NIH 3T3 cells transfected with human tumor DNA lose the transformed phenotype when treated with swainsonine.

Phenotypic expression of transformation was inhibited by swainsonine at concentrations which affect the late stages of glycoprotein processing but not growth of cells. In the presence of swainsonine, NIH 3T3 fibroblasts transfected with human tumor DNA (al-l) no longer grew in soft agar or expressed complex type oligosaccharides characteristic of transformed cells. Thus, it appears that glycoproteins with fully processed oligosaccharides are necessary for the maintenance of the transformed phenotype in these cells.