We have identified the receptor for epithelial type transforming growth factor (TGFe). TGFe, a member of the epithelin/granulin family of proteins, is present primarily in tissues of epithelial origin. It is a powerful mitogen for epithelial and fibroblastic cells. TGFe, iodinated using an immobilized glucose oxidase-lactoperoxidase method, was chemically crosslinked to receptors on membranes isolated from SW-13 adrenal carcinoma cells by the crosslinker disuccinimidyl suberate (DSS). The receptor appears to be a protein which migrates at an apparent molecular weight of approximately 170-175 kDa under reducing and nonreducing conditions in SDS-polyacrylamide gels.

This study reports on the effects of heparin, basic and acidic fibroblast growth factors (bFGF and aFGF, respectively), and transforming growth factor type-e (TGFe) on the growth of a human adrenocortical carcinoma cell line, SW-13. Heparin has previously been shown to inhibit growth in several cell types, including smooth muscle cells, certain fibroblasts, and epithelial cells, and to modulate the effects of fibroblast growth factors. Whereas bFGF and aFGF bind tightly to heparin and elute from a heparin-Sepharose column with 2 M NaCl and 1.6 M NaCl, respectively, TGFe binds to heparin with lower affinity and can be eluted from heparin-Sepharose column with 0.5 M NaCl. TGFe is a polypeptide unrelated to FGF, is present in neoplastic and nonneoplastic tissues, and stimulates the growth of certain epithelial cells and fibroblasts in soft agar and monolayer. Since the growth of SW-13 cells is stimulated by TGFe and by bFGF, we hypothesized that heparin would inhibit the growth of SW-13 cells by binding to these growth factors and that the effects of heparin could be overcome with the addition of either growth factor. Our experiments confirmed that heparin inhibits the growth of SW-13 cells. A dose-dependent growth inhibition was observed in both monolayer and soft agar. The inhibition in monolayer was partially reversed upon heparin withdrawal. The effects of heparin in both monolayer and soft agar were at least partially overcome by TGFe and by basic or acidic FGF. Overall protein synthesis does not appear to be affected by heparin as measured by [35S]methionine uptake. In contrast, epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) were unable to overcome heparin-induced inhibition both in monolayer and in soft agar. Heparin also inhibited [3H]thymidine incorporation in AKR-2B and partially inhibited AKR-2B cell stimulation by TGFe; however, it further potentiated the already potent stimulation by bFGF. We propose that heparin, TGFe, bFGF, and aFGF modulate the growth of SW-13 cells and possibly of other epithelial cells in complex ways and that heparin-like substances present in the extracellular matrix play an important role in the control of epithelial growth.

Transforming growth factor type e is a potent mitogen for epithelial and fibroblastic cells in vitro. It is primarily produced by epithelial tissues and cells, including normal skin keratinocytes. In this study we examined the effects of transforming growth factor type e in vivo and in vitro. On application of transforming growth factor type e to the chorioallantoic membrane of 8-day-old chick embryos, we noted a prominent thickening of the membrane caused primarily by fibroblastic and epithelial proliferation. In a subsequent study, transforming growth factor type e suspended in Matrigel was injected subcutaneously into the abdominal wall of Swiss National Institutes of Health mice. Significant influx of first neutrophils and then macrophages into the gel of transforming growth factor type e-treated mice, but not of control mice, was observed. Transforming growth factor type e also exhibited a potent chemoattractive effect on the J774 macrophage cell line in vitro. In transcutaneous mouse wounds, topical administration of transforming growth factor type e led first to an influx of neutrophils and macrophages, followed by an increased formation of granulation tissue in the transforming growth factor type e-treated wounds. These results suggest that transforming growth factor type e plays an important role in wound healing as a chemoattractant for neutrophils and macrophages and as a mitogen for epithelial and fibroblastic cells.