Evaluation of serum sialic acid, sialyltransferase and sialoproteins in oral cavity cancer.

Objective: Altered glycosylation of glycoconjugates is among the important molecular changes that accompany malignant transformation. The aim of our study was to investigate clinical usefulness of circulatory levels of sialic acid, sialoproteins and sialyltransferase for early diagnosis and management of oral cavity cancer (OC) patients.

Materials And Methods: Blood samples collected from 210 untreated OC patients, 100 patients with oral precancerous conditions (OPC) and 100 healthy males. OC patients were followed after initiation of anticancer treatment and 394 follow-up samples were also collected. Serum sialic acid levels were measured spectrophotometrically. Sialyltransferase activity was analysed using radioassay. Alpha 2-6 sialoproteins were isolated using lectin affinity chromatography.

Results: Serum levels of free, protein bound and total sialic acid as well as their ratio with total proteins were significantly elevated in untreated OC patients compared with healthy individuals, patients with OPC as well as complete responders (CR). Levels of the markers were comparable between untreated OC patients and non-responders. We observed positive correlation between serum levels of the markers and extent of malignant disease. Serum sialyltransferase activity showed significant elevations in OC patients compared with the controls (P<0.001), patients with OPC (P<0.05) and CR (P<0.05). Higher sialic acid levels in OC patients at the time of diagnosis showed poor survival. The changes in serum proteins with terminal alpha 2-6 sialic acid correlated well with the alterations in the levels of sialic acid forms and sialyltransferase activity.

Conclusion: Our results confirmed the elevations in sialic acid and sialyltransferase levels in OC patients and suggested potential utility of these parameters in prognostication and treatment monitoring of this neoplasm. The alterations in these parameters in circulation were in accordance with the changes in alpha 2-6 sialylated proteins.