FSP1 and histone deacetylases suppress cancer persister cell ferroptosis

Cancer persister cells which survive oncogene targeted therapies are sensitized to ferroptosis but mechanistic understanding of this vulnerability remains limited. Here, we found that while levels of iron, glutathione and various ferroptosis suppressing enzymes vary among persister cell types, ferroptosis suppressor protein 1 (FSP1) is downregulated in multiple persister cell types and persister cells which survive glutathione peroxidase 4 (GPX4) inhibition rely upon residual FSP1 to survive. Furthermore, persister cells which survive GPX4 inhibition downregulate oxidative phosphorylation, a key source of mitochondrial reactive oxygen species which are required for persister cell ferroptosis. We also found that persister cell treatment with histone deacetylase inhibitors induce reactive oxygen species and sensitize multiple persister cell types to GPX4 inhibition. Together, these findings reveal that FSP1 and histone deacetylases suppress persister cell ferroptosis. Overall design: Single cell RNA sequencing of PC9 cells with 10X Genomics. PC9 lung cancer cells were untreated (parental) or treated with 100 nM erlotinib for 10 days to derive persister cells. Additionally, parental and persister cells were both separately treated with 1 µM GPX4 inhibitor, RSL3, for 24 hours; or with 7.5 nM HDAC inhibitor, panobinostat, for 48 hours.