Tiemo Katzenberger

Recurrent Genetic Aberrations in Thymoma and Thymic Carcinoma

Apart from single reported aberrant karyotypes, genetic alterations in thymic epithelial neoplasms have not been investigated so far. In this study, 12 World Health Organization classification type A thymomas (medullary thymomas), 16 type B3 thymomas (well-differentiated thymic carcinomas), and nine type C thymomas, all of them primary thymic squamous cell carcinomas, were analyzed by comparative genomic hybridization and fluorescence in situ hybridization. With the exception of one single case, type A thymomas did not reveal chromosomal gains or losses in comparative genomic hybridization. In contrast, all type B3 thymomas showed chromosomal imbalances, with gain of 1q, loss of chromosome 6, and loss of 13q occurring in 11 (69%), six (38%), and five (31%) of 16 cases, respectively. In primary thymic squamous cell carcinoma, the most frequent chromosomal losses were observed for 16q (six of nine cases, 67%), 6 (4 of 9, 44%), and 3p and 17p (three of nine each, 33%), whereas recurrent gains of chromosomal material were gains of 1q (5 of 9, 56%), 17q, and 18 (three of nine each, 33%). This study shows that the distinct histological thymoma types A and B3 exhibit distinct genetic phenotypes, whereas type B3 thymoma and primary thymic squamous cell carcinoma partially share genetic aberrations. In addition to the possible tumorigenic role, the deletion in type B3 thymoma of chromosome 6, harboring the HLA locus, might play a role in the pathogenesis of paraneoplastic autoimmunity characteristic of thymoma.

Exclusive Detection of the t(11;18)(q21;q21) in Extranodal Marginal Zone B Cell Lymphomas (MZBL) of MALT Type in Contrast to other MZBL and Extranodal Large B Cell Lymphomas

Extranodal mucosa-associated lymphoid tissue (MALT)-type lymphomas and nodal and splenic marginal zone B cell lymphomas (MZBL) share morphological and immunophenotypic features with marginal zone B cells of reactive lymphoid tissues. Although displaying a similar immunophenotype, recent investigations suggest fundamental genetic differences among these subgroups. To determine the prevalence of the t(11;18) in a larger series of MALT-type lymphomas and to investigate a possible occurrence in other lymphomas, we screened 106 non-Hodgkins lymphomas (NHL) by interphase cytogenetics using yeast artificial chromosome (YAC) probes flanking the breakpoint at 11q21. A signal constellation indicating a disruption in 11q21 and thus pointing to the presence of the t(11;18) was observed in 9 of 33 (27%) low-grade lymphomas of MALT type. The complete absence of t(11;18)-positive cells in 32 primary and secondary extranodal high-grade lymphomas suggests that low-grade lymphomas of MALT type characterized by the t(11;18) are unlikely to transform into high-grade tumors. The absence of tumor cells carrying the t(11;18) in nodal MZBL challenges the assumption that most, if not all, of these tumors represent the nodal manifestation of a so far undetected low-grade lymphoma of MALT type. The t(11;18) was not detected in a single case of 29 splenic MZBL investigated. This observation strengthens the view that splenic MZBL are biologically different from extranodal MZBL of MALT type.

Chromosomal Gains at 9q Characterize Enteropathy-Type T-Cell Lymphoma

Genetic alterations in enteropathy-type T-cell lymphoma (ETL) are unknown so far. In this series, 38 cases of ETL were analyzed by comparative genomic hybridization (CGH). CGH revealed chromosomal imbalances in 87% of cases analyzed, with recurrent gains of genetic material involving chromosomes 9q (in 58% of cases), 7q (24%), 5q (18%), and 1q (16%). Recurrent losses of genetic material occurred on chromosomes 8p and 13q (24% each), and 9p (18%). In this first systematic genetic study on ETL, chromosomal gains on 9q (minimal overlapping region 9q33-q34) were found to be highly characteristic of ETL. Fluorescence in situ hybridization analysis on four cases of ETL, using a probe for 9q34, indicated frequent and multiple gains of chromosomal material at 9q34 (up to nine signals per case). Among 16 patients with ETL who survived initial disease presentation, patients with more than three chromosomal gains or losses (n = 11) followed a worse clinical course than those with three or less imbalances (n = 5). The observation of similar genetic alterations in ETL and in primary gastric (n = 4) and colonic (n = 1) T-cell lymphoma, not otherwise specified, is suggestive of a genetic relationship of gastrointestinal T-cell lymphomas at either localization.

A case of a diffuse large B-cell lymphoma of plasmablastic type associated with the t(2;5)(p23;q35) chromosome translocation.

Anaplastic large cell lymphomas are associated with the t(2;5)(p23;q35) chromosome translocation in 40% to 60% of cases, leading to a new chimeric gene NPM-ALK. NPM-ALK positive lymphomas are generally reported to be of either T cell or null phenotype. In this report, we describe a diffuse large B-cell lymphoma associated with the classic t(2;5) translocation and both nuclear and cytoplasmic expression of ALK. The tumor consisted of medium-sized to large immunoblasts and plasmablasts that on immunohistology were negative for CD30, CD20, and CD79a but showed monotypic cytoplasmic expression of lambda light chains. Clonality analysis confirmed B-cell lineage of the tumor cells. The t(2;5)(p23;q35) chromosome translocation was demonstrated as part of a complex karyotypic alteration by classic banding and spectral karyotyping (SKY) analyses. Reverse transcription polymerase chain reaction confirmed rearrangement of NPM and ALK genes. This case exemplifies that the t(2;5) can, albeit rarely, occur in large B-cell lymphomas and is not entirely limited to anaplastic large cell lymphomas of T or null cell phenotypes.

Cytogenetic alterations affecting BCL6 are predominantly found in follicular lymphomas grade 3B with a diffuse large B-cell component.

Recently, classical banding cytogenetic studies suggested that follicular lymphomas (FLs) grade 3 with preserved maturation to centrocytes (FL3A) are closely related to FL grades 1 and 2 and frequently harbor the t(14;18), whereas FL grade 3B, consisting of centroblasts exclusively, do frequently show 3q27 alterations. To clarify the prevalence of BCL6 and BCL2 rearrangements in FL and diffuse large B-cell lymphomas (DLBLs), we performed a large scale bicolor interphase cytogenetic (fluorescence in situ hybridization) study on 188 well-characterized B-NHLs classified according to the World Health Organization Classification of Tumors of the Lymphoid Tissues. BCL6 rearrangements were detected in a significantly higher number of FL3B with a DLBL component (12 of 22, 55%) compared with purely diffuse nodal DLBLs (19 of 77, 25%) and DLBLs with a well-documented primary extranodal origin (2 of 27, 7%) (P < 0.001). Five FL3B without a DLBL component were negative for both t(14;18) and 3q27 aberrations. FL grades 1/2 and FL3A were t(14;18)-positive in 88% and 64% of cases, respectively, but 3q27 alterations were identified in only four FL3A. These data exemplify different genetic pathways in the genesis of FLs with a high content of centroblasts and suggest that 3q27 rearrangements are predominantly associated with FL grade 3B harboring a DLBL component.

Expression Profiling and Genetic Alterations of the Selenoproteins GI-GPx and SePP in Colorectal Carcinogenesis

The trace element selenium is discussed as a chemopreventive agent in colorectal carcinogenesis. Selenocysteine-containing proteins, so-called selenoproteins, represent potential molecular targets for nutritive selenium supplementation. Due to their antioxidative potential, the selenoproteins gastrointestinal glutathione peroxidase (GI-GPx) and selenoprotein P (SePP) are considered to provide protection against reactive oxygen species (ROS), thereby reducing DNA damage and preventing development of colon cancer. GI-GPx and SePP are abundantly expressed in normal colon mucosa. Recently, we demonstrated both reduced SePP expression and increased GI-GPx expression in colorectal adenomas. In this study, we investigated the expression of SePP and GI-GPx in colorectal cancers compared with corresponding normal mucosa. Further, the occurrence of genetic alterations within the SePP and GI-GPx genes was analyzed. We observed a significant reduction or loss of SePP mRNA expression in colon cancers, whereas GI-GPx mRNA and protein expression varied between different tumor samples. In addition, we identified novel polymorphisms within the SePP and GI-GPx genes with so far unknown relevance for protein function. Our results argue against a general decrease of selenoprotein expression in colorectal carcinogenesis but imply specific differential regulation of expression of individual selenoproteins.

CDK4 and MDM2 gene alterations mainly occur in highly proliferative and aggressive mantle cell lymphomas with wild-type INK4a/ARF locus

Amplification of 12q13 locus occurs in some mantle cell lymphomas (MCL), potentially involving CDK4 and MDM2 genes. To determine the role of these genes in MCL, we have examined their gene status and expression and their relationship to INK4a/ARF and p53 gene aberrations in 69 tumors. Increased CDK4 gene copy number was detected in 4 of 19 (21%) highly proliferative blastoid variants and was associated with mRNA and protein overexpression. Three additional cases showed mRNA overexpression with no structural alterations of the gene. MDM2 gene overexpression was detected in three blastoid tumors (16%) with no relationship to gene copy gains. INK4a/ARF and p53 aberrations were observed in 13 and 12 tumors, respectively. Four of the seven lymphomas with CDK4 aberrations had concurrent inactivation of p53 gene, whereas only one case had a concomitant homozygous deletion of INK4a/ARF. No other gene alterations were found in the three cases with MDM2 overexpression. Patients with INK4a/ARF deletions or simultaneous aberrations of p53 and CDK4 had a significantly shorter median survival (17 months) than patients with isolated alterations of p53, MDM2, or CDK4 (32 months) and patients with no alterations in any of these genes (77 months). The prognostic impact of the concomitant oncogenic alterations of the p14ARF/p53 and p16INK4a/CDK4 pathways was independent of the proliferation of the tumors. These findings indicate that CDK4 and MDM2 gene alterations mainly occur in MCL with a wild-type INK4a/ARF locus and may contribute to the higher proliferation and more aggressive behavior of the tumors.

Follicular lymphoma grade 3b is a distinct neoplasm according to cytogenetic and immunohistochemical profiles

Background According to the current World Health Organization Classification of Lymphoid Tumours, follicular lymphoma is subclassified into three grades according to the number of centroblasts. Follicular lymphoma grade 3 can be further divided into types A and B. Almost all available genetic data on grade 3B follicular lymphomas have been generated from tumors with an additional diffuse large B-cell lymphoma component. The purely follicular type of follicular lymphoma grade 3B is a rare neoplasm. Design and Methods We performed a detailed immunohistochemical (CD10, IRF4/MUM1, BCL2, Ig light chains) and genetic (translocations of BCL2, BCL6, MYC, IRF4) characterization of the largest series of purely follicular cases of grade 3B follicular lymphoma available to date, comprising 23 tumor samples. We also included 25 typical grade 1 or 2 follicular lymphomas, 9 follicular lymphomas with large centrocytes and/or high proliferation indices (FL/LCC), 12 cases of follicular lymphoma grade 3A, 16 cases of diffuse large B-cell lymphoma/follicular lymphoma grade 3B and 15 follicular lymphomas in which a straightforward distinction between grades 3A and 3B was not possible. Results Translocations affecting BCL2 and BCL6 genes are rare in grade 3B follicular lymphomas (2/23, 9% and 4/23, 17%) when compared with grade 1 or 2 follicular lymphomas (22/25, 88%, P<0.001 and 0/25, P<0.05), FL/LCC (7/9, 78%, P<0.001 and 2/9, 22%), grade 3A follicular lymphomas (7/12, 58%, P<0.01 and 2/12, 17%), unclassified grade 3 follicular lymphomas (6/15, 40% and 2/15, 13%) and diffuse large B-cell lymphoma/follicular lymphoma grade 3B (2/16, 13% and 8/16, 50%, P<0.05). MYC translocations were detected occasionally in FL/LCC, follicular lymphoma grade 3B, and diffuse large B-cell lymphoma/follicular lymphoma grade 3B (13%–22%), but not in grade 1, 2 or 3A follicular lymphomas (P<0.05 when compared with follicular lymphoma grade 3B). Both follicular lymphoma grade 3B and diffuse large B-cell lymphoma/follicular lymphoma grade 3B were enriched in samples with a CD10−IRF4/MUM1+ immunophenotype (8/19, 42% and 7/16, 44%), with the vast majority of them lacking BCL2 translocations. In contrast, 42/46 grade 1 or 2 follicular lymphomas, FL/LCC and grade 3A follicular lymphomas were CD10+ (91%) while 0/46 expressed IRF4/MUM1. None of the tumor samples tested with increased IRF4/MUM1-expression harbored a translocation of the IRF4 gene locus. Conclusions Our results show that grade 3B follicular lymphomas form a distinct category of follicular lymphomas with infrequent BCL2 and BCL6 translocations, while grades 1, 2 and 3A follicular lymphomas and FL/LCC display homogeneous features with frequent BCL2 translocations and a CD10+IRF4/MUM1− immunophenotype.

Genetic rearrangement of FOXP1 is predominantly detected in a subset of diffuse large B-cell lymphomas with extranodal presentation

Genetic rearrangement of FOXP1 is predominantly detected in a subset of diffuse large B-cell lymphomas with extranodal presentation

A distinctive subtype of t(14;18)-negative nodal follicular non-Hodgkin lymphoma characterized by a predominantly diffuse growth pattern and deletions in the chromosomal region 1p36

Follicular lymphoma (FL) is a morphologically and genetically well-characterized B-cell non-Hodgkin lymphoma that can show predominantly follicular, combined follicular and diffuse, or predominantly diffuse growth patterns. Although approximately 85% of FLs harbor the translocation t(14;18)(q32;q21) and consistently display a follicular growth pattern, predominantly diffuse FLs are less well characterized on the phenotypical, molecular, and clinical level. We studied 35 predominantly diffuse FL by immunohistochemistry, classical chromosome banding analysis, fluorescence in situ hybridization (FISH), and gene expression profiling. A total of 28 of 29 analyzable cases lacked t(14;18), and 27 of 29 cases revealed a unifying chromosomal aberration, a deletion in 1p36. Morphologically, 12 FLs were grade 1 and 23 were grade 2, and the immunophenotype with frequent expression of CD10, BCL6, and CD23 was in line with a germinal center B-cell phenotype. The gene expression profiles of 4 predominantly diffuse FLs fell into the spectrum of typical FL, with a unique enrichment of specific gene signatures. Remarkably, patients with diffuse FL frequently presented with low clinical stage and large but localized inguinal tumors. These results suggest that predominantly diffuse FL represent a distinct subtype of t(14;18)-negative nodal FL with a unifying genetic alteration (deletion of 1p36) and characteristic clinical features.