Significance of cyclin D1 overexpression in progression and radio-resistance of pediatric ependymomas

// Muh-Lii Liang 1, 2 , Tsung-Han Hsieh 3, 4 , Yun-Ru Liu 3, 4 , Yi-Wei Chen 5 , Yi-Yen Lee 1 , Feng-Chi Chang 6 , Shih-Chieh Lin 7 , Ming-Chao Huang 1 , Donald Ming-Tak Ho 7 , Tai-Tong Wong 3, 8, 9, 10 , Yun Yen 3, 11, 12 and Muh-Hwa Yang 2, 13, 14, 15, 16 1 Division of Pediatric Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan 2 Institutes of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan 3 Comprehensive Cancer Center of Taipei Medical University, Taipei Medical University, Taipei, Taiwan 4 Joint Biobank, Office of Human Research, Taipei Medical University, Taipei, Taiwan 5 Department of Oncology, Taipei Veterans General Hospital, Taipei, Taiwan 6 Department of Radiology, Taipei Veterans General Hospital, Taipei, Taiwan 7 Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan 8 Department of Neurosurgery, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan 9 Neuroscience Research Center, Taipei Medical University Hospital, Taipei, Taiwan 10 Institutes of Clinical Medicine, Taipei Medical University, Taipei, Taiwan 11 PhD Program for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan 12 Research Center of Cancer Translational Medicine, Taipei Medical University, Taipei, Taiwan 13 Cancer Research Center & Genome Research Center, National Yang-Ming University, Taipei, Taiwan 14 Immunity and Inflammation Research Center, National Yang-Ming University, Taipei, Taiwan 15 Division of Hematology-Oncology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan 16 Genomic Research Center, Academia Sinica, Taipei, Taiwan Correspondence to: Muh-Hwa Yang, email: mhyang2@ym.edu.tw Yun Yen, email: yyen@tmu.edu.tw Keyword: ependymoma; pediatric; radio-resistance; CCND1 Received: June 23, 2017      Accepted: December 13, 2017      Published: December 20, 2017 ABSTRACT Due to the limited efficacy of chemotherapy, the applications of adjuvant irradiation play an important role for ependymoma treatment. However, in the young ages, the resistance of residual and recurrent tumor, and long-term intellectual sequelae remain the major obstacles of radiotherapy. Understanding the mechanism of therapeutic failure caused by radio-resistance is, therefore, crucial in ependymoma treatment. Here we retrospectively analyze clinic-pathological factors in 82 cases of ependymoma less than 20 years old and identify radio-resistant genes through gene expression microarray followed by qRT-PCR validation and immunohistochemistry staining. Thirty-one out of 82 (37.8%) patients are under 3-year-old. The 10 years PFS and OS are 38% and 60%. Gross-total resection is the single significant prognostic factor for longer 10 years PFS and OS in the multivariant analysis ( p<0.05 ). According to the microarray analysis, CCND1 is up-regulated in supratentorial and infratentorial ependymomas and is associated with DNA repair. We demonstrated that 24 primary and 16 recurrent ependymomas were up-regulated, and 5 out of 7 paired samples exhibited higher CCND1 expression in recurrent tumors. We also found RAD51, another DNA repair gene, was up-regulated in supratentorial and infratentorial ependymomas. Knocking down CCND1 reduced cell proliferation and repressed several genes associated with S-phase and DNA repair. Homologous recombination activities of DNA repair were significantly decreased in CCND1-deficient cells while the level of γH2AX was increased after irradiation. In summary, these observations suggest a robust role of CCND1 in regulating cell proliferation and radio-resistance in ependymomas, providing a potential therapeutic target for pediatric ependymomas.