Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The PTPN11 gene encodes SHP-2, a nonreceptor protein tyrosine phosphatase that relays signals from activated growth factor receptors to p21(ras) (Ras) and other signaling molecules. Somatic PTPN11 mutations are common in patients with juvenile myelomonocytic leukemia (JMML) and have been reported in some other hematologic malignancies. We analyzed specimens from 278 pediatric patients with acute myelogenous leukemia (AML) who were enrolled on Children's Cancer Group trials 2941 and 2961 for PTPN11 mutations. Missense mutations of PTPN11 were detected in 11 (4%) of these samples. None of these patients had mutations in NRAS; however, one patient had evidence of a FLT3 alteration. Four of the patients with PTPN11 mutations (36%) were boys with French-American-British (FAB) morphology M5 AML (P=0.012). Patients with mutations also presented with elevated white blood cell counts. There was no difference in clinical outcome for patients with and without PTPN11 mutations. These characteristics identify a subset of pediatric AML with PTPN11 mutations that share clinical and biologic features with JMML.
Leukemia 2004 Nov
PMID:PTPN11 mutations in pediatric patients with acute myeloid leukemia: results from the Children's Cancer Group. 1538 33

Constitutively activating internal tandem duplication (ITD) mutations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) play an important role in leukemogenesis, and their presence is associated with poor prognosis in acute myeloid leukemia (AML). To better understand FLT3 signaling in leukemogenesis, we have examined the changes in gene expression induced by FLT3/ITD or constitutively activated wild-type FLT3 expression. Microarrays were used with RNA harvested before and after inhibition of FLT3 signaling. Pim-1 was found to be one of the most significantly down-regulated genes upon FLT3 inhibition. Pim-1 is a proto-oncogene and is known to be up-regulated by signal transducer and activator of transcription 5 (STAT5), which itself is a downstream target of FLT3 signaling. Quantitative polymerase chain reaction (QPCR) confirmed the microarray results and demonstrated approximately 10-fold decreases in Pim-1 expression in response to FLT3 inhibition. Pim-1 protein also decreased rapidly in parallel with decreasing autophosphorylation activity of FLT3. Enforced expression of either the 44-kDa or 33-kDa Pim-1 isotypes resulted in increased resistance to FLT3 inhibition-mediated cytotoxicity and apoptosis. In contrast, expression of a dominant-negative Pim-1 construct accelerated cytotoxicity in response to FLT3 inhibition and inhibited colony growth of FLT3/ITD-transformed BaF3 cells. These findings demonstrate that constitutively activated FLT3 signaling up-regulates Pim-1 expression in leukemia cells. This up-regulation contributes to the proliferative and antiapoptotic pathways induced by FLT3 signaling.
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PMID:Pim-1 is up-regulated by constitutively activated FLT3 and plays a role in FLT3-mediated cell survival. 1549 59

Conventional cytogenetic analysis currently stratifies acute myelogenous leukaemia (AML) into prognostically relevant groups. However, approximately 50% of adult AMLs have normal cytogenetics (NC-AMLs), and represent a heterogeneous and poorly understood group. We analysed gene expression in 55 AML samples including 53 cases from adult patients with NC-AML (n = 36), trisomy 8, t(15;17), t(8;21), t(11;19), 7q deletion, and two cell lines using 9000-gene DNA microarrays. Global hierarchical clustering showed that NC-AMLs are a heterogeneous group. Supervised analysis distinguished two subgroups of NC-AML: one subgroup constituted a homogeneous NC cluster ('pure NC-AML'), and the other NC-AMLs were close to the AML cases with translocations ('translocation like'). Gene expression signatures were also derived for patients with trisomy 8, as well as FLT3 and MLL gene duplications. Importantly, samples from 24 NC-AML patients who could be evaluated for clinical outcome were analysed. In all, 43 genes that discriminated two classes of patients with significantly different prognosis were identified. The poor prognosis class contained a majority of 'pure NC-AMLs', whereas the 'translocation-like' AMLs were in the good prognosis class. Discriminator genes included genes involved in drug resistance (TOP2B), protein transport (MTX2, SLC35A2), and cell signalling (MAPK1, PRKAB2). Our results demonstrate the transcriptional heterogeneity of NC-AMLs, and suggest the existence of 'translocation-like' NC-AMLs and of a gene expression signature that may predict response to chemotherapy.
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PMID:Identification of new classes among acute myelogenous leukaemias with normal karyotype using gene expression profiling. 1554 37

Major strides have been made in our understanding of the molecular basis of adult and pediatric leukemias. More than one hundred disease alleles have been identified and characterized in cell culture and murine models of leukemia. In some instances, molecularly targeted therapies have been developed based on these insights that are currently in clinical trials, such as small molecule inhibitors of FLT3. In addition, it has recently been appreciated that, as with normal hematopoiesis, there is a hierarchical organization among leukemic cells that includes a rare population of leukemic stem cells that have properties of self-renewal. Understanding the characteristics of these leukemic stem cells may provide new insights into leukemia therapies that target self-renewal pathways. In Section I, Dr. Craig Jordan reviews the data that supports the existence of a "leukemia stem cell." He provides an overview of the functional properties of leukemic stem cells, their relationship to hematopoietic stem cells, and the relevance of leukemic stem cells in other human malignancies including solid tumors. He briefly discusses what is known of the pathways that regulate properties of self-renewal. Dr. Gary Gilliland provides an overview of the genetics of adult leukemias in Section II and ongoing genome-wide strategies for discovery of new disease alleles. He describes the clinical and therapeutic implications of these findings and provides examples of bench-to-bedside translation of molecularly targeted therapies for AML, including the use of FLT3 inhibitors. In Section III, Dr. Carolyn Felix reviews recent advances in our understanding of the genetics and therapy of pediatric leukemias. She provides an overview of leukemias that are common in pediatric malignancies but rarely observed in adults, including the TEL-AML1 (ETV6-RUNX1) fusion associated with pediatric B-cell ALL, the OTT-MAL fusion associated with infant megakaryoblastic leukemia, PTPN11 mutations in juvenile myelomonocytic leukemia, and MLL fusion genes in leukemogenesis, among others.
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PMID:The molecular basis of leukemia. 1556 78

CEBPalpha: mutations have been described in adult acute myeloid leukemia (AML) and conferred a favorable prognosis. However, CEBPalpha mutation has not been reported in children. We investigated 117 children with de novo AML using DNA PCR assay followed by sequencing for each PCR product. CEBPalpha mutations were detected in seven patients, four had FAB M2, two M1 and one M4. CEBPalpha mutations only occurred in patients with intermediate cytogenetics and not in 56 children with AML1-ETO, CBFbeta-MYH11, PML-RARalpha or MLL rearrangements. Five patients had mutations occurred in both N-terminal part and basic-leucine zipper (bZIP) domain, one had an N-terminal frameshift mutation and the remaining one had an inframe insertion in the bZIP domain. Cloning analysis on five samples carrying more than one mutations demonstrated one homozygous combined mutations and four heterozygous biallelic mutations. Four of seven CEBPalpha mutation(+) patients had cooperating mutations with FLT3-ITD or N-ras mutations compared to 27 in 109 CEBPalpha mutation(-) patients. Our results showed that CEBPalpha mutations occurred in 6% of childhood AML and most exhibited combined mutations in both N-terminal part and bZIP domain.
Leukemia 2005 Mar
PMID:CEBPalpha mutations in childhood acute myeloid leukemia. 1561 61

Internal tandem duplication mutations of the FLT3 gene (FLT3/ITD mutations) are the most frequent molecular abnormality in acute myeloid leukemia (AML) and are associated with a poor overall survival. While the normal FLT3 receptor is expressed in early hematopoietic progenitor cells, it has not been determined whether FLT3 mutations are present in the leukemic stem cells. In this study, we sorted primary AML samples into stem cell-enriched CD34+/CD38- fractions and then analyzed the sorted and unsorted cells for the FLT3 mutant-wild-type ratio. In each case, the FLT3 mutant-wild-type ratio was not changed by selection of CD34+/CD38- cells, implying that the mutations are present in the leukemic stem cells. We used the stem cell-enriched fraction to engraft nonobese diabetic-severe combined immunodeficient (NOD-SCID) mice and then confirmed that the FLT3/ITD mutation was present in the resultant engrafted marrow. As a final test of the importance of FLT3/ITD signaling in this engraftment model, we used a small molecule FLT3 inhibitor, CEP-701, to inhibit engraftment of FLT3/ITD stem cells. Taken together, these experiments establish that the FLT3/ITD mutations are present in leukemia stem cells, and that FLT3 inhibitors may have activity against these cells.
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PMID:Internal tandem duplications of the FLT3 gene are present in leukemia stem cells. 1579 98

The leukemia and lymphoma disease locus Evi12 was mapped to the noncoding region of a novel gene, Gnn (named for Grp94 neighboring nucleotidase), that is located immediately upstream of the Grp94/Tra1 gene on mouse chromosome 10. The Gnn gene is conserved in mice and humans. Expression of fusion constructs between GFP and Gnn cDNA isoforms in HEK-293 cells showed that Gnn proteins are located mainly in the cytoplasm. Immunoblotting experiments demonstrated the presence of multiple Gnn protein isoforms in most organs, with the lowest levels of expression of the protein detected in bone marrow and spleen. The Evi12-containing leukemia cell line NFS107 showed high levels of expression of a approximately 150-kDa Gnn isoform (Gnn107) that was not observed in control cell lines. Overexpression may be due to the viral insertion in Evi12. The Gnn107 protein is probably encoded by a Gnn cDNA isoform that is expressed exclusively in NFS107 cells and that includes sequences of TU12B1-TY, a putative protein with homology to 5'-nucleotidase enzymes. Interestingly, using Affymetrix gene expression data of a cohort of 285 patients with acute myeloid leukemia (AML), we found that GNN/TU12B1-TY expression was specifically increased in two AML clusters. One cluster consisted of all AML patients with a t(8;21) translocation, and the second cluster consisted of AML patients with a normal karyotype carrying a FLT3 internal tandem duplication. These findings suggest that we identified a novel proto-oncogene that may be causally linked to certain types of human leukemia.
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PMID:The common viral insertion site Evi12 is located in the 5'-noncoding region of Gnn, a novel gene with enhanced expression in two subclasses of human acute myeloid leukemia. 1582 39

The objective of our study was to evaluate high-dose cytarabine in consolidation therapy in patients with newly diagnosed acute promyelocytic leukemia (APL). Patients (age 16-60 years) received induction therapy according to the AIDA protocol (all-trans retinoic acid, idarubicin) followed by one cycle of ICE (idarubicin, cytarabine, etoposide) and two cycles of HAM (cytarabine 3 g/m(2) q12h, days 1-3; mitoxantrone 10 mg/m(2), days 2 and 3). From 1995 to 2003, 82 patients were enrolled. In total, 72 patients (88%) achieved a complete remission, and 10 patients (12%) died from early/hypoplastic death (ED/HD). A total of 71 patients received at least one cycle of HAM. Relapse-free survival (RFS) and overall survival (OS) after 46 months were 83 and 82%, respectively. White blood cell count above 10.0 x 10(9)/l at diagnosis and additional chromosomal aberrations were unfavorable prognostic markers for OS, whereas no prognostic markers for RFS were identified including FLT3 mutations. In conclusion, high-dose cytarabine in consolidation therapy for patients with newly diagnosed APL is an effective treatment approach.
Leukemia 2005 Jun
PMID:High-dose cytarabine and mitoxantrone in consolidation therapy for acute promyelocytic leukemia. 1584 20

Internal tandem duplications (ITDs) of the FLT3 gene have been observed in about 35% of APL cases. If FLT3-ITD is associated with a worse outcome in patients with acute myeloid leukemia (AML) in general, its prognostic value in acute promyelocytic leukemia (APL) is still a matter of debate. We investigated incidence, associated clinical features, and prognostic implication of FLT3-ITD, but also FLT3-D835 point mutation and N-Ras or K-Ras mutations in 119 APL patients, all prospectively enrolled in the two consecutive APL-93 and APL-2000 trials. Mutation incidences were 38, 20, and 4%, for FLT3-ITD, FLT3-D835, and Ras, respectively. The presence of FLT3-ITD was associated with high white blood cell count, high Sanz index, M3-variant subtype, and V/S PML-RAR alpha isoforms. Complete remission (CR), induction death, and death in CR rates were not affected by FLT3 or Ras mutations, as well as cumulative incidence of relapse. However, a trend for a shorter overall survival (P=0.09) was observed in FLT3-ITD patients, because of a very poor postrelapse survival (P=0.02). This feature, which has been also reported in patients with AML in general, is suggestive of an underlying genetic instability in FLT3-ITD patients, leading to the acquisition of additional unknown bad-prognosis gene mutations at relapse.
Leukemia 2005 Jul
PMID:Prognostic implication of FLT3 and Ras gene mutations in patients with acute promyelocytic leukemia (APL): a retrospective study from the European APL Group. 1588 56

AML1-MTG8 generated by t(8;21) contributes to leukemic transformation, but additional events are required for full leukemogenesis. We examined whether mutations in the receptor tyrosine kinase (RTK) pathway could be the genetic events that cause acute myeloblastic leukemia (AML) harboring t(8;21). Mutations in the second tyrosine kinase domain, juxtamembrane (JM) domain and exon 8 of the C-KIT gene were observed in 10, one and three of 37 AML patients with t(8;21), respectively. Three patients showed an internal tandem duplication in the JM domain of the FLT3 gene. One patient had a mutation in the K-Ras gene at codon 12. As the occurrence of these mutations was mutually exclusive, a total of 18 (49%) patients showed mutations in the RTK pathway. These results suggest that activating mutations in the RTK pathway play a role in part as an additional event leading to the development of t(8;21) AML. The 6-year cumulative incidence of relapse in patients with RTK pathway mutations was 79.8%, compared with 13.5% in patients lacking such mutations (P=0.0029). Furthermore, the 6-year relapse-free survival in patients with mutations was 18% compared to 60% in those without mutations (P=0.0340), indicating that RTK mutations are associated with the clinical outcome in t(8;21) AML.
Leukemia 2005 Aug
PMID:Mutations in the receptor tyrosine kinase pathway are associated with clinical outcome in patients with acute myeloblastic leukemia harboring t(8;21)(q22;q22). 1590 84


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