Importance of high-performance liquid chromatographic analysis of serum N-acylneuraminic acids in evaluating surgical treatment in patients with early endometrial cancer

The objectives of this study were the quantification of the two major sialic acid (Sia) forms – N-acetylneuraminic (Neu5Ac) and N-glycolylneuraminic acids (Neu5Gc) – in serum before and after surgical treatment of early endometrial cancer and the relation of their levels with the progress of surgical therapy. The major Sia forms were liberated from sera glycoconjugates by mild acid hydrolysis, separated as per-O-benzoylated derivatives by a highly sensitive reversed-phase HPLC method and detected at 231 nm. Total Sia content in sera of healthy women was not related to age and body weight. Neu5Ac was identified as the major Sia in sera from both cancer patients, healthy individuals as well as in tissue specimens (≥94% of total Sia). In patients with endometrial cancer the total Sia level before surgical treatment (709.5±306.5 mg/l) was significantly higher (p≤0.0001) than that of the control group (213.5±88.7 mg/l). The elevation in Sia level was exclusively due to Neu5Ac. Following surgical therapy, serum Neu5Ac levels (699.4±305.6 mg/l) were significantly decreased (305.9±114.5 mg/l). In one case, where Neu5Ac level was increased 15 days and eight months after surgery (1.8 and 2.5 times as compared to control, respectively), a metastasis not detected during surgery was recorded. The obtained results suggest that Neu5Ac level in serum may be used as a tumor marker in evaluating the suitability of surgical treatment in early endometrial cancer.