Adaptation of redox metabolism in drug-tolerant persister cells is a vulnerability to prevent relapse in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) remains a major unresolved disease because of its remarkable therapeutic resistance. Even patients who respond to initial therapy experience relapse in most cases. The mechanisms underlying therapy-acquired resistance supporting relapse are poorly understood. In this study, we aimed to determine the metabolic features of PDAC during relapse, specifically adaptations of mitochondrial oxidative metabolism. We used preclinical PDAC mouse models (patient-derived xenografts and murine syngeneic allografts) that present regression under initial chemotherapeutic treatment but relapse after a certain time. Relapsed tumors were analyzed ex vivo by flow cytometry to measure mitochondrial and redox characteristics. Molecular mechanisms were investigated by quantification of ATP and antioxidants levels, bulk RNA-sequencing and RT-qPCR. We show increased mitochondrial mass, ATP levels, mitochondrial superoxide anions, and total ROS levels, in relapsed compared to control tumors in both models; mitochondrial membrane potential is increased in the xenografts model only. These metabolic features are also observed in tumors during treatment-induced regression and at relapse onset. At the molecular level, antioxidant defenses are increased in relapsed tumors and during treatment. These data suggest that metabolic adaptations occurring during treatment-induced regression may favor the survival of drug-tolerant persister (DTP) cells, which persist during the subsequent minimal residual disease and are responsible for cancer relapse. Finally, the combined treatment of arsenic trioxide (ROS inducer) and buthionine sulfoximine (glutathione synthesis inhibitor) is able to completely prevent relapse in PDAC xenografts. In conclusion, redox metabolism is a vulnerability of pancreatic DTP cancer cells that can be targeted to prevent relapse.