MAMMARY-TUMORS INDUCED BY HUMAN ADENOVIRUS TYPE 9 - A ROLE FOR THE VIRAL EARLY REGION-4 GENE

Human adenovirus type 9 (Ad9) elicits exclusively estrogen-dependent m ammary tumors when injected into female rats. Three different histolog ical types of mammary tumor (benign fibroadenomas, phyllodes tumors, a nd malignant solid sarcomas) have been described in Ad9-infected anima ls, with benign fibroadenomas being seen most frequently. Interestingl y, in contrast to other adenoviruses, in which oncogenic viral functio ns are entirely encoded within the E1 region, Ad9 requires an E4 regio n transforming protein (ORF1) for its unique mammary oncogenicity. Stu dies of Ad9-induced rat mammary tumors may lead to a detailed molecula r understanding for the development of fibroadenoma, a common human br east tumor.