The Antigen Receptor as a Driver of B-Cell Lymphoma Development and Evolution

The expression of a functional antigen receptor is necessary for cell survival of normal B lymphocytes and most B-cell neoplasms alike. When the genetic modifications of the B-cell receptor locus fail to produce a functional antigen receptor or result in deleterious mutations of a previously expressed receptor, the affected B cell will undergo apoptosis. The three physiological mechanisms that generate the B-cell receptor, VDJ recombination, somatic hypermutation, and class switch recombination, can induce double-strand DNA breaks and can specifically contribute to lymphomagenesis. On the other hand, the B-cell receptor activation and signaling pathways, which provide strong survival and proliferation signals to normal B cells, can support the growth and evolution of malignant lymphocytes. As a result, an otherwise structurally normal B-cell receptor can behave, from the functional perspective, as a true oncogene. In this chapter, we provide an in-depth discussion of the most recently discovered recurrent mechanisms involving the B-cell receptor in lymphoma pathogenesis. The discussion is structured around two major topics: (1) the genetic mecha - nisms that create a functional antigen receptor and their errors leading to oncogenic events, and (2) the pathogenic activation of the B-cell receptor signaling cascade. Finally, we will briefly comment on novel emerging therapies targeting the B-cell receptor at different levels.