Glycoproteins in relation to cell differentiation and malignancy.

Differentiation and malignancy have been correlated with particular cell surface glycoproteins and may, in fact, be mediated by these glycoproteins. Theoretically, two fundamentally distinct mechanisms exist by which changes in cell surface glycoproteins in differentiation and malignancy can be effected. Firstly, a particular surface protein can be glycosylated differently. This amounts to a change in carbohydrate structure only. Secondly, a new surface protein can be synthesised that either carries a pre-existing [i.e. also attached to another surface protein (s)] or a new carbohydrate moiety; synthesis of a pre-existing protein(s) may also be suppressed. This amounts to a change in polypeptide structure that may or may not be coupled with a change in carbohydrate structure. Current evidence indicates that both mechanisms probably operate in both differentiation and malignancy.