1984 年 5 巻 5 号 p. 405-412
Tumor promoter, 12-o-tetradecanoylphorbol-13-acetate (TPA) induced the appearance of larger extrachromosomal circular DNA molecules (more than 1 μm in contour length) in mouse B16 cells, but no such effect in rat L6 cells. This may be due to the presence of a TPA-inactivating enzyme in the rat skin. Teleocidin induced an increase in the number of smaller circular DNAs (less than 1 μm in contour length) in the mouse cells, and the appearance of larger circular DNA molecules in the rat cells. The persistent effect of TPA on the appearance of circular DNAs was shown in interspecific mouse-rat reconstituted cells, in which the phenotype of unique cell morphology is reversibly changed to that of parent mouse by TPA. The persistence of induction ofcircular DNAs may be related to the irreversibility of tumor promotion at the first stage.
