PDCD1 and neoplasm: Inosine promotes T-helper 1 (Th1) differentiation by engaging the adenosine A2A receptor on T cells, thereby facilitating the recruitment of IFN-γ–producing CD4+ and CD8+ T cells within the tumor microenvironment, which augments the antitumor response induced by both anti-PD-1 and anti-CTLA-4 therapies (Liu et al., 2023).