Estradiol 16α -hydroxylation in the Mouse Correlates with Mammary Tumor Incidence and Presence of Murine Mammary Tumor Virus: A Possible Model for the Hormonal Etiology of Breast Cancer in Humans

In this report, we describe our findings on the relationship between estradiol 16α -hydroxylation and mammary tumor incidence. A close correlation between the two has been demonstrated with 16-hydroxylation being elevated in strains with a high incidence of tumors, such as RIII and C3H, and low in strains with a low incidence of cancer, such as C57BL. The extent of reaction is highly reproducible and unaffected by age or presence of overt mammary tumors. Studies on the inheritance of estradiol 16α -hydroxylase showed that it is inherited as an autosomal dominant and is not correlated with estradiol 2-hydroxylase or androgen and progestin 16α -hydroxylases. In addition, the reaction was shown to be markedly enhanced by the presence of murine mammary tumor virus and diminished in the absence of the virus. These studies establish a relationship between genetics, hormonal factors, and murine mammary tumor virus, the three key factors in mammary tumorigenesis.