Objective: Aberrant glycosylation occurs in essentially all types of experimental and human cancers, and many glycosyl epitopes constitute tumor-associated antigens (for example, CA125). Many recent studies have indicated that some, if not all, aberrant glycosylation is a result of altered sialyltransferase (ST) expression; however, there is little known of the role of the altered mRNA expression of ST in ovarian cancers.
Methods: Alterations in ST mRNA expression in postmenopausal ovarian tissues, including those of normal controls (n=24) and malignant serous ovarian cancers (n=24), were examined by means of real-time quantitative reverse transcription-polymerase chain reaction (RTQ-PCR). Maackia Amurensis Agglutinin type 2 (MAA) specific foralpha2,3-linked NeuNAc was used for immunohistochemical staining.
Results: Among these five STs, the mRNA expressions of three STs, including ST3Gal III, ST3Gal IV, and ST3Gal VI, were significantly decreased in patients with ovarian cancers, compared to the normal controls (P<0.001). By contrast, the mRNA expressions of ST3Gal I and ST6Gal I were increased in ovarian cancer tissues, compared to those of the normal controls (P<0.001). The ovarian epithelial carcinoma part showed strong positivity for MAA, whereas MAA staining in the stromal part was negative. Both the epithelial part and the stromal part of postmenopausal ovarian tissue showed negativity for MAA staining. However, clinico-pathological parameters, including stage, differentiation, amount of ascites, and serum levels of CA125, did not show any correlation to mRNA expression of any given-type ST.
Conclusions: Our results suggest that altered mRNA expressions of alpha2,3-sialyltransferase ST3Gal I, ST3Gal III, ST3Gal IV, ST3Gal VI, andalpha2,6-sialyltransferase ST6Gal I are of importance in malignant ovarian cancers. An increased expression of ST3Gal I may contribute directly to increased alpha2,3-linked sialylation in ovarian serous carcinoma.