Splice-site mutations in POU2AF1 are associated with B-cell lymphomagenesis and therapeutic response

Abstract BOB.1, encoded by POU2AF1, is one of many factors regulating physiological B-cell maturation in the germinal center. Recently, several studies have described recurrent mutations in a three-nucleotide region in the POU2AF1 splice site in the two most common B-cell non-Hodgkin lymphomas: diffuse large B-cell lymphoma and, more frequently, follicular lymphoma. In this study, we introduced a C→G mutation at the + 1 position of the POU2AF1 splice site in two B-cell lymphoma cell lines (WSU-NHL and SUDHL4) using CRISPR/Cas9 gene editing. Our results demonstrate how point mutations in the POU2AF1 splice site decreased BOB.1 expression levels. The mutation did not produce significant changes in cell proliferation, migration, or invasiveness, but did affect cell morphology, aggregation, and cell survival in a cell-line-dependent manner. Lastly, we found that the POU2AF1 mutation c.16 + 1G > C increased BCR activation, especially in SUDHL4 cells, downregulated oxidative phosphorylation (OxPhos) metabolism, and modified therapy sensitivities in both cell lines. Mutated B-cells were more sensitive to the BTK inhibitor ibrutinib. In conclusion, mutations in the POU2AF1 splice site impact B-cell lymphomagenesis at multiple levels and represent a potential therapeutic target for patients with tumors harboring this mutation.