Iron-Addicted Colorectal Cancer Escapes Oxidative Cell Death Through a Heme–Complex II–CoQ Survival Pathway: Cell Metabolism | August 2026

Introduction:

Colorectal cancer (CRC) cells require large amounts of iron to sustain rapid growth, DNA synthesis, and mitochondrial metabolism. Paradoxically, excessive intracellular iron is normally toxic because it promotes oxidative stress and ferroptosis, an iron-dependent form of cell death. This study uncovers how CRC cells survive in iron-rich environments by exploiting a previously unrecognised heme–mitochondrial complex II–coenzyme Q (CoQ) pathway that protects them from oxidative damage.

Why was this study needed?

CRC cells accumulate high levels of iron despite its inherent toxicity.

The mechanisms allowing CRC cells to resist iron-induced oxidative stress have remained unclear.

Most research has focused on canonical ferroptosis regulators such as GPX4 and SLC7A11, but their relevance in vivo has been uncertain.

Identifying alternative antioxidant pathways could reveal novel therapeutic vulnerabilities.

Targeting metabolic dependencies may improve treatment strategies for colorectal cancer.

Results:

The study demonstrated that canonical ferroptosis regulators (GPX4 and SLC7A11) were not essential for colorectal cancer growth, suggesting that CRC relies on alternative survival mechanisms.

CRC cells were highly resistant to iron-induced oxidative damage by utilizing cellular heme as a protective metabolic cofactor.

Heme maintained the activity of mitochondrial complex II (succinate dehydrogenase), which supported coenzyme Q (CoQ) production, a critical lipid antioxidant.

CoQ protected both mitochondrial and cellular membranes by neutralizing lipid reactive oxygen species (ROS) and preventing oxidative cell death.

Genetic deletion or pharmacological inhibition of complex II (SDHC) increased oxidative stress and significantly reduced tumor growth in preclinical colorectal cancer models.

These findings identify the heme–complex II–CoQ axis as a previously unrecognized metabolic defense system that enables CRC cells to tolerate otherwise lethal iron overload.

Clinical Impact:

This study challenges the current paradigm that ferroptosis resistance in colorectal cancer is primarily driven by GPX4-dependent pathways. Instead, it identifies the heme–complex II–CoQ pathway as a critical metabolic vulnerability. Therapeutic strategies targeting complex II, heme metabolism, or CoQ biosynthesis could sensitise iron-rich colorectal tumours to oxidative cell death and complement existing chemotherapy or immunotherapy. The findings also highlight the importance of metabolic rewiring as a driver of cancer survival.

Bottom Line:

Colorectal cancer cells evade iron-induced oxidative cell death through a novel heme–complex II–coenzyme Q antioxidant pathway rather than traditional ferroptosis mechanisms. Targeting this metabolic survival axis represents a promising new therapeutic strategy for iron-dependent colorectal cancers.