Displaying publications 21 - 40 of 63 in total

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  1. Fulltext Detection of medically important Candida species by absolute quantitation real-time polymerase chain reaction
    Than LT, Chong PP, Ng KP, Seow HF
    Jundishapur J Microbiol, 2015 Jan;8(1):e14940.
    PMID: 25789129 DOI: 10.5812/jjm.14940
    The number of invasive candidiasis cases has risen especially with an increase in the number of immunosuppressed and immunocom promised patients. The early detection of Candida species which is specific and sensitive is important in determining the correct administration of antifungal drugs to patients.
  2. Sequence analysis of both genome segments of two very virulent infectious bursal disease virus field isolates with distinct pathogenicity
    Kong LL, Omar AR, Hair-Bejo M, Aini I, Seow HF
    Arch Virol, 2004 Feb;149(2):425-34.
    PMID: 14745606
    The deduced amino acid sequences of segment A and B of two very virulent Infectious bursal disease virus (vvIBDV) isolates, UPM94/273 and UPM97/61 were compared with 25 other IBDV strains. Twenty amino acid residues (8 in VP1, 5 in VP2, 2 in VP3, 4 in VP4, 1 in VP5) that were common to vvIBDV strains were detected. However, UPM94/273 is an exceptional vvIBDV with usual amino acid substitutions. The differences in the divergence of segment A and B indicated that the vvIBDV strains may have been derived from genetic reassortment of a single ancestral virus or both segments have different ability to undergo genetic variation due to their different functional constraints.
  3. Positive correlation between overexpression of phospho-BAD with phosphorylated Akt at serine 473 but not threonine 308 in colorectal carcinoma
    Khor TO, Gul YA, Ithnin H, Seow HF
    Cancer Lett, 2004 Jul 16;210(2):139-50.
    PMID: 15183529
    The enhancement of cell proliferation and promotion of cell survival via the inhibition of apoptosis is thought to be the key to the initiation and progression of cancers. The phosphatidylinositol-3 kinase (PI3K)/Akt is an important survival signal pathway that has been shown to be crucial in the regulation of balance between pro-apoptotic and survival (anti-apoptotic) signal. In this study, the expression of phosphorylated Akt at Thr308 and Ser473, BCL-2-antagonist of cell death (BAD) at Ser136 and glycogen synthase kinase-3beta (GSK-3beta) at Ser9 in 47 paraffin-embedded human colorectal carcinoma (CRC) tissues were determined by immunohistochemical staining in order to dissect the alterations in the signal transduction pathways in CRC. Our results showed that there was a significant increase in the expression of these biomolecules in CRC tissues compared to the apparently normal adjacent tissues. The frequency of increased expression in tumor colonic mucosa were as follows: p-Akt1/2/3 (Thr308) = 16/47 (34%); p-Akt1 (Ser473) = 21/47 (44.7%); phospho-BAD (p-BAD) Ser136 = 27/47 (57.4%) and phospho-GSK-3beta (p-GSK-3beta) = 21/47 (44.7%). Analysis of the total p-Akt1 (Ser473), p-Akt1/2/3 (Thr308), p-GSK-3beta (Ser9) and p-BAD (Ser136) score found that there was a statistically significant relationship with each other. A statistically significant positive linear relationship was found between total p-Akt (Ser473) score and total p-GSK-3beta (Ser9) score as well as with total p-BAD (Ser136) score. On the other hand, total p-Akt1/2/3 (Thr308) scores had a statistically significant positive linear relationship with p-GSK-3beta (Ser9) only. The Akt targets, p-GSK-3beta (Ser9) and p-BAD (Ser136) were positively correlated to each other. There was no significant correlation between clinico-pathological data with total p-Akt1 (Ser473), p-Akt1/2/3 (Thr308), p-GSK-3beta (Ser9) and p-BAD (Ser136) score except for age. The total scores of p-GSK-3beta were found to be higher in patients in the age group of greater than 60. This is the first report of p-Akt1/2/3 (Thr308) and p-BAD (Ser136) expression in primary colorectal tumor tissue. Our data further supports the role of PI3K/Akt signaling pathways in the pathogenesis of CRC and contributes to the identification of target molecules in the signal transduction pathway for cancer therapy.
  4. GSK-3beta phosphorylation and alteration of beta-catenin in hepatocellular carcinoma
    Ban KC, Singh H, Krishnan R, Seow HF
    Cancer Lett, 2003 Sep 25;199(2):201-8.
    PMID: 12969793
    The aim of this study is to investigate the potential correlation between the expression of phosphorylated glycogen synthase kinase-3beta (phospho-GSK-3beta) and beta-catenin, and the mutations of beta-catenin gene at the consensus GSK-3beta phosphorylation site. The reason for this approach is to gain a better understanding of the molecular mechanisms of hepatocarcinogenesis in Malaysia. The expression of phospho-GSK-3beta and beta-catenin by immunohistochemistry and the mutations of beta-catenin were studied in 23 hepatocellular carcinoma (HCC) and surrounding tissues. Overexpression of phospho-GSK-3beta and beta-catenin was found in 12/23 (52.2%) and 13/23 (56.5%) in HCC tissues, 6/23 (26.1%) and 9/23 (39.1%) in surrounding tissues, respectively. Overexpression of beta-catenin in HCC tissues compared to the surrounding liver tissue was found to be higher in HCC tissues (p=0.015). In addition, we found that the expression of phospho-GSK-3beta was related with the accumulation of beta-catenin in surrounding tissues (p<0.05). The expression of phospho-GSK-3beta and its association with the development of HCC is reported for the first time. In addition, this is the first report from Malaysia which shows that there are no mutations at the GSK-3beta consensus phosphorylation sites on beta-catenin gene in all 23 paired HCC and surrounding tissues. This result differed from HCC in geographical areas with high aflatoxin exposure.
  5. Human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSC) inhibit the proliferation of K562 (human erythromyeloblastoid leukaemic cell line)
    Fonseka M, Ramasamy R, Tan BC, Seow HF
    Cell Biol Int, 2012 Sep;36(9):793-801.
    PMID: 22335239 DOI: 10.1042/CBI20110595
    hUCB-MSC (human umbilical cord blood-derived mesenchymal stem cells) offer an attractive alternative to bone marrow-derived MSC for cell-based therapy by being less invasive a source of biological material. We have evaluated the effect of hUCB-MSC on the proliferation of K562 (an erythromyeloblastoid cell line) and the cytokine secretion pattern of hUCB-MSC. Co-culturing of hUCB-MSC and K562 resulted in inhibition of proliferation of K562 in a dose-dependent manner. However, the anti-proliferative effect was reduced in transwells, suggesting the importance of direct cell-to-cell contact. hUCB-MSC inhibited proliferation of K562, arresting them in the G0 /G1 phase. NO (nitric oxide) was not involved in the hUCB-MSC-mediated tumour suppression. The presence of IL-6 (interleukin 6) and IL-8 were obvious in the hUCB-MSC conditioned media, but no significant increase was found in 29 other cytokines. Th1 cytokines, IFNα (interferon α), Th2 cytokine IL-4 and Th17 cytokine, IL-17 were not secreted by hUCB-MSC. There was an increase in the number of hUCB-MSC expressing the latent membrane-bound form of TGFβ1 co-cultured with K562. The anti-proliferative effect of hUCB-MSC was due to arrest of the growth of K562 in the G0 /G1 phase. The mechanisms underlying increased IL-6 and IL-8 secretion and LAP (latency-associated peptide; TGFβ1) by hUCB-MSC remains unknown.
  6. Fulltext Increase in tumour-infiltrating lymphocytes with regulatory T cell immunophenotypes and reduced zeta-chain expression in nasopharyngeal carcinoma patients
    Yip WK, Abdullah MA, Yusoff SM, Seow HF
    Clin Exp Immunol, 2009 Mar;155(3):412-22.
    PMID: 19220831 DOI: 10.1111/j.1365-2249.2008.03793.x
    The pathological significance of the mechanisms of tumour immune-evasion and/or immunosuppression, such as loss of T cell signalling and increase in regulatory T cells (T(regs)), has not been well established in the nasopharyngeal carcinoma (NPC) microenvironment. To evaluate the T(reg) immunophenotypes in tumour-infiltrating lymphocytes (TILs), we performed a double-enzymatic immunostaining for detection of forkhead box P3 (FoxP3) and other markers including CD4, CD8, and CD25 on 64 NPC and 36 non-malignant nasopharyngeal (NP) paraffin-embedded tissues. Expression of CD3 zeta and CD3 epsilon was also determined. The prevalence of CD4(+)FoxP3(+) cells in CD4(+) T cells and the ratio of FoxP3(+)/CD8(+) were increased significantly in NPC compared with those in NP tissues (P < 0.001 and P = 0.025 respectively). Moreover, the ratio of FoxP3(+)/CD25(+)FoxP3(-) in NPC was significantly lower than that in NP tissues (P = 0.005), suggesting an imbalance favouring activated phenotype of T cells in NPC. A significant negative correlation between the abundance of FoxP3(+) and CD25(+)FoxP3(-) cells (P < 0.001) was also identified. When histological types of NPC were considered, a lower ratio of FoxP3(+)/CD25(+)FoxP3(-) was found in non-keratinizing and undifferentiated carcinomas. Increased CD4(+)FoxP3(+)/CD4(+) proportion and FoxP3(+)/CD8(+) ratio were associated with keratinizing squamous cell carcinoma. A reduced expression of CD3 zeta in TILs was found in 20.6% of the NPC tissues but none of the NP tissues. These data provide evidence for the imbalances of T(reg) and effector T cell phenotypes and down-regulation of signal-transducing molecules in TILs, supporting their role in suppression of immune response and immune evasion of NPC.
  7. Fulltext Loss of Interleukin-17RA Expression is Associated with Tumour Progression in Colorectal Carcinoma
    Chai BY, Yip WK, Dusa N, Mohtarrudin N, Seow HF
    Pathol Oncol Res, 2020 Oct;26(4):2291-2298.
    PMID: 32462420 DOI: 10.1007/s12253-020-00820-4
    Interleukin-17 (IL-17) is a pro-inflammatory cytokine found in various cancers. Current evidence indicates that IL-17 plays a vital role in tumour initiation and progression in colorectal carcinoma (CRC) via binding with its receptor, IL-17RA. However, the association between clinicopathological features and presence of IL-17 and IL-17RA protein in primary CRC tissues remains unclear. This study also investigates the difference between the presence of IL-17 and IL-17RA in the paired tumour tissues versus adjacent normal tissues. The presence of IL-17RA and IL-17 protein in primary CRC tissues was determined by immunohistochemistry. Associations between clinicopathological features and IL-17RA and IL-17 immunoreactivity, were analyzed by χ2 tests. We found that both IL-17RA (p = 0.001) and IL-17 (p = 0.025) in tumour cells of primary CRC tissues was significantly lower as compared to adjacent normal tissue. Positive immunoreactivity for IL-17RA and IL-17 were detected in 51.0% and 16.8% of tumour tissues, respectively. Furthermore, negative immunoreactivity of IL-17R was significantly associated with advanced stage according to TNM classifier (p = 0.027), high grade of tumour (p = 0.019), increased depth of tumour invasion (p = 0.023) and vascular invasion (p = 0.039). Positive IL-17 immunoreactivity was associated with advanced stage (p = 0.008) and lymph node metastasis (p = 0.008). Thus, this study suggests that the loss of IL-17RA expression occurs as tumour progresses and this may predict the aggressiveness of tumour whilst expression of IL-17 promotes tumour progression and lymph node metastasis. Thus, loss of IL-17RA could be a useful prognostic biomarker for tumour progression in CRC patients.
  8. Fulltext Recent Updates on Mechanisms of Resistance to 5-Fluorouracil and Reversal Strategies in Colon Cancer Treatment
    Azwar S, Seow HF, Abdullah M, Faisal Jabar M, Mohtarrudin N
    Biology (Basel), 2021 Aug 31;10(9).
    PMID: 34571731 DOI: 10.3390/biology10090854
    5-Fluorouracil (5-FU) plus leucovorin (LV) remain as the mainstay standard adjuvant chemotherapy treatment for early stage colon cancer, and the preferred first-line option for metastatic colon cancer patients in combination with oxaliplatin in FOLFOX, or irinotecan in FOLFIRI regimens. Despite treatment success to a certain extent, the incidence of chemotherapy failure attributed to chemotherapy resistance is still reported in many patients. This resistance, which can be defined by tumor tolerance against chemotherapy, either intrinsic or acquired, is primarily driven by the dysregulation of various components in distinct pathways. In recent years, it has been established that the incidence of 5-FU resistance, akin to multidrug resistance, can be attributed to the alterations in drug transport, evasion of apoptosis, changes in the cell cycle and DNA-damage repair machinery, regulation of autophagy, epithelial-to-mesenchymal transition, cancer stem cell involvement, tumor microenvironment interactions, miRNA dysregulations, epigenetic alterations, as well as redox imbalances. Certain resistance mechanisms that are 5-FU-specific have also been ascertained to include the upregulation of thymidylate synthase, dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase, and the downregulation of thymidine phosphorylase. Indeed, the successful modulation of these mechanisms have been the game plan of numerous studies that had employed small molecule inhibitors, plant-based small molecules, and non-coding RNA regulators to effectively reverse 5-FU resistance in colon cancer cells. It is hoped that these studies would provide fundamental knowledge to further our understanding prior developing novel drugs in the near future that would synergistically work with 5-FU to potentiate its antitumor effects and improve the patient's overall survival.
  9. Fulltext S-phase fraction and pro-inflammatory cytokine expressions in acute lymphoblastic leukaemia
    Maha A, Cheong SK, Leong CF, Seow HF
    Malaysian Journal of Medicine and Health Sciences, 2005;1(1):41-51.
    Objective: Despite much progress in treatment strategies, long term survival of adult ALL is still inferior to that in children. The underlying mechanisms for these differences are largely unknown. Intensification of contemporary therapy has also resulted in many children being over-treated. The action of chemotherapeutic drugs used in the treatment of ALL includes cell cycle dependent agents which are effective on cells that are proliferating. Cell proliferation in haemopoietic cells is controlled by cytokines. Thus, we proposed to study the cell cycle profile of ALL cases and also expression of cytokines to determine their role in affecting treatment outcome in the different age groups.
    Methods: We determined the S-phase fraction from the cell cycle profile by flowcytometry and tested the expressions of cytokine IL-1beta, IL-6, IL-18, IFN-gamma, TNF-alpha and GM-CSF using RT-PCR in de novo ALL cases.
    Results: We found a significantly higher S-phase fraction in samples from children 2-10 years old compared to the older age group (>10 years old) (p=0.001). GM-CSF was found to be expressed in a significantly lower percentage of children compared to adults (p=0.008).
    Conclusion: Our results implied that GM-CSF may have induced cell cycle arrests in adult ALL resulting in a lower percentage of S-phase fraction. This may contribute to the poorer prognosis in adult ALL because non-cycling blasts are less sensitive to some chemotherapeutic drugs.
    Keywords: ALL, S-phase fraction, GM-CSF, age
  10. Increased tube formation and up-regulation of FGFR3 mRNA expression in microvascular endothelial cell by exosomes derived from SW480-7
    Ng CT, Yip WK, Mohtarrudin N, Jabar MF, Seow HF
    Malays J Pathol, 2023 Aug;45(2):195-204.
    PMID: 37658529
    INTRODUCTION: Extracellular vesicles (exosome-like vesicles) are small membrane vesicles ranging from 20-200nm in size that are released by various cells into the extracellular space. These extracellular vesicles play a major role in cell-to-cell communication and contain materials, such as proteins, mRNAs, microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). The effect of exosomes derived from an invasive colon cancer cell line on angiogenesis is unclear. Hence, the aim of this study is to investigate the effect of exosomes derived from an invasive colon cancer cell line on angiogenesis of endothelial cells.

    MATERIALS AND METHODS: In the present study, the exosomes from the cell culture supernatants of an invasive colon cancer cell line SW480-7 were characterised. The effect on tube formation and expression of angiogenic genes in a microvascular endothelial cell, telomerase-immortalised microvascular endothelial cell (TIME) was examined after co-cultured with exosomes secreted from SW480-7.

    RESULTS: Zetasizer result showed average diameter of exosomes derived from SW480-7 was 246.2 nm and morphological analysis showed the size of majority of exosomes were less than 200 nm. Results showed that exosomes derived from SW480-7 increased tube formation and up-regulated FGFR3 mRNA expression in TIME.

    CONCLUSION: Our findings suggest that exosomes derived from SW480-7 increased tube formation and up-regulated expression of FGFR3 mRNA in TIME.

  11. Antigenicity and immunogenicity of the immunodominant region of hepatitis B surface antigen displayed on bacteriophage T7
    Tan GH, Yusoff K, Seow HF, Tan WS
    J Med Virol, 2005 Dec;77(4):475-80.
    PMID: 16254965
    The immunodominant region of hepatitis B virus (HBV) located in the viral small surface antigen (S-HBsAg) elicits virus-neutralizing and protective antibodies. In order to develop an easy and inexpensive method to produce this region without the need for extensive purification, amino acid residues 111-156 of S-HBsAg were fused to the C-terminal end of the 10B capsid protein of T7 phage. Western blotting and ELISA confirmed the expression of the recombinant protein on the surface of the phage particles. The recombinant phage exhibited the antigenic and immunogenic characteristics of HBsAg, illustrating its potential as an immunological reagent and vaccine.
  12. Selection of high affinity ligands to hepatitis B core antigen from a phage-displayed cyclic peptide library
    Ho KL, Yusoff K, Seow HF, Tan WS
    J Med Virol, 2003 Jan;69(1):27-32.
    PMID: 12436474
    M13 phages that display random disulfide constrained heptapeptides on their gpIII proteins were used to select for high affinity ligands to hepatitis B core antigen (HBcAg). Phages bearing the amino acid sequences C-WSFFSNI-C and C-WPFWGPW-C were isolated, and a binding assay in solution showed that these phages bind tightly to full-length and truncated HBcAg with K D rel values less than 25 nM, which is at least 10 orders of magnitude higher than phage carrying the peptide sequence LLGRMK selected from a linear peptide library. Both the phages that display the constrained peptides were inhibited from binding to HBcAg particles by a monoclonal antibody that binds specifically to the immunodominant region of the particles. A synthetic heptapeptide with the amino acid sequence WSFFSNI derived from one of the fusion peptides inhibits the binding of large surface antigen (L-HBsAg) to core particles with an IC50 value of 12 +/- 2 microM. This study has identified a smaller peptide with a greater inhibitory effect on L-HBsAg-HBcAg association.
  13. Fulltext Probiotic Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 exhibit strong antifungal effects against vulvovaginal candidiasis-causing Candida glabrata isolates
    Chew SY, Cheah YK, Seow HF, Sandai D, Than LT
    J Appl Microbiol, 2015 May;118(5):1180-90.
    PMID: 25688886 DOI: 10.1111/jam.12772
    This study investigates the antagonistic effects of the probiotic strains Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 against vulvovaginal candidiasis (VVC)-causing Candida glabrata.
  14. Inhibition of transforming growth factor-β via the activin receptor-like kinase-5 inhibitor attenuates pulmonary fibrosis
    Koh RY, Lim CL, Uhal BD, Abdullah M, Vidyadaran S, Ho CC, et al.
    Mol Med Rep, 2015 May;11(5):3808-13.
    PMID: 25585520 DOI: 10.3892/mmr.2015.3193
    Idiopathic pulmonary fibrosis is a chronic pulmonary disease that is characterized by formation of scar tissue in lungs. Transforming growth factor-β (TGF-β) is considered an important cytokine in the pathogenesis of this disease. Hence, the antifibrotic effect of an inhibitor of the TGF-β type I receptor, namely, SB 431542, was investigated in our study. SB 431542 was used to treat TGF-β-treated IMR-90 cells; the expression of α-smooth muscle actin (α-SMA) was detected at the protein level by using an anti-α-SMA antibody, and at the gene level by reverse transcription-quantitative PCR. The effect of the inhibitor on cell proliferation was determined by a cell growth assay. The inhibitor was also administered into bleomycin-treated mice. Histopathological assessment and determination of total collagen levels were carried out to evaluate the severity of lung fibrosis in these mice. Our results demonstrated that treatment with SB 431542 inhibits TGF-β‑induced α-SMA expression in lung fibroblasts, at both the protein and the mRNA levels (P<0.05). However, the inhibitor did not significantly reduce lung fibroblast proliferation. In the bleomycin-induced pulmonary fibrosis mouse model, bleomycin treatment caused important morphological changes, accompanied by an increase in the collagen level of the lungs. Early treatment with SB 431542 prevented the manifestation of histopathological alterations, whereas delayed treatment significantly decreased the collagen level (P<0.05). These results suggest that inhibition of TGF-β signaling, via inhibition of the activin receptor-like kinase-5 (ALK-5) by SB 431542, may attenuate pulmonary fibrosis.
  15. Molecular alterations of Ras-Raf-mitogen-activated protein kinase and phosphatidylinositol 3-kinase-Akt signaling pathways in colorectal cancers from a tertiary hospital at Kuala Lumpur, Malaysia
    Yip WK, Choo CW, Leong VC, Leong PP, Jabar MF, Seow HF
    APMIS, 2013 Oct;121(10):954-66.
    PMID: 23992303 DOI: 10.1111/apm.12152
    Molecular alterations in KRAS, BRAF, PIK3CA, and PTEN have been implicated in designing targeted therapy for colorectal cancer (CRC). The present study aimed to determine the status of these molecular alterations in Malaysian CRCs as such data are not available in the literature. We investigated the mutations of KRAS, BRAF, and PTEN, the gene amplification of PIK3CA, and the protein expression of PTEN and phosphatidylinositol 3-kinase (PI3K) catalytic subunit (p110α) by direct DNA sequencing, quantitative real-time PCR, and immunohistochemistry, respectively, in 49 CRC samples. The frequency of KRAS (codons 12, 13, and 61), BRAF (V600E), and PTEN mutations, and PIK3CA amplification was 25.0% (11/44), 2.3% (1/43), 0.0% (0/43), and 76.7% (33/43), respectively. Immunohistochemical staining demonstrated loss of PTEN protein in 54.5% (24/44) of CRCs and no significant difference in PI3K p110α expression between CRCs and the adjacent normal colonic mucosa (p = 0.380). PIK3CA amplification was not associated with PI3K p110α expression level, but associated with male cases (100% of male cases vs 56% of female cases harbored amplified PIK3CA, p = 0.002). PI3K p110α expression was significantly higher (p = 0.041) in poorly/moderately differentiated carcinoma compared with well-differentiated carcinoma. KRAS mutation, PIK3CA amplification, PTEN loss, and PI3K p110α expression did not correlate with Akt phosphorylation or Ki-67 expression. KRAS mutation, PIK3CA amplification, and PTEN loss were not mutually exclusive. This is the first report on CRC in Malaysia showing comparable frequency of KRAS mutation and PTEN loss, lower BRAF mutation rate, higher PIK3CA amplification frequency, and rare PTEN mutation, as compared with published reports.
  16. Effects of macrophage colony-stimulating factor on microglial responses to lipopolysaccharide and beta amyloid
    Vidyadaran S, Ooi YY, Subramaiam H, Badiei A, Abdullah M, Ramasamy R, et al.
    Cell Immunol, 2009;259(1):105-10.
    PMID: 19577228 DOI: 10.1016/j.cellimm.2009.06.005
    A challenge for studies involving microglia cultures is obtaining sufficient cells for downstream experiments. Macrophage colony-stimulating factor (M-CSF) has been used to improve yield of microglia in culture. However, the effects of M-CSF on activation profiles of microglia cultures are still unclear. Microglia activation is characterised by upregulation of co-stimulatory molecules and an inflammatory phenotype. The aim of this study is to demonstrate whether M-CSF supplementation alters microglial responses in resting and activated conditions. Microglia derived from mixed glia cultures and the BV-2 microglia cell line were cultivated with/without M-CSF and activated with lipopolysaccharide (LPS) and beta amyloid (Abeta). We show M-CSF expands primary microglia without affecting microglial responses to LPS and Abeta, as shown by the comparable expression of MHC class II and CD40 to microglia grown without this growth factor. M-CSF supplementation in BV-2 cells had no effect on nitric oxide (NO) production. Therefore, M-CSF can be considered for improving microglia yield in culture without introducing activation artefacts.
  17. Immunohistochemical detection of phospho-Akt, phospho-BAD, HER2 and oestrogen receptors alpha and beta in Malaysian breast cancer patients
    Seow HF, Yip WK, Loh HW, Ithnin H, Por P, Rohaizak M
    Pathol Oncol Res, 2010 Jun;16(2):239-48.
    PMID: 19882362 DOI: 10.1007/s12253-009-9216-3
    Activation of Akt signaling pathway has been documented in various human malignancies, including breast carcinoma. The objective of this study is to determine the incidence of Akt phosphorylation in breast tumours and its relationship with expression of ER-alpha, ER-beta, HER2, Ki-67 and phosphorylated Bcl-2 associated death domain (p-BAD). Immunohistochemical staining was performed to detect these molecules on 43 paraffin-embedded breast tumour tissues with commercially available antibodies. Eighteen (41.9%), 3 (7.0%), 23 (53.5%), 35 (81.4%), 21 (48.8%), 29 (67.4%), and 34 (81.0%) of breast tumours were positive for nuclear ER-alpha, nuclear ER-beta, membranous HER2, cytonuclear p-Akt (Thr308), p-Akt (Ser473), p-BAD and Ki-67, respectively. ER-alpha expression was inversely correlated with HER2 and Ki-67 (P = 0.041 and P = 0.040, respectively). The p-Akt (Ser473) was correlated with increased level of p-BAD (Ser136) (P = 0.012). No relationship of Akt phosphorylation with HER2, ER-alpha or ER-beta was found. The p-Akt (Ser473) immunoreactivity was significantly higher in stage IV than in stage I or II (P = 0.036 or P = 0.009). The higher Ki-67 and lower ER-alpha expression showed an association with patient age of <50 years (P = 0.004) and with positive nodal status (P = 0.033), respectively. Our data suggest that the Akt phosphorylation and inactivation of its downstream target, BAD may play a role in survival of breast cancer cell. This study does not support the simple model of linear HER2/PI3K/Akt pathway in breast cancer.
  18. PIK3CA gene mutations in breast carcinoma in Malaysian patients
    Ching-Shian Leong V, Jabal MF, Leong PP, Abdullah MA, Gul YA, Seow HF
    Cancer Genet. Cytogenet., 2008 Dec;187(2):74-9.
    PMID: 19027487 DOI: 10.1016/j.cancergencyto.2008.07.005
    Somatic mutations of phosphoinositide-3-kinase, catalytic, alpha; PIK3CA gene have been reported in several types of human cancers. The majority of the PIK3CA mutations map to the three "hot spots" - E542 K and E545 K in the helical (exon 9) and H1047R in the kinase (exon 20) domains of the p110alpha. These hot spot mutations lead to a gain of function in PI3 K signaling. We aimed to determine the frequency of PIK3CA mutations in the three most common Malaysian cancers. In this study, we assessed the genetic alterations in the PIK3CA gene in a series of 20 breast carcinomas, 24 colorectal carcinomas, 27 nasopharyngeal carcinomas (NPC), and 5 NPC cell lines. We performed mutation analysis of the PIK3CA gene by genomic polymerase chain reaction (PCR) and followed by DNA direct sequencing in exons 9 and 20. No mutations were detected in any of the 24 colorectal and 27 NPC samples, but one hot spot mutation located at exon 20 was found in a NPC cell line, SUNE1. Interestingly, PIK3CA somatic mutations were present in 6/20 (30%) breast carcinomas. Two of the six mutations, H1047R, have been reported previously as a hot spot mutation. Only one out of three hot spot mutations were identified in breast tumor samples. The remaining four mutations were novel. Our data showed that a higher incidence rate of PIK3CA mutations was present in Malaysian breast cancers as compared to colorectal and nasopharyngeal tumor tissues. Our findings also indicate that PIK3CA mutations play a pivotal role in activation of the PI3 K signaling pathway in breast cancer, and specific inhibitors of PIK3CA could be useful for breast cancer treatment in Malaysia.
  19. Increased expression and hotspot mutations of the multidrug efflux transporter, CDR1 in azole-resistant Candida albicans isolates from vaginitis patients
    Looi CY, D' Silva EC, Seow HF, Rosli R, Ng KP, Chong PP
    FEMS Microbiol Lett, 2005 Aug 15;249(2):283-9.
    PMID: 16006060
    The aims of our research were to investigate the gene expression of the multidrug efflux transporter, CDR1 and the major drug facilitator superfamily transporter, MDR1 gene in azole drug-resistant Candida albicans and Candida glabrata clinical isolates recovered from vaginitis patients; and to identify hotspot mutations that may be present in the C. albicans CaCDR1 gene that could be associated with drug-resistance. The relative expression of the CDR1 and MDR1 transcripts in ketoconazole and clotrimazole-resistant isolates and drug-susceptible ATCC strains were determined by semi-quantitative reverse transcription-polymerase chain reaction. Expression of CaCDR1 transcript was upregulated to varying extents in all three azole-resistant C. albicans isolates studied (1.6-, 3.7- and 3.9-fold) and all three C. glabrata isolates tested (at 1.9-, 2.3- and 2.7-fold). The overexpression level of CaCDR1 in the isolates correlated with the degree of resistance as reflected by the minimum inhibitory concentration (MIC) of the drugs. The messenger RNA for another efflux pump, MDR1, was also overexpressed in one of the azole-resistant C. albicans isolates that overexpressed CDR1. This finding suggests that drug-resistance may involve synergy between energy-dependent drug efflux pumps CDR1p and MDR1p in some but not all isolates. Interestingly, DNA sequence analysis of the promoter region of the CaCDR1 gene revealed several point mutations in the resistant clinical isolates compared to the susceptible isolates at 39, 49 and 151 nucleotides upstream from the ATG start codon. This finding provides new information on point mutations in the promoter region which may be responsible for the overexpression of CDR1 in drug-resistant isolates.
  20. Genotyping of hepatitis B virus in Malaysia based on the nucleotide sequence of preS and S genes
    Ong HT, Duraisamy G, Kee Peng N, Wen Siang T, Seow HF
    Microbes Infect., 2005 Mar;7(3):494-500.
    PMID: 15792534
    Hepatitis B virus (HBV) has been classified into eight genotypes, designated A-H. These genotypes are known to have distinct geographic distributions. The clinical importance of genotype-related differences in the pathogenicity of HBV has been revealed recently. In Malaysia, the current distribution of HBV remains unclear. The aim of this study was to determine the genotypes and subtypes of HBV by using PCR, followed by DNA sequencing, as well as to analyse the mutations in the immunodominant region of preS and S proteins. The S gene sequence was determined from HBV DNA of four apparently healthy blood donors' sera and three sera from asymptomatic chronic hepatitis B carriers. Of this batch of sera, the preS gene sequence was obtained from HBV DNA from three out of the four blood donors and two out of the three chronic carriers. Due to insufficient sera, we had to resort to using sera from another blood donor to make up for the sixth DNA sequence of the preS gene. Based on the comparative analysis of the preS sequences with the reported sequences in the GenBank database, HBV DNA from two normal carriers was classified as genotype C. Genotype B was assigned to HBV from one blood donor and two hepatitis B chronic carriers, whereas HBV of one chronic carrier was of genotype D. Based on the S gene sequences, HBV from three blood donors was of genotype C, that of one blood donor and one chronic carrier was of genotype B, and the remaining, of genotype D. In the five cases where both preS and S gene sequences were determined, the genotypes assigned based on either the preS or S gene sequences were in concordance. The nature of the deduced amino acid (aa) sequences at positions 125, 127, 134, 143, 159, 161 and 168 of the S gene enabled the classification of these sequences into subtypes, namely, adrq+, adw2 and ayw2. The clustering of our DNA sequences into genotype groups corresponded to their respective subtype, that is, adw2 in genotype B, adrq in genotype C and ayw in genotype D. Analysis of the point mutations revealed that five of the sequences contained aa substitutions at immunodominant epitopes involved in B or/and T cell recognition. In conclusion, despite the low numbers of samples studied, due to budget constraints, these data are still worthwhile reporting, as it is important for the control of HBV infections. In addition, the genotype and mutational data obtained in this study may be useful for designing new treatment regimes for HBV patients.
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