Mechanisms of mature B-cell tumour pathogenesis and of the interplay between host-immunity and these tumours.

The incidence of non-Hodgkin's lymphoma (NHL), the majority of which derived from mature B-cells, has virtually doubled in the last two decades in westernized countries. Although improved diagnosis, and AIDS associated lymphomas have contributed to this astonishing escalation of disease incidence, this contribution accounts for no more than 50% of the new cases. Amongst NHL's the Activated B-cell Diffuse Large B-cell Lymphoma (ABC-DLBCL) is the most aggressive and with the poorer clinical prognosis. Multiple Myeloma (MM) is a tumour derived from terminally differentiated mature B-cells (plasma cells) and ranks as the second most common haematological malignancy after NHL, and despite recent advances in chemotherapy it is still an incurable disease. Constitutive NF-kB activity, present in both these tumours interferes with the apoptotic effect of chemotherapy and may account for the poor response to treatment of patients with either ABC-DLBCL or MM. Using sophisticated genetic approaches that include conditional gain-of-function and/or loss-of-function in the mouse, I plan to develop bona-fide pre-clinical models of these diseases in an experimental setting that recapitulates human mature B-cell tumourigenesis as closely as currently possible. These models should prove invaluable for the elucidation of the mechanistic factors in the pathogenesis of these malignancies and provide critical information for the advancement of disease prevention and treatment. In addition to oncogenetic lesions, it has become increasingly clear that host immunity plays a fundamental role in tumour formation and progression. Cancer immune escape is an emerging "Hallmark of Cancer" and regulatory T-cells (Tregs) may play a key role in this context. However, although in solid tumours Tregs aid cancer immune escape their role in haematological malignancies remains controversial, warranting caution when attempting to extrapolate effective treatment strategies in solid tumours. I plan to determine the role of Treg cells in the initiation and progression of human ABC-DLBCL and MM, using the bona fide mouse models for these diseases described above. I expect that inter-species comparative oncogenomics of the tumours arising in mice with their human counterparts will lead to the identification of causative/driver genetic mutations, which could function as prognostic biomarkers and/or therapeutic targets. On other hand, a better understanding of Treg function in the context of haematological malignancies will provide insights on how and when to modulate their activity to stimulate the immune system to control tumour growth.

Mature B-cell derived tumours are the most frequent human haematological malignancy. Following antigen encounter, mature B-cells can differentiate into plasma cells through a reaction that exposes cells to DNA mutation and recombination in their immunoglobulin genes while rapidly dividing. Infidelity in these processes predisposes genetic lesions, including mutations that activate NF-kB and deregulate c-Myc expression, recurrently observed in the human activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) and in the plasma cell tumour multiple myeloma (MM). However, I found that co-induction of NF-kB signalling and c-Myc expression in mouse B-cells in-vivo, originates MM in 100% of the cases. In contrast, disruption of the plasma cell differentiation regulator Blimp1, promotes the development of ABC-DLBCL, consistent with its frequent inactivation in the human tumour counterpart. This work suggests that a block of B to plasma cell differentiation is required in ABC-DLBCL pathogenesis and I propose to assess alternative mechanisms by which plasma cell differentiation is blocked in the fraction of human ABC-DLBCLs, without Blimp1 inactivation. The final goal is to identify causative genetic mutations through interspecies comparative oncogenomics, which could function as prognostic biomarkers and/or therapeutic targets. In addition to oncogenetic lesions, it has become increasingly clear that host immunity plays a fundamental role in tumour formation and progression and regulatory T-cells (Tregs) may play a key role in this context. However, although in solid tumours Tregs aid cancer immune escape their role in haematological malignancies like ABC-DLBCL and MM remains controversial, warranting caution when attempting to extrapolate effective treatment strategies in solid tumours. I propose to investigate the role of Tregs in these diseases in order to gain insights on how and when to modulate their activity to stimulate the immune system to control tumour growth.

Treatment of mature B-cell derived cancers, the most common type of human haematological malignancy overall, is still a serious challenge in medicine. The incidence of these tumours has virtually doubled in the last two decades in westernized countries. Although improved diagnosis, and AIDS associated lymphomas have contributed to this astonishing escalation of disease incidence, this contribution accounts for no more than 50% of the new cases. Amongst NHL's the Activated B-cell Diffuse Large B-cell Lymphoma (ABC-DLBCL) is the most aggressive and with the poorer clinical prognosis. Multiple Myeloma (MM), a tumour derived from terminally differentiated B-cells, is the second most common haematological malignancy after NHL and despite recent advances in chemotherapy, it is still an incurable disease. The elucidation of the mechanistic factors in the pathogenesis of these malignancies is critical for the advancement of disease prevention and treatment. The current project aims to generate bona fide stochastic models of ABC-DLBCL and MM with potential pre-clinical interest, by recapitulating the gene/pathway lesions associated with these human B-cell tumour subtypes.

- I predict that achievement of the proposed aims to generate significant interest in the mainstream media.
- The investigator aims in addition to deliver a series of after school workshops to local students on the nature of cancer and how our immune system may help fight cancer. The proposed research would be important to provide additional insights and information for the success of these public sessions.

It is now clear that the study of tumour development cannot be confined to the intrinsic cellular mechanisms of oncogenic transformation, and has to take into account the interaction of pre-tumour and tumour cells with their cellular microenvironment. This includes cells of the immune system, for which cumulating evidence suggests a fundamental role in tumour suppression, leading to the establishment of the escape of tumour cells from the immune system as an emerging "Hallmark of Cancer". However, most oncology drugs are tested in systems, so-called Xenograft models, which do not take into account the contribution of the immune system in cancer development. This has been suggested to be major cause for the failure rate of cancer related drugs in clinical trials.

- The development of pre-clinical mouse models of ABC-DLBCL and MM could be applied to enhance the discovery of drugs effective in killing tumour cells in an experimental setting that recapitulates human mature B-cell tumourigenesis as closely as currently possible.
- It is expected that these models may help biotechnology and pharmaceutical company researchers to be more productive in the development of effective oncology drugs.