RESUMO
AIMS: Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal proliferative bone marrow diseases characterised by extensive megakaryocytic hyperplasia and morphological atypia. Despite knowledge of genomic defects, the pathobiological processes driving these megakaryocytic abnormalities in MPN remain poorly explained. We have explored the proliferative, apoptotic and epigenetic profiles of megakaryocytes in human MPN. METHODS: Immunohistochemical staining was performed on bone marrow trephine biopsies of 81 MPN (with and without JAK2(V617F) and CALR mutations) and 15 normal controls to assess the megakaryocytic expression of biomarkers associated with proliferation (Ki67), apoptosis (Bcl-XL, BNIP-3) and epigenetic regulation (EZH2, SUZ12). RESULTS: Myeloproliferative megakaryocytes showed significantly greater expression of proliferative Ki67 and anti-apoptotic Bcl-XL, reduced pro-apoptotic BNIP-3 and increased SUZ12 compared with controls. In essential thrombocythaemia, large-giant megakaryocytes with hyperlobated nuclei showed a trend towards a proliferative signature. In contrast, myelofibrotic megakaryocytes with condensed nuclear chromatin, and cases with CALR mutations, had significant reductions in pro-apoptotic BNIP-3. CONCLUSIONS: Uncontrolled megakaryocytic expansion in MPN results from a combination of increased proliferation, attenuated apoptosis and defective epigenetic regulation with CALR mutations favouring apoptotic failure. The higher platelet counts reported to be seen in MPN with CALR mutations may be due to greater dysregulation of megakaryocyte apoptosis.
Assuntos
Apoptose , Proliferação de Células , Epigênese Genética , Megacariócitos/patologia , Transtornos Mieloproliferativos/patologia , Biomarcadores Tumorais/análise , Biomarcadores Tumorais/genética , Biópsia , Exame de Medula Óssea , Calreticulina/genética , Estudos de Casos e Controles , Análise Mutacional de DNA , Proteína Potenciadora do Homólogo 2 de Zeste , Humanos , Hiperplasia , Imuno-Histoquímica , Janus Quinase 2/genética , Antígeno Ki-67/análise , Megacariócitos/química , Proteínas de Membrana/análise , Mutação , Transtornos Mieloproliferativos/genética , Transtornos Mieloproliferativos/metabolismo , Proteínas de Neoplasias , Complexo Repressor Polycomb 2/análise , Proteínas Proto-Oncogênicas/análise , Análise Serial de Tecidos , Fatores de Transcrição , Proteína bcl-X/análiseAssuntos
Antineoplásicos/uso terapêutico , Recidiva Local de Neoplasia/prevenção & controle , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Piperazinas/uso terapêutico , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Proto-Oncogênicas c-abl/genética , Pirimidinas/uso terapêutico , Adulto , Benzamidas , Humanos , Mesilato de Imatinib , Masculino , Terapia de Salvação , Resultado do TratamentoRESUMO
Serial quantitation of BCR-ABL mRNA levels is an important indicator of therapeutic response for patients with chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia, but there is substantial variation in the real-time quantitative polymerase chain reaction methodologies used by different testing laboratories. To help improve the comparability of results between centers we sought to develop accredited reference reagents that are directly linked to the BCR-ABL international scale. After assessment of candidate cell lines, a reference material panel comprising 4 different dilution levels of freeze-dried preparations of K562 cells diluted in HL60 cells was prepared. After performance evaluation, the materials were assigned fixed percent BCR-ABL/control gene values according to the International Scale. A recommendation that the 4 materials be established as the first World Health Organization International Genetic Reference Panel for quantitation of BCR-ABL translocation by real-time quantitative polymerase chain reaction was approved by the Expert Committee on Biological Standardization of the World Health Organization in November 2009. We consider that the development of these reagents is a significant milestone in the standardization of this clinically important test, but because they are a limited resource we suggest that their availability is restricted to manufacturers of secondary reference materials.
