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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‐α, TGF‐β and IGF‐11 but not EGF or IGF‐1. 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).