Selection of fetal bovine serum for use in the C3H/10T1/2 CL8 cell transformation assay system

The purpose of this communication is to report our experience concerning the variation in cloning efficiency and transformation frequency utilizing C3H/10T 1/2 CL8 cells with 23 different lots of fetal bovine sera. These sera were purchased from five different commercial sources. The standard cell transformation assay using 1,000 cells per dish and 3-methylcholanthrene (7.5 micrograms/ml) as the transforming agent was performed. The chemical exposure period was 3 days. The cloning efficiency was determined in parallel toxicity tests using 200 cells per dish. Only three out of 23 serum lots supported a strong response in cell transformation. The results indicated that variation in the ability of sera to support cell transformation was not supplier dependent. In addition, our results showed that serum lots exhibiting the best cloning efficiencies did not necessarily support cell transformation. It is apparent that reliance on cloning efficiency alone would be inadequate as a means of selecting a serum lot. We therefore recommend that a complete cell transformation assay be performed when selecting fetal bovine serum for use in this assay.