Estrogenic and antiestrogenic effects of raloxifene on collagen metabolismin breast cancer MCF-7 cells

We compared the effects of different concentrations of raloxifene (1, 4 and 10 muM) on collagen biosynthesis, gelatinolytic and prolidase activities a nd matrix metalloproteinase (MMP) expression (MMP-2 and MMP-9) in estradiol -stimulated (2 nM) breast cancer MCF-7 cells. Raloxifene inhibited in a dos e-dependent manner the proliferation of MCF-7 cells, independently of the p resence or absence of estradiol in the growth medium. Raloxifene at concent rations of 1 muM and 4 muM inhibited collagen biosynthesis by about 10-fold and prolidase activity by about 50%, while at a concentration of 10 muM it inhibited there processes by only about 25%. This phenomenon war accompani ed by differences in gelatinolytic activity and MMP (MMP-2 and MMP-9) expre ssion as demonstrated by zymography and Western immunoblot analysis, respec tively. In estrogen-stimulated MCF-7 cells, cultured in the presence of 1 m uM raloxifene, a dramatic increase in the activity of both collagenases was found. In contrast, addition of raloxifene at a concentration of 10 muM to the medium of the cells resulted in restoration of gelatinolytic activity to that found in control cells. Similarly, but at both doses (1 and 10 muM) , raloxifene was able to reduce MMP-2 expression in the cells. However, whe n used alone (without estradiol) a concentration of 1 muM raloxifene strong ly stimulated MMP-2 expression, while at a concentration of 10 muM the effe ct war not observed. In the case of MMP-9, only trace amounts of this gelat inase were detected, although in contrast to MMP-2, an increase in its expr ession was noticed at a concentration of 10 muM raloxifene. The data raise the possibility that in estrogen-stimulated MCF-7 cells, raloxifene at low concentrations (1 and 4 muM) evoker antiestrogenic effect on collagen biosy nthesis and prolidase activity on the one hand, and aneifrogenic effect on gelatinolytic activity on the other, while at higher concentrations (about 10 muM) it evoker an estrogenic effect on collagen biosynthesis and prolida se activity, and an antiestrogenic effect on gelatinolytic activity. Our data suggest that the effects of raloxifene on collagen synthesis, prol idase and metalloproteinase activities in breast cancer may explain its rol e in the prevention of breast cancer development.