Differential effects of epidermal growth factor, transforming growth factor, and insulin on DNA and protein synthesis and morphology in serum-free cultures of AKR-2B cells.
The effects of epidermal growth factor (EGF), insulin, and a transforming growth factor from fetal bovine serum on protein synthesis, DNA synthesis, and morphology in confluent cultures of AKR-2B mouse cells have been examined. The cells were plated and grown to confluence in serum-containing medium, and then the medium was changed to MCDB 402 containing no undefined supplements for 2 days before the addition of the polypeptides to be tested. Under these conditions, all of the factors listed above stimulated rapid increases in protein synthesis. When added to cultures singly, however, only EGF stimulated significant DNA synthesis. The effect of EGF on DNA synthesis was highly synergistic with insulin. Fetal serum transforming growth factor activity, which stimulated multiple rounds of cell replication in soft agar in serum-containing medium, did not stimulate DNA synthesis in serum-free monolayer cultures of these cells when added alone or in combination with EGF or insulin. Fetal serum transforming growth factor did, however, stimulate a rapid change in the morphology of these cells from flat, nonoverlapping cells to bipolar, multilayered cultures when added to the serum-free medium.