Abstract B055: Combinatorial drug screening identifies synergistic combinations that sensitize resistant PDAC cells to cuproptosis-inducer NSC 319726

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies and is characterized by profound therapeutic resistance and poor clinical outcome. Due to the limited efficacy of monotherapies, combination strategies represent a promising approach to simultaneously target multiple signaling pathways and overcome resistance mechanisms. NSC 319726 (ZMC1) was initially described as a mutant p53 reactivator, but emerging evidence indicates that its cytotoxicity is primarily mediated by copper-dependent mechanisms. Acting as a copper ionophore, NSC 319726 induces cuproptosis, a recently discovered regulated cell death mechanism characterized by excess intracellular copper accumulation, leading to lipoylated mitochondrial protein aggregation and loss of Fe-S cluster proteins, ultimately triggering proteotoxic stress and cell death. The aim of this study was to identify synergistic drug combinations that sensitize NSC 319726-resistant PDAC cells to cuproptosis. Therefore, a panel of 5 murine PDAC cell lines spanning a range of NSC 319726 sensitivity was screened with NSC 319726 as an anchor drug at a fixed concentration in combination with 95 compounds from a curated drug library. The most promising candidates were prioritized based on ΔAUC (delta area-under-the-curve) values and 5 top hits subsequently validated in multi-dose combinatorial matrices using long-term clonogenic assays. Drug interactions were quantified using ZIP synergy score models. Several combinations exhibited pronounced synergistic effects, effectively sensitizing previously resistant PDAC cell lines to NSC 319726. Notably, the identified hits predominantly targeted different metabolic pathways such as glycolysis, mitochondrial metabolism and redox homeostasis. Importantly, synergistic interactions were largely restricted to resistant cell lines, with little to no synergy observed in sensitive lines, suggesting a selectivity window that may be therapeutically exploitable. These findings suggest that rational combination strategies can significantly enhance the antitumor activity of NSC 319726 and identify key targets for further mechanistic and in vivo validation.