Increased sialylation of cell surface
glycoconjugates is among the key molecular changes associated with malignant transformation and
cancer progression. We investigated significance of linkage-specific sialylation changes in oral
carcinogenesis. Tissue and serum levels of total
sialic acid (
TSA), linkage-specific
sialyltransferases (ST) and
sialoproteins were analyzed from patients with oral
precancerous conditions (OPC) and
oral cancer as well as the post-treatment follow-up blood samples of
oral cancer patients.
TSA levels were measured using a spectrophotometric method. The linkage-specific
lectins, Sambusus nigra (SNA) and Maackia amurensis (MAM) detects alpha 2-6- and alpha 2-3-linked
sialic acid, respectively, were used to analyze ST activity and
sialoproteins. Malignant tissues showed significantly higher levels of
TSA, reactivity of SNA and MAM, and alpha 2,3-ST activity compared to the adjacent normal tissues. alpha 2,6-ST was also higher in malignant tissues. Similarly, the marker levels were higher in precancerous tissues than their adjacent normal tissues. Serum levels of
TSA,
TSA/ total
proteins, alpha 2-6-sialoproteins and alpha 2,6-ST were markedly increased in untreated
oral cancer patients compared to the controls and OPC as well as responder (CR) patients. Serum levels of the markers were higher or comparable between untreated
oral cancer patients and non-responders (NR). Serum levels of alpha 2-3-sialylation were elevated in non-responders compared with the responders. Further, the observed sialylation changes in tissue and serum were found to be associated with various clinicopathological features and
disease progression. Thus, the data suggest potential utility of sialylation markers in early detection, prognostication and treatment monitoring of
oral cancer.