Anemia Drug Triggers Colon Cancer Cell Death by Hitting an Unexpected Enzyme

An anemia drug currently used in clinical settings triggers cell death in colon cancer cells by unexpectedly binding to a vital cellular detoxification enzyme rather than its intended target, according to a study published in eLife. Researchers discovered that Molidustat, a medication developed to inhibit prolyl hydroxylase domain proteins, selectively targets a metabolic vulnerability in cancer cells with mutations in the adenomatous polyposis coli gene.

Uncovering an Unexpected Cancer Drug Target

Mutations in the adenomatous polyposis coli gene appear in the vast majority of colorectal cancer cases, initiating uncontrolled cell growth by hyperactivating specific signaling pathways. Scientists have long explored oxygen-sensing enzymes known as prolyl hydroxylases, particularly PHD2, as therapeutic checkpoints to disrupt these cancer pathways. However, when investigators treated human colon cancer cell lines carrying adenomatous polyposis coli mutations with Molidustat, the drug induced significant cell death that standard PHD2 inhibition could not explain. Genetic knockout experiments revealed that deleting the PHD2 gene alone did not reduce cell viability or trigger apoptosis, pointing toward an off-target mechanism.

To identify where the drug was actually binding, the research team employed thermal proteome profiling and chemical proteomics using specialized affinity matrices. These proteome-wide screens revealed glutathione S-transferase P1, an enzyme responsible for neutralizing toxic compounds and managing cellular stress, as a primary off-target of Molidustat. Biochemical assays subsequently confirmed that Molidustat directly blocks the enzymatic activity of glutathione S-transferase P1, inducing a sharp surge in reactive oxygen species within the treated cells.

Cellular Collapse Driven by Combined Inhibition

To understand the downstream consequences of this dual engagement, the authors generated single and double CRISPR-Cas9 knockout models lacking PHD2, glutathione S-transferase P1, or both. Quantitative proteomics and metabolomics showed that simultaneous loss of both proteins produced profound metabolic and energetic imbalances. The double knockout cells suffered a high AMP-to-ATP ratio, severe shifts in cellular redox indicators such as the GSSG-to-GSH ratio, and widespread depletion of tricarboxylic acid cycle intermediates.

This metabolic crisis triggered a coordinated systems-level shift toward growth arrest and apoptotic cell death. Upregulated proteins included key markers of oxidative stress and mitochondrial apoptosis, such as mitochondrial effectors DIABLO and HTRA2, alongside the tumor suppressor PML. The proteomic changes closely mirrored the cellular damage observed when intact cancer cells were exposed directly to Molidustat.

Testing Drug Sensitivity in Organoid Models

Because whole animal models faced drug delivery hurdles in reaching the colon effectively, the team evaluated Molidustat using murine intestinal organoids derived from genetically engineered mouse models. These stem-cell-derived structures faithfully reproduce the epithelial organization of human tissues. Organoids harboring adenomatous polyposis coli mutations or KRAS alterations displayed marked, dose-dependent reductions in viability when treated with Molidustat, accompanied by a sharp rise in caspase activity.

By contrast, wild-type control organoids and cultures treated with other structurally distinct hydroxylase inhibitors did not experience the same selective vulnerability. The findings suggest that Molidustat exploits a synthetic lethal interaction between glutathione S-transferase P1 and PHD2. This interaction opens new avenues for designing targeted combination therapies that harness oxidative stress vulnerabilities in specific colorectal cancer subtypes.

The research was published in eLife on November 10, 2026.