title: Identification of the soluble form of tyrosine kinase receptor Axl as a potential biomarker for intracranial aneurysm rupture.
abstract: BACKGROUND
  Subarachnoid hemorrhage caused by a ruptured intracranial aneurysm (RIA) is a devastating condition with significant morbidity and mortality. Despite the fact that RIAs can be prevented by microsurgical clipping or endovascular coiling, there are no reliable means of effectively predicting IA patients at risk for rupture. The purpose of our study was to discover differentially-expressed glycoproteins in IAs with or without rupture as potential biomarkers to predict rupture.
  
  
  METHODS
  Forty age/gender-matched patients with RIA, unruptured IA (UIA), healthy controls (HCs) and disease controls (DCs) (discovery cohort, n = 10 per group) were recruited and a multiplex quantitative proteomic method, iTRAQ (isobaric Tagging for Relative and Absolute protein Quantification), was used to quantify relative changes in the lectin-purified glycoproteins in CSF from RIAs and UIAs compared to HCs and DCs. Then we verified the proteomic results in an independent set of samples (validation cohort, n = 20 per group) by enzyme-linked immunosorbent assay. Finally, we evaluated the specificity and sensitivity of the candidate marker with receiver operating characteristic (ROC) curve methods.
  
  
  RESULTS
  The proteomic findings identified 294 proteins, 40 of which displayed quantitative changes unique to RIA, 13 to UIA, and 20 to IA. One of these proteins, receptor tyrosine kinase Axl, was significantly increased in RIA, as confirmed in CSF from the discovery cohort as well as in CSF and plasma from the validation cohort (p <0.05). Spearman's correlation analysis revealed that the CSF and plasma Axl levels were strongly correlated (r = 0.93, p <0.0001). The ROC curve indicated an optimal CSF Axl threshold of 0.12 nM for discriminating RIA from UIA with corresponding sensitivity/specificity of 73.33%/90% and an area under the curve (AUC) of 0.89 (95% CI: 0.80-0.97, p < 0.0001). The optimal threshold for plasma Axl was 1.7 nM with corresponding sensitivity/specificity of 50%/80% and an AUC of 0.71 (95% CI: 0.54-0.87, p = 0.027).
  
  
  CONCLUSIONS
  Both CSF and plasma Axl levels are significantly elevated in RIA patients. Axl might serve as a promising biomarker to predict the rupture of IA.
authors.affiliation: Department of Neurosurgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310002, China. jingxu@zju.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Neurosurgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310002, China. mafeiqiang@yahoo.com.cn.
authors.forename: Feiqiang
authors.initials: F
authors.lastname: Ma
authors.affiliation: Department of Neurosurgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310002, China. ywisyw@gmail.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Yan
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Rd, Hangzhou, Zhejiang, 310058, China. 20918012@zju.edu.cn.
authors.forename: Sen
authors.initials: S
authors.lastname: Qiao
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Rd, Hangzhou, Zhejiang, 310058, China. 843865744@qq.com.
authors.forename: Shengquan
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Rd, Hangzhou, Zhejiang, 310058, China. liyi1986@zju.edu.cn.|Department of Joint Surgery, Shandong Provincial Hospital Affiliated with Shandong University, Jinan, Shandong, 250021, China. liyi1986@zju.edu.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Rd, Hangzhou, Zhejiang, 310058, China. luojianhong@zju.edu.cn.
authors.forename: Jianhong
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Neurosurgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310002, China. zjm135@vip.sina.com.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Rd, Hangzhou, Zhejiang, 310058, China. jhjin@zju.edu.cn.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Jin
mesh_terms: D000328:Adult; D017542:Aneurysm, Ruptured / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood / Q000134:cerebrospinal fluid; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D040901:Proteomics; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012372:ROC Curve; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000209:etiology / Q000378:metabolism*; D000094963:Axl Receptor Tyrosine Kinase
chemical_list: D015415:Biomarkers; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D000094963:Axl Receptor Tyrosine Kinase; C000722289:AXL protein, human