Localization of estrogen receptors in interstitial cells of hamster kidney and in estradiol-induced renal tumors as evidence of the mesenchymal origin of this neoplasm.

The mechanism of estrogen-induced and -dependent kidney carcinogenesis in Syrian hamsters and the cell of origin of the tumor are not well understood; they have been investigated in this study by mapping the cellular locations of estrogen receptor (ER) in estrogen-dependent tumors, in kidney tissue of hamsters treated with estradiol for 0.5 and 5.5 months, and in kidneys of age-matched controls. To validate the methods used, receptors have also been localized in uteri of hamsters and rats and in female hamster kidneys. ERs have been identified in cryostat sections by immunocytochemical techniques using an affinity-purified ER antibody, ER-715. Nuclei of tumors were intensely stained for ERs. In estrogen-treated kidneys and in controls, ER protein was identified in interstitial cells and capillaries, in arteries, and in renal corpuscles, particularly in podocytes and in the parietal layers surrounding the renal corpuscles. There was no ER protein in tubular epithelia even when tubuli were surrounded by tumor cells. The ER distribution in female hamster kidneys closely matched that in male kidneys. However, the staining intensity was stronger in female than in male kidneys. In hamster uteri, there was an intense ER-positive reaction in the nuclei of stroma, in stromal vessels, and in the luminal epithelia as demonstrated previously by others in rat uteri. ER mRNA has also been demonstrated by Northern blot analysis in estrogen-treated kidneys which contained tumors but was undetectable in untreated kidneys. The localization of ERs in estrogen-dependent tumors and in interstitial cell types but not in tubular epithelia supports previous conclusions of an interstitial origin of estrogen-induced hamster kidney tumors.