Interaction between estradiol and growth factors in the regulation of specific gene expression in MCF-7 human breast cancer cells

Impact of Zinc Transport Mechanisms on Embryonic and Brain Development

The trace element zinc (Zn) binds to over ten percent of proteins in eukaryotic cells. Zn flexible chemistry allows it to regulate the activity of hundreds of enzymes and influence scores of metabolic processes in cells throughout the body. Deficiency of Zn in humans has a profound effect on development and in adults later in life, particularly in the brain, where Zn deficiency is linked to several neurological disorders. In this review, we will summarize the importance of Zn during development through a description of the outcomes of both genetic and early dietary Zn deficiency, focusing on the pathological consequences on the whole body and brain. The epidemiology and the symptomology of Zn deficiency in humans will be described, including the most studied inherited Zn deficiency disease, Acrodermatitis enteropathica. In addition, we will give an overview of the different forms and animal models of Zn deficiency, as well as the 24 Zn transporters, distributed into two families: the ZIPs and the ZnTs, which control the balance of Zn throughout the body. Lastly, we will describe the TRPM7 ion channel, which was recently shown to contribute to intestinal Zn absorption and has its own significant impact on early embryonic development.

Immunotherapy for Breast Cancer Treatment

Breast cancer, as a heterogeneous disease, includes a wide range of pathological and clinical behaviors. Current treatment protocols, including radiotherapy, chemotherapy, and hormone replacement therapy, are mainly associated with poor response and high rate of recurrence. Therefore, more efforts are needed to develop alternative therapies for this type of cancer. Immunotherapy, as a novel strategy in cancer treatment, has a potential in treating breast cancer patients. Although breast cancer has long been considered problematic to treat with immunotherapy, as it is immunologically "cold," numerous newer preclinical and clinical reports now recommend that immunotherapy has the capability to treat breast cancer patients. In this review, we highlight the different immunotherapy strategies in breast cancer treatment.

Lycorine is a novel inhibitor of the growth and metastasis of hormone-refractory prostate cancer

Lycorine, a natural alkaloid extracted from the Amaryllidaceae plant family, has been reported to exhibit a wide range of physiological effects, including the potential effect against cancer. However, the anti-prostate cancer (PCa) efficacy of Lycorine remains unrevealed. In this context, we figured out Lycorine's anti-proliferative and anti-migratory properties for PCa treatment. Lycorine inhibited proliferation of various PCa cell lines, induced cell apoptosis and cell death. Here we showed that Lycorine decreased proliferation, migration, invasion, survival and EMT of prostate cancer cell lines. Subcutaneous and orthotopic xenotransplantations by ectopic implantation of the human hormone-refractory PC-3M-luc cells were used to confirm in vivo anticancer effects of Lycorine. Lycorine inhibited both growth and metastasis in multiple organs (liver, lung, kidney, spleen and bone) in vivo and improved mice survival. Lycorine prevented EGF-induced JAK/STAT signaling. Importantly, anti-cancer effects of Lycorine were dependent on STAT expression. We suggest that Lycorine is a potential therapeutic in prostate cancer.

Kinome-wide functional screen identifies role of PLK1 in hormone-independent, ER-positive breast cancer

Estrogen receptor (ER) α-positive breast cancers initially respond to antiestrogens but eventually become estrogen independent and recur. ER(+) breast cancer cells resistant to long-term estrogen deprivation (LTED) exhibit hormone-independent ER transcriptional activity and growth. A kinome-wide siRNA screen using a library targeting 720 kinases identified Polo-like kinase 1 (PLK1) as one of the top genes whose downregulation resulted in inhibition of estrogen-independent ER transcriptional activity and growth of LTED cells. High PLK1 mRNA and protein correlated with a high Ki-67 score in primary ER(+) breast cancers after treatment with the aromatase inhibitor letrozole. RNAi-mediated knockdown of PLK1 inhibited ER expression, estrogen-independent growth, and ER transcription in MCF7 and HCC1428 LTED cells. Pharmacologic inhibition of PLK1 with volasertib, a small-molecule ATP-competitive PLK1 inhibitor, decreased LTED cell growth, ER transcriptional activity, and ER expression. Volasertib in combination with the ER antagonist, fulvestrant, decreased MCF7 xenograft growth in ovariectomized mice more potently than each drug alone. JUNB, a component of the AP-1 complex, was expressed 16-fold higher in MCF7/LTED compared with parental MCF7 cells. Furthermore, JUNB and BCL2L1 (which encodes antiapoptotic BCL-xL) mRNA levels were markedly reduced upon volasertib treatment in MCF7/LTED cells, while they were increased in parental MCF7 cells. Finally, JUNB knockdown decreased ER expression and transcriptional activity in MCF7/LTED cells, suggesting that PLK1 drives ER expression and estrogen-independent growth via JUNB. These data support a critical role of PLK1 in acquired hormone-independent growth of ER(+) human breast cancer and is therefore a promising target in tumors that have escaped estrogen deprivation therapy.

The use of a whole animal biophotonic model as a screen for the angiogenic potential of estrogenic compounds

BACKGROUND

Vascular endothelial growth factor (VEGF) is essential for normal vascular growth and development during wound repair. VEGF is estrogen responsive and capable of regulating its own receptor, vascular endothelial growth factor receptor-2 (VEGFR-2). Several agricultural pesticides (e.g., methoxychlor) have estrogenic potential that can initiate inappropriate physiological responses in estrogenic-sensitive tissues following exposure in vivo. Thus, the current study was designed to determine whether the VEGFR-2-Luciferase (Luc) reporter transgenic mouse is a useful model for evaluating estrogenic tendencies of methoxychlor by monitoring wound healing via VEGFR-2-mediated gene expression using bioluminescence and real-time imaging technology.

RESULTS

VEGFR-2-Luc gene activity peaked by d 7 (P<0.001) in all groups but was not different (P>0.05) between control and estrogen/methoxychlor exposed mice.

CONCLUSIONS

Changes in VEGFR-2-Luc gene activity associated with the dermal wound healing process were able to be measured via photonic emission. The increase in vasculature recruitment and formation is paralleled by the increase of VEGFR-2-Luc activity with a peak on day 7. However, estrogen/methoxychlor did not significantly alter wound healing mediated VEGFR-2-Luc gene expression patterns compared to controls. This suggests that the VEGFR-2-Luc transgenic mouse wound model tested in this study may not be optimal for use as a screen for the angiogenic potential of estrogenic compounds.

Estrogen receptor-positive breast cancer molecular signatures and therapeutic potentials (Review)

In this review, the advances in the study of breast cancer molecular classifications and the molecular signatures of the luminal subtypes A and B of breast cancer were summarized. Effective clinical outcomes depend mainly on successful preclinical diagnosis and therapeutic decisions. Over the last few years, the ever-expanding investigations focusing on breast cancer diagnosis and the clinical trials have provided accumulating information on the molecular characteristics of breast cancer. Specifically, among the estrogen receptor (ER)-positive types of breast cancer, the luminal subtype A breast cancer has been shown to exhibit good clinical outcomes with endocrine therapy, whereas the luminal subtype B breast cancer represents the more complicated type, diagnostically as well as therapeutically. Furthermore, even in luminal subtype A breast cancer, the resistance to treatment has become the major limitation for endocrine-based therapy. Accumulating molecular data and further clinical trials may enable more accurate diagnostic and therapeutic decisions. The molecular signatures have emerged as a powerful tool for future diagnosis and therapeutic decisions, although currently available data are limited.

Estrogen-like activity of aqueous extract from Agrimonia pilosa Ledeb. in MCF-7 cells

BACKGROUND

Postmenopausal women experience estrogen deficiency-related menopausal symptoms (e.g., hot flashes and mood swings) and a dramatic increase in the incidence of chronic diseases. Although estrogen-replacement therapy (ERT) can reduce mortality from cardiovascular disease and improve osteoporosis and menopausal symptoms, its side effects have limited recent use. This study investigated the estrogen-like activity of aqueous extract from Agrimonia pilosa Ledeb.

METHODS

The estrogenic activity of A. pilosa was investigated by using several in vitro assays. The binding activity of A. pilosa on estrogen receptors was examined using a fluorescence polarization-based competitive binding assay. The proliferative activity of A. pilosa was also examined using MCF-7 cells. Furthermore, the effect of A. pilosa on the expression of 3 estrogen-dependent genes was assessed.

RESULTS

Using liquid chromatography-mass spectrometry, the 3 major peaks of A. pilosa aqueous extract were identified as apigenin-hexose, luteolin-glucuronide, and apigenin-glucuronide. The aqueous extract induced the proliferation of estrogen receptor-positive MCF-7 cells (p < 0.05). A. pilosa-stimulated proliferation was blocked on adding the estrogen antagonist ICI 182,780. Moreover, A. pilosa treatment increased the mRNA expression of the estrogen-responsive genes pS2 and PR (p < 0.05).

CONCLUSIONS

These results suggest A. pilosa can be used to improve estrogen deficiency-related menopausal symptoms or to treat diseases in postmenopausal women.

Zinc hyperaccumulation in squirrelfish (Holocentrus adscenscionis) and its role in embryo viability

Female squirrelfish (Fam. Holocentridae) can accumulate and temporarily sequester copious amounts of zinc (Zn) in their livers. There, it is initially compartmentalized before a subsequent, estrogen-triggered redistribution to the ovaries. Here we show that cellular uptake of Zn is also influenced by estrogen signaling, and that estrogen increases concentrations of the plasma Zn-binding protein vitellogenin (VTG). However, estrogen-mediated increases in VTG are not sufficient to accommodate the magnitude of hepato-ovarian Zn transfer in female squirrelfish (Holocentrus adscensionis). These findings suggest that holocentrids have acquired the ability to use hormonal cues to drive hepatic uptake and storage of Zn, signal for its physiological redistribution, and influence the capacity for systemic transport of Zn beyond the mediation of increased plasma VTG concentrations. Such specific adaptations suggest an advantage for the oocyte, which is corroborated in further studies where we determined that oocyte Zn concentrations are positively correlated with egg viability in captive-spawned squirrelfish. The novel nature of these findings underlies the importance of Zn in squirrelfish reproductive biology.

Cellular mechanisms of zinc dysregulation: a perspective on zinc homeostasis as an etiological factor in the development and progression of breast cancer

Worldwide, breast cancer is the most commonly diagnosed cancer among women and is the leading cause of female cancer deaths. Zinc (Zn) functions as an antioxidant and plays a role in maintaining genomic stability. Zn deficiency results in oxidative DNA damage and increased cancer risk. Studies suggest an inverse association between dietary and plasma Zn levels and the risk for developing breast cancer. In contrast, breast tumor biopsies display significantly higher Zn levels compared with normal tissue. Zn accumulation in tumor tissue also correlates with increased levels of Zn importing proteins. Further, aberrant expression of Zn transporters in tumors correlates with malignancy, suggesting that altered metal homeostasis in the breast could contribute to malignant transformation and the severity of cancer. However, studies have yet to link dysregulated Zn transport and abnormal Zn-dependent functions in breast cancer development. Herein, we summarize studies that address the multi-modal role of Zn dyshomeostasis in breast cancer with respect to the role of Zn in modulating oxidative stress, DNA damage response/repair pathways and cell proliferation/apoptosis, and the relationship to aberrant regulation of Zn transporters. We also compare Zn dysregulation in breast tissue to that of prostate, pancreatic and ovarian cancer where possible.

LIV-1 promotes prostate cancer epithelial-to-mesenchymal transition and metastasis through HB-EGF shedding and EGFR-mediated ERK signaling

LIV-1, a zinc transporter, is an effector molecule downstream from soluble growth factors. This protein has been shown to promote epithelial-to-mesenchymal transition (EMT) in human pancreatic, breast, and prostate cancer cells. Despite the implication of LIV-1 in cancer growth and metastasis, there has been no study to determine the role of LIV-1 in prostate cancer progression. Moreover, there was no clear delineation of the molecular mechanism underlying LIV-1 function in cancer cells. In the present communication, we found increased LIV-1 expression in benign, PIN, primary and bone metastatic human prostate cancer. We characterized the mechanism by which LIV-1 drives human prostate cancer EMT in an androgen-refractory prostate cancer cells (ARCaP) prostate cancer bone metastasis model. LIV-1, when overexpressed in ARCaP_E (derivative cells of ARCaP with epithelial phenotype) cells, promoted EMT irreversibly. LIV-1 overexpressed ARCaP_E cells had elevated levels of HB-EGF and matrix metalloproteinase (MMP) 2 and MMP 9 proteolytic enzyme activities, without affecting intracellular zinc concentration. The activation of MMPs resulted in the shedding of heparin binding-epidermal growth factor (HB-EGF) from ARCaP_E cells that elicited constitutive epidermal growth factor receptor (EGFR) phosphorylation and its downstream extracellular signal regulated kinase (ERK) signaling. These results suggest that LIV-1 is involved in prostate cancer progression as an intracellular target of growth factor receptor signaling which promoted EMT and cancer metastasis. LIV-1 could be an attractive therapeutic target for the eradication of pre-existing human prostate cancer and bone and soft tissue metastases.

Cross-talk between non-genomic and genomic signalling pathways--distinct effect profiles of environmental estrogens

Estrogen receptor (ER) transcriptional cross-talk after activation by 17beta-estradiol (E2) has been studied in considerable detail, but comparatively little is known about the ways in which synthetic estrogen-like chemicals, so-called xenoestrogens, interfere with these signalling pathways. E2 can stimulate rapid, non-genomic signalling events, such as activation of the Src/Ras/Erk signalling pathway. We investigated how activation of this pathway by E2, the estrogenic environmental contaminants o,p'-DDT, beta-HCH and p,p'-DDE, and epidermal growth factor (EGF) influences the expression of ER target genes, such as TFF1, ER, PR, BRCA1 and CCND1, and the proliferation of breast cancer cells. Despite commonalities in their estrogenicity as judged by cell proliferation assays, the environmental contaminants exhibited striking differences in their non-genomic and genomic signalling. The gene expression profiles of o,p'-DDT and beta-HCH resembled the effects observed with E2. In the case of beta-HCH this is surprising, considering its reported lack of affinity to the "classical" ER. The expression profiles seen with p,p'-DDE showed some similarities with E2, but overall, p,p'-DDE was a fairly weak transcriptional inducer of TFF1, ER, PR, BRCA1 and CCND1. We observed distinct differences in the non-genomic signalling of the tested compounds. p,p'-DDE was unable to stimulate Src and Erk1/Erk2 activations. The effects of E2 on Src and Erk1/Erk2 phosphorylation were transient and weak when compared to EGF, but beta-HCH induced strong and sustained activation of all tested kinases. Transcription of TFF1, ER, PR and BRCA1 by E2, o,p'-DDT and beta-HCH could be suppressed partially by inhibiting the Src/Ras/Erk pathway with PD 98059. However, this was not seen with p,p'-DDE. Our investigations show that the cellular activities of estrogens and xenoestrogens are the result of a combination of extranuclear (non-genomic) and nuclear (genomic) events and highlight the need to take non-genomic effects and signalling cross-talk into consideration, when screening for environmental estrogens. Otherwise, chemicals devoid of ER affinity, such as beta-HCH, but with an effect profile otherwise similar to estrogens might be overlooked in safety testing.

Mammary gland zinc metabolism: regulation and dysregulation

Zinc (Zn) is required for numerous metabolic processes serving both a structural and catalytic role. The mammary gland has a unique Zn requirement resulting from the need to also transfer an extraordinary amount of Zn into milk (~0.5-1 mg Zn/day) during lactation. Impairments in this process can result in severe Zn deficiency in the nursing offspring which has adverse consequences with respect to growth and development. Moreover, dysregulated mammary gland Zn metabolism has recently been implicated in breast cancer transition, progression and metastasis, thus there is a critical need to understand the molecular mechanisms which underlie these observations. Tight regulation of Zn transporting mechanisms is critical to providing an extraordinary amount of Zn for secretion into milk as well as maintaining optimal cellular function. Expression of numerous Zn transporters has been detected in mammary gland or cultured breast cells; however, understanding the molecular mechanisms which regulate mammary Zn metabolism as well as the etiology and downstream consequences resulting from their dysregulation is largely not understood. In this review, we will summarize the current understanding of the regulation of mammary gland Zn metabolism and its regulation by reproductive hormones, with a discussion of the dysregulation of this process in breast cancer.

BRCA1 suppresses osteopontin-mediated breast cancer

BRCA1 is a well described breast cancer susceptibility gene thought to be involved primarily in DNA repair. However, mutation within the BRCA1 transcriptional domain is also implicated in neoplastic transformation of mammary epithelium, but responsible mechanisms are unclear. Here we show in a rat mammary model system that wild type (WT) BRCA1 specifically represses the expression of osteopontin (OPN), a multifunctional estrogen-responsive gene implicated in oncogenic transformation, particularly that of the breast. WT.BRCA1 selectively binds OPN-activating transcription factors estrogen receptor alpha, AP-1, and PEA3, inhibits OPN promoter transactivation, and suppresses OPN mRNA and protein both from an endogenous gene and a relevant model inducible gene. WT.BRCA1 also inhibits OPN-mediated neoplastic transformation characterized by morphology change, anchorage-independent growth, adhesion to fibronectin, and invasion through Matrigel. A mutant BRCA1 allele (Mut.BRCA1) associated with familial breast cancer lacks OPN suppressor effects, binds to WT.BRCA1, and impedes WT.BRCA1 suppression of OPN. Stable transfection of rat breast tumor cell lines with Mut.BRCA1 dramatically up-regulates OPN protein and induces anchorage independent growth. In human primary breast cancer, BRCA1 mutation is significantly associated with OPN overexpression. Taken together, these data suggest that BRCA1 mutation may confer increased tissue-specific cancer risk, in part by disruption of BRCA1 suppression of OPN gene transcription.

Insulin-like growth factor-I, insulin-like growth factor binding protein-3 and the risk of fibrocystic breast conditions among Chinese women

We investigated whether circulating insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels are associated with the risk of fibrocystic breast conditions (FBC), in a case-control study nested within a randomized trial of breast self-examination conducted in Shanghai, China. Participants were enrolled during 1989-1991 and were followed over 10 years for the development of breast diseases. Controls (n = 897) were frequency-matched by age to cases (n = 451), who were diagnosed with FBC between 1995 and 2000. Circulating IGF-I and IGFBP-3 levels and their molar ratio were positively associated with risk of FBC. The odds ratios (ORs) and 95% confidence intervals (CI) for the upper fourth of the distribution compared to the lowest fourth for IGF-I, IGFBP3 and their molar ratio were 3.02 (2.02-4.52), 1.92 (1.37-2.71) and 2.26 (1.52-3.36), respectively. The strength of the association between IGF-I levels and FBC was attenuated after adjustment for IGFBP-3 and that for IGFBP-3 was largely eliminated after adjustment for IGF-I. Increasing levels of IGF-I were particularly associated with increasing risk of FBC with proliferative elements (ORs and 95% CIs for the 2nd, 3rd and upper fourth of the distribution of IGF-I: 3.13 (1.50-6.53), 4.57 (2.22-9.39) and 6.30 (3.08-12.89), compared with the lowest fourth. Our results suggest that elevated levels of IGF-I may contribute to the development of FBC.

Photonic Monitoring in Real Time of Vascular Endothelial Growth Factor Receptor 2 Gene Expression under Relaxin-Induced Conditions in a Novel Murine Wound Model

Relaxin is known to promote vascular endothelial growth factor (VEGF) expression in reproductive tissue, and successful wound healing depends on good vascularization of wound sites, a process that relaxin may facilitate. Thus, the objective of this study was to evaluate the efficacy of relaxin on the development of vascular tissue at wound sites in a novel VEGF receptor 2-luc (VEGFR2-luc) transgenic mouse wound model by monitoring the rate of VEGFR2-luc-mediated gene expression using bioluminescence and real-time imaging. To this end, 12 FVB/N VEGFR2-luc transgenic male mice were assigned to treatments (six per group): saline alone or relaxin (1 g/6 h/14 days) administered intraperitoneally (i.p.). On day 0, a set of full-thickness wounds (6-mm punch) were generated under anesthesia on the dorsal aspect of each mouse. Photonic emissions were recorded (5-min collection of photons) from wound sites 10 min after the administration of luciferin (150 mg/kg i.p.) on day 0 and on days 1, 2, 4, 7, 9, 11, and 14 postwounding to quantify luciferase activity using an IVIS 100 biophotonic imaging system. Animals were sacrificed (three per group) on day 7 or 14, and wound tissue specimens were recovered for molecular and histologic analyses. Although photonic emission from wound sites increased (P < .001) over time with peak values obtained by day 7, no significant (P > .05) effect of relaxin treatment on VEGFR2-luc gene expression was noted at wound sites. Whereas measuring relaxin's effect on angiogenesis indirectly via the VEGFR2 model was not successful, photonic imaging provides an exciting new tool using alternative models (i.e., VEGF-luc mouse) to study relaxin-induced gene expression in normal (i.e., wound healing) or tumorigenic tissues in real time.

Expression levels of the putative zinc transporter LIV-1 are associated with a better outcome of breast cancer patients

We investigated the expression pattern of the breast cancer associated gene LIV-1 on mRNA and protein level in 111 human breast cancer patients by in situ hybridization as well as immunohistochemistry and focused on the unknown potential of LIV-1 expression levels as a prognostic marker. To our knowledge, this is the first study on endogenous LIV-1 protein expression. Results of our study indicate that LIV-1 mRNA and protein expression levels are only weakly correlated, suggesting posttranscriptional regulatory mechanisms. Furthermore, LIV-1 mRNA quantity in combination with a positive ER status seem to represent a better marker than the progesterone receptor status according to the prognostic significance for relapse free survival (RFS). A negative correlation of LIV-1 protein levels with tumor size, grade and stage reflects an association of LIV-1 protein expression with less aggressive tumors. High LIV-1 protein expression seems to be associated with a longer relapse free and overall survival in breast cancer patients with invasive ductal carcinoma. This association, however, seems to be dependent from other prognostic markers. Our data suggest that LIV-1 is a promising candidate for a novel marker for breast cancer patients with better outcome. Furthermore, our study presents a revised cDNA sequence of LIV-1 and demonstrates the localization of endogenous LIV-1 in the endoplasmic reticulum.

Mammalian zinc transporters

New insights into mammalian zinc metabolism have been acquired through the identification and characterization of zinc transporters. These proteins all have transmembrane domains, and are encoded by two solute-linked carrier (SLC) gene families: ZnT (SLC30) and Zip (SLC39). There are at least 9 ZnT and 15 Zip transporters in human cells. They appear to have opposite roles in cellular zinc homeostasis. ZnT transporters reduce intracellular zinc availability by promoting zinc efflux from cells or into intracellular vesicles, while Zip transporters increase intracellular zinc availability by promoting extracellular zinc uptake and, perhaps, vesicular zinc release into the cytoplasm. Both the ZnT and Zip transporter families exhibit unique tissue-specific expression, differential responsiveness to dietary zinc deficiency and excess, and differential responsiveness to physiologic stimuli via hormones and cytokines.

Mammary tumorigenesis in growth hormone deficient spontaneous dwarf rats; effects of hormonal treatments

This study was carried out to investigate mammary tumorigenesis in growth hormone (GH) deficient spontaneous dwarf rats (SDR). At 50-60 days of age, the rats were divided into five groups. Group 1 received bovine (b) GH (prolonged release formulation) administered at a dose of 40-50 mg/kg body wt. in 50 microl weekly injections; group 2 received recombinant human insulin-like growth factor-I (IGF-I) at a dose of 1 mg/kg body wt./day administered via osmotic pumps; animals in group 3 were fitted with subcutaneous silastic capsule containing 30 microg 17 beta-estradiol (E2) plus 30 mg progesterone (P4), replaced every 2 months; group 4 received both bGH and E2 plus P4 treatments at the same doses as above, and control animals (group 5) received sham treatments (vegetable oil injection, silastic capsules containing cellulose). After 1 week of treatment, all animals were injected intraperitoneally with the carcinogen N-methyl-N-nitrosourea (MNU) at a dose of 50 mg/kg body wt. Other groups of animals, receiving identical hormonal treatment to those exposed to MNU, were treated for 10 days only and then sacrificed for assessment of circulating concentrations of hormones and mammary gland characteristics at the time of carcinogen exposure. The hormonal treatments of the animals exposed to the MNU were continued for an additional 20 weeks and mammary tumor development monitored by weekly palpation and tumors collected as necessary. The rats were weighed weekly. At the end of the treatment period, all animals were sacrificed and remaining tumors were collected. Rats in all groups continued to gain weight throughout the experimental period, but the largest weight gain was see in animals receiving GH either alone or with E2 and P4. Animals treated with IGF-I also gained weight compared to controls, but this weight gain was less than that seen in GH-treated rats. GH treatment alone increased mammary tumor incidence from 4.8% in controls to 100%. Average tumor load and latency in the GH-treated rats were 7.0 +/- 0.8 tumors/tumor-bearing rat (mean +/- SEM) and 57.3 +/- 2.7 days (mean +/- SEM), respectively. As in intact Sprague-Dawley rats, approximately 90% of the tumors that developed in the GH-treated rats were ovarian dependent for growth. IGF-I treatment also increased mammary tumor development to 62.5%. Average tumor load and latency in the IGF-I-treated rats were 1.6 +/- 0.4 tumors/tumor-bearing rat (mean +/- SEM) and 96.2 +/- 14.5 days (mean +/- SEM), respectively. However E2 + P4 treatments did not significantly alter tumorigenesis and, surprisingly, simultaneous treatment with E2 + P4 and GH obliterated the GH-stimulated increase in tumor development. Prolactin (PRL) did not appear to influence mammary tumorigenesis in the SDRs, as untreated SDRs had significantly elevated serum concentration of PRL as compared with normal Sprague-Dawley (SD) rats, whereas GH-treated SDRs had PRL levels similar to that of normal SD rats. No obvious structural characteristics were associated with high or low susceptibility to mammary tumorigenesis, as assessed by mammary gland whole mounts from the different animal groups sacrificed at the time of carcinogen administration. Enhanced expression of the extracellular signal-regulated kinase 1/2 (ERK1/2), and activation (phosphorylation) of ERK1/2 were associated with an increase in mammary tumorigenesis. Similarly, the expression of the estrogen receptor-alpha (ER alpha) was significantly elevated in animal groups with the highest susceptibility to tumorigenesis, whereas the levels of cyclin D1 expression were not related to mammary tumorigenesis.

Insulin-like growth factor (IGF)-I obliterates the pregnancy-associated protection against mammary carcinogenesis in rats: evidence that IGF-I enhances cancer progression through estrogen receptor-alpha activation via the mitogen-activated protein kinase pathway

Introduction

Pregnancy protects against breast cancer development in humans and rats. Parous rats have persistently reduced circulating levels of growth hormone, which may affect the activity of the growth hormone/insulin-like growth factor (IGF)-I axis. We investigated the effects of IGF-I on parity-associated protection against mammary cancer.

Methods

Three groups of rats were evaluated in the present study: IGF-I-treated parous rats; parous rats that did not receive IGF-I treatment; and age-matched virgin animals, which also did not receive IGF-I treatment. Approximately 60 days after N-methyl-N-nitrosourea injection, IGF-I treatment was discontinued and all of the animal groups were implanted with a silastic capsule containing 17β-estradiol and progesterone. The 17β-estradiol plus progesterone treatment continued for 135 days, after which the animals were killed.

Results

IGF-I treatment of parous rats increased mammary tumor incidence to 83%, as compared with 16% in parous rats treated with 17β-estradiol plus progesterone only. Tumor incidence and average number of tumors per animal did not differ between IGF-I-treated parous rats and age-matched virgin rats. At the time of N-methyl-N-nitrosourea exposure, DNA content was lowest but the α-lactalbumin concentration highest in the mammary glands of untreated parous rats in comparison with age-matched virgin and IGF-I-treated parous rats. The protein levels of estrogen receptor-α in the mammary gland was significantly higher in the age-matched virgin animals than in untreated parous and IGF-I-treated parous rats. Phosphorylation (activation) of the extracellular signal-regulated kinase-1/2 (ERK1/2) and expression of the progesterone receptor were both increased in IGF-I-treated parous rats, as compared with those in untreated parous and age-matched virgin rats. Expressions of cyclin D₁ and transforming growth factor-β₃ in the mammary gland were lower in the age-matched virgin rats than in the untreated parous and IGF-I-treated parous rats.

Conclusion

We argue that tumor initiation (transformation and fixation of mutations) may be similar in parous and age-matched virgin animals, suggesting that the main differences in tumor formation lie in differences in tumor progression caused by the altered hormonal environment associated with parity. Furthermore, we provide evidence supporting the notion that tumor growth promotion seen in IGF-I-treated parous rats is caused by activation of estrogen receptor-α via the Raf/Ras/mitogen-activated protein kinase cascade.

Ets gene PEA3 cooperates with beta-catenin-Lef-1 and c-Jun in regulation of osteopontin transcription

Osteopontin (OPN) is a multifunctional protein implicated in mammary development, neoplastic change, and metastasis. OPN is a target gene for beta-catenin-T cell factor signaling, which is commonly disturbed during mammary oncogenesis, but the understanding of OPN regulation is incomplete. Data base-assisted bioinformatic analysis of the OPN promoter region has revealed the presence of T cell factor-, Ets-, and AP-1-binding motifs. Here we report that beta-catenin, Lef-1, Ets transcription factors, and the AP-1 protein c-Jun each weakly enhanced luciferase expression from a OPN promoter-luciferase reporter construct, transiently transfected into a rat mammary cell line. OPN promoter responsiveness to beta-catenin and Lef-1, however, was considerably enhanced by Ets transcription factors including Ets-1, Ets-2, ERM, and particularly PEA3. PEA3 also enhanced promoter responsiveness to the AP-1 protein c-Jun. Co-transfection of cells with beta-catenin, Lef-1, PEA3, and c-Jun in combination increased luciferase expression by up to 280-fold and induced expression of endogenous rat OPN. In six human breast cell lines, those that highly expressed OPN also expressed PEA3 and Ets-1. Moreover, there was a significant association of immunocytochemical staining for OPN and one of beta-catenin, Ets-1, Ets-2, PEA3, or c-Jun, in the 29 human breast carcinomas tested. This study shows that beta-catenin/Lef-1, Ets, and AP-1 transcription factors can cooperate in a rat mammary cell line in stimulating transcription of OPN and that their independent presence is associated with that of OPN in a group of human breast cancers. These results suggest that the presence of these transcription factors in human breast cancer is responsible in part for the overexpression of OPN that, in turn, is implicated in mammary neoplastic progression and metastasis.

Metalloregulation of yeast membrane steroid receptor homologs

Zinc is an essential micronutrient that can also be toxic. An intricate mechanism exists in yeast that maintains cellular zinc within an optimal range. The centerpiece of this mechanism is the Zap1p protein, a transcription factor that senses zinc deficiency and responds by up-regulating genes involved in zinc metabolism. A microarray screen for novel Zap1p target genes suggested a role in zinc homeostasis for four homologous yeast genes. The expression of two of these genes, YDR492w and YOL002c, suggested direct regulation by Zap1p, whereas the expression of YOL002c and a third homologous gene, YOL101c, was induced by high zinc. YDR492w and YOL002c are confirmed to be direct Zap1p target genes. The induction of YOL002c and YOL101c by toxic metal ion exposure is shown to be mediated by the Mga2p hypoxia sensor. Furthermore, YOL101c is induced by deletion of the Aft1p iron-responsive transcription factor. These three genes, along with a fourth yeast homolog, YLR023c, have phenotypic effects on zinc tolerance and Zap1p activity. Because of their metalloregulation, zinc-related phenotypes, and highly conserved motifs containing potential metal-binding residues, this family has been renamed the IZH gene family (Implicated in Zinc Homeostasis). Furthermore, these genes are regulated by exogenous fatty acids, suggesting a dual role in lipid metabolism. The IZH genes encode membrane proteins that belong to a ubiquitous protein family that includes hemolysin III and vertebrate membrane steroid receptors. We propose that the IZH genes affect zinc homeostasis either directly or indirectly by altering sterol metabolism.

The SLC39 family of metal ion transporters

SLC39 proteins are members of the broader ZIP family of metal ion transporters found in organisms at all phylogenetic levels. Most ZIP transporters have eight predicted transmembrane domains and a similar predicted topology. Their biochemical mechanism(s) of substrate transport are not yet known. Where characterized, these proteins have been found to transport metal ions from the cell exterior or lumen of intracellular organelles into the cytoplasm. Furthermore, members of the ZIP family have been implicated in the transport of zinc, iron, and/or manganese indicating that these proteins have diverse functions. There are 14 SLC39-related proteins encoded by the human genome. Studies of SLC39A1, SLC39A2, and SLC39A4, encoding the proteins hZip1, hZip2, and hZip4, have indicated roles in zinc uptake across the plasma membrane of various cell types. Genetic studies have specifically implicated SLC39A4 in the uptake of dietary zinc into intestinal enterocytes. Mutations in SLC39A4 have been identified in patients with acrodermatitis enteropathica, a genetic disease of zinc deficiency.

Breast cancer classification and prognosis based on gene expression profiles from a population-based study

Comprehensive gene expression patterns generated from cDNA microarrays were correlated with detailed clinico-pathological characteristics and clinical outcome in an unselected group of 99 node-negative and node-positive breast cancer patients. Gene expression patterns were found to be strongly associated with estrogen receptor (ER) status and moderately associated with grade, but not associated with menopausal status, nodal status, or tumor size. Hierarchical cluster analysis segregated the tumors into two main groups based on their ER status, which correlated well with basal and luminal characteristics. Cox proportional hazards regression analysis identified 16 genes that were significantly associated with relapse-free survival at a stringent significance level of 0.001 to account for multiple comparisons. Of 231 genes previously reported by others [van't Veer, L. J., et al. (2002) Nature 415, 530-536] as being associated with survival, 93 probe elements overlapped with the set of 7,650 probe elements represented on the arrays used in this study. Hierarchical cluster analysis based on the set of 93 probe elements segregated our population into two distinct subgroups with different relapse-free survival (P < 0.03). The number of these 93 probe elements showing significant univariate association with relapse-free survival (P < 0.05) in the present study was 14, representing 11 unique genes. Genes involved in cell cycle, DNA replication, and chromosomal stability were consistently elevated in the various poor prognostic groups. In addition, glutathione S-transferase M3 emerged as an important survival marker in both studies. When taken together with other array studies, our results highlight the consistent biological and clinical associations with gene expression profiles.

Growth factors and chemotherapeutic modulation of breast cancer cells

A variety of molecules including growth factors are involved in the metastasis of breast cancer cells to bone. We have investigated the effects of osteoblast derived growth factors, such as insulin-like growth factor-1 (IGF-1) and transforming growth factor beta-1 (TGF-beta1), on doxorubicin (adriamycin)-induced apoptosis and growth arrest of estrogen receptor positive (ER+) (MCF-7) and negative (ER-) (MDA-MB-435) breast cancer cell lines. Human breast normal epithelial (MCF-10A), breast cancer (MCF-7) and metastatic breast cancer (MDA-MB-435) cell lines were exposed to different doses of doxorubicin (0.1, 1 or 10 microM) at various exposure times (12, 24 or 48 h). The doxorubicin cytotoxicity was found to be higher in cancer cell lines (MDA-MB-435 and MCF-7) compared with normal breast epithelial cells (MCF-10A cells). Doxorubicin appeared to exert a blockade of MCF-7 and MDA-MB-435 cells at the G2/M phase, and induced apoptosis in MDA-MB-435 (29 +/- 4.2% vs 3.4 +/- 1.9% control) as assessed by flow cytometry, DNA fragmentation and terminal deoxynucleotidyl-transferase mediated deoxyuridine 5-triphosphate and biotin nick-end labelling (TUNEL) assays. Estradiol (E2) stimulated the growth of MCF-7 cells and increased the distribution of the cells at the G2/M and S phases. Exogenous IGF-1 partially neutralized the doxorubicin cytotoxicity in both cancer cell lines (MCF-7 and MDA-MB-435). Similarly, TGF-beta1 partially neutralized the doxorubicin cytotoxicity in MDA-MB-435 cells by reducing the number of cells at the <G1 phase (from 29% to 6.4%) and enhanced the doxorubicin blockade of MCF-7 (E2-) at the G0/G1 phase. Results showed that the osteoblast-derived growth factors could affect the chemotherapy response of breast cancer cells, thereby allowing for the possibility of chemotherapeutic modulation.

Heregulin-beta1 regulates the estrogen receptor-alpha gene expression and activity via the ErbB2/PI 3-K/Akt pathway

This study examines whether the serine/threonine protein kinase, Akt, is involved in the crosstalk between the ErbB2 and estrogen receptor-alpha (ER-alpha) pathways. Treatment of MCF-7 cells with 10(-9) M heregulin-beta1 (HRG-beta1) resulted in a rapid phosphorylation of Akt and a 15-fold increase in Akt activity. Akt phosphorylation was blocked by inhibitors of phosphatidylinositol 3-kinase (PI 3-K), by antiestrogens, the protein tyrosine kinase inhibitor, genistein, and by AG825, a selective ErbB2 inhibitor; but not by AG30, a selective EGFR inhibitor. Akt phosphorylation by HRG-beta1 was abrogated by an arginine to cysteine mutation (R25C) in the pleckstrin homology (PH) domain of Akt, and HRG-beta1 did not induce Akt phosphorylation in the ER-negative variant of MCF-7, MCF-7/ADR. Transient transfection of ER-alpha into these cells restored Akt phosphorylation by HRG-beta1, suggesting the requirement of ER-alpha. HRG-beta1 did not activate Akt in MCF-7 cells stably transfected with an anti-ErbB2-targeted ribozyme, further confirming a role for ErbB2. Stable transfection of the cells with a dominant negative Akt or with the R25C-Akt mutant, as well as PI 3-K inhibitors, blocked the effect of HRG-beta1 on ER-alpha expression and activity and on the growth of MCF-7 cells. Stable transfection of MCF-7 cells with a constitutively active Akt mimicked the effect of HRG-beta1. Experiments employing selective ErbB inhibitors demonstrate that the effect of HRG-beta1 on ER-alpha expression and activity is also mediated by ErbB2 and not by EGFR, demonstrating that ErbB2 is the primary mediator of the effects of HRG-beta1 on ER-alpha regulation. Taken together, our data suggest that HRG-beta1, bound to the ErbB2 ErbB3 heterodimer, in the presence of membrane ER-alpha, interacts with and activates PI 3-K/Akt. Akt leads to nuclear ER-alpha phosphorylation, thereby altering its expression and transcriptional activity.

Selective estrogen receptor modulators inhibit the effects of insulin-like growth factors in hyperparathyroidism

BACKGROUND

Primary hyperparathyroidism (HPT) predominantly affects perimenopausal women, leading to speculations that an estrogen imbalance may be liable. We have previously demonstrated the importance of the insulin-like growth factor (IGF) axis in HPT. Because the antiestrogen tamoxifen has been shown to modulate the IGF axis, we examined the interactions of selective estrogen receptor modulators (SERMs) and IGF in HPT. METHODS; Estrogen receptors were evaluated by Western immunoligand blotting. Sixteen parathyroid glands from 19 patients were included. After adhesion, the cells were treated with IGF (I or II) +/- estrogen +/- SERMs (tamoxifen, ICI 182,780) for 96 hours in serum-free media. Proliferation was assessed by measuring tritiated thymidine incorporation.

RESULTS

Both primary and secondary HPT express estrogen receptors alpha and beta. Primary and secondary HPT had comparable responses to SERMs, they were analyzed together. Compared with control (100%), IGFs (I and II) induced a significant increase in DNA synthesis. Estradiol at 10(-8) and 10(-7) mol/L (physiologic range) had no significant effects on IGF (I and II, P >.05). Both tamoxifen and ICI 182,780 inhibited basal DNA synthesis (P <.05) and abolished the effects of both IGF I and II (P <.05).

CONCLUSIONS

SERMs are capable of reducing basal and IGF-stimulated DNA synthesis. This reduction in proliferation has implications for cancer biology and therapeutic potential for SERMs in HPT.

Mycobacterium bovis BCG cell wall and lipopolysaccharide induce a novel gene, BIGM103, encoding a 7-TM protein: identification of a new protein family having Zn-transporter and Zn-metalloprotease signatures

To identify novel genes induced during innate immune activation, we screened a cDNA library prepared from monocytes stimulated with Mycobacterium bovis BCG cell wall. A novel transcript with three-protein coding potential was identified, and the expressed proteins from individual frames showed distinct intracellular localization. Live and heat-killed Mycobacterium, bacterial cell wall, and inflammatory cytokines like TNFalpha were found to be potent inducers of the transcript. Expression of this gene is very low or undetectable in unstimulated monocytes, while a steady expression level was observed during differentiation of monocytes to dendritic cells and macrophages. The entire gene consisted of eight major exons and was localized on chromosome 4q22-q24, spanning approximately 84 kb. The main open reading frame of the transcript encoded a putative seven-transmembrane (TM) protein that showed homology with a number of functionally unknown proteins in the database. Further analysis revealed that all of these proteins have detectable similarity with the ZIP family of metal transporters. In fact, increased accumulation of intracellular Zn(2+) was observed due to the expression of BIGM103 in CHO cells. However, the identified proteins are structurally unique compared to known ZIP members and they also possess the hallmark of Zn-metalloproteases, suggesting a new class of multi-TM protein with dual features. Here we present a collection of these proteins and discuss the functional aspects of BIGM103, based on our results and current findings on two members of the family, Drosophila Catsup and Arabidopsis IAR1.

Overview of in vitro tools to assess the estrogenic and antiestrogenic activity of phytoestrogens

There is an intense discussion in the scientific and even more so in the public community as well as regulatory agencies about the potential benefits or detrimental effects of plant-derived compounds that may affect the endocrine system, especially estrogen signaling pathways. These so-called phytoestrogens are found in the normal western diet and predominantly in an eastern or soy-based diet and the potency of the isolated compounds to interact with the known receptors for estrogen varies tremendously. The estrogen receptors, ER alpha and ER beta, mediate the effects of endogenous estrogens, i.e. regulation of reproductive function, tissue development, cell proliferation and differentiation. In this review, in vitro test systems available to date for the screening of estrogenic and antiestrogenic activity including mechanism-based assays are described. The potency of phytoestrogens determined using these in vitro assays are compared with the potency of endogenous estrogens and results obtained in vitro are compared with effects in vivo. Finally, the impact of in vitro assays to determine estrogenicity on human hazard assessment is discussed as well as other non ER-mediated mechanisms that may contribute to potential beneficial or adverse effects of phytoestrogens in man.

Genes that co-cluster with estrogen receptor alpha in microarray analysis of breast biopsies

The estrogen receptor plays a critical role in the pathogenesis and clinical behavior of breast cancer. To better understand the molecular basis of estrogen-dependent forms of this disease we studied gene expression profiles from 53 primary breast cancer biopsies. Gene expression data for more than 7000 genes were generated from each tumor sample with oligo microarrays. A standard correlation-clustering algorithm identified 18 genes that co-clustered with estrogen receptor alpha. Eleven of these genes had previously been associated with estrogen regulation or breast tumorigenesis including trefoil factor 1 and estrogen regulated LIV-1. Additional study of these 18 genes may further delineate the role of estrogen receptor in breast cancer, generate new predictive biomarkers for response to endocrine therapies and identify novel therapeutic targets.

MAP kinase/estrogen receptor cross-talk enhances estrogen-mediated signaling and tumor growth but does not confer tamoxifen resistance

The estrogen receptor alpha (ERalpha) signaling plays an essential role in breast cancer progression and endocrine therapy. Mitogen-activated protein kinase (MAPK/Erk1/2) has been implicated in ligand-independent activation of ER, resulting in the cross-talk between growth factor and ER mediated signaling. In this study, we examined the effect of the cross-talk on estradiol (E(2))-mediated signaling, tumor growth and its effect on anti-estrogen therapy. Our findings demonstrate that expression of constitutively activated mitogen activated kinase kinase (MEK1), an immediate upstream activator of MAPK in estrogen receptor positive MCF-7 breast cancer cells (MEK/MCF-7), showed an increase in ERalpha-driven transcriptional activation. In MEK/MCF-7 cells maximal transactivation levels were achieved in response to treatment with much lower E(2) concentrations (10(-10) M E(2)) when compared to MCF-7 control cells (10(-8) M E(2)). Furthermore, we have seen an increased association between ERalpha and its nuclear coactivators AIB1 or TIF-2, in MEK/MCF-7 cells relative to those seen in MCF-7 control cells. In addition, in vivo studies show that MEK/MCF-7 cell tumors are approximately threefold larger than those of MCF-7 cell, in the presence of E(2). Immunohistochemical staining demonstrates that progesterone receptor (PR) and pS2, two E(2)-regulated gene products, are significantly increased in MEK/MCF-7 cell tumors compared to those of MCF-7 control tumors, suggesting that activation of ERalpha by MAPK enhances the expression of E(2)-regulated genes and accelerates tumor growth. Remarkably, the antiestrogens tamoxifen and ICI 182,780, were shown both in vitro and in vivo studies to efficiently antagonize the stimulatory effects of E(2) on ER regulated transactivation and tumor growth in MEK/MCF-7 as well as MCF-7 cell lines. Taken together, these data suggest that MAPK/ER cross-talk enhances ERalpha-mediated signaling and accelerates E(2)-dependent tumor growth without diminishing sensitivity to the inhibitory effects of anti-estrogens.

Differential modulation of transcriptional activity of estrogen receptors by direct protein-protein interactions with the T cell factor family of transcription factors

Two major signaling pathways, those triggered by estrogen (E(2)) and by the Wnt family, interact in the breast to cause growth and differentiation. The estrogen receptors ER(alpha) and ER(beta) are activated by binding E(2) and act as ligand-dependent transcription factors. The effector for the Wnt family is the Tcf family of transcription factors. Both sets of transcription factors recognize discrete but different nucleotide sequences in the promoters of their target genes. By using transient transfections of reporter constructs for the osteopontin and thymidine kinase promoters in rat mammary cells, we show that Tcf-4 antagonizes and Tcf-1 stimulates the effects of activated ER/E(2). For mutants of the former promoter, the stimulatory effects of ER(alpha)/E(2) can be made to be dependent on Tcf-1, and for the latter promoter the effects of the T cell factors (TCFs) are dependent on ER/E(2). Direct interaction between ERs and Tcfs either at the Tcf/ER(alpha)-binding site on the DNA or in the absence of DNA is established by gel retardation assays or by coimmunoprecipitation/biosensor methods, respectively. These results show that the two sets of transcription factors can interact directly, the interaction between ERs and Tcf-4 being antagonistic and that between ERs and Tcf-1 being synergistic on the activity of the promoters employed. Since Tcf-4 is the major Tcf family member in the breast, it is suggested that the antagonistic interaction is normally dominant in vivo in this tissue.

Effects of hypothalamically elicited emotional behaviors on the plasma levels of estradiol and IGF-1

We examined changes in the plasma levels of estradiol (E2), insulin-like growth factor-1 (IGF-1), ACTH, cortisol and catecholamines accompanying various kinds of hypothalamically elicited emotional behaviors in female cats. The emotional behaviors consisting of restlessness, threat and searching-biting (S-B) were elicited intermittently for 6 h by electrical stimulation of the anterior hypothalamus (AH), ventromedial hypothalamus (VMH) and lateral hypothalamus (LH), respectively, in awake and free-moving conditions. The blood was sampled three times immediately before, 1 h after and 6 h after the start of stimulation. The plasma levels of ACTH, cortisol and catecholamines significantly increased in both restlessness and threat behaviors, whereas in the S-B behavior, the ACTH level significantly increased, while the cortisol level showed a slight nonsignificant increase. No changes were observed in the plasma catecholamine levels in the S-B behavior. The plasma E2 level significantly increased in threat behavior after 1 and 6 h of stimulation compared to the prestimulation levels, and the level also increased in comparison to the control group after 1 h. In contrast, the restlessness and S-B behaviors had little or no effect on the E2 level. No significant changes were observed in the plasma levels of IGF-1 in all behavior groups. These findings suggest that various hypothalamically elicited emotional behaviors have differential effects on the plasma E2, but not on the IGF-1 levels. Therefore, E2 and IGF-1 are regulated independently of each other.

Cytostatic effects of 3,3'-diindolylmethane in human endometrial cancer cells result from an estrogen receptor-mediated increase in transforming growth factor-alpha expression

3,3'-Diindolylmethane (DIM), a major in vivo product of indole-3-carbinol (I3C), is a promising anticancer agent derived from vegetables of the Brassica genus including broccoli, Brussels sprouts and cabbage. We report here that DIM has a potent cytostatic effect in cultured human Ishikawa endometrial cancer cells. A combination of northern blot and quantitative PCR analyses revealed that DIM induced the level of TGF-alpha transcripts by approximately 4-fold within 24 h of indole treatment. DIM also induced a 4-fold increase in the activity of the estrogen response marker, alkaline phosphatase (AP). Co-treatment of cells with the estrogen receptor (ER) antagonist ICI, or with the inhibitor of PKA-mediated activation of the ER, H89, ablated the DIM induction of both TGF-alpha expression and AP activity. Furthermore, DIM increased the maximum stimulatory effect of estrogen on TGF-alpha expression. Co-treatment with the protein synthesis inhibitor, cycloheximide, abolished the inductive effects of DIM, indicating differences in the mechanistic requirements of DIM and estrogen. DIM treatment also stimulated levels of secreted TGF-alpha protein by >10-fold. The ectopic addition of TGF-alpha inhibited the growth of Ishikawa cells, whereas incubation with a TGF-alpha antibody partially reversed the growth inhibitory effects of DIM. Taken together, these results extend our previous findings of the ligand independent estrogen receptor agonist activity of DIM, and uncover an essential role for the stimulation in TGF-alpha expression and the TGF-alpha activated signal transduction pathway in the potent cytostatic effects of DIM in endometrial cancer cells.

Role of insulin-like growth factor-I in regulating estrogen receptor-alpha gene expression

The role of insulin-like growth factor-I (IGF-I) in regulating estrogen receptor-alpha (ER-alpha) gene expression and activity was investigated in the human breast cancer cell line MCF-7. Treatment of cells with 40 ng/ml IGF-I resulted in a 60% decrease in ER-alpha protein concentration by 3 h, and the amount of ER-alpha remained suppressed for 24 h. A multiple-dose ligand-binding assay demonstrated that the decrease in ER-alpha protein corresponded to a similar decrease of 50% in estradiol-binding sites with no effect on the binding affinity of ER-alpha. The dissociation constant of the estradiol-ER-alpha complex in the absence of IGF-I (K(d) = 3 x 10(-10) +/- 0.5 x 10(-10) M) was similar to the dissociation constant in the presence of IGF-I (K(d) = 6 x 10(-10) +/- 0.3 x 10(-10) M). The decrease in ER-alpha protein concentration was paralleled by an 80% decrease in the steady-state amount of ER-alpha mRNA by 3 h. The IGF-I induced decrease in ER-alpha mRNA was due to the inhibition of ER-alpha gene transcription. When an 128-base pair ER-alpha-promoter-CAT construct was transfected into MCF-7 cells, treatment with IGF-I resulted in a 40% decrease in CAT activity. In contrast to the effects on ER-alpha, treatment with IGF-I induced two endogenous estrogen-regulated genes, progesterone receptor and pS2, by 4- and twofold, respectively. The pure antiestrogen ICI-164, 384 blocked this induction, suggesting that ER-alpha mediates the effects of IGF-I. Transient co-transfections of wild-type ER-alpha and an estrogen response element-CAT reporter into COS-1 cells demonstrated that IGF-I increased reporter gene activity. This effect was also blocked by ICI 164,384. Protein kinase A and phosphatidylinositol 3-kinase inhibitors blocked the IGF-I effects on ER-alpha expression and activity, suggesting that these kinases may be involved in the cross-talk between the IGF-I and ER-alpha pathways.

Progesterone receptor involvement in independent tumor growth in MPA-induced murine mammary adenocarcinomas

We have developed a model of hormonal carcinogenesis in BALB/c female mice, in which MPA induced ductal mammary adenocarcinomas, expressing high levels of estrogen and progesterone receptors (ER and PR). A series of tumor lines, retaining both PR and ER expression, were obtained from selected tumors, which are maintained by syngeneic passages. In this model progesterone behaves as the growth-stimulating hormone (progesterone-dependent or PD tumors), whereas estrogens induce tumor regression. Through selective treatments we were able to derive a series of progesterone-independent (PI) variants. These lines do not require progesterone treatment to grow in ovariectomized female BALB/c mice, but retain, however, the expression of ER and PR. The aim of this paper is to investigate a possible regulatory role of the progesterone receptor (PR) on PI tumor growth. ER and PR were detected by immunocytochemistry in all lines studied. They were also characterized using biochemical assays and Scatchard plots. No differences in Kd of PR or ER were detected in PI variants. AR or GR were not detected in tumor samples using biochemical assays. Estradiol (5 mg silastic pellet) induced complete tumor regression in all tumors tested. We also evaluated the effects of different antiprogestins on tumor growth. Onapristone (10 mg/kg/day) and mifepristone (4.5 mg/kg/day) were able to induce complete tumor regression. The antiandrogen flutamide (5 mg silastic pellet) had no effect on tumor growth in agreement with the lack of androgen receptors. We used an in vitro approach to corroborate that the antiprogestin-induced inhibition was not attributable to an intrinsic effect. Cultures of a selected PI line were treated with PR antisense oligodeoxynucleotides (ASPR) to inhibit in vitro cell proliferation. A significant decrease of 3H-thymidine uptake was observed in cells of a PI line growing in the presence of 2.5% charcoalized fetal calf serum and 0.8-20 microg/ml ASPR. It can be concluded that the PR pathway is an essential path in the growth stimulation of PI tumors.