Glycomic mapping of pseudomucinous human ovarian cyst glycoproteins: Identification of Lewis and sialyl Lewis glycotopes

• Published in: Proteomics (Weinheim) 2007-10, Vol.7 (20), p.3699-3717
• Main Authors: Wu, Albert M, Khoo, Kay-Hooi, Yu, Shin-Yi, Yang, Zhangung, Kannagi, Reiji, Watkins, Winifred M
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Antigens, Tumor-Associated, Carbohydrate - analysis; Biological and medical sciences; Biomarkers, Tumor - analysis; Carbohydrate Sequence; Epitopes - analysis; Epitopes - chemistry; Female; Female genital diseases; Fundamental and applied biological sciences. Psychology; Gangliosides - analysis; Glycomics; Gynecology. Andrology. Obstetrics; Human ovarian cyst glycoproteins; Humans; Lewis Blood-Group System - analysis; Lewis Blood-Group System - chemistry; Medical sciences; Miscellaneous; Molecular Sequence Data; Oligosaccharides - analysis; Ovarian Cysts - metabolism; Ovarian Cysts - pathology; Polysaccharides - analysis; Proteins; Sialoglycoprotein; Sialoglycoproteins - analysis; Sialoglycoproteins - chemistry; Sialyl Lewis a; Sialyl Lewis x; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tumors
• ISSN: 1615-9853; 1615-9861
• DOI: 10.1002/pmic.200700356

Expression of sialyl Lewis x (sLex) and sialyl Lewis a (sLea) on cell-surface glycoproteins endows cells with the ability to adhere to E-, P-, and L-selectins present on endothelia, platelets, or leukocytes. Special arrangements of these glycotopes in cancers are thought to play a key role in metastasis. Previous studies have mostly described membrane-bound sLex and sLea activities. In this report, the major O-glycans of the secreted human ovarian cyst sialoglycoproteins from a Le(a+) nonsecretor individual (human ovarian cyst sample 350) were characterized by MS/MS analyses and immuno-/lectin-chemical assays. The results showed that HOC 350 carries a large number of epitopes for sLex, sLea, and Lea reactive antibodies. Advanced MS/MS sequencing coupled with mild periodate oxidation and exoglycosidase digestions further revealed that the O-glycans from HOC 350 are mostly of core 1 and 2 structures, extended and branched on the 3-arm with both type I and type II chains, complete with variable degrees of terminal sialylation and/or fucosylation to yield the sLex or sLea epitopes. Thus, the underlying core and peripheral backbone structures are similar to that of a previously proposed composite structural model for nonsialylated human ovarian cysts O-glycans, but with some notable distinguishing structural features in addition to sialylation.