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Effect of 12-O-Tetradecanoylphorbol-13-acetate on the Morphology and Growth of C3H/10T1/2 Mouse Embryo Cells¹

University of Southern California Cancer Center, Los Angeles, California 90033

The effects of the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on the morphology and growth properties of C3H/10T1/2 clone 8 cells were examined. The morphology of these cells was changed within 30 min following treatment with 0.1 µg of TPA per ml; they became smaller and refractile with long beady processes. Such changes were observed in both logarithmic and confluent cultures and lasted about 72 hr. Subsequent treatments were much less effective in inducing these changes. Scanning electron microscopy showed cell retraction and rounding as the most significant immediate effects of TPA treatment; many cells remained partially rounded 48 hr afterwards. Long-term surface modifications ascribable to TPA treatment were not detected. TPA had only minor effects on the growth of cultured C3H/10T1/2 cells in the presence of 10% fetal calf serum. Slight increases in plating efficiencies and saturation densities were generally observed in the presence of TPA but not with the related non-tumor-promoting compound phorbol. The cells grew slowly in 1% fetal calf serum and demonstrated serum batch-dependent alterations in their growth properties when exposed to TPA. Under conditions that produce doubling times of 70 hr or greater, TPA, but not phorbol, reduced the doubling time to about 50 hr. Saturation densities were also increased by TPA in 1% fetal calf serum. The effects of TPA on the growth of an oncogenically transformed variant of C3H/10T1/2 were quite different. While minimal effects of TPA were observed when transformed cells were treated in the presence of 10% fetal calf serum, TPA treatment in 1% fetal calf serum significantly inhibited cell growth.

¹ This work was supported by Contract NO1-CP-65831 from the National Cancer Institute, NIH, and Grant R80-5208 from the Environmental Protection Agency.

² Present address: Chemical Industry Institute of Toxicology, P. O. Box 12137, Research Triangle Park, N. C. 27709.

³ Pasadena Foundation for Medical Research, Pasadena, Calif. 91106.

⁴ To whom requests for reprints should be addressed.

Received 6/ 6/80. Accepted 9/11/80.