THE EXPRESSION OF BASIC FIBROBLAST GROWTH-FACTOR AND ITS RECEPTOR IN CELL-LINES DERIVED FROM NORMAL HUMAN MAMMARY-GLAND AND A BENIGN MAMMARY LESION

mRNA for basic Fibroblast Growth Factor (bFGF) was expressed in a seri es of SV40-transformed human mammary cell lines as molecules of 7.1, 3 .6, 2.0 and 1.2 kb. This expression was much weaker in those lines of epithelial morphology than in myoepithelial-like cell lines derived fr om them. It was confirmed, using northern hybridization to single-stra nded RNA probes, that the multiple mRNAs were transcribed from the cod ing strand for bFGF. bFGF activity was detected in extracts of the cel ls and the relative amounts of activity corresponded in general to the amounts of mRNA found. Similar results were obtained from spontaneous ly transformed cell lines derived from a human benign breast lesion. T he presence of bFGF protein in the extracts was confirmed by western b lotting, which showed a band of 18-19 kDa, migrating in the same posit ion as authentic bFGF; in addition, the myoepithelial-like cells showe d prominent bands of bFGF at 24 and 26 kDa. No FGF receptor was detect able by the binding of I-125-bFGF to the SV40-transformed cell lines o r to the epithelial cell lines from the benign breast lesion, but both high- and low-affinity receptors were found on myoepithelial-like cel ls derived from the latter. The results indicate that differentiation to the human myoepithelial-like phenotype in culture is associated wit h the enhanced expression of bFGF, and it is suggested that bFGF, immu nocytochemically detected in the basement membrane of the human breast , may arise, at least in part, from the myoepithelial cells of the mam mary parenchyma.