Study of synergistic tumor toxicity in pancreatic cancer cells through liposomal drug combination therapy

Pancreatic cancer is a lethal malignancy, frequently diagnosed at an advanced stage due to its asymptomatic progression. Current combinatorial therapies show the benefits of the multi-drug approach; however, the side effects of these therapeutic protocols remain severe. Therefore, there is an urgent need for new combination therapies that are better tolerated by patients. In this study, we highlight the interest of combining disulfiram, a repurposed anti-alcoholism drug, with gemcitabine, based on evidence of synergism between the two molecules. Liposomal formulations were then developed to deliver gemcitabine and its lipophilic prodrug 4-(N)-stearoyl-gemcitabine, and combined with disulfiram. The formulations were characterized for their size, polydispersity index, zeta-potential, encapsulation efficiency, and drug release profile. The 4-(N)-stearoyl-gemcitabine-loaded liposomes exhibited a more sustained release profile compared to gemcitabine-loaded liposomes. The combination of free gemcitabine with disulfiram significantly improved the in vitro efficacy of the molecule in gemcitabine-resistant pancreatic ductal adenocarcinoma cell line PANC-1. The synergistic effect was confirmed by the combination index analysis. In parallel we demonstrated that the delayed release of gemcitabine from the liposomes greatly influences the efficacy of the combination. This study provides a systematic comparison of the doses required to achieve synergy when administering free molecules versus molecules encapsulated in nano-systems. It demonstrates the importance of considering prolonged release in order to achieve the same results as with free molecules, and this should be considered when translating the study into preclinical and clinical settings.