Punicalagin as an Artemis inhibitor synergizes with photodynamic therapy in tumor suppression

Photodynamic therapy (PDT) is a minimally invasive treatment that utilizes a photosensitizer, specific light wavelengths, and oxygen to generate reactive oxygen species (ROS), causing oxidative damage and tumor cell death. However, the effectiveness of PDT can be reduced by the intrinsic antioxidant and DNA repair mechanisms of tumor cells. Artemis (SNM1C/DCLRE1C) is an endonuclease essential for repairing DNA double-strand breaks (DSBs) via non-homologous end-joining (NHEJ). Herein, we conducted a high-throughput small-molecule screening and identified Punicalagin (PUG), a natural polyphenol from pomegranate, as a novel Artemis inhibitor with an IC₅₀ value of 296.1 nM. We also investigated the effects of PUG combined with PDT in tumor treatment, using the pentalysine β-carbonylphthalocyanine zinc (ZnPc5K) as the photosensitizer. In HeLa cells, ZnPc5K-based PDT induced significant DSBs, which could be repaired by the intrinsic DNA repair mechanisms within 12 h. Co-treatment with PUG compromised DNA repair, promoted cell apoptosis, inhibited cell invasion, and suppressed the growth of various tumor cells. Furthermore, in a mouse xenograft model, the combination of PUG and ZnPc5K-PDT effectively inhibited tumor growth with minimal side effects. These findings suggest that PUG, as an Artemis inhibitor, can enhance the therapeutic efficacy of PDT in tumor suppression by impairing DNA repair through the NHEJ pathway.