Epithelial ovarian cancer is diagnosed less than 25% of the time when the
cancer is confined to the ovary, leading to 5-year survival rates of less than 30%. Therefore, there is an urgent need for early diagnostics for
ovarian cancer. Our study using glycotranscriptome comparative analysis of endometrioid
ovarian cancer tissue and normal ovarian tissue led to the identification of distinct differences in the transcripts of a restricted set of
glycosyltransferases involved in N-linked glycosylation. Utilizing
lectins that bind to
glycan structures predicted to show changes, we observed differences in
lectin-bound
glycoproteins consistent with some of the transcript differences. In this study, we have extended our observations by the use of selected
lectins to perform a targeted glycoproteomic analysis of
ovarian cancer and normal ovarian tissues. Our results have identified several
glycoproteins that display
tumor-specific glycosylation changes. We have verified these glycosylation changes on
glycoproteins from tissue using immunoprecipitation followed by
lectin blot detection. The
glycoproteins that were verified were then analyzed further using existing microarray data obtained from benign ovarian
adenomas, borderline ovarian
adenocarcinomas, and malignant ovarian
adenocarcinomas. The verified
glycoproteins found to be expressed above control levels in the microarray data sets were then screened for
tumor-specific
glycan modifications in serum from
ovarian cancer patients. Results obtained from two of these
glycoprotein markers,
periostin and
thrombospondin, have confirmed that
tumor-specific
glycan changes can be used to distinguish
ovarian cancer patient serum from normal serum.