Steroid hormone receptors and coregulators in endocrine-resistant and estrogen-independent breast cancer cells

Bromodomain-containing protein 4 activates androgen receptor transcription and promotes ovarian fibrosis in PCOS

Polycystic ovary syndrome (PCOS) is an endocrine disorder and the main cause of anovulatory infertility, in which persistent activation of androgen receptor (AR) due to aberrant acetylation modifications of transcription is a potential trigger; however, the precise mechanisms of AR activation are poorly understood. In this study, AR activation in dehydroepiandrosterone- and letrozole-induced rat PCOS ovaries coincided with a marked increase of a chromatin acetylation "reader" BRD4. Further bioinformatic analysis showed that the AR promoter contained highly conserved binding motifs of BRD4 and HIF-1α. BRD4 and HIF-1α inducibly bound to the histone 3/4 acetylation-modified AR promoter, while administration of a BRD4-selective inhibitor JQ1 reduced the binding and AR transcription and improved the adverse expression of the core fibrotic mediators in PCOS ovaries and DHT-treated granulosa cells. Our data indicate that BRD4 upregulation and the resultant AR transcriptional activation constitute an important regulatory pathway that promotes ovarian fibrosis in PCOS.

Hormonal Homologies between Canine Mammary Cancer and Human Breast Cancer in a Series of Cases

Simple Summary

There is worldwide interest in understanding the cancerous diseases that are causing increasing deaths in humans. In recent years, interest has grown in finding suitable models of different types of cancer in animals to lead the scientific community to a better understanding of the disease, in order to win the battle against cancer. The aim of this investigation was to compare breast cancer samples and canine mammary tumors from a hormonal point of view to validate the canine species as a model to study human breast cancer. There was a close similarity between premenopausal human breast cancer and canine mammary cancer in terms of hormonal receptors. In both species, all hormones assayed were increased in tumors compared to normal mammary gland samples. This research not only further supports canine mammary cancer as a spontaneous model for the study of human breast cancer but is also important in providing a deeper understanding of the hormonal pathogenesis of breast/mammary cancer in each independent species.

Abstract

The validity of spontaneous canine mammary cancer (CMC) as a natural model for the study of human breast cancer (HBC) from a hormonal point of view has never been thoroughly investigated. In this study, we analyzed the immunohistochemical expression of aromatase (Arom) and steroid receptors [estrogen receptor α (ER α), estrogen receptor β (ER β), progesterone receptor (PR) and androgen receptor (AR)] and intratumor steroid hormone levels of 17β-estradiol (E2), estrone sulfate (SO4E1), progesterone (P4), androstenedione (A4), dehydroepiandrosterone (DHEA), and testosterone (T) in 78 samples of mammary cancer—51 human breast cancer (HBC) and 27 canine mammary cancer (CMC)—and corresponding controls. Frequency of tumors expressing Arom, ERβ, PR, and AR was similar in both species, whereas ERα+ tumors were less frequent in the canine species. There was a closer similarity between premenopausal HBC and CMC. In HBC and CMC, all hormones assayed were increased in tumors compared to control samples. Intratumor androgen levels were similar in the two species, although levels of progesterone and estrogens were higher in the HBC samples than the CMC samples. Statistical associations among Arom, receptors, and hormones analyzed suggest that the major hormonal influence in both species is estrogenic through the ER, being the α isoform predominant in the human samples. Our findings further support CMC as a spontaneous model for the study of HBC, especially premenopausal HBC, although several differences, such as the more prevalent ERα immunoexpression and higher intratumor levels of estrogens and P4 in HBC, should be taken into account in comparative hormonal studies.

Molecular aspects of bovine cystic ovarian disease pathogenesis

Cystic ovarian disease (COD) is one of the main causes of reproductive failure in cattle and causes severe economic loss to the dairy farm industry because it increases both days open in the post partum period and replacement rates due to infertility. This disease is the consequence of the failure of a mature follicle to ovulate at the time of ovulation in the estrous cycle. This review examines the evidence for the role of altered steroid and gonadotropin signaling systems and the proliferation/apoptosis balance in the ovary with cystic structures. This evidence suggests that changes in the expression of ovarian molecular components associated with these cellular mechanisms could play a fundamental role in the pathogenesis of COD. The evidence also shows that gonadotropin receptor expression in bovine cystic follicles is altered, which suggests that changes in the signaling system of gonadotropins could play a fundamental role in the pathogenesis of conditions characterized by altered ovulation, such as COD. Ovaries from animals with COD exhibit a disrupted steroid receptor pattern with modifications in the expression of coregulatory proteins. These changes in the pathways of endocrine action would trigger the changes in proliferation and apoptosis underlying the aberrant persistence of follicular cysts.

Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R251/suppl/DC1.

Reduced expression of miR-200 family members contributes to antiestrogen resistance in LY2 human breast cancer cells

INTRODUCTION

The role of miRNAs in acquired endocrine-resistant breast cancer is not fully understood. One hallmark of tumor progression is epithelial-to-mesenchymal transition (EMT), characterized by a loss of cell adhesion resulting from reduced E-cadherin and increased cell mobility. miR-200 family members regulate EMT by suppressing expression of transcriptional repressors ZEB1/2. Previously we reported that the expression of miR-200a, miR-200b, and miR-200c was lower in LY2 endocrine-resistant, mesenchymal breast cancer cells compared to parental, endocrine sensitive, epithelial MCF-7 breast cancer cells. Here we investigated the regulation of miR-200 family members and their role in endocrine-sensitivity in breast cancer cells.

RESULTS

miR-200 family expression was progressively reduced in a breast cancer cell line model of advancing endocrine/tamoxifen (TAM) resistance. Concomitant with miR-200 decrease, there was an increase in ZEB1 mRNA expression. Overexpression of miR-200b or miR-200c in LY2 cells altered cell morphology to a more epithelial appearance and inhibited cell migration. Further, miR-200b and miR-200c overexpression sensitized LY2 cells to growth inhibition by estrogen receptor (ER) antagonists TAM and fulvestrant. Knockdown of ZEB1 in LY2 cells recapitulated the effect of miR-200b and miR-200c overexpression resulting in inhibition of LY2 cell proliferation by TAM and fulvestrant, but not the aromatase inhibitor exemestane. Demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC) in combination with histone deacetylase inhibitor trichostatin A (TSA) increased miR-200b and miR-200c in LY2 cells. Concomitant with the increase in miR-200b and miR-200c, ZEB1 expression was decreased and cells appeared more epithelial in morphology and were sensitized to TAM and fulvestrant inhibition. Likewise, knockdown of ZEB1 increased antiestrogen sensitivity of LY2 cells resulting in inhibition of cell proliferation.

CONCLUSIONS

Our data indicate that reduced miRNA-200b and miR-200c expression contributes to endocrine resistance in breast cancer cells and that the reduced expression of these miR-200 family members in endocrine-resistant cells can be reversed by 5-aza-dC+TSA.

Alteration in localization of steroid hormone receptors and coregulatory proteins in follicles from cows with induced ovarian follicular cysts

Cystic ovarian disease (COD) is an important cause of infertility in cattle. The altered follicular dynamics and cellular differentiation observed in COD may be mediated through a disruption of the expression of steroid receptors and their associated transcriptional cofactors. The aim of this study was to determine the protein expression profiles of ESR1, ESR2, PGR, AR, NCOA3, NCOR2, and PHB2 (REA) in ovarian follicles in an experimental model of COD induced by the administration of ACTH. Ovaries were collected and follicles were dissected from heifers during the follicular phase (control) or from heifers treated with ACTH to induce the formation of ovarian follicular cysts. Ovaries were fixed, sectioned, and stained immunohistochemically for steroid receptors and the associated transcription factors. The relative expression of ESR1 was similar in follicular cysts and in tertiary follicles from both control and cystic cows and was significantly higher than in secondary follicles. The expression of ESR2 in the granulosa was higher in cystic follicles. No differences were seen for PGR. The expression of androgen receptor was significantly increased in tertiary follicles with lower immunostaining in cysts. The expression of NCOA3 was observed in the granulosa and theca with a significantly increased expression in the theca interna of cystic follicles. The highest levels of NCOR2 expression in granulosa, theca interna, and theca externa were observed in cysts. In granulosa cells, NCOR2 levels increase progressively as follicles mature and the treatment had no effect. In summary, ovaries from animals with induced COD exhibited altered steroid receptor expression compared with normal animals, as well as changes in the expression of their regulators. It is reasonable to suggest that in conditions characterized by altered ovulation and follicular persistence, such as COD, changes in the intra-ovarian expression of these proteins could play a role in their pathogenesis.

Elevated nuclear expression of the SMRT corepressor in breast cancer is associated with earlier tumor recurrence

Silencing mediator of retinoic acid and thyroid hormone receptor (SMRT), also known as nuclear corepressor 2 (NCOR2) is a transcriptional corepressor for multiple members of the nuclear receptor superfamily of transcription factors, including estrogen receptor-α (ERα). In the classical model of corepressor action, SMRT binds to antiestrogen-bound ERα at target promoters and represses ERα transcriptional activity and gene expression. Herein SMRT mRNA and protein expression was examined in a panel of 30 breast cancer cell lines. Expression of both parameters was found to vary considerably amongst lines and the correlation between protein and mRNA expression was very poor (R (2) = 0.0775). Therefore, SMRT protein levels were examined by immunohistochemical staining of a tissue microarray of 866 patients with stage I-II breast cancer. Nuclear and cytoplasmic SMRT were scored separately according to the Allred score. The majority of tumors (67 %) were negative for cytoplasmic SMRT, which when detected was found at very low levels. In contrast, nuclear SMRT was broadly detected. There was no significant difference in time to recurrence (TTR) according to SMRT expression levels in the ERα-positive tamoxifen-treated patients (P = 0.297) but the difference was significant in the untreated patients (P = 0.01). In multivariate analysis, ERα-positive tamoxifen-untreated patients with high nuclear SMRT expression (SMRT 5-8, i.e., 2nd to 4th quartile) had a shorter TTR (HR = 1.94, 95 % CI, 1.24-3.04; P = 0.004) while there was no association with SMRT expression for ERα-positive tamoxifen-treated patients. There was no association between SMRT expression and overall survival for patients, regardless of whether they received tamoxifen. Thus while SMRT protein expression was not predictive of outcome after antiestrogen therapy, it may have value in predicting tumor recurrence in patients not receiving adjuvant tamoxifen therapy.

Inhibition of FOSL1 overexpression in antiestrogen-resistant MCF-7 cells decreases cell growth and increases vacuolization and cell death

Elevated activator protein-1 (AP-1) activity in breast cancer cells has been linked to Tamoxifen (TAM) resistance. Fos-like antigen-1 (FOSL1) is a member of the AP-1 transcription factor and is overexpressed in a variety of human cancers including breast tumors. We have previously established an estrogen-independent and antiestrogen Toremifene (TOR)-resistant subline of MCF-7 breast cancer cells. In these cells, the expression of FOSL1 is upregulated when compared to the parental cells. In the present study, partial inhibition of FOSL1 expression in these cells by small interfering RNA resulted in a marked decrease of cell growth. The inhibition of cell growth paralleled with changes in cell morphology such as increased formation of vacuoles followed by an increase in the number of dead cells. The inhibition of FOSL1 expression in these cells also restored sensitivity to TOR. Our results suggest that chemotherapy targeting overexpression of FOSL1 could be a potent strategy for treating endocrine resistant breast cancers.

Distinctive functions of p160 steroid receptor coactivators in proliferation of an estrogen-independent, tamoxifen-resistant breast cancer cell line

Elevated expression of steroid receptor coactivator-3 (SRC-3), a member of the p160 family of nuclear receptor coactivators, has been implicated in tamoxifen resistance of breast tumors while the involvement of the two other members of this family, SRC-1 and SRC-2, is less well characterized. In this study, using small interfering RNA-based silencing, the role of each SRC coactivator in the growth of the LCC2 estrogen-independent and tamoxifen-resistant breast cancer cell line was evaluated. The loss of SRC-1, SRC-2, or SRC-3 did not significantly alter LCC2 proliferation or cell cycle distribution of 4-hydroxytamoxifen- versus vehicle-treated cells. However, depletion of SRC-2 and SRC-3, but not SRC-1, decreased basal cell proliferation and increased apoptosis. Cell cycle analyses further illustrated the divergent contributions of SRC-2 and SRC-3 with depletion of the former increasing the percentage of cells in the G(0)G(1) and sub-G(0)G(1) phases of cell cycle yet maintaining sensitivity to estradiol and ICI 182 780 antiestrogen, while SRC-3 depletion increased cells in the sub-G(0)G(1) phase and ablated response to estrogen receptor α (ERα) ligands. Surprisingly, the effects of SRC coactivator depletion on ERα transcriptional activity, as measured by luciferase reporter gene, did not correspond to the observed effects on proliferation (e.g. SRC-1 knockdown increases ERα activity). Collectively, these data indicate that SRC control of basal and hormone-regulated proliferations is not solely mediated by ERα, and suggest that targeting growth inhibition by disrupting SRC-2 and SRC-3 function may be an effective approach to inhibit the growth of tamoxifen-resistant breast cancer.

Inhibition of MAP kinase promotes the recruitment of corepressor SMRT by tamoxifen-bound estrogen receptor alpha and potentiates tamoxifen action in MCF-7 cells

Estrogen receptor alpha (ERalpha), a ligand controlled transcription factor, plays an important role in breast cancer growth and endocrine therapy. Tamoxifen (TAM) antagonizes ERalpha activity and has been applied in breast cancer treatment. TAM-bound ERalpha associates with nuclear receptor-corepressors. Mitogen-activated protein kinase (MAPK) has been elucidated to result in cross-talk between growth factor and ERalpha mediated signaling. We show that activated MAPK represses interaction of TAM-bound ERalpha with silencing mediator for retinoid and thyroid hormone receptors (SMRT) and inhibits the recruitment of SMRT by ERalpha to certain estrogen target genes. Blockade of MAPK signaling cascade with MEK inhibitor U0126 promotes the interaction and subsequently inhibits ERalpha activity via enhanced recruitment of SMRT, leading to reduced expression of ERalpha target genes. The growth rate of MCF-7 cells was decelerated when treated with both TAM and U0126. Moreover, the growth of MCF-7 cells stably expressing SMRT showed a robust repression in the presence of TAM and U0126. These results suggest that activated MAPK signaling cascade attenuates antagonist-induced recruitment of SMRT to ERalpha, suggesting corepressor mediates inhibition of ERalpha transactivation and breast cancer cell growth by antagonist. Taken together, our finding indicates combination of antagonist and MAPK inhibitor could be a helpful approach for breast cancer therapy.

Cooperative activation of cyclin D1 and progesterone receptor gene expression by the SRC-3 coactivator and SMRT corepressor

Although the ability of coactivators to enhance the expression of estrogen receptor-alpha (ERalpha) target genes is well established, the role of corepressors in regulating 17beta-estradiol (E2)-induced gene expression is poorly understood. Previous studies revealed that the silencing mediator of retinoic acid and thyroid hormone receptor (SMRT) corepressor is required for full ERalpha transcriptional activity in MCF-7 breast cancer cells, and we report herein the E2-dependent recruitment of SMRT to the regulatory regions of the progesterone receptor (PR) and cyclin D1 genes. Individual depletion of SMRT or steroid receptor coactivator (SRC)-3 modestly decreased E2-induced PR and cyclin D1 expression; however, simultaneous depletion revealed a cooperative effect of this coactivator and corepressor on the expression of these genes. SMRT and SRC-3 bind directly in an ERalpha-independent manner, and this interaction promotes E2-dependent SRC-3 binding to ERalpha measured by co-IP and SRC-3 recruitment to the cyclin D1 gene as measured by chromatin IP assays. Moreover, SMRT stimulates the intrinsic transcriptional activity of all of the SRC family (p160) coactivators. Our data link the SMRT corepressor directly with SRC family coactivators in positive regulation of ERalpha-dependent gene expression and, taken with the positive correlation found for SMRT and SRC-3 in human breast tumors, suggest that SMRT can promote ERalpha- and SRC-3-dependent gene expression in breast cancer.

Oestradiol and SERM treatments influence oestrogen receptor coregulator gene expression in human skeletal muscle cells

AIM

Oestrogen receptors (ER) are present in human skeletal muscle (hSkM) cells; however, the function of the receptor is currently unknown. We investigated the influence of oestradiol and selective ER modulators [tamoxifen (TAM), raloxifene (RAL)] on ER coregulator mRNA expression in hSkM.

METHODS

Human skeletal muscle cells were treated with 10 nm oestradiol, 5 microm TAM and 10 microm RAL over a 24-h period. Following the treatment period, mRNA expression was quantified using real-time PCR to detect changes in ER-alpha, ER-beta, steroid receptor coactivator (SRC), silencing mediator for retinoid and thyroid hormone receptors (SMRT), MyoD, GLUT4 and c-fos.

RESULTS

ER-alpha mRNA expression increased with all three drug treatments (P < 0.05) while there was no change in mRNA expression of ER-beta in hSkM cells. mRNA expression of SRC increased and SMRT decreased with oestradiol, TAM and RAL in hSkM cells (P < 0.05). Importantly, mRNA expression of MyoD increased with oestradiol and decreased with TAM and RAL in hSkM cells (P < 0.05). mRNA expression of GLUT4 increased with oestradiol and RAL and decreased with TAM in hSkM cells (P < 0.05).

CONCLUSIONS

These findings are novel in that they provide the first evidence that oestradiol and selective ER modulators influence ER-alpha function in hSkM cells. This demonstrates the importance of the ER and alterations in its coregulators, to potentially prevent sarcopenia and promote muscle growth in postmenopausal women using these forms of hormone replacement therapy.

Gene expression changes during the development of estrogen-independent and antiestrogen-resistant growth in breast cancer cell culture models

We have established estrogen-independent and antiestrogen-resistant cell lines from hormone-dependent MCF-7 breast cancer cells by long-term culture in the absence of estrogen, or in the presence of antiestrogen toremifene, respectively. By using a cDNA microarray we compared gene expression profiles among estrogen-independent, antiestrogen-resistant and long-term estrogen-treated MCF-7 cells. We also determined how the expression of the differentially expressed genes has developed during the long-term culture of the cell lines. Of the screened 1176 cancer-related genes, FOSL1, TIMP1, L1CAM, GDF15, and MYBL2 were found to be differentially expressed between the cell lines. A change in FOSL1 and TIMP1 expression could be attributed to the development of antiestrogen resistance, whereas induced L1CAM expression was implicated in the development of estrogen-independent growth of the cells. Estrogen regulated genes GDF15 and L1CAM became regulated by toremifene in the later passage number of toremifene-resistant cells, which might be an indication of the developed estrogen-agonistic activity of toremifene in these cells. Our findings suggest a pattern where the hormone-responsive cancer cells, which survive E2 deprivation and/or antiestrogen treatment, first acquire necessary changes in gene expression for transition to maximal growth in the new hormonal environment. Then, after prolonged treatment with antiestrogen, the antiestrogen-resistant cells may eventually generate an E2-agonistic response to antiestrogen, probably acquiring additional growth advantage.

Estradiol and tamoxifen mediate rescue of the dominant-negative effects of estrogen response element-binding protein in vivo and in vitro

Biological responses to estrogens are dependent on the integrated actions of proteins, including the estrogen receptor (ER)-alpha, that regulate the transcription of estrogen response element (ERE)-containing target genes. We have identified a naturally occurring ERE antagonist, termed an ERE-binding protein (BP). To verify that ERE-BP can induce estradiol (E(2)) resistance in vivo, we generated transgenic mice that overexpress this protein in breast tissue. Female transgenic mice with high levels of ERE-BP were unable to lactate, and we hypothesized that this effect was dependent on the relative levels of ERE-BP and ERalpha ligand. To test this hypothesis, wild-type and ERE-BP-expressing female mice were implanted with capsules containing E(2), the selective estrogen receptor modulator tamoxifen, or placebo. Histological analysis of nonlactating mammary glands showed a 4.5-fold increase in gland branch number and 3.7-fold increase in ducts in ERE-BP mice treated with E(2) (7.5 mg, 21 d) compared with placebo-treated ERE-BP mice. Wild-type mice showed a 5.3-fold increase in branches and 1.4-fold increase in ducts under the same conditions. Similar results were obtained with tissue from lactating mice, in which tamoxifen also increased mammary gland branch number. Studies using ERE-BP-expressing MCF-7 breast cells showed that high doses of E(2) (1000 nM) restored normal ERalpha-chromatin interaction in these cells, whereas tamoxifen was able to achieve this effect at a dose of 10 nM. These data highlight the importance of ERE-BP as an attenuator of normal ERalpha signaling in vivo and further suggest that ERE-BP is a novel target for modulation by selective estrogen receptor modulators.

Unique roles of p160 coactivators for regulation of breast cancer cell proliferation and estrogen receptor-alpha transcriptional activity

Each of the three members of the p160 steroid receptor coactivator (SRC) family of coactivators (SRC-1, SRC-2 and SRC-3) stimulates estrogen receptor (ER)-alpha function in trans-activation assays. Consequently, we sought to elucidate their contributions to the ER-regulated processes of cell proliferation, apoptosis, and the expression of ERalpha target genes in MCF-7 breast cancer cells. The small interfering RNA depletion of SRC-2 or SRC-3 but not SRC-1 inhibited growth of MCF-7 cells, and this was reflected in decreased cell cycle progression and increased apoptosis in SRC-2- or SRC-3-depleted cells as well as a reduction in ERalpha transcriptional activity measured on a synthetic reporter gene. However, only SRC-3 depletion blocked estradiol stimulated cell proliferation. Depletion of SRC-1 did not affect these events, and together this reveals functional differences between each of the three SRC family coactivators. Regulation of the endogenous ERalpha target gene, c-myc was not affected by depletion of any of the p160 coactivators although depletion of each of them decreased pS2 mRNA expression in estradiol-treated MCF-7 cells. Moreover, progesterone receptor and cyclin D1 gene expression were decreased in SRC-3 small interfering RNA-treated cells. Expression of mRNA and protein levels for the antiapoptotic gene, Bcl-2 was dependent on SRC-3 expression, whereas Bcl-2 protein but not mRNA expression also was sensitive to SRC-1 depletion. Together these data indicate that the closely related p160 coactivators are not functionally redundant in breast cancer cells because they play gene-specific roles in regulating mRNA and protein expression, and they therefore are likely to make unique contributions to breast tumorigenesis.

Comparison of an Automated Pattern Analysis Machine Vision Time-lapse System with Traditional Endpoint Measurements in the Analysis of Cell Growth and Cytotoxicity

Machine vision is an application of computer vision. It both collects visual information and interprets the images. Although the machine obviously does not ‘see’ in the same sense that humans do, it is possible to acquire visual information and to create programmes to identify relevant image features in an effective and consistent manner. Machine vision is widely applied in industrial automation, but here we describe how we have used it to monitor and interpret data from cell cultures. The machine vision system used (Cell-IQ) consisted of an inbuilt atmosphere-controlled incubator, where cell culture plates were placed during the test. Artificial intelligence (AI) software, which uses machine vision technology, took care of the follow-up analysis of cellular morphological changes. Basic endpoint and staining methods to evaluate the condition of the cells, were conducted in parallel to the machine vision analysis. The results showed that the automated system for pattern analysis of morphological changes yielded comparable results to those obtained by conventional methods. The inbuilt software analysis offers a promising way of evaluating cell growth and various cell phases. The continuous follow-up and label-free analysis, as well as the possibility of measuring multiple parameters simultaneously from the same cell population, were major advantages of this system, as compared to conventional endpoint measurement methodology.

Epidermal growth factor receptor (EGFR) and the estrogen receptor modulator amplified in breast cancer (AIB1) for predicting clinical outcome after adjuvant tamoxifen in breast cancer

The epidermal growth factor receptor (EGFR) and the estrogen receptor (ER) modulator Amplified In Breast cancer-1 (AIB1) have been reported to be of importance for the prognosis of breast cancer patients. We have analyzed AIB1 and EGFR by immunohistochemistry in primary breast cancers (n = 297) arranged in a tissue microarray in order to predict outcome after adjuvant endocrine therapy with tamoxifen for two years. High expression of AIB1 was associated with DNA-nondiploidy, high S-phase fraction, HER2 amplification, and short term (<or=2 years) distant disease-free survival (DDFS), independent of ER status. High expression of EGFR was strongly associated to ER negativity and also correlated with progesterone receptor negativity, high S-phase fraction, and inversely correlated with nodal metastases. In univariate analysis, high EGFR was associated with shorter DDFS (hazard ratio 2.1; P = 0.017), and reached borderline significance in a multivariate analysis, adjusting for ER, menopausal and lymph node status, tumor size, and HER2 (P = 0.057). In conclusion, both AIB1 and EGFR were associated to DDFS for breast cancer patients treated with two years of adjuvant tamoxifen; AIB1 with the development of early distant recurrences, indicating association between high AIB1 and resistance to tamoxifen during treatment, and EGFR with distant recurrences up to a follow up of five years.

Identification of VDR-responsive gene signatures in breast cancer cells

OBJECTIVES

Defining transcriptional profiles which predict cancer cell anti-proliferative responsiveness towards 1,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] is required to improve and tailor the chemotherapeutic application of this seco-steroid hormone to individual cancer patients.

METHODS

We undertook a transcriptomic approach with Affymetrix human U133 GeneChips to determine responsive and resistant gene signatures in MCF-7 breast cancer cells and 1alpha,25(OH)(2)D(3)-resistant MCF-7(Res) cells, respectively. Principal component and hierarchical clustering analyses demonstrated that the patterns of responsiveness between the 2 cell types differed clearly and were used to generate heat maps. Differentially regulated gene targets were validated with Q-RT-PCR and the biological impact upon proliferation measured.

RESULTS

In untreated MCF-7(Res) cells, 163 genes were up-regulated and 274 down-regulated (with a log(2) ratio of >0.5) compared to the MCF-7 controls. Using the same gene expression threshold, 1alpha,25(OH)(2)D(3) treatment (100 nM, 6 h) of MCF-7 cells up-regulated 91 genes and down-regulated 5, whereas in MCF-7(Res), despite their resistance to the anti-proliferative effects, 156 genes were modulated with 91 being down-regulated. Strikingly, CYP24 was the only induced gene that was common to the genetic profiles of the 2 sets of 1alpha,25(OH)(2)D(3)-treated cells. Heat map analyses defined 2 sub-clusters of genes: (1) basal expression patterns associated with insensitivity towards 1alpha,25(OH)(2)D(3) and (2) regulated expression patterns associated with 1alpha,25(OH)(2)D(3) sensitivity. This latter cluster contained BAX, GADD45alpha, IGFBP-3, EGFR, MAPK4 and TGF-beta(2). Time course studies confirmed the 1alpha,25(OH)(2)D(3) regulation of TGF-beta(2) in MCF-7 and non-tumourigenic MCF-12A cells but not in MCF-7(Res) cells. Co-treatment of MCF-7(Res) cells with exogenous TGF-beta(2) plus 1alpha,25(OH)(2)D(3) enhanced anti-proliferative and vitamin D receptor transcriptional effects.

CONCLUSIONS

Basal and regulated gene patterns can be used to predict and monitor the cellular response towards vitamin D(3) compounds and may possibly be applied as a further diagnostic tool.

Quantitative structure spectroscopy relationships of carbon-13 nuclear magnetic resonance chemical shifts of steroids

Quantitative structure spectroscopy relationships (QSSRs) are systematically studied for carbon-13 nuclear magnetic resonance ((13)C NMR) spectroscopic simulation of steroid compounds. Both the atomic electronegativity interaction vector (AEIV) and the atomic hybridization state index (AHSI) are used for the expression of local chemical microenvironment and atomic hybridization state of 4434 resonance carbon atoms in 203 steroid molecules. A multiple linear regression (MLR) model is built after screening some insignificant parameters with the stepwise multiple regression (SMR) technique. Correlation coefficients of the developed model are R(cum)(2)=0.9341 and Q(LOO)(2)=0.9336 for classical estimation of molecular modeling and the cross-validation with leave-one-out (LOO) procedures, respectively, primarily indicating that the MLR model has good modeling stability and prediction ability. Furthermore, the superior performance of the MLR model is tested by the leave-33%-out (L33%O) cross-validation method, where the mean correlation coefficients of three test sets are Q(2)=0.9310 and Q(ext)(2)=0.9196 for both internal and external sets. In conclusion, AEIV and AHSI descriptors can be used for estimating and predicting (13)C NMR chemical shifts of steroids.