Inosine, a key intermediate of purine metabolism produced by both host and microbiota, enhances effector T cell activity via the adenosine A2A receptor (A2AR)–cyclic adenosine monophosphate (cAMP)–protein kinase A (PKA) axis and synergizes with PD-1/CTLA-4 blockade, showing translational potential in colorectal cancer (65). Here, ADORA2A is linked to colorectal cancer.