Influence of estradiol on the total uptake and incorporation of thymidine in human breast cancer (MCF-7) in long-term cell culture. Comparison of autoradiographic and biochemical methods.

The total uptake and incorporation into DNA of 3H-thymidine in MCF-7 cells is stimulated by estradiol after an incubation period of 24 h. Prolonged incubations show a decreased rate of both uptake and incorporation of 3H-thymidine, but the labeling index remains elevated up to 48 h. It appears that this is the only exception to the observed good relationship between labeling index and total uptake of 3H-thymidine. This correlation may be of use in comparing autoradiographic and biochemical data on DNA synthesis in the case of culturing both primary mammary tumors and mammary cancer cell lines.