New Gene Tech Targets Cancer DNA with Fewer Markers

Abstract

Triggering cancer cell death by inducing DNA damage is the primary aim of radiotherapy; however, normal cells are also damaged. In this study, we showed that delivery of only four synthetic guide RNAs with Cas9 endonuclease efficiently induced simultaneous DNA double-strand breaks, resulting in efficient cell death in a cell type-specific manner. Off-target effects of Cas9 endonuclease were prevented by using Cas9-nickase to induce DNA single-strand breaks and blocking their repair with PARP inhibitors (PARPi). When recombinant Cas9-nickase protein and multiple synthetic guide RNAs were delivered with PARPis into cultured cells, in vivo xenografts, and patient-derived cancer organoids via lipid nanoparticles, cancer cells were unable to tolerate the induced DNA damage even in the presence of a functional BRCA2 gene. This approach has the potential to expand the use of PARPis with verified safety and thus is a potentially powerful tool for personalized genome-based anticancer therapy.

Researchers from the Department of Biomedical Engineering at UNIST and the Center for Genomic Integrity at the Institute for Basic Science (IBS) have announced a breakthrough in cancer gene therapy. Their innovative method enables precise destruction of cancer cell DNA by targeting only a single strand of the DNA double helix, significantly simplifying the process and reducing potential side effects.

Previously, in 2022, the team introduced a CRISPR-based approach that required delivering over 20 guide RNAs simultaneously to induce multiple double-strand breaks (DSBs) in cancer DNA, effectively killing the cells. However, this method faced challenges related to delivery complexity and the risk of damaging normal tissues.

Figure 1. Synthetic lethality of combined CRISPR/Cas9 and DNA damage-inducing treatments. (A) Bar plots showing the viability of cells treated with multiplexed CRISPR/Cas9WT RNPs plus irradiation. (B) Schematic illustrating synthetic lethality of CRISPR/Cas9 targeting, followed by DNA damage-inducing treatment or DNA repair inhibitors such as additional CRISPR/Cas, irradiation, or a PARPi. NT, nontarget control sgRNA. Statistical significance was calculated using an unpaired two-tailed Student t test.

The newly developed technique requires only four guide RNAs and exploits the synergy between CRISPR and PARP inhibitors-drugs that block a critical DNA repair protein. By inducing single-strand breaks (SSBs) instead of DSBs and preventing their repair, this approach effectively triggers cancer cell death with fewer guide RNAs, minimizing off-target effects and enhancing safety.

PARP inhibitors are well-established targeted therapies, primarily used for ovarian and breast cancers with BRCA mutations. This combined strategy broadens their application to other cancer types lacking such genetic alterations.

Professor Seung Woo Cho, the lead corresponding author from UNIST, explained, "This advancement reduces the complexity of gene delivery and minimizes cellular toxicity, paving the way for clinical applications." He further added, "It also extends the potential use of PARP inhibitors beyond current indications."

The research demonstrated the effectiveness of this approach in patient-derived organoids from colorectal cancer and in vivo tumor models. In mouse experiments, tumor growth was reduced by over 50% within six weeks.

Additionally, this strategy shows promise in enhancing existing radiation therapies. Since radiation damages both cancerous and normal DNA, combining it with targeted gene editing could enable lower radiation doses, reducing side effects while maintaining therapeutic efficacy.

The researchers anticipate that when used alongside other targeted therapies or radiation, this method could produce synergistic effects, opening new pathways for personalized and combination cancer treatments.

This study was published in Cancer Research, the official journal of the American Association for Cancer Research (AACR) on August 1, 2025.

Journal Reference

Soyoung Lee, Kyunghwan Kim, Hye-Jin Jeong, et al., "Combining Multiplexed CRISPR/Cas9-Nickase and PARP Inhibitors Efficiently and Precisely Targets Cancer Cells," Cancer Research, (2025).