Loss of <i>IRF2BP2</i> Drives an Actionable IL-1β/IL-1R Signaling Loop in DLBCL

Diffuse large B cell lymphoma (DLBCL) is a highly heterogeneous disease and is the most common lymphoid malignancy in adults (Swerdlow et al., 2016, Alizadeh et al., 2000). It is traditionally divided into two subtypes based on the cell-of-origin: Activated B cell-like (ABC) DLBCL and germinal center B cell-like (GCB) DLBCL (Alizadeh et al., 2000). DLBCL can be further subdivided into clusters A53, ST2, N1, BN2, EZB, and MCD based on the mutational profiles of the tumors (Schmitz et al., 2018, Wright et al., 2020). While cure rates of ~65% are achievable in DLBCL patients with frontline combination chemo-immune therapy (e.g. R-CHOP), treating relapsed or refractory disease remains a challenge, particularly in ABC-DLBCL and MCD patients (Pfreundschuh et al., 2011, Tilly et al., 2015, Schmitz et al., 2018). Interferon regulatory factor 2 binding protein 2 (IRF2BP2) is a transcriptional repressor that is frequently mutated in MCD patients, with many of these mutations predicted to be loss-of-function (Schmitz et al., 2018). Besides human DLBCL tumors, in previously published MCD mouse models, which harbor a B cell-specific loss of Prdm1, expression of mutant Myd88p.L252P, overexpression of BCL2, and in some cases expression of a Cd79b ITAM mutation, Irf2bp2 is also one of the most frequently co-mutated genes (Knittel et al., 2016, Flümann et al., 2023, Flümann et al., 2024). However, the role of IRF2BP2 in lymphoma biology and as a potential tumor suppressor gene in DLBCL has not been investigated. To understand the role of IRF2BP2 in the germinal center reaction, we analyzed the B cell compartment of autochthonous mice which harbor a B cell specific knockout of Irf2bp2 at a premalignant age. We observed a dramatic decrease in germinal center B cells in Irf2bp2 knockout mice compared to controls, as well as a higher relative memory B cell output and reduced class switch recombination. This preliminary dataset suggests that Irf2bp2 may play a role in the dynamics of the germinal center reaction and B cell differentiation. Moreover, we show that CRISPR/Cas9-mediated loss of IRF2BP2 in human ABC-DLBCL cell lines leads to increased proliferation and NF-KB signaling, compared to IRF2BP2-proficient cells. Additionally, we find that IRF2BP2 knockout ABC-DLBCL cells express higher interleukin-1 beta (IL1β) and are sensitive to anti-IL1β inhibition both in vitro and in vivo, while IRF2BP2-proficient cells remain insensitive. Furthermore, murine lymphoma cell lines derived from MCD mouse models, which harbor a spontaneous Irf2bp2 mutation are also sensitive to anti-IL1β inhibition in vitro and retain sensitivity over several weeks. Our findings suggest that IL1β is the primary mediator of increased NF-KB signaling upon IRF2BP2 perturbation and anti-IL1β therapy could be a potential treatment strategy for IRF2BP2-mutant patients.