Marked instability of character of cloned epithelial cells.

Cell lines derived from 7,12-dimethylbenzanthracene-induced rat mammary carcinomas show a marked drift in properties when cultured in vitro. The following characteristics alter progressively with the number of passages: cloning efficiency, requirement for hydrocortisone, requirement for fetal sera, growth response to conditioning factor(s) and ease of detachment from the culture vessel by trypsinization.