Isolation of a subclonal cell line of PC12 transfected with dexamethasone-regulated ras oncogene: morphological differentiation, biochemical properties, and tumorigenicity.

We have isolated and characterized a new subclonal cell line designated as MR31, which was obtained by transfection of PC12 cells with a glucocorticoid-regulated ras oncogene. The mRNA derived from the c-Ha-ras gene was proved to be expressed on exposure of the MR31 cells to dexamethasone, the highest value being attained at 8 h. MR31 cells rapidly extended neurite-like processes within 24 h in response to dexamethasone as well as nerve growth factor (NGF). The time of onset of neurite outgrowth induced by dexamethasone corresponded to the time when the highest ras mRNA level was observed. The catecholamine content of MR31 cells was found to be twice that of PC12 cells. A time course study on the effects of dexamethasone or NGF on cells showed that the former caused an increase in dopamine, a major catecholamine, to twofold the control level at 48 h after the treatment, while the latter caused a decrease in the dopamine level. These effects on catecholamines were almost the same in MR31 and PC12 cells. The acetylcholinesterase activity of MR31 cells was enhanced by both dexamethasone and NGF, whereas that of PC12 cells was enhanced by NGF, but not by dexamethasone. The changes in acetylcholinesterase activity were correlated with neurite outgrowth. Electron-microscopically, MR31 cells were not different from PC12 cells. MR31 cells exhibited extremely decreased tumorigenicity as compared with PC12 cells. The morphological and biochemical properties of MR31 cells remained constant, even after repeated passages.(ABSTRACT TRUNCATED AT 250 WORDS)