腺病毒介导的hepaCAM基因对膀胱癌细胞周期的影响

目的：以腺病毒为载体,研究hepaCAM基因对膀胱癌细胞T24和BIU-87的细胞周期影响。方法：以带有hepaCAM基因的腺病毒载体pAdH5-hepaCAM感染两株细胞,采用RT-QPCR和Western-blot、细胞免疫荧光方法检测感染pAdH5-hepaCAM组,pAdH5空载组和未感染组的hepaCAM mRNA 、蛋白的表达及其细胞定位。并采用流式细胞术检测hepaCAM对两株细胞周期影响,Western-blot方法检测细胞周期蛋白cyclinD1。结果：感染hepaCAM的T24和BIU-87细胞,hepaCAM mRNA和蛋白水平明显升高。流式结果显示hepaCAM阻滞T24与BIU-87细胞于G0/G1期。Western-blot检测实验组cyclinD1明显低于空载和空白组。细胞免疫荧光显示hepaCAM在单个细胞中主要表达于细胞浆中,在细胞之间表达于细胞连接处。结论：hepaCAM能阻滞膀胱癌细胞T24和BIU-87于G0/G1期,并使G1期关键周期蛋白cyclinD1下调。     

GlialCAM, an immunoglobulin-like cell adhesion molecule is expressed in glial cells of the central nervous system

Using structure based genome mining targeting vascular endothelial and platelet derived growth factor immunoglobulin (Ig) like folds, we have identified a sequence corresponding to a single transmembrane protein with two Ig domains, which we cloned from a human brain cDNA library. The cDNA is identical to hepatocyte cell adhesion molecule (hepaCAM), which was originally described as a tumor suppressor gene in liver. Here, we show that the protein is predominantly expressed in the mouse and human nervous system. In liver, the expression is very low in humans, and is not detected in mice. To identify the central nervous system (CNS) regions and cell types expressing the protein, we performed a LacZ reporter gene assay on heterozygous mice in which one copy of the gene encoding the novel protein had been replaced with beta-galactosidase. beta-galactosidase expression was prominent in white matter tracts of the CNS. Furthermore, expression was detected in ependymal cells of the brain ventricular zones and the central canal of the spinal cord. Double labeling experiments showed expression mainly in CNPase positive oligodendrocytes (OL). Since the protein is predominantly expressed in the CNS glial cells, we named the molecule glial cell adhesion molecule (GlialCAM). A potential role for GlialCAM in myelination was supported by its up-regulation during postnatal mouse brain development, where it was concomitantly expressed with myelin basic protein (MBP). In addition, in vitro, GlialCAM was observed in various developmental stages of OL and in astrocytes in processes and at cell contact sites. In A2B5 positive OL, GlialCAM colocalizes with GAP43 in OL growth cone like structures. Overall, the data presented here indicate a potential function for GlialCAM in glial cell biology.     

Cloning and characterization of hepaCAM, a novel Ig-like cell adhesion molecule suppressed in human hepatocellular carcinoma

BACKGROUND/AIMS: Previously, we reported on gene HEPN1 that was silenced in hepatocellular carcinoma (HCC) and its capability of arresting cell growth. In this study, we identified another novel gene hepaCAM from the liver, which contains the full-length HEPN1 on its antisense strand in the 3'-noncoding region, and assessed its expression, characteristics and functions in HCC. METHODS: Full-length hepaCAM cDNA was isolated by rapid amplification of cDNA ends. The gene expression was examined by semi-quantitative RT-PCR in 23 paired HCC liver specimens and 5 HCC cell lines. Transfection studies, coupled with immunocytochemistry, cellular interaction analyses, colony formation and microtetrazolium assay, were employed to elucidate the localization and functions of hepaCAM. RESULTS: The expression of hepaCAM decreased in 20/23 of HCC samples and was undetectable in 5 HCC cell lines tested. The gene product consisting of 416 amino acids displayed the typical structure of Ig-like cell adhesion molecules. The protein was glycosylated and predominantly localized on the cytoplasmic membrane. When re-expressed in HepG2, hepaCAM accelerated cell spreading (P<0.001), increased cell motility (P=0.0011), reduced colony formation (P=0.0022), and inhibited cell growth (P<0.001). CONCLUSIONS: Gene hepaCAM, frequently silenced in HCC, encodes an Ig-like transmembrane glycoprotein and is involved in cell adhesion and growth control.     

Identification of Hypermethylation in Hepatocyte Cell Adhesion Molecule Gene Promoter Region in Bladder Carcinoma

Background: Epigenetic regulation such as aberrant hypermethylation of CpG islands in promoter plays a key role in tumorigenesis. 5-Aza-2''-deoxycytidine (5-aza-CdR) which is a potent inhibitor of DNA methylation can reverse the abnormal hypermethylation of the silenced tumor suppressor genes (TSGs). It has been reported that hepatocyte cell adhesion molecule (hepaCAM) acts as a tumor suppressor gene and expression of its mRNA and protein were down-regulated in bladder cancer. Over-expression of hepaCAM can inhibit cancer growth and arrest renal cancer cells at G0/G1 phase. In this study, we investigated the methylation status of hepaCAM gene, as well as the influence of 5-aza-CdR on expression of hepaCAM gene in bladder cancer cells. Methods: CpG islands in hepaCAM promoter and methprimers were predicted and designed using bioinformatics program. Methylation status of hepaCAM promoter was evaluated in bladder cancer tissues and two cell lines (T24 and BIU-87) by Methylation-specific PCR; Western blot and Immunofluorescence were used to detect expression of hepaCAM protein after 5-aza-CdR treatment; Flow cytometry assay was performed to determine effectiveness of 5-aza-CdR on cell cycle profile. Results: CpG island in promoter of hepaCAM gene was hyper-methylated both in bladder carcinoma tissues and cell lines (T24 and BIU-87). Otherwise, aberrant methylation of its promoter was associated with its decreased expression. Hypermethylation of hepaCAM gene was reversed and expression of its mRNA and protein were re-activated in two cell lines by DNA methyltransferases inhibitor 5-aza-CdR. Flow cytometry assay demonstrated that 5-aza-CdR can inhibit growth of cancer cells by arresting cancer cells at G0/G1 phase. Conclusion: Abnormal hypermethylation in CpG island of hepaCAM promoter is involved in absence of hepaCAM gene expression when bladder cancer occurs. Re-activation of hepaCAM gene by 5-aza-CdR can inhibit growth of cancer cells and arrest cells at G0/G1 phase.