Further changes in differentiation state accompanying the conversion of Chinese hamster cells of fibroblastic form by dibutyryl adenosine cyclic 3':5'-monophosphate and hormones.

The morphological conversion in vitro of Chinese hamster ovary cells to a fibroblast form by a relatively large amount of dibutyryl adenosine cyclic 3':5'-monophosphate, or by a combination of small amounts of this compound and testosterone, is attended by appearance of the following additional properties: acquisition of strict contact inhibition of growth; reorientation of the random growth pattern into one in which cells grow parallel to their long dimension; disappearance of the randomly distributed, knob-like, pseudopodal structures around the cell periphery; induction of collagen synthesis; and decrease in the ability to be agglutinated and rounded up by plant agglutinins and specific cell antibodies. The changes in these characteristics are consistent with the conversion from a malignant to a normal fibroblastic state. This conversion is under genetic control, as demonstrated by the production of specific mutants with altered characteristics. The response to testosterone is specific since steroids like estradiol and hydrocortisone are inactive, and others have limited activity. Some prostaglandins are equal in activity to testosterone and 5alpha-dihydrotestosterone. This system appears useful in study of the regulation of phenotypic expression in mammalian cells.