Amplification of the translocated c-myc genes in three Burkitt lymphoma cell lines

Khaira, P; James, C D; Leffak, Michael

doi:10.1016/s0378-1119(98)00104-8

Cited by 6 publications

(3 citation statements)

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“…It was concluded that amplified copies of the translocated myc exons are associated with chromosomal DNA only in ST486 cells and persistent extrachromosomal elements are present in both lines. 16 The presence of amplified myc exons is consistent with our FISH detection of additional double signals on der t(8;14;18) to a total of four copies in ST486 line. Notably, the CGH profile shows DNA overrepresentation confined to 8q24.…”

Section: Figuresupporting

confidence: 86%

Novel genomic imbalances and chromosome translocations involving c-myc gene in Burkitt's lymphoma

2001

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In this study, CA46 and ST486, two Epstein-Barr (EBV) negative cell lines derived from sporadic BL, were analyzed by multicolor spectral karyotyping, G-banding, fluorescence in situ hybridization with single-copy gene probes, and comparative genomic hybridization (CGH). In addition to reciprocal t(8;14)(q24;q32) translocation involving c-myc and IgH loci, we identified a t(7;8;14)(q11.2;q24;q32) translocation in CA 46 cells and t(8;14;18)(q24;q32;q23) in ST486 cells. Both rearrangements were not previously described in BL and resulted in transposition of myc sequences in a new genomic configuration. Several DNA imbalances mapped by CGH at the same sites in both lines, may reflect recurrent genomic changes that are relevant to pathogenesis of BL. We tested the tumorigeni-

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Section: Figuresupporting

confidence: 86%

Novel genomic imbalances and chromosome translocations involving c-myc gene in Burkitt's lymphoma

2001

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“…Gene amplification can be intrachromosomal and can be visualized as homogeneously staining regions (HSRs), or it can be found extrachromosomally in the form of double minutes (DMs) (6,9,22,23), also referred to as extrachromosomal elements (EEs). In many cases, EEs have been shown to carry oncogenes (12) and drug-resistant genes (20,29). Recently, Wiener et al (30) described a population of c-myc/IgH-carrying EEs that were able to actively transcribe c -myc mRNA and functionally replace a Myc-activating chromosomal translocation.…”

Section: Introductionmentioning

confidence: 99%

Isolation of Extrachromosomal Elements by Histone Immunoprecipitation

Kuschak

Smith

et al. 2001

BioTechniques

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Here, we describe a gentle and effective method for the rapid and reproducible isolation of histone-bound extrachromosomal DNA molecules called extrachromosomal elements (EEs). This method facilitates the harvest of a specific population of EEs following their isolation from cultured cells, primary tissues, and tumor cells. Active EEs are bound to histone proteins, and these histone-bound EEs carry actively transcribing genes such as c-myc. Our method exploits the presence of histones on EEs and serves as a first-step purification procedure, allowing for the cloning or multivariant analysis of an immunopurified sample of EEs. We isolated EEs from 4-hydroxytamoxifen (4-HT)-activated Myc-ER-regulatable Pre-B ABM cells. Following one round of immunoprecipitation, we demonstrate the purification of histone-bound EEs. We confirmed that our purification enriched for EEs that carry genes by fluorescent in situ hybridization of EEs (FISH-EEs), and we probed non-enriched and immunopurified EEs with a dihydrofolate reductase (DHFR) cDNA probe that is known to detect extrachromosomal amplification in Myc-activated cells. We demonstrate the enrichment of immunoprecipitated DHFR-containing extrachromosomal DNA molecules.

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“…Virtually all BLs show translocation of the c-myc gene with the heavy-or light-chain immunoglobulin (Ig) locus, and most of them also contain somatic mutations (Cesarman et al, 1987;Dalla-Favera et al, 1982;Khaira et al, 1998). Diffuse large B-cell lymphomas (DLBCLs) display c-myc translocations in 1 to 15% of cases (Cigudosa et al, 1999;Kramer et al, 1998;Vitolo et al, 1998), amplifications in 15% (Rao et al, 1998), and somatic mutations in 32% of tumors (Pasqualucci et al, 2001 143 structural alterations were accompanied by an altered pattern of c-myc transcription, specifically the removal of the block on transcriptional elongation (Bradley et al, 1993;Cesarman et al, 1987).…”

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confidence: 99%

Development of a Real-Time Reverse Transcription Polymerase Chain Reaction Assay for c-myc Expression That Allows the Identification of a Subset of c-myc+ Diffuse Large B-Cell Lymphoma

Sáez¹,

Artiga

Romero

et al. 2003

Laboratory Investigation

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SUMMARY:Absence of a reliable method for determining the level of c-myc expression has impeded the analysis of its biological and clinical relevance in tumors. We have standardized the conditions for a real-time reverse transcription polymerase chain reaction analysis for c-myc expression, including the selection of an endogenous reference (18S rRNA), the adequate number of measurements for each sample (2 cDNA in triplicate), and suitable controls for determining inter-and intrarun variability (standard curve and calibrator). Subsequently, in a series of 56 non-Hodgkin's lymphomas, we analyzed the expression of c-myc mRNA, using real-time reverse transcription polymerase chain reaction, and of other functionally related proteins (bcl-6, p27, cyclin D3, and p53). As expected, all eight Burkitt's lymphoma cases analyzed had high levels of c-myc mRNA expression compared with that observed in reactive lymphoid tissue. There was a wider range of expression in diffuse large B-cell lymphoma, with 30% (15 of 48) of cases overexpressing c-myc. This overexpression was largely independent of c-myc translocations (4 of 5), as demonstrated by fluorescence in situ hybridization. In this large B-cell lymphoma series, a high level of c-myc expression predicted lower survival probability, irrespectively of the International Prognostic Index risk group classification. A slightly increased frequency of p53 inactivation was observed in the cases with c-myc overexpression, which suggests a growth advantage in lymphomas with concurrent deregulation of c-myc and p53. In addition, a moderate increase in bcl-6 protein expression was observed in the c-myc-positive cases, suggesting the existence of a complex interrelationship between these two genes. These findings suggest that c-myc may play a relevant role in the pathogenesis of a subset of large B-cell lymphoma and suggest the existence of additional regulatory mechanisms of c-myc expression to c-myc rearrangements. (Lab Invest 2003, 83:143-152). C-myc is a multifunctional gene involved in important cellular processes, such as cell proliferation, differentiation, and apoptosis. c-myc targets include critical genes involved in growth, the cell cycle, signaling, and adhesion (eg, cyclin D2, cyclin D3, DP1, p27 KIP1 , p21 CIP1 , AKT, Cul-1, TGFR-2, CDC25C, API2, BclII) (Coller et al, 2000;Eischen et al, 2001;Guo et al, 2000;Nasi et al, 2001;Neiman et al, 2001;Nesbit et al, 2000;O'Hagan et al, 2000;Schuhmacher et al, 2001).Although c-myc gene was initially described as being involved in t(8;14) in Burkitt's lymphoma (BL), overexpression of c-myc has been found in other solid tumors such as breast, prostate, and gastrointestinal carcinomas and in melanoma. In these neoplasias, c-myc expression has been shown to be dependent on amplifications of the gene or to be derived from deregulation of upstream genes in the c-myc pathway, such as BRCA1, PTEN, and ␤-catenin/APC (Nesbit et al, 1999). In addition, N-myc has been implicated in the pathogenesis of neuroblastomas (Fulda et al, 1999).c-myc ...

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Amplification of the translocated c-myc genes in three Burkitt lymphoma cell lines

Cited by 6 publications

References 47 publications

Novel genomic imbalances and chromosome translocations involving c-myc gene in Burkitt's lymphoma

Novel genomic imbalances and chromosome translocations involving c-myc gene in Burkitt's lymphoma

Isolation of Extrachromosomal Elements by Histone Immunoprecipitation

Development of a Real-Time Reverse Transcription Polymerase Chain Reaction Assay for c-myc Expression That Allows the Identification of a Subset of c-myc+ Diffuse Large B-Cell Lymphoma

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