CD24 is a promising immunotherapeutic target for enhancing efficacy of third-generation EGFR-TKIs on EGFR-mutated lung cancer

<b>Background</b>: Third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) show initial efficacy in EGFR-mutated lung cancer, but residual disease persists. This study aimed to investigate cluster of differentiation 24 (CD24) as a translational immunotherapeutic target for enhancing third-generation EGFR-TKI efficacy.<b>Methods</b>: We conducted RNA-sequencing (RNA-seq) on drug-responsive, -tolerant persister, and -resistant cells to identify therapeutic targets to pair with EGFR-TKIs. For validation, we integrated single-cell RNA-seq data from 29 lung cancer specimens and used single-nucleus RNA-seq and immunohistochemistry on clinical residual tumor samples following TKI therapy (TKI-residual). With CRISPR/Cas9, we studied the effect of CD24 on proliferation and phagocytic clearance during EGFR-TKI treatment. We tested CD24 knockout or ATG-031 (a first-in-class CD24 antibody) with EGFR-TKIs <i>in vitro</i>, xenografts, and spontaneous lung cancer models. To explore mechanisms, we used DNA affinity precipitation, chromatin immunoprecipitation sequencing, and luciferase assays to identify transcription factors regulating CD24. Co-immunoprecipitation combined with mass spectrometry and phosphoproteomics were used to study YIN-YANG-1 (YY1) S247 phosphorylation’s expression and function, while kinase inhibitors assessed upstream phosphorylation of YY1 S247 and its regulation of CD24.<b>Results</b>: CD24 expression rose in drug-responsive, -resistant, and -tolerant lung cancer cells and post-EGFR-TKI treatment clinical specimens. This elevation promoted cell proliferation and shielded tumor cells from macrophage-mediated phagocytosis. Genetic depletion of CD24 or treatment with ATG-031 significantly enhanced phagocytosis and tumor eradication in vitro, in xenografts, and in mice harboring EGFR^L858R·T790M-driven spontaneous lung tumors. Furthermore, we revealed that YY1 S247 phosphorylation was responsible for the upregulation of CD24 upon EGFR-TKI treatment, facilitating YY1 dimerization and the formation of promoter-enhancer loops that regulate CD24 expression.<b>Conclusions</b>: CD24 is a promising target in EGFR-mutated lung cancers, potentially enhancing efficacy of third-generation EGFR-TKIs.