A GPX1-OSBPL8 axis mediates noncanonical in vivo ferroptosis and cancer growth suppression.

Ferroptosis is a tumor-suppressive mechanism with therapeutic potential. While canonical ferroptosis is usually triggered by inducers, such as erastin and RSL-3, or by glutathione peroxidase (GPX)4 loss, how ferroptosis occurs naturally in vivo without these triggers has been unclear. Building on evidence that p53 can mediate ferroptosis as a natural tumor-suppressive pathway, we describe a noncanonical, in vivo ferroptosis driven by reactive oxygen species (ROS)-induced phosphatidic acid (PA) peroxidation that proceeds without inducers. We identify GPX1 as a key regulator of this ROS-induced ferroptosis by modulating PA peroxidation. GPX1's effects depend on OSBPL8, an endoplasmic reticulum (ER)-membrane-associated oxysterol-binding protein. ROS-driven lipid peroxidation accumulates at the ER before plasma membrane rupture and cell death; GPX1 is recruited to the ER via OSBPL8 and directly reduces oxidized PA. OSBPL8 and GPX1 are overexpressed in cancers; knockdown of either promotes ROS-induced ferroptosis and suppresses tumor growth. Our data link the GPX1-OSBPL8 axis to in vivo ferroptosis and tumor suppression.