Studies on carcinogenesis by avian sarcoma viruses. VI. Differential multiplication of uninfected and of converted cells in response to insulin

Insulin can replace the factor(s) in calf serum whose amount is limiting for multiplication in cell culture of chicken embryo fibroblasts and of chicken embryo fibroblasts infected and converted by avian sarcoma virus. In serum‐free, insulin‐containing medium, converted cells multiply more than do uninfected cells. It appears, therefore, that the increased multiplication in cell culture of converted cells as compared with uninfected cells results from a decreased requirement by the converted cells for an insulin‐like activity found in serum.