[Influence of endocrine therapy on the proliferation of estrogen (ER) positive cells and ER negative cells of human breast cancer (MCF-7)].

The influence of endocrine therapy on the proliferation of estrogen receptor (ER) positive cells and ER negative cells of human breast cancer (MCF-7) serially transplanted into nude mice was analyzed by tumor growth, dextran-coated charcoal (DCC) method, ER-immunocytochemical assay (ER-ICA) and ER-immunocytochemically stained 3H-thymidine autoradiography. In the tamoxifen (TAM) group and the medroxyprogesterone acetate (MPA) group, tumor growth was inhibited, but it was promoted in the 17 beta-estradiol dipropionate (E2) group. The ER level by the DCC method significantly decreased in the TMA, the MPA and the E2 groups. The ER-ICA showed that the ER positive cells rate in the TAM and the MPA group decreased, but it increased in E2 group. However, the ER-immunocytochemically stained 3H-thymidine autoradiography showed that not only the labelling index of ER-positive cells but also that of ER negative cells significantly decreased in the TAM and the MPA groups, but significantly increased in the E2 groups. Therefore it was concluded that endocrine therapy affected the proliferation of both ER positive cells and ER negative cells of ER positive breast cancer.