Salivary glyco-sialylation changes monitors oral carcinogenesis

Alterations in cell membrane glycosylation play important role in oral carcinogenesis. The present study evaluated salivary sialylation changes i.e. total sialic acid (TSA), sialidase activity, linkage specific (α2-3 and α2-6) sialoproteins and sialyl transferase (ST) activity in controls, patients with oral precancerous conditions (OPC) and oral cancer. Subjects enrolled included 100 controls, 50 patients with OPC, 100 oral cancer patients, and 30 post treatment follow-ups. TSA was estimated by spectrophotometric method, sialidase activity by spectrofluorometric assay and linkage specific biotinylated lectins (α2-3: sambucus nigra agglutinin and α2-6: maackia amurensis agglutinin) were used to detect α-2,3 and α-2,6 STs and sialoproteins by ELISA and dot blot respectively. An increasing trend of salivary TSA/TP ratio, sialidase activity, α2-3 sialoproteins, α-2,3 and α-2,6 ST activities was observed from controls to patients with OPC to oral cancer patients and levels were significantly elevated in oral cancer patients as compared to the controls. Sialidase activity exhibited significant association with metastasis and infiltration. Sialidase activity, TSA/TP ratio, α-2,3 and α-2,6 ST activities were found to be higher in patients with metastasis as compared to patients without metastasis. A progressive increase in TSA/TP ratio, sialidase activity, α2-3 and α2-6 sialoproteins was observed from controls to early to advanced stage of the disease. Sialidase activity, α2-3 and α2-6 sialoproteins and ST activities were found to be decreased in complete responders; while levels were elevated in non-responders. The results documented utility of salivary sialylation endpoints, a non invasive tool in monitoring of oral carcinogenesis.