Alshareeda Alaa Tarig, Negm Ola H, Aleskandarany Mohammed A, Green Andrew R, Nolan Christopher, TigHhe Patrick J, Madhusudan Srinivasan, Ellis Ian O, Rakha Emad A
Division of Cancer and Stem Cells, School of Medicine, The University of Nottingham and Nottingham University Hospitals NHS Trust, Nottingham City Hospital, Nottingham, UK.
King Abdullah International Medical Research Center, Riyadh, Kingdom of Saudi Arabia.
Breast Cancer Res Treat. 2016 Aug;159(1):41-53. doi: 10.1007/s10549-016-3915-8. Epub 2016 Jul 27.
Impaired DNA damage response (DDR) may play a fundamental role in the pathogenesis of breast cancer (BC). RAD51 is a key player in DNA double-strand break repair. In this study, we aimed to assess the biological and clinical significance of RAD51 expression with relevance to different molecular classes of BC and patients' outcome. The expression of RAD51 was assessed immunohistochemically in a well-characterised annotated series (n = 1184) of early-stage invasive BC with long-term follow-up. A subset of cases of BC from patients with known BRCA1 germline mutations was included as a control group. The results were correlated with clinicopathological and molecular parameters and patients' outcome. RAD51 protein expression level was also assayed in a panel of cell lines using reverse phase protein array (RPPA). RAD51 was expressed in the nuclei (N) and cytoplasm (C) of malignant cells. Subcellular co-localisation phenotypes of RAD51 were significantly associated with clinicopathological features and patient outcome. Cytoplasmic expression (RAD51C(+)) and lack of nuclear expression (RAD51 N(-)) were associated with features of aggressive behaviour, including larger tumour size, high grade, lymph nodal metastasis, basal-like, and triple-negative phenotypes, together with aberrant expression of key DDR biomarkers including BRCA1. All BRCA1-mutated tumours had RAD51C(+)/N(-) phenotype. RPPA confirmed IHC results and showed differential expression of RAD51 in cell lines based on ER expression and BRCA1 status. RAD51 N(+) and RAD51C(+) tumours were associated with longer and shorter breast cancer-specific survival (BCSS), respectively. The RAD51 N(+) was an independent predictor of longer BCSS (P < 0.0001). Lack of RAD51 nuclear expression is associated with poor prognostic parameters and shorter survival in invasive BC patients. The significant associations between RAD51 subcellular localisation and clinicopathological features, molecular subtype and patients' outcome suggest that the trafficking of DDR proteins between the nucleus and cytoplasm might play a role in the development and progression of BC.
DNA损伤反应（DDR）受损可能在乳腺癌（BC）的发病机制中起重要作用。RAD51是DNA双链断裂修复中的关键因子。在本研究中，我们旨在评估RAD51表达与不同分子类型的BC及患者预后相关的生物学和临床意义。采用免疫组织化学方法，对一组具有详细注释且长期随访的早期浸润性BC病例（n = 1184）进行RAD51表达评估。将已知BRCA1种系突变患者的一部分BC病例作为对照组。结果与临床病理和分子参数以及患者预后相关。还使用反相蛋白阵列（RPPA）在一组细胞系中检测RAD51蛋白表达水平。RAD51在恶性细胞核（N）和细胞质（C）中表达。RAD51的亚细胞共定位表型与临床病理特征和患者预后显著相关。细胞质表达（RAD51C(+)）和缺乏核表达（RAD51 N(-)）与侵袭性行为特征相关，包括肿瘤较大、高级别、淋巴结转移、基底样和三阴性表型，以及包括BRCA1在内的关键DDR生物标志物的异常表达。所有BRCA1突变肿瘤均具有RAD51C(+)/N(-)表型。RPPA证实了免疫组化结果，并显示基于雌激素受体（ER）表达和BRCA1状态，RAD51在细胞系中的表达存在差异。RAD51 N(+)和RAD51C(+)肿瘤分别与较长和较短的乳腺癌特异性生存（BCSS）相关。RAD51 N(+)是较长BCSS的独立预测因子（P < 0.0001）。缺乏RAD51核表达与浸润性BC患者的不良预后参数和较短生存期相关。RAD51亚细胞定位与临床病理特征、分子亚型和患者预后之间的显著关联表明，DDR蛋白在细胞核和细胞质之间的转运可能在BC的发生和发展中起作用。
