Table 3.
Sialylation changes associated with malignant transformation and tumor progression
| Sialic acid | Linkage | Glycan | Glycan carrier | Type of cancer | Mechanistic and practical significance |
|---|---|---|---|---|---|
| Sia | Various | Various | Various | Many | Reduction of cell–cell interactions? Protection from complement? Alteration of interactions with collagen? |
| Sia | α2-3Gal | Lewis X/A | Mucins | Most carcinomas | Tumor marker. Poor prognosis. Facilitation of platelet–leukocyte interactions in metastasis |
| Sia | α2-6Gal | N-glycan | Integrins? | Some carcinomas | Alteration of integrin function? Enhancement of invasion? Poor prognosis in some cancers |
| Sia | α2-6GalNAc | Tn | Mucins | Some carcinomas | Enhancement of invasion? Tumor marker. Target for immunotherapy |
| Sialic acid | α2-8Sia | N-glycan | N-CAM | Brain tumors, myelomas | Reduction of cell–cell interactions? Facilitates metastasis? |
| Neu5Gc | Various | Various | Various | Most carcinomas | Accumulated from dietary sources? Associated with anti-Neu5Gc antibodies |
| 9-O-Ac | α2-8Sia | GD3 | Ganglioside | Melanomas | Tumor marker. Protects from GD3-mediated apoptosis? |
| 9-O-Ac | α2-6GalNAc | O-glycans | Mucins? | Leukemias | Prognostic marker? |
Abbreviations: N-CAM, neural cell adhesion molecule; Tn, Siaα2-3GalNAcα-Ser/Thr.