NT5E and central nervous system cancer: While studies in human and rat glioma and medulloblastoma cell lines in vitro also demonstrate significantly higher levels of CD73 compared to normal astrocytes (Wink et al., 2003; Cappellari et al., 2012, 2015; Xu et al., 2013), closer analysis reveals that CD73 differentiates primary tumor cell lines, which express CD73, from metastatic cell lines which do not express the enzyme (Cappellari et al., 2012).