CD8A and neoplasm: Since antitumor efficacy of IL-27 was first evaluated in 2004 [7], accumulating evidence has revealed that IL-27 has potent antitumor activity, which is mediated by multiple mechanisms including CD8+ T cells [7]–[9], [33], NK cells [10], [34], ADCC [11], anti-angiogenesis [12], [14]–[16], [35], [36], direct suppression of tumor growth [13], and inhibition of cyclooxygenase-2 expression [37], depending on the characteristics of individual tumors.