The analysis of CSF samples obtained from normal and tumor-bearing mice (immunocompetent glioma mice model with GL261 cells) by puncturing the cisterna magna revealed that PDL1 is present in normal samples at a concentration of around 1 ng/ml and increases to up to 2.8 ng/ml in mice with tumors (Figure 1D, graph) (see methods for technique of CSF collection and analysis). Here, CD274 is linked to glioma.