNA interference mediated therapy for multiple myeloma.
  13. Short hairpin RNA silencing of interleukin-6 in human bone marrow-derived mesenchymal stromal cells inhibits multiple myeloma cell growth
    Teoh HK, Chong PP, Abdullah M, Sekawi Z, Tan GC, Leong CF, et al.
    Pathology, 2016 Feb;48 Suppl 1:S99.
    PMID: 27773219 DOI: 10.1016/j.pathol.2015.12.283
  14. Challenges of Covid-19 testing
    Tan GC, Cheong SK
    Malays J Pathol, 2020 Apr;42(1):1.
    PMID: 32342925
    No abstract available.
  15. MJP going green
    Tan GC, Cheong SK
    Malays J Pathol, 2023 Dec;45(3):315.
    PMID: 38155374
    No abstract available.
  16. Potential of human decidua stem cells for angiogenesis and neurogenesis
    Hayati AR, Nur Fariha MM, Tan GC, Tan AE, Chua K
    Arch Med Res, 2011 May;42(4):291-300.
    PMID: 21820607 DOI: 10.1016/j.arcmed.2011.06.005
    Placenta as a fetomaternal organ is a potential source of fetal as well as maternal stem cells. This present study describes novel properties of the cells isolated from the maternal part of term placenta membrane, the decidua basalis.
  17. Quantitative RT PCR approach to evaluate the neurogenic and gliagenic gene expression of cultured human amniotic epithelial cells
    Tan GC, Simat SF, Abdul Rahman H, Tan AE, Chua KH
    Med J Malaysia, 2008 Jul;63 Suppl A:51-2.
    PMID: 19024979
    The aim of the study is to determine the neuronal and glial gene expression of cultured human amniotic epithelial cells (HAECs) in serial passages. HAECs obtained from human term placentae were cultured in F12:DMEM (1:1) + 10% FBS +10ng/ml EGF in serial passages. Quantitative RT-PCR was used to assess the gene expression analysis. The results showed that the cultured HAECs expressed the neural stem cell genes (Nestin, NSE and Vimentin), mature neuronal genes (TH, MAP-2, beta-III-tubulin and NFM) and glial genes (CNPase, MBP and Olig). These neural stem cell genes increased with serial passages while the genes expression for mature neuronal and glial cells were downregulated. These results suggested that HAECs may promote or involve in neurogenesis and gliagenesis.
  18. Upregulation of SOX-2, FZD9, Nestin, OCT-4 and FGF-4 expression in human chorion derived-stem cells after angiogenic induction
    Abdul Rahman H, Manzor NF, Tan GC, Tan AE, Chua KH
    Med J Malaysia, 2008 Jul;63 Suppl A:57-8.
    PMID: 19024982
    Angiogenic induction was made to promote angiogenesis by differentiating stem cells towards endothelial cells. However, the stemness property of induced cells has not been revealed yet. Hence, we aim to evaluate the differential mRNA expression of stemness genes in human chorion-derived stem cells (CDSC) after being cultured in EDM50 comprised bFGF and VEGF. Results indicated that CDSC cultured in EMD50 expressed significantly higher mRNA level of Sox-2, FZD9, BST-1 and Nestin. In addition Oct-4, FGF-4 and ABCG-2 were also upregulated. Our finding suggested that CDSC after angiogenic induction enhanced its stem cell properties. This could be contributed for the mechanism of stem cell therapy in ischemic problem.
  19. Fulltext IsomiRs have functional importance
    Tan GC, Dibb N
    Malays J Pathol, 2015 Aug;37(2):73-81.
    PMID: 26277662 MyJurnal
    Since the inception of deep sequencing, isomiRs are consistently observed to be produced by most miRNA genes in a variety of cell types. IsomiRs appear as a variation in length from the canonical sequence annotated in miRBase, due to an addition or deletion of one or more nucleotides at the 5(') or 3(') ends or both. As the seed sequence is located at the 5(') end of the microRNA, the target mRNA will be theoretically different. Therefore, 5(')isomiRs might potentially target a new set mRNA compared to their canonical counterpart. This article gives an overview of investigations that explored the functional potential of isomiRs such as their ability to incorporate into Argonaute protein, the differential expression of isomiRs in various tissue types and cell lines, and the differences of mRNA targets between isomiR and its canonical microRNA. In addition, this article provides a brief introduction of RNA sponges as a potential way to inhibit isomiRs.
  20. Construction of a doxycycline inducible lentivirus that expresses stem cell-specific miR-302 cluster
    Tan GC, Wong YP, Cui W, Dibb N
    Malays J Pathol, 2020 Apr;42(1):91-97.
    PMID: 32342936
    INTRODUCTION: The polycistronic miR-302 cluster encodes five miRNA genes that have an important role in the regulation of embryonic stem cell function. Studies showed that the miR-302 cluster can reprogram both mouse and human fibroblasts to induced pluripotent stem cells (iPSCs) with high efficiency. The aim of this study was to generate an inducible lentivirus that expresses miR-302 cluster in order to further investigate somatic cell reprogramming by these miRNAs.

    MATERIALS AND METHODS: The miR-302 cluster was amplified by polymerase chain reaction technique from human genomic DNA and was ligated into pTRIPz, an inducible lentiviral vector.

    RESULTS: MRC5 fibroblasts and HEK293 (human embryonic kidney) cells were infected with pTRIPz-302 cluster lentivirus and the family of 302 miRNAs were strongly expressed in HEK293 cells but lowly expressed in MRC5 fibroblasts. When cultured in hESC conditions, MRC5 cells expressed only low levels of DNMT3B, Nanog, Oct4 and Lin28 and failed to show stem cell induction. The red fluorescent expression seen in the majority of MRC5 cells, indicated that the rate of infection by lentivirus was efficient.

    DISCUSSION: The efficiency of reprogramming may be improved perhaps by either using a different cell type or a high expression vector with a different type of promoter.

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