CD274 and renal cell carcinoma: In addition to the PD-1/PD-L1 axis, also the PD-1/PD-L2 interaction may play an important role in evading anti-tumor immunity, suggesting that PD-1/PD-L2 blockade must be considered for optimal immunotherapy in PD-L2-expressing cancers, such as RCC and NSCLC (20, 21).