PDCD1 and neoplasm: The combination treatment of ciforadenant with anti-PD-1 improved tumor regression compared to treatment with anti-PD-1 alone [191], and one possible mechanism may due to a decrease in PD-1 expression in A2AR antagonist treated CD8+ T cells since decreasing PD-1 expression in CD8+ T cells may lower the threshold and increase the sensitivity of anti-PD-1 therapy [192].