| Abstract: | Intracellular transforming growth factors (TGFs) were extracted from a human rhabdomyosarcoma cell line and purified to apparent homogeneity by using gel filtration, cation-exchange, and high-performance liquid chromatography. Two types of transforming growth factor activities, TGF-alpha and TGF-beta, were detected. The intracellular polypeptides which belonged to the TGF-alpha family required TGF-beta for full activity in inducing nonneoplastic normal rat kidney fibroblasts to grow in soft agar. These peptides also bound to the membrane receptor for epidermal growth factor. As determined by sodium dodecyl sulfate-polyacrylamide gels, the apparent molecular weight of these intracellular TGF-alpha's was 18 000. Intracellular TGF-beta required either epidermal growth factor or TGF-alpha for stimulation of soft agar growth. The intracellular TGF-beta was purified to homogeneity as judged by a single peak after reverse-phase high-performance liquid chromatography and a single band on a sodium dodecyl sulfate-polyacrylamide gel. The intracellular TGF-beta from the human tumor cell line was similar in all respects tested (migration on sodium dodecyl sulfate-polyacrylamide gels, stimulation of soft agar growth, binding to the membrane receptor for TGF-beta, and amino acid composition) to intracellular TGF-beta from normal human placenta. |
