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Fluorescence in situ hybridisation in acute myeloid leukaemia
Pathology (2010) 42(S1), pp. S37–S41
Haematology
MYELOPROLIFERATIVE DISEASES: IT’S BEGINNING TO MAKE SENSE Kenneth Kaushansky University of California, San Diego, United States Until very recently the aetiologies of polycythemia vera (PV), myelofibrosis (IMF) and essential thrombocythemia (ET), the chronic myeloproliferative disorders (CMDs), were poorly understood. Recent work has shown that many, if not most patients with these disorders display an acquired, activating mutation of the signalling kinase JAK2, providing important new insights into the molecular aetiologies of these disorders, work which has already begun to revolutionise the diagnosis, prognostication and therapy of these disorders. In the 1970s the clonal origin of the CMDs was established, and a peculiar property, endogenous erythroid colony (EEC) formation was described, which we now know is due to hypersensitivity of progenitor cells to multiple haematopoietic growth factors (HGFs). Simultaneous with these findings, work with purified HGFs and their receptors revealed numerous intracellular signalling pathways activated by erythropoietin, granulocyte colony-stimulating factor and thrombopoietin, cytokines that employ the Janus family of cytoplasmic tyrosine kinases (JAKs) to transduce survival and proliferation signals. A link between cytokine signalling and the CMDs was theorised when it was appreciated that the unregulated expression of many of the signalling molecules activated by JAKs could induce a CMD in mice, and that many of the signalling pathways were chronically activated in marrow cells from patients with CMDs. With the discovery that a mutation of JAK2 can lead to HGF hypersensitivity both in vitro and in vivo, and that depending on the dose of mutant JAK2 expressed in cells, the phenotypes of erythrocytosis or thrombocytosis can be reproduced, new insights have been gained. However, additional mutations have been identified in patients with PV, ET and IMF, and the genetics, cell biology, molecular biology and in vivo models of these complex disorders is now being unravelled. The talk will focus on the molecular origins of the CMDs, and newer approaches to control the neoplastic haematopoiesis that characterises these disorders.
MOLECULAR STRATIFICATION OF PROGNOSIS AND TREATMENT DECISIONS IN ACUTE MYELOID LEUKAEMIA David Ritchie Division of Haematology and Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, and Bone Marrow Transplant Unit, Royal Melbourne Hospital, Parkville, Victoria, Australia The prognosis of acute myeloid leukaemia (AML) is highly dependent on the AML subtype, the presence of cytogenetic
(CG) abnormalities and the age and performance status of the patient. The non-random CG abnormalities t(15:17), t(8:21) and inv16 when present at diagnosis are pathognomonic of AML subtypes, indicate the requirement of particular directed therapies and determine a relatively favourable prognosis. Conversely, CG abnormalities such as 75, 77, t(9:22), translocations of the MLL gene, or complex karyotypes confer a poor prognosis with increased refractoriness to induction chemotherapy or early AML relapse. Prognostically midway between these CG groups lies *50% of AML patients with normal cytogenetic (NCG) AML. NCG AML can be further stratified by detectable mutations that confer either a poor (FLT-3, c-Kit or MLL), or a favourable (NPM-1, CEBPA) prognosis. However, the prognostic interactions between molecular abnormalities and therapeutic decisions are complex, with the favourable impact of NPM-1 and CEPBA only seen in those AML cases without FLT-3 mutations, and c-kit mutations reversing the favourable prognosis of t(8:21) AML, whilst the positive impact of allogeneic transplantation is only seen in patients without a favourable molecular profile. Using these molecular markers a prognostic hierarchy can be constructed to assist in determining AML treatment decisions.
FLUORESCENCE IN SITU HYBRIDISATION IN ACUTE MYELOID LEUKAEMIA Lynda J. Campbell Victorian Cancer Cytogenetics Service, St Vincent’s Hospital Melbourne, Fitzroy, Victoria, Australia The 2008 WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues subdivides acute myeloid leukaemia (AML) into a number of categories based upon the cytogenetic abnormalities observed. Therefore, it is no longer possible to diagnose AML on the basis of morphology alone. Fluorescence in situ hybridisation (FISH) is a valuable adjunct to conventional cytogenetic analysis. It allows the identification of genetic abnormalities in both dividing and non-dividing cells and reveals cryptic insertions and translocations. Thus, genetic rearrangements may be identified despite failure to produce metaphase spreads for analysis from cultured AML cells. Cytogenetic analysis of AML identifies chromosomal abnormalities in 55–60% cases. The critical abnormalities associated with a favourable outcome include t(15;17) in acute promyelocytic leukaemia (APL), t(8;21) in AML with maturation and inversion 16 in acute myelomonocytic leukaemia. RT-PCR also identifies most abnormalities in these disorders but, when there is no clear cytogenetic abnormality, FISH is recommended to detect variant translocations or rearrangements. FISH is also capable of unravelling the complexity of seemingly random chromosome abnormalities and discerning new patterns of genetic gain and loss in AML that may lead, in the future, to the identification of targeted therapies for this increasingly common disorder.
Print ISSN 0031-3025/Online ISSN 1465-3931 # 2010 Royal College of Pathologists of Australasia DOI: 10.3109/00313021003600648
Haematology
MYELOPROLIFERATIVE DISEASES: IT’S BEGINNING TO MAKE SENSE Kenneth Kaushansky University of California, San Diego, United States Until very recently the aetiologies of polycythemia vera (PV), myelofibrosis (IMF) and essential thrombocythemia (ET), the chronic myeloproliferative disorders (CMDs), were poorly understood. Recent work has shown that many, if not most patients with these disorders display an acquired, activating mutation of the signalling kinase JAK2, providing important new insights into the molecular aetiologies of these disorders, work which has already begun to revolutionise the diagnosis, prognostication and therapy of these disorders. In the 1970s the clonal origin of the CMDs was established, and a peculiar property, endogenous erythroid colony (EEC) formation was described, which we now know is due to hypersensitivity of progenitor cells to multiple haematopoietic growth factors (HGFs). Simultaneous with these findings, work with purified HGFs and their receptors revealed numerous intracellular signalling pathways activated by erythropoietin, granulocyte colony-stimulating factor and thrombopoietin, cytokines that employ the Janus family of cytoplasmic tyrosine kinases (JAKs) to transduce survival and proliferation signals. A link between cytokine signalling and the CMDs was theorised when it was appreciated that the unregulated expression of many of the signalling molecules activated by JAKs could induce a CMD in mice, and that many of the signalling pathways were chronically activated in marrow cells from patients with CMDs. With the discovery that a mutation of JAK2 can lead to HGF hypersensitivity both in vitro and in vivo, and that depending on the dose of mutant JAK2 expressed in cells, the phenotypes of erythrocytosis or thrombocytosis can be reproduced, new insights have been gained. However, additional mutations have been identified in patients with PV, ET and IMF, and the genetics, cell biology, molecular biology and in vivo models of these complex disorders is now being unravelled. The talk will focus on the molecular origins of the CMDs, and newer approaches to control the neoplastic haematopoiesis that characterises these disorders.
MOLECULAR STRATIFICATION OF PROGNOSIS AND TREATMENT DECISIONS IN ACUTE MYELOID LEUKAEMIA David Ritchie Division of Haematology and Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, and Bone Marrow Transplant Unit, Royal Melbourne Hospital, Parkville, Victoria, Australia The prognosis of acute myeloid leukaemia (AML) is highly dependent on the AML subtype, the presence of cytogenetic
(CG) abnormalities and the age and performance status of the patient. The non-random CG abnormalities t(15:17), t(8:21) and inv16 when present at diagnosis are pathognomonic of AML subtypes, indicate the requirement of particular directed therapies and determine a relatively favourable prognosis. Conversely, CG abnormalities such as 75, 77, t(9:22), translocations of the MLL gene, or complex karyotypes confer a poor prognosis with increased refractoriness to induction chemotherapy or early AML relapse. Prognostically midway between these CG groups lies *50% of AML patients with normal cytogenetic (NCG) AML. NCG AML can be further stratified by detectable mutations that confer either a poor (FLT-3, c-Kit or MLL), or a favourable (NPM-1, CEBPA) prognosis. However, the prognostic interactions between molecular abnormalities and therapeutic decisions are complex, with the favourable impact of NPM-1 and CEPBA only seen in those AML cases without FLT-3 mutations, and c-kit mutations reversing the favourable prognosis of t(8:21) AML, whilst the positive impact of allogeneic transplantation is only seen in patients without a favourable molecular profile. Using these molecular markers a prognostic hierarchy can be constructed to assist in determining AML treatment decisions.
FLUORESCENCE IN SITU HYBRIDISATION IN ACUTE MYELOID LEUKAEMIA Lynda J. Campbell Victorian Cancer Cytogenetics Service, St Vincent’s Hospital Melbourne, Fitzroy, Victoria, Australia The 2008 WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues subdivides acute myeloid leukaemia (AML) into a number of categories based upon the cytogenetic abnormalities observed. Therefore, it is no longer possible to diagnose AML on the basis of morphology alone. Fluorescence in situ hybridisation (FISH) is a valuable adjunct to conventional cytogenetic analysis. It allows the identification of genetic abnormalities in both dividing and non-dividing cells and reveals cryptic insertions and translocations. Thus, genetic rearrangements may be identified despite failure to produce metaphase spreads for analysis from cultured AML cells. Cytogenetic analysis of AML identifies chromosomal abnormalities in 55–60% cases. The critical abnormalities associated with a favourable outcome include t(15;17) in acute promyelocytic leukaemia (APL), t(8;21) in AML with maturation and inversion 16 in acute myelomonocytic leukaemia. RT-PCR also identifies most abnormalities in these disorders but, when there is no clear cytogenetic abnormality, FISH is recommended to detect variant translocations or rearrangements. FISH is also capable of unravelling the complexity of seemingly random chromosome abnormalities and discerning new patterns of genetic gain and loss in AML that may lead, in the future, to the identification of targeted therapies for this increasingly common disorder.
Print ISSN 0031-3025/Online ISSN 1465-3931 # 2010 Royal College of Pathologists of Australasia DOI: 10.3109/00313021003600648