Exploiting Synthetic Lethality for the Therapy of ABC Diffuse Large B Cell Lymphoma

Knowledge of essential oncogenic mutations can inspire therapeutic strategies that are synthetically lethal, affecting cancer cells bearing an oncogenic mutation while sparing normal cells. Lenalidomide is emerging as an active agent in diffuse large B cell lymphoma (DLBCL), especially for the activated B cell-like (ABC) subtype, but the mechanism of its action is unknown. Here we show that lenalidomide kills ABC DLBCL cells by augmenting the production of interferon 3/4, which these cells are predisposed to produce by their oncogenic MYD88 mutations. Lenalidomide stimulates the type I interferon pathway by suppressing IRF4, a repressor of IRF7. IRF4 is required for ABC DLBCL viability and is both a target and an amplifier of NF-kB signaling in this lymphoma subtype. Blockade of B cell receptor (BCR) signaling synergized with lenalidomide to reduce IRF4 levels, increase interferon 3/4 secretion, decrease NF-kB, and kill ABC DLBCL cells, suggesting therapeutic combinations that exploit the oncogenic signaling pathways in this cancer. For the OCILY10 cell line treated with 10 uM lenalidamide, a four point time course of 3, 6, 24, and 48 hours was analyzed (n=4). For the TMD8 cell line treated with 10 uM lenalidamide, a four point time course of 3, 6, 24, and 48 hours was analyzed (n=4).