Expression of multiple species of basic fibroblast growth factor mRNA and protein in normal and tumor-derived mammary epithelial cells in culture.

We examined the expression of the basic fibroblast growth factor (bFGF) gene in cultured normal and tumor-derived human mammary epithelial cells at both the transcriptional and translational level. Northern blot analysis revealed three bFGF mRNA transcripts of 7.5, 4.4, and 2.2 kilobases in all four strains (donors) of normal cells (HMECs) we examined and in the immortal mammary cell line HBL-100. Of the four mammary tumor-derived cell lines we examined (MCF-7, BT-474, T-47D, and Hs578T), only the Hs578T cells produced detectable levels of bFGF mRNA. Western blot analysis of cell lysates using an anti-bFGF monoclonal antibody revealed corresponding results. bFGF protein was detected in normal HMEC strains 161 and 48 (other normal strains not tested), in HBL-100 cells, and in Hs578T cells, but not in the other tumor cell lines. In each case, three distinct molecular weight species of bFGF protein were detected which migrated in sodium dodecyl sulfate-polyacrylamide gel at 18, 24, and 27 kDa. We also investigated the ability of bFGF to stimulate the proliferation of normal and tumor-derived mammary epithelial cells. Addition of bFGF to serum-free cultures of these cells had no effect on the proliferation of HMECs under a variety of conditions and was weakly mitogenic for Hs578T cells. Our results indicate that normal HMECs produce bFGF mRNA and protein(s), whereas only some mammary tumor-derived cells express this gene. Thus, our results do not support a general role for expression/overexpression of bFGF in the development of mammary tumors. However, bFGF could play a role in the normal development and homeostasis of the mammary gland.