HHS Public Access Author manuscript Author Manuscript
J Proteome Res. Author manuscript; available in PMC 2017 October 12. Published in final edited form as: J Proteome Res. 2016 March 04; 15(3): 1002–1010. doi:10.1021/acs.jproteome.5b01071.
Protein-Specific Differential Glycosylation of Immunoglobulins in Serum of Ovarian Cancer Patients L. Renee Ruhaak*,†,⊥, Kyoungmi Kim‡, Carol Stroble†,§, Sandra L. Taylor‡, Qiuting Hong†, Suzanne Miyamoto§, Carlito B. Lebrilla†, and Gary Leiserowitz§,‖ †Department
of Chemistry, University of California, Davis, California 95616, United States
Author Manuscript
‡Division
of Biostatistics, Department of Public Health Sciences, University of California, Davis, California 95616, United States §University
of California Davis Medical Center, Sacramento, California 95817, United States
‖Division
of Gynecologic Oncology, University of California Davis Medical Center, Sacramento, California 98517, United States
Abstract
Author Manuscript
Previous studies indicated that glycans in serum may serve as biomarkers for diagnosis of ovarian cancer; however, it was unclear to which proteins these glycans belong. We hypothesize that protein-specific glycosylation profiles of the glycans may be more informative of ovarian cancer and can provide insight into biological mechanisms underlying glycan aberration in serum of diseased individuals. Serum samples from women diagnosed with epithelial ovarian cancer (EOC, n = 84) and matched healthy controls (n = 84) were obtained from the Gynecologic Oncology Group. Immunoglobulin (IgG, IgA, and IgM) concentrations and glycosylation profiles were quantified using multiple reaction monitoring mass spectrometry. Differential and classification analyses were performed to identify aberrant protein-specific glycopeptides using a training set. All findings were validated in an independent test set. Multiple glycopeptides from immunoglubins IgA, IgG, and IgM were found to be differentially expressed in serum of EOC patients compared with controls. The protein-specific glycosylation profiles showed their potential in the diagnosis of EOC. In particular, IgG-specific glycosylation profiles are the most powerful in discriminating between EOC case and controls. Additional studies of protein- and site-specific glycosylation profiles of immunoglobulins and other proteins will allow further elaboration on the characteristics of biological functionality and causality of the differential glycosylation in ovarian cancer and thus ultimately lead to increased sensitivity and specificity of diagnosis.
Author Manuscript
Graphical abstract
*
Corresponding Author: [email protected]. Phone: +31 71 526 6397. ⊥Present Address: (L.R.R.) L.R. Ruhaak. Leidin University Medical Center, Department of Clinical Chemistry and Laboratory Medicine, Albinusdreef 2, 2333 ZA Leiden, The Netherlands. Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jproteome.5b01071. Notes The authors declare no competing financial interest.
Ruhaak et al.
Page 2
Author Manuscript Author Manuscript Keywords N-glycosylation; serum; biomarker; ovarian cancer; immunoglobulin
Author Manuscript
INTRODUCTION Ovarian cancer accounts for 6% of the cancer deaths in women in the United States.1 Most of the ovarian cancer cases are diagnosed in the advanced stages (III and IV),2 where treatment is difficult and the 5 year survival rate is
J Proteome Res. Author manuscript; available in PMC 2017 October 12. Published in final edited form as: J Proteome Res. 2016 March 04; 15(3): 1002–1010. doi:10.1021/acs.jproteome.5b01071.
Protein-Specific Differential Glycosylation of Immunoglobulins in Serum of Ovarian Cancer Patients L. Renee Ruhaak*,†,⊥, Kyoungmi Kim‡, Carol Stroble†,§, Sandra L. Taylor‡, Qiuting Hong†, Suzanne Miyamoto§, Carlito B. Lebrilla†, and Gary Leiserowitz§,‖ †Department
of Chemistry, University of California, Davis, California 95616, United States
Author Manuscript
‡Division
of Biostatistics, Department of Public Health Sciences, University of California, Davis, California 95616, United States §University
of California Davis Medical Center, Sacramento, California 95817, United States
‖Division
of Gynecologic Oncology, University of California Davis Medical Center, Sacramento, California 98517, United States
Abstract
Author Manuscript
Previous studies indicated that glycans in serum may serve as biomarkers for diagnosis of ovarian cancer; however, it was unclear to which proteins these glycans belong. We hypothesize that protein-specific glycosylation profiles of the glycans may be more informative of ovarian cancer and can provide insight into biological mechanisms underlying glycan aberration in serum of diseased individuals. Serum samples from women diagnosed with epithelial ovarian cancer (EOC, n = 84) and matched healthy controls (n = 84) were obtained from the Gynecologic Oncology Group. Immunoglobulin (IgG, IgA, and IgM) concentrations and glycosylation profiles were quantified using multiple reaction monitoring mass spectrometry. Differential and classification analyses were performed to identify aberrant protein-specific glycopeptides using a training set. All findings were validated in an independent test set. Multiple glycopeptides from immunoglubins IgA, IgG, and IgM were found to be differentially expressed in serum of EOC patients compared with controls. The protein-specific glycosylation profiles showed their potential in the diagnosis of EOC. In particular, IgG-specific glycosylation profiles are the most powerful in discriminating between EOC case and controls. Additional studies of protein- and site-specific glycosylation profiles of immunoglobulins and other proteins will allow further elaboration on the characteristics of biological functionality and causality of the differential glycosylation in ovarian cancer and thus ultimately lead to increased sensitivity and specificity of diagnosis.
Author Manuscript
Graphical abstract
*
Corresponding Author: [email protected]. Phone: +31 71 526 6397. ⊥Present Address: (L.R.R.) L.R. Ruhaak. Leidin University Medical Center, Department of Clinical Chemistry and Laboratory Medicine, Albinusdreef 2, 2333 ZA Leiden, The Netherlands. Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jproteome.5b01071. Notes The authors declare no competing financial interest.
Ruhaak et al.
Page 2
Author Manuscript Author Manuscript Keywords N-glycosylation; serum; biomarker; ovarian cancer; immunoglobulin
Author Manuscript
INTRODUCTION Ovarian cancer accounts for 6% of the cancer deaths in women in the United States.1 Most of the ovarian cancer cases are diagnosed in the advanced stages (III and IV),2 where treatment is difficult and the 5 year survival rate is
