Deep in the cells of chemotherapy-resistant ovarian cancers, a hidden metabolic pathway has been quietly enabling tumors to repair the very DNA damage that should kill them—until now. Scientists at The Wistar Institute in Philadelphia have identified the precise molecular mechanism behind this resistance, opening a door to overcoming one of oncology's most stubborn challenges.
For decades, ovarian cancer patients whose tumors can repair their own DNA have faced grim odds. When standard platinum-based chemotherapy damages cancer cell DNA, most tumors die from the injury. But a subset of ovarian cancers possess sophisticated repair machinery that patches the damage and survives treatment, leaving patients with poor prognosis and tumors commonly recurring within six months. "With these types of ovarian cancers, clinicians throw everything they can at them, and the prognosis is still quite poor," said Katherine Aird, Ph.D., professor and co-leader of the Molecular and Cellular Oncogenesis Program at The Wistar Institute's Ellen and Ronald Caplan Cancer Center.
The breakthrough came through a detective story that upended decades of conventional thinking. Aird's team discovered that alpha-ketoglutarate (αKG), a metabolite that accumulates in DNA repair-proficient ovarian tumors, was the linchpin. But rather than controlling DNA repair through the well-established methylation pathway that researchers had studied for nearly two decades, αKG was working through an entirely separate route that no one had previously described.
Using sophisticated CRISPR-based techniques to systematically search for the responsible enzyme, the team identified TMLHE, an enzyme that kickstarts the body's natural synthesis of carnitine—a molecule traditionally associated with energy metabolism. "Everyone in the field would have told us to look at the demethylases," Aird reflected. "That's what the literature pointed to. Finding TMLHE was the moment I thought, 'Okay, this is going to be something bigger than what we expected.'"
Working with collaborators including Nathaniel Snyder, Ph.D., at Temple University's Lewis Katz School of Medicine, the team mapped the previously unknown metabolic pathway: elevated αKG activates TMLHE, which drives carnitine production. Carnitine then acts as a molecular shuttle, ferrying acetyl groups from mitochondria into the cell nucleus, where they loosen the grip of the DNA-histone complex. This loosening grants cancer cells' repair machinery the access it needs to fix damaged DNA. When researchers blocked either TMLHE or carnitine synthesis, the repair machinery failed to assemble, and cancer cells became significantly more sensitive to chemotherapy.
To move toward the clinic, the team tested mildronate, an existing carnitine synthesis inhibitor with a known safety profile in humans. When combined with cisplatin, a platinum-based chemotherapy drug, mildronate reduced tumor burden in mouse models of ovarian cancer—while neither drug alone produced significant effects. The findings, published in Nature and representing collaboration across multiple institutions, point to a concrete strategy for breaking through chemotherapy resistance.
This discovery transforms how researchers understand not just ovarian cancer, but the broader relationship between metabolism and DNA repair. It also offers hope to patients who have exhausted conventional options: an existing drug, already deemed safe for human use, now has a clear target and a clear purpose in turning deadly resistance into vulnerability.