Inactivation of the tumour suppressor p53 is the most common defect in cancer cells. p53 is a sequence specific transcription factor that is activated in response to various forms of genotoxic stress to induce cell cycle arrest and apoptosis. Induction of p53 is subjected to complex and strict control through several pathways, as it will often determine cellular fate. The p73 protein shares strong structural and functional similarities with p53 such as the potential to activate p53 responsive genes and the ability to induce apoptosis. In addition to alternative splicing at the carboxyl terminus which yields several p73 isoforms, a p73 variant lacking the Nterminal transactivation domain (DNp73) was described in mice. In this study, we report the cloning and characterisation of the human DNp73 isoforms, their regulation by p53 and their possible role in carcinogenesis. As in mice, human DNp73 lacks the transactivation domain and starts with an alternative exon (exon 3'). Its expression is driven by a second promoter located in a genomic region upstream of this exon, supporting the idea of two independently regulated proteins, derived from the same gene. As anticipated, DNp73 is capable of regulating TAp73 and p53 function since it is able to block their transactivation activity and their ability to induce apoptosis. Interestingly, expression of the DNp73 is strongly upregulated by the TA isoforms and by p53, thus creating a feedback loop that tightly regulates the function of TAp73 and more importantly of p53. The regulation of DNp73 is exerted through a p53 responsive element located on the DN promoter. Expression of DNp73 not only regulates the function of p53 and TAp73 but also shuts off its own expression, once again finely regulating the whole system. Our data also suggest that increased expression of DNp73, functionally inactivating p53, could be involved in tumorogenesis. An extensive analysis of the expression pattern of DNp73 in primary tumours would clarify this issue. Cell Death and Differentiation (2001) 8, 1213 ± 1223.

Summary Background Biologically distinct subtypes of diffuse large B-cell lymphoma can be identified using gene-expression analysis to determine their cell of origin, corresponding to germinal centre or activated B cell. We aimed to investigate whether adding bortezomib to standard therapy could improve outcomes in patients with these subtypes. Methods In a randomised evaluation of molecular guided therapy for diffuse large B-cell lymphoma with bortezomib (REMoDL-B), an open-label, adaptive, randomised controlled, phase 3 superiority trial, participants were recruited from 107 cancer centres in the UK (n=94) and Switzerland (n=13). Eligible patients had previously untreated, histologically confirmed diffuse large B-cell lymphoma with sufficient diagnostic material from initial biopsies for gene-expression profiling and pathology review; were aged 18 years or older; had ECOG performance status of 2 or less; had bulky stage I or stage II–IV disease requiring full-course chemotherapy; had measurable disease; and had cardiac, lung, renal, and liver function sufficient to tolerate chemotherapy. Patients initially received one 21-day cycle of standard rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP; rituximab 375 mg/m 2 , cyclophosphamide 750 mg/m 2 , doxorubicin 50 mg/m 2 , and vincristine 1·4 mg/m 2 [to a maximum of 2 mg total dose] intravenously on day 1 of the cycle, and prednisolone 100 mg orally once daily on days 1–5). During this time, we did gene-expression profiling using whole genome cDNA-mediated annealing, selection, extension, and ligation assay of tissue from routine diagnostic biopsy samples to determine the cell-of-origin subtype of each participant (germinal centre B cell, activated B cell, or unclassified). Patients were then centrally randomly assigned (1:1) via a web-based system, with block randomisation stratified by international prognostic index score and cell-of-origin subtype, to continue R-CHOP alone (R-CHOP group; control), or with bortezomib (RB-CHOP group; experimental; 1·3 mg/m 2 intravenously or 1·6 mg/m 2 subcutaneously) on days 1 and 8 for cycles two to six. If RNA extracted from the diagnostic tissues was of insufficient quality or quantity, participants were given R-CHOP as per the control group. The primary endpoint was 30-month progression-free survival, for the germinal centre and activated B-cell population. The primary analysis was on the modified intention-to-treat population of activated and germinal centre B-cell population. Safety was assessed in all participants who were given at least one dose of study drug. We report the progression-free survival and safety outcomes for patients in the follow-up phase after the required number of events occurred. This study was registered at ClinicalTrials.gov ,...

The BCL6 proto-oncogene encodes a transcriptional repressor that is required for germinal center (GC) formation and whose deregulation by genomic lesions is implicated in the pathogenesis of GC-derived diffuse large B cell lymphoma (DLBCL) and, less frequently, follicular lymphoma (FL). The biological function of BCL6 is only partially understood because no more than a few genes have been functionally characterized as direct targets of BCL6 transrepression activity. Here we report that the anti-apoptotic proto-oncogene BCL2 is a direct target of BCL6 in GC B cells. BCL6 binds to the BCL2 promoter region by interacting with the transcriptional activator Miz1 and suppresses Miz1-induced activation of BCL2 expression. BCL6-mediated suppression of BCL2 is lost in FL and DLBCL, where the 2 proteins are pathologically coexpressed, because of BCL2 chromosomal translocations and other mechanisms, including Miz1 deregulation and somatic mutations in the BCL2 promoter region. These results identify an important function for BCL6 in facilitating apoptosis of GC B cells via suppression of BCL2, and suggest that blocking this pathway is critical for lymphomagenesis.apoptosis ͉ DLBCL ͉ germinal center T he BCL6 proto-oncogene encodes a transcriptional repressor of the POZ/BTB zinc-finger protein family (1, 2), which binds to specific DNA sequences and represses the transcription of its target genes via recruitment of corepressor complexes (1-4). In the B-cell lineage, BCL6 is expressed in germinal centers (GC) (5), the site in which B cells undergo somatic hypermutation (SHM) and class-switch recombination (CSR) of immunoglobulin (Ig) genes, and are selected on the basis of the production of antibodies with high affinity for the antigen (6). BCL6 is also an essential requirement for GC formation, because mice lacking BCL6 cannot form these structures (7-9). BCL6 expression is then turned off at the end of the GC reaction by a variety of signals, including CD40 receptor engagement (10-12), B-cell receptor (BCR) signaling (13), and genotoxic stress (14). Downregulation of BCL6 is necessary for GC B cells to mature toward plasma cells, because BCL6 is a repressor of PRDM1, a master regulator of plasma cell differentiation (15,16).In Ϸ30% of diffuse large B cell lymphoma (DLBCL) and 10% of follicular lymphoma (FL) cases, chromosomal translocations juxtapose heterologous partner chromosomes to the intact coding region of BCL6 (17-19), leading to its deregulated expression by promoter substitution (20). In addition, SHM-derived mutations in the BCL6 5Ј regulatory region (21-23) deregulate BCL6 expression by disrupting its negative autoregulatory circuit in Ϸ10% of DL-BCL (24, 25) and by preventing CD40-induced IRF4-mediated downregulation in a minority of cases (12). The role of BCL6 in lymphoma pathogenesis is underscored by the fact that mice expressing deregulated BCL6 alleles develop DLBCL (26).A critical issue in the understanding of BCL6 function in GC development and lymphomagenesis is the identification of its regulatory pr...

IntroductionMarginal zone lymphoma (MZL), a B-cell non-Hodgkin lymphoma (B-NHL) derived from marginal zone B cells, is currently classified as extranodal MZL (EMZL), nodal MZL (NMZL), and splenic MZL (SMZL). 1 Four recurrent and mutually exclusive chromosomal translocations: t(11;18)(q21; q21), t(1;14)(p22;q32), t(14;18)(q32;q21), and t(3;14)(p14.1; q32), have been described in EMZLs, but not in NMZLs or SMZLs, with frequencies ranging from 0% to 40% depending on the anatomic site and geographic regions. [2][3][4] At least 3 of these translocations, t(11;18) API2/MALT1, t(1;14) IgH/ BCL10, and t(14;18) IgH/MALT, result in constitutive activation of nuclear factor-B (NF-B), a transcription factor complex regulating multiple cellular processes, including cell growth and survival. 5 In addition, trisomy 3 or 18 has been reported in 30% to 60% of all MZLs and 7q22-32 deletions or translocations of the immunoglobulin heavy chain gene with various partners are found in 7% to 40% of SMZLs. 6,7 The functional consequences of these aberrations are, however, unknown. Currently, approximately 25% of MZLs lack any recognizable recurrent genetic alteration, and evidence of lesions affecting tumor suppressor genes in MZL is limited. 8,9 Recently, deletions of the 6q23.3-q24.1 region containing the tumor necrosis factor alpha-induced protein 3 (TNFAIP3, A20), a negative regulator of NF-B, were described in ocular adnexal MZLs. 10 Here, we report that A20 is targeted and inactivated by both somatic mutations and/or deletions in a significant fraction of MZL subtypes, indicating a role of NF-B deregulation in the pathogenesis of these B-NHLs. Methods Case selectionFrozen samples of newly diagnosed MZL (lesional content Ͼ 70%) and matched normal control tissue were obtained from the tumor banks of the Departments of Pathology, Columbia University and the Division of Hematology, Amedeo Avogadro University of Eastern Piedmont. Hematoxylin and eosin-stained sections were used for morphologic analysis. Immunohistochemical (IHC) staining and 4-color flow cytometry were performed for phenotypic characterization using antibodies described in Document S1 (available on the Blood website; see the Supplemental Materials link at the top of the online article). MZLs were classified according to the current WHO classification 1 as EMZL (n ϭ 11: 4 lung, 4 parotid gland, 1 skin, 1 jejunum, 1 orbit), NMZL (n ϭ 9), and SMZL (n ϭ 12; Table S1). The institutional review boards of Columbia University Medical Center and University of Eastern Piedmont approved this study. For personal use only. on May 11, 2018. by guest www.bloodjournal.org From formed as previously described. 11,12 FISH probes included IgH and MALT1 dual-color break-apart probes and centromeric probes for chromosomes 3 and 18 for all cases, and IAP2/MALT1 dual-color dual-fusion probes as indicated (Vysis, Downers Grove, IL). FISH analysis of the A20 locus was performed using BAC clones RP11-703G8 and RP11-102P5 spanning the gene (BACPAC Resources, http://bacpac.chori.org). A locus-spe...