Estrogen inhibition of MPA-induced mouse mammary tumor transplants.

KORDON EC; LANARI C; MOLINOLO AA; ELIZALDE P; CHARREAU E; DOSNE DE PASQUALINI, CHRISTIANE

INTERNATIONAL JOURNAL OF CANCER. JOURNAL INTERNATIONAL DU CANCER.

JOHN WILEY & SONS INC

Año: 1991 p. 900 - 905

0020-7136

Estrogen compounds were used to treat mice bearing syngeneic transplants of medroxyprogesterone acetate(MPA)-induced BALB/c mammary adenocarcinomas. Both MPA-dependent and MPA-independent tumor lines were used. These lines expressed estrogen (ER) and progesterone receptors (PR). We demonstrate that different doses of estradiol benzoate (EB) and 17-beta-estradiol (E2) inhibit tumor growth and induce tumor regression in both MPA-independent and -dependent tumors, even in the presence of MPA or progesterone (P). EB was unable to induce regression of (ER-) hormone-independent tumor lines. A few MPA-dependent tumors became resistant to the estrogenic treatment; in subsequent passages some of these tumors retained their MPA-responsiveness, although estrogen sensitivity was not recovered.