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Biomedical subjects

S Meyers

Publications and source records attributed to S Meyers.

At least 55 records · Page 3Linked to original sources
PubMed1995

The t(8;21) fusion protein interferes with AML-1B-dependent transcriptional activation.

The AML-1/CBF beta transcription factor complex is targeted by both the t(8;21) and the inv(16) chromosomal alterations, which are frequently observed in acute myelogenous leukemia. AML-1 is a site-specific DNA-binding protein that recognizes the enhancer core motif TGTGGT. The t(8;21) translocation fuses the first 177 amino acids of AML-1 to MTG8 (also known as ETO), generating a chimeric protein that retains the DNA-binding domain of AML-1. Analysis of endogenous AML-1 DNA-binding complexes suggested the presence of at least two AML-1 isoforms. Accordingly, we screened a human B-cell cDNA library and isolated a larger, potentially alternatively spliced, form of AML1, termed AML1B. AML-1B is a protein of 53 kDa that binds to a consensus AML-1-binding site and complexes with CBF beta. Subcellular fractionation experiments demonstrated that both AML-1 and AML-1/ETO are efficiently extracted from the nucleus under ionic conditions but that AML-1B is localized to a salt-resistant nuclear compartment. Analysis of the transcriptional activities of AML-1, AML-1B, and AML-1/ETO demonstrated that only AML-1B activates transcription from the T-cell receptor beta enhancer. Mixing experiments indicated that AML-1/ETO can efficiently block AML-1B-dependent transcriptional activation, suggesting that the t(8;21) translocation creates a dominant interfering protein.

Alternative Splicing↗
PubMed1995

Indirect and direct disruption of transcriptional regulation in cancer: E2F and AML-1.

The disruption of transcriptional regulatory circuits through the elimination of negative regulatory factors (tumor suppressors), the activation of positive acting factors (oncogenes), or when chimeric proteins result from chromosomal translocations, is likely a key event in multistep tumorigenesis. Here, using the transcription factors E2F and AML-1 as model systems, we discuss the disruption of coordinate transcriptional regulation in oncogenesis. E2F oncogenic signals are released when the pRb tumor suppressor is inactivated, and E2F activation may necessitate the coordinate inactivation of a second tumor suppressor, p53. AML-1 is the target of the (8;21) translocation, found in approximately 15% of acute myeloid leukemia (AML) cases, and the t(12;21), found in up to 30% of childhood B-cell acute lymphoblastic leukemias. The t(8;21) creates a fusion protein between AML-1 and a gene of unknown function, mtg8 (ETO), whereas the t(12;21) fuses the TEL (translocation-ets-leukemia) transcription factor to the N-terminus of AML-1. The inv(16), which is the most frequent anomaly found in AML, also targets AML-1, by fusing the gene that encodes AML-1's heterodimeric partner CBF beta to the smooth muscle myosin heavy chain gene MYHll. Thus, E2F and AML-1 provide excellent models for the disruption of transcriptional regulation in cancer.

Carrier Proteins↗
PubMed1994

PEBP2/CBF, the murine homolog of the human myeloid AML1 and PEBP2 beta/CBF beta proto-oncoproteins, regulates the murine myeloperoxidase and neutrophil elastase genes in immature myeloid cells.

The myeloperoxidase (MPO) and neutrophil elastase genes are expressed specifically in immature myeloid cells. The integrity of a polyomavirus enhancer core sequence, 5'-AACCACA-3', is critical to the activity of the murine MPO proximal enhancer. This element binds two species, myeloid nuclear factors 1 alpha and 1 beta (MyNF1 alpha and -beta), present in 32D cl3 myeloid cell nuclear extracts. The levels of the MyNF1s increase during early 32D cl3 cell granulocytic differentiation. Both MyNF1 alpha and -beta supershift with an antiserum raised by using a peptide derived from the N terminus of polyomavirus enhancer-binding protein 2/core-binding factor (PEBP2/CBF) alpha subunit. The specific peptide inhibits these supershifts. In vitro-translated PEBP2/CBF DNA-binding domain binds the murine MPO PEBP2/CBF site. An alternate PEBP2/CBF consensus site, 5'-GACCGCA-3', but not a simian virus 40 enhancer core sequence, 5'-TTCCACA-3', binds the MyNF1s in vitro and activates a minimal murine MPO-thymidine kinase promoter in vivo. The murine neutrophil elastase gene 100-bp 5'-flanking sequences contain several functional elements, including potential binding sites for PU.1, C/EBP, c-Myb, and PEBP2/CBF. The functional element 5'-GGCCACA-3' located at positions -66 to 72 differs from the PEBP2/CBF consensus (5'-PuACCPuCA-3') only by an A-to-G transition at position 2. This DNA element binds MyNF1 alpha and -beta weakly. The N terminis of two PEBP2/CBF alpha subunit family members, PEBP2 alpha A and PEBP2 alpha B (murine AML1), are nearly identical, and 32D c13 cl3 cells contain both corresponding mRNAs. Since t(8;21), t(3;21), and inv(16), associated with myeloid leukemias, disrupt subunits of PEBP2/CBF, we speculate that the resulting oncoproteins, AML1-ETO, AML1-EAP, AML1-Evi1, and CBF beta-MYH11, inhibit early myeloid differentiation.

Animals↗
PubMed1993

Pharmacokinetic/pharmacodynamic interactions of intensive cyclophosphamide, cisplatin, and BCNU in patients with breast cancer.

Combinations of alkylating agents in intensive doses with autologous hematopoietic cell support (AHCS) are commonly used to treat advanced, solid tumors. Relatively little is known about the pharmacokinetic or pharmacodynamic aspects of their use. The cyclophosphamide, cisplatin, and BCNU (CPA/cDDP/BCNU) regimen is often used in patients with breast cancer. In these individuals, the blood levels of BCNU vary by more than tenfold. In rats given BCNU, the blood level variability is associated with cisplatin pretreatment, and mean levels are much higher than those that occur when cisplatin pretreatment is omitted. These observations suggest that a major elimination pathway for BCNU is metabolic and is subject to cisplatin disruption. Between 30-50% of patients receiving the CPA/cDDP/BCNU regimen experience a steroid-responsive pulmonary injury that can be fatal if untreated. Blood levels of BCNU are positively correlated with the risk of pulmonary injury in these patients. Others have demonstrated that blood levels of CPA can be inversely correlated with the likelihood of cardiac toxicity and 2-year, relapse-free survival in patients with breast cancer. Emerging data suggest that circulating drug levels, rather than the calculated dose, best explain the variability of outcome in patients treated with combination alkylating agents and AHCS.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Identification of AML-1 and the (8;21) translocation protein (AML-1/ETO) as sequence-specific DNA-binding proteins: the runt homology domain is required for DNA binding and protein-protein interactions.

The AML1 gene on chromosome 21 is disrupted in the (8;21)(q22;q22) translocation associated with acute myelogenous leukemia and encodes a protein with a central 118-amino-acid domain with 69% homology to the Drosophila pair-rule gene, runt. We demonstrate that AML-1 is a DNA-binding protein which specifically interacts with a sequence belonging to the group of enhancer core motifs, TGT/cGGT. Electrophoretic mobility shift analysis of cell extracts identified two AML-1-containing protein-DNA complexes whose electrophoretic mobilities were slower than those of complexes formed with AML-1 produced in vitro. Mixing of in vitro-produced AML-1 with cell extracts prior to gel mobility shift analysis resulted in the formation of higher-order complexes. Deletion mutagenesis of AML-1 revealed that the runt homology domain mediates both sequence-specific DNA binding and protein-protein interactions. The hybrid product, AML-1/ETO, which results from the (8;21) translocation and retains the runt homology domain, both recognizes the AML-1 consensus sequence and interacts with other cellular proteins.

Animals↗
PubMed1992

Interaction of the yeast pleiotropic drug resistance genes PDR1 and PDR5.

The network of genes which mediates multiple drug resistance in yeast includes, among others, the PDR1 gene, which encodes a putative regulator of gene expression, and PDR5, a locus whose amplification leads to resistance. We demonstrate that disruption of PDR5 causes marked hypersensitivity not only to cycloheximide but also to sulphometuron methyl and the mitochondrial inhibitors chloramphenicol, lincomycin, erythromycin and antimycin. Genetic analysis of double mutants containing an insertion in PDR5 (pdr5:Tn5), which renders cells hypersensitive to cycloheximide, and a pdr1 mutation, which confers resistance to this inhibitor, indicates that the expression of resistance requires a functional PDR5 gene. The same interdependency is observed for chloramphenicol, but not for oligomycin, lincomycin, erythromycin or sulphometuron methyl. Northern analysis of PDR1 and PDR5 transcripts reveals that the 5.2 kbp PDR5 transcript is overexpressed in pdr1 (resistant) mutants, but underexpressed in a disruption of PDR1. These observations provide strong experimental support for our former proposal that the PDR5 gene is a target for regulation by the PDR1 gene product.

Anti-Bacterial Agents↗
PubMed1992

Evidence for the localization of a malignant hyperthermia susceptibility locus (MHS2) to human chromosome 17q.

Malignant hyperthermia susceptibility is a lethal autosomal dominant disorder of skeletal muscle metabolism that is triggered by all potent inhalation anesthetic gases. Recent linkage studies suggest a genetic locus for this disorder on 19q13.1. We have previously reported three unrelated families diagnosed with MHS that are unlinked to markers surrounding this locus on 19q13.1. In this report we extend these observations and present linkage studies on 16 MHS families. Four families (25%) were found linked to the region 19q12-q13.2 (Zmax = 2.96 with the ryanodine receptor at theta = 0.0). Five families (31%) were found closely linked to the anonymous marker NME1 (previously designated NM23) on chromosome 17q11.2-q24 (Zmax = 3.26 at theta = 0.0). Two families (13%) were clearly unlinked to either of these chromosomal regions. In five additional families, data were insufficient to determine their linkage status (they were potentially linked to two or more sites). The results of our heterogeneity analyses are consistent with the hypothesis that MHS can be caused in humans by any one of at least three distinct genetic loci. Furthermore, we provide preliminary linkage data suggesting the localization of a gene in human MHS to 17q11.2-q24 (MHS2), with a gene frequency of this putative locus approximately equal to that of the MHS1 locus on 19q.

Adult↗
PubMed1992

Amyloidosis and inflammatory bowel disease. A 50-year experience with 25 patients.

Amyloidosis is a rare but serious complication of inflammatory bowel disease (IBD), especially Crohn's disease (CD). It occurred in 15 of our 1709 patients with CD (0.9%) (706 with ileocolitis, 310 with colitis, and 693 with enteritis), but in only 1 of our 1341 patients with ulcerative colitis (UC) (0.07%), admitted to The Mount Sinai Hospital between 1960 and 1985. Eleven of the patients with CD who had amyloidosis had ileocolitis, 2 colitis, and 2 ileitis; these figures represent a frequency within each group of 1.6%, 0.6%, and 0.3%, respectively. Amyloidosis was thus associated 4.4 times more often with CD of the colon than with pure small bowel disease. We have added to this group of 15 patients the 5 cases of CD that were originally reported by Werther et al in 1960, plus another 4 (2 with UC and 2 with CD) who have been seen since 1985, making a total of 25 patients in this series, 22 with CD and 3 with UC. There was a striking male preponderance, 16 of 22, among patients with CD, although 2 of the 3 patients with UC were female. Amyloid disease was diagnosed at a mean age of 40 years, 15 years (range, 1-42) after the onset of CD. Six major forms of amyloidosis occurred: nephropathy, enteropathy, cardiomyopathy, hepatosplenomegaly, thyroid mass, and generalized amyloidosis. Renal disease with proteinurea and/or renal insufficiency occurred in 18 of the 22 patients with CD and in all 3 with UC. Nephropathy was by far the most common lethal manifestation of IBD-associated amyloidosis in this series. Nephrotic syndrome developed in 15 patients with CD and was accompanied by renal failure, the major contributor to mortality, in 10 of the 13 patients who died. Amyloidosis may be associated with suppurative or other extraintestinal manifestations of IBD. Fifteen of the 22 patients with CD who had amyloidosis also had suppurative complications of their bowel disease, although the other 7 had no recognizable suppuration. Extraintestinal manifestations were also common in this series, occurring in 12 of 22 patients with CD and in 2 of the 3 patients with UC; 6 of the 18 patients with nephrotic syndrome also had arthritis. However, there is no evidence that patients with IBD with amyloidosis have extraintestinal manifestations more frequently than do IBD patients without amyloidosis. Earlier reports of amyloid associated with IBD came from autopsy series. In recent years, biopsy has allowed diagnosis to be made during life.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Lymphomas with acquired mouse mammary tumor virus proviruses resemble distinct prethymic and intrathymic phenotypes defined in vivo.

A number of murine T cell lymphomas expressing the T cell Ag Thy-1 contain acquired mouse mammary tumor (MMTV) proviruses. These lymphomas all express detectable levels of MMTV RNA, yet the majority of the tumors fail to produce MMTV particles. To determine if the ability of lymphomas to produce MMTV is a reflection of the differentiation state of the tumor, we examined eight lymphomas for expression of surface B and T cell Ag as well as for rearrangements and expression of TCR genes. All tumors could be grouped into three categories observed in vivo, including early lymphoid, nonmature intrathymic T cells, and immature intrathymic T cells. Cell lines corresponding to all three phenotypes produced MMTV particles, suggesting that production of virus is not linked to the differentiation state of lymphoid cells. These studies highlight the potential advantage of studying T cell lymphomas vs mixed primary populations or T cell hybridomas for evaluation of both phenotypic and molecular markers in clonal T cells.

Animals↗
PubMed1989

Angiographic coronary morphology in postinfarction angina.

To investigate the pathophysiologic relevance of angiographically irregular coronary stenoses in postinfarction angina (PIA), we analyzed the clinical course and coronary angiograms of 73 patients studied within 30 days of infarction. Coronary lesions were classified as smooth or irregular. Thirty-six patients had PIA (Group 1) and 37 had an uncomplicated course (Group 2). Irregular lesion(s) in patent infarct-related arteries were found in 77% of Group 1 vs. 24% of Group 2 patients (P less than 0.005). Irregular lesion(s) in any coronary artery were found in 58% of Group 1 versus 19% of Group 2 patients (P less than 0.002). Other univariate predictors of PIA included older age, hypertension, angina before myocardial infarct, lower peak creatine kinase, three-vessel disease, and higher modified Gensini score. Multivariate analysis ranked lesion irregularity as the strongest predictor of PIA. Our data suggests that ruptured atherosclerotic plaques may be important in the pathogenesis of PIA. It is possible that lesion irregularity is associated with an active process and/or a residual thrombus, which may be responsible for postinfarction angina.

Angina Pectoris↗
PubMed1989

The "natural history" of ulcerative colitis: an analysis of the placebo response.

We have attempted to elucidate the "natural history" of ulcerative colitis by studying the placebo groups of 11 controlled trials of 185 patients with active disease. Most (182) of the patients were mild to moderately ill, but 3 had severe colitis. They were studied by endoscopic, pathologic, and/or clinical criteria and followed for 15-42 days. Up to 52% improved clinically and 59% sigmoidoscopically. Relapses commonly occurred within 2 months of these "spontaneous" improvements. In another six trials of 174 patients in remission receiving only placebo therapy (134 followed for 6 months and 40 for 12 months), up to 51% remained in remission. Favorable predictive factors for continued remission included a normal rectal mucosa on sigmoidoscopy, limited extent of colitis, and remission recently achieved by active therapy or maintained by therapy for at least 1 year before study entry. Thus, patients can get and stay better with no "specific" therapy. We have clarified advantageous predictive factors.

Adult↗