Differential modulation of basement membrane gene expression in human fibrosarcoma HT-1080 cells by transforming growth factor-beta 1. Enhanced type IV collagen and fibronectin gene expression correlates with altered culture phenotype of the cells.

The effects of transforming growth factor-beta 1 (TGF-beta 1) on the regulation of basement membrane gene expression were studied in human fibrosarcoma HT-1080 cell cultures. Treatment of cells with TGF-beta 1 resulted in a time- and dose-dependent enhancement of type IV collagen and fibronectin gene expression, as detected both at the mRNA level by Northern hybridizations and at the protein level by semi-quantitative indirect immunofluorescence analyses. These changes were accompanied by profoundly altered morphology of the cell cultures. In contrast, laminin B1 and B2 chain, and nidogen mRNA levels remained unaltered by TGF-beta 1 in the same cultures, indicating uncoordinate modulation of the expression of basement membrane components by TGF-beta 1. Cycloheximide experiments provided evidence that the TGF-beta 1-elicited upregulation of the expression of the fibronectin gene is, but that of type IV collagen is not, entirely dependent on protein synthesis, suggesting two different mechanisms for enhancement of gene expression. Incubation of HT-1080 cells with TGF-beta 1 also resulted in a slightly enhanced expression of beta 1 and alpha 5 integrin mRNAs, as well as beta 1 integrin epitopes. Furthermore, incubation of the cells with anti-beta 1 integrin antibodies partially counteracted the TGF-beta 1-induced morphologic alterations. These studies provide evidence for the role of beta 1 integrins in TGF-beta 1 elicited alterations in HT-1080 cell culture morphology, possibly mediated by the expression of ligand proteins for these integrins, such as type IV collagen and fibronectin.