Effect of cell density on the in vitro transformation of C3H-10T 1/2 mouse embryo fibroblast cells by x rays

The mouse embryo fibroblast derived C3H-10T 1/2 cell line has been used widely as an in vitro model for studying carcinogenesis. This cell line shows postconfluent contact inhibition of growth except when treated with chemical or physical carcinogens in which case a dose dependent incidence of transformed foci (Types II and III) is observed. This investigation was undertaken in order to better characterize the phenomenon of increased transformation at low cell density and to confirm some of the assumptions concerning the culture conditions for C3H-10T 1/2 cells about to be used in experiments. In particular, two hypotheses were tested: (1) cell density does play a role in x-ray transformation frequency, and (2) freshly confluent cells that are trypsinized and replated approximately 24 hours prior to x-ray treatment are an asynchronous, exponential growing population of single cells at the time of x-irradiation