Development of transformed characteristics by sheep thyroid cells irradiated as differentiated primary cultures.

A method has been developed which allows four stages of transformation to be detected in subcultured populations of sheep thyroid cells exposed to gamma irradiation as differentiated primary cultures. The cell populations initially irradiated and the subcultures deriving from these retain a number of differentiated properties of thyroid cells, including iodine uptake, follicle formation and T4 production. The stages of transformation which develop in the subcultures are nonsenescence, focus development on a confluent monolayer, i.e. loss of contact inhibition, colony formation in soft agar, i.e. anchorage independence, and reduced serum dependence. The technique offers a method for detecting the development of transformation in primary differentiated epithelial cultures.