Tenascin‐C induction by the diffusible factor epidermal growth factor in stromal‐epithelial interactions

Tenascin‐C, a six‐armed extracellular matrix glycoprotein, is expressed in a temporally and spatially restricted pattern during carcinogenesis and invasion or metastasis of carcinoma cells in association with stromal‐epithelial interactions. The human epidermoid carcinoma‐derived cell lines, A431 and HEp‐2, which do not express tenascin‐C by themselves in vitro, do express tenascin‐C after transplantation into nude mice, and transforming growth factor β1 (TGF‐β1) induces them to express tenascin‐C in vitro. Epidermal growth factor (EGF) induced tenascin‐C in these cells more effectively (about 3.5‐fold greater) than did TGF‐β1. Hepatocyte growth factor (HGF) and platelet‐derived growth factor (PDGF) had little effect on the induction of tenascin‐C. EGF also induced other extracellular matrix components, fibronectin and laminin. Tenascin‐C was also induced when the carcinoma cells were co‐cultured with embryonic fibroblasts from mice which were homozygous for a null mutation in the tenascin‐C gene, or when the conditioned medium from these cells was added. The induction of tenascin‐C in the co‐culture was reduced by treating the cells with antibodies against EGF or its receptor. The addition of EGF caused both cell types to disrupt their cytoskeleton and focal contacts as evidenced by the loss of stress fibers and vinculin plaques. EGF did neither induce tenascin‐C nor affect the morphology in tenascin‐C‐nonproducing A549 carcinoma cells, which did not produce tenascin‐C after transplantation. Thus, EGF induces tenascin‐C in tenascin‐C‐nonproducing human carcinoma cells through EGF receptors. Furthermore, in stromalepithelial interactions, the diffusible factor EGF participates in the induction of human tenascin‐C in these cells through EGF receptors. © 1995 Wiley‐Liss Inc.