Transformation of Bowes melanoma cells with SV40 T antigen.

A serum-dependent and two serum-independent variants of the Bowes melanoma cell line, RPMI7272, were transfected with plasmids containing a geneticin-resistance (neo) gene transcribed by the HSV thymidine kinase promoter and an SV40 T antigen gene under control of the mouse metallothionein I promoter. T-antigen increased the cloning efficiency of the serum-dependent cell line in soft-agar more than 50-fold, but cloning efficiency of serum-independent lines was not increased. Trypsinization of serum-independent lines required 100 times lower concentrations of trypsin than serum-dependent cells. Human metal-inducible T-antigen-producing (HMT) melanoma cells supported replication of transfected plasmids containing an SV40 origin of replication. Transient expression of interferon or plasminogen activator from such plasmids was 40-fold higher than in untransformed melanoma cells and could be enhanced 30-fold more by stimulation of transcription of the T antigen gene with cadmium chloride. HMT cells can be grown in suspension and thus may represent an attractive alternative to monkey kidney COS cells.