Cayman scientists perform a redox-targeted lipidomics analysis of ferroptosis-sensitive cancer cells to map the activity of a newly identified enzyme in the lipid peroxidation step in ferroptosis.

Yilong Zou, Haoxin Li, Emily T. Graham, Amy A. Deik, John K. Eaton, Wenyu Wang, Gerardo Sandoval-Gomez, Clary B. Clish, John G. Doench, and Stuart L. Schreiber

Highlights

• A CRISPR-Cas9 screen is used to find enzymes other than lipoxygenases that catalyze lipid peroxidation, leading to ferroptotic cell death.
• Cytochrome P450 (CYP) oxidoreductase (POR), which plays a role in cellular redox homeostasis and xenobiotic detoxification by donating electrons to CYPs, cytochrome b, heme oxygenase, and squalene monooxygenase, was identified as a hit.
• Lipidomic profiling revealed that unlike ACSL4 or LPCAT3, POR does not induce ferroptosis by reshaping the PUFA lipidome. Its mechanism of action likely involves the donation of electrons to downstream effectors (e.g., cycling between Fe²⁺ and Fe³⁺ in the heme component of CYPs).
• Redox lipidomics performed at Cayman identified a reduction in oxidized PUFAs generated in the absence of POR.
• A majority of cancer cell lines highly express POR whereas lipoxygenase mRNA has limited tissue expression in these cells, suggesting that lipoxygenases may not have an essential contribution in promoting ferroptosis and that POR may represent a druggable target for protecting cells from ferroptosis.

Abstract

Ferroptosis is widely involved in degenerative diseases in various tissues including kidney, liver and brain, and is a targetable vulnerability in multiple primary and therapy-resistant cancers. Accumulation of phospholipid hydroperoxides in cellular membranes is the hallmark and rate-limiting step of ferroptosis; however, the enzymes contributing to lipid peroxidation remain poorly characterized. Using genome-wide, CRISPR–Cas9-mediated suppressor screens, we identify cytochrome P450 oxidoreductase (POR) as necessary for ferroptotic cell death in cancer cells exhibiting inherent and induced susceptibility to ferroptosis. By genetic depletion of POR in cancer cells, we reveal that POR contributes to ferroptosis across a wide range of lineages and cell states, and in response to distinct mechanisms of ferroptosis induction. Using systematic lipidomic profiling, we further map POR’s activity to the lipid peroxidation step in ferroptosis. Hence, our work suggests that POR is a key mediator of ferroptosis and potential druggable target for developing antiferroptosis therapeutics.

Read this paper

Learn more about Cayman’s Lipidomics Services

See Ferroptosis Research Tools Available from Cayman