Starvation mediates pancreatic cancer cell sensitivity to ferroptosis via ERK1/2, JNK and changes in the cell mesenchymal state

Pancreatic cancer is a highly metastatic and therapy-resistant disease. In the present study, the prospects of a novel approach to kill pancreatic cancer cells were examined: Starvation combined with ferroptosis induction. Established pancreatic cancer cell lines (Miapaca2, Panc-1, Su.86.86 and T3M4), as well as a unique cell line, Capan-26, which was originally derived in the authors' laboratory, were used. Cells were deprived from growth factors, amino acids and pseudo-starved using treatment with mTOR inhibitors; erastin was used to induce ferroptosis. Cell viability and lipid peroxidation measurements using flow cytometry revealed that the starved pancreatic cancer cells reacted differently to ferroptosis induction: The Panc-1, Su.86.86 and T3M4 cells gained sensitivity, while the Miapaca2 cells acquired resistance. Fluorescence microscopy revealed that ERK1/2 translocated to the nucleus of the starved pancreatic cancer cells. Moreover, ERK1/2 pharmacological inhibition with SCH772984 prevented erastin-induced ferroptosis in the starved Panc-1, Su.86.86 and T3M4 cells. Confocal microscopy also indicated JNK activation. However, the inhibition of this kinase revealed its unexpected role in oxidative stress management: Treatment with the JNK inhibitor, SP600125, increased the viability of pseudo-starved cells following erastin treatment. In addition, the FBS-starved Miapaca2 and Capan-26 cells transitioned between epithelial and mesenchymal cell states. The results were further confirmed using wound healing assays, western blot analysis and microscopic analysis of epithelial-to-mesenchymal transition (EMT) markers. Mesenchymal properties were associated with a higher sensitivity to erastin, whereas epithelial-like cells were more resistant. Finally, it was demonstrated that compounds targeting EMT-related signaling pathways increased cell sensitivity to erastin. On the whole, these results confirm that in starved pancreatic cancer cells, ERK1/2 and JNK signaling, as well as switching between epithelial and mesenchymal states mediates sensitivity to erastin and reveal novel therapeutic prospects of the combination of starvation with ferroptosis induction.