Generation and Surgical Analysis of Genetic Mouse Models to Study NF-κB-Driven Pathogenesis of Diffuse Large B Cell Lymphoma.

Enforced activation of NF-κB signaling can be achieved by constitutive NF-κB-inducing kinases, IKK2 and NIK, or via lymphoma-associated mutants of MYD88, CARD11, and CD79B. In order to model Diffuse Large B Cell Lymphoma (DLBCL) in mice, conditional alleles for these proteins are combined with alleles targeting Cre recombinase expression in mature B cells. However, unopposed NF-κB signaling promotes plasmablast differentiation, and as a consequence the model system must be complemented with further mutations that block differentiation, such as Prdm1/BLIMP1 inactivation or overexpression of BCL6. Here, we describe the currently available tools for DLBCL models in mice and their relative advantages and drawbacks. Furthermore, we describe methods to monitor lymphomagenesis, using ultrasound tomography of the spleen, and the technique of partial splenectomy surgery with recovery. These powerful techniques allow paired comparison of individual lymphoma cases before and after interventions, including therapies, and to study the evolution of lymphoma over time. NF-κB activation also promotes widespread nodal involvement with lymphoma and we describe the post-mortem dissection of major nodal groups.

Mitochondrial DNA damage is uncommon in cancer but can promote aggressive behaviour.

The mitochondrial genome (mtDNA) has been implicated in carcinogenesis. It is more susceptible than nuclear DNA to damage from reactive oxygen species and mutagens, and has a limited DNA repair machinery. Studies of human cancer have shown that a small proportion of tumours carry significant mtDNA mutations but methodological flaws undermine some of these findings. Mutations in mtDNA are often associated with elevated levels of reactive oxygen species and stabilisation of Hypoxia-Inducible Factor-1 (HIF1), but it has not been clearly demonstrated that these relationships are causal. Some mutations in the coding region of mtDNA can confer increased tumourigenicity, motility and metastasis on cells in vitro and in vivo but these mutations are only rarely found in ex vivo samples. Mitochondrial DNA does not play a major role in common types of cancer, but may promote aggressive behaviour in some cases. Shortcomings in mtDNA repair mechanisms could be exploited to promote apoptosis of tumour cells.