Expression of the gene coding for the Mr 78,000 glucose-regulated protein (GRP78) was examined in nontransformed and chemically and radiation-transformed C3H 10T1/2 Cl 8 mouse embryo cells. When cells were grown in complete medium with 10% fetal bovine serum, GRP78 mRNA was increased 4- to 9-fold in 3-methylcholanthrene (MCA; Clones 15 and 16)-, bleomycin (Bleo 1)-, and ultraviolet light (UV-C3)-transformed cell lines compared to nontransformed 10T1/2 clone 8 cells (Cl 8) at similar cell number and growth phase. Increased steady-state levels of GRP78 protein in MCA Cl 15 compared to Cl 8 cells were confirmed by 2-dimensional gel electrophoresis. Under these conditions transformed MCA Cl 15 exhibited increased GRP78 RNA within 24 h after addition of fresh glucose-containing medium, whereas nontransformed Cl 8 cells did not increase expression of this gene even after 5 days of culture in conditioned medium. Incubation of Cl 8 and MCA Cl 15 in glucose-free medium for 16 h caused a 3- and 15-fold induction of GRP78 RNA, respectively. In addition, chemically transformed cells were highly sensitive to glucose deprivation and responded by rounding up and detaching from the substratum. Cl 8 cells exhibited no such sensitivity to glucose deprivation. These results extend earlier reports on virally transformed cells to include chemically and radiation-transformed cells and expand earlier reports to include mRNA expression and 2-dimensional gel electrophoresis of GRP78 protein.