endothelin-1 and Brain-Neoplasms

The aim of the present investigation was to study the effect of hypoxia on the expression of genes encoding endothelin-1 (EDN1) and its cognate receptors (EDNRA and EDNRB) as well as endothelin converting enzyme 1 (ECE1) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) for evaluation of their possible significance in the control of glioma growth through ERN1 and hypoxia.. The expression level of EDN1, EDNRA, EDNRB, and ECE1 genes as well as micro-RNA miR-19, miR-96, and miR-206 was studied in control and ERN1 knockdown U87 glioma cells under hypoxia by quantitative polymerase chain reaction.. It was shown that the expression level of EDN1, EDNRA, EDNRB, and ECE1 genes was up-regulated in ERN1 knockdown glioma cells in comparison with the control glioma cells, being more significant for endothelin-1. We also observed down-regulation of microRNA miR-206, miR-96, and miR-19a, which have specific binding sites in mRNA EDN1, EDNRA, and EDNRB, correspondingly, and can participate in posttranscriptional regulation of these mRNA expressions. Furthermore, inhibition of ERN1 endoribonuclease lead to up-regulation of EDNRA and ECE1 gene expressions and down-regulation of the expression level of EDN1 and EDNRB genes in glioma cells. Thus, the expression of EDNRA and ECE1 genes is regulated by ERN1 endoribonuclease, but EDN1 and EDNRB genes preferentially by ERN1 protein kinase. We have also shown that hypoxia enhanced the expression of EDN1, EDNRA, and ECE1 genes and that knockdown of ERN1 signaling enzyme function significantly modified the response of all studied gene expressions to hypoxia. Thus, effect of hypoxia on the expression level of EDN1 and ECE1 genes was significantly or completely reduced in ERN1 knockdown glioma cells since the expression of EDNRA gene was down-regulated under hypoxia. Moreover, hypoxia is induced the expression of EDNRB gene in ERN1 knockdown glioma cells.. Results of this investigation demonstrate that ERN1 knockdown significantly increased the expression of endothelin-1 and its receptors as well as ECE1 genes by different mechanisms and that all studied gene expressions were sensitive to hypoxia. It is possible that hypoxic regulation of the expression of these genes is a result of complex interaction of variable ERN1 related transcription and regulatory factors with HIF1A and possibly contributed to the control of glioma growth.

Topics: Brain Neoplasms; Cell Hypoxia; Cell Line, Tumor; Endoribonucleases; Endothelin-1; Endothelin-Converting Enzymes; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Glioma; Humans; Hypoxia; Protein Serine-Threonine Kinases; Receptor, Endothelin A; Receptor, Endothelin B; Tumor Hypoxia

The invasive growth, proliferation, and transcriptional regulation of glioma C6 cells treated with endothelin-1 and PD98059, a specific inhibitor of ERK1/2 were studied. The proliferation of glioma C6 cells was assessed in different growth conditions by prior in vitro treatment with endothelin-1 followed by implantation into the brain. In vitro studies showed that PD98059 inhibited the proliferation of cultured glioma C6 cells and activated transcription factors E2F1 and Myc-Max. Endothelin-1 significantly increased the proliferation of glioma C6 cells. The model used in this study was experimental and may allow the specific features of the in vitro behavior of cultured invasive cells to be identified.

Topics: Animals; Basic-Leucine Zipper Transcription Factors; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Cells, Cultured; E2F1 Transcription Factor; Endothelin-1; Flavonoids; Glioblastoma; Mitogen-Activated Protein Kinase Kinases; Neoplasm Invasiveness; Neoplasm Transplantation; Proto-Oncogene Proteins c-myc; Rats; Rats, Wistar

The authors have monitored C6 glioma cell invasive growth, proliferation and transcriptional regulation after pretreatment with endothelin-1 and ERK1/2 specific inhibitor PD98059. To explore proliferation of C6 glioma cells in different growth conditions, they were treated in vitro with endothelin-1 and implanted into the brain. In vitro studies have indicated that PD98059 inhibited the proliferation of cultured C6 glioma cells and induced the activation of E2F1 and Myc-Max transcriptional factors. Endothelin-1 strongly increased C6 glioma cell proliferation. The model used in this study is experimental, but it may provide an insight into the specific behavior of in vitro cultured invasive cells.

Topics: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; E2F2 Transcription Factor; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Glioblastoma; Male; Neoplasm Transplantation; Neuropeptides; Proto-Oncogene Proteins c-myc; Rats; Rats, Wistar

Glioblastomas multiforme (GBMs) are hypervascular tumors characterized by endothelial cell (EC) proliferation. There is increasing evidence that ECs that infiltrate systemic tumors are different from normal blood vessel cells; whether this difference is seen in the central nervous system between GBM and normal brain tissue is not known. The goal of this investigation was to characterize and compare the functional and phenotypic properties of GBM-associated ECs and normal brain ECs.. Human ECs were isolated from fresh tissue specimens, purified using flow cytometry, and characterized by immunostaining. Proliferation was measured by determining bromodeoxyuridine incorporation and Ki-67 staining, and by performing the monotetrazolium assay. The migration rate of the cells was determined using the modified Boyden chamber technique. Apoptosis was evaluated by performing the TUNEL assay, cell death enzyme-linked immunosorbent assay (ELISA), and annexin V staining. Growth factor production was analyzed using the ELISA technique. The brain tumor ECs differed from normal brain ECs morphologically and by their expression and distribution of specific markers (that is, vascular endothelial cadherin [VE-cadherin] and CD31). Functional differences between the two cell populations were also evident. The brain tumor ECs proliferated more slowly and underwent less apoptosis than normal brain ECs; however, the tumor ECs migrated faster than the normal ECs. The normal ECs were sensitive to growth factors such as vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1), whereas the tumor ECs were not. In addition, the brain tumor ECs constitutively produced higher levels of ET-1 and VEGF, compared with the normal ECs.. The data demonstrated that ECs derived from normal brain and from GBMs have significant phenotypic and functional distinctions. Further characterization of brain tumor ECs is essential for efficient antiangiogenic treatment of gliomas.

Topics: Apoptosis; Brain; Brain Neoplasms; Cell Movement; Cell Proliferation; Endothelial Cells; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Glioblastoma; Humans; In Situ Nick-End Labeling; Neovascularization, Pathologic; Phenotype; Tumor Cells, Cultured; Vascular Endothelial Growth Factor A

Endothelin-1 (ET-1), a vasoactive and mitogenic peptide mainly produced by vascular endothelial cells, may be involved in the progression of several human tumors. Here, we present an immunohistochemical analysis of the expression pattern of ET-1 receptor subtypes (ET(A)-R and ET(B)-R) and a functional study of their potential role in human oligodendrogliomas and oligoastrocytomas. By comparison, we assessed the corresponding expression patterns of glioblastomas. Interestingly, a nuclear localization of ET-1 receptor subtypes (associated or not with a cytoplasmic labeling) was constantly observed in tumor cells from all three glioma types. Moreover, we noted a distinct receptor distribution in the different gliomas: a nuclear expression of ET(B)-R by tumor cells was found to be restricted to oligodendrogliomas and oligoastrocytomas, while a nuclear expression of ET(A)-R was only detected in tumor cells from some glioblastomas. Using primary cultures of oligodendroglial tumor cells, we confirmed the selective expression of nuclear ET(B)-R, together with a plasma membrane expression, and further demonstrated that this receptor was functionally coupled to intracellular signaling pathways known to be involved in cell survival and/or proliferation: extracellular signal-regulated kinase and focal adhesion kinase activation, actin cytoskeleton reorganization. In addition, impairment of ET(B)-R activation in these cells by in vitro treatment with an ET(B)-R-specific antagonist induced cell death. These data point to ET-1 as a possible survival factor for oligodendrogliomas via ET(B)-R activation and suggest that ET(B)-R-specific antagonists might constitute a potential therapeutic alternative for oligodendrogliomas.

Topics: Actin Cytoskeleton; Antihypertensive Agents; Astrocytoma; Brain Neoplasms; Cell Membrane; Cell Nucleus; Cell Survival; Cytoplasm; Endothelin B Receptor Antagonists; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Glioblastoma; Humans; Immunohistochemistry; Oligodendroglioma; Oligopeptides; Piperidines; Protein-Tyrosine Kinases; Receptor, Endothelin A; Receptor, Endothelin B; Tumor Cells, Cultured

An increased level of endothelin (ET)-1 seems to be involved in the development of augmented cerebrovascular resistance in different pathological conditions, most notably vasospasm after subarachnoid hemorrhage. Therefore, interfering with the ET synthesis or ET receptor blockade may be a promising approach in the treatment of cerebral vasospasm after subarachnoid hemorrhage. Although the receptors mediating the effects of ET-1 human cerebrovasculature are well characterized, data concerning the functionally relevant ET-converting enzyme (ECE) activity are scarce.. ECE activity was determined in organ bath studies by the use of intraoperatively harvested human pial arteries. The level of ECE activity was analyzed by comparing the shift in the concentration effect curves obtained for ET-1 and its precursor, big ET-1. In addition, the presence of ECE-1alpha immunoreactivity was studied in human cerebral tissue.. ECE-1alpha immunoreactivity was found, although not consistently, in human cerebral arteries and was restricted to the endothelium. In isolated pial arterial segments, ET-1 and big ET-1 induced concentration-related contractions with mean pD(2) values of 9.25 +/- 0.34 and 7.13 +/- 0.17, respectively, yielding a 123-fold shift of big ET-1 versus mature ET-1. Preincubation with phosphoramidon (10(-4) mol/L) resulted in a small yet significant inhibition of the contraction induced by big ET-1.. The results of our study indicate the presence of functional ECE activity and ECE-1alpha immunoreactivity in human cerebral arteries. Furthermore, the data suggest the presence of ECE-like activity that differs from that of ECE-1alpha.

Topics: Adult; Arteries; Aspartic Acid Endopeptidases; Brain Neoplasms; Cerebrovascular Circulation; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Endothelium, Vascular; Epilepsy; Female; Glycopeptides; Humans; Immunohistochemistry; In Vitro Techniques; Intraoperative Period; Isoenzymes; Male; Metalloendopeptidases; Middle Aged; Osmolar Concentration; Pia Mater; Protein Precursors; Tissue Distribution; Vasoconstriction

We have recently shown that endothelin-1 activates two types of Ca2+-permeable nonselective cation channels (NSCC-1 and NSCC-2) in C6 glioma cells. These channels can be distinguished by their sensitivity to blockers of the receptor-operated Ca2+ channel, 1-[b-(3-[4-methoxyphenyl]propoxy)-4-methoxyphenethyl]-1H-imidazole hydrochloride (SK&F 96365) and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxyphenyl)ethyl]-acetamide (LOE 908). NSCC-1 is sensitive to LOE 908 and resistant to SK&F 96365, whereas NSCC-2 is sensitive to both LOE 908 and SK&F 96365. Moreover, extracellular Ca2+ influx through these channels plays an essential role in endothelin-1-induced mitogenesis in C6 glioma cells. The purpose of the present study was to investigate the effects of extracellular Ca2+ influx on intracellular pathways of endothelin-1-induced mitogenic responses in C6 glioma cells. We focused on extracellular signal-regulated kinase 1 and 2 (ERK1/2) in this context. An inhibitor of mitogen-activated protein kinase, 2-[2-amino-3-methoxyphenyl]-4H-1-benzopyran-4-one (PD 98059), abolished the endothelin-1-induced increase in ERK1/2 activity, but only partially suppressed the mitogenic response. ERK1/2 activation by endothelin-1 was partially suppressed in the absence of extracellular Ca2+. On the basis of the sensitivity to LOE 908 and SK&F 96365, Ca2+ influx through NSCC-1 and NSCC-2 plays an essential role in the extracellular Ca2+-dependent component of ERK1/2 activity. In contrast, Ca2+ influx through NSCC-2 is involved in the ERK1/2-independent component of endothelin-1-induced mitogenesis. These results indicate that (1) the endothelin-1-induced mitogenic response involves both ERK1/2-dependent and -independent mechanisms, (2) ERK1/2 activation by endothelin-1 involves an extracellular Ca2+ influx-dependent cascade as well as an extracellular Ca2+ influx-independent cascade, (3) because endothelin-1-induced mitogenesis is completely dependent on extracellular Ca2+ influx, extracellular Ca2+ influx also plays an important role in mitogenic pathways downstream of ERK1/2, (4) extracellular Ca2+ influx through NSCC-1 and NSCC-2 has an important role in the extracellular Ca2+ influx-dependent component of ERK1/2-dependent mitogenesis, (5) extracellular Ca2+ influx through NSCC-2 has an important role in ERK1/2-independent mitogenesis, and (6) Ca2+ influx through each Ca2+ channel may play a distinct role in intracellular mitogenic ca

Topics: Acetamides; Animals; Brain Neoplasms; Calcium; Calcium Channel Blockers; Calcium Channels; DNA; Drug Interactions; Endothelin-1; Enzyme Inhibitors; Flavonoids; Glioma; Imidazoles; Isoquinolines; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Mitogens; Rats; Thymidine; Tritium; Tumor Cells, Cultured

There are conflicting results concerning the receptor subtype(s) involved in calcium-mediated endothelin signaling in the glial cells. In order to elucidate the role of endothelin A and B receptors in these processes, we have studied the effect of a complex spectrum of endothelin receptor ligands on intracellular calcium concentration changes in proliferating and differentiated C6 rat glioma cells. Cell differentiation was induced by dibutyryl-cAMP and assessed by the glial fibrillar acidic protein content. Intracellular calcium changes were measured in cell suspensions using fluorescent probe Fura-2. The specific endothelin B receptor agonists sarafotoxin S6c and IRL-1620 did not influence the intracellular calcium concentration. However, calcium changes induced by endothelin-1 and especially by endothelin-3 after the pretreatment of cells with one of these endothelin B receptor specific agonists were significantly enhanced even above the values attained by the highest effective endothelin concentrations alone. Such endothelin B-receptor ligand-induced sensitization of calcium signaling was not observed in differentiated C6 cells. Moreover, endothelin-induced calcium oscillations in differentiated C6 cells were less inhibited by BQ-123 and BQ-788 than in their proliferating counterparts. In conclusion, the specific activation of endothelin B receptor in C6 rat glioma cells does not affect intracellular calcium per se, but probably does so through interaction with the endothelin A receptor. The pattern and/or functional parameters of endothelin receptors in C6 rat glioma cells are modified by cell differentiation.

Topics: Animals; Brain Neoplasms; Calcium; Cell Differentiation; Endothelin-1; Endothelin-3; Fluorescent Dyes; Fura-2; Glioma; Oligopeptides; Piperidines; Rats; Receptor Cross-Talk; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Signal Transduction; Tumor Cells, Cultured; Viper Venoms

Ca(2+) channels activated by endothelin-1 (ET-1) in C6 glioma cells (C6 cells) were characterized using whole-cell patch-clamps and by monitoring the intracellular free Ca(2+) concentration ([Ca(2+)](i)), when administering Ca(2+) channel blockers such as LOE 908 and SK&F 96365. Using this methodology, the Ca(2+) channels involved in ET-1-induced mitogenesis were identified. The patch-clamp study and [Ca(2+)](i) monitoring showed that 10 nM ET-1 activated two types of Ca(2+)-permeable nonselective cation channels (NSCC); one was sensitive to LOE 908 but resistant to SK&F 96365 (NSCC-1) and the other was sensitive to both LOE 908 and SK&F 96365 (NSCC-2). Conversely, 0.1 nM ET-1 activated only NSCC-1.ET-1-induced mitogenesis in a concentration-dependent manner, with the maximum effect arising at concentrations > or =10 nM. LOE 908 completely suppressed the 10 nM ET-1-induced mitogenesis, whereas SK&F 96365 only partially suppressed it. The IC(50) values of these blockers for the ET-1-induced mitogenesis were similar to those for the 10 nM ET-1-induced increase in [Ca(2+)](i). In contrast, LOE 908 completely suppressed 0.1 nM ET-1-induced mitogenesis, whereas SK&F 96365 did not affect it.Collectively, these results demonstrate that the sustained increase in [Ca(2+)](i), via NSCC-1 and NSCC-2, may be essential for ET-1-induced mitogenesis in C6 cells. Moreover, the sensitivity of NSCC-1 to ET-1 is higher than that of NSCC-2 to ET-1.

Topics: Acetamides; Animals; Brain Neoplasms; Calcium; Cell Division; Cell Line; Electrophysiology; Endothelin-1; Glioma; Imidazoles; Ion Channels; Isoquinolines; Mitosis; Patch-Clamp Techniques; Rats; Tumor Cells, Cultured

Endothelins (ETs) are a family of potent vasoconstrictor and comitogenic polypeptides consisting of 21-amino acids. Using in situ hybridization, ET-1 mRNA has previously been localized to neuronal cell bodies in fourteen human brain regions. However, because in situ hybridization has a limited detection sensitivity of 20 mRNA copies per cell, ET-1 mRNA may be present in previously undetected areas. Hence, our objective was to localize ET-1 mRNA in specific human brain regions and astrocytic tumours using the more sensitive in situ reverse transcriptase polymerase chain reaction (in situ RT-PCR). Human brain autopsy tissue and surgical cerebral tumour tissue were treated with proteinase K and DNase, followed by RT-PCR using primers specific for ET-1 mRNA and digoxygenin-labelled dUTP in the PCR mixture. The DIG-dUTP was localized with an immunodetection system. We demonstrate ET-1 mRNA labelling in twenty two of the twenty four brain regions studied including those regions in which ET-1 mRNA has been observed by in situ hybridization. In addition, the localization of ET-1 mRNA observed in astrocytomas suggests a role for ET-1 in tumour pathogenesis. In situ RT-PCR has proven to be highly sensitive in its ability to detect low mRNA expression at the cellular level. Our results confirm a role for ET-1 in the human nervous system.

Topics: Astrocytoma; Brain Chemistry; Brain Neoplasms; Endothelin-1; Humans; In Vitro Techniques; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Endothelin-1 (ET-1) is a powerful mitogenic and/or anti-apoptotic peptide produced by many cancer cells. To evaluate the potential role of the endothelin system in glioblastoma we first determined the cellular distribution of the mRNA and proteins of the components of the endothelin system, preproendothelin-1 (PPET-1), endothelin-converting enzyme-1 (ECE-1), and ET(A) and ET(B) receptors in human glioblastoma tissue and glioblastoma cell lines. PPET-1, ECE-1, and ET(A) receptor were highly expressed in glioblastoma vessels and in some scattered glioblastoma areas whereas ET(B) receptor was mainly found in cancer cells. This suggests that glioblastoma vessels constitute an important source of ET-1 that acts on cancer cells via the ET(B) receptor. Four human glioblastoma cell lines expressed mRNA for all of the components of the ET-1 pathway. Bosentan, a mixed ET(A) and ET(B) receptor antagonist, induced apoptosis in these cell lines in a dose-dependent manner. Apoptosis was potentiated by Fas Ligand (APO-1L, CD95L), a pro-apoptotic peptide, only in LNZ308 cells, corresponding to the known functional Fas expression in these cell lines. LNZ308 cells also expressed the long and short forms of the cellular FLICE/caspase-8 inhibitory protein (FLIP). Bosentan and a protein kinase C inhibitor down-regulated short FLIP in these cells. ET-1 induced transient phosphorylation of extracellular signal-regulated kinase but did not induce long-term thymidine incorporation in LNZ308 glioblastoma cells. These results suggest that, in glioblastoma cells, ET-1, mainly acting via the ET(B) receptor, is a survival/antiapoptotic factor produced by tumor vasculature, but not a proliferation factor, involving protein kinase C and extracellular signal-regulated kinase pathways, and stabilization of the short form of FLIP.

Topics: Base Sequence; Brain Neoplasms; DNA Primers; Endothelin-1; Fas Ligand Protein; fas Receptor; Glioblastoma; Humans; Immunohistochemistry; Membrane Glycoproteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured

Endothelin-1 (ET) has been shown to be involved in human pathological conditions, but its physiological function remains to be elucidated. The aim of this work was to assess whether endothelium-derived ET was involved in the overall responsiveness of freshly isolated human pial arteries.. Samples of cerebral cortex, otherwise discarded, were obtained during tumor or epileptic lesion resections (n = 10 donors). Arterial segments were isolated and mounted on a microvessel myograph.. Inhibition of nitric oxide (NO) formation with N omega-nitro-L-arginine (L-NA, 100 micromol/L) increased basal tone by 7+/-1% Emax (n=5). This increase in tone was fully abolished in the presence of BQ123 (1 micromol/L; ET(A) receptor antagonist, P<.05) but potentiated by a subthreshold concentration of exogenous ET (1 nmol/L; 33+/-8% Emax; P<.05). In the presence of L-NA, serotonin (10 micromol/L)-induced tone was doubled compared with the control response (P<.05) but reduced by 90% in the presence of BQ123 (P<.05). In the absence of L-NA, BQ123 prevented serotonin-induced tone (n=3). Oxymetazoline, a selective alpha2-adrenergic receptor agonist, induced an endothelium-dependent relaxation of preconstricted human pial arteries. The relaxation was partially sensitive to NO synthase inhibition and fully prevented by the addition of ET, whereas substance P-induced relaxation was preserved. Glibenclamide (1 micromol/L), an inhibitor of ATP-sensitive K+ channels and tetraethylammonium (1 mmol/L), an inhibitor of Ca2+-activated K+ channels had no effect on oxymetazoline-induced relaxation.. The results of this study suggest first that ET is involved in the tonic response induced by NO synthase inhibition; second, part of the contractile response induced by serotonin is endothelium-dependent and sensitive to BQ123; and third, the data suggest that activation of alpha2-adrenergic receptors generated an endothelium-dependent relaxation that was selectively inhibited by exogenous ET.

Topics: Adolescent; Adrenergic alpha-Agonists; Adult; Arteries; Brain Neoplasms; Cerebral Cortex; Endothelin Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Epilepsy; Female; Glyburide; Humans; Hypoglycemic Agents; Male; Middle Aged; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxymetazoline; Peptides, Cyclic; Pia Mater; Potassium Channel Blockers; Serotonin; Substance P; Tetraethylammonium; Vasoconstrictor Agents; Vasodilator Agents

Agonist-induced intracellular signal transduction often involves activation of protein kinase C by diacylglycerol (DAG) released from membrane phospholipids by phospholipases. Using either DAG kinase or HPLC assays to quantitatively determine DAG mass, we observed a time-dependent increase in DAG accumulation upon incubation of rat C6 glioma cells with 200 nM endothelin-1 (ET-1). Total cell DAG rapidly increased by 25-35% from a basal level of 4.5 +/- 0.3 nmol/mg protein during one min of ET-1 treatment and remained constant or slightly decreased between 1 and 2 min. Thereafter, DAG increased to a maximum (1.6-fold above basal) by 5-10 min. and remained elevated to 30 min. Resolution of DAG molecular species by HPLC after incubation of cells with ET-1 revealed that accumulation of DAG species differed in total cell lysate and subcellular compartments. In plasma membrane, major DAG species increased at 1 min. followed by a decrease at 10 min. whereas in microsomes DAG species did not change at 1 min. and decreased at 10 min. Although phospholipid sources of DAG species were not identified specifically, there was preferential hydrolysis of molecular species of phospholipid for DAG production. We propose that molecular species of DAG produced at the plasma membrane may be transferred to the endoplasmic reticulum so that phospholipid resynthesis can replenish molecular species initially utilized in signal transduction.

Topics: Angiotensin II; Animals; Bradykinin; Brain Neoplasms; Cell Membrane; Chromatography, High Pressure Liquid; Diglycerides; Endoplasmic Reticulum; Endothelin-1; Fibroblasts; Glioma; Humans; Membrane Lipids; Mice; Microsomes; Neurotensin; Phospholipids; Rats; Serotonin; Signal Transduction; Tumor Cells, Cultured

Because the prominent neovascularization characteristic of high grade primary brain tumors is composed mostly of vascular smooth muscle cells (VSMC), we studied the expression of the potent smooth muscle mitogen endothelin-1 (ET-1) and one of its secretagogues, transforming growth factor beta 1 (TGF-beta 1) in a series of astrocytic tumors. TGF-beta 1 is also of interest due to its known activity as an angiogenic factor. Using immunohistochemical methods, we examined 30 surgical cases: 10 glioblastoma multiforme, 10 anaplastic astrocytomas, and 10 low-grade astrocytomas. Using a monoclonal antibody to TGF-beta 1 and a polyclonal antibody to ET-1, we detected both growth factors in all cases of glioblastoma examined. In cases of anaplastic astrocytoma, 4 tumors were positive for both factors; 2 contained only ET-1; 2 contained only TGF-beta 1; and 2 exhibited no tumor cell immunoreactivity for either factor. In low-grade astrocytoma, 4 of 10 tumors showed weak ET-1 immunoreactivity; 2 of those contained TGF-beta 1 immunopositive tumor astrocytes: 6 tumors were negative for both factors. In all tumors that expressed both factors, serial sections showed that regions of ET-1 immunopositivity also tended to be positive for TGF-beta 1. Endothelial cells within all tumors were positive for ET-1. ET-1 and TGF-beta 1 are present in human astrocytomas and their expression correlates with tumor vascularity and malignancy. These results suggest roles for both ET-1 and TGF-beta 1 in the growth and progressive angiogenesis of the human glioma.

Topics: Blood Vessels; Brain Neoplasms; Endothelin-1; Glioma; Humans; Immunohistochemistry; Staining and Labeling; Transforming Growth Factor beta