KDM6B inhibition enhances chemotherapeutic response in small cell lung cancer via epigenetic regulation of apoptosis and ferroptosis.

backgroundSmall cell lung cancer (SCLC) is a highly aggressive malignancy characterized by rapid progression and the frequent emergence of resistance to standard chemotherapeutic agents such as cisplatin (DDP) and etoposide (VP16), resulting in poor clinical outcomes. METHODS AND

resultsTo elucidate mechanisms underlying chemoresistance, we conducted a genome-wide CRISPR/Cas9 knockout screen, which identified the histone demethylase KDM6B as a critical mediator of drug resistance in SCLC. Genetic silencing of KDM6B significantly reduced IC₅₀ values of DDP and VP16, particularly in H69-AR cells, and enhanced chemotherapy-induced apoptosis. Consistently, pharmacological inhibition of KDM6B using the dual KDM6A/B inhibitor Gskj1 markedly potentiated the effects of DDP and VP16, while exhibiting minimal cytotoxicity as monotherapy. Overexpression of KDM6B rescued the chemosensitizing effect of Gskj1, thereby excluding confounding contributions from KDM6A. In vivo, the combination of Gskj1 with chemotherapy synergistically suppressed tumor growth without detectable systemic toxicity. To explore the downstream regulatory pathways, we performed transcriptome analysis via RNA-seq followed by KEGG pathway enrichment analysis, which revealed that Gskj1 treatment modulates key oncogenic signaling pathways. Integration of RNA-seq with H3K27me3 ChIP-seq data identified EGR3 as a direct epigenetic target of KDM6B inhibition. STRING analysis further suggested that EGR3 is co-expressed with c-FOS. Functional assays, including qRT-PCR, Western blotting, Co-immunoprecipitation (Co-IP), and dual-luciferase reporter assays, confirmed that EGR3 transcriptionally activates c-FOS, establishing an EGR3/c-FOS regulatory axis downstream of KDM6B. Mechanistically, inhibition of this axis enhanced chemosensitivity by promoting apoptosis, as evidenced by activation of caspase signaling, and by inducing ferroptosis through downregulation of GPX4, upregulation of ACSL4, lipid peroxidation, and modulation of HO-1. Rescue experiments with Z-VAD and ferrostatin-1 further validated that both apoptosis and ferroptosis contribute to the chemosensitizing effects of KDM6B inhibition.

conclusionFinally, in vivo experiments using patient-derived xenograft (PDX) models demonstrated that Gskj1 effectively enhances the antitumor efficacy of chemotherapy in SCLC, providing compelling evidence for the clinical potential of targeting KDM6B to overcome chemoresistance.