PDCD1 and neoplasm: Since a higher expression of A2AR and A2BR has been associated with tumor cell growth signals, the inhibition of NK cell cytotoxicity [23,31], and limiting the maturation of NK cells [26] in previous studies, the suppression of tumor growth with respect to tumor size in our study could be explained by the enhanced function of NK cell cytotoxicity to tumor cells despite the lower NK cell signals after combined cordycepin and anti-PD1 therapy.