该DNA修复基因失控，暴露了癌症的一个弱点

但新的研究表明，拥有过多的某种DNA修复蛋白也可能是个问题。 宾夕法尼亚州立大学医学院的研究人员发现，EXO1基因的过度活跃会损害DNA而不是保护它。过多的EXO1非但不能修复遗传物质，反而会分解DNA并破坏基因组稳定性，这是癌症的一个关键特征。 这些发表在《自然-通讯》上的研究结果表明，EXO1在20%至30%的乳腺癌和卵巢癌中存在过表达，在黑色素瘤、睾丸癌、宫颈癌以及发生在肝脏、胆囊和胆管的肝胆癌中也存在过表达。 研究团队还发现，EXO1水平异常高的癌细胞其行为与携带BRCA突变的细胞非常相似，后者因增加遗传性乳腺癌和卵巢癌的风险而闻名。重要的是，即使不存在BRCA突变，这些类BRCA行为也会发生。 **EXO1可能有助于识别适合靶向治疗的患者** 研究人员发现，EXO1水平升高的肿瘤对治疗的反应方式与BRCA突变型癌症非常相似。 该研究的资深作者、分子与精准医学教授乔治-卢西安·莫尔多万说：“EXO1并不能预测癌症风险，但它有可能作为一种生物标志物，帮助预测哪些患者更有可能对某些化疗产生反应，从而实现更个性化的治疗。那些专门用于治疗BRCA突变肿瘤且副作用较小的药物，可能被用于治疗没有BRCA突变但EXO1过表达的肿瘤。这将扩大这些药物的适用范围。” 为了研究EXO1的作用，研究人员分析了来自“癌症基因组图谱”（美国国家癌症研究所的一项癌症基因组计划）的肿瘤数据。他们在多种癌症类型中发现了EXO1过量产生的证据，包括乳腺、皮肤、肝脏和宫颈肿瘤，这与早期的研究一致。EXO1水平升高尤其与基底样乳腺癌（一种侵袭性很强的疾病）相关。 **过量EXO1如何损伤DNA** 随后，研究团队使用市售的人类癌细胞进行了实验室实验。 研究人员在细胞中人为增加了EXO1的产生，以确定过量的该蛋白如何影响DNA。他们还构建了一种失活版本的EXO1，它能产生蛋白质但缺乏正常的生化活性。这使他们能够确认，任何观察到的DNA损伤都是由该蛋白的活性引起的，而不仅仅是由于其存在。 在正常条件下，EXO1的功能就像一把分子剪刀，帮助修剪和修复受损的DNA。然而，当EXO1过多时，这些剪刀就会开始切割本应保持完整的DNA结构。 * *Key terms:* excess EXO1 (过量的EXO1), destabilizes (破坏稳定性), newly formed DNA (新形成的DNA), mechanisms (机制), expanding single-stranded DNA gaps (扩大单链DNA缺口), degrading reversed replication forks (降解逆转复制叉), erode DNA (侵蚀DNA), localized loss of genetic material (局部遗传物质丢失). * *Draft:* 研究人员发现，过量的EXO1通过两种主要机制破坏新形成DNA的稳定性：扩大单链DNA缺口和降解逆转复制叉。Moldovan解释说，这两个过程都会侵蚀DNA并导致遗传物质的局部丢失。 * *Paragraph 2:* "Regardless of which pathway, EXO1 overexpression leads to the generation and accumulation of toxic lesions in DNA, such as double strand breaks, which we ultimately think is what makes the tumor more sensitive to chemotherapy and increases cell death," said Alexandra Nusawardhana, the lead author of the study and who earned her doctorate in biomedical sciences this year from Penn State College of Medicine. * *Key terms:* pathway (途径), EXO1 overexpression (EXO1过表达), toxic lesions (毒性损伤), double strand breaks (双链断裂), chemotherapy (化疗), cell death (细胞死亡), lead author (第一作者), doctorate in biomedical sciences (生物医学科学博士学位), Penn State College of Medicine (宾夕法尼亚州立大学医学院). * *Draft:* 该研究的第一作者、今年刚从宾夕法尼亚州立大学医学院获得生物医学科学博士学位的Alexandra Nusawardhana说：“无论通过哪种途径，EXO1过表达都会导致DNA中毒性损伤（如双链断裂）的产生和积累，我们最终认为这正是使肿瘤对化疗更敏感并增加细胞死亡的原因。” * *Paragraph 3:* "Why EXO1 Mimics BRCA Mutations" * *Draft:* 为什么EXO1会模拟BRCA突变 * *Paragraph 4:* "BRCA genes normally produce proteins that help protect vulnerable DNA structures during replication. When BRCA genes are mutated, cells lose part of this protective function, which can contribute to cancer development." * *Key terms:* BRCA genes (BRCA基因), vulnerable DNA structures (脆弱的DNA结构), replication (复制), mutated (突变), protective function (保护功能), cancer development (癌症发生/发展). * *Draft:* BRCA基因通常产生有助于在复制过程中保护脆弱DNA结构的蛋白质。当BRCA基因发生突变时，细胞会失去部分保护功能，这可能导致癌症的发展。 * *Paragraph 5:* "In the current study, however, researchers found that excessive EXO1 activity was able to overwhelm those protective mechanisms even when BRCA genes were functioning normally and carried no mutations." * *Key terms:* excessive EXO1 activity (过度的EXO1活性), overwhelm (压倒/破坏/使不堪重负), protective mechanisms (保护机制), functioning normally (功能正常). * *Draft:* 然而，在当前的研究中，研究人员发现，即使BRCA基因功能正常且未携带突变，过度的EXO1活性也能够破坏这些保护机制。 * *Paragraph 6:* "The team also discovered that EXO1 works alongside another protein called MRE11 to enlarge DNA gaps and generate dangerous DNA breaks." * *Key terms:* works alongside (协同作用), MRE11, enlarge DNA gaps (扩大DNA缺口), generate dangerous DNA breaks (产生危险的DNA断裂). * *Draft:* 研究小组还发现，EXO1与另一种名为MRE11的蛋白质协同作用，扩大DNA缺口并产生危险的DNA断裂。 * *Paragraph 7:* "Mechanistically, this overexpression does exactly what the loss of the BRCA pathway does in BRCA-mutant tumor cells," Moldovan said. * *Key terms:* Mechanistically (从机制上讲), loss of the BRCA pathway (BRCA通路缺失). * *Draft:* Moldovan说：“从机制上讲，这种过表达的作用与BRCA突变肿瘤细胞中BRCA通路缺失的作用完全一致。” * *Paragraph 8:* "He noted that EXO1 overexpression differs from BRCA mutations in an important way. It is not inherited, and researchers do not yet know whether it directly causes cancer." * *Key terms:* inherited (遗传), directly causes cancer (直接导致癌症). * *Draft:* 他指出，EXO1过表达在一个重要方面不同于BRCA突变。它不是遗传的，研究人员尚不清楚它是否会直接导致癌症。 * *Paragraph 9:* "Potential Impact on Cancer Treatment" * *Draft:* 对癌症治疗的潜在影响 * *Paragraph 10:* "Because EXO1-overexpressing tumors behaved so much like BRCA-mutant tumors, the researchers investigated whether they would also respond similarly to treatment." * *Key terms:* EXO1-overexpressing tumors (EXO1过表达肿瘤), BRCA-mutant tumors (BRCA突变肿瘤), respond similarly (反应相似). * *Draft:* 由于EXO1过表达肿瘤的表现与BRCA突变肿瘤非常相似，研究人员调查了它们对治疗的反应是否也相似。 * *Paragraph 11:* "They tested olaparib, a drug commonly used against BRCA-mutant cancers that targets cellular DNA repair pathways. Tumors with elevated EXO1 were highly sensitive to the treatment and responded in a manner similar to BRCA-mutant cancers." * *Key terms:* olaparib (奥拉帕利), targets cellular DNA repair pathways (靶向细胞DNA修复通路), elevated EXO1 (EXO1水平升高). * *Draft:* 他们测试了奥拉帕利（olaparib），这是一种常用于治疗BRCA突变癌症、靶向细胞DNA修复通路的药物。EXO1水平升高的肿瘤对该治疗高度敏感，其反应方式与BRCA突变癌症相似。 * *Paragraph 12:* "The results suggest that patients whose tumors overexpress EXO1 could potentially benefit from the same repair-targeted therapies, even if they do not carry BRCA mutations." * *Key terms:* repair-targeted therapies (靶向修复疗法). * *Draft:* 结果表明，肿瘤过表达EXO1的患者可能从同样的靶向修复疗法中受益，即使他们不携带BRCA突变。 * *Paragraph 13:* "The researchers also found that EXO1-overexpressing tumors responded to cisplatin, a widely used chemotherapy drug. Their findings raise the possibility that lower doses of cisplatin might achieve comparable tumor shrinkage while reducing side effects." * *Key terms:* cisplatin (顺铂), chemotherapy drug (化疗药物), lower doses (较低剂量), comparable tumor shrinkage (相当的肿瘤缩小效果), side effects (副作用). * *Draft:* 研究人员还发现，EXO1过表达肿瘤对顺铂（一种广泛使用的化疗药物）有反应。他们的发现提出了一种可能性，即较低剂量的顺铂可能实现相当的肿瘤缩小效果，同时减少副作用。 * *Paragraph 14:* "Because EXO1 overexpression appears in a wider range of tumors than BRCA mutations, Moldovan said it could become a valuable biomarker for guiding treatment decisions." * *Key terms:* wider range of tumors (更广泛的肿瘤范围), biomarker (生物标志物), guiding treatment decisions (指导治疗决策). * *Draft:* Moldovan表示，由于EXO1过表达出现在比BRCA突变更广泛的肿瘤中，它可能成为指导治疗决策的有价值的生物标志物。 * *Paragraph 15:* "We shouldn't treat cancers based on what tissue they come from but based on the landscape of the genetic mutations present in the tumors," Moldovan said. "That would result in high efficiency treatment. That's the future of cancer treatment." * *Key terms:* tissue (组织), landscape of the genetic mutations (基因突变图谱/景观), high efficiency treatment (高效治疗). * *Draft:* Moldovan说：“我们不应根据癌症来源的组织来治疗癌症，而应根据肿瘤中存在的基因突变图谱来进行治疗。这将带来高效的治疗。这就是癌症治疗的未来。” 3. **Review and Refine:** * Check for flow and terminology consistency. * "Destabilizes" -> 破坏稳定性 (Good). * "Reversed replication forks" -> 逆转复制叉 (Standard term). * "Single-stranded DNA gaps" -> 单链DNA缺口 (Standard term). * "Toxic lesions" -> 毒性损伤 (Good). * "Double strand breaks" -> 双链断裂 (Standard term). * "Mimics" -> 模拟 (Good). * "Overwhelm" -> 破坏/ 研究团队计划继续研究EXO1，其长期目标是针对肿瘤中该基因过表达的患者开展临床试验。 宾夕法尼亚州立大学医学院分子与精准医学助理教授Claudia Nicolae也参与了这项研究。 该研究得到了美国国立卫生研究院和四钻石基金的资助。