PDCD1 and neoplasm: The rationale behind the use of durvalumab and tremelimumab combination is to enhance antitumor immune activity through two different mechanisms related to the inhibition of PD-L1/programmed cell death-1 (PD-1) and CTLA-4 pathways: anti-PD-L1/anti-PD-1 operates in the tumor microenvironment and prevents T cell function inhibition, whilst anti-CTLA-4 acts in the lymphoid compartment to increase the number of tumor-reactive T cells [39,40].