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Brian J P Huntly

Publications and source records attributed to Brian J P Huntly.

At least 19 recordsLinked to original sources
PubMed2026

A step-wise, deterministic and fatal mouse model of myeloid neoplasm with spontaneous acquisition of patient-relevant RTK-RAS mutations.

Leukaemia arises through the stepwise transformation of healthy haematopoietic cells, yet the asymptomatic premalignant phase and its progression to overt disease remain poorly understood. To model this process, we engineered a patient-derived CEBPA mutation into Hoxb8-FL multipotent murine progenitors and transplanted them into syngeneic mice, capturing a clinically silent premalignant stage. All recipients developed overt disease after ~12 months with 100% penetrance and all acquired secondary RTK-RAS mutations, often with identical amino acid changes to those in patients. Single-cell transcriptomics and phenotypic profiling showed that premalignant mutant cells adopt a plasmacytoid dendritic progenitor-like state in vitro which generates both myeloid and B-lymphoid lineages during premalignancy in vivo, with individual tumours restricted to one lineage. The specificity for RTK-RAS mutations coupled with ongoing differentiation, reflects clinically relevant biological contexts thus providing a tractable model of myeloid neoplasm for mechanistic studies and drug discovery.

Journal Article↗
PubMed2006

Cdx4 dysregulates Hox gene expression and generates acute myeloid leukemia alone and in cooperation with Meis1a in a murine model.

HOX genes have emerged as critical effectors of leukemogenesis, but the mechanisms that regulate their expression in leukemia are not well understood. Recent data suggest that the caudal homeobox transcription factors CDX1, CDX2, and CDX4, developmental regulators of HOX gene expression, may contribute to HOX gene dysregulation in leukemia. We report here that CDX4 is expressed normally in early hematopoietic progenitors and is expressed aberrantly in approximately 25% of acute myeloid leukemia (AML) patient samples. Cdx4 regulates Hox gene expression in the adult murine hematopoietic system and dysregulates Hox genes that are implicated in leukemogenesis. Furthermore, bone marrow progenitors that are retrovirally engineered to express Cdx4 serially replate in methylcellulose cultures, grow in liquid culture, and generate a partially penetrant, long-latency AML in bone marrow transplant recipients. Coexpression of the Hox cofactor Meis1a accelerates the Cdx4 AML phenotype and renders it fully penetrant. Structure-function analysis demonstrates that leukemic transformation requires intact Cdx4 transactivation and DNA-binding domains but not the putative Pbx cofactor interaction motif. Together, these data indicate that Cdx4 regulates Hox gene expression in adult hematopoiesis and may serve as an upstream regulator of Hox gene expression in the induction of acute leukemia. Inasmuch as many human leukemias show dysregulated expression of a spectrum of HOX family members, these collective findings also suggest a central role for CDX4 expression in the genesis of acute leukemia.

Adult↗
PubMed2006

Mutation of JAK2 in the myeloproliferative disorders: timing, clonality studies, cytogenetic associations, and role in leukemic transformation.

The identification of an acquired mutation of JAK2 in patients with myeloproliferative disorders has raised questions about the relationship between mutation-positive and mutation-negative subtypes, timing of the JAK2 mutation, and molecular mechanisms of disease progression. Here we demonstrate that patients with V617F(-) essential thrombocythemia do not commonly progress to become V617F(+). Consistent with the concept of distinct pathogenetic mechanisms, we show that patients with and without the JAK2 mutation have different patterns of cytogenetic abnormality, with virtually all patients carrying the 20q deletion or trisomy 9 being V617F(+). We also investigated the existence of a "pre-JAK2" phase by comparing the proportion of clonally derived granulocytes, estimated from X-chromosome inactivation patterns (XCIPs), with the proportion of V617F(+) granulocytes. Our results demonstrate that inherent XCIP variability between granulocytes and T cells produces a systematically biased pattern of results that may be misinterpreted as evidence for an excess of clonally derived granulocytes, an observation that limits the utility of XCIP analysis in this context. Lastly, we studied 4 patients with V617F(+) myeloproliferative disorders who subsequently developed acute myeloid leukemia. In 3 patients the leukemic cells were V617F(-), suggesting that in these patients the leukemia arose in a V617F(-) cell.

Cell Transformation, Neoplastic↗
PubMed2006

An acquired translocation in JAK2 Val617Phe-negative essential thrombocythemia associated with autosomal spread of X-inactivation.

The acquired mutation Val617Phe in the tyrosine kinase JAK2 was recently identified in most but not all patients with classical myeloproliferative disorders. We describe a cytogenetic and molecular study of a JAK2Val617Phe-negative case of essential thrombocythemia harboring the acquired translocation t(X;5)(q13;q33). We show that this involves the inactive X-chromosome and is associated with silencing of autosomal genes within the adjacent 5q minus syndrome common deleted region. This is the first documented example of autosomal gene silencing adjacent to an X-autosome breakpoint in human malignancy and such a mechanism may underlie the pathogenesis of related disorders with translocations involving Xq13.

Amino Acid Substitution↗
PubMed2005

FGFR3 as a therapeutic target of the small molecule inhibitor PKC412 in hematopoietic malignancies.

Reccurent chromosomal translocation t(4;14) (p16.3;q32.3) occurs in patients with multiple myeloma (MM) and is associated with ectopic overexpression of fibroblast growth factor receptor 3 (FGFR3) that sometimes may contain the activation mutations such as K650E thanatophoric dysplasia type II (TDII). Although there have been significant advances in therapy for MM including the use of proteasome inhibitors, t(4;14) MM has a particularly poor prognosis and most patients still die from complications related to their disease or therapy. One potential therapeutic strategy is to inhibit FGFR3 in those myeloma patients that overexpress the receptor tyrosine kinase due to chromosomal translocation. Here we evaluated PKC412, a small molecule tyrosine kinase inhibitor, for treatment of FGFR3-induced hematopoietic malignancies. PKC412 inhibited kinase activation and proliferation of hematopoietic Ba/F3 cells transformed by FGFR3 TDII or a TEL-FGFR3 fusion. Similar results were obtained in PKC412 inhibition of several different t(4;14)-positive human MM cell lines. Furthermore, treatment with PKC412 resulted in a statistically significant prolongation of survival in murine bone marrow transplant models of FGFR3 TDII-induced pre-B cell lymphoma, or a peripheral T-cell lymphoma associated TEL-FGFR3 fusion-induced myeloproliferative disease. These data indicate that PKC412 may be a useful molecularly targeted therapy for MM associated with overexpression of FGFR3, and perhaps other diseases associated with dysregulation of FGFR3 or related mutants.

Animals↗
PubMed2005

FLT3 internal tandem duplication mutations induce myeloproliferative or lymphoid disease in a transgenic mouse model.

Activating FMS-like tyrosine kinase 3 (FLT3) mutations have been identified in approximately 30% of patients with acute myelogenous leukemia (AML), and recently in a smaller subset of patients with acute lymphoblastic leukemia (ALL). To explore the in vivo consequences of an activating FLT3 internal tandem duplication mutation (FLT3-ITD), we created a transgenic mouse model in which FLT3-ITD was expressed under the control of the vav hematopoietic promoter. Five independent lines of vav-FLT3-ITD transgenic mice developed a myeloproliferative disease with high penetrance and a disease latency of 6-12 months. The phenotype was characterized by splenomegaly, megakaryocytic hyperplasia, and marked thrombocythemia, but without leukocytosis, polycythemia, or marrow fibrosis, displaying features reminiscent of the human disease essential thrombocythemia (ET). Clonal immature B- or T-lymphoid disease was observed in two additional founder mice, respectively, that could be secondarily transplanted to recipient mice that rapidly developed lymphoid disease. Treatment of these mice with the FLT3 tyrosine kinase inhibitor, PKC412, resulted in suppression of disease and a statistically significant prolongation of survival. These results demonstrate that FLT3-ITD is capable of inducing myeloproliferative as well as lymphoid disease, and indicate that small-molecule tyrosine kinase inhibitors may be an effective treatment for lymphoid malignancies in humans that are associated with activating mutations in FLT3.

Animals↗
PubMed2005

The JAK2V617F activating mutation occurs in chronic myelomonocytic leukemia and acute myeloid leukemia, but not in acute lymphoblastic leukemia or chronic lymphocytic leukemia.

Activating mutations in tyrosine kinases have been identified in hematopoietic and nonhematopoietic malignancies. Recently, we and others identified a single recurrent somatic activating mutation (JAK2V617F) in the Janus kinase 2 (JAK2) tyrosine kinase in the myeloproliferative disorders (MPDs) polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis. We used direct sequence analysis to determine if the JAK2V617F mutation was present in acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML)/atypical chronic myelogenous leukemia (aCML), myelodysplastic syndrome (MDS), B-lineage acute lymphoblastic leukemia (ALL), T-cell ALL, and chronic lymphocytic leukemia (CLL). Analysis of 222 patients with AML identified JAK2V617F mutations in 4 patients with AML, 3 of whom had a preceding MPD. JAK2V617F mutations were identified in 9 (7.8%) of 116 CMML/a CML samples, and in 2 (4.2%) of 48 MDS samples. We did not identify the JAK2V617F disease allele in B-lineage ALL (n = 83), T-cell ALL (n = 93), or CLL (n = 45). These data indicate that the JAK2V617F allele is present in acute and chronic myeloid malignancies but not in lymphoid malignancies.

Aged↗
PubMed2005

Constitutively activated FGFR3 mutants signal through PLCgamma-dependent and -independent pathways for hematopoietic transformation.

Ectopic expression of fibroblast growth factor receptor 3 (FGFR3) associated with t(4;14) has been implicated in the pathogenesis of human multiple myeloma. Some t(4;14) patients have activating mutations of FGFR3, of which a minority are K650E (thanatophoric dysplasia type II [TDII]). To investigate the role of autophosphorylated tyrosine residues in FGFR3 signal transduction and transformation, we characterized a series of FGFR3 TDII mutants with single or multiple Y-->F substitutions. Phenylalanine substitution of Y760, essential for phospholipase Cgamma (PLCgamma) binding and activation, significantly attenuated FGFR3 TDII-mediated PLCgamma activation, as well as transformation in Ba/F3 cells and a murine bone marrow transplant leukemia model. In contrast, single substitution of Y577, Y724, or Y770 had minimal to moderate effects on TDII-dependent transformation. Substitution of all 4 non-activation loop tyrosine residues significantly attenuated, but did not abolish, TDII transforming activity. Similar observations were obtained in the context of a constitutively activated fusion TEL-FGFR3 associated with t(4;12)(p16;p13) peripheral T-cell lymphomas. Moreover, 2 independent EmuSR-FGFR3 TDII transgenic mouse lines developed a pro-B-cell lymphoma, and PLCgamma was highly activated in primary lymphoma cells as assessed by tyrosine phosphorylation. These data indicate that engagement of multiple signaling pathways, including PLCgamma-dependent and PLCgamma-independent pathways, is required for full hematopoietic transformation by constitutively activated FGFR3 mutants.

Amino Acid Substitution↗
PubMed2005

Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis.

Polycythemia vera (PV), essential thrombocythemia (ET), and myeloid metaplasia with myelofibrosis (MMM) are clonal disorders arising from hematopoietic progenitors. An internet-based protocol was used to collect clinical information and biological specimens from patients with these diseases. High-throughput DNA resequencing identified a recurrent somatic missense mutation JAK2V617F in granulocyte DNA samples of 121 of 164 PV patients, of which 41 had homozygous and 80 had heterozygous mutations. Molecular and cytogenetic analyses demonstrated that homozygous mutations were due to duplication of the mutant allele. JAK2V617F was also identified in granulocyte DNA samples from 37 of 115 ET and 16 of 46 MMM patients, but was not observed in 269 normal individuals. In vitro analysis demonstrated that JAK2V617F is a constitutively active tyrosine kinase.

Adult↗
PubMed2005

Leukaemia stem cells and the evolution of cancer-stem-cell research.

Many cancers seem to depend on a small population of 'cancer stem cells' for their continued growth and propagation. The leukaemia stem cell (LSC) was the first such cell to be described. The origins of these cells are controversial, and their biology - like that of their normal-tissue counterpart, the haematopoietic stem cell (HSC) - is still not fully elucidated. However, the LSC is likely to be the most crucial target in the treatment of leukaemias, and a thorough understanding of its biology - particularly of how the LSC differs from the HSC - might allow it to be selectively targeted, improving therapeutic outcome.

Animals↗
PubMed2004

Blasts from the past: new lessons in stem cell biology from chronic myelogenous leukemia.

Cancer can be viewed as a hierarchical system that is dependent on a small population of "cancer stem cells" with unlimited self-renewal potential for continued growth and propagation of tumors. The identity and nature of these cells remains enigmatic, but an improved understanding of their biology may allow for selective therapeutic targeting. A recent report by sheds new light on leukemia stem cells by identifying the cells with in vitro self-renewing properties in various phases of chronic myelogenous leukemia, and linking the self-renewal properties of this population to activation of beta-catenin, a major effector of the canonical Wnt signaling pathway.

Cell Division↗
PubMed2004

MOZ-TIF2, but not BCR-ABL, confers properties of leukemic stem cells to committed murine hematopoietic progenitors.

To better understand the origin of leukemic stem cells, we tested the hypothesis that all leukemia oncogenes could transform committed myeloid progenitor cells lacking the capacity for self-renewal, as has recently been reported for MLL-ENL. Flow-sorted populations of common myeloid progenitors and granulocyte-monocyte progenitors were transduced with the oncogenes MOZ-TIF2 and BCR-ABL, respectively. MOZ-TIF2-transduced progenitors could be serially replated in methylcellulose cultures and continuously propagated in liquid culture, and resulted in an acute myeloid leukemia in vivo that could be serially transplanted. In contrast, BCR-ABL transduction conferred none of these properties to hematopoietic progenitors. These data demonstrate that some, but not all, leukemia oncogenes can confer properties of leukemic stem cells to hematopoietic progenitors destined to undergo apoptotic cell death.

Acute Disease↗
PubMed2004

Characterization of the imprinted polycomb gene L3MBTL, a candidate 20q tumour suppressor gene, in patients with myeloid malignancies.

Chromosome 20q deletion is a recurrent chromosomal abnormality associated with myeloid malignancies. L3MBTL represents a strong candidate tumour suppressor gene since it lies within the common deleted region, is a member of the Polycomb-like family, encodes the human homologue of a Drosophila tumour suppressor and is expressed within haematopoietic progenitor cells. We describe the structure of L3MBTL, identify two putative promoters each associated with two CpG islands and characterize a complex pattern of alternative splicing events. Mutation analysis of the gene in patients with and without a 20q deletion identified several polymorphisms but no acquired mutations. The two CpG islands spanning promoter 2 undergo monoallelic methylation in normal haematopoietic cells consistent with imprinting of L3MBTL. Samples from patients with a 20q deletion retained either the methylated or unmethylated allele but retention of the methylated allele did not correlate with reduction in L3MBTL mRNA levels. The absence of a correlation between L3MBTL methylation and transcription could be shown to reflect loss of imprinting in one patient. In addition, our results demonstrate that inactivation of L3MBTL is not a common occurrence in patients with a 20q deletion or in cytogenetically normal patients with polycythaemia vera.

Alternative Splicing↗
PubMed2003

The EOL-1 cell line as an in vitro model for the study of FIP1L1-PDGFRA-positive chronic eosinophilic leukemia.

We recently identified the chimeric kinase FIP1L1-platelet-derived growth factor receptor alpha (PDGFRalpha) as a cause of the hypereosinophilic syndrome and of chronic eosinophilic leukemia. To investigate the role of FIP1L1-PDGFRA in the pathogenesis of acute leukemia, we screened 87 leukemia cell lines for the presence of FIP1L1-PDGFRA. One cell line, EOL-1, expressed the FIP1L1-PDGFRA fusion. Three structurally divergent kinase inhibitors--imatinib (STI-571), PKC412, and SU5614--inhibited the growth of EOL-1 cells. These results indicate that the fusion of FIP1L1 to PDGFRA occurs rarely in leukemia cell lines, but they identify EOL-1 as an in vitro model for the study of FIP1L1-PDGFRA-positive chronic eosinophilic leukemia and for the analysis of small molecule inhibitors of FIP1L1-PDGFRalpha.

Apoptosis↗
PubMed2003

Imatinib improves but may not fully reverse the poor prognosis of patients with CML with derivative chromosome 9 deletions.

Deletions of the derivative chromosome 9 occur in a subset of patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML) and are associated with a poor prognosis on standard drug therapy. However, it is currently unknown if the presence of deletions influences the response to imatinib, an Abl-specific tyrosine kinase inhibitor, that has recently shown excellent hematologic and cytogenetic responses in patients with CML. We, therefore, compared hematologic and cytogenetic responses with imatinib in 397 patients with CML, and survival and progression in 354 of these patients, according to deletion status and disease phase. We found no difference in survival between patients with and without deletions, contrasting with previous reports in cohorts with a lower proportion of patients treated with imatinib. However, the time to disease progression on imatinib treatment was significantly shorter for patients with deletions, both in chronic phase (P =.02) and advanced phases (P =.02). Moreover, both in chronic phase and more advanced phases of CML, hematologic and cytogenetic responses were uniformly lower in patients with deletions, with significant differences seen for hematologic response (P =.04), for major cytogenetic response (P =.008) in chronic phase, and for hematologic response in advanced phases (P =.007) of CML. This finding suggests that differences in survival may become apparent with longer follow-up.

Adult↗
PubMed2003

Double jeopardy from a single translocation: deletions of the derivative chromosome 9 in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by formation of a BCR-ABL fusion gene, usually as a consequence of the Philadelphia (Ph) translocation between chromosomes 9 and 22. Recently the development of new fluorescence in-situ hybridization (FISH) techniques has allowed identification of unexpected deletions of the reciprocal translocation product, the derivative chromosome 9, in 10% to 15% of patients with CML. These deletions are large, span the translocation breakpoint, and occur at the same time as the Ph translocation. Such deletions therefore give rise to previously unsuspected molecular heterogeneity from the very beginning of this disease, and there is mounting evidence for similar deletions associated with other translocations. Several studies have demonstrated that CML patients who carry derivative chromosome 9 deletions exhibit a more rapid progression to blast crisis and a shorter survival. Deletion status is independent of, and more powerful than, the Sokal and Hasford/European prognostic scoring systems. The poor prognosis associated with deletions is seen in patients treated with hydroxyurea or interferon, and preliminary evidence suggests that patients with deletions may also have a worse outcome than nondeleted patients following stem cell transplantation or treatment with imatinib. Poor outcome cannot be attributed to loss of the reciprocal ABL-BCR fusion gene expression alone, and is likely to reflect loss of one or more critical genes within the deleted region. The molecular heterogeneity associated with the Philadelphia translocation provides a new paradigm with potential relevance to all malignancies associated with reciprocal chromosomal translocations and/or fusion gene formation.

Animals↗
PubMed2003

Survival implications of molecular heterogeneity in variant Philadelphia-positive chronic myeloid leukaemia.

The BCR-ABL fusion in chronic myeloid leukaemia (CML) is generated by the Philadelphia (Ph) translocation t(9;22) or, in 10% of patients, variants thereof (vPh). Deletion encompassing the reciprocal product (ABL-BCR) from the derivative chromosome 9 [der(9)] occurs in 15% of all patients, but with greater frequency in vPh patients. Reports of physical separation of ABL-BCR in non-deleted patients, as well as evolution from classical to variant Ph, introduce further heterogeneity to the vPh subgroup and raise the possibility that such translocations may herald disease progression. Survival analyses, however, have thus far yielded contradictory results. We assessed the frequency of der(9) deletions, ABL-BCR abrogation, cytogenetic evolution and cryptic rearrangement in a large cohort of 54 patients with vPh CML. Deletions encompassing ABL-BCR were detected in 37% of patients, consistent with a model in which a greater number of chromosome breaks increases the risk of genomic loss. The components of ABL-BCR were physically separated in a further 52% of patients while fused in the remaining 11%. Evolution from classical to vPh was demonstrated in three patients. The difference in survival, as indicated by Kaplan-Meier analysis, was marked between classical and vPh patients (105 vs 60 months respectively; P = 0.0002). Importantly, this difference disappeared when patients with deletions were removed from the analysis. Our study showed that, despite the existence of several levels of genomic heterogeneity in variant Ph-positive CML, der(9) deletion status is the key prognostic factor.

Chromosomes, Human, Pair 9↗