Biomedical subjects

E F Adams

Publications and source records attributed to E F Adams.

At least 19 recordsLinked to original sources

PubMed1998

Expression and growth stimulatory effect of fibroblast growth factor 9 in human brain tumors.

OBJECTIVE: Fibroblast growth factor 9 (FGF-9) is a relatively new member of the FGF family isolated from the conditioned medium of a human glioblastoma cell line as a secreting type factor that exhibits a growth-stimulating effect on primary glial cells. To elucidate the roles of FGF-9 in human brain tumors, the expression and biological activities of FGF-9 were studied using culture cells and surgically obtained tumor specimens. METHODS: Measurement of FGF-9 and basic FGF in conditioned media of cell cultures was performed by using a sandwich enzyme immunoassay. The mitogenic effect of FGF-9 was evaluated by cell growth studies. FGF-9 expression in vivo was demonstrated by immunohistochemistry. RESULTS: One of 4 glioma cell lines and 4 of 16 human meningiomas examined actually secreted detectable amounts of FGF-9 proteins. In comparison, basic FGF production was detected from 3 of 4 glioma cell lines and 11 of 16 human meningiomas. Similarly to basic FGF, recombinant human FGF-9 significantly stimulated the in vitro cell proliferation in three of four glioma cell lines investigated in a dose-dependent manner. A time course growth study using U87 MG cells revealed an accelerated growth stimulation by FGF-9 after Day 4. The growth stimulatory activity was also shown in three of four human meningiomas studied. Moderate to strong immunoreactivity for FGF-9 was observed in 40 (82%) of 49 human brain tumors examined irrespective of origin, tumor type, grade of malignancy, or whether initial or recurrent. In contrast, strong immunostaining was localized in neurons in the normal human cerebral cortex. CONCLUSION: The present findings suggest that FGF-9 may be involved in the biology of human brain tumors with a possible importance in tumor cell growth. Whether the growth factor is more generally involved in oncogenesis of human tumors awaits further investigation.

Brain↗

PubMed1998

Presence of growth hormone secretagogue receptor messenger ribonucleic acid in human pituitary tumors and rat GH3 cells.

A novel G11-protein-coupled receptor specific for synthetic GH-releasing peptides (GHRPs) has recently been cloned and sequenced. Two forms exist, types 1a and 1b, the latter of which is biologically inactive. Using RT-PCR, we looked for the presence in tumorous pituitary cells of messenger ribonucleic acid (mRNA) for this novel GH secretagogue receptor (GHS-R). Both subtypes of GHS-R mRNA were detected in all six human pituitary somatotropinomas removed from patients with acromegaly. In culture, four of the tumors exhibited strong responses to GHRP-2 in terms of both phosphatidylinositol (PI) hydrolysis and GH secretion, but two were resistant. There was no apparent difference in the type 1a and type 1b expression pattern, as judged by RT-PCR, between responsive and nonresponsive tumors. Similarly, the rat pituitary tumor cell line, GH3, was found to express GHS-R mRNA, although these cells also did not respond to GHRPs. RT-PCR failed to detect GHS-R mRNA in eight functionless human pituitary tumors. In contrast, prolactinomas were found to express the receptor and, in culture, significant stimulation of PRL secretion and PI hydrolysis occurred in two of three tumors tested. These results demonstrate that tumorous somatotrophs express the GHS-R gene and that the occasionally observed nonresponsiveness of somatotropinomas to GHRPs is not due to the absence of the biologically active type 1a receptor. Additionally, human pituitary prolactinomas also express GHS-R and are able to respond to GHRPs in terms of PI hydrolysis and PRL secretion. In contrast, GHS-R gene expression does not appear to be associated with human functionless pituitary tumors.

Animals↗

PubMed1998

Comparative genomic hybridization analysis of nonfunctioning pituitary tumors.

Clinically nonfunctioning pituitary adenomas constitute about one third of pituitary neoplasms and are considered monoclonal tumors. The molecular mechanisms of tumorigenesis in these neoplasms are poorly understood, as evidenced by the paucity of reported somatic genetic alterations. Furthermore, the somatic mutations detected to date were primarily ascribed to candidate genes or chromosomal regions: gsp, ras, p53 mutations, and allelic losses of 11q and 13q. To gain insight into which chromosomal regions bear genes involved in nonfunctioning pituitary tumorigenesis, we examined 23 such tumors by comparative genomic hybridization. Four tumors showed no genetic abnormality, and the rest (17 of 23, 74%) exhibited at least one chromosomal region of abnormality. Gains and losses affected all chromosomes (except for chromosome 14). Notably, 8 of 23 tumors (34.7%) displayed sex chromosome and chromosome 18 aberrations (amplifications or deletions). Nonrandom DNA amplification of sub-chromosomal regions on 4q, 5q (5q13-->5q23), 9p (9p21-->9pter), 13q (13q21-->13q32), and 17q were detected in 10-30% of the tumors. Noteworthy, no tumor displayed deletion of 11q, the MEN1 gene locus. These findings suggest that genes localized to previously undescribed chromosomal regions play a role in the tumorigenesis of nonfunctioning pituitary adenomas.

Adenoma↗

PubMed1997

Relationship between invasiveness of pituitary somatotrophinomas and structural abnormalities of protein kinase C gene in human.

The potential role of the protein kinase C (PKC) transduction system in controlling proliferation of human pituitary somatotrophinomas was investigated. Twenty somatotrophinomas were studied using PCR and direct sequencing methods. No point mutation within the alpha PKC gene, previously thought to be associated with invasive pituitary tumors, was found in any of the 20 somatotrophinomas. It is concluded that PKC transduction system may play an important role in controlling pituitary somatotrophinoma proliferation, but there is no correlation between invasiveness and the previously reported alpha PKC gene mutation.

Adenoma↗

PubMed1997

Relationship between GHRP-6 and TPA in the regulation of growth hormone secretion by human pituitary somatotrophinomas.

Growth hormone releasing peptide (GHRP-6) is a synthetic hexapeptide which specifically stimulates secretion of growth hormone (GH) by pituitary somatotrophs. Phorbel ester, 1, 2 tetradecanoylphorbol 13 acetate (TPA) can also stimulate releasing of GH. The precise intracellular mechanism has not been entirely deciphered. We used cell cultures of human pituitary somatotrophinomas to investigate the relation between GHRP-6 and TPA on membrane phosphatidylinositol (PI) turnover and GH secretion. The results showed that the working mechanisms of GHRP-6 and TPA are not identical, although they all can stimulate GH secretion in human pituitary somatotrophinomas. This indicates that PI-PKC signal transduction system may play a crucial role in the regulation of GH secretion.

Adenoma↗

PubMed1997

Human meningiomas possess muscarinic acetylcholine receptors: stimulation of phosphatidylinositol turnover by carbachol.

The effect of carbachol, an acetylcholine receptor agonist, on rate of phosphatidylinositol (PI) turnover in cultured human meningioma cells was investigated. Exposure of meningioma cells for 2 h to carbachol (3.12-200 mumol/L) resulted in a dose-dependent stimulation of PI turnover to a maximum of 5.5-fold over basal controls. A time course study showed stimulation of IP3 formation after 30 s followed by increases in IP1 and IP2. The stimulatory effect of carbachol on PI turnover was completely abolished by the muscarinic receptor antagonist, atropine, but was unaltered by the nicotinic antagonist, hexamethonium. Reverse-transcription of meningioma-derived RNA into cDNA followed by amplification by the polymerase chain reaction using specific primers revealed presence of ml type muscarinic receptor mRNA. These results provide evidence that human meningioma cells possess muscarinic acetylcholine receptors the activation of which leads to PI hydrolysis.

Atropine↗

PubMed1997

Progesterone receptor gene expression in craniopharyngiomas and evidence for biological activity.

OBJECTIVE: Previous studies have demonstrated the presence of estrogen receptors in human craniopharyngiomas, raising the possibility that these lesions can be influenced by steroids. To complement these earlier findings, we examined for the presence of progesterone receptor (PR) messenger RNA in surgically removed craniopharyngiomas and performed some studies to determine whether progestogens can exert biological effects on these tumors in vitro. METHODS: Total RNA was extracted from fresh surgically removed craniopharyngiomas and reverse-transcribed into cDNA. The polymerase chain reaction was applied to this craniopharyngioma-derived cDNA using amplimers complementary to exons 4 and 7 of the PR gene. Additionally, craniopharyngioma cell cultures were established, and the in vitro effects of progesterone and 6 alpha-methyl-17 alpha-hydroxyprogesterone acetate on [3H]thymidine uptake and 17 beta-estradiol oxidoreductase activity were determined. RESULTS: Reversed-transcribed polymerase chain reaction of craniopharyngioma-derived RNA yielded bands of predicted size (389 base pairs) in six of seven tumors studied. Hinfl digestion and direct sequencing of the bands confirmed that the polymerase chain reaction DNA was representative of PR messenger RNA. Treatment of craniopharyngioma cell cultures with progesterone resulted in reduced [3H]thymidine uptake. Both progesterone and 6 alpha-methyl-17 alpha-hydroxyprogesterone acetate powerfully increased oxidative 17 beta-estradiol oxidoreductase activity. CONCLUSION: These results provide evidence that PR messenger RNA can be produced by at least some human craniopharyngiomas and indirectly show that this is translated into biologically active receptor protein.

Adolescent↗

PubMed1996

Hormonal dependency of cerebral meningiomas.

Though meningiomas are benign intracranial tumors, a minor group invades the skull base and the connective tissue of the sinus cavernous inducing neurological deficits. These patients can not be cured by surgical treatment. Therefore, the development of an adjuvant medical therapy has been the goal during the last decade. We report here on different medical concepts which are based on steroids, amines, growth factor antagonists and cytokines. In addition, our data give evidence that the growth of intracranial meningiomas is under multifactorial proliferative control.

Brain↗

PubMed1996

Molecular biology of growth-hormone-secreting human pituitary tumours: biochemical consequences and potential clinical significance.

Molecular biological studies have revealed that 30-40% of GH-secreting human pituitary tumours, associated with acromegaly, harbour single-base missense mutations within the Gs alpha gene, termed gsp oncogenes. In addition, a large proportion of GH-secreting tumours inappropriately express the GH-releasing factor (GRF) gene. Gsp-oncogenes result in elevated adenylyl cyclase activity with consequent abnormally high cAMP production. In culture, GH-secreting tumours expressing gsp oncogenes respond more efficiently to the somatostatin analogue, octreotide (SMS), raising the possibility that acromegalics harbouring gsp-positive tumours may be those who optimally benefit from SMS therapy. Inappropriate expression of GRF may result in abnormal presence of a positive autocrine feedback loop, in which secreted GRF acts on the same cells to promote cellular proliferation and GH secretion. Blockade of GRF mRNA translation by means of anti-sense oligonucleotide approaches may prove to be of value in inhibiting tumour function.

Acromegaly↗

PubMed1996

Proliferation parameters for pituitary adenomas.

In this review, the value of assessing proliferation parameters in surgically resected pituitary tumour tissue is analyzed. Histological examination of basal dura biopsies identifies invasive growth even when intraoperatively not apparent to the surgeon. Determination of DNA-polymerase activity, Ki-67 immunohistochemistry and DNA-flow-cytometry shows a clear difference in the proliferative potential of enclosed and invasive pituitary adenomas. Among the various endocrinologically differentiated groups ACTH-secreting adenomas associated with Nelson's syndrome and thyrotropinomas were the most rapidly proliferating. At present, however, our results reveal that the prognosis of an individual patient cannot be reliably predicted on the basis of such studies.

Adenoma↗

PubMed1996

Relationship between cAMP induced inhibition of human meningioma cell proliferation and autocrine secretion of interleukin-6.

Previous studies have suggested that activation of the adenylyl cyclase - cAMP system in meningiomas results in decreased mitosis. We have used meningioma cell culture to further investigate this phenomenon and to examine the potential role played by interleukin-6 (IL6). Incubation of cultured meningioma cells for 4-6 days with cholera toxin and theophylline, both of which increase intracellular cAMP levels, markedly stimulated IL6 secretion and inhibited cell growth rate. Similar effects were observed with 8-bromo-cAMP. In contrast, a neutralising polyclonal antibody against IL6 significantly stimulated meningioma proliferation and reduced the inhibitory effects of 8-bromo-cAMP. These results support the concept that IL6 acts as an autocrine / paracrine inhibitory factor for meningioma proliferation, and that the inhibition exerted by elevated intracellular cAMP levels may be at least partially mediated via increased secretion of the cytokine.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1996

Pituitary adenylate cyclase-activating polypeptide directly stimulates LH and FSH secretion by human pituitary gonadotrophinomas.

The effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on LH and FSH secretion by human pituitary gonadotrophinomas in cell culture was studied. PACAP (1-38 peptide, 0.2-20 nmol/L) dose-dependently stimulated both LH and FSH secretion after 24 hours incubation. Of 11 tumours studied, PACAP (20 nmol/L) stimulated LH and/or FSH secretion by 1.7-4 fold in 9 cases. Two tumours did not respond to PACAP, although LHRH was stimulatory in these. None of the 11 tumours contained gsp mutations, excluding the possibility that these were the cause of the occassionally observed non-responsiveness to PACAP. A combination of PACAP (20 nmol/L) together with TRH (25 nmol/L) resulted in greater stimulatory effects on LH and FSH secretion than exerted by either peptide alone, but this was not observed with LHRH. In 3 tumours tested, PACAP stimulated cAMP production 2-3 fold by cultured human pituitary gonadotrophinomas but had no effect on rate of phosphatidylinositol (PI) turnover. These results indicate that PACAP can directly stimulate LH and FSH secretion by human pituitary gonadotrophs and that PACAP-receptors in gonadotrophin-secreting tumours are coupled with adenylate cyclase but not the PI second messenger system. We conclude that PACAP may play a role in controlling gonadotroph function in the human pituitary gland.

Adult↗

PubMed1996

Relationship between protein kinase C and adenylyl cyclase activity in the regulation of growth hormone secretion by human pituitary somatotrophinomas.

OBJECTIVE: To determine the potential role of protein kinase C (PKC) and its relationship to adenylyl cyclase activity in controlling growth hormone (GH) secretion by human pituitary somatotrophinomas. METHODS: Twenty-eight somatotrophinomas were placed into cell culture, and the in vitro effects of the PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA) and the PKC inhibitor staurosporine on basal and GH-releasing hormone (GHRH)-stimulated GH secretion were examined. In addition, the influence of chronic exposure of cultured somatotrophinoma cells to TPA on the rate of inositol 1,4,5-trisphosphate production was determined. Each tumor was assessed for the presence of gsp oncogenes, and thus constitutive adenylyl cyclase activity, by direct sequence analysis of polymerase chain reaction-generated deoxyribonucleic acid. GH secretory responses of tumors with and without these oncogenes were compared. RESULTS: TPA consistently stimulated GH secretion by cultured somatotrophinoma cells. There was no difference in response between somatotrophinomas with and without gsp oncogenes, and the effects did not correlate with the variable stimulation exerted by GHRH. Tumors in which GHRH had no significant effect nevertheless responded to TPA. In combination, TPA and GHRH exerted additive stimulation. TPA treatment of cultured somatotrophinoma cells eventually resulted in suppression of inositol 1,4,5-trisphosphate production, probably reflecting down-regulation of membrane phosphatidylinositol hydrolysis, a second messenger system that also generates the endogenous PKC activator diacylglycerol. GHRH had no effect on phosphatidylinositol hydrolysis. In contrast to the effects of TPA, the PKC inhibitor staurosporine tended to reduce GH secretion, although this effect was not observed in all tumors examined. As with TPA, the effects of staurosporine did not correlate with presence or absence of gsp oncogenes. Furthermore, staurosporine did not reduce the stimulatory effects exerted by GHRH on GH secretion. CONCLUSION: These results demonstrate a role for the phosphatidylinositol-PKC second messenger cascade in controlling GH secretion by human pituitary somatotrophinomas. The results also show that the system operates relatively independent of intracellular adenylyl cyclase and, thus, protein kinase A.

Adenoma↗

PubMed1996

Protein kinase C-dependent growth hormone releasing peptides stimulate cyclic adenosine 3',5'-monophosphate production by human pituitary somatotropinomas expressing gsp oncogenes: evidence for crosstalk between transduction pathways.

The effects of the synthetic GH-releasing peptides, GHRP-2 and GHRP-6, on phosphatidylinositol (PI) hydrolysis and cAMP production have been examined in human pituitary somatotropinomas with and without adenylyl cyclase-activating gsp oncogenes. Both peptides dose-dependently stimulated the rate of PI hydrolysis and GH secretion by cell cultures of both types of somatotropinoma. GHRP-2 was considerably more potent than GHRP-6. The effects on GH secretion were reduced or abolished by phloretin, an inhibitor of protein kinase C, and W7, an inhibitor of calmodulin. However, antagonism of the GHRH-receptor and of protein kinase A with (N-Ac-Tyr1,D-Arg2)GRF-(1-29)-NH2 and Rp-adenosine-3',5'-cyclic monophosphothioate, respectively, did not alter the stimulatory effects of GHRP-2 and GHRP-6 on GH secretion. The effect of GHRP-2 and/or GHRP-6 on cAMP production was studied in 15 tumors, seven of which possessed constitutive adenylyl cyclase activity as evidenced by presence of gsp oncogenes. Both peptides stimulated cAMP production in the latter but not former types of tumor. Moreover, GHRP-2 and GHRP-6 potentiated the stimulation of cAMP production induced by GHRH and pituitary adenylate cyclase-activating polypeptide in tumors without gsp oncogenes. These results demonstrate that GHRP-2 and GHRP-6 exert identical effects on human pituitary somatotropinomas, except for differences in potency. Additionally, under conditions of adenylyl cyclase activity above basal levels (i.e. through stimulation of G2-protein coupled receptors or because of gsp oncogene expression), cAMP production can be increased even further by GHRP, providing evidence for cross-talk between the PI and adenylyl cyclase transduction systems in pituitary cells.

Base Sequence↗

PubMed1996

Autocrine growth stimulation of human meningioma cells by platelet-derived growth factor.

The authors have previously shown that meningioma-derived conditioned medium profoundly stimulates the in vitro proliferation of meningioma cells. In this paper, self mitogenic agents found in the conditioned medium-autocrine growth-stimulatory factors actually secreted by human meningioma cells-are characterized as proteins related to the B chain of platelet-derived growth factor (PDGF) and possibly to the A chain of PDGF as well. The addition to conditioned medium of a neutralizing antibody against PDGF-BB caused a significant inhibition of the conditioned medium-stimulated DNA synthesis in all three meningioma cultures studied. A similar neutralizing effect was observed with an anti-PDGF-AA antibody in one meningioma culture studied. Gel filtration chromatography of concentrated conditioned medium from two different meningiomas using a Sephadex G-100 column revealed similar profiles from both conditioned media with a major peak of mitogenic activity against meningioma cells at a molecular weight (M(r)) of approximately 32 to 36 kD, accompanied by a minor peak at approximately 22 kD. The major peak mitogenic activity was significantly reduced by addition of an anti-PDGF-BB antibody. Western blot analysis of protein extracts from five meningioma specimens was performed using a monoclonal antibody against the B chain of PGDF, and a major band of PDGF-B immunoreactivity was detected at an M(r) of approximately 19 kD in all five meningiomas under both reducing and nonreducing conditions. Exogenous human and porcine PDGFs both exhibited a significant dose-dependent stimulation of DNA synthesis in two of three and three of five meningioma cultures examined, respectively. Although not all meningiomas investigated proved to share the biological activity associated with PDGF and these results may be preliminary, it seems that the autocrine growth-stimulatory loop established by PDGF-B-related molecules plays an important functional role in meningioma cell proliferation.

Brain Neoplasms↗

PubMed1995

The growth hormone secretagogue, L-692,429, induces phosphatidylinositol hydrolysis and hormone secretion by human pituitary tumors.

L-692,429 is a non-peptidyl GH secretagogue. We examined the effects of L-692,429 on cultured human pituitary tumors removed from patients with acromegaly. Dose-dependent stimulation of GH secretion was observed, with 1 mumol/L leading to 2 or 3-fold increases. Prolactin (PRL) secretion by a mixed somatotrophic-lactotrophic tumor was also stimulated. The effects of L-692,429 were abolished by phloretin and W7 but not Rp-cAMPS. Rate of phosphatidylinositol turnover was markedly increased up to 3-fold by L-692,429. These results show that L-692,429 increases hormone secretion by human pituitary cells via a protein kinase C and Ca2+ dependent mechanism.

Acromegaly↗

PubMed1995

Biochemical characteristics of human pituitary somatotropinomas with and without gsp mutations: in vitro cell culture studies.

Gsp oncogenes are present in about 40% of somatotropinomas. They result in excessive cAMP production and have been proposed to be the cause of increased GH secretion. We have used in vitro cell culture to compare the biochemical characteristics of somatotropinomas with and without gsp oncogenes (gsp-positive and gsp-negative tumors, respectively). Of 30 somatotropinomas examined, 10 proved to be gsp positive, as determined by sequence analysis of DNA generated by the polymerase chain reaction. The somatostatin analog, octreotide, powerfully inhibited GH secretion by gsp-positive somatotropinomas, but had no effect on 8 of 13 gsp-negative tumors. Five of 20 gsp-negative and 4 of 10 gsp-positive tumors failed to respond to GHRH, whereas stimulatory effects ranging from 37-500% increases in GH secretion occurred in the remainder. However, strong stimulation (> 4-fold) occurred only in 5 of the gsp-negative tumors. The basal phosphatidylinositol turnover rate was elevated in about 25% of gsp-negative somatotropinomas. These results demonstrate similar and highly variable effects of GHRH on both types of somatotropinoma, whereas the absence of gsp oncogenes is often associated with resistance to octreotide. The phosphatidylinositol turnover data suggest that defects within this second messenger system may be present in a subset of somatotropinomas without gsp oncogenes.

Base Sequence↗

PubMed1995

Growth hormone releasing peptide (GHRP-6) stimulates phosphatidylinositol (PI) turnover in human pituitary somatotroph cells.

Growth hormone releasing peptide (GHRP-6) is a synthetic hexapeptide which specifically stimulates secretion of growth hormone (GH) by pituitary somatotrophs. The precise intracellular mechanism by which this is achieved has not been deciphered although it is known to involve protein kinase C (PKC) and Ca2+ but to be cAMP-independent. We have used cell cultures of human pituitary somatotrophinomas to demonstrate powerful effects of GHRP-6 on membrane phosphatidylinositol (PI) turnover, a second messenger system which leads to activation of PKC and mobilisation of intracellular Ca2+ reserves. Incubation of somatotrophinoma cells with GHRP-6 led to a dose-dependent stimulation of rate of PI turnover. GH secretion was increased in parallel. Effects were discernable after only 15 minutes incubation and rose to a maximum at 2 hours. PI turnover was stimulated by GHRP-6 in 8 of 8 tumours examined, effects ranging from 2.1 - 7.9 fold increases. Stimulation of GH secretion by GHRP-6 was independent of presence of gsp oncogenes, emphasising the cAMP-independent nature of its effects. These results provide evidence that the GH-stimulatory effects of GHRP-6 are achieved through activation of the PI second messenger system and thus support earlier findings that PKC and Ca2+ play central roles in mediating the effects of GHRP-6.

Calcium↗