Molecular characterization of the craniosynostosis-associated interleukin-11 receptor variants p.T306_S308dup and p.E364_V368del.

Interleukin-11 (IL-11) is a member of the IL-6 family of cytokines and is an important factor for bone homeostasis. IL-11 binds to and signals via the membrane-bound IL-11 receptor (IL-11R, classic signaling) or soluble forms of the IL-11R (sIL-11R, trans-signaling). Mutations in the IL11RA gene, which encodes the IL-11R, are associated with craniosynostosis, a human condition in which one or several of the sutures close prematurely, resulting in malformation of the skull. The biological mechanisms of how mutations within the IL-11R are linked to craniosynostosis are mostly unexplored. In this study, we analyze two variants of the IL-11R described in craniosynostosis patients: p.T306_S308dup, which results in a duplication of three amino-acid residues within the membrane-proximal fibronectin type III domain, and p.E364_V368del, which results in a deletion of five amino-acid residues in the so-called stalk region adjacent to the plasma membrane. The stalk region connects the three extracellular domains to the transmembrane and intracellular region of the IL-11R and contains cleavage sites for different proteases that generate sIL-11R variants. Using a combination of bioinformatics and different biochemical, molecular, and cell biology methods, we show that the IL-11R-T306_S308dup variant does not mature correctly, is intracellularly retained, and does not reach the cell surface. In contrast, the IL-11R-E364_V368del variant is fully biologically active and processed normally by proteases, thus allowing classic and trans-signaling of IL-11. Our results provide evidence that mutations within the IL11RA gene may not be causative for craniosynostosis and suggest that other regulatory mechanism(s) are involved but remain to be identified.

Interleukin-11 is important for vascular smooth muscle phenotypic switching and aortic inflammation, fibrosis and remodeling in mouse models.

Transforming growth factor beta-1 (TGFß1) is a major driver of vascular smooth muscle cell (VSMC) phenotypic switching, an important pathobiology in arterial disease. We performed RNA-sequencing of TGFß1-stimulated human aortic or arterial VSMCs which revealed large and consistent upregulation of Interleukin 11 (IL11). IL11 has an unknown function in VSMCs, which highly express the IL11 receptor alpha, suggestive of an autocrine loop. In vitro, IL11 activated ERK signaling, but inhibited STAT3 activity, and caused VSMC phenotypic switching to a similar extent as TGFß1 or angiotensin II (ANGII) stimulation. Genetic or therapeutic inhibition of IL11 signaling reduced TGFß1- or ANGII-induced VSMC phenotypic switching, placing IL11 activity downstream of these factors. Aortas of mice with Myh11-driven IL11 expression were remodeled and had reduced contractile but increased matrix and inflammatory genes expression. In two models of arterial pressure loading, IL11 was upregulated in the aorta and neutralizing IL11 antibodies reduced remodeling along with matrix and pro-inflammatory gene expression. These data show that IL11 plays an important role in VSMC phenotype switching, vascular inflammation and aortic pathobiology.

Antiviral activity of interleukin-11 as a response to porcine epidemic diarrhea virus infection.

Interleukin-11 (IL-11), a well-known anti-inflammatory factor, provides protection from intestinal epithelium damage caused by physical or chemical factors. However, little is known of the role of IL-11 during viral infections. In this study, IL-11 expression at mRNA and protein levels were found to be high in Vero cells and the jejunum of piglets during porcine epidemic diarrhea virus (PEDV) infection, while IL-11 expression was found to be positively correlated with the level of viral infection. Pretreatment with recombinant porcine IL-11 (pIL-11) was found to suppress PEDV replication in Vero E6 cells, while IL-11 knockdown promoted viral infection. Furthermore, pIL-11 was found to inhibit viral infection by preventing PEDV-mediated apoptosis of cells by activating the IL-11/STAT3 signaling pathway. Conversely, application of a STAT3 phosphorylation inhibitor significantly antagonized the anti-apoptosis function of pIL-11 and counteracted its inhibition of PEDV. Our data suggest that IL-11 is a newfound PEDV-inducible cytokine, and its production enhances the anti-apoptosis ability of epithelial cells against PEDV infection. The potential of IL-11 to be used as a novel therapeutic against devastating viral diarrhea in piglets deserves more attention and study.

Mutations in Craniosynostosis Patients Cause Defective Interleukin-11 Receptor Maturation and Drive Craniosynostosis-like Disease in Mice.

Premature closure of the sutures that connect the cranial bones during development of the mammalian skull results in a phenotype called craniosynostosis. Recently, several craniosynostosis patients with missense mutations within the gene encoding the interleukin-11 receptor (IL-11R) have been described, but the underlying molecular mechanisms have remained elusive. IL-11 is a cytokine that has a crucial role in bone remodeling and activates cells via binding to the IL-11R. Here, we show that patient mutations prevented maturation of the IL-11R, resulting in endoplasmic reticulum retention and diminished cell surface appearance. Disruption of a conserved tryptophan-arginine zipper within the third domain of the IL-11R was the underlying cause of the defective maturation. IL-11 classic signaling via the membrane-bound receptor, but not IL-11 trans-signaling via the soluble receptor, was the crucial pathway for normal skull development in mice in vivo. Thus, the specific therapeutic inhibition of IL-11 trans-signaling does not interfere with skull development.

GM-CSF and IL-4 are not involved in IVIG-mediated amelioration of ITP in mice: a role for IL-11 cannot be ruled out.

Previously, we have reported that interleukin (IL)-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-11, but not IL-33, are up-regulated in two strains of mice with immune thrombocytopenia (ITP) that are responsive to intravenous immunoglobulin (IVIg) treatment. Previously, IL-4 was ruled out in the mechanism of IVIg; however, other publications have suggested this cytokine as a major player in the mechanism of IVIg action. Thus, we sought to further investigate a role for IL-4 and, in addition, GM-CSF and IL-11 in the mechanism of action of IVIg using a murine model of ITP. A passive platelet antibody model was used to generate ITP in IL-4 receptor knock-out (IL-4R-/- ), IL-11 receptor knock-out (IL-11Rα-/- ) and GM-CSF knock-out (Csf2-/- ) mice. We also used a neutralizing antibody to IL-11 and recombinant human IL-11 (rhIL-11) in addition to depleting basophils in vivo to study the effect of IVIg to ameliorate ITP. Our results showed that basophils, IL-4 and GM-CSF were unimportant in both ITP induction and its amelioration by IVIg. The role of IL-11 in these processes was less clear. Even though IL-11Rα-/- mice with ITP responded to IVIg similarly to wild-type (WT) mice, treatment of ITP WT mice with rhIL-11 instead of IVIg showed an increase in platelet numbers and WT mice administered anti-IL-11 showed a significant reduction in the ability of IVIg to ameliorate the ITP. Our findings indicate that neither IL-4, basophils or GM-CSF have roles in IVIg amelioration of ITP; however, a role for IL-11 requires further study.

Two N-Linked Glycans Differentially Control Maturation, Trafficking and Proteolysis, but not Activity of the IL-11 Receptor.

BACKGROUND/AIMS: The cytokine interleukin-11 (IL-11) has important pro- and anti-inflammatory functions. It activates its target cells through binding to the IL-11 receptor (IL-11R), and the IL-11/IL-11R complex recruits a homodimer of glycoprotein 130 (gp130). N-linked glycosylation, a post-translational modification where complex oligosaccharides are attached to the side chain of asparagine residues, is often important for stability, folding and biological function of cytokine receptors. METHODS: We generated different IL-11R mutants via site-directed mutagenesis and analyzed them in different cell lines via Western blot, flow cytometry, confocal microscopy and proliferation assays. RESULTS: In this study, we identified two functional N-glycosylation sites in the D2 domain of the IL-11R at N127 and N194. While mutation of N127Q only slightly affects cell surface expression of the IL-11R, mutation of N194Q broadly prevents IL-11R appearance at the plasma membrane. Accordingly, IL-11R mutants lacking N194 are retained within the ER, whereas the N127 mutant is transported through the Golgi complex to the cell surface, uncovering a differential role of the two N-glycan sequons for IL-11R maturation. Interestingly, IL-11R mutants devoid of one or both N-glycans are still biologically active. Furthermore, the IL-11RN127Q/N194Q mutant shows no inducible shedding by ADAM10, but is rather constitutively released into the supernatant. CONCLUSION: Our results show that the two N-glycosylation sites differentially influence stability and proteolytic processing of the IL-11R, but that N-linked glycosylation is not a prerequisite for IL-11 signaling.

The SNP rs4252548 (R112H) which is associated with reduced human height compromises the stability of IL-11.

Height is a complex human phenotype that is influenced by variations in a high number of genes. Recently, a single nucleotide polymorphism (SNP) within IL11 (rs4252548) has been described to be associated with height in adults of European ancestry. This coding SNP leads to the exchange of Arg-112 to His-112 within the cytokine Interleukin-11 (IL-11), which has a well-established role in osteoclast development and bone turnover. The functional consequences of the R112H mutation are unknown so far. In this study, we show by molecular replacement that Arg-112 does not participate in binding of IL-11 to its receptors IL-11R and glycoprotein 130 (gp130). Recombinant IL-11 R112H expressed in E. coli displays a correct four-helix-bundle folding topology, and binds with similar affinity to IL-11R and the IL-11/IL-11R/gp130 complex. IL-11 R112H induces cell proliferation and phosphorylation of the downstream transcription factor STAT3 indistinguishable from IL-11. However, IL-11 R112H fails to support the survival of osteoclast progenitor cells and is less thermally stable, which is caused by the loss of the positive charge on the protein surface since protonation of the histidine side chain recovers stability.

Cleavage of the Interleukin-11 receptor induces processing of its C-terminal fragments by the gamma-secretase and the proteasome.

The cytokine Interleukin-11 (IL-11) signals through the membrane-bound IL-11 receptor (IL-11R), which is expressed in a cell-type specific manner. We have recently shown that the metalloprotease ADAM10 can cleave the IL-11R. The liberated soluble IL-11R (sIL-11R) ectodomain can bind its ligand, and the resulting IL-11/sIL-11R complex can activate cells that do not express the IL-11R (trans-signaling). In this study, we show that the remaining C-terminal fragment (CTF1) after ADAM10-mediated cleavage is subsequently cleaved within the membrane by the gamma-secretase complex, and that the resulting shorter CTF2 is further degraded by the proteasome. In contrast to other transmembrane receptors, e.g. Notch, we find no evidence that the IL-11R CTF can translocate into the nucleus to act as a transcription factor, suggesting that regulated intramembrane proteolysis of the IL-11R CTF acts as a mechanism to clear the plasma membrane from remaining protein fragments after cleavage of its ectodomain.

Proteolytic control of Interleukin-11 and Interleukin-6 biology.

Interleukin-11 (IL-11) and IL-6 are secreted glycoproteins which fulfill important homeostatic functions. Activation of target cells occurs via membrane-bound IL-11 and IL-6 receptors (IL-11R and IL-6R, respectively). Formation of IL-11/IL-11R and IL-6/IL-6R complexes triggers the recruitment of a homodimer of the ubiquitously expressed signal-transducing ß-receptor gp130 (classic signaling). IL-11R and IL-6R can be shed by several proteases, albeit with different preferences and specificities, and these soluble receptors (sIL-11R and sIL-6R) act as agonists and can activate in principle all cells via gp130. We have termed these protease-controlled pathways IL-6 and IL-11 trans-signaling. In this review, we describe the basic biology of both cytokines and summarize the current knowledge how proteases control and shape the trans-signaling pathways of the two cytokines. We will further highlight how the underlying molecular mechanisms can be used to design specific inhibitors that block trans, but not classic signaling of IL-11 and IL-6. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Enhancing Interleukin-6 and Interleukin-11 receptor cleavage.

Proteolytic cleavage of the membrane-bound Interleukin-6 receptor (IL-6R) by the metalloprotease ADAM17 releases an agonistic soluble form of the IL-6R (sIL-6R), which is responsible for the pro-inflammatory trans-signaling branch of the cytokine's activities. This proteolytic step, which is also called ectodomain shedding, is critically regulated by the cleavage site within the IL-6R stalk, because mutations or small deletions within this region are known to render the IL-6R irresponsive towards proteolysis. In the present study, we employed cleavage site profiling data of ADAM17 to generate an IL-6R with increased cleavage susceptibility. Using site-directed mutagenesis, we showed that the non-prime sites P3 and P2 and the prime site P1' were critical for this increase in proteolysis, whereas other positions within the cleavage site were of minor importance. Insertion of this optimized cleavage site into the stalk of the Interleukin-11 receptor (IL-11R) was not sufficient to enable ADAM17-mediated proteolysis, but transfer of different parts of the IL-6R stalk enabled shedding by ADAM17. These findings shed light on the cleavage site specificities of ADAM17 using a native substrate and reveal further differences in the proteolysis of IL-6R and IL-11R.

Cancer-associated fibroblasts treated with cisplatin facilitates chemoresistance of lung adenocarcinoma through IL-11/IL-11R/STAT3 signaling pathway.

Cancer-associated fibroblasts (CAF) are recognized as one of the key determinants in the malignant progression of lung adenocarcinoma. And its contributions to chemoresistance acquisition of lung cancer has raised more and more attention. In our study, cancer associated fibroblasts treated with cisplatin conferred chemoresistance to lung cancer cells. Meanwhile, Interleukin-11(IL-11) was significantly up-regulated in the CAF stimulated by cisplatin. As confirmed in lung adenocarcinoma cells in vivo and in vitro, IL-11 could protect cancer cells from cisplatin-induced apoptosis and thus promote their chemoresistance. Furthermore, it was also observed that IL-11 induced STAT3 phosphorylation and increased anti-apoptotic protein Bcl-2 and Survivin expression in cancer cells. The effect could be abrogated by suppressing STAT3 phosphorylation or silencing IL-11Rα expression in cancer cells. In conclusion, chemotherapy-induced IL-11 upregulation in CAF promotes lung adenocarcinoma cell chemoresistance by activating IL-11R/STAT3 anti-apoptotic signaling pathway.

Generation of Soluble Interleukin-11 and Interleukin-6 Receptors: A Crucial Function for Proteases during Inflammation.

The cytokines interleukin-11 (IL-11) and IL-6 are important proteins with well-defined pro- and anti-inflammatory functions. They activate intracellular signaling cascades through a homodimer of the ubiquitously expressed signal-transducing ß-receptor glycoprotein 130 (gp130). Specificity is gained through the cell- and tissue-specific expression of the nonsignaling IL-11 and IL-6 α-receptors (IL-11R and IL-6R), which determine the responsiveness of the cell to these two cytokines. IL-6 is a rare example, where its soluble receptor (sIL-6R) has agonistic properties, so that the IL-6/sIL-6R complex is able to activate cells that are usually not responsive to IL-6 alone (trans-signaling). Recent evidence suggests that IL-11 can signal via a similar trans-signaling mechanism. In this review, we highlight similarities and differences in the functions of IL-11 and IL-6. We summarize current knowledge about the generation of the sIL-6R and sIL-11R by different proteases and discuss possible roles during inflammatory processes. Finally, we focus on the selective and/or combined inhibition of IL-6 and IL-11 signaling and how this might translate into the clinics.

Proteolytic Cleavage Governs Interleukin-11 Trans-signaling.

Interleukin (IL)-11 has been shown to be a crucial factor for intestinal tumorigenesis, lung carcinomas, and asthma. IL-11 is thought to exclusively mediate its biological functions through cell-type-specific expression of the membrane-bound IL-11 receptor (IL-11R). Here, we show that the metalloprotease ADAM10, but not ADAM17, can release the IL-11R ectodomain. Chimeric proteins of the IL-11R and the IL-6 receptor (IL-6R) revealed that a small juxtamembrane portion is responsible for this substrate specificity of ADAM17. Furthermore, we show that the serine proteases neutrophil elastase and proteinase 3 can also cleave the IL-11R. The resulting soluble IL-11R (sIL-11R) is biologically active and binds IL-11 to activate cells. This IL-11 trans-signaling pathway can be inhibited specifically by the anti-inflammatory therapeutic compound sgp130Fc. In conclusion, proteolysis of the IL-11R represents a molecular switch that controls the IL-11 trans-signaling pathway and widens the number of cells that can be activated by IL-11.

Interleukin-11 alters placentation and causes preeclampsia features in mice.

Preeclampsia (PE) is a pregnancy-specific disorder characterized by hypertension and proteinuria after 20 wk gestation. Abnormal extravillous trophoblast (EVT) invasion and remodeling of uterine spiral arterioles is thought to contribute to PE development. Interleukin-11 (IL11) impedes human EVT invasion in vitro and is elevated in PE decidua in women. We demonstrate that IL11 administered to mice causes development of PE features. Immunohistochemistry shows IL11 compromises trophoblast invasion, spiral artery remodeling, and placentation, leading to increased systolic blood pressure (SBP), proteinuria, and intrauterine growth restriction, although nonpregnant mice were unaffected. Real-time PCR array analysis identified pregnancy-associated plasma protein A2 (PAPPA2), associated with PE in women, as an IL11 regulated target. IL11 increased PAPPA2 serum and placental tissue levels in mice. In vitro, IL11 compromised primary human EVT invasion, whereas siRNA knockdown of PAPPA2 alleviated the effect. Genes regulating uterine natural killer (uNK) recruitment and differentiation were down-regulated and uNK cells were reduced after IL11 treatment in mice. IL11 withdrawal in mice at onset of PE features reduced SBP and proteinuria to control levels and alleviated placental labyrinth defects. In women, placental IL11 immunostaining levels increased in PE pregnancies and in serum collected from women before development of early-onset PE, shown by ELISA. These results indicate that elevated IL11 levels result in physiological changes at the maternal-fetal interface, contribute to abnormal placentation, and lead to the development of PE. Targeting placental IL11 may provide a new treatment option for PE.

IL-11Rα: a novel target for the treatment of osteosarcoma.

Recent advances have shown that cell surface receptors are expressed differentially in normal and pathological conditions. Novel organ specific and disease specific proteins expressed on tumor vasculature have been identified by in vivo phage display technology and the diversity of the tumor-associated vasculature has provided the basis for the development of targeted therapeutics. Investigators recently screened a phage display library in a human cancer patient. An IL-11 mimic phage displaying the cyclic peptide CGRRAGGSC (single letter amino acid code) specifically bound to immobilized IL-11Rα. It has been demonstrated that the expression of the IL-11Rα is increased in several other types of tumors including osteosarcoma. The ability to selectively target the IL-11Rα may provide an alternative treatment of for a disease where new treatment options are truly needed.

Sod1 deficiency reduces incubation time in mouse models of prion disease.

Prion infections, causing neurodegenerative conditions such as Creutzfeldt-Jakob disease and kuru in humans, scrapie in sheep and BSE in cattle are characterised by prolonged and variable incubation periods that are faithfully reproduced in mouse models. Incubation time is partly determined by genetic factors including polymorphisms in the prion protein gene. Quantitative trait loci studies in mice and human genome-wide association studies have confirmed that multiple genes are involved. Candidate gene approaches have also been used and identified App, Il1-r1 and Sod1 as affecting incubation times. In this study we looked for an association between App, Il1-r1 and Sod1 representative SNPs and prion disease incubation time in the Northport heterogeneous stock of mice inoculated with the Chandler/RML prion strain. No association was seen with App, however, significant associations were seen with Il1-r1 (P = 0.02) and Sod1 (P<0.0001) suggesting that polymorphisms at these loci contribute to the natural variation observed in incubation time. Furthermore, following challenge with Chandler/RML, ME7 and MRC2 prion strains, Sod1 deficient mice showed highly significant reductions in incubation time of 20, 13 and 24%, respectively. No differences were detected in Sod1 expression or activity. Our data confirm the protective role of endogenous Sod1 in prion disease.

Regulation of human endometrial stromal proliferation and differentiation by C/EBPß involves cyclin E-cdk2 and STAT3.

During each menstrual cycle, the human uterus undergoes a unique transformation, known as decidualization, which involves endometrial stromal proliferation and differentiation. During this process, the stromal cells are transformed into decidual cells, which produce factors that prepare the uterus for potential embryo implantation. We previously identified the transcription factor CCAAT/enhancer-binding protein (C/EBP)ß as a regulator of endometrial stromal proliferation and differentiation in mice. In this study, we addressed the role of C/EBPß in human endometrial decidualization. Using small interfering RNA targeted to C/EBPß mRNA, we demonstrated that C/EBPß controls the proliferation of primary human endometrial stromal cells (HESCs) by regulating the expression of several key cell cycle-regulatory factors during the G(1)-S phase transition. Additionally, loss of C/EBPß expression blocked the differentiation of HESCs in response to estrogen, progesterone, and cyclic AMP. Gene expression profiling of normal and C/EBPß-deficient HESCs revealed that the receptor for the cytokine IL-11 and its downstream signal transducer signal transducer and activator of transcription 3 (STAT3) are targets of regulation by C/EBPß. Chromatin immunoprecipitation analysis indicated that C/EBPß controls the expression of STAT3 gene by directly interacting with a distinct regulatory sequence in its 5'-flanking region. Attenuation of STAT3 mRNA expression in HESCs resulted in markedly reduced differentiation of these cells, indicating an important role for STAT3 in decidualization. Gene expression profiling, using STAT3-deficient HESCs, showed an extensive overlap of pathways downstream of STAT3 and C/EBPß during stromal cell differentiation. Collectively, these findings revealed a novel functional link between C/EBPß and STAT3 that is a critical regulator of endometrial differentiation in women.

Inflammation-induced lethargy is mediated by suppression of orexin neuron activity.

In response to illness, animals subvert normal homeostasis and divert their energy utilization to fight infection. An important and unexplored feature of this response is the suppression of physical activity and foraging behavior in the setting of negative energy balance. Inflammatory signaling in the hypothalamus mediates the febrile and anorectic responses to disease, but the mechanism by which locomotor activity (LMA) is suppressed has not been described. Lateral hypothalamic orexin (Ox) neurons link energy status with LMA, and deficiencies in Ox signaling lead to hypoactivity and hypophagia. In the present work, we examine the effect of endotoxin-induced inflammation on Ox neuron biology and LMA in rats. Our results demonstrate a vital role for diminished Ox signaling in mediating inflammation-induced lethargy. This work defines a specific population of inflammation-sensitive, arousal-associated Ox neurons and identifies a proximal neural target for inflammatory signaling to Ox neurons, while eliminating several others.

Differential endometrial gene expression in pregnant and nonpregnant sows.

In an attempt to unveil molecular processes controlling the porcine placentation, we have investigated the pregnancy-induced gene expression in the endometrium using the Affymetrix GeneChip Porcine Genome Array. At Day 14 after insemination, at the time of initial placentation, samples were obtained from the endometrium of pregnant sows and sows inseminated with inactivated semen. Analysis of the microarray data revealed 263 genes to be significantly differentially expressed between the pregnant and nonpregnant sows. Most gene ontology terms significantly enriched at pregnancy had allocated more up-regulated genes than down-regulated genes. These terms included developmental process, transporter activity, calcium ion binding, apoptosis, cell motility, enzyme-linked receptor protein signaling pathway, positive regulation of cell proliferation, ion homeostasis, and hormone activity. Only the three terms oxidoreductase activity, lipid metabolic process, and organic acid metabolic process had an overrepresentation of down-regulated genes. A gene interaction network based on the genes identified in the gene ontology term developmental processes identified genes likely to be involved in the process of placentation. Pregnancy-specific localization of IL11RA to the surface epithelium of the endometrium suggests a role of interleukin 11 signaling in formation of the porcine epitheliochorial placenta. Furthermore, up-regulation of FGF9 mRNA in pregnant endometrium and localization of FGF9 to the apical cell domain of the glandular epithelium suggest the concept of endometrial FGF9 acting as an embryonic growth factor in the pig.

Interleukin-11 in endometrial adenocarcinoma is regulated by prostaglandin F2alpha-F-prostanoid receptor interaction via the calcium-calcineurin-nuclear factor of activated T cells pathway and negatively regulated by the regulator of calcineurin-1.

Interleukin-11 (IL-11) up-regulates the proliferative and invasive capacity of many cancers. Coexpression of glycoprotein 130 (GP130) and IL-11 receptor alpha (IL-11Ralpha) is necessary for high-affinity binding of IL-11 to IL-11Ralpha. This study investigated the expression of IL-11 and role of prostaglandin F(2alpha)-F-prostanoid receptor (FP receptor) signaling in the modulation of IL-11 expression in endometrial adenocarcinoma cells. Localization of IL-11, IL-11Ralpha, and GP130 expression was performed by immunohistochemistry. IL-11 and regulator of calcineurin 1 isoform 4 (RCAN1-4) mRNA and protein expression were determined by real-time RT-PCR and/or enzyme-linked immunosorbent assay/Western blot analysis using Ishikawa endometrial adenocarcinoma cells stably expressing the FP receptor (FPS cells) and endometrial adenocarcinoma explants. IL-11 mRNA expression was significantly elevated in endometrial adenocarcinoma samples compared with normal endometrium and increased with tumor grade. IL-11 protein expression localized with FP receptor, IL-11Ralpha, and GP130 in the neoplastic glandular epithelium of endometrial adenocarcinomas. Prostaglandin F(2alpha)-FP receptor signaling significantly elevated the expression of IL-11 mRNA and protein in a Gq-protein kinase C-calcium-calcineurin-nuclear factor of activated T cells-dependent manner in FPS cells. The calcineurin signaling pathway is known to be controlled by the RCAN (RCAN1-4). Indeed, RCAN1-4 expression was significantly elevated in well-differentiated endometrial adenocarcinoma compared with normal endometrium and was found to decrease with tumor grade and negatively regulate IL-11 expression in vitro. This study has highlighted a new mechanism regulating IL-11 expression in endometrial adenocarcinoma cells by the FP receptor via the calcium-calcineurin-nuclear factor of activated T cells pathway.