Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
Clin Cancer Res. 2010 Jan 1;16(1):99-108. doi: 10.1158/1078-0432.CCR-09-2434. Epub 2009 Dec 15.
Hereditary breast cancer is partly explained by germline mutations in BRCA1 and BRCA2. Although patients carry heterozygous mutations, their tumors have typically lost the remaining wild-type allele. Selectively targeting BRCA deficiency may therefore constitute an important therapeutic approach. Clinical trials applying this principle are underway, but it is unknown whether the compounds tested are optimal. It is therefore important to identify alternative compounds that specifically target BRCA deficiency and to test new combination therapies to establish optimal treatment strategies.
We did a high-throughput pharmaceutical screen on BRCA2-deficient mouse mammary tumor cells and isogenic controls with restored BRCA2 function. Subsequently, we validated positive hits in vitro and in vivo using mice carrying BRCA2-deficient mammary tumors.
Three alkylators-chlorambucil, melphalan, and nimustine-displayed strong and specific toxicity against BRCA2-deficient cells. In vivo, these showed heterogeneous but generally strong BRCA2-deficient antitumor activity, with melphalan and nimustine doing better than cisplatin and the poly-(ADP-ribose)-polymerase inhibitor olaparib (AZD2281) in this small study. In vitro drug combination experiments showed synergistic interactions between the alkylators and olaparib. Tumor intervention studies combining nimustine and olaparib resulted in recurrence-free survival exceeding 330 days in 3 of 5 animals tested.
We generated and validated a platform for identification of compounds with specific activity against BRCA2-deficient cells that translates well to the preclinical setting. Our data call for the re-evaluation of alkylators, especially melphalan and nimustine, alone or in combination with the poly-(ADP-ribose)-polymerase inhibitors, for the treatment of breast cancers with a defective BRCA pathway.
遗传性乳腺癌部分归因于 BRCA1 和 BRCA2 种系突变。尽管患者携带杂合突变，但他们的肿瘤通常失去了剩余的野生型等位基因。因此，选择性靶向 BRCA 缺陷可能是一种重要的治疗方法。正在进行应用这一原则的临床试验，但尚不清楚所测试的化合物是否最佳。因此，确定专门针对 BRCA 缺陷的替代化合物并测试新的联合治疗方法以建立最佳治疗策略非常重要。
我们对 BRCA2 缺陷型小鼠乳腺肿瘤细胞和具有恢复 BRCA2 功能的同源对照进行了高通量药物筛选。随后，我们使用携带 BRCA2 缺陷型乳腺肿瘤的小鼠在体外和体内验证了阳性结果。
三种烷化剂-苯丁酸氮芥、美法仑和尼莫司汀对 BRCA2 缺陷细胞显示出强烈和特异性的毒性。在体内，这些药物表现出异质但通常强烈的 BRCA2 缺陷型抗肿瘤活性，其中美法仑和尼莫司汀在这项小型研究中优于顺铂和聚（ADP-核糖）-聚合酶抑制剂奥拉帕利（AZD2281）。体外药物联合实验显示烷化剂与奥拉帕利之间存在协同相互作用。联合尼莫司汀和奥拉帕利的肿瘤干预研究导致 5 只测试动物中有 3 只的无复发生存期超过 330 天。
我们生成并验证了一种针对 BRCA2 缺陷细胞具有特异性活性的化合物识别平台，该平台在临床前环境中得到了很好的转化。我们的数据呼吁重新评估烷化剂，特别是美法仑和尼莫司汀，单独使用或与聚（ADP-核糖）-聚合酶抑制剂联合使用，用于治疗 BRCA 途径缺陷的乳腺癌。
