Gertjan J L Kaspers

VU University Medical Center, Amsterdamo, North Holland, Netherlands

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Publications (374)2131.28 Total impact

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    ABSTRACT: Chemotherapy resistant leukaemic stem cells (LSC) are thought to be responsible for relapses after therapy in acute myeloid leukaemia (AML). Flow cytometry can discriminate CD34(+) CD38(-) LSC and normal haematopoietic stem cells (HSC) by using aberrant expression of markers and scatter properties. However, not all LSC can be identified using currently available markers, so new markers are needed. CD45RA is expressed on leukaemic cells in the majority of AML patients. We investigated the potency of CD45RA to specifically identify LSC and HSC and improve LSC quantification. Compared to our best other markers (CLL-1, also termed CLEC12A, CD33 and CD123), CD45RA was the most reliable marker. Patients with high percentages (>90%) of CD45RA on CD34(+) CD38(-) LSC have 1·69-fold higher scatter values compared to HSC (P < 0·001), indicating a more mature CD34(+) CD38(-) phenotype. Patients with low (<10%) or intermediate (10-90%) CD45RA expression on LSC showed no significant differences to HSC (1·12- and 1·15-fold higher, P = 0·31 and P = 0·44, respectively). CD45RA-positive LSC tended to represent more favourable cytogenetic/molecular markers. In conclusion, CD45RA contributes to more accurate LSC detection and is recommended for inclusion in stem cell tracking panels. CD45RA may contribute to define new LSC-specific therapies and to monitor effects of anti-LSC treatment.
    No preview · Article · Jan 2016 · British Journal of Haematology
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    ABSTRACT: Expression of apoptosis regulating proteins (BCL-2, MCL-1, BCL-X and BAX) in acute myeloid leukemia (AML) blasts at diagnosis is associated with disease-free survival. We previously found that the initially high apoptosis-resistance of AML cells decreased after therapy, while regaining high levels at relapse. Herein, we further explored this aspect of dynamic apoptosis regulation in AML. Firstly, we showed that the intra-individual ex vivo apoptosis-related profiles of normal lymphocytes and AML blasts within the bone marrow of AML patients were highly correlated. The expression values of apoptosis regulating proteins were far beyond healthy control lymphocytes, which implicates the influence of microenvironmental factors. Secondly, we demonstrated that apoptosis-resistant primary AML blasts, as opposed to apoptosis-sensitive cells, were able to up-regulate BCL-2 expression in sensitive AML blasts in contact cultures (p=0.0067 and p=1.0 respectively). Using secretome proteomics we identified novel proteins possibly engaged in apoptosis regulation. Intriguingly, this analysis revealed that major functional protein clusters engaged in global gene regulation including mRNA splicing, protein translation and chromatin remodeling were more abundant (P=4.01E-06) in secretomes of apoptosis-resistant AML. These findings were confirmed by subsequent extracellular vesicle proteomics. Finally, confocal microscopy-based colocalization studies show that splicing factors-containing vesicles secreted by high AAI cells are taken up by low AAI cells. The current results constitute the first comprehensive analysis of proteins released by apoptosis-resistant and sensitive primary AML cells. Together the data point to vesicle-mediated release of global gene regulatory protein clusters as a plausible novel mechanism of induction of apoptosis resistance. Deciphering the modes of communication between apoptosis-resistant blasts may in perspective lead to the discovery of prognostic tools and development of novel therapeutic interventions, aimed at limiting or overcoming therapy resistance.
    Full-text · Article · Jan 2016 · Molecular & Cellular Proteomics
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    ABSTRACT: Objective: The Psychosocial Assessment Tool (PAT) was developed to screen for psychosocial risk in families of a child diagnosed with cancer. The current study is the first describing the cross-cultural adaptation, reliability, validity, and usability of the PAT in an European country (Dutch translation). METHODS: A total of 117 families (response rate 59%) of newly diagnosed children with cancer completed the PAT2.0 and validation measures. RESULTS: Acceptable reliability was obtained for the PAT total score (α = .72) and majority of subscales (0.50-0.82). Two subscales showed inadequate internal consistency (Social Support α = .19; Family Beliefs α = .20). Validity and usability were adequate. Of the families, 66% scored low (Universal), 29% medium (Targeted), and 5% high (Clinical) risk. CONCLUSIONS: This study confirms the cross-cultural applicability, reliability, and validity of the PAT total score. Reliability left room for improvement on subscale level. Future research should indicate whether the PAT can be used to provide cost-effective care.
    No preview · Article · Dec 2015 · Journal of Pediatric Psychology
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    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.
    Full-text · Article · Dec 2015 · Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K
  • J Parigger · C.M. Zwaan · D Reinhardt · G.J.L. Kaspers
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    ABSTRACT: Gemtuzumab ozogamicin, an anti-tumour antibiotic linked to an anti-CD33 antibody (Mylotarg®), has been well studied in AML in adults but to a lesser extent in children. No review has yet been published on the dose-related toxicity and efficacy of gemtuzumab ozogamicin in pediatric AML patients. Here we looked at 14 studies then scatterplots and linear regressions were used to estimate the relationship between the dose of gemtuzumab and its toxicity and efficacy. A non-significant increase in bilirubin level and in incidence of veno-occlusive disease was seen with higher doses of gemtuzumab ozogamicin when used as single-agent. In terms of efficacy, even a low dose of 3 mg/m(2) of gemtuzumab ozogamicin can have antileukemic effect, but available data do not allow conclusions on its dose-dependency. Data indicate that higher doses of gemtuzumab ozogamicin account for more adverse events. The data do not show that a high dose is required for anti-leukemic efficacy of gemtuzumab ozogamicin. This study also indicates that there seems to be a role for gemtuzumab ozogamicin in the treatment of pediatric AML and further studies are required to assess its optimal dose, schedule and balance between efficacy and side-effects.
    No preview · Article · Dec 2015 · Expert Review of Anti-infective Therapy
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    ABSTRACT: Pediatric acute myeloid leukemia (AML) is a heterogeneous disease, characterized by different collaborating karyotypic and molecular abnormalities, which are used in risk group stratification. In ∼20% of the pediatric AML cases a specific genetic aberration is still unknown. Minimally differentiated myeloid leukemia or FAB-type M0 is a rare morphological subtype of AML. The translocation t(10;17)(p15;q21) is described to be recurrent in minimally differentiated AML, but the involved genes and location of the breakpoints have so far not been identified. In this study, we show that this translocation results in an in-frame translocation fusing exon 12 of the tumor suppressor gene ZMYND11 to exon 3 of the chromatin protein MBTD1, encoding a protein of 1,054 amino acids, while the reciprocal fusion product is predicted to lack a productive start codon. Gene expression profiling of the leukemic cells showed high HOXA expression. ZMYND11, also known as BS69, is a tumor suppressor that specifically recognizes H3K36me3, which is linked to aberrant HOXA expression in leukemogenesis. Aberrant expression of the genes involved in this fusion may thus contribute to the HOXA-phenotype observed with gene expression profiling. © 2015 Wiley Periodicals, Inc.
    No preview · Article · Nov 2015 · Genes Chromosomes and Cancer
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    ABSTRACT: Purpose: This study assessed cardiorespiratory fitness (CRF), physical activity (PA), and sedentary behavior (SB), as well as factors associated with these outcomes in children during or shortly after cancer treatment. Methods: Cross-sectionally, CRF data, obtained by the cardiopulmonary exercise test, and PA and SB data, obtained by an accelerometer, were assessed in children with cancer (8-18 years old). Linear regression models were used to determine associations between CRF, PA, or SB and patient characteristics. Results: Among 60 children with cancer, mean age 12.6 years, 35 boys, 28 % were during cancer treatment. CRF, reported as the z score of VO2peak, showed that 32 children had a VO2peak z score which was -2 below the predicted value. CRF was significantly associated with PA and SB: each additional activity count per minute resulted in 0.05 ml/kg/min VO2peak increase and each additional minute sedentary reduced VO2peak by 0.06 ml/kg/min. Multiple linear regression models of PA and SB showed that decreased activity was significantly associated with higher age, being fatigued, being during childhood cancer treatment (p < 0.001), or having a higher percentage of fat mass. The multiple linear regression model showed that lower CRF was significantly associated with increased fatigue, being during cancer treatment, having a higher percentage of fat mass, and lower belief of own athletic competence (p < 0.001). Conclusion: This study revealed that children during or shortly after cancer treatment have low CRF scores. The most inactive children had a higher fat mass, were fatigued, older, and during childhood cancer treatment. Unexpectedly, treatment-related factors showed no significant association with activity behavior.
    Full-text · Article · Nov 2015 · Supportive Care in Cancer
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    ABSTRACT: Purpose: This retrospective cohort study aimed to determine the predictive relevance of clinical characteristics, additional cytogenetic aberrations, and cKIT and RAS mutations, as well as to evaluate whether specific treatment elements were associated with outcomes in pediatric t(8;21)-positive patients with acute myeloid leukemia (AML). Patients and methods: Karyotypes of 916 pediatric patients with t(8;21)-AML were reviewed for the presence of additional cytogenetic aberrations, and 228 samples were screened for presence of cKIT and RAS mutations. Multivariable regression models were used to assess the relevance of anthracyclines, cytarabine, and etoposide during induction and overall treatment. End points were the probability of achieving complete remission, cumulative incidence of relapse (CIR), probability of event-free survival, and probability of overall survival. Results: Of 838 patients included in final analyses, 92% achieved complete remission. The 5-year overall survival, event-free survival, and CIR were 74%, 58%, and 26%, respectively. cKIT mutations and RAS mutations were not significantly associated with outcome. Patients with deletions of chromosome arm 9q [del(9q); n = 104] had a lower probability of complete remission (P = .01). Gain of chromosome 4 (+4; n = 21) was associated with inferior CIR and survival (P < .01). Anthracycline doses greater than 150 mg/m(2) and etoposide doses greater than 500 mg/m(2) in the first induction course and high-dose cytarabine 3 g/m(2) during induction were associated with better outcomes on various end points. Cumulative doses of cytarabine greater than 30 g/m(2) and etoposide greater than 1,500 mg/m(2) were associated with lower CIR rates and better probability of event-free survival. Conclusion: Pediatric patients with t(8;21)-AML and additional del(9q) or additional +4 might not be considered at good risk. Patients with t(8;21)-AML likely benefit from protocols that have high doses of anthracyclines, etoposide, and cytarabine during induction, as well as from protocols comprising cumulative high doses of cytarabine and etoposide.
    No preview · Article · Nov 2015 · Journal of Clinical Oncology
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    ABSTRACT: Methotrexate (MTX), a folate antagonist which blocks de novo nucleotide biosynthesis and DNA replication, is an anchor drug in acute lymphoblastic leukemia (ALL) treatment. However, drug resistance is a primary hindrance to curative chemotherapy in leukemia and its molecular mechanisms remain poorly understood. We have recently shown that impaired folylpolyglutamate synthetase (FPGS) splicing possibly contributes to the loss of FPGS activity in MTX-resistant leukemia cell line models and adult leukemia patients. However, no information is available on the possible splicing alterations in FPGS in pediatric ALL. Here, using a comprehensive PCR-based screen we discovered and characterized a spectrum of FPGS splicing alterations including exon skipping and intron retention, all of which proved to frequently emerge in both pediatric and adult leukemia patient specimens. Furthermore, an FPGS activity assay revealed that these splicing alterations resulted in loss of FPGS function. Strikingly, pulse-exposure of leukemia cells to antifolates and other chemotherapeutics markedly enhanced the prevalence of several FPGS splicing alterations in antifolate-resistant cells, but not in their parental antifolate-sensitive counterparts. These novel findings suggest that an assortment of deleterious FPGS splicing alterations may constitute a mechanism of antifolate resistance in childhood ALL. Our findings have important implications for the rational overcoming of drug resistance in individual leukemia patients. This article is protected by copyright. All rights reserved.
    No preview · Article · Nov 2015 · International Journal of Cancer

  • No preview · Article · Nov 2015 · Pediatric Blood & Cancer
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    ABSTRACT: Objective: Although survival rates in childhood cancer have improved, prevention and reduction of late effects remain important. This study evaluates the effects of a combined physical exercise and psychosocial intervention on health-related quality of life (HrQoL) and psychosocial functioning in childhood cancer patients. Methods: In this multicenter randomized controlled trial, cancer patients (aged 8-18 years) and their parents filled in questionnaires on HrQoL, depressive symptoms, behavioral problems, and self-esteem. Measurements were conducted at baseline, shortly after the 12-week intervention period and 12 months after baseline. Generalized estimating equations analyses were performed to assess short-term and long-term psychosocial effects. Results: Of the 174 eligible patients, 68 (39.1%) participated. The intervention group consisted of 30 participants at baseline [mean age 13.0 (SD 3.0) years; 53% male], 26 at short-term and 22 at long-term follow-up. The 'care as usual' control group consisted of 38 participants at baseline [mean age 12.6 (SD 3.1) years; 53% male], 33 at short-term and 31 at long-term follow-up. Overall, the intervention did not improve psychosocial functioning and HrQoL. According to parent-proxy reports, the intervention leads to a greater improvement on pain-related HrQoL on both the short (β = 13.4; 95% CI: 3.0; 23.8) and long term (β = 13.0; 95% CI: 1.6; 24.4) and to greater improvement on procedural anxiety immediately after the intervention (β = 12.6; 95% CI: 1.9; 23.3). Conclusion: A combined physical and psychosocial training for children with cancer did not have effects on HrQoL or psychosocial functioning, with exception of modest positive effects on parent-reported pain and procedural anxiety Copyright © 2015 John Wiley & Sons, Ltd.
    Full-text · Article · Oct 2015 · Psycho-Oncology
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    ABSTRACT: Background: More than 90% of patients with diffuse intrinsic pontine glioma (DIPG) will die within 2 years of diagnosis. Patients deteriorate rapidly during the disease course, which severely impairs their quality of life. To date, no specific research on this clinically important subject has been conducted. This study aimed to compile an inventory of symptoms experienced, interventions applied, and current service provision in end-of-life care for DIPG. Methods: We performed a retrospective cohort study of children with DIPG, aged 0-18 years, who received treatment under the care of 2 London hospitals. Symptoms, interventions, and services applied during the 12 weeks before death were analyzed. In addition, we conducted a global questionnaire-study among health care professionals. Results: In more than 78% of DIPG patients, problems concerning mobility, swallowing, communication, consciousness, and breathing arose during end-stage disease. Supportive drugs were widely prescribed. The use of medical aids was only documented in <15% of patients. Palliative and end-of-life care was mostly based on the health care professional's experience; only 21% of the questionnaire respondents reported to have a disease-specific palliative care guideline available. Conclusions: This research assessed the current state of palliative and end-of-life care for children with DIPG. Our results show the variability and complexity of symptoms at end-stage disease and the current lack of disease-specific guidelines for this vulnerable group of patients. This first descriptive paper is intended to act as a solid basis for developing an international clinical trial and subsequent guideline to support high-quality palliative and end-of-life care.
    No preview · Article · Oct 2015 · Neuro-Oncology
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    ABSTRACT: The first cohorts to survive childhood lymphoid malignancies treated with cranial irradiation are now aging into adulthood, and concerns are growing about the development of radiotherapy-induced cognitive deficits in the aging brain. These deficits are hypothesized to increase over time. Their impact on daily functioning of older survivors, and the accompanying need for interventions, should be anticipated. By describing a detailed profile of executive function deficits and their associations with age, specific targets for neuropsychological intervention can be identified. Fifty survivors of childhood lymphoid malignancies and 58 related controls were assessed with the Amsterdam Neuropsychological Tasks program. The survivors were on average 31.1 (4.9) years old, treated with 22.5 (6.8) Gy cranial irradiation, and examined on average 25.5 (3.1) years after diagnosis. The survivors showed significantly decreased response speed, irrespective of the task at hand. Furthermore, we found deficits in working memory capacity, inhibition, cognitive flexibility, executive visuomotor control, attentional fluctuations, and sustained attention. Older age was associated with poorer performance on executive visuomotor control and inhibition. On executive visuomotor control, 50% of female survivors performed more than 1.5 SD below average, versus 15.4% of male survivors. The combination of visuospatial working memory problems and decreasing executive visuomotor control could result in difficulty with learning new motor skills at older ages, like walking with a cane. Deterioration of executive control and inhibition may result in decreased behavioral and emotional regulation in aging survivors. Especially the deficiency in executive visuomotor control in female survivors should be considered for (prophylactic) intervention. ( JINS , 2015, 21 , 1–13)
    Full-text · Article · Sep 2015 · Journal of the International Neuropsychological Society
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    ABSTRACT: Diagnosis, treatment, response monitoring, and outcome of pediatric acute myeloid leukemia (AML) have made enormous progress during the past decades. Because AML is a rare type of childhood cancer, with an incidence of approximately seven occurrences per 1 million children annually, national and international collaborative efforts have evolved. This overview describes these efforts and includes a summary of the history and contributions of each of the main collaborative pediatric AML groups worldwide. The focus is on translational and clinical research, which includes past, current, and future clinical trials. Separate sections concern acute promyelocytic leukemia, myeloid leukemia of Down syndrome, and relapsed AML. A plethora of novel antileukemic agents that have emerged, including new classes of drugs, are summarized as well. Finally, an important aspect of the treatment of pediatric AML-supportive care-and late effects are discussed. The future is bright, with a wide range of emerging innovative therapies and with more and more international collaboration that ultimately aim to cure all children with AML, with fewer adverse effects and without late effects.
    No preview · Article · Aug 2015 · Journal of Clinical Oncology
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    ABSTRACT: Use of complementary and alternative medicine (CAM) is common among patients with childhood cancer. Health-care providers (HCP) should address this need properly. Geographical and cultural differences seem likely. This study explores perspectives on CAM of HCP involved in the care of children with cancer in Netherlands and Indonesia. Health beliefs, components of CAM, encouraging or discouraging CAM, and knowledge about CAM were assessed. We conducted a cross-sectional study using semi-structured questionnaires at a Dutch and Indonesian academic hospital. A total of 342 HCP participated: 119 Dutch (response rate 80%) and 223 Indonesian (response rate 87%). Chemotherapy can cure cancer according to more Dutch than Indonesian HCP (87% vs. 53% respectively, P < 0.001). Combination of chemotherapy and CAM is the best way to cure cancer according to more Indonesian than Dutch HCP (45% vs. 25%, P < 0.001). Dutch and Indonesian HCP recommend and discourage CAM use differently. Most Dutch (77%) and Indonesian HCP (84%) consider their knowledge about CAM to be inadequate (P = ns). Fewer Dutch doctors than other HCP want to learn more about CAM (51% vs. 76%, P = 0.007), whereas there is no significant difference in eagerness to learn about CAM between Indonesian doctors (64%) and other HCP (72%). Indonesian HCP have more positive views about CAM than their Dutch colleagues. Both Dutch and Indonesian HCP consider their knowledge about CAM to be inadequate. Therefore, education programs about CAM tailored to the needs of HCP are recommended, knowing that CAM is used frequently. Pediatr Blood Cancer © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    Full-text · Article · Aug 2015 · Pediatric Blood & Cancer
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    ABSTRACT: At the government, hospital, and health-care provider level, corruption plays a major role in health-care systems in Africa. The returns on health investments of international financial institutions, health organisations, and donors might be very low when mismanagement and dysfunctional structures of health-care systems are not addressed. More funding might even aggravate corruption. We discuss corruption and its effects on cancer care within the African health-care system in a sociocultural context. The contribution of high-income countries in stimulating corruption is also described. Corrupt African governments cannot be expected to take the initiative to eradicate corruption. Therefore, international financial institutions, health organisations, and financial donors should use their power to demand policy reforms of health-care systems in Africa troubled by the issue of corruption. These modifications will ameliorate the access and quality of cancer care for patients across the continent, and ultimately improve the outcome of health care to all patients. Copyright © 2015 Elsevier Ltd. All rights reserved.
    No preview · Article · Aug 2015 · The Lancet Oncology

  • No preview · Article · Aug 2015 · Cancer Research
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    ABSTRACT: Background: Retinoblastoma is a pediatric eye cancer associated with RB1 loss or MYCN amplification (RB1+/+MYCNA). There are controversies concerning the existence of molecular subtypes within RB1−/− retinoblastoma. To test whether these molecular subtypes exist, we performed molecular profiling. Methods: Genome-wide mRNA expression profiling was performed on 76 primary human retinoblastomas. Expression profiling was complemented by genome-wide DNA profiling and clinical, histopathological, and ex vivo drug sensitivity data. Findings: RNA and DNA profiling identified major variability between retinoblastomas. While gene expression differences between RB1+/+MYCNA and RB1−/− tumors seemed more dichotomous, differences within the RB1−/− tumors were gradual. Tumors with high expression of a photoreceptor gene signature were highly differentiated, smaller in volume and diagnosed at younger age compared with tumors with low photoreceptor signature expression. Tumors with lower photoreceptor expression showed increased expression of genes involved in M-phase and mRNA and ribosome synthesis and increased frequencies of somatic copy number alterations. Interpretation: Molecular, clinical and histopathological differences between RB1−/− tumors are best explained by tumor progression, reflected by a gradual loss of differentiation and photoreceptor expression signature. Since copy number alterations were more frequent in tumors with less photoreceptorness, genomic alterations might be drivers of tumor progression. Research in context: Retinoblastoma is an ocular childhood cancer commonly caused by mutations in the RB1 gene. In order to determine optimal treatment, tumor subtyping is considered critically important. However, except for very rare retinoblastomas without an RB1 mutation, there are controversies as to whether subtypes of retinoblastoma do exist. Our study shows that retinoblastomas are highly diverse but rather than reflecting distinct tumor types with a different etiology, our data suggests that this diversity is a result of tumor progression driven by cumulative genetic alterations. Therefore, retinoblastomas should not be categorized in distinct subtypes, but be described according to their stage of progression.
    Full-text · Article · Jul 2015 · EBioMedicine

  • No preview · Conference Paper · Jun 2015
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    ABSTRACT: Methotrexate (MTX) eradicates leukemic cells by disrupting de novo nucleotide biosynthesis and DNA replication, resulting in cell death. Since its introduction in 1947, MTX-containing chemotherapeutic regimens have proven instrumental in achieving curative effects in acute lymphoblastic leukemia (ALL). However, drug resistance phenomena pose major obstacles to efficacious ALL chemotherapy. Moreover, clinically relevant molecular mechanisms underlying chemoresistance remain largely obscure. Several alterations in MTX metabolism, leading to impaired accumulation of this cytotoxic agent in tumor cells, have been classified as determinants of MTX resistance. However, the relation between MTX resistance and long-term clinical outcome of ALL has not been shown previously. We have collected clinical data for 235 childhood ALL patients, for whom samples taken at the time of diagnosis were also broadly characterized with respect to MTX resistance. This included measurement of concentrations of MTX polyglutamates in leukemic cells, mRNA expression of enzymes involved in MTX metabolism (FPGS, FPGH, RFC, DHFR, and TS), MTX sensitivity as determined by the TS inhibition assay, and FPGS activity. Herein we demonstrate that higher accumulation of long-chain polyglutamates of MTX is strongly associated with better overall (10-year OS: 90.6 vs 64.1 %, P = 0.008) and event-free survival (10-year EFS: 81.2 vs 57.6 %, P = 0.029) of ALL patients. In addition, we assessed both the association of several MTX resistance-related parameters determined in vitro with treatment outcome as well as clinical characteristics of pediatric ALL patients treated with MTX-containing combination chemotherapy. High MTX sensitivity was associated with DNA hyperdiploid ALL (P < 0.001), which was linked with increased MTX accumulation (P = 0.03) and elevated reduced folate carrier (RFC) expression (P = 0.049) in this subset of ALL patients. TEL-AML1 fusion was associated with increased MTX resistance (P = 0.023). Moreover, a low accumulation of MTX polyglutamates was observed in MLL-rearranged and TEL-AML1 rearranged ALL (P < 0.05). These findings emphasize the central role of MTX in ALL treatment thereby expanding our understanding of the molecular basis of clinical differences in treatment response between ALL individuals. In particular, the identification of patients that are potentially resistant to MTX at diagnosis may allow for tailoring novel treatment strategies to individual leukemia patients.
    Full-text · Article · May 2015 · Journal of Hematology & Oncology

Publication Stats

7k Citations
2,131.28 Total Impact Points


  • 2002-2015
    • VU University Medical Center
      • • Department of Clinical Genetics
      • • Department of Pediatrics
      • • Department of Orthopedic Surgery
      • • Department of Haematology
      Amsterdamo, North Holland, Netherlands
    • University of Hamburg
      Hamburg, Hamburg, Germany
    • EUREGIO-KLINIK Albert-Schweitzer-Straße GmbH
      Nordhorn, Lower Saxony, Germany
    • Karmanos Cancer Institute
      Detroit, Michigan, United States
  • 1993-2015
    • VU University Amsterdam
      • Department of Pediatric Hematology/Oncology
      Amsterdamo, North Holland, Netherlands
  • 2013
    • University Medical Center Utrecht
      Utrecht, Utrecht, Netherlands
  • 2006-2013
    • Dutch Childhood Oncology Group
      Rotterdam, South Holland, Netherlands
  • 2009
    • University of Groningen
      Groningen, Groningen, Netherlands
    • Charles University in Prague
      • Department of Paediatric Haematology and Oncology (2. LF)
      Praha, Praha, Czech Republic
    • Aarhus University Hospital
      • Department of Pediatrics
      Aarhus, Central Jutland, Denmark
    • Erasmus MC
      Rotterdam, South Holland, Netherlands
  • 2008
    • Università degli Studi di Milano-Bicocca
      Milano, Lombardy, Italy
  • 2003-2005
    • Oregon Health and Science University
      Portland, Oregon, United States
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany
    • Kent Hospital
      Warwick, Rhode Island, United States
  • 1993-2000
    • University of Amsterdam
      • Department of Paediatrics
      Amsterdamo, North Holland, Netherlands
  • 1995
    • Erasmus Universiteit Rotterdam
      Rotterdam, South Holland, Netherlands
  • 1994
    • Post University
      Post, Texas, United States