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 N-terminal transactivation domain (ΔNp73) was described in mice. In this study, we report the cloning and characterisation of the human ΔNp73 isoforms, their regulation by p53 and their possible role in carcinogenesis. As in mice, human ΔNp73 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, ΔNp73 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 ΔNp73 is strongly up-regulated 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 ΔNp73 is exerted through a p53 responsive element located on the ΔN promoter. Expression of ΔNp73 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 ΔNp73, functionally inactivating p53, could be involved in tumorogenesis. An extensive analysis of the expression pattern of ΔNp73 in primary tumours would clarify this issue.

Unique and shared cytogenetic abnormalities have been documented for marginal zone lymphomas (MZLs) arising at different sites. Recently, homozygous deletions of the chromosomal band 6q23, involving the tumor necrosis factor alpha–induced protein 3 (TNFAIP3, A20) gene, a negative regulator of NF-κB, were described in ocular adnexal MZL, suggesting a role for A20 as a tumor suppressor in this disease. Here, we investigated inactivation of A20 by DNA mutations or deletions in a panel of extranodal MZL (EMZL), nodal MZL (NMZL), and splenic MZL (SMZL). Inactivating mutations encoding truncated A20 proteins were identified in 6 (19%) of 32 MZLs, including 2 (18%) of 11 EMZLs, 3 (33%) of 9 NMZLs, and 1 (8%) of 12 SMZLs. Two additional unmutated nonsplenic MZLs also showed monoallelic or biallelic A20 deletions by fluorescent in situ hybridization (FISH) and/or SNP-arrays. Thus, A20 inactivation by either somatic mutation and/or deletion represents a common genetic aberration across all MZL subtypes, which may contribute to lymphomagenesis by inducing constitutive NF-κB activation.

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.

Marginal zone B-cell lymphomas (MZLs) have been divided into 3 distinct subtypes (extranodal MZLs of mucosa-associated lymphoid tissue [MALT] type, nodal MZLs, and splenic MZLs). Nevertheless, the relationship between the subtypes is still unclear. We performed a comprehensive analysis of genomic DNA copy number changes in a very large series of MZL cases with the aim of addressing this question. Samples from 218 MZL patients (25 nodal, 57 MALT, 134 splenic, and 2 not better specified MZLs) were analyzed with the Affymetrix Human Mapping 250K SNP arrays, and the data combined with matched gene expression in 33 of 218 cases. MALT lymphoma presented significantly more frequently gains at 3p, 6p, 18p, and del(6q23) (TNFAIP3/A20), whereas splenic MZLs was associated with del(7q31), del(8p). Nodal MZLs did not show statistically significant differences compared with MALT lymphoma while lacking the splenic MZLs-related 7q losses. Gains of 3q and 18q were common to all 3 subtypes. del(8p) was often present together with del(17p) (TP53). Although del(17p) did not determine a worse outcome and del(8p) was only of borderline significance, the presence of both deletions had a highly significant negative impact on the outcome of splenic MZLs.

Given the vast phenotypic and genetic heterogeneity of acute and chronic myeloid malignancies, hematologists have eagerly awaited the introduction of next-generation sequencing (NGS) into the routine diagnostic armamentarium to enable a more differentiated disease classification, risk stratification, and improved therapeutic decisions. At present, an increasing number of hematologic laboratories are in the process of integrating NGS procedures into the diagnostic algorithms of patients with acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and myeloproliferative neoplasms (MPNs). Inevitably accompanying such developments, physicians and molecular biologists are facing unexpected challenges regarding the interpretation and implementation of molecular genetic results derived from NGS in myeloid malignancies. This article summarizes typical challenges that may arise in the context of NGS-based analyses at diagnosis and during follow-up of myeloid malignancies.

HIV‐infection is an important risk factor for developing Kaposi sarcoma (KS), but it is unclear whether HIV‐positive persons are also at increased risk of co‐infection with human herpesvirus 8 (HHV‐8), the infectious cause of KS. We systematically searched literature up to December 2012 and included studies reporting HHV‐8 seroprevalence for HIV‐positive and HIV‐negative persons. We used random‐effects meta‐analysis to combine odds ratios (ORs) of the association between HIV and HHV‐8 seropositivity and conducted random‐effects meta‐regression to identify sources of heterogeneity. We included 93 studies with 58,357 participants from 32 countries in sub‐Saharan Africa, North and South America, Europe, Asia, and Australia. Overall, HIV‐positive persons were more likely to be HHV‐8 seropositive than HIV‐negative persons (OR 1.99, 95% confidence interval [CI] 1.70–2.34) with considerable heterogeneity among studies (I² 84%). The association was strongest in men who have sex with men (MSM, OR 3.95, 95% CI 2.92–5.35), patients with hemophilia (OR 3.11, 95% CI 1.19–8.11), and children (OR 2.45, 95% CI 1.58–3.81), but weaker in heterosexuals who engage in low‐risk (OR 1.42, 95% CI 1.16–1.74) or high‐risk sexual behavior (OR 1.66, 95% CI 1.27–2.17), persons who inject drugs (OR 1.66, 95% CI 1.28–2.14), and pregnant women (OR 1.68, 95% CI 1.15–2.47), p value for interaction <0.001. In conclusion, HIV‐infection was associated with an increased HHV‐8 seroprevalence in all population groups examined. A better understanding of HHV‐8 transmission in different age and behavioral groups is needed to develop strategies to prevent HHV‐8 transmission.