Sung Koangyong, Hosoya Kenji, Deguchi Tatsuya, Yamashita Koya, Kim Sangho, Sunaga Takafumi, Yasui Hironobu, Inanami Osamu, Okumura Masahiro
Laboratory of Veterinary Surgery, Department of Veterinary Clinical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Veterinary Teaching Hospital, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Sci Rep. 2025 May 23;15(1):18017. doi: 10.1038/s41598-025-02569-9.
Radio-resistance of cancer stem-like cells (CSCs) is associated with the failure of radiation therapy. ZsGreen1-positive (ZsG⁺) cells, which exhibit low proteasome activity, have been used to enable the detection and isolation of CSCs. However, the mechanisms of radio-resistance in canine tumor cells with low proteasome activity remain unclear. This study aimed to elucidate the radio-resistance mechanisms of ZsG cells by identifying a potential target of canine CSCs. ZsG cells, isolated using flow cytometric cell sorting, were compared with ZsG cells. Sulfasalazine was used to suppress glutathione (GSH) synthesis by inhibiting xCT. In vitro experiments demonstrated a significantly higher radio-resistance in ZsG cells than in ZsG cells. After X-irradiation, ZsG cells had fewer p53‑binding protein 1 (53BP1) foci, low reactive oxygen species (ROS) accumulation, and high GSH content. Sulfasalazine caused radiosensitization of ZsG cells with an increased number of 53BP1 foci by decreasing GSH contents and increasing ROS accumulation. The low proteasome activity played a role in xCT upregulation. In conclusion, canine tumor cells with low proteasome activity are radio-resistant due to high GSH content and low ROS accumulation. Sulfasalazine causes radiosensitization of the tumor cells by altering redox balance by inhibiting GSH synthesis for effective targeting of canine CSCs.
癌症干细胞（CSCs）的放射抗性与放射治疗的失败相关。蛋白酶体活性低的ZsGreen1阳性（ZsG⁺）细胞已被用于CSCs的检测和分离。然而，蛋白酶体活性低的犬肿瘤细胞的放射抗性机制仍不清楚。本研究旨在通过鉴定犬CSCs的潜在靶点来阐明ZsG细胞的放射抗性机制。使用流式细胞术细胞分选分离的ZsG细胞与ZsG细胞进行比较。柳氮磺胺吡啶用于通过抑制xCT来抑制谷胱甘肽（GSH）合成。体外实验表明，ZsG细胞的放射抗性明显高于ZsG细胞。X射线照射后，ZsG细胞的p53结合蛋白1（53BP1）病灶较少，活性氧（ROS）积累较低，GSH含量较高。柳氮磺胺吡啶通过降低GSH含量和增加ROS积累，使ZsG细胞的53BP1病灶数量增加，从而导致放射增敏。低蛋白酶体活性在xCT上调中起作用。总之，蛋白酶体活性低的犬肿瘤细胞由于GSH含量高和ROS积累低而具有放射抗性。柳氮磺胺吡啶通过抑制GSH合成改变氧化还原平衡，从而使肿瘤细胞放射增敏，有效靶向犬CSCs。
