Expression Of LGR4 Research Articles

Inhibitory Effect of MiR-449b on Cancer Cell Growth and Invasion through LGR4 in Non-Small-Cell Lung Carcinoma.

Non-small-cell lung carcinoma (NSCLC) is one of the most frequently diagnosed malignancies worldwide. Previous studies have shown that microRNA-449b (miR-449b) functions as a tumor suppressor in many cancers. However, the role of miR-449b in NSCLC is still unknown. In the present study, miR-449b was significantly downregulated in NSCLC samples and cell lines. Bioinformatics analysis revealed that 3'-UTR region of leucine rich repeat containing G protein-coupled receptor 4 (LGR4) mRNA had putative complementary sequences to miR-449b,which was further confirmed by the luciferase assay. Western blotting showed that restoration of miR-449b in NSCLC cells decreased the expression of LGR4. Interestingly, over-expression of miR-449b inhibited growth and invasion of NSCLC cells in vitro. Furthermore, ectopic expression of LGR4 reversed miR-449b-suppressed proliferation and invasion of NSCLC cells. Therefore, the data of the present study demonstrate that miR-449b inhibits tumor cell growth and invasion by targeting LGR4 in NSCLC.

Effects and diagnostic value of G protein-coupled receptor 4 on the establishment of neovascularization of human papillomavirus infection in cervical cancer tissues

Objective To explore the effect and diagnostic value of G protein coupled receptor 4 (LGR4) on the establishment of neovascularization of HPV infected cervical cancer tissue. Methods From March 2016 to December 2017, thirty cases of HPV infected cervical cancer, cervical precancerous lesion and cervical health in Lan County Maternal and Child Health and Family Planning Service Center were selected as subjects.After the consent of the subjects, specimens were collected.Immunohistochemical method was used to observe the positive rate of LGR4 in three kinds of tissue specimens.The diagnostic value of LGR4 in differentiation, staging and typing of cervical cancer was observed by screening test, and the expression of related pro-angiogenic factors in LGR4-positive tissues was observed. Results The difference in the expression of LGR4 in healthy tissue, precancerous lesions and cervical cancer tissues was statistically significant(χ2=24.104, P=0.000). The positive rate of LGR4 expression in cervical cancer tissue was 80% (24/30), which was significantly higher than that in healthy group 16.7% (5/30) and precancerous lesion tissue 50% (15/30), the differences were statistically significant (P<0.05). The sensitivity of LGR4 was 80.00%, the specificity was 83.33%, the positive predictive value was 82.76%, the negative predictive value was 80.65%, the diagnostic accuracy was 81.67% and the Kappa value was 0.63, which has good consistency.The differences of LGR4 positive rate in different age, different degree of differentiation and different clinical stages were statistically significant (P<0.05). Laboratory results showed that CRP, PCT, VEGF and TGF-β in LGR4-positive tissues of cervical precancerous lesions and cervical cancer were significantly higher than those in LGR4-negative tissues, the differences were statistically significant (t=9.247, 2.925, 39.669, 15.348, P<0.05). Conclusion LGR4 can promote the establishment of neovascularization in cervical cancer and has certain diagnostic value for cervical cancer and cervical precancerous lesions. Key words: G-protein coupled receptor 4; HPV infection; Cervical cancer; Vascular establishment; Diagnostic value

Alteration of Wnt5a expression and of the non-canonical Wnt/PCP and Wnt/PKC-Ca2+ pathways in human osteoarthritis osteoblasts.

ObjectiveClinical and in vitro studies suggest that subchondral bone sclerosis due to abnormal osteoblasts (Ob) is involved in the progression and/or onset of osteoarthritis (OA). Human Ob isolated from sclerotic subchondral OA bone tissue show an altered phenotype, a decreased canonical Wnt/β-catenin signaling pathway (cWnt), and a reduced mineralization in vitro. In addition to the cWnt pathway, at least two non-canonical signaling pathways, the Wnt/PKC and Wnt/PCP pathway have been described. However, there are no reports of either pathway in OA Ob. Here, we studied the two non-canonical pathways in OA Ob and if they influence their phenotype.MethodsHuman primary subchondral Ob were isolated from the subchondral bone plate of tibial plateaus of OA patients undergoing total knee arthroplasty, or of normal individuals at autopsy. The expression of genes involved in non-canonical Wnt signaling was evaluated by qRT-PCR and their protein production by Western blot analysis. Alkaline phosphatase activity and osteocalcin secretion (OC) were determined with substrate hydrolysis and EIA, respectively. Mineralization levels were evaluated with Alizarin Red Staining, Wnt/PKC and Wnt/PCP pathways by target gene expression and their respective activity using the NFAT and AP-1 luciferase reporter assays.ResultsOA Ob showed an altered phenotype as illustrated by an increased alkaline phosphatase activity and osteocalcin release compared to normal Ob. The expression of the non-canonical Wnt5a ligand was increased in OA Ob compared to normal. Whereas, the expression of LGR5 was significantly increased in OA Ob compared to normal Ob, the expression of LGR4 was similar. Wnt5a directly stimulated the expression and production of LGR5, contrasting, Wnt5a did not stimulate the expression of LGR4. Wnt5a also stimulated the phosphorylation of both JNK and PKC, as well as the activity of both NFAT and AP-1 transcription factors. The inhibition of Wnt5a expression partially corrects the abnormal mineralization, OC secretion and ALPase activity of OA Ob.ConclusionThese data indicate that the alteration of Wnt5a, a non-canonical Wnt signaling activator, is implicated in the modified signalisation and phenotype observed in OA Ob.

BMP-2 Enhances Lgr4 Gene Expression in Osteoblastic Cells.

Osteoporosis is one of the most prevalent diseases and the number of patients suffering from this disease is soaring due to the increase in the aged population in the world. The severity of bone loss in osteoporosis is based on the levels of impairment in the balance between bone formation and bone resorption, two arms of the bone metabolism, and bone remodeling. However, determination of bone formation levels is under many layers of control that are as yet fully defined. Bone morphogenetic protein (BMP) plays a key role in regulation of bone formation while its downstream targets are still incompletely understood. Lgr4 gene encodes an orphan receptor and has been identified as a genetic determinant for bone mass in osteoporotic patients. Here, we examine the effects of BMP on the expression of Lgr4 in osteoblastic cells. Lgr4 gene is expressed in an osteoblastic cell line, MC3T3E1 in a time dependent manner during the culture. BMP treatment enhances Lgr4 mRNA expression at least in part via transcriptional event. When Lgr4 mRNA is knocked down, the levels of BMP-induced increase in alkaline phosphatase (Alp) activity and Alp mRNA are suppressed. BMP enhancement of Lgr4 gene expression is suppressed by FGF and reversed by dexamethasone. BMP also enhances Lgr4 expression in primary cultures of calvarial osteoblasts. These data indicate that Lgr4 gene is regulated by BMP and is required for BMP effects on osteoblastic differentiation. J. Cell. Physiol. 231: 887-895, 2016. © 2015 Wiley Periodicals, Inc.

Lgr4 deficiency attenuates tumor formation by reprograming macrophage polarization in lung cancer (TUM6P.973)

Abstract Macrophage polarization is increasingly recognized as an important pathogenetic factor in tumor formation. Our previous study has shown that Lgr4 negatively regulates TLR2/4 associated pattern recognition in innate immune responses. However, the exact roles and mechanisms of Lgr4 in macrophage polarization remain largely unknown. Here, we found that patients with Lgr4-high lung cancers displayed much poorer survival than the rest of the cohorts. Meanwhile, Lgr4 is also aberrantly expressed at high levels in macrophages from clinical lung adenocarcinomas (ADs), implying the potential role of Lgr4 in tumor-associated macrophages (TAMs). In addition, the expression of Lgr4 in bone marrow derived macrophages (BMMs) was reduced by IFN-γ and increased by IL-4 significantly. Interestingly, Lgr4 deficiency BMMs showed a obviously increased M1 phenotypes and reduced M2 phenotypes. Accordingly, host deficiency in Lgr4 resulted in defective and reduced growth of subcutaneously implanted Lewis lung carcinoma (LLC). Consistent with the defective growth, LLC cells implanted into Lgr4 conditional knockout mice also displayed reduced TAMs and increased M1 like macrophages in tumor tissues, suggesting impaired TAMs polarization. These findings suggest that deletion of Lgr4 may inhibits tumor growth via reprograming TAMs polarization. Thus, Lgr4 expressed in TAMs may potentially become a novel target for cancer therapy.

Lgr4 gene regulates corpus luteum maturation through modulation of the WNT-mediated EGFR-ERK signaling pathway.

Luteal-phase insufficiency is one of the major causes of female infertility, but the molecular mechanisms are still largely unknown. Here we found that disruption of Lgr4/Gpr48, the newly identified receptor for R-spondins, greatly reduced female fertility in mice. The expression of Lgr4 was induced specifically in granulosa-lutein cells during luteinization. In Lgr4-deficient female mice, the estrous cycle was prolonged and serum progesterone levels were dramatically downregulated. In Lgr4(-/-) corpora lutea, the expression of key enzymes for steroidogenesis as well as common luteal marker genes was significantly decreased. Additionally, the activity of epidermal growth factor receptor (EGFR)-ERK signaling was attenuated in Lgr4(-/-) granulosa-lutein cells. We found that the maturation of Lgr4(-/-) cells was impaired in cultured primary granulosa cells, but the defect was partially rescued by reactivation of EGFR signaling by heparin-binding EGF-like growth factor treatment. We found that the expression of wingless-type MMTV integration site family (WNT)/catenin (cadherin associated protein), beta 1 (CTNNB1) downstream targets, including matrix metalloproteinase 9, which is a critical matrix metalloproteinase for activation of EGF-like factors, was significantly downregulated in Lgr4(-/-) ovaries. Matrix metalloproteinase 9 inhibitor treatment attenuated human chorionic gonadotropin- but not heparin-binding EGF-like growth factor-induced ERK activation and luteinization in primary granulosa cells. Together, we report that Lgr4 modulates WNT-mediated EGFR-ERK signaling to facilitate corpus luteum maturation and ovarian steroidogenesis to maintain female reproduction.

Lgr4-Mediated Potentiation Of Wnt/β-Catenin Signaling Promotes MLL Leukemogenesis Via An Rspo3/Wnt3a-Gnaq Pathway In Leukemic Stem Cells

Although the clinical importance of aberrant Wnt/β-catenin signaling has been recognized in various cancers, including MLL-rearranged acute myeloid leukemia (MLL AML), its key tractable pathway components have not yet been discovered in leukemic stem cells (LSC). Our studies have identified an Rspo3/Wnt3a-Lgr4-Gnaq pathway, which significantly potentiates β-catenin signaling in MLL LSC. Genetic and pharmacological targeting of this pathway impairs LSC self-renewal and survival, inhibiting MLL-AF9-induced leukemia progression in vivo.Gene expression analysis of AML patient samples (Nucleic Acids Res, 41:D1034-9, 2013) revealed an approximately 3-fold increase (p=0.00002) in expression of leucine-rich repeat-containing G protein-coupled receptor 4 (Lgr4) in leukemic cells from patients with MLL AML compared to normal human hematopoietic stem cells (HSC). As recent studies have highlighted a critical link between R-spondin (Rspo)/Lgr4 and Wnt/β-catenin signaling pathways, we hypothesized that up-regulation of Lgr4 is associated with aberrant activation of β-catenin signaling in MLL LSC. We have previously demonstrated that β-catenin is highly expressed in HSC transformed by MLL-AF9 and is lower in HSC transduced with leukemic oncogenes such as Hoxa9/Meis1, while increased β-catenin expression is correlated with a poor survival rate in mice. In this study, western blots confirmed high levels of Lgr4 expression in HSC expressing MLL-AF9 compared to Hoxa9/Meis1. ShRNA-mediated stable knockdown of Lgr4 markedly reduced colony formation of HSC expressing MLL-AF9 by 55-65% (p=0.0001) and significantly prolonged mouse survival (p=0.0019) through its inhibition of endogenous β-catenin expression. This deficient phenotype could be rescued by expression of a constitutively active form of β-catenin. Furthermore, ectopic expression of Lgr4 alone was not sufficient for triggering the leukemic transformation of HSC but conferred a growth advantage in vivo to HSC expressing Hoxa9/Meis1 and significantly accelerated the onset of Hoxa9/Meis1-induced AML in mice (p=0.0011). These data support an oncogenic role of Lgr4 in promoting tumor formation through activation of β-catenin signaling. As Lgr4 has recently been identified as a receptor for the Rspo family of secreted proteins (Rspo1–Rspo4), we sought to determine if Rspo is a positive regulator of β-catenin signaling in MLL AML. We found that only the combination of Rspo3 and Wnt3a potently enhanced β-catenin signaling in HSC expressing MLL-AF9 whereas Rspo and Wnt3a alone or the combination of Wnt3a with other Rspo had no effects on β-catenin activity. Depletion of Lgr4 completely abolished Rspo3/Wnt3a-induced β-catenin signaling, suggesting Rspo3/Wnt3a potentiating β-catenin signaling through Lgr4. Next, we assessed if Lgr4 signals through G protein pathways. By testing G protein alpha inhibitors in MLL LSC, we demonstrated that G protein alpha-q (Gnaq) was required for maintenance of stem cell properties by chemical suppression of the Gnaq-activated β-catenin pathway with a Gnaq selective inhibitor, which exhibited a 3-fold decrease in colony formation (p=0.0001) and a 4-fold reduction in cell number (p=0.0009), and was sufficient to induce substantial cell differentiation and apoptosis. Treatment with Gnaq inhibitor abolished the effect of Lgr4 on β-catenin transactivation, implicating an Lgr4-Gnaq-β-catenin signaling pathway in MLL LSC. Microarray analysis of gene expression confirmed enrichment of genes related to cancer cell proliferation, migration and growth, as well as enrichment of Wnt target genes in LSC expressing Lgr4.Taken together, we report here an Rspo3/Wnt3a-Lgr4-Gnaq-β-catenin signaling circuit in MLL leukemogenesis. Interference with components of the circuit can block β-catenin signaling and perturb leukemia development. Thus, our findings provide potential therapeutic targets in treating LSC-based hematological malignancy driven by Wnt/β-catenin signaling. Disclosures:No relevant conflicts of interest to declare.

Analysis of LGR4 Receptor Distribution in Human and Mouse Tissues

LGR4 is an R-spondin receptor with strong positive effect on Wnt signaling. It plays a critical role in development as its ablation in the mouse led to total embryonic/neonatal lethality with profound defects in multiple organs. Haplotype insufficiency of LGR4 in human was associated with several diseases, including increased risk of squamous cell carcinoma of the skin, reduced birth weights, electrolyte imbalance, and decreased levels of testosterone, which are similar to the phenotypes of LGR4-hypomorphic mice. Tissue distribution of LGR4 was extensively analyzed in the mouse using gene-trap reporter enzyme alleles. However, its expression pattern in human tissues remained largely unknown. We have developed LGR4-specific monoclonal antibodies and used them to examine the expression of LGR4 in selected adult human and mouse tissues by immunohistochemical analysis. Intense LGR4-like immunoreactivity was observed in the epidermis and hair follicle of the skin, pancreatic islet cells, and epithelial cells in both the male and female reproductive organs. Of particular interest is that LGR4 is highly expressed in germ cells and pancreatic islet cells, which have important implications given the role of R-spondin-LGR4 signaling in the survival of adult stem cells. In addition, the majority of colon tumors showed elevated levels of LGR4 receptor. Overall, the expression pattern of LGR4 in human tissues mapped by this IHC analysis is similar to that in the mouse as revealed from gene trap alleles. Importantly, the pattern lends strong support to the important role of LGR4 in the development and maintenance of skin, kidney, reproductive systems, and other organs.

Abstract 2714: Expression and functional analysis of LGR4 in normal and cancer cells of human colon.

Abstract LGR4 (leucine-rich repeat containing G protein-coupled receptor 4) and its two closely related homologues LGR5 and LGR6 have been shown to function as receptors of R-spondins to potentiate Wnt signaling. The RSPO/LGR4-6 ligand receptor system has essential functions in embryonic development, cell proliferation and survival of adult stem cells. Particularly, LGR4 is required for the survival of intestinal stem cells and the maintenance of gut epithelium while LGR5 is specifically expressed in crypt stem cells. Wnt signaling is frequently dysregulated in various types of cancer, especially in colorectal cancers of which 90% of cases are mutated within this pathway. Most recently, ∼10% of colon cancers were found to contain RSPO gene fusions, but not APC or β-catenin alterations, as an alternative mechanism of Wnt signaling activation. However, expression pattern and function of LGR4 in normal and cancer cells of human colon are largely unknown. The underlying receptor mediating the carcinogenic functions of RSPO gene fusion in colorectal cancers is also unidentified. We developed and validated a panel of LGR4 antibodies that can detect either native or denatured LGR4 with high specificity and sensitivity. Immunohistochemistry analyses were carried out in multiple matched pairs of normal and cancer tissues of human colon. In normal colon LGR4 is expressed most abundantly in epithelial cells located at the bottom of the crypts, consistent with expression data from the mouse intestine. In colon cancer, level of LGR4 is dramatically increased when compared to that of the crypt cells of the matched normal tissues. Next, we used an LGR4 antibody to isolate LGR4-high and LGR4-low cells from a colorectal cancer cell line, and compared the cell populations in rate of proliferation, migration, invasion in vitro and tumor formation and growth in xenografts. Data from these expression and functional analyses will be presented and discussed. Citation Format: Jing Yi, Wei Xiong, Xing Gong, Qingyun Liu. Expression and functional analysis of LGR4 in normal and cancer cells of human colon. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2714. doi:10.1158/1538-7445.AM2013-2714

Abstract 4900: Functional and mechanism analysis of LGR4 in human lung cancer cells.

Abstract LGR4 (leucine-rich repeat containing G protein-coupled receptor 4) and its two closely related homologues LGR5 and LGR6 (LGR4-6) are members of the seven transmembrane domain (7TM) receptors with critical functions in embryonic development and adult stem cells. Recently, we and others discovered that LGR4-6 function as receptors of R-spondins (RSPO) to potentiate Wnt signaling. RSPOs are a group of four secreted proteins (RSPO1-4) with essential roles in organ development, sex determination, carcinogenesis, etc. Particularly, RSPO2 is required for normal lung development through enhancement of Wnt signaling and LGR6 is expressed in adult lung stem cells in the mouse. Among the 900 or so 7TM receptors, LGR4 was found to be one of the few that were highly upregulated in both squamous cell carcinoma (SqCC) and adenocarcinoma (AC) of the lung. Alterations in the Wnt signaling pathways were found in a small percentage of lung cancer. Concurrent activation of β-catenin signaling enhances tumor growth and metastasis of lung cancer cells with KRAS mutation. Furthermore, RSPO3 and LGR4 are co-expressed at high levels in ∼20% of lung cancer cell lines. However, potential roles of RSPO3-LGR4 in lung carcinogenesis have not been investigated. We developed and validated a panel of LGR4 antibodies that can detect either native or denatured LGR4 with high specificity and sensitivity. Immunohistochemistry analyses confirmed that LGR4 was highly expressed in the majority of SqCC and AC of the lung. Knockdown of LGR4 in a lung cancer cell line with high levels of and LGR4 and RSPO3 leads to dramatic decrease in endogenous Wnt signaling and significant reduction in cell growth, migration, and colony formation in vitro. The effect of knockdown on tumor growth in vivo is being tested. Data from these expression and functional analyses of LGR4 in human lung cancer will be presented and discussed. Citation Format: Xing Gong, Wei Xiong, Jing Yi, Kendra S. Carmon, Qingyun Liu. Functional and mechanism analysis of LGR4 in human lung cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4900. doi:10.1158/1538-7445.AM2013-4900

Leucine-Rich Repeat-Containing, G Protein-Coupled Receptor 4 Null Mice Exhibit Intrauterine Growth Retardation Associated with Embryonic and Perinatal Lethality

Leucine-rich repeat-containing, G protein-coupled receptors (LGRs) belong to the largest mammalian superfamily of proteins with seven-transmembrane domains. LGRs can be divided into three subgroups based on their unique domain arrangement. Although two subgroups have been found to be receptors for glycoprotein hormones and relaxin-related ligands, respectively, the third LGR subgroup, consisting of LGR4-6, are orphan receptors with unknown physiological roles. To elucidate the functions of this subgroup of LGRs, LGR4 null mice were generated using a secretory trap approach to delete the majority of the LGR4 gene after the insertion of a beta-galactosidase reporter gene immediately after exon 1. Tissues expressing LGR4 were analyzed based on histochemical staining of the transgene driven by the endogenous LGR4 promoter. LGR4 was widely expressed in kidney, adrenal gland, stomach, intestine, heart, bone/cartilage, and other tissues. The expression of LGR4 in these tissues was further confirmed by immunohistochemical studies in wild-type animals. Analysis of the viability of 250 newborn animals suggested a skewed inheritance pattern, indicating that only 40% of the expected LGR4 null mice were born. For the LGR4 null mice viable at birth, most of them died within 2 d. Furthermore, the LGR4 null mice showed intrauterine growth retardation as reflected by a 14% decrease in body weight at birth, together with 30% and 40% decreases in kidney and liver weights, respectively. The present findings demonstrate the widespread expression of LGR4, and an essential role of LGR4 for embryonic growth, as well as kidney and liver development. The observed pre- and postnatal lethality of LGR4 null mice illustrates the importance of the LGR4 signaling system for the survival and growth of animals during the perinatal stage.