UC Irvine researchers have discovered that two existing cancer drugs, when combined, trigger an "alarm signal" inside tumor cells that recruits the immune system to attack them—a finding that could reshape how doctors approach DNA-damaging cancer treatments.
The discovery hinges on a molecular mechanism that begins the moment cancer cells encounter the combination treatment. Postdoctoral fellow Elodie Bournique and her team in the laboratory of Associate Professor Rémi Buisson found that when PARP inhibitors—drugs that prevent cancer cells from repairing their own DNA—are paired with topoisomerase 1-blocking drugs, something unexpected happens: PARP1 becomes trapped on the DNA damage caused by the topoisomerase inhibitor, triggering a cascade that goes far beyond simple cell death.
That cascade activates the NF-κB pathway, an inflammatory signaling route that is central to immune activation. In essence, the drug combination doesn't just damage cancer-cell DNA more thoroughly; it broadcasts the cancer's presence to the body's immune system. "This causes additional DNA damage and activates an inflammatory pathway driven by NF-κB," Bournique explains, noting that this nuclear factor is critical for regulating immune response. The researchers discovered that PARP1 trapping activates an ATM-mediated NF-κB signaling pathway, making cancer cells both more damaged and more visible to immune cells hunting for threats.
For oncology, this represents a significant conceptual shift. PARP inhibitors and topoisomerase 1 inhibitors have long been used separately in cancer treatment, each with a distinct role: TOP1 inhibitors damage cancer-cell DNA, while PARP inhibitors prevent cells from repairing the damage they've sustained. Doctors understood these mechanisms independently, but the interplay between them remained murky. "We still do not fully understand how combining them changes cancer-cell behavior," Buisson acknowledged before the study, underscoring how little was known about their synergy.
What makes this finding particularly promising is its potential to personalize cancer treatment. The researchers stress that the benefit of PARP inhibitors may depend on matching them with the right type of cancer therapy and the right tumor context. Graduate student researcher Ambrocio Sanchez and the team now plan to test whether the inflammatory signals induced by this drug combination can actually promote immune-cell recruitment and improve anti-tumor immune responses in more realistic models—including additional cancer cell lines, organoid systems, and eventually in living organisms. Identifying which tumor types are most likely to benefit from this therapeutic pairing is a key goal.
Bournique sees the work as a stepping stone toward precision medicine: "In the future, this could help guide more precise treatment combinations for patients whose tumors are most likely to respond." The study, published in Nucleic Acids Research in 2026, opens a new chapter in understanding how to harness the immune system alongside conventional cancer drugs. Rather than asking cancer-fighting drugs to do one job, this research suggests that the right combination can accomplish two: kill cancer cells directly and wake up the immune system to finish the job.