Exploring Resistance to ETS Targeting Agents in Diffuse Large B-Cell Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) remains a challenging disease with limited therapeutic options beyond standard immunochemotherapy. ETS transcription factors, including SPIB and SPI1, are implicated in lymphoma pathogenesis and can be targeted by the small molecule TK216, which disrupts ETS-DHX9 interactions. To explore mechanisms of resistance, we generated stable TK216-resistant clones from the ABC-DLBCL line U2932. Resistant clones exhibited a 4-5-fold increase in IC50 values and lost the ability to undergo G2-M arrest upon treatment. Transcriptomic and mutational analyses revealed three resistance patterns: (i) MDR1/ABCB1 overexpression, leading to multidrug efflux; (ii) Cluster A, enriched for proliferation, Wnt, and transcriptional programs, with mutations in ESR2, USP24, and SFSWAP; and (iii) Cluster B, characterized by actin/microtubule remodeling, altered metabolism, and mutations in SRSF11 and PATJ. Pharmacologic screening revealed an increased sensitivity of resistant cells to BCL2, MCL1, and XPO1 inhibitors, while also showing reduced sensitivity to aurora kinase and microtubule-targeting agents. Venetoclax and selinexor retained activity in resistant models, supporting their potential for rational combinations with TK216. These findings demonstrate that multiple, heterogeneous mechanisms drive resistance to ETS inhibition in DLBCL, highlighting therapeutic strategies to overcome it.