Elucidation of cellular and molecular mechanisms of lymphoma induction and evolution to identify therapeutic targets

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Malignant lymphomas are the 5th most common cancers in the world, accounting for ~5% of all tumours. They may be derived from the B-Cell or T-cell lineage and are generally mature in nature. The prognosis of lymphomas greatly varies and is dependent on the stage and histology of the disease. Although up to 60% of young patients (<60y) with aggressive Diffuse Large B-Cell Lymphoma (DLBCL) are cured by combination immune-chemotherapy, older patients have a fairly dismal outlook. In addition, although monoclonal antibodies and small molecule inhibitors have improved survival in patients with low-grade indolent disease such as Follicular lymphoma (FL), these diseases are commonly incurable. In addition, all of the aforementioned therapies are toxic and may lead to significant morbidities and occasional mortalities in lymphoma patients. Worryingly, the incidence of malignant lymphomas continues to rise, and at 3-4% per year4 appears far in excess of what would be expected simply from the ageing of the population. The identification of critical mediators of lymphomagenesis and novel therapies that target them is therefore a priority for this increasingly common malignancy and unmet medical need.Despite their clinical importance, we actually know very little about the molecular and cellular biology of lymphomas. Next generation sequencing (NGS) efforts are beginning to uncover mutations that occur in lymphomas, however the order of these mutations and how they collaborate to generate lymphomas remains mysterious. Likewise gene expression studies have identified critical genes that are drive lymphoma but for other pathways we do not know if these are cause or consequence of malignant transformation. In addition, we know that normal B-cell survival is dependent upon t singling events at the cell surface. Furthermore mutations that alter cell singling often occur in lymphomas suggesting that lymphomas are also dependent upon abnormal singling events. However, exactly how and where this occurs during the development of the lymphoma and the role that it plays in this evolution is unknown. Moreover, the cell biology of lymphoma is poorly characterized. Our knowledge of the cells from which lymphomas derive initially and the role that this cell typemight play in the eventual phenotype of the lymphoma are poorly understood, although initial transforming steps in haematopoietic stem and progenitor cells have been shown for the similar B-cell malignancies chronic lymphocytic leukaemia (CLL), hairy cell leukaemia (HCL) and for some T-cell lymphomas. We will address all of these questions within this application using a combination of mouse models, human cell lines and powerful genome-wide analysis.We will use unique mouse models that we have developed that generate loss of Crebbp at defined times within B-cell development, and will engineer within these models the ability to generate and identify further progression events by engineering a mutation inducing system that jumps around DNA sequences specifically in B cells. This system will allow us to robustly answer the question of the contribution of the initial cell-type to outcome and phenotype of lymphoma. Using the presence of a unique but easily identifiable premalignant phase within the model, we will also characterize alterations gene expression and signaling that occur during lymphoma evolution, through a combination of stat-of-the-art genomic techniques. Finally we will test a priori hypotheses about the requirement for specific DNA repair pathways and residual CREBBP/P300 function in these Crebbp-/- lymphomas, as well as performing a genomewide screen to identify further vulnerabilities in CREBBP mutated lymphoma cells, a subset of which will be further tested in our in vivo model