DNA Repair Gene Could Expand Cancer Treatment Options

A gene designed to protect our DNA might actually hold the key to treating more cancer patients with fewer side effects.

Researchers at Penn State College of Medicine discovered that EXO1, a gene normally responsible for repairing damaged DNA, can paradoxically create vulnerabilities in tumors when it goes into overdrive. The twist makes these cancers behave just like tumors with BRCA mutations, the genetic changes associated with inherited breast and ovarian cancer.

The discovery matters because it could expand access to targeted cancer drugs that currently work only for patients with BRCA mutations. These treatments are highly effective and cause fewer side effects than traditional chemotherapy.

"EXO1 doesn't predict cancer risk, but it could potentially serve as a biomarker to help predict which patients are more likely to respond to certain chemotherapy treatments," said Dr. George-Lucian Moldovan, who led the study published in Nature Communications.

The team found elevated EXO1 levels in 20% to 30% of breast and ovarian cancers, as well as in melanoma, testicular, cervical, and liver cancers. That's significantly more common than BRCA mutations, which affect a smaller percentage of patients.

When cells produce too much EXO1, the protein starts cutting DNA that should remain intact. Instead of acting like molecular scissors that repair damage, excess EXO1 begins creating the very problems it's supposed to fix.

The researchers tested whether these EXO1-overexpressing tumors would respond to olaparib, a drug currently reserved for BRCA-mutant cancers. The results were striking: the tumors proved highly sensitive to the treatment, responding just like BRCA-mutant cancers do.

They also found these tumors responded well to cisplatin, a common chemotherapy drug. The findings suggest doctors might achieve similar results with lower doses, potentially reducing the harsh side effects many cancer patients endure.

The Ripple Effect

This discovery could transform treatment for thousands of cancer patients who previously had limited options. Because EXO1 overexpression occurs more frequently than BRCA mutations across many tumor types, it opens the door to personalized medicine for a much larger group of people.

Lead researcher Alexandra Nusawardhana, who earned her doctorate at Penn State this year, explains that excess EXO1 leads to toxic DNA breaks that make tumors more sensitive to treatment and increase cancer cell death. Unlike BRCA mutations, EXO1 overexpression isn't inherited, though researchers don't yet know if it causes cancer.

The next step involves clinical trials to confirm these laboratory findings translate to real patient outcomes.

For now, the research offers something precious to cancer patients and their families: expanded hope that more people might benefit from the targeted, gentler treatments that represent the future of cancer care.