Gascoyne, R.D (R. D.)
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- Deregulation of the telomerase reverse transcriptase (TERT) gene by chromosomal translocations in B-cell malignancies(American Society of Hematology, 2010) Gascoyne, R.D (R. D.); Tönnies, H. (Holger); Ammerpohl, O. (Ole); Dyer, M.J.S. (Martin J. S.); Martinez-Climent, J.A. (José Ángel); Nagel, I. (Inga); Akasaka, T. (T.); Horsman, D. (D.); Gesk, S. (Stefan); Harder, L. (Lana); Klapper, W. (Wolfram); Callet-Bauchu, E. (E.); Siebert, R. (Reiner); Szczepanowski, M. (Monika); Stilgenbauer, S. (Stepahn); Majid, A. (Aneela); Martin-Subero, J.I. (Jose Ignacio)Sequence variants at the TERT-CLPTM1L locus in chromosome 5p have been recently associated with disposition for various cancers. Here we show that this locus including the gene encoding the telomerase reverse-transcriptase TERT at 5p13.33 is rarely but recurrently targeted by somatic chromosomal translocations to IGH and non-IG loci in B-cell neoplasms, including acute lymphoblastic leukemia, chronic lymphocytic leukemia, mantle cell lymphoma and splenic marginal zone lymphoma. In addition, cases with genomic amplification of TERT locus were identified. Tumors bearing chromosomal aberrations involving TERT showed higher TERT transcriptional expression and increased telomerase activity. These data suggest that deregulation of TERT gene by chromosomal abnormalities leading to increased telomerase activity might contribute to B-cell lymphomagenesis.
- Lymphoma stem cells: enough evidence to support their existence?(Pensiero Scientifico / Ferrata Storti Foundation, 2010) Gascoyne, R.D (R. D.); Martinez-Climent, J.A. (José Ángel); Siebert, R. (Reiner); Fontan, L. (Lorena); Prosper-Cardoso, F. (Felipe)While leukemia-originating stem cells are critical in the initiation and maintenance of leukemias, the existence of similar cell populations that may generate B-cell lymphoma upon mutation remains uncertain. Here we propose that committed lymphoid progenitor/precursor cells with an active V-D-J recombination program are the initiating cells of follicular lymphoma and mantle cell lymphoma when targeted by immunoglobulin (IG)- gene translocations in the bone marrow. However, these pre-malignant lymphoma-initiating cells cannot drive complete malignant transformation, requiring additional cooperating mutations in specific stem-cell programs to be converted into the lymphoma-originating cells able to generate and sustain lymphoma development. Conversely, diffuse large B-cell lymphoma and sporadic Burkitt’s lymphoma derive from B lymphocytes that acquire translocations through IG-hyper-mutation or class-switching errors within the germinal center. Although secondary reprogramming mutations are generally required, some cells such as centroblasts or memory B cells that have certain stem cell-like features, or lymphocytes with MYC rearrangements that deregulate self-renewal pathways, may bypass this need and directly function as the lymphoma-originating cells. An alternative model supports an aberrant epigenetic modification of gene sets as the first occurring hit, which either leads to retaining stem-cell features in hematopoietic stem or progenitor cells, or reprograms stemness into more committed lymphocytes, followed by secondary chromosomal translocations that eventually drive lymphoma development. Isolation and characterization of the cells that are at the origin of the different B-cell non-Hodgkin’s lymphomas will provide critical insights into the disease pathogenesis and will represent a step towards the development of more effective therapies.
- Amplification of IGH/MYC fusion in clinically aggressive IGH/BCL2-positive germinal center B-cell lymphomas(Wiley-Blackwell, 2005) Gascoyne, R.D (R. D.); Cigudosa, J.C. (Juan Cruz); Sanz-Garcia, E. (Eduardo); Siebert, R. (Reiner); Novo-Villaverde, F. J. (Francisco Javier); Hernandez, R. (Roberto); Ardanaz, M.T. (M.T.); Calasanz-Abinzano, M.J. (Maria Jose); Odero, M.D. (Maria Dolores); Aguirre-Ena, X. (Xabier); Martin-Subero, J.I. (Jose Ignacio); Saez, B. (Borja)Activation of an oncogene via its juxtaposition to the IGH locus by a chromosomal translocation or, less frequently, by genomic amplification is considered a major mechanism of B-cell lymphomagenesis. However, amplification of an IGH/oncogene fusion, coined a complicon, is a rare event in human cancers and has been associated with poor outcome and resistance to treatment. In this article are descriptions of two cases of germinal-center-derived B-cell lymphomas with IGH/BCL2 fusion that additionally displayed amplification of an IGH/MYC fusion. As shown by fluorescence in situ hybridization, the first case contained a IGH/MYC complicon in double minutes, whereas the second case showed a BCL2/IGH/MYC complicon on a der(8)t(8;14)t(14;18). Additional molecular cytogenetic and mutation analyses revealed that the first case also contained a chromosomal translocation affecting the BCL6 oncogene and a biallelic inactivation of TP53. The second case harbored a duplication of REL and acquired a translocation affecting IGL and a biallelic inactivation of TP53 during progression. Complicons affecting Igh/Myc have been reported previously in lymphomas of mouse models simultaneously deficient in Tp53 and in genes of the nonhomologous end-joining DNA repair pathway. To the best of our knowledge, this is the first time that IGH/MYC complicons have been reported in human lymphomas. Our findings imply that the two mechanisms resulting in MYC deregulation, that is, translocation and amplification, can occur simultaneously.