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Molecular and functional studies of the BCR/ABL1 fusion gene

Johnels, Petra LU (2006)
Abstract
The BCR/ABL1 fusion gene is associated with chronic myeloid leukemia and a subgroup of acute lymphoblastic leukemia. The general aim of this thesis was to increase the understanding of BCR/ABL1-induced leukemogenesis by molecular and functional studies of this fusion gene. In Article I, an experimental U937 cell line model with inducible expression of BCR/ABL1 was established and characterized. Expression of BCR/ABL1 activated the JAK/STAT pathway, but showed no marked effects on proliferation, differentiation, and apoptosis. In addition, a reversible upregulation of the cell-surface marker CEACAM1, implicated in cell adhesion and signal transduction, was identified upon expression of BCR/ABL1. In Article II, the BCR/ABL1-inducible U937... (More)
The BCR/ABL1 fusion gene is associated with chronic myeloid leukemia and a subgroup of acute lymphoblastic leukemia. The general aim of this thesis was to increase the understanding of BCR/ABL1-induced leukemogenesis by molecular and functional studies of this fusion gene. In Article I, an experimental U937 cell line model with inducible expression of BCR/ABL1 was established and characterized. Expression of BCR/ABL1 activated the JAK/STAT pathway, but showed no marked effects on proliferation, differentiation, and apoptosis. In addition, a reversible upregulation of the cell-surface marker CEACAM1, implicated in cell adhesion and signal transduction, was identified upon expression of BCR/ABL1. In Article II, the BCR/ABL1-inducible U937 cells were used to investigate the transcriptional effects of BCR/ABL1. Approximately 60 genes were induced by BCR/ABL1, including genes encoding transcription factors, kinases, and signal transduction molecules. About one third of the genes were IFN-responsive, which may indicate an overlap with IFN-induced signal transduction or activation of cellular defense and/or negative feedback mechanisms. In Article III, the tyrosine kinase activity of BCR/ABL1 was blocked with imatinib in five Ph-positive cell lines. Approximately 140 genes, mainly involved in signal transduction and metabolic pathways, were identified as affected by BCR/ABL1. Several genes implicated in negative feedback-regulation of well-known signaling pathways were positively regulated by BCR/ABL1, which may act to suppress tumor-promoting effects elicited by the fusion gene. In Article IV, the P190 or the P210 BCR/ABL1 fusion variant was retrovirally expressed in primitive human cord blood cells. In these cells, expression of both P190 and P210 BCR/ABL1 resulted in increased proliferation and differentiation towards the erythroid lineage. Approximately 220 genes were identified as targets of P190/P210 BCR/ABL1-mediated signaling. The similar biological and transcriptional effects induced by these two variants indirectly support the hypothesis of a separate cellular origin for these fusion genes to explain their association with different leukemias. A recurrent finding between the three experimental models was a deregulated expression of different SOCS family members, which regulate signaling mediated particularly via the JAK/STAT pathway. Apart from providing important pathogenetic insights into BCR/ABL1-induced leukemogenesis, the present study identified a number of pathways/individual genes that may provide attractive targets for the development of novel therapies against Ph-positive leukemias. (Less)
Abstract (Swedish)
Popular Abstract in Swedish

Molekylärgenetiska och funktionella studier av BCR/ABL1 fusionsgenen:



Det finns tre sorters blodkroppar, röda, vita och trombocyter, som alla bildas från gemensamma stamceller i benmärgen. När stamcellerna delar sig bildas det antingen nya stamceller eller förstadier till blodkroppar som efter ytterligare delningar blir till mogna blodkroppar. Ibland uppkommer särskilda genetiska förändringar i något av dessa förstadier eller stamceller, vilket omvandlar normala celler till cancerceller. Vid leukemi trängs den normala blodbildningen undan av en kraftig expansion av dessa leukemiceller vilket orsakar brist på normala mogna blodkroppar samtidigt som en ökad mängd omogna vita... (More)
Popular Abstract in Swedish

Molekylärgenetiska och funktionella studier av BCR/ABL1 fusionsgenen:



Det finns tre sorters blodkroppar, röda, vita och trombocyter, som alla bildas från gemensamma stamceller i benmärgen. När stamcellerna delar sig bildas det antingen nya stamceller eller förstadier till blodkroppar som efter ytterligare delningar blir till mogna blodkroppar. Ibland uppkommer särskilda genetiska förändringar i något av dessa förstadier eller stamceller, vilket omvandlar normala celler till cancerceller. Vid leukemi trängs den normala blodbildningen undan av en kraftig expansion av dessa leukemiceller vilket orsakar brist på normala mogna blodkroppar samtidigt som en ökad mängd omogna vita blodkroppar släpps ut i blodet.



I Sverige insjuknar ungefär 1000 personer årligen i en akut eller kronisk leukemi, varav ca 100 fall utgörs av kronisk myeloisk leukemi (KML) (http://cancerfonden.se). Medan de akuta leukemierna ses hos både barn och vuxna förekommer kronisk leukemi främst bland vuxna. KML karaktäriseras av olika faser där den första kroniska fasen är ganska lätt att kontrollera, medan den slutliga blastfasen istället liknar en akut leukemi. I majoriteten av alla fall av KML uppkommer ytterligare genetiska avvikelser under sjukdomsutvecklingen, vilket man tror kan ha betydelse för leukemins framskridande.



De allra flesta fall av KML, samt 15-20% av akut lymfatisk leukemi (ALL), kännetecknas av en specifik kromosomavvikelse, Philadelphia (Ph) kromosomen. Denna specifika avvikelse uppkommer genom en translokation (utbyte av genetiskt material) mellan kromosomerna 9 och 22. Resultatet blir att tyrosinkinasgenen ABL1 på kromosom 9 sätts ihop med BCR genen på kromosom 22, vilket leder till att antingen ett P190 eller P210 BCR/ABL1 fusionsprotein med förhöjd tyrosinkinasaktivitet bildas. Medan P190 BCR/ABL1 varianten främst är förknippad med ALL, ses P210 i både KML och i 30-50% av patienterna med Ph-positiv ALL. Under senare år har det utvecklats lovande läkemedel som syftar till att hämma aktiviteten av BCR/ABL1 proteinet i cellen. Tyvärr utgör dessa mediciner ingen bot mot sjukdomen och många patienter utvecklar så småningom resistens mot dem vilket gör att leukemin återkommer.



För att förstå och så småningom bota denna sjukdom är det viktigt att känna till hur BCR/ABL1 proteinet signalerar och påverkar omvandlingen till leukemiceller. Senare års forskning har inriktat sig på att försöka förstå hur BCR/ABL1 ger upphov till leukemi och varför P190 och P210 BCR/ABL1 företrädesvis är associerade med olika typer av leukemier. Studier har visat att både P190 och P210 uppvisar transformerande egenskaper i olika experimentella system och ett flertal proteiner och signalvägar, viktiga för bl.a. reglering av celltillväxt och programmerad celldöd, har visats interagera med eller aktiveras av BCR/ABL1. Detta gör det sannolikt att BCR/ABL1 uttrycket leder till aktivering eller nedreglering av ett flertal målgener. Mycket lite är emellertid känt om vilka dessa gener är.



Systematiska studier av de genetiska program och signalvägar som påverkas av BCR/ABL1 har saknats. I denna avhandling har olika experimentella system utvecklats för att studera hur signalering via P190 och P210 BCR/ABL1 proteinerna påverkar cellerna. Genom att använda olika cellbiologiska och molekylärgenetiska metoder har de fenotypiska och transkriptionella effekterna av BCR/ABL1 aktivering undersökts. De erhållna resultaten utgör ett bidrag till vår kunskap om de cellulära effekter och förändringar på gennivå som styrs av BCR/ABL1 fusionen, vilket på sikt skulle kunna få betydelse för utvecklingen av nya behandlingsstrategier. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Melo, Junia, Dept of Haematology,Imperial College London, Hammersmith Hospital, UK
organization
publishing date
type
Thesis
publication status
published
subject
keywords
extracellular fluids, Hematologi, Haematology, onkologi, Cytologi, cancerology, oncology, Cytology, gene expression profiling, acute lymphoblastic leukemia, chronic myeloid leukemia, Ph chromosome, BCR/ABL, extracellulära vätskor, Clinical genetics, Klinisk genetik, cancer
publisher
Department of Clinical Genetics, Lund University
defense location
Föreläsningssal F3, centralblocket, Universitetssjukhuset i Lund
defense date
2006-10-13 10:00:00
ISBN
91-85559-19-9
language
English
LU publication?
yes
additional info
id
3acc36bb-08d1-4a0e-b54e-c1ad217363cc (old id 547252)
date added to LUP
2016-04-01 17:08:25
date last changed
2018-11-21 20:46:57
@phdthesis{3acc36bb-08d1-4a0e-b54e-c1ad217363cc,
  abstract     = {The BCR/ABL1 fusion gene is associated with chronic myeloid leukemia and a subgroup of acute lymphoblastic leukemia. The general aim of this thesis was to increase the understanding of BCR/ABL1-induced leukemogenesis by molecular and functional studies of this fusion gene. In Article I, an experimental U937 cell line model with inducible expression of BCR/ABL1 was established and characterized. Expression of BCR/ABL1 activated the JAK/STAT pathway, but showed no marked effects on proliferation, differentiation, and apoptosis. In addition, a reversible upregulation of the cell-surface marker CEACAM1, implicated in cell adhesion and signal transduction, was identified upon expression of BCR/ABL1. In Article II, the BCR/ABL1-inducible U937 cells were used to investigate the transcriptional effects of BCR/ABL1. Approximately 60 genes were induced by BCR/ABL1, including genes encoding transcription factors, kinases, and signal transduction molecules. About one third of the genes were IFN-responsive, which may indicate an overlap with IFN-induced signal transduction or activation of cellular defense and/or negative feedback mechanisms. In Article III, the tyrosine kinase activity of BCR/ABL1 was blocked with imatinib in five Ph-positive cell lines. Approximately 140 genes, mainly involved in signal transduction and metabolic pathways, were identified as affected by BCR/ABL1. Several genes implicated in negative feedback-regulation of well-known signaling pathways were positively regulated by BCR/ABL1, which may act to suppress tumor-promoting effects elicited by the fusion gene. In Article IV, the P190 or the P210 BCR/ABL1 fusion variant was retrovirally expressed in primitive human cord blood cells. In these cells, expression of both P190 and P210 BCR/ABL1 resulted in increased proliferation and differentiation towards the erythroid lineage. Approximately 220 genes were identified as targets of P190/P210 BCR/ABL1-mediated signaling. The similar biological and transcriptional effects induced by these two variants indirectly support the hypothesis of a separate cellular origin for these fusion genes to explain their association with different leukemias. A recurrent finding between the three experimental models was a deregulated expression of different SOCS family members, which regulate signaling mediated particularly via the JAK/STAT pathway. Apart from providing important pathogenetic insights into BCR/ABL1-induced leukemogenesis, the present study identified a number of pathways/individual genes that may provide attractive targets for the development of novel therapies against Ph-positive leukemias.},
  author       = {Johnels, Petra},
  isbn         = {91-85559-19-9},
  language     = {eng},
  publisher    = {Department of Clinical Genetics, Lund University},
  school       = {Lund University},
  title        = {Molecular and functional studies of the BCR/ABL1 fusion gene},
  url          = {https://lup.lub.lu.se/search/files/4886618/547253.pdf},
  year         = {2006},
}