Targeting TROP2 and Exploiting AUNIP as a Determinant of ADC Cytotoxicity and Chemosensitivity in HNSCC and ESCA Cancers.

Head and neck squamous cell carcinoma (HNSCC) and esophageal carcinoma (ESCA) are anatomically contiguous, frequently co-occurring malignancies that collectively account for substantial global cancer mortality. With half of patients progressing to recurrent or metastatic disease, alternative therapeutic strategies are urgently needed. Antibody-drug conjugates (ADCs) offer promise, but their clinical impact requires identification of robust target antigens and elucidation of resistance mechanisms. Through single-cell transcriptomic analysis followed by experimental validation, we identified TROP2 as a consistently and highly overexpressed cell-surface antigen in HNSCC and ESCA. DS-1062a, a TROP2-directed ADC delivering the camptothecin (CPT)-like topoisomerase I inhibitor deruxtecan (Dxd), demonstrated marked tumor regression in HNSCC and ESCA xenografts. This pronounced sensitivity may be attributable to prevalent homologous recombination deficiency (HRD) in these cancers, conferring vulnerability to DNA single-strand break (SSB)-inducing agents such as PARP inhibitors. However, therapeutic potential is constrained by an incomplete understanding of the regulators of drug sensitivity. To systematically dissect genetic modifiers of SSB-induced cytotoxicity, we performed a genome-wide CRISPR/Cas9 sgRNA knockout screen and identified AUNIP as a determinant of chemosensitivity. AUNIP loss profoundly enhanced DS-1062a cytotoxicity and multiple SSB-inducing chemotherapies across diverse HNSCC and ESCA models. Mechanistically, AUNIP deficiency led to impaired DNA repair, attenuated stress response signaling, and heightened apoptotic susceptibility. These findings establish TROP2 as a therapeutically actionable target and reveal AUNIP as a genetic rheostat governing ADC and chemotherapy response. Co-targeting AUNIP represents a promising strategy to potentiate SSB-inducing therapies and improve outcomes in patients with squamous carcinomas of the upper aerodigestive tract.