Director Kyungjae Myung's team at the Institute for Basic Science has found a way to disarm cancer's most sophisticated defense mechanism — and the discovery could rescue one of medicine's most promising drugs from the graveyard of failed treatments.
Cancer cells are relentless survivors. They've evolved to repair the DNA damage that therapies are designed to inflict, which is why tumors so often bounce back after initial treatment. PARP inhibitors were hailed as a breakthrough precisely because they exploited a weakness in this repair system. But within months or years, many cancers adapt. They restore their DNA repair capabilities and become resistant, leaving patients with dwindling options.
Now researchers at the IBS Center for Genomic Integrity, working with Joo-Yong Lee of Chungnam University, have discovered something counterintuitive: instead of trying to mutate cancer cells into submission, they can simply starve them of the proteins they need to survive. The team identified a small molecule called UNI418 that triggers the destruction of critical DNA repair proteins, including RAD51 and CHK1. Without enough of these proteins, cancer cells lose their ability to fix damaged DNA — even if they had previously regained it.
The mechanism is elegant. UNI418 interferes with a metabolic signaling pathway involving inositol phosphate metabolism, causing levels of a molecule called IP6 to drop. Under normal conditions, IP6 acts as a brake on a protein disposal system known as the Cul4A ubiquitin ligase complex. When IP6 declines, that brake is released. The Cul4A complex then teams up with an adaptor protein called WDR5 to systematically dismantle the cell's DNA repair machinery, marking repair proteins like RAD51 for destruction.
The result, as Lee explained, is "a mechanism in which key DNA repair proteins are actively degraded inside the cell," creating a vulnerability that persists even in resistant tumors.
In cell-based studies, UNI418 restored cancer cells' sensitivity to PARP inhibitors — the very drugs they had learned to resist. The effect was especially striking in already-resistant cancers, where adding UNI418 made them responsive to treatment once again. When researchers moved to animal models, tumors implanted in mice slowed their growth when treated with UNI418 alongside the PARP inhibitor Olaparib, even in models designed to mimic treatment-resistant disease.
What makes this discovery significant extends beyond the immediate therapeutic potential. By showing that IP6 signaling influences protein degradation pathways that affect DNA repair, the research reveals an unexpected bridge between cellular metabolism and genome stability. The findings suggest that the way cells burn fuel and process nutrients directly shapes how effectively they fix genetic damage — a connection that could open entirely new avenues for cancer research.
Director Myung framed the broader implication: "By weakening the DNA repair system, we can re-sensitize tumors that have become resistant to existing therapies. This suggests a new strategy for expanding the effectiveness of PARP inhibitors."
Cancer's evolutionary arms race with medicine continues, but this discovery suggests a new tool for tipping the balance. By targeting not the mutations cancer cells accumulate, but the fragile protein machinery they depend on, researchers may have found a way to transform resistant tumors back into vulnerable ones.