Effects of Transforming Growth Factor β on the Anchorage-independent Growth of Murine Epithelial JB6 Cells

The work described in this paper demonstrates that transforming growth factor, Â(¡TGF-/3) induces the soft agar growth of murine epidermal JB6 clone 41 (Cl 41) cells. In this regard, TGF-/S is more effective than either 12-O-tetradecanoylphorbol-l 3-acetate or epidermal growth factor. Together, I (•!•a'n-d,'! epidermal growth factor produce a greater stim ulation of soft agar growth than either growth factor alone. In contrast, addition of TGF-/31 and 12-0-tetradecanoylphorbol-13-acetate together does not stimulate soft agar growth beyond that produced by I (¡I-/>'I alone. Interestingly, retinoic acid inhibits the ability of all three factors to induce the anchorage-independent growth of CI 40 cells. K.l-.i also exerts long-term effects on Cl 41 cells. This was determined by isolating TGF-/3-induced soft agar colonies and examining their dependence on TGF-/3. Five of the six anchorage-independent clones isolated after TGFß\ treatment were found to exhibit anchorage-independent growth in the absence of TGF-/3. In addition, these clones respond far more strongly to TGF-/91 than do the parental Cl 41 cells in terms of both the numbers and the sizes of colonies formed in soft agar. The findings reported here are compatible with the proposal that TGF-/3 mediates some effects of 12-O-tetradecanoylphorbol-13-acetate.