1. Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
2. Department of Oncology, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P.R. China
3. Department of Laboratory Medicine, the Second People's Hospital of Guangdong Province, Southern Medical University, Guangzhou, Guangdong 510317, P.R. China