Nucleophosmin mutations in childhood acute myelogenous leukemia with normal karyotype
http://www.100md.com
《血液学杂志》
the University of Milan-Bicocca, Pediatric Clinic, M. Tettamanti Research Center, San Gerardo Hospital, Monza, Italy
the University of Perugia, Institute of Hematology, Perugia, Italy
the University of Padua, Pediatric Clinic, Onco-Hematology, Padova, Italy
the University of Bologna, Institute of Hematology and Medical Oncology Seragnoli, Bologna, Italy
the Paediatric Haematology and Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Policlinico San Matteo, Pavia, Italy.
Abstract
Nucleophosmin (NPM) is a nucleocytoplasmic shuttling protein involved in leukemia-associated chromosomal translocations, and it regulates the alternate reading frame (ARF)-p53 tumorsuppressor pathway. Recently, it has been demonstrated that mutations of the NPM1 gene alter the protein at its C-terminal, causing its cytoplasmic localization. Cytoplasmic NPM was detected in 35% of adult patients with primary non-French-American-British (FAB) classification M3 acute myeloid leukemia (AML), associated mainly with normal karyotype. We evaluated the prevalence of the NPM1 gene mutation in non-M3 childhood AML patients enrolled in the ongoing Associazione Italiana di ematologia e Oncologia Pediatrica (AIeOP-AML02) protocol in Italy. NPM1 mutations were found in 7 (6.5%) of 107 successfully analyzed patients. NPM1- mutated patients carried a normal karyotype (7/26, 27.1%) and were older in age. Thus, the NPM1 mutation is a frequent abnormality in AML patients without known genetic marker; the mutation may represent a new target to monitor minimal residual disease in AML and a potential candidate for alternative and targeted treatments. (Blood. 2005;106:1419-1422)
Introduction
Childhood acute myelogenous leukemia (AML) is a clinically and molecularly heterogeneous disease.1,2 The identification of recurrent chromosomal abnormalities allows different prognostic subgroups to be defined.1 Unfortunately, this is not yet feasible in a large proportion of cases (20%-25%) in which no chromosomal abnormalities are visible by conventional karyotyping and the underlying genetic lesion is still unknown.
Progress has been recently made in the molecular characterization of adult AML with normal karyotype. Falini et al3 reported that nucleophosmin 1 (NPM1), a nucleus-cytoplasm shuttling protein4-7 involved in rearrangements in leukemias and lymphomas,8-10 showed mutations at its C-terminal region, causing an aberrant cytoplasmic expression in the leukemic cells of about 35% of primary adult AML. NPM1 is a multifunctional protein that prevents protein aggregation in the nucleolus and regulates the assembly and transport of preribosomal particles through the nuclear membrane.4 Since NPM1 is a multifunctional protein involved in the regulation of the ARF-p53 pathway,11-14 it is likely that the mutation and/or ectopic location of the protein may play a leukemogenic role.3,15
This finding prompted us to investigate the prevalence of NPM1 mutations in a large group of childhood AML patients and to correlate this finding with the major biologic and clinical features.
Study design
Patient samples
DNA from one NPM1-mutated patient at diagnosis was also investigated at remission. Informed consent has been obtained at each participating center. This study was approved by the AIeOP-AML Scientific Committee.
Cytogenetic and molecular analyses
Cytogenetic investigations were performed by standard procedures. Reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis for promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha), acute myelogenous leukemia 1-eight twenty-one (AML1-eTO), and core binding factor beta-myosin heavy chain 11 (CBFB-MYH11); analysis of MLL gene status by fluorescence in situ hybridization (FISH); and mutational analysis of the FLT3 gene (internal tandem duplication [ITD] and 835-836 amino acidic residues) were performed as previously described.16-19
Mutational analysis of NPM1
Genomic DNA was extracted from BM mononuclear cells at diagnosis by standard methods. The exon 12 of the NPM1 gene was amplified from genomic DNA, using a forward primer (NPM1-F) in intron 11 and a reverse primer (NPM1-R) in the 3' gene flanking region, as previously described.3 Purified PCR products were directly sequenced using primer NPM1_1112R.3
Results and discussion
Mutations in NPM1 exon 12 in childhood AML
RT-PCR and direct sequencing of the NPM1 coding region revealed mutations affecting exon 12 in 7 (6.5%) of 107 childhood AML cases (Table 2). Six sequence variants were observed among our cases. Four cases corresponded to nucleotide deletions and insertion observed in adult AML (1 type A, 1 type B, and 2 type D)3; in one additional case, the protein sequence was identical to type e of adult series, with a different nucleotide sequence; 2 new variants were observed (here provisionally called mutations G and H). As for the adult cases, all mutations consisted of either the insertion of 4 nucleotides at position 960 (types A to D) or, alternatively, the deletion of 5 nucleotides (positions 965-969) and the insertion at the same position of 9 new nucleotides (types e to H). Independent of the types, all mutations caused a frameshift in the region encoding the C-terminal of the NPM protein, resulting in the replacement of the last 7 amino acids (WQWRKSL) with 11 different residues. As for the adult cases, all NPM mutant proteins showed mutations in at least one of the tryptophan residues at positions 288 and 290, and shared the same last 5 amino acid residues (VSLRK). Thus, despite the heterogeneity at the DNA level, all NPM1 gene mutations resulted in the same sequence at the NPM protein C-terminus.
The mutations were heterozygous and were related only to the leukemic clone, since they were not present in a BM specimen tested at the time of complete remission (not shown).
Features of mutated AML
Mutations of NPM1 were found in different FAB subtypes: M1, 1 of 21 cases; M2, 2 of 19 cases; M4 3 of 13 cases; and M6, 1 of 3 cases (Tables 1-2). This distribution over the FAB subtypes is similar to that observed in adult AML, with the exception of the M5 subtype, which was never found mutated in 18 pediatric cases. As in the adult series, NPM1- mutated patients were CD34- at diagnosis.
There was no significant difference between NPM1-mutated and wild-type (wt) patients at presentation in terms of sex and white blood cell (WBC) count.
RT-PCR data on AML1-eTO and CBFB-MYH11 fusion genes, FISH data for MLL gene status, and standard cytogenetic data were available for 96 (89.7%) of 107 patients. Consistent with the report on adult AML,3 we found that all of the NPM1-mutated patients carried a normal karyotype, although they account for a lower number of childhood AML with normal karyotype (ie, 7 [26.9%] of 26 cases versus 60% in adults).3
Although the median ages of NPM1-mutated and wt patients were not significantly different (10.1 versus 7.6 years, P = .134), there is a clear gradient indicating a tendency to have a higher probability of NPM1 mutations for older AML children. This observation is in agreement with what was observed in adult AML, where the percentage of NPM1 mutations increased from 21.6% in the 15-to-30 age group to 44.1% in the 51-to-60 age group (B.F., personal oral communication, 2005). Moreover, 5 (35.7%) of 14 childhood AML patients older than 10 years and with normal karyotype were NPM1 mutated. This age-dependent distribution was already observed for other genetic abnormalities,20 and together with the association with the absence of visible abnormalities may reflect a specific pathogenesis.
Overall, 13 (13.5%) of 96 cases carried a mutation in the FLT3 gene (11 ITDs and 2 mutations at residue 835). Of interest, one patient carried both FMS-like tyrosine kinase 3(FLT3)-ITD and NPM1 gene mutations, in a normal karyotype.
Although all mutated patients achieved complete remission, the time of observation is too short to derive a significant conclusion about the prognostic value of NPM1 mutation in childhood AML. None of the patients relapsed, 6 underwent bone marrow transplantation (BMT), and 5 of 7 are alive at last follow-up (Table 2). Two patients died of a BMT-related event.
In conclusion, we demonstrated that the NPM1 gene mutations are frequent in childhood AML patients with normal karyotype and older age, although the prevalence is lower with respect to adult AML.3 The children and adults with NPM1 mutations also share morphologic, phenotypical, and clinical features, such as wide morphologic spectrum, lack of CD34 expression, and a good response to induction chemotherapy.3 Our findings confirm in the childhood AML setting the importance of deregulated NPM1 in tumorigenesis and may have diagnostic and clinical relevance.21
The consistent deletion/insertion feature of the NPM1 mutations reconstitutes a patient- and leukemia-specific NPM1 sequence, which, similar to FLT3-ITD,22 can be considered as a clonal marker for patients with normal karyotype, in which no alternative molecular markers are available. Thus, immunohistochemistry and mutational analysis of NPM1 may now enter into the routine diagnostic of AML, in order to identify cases in which minimal residual disease can potentially be monitored during therapy, to drive future interventions.
Acknowledgements
We are grateful to the work of Anna Leszl (cytogenetic analyses), emanuela Frascella (RT-PCR analyses), Francesca Predieri and Monica Spinelli (samples and data collection), and the physicians from all AIeOP centers treating the children with AML included in the study.
Footnotes
Prepublished online as Blood First edition Paper, May 3, 2005; DOI 10.1182/blood-2005-03-0899.
Supported in part by grants from Fondazione Cariplo, Fondazione Tettamanti (Monza), an Associazione Italiana per la Ricerca sul Cancro (AIRC) national grant, and an AIRC Regional grant (emilia Romagna), Ministero Istruzione Università e Ricerca, Fondo per gli Investimenti della Ricerca di Base (FIRB), and Fondazione Città della Speranza (Padova).
G.C. coordinated the work, analyzed data, and wrote the paper; M.G.D. and V.R. performed mutation analysis; A.B., C.M., and B.F. designed the research; e.G., G.B., and R.M. collected patients' samples and data; A.P. is the chair of the Associazione Italiana di ematologia e Oncologia Pediatrica-Acute Myelogenous Leukemia 2002 (AIeOP-AML02) protocol; F.L. is chair of the Bone Marrow Transplantation Study Group of the AIeOP association; and M.F.M. is director of the Institute of Hematology in Perugia.
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
References
Pui CH, Schrappe M, Ribeiro RC, Niemeyer CM. Childhood and adolescent lymphoid and myeloid leukemia. Hematology (Am Soc Hematol educ Program). 2004; 118-145.
Gilliland DG, Jordan CT, Felix CA. The molecular basis of leukemia. Hematology (Am Soc Hematol educ Program). 2004; 80-97.
Falini B, Mecucci C, Tiacci e, et al. Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype. N engl J Med. 2005;352: 254-266.
Cordell JL, Pulford KA, Bigerna B, et al. Detection of normal and chimeric nucleophosmin in human cells. Blood. 1999;93: 632-642.
Falini B, Pulford K, Pucciarini A, et al. Lymphomas expressing ALK fusion protein(s) other than NPM-ALK. Blood. 1999;94: 3509-3515.
Borer RA, Lehner CF, eppenberger HM, Nigg eA. Major nucleolar proteins shuttle between nucleus and cytoplasm. Cell. 1989;56: 379-390.
Falini B, Mason DY. Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry. Blood. 2002;99: 409-426.
Morris SW, Kirstein MN, Valentine MB, et al. Fusion of a kinase gene, ALK, to a nucleolar protein gene, NPM, in non-Hodgkin's lymphoma. Science. 1994;263: 1281-1284.
Redner RL, Rush eA, Faas S, Rudert WA, Corey SJ. The t(5;17) variant of acute promyelocytic leukemia expresses a nucleophosmin-retinoic acid receptor fusion. Blood. 1996;87: 882-886.
Yoneda-Kato N, Look AT, Kirstein MN, et al. The t(3;5)(q25.1;q34) of myelodysplastic syndrome and acute myeloid leukemia produces a novel fusion gene, NPM-MLF1. Oncogene. 1996;12: 265-275.
Bertwistle D, Sugimoto M, Sherr CJ. Physical and functional interactions of the Arf tumor suppressor protein with nucleophosmin/B23. Mol Cell Biol. 2004;24: 985-996.
Brady S, Yu Y, Maggi LB, Weber J. ARF impedes NPM/B23 shuttling in an Mdm2-sensitive tumor suppressor pathway. Mol Cell Biol. 2004;21: 9327-9338.
Korgaonkar C, Hagen J, Tompkins V, et al. Nucleophosmin (B23) targets ARF to nucleoli and inhibits its function. Mol Cell Biol. 2005;25: 1258-1271.
Colombo e, Marine JC, Danovi D, Falini B, Pelicci PG. Nucleophosmin regulates the stability and transcriptional activity of p53. Nat Cell Biol. 2002;4: 529-533.
Grisendi S, Pandolfi PP. NPM mutations in acute myelogenous leukemia. N engl J Med. 2005;352: 291-292.
van Dongen JJ, Macintyre eA, Gabert JA, et al. Standardized RT-PCR analysis of fusion gene transcripts from chromosome aberrations in acute leukemia for detection of minimal residual disease: report of the BIOMeD-1 Concerted Action: investigation of minimal residual disease in acute leukemia. Leukemia. 1999;13: 1901-1928.
Frascella e, Rondelli R, Pigazzi M, et al. Clinical features of childhood acute myeloid leukaemia with specific gene rearrangements. Leukemia. 2004;18: 1427-1429.
van der Burg M, Poulsen TS, Hunger SP, et al. Split-signal FISH for detection of chromosome aberrations in acute lymphoblastic leukemia. Leukemia. 2004;18: 895-908.
Arrigoni P, Beretta C, Silvestri D, et al. FLT3 internal tandem duplication in childhood acute myeloid leukaemia: association with hyperleucocytosis in acute promyelocytic leukaemia. Br J Haematol. 2003;120: 89-92.
Greaves M. Molecular genetics, natural history and the demise of childhood leukaemia. eur J Cancer. 1999;35: 173-185.
Kau TR, Way JC, Silver PA. Nuclear transport and cancer: from mechanism to intervention. Nat Rev Cancer. 2004;4: 106-117.
Beretta C, Gaipa G, Rossi V, et al. Development of a quantitative-PCR method for specific FLT3/ITD monitoring in acute myeloid leukemia. Leukemia. 2004;18: 1441-1444.(Giovanni Cazzaniga, Maria)
the University of Perugia, Institute of Hematology, Perugia, Italy
the University of Padua, Pediatric Clinic, Onco-Hematology, Padova, Italy
the University of Bologna, Institute of Hematology and Medical Oncology Seragnoli, Bologna, Italy
the Paediatric Haematology and Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Policlinico San Matteo, Pavia, Italy.
Abstract
Nucleophosmin (NPM) is a nucleocytoplasmic shuttling protein involved in leukemia-associated chromosomal translocations, and it regulates the alternate reading frame (ARF)-p53 tumorsuppressor pathway. Recently, it has been demonstrated that mutations of the NPM1 gene alter the protein at its C-terminal, causing its cytoplasmic localization. Cytoplasmic NPM was detected in 35% of adult patients with primary non-French-American-British (FAB) classification M3 acute myeloid leukemia (AML), associated mainly with normal karyotype. We evaluated the prevalence of the NPM1 gene mutation in non-M3 childhood AML patients enrolled in the ongoing Associazione Italiana di ematologia e Oncologia Pediatrica (AIeOP-AML02) protocol in Italy. NPM1 mutations were found in 7 (6.5%) of 107 successfully analyzed patients. NPM1- mutated patients carried a normal karyotype (7/26, 27.1%) and were older in age. Thus, the NPM1 mutation is a frequent abnormality in AML patients without known genetic marker; the mutation may represent a new target to monitor minimal residual disease in AML and a potential candidate for alternative and targeted treatments. (Blood. 2005;106:1419-1422)
Introduction
Childhood acute myelogenous leukemia (AML) is a clinically and molecularly heterogeneous disease.1,2 The identification of recurrent chromosomal abnormalities allows different prognostic subgroups to be defined.1 Unfortunately, this is not yet feasible in a large proportion of cases (20%-25%) in which no chromosomal abnormalities are visible by conventional karyotyping and the underlying genetic lesion is still unknown.
Progress has been recently made in the molecular characterization of adult AML with normal karyotype. Falini et al3 reported that nucleophosmin 1 (NPM1), a nucleus-cytoplasm shuttling protein4-7 involved in rearrangements in leukemias and lymphomas,8-10 showed mutations at its C-terminal region, causing an aberrant cytoplasmic expression in the leukemic cells of about 35% of primary adult AML. NPM1 is a multifunctional protein that prevents protein aggregation in the nucleolus and regulates the assembly and transport of preribosomal particles through the nuclear membrane.4 Since NPM1 is a multifunctional protein involved in the regulation of the ARF-p53 pathway,11-14 it is likely that the mutation and/or ectopic location of the protein may play a leukemogenic role.3,15
This finding prompted us to investigate the prevalence of NPM1 mutations in a large group of childhood AML patients and to correlate this finding with the major biologic and clinical features.
Study design
Patient samples
DNA from one NPM1-mutated patient at diagnosis was also investigated at remission. Informed consent has been obtained at each participating center. This study was approved by the AIeOP-AML Scientific Committee.
Cytogenetic and molecular analyses
Cytogenetic investigations were performed by standard procedures. Reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis for promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha), acute myelogenous leukemia 1-eight twenty-one (AML1-eTO), and core binding factor beta-myosin heavy chain 11 (CBFB-MYH11); analysis of MLL gene status by fluorescence in situ hybridization (FISH); and mutational analysis of the FLT3 gene (internal tandem duplication [ITD] and 835-836 amino acidic residues) were performed as previously described.16-19
Mutational analysis of NPM1
Genomic DNA was extracted from BM mononuclear cells at diagnosis by standard methods. The exon 12 of the NPM1 gene was amplified from genomic DNA, using a forward primer (NPM1-F) in intron 11 and a reverse primer (NPM1-R) in the 3' gene flanking region, as previously described.3 Purified PCR products were directly sequenced using primer NPM1_1112R.3
Results and discussion
Mutations in NPM1 exon 12 in childhood AML
RT-PCR and direct sequencing of the NPM1 coding region revealed mutations affecting exon 12 in 7 (6.5%) of 107 childhood AML cases (Table 2). Six sequence variants were observed among our cases. Four cases corresponded to nucleotide deletions and insertion observed in adult AML (1 type A, 1 type B, and 2 type D)3; in one additional case, the protein sequence was identical to type e of adult series, with a different nucleotide sequence; 2 new variants were observed (here provisionally called mutations G and H). As for the adult cases, all mutations consisted of either the insertion of 4 nucleotides at position 960 (types A to D) or, alternatively, the deletion of 5 nucleotides (positions 965-969) and the insertion at the same position of 9 new nucleotides (types e to H). Independent of the types, all mutations caused a frameshift in the region encoding the C-terminal of the NPM protein, resulting in the replacement of the last 7 amino acids (WQWRKSL) with 11 different residues. As for the adult cases, all NPM mutant proteins showed mutations in at least one of the tryptophan residues at positions 288 and 290, and shared the same last 5 amino acid residues (VSLRK). Thus, despite the heterogeneity at the DNA level, all NPM1 gene mutations resulted in the same sequence at the NPM protein C-terminus.
The mutations were heterozygous and were related only to the leukemic clone, since they were not present in a BM specimen tested at the time of complete remission (not shown).
Features of mutated AML
Mutations of NPM1 were found in different FAB subtypes: M1, 1 of 21 cases; M2, 2 of 19 cases; M4 3 of 13 cases; and M6, 1 of 3 cases (Tables 1-2). This distribution over the FAB subtypes is similar to that observed in adult AML, with the exception of the M5 subtype, which was never found mutated in 18 pediatric cases. As in the adult series, NPM1- mutated patients were CD34- at diagnosis.
There was no significant difference between NPM1-mutated and wild-type (wt) patients at presentation in terms of sex and white blood cell (WBC) count.
RT-PCR data on AML1-eTO and CBFB-MYH11 fusion genes, FISH data for MLL gene status, and standard cytogenetic data were available for 96 (89.7%) of 107 patients. Consistent with the report on adult AML,3 we found that all of the NPM1-mutated patients carried a normal karyotype, although they account for a lower number of childhood AML with normal karyotype (ie, 7 [26.9%] of 26 cases versus 60% in adults).3
Although the median ages of NPM1-mutated and wt patients were not significantly different (10.1 versus 7.6 years, P = .134), there is a clear gradient indicating a tendency to have a higher probability of NPM1 mutations for older AML children. This observation is in agreement with what was observed in adult AML, where the percentage of NPM1 mutations increased from 21.6% in the 15-to-30 age group to 44.1% in the 51-to-60 age group (B.F., personal oral communication, 2005). Moreover, 5 (35.7%) of 14 childhood AML patients older than 10 years and with normal karyotype were NPM1 mutated. This age-dependent distribution was already observed for other genetic abnormalities,20 and together with the association with the absence of visible abnormalities may reflect a specific pathogenesis.
Overall, 13 (13.5%) of 96 cases carried a mutation in the FLT3 gene (11 ITDs and 2 mutations at residue 835). Of interest, one patient carried both FMS-like tyrosine kinase 3(FLT3)-ITD and NPM1 gene mutations, in a normal karyotype.
Although all mutated patients achieved complete remission, the time of observation is too short to derive a significant conclusion about the prognostic value of NPM1 mutation in childhood AML. None of the patients relapsed, 6 underwent bone marrow transplantation (BMT), and 5 of 7 are alive at last follow-up (Table 2). Two patients died of a BMT-related event.
In conclusion, we demonstrated that the NPM1 gene mutations are frequent in childhood AML patients with normal karyotype and older age, although the prevalence is lower with respect to adult AML.3 The children and adults with NPM1 mutations also share morphologic, phenotypical, and clinical features, such as wide morphologic spectrum, lack of CD34 expression, and a good response to induction chemotherapy.3 Our findings confirm in the childhood AML setting the importance of deregulated NPM1 in tumorigenesis and may have diagnostic and clinical relevance.21
The consistent deletion/insertion feature of the NPM1 mutations reconstitutes a patient- and leukemia-specific NPM1 sequence, which, similar to FLT3-ITD,22 can be considered as a clonal marker for patients with normal karyotype, in which no alternative molecular markers are available. Thus, immunohistochemistry and mutational analysis of NPM1 may now enter into the routine diagnostic of AML, in order to identify cases in which minimal residual disease can potentially be monitored during therapy, to drive future interventions.
Acknowledgements
We are grateful to the work of Anna Leszl (cytogenetic analyses), emanuela Frascella (RT-PCR analyses), Francesca Predieri and Monica Spinelli (samples and data collection), and the physicians from all AIeOP centers treating the children with AML included in the study.
Footnotes
Prepublished online as Blood First edition Paper, May 3, 2005; DOI 10.1182/blood-2005-03-0899.
Supported in part by grants from Fondazione Cariplo, Fondazione Tettamanti (Monza), an Associazione Italiana per la Ricerca sul Cancro (AIRC) national grant, and an AIRC Regional grant (emilia Romagna), Ministero Istruzione Università e Ricerca, Fondo per gli Investimenti della Ricerca di Base (FIRB), and Fondazione Città della Speranza (Padova).
G.C. coordinated the work, analyzed data, and wrote the paper; M.G.D. and V.R. performed mutation analysis; A.B., C.M., and B.F. designed the research; e.G., G.B., and R.M. collected patients' samples and data; A.P. is the chair of the Associazione Italiana di ematologia e Oncologia Pediatrica-Acute Myelogenous Leukemia 2002 (AIeOP-AML02) protocol; F.L. is chair of the Bone Marrow Transplantation Study Group of the AIeOP association; and M.F.M. is director of the Institute of Hematology in Perugia.
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
References
Pui CH, Schrappe M, Ribeiro RC, Niemeyer CM. Childhood and adolescent lymphoid and myeloid leukemia. Hematology (Am Soc Hematol educ Program). 2004; 118-145.
Gilliland DG, Jordan CT, Felix CA. The molecular basis of leukemia. Hematology (Am Soc Hematol educ Program). 2004; 80-97.
Falini B, Mecucci C, Tiacci e, et al. Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype. N engl J Med. 2005;352: 254-266.
Cordell JL, Pulford KA, Bigerna B, et al. Detection of normal and chimeric nucleophosmin in human cells. Blood. 1999;93: 632-642.
Falini B, Pulford K, Pucciarini A, et al. Lymphomas expressing ALK fusion protein(s) other than NPM-ALK. Blood. 1999;94: 3509-3515.
Borer RA, Lehner CF, eppenberger HM, Nigg eA. Major nucleolar proteins shuttle between nucleus and cytoplasm. Cell. 1989;56: 379-390.
Falini B, Mason DY. Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry. Blood. 2002;99: 409-426.
Morris SW, Kirstein MN, Valentine MB, et al. Fusion of a kinase gene, ALK, to a nucleolar protein gene, NPM, in non-Hodgkin's lymphoma. Science. 1994;263: 1281-1284.
Redner RL, Rush eA, Faas S, Rudert WA, Corey SJ. The t(5;17) variant of acute promyelocytic leukemia expresses a nucleophosmin-retinoic acid receptor fusion. Blood. 1996;87: 882-886.
Yoneda-Kato N, Look AT, Kirstein MN, et al. The t(3;5)(q25.1;q34) of myelodysplastic syndrome and acute myeloid leukemia produces a novel fusion gene, NPM-MLF1. Oncogene. 1996;12: 265-275.
Bertwistle D, Sugimoto M, Sherr CJ. Physical and functional interactions of the Arf tumor suppressor protein with nucleophosmin/B23. Mol Cell Biol. 2004;24: 985-996.
Brady S, Yu Y, Maggi LB, Weber J. ARF impedes NPM/B23 shuttling in an Mdm2-sensitive tumor suppressor pathway. Mol Cell Biol. 2004;21: 9327-9338.
Korgaonkar C, Hagen J, Tompkins V, et al. Nucleophosmin (B23) targets ARF to nucleoli and inhibits its function. Mol Cell Biol. 2005;25: 1258-1271.
Colombo e, Marine JC, Danovi D, Falini B, Pelicci PG. Nucleophosmin regulates the stability and transcriptional activity of p53. Nat Cell Biol. 2002;4: 529-533.
Grisendi S, Pandolfi PP. NPM mutations in acute myelogenous leukemia. N engl J Med. 2005;352: 291-292.
van Dongen JJ, Macintyre eA, Gabert JA, et al. Standardized RT-PCR analysis of fusion gene transcripts from chromosome aberrations in acute leukemia for detection of minimal residual disease: report of the BIOMeD-1 Concerted Action: investigation of minimal residual disease in acute leukemia. Leukemia. 1999;13: 1901-1928.
Frascella e, Rondelli R, Pigazzi M, et al. Clinical features of childhood acute myeloid leukaemia with specific gene rearrangements. Leukemia. 2004;18: 1427-1429.
van der Burg M, Poulsen TS, Hunger SP, et al. Split-signal FISH for detection of chromosome aberrations in acute lymphoblastic leukemia. Leukemia. 2004;18: 895-908.
Arrigoni P, Beretta C, Silvestri D, et al. FLT3 internal tandem duplication in childhood acute myeloid leukaemia: association with hyperleucocytosis in acute promyelocytic leukaemia. Br J Haematol. 2003;120: 89-92.
Greaves M. Molecular genetics, natural history and the demise of childhood leukaemia. eur J Cancer. 1999;35: 173-185.
Kau TR, Way JC, Silver PA. Nuclear transport and cancer: from mechanism to intervention. Nat Rev Cancer. 2004;4: 106-117.
Beretta C, Gaipa G, Rossi V, et al. Development of a quantitative-PCR method for specific FLT3/ITD monitoring in acute myeloid leukemia. Leukemia. 2004;18: 1441-1444.(Giovanni Cazzaniga, Maria)