Wolfram Klapper

Gene expression profiling of isolated tumour cells from anaplastic large cell lymphomas: insights into its cellular origin, pathogenesis and relation to Hodgkin lymphoma

Anaplastic large cell lymphoma (ALCL) is a main type of T-cell lymphomas and comprises three distinct entities: systemic anaplastic lymphoma kinase (ALK) positive, systemic ALK− and cutaneous ALK− ALCL (cALCL). Little is known about their pathogenesis and their cellular origin, and morphological and immunophenotypical overlap exists between ALK− ALCL and classical Hodgkin lymphoma (cHL). We conducted gene expression profiling of microdissected lymphoma cells of five ALK+ and four ALK− systemic ALCL, seven cALCL and sixteen cHL, and of eight subsets of normal T and NK cells. The analysis supports a derivation of ALCL from activated T cells, but the lymphoma cells acquired a gene expression pattern hampering an assignment to a CD4+, CD8+ or CD30+ T-cell origin. Indeed, ALCL display a down-modulation of many T-cell characteristic molecules. All ALCL types show significant expression of NFκB target genes and upregulation of genes involved in oncogenesis (e.g. EZH2). Surprisingly, few genes are differentially expressed between systemic and cALCL despite their different clinical behaviour, and between ALK− ALCL and cHL despite their different cellular origin. ALK+ ALCL are characterized by expression of genes regulated by pathways constitutively activated by ALK. This study provides multiple novel insights into the molecular biology and pathogenesis of ALCL.

Clinical, pathological and genetic features of primary mediastinal large B-cell lymphomas and mediastinal gray zone lymphomas in children

Background Primary mediastinal large B-cell lymphoma is a rare lymphoma accounting for no more than 3% of all B-cell lymphomas in children and adolescents. However, patients in this young age group with this lymphoma have the shortest event-free survival of patients with any B-cell lymphoma under current standard chemotherapy protocols. Lymphomas with features intermediate between primary mediastinal large B-cell lymphoma and classical Hodgkin’s lymphoma (mediastinal gray zone lymphomas) have been acknowledged in the latest World Health Organization classification. Recent studies suggest that mediastinal gray zone lymphomas have an aggressive clinical course whereas patients, at least adult ones, with primary mediastinal large B-cell lymphoma might respond very well to chemotherapy in combination with anti-CD20 antibody. Design and Methods We aimed to evaluate whether biological differences or so far unrecognized admixed mediastinal gray zone lymphomas might explain the relatively poor outcome of pediatric patients with apparent primary mediastinal large B-cell lymphoma. We, therefore, performed a retrospective histopathological, immunohistochemical and interphase cytogenetic analysis of 52 pediatric lymphomas. Results The childhood primary mediastinal large B-cell lymphomas (n=44) showed a similar pattern of histology, immunophenotype and gains at 9p (59%) and 2p (41%) as adult cases, as determined from published data. We identified only four so far unrecognized cases of mediastinal gray zone lymphoma among 52 lymphomas registered in previous trials. Conclusions Mediastinal gray zone lymphoma is very rare in children and adolescents. It does, therefore, seem unlikely that these lymphomas account for the unsatisfactory clinical results with current therapy protocols in pediatric patients. These data have major implications for the design of future treatment protocols for mediastinal lymphomas in children and adolescents.

Pathway activation patterns in diffuse large B-cell lymphomas.

Deregulation of cell signaling pathways controlling cell growth and cell survival is a common feature of all cancers. Although a core repertoire of oncogenic mechanisms is widely conserved between various malignancies, the constellation of pathway activities can vary even in patients with the same malignant disease. Modern molecularly targeted cancer drugs intervene in cell signaling compensating for pathway deregulation. Hence characterizing tumors with respect to pathway activation will become crucial for treatment decisions. Here we have used semi-supervised machine learning methodology to generate signatures of eight oncogene-inducible pathways, which are conserved across epithelial and lymphoid tissues. We combined them to patterns of pathway activity called PAPs for pathway activation patterns and searched for them in 220 morphologically, immunohistochemically and genetically well-characterized mature aggressive B-cell lymphomas including 134 cases with clinical data available. Besides Burkitt lymphoma, which was characterized by a unique pattern, the PAPs identified four distinct groups of mature aggressive B-cell lymphomas across independent gene expression studies with distinct biological characteristics, genetic aberrations and prognosis. We confirmed our findings through cross-platform analysis in an independent data set of 303 mature aggressive B-cell lymphomas.

Different biological risk factors in young poor-prognosis and elderly patients with diffuse large B-cell lymphoma

Prognostically relevant risk factors in patients with diffuse large B-cell lymphoma (DLBCL) have predominantly been evaluated in elderly populations. We tested whether previously described risk factors are also valid in younger, poor-prognosis DLBCL patients. Paraffin-embedded samples from 112 patients with de novo DLBCL, enrolled in the R-MegaCHOEP trial of the German High Grade Non-Hodgkin Lymphoma Study Group (DSHNHL) were investigated using immunohistochemistry (MYC, FOXP1, LMO2, GCET1, CD5, CD10, BCL2, BCL6, IRF4/MUM1) and fluorescence in situ hybridization (MYC, BCL2, BCL6). MYC, BCL2 and BCL6 breaks occurred in 14, 21 and 31%, respectively. In the majority of cases, MYC was simultaneously rearranged with BCL2 and/or BCL6. The adverse impact of MYC rearrangements was confirmed, but the sole presence of BCL2 breaks emerged as a novel prognostic marker associated with inferior overall survival (OS) (P=0.002). Combined overexpression of MYC and BCL2 showed only limited association with inferior OS. All immunohistochemical cell of origin classifiers applied failed to predict survival time. DLBCL tumors with significant proportion of immunoblastic and/or immunoblastic-plasmacytoid cells had inferior OS, independently from from BCL2 break. Younger, poor-prognosis DLBCL patients, therefore, display different biological risk factors compared with an elderly population, with BCL2 translocations emerging as a powerful negative prognostic marker.