It is likely that microglia-derived TGFβ1 also contributes to canine glioma cell malignancy, as our laboratory observed robust TGFβ1 immunoreactivity (IR) at the leading edge of the tumor mass corresponding with increased GAM density in canine astrocytoma [15]. The gene discussed is TGFB1; the disease is astrocytoma (excluding glioblastoma).