Although the identification and characterization of translocations have rapidly increased, little is known about the mechanisms of how translocations occur in vivo. We used anaplastic large cell lymphoma (ALCL) with and without the characteristic t(2;5)(p23;q35) translocation to study the mechanisms of formation of translocations and of ALCL transformation. We report deregulation of several genes located near the ALCL translocation breakpoint, regardless of whether the tumor contains the t(2;5). The affected genes include the oncogenic transcription factor Fra2 (located on 2p23), the HLH protein Id2 (2p25), and the oncogenic tyrosine kinase CSF1-receptor (5q33.1). Their up-regulation promotes cell survival and repression of T cellspecific gene expression programs that are characteristic for ALCL. The deregulated genes are in spatial proximity within the nuclear space of t(2;5)-negative ALCL cells, facilitating their translocation on induction of double-strand breaks. These data suggest that deregulation of breakpoint-proximal genes occurs before the formation of translocations, and that aberrant transcriptional activity of genomic regions is linked to their propensity to undergo chromosomal translocations. Also, our data demonstrate that deregulation of breakpoint-proximal genes has a key role in ALCL.cancer genetics ͉ signal transduction ͉ nuclear architecture ͉ lymphomatoid papulosis B alanced chromosomal translocations are a hallmark of cancer cells, and are thought to be important, if not causal, for hematopoietic and mesenchymal tumorigenesis (1). At the molecular level, translocations generally result in either altered expression of genes located directly at a breakpoint, or in fusion of genes located at the 2 breakpoints (1). In most cases, the affected genes are transcription factors or tyrosine kinases, and the translocation generally leads to their inactivation or constitutive activation. This defect often causes inhibition of differentiation or uncontrolled proliferation. Nevertheless, translocations are, at least in some cases, not sufficient to fully transform cells, because chromosomal disease-associated translocations are present in healthy individuals (2), and transgenic mice expressing known tumor fusion proteins do not spontaneously develop tumors in most cases (1, 2).The translocation t(2;5)(p23;q35) is characteristic for anaplastic large cell lymphoma (ALCL), a subgroup of peripheral T cell lymphomas (TCL) (3, 4). By fusion of the 5Ј oligomerization domain of the nucleophosmin (NPM1) gene (located on 5q35) with the 3Ј anaplastic lymphoma kinase (ALK) tyrosine kinase domain (2p23), this translocation results in a NPM-ALK fusion protein with constitutive activation of the ALK kinase (3). Several questions regarding the pathogenesis of ALCL are unresolved. First, in Ϸ40% of systemic ALCL, the translocation t(2;5) is not present (4), suggesting yet unknown alternative mechanisms of transformation. Second, the expression of NPM-ALK per se might not be sufficient for malignant transformation to ALC...

Human herpesvirus 6 (HHV-6) genome has been detected in several human lymphoproliferative disorders with no signs of active viral infection, and found to be integrated into chromosomes in some cases. We previously reported a woman with HHV-6–infected Burkitt’s lymphoma. Fluorescence in situ hybridization showed that the viral genome was integrated into the long arm of chromosome 22 (22q13). The patient’s asymptomatic husband also carried HHV-6 DNA integrated at chromosome locus 1q44. To assess the possibility of chromosomal transmission of HHV-6 DNA, we looked for HHV-6 DNA in the peripheral blood of their daughter. She had HHV-6 DNA on both chromosomes 22q13 and 1q44, identical to the site of viral integration of her mother and father, respectively. The findings suggested that her viral genomes were inherited chromosomally from both parents. The 3 family members were all seropositive for HHV-6, but showed no serological signs of active infection. To confirm the presence of HHV-6 DNA sequences, we performed polymerase chain reaction (PCR) with 7 distinct primer pairs that target different regions of HHV-6. The viral sequences were consistently detected by single-step PCR in all 3 family members. We propose a novel latent form for HHV-6, in which integrated viral genome can be chromosomally transmitted. The possible role of the chromosomally integrated HHV-6 in the pathogenesis of lymphoproliferative diseases remains to be explained.

Background:We searched for a viral aetiology for non-small cell lung cancer (NSCLC), focusing on Merkel cell polyomavirus (MCPyV).Methods:We analysed 112 Japanese cases of NSCLC for the presence of the MCPyV genome and the expressions of RNA transcripts and MCPyV-encoded antigen. We also conducted the first analysis of the molecular features of MCPyV in lung cancers.Results:PCR revealed that 9 out of 32 squamous cell carcinomas (SCCs), 9 out of 45 adenocarcinomas (ACs), 1 out of 32 large-cell carcinomas, and 1 out of 3 pleomorphic carcinomas were positive for MCPyV DNA. Some MCPyV DNA-positive cancers expressed large T antigen (LT) RNA transcripts. Immunohistochemistry showed that MCPyV LT antigen was expressed in the tumour cells. The viral integration sites were identified in one SCC and one AC. One had both episomal and integrated/truncated forms. The other carried an integrated MCPyV genome with frameshift mutations in the LT gene.Conclusion:We have demonstrated the expression of a viral oncoprotein, the presence of integrated MCPyV, and a truncated LT gene with a preserved retinoblastoma tumour-suppressor protein-binding domain in NSCLCs. Although the viral prevalence was low, the tumour-specific molecular signatures support the possibility that MCPyV is partly associated with the pathogenesis of NSCLC in a subset of patients.

Human herpesvirus 6 (HHV‐6) genome has been found in several human lymphoid malignancies, but configuration of the HHV‐6 genome has not been well delineated. We established the HHV‐6‐positive, Epstein‐Barr virus‐negative Burkitt's lymphoma cell line Katata. In this study we investigated the status of the HHV‐6 genome in Katata cells. Neither linear nor circular HHV‐6 DNA was detected by Gardella gel analysis. The fluorescence in situ hybridization technique enabled us to directly visualize the integrated HHV‐6 DNA at the single‐cell level. Only one integrated site of viral DNA was detected in metaphase chromosomes and it was preferentially located at the long arm of chromosome 22 (22q13). Treatment of the cells with 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA) or with calcium ionophore A23187 led to induction of the HHV‐6 immediate‐early gene as well as the late gene. Sodium n‐butyrate also gave rise to expression of the HHV‐6 genes. The TPA inducibility was synergistically enhanced when combined with A23187 or n‐butyrate. Our study provides, for the first time, an in vitro model system of latent HHV‐6 infection whose genome is integrated into host DNA of lymphoma cells.

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