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A Migliazza

Publications and source records attributed to A Migliazza.

18 recordsLinked to original sources
PubMed1999

Genetic characterization of HHV-8/KSHV-positive primary effusion lymphoma reveals frequent mutations of BCL6: implications for disease pathogenesis and histogenesis.

Human herpesvirus-8/Kaposi sarcoma-associated herpesvirus-positive primary effusion lymphoma (PEL) is a recently identified B-cell non-Hodgkin lymphoma category characterized by liquid growth in the serous body cavities. Apart from viral infection, no genetic alteration is known to be associated with PEL and no recurrent cytogenetic abnormality has been identified in these lymphomas. Yet the consistent monoclonality of PEL indicates that the disease is not solely a virus-driven proliferation. Here we report that PEL is associated with a high frequency of mutations of BCL6 5' noncoding regions, and we identify karyotypic abnormalities that may be recurrently involved in these lymphomas. Mutations of BCL-6 5' noncoding regions occurred in 8/13 PEL. Mutations occurred in the absence of BCL6 gross rearrangements were often multiple in the same patient (7/8 mutated cases), and occurred in both HIV-positive and HIV-negative individuals. Since BCL6 mutations are regarded as a genetic marker of B-cell transition through the germinal center (GC), these data are consistent with histogenetic derivation of PEL from GC or post-GC B-cells. Cytogenetic and FISH analysis of seven PEL cell lines showed frequent occurrence of complete or partial trisomy 12 (7/7 cases), trisomy 7 (4/7 cases), and abnormalities of bands Iq21-25 (5/7 cases).

5' Untranslated Regions↗
PubMed1998

BCL-6 gene mutations in posttransplantation lymphoproliferative disorders predict response to therapy and clinical outcome.

Posttransplantation lymphoproliferative disorders (PT-LPDs) represent a heterogeneous group of Epstein-Barr virus-associated lymphoid proliferations that arise in immunosuppressed transplant recipients. Some of these lesions regress after a reduction in immunosuppressive therapy, whereas some progress despite aggressive therapy. Morphological, immunophenotypic, and immunogenotypic criteria have not been useful in predicting clinical outcome. Although structural alterations in oncogenes and/or tumor suppressor genes identified in some PT-LPDs correlate with a poor clinical outcome, the presence of these alterations has not been a consistently useful predictor of lesion regression after reduction of immunosuppression. We examined 57 PT-LPD lesions obtained from 36 solid organ transplant recipients for the presence of mutations in the BCL-6 proto-oncogene using single-strand conformation polymorphism and sequence analysis, followed by correlation with histopathologic classification and clinical outcome, which was known in 33 patients. BCL-6 gene mutations were identified in 44% of the specimens and in 44% of the patients; none were identified in the cases classified as plasmacytic hyperplasia. However, mutations were present in 43% of the polymorphic lesions and 90% of the PT-LPDs diagnosed as non-Hodgkin's lymphoma or multiple myeloma. BCL-6 gene mutations predicted shorter survival and refractoriness to reduced immunosuppression and/or surgical excision. Our results suggest that the BCL-6 gene structure is a reliable indicator for the division of PT-LPDs into the biological categories of hyperplasia and malignant lymphoma, of which only the former can regress on immune reconstitution. The presence of BCL-6 gene mutations may be a useful clinical marker to determine whether reduction in immunosuppression should be attempted or more aggressive therapy should be instituted.

Cell Transformation, Neoplastic↗
PubMed1998

BCL-6 mutations in normal germinal center B cells: evidence of somatic hypermutation acting outside Ig loci.

The molecular mechanism involved in the process of antigen-driven somatic hypermutation of Ig genes is unknown, but it is commonly believed that this mechanism is restricted to the Ig loci. B cell lymphomas commonly display multiple somatic mutations clustering in the 5'-regulatory region of BCL-6, a proto-oncogene encoding for a POZ/Zinc finger transcriptional repressor expressed in germinal center (GC) B cells and required for GC formation. To determine whether BCL-6 mutations represent a tumor-associated phenomenon or reflect a physiologic mechanism, we screened single human tonsillar GC B cells for mutations occurring in the BCL-6 5'-noncoding region and in the Ig variable heavy chain sequences. Thirty percent of GC B cells, but not naive B cells, displayed mutations in the 742 bp region analyzed within the first intron of BCL-6 (overall frequency: 5 x 10(-4)/bp). Accordingly, an expanded survey in lymphoid malignancies showed that BCL-6 mutations are restricted to B cell tumors displaying GC or post-GC phenotype and carrying mutated Ig variable heavy chain sequences. These results indicate that the somatic hypermutation mechanism active in GC B cells physiologically targets non-Ig sequences.

B-Lymphocytes↗
PubMed1998

The molecular and phenotypic profile of primary central nervous system lymphoma identifies distinct categories of the disease and is consistent with histogenetic derivation from germinal center-related B cells.

Primary central nervous system lymphoma (PCNSL) is a major cause of morbidity and mortality among human immunodeficiency virus (HIV)-infected individuals. The precise histogenetic derivation and the molecular pathogenesis of PCNSL is poorly understood. In an attempt to clarify the histogenesis and pathogenesis of these lymphomas, 49 PCNSL (26 acquired immunodeficiency syndrome [AIDS]-related and 23 AIDS-unrelated) were analyzed for multiple biologic markers, which are known to bear histogenetic and pathogenetic significance for mature B-cell neoplasms. PCNSL associated frequently (50.0%) with mutations of BCL-6 5' noncoding regions, which are regarded as a marker of B-cell transition through the germinal center (GC). Expression of BCL-6 protein, which is restricted to GC B cells throughout physiologic B-cell maturation, was detected in 100% AIDS-unrelated PCNSL and in 56.2% AIDS-related cases. Notably, among AIDS-related PCNSL, expression of BCL-6 was mutually exclusive with expression of Epstein-Barr virus (EBV)-encoded latent membrane protein (LMP)-1 and, with few exceptions, also of BCL-2. All but one PCNSL expressed hMSH2, which among mature B cells selectively stains GC B cells. These data suggest that PCNSL may be frequently related to GC B cells and may be segregated into two major biologic categories based on the expression pattern of BCL-6, LMP-1, and BCL-2. BCL-6(+)/LMP-1(-)/BCL-2(-) PCNSL occur both in the presence and in the absence of HIV infection and consistently display a large noncleaved cell morphology. Conversely, BCL-6(-)/LMP-1(+)/BCL-2(+) PCNSL are restricted to HIV-infected hosts and are represented by lymphomas with immunoblastic features. These data are relevant for the pathogenesis and histogenesis of PCNSL and may be helpful to segregate distinct biologic and prognostic categories of these lymphomas.

B-Lymphocyte Subsets↗
PubMed1998

BCL-6 in aids-related lymphomas: pathogenetic and histogenetic implications.

AIDS-related non-Hodgkin's lymphomas (AIDS-NHL) are classified into Burkitt's lymphoma, diffuse large cell lymphoma (DLCL), and body cavity based lymphoma. The molecular pathogenesis of AIDS-NHL is complex and involves the genetic alteration of several cancer related genes, including the BCL-6 proto-oncogene. BCL-6 encodes a zinc finger transcription factor which is selectively expressed by germinal center (GC) B-cells, but not by pre-GC or post-GC B-cells. Genetic alterations of BCL-6 occur frequently among B-cell NHL and comprise gross rearrangements as well as small mutations of the 5' noncoding region of the gene. Gross rearrangements of BCL-6 among AIDS-NHL cluster with 20% AIDS-DLCL. Conversely, mutations of the 5' noncoding region of BCL-6 occur at sustained frequency throughout the clinico-pathologic spectrum of AIDS-NHL and represent the most common genetic alteration presently detectable in these lymphomas. The frequency of BCL-6 mutations, as well as their location in the proximity of the BCL-6 regulatory regions, suggest that they may play a pathogenetic role in AIDS-related lymphomagenesis. Beside their pathogenetic implications, the occurrence of BCL-6 mutations among AIDS-NHL bears histogenetic relevance because BCL-6 mutations are regarded as a marker of B-cell transition through the GC. Thus, it is conceivable that a large fraction of AIDS-NHL is histogenetically related to GC or post-GC B-cells. This notion is further confirmed by the observation that AIDS-NHL frequently express the BCL-6 protein, which stains selectively GC B-cells throughout B-cell differentiation.

Gene Rearrangement↗
PubMed1997

Cloning and gene mapping of the chromosome 13q14 region deleted in chronic lymphocytic leukemia.

Frequent deletions and loss of heterozygosity in a segment of chromosome 13 (13q14) in cases of B-cell chronic lymphocytic leukemia (CLL) have suggested that this malignancy is caused by inactivation of an unknown tumor suppressor gene located in this region. Toward the identification of the putative CLL tumor suppressor, we have constructed a high-resolution physical map of YAC, PAC, and cosmid contigs covering 600 kb of the 13q14 genomic region. In addition to densely positioned genetic markers and STSs, this map was further annotated by localization of 32 transcribed sequences (ESTs) using a combination of exon trapping, direct cDNA selection, sample sequencing of cosmids and PACs, and homology searches. On the basis of these mapping data, allelic loss analyses at 13q14 using CLL tumor samples allowed narrowing of the genomic segment encompassing the putative CLL gene to <300 kb. Twenty-three ESTs located within this minimally deleted region are candidate exons for the CLL-associated tumor suppressor gene.

Alleles↗
PubMed1997

Frequent mutation of the 5' noncoding region of the BCL-6 gene in acquired immunodeficiency syndrome-related non-Hodgkin's lymphomas.

Acquired immunodeficiency syndrome (AIDS)-related non-Hodgkin's lymphomas (AIDS-NHL), a major source of morbidity and mortality among human immunodeficiency virus (HIV)-infected individuals, are derived from B cells and are classified into two major categories, Burkitt's lymphoma (BL) and diffuse large cell lymphoma (DLCL). Anaplastic large cell lymphoma (ALCL) and body-cavity-based lymphoma (BCBL) represent less frequent AIDS-NHL types. The molecular pathogenesis of AIDS-NHL is characterized by distinct genetic pathways, including chromosomal rearrangements of c-MYC and BCL-6 in AIDS-BL and AIDS-DLCL, respectively. In addition to gross rearrangements, recent evidence has suggested that BCL-6 may also be affected by mutations of the gene 5' noncoding regions. Here we have investigated the distribution of BCL-6 mutations in a panel representative of all the AIDS-NHL subtypes. Forty-three AIDS-NHL were analyzed for mutations in the first exon-first intron boundary region of BCL-6. Mutations were detected in all categories of AIDS-NHL (25 of 43 cases; 58%), including 12 of 20 AIDS-BL, 10 of 15 AIDS-DLCL, two of three AIDS-ALCL, and one of five of AIDS-BCBL. BCL-6 mutations occurred independent of BCL-6 rearrangements and presence of other genetic lesions frequently associated with AIDS-NHL. These results indicate that mutations of BCL-65' noncoding regions represent the most common genetic alteration presently detectable in AIDS-NHL. The frequency of these mutations, as well as their location in the proximity of BCL-6 regulatory sequences, suggest that they may play a role in AIDS-related lymphomagenesis.

Biomarkers, Tumor↗
PubMed1997

Involvement of the bcl-6 gene in AIDS-related lymphomas.

BACKGROUND: Non-Hodgkin's lymphoma (NHL) represents a major complication of AIDS. Systemic AIDS-related NHLs (AIDS-NHLs) derive from B cells and are classified into four distinct groups, including small noncleaved-cell lymphoma (SNCCL), diffuse large-cell lymphoma (DLCL), anaplastic large-cell lymphoma (ALCL), and body-cavity-based lymphoma (BCBL). The molecular pathogenesis of AIDS-NHL is characterized by the association of specific genetic lesions with distinct AIDS-NHL categories. Genetic lesions of AIDS-NHL involve proto-oncogenes (c-myc, Ras), tumor suppressor loci (p53, 6q), and viral infection (Epstein-Barr virus, human herpesvirus type 8). DESIGN: The aim of this work was to define the involvement of the bcl-6 gene in AIDS-related lymphomagenesis by investigating the distribution of bcl-6 structural alterations throughout the pathologic spectrum of AIDS-NHL. Both gross rearrangements and mutations in the 5' noncoding regions of the gene were investigated. RESULTS: Gross rearrangements of bcl-6 are confined to a fraction of AIDS-DLCL cases among AIDS-NHLs. Conversely, mutations of the 5' noncoding regions of bcl-6 are detected in a large proportion of AIDS-SNCCLs, AIDS-DLCLs and AIDS-ALCLs independent of the concomitant presence of bcl-6 rearrangements. CONCLUSIONS: Mutations of the 5' noncoding regions of bcl-6 represent the most frequent genetic lesion presently detectable among systemic AIDS-NHLs. The frequency of these mutations and their location in the proximity of bcl-6 regulatory regions suggest that they may play a role in AIDS-related lymphomagenesis.

DNA-Binding Proteins↗
PubMed1996

The involvement of the candidate proto-oncogene NFKB2/lyt-10 in lymphoid malignancies.

NF-kappa B transcription factors regulate the expression of a variety of genes involved in immune responses and cell growth. In higher vertebrates, the NF-kappa B family encompasses five distinct members. Three NF-kappa B proteins, p65/RelA, RelB, and c-rel/Rel, have high transactivating potential in addition to their DNA binding activity. Two subunits, NF-kappa B1p50 and NF-kappa B2p52, coded respectively by the NFKB1 and NFKB2 genes, may only have DNA binding activity. Moreover, p50 and p52 subunits are translated as precursors, respectively p105 and p100, which can be processed into the mature active forms by the removal of their carboxy-terminal ankyrin domain. The five proteins share a homologous amino-terminal domain (rel domain) involved in DNA binding, dimerization, nuclear transport, and binding of regulatory subunits. All members form homo- and heterodimeric complexes with different DNA binding specificity and transactivating potential. Structural alterations of some members of the NF-kappa B gene family have been observed in lymphoid malignancies. In particular, the NFKB2 gene, localized on chromosome 10q24, represents a candidate proto-oncogene, since it has been found rearranged in certain types of lymphoma and more commonly in cutaneous lymphoma. Molecular analysis indicated that these rearrangements may occur as a consequence of chromosomal translocations or small internal chromosomal deletions. Rearrangements cluster within the carboxy-terminal ankyrin domain of the NFKB2 gene leading to the production of carboxy-terminally truncated proteins which, in some cases, are fused to heterologous protein domains. Experimental data showed that these abnormal proteins are constitutively localized in the nucleus, have lost the transcriptional repressor functions typical of normal NF-kappa B2p52 and may be capable of transactivation activity. These findings suggest that abnormal NFKB2 proteins may contribute to lymphomagenesis by altering the NF-kappa B system, both quantitatively and qualitatively, and leading to the activation of specific subsets of kappa B-controlled genes.

Chromosome Mapping↗
PubMed1995

Frequent somatic hypermutation of the 5' noncoding region of the BCL6 gene in B-cell lymphoma.

The BCL6 gene encodes a zinc-finger transcription factor and is altered by chromosomal arrangements in its 5' noncoding region in approximately 30% of diffuse large-cell lymphoma (DLCL). We report here that, in 22/30 (73%) DLCL and 7/15 (47%) follicular lymphoma (FL), but not in other tumor types, the BCL6 gene is also altered by multiple (1.4 x 10(-3) -1.6 x 10(-2) per bp), often biallelic, mutations clustering in its 5' noncoding region. These mutations are of somatic origin and are found in cases displaying either normal or rearranged BLC6 alleles indicating their independence from chromosomal rearrangements and linkage to immunoglobulin genes. These alterations identify a mechanism of genetic instability in malignant B cells and may have been selected during lymphomagenesis for their role in altering BCL6 expression.

Alleles↗
PubMed1995

Structural and functional characterization of the promoter regions of the NFKB2 gene.

In order to clarify the transcriptional regulation of the NFKB2 gene (lyt-10, NF-kappa Bp100), we have characterized the structure and function of its promoter regions. Based on the nucleotide sequence of cDNA clones and the 5' flanking genomic region of the NFKB2 gene, RT-PCR analysis in a number of human cell lines demonstrated the presence of two alternative noncoding first exons (1a and 1b). Two distinct promoter regions, P1 and P2, were identified upstream of each exon, containing multiple sites of transcription initiation, as shown by RNase protection analysis. Sequence analysis of these regions showed a CAAT box upstream of exon 1a and high G-C content regions within both P1 and P2. Consensus binding sites for transcription factors, including SP1, AP1 and putative NF-kappa B (kappa B sites), were found upstream of each exon. In particular, six kappa B sites were identified, all but one of them capable of binding NF-kappa B complexes in vitro. Transfection in HeLa cells of plasmids containing P1 and P2 sequences linked to a chloramphenicol acetyltransferase reporter gene indicated that both P1 and P2 can act independently as promoters. Co-transfection of NF-kappa B effector plasmids (NF-kappa Bp52 and RelA) with a reporter gene linked to P1 and P2 showed that the NFKB2 promoter regions are regulated by NF-kappa B factors. RelA transactivates the NFKB2 promoter in a dose-dependent manner, whereas NF-kappa Bp52 acts as a repressor, indicating that the NFKB2 gene may be under the control of a negative feedback regulatory circuit.

Base Sequence↗
PubMed1994

Heterogeneous chromosomal aberrations generate 3' truncations of the NFKB2/lyt-10 gene in lymphoid malignancies.

The NFKB2(lyt-10) gene codes for a protein that is a member of the NK-kappa B/rel family of transcription factors containing a DNA-binding rel domain and a carboxy-terminal ankyrin-like domain. The NFKB2 gene represents a candidate proto-oncogene, since it has been found to be involved in a chromosomal translocation t(10;14)(q24;q32) in one case of B-cell lymphoma and in gene rearrangements in various types of lymphoid malignancies. To elucidate the structural and functional consequences of NFKB2 rearrangements, we report the molecular characterization of three novel rearranged NFKB2 genes in lymphoid tumors. In one case of multiple myeloma (MM), cloning and sequencing analysis of reciprocal breakpoint sites showed that they occurred within intron 15 of the NFKB2 gene and led to the complete deletion of the 3' portion of the gene coding for the ankyrin domain. Fluorescent in situ hybridization (FISH) analysis showed that the novel regions involved in the NFKB2 rearrangement originated from chromosome 7q34, thus implying the occurrence of a t(7;10)(q34;q24) reciprocal chromosomal translocation. In one case of T-cell cutaneous lymphoma (CTCL) and in one of B-cell chronic lymphocytic leukemia (B-CLL), NFKB2 rearrangements occurred, respectively, within exons 18 and 20 of the gene and involved recombinations with distinct regions of chromosome 10q24. Molecular analysis suggested that these rearrangements may occur as a consequence of small internal chromosomal deletions. In both of these cases, the rearrangements led to specific carboxy-terminal truncations of NFKB2 generating abnormal transcripts that coded for proteins lacking portions of the ankyrin domain. These proteins localize in the nucleus, suggesting their constitutive activation in vivo. Overall, our results indicate that NFKB2 rearrangements in lymphoid neoplasia may occur by heterogeneous mechanisms, including internal chromosomal deletion or chromosomal translocation. The common consequence of these rearrangements appears to be the deletion of 3' sequences of NFKB2 leading to the production of carboxy-truncated constitutively nuclear proteins that may be involved in tumorigenesis.

Amino Acid Sequence↗
PubMed1994

BCL-6 and the molecular pathogenesis of B-cell lymphoma.

The results presented identify the first genetic lesion associated with DLCL, the most clinically relevant form of NHL. Although no proof yet exists of a role for these lesions in DLCL pathogenesis, the feature of the BCL-6 gene product, its specific pattern of expression in B cells, and the clustering of lesions disrupting its regulatory domain strongly suggest that deregulation of BCL-6 expression may contribute to DLCL development. A more precise definition of the role of BCL-6 in normal and neoplastic B-cell development is the goal of ongoing study of transgenic mice engineered either to express BCL-6 under heterologous promoters or lacking BCL-6 function due to targeted deletions. In addition to contributing to the understanding of DLCL pathogenesis, the identification of BCL-6 lesions may have relevant clinical implications. DLCL represent a heterogeneous group of neoplasms which are treated homogeneously despite the fact that only 50% of patients experience long-term disease-free survival (Schneider et al. 1990). The fact that BCL-6 rearrangements identify biologically and clinically distinct subsets of DLCL suggests that these lesions may be useful as markers in selection of differential therapeutic strategies based on different risk groups. Furthermore, the BCL-6 rearrangements can be used to identify and monitor the malignant clone with sensitive PCR-based techniques. Since clinical remission has been observed in a significant fraction of DLCL cases, these markers may serve as critical tools for sensitive monitoring of minimal residual disease and early diagnosis of relapse (Gribben et al. 1993).

Animals↗
PubMed1993

Structural alterations of the NF-kappa B transcription factor lyt-10 in lymphoid malignancies.

We have previously reported the identification of a novel putative proto-oncogene involved in the breakpoint of a t(10;14)(q24;q32) chromosomal translocation in a case of B-cell lymphoma. This gene, called lyt-10 (NFKB2/p52), is a member of the NF-kappa B family of transcription factors and displays a high degree of homology with the NFKB1/p50. Here we describe the genomic organization of the lyt-10 gene based on the restriction analysis of genomic phage clones and the sequence determination of exon-intron boundaries. The lyt-10 gene spans a genomic region of about 8 kb on 10q24, and contains 24 exons, ranging in size between 41 and 258 base pairs. To improve the understanding of the role of lyt-10 in lymphomagenesis, we performed Southern blot analysis to detect alterations of the lyt-10 gene in a large panel of cases representative of different types of lymphoid malignancies. We found rearrangements in 5 of 228 (approximately 2%) cases analysed: two cases of B-cell lymphoma, one case of multiple myeloma and two cases of T-cell lymphoma. The use of various probes specific for different regions of the lyt-10 locus revealed that rearrangements in positive cases lead to the partial or total deletion of the carboxy-terminal region containing the ankyrin domain. Taken together, our results indicate that lyt-10 gene rearrangements represent a recurrent lesion that may be involved in the pathogenesis of both B- and T-cell malignancies, and suggest that truncation of the ankyrin domain may be a common mechanism of lesion leading to abnormal lyt-10 activation in lymphoid neoplasia.

Amino Acid Sequence↗
PubMed1992

Efficient selection of phleomycin-resistant Saccharomyces cerevisiae transformants.

The recently described dominant yeast marker Tn5ble confers phleomycin resistance on the yeast Saccharomyces cerevisiae (Gatignol, Baron and Tiraby, 1987. Mol. Gen. Genet. 207, 342-348). Incubation in non-selective medium prior to selection is critical, however, for getting phleomycin-resistant transformants. A 6-h incubation period was found to give optimal transformation frequencies, up to 10(5) transformants/micrograms plasmid, comparable to selection for uracil prototrophy (Ura+).

Drug Resistance, Microbial↗
PubMed1992

Identification of the product of two oncogenic rearranged forms of the RET proto-oncogene in papillary thyroid carcinomas.

In papillary thyroid carcinomas, we have identified two tumor-specific rearrangements of the RET proto-oncogene leading to the formation of different transforming fusion products sharing the tyrosine kinase (tk) domain of the proto-oncogene and designated ptc-1 and ptc-2. We have analysed ptc-1 and ptc-2 products by immunoprecipitation with specific anti-RET antibodies followed by immunoblotting with the same reagent or with antibodies specific for phosphotyrosine (P-tyr) residues. The anti-RET antibodies were reactive with 64-kDa (p64ptc-1) and 81-kDa (p81ptc-2) proteins from lysates of ptc-1 and ptc-2 transformed cells, respectively, and identified two proteins of 140 kDa and 160 kDa from extracts of SK-N-SH, a neuroblastoma cell line previously shown to express two differently glycosylated forms of the normal RET product. The anti P-tyr antibodies, while detecting the same p64ptc-1 and p81ptc-2 proteins from ptc-1 and ptc-2 extracts, did not show any specific band in the neuroblastoma lysates. An additional set of experiments led us to conclude that, whereas the normal product of the RET proto-oncogene is a membrane-associated receptor-like molecule not intrinsically phosphorylated on tyrosine, both oncogenic forms of RET, ptc-1 and ptc-2, are constitutively phosphorylated on tyrosine, display an 'in vitro' autophosphorylation activity, are translocated from the membrane to the cytoplasm and are apparently unaffected by protein kinase C modulation.

3T3 Cells↗