Fas-signaling and effects on receptor tyrosine kinase signal transduction in human breast epithelial cells.

Fas-mediated cell death was examined in MCF-10AT preneoplastic human breast epithelial cells. Treatment with anti-Fas for 48 h induced apoptosis with cells exhibiting typical apoptotic features including loss of cell contact, condensation of chromatin, and increased staining of the nuclear membrane. DNA fragmentation occurred in response to anti-Fas treatment. Anti-Fas treatment resulted in decreased p53 protein levels, while bcl-2 and bax protein levels remained unaffected. Cells treated with anti-Fas also exhibited increased tyrosine phosphorylation of the c-met growth factor receptor tyrosine kinase. Immunoprecipitation experiments demonstrated that Fas associated with c-erbB2 and c-met in untreated cells. Treatment with anti-Fas, however, significantly decreased Fas-c-erbB2 and Fas-c-met association. Anti-Fas treatment of these cells caused a significant decrease in p120-GAP levels, ERK-1 levels, and phosphorylation, as well as Grb2-Sosl and MEK-1-ERK-1 association. These results show that Fas-signaling exerted a suppressive effect on p53 levels and on downstream effectors of receptor tyrosine kinase signal transduction, thereby ensuring cell death.