The elevated requirement for methionine by transformed rat liver epithelial cells in vitro.

Growth constants appear to constitute a useful tool in comparing the behavior for transformed and untransformed cells in culture. The substitution of homocysteine for methionine in culture medium caused a greater depression of growth with 3/4 of the transformed epithelial and with 10/14 other cell lines tested compared to the growth depression seen in similar untransformed lines. The greater growth depression exhibited by transformed lines on methionine-deficient, homocysteine-supplemented medium could generally be attributed to: 1. Greater growth of transformed cells in complete medium, and 2. The lower levels of methyltransferase generally found in the transformed lines. Finally methyltransferase appears to be a major determinant of growth of both normal an transformed cells growing in a methionine-deficient, homocysteine-supplemented medium.