NOS2 and astrocytoma (excluding glioblastoma): Increased expression of VAV3 in high compared to low grade astrocytoma [34, 35], increased NOS2 expression in tumours of higher compared to lower malignancy and in brain tumours compared to healthy tissue [36–39], and increased SPC24 expression in other tumour types compared to healthy tissue [40] all support their tumorigenic function.