Altered expression of the suppressors PML and p53 in glioblastoma cells with the antisense-EGF-receptor

Ginsenoside Rh2 inhibits growth of glioblastoma multiforme through mTor

Being the most malignant primary brain tumor in humans, glioblastoma multiforme (GBM) has a fairly poor patient survival after current combined treatment with chemotherapy, radiation, and surgery. Ginsenoside Rh2 (GRh2) has been reported to have a therapeutic effect on some tumors, and we recently reported its inhibitory effect on GBM growth in vitro and in vivo, possibly through an epidermal growth factor receptor (EGFR) signaling pathway. Here, using specific inhibitors, we found that the activation of EGFR signaling promoted GBM growth through PI3k/Akt/mTor signaling pathways. Moreover, GRh2 efficiently inhibited activation of this pathway at the receptor level. Together with our previous findings, these data suggest that GRh2 may suppress GBM growth through its competition with EGFR ligands for binding to the EGFR, and binding to EGFR by GRh2 does not lead to receptor phosphorylation. Thus, our data highlight a previous unappreciated role for GRh2 to inhibit EGFR signaling. GRh2 thus appears to be a promising therapy for cancers that require EGFR signaling to growth.

Inhibition of FoxO1 nuclear exclusion prevents metastasis of glioblastoma

Glioblastoma is the most aggressive malignant primary brain tumor in humans, with extremely poor patient survival. Although previous studies have demonstrated that expression of matrix metalloproteinase-9 (MMP9) in glioblastoma promotes cancer metastasis, the upstream molecular signaling cascades that control activation of MMP9 remain largely unknown. Here, we used a human glioblastoma line, A-172, to examine molecular signaling to activate MMP9. We found that epidermal growth factor (EGF)-induced activation of epidermal growth factor receptor (EGFR) in A-172 cells activated MMP9, resulting in an increase in cancer invasiveness. A specific inhibitor for EGFR efficiently blocked EGF-induced activation of MMP9 and then cancer invasiveness. Moreover, an inhibitor for phosphatidylinositol 3-kinase (PI-3 K)/protein kinase B (Akt) significantly inhibited the EGF-induced activation of MMP9. Furthermore, nuclear exclusion of a major Akt downstream target, Forkhead box protein O1 (FoxO1), was induced by Akt activation, which could be inhibited by either an EGFR inhibitor or by PI-3 K/Akt inhibitor. An expression of a constitutive nuclear form of FoxO1 significantly inhibited MMP9 activation induced by EGF. Taken together, these findings suggest that EGF/EGFR signaling activates downstream PI-3 K/Akt to induce FoxO1 nuclear exclusion, which activates MMP9 to promote glioblastoma invasiveness. Thus, FoxO1 appears to be a novel therapeutic target for inhibiting metastasis of glioblastoma.

EGFR signaling-dependent inhibition of glioblastoma growth by ginsenoside Rh2

Glioblastoma is the most common and most aggressive malignant primary brain tumor in humans, accounting for 52 % of all functional tissue brain tumor cases and 20 % of all intracranial tumors. The typical treatment involves a combination of chemotherapy, radiation, and surgery, whereas it still achieves fairly poor patient survival. Ginsenoside Rh2 has been reported to have a therapeutic effect on some tumors, but its effect on glioblastoma has not been extensively evaluated. Here, we show that ginsenoside Rh2 can substantially inhibit the growth of glioblastoma in vitro and in vivo in a mouse model. Moreover, the inhibition of the tumor growth appears to result from combined effects on decreased tumor cell proliferation and increased tumor cell apoptosis. Further analyses suggest that ginsenoside Rh2 may have its antiglioblastoma effect through inhibition of the epidermal growth factor receptor (EGFR) signaling pathway in tumor cells. In a lose-of-function experiment, recombinant EGFR was given together with ginsenoside Rh2 to the tumor cells in vitro and in vivo, which completely blocked the antitumor effects of ginsenoside Rh2. Thus, our data not only reveal an anti-glioblastoma effect of ginsenoside Rh2 but also demonstrate that this effect may function via inhibition of EGFR signaling in glioblastoma cells.

Promyelocytic leukemia (PML) protein plays important roles in regulating cell adhesion, morphology, proliferation and migration

PML protein plays important roles in regulating cellular homeostasis. It forms PML nuclear bodies (PML-NBs) that act like nuclear relay stations and participate in many cellular functions. In this study, we have examined the proteome of mouse embryonic fibroblasts (MEFs) derived from normal (PML^+/+) and PML knockout (PML^−/−) mice. The aim was to identify proteins that were differentially expressed when MEFs were incapable of producing PML. Using comparative proteomics, total protein were extracted from PML^−/− and PML^+/+ MEFs, resolved by two dimensional electrophoresis (2-DE) gels and the differentially expressed proteins identified by LC-ESI-MS/MS. Nine proteins (PML, NDRG1, CACYBP, CFL1, RSU1, TRIO, CTRO, ANXA4 and UBE2M) were determined to be down-regulated in PML^−/− MEFs. In contrast, ten proteins (CIAPIN1, FAM50A, SUMO2 HSPB1 NSFL1C, PCBP2, YWHAG, STMN1, TPD52L2 and PDAP1) were found up-regulated. Many of these differentially expressed proteins play crucial roles in cell adhesion, migration, morphology and cytokinesis. The protein profiles explain why PML^−/− and PML^+/+ MEFs were morphologically different. In addition, we demonstrated PML^−/− MEFs were less adhesive, proliferated more extensively and migrated significantly slower than PML^+/+ MEFs. NDRG1, a protein that was down-regulated in PML^−/− MEFs, was selected for further investigation. We determined that silencing NDRG1expression in PML^+/+ MEFs increased cell proliferation and inhibited PML expression. Since NDRG expression was suppressed in PML^−/− MEFs, this may explain why these cells proliferate more extensively than PML^+/+ MEFs. Furthermore, silencing NDRG1expression also impaired TGF-β1 signaling by inhibiting SMAD3 phosphorylation.

The PML gene is not involved in the regulation of MHC class I expression in human cell lines

The promyelocytic leukemia gene, PML, is a growth and transformation suppressor. An additional role for PML as a regulator of major histocompatibility complex (MHC) class I antigen presentation has been proposed in a murine model, which would account for evasion from host immunity of tumors bearing malfunctioning PML, such as acute promyelocytic leukemia. Here we investigated a possible role of PML for the control MHC class I expression in human cells. PML function was perturbed in human cell lines either by PML/RAR alpha transfection or by PML- specific RNA interference. Impairment of wild-type PML function was proved by a microspeckled disassembly of nuclear bodies (NBs), where the protein is normally localized, or by their complete disappearance. However, no MHC class I down-regulation was observed in both instances. We next constructed a PML mutant, PML mut ex3, that is a human homolog of the murine PML mutant, truncated in exon 3, that was shown to down-regulate murine MHC class I. PML mut ex3 transfected in human cell lines exerted a dominant-negative effect since no PML molecules were detected in NBs but, instead, in perinuclear and cytoplasmic larger dot-like structures. Nevertheless, no down-regulation of MHC class I expression was evident. Moreover, neither transfection with PML mut ex3 nor PML-specific RNA interference affected the ability of gamma-interferon to up-regulate MHC class I expression. We conclude that, in human cell lines, PML is not involved directly in the regulation of MHC class I expression.

E1A-mediated suppression of EGFR expression and induction of apoptosis in head and neck squamous carcinoma cell lines

Previous studies have shown early region 1A (E1A) gene to inhibit the proliferation of tumour cells with wild-type, but not mutant, p53. E1A has also been shown to downregulate c-erb-B-2/neu expression, resulting in inhibition of growth in c-erb-B-2/neu overexpressing tumour cells. In this study, we have investigated the effect of E1A expression on four head and neck squamous cell carcinoma (HNSCC) cell lines that do not overexpress c-erb-B-2/neu. Cell cycle and Western blot analysis show E1A-mediated induction of apoptosis in all cell lines examined. This induction of apoptosis was independent of the p53 status as it occurred in the cell lines with wild-type, mutated or deleted p53. However, there was no evidence of E1A-induced apoptosis in a p53(+ve) normal human fibroblast cell line, 1BR3. Analysis of apoptosis in the SCC cell lines demonstrated E1A-mediated downregulation of EGFR, which was overexpressed in each of these cell lines. Overexpression of an exogenously introduced EGFR, under the control of an E1A-insensitive heterologous promoter, blocked E1A induction of apoptosis in these cells. Therefore, E1A-mediated downregulation of EGFR expression appears to be the cause, rather than a consequence of E1A-induced apoptosis in these SCC cell lines. Previous studies have shown downregulation of EGFR expression by PML. Interestingly, E1A expression in the HNSCC cells altered the pattern of PML distribution and induced the level of PML protein, thus suggesting that E1A-mediated downregulation of EGFR may occur via direct or indirect interactions with PML. These findings demonstrate a novel pathway by which E1A can induce apoptosis and identify EGFR as a potential target for the development of therapeutic strategies against epithelial malignancies, the majority of which have abnormal EGFR expression.

Antisense epidermal growth factor receptor RNA transfection in human glioblastoma cells down-regulates telomerase activity and telomere length

Epidermal growth factor receptor is overexpressed and/or amplified in up to 50% of glioblastomas, suggesting an important role of this gene in glial tumorigenesis and progression. In the present study we demonstrated that epidermal growth factor receptor is involved in regulation of telomerase activity in glioblastoma. Antisense-epidermal growth factor receptor approach was used to inhibit epidermal growth factor receptor expression of glioblastoma U87MG cells. Telomerase activity in antisense-epidermal growth factor receptor cells decreased by up to 54 folds compared with control cells. Moreover, the telomere lengths of antisense-epidermal growth factor receptor cells were shortened. In addition, the tumorigenicity of antisense-epidermal growth factor receptor cells was significantly inhibited. Taken together, there were strong correlations between tumorigenicity and epidermal growth factor receptor expression levels, and between tumorigenicity and telomerase activity. These results provide evidence that epidermal growth factor receptor plays an important role in the regulation of telomerase activity of glioma cells. Our findings provide new insights into both the biological functions of epidermal growth factor receptor and the regulation of telomerase activity. The inhibition of telomerase activity triggered by antisense-epidermal growth factor receptor treatment may reflect yet another mechanism of antisense-epidermal growth factor receptor approach in tumour suppression.

Receptor-mediated delivery of an antisense gene to human brain cancer cells

BACKGROUND

The goal of this work was the development of a gene targeting technology that will enable the delivery of therapeutic genes to brain cancer cells in vivo following intravenous administration. High-grade brain gliomas overexpress the epidermal growth factor receptor (EGFR) and EGFR antisense gene therapy could reduce the growth of EGFR-dependent gliomas.

METHODS

A human EGFR antisense gene driven by the SV40 promoter in a non-viral plasmid carrying elements that facilitate extra-chromosomal replication was packaged in the interior of 85 nm pegylated immunoliposomes (PILs). The PILs were targeted to U87 human glioma cells with the 83-14 murine monoclonal antibody (MAb) to the human insulin receptor (HIR).

RESULTS

Confocal fluorescent microscopy demonstrated that the unconjugated HIR MAb is rapidly internalized by the glioma cells. Endocytosis followed by entry into the nucleus was also demonstrated for the HIR MAb conjugated PILs carrying fluorescein-labeled plasmid DNA. The PILs delivered exogenous genes to virtually all cells in culture, based on beta-galactosidase histochemistry. The targeting of a luciferase gene to the U87 cells with the PILs resulted in luciferase levels in excess of 150 pg/mg protein after 72 h of incubation. The level of luciferase gene expression in the U87 cells achieved with the PIL gene targeting system was comparable to that with lipofectamine. Targeting the EGFR antisense gene to U87 glioma cells with the PILs resulted in more than 70% reduction in [(3)H]thymidine incorporation into the cells; this was paralleled by a 79% reduction in the level of immunoreactive EGFR.

CONCLUSION

The present work describes the targeting of an EGFR antisense gene to human brain cancer cells, which results in a 70-80% inhibition in cancer cell growth. PILs provide a new approach to gene targeting that is effective in vivo following intravenous administration without viral vectors.

Proteome alterations in human hepatoma cells transfected with antisense epidermal growth factor receptor sequence

The epidermal growth factor (EGF) is a member of the growth factor superfamily that can stimulate the proliferation of many types of cells. Overexpression of EGF receptor (EGFR) was observed in many types of cancer cells. Anti-EGFR antibodies or antisense nucleic acid sequences of EGFR can suppress the growth of hepatoma cells. In order to further investigate the proteome alterations associated with malignant growth of the human hepatoma cells and the influence of EGFR signal pathway on the cellular proteome, we have comparatively analyzed the proteomes of human hepatoma cells transfected with antisense EGFR sequence (cell strain JX-1) and its control cells (cell strain JX-0) by two-dimensional (2-D) gel electrophoresis and mass spectrometry. Image analysis of silver-stained 2-D gels revealed that 40 protein spots showed significant expression changes in JX-1 cells compared to JX-0 cells. Three of them, including the tumor suppressor protein maspin, changed with tendency to the normal levels. Two protein spots were identified as HSP27 in the same gel, and one of them had a reduced level in JX-1 cells. The apparent alterations of HSP27 in expression level might be the results from their differential chemical modifications, suggesting the effect of dynamic post-translational modifications of proteins on the growth of hepatoma cells. Other proteins such as glutathione peroxidase (GPX-1) and 14-3-3-sigma also exhibited altered expression in JX-1 cells, and their functional implications are discussed.

Differential expression of a stress-modulating gene, BRE, in the adrenal gland, in adrenal neoplasia, and in abnormal adrenal tissues

Genes that modulate the action of hormones and cytokines play a critical role in stress response, survival, and in growth and differentiation of cells. Many of these biological response modifiers are responsible for various pathological conditions, including inflammation, infection, cachexia, aging, genetic disorders, and cancer. We have previously identified a new gene, BRE, that is responsive to DNA damage and retinoic acid. Using multiple-tissue dot-blotting and Northern blotting, BRE was recently found to be strongly expressed in adrenal cortex and medulla, in testis, and in pancreas, whereas low expression was found in the thyroid, thymus, small intestine and stomach. In situ hybridization and immunohistochemical staining indicated that BRE was strongly expressed in the zona glomerulosa of the adrenal cortex, which synthesizes and secretes the mineralocorticoid hormones. It is also highly expressed in the glial and neuronal cells of the brain and in the round spermatids, Sertoli cells, and Leydig cells of the testis, all of which are associated with steroid hormones and/or TNF synthesis. However, BRE expression was downregulated in human adrenal adenoma and pheochromocytoma, whereas its expression was enhanced in abnormal adrenal tissues of rats chronically treated with nitrate or nitrite. These data, taken together, indicate that the expression of BRE is apparently associated with steroids and/or TNF production and the regulation of endocrine functions. BRE may play an important role in the endocrine and immune system, such as the cytokine-endocrine interaction of the adrenal gland.