Brain tumors, whether primary or metastatic, remain a significant cause of cancer-related mortality and are characterized by a profoundly immunosuppressive tumor microenvironment (TME). Among the signaling pathways that shape this environment, purinergic signaling—particularly the adenosine (ADO) axis—has emerged as a central regulator of tumor progression. In the TME, extracellular ATP (eATP) is sequentially converted into AD...