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Matthew Meyerson

Publications and source records attributed to Matthew Meyerson.

At least 37 records · Page 2Linked to original sources
PubMed2006

Phosphorylation of the menin tumor suppressor protein on serine 543 and serine 583.

Multiple endocrine neoplasia type 1 (MEN-1) is a heritable syndrome typified by tumors in multiple endocrine organs, including the pituitary, parathyroids, and pancreatic islets. MEN-1 is attributable to mutations in the MEN1 tumor-suppressor gene that encodes the menin protein. Recent studies have implicated menin in transcriptional regulation and in covalent histone modification; however, little is known about modifications of the menin protein. Here, we report that menin is subject to phosphorylation on serine residues, including Ser543 and Ser583. Phosphorylation-defective mutants of either or both of these residues retain the associated histone methyltransferase activity of menin, as well as binding to the trithorax complex members Ash2L, Rbbp5, and MLL2 and to RNA polymerase II. Chromatin immunoprecipitation experiments reveal that binding of menin to the Hoxc8 locus is not affected by phosphorylation on Ser543 or Ser583.

Cell Differentiation↗
PubMed2006

Epidermal growth factor receptor activation in glioblastoma through novel missense mutations in the extracellular domain.

BACKGROUND: Protein tyrosine kinases are important regulators of cellular homeostasis with tightly controlled catalytic activity. Mutations in kinase-encoding genes can relieve the autoinhibitory constraints on kinase activity, can promote malignant transformation, and appear to be a major determinant of response to kinase inhibitor therapy. Missense mutations in the EGFR kinase domain, for example, have recently been identified in patients who showed clinical responses to EGFR kinase inhibitor therapy. METHODS AND FINDINGS: Encouraged by the promising clinical activity of epidermal growth factor receptor (EGFR) kinase inhibitors in treating glioblastoma in humans, we have sequenced the complete EGFR coding sequence in glioma tumor samples and cell lines. We identified novel missense mutations in the extracellular domain of EGFR in 13.6% (18/132) of glioblastomas and 12.5% (1/8) of glioblastoma cell lines. These EGFR mutations were associated with increased EGFR gene dosage and conferred anchorage-independent growth and tumorigenicity to NIH-3T3 cells. Cells transformed by expression of these EGFR mutants were sensitive to small-molecule EGFR kinase inhibitors. CONCLUSIONS: Our results suggest extracellular missense mutations as a novel mechanism for oncogenic EGFR activation and may help identify patients who can benefit from EGFR kinase inhibitors for treatment of glioblastoma.

Animals↗
PubMed2005

Allele-specific amplification in cancer revealed by SNP array analysis.

Amplification, deletion, and loss of heterozygosity of genomic DNA are hallmarks of cancer. In recent years a variety of studies have emerged measuring total chromosomal copy number at increasingly high resolution. Similarly, loss-of-heterozygosity events have been finely mapped using high-throughput genotyping technologies. We have developed a probe-level allele-specific quantitation procedure that extracts both copy number and allelotype information from single nucleotide polymorphism (SNP) array data to arrive at allele-specific copy number across the genome. Our approach applies an expectation-maximization algorithm to a model derived from a novel classification of SNP array probes. This method is the first to our knowledge that is able to (a) determine the generalized genotype of aberrant samples at each SNP site (e.g., CCCCT at an amplified site), and (b) infer the copy number of each parental chromosome across the genome. With this method, we are able to determine not just where amplifications and deletions occur, but also the haplotype of the region being amplified or deleted. The merit of our model and general approach is demonstrated by very precise genotyping of normal samples, and our allele-specific copy number inferences are validated using PCR experiments. Applying our method to a collection of lung cancer samples, we are able to conclude that amplification is essentially monoallelic, as would be expected under the mechanisms currently believed responsible for gene amplification. This suggests that a specific parental chromosome may be targeted for amplification, whether because of germ line or somatic variation. An R software package containing the methods described in this paper is freely available at http://genome.dfci.harvard.edu/~tlaframb/PLASQ.

Alleles↗
PubMed2005

The menin tumor suppressor protein is an essential oncogenic cofactor for MLL-associated leukemogenesis.

The Mixed-Lineage Leukemia (MLL) protein is a histone methyltransferase that is mutated in clinically and biologically distinctive subsets of acute leukemia. MLL normally associates with a cohort of highly conserved cofactors to form a macromolecular complex that includes menin, a product of the MEN1 tumor suppressor gene, which is mutated in heritable and sporadic endocrine tumors. We demonstrate here that oncogenic MLL fusion proteins retain an ability to stably associate with menin through a high-affinity, amino-terminal, conserved binding motif and that this interaction is required for the initiation of MLL-mediated leukemogenesis. Furthermore, menin is essential for maintenance of MLL-associated but not other oncogene induced myeloid transformation. Acute genetic ablation of menin reverses aberrant Hox gene expression mediated by MLL-menin promoter-associated complexes, and specifically abrogates the differentiation arrest and oncogenic properties of MLL-transformed leukemic blasts. These results demonstrate that a human oncoprotein is critically dependent on direct physical interaction with a tumor suppressor protein for its oncogenic activity, validate a potential target for molecular therapy, and suggest central roles for menin in altered epigenetic functions underlying the pathogenesis of hematopoietic cancers.

Amino Acid Motifs↗
PubMed2005

Oncogenic transformation by inhibitor-sensitive and -resistant EGFR mutants.

BACKGROUND: Somatic mutations in the kinase domain of the epidermal growth factor receptor tyrosine kinase gene EGFR are common in lung adenocarcinoma. The presence of mutations correlates with tumor sensitivity to the EGFR inhibitors erlotinib and gefitinib, but the transforming potential of specific mutations and their relationship to drug sensitivity have not been described. METHODS AND FINDINGS: Here, we demonstrate that EGFR active site mutants are oncogenic. Mutant EGFR can transform both fibroblasts and lung epithelial cells in the absence of exogenous epidermal growth factor, as evidenced by anchorage-independent growth, focus formation, and tumor formation in immunocompromised mice. Transformation is associated with constitutive autophosphorylation of EGFR, Shc phosphorylation, and STAT pathway activation. Whereas transformation by most EGFR mutants confers on cells sensitivity to erlotinib and gefitinib, transformation by an exon 20 insertion makes cells resistant to these inhibitors but more sensitive to the irreversible inhibitor CL-387,785. CONCLUSION: Oncogenic transformation of cells by different EGFR mutants causes differential sensitivity to gefitinib and erlotinib. Treatment of lung cancers harboring EGFR exon 20 insertions may therefore require the development of alternative kinase inhibition strategies.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Epidermal growth factor-independent transformation of Ba/F3 cells with cancer-derived epidermal growth factor receptor mutants induces gefitinib-sensitive cell cycle progression.

Epidermal growth factor receptor (EGFR) plays critical roles in many biological processes and in tumorigenesis. Here, we show that two mutated EGFRs found in lung and other malignancies, EGFR-G719S and EGFR-L858R, could transform Ba/F3 cells to interleukin-3 (IL-3)-independent growth, in a ligand-independent manner, an activity associated with the transforming function of other mutated tyrosine kinases. The mutated receptors are autophosphorylated in the absence of IL-3 without EGF stimulation, and their expression led to the constitutive activation of signal transducers and activators of transcription 5, extracellular signal-regulated kinase 1/2 (ERK1/2), ERK5, and AKT. In wild-type EGFR-expressing Ba/F3 cells, the major EGF-mediated signaling pathways were still intact. Gefitinib inhibited the growth of mutant EGFR-transformed Ba/F3 cells. Strikingly, the gefitinib sensitivity of cells expressing the L858R mutant was significantly greater than that of cells expressing the G719S mutant form, suggesting that distinct EGFR mutations may be differentially sensitive to small-molecule inhibitors. Furthermore, our data showed an antiproliferative effect of gefitinib on the EGFR-transformed Ba/F3 cells. Our results provide a model system to study the function of mutated EGFR and the differential effects of pharmacologic EGFR inhibition on the distinct mutant forms of this tyrosine kinase.

Animals↗
PubMed2005

Menin regulates pancreatic islet growth by promoting histone methylation and expression of genes encoding p27Kip1 and p18INK4c.

Menin, the product of the Men1 gene mutated in familial multiple endocrine neoplasia type 1 (MEN1), regulates transcription in differentiated cells. Menin associates with and modulates the histone methyltransferase activity of a nuclear protein complex to activate gene expression. However, menin-dependent histone methyltransferase activity in endocrine cells has not been demonstrated, and the mechanism of endocrine tumor suppression by menin remains unclear. Here, we show that menin-dependent histone methylation maintains the in vivo expression of cyclin-dependent kinase (CDK) inhibitors to prevent pancreatic islet tumors. In vivo expression of CDK inhibitors, including p27 and p18, and other cell cycle regulators is disrupted in mouse islet tumors lacking menin. Chromatin immunoprecipitation studies reveal that menin directly associates with regions of the p27 and p18 promoters and increases methylation of lysine 4 (Lys-4) in histone H3 associated with these promoters. Moreover, H3 Lys-4 methylation associated with p27 and p18 is reduced in islet tumors from Men1 mutant mice. Thus, H3 Lys-4 methylation is a crucial function of menin in islet tumor suppression. These studies suggest an epigenetic mechanism of tumor suppression: by promoting histone modifications, menin maintains transcription at multiple loci encoding cell cycle regulators essential for endocrine growth control.

Animals↗
PubMed2005

An alternative inhibitor overcomes resistance caused by a mutation of the epidermal growth factor receptor.

Mutations of the epidermal growth factor receptor (EGFR) gene have been identified in non-small cell lung cancer specimens from patients responding to anilinoquinazoline EGFR inhibitors. However, clinical resistance to EGFR inhibitor therapy is commonly observed. Previously, we showed that such resistance can be caused by a second mutation of the EGFR gene, leading to a T790M amino acid change in the EGFR tyrosine kinase domain and also found that CL-387,785, a specific and irreversible anilinoquinazoline EGFR inhibitor, was able to overcome this resistance on the biochemical level. Here, we present the successful establishment of a stable Ba/F3 cell line model system for the study of oncogenic EGFR signaling and the functional consequences of the EGFR T790M resistance mutation. We show the ability of gefitinib to induce growth arrest and apoptosis in cells transfected with wild-type or L858R EGFR, whereas the T790M mutation leads to high-level functional resistance against gefitinib and erlotinib. In addition, CL-387,785 is able to overcome resistance caused by the T790M mutation on a functional level, correlating with effective inhibition of downstream signaling pathways. Similar data was also obtained with the use of the gefitinib-resistant H1975 lung cancer cell line. The systems established by us should prove useful for the large-scale screening of alternative EGFR inhibitor compounds against the T790M or other EGFR mutations. These data also support the notion that clinical investigations of compounds similar to CL-387,785 may be useful as a treatment strategy for patients with resistance to EGFR inhibitor therapy caused by the T790M mutation.

Animals↗
PubMed2005

Homozygous deletions and chromosome amplifications in human lung carcinomas revealed by single nucleotide polymorphism array analysis.

Genome-wide copy number changes were analyzed in 70 primary human lung carcinoma specimens and 31 cell lines derived from human lung carcinomas, with high-density arrays representing approximately 115,000 single nucleotide polymorphism loci. In addition to previously characterized loci, two regions of homozygous deletion were found, one near the PTPRD locus on chromosome segment 9p23 in four samples representing both small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) and the second on chromosome segment 3q25 in one sample each of NSCLC and SCLC. High-level amplifications were identified within chromosome segment 8q12-13 in two SCLC specimens, 12p11 in two NSCLC specimens and 22q11 in four NSCLC specimens. Systematic copy number analysis of tyrosine kinase genes identified high-level amplification of EGFR in three NSCLC specimens, FGFR1 in two specimens and ERBB2 and MET in one specimen each. EGFR amplification was shown to be independent of kinase domain mutational status.

Carcinoma, Non-Small-Cell Lung↗
PubMed2005

Genomic and proteomic profiling of lung cancers: lung cancer classification in the age of targeted therapy.

Both proteomic and genomic methods offer promise for the classification of human lung carcinomas. This review summarizes the range of proteomic methods in development for lung cancer classification, and describes a number of recent analyses of messenger RNA expression in lung cancer. Multiple independent studies of mRNA expression profiles in lung adenocarcinoma have proven highly reproducible. Analyses of the relationship between expression profiles and tumor development and differentiation, the presence or absence of specific pathogenic mutations, patient prognosis and survival after surgical treatment, and specific histopathology all appear to be promising.

Gene Expression Profiling↗
PubMed2005

EGFR mutation and resistance of non-small-cell lung cancer to gefitinib.

Mutations of the epidermal growth factor receptor (EGFR) gene have been identified in specimens from patients with non-small-cell lung cancer who have a response to anilinoquinazoline EGFR inhibitors. Despite the dramatic responses to such inhibitors, most patients ultimately have a relapse. The mechanism of the drug resistance is unknown. Here we report the case of a patient with EGFR-mutant, gefitinib-responsive, advanced non-small-cell lung cancer who had a relapse after two years of complete remission during treatment with gefitinib. The DNA sequence of the EGFR gene in his tumor biopsy specimen at relapse revealed the presence of a second point mutation, resulting in threonine-to-methionine amino acid change at position 790 of EGFR. Structural modeling and biochemical studies showed that this second mutation led to gefitinib resistance.

Aged↗
PubMed2005

Interlaboratory comparability study of cancer gene expression analysis using oligonucleotide microarrays.

A key step in bringing gene expression data into clinical practice is the conduct of large studies to confirm preliminary models. The performance of such confirmatory studies and the transition to clinical practice requires that microarray data from different laboratories are comparable and reproducible. We designed a study to assess the comparability of data from four laboratories that will conduct a larger microarray profiling confirmation project in lung adenocarcinomas. To test the feasibility of combining data across laboratories, frozen tumor tissues, cell line pellets, and purified RNA samples were analyzed at each of the four laboratories. Samples of each type and several subsamples from each tumor and each cell line were blinded before being distributed. The laboratories followed a common protocol for all steps of tissue processing, RNA extraction, and microarray analysis using Affymetrix Human Genome U133A arrays. High within-laboratory and between-laboratory correlations were observed on the purified RNA samples, the cell lines, and the frozen tumor tissues. Intraclass correlation within laboratories was only slightly stronger than between laboratories, and the intraclass correlation tended to be weakest for genes expressed at low levels and showing small variation. Finally, hierarchical cluster analysis revealed that the repeated samples clustered together regardless of the laboratory in which the experiments were done. The findings indicate that under properly controlled conditions it is feasible to perform complete tumor microarray analysis, from tissue processing to hybridization and scanning, at multiple independent laboratories for a single study.

Adenocarcinoma↗
PubMed2005

Menin and MLL cooperatively regulate expression of cyclin-dependent kinase inhibitors.

Mutations in the MEN1 gene are associated with the multiple endocrine neoplasia syndrome type 1 (MEN1), which is characterized by parathyroid hyperplasia and tumors of the pituitary and pancreatic islets. The mechanism by which MEN1 acts as a tumor suppressor is unclear. We have recently shown that menin, the MEN1 protein product, interacts with mixed lineage leukemia (MLL) family proteins in a histone methyltransferase complex including Ash2, Rbbp5, and WDR5. Here, we show that menin directly regulates expression of the cyclin-dependent kinase inhibitors p27Kip1 and p18Ink4c. Menin activates transcription by means of a mechanism involving recruitment of MLL to the p27Kip1 and p18Ink4c promoters and coding regions. Loss of function of either MLL or menin results in down-regulation of p27Kip1 and p18Ink4c expression and deregulated cell growth. These findings suggest that regulation of cyclin-dependent kinase inhibitor transcription by cooperative interaction between menin and MLL plays a central role in menin's activity as a tumor suppressor.

Carrier Proteins↗
PubMed2005

Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis.

Polycythemia vera (PV), essential thrombocythemia (ET), and myeloid metaplasia with myelofibrosis (MMM) are clonal disorders arising from hematopoietic progenitors. An internet-based protocol was used to collect clinical information and biological specimens from patients with these diseases. High-throughput DNA resequencing identified a recurrent somatic missense mutation JAK2V617F in granulocyte DNA samples of 121 of 164 PV patients, of which 41 had homozygous and 80 had heterozygous mutations. Molecular and cytogenetic analyses demonstrated that homozygous mutations were due to duplication of the mutant allele. JAK2V617F was also identified in granulocyte DNA samples from 37 of 115 ET and 16 of 46 MMM patients, but was not observed in 269 normal individuals. In vitro analysis demonstrated that JAK2V617F is a constitutively active tyrosine kinase.

Adult↗
PubMed2005

The parafibromin tumor suppressor protein is part of a human Paf1 complex.

Parafibromin, the product of the HRPT2 (hyperparathyroidism-jaw tumor syndrome 2) tumor suppressor gene, is the human homologue of yeast Cdc73, part of the yeast RNA polymerase II/Paf1 complex known to be important for histone modification and connections to posttranscriptional events. By purifying cellular parafibromin and characterizing its associated proteins, we have identified a human counterpart to the yeast Paf1 complex including homologs of Leo1, Paf1, and Ctr9. Like the yeast complex, the parafibromin complex associates with the nonphosphorylated and Ser2 and Ser5 phosphorylated forms of the RNA polymerase II large subunit. Immunofluorescence experiments show that parafibromin is a nuclear protein. In addition, cotransfection data suggest that parafibromin can interact with a histone methyltransferase complex that methylates histone H3 on lysine 4. Some mutant forms of parafibromin lack association with hPaf1 complex members and with the histone methyltransferase complex, suggesting that disruption of these complexes may correlate with the oncogenic process.

Cell Cycle Proteins↗
PubMed2004

Activating mutations of the noonan syndrome-associated SHP2/PTPN11 gene in human solid tumors and adult acute myelogenous leukemia.

The SH2 domain-containing protein-tyrosine phosphatase PTPN11 (Shp2) is required for normal development and is an essential component of signaling pathways initiated by growth factors, cytokines, and extracellular matrix. In many of these pathways, Shp2 acts upstream of Ras. About 50% of patients with Noonan syndrome have germ-line PTPN11 gain of function mutations. Associations between Noonan syndrome and an increased risk of some malignancies, notably leukemia and neuroblastoma, have been reported, and recent data indicate that somatic PTPN11 mutations occur in children with sporadic juvenile myelomonocytic leukemia, myelodysplasic syndrome, B-cell acute lymphoblastic leukemia, and acute myelogenous leukemia (AML). Juvenile myelomonocytic leukemia patients without PTPN11 mutations have either homozygotic NF-1 deletion or activating RAS mutations. Given the role of Shp2 in Ras activation and the frequent mutation of RAS in human tumors, these data raise the possibility that PTPN11 mutations play a broader role in cancer. We asked whether PTPN11 mutations occur in other malignancies in which activating RAS mutations occur at low but significant frequency. Sequencing of PTPN11 from 13 different human neoplasms including breast, lung, gastric, and neuroblastoma tumors and adult AML and acute lymphoblastic leukemia revealed 11 missense mutations. Five are known mutations predicted to result in an activated form of Shp2, whereas six are new mutations. Biochemical analysis confirmed that several of the new mutations result in increased Shp2 activity. Our data demonstrate that mutations in PTPN11 occur at low frequency in several human cancers, especially neuroblastoma and AML, and suggest that Shp2 may be a novel target for antineoplastic therapy.

Adult↗
PubMed2004

Gefitinib induces apoptosis in the EGFRL858R non-small-cell lung cancer cell line H3255.

Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) have recently been described in patients with non-small-cell lung cancer (NSCLC) who achieve radiographic regressions to the EGFR inhibitor gefitinib. One of these mutations, L858R (Leu-->Arg), is also found in NSCLC cell line H3255, which is very sensitive to gefitinib treatment. We characterized nine NSCLC cell lines (three isolated from patients with bronchioloalveolar carcinoma and six isolated from patients with adenocarcinoma) for their in vitro sensitivity to gefitinib. Of these, only H3255 (EGFR(L858R)) and H1666 (EGFR(WT)) are sensitive to gefitinib with IC(50) values of 40 nmol/L and 2 micromol/L, respectively. We examined the effects of gefitinib on H3255 and cell lines containing wild-type EGFR that are either sensitive (H1666) or resistant (A549 and H441) to gefitinib exposure in vitro. Gefitinib treatment (1 micromol/L) leads to significant apoptosis accompanied by increased poly(ADP-ribose) polymerase cleavage only in the H3255 cell line, leads to G(1)-S arrest in H1666, and has no effects in the A549 and H441 cell lines. Although EGFR and AKT are constitutively phosphorylated in H3255, H1666, and H441 cell lines, AKT is completely inhibited by gefitinib treatment only in the H3255 cell line. These findings further characterize a mechanism by which gefitinib treatment of NSCLC harboring EGFR(L858R) leads to a dramatic response to gefitinib.

Adenocarcinoma↗