We have previously demonstrated that androgens are potent inhibitors of breast cancer cell proliferation under both basal and estrogen-induced incubation conditions, while they suppress expression of the estrogen and progesterone receptors. To better understand the mechanisms responsible for the antagonism between androgens and estrogens in breast cancer and to obtain a new tumor marker for the actions of these two steroids, we have investigated the effects of androgens and estrogens on expression of the major protein found in human breast gross cystic disease fluid, namely GCDFP-24. This study was performed in ZR-75-1 and MCF-7 human breast cancer cells. After a 9-day incubation period, physiological concentrations of 17 beta-estradiol stimulated proliferation of ZR-75-1 and MCF-7 cells by 2- to 3.5-fold while simultaneously exerting a marked 70-90% inhibition of GCDFP-24 secretion. The estrogenic effects on GCDFP-24 secretion and cell proliferation were both competitively blocked by simultaneous incubation with the new steroidal pure antiestrogen EM-139. On the other hand, a maximal concentration (10 nM) of the nonaromatizable androgen dihydrotestosterone decreased by 50% the proliferation of ZR-75-1 cells; the half-maximal inhibitory effect was exerted at 0.01 nM. The androgen exerted a 3- to 4-fold stimulatory effect on GCDFP-24 secretion at an EC50 value of 0.01 nM. The effect of dihydrotestosterone on these parameters was competitively blocked by simultaneous incubation with the pure antiandrogen OH-flutamide. The present data show that the effects of estrogens and androgens in ZR-75-1 cells on GCDFP-24 secretion and cell growth are opposite. Similarly, in MCF-7 cells, estrogens stimulate cell growth, while GCDFP-24 secretion is inhibited. The present data also suggest that GCDFP-24 could well be a good biochemical marker for monitoring the response to androgenic and antiestrogenic compounds in the therapy of advanced breast cancer.

Recent elucidation of the amino acid sequence of the progesterone-binding protein GCDFP-24, the major protein found in human breast gross cystic disease fluid, reveals that this glycoprotein corresponds to apolipoprotein-D (apo-D), a member of the alpha 2-microglobulin superfamily which binds small hydrophobic ligands. The present study describes the multiple hormonal control of apo-D mRNA levels, intracellular protein content, as well as secretion compared to cell proliferation in human ZR-75-1 breast cancer cells. In these cells, exposure to the synthetic glucocorticoid dexamethasone (DEX) markedly decreases basal as well as 17 beta-estradiol (E2)-induced cell proliferation while causing a maximal 10-fold stimulation of apo-D secretion in the presence or absence of E2. Incubation with 500 nM DEX or 10 nM dihydrotestosterone (DHT), alone and in combination, markedly increased apo-D mRNA/actin mRNA ratios by 16-, 22-, and 28-fold, respectively. Exposure to 1 nM E2 decreased the apo-D mRNA/actin mRNA ratio by 65%. In E2-treated cells, simultaneous exposure to DHT, DEX, and DHT plus DEX markedly increased the apo-D mRNA/actin mRNA ratios by 50-, 35-, and 105-fold, respectively. The stimulatory effect of DEX on intracellular apo-D content and secretion was also additive to that of the androgen DHT in the presence or absence of E2. The present study provides the first data describing the hormonal regulation of apo-D mRNA levels and intracellular protein content and demonstrates the effect of glucocorticoids alone as well as their interaction with androgens and estrogens on these parameters as well as on apo-D secretion. As shown in the present data, the effects of steroids on apo-D gene expression, intracellular apo-D protein content, and secretion are opposite their respective specific effects on cell proliferation in human ZR-75-1 breast cancer cells.

Human breast gross cystic disease is a common benign breast disease which occurs most frequently in the age range of 40-50 years, then becomes very infrequent after menopause.' It is characterized by production of a unique fluid secretion which accumulates in the breast cysts. Biochemical analysis of the fluid has been investigated over the past decade with regard to protein, steroid, and ionic composition?-9 Four major component proteins have been identified in breast gross cystic disease fluid and termed by their monomer molecular size as 44,24, and 15." The GCDFP-70 is immunologically identical to albumin; the GCDFP-44 is identical to Zn alpha,glycoprotein; the GCDFP-24 has a plasma analogue which remains uncharacterized, and the protein in breast cyst fluid has been shown to bind progesterone and pregnenolone?

A retrospective immunoperoxidase staining study for a glycoprotein isolated from human breast gross cystic disease fluid (GCDFP-15) in 562 primary breast carcinomas in 539 patients was conducted to correlate its immunohistochemistry with pathologic and clinical factors. Overall, 55% of the carcinomas studied stained positively for GCDFP-15. In certain histologic subtypes, the percentage of carcinomas that stained positively was greater: those subtypes with apocrine histologic features (75%), intraductal carcinoma (70%), and infiltrating lobular carcinoma with signet-ring cell differentiation (90%). In contrast, only 5% of medullary carcinomas exhibited positive staining. Only 23% of breast carcinomas without apocrine features stained positively for GCDFP-15. Carcinomas that stained positively were more likely to have involved axillary lymph nodes (P less than 0.054). The staining was independent of nuclear grade, mitotic index, tumor size, and estrogen receptor status. Positive staining was related to a history of gross cystic disease but not to age, parity, menopausal status, or age at first birth. A positive stain was not related to risk of recurrence or survival.