Estrogen Receptor Signaling in the Endometrium: pathway analysis of agonists and antagonists

Endometrial cancer is the most common gynecological malignancy in Europe and the USA. In the normal endometrium, growth and differentiation is controlled by the ovarian hormones estrogen and progesterone. After menopause, the absence of follicle recruitment in the ovary results in a decline in serum levels of estrogen and progesterone, and consequently results in an atrophic/inactive state of the endometrium. However, in some women increased levels of estrogen (either endogenous or exogenous) are present, which will stimulate the endometrium. This estrogen-induced growth of the endometrium may result in uncontrolled growth, which can eventually develop into cancer. As in the normal endometrium, progesterone inhibits growth of endometrial cancer cells and is therefore used in the clinic as adjuvant therapy. Tamoxifen, a selective estrogen receptor modulator (SERM), is standard adjuvant therapy for patients with estrogen receptor positive (ER+) breast cancer (estrogen-antagonistic effect). In the endometrium, however, tamoxifen displays an estrogen-agonistic effect, and use of tamoxifen is therefore associated with an increased risk for development of endometrial pathologies, including endometrial cancer. For the endometrium, but also for many other organs, growth factors and growth factor receptors play a central role in mediating the effects of steroid hormones. Growth factors like IGF-1 and EGF mediate estrogen receptor signaling and are therefore also involved in the regulation of proliferation of the endometrium and endometrial cancer. The emphasis of this thesis is on the molecular mechanisms of estrogen receptor controlled proliferation of the human endometrium and subsequent induction of endometrial cancer. We postulated and addressed the following questions in this thesis: 1. What are the molecular mechanisms underlying estrogen-induced growth stimulation and progesterone-induced growth inhibition of endometrial cancer cells? 2. Does activation of the ER signaling pathway result in activation of IGF and/or EGF signaling, and vice versa, does activation of the IGF and EGF signaling pathways result in activation of ER signaling? 3. Which genes are regulated by estrogen, tamoxifen, raloxifene and the anti-estrogen ICI182780 in endometrial cancer cells, and do the four ER-ligands regulate similar genes, in the same cellular processes or pathways? 4. Which genes are regulated in endometrial tissues of tamoxifen-users compared to nonusers, and can we, based on the generated gene-expression profiles, elucidate which pathways are activated by tamoxifen during the early changes which may lead to endometrial cancer formation

Progestogenic effects of tibolone on human endometrial cancer cells

Tibolone, a synthetic steroid acting in a tissue-specific manner and used in hormone replacement therapy, is converted into three active metabolites: a Delta(4) isomer (exerting progestogenic and androgenic effects) and two hydroxy metabolites, 3 alpha-hydroxytibolone (3 alpha-OH-tibolone) and 3beta-OH-tibolone (exerting estrogenic effects). In the present study an endometrial carcinoma cell line (Ishikawa PRAB-36) was used to investigate the progestogenic properties of tibolone and its metabolites. This cell line contains progesterone receptors A and B, but lacks estrogen and androgen receptors. When tibolone was added to the cells, complete conversion into the progestogenic/androgenic Delta(4) isomer was observed within 6 d. Furthermore, when cells were cultured with tibolone or when the Delta(4) isomer or the established progestagen medroxyprogesterone acetate was added to the medium, marked inhibition of growth was observed. Interestingly, 3 beta-OH-tibolone also induces some inhibition of growth. These growth inhibitions were not observed in progesterone receptor-negative parental Ishikawa cells, and progestagen-induced growth inhibition of PRAB-36 cells could readily be reversed using the antiprogestagen Org-31489. Upon measuring the expression of two progesterone-regulated genes (fibronectin and IGF-binding protein-3), tibolone, the Delta(4) isomer and medroxyprogesterone acetate showed similar gene expression regulation. These results indicate that tibolone, the Delta(4) metabolite, and to some extent 3 beta-OH-tibolone exert progestogenic effects. Tibolone and most likely 3 beta-OH-tibolone are converted into the Delta(4) metabolite

Peer feedback content and sender’s competence level in academic writing revision tasks: Are they critical for feedback perceptions and efficiency?

Peer feedback content is a core component of peer assessment, but the impact of various contents of feedback is hardly studied. Participants in the study were 89 graduate students who were assigned to four experimental and a control group. Experimental groups received a scenario with Concise General (CGF) or Elaborated Specific (ESF) feedback by a high or low competent peer. ESF by a high competent peer was perceived as more adequate, but led to more negative affect. Students in CGF groups outperformed ESF groups during treatment. Groups with a low competent peer outperformed groups with a high competent peer during the posttest. Feedback perceptions and performance were uncorrelated

Consequences of loss of progesterone receptor expression in development of invasive endometrial cancer

PURPOSE: In endometrial cancer, loss of progesterone receptors (PR) is associated with more advanced disease. This study aimed to investigate the mechanism of action of progesterone and the loss of its receptors (PRA and PRB) in development of endometrial cancer. EXPERIMENTAL DESIGN: A 9600-cDNA microarray analysis was performed to study regulation of gene expression in the human endometrial cancer subcell line Ishikawa PRAB-36 by the progestagen medroxy progesterone acetate (MPA). Five MPA-regulated genes were selected for additional investigation. Expression of these genes was studied by Northern blot and by immunohistochemistry in Ishikawa subcell lines expressing different PR isoforms. Additionally, endometrial cancer tissue samples were immunohistochemically stained to study the in vivo protein expression of the selected genes. RESULTS: In the PRAB-36 cell line, MPA was found to regulate the expression of a number of invasion- and metastasis-related genes. On additional investigation of five of these genes (CD44, CSPG/Versican, Tenascin-C, Fibronectin-1, and Integrin-beta 1), it was observed that expression and progesterone regulation of expression of these genes varied in subcell lines expressing different PR isoforms. Furthermore, in advanced endometrial cancer, it was shown that loss of expression of both PR and E-cadherin was associated with increased expression CD44 and CSPG/Versican. CONCLUSION: The present study shows that progestagens exert a modulatory effect on the expression of genes involved in tumor cell invasion. As a consequence, loss of PR expression in human endometrial cancer may lead to development of a more invasive phenotype of the respective tumor

Exercise Improves Cognitive Responses to Psychological Stress through Enhancement of Epigenetic Mechanisms and Gene Expression in the Dentate Gyrus

Background We have shown previously that exercise benefits stress resistance and stress coping capabilities. Furthermore, we reported recently that epigenetic changes related to gene transcription are involved in memory formation of stressful events. In view of the enhanced coping capabilities in exercised subjects we investigated epigenetic, gene expression and behavioral changes in 4-weeks voluntarily exercised rats. Methodology/Principal Findings Exercised and control rats coped differently when exposed to a novel environment. Whereas the control rats explored the new cage for the complete 30-min period, exercised animals only did so during the first 15 min after which they returned to sleeping or resting behavior. Both groups of animals showed similar behavioral responses in the initial forced swim session. When re-tested 24 h later however the exercised rats showed significantly more immobility behavior and less struggling and swimming. If rats were killed at 2 h after novelty or the initial swim test, i.e. at the peak of histone H3 phospho-acetylation and c-Fos induction, then the exercised rats showed a significantly higher number of dentate granule neurons expressing the histone modifications and immediate-early gene induction. Conclusions/Significance Thus, irrespective of the behavioral response in the novel cage or initial forced swim session, the impact of the event at the dentate gyrus level was greater in exercised rats than in control animals. Furthermore, in view of our concept that the neuronal response in the dentate gyrus after forced swimming is involved in memory formation of the stressful event, the observations in exercised rats of enhanced neuronal responses as well as higher immobility responses in the re-test are consistent with the reportedly improved cognitive performance in these animals. Thus, improved stress coping in exercised subjects seems to involve enhanced cognitive capabilities possibly resulting from distinct epigenetic mechanisms in dentate gyrus neurons