Experimental endocrinotherapy with tamoxifen of human ovarian dysgerminoma transplanted into nude mice.

The effect of Tamoxifen (TAM) on tumor growth was investigated experimentally using ovarian dysgerminoma serially transplanted into nude mice. The mice were divided into two groups according to estrogen receptor (ER) content of initially transplanted tumor; groups TAM-A and -B indicated ER rich and ER poor tumor, respectively. Their own control (CNT) was included in each group. After TAM treatment, the tumor size of TAM-A and -B groups was 150 fold and 350 fold that of initial tumor respectively, while that of group CNT was over 500 fold, suggesting that a strong anti-tumor effect of TAM was exerted especially on ER rich tumor. Histological changes following tamoxifen treatment such as a decline in the size of tumor cells and nuclei as well, and a decrease in the mitotic index were observed only in the TAM-A group. The concentration of ER and progesterone receptor (PR) in the cytosol of these tumors were measured. The ER levels in the initial tumor tissue of TAM-A and -B were 14.7 and 3.3 fmol/mg protein, respectively. The significant increase in PR content in TAM-A following TAM administration obviously indicated a so-called TAM-dependent PR induction effect. These results indicated that ovarian cancer containing ER, even though it originated from germ cells, would be responsible for antiestrogen therapy.