Thorsten Zenz

National Center for Tumor Diseases (NCT) Heidelberg, Heidelburg, Baden-Württemberg, Germany

Are you Thorsten Zenz?

Claim your profile

Publications (92)738.17 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Telomere shortening is of pathogenic and prognostic importance in cancers. Here we analyzed telomere length in 73 mantle cell lymphoma (MCL), 55 chronic lymphocytic leukemia (CLL) and 20 normal B-cell samples using quantitative PCR (Q-PCR) to study its association with disease characteristics as well as outcome. Telomere length was found highly variable in MCL (range 2.2-13.8 kb, median 4.3 kb). Telomere dysfunction in MCL was evident from comparison with normal B-cells (median 7.5 kb) but had no significant association with any biological or clinical feature. This was in contrast to CLL, where a significant correlation of short telomeres with poor prognostic subgroups was confirmed. There was a trend towards an increased number of genomic aberrations with shortening of telomeres in MCL. No difference in survival was observed between the groups with short and long telomeres, indicating that, as opposed to CLL, telomere length is not of prognostic relevance in MCL.
    Blood 12/2012; · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic lymphocytic leukemia (CLL) with 17p deletion or mutations of the TP53 gene has a very poor outcome. Optimal treatment of these patients remains a major clinical challenge, and disagreement on the optimal treatment approach exists. Conventional chemo-immunotherapy with rituximab in combination with purine analogues yields lower response-rates and less satisfactory results than for CLL patients with intact p53. Allogeneic stem cell transplantation may allow long-term remissions in this challenging group of patients. In this review, we will discuss current treatment options as well as experimental approaches in clinical trials for CLL patients with deleted or mutated TP53. Particular emphasis will be placed on novel agents with the potential to change clinical practice and future perspectives for the management of these "highest risk" patients.
    Current Hematologic Malignancy Reports 11/2012;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Burkitt lymphoma is a mature aggressive B-cell lymphoma derived from germinal center B cells. Its cytogenetic hallmark is the Burkitt translocation t(8;14)(q24;q32) and its variants, which juxtapose the MYC oncogene with one of the three immunoglobulin loci. Consequently, MYC is deregulated, resulting in massive perturbation of gene expression. Nevertheless, MYC deregulation alone seems not to be sufficient to drive Burkitt lymphomagenesis. By whole-genome, whole-exome and transcriptome sequencing of four prototypical Burkitt lymphomas with immunoglobulin gene (IG)-MYC translocation, we identified seven recurrently mutated genes. One of these genes, ID3, mapped to a region of focal homozygous loss in Burkitt lymphoma. In an extended cohort, 36 of 53 molecularly defined Burkitt lymphomas (68%) carried potentially damaging mutations of ID3. These were strongly enriched at somatic hypermutation motifs. Only 6 of 47 other B-cell lymphomas with the IG-MYC translocation (13%) carried ID3 mutations. These findings suggest that cooperation between ID3 inactivation and IG-MYC translocation is a hallmark of Burkitt lymphomagenesis.
    Nature Genetics 11/2012; · 35.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In chronic lymphocytic leukaemia (CLL), TP53 mutation and deletion are strongly associated with one another and with adverse clinical outcome. Mutant TP53 protein typically accumulates to high levels and has been reported to have transcriptional regulatory activity distinct from that of wild-type TP53. To investigate whether such an effect is relevant to CLL, carefully balanced primary CLL samples with or without TP53 mutation/deletion were compared for their gene expression profiles using high-density DNA microarrays. Ninety-six and eight differentially expressed genes were identified, respectively, using two alternative statistical approaches with different stringencies. None of the differentially expressed genes were known to be regulated by mutant TP53, and only four of the 67 under-expressed genes were known transcriptional targets of wild-type TP53. Significantly, both approaches showed that gene under-expression was the dominant feature of TP53-mutant CLL samples. Furthermore, a disproportionate number of the under-expressed genes were located on chromosome 17p, the most significant being TP53 itself. Together, these results indicate that any transcriptional regulatory effects of mutant TP53 in CLL cells are overshadowed by the under-expression of co-deleted TP53 and other genes on chromosome 17p. Our findings have implications for emerging therapeutic strategies that target mutant TP53.
    British Journal of Haematology 10/2012; · 4.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: ABSTRACT BRAF mutations have been shown to occur at high frequency in melanoma and thyroid cancer, but also at lower frequencies in hematological malignancies. To assess the potential role of BRAF, we have sequenced exon 11 and 15 of BRAF in 138 cases with CLL and 32 cases of B-PLL. We found an incidence of BRAF mutations of 2.8% in CLL (4/138), while no cases with B-PLL showed BRAF mutations. The analysis of a cohort of F-refractory patients (n=87) showed no increase in the mutation incidence suggesting that this mutation is not selected for during the disease progression. A limited analysis of the effect of BRAF inhibition in primary CLL cells showed no cell death induction in CLL samples with and without BRAF mutations. Our analysis suggests that BRAF mutations occur at low frequency in CLL. The pharmacological inhibition of MEK/ERK signaling using the mutant BRAF inhibitor PLX4720 showed no effect on viability in vitro in CLL cases.
    Leukemia & lymphoma 10/2012; · 2.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Translocations affecting chromosome subband 6p25.3 containing the IRF4 gene have been recently described as characteristic alterations in a molecularly distinct subset of germinal center B-cell-derived lymphomas. Secondary changes have yet only been described in few of these lymphomas. Here, we performed array-comparative genomic hybridization and molecular inversion probe microarray analyses on DNA from 12 formalin-fixed paraffin-embedded and two fresh-frozen IRF4 translocation-positive lymphomas, which together with the previously published data on nine cases allowed the extension of copy number analyses to a total of 23 of these lymphomas. All except one case carried chromosomal imbalances, most frequently gains in Xq28, 11q22.3-qter, and 7q32.1-qter and losses in 6q13-16.1, 15q14-22.31, and 17p. No recurrent copy-neutral losses of heterozygosity were observed. TP53 point mutations were detected in three of six cases with loss of 17p. Overall this study unravels a recurrent pattern of secondary genetic alterations in IRF4 translocation-positive lymphomas. © 2012 Wiley Periodicals, Inc.
    Genes Chromosomes and Cancer 10/2012; · 3.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To identify genomic alterations in chronic lymphocytic leukemia (CLL), we performed single-nucleotide polymorphism (SNP)-array analysis (Affymetrix 6.0) on 353 samples from untreated patients entered on the CLL8 treatment trial. Based on paired-sample analysis (n=144), a mean of 1.8 copy number alterations (CNAs) per case were identified; about 60% of cases carried no CNAs other than those detected by fluorescence in-situ hybridization analysis. Copy-neutral loss-of-heterozygosity was detected in 6% of cases, and most frequently found on 13q, 17p and 11q. Minimally deleted regions were refined on 13q14 (deleted in 61% of cases) to the DLEU1 and DLEU2 genes, on 11q22.3 (27%) to ATM, on 2p16.1-2p15 (gained in 7%) to a 1.9 Mb fragment containing 9 genes, and on 8q24.21 (5%) to a segment 486 Kb proximal of the MYC locus. 13q deletions exhibited proximal and distal breakpoint cluster regions. Among the most common novel lesions were deletions at 15q15.1 (4%), with the smallest deletion (70.48 Kb) found in the MGA locus. Sequence analysis of MGA in 59 samples revealed a truncating mutation in one case lacking a 15q deletion. MNT at 17p13.3, which in addition to MGA and MYC encodes for the network of MAX-interacting proteins, was also found recurrently deleted.
    Blood 10/2012; · 9.78 Impact Factor
  • Source
    Mikołaj Słabicki, Thorsten Zenz
    Leukemia & lymphoma 08/2012; 53(11):2101-2. · 2.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, the p53-miR-34a network has been identified to have an important role in tumorigenesis. As in acute myeloid leukemia with complex karyotype (CK-AML) TP53 alterations are the most common known molecular lesion, we further analyzed the p53-miR-34a axis in a large cohort of CK-AML with known TP53 status (TP53(altered), n=57; TP53(unaltered), n=31; altered indicates loss and/or mutation of TP53). Profiling microRNA (miRNA) expression delineated TP53 alteration-associated miRNA profiles, and identified miR-34a and miR-100 as the most significantly down- and upregulated miRNA, respectively. Moreover, we found a distinct miR-34a expression-linked gene expression profile enriched for genes belonging to p53-associated pathways, and implicated in cell cycle progression or apoptosis. Clinically, low miR-34a expression and TP53 alterations predicted for chemotherapy resistance and inferior outcome. Notably, in TP53(unaltered) CK-AML, high miR-34a expression predicted for inferior overall survival (OS), whereas in TP53(biallelic altered) CK-AML, high miR-34a expression pointed to better OS. Thus, detailed molecular profiling links impaired p53 to decreased miR-34a expression, but also identifies p53-independent miR-34a induction mechanisms as shown in TP53(biallelic altered) cell lines treated with 15-deoxy-Δ(12,14)-prostaglandin. An improved understanding of this mechanism might provide novel therapeutic options to restore miR-34a function and thereby induce cell cycle arrest and apoptosis in TP53(altered) CK-AML.Leukemia advance online publication, 10 August 2012; doi:10.1038/leu.2012.208.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 07/2012; · 10.16 Impact Factor
  • New England Journal of Medicine 05/2012; 366(21):2038-40. · 51.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Standardized criteria for diagnosis and response evaluation in chronic lymphocytic leukemia (CLL) are essential to achieve comparability of results and improvement of clinical care. With the increasing range of therapeutic options, the treatment context is important when defining refractory CLL. Refractory CLL has been defined as no response or response lasting ≤ 6 months from last therapy. This subgroup has a very poor outcome, and many trials use this group as an entry point for early drug development. With the intensification of first-line regimens, the proportion of patients with refractory CLL using these criteria decreases. This has immediate consequences for recruitment of patients into trials as well as salvage strategies. Conversely, patients who are not refractory according to the traditional definition but who have suboptimal or short response to intense therapy also have a very poor outcome. In this Perspective, we discuss recent results that may lead to a reassessment of risk categories in CLL focusing on fit patients who are eligible for all treatment options. We cover aspects of the history and biologic basis for refractory CLL and will focus on how emerging data on treatment failure from large trials using chemoimmunotherapy may help to define risk groups in CLL.
    Blood 03/2012; 119(18):4101-7. · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic lymphocytic leukemia (CLL) shows a heterogeneous clinical course, which can be explained in part by prognostic factors. Most patients do not need treatment at the time of first diagnosis. The identification of prognostic factors is of major interest if strategies can be devised to treat patients according to their individual risk profile or biological subgroup. Currently, in spite of a wealth of prognostic factors, individualized treatment approaches in different genetic or risk groups are the exemption in CLL. This review summarizes the most important prognostic and predictive factors in CLL, with particular emphasis on factors affecting treatment decisions in clinical trials and routine practice.
    Current Hematologic Malignancy Reports 03/2012; 7(1):3-12.
  • [Show abstract] [Hide abstract]
    ABSTRACT: To determine the clinical significance of flow cytometric minimal residual disease (MRD) quantification in chronic lymphocytic leukemia (CLL) in addition to pretherapeutic risk factors and to compare the prognostic impact of MRD between the arms of the German CLL Study Group CLL8 trial. MRD levels were prospectively quantified in 1,775 blood and bone marrow samples from 493 patients randomly assigned to receive fludarabine and cyclophosphamide (FC) or FC plus rituximab (FCR). Patients were categorized by MRD into low- (< 10(-4)), intermediate- (≥ 10(-4) to <10(-2)), and high-level (≥ 10(-2)) groups. Low MRD levels during and after therapy were associated with longer progression-free survival (PFS) and overall survival (OS; P < .0001). Median PFS is estimated at 68.7, 40.5, and 15.4 months for low, intermediate, and high MRD levels, respectively, when assessed 2 months after therapy. Compared with patients with low MRD, greater risks of disease progression were associated with intermediate and high MRD levels (hazard ratios, 2.49 and 14.7, respectively; both P < .0001). Median OS was 48.4 months in patients with high MRD and was not reached for lower MRD levels. MRD remained predictive for OS and PFS in multivariate analyses that included the most important pretherapeutic risk markers in CLL. PFS and OS did not differ between treatment arms within each MRD category. However, FCR induced low MRD levels more frequently than FC. MRD levels independently predict OS and PFS in CLL. Therefore, MRD quantification might serve as a surrogate marker to assess treatment efficacy in randomized trials before clinical end points can be evaluated.
    Journal of Clinical Oncology 02/2012; 30(9):980-8. · 18.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent evidence suggests that - in addition to 17p deletion - TP53 mutation is an independent prognostic factor in chronic lymphocytic leukemia (CLL). Data from retrospective analyses and prospective clinical trials show that ∼5% of untreated CLL patients with treatment indication have a TP53 mutation in the absence of 17p deletion. These patients have a poor response and reduced progression-free survival and overall survival with standard treatment approaches. These data suggest that TP53 mutation testing warrants integration into current diagnostic work up of patients with CLL. There are a number of assays to detect TP53 mutations, which have respective advantages and shortcomings. Direct Sanger sequencing of exons 4-9 can be recommended as a suitable test to identify TP53 mutations for centers with limited experience with alternative screening methods. Recommendations are provided on standard operating procedures, quality control, reporting and interpretation. Patients with treatment indications should be investigated for TP53 mutations in addition to the work-up recommended by the International workshop on CLL guidelines. Patients with TP53 mutation may be considered for allogeneic stem cell transplantation in first remission. Alemtuzumab-based regimens can yield a substantial proportion of complete responses, although of short duration. Ideally, patients should be treated within clinical trials exploring new therapeutic agents.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 02/2012; 26(7):1458-61. · 10.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the frequency of TP53 alterations and their correlation with other genetic changes and outcome in acute myeloid leukemia with complex karyotype (CK-AML), we performed integrative analysis using TP53 mutational screening and array-based genomic profiling in 234 CK-AMLs. TP53 mutations were found in 141 of 234 (60%) and TP53 losses were identified in 94 of 234 (40%) CK-AMLs; in total, 164 of 234 (70%) cases had TP53 alterations. TP53-altered CK-AML were characterized by a higher degree of genomic complexity (aberrations per case, 14.30 vs 6.16; P < .0001) and by a higher frequency of specific copy number alterations, such as -5/5q-, -7/7q-, -16/16q-, -18/18q-, +1/+1p, and +11/+11q/amp11q13∼25; among CK-AMLs, TP53-altered more frequently exhibited a monosomal karyotype (MK). Patients with TP53 alterations were older and had significantly lower complete remission rates, inferior event-free, relapse-free, and overall survival. In multivariable analysis for overall survival, TP53 alterations, white blood cell counts, and age were the only significant factors. In conclusion, TP53 is the most frequently known altered gene in CK-AML. TP53 alterations are associated with older age, genomic complexity, specific DNA copy number alterations, MK, and dismal outcome. In multivariable analysis, TP53 alteration is the most important prognostic factor in CK-AML, outweighing all other variables, including the MK category.
    Blood 12/2011; 119(9):2114-21. · 9.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is remarkable heterogeneity in the clinical course and biological characteristics of patient subgroups with chronic lymphocytic leukemia (CLL). Mutations of key tumor suppressors (ATM, miR-15a/16-1 and TP53) have been identified in CLL, and these aberrations are important "drivers" of the disease and some of its clinical characteristics. While some mutations are associated with poor outcome [particularly del(17p) and TP53 mutation], others are linked to a favorable clinical course [e.g. del(13q) as sole aberration]. In addition to genetic aberrations, antigen drive and microenvironmental interactions contribute to the pathogenesis of CLL. How the genetic aberrations impact on the process of antigen drive or microenvironmental interactions is currently unclear. Our improved understanding of the biology and clinical course of specific genetic subgroups is beginning to be translated into more specific and targeted treatment approaches. As a result, genetic subgroups are treated in distinct protocols. This review summarizes the contribution of the microenvironment and the most important genetic aberrations in CLL and how our improved knowledge of the biology of CLL may translate into improved treatment results.
    Leukemia & lymphoma 12/2011; 53(6):1023-31. · 2.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Environmental conditions in lymph node proliferation centers protect chronic lymphocytic leukemia (CLL) cells from apoptotic triggers. This situation can be mimicked by in vitro stimulation with CD40 ligand (CD40L) and interleukin 4 (IL-4). Our study investigates the impact of the drug leflunomide to overcome apoptosis resistance of CLL cells. CLL cells were stimulated with CD40L and IL-4 and treated with fludarabine and the leflunomide metabolite A771726. Resistance to fludarabine-mediated apoptosis was induced by CD40 activation alone stimulating high levels of BCL-XL and MCL1 protein expression. Apoptosis resistance was further enhanced by a complementary Janus-activated kinase (JAK)/STAT signal induced by IL-4. In contrast, CLL proliferation required both a CD40 and a JAK/STAT signal and could be completely blocked by pan-JAK inhibition. Leflunomide (A771726) antagonized CD40L/IL-4-induced proliferation at very low concentrations (3 μg/mL) reported to inhibit dihydroorotate dehydrogenase. At a concentration of 10 μg/mL, A771726 additionally attenuated STAT3/6 phosphorylation, whereas apoptosis of CD40L/IL-4-activated ("resistant") CLL cells was achieved with higher concentrations (IC(50): 80 μg/mL). Apoptosis was also effectively induced by A771726 in clinically refractory CLL cells with and without a defective p53 pathway. Induction of apoptosis involved inhibition of NF-κB activity and loss of BCL-XL and MCL1 expression. In combination with fludarabine, A771726 synergistically induced apoptosis (IC(50): 56 μg/mL). We thus show that A771726 overcomes CD40L/IL-4-mediated resistance to fludarabine in CLL cells of untreated as well as clinically refractory CLL cells. We present a possible novel therapeutic principle for attacking chemoresistant CLL cells.
    Clinical Cancer Research 11/2011; 18(2):417-31. · 7.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The tetraspanin CD37 is widely expressed in B-cell malignancies and represents an attractive target for immunotherapy with mAbs. We have chimerized a high-affinity mouse Ab to CD37 and engineered the CH2 domain for improved binding to human Fcγ receptors. The resulting mAb 37.1 showed high intrinsic proapoptotic activity on malignant B cells accompanied by homotypic aggregation. Furthermore, the Ab-mediated high Ab-dependent cell-mediated cytotoxicity (ADCC) on lymphoma and primary CLL cells. mAb 37.1 strongly depleted normal B cells as well as spiked B-lymphoma cells in blood samples from healthy donors as well as malignant B cells in blood from CLL patients. In all assays, mAb 37.1 was superior to rituximab in terms of potency and maximal cell lysis. A single dose of mAb CD37.1 administered to human CD37-transgenic mice resulted in a reversible, dose-dependent reduction of peripheral B cells. In a Ramos mouse model of human B-cell lymphoma, administration of mAb 37.1 strongly suppressed tumor growth. Finally, a surrogate Fc-engineered Ab to macaque CD37, with in vitro proapoptotic and ADCC activities very similar to those of mAb 37.1, induced dose-dependent, reversible B-cell depletion in cynomolgus monkeys. In conclusion, the remarkable preclinical pharmacodynamic and antitumor effects of mAb 37.1 warrant clinical development for B-cell malignancies.
    Blood 07/2011; 118(15):4159-68. · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic lymphocytic leukaemia (CLL) cells convert CD14(+) cells from patients into 'nurse-like' cells (NLCs). CLL cells can also convert CD14(+) peripheral blood mononuclear cells (PBMCs) from healthy donors into cells with morphological similarities to NLCs (CD14(CLL) -cells). However it is unclear whether only CLL cells induce this conversion process. This study showed that CD14(+) PBMCs from healthy donors could also be converted into differentiated cells (CD14(B) -cells) by non-malignant B-cells. In order to identify changes specifically induced by CLL cells, we compared gene expression profiles of NLCs, CD14(CLL) -cells and CD14(B) -cells. CD14(+) cells cultured with CLL cells were more similar to NLCs than those cultured with non-malignant B-cells. The most significant changes induced by CLL cells were deregulation of the antigen presentation pathway and of genes related to immunity. NLCs had reduced levels of lysozyme activity, CD74 and HLA-DR in-vitro while expression of inhibitory FCGR2B was increased. These findings suggest an impaired immunocompetence of NLCs which, if found in-vivo, could contribute to the immunodeficiency in CLL patients.
    British Journal of Haematology 05/2011; 154(3):349-56. · 4.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recurrent losses or gains of genomic material as well as mutations of key tumor suppressors (ATM and TP53) have been identified in chronic lymphocytic leukemia (CLL). These aberrations are important "drivers" of the disease and some of its clinical characteristics. There is a remarkable heterogeneity in the clinical course between patient subgroups with distinct genetic features. While some mutations are associated with poor outcome (particularly 17p- and TP53 mutation and to a lesser extend 11q-) others are linked to a favorable outcome (13q- as sole aberration; mutated IGHV). Our improved understanding of the clinical course of specific genetic subgroups is beginning to be translated into genotype specific treatment approaches where genetic subgroups (e.g. 17p-) are channeled into separate treatment protocols. This review will summarize the most important genetic aberrations in CLL and how our improved knowledge of the genetic make-up of leukemic cells may translate into improved treatment results.
    Blood reviews 03/2011; 25(3):131-7. · 7.19 Impact Factor

Publication Stats

2k Citations
738.17 Total Impact Points

Institutions

  • 2012–2014
    • National Center for Tumor Diseases (NCT) Heidelberg
      Heidelburg, Baden-Württemberg, Germany
    • Masaryk University
      Brünn, South Moravian, Czech Republic
  • 2010–2013
    • German Cancer Research Center
      • • Division of Molecular Genetics
      • • Division of Translational Oncology
      Heidelberg, Baden-Wuerttemberg, Germany
    • Universität Heidelberg
      • • V. Medicine Clinic
      • • University Hospital of Internal Medicine
      Heidelberg, Baden-Wuerttemberg, Germany
    • University of Cologne
      Köln, North Rhine-Westphalia, Germany
  • 2003–2013
    • Universität Ulm
      • Department of Internal Medicine
      Ulm, Baden-Wuerttemberg, Germany
  • 2011
    • University of Texas MD Anderson Cancer Center
      Houston, Texas, United States