BRCA1 缺陷型乳腺癌患者来源异种移植模型中治疗抵抗的机制。
Mechanisms of Therapy Resistance in Patient-Derived Xenograft Models of BRCA1-Deficient Breast Cancer.
机构信息
Affiliations of authors: Division of Molecular Pathology and Cancer Genomics Centre Netherlands (PtB, PK, EvdB, UB, MdM, EL, LM, JdR, JW, JJ), Division of Molecular Carcinogenesis (IM), Department of Epidemiology and Biostatistics (KJ), and Family Cancer Clinic and Department of Pathology (FH), The Netherlands Cancer Institute, Amsterdam, the Netherlands; Cancer Epigenetics and Biology Program (PEBC), Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Catalonia, Spain (CM, ME); The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK (HG, NT); Laboratory of Preclinical Investigation, Translational Research Department, Curie Institute, Paris, France (EM); Department of Medical Genetics, University Medical Center Utrecht, Utrecht, the Netherlands (WK, MvR, KD, EC); Department of Physiological Sciences II, School of Medicine, University of Barcelona, Barcelona, Catalonia, Spain (ME); Institucio Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Catalonia, Spain (ME).
出版信息
J Natl Cancer Inst. 2016 Jul 5;108(11). doi: 10.1093/jnci/djw148. Print 2016 Nov.
BACKGROUND
Although BRCA1-deficient tumors are extremely sensitive to DNA-damaging drugs and poly(ADP-ribose) polymerase (PARP) inhibitors, recurrences do occur and, consequently, resistance to therapy remains a serious clinical problem. To study the underlying mechanisms, we induced therapy resistance in patient-derived xenograft (PDX) models of BRCA1-mutated and BRCA1-methylated triple-negative breast cancer.
METHODS
A cohort of 75 mice carrying BRCA1-deficient breast PDX tumors was treated with cisplatin, melphalan, nimustine, or olaparib, and treatment sensitivity was determined. In tumors that acquired therapy resistance, BRCA1 expression was investigated using quantitative real-time polymerase chain reaction and immunoblotting. Next-generation sequencing, methylation-specific multiplex ligation-dependent probe amplification (MLPA) and Target Locus Amplification (TLA)-based sequencing were used to determine mechanisms of BRCA1 re-expression in therapy-resistant tumors.
RESULTS
BRCA1 protein was not detected in therapy-sensitive tumors but was found in 31 out of 42 resistant cases. Apart from previously described mechanisms involving BRCA1-intragenic deletions and loss of BRCA1 promoter hypermethylation, a novel resistance mechanism was identified in four out of seven BRCA1-methylated PDX tumors that re-expressed BRCA1 but retained BRCA1 promoter hypermethylation. In these tumors, we found de novo gene fusions that placed BRCA1 under the transcriptional control of a heterologous promoter, resulting in re-expression of BRCA1 and acquisition of therapy resistance.
CONCLUSIONS
In addition to previously described clinically relevant resistance mechanisms in BRCA1-deficient tumors, we describe a novel resistance mechanism in BRCA1-methylated PDX tumors involving de novo rearrangements at the BRCA1 locus, demonstrating that BRCA1-methylated breast cancers may acquire therapy resistance via both epigenetic and genetic mechanisms.
背景
尽管 BRCA1 缺陷型肿瘤对 DNA 损伤药物和聚（ADP-核糖）聚合酶（PARP）抑制剂极其敏感，但仍会发生复发，因此，对治疗的耐药性仍然是一个严重的临床问题。为了研究潜在的机制，我们在 BRCA1 突变和 BRCA1 甲基化三阴性乳腺癌的患者来源异种移植（PDX）模型中诱导了治疗耐药性。
方法
一组携带 BRCA1 缺陷型乳腺 PDX 肿瘤的 75 只小鼠接受顺铂、美法仑、尼莫司汀或奥拉帕利治疗，并确定治疗敏感性。在获得治疗耐药性的肿瘤中，使用定量实时聚合酶链反应和免疫印迹法研究 BRCA1 表达。下一代测序、甲基化特异性多重连接依赖性探针扩增（MLPA）和靶向基因座扩增（TLA）测序用于确定治疗耐药性肿瘤中 BRCA1 再表达的机制。
结果
BRCA1 蛋白在治疗敏感的肿瘤中未检测到，但在 42 例耐药病例中的 31 例中发现。除了先前描述的涉及 BRCA1 基因内缺失和 BRCA1 启动子超甲基化丢失的机制外，在 7 例 BRCA1 甲基化 PDX 肿瘤中发现了一种新的耐药机制，这 4 例肿瘤重新表达 BRCA1 但保留 BRCA1 启动子超甲基化。在这些肿瘤中，我们发现了新的基因融合，使 BRCA1 置于异源启动子的转录控制下，导致 BRCA1 的重新表达和获得治疗耐药性。
结论
除了先前描述的 BRCA1 缺陷型肿瘤中具有临床意义的耐药机制外，我们还描述了 BRCA1 甲基化 PDX 肿瘤中一种新的耐药机制，涉及 BRCA1 基因座的新重排，表明 BRCA1 甲基化乳腺癌可能通过表观遗传和遗传机制获得治疗耐药性。
Zotero 插件