No description available.

The PIM family kinases promote growth and survival of tumor cells and are expressed in a wide variety of human cancers. Their potential as therapeutic targets, however, is complicated by overlapping activities with multiple other pathways and remains poorly defined in most clinical scenarios. Here we explore activity of the new pan-PIM inhibitor PIM447 in a variety of lymphoid-derived tumors. We find strong activity in cell lines derived from the activated B-cell subtype of diffuse large B-cell lymphoma (ABC-DLBCL). Sensitive lines show lost activation of the mTORC1 signaling complex and subsequent lost activation of cap-dependent protein translation. In addition, we characterize recurrent PIM1 protein-coding mutations found in DLBCL clinical samples and find most preserve the wild-type protein's ability to protect cells from apoptosis but do not bypass activity of PIM447. Pan-PIM inhibition therefore may have an important role to play in the therapy of selected ABC-DLBCL cases.

Myc oncogenes encode transcription factors that bind to E-box sequences in DNA, driving the expression of a large number of target genes and are deregulated in approximately 70% of human cancers. Deregulated Myc expression cause enhanced proliferation (which is counteracted by apoptosis), angiogenesis and cancer. Though Myc’s importance in induction of S phase has been established, less is known about its functions in the G2 and M phases of the cell cycle. Paper I addresses the targeting of the Myc targets Aurora kinase A and B that have roles in G2/M transition and provide evidence that pharmaceutical Aurora kinase inhibition causes cell cycle arrest and apoptosis in a Myc-selective manner and is useful in treating Myc-induced lymphomas in vivo. The assumption that the important target genes responsible for the biological effects of Myc overexpression were those encoding components of the cell cycle machinery lead to little interest in other potentially important groups of target genes. However, recent work challenged this view by indicating that Myc target genes encoding metabolic enzymes may be critical for Myc-induced tumorigenesis. Importantly, the targeting of Myc target genes encoding metabolic enzymes has the potential of providing a new treatment strategy of Myc-induced cancers. Paper II covers the pharmaceutical targeting of the Myc-induced spermidine synthase (Srm) that shows promise as a tool for chemoprevention by affecting proliferation, but not for the treatment of established tumors. Paper III focuses on the negligible effect an Ldha mutation has on Myc- induced lymphomagenesis. Ldha has long been known to be a Myc target gene and in vitro experiments have recently indicated it to be important for transformation. It seems the negligible effect of the Ldh mutation can be explained by the high frequency of loss of either Arf or p53 in this mouse model, since enforced Ras-Myc oncogenic cooperation in soft agar assays of Ldh mutant MEFs effectively inhibits colony formation, and λ-Myc;Ldh mutant bone marrow infected with oncogenic Ras does not give rise to tumors when transplanted into wild-type mice. A role for Ldh in the ability of tumors to evade the immune system was also indicated in this study. The combined experiences and very different outcome of the three studies included in this thesis draw attention to the value of in vivo assessment of Myc downstream targets in Myc-induced lymphomagenesis.

No description available.

Mouse models of human disease are valuable tools for studying pathogenesis and for evaluating novel therapies. T-cell lymphoma is a relatively rare disease in humans, affecting 100-150 persons yearly in Sweden. It exists in both aggressive and more indolent forms. We have established a mouse model for an aggressive T-cell lymphoma, the T-cell lymphoma/leukemia (TLL) mouse. In the present thesis, the TLL mouse model was characterized and used for experimental therapeutic and primary prevention studies. The TLL mouse was established unintentionally in our laboratory during work on VH-gene replacement in a “knock-in” mouse experimental setting. The generated chimeras all developed aggressive T-cell lymphomas affecting the lymphoid organs, lungs, kidneys and liver. The lymphoma phenotype segregated from the targeted locus and we could demonstrate the presence of Moloney murine leukemia virus (MMLV) in the germline of the affected mice. MMLV is a retrovirus known to induce T-cell lymphomas when inoculated in newborn mice.  We further characterized two TLL substrains; TLL-2 and TLL-14 carrying the proviral integrations on chromosomes 2 and 14 respectively. Significant differences were found between the substrains regarding lymphoma frequency and immunophenotype, the TLL-14 substrain developing tumors with higher frequency than TLL-2 and with a more mature immunophenotype. A transfer model was developed in which TLL cells could be readily transferred intravenously to syngenic recipients causing aggressive lymphomas. The transfer model was used in a therapeutic study where the selective COX-2 inhibitor celecoxib was evaluated as a single agent and in combination with the established anti-tumor agent cyclophosphamide. The study was based on results from other tumor types that have indicated celecoxib, originally an anti-inflammatory and analgetic drug, to have possible anti-tumor effects. In our TLL model, however, we could not demonstrate any benefit of celecoxib monotherapy or any additive effect to cyclophosphamide. Dietary fatty acids, in particular omega-3 fatty acids, have been a focus of public and scientific interest due to observed effects on the prevention of cardiovascular disease, cancer and inflammatory conditions. In addition, omega-3 fatty acids inhibit T-cell proliferation in vitro. We supplemented the diet of TLL mice with omega-3 and omega-6 fatty acids respectively and could demonstrate a significant delay in lymphoma onset between 5-8 months of age in the group receiving an omega-3 rich diet.

No description available.

Les Lymphomes Primitifs Vitréo-Rétiniens (LPVR) représentent un sous-type de Lymphome Primitif du Système Nerveux Central (LPSNC). Ces hémopathies très rares sont caractérisées par leur localisation anatomique atypique, dans des sites physiologiquement dépourvus de lymphocytes B. Les lymphomes du SNC sont rattachés histologiquement aux Lymphomes B Diffus à Grandes Cellules (LBDGC) de type post-germinatif (ABC). L’objectif de notre étude était de définir le répertoire immunologique (chaînes lourdes et légères) des LPVR et des LPSNC, et de les comparer aux LBDGC. Nous avons mené une étude immunologique détaillée de ces tumeurs afin de rechercher des éléments de réponse expliquant ces localisations ectopiques. Notre projet, réalisé sur la plus grande série de LPVR à ce jour, a mis en évidence un biais de répertoire majeur, avec une sur-représentation massive du gène IGHV4-34 (63,6% des cas), significativement plus utilisé dans les LPVR comparativement aux LPSNC et aux LBDGC systémiques. Bien que la proportion de ce gène soit élevée dans d’autres SLP, cette fréquence n’a jamais été atteinte. Un subset a été décrit pour 50% des LPVR utilisant le gène IGHV3-7. Ces données suggèrent fortement l’implication d’un antigène dans leur développement. En conclusion, le LPVR représente un modèle surprenant et singulier de lymphome dirigé par l’antigène, dont l’identification offrirait des perspectives physiopathologiques et thérapeutiques prometteuses. / Primary vitroretinal lymphoma (PVRL) is a high-grade lymphoma considered as a subtype of primary central nervous system lymphoma (PCNSL). Unusual localization is a feature of these rare entities. The vast majority of cases are diffuse large B cell lymphoma (DLBCL), mostly of activated B-cell (ABC). To investigate whether PVRLs display a specific IG repertoire contributing to explain their unusual localization, we analysed in detail the IG heavy and light chain sequences from PVRL and PCNSL cases, and we compared their repertoire to that of a publicly available IG heavy chain sequences dataset from systemic ABC-type DLBCLs. Our study was carried out on the largest PVRL series reported to date and showed that PVRL displayed a strikingly biased repertoire as the IGHV4-34 gene was used in 63.6% of cases. The frequency was significantly higher in PVRL compared to PCNSL and DLBCL. This gene has been repeatedly found to be preferentially used in various B-cell malignancies, but never to such an extent. Half of PVRL cases expressing the IGHV3-7 gene had stereotyped VH CDR3 features (subset). Altogether our data showed that PVRLs display a very biased IG repertoire strongly suggesting that antigen selection plays a major role in their development. Thus, PVRL display a highly restricted IG repertoire indicative of antigen selection, and distinct from that of PCNSL. Antigen(s) identification may provide promising perspectives in physiopathology concepts and therapeutic approaches.