CUHK electronic theses & dissertations collection

Aim. In this study, we attempted to identify HCC-specific serum glycoproteins by using glycoproteomic technologies. We targeted at finding glycoforms with aberrant alpha-2,6-sialylation and alpha-1,6-fucosylation in sera of HCC patients. These glycoforms may have potentials to be used as tumor marker(s) in the diagnosis of HCC.Among the validated differential glycoproteins, Hp was the only glycoprotein, glycoforms of which were found to be significantly up-regulated in the HCC group when examining both the sialylated glycoprotein profiles and the fucosylated glycoprotein profiles. This glycoprotein was selected for further investigation. In the independent validation group, increased serum levels of Hp (total), alpha-2,6 sialylated Hp and alpha-1,6 fucosylated Hp was observed in the HCC patients. A unique pattern of Hp glycoforms comprising both hypersialylated fucosylated and hyposialytated fucosylated species was found in the HCC patients. Serum concentrations of these glycoforms were significantly higher in the HCC patients with advanced tumor, suggesting their tumor-specific nature. Besides, we have performed quantitative profiling of N-glycans of serum Hp in the HCC patients, CLD patients and normal subjects, and have attempted to identify HCC-associated N-glycans for HCC diagnosis. Combined used of serum alpha-fetoprotein, serum Hp and its N-glycans, we could achieve 84% sensitivity at 100% and 93% specificities when distinguishing the HCC patients from the CLD patients and from the normal subjects, respectively.Background. Hepatocellular carcinoma (HCC) often arises in patients with coexisting chronic liver disease (CLD). Since alpha-fetoprotein, a conventional biomarker, may also be raised in patients with uncomplicated CLD, the use of alpha-fetoprotein in early detection of HCC is limited. Identification of additional biomarkers may improve early detection. Previous studies have shown that levels of alpha-2,6-sialyltransferase and alpha-1,6-fucosyltransferase change in liver cancer, leading to aberrant glycosylations on some serum proteins.Conclusion. By undertaking glycoproteomic approach, we have identified a panel of potential biomarkers for diagnosis of HCC. These biomarkers were useful for classifying among normal healthy subjects, CLD patients, patients with early HCC and patients with advanced HCC. Some of them were validated with the independent cases. Finally, we have identified a unique pattern of Hp glycoforms comprising both hypersialylated fucosylated and hyposialylated fucosylated species in the HCC patients. Serum Hp and its N-glycans have been shown to have potential values for aiding the diagnosis of HCC.Methodology. There are four parts in this study. The first part is "method development". A method for obtaining quantitative profiles of serum glycoproteins with alpha-2,6-sialylation or alpha-1,6-fucosylation was developed by combined use of lectin affinity chromatography, two-dimensional polyacrylamide gel electrophoresis and enzyme-linked lectin assay. The second part is "biomarker discovery". The quantitative profiles of the serum glycoproteins from 20 HCC patients and 10 CLD patients (control) were compared by bioinformatic approaches to identify potential biomarkers for diagnosis of HCC. The protein identities of the potential targets were obtained by using MALDI-TOF/TOF mass spectrometry. The third part is "validation". An independent set of serum samples from 40 HCC patients, 30 CLD patients and 20 normal subjects was used to evaluate the diagnostic values of the potential biomarkers. The last part of this study was aimed to identify HCC-associated N-glycans on one of potential biomarkers found, and examine their values in diagnosis of HCC.Result. When analyzing alpha-2,6-sialylated glycoproteins, 53 glycoprotein spots were significantly different between the HCC and CLD groups, of which 44 spots belonged to 13 glycoproteins. Bioinformatic analyses revealed that these differential sialoglycoprotein profiles contained valuable information for differentiating the HCC patients from CLD patients, and classifying between early HCC and advanced HCC patients. When analyzing alpha-1,6-fucosylated proteins, 11 glycoprotein spots were significant different between the two study groups, of which 8 spots belonged to 1 glycoprotein. Majority of the protein identities were successfully obtained by MALDI-TOF/TOF mass spectrometry. Among the differential glycoproteins, we have identified a subgroup with a unique pattern of glycosylation. These glycoproteins were characterized by the presence of hypersialylated and fucosylated glycoforms. The differential patterns and the diagnostic values of some of these serum glycoproteins were confirmed in the independent validation group by measuring their serum levels with immunoassays. The results of the logistic regression analyses suggest that complement factor B and haptoglobin (Hp) can be used in combination with alpha-fetoprotein to improve the diagnosis of HCC.Ang, Ling.Adviser: Tereng Chuen Wai Poon.Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0947.Thesis (Ph.D.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (leaves 215-238).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstract also in Chinese.School code: 1307