- Hematology/Oncology/Stem Cell Transplant, Pediatric
- Oncology (Cancer), Pediatric
- AML, childhood and adolescent/young adult
- ALL, childhood and adolescent/young adult
- lymphoblastic lymphoma, childhood
- Hematology and Oncology
Member, Cancer Center (2007 - Present)
Myeloid Steering Committee, Children's Oncology Group (2007 - Present)
Honors & Awards
Member, Alpha Omega Alpha (1990)
New Approaches in Pediatric Myeloid Leukemia, V Foundation (10/09-09/12)
Banking Acute Leukemia Specimens at Lucile Packard Childrens Hospital: Hyundai Infrastructure Grant, Hyundai Foundation (10/11-09/12)
Molecular and Pharmacologic Correlates of Acute Myeloid Leukemia in Down Syndrome, NIH ROI subcontract from Wayne State University (01/09-04/16)
Medical Education:University of California at San Francisco School of Medicine (1989) CA
Internship:UCSF Medical Center (1990) CA
Residency:UCSF Medical Center (1992) CA
Fellowship:Stanford University Medical Center (1995) CA
MD, U.C., San Francisco, Medicine (1989)
BA, U. C., Berkeley, Biochemistry (1985)
Current Research and Scholarly Interests
Pediatric Hematology/Oncology, Phase I drug studies for refractory and relapsed leukemia; genomic studies, biologic risk-stratification and treatment of acute myeloid leukemia; prediction or induction response and risk of relapse using phosphoproteomics in childhood AML; novel MRD techniques in childhood ALL.
A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, Immunogenicity, and Preliminary Efficacy of Atezolizumab (Anti-Programmed Death-Ligand 1 [PD-L1] Antibody) in Pediatric and Young Adult Participants With Solid Tumors
This early phase, multicenter, open-label, single-arm study will evaluate the safety, tolerability, pharmacokinetics, immunogenicity, and preliminary efficacy of atezolizumab in pediatric and young adult participants with solid tumors for which prior treatment was proven to be ineffective.
Carfilzomib in Combination With Cyclophosphamide and Etoposide for Children
This study evaluates the use of carfilzomib in combination with cyclophosphamide and etoposide for children with relapsed/refractory solid tumors or leukemia. The medications cyclophosphamide and etoposide are standard drugs often used together for the treatment of cancer in children with solid tumors or leukemia. Carfilzomib is FDA (Food and Drug Administration) approved in the United States for adults with multiple myeloma (a type of cancer). However, this drug is not approved for the disease being treated in this study. Since carfilzomib has not yet been used in this setting to treat this condition, the investigators must first find the best dose to give. The investigators are looking for the highest dose of carfilzomib that can be given safely. Therefore, not all children taking part in this study will receive the same dose of the study drug in the first part of the trial.
Clofarabine Plus Cytarabine Versus Conventional Induction Therapy And A Study Of NK Cell Transplantation In Newly Diagnosed Acute Myeloid Leukemia
The purpose of this study is to assess the feasibility and efficacy of a novel form of therapy—haploidentical NK cell transplantation—in patients with standard-risk AML. In addition, we will investigate the efficacy of clofarabine + cytarabine (Clo/AraC) in newly diagnosed patients with AML and attempt to optimize outcome through the use of MRD-adapted therapy and further improvements in supportive care.
Oral TRK Inhibitor LOXO-101 (Larotrectinib) for Treatment of Advanced Pediatric Solid or Primary Central Nervous System Tumors
This is a multicenter, open label, Phase 1/2 study in pediatric patients with advanced solid or primary CNS tumors. LOXO‑101 (larotrectinib) will be administered orally (PO) twice daily (BID), with the dose adjusted by body surface area (BSA).
Panobinostat With Fludarabine and Cytarabine for Treatment of Children With Acute Myeloid Leukemia or Myelodysplastic Syndrome
Cancer is the uncontrolled growth of human cells. The growth of normal human cells is controlled by multiple mechanisms. Panobinostat belongs to a class of chemotherapy drugs called "histone deacetylase (HDAC) inhibitors." HDAC inhibitors like panobinostat block enzymes known as histone deacetylases, which stops cancer cells from dividing and causes them to die. Fludarabine and cytarabine are chemotherapy drugs that are commonly used to treat pediatric patients with refractory or relapsed acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). The purpose of this study is to test the safety of panobinostat and to find the highest dose of panobinostat that can be given safely when it is combined with fludarabine and cytarabine. This pilot study will be done in two parts: The goal of Part 1 of the study is to find the highest tolerable dose of panobinostat that can be given to patients with AML or MDS, when it is combined with fludarabine and cytarabine. Once that dose is determined, participants will be enrolled on Part 2: Dose Expansion, to look at the effect of the panobinostat/fludarabine/cytarabine combination in patients with leukemia/MDS. PRIMARY OBJECTIVE: - Determine a tolerable dose of panobinostat when given in combination with fludarabine and cytarabine in pediatric patients with relapsed or refractory AML or MDS. SECONDARY OBJECTIVES: - Characterize the pharmacokinetics of panobinostat after the first dose and at steady-state. - Estimate the overall response rate to the combination of panobinostat, fludarabine, and cytarabine.
Selinexor With Fludarabine and Cytarabine for Treatment of Refractory or Relapsed Leukemia or Myelodysplastic Syndrome
The purpose of this study is to test the safety of selinexor (KPT-330) and to find the highest dose of selinexor (KPT-330) that can be given safely when it is combined with two chemotherapy drugs (fludarabine and cytarabine). This study will be done in two parts: Phase I and Phase II. The goal of Phase I is to find the highest tolerable dose of selinexor (KPT-330) that we can give to patients with leukemia or MDS, when it is combined with fludarabine and cytarabine. The goal of the subsequent Phase II portion of the study (insert NCT ID of SELHEM-2) is to give the highest dose of selinexor (KPT-330) in combination with fludarabine/cytarabine that was found in Phase I to be safe for children with leukemia or MDS. The investigators will examine the effect of this combination treatment. PRIMARY OBJECTIVE: - Determine a tolerable combination of selinexor, fludarabine, and cytarabine in pediatric patients with relapsed or refractory hematologic malignancies included acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), mixed phenotype acute leukemia (MPAL) and myelodysplastic syndrome (MDS). SECONDARY OBJECTIVES: - To characterize the pharmacokinetics of selinexor, when administered in tablet form, after the first dose and at steady-state, as well as in combination with fludarabine and cytarabine - To estimate the overall response rate of selinexor given with fludarabine and cytarabine in patients with relapsed or refractory hematologic malignancies
A Pharmacokinetic (PK) Study of Nilotinib in Pediatric Patients With Philadelphia Chromosome-positive (Ph+) Chronic Myelogenous Leukemia (CML) or Acute Lymphoblastic Leukemia (ALL)
This study will assess the pharmacokinetics of nilotinib in Ph+ CML pediatric patients that are newly diagnosed or resistant or intolerant to imatinib or dasatinib or refractory or relapsed Ph+ ALL compared to the adult populations. It will also evaluate safety and activity of nilotinib as secondary objectives.
Stanford is currently not accepting patients for this trial. For more information, please contact Alyson Falwell, 650736428.
Efficacy and Safety of Decitabine as Epigenetic Priming With Induction Chemotherapy in Pediatric Acute Myelogenous Leukemia (AML) Subjects
The purpose of this study is to provide data on the activity of a standard daunorubicin, cytarabine, and etoposide (ADE) induction plus epigenetic priming with decitabine as assessed by standard measures of complete remission (CR), leukemia free survival (LFS) and overall survival (OS), as well as, on minimal residual disease (MRD). It will also provide necessary data on the safety and Pharmacokinetics (PK) of decitabine in pediatric patients that is currently unavailable.
Stanford is currently not accepting patients for this trial.
Efficacy and Safety of Donepezil Hydrochloride in Preadolescent and Adolescent Children With Attention Impairment Following Cancer Treatment
The purpose of this study is to evaluate the efficacy, safety and tolerability of donepezil in children with persistent attention impairment that is present at least 12 months after the completion of cancer treatment.
Stanford is currently not accepting patients for this trial. For more information, please contact Jennifer Lew, (650) 725 - 4318.
Genome, Proteome and Tissue Microarray in Childhood Acute Leukemia
We will study gene and protein expression in leukemia cells of children diagnosed with acute leukemia. We hope to identify genes or proteins which can help us grade leukemia at diagnosis in order to: (a) develop better means of diagnosis and (b) more accurately choose the best therapy for each patient.
Stanford is currently not accepting patients for this trial. For more information, please contact Norman J Lacayo, 650-723-5535.
Open Label, Phase II Study to Evaluate Efficacy and Safety of Oral Nilotinib in Philadelphia Positive (Ph+) Chronic Myelogenous Leukemia (CML) Pediatric Patients.
To evaluate the safety, efficacy and concentration of nilotinib over time in the Ph+ chronic myelogenous leukemia (CML) in pediatric patients (from 1 to <18 years).
Stanford is currently not accepting patients for this trial. For more information, please contact Contact, 650-723-5117.
Study of OTO-104 in Subjects at Risk From Cisplatin-Induced Hearing Loss
This is a multicenter, Phase 2 study to assess the feasibility, safety and efficacy of OTO-104 given by intratympanic administration in subjects at risk for ototoxicity from cisplatin chemotherapy regimens in the treatment of cancer.
Stanford is currently not accepting patients for this trial. For more information, please contact Cancer Clinical Trials Office (CCTO), 650-498-7061.
Total Therapy for Infants With Acute Lymphoblastic Leukemia (ALL) I
The purpose of this study is to test the good and bad effects of the study drugs bortezomib and vorinostat when they are given in combination with chemotherapy commonly used to treat acute lymphoblastic leukemia (ALL) in infants. For example, adding these drugs could decrease the number of leukemia cells, but it could also cause additional side effects. Bortezomib and vorinostat have been approved by the US Food and Drug Administration (FDA) to treat other cancers in adults, but they have not been approved for treating children with leukemia. With this research, we plan to meet the following goals: PRIMARY OBJECTIVE: - Determine the tolerability of incorporating bortezomib and vorinostat into an ALL chemotherapy backbone for newly diagnosed infants with ALL. SECONDARY OBJECTIVES: - Estimate the event-free survival and overall survival of infants with ALL who are treated with bortezomib and vorinostat in combination with an ALL chemotherapy backbone. - Measure minimal residual disease (MRD) positivity using both flow cytometry and PCR. - Compare end of induction, end of consolidation, and end of reinduction MRD levels to Interfant99 (ClinicalTrials.gov registration ID number NCT00015873) participant outcomes.
Stanford is currently not accepting patients for this trial. For more information, please contact Norman J. Lacayo, MD, 650-497-8953.
Treatment of Patients With Newly Diagnosed Acute Myeloid Leukemia or Myelodysplasia
The purpose of this study is to compare the effectiveness of two multi-agent chemotherapy regimens using different dosages of cytarabine to eliminate all detectable leukemia.
Stanford is currently not accepting patients for this trial. For more information, please contact LPCH New Patient Coordinator, (650) 725 - 1072.
- Independent Studies (5)
Improved outcomes for myeloid leukemia of Down syndrome: a report from the Children's Oncology Group AAML0431 trial.
Patients with myeloid leukemia of Down syndrome (ML-DS) have favorable event-free survival (EFS), but experience significant treatment-related morbidity and mortality. ML-DS blast cells ex vivo have increased sensitivity to cytarabine (araC) and daunorubicin, suggesting that optimizing drug dosing may improve outcomes while reducing toxicity. The Children's Oncology Group (COG) AAML0431 trial consisted of 4 cycles of induction and 2 cycles of intensification therapy based on the treatment schema of the previous COG A2971 trial with several modifications. High-dose araC (HD-araC) was used in the second induction cycle instead of the intensification cycle, and 1 of 4 daunorubicin-containing induction cycles was eliminated. For 204 eligible patients, 5-year EFS was 89.9% and overall survival (OS) was 93.0%. The 5-year OS for 17 patients with refractory/relapsed leukemia was 34.3%. We determined the clinical significance of minimal residual disease (MRD) levels as measured by flow cytometry on day 28 of induction I. MRD measurements, available for 146 of the 204 patients, were highly predictive of treatment outcome; 5-year disease-free survival for MRD-negative patients (n = 125) was 92.7% vs 76.2% for MRD-positive patients (n = 21) (log-rank P = .011). Our results indicated that earlier use of HD-araC led to better EFS and OS in AAML0431 than in past COG studies. A 25% reduction in the cumulative daunorubicin dose did not impact outcome. MRD, identified as a new prognostic factor for ML-DS patients, can be used for risk stratification in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00369317.
View details for DOI 10.1182/blood-2017-01-764324
View details for PubMedID 28389462
Phase I Study of Selinexor, a Selective Inhibitor of Nuclear Export, in Combination With Fludarabine and Cytarabine, in Pediatric Relapsed or Refractory Acute Leukemia
JOURNAL OF CLINICAL ONCOLOGY
2016; 34 (34): 4094-?
Purpose To characterize the toxicity, pharmacokinetics, and pharmacodynamics of selinexor, a selective inhibitor of nuclear export, when combined with fludarabine and cytarabine, in children with relapsed or refractory leukemia. Patients and Methods Eighteen patients with relapsed or refractory acute leukemia were enrolled in the SELHEM (Selinexor With Fludarabine and Cytarabine for Treatment of Refractory or Relapsed Leukemia or Myelodysplastic Syndrome) clinical trial (NCT02212561). Selinexor, initially at 30 mg/m(2) per dose, was given orally on days 1, 3, 8, 10, 22, and 24 and was escalated according to a rolling-six design. Fludarabine 30 mg/m(2) and cytarabine 2 g/m(2) were administered on days 15 to 19. Pharmacokinetic and pharmacodynamic studies were performed on days 1 and 22. Response evaluations were performed on day 15 and at the completion of course 1. Results Among the 17 patients who were evaluable for toxicity, three were treated at 30 mg/m(2), three at 40 mg/m(2), six at 55 mg/m(2), and five at 70 mg/m(2). The most common grade 3 nonhematologic toxicity was asymptomatic hyponatremia. Two patients who were treated at 70 mg/m(2) experienced reversible cerebellar toxicity, thereby defining the dose-limiting toxicity. Pharmacokinetic parameters demonstrated that plasma exposure was dose proportional. Fifteen of 16 patients demonstrated at least a twofold increase of XPO1 mRNA, indicating inhibition of the XPO1 protein. In this group of heavily pretreated, relapsed, and refractory patients, seven of 15 evaluable patients (47%) achieved complete response or complete response with incomplete count recovery. Conclusion Selinexor, in combination with fludarabine and cytarabine, is tolerable at doses up to 55 mg/m(2) in pediatric patients with relapsed or refractory leukemia. All patients who received selinexor at ≥ 40 mg/m(2) demonstrated XPO1 target inhibition. Response rates are promising and will be further explored in a phase II trial.
View details for DOI 10.1200/JCO.2016.67.5066
View details for Web of Science ID 000388929900008
View details for PubMedID 27507877
Small molecule inhibition of cAMP response element binding protein in human acute myeloid leukemia cells.
The transcription factor CREB (cAMP Response-Element Binding Protein) is overexpressed in the majority of acute myeloid leukemia (AML) patients, and this is associated with a worse prognosis. Previous work revealed that CREB overexpression augmented AML cell growth, while CREB knockdown disrupted key AML cell functions in vitro. In contrast, CREB knockdown had no effect on long-term hematopoietic stem cell activity in mouse transduction/transplantation assays. Together, these studies position CREB as a promising drug target for AML. To test this concept, a small molecule inhibitor of CREB, XX-650-23, was developed. This molecule blocks a critical interaction between CREB and its required co-activator CBP (CREB Binding Protein), leading to disruption of CREB-driven gene expression. Inhibition of CBP-CREB interaction induced apoptosis and cell-cycle arrest in AML cells, and prolonged survival in vivo in mice injected with human AML cells. XX-650-23 had little toxicity on normal human hematopoietic cells and tissues in mice. To understand the mechanism of XX-650-23, we performed RNA-seq, ChIP-seq and Cytometry Time of Flight with human AML cells. Our results demonstrate that small molecule inhibition of CBP-CREB interaction mostly affects apoptotic, cell-cycle and survival pathways, which may represent a novel approach for AML therapy.
View details for DOI 10.1038/leu.2016.139
View details for PubMedID 27211267
View details for PubMedCentralID PMC5143163
Replication factor C3 is a CREB target gene that regulates cell cycle progression through the modulation of chromatin loading of PCNA
2015; 29 (6): 1379-1389
CREB (cyclic AMP response element-binding protein) is a transcription factor overexpressed in normal and neoplastic myelopoiesis and regulates cell cycle progression, although its oncogenic mechanism has not been well characterized. Replication factor C3 (RFC3) is required for chromatin loading of proliferating cell nuclear antigen (PCNA) which is a sliding clamp platform for recruiting numerous proteins in the DNA metabolism. CREB1 expression, which was activated by E2F, was coupled with RFC3 expression during the G1/S progression in the KG-1 acute myeloid leukemia (AML) cell line. There was also a direct correlation between the expression of RFC3 and CREB1 in human AML cell lines as well as in the AML cells from the patients. CREB interacted directly with the CRE site in RFC3 promoter region. CREB-knockdown inhibited primarily G1/S cell cycle transition by decreasing the expression of RFC3 as well as PCNA loading onto the chromatin. Exogenous expression of RFC3 was sufficient to rescue the impaired G1/S progression and PCNA chromatin loading caused by CREB knockdown. These studies suggest that RFC3 may have a role in neoplastic myelopoiesis by promoting the G1/S progression and its expression is regulated by CREB.
View details for DOI 10.1038/leu.2014.350
View details for Web of Science ID 000355615000017
View details for PubMedID 25541153
Altered resting state functional connectivity in young survivors of acute lymphoblastic leukemia.
Pediatric blood & cancer
2014; 61 (7): 1295-1299
Chemotherapy treatment for pediatric acute lymphoblastic leukemia (ALL) has been associated with long-term cognitive impairments in some patients. However, the neurobiologic mechanisms underlying these impairments, particularly in young survivors, are not well understood. This study aimed to examine intrinsic functional brain connectivity in pediatric ALL and its relationship with cognitive status.We obtained resting state functional magnetic resonance imaging (rsfMRI) and cognitive testing data from 15 ALL survivors age 8-15 years and 14 matched healthy children. The ALL group had a history of intrathecal chemotherapy treatment but were off-therapy for at least 6 months at the time of enrollment. We used seed-based analyses to compare intrinsic functional brain network connectivity between the groups. We also explored correlations between connectivity and cognitive performance, demographic, medical, and treatment variables.We demonstrated significantly reduced connectivity between bilateral hippocampus, left inferior occipital, left lingual gyrus, bilateral calcarine sulcus, and right amygdala in the ALL group compared to controls. The ALL group also showed regions of functional hyperconnectivity including right lingual gyrus, precuneus, bilateral superior occipital lobe, and right inferior occipital lobe. Functional hypoconnectivity was associated with reduced cognitive function as well as younger age at diagnosis in the ALL group.This is the first study to demonstrate that intrinsic functional brain connectivity is disrupted in pediatric ALL following chemotherapy treatment. These results help explain cognitive dysfunction even when objective test performance is seemingly normal. Children diagnosed at a younger age may show increased vulnerability to altered functional brain connectivity.
View details for DOI 10.1002/pbc.25022
View details for PubMedID 24619953
View details for PubMedCentralID PMC4028071
Development and validation of a single-cell network profiling assay-based classifier to predict response to induction therapy in paediatric patients with de novo acute myeloid leukaemia: a report from the Children's Oncology Group
BRITISH JOURNAL OF HAEMATOLOGY
2013; 162 (2): 250-262
Single cell network profiling (SCNP) is a multi-parameter flow cytometry technique for simultaneous interrogation of intracellular signalling pathways. Diagnostic paediatric acute myeloid leukaemia (AML) bone marrow samples were used to develop a classifier for response to induction therapy in 53 samples and validated in an independent set of 68 samples. The area under the curve of a receiver operating characteristic curve (AUCROC ) was calculated to be 0·85 in the training set and after exclusion of induction deaths, the AUCROC of the classifier was 0·70 (P = 0·02) and 0·67 (P = 0·04) in the validation set when induction deaths (intent to treat) were included. The highest predictive accuracy was noted in the cytogenetic intermediate risk patients (AUCROC 0·88, P = 0·002), a subgroup that lacks prognostic/predictive biomarkers for induction response. Only white blood cell count and cytogenetic risk were associated with response to induction therapy in the validation set. After controlling for these variables, the SCNP classifier score was associated with complete remission (P = 0·017), indicating that the classifier provides information independent of other clinical variables that were jointly associated with response. This is the first validation of an SCNP classifier to predict response to induction chemotherapy. Herein we demonstrate the usefulness of quantitative SCNP under modulated conditions to provide independent information on AML disease biology and induction response.
View details for DOI 10.1111/bjh.12370
View details for Web of Science ID 000321211300012
View details for PubMedID 23682827
- Prognostic features in acute megakaryoblastic leukemia in children without Down syndrome: a report from the AML02 multicenter trial and the Children's Oncology Group Study POG 9421 LEUKEMIA 2013; 27 (3): 731-734
AKT Signaling as a Novel Factor Associated with In Vitro Resistance of Human AML to Gemtuzumab Ozogamicin
2013; 8 (1)
Gemtuzumab ozogamicin (GO), an immunoconjugate between an anti-CD33 antibody and a calicheamicin-γ(1) derivative, induces remissions and improves survival in a subset of patients with acute myeloid leukemia (AML). As the mechanisms underlying GO and calicheamicin-γ(1) resistance are incompletely understood, we herein used flow cytometry-based single cell network profiling (SCNP) assays to study cellular responses of primary human AML cells to GO. Our data indicate that the extent of DNA damage is quantitatively impacted by CD33 expression and drug efflux activity. However, although DNA damage is required for GO-induced cytotoxicity, it is not sufficient for effective cell kill, suggesting that downstream anti-apoptotic pathways may function as relevant resistance mechanisms. Supporting this notion, we found activated PI3K/AKT signaling to be associated with GO resistance in vitro in primary AML cells. Consistently, the investigational AKT inhibitor MK-2206 significantly sensitized various human AML cells to GO or free calicheamicin-γ(1) with particularly pronounced effects in otherwise GO or free calicheamicin-γ(1)-resistant cells. Likewise, MK-2206 also sensitized primary AML cells to calicheamicin-γ(1). Together, our findings illustrate the capacity of SCNP assays to discover chemotherapy-related biological pathways and signaling networks relevant to GO-induced genotoxic stress. The identification of AKT signaling as being associated with GO resistance in vitro may provide a novel approach to improve the in vivo efficacy of GO/calicheamicin-γ(1) and, by extrapolation, other DNA damage-based therapeutics.
View details for DOI 10.1371/journal.pone.0053518
View details for Web of Science ID 000313429800056
View details for PubMedID 23320091
Massive evolution of the immunoglobulin heavy chain locus in children with B precursor acute lymphoblastic leukemia
2012; 120 (22): 4407-4417
The ability to distinguish clonal B-cell populations based on the sequence of their rearranged immunoglobulin heavy chain (IgH) locus is an important tool for diagnosing B-cell neoplasms and monitoring treatment response. Leukemic precursor B cells may continue to undergo recombination of the IgH gene after malignant transformation; however, the magnitude of evolution at the IgH locus is currently unknown. We used next-generation sequencing to characterize the repertoire of IgH sequences in diagnostic samples of 51 children with B precursor acute lymphoblastic leukemia (B-ALL). We identified clonal IgH rearrangements in 43 of 51 (84%) cases and found that the number of evolved IgH sequences per patient ranged dramatically from 0 to 4024. We demonstrate that the evolved IgH sequences are not the result of amplification artifacts and are unique to leukemic precursor B cells. In addition, the evolution often follows an allelic exclusion pattern, where only 1 of 2 rearranged IgH loci exhibit ongoing recombination. Thus, precursor B-cell leukemias maintain evolution at the IgH locus at levels that were previously underappreciated. This finding sheds light on the mechanisms associated with leukemic clonal evolution and may fundamentally change approaches for monitoring minimal residual disease burden.
View details for DOI 10.1182/blood-2012-05-429811
View details for Web of Science ID 000313111300023
View details for PubMedID 22932801
Comparison of High-Throughput Sequencing and Flow Cytometry for Measuring Minimal Residual Disease in Pediatric Acute Lymphoblastic Leukemia: A Children's Oncology Group Cohort
54th Annual Meeting and Exposition of the American-Society-of-Hematology (ASH)
AMER SOC HEMATOLOGY. 2012
View details for Web of Science ID 000313838905193
Assessing signaling pathways associated with in vitro resistance to cytotoxic agents in AML
2012; 36 (7): 900-904
This study uses single cell network profiling (SCNP) to characterize biological pathways associated with in vitro resistance or sensitivity to chemotherapeutics commonly used in acute myeloid leukemia (AML) (i.e. cytarabine/daunorubicin, gemtuzumab ozogamicin (GO), decitabine, azacitidine, clofarabine). Simultaneous measurements at the single cell level of changes in DNA damage, apoptosis and signaling pathway responses in AML blasts incubated in vitro with the above drugs showed distinct profiles for each sample and mechanistically different profiles between distinct classes of agents. Studies are ongoing to assess the clinical predictive value of these findings.
View details for DOI 10.1016/j.leukres.2012.02.022
View details for Web of Science ID 000304353400030
View details for PubMedID 22521550
Circular RNAs Are the Predominant Transcript Isoform from Hundreds of Human Genes in Diverse Cell Types
2012; 7 (2)
Most human pre-mRNAs are spliced into linear molecules that retain the exon order defined by the genomic sequence. By deep sequencing of RNA from a variety of normal and malignant human cells, we found RNA transcripts from many human genes in which the exons were arranged in a non-canonical order. Statistical estimates and biochemical assays provided strong evidence that a substantial fraction of the spliced transcripts from hundreds of genes are circular RNAs. Our results suggest that a non-canonical mode of RNA splicing, resulting in a circular RNA isoform, is a general feature of the gene expression program in human cells.
View details for DOI 10.1371/journal.pone.0030733
View details for Web of Science ID 000301977500016
View details for PubMedID 22319583
View details for PubMedCentralID PMC3270023
Next-Generation Sequencing of Immunoglobulin Heavy Chain Variable Region in Diagnostic Samples of Pediatric Acute Lymphoblastic Leukemia Identifies Hundreds of Clonal Subpopulations with Multiple Immunophenotypes
53rd Annual Meeting and Exposition of the American-Society-of-Hematology (ASH)
AMER SOC HEMATOLOGY. 2011: 624–24
View details for Web of Science ID 000299597102031
- Dorsolateral Midbrain MRI Abnormalities and Ocular Motor Deficits Following Cytarabine-Based Chemotherapy for Acute Myelogenous Leukemia JOURNAL OF NEURO-OPHTHALMOLOGY 2011; 31 (1): 52-53
A pilot study of an online cognitive rehabilitation program for executive function skills in children with cancer-related brain injury
2011; 25 (1): 101-112
Children with a history of cancer are at increased risk for cognitive impairments, particularly in executive and memory domains. Traditional, in-person cognitive rehabilitation strategies may be unavailable and/or impractical for many of these children given difficulties related to resources and health status. The feasibility and efficacy of implementing a computerized, home-based cognitive rehabilitation curriculum designed to improve executive function skills was examined in these children.A one-arm open trial pilot study of an original executive function cognitive rehabilitation curriculum was conducted with 23 paediatric cancer survivors aged 7-19.Compliance with the cognitive rehabilitation program was 83%, similar to that of many traditional programs. Following the cognitive intervention, participants showed significantly increased processing speed, cognitive flexibility, verbal and visual declarative memory scores as well as significantly increased pre-frontal cortex activation compared to baseline.These results suggest that a program of computerized cognitive exercises can be successfully implemented at home in young children with cancer. These exercises may be effective for improving executive and memory skills in this group, with concurrent changes in neurobiologic status.
View details for DOI 10.3109/02699052.2010.536194
View details for Web of Science ID 000288101700011
View details for PubMedID 21142826
Minimal residual disease-directed therapy for childhood acute myeloid leukaemia: results of the AML02 multicentre trial
2010; 11 (6): 543-552
We sought to improve outcome in patients with childhood acute myeloid leukaemia (AML) by applying risk-directed therapy that was based on genetic abnormalities of the leukaemic cells and measurements of minimal residual disease (MRD) done by flow cytometry during treatment.From Oct 13, 2002, to June 19, 2008, 232 patients with de-novo AML (n=206), therapy-related or myelodysplasia-related AML (n=12), or mixed-lineage leukaemia (n=14) were enrolled at eight centres. 230 patients were assigned by block, non-blinded randomisation, stratified by cytogenetic or morphological subtype, to high-dose (18 g/m(2), n=113) or low-dose (2 g/m(2), n=117) cytarabine given with daunorubicin and etoposide (ADE; induction 1). The primary aim of the study was to compare the incidence of MRD positivity of the high-dose group and the low-dose group at day 22 of induction 1. Induction 2 consisted of ADE with or without gemtuzumab ozogamicin (GO anti-CD33 monoclonal antibody); consolidation therapy included three additional courses of chemotherapy or haematopoietic stem-cell transplantation (HSCT). Levels of MRD were used to allocate GO and to determine the timing of induction 2. Both MRD and genetic abnormalities at diagnosis were used to determine the final risk classification. Low-risk patients (n=68) received five courses of chemotherapy, whereas high-risk patients (n=79), and standard-risk patients (n=69) with matched sibling donors, were eligible for HSCT (done for 48 high-risk and eight standard-risk patients). All 230 randomised patients were analysed for the primary endpoint. Other analyses were limited to the 216 patients with AML, excluding those with mixed-lineage leukaemia. This trial is closed to accrual and is registered with ClinicalTrials.gov, number NCT00136084.Complete remission was achieved in 80% (173 of 216 patients) after induction 1 and 94% (203 of 216) after induction 2. Induction failures included two deaths from toxic effects and ten cases of resistant leukaemia. The introduction of high-dose versus low-dose cytarabine did not significantly lower the rate of MRD-positivity after induction 1 (34%vs 42%, p=0.17). The 6-month cumulative incidence of grade 3 or higher infection was 79.3% (SE 4.0) for patients in the high-dose group and 75.5% (4.2) for the low-dose group. 3-year event-free survival and overall survival were 63.0% (SE 4.1) and 71.1% (3.8), respectively. 80% (155 of 193) of patients achieved MRD of less than 0.1% after induction 2, and the cumulative incidence of relapse for this group was 17% (SE 3). MRD of 1% or higher after induction 1 was the only significant independent adverse prognostic factor for both event-free (hazard ratio 2.41, 95% CI 1.36-4.26; p=0.003) and overall survival (2.11, 1.09-4.11; p=0.028).Our findings suggest that the use of targeted chemotherapy and HSCT, in the context of a comprehensive risk-stratification strategy based on genetic features and MRD findings, can improve outcome in patients with childhood AML.National Institutes of Health and American Lebanese Syrian Associated Charities (ALSAC).
View details for DOI 10.1016/S1470-2045(10)70090-5
View details for Web of Science ID 000279019500026
View details for PubMedID 20451454
Phase I Study of Valspodar (PSC-833) With Mitoxantrone and Etoposide in Refractory and Relapsed Pediatric Acute Leukemia: A Report From the Children's Oncology Group
PEDIATRIC BLOOD & CANCER
2010; 54 (5): 694-702
Valspodar, a non-immunosuppressive analog of cylosporine, is a potent P-glycoprotein (MDR1) inhibitor. As MDR1-mediated efflux of chemotherapeutic agents from leukemic blasts may contribute to drug resistance, a phase 1 study of valspodar combined with mitoxantrone and etoposide in pediatric patients with relapsed or refractory leukemias was performed.Patients received a valspodar-loading dose (2 mg/kg) followed by a 5-day continuous valspodar infusion (8, 10, 12.5, or 15 mg/kg/day) combined with lower than standard doses of mitoxantrone and etoposide. The valspodar dose was escalated using a standard 3 + 3 phase I design.Twenty-one patients were evaluable for toxicity and 20 for response. The maximum tolerated dose (MTD) of valspodar was 12.5 mg/kg/day, combined with 50% dose-reduced mitoxantrone and etoposide. The clearance of mitoxantrone and etoposide was decreased by 64% and 60%, respectively, when combined with valspodar. Dose-limiting toxicities included stomatitis, ataxia, and bone marrow aplasia. Three of 11 patients with acute lymphoblastic leukemia (ALL) had complete responses while no patient with acute myeloid leukemia (AML) had an objective response. In vitro studies demonstrated P-glycoprotein expression on the blasts of 5 of 14 patients, although only 1 had inhibition of rhodamine efflux by valspodar.While this regimen was tolerable, responses in this heavily pretreated population were limited to a subset of patients with ALL.
View details for DOI 10.1002/pbc.22366
View details for Web of Science ID 000275935700009
View details for PubMedID 20209646
Prevalence and prognostic significance of KIT mutations in pediatric patients with core binding factor AML enrolled on serial pediatric cooperative trials for de novo AML
2010; 115 (12): 2372-2379
KIT receptor tyrosine kinase mutations are implicated as a prognostic factor in adults with core binding factor (CBF) acute myeloid leukemia (AML). However, their prevalence and prognostic significance in pediatric CBF AML is not well established. We performed KIT mutational analysis (exon 8 and exon 17) on diagnostic specimens from 203 pediatric patients with CBF AML enrolled on 4 pediatric AML protocols. KIT mutations were detected in 38 (19%) of 203 (95% CI, 14%-25%) patient samples of which 20 (52.5%) of 38 (95% CI, 36%-69%) involved exon 8, 17 (45%) of 38 (95% CI, 29%-62%) involved exon 17, and 1 (2.5%; 95% CI, 0%-14%) involved both locations. Patients with KIT mutations had a 5-year event-free survival of 55% (+/- 17%) compared with 59% (+/- 9%) for patients with wild-type KIT (P = .86). Rates of complete remission, overall survival, disease-free survival, or relapse were not significantly different for patients with or without KIT mutations. Location of the KIT mutation and analysis by cytogenetic subtype [t(8;21) vs inv(16)] also lacked prognostic significance. Our study shows that KIT mutations lack prognostic significance in a large series of pediatric patients with CBF AML. This finding, which differs from adult series and a previously published pediatric study, may reflect variations in therapeutic approaches and/or biologic heterogeneity within CBF AML. Two of 4 studies included in this analysis are registered at http://clinicaltrials.gov as NCT00002798 (CCG-2961) and NCT00070174 (COG AAML03P1).
View details for DOI 10.1182/blood-2009-09-241075
View details for Web of Science ID 000275981900010
View details for PubMedID 20056794
WT1 Expression at Diagnosis Does Not Predict Survival in Pediatric AML: A Report From the Children's Oncology Group
PEDIATRIC BLOOD & CANCER
2009; 53 (6): 1136-1139
WT1 is a transcription factor that is aberrantly overexpressed in acute and chronic leukemias. Overexpression of WT1 in pediatric acute myeloid leukemia has been reported, but the prognostic significance is unclear because sample sizes in these studies have been relatively small. WT1 expression was measured by quantitative RT-PCR in samples obtained at diagnosis from 155 pediatric AML patients treated on a cooperative group protocol. Neither overall survival nor event-free survival was correlated with WT1 expression.
View details for DOI 10.1002/pbc.22142
View details for Web of Science ID 000270440900043
View details for PubMedID 19618455
- Speeding the Flow Toward Personalized Therapy in Childhood Acute Leukemia PEDIATRIC BLOOD & CANCER 2009; 53 (4): 525-526
Molecular inversion probes reveal patterns of 9p21 deletion and copy number aberrations in childhood leukemia
CANCER GENETICS AND CYTOGENETICS
2009; 193 (1): 9-18
Childhood leukemia, which accounts for >30% of newly diagnosed childhood malignancies, is one of the leading causes of death for children with cancer. Genome-wide studies using microarray chips to identify copy number changes in human cancer are becoming more common. In this pilot study, 45 pediatric leukemia samples were analyzed for gene copy aberrations using novel molecular inversion probe (MIP) technology. Acute leukemia subtypes included precursor B-cell acute lymphoblastic leukemia (ALL) (n=23), precursor T-cell ALL (n=6), and acute myeloid leukemia (n=14). The MIP analysis identified 69 regions of recurring copy number changes, of which 41 have not been identified with other DNA microarray platforms. Copy number gains and losses were validated in 98% of clinical karyotypes and 100% of fluorescence in situ hybridization studies available. We report unique patterns of copy number loss in samples with 9p21.3 (CDKN2A) deletion in the precursor B-cell ALL patients, compared with the precursor T-cell ALL patients. MIPs represent an attractive technology for identifying novel copy number aberrations, validating previously reported copy number changes, and translating molecular findings into clinically relevant targets for further investigation.
View details for DOI 10.1016/j.cancergencyto.2009.03.005
View details for Web of Science ID 000268922900002
View details for PubMedID 19602459
View details for PubMedCentralID PMC2776674
- Genomics of childhood leukemias: The virtue of complexity JOURNAL OF CLINICAL ONCOLOGY 2008; 26 (27): 4367-4368
Tissue microarrays from bone marrow aspirates for high-throughput assessment of immunohistologic markers in pediatric acute leukemia
PEDIATRIC AND DEVELOPMENTAL PATHOLOGY
2008; 11 (4): 283-290
Gene expression profiling studies have been employed to investigate prognostic subgroups in pediatric acute leukemia. Tissue microarrays (TMAs) are useful for high-throughput analysis of protein expression of target genes in acute leukemia samples and for validation of gene microarray analysis. Using cryopreserved samples of pediatric acute leukemia bone marrow aspirates, we constructed TMA from as few as 1 million cells. Bone marrow core biopsies from the same patients were included on the same TMA for comparison. A panel of 15 immunohistochemical markers typically used for diagnosis as well as those targeting recently characterized, prognostically relevant molecules of interest in pediatric acute leukemia was used to evaluate protein expression. Staining results confirm that suspension cells from bone marrow aspirates can be effectively used to derive protein expression data from multiple cases simultaneously with comparable efficacy to that of biopsy tissue. This method allows for new markers of diagnostic, prognostic, or therapeutic importance to be screened on large numbers of study patients. Furthermore, this technique may facilitate the inclusion of small samples, aspirates, and body fluids in large-scale studies of protein expression in clinical trials and protocols in which tissue biopsies are often unavailable.
View details for DOI 10.2350/07-04-0253.1
View details for Web of Science ID 000259353300005
View details for PubMedID 17990919
- Acute leukemia in children DM DISEASE-A-MONTH 2008; 54 (4): 202-225
The incidence and clinical significance of nucleophosmin mutations in childhood AML
2007; 110 (3): 979-985
Frameshift mutations in exon 12 of the nucleophosmin gene (NPM1) result in aberrant cytoplasmic localization of the NPM protein (NPMc(+)) and occur in 25% to 35% of adult acute myeloid leukemia (AML). In adults with AML, NPMc(+) has been associated with normal karyotype, FLT3/ITD mutations, high remission induction rates, and improved survival (particularly in patients lacking FLT3/ITD). NPMc(+) has not been well characterized in childhood AML. This study examines the incidence and clinical significance of NPMc(+) in 295 children with newly diagnosed AML treated on a large cooperative group clinical trial (POG-9421). We find that NPMc(+) is relatively uncommon in childhood AML (23 of 295 patients, 8%); and is significantly associated with FLT3/ITD mutations (P = .046), female sex (P = .029), older age (P = .047), and normal cytogenetics (P < .001). There is a favorable impact of NPMc(+) on survival in children lacking FLT3/ITD (5-year EFS, 69% vs 35%; hazard ratio, 0.39; P = .051), which is similar in magnitude to the favorable impact of t(8;21) and inv(16). We conclude that NPMc(+) is relatively rare in childhood AML, particularly in younger children. NPMc(+) does not abrogate the negative prognostic influence of FLT3/ITD mutations, but may contribute to risk stratification in children who lack FLT3/ITD mutations by identifying a group with superior prognosis.
View details for DOI 10.1182/blood-2007-02-076604
View details for Web of Science ID 000248514700035
View details for PubMedID 17440048
Differential gene expression patterns and interaction networks in BCR-ABL-positive and -negative adult acute lymphoblastic leukemias
JOURNAL OF CLINICAL ONCOLOGY
2007; 25 (11): 1341-1349
To identify gene expression patterns and interaction networks related to BCR-ABL status and clinical outcome in adults with acute lymphoblastic leukemia (ALL).DNA microarrays were used to profile a set of 54 adult ALL specimens from the Medical Research Council UKALL XII/Eastern Cooperative Oncology Group E2993 trial (21 p185BCR-ABL-positive, 16 p210BCR-ABL-positive and 17 BCR-ABL-negative specimens).Using supervised and unsupervised analysis tools, we detected significant transcriptomic changes in BCR-ABL-positive versus -negative specimens, and assessed their validity in an independent cohort of 128 adult ALL specimens. This set of 271 differentially expressed genes (including GAB1, CIITA, XBP1, CD83, SERPINB9, PTP4A3, NOV, LOX, CTNND1, BAALC, and RAB21) is enriched for genes involved in cell death, cellular growth and proliferation, and hematologic system development and function. Network analysis demonstrated complex interaction patterns of these genes, and identified FYN and IL15 as the hubs of the top-scoring network. Within the BCR-ABL-positive subgroups, we identified genes overexpressed (PILRB, STS-1, SPRY1) or underexpressed (TSPAN16, ADAMTSL4) in p185BCR-ABL-positive ALL relative to p210BCR-ABL-positive ALL. Finally, we constructed a gene expression- and interaction-based outcome predictor consisting of 27 genes (including GRB2, GAB1, GLI1, IRS1, RUNX2, and SPP1), which correlated with overall survival in BCR-ABL-positive adult ALL (P = .0001), independent of age (P = .25) and WBC count at presentation (P = .003).We identified prominent molecular features of BCR-ABL-positive adult ALL, which may be useful for developing novel therapeutic targets and prognostic markers in this disease.
View details for DOI 10.1200/JCO.2006.09.3534
View details for Web of Science ID 000245851900009
View details for PubMedID 17312329
Gene expression profiling predicts outcome in de novo acute myeloid leukemia (AML) with normal karyotype: Results of children's oncology group (COG) study POG #9421.
48th Annual Meeting of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2006: 542A–542A
View details for Web of Science ID 000242440002433
Differential gene expression patterns and interaction networks in BCR/ABL positive and negative adult acute lymphoblastic leukemias.
48th Annual Meeting of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2006: 520A–520A
View details for Web of Science ID 000242440002354
- CpG island methylator phenotype and childhood leukemia CLINICAL CANCER RESEARCH 2006; 12 (16): 4787-4789
Low or absent SPARC expression in acute myeloid leukemia with MLL rearrangements is associated with sensitivity to growth inhibition by exogenous SPARC protein
2006; 20 (3): 426-432
Secreted protein, acidic and rich in cysteine (SPARC), is a matricellular glycoprotein with growth-inhibitory and antiangiogenic functions. Although SPARC has been implicated as a tumor suppressor in humans, its function in normal or malignant hematopoiesis has not previously been studied. We found that the leukemic cells of AML patients with MLL gene rearrangements express low to undetectable amounts of SPARC whereas normal hematopoietic progenitors and most AML patients express this gene. SPARC RNA and protein levels were also low or undetectable in AML cell lines with MLL translocations. Consistent with its tumor suppressive effects in various solid tumor models, exogenous SPARC protein selectively reduced the growth of cell lines with MLL rearrangements by inhibiting cell cycle progression from G1 to S phase. The lack of SPARC expression in MLL-rearranged cell lines was associated with dense promoter methylation. However, we found no evidence of methylation-based silencing of SPARC in primary patient samples. Our results suggest that low or absent SPARC expression is a consistent feature of AML cells with MLL rearrangements and that SPARC may function as a tumor suppressor in this subset of patients. A potential role of exogenous SPARC in the therapy of MLL-rearranged AML warrants further investigation.
View details for DOI 10.1038/sj.leu.2404102
View details for Web of Science ID 000235537800007
View details for PubMedID 16424866
Randomized use of cyclosporin A (CsA) to modulate P-glycoprotein in children with AML in remission: Pediatric Oncology Group Study 9421
2006; 107 (4): 1315-1324
Relapse is a major obstacle in the cure of acute myeloid leukemia (AML). The Pediatric Oncology Group AML Study 9421 tested 2 different strategies to improve event-free survival (EFS) and overall survival (OS). Patients were randomized to receive standard-dose DAT (daunorubicin, cytarabine, and thioguanine) or high-dose DAT during induction. To interfere with P-glycoprotein (P-gp)-dependent drug efflux, the second randomization tested the benefit of cyclosporine (CsA) added to consolidation chemotherapy. Of the 282 children randomly assigned to receive standard DAT induction, 248 (87.9%) achieved remission compared to 253 (91%) of the 278 receiving high-dose DAT (P = ns). Children with HLA-identical sibling donors who achieved a complete remission received an allogeneic bone marrow transplant as consolidation. For the 83 patients receiving a matched related donor bone marrow transplantation (BMT), the 3-year disease-free survival (DFS) is 67%. Of the 418 children who achieved remission and went on to consolidation with and without CsA, the DFS was 40.6% and 33.9%, respectively (P = .24). Overexpression of P-gp was infrequent (14%) in this pediatric population. In this study, intensifying induction with high-dose DAT and the addition of CsA to consolidation chemotherapy did not prolong the durations of remission or improve overall survival for children with AML.
View details for DOI 10.1128/blood-2004-08-3218
View details for Web of Science ID 000235296100018
View details for PubMedID 16254147
Gene expression profiling and FLT3 status correlate with outcome in de novo acute myeloid leukemia (AML) with normal karyotype: Results of children's oncology group (COG) study POG #9421.
47th Annual Meeting of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2005: 667A–667A
View details for Web of Science ID 000233426004219
Osteonectin/SPARC is epigenetically silenced in AML with MLL gene rearrangements and selectively inhibits the growth of MLL rearranged cell lines
46th Annual Meeting of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2004: 314A–314A
View details for Web of Science ID 000225127501108
Gene expression profiles at diagnosis in de novo childhood AML patients identify FLT3 mutations with good clinical outcomes
2004; 104 (9): 2646-2654
Fms-like tyrosine kinase 3 (FLT3) mutations are associated with unfavorable outcomes in children with acute myeloid leukemia (AML). We used DNA microarrays to identify gene expression profiles related to FLT3 status and outcome in childhood AML. Among 81 diagnostic specimens, 36 had FLT3 mutations (FLT3-MUs), 24 with internal tandem duplications (ITDs) and 12 with activating loop mutations (ALMs). In addition, 8 of 19 specimens from patients with relapses had FLT3-MUs. Predictive analysis of microarrays (PAM) identified genes that differentiated FLT3-ITD from FLT3-ALM and FLT3 wild-type (FLT3-WT) cases. Among the 42 specimens with FLT3-MUs, PAM identified 128 genes that correlated with clinical outcome. Event-free survival (EFS) in FLT3-MU patients with a favorable signature was 45% versus 5% for those with an unfavorable signature (P = .018). Among FLT3-MU specimens, high expression of the RUNX3 gene and low expression of the ATRX gene were associated with inferior outcome. The ratio of RUNX3 to ATRX expression was used to classify FLT3-MU cases into 3 EFS groups: 70%, 37%, and 0% for low, intermediate, and high ratios, respectively (P < .0001). Thus, gene expression profiling identified AML patients with divergent prognoses within the FLT3-MU group, and the RUNX3 to ATRX expression ratio should be a useful prognostic indicator in these patients.
View details for DOI 10.1182/blood-2004-12-4449
View details for Web of Science ID 000224795700014
View details for PubMedID 15251987
Modulation of resistance to idarubicin by the cyclosporin PSC 833 (valspodar) in multidrug-resistant cells.
Journal of experimental therapeutics & oncology
2003; 3 (3): 127-135
Idarubicin (IDA) is an anthracycline anticancer drug utilized in the treatment of acute leukemias. There are conflicting data published with regard to the cross-resistance of IDA in multidrug-resistant (MDR) cells expressing P-glycoprotein (P-gp). We evaluated the cytotoxicity and cellular accumulation of IDA in a panel of anthracycline-selected MDR cell lines. Leukemia K562/R7 cells and sarcoma MES-SA/Dx5 cells expressing high levels of the MDR1 (ABCB1) gene were resistant to IDA (42-fold and 150-fold, respectively). In both of these cell lines, resistance to IDA was equivalent to that for doxorubicin, the drug used to select for the MDR variants. The P-gp inhibitor PSC 833 (valspodar) at 2 microM completely restored sensitivity to IDA. IDA accumulation was decreased 12-fold in MES-SA/Dx5 cells vs parental cell line, and drug uptake was restored to control levels by PSC 833. Reduced intracellular IDA was correlated with P-gp content by flow cytometry. Experiments in NIH3T3 murine cells transfected with the human MDR1 gene substantiated the findings of cross-resistance to IDA and reversal of resistance by PSC 833. Our data indicate that IDA is a high-affinity substrate for P-gp.
View details for PubMedID 14641819
Preferential expression of a mutant allele of the amplified MDR1 (ABCB1) gene in drug-resistant variants of a human sarcoma
GENES CHROMOSOMES & CANCER
2002; 34 (4): 372-383
Activation of the MDR1 (ABCB1) gene is a common event conferring multidrug resistance (MDR) in human cancers. We investigated MDR1 activation in MDR variants of a human sarcoma line, some of which express a mutant MDR1, which facilitated the study of allelic gene expression. Structural alterations of MDR1, gene copy numbers, and allelic expression were analyzed by cytogenetic karyotyping, oligonucleotide hybridization, Southern blotting, polymerase chain reaction, and DNA heteroduplex assays. Both chromosome 7 alterations and several cytogenetic changes involving the 7q21 locus are associated with the development of MDR in these sarcoma cells. Multistep-selected cells and their revertants contain three- to six-fold MDR1 gene amplification compared with that of the drug-sensitive parental cell line MES-SA and single-step doxorubicin-selected mutants. MDR1 gene amplification precedes the emergence of a mutant allele in cells that were coselected with doxorubicin and a cyclosporin inhibitor of P-glycoprotein (P-gp). Allele-specific oligonucleotide hybridization showed that the endogenous mutant allele was present as a single copy, with multiple copies of the normal allele. Reselection of revertant cells with doxorubicin in either the presence or the absence of the P-gp inhibitor resulted in exclusive reexpression of the mutant MDR1 allele, regardless of the presence of multiple wild-type MDR1 alleles. These data provide new insights into how multiple alleles are regulated in the amplicon of drug-resistant cancer cells and indicate that increased expression of an amplified gene can result from selective transcription of a single mutant allele of the gene.
View details for DOI 10.1002/gcc.10067
View details for Web of Science ID 000176495400004
View details for PubMedID 12112526
Pharmacokinetic interactions of cyclosporine with etoposide and mitoxantrone in children with acute myeloid leukemia
2002; 16 (5): 920-927
The purpose of this study was to assess the effect of the multidrug resistance modulator cyclosporine (CsA) on the pharmacokinetics of etoposide and mitoxantrone in children with de novo acute myeloid leukemia (AML). Serial blood samples for pharmacokinetic studies were obtained in 38 children over a 24-h period following cytotoxin treatment with or without CsA on days 1 and 4. Drug concentrations were quantitated using validated HPLC methods, and pharmacokinetic parameters were determined using compartmental modeling with an iterative two-stage approach, implemented on ADAPT II software. Etoposide displayed a greater degree of interindividual variability in clearance and systemic exposure than mitoxantrone. With CsA treatment, etoposide and mitoxantrone mean clearance declined by 71% and 42%, respectively. These effects on clearance, in combination with the empiric 40% dose reduction for either cytotoxin, resulted in a 47% and 12% increases in the mean AUC for etoposide and mitoxantrone, respectively. There were no differences in the rates of stomatitis or infection between the two groups. CsA treatment resulted in an increased incidence of hyperbilrubinemia, which rapidly reversed upon conclusion of drug therapy. The variability observed in clearance, combined with the empiric 40% dose reduction of the cytotoxins, resulted in statistically similar systemic exposure and similar toxicity.
View details for DOI 10.1038/sj/leu/2402455
View details for Web of Science ID 000175631200020
View details for PubMedID 11986955
Mitoxantrone, etoposide, and cyclosporine therapy in pediatric patients with recurrent or refractory acute myeloid leukemia
JOURNAL OF CLINICAL ONCOLOGY
2000; 18 (9): 1867-1875
To determine the remission rate and toxicity of mitoxantrone, etoposide, and cyclosporine (MEC) therapy, multidrug resistance-1 (MDR1) status, and steady-state cyclosporine (CSA) levels in children with relapsed and/or refractory acute myeloid leukemia.MEC therapy consisted of mitoxantrone 6 mg/m(2)/d for 5 days, etoposide 60 mg/m(2)/d for 5 days, and CSA 10 mg/kg for 2 hours followed by 30 mg/kg/d as a continuous infusion for 98 hours. Because of pharmacokinetic interactions, drug doses were decreased to 60% of those found to be effective without coadministration of CSA. MDR1 expression was evaluated by reverse transcriptase polymerase chain reaction, flow cytometry, and the ability of CSA at 2.5 micromol/L to increase intracellular accumulation of (3)H-daunomycin in blasts from bone marrow specimens.The remission rate was 35% (n = 23 of 66). Overall, 35% of patients (n = 23) achieved complete remission (CR), 12% of patients (n = 8) achieved partial remission, and 9% of patients (n = 6) died of infection. Exposure to CSA levels of greater than 2,400 ng/mL was achieved in 95% of patients (n = 56 of 59). Toxicities included infection, cardiotoxicity, myelosuppression, stomatitis, and reversible increases in serum creatinine and bilirubin. In most who had relapsed while receiving therapy or whose induction therapy had failed, response was not significantly different for MDR1-positive and MDR1-negative patients.Serum levels of CSA capable of reversing multidrug resistance are achievable in children with acceptable toxicity. The CR rate of 35% achieved in this study is comparable to previously reported results using standard doses of mitoxantrone and etoposide. The use of CSA may have improved the response rate for the MDR1-positive patients so that it was not different from that for the MDR1-negative patients.
View details for Web of Science ID 000086873900008
View details for PubMedID 10784627
Loss of cyclosporin and azidopine binding are associated with altered ATPase activity by a mutant p-glycoprotein with deleted Phe(335)
2000; 57 (4): 769-777
In this study, we further characterize a mutant P-glycoprotein (P-gp) that has a deletion of Phe(335) and is resistant to inhibition by cyclosporins. Photoaffinity labeling with [(3)H]cyclosporine and [(3)H]azidopine revealed markedly decreased binding to the mutant P-gp compared with wild-type P-gp. Expression of the mutant P-gp in multidrug-resistant variant cell line MES-SA/DxP (DxP) cells was associated with a 2-fold higher basal ATPase activity relative to multidrug-resistant cell line MES-SA/Dx5 (Dx5) cells with wild-type P-gp. Cyclosporine inhibited ATPase activity in both cell types, whereas the cyclosporin D analog valspodar (PSC 833), vinblastine, and dactinomycin stimulated ATPase activity in Dx5 but not in mutant DxP cells. Moreover, the cell lines differed in their responses to verapamil, which produced greater stimulation of ATPase in Dx5 than DxP cells. Verapamil significantly reversed the [(3)H]daunorubicin accumulation defect in wild-type Dx5 cells, but it had no significant effect on [(3)H]daunorubicin accumulation in the mutant DxP cells. Verapamil was not transported by cells expressing either mutant or wild-type P-gp. Vanadate trapping of azido-ATP was markedly impaired in mutant P-gp. In conclusion, our data demonstrate that Phe(335) of transmembrane 6 is an important amino acid residue for the formation of cyclosporine and azidopine drug-binding site(s). Phe(335) also plays a role in the coupling of verapamil binding and modulation of daunorubicin intracellular accumulation in wild-type P-gp. In addition, Phe(335) in transmembrane 6 may play a role in coupling drug binding to ATPase activity. The deletion of Phe(335) results in a significant increase in the basal ATPase activity with a concomitant decrease in its ability to trap ATP and transport some P-gp substrates.
View details for Web of Science ID 000086066500017
View details for PubMedID 10727524
Multidrug-resistant human sarcoma cells with a mutant P-glycoprotein, altered phenotype, and resistance to cyclosporins
JOURNAL OF BIOLOGICAL CHEMISTRY
1997; 272 (9): 5974-5982
A variant of the multidrug-resistant human sarcoma cell line Dx5 was derived by co-selection with doxorubicin and the cyclosporin D analogue PSC 833, a potent inhibitor of the multidrug transporter P-glycoprotein. The variant DxP cells manifest an altered phenotype compared with Dx5, with decreased cross-resistance to Vinca alkaloids and no resistance to dactinomycin. Resistance to doxorubicin and paclitaxel is retained. The multidrug resistance phenotype of DxP cells is not modulated by 2 microM PSC 833 or cyclosporine. DxP cells manifest a decreased ability to transport [3H]cyclosporine. DNA heteroduplex analysis and sequencing reveal a mutant mdr1 gene (deletion of a phenylalanine at amino acid residue 335) in the DxP cell line. The mutant P-glycoprotein has a decreased affinity for PSC 833 and vinblastine and a decreased ability to transport rhodamine 123. Transfection of the mutant mdr1 gene into drug-sensitive MES-SA sarcoma cells confers resistance to both doxorubicin and PSC 833. Our study demonstrates that survival of cells exposed to doxorubicin and PSC 833 in a multistep selection occurred as a result of a P-glycoprotein mutation in transmembrane region 6. These data suggest that Phe335 is an important binding site on P-glycoprotein for substrates such as dactinomycin and vinblastine and for inhibitors such as cyclosporine and PSC 833.
View details for Web of Science ID A1997WK74700086
View details for PubMedID 9038218