Estrogen receptor content in adenovirus type 9-induced rat mammary tumors

Hormonal factors play an important role in the induction of mammary tumors and tumor-like lesions in adenovirus type 9-inoculated W/Fu rats. Primary Ad 9-induced fibroadenomas contained significantly higher amounts of estrogen receptor (determined by means of enzyme immunoassay) in comparison to normal breast tissue (p = 0.01**) and 'spontaneous' fibroadenomas (p = 0.03*), used as control tissues. The receptor content of serially isografted virus-induced fibroadenomas did not differ significantly from the two types of control tissue. The findings suggest that changes in the estrogen receptor level are of importance in the tumor induction process, but also that additional factors are required for the preservation of tumor characteristics as well as for lipoma induction.