Loss of ELF2 drives topotecan resistance in retinoblastoma revealed by genome-wide CRISPR-Cas9 screening.

The topoisomerase I inhibitor topotecan is an effective chemotherapeutic agent for retinoblastoma; however, treatment resistance remains a major clinical challenge, and its mechanisms remain elusive. Using genome-wide CRISPR-Cas9 knockout screening, we identified ELF2 as a key gene involved in topotecan resistance. Here, we show that surviving retinoblastoma cells exposed to topotecan showed progressively decreased ELF2 expression, accompanied by reduced apoptosis. In a mouse xenograft model, ELF2 disruption diminished the antitumor efficacy of topotecan, with ELF2-knockout cells exhibiting reduced topotecan-induced apoptosis. RNA sequencing further revealed that the MT-CYB pathway, associated with ATP synthesis, contributes to ELF2-mediated resistance. Importantly, clinical analysis demonstrated a correlation between ELF2 expression and tumor volume in retinoblastoma patients treated with topotecan. Together, these findings interrogate the mechanisms underlying topotecan resistance in retinoblastoma and suggest ELF2 as a potential therapeutic target to overcome drug resistance.