Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the United States, tumors of the central nervous system remain the third leading cancer-related cause of death in young adults with a median survival time of < 1 year. A recent case study suggested that Capecitabine (a novel, fluoropyrimidine prodrug) may be effective in the treatment of brain metastases. Pharmacogenomic studies have correlated the antitumor response to Capecitabine with the expression of the drug metabolizing enzymes thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD). In the current study, we examined TP and DPD expression in normal human brain tissues and in glioblastoma multiforme, the most common and malignant type of brain tumor. Because previous reports suggest a tumor necrosis factor (TNF)-alpha-mediated increase in TP expression after irradiation (a current standard of care for glioblastoma multiforme), we also examined the effect of irradiation on the expression of TP, DPD, and TNF-alpha in both irradiated and lead-shielded contralateral U87MG glioma xenografts within the same animal. Expression levels were determined using real-time quantitative PCR as described previously. Results demonstrate an approximately 70-fold increase in TP mRNA levels 4 days after irradiation, relative to initial control levels. Interestingly, TP mRNA in the lead-shielded tumors (contralateral to irradiated tumors) increased approximately 60-fold by day 10 relative to initial control levels. Elevated TP levels were sustained for 20 days in irradiated xenografts but began to decrease after 15 days in the shielded/contralateral tumors, returning to baseline by 20 days. TP mRNA levels in normal mouse liver were unaltered, suggesting a tumor-associated effect. TNF-alpha mRNA levels did not increase after irradiation; therefore, mRNA expression of 11 additional cytokines [interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, and IFN-gamma] in both the irradiated and shielded xenografts was quantitated. Results demonstrated increased levels of IFN-gamma, IL-10, and IL-1 alpha by 6.3-, 3.7-, and 1.6-fold, respectively, in irradiated tumors only. DPD mRNA levels did not change after irradiation. The tumor-associated induction of TP in irradiated and lead-shielded tumors within the same animal may have significant implications for the combined modality treatment of cancer patients with Capecitabine in conjunction with radiotherapy and may apply to the treatment of distant tumors and or metastatic disease.
Mol Cancer Ther 2002 Oct
PMID:Induction of thymidine phosphorylase in both irradiated and shielded, contralateral human U87MG glioma xenografts: implications for a dual modality treatment using capecitabine and irradiation. 1248 38

The DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT) removes alkylating adducts from the O(6) position of guanine and protects cells from cytotoxic and mutagenic effects. Expression of MGMT is decreased in some cancers, which may be the result of methylation of CpG islands of both the promoter and coding regions of the gene. We studied the methylation status of the MGMT promoter in a very large collection of brain tumors (85) using methylation-specific polymerase chain reaction (PCR). Aberrant methylation occurred in 48% of 85 human brain tumor samples. Quantitative real-time PCR showed that expression of MGMT mRNA levels was significantly decreased (P < 0.001) in those brain tumors that had methylation of the promoter region of their MGMT gene. MGMT can prevent G to A mutations by removing alkyl groups from the O(6) position of guanine. We found a significantly increased frequency of G:C to A:T mutations of the p53 gene in brain tumors having a methylated MGMT promoter compared with those having an unmethylated MGMT promoter (P < 0.05), and all the non-CpG dinucleotide G:C to A:T mutations of p53 were in samples with a methylated MGMT promoter.
Mol Carcinog 2003 Jan
PMID:DNA repair gene O6-methylguanine-DNA methyltransferase: promoter hypermethylation associated with decreased expression and G:C to A:T mutations of p53 in brain tumors. 1250 76

The oncogene H-ras plays an important role in tumor growth and maintenance and could serve as a target treatment for brain tumors. In this study, diallyl disulfide (DADS), an inhibitor of H-ras was used to treat experimental brain glioma in a rat model. One hundred and twenty-five Sprague-Dawley rats (175-200 g) were implanted with 2 x 10(5) C6 glioma cells into the intra striatal region of the brain. Animals were treated with DADS (33 micromol) either before or after implantation of tumor cells. Control animals received soybean oil. Treatment outcome was evaluated based on H-ras expression in tumor tissue, animal's neurological status, tumor size, and life span. Application of DADS 7 days before implantation of tumor cells reduced the tumor size (P<0.05), improved neurological status (P<0.05), and increased the animal life span (P<0.05) when compared to the control group (no treatment). The expression of H-ras was significantly (P<0.05) reduced in brain tumor tissue of animals treated with DADS before implantation. Application of DADS after tumor implantation failed to improve clinical status or life span. This study demonstrates that pretreatment with DADS is capable of inhibiting the expression of H-ras in experimental brain C6 glioma which leads to an improved neurological status and an extended life span in the rat. Higher doses of DADS or other more potent inhibitors need to be used after tumor has been implanted.
Brain Res Mol Brain Res 2003 Mar 17
PMID:Inhibition of H-ras as a treatment for experimental brain C6 glioma. 1265 4

Convection-enhanced delivery of fusion proteins is a novel therapeutic approach for patients with relapsed or refractory high-grade gliomas. Multiple different fusion proteins have been produced that target different receptors on brain tumor cells. The sensitivity of different gliomas to fusion proteins has been shown to depend in part on the expression of the target receptor. We undertook a comparative study of the presence of the epidermal growth factor receptor (EGFR), interleukin-13 receptor (IL13R), interleukin-4 receptor (IL4R), and transferrin receptor (TfR) determined by immunofluorescence microscopy among fresh frozen tumor samples from 38 patients with high-grade gliomas (glioblastoma multiforme or anaplastic astrocytoma). The frequency of high receptor expression was 32 of 38 (84%) for EGFR, 30 of 38 (79%) for IL13R, 25 of 38 (66%) for TfR, and 17 of 38 (45%) for IL4R. Reactivity of normal brain endothelium was observed for TfR, and reactivity of normal brain astrocytes was observed for IL4R. Because of cross-reactivity of interleukin-13 with the IL4R-IL13Ralpha1 receptor, we infer reactivity of interleukin-13 with normal astrocytes. In contrast, EGFR was not observed in normal brain. A number of patients (10 of 38 patients) showed unequal expression of EGFR and IL13R. Thus, some patients may benefit more from interstitial therapy with an EGFR-directed fusion protein than from therapy with an IL13R-directed fusion protein and vice versa. The safety profile may be improved with an agent directed to EGFR versus agents directed to TfR, IL4R, or IL13R. Design of clinical trials of fusion proteins in patients with brain tumors may be enhanced by inclusion of relevant receptor density measurements.
Mol Cancer Ther 2003 Aug
PMID:Growth factor receptor expression varies among high-grade gliomas and normal brain: epidermal growth factor receptor has excellent properties for interstitial fusion protein therapy. 1293 68

We report the development of a novel dual-modality fusion reporter gene system consisting of Escherichia coli xanthine phosphoribosyltransferase (XPRT) for nuclear imaging with radiolabeled xanthine and Discosoma red fluorescent protein for optical fluorescent imaging applications. The dsRed/XPRT fusion gene was successfully created and stably transduced into RG2 glioma cells, and both reporters were shown to be functional. The level of dsRed fluorescence directly correlated with XPRT enzymatic activity as measured by ribophosphorylation of [14C]-xanthine was in vitro (Ki = 0.124 +/- 0.008 vs. 0.00031 +/- 0.00005 mL/min/g in parental cell line), and [*]-xanthine octanol/water partition coefficient was 0.20 at pH = 7.4 (logP = -0.69), meeting requirements for the blood-brain barrier (BBB) penetrating tracer. In the in vivo experiment, the concentration of [14C]-xanthine in the normal brain varied from 0.20 to 0.16 + 0.05% dose/g under 0.87 + 0.24% dose/g plasma radiotracer concentration. The accumulation in vivo in the transfected flank tumor was to 2.4 +/- 0.3% dose/g, compared to 0.78 +/- 0.02% dose/g and 0.64 +/- 0.05% dose/g in the control flank tumors and intact muscle, respectively. [14C]-Xanthine appeared to be capable of specific accumulation in the transfected infiltrative brain tumor (RG2-dsRed/XPRT), which corresponded to the 585 nm fluorescent signal obtained from the adjacent cryosections. The images of endogenous gene expression with the "sensory system" have to be normalized for the transfection efficiency based on the "beacon system" image data. Such an approach requires two different "reporter genes" and two different "reporter substrates." Therefore, the novel dsRed/XPRT fusion gene can be used as a multimodality reporter system in the biological applications requiring two independent reporter genes, including the cells located behind the BBB.
Mol Imaging 2003 Apr
PMID:Development of a new reporter gene system--dsRed/xanthine phosphoribosyltransferase-xanthine for molecular imaging of processes behind the intact blood-brain barrier. 1296 7

Gliomas of astrocytic origin are the most common primary brain tumors, accounting for over 40 to 50% of all central nervous system tumors. The TP53 tumor suppressor gene is the most frequently mutated gene found in human malignancies. A mutation of this gene can lead to an increased half-life of the resulting protein and loss of biological function. High levels of p53 have been detected in the serum of colon cancer patients, although p53 protein has not been detected in the serum of brain tumor patients. Besides circulating p53, several studies have detected antibodies against p53 in patients with lung and breast cancer, as well as those with other types of cancer. We studied p53 protein and anti-p53 antibodies in the plasma of Brazilian brain tumor patients. Plasma samples were drawn from 24 untreated brain tumor patients and from 15 healthy donors without clinical signs of cancer. Western blotting techniques were used to detect p53 protein and anti-p53 antibodies. We found anti-p53 antibodies in 5/24 brain tumor patients. Age appears to affect the immune response, as four of six tumor patients under 16 years old had detectable anti-p53 antibodies, while these were found in only 1 of 18 adults (over 16 years old). We found no p53 protein in any of the serum samples from the brain tumors. Possibly the presence of this protein is affected by tumor type or by the organs that are sampled.
Genet Mol Res 2003 Jun 30
PMID:Anti-P53 antibodies in Brazilian brain tumor patients. 1496 83

The new, simple, and reliable method for the diagnosis of brain tumors is described. It is based on a TLC quantitative determination of 5-methylcytosine (m(5)C) in relation to its damage products of DNA from tumor tissue. Currently, there is evidence that oxidative stress through reactive oxygen species (ROS) plays an important role in the etiology and progression of several human diseases. Oxidative damage of DNA, lipids, and proteins is deleterious for the cell. m(5)C, along with other basic components of DNA, is the target for ROS, which results in the appearance of new modified nucleic acid bases. If so, m(5)C residue constitutes a mutational hotspot position, whether it occurs within a nucleotide sequence of a structural gene or a regulatory region. Here, we show the results of the analysis of 82 DNA samples taken from brain tumor tissues. DNA was isolated and hydrolyzed into nucleotides, which, after labeling with [gamma-(32)P]ATP, were separated on TLC. Chromatograms were evaluated using PhosphorImager and the amounts of 5-methyldeoxycytosine (m(5)dC) were calculated as a ratio (R) of m(5)dC to m(5)dC + deoxycytosine + deoxythymidine spot intensities. The R value could not only be a good diagnostic marker for brain tumors but also a factor differentiating low-grade and high-grade gliomas. Therefore, DNA methylation pattern might be a useful tool to give a primary diagnosis of a brain tumor or as a marker for the early detection of the relapse of the disease. This method has several advantages over those existing nowadays.
Mol Cancer Res 2004 Mar
PMID:A simple epigenetic method for the diagnosis and classification of brain tumors. 1503 58

We have previously labeled cyclic RGD peptide c(RGDyK) with fluorine-18 through conjugation labeling via a prosthetic 4-[18F]fluorobenzoyl moiety and applied this [18F]FB-RGD radiotracer for alphav-integrin expression imaging in different preclinical tumor models with good tumor-to-background contrast. However, the unfavorable hepatobiliary excretion and rapid tumor washout rate of this tracer limit its potential clinical applications. The aims of this study were to modify the [18F]FB-RGD tracer by inserting a heterobifunctional poly(ethylene glycol) (PEG, M.W. =3,400) between the 18F radiolabel and the RGD moiety and to test this [18F]FB-PEG-RGD tracer for brain tumor targeting and in vivo kinetics. [18F]FB-PEG-RGD was prepared by coupling the RGD-PEG conjugate with N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) under slightly basic conditions (pH=8.5). The radiochemical yield was about 20-30% based on the active ester [18F]SFB, and specific activity was over 100 GBq/micromol. This tracer had fast blood clearance, rapid and high tumor uptake in the subcutaneous U87MG glioblastoma model (5.2+/-0.5%ID/g at 30 min p.i.). Moderately rapid tumor washout was observed, with the activity accumulation decreased to 2.2+/-0.4%ID/g at 4 h p.i. MicroPET and autoradiography imaging showed a very high tumor-to-background ratio and limited activity accumulation in the liver, kidneys and intestinal tracts. U87MG tumor implanted into the mouse forebrain was well visualized with [18F]FB-PEG-RGD. Although uptake in the orthotopic tumor was significantly lower (P<0.01) than in the subcutaneous tumor, the maximum tumor-to-brain ratio still reached 5.0+/-0.6 due to low normal brain background. The results of H&E staining post mortem agreed with the anatomical information obtained from non-invasive microPET imaging. In conclusion, PEGylation suitably modifies the physiological behavior of the RGD peptide. [18F]FB-PEG-RGD gave improved tumor retention and in vivo kinetics compared with [18F]FB-RGD.
Eur J Nucl Med Mol Imaging 2004 Aug
PMID:MicroPET imaging of brain tumor angiogenesis with 18F-labeled PEGylated RGD peptide. 1511 44

Amino acid imaging is increasingly being used for assessment of brain tumor malignancy, extent of disease, and prognosis. This study explores the relationship between proliferative activity, amino acid transport, and glucose metabolism in three glioma cell lines (U87, Hs683, C6) at different phases of growth in culture. Growth phase was characterized by direct cell counting, proliferation index determined by flow cytometry, and [(3)H]thymidine (TdR) accumulation, and was compared with the uptake of two non-metabolized amino acids ([(14)C]aminocyclopentane carboxylic acid (ACPC) and [(14)C]aminoisobutyric acid (AIB)), and [(18)F]fluorodeoxyglucose (FDG). Highly significant relationships between cell number (density), proliferation index, and TdR accumulation rate were observed in all cell lines ( r>0.99). Influx ( K(1)) of both ACPC and AIB was directly related to cell density, and inversely related to the proliferation index and TdR accumulation in all cell lines. The volume of distribution ( V(d)) for ACPC and AIB was lowest during rapid growth and highest during the near-plateau growth phase in all cell lines. FDG accumulation in Hs683 and C6 cells was unaffected by proliferation rate, growth phase, and cell density, whereas FDG accumulation was correlated with TdR accumulation, growth phase, and cell density in U87 cells. This study demonstrates that proliferation rate and glucose metabolism are not necessarily co-related in all glioma cell lines. The values of K(1) and V(d) for ACPC and AIB under different growth conditions suggest that these tumor cell lines can up-regulate amino acid transporters in their cell membranes when their growth conditions become adverse and less than optimal.
Eur J Nucl Med Mol Imaging 2004 Sep
PMID:Proliferation-dependent changes in amino acid transport and glucose metabolism in glioma cell lines. 1561 65

Although any patient with a suspected brain tumor, either primary or metastatic, should be studied with anatomic imaging modalities such as angiography, computerized tomagraphy (CT) or magnetic resonance imaging (MRI), nuclear medicine techniques are available to further characterize some biological features of brain lesions and help in diagnosis and therapy planning. Bloob-brain-barrier disruption can be easily assessed with single-photon emission tomography (SPET), whereas focal metabolic changes can be better demonstrated by positron emission tomography (PET) as specific radiopharmaceuticals are available to detect changes in glucose utilization and aminoacid uptake with this technique. Expression of specific tumoral antigens is the basis of imaging with radioimmunoscintigraphy, a promising technique that can be applied to brain tumor therapy. The major clinical applications of nuclear medicine in the study of brain tumors -- evaluation of the extension of a tumoral mass, differential diagnosis and evaluation of therapy and prognosis -- are discussed.
Q J Nucl Med Mol Imaging 2004 Jun
PMID:Position of nuclear medicine techniques in the diagnostic work-up of brain tumors. 1524 5


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