Chronic hypoxia decreases synthesis of homologous recombination proteins to offset chemoresistance and radioresistance
Chronic hypoxia decreases synthesis of homologous recombination proteins to offset chemoresistance and radioresistance
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DOI：
10.1158/0008-5472.can-07-5472
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发表时间：
2008-01-15
期刊：
影响因子：
11.2
通讯作者：
Bristow, Robert G.
中科院分区：
文献类型：
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作者：
Chan, Norman;Koritzinsky, Marianne;Bristow, Robert G.
缺氧和/或缺氧的肿瘤细胞可以增加突变率和改变DNA修复蛋白的表达。然而，关于缺氧引起的DNA双链断裂修复中蛋白质表达变化的功能后果，我们所知甚少。我们开发了一种独特的缺氧模型系统，使用表达集成的直接重复绿色荧光蛋白（DR-GFP）同源重组（HR）报告系统的H1299细胞来研究长时间慢性缺氧（0.2% O-2下长达72小时）下的HR，而不受增殖改变、细胞周期检查点激活或严重细胞毒性的影响。我们观察到由于一种涉及HR蛋白合成减少的新机制，HR蛋白的表达减少。DR-GFP报告系统测量的无差错HR在0.2% 02下被抑制3倍。这种功能性HR的降低导致对DNA交联剂丝裂霉素C和顺铂的敏感性增加，但对微管干扰剂紫杉醇的敏感性没有增加。与急性缺氧或缺氧细胞（OER, 1.96-2.61）相比，慢性缺氧的H1299细胞功能HR降低，对辐射相对敏感[氧增强比（OER）， 1.37]。利用CAPAN1细胞BRCA2和siRNA与RAD51的等基因，我们证实了缺氧诱导的放射敏感性是由于HR容量下降。肿瘤微环境对HR功能的持续下调可能导致低保真DNA修复，并对人类癌症的治疗反应和遗传不稳定性具有重要意义。
Hypoxic and/or anoxic tumor cells can have increased rates of mutagenesis and altered DNA repair protein expression. Yet very little is known regarding the functional consequences of any hypoxia-induced changes in the expression of proteins involved in DNA double-strand break repair. We have developed a unique hypoxic model system using H1299 cells expressing an integrated direct repeat green fluorescent protein (DR-GFP) homologous recombination (HR) reporter system to study HR under prolonged chronic hypoxia (up to 72 h under 0.2% O-2) without bias from altered proliferation, cell cycle checkpoint activation, or severe cell toxicity. We observed decreased expression of HR proteins due to a novel mechanism involving decreased HR protein synthesis. Error-free HR was suppressed 3-fold under 0.2% 02 as measured by the DR-GFP reporter system. This decrease in functional HR resulted in increased sensitivity to the DNA cross-linking agents mitomycin C and cisplatin but not to the microtubule-interfering agent, paclitaxel. Chronically hypoxic H1299 cells that had decreased functional HR were relatively radiosensitive [oxygen enhancement ratio (OER), 1.37] when compared with acutely hypoxic or anoxic cells (OER, 1.96-2.61). Using CAPAN1 cells isogenic for BRCA2 and siRNA to RAD51, we confirmed that the hypoxia-induced radiosensitivity was due to decreased HR capacity. Persistent down-regulation of HR function by the tumor microenvironment could result in low-fidelity DNA repair and have significant implications for response to therapy and genetic instability in human cancers.