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P Meltzer

Publications and source records attributed to P Meltzer.

At least 37 records · Page 2Linked to original sources
PubMed2000

Thyroid hormone regulation of hepatic genes in vivo detected by complementary DNA microarray.

The liver is an important target organ of thyroid hormone. However, only a limited number of hepatic target genes have been identified, and little is known about the pattern of their regulation by thyroid hormone. We used a quantitative fluorescent cDNA microarray to identify novel hepatic genes regulated by thyroid hormone. Fluorescent-labeled cDNA prepared from hepatic RNA of T3-treated and hypothyroid mice was hybridized to a cDNA microarray, representing 2225 different mouse genes, followed by computer analysis to compare relative changes in gene expression. Fifty five genes, 45 not previously known to be thyroid hormone-responsive genes, were found to be regulated by thyroid hormone. Among them, 14 were positively regulated by thyroid hormone, and unexpectedly, 41 were negatively regulated. The expression of 8 of these genes was confirmed by Northern blot analyses. Thyroid hormone affected gene expression for a diverse range of cellular pathways and functions, including gluconeogenesis, lipogenesis, insulin signaling, adenylate cyclase signaling, cell proliferation, and apoptosis. This is the first application of the microarray technique to study hormonal regulation of gene expression in vivo and should prove to be a powerful tool for future studies of hormone and drug action.

Adenylyl Cyclases↗
PubMed2000

Alleles of the estrogen receptor alpha-gene and an estrogen receptor cotranscriptional activator gene, amplified in breast cancer-1 (AIB1), are associated with quantitative calcaneal ultrasound.

Quantitative bone ultrasound (QUS) has a significant heritable component. Because estrogen is required for attainment of peak bone mass, we studied alleles of two genes, estrogen receptor alpha (ER1) and amplified in breast cancer-1 (AIB1), for their association with QUS. In a volunteer sample of 663 white women aged 18-35 years, bone ultrasound attenuation (BUA), speed of sound (SOS), and heel stiffness index (SI), the latter consisting of the component measures of BUA and SOS, were measured at the right calcaneus by QUS. Subjects were genotyped for the ER1 polymorphisms Xba I and Pvu II and for the AIB1 polyglutamine tract polymorphism. In a multiple regression analysis, ER1 genotype was an independent predictor of QUS-SI (p = 0.03). Because AIB1 and ER1 enhance gene expression in a coordinate manner, we also searched for interactions. A gene-by-gene interaction effect was seen for QUS-SI (p = 0.009), QUS-BUA (p = 0.03), and QUS-SOS (p = 0.004). These remained significant after the inclusion of clinically relevant variables into the final regression model. Overall, these clinical and genetic factors accounted for up to 16% of the variance in peak QUS; the genetic markers alone accounted for 4-7%. This is the first demonstration of specific genetic effects on calcaneal QUS encoded by alleles of genes directly involved in mediating estrogen effects on bone.

Adolescent↗
PubMed2000

Identification of potential mRNA biomarkers in peripheral blood lymphocytes for human exposure to ionizing radiation.

Since early in the Atomic Age, biological indicators of radiation exposure have been sought, but currently available methods are not entirely satisfactory. Using cDNA microarray hybridization to discover new potential biomarkers, we have identified genes expressed at increased levels in human peripheral blood lymphocytes after ex vivo irradiation. We recently used this technique to identify a large set of ionizing radiation-responsive genes in a human cell line (Oncogene 18, 3666-3672, 1999). The present set of radiation markers in peripheral blood lymphocytes was identified 24 h after treatment, and while the magnitude of mRNA induction generally decreased over time, many markers were still significantly elevated up to 72 h after irradiation. In all donors, the most highly responsive gene identified was DDB2, which codes for the p48 subunit of XPE, a protein known to play a crucial role in repair of ultraviolet (UV) radiation damage in DNA. Induction of DDB2, CDKN1A (also known at C1P1/WAF1) and XPC showed a linear dose-response relationship between 0.2 and 2 Gy at 24 and 48 h after irradiation, with less linearity at earlier or later times. These results suggest that relative levels of gene expressions in peripheral blood cells may provide estimated of environmental radiation exposures.

Adult↗
PubMed2000

Frequent amplification of chromosomal region 20q12-q13 in ovarian cancer.

DNA amplification at chromosomal region 20q12-q13, which is common in breast cancer, has recently been described also in ovarian tumors. We studied the amplification of the recently identified candidate oncogenes in this region in 24 sporadic, 3 familial and 4 hereditary ovarian carcinomas, and in 8 ovarian cancer cell lines. High-level amplification of at least one of the five nonsyntenic regions at 20q12-q13.2 was found in 13 sporadic (54%) and in all four hereditary tumors. Typically, two or more distinct amplicons (separated by nonamplified DNA) were found coamplified in various combinations. The regions defined by the AIB1 and PTPN1 genes (at 20q12 and 20q13.1, respectively) were amplified in 25% and 29% of the sporadic tumors, also without simultaneous coamplification of other regions. Amplification of AIB1 (a steroid receptor coactivator gene) was associated with estrogen receptor positivity in sporadic ovarian carcinomas (P = 0.01) and showed a tendency to correlate with poor survival of patients. Of the genes amplified in breast cancer, the BTAK gene was amplified in 21%, the MYBL2 gene in 17%, and the ZNF217 gene in 12.5% of the sporadic tumors. The high frequency of gene amplification at 20q12-q13.2 suggests that the genes amplified therein may play a central role in the pathogenesis of sporadic and hereditary ovarian carcinoma.

Chromosomes, Human, Pair 20↗
PubMed1999

Informatic selection of a neural crest-melanocyte cDNA set for microarray analysis.

With cDNA microarrays, it is now possible to compare the expression of many genes simultaneously. To maximize the likelihood of finding genes whose expression is altered under the experimental conditions, it would be advantageous to be able to select clones for tissue-appropriate cDNA sets. We have taken advantage of the extensive sequence information in the dbEST expressed sequence tag (EST) database to identify a neural crest-derived melanocyte cDNA set for microarray analysis. Analysis of characterized genes with dbEST identified one library that contained ESTs representing 21 neural crest-expressed genes (library 198). The distribution of the ESTs corresponding to these genes was biased toward being derived from library 198. This is in contrast to the EST distribution profile for a set of control genes, characterized to be more ubiquitously expressed in multiple tissues (P < 1 x 10(-9)). From library 198, a subset of 852 clustered ESTs were selected that have a library distribution profile similar to that of the 21 neural crest-expressed genes. Microarray analysis demonstrated the majority of the neural crest-selected 852 ESTs (Mel1 array) were differentially expressed in melanoma cell lines compared with a non-neural crest kidney epithelial cell line (P < 1 x 10(-8)). This was not observed with an array of 1,238 ESTs that was selected without library origin bias (P = 0.204). This study presents an approach for selecting tissue-appropriate cDNAs that can be used to examine the expression profiles of developmental processes and diseases.

Calibration↗
PubMed1999

Fluorescent cDNA microarray hybridization reveals complexity and heterogeneity of cellular genotoxic stress responses.

The fate of cells exposed to ionizing radiation (IR) may depend greatly on changes in gene expression, so that an improved view of gene induction profiles is important for understanding mechanisms of checkpoint control, repair and cell death following such exposures. We have used a quantitative fluorescent cDNA microarray hybridization approach to identify genes regulated in response to 7-irradiation in the p53 wild-type ML-1 human myeloid cell line. Hybridization of the array to fluorescently-labeled RNA from treated and untreated cells was followed by computer analysis to derive relative changes in expression levels of the genes present in the array, which agreed well with actual quantitative changes in expression. Forty-eight sequences, 30 not previously identified as IR-responsive, were significantly regulated by IR. Induction by IR and other stresses of a subset of these genes, including the previously characterized CIP1/ WAF1, MDM2 and BAX genes, as well as nine genes not previously reported to be IR-responsive, was examined in a panel of 12 human cell lines. Responses varied widely in cell lines with different tissues of origin and different genetic backgrounds, highlighting the importance of cellular context to genotoxic stress responses. Two of the newly identified IR-responsive genes, FRA-1 and ATF3, showed a p53-associated component to their IR-induction, and this was confirmed both in isogenic human cell lines and in mouse thymus. The majority of the IR-responsive genes, however, showed no indication of p53-dependent regulation, representing a potentially important class of stress-responsive genes in leukemic cells.

Animals↗
PubMed1999

Detection of EWS-FLI-1 fusion in Ewing's sarcoma/peripheral primitive neuroectodermal tumor by fluorescence in situ hybridization using formalin-fixed paraffin-embedded tissue.

The balanced translocation t(11;22)(q24;q12) is specific for the Ewing's sarcoma/peripheral primitive neuroectodermal tumors (ES/PNETs) and results in the EWS/FLI-1 fusion transcript, which can be detected by reverse transcription polymerase chain reaction (RT-PCR). Recent studies also have used fluorescence in situ hybridization (FISH) to show the translocation; however, most of these have been performed on cell lines or touch preparations and short-term cultures of tumors. Moreover, the existing probes generally have shown only the break in the specific chromosomes rather than the translocation itself. We describe our findings with a new set of probes that localize to 22q12 (EWS) and 11q24 (FLI-1) and directly show the translocation as juxtaposed red-green signals on der(22) in nuclei extracted from formalin-fixed, paraffm-embedded tissues. After establishing the specificity of the probes (on metaphase spreads and interphase nuclei in two translocation-positive cell lines and normal peripheral blood lymphocytes), we evaluated 11 ES/PNETs and 10 other tumors (four alveolar rhabdomyosarcomas, three neuroblastomas, two lymphomas, one extramedullary myeloid tumor) using a two-color FISH assay. All 11 ES/PNETs showed fusion signals in 20% to 80% of evaluable nuclei. In two lymphoma cases, random overlapping signals were present in 2% and 4% of nuclei, whereas the remaining eight tumors were negative. The presence of t(11;22) was confirmed by RT-PCR in 10 of 11 ES/PNETs. We conclude that FISH analysis with this newly designed probe pair is a specific and sensitive method of detecting t(11;22) on routinely processed tissue and can be useful in the differential diagnosis of ES/PNETs from other small round blue cell tumors when only fixed tissue is available.

Adolescent↗
PubMed1999

Absence of EWS/FLI1 fusion in olfactory neuroblastomas indicates these tumors do not belong to the Ewing's sarcoma family.

The balanced reciprocal translocation t(11;22)(q24;q12) is a specific molecular marker for the Ewing's sarcoma family of tumors (ESFT). Based on the detection of this translocation in some olfactory neuroblastomas (ONBs), it has been proposed that ONBs also belong to the ESFT. Others have challenged this hypothesis; however, the rarity of ONBs, as well as the lack of molecular techniques that work reliably on formalin fixed tissue, have precluded the molecular analysis of a significant number of cases. We evaluated the immunophenotypic and molecular features of 17 paranasal small round neuroectodermal tumors using routinely fixed tissue. Probes localizing to 22q12 (EWS) and 11q24 (FLI-1) were used in a standard 2-color fluorescence in situ hybridization (FISH) assay to evaluate EWS/FLI1 fusion on the der(22). Sixteen tumors were mic-2 negative, whereas 1 tumor was mic-2 positive, compatible with ONB and ESFT, respectively. Thirteen of 15 ONBs could be evaluated by FISH, and all 13 were negative for the EWS/FLI1 fusion. Distinct fusion signals were identified in the single paranasal ESFT. Our findings indicate that ONBs lack the EWS/FLI1 fusion and are unrelated to the ESFT; however, true ESFTs may rarely occur as primary sinonasal tumors.

Adolescent↗
PubMed1999

Expression profiling using cDNA microarrays.

cDNA microarrays are capable of profiling gene expression patterns of tens of thousands of genes in a single experiment. DNA targets, in the form of 3' expressed sequence tags (ESTs), are arrayed onto glass slides (or membranes) and probed with fluorescent- or radioactively-labelled cDNAs. Here, we review technical aspects of cDNA microarrays, including the general principles, fabrication of the arrays, target labelling, image analysis and data extraction, management and mining.

Animals↗
PubMed1999

The complexity of radiation stress responses: analysis by informatics and functional genomics approaches.

Molecular responses to genotoxic stress are complex and are mediated by a variety of regulatory pathways. One key element in cellular response is the stress gene transcription factor p53, which can regulate nearly 100 genes that have already been identified. Although p53 plays a central role in the cellular response to DNA-damaging agents such as ionizing radiation (IR), other pathways can also have important roles. One example is the transcriptional responses associated with IR-induced apoptosis, where induction of some genes is limited to p53 wild-type (wt) cells that also have the ability to undergo rapid apoptosis after irradiation. In contrast, other genes are triggered after IR in lines undergoing rapid apoptosis regardless of p53 status. From this and other examples, it is apparent that the pattern of stress gene expression is cell type specific in both primary and transformed lines. The premise will be developed that such differences in stress gene responsiveness can be employed as molecular markers using a combination of informatics and functional genomics approaches. An example is given using the panel of lines of the NCI anticancer drug screen where both the p53 status and sensitivity to a large collection of cytotoxic agents have been determined. The utility of cDNA microarray hybridization to measure IR-stress gene responses has recently been demonstrated and a large number of additional IR-stress genes have been identified. The responses of some of these genes to IR and other DNA-damaging agents varied widely in cell lines from different tissues of origin and different genetic backgrounds, highlighting the importance of cellular context to genotoxic stress responses; this also highlights the need for informatics approaches to discover and prioritize hypotheses regarding the importance of particular cellular factors. The aim of this review is to demonstrate the utility of combining an informatics approach with functional genomics in the study of stress responses.

Animals↗
PubMed1998

Clinical differentiation between Proteus syndrome and hemihyperplasia: description of a distinct form of hemihyperplasia.

Proteus syndrome is a rare and highly variable hamartomatous syndrome that can affect multiple organ systems. It is characterized by hyperplastic lesions of connective tissue, vascular malformations, linear verrucous epidermal nevi, and hyperostoses. The cause of the disorder is unknown, but the current working hypothesis is that it is caused by a mosaic alteration that leads to a highly variable phenotype, equal sex ratio, sporadic occurrence, and discordant monozygotic twins. Herein we describe our experience with 18 patients with a referring diagnosis of Proteus syndrome. It was found that imaging studies are very useful for the characterization of the syndrome. One finding was that splenic hyperplasia can be a manifestation of Proteus syndrome. Analysis of the clinical data shows that Proteus syndrome is frequently confused with "hemihyperplasia." A distinct subtype of hemihyperplasia is defined that includes static or mildly progressive hemihyperplasia and multiple lipomata.

Adolescent↗
PubMed1998

Data management and analysis for gene expression arrays.

Microarray technology makes it possible to simultaneously study the expression of thousands of genes during a single experiment. We have developed an information system, ArrayDB, to manage and analyse large-scale expression data. The underlying relational database was designed to allow flexibility in the nature and structure of data input and also in the generation of standard or customized reports through a web-browser interface. ArrayDB provides varied options for data retrieval and analysis tools that should facilitate the interpretation of complex hybridization results. A sampling of ArrayDB storage, retrieval and analysis capabilities is available (www.nhgri.nih.gov/DIR/LCG/15K/HTML/ ), along with information on a set of approximately 15,000 genes used to fabricate several widely used microarrays. Information stored in ArrayDB is used to provide integrated gene expression reports by linking array target sequences with NCBI's Entrez retrieval system, UniGene and KEGG pathway views. The integration of external information resources is essential in interpreting intrinsic patterns and relationships in large-scale gene expression data.

Computer Communication Networks↗
PubMed1998

In breast cancer, amplification of the steroid receptor coactivator gene AIB1 is correlated with estrogen and progesterone receptor positivity.

The AIB1 gene was isolated upon microdissection of the homogeneously staining regions observed in breast cancer cell lines. It was subsequently shown to map at a region at 20q12 that is frequently amplified in breast tumors. In a screen of breast tumor cell lines, of all the genes mapping to the region, AIB1 appeared to be the most consistently amplified and overexpressed. AIB1 shares homology with the SRC-1 family of nuclear receptor coactivators. It was found to interact in a ligand-dependent manner with the estrogen receptor (ER) and to result in increased levels of estrogen-dependent transcription. These properties could be of important biological significance in breast and ovarian cancerigenesis, and we were, therefore, interested in determining whether the amplification of the AIB1 gene was associated with a particular phenotype or subgroup in these tumors. We tested a population of 1157 breast and 122 ovarian tumors in which DNA amplification had been determined previously at 15 chromosomal locations. Amplification of the AIB1 gene was observed in 4.8% of breast cancers and 7.4% of ovarian cancers. In breast tumors, AIB1 was correlated with ER and progesterone receptor positivity, as well as with tumor size. Correlation was also observed with the amplification of MDM2 and FGFR1 genes, but interestingly, no correlation was found with the amplification of CCND1, which is known to be strongly associated with ER. Furthermore, analyzing at 20q12-q13 range, we show the existence of three amplification cores, represented by AIB3/AIB4, AIB1, and RMC20C001. AIB1 and CCND1 amplifications may, thus, represent two different subsets of ER-positive breast tumors.

Breast Neoplasms↗
PubMed1997

SPECT imaging of dopamine transporter sites in normal and MPTP-Treated rhesus monkeys.

UNLABELLED: Parkinson's disease is characterized by degeneration of dopamine (DA) neurons and their terminals. Since these neurons contain dopamine transporters (DAT), radioligands that bind to these sites are promising radiopharmaceuticals for diagnosis and therapeutic monitoring of disease progression. We evaluated [123I]-2 beta-carbomethoxy- 3 beta-(4-fluorophenyl)-N-(1-iodoprop-1-en-3-yl)nortropane ([123I]IACFT) for SPECT imaging in an MPTP model of parkinsonism. METHODS: Three rhesus monkeys were imaged before and at 1 and 2 mo after treatment with MPTP. The SPECT results were correlated with motor behavior and PET imaging with [11C]-2 beta-carbomethoxy-3 beta-aryltropane ([11C]-CFT). Also, biodistribution was measured by planar imaging. RESULTS: In normal animals, striatal accumulation of radioactivity was rapid and peaked within 30 min. Striatal accumulation of [123I]IACFT was nearly completely displaceable with unlabeled CFT (1 mg/kg) but was not affected by a similar dose of the serotonin (5-HT) transport inhibitor, citalopram. The striatal to cerebellar ratio measured at 30 min, after injection of [123I]IACFT was significantly higher (p < 0.01) than with [11C]CFT; approximately 6; 1 versus approximately 2.5; 1. After MPTP treatment this ratio decreased to 1.02:1 with IACFT and 1.23:1 with [11C]CFT. Blood clearance of [123I]IACFT was rapid with a terminal t1/2 of approximately 30 min. HPLC of plasma samples demonstrated that the concentration of intact ligand decreases rapidly, approaching zero by 60 min. Low levels of accumulation were measured in extracranial tissues. CONCLUSION: These results demonstrate that [123I]IACFT is an excellent SPECT ligand for dopamine transporter sites that combines the critical characteristics of: (a) high striatal to cerebellar ratios, (b) high selectivity for dopamine versus 5-HT transporter sites, (c) convenient preparation at high-specific activity and radiochemical purity and (d) a striatal localization rate that is well matched to the physical t1/2 of 123I.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

Use of microgenomic technology for analysis of alterations in DNA copy number and gene expression in malignant melanoma.

Chromosome abnormalities in human malignancies have identified the genomic location of several important growth-regulatory genes, including cellular oncogenes and tumour suppressor genes. Melanomas are characterized by recurring chromosome alterations, and it is important to identify those genes whose altered expression may be causally related to melanocytic transformation. This short report presents an overview of strategies used which combine the materials and technologies of the Human Genome Project with clinically directed studies of melanoma biology. The Human Genome Project combines various technologies, including cytogenetic, physical mapping, genetic mapping and DNA sequencing, in order to identify all of the human genes, but especially the 4000 estimated to contribute to human disease. This report focuses first on advances in genome technology that provide information on chromosome rearrangements and DNA copy number changes. This includes a discussion of chromosome microdissection as well as the microexcision of tissue specimens to gain insights into chromosome regions altered in association with melanocyte transformation. Next, there is a brief discussion of the generation and characterization of subtracted cDNA sublibraries which allow the identification of genes uniquely expressed in association with the transformed phenotype of human melanoma cells. Finally, we briefly discuss the feasibility of using a recently developed system for parallel examination of multiple genes based upon robotic printing of cDNAs on glass slides, and simultaneous two-colour fluorescence hybridization to study the expression patterns of cDNAs for their association with melanoma tumour suppression. The combination of these varied molecular technologies may provide insights into previously unrecognized genes involved causally in the pathobiology of this important neoplasm, and may provide new targets for clinical intervention.

Chromosome Mapping↗
PubMed1996

Independent amplification and frequent co-amplification of three nonsyntenic regions on the long arm of chromosome 20 in human breast cancer.

DNA amplification at 20q13.2 is common in breast cancer, correlates with poor prognosis, and may reflect location of an important oncogene. Recently, other regions along 20q were also found to undergo amplification. Here, amplification levels and patterns of co-amplification were analyzed by interphase fluorescence in situ hybridization at 14 loci along 20q in 146 uncultured breast carcinomas and 14 cell lines. Three regions were independently amplified in uncultured tumors: RMC20C001 region at 20q13.2 (highly amplified in 9.6% of the cases), PTPN1 region 3 Mb proximal (6.2%), and AIB3 region at 20q11 (6.2%). Co-amplifications involving two or three of these regions were seen in 11 of the 19 highly amplified tumors. The results suggest that three distinct nonsyntenic regions along 20q may be important and that complex chromosomal rearrangements underlie their frequent co-amplification in breast cancer.

Breast Neoplasms↗
PubMed1996

Twelve amplified and expressed genes localized in a single domain in glioma.

Gene amplification has been associated both with tumor stage and progression in human gliomas. Several distinct amplified loci have been identified by comparative genomic hybridization and Southern blot analysis. It has been increasingly recognized that amplified domains comprise multiple genes. Here, we demonstrate amplification of up to 12 different genes from an amplified domain at 12q13-15 that has been found in approximately 15% of astrocytomas and glioblastomas. The amplified genes were GLI, WNT1, MDM2, SAS, CDK4 OS-4, GAS16, GAS27, GAS41, GAS56, GAS 64 and GAS89. In one glioblastoma all 12 amplified genes were also found to be expressed. These results strongly warrant the search for as yet unidentified genes in regions previously reported to be amplified.

Animals↗