Growth regulatory peptide production by human breast carcinoma cells

Fibroblasts in the Tumor Microenvironment

The implications of a tumor microenvironment in cancer initiation and progression have drawn interest in recent years. Within the tumor stroma, fibroblasts represent a predominant cell type and are responsible for the majority of extracellular components within the tumor microenvironment, such as matrix and soluble factors. A switch from quiescent fibroblasts to cancer-associated fibroblasts triggers a large variety of pro-tumorigenic signals that support tumor progression and shape the surrounding pathological stroma, with the remodeling of tissue architecture and repression of the local immune response. The heterogeneous nature of cancer-associated fibroblasts and their multiple functions are subject of active research as they could represent promising targets for cutting-edge therapeutic approaches to cancer and the tumor microenvironment.

D-ring modified estrone derivatives as novel potent inhibitors of steroid sulfatase

A series of novel D-ring modified derivatives of estrone was synthesized and tested as inhibitors of steroid sulfatase (STS). The steroidal D-ring was cleaved via an iodoform reaction and thermal condensation of the resulting marrianolic acid derivative gave 16,17-seco-estra-1,3,5(10)-triene-16,17-imide derivatives, where a piperidinedione moiety is in place of the D-ring. This synthetic approach was found to give a higher overall yield than the literature method of Beckmann rearrangement. A range of alkyl side chains have been introduced on the nitrogen atom of the imido-ring and the corresponding 3-O-sulfamates synthesized. The new D-ring modified estrone derivatives bearing a propyl (39) and a 1-pyridin-3-ylmethyl (46) moiety had IC(50) values of 1 nM when tested in placental microsomes for the inhibition of STS. These compounds are therefore up to 18-fold more potent than EMATE, the very first highly potent irreversible steroidal STS inhibitor.

Estrone 3-sulfate mimics, inhibitors of estrone sulfatase activity: homology model construction and docking studies

Steroid sulfatase (STS) is a new target for the endocrine therapy of breast cancer. To ascertain some of the requirements for inhibition of estrone sulfatase activity, a number of novel analogues of estrone 3-O-sulfate possessing sulfate surrogates were synthesized and evaluated as inhibitors of estrone sulfatase (STS) in comparison to a lead inhibitor, estrone-3-O-methylthiophosphonate (E1-3-MTP). Using a selective enzyme digestion, one of the diastereoisomers of this compound, (R(p))-E1-3-MTP, could be prepared and evaluated. From structure-activity studies, we show that chirality at the phosphorus atom, hydrophobicity, basicity, size, and charge all influence the ability of a compound to inhibit estrone sulfatase activity. Of these, hydrophobicity seems to be the most important since simple, active nonsteroidal inhibitors, based on 5,6,7,8-tetrahydronaphth-2-ol (THN), can be prepared, provided that they are lipophilic enough to partition into a nonpolar environment. Also, a negatively charged group is favorable for optimal binding, although it appears that the presence of a potentially cleavable group can compensate for lack of charge in certain cases. A homology model of STS has been constructed from the STS sequence, and molecular docking studies of inhibitors have been performed to broaden the understanding of enzyme/inhibitor interactions. This model clearly shows the positions of the key amino acid residues His136, His290, Lys134, and Lys368 in the putative catalytic region of the formylglycine at position 75, with residues Asp35, Asp36, Asp342, and Gln343 as ligands in the coordination sphere of the magnesium ion. Docking studies using the substrate and estrone-3-sulfate mimics that are active inhibitors indicate they are positioned in the area of proposed catalysis, confirming the predictive power of the model.

Synergistic proliferative action of insulin-like growth factor I and 17 beta-estradiol in MCF-7S breast tumor cells

We have analyzed the mechanism by which the combination of insulin-like growth factor I (IGF-I) and 17 beta-estradiol (E2) induces cell cycle progression in MCF-7S cells. This cell line differs from many other breast cancer-derived cell lines in that E2 (1 nM) does not induce cell cycle progression, whereas the combination of submitogenic concentrations of IGF-I (2 ng/ml) and E2 does. We find that addition of IGF-I to MCF-7S cells leads to a dose-dependent activation of the IGF type I receptor and of the MAP kinase and PI3-kinase signaling pathways. No synergy of IGF-I and E2 was detected in the activation of these signaling cascades. In terms of cell cycle-related molecules, we find that IGF-I dose-dependently raises cyclin D1 levels in serum-starved cells. Subsequent activation of cyclin E/CDK2, hyperphosphorylation of pRb, and DNA synthesis are only induced by mitogenic concentrations of IGF-I (> or =20 ng/ml). Treatment of the cells with E2 also results in the induction of cyclin D1, but in the absence of IGF-I the cells remain arrested in G1 phase. We conclude that in MCF-7S cells, the synergistic action of E2 and IGF-I derives from the ability of both hormones to induce cyclin D1 expression. The action of IGF-I is required in these cells to induce activity of the cyclin D1/CDK4 complex, which triggers progression through the cell cycle.

Effect of resveratrol on the expression of autocrine growth modulators in human breast cancer cells

The effect of resveratrol on the growth of human breast cancer cells was examined. Resveratrol inhibited the growth of estrogen receptor-positive MCF-7 cells cultivated in the presence of estradiol in a dose-dependent fashion. At 10(-5) M, resveratrol maximally inhibited the growth stimulatory effect mediated by 10(-9) M estradiol without affecting cell viability. At the molecular level, resveratrol in a dose-dependent fashion antagonized the stimulation by estradiol of an estrogen response element reporter gene construct and of progesterone receptor gene expression in MCF-7 cells. Resveratrol also inhibited the proliferation of the estrogen-receptor negative human breast carcinoma cell line MDA-MB-468. These later data suggest that resveratrol can also inhibit breast cancer cell proliferation by another mechanism besides estrogen receptor antagonism. We show here that resveratrol altered the expression of several autocrine growth modulators and their receptors in MCF-7 cells. Resveratrol at 10(-5) M inhibited the expression of the autocrine growth stimulators transforming growth factor-alpha (TGF-alpha), PC cell-derived growth factor, and insulin-like growth factor I receptor mRNA. In addition, resveratrol significantly elevated the expression of the growth inhibitor TGF-beta2 mRNA without changes in TGF-beta1 and TGF-beta3 expression. These data suggest that resveratrol inhibits proliferation by altering autocrine growth modulator pathways in breast cancer cells.

Resveratrol, a natural product derived from grape, exhibits antiestrogenic activity and inhibits the growth of human breast cancer cells

Resveratrol is a natural phytoalexin compound found in grapes and other food products. In this study, the effect of resveratrol on the growth of human breast cancer cells was examined. Results show that resveratrol inhibits the growth of estrogen receptor(ER)-positive MCF-7 cells in a dose-dependent fashion. Detailed studies with MCF-7 cells demonstrate that resveratrol antagonized the growth-promoting effect of 17-beta-estradiol (E2) in a dose-dependent fashion at both the cellular (cell growth) and the molecular (gene activation) levels. At 5 x 10(-6) M, resveratrol abolished the growth-stimulatory effect mediated by concentrations of E2 up to 10(-9) M. The antiestrogenic effect of resveratrol could be observed at a concentration of 10(-6) M and above. The antiestrogenic effect of resveratrol was also demonstrated at the molecular level. Resveratrol in a dose-dependent fashion antagonized the stimulation by E2 of progesterone receptor gene expression in MCF-7 cells. Moreover, expression of transforming growth factor-alpha and insulin-like growth factor I receptor mRNA was inhibited while the expression of transforming growth factor beta2 mRNA was significantly elevated in MCF-7 cells cultivated in the presence of resveratrol (10(-5) M). In summary, our results show that resveratrol, a partial ER agonist itself, acts as an ER antagonist in the presence of estrogen leading to inhibition of human breast cancer cells.

Androgens influence estrogen-induced responses in human breast carcinoma cells through cytochrome P450 aromatase

The aromatase cytochrome P450 complex is responsible for the in vivo conversion of androgens to estrogens. Although breast cancer epithelial cells have been reported to have appreciable aromatase activity, its biologic significance remains uncertain. To address this, the effect of androgens on the expression of the estrogen-regulated gene pS2 in hormone-dependent human breast carcinoma cells in vitro was examined. Steroid-deprived MCF-7 cells were exposed to varying concentrations (1 nM, 10 nM, and 100 nM of androstenedione or testosterone for 2,4, and 6 days. Baseline aromatase activity was 4.9 (+/-3.1) fmol 3H2O/hour/microgram DNA [34.3 (+/-21.3) fmol/hr/10(6) cells] and was not influenced by the androgens. As an indication of estrogen biosynthesis, northern analysis was performed to quantitate pS2 mRNA expression. Although no significant pS2 induction was observed at 2 days, both 4 and 6 day exposure to 100 nM testosterone resulted in a 3-fold increase in pS2 mRNA expression. 5 alpha-dihydrotestosterone (5 alpha-DHT) failed to elicit a similar pS2 response. This testosterone-induced response was inhibited with the aromatase inhibitor 7 alpha (4'-amino) phenylthio-1,4-androstadiene-3,17-dione (7 alpha-APTADD) and with 10 microM tamoxifen. MCF-7 breast cancer cells possess endogenous aromatase activity at high enough levels to convert androgens to estrogens and elicit an estrogen-induced response. The expression of aromatase may offer a potential advantage to hormone-responsive cells, providing an additional autocrine growth pathway which may be exploited.

Estrone sulfonates as inhibitors of estrone sulfatase

In our continuing quest to design efficient inhibitors of estrone sulfatase activity and to assess the recognition of estrone sulfate surrogates by estrone sulfatase, we synthesized and evaluated several sulfonate derivatives of 5,6,7,8-tetrahydronaphth-2-ol and estrone. 5,6,7,8-Tetrahydronaphth-2-methanesulfonate (11), and 5,6,7,8-tetrahydronaphth-2-(p-toluene)sulfonate (12) were found not to inhibit estrone sulfatase activity; estrone-3-methane-sulfonate (5), estrone-3-ethanesulfonate (6), estrone-3-butanesulfonate (7), and estrone-3-[(+)10-camphor]sulfonate (8) all weakly inhibited estrone sulfatase, and the best inhibitor, from this class of compounds, was estrone-3-(p-toluene)sulfonate (9). At 10 microM, it inhibited estrone sulfatase activity by 91%. These results emphasize some of the requirements needed for high-affinity binding to the enzyme.

Short-term effects of pure anti-oestrogen ICI 182780 treatment on oestrogen receptor, epidermal growth factor receptor and transforming growth factor-alpha protein expression in human breast cancer

Expression of oestrogen receptor (ER), epidermal growth factor receptor (EGFR) and transforming growth factor-alpha (TGF alpha) proteins was assessed by immunocytochemistry on primary breast cancer specimens obtained before and following short-term (7-day) presurgical exposure to pure anti-oestrogen (7 alpha- [9- (4,4,5,5,5-pentafluoropentylsulphinyl) nonyl] estra-1,3,5, (10)-triene-3,17 beta-diol, ICI 182780) treatment and compared with no-treatment controls. Paired needle-core and mastectomy samples were obtained from 21 patients. Effects of ICI 182780 (10(-7)M) on MCF7 breast cancer cell ER, EGFR and TGF alpha expression were also examined over 14 days. ER protein was significantly suppressed by ICI 182780 in vivo (P = 0.009) and comparative analysis of short term ICI 182780 effects in vitro, using ER-positive MCF7 cells, gave largely equivalent results. EGFR and TGF alpha protein levels were unaltered by treatment. ICI 182780 suppresses ER without a concomitant rise in either EGFR or TGF alpha.

Effects of dexamethasone on the expression of transforming growth factor-beta in mouse embryonic palatal mesenchymal cells

The central role of TGF-beta in the development of the embryonic palate has been well characterized. TGF-beta inhibits mesenchymal cell proliferation, induces medial edge epithelial cell differentiation, and modulates the expression of extracellular matrix proteins as well as the proteases that act upon them. Mechanisms by which TGF-beta expression itself is regulated are less well understood. Glucocorticoids are recognized in several cellular systems as able to regulate the expression of TGF-beta. This study was therefore designed to examine whether glucocorticoids affect the expression of TGF-beta isoforms in embryonic palatal cells. Based on flow cytometric analysis and viability determination, confluent primary cultures of mouse embryonic palate mesenchymal (MEPM) cells exposed to up to 10(-6) M dexamethasone (dex) exhibited no signs of cytotoxicity after 24 hours of exposure. Northern blot analyses revealed that dexamethasone reduced steady-state mRNA levels of TGF-beta 3 in a dose-dependent manner as early as 4 hours after treatment but had little effect on TGF-beta 1 and TGF-beta 2 expression up to 24 hours of dex exposure. Dex also reduced the synthesis of both latent and mature forms of TGF-beta protein by approximately four-fold as determined by the mink lung epithelial cell growth inhibition bioassay. Assessment of the ratio of mature to latent protein found in conditioned medium of control compared to dex-treated cultures indicated that dexamethasone may reduce the activation of latent TGF-beta to mature biologically active TGF-beta. Dexamethasone inhibited the proliferation of MEPM cells despite the down-regulation of TGF-beta suggesting that dex-induced growth inhibition of MEPM cells is not mediated by TGF-beta. These data suggest that dex modulates TGF-beta signaling pathways directly by down-regulating TGF-beta expression and possibly indirectly by altering the availability of mature TGF-beta necessary to exert its biological effects in the developing palate.

Heteroatom-substituted analogues of the active-site directed inhibitor estra-1,3,5(10)-trien-17-one-3-sulphamate inhibit estrone sulphatase by a different mechanism

Estrogens have a pivotal role in the growth and development of hormone-dependent breast cancers. In postmenopausal women, the hydrolysis of the conjugate estrone sulphate (E1S) to estrone (E1) by the enzyme estrone sulphatase is the major source of breast tumour estrogen. Inhibitors of estrone sulphatase should therefore have considerable therapeutic potential for the treatment of hormone-dependent tumours of the breast, either as the sole agent or in conjunction with aromatase inhibitors. Several inhibitors of estrone sulphatase have now been developed of which estra-1,3,5(10)-trien-17-one-3-sulphamate (EMATE) is the most potent and also inhibits the enzyme in a time- and concentration-dependent manner, showing that it acts as an irreversible inhibitor. Analogues of EMATE in which the 3-O-atom is replaced by other heteroatoms (S and N) were synthesized and tested for inhibition against estrone sulphatase. 4-Methoxyphenylsulphamide (1), 4-chlorothiophenyl-S-(N,N-dimethyl)sulphamate (2), estra-1,3,5(10)-trien-17-one-3-sulphamide (3), estra-1,3,5(10)-trien-17-one-3-S-sulphamate (4) and estra-1,3,5(10)-trien-17-one-3-S-(N,N-dimethyl)sulphamate (5) were found to inhibit estrone sulphatase weakly, but none of these compounds appears to behave as a time-dependent inhibitor. A model of the mechanism of enzyme inhibition by EMATE is proposed and we conclude that the sulphamate bridging oxygen atom of EMATE is essential for active site-directed inhibition of estrone sulphatase.

Antiproliferative and recovery effects during treatment of breast and ovarian carcinoma cell cultures with interferon-gamma

We studied the antiproliferative effects of human interferon-gamma (IFN-gamma) on cell lines derived from human carcinomas (three breast, two ovarian, and one renal) and recovery from these effects when IFN-gamma was removed after 6 or 72 h. IFN-gamma led to a dose-dependent and time-dependent cytostatic inhibition of all six tumor cell lines; the renal carcinoma cells were by far the most sensitive, and with these, cytotoxic effects were also seen. The 50% inhibitory dose (ID50) for each cell line was different and remarkably constant over many months. When cells were exposed to IFN-gamma for only 9 or 72 h, those from three lines recovered completely from the growth inhibitory effects, but from three only partially. When cultured for several weeks in the presence of 1600 U/ml of IFN-gamma, two lines developed increased resistance to IFN-gamma, one became much less sensitive, and two showed no changes in sensitivity. We saw no correlations between these changes during continuous exposure to IFN-gamma and the antiproliferative ID50 for each cell or whether the cells recovered completely from the inhibitory effects of IFN-gamma after short-term exposure. Nevertheless, cells with a population doubling time of less than 48 h had low to moderate sensitivity to IFN-gamma and seemed to recover more completely than those doubling in more than 61 h. Our results indicate great individual variation in the in vitro sensitivity of carcinoma cells to the antiproliferative effects of IFN-gamma.

Antiproliferative actions of insulin-like growth factor binding protein (IGFBP)-3 in human breast cancer cells

A number of lines of evidence suggest that IGFs are important mitogens in human breast cancer: (1) IGFs are the most potent growth factor in human breast cancer cells; (2) estrogen stimulates expression of IGF-II and the type 1 IGF receptor; and (3) stromal cells express IGFs, which may act in a paracrine manner. Numerous studies have demonstrated that IGFBPs modulate the mitogenic effects of IGFs in the local environment. In particular, we have recently demonstrated that IGFBP-3 inhibits the growth of Hs578T and MDA-MB-231 human breast cancer cells in an IGF-independent manner. Further studies revealed the existence of cell surface-associated IGFBP-3 receptors. Receptor binding and the subsequent antiproliferative action of IGFBP-3 was inhibited by IGFs, owing to the formation of an IGF-IGFBP-3 complex that prevents the binding of IGFBP-3 to its receptors. In addition, exogeneously added soluble heparin or heparan sulfate inhibited the binding of IGFBP-3 to the cell surface in a dose-dependent manner. However, when heparin and heparan sulfate linkages of glycosaminoglycans on the cell surface were enzymatically remove, IGFBP-3 binding was only minimally affected. These data suggest that soluble heparin or heparan sulfate forms a complex with IGFBP-3, thereby inhibiting receptor binding of IGFBP-3, rather than competing with cell-surface glycosaminoglycans for binding of IGFBP-3. Additionally, the role of IGFBP-3 in the antiproliferative effects of transforming growth factor (TGF)-beta and retinoic acid (RA) is supported by our observations that: (1) inhibition of IGFBP-3 gene expression using an IGFNBP-3 antisense oligodeoxynucleotide not only blocks TGF-beta and RA simulation of IGFBP-3 production by up to 90%m but also inhibits their antiproliferative effects by 40-60%; and (2) treatment with IGF-II and IGF-II analogs diminish TGF-beta effects by blocking TGF-beta induced binding of IGFBP-3 to the cell surface. Taken together, our results support the hypothesis that IGFBP-3 is an important antiproliferative factor in human breast cancer, acting in an IGF-independent manner in addition to its ability to modulate the binding of IGF peptides to IGF receptors.

Absence of transforming growth factor-beta responsiveness in the tamoxifen growth-inhibited human breast cancer cell line CAMA-1

Tamoxifen has been an effective antiestrogen in suppressing breast cancer growth which is estrogen-responsive or dependent. Early studies have provided circumstantial evidence that transforming growth factor-beta (TGF-beta) may be an autocrine mediator of tamoxifen action. Therefore, it is both fundamentally important and clinically relevant to investigate the relationship between tamoxifen and TGF-beta. In this study, we demonstrated that CAMA-1 cells, which are sensitive to tamoxifen inhibition, did not respond to TGF-beta growth inhibition. The type I and II TGF-beta receptors were undetectable by the radio-ligand affinity labeling technique. Despite the presence of a normal TGF-beta type II receptor gene, the mRNA transcript of the gene was undetectable by the extremely sensitive Intron-differential RNA/PCR method. The possibility that the lack of TGF-beta receptors might be intimately linked to the absence of normal retinoblastoma (Rb) gene products, as suggested by previous studies of retinoblastoma cells, was further investigated. The lack of TGF-beta receptor expression was found due to reasons other than the absence, deletion or abnormality of the Rb gene because a normal Rb gene and its hyper- and hypo-phosphorylated protein products were detected in CAMA-1 cells. In conclusion, our results suggest that the TGF-beta system is not obligatory for antiestrogen growth inhibition of CAMA-1 cells.

Effect of two-4-hydroxyandrostenedione doses on serum insulin-like growth factor I levels in advanced breast cancer

A number of endocrine treatments for advanced breast cancer seem to affect serum insulin-like growth factor I (IGF-I). The aim of our study was to investigate IGF-I levels in 33 postmenopausal patients with metastatic disease receiving the selective aromatase inhibitor 4-hydroxyandrostenedione: 250 mg (16 patients) or 500 mg (17 patients) i.m. fortnightly. Blood samples were collected before, and at one month and 3 months after the beginning of treatment for radioimmunoassay determinations. The median patient age was 56 and 60 years in the 250 and 500 mg groups respectively. Most patients had a disease free interval > or = 2 years and were oestrogen receptor positive. Objective responses were obtained in 3 patients (complete response, 1) in the 250 mg group, and in 7 patients (complete response, 3) in the 500 mg group. No significant IGF-I variations were seen in the 250 mg group, whereas a significant increase after 3 months (181.57 +/- 84.78 ng/ml versus 272.47 +/- 213.22 ng/ml, p = 0.0032) was observed in the 500 mg group. No IGF-I variations were seen between responsive and unresponsive patients in either treatment group. Our results in the 500 mg group are close to those obtained with aminoglutethimide and seem to agree with the hypothesis of an oestrogen-induced suppression of IGF-I circulating levels.

Does early physical maturity influence breast cancer risk?

Earlier onset of menarche and tallness in adult women are mainly confirmed as risk markers for breast cancer. Recent disparate case-control studies have reported abdominal-type obesity and higher circulating levels of insulin, testosterone and insulin-like growth factor 1, to be further risk markers for breast cancer. There is evidence that abdominal-type obesity is recognisable in girls even before puberty, and disparate studies have shown it to be correlated with earlier onset of menarche, insulin resistance leading to hyperinsulinaemia, and an abnormal sex steroid profile. The implications are that earlier onset of puberty in a subset of girls can lead to more prolonged exposure of developing breast tissue to an abnormal sex steroid profile and also to a higher circulating level of insulin. It is postulated that these metabolic/endocrine concomitants of abdominal-type obesity could play a role in promoting mammary carcinogenesis at a young age, particularly if genetic predisposition is present.

Catecholestrogens are MCF-7 cell estrogen receptor agonists

Catecholestrogens are important metabolites of estradiol and estrone in the human. Considerable interest has focused on the catecholestrogens 2-hydroxy- and 4-hydroxyestradiol since they bind to the estrogen receptor with an affinity in the range of estradiol. Using the MCF-7 cell line, we analysed the capacity of purified catecholestrogens to transform the estrogen receptor into its high affinity nuclear binding form and to affect receptor-dependent processes such as proliferation and expression of the progesterone receptor (PR). Incubations with 2-hydroxy- and 4-hydroxyestradiol at 10(-8) M for 1 h resulted in tight nuclear binding of the estrogen receptor. During treatment of the cells with catecholestrogens we obtained a marked increase in proliferation rate of 36 and 76% for 2-hydroxy- and 4-hydroxyestradiol, respectively, relative to the inductive effect of estradiol (100%). The PR level, was slightly increased by treatment with 2-hydroxyestradiol (10%), whereas treatment with 4-hydroxyestradiol increased the PR level at 28%, compared to estradiol (100%). From these results we conclude that the 2- and 4-hydroxylated derivatives of estradiol are active hormones and are able to initiate estrogen receptor mediated processes in MCF-7 cells.

Identification of multiple proliferative growth factors in breast cyst fluid

Gross cystic disease is a common benign breast disease that is associated with a twofold to fourfold increase in breast cancer risk. Both diseases are hormonally induced and may share a common biochemical environment conducive to abnormal proliferative responses. A large collection of breast cyst fluid samples was analyzed for growth factors associated with cell proliferation: epidermal growth factor (EGF), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), platelet-derived growth factor (PDGF), transforming growth factor-alpha (TGF-alpha), and transforming growth factor-beta (TGF-beta). The data demonstrate that significant amounts of proliferative growth factors are present in breast cyst fluid of all cyst subtypes. The presence of IGF-II, PDGF, and TGF-beta in breast cyst fluid was confirmed for the first time. EGF, PDGF, and TGF-beta concentrations in breast cyst fluid were several times greater than reported for serum; IGF-I and IGF-II concentrations were several times lower. In the first 100 samples tested, no TGF-alpha was detected. Only EGF and IGF-II levels demonstrated a consistent correlation with apocrine type 1 cysts. These results demonstrated that effective concentrations of proliferative growth factors are in breast cyst fluid and suggest that adjacent breast tissue may be a probable source of synthesis. Growth factor profiles of breast cyst fluid may indicate the presence in breast tissue of a hormonal and proliferative environment permissive to subsequent cancer growth.

TGF alpha and TGF beta expression in mammary carcinoma

TGF alpha and beta expression was examined using rabbit polyclonal antibodies and immunohistochemistry on a series of 195 breast carcinomas. TGF alpha immunoreactivity was observed in all but nine of the tumours, with over 50 per cent staining strongly. The polyclonal TGF alpha antibody (CIM1), when compared with a commercially available mouse monoclonal TGF alpha antibody used on the same sections, gave a good correlation (r = 0.52, P < 0.001). Both TGF alpha antibodies produced a granular cytoplasmic staining pattern, that with CIM1 being coarser, suggestive of binding to an aggregated protein or organelle. Eighty-one per cent of tumours stained with the TGF beta antibody, 35 per cent strongly. There was significant co-expression of TGF alpha and TGF beta (P < 0.001). However, they were not found to be useful prognostic indicators, lacking any significant correlation with histological classification, tumour size, nodal status, oestrogen receptor status, S-phase fraction, or overall survival over a 9-12 year period. The expression of these growth factors in most breast carcinomas suggests that they have important biological roles, but the exact nature of these roles remains unclear at the moment.

Expression of epidermal growth factor receptor (proto-oncogene c-erbB-1) and estrogen receptor in human breast carcinoma. An immunocytochemical study of 70 cases

In vitro studies have shown that growth factors may mediate the growth stimulatory effect of estrogen in hormone-dependent human breast carcinomas while the constitutive expression of same growth factors might by-pass the need for estrogenic stimulus in hormone-independent neoplasms. We have performed immunocytochemical analysis of the expression of epidermal growth factor receptor (EGF-R or proto-oncogen c-erbB-1) and estrogen receptor (ER) in 70 cases of human breast carcinoma. We found an inverse relationship between the expression of EGF-R and ER (Kendall's tau b = -0.1997, P < 0.03), which prompts us to conclude that ER(-) breast carcinomas may grow in a hormone-independent manner through the over-expression of the proto-oncogene c-erbB-1, which is the receptor for epidermal (EGF) and alpha transforming (TGFalfa) growth factors.

Epidermal growth factor, insulin-like growth factor-1 and basic fibroblast growth factor modulate the cytostatic effect of tumour necrosis factor-alpha on the breast cancer cell line, T47D

The effect of epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and insulin-like growth factor-1 (IGF-1) on the cytostatic activity of tumour necrosis factor-alpha (TNF-alpha) was studied on the breast cancer cell line, T47D. TNF-alpha completely blocked the potent growth-promoting activity of all three factors on T47D cells. EGF, bFGF and IGF-1 partially antagonized the inhibition of cell growth and thymidine incorporation induced by TNF-alpha. These data suggest that the growth of these breast cancer cells is regulated, in part, by the antagonistic interaction between the cytostatic effect of TNF-alpha and the growth-promoting activity of factors such as EGF, IGF-1 and bFGF.

Isolation and characterization of an oestrogen-responsive breast-cancer cell line, EFF-3

A novel oestrogen-responsive breast-tumour cell line, EFF-3, has been established from a pleural exudate of a patient with metastatic breast cancer. The cells show morphological and immunohistochemical features consistent with their origin from a metastatic breast carcinoma. The cells aggregate and form sheets in culture, and electron microscopy confirms the presence of cell-surface microvilli and intercellular tight junctions. The epithelial origin of EFF-3 cells was confirmed by their expression of low-molecular-weight cytokeratins and carcinoembryonic antigen. The karyotype of the cells is markedly abnormal and there are large numbers of structurally abnormal chromosomes. EFF-3 cells express oestrogen receptor, oestrogen-receptor mRNA, their growth is oestrogen-responsive, and specific genes are regulated by oestrogens. The pNR-2/pS2 and pNR-25 oestrogen-regulated mRNAs are induced 15- and 13-fold respectively by oestrogen, whereas the oestrogen-receptor and cathepsin D mRNAs are not regulated. This pattern of regulation differs from that reported previously for other cell lines. The EFF-3 cell line should be useful for studying the mechanisms involved in oestrogen-stimulated proliferation and the factors determining the regulation of specific genes by oestrogens.

William L. McGuire Memorial Symposium. Control of breast cancer cell growth by steroids and growth factors: interactions and mechanisms

Over the past two decades, the simple model for control of breast cancer growth involving one or two factors acting directly or indirectly via endocrine pathways has turned into a complex model implicating numerous interacting factors and the diverse cell populations constituting breast tumors. Current approaches to breast cancer therapy now require integration of these multiple parameters and enhanced understanding of the different levels of their intricate interactions.

Antiestrogen-liganded estrogen receptor interaction with estrogen responsive element DNA in vitro

The mechanism whereby antiestrogens alter the ability of the estrogen receptor (ER) to enhance transcription of estrogen-regulated genes is largely unknown. The effect that selected estrogenic and antiestrogenic ligands have on binding of ER to specific DNA sequences, estrogen responsive elements (EREs) has been quantitated. No differences in purification properties of calf uterine ER liganded with 4-hydroxytamoxifen (4-OHT-ER), ICI 164,384 (ICI 164,384-ER) or estradiol (E2-ER) were detected. A microtiter well plate assay was employed in which liganded ER bound to plasmid DNA is preferentially retained compared to free liganded ER. Binding of E2-ER, 4-OHT-ER, or ICI 164,384-ER was measured to plasmids containing or lacking a 38bp consensus ERE in vitro. The EREs tested contain an inverted repeat (5'-CAGGTCAGAGTGACCTG-3'). Both E2-ER and 4-OHT-ER showed similar high affinity specific binding (Kd = 0.24 and 0.16 nM, respectively) to one copy of the ERE. ICI 164,384-ER did not bind to plasmids containing one ERE. At saturation, however, 4-OHT-ER binding was about 50% of that observed for E2-ER. When the plasmid contained 3 or 4 tandem copies of the ERE, binding of E2-ER, 4-OHT-ER, and ICI 164,384-ER binding was measurable. E2-ER bound in a cooperative manner as suggested by convex Scatchard plots and Hill coefficients > 1.5. In contrast, 4-OHT-ER binding displayed much reduced cooperativity, and ICI 164,384-ER did not display cooperative binding. From these results, we propose that the conformation of ER induced by 4-OHT reduces its binding capacity to this consensus ERE without altering its affinity of binding. Furthermore, higher order protein-protein interactions between antiestrogen-liganded ER bound to DNA differ from those of E2-ER bound to ERE.

Modulation of the proliferative response of breast cancer cells to growth factors by oestrogen

A number of growth factors have been implicated in the control of the proliferation of breast cancer cells and some have been reported to mediate the proliferative effects of oestradiol. MCF-7 cells were treated with growth factors in the presence and absence of oestradiol. Oestradiol increased the response of cells to the proliferative effects of epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha) and basic fibroblast growth factor (bFGF). Platelet derived growth factor (PDGF) and cathepsin D had no effect in the presence or absence of oestradiol while TGF-beta slightly reduced the stimulation by oestradiol. In the absence of oestradiol, there was little effect of combinations of growth factors although the effects of bFGF and IGF-I were additive. In the presence of oestradiol, the effects of bFGF and TGF-alpha were additive whereas bFGF acted as an IGF-I antagonist. Overall, bFGF had the greatest effect on cell proliferation although this was less marked than the previously described effect of the IGFs and insulin. The effects of oestradiol on the sensitivity of cells to the proliferative effects of bFGF did not appear to result from regulation of bFGF receptor expression.

The effect of endocrine therapy with medroxyprogesterone acetate, 4-hydroxyandrostenedione or tamoxifen on plasma concentrations of insulin-like growth factor (IGF)-I, IGF-II and IGFBP-1 in women with advanced breast cancer

Tamoxifen treatment of women with advanced breast cancer has previously been reported to reduce plasma insulin-like growth factor-type I (IGF-I) concentrations. In this study we have examined the effect of treatment with Tamoxifen, medroxyprogesterone acetate (MPA) or 4-hydroxyandrostenedione (4-OHA) on plasma IGF-I and IGF-II concentrations. As IGF-binding proteins (IGFBPs) can modulate the biological effects of IGF-I, plasma IGFBP-I levels were also measured. Treatment with Tamoxifen for 2 weeks resulted in a small, but significant, decrease in IGF-I levels, but increase in the plasma concentration of IGFBP-I. In contrast, treatment with MPA increased levels of IGF-I, but significantly reduced plasma IGFBP-I concentrations. Treatment with 4-OHA had no significant overall effect on plasma IGF-I or IGFBP-I levels, although changes were detected for some subjects. Plasma IGF-II concentrations were not altered by treatment with Tamoxifen, MPA or 4-OHA. It is concluded that although treatment with Tamoxifen or MPA produced significant changes in plasma IGF-I concentrations, any physiological effects of such changes are likely to be modulated by the corresponding alterations in plasma IGFBP-I concentrations.

Identification, paracrine generation, and possible function of human breast carcinoma myofibroblasts in culture

Myofibroblasts from human breast carcinomas were identified and experimentally generated in culture, and a possible function was examined. The frequency of alpha-smooth muscle actin immunoreactive cells was evaluated as a measure of myofibroblast differentiation in primary culture. Few or no alpha-smooth muscle actin-positive stromal cells (6.1 +/- 8.4%) were identified in primary cultures from normal breast tissue (n = 9). In contrast, high frequencies (68.8 +/- 15.1%) were observed in primary cultures from carcinomas (n = 19). The frequencies of myofibroblasts in primary cultures were almost identical to those obtained in the corresponding cryostat sections (69.1 vs. 68.8%). A possible precursor cell to the myofibroblast was looked for among typical fibroblasts and vascular smooth muscle cells. Purified blood vessels containing both fibroblasts and vascular smooth muscle cells were embedded in collagen gel and incubated with medium conditioned by breast epithelial cells. Fibroblasts rather than smooth muscle cells were recruited from the blood vessels. In medium conditioned by carcinoma cell lines or in co-cultures of carcinoma cell lines and purified fibroblasts, alpha-smooth muscle actin and the typical myofibroblast phenotype were induced in otherwise alpha-smooth muscle actin-negative fibroblasts. The effect of myofibroblasts on cellular movement--essential to neoplastic cells--was analyzed. Spontaneous motility of tumor cells (MCF-7) was entirely suppressed in a collagen gel assay. Under these conditions tumor cell motility was selectively mediated by direct cell-to-cell interaction between tumor cells and myofibroblasts. Under chemically defined conditions, interaction was dependent on the presence of plasminogen. Anti-plasminogen, soybean trypsin inhibitor, and anti-fibronectin partly neutralized the effect of plasminogen. It is concluded that elements of myofibroblast differentiation and function may be studied in culture.

The gene expressions of macrophage colony-stimulating factor (MCSF) and MCSF receptor in the human myometrium during pregnancy: regulation by sex steroid hormones

We investigated the biological effect of sex-steroid hormones, secreted from the corpus luteum and placenta, on the induction of mRNA encoding macrophage colony-stimulating factor (MCSF) and c-fms proto-oncogene (MCSF receptor) in the human uterine myometrium. Poly(A)+RNA was extracted from the myometrium of pregnant and non-pregnant uterine myometrium and then Northern blot analysis was performed on poly(A)+RNA. The myometrium of non-pregnant women expressed neither mRNA of macrophage colony-stimulating factor (MCSF) nor any transcript related to the c-fms proto-oncogene. On the other hand the myometrium of pregnant women expressed MCSF mRNA (4.7 kb) and two kinds of transcript related to the c-fms proto-oncogene (3.9 and 1.3 kb). The mRNAs of both MCSF and c-fms proto-oncogene were induced in the uterine myometrium of non-pregnant women under pseudopregnant therapy of mestranol and norethindrone. These results indicate that sex steroid hormone secreted from the corpus luteum of pregnancy and/or placenta may be deeply involved in the hypertrophic change of uterus during pregnancy by inducing MCSF and MCSF receptor (c-fms proto-oncogene protein product) in the myometrium.

Inhibition of T47D human breast cancer cell growth by the synthetic progestin R5020: effects of serum, estradiol, insulin, and EGF

The mechanism of the antiproliferative effects of progestins on human breast cancer cells is not known. In view of the ability of estrogen to stimulate human breast cancer cell production of peptide growth factors, and since previous studies have suggested that the inhibitory action of progestins is dependent on estrogen-stimulated growth, the present study examined the interaction of growth factors and the synthetic progestin R5020 on the proliferation of T47D human breast cancer cells. In this study, the concentrations of estradiol, insulin, and EGF for optimal stimulation of T47D cell growth in 3% dextran-charcoal treated fetal bovine serum (DCC-FBS) were determined to be 1 nM, 100 nM, and 1 nM, respectively. Furthermore, incubation with these optimal concentrations of estradiol, insulin, and EGF in various combinations produced additive effects on T47D cell proliferation, suggesting that these agents act, at least in part, by different mechanisms. In contrast, in a chemically defined medium (DM), both estradiol and EGF were unable to stimulate T47D cell proliferation. In the case of estradiol, the inability to demonstrate stimulation of T47D cell growth in DM was not due to down-regulation of the estrogen receptor. R5020 inhibited the growth of T47D cells, although its effect was more marked in the presence of 3% DCC-FBS than in DM. Stimulation of T47D cell growth by either estradiol or insulin in 3% DCC-FBS was effectively inhibited by R5020. In contrast, growth of T47D cells stimulated by EGF in the absence of estradiol was not markedly inhibited by R5020, the growth being comparable to that of untreated control cells. These findings suggest that the inhibitory effect of R5020 on T47D cell proliferation is dominant over the action of some, but not all, breast cancer mitogens.

Interaction between hormone-dependent and hormone-independent human breast cancer cells

We developed two different models based on in vitro co-culture of hormone-dependent and hormone-independent cell lines to simulate the cell population heterogeneity of human breast cancer tumours. Oestrogen-dependent (MCF-7, ZR 75.1) and oestrogen-independent cell lines (MDAMB-231 BT-20) were grown under serum-free conditions. Co-culture of hormone-dependent and hormone-independent cell lines resulted in an increased cell yield compared to single cell cultures carried out at the same seeding ratios. Such an increase was not affected by addition of oestradiol and single growth factors (EGF, bFGF and IGF-I). These results allow us to conclude that in a heterogeneous cell population like human breast tumours, interaction between hormone-dependent and hormone-independent cell lines may result in a complex regulation of cell growth.

Radioimmunoassay for human insulin-like growth factor-I receptor: applicability to breast carcinoma specimens and cell lines

A radioimmunoassay for the human insulin-like growth factor-I (IGF-I) receptor was developed using a rabbit polyclonal antibody to the human IGF-I receptor and a highly purified IGF-I receptor. The purified receptor was radiolabeled with 125I-Bolton-Hunter reagent. Over 18% of the radiolabeled receptor was immunoprecipitated with the polyclonal antireceptor antibody. Purified IGF-I receptor concentrations as low as 5 ng/0.5 mL inhibited the radiolabeled IGF-I receptor binding. Purified insulin receptor weakly inhibited this binding, while the ligand IGF-I did not show inhibition. The radioimmunoassay was applicable to the measurements of IGF-I receptors in the Triton X-100 extracts of various tissues and cells. Breast cancer tissues and cells showed detectable IGF-I receptors, which correlated with IGF-I ligand binding. Receptor content was measurable in placenta and IM-9 cells, but receptor content was not measurable in liver and muscle extracts.

Multiple steroid metabolic pathways in ZR-75-1 human breast cancer cells

In order to characterize the main enzymatic systems involved in androgen and estrogen formation as well as metabolism in ZR-75-1 human breast cancer cells, incubation of intact cells was performed for 12 or 24 h at 37 degrees C with tritiated estradiol (E2), estrone (E1), androst-5-ene-3 beta, 17 beta-diol (5-ene-diol), dehydroepiandrosterone (DHEA), testosterone (T), androstenedione (4-ene-dione), dihydrotestosterone (DHT) or androsterone (ADT). The extra- and intracellular steroids were extracted, separated into free steroids, sulfates and non-polar derivatives (FAE) and identified by HPLC coupled to a Berthold radioactivity monitor. Following incubation with E2, 5-ene-diol or T, E1, DHEA and 4-ene-dione were the main products, respectively, thus indicating high levels of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD). When 4-ene-dione was used, on the other hand, a high level of transformation into 5 alpha-androstane-3,17-dione (A-dione), Epi-ADT and ADT was found, thus indicating the presence of high levels of 5 alpha-reductase as well as 3 alpha- and 3 beta-hydroxysteroid dehydrogenase. Moreover, some T was formed, due to oxidation by 17 beta-HSD. No estrogen was detected with the androgen precursors T or 4-ene-dione, thus indicating the absence of significant aromatase activity. Moreover, significant amounts of sulfates and non-polar derivatives were found with all the above-mentioned substrates. The present study shows that ZR-75-1 human breast cancer cells possess most of the enzymatic systems involved in androgen and estrogen formation and metabolism, thus offering an excellent model for studies of the control of sex steroid formation and action in breast cancer tissue.

Rapid induction of the c-jun protooncogene in the avian oviduct by the antiestrogen tamoxifen

This report describes a rapid regulation of the expression of the c-jun protooncogene by the antiestrogen tamoxifen (Tam). The c-jun protooncogene codes for an important component of the AP-1 transcription factor complex, which regulates the expression of many unlinked genes. Repeated experiments have shown that Tam rapidly increases the steady-state c-jun mRNA levels in the avian oviduct but decreases the levels in the liver. The Tam effects are time- and dose-dependent. These results are supported by other studies that have demonstrated that 17 beta-estradiol decreases steady-state levels of c-jun protooncogene mRNA in oviducts of animals fully withdrawn from estradiol. The effect of Tam in the avian oviduct is in contrast to the reported effects of Tam on the expression of practically all other genes in the avian oviduct and other animal tissues. Transcription analyses using nuclear runoff experiments with oviduct nuclei demonstrate a decrease in the c-jun gene transcription within minutes after Tam treatment with a return to 75% of control values by 4 hr. The fact that Tam transiently decreases the transcription of the c-jun gene but increases the steady-state c-jun mRNA levels suggests that Tam must alter both transcriptional and post-transcriptional events. The results support a role of the c-jun protooncogene as a regulatory gene in the cascade model for steroid action whereby steroids rapidly regulate the regulatory genes, which in turn regulate many other structural genes.

Effects of antiestrogen versus antiprogestin on transformed and nontransformed steroid receptors

In order to determine if different physicochemical properties exist among antihormone-receptor complexes, we have compared the interaction of the antiprogestin RU486 with progesterone receptor (PR) versus the triphenylethylene antiestrogen H1285 (4-(N,N-diethyl-aminoethoxy)-4'-methoxy-alpha-(p-hydroxyphenyl-alp ha'- ethylstilbene] with estrogen receptor (ER) from rabbit uterine tissue. Contrary to other reports, we observed no difference in the sedimentation properties of transformed PR (4S) when bound by the antagonist RU486 versus the progesterone agonist R5020 in either cytosol or DEAE partially-purified receptor preparations analyzed on sucrose gradients containing 0.3 M KCl. In addition, we found no difference in the sedimentation properties of these receptor preparations in the presence of 10 mM sodium molybdate: the nontransformed RU486-PR and nontransformed R5020-PR both sedimented as a 6S species. These same results were obtained when the receptor preparation and gradient analysis were performed in the absence of monothioglycerol. Likewise, there was no change in the sedimentation properties of the transformed PR when the receptor, partially purified in the absence of molybdate, was analyzed on sucrose gradients containing 10 mM sodium molybdate to prevent receptor alteration during centrifugation. From DNA-cellulose assays performed with partially purified PR in the absence of molybdate we determined that the 4S form of R5020-PR and RU486-PR is transformed receptor; whereas in the presence of molybdate, the 6S species is nontransformed. In contrast, we found a different pattern of sedimentation when comparing transformed antiestrogen-receptor complexes with transformed estrogen-receptor complexes. In this case, transformed H1285-ER sedimented as 6S and estradiol-ER sedimented as 4S. We conclude from these experiments that these two antihormones, RU486 and H1285, may have different mechanisms of action in their antagonism of steroid hormone action. Antiestrogen stabilizes the salt-transformed ER as a dimer while antiprogestin appears to permit dissociation of the oligomeric form of the receptor to the monomeric form.

Influence of culture conditions on the estrogenic cell growth stimulation of human breast cancer cells

17 beta-Estradiol is a potent mitogen for hormone-dependent cell lines (MCF-7, T47D and ZR 75.1). However, the degree of hormone sensitivity is very much influenced by culture conditions. In order to understand which factors modulate estrogenic effects on cell growth, four different culture conditions were used: (a) medium with dextran-coated charcoal-treated fetal calf serum (DCC-FCS); (b) medium with dextran-coated charcoal-treated growth factor-inactivated serum (DCC-FCSd); (c) serum-free medium, after a 24-h incubation with serum to allow cell attachment; and (d) serum-free medium on collagen IV-treated plates. In all cell lines the highest cell growth stimulation was achieved when estradiol was added in the presence of 5% DCC-FCS, whereas reducing or removing serum from the culture medium resulted in a decrease in cell proliferation stimulation. We postulate that serum contains some still unknown components able to modulate the degree of estrogenic action in endocrine-dependent breast cancer cell lines.

Growth stimulation by androgens, glucocorticoids or fibroblast growth factors and the blocking of the stimulated growth by antibody against basic fibroblast growth factor in protein-free culture of Shionogi carcinoma 115 cells

Shionogi carcinoma 115 (SC115) has been accepted for 20 years as an androgen-responsive mouse mammary tumor. We have established an androgen-dependent cloned cell line (SC-3) from a SC115 tumor. In a serum-free medium, testosterone (T) or fibroblast growth factors (FGFs) markedly stimulate the growth of SC-3 cells, and the T-induced growth was shown to be mediated through FGF-like peptide(s) in an autocrine mechanism. Since we used the serum-free culture including 0.1% bovine serum albumin (BSA), a partially serum-containing condition, putative roles of BSA- or serum-borne growth factors in growth stimulation of autocrine production of FGF-like peptide(s) could not be excluded. This paper reports findings performed in a protein-free medium including plating [Ham's F-12:MEM (1:1; v/v)]. In the protein-free culture, the growth of SC-3 cells was significantly stimulated by the addition of greater than or equal to 10(-10) M T (up to 20-fold), greater than or equal to 10(-7) M dexamethasone (Dex; up to 7-fold) or greater than or equal to 1 ng/ml basic (b) or acidic FGF (up to 10-fold); other various growth factors had no such effects. Furthermore, DNA synthesis of SC-3 cells induced by T, Dex or bFGF was similarly and markedly inhibited by bFGF neutralizing antibody IgG. Therefore, the present findings seem to demonstrate that androgens or high levels of glucocorticoids induce the production and secretion of FGF-like peptide(s) from SC-3 cells for their growth even in the absence of additional support by other factors.

Stimulation of progesterone receptors by phorbol ester and cyclic AMP in fetal uterine cells in culture

The role of growth factor signal transducers in the induction of the progesterone receptor by epidermal growth factor (EGF) and the potential sites of EGF antagonism by an antiestrogen were studied in fetal uterine cells in culture. The effects of EGF and estradiol were not additive, suggesting that EGF and estradiol are acting through common mechanisms where antiestrogens could possibly intervene. Fetal uterine cells in culture were found to contain specific, high affinity binding sites for [125I]EGF. Estradiol treatment of the cells led to a higher number of binding sites, but the site of action of 4-hydroxytamoxifen is not the EGF receptor because this antiestrogen had no effect on EGF binding. Activation of protein kinase C by a phorbol ester (12-O-tetradecanoylphorbol 13-acetate) increased progesterone receptor levels to a similar extent as EGF or estradiol. Increasing the intracellular cAMP concentrations by either adding dibutyryl cyclic AMP or activating adenylate cyclase with forskolin also raised progesterone receptor concentrations. Neither the phorbol ester nor dibutyryl cAMP had any effect on cell proliferation. 4-Hydroxytamoxifen completely abolished the effects of the phorbol ester and cAMP. In conclusion, the levels of an estrogen-induced steroid hormone receptor can be regulated by molecules involved in the signal transduction pathway of peptide factors. Moreover, in fetal uterine cells, a potent antiestrogen appears to act as a multiple antagonist but only on an estrogen-inducible response.

Formation of glucuronides of estradiol-17 beta by human mammary cancer cells

The formation of glucuronides of estradiol-17 beta by human mammary cancer cell lines is reported for the first time. When incubated with [3H]estradiol-17 beta (1 nM) for 16 h, ZR-75-1 and T47-D cells formed estradiol-3-glucuronide and estradiol-17 beta-glucuronide in approximately equal proportions, whereas MCF-7 cells formed E2-3-glucuronide only. Yields of monoglucuronides from MCF-7 and ZR-75-1 cells were 0.35 pmol/mg DNA, which represented 20-26% of the yield of estradiol-monosulphates. A HPLC system capable of separating most estradiol monosulphates, monoglucuronides and mixed conjugates, is described.

Antagonism between estrogens and androgens on GCDFP-15 gene expression in ZR-75-1 cells and correlation between GCDFP-15 and estrogen as well as progesterone receptor expression in human breast cancer

The androgen dihydrotestosterone (DHT) caused a maximal 65% inhibition of proliferation of the human breast cancer cells ZR-75-1 after a 10-day incubation period. The same treatment, on the other hand, stimulated by 25-fold the secretion of the breast marker protein GCDFP-15 (gross cystic disease fluid protein-15). The stimulatory effect of DHT on GCDFP-15 mRNA accumulation was already significant (1.6-fold, P less than 0.01) after a 12 h exposure and reached a maximal 25-fold increase after a 12-day incubation period. On the other hand, a 2-day exposure to 1 nM 17 beta-estradiol (E2) alone decreased by 60% GCDFP-15 mRNA levels while it completely blocked the 2.5-fold stimulation of GCDFP-15 secretion induced by concomitant incubation with DHT. Furthermore, a 10-day incubation with E2 increased by 4-fold the proliferation of ZR-75-1 cells whereas such treatment decreased by about 85% both GCDFP-15 mRNA accumulation and the secretion of the glycoprotein. The presence of GCDFP-15 mRNA in human breast cancer samples was restricted to estrogen receptor positive tumors and was significantly correlated with progesterone receptor expression.