Type II estrogen binding sites and antiproliferative activity of quercetin in human meningiomas

Eleven cases of meningiomas were investigated for the presence of estrogen and progesterone receptors. These tumors specifically bound estradiol. This binding activity almost exclusively resulted from the presence of high numbers of type II estrogen binding sites (EBS). Estrogen receptors were absent or present at low concentrations. Competition analysis showed that the flavonoid, quercetin, competed for tritiated estradiol binding to type II EBS; both rutin and hesperidin did not. In addition, 10 microM quercetin, unlike rutin or hesperidin, was effective in inhibiting in vitro bromodeoxyuridine incorporation by meningioma cells. Although the mechanism of the antiproliferative activity of quercetin remains to be clarified, it is possible that this flavonoid may regulate cell growth through a ligand interaction with type II EBS.