[Experimental study of the treatment of uterine leiomyosarcoma in the mouse with progestogen]

Because of its rare occurrence in the human, the endocrinologic and receptor-related aspects of an uterine leiomyosarcoma (LMS) are poorly understood when compared to what is known of, say, human endometrial cancer. Thus, to increase our understanding, we have succeeded, by the string method, in inducing an uterine LMS in the mouse and have studied the possibility of hormonal therapy as a method of treatment. The findings of our study are enumerated as follows: 1. The induced uterine LMS had an estrogen receptor, which was confirmed by a biochemical assay and, morphologically, by a PAP (the peroxidase anti-peroxidase technique); 2. The growth of this tumor was significantly inhibited by MPA (medroxyprogesterone acetate) therapy (100 mg/kg); 3. After MPA therapy, the estrogen receptor levels were increased, especially in the nucleus; and, 4. The growth of a secondary tumor, transplanted after the initial hormone therapy, was not inhibited by the readministration of MPA. Our results suggest that this experimentally-induced uterine LMS in the mouse provides a useful means to study therapeutic treatment, and may assist in furthering our understanding of human uterine LMS and lead to finding an effective therapy.