A PARACRINE ROLE FOR MYOEPITHELIAL CELL-DERIVED FGF2 IN THE NORMAL HUMAN BREAST

We have studied separated normal human breast epithelial and myoepithe lial cells for the presence of basic fibroblast growth factor (FGF2) a nd its receptors, both low (heparan sulfate proteoglycans) and high af finity (FGFR1), and for the effects of FGF2 on the proliferation of bo th cell types. Our results indicate that these cells differ markedly i n their synthesis and response to FGF2. We found, using PCR of purifie d cell populations, mRNA for FGF2 only in the myoepithelial cells, whe reas immunostaining and Western blotting results demonstrated the pres ence of FGF2 protein in both epithelial and myoepithelial cells. FGF2 had no effect on the proliferation of myoepithelial cells, but it did maintain the survival of the separated epithelial cells in low serum a nd stimulate their growth in 5% and 10% FCS. Immunostainable FGFR1 was present in epithelial cells and, to a lesser extent, in myoepithelial cells. Low-affinity binding sites for FGF2 mere synthesized by epithe lial and myoepithelial cells, but myoepithelial cells possessed a grea ter proportion of higher affinity heparan sulfate proteoglycans. These results indicate that myoepithelial cell-derived FGF2 may be an impor tant paracrine factor controlling epithelial cell survival and growth in the normal human breast.