Effects of the tumor promoter TPA on the induction of DNA synthesis in normal and RSV-transformed rat fibroblasts

✍ Scribed by Magun, Bruce E. ;Bowden, G. T.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1979
• Tongue: English
• Weight: 579 KB
• Volume: 12
• Category: Article
• ISSN: 0091-7419
• DOI: 10.1002/jss.400120107

✦ Synopsis

Induction of DNA synthesis by the tumor promoter tetradecanoyl phorbol acetate (TPA) was studied in aline of cultured rat fibroblasts (Rat-1) and their Rous sarcoma virus-transformed derivative (Rat-l(RSV)). Following serum deprivation for 54 h t o achieve quiescence, semiconservative DNA replication was measured by incubation of cells in BrdUrd and FdUrd after serum stimulation in the presence or absence of TPA. Optimal concentrations of TPA (0.1-0.5 pg/ml) in serum-free medium induced a small increase (10-15%) in the amount of DNA made over a 30-h period in both Rat-1 and Rat-l(RSV) cells. When Rat-1 cells were stimulated by a 4-h serum pulse, 30% of the DNA was replicated by 3 0 h. If the serum pulse was followed by TPA addition, 70% DNA replication was observed. If the serum pulse was preceded by TPA addition, the onset of DNA synthesis was delayed by several hours, but stimulation of DNA synthesis occurred. In contrast, the Rat-1(RSV) cells did ndt show an increase in DNA synthesis induced by TPA in similar protocols, but the seruminduced onset of DNA synthesis was delayed by several hours in the presence of TPA. Therefore, TPA acts as a cc-inducer of DNA synthesis in the Rat-1 but not in the Rat-1(RSV) cells. The parent alcohol, phorbol, was inactive in Rat-1 cells, but delayed the onset of DNA synthesis in the Rat-l(RSV) cells. We conclude that the cc-inducing and delaying activities of TPA on DNA synthesis appear to be distinct and t o act at different points in the G I phase of the cell cycle.