Epstein-Barr virus facilitates the malignant potential of immortalized epithelial cells: from latent genome to viral production and maintenance.

Epstein-Barr virus (EBV) is closely associated with several malignancies, including nasopharyngeal carcinoma. To investigate the EBV activity in tumor development, we tried to establish a malignant model of EBV-infected cells in nude mice. On the basis of the Maxi-EBV system, a human embryonic kidney epithelial cell line (293) with a low malignant potential was used for a stable EBV genome infection. The derived cell line, termed 293-EBV, exhibited obvious morphological transformation and significantly increased growth ability, with the cell cycle redistributed. The clonability and tumorigenicity were also substantially accelerated. In 293-EBV cells, the expression level of the transcription factor NF-kappaB and JNK2 were upregulated. The result suggested that latent membrane protein 1 (LMP1) was an important viral protein responsible for the enhanced malignant potential. Matured and budding virus particles were observed in tumor tissues, confirming the spontaneous reactivation of EBV from latent genome to lytic cycle at the site of tumor development. Primary culture of tumor tissues showed two patterns about the EBV maintenance or not in newly grown cells, and this was dependent on the thickness of the planted tissues. Moreover, the tumor cells lost EBV genome easily when subcultured at low density. Our findings revealed the cell-to-cell contact mechanism, which was required for the EBV maintenance in the tumor cells during the expansion of EBV-infected cells. This mechanism might give an explanation to the phenomenon that EBV genome in epithelial tumor cells becomes easily lost during subculture in vitro. Our results provided further evidence of a function for EBV in the etiology of tumor development.

[Effect of all-trans-retinoic acid on C6 glioma cell proliferation and differentiation].

OBJECTIVE: To explore the effect of all-trans-retinoic acid (ATRA) on the growth inhibition and cellular differentiation of C6 glioma cells. METHODS: Human glioma C6 cells were treated with 5 mg/L ATRA,and the inhibition of cell growth was assessed by methyl thiazolyl tetrazolium assay. The differentiation of C6 cells was determined by flow cytometry, microscopy,transmission electron microscope, and immunohistochemical technique. RESULTS: Treatment of ATRA could result in the growth inhibition of C6 cells, and the cell density significantly decreased(P<0.01). The cell cycle distribution was changed, G0/G1 phase was prolonged, and cells at S phase decreased(P<0.01). The C6 glioma cells displayed normal fibroblast-like morphology under the microscope before the induction, and the ATRA-treated C6 cells became slightly long, turned into round in the middle, and had protrusions at both ends. The ATRA-treated C6 cells did not display obvious apoptosis by flow cytometry(P>0.05).Whereas, early apoptosis was observed under the transmission electron microscope, the vacuoles increased, the mitochondria and endoplasmic reticulum were abundant in the cytoplasm, and the cellular structures tended to be normal.The expression of glial fibrillaryacidic protein in C6 cells increased in the treatment group. CONCLUSION: ATRA can inhibit the proliferation, and induce the differentiation of C6 glioma cells.

Probucol mediates vascular remodeling after percutaneous transluminal angioplasty via down-regulation of the ERK1/2 signaling pathway.

Although probucol is known to prevent restenosis by regulating vascular remodeling after percutaneous transluminal coronary angioplasty, the mechanisms remain unclear. The present study was designed to investigate whether probucol mediates vascular remodeling via the extracellular signal-regulated kinase 1/2 (ERK1/2) signalling pathway. A rabbit restenosis model was used, in which the New Zealand white rabbits received angioplasty with a 3.5 F angioplasty balloon catheter and the proliferation and migration of smooth muscle cells (SMCs) was induced by oxidized low-density lipoprotein (ox-LDL). We evaluated several vascular remodeling parameters and found that probucol prevented lumen restenosis and mediated expansive remodeling with a remodeling index greater than 1 and that the proliferation and migration of SMCs was inhibited. Based on Western blot analyses, probucol decreased the expression of phospho-mitogen-activated protein kinase kinases 1 (p-MEK1) and phospho-ERK1/2 and enhanced the expression of mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) and caveolin-1. Cells treated with the MEK1 inhibitor PD98059 demonstrated a remarkable suppression of the effects of probucol. Furthermore, immunofluorescence analysis showed that probucol inhibited the activation of ERK1/2 by preventing its translocation to the nucleus. It was also found that c-myc expression in aortic tissue after angioplasty and the activator protein 1 (AP1) activity in SMCs induced by ox-LDL were decreased with probucol treatment. In conclusion, probucol mediated vascular remodeling to prevent restenosis after angioplasty by down-regulating the ERK1/2 signaling pathway.

[Expression absence of LRRC4 gene in glioblastoma cell lines].

OBJECTIVE: To examine the expression absence of LRRC4 gene in glioblastoma cell lines. METHODS: RT-PCR and Northern blot were used to detect the expression of LRRC4 gene in 6 glioblastomas cells lines. Polymerase chain reaction and DNA sequencing were used to screen the LRRC4 gene mutation, while bioinformation assay was used to search for the reason of LRRC4 gene absence in U251 cell lines. RESULTS: The expression of LRRC4 was absent in 6 malignant glioma cell lines (U251, U87, BT325, SF126, SF767 and M17), which were examined by Northern-blot and RT-PCR assay. All sequencing of PCR products from gDNA of SF126, SF767, and M17 cell lines contained the point mutation at the same position ( LRRC4 geneT977A) (3/5), which was a synonymous mutation. However, PCR products from gDNA of U251 and U87 cell lines (2/5) were not obtained. The expression absence of LRRC4 was ascribed to the loss of homozygosity of 7q32-ter in U251 cell lines. CONCLUSION: The expression of LRRC4 gene is absent in glioblastoma cell lines, and it offers the important experiment proof for LRRC4 to act as a new candidate of brain tumor suppressor gene from glioma. The loss of homozygosity of 7q32-ter contributed to the expression absence of LRRC4 in U251 cell lines.

[Inhibitory effect of LRRC4 on the mobility and invasion of glioblastomas through the SDF-1alpha/CXCR4 axis].

OBJECTIVE: To explore the effect of LRRC4 on the mobility and invasion of glioblastomas U251 cells through the SDF-1alpha/CXCR4 axis. METHODS: RT-PCR, transfilter cell invasion assay, adhesion assay, scraping test, scrape loading, and dye transfer assay were used to determine the effect of LRRC4 on U251 cells. RESULTS: SDF-1 alpha could increase the invasion in U251 which expressed CXCR4. The reintroduction of LRRC4 in U251 cells could inhibit the expression of CXCR4. LRRC4 also inhibited the adhesion ability of U251 to ECV304 as well as the mobility and invasion ability in vitro, which was mediated by the SDF-1alpha/CXCR4 axis. Furthermore, LRRC4 could greatly enhance the gap junctional intercellular communication of U251 cells. CONCLUSION: The reintroduction of LRRC4 in U251 cells can inhibit the expression of CXCR4 and the SDF-1alpha/CXCR4 axis-mediated cell invasion in vitro.

The role of NGX6 and its deletion mutants in the proliferation, adhesion and migration of nasopharyngeal carcinoma 5-8F cells.

OBJECTIVE: To demonstrate the subcellular localization of nasopharyngeal carcinoma (NPC)-associated gene 6 (NGX6) and its basic structure and function. METHODS: The deletion mutants of NGX6 were constructed by one-step PCR and transfected into NPC cell line 5-8F. The subcellular location of NGX6 or its mutants was detected by immunofluorescence staining of cytoplasm (CYTO) and nuclear protein, and immunoelectron-microscopic analysis. The role of NGX6 and its mutants in the proliferation, adhesion and migration of NPC 5-8F cells was detected using the following assays: growth curve, colony formation in soft agar, cell adhesion, in vitro Matrigel invasion, and in vitro scratch wound healing. RESULTS AND CONCLUSIONS: NGX6 and its mutants were distributed on the plasma membrane, nuclear membrane, endoplasmic reticulum membrane, and other membrane structures in the cytosol. The deleted domains did not affect its distribution in 5-8F cells. NGX6 could increase the adhesion but inhibited the proliferation, growth and migration of 5-8F cells. The epidermal growth factor-like domain and CYTO region were found to be important for NGX6 to modulate cell adhesion, and CYTO was found to be essential for NGX6 involved in the regulation of growth, proliferation, and migration of 5-8F cells.

Detection and location of Helicobacter pylori in human gastric carcinomas.

AIM: To define the infection status of Helicobacter pylori in 109 patients with gastric cancers and H pylori localization in gastric carcinoma tissues in South China. METHODS: The incidence of H pylori infection in gastric carcinomas was estimated by polymerase chain reaction (PCR), simultaneously; both morphological features and the localization of H pylori in gastric carcinomas were demonstrated by Warthin-Starry (WS) staining. The relationships between H pylori infection and the clinical-pathologic factors of gastric carcinomas were analyzed by software SPSS10.0. RESULTS: H pylori was found in 42 (39.03%) and 58 (53.21%) cases of 109 patients with gastric carcinomas by PCR and WS, respectively. H pylori infection rate detected in gastric carcinomas by WS was higher than that by PCR (chi2 = 9.735, P < 0.005 < 0.01). WS stain showed that H pylori existed in the gastric antrum mucus, mucosal gland of normal tissues adjacent to gastric carcinomas and the gland, mucus pool of cancer tissues. The positive rate of H pylori in normal tissues adjacent to carcinomas was higher than that in cancer tissues (chi2 = 15.750, P < 0.005 < 0.01). No significant differences in age, sex, site, histological types and lymph node metastasis were found between H pylori-positive gastric carcinomas and H pylori-negative cases by both methods, but there were statistically significant differences of H pylori positive rate between early and advanced stage of gastric carcinomas (chi2 = 4.548 or 5.922, P = 0.033 or 0.015 < 0.05). CONCLUSION: These results suggested that H pylori infection might play a certain role in the early stage of carcinogenesis of human gastric mucosa epithelia.