POLR1A inhibits ferroptosis by regulating TFAM-mediated mitophagy and iron homeostasis

Abstract

Evasion of programmed cell death (PCD) is a hallmark of cancer, yet the mechanisms underlying resistance to ferroptosis - an iron-dependent form of PCD triggered by excessive lipid peroxidation - remain incompletely understood. Here, we identify a previously unrecognized nucleolar-mitochondrial signaling axis that promotes ferroptosis resistance in pleural mesothelioma (PM) and potentially other cancers. This pathway involves RNA polymerase I (PolI) catalytic subunit A (POLR1A) and mitochondrial transcription factor A (TFAM), which together regulate mitophagy and intracellular iron metabolism to suppress ferroptosis. Mechanistically, POLR1A controls TFAM expression via the transcription factor ATF4, and this POLR1A-ATF4-TFAM axis inhibits mitophagy and limit mitophagy-dependent labile Fe²⁺ release, thereby preventing Fe²⁺-driven lipid peroxidation. Disruption of this pathway through POLR1A or TFAM inhibition leads to Fe²⁺ accumulation and increased sensitivity to ferroptosis inducers (FINs). Notably, CX-5461, a first-in-class RNA PolI inhibitor currently in clinical trials, synergizes with GPX4 blockade to induce ferroptotic cell death both in vitro and in vivo. This therapeutic synergy extends beyond PM, suggesting broader relevance in ferroptosis-resistant cancers. Together, our findings reveal a novel mechanism of ferroptosis evasion and establish a promising combinatorial strategy to overcome therapy resistance in cancer.

Keywords: ATF4; Ferroptosis; Iron metabolism; POLR1A; TFAM; mitophagy.