Biomedical subjects

S Y Cheng

Publications and source records attributed to S Y Cheng.

At least 37 records · Page 2Linked to original sources

PubMed2000

Trace elements and lipid peroxidation in human seminal plasma.

In the present study, the concentrations of copper, iron, zinc, and malondialdehyde in human seminal plasma were measured and correlated with the sperm count and motility in human semen. Copper, iron, and zinc were analyzed by atomic absorption spectrometry, whereas malondialdehyde was measured by high-performance liquid chromatography. The malondialdehyde concentrations in asthenospermia and oligoasthenospermia were significantly higher than in normospermia. Copper and iron levels were higher in asthenospermia, whereas the zinc concentrations in both oligospermia and asthenospermia were lower than in normal controls. A negative correlation (r = -0.28, p < 0.05) between the malondialdehyde concentration and sperm motility was observed in the abnormal groups. There was no association among copper, iron, zinc, and malondialdehyde in seminal plasma. We concluded that changes in trace elements may be related to sperm quality and that lipid peroxidation, although it is not promoted in the seminal plasma by copper or iron or ameliorated by zinc, may be involved in the loss of sperm motility.

Humans↗

PubMed1999

Chronic exercise enhances vascular responses to clonidine in rats by increasing endothelial alpha2-adrenergic receptor affinity.

Chronic exercise increases endothelium-dependent vasodilating responses. To investigate whether endothelial alpha2-adrenergic receptor upregulation is involved in the enhancement of clonidine-induced vasorelaxation by chronic exercise, 4-week-old male Wistar rats were used. They were divided into control and exercise groups. The trained animals ran on a treadmill at a moderate intensity for 60 min per day, 5 days per week for 10 weeks in total. Resting heart rates were measured by a tail-cuff method to confirm training effects. After training, rings of the thoracic aorta were prepared to evaluate vasodilating responses to clonidine, an alpha2 agonist. Released endothelium-derived relaxing factors were pharmacologically identified by treatment of N(omega)-nitro-L-arginine, a nitric oxide (NO) synthase inhibitor, or tetraethylammonium chloride, an endothelium-derived hyperpolarization factor (EDHF) inhibitor. Receptor binding assays were performed by using 3H-labeled clonidine as a tracer. We found that chronic exercise enhanced vascular responses to clonidine by stimulating the release of both NO and EDHF. It also increased the binding affinity of endothelial cell alpha2 receptor without changing the number of binding sites. Therefore, the elevated vasorelaxing responses to clonidine after chronic exercise may be partially resulted from an increase in endothelial alpha2 receptor binding affinity.

Adrenergic alpha-Agonists↗

PubMed1999

Expression of the mutant thyroid hormone receptor PV in the pituitary of transgenic mice leads to weight reduction.

Resistance to thyroid hormone (RTH) is a genetic disease caused by mutations of the thyroid hormone receptor beta gene (TRbeta). One of the symptoms in some affected individuals is growth retardation. To understand the molecular basis of growth retardation in these patients with RTH, a transgenic mouse was prepared in which the expression of the TRbeta1 mutant PV was targeted to the pituitary using the promoter of the glycoprotein hormone alpha-subunit. The PV mutant was originally identified in a patient with severe growth impairment. The PV mutation is a C-insertion at codon 448 of the TRbeta gene and leads to a frame-shift of the carboxyl-terminal 14 amino acids of TRbeta1, resulting in total loss of triiodothyronine (T3) binding and transcriptional activation. PV was selectively expressed in the pituitary of the transgenic mouse and not in other tissues examined. The transgenic mice showed a significant impairment in weight gain. However, no changes in the serum level of thyroid-stimulating hormone were seen, and no elevation of thyroid hormones was detected in the transgenic mice. The circulating levels of growth hormone and insulin-like growth factor I were not affected in the transgenic mice, suggesting that the growth impairment in RTH is complex and is mediated by pathways that are yet to be elucidated.

Animals↗

PubMed1999

Tissue-specific differential repression of gene expression by a dominant negative mutant of thyroid hormone beta1 receptor.

Resistance to thyroid hormone (RTH) is a genetic disease caused by the mutations of the thyroid hormone beta receptor (TRbeta) gene, producing receptors with a dominant negative action. The present study addressed the question as to whether tissue-specific factors modulate the dominant negative function in different tissues. We prepared stably transfected pituitary GH3 (GH3-PV) and liver SK-Hep-1 (SK-Hep-1-PV) cell lines with a potent dominant negative mutant, PV. The growth hormone (GH) and the malic enzyme genes (ME) in GH3 and SK-Hep-1, respectively, are directly regulated by the thyroid hormone, 3,3,'5-triiodo-L-thyronine (T3). The ratio of the expressed PV/endogenous TRbeta1 proteins was approximately 20 and 5 for GH3-PV and SK-Hep-1-PV cells, respectively. However, the T3-activated expression of the GH gene in GH3-PV and ME gene in SK-Hep-1-PV was repressed by approximately 30% and 90%, respectively, indicating the lack of correlation of PV/TRpbeta1 protein ratio with the dominant negative potency of mutant PV. Furthermore, the synergistic effect of the pituitary-specific factor 1 on the TR-mediated GH promoter activity was not repressed by mutant PV. Taken together, these results suggest that the dominant negative effect of mutant TR is variable in the tissues studied.

Animals↗

PubMed1999

Thyroid hormone-induced cell proliferation in GC cells is mediated by changes in G1 cyclin/cyclin-dependent kinase levels and activity.

The thyroid hormone, 3,3', 5-triiodo-L-thyronine (T3), is essential for growth and regulation of metabolic functions. The biological activities of T3 are mediated by its interaction with the thyroid hormone nuclear receptors (TRs). The mechanism by which TRs mediate cell growth is unknown. We found that T3 stimulated cell growth in GC cells by shortening the doubling time approximately 3-fold. Flow cytometric analysis indicated that the growth stimulatory effect was mainly due to shortening of G1 phase accompanied by increases in S and G2/M phases of the cell cycle. These changes correlated with T3-induced increases in messenger RNA and protein levels of two key regulators of G1 progression, cyclins D1 and E, as well as cdk2. Furthermore, the kinase activities associated with cyclin D1 and E were activated up to 4-fold by T3, which led to increased phosphorylation of the retinoblastoma protein (Rb), the driving force in G1 to S cell cycle progression. These results show for the first time that the growth promoting effect of T3 in GC cells is mediated, at least in part, by increases in cyclin/cdk activities and the phosphorylation state of Rb. The functional link of T3 to Rb has important implications for the understanding of the biology of normal and cancer cells.

Animals↗

PubMed1998

Hormone-induced translocation of thyroid hormone receptors in living cells visualized using a receptor green fluorescent protein chimera.

Thyroid hormone nuclear receptors (TRs) are ligand-dependent transcription factors that regulate growth, differentiation, and development. To understand the role of the hormone, 3,3', 5-triiodo-L-thyronine (T3), in the nuclear translocation and targeting of TRs to the regulatory sites in chromatin, we appended green fluorescent protein (GFP) to the human TR subtype beta1 (TRbeta1). The fusion of GFP to the amino terminus of TRbeta1 protein did not alter T3 binding or transcriptional activities of the receptor. The subcellular localization of GFP-TRbeta1 in living cells was visualized by laser-scanning confocal microscopy. In the presence of T3, the expressed GFP-TRbeta1 was predominately localized in the nucleus, exhibiting a nuclear/cytoplasmic ratio of approximately 5.5. No GFP-TRbeta1 was detected in the nucleolus. In the absence of T3, more GFP-TRbeta1 was present in the cytoplasm, exhibiting a nuclear/cytoplasmic ratio of approximately 1.5. In these cells, cytoplasmic GFP-TRbeta1 could be induced to enter the nucleus by T3. The T3-induced translocation was blocked when Lys184-Arg185 in domain D of TRbeta1 was mutated to Ala184-Ala185. Furthermore, the inability of the mutant TR to translocate to the nucleus correlated with the loss of most of its transcriptional activity. These results suggest that TR functions may, in part, be regulated by T3-induced nuclear entry.

Biological Transport↗

PubMed1998

Direct determination of selenium in human blood plasma and seminal plasma by graphite furnace atomic absorption spectrophotometry and clinical application.

Direct determination of selenium (Se) in body fluids by graphite furnace atomic absorption spectrophotometry (GFAAS) may suffer from problems like severe background, matrix effects, preatomization losses, and spectral interferences. In this study we evaluate critically the influence on the accuracy of the direct determination of Se in blood plasma and seminal plasma by GFAAS, and propose a simple, rapid, and accurate method, suitable for routine clinical analysis. The method for blood plasma is mainly based on studies by the use of matched matrix and a Pd-Ni modifier, but for seminal plasma only a Pd modifier is required. The method developed was also applied to study the Se distribution in plasma protein fractions of patients with hepatocellular carcinoma. The Se in plasma of patients was significantly lower than that of the controls. The distribution pattern of Se in blood plasma fractions of patients was also different from that of the controls.

Adult↗

PubMed1998

Expression of vascular endothelial growth factor in human brain tumors.

Compared to normal brain an increased expression of vascular endothelial growth factor (VEGF) has been reported in many types of brain tumors. However, the numbers of samples analyzed and information about the cellular distribution of VEGF have been limited. Here we used novel monoclonal antibodies against VEGF to analyze, using immunohistochemistry, Western blotting and enzyme-linked immunosorbent assay, its expression in 108 human brain tumors that included astrocytic tumors, meningiomas, pituitary adenomas, primary intracranial germ cell tumors and neuronal tumors. The results showed that 37 of 48 astrocytic tumors (77%) and 15 of 19 meningiomas (79%) were immunoreactive for VEGF, consistent with previous reports. However, in contrast to a previous report that analyzed only VEGF mRNA; all of our 15 pituitary adenomas showed specific immunoreactivity for VEGF. We also extended the studies to previously unanalyzed neoplasms: 13 of 15 primary intracranial germ cell tumors (82%), and 7 of 10 neuronal tumors (70%) were immunoreactive for VEGF. Direct protein analysis by Western blotting confirmed the expression of VEGF in those tumors, and showed differential expression of the isoforms of VEGF protein; a pituitary adenoma expressed both VEGF165 and VEGF189 proteins, a central neurocytoma expressed only VEGF165, while an immature teratoma expressed only VEGF189. The data herein show that VEGF is expressed in a wide spectrum of brain tumors and suggest differences among tumor entities in the mechanisms of VEGF up-regulation as well as their employment of distinct VEGF isoforms for neovascularization.

Adenoma↗

PubMed1998

Thyroid hormone receptor is a negative regulator in p53-mediated signaling pathways.

Thyroid hormone nuclear receptors (TRs) are ligand-dependent transcription factors which regulate growth, differentiation, and development. The molecular mechanism by which TRs mediated these effects remains unclear. A prevailing hypothesis is that TRs exert their biological effects by cooperating with other transcription factors. We have recently shown that the human TR subtype beta1 (hTRbeta1) interacts with the tumor suppressor p53, which plays a critical role in cell-cycle regulation and tumorigenesis. This interaction of hTRbeta1 with p53 leads to an impairment of TR function. The present study examined whether hTRbeta1 could modulate the function of p53. Mapping of the domains of p53 responsible for the interaction with hTRbeta1 indicated that the regions involved resided in the DNA-binding domain and carboxy terminus of p53. In agreement with this finding, hTRbeta1 increased the binding of p53 to p53 DNA-binding elements. This increase in DNA binding, however, resulted in repression of p53-dependent transcription activation in transfected cells. Furthermore, hTRbeta1 led to an inhibition of the p53-mediated induction of bax and gadd45 expression. In contrast, the p53-induced expression of p21 was not affected by hTRbeta1, suggesting that the expression of p53-regulated genes is differentially modulated by hTRbeta1. Because the expressions of bax, gadd45, and p21 are directly regulated by p53, these results indicate that hTRbeta1 can modulate p53-regulated gene expression and support the hypothesis that there is cross-talk between these two regulatory pathways. The cross-talk between these two transcription factors could play an important role in the biology of normal and cancer cells.

Breast Neoplasms↗

PubMed1998

Expression of insulin-like growth factor-binding protein-1 (IGFBP-1) mRNA in embryos and endometrial stromal cells.

The objective of the present study was to investigate the effects of insulin-like growth factor-binding protein-1 (IGFBP-1) on the interaction between mouse embryos and endometrial stromal cells in co-culture systems. To explore quantitatively the changes in expression of IGFBP-1 mRNA from endometrial stromal cells cultured alone or co-cultured with embryos, a combination of reverse transcription-polymerase chain reaction (RT-PCR) and Southern blotting followed by a densitometric analysis was used. In co-culture systems, development of embryos was significantly improved and the production of IGFBP-1 from endometrial stromal cells was stimulated by the embryos. Quantitative analysis showed that expression of IGFBP-1 mRNA in endometrial stromal cells co-cultured with embryos was higher on days 3,5 and 8 (1.6-, 4.5- and 2.3-fold respectively) than in endometrial stromal cells cultured alone. In addition, intensity of PCR products for IGFBP-1 mRNA in endometrial stromal cells co-cultured with embryos was higher on day 5 than on days 3 and 8. However, the expression of IGFBP-1 mRNA in embryos cultured alone was very low. In conclusion, co-culture of embryos with endometrial stromal cells improved the development of embryos and may be associated with the production of IGFBP-1 by the co-cultured endometrial stromal cells. A combination of RT-PCR and Southern blotting followed by a densitometric analysis appeared to be a sufficiently quantitative method to determine changes in IGFBP-1 mRNA values.

Animals↗

PubMed1997

Intracerebral tumor-associated hemorrhage caused by overexpression of the vascular endothelial growth factor isoforms VEGF121 and VEGF165 but not VEGF189.

The vascular endothelial growth factor (VEGF) has been shown to be a significant mediator of angiogenesis during a variety of normal and pathological processes, including tumor development. Human U87MG glioblastoma cells express the three VEGF isoforms: VEGF121, VEGF165, and VEGF189. Here, we have investigated whether these three isoforms have distinct roles in glioblastoma angiogenesis. Clones that overexpressed each isoform were derived and inoculated into mouse brains. Mice that received VEGF121- and VEGF165-overexpressing cells developed intracerebral hemorrhages after 60-90 hr. In contrast, mice implanted with VEGF189-overexpressing cells had only slightly larger tumors than those caused by parental cells and little evidence of hemorrhage at these early times after implantation, whereas, after longer periods of growth, enhanced angiogenicity and tumorigenicity were apparent. There was rapid blood vessel growth and breakdown around the tumors caused by cells overexpressing VEGF121 and VEGF165, whereas there was similar vascularization but no eruption in the vicinity of those tumors caused by cells overexpressing VEGF189, and none on the border of the tumors caused by the parental cells. Thus, by introducing VEGF-overexpressing glioblastoma cells into the brain, we have established a reproducible and predictable in vivo model of tumor-associated intracerebral hemorrhage caused by the enhanced expression of single molecular species. Such a model should be useful for uncovering the role of VEGF isoforms in the mechanisms of angiogenesis and for investigating intracerebral hemorrhage due to ischemic stroke or congenital malformations.

Adult↗

PubMed1997

The differential hormone-dependent transcriptional activation of thyroid hormone receptor isoforms is mediated by interplay of their domains.

Human thyroid hormone nuclear receptor isoforms (TRalpha1 and TRbeta1) express differentially in a tissue-specific and development-dependent manner. It is unclear whether these two isoforms have differential functions. We analyzed their interaction with a thyroid hormone response element with half-site binding motifs arranged in an everted repeat separated by six nucleotides (F2). Despite extensive sequence homologies, the two isoforms bound to F2 with different affinities and ratios of homodimer/monomer. Using F2-containing reporter gene, we found that the transcriptional activity of TRbeta1 was approximately 6-fold higher than that of TRalpha1. The lower activity of TRalpha1 was not due to differences in expression of the two isoforms because similar nuclear localization patterns were observed. To understand the structural determinants responsible for these differences, we constructed chimeric receptors in which hinge regions (domain D), hormone binding domains (domain E), and domains (D + E) were sequentially interchanged and their activities were compared. Chimeric TRs containing the domains D, E or (D + E) of TRbeta1 showed increased propensities to form homodimers and mediated higher transactivation activities than TRalpha1. Thus, differential transactivation activities of TR isoforms are mediated by interplay of their domains and could serve as an important regulatory mechanism to achieve diversity and specificity of pleiotropic T3 effect.

Binding Sites↗

PubMed1997

A probability-based approach for predicting HIV infection in a low prevalent population of injection drug users.

This article proposes a method for estimating HIV risk in low-HIV-prevalent populations. Allard's risk probability model was used to compute individual risk scores. Based on a sample of 3854 injection drug users (IDUs) who were confidentially tested for HIV at five methadone treatment clinics in Los Angeles County, the following self-reported risk behaviors were used to derive an individual IDU risk score: (i) frequency of injection, (ii) frequency of using uncleaned needles, (iii) number of people sharing a needle, (iv) frequency of needle sharing, and (v) type of needle sharing practice. The overall HIV prevalence for the IDU sample was 2%. The risk score was strongly associated with HIV seropositivity (chi-square = 16.1, p < 0.0001), but only one of the individual IDU risk behaviors (needle cleaning) was significantly associated with HIV seropositivity (chi-square = 10.9, P < 0.001). In addition, the risk score was strongly associated with HIV serostatus for both males and females. For females, however, none of the individual IDU risk behaviors were associated with HIV serostatus. Our findings indicate that when predicting HIV infection in a low-prevalence population, the probability-based risk score makes a statistically significant contribution over individual IDU risk behaviors.

Adult↗

PubMed1997

Hormone-activated phosphorylation of human beta1 thyroid hormone nuclear receptor.

To understand the role of phosphorylation in the hormone-dependent transcriptional activation of thyroid hormone receptors (TRs), the present study evaluated the effect of the thyroid hormone, 3,3',5-triiodo-L-thyronine (T3) on the phosphorylation of TR, human subtype beta1 (h-TRbeta1). The extent of phosphorylation was compared in cells cultured in T3-depleted (Td) or T3-supplemented medium (Td + T3). T3 was found to activate phosphorylation of h-TRbeta1 approximately threefold. Taking into account the T3-induced fourfold downregulation in the expression of h-TRbeta1 in the same period, the specific T3-activated phosphorylation was increased approximately twelvefold. Phosphoamino acid analysis indicates that the phosphorylation of serine and threonine in a ratio of approximately 10:1 was increased approximately threefold by T3. Comparison of the [32P]-labeled tryptic maps of h-TRbeta1 phosphorylated in cells cultured in Td medium or Td + T3 medium indicates that the latter had fewer fragments and changes of intensities in several common fragments, indicating that the phosphorylation sites activated by T3-treatment differed from those of basal phosphorylation. Partial V8 and chymotrypic proteolysis indicates that h-TRbeta1 phosphorylated in cells cultured in Td + T3 medium was more resistant to proteolysis. These results indicate that T3-activated phosphorylation altered the protease susceptibility of h-TRbeta1 that could reflect structural changes in h-TRbeta1. These results raise the possibility that T3-activated phosphorylation may play an important role in transcriptional activation of h-TRbeta1.

Cell Line↗

PubMed1997

Guillain-Barré syndrome in Taiwan: a clinical study of 167 patients.

OBJECTIVE: To identify clinical characteristics of various forms of Guillain-Barré syndrome in Taiwan. METHODS: The clinical and electrophysiological data of 167 consecutive patients with Guillain-Barré syndrome admitted to Chang Gung Memorial Hospital, a general paediatric and adult hospital in Taiwan, were reviewed. RESULTS: Analysis of age distribution disclosed a high incidence (21%) among patients under the age of 10 years. Seasonal preponderance in Spring (March to May) was found. Utilizing clinical and electrophysiological data, these 167 patients with Guillain-Barré syndrome were subclassified; 82 (49%) had acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 32 (19%) had Fisher syndrome (FS), and six (4%) had axonal forms of Guillain-Barré syndrome. The remaining 47 (28%) patients were unclassified. Patients with AIDP and FS had many common clinical features, including seasonal distribution, history of preceding illness, sensory abnormalities, cranial nerve involvement except for extraocular motor nerves, and albuminocytological dissociation on examination of CSF. Follow up study on 145 patients disclosed that 127 (87%) recovered satisfactorily, 14 (10%) were persistently disabled, and four (3%) died during admission to hospital. Clinical features associated with poor outcome (persistent disability or death) were requirement for mechanical ventilation, a low mean compound muscle action potential amplitude (< or = 10% of the lower limit of normal), and age greater than 40 years. CONCLUSION: Guillain-Barré syndrome in Taiwan showed a peculiar age and seasonal distribution and a high frequency of FS not seen in other series. Given that patients with AIDP and FS had many common clinical features, AIDP and FS may have similar underlying pathological mechanisms.

Adolescent↗

PubMed1997

Dominant negative activity of mutant thyroid hormone alpha1 receptors from patients with hepatocellular carcinoma.

Complementary DNAs for two mutant thyroid hormone alpha1 receptors (TR alpha1) were isolated from hepatocellular carcinomas of two patients. Sequence analyses of the complementary DNAs showed a single Val390Ala and double Pro398Ser/Glu350Lys mutations in mutants H and L, respectively. We characterized their hormone-binding, DNA-binding, and dominant negative activities. Mutants H and L did not bind the hormone T3. Their DNA-binding activities were analyzed using three types of thyroid hormone response elements (TREs) in which the half-site binding motifs are arranged in an everted repeat (Lys), an inverted repeat (Pal), or a direct repeat separated by four nucleotides (DR4). Compared with wild-type TR alpha1 (w-TR alpha1), which bound these TREs with different homodimer/monomer ratios, binding of mutant L to the three TREs as homodimers was reduced by approximately 90%. However, binding of mutant H to these TREs was more complex. Although it bound normally to DR4 as homodimers, its binding to Lys as homodimers was reduced by approximately 80%. Surprisingly, its binding to Pal was markedly enhanced compared with w-TR alpha1. The binding of these two mutants to the three TREs as heterodimers with retinoid X receptors (RXR alpha and -beta) was not significantly affected. Consistent with the lack of T3-binding activity, both mutants had lost their trans-activation capacity. Mutants H and L exhibited dominant negative activity, but differed in their TRE dependency. The dominant negative potency of mutant H was in the rank order of Pal > DR4 > Lys, whereas no TRE dependency was observed for mutant L. The present study indicates that mutations of the TR alpha gene do occur in patients and that these novel TR alpha1 mutants provide a valuable tool to further understand the molecular basis of the dominant negative action of mutant TRs.

Base Sequence↗

PubMed1997

Differential sensitivity of thyroid hormone receptor isoform homodimers and mutant heterodimers to hormone-induced dissociation from deoxyribonucleic acid: its role in dominant negative action.

General resistance to thyroid hormone is an inheritable disease with resistance of peripheral tissues to elevated levels of thyroid hormone. Genetic studies have shown that it is due to interference in the functions of wild-type thyroid hormone nuclear receptors (wTRs) via the dominant negative effect of mutant TRs (mTRs). The present study compared the heterodimerization of the two TR isoforms, TR beta1 and TR alpha1, with mutant TRs to understand if mTRs had isoform-dependent dominant negative action. Using electrophoresis gel mobility shift assay, we have demonstrated that mutant PV, S, ED, and OK form heterodimers with wTR alpha1 and deltaTR beta1 (in which the A/B domain of wTR beta1 has been deleted), on the F2-thyroid hormone response element (TRE). In the presence of T3, both homo- and heterodimer complexes are dissociated in a T3 concentration dependent manner. The ED50 for deltaTR beta1 homodimers was 3-fold higher than that of wTR alpha1 homodimers. ED50s for deltaTR beta1/mTR heterodimers were 10- to 40-fold higher than the corresponding wTR alpha1/mTR heterodimers. Mutant ED and OK homodimers were only partially dissociated at the highest T3 concentrations used (100 nM), whereas no dissociation could be detected for PV and S homodimers, indicating differential sensitivity of the F2-bound TR dimers to the T3-induced dissociation. We presented a model that indicates the dissociation of any particular TR dimer from F2 is determined by competition of T3 for both of its constituent TRs. By transfection assays, we showed that the potency of the dominant negative action of PV on TR alpha1 and TR beta1 inversely correlated with the sensitivity of the appropriate mTR/wTR heterodimer to T3-induced dissociation from F2. The differential dominant negative action of mutants on the two TR isoforms could play an important role in the heterogeneity of tissue-specific manifestations in patients with resistance to thyroid hormone.

Animals↗

PubMed1996

Suppression of glioblastoma angiogenicity and tumorigenicity by inhibition of endogenous expression of vascular endothelial growth factor.

The development of new capillary networks from the normal microvasculature of the host appears to be required for growth of solid tumors. Tumor cells influence this process by producing both inhibitors and positive effectors of angiogenesis. Among the latter, the vascular endothelial growth factor (VEGF) has assumed prime candidacy as a major positive physiological effector. Here, we have directly tested this hypothesis in the brain tumor, glioblastoma multiforme, one of the most highly vascularized human cancers. We introduced an antisense VEGF expression construct into glioblastoma cells and found that (i) VEGF mRNA and protein levels were markedly reduced, (ii) the modified cells did not secrete sufficient factors so as to be chemoattractive for primary human microvascular endothelial cells, (iii) the modified cells were not able to sustain tumor growth in immunodeficient animals, and (iv) the density of in vivo blood vessel formation was reduced in direct relation to the reduction of VEGF secretion and tumor formation. Moreover, revertant cells that recovered the ability to secrete VEGF regained each of these tumorigenic properties. These results suggest that VEGF plays a major angiogenic role in glioblastoma.

Animals↗