Marginal activity of progesterone receptor B (PR-B) in dogs but high incidence of mammary cancer

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

No significant association between progesterone receptor exon 4 Val660Leu G/T polymorphism and risk of ovarian cancer

Epidemiological studies suggest that ovarian cancer is an endocrine-related tumour, and progesterone exposure specifically may decrease the risk of ovarian cancer. To assess whether the progesterone receptor (PR) exon 4 valine to leucine amino acid variant is associated with specific tumour characteristics or with overall risk of ovarian cancer, we examined 551 cases of epithelial ovarian cancer and 298 unaffected controls for the underlying G-->T nucleotide substitution polymorphism. Stratification of the ovarian cancer cases according to tumour behaviour (low malignant potential or invasive), histology, grade or stage failed to reveal any heterogeneity with respect to the genotype defined by the PR exon 4 polymorphism. Furthermore, the genotype distribution did not differ significantly between ovarian cancer cases and unaffected controls. Compared with the GG genotype, the age-adjusted odds ratio (95% confidence interval) for risk of ovarian cancer was 0.78 (0.57-1.08) for the GT genotype, and 1.39 (0.47-4.14) for the TT genotype. In conclusion, the PR exon 4 codon 660 leucine variant encoded by the T allele does not appear to be associated with ovarian tumour behaviour, histology, stage or grade. This variant is also not associated with an increased risk of ovarian cancer, and is unlikely to be associated with a large decrease in ovarian cancer risk, although we cannot rule out a moderate inverse association between the GT genotype and ovarian cancer.

The progesterone receptor exon 4 Va1660Leu G/T polymorphism and risk of breast cancer in Australian women

An Alu insertion polymorphism of the progesterone receptor (PR) was reported recently to be associated with a reduced risk of breast cancer, with risks of 0.8- and 0.3-fold associated with the heterozygote and homozygote genotypes, respectively. This intronic variant is considered to be in linkage disequilibrium with an exon 4 hinge region G to T Val660Leu polymorphism. We investigated whether the exon 4 PR polymorphism was associated with breast cancer in Australian women, using a population-based study of 1452 cases and 793 controls, half of whom were

Evaluation of estrogen receptor alpha and beta and progesterone receptor expression and correlation with clinicopathologic factors and proliferative marker Ki-67 in breast cancers

To elucidate the molecular profile of hormonal steroid receptor status, we analyzed ER-alpha, ER-beta, and PGR mRNA and protein expression in 80 breast carcinomas using reverse transcriptase polymerase chain reaction (RT-PCR), quantitative RT-PCR, and immunohistochemical analysis. Qualitative analysis revealed positive expression of ER-alpha, ER-beta, and PGR mRNA in 48%, 59%, and 48% of the breast carcinomas, respectively. ER-alpha, ER-beta, and PGR transcript overexpression was observed in 51%, 0%, and 12% of the cases, respectively, whereas moderate or strong protein expression was detected in 68%, 78%, and 49% of the cases, respectively. Tumor grade was negatively correlated with transcript and protein levels of ER-alpha (P = .0169 and P = .0006, respectively) and PGR (P = .0034 and P = .0005, respectively). Similarly, proliferative index Ki-67 was negatively associated with transcript and protein levels of ER-alpha (P = .0006 and P < .0001, respectively) and PGR (P = .0258 and P =. 0005, respectively). These findings suggest that ER-alpha and PGR expression are associated with well-differentiated breast tumors and less directly related to cell proliferation. A significant statistical difference was observed between lymph node status and ER-beta protein expression (P = .0208). In ER-alpha-negative tumors, we detected a correlation between ER-beta protein expression and high levels of Ki-67. These data suggest that ER-beta could be a prognostic marker in human breast cancer. (C) 2008 Elsevier B.V. All rights reserved.

The extreme C terminus of progesterone receptor contains a transcriptional repressor domain that functions through a putative corepressor.

Binding of a hormone agonist to a steroid receptor leads to the dissociation of heat shock proteins, dimerization, specific DNA binding, and target gene activation. Although the progesterone antagonist RU486 can induce most of these events, it fails to activate human progesterone receptor (hPR)-dependent transcription. We have previously demonstrated that a conformational change is a key event leading to receptor activation. The major conformational distinction between hormone- and antihormone-bound receptors occurs within the C-terminal portion of the molecule. Furthermore, hPR mutants lacking the C terminus become transcriptionally active in the presence of RU486. These results suggest that the C terminus contains a repressor domain that inhibits the transcriptional activity of the RU486-bound hPR. In this study, we have defined a 12 amino acid (12AA) region in the C terminus of hPR that is necessary and sufficient for the repressor function when fused to the C-terminal truncated hPR or to the GAL4 DNA-binding domain. Mutations in the 12AA domain (aa 917-928) generate an hPR that is active in the presence of RU486. Furthermore, overexpression of the 12AA peptide activates the RU486-bound wild-type hPR without affecting progesterone-dependent activation. These results suggest that association of the 12AA repressor region with a corepressor might inactivate hPR activity when it is bound to RU486. We propose that binding of a hormone agonist to the receptor changes its conformation in the ligand-binding domain so that association with coactivator is promoted and activation of target gene occurs.

16 alpha-substituted analogs of the antiprogestin RU486 induce a unique conformation in the human progesterone receptor resulting in mixed agonist activity.

Previously, we have shown that agonists and antagonists interact with distinct, though overlapping regions within the human progesterone receptor (hPR) resulting in the formation of structurally different complexes. Thus, a link was established between the structure of a ligand-receptor complex and biological activity. In this study, we have utilized a series of in vitro assays with which to study hPR pharmacology and have identified a third class of hPR ligands that induce a receptor conformation which is distinct from that induced by agonists or antagonists. Importantly, when assayed on PR-responsive target genes these compounds were shown to exhibit partial agonist activity; an activity that was influenced by cell context. Thus, as has been shown previously for estrogen receptor, the overall structure of the ligand-receptor complex is influenced by the nature of the ligand. It appears, therefore, that the observed differences in the activity of some PR and estrogen receptor ligands reflect the ability of the cellular transcription machinery to discriminate between the structurally different complexes that result following ligand interaction. These data support the increasingly favored hypothesis that different ligands can interact with different regions within the hormone binding domains of steroid hormone receptors resulting in different biologies.

Modulation of AP-1 activity by the human progesterone receptor in endometrial adenocarcinoma cells.

The composite transcription factor activating protein 1 (AP-1) integrates various mitogenic signals in a large number of cell types, and is therefore a major regulator of cell proliferation. In the normal human endometrium, proliferation and differentiation alternate in a cyclic fashion, with progesterone being largely implicated in the latter process. However, the effects of progesterone and the progesterone receptor (hPR) on AP-1 activity in the human endometrium are not known. To address this issue, HEC-1-B endometrial adenocarcinoma cells, which are devoid of hPR, were transfected with luciferase reporter constructs driven by two different AP-1-dependent promoters. Unexpectedly, cotransfection of hPR caused a marked induction of luciferase activity in the absence of ligand on both promoters. The magnitude of this induction was similar to that observed in response to the phorbol ester TPA. Addition of ligand reversed the stimulating effect of the unliganded hPR on AM activity in these cells. These effects were specific for hPR, and were not observed with either human estrogen receptor or human glucocorticoid receptor. Furthermore, they strictly depended on the presence of AP-1-responsive sequences within target promoters. Finally, the described effects of hPR on AP-1 activity were shown to be cell-type specific, because they could not be demonstrated in SKUT-1-B, JEG-3, and COS-7 cells. To our knowledge this is the first report of an unliganded steroid receptor stimulating AP-1 activity. This effect and its reversal in the presence of ligand suggest a novel mechanism, through which hPR can act as a key regulator of both proliferation and differentiation in the human endometrium.

Oestrogen and Progesterone Receptor Gene Expression in Canine Oocytes and Cumulus Cells Throughout the Oestrous Cycle

The aim of this research was to analyze oestrogen receptor-alpha (ER alpha), ER beta and progesterone receptor (PR) gene expression in the canine oocyte and cumulus cells throughout the oestrous cycle. Ovaries from 38 bitches were recovered after ovariohysterectomy and sliced. The phase of the oestrous cycle was determined by vaginal cytology, vaginoscopy and serum hormonal measurements. Oocytes were mechanically denuded by repeated pipetting. For each phase of the cycle, a sample was composed by a pool of 50 oocytes (sample number: prooestrus = 3, oestrus = 8, dioestrus = 5 and anoestrus = 5) or a pool of cumulus cells (prooestrus = 4, oestrus = 7, dioestrus = 4 and anoestrus = 6). Oocyte and cumulus cells` total RNA was isolated and reverse transcription was conducted to perform real-time PCR. Oestrogen receptor-alpha was expressed throughout the cycle in the oocyte (33.33%, 25.0%, 20.0% and 60.0% for prooestrus, oestrus, dioestrus and anoestrus, respectively) and cumulus cells (50.0%, 47.14%, 25.0% and 66.67% for prooestrus, oestrus, dioestrus and anoestrus, respectively). In the oocyte, the ER beta was also expressed in all phases of the cycle (33.33%, 50.0%, 20.0% and 60.0% for prooestrus, oestrus, dioestrus and anoestrus, respectively), whereas in cumulus cells, ER beta was only expressed during prooestrus (50%) and oestrus (14.29%). Interestingly, while the oocyte PR was not detected in any phase of the cycle, this receptor was expressed during prooestrus (50%), oestrus (42.86%) and anoestrus (16.67%) in cumulus cells. In conclusion, canine oocytes express ER alpha and ER beta throughout the oestrous cycle, however, there is a lack of PR expression in all these phases. Moreover, in cumulus cells, only ER alpha was expressed throughout the oestrous cycle.

Polymorphism in CYP17, GSTM1 and the progesterone receptor genes and its relationship with mammographic density

Radiologic breast density is one of the predictive factors for breast cancer and the extent of the density is directly related to postmenopause. However, some patients have dense breasts even during postmenopause. This condition may be explained by the genes that codify for the proteins involved in the biosynthesis, as well as the activity and metabolism of steroid hormones. They are polymorphic, which could explain the variations of individual hormones and, consequently, breast density. The constant need to find markers that may assist in the primary prevention of breast cancer as well as in selecting high risk patients motived this study. We determined the influence of genetic polymorphism of CYP17 (cytochrome P450c17, the gene involved in steroid hormone biosynthesis), GSTM1 (glutathione S-transferase M1, an enzyme involved in estrogen metabolism) and PROGINS (progesterone receptor), for association with high breast density. One hundred and twenty-three postmenopausal patients who were not on hormone therapy and had no clinical or mammographic breast alterations were included in the present study. The results of this study reveal that there was no association between dense breasts and CYP17 or GSTM1. There was a trend, which was not statistically significant (P = 0.084), towards the association between PROGINS polymorphism and dense breasts. However, multivariate logistic regression showed that wild-type PROGINS and mutated CYP17, taken together, resulted in a 4.87 times higher chance of having dense breasts (P = 0.030). In conclusion, in the present study, we were able to identify an association among polymorphisms, involved in estradiol biosyntheses as well as progesterone response, and radiological mammary density.

Activation of Progesterone Receptor by ATP

Progesterone-receptor complex from freshly prepared hen oviduct cytosol acquired the ability to bind to isolated nuclei, DNA-cellulose and ATP-Sepharose when incubated with 5-10 mM ATP at 4°C. The extent of this ATP-dependent activation was higher when compared with heat-activation achieved by warming the progesterone- receptor complex at 23 °C. The transformation of progesterone-receptor complex which occurred in a time-dependent manner was only partially dependent on hormone presence. The ATP effect was selective in causing this transformation whereas ADP, AMP and cAMP failed to show any such effect. The non-hydrolizable analogs of ATP, adenosine 5'-[a,/3-methylene]triphosphate and adenosine 5-[/l,y-imido]triphosphate were also found to be ineffective. Presence of 10 mM sodium molybdate blocked both the ATP and the heat-activation of progesterone-receptor complex. Mn" or Mg` had no detectable effect on the receptor activation but the presence of Ca" increased the extent of ATP-activation slightly. EDTA presence (> 5 mM) decreased the extent of receptor activation by about 40 % and was, therefore, not included in the buffers used for activation studies. Divalent cations were also ineffective when tested in the presence of 1- 5 mM EDTA. The properties of progesterone-receptor complex remained intact under the above conditions when analyzed for steroid-binding specificity and Scatchard analysis. However, the ATP-activated progesterone-receptor complex lost the ability to aggregate when tested on low-salt sucrose gradients. ATP was equally effective in activating the rat-uterine estradiol-receptor complex at 4 "C and influenced the transformation of 4-S receptor form into a 5-S form when analyzed on sucrose gradients containing 0.3 M KCI. The presence of ATP also increased the rate of activation of progesterone-receptor complex at 23 °C. These findings suggest a role for ATP in receptor function and offer a convenient method of studying the process of receptor activation at low temperature and mild assay conditions.

Melatonin and ethanol intake exert opposite effects on circulating estradiol and progesterone and differentially regulate sex steroid receptors in the ovaries, oviducts, and uteri of adult rats

Chronic ethanol intake is associated with sex hormone disturbances, and it is well known that melatonin plays a key role in regulating several reproductive processes. We report the effects of ethanol intake and melatonin treatment (at doses of 100. μg/100. g. BW/day) on sex hormones and steroid receptors in the ovaries, oviducts and uteri of ethanol-preferring rats. After 150 days of treatment, animals were euthanized, and tissue samples were harvested to evaluate androgen, estrogen, progesterone and melatonin receptor subunits (AR, ER-α and ER-β, PRA, PRB and MT1R, respectively). Melatonin decreased estradiol (E2) and increased progesterone (P4) and 6-sulfatoxymelatonin (6-STM), while an ethanol-melatonin combination reduced both P4 and E2. Ovarian AR was not influenced by either treatment, and oviduct AR was reduced after ethanol-melatonin combination. Oviduct ER-α, ER-β and uterine ER-β were down-regulated by either ethanol or melatonin. Conversely, ovarian PRA and PRB were positively regulated by ethanol and ethanol-melatonin combination, whereas PRA was down-regulated in the uterus and oviduct after ethanol consumption. MT1R was increased in ovaries and uteri of melatonin-treated rats. Ethanol and melatonin exert opposite effects on E2 and P4, and they differentially regulate the expression of sex steroid receptors in female reproductive tissues. © 2013 Elsevier Inc.

Tyrosine kinase receptor B (TrkB) expression in colorectal cancers highlights anoikis resistance as a survival mechanism of tumour budding cells.

AIMS Tumour buds in colorectal cancer represent an aggressive subgroup of non-proliferating and non-apoptotic tumour cells. We hypothesize that the survival of tumour buds is dependent upon anoikis resistance. The role of tyrosine kinase receptor B (TrkB), a promoter of epithelial-mesenchymal transition and anoikis resistance, in facilitating budding was investigated. METHODS AND RESULTS Tyrosine kinase receptor B immunohistochemistry was performed on a multiple-punch tissue microarray of 211 colorectal cancer resections. Membranous/cytoplasmic and nuclear expression was evaluated in tumour and buds. Tumour budding was assessed on corresponding whole tissue slides. Relationship to Ki-67 and caspase-3 was investigated. Analysis of Kirsten Ras (KRAS), proto-oncogene B-RAF (BRAF) and cytosine-phosphate-guanosine island methylator phenotype (CIMP) was performed. Membranous/cytoplasmic and nuclear TrkB were strongly, inversely correlated (P < 0.0001; r = -0.41). Membranous/cytoplasmic TrkB was overexpressed in buds compared to the main tumour body (P < 0.0001), associated with larger tumours (P = 0.0236), high-grade budding (P = 0.0011) and KRAS mutation (P = 0.0008). Nuclear TrkB was absent in buds (P <0.0001) and in high-grade budding cancers (P =0.0073). Among patients with membranous/cytoplasmic TrkB-positive buds, high tumour membranous/cytoplasmic TrkB expression was a significant, independent adverse prognostic factor [P = 0.033; 1.79, 95% confidence interval (CI) 1.05-3.05]. Inverse correlations between membranous/cytoplasmic TrkB and Ki-67 (r = -0.41; P < 0.0001) and caspase-3 (r =-0.19; P < 0.05) were observed. CONCLUSIONS Membranous/cytoplasmic TrkB may promote an epithelial-mesenchymal transition (EMT)-like phenotype with high-grade budding and maintain viability of buds themselves.

Detection and functional portrayal of a novel class of dihydrotestosterone derived selective progesterone receptor modulators (SPRM).

In early pregnancy, abortion can be induced by blocking the actions of progesterone receptors (PR). However, the PR antagonist, mifepristone (RU38486), is rather unselective in clinical use because it also cross-reacts with other nuclear receptors. Since the ligand-binding domain of human progesterone receptor (hPR) and androgen receptor (hAR) share 54% identity, we hypothesized that derivatives of dihydrotestosterone (DHT), the cognate ligand for hAR, might also regulate the hPR. Compounds designed and synthesized in our laboratory were investigated for their affinities for hPRB, hAR, glucocorticoid receptor (hGRα) and mineralocorticoid receptor (hMR), using whole cell receptor competitive binding assays. Agonistic and antagonistic activities were characterized by reporter assays. Nuclear translocation was monitored using cherry-hPRB and GFP-hAR chimeric receptors. Cytostatic properties and apoptosis were tested on breast cancer cells (MCF7, T-47D). One compound presented a favorable profile with an apparent neutral hPRB antagonistic function, a selective cherry-hPRB nuclear translocation and a cytostatic effect. 3D models of human PR and AR with this ligand were constructed to investigate the molecular basis of selectivity. Our data suggest that these novel DHT-derivatives provide suitable templates for the development of new selective steroidal hPR antagonists.