Chee Wai Chua

Georgetown University, Washington, D. C., DC, United States

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Publications (10)43.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Studies have shown that the expression of inhibitor of differentiation (Id-1) is increased in bladder cancer and is associated with drug resistance. S-allylmercaptocysteine (SAMC), a water-soluble component of garlic, is known to have a potent therapeutic effect on human cancer. The aim of this study was to investigate whether Id-1 expression mediates SAMC-induced cell death in bladder cancer cells. After generating stable Id-1-expressing and si-Id-1 transfectants in various bladder cancer cell lines, cell sensitivity to SAMC was compared by colony formation and MTT assays. The results indicated that Id-1 overexpression reduced the positive effect of SAMC on cell survival, while the inactivation of Id-1 increased cellular susceptibility to SAMC. Using DAPI staining, the apoptosis of bladder cancer cells induced by SAMC was shown to be negatively regulated by Id-1 expression. The expression of apoptosis-related proteins analyzed by Western blotting further supported the negative role of Id-1 in SAMC-induced apoptosis. Furthermore, by wound closure and type I collagen invasion assays, the inhibitory effect of SAMC on the invasion and migration of bladder cancer cells was found to be associated with the down-regulation of Id-1. Our results demonstrated that SAMC-induced apoptosis is associated with the Id-1 pathway, and that the inactivation of Id-1 enhances the ability of SAMC to inhibit the survival, invasion and migration of bladder cancer cells. These findings may lead to the development of novel therapeutic strategies for the treatment of bladder cancer.
    Molecular Medicine Reports 01/2011; 4(1):9-16. · 1.17 Impact Factor
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    ABSTRACT: Recurrence and progression are the major problems in the treatment of bladder cancer. Increased expression of Id-1, a basic helix-loop-helix transcription factor, has recently been shown in several types of advanced cancer. Some studies have provided evidence to suggest that Id-1 can be considered a potential therapeutic target. The objective of this study was to investigate the role of Id-1 in the chemosensitivity of bladder cancer cells, and the effect of Id-1 on chemotherapeutic drug-induced apoptosis in bladder cancer cells. We compared the different sensitivity to epirubicin in RT112 and MGH-U1 cell lines with different Id-1 expression. Then, we transfected different vectors into RT112 and MGH-U1 respectively, and generated the stable Id-1 up-regulation and down-regulation transfectants. The results of cell viability assay showed up-regulation of Id-1 in RT112 leading to increased sensitivity in response to epirubicin, and down-regulation of Id-1 increased cellular sensitivity to epirubicin. Furthermore, the analysis of apoptosis related protein revealed that up-regulation of Id-1 suppressed epirubicin-induced apoptosis and down-regulation of Id-1 leading to increased epirubicin-induced apoptosis. Wound closure assay showed up-regulation of Id-1 leading to improved migration abilities of bladder cancer cells under chemotherapy. Our results suggest that up-regulation of Id-1 in bladder cancer cells lead to increased cell viability in response to epirubicin by its improved anti-apoptotic role, and down-regulation of Id-1 increases cellular sensitivity to epirubicin by increased anticancer drug-induced apoptosis.
    Oncology Reports 05/2009; 21(4):1053-9. · 2.30 Impact Factor
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    ABSTRACT: The recent introduction of docetaxel in the treatment of hormone refractory prostate cancer (HRPC) has made a small but significant impact on patient survival. However, its effect is limited by intolerance and resistance. The aim of our study was to investigate if the garlic-derived compound, S-allylmercaptocysteine (SAMC), was able to act as a docetaxel sensitizing agent. First, the effect of SAMC on docetaxel sensitivity was examined on 3 HRPC cell lines by colony forming assay. We found that SAMC increased the efficacy of docetaxel on colony forming inhibition by 9-50% compared to single agent treatment. Second, using the HRPC CWR22R nude mice model, we found that the combination of SAMC and docetaxel was 53% more potent than docetaxel alone (p = 0.037). In addition, there was no additive toxicity in the mice treated with the combination therapy evidenced by histological and functional analysis of liver, kidney and bone marrow. These results suggest that SAMC is able to increase the anticancer effect of docetaxel without causing additional toxic effect in vivo. Third, flow cytometry and Western blotting analysis on HRPC cell lines demonstrated that SAMC promoted docetaxel-induced G2/M phase cell cycle arrest and apoptotic induction. In addition, immunohistochemistry on CWR22R xenograft revealed a suppression of Bcl-2 expression and upregulation of E-cadherin in the SAMC and docetaxel treated animals. These results suggest that SAMC may promote docetaxel-induced cell death through promoting G2/M cell cycle arrest and apoptosis. Our study implies a potential role for SAMC in improving docetaxel based chemotherapy for the treatment of HRPC.
    International Journal of Cancer 06/2008; 122(9):1941-8. · 6.20 Impact Factor
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    ABSTRACT: The presence of circulating tumor cells (CTC) is common in prostate cancer patients, however until recently their clinical significance was unknown. The CTC stage is essential for the formation of distant metastases, and their continuing presence after radical prostatectomy has been shown to predict recurrent or latent disease. Despite their mechanistic and prognostic importance, due both to their scarcity and difficulties in their isolation, little is known about the characteristics that enable their production and survival. The aim of this study was to investigate the molecular mechanisms underlying the survival of CTC cells. A novel CTC cell line from the bloodstream of an orthotopic mouse model of castration-resistant prostate cancer was established and compared with the primary tumor using attachment assays, detachment culture, Western blot, flow cytometry and 2D gel electrophoresis. Decreased adhesiveness and expression of adhesion molecules E-cadherin, beta4-integrin and gamma-catenin, together with resistance to detachment and drug-induced apoptosis and upregulation of Bcl-2 were integral to the development of CTC and their survival. Using proteomic studies, we observed that the GRP94 glycoprotein was suppressed in CTC. GRP94 was also shown to be suppressed in a tissue microarray study of 79 prostate cancer patients, indicating its possible role in prostate cancer progression. Overall, this study suggests molecular alterations accounting for the release and survival of CTC, which may be used as drug targets for either anti-metastatic therapy or the suppression of latent disease. We also indicate the novel involvement of GRP94 suppression in prostate cancer metastasis.
    Clinical and Experimental Metastasis 02/2008; 25(5):497-508. · 3.46 Impact Factor
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    ABSTRACT: Epidermal growth factor receptor (EGFR) is suggested as one of the positive regulators in the invasive progression of renal cell cancer (RCC). Recently, Id-1 (inhibitor of differentiation or DNA binding), a helix-loop-helix transcription factor, has been identified as one of the key factors in the EGFR signalling pathway. The aim of this study was to investigate the significance of Id-1 expression in renal cell cancer and to study its relationship with EGFR. Id-1 and EGFR expression was examined in tissue microarray (TMA) samples of 107 RCC and 32 normal kidney specimens by immunohistochemistry. Relative Id-1 and EGFR protein expression was quantified by estimating the staining intensity on a four-grade scale. We found that while negative to weak expression of Id-1 and EGFR was observed in non-malignant kidney tissues, most RCCs showed significant positive Id-1 and EGFR expression in tumour cells. In addition, Id-1 immunostaining intensity was positively associated with increased tumour staging, grading and EGFR expression. Overexpression of Id-1 is a novel marker for advanced RCC which is positively correlated with EGFR expression. Our results suggest that Id-1 may play an important role in the development of RCC and indicate that Id-1 is a potential marker of patients with a poor prognosis.
    Histopathology 04/2007; 50(4):484-90. · 2.86 Impact Factor
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    ABSTRACT: Recently, TWIST, a basic helix-loop-helix transcription factor, has been reported to play a key role in the metastatic progression of several types of human cancer. The aim of this study was to investigate the significance of TWIST expression in bladder cancer using tissue microassays generated from 226 bladder tissue specimens. Using immunohistochemical staining, we studied TWIST expression levels in nonmalignant bladder tissues (n = 37), primary bladder cancer tissues (n = 164), and 25 cases of matched lymph node metastatic lesions. The association between TWIST expression levels and tumor staging and grading, as well as metastatic potential, was analyzed by statistical analysis. Our results showed that TWIST protein expression was significantly higher in bladder cancer specimens compared with nonmalignant tissues (P < .001), indicating its positive role in the development of bladder cancer. In addition, increased TWIST expression levels were associated with advanced-stage and high-grade tumors, suggesting its involvement in the progression of this cancer. Furthermore, TWIST expression was much higher in the metastatic lesion compared with its primary site (P < .05). More importantly, the increased TWIST expression in bladder cancer specimens was correlated with decreased membranous expression of E-cadherin, a cell adhesion molecule that plays a key role in the metastatic progression of human cancer. Our results demonstrate TWIST as a novel positive factor in the development and progression of bladder cancer and suggest a marker for advanced bladder cancer.
    Human Pathlogy 04/2007; 38(4):598-606. · 2.84 Impact Factor
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    ABSTRACT: There is epidemiologic evidence that high garlic consumption decreases the incidence of prostate cancer, and compounds isolated from garlic have been shown to have cancer-preventive and tumor-suppressive effects. Recent in vitro studies in our laboratory have shown that garlic-derived organosulfur compound S-allylmercaptocysteine suppresses invasion and cell motility of androgen-independent prostate cancer cells via the up-regulation of cell-adhesion molecule E-cadherin. S-allylmercaptocysteine is therefore a potential antimetastatic drug with broad clinical applications that we tested in vivo for the first time in this study. We used a newly established fluorescent orthotopic androgen-independent prostate cancer mouse model to assess the ability of S-allylmercaptocysteine to inhibit tumor growth and dissemination. We showed that oral S-allylmercaptocysteine not only inhibited the growth of primary tumors by up to 71% (P < 0.001) but also reduced the number of lung and adrenal metastases by as much as 85.5% (P = 0.001) without causing notable toxicity. This metastatic suppression was accompanied by a 91% reduction of viable circulating tumor cells (P = 0.041), suggesting that S-allylmercaptocysteine prevents dissemination by decreasing tumor cell intravasation. Our results provide in vivo evidence supporting the potential use of S-allylmercaptocysteine as an E-cadherin up-regulating antimetastatic agent for the treatment of androgen-independent prostate cancer. This is the first report of the in vivo antimetastatic properties of garlic, which may also apply to other cancer types.
    Clinical Cancer Research 03/2007; 13(6):1847-56. · 7.84 Impact Factor
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    ABSTRACT: Epidermal growth factor receptor (EGFR) is suggested to be one of the positive factors in the invasive progression of bladder cancer. Id-1 (inhibitor of differentiation or DNA binding), a helix-loop-helix (HLH) transcription factor, was recently identified as a key factor in the EGFR signalling pathway. The aim of this study was to investigate the role of Id-1 in bladder cancer progression and its relation-ship with EGFR. Using clinical specimens from different stages of bladder cancer, immunohistochemical staining was performed to determine if Id-1 expression was positively associated with tumour staging and EGFR expression. The direct role of Id-1 in cancer cell invasion was also investigated through ectopically expressing the Id-1 gene in a RT112 bladder cancer cell line by wound closure and collagen invasion assays. To explore the therapeutic potential of targeting the Id-1 gene in the treatment of invasive bladder cancer, we studied if inactivation of the Id-1 gene through small RNA interference could lead to the suppression of invasion in a MGHU1 bladder cancer cell line. Our results showed that the up-regulation of Id-1 was associated with increased EGFR expression, clinical staging and the invasion ability of bladder cancer cells. Inactivation of Id-1 may be a potential therapeutic target to inhibit the invasion by bladder cancer cells.
    International Journal of Oncology 05/2006; 28(4):847-54. · 2.66 Impact Factor
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    ABSTRACT: Androgen-independent metastatic prostate cancer is the main cause of cancer related death in men. One of the reasons for this is the lack of understanding of the molecular mechanisms leading to the metastatic progression of prostate cancer. In this study, we have demonstrated that overexpression of Id-1 (inhibitor of differentiation/DNA synthesis), a member of the helix-loop-helix family proteins, is a key factor in promoting angiogenesis through activation of the vascular endothelial growth factor (VEGF) in prostate cancer cells. Using prostate cancer cells ectopically transfected with the Id-1 gene, we found that upregulation of Id-1 induced VEGF secretion through activation of the VEGF gene transcription. Downregulation of Id-1, however, led to the suppression of VEGF secretion and its gene promoter activity. The association between Id-1 and VEGF was also confirmed on human xenografts by immunohistochemical staining. In addition, the growth medium generated by the Id-1 expressing cells was able to promote morphological changes as well as capillary tube formation in human umbilical vein endothelial cells (HUVECs) at similar degrees to the recombinant human VEGF. Furthermore, inhibition of VEGF function by the treatment with an Flk-1 inhibitor, SU1498, or with the VEGF neutralizing antibody resulted in the reverse of the angiogenic effect on HUVECs. Our results suggest that overexpression of Id-1 in prostate cancer cells may provide an autocrine signal to promote angiogenesis through the activation of VEGF. Since increased Id-1 has been reported in many types of advanced human cancers, our results indicate that downregulation of Id-1 may be a novel target to inhibit the growth of metastatic cancers through the suppression of angiogenesis.
    Carcinogenesis 11/2005; 26(10):1668-76. · 5.64 Impact Factor
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    ABSTRACT: Androgen-independent metastatic prostate cancer is the main obstacle in the treatment of this cancer. Unlike a majority of solid cancers, prostate cancer usually shows poor response to chemotherapeutic drugs. In this study, we have shown a potential novel target, TWIST, a highly conserved bHLH transcription factor, in the treatment of prostate cancer. Using malignant and nonmalignant prostate tissues, we found that TWIST expression was highly expressed in the majority (90%) of prostate cancer tissues but only in a small percentage (6.7%) of benign prostate hyperplasia. In addition, the TWIST expression levels were positively correlated with Gleason grading and metastasis, indicating its role in the development and progression of prostate cancer. Furthermore, down-regulation of TWIST through small interfering RNA in androgen-independent prostate cancer cell lines, DU145 and PC3, resulted in increased sensitivity to the anticancer drug taxol-induced cell death which was associated with decreased Bcl/Bax ratio, leading to activation of the apoptosis pathway. More importantly, inactivation of TWIST suppressed migration and invasion abilities of androgen-independent prostate cancer cells, which was correlated with induction of E-cadherin expression as well as morphologic and molecular changes associated with mesenchymal to epithelial transition. These results were further confirmed on the androgen-dependent LNCaP cells ectopically expressing the TWIST protein. Our results have identified TWIST as a critical regulator of prostate cancer cell growth and suggest a potential therapeutic approach to inhibit the growth and metastasis of androgen-independent prostate cancer through inactivation of the TWIST gene.
    Cancer Research 07/2005; 65(12):5153-62. · 8.65 Impact Factor

Publication Stats

406 Citations
43.60 Total Impact Points

Institutions

  • 2008
    • Georgetown University
      • Department of Internal Medicine
      Washington, D. C., DC, United States
    • The University of Hong Kong
      • Department of Anatomy
      Hong Kong, Hong Kong