Abstract
Enzyme-linked immunosorbent assay (ELISA) is a common tool to study single or a panel of biomarkers for glioblastoma (GBM) among body fluids including cerebrospinal fluid (CSF). Limitation of ELISA and blood contamination in CSF are challenging issues. In this study, 90 CSF samples were collected from lumbar puncture or Ommya reservoir from 60 patients, predominantly diagnosed of recurrent GBM and metastatic CNS tumors (Mets). There were repeated collections from 10 patients. Detection methods are immuno-blot and semi-quantitative mass spectrometric (MS) analysis. We found that immuno-blot showed GBM, but not metastatic CNS tumor (Mets), is associated with elevated chitiase-3-like protein 1 (YKL-40). However YKL-40 antibody from Quidel ELISA kit failed to detect YKL-40 purified protein by immune-blot. In a series analysis of CSF from the same patient, we detected YKL-40 elevation 2 months prior to radiographic evidence of GBM progression. YKL-40 from one subject’s CSF reduced after initiation of intrathecal chemotherapy and the level remained low until 3 months later when GBM progressed. We found that MS can detect more than 300 proteins from each sample. Ceruloplasmin (CP) is found having a narrower range of variation than serotransferrin or albumin. Normalized with CP, we found that YKL-40 (YKL-40/CP) was significantly higher in recurrent GBM group (1.12 ± 0.46; n=22) than Mets (0.54 ± 0.24; n=19) or non-tumor group (0.56 ± 0.19; n=16), p<0.05, respectively. In contrast, CSF total protein, glucose, normalized osteopontin and insulin like growth factor binding protein 2 showed no difference among groups. We conclude 1) MS is a useful tool to study GBM biomarkers in CSF; 2) CP is a better internal protein than albumin for normalization in CSF; 3) elevated YKL-40 is associated with GBM recurrence and it is a potential biomarker for early detection of disease progression.