PO.MCB05.02 · 分子与细胞生物学

Caspase-4缺失损害核肌动蛋白介导的DNA双链断裂修复并增加癌细胞的放射敏感性

Caspase-4 deficiency impairs nuclear actin-mediated DNA double-strand break repair and increases radiosensitivity in cancer cells

编号 518 展板 9 时间 4/19 02:00–05:00 区域 Section 21 主讲 Shohei Nagasaka, MD

分会场 Mechanisms and Targets in DNA Damage Repair

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作者与单位 Authors & Affiliations

Shohei Nagasaka¹, Tomomitsu Doi², Kunie Obayashi³, Masaoki Kohzaki⁴, Kazuhiro Sumida³, Yosuke Chiba³, Junkoh Yamamoto⁵, Motoyoshi Endo³

¹Neurosurgery and Molecular Biology, University of Occupational and Environmental Health, Kitakyushu, Japan,²Molecular Biology and Cellular Biology, University of Occupational and Environmental Health, Kitakyushu, Japan,³Molecular Biology, University of Occupational and Environmental Health, Kitakyushu, Japan,⁴Radiobiology and Hygiene Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan,⁵Neurosurgery, University of Occupational and Environmental Health, Kitakyushu, Japan

摘要 Abstract

中文摘要

背景：放疗主要通过DNA双链断裂（DSBs）产生细胞毒性，而DSB修复的效率是决定肿瘤放射敏感性的关键因素。Caspase-4（CASP4）在人类恶性肿瘤中常过表达，已被认为与肌动蛋白细胞骨架重塑有关；然而，其在核肌动蛋白动态和DNA修复中的作用仍不清楚。方法：我们使用CASP4基因敲除（KO）的HepG2和NCI-H292细胞研究了CASP4在放射应答中的功能作用。采用集落形成实验、53BP1焦点分析，以及一种新开发的可定量核肌动蛋白水平的测量系统，评估DNA修复效率和肌动蛋白分布。通过强制核肌动蛋白表达来评估其挽救CASP4依赖性缺陷的能力。结果：CASP4 KO显著使肿瘤细胞对电离辐射敏感，伴随集落形成减少和53BP1焦点持续存在，提示DSB消解受损。尽管CASP4缺失细胞表现出胞质F-actin升高，但在总肌动蛋白水平相当的情况下核肌动蛋白转位减少，提示肌动蛋白穿梭存在缺陷。定量成像证实CASP4 KO细胞中核肌动蛋白信号显著减弱。值得注意的是，强制核肌动蛋白表达恢复了CASP4缺失细胞中53BP1焦点的消解。结论：这些发现揭示了CASP4通过调节核肌动蛋白动态促进DNA DSB修复的一个此前未被认识的作用。CASP4促进胞质与核肌动蛋白之间的平衡，以维持高效的DNA修复并增强放射抵抗性。因此，靶向CASP4可能代表一种克服肿瘤对电离辐射抵抗的有前景的策略。

查看英文原文 English abstract

Background: Radiotherapy induces cytotoxicity primarily through DNA double-strand breaks (DSBs), and the efficiency of DSB repair is a key determinant of tumor radiosensitivity. Caspase-4 (CASP4), frequently overexpressed in human malignancies, has been implicated in actin cytoskeletal remodeling; however, its involvement in nuclear actin dynamics and DNA repair remains unclear. Methods: We investigated the functional role of CASP4 in radioresponse using CASP4 knockout (KO) HepG2 and NCI-H292 cells. Colony formation assays, 53BP1 foci analysis, and a newly developed measurement system that enables the quantification of nuclear actin levels were used to assess DNA repair efficiency and actin distribution. Forced nuclear actin expression was used to evaluate its ability to rescue CASP4-dependent defects. Results: CASP4 KO significantly sensitized tumor cells to ionizing radiation, associated with decreased colony formation and persistent 53BP1 foci, indicative of impaired DSB resolution. Although CASP4-deficient cells exhibited elevated cytoplasmic F-actin, nuclear actin translocation was reduced despite comparable total actin levels, suggesting defective actin shuttling. Quantitative imaging confirmed substantially diminished nuclear actin signals in CASP4 KO cells. Notably, enforced nuclear actin expression restored 53BP1 foci resolution in CASP4-deficient cells. Conclusions: These findings identify a previously unrecognized role of CASP4 in promoting DNA DSB repair through regulation of nuclear actin dynamics. CASP4 facilitates the balance between cytoplasmic and nuclear actin to maintain efficient DNA repair and enhance radioresistance. Targeting CASP4 may therefore represent a promising strategy to overcome tumor resistance to ionizing radiation.

利益披露 Disclosure

S. Nagasaka, None.. T. Doi, None.. K. Obayashi, None.. M. Kohzaki, None.. K. Sumida, None.. Y. Chiba, None.. J. Yamamoto, None.. M. Endo, None.

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