Neoplastic transformation of rat 3Y1 cells by a transcriptionally activated human c-myc gene and stabilization of p53 cellular tumor antigen in the transformed cells.

Transformed foci were obtained in rat 3Y1 fibroblasts cotransfected with pRmyc 27 (transcriptionally activated c-myc) and pSV2neo DNA. RmycY cell lines (1 to 7) were established from these foci. RmycY cells were small and round and contained enlarged nucleoli in the nucleus. The myc gene was expressed in these cell lines at a much higher level than in 3Y1 cells and at a level similar to that in HL-60 cells. These cell lines formed colonies in soft-agar culture and tumors in syngeneic rats transplanted with RmycY cells. Expression of the gene and colony formation in soft-agar culture were analyzed in subclones from RmycY cell line 1. A correlation between myc gene expression and the ability to form colonies in soft-agar culture was observed in these cells. Antibody against p53 cellular tumor antigen was detected in some sera from tumor-bearing rats. p53 cellular tumor antigen stabilized and accumulated in RmycY cells to the same extent as in simian virus 40-transformed cells. The results suggest that elevated c-myc expression and an increased amount of p53 cause 3Y1 cells to become a more tumorigenic cell line.