Department of Histopathology and School of Molecular Medical Sciences, The University of Nottingham and Nottingham University Hospitals NHS Trust, Nottingham City Hospital, Nottingham, UK.
Breast Cancer Res Treat. 2013 Jun;139(2):301-10. doi: 10.1007/s10549-013-2542-x. Epub 2013 Apr 28.
Although the role of BRCA1 and the homologous recombination (HR) pathway in breast cancer (BC) has been extensively studied, the alternative repair pathway for DNA double-strand breaks (DSBs), non-homologous end-joining (NHEJ) remains to be defined. Ku proteins bind to DNA DSB ends and play a key role in NHEJ. In this study we aimed to assess the expression and biological significance of the KU70/KU80 heterodimer in the different molecular classes of BC. The expression of KU70/KU80 was assessed immunohistochemically in a well-characterised and annotated series of 1302 unselected invasive BC cases with a long-term follow-up together with 25 cases with known BRCA1 mutations. The results were correlated with clinicopathological parameters, other DNA repair proteins and patient outcome. The expression of KU70/KU80 protein was further evaluated in various BC cell lines using western blotting and reverse-phase protein microarray (RPPA). Nuclear KU70/KU80 expression was correlated with features of poor prognosis including higher histological grade, lymphovascular invasion, negative oestrogen receptor expression, basal-like phenotype, P53 and CHK1 positivity. KU70/KU80 was expressed in all BRCA1-associated tumours and showed an inverse correlation with nuclear BRCA1 protein and aberrant cytoplasmic RAD51 expression. RPPA confirmed these results and showed higher expression of KU70/KU80 in BRCA1-deficient cell line compared to BRCA1-proficient cell line. KU70/KU80 expression showed an association with disease-free interval; however, it was not an independent predictor of outcome. As a conclusion, KU70/KU80 may play a role in DNA DSBs repair in HR-deficient tumours. Further study of other NHEJ markers in sporadic BC is warranted.
虽然 BRCA1 及其同源重组 (HR) 通路在乳腺癌 (BC) 中的作用已得到广泛研究，但 DNA 双链断裂 (DSB) 的替代修复途径——非同源末端连接 (NHEJ) 仍有待确定。Ku 蛋白与 DNA DSB 末端结合，在 NHEJ 中发挥关键作用。在这项研究中，我们旨在评估 Ku70/KU80 异二聚体在不同分子类型的 BC 中的表达和生物学意义。使用免疫组织化学方法评估了 1302 例未经选择的浸润性 BC 病例的 Ku70/KU80 表达，这些病例具有长期随访结果，并伴有 25 例已知 BRCA1 突变的病例。将结果与临床病理参数、其他 DNA 修复蛋白和患者预后相关联。使用 Western blot 和反相蛋白微阵列 (RPPA) 进一步评估了各种 BC 细胞系中 Ku70/KU80 蛋白的表达。核 Ku70/KU80 表达与预后不良的特征相关，包括更高的组织学分级、脉管侵犯、阴性雌激素受体表达、基底样表型、P53 和 CHK1 阳性。KU70/KU80 在所有 BRCA1 相关肿瘤中均有表达，并与核 BRCA1 蛋白和异常细胞质 RAD51 表达呈负相关。RPPA 证实了这些结果，并显示 BRCA1 缺陷细胞系中 Ku70/KU80 的表达高于 BRCA1 阳性细胞系。KU70/KU80 的表达与无病间隔时间有关；然而，它不是预后的独立预测因素。总之，KU70/KU80 可能在 HR 缺陷肿瘤的 DNA DSBs 修复中发挥作用。在散发性 BC 中进一步研究其他 NHEJ 标志物是必要的。
