Selective effects of trypsinization on established and tumour-derived mouse 3T3 cells.

Explanted tumour cells are much more sensitive to the deleterious effects of routine trypsinization than are the parent 3T3 or SV40 transformed established cell lines. This differential sensitivity causes the disappearance of tumour-derived cells when grown in co-culture with untransformed 3T3 cells and accounts in some tumor explants for the emergence of trypsin-resistant varient cells which have lost tumour-specific properties.