Expression of multiple growth factors in a human lung cancer cell line.

U-1810, a human large-cell lung cancer line, was found to express a PDGF-like growth factor. 35S-cysteine labelling and immunoprecipitation revealed the synthesis and secretion of a 31-kDa PDGF-like protein. Serum-free conditioned medium contained PDGF-receptor-competing and mitogenic activity when tested on human fibroblasts. Whereas the receptor-competing activity was fully neutralized by anti-PDGF antibodies, the mitogenic activity was only partially affected. We therefore probed U-1810 mRNA with a panel of growth-factor DNA clones. We found expression of the genes for PDGF A- and B-chains, TGF-alpha, TGF-beta and IGF-II but not EGF or IGF-I. U-1810 cells lacked specific binding sites for PDGF but showed specific binding of EGF and expressed EGF-receptor transcripts. Thus, U-1810 is an example of a human tumor cell line that expresses multiple growth factor genes; in the intact tumor the corresponding growth factors may operate in autocrine stimulation of the tumor cells as well as in paracrine growth reactions (i.e. stroma recruitment).