Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The majority of non-Hodgkin's B-cell lymphomas contain a t(14;18) translocation that places the bc12 gene into juxtaposition with the transcriptically active Ig heavy-chain locus, thus deregulating the expression of this proto-oncogene. The bc12 gene product is a membrane-associated mitochondrial protein that regulates cell survival through unknown mechanisms. Although overproduction of the normal protein appears sufficient for conferring a selective growth or survival advantage to B cells, point mutations that alter the coding region of translocated bc12 genes have been described previously by others in a lymphoma cell line. However, it is not known whether somatic mutations that alter BCL2 proteins occur in vivo or whether they result from chemotherapy or arise through other mechanisms. For these reasons, we obtained DNA from the t(14;18)-containing tumors of five patients who had not undergone treatment for their disease, and used a polymerase chain reaction (PCR)-mismatch technique for rapid identification of point mutations in a portion of the bc12 open reading frame (ORF) corresponding to the first 131 aminoacids (aa) of the 239 aa p26 BCL2 protein. DNAs from two t(14;18)-containing cell lines were also analyzed. Point mutations in this region of the bc12 gene ORF were detected in three of five patients' tumors and in both cell lines. PCR-mismatch analysis of bc12 in cell lines and non-Hodgkin's lymphoma cases that lacked the t(14;18) translocation was negative, thus establishing the specificity of these results. DNA sequencing determined that these mutations are predicted to produce aa substitutions in the BCL2 proteins of two of the primary tumors and one of the cell lines. Interestingly, two of the patients contained an identical C----T transition that resulted in a nonconservative aa substitution (proline----serine) at position 59 of the BCL2 protein. Further analysis excluded the possibility that these mutations represented hereditary polymorphisms or PCR artifacts. A cluster of four point mutations within the translocation + bc12 allele of one patient had hallmarks of the somatic hypermutation mechanism that is associated with Ig genes and that contributes to antibody diversity. Because of the region of the bcl2 gene analyzed in these t(14;18) translocations is located nearly 300 kbp from the Ig heavy-chain locus, our data suggest that the Ig gene somatic hypermutation mechanism can act over extreme distances of DNA. It remains to be established whether these somatic mutations that alter BCL2 proteins influence the pathobiology of nonHodgkin's lymphomas.
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PMID:Frequent incidence of somatic mutations in translocated BCL2 oncogenes of non-Hodgkin's lymphomas. 133 99

Two t(14;18)-negative follicular B-non-Hodgkin's lymphomas with the same chromosomal abnormality, dup(12)(q13----qter), are presented. The absence of a BCL2 gene rearrangement was confirmed by molecular studies in both cases. Instead, duplication of a 12q segment was found. Further evidence for the presence of the dup(12)(q13----qter) was found using fluorescence in situ hybridization. dup(12q) may be equivalent to the trisomy 12 originally described in B-chronic lymphocytic leukemia. This chromosome anomaly has also been reported in B-non-Hodgkin's lymphomas, usually in association with other chromosome anomalies and a more aggressive tumor phenotype. Occurrence of dup(12q) in two histologically similar cases of follicular small cleaved-cell lymphoma without a typical t(14;18), suggests that this karyotypic change may play a critical role in some cases of follicle center-cell lymphomas.
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PMID:dup(12)(q13----qter) in two t(14;18)-negative follicular B-non-Hodgkin's lymphomas. 137 36

The presence of the translocation t(8;14)(q24;q32) has not been well described in follicular lymphoma (FL). In a consecutive series of 278 karyotypically abnormal non-Hodgkin's lymphomas (NHL), six patients with FL showing a t(8;14) without a t(14;18)(q32;q21) were identified. They ranged in age from 45 to 73 years. The cell type was mixed in four patients, small-cleaved in one, and large-cleaved in one; four cases also contained diffuse areas. All cases tested displayed monoclonal surface Ig. The clinical courses were consistent with the histologic subtypes, being less aggressive than other t(8;14)-bearing NHL. In five cases, frozen tissue was available for Southern blotting. The BCL2 gene showed a germline configuration when studied with the MBR, MCR, and 5' cDNA probes. The MYC gene also appeared unrearranged using an exon-1 probe with EcoRI or HindIII digestion. Analysis of the Ig heavy chain (IgH) gene with a JH region probe and BamHI or EcoRI digestion showed only one rearranged band in all cases, indicating that the 14q32 breakpoint did not lie in either the J or switch-mu (SM) regions. In four cases, the exon-1/intron-1 border of the MYC gene, a target area for point mutations in cases of t(8;14) that do not display rearrangements of the MYC gene, was enzymatically amplified and sequenced; no point mutations were identified. The indolent behavior of our six cases, and the finding that the molecular structure of the t(8;14) in these cases does not follow the pattern of breakpoint sites and point mutations defined in other histologic subtypes of NHL with this translocation, suggest that the t(8;14) in these cases is cytogenetically and molecularly distinct from the t(8;14) seen in high-grade NHLs, and is relatively ineffectual in terms of MYC deregulation, or that other genetic elements at these chromosomal sites may be involved. Further analysis of these tumors may provide insights into MYC deregulation and BCL2-independent FL.
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PMID:Follicular lymphoma with t(8;14)(q24;q32): a distinct clinical and molecular subset of t(8;14)-bearing lymphomas. 156 38

The bcl2 protooncogene was originally discovered because of its involvement in t(14;18) chromosomal translocations frequently found in non-Hodgkin's lymphomas. The expression of this gene is reported to be highly tissue specific, with bcl2 mRNAs being readily detectable only in hematolymphoid tissues and brain. To explore the possible involvement of bcl2 in neural tumors, we surveyed a variety of tumor cell lines for the presence of the p26-BCL2 protein by immunoprecipitation and immunoblotting methods. Very high levels of BCL2 protein were found in three of nine neuroblastoma (NB) cell lines examined; these levels of p26-BCL2 were comparable to lymphoma cell lines that contain a t(14;18). Despite the impressive relative amounts of BCL2 protein, however, no structural alterations or changes in the methylation status of bcl2 genes were detected in these NB cell lines by conventional Southern blotting. Of the other NB cell lines surveyed, three contained intermediate levels of BCL2 and another three cell lines had little or no detectable BCL2 protein, raising the possibility that determination of relative levels of BCL2 protein may help to segregate neuroblastomas into groups with different biological and clinical characteristics. BCL2 protein levels were not influenced by induction of neuronal differentiation with nerve growth factor in two of the two cell lines examined [SH-SY5Y (high BCL2); GICAN (low BCL2)] and did not correlate with N-MYC gene amplification or expression of nerve growth factor receptors. NB cell lines that contained little or no detectable BCL2 protein, however, tended to contain significant proportions of flat epithelioid cells, whereas bcl2-expressing cell lines were composed primarily of neuronal-like cells, suggesting that expression of this protooncogene correlates with the differentiation characteristics of these tumor cell lines. In addition to NBs, lower levels of BCL2 protein were also found in a variety of other neural crest-derived tumors and tumor cell lines, including some neuroepitheliomas, Ewing's sarcomas, neurofibromas, and melanomas. With regard to tumors of central nervous system origin, bcl2 expression was absent from most medulloblastomas but was detected at moderate to low levels in a retinoblastoma and some glioblastoma multiforme cell lines. Taken together, these findings imply that bcl2 protooncogene expression is differentially regulated within the various lineages of cells that give rise to the nervous system.
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PMID:Differential expression of bcl2 protooncogene in neuroblastoma and other human tumor cell lines of neural origin. 174 26

The molecular structure of reciprocal translocations associated with low grade and high grade non-Hodgkin's lymphomas occurring together was analysed in two tumors. Sequential biopsies documented histological transformation of a large cell lymphoma to an immunoblastic lymphoma bearing t(14;18)(q32;q21) and t(8;22)(q24;q11). A second tumor, a small non-cleaved cell lymphoma, demonstrated a t(8;14)(q24;q11) as well as t(18;22)(q21;q11). DNA analysis from these tumors showed rearrangements at the Ig heavy chain, kappa and lambda light chains, BCL2 and c-MYC loci. Utilizing multiple enzyme digests and different probes spanning the BCL2, c-MYC and Ig genes, mapping of DNA break-points was performed. In both these tumors primary translocation events dysregulating the BCL2 or c-MYC were identified to have occurred in a pre-B-cell. Based on these results and those published previously, a sequence of B-cell development during which somatic recombination errors lead to the genesis of specific translocations is proposed. From these studies it is inferred that secondary dysregulation of a c-MYC in a lymphoma tumor carrying dysregulated BCL2 gene leads to rapid progression to high grade disease.
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PMID:Molecular structure of double reciprocal translocations: significance in B-cell lymphomagenesis. 199 41

The identification of recurring chromosomal translocations has provided clues to the gene regions important in lymphoma development. Among 157 patients with non-Hodgkin lymphoma studied by cytogenetic analysis, four new recurring translocations have been identified--t(8;9) (q24;p13), t(11;18)(q21;q21), t(14,15)(q32;q15), and an unbalanced translocation giving rise to der(22)t(17;22) (q11;p11). Each translocation appeared twice. The t(11;18) was the only karyotypic abnormality in the two patients with it, and the t(14;15) was the sole karyotypic abnormality in one patient. All translocations were found in B-cell malignancies and were associated with both nodal and extranodal disease. Among the regions affected, only the immunoglobulin heavy-chain gene MYC, and BCL2, have thus far been associated with lymphoma. The breakpoint sites identified by these translocations warrant further investigation at the molecular level.
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PMID:Four new recurring translocations in non-Hodgkin lymphoma. 250 53

Although translocations of the BCL2 gene are frequent in B-cell non-Hodgkin's lymphomas (B-NHL) the incidence, nature, and prognostic significance of similar translocations in the phenotypically related chronic leukemias of mature B cells are unknown. Therefore, we examined 170 cases of B-cell chronic lymphocytic leukemia (B-CLL), 7 cases of B-cell prolymphocytic leukemia (B-PLL), 25 cases of hairy cell leukemia (HCL) and 22 cases of splenic lymphoma with villous lymphocytes (SLVL) with defined cytogenetic abnormalities by DNA blot using both 5' and 3' BCL2 probes to search for rearrangement of the BCL2 locus. Translocation t(14;18) (q32.3;q21.3) was detected cytogenetically in 3 cases of B-CLL. All had breakpoints in the 3' region of BCL2, mapping between the major breakpoint region (MBR) and the minor cluster region (mcr), the breakpoint clusters commonly detected in B-NHL. In 2 of the 3 cases, the breakpoint within BCL2 was mapped to a 1.0-kb EcoRI-HindIII fragment indicating a clustering of breakpoints. Two cases of B-CLL had cytogenetically detectable t(2;18)(p11;q21.3) or t(18;22)(q21.3;q11). Both had rearranged the 5' region of the BCL2 gene to the corresponding lg light-chain gene. Molecular cloning of the t(18;22)(q21.3;q11) showed that the translocation disrupted the BCL2 promoter region and the first untranslated BCL2 exon. Nevertheless, high levels of BCL2 protein were seen in this case. Only 2 other cases in whom cytogenetic analysis was not successful showed rearrangement of the 5' region of BCL2, an overall incidence of 2.3%. No cases of B-PLL, HCL, or SLVL showed either 5' or 3' BCL2 rearrangement. These data confirm the cytogenetic observations that translocations involving the BCL2 locus in all forms of leukemia of mature B cells are rare, and limited to a minor subset of B-CLL. BCL2 translocations in B-CLL involve hot spots of recombination of both the 5' and 3' regions of the BCL2 gene, which are distinct from those commonly seen in B-NHL, suggesting distinct pathogenic mechanisms.
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PMID:BCL2 translocations in leukemias of mature B cells. 820 92

Translocation t(3;22)(q27;q11) has recently been recognized as a recurrent abnormality in non-Hodgkin's malignant lymphoma (NHL). A new gene, LAZ3, has been shown to be involved in NHL with 3q27 rearrangement. Two patients with B-cell NHL were studied by chromosome painting and Southern blot analysis. Fluorescence in situ hybridization to metaphase chromosomes was shown to be an easy way to detect the chromosomal abnormality even in metaphase cells with poorly defined chromosomes. The gene LAZ3 was rearranged in one patient in the 'major translocation cluster region'. The comigration of rearranged LAZ3 and of IGL bands suggests that the translocation resulted in the juxtaposition of the two genes. This juxtaposition makes possible a potential deregulation of the LAZ3 gene expression, as previously shown for the MYC and BCL2 genes in Burkitt and follicular lymphoma translocations.
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PMID:Translocation t(3;22)(q27;q11) in non-Hodgkin's malignant lymphoma: chromosome painting and molecular studies. 825 95

Twelve B-cell non-Hodgkin's lymphomas with BCL6/LAZ3 rearrangement selected from a series of 30 lymphomas with cytogenetically detectable 3qter abnormalities were characterized at the histological, clinical, and cytogenetic levels, including fluorescence in situ hybridization (FISH) analysis, which was performed in all cases but one. A classical t(3;14) and t(3;22) were found in three patients (25%). In the remaining cases, eleven different 3q27 abnormalities were demonstrated and characterized with the use of chromosome painting. Seven of twelve "variant" rearrangements identified in our series affecting 1p32, 1p34, 3p14, 6q23, 12p13, 14q11, and 16p13 have not been reported before. Moreover, involvement of both homologs of chromosome 3 in distinct translocations was detected as an unexpected result in two cases and was confirmed via FISH in a third case. The putative bichromosomal rearrangements of the 3q27 region were evidenced by Southern analysis in one of these cases. In another case, FISH with a cosmid spanning the 3q27 breakpoint region demonstrated the involvement of BCL6/LAZ3 only in one of two t(3q27). In our series, which was selected on cytogenetic and molecular criteria, 50% (6 of 12) of cases with BCL6/LAZ3 rearrangement were diagnosed as diffuse, large B-cell lymphomas (DLCL). Another 33% (4 of 12) of cases were diagnosed as follicular center lymphomas (FL), with t(14;18)/BCL2 rearrangement in all but one case. Furthermore, in three follicular lymphoma cases in which multiple samples were analyzed, the disease showed no evidence of histological progression during a follow-up period of 3-14 years.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fluorescence in situ hybridization identifies new chromosomal changes involving 3q27 in non-Hodgkin's lymphomas with BCL6/LAZ3 rearrangement. 852 78

Concurrent activation of BCL2 and MYC usually occurs in B cell non-Hodgkin lymphoma (B-NHL) by translocation of both oncogenes to both immunoglobulin heavy chain (IGH) alleles: this abrogates immunoglobulin synthesis. We have studied three B-NHL cell lines (DoHH2, VAL and ROS 50) and show that concurrent activation of BCL2 and MYC may follow translocation of both oncogenes to the same IGH allele. Conventional cytogenetics of DoHH2 suggested the presence of a t(14;18)(q32;q21) translocation. However, fluorescent in situ hybridization (FISH) studies using whole chromosome paints, alpha satellite probes and flow-sorted chromosomes as probes revealed an unexpected complexity of rearrangements involving chromosomes 8, 14 and 18, namely t(8;14;18)(q24;q32;q21). DNA blot and previous PCR analysis confirmed the juxtaposition of BCL2 major breakpoint region (mbr) with IGJH6, but also demonstrated a rearrangement within the first exon of MYC. The centromeric (5') MYC rearranged fragment comigrated with the BCL2-JH6 rearranged fragment in BamHI, EcoRI and Bg/II restriction digests. The der(8)t(8;14;18) therefore comprised 5' MYC (exon I)-Sgamma4-JH6-BCL2 mbr. Similar rearrangements were observed in both ROS 50 and VAL cell lines which contained two and three copies of the der(8)t(8;14;18) respectively. Quantitative flow cytometry for BCL2 and MYC expression showed abundant expression of both proteins in all three lines. These data indicate the der(14)t(14;18)(q32;q21) may itself be the target for any second translocation. The presence of the intact BCL2-JH fusion gene on the der(8)t(8;14;18) allowed concurrent activation of both BCL2 and MYC with no loss of immunoglobulin expression.
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PMID:Concurrent activation of MYC and BCL2 in B cell non-Hodgkin lymphoma cell lines by translocation of both oncogenes to the same immunoglobulin heavy chain locus. 868 2


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