Tumour cells which develop resistance to cytolysis by tumour necrosis factor have a different glycoform of a 105-kDa glycoprotein and lose the capacity to invade and metastasize.

A plastic-adherent variant of human myelomonocytic leukaemia cells (U937) is highly susceptible to direct TNF cytolysis in vitro. Previously, we found that a subline selected for resistance to TNF cytolysis (U937/R) was much less motile and more plastic-adherent than the parental line. In the present study we show that U937 and U937/R cells have different glycoforms of a 105-kDa cell-surface glycoprotein. This protein is predominantly N-glycosylated and has the physicochemical properties of the LAMP-I glycoprotein. In nude mice, U937 cells are highly malignant whereas U937/R cells form a benign, encapsulated tumour. Therefore, possession of a different glycoform of the 105-kDa glycoprotein by U937/R cells correlates not only with loss of TNF susceptibility but also with reduced invasiveness and metastasis.