ABSTRACT
G protein-coupled receptors (GPCRs) are important signal transduction mediators and pharmacological therapeutic targets. G protein-coupled receptor 137 (GPR137) was initially reported as a novel orphan GPCR around 10 years ago. Some orphan GPCRs have been implicated in cancer cell proliferation and migration. The aim of this study is to investigate the role of GPR137 in hepatocellular carcinoma (HCC). GPR137 is widely expressed in several human HCC cell lines, as determined by real-time PCR. We then applied lentivirus mediated RNA interference (RNAi) to knock down GPR137 expression in two HCC cell lines HepG2 and Bel7404. Depletion of GPR137 remarkably inhibited cell proliferation and colony formation capacity. Knockdown of GPR137 in HepG2 cells led to cell cycle arrest at G0/G1 phase and G2/M phase, and induced cell apoptosis, as determined by flow cytometry analysis, which contributed to cell growth inhibition. Our findings suggested that GPR137 could facilitate HCC cell proliferation and thus promote hepatocarcinogenesis.
Subject(s)
RNA Interference , Receptors, G-Protein-Coupled/metabolism , Apoptosis , Carcinoma, Hepatocellular/metabolism , Carcinoma, Hepatocellular/pathology , Cell Cycle Checkpoints , Cell Line, Tumor , Cell Proliferation , Down-Regulation , Hep G2 Cells , Humans , Liver Neoplasms/metabolism , Liver Neoplasms/pathology , RNA, Small Interfering/metabolism , Receptors, G-Protein-Coupled/antagonists & inhibitors , Receptors, G-Protein-Coupled/geneticsABSTRACT
BACKGROUND: We investigated the distribution and clinical significance of mobilized endothelial progenitor cells (EPCs) in hepatocellular carcinoma (HCC). We found that many more EPCs were recruited to nonmalignant liver tissue (especially into adjacent non-tumor tissues (AT)) than to tumor vessels. These results suggest that the mechanism underlying the recruitment of EPCs into microvessels in AT merits further investigation METHODS: Angiogenic factors were detected in three tissue microarrays comprising normal liver, paired tumor tissue (TT) and AT from 105 patients (who had undergone hepatectomy for HCC) using immunohistochemistry. Also, the number of EPCs (positive for Sca-1, Flk-1 and c-Kit) in the blood and liver of cirrhotic mice were determined by flow cytometry and immunohistochemistry. The distribution of these labeled EPCs in tumor and non-tumor tissues was then studied. RESULTS: The results from the tissue microarrays showed that the expression levels of VEGF-A, bFGF, TGF-ß, MCP-1, TSP-1, MMP-9, TIMP-2, and endostatin were significantly higher in AT than in either normal liver or TT (p < 0.05), but no significant difference was found in the expression levels of COX-2 and NOS-2 between AT and TT. The expression of VEGF-A, bFGF, TGF-ß, MCP-1, TSP-1, MMP-9, TIMP-2, endostatin, COX-2, and NOS-2 in normal liver tissue was weaker than that in AT or TT. In cirrhotic mice, the number of circulating endothelial progenitor cells gradually increased, before decreasing again. In this mouse model, increased numbers of EPCs were recruited and homed specifically to the cirrhotic liver. CONCLUSIONS: Both liver cirrhosis and HCC led to increased expression of pro-angiogenic factors, which resulted in the recruitment of EPCs into AT. Also, EPCs were mobilized, recruited and homed to cirrhotic liver. The unique pathology of HCC coupled with liver cirrhosis may, therefore, be associated with the distribution and function of EPCs.
Subject(s)
Carcinoma, Hepatocellular/pathology , Endothelial Cells/transplantation , Liver Cirrhosis/pathology , Liver Neoplasms/pathology , Liver/pathology , Neovascularization, Pathologic , Stem Cells/pathology , Angiogenesis Inducing Agents , Animals , Biomarkers, Tumor , Carcinoma, Hepatocellular/metabolism , Endothelial Cells/metabolism , Endothelial Cells/pathology , Female , Flow Cytometry , Humans , Immunoenzyme Techniques , Liver/metabolism , Liver Cirrhosis/metabolism , Liver Neoplasms/metabolism , Male , Mice , Middle Aged , Stem Cells/metabolism , Tissue Array AnalysisABSTRACT
The neurite outgrowth inhibitor Nogo has attracted great interest, but its relevance with hepatocellular carcinoma has not been reported. This paper first found mutations of Nogo-C in HCC patients from Qidong in China: A172G (Thr58Ala), A340G (Arg114Gly), A571G (Ile191Val). In six examined patient cases from Qidong, the mutations occurred in five cases. The mutation Arg114Gly was predicted bioinformatically to affect Nogo-66 dimensional structure of Nogo-C. Our previous works also had indicated that mutant Nogo-C promoted liver cancer cell line apoptosis and resulted in molecular marker of HCC p53 gene transfer from nucleus to cytoplast. Above results revealed a new physiological role and clinical implications of Nogo-C on HCC.
Subject(s)
Carcinoma, Hepatocellular/genetics , Mutation, Missense , Myelin Proteins/genetics , Adult , Aged , China , Female , Humans , Male , Middle Aged , Nogo Proteins , Protein ConformationABSTRACT
BACKGROUND: Endoglin (CD105) has been considered a prognostic marker for hepatocellular carcinoma (HCC), and widely used as an appropriate targeting for antiangenesis therapy in some cancers. Our aim was to evaluate the distribution and expression of CD105 in the liver of patients with HCC, and to discuss whether CD105 may be used as an appropriate targeting for antiangenesis therapy in HCC. METHODS: Three parts of liver tissues from each of 64 patients with HCC were collected: tumor tissues (TT), adjacent non-tumor (AT) liver tissues within 2 cm, and tumor free tissues (TF) 5 cm far from the tumor edge. Liver samples from 8 patients without liver diseases served as healthy controls (HC). The distribution and expression of CD105 in tissues were evaluated by immunohistochemistry, Western blotting analysis, and real-time PCR. HIF-1alpha and VEGF165 protein levels in tissues were analyzed by Immunohistochemistry and Western blotting analysis or ELISA. RESULTS: CD105 was positively stained mostly in a subset of microvessels 'endothelial sprouts' in TT of all patients while CD105 showed diffuse positive staining, predominantly on hepatic sinus endothelial cells in the surrounding of draining veins in TF and AT. The mean score of MVD-CD105 (mean +/- SD/0.74 mm2) was 19.00 +/- 9.08 in HC, 153.12 +/- 53.26 in TF, 191.12 +/- 59.17 in AT, and 85.43 +/- 44.71 in TT, respectively. Using a paired t test, the expression of CD105 in AT and TF was higher than in TT at protein (MVD, p = 0.012 and p = 0.007, respectively) and mRNA levels (p < 0.001 and p = 0.009, respectively). Moreover, distribution and expression of CD105 protein were consistent with those of HIF-1alpha and VEGF165 protein in liver of patients with HCC. The level of CD105 mRNA correlated with VEGF165 level in TF (r = 0.790, p = 0.002), AT (r = 0.723, p < 0.001), and TT (r = 0.473, p = 0.048), respectively. CONCLUSION: It is demonstrated that CD105 was not only present in neovessels in tumor tissues, but also more abundant in hepatic sinus endothelium in non-tumor tissues with cirrhosis. Therefore, CD105 may not be an appropriate targeting for antiangenesis therapy in HCC, especially with cirrhosis.
