Raloxifene plus 17beta-estradiol inhibits proliferation of primary cultured vascular smooth muscle cells and human mammary endothelial cells via the janus kinase/signal transducer and activator of transcription3 cascade

Long-term use of estrogen replacement therapy increases the risk of breast cancer. Presently, we investigated the effects and mechanisms of Raloxifene, a second generation selective estrogen receptor modulator, plus 17beta-estradiol on the proliferation of primary cultured vascular smooth muscle cells (VSMC) and human mammary endothelial cells (HMEC). Raloxifene plus 17beta-estradiol inhibited angiotensinII-induced VSMC proliferation and rapid phosphorylation of STAT3; these effects were blocked by AG490, the janus kinase/signal transducer and activator of transcription3 (JAK/STAT3) inhibitor. STAT3 production was not affected. In primary cultured HMEC, immunofluorescence identified the ERbeta subtype, but not the ERalpha subtype, in the nucleus. Raloxifene plus 17beta-estradiol inhibited 17beta-estradiol-induced proliferation of HMEC. Western blot analysis established that Raloxifene attenuated the 17beta-estradiol-induced phosphorylation of STAT3, and that this effect was blocked by AG490. We conclude that Raloxifene plus 17beta-estradiol inhibits the proliferation of VSMC and HMEC through the JAK/STAT3 cascade, which in primary cultured HMEC may be implemented through ERbeta.