Relationship between 90-kilodalton heat shock protein, estrogen receptor, and progesterone receptor in human mammary tumors.

To determine, if, as previously observed with rodent uterus, the 90 kilodalton heat shock protein (HSP-90) might be under estrogenic regulation in human mammary tumors, we analyzed its relationship with estrogen and progesterone receptors. A positive relationship between estrogen receptor and HSP-90 was observed when these were normalized to HSP-70 levels (to normalize for the intrinsic variations in each tumor, independent of any hormonal dependence).