Oncogene rearrangement in non-Hodgkin's lymphoma with a 14q+ chromosome of unknown origin

Southern blot analysis was performed with a panel of DNA probes to detect rearrangements of c-myc, bcl-1, bcl-2 and bcl-3 in 14 cases of B-cell non-Hodgkin's lymphoma (NHL) with a clonal cytogenetic rearrangement involving the chromosome 14q32 locus and no known donor chromosome [t(14;?)(q32;?)]. In our experience, 21% of all chromosomal abnormalities involving the 14q32 locus in B-cell NHL are of this type. We found oncogene rearrangements in five of the 14 cases: bcl-1 rearrangement on one mantle zone lymphoma, bcl-2 rearrangements in two follicular lymphomas, and c-myc rearrangements in two small noncleaved cell lymphomas. We conclude that a 14q32+ abnormality of unknown origin is a relatively frequent karyotypic finding in B-cell NHL. In one third of the cases, known oncogenes that have been previously described in reciprocal translocations involving the immunoglobulin heavy chain locus were shown to be involved in the 14q32+ abnormality. The translocations in the other cases are likely to have involved one of the above oncogenes with breakpoints not revealed by the probes employed, other known oncogenes, or oncogenes that have not yet been identified.     

BCL-6 and other genomic alterations in non-Hodgkin's lymphoma (NHL)

This study reports on the frequency and disease association pattern of a number of gene rearrangements in a large panel of lymphoid tumours (n = 94). We detected the t(11;14) translocation, involving rearrangement of the BCL-1 locus, in 60% of mantle cell lymphomas. The BCL-2 gene, located at band 18q21, was rearranged in 42% of follicle centre lymphomas (FCL) and in 15% of diffuse large B-cell (DLBC) lymphomas. In this study, 80% of the c-MYC rearrangements were detected in aggressive diffuse lymphoma subsets but, interestingly, 9% of FCL showed involvement of t(8q24) translocation. In our study, rearrangements of the BCL-6 gene at band 3q27 were found in 31% of DLBC lymphomas. Interestingly, 50% of the BCL-6 rearrangement positive lymphoma cases had coexisting gene rearrangements involving all of the aforementioned gene loci. The molecular dissection of these genes will improve our understanding of the genesis of the diverse clinicopathological subtypes.     

Rearrangements of the BCL6 gene and chromosome aberrations affecting 3q27 in 54 patients with non-Hodgkin's lymphoma

Chromosome aberrations affecting 3q27 are among the most frequent non-random abnormalities in non-Hodgkin's lymphomas (NHL), especially the diffuse, large cell type. Recently, an association between BCL6 rearrangement and frequent extranodal lesions, rare bone marrow infiltration and a favorable clinical outcome was reported. We performed molecular studies of the BCL6 gene in 54 patients with NHL. Twelve patients (22%) with rearranged BCL6 genes were selected for histological, clinical, molecular, and cytogenetic studies. Ten of these cases were diffuse, large cell type lymphoma, one a follicular lymphoma, and one a mantle cell lymphoma (MCL). All cases were of the B-cell type and this is the first time a rearranged BCL6 gene has been found in an MCL. Cytogenetic data for 10 cases were available and the partner sites of the 3q27 translocation were determined in 7 of 10 patients. These locations were variable, including 6p21.3, 9p22, and 14q11 in addition to the immunoglobulin loci 14q32 (IGH), 2p12 (IGK), and 22q11 (IGL). The heterogeneity in partner sites is distinct from other lymphoma subgroups and may suggest that the genetic events are not uniform among patients with BCL6 rearrangements.     

Multiple breakpoints within the BCL-1 locus in B-cell lymphoma: rearrangements of the cyclin D1 gene

Centrocytic lymphoma (CC) and intermediately differentiated lymphocytic lymphoma (IDL) are B-cell non-Hodgkin's lymphomas composed of lymphocytes presumably derived from follicle mantle cells. In these lymphomas, a specific chromosomal translocation, t(11;14)(q13;q32), has been described. Previous studies suggested an association between t(11;14) chromosomal translocations and BCL-1 rearrangements. To evaluate the association between BCL-1 rearrangements and CC/IDL, Southern blot analysis was performed on a panel of 20 cases of CC/IDL, 22 cases of morphologically similar non-Hodgkin's lymphomas, 11 cases of chronic B-cell leukemias, and 2 cases of myelomas. We used various probes covering a considerable proportion of the 120-kilobase BCL-1 locus, and rearrangements in 50% of CC/IDL (10 of 20) were detected. In CC, all 4 breakpoints were located at the major translocation cluster (MTC). In contrast, in IDL, rearrangements were detected in 3 different cluster regions: 2 cases in the MTC, 2 cases with a breakpoint 24 kilobases outside the MTC, and 2 additional cases with breakpoints found 3 kilobases 5' of the first exon of the PRAD1/CCND1 gene, which is located 120 kilobases outside the MTC. In addition, one leukemia showed a breakpoint 63 kilobases outside the MTC. In all cases, there was comigration of the rearranged 11q13 fragment and the immunoglobulin heavy chain-joining gene complex, indicating a t(11;14)(q13;q32) chromosomal rearrangement. Our results show that Southern blot analysis is helpful to identify CC/IDL, but multiple breakpoints are present over a large region, and therefore, many probes are necessary to cover all breakpoints.     

Detection of residual disease in follicular lymphomas using the PCR technique: importance of clono-specific probes

Follicular lymphoma constitutes 30-40% of non-Hodgkin's lymphomas. Most patients have widespread disease at diagnosis. The clinical course is generally indolent, and it is not usually curable with available treatment. The source of relapse in patients who achieve complete clinical remission is residual neoplastic cells that are present below the limits of detection using standard techniques. With the development of PCR technology, the presence of these residual malignant cells [Minimal Residual Disease (MRD)] has been demonstrated clearly. Recently, an association of high-dose chemotherapy with autologous bone marrow or peripheral blood progenitor cell autograft appeared promising in the treatment of these lymphomas. In the search of clonal markers for the detection of MRD in follicular lymphomas, two strategies can be used. In the cases associated with the t(14;18) (q32;q21) chromosomal translocation, the bcl-2/JH junctional regions are amplified by PCR in approximately equal to 50% of cases and then sequenced in order to synthesize an anti-junction oligonucleotide probe specific for each patient's malignant clone (clonospecific probe). In the cases negative for this translocation, an alternative strategy consists in the amplification of immunoglobulin high chain (IgH) gene rearrangement (approximately equal to 75% of cases). The present review highlights the value of molecular markers such as bcl-2/JH and VH/JH rearrangements to follow the neoplastic clone and to detect MRD in patients with follicular lymphomas.     

All patients with persistent polyclonal B cell lymphocytosis present Bcl-2/Ig gene rearrangements

The bcl-2 gene belongs to a class of oncogenes involved in the inhibition of apoptosis. Most follicular lymphomas are associated with the t(14;18) translocation that juxtaposes the bcl-2 gene located on chromosome 18 to the immunoglobulin gene locus located on chromosome 14. Consequently, the bcl-2 gene is overly expressed and leads to an accumulation of mature clonal B cells. Prolonged survival of the B cell clone appears to be the early event in tumorigenesis, creating an increased risk of cumulative mutations. Interestingly, bcl-2/Ig gene rearrangements may be identified in nearly 50% of normal individuals but the outcome of normal individuals carrying high levels of t(14;18) is not well defined. Persistent polyclonal B cell lymphocytosis (PPBL) is a unique polyclonal lymphoproliferative disorder mostly restricted to women. We have recently demonstrated that PPBL is also associated with multiple bcl-2/Ig gene rearrangements. In this report, we have extended our analysis to additional patients and demonstrated that all patients presented multiple detectable t(14;18) translocated clones. In addition, Bcl-2 protein expression was increased. Our findings, along with the clinical features of PPBL, make this disorder an exceptional model for the study of B-cell homeostasis.     

A t(3;8) chromosomal translocation associated with hepatitis B virus intergration involves the carboxypeptidase N locus

Integrated hepatitis B virus (HBV) DNA is found in the great majority of human hepatocellular carcinomas, suggesting that these viral integrations may be implicated in liver oncogenesis. Besides the insertional mutagenesis characterized in a few selected cases and the contribution of viral transactivators to cell transformation to malignancy, HBV has been shown to generate gross chromosomal rearrangements potentially involved in carcinogenesis. Here, we report a t(3;8) chromosomal translocation present in a hepatocellular carcinoma developed in noncirrhotic liver tissue. One side of the translocation, in 8p23, is shown to be in the vicinity of the carboxypeptidase N gene, a locus that is heavily transcribed in liver tissue and frequently deleted in hepatocellular carcinomas and other epithelial tumors. The other side of the translocation, in 3q27-29, is widely implicated in several types of translocations occurring in different malignancies, such as large-cell lymphomas. The present data strongly support a model in which HBV-induced chromosomal rearrangements play a key role during multistep liver oncogenesis.     

BCL6 gene rearrangements also occur in marginal zone B-cell lymphoma

Marginal zone B-cell lymphoma (MZBCL) represents a distinct subtype of B-cell non-Hodgkin's lymphoma (NHL) which has been recently recognized and defined as a disease entity. Cytogenetically, these lymphomas reveal a high prevalence of trisomy 3, and recent data obtained by comparative genomic hybridization indicate that the chromosomal regions 3q21-23 and 3q25-29 might be of particular pathogenetic significance. We identified structural chromosomal abnormalities involving the region 3q27 and rearrangements of the BCL6 proto-oncogene in three out of 34 (9%) well-defined cases of extranodal, nodal and splenic MZBCL using cytogenetic analysis. Southern blot, and fluorescence in situ hybridization (FISH). All three cases were characterized by a t(3;14)(q27;q32). Two of them showed additional chromosomal abnormalities including trisomy 3, which was found in one case. The patients displayed extranodal disease and did not demonstrate any striking clinical and histological differences when compared with MZBCL lacking BCL6 rearrangement. The present study for the first time demonstrates the occurrence of t(3;14)/BCL6 gene rearrangement in MZBCL, thus suggesting a role of the BCL6 proto-oncogene in the pathogenesis of MZBCL.     

儿童侵袭性成熟B细胞淋巴瘤的临床病理学及分子遗传学特点

目的 分析总结中国儿童各类型侵袭性成熟B细胞淋巴瘤的临床病理学及分子遗传学特点,为其诊断的标准化提供依据.方法 收集97例儿童侵袭性成熟B细胞淋巴瘤石蜡包埋组织标本,包括伯基特淋巴瘤(BL)81例、弥漫大B细胞淋巴瘤(DLBCL)8例、介于BL和DLBCL间的不能分类的B细胞淋巴瘤(BL/DLBCL)8例,利用免疫组织化学技术和间期荧光原位杂交(FISH)技术检测其免疫表型和分子遗传学特征.结果 BL的bcl-2和MUM1的阳性率分别为3%(2/66)和17%(12/71),DLBCL分别为50%(4/8)和63%(5/8),BL/DLBCL分别为50%(4/8)和63%(5/8).BL、DLBCL和BL/DLBCL的Ki-67平均值分别为(93±4.4)%、(83±14.3)%和(80±11.5)%.BL、DLBCL和BL/DLBCL的c-myc基因易位的比例分别为98%(79/81)、38%(3/8)和50%(4/8).38%(3/8)的DLBCL和25%(2/8)的BL/DLBCL存在bcl-6基因的多拷贝,BL与DLBCL之间、BL与BL/DLBCL之间bcl-2、MUM1和Ki-67平均值的差异及c-myc基因易位和bcl-6基因多拷贝的差异均有统计学意义(均P＜0.05).结论 儿童侵袭性成熟B细胞淋巴瘤的诊断和分型需要综合分析形态学、免疫表型和分子遗传学特征.儿童BL/DLBCL可能是DLBCL的一个亚型.CD10+、bcl-6+、bcl-2-、Ki-67＞90%、伴有IGH/c-myc重排、不伴有bcl-2和bcl-6重排时,支持BL的诊断;bcl-2+、Ki-67为50%～90%,同时伴有bcl-6基因的多拷贝时,支持DLBCL或BL/DLBCL的诊断.     

Pharmacological intervention in age-associated brain disorders by Flupirtine: Alzheimer''s and prion diseases

The study of chromosomal changes related to tumor progression in NHL is complicated by the various histologic classification systems and the lack of large serial studies comparing abnormalities at different disease stages. The T-cell lymphomas frequently involve rearrangements of the T-cell receptors and tumor progression is marked by a change from single cell aberrations and polyclonality in low grade disease to monoclonal formation, complex clones, polyploidy, and abnormalities of 1p, 6q, 7, and 13 in high grade T-NHL. In B-cell NHL, specific translocations and oncogene rearrangements are associated with specific NHL subtypes de novo; many of these translocations involve immunoglobulin genes, such as t(14;18) in follicular lymphoma, t(11;14) in MCL, t(3;14) in DLLC, and t(8;14) in Burkitt's lymphoma. Tumor progression is associated with secondary abnormalities which are generally not confined to a particular NHL subtype. Some abnormalities, such as those involving chromosomes 1, 6, and 17, >4-6 clonal markers/cell, and rearrangements of c-MYC and TP53, have prognostic significance while others, such as trisomies 7, 12, 18, and X, are associated with tumor progression but their influence on overall survival is uncertain.     

Structure of Bcl-1 and IgH-CDR3 rearrangements as clonal markers in mantle cell lymphomas

Mantle cell lymphoma represent a clinicopathologically distinct entity of malignant non-Hodgkin's lymphoma (NHL) and are characterized by a specific chromosomal translocation t(11;14)(q13;q32) involving the cyclin D1 gene also designated as bcl-1/PRAD1 gene on chromosome 11 and the heavy chain immunoglobulin joining region on chromosome 14. We have established a PCR method to amplify t(11;14) junctional sequences in DNA from fresh frozen and paraffin-embedded tissue by bcl-1-specific primers in combination with a consensus immunoglobulin JH primer. A total of 65 cases histologically classified as mantle cell lymphoma (MCL) were analyzed for the presence of a t(11;14) translocation and monoclonal IgH-CDR3 rearrangements. From 26 patients with classical MCL and three cases with the anaplastic variant of MCL fresh frozen biopsy material was available for DNA extraction. We detected a bcl-1/JH rearrangement in 12 out of 29 samples (41%). In 36 cases paraffin-embedded lymph node tissue was the only source of DNA. In this material we found a bcl-1/JH rearrangement in six out of 31 samples with intact DNA (20%). To confirm the specificity of the PCR and to determine the bcl-1/JH junctional region sequences as clone-specific marker in individual patients we characterized the junctional DNA sequences by direct PCR sequencing in 16 cases. Interestingly we found that six bcl-1/JH junctions harbored DH segments in their N regions indicating that bcl-1/JH rearrangements can occur in a later stage of B cell ontogeny during which the complete VH to DH-JH joining or VH-replacement takes place. To investigate the suitability of IgH-CDR3 as sensitive molecular marker for those MCL patients in which a t(11;14) translocation can not easily be amplified, we additionally analysed 60 cases for the presence of monoclonally rearranged IgH genes by IgH-CDR3-PCR. A monoclonal IgH-CDR3 PCR product could be identified in 24 out of 29 fresh frozen samples (79%) whereas only 11 out of 31 samples (36%) with paraffin-derived DNA were positive. We demonstrate that automated fluorescence detection of monoclonal IgH-CDR3 PCR products allows the rapid and sensitive monitoring of minimal residual disease also in cases that lack a PCR amplifiable t(11;14) translocation. In combination with allele-specific primers the procedure may improve current experimental approaches for detection of occult MCL cells at initial staging and residual disease during and after therapy.     

Restriction fragment length polymorphism analysis of Mycobacterium bovis isolates from captive and free-ranging animals

c-myc gene abnormalities associated with lymphomagenesis, including rearrangements and mutations in the regulatory region between exon I and intron I, have been studied in 54 MALT lymphomas (43 low and 11 high grade) and 36 nodal lymphomas (27 low and 9 high grade). By Southern blot analysis, none of the 54 MALT lymphomas but 2 of 36 nodal lymphomas had c-myc gene rearrangements. Defined tumour cell populations from all MALT lymphoma cases were isolated by microdissection from frozen tissue sections and analysed by polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) and direct sequencing for somatic mutations in the exon I/intron I region of the gene. Point mutations in this region were identified in nine cases of MALT lymphomas (7/43 = 16.2 per cent of low grade; 2/11 = 18.1 per cent of high grade). These mutations were located at either the exon I/intron I border of myc intron factor (MIF) binding sites, which are critical in the negative regulation of c-myc expression. Of the nodal lymphomas, only the two cases (5-6 per cent) with c-myc gene rearrangement showed scattered or clustered mutations. These results suggest that c-myc mutations in MALT lymphomas are unlikely to be associated with chromosome translocation, which is the main cause of somatic mutations observed in other types of lymphomas. The mutations involving the c-myc regulatory regions may play a pathogenetic role in at least a proportion of MALT lymphomas.     

The t(11;18)(q21;q21) chromosome translocation is a frequent and specific aberration in low-grade but not high-grade malignant non-Hodgkin's lymphomas of the mucosa-associated lymphoid tissue (MALT-) type

Primary extranodal malignant non-Hodgkin's lymphoma arising from the mucosa-associated lymphoid tissue (MALT-type lymphoma) represents a subtype of B-cell lymphoid malignancies with distinct clinicopathological features and is often associated with a favorable prognosis. Unlike the situation in nodal non-Hodgkin's lymphoma of B-cell lineage, few data are still available concerning the chromosomal constitution of MALT-type lymphomas. Until now, cytogenetic data from 29 low-grade MALT lymphomas with karyotypic alterations have been reported from different institutions, and virtually no data were available for high-grade MALT-type lymphomas. We have analyzed the cytogenetics of 44 MALT lymphomas arising in the stomach, parotid gland, thyroid gland, lung, breast, and conjunctiva. Clonal chromosome aberrations have been detected in 13 of 20 (65%) low-grade and 20 of 24 (83%) high-grade tumors. More than half of the low-grade lymphomas with abnormal karyotypes (7 of 13 cases, 53%) displayed clonal t(11;18)(q21;q21), thus specifically associating this translocation with MALT-type lymphomas for the first time in a larger series. In contrast, t(11;18) was not found in a single case of 20 high-grade MALT-type lymphomas with abnormal karyotypes, nor were translocations t(14;18) or t(3;14), characterizing about 10-35% of primary nodal large cell lymphomas. Instead, these lymphomas were associated with t(8;14)(q24;q32) in three cases, frequent deletions in the long arm of chromosome 6, and partial or whole gains of chromosomes 3, 7, 17, 18, and 21.     

Lack of ETV6 (TEL) gene rearrangements or p16INK4A/p15INK4B homozygous gene deletions in infant acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) occurring in infants less than 1 year of age differs clinically and biologically from that observed in older children. Cytogenetically, 11q23 translocations are detected in approximately 50% of infant ALLs and fuse the 11q23 gene HRX with a variety of partner chromosomal loci. Overall, HRX rearrangements are detected molecularly in 70-80% of infant ALLs as compared to 5-7% of ALLs arising in older children. Two recently described molecular abnormalities in childhood ALL are ETV6 gene rearrangements and homozygous deletions of p16(INK4A) and/or p15(INK4B). Each of these abnormalities occurs in 15-20% of all childhood ALLs, and neither can be accurately identified by routine cytogenetic analyses. The incidence of these genetic abnormalities and their potential relationship to HRX gene status in infant ALL is unknown. Using Southern blot analyses, we determined ETV6 and p16(INK4A)/p15(INK4B) gene status in a cohort of infant ALLs. No ETV6 rearrangements or homozygous deletions (n=69) or homozygous p16(INK4A) and/or p15(INK4B) gene deletions (n=54) were detected in any of the infant ALLs. Therefore, ETV6 and p16(INK4A)/p15(INK4B) do not play a significant role in the pathogenesis of infant ALL, further emphasizing the distinctive biology of this subset of leukemias.     

Fluorescence in situ hybridization analyses of hematologic malignancies reveal frequent cytogenetically unrecognized 12p rearrangements

Thirty-two hematologic malignancies--nine with cytogenetically identified 12p abnormalities and 23 with whole or partial losses of chromosome 12--were selected for fluorescence in situ hybridization (FISH) investigations of 12p. These analyses revealed structural 12p changes, such as translocations, deletions, insertions, inversions and amplification, in 20 cases. ETV6 rearrangements were detected in three acute leukemias. One acute undifferentiated leukemia had t(4;12)(q12;p13) as the sole anomaly. The second case, an acute myeloid leukemia (AML), displayed complex abnormalities involving, among others, chromosomes 9 and 12. The third case, also an AML, had an insertion of the distal part of ETV6 into chromosome arm 11q and into multiple ring chromosomes, which also contained chromosome 11 material, resulting in an amplification of a possible fusion gene. The fusion partners in these cases remain to be identified. Thirty-one additional breakpoints on 12p could be characterized in detail. The majority of these breaks were shown to result in interchromosomal rearrangements, possibly indicating the location of hitherto unrecognized genes of importance in the pathogenesis of hematologic malignancies. The FISH analyses disclosed terminal or interstitial 12p deletions in 18 cases. Seven myeloid malignancies showed deletions restricted to a region, including ETV6 and CDKN1B, which has been reported to be frequently lost in leukemias. In four cases, the deletions involved both these genes, whereas two AML displayed loss of CDKN1B but not ETV6, supporting previously reported findings indicating a region of deletion not including this gene. However, one myelodysplastic syndrome lacked one copy of ETV6 but not CDKN1B. Hence, we suggest a minimal region of deletion on 12p located between the ETV6 and CDKN1B genes.