Reduction in the formation of carcinogen-induced transformed foci by pencillin G sodium in the C3H/10T1/2 CL8 cell lines.

The C3H/10T1/2 CL8 cell line is being widely used to study mechanisms of malignant transformation in vitro. As currently employed, the standard assay system uses a combination of penicillin (100 I.U./ml) and streptomycin (50 micrograms/ml) to reduce the occurrence of bacterial contamination. The penicillin component of this mixture has been discovered to cause a reduction in the number of transformed foci which develop after exposure of cells to MCA, DMBA and X-rays. This reduction is dose dependent; 500 I.U./ml virtually eliminates transformation, while 100 I.U./ml causes an approximate 50% decrease in the number of foci. This effect does not appear to be due to overt toxicity and is largely reversible on removal of the antibiotic. Gentamicin (25 micrograms/ml) causes no reduction in the formation of transformed foci when compared to cultures maintained in antibiotic-free medium and offers the advantages of chemical stability, a wider spectrum of antibacterial activity in comparison with penicillin/streptomycin and, in addition, is active against many mycoplasma. It is suggested that future studies with this cell line should ideally be performed without antibiotics or should employ Gentamicin for antibacterial protection.