Timothy Hughes | The University of Adelaide (original) (raw)

Papers by Timothy Hughes

Research paper thumbnail of The impact of multiple low-level BCR-ABL1 mutations on response to ponatinib

Blood, Jan 14, 2016

The third-generation tyrosine kinase inhibitor (TKI) ponatinib shows activity against all common ... more The third-generation tyrosine kinase inhibitor (TKI) ponatinib shows activity against all common BCR-ABL1 single mutants, including the highly resistant BCR-ABL1-T315I-mutant, improving outcome for patients with refractory chronic myeloid leukemia (CML). However, responses are variable, and causal baseline factors have not been well studied. The type and number of low-level BCR-ABL1 mutations present after imatinib resistance has prognostic significance for subsequent treatment with nilotinib or dasatinib as second-line therapy. We therefore investigated the impact of low-level mutations detected by sensitive mass-spectrometry before ponatinib initiation (baseline) on treatment response in 363 TKI-resistant patients enrolled in the PACE trial, including 231 patients in chronic phase (CP-CML). Low-level mutations were detected in 53 patients (15%, including low-level T315I in 14 patients); most, however, did not undergo clonal expansion during ponatinib treatment, and moreover, no sp...

Research paper thumbnail of Compound mutations in BCR-ABL1 are not major drivers of primary or secondary resistance to ponatinib in CP-CML patients

Blood, Jan 24, 2015

BCR-ABL1 kinase domain mutations can confer resistance to first- and second-generation tyrosine k... more BCR-ABL1 kinase domain mutations can confer resistance to first- and second-generation tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). In pre-clinical studies, clinically achievable concentrations of the third-generation BCR-ABL1 TKI ponatinib inhibit T315I and all other single BCR-ABL1 mutants except T315M, which generates a single amino acid exchange, but requires 2 sequential nucleotide exchanges. Additionally, certain compound mutants (containing ≥2 mutations in cis) confer resistance. Initial analyses based largely on conventional Sanger sequencing (SS) have suggested that the preclinical relationship between BCR-ABL1 mutation status and ponatinib efficacy is generally recapitulated in patients on therapy. Thus far, however, such analyses have been limited by the inability of SS to definitively identify compound mutations or mutations representing less than ~20% of total alleles (referred to as low-level mutations), as well as limited patient follow-up. Her...

Research paper thumbnail of KIR2DL5B genotype predicts outcomes in CML patients treated with response directed sequential imatinib / nilotinib strategy

Blood, Jan 23, 2015

Killer immunoglobulin-like receptors (KIR) on natural killer cells have been shown to predict for... more Killer immunoglobulin-like receptors (KIR) on natural killer cells have been shown to predict for response in Chronic Phase Chronic Myeloid Leukaemia (CP-CML) patients treated with tyrosine kinase inhibitors. We performed KIR genotyping in 148 newly diagnosed CP-CML patients treated with a novel sequential imatinib/nilotinib strategy aimed at achievement of optimal molecular responses at defined time-points. We found the presence of KIR2DL5B to be associated with inferior transformation-free survival and event-free survival, and an independent predictor of inferior major molecular response (MMR, BCR-ABL1 ≤0.1%) and molecular response 4.5 (MR(4.5), BCR-ABL1 ≤0.0032%). This suggests a critical early role for NK cells in facilitating response to imatinib that cannot be overcome by subsequent intensification of therapy. KIR genotyping may add valuable prognostic information to future baseline predictive scoring systems in CP-CML patients and facilitate optimal frontline treatment select...

Research paper thumbnail of Imatinib-induced gastric antral vascular ectasia in three patients with chronic myeloid leukaemia

International journal of hematology, Jan 2, 2015

Imatinib is generally well tolerated, but gastric antral vascular ectasia (GAVE) remains a rare b... more Imatinib is generally well tolerated, but gastric antral vascular ectasia (GAVE) remains a rare but significant complication of imatinib therapy. Whilst this complication has been described in other disease settings, only one other case of GAVE has been reported in a chronic myeloid leukaemia (CML) patient receiving imatinib. Herein, we present three CML patients with GAVE complicating imatinib therapy. In all cases, GAVE resolved only with cessation of imatinib. This confirms a causal relationship between GAVE and imatinib. GAVE should be considered as a possible cause of anaemia and upper gastrointestinal bleeding in patients receiving imatinib therapy.

Research paper thumbnail of Competitive polymerase chain reaction to estimate the number of BCR-ABL transcripts in chronic myeloid leukemia patients after bone marrow transplantation

Blood, Jan 15, 1993

We have developed a competitive polymerase chain reaction (PCR) titration assay that estimates th... more We have developed a competitive polymerase chain reaction (PCR) titration assay that estimates the number of BCR-ABL transcripts in chronic myeloid leukemia patients to monitor minimal residual disease after bone marrow transplantation (BMT). The assay gave reproducible results and allowed differences in BCR-ABL message levels of half an order of magnitude to be distinguished. Of 91 patients studied by nonquantitative PCR, 28 who had a positive PCR result on at least one occasion posttransplant were analyzed by competitive PCR. Seventeen patients had no evidence in their marrow of cytogenetic relapse during the period of observation; BCR-ABL transcript numbers in these cases ranged from approximately 10 to 800/micrograms RNA. Ten of the 11 patients who relapsed cytogenetically were studied when Philadelphia-positive metaphases were first detected in their marrow; transcript numbers ranged from 1,600 to 7 x 10(5)/micrograms RNA. Patients in hematologic relapse had between 9 x 10(4) a...

Research paper thumbnail of Many BCR-ABL1 compound mutations reported in chronic myeloid leukemia patients may actually be artifacts due to PCR-mediated recombination

Research paper thumbnail of Juxtamembrane mutant V560GKit is more sensitive to Imatinib (STI571) compared with wild - type c - KIT whereas the kinase domain mutant D816VKit is resistant

Imatinib (Glivec; STI571) is an ATP-competitive kinase inhibitor of c-Abl, BCR/ABL, c-Kit, and pl... more Imatinib (Glivec; STI571) is an ATP-competitive kinase inhibitor of c-Abl, BCR/ABL, c-Kit, and platelet-derived growth factor receptor. Overexpression or constitutive activation of Kit by mutations have been associated with various malignancies. Mutations in the intracellular juxtamembrane region of Kit (e.g., V560G) are common in gastrointestinal stromal tumors and have been linked to poor prognosis. Mutations in the kinase domain of Kit (e.g., D816V) have been detected in mastocytosis, acute myeloid leukemia, and germ-cell tumors. To determine the sensitivity of Kit mutants to Imatinib in the same cellular background, wild-type Kit (WTKit), V560GKit and D816VKit were expressed in FDC-P1 cells. Growth of FDC(WTKit) was inhibited by Imatinib with GI50 (a concentration of drug at which 50% inhibition of growth occurs) of 0.1-0.2 microM but FDC(V560GKit) were more sensitive to Imatinib with a GI50 of 0.01-0.025 microM and FDC(D816VKit) were resistant to Imatinib with a GI50 greater than 5 microM. The naturally occurring isoforms of c-Kit did not differ in their sensitivity to Imatinib. Immunoprecipitation and Western blot analysis indicated that 1 microM Imatinib reduced phosphorylation of WTKit and completely blocked phosphorylation of V560GKit but did not affect D816VKit phosphorylation. In signaling studies, addition of stem cell factor (SCF) induced phosphorylation of ERK and Akt by WTKit, and ERK, Akt and STAT3 by V560GKit, which were all blocked by Imatinib. Imatinib also blocked the constitutive activation of Akt and STAT3 by V560GKit but had no affect on the constitutive activation of ERK, Akt, and STAT3 by D816VKit. Overall, these findings demonstrate the increased susceptibility of the Kit juxtamembrane mutant, V560G, and the resistance of the kinase domain mutant, D816V, to Imatinib compared with WTKit.

Research paper thumbnail of The FLX Gene of Arabidopsis is Required for FRI-Dependent Activation of FLC Expression

Plant and Cell Physiology, 2007

The Arabidopsis FLOWERING LOCUS C (FLC) gene encodes a MADS box protein that acts as a dose-depen... more The Arabidopsis FLOWERING LOCUS C (FLC) gene encodes a MADS box protein that acts as a dose-dependent repressor of flowering. Mutants and ecotypes with elevated expression of FLC are late flowering and vernalization responsive. In this study we describe an early flowering mutant in the C24 ecotype, flc expressor (flx), that has reduced expression of FLC. FLX encodes a protein of unknown function with putative leucine zipper domains. FLX is required for FRIGIDA (FRI)-mediated activation of FLC but not for activation of FLC in autonomous pathway mutants. FLX is also required for expression of the FLC paralogs MADS AFFECTING FLOWERING 1 (MAF1) and MAF2.

Research paper thumbnail of Detection of minimal residual disease in an AML patient with trisomy 8 using interphase FISH

Pathology, 1997

Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal... more Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal chromosomal abnormalities. Using a probe for the centromeric region of chromosome 8, fluorescence in situ hybridization (FISH) on interphase cells was used to detect trisomy 8 in an AML patient whose leukemia was characterised by the karyotype 47, XY, +8, del(9) (q21.1q32). We have demonstrated using FISH the presence of the trisomy at all stages of the patient's disease course (including remission, peripheral blood cell harvest and relapse), whereas conventional karyoptypic analysis was only able to detect the trisomy at diagnosis and clinical relapse. We have also shown using immunophenotyping, cell sorting and FISH, that the trisomic cells in this patient were restricted to the CD34+ subset of blood and bone marrow and could not be found in the CD 34-, T or B cell compartment. Overall we have shown FISH to be a rapid, quantitative method for the detection of cells with numerical chromosome abnormalities. FISH analysis of interphase cells provides valuable information on the status of the whole population, rather than just cycling cells, and can be applied successfully to monitor the level of leukemic cells.

Research paper thumbnail of Nilotinib versus Imatinib for Newly Diagnosed Chronic Myeloid Leukemia

New England Journal of Medicine, 2010

Research paper thumbnail of Lin28 promotes transformation and is associated with advanced human malignancies

Research paper thumbnail of OCT-1 activity measurement provides a superior imatinib response predictor than screening for single-nucleotide polymorphisms of OCT-1

Leukemia, 2010

ABSTRACT Leukemia is one of the leading journals in hematology and oncology. It is published mont... more ABSTRACT Leukemia is one of the leading journals in hematology and oncology. It is published monthly and covers all aspects of the research and treatment of leukemia and allied diseases. Studies of normal hemopoiesis are covered because of their comparative relevance.

Research paper thumbnail of Successful peripheral blood stem cell mobilization with granulocyte colony-stimulating factor in a patient with chronic myeloid leukemia achieving a complete cytogenetic remission with dasatinib after failing imatinib

Leukemia, 2008

... I Gabriel 1 , A Chaidos 1 , J Sorouri 1 , E Dannie 1 , J Davis 1 , J Goldman 1 , J Apperley 1... more ... I Gabriel 1 , A Chaidos 1 , J Sorouri 1 , E Dannie 1 , J Davis 1 , J Goldman 1 , J Apperley 1 and D Marin 1. ... Blood 2007; 109: 4143–4150. | Article | PubMed | ISI | ChemPort |; Cortes J, Rousselot P, Kim DW, Ritchie E, Hamerschlak N, Coutre S et al. ...

Research paper thumbnail of BCR-ABL1-positive CML and BCR-ABL1-negative chronic myeloproliferative disorders: some common and contrasting features

Research paper thumbnail of Six-year follow-up of patients receiving imatinib for the first-line treatment of chronic myeloid leukemia

Leukemia, 2009

Imatinib mesylate is considered standard of care for firstline treatment of chronic phase chronic... more Imatinib mesylate is considered standard of care for firstline treatment of chronic phase chronic myeloid leukemia (CML-CP). In the phase III, randomized, open-label International Randomized Study of Interferon vs STI571 (IRIS) trial, previously untreated CML-CP patients were randomized to imatinib (n ¼ 553) or interferon-a (IFN) plus cytarabine (n ¼ 553). This 6-year update focuses on patients randomized to receive imatinib as first-line therapy for newly diagnosed CML-CP. During the sixth year of study treatment, there were no reports of disease progression to accelerated phase (AP) or blast crisis (BC). The toxicity profile was unchanged. The cumulative best complete cytogenetic response (CCyR) rate was 82%; 63% of all patients randomized to receive imatinib and still on study treatment showed CCyR at last assessment. The estimated event-free survival at 6 years was 83%, and the estimated rate of freedom from progression to AP and BC was 93%. The estimated overall survival was 88%--or 95% when only CMLrelated deaths were considered. This 6-year update of IRIS underscores the efficacy and safety of imatinib as first-line therapy for patients with CML.

Research paper thumbnail of Chronic Myeloid Leukemia CD34+ cells have reduced uptake of imatinib due to low OCT-1 Activity

Research paper thumbnail of Nilotinib versus imatinib for the treatment of patients with newly diagnosed chronic phase, Philadelphia chromosome-positive, chronic myeloid leukaemia: 24-month minimum follow-up of the phase 3 randomised ENESTnd trial

The Lancet Oncology, 2011

Background Nilotinib has shown greater effi cacy than imatinib in patients with newly diagnosed P... more Background Nilotinib has shown greater effi cacy than imatinib in patients with newly diagnosed Philadelphia chromosome-positive chronic myeloid leukaemia (CML) in chronic phase after a minimum follow-up of 12 months. We present data from the Evaluating Nilotinib Effi cacy and Safety in clinical Trials-newly diagnosed patients (ENESTnd) study after a minimum follow-up of 24 months.

Research paper thumbnail of Phase III, Randomized, Open-Label Study of Daily Imatinib Mesylate 400 mg Versus 800 mg in Patients With Newly Diagnosed, Previously Untreated Chronic Myeloid Leukemia in Chronic Phase Using Molecular End Points: Tyrosine Kinase Inhibitor Optimization and Selectivity Study

Journal of Clinical Oncology, 2010

To evaluate the safety and efficacy of initial treatment with imatinib mesylate 800 mg/d (400 mg ... more To evaluate the safety and efficacy of initial treatment with imatinib mesylate 800 mg/d (400 mg twice daily) versus 400 mg/d in patients with newly diagnosed chronic myeloid leukemia in chronic phase. A total of 476 patients were randomly assigned 2:1 to imatinib 800 mg (n = 319) or 400 mg (n = 157) daily. The primary end point was the major molecular response (MMR) rate at 12 months. At 12 months, differences in MMR and complete cytogenetic response (CCyR) rates were not statistically significant (MMR, 46% v 40%; P = .2035; CCyR, 70% v 66%; P = .3470). However, MMR occurred faster among patients randomly assigned to imatinib 800 mg/d, who had higher rates of MMR at 3 and 6 months compared with those in the imatinib 400-mg/d arm (P = .0035 by log-rank test). CCyR also occurred faster in the 800-mg/d arm (CCyR at 6 months, 57% v 45%; P = .0146). The most common adverse events were edema, gastrointestinal problems, and rash, and all were more common in patients in the 800-mg/d arm. Grades 3 to 4 hematologic toxicity also occurred more frequently in patients receiving imatinib 800 mg/d. MMR rates at 1 year were similar with imatinib 800 mg/d and 400 mg/d, but MMR and CCyR occurred earlier in patients treated with 800 mg/d. Continued follow-up is needed to determine the clinical significance of earlier responses on high-dose imatinib.

Research paper thumbnail of Dasatinib in the Treatment of Chronic Myeloid Leukemia in Accelerated Phase After Imatinib Failure: The START A Trial

Journal of Clinical Oncology, 2009

PURPOSE Patients with chronic myelogenous leukemia in accelerated phase (CML-AP) that is resistan... more PURPOSE Patients with chronic myelogenous leukemia in accelerated phase (CML-AP) that is resistant or intolerant to imatinib have limited therapeutic options. Dasatinib, a potent inhibitor of BCR-ABL and SRC-family kinases, has efficacy in patients with CML-AP who have experienced treatment failure with imatinib. We now report follow-up data from the full patient cohort of 174 patients enrolled onto a phase II trial to provide a more complete assessment of the efficacy and safety of dasatinib in this population. PATIENTS AND METHODS Patients with imatinib-resistant (n = 161) or -intolerant (n = 13) CML-AP received dasatinib 70 mg orally twice daily. Results At a median follow-up of 14.1 months (treatment duration, 0.1 to 21.7 months), major and complete hematologic responses were attained by 64% and 45% of patients, respectively, and major and complete cytogenetic responses were achieved in 39% and 32% of patients, respectively. Responses were achieved irrespective of imatinib status (resistant or intolerant), prior stem-cell transplantation, or the presence of prior BCR-ABL mutation. The 12-month progression-free survival and overall survival rates were 66% and 82%, respectively. Dasatinib was generally well tolerated; the most frequent nonhematologic severe treatment-related adverse event was diarrhea (52%; grade 3 to 4, 8%). Cytopenias were common, including grade 3 to 4 neutropenia (76%) and thrombocytopenia (82%). Pleural effusion occurred in 27% of patients (grade 3 to 4, 5%). CONCLUSION Dasatinib is effective in patients with CML-AP after imatinib treatment failure.

Research paper thumbnail of Functional Activity of the OCT-1 Protein Is Predictive of Long-Term Outcome in Patients With Chronic-Phase Chronic Myeloid Leukemia Treated With Imatinib

Journal of Clinical Oncology, 2010

Organic cation transporter-1 (OCT-1) activity (OA), a measure of the OCT-1-mediated influx of ima... more Organic cation transporter-1 (OCT-1) activity (OA), a measure of the OCT-1-mediated influx of imatinib into CML mononuclear cells (MNCs), is predictive of major molecular response (MMR) at 12 and 24 months in patients with untreated CML. We now report the impact of OA on loss of response, disease transformation, and survival after 5 years of imatinib. OA is defined as the difference in intracellular concentration of carbon-14-imatinib with and without OCT-1 inhibition. OA was measured in blood from 56 patients with untreated chronic-phase CML. More patients who had high OA (ie, > median OA value) achieved MMR by 60 months compared with patients who had low OA (89% v 55%; P = .007). A low OA was associated with a significantly lower overall survival (87% v 96%; P = .028) and event-free survival (EFS; 48% v 74%; P = .03) as well as a higher kinase domain mutation rate (21% v 4%; P = .047). These differences were highly significant in patients who averaged less than 600 mg/d of imatinib in the first 12 months but were not significant in patients averaging >/= 600 mg/d. Patients with very low OA (ie, quartile 1) were the only group who developed leukemic transformation (21% in quartile 1 v 0% in all other quartiles; P = .002). Measurement of OA pretherapy is a predictor for the long-term risk of resistance and transformation in patients with imatinib-treated CML. Early dose-intensity may reduce the negative prognostic impact of low OA. We propose that OA could be used to individualize dosage strategies for patients with CML to maximize molecular response and optimize long-term outcome.

Research paper thumbnail of The impact of multiple low-level BCR-ABL1 mutations on response to ponatinib

Blood, Jan 14, 2016

The third-generation tyrosine kinase inhibitor (TKI) ponatinib shows activity against all common ... more The third-generation tyrosine kinase inhibitor (TKI) ponatinib shows activity against all common BCR-ABL1 single mutants, including the highly resistant BCR-ABL1-T315I-mutant, improving outcome for patients with refractory chronic myeloid leukemia (CML). However, responses are variable, and causal baseline factors have not been well studied. The type and number of low-level BCR-ABL1 mutations present after imatinib resistance has prognostic significance for subsequent treatment with nilotinib or dasatinib as second-line therapy. We therefore investigated the impact of low-level mutations detected by sensitive mass-spectrometry before ponatinib initiation (baseline) on treatment response in 363 TKI-resistant patients enrolled in the PACE trial, including 231 patients in chronic phase (CP-CML). Low-level mutations were detected in 53 patients (15%, including low-level T315I in 14 patients); most, however, did not undergo clonal expansion during ponatinib treatment, and moreover, no sp...

Research paper thumbnail of Compound mutations in BCR-ABL1 are not major drivers of primary or secondary resistance to ponatinib in CP-CML patients

Blood, Jan 24, 2015

BCR-ABL1 kinase domain mutations can confer resistance to first- and second-generation tyrosine k... more BCR-ABL1 kinase domain mutations can confer resistance to first- and second-generation tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). In pre-clinical studies, clinically achievable concentrations of the third-generation BCR-ABL1 TKI ponatinib inhibit T315I and all other single BCR-ABL1 mutants except T315M, which generates a single amino acid exchange, but requires 2 sequential nucleotide exchanges. Additionally, certain compound mutants (containing ≥2 mutations in cis) confer resistance. Initial analyses based largely on conventional Sanger sequencing (SS) have suggested that the preclinical relationship between BCR-ABL1 mutation status and ponatinib efficacy is generally recapitulated in patients on therapy. Thus far, however, such analyses have been limited by the inability of SS to definitively identify compound mutations or mutations representing less than ~20% of total alleles (referred to as low-level mutations), as well as limited patient follow-up. Her...

Research paper thumbnail of KIR2DL5B genotype predicts outcomes in CML patients treated with response directed sequential imatinib / nilotinib strategy

Blood, Jan 23, 2015

Killer immunoglobulin-like receptors (KIR) on natural killer cells have been shown to predict for... more Killer immunoglobulin-like receptors (KIR) on natural killer cells have been shown to predict for response in Chronic Phase Chronic Myeloid Leukaemia (CP-CML) patients treated with tyrosine kinase inhibitors. We performed KIR genotyping in 148 newly diagnosed CP-CML patients treated with a novel sequential imatinib/nilotinib strategy aimed at achievement of optimal molecular responses at defined time-points. We found the presence of KIR2DL5B to be associated with inferior transformation-free survival and event-free survival, and an independent predictor of inferior major molecular response (MMR, BCR-ABL1 ≤0.1%) and molecular response 4.5 (MR(4.5), BCR-ABL1 ≤0.0032%). This suggests a critical early role for NK cells in facilitating response to imatinib that cannot be overcome by subsequent intensification of therapy. KIR genotyping may add valuable prognostic information to future baseline predictive scoring systems in CP-CML patients and facilitate optimal frontline treatment select...

Research paper thumbnail of Imatinib-induced gastric antral vascular ectasia in three patients with chronic myeloid leukaemia

International journal of hematology, Jan 2, 2015

Imatinib is generally well tolerated, but gastric antral vascular ectasia (GAVE) remains a rare b... more Imatinib is generally well tolerated, but gastric antral vascular ectasia (GAVE) remains a rare but significant complication of imatinib therapy. Whilst this complication has been described in other disease settings, only one other case of GAVE has been reported in a chronic myeloid leukaemia (CML) patient receiving imatinib. Herein, we present three CML patients with GAVE complicating imatinib therapy. In all cases, GAVE resolved only with cessation of imatinib. This confirms a causal relationship between GAVE and imatinib. GAVE should be considered as a possible cause of anaemia and upper gastrointestinal bleeding in patients receiving imatinib therapy.

Research paper thumbnail of Competitive polymerase chain reaction to estimate the number of BCR-ABL transcripts in chronic myeloid leukemia patients after bone marrow transplantation

Blood, Jan 15, 1993

We have developed a competitive polymerase chain reaction (PCR) titration assay that estimates th... more We have developed a competitive polymerase chain reaction (PCR) titration assay that estimates the number of BCR-ABL transcripts in chronic myeloid leukemia patients to monitor minimal residual disease after bone marrow transplantation (BMT). The assay gave reproducible results and allowed differences in BCR-ABL message levels of half an order of magnitude to be distinguished. Of 91 patients studied by nonquantitative PCR, 28 who had a positive PCR result on at least one occasion posttransplant were analyzed by competitive PCR. Seventeen patients had no evidence in their marrow of cytogenetic relapse during the period of observation; BCR-ABL transcript numbers in these cases ranged from approximately 10 to 800/micrograms RNA. Ten of the 11 patients who relapsed cytogenetically were studied when Philadelphia-positive metaphases were first detected in their marrow; transcript numbers ranged from 1,600 to 7 x 10(5)/micrograms RNA. Patients in hematologic relapse had between 9 x 10(4) a...

Research paper thumbnail of Many BCR-ABL1 compound mutations reported in chronic myeloid leukemia patients may actually be artifacts due to PCR-mediated recombination

Research paper thumbnail of Juxtamembrane mutant V560GKit is more sensitive to Imatinib (STI571) compared with wild - type c - KIT whereas the kinase domain mutant D816VKit is resistant

Imatinib (Glivec; STI571) is an ATP-competitive kinase inhibitor of c-Abl, BCR/ABL, c-Kit, and pl... more Imatinib (Glivec; STI571) is an ATP-competitive kinase inhibitor of c-Abl, BCR/ABL, c-Kit, and platelet-derived growth factor receptor. Overexpression or constitutive activation of Kit by mutations have been associated with various malignancies. Mutations in the intracellular juxtamembrane region of Kit (e.g., V560G) are common in gastrointestinal stromal tumors and have been linked to poor prognosis. Mutations in the kinase domain of Kit (e.g., D816V) have been detected in mastocytosis, acute myeloid leukemia, and germ-cell tumors. To determine the sensitivity of Kit mutants to Imatinib in the same cellular background, wild-type Kit (WTKit), V560GKit and D816VKit were expressed in FDC-P1 cells. Growth of FDC(WTKit) was inhibited by Imatinib with GI50 (a concentration of drug at which 50% inhibition of growth occurs) of 0.1-0.2 microM but FDC(V560GKit) were more sensitive to Imatinib with a GI50 of 0.01-0.025 microM and FDC(D816VKit) were resistant to Imatinib with a GI50 greater than 5 microM. The naturally occurring isoforms of c-Kit did not differ in their sensitivity to Imatinib. Immunoprecipitation and Western blot analysis indicated that 1 microM Imatinib reduced phosphorylation of WTKit and completely blocked phosphorylation of V560GKit but did not affect D816VKit phosphorylation. In signaling studies, addition of stem cell factor (SCF) induced phosphorylation of ERK and Akt by WTKit, and ERK, Akt and STAT3 by V560GKit, which were all blocked by Imatinib. Imatinib also blocked the constitutive activation of Akt and STAT3 by V560GKit but had no affect on the constitutive activation of ERK, Akt, and STAT3 by D816VKit. Overall, these findings demonstrate the increased susceptibility of the Kit juxtamembrane mutant, V560G, and the resistance of the kinase domain mutant, D816V, to Imatinib compared with WTKit.

Research paper thumbnail of The FLX Gene of Arabidopsis is Required for FRI-Dependent Activation of FLC Expression

Plant and Cell Physiology, 2007

The Arabidopsis FLOWERING LOCUS C (FLC) gene encodes a MADS box protein that acts as a dose-depen... more The Arabidopsis FLOWERING LOCUS C (FLC) gene encodes a MADS box protein that acts as a dose-dependent repressor of flowering. Mutants and ecotypes with elevated expression of FLC are late flowering and vernalization responsive. In this study we describe an early flowering mutant in the C24 ecotype, flc expressor (flx), that has reduced expression of FLC. FLX encodes a protein of unknown function with putative leucine zipper domains. FLX is required for FRIGIDA (FRI)-mediated activation of FLC but not for activation of FLC in autonomous pathway mutants. FLX is also required for expression of the FLC paralogs MADS AFFECTING FLOWERING 1 (MAF1) and MAF2.

Research paper thumbnail of Detection of minimal residual disease in an AML patient with trisomy 8 using interphase FISH

Pathology, 1997

Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal... more Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal chromosomal abnormalities. Using a probe for the centromeric region of chromosome 8, fluorescence in situ hybridization (FISH) on interphase cells was used to detect trisomy 8 in an AML patient whose leukemia was characterised by the karyotype 47, XY, +8, del(9) (q21.1q32). We have demonstrated using FISH the presence of the trisomy at all stages of the patient's disease course (including remission, peripheral blood cell harvest and relapse), whereas conventional karyoptypic analysis was only able to detect the trisomy at diagnosis and clinical relapse. We have also shown using immunophenotyping, cell sorting and FISH, that the trisomic cells in this patient were restricted to the CD34+ subset of blood and bone marrow and could not be found in the CD 34-, T or B cell compartment. Overall we have shown FISH to be a rapid, quantitative method for the detection of cells with numerical chromosome abnormalities. FISH analysis of interphase cells provides valuable information on the status of the whole population, rather than just cycling cells, and can be applied successfully to monitor the level of leukemic cells.

Research paper thumbnail of Nilotinib versus Imatinib for Newly Diagnosed Chronic Myeloid Leukemia

New England Journal of Medicine, 2010

Research paper thumbnail of Lin28 promotes transformation and is associated with advanced human malignancies

Research paper thumbnail of OCT-1 activity measurement provides a superior imatinib response predictor than screening for single-nucleotide polymorphisms of OCT-1

Leukemia, 2010

ABSTRACT Leukemia is one of the leading journals in hematology and oncology. It is published mont... more ABSTRACT Leukemia is one of the leading journals in hematology and oncology. It is published monthly and covers all aspects of the research and treatment of leukemia and allied diseases. Studies of normal hemopoiesis are covered because of their comparative relevance.

Research paper thumbnail of Successful peripheral blood stem cell mobilization with granulocyte colony-stimulating factor in a patient with chronic myeloid leukemia achieving a complete cytogenetic remission with dasatinib after failing imatinib

Leukemia, 2008

... I Gabriel 1 , A Chaidos 1 , J Sorouri 1 , E Dannie 1 , J Davis 1 , J Goldman 1 , J Apperley 1... more ... I Gabriel 1 , A Chaidos 1 , J Sorouri 1 , E Dannie 1 , J Davis 1 , J Goldman 1 , J Apperley 1 and D Marin 1. ... Blood 2007; 109: 4143–4150. | Article | PubMed | ISI | ChemPort |; Cortes J, Rousselot P, Kim DW, Ritchie E, Hamerschlak N, Coutre S et al. ...

Research paper thumbnail of BCR-ABL1-positive CML and BCR-ABL1-negative chronic myeloproliferative disorders: some common and contrasting features

Research paper thumbnail of Six-year follow-up of patients receiving imatinib for the first-line treatment of chronic myeloid leukemia

Leukemia, 2009

Imatinib mesylate is considered standard of care for firstline treatment of chronic phase chronic... more Imatinib mesylate is considered standard of care for firstline treatment of chronic phase chronic myeloid leukemia (CML-CP). In the phase III, randomized, open-label International Randomized Study of Interferon vs STI571 (IRIS) trial, previously untreated CML-CP patients were randomized to imatinib (n ¼ 553) or interferon-a (IFN) plus cytarabine (n ¼ 553). This 6-year update focuses on patients randomized to receive imatinib as first-line therapy for newly diagnosed CML-CP. During the sixth year of study treatment, there were no reports of disease progression to accelerated phase (AP) or blast crisis (BC). The toxicity profile was unchanged. The cumulative best complete cytogenetic response (CCyR) rate was 82%; 63% of all patients randomized to receive imatinib and still on study treatment showed CCyR at last assessment. The estimated event-free survival at 6 years was 83%, and the estimated rate of freedom from progression to AP and BC was 93%. The estimated overall survival was 88%--or 95% when only CMLrelated deaths were considered. This 6-year update of IRIS underscores the efficacy and safety of imatinib as first-line therapy for patients with CML.

Research paper thumbnail of Chronic Myeloid Leukemia CD34+ cells have reduced uptake of imatinib due to low OCT-1 Activity

Research paper thumbnail of Nilotinib versus imatinib for the treatment of patients with newly diagnosed chronic phase, Philadelphia chromosome-positive, chronic myeloid leukaemia: 24-month minimum follow-up of the phase 3 randomised ENESTnd trial

The Lancet Oncology, 2011

Background Nilotinib has shown greater effi cacy than imatinib in patients with newly diagnosed P... more Background Nilotinib has shown greater effi cacy than imatinib in patients with newly diagnosed Philadelphia chromosome-positive chronic myeloid leukaemia (CML) in chronic phase after a minimum follow-up of 12 months. We present data from the Evaluating Nilotinib Effi cacy and Safety in clinical Trials-newly diagnosed patients (ENESTnd) study after a minimum follow-up of 24 months.

Research paper thumbnail of Phase III, Randomized, Open-Label Study of Daily Imatinib Mesylate 400 mg Versus 800 mg in Patients With Newly Diagnosed, Previously Untreated Chronic Myeloid Leukemia in Chronic Phase Using Molecular End Points: Tyrosine Kinase Inhibitor Optimization and Selectivity Study

Journal of Clinical Oncology, 2010

To evaluate the safety and efficacy of initial treatment with imatinib mesylate 800 mg/d (400 mg ... more To evaluate the safety and efficacy of initial treatment with imatinib mesylate 800 mg/d (400 mg twice daily) versus 400 mg/d in patients with newly diagnosed chronic myeloid leukemia in chronic phase. A total of 476 patients were randomly assigned 2:1 to imatinib 800 mg (n = 319) or 400 mg (n = 157) daily. The primary end point was the major molecular response (MMR) rate at 12 months. At 12 months, differences in MMR and complete cytogenetic response (CCyR) rates were not statistically significant (MMR, 46% v 40%; P = .2035; CCyR, 70% v 66%; P = .3470). However, MMR occurred faster among patients randomly assigned to imatinib 800 mg/d, who had higher rates of MMR at 3 and 6 months compared with those in the imatinib 400-mg/d arm (P = .0035 by log-rank test). CCyR also occurred faster in the 800-mg/d arm (CCyR at 6 months, 57% v 45%; P = .0146). The most common adverse events were edema, gastrointestinal problems, and rash, and all were more common in patients in the 800-mg/d arm. Grades 3 to 4 hematologic toxicity also occurred more frequently in patients receiving imatinib 800 mg/d. MMR rates at 1 year were similar with imatinib 800 mg/d and 400 mg/d, but MMR and CCyR occurred earlier in patients treated with 800 mg/d. Continued follow-up is needed to determine the clinical significance of earlier responses on high-dose imatinib.

Research paper thumbnail of Dasatinib in the Treatment of Chronic Myeloid Leukemia in Accelerated Phase After Imatinib Failure: The START A Trial

Journal of Clinical Oncology, 2009

PURPOSE Patients with chronic myelogenous leukemia in accelerated phase (CML-AP) that is resistan... more PURPOSE Patients with chronic myelogenous leukemia in accelerated phase (CML-AP) that is resistant or intolerant to imatinib have limited therapeutic options. Dasatinib, a potent inhibitor of BCR-ABL and SRC-family kinases, has efficacy in patients with CML-AP who have experienced treatment failure with imatinib. We now report follow-up data from the full patient cohort of 174 patients enrolled onto a phase II trial to provide a more complete assessment of the efficacy and safety of dasatinib in this population. PATIENTS AND METHODS Patients with imatinib-resistant (n = 161) or -intolerant (n = 13) CML-AP received dasatinib 70 mg orally twice daily. Results At a median follow-up of 14.1 months (treatment duration, 0.1 to 21.7 months), major and complete hematologic responses were attained by 64% and 45% of patients, respectively, and major and complete cytogenetic responses were achieved in 39% and 32% of patients, respectively. Responses were achieved irrespective of imatinib status (resistant or intolerant), prior stem-cell transplantation, or the presence of prior BCR-ABL mutation. The 12-month progression-free survival and overall survival rates were 66% and 82%, respectively. Dasatinib was generally well tolerated; the most frequent nonhematologic severe treatment-related adverse event was diarrhea (52%; grade 3 to 4, 8%). Cytopenias were common, including grade 3 to 4 neutropenia (76%) and thrombocytopenia (82%). Pleural effusion occurred in 27% of patients (grade 3 to 4, 5%). CONCLUSION Dasatinib is effective in patients with CML-AP after imatinib treatment failure.

Research paper thumbnail of Functional Activity of the OCT-1 Protein Is Predictive of Long-Term Outcome in Patients With Chronic-Phase Chronic Myeloid Leukemia Treated With Imatinib

Journal of Clinical Oncology, 2010

Organic cation transporter-1 (OCT-1) activity (OA), a measure of the OCT-1-mediated influx of ima... more Organic cation transporter-1 (OCT-1) activity (OA), a measure of the OCT-1-mediated influx of imatinib into CML mononuclear cells (MNCs), is predictive of major molecular response (MMR) at 12 and 24 months in patients with untreated CML. We now report the impact of OA on loss of response, disease transformation, and survival after 5 years of imatinib. OA is defined as the difference in intracellular concentration of carbon-14-imatinib with and without OCT-1 inhibition. OA was measured in blood from 56 patients with untreated chronic-phase CML. More patients who had high OA (ie, > median OA value) achieved MMR by 60 months compared with patients who had low OA (89% v 55%; P = .007). A low OA was associated with a significantly lower overall survival (87% v 96%; P = .028) and event-free survival (EFS; 48% v 74%; P = .03) as well as a higher kinase domain mutation rate (21% v 4%; P = .047). These differences were highly significant in patients who averaged less than 600 mg/d of imatinib in the first 12 months but were not significant in patients averaging >/= 600 mg/d. Patients with very low OA (ie, quartile 1) were the only group who developed leukemic transformation (21% in quartile 1 v 0% in all other quartiles; P = .002). Measurement of OA pretherapy is a predictor for the long-term risk of resistance and transformation in patients with imatinib-treated CML. Early dose-intensity may reduce the negative prognostic impact of low OA. We propose that OA could be used to individualize dosage strategies for patients with CML to maximize molecular response and optimize long-term outcome.