Gremlin 1 Expression Research Articles

Gremlin-1 associates with fibrillin microfibrils in vivo and regulates mesothelioma cell survival through transcription factor slug

Malignant mesothelioma is a form of cancer that is highly resistant to conventional cancer therapy for which no major therapeutic advances have been introduced. Here, we identify gremlin-1, a known bone morphogenetic protein inhibitor crucial for embryonic development, as a potential therapeutic target for mesothelioma. We found high expression levels of gremlin-1 in the mesothelioma tumor tissue, as well as in primary mesothelioma cells cultured from pleural effusion samples. Downregulation of gremlin-1 expression by siRNA-mediated silencing in a mesothelioma cell line inhibited cell proliferation. This was associated with downregulation of the transcription factor slug as well as mesenchymal proteins linked to cancer epithelial-to-mesenchymal transition. Further, resistance to paclitaxel-induced cell death was associated with high gremlin-1 and slug expression. Treatment of gremlin-1-silenced mesothelioma cells with paclitaxel or pemetrexed resulted in efficient loss of cell survival. Finally, our data suggest that concomitant upregulation of fibrillin-2 in mesothelioma provides a mechanism for extracellular localization of gremlin-1 to the tumor microenvironment. This was supported by the demonstration of interactions between gremlin-1, and fibrillin-1 and -2 peptides as well as by colocalization of gremlin-1 to fibrillin microfibrils in cells and tumor tissue samples. Our data suggest that gremlin-1 is also a potential target for overcoming drug resistance in mesothelioma.

Downregulated bone morphogenetic protein signaling in nitrofen-induced congenital diaphragmatic hernia

Bone morphogenetic proteins (BMP) have been shown to play crucial roles in not only lung and heart development, but also in the pathogenesis of pulmonary vascular remodeling in pulmonary hypertension (PH). We therefore hypothesized that BMP signaling could be altered in nitrofen-induced congenital diaphragmatic hernia (CDH) and associated PH. Pregnant rats were exposed to either 100mg nitrofen or vehicle on embryonic day (E) 9.5. On E17 and E21, fetuses were delivered by cesarean section, killed and checked for left-sided CDH. The tissue was then harvested for pathobiological evaluation. In nitrofen-induced CDH, pulmonary expressions of BMP4, BMP receptor (BMPR) type 2 and Id1 decreased on E17 and E21. On E17, pulmonary gremlin-1 expression increased, while BMP7 decreased. In the lungs, Id1 expression was correlated to BMP4 and BMPR2 and inversely correlated to gremlin-1 expression. Myocardial expressions of BMPR2, BMPR1A, BMP7 and SERCA-2A decreased, while gremlin-1 and noggin expressions increased on E17. On E21, myocardial expressions of Id1 and SERCA-2A decreased, while gremlin-1 expression increased. Moreover, BMPR2 and BMPR1A expressions were correlated to SERCA-2A expression and inversely correlated to pro-apoptotic Bax/Bcl2 ratio within the myocardium. Downregulation of BMP signaling seems to contribute to pulmonary and myocardial anomalies observed in nitrofen-induced CDH.

GREM1, FRZB and DKK1 mRNA levels correlate with osteoarthritis and are regulated by osteoarthritis-associated factors

IntroductionOsteoarthritis is, at least in a subset of patients, associated with hypertrophic differentiation of articular chondrocytes. Recently, we identified the bone morphogenetic protein (BMP) and wingless-type MMTV integration site (WNT) signaling antagonists Gremlin 1 (GREM1), frizzled-related protein (FRZB) and dickkopf 1 homolog (Xenopus laevis) (DKK1) as articular cartilage’s natural brakes of hypertrophic differentiation. In this study, we investigated whether factors implicated in osteoarthritis or regulation of chondrocyte hypertrophy influence GREM1, FRZB and DKK1 expression levels.MethodsGREM1, FRZB and DKK1 mRNA levels were studied in articular cartilage from healthy preadolescents and healthy adults as well as in preserved and degrading osteoarthritic cartilage from the same osteoarthritic joint by quantitative PCR. Subsequently, we exposed human articular chondrocytes to WNT, BMP, IL-1β, Indian hedgehog, parathyroid hormone-related peptide, mechanical loading, different medium tonicities or distinct oxygen levels and investigated GREM1, FRZB and DKK1 expression levels using a time-course analysis.ResultsGREM1, FRZB and DKK1 mRNA expression were strongly decreased in osteoarthritis. Moreover, this downregulation is stronger in degrading cartilage compared with macroscopically preserved cartilage from the same osteoarthritic joint. WNT, BMP, IL-1β signaling and mechanical loading regulated GREM1, FRZB and DKK1 mRNA levels. Indian hedgehog, parathyroid hormone-related peptide and tonicity influenced the mRNA levels of at least one antagonist, while oxygen levels did not demonstrate any statistically significant effect. Interestingly, BMP and WNT signaling upregulated the expression of each other’s antagonists.ConclusionsTogether, the current study demonstrates an inverse correlation between osteoarthritis and GREM1, FRZB and DKK1 gene expression in cartilage and provides insight into the underlying transcriptional regulation. Furthermore, we show that BMP and WNT signaling are linked in a negative feedback loop, which might prove essential in articular cartilage homeostasis by balancing BMP and WNT activity.

Expression of gremlin 1 correlates with increased angiogenesis and progression-free survival in patients with pancreatic neuroendocrine tumors

Gremlin 1 (GREM1) is a bone morphogenetic protein antagonist and a novel proangiogenic factor. Our aim was to evaluate the prognostic value of GREM1 expression and GREM1-related factors in tumor-associated angiogenesis in pancreatic neuroendocrine tumors (NETs). The immunohistochemical expression of GREM1 and microvessel density (MVD) were examined in 35 patients with pancreatic NETs and then compared with other clinicopathologic characteristics, including the World Health Organization classification. The presence of expression of GREM1 (p = 0.016) and high MVD (p = 0.020) were significant and favorable prognostic factors. Moreover, GREM1 expression was significantly associated with high MVD (p = 0.011). MVD was significantly higher in well-differentiated NETs than in well-differentiated or poorly differentiated neuroendocrine carcinomas (p < 0.001). GREM1 expression was correlated with tumor-associated angiogenesis and was found to be a novel prognostic marker in pancreatic NETS. Our data support a tumor suppressor role of GREM1 in pancreatic NETs.

Using Gene Expression to Predict Differences in the Secretome of Human Omental vs. Subcutaneous Adipose Tissue

The objective of this study was to characterize differences in the secretome of human omental compared with subcutaneous adipose tissue using global gene expression profiling. Gene expression was measured using Affymetrix microarrays (Affymetrix, Santa Clara, CA) in subcutaneous and omental adipose tissue in two independent experiments (n = 5 and n = 3 independent subjects; n = 16 arrays in total, 2 for each subject). Predictive bioinformatic algorithms were employed to identify secreted proteins. Microarray analysis identified 22 gene probe sets whose expression was significantly different with a fold change (FC) greater than 5 in expression in both experiments between omental and subcutaneous adipose tissue. Using bioinformatic predictive programs 11 of these 22 probe sets potentially coded for secreted proteins. Pathway network analysis of the secreted proteins showed that three of the proteins are part of a common pathway network. These proteins gremlin 1 (GREM1), pleiotrophin (PTN), and secretory leukocyte peptidase inhibitor (SLPI) are expressed respectively 43×, 23×, and 5× in omental adipose tissue relative to subcutaneous adipose tissue as determined by real-time PCR. The presence of GREM1, PTN, and SLPI protein in human adipose tissue was confirmed by western blotting. All three proteins are expressed in the human Simpson-Golabi-Behmel syndrome (SGBS) preadipocyte cell line. The expression of GREM1, PTN, and SLPI changed with the differentiation of the preadipocytes into mature adipocytes. Gene expression coupled with predictive bioinformatic algorithms have identified several genes coding for secreted proteins which are expressed differently in omental adipose tissue compared to subcutaneous adipose tissue proving a valid alternative approach to help further define the adipocyte secretome.

BMP2 Differentially Regulates the Expression of Gremlin1 and Gremlin2, the Negative Regulators of BMP Function, During Osteoblast Differentiation

Bone morphogenetic proteins (BMPs) control the expressions of many genes involved in bone formation. On the basis of our hypothesis that BMP2 stimulation-regulated gene expression plays a critical role in osteoblast differentiation, we performed genome-wide screening of messenger RNA from BMP2-treated and -untreated C2C12 cells using a DNA microarray technique. We found that the expressions of Gremlin1 and Gremlin2, which are known BMP antagonists, were bidirectionally regulated by BMP2. Gremlin1 was down-regulated by BMP2, while Gremlin2 was up-regulated in both time- and dose-dependent manners. Ablation of Gremlin1 or Gremlin2 enhanced osteoblast differentiation induced by BMP2. On the other hand, treatment with recombinant Gremlin1 inhibited BMP2-induced osteoblast differentiation. Furthermore, treatment with Smad4 siRNA and the p38 MAPK inhibitor SB203580 suppressed BMP2-induced Gremlin2 gene expression. The differential regulation of Gremlin1 and Gremlin2 gene expressions by BMP2 may explain the critical function of these genes during osteoblast differentiation.

Gremlin-1 Is Overexpressed in Endothelial Cells of Patients with Loeys-Dietz Syndrome Due to Dysregulation of TGF-β Signalling,

Abstract 3269The Loeys-Dietz syndrome (LDS) is an inherited connective tissue disorder with symptoms similar to those of Marfan syndrome and the vascular type of Ehlers-Danlos syndrome. Most patients with LDS develop severe aortic aneurysms resulting in early need of surgical intervention. Patients with LDS harbour a mutation in the transforming growth factor β (TGF-β) receptors TGFBR1 (also named ALK-5) or TGFBR2. Since the TGF-β pathway plays a crucial role in many cellular processes including angiogenesis, we focussed our analyses on endothelial cell dysfunction in patients with Loeys-Dietz syndrome.We isolated circulating outgrowth endothelial cells (OEC) from the peripheral blood of two LDS patients (one female, 54 years; one male, 26 years old) both harbouring a mutation in the TGFBR2 gene. Gene expression profiles of OEC clones were performed using Affymetrix Human Genome U133 Plus 2.0 Arrays and confirmed by quantitative PCR analysis for genes of interest. OEC clones isolated from age- and sex-matched healthy controls served as reference subjects.We demonstrate that several genes belonging to the TGF-β pathway had altered expression in OECs isolated from LDS patients compared to those from healthy controls. For example, mRNA levels of bone morphogenic proteins (BMP) 2 and 4 were decreased in both LDS OEC clones (mean decrease 4 and 6 fold, respectively) whereas gene expression of inhibitory downstream molecule SMAD-6 was increased 2-fold.In both analysed OEC clones from LDS patients, gene expression of BMP antagonist Gremlin-1 (also known as Drm) showed the most prominent dysregulation with a 1136-fold and 164-fold higher expression in LDS OECs compared to healthy controls, respectively.Interestingly, in OECs isolated from healthy donors, Gremlin-1 expression was significantly down-regulated after incubation with SB431542 (5 μM), a small molecule inhibitor of the TGF-β receptor complex (mean decrease 4 fold; t-test: p = 0.002; n = 6). In contrast, the stimulation of OEC clones with TGF-β1 (1 ng/ml) resulted in significant up-regulation of Gremlin-1 mRNA levels (mean increase 7 fold; t-test: p = 0.014; n = 6). Apparently, the up-regulation of Gremlin-1 in LDS OECs seems to mirror an activated TGF-β signalling cascade in outgrowth endothelial cells. These findings are in line with other studies published on LDS where hyperactivity of the TGF-β downstream signalling was demonstrated by higher phosphorylation levels of SMAD-2 in the aortic media of LDS patients (Loeys et al., Nat Genet. 2005 Mar;37(3):275–81). Gremlin-1 might represent a second gene supporting the concept of increased TGF-β signalling in Loeys-Dietz syndrome.Gremlin-1 itself displays opposing effects on angiogenesis. First, it is known as a pro-angiogenic factor and was recently shown to stimulate angiogenesis via direct binding to the VEGF receptor 2 (Mitola et al., Blood. 2010 Nov 4;116(18):3677–80). On the other hand, as antagonist of bone morphogenic proteins, Gremlin-1 possesses anti-angiogenic properties by suppressing pro-angiogenic effects of BMP-2 and BMP-4.In summary, we believe that due to its drastic up-regulation in OECs of LDS patients, Gremlin-1 represents a crucial effector of dysregulated TGF-β signalling in endothelial cells inducing vascular pathology in Loeys-Dietz syndrome. Disclosures:Fiedler:Pfizer: Research Funding.

Elevated levels of gremlin-1 in eutopic endometrium and peripheral serum in patients with endometriosis

To examine the expression of gremlin-1 (GREM1) on the levels of messenger RNA (mRNA) and protein in eutopic endometrium and its serum level in patients with endometriosis. Prospective, experimental study using reverse-transcription polymerase chain reaction, Western blot, immunofluorescence, and ELISA. Gynecological oncology laboratory in a department of obstetrics and gynecology in a medical college in China. Thirty-five patients with endometriosis and 23 healthy control women. During surgery, the eutopic endometria and peripheral serum were obtained from the patients with endometriosis and the control women. The cellular compartment location of GREM1 expression was examined by using immunofluorescent double staining. The expression levels of mRNA and protein for GREM1 were determined by reverse-transcription polymerase chain reaction and Western blot, respectively. The serum level of GREM1 was measured by indirect ELISA. The expression of GREM1 was defined within endometrial blood vessel endothelium exclusively, with the concomitant expressions of GREM1 and CD146. The expression of GREM1 on the levels of mRNA and protein was significantly higher in eutopic endometria of patients with endometriosis than in those from healthy control women. According to the ELISA established in our laboratory, the concentration of GREM1 in peripheral serum that was collected during the follicular menstrual phase of patients with endometriosis was significantly higher than that in serum from healthy control women. Gremlin-1 plays a role to some extent in the aberrant angiogenesis of eutopic endometrium in patients with endometriosis. It is possible that the peripheral serum level of GREM1 is a prospective serum biomarker of endometriosis.