FIG. 4.

Rapamycin potentiation of TGF-β-induced growth arrest is mediated by rapamycin binding to FK506 binding protein(s). (A) MDA-MB-231 cells were treated for 24 h with normal growth medium (C), dimethyl sulfoxide vehicle (V), 10 ng of TGF-β/ml (T), 100 nM rapamycin (R), or 10 ng of TGF-β/ml plus 100 nM rapamycin (T + R), and ¹²⁵I-TGF-β affinity cross-linking experiments were performed as described in Materials and Methods. Puro. Cont. cells (B) or DU145 cells (C) were treated with 10 ng of TGF-β/ml and various combinations of rapamycin, the Novartis rapamycin derivative RAD001, or FK506 for 24 h as indicated, and [³H]thymidine incorporation assays were performed as for Fig. 2.