GABA stimulates human hepatocellular carcinoma growth through overexpressed GABAA receptor theta subunit

AIM: To investigate the function of gamma-aminobutyric acid (GABA) and gamma-aminobutyric acid A receptor θ subunit (GABRQ) in hepatocellular carcinoma (HCC). METHODS: Semiquantitative polymerase chain reaction was used for detecting the expression of GABRQ receptor among HCC cell line HepG2, normal liver cell line L-02, non-malignant Chang's liver cells, 8 samples of HCC tissues and paired non-cancerous tissues. HepG2 cells were treated with GABA at serial concentrations (0, 1, 10, 20, 40 and 60 μmol/L), and their proliferating abilities were analyzed with the methyl thiazolyl tetrazolium assay, cell cycle analysis and tumor implanted in nude mice. Small interfering RNA was used for knocking down the endogenous GABRQ in HepG2. Proliferating abilities of these cells treated with or without GABA were analyzed. RESULTS: We identified the overexpression of GABRQ in HCC cell lines and half of the tested HCC tissues. Knockdown of endogenous GABRQ expression in HepG2 attenuated HCC cell growth, suggesting its role in HCC cell viability. We studied the effect of GABA in the proliferation of GABRQ-positive cell lines in vitro and in vivo , and found that GABA increased HCC growth in a dosedependent manner. Notably, the addition of GABA into the cell culture medium promoted the proliferation of GABRQ-expressing HepG2 cells, but not GABRQ-knockdown HepG2 cells, which means that GABA stimulates HepG2 cell growth through GABRQ. CONCLUSION: GABRQ play important roles in HCC development and progression and could be a promising molecular target for the development of new diagnostic and therapeutic strategies of HCC.

Comparative genomic study of gastric epithelial cells co-cultured with Helicobacter pylori

AIM:To identify genes potentially involved in Helicobacter pylori(H.pylori)-induced gastric carcinogenesis.METHODS:GES-1 cells were co-cultured with H.pylori strains isolated from patients with gastric carcinoma(GC,n = 10) or chronic gastritis(CG,n = 10) for in vitro proliferation and apoptosis assays to identify the most and least virulent strains.These two strains were cagA-genotyped and used for further in vivo carcinogenic virulence assays by infecting Mongolian gerbils for 52 wk,respectively;a broth free of H.pylori was lavaged as control.Genomic profiles of GES-1 cells cocultured with the most and least virulent strains were determined by microarray analysis.The most differentially expressed genes were further verified using quantitative real-time polymerase chain reaction in GES-1cells infected with the most and least virulent strains,and by immunohistochemistry in H.pylori positive CG,precancerous diseases,and GC biopsy specimens in an independent experiment.RESULTS:GC-derived H.pylori strains induced a potent proliferative effect in GES-1 cells in co-culture,whereas CG-derived strains did not.The most(from a GC patient) and least(from a CG patient) virulent strains were cagA-positive and negative,respectively.At week 52,CG,atrophy,metaplasia,dysplasia,and GC were observed in 90.0%,80.0%,80.0%,90%,and 60.0%,respectively,of the animals lavaged with the most virulent strain.However,only mild CG was observed in 90% of the animals lavaged with the least virulent strain.On microarray analysis,800 differentially expressed genes(49 up-and 751 down-regulated),involving those associated with cell cycle regulation,cell apoptosis,cytoskeleton,immune response,and substance and energy metabolisms,were identified in cells co-cultured with the most virulent strain as compared with those co-cultured with the least virulent strain.The six most differentially expressed genes(with a betweenness centrality of 0.1-0.2) were identified among the significant differential gene profile network,including JUN,KRAS,BRCA1,SMAD2,TRAF1,and HDAC6.Quantitative real-time polymerase chain reaction analyses verified that HDAC6 and TRFA1 mRNA expressions were significantly more up-regulated in GES-1 cells cocultured with the most virulent strain than in those cocultured with the least virulent strain.Immunohistochemistry of gastric mucosal specimens from H.pyloripositive patients with CG,intestinal metaplasia(IM),dysplasia,and GC showed that moderately positive and strongly positive HDAC6 expression was detected in 21.7% of CG patients,30.0% of IM patients,54.5% of dysplasia patients,and 77.8% of GC patients(P < 0.001).The up-regulation of TRAF1 expressions was detected in 34.8%,53.3%,72.7%,and 88.9% specimens of CG,IM,dysplasia,and GC,respectively(P < 0.001).CONCLUSION:The overexpression of HDAC6 and TRAF1 in GES-1 cells co-cultured with the GC-derived strain and in H.pylori-positive dysplasia and GC suggests that HDAC6 and TRAF1 may be involved in H.pyloriinduced gastric carcinogenesis.