This study aims to explore whether E545K, the most common hotspot mutation of PIK3CA in cervical cancer, confers radioresistance to cervical cancer cells, to demonstrate the underling mechanism, and to develop the effective targets. SiHa and MS751 cells with PIK3CA-WT and PIK3CA-E545K were established by lentiviral transfection. The radiosensitivity was assessed by colony formation, cell cycle, cell apoptosis, DNA damage, and repair assay. The growth and immunohistochemical assay of xenograft tumor–related toxicity were evaluated in vivo. It was indicated that more cells with PIK3CA-E545K arrested in S phase. Irradiation (IR) led to more survival percentage, less apoptosis, fewer pH2A.X foci, and higher expression of Chk1/2 in SiHa and MS751 cells bearing PIK3CA-E545K. Mechanically, AKT/GSK3β/β-catenin pathway was highly activated, and more β-catenin was found accumulated in nucleus in cells with PIK3CA-E545K after IR. Furthermore, targeting β-catenin by shRNA or XAV939 enhanced IR sensitivity in cells with PIK3CA-WT and PIK3CA-E545K, whereas it was more notably in the latter. β-Catenin shRNA and XAV939 increased IR-mediated inhibition of colony formation with highly activated p53/bcl2/bax pathway. XAV939 enhanced IR-caused apoptosis, DNA damage, overcame S-phase arrest, DNA repair and reversed β-catenin nuclear accumulation in MS751 cells with PIK3CA-E545K. In vivo, XAV939 enhanced the radiosensitivity of cervical cancer xenografts with PIK3CA-E545K with invisible viscera toxicity. The findings demonstrate that cervical cancer cells with PIK3CA-E545K are resistant to IR by enhancing the expression and nuclear accumulation of β-catenin. Targeting β-catenin reverses the radioresistance, which suggests possible areas for preclinical research on β-catenin inhibition for strengthening the radiosensitivity of cervical cancer.

中文翻译：

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靶向 β-catenin 可逆转 PIK3CA E545K 突变的宫颈癌的放射抗性

本研究旨在探讨宫颈癌中最常见的PIK3CA热点突变E545K是否赋予宫颈癌细胞放射抗性，证明其潜在机制并开发有效靶点。通过慢病毒转染建立具有 PIK3CA-WT 和 PIK3CA-E545K 的 SiHa 和 MS751 细胞。通过集落形成、细胞周期、细胞凋亡、DNA 损伤和修复测定来评估放射敏感性。在体内评估了异种移植肿瘤相关毒性的生长和免疫组织化学测定。表明更多具有 PIK3CA-E545K 的细胞停留在 S 期。辐照 (IR) 导致更高的存活率、更少的细胞凋亡、更少的 pH2A.X 病灶以及在携带 PIK3CA-E545K 的 SiHa 和 MS751 细胞中 Chk1/2 的更高表达。在机械上，AKT/GSK3β/β-catenin 通路被高度激活，IR后发现PIK3CA-E545K细胞核内积累更多β-catenin。此外，shRNA 或 XAV939 靶向 β-catenin 增强了 PIK3CA-WT 和 PIK3CA-E545K 细胞的 IR 敏感性，而后者更显着。β-Catenin shRNA 和 XAV939 通过高度激活的 p53/bcl2/bax 途径增加了 IR 介导的集落形成抑制。XAV939 增强 IR 引起的细胞凋亡、DNA 损伤、克服 S 期停滞、DNA 修复和逆转 PIK3CA-E545K 的 MS751 细胞中的 β-连环蛋白核积累。在体内，XAV939 用 PIK3CA-E545K 增强了宫颈癌异种移植物的放射敏感性，具有不可见的内脏毒性。研究结果表明，具有 PIK3CA-E545K 的宫颈癌细胞通过增强 β-catenin 的表达和核积累对 IR 具有抗性。