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Background Germinal center-derived B cell lymphomas are tumors of the lymphoid tissues representing one of the most heterogeneous malignancies. Here we characterize the variety of transcriptomic phenotypes of this disease based on 873 biopsy specimens collected in the German Cancer Aid MMML (Molecular Mechanisms in Malignant Lymphoma) consortium. They include diffuse large B cell lymphoma (DLBCL), follicular lymphoma (FL), Burkitt’s lymphoma, mixed FL/DLBCL lymphomas, primary mediastinal large B cell lymphoma, multiple myeloma, IRF4-rearranged large cell lymphoma, MYC-negative Burkitt-like lymphoma with chr. 11q aberration and mantle cell lymphoma. Methods We apply self-organizing map (SOM) machine learning to microarray-derived expression data to generate a holistic view on the transcriptome landscape of lymphomas, to describe the multidimensional nature of gene regulation and to pursue a modular view on co-expression. Expression data were complemented by pathological, genetic and clinical characteristics. Results We present a transcriptome map of B cell lymphomas that allows visual comparison between the SOM portraits of different lymphoma strata and individual cases. It decomposes into one dozen modules of co-expressed genes related to different functional categories, to genetic defects and to the pathogenesis of lymphomas. On a molecular level, this disease rather forms a continuum of expression states than clearly separated phenotypes. We introduced the concept of combinatorial pattern types (PATs) that stratifies the lymphomas into nine PAT groups and, on a coarser level, into five prominent cancer hallmark types with proliferation, inflammation and stroma signatures. Inflammation signatures in combination with healthy B cell and tonsil characteristics associate with better overall survival rates, while proliferation in combination with inflammation and plasma cell characteristics worsens it. A phenotypic similarity tree is presented that reveals possible progression paths along the transcriptional dimensions. Our analysis provided a novel look on the transition range between FL and DLBCL, on DLBCL with poor prognosis showing expression patterns resembling that of Burkitt’s lymphoma and particularly on ‘double-hit’ MYC and BCL2 transformed lymphomas. Conclusions The transcriptome map provides a tool that aggregates, refines and visualizes the data collected in the MMML study and interprets them in the light of previous knowledge to provide orientation and support in current and future studies on lymphomas and on other cancer entities. Electronic supplementary material The online version of this article (10.1186/s13073-019-0637-7) contains supplementary material, which is available to authorized users.

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.

Lymphomas are assumed to originate at different stages of lymphocyte development through chromosomal aberrations. Thus, different lymphomas resemble lymphocytes at distinct differentiation stages and show characteristic morphologic, genetic, and transcriptional features. Here, we have performed a microarray-based DNA methylation profiling of 83 mature aggressive B-cell non-Hodgkin lymphomas (maB-NHLs) characterized for their morphologic, genetic, and transcriptional features, including molecular Burkitt lymphomas and diffuse large B-cell lymphomas. Hierarchic clustering indicated that methylation patterns in maB-NHLs were not strictly associated with morphologic, genetic, or transcriptional features. By supervised analyses, we identified 56 genes de novo methylated in all lymphoma subtypes studied and 22 methylated in a lymphoma subtype–specific manner. Remarkably, the group of genes de novo methylated in all lymphoma subtypes was significantly enriched for polycomb targets in embryonic stem cells. De novo methylated genes in all maB-NHLs studied were expressed at low levels in lymphomas and normal hematopoietic tissues but not in nonhematopoietic tissues. These findings, especially the enrichment for polycomb targets in stem cells, indicate that maB-NHLs with different morphologic, genetic, and transcriptional background share a similar stem cell–like epigenetic pattern. This suggests that maB-NHLs originate from cells with stem cell features or that stemness was acquired during lymphomagenesis by epigenetic remodeling.

Purpose To identify novel genomic regions of interest in acute myeloid leukemia (AML) with complex karyotypes, we applied comparative genomic hybridization to microarrays (array-CGH), allowing high-resolution genome-wide screening of genomic imbalances. Patients and Methods Sixty AML cases with complex karyotypes were analyzed using array-CGH; parallel analysis of gene expression was performed in a subset of cases. Results Genomic losses were found more frequently than gains. The most frequent losses affected 5q (77%), 17p (55%), and 7q (45%), and the most frequent genomic gains 11q (40%) and 8q (38%). Critical segments could be delineated to genomic fragments of only 0.8 to a few megabase-pairs of DNA. In lost/gained regions, gene expression profiling detected a gene dosage effect with significant lower/higher average gene expression levels across the genes located in the respective regions. Furthermore, high-level DNA amplifications were identified in several regions: 11q23.3-q24.1 (n = 7), 21q22 (n = 6), 11q23.3 (n = 5), 13q12 (n = 3), 8q24 (n = 3), 9p24 (n = 2), 12p13 (n = 2), and 20q11 (n = 2). Parallel analysis of gene expression in critical amplicons displayed overexpressed candidate genes (eg, C8FW and MYC in 8q24). Conclusion In conclusion, a large spectrum of genomic imbalances, including novel recurring changes in AML with complex karyotypes, was identified using array-CGH. In addition, the combined analysis of array-CGH data with gene expression profiles allowed the detection of candidate genes involved in the pathogenesis of AML.

Gliomas are the most frequent primary brain tumors and comprise a group of morphologically, biologically and clinically heterogeneous neoplasms. The different glioma types are associated with distinct genetic aberrations, which may provide useful information for tumor classification as well as prediction of prognosis and response to therapy. To facilitate the molecular classification of gliomas, we established a genomic microarray that consists of bacterial artificial chromosome (BAC) and P1-derived artificial chromosome (PAC) clones representing tumor suppressor genes, proto-oncogenes and chromosomal regions frequently gained or lost in gliomas. In addition, reference clones distributed evenly throughout the genome in approximately 15 Mbp intervals were spotted on the microarray. These customized microarrays were used for matrix-based comparative genomic hybridization (matrix CGH) analysis of 70 gliomas. Matrix CGH findings were validated by molecular genetic analyses of candidate genes, loss of heterozygosity studies and chromosomal CGH. Our results indicate that matrix CGH allows for the sensitive and specific detection of gene amplifications as well as low-level copy number gains and losses in clinical glioma samples. Furthermore, molecular classification based on matrix CGH data closely paralleled histological classification and was able to distinguish with few exceptions between diffuse astrocytomas and oligodendrogliomas, anaplastic astrocytomas and anaplastic oligodendrogliomas, anaplastic oligodendrogliomas and glioblastomas, as well as primary and secondary glioblastomas. Thus, matrix CGH is a powerful technique that allows for an automated genomic profiling of gliomas and represents a promising new tool for their molecular classification.

Genomic analyses aimed at the detection of high-level DNA amplifications were performed on 13 widely used pancreatic cancer cell lines and 6 pancreatic tumor specimens. For these analyses, array-based comparative genomic hybridization (Matrix-CGH) onto dedicated microarrays was used. In comparison with chromosomal CGH (eight amplifications), a >3-fold number of DNA amplifications was detected (n = 29). The most frequent amplifications mapped to 7p12.3 (three pancreatic cancer cell lines and three pancreatic tumor specimens), 8q24 (four pancreatic cancer cell lines and one pancreatic tumor specimen), 11q13 (three pancreatic cancer cell lines and three pancreatic tumor specimens), and 20q13 (four pancreatic cancer cell lines and three pancreatic tumor specimens). Genes contained in the consensus regions were MYC (8q24), EGFR (7p12.3), and FGF3 (11q13). In six of seven pancreatic cancer cell lines and pancreatic tumor specimens with 20q13 amplifications, the novel candidate gene NFAT C2, which plays a role in the activation of cytokines, was amplified. Other amplifications also affected genes for which a pathogenetic role in pancreatic carcinoma has not been described, such as BCL10 and BCL6, two members of the BCL family. A subset of amplified genes was checked for overexpression by means of real-time PCR, revealing the highest expression levels for BCL6 and BCL10. Thus, Matrix-CGH allows the detection of a high number of amplifications, resulting in the identification of novel candidate genes in pancreatic cancer.

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.

Follicular lymphoma (FL) is characterized by a large number of chromosomal aberrations. However, their exact genomic extension and involved target genes remain to be determined. For this purpose, we used array-based intermediate-high resolution genomic profiling in combination with Affymetrix gene expression analysis. Tumor specimens from 128 FL patients were analyzed for the presence of genomic aberrations and the results were correlated to clinical data sets and mRNA expression levels. In 114 (89%) of the 128 analyzed cases, a total of 688 genomic aberrations (384 gains/amplifications and 304 losses) were detected. Frequent genomic aberrations were: -1p36 (18%), +2p15 (24%), -3q (14%), -6q (25%), +7p (19%), +7q (23%), +8q (14%), -9p (16%), -11q (15%), +12q (20%), -13q (11%), -17p (16%), +18p (18%), and +18q (28%). Critical segments of these imbalances were delineated to genomic fragments with a minimum size down to 0.2 Mb. By comparison of these with mRNA gene expression data, putative candidate genes were identified. Moreover, we found that deletions affecting the tumor suppressor gene CDKN2A/B on 9p21 were detected in nontransformed FL grade I-II. For this aberration as well as for -6q25 and -6q26, an association with inferior survival was observed.

Background The identification of genomic signatures of colorectal cancer for risk stratification requires the study of large series of cancer patients with an extensive clinical follow-up. Multicentric clinical studies represent an ideal source of well documented archived material for this type of analyses. Methods To verify if this material is technically suitable to perform matrix-CGH, we performed a pilot study using macrodissected 29 formalin-fixed, paraffin-embedded tissue samples collected within the framework of the EORTC-GI/PETACC-2 trial for colorectal cancer. The scientific aim was to identify prognostic genomic signatures differentiating locally restricted (UICC stages II-III) from systemically advanced (UICC stage IV) colorectal tumours. Results The majority of archived tissue samples collected in the different centers was suitable to perform matrix-CGH. 5/7 advanced tumours displayed 13q-gain and 18q-loss. In locally restricted tumours, only 6/12 tumours showed a gain on 13q and 7/12 tumours showed a loss on 18q. Interphase-FISH and high-resolution array-mapping of the gain on 13q confirmed the validity of the array-data and narrowed the chromosomal interval containing potential oncogenes. Conclusion Archival, paraffin-embedded tissue samples collected in multicentric clinical trials are suitable for matrix-CGH analyses and allow the identification of prognostic signatures and aberrations harbouring potential new oncogenes.

A broad range of malignant diseases, such as mantle cell lymphoma (MCL), is associated with complex genomic alterations, demanding multimodal functional testing of candidate genes. To assess such candidate disease genes, we have developed a bidirectional targeted transgenesis tool, which allows well-controlled modulation of individual gene activities within a cellular MCL system. The engineered versatile transgenesis system permits functional analysis of virtually any candidate gene: for tumor suppressor genes by complementation via integration of respective genomic DNA or for oncogenes by inactivation via integrated shRNA coding plasmids. Complementation by genomic DNA ensures wild-type (WT) regulated gene expression, whereas genomic integration of shRNA coding inserts by an advanced RNAi-strategy mediates specific knock-down of gene expression. Site-specific genomic integration of an unmodified BAC, which contains the CDKN2A/B genes absent in the MCL model system, restored CDKN2A/B expression resulting in the inhibition of cell proliferation. CCND1, strongly overexpressed in the model system, was down-regulated via shRNA expression, again inhibiting proliferation. Notably, the presented site-specific shRNA-strategy circumvents interference by IFN-response induced when using other RNAi gene knock-down methods. In conclusion, we here demonstrate that adequate restoration of a range of different gene activities yields in a desired antiproliferative effect in MCL-derived cells. By antagonizing inactivated tumor suppressor genes or activated oncogenes, the presented approach can be readily used for the functional analysis of a broad range of disease-related genetic defects.

DNA amplifications are important mechanisms for proto-oncogene activation. Comparative genomic hybridization (CGH) to metaphase chromosome preparations has revealed amplifications in 10–20% of B-cell lymphomas (B-NHL). We analysed a series of 16 aggressive non-Hodgkin lymphomas by the new approach termed Matrix-CGH (M-CGH) using genomic DNA microarrays as hybridization target. For M-CGH, a dedicated B-cell lymphoma chip was constructed containing 496 genomic targets covering oncogenes, tumor suppressor genes as well as chromosome regions frequently altered in B-NHL. In 10 of 16 samples a total of 15 DNA amplifications were identified. The amplicons included BCL2, REL, CCND1, CCND2, JAK2, FGF4 and MDM2. Four of the 15 amplifications remained undetected by chromosomal CGH. The respective amplicons mapped to bands 2p13, 9p13–p21 and 12q24 and, were confirmed by fluorescence in situ hybridization. Furthermore, for four genomically amplified genes real-time quantitative reverse transcription polymerase chain reaction revealed elevated mRNA expression levels. These data show the superior diagnostic sensitivity of the newly developed diagnostic tool. As only a small portion of the genome (approximately 1.5%) has been analysed by the present DNA array, it is likely that gene amplifications are much more common in aggressive lymphomas than previously assumed.

Recently, DNA microarray technology has opened new avenues for the understanding of lymphomas. By hybridization of cDNA to arrays containing >10,000 different DNA fragments, this approach allows the simultaneous evaluation of the mRNA expression of thousands of genes in a single experiment. Using sophisticated bioinformatic tools, the huge amount of raw data can be clustered resulting in (1) tumor subclassification, (2) identification of pathogenetically relevant genes, or (3) biological predictors for the clinical course. This approach already has provided novel insights into different entities of B-cell non-Hodgkin's lymphomas. Genomic DNA chip hybridization (matrix-CGH) is a complementary approach focussing on genomic aberrations. In this review, we discuss the impact of this new technology both with regard to methodological aspects as well as to novel findings influencing our understanding of lymphomas.

Genome-wide screening for chromosomal imbalances using comparative genomic hybridization (CGH) revealed a wealth of data on previously unrecognized tumor-specific genomic alterations. CGH to microarrays of DNA, an approach termed matrix-CGH, allows detection of genomic imbalances at a much higher resolution. We show that matrix CGH is also feasible from small tissue samples requiring universal amplification of genomic DNA. Because widespread application of matrix-CGH experiments using large numbers of DNA targets demands a high degree of automation, we have developed a protocol for a fully automated procedure. The use of specialized instrumentation for the generation of DNA chips, their hybridization, scanning, and evaluation required numerous alterations and modifications of the initial protocol. We here present the elaboration and testing of automated matrix-CGH. A chip consisting of 188 different genomic DNA fragments, cloned in bacterial artificial chromosome (BAC) or P1-derived artificial chromosome (PAC) vectors and immobilized in replicas of 10, was used to assess the performance of the automated protocol in determining the gene dosage variations in tumor cell lines COLO320-HSR, HL60, and NGP. Although ratios of matrix-CGH were highly concordant with results of chromosomal CGH (85%), the dynamic range of the matrix-CGH ratios was highly superior. Investigation of the two amplicons on 8q24 in COLO320-HSR and HL60, containing the MYC gene, revealed a homogeneous amplicon in COLO320-HSR but a heterogeneous amplification pattern in HL60 cells. Although control clones for normalization of the signal ratios can be predicted in cases with defined chromosomal aberrations, in primary tumors such data are often not available, requiring alternative normalization algorithms. Testing such algorithms in a primary high-grade B-cell lymphoma, we show the feasibility of this approach. With the matrix-CGH protocol presented here, robust and reliable detection of genomic gains and losses is accomplished in an automated fashion, which provides the basis for widespread application in tumor and clinical genetics.

Background: Chromosomal abnormalities are detectable in virtually all patients with multiple myeloma (MM) by the use of molecular cytogenetic techniques (e.g. fluorescence in-situ hybridization, FISH; comparative genomic hybridization, CGH). Genomic rearrangements play a crucial role in the pathogenesis of clonal plasma cell disorders and can deliver important prognostic information. Microarray-based comparative genomic hybridization (mCGH) is an innovative technique that enables a genome-wide, high-resolution tumor cell screening for chromosomal imbalances in a single experiment. The aim of the present study was the detailed characterization of genomic gains and losses in MM - in particular the delineation of critical regions - by the use of mCGH. Methods: So far, bone marrow specimens from 55 patients with Salmon &Durie stage II or III MM were analyzed. To achieve a plasma cell proportion greater than 50% before hybridization, CD 138-enrichment by immunomagnetic separation was performed whenever necessary. mCGH chips consisting of approximately 6.400 DNA clones, among them ~3.200 clones covering the whole human genome in 1 Mb increments, the remaining forming contigs from specific genomic regions or containing tumor-relevant genes were applied. Results: 52 out of 55 patients (94.5%) were evaluable by mCGH. Gains and losses of chromosomal material were found in 51 out of 52 patients (98%). In one case, mCGH did not exhibit imbalances but +9q34 and +11q25 was diagnosed by FISH for yet unknown reasons. Genomic losses most frequently involved chromosomes 13 (65%), 1p (39%), 16 (31%), 6 (27%), and 12 (21%), while gains commonly affected chromosomes 1q, 9, 11, 15 (46%), and 19 (35%). High-level amplifications were identified on chromosome 16 in two cases (overall three amplicons involving chromosome bands 16p11-p13, 16q12, and 16q21, respectively) as well as on chromosomes 8 (three amplified segments, one of them containing c-myc at 8q24) and 20q (2 amplifications involving bands 20q13.1 and 20q13.3) in one case each. Data on chromosome 13 deletion was consistent with monosomy 13 in 28 out of 34 cases (82.3%). For the remaining 6 cases with a partial 13q loss, no commonly deleted region could be delineated. In contrast, single critical regions were identified on other chromosomes, e.g. chromosome 14 (+14q23.2-q24.3). A small genomic region defined by only four closely adjacent 11q DNA clones was gained in 23 out of 24 (96%) cases with chromosome 11 extra copies. Conclusions: mCGH allows the detection of genomic imbalances including high-level amplifications in almost all patients with MM and enables a precise delineation of critical regions in this disease. Evaluation of mCGH raw data is ongoing and confirmative FISH analyses are currently under way. Supported by grants from the Deutsche José Carreras Leukämie-Stiftung (DJCLS-R04/04) and the Wilhelm Sander-Stiftung (No. 2002.098.1) to P.L.

Follicular Lymphoma (FL), one of the most frequent lymphoma entities in the western world, is characterized by a highly variable clinical course reaching from rapid progression with fatal outcome to cases with long term survival. In a recent study applying chromosomal comparative hybridization (CGH) to FL, in 70% of the cases genomic aberrations were detectable and a loss of genomic material on chromosomal bands 6q25-q27 was the strongest predictor for short overall survival. However, limitations of CGH as a screening method are a restricted genomic resolution to 3–10 Mbp and demanding non-automated evaluation procedures. Thus, high throughput analysis of genomic alterations for risk adapted patient stratification and monitoring within treatment trials should rely on efficient and automated diagnostic techniques. In this study, we used array CGH to a novel generation of DNA Chips containing 2800 genomic DNA probes. Target clones comprised i) contigs mapping to genomic regions of possible pathogenetic relevance in lymphoma (n=610 target clones mapping to e.g. 1p, 2p, 3q, 7q, 9p, 11q, 12q, 13q, 17p, 18q, X); ii) selected oncogenes and tumor suppressor genes (n=686) potentially relevant in hematologic neoplasms; and iii) a large genome-wide cluster of 1502 target DNA clones covering the genome at a distance of app. 2 Mbp (part of the golden path clone set). This chip represents a median genomic resolution of app. 1.5 Mbp. In total, DNAs from 70 FL samples were analyzed and results were compared to data from chromosomal CGH experiments and clinical data sets. The sensitivity of array CGH was considerably higher compared to chromosomal CGH (aberrations in 95% of cases vs 70% of cases). Most frequent aberrations were gain mapping to chromosome arms 2p (21%), 7p (24%), 7q (30%), 12p (17%), 12q (21%), 18p (21%) and 18q (34%) as well as losses mapping to chromosome arms 1p (19%), 6q (23%), 7p (20%), 11q (26%) and 17p (20%). In addition, several genomic aberrations were identified which have not been described before in FL. Currently, these aberrations are characterized in more detail and results will be correlated with the clinical data set. Moreover, three recurrent sites of genomic polymorphisms in human beings affecting chromosomes 5q, 14q and 15q were identified. In conclusion, these data underline the potential of array CGH for the sensitive detection of genomic imbalances in FL.

Chronic lymphocytic leukemia of B-cell type (B-CLL) is characterized by a number of typical genomic aberrations. In comparison to patients with normal karyotypes or 13q deletions patients with high risk imbalances such as deletions of 11q, 17p or unmutated IgVH status have a higher risk for advanced disease and a significantly shorter survival. For a precise mapping of chromosomal imbalances as well as to verify the number of aberrations per case in different genetic subgroups of B-CLL (e.g. del11q, del13q, del17p, +12 or unmutated IgVH status) we performed high resolution genomic profiling using a genomic DNA-chip containing 2.800 probes. Target clones compriseda large genome-wide cluster of clones covering the genome at a distance of approx. 1.5Mb andclones mapping to genomic regions or genes of possible pathogenetic relevance in lymphoma. This chip covers approximately 10% of the human genome. In 93 (70%) of 133 analyzed B-CLL cases 171 genomic imbalances were identified (between 1–7 aberrations/case). Besides the confirmation of known recurrent chromosomal aberrations, previously unknown recurrent imbalances were detectable on 2p (8%), 4p (4%), 7p-q (5%), 10q (5%) and 20p (3%). Most of these imbalances were of larger extension (> 10 Mb) and therefore impeded a further delineation of minimal aberrant regions and the identification of possible candidate genes. The mean number of chromosomal aberrations per case (= genomic complexity) in IgVH unmutated CLLs was approx. 2 times higher than in mutated cases (0,77 vs. 1,58 per case). 84% of samples with > 2 aberrations showed an unmutated IgVH status. Moreover, most of the previously unknown imbalances were identified within this group. A higher genomic complexity was also shown for samples with gain on 2p vs. balanced 2p status (2.2 times higher; 2.5 vs. 1.2) and in samples with del17p vs. balanced 17p status (3.7 times higher; 3.52 vs. 0.95). 11q aberrations had no impact on the number of genomic aberrations per case (1.6 vs. 1.2). Moreover, we found a strong association of 2p gains and an unmutated IgVH status (100%). Array based genomic profiling confirmes the chromosomal aberration structure and underlines the consistency of chromosomal aberration patterns of B-CLL. The biological and prognostic relevance of 2p gains and unmutated IgVH mutational status have to be further investigated.