Amplification and overexpression of the met gene in spontaneously transformed NIH3T3 mouse fibroblasts.

Abstract

We have identified a class of transformed NIH3T3 mouse fibroblasts that arise at low frequencies in transfection experiments with DNA from both neoplastic and non‐neoplastic cells and that may result from a low level of spontaneous transformation of NIH3T3 cells. DNA from the transformed cells was unable to transform NIH3T3 cells in a second cycle of transfection and, where examined, the cells showed no evidence for the uptake of the transfected DNA sequences. The results of Southern analyses demonstrate that a mouse homologue of the human met oncogene is amplified 4‐ to 8‐fold in 7 of 10 lines of these transformed NIH3T3 mouse fibroblasts. The cells containing the amplified gene also exhibit at least a 20‐fold overexpression of an 8.5‐kb mRNA that is homologous to met. To test the hypothesis that met encodes a growth factor receptor, we examined the binding of platelet‐derived growth factor, epidermal growth factor, insulin‐like growth factor I and gastrin‐releasing peptide to transformed and non‐transformed NIH3T3 cells. The results show that there is no significant elevation of the binding of these growth factors to cells containing amplification and overexpression of met.