No description available.

No description available.

Background: The t(8;14) translocation in Burkitt’s lymphoma (BL) was the first non-random cytogenetic lesion to be described in lymphoproliferative disorders. This lesion occurs in 75-85% of all BL cases. However, the breakpoints in this cytogenetic lesion are very variable and far apart such that the t(8;14) translocation is not always amenable to standard polymerase chain reaction analysis. This is mainly due to the inability of the Thermus aquaticus (Taq) polymerase enzyme to synthesize long DNA products. Long range polymerase chain reaction (LD-PCR) with a high fidelity polymerase enzyme mix capable of longer PCR product synthesis has recently become available. In early studies, LD-PCR appeared to be capable of amplifying the t(8;14) translocation in the majority of published sporadic Burkitt’s lymphoma analyses. The utility of t(8;14) translocation LD-PCR for routine use in the diagnosis of BL in our setting has not yet been studied. The aim of this study was to establish and optimize the t(8;14) LD-PCR technique and to apply it in the retrospective analysis of all BL diagnosed in the University of the Witwatersrand teaching hospitals in a ten year period from January 1994 to December 2003. Materials and methods: High molecular weight non-degraded DNA was extracted from control cell lines as well as stored, unstained bone marrow slides remaining after routine diagnostic workup of previously identified Burkitt’s lymphoma patients. Three hundred nanograms of patient and control DNA were amplified with the LD-PCR high fidelity polymerase enzyme mix under reaction conditions which were optimized using the tissue plasminogen activator (tPA) gene as well as known Burkitt’s lymphoma cell lines as controls. Each control and patient DNA sample was amplified with tPA primers as well as four pairs of MYC/IgH primer sets. The resulting amplicons were size fractionated on an agarose gel and visualized with ethidium bromide under ultraviolet (UV) light. The fractionated DNA fragment sizes were compared to those of the t(8;14) translocation positive controls, tPA controls and known DNA molecular weight markers. Results: One hundred and ten Burkitt’s lymphoma diagnoses were made in the three teaching hospitals of the University of the Witwatersrand from January 1994 to December 2003. Bone marrow involvement by BL was present in 84 of these cases. Archival bone marrow slides were available in 74 of the 84 BL patients. Intact high molecular DNA on which the t(8;14) LD-PCR analysis could be performed was present in 41 of the 74 BL patients. In the presence of appropriate controls, an t(8;14) translocation specific product was demonstrable by t(8;14) LD-PCR analysis in only 6 of 41 BL patients. Conclusion: In this t(8;14) LD-PCR retrospective analysis of a large number known Burkitt’s lymphomas, the diagnostic yield in carefully selected patients was extremely poor. With five primer pairs required per BL sample analysis, this technique was found too labour intensive and costly in our hands making it unsuitable for routine diagnostic use. The reasons for the poor diagnostic yield remains unclear and may need to be explored in future studies. Emerging alternative techniques for the diagnosis of BL such as fluorescence in situ hybridization and microarray gene expression analyses may prove to be better diagnostic tools than LD-PCR in its current form.

No description available.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 46-69).

The purposes of this study was to demonstrate the induction of alpha interferon mRNA in Sendai virus-induced Namalava cells, to follow the level of alpha interferon mRNA synthesis at the transcriptional level, and to determine whether the Namalava cell line expresses the c-myc oncogene and to what degree. The amount of c-myc message deteted in Namalva cell RNA was about one-tenth that of Daudi cell RNA, whereas no difference in the amount of the c-Ha-ras message was observed between the two cell lines.

Tumour-associated macrophages (TAMs) have been shown to play an important role in tumour survival and progression. Thus, high numbers of macrophages in the tumour tissue are often associated with a poor prognosis. Identification of factors responsible for recruiting macrophages to the sites of different types of tumours might help to develop more effective cancer treatment. Burkitt's lymphoma (BL) is characterised by uncontrolled cell proliferation, high rate of spontaneous apoptosis and significant macrophage infiltration. Although BL cells undergo extensive apoptosis, in situ their corpses are cleared very effectively by macrophages infiltrating the tumour. It is now widely believed that dying cells are themselves able to release chemotactic molecules to ensure macrophage chemotaxis and subsequent clearance of their site of death. Previous work carried out in this laboratory identified fractalkine/CX3CL1 (FKN) released from dying BL cells to be an important player in macrophage chemotaxis to BL. Yet, these results have also indicated that FKN may not be the only chemokine involved in this process. Following from those observations, the first part of this work focused on examination of the potential role of monocyte chemoattractant protein-1 (MCP-1) in macrophage recruitment to BL. Despite the initial promising results, careful analysis of the data obtained by various techniques led to the conclusion that MCP-1 is, probably, not expressed by BL cells. Subsequently, effort was concentrated on understanding mechanisms regulating FKN processing during cell death. The studies performed before in this laboratory identified a new form of FKN to be present in apoptotic BL cells and showed that this is the form that is, most likely, responsible for mediating macrophage migration. Here, this apoptosis-related 60 kDa FKN was found to be a likely caspase-3 cleavage product. Moreover, it was demonstrated that FKN and active caspase-3 are released together in apoptotic BL cell-derived microparticles, suggesting that the proteolytic events could take place also extracellularly. In the final results chapter the differences between BL cell lines in the way they process FKN during cell death were revealed and a new cell death-associated 55 kDa FKN was observed. Through several lines of evidence, this new form was identified to be a possible product of calpain-mediated proteolysis. To conclude, this work provides the first evidence for a possible direct participation of the two major cell death executioner proteases – caspases and calpains, in production of ‘find me’ signals for macrophages and thus, ensuring effective clearance of dying cells. These results indicate that FKN cleavage and release might be of key importance during cell death. Moreover, the studies presented here contribute to better understanding of the process of FKN secretion.

No description available.

Le cancer est un problème majeur de santé public, tuant chaque année plusieurs millions de personnes. L’inhibition de la mort cellulaire programmée, l’apoptose, est considérée comme l’un des paramètres principaux impliqués dans son initiation et son développement. La régulation de la voie intrinsèque (mitochondriale) de l’apoptose est régulée par la famille Bcl-2. Jusqu’à maintenant, on pensait que la protéine PUMA, une protéine pro-apoptotique, était principalement exprimée au niveau mitochondrial. Nous avons montré qu’à l’état basal, PUMA était exprimé au niveau du cytosol des lymphocytes B humains. Cependant, suite à un signal apoptotique, PUMA est capable de transloquer du cytosol à la mitochondrie, de façon indépendante des caspases mais dépendante de l’activation de la MAPKinase p38, permettant ainsi son interaction avec les protéines anti-apoptotiques Bcl-2 et Mcl-1 dont l’inhibition conduit à l’apoptose. Les protéines anti-apoptotiques, Mcl-1 notamment, sont souvent surexprimées dans les tumeurs. Mcl-1 est une protéine à courte demi-vie, rapidement dégradée par le protéasome. Cette dégradation dépend de son ubiquitination réalisée par des E3 ligases (E3). Quelques E3 et une déubiquitinase (DUB), hydrolysant les chaînes d’ubiquitine, régulant l’expression de Mcl-1 ont été décrites. Cependant, ces protéines sont soit très peu exprimées, soit leur inhibition n’a pas d’impact sur l’expression de Mcl-1 dans notre modèle. Nous avons donc entrepris de caractériser de nouvelles E3 et DUB régulant l’ubiquitination de Mcl-1. Après une immunoprécipitation de Mcl-1 dans nos cellules, suivie d’une analyse par spectrométrie de masse, nous avons identifié la DUB USP14. Lorsque son expression est diminuée, l’expression et la stabilité de Mcl-1 augmentent de façon sélective. Nos résultats pourraient contribuer à une approche à double-tranchant dans le traitement du cancer, en retirant les freins à l’apoptose via une diminution de l’expression de Mcl-1 d’une part et en l’activant via PUMA de l’autre. / Cancer is a major public health issue, killing millions of people worldwide each year. The inhibition of apoptosis, a programmed cell death, in its onset and development has been well documented, making it one of the hallmarks of cancer. The regulation of the intrinsic (mitochondrial) pathway of apoptosis is regulated by the Bcl-2 (B cell lymphoma-2) family. Up until now, PUMA, a pro-apoptotic protein, was thought to be mainly expressed at the mitochondria, based on experiments where it had been overexpressed. We showed that endogenous PUMA is mainly expressed in the cytosol of activated or resting B cells. However, upon apoptotic stress, PUMA was able to translocate from the cytosol to the mitochondria, in a caspase-independent but p38-dependent manner, allowing PUMA to bind and inhibit the anti-apoptotic proteins Bcl-2 and Mcl-1, and thereby leading to cell death. The anti-apoptotic proteins, especially Mcl-1, are often overexpressed in tumors. Mcl-1 is a protein with a short half-life, degraded rapidly by the proteasome. This degradation is ubiquitin-dependent, requiring E3 ligases (E3). A handful of E3s and one deubiquitinase (DUB), that hydrolyses the ubiquitin chains, have been reported to regulate Mcl-1 expression. However, they were either very poorly expressed or their inhibition had no impact on Mcl-1 expression in our model. We thus undertook to characterize new E3s and DUBs mediating Mcl-1 ubiquitination. After an immunoprecipitation of Mcl-1 in our cells, followed by a mass spectrometry analysis, we identified the DUB USP14. When knockdown, Mcl-1 expression was selectively increased and its stability enhanced. Our results could help build “double-edge” therapies, removing the breaks on apoptosis on one hand via Mcl-1 downregulation while activating it on the other via PUMA translocation.

No / The in vitro measurement of drug-induced apoptosis provides a mechanism-based test for the chemosensitivity of tumor cells isolated from a patient or from a specific cell line. The goal of this study was to investigate the effects of p-glycoprotein reversal agents on apoptosis and necrosis in Burkitt lymphoma cells. These effects were determined by microscopic observation and by electrophoretic separation of DNA fragments. We demonstrated induction of apoptosis in Burkitt lymphoma Raji Thymidine Kinase+ (TK+)and TK- cells using different subclasses of p-glycoprotein reversal agents. A low dose of doxorubicin was also used. The selective clonal expansion of mutant lymphocytes is based upon the phenotypic properties of TK-deficient cells. The first phase of the present study involved morphological analyses and DNA degradation on agarose gel electrophoresis. The second phase analyzed DNA damage using the Comet assay and tail moments calculated with Komet imaging software. Electrophoretic separation resulted in a ladder pattern, indicating that the p-glycoprotein reversal agents were able to induce apoptosis and necrosis. The morphological frequency of apoptosis and necrosis in the cells was significantly increased. Most p-glycoprotein reversal agents showed an increase in tail moments in the Comet assay. The results indicate that indomethacin and quercetin may help to overcome chemoresistance in Burkitt’s lymphoma.