低浓度外源性一氧化碳对重离子旁效应信号的调控作用和机理研究

It is considered that heavy ion therapy has better future comparing to the conventional photon therapy for its unique advantages. The original “radiation-induced secondary cancer”, threating the health of heavy ion therapy survivals, beyond the irradiated area after radiotherapy has tight relationship with radiation-induced bystander effect (RIBE). RIBE is defined as the irradiated cells would release damage signal(s) to cause genotoxicity, such as cell proliferation, DNA or chromosome damage, gene mutation or even tumor formation, in the neighboring or even abscopal non-irradiated cells or tissues. It is necessary that modulating or inhibiting RIBE effectively to decrease the health risk of non-irradiated tissue in radiotherapy. Low concentration of carbon monoxide (CO), an important molecule modulating many signal pathways in organisms, has plenty of potential clinic application. We have approved exogenous low concentration of CO could modulate low LET radiation-induced bystander effect and protect the bystander cells. Herein, we go on this study in heavy ion radiation-induced bystander effect. We will detect the level of DNA damage, DNA methylation and persistent damages (in progeny bystander cells)，which is specific in heavy ion RIBE, to evaluate RIBE modulation by CO. The mechanisms studies will focus on how CO modulating the expression and function of critical proteins of various RIBE signal pathways. We hope our study will help to understand well low concentration of CO as potential protective agent to decrease the genetic risk of bystander tissues after heavy ion therapy.

重离子凭借其独特的优势，成为肿瘤放射治疗的重要发展方向。重离子放疗后，辐射区域外的原发“二次”癌症与辐射旁效应紧密关联。旁效应导致受辐射细胞/组织释放出损伤信号，对附近或远端细胞/组织造成遗传毒性，导致细胞增殖、遗传物质损伤和基因突变等直至肿瘤形成。寻找有效的调控方法，降低旁效应造成的健康风险，十分重要。低浓度一氧化碳（CO）是机体内重要信号调控分子，有广阔的临床应用价值。申请人已证实低浓度CO可有效调控低LET辐射引发的旁效应传递，保护旁细胞。申请人拟在细胞模型中，通过评估旁细胞中的DNA损伤、DNA甲基化水平和重离子辐射特有的（子代旁细胞）持续性损伤，研究低浓度CO调控重离子辐射旁效应的作用规律；通过研究CO对旁效应信号通路中关键蛋白表达和功能的影响，探索调控的可能机理。研究结果将有利于推进低浓度CO作为重离子放疗防护剂，降低辐射区域外遗传风险的研究。

本项目开展了低浓度CO对碳重离子旁效应的调控作用和机理研究。研究结果表明：低浓度CO（来自CO释放分子CORM-3）对重离子辐射旁效应的调控表现出浓度依赖性，CORM-3可以有效保护旁细胞，有效降低其中的DNA双链断裂、微核水平，对直接辐射细胞未见显著影响；CORM-3可抑制重离子辐射旁效应产生的持续性遗传损伤。机理研究方面，现已排除诱导型一氧化氮合成酶（iNOS）和环氧化酶2（COX-2）相关信号通路的作用，提示与低LET辐射相比，CO调控重离子辐射旁效应的机制有所区别，可能是调控了旁效应传递的其他信号通路。鉴于重离子试验机时有限，进一步的机理研究有待2020年度试验中开展。