Obama Kazutaka, Satoh Seiji, Hamamoto Ryuji, Sakai Yoshiharu, Nakamura Yusuke, Furukawa Yoichi
Laboratory of Molecular Medicine, Human Genome Center and Division of Clinical Genome Research, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Clin Cancer Res. 2008 Mar 1;14(5):1333-9. doi: 10.1158/1078-0432.CCR-07-1381.
Intrahepatic cholangiocarcinoma (ICC) is the second most common primary cancer in the liver, and its incidence is increasing in developed countries.
To discover novel molecular targets for the diagnosis and treatment of ICCs, we earlier analyzed expression profiles of 25 ICCs using a cDNA microarray containing 27,648 genes. In this study, we focused on the RAD51 associating protein-1 (RAD51AP1) gene because its expression was frequently elevated in our microarray data.
Quantitative PCR confirmed that RAD51AP1 expression was elevated in the great majority of the ICCs examined. Immunohistochemical analysis with anti-RAD51AP1 antibody further corroborated its accumulation in 14 of 23 ICC tissues (61%). Notably, suppression of RAD51AP1 by short interfering RNA resulted in growth suppression of cholangiocarcinoma cells, suggesting its involvement in the development and/or progression of ICC. Because RAD51AP1 interacts with RAD51, a molecule involved in DNA repair, we investigated whether RAD51AP1 is implicated in DNA strand breaks using gamma-irradiation. As a result, gamma-irradiation augmented RAD51AP1 protein expression and brought a focus formation in the nuclei, where accumulated RAD51AP1 colocalized with phosphorylated histone 2AX (gamma-H2AX) and RAD51. These data suggest that RAD51AP1 may play a role in cell proliferation as well as DNA repair.
Our findings may contribute to the better understanding of cholangiocarcinogenesis and open a new avenue to the development of novel therapeutic and/or diagnostic approach to this type of tumor.
肝内胆管癌（ICC）是肝脏中第二常见的原发性癌症，在发达国家其发病率正在上升。
为了发现用于ICC诊断和治疗的新分子靶点，我们 earlier 使用包含27,648个基因的cDNA微阵列分析了25个ICC的表达谱。在本研究中，我们聚焦于RAD51相关蛋白1（RAD51AP1）基因，因为其表达在我们的微阵列数据中经常升高。
定量PCR证实，在所检测的绝大多数ICC中，RAD51AP1表达升高。用抗RAD51AP1抗体进行的免疫组织化学分析进一步证实其在23个ICC组织中的14个（61%）中积累。值得注意的是，短干扰RNA抑制RAD51AP1导致胆管癌细胞生长受抑制，表明其参与ICC的发生和/或进展。由于RAD51AP1与参与DNA修复的分子RAD51相互作用，我们使用γ射线照射研究RAD51AP1是否与DNA链断裂有关。结果，γ射线照射增加了RAD51AP1蛋白表达，并在细胞核中形成一个焦点，积累的RAD51AP1与磷酸化组蛋白2AX（γ-H2AX）和RAD51共定位。这些数据表明RAD51AP1可能在细胞增殖以及DNA修复中发挥作用。
我们的发现可能有助于更好地理解胆管癌发生，并为开发针对这类肿瘤的新型治疗和/或诊断方法开辟一条新途径。
