Pauline P Leung

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (11)54.08 Total impact

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    ABSTRACT: Vascular endothelial growth factor (VEGF) promotes tumor angioinvasion while VEGF-C is a potent lymphangiogenic factor. This study aims at evaluating serum VEGF (sVEGF) and sVEGF-C levels in recurrent papillary thyroid carcinoma (PTC) patients. Serum samples were collected preoperatively from 85 patients with primary PTC, 44 with benign thyroid diseases, and 19 with recurrent PTC. sVEGF and sVEGF-C levels were measured by enzyme-linked immunosorbent assay. Twelve patients had locoregional recurrence only while 7 patients had distant metastases, including 6 with concomitant or history of locoregional recurrence. Patients with recurrent PTC had significantly higher sVEGF (432 vs 263 pg/mL, P = .004) and sVEGF-C (6,433 vs 5,289 pg/mL, P = .006) levels than benign controls. sVEGF level was significantly elevated in patients with distant metastases compared with those of local recurrences only (580 vs 345 pg/mL, P = .037) while there was no significant difference of sVEGF-C level in both subgroup of patients. sVEGF, but not VEGF-C, showed a linear correlation with thyroglobulin levels in recurrent PTC patients. Both sVEGF and sVEGF-C levels are elevated in patients with recurrent PTC, and sVEGF distinguishes the presence of distant metastasis. Angiogenic markers should be further evaluated for their clinical relevance in monitoring and predicting the type of recurrence.
    Surgery 01/2009; 144(6):934-40; discussion 940-1. · 3.37 Impact Factor
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    ABSTRACT: To evaluate the clinical relevance of serum vascular endothelial growth factor (VEGF) and VEGF-C in papillary thyroid carcinoma (PTC). VEGF is a potent angiogenic factor promoting tumor angioinvasion and distant metastases, whereas VEGF-C enhances nodal metastases because of its lymphangiogenic effect. Although both tissues VEGF and VEGF-C have been shown to contribute to tumor metastases in PTC, the clinical relevance of serum VEGF (sVEGF) and sVEGF-C remains unknown. Preoperative serum samples collected from 85 primary PTC patients and 44 control subjects with benign thyroid diseases were measured for sVEGF and sVEGF-C levels. Potential correlations between their serum levels and clinicopathologic features as well as the commonly adopted risk group stratification profiles of the tumors were analyzed. Preoperative sVEGF and sVEGF-C levels of PTC patients were significantly higher compared with those of control subjects (P = 0.001 and P < 0.001, respectively). sVEGF-C level was significantly elevated in older patients, those with extrathyroidal invasion and with lymph node metastases whereas sVEGF level was significantly increased in multifocal tumors. sVEGF-C, but not sVEGF, correlated significantly with high risk tumors in all commonly adopted risk group stratification profiles. An elevated preoperative sVEGF-C level of >7200 pg/mL was shown to be the only independent risk factor for nodal metastases. sVEGF-C levels declined significantly at 3 months after thyroidectomy in PTC but not control patients. sVEGF-C levels in PTC patients correlated significantly with the presence of nodal metastases and advanced tumor stages. Its clinical relevance needs further evaluation.
    Annals of Surgery 04/2008; 247(3):483-9. · 6.33 Impact Factor
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    ABSTRACT: Alterations of the p16 gene are common in human cancers, but their roles in thyroid cancers have not been clearly defined. The aim of the present study was to investigate the clinicopathological roles of the p16 gene in papillary thyroid carcinoma (PTC). p16 gene alterations were investigated in 44 patients with PTC (9 men, 35 women) by immunohistochemistry, reverse transcriptase-polymerase chain reaction and methylation-specific polymerase chain reaction. The findings were correlated with their clinicopathological features. p16 protein expression, mRNA alterations, and promoter methylation were detected in 89% (n = 39), 77% (n = 33), and 41% (n = 18) of patients with PTC, respectively. There was no marked relationship between p16 protein expression, mRNA alteration, and promoter methylation. In follicular variant of PTC (FVPTC), there was a frequent lack of p16 protein expression and promoter methylation. PTCs showing p16 promoter methylation were often associated with a high AMES (age, metastasis to distant sites, extrathyroidal invasion, size) risk group and advanced pTNM (tumor-lymph node-metastasis) stages. p16 gene alterations are common and correlate with histological features and biological aggressiveness in PTC, suggesting that they might play an important role in its pathogenesis.
    Annals of Surgical Oncology 06/2007; 14(5):1772-9. · 4.12 Impact Factor
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    ABSTRACT: Hepatic stellate cells (HSCs) play a key role in fibrogenesis. Here, we used mannose-6-phosphate-modified human serum albumin (M6P(26)-HSA) as a selective carrier to deliver antifibrotic drug 18beta-glycyrrhetinic acid (18beta-GA) in experimental fibrosis animals, and tested its effect in injured liver tissues. Bile duct ligation (BDL) was performed to induce liver damage in rats. Masson's stain and immunocytochemistry were used to assess hepatic collagen deposits and uptakes of M6P(26)-HSA-GA in HSCs in rat livers. Gene expression profiles of procollagen type I alpha2, smooth muscle actin (SMA), and transforming growth factor-beta1 (TGF-beta1) were analysed by TaqMan and quantitative polymerase chain reaction assays. The depositions of M6P(26)-HSA-GA in the HSC-T6 cell line and primary HSCs were assessed by immunofluorescent staining. Treatment with M6P(26)-HSA-GA at 10 mg/kg (three times/week for 2 weeks), but not the equivalent doses of free 18beta-GA and M6P(26)-HSA carrier alone, could significantly attenuate collagen deposits in BDL rat liver. Masson's stain and TaqMan assay revealed significant modulation of procollagen type I alpha2 in the BDL-injured liver. The depositions of M6P(26)-HSA-GA in HSCs were revealed by immunostaining with HSA and SMA markers. M6P(26)-HSA bound activated HSCs in vitro and the immunoreactivity of M6P(26)-HSA-GA was detected in the cytoplasm and cell surface of HSCs and HSC-T6 cells. The gene transcript levels of SMA and TGF-beta1 were modulated in HSC-T6 cells treated with M6P(26)-HSA-GA. The M6P(26)-HSA holds promise as a targeting carrier for the liver or HSCs, which may be used to deliver 18beta-GA as a therapeutic agent to treat liver fibrosis.
    Liver international: official journal of the International Association for the Study of the Liver 05/2007; 27(4):548-57. · 3.87 Impact Factor
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    ABSTRACT: Hepatocellular carcinoma (HCC), the most common form of liver cancer, is a leading cause of cancer death worldwide. We previously showed that aberrant mRNA splicing of the liver intestine-cadherin gene CDH17 in liver tissues was triggered by the specific constellation of two CDH17 single nucleotide polymorphisms (651T and IVS6+35G). CDH17 aberrant splicing was highly associated with tumor dissemination and shorter survival of HCC patients. Consequently, it is highly relevant to assess whether the presence of these single nucleotide polymorphisms in the general population represents a risk to the development of HCC. We conducted a case-control study including 164 HCC and 99 cirrhosis patients and 293 healthy controls. Genotyping was done by PCR and direct sequencing. Odds ratio (OR) and chi2 analysis were used to analyze genotypes and haplotypes. Genotypes 651TT [OR, 2.62; 95% confidence interval (95% CI), 1.34-5.03] and IVS6+35 GG (OR, 1.95; 95% CI, 1.04-3.62) were highly associated with HCC disease. The 651T (C>T) and IVS6+35G (A>G) alleles were also overrepresented in HCC patients and, in particular, the T-G haplotype was the most prevalent in HCC patients when compared with healthy controls (OR, 1.57; 95% CI, 1.167-2.109; P=0.004), which was in agreement with the aberrant splicing observed in tumor tissues. There was no significant difference in genotype and allele frequencies between cirrhosis patients and controls. The functional T-G haplotype of CDH17 (651 C>T and IVS6+35A>G) is a genetic susceptibility factor for the development of HCC in a Chinese population.
    Clinical Cancer Research 09/2006; 12(17):5248-52. · 7.84 Impact Factor
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    ABSTRACT: This study was undertaken to determine AM expression in carbon tetrachloride (CCl4)-induced liver cirrhosis developed with peritoneal ascites. Sprague-Dawley rats received subcutaneous injections of CCl4 twice weekly in olive oil (1:1, 0.3 ml per kg body weight) for 6 or 12 weeks until ascites developed, or saline in olive oil as control. At 6 weeks, fibrosis developed and at 12 weeks cirrhosis developed with ascites formation. At both 6 and 12 weeks, increases in plasma renin and AM were evident, as was the gene expression of AM. At 12 weeks after CCl4 injection, the gene expression of calcitonin-like-receptor (CRLR) and receptor activity modifying proteins (RAMP1, RAMP2 and RAMP3) were all elevated when compared to the control. The results suggest that liver cirrhosis increases mRNA expressions of AM, CRLR and RAMP1, RAMP2 and RAMP3 and that the increase in AM gene expression precedes the development of cirrhosis. The increase in AM synthesis as reflected by an increase in AM gene expression, together with a lack of increase in AM peptide at both 6 and 12 weeks may suggest an elevation of AM release. Given the potent vasodilatory action of AM, the increase in the synthesis and release of AM in the cirrhotic liver may also contribute to peripheral vasodilatation in liver cirrhosis.
    Regulatory Peptides 08/2006; 135(1-2):69-77. · 2.06 Impact Factor
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    ABSTRACT: Tight junction (TJ) constitutes the barrier by controlling the passage of ions and molecules via paracellular pathway and the movement of proteins and lipids between apical and basolateral domains of the plasma membrane. Claudins, occludin, and junctional adhesion molecules are the major three transmembrane proteins at TJ. This study focuses a newly identified mammalian TJ gene, claudin-19, in kidneys. Mouse claudin-19 composes of 224 amino acids and shares 98.2% and 95% amino acid homology with rat and human, respectively; the most evolutionary-related claudins are claudin-1 and -7, which share approximately 75% DNA sequence homology with claudin-19. Claudin-19 is abundantly expressed in the mouse and rat kidneys among the organs examined by Northern blots, and to a much less extent, also found in brain by RT-PCR. Claudin-19 and zonula occludens-1 (ZO-1) are localized at junctional regions of Madin-Darby canine kidney (MDCK) cells by immunofluorescent microscopy. In addition, ZO-1 is found in the claudin-19-associated protein complexes in MDCK cells by co-immunoprecipitation. Using aquaporin-1 and aquaporin-2 antibodies as markers for different renal segment, strong expression of claudin-19 was observed in distal tubules of the cortex as well as in the collecting ducts of the medulla. To less extent, claudin-19 is also present in the proximal tubules (cortex) and in the loop of Henle (medulla). Furthermore, intense claudin-19 immunoreactivity is found co-localized with the ZO-1 in kidneys from postnatal day 15, day 45, and adult rats and mice. Similar localizations of claudin-19 and ZO-1 are also observed in human kidneys. Since these renal segments are mainly for controlling the paracellular cation transport, it is suggested that claudin-19 may participate in these processes. In human polycystic kidneys, decreased expression and dyslocalization of claudin-19 are noticed, suggesting a possible correlation between claudin-19 and renal disorders. Taken together, claudin-19 is a claudin isoform that is highly and specifically expressed in renal tubules with a putative role in TJ homeostasis in renal physiology.
    FEBS Letters 03/2006; 580(3):923-31. · 3.58 Impact Factor
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    ABSTRACT: Despite recent studies showing that vascular endothelial growth factor C (VEGF-C) mRNA is up-regulated in papillary thyroid carcinoma (PTC), the role of VEGF-C in lymph node metastasis is still unclear. The aim of this study is to investigate the expression pattern of VEGF-C immunoreactive protein in PTC and its relationship with cervical lymph node metastasis. Tissue samples were obtained from 39 specimens of PTC (20 with and 19 without lymph node metastasis) as well as 20 benign thyroid nodules. Overexpression of the VEGF-C protein was evaluated by immunoblotting with specific anti-VEGF-C antibody in paired tumor and nontumor tissues from PTC. The data were compared with patients' clinicopathologic features and lymph node metastasis. Immunohistochemical staining was done on selected paraffin sections to determine cellular localization of VEGF-C and to assess flt-4 (or VEGFR-3)-positive vessel density in PTC lesions. Overexpression of VEGF-C was detected in 69% of the PTC and in 5% of the benign thyroid specimens. When comparing between the metastatic and nonmetastatic groups of PTC, a higher expression level of VEGF-C was detected in both the tumor (P = 0.004) and adjacent nontumor tissues (P = 0.011). Positive immunostaining for VEGF-C was confirmed in PTC tumor tissues and metastatic lymph nodes, which correlated with flt-4-positive vessel density in tumor and peritumor tissues. The increased expression of VEGF-C protein in PTC is associated with lymph node metastasis (P = 0.004) and lymphovascular permeation (P = 0.001) but is independent of other clinicopatholgic variables. The VEGF-C immunoreactive protein is overexpressed in PTC lesions, which correlates with lymph node metastases. VEGF-C expression may play a role in lymphangiogenesis of PTC and further study is necessary to evaluate the clinical application of VEGF-C as a molecular marker for tumor metastases to cervical lymph nodes.
    Clinical Cancer Research 12/2005; 11(22):8063-9. · 7.84 Impact Factor
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    Chung-Yau Lo, Alfred Lam, Pauline P Leung, John M Luk
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    ABSTRACT: BACKGROUND: Cyclooxygenase-2 (COX-2) seems to play a role in the development and carcinogenesis of papillary thyroid carcinoma. Its incidence of expression and potential application as a tumor marker remain to be elucidated.Materials and methods: Immunohistochemical staining for COX-2 expression was performed for 30 papillary thyroid carcinoma (PTC) and 40 benign thyroid specimens. COX-2 mRNA expression was analyzed using a reverse transcriptase-polymerase chain reaction (RT-PCR) for paired fresh frozen tissues removed from surgically resected PTC specimens. RESULTS: COX-2 expression was detected by immunohistochemistry in 27 of 30 (90%) PTC but was absent in 40 benign thyroid specimens, including 27 nodular hyperplasia, 7 follicular adenoma and 6 lymphocytic thyroiditis. Two of the three COX-2 negative carcinomas were follicular variant of PTC. RT-PCR analysis confirmed COX-2 mRNA over-expression in 14 of 20 (70%) paired specimens of PTC. Real-time quantitative RT-PCR showed that the level of COX-2 mRNA expression was significantly higher in PTC than in both the adjacent non-cancerous tissues and the benign thyroid specimens. CONCLUSION: COX-2 is frequently expressed in PTC but not in benign thyroid specimens. COX-2 expression may serve as a useful molecular marker for PTC in cases of diagnostic difficulty. Yes Yes
    European Journal of Endocrinology 05/2005; · 3.14 Impact Factor
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    ABSTRACT: Intraoperative quick parathyroid hormone (PTH) assay for tissue aspirate facilitates the confirmation of parathyroid tissue identity and allows a more selective use of frozen section examination during parathyroidectomy for primary hyperparathyroidism. A retrospective review of a prospective protocol of the applicability and accuracy of quick PTH assay for tissue aspirate as a biochemical frozen section tool. A university hospital department of surgery. Quick PTH assay for aspirate obtained from suspected parathyroid gland excised during parathyroidectomy for primary hyperparathyroidism. The accuracy of this biochemical identification of parathyroid tissue identity was correlated with histological examination and outcome. Quick PTH assay was performed for aspirate from at least 1 excised parathyroid gland in 122 (98%) of 125 patients while 13 patients (10%) had PTH aspirate for nonparathyroid tissues including thyroid (n = 10), thymic (n = 2) and lymphatic (n = 1) tissues. Frozen section examination was performed for 15 patients (12%), including the 3 patients who did not undergo tissue aspirate for quick PTH assay. All except 3 patients had an aspirate assay value of greater than 1500 pg/mL (range, 625 to >1500 pg/mL) for parathyroid tissue while the value of PTH aspirate for nonparathyroid tissue ranged from 27 to 229 pg/mL (median, 72 pg/mL) in 13 patients. The median size of abnormal parathyroid gland was 70 to 15,000 mg (median, 775 mg). With the availability of quick PTH assay, tissue aspirate for PTH assay can be adopted as an alternative to traditional frozen section examination to confirm parathyroid gland identity. Frozen section examination can be employed more selectively.
    Archives of Surgery 03/2005; 140(2):146-9; discussion 150. · 4.10 Impact Factor
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    ABSTRACT: To identify alternative splicing of the liver intestine-cadherin (LI-cadherin) gene in hepatocellular carcinoma (HCC) and correlate its aberrant expression with clinical outcomes. Reverse transcription-PCR (RT-PCR) and quantitative real-time RT-PCR were used to examine alternative mRNA splicing and mRNA level of LI-cadherin in 50 paired tumor-peritumor tissues of 50 HCC and 8 normal liver specimens. The minigene exon-trapping strategy was employed to investigate the splicing mechanism introduced by nucleotide polymorphisms. Association of LI-cadherin splicing with tumor venous infiltration, first-year tumor recurrence, and overall survival after partial hepatectomy were determined. Alternative mRNA splicing of LI-cadherin was identified in half of the HCC specimens. Sequencing analysis indicated the loss of exon 7 in the spliced LI-cadherin gene. LI-cadherin mRNA was up-regulated from 2.58-fold to 800-fold in over 80% of HCC samples when compared with normal liver by quantitative PCR. Furthermore, nucleotide polymorphisms were identified in putative branch point at IVS6 + 35 (intron 6) as well as in coding sequence 651 (exon 6) in HCC tissues, which may affect alternative mRNA splicing. Clinically, those patients who harbored the alternative splicing of LI-cadherin were strongly associated with shorter overall survival time (P < 0.01) as well as higher incidences of tumor recurrences and venous infiltration (both P < 0.05) after hepatectomy. Over-expression of LI-cadherin was frequently detected in liver cancer patients. Aberrant alternative splicing of LI-cadherin was detected in 50% of HCC specimens and its clinical significance hinted at early tumor recurrence and poor overall survival of HCC patients.
    Clinical Cancer Research 02/2005; 11(2 Pt 1):483-9. · 7.84 Impact Factor

Publication Stats

229 Citations
54.08 Total Impact Points

Institutions

  • 2005–2009
    • The University of Hong Kong
      • • Department of Surgery
      • • Centre for the Study of Liver Disease and Department of Surgery
      Hong Kong, Hong Kong
  • 2007
    • Griffith University
      • School of Medicine
      Brisbane, Queensland, Australia
  • 2006
    • Queen Mary Hospital
      Hong Kong, Hong Kong