Christine Damm-Welk

The human formin-binding protein 17 (FBP17) interacts with sorting nexin, SNX2, and is an MLL-fusion partner in acute myelogeneous leukemia

We have cloned a fusion partner of the MLL gene at 11q23 and identified it as the gene encoding the human formin-binding protein 17, FBP17. It maps to chromosome 9q34 centromeric to ABL. The gene fusion results from a complex chromosome rearrangement that was resolved by fluorescence in situ hybridization with various probes on chromosomes 9 and 11 as an ins(11;9)(q23;q34)inv(11)(q13q23). The rearrangement resulted in a 5′-MLL/FBP17-3′ fusion mRNA. We retrovirally transduced murine-myeloid progenitor cells with MLL/FBP17 to test its transforming ability. In contrast to MLL/ENL, MLL/ELL and other MLL-fusion genes, MLL/FBP17 did not give a positive readout in a serial replating assay. Therefore, we assume that additional cooperating genetic abnormalities might be needed to establish a full malignant phenotype. FBP17 consists of a C-terminal Src homology 3 domain and an N-terminal region that is homologous to the cell division cycle protein, cdc15, a regulator of the actin cytoskeleton in Schizosaccharomyces pombe. Both domains are separated by a consensus Rho-binding motif that has been identified in different Rho-interaction partners such as Rhotekin and Rhophilin. We evaluated whether FBP17 and members of the Rho family interact in vivo with a yeast two-hybrid assay. None of the various Rho proteins tested, however, interacted with FBP17. We screened a human kidney library and identified a sorting nexin, SNX2, as a protein interaction partner of FBP17. These data provide a link between the epidermal growth factor receptor pathway and an MLL fusion protein.

Correlation of the autoantibody response to the ALK oncoantigen in pediatric anaplastic lymphoma kinase–positive anaplastic large cell lymphoma with tumor dissemination and relapse risk

Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) constitutes an ideal model disease to study tumor-specific immune responses. All the tumor cells express oncogenic ALK resulting from a chromosomal translocation involved in lymphomagenesis. Although antibodies and T-cell responses to ALK have previously been detected in ALK-positive ALCL patients, their prognostic significance is unknown. We investigated a large cohort of uniformly treated ALK-positive pediatric ALCL patients to ascertain whether the titers of preexisting ALK autoantibodies correlated with clinical and histologic characteristics, tumor dissemination, and patient outcome. ALK autoantibodies were analyzed in pretherapeutic serum samples from 95 patients enrolled into 2 therapy studies between 1996 and 2007. ALK autoantibodies were detected in 87/95 patients. The titers inversely correlated with stage and amount of circulating tumor cells. High antibody titers correlated with significantly lower cumulative incidence of relapses (CI-R): titers > or = 1/60 750, n = 29, CI-R 11% +/- 6%; titers 1/2025-< 1/60 750, n = 39, CI-R 31% +/- 8%; and titers 0-< or = 1/750, n = 27, CI-R of 63% +/- 10% (P < .001). Our results provide the first clinical evidence that a robust preexisting immune response to an oncoantigen resulting from an oncogenic chromosomal translocation inhibits lymphoma dissemination and decreases the risk of relapse.

A recurrent 11q aberration pattern characterizes a subset of MYC-negative high-grade B-cell lymphomas resembling Burkitt lymphoma

The genetic hallmark of Burkitt lymphoma (BL) is the t(8;14)(q24;q32) and its variants leading to activation of the MYC oncogene. It is a matter of debate whether true BL without MYC translocation exists. Here, we identified 59 lymphomas concordantly called BL by 2 gene expression classifiers among 753 B-cell lymphomas. Only 2 (3%) of these 59 molecular BL lacked a MYC translocation, which both shared a peculiar pattern of chromosome 11q aberration characterized by interstitial gains including 11q23.2-q23.3 and telomeric losses of 11q24.1-qter. We extended our analysis to 17 MYC-negative high-grade B-cell lymphomas with a similar 11q aberration and showed this aberration to be recurrently associated with morphologic and clinical features of BL. The minimal region of gain was defined by high-level amplifications in 11q23.3 and associated with overexpression of genes including PAFAH1B2 on a transcriptional and protein level. The recurrent region of loss contained a focal homozygous deletion in 11q24.2-q24.3 including the ETS1 gene, which was shown to be mutated in 4 of 16 investigated cases. These findings indicate the existence of a molecularly distinct subset of B-cell lymphomas reminiscent of BL, which is characterized by deregulation of genes in 11q.

Non-Hodgkin Lymphoma in Children and Adolescents: Progress Through Effective Collaboration, Current Knowledge, and Challenges Ahead.

Non-Hodgkin lymphoma is the fourth most common malignancy in children, has an even higher incidence in adolescents, and is primarily represented by only a few histologic subtypes. Dramatic progress has been achieved, with survival rates exceeding 80%, in large part because of a better understanding of the biology of the different subtypes and national and international collaborations. Most patients with Burkitt lymphoma and diffuse large B-cell lymphoma are cured with short intensive pulse chemotherapy containing cyclophosphamide, cytarabine, and high-dose methotrexate. The benefit of the addition of rituximab has not been established except in the case of primary mediastinal B-cell lymphoma. Lymphoblastic lymphoma is treated with intensive, semi-continuous, longer leukemia-derived protocols. Relapses in B-cell and lymphoblastic lymphomas are rare and infrequently curable, even with intensive approaches. Event-free survival rates of approximately 75% have been achieved in anaplastic large-cell lymphomas with various regimens that generally include a short intensive B-like regimen. Immunity seems to play an important role in prognosis and needs further exploration to determine its therapeutic application. ALK inhibitor therapeutic approaches are currently under investigation. For all pediatric lymphomas, the intensity of induction/consolidation therapy correlates with acute toxicities, but because of low cumulative doses of anthracyclines and alkylating agents, minimal or no long-term toxicity is expected. Challenges that remain include defining the value of prognostic factors, such as early response on positron emission tomography/computed tomography and minimal disseminated and residual disease, using new biologic technologies to improve risk stratification, and developing innovative therapies, both in the first-line setting and for relapse.

Use of minimal disseminated disease and immunity to NPM-ALK antigen to stratify ALK-positive ALCL patients with different prognosis

We studied the prognostic value of minimal disseminated disease (MDD) and anti-ALK immune response in children with NPM-ALK-positive anaplastic-large cell lymphoma (ALCL) and evaluated their potential for risk stratification. NPM-ALK transcripts were analyzed by RT-PCR in bone marrow/peripheral blood of 128 ALCL patients at diagnosis, whereas ALK antibody titers in plasma were assessed using an immunocytochemical approach. MDD was positive in 59% of patients and 96% showed an anti-ALK response. Using MDD and antibody titer results, patients could be divided into three biological risk groups (bRG) with different prognosis: high risk (bHR): MDD-positive and antibody titer ⩽1/750, 26/128 (20%); low risk (bLR): MDD negative and antibody titer >1/750, 40/128 (31%); intermediate risk (bIR): all remaining patients, 62/128 (48%). Progression-free survival was 28% (s.e., 9%), 68% (s.e., 6%) and 93% (s.e., 4%) for bHR, bIR and bLR, respectively (P<0.0001). Survival was 71% (s.e., 9%), 83% (s.e., 5%) and 98% (s.e., 2%) for bHR, bIR and bLR (P=0.02). Only bHR and histology other than common type were predictive of higher risk of failure (hazard ratio 4.9 and 2.7, respectively) in multivariate analysis. Stratification of ALCL patients based on MDD and anti-ALK titer should be considered in future ALCL trials to optimize treatment.

Pediatric precursor T lymphoblastic leukemia and lymphoblastic lymphoma: Differences in the common regions with loss of heterozygosity at chromosome 6q and their prognostic impact

Deletions on chromosome 6q are frequently reported in hematological malignancies. However, their biological or prognostic impact has not yet been clarified. This study analyzed loss of heterozygosity (LOH) at chromosome 6q and compared the LOH findings in pediatric precursor T lymphoblastic lymphoma (T-LBL) with the LOH findings in precursor-T lymphoblastic leukemia (T-ALL). For LOH analyses, a set of 25 microsatellite-markers on 6q14-q24 were examined. All patients were treated uniformly according to ALL-BFM-type treatment-strategy. A total of 1671 markers were successfully analyzed from 108 T-LBL patients. LOH was detected in 21 T-LBL patients. There was clear association between LOH at 6q and an increased risk of relapse. In comparison, 3109 markers were successfully analyzed from 127 T-ALL-patients. LOH was detected in 16 patients, but was not associated with increased relapse-rate. The localization of the common LOH regions identified for T-LBL and T-ALL samples did not overlap. Therefore patterns of LOH at 6q and the prognostic impact of LOH differ between T-ALL and T-LBL. These results hint at biologic differences between the two diseases.

Distribution of NPM1‐ALK and X‐ALK fusion transcripts in paediatric anaplastic large cell lymphoma: a molecular–histological correlation

Anaplastic large cell lymphomas (ALCL) in children express anaplastic lymphoma kinase (ALK) fusion genes, most commonly NPM1‐ALK. The distribution of X‐ALK among 66 childhood ALCLs was analysed. One ALCL was ALK‐negative. Reverse transcription polymerase chain reaction detected NPM1‐ALK in 58 tumours, all showing nuclear and cytoplasmic ALK staining. The remaining seven ALCL stained for ALK in the cytoplasm only: two expressed TPM3‐ALK, one ATIC‐ALK, one MYH9‐ALK; three no TPM3‐, TFG‐, ATIC‐, CLTC‐ or MYH9‐ALK. Almost 90% of paediatric ALK‐positive ALCLs express NPM1‐ALK. There was complete concordance between ALK staining pattern and the presence of a typical/variant ALK fusion partner.

Recurrent RHOA Mutations in Pediatric Burkitt Lymphoma Treated According to the NHL-BFM Protocols

Burkitt lymphoma (BL) is the most frequent B‐cell lymphoma in childhood. Genetically, it is characterized by the presence of an IG‐MYC translocation which is supposed to be an initiating but not sufficient event in Burkitt lymphomagenesis. In a recent whole‐genome sequencing study of four cases, we showed that the gene encoding the ras homolog family member A (RHOA) is recurrently mutated in pediatric BL. Here, we analyzed RHOA by Sanger sequencing in a cohort of 101 pediatric B‐cell lymphoma patients treated according to Non‐Hodgkins Lymphoma Berlin–Frankfurt–Münster (NHL‐BFM) study protocols. Among the 78 BLs in this series, an additional five had RHOA mutations resulting in a total incidence of 7/82 (8.5%) with c.14G>A (p.R5Q) being present in three cases. Modeling the mutational effect suggests that most of them inactivate the RHOA protein. Thus, deregulation of RHOA by mutation is a recurrent event in Burkitt lymphomagenesis in children.

Targeting oncogenic fusion genes in leukemias and lymphomas by RNA interference.

Leukemias and lymphomas are often characterized by non-random chromosomal translocations that, at the molecular level, induce the activation of specific oncogenes or create novel chimeric genes. They have frequently been regarded as optimal targets for gene-silencing approaches because of the large body of evidence that these single abnormalities directly initiate and maintain the malignant process. Herein, we discuss RNA interference (RNAi)-based approaches for targeting the fusion sites of chromosomal translocations as a future treatment option in leukemias and lymphomas.

Inhibition of anaplastic lymphoma kinase (ALK) activity provides a therapeutic approach for CLTC-ALK-positive human diffuse large B cell lymphomas.

ALK positive diffuse large B-cell lymphomas (DLBCL) are a distinct lymphoma subtype associated with a poor outcome. Most of them feature a t(2;17) encoding a clathrin (CLTC)-ALK fusion protein. The contribution of deregulated ALK-activity in the pathogenesis and maintenance of these DLBCLs is not yet known. We established and characterized the first CLTC-ALK positive DLBCL cell line (LM1). LM1 formed tumors in NOD-SCID mice. The selective ALK inhibitor NVP-TAE684 inhibited growth of LM1 cells in vitro at nanomolar concentrations. NVP-TAE684 repressed ALK-activated signalling pathways and induced apoptosis of LM1 DLBCL cells. Inhibition of ALK-activity resulted in sustained tumor regression in the xenotransplant tumor model. These data indicate a role of CLTC-ALK in the maintenance of the malignant phenotype thereby providing a rationale therapeutic target for these otherwise refractory tumors.