Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The epidermal growth factor receptor binds the mitogens epidermal growth factor and transforming growth factor-alpha. Increased expression of the epidermal growth factor receptor has been noted in many types of tumors and is associated with gene amplification in several including epidermoid carcinoma, lung carcinoma, breast carcinoma and glioblastoma. We have recently observed increased expression of the epidermal growth factor receptor messenger RNA in neoplastic tissue relative to normal kidney tissue from patients with renal cell carcinoma. To determine if epidermal growth factor receptor gene amplification was present in renal cell carcinoma, DNA was extracted from renal cell carcinoma cell lines and from normal kidney and renal cell carcinoma tissues derived from radical nephrectomy specimens from thirty patients. DNA was analyzed by Southern blot hybridization. There was no epidermal growth factor receptor gene amplification detected in the renal cell carcinoma samples studied, indicating the increased epidermal growth factor gene expression observed in renal cell carcinoma does not occur through gene amplification. Unlike other tumors with enhanced epidermal growth factor receptor gene expression, amplification of this gene does not appear to be a common feature of renal cell carcinoma.
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PMID:Epidermal growth factor receptor gene analysis in renal cell carcinoma. 229 52

Various growth factors and basement membrane proteins have been implicated in the pathobiology of astrocytomas. The goal of this study was to determine the relative contribution of these two factors in modulating the phenotype of U-373 MG glioblastoma cells as determined by the expression of the intermediate filament proteins glial fibrillary acidic protein, vimentin, and nestin. For these determinations, cells plated in serum-free medium were treated either with growth factors binding to tyrosine kinase receptors including transforming growth factor-alpha, epidermal growth factor, platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 or with basement membrane proteins including collagen IV, laminin, and fibronectin. The changes in the expression levels of intermediate filament proteins in response to these treatments were analyzed by quantitation of immunoblots. The results demonstrate that collagen IV and growth factors binding to tyrosine kinase receptors decrease the glial fibrillary acidic protein content of U-373 MG cells. Growth factors binding to tyrosine kinase receptors also decrease the vimentin content of these cells but do not affect their nestin content. On the other hand, basement membrane proteins decrease the nestin content of U-373 MG cells but do not affect their vimentin content. The significance of these results with respect to the role played by different factors in modulating the phenotype of neoplastic astrocytes during tumor progression is discussed.
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PMID:Effects of growth factors and basement membrane proteins on the phenotype of U-373 MG glioblastoma cells as determined by the expression of intermediate filament proteins. 977 47

We previously reported that schwannoma-derived growth factor (SDGF), a member of heparin-binding epidermal growth factor (EGF) family, participates in autocrine pathways and promotes rat glioma cell growth. To investigate the potential role of similar molecules in human gliomas, we examined 7 human glioma cell lines and 11 glioblastoma specimens for expression of the human homologue of SDGF, amphiregulin (AR), as well as heparin-binding EGF-like growth factor (HB-EGF). Northern blot analysis revealed that only one cell line and no tumor specimens expressed AR mRNA. In contrast, HB-EGF mRNA was expressed in all human glioma cell lines and its level of expression was two- to five-fold higher than that of control brain tissues in 8 of 11 glioblastoma cases. Immunohistochemistry demonstrated that membrane-anchored HB-EGF (proHB-EGF) and EGFR were co-expressed in 44% of 34 human malignant gliomas. Introduction of exogenous HB-EGF (10 ng/ml) increased human glioma cell proliferation, and anti-HB-EGF blocking antibodies reduced the growth of glioma cells by 30-40%, confirming the presence of an autocrine loop. When added to the medium, transforming growth factor-alpha, basic fibroblast growth factor, or HB-EGF rapidly induced HB-EGF mRNA expression. These results indicate that HB-EGF and proHB-EGF contribute to the growth of human malignant glioma cells, most likely through autocrine and juxtacrine mechanisms.
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PMID:Heparin-binding epidermal growth factor-like growth factor stimulates mitogenic signaling and is highly expressed in human malignant gliomas. 979 95

p53 protein is a transcription factor involved in multiple tumor-suppressor activities including cell cycle control and apoptosis. TP53 gene is frequently mutated in glioblastoma, suggesting the importance of inactivation of this gene product in gliomagenesis. Restoration of p53 function in glioblastoma cell lines deficient for p53 has shown that p53 induces growth arrest or apoptosis depending on the cell line and vector used to transduce wild-type TP53 alleles. Considering that astrocytes grow and express p53, it is not clear whether these results reflect physiologic responses or the result of p53 overexpression in combination with cellular responses to viral vector infection. Here, we reassessed this issue using a glioblastoma cell line (LN382) that expresses an endogenous temperature-sensitive mutant p53. This cell line expresses TP53 alleles (100% as determined by a p53 transcriptional assay in yeast) mutated at codon 197 GTG (Val) > CTG (Leu). We found that the p53 protein in these cells acted as an inactive mutant at 37 degrees C and as a functional wild-type p53 below 34 degrees C as demonstrated by several lines of evidence, including (i) restoration of transactivating ability in yeast, (ii) induction of p53-modulated genes such as CDKN1(p21) and transforming growth factor-alpha, (iii) disappearance of accumulated p53 protein in the nucleus and (iv) decrease in steady state p53 protein levels. This temperature switch allowed p53 levels, which were close to physiological levels to dramatically reduce LN382 cell proliferation by inducing a G(1)/S cell cycle block, but not to induce apoptosis. The lack of apoptosis was considered to be a result of the low level p53 expression, because increasing wild-type p53 levels by adenoviral-mediated gene transfer caused apoptosis in these cells. The LN382 cell line will be extremely useful for investigations into the roles of p53 in cellular responses to a variety of stimuli or damages.
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PMID:Restoration of endogenous wild-type p53 activity in a glioblastoma cell line with intrinsic temperature-sensitive p53 induces growth arrest but not apoptosis. 1166 76

Antisense oligonucleotides (oligos) complementary to mRNA encoding transforming growth factor-alpha (TGF-alpha) and its target, the epidermal growth factor receptor (EGFR), are efficacious against human prostate and breast cancers carried in athymic nude mice. Glioblastomas, also regulated by EGFR expression, would appear to be similarly susceptible, and we now employ them against the T98G tumor model. T98G cells were distributed into wells and allowed to adhere prior to addition of oligos (12.5 microM) directed against TGF-alpha and/or EGFR for 6 d of treatment before thymidine radiolabeling. Supplemental media and oligos (25 microM final concentration) were added after d 3. Statistically significant inhibition by oligos directed against TGF-alpha, EGFR, and their combination was 13.8%, 26.3%, and 18.1%, respectively. In a subsequent experiment cells were incubated with increasing amounts of each oligo and their combination for 3 d prior to radiolabeling. Statistically significant inhibition of growth for either oligo at every concentration was found. Cells incubated with 6.25, 12.5, 25, and 50 microM antisense directed against TGF-alpha had a mean inhibition of 29.3%, 33.3%, 21.7%, and 46.6%, respectively. Cells similarly treated with oligos against EGFR had a mean inhibition of 77.9%, 80.3%, 82.0%, and 83.7%, respectively, and cells incubated with 6.25, 12.5, 25 and 50 microM of each oligo had a mean inhibition of 74.7%, 70.6%, 70.8%, and 76.3%, respectively. Lastly, in a paired experiment, cells treated with 0, 0.39, 0.78, 1.56, 3.125, and 6.25 microM of oligos, either specifically directed against EGFR or a random control, for 3 d were evaluated for both thymidine incorporation and EGFR expression. Statistically significant inhibition of 3H-thymidine incorporation was seen in cells with the oligo specifically directed against EGFR at 3.125 microM and 6.25 microM when compared to non-oligo containing controls. This was accompanied by a comparable significantly decreased expression of a low-MW reactive derivative of EGFR at 3.125 microM and 6.25 microM in Western blots, and of a high-MW reactive EGFR at 6.25 microM. The significant effect against high-MW EGFR was observed vs both the non-oligo containing control and the random sequence. Oligo concentrations between 0.78 and 1.5 microM also resulted in decreased expression of the low-MW form, but not significant differences in thymidine radiolabeling. In recovery experiments, cells treated initially with greater oligo concentrations required significantly increased time to recover, particularly in cells treated with EGFR directed oligos. Intracellular uptake and nuclear localization was demonstrated with FITC tagged oligos. In summary, even at relatively low oligo concentrations and short exposure, oligos against TGF-alpha, and particularly EGFR, significantly inhibit in vitro growth of the T98G glioblastoma, possibly mediated by decreased EGFR expression.
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PMID:Treatment of the T98G glioblastoma cell line with antisense oligonucleotides directed toward mRNA encoding transforming growth factor-alpha and the epidermal growth factor receptor. 1177 57

The epidermal growth factor receptor (EGFR) gene is commonly amplified and rearranged in glioblastoma multiforme leading to overexpression of wild-type and mutant EGFRs. Expression of wild-type EGFR ligands, such as transforming growth factor-alpha (TGF-alpha) or heparin-binding EGF (HB-EGF), is also often increased in gliomas resulting in an autocrine loop that contributes to the growth autonomy of glioma cells. Glioblastoma multiformes express a characteristic EGFR mutant (EGFRvIII, de 2-7) that does not bind ligand, signals constitutively, and is more tumorigenic than the wild-type receptor. However, the downstream signals that mediate this increased tumorigenicity are not well understood. We hypothesized that signals induced specifically by EGFRvIII and not the wild-type receptor are more likely to mediate its increased tumorigenic activity and examined the gene expression profiles resulting from inducible expression of comparable levels of either wild-type EGFR or EGFRvIII in a U251-MG glioma cell line. Expression of EGFRvIII resulted in specific up-regulation of a small group of genes. Remarkably, all these genes, which include TGFA, HB-EGF, EPHA2, IL8, MAP4K4, FOSL1, EMP1, and DUSP6, influence signaling pathways known to play a key role in oncogenesis and function in interconnected networks. Increased expression of EGFRvIII-induced genes was validated by real-time PCR. The mutant receptor does not bind ligand, and EGFRvIII-induced expression of TGF-alpha and HB-EGF suggests that EGFRvIII plays a role in generating an autocrine loop using the wild-type EGFR in glioma. It also raises the possibility that EGFRvIII may signal, at least in part, through the wild-type receptor. Indeed, we show that inhibiting the activity of HB-EGF, a potent mitogen, with neutralizing antibodies reduces cell proliferation induced by expression of EGFRvIII. This suggests that the EGFRvIII-HB-EGF-wild-type EGFR autocrine loop plays an important role in signal transduction by EGFRvIII in glioma cells. We also show by immunohistochemistry that HB-EGF expression correlates with the presence of EGFRvIII in glioblastoma multiforme. Thus, our study provides a new insight into oncogenic signaling by EGFRvIII and improves our understanding of how autocrine loops are generated in glioma.
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PMID:Differential gene expression analysis reveals generation of an autocrine loop by a mutant epidermal growth factor receptor in glioma cells. 1642 19

Antisense oligonucleotides (oligos) against transforming growth factor-alpha (TGF-alpha) (MR1) and its binding site, the epidermal growth factor receptor (EGFR) (MR2), are efficacious against the UACC 897 breast, PC-3 and LNCaP prostate, and T98G glioblastoma tumor lines in both in vitro and in vivo studies. Oligos against the anti-apoptosis protein bcl-2 (MR4) are also efficient against PC-3 and LNCaP tumors in similar in vitro experiments. To enhance activity, and also to introduce a derivative type of multifunctional oligo into this field, "bispecifics" were constructed containing two truncated complementary DNA sequences (from either MR1 or MR2) designed to bind targeted mRNA about their respective AUG initiation codons, and/or a similar sequence adjacent to the AUG site of mRNA encoding bcl-2. Tandem pairs of bispecifics were constructed: The first had complementary sequences for TGF-alpha and EGFR mRNA, but differed in 5' to 3' tandem orientation (TGF-alpha/EGFR [MR12] and EGFR/TGF-alpha [MR21] sequences); a second pair had binding sites associated with EGFR and bcl-2, also differing in orientation (EGFR/bcl-2 [MR24] and bcl-2/EGFR [MR42]). In studies targeting PC-3 and LNCaP cells, bispecifics demonstrated significant in vitro activity, and the second pair was significantly better than the original monospecifics. These studies are now extended to the MCF-7 breast cancer model in order to determine whether these particular bispecifics have similar anti-breast cancer activity and if they are significantly better than monospecific oligos from which they were derived. We conclude that bispecific oligos significantly inhibit MCF-7 growth, however, in contrast to results obtained with PC-3 and LNCaP, the monospecific oligos directed against EGFR and bcl-2 have significantly greater activity than the bispecifics targeting a combination of TGF-alpha, EGFR, or bcl-2. These data suggest that the relative activities of oligos, whether mono- or bispecific, change with tumor type. Bispecific oligos which target different proteins, possibly those which regulate estrogen utilization, may be more effective against MCF-7 cells and warrant additional investigation, particularly if co-administered with traditional chemotherapeutics.
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PMID:Treatment of MCF-7 breast cancer cells employing mono- and bispecific antisense oligonucleotides having binding specificity toward proteins associated with autocrine regulated growth and BCL-2. 1797 23

The mechanisms and biological implications of coordinated receptor tyrosine kinase coactivation remain poorly appreciated. Epidermal growth factor receptor (EGFR) and c-Met are frequently coexpressed in cancers, including those associated with hepatocyte growth factor (HGF) overexpression, such as malignant astrocytoma. In a previous analysis of the HGF-induced transcriptome, we found that two EGFR agonists, transforming growth factor-alpha and heparin-binding epidermal growth factor-like growth factor (HB-EGF), are prominently up-regulated by HGF in human glioma cells. We now report that stimulating human glioblastoma cells with recombinant HGF induces biologically relevant EGFR activation. EGFR phosphorylation at Tyr(845) and Tyr(1068) increased 6 to 24 h after cell stimulation with HGF and temporally coincided with the induction of transforming growth factor-alpha (~5-fold) and HB-EGF (~23-fold) expression. Tyr(845) and Tyr(1068) phosphorylation, in response to HGF, was inhibited by cycloheximide and actinomycin D, consistent with a requirement for DNA transcription and RNA translation. Specifically, blocking HB-EGF binding to EGFR with the antagonist CRM197 inhibited HGF-induced EGFR phosphorylation by 60% to 80% and inhibited HGF-induced S-G(2)-M transition. CRM197 also inhibited HGF-induced anchorage-dependent cell proliferation but had no effect on HGF-mediated cytoprotection. These findings establish that EGFR can be activated with functional consequences by HGF as a result of EGFR ligand expression. This transcription-dependent cross-talk between the HGF receptor c-Met and EGFR expands our understanding of receptor tyrosine kinase signaling networks and may have considerable consequences for oncogenic mechanisms and cancer therapeutics.
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PMID:Transcription-dependent epidermal growth factor receptor activation by hepatocyte growth factor. 1823 69